DESULFURIZATION OF LIGHT AND HEAVY GAS OIL FROM CRUDES OF KURDISTAN REGION-IRAQ BY OXIDATION, SOLVENT EXTRACTION AND ADSORPTION
A thesis Submitted to the Council of The College of Science at the University of Sulaimani in partial fulfillment of the requirements for the degree of Master of Science in Chemistry (Petroleum Chemistry) By
Barham Sharif Ahmed B.Sc. Chemistry (2011), University of Sulaimani
Supervised by Dr. Abdul-Salam R. Karim Professor
March 2017
&
Dr. Luqman O. Hama Salih Lecturer
Rashame 2716
حمَنِ الرَّحِيمِ بسم اهلل الرَّ ْ
یوسف /آیة 76
Supervisor Certification I certify that the preparation of thesis titled “Desulfurization of Light and Heavy Gas Oil from Crudes of Kurdistan Region-Iraq by Oxidation, Solvent Extraction and Adsorption’’ accomplished by (Barham Sharif Ahmed), was prepared under our supervision at the College of Science, University of Sulaimani, as a partial fulfillment of the requirements for the degree of Master of Science in Chemistry.
Signature:
Signature:
Name: Dr. Abdul- Salam R. Karim
Name: Dr. Luqman O. Hama Salih
Title: Professor
Title: Lecturer
Date: / / 2017
Date: / / 2017
In view of the available recommendation, I forward this thesis for debate by the examining committee.
Signature: Name: Dr. Bakhtyar Kamal Aziz Title: Assistant Professor Head of Department of Chemistry Date: / / 2017
Examining Committee Certification We certify that we have read this thesis entitled “Desulfurization of Light and Heavy Gas Oil from Crudes of Kurdistan Region-Iraq by Oxidation, Solvent Extraction and Adsorption” prepared by (Barham Sharif Ahmed), and as Examining Committee, examined the student in its content and what is connected with it, in our opinion it meets the basic requirements toward the degree of Master of Science in Chemistry (Petroleum Chemistry).
Signature: Name: Dr. Hashim J. Aziz Title: Professor Date: 1 / 3 / 2017 (Chairman)
Signature: Signature: Name: Dr. Ahmad M. Abdullah Title: Assistant Professor Date: 1 / 3 / 2017 (Member)
Signature: Name: Dr. Safya S. Taha Title: Assistant Professor Date: 1 / 3 / 2017 (Member)
Signature: Name: Dr. Abdulsalam R. Karim Title: Professor Date: 1 / 3 / 2017 (Supervisor – Member) Signature : Name: Dr. Luqman O. Hama Salih Title: Lecturer Date: 1 / 3 / 2017 (Co-supervisor – Member)
Approved by the Dean of the College of Science: Signature: Name: Dr. Bakhtiar Qader Aziz Title: Professor Date: / / 2017
Linguistic Evaluation Certification
This is to certify that I, Jutyar Salih, have proofread this thesis entitled “Desulfurization of Light and Heavy Gas Oil from Crudes of Kurdistan Region-Iraq by Oxidation, Solvent Extraction and Adsorption” by (Barham Sharif Ahmed). After marking and correcting the mistakes, the thesis was handed again to the researcher to make the corrections in the last copy.
Signature: Name: Jutyar Salih Position: Department of English, College of Languages, University of Sulaimani. Date: 25 / 1 / 2017
Dedication
This Thesis is Dedicate to: Whoever taught me and supported me in my life, My parents, My sisters and brothers, All my close friends
Acknowledgements Firstly, I thank God for helping me in every moment and giving me health and strength to per-form and complete this study. It is my pleasure to express my gratitude and sincere appreciation to my supervisors Prof. Dr. Abdul-Salam Rahim and Dr. Luqman Omer whose contribution in stimulating suggestions and encouragement helped me to coordinate my project especially in rectifying my report writing. My gratitude and thanks go to the Council of the College and all of the staff of Chemistry Department, especially Dr. Bakhtyar, Head of the Department, and Mr. Yassin, decider of the department, for helping and offering all necessary requirements for the completion of this work. I would like to thank Mr. Swara who helped me in identifying the compounds by performing IR. I greatly appreciate Dr. Dler’s help in analyzing metals in my samples by ICP instrument. My thanks and appreciation also goes to Mr. Zana, for helping me in using energy disperse X-Ray fluorescence. I would also like to thank Mr. Bahjat, for providing the chemicals and the equipment for the project. I am very grateful for Dr. Omed, Dr. Dlzar, Dr. Dyare, Mr. Dana, Mr. Karzan, Mr. Rebaz, Mr. Hemn, Mr. Aso, Mr. Arkan, Mr. Azad, Mr. Amanj, Mr. Mozart, Ms. Hanar, Ms. Renas, Ms. Aveen, and Ms. Kurdistan for helping me making my project. My utmost regards and thanks go to my family for their blessings. Without them I would not be here. Thanks very much for the extra help you gave me so I could complete my project. Last but not least, I want to thank whoever taught me and supported me in my life .
Abstract Four types of crude oil namely Taq-Taq (TQ), Sarqala (SA), Khurmala (Kh) and Tawke (TA) from different oil fields in Kurdistan Region-Iraq have been studied and fractionated to five different cuts (naphtha, kerosene, light gas oil, heavy gas oil and fuel oil), the volume percent (V/V %) determined for all cuts, two distillation cuts light gas oil (LGO) from 241 to 300ºC, and heavy gas oil (HGO) from 301 to 360 ºC, have been fully evaluated according to standard American Society for Testing and Materials (ASTM) and Iraqi specification. Lights and heavy gas oils contained different levels of organic sulfur compound, which caused environmental pollution and is harmful to human health during combustion in compression engine, manufacturing and power generation . Oxidation desulfurization process by using Hydrogen peroxide as an oxidant and acetic acid as a catalyst, at different operation condition (temperature, time, amount of acetic acid and hydrogen peroxide) was carried out for removing sulfur, after oxidation still sulfur content was high, but sulfur compound convert to sulfone and sulfoxide, which have higher polarity than sulfur compound less deleterious. Solvent extraction by using three different polar solvents (acetonitrile, methanol and acetic acid) was conducted in batch system for removing oxidized sulfur compound. After oxidation, the color of oxidized gas oil changed into orange, adsorption by different adsorbent alumina (AL), activated Kany saze jam clay (KS) and Arz room clay (AR), employed to sulfur removal and improvement of color. After each step of oxidation, liquid-liquid extraction and adsorption for removing of sulfur compound, the total sulfur content of gas oils sample have been determined by using energy disperse X-Ray fluorescence based on ASTM D4294 method.
I
After treatment, for more evaluation and explaining the effect of oxidation, solvent extraction and adsorption on sulfur removal, Gas chromatographic technique was used, which is coupled with pulls flame photometric detector (PFPD), this detector is a sensitive and selective detector for organic sulfur compound, used to illustrate the effect of each desulfurization step.
II
Table of Contents Title
Page No.
Abstract ……………………………………………………..….….………............I Table of contents …………….………………..……………………..…………...III List of figures …………………………………………………….…....................VI List of tables ………………………………………………………..…..............XIII List of abbreviations …………………………………………………..…..............X Chapter One: Introduction and Literature Review 1. Introduction ........................................................................................................... 1 1.1 Definitions and terminology of petroleum .......................................................... 1 1.2 Petroleum history in kurdistan ............................................................................ 1 1.2.1 Taq-Taq oil field............................................................................................... 2 1.2.2 Tawke oil field ................................................................................................. 2 1.2.3 Khurmala oil field……………………………………………………..….......4 1.2.4 Garmian block field .......................................................................................... 4 1.3 Hydrocarbon groups in crude oil......................................................................... 4 1.4 Crude oil distillation and fractionation ............................................................... 8 1.5 Gas oil.................................................................................................................. 9 1.6 Sulfur compounds in petroleum fractions ......................................................... 11 1.6.1 The origin and types of sulfur compounds in petroleum fractions ................ 11 1.6.2 The effect of sulfur compounds on petroleum fractions and environment .... 12 1.6.3 Fuel sulfur specifications ............................................................................... 13 1-7 Classification of desulfurization technologies .................................................. 14 1.7.1 Conventional hydrodesulfurization (HDS) .................................................... 14 1.7.2 Non-hydrodesulfurization based .................................................................... 17 1.7.2.1 Desulfurization by adsorption on a solid adsorbent .................................... 17 1.7.2.2 Oxidative desulfurization and solvent extraction ....................................... 19 1.8 Literature review ............................................................................................... 22 III
1.9 Aim of present study ......................................................................................... 26 Chapter Two: Experimental Part 2. Experimental part ................................................................................................ 27 2.1 Chemical reagents: ............................................................................................ 27 2.2 Apparatus and instruments ................................................................................ 28 2.3 Procedure ........................................................................................................... 29 2.3.1 Distillatoin: ..................................................................................................... 29 2.3.1. A-Distillation of crude oil ASTM D 1160 .................................................... 29 2.3.1. B-Distillation of petroleum products: IP-123/ ASTM D 86 ......................... 30 2.3.2 Density, specific gravity and API gravity of crude oil and liquid petroleum products ASTM D1298 ........................................................................................... 30 2.3.3 Determination of aniline point ASTM D611 ................................................. 30 2.3.4 Measurement of kinematics viscosity ASTM D445 ...................................... 31 2.3.5 Determination of copper corrosion ASTM D130 .......................................... 31 2.3.6 Procedure for gas chromatographic analysis ................................................. 31 2.3.7 ED-XRF-calibration for determination of total sulfur content ...................... 32 2.3.8 SARA- analysis .............................................................................................. 33 2.3.9 Hydrogen peroxide concentration determination........................................... 34 2.3.10 Oxidation of light and heavy gas oil samples .............................................. 35 2.3.11 Liquid-liquid extraction ............................................................................... 35 2.3.12 Treatment of samples by adsorption ............................................................ 35
Chapter Three: Results and Discussion 3 PART ONE ........................................................................................................ ..37 3.1 Evaluation of crude oils and gas oils ................................................................ 37 3.1.1 Fractionation of crude oil to obtain different boiling point fraction .............. 37 3.1.2 Specific gravity, API gravity and sulfur content ......................................... ..40 IV
3.1.3 Metal content determination in crude oils...................................................... 42 3.1.4 Saturate, aromatic, resin and asphaltene fractionation................................... 44 3.1.5 Evaluation of light and heavy gas oils ........................................................... 46 PART TWO ............................................................................................................. 53 3.2 Oxidation desulfurization, solvent extraction and adsorption for light and heavy gas oils. .................................................................................................................... 53 3.2.1 Oxidation desulfurization ............................................................................... 53 3.2.1.1 Effect of operating reaction temperature on ODS ...................................... 54 3.2.1.2 Effect of acetic acid as a catalyst on ODS process ..................................... 55 3.2.1.3 Effect of H2O2 on ODS process .................................................................. 56 3.2.1.4 Effect of reaction time on ODS process...................................................... 57 3.2.2 The selection of the most efficient condition for oxidative desulfurization of LGO and HGO ........................................................................................................ 60 3.2.3 Solvent extruction of oxidized sulfur compounds. ........................................ 66 3.2.4 Adsorption of oxidized gas oil after solvent extraction ................................. 76 Conclusions………………………………………………………………….…….83 Appendix……………………………………………………………………..……84 References…………………………………………………………..…...…….......96
V
List of Figures Figure No.
Figure Title
Page No.
Figure 1: Map of oil filed in kurdistan region of iraq……………………..….............3 Figure 2: SARA- separation scheme……………………………………….…..........5 Figure 3: Molecular structure of: A) Resin, B) Asphaltenes……………....….……...7 Figure 4: Acidic and non-acidic sulfur compounds……………………...................12 Figure 5: Relationship between the reactivity of hydrodesulfurization and the size Of sulfur containing model compounds…….....................……………………...…16 Figure 6: Adsorptive desulfurization process…...………………………….………18 Figure 7: Oxidation reactions of refractory organosulfur compounds……………..20 Figure 8: The ideal reaction in ODS process for methyl dibenzothiophenes…........21 Figure 9: Asoma phoenix II (ED-XRF)………………………………....………….33 Figure 10: Distillation curve of TQ, SA, Kh and TA crude oils……….…...............42 Figure 11: Distribution diagram of SARA fraction in crude oil…………..………..46 Figure 12: Effect of (T) ºC on ODs Processes…………………………...................59 Figure 13: Effect of volume HAc on ODS processes...............................................59 Figure 14: Effect of volume H2O2 on ODS Processes ……………...……...............59 Figure 15: Effect of time on ODS Processes…………………………….................59 Figure 16: Oxidation desulfurization processes…………………………………....61 Figure 17: GC-PFPD for tetrahydrofuran solvent……………………………….....63 Figure 18: GC-PFPD for LGO TA A) before oxidation B) after oxidation………...64 Figure 19: GC-PFPD for HGO TA A) before oxidation B) after oxidation………..65 Figure 20: GC-PFPD for unoxidized LGO TA after solvent extraction by A) MeCN, B) MeOH C) HAc……………………………………………………...70 Figure 21: GC-PFPD for LGO TA after solvent extraction by A) MeCN B) MeOH C) HAc………………………………………………………..…..........71 VI
Figure 22: GC-PFPD for HGO TA after solvent extraction by A) MeCN B) MeOH C) HAc……………………………………………………..…..….........73 Figure 23: IR Spectrum of LGO TA before oxidation………………..…...…..........74 Figure 24: IR spectrum for LGO TA, A) after oxidation B) after extraction by acetonitrile…….…………………….…………………………..…………………75 Figure 25: LGO A) before oxidation B) after oxidation C) after adsorption………..77 Figure 26: HGO A) before oxidation B) after oxidation C) after adsorption….........77 Figure 27: Color of alumina A) before adsorption B) after adsorption……………..81 Figure 28: GC-PFPD HGO TA after adsorption by A) AL, B) KS, C) AR adsorbent……………………………………………………………………..........82 Figure 29: GC-PFPD for LGO TQ A) before oxidation B) after oxidation…….…84 Figure 30: GC-PFPD for LGO SA A) before oxidation B) after oxidation…….…85 Figure 31: GC-PFPD for LGO K A) before oxidation B) after oxidation….…......86 Figure 32: GC-PFPD for HGO TQ A) before oxidation B) after oxidation……….87 Figure 33: GC-PFPD for HGO SA A) before oxidation B) after oxidation……….88 Figure 34: GC-PFPD for HGO K A) before oxidation B) after oxidation…………89 Figure 35: GC-PFPD for LGO TQ after solvent extraction by A) MeCN B) MeOH C) HAc…………………………………………………………………90 Figure 36: GC-PFPD for LGO SA after solvent extraction by A) MeCN B) MeOH C) HAc…………………………………………………………………91 Figure 37: GC-PFPD for LGO K after solvent extraction by A) MeCN B) MeOH C) HAc………………………………………………..………………...92 Figure 38: GC-PFPD for HGO TQ after solvent extraction by A) MeCN B) MeOH C) HAc……………………………………………………..……..........93 Figure 39: GC-PFPD for HGO SA after solvent extraction by A) MeCN B) MeOH C) HAc…………………………………………………………………94 Figure 40: GC-PFPD for HGO K after solvent extraction by A) MeCN B) MeOH C) HAc…………………………………………………..………..........95 VII
List of Tables Table No.
Table Title
Page No.
Table 1: Crude distillation products………………………………….......................8 Table 2: Typical process conditions for various HDS processes………………...…15 Table 3: Chemicals used in this work and their suppliers……..……………………27 Table 4: Chemical analysis (wt. %) of adsorbent…………………………………..28 Table 5: Physicochemical parameters of kurdistan crude oils…….…………..........38 Table 6: (%Vol) ml versus (T)ºC for TQ, SA, Kh and TA crude oils….……………39 Table 7: (%v/v) obtained from TQ, SA, Kh and TA crude oils…………..…………40 Table 8: Crude oil classes in kurdistan………...…………..……………………….41 Table 9: Concentration of some metals in kurdistan crude oils…..….……………..43 Table 10: Weight percent of SARA fraction………...………………………..........45 Table 11: Evaluation LGO and HGO fractions obtained from TQ…...…….............47 Table 12: Evaluation LGO and HGO fractions obtained from SA……....................48 Table 13: Evaluation LGO and HGO fractions obtained from Kh.....…...................49 Table 14: Evaluation LGO and HGO fractions obtained from TA………................50 Table 15: ASTM D 86 for TQ, SA, Kh and TA light gas oil……..…........................51 Table 16: ASTM D 86 for TQ, SA, Kh and TA heavy gas oil…..….……….............52 Table 17: Effect of temperature on oxidation desulfurization……………...............55 Table 18: Effect of HAc on oxidation desulfurization…...…….………..………….56 Table 19: Effect of H2O2 on oxidation desulfurization……...……..…….................57 Table 20: Effect of time on oxidation desulfurization……………….......................58 Table 21: Sulfur removal LGO and HGO after oxidation…………………….........62 Table 22: Physical properties of solvents……………………………………..........66 Table 23: Extraction of LGO TA by MeOH, MeCN and HAc solvent……..............67 Table 24: Sulfur content and recovery after solvent extraction….…………………69 VIII
Table 25: Sulfur content and recovery of LGO and HGO after adsorption for acetonitrile solvent……………………………………………….……….........78 Table 26: Sulfur content and recovery of LGO and HGO after adsorption for methanol solvent………………………………………………………………79 Table 27: Sulfur content and recovery of LGO and HGO after adsorption for acetic acid solvent...……………………………………………………………..…80
IX
List of Abbreviations
Symbols
Terms
AL
Alumina
API
American Petroleum Institute
AR
Arz room clay
ASTM BPD
American Society for Testing and Materials Barrel Per Day
DBT
Dibenzothiophen
EHN
2-Ethylhexyl Nitrate
EPA
Environmental Protection Agency
EPEFE GC
European Programme on Emission Fuels and Engine Technology Gas Chromatography
HAc
Acetic acid
HGO
Heavy Gas Oil
IEA
International Energy Agency
IP
Institute of Petroleum
Kh
Khurmala Crude Oil
KS
Activated Kany Sazy jam clay
LHSV
Liquid Hourly Space Velocity
LGO
Light Gas Oil
mbo
million barrels of oil
MeCN
Acetonitrile
MeOH
Methanol
NOX
Nitrogen Oxide
ODS
Oxidation Desulfurization X
OSCs
Organic Sulfur Compounds
PFPD
Pulls Flame Photometric Detector
SA
Sarqala Crude Oil
SOX
Sulfur Oxide
TA
Tawke Crude Oil
t-BuOCl
t-Butyl Hypochlorite
THF
Tetra Hydro Furan
TQ
Taq-Taq Crude Oil
XI
Chapter One Introduction and Literature Review
Chapter One
Introduction and Literature Review
Chapter One: Introduction and Literature Review 1. Introduction 1.1 Definitions and terminology of petroleum Petroleum is not a uniform material. It is a naturally occurring mixture[1]. In fact, its chemical and physical composition can vary not only with the location and age of the oil field but also with the depth of the individual well. Indeed, two adjacent wells may produce petroleum with markedly different characteristics[2]. Crude oil is a complex liquid mixture made up of a vast number of hydrocarbon compounds that consist mainly of carbon and hydrogen in differing proportions. In addition, small amounts of organic compounds containing sulfur, oxygen, nitrogen and metals such as vanadium, nickel, iron and copper are also present. Hydrogen to carbon ratios affects the physical properties of crude oil [3],[4]. 1.2 Petroleum history in Kurdistan Petroleum age in Kurdistan region of Iraq started when the production sharing contracts (PSC) law was employed. Since that time, Kurdistan region of government (KRG) has signed exploration agreements with several oil companies. The initial production sharing contract (PSC) was issued by the (KRG) to Genel Energy in July 2002 covering lands that included the Taq-Taq structure, During June 2004, DNO International was awarded a production sharing agreement that included the Tawke structure[5]. The International Energy Agency (IEA) estimated that the Iraqi Kurdistan Region contained 4 billion barrels of proved reserves; KRG’s estimate is much higher because it includes unproved resources. KRG estimates that it holds 45 1
Chapter One
Introduction and Literature Review
billion barrels[6]. The Kurdish Government solicited foreign companies to invest in 40 new oil sites, with the hope of increasing regional oil production, notable companies active in Kurdistan include Exxon, Chevron, Talisman Energy, Genel Energy, Hunt Oil, Gulf Keystone Petroleum, and Marathon Oil. 1.2.1 Taq-Taq oil field Geographically Taq-Taq oil field is located in the Kurdistan Region of Iraq within Zagros Oil Province, some 60 kilometers northeast of Kirkuk, 80 kilometers southeast of Hawler and 120 kilometers northwest of Sulaimani city[5]. i.e. between 36.1° latitudes and 44.6° longitude. Drilling in Taq-Taq field spudded in February 1960 [7]. During the period from 1991 to 2004, there was some small development of Taq-Taq field for local use, because, the Kurds did not have the technical or financial resources to make significant progress on exploring or developing petroleum in their area[8]. The Taq-Taq field has been producing since 2006, this field produced a gross average of 116,000 bpd in 2015, compared to 103,000 bpds in 2014, representing %13 growth year-on-years. As shown in figure1, is expected to increase production capacity for Taq-Taq field to 200,000 bpds by December 2015[9]. Reserves of this field 647 mbo, is currently Taq-Taq Operation Company, which is in charge of developing the field [10]. 1.2.2 Tawke oil field Tawke oil field was discovered in June 2006 by DNO Company (DNO started working in Kurdistan in 2004 as one of the first international oil companies in the region and has a leading position in reserves and production) in an area which was part of the Duhok city[5].
2
Chapter One
Introduction and Literature Review
Tawke oil filed
Taq-Taq oil filed
Khurmala oil filed
Garmian oil field
Figure 1: Map of Oil Filed in Kurdistan Region of Iraq[10].
3
Chapter One
Introduction and Literature Review
The Tawke discovery comprises a large east-west trending anticline located close to the Turkish border in Kurdistan Region, Tawke oil field was located between 37° latitudes and 43° longitudes. The production capacity of the Tawke oils field 200,000 bpd ended in 2014, while Reserves of this field was 771 mbo[10]. 1.2.3 Khurmala oil field On July 2009, the first oil from the Khurmala Dome central process stations was processed and transported by a pipeline to supply the new 20,000 barrel per day Erbil Refinery. The Khurmala dome is the northern most dome of the Kirkuk oil field structure. The field is approximately 20 kilometers in length and lies fully on the territory of Erbil Governorate, geographically located between 35.9° latitudes and 43.8° longitudes[5].The Production capacity of Khurmala fields is 150,000 bpd[10]. 1.2.4 Garmian block field Sarqala oil field geographically locates in the Kurdistan Region of Iraq, some kilometers northwest of Sulaimani, located between 34.7° latitude and 55.2° longitudes. Sarqala-1 was the first well discovered in this field at 2011, western Zagros company which is in charge of developing the field, the production capacity for Sarqala -1 field was 5000-5500 bpd, and reservoir of the field was 311 mbo [10]. Figure 1 shows the oil fields in Kurdistan Region-Iraq. 1.3 Hydrocarbon groups in crude oil Even though crude oil contains several thousands of different hydrocarbon molecules, due to the complex composition of crude oils, characterization by the individual molecular types is difficult and elemental analysis is unattractive because it gives only limited information about the constitution of petroleum due to the 4
Chapter One
Introduction and Literature Review
constancy of elemental composition. Instead, hydrocarbon groups type analysis is commonly employed[11],[12]. The hydrocarbons in crude oil can be classified into four main classes, Saturates, Aromatics, Resins, and the Asphaltene[13], [14]. these four groups are called (SARA) group, and they can be separated from one another based on polarity and solubility in different solvent, as shown in Figure 2, each of these classes contains hundreds of individual compounds[15].
Crude oil
n-hexane
Soluble
Precipitate
Maltenes
Asphaltenes
Liquid chromatography on silica gel column
Saturates
Aromatics
Resins
Figure 2: SARA- separation scheme [16].
The SARA classifies crude oils based on their solubility and polarity through a chromatographic technique that divides the oil into four main fractions. These fractions provide the name for the analysis[17]. Saturates: Saturated hydrocarbons are non-polar and consist of normal alkanes, branched alkanes and cyclo-alkanes. Saturates are the largest single source of hydrocarbon or petroleum waxes, which are generally classified as paraffin wax, 5
Chapter One
Introduction and Literature Review
microcrystalline wax. the paraffin wax is the major constituent of most semi solid deposits from crude oils[18][19]. In general, saturates are the largest component, accounting for more than 50% of the mass of fresh oils in 68% of the oils studied, as oils evaporate, saturate contents almost always decrease[20]. Aromatic: Aromatic crude oil has an unsaturated ring compound having a basic 6- carbon atom ring the general formula is CnH2n-6. The aromatic series of hydrocarbons are chemically and physically very different from the paraffin base and naphthenic base crude oil[21],[18]. The most common aromatic compounds in crude oils are benzene, benzene derivatives (like, alkylbenzenes) and fused benzene ring compounds, The concentration of benzene in crude oil has been reported to range between 0.01 % and 1 %[19]. Resins: Resins are the most polar and aromatic species present in deasphalted oil and, has been suggested, contribute to the enhanced solubility of asphaltenes in crude oil by solvating the polar and aromatic portions of the asphaltenic molecules and aggregates[22]. The structure of resins is not well understood. It is accepted that resins are the pre-cursors for the formation of asphaltenes[23]. Resins compared to asphaltenes have a lower content of aromatics, and play a role of surfactants in stabilizing colloidal particles of asphaltenes in oil, and the presence of resins in oil prevents the precipitation of asphaltenes by keeping the same particles in colloidal suspension. When a solvent such as n-alkanes (n-hexane) added to crude oil, resins are dissolved in the liquid solvent[24]. And leaving active areas of asphaltene particles, which allow the aggregation of the asphaltene particle and, consequently, precipitation[25]. Asphaltenes: Asphaltenes is the heaviest and most complex fraction in a crude oil with the highest aromaticity. They are defined as the fraction of the crude oil which is soluble in toluene and precipitate in light alkanes[26],[27]. Asphaltenes are 6
Chapter One
Introduction and Literature Review
regarded to be polar species, formed by condensed polyaromatic structures, containing alkyl chains[28]. And small quantities of heteroatoms such as oxygen (0.3% − 4.9%), sulfur (0.3% − 10.3%) and nitrogen (0.6% − 3.3%), and trace quantities of metals such as nickel, vanadium and iron in ppm levels[29]. The term originated in 1837 when J.B. Boussingault defined asphaltenes as the residue of the distillation of bitumen: insoluble in alcohol and soluble in turpentine[30]. Heavy Crude oils contain large quantities of asphaltenes [31]. When asphaltene deposits an array of problems emerges such as permeability reduction, pipeline plugging, and pumps failure of the surface and catalyst poisoning [32],[33],[34]. The molecular weight of asphaltene molecules has been difficult to measure due to the asphaltenes tendency to self-aggregate, but molecular weights are in the range 500-2000 g/mole while molecular weight of Resins are(< 1000 g/mole), but Resins have a higher H/C ratio than asphaltenes, 1.2-1.7 compared to 0.9-1.2 for the asphaltenes[12],[35]. It has been reported that the asphaltene content of a crude oil sample increases as a result of the presence of high amount of sulfur content. The molecular structures below in Figure (3) are
shows resins and asphaltenes
structure[36],[37],[38].
A) Resin
B) Asphaltenes
Figure 3: Molecular structure of: A) Resin, B) Asphaltenes[38]. 7
Chapter One
Introduction and Literature Review
1.4 Crude oil Distillation and fractions Crude oil is a mixture of many thousands of components varying from light hydrocarbons such as methane, ethane, etc., to very high molecular weight components[39]. Many useful products can be made from these hydrocarbons by a process called Fractional Distillation[40]. Crude distillation is physical separation and one of the first and most critical steps of the petroleum refining process. It separates crude oil, into fractions based on the boiling points of the hydrocarbons [41],[42]. Crude oils are first desalted and then introduced with steam to an atmospheric distillation column. The atmospheric residue was then introduced to a vacuum distillation tower operating at about 50 mmHg, where heavier products are obtained. Typical products from both columns are listed in Table 1 [3]. Table 1: Crude distillation products [3]. Atmospheric distillation
Yield (wt %)
True boiling temperature °C °F
Refinery gases (C1-C2)
0.10
-
-
Liquid petroleum gases
0.69
-42
44
Light straight run
3.47
32–82
90–180
Heavy straight run
10.17
82–193
180–380
Kerosene
15.32
193–271
380–520
Light gas oil (LGO)
12.21
271–321
520–610
Heavy gas oil (HGO)
21.10
321–427
610–800
Vacuum gas oil (VGO)
16.80
427–566
800–1050
Vacuum residue (VR)
20.30
+566
+1050
Vacuum distillation
8
Chapter One
Introduction and Literature Review
After the separation of the crude oil into different fractions by atmospheric distillation, these streams are transformed into products with a high additional value through a wide variety of catalytically promoted chemical reactions such as, isomerization, aromatization, alkylation, cracking and hydrotreating [43]. The crude oil distillation systems, including distillation columns and their heat recovery systems, It is a highly energy intensive process, consuming fuels at an equivalent of 1 to 2% of the crude oil processed[44]. 1.5 Gas Oil Gas Oil or is one of the petroleum products, which is used in all kinds of compression ignition engines as a fuel[45]. It is obtained by atmospheric or vacuum distillation of crude oil, at the boiling range of 215-337 oC for light gas oil or 320426 oC for heavy gas oil[46]. The density of diesel fuel is between 820 to 950 (g/l). The average empirical formula for Gas Oil lies in the range of C10H22 to C15H32[47]. This hydrocarbon mixture containing straight-chain alkanes, naphthenic and aromatics, It contains some heterogeneous compounds rather than carbon and hydrogen such as sulfur, nitrogen and oxygen as well as traces of metallic constituents such as nickel and vanadium[48]. Straight-run and vacuum gas oils typically contain 70-80% aliphatic hydrocarbons, 20-30% aromatic and less than 5% of olefins. But cracked gas oils may contain up to 75% of aromatic and up to 10% olefins. Since part of the gas oils distil above 350°C, they may contain minor concentrations of 4 to 6 rings polycyclic aromatic hydrocarbons[46],[49]. Vacuum gas oil is the distillate which has high boiling point. This is not a saleable product and is used as feed to secondary processing units, such as fluid catalytic cracking units, and hydrocrackers, for conversion to light and middle distillates[50]. 9
Chapter One
Introduction and Literature Review
Some properties are important to gas oil such as (flash point, viscosity, pour point, ash content, sulfur content and cetane number), The cetane number is a measure of how readily the fuel starts to burn (auto ignites) under diesel engine conditions. A fuel to a high cetane numbers starts to burn shortly after it is injected into the cylinder; therefore, it has a short ignition delay period and vice versa [51],[52]. Increasing the cetane number improves fuel combustion, reduces white smoke on startup, and reduce nitrogen oxide and particulate matter emissions, EPEFE found that increasing the cetane number from 50 to 58 would reduce HC and CO each by 26%[53]. Thus Cetane number improvers are used for reducing combustion noise and smoke. 2-Ethylhexyl nitrate EHN is the most widely used cetane number improver. It is thermally unstable and decomposes rapidly at the high temperatures in the combustion chamber. The products of decomposition help initiate fuel combustion and, thus, shorten the ignition delay period. EHN typically is used in the concentration range of 0.05 to 0.4 mass % and this may yield a 3 to 8 Cetane number benefit[54]. Another significant property of gas oil is sulfur content, engine wear and deposits can vary due to the sulfur content of the fuel. Today, the greater concern is the impact that sulfur could have on emission control devices. As such, sulfur limits are now set by the U.S. Environmental Protection Agency (EPA), that limited the sulfur content of on-road diesel fuel to 15 ppm starting in 2006 [52]. The main sulfur compounds in gas oil are dibenzothiophenes and their alkylated derivatives, which represent the most refractory and stable sulfur compounds[55].
10
Chapter One
Introduction and Literature Review
1.6 Sulfur Compounds in Petroleum Fractions 1.6.1 The Origin and Types of Sulfur Compounds in Petroleum Fractions Sulfur is the third most abundant element in crude petroleum, falling behind only carbon and hydrogen. Crude petroleum, from whatever source, contains sulfur. Several different sources of sulfur compound which occur in petroleum have been suggested. If the theory that the oil is derived from decayed animal remains be accepted, no other source of the sulfur need be sought, because sulfur an essential constituent of all proteins [56]. Sulfur in crude oil presents in the form of free elemental sulfur, hydrogen sulfide and organic sulfur compound such as (thiols, sulfide,
disulfide,
polysulfide,
thiophenes,
dibenzothiophene
and
their
derivatives)[57],[58],[59]. The crude oil can be sweet when the total sulfur in it less than 0.5% [60]. and become sour as the sulfur content more 1.5%wt. The area in between is sometimes called intermediate sweet or intermediate sour[61]. Sweet crude oil is more preferred by refineries as it contains valuable chemicals which are needed to produce the light distillates and high quality feed stocks. The sulfur content of petroleum varies from less than 0.05 to more than 14% wt. but generally falls in the range 1 to 4% wt. The highest percent of sulfur for Iraqi crude oil is (8%) for Qayarah crude oil in Northeast Iraq[62]. Organosulfur compounds may generally be classified as acidic and non-acidic [63]. Acidic sulfur compounds when dissolved in water are mildly acidic, like thiols, while the thiophenes are examples of non-acidic sulfur compounds as shown in figure 4[64]. Generally the proportion of sulfur compound will increase with the boiling point of the crude oil fraction, It is also reported that The average sulfur contents of all the crude oils refined in the five regions of the U.S. increased from 11
Chapter One
Introduction and Literature Review
0.89%wt. in 1981 to 1.25 %wt in 1997, while the corresponding API gravity decreased from 33.74° in 1981 to 31.07° in 1997[65],[66].
Acidic sulfur compound SH
SH
CH3SH
methyl mercaptan
phenyl mercaptan
cyclohexylthiol
Non-acidic sulfur compound S
S
CH3SCH3 dimethylsulfide
Thiophene
S
Benzothiophene H3C
dibenzothiophene
S
CH3
4,6 dimethyldibenzothiophene
Figure 4: Acidic and non-acidic sulfur compounds [64]. 1.6.2 The Effect of Sulfur Compounds on Petroleum Fractions and environment High sulfur content is generally harmful to petroleum products, and removal of sulfur compounds or their conversion to less deleterious types is an important part of refining practice. Some sulfur compounds in gasoline may corrode various metallic parts of internal combustion engines [67]. And sulfur compounds in gas oils cause wear due to corrosive nature of the combustion products and increase the amount of deposits in combustion chambers and on pistons. But Sulfur does not only have negative effects, it acts as a lubricant, which is positive for engine performance by minimizing engines wear[68],[69]. 12
Chapter One
Introduction and Literature Review
In petrochemical sulfur compounds are of concern because they poison catalysts and cause corrosion. In particular, Thiols, sulfides and disulfides are toxic and have bad odor and therefore potentially harmful to humans[70]. These compounds are major pollutant contributors to the environment in the form of sulfur oxide SOX during combustion processes. In a combustion process most of sulfur (about 95-98%) contained in diesel oil is being oxidized to SO2[71]. SOX is the major contributor to acid rain and climate change. Major emissions of NOx, SOx,CO2 and particulate matter are the causes of most concern for pollution in our environment[72]. Human exposure to SOx in the ambient air has been related to increased incidence of respiratory system diseases, irritation of the eyes, nose, and throat, and even lung cancer. Moreover, the catalysts applied in motor vehicle exhaust gas treatment systems, are always poisoned by SO2 and hence the emissions of nitrogen oxides (NOx) and total suspended solids increase[73]. Different studies show that there is a relation between the amount of sulfur contained in diesel oil and environmental pollution, The EPA estimates that reducing sulfur levels from 400 ppm to 50 ppm reduces emissions of hydrocarbons by 45.9%, NOx by 7.01%, and CO by 31.12% Obviously, emissions of SOx are also reduced by an amount equivalent to the sulfur reduction[74]. While reducing sulfur from 500 ppm to 30 ppm has been predicted to reduce particulate matter by 9-12% for heavy duty engines[75]. 1.6.3 Fuel sulfur specifications Gasoline, diesel and non-transportation fuels account for 75-80％ of all refinery products. Sulfur present in these fuels cause air pollution during combustion, to minimize the negative health and environmental effects of automotive exhaust emissions, the sulfur level in fuels must be minimized[76]. 13
Chapter One
Introduction and Literature Review
Therefore, the specifications for sulfur in diesel have undergone dramatic revisions in many countries. EPA has recommended significantly reduce the level of sulfur in gasoline and diesel fuels for meeting lower vehicle emission standards in the United States by 2006. EPA regulations will limit gasoline sulfur levels to 30 ppm and diesel sulfur levels to 15 ppm by 2006[77]. The European Union has passed legislation to reduce sulfur levels in both gasoline and diesel to 50 ppm in 2005 and to 10 ppm in 2009. In Japan, sulfur levels in gasoline and diesel lows limited to 50 ppm by 2005 and further to 10 ppm at 2007[78]. Hydrodesulfurization (HDS) is commonly used for sulfur removal and highly efficient for removal of thiols, sulfides, and disulfides[79]. but these strict sulfur mandates led to a surge of development of alternative desulfurization technologies because of the increased difficulty in removing the last few alkyl substituted dibenzothiophenes from diesel fuels by (HDS) process[80]. because this process involves high temperature, pressure, metal catalysts, high cost
and large
reactors[77],[81],[82]. 1-7 Classification of desulfurization technologies There is no unique way of classifying the desulfurization processes. They can be categorized by the type of sulfur compound being removed, the role of hydrogen[83]. There are two approaches used to reduce sulfur level in petroleum refining business (1) conventional hydrodesulfurization (HDS) and (2) non-hydrogen consuming desulfurization (non-HDS based)[84]. 1.7.1 Conventional Hydro desulfurization (HDS) Hydrodesulfurization (HDS) is one of the most common desulfurization methods that have been used in refinery processes and is a catalytic chemical process 14
Chapter One
Introduction and Literature Review
commonly used to remove sulfur from natural gas and from refined petroleum products[85]. The Hydrodesulfurization can be classified as destructive and nondestructive hydrogenation[83],[62]. In this process, the feed is mixed with hydrogen, heated to the proper temperature and pressure, and introduced to the reactor containing the catalyst[86]. The mechanism is based on reactive adsorption in which metal based adsorbents, such as CoMo/Al2O3 and NiMo/Al2O3, capture sulfur to form metal sulfides. The exhausted metal sulfide is sent to regeneration reactor and after reduction with hydrogen is again introduced into the system to remove sulfur from feed[83]. After a periodical use of the catalysts, due to the poisoning effect of foreign materials and impurities which deposit on the surface of the catalyst, they will become inactive therefore, fresh catalysts must be used[87]. Hydrotreating is applied prior to processes, such as catalytic reforming and catalytic cracking. The main differences for the HDT processes of each feed are operating conditions (temperature, H2 partial pressure, H2/Oil, liquid hourly space velocity LHSV), type of catalyst, reactor configuration, and reaction system[89]. Table 2 shows typical range of operating conditions for HDS of different petroleum fractions. The structure of the sulfur compounds affects the ease of sulfur removal[90]. Table 2: Typical process conditions for various HDS processes[88]. Feedstock
Temperature (K)
Pressure (atm)
LHSV (hr-1)
Naphtha
593
15-30
3-8
Kerosene
603
30-45
2-5
Atmospheric gas oil
613
38-60
1.5-4
Vacuum gas oil
633
75-135
1-2
Atmospheric residue
643-683
120-195
0.2-0.5
Vacuum residue
673-713
150-225
0.2-0.5
15
Chapter One
Introduction and Literature Review
The traditional hydro desulfurization is a high-pressure, high-temperature catalytic process which can effectively remove aliphatic and acyclic sulfur compounds such as thiols, and disulfides[91], but HDS are less effective against removing heterocyclic sulfur-compounds such as benzothiophene, dibenzothiophene (DBT) and their derivatives ,are quite refractory to this treatment[92]. As the number of the rings and methyl substituents are increased, the reactivity of the sulfur compounds for hydrodesulfurization from mercaptans to alkyl derivate dibenzothiophenes is greatly reduced, as shown in Figure 5 [93],[94]. It is reported that the reactivity of 4,6-DMDBT over CoMo catalyst is 4 to 10 times less than DBT[95].
Figure 5: Relationship between the reactivity of hydrodesulfurization and the size
of sulfur containing model compounds [93]. 16
Chapter One
Introduction and Literature Review
This limitation can be attributed to both the steric hindrance to the aromatic sulfur species and to the high electron density around the sulfur atom[96]. The cost of sulfur removal of refractory compounds is high. According to Atlas’s research, the cost of desulfurization to lower the sulfur level from 500 to 200 mg/kg (ppm) is approximately one cent per gallon, but, cost of lowering the sulfur level from 200 to 50 mg/kg is four times higher[97]. Therefore, conventional hydro treatment must be modified and revamped if it is to produce ultra-low sulfur diesel due to this reason, many groups have been engaged in the exploitation of non-HDS technologies, such as extraction, bio desulfurization [98],oxidation[99], alkylation [100] and adsorption[101]. 1.7.2 Non-Hydrodesulfurization based Non-Hydro desulfurization were technologies that do not use hydrogen for catalytic decomposition of organic sulfur compounds. 1.7.2.1 Desulfurization by adsorption on a solid adsorbent Adsorption is a mass transfer process where in molecules in a free phase become bound to a surface by intermolecular forces[102]. Adsorption is one of the most promising processes of desulfurization of fuel, this process is effective against the selective removal of low concentration materials from liquids, desulfurization by adsorption depends on the ability of a solid sorbent to selectively adsorb sulfur compounds from the refinery stream[103],[104]. This process can be subdivided according to the interaction mechanism between the sulfur compound and the adsorbent to adsorptive desulfurization and reactive adsorption[105]. Figure 6 illustrated adsorption desulfurization process.
17
Chapter One
Introduction and Literature Review
Desulfurized Product Spent Sorbent
Adsorber
Reactivator Reactivator
Desorbed hydrocarbons
Reactivating gas with sulfur
Reactivating gas Fresh Sorbent
Liquid Feed Stock
Figure 6: Adsorptive desulfurization process. Adsorptive desulfurization (physical adsorption) is based on the interaction of the organosulfur compounds on the solid sorbent surface by weak Vander Waals forces. Therefore, the sorbent can be easily regenerated, usually by flushing the spent sorbent with an inert gas, and while reactive adsorption occurs through the formation of true chemical bonds between the S-containing compounds and the adsorbent. Sulfur is fixed in the sorbent, usually as sulfide, and the S-free hydrocarbon is released into the purified fuel stream. Regeneration of the spent sorbent is usually conducted in the presence of air, which oxidizes the sulfide into Sulfur oxide[72]. The efficiency of this method depends on the properties of the sorbent material, selectivity to organosulfur compounds relative to hydrocarbons, adsorption capacity, durability, and regenerability[106]. Adsorptive desulfurization processes are considered among the most economically attractive techniques due to their simple operating conditions and the availability of inexpensive and re-generable adsorbents[107]. 18
Chapter One
Introduction and Literature Review
Various adsorbents, such as reduced metals, metal oxides, activated charcoal, alumina, metal sulfides, zeolites, clay and silica, are utilized in this process[108]. 1.7.2.2 Oxidative desulfurization and solvent extraction Much interest has been shown over the last decade of the application of oxidative desulfurization (ODS). This has been because of the very stringent environmental regulations that have limited the level of sulfur in diesel to less than 15 ppm [109]. Gas oil, and other heavier streams; contain primarily heavy poly nuclear aromatics that include a thiophene structure, It is reported that 70 % of sulfur in diesel fuels are dibenzothiophene DBT and their derivatives[110]. Achieving lower sulfur contents of fuels with current (HDS) technology requires the use larger reactor volume and a higher reaction temperature and pressure [111],[112], or more active catalysts[113]. All of these cost money, because of HDS is less effective for refractory sulfur compounds, such as 4,6-DMDBT. These molecules are common in diesel fuels[114],[115],[116]. These compounds are sterically hindered [117]. Whenever the n-electrons of the sulfur can resonate with π electrons, the energy of the carbon-sulfur bond (C-S) becomes practically identical with that of a C-C bond. Then the selectivity of hydrodesulfurization is reduced, and hydrogenation of carbon-carbon bonds will occur [77],[118]. The ODS process consists of two following consecutive steps: Initially, the sulfur compounds are oxidized to their corresponding sulfoxides or sulfones by an oxidizing agent and catalyst. afterward, highly polarized sulfoxides or sulfones are extracted by an appropriate polar solvent [119]. Sulfur has a strong affinity for oxygen, the sulfur atoms have d orbital, which enables oxidation of organic sulfur species into sulfone and sulfoxide. 19
Chapter One
Introduction and Literature Review
For oxidation to take place, the oxidant needs to be in contact with fuel oils under optimum conditions, and the oxidant donates oxygen atoms to the sulfur in BT, DBT and its derivatives to form sulfoxides and sulfones as shown in Figure (7). In the ODS reactivity of sulfur compounds increased with the increase of electron density of sulfur atoms. The reactivity’s of DBT derivatives are influenced by the electron donation of substituted methyl groups, therefore, the reactivity decreases in the order of 4,6-DMDBT > 4-MDBT > DBT, reversing the order of reactivities for HDS[120]. After oxidation, Liquid-liquid extraction of the oxidized sulfur compounds were carried out in figure (8) by contacting oxidized sulfur compound with a non-miscible solvent which is selective for the oxidized sulfur compounds, the choice of solvent for the extraction of sulfone is critical. The solvents should be sufficiently polar to be selective sulfone in the process of extraction, because sulfones have more polarity than the unoxidized sulfur compounds, which raises selectivity during extraction [64]. Additionally, the C–S bond’s strength is decreased when the sulfur is oxidized; therefore, it is easier to remove[112].
O R2
R2
S R3
O S R3
Oxidant Catalyst R1
R1
Alkyl-substituted dibenzothiophene
Alkyl-substituted dibenzothiophene sulfone
R1, R2, R3 =H, Methyl, ethyl, etc.
Figure 7: Oxidation reactions of refractory organosulfur compounds[121].
20
Chapter One
Introduction and Literature Review
Examples of polar solvents include those with high values of the Hildebrand solubility parameter “Δ”; liquids with a high value of Δ have been successfully used to extract these compounds, water-soluble polar solvents such as, dimethyl sulfoxide, and acetonitrile are usually employed for the desulfurization of petroleum product[122]. Therefore, (ODS) processes as alternatives to HDS have been proposed, because they have some potential advantages over HDS namely: (i) mild reaction conditions at low temperature (<100 °C) and under atmospheric pressure[123]. (ii) does not require any hydrogen[124] and (iii) higher reactivity for converting stable sulfur compounds DBT [125].
Figure 8: The ideal reaction in ODS process for alkyl dibenzothiophenes [64].
Various oxidative agents have been reported to be used for oxidative desulfurization, such as organic hydroperoxides, molecular oxygen, ozone, air, hydrogen peroxide[126], nitric acid and sulfuric acid[127]. Among all of them, 21
Chapter One
Introduction and Literature Review
hydrogen peroxide is considered as the most promising oxidant in terms of availability, safety, cost effectiveness and environmental influence[128]. There are several drawbacks of ODS. The major problem is that the oxidants used in ODS are highly corrosive which can raise the limitation on operation conditions[129]. Another of them is the insufficient selectivity of the used oxidants. Insufficient selectivity causes partial oxidation of the hydrocarbons resulting in the decrease of the quality and the yield of desulfurized fuels and the by-products formation[130]. 1.8 Literature Review In the ODS process, the sulfur containing compounds are oxidized by using appropriate oxidants to convert these compounds to their corresponding sulfoxides and sulfones. The oxidized compounds can be extracted from the light oil by using a non-miscible solvent. And then the oxidized compounds and solvent are separated from the light oil by gravity separation or centrifugation. The solvent is separated from the mixture of solvent and oxidized compounds by a simple distillation for recycling and re-use. By using this process, the maximum sulfur removal is achieved with minimum impact on the fuel quality. The first ODS process was proposed in 1974 by Guth and Diaz by using NO2 as oxidant followed by extraction with methanol to remove both S- and N-containing compounds from oil fractions[131]. Tam et al. (1990) described a process for purifying hydro carbonaceous oils containing both heteroatom sulfur and heteroatom nitrogen compound impurities, such as shale oils, by first reacting the oil with an oxidizing gas containing nitrogen oxides and then extracting the oxidized oil with butyrolactone solvent. The oxidation-extraction process was carried out at ambient pressure and low temperature (typically 0-30 °C)[132].
22
Chapter One
Introduction and Literature Review
Oxidation of petroleum oils has a long history. The most popular oxidants in the study of ODS are nitric acid and nitrogen oxides and used largely because they have double effects of oxidizing sulfur compounds and nitrating the aromatic compounds present in the oil, nitroaromatics are thought to have high cetane numbers[133]. Otsuki et al. (2000) used a mixture of hydrogen peroxide and formic acid, reported the thiophene and thiophene derivatives with lower electron densities on the sulfur atoms could not be oxidized in the H2O2/formic acid system at 50 °C, while dibenzothiophenes with higher electron densities were oxidized. This is in accordance with the conventional concept that thiophene cannot be oxidized by H2O2 under mild conditions owing to its aromaticity. After the oxidation process, sulfones separation can be achieved by extraction using polar solvents or by adsorption [134]. T. Kabe et al. (2001) were studied the oxidation of dibenzothiophene (DBT) was conducted using t-butyl hypochlorite (t-BuOCl) in the presence of platinum chloride (PtCl2) and Al2O3 catalysts. under ambient pressure at 30-70°C, more than 90%wt of DBT could be oxidized in the decahydronaphthalene (decalin) solution [135]. But oxidation with t-BuOCl carries the risk of contamination of the reacted oil with chlorine compounds, such as unreacted t-BuOCl, t-BuCl and other chlorinated compounds, and the resultant environmental pollution. It is necessary to remove tBuOCl and t-BuCl from the reacted oil by distillation and to minimize the amount of t-BuOCl used to avoid the formation of other chlorination compounds. Therefore, tbutyl hydroperoxide (t-BuOOH)
is used as oxidant for oxidation of sulfur
compounds in kerosene in the presence of various catalysts (CrO3/Al2O3, WO3/Al2O3, V2O5/Al2O3, Nb2O5/Al2O3, and ZrO2/Al2O3)[136]. Hai Mei et al. (2003) were used H2O2 for oxidation of DBT in the presence of tetraoctylammonium bromide and phosphotungstic acid, the mixture was irradiated by ultrasound. 23
Chapter One
Introduction and Literature Review
It was seen that the oxidation of dibenzothiophene DBT to dibenzothiophene sulfone DBTO reached over 85% within 1 min of ultrasonication, In 7 min, DBT can be completely oxidized to DBTO. In comparison, the conversion of DBT to DBTO in the absence of ultrasound was only 21% in 1 min and reached barely above 80% in 7 min[137]. S. Murata et al. (2003) were tried to desulfurization of commercial diesel oil, it was treated with metal salts (cobalt acetate) and aldehydes n-octanal at 40 °C for 16 h under oxygen and ambient pressure. Oxidized S-compounds were removed from the feed by adsorption with alumina. Concentration of sulfur could be reduced from 193 ppm to less than 5 ppm [138]. J. Sampanthar et al. (2006) were founded that manganese and cobalt oxide catalysts supported on Al2O3 to be effective in catalyzing air oxidation of the sulfur in diesel to corresponding sulfones at a temperature range of 130–200 °C and atmospheric pressure. The sulfones were removed by extraction with polar solvent to reduce the sulfur level in diesel from 430 to 64 ppm [139]. D. Zhao et al. (2007) improved solubility of the oxidized sulfur compound, a formic acid/H2O2 system with some quaternary ammonium salts (tetrabutyl ammonium bromide, tetrapropyl ammonium bromide, tetraethyl ammonium bromide, and tetramethyl ammonium bromide) as phase transfer catalysts was employed in the oxidation of thiophene. Four catalytic systems with ultrasound were carried out, tetrabutyl ammonium bromide behaved as the optimum active catalyst, and the desulfurization rate was 94.67% while without these catalyst the desulfurization rate was 28.37%wt[140]. Y. Dai et al. (2008) focused on the desulfurization ability of a fenton's reagent system both with/without ultrasound, in the presence of hydrogen peroxide and acetic acid.
24
Chapter One
Introduction and Literature Review
Results showed the addition of fenton's reagent could enhance the desulfurization for diesel fuels and sono-oxidation treatment in combination with fenton's reagent shows a good synergistic effect. under our best operating condition for the oxidative desulfurization, total sulfur removal in (H2O2-CH3COOH) (fenton’s-H2O2CH3COOH) and (fenton’s-US-H2O2-CH3COOH) system are %29.4, %52.6, and %93.6 %wt respectively[141]. Y. Wang et al. (2009) prepared a N-butyl pyridinium based ionic liquid [BPy]BF4, and the effect of extraction desulfurization on model oil with thiophene and dibenzothiophene was investigated, the results show that the ionic liquid [BPy]BF4 has a better desulfurization effect. The ratio of desulfurization to thiophene and dibenzothiophen reached 78.5% and 84.3% respectively, which is much higher than extraction desulfurization with simple solvent[142]. L. Ban et al. (2013) investigated the ability of the 1-butyl-3-methylimidazolium tetrachloroferrate to remove sulfur from model diesel fuels, in the presence of dielectric barrier discharge (DBD) plasma, air as the oxygen resource and diperiodatocuprate (III) as the catalyst. They found sulfur content of diesel fuels decreased from 200 ppm to 4.92 ppm (S-removal rate up to 97.5%) under the following optimal reaction conditions: air flow rate of 60 ml/min, amplitude of applied voltage on DBD of 16 kV, input frequency of 79 kHz, catalyst amount of 1.25 wt% and reaction time of 10 min[143]. J. Wu et al. (2014) investigated the ability of various masses of 1methylimidazolium-3-propylsulfonate hydrosulfate (PSMIMHSO4) were supported on the Zr metal–organic framework (UIO-66) as catalysts, which were used for catalytic oxidative desulfurization. They found that they were able to get up to 94% desulfurization of fuel consisting primarily of Benzothiophene as the sulfur contaminant, at 313 K for 20 min[144]. 25
Chapter One
Introduction and Literature Review
1.9 Aim of Present Study The major aims for this research project are: Evaluation of some Kurdistan crude oils, and SARA analysis of these crude oils, Production of the light and heavy gas oil by fractional distillation from TQ, SA, Kh and TA of Kurdistan crude oils, Full evaluation of the light and heavy gas oil products according to ASTM and Iraqi specification, Oxidation of organic sulfur compound by hydrogen peroxide and acetic acid, Choosing best operation conditions for oxidation desulfurization, Liquid-liquid extraction for oxidized sulfur compound, Using different adsorbent to remove organic sulfur compound and improve it is color. GC-PFPD used for illustration the effect of desulfurization process.
26
Chapter Two Experimental Part
Chapter Two
Experimental Part
Chapter Two: Experimental Part 2. Experimental Part 2.1 Chemical reagents: The Chemical reagents used were of high purity; therefore, they did not require further purification. The chemicals used in this work and their suppliers are listed in table 3: Table 3: Chemicals used in this work and their suppliers. Compounds
Suppliers
1
n-Hexane 99% v/v
Fluka
2
Methanol 99.9 % v/v
Fluka
3
Hydrogen peroxide 48.7% wt/wt
Arkema
4
Butyl sulfide 97% v/v
Sigma Aldrich
5
Aniline 98% v/v
Sigma Aldrich
6
Acetonitrile 99% v/v
Merck
7
Concentrate acetic acid 98% v/v
Merck
8
Toluene 99% v/v
Merck
9
Tetrahydrofuran 99.5% v/v
Merck
10
1,4-Dioxane 99% v/v
Merck
11
Silica gel
Merck
12
Iodine
Merck
13
Potassium iodide
Merck
14
Potassium iodate
Merck
15
Sodium thiosulfate
Merck
16
Nitric acid 99.5% v/v
Merck 27
Chapter Two
Experimental Part
Four types of Crude oils namely Taq-Taq (TQ), Khurmala (Kh), Tawke (TA) and Sarqala (SA)) have been fractionated to yield five different products. Three types of adsorbent namely (Arz room clay (AR) and kany saze jam activated clay (KS) from Iran and Alumina (AL)) used for adsorption desulfurization process, table 4 shows the chemical composition of adsorbents. Table 4: Chemical analysis (wt. %) of adsorbent[145]. Composition
Arz room (AR)
Kane sazy jam (KS)
Alumina (AL)
SiO2
67.80
74.55
-
Al2O3
11.443
7.41
99.5
Fe2O3
1.046
0.58
-
CaO
4.236
1.2
-
Na2O
0.463
0.15
-
K2O
0.67
0.48
-
MgO
2.196
-
-
TiO2
0.08
-
-
P2O5
0.036
-
-
L.O.I
12.03
15.33
-
2.2Apparatus and Instruments 1- True boiling point apparatus consists of distillation flask, electrical heating mental, fractional column, condenser, Buchner flask, graduated receiver, ice bath with water recyclization, thermometer and Javac vacuum pump. 2- Inductively coupled plasma ICP Spectrometer (Perkin Elmer-Optima 2100Dv.Spectrometer). 28
Chapter Two
Experimental Part
3- Gas Liquid Chromatography of CP- 3800 from Varian, equipped with 8200 auto sampler and micro liter syringe, 1177 injector , and pulsed flame photometric detector (PFPD) operated in sulfur mode. The capillary column of 30 meter in length, 0.25 millimeter internal diameter and 0.25 μm film thickness of 50 % phenyl and 50 % methyl silicon stationary phase, of Varian equivalent: CP-Sil 24 CB, CP7821. 4- ASOMA PHOENIX II Energy Dispersive X-Ray Fluorescent (ED-XRF) spectrometer. 5- The IR Spectra were recorded on a Perkin-Elmer FT/IR spectrometer in the (4004000 cm-1) range using KBr pellets (νmax in cm-1), from UK. 6- Muffle furnace of capacity from (50-1100°C) from (BEGO, Germany), and glass desiccator. 7- Digital electric thermo state shaker with temperature and time programming (GFL, type 1083, of serial number 11496502L) 8- Aniline point apparatus consist of water bath, electrical heater, thermometer, and copper stirrer for stirring 9- Copper corrosion apparatus according to ASTM D130. 10- Apparatus for measurement of Kinematics Viscosity according to ASTM D445. 2.3 Procedure 2.3.1 Distillation 2.3.1. A-Distillation of Crude Oil ASTM D1160 A crude oil sample taken by graduated cylinder and added to a distillation flask and the apparatus of distillation is constructed. With raising the temperature of heating mental under vacuum at 240 mmHg, the crude oil will boil and the lighter vapors will rise to fractional column and condense through condenser and five fraction cuts were collected as follows: 29
Chapter Two
Experimental Part
1-From initial boiling point to 174 °C was taken and named as naphtha. 2- From 175 °C to 240 °C was taken and named as kerosene. 3- From 241 to 300 °C was taken and named as light Gas Oil (LGO). 4- From 301 to 360 °C was taken and named as Heavy Gas Oil (HGO). 5- Above 360 °C was taken and named as fuel oil. 2.3.1. B-Distillation of petroleum products: IP-123/ ASTM D 86 100 ml of sample (LGO and HGO) was distilled under prescribed condition which is appropriate to its nature, systematic observation of thermometer readings and volumes of condensate were made; and from these data, the results of the test were calculated and reported[146]. 2.3.2 Density, Specific gravity and API gravity of Crude Oil and Liquid Petroleum products ASTM D1298 The sample (Crude oil or petroleum fraction) was brought to the prescribed temperature. The appropriate hydrometer was allowed to settle. After the temperature equilibrium has been reached, the hydrometer scale was read, and the temperature of the sample was noted. If necessary, the cylinder and its contents were placed in a constant temperature, both to avoid excessive temperature variation during the test[147]. 2.3.3 Determination of Aniline Point ASTM D611 Specified volumes of aniline and sample (light and heavy gas oil) were placed in a tube and mixed mechanically. The mixture was heated at a controlled rate until the two phases became miscible. The mixture was cooled at a controlled rate and the 30
Chapter Two
Experimental Part
temperature at which two phases separated was recorded as the aniline point or mixed aniline point[148]. 2.3.4 Measurement of Kinematics Viscosity ASTM D445 The time was measured in second, for a fixed volume of liquid to flow under gravity through the capillary of a calibrated viscometer under a reproducible driving head and at a closely controlled temperature. The kinematics viscosity is the product of the measured flow time and the calibration constant of the viscometer[149]. 2.3.5 Determination of Copper Corrosion ASTM D130 A polished copper strip is immersed in a specific volume of the crude oils sample being tested and heated under conditions of temperature and time that are specific to the class of material being tested. At the end of the heating period, the copper strip is removed, washed and the color and tarnish level assessed against the ASTM copper strip corrosion standard[150]. 2.3.6 Procedure for Gas Chromatographic Analysis 1- The DB-17 column 30 meter in length, 0.25 millimeter internal diameter and 0.25 μm film thickness of 50 % phenyl and 50 % methyl silicone stationary phase, Varian equivalent: CP-Sil 24 CB, CP7821, which is a specific type column for separation of sulfur compounds, was programmed from 50- 280 °C, with the rate of heating 10°C/ minute following a 2 minute as an initial hold at 50°C, 20 minutes as final hold at 280°C, and total run time becomes 45 minute. 2- The temperature of the rear injector (1177) was adjusted at 285 °C, the split ratio 1:50, and PFPD detector were adjusted at 330°C, which is a selective type detector for sulfur compounds.
31
Chapter Two
Experimental Part
3- The flow rate of gasses, Air 1 was 17 ml/min., Air 2 was 10 ml/min., and H 2 was 13 ml/min. And Helium (He) as carrier gas was 2.2 ml/ min., and the pressure of the gasses, Air was (60) psi, H2 was (42) psi, and He was (80) psi. 4- 1 μl of samples was injected by microsring, run was started, and waited for getting the chromatogram of each run. Gas Chromatographic analysis has been done for LGO and HGO samples obtained from (TQ, SA, Kh and TA) before and after treatment by chemical reagents such as (H2O2, HAc, adsorbents). 2.3.7 ED-XRF-Calibration for the Determination of Total Sulfur Content Based on ASTM D4294 method, Energy-Dispersive X-Ray Fluorescence (EDXRF) was used to determine the total sulfur content in samples. The Sulfur-in-Oil Analyzer (ASOMA PHOENIX II Energy Dispersive X-Ray Fluorescent (ED-XRF) spectrometer), was employed to determine any sample with total sulfur content range from 0 to 5 %wt. of sulfur. Figure 9 shows the ED-XRF used in the current study. The calibration of the setup is necessary to measure the sulfur content of oil fractions; two types of calibration solution were prepared as follows: A- High concentration calibration curve: (5, 4, 3, 2, 1, 0.8, 0.6, 0.4, 0.2 and %0.1) %wt of sulfur in standard butyl sulfide prepared in 1,4-dioxane as a solvent in 50 ml volumetric flask, then 5 gm of these solutions was taken by sensitive balance and calibrated the instrument. B- Low concentration calibration curve: (100, 200, 400, 600, 800 and 1000) ppm (wt) of sulfur in standard butyl sulfide prepared in 1,4-dioxane as a solvent in 50 ml volumetric flask, solution prepared and the procedure continued as the above (A) method.
32
Chapter Two
Experimental Part
Figure 9: ASOMA PHOENIX II (ED-XRF) 2.3.8 SARA- Analysis The crude oil samples were heated to 65°C to evaporate very low volatile compound, then Asphaltenes was precipitated with an excess of n-hexane (1 crude oil:40 n-hexane). The mixture was shaken for 4 hours, in water bath shaker 120 rpm at 25°C, and then stored overnight in the dark place to equilibrate. The mixture of nhexane and solid black particles were filtered through a 0.45µm filter paper in order to obtain asphaltenes. The filter that contained the asphaltene precipitate was washed with fresh n-hexane several times until the effluent liquid is colorless. After that, the asphaltene precipitate dried in oven at 80 °C until constant weight. The n-hexane soluble fraction is called (maltene). It was concentrated in a rotary evaporator at reduced pressure 347 mbar and oil bath 60°C to recover the solvent nhexane. The maltene fraction further fractionated to saturate aromatic and resin fraction through an open column chromatography. 33
Chapter Two
Experimental Part
The column was washed and cleaned by acetone and then dried in air. The column carefully packed with slurry of 10 gram activated silica gel for 24 hr., at 130°C and 25 ml of n-hexane. For all maltene fraction from crude oils, 3 g was dissolved in a minimum amount of n-hexane, then were loaded on the top of column and eluted successively with 250 ml of n-hexane to elute saturate fraction, 250 ml of n-hexane/toluene 80/20 to elute naphthenic fraction, 200 ml of toluene to elute aromatic fraction. Finally, the polarity of mobile phase was increased by using 200 ml mixture of toluene/methanol (90:10) to elute resin fraction. The flow rate of elution was 2ml/min. After elution, the mobile phase were removed from individual eluted fraction by rotary evaporator under reduced pressure depending on the solvent mixture at 60°C, oil bath, then the gravimetric percentage was calculated for individual fraction. 2.3.9 Hydrogen Peroxide Concentration Determination 10 ml of concentrate hydrogen peroxide was diluted by distilled water in 100 ml volumetric flask, then 10 ml of diluted hydrogen peroxide was contacted with 10 ml of 1 molar (M) potassium iodide (KI) solution in an acidic medium (50 ml, 2 M H2SO4) in a 250 ml conical flask. Under this condition, hydrogen peroxide is reduced by KI to liberate iodine. The equivalent amount of iodine liberated was titrated against 0.1 M standard sodium thiosulphate. When the color of the iodine had almost disappeared, 1-2 ml of the starch suspension (0.2%wt) was added, followed by the dropwise addition of thiosulphate solution until the blue color disappears[151]. The reaction below was used to calculate the amount of iodide ions that reacts with each mole of peroxide ions. 2I- + S4O62-
I2 + 2S2O3234
Chapter Two
Experimental Part
2.3.10 Oxidation of light and heavy gas oil samples In each experimental run, 750 ml of untreated LGO and HGO were introduced into a round bottom flask reactor, then stirred continuously at constant mixing speed (1300 rpm) and heated to the desired reaction temperature 75 °C, using the magnetic stirrer heater. When the mixture reached the selected reaction temperature 75 °C, the specified amount of acetic acid and hydrogen peroxide was added to the reaction mixture. The reaction time was set to be 12 hr. Then, the solution was allowed to settle in a 1 liter separating funnel where clear distinguishable phases were obtained. After that sample was withdrawn, and then analyzed for their sulfur content by XRF and GC-PFPD. 2.3.11 Liquid-liquid extraction The extraction of LGO and HGO was conducted after oxidation by using reflex process in the presence of acetonitrile, methanol and acetic acid solvents; LGO and HGO were mixed with each solvent by 1:1 ratio. Then, the mixture was stirred at 1000 rpm for 2 hr. at 50°C, after that the gas oil and solvent layers were separated by using 500 ml separation funnels, and then analyzed for their sulfur content by EDXRF and GC-PFPD. 2.3.12 Treatment of Samples by Adsorption A- Three different type of adsorbents (Arz room clay (AR) and kany saze jam (KS) from Iran, and Alumina (AL) were used and activated by pre heating in oven at 120°C. For 4 hours, and cooled in desiccator.
35
Chapter Two
Experimental Part
B- Batch experiments were conducted by adding 1.5 gm of each adsorbent and 50 ml of LGO and HGO samples to 250 mL stoppered Erlenmeyer flasks. The formulations were mixed using a thermostatic shaker, at 50°C and 500 rpm, for 2 hours. C-The LGO and HGO samples were recovered from adsorbent by filtration. D- The quantitative total sulfur content was done for each treated sample by EDXRF.
36
Chapter Three Results and Discussion
Chapter Three/Part One
Result and Discussion
Chapter Three: Results and Discussion Part One 3.1 Evaluation of Crude Oils and Gas Oils 3.1.1 Fractionation of crude oil to obtain different boiling point fraction Fractional distillation was used to obtain different boiling point fraction. Four types crude oil were used in this work in four different oil fields in Kurdistan which have high production capacity. These are namely: 1- TQ from Taq-Taq region near Koya city. 2- SA from Sarqala (Garmian oil field) 3- Kh from Khurmala oil field near Hawler. 4- TA from Tawke oil field near Zakho. Physical and chemical parameters of all four types are shown in Table 5 and 6. Distillation is a common method for fractionation of crude oil that is used in the laboratory as well as in refineries. It indicates the vaporization temperature after a certain amount of liquid mixture vaporized based on 100 unit volumes. Table 6 and Figure 10, illustrated the fractional distillation data of each type of Taq-Taq, Sarqala, Khurmala and Tawke crude oils and temperature were recorded at each 5 ml distilled until 360 ºC. At volume zero, the initial boiling point of the crude oils which is different from one to another, the volume of the final boiling point different to TQ which has a wide volume ranges started from 0 to 83.5 mls.
37
Chapter Three/Part One
Result and Discussion
For SA started from 0 to 76.5 ml, but for Kh started from 0 to 68.5 ml and for TA started from 0 to 67.5 ml. Table 5: Physicochemical parameters of Kurdistan crude oils. Test
SA
Kh
TA
0.7888
0.8229
0.8594
0.8923
Conversion
0.7896
0.8237
0.8603
0.893
Calculated
47.69
40.26
32.97
26.91
ASTM D 482
0.053
0.062
flammable
flammable
Method
density @ 15 °C g/ml Specific gravity @ 60 °F API gravity @ 60 °F Ash content %wt
ASTM D1298
Flash point (Abel) °C Pour point °C
IP 170
Water content %V Sulfur content wt% Copper strip corrosion ASTM colour
ASTM 95
Kin.Viscosity @40°C Cst Kin. Viscosity @50°C Cst Kin. Viscosity @70°C Cst Kin. Viscosity @80°C Cst
ASTM D 97
ASTM D4294
TQ
-27
-33
0.076 flammable -36
0.0976 flammable -36
Nil
Nil
Nil
>0.05
0.68
1.13
2.17
2.73
1b
2b
2a
2c
ASTM D 130 ASTM D1500
ASTM D 445
darker than 8.0 1.73
darker than 8.0 3.11
darker than 8.0 6.16
1.54
2.75
5.17
9.08
1.18
1.84
4.10
6.019
1.06
1.62
3.04
4.68
38
darker than 8.0 11.68
Chapter Three/Part One
Result and Discussion
Table 6: %Volume (ml) versus T ºC for TQ, SA, Kh and TA crude oils. %Volume (ml) I.B.P 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 F.B.P
Temperature (T) ºC TQ 51 84 100 117 127 141 155 170 186 204 221 243 268 291 313 332 351 360
SA 62 103 123 138 153 170 181 204 226 247 271 294 319 334 349 356 360
Kh 68 124 147 172 189 213 232 263 282 298 318 340 349 356 360
TA 62 104 130 154 180 208 233 250 275 288 311 330 345 353 360
Table 7 shows the yield (%v/v) of the naphtha, kerosene, light gas oil (LGO), heavy gas oil (HGO) and residue for each type of crude oils. The result shows that the volume percent of naphtha and kerosene obtained from TQ and SA are higher when compared with the same fractions obtained from Kh and TA.
39
Chapter Three/Part One
Result and Discussion
Table 7: (%v/v) obtained from TQ, SA, Kh and TA crude oils. Boiling point range ºC
TQ
SA
Kh
TA
Naphtha
IBP-174
36.5
27
16
18.5
Kerosene
175-240
17.5
16.5
15.5
15
241-300
13.5
13
14
15
301-360
16
20
23
19
14.5
22
29.5
30
2
1.5
2
2.5
Name of Fraction
Light Gas Oil LGO Heavy Gas Oil HGO Fuel Oil Loss
> 360 ºC -
Fraction yield (%v/v)
While the (LGO), (HGO) and residue fractions obtained From Kh and TA are higher than TQ and SA. This indicates that the crude accumulates in there receiver rocks in TQ and SA have longer geological periods and within higher depth have been completely reacted, thus it contain a higher ratio of light products. 3.1.2 Specific gravity, API gravity and sulfur content These are important parameters commonly used for the classification of crude oil samples. Generally API gravity of crude oil is known to increase as the specific gravity decreases. API gravity has also been reported to have an inverse relationship with sulfur contents of crude oil. Also, sulfur content of crude oil is known to increase as the specific gravity increases. This can be explained in terms of the geologic composition of the areas where these crude oils are found. It has been found that, areas where heavy crude oil 40
Chapter Three/Part One
Result and Discussion
samples are reportedly in abundance are also associated with high deposits of sulfur rick rocks. While light crude oil samples are found mostly in areas with low deposits of sulfur rocks. API gravity and sulfur content determines the grade or quality of crude oils as shown in Table 8, a comparison of the values of API gravity and sulfur content obtained for the Kurdistan crude oil in this study shows that, the TQ crude oil can be classifying as a light intermediate sweet crude oil, Kh sour intermediate crude oil, but TA sulfur content was 2.73 wt% this means sour heavy crude oil, The specific gravity of the crude oil gives a rough measure of the amount of lighter hydrocarbons present. Lower the specific gravity and higher API gravity, the greater are the yield of light fractions by distillation. There for TQ Light crude oils are in high demand and are of high market value because TA Heavy crude is harder to handle (it is too thick to pump easily through pipelines unless diluted with light crude) and is more expensive to refine to produce the most valuable petroleum products such as gasoline, kerosene and aviation fuel. Table 8: Crude oil classes in Kurdistan. samples
Sulfur wt%
API Gravity
Crude Oil Class
Taq-Taq (TQ)
0.68
47.69
Light Intermediate sweet
Sarqala (SA)
1.13
40.26
Light sour
Khurmala (Kh)
2.17
32.97
Intermediate sour
Tawke (TA)
2.73
26.91
heavy sour
The Copper Corrosion test is a qualitative method that is used to evaluate the corrosive tendencies of oils to copper containing materials. It also detects the presence of harmful corrosive substances, like acidic or sulfur compounds, which 41
Chapter Three/Part One
Result and Discussion
may corrode the equipment, the result shows the TA has high tendency to corrode the copper containing alloy. 400 350
Temperature C
300 250 TQ 200
SA K
150
TA 100 50 0 0
20
40
V ml
60
80
100
Figure 10: Distillation curve of TQ, SA, Kh and TA crude oils. 3.1.3 Metals content determination in crude oils Petroleum, as recovered from the reservoir, contains metallic constituents but also picks up metallic constituents during recovery, transportation, and storage. Even trace amounts of these metals can be deleterious to refining processes, especially processes in which catalysts are used. Trace components, such as metallic constituents, can also produce adverse effects in refining either by causing corrosion or by affecting the quality of refined products. Hence, it is important to have test methods that can determine metals. Inductive coupled plasma ICP technique was used for determination of metals in crude oil. Ten elements were analyzed in crude oils as shown in Table 9. Heavy crude oil TA has the highest concentration of the following metals Cu (0.323), Fe (2.788), Zn (6.014) and Ni (1.288) ppm. 42
Chapter Three/Part One
Result and Discussion
Table 9: Concentration of some metals in kurdistan crude oils. Elements (ppm)
TQ
SA
Kh
TA
Potassium(K)
1.97
23.48
8.664
18.75
Calcium(Ca)
3.037
22.19
2.734
13.64
Aluminum (Al)
1.729
4.04
1.453
1.209
Cupper(Cu)
0.102
0.083
0.126
0.323
Iron(Fe)
0.413
0.789
0.706
2.788
Sodium(Na)
4.254
25.14
4.301
23.48
Zinc(Zn)
1.456
1.129
1.198
6.014
Lead(Pb)
0.111
0.102
1.672
0.065
Nickel(Ni)
0.357
0.585
0.982
1.288
Vanadium(V)
6.533
6.021
3.060
2.742
Light crude oil TQ has the highest concentration of the V metals and SA has the highest concentration of the (K, Ca, Al and Na), The metal concentrations of the medium crude oil Kh fall in between the range of both the light and heavy crude oils, Nickel and vanadium are the two most common metals in crude oils and vanadiumto-nickel ratio (V/Ni) provides possible information about the likely source of oil. From the results obtained, the TQ crude oil had a V/Ni ratio of 18.29, and the SA had a V/Ni ratio of 10.19 and Kh had V/Ni ratio 3.11 while the TA heavy crude oil had a V/Ni ratio of 2.12. The low V/Ni ratio of TA heavy crude oil indicated that the oil was derived from marine organic matter, while the high V/Ni ratio for the TQ and SA light oil indicated that the oil was derived from terrestrial organic matter. The Kh crude oil was classified as been originated from a mixture of the marine and
43
Chapter Three/Part One
Result and Discussion
terrestrial organic matter, owing to the migration of hydrocarbon. The V/Ni ratio also increased as the sulfur content (wt %) of the oil decreased[152]. 3.1.4 Saturate, aromatic, resin and asphaltene fractionation SARA analysis is a method that uses polarity and solubility to characterize the components of crude oils by separating them into smaller fractions, Saturated (paraffinic and naphthenic), Aromatics, Resins and Asphaltenes, two general separation methods have been used to isolate molecular fractions from crude oils. The first of these involves initially an n-paraffinic extraction of the maltenes (solubles) and asphaltenes (insoluble) from crude oils, then liquid-solid chromatographic separation of the maltenes into saturated, aromatics and resins, because asphaltenes can irreversibly absorb to the stationary phase, the first step of this procedure is to precipitate the asphaltene fraction with an excess of n-hexane. Saturate hydrocarbons in n-hexane eluant, are not absorbed on activated silica under the conditions specified, but it is eluted from the column with 250 ml of nhexane. The solvent is removed using a rotary vacuum evaporator to recover saturates fraction. The result in table 10 shows that TQ and SA crude have the highest wt % 47.64 and %39 of n-alkanes (saturate) which characterize it as light crude. Aromatic hydrocarbons are more polar than saturated hydrocarbon, and their adsorbed on activated silica in the presence of n-hexane, and desorbed by toluene after removal of the saturate under the conditions specified. TA oil contains a smaller percentage of saturate fraction and high percentage % 21.74 of aromatic compared to other type of crude oils. For elution of resin fraction required a polar solvent like a mixture of 90/10 toluene/methanol. Kh crude oil has a high percentage of polar compound (resin) 58.54%; therefore, it can be considered as a stable crude oil and there is no problem of asphaltene deposit.
44
Chapter Three/Part One
Result and Discussion
Table 10: Weight percent (wt/wt %) of SARA fraction. Fractions
TQ
SA
Kh
TA
47.64
39
20.66
12.96
Naphthenic
6.4
8.02
9.4
9.63
Aromatic
5.1
5.56
6.89
21.74
Resin
36.8
43.75
58.54
49.02
Asphaltene
0.13
0.78
1.81
5.97
96.07
97.11
97.3
99.32
Saturate
%100
Petroleum resins provide a transition between the polar (asphaltene) and the relatively non-polar (saturate) fractions in petroleum, thus preventing the assembly of polar aggregates that would be non-dispersible in the oil. The stability of asphaltenes in crude oil is proposed to be due to the presence of some polar substances, resins among them, present in crude oil, both asphaltene and resins molecules are polar and associated as micelles, thanks to the positively charged asphaltenes that would be dispersed in the crude oil by negatively charged resins through electron donor acceptors and hydrogen bonding interactions. TA contained 5.97%wt. asphaltene which was make a heavy crude oil. Figure (11) explained the distribution diagram of SARA fraction in four crude oils by weight percent. The fractionation of crude oils by open column chromatography technique suffers from the problem of the loss of some polar parts that could not be removed from the surface of stationary phase (silica gel) and there is some light hydrocarbon lost through recovering the solvent from saturate fraction, as shown in the table 10, which is explaining that the few percentage missing. 45
Chapter Three/Part One
Result and Discussion
60 50 TQ
40
%wt
SA K
30
TA 20
10 0 Saturate
Naphthenic
Aromatic
Resin
Asphaltene
Figure 11: Distribution diagram of SARA fraction in crude oil.
3.1.5 Evaluation of light and heavy gas oils Gas oil consisted mostly of a complex mixture of hydrocarbon derived from crude oil, two different gas oil fractions, with various boiling point ranges, were obtained by fractional distillation of TQ, SA, Kh and TA crude oils, high volume percent of LGO and HGO were obtained from TA and Kh respectively, volume percent of gas oils were showed in Table 8, each gas oil fraction was analyzed according to the standard ASTM methods, and compared to the Iraqi marketing specification of gas oil. Results are shown in tables (11 -14). The first property used in specific gravity or API gravity indicate that the light gas oil obtained from all crude oils are in the range of marketing Iraqi specification, generally all property of all light gas oils, When these data are compared to the marketing specification of Iraqi petroleum products, they are in a good agreement with the Iraqi specification, except of total sulfur content in light gas oil obtained 46
Chapter Three/Part One
Result and Discussion
from Kh and TA were (2.02, 1.75) by weight respectively, while sulfur content in Iraqi specification %1, so their light gas oil required desulfurization process. Table 11: Evaluation of LGO and HGO fractions obtained from TQ. Test
Standard
LGO
HGO
Iraqi specification
Specific gravity@ 15.6ºC
ASTM D- 1298 0.8214
0.8543
(0.84)(Max)
A.P.I gravity
ASTM D-1298
40.76
34.13
(37) (Min)
Flash point ºC (P.M)
ASTM D-93
54
67
54(Min.)
Water content %v
ASTM D-95
Nil
Nil
0.1(Max)
Vis.@38 ºC /Cst
ASTM D -445
2.69
6.44
Vis.@50 ºC /Cst
ASTM D -445
2.2
4.87
5 (Max)
Pour point ºC
ASTM D -97
-9
+15
-9 (Max)
Sulfur content %wt
ASTM D -4294 0.64
1.56
1.0(Max)
Diesel Index
Ip-21
65.13
59.45
55(Min.)
Cetane Number
56.89
52.8
53(Min.)
Calorific value (Kcal/Kg)
10983
10867
10800(gross)
Method
6 (Max)
Ash(%w)
ASTM D-482
0.009
0.013
0.01(Max)
Distilled at (350 ºC)(%v)
ASTM D- 86
100
70
85 %( Min.)
Aniline point ºC
ASTM D 611
71
79
Recorded
For heavy gas oil, as indicated from the results of Table (11-14), specific gravity was high and API gravity of heavy gas oils was lower than the minimum permissible API gravity according to the regulated Iraqi specification, during combustion the fuel density affects engine power. High-density fuels also have a higher viscosity thus, influence injection characteristics.
47
Chapter Three/Part One
Result and Discussion
Thus, the fuel density affects engine combustion and emissions, also increase deposition in combustion chamber due to non-complete burning, and particulate matter generally increase with increase in fuel density. Table 12: Evaluation of LGO and HGO fractions obtained from SA. Standard Tests
Method
Iraqi LGO
HGO
Specification
Specific gravity@ 15.6ºC
ASTM D- 1298 0.826
0.853
(0.84)(Max)
A.P.I gravity
ASTM D-1298
39.8
34.38
(37) (Min)
Flash point ºC (P.M)
ASTM D-93
56
69
54(Min.)
Water content %v
ASTM D-95
Nil
Nil
0.1(Max)
Vis.@38 ºC /Cst
ASTM D -445
2.93
5.39
6 (Max)
Vis.@50 ºC /Cst
ASTM D -445
2.33
4.13
5 (Max)
Pour point ºC
ASTM D -97
-12
+ 12
-9 (Max)
Sulfur content
ASTM D -4294 0.72
2.05
1.0(Max)
Diesel Index
Ip-21
67.18
59.27
55(Min.)
Cetane Number
58.38
52.67
53(Min.)
Calorific value (Kcal/Kg)
10967
10872
10800(gross)
Ash(%wt)
ASTM D-482
0.0096
0.017
0.01(Max)
Distilled at (350 ºC) (%v)
ASTM D- 86
100
67
85 %( Min.)
Aniline point ºC
ASTM D 611
76
78
Recorded
The HGO obtained from all crude oils have higher pour points than the maximum permissible according to the Iraqi marketing specification, so, it must be dewaxed or required addition of some pour point depressant additives for the improvement of pour point during winter season, which is an indication of the lowest temperature at 48
Chapter Three/Part One
Result and Discussion
which a gas oil can be stored and still be capable of flowing under gravitational forces. Cetan number of light and heavy gas oil calculated according to relation below[153]. Cetan number = diesel index * 0.72 + 10 TQ HGO has higher pour point +15 while TA HGO has lower pour point +6. Another important properties of HGO was total sulfur content, all HGO have high level of sulfur (1.56, 2.05, 3.40 and 3.67) %wt. for TQ, SA, TA and Kh of heavy gas oil respectively. Table 13: Evaluation of LGO and HGO fractions obtained from Kh. Standard Tests
Method
Iraqi LGO
HGO
Specification
Specific gravity@ 15.6ºC
ASTM D- 1298 0.825
0.885
(0.84)(Max)
A.P.I gravity
ASTM D-1298
40.01
28.38
(37) (Min)
Flash point ºC (P.M)
ASTM D-93
53
76
54(Min.)
Water content %v
ASTM D-95
Nil
Nil
0.1(Max
Vis.@38 ºC /Cst
ASTM D -445
2.51
8.15
6 (Max)
Vis.@50 ºC /Cst
ASTM D -445
2.06
6.82
5 (Max)
Pour point ºC
ASTM D -97
-15
+9
-9 (Max)
Sulfur content %wt
ASTM D -4294 2.02
3.67
1.0(Max)
Diesel Index
Ip-21
63.93
46.37
55(Min.)
Cetane Number
56.02
43.38
53(Min.)
Calorific value (Kcal/Kg)
10970
10755
10800(gross)
Ash (%wt.)
ASTM D-482
0.0106
0.03
0.01(Max)
Distilled at (350 ºC) (%v)
ASTM D- 86
100
60
85 %( Min.)
Aniline point ºC
ASTM D 611
71
73
Recorded
49
Chapter Three/Part One
Result and Discussion
The wear of pistons, rings, and cylinders in a diesel engine generally increases when there is an excessive amount of sulfur in the gas oil. Sulfur also combines with water to form corrosives as a result of the combustion process. These corrosives can etch finished surfaces. The result indicated that heavy gas oils have more than the maximum permissible sulfur content according to the regulated Iraqi specification, this means that this heavy gas oil fractions required deep desulfurization process to reach minimum than %1by weight of sulfur, minimize the sulfur oxide and particulate matter. Table 14: Evaluation of LGO and HGO fractions obtained from TA. Standard Tests
Method
Iraqi LGO
HGO
Specification
Specific gravity@ 15.6ºC
ASTM D- 1298 0.838
0.882
(0.84)(Max)
A.P.I gravity
ASTM D-1298
37.31
28.76
(37) (Min)
Flash point ºC (P.M)
ASTM D-93
62
74
54(Min.)
Water content %v
ASTM D-95
Nil
Nil
0.1(Max
Vis.@38 ºC /Cst
ASTM D -445
2.839
8.15
6 (Max)
Vis.@50 ºC /Cst
ASTM D -445
2.30
5.02
5 (Max)
Pour point ºC
ASTM D -97
-15
+6
-9 (Max)
Sulfur content %wt
ASTM D -4294 1.75
3.40
1.0(Max)
Diesel Index
Ip-21
56.26
44.40
55(Min.)
Cetane Number
50.50
41.96
53(Min.)
Calorific value (Kcal/Kg)
10925
10766
10800(gross)
Ash(%wt)
ASTM D-482
0.012
0.028
0.01(Max)
Distilled at (350 ºC) (%v)
ASTM D- 86
100
65
85 %( Min.)
Aniline point ºC
ASTM D 611
66
68
Recorded
50
Chapter Three/Part One
Result and Discussion
The calorific value is another test used for these fractions which is defined as the heat of combustions of petroleum products and calculated by using equation below, where (d) is the specific gravity at 15.6ºC [154]. Calorific value = 12400-2100d2 Table 15: ASTM D 86 for TQ, SA, Kh and TA Light Gas Oil. %Volume(ml)
LGO TQ
LGO SA
LGO Kh
LGO TA
IBP 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
213 228 237 240 244 249 252 257 260 264 270 275 279 284 289 296 299 303 309 313 -
215 230 234 241 245 249 252 255 258 261 264 267 270 275 279 283 288 294 302 310
209 221 226 233 239 243 245 248 251 257 261 264 269 273 276 282 289 297 308 -
-
-
207 220 232 237 241 246 250 254 260 265 269 273 278 284 289 292 297 301 306 312 -
51
Chapter Three/Part One
Result and Discussion
Tables (15 and 16), show ASTM D86 distillation data for the light and heavy gas oil fractions. According to ASTM D86 the recovered heavy gas oils at 350 ºC in the range 60-70%v/v, and light gas oils completely recovered below 320 ºC that means light gas oil are in a good agreement with the requirements of Iraqi marketing specification.
Table 16: ASTM D 86 for TQ, SA, Kh and TA Heavy Gas Oil. %Volume(ml)
HGO TQ
HGO SA
HGO Kh
HGO TA
IBP 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
271 284 290 298 304 310 317 322 326 330 333 339 343 347 350 354 357 361 366 -
252 266 278 285 298 305 313 319 325 329 336 340 345 349 352 355 360 364 -
243 255 288 294 302 309 315 322 329 334 340 346 350 353 358 361 365 369 -
259 278 291 296 305 309 315 324 330 334 339 343 346 350 353 357 360 364 368 -
52
-
Chapter Three/Part Two
Result and Discussion
Part Two 3.2 Oxidation Desulfurization, Solvent Extraction and Adsorption for light and heavy gas oils. 3.2.1 Oxidation desulfurization Oxidative
desulfurization
is
considered
as
the
latest
unconventional
desulfurization process which involves chemical oxidation of organic sulfur compounds to the corresponding divalent sulfur, also known as sulfone. The physical and chemical properties of sulfones, for instance boiling points, polarity and solubility in various solvents, are significantly different from the original sulfur compounds. In general, sulfones have higher boiling points and increased polarity which leads to higher solubility in polar solvent. Therefore, sulfones can be easily separated from fuels through solvent extraction or adsorption. Oxidizing agent is one of the key elements in any oxidative desulfurization process. We choose hydrogen peroxide (H2O2) is considered as “green” reagent which is commonly used in (ODS) processes. With the aid of catalysts, hydrogen peroxide can oxidize OSCs to the corresponding sulfones in ambient conditions. During reactions, water and oxygen are the only by-products which are in general, considered to have no adverse effect on the environment. Although pure hydrogen peroxide has a high active oxygen ratio (47.1 %wt) compared to other oxidizing agent[155]. The experimental runs were carried out in two – stage testing, preliminary and main study.
53
Chapter Three/Part Two
Result and Discussion
The first one includes study for selection of the best operational conditions for ODS processes, this study included evaluation effect of the temperature, acetic acid, time of reaction and amount of oxidant. The other included used best operation condition for deep desulfurization of LGO and HGO. All the experiments carried out in this chapter were in a batch reactor, with a total desulfurization rate (%X) of sulfur present in light and heavy gas oils were calculated using their initial concentration (Co) and concentration after treatment (Cs), as shown in the relation bellow:
%X =
𝑪𝒐−𝑪𝒔 𝑪𝒐
×100
3.2.1.1 Effect of operating reaction temperature on ODS The desulfurization of Taq-Taq light gas oil was carried out by using 15 ml H2O2 as oxidant and 20 ml acetic acid as catalyst with stirring speed at 1100 rpm. The reaction was conducted at temperatures 50, 60, and 75 ºC for 6 hr. at constant other parameters, upon the oxidation stage, different sulfur containing compounds are oxidized to their corresponding sulfoxides and sulfones subsequently. After treatment, the collected samples were left to settle for few minutes after which two layers were formed; the top layer (LGO TQ) and the bottom layer (oxidant-catalyst). The top layer was analyzed by ED-XRF in order to determine the sulfur content, figure 12 shows the oxidation of LGO TQ with H2O2/HAc oxidant catalyst system as a function of operating reaction temperatures. Generally, increasing temperature will significantly accelerate most of the organic reactions. The oxidation results of LGO TQ also indicated that the oxidation activities increased with the increasing oxidation reaction temperature.
54
Chapter Three/Part Two
Result and Discussion
Table 17: Effect of temperature on oxidation desulfurization. Vml LGO TQ 45
Temp ºC 50
Initial %S, wt 0.64
%S in oxidized LGO TQ 0.44
%X 31.25
45
60
0.64
0.38
40.62
45
75
0.64
0.33
48.43
The remaining sulfur in the LGO TQ after 6 hr. at reaction temperatures, 50, 60, and 75 ºC were 0.44, 0.38 and 0.33%wt respectively, as showed in Table 17. Gas oil are very complex mixtures that contain alkenes and aromatics, and these compounds can also be oxidized consuming part of the oxidizing agent and degrading the quality of the gas oil. These undesirable oxidation reactions are evident at temperatures of about 80-90ºC For this reason, the reaction has to be conducted at temperatures lower than 80 ºC[122]. 3.2.1.2 Effect of acetic acid as a catalyst on ODS process H2O2 in short-chain carboxylic acids (acetic acid) as catalysts is considered as the common oxidative desulfurization system. The mechanism of sulfur oxidation to sulfoxides and sulfone by using H2O2-organic acid was studied, hydrogen peroxide first reacts with organic acid quickly and generates peroxide acid, and then the proxy acid reacts with nonpolar sulfur compounds and generates relative sulfone or sulfoxide[112]. In this section, the effect of acetic acid (HAc) as a catalyst, on oxidation desulfurization was studied. Different amounts of the (HAc) were used in the oxidation of LGO TQ to show its effect on the oxidation reaction at 75 ºC and 15 ml H2O2 for 6 hours. 55
Chapter Three/Part Two
Result and Discussion
Table 18: Effect of HAc on oxidation desulfurization. Vml LGO TQ 45
Vml HAc 98%v/v
Initial %S
%S in oxidized LGO TQ
%X
10
0.64
0.48
25
45
20
0.64
0.33
48.43
45
30
0.64
0.31
51.56
It can be seen from the table 18 and figure 13 that increasing the amount of the catalyst increases desulfurization rate, because acetic acid catalyzes the oxidation reaction of sulfur containing compounds via forming peracetic acetic, which acts as an oxidizing agent giving its oxygen atom to the sulfur-containing compounds present in gas oil. Due to the feasibility of economical concerns, many catalyst may not necessarily need to run the entire process; henceforth, in this section, different amounts of catalyst usage been put to the procedural testing. 3.2.1.3 Effect of H2O2 on ODS process Hydrogen peroxide is used as oxidant in the ODS process. The amount of aqueous H2O2 is an important variable in the process design consideration of oxidation rate, nonproductive decomposition, cost and safety. Different amount of oxidant (hydrogen peroxide) were used in the different study of the oxidative sulfur removal for model sulfur compounds and real fuel. Here the effect of the amount of oxidant on the oxidation of organic sulfur compound in LGO TQ under various amount of Oxidant was studied in the presence of 20 ml HAc at 75 ºC. As shown in Table 19 and Figure 14, at oxidant amount equal to 10 ml the desulfurization efficiency was 29.68%. As the amount of H2O2 increases
56
Chapter Three/Part Two
Result and Discussion
from 10 to 15, 20 and 25 ml, the amount of sulfur content increased for the light gas oil to 0.33, 0.30 and 0.29wt% respectively within 6 hr.
Table 19: Effect of H2O2 on oxidation desulfurization. V ml Vml H2O2 Initial sample 48.7%wt/wt %S, wt 45 10 0.64
%S in oxidized LGO TQ 0.45
%X
29.68
45
15
0.64
0.33
48.43
45
20
0.64
0.30
53.12
45
25
0.64
0.29
54.68
This can be attributed to the generation of more hydroxyl radicals from the H2O2, which oxidize more sulfur compounds; the suitable amount of oxidant is 20 ml. The negative effect of 25 ml of H2O2 can be attributed to the presence of large amount of water. The larger the amount of water, the less is the probability for the interaction between the sulfur compounds dissolved in the oil phase and H2O2 present in the water phase. By increasing the amount of oxidant, more conversion occurs, however, it should be considered that by increasing its amount, the operational cost increases dramatically and it is recommended that the amount of oxidant be chosen by the commercial conditions of a project[156]. 3.2.1.4 Effect of reaction time on ODS process Table 20 and figure 15 show sulfur removal of LGO TQ as a function of reaction time at operating temperature 75 ºC, amount of H2O2 15 ml and 20 ml acetic acid. The results were improved by increasing time of the reaction. The remaining sulfur in gas oil decreased with increasing reaction time. 57
Chapter Three/Part Two
Result and Discussion
For example at reaction time of 4, 10, 12 hr. the remaining sulfur content were 0.51, 0.18 and 0.15 %wt respectively. This could be explained by describing interaction of oxidizing agents as time proceeds H2O2 and acetic acid can interact with OSCs to produce sulfone and sulfoxide. This reaction like any other reaction needs enough time to complete and promotes as time goes on. Best results were observed at 12 hr.
Table 20: Effect of time on oxidation desulfurization V ml sample 45
Time hr. 4
Initial %S, wt 0.64
%S in oxidized LGO TQ 0.51
45
6
0.64
0.33
48.43
45
8
0.64
0.24
62.5
45
10
0.64
0.18
71.87
45
12
0.64
0.15
76.56
58
%X 20.31
Chapter Three/Part Two
Result and Discussion
55
55
45
%X
%X
45
35
35
25
25
15
15 40
50
TC
60
70
5
80
15
25
35
V ml HAc
Figure 12: Effect of (T) ºC on ODS
Figure 13: Effect of volume of HAc on
Processes.
ODS processes.
60
85 70 55
40
%X
%X
50
40
30 25
20 5
10
15
20
10
25
2
Vml H2O2
Figure 14: effect of concentration
4
6
Time hr.
8
10
Figure 15: effect of Time on ODS
of H2O2 on ODS processes.
processes.
59
12
Chapter Three/Part Two
Result and Discussion
3.2.2 The Selection of the Most Efficient condition for oxidative desulfurization of LGO and HGO Although, many studies have been conducted in the field of ODS and its benefits are clear in comparison with other desulfurization processes, commercial technologies of ODS of petroleum fractions have not yet been developed due to some obstacles including, the need for an accurate design of a process including two stages of oxidation and extraction or adsorption for removal of oxidation products and need an accurate selection of oxidizing agent, catalyst and solvent for extraction of oxidized sulfur compound, through they have to provide ODS with the highest efficiency compared with other desulfurization methods, especially HDS[112]. Figure 16 shows general desulfurization processes for reduction of sulfur from LGO and HGO, The purpose of response surface optimization in this research is to find the optimal process conditions for maximum yield of sulfur elimination in real LGO and HGO. Moreover, minimizing H2O2 and catalyst consumption are the other two principal targets for the industrial interests. Based on the above results using the more severe reaction condition, Temperature 75ºC, time 12 hr., H2O2: gas oil ratio 1:3 and HAc: gas oil ratio by volume 1:2.25 was used as a best condition for ODS processes in this research. Despite of LGO and HGO contained different amount of sulfur compound from 0.64 for LGO TQ to 3.67%wt HGO Kh. In oxidation desulfurization of gas oil, sulfur containing compounds are present in the gas oil phase while the oxidant and the catalyst are present in the aqueous phase. Oxidation reaction rates in biphasic systems are low because of mass transfer limitations across the interface. The reaction may take place at the interface or in the bulk of one of the phases[109]. This disadvantage has been overcome by increasing the mixing speed to 1300 rpm as optimum condition due to the large volume of reactant mixture. 60
Chapter Three/Part Two
Result and Discussion
LGO and HGO ODS 12 hr. / Sep 3min
Solvent extraction by
Acetonitrile
Methanol
Acetic acid
Adsorption
AL
KS
AR
AL
KS
AR
AL
KS
AR
Figure 16: oxidation desulfurization processes. The mixture of gas oil and oxidant became two layers after oxidation: oil layer (top), and aqueous layer (oxidant, catalyst and water). The recovery and the sulfur contents of oxidized gas oil are summarized in Table 21. The recovery gas oil (Re) was calculated according to the relation bellow
%Re = {(V ml of the raffinate layer)/ (Vml of the feed)} x 100
It was found that with the oxidation of the gas oil feedstock, 74.25% and 51.49% of the total sulfur was removed from the original LGO Kh and HGO Kh, i.e., the sulfur content of the gas oil decreases from 2.02 to 0.52 and 3.67 to 1.78 %wt. respectively.
61
Chapter Three/Part Two
Result and Discussion
Table 21: Sulfur removal LGO and HGO after oxidation Gas oil
S, wt% after oxidation 0.16
%X
%Re
LGO TQ
Initial S, wt.% 0.64
75
96.28
LGO SA
0.72
0.11
84.72
95.57
LGO Kh
2.02
0.52
74.25
94.14
LGO TA
1.75
0.50
71.42
94.42
HGO TQ
1.56
0.55
64.74
93.3
HGO SA
2.05
0.77
62.43
93.8
HGO Kh
3.67
1.78
51.49
92.71
HGO TA
3.40
1.54
54.70
92.9
This has been achieved by simultaneous extraction of oxidized sulfur containing compounds to the aqueous phase in the oxidation media, which is a mixture of acetic acid and hydrogen peroxide. As a result of the oxidation reaction, the polarity of the sulfur containing compounds is increased, and hence, their extractability in the polar aqueous phase in the oxidation media increases. The result illustrated the rate of sulfur removal of each gas oil was different due to different types of sulfur compound like sulfides, thiophenes and their derivatives which present in LGO and HGO were differ in their chemical reactivity toward ODS processes. After desulfurization process for LGO TQ, concentration of H2O2 was determined by Iodometry method which was 3.06 %wt., but for HGO Kh only 0.35 %wt. of H2O2 remain after reaction due to the high sulfur content, while concentration of the original H2O2 was 48.7%wt/wt. Gas chromatograph (GC) coupled with sulfur selective detectors such as pulsed flame photometric detector (PFPD), The (PFPD) detector is a special type of GC 62
Chapter Three/Part Two
Result and Discussion
detectors which is used for detection of sulfur or phosphorus containing compounds and do not responded to the normal hydrocarbon compound, The main objective of this work was to examine and compare the performance of a oxidation, solvent extraction and adsorption in the desulfurization rate of LGO and HGO in batch system at specify operated condition. Figure 17 shows the chromatogram of Tetrahydrofuran THF solvent, which is used as solvent for preparation of a solution of gas oil samples for GC-PFPD, where the chromatogram shows significant signal has a dead time 2.457 mints, and this means that THF contained sulfur compound, in many chromatograms two peaks appears which have a retention time between 1.5 to 3 mint which is related to the solvent.
mVolts
mVolts
15
dead time = 2.457 mints.
2.457
44.940
10
5
0
-3 10
20
30
40
time Minutes
Figure 17: GC-PFPD for Tetrahydrofuran solvent.
Figure 18 and 19 shown GC-PFPD chromatograms of light and heavy gas oils obtained from Tawke crude oil before and after oxidation process, which illustrates the complexity of the real gas oil samples and the overlapping of organic sulfur compound with each other. 63
2.5
10 23.214
5.0
20
relative to untreated samples.
64 30 40 42.817
30
40.127
32.978
20
31.862 32.358 32.827 33.306 33.627 33.885 34.322 34.78034.561 35.029 35.460 35.829 36.033 36.514 36.750 37.014 37.511 37.898 37.936 38.436 38.737 39.087 39.207 39.447
B 26.769
15.868
23.531
16.372
A
40.821 41.100
7.5 24.104 24.514
10.0
25.210
10
24.804 25.037 25.325 25.459 25.587 25.696 25.840 26.081 26.291 26.441 26.530 27.011 27.146 27.267 27.516 27.619 27.720 27.827 28.037 28.196 28.460 28.697 28.782 29.030 29.203 29.457 29.585 29.721 29.920 30.026 30.192 30.355 30.596 30.753 30.867 31.101 31.268 31.462
24.211 24.304
13.109 13.210 13.297 13.467 13.648 13.798 13.932 13.992 14.103 14.182 14.305 14.387 14.498 14.462 14.577 14.775 14.822 15.114 15.294 15.387 15.460 15.591 15.703 16.043 16.131 16.189 16.275 16.503 16.871 17.168 17.339 17.444 17.510 17.663 17.744 17.88317.978 18.15718.345 18.233 18.439 18.602 18.799 18.874 18.987 19.09019.240 19.314 19.482 19.611 19.693 19.796 19.837 19.895 19.994 20.145 20.269 20.405 20.442 20.499 20.582 20.689 20.810 20.920 20.966 21.053 21.158 21.243 21.304 21.453 21.538 21.670 21.809 21.934 22.044 22.142 22.219 22.402 22.537 22.586 22.677 22.830 22.898 22.982 23.090 23.177 23.259 23.338 23.389 23.473 23.664 23.76123.855 23.930 24.035 24.173 24.219 24.297 24.451 24.529 24.593 24.685 24.919 24.761 24.848 25.059 25.123 25.258 25.305 25.383 25.450 25.518 25.713 25.799 25.910 25.999 26.124 26.266 26.351 26.413 26.628 26.798 26.920 27.187 27.385 27.487 27.552 27.838
12.180 12.527
11.353 11.399
1.544
0.25
23.825
12.5 10.013 10.335 10.609
2.476
15.909 16.346 16.744
14.634 14.951 14.935
Volts
21.636 21.876 22.088 22.238 22.404 22.710 22.921 23.379 23.553 23.708
1.666
mVolts 1.00
18.640
2.524
mVolts
Chapter Three/Part Two Result and Discussion
S =1.75 %wt
0.75
0.50
0.00
-0.10 40
mVolts Minutes
S =0.50 wt%
0.0
-1.7
Minutes
time
Figure 18: GC-PFPD for LGO TA A) before oxidation B) after oxidation.
As can be observed, the numbers, heights, and positions of these peaks change,
the peaks of sulfur-containing compounds in oxidized samples are appeared later
50
10 20
65 30 40.185
36.572
35.878
33.938
33.039
30
40.860 41.160
36.791 37.049 37.561 37.986 38.496 38.830 39.053 39.293 39.533
34.376 34.619 35.051 35.543
32.399
30.902
B
33.354
31.502
20
31.922
25.949 26.31026.410 26.813 27.240 27.545 27.850 28.106 28.326 28.607 28.833 29.042 29.223 29.496 30.027 30.189 30.447 30.706 30.934 31.123 31.334 31.844 32.084 32.331 32.595 32.840 33.080 33.293 33.544 33.816
41.640
40.138 40.511 40.893
37.456 37.605 38.155 38.650 38.992 39.287 39.507
36.797
35.715 35.894
34.460 34.880 35.117
21.476
25.120
19.478 19.838
17.739 18.235
22.850 23.377 23.181 23.826 24.045
22.228
0.25 21.983
20.287 20.560 20.802 21.025 21.13221.191
17.170 17.39217.467 17.955 18.410 18.608 18.815 19.022 19.255 19.643
14.936
26.653
25.738
14.609
0.50
15.436 15.656
13.102 13.288 13.463 13.774 13.973 14.181
1.537
24.825
16.741
25.295
15.902
0.75
31.295
24.121 24.558 24.822 25.045 25.346 25.565 25.623 25.846 26.102 26.480 26.807 27.047 27.303 27.654 27.621 27.864 28.101 28.495 28.820 29.087 29.245 29.599 30.015 30.348
10 12.519
11.928
2.487
24.591
22.414
16.343
25.526
24.306
23.544
A
23.239 23.400 23.848 24.276
25 2.474
mVolts 1.00
22.423
1.648
mVolts
Chapter Three/Part Two Result and Discussion
Volts
S =3.40 wt%
0.00
-0.10 40
mVolts Minutes
S =1.54 wt%
100
75
0
-11 40
time Minutes
Figure 19: GC-PFPD for HGO TA A) before oxidation B) after oxidation.
Besides, the peak intensity of sulfur-containing compounds in oxidized samples
is lower than that of untreated samples due to partial extraction of oxidized sulfur
containing compounds by means of the aqueous phase in oxidation media. From
retention time it is appears most sulfur compound oxidized to their corresponding
Chapter Three/Part Two
Result and Discussion
sulfoxide or sulfones which have high polarity and higher boiling point, and required more time for eluted from the column. The chromatograms of other LGO and HGO before and after oxidation were showed in the appendix. Since the amount of sulfur still remained in the gas oil phase was high, the additional treatment is needed. Therefore, the solvent extraction of oxidized gas oil is employed for further reduction of the sulfur content in the gas oil. 3.2.3 Solvent Extraction of Oxidized Sulfur Compounds. The second stage of this process is separation of oxidized sulfur compounds via liquid-liquid extraction with selective solvent. Obviously for separating the oxidized sulfuric compounds from gas oil[157]. This process is based on the solvent's polarity. For this process to be efficient, solvents should show higher solubility of the organosulfur compounds contained in the gas oil when compared with their solubility’s in the hydrocarbons. Thus, increasing the efficiency of this process is related to the optimization of the operating conditions to maximize the sulfur extraction and the careful selection of the required extractant. The main target of solvent extraction after oxidation is to further increase the desulfurization by the extraction of the remaining oxidized sulfur-containing compounds, in this stage acetonitrile, methanol and acetic acid were chosen as solvents. Table 22 shows physical properties of solvent.
Table 22: Physical properties of solvents[158]. Solvent
Specific gravity Boiling point ºC
Acetonitrile (MeCN) 99%v/v
0.782
81.6
Methanol(MeOH) 99.9%v/v
0.792
64
Acetic acid (HAc) 98%v/v
1.051
118
66
Chapter Three/Part Two
Result and Discussion
The LGO TA was used to relatively measure the efficiency of Acetonitrile (MeCN), methanol (MeOH), and acetic acid (HAc) solvent extraction before and after oxidation. Table 23 shows the results of extraction of (LGO TA) before and after oxidation by using (MeCN), (MeOH), and (HAc) solvent at solvent to gas oil ratio 1:1, from the results of extracting LGO TA before and after oxidation, it can be observed that HAc is not an effective solvent for sulfur in the case of extraction unoxidized LGO TA, whereas the MeCN and MeOH can achieve substantial desulfurization, albeit relatively low yields, but, when the LGO TA was first oxidized and then treated with various solvents, a further substantial reduction of sulfur content could be obtained. Table 23: Extraction of LGO TA by MeOH, MeCN and HAc solvent. Unoxidized LGO TA Solvent
Initial S = 1.75 %wt/wt %X
%Re
MeCN
S, wt/wt% 1.41
19.42
MeOH
1.55
HAc
1.63
Oxidized LGO TA Initial S = 0.5%wt/wt %X
%Re
95.5
S, wt/wt% 0.07
86
91.8
11.42
94.8
0.09
82
90.7
6.85
97.5
0.116
76.8
94.5
In this particular case it was found that MeCN is as effective among the two solvents (MeOH and HAc). It was found that the single extraction process leads to19.42, 11.42 and 6.85% desulfurization by MeCN, MeOH and HAc solvent, while the oxidation before the extraction process enhances the desulfurization to 86, 82 and 76.8% wt. respectively. The recoveries of oxidized gas oil were in the range 3-4.1 v% lowers than that of unoxidized gas oil. 67
Chapter Three/Part Two
Result and Discussion
Before oxidation, the polarity of the organo sulfur-containing compounds is not much higher than that of the corresponding hydrocarbon compounds, and therefore, the extraction is not efficient, and the extent desulfurization decreased in order: acetonitrile > methanol > acetic acid, however, in the ODS process, a major desulfurization of gas oil is obtained by the extraction of oxidized sulfur-containing compounds into the aqueous phase of oxidation media, and thus, the polarities of the remaining oxidized sulfur-containing compounds are changed in such a way that they can be extracted more effectively. Table 24 show the result of sulfur removal rate and recovery for oxidized LGO and HGO after solvent extraction. The sulfur contents of oxidized LGO and HGO after extraction with the three polar solvents were in the range of 0.0291 to 0.70 wt %, whereas these before extraction were 0.11 to 1.78 wt%. All solvents were effective to extract the oxidized sulfur compounds in oxidized gas oil. MeCN was the most effective solvent among three polar solvents for sulfur redaction. On the other hand, the recovery of the hydrocarbon layer was the lowest with MeOH and highest with HAc solvent. In the separation of oxidized sulfur-containing compounds of gas oil, the solubility of gas oil in the solvent is very important, because it determines the gas oil recovery after extraction. In the case of inappropriate solvent selection, it is likely to extract oxidized sulfur-containing compound from the gas oil very efficiently but with a high gas oil loss after extraction due to high solubility of gas oil in the extraction solvent. This is practically unacceptable. Figure 20 shows chromatograms of unoxidized gas oil LGO TA after extraction, when compared with figure 18 A, it is clear acetonitrile more effective for remove of unoxidized organic sulfur compound and decrease intensity and eliminated some peak in chromatogram, and there was not much difference between original and extracted gas oil by methanol and acetic acid solvent. 68
Chapter Three/Part Two
Result and Discussion
Table 24: Sulfur content and recovery after solvent extraction
Gas oil
S, wt/wt% in oxidized gas oil
acetonitrile S,
%Re
acetic acid
methanol %X
wt/wt%
S,
%Re %X
wt/wt%
S,
%Re
%X
wt/wt%
LGO TQ
0.16
0.0428
92.15
73.25
0.0395
92.5
75.31
0.0437
96
72.68
LGO SA
0.11
0.0330
92
70
0.0291
91
73.54
0.0353
95.5
67.90
LGO Kh
0.52
0.0529
91.4
89.82
0.0613
89.5
88.21
0.0705
93
86.44
LGO TA
0.50
0.0700
91.8
86
0.0900
90.7
82
0.1160
94.5
76.8
HGO TQ
0.55
0.0626
88.9
88.61
0.1013
89.5
81.58
0.1214
93.75
77.92
HGO SA
0.77
0.12
90.5
84.41
0.16
89
79.22
0.19
92.5
75.32
HGO Kh
1.78
0.37
89.5
79.21
0.58
87.9
67.41
0.70
91
60.67
HGO TA
1.54
0.21
89
86.36
0.50
88.15
67.53
0.55
91.9
64.28
69
Chapter Three/Part Two
Result and Discussion
10
23.525
Volts
15.864
0.50
0.25
C
0.25
15.908 16.339 16.739
14.627 14.932
23.530
16.365
15.908 16.341 16.742
14.627 14.936
Volts
13.104 13.458 13.641 13.792 13.927 13.982 14.177 14.298 14.381 14.459 14.487 14.571 14.764 14.816 15.108 15.287 15.381 15.454 15.585 15.696 15.860 16.121 16.181 16.036 16.264 16.496 16.864 17.156 17.329 17.434 17.505 17.655 17.733 17.874 17.968 18.149 18.34318.431 18.224 18.595 18.792 18.868 18.982 19.083 19.235 19.305 19.605 19.475 19.685 19.789 19.832 19.892 19.987 20.137 20.264 20.400 20.434 20.490 20.576 20.684 20.805 20.961 21.049 21.154 21.239 21.299 21.450 21.533 21.667 21.803 21.929 22.037 22.139 22.212 22.272 22.532 22.583 22.406 22.675 22.826 22.894 22.975 23.173 23.255 23.335 23.383 23.470 23.661 23.760 23.853 23.928 24.033 24.171 24.216 24.295 24.448 24.526 24.591 24.684 24.758 24.846 24.915 24.990 25.057 25.120 25.253 25.302 25.380 25.44825.515 25.711 25.794 25.907 25.996 26.122 26.267 26.349 26.412 26.628 26.794 26.920 27.189 27.484 27.552 27.837
12.172
11.344
0.25
13.106 13.205 13.293 13.462 13.644 13.795 13.929 13.987 14.099 14.179 14.301 14.383 14.460 14.492 14.573 14.771 14.818 15.109 15.290 15.382 15.456 15.587 15.699 15.775 16.039 16.126 16.184 16.269 16.499 16.566 16.867 17.161 17.332 17.438 17.507 17.658 17.739 17.876 17.973 18.154 18.228 18.341 18.434 18.598 18.795 18.870 18.979 19.087 19.310 19.236 19.479 19.608 19.688 19.792 19.834 19.89419.990 20.141 20.266 20.400 20.438 20.495 20.578 20.688 20.807 20.917 20.963 21.052 21.156 21.243 21.303 21.444 21.535 21.668 21.806 21.932 22.043 22.214 22.401 22.536 22.585 22.678 22.829 22.896 22.980 23.088 23.176 23.257 23.339 23.389 23.472 23.663 23.761 23.854 23.929 24.036 24.174 24.219 24.297 24.45224.529 24.593 24.684 24.91924.760 24.847 25.059 25.122 25.256 25.304 25.383 25.451 25.517 25.715 25.800 25.910 26.001 26.125 26.266 26.350 26.413 26.629 26.797 26.923 27.192 27.387 27.488 27.553 27.840
12.174 12.521
10.597
10.016
2.467
23.527
16.737
14.624
0.50
13.102 13.203 13.288 13.459 13.640 13.791 13.925 13.983 14.096 14.175 14.298 14.380 14.456 14.488 14.570 14.765 14.815 15.137 15.106 15.287 15.380 15.452 15.583 15.695 15.769 15.862 16.036 16.123 16.180 16.265 16.494 16.862 17.156 17.330 17.434 17.503 17.653 17.735 17.874 18.14917.970 18.224 18.340 18.430 18.594 18.791 18.866 18.979 19.083 19.306 19.233 19.475 19.604 19.684 19.788 19.829 19.890 19.987 20.137 20.262 20.398 20.434 20.488 20.577 20.683 20.804 20.914 20.959 21.046 21.152 21.238 21.298 21.444 21.531 21.661 21.802 21.928 22.038 22.137 22.213 22.396 22.531 22.581 22.672 22.824 22.894 22.976 23.086 23.171 23.254 23.333 23.387 23.467 23.658 23.754 23.849 23.924 24.031 24.170 24.215 24.292 24.45024.524 24.588 24.680 24.914 24.756 24.843 24.989 25.054 25.118 25.252 25.300 25.378 25.446 25.513 25.709 25.795 25.904 25.996 26.120 26.263 26.347 26.411 26.625 26.792 26.916 26.990 27.185 27.376 27.483 27.550 27.834
12.172 12.518
1.00
10.018
2.457
mVolts 1.00
10.016
2.450
mVolts
14.934 15.906
mVolts
Volts
16.344
Chapter Three/Part Two Result and Discussion
1.00
A S =1.41 wt%
0.75
0.00
-0.10 10 20
10 30
B
20 30
20
30
70
40 Minutes
S =1.55 wt%
0.75
-0.10 0.00
40 Minutes
S =1.63 wt%
0.75
0.50
-0.10
0.00
40
Minutes
time
Figure 20: GC-PFPD for unoxidized LGO TA after solvent extraction by A) MeCN, B) MeOH C) HAc
Chapter Three/Part Two
Result and Discussion
Figure 21 shows GC-Chromatograph shows the potential of the application of solvent extraction after oxidation for LGO TA. As can be observed, extraction after oxidation leads to diminishing sulfur-containing compounds peaks in the treated gas oil, from the chromatograms it was clear that the acetonitrile was a more effective solvent for extraction of oxidized sulfur compound (sulfone and sulfoxide), sulfur removal rate by Acetonitrile was 86% when compared to acetic acid 76.8%, while recovery gas oil obtained from acetic acid was higher than methanol and acetonitrile. The chromatogram of HGO TA in figure 22A illustrates that the acetonitrile has high efficiency for extraction of oxidized sulfur compound in heavy gas oil which was reach 86.36%, while sulfur removal rate for methanol and acetic acid were 67.53% and 64.28% respectively. The chromatogram of other LGO and HGO after solvent extraction were shown in appendix. Efficiency of HAc for extraction sulfur in TA HGO very low 64.28%wt compared to MeCN 86.36%wt, due to the complex structure of organic sulfur compound. But, from the result of solvent extraction it is clears that, besides HAc is a good catalyst, and it is also act as a good solvents for extraction of oxidized organo sulfurcontaining compounds and lower cost than MeCN. After oxidation and solvent extraction for HGO Kh at specified condition, still high level of sulfur remain in gas oil, in order to reach deep desulfurization required a more quantity of oxidant and catalyst, by using HGO Kh: H2O2: HAc ratio 1.25:1:1 respectively for 17 hr., and solvent extraction by acetonitrile sulfur content reach to 0.0708%wt.
71
1 10
7
10
20
72
20
-1
30 35.905
B
30
C 36.667
33.007
32.396
30.801 31.133 31.507
27.853 28.173 28.452 28.818 29.219 29.587
20
32.981
1.0 25.531 26.073 26.338 26.802 27.287
2.5
24.536
2.483
10
27.854 28.200 28.475 28.840 29.230
1.617
32.433
30.344 30.627 30.922 31.327
26.120 26.493 26.760
24.465 25.008
2.480
1
26.087 26.493 26.800 27.297
2.444
mVolts
mVolts 3
24.515
1.602
mVolts
Chapter Three/Part Two Result and Discussion
mVolts
A
2
S =0.07 wt%
0
-1 30 40 Minutes
mVolts
S =0.09 wt%
2.0
1.5
0.5
0.0
-0.5 40
mVolts Minutes
6
S =0.116 wt%
5
4
3
2
0
40
time
Figure 21: GC-PFPD for LGO TA after solvent extraction by A) MeCN B) MeOH C) HAc
Minutes
2.456
24.523
4
3
2
10
20
B) MeOH C) HAc
73
30
30
40.094
40.102
30
41.084
38.435 38.705
37.896 38.433 38.733
B 36.511
31.466
7
35.826
32.985
29.224
40.132
36.596 36.933
36.006
35.013
32.453 32.985 33.360 33.947
31.523
30.362 30.887
A
36.707 36.980
35.449
33.907
33.307
34.554 35.019
34.311
31.875 32.369
30.867
26.845 27.282
2.472
mVolts 2.0
39.480
37.483 37.871
C
34.305 34.557 34.748 35.012 35.443 36.000 36.515 36.680 36.975
32.980 33.306 33.909
31.867 32.093 32.381
30.357
5
33.613
29.204
6 20
30.357 30.813 31.080 31.272 31.461
10
29.570
4
27.285 27.846 28.093 28.460 28.811 29.211 29.587
3
26.087 26.454 26.791 27.031
6
20
29.960
24.813 25.025 25.555
10
25.666 26.084 26.457 26.790 27.034 27.275 27.583 27.843 28.170 28.455 28.809 29.035
2.459
mVolts 0.5
24.813 25.017
mVolts
Chapter Three/Part Two Result and Discussion
mVolts
2.5
S =0.21 wt%
1.5
1.0
0.0
-0.4 40
mVolts
Minutes
%S =0.50 S =0.50 wt%
2
1
0
-1 40 Minutes
mVolts
S =0.55 wt%
5
1
0
-1
time
40
Figure 22: GC-PFPD for HGO TA after solvent extraction by A) MeCN
Minutes
Chapter Three/Part Two
Result and Discussion
Infrared spectroscopy (IR) is powerful technique that yields information about the functional features of various petroleum constituents. The structure of the light gas oil obtained from Tawke crude oil LGO TA before oxidation was detected by IR and the result is presented in figure 23 the aliphatic C-H stretching at the range of 2955 cm-1 and 2854 cm-1for stretching of CH3 groups. Whereas CH2 methylene groups have bands at 2924 cm-1, the bending vibration of symmetry methyl appears at 1377 cm-1, while methylene bending appears at 1463 cm-1 [5].
120
%T
100 741
80 1377
60
1463 2854
40
2955
2924
20 400
1000
1600
2200
2800
3400
cm
-1
4000
Figure 23: IR Spectrum of LGO TA before oxidation. Figure 24 A, shows IR Spectrum of LGO TA after oxidation, in these spectra, the sulfone band was observed symmetry stretching at 1154 cm-1 and 1306 cm-1 for asymmetric stretching[134]. This indicated that organic sulfur compound convert to corresponded sulfone, and this sulfone compounds effectively removed by solvent extraction as shown in figure 24 B. 74
Chapter Three/Part Two
Result and Discussion
110
A
100
%T
90 80 722
1154 1306 1378
70 1463 2958
2855
60
2922
50 400
1000
1600
2200
2800
3400
cm -1
4000
140
B
%T
120 100
721
80
1377 1464
60
2956
2854
40
2925
20 400
1000
1600
2200
2800
3400
cm -1
4000
Figure 24: IR spectrum for LGO TA, A) after oxidation B) after extraction by acetonitrile
75
Chapter Three/Part Two
Result and Discussion
3.2.4 Adsorption of oxidized gas oil after solvent extraction Adsorption is a process of accumulation of one substance over another[159]. The organo sulfur compounds present in gas oil can be removed by adsorption on a solid sorbent, but, like extraction processes, adsorption alone cannot technologically reach the deep desulfurization levels for gas oil, Adsorption desulfurization was studied using a light and heavy gas oil, which contains organic sulfur compounds, over three different adsorbents (AL, KS and AR) in a batch adsorption system. Table 25 shows sulfur removal capacity of three adsorbents after extraction by MeCN, the result indicated that the alumina is the best adsorbent in the three adsorbents for total sulfur removal, maximum rate of desulfurization for LGO and HGO achieved by alumina was 43.49% for LGO SA, and while KS adsorbent has the lowest capacity for sulfur removal was 5.12% for HGO TQ. Table 26 shows best results for adsorption desulfurization rate was 31.49, 27.83 and 28.52%wt for AL, KS and AR adsorbent respectively for LGO SA, and while all three adsorbents have lower capacity for elimination sulfur from HGO TA. The result in both table 25 and 26, showed LGO and HGO from the Sarqala oil field have a better response for adsorption desulfurization. Table 27 illustrates that total sulfur removal by adsorption for LGO and HGO after extraction with acetic acid solvent, the result indicates that alumina has lower adsorption capacity for desulfurization compared to AR and KS adsorbent, after extraction by acetic acid some particle of acetic acid will remain in the recovered gas oil, and it is reported that alumina and acetic acid react with each other to produce oxonium cation +O[Al(OAc)2]3[160].
76
Chapter Three/Part Two
Result and Discussion
Jian S. Q et al. founded alumina effective adsorbent for remove acetic acid in liquid hydrocarbon mixture[161]. Due to both factor decrease the capacity of alumina for adsorption of sulfur compound, in order to over com this problem the gas oil layer must be washed with hot water for remove acetic acid and decrease total acid number of gas oil. It should be noted that colors of oxidized LGO were darker than fresh sample, but color of oxidized gas oils after adsorption turned to pale white as shown in figure 25 and 26. For adsorption process generally capacity of adsorbent for sulfur removal decrese in this order AL> KS > AR.
A
B
A
C
B
C
Figure 25: LGO A) before oxidation
Figure 26: HGO A) before oxidation
B) after oxidation C) after adsorption.
B) after oxidation C) after adsorption.
77
Chapter Three/Part Two
Result and Discussion
Table 25: Sulfur content and recovery of LGO and HGO after adsorption for acetonitrile solvent.
Gas Oil
Initial S, ppm
Al2O3 adsorbent
KS adsorbent
AR adsorbent
S, ppm
%X
%Re
S, ppm
%X
%Re
S, ppm
%X
%Re
LGO TQ
428
364.25
14.89
97.6
368.14
13.98
96.4
378.3
11.61
95.2
LGO SA
330
186.47
43.49
97.2
201.7
38.87
95.8
215.42
34.72
96.4
LGO K
529
460
13.04
96.6
469.9
11.17
96.2
485
8.13
95.6
LGO TA
700
569.4
18.65
96.2
498.6
28.77
95.8
514
26.57
95.4
HGO TQ
626
580.8
7.22
96
593.9
5.12
95.8
584.16
6.68
95
HGO SA
1200
943
21.41
95.6
929
22.58
94.8
935
22.08
94
HGO K
3700
3300
10.81
95.8
3400
8.1
95.4
3400
8.1
94.8
HGO TA
2100
1800
14.28
95.2
1900
9.52
95.6
1900
9.52
94.4
78
Chapter Three/Part Two
Result and Discussion
Table 26: Sulfur content and recovery of LGO and HGO after adsorption for methanol solvent. Gas Oil
Initial S, ppm
Al2O3 adsorbent
KS adsorbent
AR adsorbent
S, ppm
%X
%Re
S, ppm
%X
%Re
S, ppm
%X
%Re
LGO TQ
395
275.74
30.19
96.8
292.55
25.93
96
293.11
25.79
95.6
LGO SA
291
199.35
31.49
96.2
210
27.83
95.6
208
28.52
96
LGO K
613
543
11.41
97
551
10.11
95.4
557
9.13
96.2
LGO TA
900
651.3
27.63
95.6
650
27.77
94.6
648
28
94.2
HGO TQ
1013
864
14.70
96.8
858
15.3
95.2
871.3
13.98
95.8
HGO SA
1600
1216
24
95.8
1198
25.12
94.4
1207
24.56
94.8
HGO K
5800
5300
8.62
96.2
5500
5.17
95.2
5500
5.17
94.4
HGO TA
5000
4700
6
94.6
4800
4
94.2
4800
4
95
79
Chapter Three/Part Two
Result and Discussion
Table 27: Sulfur content and recovery of LGO and HGO after adsorption for acetic acid solvent. Gas Oil
Initial S, ppm
Al2O3 adsorbent
KS adsorbent
AR adsorbent
S, ppm
%X
%Re
S, ppm
%X
%Re
S, ppm
%X
%Re
LGO TQ
437
350.6
19.77
96.6
341
21.96
95.2
346.9
20.61
96
LGO SA
353
301
14.73
96
281
20.39
94.8
294.2
16.65
96
LGO K
705
632.3
10.31
96.4
593
15.88
96
624
11.48
95.2
LGO TA
1160
872.2
24.81
94.8
869
25.08
94
841
27.5
94.6
HGO TQ
1214
995.3
18.01
96.2
982.6
19.11
95.8
983.7
18.97
95
HGO SA
1900
1600
15.78
95.6
1500
21.05
94.2
1600
15.78
95.2
HGO K
7000
6600
5.71
95.4
6500
7.14
93.8
6500
7.14
94.4
HGO TA
5500
5200
5.45
96
5200
5.45
94
5200
5.45
94
80
Chapter Three/Part Two
Result and Discussion
From the result of the adsorption, it is clear that the desulfurization rate of light gas oil is better than heavy gas oil; organic sulfur compound in heavy gas oil has higher boiling range and is more alkyl substitute dibenzothiophene. From literature, it was founded thiophene and dibenzothiophen have much higher adsorption selectivity due to direct interaction between the sulfur atom and adsorptive sites, methyl groups at the 4-MDBT and 4,6- DMDBT inhibit the interaction between the S-atom in DBTs and the active sites on the catalyst, which results in the decrease of adsorption capacities of in 4-MDBT and 4,6- DMDBT on the catalyst[162]. Figure 27 shows the color of alumina change from white to congo pink after adsorption. Figure 28 shows chromatogram for the adsorption of HGO TA after extraction by acetic acid solvent, the result illustrated there is not much different from the original and treated gas oil. This means the main purpose of the adsorption is to improve the color of oxidized gas oil and remove of sulfur.
A
B
Figure 27: Color of alumina A) before adsorption B) after adsorption.
81
1
2.444
1.582
2
3
4
10
20
20
Adsorbents.
82
30
30
C 41.091
40.118
30
36.672 36.983 37.492 37.897 38.443 38.707 39.110 39.457
32.985 33.318
B 34.309 34.765 35.022 35.449 36.016
33.931
31.874 32.406 33.640
32.120
29.216 30.369 30.823 31.107 31.287 31.471
29.77329.586 29.987
24.518 24.824 25.048 25.534
29.592
41.114
40.129
36.680 36.995 37.493 37.914 38.472 38.733 39.092 39.485
29.217
33.001 33.321 33.936 34.321 34.580 34.773 35.036 35.466 36.018
33.646
30.376 30.836 31.107 31.286 31.470 31.900 32.147 32.407
29.971
26.800 27.049 27.288 27.593 27.852 28.165 28.469 28.820 29.041
26.089 26.458
mVolts
A
35.043 35.428
10
33.917
3
26.456 26.793 27.290 27.583 27.854 28.179 28.466 28.802
5
20
32.960 33.294
2
25.696 26.088
10
32.820 33.038
24.526 24.811 25.027
2.479
1.633
1
29.201 29.697 29.582 29.893 30.030 30.196 30.357 30.752 30.855 31.268 31.453 31.632 31.843 31.895
26.765 27.274 27.601 27.822 28.194 28.449 28.687 28.773 28.842 27.009
2.465
1.660
mVolts 2
33.601
25.830
mVolts
Chapter Three/Part Two Result and Discussion
mVolts
4
3
S =0.52 %wt
0
-1 40 Minutes
mVolts
S =0.52 %wt S =0.52 %wt
4
1
0
-1 40
mVolts
Minutes
5
S =0.52 %wt
0
-1
40
time
Minutes
Figure 28: GC-PFPD HGO TA after adsorption by A) AL, B) KS, C) AR
Conclusions Crude oil fields in Kurdistan region of Iraq has wide range of API gravity and sulfur content which can be classify it as light intermediate sweet, medium and heavy sour. From distillation data it was found that the crude oils from TQ and SA contain high amount of naphtha, and while K and TA contain high level of light and heavy gas oils which are more suitable for production of gas oil. It was found that LGO TQ has low total sulfur content 0.64%wt in comparison with HGO K were 3.67%wt. Most of organic sulfur compounds present in the LGO fractions could be removed by oxidation, solvent extraction and adsorption process, while in HGO K 0.65%wt sulfur remains after these process, which was required hard condition for deep desulfurization. The gas chromatographic instrument with pulsed flame photometric detector (GCPFPD) could be used for illustration the effect of each desulfurization steps for elimination of organic sulfur compound in LGO and HGO.
83
Appendix GC-PFPD Chromatograms
Appendix
GC-Chromatogram
1.625
24.355 24.503 24.920 24.971 25.496
10 20
84 30 33.202
30
40.116
37.952 38.438
B
36.512 36.732
33.875
31.458 32.601
28.969 29.250
27.484 27.856
26.382 26.682
25.237 25.443 25.521
23.268
21.502 21.924
20.477 20.720 20.880
18.334 18.691 19.143 19.540 19.817
17.312 17.770
15.413 15.927
14.103 14.573
12.625 12.769 13.233
12.020
24.308 24.726
16.772
14.976
23.835
16.378
22.421 22.762 23.550
A
35.838
34.550 35.017 35.077
34.307
32.983
3 30.874
20
32.364
30.313
10
28.493
mVolts 10.027 10.377 10.663 11.209
9.264
1.797
mVolts Volts
26.091 26.371 26.813 27.293 27.533
22.692 22.950 23.259 23.738
1 2.477
mVolts
Appendix GC-Chromatogram
1.00
S =0.64 %wt
0.75
0.50
0.25
0.00
-0.10 40 Minutes
S =0.16%wt
4
2
0
-1 40
time Minutes
Figure 29: GC-PFPD for LGO TQ A) before oxidation B) after oxidation.
mVolts
mVolts 1.553
10
10 23.844
20
20
85
26.395 26.699
16.362
23.549
A
30
B
30
37.586
32.644
28.755 29.307
27.492 27.862
22.426
16.765
14.960
300
24.318 24.736 24.880 25.102 25.492 25.523
22.848 23.218
20.521 20.720 20.806 21.140 21.485
19.147 19.517 19.899
18.328
17.441 17.739
15.936
100
15.592
13.896 14.205 14.620
12.192 12.703 13.232 13.413
500
9.962 10.537 11.042 11.423
2.506
mVolts
Appendix GC-Chromatogram
mVolts
S =0.72%wt
400
200
0
-52 40 Minutes
8
S =0.11%wt
7
6
5
4
3
2
1
0
-1 40
time Minutes
Figure 30: GC-PFPD for LGO SA A) before oxidation B) after oxidation.
10 20
86
5
30 36.554
27.858
B
35.868
31.492
30.904
24.846 25.006
27.533 27.841
16.749
14.946
16.349
14.628
A
34.600 35.056
33.920
33.016
30.382
28.083 28.483 28.831 29.216 29.595
24.520
15 25.608 25.493 25.865 26.083 26.460 26.812 27.024 27.294
20
33.347
10 22.716 22.955 23.331 23.248 23.856 24.210 24.185
10
32.399
22.079
0.25 17.181 17.468 17.737 17.959 18.233 18.406 18.605 18.816 19.025 19.252 19.640 19.479 19.839 20.280 20.560 20.798 21.012 21.169 21.465 21.981 22.223 22.417 22.842 23.154 23.353 23.540 23.830 24.302 24.598 24.830 25.104 25.283 25.519 25.725 25.947 26.286 26.412 26.639 26.813
15.907
0.75
15.453 15.643
13.469 13.779 13.996 14.186
1.542
mVolts Volts
7.252 7.787 8.002 8.288 8.489 8.646 8.912 9.214 9.530 9.976 10.338 10.630 11.092 11.370 11.697 11.936 12.128 12.404 12.736 13.120 13.275
2.480
0.50
2.445
1.641
mVolts
Appendix GC-Chromatogram
S =2.02%wt
1.00
0.00
-0.12 30 40 Minutes
mVolts
25
S =0.52%wt
20
0
-3 40
time Minutes
Figure 31: GC-PFPD for LGO Kh A) before oxidation B) after oxidation.
1.662
10 20
87
10
30
Figure 32: GC-PFPD for HGO TQ A) before oxidation B) after oxidation. 43.019
33.916
30
40.182 40.589 40.820
36.571
35.875
34.610
B
36.823 37.030 37.539 37.945 38.494 38.814 39.308
36.123
35.092
20
34.374
40
35.355 35.518
30 33.031
20
25.985 26.298
37.508
34.473 34.925 35.165 35.704
31.180 31.347 31.886 32.111 32.364 32.620 32.869 33.117 33.557 33.848
24.828
26.830
25.111
16.355
0.25
27.249 27.559 27.872 28.135 28.367 28.678 28.839 29.055 29.276 29.702 30.054 30.249 30.523
22.882 23.192 23.347
20.559 20.831 20.998 21.210 21.496 21.772 21.985 22.235
16.750 17.171 17.392 17.486 17.742 17.968 18.249 18.443 18.620 18.826 19.034 19.247 19.501 19.622 19.841 19.976
26.448
24.757 25.311
0.50
33.238
31.499
10 14.151 14.587 14.945 15.413 15.916
23.830
26.667
24.647 25.538
24.321
A
32.388
60
30.896
70 13.095 13.469
23.556
25.751
22.417
mVolts
1.00
30.314
1.547 2.480
0.75
24.984
2.461
mVolts
Appendix GC-Chromatogram
Volts
S =1.56%wt
0.00
-0.10 40 Minutes
mVolts
S =0.55%wt
50
0
-7 40
time Minutes
10 20
88 30 40
Figure 33: GC-PFPD for HGO SA A) before oxidation B) after oxidation. 44.280
42.843
36.552
35.864
33.906
30
40.149 40.197 40.572 40.795
37.932 38.483 38.796 39.270
37.514
36.799 37.015
36.113
35.501
34.592
31.486
28.836 29.057 29.275 29.410 29.718
22.412
26.656
23.775 24.704
A
35.081
34.364
33.227
20 33.017
B
32.385
30 30.889
20
30.315 30.618
29.238 29.613
27.858 28.223
16.349
0.25 19.496 19.848 20.006 20.280 20.798 20.984 21.067 21.178 21.265 21.468 21.555 21.817 21.949 22.241 22.556 22.603 22.855 22.927 23.199 23.282 23.690 24.062 24.129 24.209 24.315 24.489 24.550 24.933 24.979 25.076 25.148 25.409 25.282 25.473 25.330 25.684 25.827 25.935 26.034 26.097 26.185 26.287 26.450 26.841 26.955 27.050 27.087 27.223 27.414 27.531 27.594 27.882 28.149 28.391
17.746 18.239 18.447
16.745
15.858 15.913 16.042
14.569 14.625 14.814 14.938
0.50
26.087 26.314 26.463 26.557 26.789 26.847 27.028 27.293
10 14.181
13.465
2.464
25.544 25.747
24.611 24.784 24.866
23.541 23.560 23.873
1.543
mVolts
1.00
25.331
40
24.113
2.454
1.648
mVolts
Appendix GC-Chromatogram
1.25 Volts
S = 2.05%wt
0.75
0.00
-0.12 40 Minutes
mVolts
S =0.77%wt
10
0
-4
Minutes
time
5
10 20 30
89 35.960
30
40.281
B
36.651 36.876 37.122 37.613 38.065 38.572 38.888
34.009
33.084
20
34.687 35.134
33.400
10 31.558
30.966
20
32.463
16.747 17.198 17.328 17.447 17.511 17.667 17.747 17.884 17.983 18.074 18.158 18.236 18.362 18.443 18.610 18.809 18.976 19.101 19.247 19.622 19.492 19.697 19.841 19.905 20.003 20.151 20.276 20.452 20.504 20.583 20.644 20.700 20.818 20.789 20.933 20.978 21.063 21.172 21.258 21.314 21.55021.461 21.683 21.813 21.945 22.040 22.155 22.233 22.416 22.294 22.549 22.597 22.688 22.909 22.845 23.001 23.105 23.192 23.278 23.357 23.416 23.443 23.678 23.775 23.869 23.947 24.052 24.127 24.193 24.238 24.313 24.487 24.546 24.701 24.929 24.974 25.016 25.074 25.141 25.27925.326 25.403 25.470 25.676 25.819 25.930 26.027 26.091 26.151 26.29626.441 26.380 26.651 26.829 26.950 27.021 27.090 27.222 27.340 27.404 27.521 27.588 27.875 28.142 28.306 28.392 28.566 28.648 28.830 29.052 29.262 29.404 29.502 29.709
15.914 16.351
250 15.462 15.596 15.778 15.86216.045 16.129 16.191 16.270
13.075 13.106 13.297 13.468 13.745 14.183 14.311 14.458 14.573 14.815 14.942
25.739
24.779 25.538
14.628
500
30.422
10 11.693
10.605
9.517
2.460
24.610 24.865
750
27.908 28.120 28.529 28.878 29.258 29.640
24.140 24.584 24.853 25.066 25.356 25.613 25.900 26.140 26.494 26.834 27.080 27.333
1.593
mVolts
23.546
A
23.419 23.865
22.447
2.486
mVolts
Appendix GC-Chromatogram
mVolts
S =3.67%wt
0
-90 40 Minutes
mVolts
S =1.78%wt
15
0
-3 40
time
Figure 34: GC-PFPD for HGO Kh A) before oxidation B) after oxidation. Minutes
Appendix
GC-Chromatogram
mVolts
5
A
S =0.0428%wt
4
3
34.592
32.999
31.498
2
2.006 2.468
1
0
-1 10
20
30
40 Minutes
mVolts
S =0.0395%wt
B
10.0
2.471
7.5
5.0
37.854
34.998
1.609
24.554
26.827
2.5
0.0
-1.4 10
20
30
40 Minutes
mVolts
S =0.0437%wt
C
4
3
37.577
34.698
33.040
34.000
31.518
28.538
1.590
2.463
1
26.000 26.480
25.065
2
0
-1 10
20
30
40 Minutes
Figure 35: GC-PFPD for LGO TQ after solvent extraction by A) MeCN B) MeOH C) HAc 90
Appendix
GC-Chromatogram
mVolts
2.5
2.456
2.0
S =0.033%wt
A
1.5
0.5
2.001
1.0
0.0
-0.4 10
20
30
40
2.471
Minutes
mVolts 8
B
7
S =0.0291%wt
6
5
4
3
2
31.125
1
0
-1 10
20
30
40 Minutes
mVolts
S =0.0353%wt
C
7.5
5.0
40.160
38.667
36.960
33.867
33.145
30.874
31.750
28.000
29.173
2.512
27.059
2.5
0.0
-1.0 10
20
30
40 Minutes
Figure 36: GC-PFPD for LGO SA after solvent extraction by A) MeCN B) MeOH C) HAc 91
Appendix
GC-Chromatogram
mVolts 2.5
A
2.0
S =0.0529%wt
2.012 2.489
0.5
31.140
28.870
27.292
23.240
1.0
27.880
24.930 25.107 25.599 25.949 26.493
1.5
0.0
-0.4 10
20
30
40 Minutes
mVolts 6
S =0.0613%wt
B
5
4
3
30.940
28.467 28.840 29.204
1.686
1
26.048 26.350 26.810 27.293 27.587
24.505 24.999
2.464
2
0
-1 10
20
30
40 Minutes
mVolts
S =0.0705%wt
C
3
34.017
32.113
29.960 30.387
27.880
1.656
23.851
28.460 28.867
24.993 2.478
1
25.965 26.344 26.815 27.280
2
0
-1 10
20
30
40 Minutes
Figure 37: GC-PFPD for LGO Kh after solvent extraction by A) MeCN B) MeOH C) HAc 92
Appendix
GC-Chromatogram
A
S=0.0626%wt wt
mVolts
5
B
S=0.1013%w t
4
40.125
38.481 38.788
35.890 36.147 36.572 36.813
33.020
34.621 35.089
32.427
30.399 30.924
29.237
2.503
2
33.941
31.504
3
1.649
1
0
-1 10
20
30
40 Minutes
mVolts 4
S=0.1214%w t
C
40.824
37.897
39.115
36.147 36.571 36.97236.787
1.610
1
33.906
33.010 32.380
30.910
2
34.591
2.467
31.492
3
0
-1 10
20
30
40 Minutes
Figure 38: GC-PFPD for HGO TQ after solvent extraction by A) MeCN B) MeOH C) HAc 93
10
20
B) MeOH C) HAc
94
30
33.320
35.098
30
40.162
C
37.533 37.987 38.493 38.796 39.267
38.773
36.564 36.797 37.018
34.623 35.093
B
35.910
34.720
31.504
33.016
30
1
43.735
34.617
33.938
33.105 33.363 33.926 34.007
30.895
36.537
34.563
33.901
32.998
31.479 32.055
A
35.895 36.120 36.571 37.02736.809
34.388
20
33.027
3
31.505
29.246
2.002
1
32.420
2
30.920
27.878 28.241
26.833
20
30.382
4
29.240
10
26.813
3
27.886 28.093
1
25.001
1.691
10
26.007
24.518 25.034
2.533
2
2.480
1.642
2.465
Appendix GC-Chromatogram
mVolts
4
3
S =0.12%wt
2
0
-1 40
mVolts Minutes
S =0.16%wt
0
-1 40 Minutes
mVolts
S =0.19%wt
0
-1
40
Minutes
Figure 39: GC-PFPD for HGO SA after solvent extraction by A) MeCN
1
1.633
2.504
10
3
20
B) MeOH C) HAc
95
30
33.026 33.360 33.956
30
40.157
38.754
36.659
30
40.187
38.776
38.031
C 35.995
34.681 35.013
33.959
B
36.640
30.931 31.515 32.453 32.998 33.360
40.223
38.803
38.016
36.674
35.966
34.747 35.067
33.999
33.043
32.478
31.527
30.942
29.680
28.864
27.968 28.086
26.806
2.514
A
35.928
34.654 35.037
31.524
4
31.920 32.430
20
30.348
28.894 29.218 29.573
27.890
26.794 27.273
20
30.336 30.925
7
28.869 29.242 29.627
10
26.819 27.347
10
28.080 27.917
24.975
2.5
26.049
24.960
1.644
10.0
26.081
24.967
2.415
1.591
Appendix GC-Chromatogram
mVolts
S =0.37%wt
7.5
5.0
0.0
-1.4 40
mVolts Minutes
15
S =0.58%wt
10
5
0
-2 40 Minutes
mVolts
S =0.70%wt
6
5
2
0
-1
40
Minutes
Figure 40: GC-PFPD for HGO Kh after solvent extraction by A) MeCN
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ولتوضيح وتقييم ومتابعة لعمليات األكسدة ،واألستخالص بالمذيبات واألمتزاز التى أجريت الزالة المواد الكبريتية ،تم أستخدم تقنية الغاز كروماتوغرافيا مستخدماً حساس نوع ( )PFPDالخاص بتحسس المركبات العضوية الكبريتية.
الخالصة تمت دراسة أربعة أنواع من النفط الخام المنتج فى حقول كردستان تحديدًا من حقول (طق طق ،سرقال، خورماله ،و طاوكى) حيث تمت تجزئتها الى خمسة قطوفات متخلفة (النافثا ،النفط األبيض ،زيت الغاز الخفيف، زيت الغاز الثقيل و زيت الوقود) وتم تحديد النسب الحجمية لكل قطيفة ،وأختير قطيفتى زيت الغاز الخفيف (درجة الغليان من ٢٤١الى ٣٠٠م )°والثقيل (من ٣٠١الى ٣٦٠م )°للتقيم والدراسة الكاملة بموجب الطرق القياسية المعتمدة من قبل الجمعية االمريكية للفحص والمواد والطرق القياسية العراقية ،وقد تبين بأن زيت الغازالخفيف والثقيل يحتويان على كميات مختلفة من المواد العضوية الكبريتية التى تسبب تلوثا للبيئة وتكون موْذية لصحة البشر عند أحتراقها فى مكائن األحتراق الداخلي وأثناء التصنيع وتوليد الطاقة. أستخدم طريقة األكسدة إلزالة المواد الكبريتية بواسطة بيروكسيد ألهيدروجين كعامل مؤكسد وحامض الخليك کعامل مساعد بظروف تشغيلية مختلفة من (درجة الحرارة ،الزمن ،وتركيز حامض الخليك وبيروكسيد الهايدروجين). وقد تبيين بأن نسبة المواد الكبريتية تبقى عالية بعد عملية األكسدة ولكنها تتحول الى صيغات تركيبية أخرى (سلفوکسايد وسلفون) التى هي أقل ضررا واكثر قطبية من الصيغ الترکیبة األولية. تم أستخدم ثالثة أنواع مختلفة من المذيبات القطبية فى عملية األستخالص بالمذيبات وهى (أسيتونايترال، ميثانول ،وحامض الخليك) بنظام الوجبات ألزالة المواد الكبريتية المؤكسدة. تم قصر لون نماذج زيت الغاز المؤكسد بأستخدام عملية األمتزاز بواسطة ثالثة أنواع من المواد الممتزة ]الومينا ( ،)ALطين كانى سازجم ( )KSوطين أرضروم ( [)ARوالتى ساعدت فى ازالة المواد الكبريتية وتحسين اللون. بعد كل عملية أكسدة واألستخالص بالمذيبات واألمتزاز ألزالة المواد الكبريتية ،تمت متابعة المحتوى الكبريتى الكلى لنماذج زيت الغاز بأستخدام جهاز فلورسة األشعة السينيه باألستناد الى طريقة .ASTM D4294
إزالة الكبريت من زيت الغاز الخفيف والثقيل المنتج من حقول نفط كردستان-العراق بطريقة األكسدة ،األستخالص بالمذيب و اإلمتزاز
رسالة مقدمة إلى مجليس كلية العلوم جامعة السليمانية كجزء من المتطلبات نيل شهادة ماجستير فى علوم الكيمياء (كيمياء النفط)
من قبل برهم شريف احمد بكالوريوس في الكيمياء ،٢٠١١جاميعة السليمانية
باشراف د .عبدالسالم رحيم كريم أستاذ جمادى الثانى ١٤٣٨
&
د .لقمان عمر حمه صالح مدرس مارس ٢٠١٧
ئامێری ووزه پهرتكهرى تيشكى ئێكسى درهوشاوه ( )energy disperse X-Ray fluorescenceمان به کارهێنا بۆ دیاری کردنی بڕی گشتی گۆگرد له گازئۆيڵهکاندا له سهر بنهمای ( )ASTM D4294له پاش ههموو قۆناغهکانی چارەسهرکردن بۆ البردن و کهم کردنهوەى بڕی گۆگرد. له پاش چارهسهركردنى گازئۆيلهكان به ههريهكه له ڕێگاكانى (ئۆكساندن ،دهرهێنان به توێنهرو ڕوومژين) تهكنيكى گازكڕۆماتۆگرافى بهسترا لهگهڵ ههستيارى ( )pulls flame photometric detectorكه دۆزهره وهيهكى ههستيارو تايبهته به مادده ئهنداميه گۆگردهكان ،بهكارهێنرا بۆ زياتر نيشاندان و روونكردنهوهى كاريگهرييهكانى قۆناغهكانى البردن و كهمكردنهوهى بڕى گۆگرد.
پوخته چوارجۆرنهوتى خاو كه له كێڵگه نهوتيه جياوازهكانى كوردستان وهرگيراون كه بريتين له نهوتى كێڵگه کانى (تهقتهق ،سهر قهاڵ ،خورمهڵه و تاوكێ) به ڕێگهى دڵۆپاندن كراون به پێنج به شهوه که بریتین له (نهفثا ،نه وتى سپى ،گازئۆیڵى سوک ،گازئۆیڵى قورس و چهورى سوتهمهنى) وە ڕێژهى سهدى قهبارهيى ( )V/V%ههر يهكێك لهو بهشانه دياريكران ،دوو لهوبهشانه كه بريتين له گازئۆيڵى سوك ( )light gas oilله پلهى كواڵنى ٢٤١بۆ،٣٠٠ وه گازئۆيڵى قورس ( )heavy gas oilله پلهى كواڵنى ٣٠١بۆ ٣٦٠پلهى سيليزى به تهواويى شيكاريان بۆ كرا به گوێرهى پێوهرى پێوانهيى ئهمهريكى ( )ASTMو پێوانهيى عيراقى ،ئهم دوو جۆره گازئۆيڵه ماددهى ئهندامى گۆگرديان تێدايه به ڕێژهى جياواز كاتێك دهسووتێنرێن له وێستگهكانى بهرههم هێنانى كارهباو پيشهسازى و مهكينهى ئۆتۆمبيل دا دهبنه هۆى پيس بوونى ژينگهو زيانيان بۆ تهندروستى مرۆڤ ههيه. بۆ البردنى مادده گۆگرديه ئهنداميهکان ڕێگهى ئۆكساندنمان ههڵبژارد ،به بهكارهێنانى هايدرۆجين پيرۆكسايد وهكو كاراى ئۆكسێنهر ،ترشى سركيك وهكو كاراى ياريدهدهر به بهكارهێنانى باروودۆخى جياواز بۆ كارلێكهكه له ڕێگهى كۆنترۆڵ كردنى (پلهى گهرمى ،كات ،بڕى هايدرۆجين پيرۆكسايد و ترشى سركيك) .دواى قۆناغى ئۆكساندن هێشتا بڕى گۆگرد زۆره ،بهاڵم مادده ئهندامييه گۆگردهكه گۆراوه بۆ جۆرى سهلفون سهلفوكسايد ،كه جهمسه ردارييان زياترهو زيانيان كهمتره. بۆ البردنى مادده گۆگرديه ئهندامیهکان که ئۆكسانيان بهسهردا هاتووه ڕێگهى دەرهێنان به توێنەر (solvent )extractionمان به كار هێنا له ڕێگهى سێ توێنهرهوه كه بريتين له (ئهسيتۆنايترايل ،كهولى مه ثيلى و ترشى سركيك). وه به كاريگهرى ئۆكساندن ڕهنگى گازئۆيڵهكان دهگۆڕێت بۆ پرتهقاڵى ،بۆ چارهسهركردنى ئهو ڕهنگهو البردنى بڕێك له گۆگرد ڕێگهى روو مژين ( )adsorptionمان به كارهێنا ،به بهكارهێنانى سێ جۆر روو مژه ( )adsorbentکه بریتین له (ئهلۆمینا( )ALو گڵی کانی سازى جم( )KSلهگهڵ گڵی ئهرزڕووم(. ()AR
البردنى گۆگرد له گازئۆيڵى سووك و قورس بهرههم هاتوو له كێڵگه نهوتيهكانى كوردستان-عێراق به ڕێگهى ئۆكساندن ،دهرهێنان به توێنهر و ڕوو مژين
نامهیهکه پێشکهشکراوە به ئهنجومهنى کۆلێجى زانست له زانکۆى سلێمانى وهک بهشێک له پێداویستیهکانى بهدەستهێنانى بڕوانامهى ماستهر له زانستى کیمیادا (كيمياى نهوت)
لهاليهن بهرههم شريف احمد بهکالۆریوس له كيميا ( ،)٢٠١١زانكۆى سلێمانى
به سهرپهرشتى د .عبدالسالم ڕهحيم كريم پرۆفيسۆر
ڕهشهمێ ٢٧١٦
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د .لوقمان عمر حهمهصاڵح مامۆستا
ئازار ٢٠١٧
