Deasphalting of crude oils using supercritical fluids

A crude oil has four main SARA constituents: saturates, aromatics, resins, and asphaltenes. The asphaltenes in crude oil are the most complex and heavy organic compounds. The asphaltenes contain highly polar substituents and are insoluble in an excess of n-heptane (or n-pentane). The classic definition of asphaltenes is based on the solution properties of petroleum residuum in various solvents. Asphaltenes are a solubility range that is soluble in light aromatics such as benzene and toluene, but is insoluble in lighter paraffins. The particular paraffins, such as n-pentane and n-heptane, are used to precipitate asphaltenes from crude oil. The effects of four different solvents (water, carbon dioxide, propane, and ethanol) on the deasphalting process under the supercritical conditions were reviewed. Supercritical water is an excellent solvent for removing of high molecular weight organic compounds such as asphaltenes from crude oils under the supercritical conditions.     

APPLICATION OF HIGH PERFORMANCE LIQUID CHROMATOGRAPHY FOR HYDROCARBON GROUP TYPE ANALYSIS OF CRUDE OILS

High performance liquid chromatography (HPLC) was applied to four commercial grade Saudi Arabian crude oils having API gravity in the range 28 to 38 for the determination of hydrocarbon group types namely asphaltenes, saturates, aromatics and polars. Each of these crude oils was separated into asphaltenes and maltenes using n-hexane as the precipitating solvent. The maltenes (n-hexane soluble) were fractionated into saturates, aromatics and polars fractions by n-hexane elution on a column packed with amino propylsilane chemically bonded to porous silica particles.

The data obtained shows that the weight percent saturates increase whereas aromatics, polars and asphaltenes decrease from Arab Heavy to Arab Bern through Arab Medium and Arab Light crude oil. The results obtained from HPLC were in comparison with those obtained from ASTM method D2007. This method is easier, faster and offer good repeatability. This method can be applied to other crude oils.     

APPLICATION OF HIGH PERFORMANCE LIQUID CHROMATOGRAPHY FOR HYDROCARBON GROUP TYPE ANALYSIS OF CRUDE OILS

ABSTRACT

High performance liquid chromatography (HPLC) was applied to four commercial grade Saudi Arabian crude oils having API gravity in the range 28 to 38 for the determination of hydrocarbon group types namely asphaltenes, saturates, aromatics and polars. Each of these crude oils was separated into asphaltenes and maltenes using n-hexane as the precipitating solvent. The maltenes (n-hexane soluble) were fractionated into saturates, aromatics and polars fractions by n-hexane elution on a column packed with amino propylsilane chemically bonded to porous silica particles.

The data obtained shows that the weight percent saturates increase whereas aromatics, polars and asphaltenes decrease from Arab Heavy to Arab Bern through Arab Medium and Arab Light crude oil. The results obtained from HPLC were in comparison with those obtained from ASTM method D2007. This method is easier, faster and offer good repeatability. This method can be applied to other crude oils.     

PHYSICAL AND CHEMICAL CHARACTERIZATIONS OF ASPHALTENES FROM DIFFERENT SOURCES

Asphaltenes and resins are two of the several, but important, heavy organics present in petroleum fluids. Asphaltenes are operationally defined as the non-colatile and polar fraction of petroleum that is insoluble in n-alkanes (i.e., n-pentane). Conversely resins are defined as the non-colatile and polar fraction of petroleum that is soluble in n-alkanes (i.e., n-pentane), and aromatic solvents (i.e., toluene), and insoluble in ethyl acetate. A commonly accepted view in the petroleum chemistry is that crude oil asphaltenes form micelles which are stabilized by adsorbed resins kept in solution by aromatics. Two key parameters that control the stability of asphaltene micelles in a crude oil are the ratio of aromatics to saturates and that of resins to asphaltenes. When these ratios decrease, asphaltene micelles will coalesce and form larger aggregates. The precipitation of asphaltene aggregates can cause problems such as reservoir plugging and wettability reversal.     

EVALUATION OF FEEDSTOCKS FOR DEVELOPMENT OF HYDROCRACKING CATALYSTS FOR HEAVY OIL

A number of feedstocks namely Arab Light atmospheric residue (ALAR), Arab Heavy atmospheric residue (AHAR), vacuum gas oil (VGO) and hydrotreated vacuum gas oil (HT-VGO), were evaluated for their physical and chemical characteristics. The characterization results of the feedstocks show the complex nature and composition of both residues and gas oils. The distillation results showed that about 50 weight percent of Arab Light crude consists of atmospheric residue. The elemental analysis of the ALAR showed that high amount of carbon, sulfur and nitrogen is present along with heavy metals such as nickel and vanadium. In case of Arab Heavy crude oil, the atmospheric residue is even higher, that is 57 percent and contains higher amount of metals along with more carbon, sulfur and nitrogen contents. The determination of hydrocarbon types by HPLC exhibited that ALAR contains higher amount of saturates compared to AHAR but less amount of aromatics, polars and asphaltenes. ALAR was found to have 55% saturates, 27% aromatics, 12% polars and 6% asphaltenes while AHAR has 30% saturates, 42% aromatics, 18% polars and 10% asphaltenes. Molecular weight determination indicated that the molecular weight of ALAR was determined to be 511 compared to 595 for AHAR. ALAR being lighter, showed 54% distillation at 547°C while AHAR exhibited 45% distillation at 543°C. VGO was found to have 13% saturates, 68% aromatics and 19% polars while HT-VGO had 29% saturates, 63% aromatics and 8% polars. VGO was found to have high IBP and FBP compared to HT-VGO. On the basis of the characterization data, VGO was selected to be use with catalysts containing high pore size supports such as alumina, silica alumina and clay while HT-VGO was selected as feedstock for performance evaluation of zeolite based catalysts. ALAR and AHAR will be utilized in the later stages of the catalysts development work.     

EVALUATION OF FEEDSTOCKS FOR DEVELOPMENT OF HYDROCRACKING CATALYSTS FOR HEAVY OIL

A number of feedstocks namely Arab Light atmospheric residue (ALAR), Arab Heavy atmospheric residue (AHAR), vacuum gas oil (VGO) and hydrotreated vacuum gas oil (HT-VGO), were evaluated for their physical and chemical characteristics. The characterization results of the feedstocks show the complex nature and composition of both residues and gas oils. The distillation results showed that about 50 weight percent of Arab Light crude consists of atmospheric residue. The elemental analysis of the ALAR showed that high amount of carbon, sulfur and nitrogen is present along with heavy metals such as nickel and vanadium. In case of Arab Heavy crude oil, the atmospheric residue is even higher, that is 57 percent and contains higher amount of metals along with more carbon, sulfur and nitrogen contents. The determination of hydrocarbon types by HPLC exhibited that ALAR contains higher amount of saturates compared to AHAR but less amount of aromatics, polars and asphaltenes. ALAR was found to have 55% saturates, 27% aromatics, 12% polars and 6% asphaltenes while AHAR has 30% saturates, 42% aromatics, 18% polars and 10% asphaltenes. Molecular weight determination indicated that the molecular weight of ALAR was determined to be 511 compared to 595 for AHAR. ALAR being lighter, showed 54% distillation at 547°C while AHAR exhibited 45% distillation at 543°C. VGO was found to have 13% saturates, 68% aromatics and 19% polars while HT-VGO had 29% saturates, 63% aromatics and 8% polars. VGO was found to have high IBP and FBP compared to HT-VGO. On the basis of the characterization data, VGO was selected to be use with catalysts containing high pore size supports such as alumina, silica alumina and clay while HT-VGO was selected as feedstock for performance evaluation of zeolite based catalysts. ALAR and AHAR will be utilized in the later stages of the catalysts development work.     

PHYSICAL AND CHEMICAL CHARACTERIZATIONS OF ASPHALTENES FROM DIFFERENT SOURCES

ABSTRACT

Asphaltenes and resins are two of the several, but important, heavy organics present in petroleum fluids. Asphaltenes are operationally defined as the non-colatile and polar fraction of petroleum that is insoluble in n-alkanes (i.e., n-pentane). Conversely resins are defined as the non-colatile and polar fraction of petroleum that is soluble in n-alkanes (i.e., n-pentane), and aromatic solvents (i.e., toluene), and insoluble in ethyl acetate. A commonly accepted view in the petroleum chemistry is that crude oil asphaltenes form micelles which are stabilized by adsorbed resins kept in solution by aromatics. Two key parameters that control the stability of asphaltene micelles in a crude oil are the ratio of aromatics to saturates and that of resins to asphaltenes. When these ratios decrease, asphaltene micelles will coalesce and form larger aggregates. The precipitation of asphaltene aggregates can cause problems such as reservoir plugging and wettability reversal.     

Resolution and Quantification of Ring Type Aromatics by HPLC Method Using n-Hexane Elution

A method is described for the ring type separation of aromatic fraction of crude oils. The crude oils were dissolved in n-hexane to precipitate asphaltenes. The n-hexane dissolved portion of the crude oil was separated into saturates, aromatic types, and polars using high performance liquid chromatography. The aromatics were differentiated into monoaromatics (1R), diaromatics (2R), triaromatics (3R), tetraaromatics (4R), and polyaromatics (5R+). This method was applied to four commercial Saudi Arabian crude oils namely Arab Berri, Arab Light, Arab Medium, and Arab Heavy having API gravity in the range 28.0-38.5. The HPLC separation was carried out by n-hexane elution on a amino propylsilane silica column. The hydrocarbon group types were determined on weight percent basis. The saturates and total aromatics were found decreasing with decreasing API gravity while polars and asphaltenes increased. This trend may be due to the reason that the condensed polycyclic compounds and heteroatomic contents increase with decreasing API gravity in crude oils. This method may be applied to other crude oils for aromatic types determination.     

胜利减压渣油胶质热反应生焦特性的研究

以胜利减压渣油中的饱和分、芳香分和胶质为原料，通过其热反应行为的考察，表明在本反应条件下，饱和分不转化成沥青质和甲苯不溶物；仅有少量芳香分转化成沥青质和甲苯不溶物；在热反应中沥青质和甲苯不溶物的生成主要来自胶质的缩合反应。还比较了饱和分、芳香分和胶质的裂解与缩合性能。研究表明，纯胶质的热反庆体系，其胶溶沥青质的能力很强；原生胶质经热反应后所生成的次生胶质和次生沥青质与减压渣油中的原生胶质和原生沥青     

STRUCTURAL CHARACTERIZATION OF ARABIAN HEAVY CRUDE OIL RESIDUE

The residue (370°C+) from Arabian Heavy Crude Oil was separated into four fractions, asphaltenes, resins, aromatcis and saturates. The four fractions were found to be free of artifacts and analytically significant in themselves. Each fraction was further characterized by elemental analysis, infrared spectroscopy, n.m.r. spectroscopy and mass spectroscopy. The aromatics are the major constituent of the residue and the ratio of asphaltenes, resins, aromatics and saturates is about 2:3:8:3. The strucutral characterization study led to the conclusion that asphaltene fraction is maximum hydrogen deficient followed by resins, aromatics and saturates thus suggesting larger degree of ring condensation in the structure of asphaltenes than resins and aromatics.     

STRUCTURAL CHARACTERIZATION OF ARABIAN HEAVY CRUDE OIL RESIDUE

ABSTRACT

The residue (370°C+) from Arabian Heavy Crude Oil was separated into four fractions, asphaltenes, resins, aromatcis and saturates. The four fractions were found to be free of artifacts and analytically significant in themselves. Each fraction was further characterized by elemental analysis, infrared spectroscopy, n.m.r. spectroscopy and mass spectroscopy. The aromatics are the major constituent of the residue and the ratio of asphaltenes, resins, aromatics and saturates is about 2:3:8:3. The strucutral characterization study led to the conclusion that asphaltene fraction is maximum hydrogen deficient followed by resins, aromatics and saturates thus suggesting larger degree of ring condensation in the structure of asphaltenes than resins and aromatics.     

胜利原油各组分对界面膜扩张流变性的影响

 采取经典的四组分分离方法(SARA)将胜利原油分离得到饱和分、芳香分、胶质和沥青质,利用醇碱萃取法得到酸性组分。通过滴外形分析方法系统研究了上述5类原油组分及稀释原油的界面扩张流变性质,考察了振荡频率和各组分质量分数的影响。结果表明,各类活性组分及稀释原油表现出与表面活性剂类似的界面扩张行为,扩张模量均随振荡频率增大而增大,随质量分数的增加先增大后减小;相角随振荡频率增大而降低,随质量分数增大而增加。各组分模拟油及稀释原油形成的界面膜均表现出较强的弹性行为,且按其界面行为可以分为3组：稀释原油和饱和分、酸性组分和胶质、芳香分和沥青质。模量最大值对应的质量分数高低顺序为稀释原油和饱和分、酸性组分和胶质、芳香分和沥青质。沥青质扩张模量的最大值在 25 mN/m 左右,略高于稀释原油和其它活性组分。     

Resolution and Quantification of Ring Type Aromatics by HPLC Method Using n -Hexane Elution

Abstract

A method is described for the ring type separation of aromatic fraction of crude oils. The crude oils were dissolved in n-hexane to precipitate asphaltenes. The n-hexane dissolved portion of the crude oil was separated into saturates, aromatic types, and polars using high performance liquid chromatography. The aromatics were differentiated into monoaromatics (1R), diaromatics (2R), triaromatics (3R), tetraaromatics (4R), and polyaromatics (5R+). This method was applied to four commercial Saudi Arabian crude oils namely Arab Berri, Arab Light, Arab Medium, and Arab Heavy having API gravity in the range 28.0–38.5. The HPLC separation was carried out by n-hexane elution on a amino propylsilane silica column. The hydrocarbon group types were determined on weight percent basis. The saturates and total aromatics were found decreasing with decreasing API gravity while polars and asphaltenes increased. This trend may be due to the reason that the condensed polycyclic compounds and heteroatomic contents increase with decreasing API gravity in crude oils. This method may be applied to other crude oils for aromatic types determination.     

PETROLEUM RESINS: SEPARATION, CHARACTER, AND ROLE IN PETROLEUM

In petroleum science, the term resin generally implies material that has been eluted from various solid adsorbents, whereas the term maltenes (or petrolenes) indicates a mixture of the resins and oils obtained as filtrates from the asphaltene precipitation. Thus, after the asphaltenes are precipitated, adsorbents are added to the n-pentane solutions of the resins and oils, by which process the resins are adsorbed and subsequently recovered by the use of a more polar solvent, and the oils remain in solution. The resin fraction plays an important role in the stability of petroleum and prevents separation of the asphaltene constituents as a separate phase. Indeed, the absence of the resin fraction (produced by a variety of methods) from the maltenes influences the ability of the de-resined maltenes to accommodate the asphaltenes either in solution or as a stable part of a colloidal system. In spite of the fact that the resin fraction is extremely important to the stability of petroleum, there is surprisingly little work reported on the characteristics of the resins. This article summarizes the work that has been carried out in determining the character and properties of the resin constituents. Suggestions are also made regarding current thoughts of the role of these constituents on the structure and stability of petroleum.     

Surface properties of petroleum oil polar fraction as investigated by Zetametry and DRIFT spectroscopy

The polar fractions of various transformer petroleum oils (one new and two used oils) were extracted from the neat oils using silica as solid support. We found that the amount of the polar fraction adsorbed on the silica was higher for the used oils as compared to the new one. Such oil polar fractions are insoluble in low molecular weight paraffins (n-hexane and n-heptane) and are soluble in ethanol. The analysis of the diffuse reflectance infrared Fourier transform (DRIFT) spectra of the silica samples coated with oil polar components indicate the presence of oil polar functional groups such as hydroxyl, aromatic and carboxyl groups resembling asphaltenes or resins. In addition, we studied the electrical properties of the oil polar fraction by determining the ζ potential, in water, of the coated silica. In order to compare the modified and the non-modified silica surface properties, we made blank experiments by measuring the surface charge in water of the bare SiO₂ particles. The negative surface charge at the water/oil–silica interface was found to increase with pH, resulting from the increase in ionisation of the oil polar fraction acidic surface groups. The objective of varying the pH was to analyse the possible acid–base interactions at the water–oil interface for substrates having various oil polar fraction contents. The polar components in the neat oil adsorb on the silica surface and increase its surface charge and stabilisation in water. We found a good correlation between the amounts of the oil polar fractions, the surface concentration of their functional groups (carboxylic and phenolic groups) and the magnitude of their ζ potential at the water/oil–silica interface.     

乙醇胺与胜坨油田坨28 区块原油活性组分 相互作用对动态界面张力的影响

为明确胜坨油田坨28区块原油中活性组分与有机碱乙醇胺间的相互作用对动态界面张力的影响,采用SARA四组分分离方法对坨28区块原油进行分离,获得饱和分、芳香分、胶质和沥青质等组分;利用醇碱萃取法获得酸性组分;通过旋转滴界面张力仪测定了乙醇胺与坨28区块原油活性组分模拟油间的动态界面张力。研究结果表明:酸性组分是原油的主要活性组分,其质量分数及结构对有机碱与原油间界面张力的行为具有关键性影响,体系动态界面张力的最低值可达10-2m N/m数量级;酸性组分质量分数越大,低界面张力维持时间越长。对于坨28区块原油,与乙醇胺作用的难易顺序为:酸性组分最强,胶质次之,沥青质、饱和分和芳香分与之作用比较微弱。     

塔河常压渣油及其亚组分的非等温热转化反应性能研究

采用热重分析法对塔河常压渣油(THAR)及其亚组分的热转化反应性能进行了考察;在Sharp微分法基础上,采用分段动力学拟合,获得了渣油及其亚组分热转化速率峰值、速率峰值处的反应温度、转化率和剧烈裂解温度区间等动力学基本数据以及各亚组分的生焦性能。结果表明：各亚组分生焦率由低到高依次为饱和分＜芳香分＜胶质＜沥青质,沥青质是焦炭的主要来源;四组分按组成加权后的生焦率较THAR生焦率高4.21百分点,表明THAR亚组分混合物共焦化有利于抑制各亚组分的生焦;饱和分可促进其它亚组分生焦,而芳香分和胶质可抑制沥青质生焦,且芳香分的抑焦性能更强;在热转化反应过程中,裂化反应活性由高到低的顺序为饱和分＞芳香分＞胶质＞沥青质,各亚组分在低温段和高温段的活化能由低到高的顺序均为饱和分＜芳香分＜胶质＜沥青质,表明胶质和沥青质大分子的热转化过程需要提供较多的能量。     

ASPHALTENIC CRUDE OIL CHARACTERIZATION: AN EXPERIMENTAL INVESTIGATION OF THE EFFECT OF RESINS ON THE STABILITY OF ASPHALTENES

High performance liquid chromatography (HPLC) and Thin Layer Chromatographic (TLC) latroscan were used to characterize an asphaltenic stock tank oil (STO) from the North Sea. The whole STO was separated into saturates, aromatics, polars 1 (resins 1), polars 2 (resins 2) and asphaltene fractions. The separated resins (1) and the more polar resins (2), also termed asphaltene peptizing agents, were further characterized by HPLC in terms of their neutral, basic, pyrrolic and acidic components. Resins (1) and resins (2) were mixed in different proportions with whole (original) STO; the resulting mixtures were tested for asphaltene onsets of precipitation due to n-C5 injection at 25° C and 690 kPa. Results of these tests are presented and the observed trends are explained in terms of resins characters and/ or major constituents.     

减压渣油及其四组分在接触剂上的裂化反应规律

以减压渣油为原料,采用热解色谱和热重-质谱,考察了减压渣油及其四组分(饱和分、芳香分、胶质和沥青质)在惰性接触剂LHBK和酸性接触剂C上的裂化反应。结果表明：四组分在有孔无酸剂LHBK上裂化程度由强到弱的顺序为胶质、沥青质、芳香分、饱和分,在有孔有酸剂C上裂化程度由强到弱的顺序为饱和分、芳香分、胶质≈沥青质。四组分在2种接触剂上缩合反应生成的积炭均比减压渣油在接触剂上缩合反应生成的积炭具有更低的H/C摩尔比;接触剂的酸性明显促进了四组分的裂化,C_20-馏分产率明显增加;且增加了减压渣油裂化反应的生焦率,增加部分主要来自芳香分和胶质的催化裂化生焦。说明接触剂的酸性能促进饱和分C—C键、芳香分侧链C—C键断裂以及胶质和沥青质中键能较低的键断裂。     

热反应对辽河重油胶质及沥青质性质的影响

辽河重油于高压反应釜中分别在350,375,400 ℃下加热反应2 h。对油样的饱和分、芳香分、胶质和沥青质进行了分离。并对其沥青质和胶质进行了元素分析,VPO相对分子质量测定,IR分析和H-NMR分析。结果表明：反应温度升高,(沥青质+饱和分)/(胶质+芳香分)比值上升,胶体的稳定性下降。热反应中,沥青质、胶质的分子骨架结构未发生破坏,但是侧链发生断裂;反应温度375 ℃后,沥青质、胶质等重组分分子侧链的断裂变化较小,而缔合程度增强。