THERMAL DECOMPOSITION OF SAUDI CRUDE OIL ASPHALTENES

Abstract

Asphaltenes precipitated by the use of pentane, heptane and decane solvents from Saudi Arabian Light (AL) and Saudi Arabian Heavy (AH) crude oils 370^°C + residua have been investigated by thermal gravimetric analysis and pyrolysis - gas chromatographic analysis at 350^°C and 520^°C. Gas chromatographic analysis of the gases evolved during pyrolysis has shown that CO, CO₂ and CH₄ constitute the major portion of the gases evolved at 350^°C from pentane and heptane asphaltenes of AH residue and from pentane asphaltenes of AL residue. Whereas gases evolved from decane asphaltenes are dominated by CO₂ and C₂-C₄ hydrocarbon gases. At 520^°C, hydrogen and methane represent 56-80 vol %of the gases evolved from all the four asphaltenes. The amounts of C₁-C₄ hydrocarbon gases increased with an increase in the carbon number of the precipitating solvent at 350^°C and decreased at 520^°C. The presence of up to C₃₆ normal alkane hydrocarbon has been indicated in the maltenes produced from these asphaltenes. The loss of nitrogen from AH asphaltenes during pyrolysis remained low (1-6 wt %), whereas the losses of oxygen and sulphur ranged from 58 to 74 wt % and 10 to 29 wt %, respectively.     

ASPHALTENES IN SAUDI ARABIAN HEAVY CRUDE OIL SOLUBILITY AND MOLECULAR WEIGHTS IN HYDROCARBON SOLVENTS

The asphaltenes from Saudi Arabian Heavy crude oil residue ( 370°C+ ) were precipitated by adding n-alkane solvents ( n-C₅ to n-C ₁₀ ) to the crude oil / residue.     

沙中原油减压馏分油的分离及表征

采用溶剂脱蜡法和溶剂萃取法将沙中原油的减压馏分油分离为正构烷烃相、轻芳烃-饱和烃相、中芳烃相和重芳烃相等亚组分,采用气相色谱、气相色谱-质谱联用、固体核磁共振等方法分析了减压馏分油及其亚组分的基本性质、烃类组成和结构参数,同时考察了上述分离过程中各组分的分离百分率。结果表明：溶剂脱蜡法和溶剂萃取法分别分离减压馏分油中链烷烃和多环芳烃的选择性及分离效率均较高;采用溶剂脱蜡法得到的正构烷烃相中链烷烃含量在88.3％～95.2％之间,其碳数呈正态分布,链烷烃分离百分率在24.4%~36.8%之间,约是环烷烃分离百分率的12倍;采用两段溶剂萃取法得到的重芳烃相和中芳烃相具有随着馏分油变重CA降低,CN,CP,RA,RN增加,平均分子式中S和N原子数增加的规律,重芳烃相和中芳烃相中芳烃含量分别为85.4%~88.8%和73.2％～78.5％,三环及以上芳烃的分离百分率在72.8%~75.5%之间,分别是链烷烃和环烷烃分离百分率的5~8倍和4~5倍。     

CHARACTERIZATION OF ASPHALTENES FROM SAUDI ARABIAN CRUDE OILS BY NONAQUEOUS POTENTIOMETRIC TITRATION AND ELEMENTAL ANALYSIS

ABSTRACT

Nonaqueous poientiometric titration was employed for the estimation of basic functionalities in the asphaltanes. A series of model basic compounds were titrated in a solvent mixture containing chlorobenzene and acetic anhydride. Perchloric acid in dioxane was used as the titrant. The model basic compounds were classified into very weak bases, weak bases and strong bases, based on their pKa (H₂O) values. Pure asphaltenc samples were titrated under similar titration conditions. The titration curves for the pure asphaltenes showed two end points corresponding to HNP values of about 350 mV and 600 mV. The first end point was due to strong bases (HNP : 350 mV) and the second end point was due to weak bases (HNP : 600 mv). Asphaltene samples spiked with known amounts of model basic compounds were also titrated. The spiking titrations showed three end points corresponding to storng bases, weak bases and very weak bases (HNP : 700 mV). The nonaqueous potentiometric titrations suggested the presence of very weak, weak and strong basic functionalities in the asphaltenes which were due to indole, phenazine and pyridine groups, respectively. The proportions of these functionalities were higher in the higher alkane precipitated asphaltenes. The amounts of total titratable bases were 0.49 mM/g for nC5-precipitated asphaltenes and 0.60 mM/g for the nC10-precipitated asphaltenes from Arabian Heavy Crude Oil. The quantities of very weak bases of the indole type were high in these asphaltenes and represented about 50% of the total titratable bases.     

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。     

AGGREGATION OF ASPHALTENES OBTAINED FROM A BRAZILIAN CRUDE OIL IN AROMATIC SOLVENTS

Abstract

Surface and interfacial tensions in model systems formed by a Brazilian crude oil n-pentane insolubles (C5I) and n-heptane insolubles (C7I) in three different aromatic solvents: toluene, pyridine and nitrobenzene, were measured at room temperature, employing an automatic tensiometer and using the ring method. The results obtained indicated possible asphaltene aggregation and allowed the determination of critical micelle concentrations (c.m.c) for both C5I and C7I fractions in each of the three solvents considered. In toluene and pyridine solutions, the C5I fraction consistently presented higher c.m.c. values indicating a lower tendency of association for the organic fraction contained in the C5I, and absent in the C7I. In nitrobenzene solutions, this extra organic fraction appears to facilitate asphaltene association, possibly due to the formation of mixed aggregates. Average molecular areas for asphaltenes adsorbed at different interfaces were estimated using measured tensions and found to be in agreement with literature values and suggest a the flatwise surface adsorption of asphaltene molecules. This is consistent with the currently accepted stacking aggregation mechanism of asphaltenes.     

AGGREGATION OF ASPHALTENES OBTAINED FROM A BRAZILIAN CRUDE OIL IN AROMATIC SOLVENTS

Surface and interfacial tensions in model systems formed by a Brazilian crude oil n-pentane insolubles (C5I) and n-heptane insolubles (C7I) in three different aromatic solvents: toluene, pyridine and nitrobenzene, were measured at room temperature, employing an automatic tensiometer and using the ring method. The results obtained indicated possible asphaltene aggregation and allowed the determination of critical micelle concentrations (c.m.c) for both C5I and C7I fractions in each of the three solvents considered. In toluene and pyridine solutions, the C5I fraction consistently presented higher c.m.c. values indicating a lower tendency of association for the organic fraction contained in the C5I, and absent in the C7I. In nitrobenzene solutions, this extra organic fraction appears to facilitate asphaltene association, possibly due to the formation of mixed aggregates. Average molecular areas for asphaltenes adsorbed at different interfaces were estimated using measured tensions and found to be in agreement with literature values and suggest a the flatwise surface adsorption of asphaltene molecules. This is consistent with the currently accepted stacking aggregation mechanism of asphaltenes.     

试炼沙特阿拉伯轻质原油

介绍了单炼沙特阿拉伯轻质含硫原油时相应的一、二次加工装置的生产方案，物料平衡、产品质量及存在的问题。常减压蒸馏装置和固定床重整装置适应难度不大；加氢裂化装置主要是反应器温升大、氢耗大，不可能满负荷运行；焦化装置必须解决高硫焦的出路和相应产品的精制能力。单炼该油，则总流程还有个系统的硫平衡即硫磺回收装置实际能力的配套问题，如果硫磺回收能力偏小，酸性气和含硫污水就将过剩。     

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

ABSTRACT

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.     

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.     

沙中原油研制70号优质重交通道路沥青

镇海炼油化工公司, 选用蜡含量低的沙中原油为原料通过减压深拔、减压渣油调合糠醛精制抽出油、减压渣油浅度氧化三种途径研制７０号优质重交沥青, 取得了满意的结果     

用沙特阿拉伯中质原油经减压蒸馏研制70号高等级道路沥青

用沙特阿拉伯中质原油经常规实沸点蒸馏及燃料型减压分馏直接生产的70号沥青不能满足中国石化集团公司的1号高等级道路沥青AH－70标准。采用二次减压蒸馏工艺可以直馏生产70号高等级道路沥青,分析了残留低相对分子质量组分对高等级道路沥青性能的影响,沥青中蜡油残留得多,针入度比低。第一次减压蒸馏的深度不能过大,切割温度以不超过500℃为宜;第二次减压蒸馏需提高真空度,进料温度以不超过360℃为好。     

热解Tmax值在预测生油门限,地温和成熟度中的新应用

通过热解T_(max)值的ΔT_(max)值变化,对伊舒地堑探井进行了综合预测和评价。根据地温、镜质体反射率和T_(max)值的生油关系提出预测评价方法。该方法预测速度快,可超前预测,对石油勘探开发应用具有一定的参考意义。     

CHANGE OF PHYSICAL AND THERMAL DECOMPOSITION PROPERTIES OF IN SITU HEAVY OIL WITH STEAM TEMPERATURE

Ikiztepe crude oil was subjected to four different steam temperatures during steam injection which was applied as an enhanced oil recovery process on a linear limestone model saturated with oil. Produced oils were characterized using density, viscosity measurements, pyrolysis experiments utilizing TGA and elemental analysis runs. Results showed that produced crude oils change in measured characteristics as compared to the original oil. These changes include an increase in H/C, and cracking activation energy, decrease in density, viscosity and amount of residue remaining after cracking (coke). Also, decrease in asphaltene amount, changes in the elemental composition of asphaltenes and increase in the cracking activation energies were observed at 225 °C run. These measurements show that the produced oils get lighter and differ compositionally from the original oil as steam temperature increases. Decrease in elemental sulphur amount is one of the major changes when environmental considerations are concerned. Residual oil left in the limestone pack on the other hand shows an increase in the low temperature oxidation (LTO), fuel deposition (FD) and high temperature oxidation (HTO) activation energies as determined from TGA combustion experiments on the samples taken from the pack after steam injection experiments.     

CHANGE OF PHYSICAL AND THERMAL DECOMPOSITION PROPERTIES OF IN SITU HEAVY OIL WITH STEAM TEMPERATURE

ABSTRACT

Ikiztepe crude oil was subjected to four different steam temperatures during steam injection which was applied as an enhanced oil recovery process on a linear limestone model saturated with oil. Produced oils were characterized using density, viscosity measurements, pyrolysis experiments utilizing TGA and elemental analysis runs. Results showed that produced crude oils change in measured characteristics as compared to the original oil. These changes include an increase in H/C, and cracking activation energy, decrease in density, viscosity and amount of residue remaining after cracking (coke). Also, decrease in asphaltene amount, changes in the elemental composition of asphaltenes and increase in the cracking activation energies were observed at 225 °C run. These measurements show that the produced oils get lighter and differ compositionally from the original oil as steam temperature increases. Decrease in elemental sulphur amount is one of the major changes when environmental considerations are concerned. Residual oil left in the limestone pack on the other hand shows an increase in the low temperature oxidation (LTO), fuel deposition (FD) and high temperature oxidation (HTO) activation energies as determined from TGA combustion experiments on the samples taken from the pack after steam injection experiments.     

APPLICATION OF MULTICOLUMN VALVE SWITCHING GAS CHROMATOGRAPHY FOR THE ANALYSIS OF NAPHTHA AND KEROSENE FRACTIONS OF SAUDI ARABIAN LIGHT CRUDE OIL

Abstract

The straight run naphtha and kerosene fractions of Saudi Arabian Light crude oil were analyzed for paraffins, olefins, naphthenes and aromatics (PONA) using a gas chromatographic technique. This method is based upon group type separation according to carbon numbers using a programmed multiple valve switching sequence and employing multicolumn approach. The chromatographic operating conditions and carrier gas flow rates were selected to determine PONA contents of naphtha and kerosene fractions. These straight run fractions were produced by an automatic true boiling point (TBP) apparatus. Boiling range distributions of these fractions were determined using a standard ASTM method of simulated distillation. PONA results were compared with the literature. Total paraffins, naphthenes and aromatics agreed with each other.     

CHARACTERIZATION OF ASPHALTENES AND RESINS FROM PROBLEMATIC MEXICAN CRUDE OILS

Asphaltenes and resins have been separated from four mexican oils suffering from the deposition of asphaltenic material during recovery operations. A SARA separation of the oils was performed and the resins and asphaltenes further analyzed. Characterization methods employed were FTIR, elemental composition both of CHNSO, and trace metals and molecular weight determination using size exclusion chromatography. NMR techniques were applied to two asphaltene samples. The overall scope of the work was to get a better understanding of the nature of the asphaltene stability at a molecular level in these problematic oils. Separation of resin in two fractions indicates that there is no long alkyl chains in these as given by FTIR, which may be the cause of the lack of stability along with the large difference in bubble point and reservoir pressure.     

APPLICATION OF MULTICOLUMN VALVE SWITCHING GAS CHROMATOGRAPHY FOR THE ANALYSIS OF NAPHTHA AND KEROSENE FRACTIONS OF SAUDI ARABIAN LIGHT CRUDE OIL

The straight run naphtha and kerosene fractions of Saudi Arabian Light crude oil were analyzed for paraffins, olefins, naphthenes and aromatics (PONA) using a gas chromatographic technique. This method is based upon group type separation according to carbon numbers using a programmed multiple valve switching sequence and employing multicolumn approach. The chromatographic operating conditions and carrier gas flow rates were selected to determine PONA contents of naphtha and kerosene fractions. These straight run fractions were produced by an automatic true boiling point (TBP) apparatus. Boiling range distributions of these fractions were determined using a standard ASTM method of simulated distillation. PONA results were compared with the literature. Total paraffins, naphthenes and aromatics agreed with each other.     

CHARACTERIZATION OF ASPHALTENES AND RESINS FROM PROBLEMATIC MEXICAN CRUDE OILS

Asphaltenes and resins have been separated from four mexican oils suffering from the deposition of asphaltenic material during recovery operations. A SARA separation of the oils was performed and the resins and asphaltenes further analyzed. Characterization methods employed were FTIR, elemental composition both of CHNSO, and trace metals and molecular weight determination using size exclusion chromatography. NMR techniques were applied to two asphaltene samples. The overall scope of the work was to get a better understanding of the nature of the asphaltene stability at a molecular level in these problematic oils. Separation of resin in two fractions indicates that there is no long alkyl chains in these as given by FTIR, which may be the cause of the lack of stability along with the large difference in bubble point and reservoir pressure.

     

沙轻减渣与油浆丁脱沥青制备高等级道路沥青的研究

溶剂沥青是一种有效的渣同深加工工艺。本文对沙轻减渣与催化裂化油浆的混合物的脱油沥青调和重交沥青的可行性进行了研究。结果表明：沙轻减渣与催化裂化油浆混合物溶剂沥青得到的脱油沥青与减渣可以调和出各种牌号的高等级道路沥青。