SUPERCRITICAL EXTRACTION OF ISRAELI MISHOR ROTEM OIL SHALE 1. BATCH EXTRACTION WITH TOLUENE

Recovery of organic material from Israeli Mishor Rotem oil shale with toluene under supercritical conditions was investigated. The rate of solubilization, change of structural aspects and molecular weights of solubilized products with time were investigated. Experiments to recover organic material from shale were performed in a stainless steel high pressure autoclave. Shale Sample was charged in a sintered glass crucible suspended from the cap of the autoclave; toluene was the solvent in all experiments. Solvent/shale ratio was 20; experimental temperature was 34O^°C. The gaseous products were analyzed by gas chromatography. Molecular weights of the organic material recovered was measured by gel permeation chromatography technique. FTIR spectra of the organic material recovered and fractions isolated by extractive and chromatographical methods were measured. The amount of kerogen remaining in the spent shale was determined by oxidative derivative thermal gravimetry. A steady state in the production of solubles was reached within 60 minutes at 340^°C with a yield of 60 percent. After this time no further amounts of organic material was recovered. The molecular weights of the recovered organic material decreased at extended times after the steady state was reached. It appeared that the structure of the organic material recovered remained unchanged until the steady state condition is reached whereupon some structural changes occurred. At extended times the organic material was converted into more aromatic and less hydroxyl containing structures of lower molecular weight. The organic material recovered upon reaching steady state was fractionated into 63 percent oils (pentane solubles) and 32 percent asphaltenes (toluene solubles). The oile contained aliphatics and monoaromatic structures and the asphaltenes contained polyaromatic polar structures. Gases which constituted 4 percent of the initial kerogen were produced during the heating period to 340^°C. The amount of carbon monoxide produced remained constant and amounts of hydrogen, carbon dioxide and methane decreased after supercritical conditions were attained.     

RECOVERY OF ORGANIC MATERIAL BY SUPERCRITICAL TOLUENE FROM TURKISH GOYNOK OIL SHALE 1. IDENTIFICATION OF THE MINERALS AND THEIR EFFECT ON THE RECOVERY OF OKGANIC MATERIAL

ABSTRACT

Effect of the mineral matrix on the recovery of organic material by supercritical toluene extraction from Turkish Göynük oil shale was investigated. Samples were prepared by successive demineralization procedures to study the interaction of different mineral groups during the supercritical interaction. Extraction experiments were done in a stainless steel autoclave of 75 ml capacity at 350^°C for 60 minutes. Effect of the toluene/kerogon ratio and reaction time on the recovery of organic material was studied. Infrared spectra of the spent material uere measured to determine the structure of the organic material remaining after the supercritical treatment. The inorganic matrix of the shale was composed of calcite, silicate and pyrite minerals. Recovery of the organic material in the supercritical extraction experiments increased from 42% to 98% as the toluene/kerogen ratio was increased from 23.5 to 275. The extent of depolymerization seemed to be dependent on the to!uene/kerogen ratio and this suggested the possible cleavage of bonds due to solvent attack. Dissolution of carbonates and. Silicates decreased the organic material recovery extensively. The organic material recovered from the carbonate–free shale were about 50% lower than the organic material recovered from the original shale. Removal of pyrites did not affect the recovery of the organic matter. Percentage of the organic material recovered increased when CaCO₃ Or SiO₂ was added to kerogen and silicate free shale. These findings indicated that carbonate and silicate ninerals originally present in the shale might increase the organic matter recovery by supercritical toluene extraction. The raise of the toluene/kerogen ratio yielded more polar organic material. The aliphatic content of the recovered material was not affected by an increase in the toluene/kerogen ratio.     

RECOVERY OF ORGANIC MATTER FROM GREEN RIVER OIL SHALE AT TEMPERATURES OF 400°C AND BELOW

ABSTRACT

Experiments to recover organic matter from Green River oil shale in high yields at temperatures of 400^°C and below are described. Three different recovery procedures are discussed: 1) experiments wherein liquid organic materials were extracted at atmospheric pressure and temperatures below 75^°C by solvents of different strengths, 2) autoclave experiments where liquid organics were recovered by heating the shale with a variety of solvents at temperatures between 300 and 400^°C and pressures between 5 and 32 MPa, and 3) an autoclave experiment where liquid organics were recovered by heating shale in an argon atmosphere for 1 hour at 400^°C. The liquid organic materials recovered in these experiments represent from four to 90 weight percent of the total organic material in the shale. The liquid organic materials have an average molecular weight of between 500 and 600 amu as compared to a typical shale oil that has an average molecular weight of 300 to 350 amu. Elemental analyses show that the liquid organic materials contain high percentages of hydrogen and nitrogen, as does shale oil. Moreover, the liquid organic materials also contain much larger concentrations of oxygen-containing compounds than shale oil. The experimental results suggest the possibility of developing a new process for recovering both organic and inorganic material from Green River shale.     

SUPERCRITICAL FLUID EXTRACTION OF TURKISH LIGNITES AND OIL SHALE WITH TOLUENE MIXTURES

Abstract

Supercritical -Fluid extraction (SFE) of two Turkish lignites and oil shale with toluene mixtures were investigated. Experiments were performed in a batch autoclave at 623 K. Extracts recovered from SFE were fractionated into oils, asphaltenes and preasphal-tenes by solvent extraction.

The conversion of lignites decreased with increasing n-pentane content in the mixture. The extraction yield and the products (oils, AS, PAS) increased with increasing n-pentane content in its range below 15 %

The conversion and the extract yield obtained from Cöynük ail shale is higher with toluene mixture than toluene.     

The material balance of organic matter of Domanic shale formation after thermal treatment

In this paper, we discuss the amount of generated gaseous and liquid hydrocarbons as a product of artificial maturation of organic matters of Domanic black shale. The material balance of organic matter for initial rock sample and after thermal treatment at 300 and 500?°С were estimated. The amount of generated liquid hydrocarbon was minimum at 500?°С. As a result of kerogen destruction, no asphaltenes were observed during generation of liquid hydrocarbons. Based on the results of elemental analysis, Van Krevelen diagram was plotted.     

CHARACTERIZATION OF ORGANIC MATTER RECOVERED FROM GREEN RIVER OIL SHALE AT TEMPERATURES OF 400°C AND BELOW

ABSTRACT

Organic matter extracted from Green River oil shale by supercritical extraction experiments was characterized by elemental analysis, number average molecular weight determination and field ionization mass spectrometry. The organic matter was also separated into fractions of organic acids, bases, and hydrocarbons. Characterization data demonstrate that the organic matter recovered in high yield from autoclave experiments is similar in composition to organic matter extracted in low yield at solvent reflux temperatures. The composition of organic matter extracted from Green River shale by supercritical techniques is compared with the composition of Green River shale oil produced by several pilot-scale retorting processes.     

SEPARATION OF ASPHALTENES BY POLARITY USING LIQUID-LIQUID EXTRACTION

ABSTRACT

In order to investigate the nature of petroleum asphaltenes in terms of polarity a process was developed using initial liquid-liquid extraction of the oil phase followed by precipitation of the asphaltenes using n-heptane. The liquid-liquid extraction was performed using toluene-methanol mixtures with increasing content of toluene. Although large fractions of the crude oil (Alaska '93) was extracted in the higher polarity solvents (high concentration of methanol), the asphaltene content of the dissolved material was low As the toluene content increased more asphaltenes were transferred to the solvent phase. The asphaltenes were analysed using FTir, Elemental analysis, and HPLC-SEC with a diode array detector. With increasing content of toluene in the methanol the molecular weight distribution of the asphaltenes significantly move to higher molecular weights. The content of nitrogen and sulfur of the mallene phase also increase while H/C decreases. The content of heteroatoms in the asphaltenes are relatively higher and apparently increase with the polarity of the solvent. It is concluded that these asphaltenes are indeed dominated by high molecular weight substances that cannot be extracted in the high polarity solvents     

RECOVERY OF ORGANIC MATTER FROM GREEN RIVER OIL SHALE AT TEMPERATURES OF 400°C AND BELOW

Experiments to recover organic matter from Green River oil shale in high yields at temperatures of 400^°C and below are described. Three different recovery procedures are discussed: 1) experiments wherein liquid organic materials were extracted at atmospheric pressure and temperatures below 75^°C by solvents of different strengths, 2) autoclave experiments where liquid organics were recovered by heating the shale with a variety of solvents at temperatures between 300 and 400^°C and pressures between 5 and 32 MPa, and 3) an autoclave experiment where liquid organics were recovered by heating shale in an argon atmosphere for 1 hour at 400^°C. The liquid organic materials recovered in these experiments represent from four to 90 weight percent of the total organic material in the shale. The liquid organic materials have an average molecular weight of between 500 and 600 amu as compared to a typical shale oil that has an average molecular weight of 300 to 350 amu. Elemental analyses show that the liquid organic materials contain high percentages of hydrogen and nitrogen, as does shale oil. Moreover, the liquid organic materials also contain much larger concentrations of oxygen-containing compounds than shale oil. The experimental results suggest the possibility of developing a new process for recovering both organic and inorganic material from Green River shale.     

CHARACTERIZATION OF ORGANIC MATTER RECOVERED FROM GREEN RIVER OIL SHALE AT TEMPERATURES OF 400°C AND BELOW

Organic matter extracted from Green River oil shale by supercritical extraction experiments was characterized by elemental analysis, number average molecular weight determination and field ionization mass spectrometry. The organic matter was also separated into fractions of organic acids, bases, and hydrocarbons. Characterization data demonstrate that the organic matter recovered in high yield from autoclave experiments is similar in composition to organic matter extracted in low yield at solvent reflux temperatures. The composition of organic matter extracted from Green River shale by supercritical techniques is compared with the composition of Green River shale oil produced by several pilot-scale retorting processes.     

Variation in Composition of Subfractions of Petroleum Asphaltenes

ABSTRACT

Boscan asphaltenes were precipitated from the crude oil using mixtures of toluene and heptane at temperatures of 24, 50, and 80°C. Another process of extracting solid n-heptane asphaltenes (24°C) using the same solvent systems and temperatures was also investigated. Asphaltene yield is different by the two processes at similar conditions although both increases in temperature or toluene content lead to lower solid yield. This way the asphaltene continuum was investigated from incipient flocculation to total n-heptane precipitated asphaltenes. The asphaltenes were analyzed using elemental analysis, fluorescence spectroscopy, vapor pressure osmometry, and HPLC size exclusion chromatography. The distribution of porphyrins was also measured using absor-bance spectroscopy. The asphaltenes were found to follow a regular trend in elemental ratios, H/C and N/C, indicating increased aromaticity and nitrogen content as the solid yield decreases. Also the molecular weight was seen to increase. Size exclusion chro-matograms and fluorescence spectra were found to be different comparing solids from the two separation processes. This indicates that the asphaltene fractions obtained by extraction of solid asphaltenes are altered relative to asphaltenes obtained by ordinary precipitation. The porphyrin concentration was found to diminish rapidly with solid yield decrease in both precipitation and extraction experiments, the latter fractions, however, containing significantly less asphaltenes indicating an adsorption step in the coprecipitation of porphyrins. Soluble fractions were found to exhibit relatively low molecular weights and an apparent lack of indications of association up to a point of solubles exceeding 50 % of the total asphaltenes. The-latter have implications for the further understanding and experimental investigation. of the associating nature of asphaltenes such as concentration effects during analytical characterization.     

RECOVERY OF ASPHALTENES FROM TAR SAND BY SUPERCRITICAL FLUID EXTRACTION

ABSTRACT

Many non-oil producing countries are enriched with other sources of energy, for example tar sand, oil shale, coal, biomass, and uranium, that are not fully utilized. Supercritical fluid extraction (SFE) of tar sand was carried out in a batch autoclave at different temperatures. Extracts recovered from SFE were fractionated into oils, asphaltenes, preasphaltenes and gases by solvent extraction. The highest yield) of SFE (24.3 wt % dry basis) from tar sand was obtained with n-pentane/benzene (1/1, v/v’) mixture at 655 K. Comparison of the amount of n-alkanes (C1–C4) evolved at 585 K and 685 K shows that the amount of methane is significantly increased at 685 K whereas the amount of C4 alkane is reduced. At 685 K, hydrogen and methane represent 45·1 vol % of the gases evolved from the SFE. The yields of C1–C3 alkane hydrocarbons were higher for supercritical fluid extracts at 685 K as compared to those obtained at 585 K. The quantity of olefines (C₂H₄ + C₃H₆) was found between 5·1 and 10·1 vol %.     

RECOVERY OF ASPHALTENES FROM TAR SAND BY SUPERCRITICAL FLUID EXTRACTION

Many non-oil producing countries are enriched with other sources of energy, for example tar sand, oil shale, coal, biomass, and uranium, that are not fully utilized. Supercritical fluid extraction (SFE) of tar sand was carried out in a batch autoclave at different temperatures. Extracts recovered from SFE were fractionated into oils, asphaltenes, preasphaltenes and gases by solvent extraction. The highest yield) of SFE (24.3 wt % dry basis) from tar sand was obtained with n-pentane/benzene (1/1, v/v') mixture at 655 K. Comparison of the amount of n-alkanes (C1-C4) evolved at 585 K and 685 K shows that the amount of methane is significantly increased at 685 K whereas the amount of C4 alkane is reduced. At 685 K, hydrogen and methane represent 45·1 vol % of the gases evolved from the SFE. The yields of C1-C3 alkane hydrocarbons were higher for supercritical fluid extracts at 685 K as compared to those obtained at 585 K. The quantity of olefines (C₂H₄ + C₃H₆) was found between 5·1 and 10·1 vol %.     

SEPARATION OF ASPHALTENES BY POLARITY USING LIQUID-LIQUID EXTRACTION

In order to investigate the nature of petroleum asphaltenes in terms of polarity a process was developed using initial liquid-liquid extraction of the oil phase followed by precipitation of the asphaltenes using n-heptane. The liquid-liquid extraction was performed using toluene-methanol mixtures with increasing content of toluene. Although large fractions of the crude oil (Alaska '93) was extracted in the higher polarity solvents (high concentration of methanol), the asphaltene content of the dissolved material was low As the toluene content increased more asphaltenes were transferred to the solvent phase. The asphaltenes were analysed using FTir, Elemental analysis, and HPLC-SEC with a diode array detector. With increasing content of toluene in the methanol the molecular weight distribution of the asphaltenes significantly move to higher molecular weights. The content of nitrogen and sulfur of the mallene phase also increase while H/C decreases. The content of heteroatoms in the asphaltenes are relatively higher and apparently increase with the polarity of the solvent. It is concluded that these asphaltenes are indeed dominated by high molecular weight substances that cannot be extracted in the high polarity solvents     

VARIATION IN THE CHEMICAL NATURE OF ASPHALTENES WITH THE PROCESS,THE COAL AND THE REACTION CONDITIONS

ABSTRACT

Average structure data for twelve asphaltenes are reported, based on ¹³C- and H- n.m.r. spectroscopy combined with elemental, molecular weight and functional group analyses. The asphaltenes were from supercritical gas extraction, flash pyrolysis and hydrogenation of a brown and a bituminous coal. The effect of the reaction temperature and, for hydrogenation, the catalyst and solvent on the nature of the asphaltene produced was studied. The asphaltene obtained from supercritical gas extraction of the brown coal at 350°C was the least aromatic (f_a = 0.44) with the highest H/C atomic ratio (1.16) and probably consists mainly of single ring aromatlcs with about half of the aromatic sites substituted. A significant proportion of the carbon in this asphaltene is in long alkyl chains and the hydroxyl content is high. Whereas, the asphaltenes produced by hydrogenatlon of the bituminous coal at 450°C were far more aromatic with more highly condensed but less substituted aromatic ring systems and few, if any, long alkyl chains, together with a lower hydroxyl content. The asphaltenes obtained from the brown coal are less aromatic with less condensed aromatic ring systems but a higher degree of aromatic substitution than those produced from the bituminous coal under the same conditions. The asphaltenes formed at 450°C had lower H/C atomic ratios, molecular weights and degree of aromatic substitution, but higher aromaticities Ohan those produced at 35O°C or 400°C under like processing conditions. The asphaltene produced in the presence of both stannous chloride catalyst and tetralin was less aromatic than when either of these species was absent.     

Variation in Composition of Subfractions of Petroleum Asphaltenes

Boscan asphaltenes were precipitated from the crude oil using mixtures of toluene and heptane at temperatures of 24, 50, and 80°C. Another process of extracting solid n-heptane asphaltenes (24°C) using the same solvent systems and temperatures was also investigated. Asphaltene yield is different by the two processes at similar conditions although both increases in temperature or toluene content lead to lower solid yield. This way the asphaltene continuum was investigated from incipient flocculation to total n-heptane precipitated asphaltenes. The asphaltenes were analyzed using elemental analysis, fluorescence spectroscopy, vapor pressure osmometry, and HPLC size exclusion chromatography. The distribution of porphyrins was also measured using absor-bance spectroscopy. The asphaltenes were found to follow a regular trend in elemental ratios, H/C and N/C, indicating increased aromaticity and nitrogen content as the solid yield decreases. Also the molecular weight was seen to increase. Size exclusion chro-matograms and fluorescence spectra were found to be different comparing solids from the two separation processes. This indicates that the asphaltene fractions obtained by extraction of solid asphaltenes are altered relative to asphaltenes obtained by ordinary precipitation. The porphyrin concentration was found to diminish rapidly with solid yield decrease in both precipitation and extraction experiments, the latter fractions, however, containing significantly less asphaltenes indicating an adsorption step in the coprecipitation of porphyrins. Soluble fractions were found to exhibit relatively low molecular weights and an apparent lack of indications of association up to a point of solubles exceeding 50 % of the total asphaltenes. The-latter have implications for the further understanding and experimental investigation. of the associating nature of asphaltenes such as concentration effects during analytical characterization.     

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.     

OXYGENIC KEROGENIZATION OF ASPHALTENES FROM THE DEAD SEA BASIN (ISRAEL)

A kerogen-like material was generated during a laboratory heating experiment with asphaltenes in the presence of O₂. The asphaltenes had been extracted from a floating block of Dead Sea asphalt, and heated at 100 - 200 C for 1–12 days. This oxygenic kerogenization reaction follows first-order kinetics. The half-life (t_1/2) of the asphaltenes (i.e. the time in which 50% of the asphaltenes had been converted to artificial kerogen) varied from 2,300 days at OC, to 2 days at 100 C. Similar results were obtained with asphaltenes which had been extracted from a number of bitumen-bearing rocks in the Dead Sea area (from the Amiaz, Ein Boqeq, Nebi Mussa and Ef'e boreholes), and also from sandstones from the Heimar and IPRG boreholes which were impregnated with heavy or asphaltic crudes.
These and other results suggest that low-temperature (≤100C) oxygenic kerogenization of Dead Sea asphaltenes (with or without the mediation of meteoric waters) may be a pathway for the formation of kerogen. Asphaltenes extracted from other bituminous rocks — the La Luna limestone (U. Cretaceous, Venezuela); the Serpiano marl (M. Triassic, Switzerland); the Messel shale (Tertiary, Germany); and the Aleksinac shale (Tertiary, Yugoslavia) — underwent laboratory kerogenization in a similar fashion to the Dead Sea materials. This suggests that oxygenic kerogenization may be widespread in porous and fractured, bitumen-bearing rocks.     

Modeling of oil generation by Domanik carbonaceous shale

Experiments on artificial maturation of carbonaceous rock of the Domanik age in an autoclave in the presence of water at temperatures of 250, 275, 300 and 325°C have been performed. It has been shown that a significant amount of soluble organic matter (OM) is produced from insoluble OM under these conditions. Changes have been observed in both the biomarker composition of the bitumen and the Rock-Eval OM maturity parameters characteristic of natural catagenesis. By the solid-state ¹³C NMR technique, it has been shown that the amount of aliphatic units decreases and that of aromatic units increases in residual kerogen. Study the product composition of the pyrolysis of residual kerogen has revealed that the relative amount of precursors of n-alkyl structures increases as compared with low-molecular-weight aromatic and thiophenic structures.     

渝东南地区海相页岩有机质孔隙发育特征及演化

页岩气在储层内的有效赋存及渗流由有机质孔隙决定。由此,以渝东南地区下志留统龙马溪组和下寒武统牛蹄塘组高—过成熟度典型富有机质黑色海相页岩为研究对象,使用电子显微镜观察2套页岩层位的有机质孔隙结构。结果表明：龙马溪组页岩有机质孔隙主要发育在焦沥青内部,而固体干酪根内仅发育少量直径较小的有机质孔隙;牛蹄塘组页岩的焦沥青和固体干酪根均不发育有机质孔隙;2套页岩的总有机碳含量、全岩矿物组成及干酪根类型均具有相似特征,但牛蹄塘组页岩的热成熟度要远高于龙马溪组页岩,且已达到变质期,其固体干酪根和焦沥青的物理化学性质均趋近于石墨,导致其有机质内部不发育孔隙。过高的热成熟度不利于页岩中有机质孔隙的保存,所以渝东南地区下寒武统牛蹄塘组高—过成熟度海相页岩气的勘探开发应重点寻找热成熟度低于3.5%的地区。     

重庆周缘龙马溪组和牛蹄塘组页岩有机质孔隙发育特征

针对牛蹄塘组页岩气勘探开发过程中存在产气量较低,产气持续时间较短等问题,以渝东南下志留统龙马溪组页岩和渝东北下寒武统牛蹄塘组页岩为对象进行对比,重点剖析2套页岩的孔隙储集能力及其演化特征。结果表明：龙马溪组页岩和牛蹄塘组页岩的有机质孔隙发育特征存在较大差别：龙马溪组页岩内部的固体干酪根有机质孔隙数量少,孔径小,连通性差,但其焦沥青内部有机质孔隙数量多,孔径大,连通性好。牛蹄塘组页岩内部的固体干酪根和焦沥青均不发育有机质孔隙。储层热演化程度对页岩有机质孔隙的发育有着直接的控制作用。龙马溪组页岩由于古埋深较牛蹄塘组页岩浅,所经历的热演化作用相对较弱,适宜的热演化程度保留了龙马溪组页岩焦沥青内部大量的有机质孔隙,但其固体干酪根由于演化时间相对较长,有机质孔隙数量减少。渝东北牛蹄塘组页岩埋深过大,储层过度演化达到变质期导致其内部固体干酪根和焦沥青均不发育有机质孔隙。针对牛蹄塘组页岩气的高效勘探开发应寻找热演化程度适中的页岩分布区。