Oil Shale Kerogen Research Articles

STEAM PYROLYSIS OF BULGARIAN OIL SHALE KEROGEN

The effect of water vapor on the yield and composition of products formed at thermal treatment of Bulgarian oil shale kerogen at atmospheric pressure has been studied. It was found that water steam reacts with oil shale organic matter significantly affecting the yield and composition of liquid and gaseous products. As for the yield of liquid products, it is about 20% higher than the yield obtained at Fischer Assay. The yield of semicoke is about 10% less. Liquid products formed in the presence of water vapor are richer in aromatic and aliphatic hydrocarbons among which long-chain paraffins with up to 33 carbon atoms predominate.

Kinetic and mechanism of Tarfaya (Morocco) oil shale and LDPE mixture pyrolysis

A kinetic study of the pyrolysis of oil shale mixed with LDPE was carried out by thermogravimetric analysis (TGA). Different runs were performed at heating rates between 2 and 50 K min −1. The results obtained from this comprehensive investigation indicated that they are three main degradation steps and the increase in the heating rate caused a lateral shift in the thermograms. The difference of weight loss ( Δ w ) between experimental and theoretical, calculated as algebraic sums of the mixture for different heating rates of 2, 10, 20 and 50 K min −1, is about 8–11% at 670–840 K. These experimental results indicate a significant synergistic effect during pyrolysis of oil shale mixed with LDPE. Kissinger–Akahira–Sunose method, Friedman's method, Flynn–Wall–Ozawa method and Coats–Redfern have been used to determine the activation energies of materials degradation. The analyses of the processes mechanism of materials by Criado et al. method and Coats–Redfern method showed: the most probable model for the pyrolysis process of oil shale kerogen agrees with diffusion model (D4 mechanism); and the thermal degradation process of LDPE goes to a mechanism involving “Contracting cylinder” model (R2 mechanism), whereas the mixture degrades following a kinetic model of D4.

Combined Process of Solvent Extraction and Gamma-Ray Radiation for the Extraction of Oil from Oil Shale

Jordanian oil shale kerogen was studied by using several solvents under the gamma radiation condition to extract oil from shale. According to the result obtained, the possibility to extract oil at room temperature and using solvent was successfully obtained. The solvent used in this research study was water, benzene, acetone and kerosene. Experiments was conducted by using a mixture of solvents such acetone water, benzene-acetone, benzene-kerosene, and benzene, kerosene, water alone without mixing. The percentage of yield was found to be with in the range of 13–67. The result showed that acetone-water solvent mixture with 50% of each (vol%) gives the best results. In this study, the particle size was fixed at 1mm size since there was no effect size on extraction yield percentage.

KINETICS OF CO-PYROLYSIS OF TARFAYA (MOROCCO) OIL SHALE WITH HIGH-DENSITY POLYETHYLENE

Pyrolysis kinetics of oil shale mixed with high-density polyethylene (HDPE) was investigated using a thermogravimetric analysis (TGA) system at various heating rates of 2, 10, 20 and 50 K/min in the temperature range of 300-1273 K in the nitrogen atmosphere. Kissinger-Akahira-Sunose, Friedman, Flynn-Wall-Ozawa and Coats–Redfern methods have been used to determine activation energies of materials degradation. The analysis of the process mechanism by Criado and Coats-Redfern methods showed the following: the mechanism of thermal degradation process of HDPE is describable by the ”Contracting cylinder” model (R2 mechanism); and the most probable model for the pyrolysis process of oil shale kerogen is the diffusion model (D4 mechanism), while the mixture degrades following the kinetic model of D4. It has been found that during thermal decomposition of oil shale/HDPE mixture no significant interaction of solid-phase components had taken place under the experimental conditions investigated.

Kinetic studies of oxidation of residual carbon from moroccan oil shale kerogens

Residual carbons from kerogen extracted from two Moroccan oil shales (from Timahdit and Tarfaya) were oxidized in air. The oxidations were studied by isothermal thermogravimetry. Several kinetic models for mechanisms of the reactions were tested to fit the experimental data. Oxidation of the residual carbon derived from Timahdit oil shale followed a two-third order reaction with an activation energy of 58.5 kJ mol–1, whilst that from Tarfaya oil shale was a half order reaction with activation energy of 64.1 kJ mol–1.

Non-isothermal kinetics of gasification by CO2of residual carbon from timahdit and tarfaya oil shale kerogens

Abstract The gasification with carbon dioxide of residual carbons prepared from Timahdit and Tarfaya oil shale kerogens has been studied by thermal analysis techniques (TG and DTA) under heating rates varying from 5 to 48C min-1. The reactions obey first order kinetics. Activation energies have been calculated by several methods, such as Kissinger, Chen-Nuttall and Coats-Redfern methods, and are broadly comparable with literature data for similar carbons.

03/02161 Liquefaction of Estonian oil shale kerogen in sub- and supercritical ether medium 2. Composition of liquid products: Luik, H. et al. Oil Shale, 2002, 19, (4), 355–372

03/02161 Liquefaction of Estonian oil shale kerogen in sub- and supercritical ether medium 2. Composition of liquid products: Luik, H. et al. Oil Shale, 2002, 19, (4), 355–372

Solvent swelling studies of Göynük (Kerogen Type-I) and Beypazarı oil shales (Kerogen Type-II) ☆

The volumetric swelling procedure was applied to Göynük and Beypazarı oil shales from Turkey by using 10 solvents and the cross-linking in the macromolecular network of oil shales were investigated using this technique. Results from solvent swelling measurements show that the volumetric solvent swelling of oil shales samples roughly follows the regular solution theory. The theory of solvent swelling of cross-linked polymers developed Flory–Rehner and extension of this theory by Kovac–Peppas was used to calculate number average molecular weight per cross-link of kerogen structure ( M ̄ c ) in oil shale samples. Results indicate no remarkable difference between M ̄ c values for Göynük oil shale (Kerogen Type I) and Beypazarı oil shale (Kerogen Type II).

CLASSIFICATION OF ALIPHATIC HYDROCARBONS FORMED AT TEMPERATURE-PROGRAMMED CO-PYROLYSIS OF TURKISH OIL SHALES OF KEROGEN TYPES I AND II

Temperature-programmed co-pyrolysis of Goynuk and Beypazari oil shales was investigated with the aim to determine volatile product distribution and product evolution rate of co-processing. A series co-pyrolysis operation was performed using three total carbon ratios. A fixed-bed reactor was used to pyrolyse small samples of oil shale mixtures under an inert gas (argon) flow. A special sampling technique was used for collecting organic products formed at different temperature and time intervals. The co-pyrolysis products were analyzed by capillary gas chromatography and the total product evolution rate was investigated as a function of temperature and time. n-Paraffins and 1-olefins in aliphatic fraction of pyrolysis products were classified by their carbon number. In addition, the recovery of total organic carbon as an organic volatile product was determined. The effect of co-processing was determined comparing the results with the data of their separate pyrolysis. The effect of oil shale kerogen type on co-pyrolysis operation was also investigated. Conversion into volatile hydrocarbons was found to lower with increasing Beypazari oil shale share in the mixture while the amounts of C1–C15 hydrocarbons and coke to increase in the presence of this oil shale.

The stereochemistry of bound and extractable pentacyclic triterpenoids during closed system pyrolysis

The distributions of hopanoic acids, ranging from C30 to C34, in the Messel oil shale were characterized in both the free and bound states. The bound acids were released by thermochemolysis in the presence of tetramethylammonium hydroxide (TMAH). These were compared with the distributions of the hopanoic acids and hopanes released or generated from Messel oil shale kerogen following closed system microscale pyrolysis. This comparison revealed that epimerization had occurred at C-17, C-21 and C-22 during heating. It was also clear that the residual bound hopanoic acids had undergone configurational isomerization. During the pyrolysis there is a large loss of hopanoic acids following their rapid release from the kerogen into the free fraction even at 250 °C. In these particular experiments this loss does not appear to result in exclusive formation of hopanes, by way of decarboxylation or reduction reactions, unless the resulting hopanes are either themselves rapidly transformed into other compounds or the reaction rates are a function of the total number of carbon atoms in each hopanoic acid precursor.

Study of pyrolysis kinetics of oil shale

The pyrolysis experiments on oil shale samples from Fushun, Maoming, Huangxian, China, and Colorado, USA, were carried out with the aid of thermogravimetric analyzer (TGA) at a constant heating rate of 5 °C/min. A kinetic model was developed which assumes several parallel first-order reactions with changed activation energies and frequency factors to describe the oil shale pyrolysis. The kinetic parameters of oil shale pyrolysis were determined on the basis of TGA data. The relationship between the kinetic parameters was further investigated and the correlation equations of x ∞– E and ln A– E were obtained. These equations show that the final fractional conversion of each parallel reaction, x ∞( j), can be expressed as an exponential function of the corresponding activation energy. The plot of ln A– E for different reactions becomes a straight line. These relationship equations can provide important information to understand the pyrolysis mechanism and to investigate the chemical structure of oil shale kerogen.

Kerogen-bound and free hopanoic acids in the Messel oil shale kerogen

Kerogen-bound and free hopanoic acids in the Messel oil shale kerogen

Structural study of the Moroccan Timahdit (Y-layer) oil shale kerogen using chemical degradations

Source rock screening reveals five laterally extending potential sources (PS) in the Paleogene. The PSs are SR5 and SR6 in dominantly marine early Eocene to late Paleocene Cambay Shale formation, and SR7, SR8/9, and SR11/12 in dominantly freshwater early Paleocene Olpad formation. Only 3 PSs, SR11/12, SR8/9, and SR7 have attained vitrinite reflectance of 0.75% at 45, 7, and 2 mybp, respectively. Chromatographic and isotope data of oils and PS samples suggest that mainly the Olpad source rocks: SR7 and SR8/9 contributed to the discovered oils. The Cambay Shale source rocks, SR5 and SR6, contrary to the prevalent view, possibly have no significant contribution towards the accumulated oils.

Characterization of the Moroccan Timahdit (X-layer) oil shale kerogen using pyrolysis and thermally assisted hydrolysis and methylation

The organic matter of the Moroccan Timahdit (X-layer) oil shale (Upper Cretaceous), mainly present as kerogen (or insoluble organic matter), was investigated using spectroscopic and pyrolytic methods. FT-IR and NMR indicate a dominant aliphatic nature for the studied material with a significant abundance of O-containing chemical groups. GC analysis of classical flash pyrolysate afforded only linear hydrocarbons as alkene/alkane doublets giving confirmation that decarboxylation of carboxylic acid groups can be a dominant process under these conditions. Flash and preparative thermally assisted hydrolysis and methylation (THM as defined by Challinor) techniques indicated that ester groups are significantly involved in the fixation or cross-linking of aliphatic chains in the kerogen. The identified tetra- and pentacyclic triterpenoids gave evidence that the studied sediment is immature, the evolution stage corresponding to diagenesis with a limited isomerization of triterpanes. The mechanisms of bond cleavage appear to differ when using flash or preparative THM techniques, probably as a consequence of experimental (temperature) conditions. Flash and preparative THM should be considered as complementary techniques which can be very useful for the structural investigation of complex forms of organic matter.

Structural study of the Moroccan Timahdit (Y-layer) oil shale kerogen using chemical degradations

This paper deals with the structural characterization of the Moroccan Timahdit (Y-layer) oil shale kerogen. For this purpose, the kerogen concentrate was submitted to stepwise hydrolysis under phase transfer catalysis conditions. The results show that aliphatic and aromatic dicarboxylic acids are involved in the cross-linking of the kerogen matrix, acting as bridges, while aliphatic and aromatic monocarboxylic acids, and alcohols represent monosubstituents of the matrix. Aliphatic mono- and dicarboxylic acids are produced on ruthenium tetroxide oxidation of the kerogen. These acids arise from a variety of reactions including cleavage of ester linkages. 17α(H),21β(H)- and 17β(H),21α(H)-hopanoic acids, probably bound to the kerogen by ether groups, were identified in the oxidation products.

Kerogen-bound and free hopanoic acids in the messel oil shale kerogen.

The distribution of the free and bound hopanoic acids in both unheated and heated (350 degrees C for 50 h) kerogens, isolated from the Messel oil shale, were analyzed by GC-MS. The bound acids were released by subjecting the kerogen to three different treatments, namely, thermochemolysis in the presence of tetramethylammonium hydroxide (TMAH), as well as basic and acidic hydrolyses. All of these methods gave a series of hopanoic acids ranging from C(30) to C(34), in which the biological 17beta, 21beta(H) configuration is prominent. Both 22R and 22S epimers are present for the C(30) acid, whereas the others are dominated by the sidechain 22R-configuration. Thermochemolysis in the presence of TMAH was the most efficient in releasing kerogen-bound hopanoids. Following pyrolysis, the acids are generated and released into the free fraction with apparent epimerization occurring at C-17, C-21, and C-22. The bound hopanoic acids may be both chemically bonded as well as possibly being physically encapsulated within the macromolecular fraction of sedimentary organic matter. They are therefore either generated by breaking the bonds which bind them to the kerogen or they are released as a result of the macromolecular cage being broken apart.

Predictive Heat Model for Australian Oil Shale Drying and Retorting

The exploitation of Australia's oil shale reserves has been the subject of much research over several decades. The extraction of oil from shale is usually a thermal process and therefore oil shale processing is dominated by heat-transfer and thermal reactions. To fully develop any oil shale processing technology, knowledge of an oil shale's thermodynamic properties is desirable. This paper presents a novel approach for the determination of an oil shale's thermodynamic properties and subsequent development of a predictive heat model. This approach involves experimental determination of the thermodynamic properties of an oil shale's individual components, in particular, the unique kerogen and clay minerals in Australian oil shale. The experimental data was then used to develop a predictive heat model for Australian oil shale based upon its kerogen and mineral, composition, and concentrations. The predictive heat model allows investigation of heat capacity, enthalpy, and total enthalpy for Australian oil shale during the process temperatures of drying and retorting.

Influence of depyritization on NMR relaxation parameters of Aleksinac oil shale kerogen

Parallel proton and cross-polarization/magic-angle spinning (CP/MAS) nuclear magnetic resonance (NMR) relaxation measurements are reported on Aleksinac oil shale kerogen concentrate and pyrite-free kerogen concentrate. Possible relaxation mechanisms considered include proton-proton and 13C-proton interactions. The influence of depyritization on relaxation parameters is estimated. Depyritization prolongs the T 1H relaxation time constant by about five times. However, depyritization has no significant influence on relaxation in the rotating frame (<5%). The probable explanation is that there is a certain motion of structural units with spectral density in the kHz region, which averages dipolar interactions between protons and pyrite. The repetition delay is found to be 150 ms for kerogen concentrate and 1–2 s for depyritized kerogen concentrate. The favourable value of contact time is identical for both samples, i.e., 1 ms. At the same time there are no significant changes observed in the CP/MAS spectra of Aleksinac oil shale kerogen due to depyritization treatment, except for a small band (≈60 ppm) assigned to alcoholic groups which appeared as a result of the partial reduction of carbonyl groups. Use of the pyrite-containing B 6 sample in solid-state NMR investigations is found to be more favourable because of its shorter T 1H relaxation time and, consequently, shorter (by a factor of about five) experimental time.

Nitrogen Fate during Laboratory Maturation of a Type I Kerogen (Oligocene, Turkey) and Related Algaenan: Nitrogen Mass Balances and Timing of N2 Production versus Other Gases

Parallel pyrolytic studies were carried out on an immature, ultralaminae-rich, type I kerogen (Goynuk oil shale kerogen) and a related algaenan (isolated from the extant green microalga Scenedesmus...

Evidence for porphyrins bound, via ester bonds, to the Messel oil shale kerogen by selective chemical degradation experiments

High amounts of nickel mono- and di-acid porphyrins were released from Messel oil shale kerogen (Eocene, Germany) by selective chemical degradation (acid and base hydrolysis). The released porphyrin fractions were quantified (UV-vis) and their constituents isolated and characterized at the molecular level (UV-vis, MS, NMR). The mono-acid porphyrin fraction released contained four compounds of similar abundance which arise from an obvious chlorophyll or bacteriochlorophyll precursor. The di-acid porphyrin fraction was, however, dominated by far by one compound, mesoporphyrin IX, which must have originated from heme-like precursors (heme, cytochromes, etc.). These results show unambigously that the released mono- and di-acid porphyrins were linked to the macromolecular kerogen network via ester bonds and suggest that precursor heme-like pigments could be selectively and/or more readily incorporated into the macromolecular kerogen network than precursor chlorophylls and bacteriochlorophylls.