Oil Shale Kerogen Research Articles

Generation of Hydrocarbon Gases in Stepwise Pyrolysis of Artificially Matured Domanik Oil Shale Kerogen

Generation of Hydrocarbon Gases in Stepwise Pyrolysis of Artificially Matured Domanik Oil Shale Kerogen

Exploring the influence of external electric fields on the catalytic pyrolysis of oil shale kerogen molecules

Oil shale is a widely distributed and abundant sedimentary rock that can be converted into shale oil through pyrolysis, providing a supplementary solution to the increasing scarcity of conventional fossil energy. However, the traditional pyrolysis process of oil shale faces problems such as low oil yield, high energy consumption, and poor oil quality. Recent experiments have demonstrated that using an external electric field to catalyze the pyrolysis of oil shale can address these problems. However, due to the complex physical and chemical properties of oil shale and its pyrolysis process, the catalytic mechanisms and effects have not been reasonably explained. To address these issues, this study uses density functional theory to calculate the properties of oil shale molecules under external electric fields of different directions and strengths. The results indicate that at electric field strengths far exceeding experimental conditions, the external electric field does have a certain catalytic effect on oil shale, which varies depending on the molecule. However, at electric field strengths achievable in actual laboratory conditions, the catalytic effect of the electric field on oil shale is not significant. Therefore, the mechanisms revealed by past experiments on the catalytic effects of electric fields on oil shale pyrolysis may be partially flawed. This study not only fills the gap in understanding the mechanisms of external electric field catalysis of oil shale but also provides a theoretical foundation for future applications of electric fields in catalyzing oil shale.

Catalytic Conversion of Oil Shale over Fe or Ni Catalysts under Sub-Critical Water

Sub-critical water is an environment-friendly solvent. It is widely used for the extraction of various organic compounds. It can be used to dissolve and transport organic matter in oil shale. In this study, the conversion of oil shale was synergistically catalyzed by the addition of Fe or Ni to the Fe inherent in samples under sub-critical water conditions. Oil shale can be converted to gas, oil and residues of oil. Thermogravimetric (TG) analysis results presented that the weight loss of raw oil shale was up to 15.85%. After sub-critical water extraction, the weight loss rate of the residues was reduced to 8.41%. With the application of a metal catalyst, Fe or Ni, the weight loss of residues was further reduced to 7.43% and 6.57%, respectively. According to DTG curves, it was found that there were two weight-loss rate peaks. The decomposition process of kerogen in oil shale could be divided into two cracking processes. One is decomposed at a high velocity at around 420 °C, and another is decomposed at a low velocity at around 515 °C. Gas chromatography (GC) results of gas products indicated that Fe or Ni could contribute to producing normal alkanes, such as methane, ethane, propane, etc., which are produced by the hydrogenation of alkenes via hydrogen transfer during the conversion process of kerogen. Gas chromatography-mass spectrometry (GC–MS) was conducted to analyze the components of the liquid products. The results showed that n-alkanes, iso-alkane, oxygenated hydrocarbons and aromatic compounds were the major components of the kerogen cracking products. When Ni was introduced as a catalyst, the contents of aromatic compounds and oxygenated hydrocarbons in the liquid products were increased from 19.55% and 6.87% to 22.38% and 13.77%, respectively. This is due to the synergistic effect of the addition of Ni with the inherent Fe in oil shale under sub-critical water which ensures kerogen is more easily cracked to produce aromatic compounds and oxygenated hydrocarbons.

Pyrolysis behavior and pyrolysate characteristics of Huadian oil shale kerogen catalyzed by nickel-modified montmorillonite

Pyrolysis behavior and pyrolysate characteristics of Huadian oil shale kerogen catalyzed by nickel-modified montmorillonite

Deformation characteristics and exploration potential of the West Kunlun foreland fold-and-thrust belt

Deformation characteristics and exploration potential of the West Kunlun foreland fold-and-thrust belt

Effect of methanol on the pyrolysis behaviour of kerogen by ReaxFF molecular dynamics simulations

ABSTRACTA series of molecular dynamics simulations were performed using the ReaxFF reactive force field to investigate the pyrolysis of Longkou oil shale kerogen in the presence of methanol. The roles of methanol in kerogen pyrolysis were deeply explored to reveal the microscopic mechanism of methanolysis by analyzing the distribution of products, the consumption of methanol, and the formation processes of typical products at different temperatures. The results demonstrate that the yield of shale oil in the presence of methanol is consistently higher than that of kerogen direct pyrolysis at the same temperature, which is consistent with the trend of oil yield with temperature reported by previous methanolysis experiments. Methanol supplies a large number of small radicals under the pyrolysis condition, which can facilitate the breakage of weak bonds and take part in the formation of products through combining with the radical fragments generated by the pyrolysis of kerogen. This study will provide theoretical guidance for understanding the methanolysis process of oil shale.

Study on the kinetic-guided pyrolysis of oil shale kerogen catalyzed by needle-like NiFe-LDH

An in-depth understanding of the thermo-physicochemical behavior of kerogen catalytic pyrolysis is helpful to realize the efficient utilization of oil shale. In this work, the pyrolysis behavior of Barkol Kerogen and its product distribution were investigated by dry distilled experiment with needle-like NiFe-LDH as Catalyst, which was designed based on the kinetic experiments. As a result, NiFe-LDH has low-temperature and high-efficiency pyrolysis catalytic activity in the oil shale recovery and product selectivity. The initial pyrolysis catalytic temperature of kerogen was advanced to 250 °C, and the optimum pyrolysis temperature was decreased by 42.02 °C. The catalytic pyrolysis temperature was selected as 400 °C because of the maximum temperature weight loss in thermal analysis. NiFe-LDH not only increased the oil yield of kerogen by 5.18% and alkane selectivity by 2.62% but also reduced the content of heteroatomic hydrocarbon by 6.46%. Simultaneously, according to the change of activation energy during thermal analysis and the results of pyrolysis experiment, the catalytic pyrolysis process was speculatively divided into three possible stages. This resolution is helpful to understand the catalytic effect of NiFe-LDH on kerogen. Thus, NiFe-LDH plays a distinct role in the catalytic pyrolysis of kerogen and its kinetic regulation.

VARIABLE HYDROPYROLYSISREACTIVITY OF KEROGEN FROM TARFAYA OIL SHALE DEPOSIT (MOROCCO). MODELING IN HETEROGENEOUS KINETICS

Hydrogen treatment of oil shale kerogen is highly beneficial, firstly because it improves the yield of oil produced compared with pyrolysis, secondly because the oils produced are of light quality and thirdly because the kinetics of this heterogeneous reaction are simpler (A.Attaoui: 2023). The latter, often discussed in true thermogravimetry (dynamic regime), can be adapted to several mathematical models for processing values.In this work we are going to follow this primary hydropyrolysis reaction in the dynamic regime using thermogravimetry, and we are going to develop a method for processing the experimental values in order to access the energies of the different oil shale layers at different heating rates.The aim of this study is to establish the activation energy balance for the different layers of the Tafaya primary hydropyrolysis deposit. We used the Red-Croft thermobalance to carry out these reactions. We note the close dependence between the experimental technique, the data processing model and the activation energies search for.

Utilisation of raw oil shale as fine aggregate to replace natural sand in concrete: Microstructure, surface chemistry and macro properties

This study set out to examine the unconventional use of raw oil shale (OS) as fine aggregate in concrete instead of its traditional utilisation as a pollutant energy source aiming to hinder the depletion of natural resources. Oil shale particles have been used to replace sand in concrete with 30 wt.-% and 50 wt.-% ratios. Part of the used OS particles was treated with silane prior to their addition in concrete. The fresh, mechanical, and durability properties, along with the micro-properties and surface chemistry of mixtures, were analysed by running the slump, compressive strength, permeability, scanning electron microscopy (SEM) and fourier transform infrared spectroscopy (FTIR) tests, respectively. Five concrete mixtures consisting of 30 samples with the size of 150 mm x 150 mm x 150 mm were prepared to serve the testing programme of the study. The results revealed the formation of a well-bonded interfacial transition zone between untreated OS particles and the cementitious matrix due to the presence of pozzolanic materials in OS. However, micro cracks and enlarged capillary pores were witnessed in treated OS mixtures along with a weak interfacial transition zone between the treated OS and the cementitious matrix. Moreover, the use of 30 wt.-% untreated OS reduced the water absorption of concrete by 9% (absorption rate of 9.5%), while other mixtures experienced an increase in their water absorption with a maximum increase of 42% when using 50 wt.-% treated OS (absorption rate of 10.7%). All mixtures attained a reduction in their compressive strength compared to control sample when employing treated and untreated OS in concrete, with a minimum reduction of 13% when using 30 wt.-% untreated OS (compressive strength of 26 MPa). The strength reduction in untreated OS mixtures is due to the formation of free CaO and free SiO2, which promote concrete expansion. The interference between silane and kerogen in OS was the main reason behind the strength reduction in treated OS mixtures. However, this reduction in mixtures’ strength is considered minimal, allowing for their potential use in different construction applications like rigid pavement.

Unexpected Structural Effects on the Onset of Thermal Reactions of Aromatic Hydrocarbons

This work aims to study the reactivity of a broad range of aromatic hydrocarbons to better understand the reactivities of more complex hydrocarbon mixtures. A set of closed-system pyrolysis experiments were conducted on a diverse range of ∼30 polycyclic aromatic hydrocarbons (PAHs) at the thermal onset reaction temperature of 400 °C to understand structural effects on reactivities and shed light on the early events of thermal reaction mechanisms. Thermal transformations, including methyl transfer (alkylation/dealkylation), rearrangement, condensation, molecular growth, and other chemical transformations, are often indicated by dark carbon materials composed of complex mixtures. Thermal transformation was confirmed by phenomenological changes (color and solubility) and chemical analysis using nuclear magnetic resonance, thermogravimetric analysis, gas chromatography, and electron spin resonance. Unsubstituted PAHs (e.g., phenanthrene, anthracene, pyrene, chrysene, etc.) were unaffected by heating at this temperature, with the exception of tetracene and pentacene which readily transformed into dark and insoluble materials. The reactivity of these unsubstituted PAHs is consistent with aromaticity predicted by the Clar theory. On the contrary, most alkyl-substituted PAHs can be transformed into carbon materials at 400 °C; however, alkyl-substituted phenanthrenes (2,7-dimethyl, 2-ethyl, or 7-ethyl) and benzenes (xylenes and pentamethylbenzene) were unreactive. CH2-containing PAH molecules were unreactive if in a five-membered ring (e.g., fluorene and benzofluorene) but became reactive if in a six-membered ring (9,10-dihydroanthracene), likely as a result of aromatization of the latter. The reactivity of the aryl–aryl linkage depends upon the aromatic moieties to which it is connected. While it is unreactive when connecting phenyl groups, such as in p-terphenyl, it is reactive when connecting pyrenes, such as in 1,1′-bispyrene. These results were unexpected and challenge the conventional thinking about hydrocarbon reactivities. Explanations and possible hypotheses are proposed, but more questions remain unanswered to understand the structural effects on reactivities. These findings are conducive to the sustainable use of aromatic hydrocarbons for higher value carbon materials and relevant to numerous pyrolysis studies on oil shale kerogens, biomass, and waste plastics.

Oil shale kerogen-derived adsorbents and their application to trichloroethylene adsorption from aqueous solutions

This paper examines microporous oil shale kerogen-derived semicokes as potential sorbents for environmental cleanup applications. This carbonaceous residue (“semicoke”) left behind during the processing of oil shale kerogen is the main source of adsorptive potential in the processed oil shale. The surface area and porosity of model microporous semicokes were determined using N2 and CO2 adsorption techniques. The model semicoke material had a BET surface area of 494 m2/g of char (net of the minerals), which could be increased by mild thermal activation in the air at 698 K (425 °C) to 857 m2/g-char. The semicokes were tested as potential sorbents by measuring their efficacy at removing trichloroethylene (TCE) from aqueous solutions at 295 K in the concentration range from about 0.1 to 7 mg/L. TCE adsorption isotherms were determined for seven different sorbents – the model semicoke, the air-activated model semicoke, raw unprocessed oil shale, three commercially prepared semicokes, and, for reference, a commercial granulated activated carbon. The present results show that the kerogen-derived carbons have TCE adsorptive capacity values which are comparable to those of a commercial activated carbon (e.g., 70 mg/g-C). The results pointed to the importance of a particular micropore size range for adsorption. While air activation increased the pore volume and surface area of the materials as measured by nitrogen and carbon dioxide, this did not result in an increase in adsorptive capacity for TCE. The critical pore size appears to be in the range of 0.5–0.8 nm.

Molecular and experimental study on hydrogen sulfide formation mechanism during Chang 7 type-II oil shale kerogen pyrolysis

Hydrogen sulfide is a volatile toxic gas associated with oil and gas production, causing corrosion to surface equipment such as wellbores and doing harm to the environment. This study aims to investigate the formation mechanism of hydrogen sulfide during the pyrolysis process of Chang 7 type-II oil shale kerogen. XPS spectra are obtained with the usage of Kratos Analytical Axis UltraDLD to analyze the occurrence forms of hybrid atoms. S 2p XPS spectrum and its fitted curves are gained from full spectrum wide spectrum scanning and narrow spectrum scanning of the sulfur element. The pyrolysis characteristics and processes of kerogen with three initial structures under different temperatures are implemented with ReaxFF. The results of the hydrogen sulfide formation pathway are tracked. The sulfur element in Chang 7 II kerogen is mainly in the form of organic sulfur, with a molar ratio of 77.74%. The kerogen initial structure with fewer CC bonds containing more H atoms has a higher oil yield. The desulfurization rate sharply increases with the increase in pyrolysis temperature. Hydrogen sulfide production is affected by sulfur-containing functional groups (aliphatic sulfur, aromatic sulfur, sulfoxide, sulfone). Hydrogen sulfide formation paths mainly include capturing H radicals through HS radicals and capturing H radicals through high sulfur to form -SH2-.

Characterization of oil shale kerogen semi-coke and its application to remove chemical pollutants from aqueous solutions

Characterization of oil shale kerogen semi-coke and its application to remove chemical pollutants from aqueous solutions

The non-isothermal thermal decomposition evolution of the Fushun oil shale kerogen based on ReaxFF molecular dynamics simulation

The non-isothermal thermal decomposition evolution of the Fushun oil shale kerogen based on ReaxFF molecular dynamics simulation

The mechanism of H2O in the superheated steam affecting the quality of in-situ pyrolysates of oil shale kerogen: Part B-favorable conversion of residues

In this work, ReaxFF molecular dynamics (MD) simulation was applied to elucidate the enhancement effect of superheated steam on the conversion of residues into shale oil and gas during the initial pyrolysis of Barkol kerogen (BLK), and the corresponding mechanism was revealed. The weight loss rate (DTG) of BLK pyrolysis obtained from ReaxFF MD simulation agreed well with that form thermogravimetric experiment. Reaction pathways of the H2OSS molecules (SS refers the superheated steam) and partial C40+ obtained from the extracted residues were analyzed. The results indicate that H2OSS facilitated the conversion of residues to oil and gas in aspects of yield, heteroatomic removal rate, number of broken bonds of CC, CN, CS, distribution of carbon number of C40+, aromaticity and porosity. And this enhancement effect of H2OSS is attributed to decomposition of H2OSS molecules with inducement of kerogen and participation of H2OSS as reactants in reactions during the initial pyrolysis of BLK. Analysis of typical reaction pathways shows that H2OSS molecules were involved in disintegration of CC, CN, and CS bonds, shedding of aromatic substituents, ring-opening of aromatic heterocycles, removing aromatic heteroatoms, and further conversion of aromatics into aliphatics. These chemical reactions increase the porosity and pore connectivity of residues. Simultaneously, H2OSS expansion promoted the deformation of the kerogen carbon skeleton, resulting in initial increase of porosity of kerogen. In addition, the mechanism of further conversion of aromatics to aliphatics for steam-pyrolytic residues was given. This paper provides theoretical guidance for in-situ conversion process (ICP) of kerogen with the superheated steam injection in the further understanding mechanism of H2OSS on initial pyrolysis of kerogen and corresponding catalyst development and preparation.

Hydrocarbon regulation and lower temperature pyrolysis of balikun oil shale kerogen

Oil shale kerogen is a kind of composite nature of fossil energy polymer. Kerogen pyrolysis is a feasible and alternative strategy to produce fossil fuels from shales. However, the disadvantages including the high energy consumption, the high cost, and the low hydrocarbon conversion, significantly hinder the development and utilization of unconventional hydrocarbon resources. Herein, the hexagonal crystal structural layered double hydroxides (LDHs) with the Ni/Fe ratio of 5.64:2.36 is proposed as pyrolysis catalyst to improve the catalytic efficiency, the selectivity of target hydrocarbons, and lower the temperature for the process of kerogen pyrolysis. As a result, needle-like nanoscale NiFe-LDHs are prepared successfully to perform the fast thermal upgrading of Balikun oil shale kerogen. The catalytic pyrolysis performance has been observed that the temperature for maximum conversion (Tmax) is 401.18 °C, presenting a Tmax reduction of 37.84 °C, the yield of shale oil is increased by 7.83 wt%. And during 350°C– 400°C, a progressive increment of 147.67%, 230.86%, and 310.61% is obtained corresponding to the content of C1-C5, C6-C14, and C14 + hydrocarbons, respectively. This finding enriches the catalyst candidates for kerogen pyrolysis and provides new insights into industrial applications of in-situ pyrolysis technology for oil shale recovery processes.

Experimental and Molecular Simulation Studies of Huadian Oil Shale Kerogen.

Microscopic details on the intrinsic chemical reactivity of Huadian oil shale kerogen associated with electron properties of kerogen were investigated by the combination of experimental analyses and molecular simulations. Multimolecular structure models of kerogen with different densities were constructed for examining the accuracy of the proposed kerogen model. Results revealed that the simulated density of the kerogen model is in good agreement with the experimental value. Evaluation of the kerogen model revealed that the energy optimization process is mainly related to the change in the bond angle caused by atom displacement. According to the results from the Hirshfeld analysis of atomic charges, the S atoms in thiophene and S=O structures exhibit positive charges. By contrast, the concentration of electrons on the S atom led to the electronegativity of the sulfhydryl group. To investigate the distribution characteristics of electrons in kerogen, the molecular electrostatic potential (MEP) of a complete kerogen molecule was calculated. Notably, this is the first report of an MEP diagram of the kerogen model that can provide valuable information on the determination of electrophilic or nucleophilic reaction sites for kerogen.

The mechanism of superheated steam affecting the quality of in-situ pyrolysates of oil shale kerogen: Part A-saturation of pyrolytic organics

In this work, the effect of superheated steam on pyrolysates for in-situ pyrolysis of kerogen was investigated through ReaxFF molecular dynamics simulation in terms of the saturation of pyrolytic shale gas and light shale oil. The double bond equivalents were adopted to characterize the saturation of gas, light shale oil and the hydrocarbon. The existence form of H2O molecules, introduced by superheated steam (named the environmental H2O molecule, H2Owater), were obtained using python scripts to analyze bond order file. And the reaction pathways of several representative pyrolysates (propanol, methanol, phenols and H2), generated by the participation of H2Owater molecules, were analyzed. The results indicated that, compared with pyrolysis at nitrogen atmosphere, saturation of shale gas and light shale oil were both promoted at superheated steam atmosphere, especially for the light shale oil. Under superheated steam circumstance, the inhibited dehydrogenation of kerogen is the primary reason for the saturation improvement of products. The secondary cause is the bonding of Hwater and OHwater radicals to carbon-containing radicals, which may have a hampering effect on the radical recombination reaction of short chains. During pyrolysis of kerogen with superheated steam injection, H2Owater molecules could be involved in a serious of chemical reactions: the decomposition of char and heavy shale oil, opening reaction of heterocyclic rings, transmission and exchange of OH radicals and the formation of products (hydrocarbon, alcohols, NH3, H2S, H2, etc.), principally via attacking radicals or fragments. The typical reactions in which H2Owater molecules involved were given. This study would provide theoretical support for in-situ pyrolysis technology of oil shale with superheated steam injection.

Comprehensive preparation and multiscale characterization of kerogen in oil shale

Despite the importance of kerogen as the organic backbone of hydrocarbon production from source rocks such as oil shale, properties of kerogen at both the atomic and micron scales remain unexplored under non-destructive conditions. As the demand for the utilization of kerogen in oil shale rises, identifying its atomic anisotropy and three-dimensional (3D) distribution in oil shale becomes even more important. In this study, using a hybrid preparation-analysis method, we propose a panel of physical preparation methods, including mechanical stripping and polishing thinning, and characterization techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), terahertz time-domain spectroscopy (THz-TDS), and oblique incidence reflectance difference (OIRD) analysis without considering pyrolysis and the chemical separation of kerogen. We investigated kerogen's anisotropy at the atomic scale and its 3D distribution as flocculants and strips and developed a new OIRD computed tomography (CT) method (OIRD-CT) amenable to experimental validation, including SEM and THz scanning. Thus, the multiscale properties of kerogen detected using the combination of physical preparation and advanced characterization techniques, especially OIRD-CT, are helpful in improving our understanding of the precise utilization of oil shale.

Chemical structure characteristics and multidimensional model construction of Fushun oil shale kerogen: An experimental and simulation study

Solid state 13C nuclear magnetic resonance (13C NMR), Fourier transform infrared (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) were carried out to characterize the chemical structure characteristics and to establish the average molecular structure of kerogen extracted from Fushun oil shale. NMR predictor was used to calculate the chemical shift of carbon atoms to verify the rationality of the constructed model. And the stability of 3D model was studied by molecular dynamics (MD) simulations. 13C NMR results demonstrate that Fushun kerogen consists of 76.98% of aliphatic structure dominated by long linear methylene and 21.6% of aromatic structure (mainly protonated aromatic carbon). Functional groups observed in 13C NMR spectra were also detected in FT-IR spectra at wavenumber range of 1800-1000 cm−1. XPS analysis indicates that nitrogen-containing groups were pyrrole, pyridine and primary amines, and sulfur existed as sulfoxides, thiophenes and mercaptans. By comparing the calculated 13C NMR and experimental 13C NMR, it was found that the aromatic structure condensed in two aromatic rings and the aliphatic structure without alicyclic and epoxy ether were more rational for the chemical structure model of Fushun kerogen. A new method to evaluate the average methylene chain length was proposed. Finally, a relatively rational 2D molecular structure with a molecular formula of C228H350O10N6S3 was constructed. The most stable 3D periodic structure (20 optimized molecules, 48.44 × 49.63 × 50.28 Å3) with the lowest total potential energy was obtained by MD simulation and density of it was 0.943 g/cm3.