Non-isothermal conversion of the Kashpir sulfur-rich oil shale in a supercritical water flow

Comparative study on the pyrolysis behavior and pyrolysate characteristics of Fushun oil shale during anhydrous pyrolysis and sub/supercritical water pyrolysis

Injected steam can be converted to the sub/supercritical state during the in situ exploitation of oil shale. Thus, the pyrolysis behavior and pyrolysate characteristic of Fushun oil shale during anhydrous pyrolysis and sub/supercritical water pyrolysis were fully compared. The results revealed that the discharged oil yields from sub/supercritical water pyrolysis were 5.44 and 14.33 times that from anhydrous pyrolysis at 360 °C and 450 °C, which was due to the extraction and driving effect of sub/supercritical water. Also, sub/supercritical water could facilitate the discharge and migration of shale oil from the pores and channels. The H₂ and CO₂ yields in sub/supercritical water pyrolysis were higher than that in anhydrous pyrolysis, resulting from the water–gas shift reaction. The component of shale oil was dominated by saturated hydrocarbons in anhydrous pyrolysis, which accounted for 50–65%. In contrast, a large amount of asphaltenes and resins was formed during pyrolysis in sub/supercritical water due to the solvent effect and weak thermal cracking. The shale oil from anhydrous pyrolysis was lighter than that from sub/supercritical water pyrolysis. Sub/supercritical water reduced the geochemical characteristic indices and lowered the hydrocarbon generation potential and maturity of solid residuals, which can be attributed to the fact that more organic matter was depolymerized and released. The pyrolysate characteristic of oil shale in sub/supercritical water pyrolysis was controlled by multiple mechanisms, including solvent and driving effect, chemical hydrogen-donation and acid–base catalysis.

Sub/supercritical water can directly extract oil and gas from oil shale due to the solvent and driving effects. Also, they can be considered as an acid–base catalyst, which can catalyze some reactions such as hydrolysis, addition and rearrangement.

Effect of the Fuel Equivalence Ratio on the Mechanisms of Thiophene Oxidation in Water Vapor at Increased Density of the Reagents

The article presents the results of a study of thiophene oxidation in high-density C₄H₄S/O₂ mixtures (ρ_Thi = 0.12 and 0.15 mol/dm³, ρ_O2 = 0.74-1.26 mol/dm³), diluted with water vapor and argon (dilution level x _D = 35-65% mol), at uniform heating (1 K/min) of a stainless-steel tubular reactor up to 823 K. It is established that the temperature of thiophene oxidation onset weakly depends on the nature of the diluent and the oxygen content in the reaction mixture. From the time dependences of the reaction mixtures on temperature and pressure, it follows that the oxidation of thiophene in the water vapor and argon media proceeds according to the mechanisms of homogeneous and heterogeneous reactions. Upon oxidation of thiophene in the stoichiometric mixtures in argon with a small amount of water vapor, as well as in the lean mixtures in water vapor, the contribution of reactions on the surface of the Pt-Rh/Pt thermocouple, inserted into the center of the reaction volume, is increased. Upon oxidation of thiophene in water vapor in the fuel-enriched and stoichiometric mixtures, reactions on the oxidized surface of the reactor wall (primarily iron oxides) prevail. Increasing the density of water vapor both reduces the contribution of heterogeneous reactions on the reactor wall and prevents complete carbon burnout. It is shown that the neutralization of sulfuric acid, resulting from the oxidation of thiophene, with calcium carbonate reduces the corrosion of stainless steel. The X-ray diffraction analysis revealed the presence of ferrochromite, iron and chromium oxides, iron, nickel, and chromium sulfates in the corrosion products.

Heavy Oil Hydrocarbons and Kerogen Destruction of Carbonate–Siliceous Domanic Shale Rock in Sub- and Supercritical Water

This paper discusses the results of the influences of subcritical (T = 320 °C; P = 17 MPa) and supercritical water (T = 374 °C; P = 24.6 MPa) on the yield and composition of oil hydrocarbons generated from carbonaceous–siliceous Domanic shale rocks with total organic content (Corg) of 7.07%. It was revealed that the treatment of the given shale rock in sub- and supercritical water environments resulted in the decrease of oil content due to the intensive gas formation. The content of light hydrocarbon fractions (saturated and aromatic hydrocarbons) increased at 320 °C from 33.98 to 39.63%, while at 374 °C to 48.24%. Moreover, the content of resins decreased by almost twice. Insoluble coke-like compounds such as carbene–carboids were formed due to decomposition of kerogen after supercritical water treatment. Analysis of oil hydrocarbons with FTIR method revealed a significant number of oxygen-containing compounds, which are the hydrogenolysis products of structural fragments formed after destruction of kerogen and high-molecular components of oil. The gas chromatography–mass spectroscopy (GC–MS) method was applied to present the changes in the composition of mono- and dibenzothiophenes, which indicate conversion of heavy components into lighter aromatic hydrocarbons. The specific features of transforming trace elements in rock samples, asphaltenes, and carbene–carboids were observed by using the isotopic mass-spectrometry method.