Solid Fuel Chemistry最新文献

The property of the coal surface to be wetted with various liquids is important for many technological processes of coal mining, sorting, processing, and transportation. In this work, we used the determination of the contact angle of the coal surface and the filtration of liquid through a layer of coal powder to characterize the wettability. The influence of changes in the chemical composition and porosity of coals in the series of their metamorphism on the wettability characteristics was estimated. It was shown that the wettability and filtration properties of coals exhibited an extreme dependence with a minimum at the middle stage of metamorphism.

The paper presents the results of an assessment of the influence of coals’ structural features on their proneness to spontaneous combustion. Fifteen samples of hard coals and anthracite from different deposits of the Russian Federation were used as objects of study. Based on the deconvolution of coal vitrinite Raman spectra, a structural index characterizing the ratio between amorphous and crystallite forms of carbon compounds has been identified. It is noted that this index differs significantly for coals with a close stage of metamorphism. For the studied coals, the activity to ozone was determined for two types of sites that are differing in the rate of deactivation when interacting with it. It is shown that the activity of sites of the first type (with a higher deactivation rate when interacting with ozone) grows with an increase in the proportion of crystalline carbon in the coals’ vitrinite. Whereas, the activity of sites of the second type (with a low rate of deactivation) generally decreases. The kinetic parameters of coal combustion (ignition temperature and activation energy) were estimated according to their thermogravimetric analysis in the air environment. It is shown that with an increase in the proportion of amorphous carbon compounds in vitrinite of coals, both the ignition temperature and the activation energy of coal combustion decrease, which altogether leads to an increase of a risk of spontaneous combustion.

The distribution of organic chlorine in the fractions of semicoking resin of the oil shale from the Perelyubskoye deposit was studied. The highest concentrations of organochlorine compounds were determined in the resin fractions with boiling ranges of 100–120, 140–160, 240–260, and 280–320°C. Based on the experimental data, possible ways of further use of shale resin were proposed.

The sedimentation in high-paraffin oil with the addition of different resins and an inhibiting additive was studied. It was found that the amount of oil sediment decreased with an increase in the concentration of resins in oil with a lower surface tension and a large number of heteroatomic components. With an increase in the fraction of resins with a higher content of polysubstituted aromatic structures, an increase in the amount of oil sediment and a decrease in the efficiency of the inhibiting additive were observed. With an increase in the amount of oil resin additives, the fraction of low-molecular-weight n-alkanes in the composition of asphalt–resin–paraffin deposits (ARPD) decreased and the average sizes of paraffin hydrocarbon aggregates decreased.

The article presents the results of studying resins isolated from the liquid cracking products of sulfur tar from the Omsk Oil Refinery. Thermal treatment was carried out at 500°C for 15, 30, 45, and 60 min. It was found that the yield of coke increased with the duration of tar cracking due to the condensation of resins into asphaltenes and then into coke. Changes in the structural-group parameters of resins in the course of cracking process were established using ¹H NMR spectroscopic data, elemental composition, and the results of molecular weight measurements. Averaged resin molecules became more condensed, and they were characterized by an increased concentration of aromatic fragments and a decrease in the numbers of naphthenic fragments and aliphatic substituents. The set of data on changes in the composition of cracking products together with an analysis of sulfur distribution in the products indicated a significant contribution of sulfur-containing structural fragments of resins to the accumulation processes of thiophene derivatives. It was shown that the cracking of resins was accompanied by the formation of a wide range of low-molecular-weight sulfur-containing compounds in the composition of oils.

The paper presents the results of the initiation of chemical transformations of humic acids (HAs) in a barrier discharge plasma. The HAs were treated with ammonia vapor in the presence of various gas atmospheres like ethylene, air, oxygen, carbon dioxide, and mixtures with argon. A decrease in the number of paramagnetic centers after treatment of HAs in a barrier discharge was revealed using EPR spectroscopy, which indicated the recombination of free radicals in their structure. As revealed by IR spectroscopy, the intensity of an absorption band at 1383 cm^–1 corresponding to the NO₃ group increased when HAs were exposed to discharge plasma in air. When HAs were treated with ammonia vapor in an argon atmosphere, ammonium humate, which is completely soluble in water, was formed.

Changes in the structural parameters of secondary resins and asphaltenes formed upon the cracking of asphaltenes, resins, and their mixture were assessed at different process durations. Resins and asphaltenes isolated from heavy methane oil of the Zyuzeevskoye oil field (Tatarstan) and their mixture were cracked in a batch reactor at 450°C for 60, 90, and 120 min. With increasing the duration of resin and asphaltene cracking, condensation reactions leading to an increase in the yield of coke and the formation of low-molecular-weight highly aromatic secondary resin and asphaltene molecules accelerated. It was found that the directions of thermal transformations of resin and asphaltene molecules were similar. The joint presence of resins and asphaltenes in the mixture changed the direction of their thermal transformations in the course of cracking, which was reflected in the quantitative data on the mass balance and structural parameters of secondary resins and asphaltenes formed upon the cracking of a mixture of resins with asphaltenes. Differences in the structural characteristics of resins and asphaltenes formed upon the cracking of single-component samples and their mixture were revealed.

The microstructure and functional compositions of the asphaltenes of bituminous oils from the Ashalchinskoye (Permian), Usinskoye (Permo-Carboniferous), and Nurlatskoye (Devonian) oil fields and their high- and low-molecular-weight components were studied using infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy. It was shown that asphaltenes from the Ashalchinskoye oil were characterized by a smooth surface, while asphaltenes from the Usinskoye and Nurlatskoye oils had rough and porous surfaces. The sizes of asphaltene nanoaggregates from the Usinskoye and Nurlatskoye oils were smaller than those of the Ashalchinskoye oil. At the same time, asphaltene nanoaggregates from the Ashalchinskoye and Nurlatskoye fields formed a disordered tangled structure. A distinctive feature of asphaltenes from the Usinskoye oil was the presence of more ordered layers characteristic of crystal-like formations. Asphaltenes of Ashalchinskoye and Nurlatskoye oils were characterized by increased degrees of aromaticity and branching of aliphatic substituents in their macromolecules and a high relative concentration of fragments with a sulfoxide group. Their high-molecular-weight asphaltenes were less aromatic than low-molecular-weight ones, and their composition had a lower tentative concentration of carbonyl and sulfoxide groups. In the structure of asphaltenes form the Usinskoye oil, the fraction of aliphatic fragments and fragments containing a carbonyl group was increased. High-molecular-weight asphaltenes of this oil also contained fewer sulfoxide and carbonyl groups but more aromatic fragments than their low-molecular-weight asphaltenes.

The hydrocarbon composition of oils from asphaltene cracking products was studied. The experiments were carried out in three different modes: without additives (a control experiment without water and catalyst), in supercritical water without catalyst, and in supercritical water with an iron oxide–based catalyst. Cracking was carried out in a reactor at 450°C; the experiment duration was 60 min, and the catalyst was obtained in situ from iron(III) tris(acetylacetonate). Individual hydrocarbon composition of oils isolated from cracking products was determined by gas chromatography–mass spectrometry (GC–MS) analysis using a Shimadzu GCMS-QP5050A quadrupole system. The hydrocarbon composition of asphaltene cracking products obtained in supercritical water differed in qualitative and quantitative characteristics from the products obtained without water. Upon asphaltene cracking in water, the composition changed significantly compared to that in the control experiment, and an increase in the fraction of saturated hydrocarbons was noted. In cracking products obtained in an aqueous medium with the addition of a catalyst, saturated hydrocarbons also predominated, while the concentration of phthalates, alkenes, and sulfur-containing compounds increased significantly.

The article presents the results of a comparative evaluation of the oil-displacing capacity of a new composition based on deep eutectic solvents (DESs) and surfactants with that of the IPC-PRO composition developed previously at the Institute of Petroleum Chemistry, Siberian Branch, Russian Academy of Sciences. Laboratory simulation of the oil displacement process for heavy oil from the Usinskoye field using models of a heterogeneous formation with a carbonate reservoir type showed that both compositions had high oil-displacing capacity in a wide temperature range to open up the possibility of their use at any stage of oilfield development.