Himiâ tverdogo topliva

A research-based mechanism for cryostructuring aqueous solutions of polyvinyl alcohol, i.e., converting solutions from a fluid state into elastic bodies (cryogels), is proposed. In addition to the theoretical substantiation of the mechanism, experimental results of rheological and spectral studies of the cryogels obtained are also presented. An explanation is given for the significant difference between the cryostructuring temperature of an aqueous solution of polyvinyl alcohol and the melting temperature of formed elastic cryogels.

The effect of electromagnetic field on colloidal dispersion properties of water-oil emulsions of two resinous low paraffin oils is studied. It is shown that the maximum result of water-oil emulsion stratification is achieved after 15 minute treatment at a frequency of 250 Hz and a voltage of 17 kV for 10 wt % of emulsions and 500 Hz and 15 kV for 30 wt % of emulsions, respectively. With increasing time of emulsion treatment, the size and number of droplets in the oil phase decrease and the residual water content of the treated emulsions after stratification does not exceed 0.5 wt %. In an electromagnetic field, the drop-drop coalescence process in the emulsion is intensified due to the rapid destruction of the armor shells of water globules, the formation of new resin-asphaltene aggregates of a larger or smaller size, and the redistribution of components between the dispersion medium and the dispersed phase.

The microstructure and functional composition of asphaltenes of bituminous oils from the Ashalchinskoye (Permian), Usinskoye (Permian-Carbon) and Nurlatskoye (Devonian) fields (referred to here as the Ashalchinskaya, Usinskaya and Nurlatskaya oils, respectively) and their high- and low-molecular components are studied using infrared spectroscopy and scanning and transmission electron microscopy. It is shown that asphaltenes of the Ashalchinskaya oil are characterized by smooth surface, while those of the Usinskaya and Nurlatskaya oils – by rough and porous surfaces. The sizes of asphaltene nanoaggregates of the Usinskaya and Nurlatskaya oils are smaller than those of the Ashalchinskaya oil, while the asphaltene nanoaggregates of oils from the Ashalchinskaya and Nurlatskaya oils form disordered tangled structures. A distinctive feature of the Usinskaya oil asphaltenes is the presence of better-ordered layers, which are typically associated with crystal-like formations. Asphaltenes of Ashalchinskaya and Nurlatskaya oils are characterized by enhanced aromaticity and branching of aliphatic substituents of their macromolecules, as well as a high relative content of the fragments with a sulfoxide group. Their high-molecular asphaltenes are less aromatic than the low-molecular ones, and the conditional content of carbonyl and sulfoxide groups in their composition is lower. The content of aliphatic fragments and those containing carbonyl groups in the Usinskaya oil asphaltenes is higher. The content of sulfoxide and carbonyl groups in high-molecular asphaltenes of this oil is lower than that in low-molecular asphaltenes, while the content of aromatic fragments is, on the contrary, higher.

The results of investigation of asphaltenes isolated from liquid products of initiated cracking of two tar samples at 500°C in the presence of calcium acetate additive are presented. Characteristic changes in the composition of cracking products depending on the amount of the additive are shown. It is established that the formation of solid products of compaction depends not only on the initial content of asphaltenes, but also on their structure. Changes in the structure-group parameters of asphaltenes in the process of initiated cracking of tar sands have been studied. A distinctive feature of tar cracking in the presence of calcium acetate is that the use of the additive promotes both the destruction of structural blocks and a significant decrease in their number in the composition of asphaltene molecules. In addition, due to the destruction of aliphatic substituents and naphthenic cycles, the averaged asphaltene molecules become more compact and the proportion of condensed aromatic structures in their composition increases significantly.

The results of the study of resins isolated from liquid cracking products of sulfuric vacuum residue from Omsk refinery are presented. Thermal treatment was carried out at 500 °C and duration of 15, 30, 45 and 60 minutes. It was found that with increasing duration of vacuum residue cracking there is an increase in coke yield due to condensation of resins into asphaltenes and further into coke. Using the data of 1H-NMR spectroscopy, elemental composition and results of molecular weight measurement the changes of structural-group parameters of resins in the process of cracking were established. The averaged resin molecules become more condensed, characterized by an increased content of aromatic fragments, a decrease in the number of naphthenic fragments and the number of aliphatic substituents. The totality of data on changes in the composition of cracking products, together with the analysis of sulfur distribution in the composition of products, indicates a significant contribution of sulfur-containing structural fragments of resins to the accumulation of thiophene derivatives. It is shown that cracking of resins is accompanied by formation of a wide range of low-molecular-weight sulfur-containing compounds that are incorporated into oils.

The results of studies of polyaromatic hydrocarbons (PAHs) in oil shales (HS) of Barzasskoye (Barzassite) and Budagovskoye (Sapropelite) deposits and their ash residues obtained by thermal degradation at T = 300, 500 and 750°C with free oxygen access are presented. The complex of physicochemical methods of analysis (extraction, infrared spectroscopy, high-performance liquid chromatography) allowed to establish the composition of priority PAHs of oil shale and trace the changes occurring under thermal influence. As a result of the performed work it is shown that the yield of ash residues of oil shale is dependent on the initial composition of HS, ranging from 5 to 82 wt % depending on the temperature of degradation. PAH content in ash residues does not exceed 9.5 wt %.

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