Vol 53, No 6 (2019)

The subject of this study is the inverse problems of identifying the mechanisms of complex chemical reactions. A graph-theoretic method for determining the basis of the parametric functions of the kinetic parameters of mathematical models for complex catalytic reactions is proposed. Based on the developed algorithm, a program for analyzing the information content of a mathematical model of the mechanism of catalytic reactions has been implemented. The operation of the algorithm is illustrated by the reaction of isotopic exchange of protium for deuterium.

By solid-phase synthesis, macrocrystalline Cu_2 − δZn_2 − xSn_xS_4 − ySe_y monograin powders have been prepared, the chemical composition of which was shown by XRD and Raman spectroscopy to be different in powder fractions of different sizes formed during the synthesis. The influence of synthesis conditions on the decay kinetics of photogenerated charge carriers in different fractions has been studied using the frequency–time-resolved microwave photoconductivity method. The characteristic photoresponse half-life, τ_1/2, increased with increasing grain size. The smallest values of the lifetime were observed for the fraction with sizes of 50–70 μm (τ_1/2 <5 ns), and the largest values were for the fraction with a grain size of 70–90 μm (τ_1/2 ~ 12 ns).

Quenching of the eosin triplet state by europium(III) in water has been studied in the absence and in the presence of cucurbit[6–8]uril by means of phosphorescence and triplet–triplet absorption in a deoxygenated aqueous solution at room temperature. The quenching is due to photoinduced electron transfer from eosin to europium and to its complexes with cucurbit[6–8]urils. The value of the quenching rate constant of eosin phosphorescence by europium in the absence of cavitands is 1.9 × 10⁶ L mol^–1 s^–1, whereas in the presence of CB6, CB7, and CB8, the values of the rate constant increase to 2.1, 2.2, and 2.6 × 10⁶ L mol^–1 s^–1, respectively. Simultaneously with the decrease in the lifetime of the eosin molecule in the triplet state, an increase in the yield of the eosin semioxidized form was observed as a product of photoinduced electron transfer. It has been also shown that with an increase in the concentration of CB7 and CB8, the quenching rate constant increases two times. The difference in the values of the quenching rate constants may be due to the fact that europium, being as a quencher, is present in the form of complexes of different compositions with cucurbit[6–8]urils.

Changes in physicochemical parameters, such as resistivity, viscosity, and density, and the formation of gaseous products (Н₂, СН₄, С₂Н₄, С₂Н₆, С₃Н₈, С₄Н₁₀, С₅Н₁₂, and С₆Н₁₄) depending on the absorbed dose in the range of 29.7–237.6 kGy have been studied. It has been found that the chemical composition of transformer oil is changed by γ-irradiation and this change is accompanied by changes in the resistivity, viscosity, and density of the oil. The degree of conversion depends on the absorbed dose and increases with it. The IR spectra exhibit =С–Н stretching vibrations, –С=С in-plane bending vibrations, and –СН out-of-plane bending vibrations in aromatic compounds. In addition, –С–Н stretching vibrations and–С–СН₃ bending vibrations (antisymmetric and symmetric) in alkanes are observed. The IR absorption spectra have been observed in the ranges of \({\Delta }{{\lambda }_{1}} = 2800 - 3300\,{\text{c}}{{{\text{m}}}^{{ - 1}}},\)\({\Delta }{{\lambda }_{2}} = 2000~\,{\text{c}}{{{\text{m}}}^{{ - 1}}},\)\({\Delta }{{\lambda }_{3}} = 1350 - 1450\,\,{\text{c}}{{{\text{m}}}^{{ - 1}}}\), and \({\Delta }{{\lambda }_{4}} = 600 - 1200~\,\,{\text{c}}{{{\text{m}}}^{{ - 1}}}.\) The absorption band at \({\Delta }{{\lambda }_{4}} = 600 - 1200~\,{\text{c}}{{{\text{m}}}^{{ - 1}}}\) is a diffuse part of the spectrum, which includes a number of weak absorption bands.

Samples of AI-92 and AI-95 gasoline from Azerbaijani oils have been used as test materials. Laboratory studies have been carried out on a ⁶⁰Co γ-radiation source at a dose rate of P = 0.18 Gy/s at room temperature and various absorbed doses D = 15–150 kGy. The effect of ionizing radiation on the structural-group composition of gasoline under static conditions has been examined using a standard procedure before and after irradiation. The results of these studies make it possible to evaluate the radiation resistance of fuels and to determine the effect of irradiation on the overall composition of fuels and possible changes in the quality of fuels.

The effect of the volumetric flow rate of reaction mixture components on the nonoxidative reforming of methane with admixed water in dielectric-barrier discharge has been studied. An increase in the volumetric flow rate of water from 1.3 to 6 cm³/h did not exert a noticeable effect on the conversion of methane and on the concentrations of hydrogen and ethane in gaseous reaction products. An increase in the concentration of propane and butanes was observed, whereas the total ethylene and propylene content of the products decreased. An increase in the volumetric flow rate of methane from 5 to 60 cm³/min led to a decrease in the conversion of methane from 29.3 to 6.2 vol % and a decrease in energy consumption for its reforming from 88.3 to 34.7 eV/molecule, and it was also accompanied by a decrease in the rate of formation of gaseous alkanes and olefins. The experimental data confirmed previous conclusions on the reaction mechanism and kinetics of the nonoxidative reforming of methane in dielectric-barrier discharge, which were made using a mathematical model.