Том 58, № 1 (2017)

The inhibiting effect of multiatomic gases has been investigated by numerical simulation of hydrogen oxidation with account taken of the nonequilibrium state of the initial components, intermediates, and reaction products behind the shock wave in the framework of a vibrationally nonequilibrated model. The central feature of the model is successively taking into account the vibrational disequilibrium of the HO₂ radical as the most important intermediate in the chain branching process. The inhibiting effect can be explained by the influence of the multiatomic gases on the rate of the vibrational relaxation of the vibrationally excited HO₂ radical resulting from the reaction. Methane, tetrafluoromethane, fluoromethane, difluoromethane, chlorofluoromethane, formaldehyde, ethane, hexafluoroethane, ethylene, tetrafluoroethylene, and propane have been considered as inhibitory admixtures.

The O−H bond dissociation energy (D_O−H) has been determined for eight alkylseleno-substituted phenols, one alkyltelluro-substituted phenol, and one alkyltelluro-substituted pyridinol. D_O−H has been estimated by the intersecting-parabolas method from kinetic data using five reference compounds: α-tocopherol (D_O−H = 330.0 kJ/mol), 3,5-di-tert-butyl-4-methoxyphenol (D_O−H = 347.6 kJ/mol), 4-methylphenol (D_O−H = 361.6 kJ/mol), 2,6-di-tert-butyl-4-methylthiophenol (D_O−H = 336.3 kJ/mol), and 2,6-di-ter-tbutyl-4-methylphenol (D_O−H = 338.0 kJ/mol). The following D_O−H values (kJ/mol) have been obtained: 335.9 for 2,5,7,8-tetramethyl-2-phytyl-6-hydroxy-3,4-dihydro-2H-1-benzoselenopyran, 342.6 for 2-methyl-5-hydroxy-2,3-dihydrobenzoselenophene, 333.5 for 2,4,6,7-tetramethyl-5-hydroxy-2,3-dihydrobenzoselenophene, 339.4 for 2-tert-butyl-4-methoxy-6-octylselenophenol, 357.9 for dodecyl 3-(4-hydroxyphenyl) propyl selenide, 348.5 for dodecyl 3-(3,5-dimethyl-4-hydroxyphenyl)propyl selenide, 350.9 for dodecyl 3-(3-tert-butyl-4-hydroxyphenyl)propyl selenide, 338.0 for dodecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propyl selenide, 343.0 for 2,6-di-tert-butyl-4-(tellurobutyl-4′-phenoxy)phenol, and 338.8 for 6-octyltelluro-3-pyridinol. The stabilization energies of phenoxyl radicals containing R substituents (X = O, S, Se, Te) have been compared.

The catalysts based on MoO₃/Al₂O₃ were synthesized and tested using aqueous hydrogen peroxide as the oxidant in the oxidative desulfurization of thiophene, benzothiophene (BT) and dibenzothiophene (DBT) into the corresponding sulfones. Among catalysts tested, 15%(MoO₃–WO₃)/Al₂O₃ prepared by a conventional impregnation method was considerably active for the oxidation of thiophene, BT and DBT, which could achieve higher than 99.2% conversions at lower reaction temperature (≤338 K). The use of hexadecyltrimethyl ammonium bromide as the phase-transfer reagent in small amounts could promote the reaction efficiently.

Nitrogen-containing compounds have been studied as stabilizing additives for a complex molybdenum catalyst for propylene epoxidation with ethylbenzene hydroperoxide. Introducing the additives increases the half-life period by a factor of 10–14. The effective constants and rates of the decomposition of the catalytic complex in the presence of stabilizing agents have been calculated. Two possible mechanisms of the action of the nitrogen-containing additives have been suggested.

The reactivity of thiophene, dibenzothiophene (DBT), and 4,6-dimethyldibenzothiophene (4,6-DMDBT), which are the representatives of the main classes of sulfur compounds that are the constituents of diesel fractions, was studied in the course of their oxidative desulfurization with oxygen on a CuO/ZnO/Al₂O₃ catalyst modified with boron and molybdenum additives. At T ≥ 375°C, the reactivity increased in the order thiophene < DBT < 4,6-DMDBT. The degree of sulfur removal in the form of SO₂ from hydrocarbon fuel, which was simulated by a solution of 4,6-DMDBT in toluene, was 80%. Under the assumption of a first order reaction with respect to sulfur compound and oxygen, the apparent activation energies of the test processes were calculated. An attempt was made to reveal the role of the adsorption of sulfur compounds in the overall process of oxidative desulfurization with the use of X-ray diffraction analysis, X-ray photoelectron spectroscopy, and differential thermal and thermogravimetric analysis with the massspectrometric monitoring of gas phase composition.

The results of development of an industrial supported cobalt–silica gel catalyst for the Fischer–Tropsch synthesis are reported. The studies included the selection of a support and the determination of an optimum active component content, a calcination temperature, and the effect of doping with aluminum oxide on the physicochemical and catalytic properties of the Co–SiO₂ system. The catalyst samples were characterized by a set of physicochemical methods. The on-stream stability of the supported cobalt–silica gel catalyst was tested in the continuous mode for 1000 h. In the course of the entire test cycle, the catalyst exhibited stable operation under varied synthesis temperature and gas space velocity, and it can be recommended for industrial applications. The experimental results were used for the preparation of a pilot batch of the catalyst.