Том 57, № 5 (2016)

The formation of soot particles in the pyrolysis and oxidation of various aromatic and aliphatic hydrocarbons in argon behind reflected shock waves has been investigated by computational and theoretical methods. The hydrocarbons examined include methane, ethane, propane (aliphatic hydrocarbons with ordinary bonds), acetylene, ethylene, propylene (aliphatic hydrocarbons with multiple bonds), benzene, toluene, and ethylbenzene (simplest aromatic hydrocarbons). Soot formation in the pyrolysis and oxidation of both aromatic and aliphatic hydrocarbons can be simulated in detail within a unified kinetic model. The predictive power of the unified kinetic model has been verified by directly comparing the calculated kinetic data for the formation of products and reactive radicals in the pyrolysis and oxidation of various hydrocarbons to the corresponding experimental data. In all calculations, all the kinetic parameters of the unified kinetic model were strictly fixed. A good quantitative fit between the data calculated via the unified kinetic model and experimental data has been attained.

In this study, degradation of the effluent solution using sonolysis, sonocatalysis, photocatalysis and sonophotocatalysis was investigated. For this purpose, an artificial effluent solution (AES) containing Acid Black 1 and Acid Blue 62 dyestuffs was prepared. The initial AES concentration, catalyst amount, light intensity and the power of ultrasound energy were chosen as the reaction parameters.The degradation rate of AES followed the pseudo-first order kinetics inconcentration of artificial effluent solution. The results showed that the sonophotocatalysis (US + UV + TiO₂) was more effective in the degradation than sonolysis (US), sonocatalysis (US + TiO2) and photocatalysis (UV + TiO₂) performed individually. The highest and lowest degradation rates were obtained in sonophotocatalytic process and sonolytic process (US), respectively. It was found also that the synergistic effect between sonolysis and photocatalysis processes is the main reason why the maximum degradation is achievable in the sonophotocatalytic process.

Cumene is a commercially important product in the petrochemical industries. In isopropylation of benzene, 1,4-diisopropyl benzene (1,4-DIPB) is produced as low value by-product. This low value by-product DIPB is used to maximize the production of commercially important product cumene by transalkylation reaction. Reduction of crystal size in zeolite can increase surface area of the external surface and in this way bring about substantial changes in catalytic activity. Moreover modification with rare-earth metal enhances the acidity of zeolite. In this work, nanocrystalline and microcrystalline zeolite X were modified with cerium to study the combine effect of crystal size and ion modification of zeolite on selectivity of cumene in commercially important transalkylation reaction. Benzene and 1,4-diisopropylbenzene in a molar ratio of 1 to 12.5 were subjected to vapour-phase reaction in the temperature range of 498 to 593 K at atmospheric pressure with space time of 5.27–10.54 kg h/kmol. Nanosized crystalline zeolite gives much higher conversions of 1,4-DIPB than microcrystalline zeolite. Over cerium modified nanosized zeolite CeX_N 81.85% conversion of 1,4-DIPB and 97% cumene selectivity were achieved. It was found that stability and activity of CeX_N for cumene synthesis was much higher than that of CeX_M zeolite. Kinetic constants for the reactions were estimated and the activation energies for various reactions over CeX_M were determined. The activation enegy for transalkylation reaction was found to be 78.54 kJ/mol.

The catalytic cracking of heavy fuel oil was investigated over the equilibrium fluid catalytic cracking catalyst (E-Cat) as a base component with the mesoporous MCM-41 as an additive. The catalytic performance of the E-Cat/MCM-41 system was assessed in a fixed-bed MAT unit. The reaction was performed at temperatures of 500, 530, 550 and 600°C and the product distributions in both gaseous and liquid phases were studied. The yields of products including light olefins, liquefied petroleum gas (LPG), gasoline, dry gas, coke and also the conversions obtained over different temperatures were reported and some generalities discussed. The maximum yield of propylene (17.5%) was obtained at 550°C whereas the highest conversion and gasoline yield was gained at 530°C. An eight-lump kinetic model containing 11 kinetic parameters was considered. Those parameters were estimated based on experimental data at specific temperatures by fourth order Runge–Kutta algorithm and the least square method. In addition, Arrhenius equation was used to calculate apparent activation energies. The calculated data of the product yields were in a close agreement with the experimental data.

Pd–In/Al₂O₃ and Pd–In/MgAl₂O₄ catalysts prepared from dinuclear Pd–In acetate complexes were studied in the hydrogenation of alkyne compounds with different structures. The Pd–In catalysts demonstrate high selectivity in the hydrogenation of internal alkynes comparable with that of the Lindlar catalyst. Similar activity/selectivity characteristics are reached at a significantly lower Pd content. For terminal alkynes, the favorable effect of Indium introduction is considerably less pronounced. An analysis of the In effect on the selectivity and the ratio between the rates of the first and second hydrogenation steps suggests that the reaction selectivity is determined to a large extent by a thermodynamic factor (adsorption–desorption equilibrium between the reactants and the reaction products).

Cobalt-based Fischer–Tropsch synthesis (FTS) catalysts containing 1 to 40 wt % cobalt supported on multi-walled carbon nanotubes (CNTs) have been investigated. The CNTs have been characterized by low-temperature nitrogen adsorption, scanning electron microscopy, and X-ray photoelectron spectroscopy. All catalysts have been prepared by impregnating, with an ethanolic solution of cobalt nitrate, the CNTs preoxidized with concentrated nitric acid and have been tested in the FTS at 220°C and atmospheric pressure. Correlations have been established between the cobalt weight content of the catalyst and the Co particle size determined by transmission electron microscopy and X-ray diffraction. The Co content and particle size have an effect on the activity and selectivity of the catalyst and on the target fraction (C₅₊) yield in the FTS. The highest CO conversion is observed for the catalyst containing 20 wt % Co; the highest selectivity and activity, for the catalyst containing 5 wt % Co; the highest C₅₊ yield, for the catalyst containing 10 wt % Co.

The adsorption of reactant mixtures is quantitatively and qualitatively different from the adsorption of the individual reactants. Thus, O₂ is almost not adsorbed on ZrO₂; however, a considerable concentration of molecular oxygen was detected among the products of desorption after the adsorption of a mixture of NO + O₂ and the total amount of desorbed molecules was greater by a factor of 10 than their total amount after the individual adsorption of NO and O₂. Among the qualitative differences is the formation of the O₂^- radical anion on the surface only upon the adsorption of the mixture of NO + O₂. Similarly, the number of desorbed molecules upon the simultaneous adsorption of C₃H₆, NO, and O₂ was much greater than that upon their individual adsorption; this is related to the formation of paramagnetic and nonparamagnetic NO₂–hydrocarbon complexes on the surface, which contained the NO₂ group and a hydrocarbon fragment.

The kinetics of oxygen exchange in the nonstoichiometric strontium ferrite SrFeO_3–δ with the structure of cubic perovskite was studied by the oxygen partial pressure relaxation technique in the isostoichiometric regime at temperatures of 500–900°C in a range of δ from 0.24 to 0.44. An increase in the oxygen nonstoichiometry δ was accompanied by a decrease in the rate of sample relaxation and by an increase in the apparent activation energy of oxygen exchange.

La_1–xAg_xMnO_{3 ± y} (x = 0-0.3) mixed oxides have been synthesized by the pyrolysis of polymer–salt compositions using different organic compounds and different salt: organic compound ratios. The correlation between the reaction medium temperature during pyrolysis, the composition of the resulting oxide, and synthesis conditions has been investigated. The effect of these conditions on the character of the pyrolysis process, on the phase composition and microstructure of the resulting oxide particles and metallic silver, and on their mutual distribution is reported. The catalytic properties of the synthesized oxides in methane and soot oxidation are considered, and a correlation is established between the catalytic activity of the oxides and the synthesis conditions.