Kinetika i kataliz

The kinetics of allyl chloride epoxidation with hydrogen peroxide at TS-1 catalyst has been studied. The kinetic data analysis allowed us to exclude only a part of the hypotheses about the mechanism, which were formulated on the basis of the available physico-chemical information about the structure of the TS-1 active center. The characteristics of the allyl chloride epoxidation process were compared with the characteristics of allyl alcohol epoxidation. In order to adequately describe the experimental data, it is necessary to take into account the strong binding of the active sites of the catalyst with hydrogen peroxide and epichlorohydrin. The Eley–Rideal type mechanism is recognized as an adequate kinetic model. Additional physico-chemical or computational data are needed to further discriminate the remaining hypotheses. Another way is to use additional information about the kinetics of by–products formation.

The regularities of the alkene hydrocarboxylation process in conjugation with the carbon monoxide oxidation reaction in the PdBr₂–CuBr₂–THF–H₂O catalytic system were studied. Cyclohexene, styrene, 1-hexene, 1-octene, 4-vinylcyclohexene, ethylene, propylene, vinyl acetate, vinyl butyl ether were used as substrates. The obtained products were identified by gas chromatography and chromatograph mass spectrometry.

Modern developments in the field of creating fuels from alternative sources are aimed at producing liquid gasoline-type hydrocarbons with high yield. Fischer–Tropsch synthesis (FTS) is a well–known method for more than a hundred years that allows to obtain a wide range of hydrocarbons from carbon and hydrogen oxides. In this work, three metal-containing catalytic systems deposited on super-crosslinked polystyrene (HPS) have been synthesized (2% Fe– HPS, 1% Ru– HPS and 2% Fe–1% Ru– HPS) by precipitation in subcritical water, and their catalytic effect in the process of liquid-phase FTS was studied. The addition of Ru to the Fe-containing catalyst leads to an increase in the dispersion of active phase particles and, consequently, an increase in the activity of the catalytic system. The bimetallic catalyst 2% Fe–1% Ru–HPS showed a catalytic activity 1.5 times higher than that of the sample 2%Fe–HPS, selectivity with respect to alkanes C₅–C₁₁ was 98.5 mol. %. Based on data from kinetic experiments and physico-chemical studies of the bimetallic catalyst, a scheme for the liquid phase process was proposed. the Fischer–Tropsch synthesis.

The effect of 5-hydroxy-6-methyluracil, 5-hydroxy-3,6-dimethyluracil and 5-hydroxy-1,3,6-trimethyluracil on the radical chain oxidation of tetrahydrofuran was studied. It was found that the compounds are inhibitors of the radical chain process. These uracil derivatives react with the tetrahydrofuran peroxyl radical with a rate constant k₇ = (0.8÷1.2) × 10⁴ L mol^–1 s^–1. The stoichiometric inhibition coefficient was measured f = (0.9÷1.4). The effect of ascorbic acid on the antioxidant properties of 5-hydroxyuracil derivatives is considered. With the combined action of 5-hydroxyuracil and ascorbic acid, a significant decrease in the initial oxidation rate is observed, characteristic of inhibition only by ascorbic acid. The experimentally observed induction period is numerically equal to the sum of the induction periods of uracil and ascorbic acid, provided that the stoichiometric inhibition coefficient for ascorbic acid is 1. The effective inhibition rate constant (k₇ × 10⁴, L mol^–1 s^–1) was measured for the combined action of ascorbic acid and 5-hydroxy-6-methyluracil (8.1 ± 0.6), 5-hydroxy-3,6-dimethyluracil (8.8 ± 1.1) and 5-hydroxy-1,3,6-trimethyluracil (7.5 ± 0.6). It is assumed that in the initial period the decrease in the oxidation rate occurs mainly due to the reaction of ascorbic acid with tetrahydrofuran peroxyl radicals.