Kinetika i kataliz

It has been established that, contrary to previous ideas chemical processes in the propagation of flame, explosion and detonation of gases, are chain reactions proceeding according to previously unknown laws of non-isothermal chain processes. The characteristic reaction times in deflagration and detonation in the combustion zone are less than a ten-thousandth and a millionth of a second, respectively. The features of the mechanisms and laws that determine such high rates and accelerations of reactions, their extremely strong temperature dependence is revealed. Using kinetic and spectroscopic methods, the decisive role of atoms and radicals, which are formed in concentrations reaching tens of percent of the concentrations of the initial reagents, is shown. Efficient chemical methods for controlling all combustion modes have been developed.

In the present work, for the first time for stoichiometric methane–oxygen mixtures, two numerical kinetic methods reproduce the nonmonotonic boundary of the “three pressure limits” region obtained by N.N. Semenov’ coworkers experimentally in a wide pressure range ~20–600 Torr. In where take place the llow pressure ignition peninsula, range of parameters, the simulation of self-ignition delays was carried out. In this case, a nonlinear scheme of methane oxidation (150 reactions) was used to calculate ignition delays. According to the linear part of the same scheme (~20 reactions of the methyl peroxide cycle), formulas for the corresponding Jacobi matrix determinant were obtained for the first time, and for each given temperature, from the equation that determines its zero, three pressure roots were found, from which the boundary line of the region, nonmonotonic in pressure, was constructed self-ignition. Satisfactory convergence of the experimental and calculated data is shown both in terms of delay times and in terms of the position of the limits in the P–T space.

In this work graphitic carbon nitride doped by chlorine was prepared by a two-stage technique at first. At the first stage melamine was hydrothermally treated with glucose, at the second stage the mixture of as-prepared melamine with ammonium chloride was calcined. The obtained samples were investigated by the set of methods: X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy, photoelectrochemical methods. All prepared photocatalysts was tested in the reaction of photocatalytic hydrogen production from basic solutions of triethanolamine. It was shown that the highest values of the catalytic activity and short-circuit current density were obtained over the photocatalyst preparing by calcination of the mixture containing 30% ammonium chloride and 70% melamine. The highest value of the catalytic activity was 1332 μmol h^–1 g^–1 and was more than the catalytic activity of carbon nitride preparing by the melamine calcination without another treatment in 22 times.

The results of studying the kinetics of the reaction of catalytic oxidation of oleic acid methyl ester with hydrogen peroxide in a two-phase system (aqueous phase-organic phase) in the presence of a bifunctional catalyst of the composition [(Octⁿ)₃NMe]₃{PO₄[WO(O₂)₂]₄} are presented. For the selected reaction conditions, the first orders of catalyst, substrate and oxidizer are established. The value of the activation energy for the temperature range 313–353 K is 47 ± 3 kJ/mol, and the pre-exponential multiplier is (6.0 ± 0.3) × 10⁷ L² mol^–2 min^–1.

The products of catalytic hydrochlorination of acetylene-D₂ over palladium chloride complexes supported on activated carbon are a mixture of vinyl chloride stereoisomers resulting from syn- and anti-addition of the hydrogen chloride molecule to the triple bond. The reaction is accompanied by isomerization of primary trans-vinyl chloride into its cis-stereoisomer, but the characteristic isomerization times exceed significantly the duration of acetylene hydrochlorination. This fact allowed us to estimate the portion of products formed exclusively during the catalytic reaction, the difference in the effective activation energies of the syn- and anti-addition routes (~21 kJ/mol), and to demonstrate a monotonic increase in the part of the syn-addition product with increasing mass loading ω of the active metal, reaching saturation at ω > 2 wt %.