Russian Journal of Applied Chemistry最新文献

Virtually unlimited volumes of serpentine resources stimulate search for new procedures for its processing, including those involving thermal activation. Along with the calcination parameters (temperature, time), the crystal-chemical features of the initial serpentines are an important factor. They predetermine the sequence of the formation of new phases in the course of thermolysis and the content of these phases in the heat treatment product. The influence of the calcination temperature on the thermal decomposition of a serpentine mineral, antigorite, was studied by differential scanning calorimetry, X-ray diffraction analysis, and Mössbauer spectroscopy. Amorphous antigorite is not formed in the course of thermolysis, and the intermediate amorphous magnesia–silicate phase is a mixture of two dehydroxylates differing in the ability to react with acid solutions. The activity of the calcination products was determined by two different methods. The optimum calcination temperature is 750°C; it ensures the maximal content of the amorphous active magnesia–silicate phase.

The influence of various structural types of smart dispersion-filled polymer composite materials (DFPCMs) on such shape-memory effect (SME) parameters as the shape fixation and recovery coefficients (R_f and R_r) and SME kinetics characterized by the rate of the initial shape recovery (υ_r) was studied for the first time, with the polyurethane + modified silicon carbide (SiC) particles as example. The main dependences describing the relationship of the shape fixation and recovery coefficients (R_f and R_r) and of the shape recovery rate (υ_r) with the generalized parameter Θ, DFPCM structural type, and surface morphology of SiC particles were found. The contribution of the specific surface area of dispersed SiC particles (S_BET from 3 to 45 m² g^–1) to the smart properties of the disperse systems was demonstrated for the first time.

The phase composition, structure, and size of particles and agglomerates formed by annealing of the powder obtained from hydrophobizing organosilicon liquid in the presence of aluminum powder (5–10 wt %) were studied by X-ray diffraction, Fourier IR spectroscopy, and laser granulometry. The annealing temperature varied from 550 to 700°С influences the mean size of the individual particles, and the aluminum content influences the agglomerate size. An increase in the heat treatment temperature leads to a decrease in the mean diameter of separate particles. The samples containing 10% aluminum powder have the largest agglomerate size. In turn, the formation of the polycrystalline silicon phase from the amorphous silica-containing powder system in the temperature range of solid-phase reactions depends on the particle and agglomerate size. To obtain polycrystalline silicon from samples containing coarser agglomerates, it is necessary to raise the annealing temperature at equal process time. The minimal annealing temperature for the start of the polycrystalline silicon formation was 550°С, and the required amount of aluminum powder was 5%.

The possible structures of mixed-ligand NiCl₂ complexes and the thermodynamic parameters of the reaction of the hydroxymethylphosphine formation under the conditions of liquid-phase catalytic synthesis of tris(hydroxymethyl)phosphine were calculated by the density functional theory (DFT) using the hybrid density functional (B3LYP) and the LANL2DZ basis set, taking into account the hydration effects. The formation of the complex [NiCl₂–ethylenediamine] prevents the catalyst deactivation, and the formation of the complex [NiCl₂–ethylenediamine–tris(hydroxymethyl)phosphine] favors the catalyst activation.

The possibility of improving the procedure for preparing vanadyl phthalocyaninate in a mixture of normal aliphatic hydrocarbons by replacing phthalic anhydride in the starting reactants by phthalimide was evaluated. In the system with phthalimide, the vanadyl phthalocyaninate yield was thus increased by 21% and the synthesis time was decreased by a factor of 3. The formation of vanadyl phthalocyaninate was confirmed by elemental analysis, IR spectroscopy, X-ray photoelectron spectroscopy, and optical absorption spectroscopy. Vanadyl phthalocyaninate can be efficiently separated after the synthesis from other system components by dissolution of the product in concentrated H₂SO₄, followed by precipitation of the metal complex on dilution of the sulfuric acid solution with water.

Oxidative conversion of methane to С₂ hydrocarbons using a mixture of CO₂ with a small amount of O₂ as an oxidant was studied. The use of zeolite catalysts with monoatomic rhodium distribution allows the reaction to be performed at low temperatures and pressures (380–450°С, 0.1–3.0 MPa) in the gas-phase mode. When performing the oxidative conversion of methane in the flow-through mode, the use of the monoatomic catalytic system containing an additional doping component (Zn, Cu, Mg) allows the ethane yield to be increased by ~60% relative to the system without additional component. In the flow-through–circulation mode, the ethane yield on the monoatomic rhodium zeolite catalyst additionally doped with Zn increases by a factor of 2.3 relative to the flow-through mode.

The catalytic activity of C,N-chelate diaminocarbene palladium(II) complexes containing the 3,4-diaryl-1Н-pyrrol-2,5-diimine fragment in the Suzuki reaction was studied. Comparative analysis of the catalytic activity of two types of C,N-chelate diaminocarbene complexes containing in the inner sphere, along with the diaminocarbene ligand, two different ligand combinations, (1) organic isocyanide and chloride ligand and (2) two chloride ligands, was performed. The influence of the electronic effects of substituents in the catalyst on the reaction yield was examined.

The possibility of recovering and concentrating Pd(II) from simulated nitrate–nitrite PUREX process raffinate with a highly effective extractant, 4-[(hexylsulfanyl)methyl]-3,5-dimethyl-1-phenyl-1H-pyrazole (chloroform as a diluent), was examined. The 0.10 M extractant solution rapidly (within 5 min) and completely recovers Pd(II) with its tenfold preconcentration in the organic phase and highly selective separation from Fe(III), Pr(III), and Ni(II). The extracted Pd(II) and coextracted Ag(I) are stripped with a 2 M NH₄OH + 10 g L^–1 NH₄NO₃ solution to more than 99.9 and to 97.1%, respectively.