Role of silica-alumina catalyst texture in the reaction of propane oxidative dehydrogenation in the presence of sulfur dioxide

The effects of preparation conditions, component ratio, and pretreatment temperature (1000–1550‡C) of silica-alumina samples on their phase composition, texture characteristics, and catalytic properties are studied in the reaction of the oxidative dehydrogenation of propane by sulfur dioxide. It is shown that the samples contain individual silicon and aluminum oxides. The product of their interaction (mullite) is formed only at 1550°C. Mesoporous and macroporous catalysts with monoand polydispersed pore distributions over sizes are obtained. It is found that the porous structure of the catalyst plays a key role in the process of the oxidative dehydrogenation of propane in the presence of sulfur dioxide at 600–700°C. The apparent rate of propylene formation increases with an increase in the pore volume with radii between 10 and 100 nm. Propane is transformed into propylene more selectively on the catalyst where the pores with radii of 10–100 nm dominate; narrower pores (< 10 nm) are favorable for the formation of coke and complete oxidation products.     

Biodegradable composite of starch and carboxylated latex for arts and crafts

A biodegradable composite of starch and latex of carboxylated methyl methacrylate-butadiene copolymer for decorative and applied art was developed and its performance was studied. The composite degrades in the environment after the end of the service life.     

Mesomorphic and Dielectric Properties of Supramolecular 3,5-Diamino-1-dodecyl-1,2,4-triazole

The formation of a thermotropic smectic phase in 3,5-diamino-1-dodecyl-1,2,4-triazole was revealed by polarizing microscopy and DSC. Depending on heating and cooling conditions, transitions between different types of layered packings occur, which was evidenced by dielectric measurements. Quantum-chemical simulation established that the mesomorphism of 1,2,4-triazole derivatives is associated with the formation of supramolecules with a higher polarizability anisotropy. The calculation results confirmed the possibility of lateral hydrogen bonding which favors layered smectic packing.

     

Suppression of the anomaly of low-frequency permittivity in ferroelectric triglycine sulfate by microwaves

Microwave dielectric spectra of ferroelectric triglycine sulfate are measured in the littlestudied frequency range from 90 to 150GHz, and the suppression of low-frequency dielectric anomaly by microwaves at these frequencies is investigated. It is shown that suppression occurs only in the range of non-Debye dielectric dispersion. An additional dispersion mechanism based on the activation-diffusion model of orientational polarization and transit-time effects for quasi-free carriers is proposed to explain the microwave impact.     

Features of Localized Plasticity Autowaves in an FCC-Alloy

Russian Physics Journal - The kinetics of deformation processes on the yield plateau is studied in aluminum alloy 1550. It is found out that in the general case, the Lüders band fronts move...     

Oxygen Electroreduction Catalysts Based on Polymer Complexes of Nickel with Schiff Bases

In energy-storage systems such as fuel cells and metal-air batteries, the main current-forming process is the reaction of oxygen electroreduction (OER). A simple method is proposed for synthesizing OER catalysts based on polymer complexes of transition metals (nickel, palladium) with Schiff bases prepared by electrochemical polymerization of starting monomers. The OER catalysts are prepared by thermolysis of polymers in inert atmosphere. Their properties are characterized by the methods of cyclic voltammetry with the use of a rotating disk electrode. The surface state (the catalyst film density, the size and composition of particles) is controlled by scanning electron microscopy with X-ray microanalysis. The electrode demonstrates the high catalytic activity in the oxygen electroreduction reaction in alkaline solutions (higher than 750 mA/mg of the initial polymer mass).     

Three-dimensional structure of phosphorus-containing heterocycles

Conclusions By means of dynamic PMR spectrometry, UV spectra, dipole moments, and ab-initio SCF MO LCAO calculations of model compounds, it has been shown that for 2-hydro-2-oxo-4,5,7,8-dibenzo-4H-1,3,2-dioxaphosphocins there is characteristically a three-component equilibrium with the participation of both of the boat-chair forms and one boat form with equatorial position of the P-H bond. The thermodynamic characteristics of the equilibrium have been determined.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1764–1768, August, 1986.The authors wish to express their appreciation to O. V. Ovodova for assistance in the experiment.