Catalytic pyrolysis of propane-butane hydrocarbon mixture on the composite ceramic materials in an open system

Catalytic pyrolysis of propane-butane hydrocarbon mixture on the composite ceramic materials with the surface modified with zinc-, cadmium- phosphorus- and silicon-containing compounds in an open system was studied in the temperature range 500–850°C, at the rate of the gas mixture flow 20–200 ml min⁻¹, contact duration 0.75–155 s, and the values of the heterogeneity factor 2.0 to 2.9×10⁵ cm⁻¹. The catalytic activity of the systems under similar conditions was compared, the influence of various factors on the yield of ethylene and propylene was investigated and the sooting was estimated.     

Selective precipitation of rare earth orthophosphates with hydrogen peroxide from phosphoric acid solutions

It has been shown for the first time that the use of hydrogen peroxide allows precipitation of rare earth orthophosphates (La–Tb) from phosphoric acid solutions at temperatures below 100°C. Either anhydrous or hydrated orthophosphates with monazite or rhabdophane structure, respectively, can be obtained depending on rare earth element position in lanthanide series and precipitation conditions (orthophosphoric acid and hydrogen peroxide concentration). Hydrated orthophosphates with rhabdophane structure can be prepared by precipitation with hydrogen peroxide for all studied rare earth elements.     

Oxidation of CO on Zr-, Fe-, Cr-, Ni-, and Cu-containing Catalysts Prepared by Pyrolysis of Metal β-Diketonates on a Synthetic Ceramic Foam

Catalytic systems containing Zr, Fe, Cr, Ni, and Cu composite coatings were suggested for oxidation of CO to CO₂. The coatings were prepared by gas-phase thermolysis of metal acetylacetonates and hexafluoroacetylacetonates on a synthetic ceramic foam. The kinetic and activation parameters of the CO oxidation on these catalysts were determined, and the relative activities of the catalysts were evaluated.     

Oxidation of CO on Mn-Containing Catalysts Prepared by Pyrolysis of Metal β-Diketonates on Synthetic Ceramic Foam

New catalytic systems for oxidation of CO to CO₂ were developed. These systems are based on composite Mn, Mn-Ni, and Mn-Cu coatings and are prepared by gas-phase thermolysis of metal β-diketonates on a ceramic foam support. The relative activity of the new catalytic systems was examined. The kinetic and activation parameters of the oxidation of CO on these catalysts were determined.     

Kinetic features of thermal decomposition of cobalt acetylacetonate and development of catalysts for the oxidation of carbon monoxide,based on the decomposition products

The kinetic features of thermal decomposition of cobalt acetylacetonate in a vacuum were elucidated, and the volatile thermolysis products were identified. The homogeneous-heterogeneous character of the process was shown. Catalysts for the oxidation of CO to CO₂ were developed on the basis of cobalt acetylacetonate decomposition products and synthetic cellular ceramics, and the kinetic and activation parameters of the oxidation were determined.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 11, 2004, pp. 1770–1774.Original Russian Text Copyright © 2004 by Tsyganova, Didenkulova, Shekunova, Faerman, Aleksandrov.This revised version was published online in April 2005 with a corrected cover date.     

Catalytic pyrolysis of the propane-butane hydrocarbon raw material

Principal characteristics are determined of the process of pyrolysis of the propane-butane hydrocarbon raw material in a steel reactor in the presence of catalysts (ceramic film type polyphosphate covering on the steel reactor walls) containing metals of II and III groups of Periodical Table with the overall composition Me _x O _y ·z(P₂O₅), where x = 1, 2; y = 1, 3; z = 2, 3. By the investigation a sequence of catalytic activity of the samples of the metal-containing coverings by their effect on the yield of ethylene and propylene is elucidated: Zn > Cd > Sr > Ce. The similar sequence corresponds to inhibiting activity at the cocking inhibition.     

Synthesis of cerium orthophosphates with monazite and rhabdophane structure from phosphoric acid solutions in the presence of hydrogen peroxide

It has been proposed to conduct the synthesis of cerium(III) orthophosphates by reacting cerium(IV) compounds with hydrogen peroxide in the presence of concentrated orthophosphoric acid at ambient temperature. It has been shown that the reaction of H₂O₂ with CeO₂ suspensions in H₃PO₄ medium produces CePO₄ · xH₂O (rhabdophane structure), while that with CeO₂ solutions in concentrated H₃PO₄ results in CePO₄ (monazite structure).     

Thermal decomposition of cerium(III) perchlorate

Thermal decomposition of Ce(ClO₄)₃ ? 9H₂O and Ce(ClO₄)₃ to give cerium(IV) dioxide in the temperature range 240–460°C was studied by DSC–TGA, X-ray powder diffraction, IR and mass spectroscopy. The thermolysis of these salts was shown to proceed through the stage of formation of intermediate product supposedly cerium oxoperchlorate. The thermal decomposition of cerium(III) perchlorate hydrate at 460°C leads to formation of nanocrystalline cerium dioxide with particle size of 13 nm.     

Carbon monoxide oxidation by atmospheric oxygen on catalysts prepared by pyrolysis of transition metal β-diketonates on the synthetic foam ceramics

The results of development of new catalytic systems for the carbon monoxide oxidation to dioxide are systematized. The catalysts were produced by gas-phase thermal decomposition of the transition metal acetylacetonates on the synthetic foam ceramics. The kinetic and activation parameters of the oxidation on the catalysts were studied and their relative activity was explored. The activity of catalysts at the oxidation with air oxygen were found to depend on the nature of the deposited metal and the carrier. A synergistic effect in the bimetallic copper catalysts was revealed.     

Properties of electrorheological fluids based on nanocrystalline cerium dioxide

Effect of conditions of nanocrystalline cerium dioxide preparation from aqueous solutions on its composition and physicochemical properties and on dielectric characteristics of CeO₂ suspensions in polydimethylsiloxane PMS-20 and the magnitude of electrorheological effect for these suspensions has been analyzed. Relationship between physicochemical properties of CeO₂ nanopowders and polarization and functional characteristics of electrorheological fluids derived therefrom has been established.