Effect of the Nature of Coke-Forming Species on the Crystallographic Characteristics and Catalytic Properties of Metal–Filamentous Carbon Catalysts in the Selective Hydrogenation of 1,3-Butadiene

The particle morphology and surface structure of nickel metal in metal–filamentous carbon catalysts were found to depend on the nature of coke-forming species used in the synthesis of catalysts. Metal carbonization with hydrocarbons that are characterized by high thermodynamic stability results in the formation of well-cut metal particles the surface of which is formed by (110) facets. Selective hydrogenation reactions of diene and acetylene hydrocarbons to olefins are typical of these catalysts. In the catalytic decomposition of hydrocarbons with relatively low thermodynamic stability, metal particles become irregular in shape, and their surface is formed by (111) facets. In this case, the reactions of full hydrogenation of olefin, diene, and acetylene hydrocarbons to corresponding alkanes take place. These data are consistent with the found dependence of the catalytic properties of catalysts on the character of the exterior faceting of active metal particles.     

Effect of Mechanochemical Activation on the Catalytic Properties of Ferrites with the Spinel Structure

It was found experimentally that stacking defects formed in the mechanochemical activation of zinc ferrite enhanced the specific catalytic activity in the reaction of CO oxidation. The specific rate of CO oxidation was a linear function of defect concentration, which was determined using Mössbauer spectroscopy and X-ray diffraction. A conclusion was drawn that the same centers are responsible for an increase in the catalytic activity, the sorption capacity for hydrogen sulfide, and the reactivity of zinc ferrite in the interaction with hydrochloric acid. It was assumed that analogous factors caused an increase in the catalytic activity and reactivity of magnesium ferrite.     

Role of carbonate-carboxylate species during alumina coking

The role of carbonate-carboxylate species on alumina surface has been studied during alumina coking. The species are intermediates poisoning the active sites. Little O₂ added to the hydrocarbon feedstock causes further oxidation of the species and promotion of the active sites.     

Solubility and Stability of Peroxo Solvates KF·nH2O2 in Organic and Aqueous-Organic Media

The solubility and stability of the peroxo solvates KF·nH₂O₂ (n 1) and disinfectants based on them was studied in organic and aqueous-organic solvents. Polyhydric alcohols (glycerol and ethylene glycol) and Tosol (commercial antifreeze) were used as solvents.     

Synthesis of thiopheno-quinizarine derivatives

4,11-Dihydroxyanthra[2,3-b]thiophene-5,10-dione (thiophenoquinizarine) and its 3-methyl derivative were obtained by the cyclization of quinizarin-2-yl derivatives of mercaptoacetaldehyde or mercaptoacetone in acid medium. 4,11-Dimethoxy-and 4,11-dibutoxyanthra[2,3-b]thiophene-5,10-dione were synthesized by the alkylation of the hydroxyl group in the synthesized anthrathiophenes with dimethylformamide dimethylacetal or butyl iodide respectively. Radical bromination of 4,11-dimethoxy-3-methylanthra[2,3-b]thiophene-5,10-dione, depending on the amount of N-bromo-succinimide taken, leads to the formation of 3-bromomethyl-or 3-dibromomethyl-4,11-dimethoxy-anthra[2,3-b]thiophene-5,10-diones. The action of sodium acetate on the obtained bromo derivatives with subsequent hydrolysis of the intermediate acetates led to the synthesis of 3-hydroxymethyl-or 3-formyl-4,11-dimethoxy-anthra[2,3-b]thiophene-5,10-diones. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1478–1485, October, 2007.     

Dilution effect on catalytic pyrolysis of hydrocarbons

It is shown that unlike thermal pyrolysis, the rate of catalytic pyrolysis is greatly affected by dilution of hydrocarbons with inert gases. The nature of this effect has been analyzed.

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Naphthoindoles. 8. Electrophilic substitution reactions of 4,11-dimethyxynaphtho[2,3-f]indole-5,10-dione

Some electrophilic substitution reactions characteristic of indole derivatives have been investigated for 4,11-dimethoxynaphtho[2,3-f]indole-5,10-dione. The corresponding 3 derivatives were obtained as a result of Vilsmeier, Mannich, and acylation reactions.See [1] for Part 7.Russian Chemico-Technological University, Moscow 125190. Center for Drug Chemistry, All-Russian Chemical and Pharmaceutical Research Institute, Moscow 119815. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 939–941, July, 1998.     

Boehmite formation mechanism in precipitate ageing

Phase composition of the products of Al(III) hydroxide ageing at 473 K is shown to be independent of pH. Under these conditions boehmite is always formed whose morphological structure is determined by both the phase composition of freshly precipitated Al(III) hydroxides and the pH of their ageing. A possibility for the formation of needlelike boehmite crystals whose width coincides with the value of b=12.3Å of its unit cell, has been shown.

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Al(III) 473 pH, . Al(III), pH . , b=12,3 Å .

     

Mechanisms of structural bearing capacity exhaustion of large-sized pressure shells made of polymeric composite materials

In this paper, the mechanisms of structural bearing capacity exhaustion of large-sized pressure shells made of polymeric composite materials are considered. These mechanisms include strength reduction of layers within one or more elements of the pressure shell, general buckling of the pressure shell, local buckling, and specific fracture mechanisms of a composite material that take place in particular cases depending on material reinforcement.