Synthesis of methylmercaptane in the presence of base catalysts

Interaction of methanol with H₂S has been studied at 360–500°C in the presence of Al₂O₃ promoted by alkaline metal compounds. As found, catalysts, obtained via promoting Al₂O₃ by carbonate, and potassium or sodium hydroxide, are more basic in relation to tung-state samples. The total catalytic activity increased, while the selectivity toward methylmercaptane decreased with increasing surface basicity.

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360–500°C Al₂O₃, . , , Al₂O₃ , . - .

     

Structure and composition of the surface layer of Zr-containing fiberglass materials

The chemical composition and structure of Zr-containing fiberglass materials were studied by Infrared spectroscopy, X-ray photoelectron spectroscopy, and nuclear magnetic resonance spectroscopy. The domains built of three-dimensional network of silicon–oxygen tetrahedrons connected through zirconium were revealed in the bulk of fiber. The space between these domains was found to be filled with sodium silicates and carbonates (in subsurface layers). It was shown that the leaching of fiberglass materials resulted in the formation of a SiO₂ layer on the fiber surface, which was almost zirconium free.     

Mobility and reactivity of lattice oxygen in Gd-doped ceria promoted by Pt

Summary For samples of the Ce_1-xGd_xO_2-y system prepared by the Pechini route and promoted with Pt, the mobility and reactivity of lattice oxygen were found to correlate with the density of surface and bulk anion vacancies.     

Isopropanol diffusion and dehydration in zeolite Hzsm-5. Spectrokinetic study

The isopropanol diffusion and dehydration in zeolite HZSM-5 were studied by FTIR spectroscopy. The alcohol dehydration was shown to start at the temperature above 60°C. It was found that at temperatures above 350°C, the isopropanol dehydration was limited by diffusion in the mesopores of zeolite. The method developed allows studying the kinetics of interactions of the reagent molecules with the OH-groups at the external surface of the zeolite and inside its channels.     

Reactivity and transformation routes of surface nitrates in the reaction of NOx reduction by C3H8 over cation-exchanged zeolites

FITRS combined with¹⁵N and¹⁸O isotope substitution and TPD have revealed that nitrates are the most abundant ad-NO_x species on over-exchanged Cu- and Co-ZSM-5 zeolites. the transformation rates of such species under the action of a propane—oxygen mixture were found to be comparable and sufficiently high to afford steady-state catalytic activities. A scheme of the reaction mechanism including C, N-containing intermediates detected in work is suggested.     

Hydrocracking vegetable oil on borate-containing catalysts: Effect of nature of support

The structure, texture, and acid properties of platinum catalysts on oxide (Al₂O₃, ZrO₂, ZrO₂–Al₂O₃) and borate-containing supports (B₂O₃–Al₂O₃, B₂O₃–ZrO₂) are studied. The catalysts are tested in the process of hydrocracking sunflower-seed oil at 380°C, 4.0 MPa, and a weight stock feed rate of 1.0 h^–1. It has been found that aluminum oxide (A) contains the γ-Al₂O₃ phase, zirconium dioxide (Z) includes 85 and 15 rel. % of the monoclinic (M) and tetragonal (T) phases, respectively, while zirconium dioxide with the addition of 2.5 wt % Al₂O₃ (ZA) comprises 14 and 86 rel. % of the M–ZrO₂ and T–ZrO₂ phases, respectively. The B₂O₃–Al₂O₃ (BA) and B₂O₃–ZrO₂ (BZ) systems modified with boron oxide (20 wt %) are X-ray amorphous. A Pt/BA catalyst differs from a Pt/A catalyst, while a Pt/BZ catalyst has a larger specific surface area and acidity than Pt/Z and Pt/ZA catalysts and contains Bronsted acidic centers (BACs) along with Lewis acidic centers (LACs). Only LACs are present on the surface of Pt/A, Pt/Z, and Pt/ZA catalysts. The LAC/BAC ratio in Pt/BA and Pt/BZ catalysts is 0.3 and 1.0, respectively. All the catalysts provide complete oil conversion to give C₅₊ hydrocarbons with a yield of 81.7–87.3 wt %. Pt/A catalyzes mainly decarboxylation and hydrogenation–dehydration reactions, while Pt/Z and Pt/ZA provide decarboxylation. The yield of diesel fraction reaches 71.8–73.9 wt % with an n-alkane content of 94.0–95.9 wt %. One-stage oil hydrocracking with the prevalence of hydrodecarbonylation and hydrogenation–dehydration reactions occurs on Pt/BA and Pt/BZ catalysts for 20 h to give the yield of the diesel fraction of at least 81.4 and 74.4 wt % and the total content of iso-alkanes and cycloalkanes of at least 28.3 and 60.7 wt %, respectively.     

Carbonization of alumina-based catalysts in propionitrile ammonolysis

Summary The asymmetric hydrogenation of ethyl 2-acetoxyacrylate (EtA) by cinchonidine modified Pd/Al2O3 and Pt/Al2O3 catalyst is described (ee up to 60 %). This is the first example of asymmetric hydrogenation of an enol esters in heterogenized conditions.     

Effect of the microstructure of Pt/CeO2-TiO2 catalysts on their catalytic properties in CO oxidation

The microstructure of 2% Pt/CeO₂-TiO₂ catalysts has an effect on their catalytic properties in CO oxidation. The nanostructured catalysts as platinum clusters 0.3–0.5 nm in size are the most active. These clusters are stabilized at crystal boundaries formed by irregularly intergrown anatase particles. The catalyst containing platinum particles 2–5 nm in size is less active because of the decrease in the extent of dispersion of platinum and the change of its electron state.     

IR spectroscopic studies of H2S adsorption on acid and base catalysts

IR spectra of H₂S adsorbed on various types of catalysts have been studied by monitoring changes in the properties of their surfaces from the spectra of probe molecules. It is shown that H₂S is adsorbed only dissociatively on basic centers (BC); on proton centers (PC) it forms H-complexes, while with the participation of strong Lewis acid centers (LAC), it is adsorbed both associatively and dissociatively.

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- H₂S , -. , H₂S (), () -, ()- , .

     

Comparative discussion of NH

A comparative study of NH ₄ ⁺ formation on aluminosilicate surface and in an aqueous solution of hydrochloric acid has been carried out in the framework of the nonempirical method with a STO-3G basis. It is suggested that the compensation mechanisms of energy consumptions to form protonated species in both cases are similar.

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-3 - NH ₄ ⁺ - . - .