V. S. Smirnov

Influence of a catalytic reaction on the surface composition and roughness factor of palladium-ruthenium alloys

Using X-ray photoelectron spectroscopy (XPS) and differential flow methods, the surface composition and surface area of Pd−Ru alloys have been examined before and after their use as catalysts. The increase in the catalytic activity of the alloys leads to the enrichment of their surface in ruthenium. It is concluded that the catalytic activity of these alloys is governed by the composition, structure and (to a lesser degree) the roughness of the surface.AbstractДля сплавов Pd−Ru до и после использования их в качестве катализаторов исследованы состав поверхности методом рентгеновской фотоэлектронной спектроскопии и удельная поверхность дифференциальным методом натекания. С ростом активности катализатора его поверхность сильно обогащалась рутением. Сделан вывод, что активность сплава определяется составом, структурой поверхности и в меньшей степени её шероховатостью.

Effect of reaction products on dehydrogenation rate of isoamylenes on a membrane catalyst

The dehydrogenation of isoamylenes on a membrane catalyst composed of a Pd catalyst with 5.9% Ni under nongradient conditions is inhibited by isoprene, while the reaction rate passes through a maximum when the partial pressure of hydrogen in the starting mixture is increased.

Effect of composition of binary palladium alloys on direction of catalytic transformations of 1,2-cyclohexanediol

A study of the binary alloys of Pd with Ni, Ti, Cu, and Rh as regards the transformations of 1, 2-cyclohexanediol disclosed that the character of the products is strongly dependent on the nature of the second component of the alloy. Cyclohexanone and phenol predominate in the products obtained on the binary Pd alloys that contain Ni, Ti, or Cu, while the Pd-Rh alloys are selective catalysts for the dehydrogenation of 1,2-cyclohexanediol to pyrocatechol without forming phenol.

Hydrogen permeability and catalytic activity of membranes made from palladium-copper alloys in the dehydrogenation of 1,2-cyclohexanediol

Palladium-copper alloys, which contain from 37 to 42% Cu, have both a high hydrogen permeability and a substantial catalytic activity in the de hydrogenation of 1,2-cyclohexanediol, which makes it possible to use them as membrane catalysts for this reaction.

Monomerization of dicyclopentadiene and hydrogenation of cyclopentadiene in a stream of methane over palladium-ruthenium alloy

Conclusions1.Methane can be used as a heat-transfer agent for the monomerization of dicyclopentadiene and as carrier gas for the hydrogenation of cyclopentadiene (CPD) to cyclopentene at membrane catalysts consisting of a palladium alloy with 9.8% of ruthenium.2.Increases in the selectivity and in the yield of cyclopentene were found during hydrogenation of CPD with hydrogen passing through the membrane catalyst compared with the delivery of a mixture of CPD vapor and hydrogen at the same catalyst.

Kinetics of isoamylene dehydrogenation on a membrane catalyst

The kinetics of isoamylene dehydrogenation was studied by a gradientless method on a palladium-nickel membrane catalyst. The experimental dependence of the dehydrogenation rate on isoamylene partial pressure and contact time is in satisfactory agreement with the assumption that the rate-controlling step of the process is the surface reaction of chemisorbed isoamylenes.AbstractВ проточно-циркуляционной установке изучена кинетика дегидрогенизации изоамиленов на мембранном катализаторе из сплава палладия с 5,9 масс.% никеля. Полученные экспериментальные данные о влиянии парциального давления изоамиленов и времени контакта на скорость дегидрогенизации удровлетворительно согласуются с предположением, что лимитирующей стадией процесса является поверхностный акт реакции.

The effect of various types of treatment on the surface layer composition in binary palladium alloys

1. The reactions of oxidizing and reducing agents can markedly alter the surface compositions in binary alloys of palladium with aluminum, copper, and nickel. The treatment in hydrogen brings about a marked enrichment of the surface of Pd-Cu and Pd-Al alloys with respect to the low-melting metal. Air treatment covers the surface of Pd-Cu and Pd-Ni alloys with copper and nickel oxides. 2. Only catalytic dehydrogenation of cyclohexane to benzene leads to surface enrichment with respect to the second of the components in alloys of palladium with ruthenium and rhodium, redistribution of the metals between body and surface resulting in a sharp increase in the catalytic activity.

Conversions of ethylene on a silver membrane catalyst

1. Oxygen diffusing through a silver membrane catalyst is more active in the formation of products of the complete oxidation of ethylene than oxygen introduced in a mixture with ethylene. 2. The permeability of silver to oxygen passes through a minimum with increasing ethylene pressure at the output surface of the silver membrane and reaches a value equal to the permeability in the case of diffusion into vacuum.

Change in composition of surface layer of palladium-rhodium alloys during catalytic reaction

1. A substantial enrichment of the presurface layer in rhodium of palladium alloys, containing 5 and 10% Rh, after cyclohexane was dehydrogenated on them, was detected by the x-ray photoelectronic spectroscopy (XPES) method. 2. Enrichment of the surface of the foil in rhodium is accompanied by an increase in the dehydrogenation rate of cyclohexane to benzene.

The catalytic conversions of six-membered cyclanes over an aluminium-palladium catalyst

Abstract 1. 1. The conversions of cyclohexane, methylcyclohexane, and ethylcyclo- hexane over a PdAl 2 O 3 catalyst at temperatures of 350–470° and pressures of hydrogen of 10–50 arm in a continuous flow system have been studied. 2. 2. It has been shown that the rate of dehydrogenation of the hydrocarbons investigated increases with an increase in their molecular weight. 3. 3. Simultaneously with their dehydrogenation, all the hydrocarbons investigated underwent isomerization into corresponding cyclopentane and cyclohexane hydrocarbons. The maximum yields of isomers were obtained at 430–450° and a pressure of hydrogen of 50 atm. 4. 4. It has been noted that at low temperatures methylcyclohexane isomerizes predominantly into ethylcyclopentane and at high temperatures into dimethylcyclopentanes. 5. 5. The chromatographic analysis of C 5 C 8 hydrocarbons has been carried out with the evaluation of some isomeric dimethylcyclopentanes, trimethylcyclopentanes, dimethylcyclohexanes, and other compounds of normal and iso structure.