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The study investigates interactions between palladium and silver in Pd–Ag bimetallic catalysts supported on a mesoporous carbon material Sibunit and, in particular, the dependence of these interactions on the deposition sequence of the metal precursors. Using XRD and TEM results, it was shown that impregnating the support with an aqueous solution that contained nitrate salts of both metals, followed by hydrogen treatment at 500°C, generates uniformly sized Pd0.6Ag0.4 particles (dav = 5.6 nm). These particles exhibit high selectivity (79%) in the reaction of acetylene hydrogenation to ethylene. The catalysts synthesized by sequential impregnation of the support with solutions of Pd and Ag nitrates interleaved with heat treatment in H2 exhibited a lower selectivity (68–73%) due to the formation of particles non-uniform both in composition and size (about 4 to 60 nm). The IR spectroscopy data suggest this effect is presumably associated with the removal of O-containing functional groups from the carbon surface during the reduction of the supported precursor. Given that O-groups act as anchoring sites for the precursors of active components and suppress the ability of Sibunit to reduce metals from their salt solutions, the subsequent deposition of the second metal salt causes a non-uniform distribution of this metal on the surface and the generation of larger particles. [ABSTRACT FROM AUTHOR]

The catalysts 1 wt% palladium supported on carbon nanoglobules (CNGs) were shown to be highly active in the liquid-phase hydrogenation of various nitroarenes and provided nearly 100% selectivity to aromatic amines at complete conversion under mild conditions (323 K, 0.5 MPa, 1 h). The catalytic activity (in terms of turnover frequency and substrate conversion) and selectivity depend on the kind of CNGs support, catalyst preparation method and the reaction conditions (solvent nature). The Pd/CNGs catalyst can be repeatedly used while maintaining the same catalytic performance. The excellent performances of Pd/CNGs catalysts can be due to the globular morphology of the supports as well as the absence of micropores and pronounced surface defects. [ABSTRACT FROM AUTHOR]

Based on the Sibunit carbon composite, Ru–Cs(Ba)/Sibunit catalysts with Cs(Ba) : Ru molar ratios of 0.5, 1.5, and 2.5 were obtained. The catalytic activity of the obtained promoted catalysts in the decomposition of ammonia and their thermal resistance to methanation are compared. In the reaction of ammonia decomposition, the specific activity (Wsp) of barium-containing catalysts proved to be 2 times lower than the specific activity of cesium-containing samples with the same molar M : Ru ratio. Thus, Wsp at 500°С was 29.4 mmol H2 min–1 for 0.5Cs–Ru/Sibunit and 15.4 mmol H2 g–1cat min–1 for 0.5Ba–Ru/Sibunit. It was shown that the introduction of barium at molar ratios Ba : Ru = of 0.5–2.5 significantly increases the thermal stability of the samples defined as the ratio of the weight of hydrogen obtained on the catalyst to the weight of carbon subjected to methanation. There is 52 g H2 for nonpromoted Ru/Sibunit catalyst, 370 g H2 for the 0.5Ba–Ru/Sibunit sample, 200 g H2 for the 1.5Ba–Ru/Sibunit sample, and 150 g H2 for the 2.5Ba–Ru/Sibunit sample per 1 g of carbon loss. [ABSTRACT FROM AUTHOR]

The best known procedures for aluminum activation are discussed and systematized. The analysis of published data and of results of the proper physicochemical research reveals that the phenomena of surface distribution, intergrain penetration and the internal diffusion in the crystal grains underlie the nature of aluminum activation with liquid metal alloys based on gallium. The experimental investigation using X-ray fluorescent spectroscopy of diffusion processes in the systems Al-Ga-In were performed for the first time. The procedures for formation of catalytically active complexes of AlCl3 type by treating the activated aluminum in situ in reaction media with chlorinated hydrocarbons were considered. [ABSTRACT FROM AUTHOR]