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Abstract: Raney-type Ni-based catalysts containing a small amount of Cr or Co were prepared from Ni32−x Al68Cr x and Ni32−x Al68Co x (x =1, 3 or 6) rapidly quenched alloys by leaching in 1M NaOH. These degradation processes occurring at the surface and in the bulk of the alloys were used for promoting the catalytic activity of these materials. The modifications of the internal structure, chemical composition and morphology of the alloys proved to be a useful method for transforming inactive Ni–Al–Cr and Ni–Al–Co alloy precursors into active and selective catalysts. The hydrogenation of isophorone (3,5,5-trimethyl-2-cyclohexen-1-one) was used as a catalytic test for the modified materials. The catalytic tests showed that the conversion of isophorone hydrogenation increases with temperature but decreases with the addition of Cr or Co to the Ni–Al alloy. Conversely, selectivity to dihydroisophorone (3,3,5-trimethylcyclohexanone) formation drops with temperature but for Cr- or Co-containing catalysts it is distinctly higher than for that of a conventional Raney Ni catalyst. The most promising catalyst seems to be that obtained from Ni–Al–Cr1 alloy; it is characterized by both high conversion and high selectivity. Further hydrogenation of dihydroisophorone to homomenthol (3,3,5-trimethylcyclohexanol) appeared to be strongly restrained on the above catalysts and the reaction did not proceed even after 7 days under p =70atm. Scanning electron microscopy (SEM), Auger electron spectroscopy (AES), scanning Auger microscopy (SAM), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) allowed the changes occurring during the activation process to be identified, and their implications for catalytic function to be considered. [Copyright &y& Elsevier]

Abstract: Degradation processes occurring during leaching in NaOH aqueous solution at the surface and in the bulk of Ni–Al–Cr rapidly quenched alloy, initially containing 29% at. Ni, 68% at. Al and 3% at. Cr, were used for promoting its catalytic activity and selectivity for hydrogenation of isophorone (3,5,5-trimethyl-2-cyclohexen-1-one). The reaction was performed under the atmospheric pressure using gaseous hydrogen and 2-propanol as a solvent. The catalytic activity for the hydrogenation of isophorone to dihydroisophorone (3,3,5-trimethylcyclohexanone) attained a conversion level of 28% at a selectivity of ∼100% for 20°C and a conversion level of 63% at a selectivity of 83% for 80°C. Moreover, further hydrogenation of dihydroisophorone to homomenthol (3,3,5-trimethylcyclohexanol) appeared to be strongly restrained with the above catalyst. Scanning electron microscopy (SEM), scanning Auger microscopy (SAM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) allowed changes occurring during the activation process to be identified and their implications for catalytic function to be considered. A tentative mechanism of the influence of Cr addition on a selective C=C bond hydrogenation over the catalyst is discussed. [Copyright &y& Elsevier]

Abstract: The influence of Cr (1–6at.%) on the catalytic activity and selectivity of Ni–Al alloy in isophorone (3,5,5-trimethyl-2-cyclohexen-1-one) hydrogenation was studied. The catalysts were obtained from the rapidly quenched precursors by leaching in NaOH aqueous solution. The catalytic tests were performed at various temperatures (20–80°C) under the atmospheric or elevated pressure using gaseous hydrogen and 2-propanol as a solvent. Ni–Al–Cr alloy with 1at.% Cr appeared to be the most active and selective catalyst, with the conversion level and selectivity to dihydroisophorone (3,3,5-trimethylcyclohexanone) exceeding 99%. On the other hand, further hydrogenation of dihydroisophorone to homomenthol (3,3,5-trimethylcyclohexanol) was strongly restrained by the Cr-containing catalysts. Scanning electron microscopy, Auger electron spectroscopy, energy dispersive X-ray spectroscopy and X-ray diffraction allowed changes occurring during the catalyst preparation to be identified and their implications for catalytic function to be considered. [Copyright &y& Elsevier]