Selective catalytic hydrogenation of isophorone on Ni-Al alloy modified with Cr

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 (3,5,5trimethyl-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 similar to 100% for 20 degrees C and a conversion level of 63% at a selectivity of 83% for 80 degrees 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. (C) 2008 Elsevier B.V. All rights reserved.