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 (3,5,5-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.