NITROGEN MONOXIDE DECOMPOSITION CATALYSTS PREPARED FROM AMORPHOUS NI-VALVE METAL-PD ALLOYS

Surface-activated amorphous Ni-valve metal(Ta, Nb and Zr)-Pd alloys have been used for the decomposition of nitrogen monoxide. The alloys, which are first activated by immersion in hydrofluoric acid and subsequently oxidized by exposure to oxygen at 500-degrees-C, show a high activity for the decomposition of nitrogen monoxide and have superior deterioration resistance. The catalytic activity of the alloy catalysts is affected by the valve metal elements. The tantalum- and niobium-containing alloy catalysts show higher activities and nitrogen formation selectivities than those of the zirconium-containing alloy. Double oxides of NiTa2O6 and NiNb2O6 are formed during the reaction at temperatures higher than 750-degrees-C and, at the same time, the catalytic activity increases sharply. The synergistic effect of palladium and the double oxides seems to contribute to the high catalytic activity of the Ni-40Ta-1Pd and Ni-40Nb-1Pd alloys.