HYDROGEN WATER DEUTERIUM-EXCHANGE REACTION OVER MIXED-OXIDE SUPPORTED NICKEL-CATALYSTS

Three series of catalysts, Ni/Al2O3-SiO2, Ni/Al2O3-Cr2O3 and Ni/SiO2-Cr2O3, were prepared by coprecipitation. In all samples the nickel content was kept constant at 70 at.% Ni, while the support composition was varied. The nickel surface areas, which are required to measure the specific catalytic activities, were determined by hydrogen chemisorption. In the case of the single oxide supported nickel catalysts, the order of the specific catalytic activity values was: Ni/Cr2O3 > Ni/Al2O3 > Ni/SiO2. The specific catalytic activity of the Ni/Al2O3-SiO2 samples, as a function of the support composition, follows approximately the weighted sum of the specific activities of the single oxide supported nickel catalysts. The specific catalytic activity value of the Ni/Al2O3-Cr2O3 and Ni/SiO2-Cr2O3 samples more closely resembled that of Ni/Cr2O3 catalyst. The presence on chromia surface of the chromic anhydride and its tendency to spread onto are supposed to be the cause of this behaviour. Due to their enhanced activity, the Ni/Al2O3-Cr2O3 catalysts can be used for the production and detritiation of heavy water.