INFLUENCE OF METAL-OXIDES ON THE CATALYTIC ACTIVITY OF NICKEL

Nickel catalysts supported on BeO, MgO, ZnO, Al2O3, Cr2O3, SiO2, TiO2, ZrO2, ThO2, and UO2, with different metal loading, have been prepared by coprecipitation or by impregnation of the basic nickel carbonate w ith a water solution of nitrate of the support. Metal surface areas we re measured by hydrogen chemisorption. The activity of the catalysts h ave been determined under flow conditions, at atmospheric pressure, fo r the deuterium exchange reaction between ammonia and hydrogen. The re action rates normalised to metal surface area are strongly affected by the nature of the support. Generally, the presence of the support enh ances the intrinsic activity of catalyst compared to that of the nicke l black; the highest increase is shown by TiO2 (ca. 800-fold). The res ults emphasize the importance of the support in the enhancement of the catalytic activity for the deuterium exchange reaction between hydrog en and ammonia. It is assumed that the role of the support is to creat e new active sites at the interface between the metal and the support, either through a direct or an indirect involvement of the support in activation of the ammonia molecule. (C) 1997 Elsevier Science B.V.