Hydrogen-water deuterium exchange over nickel-chromia supported on alumina: I. Catalyst preparation and characterization

Abstract

In this study of catalysts for the deuterium exchange reaction between hydrogen and water, nickel-chromia supported on γ-alumina spheres was the catalyst studied. Porous γ-alumina spheres were impregnated with solutions of nickel and chromium compounds. Electron probe microanalysis was used to measure concentration profiles and total nickel and chromium content. Scanning electron microscopy was used to examine the surface morphology, and mercury porosimetry was used to measure pore volumes. Total surface areas were measured by nitrogen adsorption. Nickel from the sulfate deposited near the outside of the spheres, whereas nickel from nitrate and chloride solutions penetrated to the interior. Reducing the time of impregnation or using a wet support hindered the nickel penetration. Chromium from the nitrate and from chromic acid of low concentration was deposited near the outside of the support. If two impregnations were used consecutively, the solute from the first impregnation could redissolve and and be carried towards the center of the particle during the second impregnation. This movement could be prevented by drying and calcining after the first impregnation. Catalysts impregnated with nickelous nitrate or chromic nitrate had higher pore volumes, surface areas and pore diameters than did the support. On the other hand, the catalyst impregnated with nickelous sulfate had a lower surface area than the support.