Preparation, characterization and catalytic properties of carbon-supported platinum-zirconium alloy catalysts

Abstract

The preparation ot Pt-Zr alloys by the reduction of ZrO 2 by C in the presence of Pt has been studied. Pt 1− x Zr x solid solution formation started at about 873 K. The value of x increased with the reduction temperature and reached a limiting value of 0.25 at 1273 K. Carbon-supported alloys showed a constant Pt:Zr ratio from one metallic particle to another, but presented some heterogeneity in the particle size distribution, with φ varying from 4 – 30 mm for 10 – 20 wt.% metal loadings. The catalytic activities of carbon-supported Pt and Pt 0.75Zr 0.25 have been compared. In benzene hydrogenation and cyclohexane dehydrogenation, no alloying effect was detected. The alloying effect was found to be important in ethane hydrogenolysis, where the alloy activity was about twenty times smaller than that of platinum at 670 K. One alloying effect was further detected in the hydrogenation of carbon monoxide: Pt 0.75Zr 0.25 was an order of magnitude more active than Pt at 660 K.