EFFECTS OF SUPPORT MATERIAL AND SULFATION ON PROPANE OXIDATION ACTIVITY OVER PLATINUM

Propane oxidation is used as a model reaction to study effects of platinum concentration, support material, and catalyst sulfation. Support materials examined are γ-alumina, zirconia, and silica in a platinum dispersion range from about 0.05 to 1.0. Experiments are conducted with recirculation batch and integral flow reactors. For highly dispersed platinum, the activity decreases in the order zirconia > silica > γ-alumina. Over larger platinum particles, the batch experiments show the same turnover rate on the three supports. On highly dispersed platinum, sulfation, via SO2 oxidation or H2SO4 exposure, significantly increases the catalytic activity of Pt/γ-alumina, while Pt/silica and Pt/zirconia remain unaffected. Surface acid strength is measured with Hammett indicators. Upon sulfation, the acid strength of zirconia and γ-alumina increases, while no change is observed for silica. Acid strength does not have a major influence on propane-oxidation activity. Within the experimental error, the apparent activation energy for propane oxidation is independent of metal concentration, support material, and sulfation, suggesting that changes in activity are primarily the result of a change in reaction-site density. © 1993 by Academic Press, Inc.