Reactions of p-xylene with deuterium on supported platinum catalysts

Abstract

The exchange of the hydrogen atoms in p-xylene with deuterium and the deuteration of p-xylene were used as test reactions to examine the role which supports play in determining the catalytic properties of platinum on various substances. After allowing for differences in the dispersion of platinum by expressing rates in terms of the platinum available to chemisorb hydrogen, there was a remarkable similarity between the results obtained for catalysts on the same support but from different sources. The rates of the reactions at 100 °C followed the order: exchange of ring atoms ≥ exchange of the methyl hydrogen atoms > deuteration, but the relative rates varied as the support was changed from γ alumina to α alumina or to silica. In discussing the effect of the supports on the activity of the metal, attention is directed to a possible role of strongly held water on the supports.