Catalytic reactions of o-xylene and m-xylene with deuterium on metal films

Abstract

The exchange and deuteriation of o-xylene and m-xylene have been followed by mass spectrometric analysis using evaporated metal films of iron, palladium, platinum or tungsten as catalysts, usually at temperatures in the range 273–350 K.

Side-group exchange was rapid in all cases but the rates of exchange of ring atoms depended on the metal and were generally lower for atoms ortho to a methyl group. The formation of dimethylcyclohexanes was accompanied by further exchange, the nature of which varied with the metal. Significant amounts of trans-1,2-dimethylcyclohexanes were produced from o-xylene over palladium and iron.

The mechanisms of the reactions are discussed in terms of dissociative adsorption for all types of exchange and a contribution of a ‘roll-over’ reaction of adsorbed cyclohexenes in the formation of dimethylcyclohexanes, particularly with palladium and iron.