Reactions of 2-methylpropene and other alkenes on zinc oxide

Abstract

Studies have been made on the hydrogenation, deuteration and exchange with deuterium of ethene, propene and 2-methylpropene on zinc oxide and Arrhenius parameters for the reactions have been determined. Some general conclusions are reached about the catalytic behaviour of alkenes on zinc oxide from these and earlier results.

Exchange occurs readily with alkenes which can dissociate to allyl intermediates but can also take place via the formation of vinyl intermediates with other alkenes, particularly at higher temperatures. Similar rates of alkane formation are found with different alkenes at temperatures at which the strengths of adsorption of the alkene are equivalent. The mechanism of alkane formation does not contribute to exchange of the alkene nor give rise to double-bond movement and the probable rate-determining step is the formation of adsorbed alkyl species which are then rapidly converted to alkane.