Hydrogenation of acetylene in excess ethylene on an alumina supported palladium catalyst in a static system

Abstract

Studies have been made of the kinetics of the hydrogenation of mixtures containing 2 % of acetylene in ethylene on an alumina supported palladium catalyst in a static system. Information has been obtained about the nature of the selectivity of the reaction of acetylene. Detailed analyses of the kinetics have been made as the ratio of the pressure of acetylene to ethylene decreases and subsequently as the remaining hydrogen is used up.The poisoning action of carbon monoxide, which selectively inhibits the hydrogenation of ethylene, has also been studied.Tracer studies using carbon-13 labelled acetylene, light ethylene and hydrogen with analysis by combined gas chromatography-mass spectrometry, have shown unambiguously that ethane produced from the hydrogenation of a mixture of acetylene in ethylene comes predominantly from the ethylene.The reaction between acetylene, ethylene and deuterium gives a greater understanding of the surface processes involved and produces ethane which is mainly [2H2]ethane.It is postulated that two types of site exist on the surface, type X which hydrogenates both acetylene and ethylene and on which acetylene is adsorbed ∼2200 times more strongly than ethylene at 293 K and type Y which is easily poisoned by carbon monoxide and can hydrogenate ethylene even in the presence of acetylene.