Cu/Al2O3 catalysts modified with Pd for selective acetylene hydrogenation

Abstract

A Cu/alumina catalyst has been modified by addition of various quantities of Pd. Characterisation suggests formation of a bimetallic with the surface dominated by Cu. Optimisation of the Cu:Pd ratio (50:1) resulted in a catalyst which combined the properties of Cu and Pd (high ethylene selectivity and activity at low temperature). Using a 3:1 H2:acetylene feed, >99% acetylene conversion and >70% ethylene selectivity was attained at 373K, representing a considerable reduction in the temperature necessary to achieve equivalent activity/selectivity over monometallic Cu. Increasing the H2:acetylene ratio to 10 resulted in >99% acetylene conversion at 363K as well as enhanced ethylene selectivity (>80%). Enhanced activity of Cu at low temperature is attributed to H2 dissociation on Pd with spillover onto Cu sites where the reaction takes place. These bimetallic CuPd catalysts offer sufficient activity at low temperature and could represent a replacement to the current industrial PdAg catalysts.