Formation of polymer-grade ethylene by selective hydrogenation of acetylene over Au/CeO2 catalyst

Acetylene hydrogenation and formation of coke deposits were investigated on a gold catalyst supported on ceria. The effect of the H-2/C2H2 ratio was studied over a range of values. In all cases, the catalyst revealed a selectivity of 100% below 300 degrees C. Above this temperature, the only byproduct was methane formed via carbene intermediates, which polymerize above 300 degrees C, provoking deactivation. The deactivation was studied by TPO; accumulation of carbon at low temperature provoked deactivation only after several hours of operation, but did not affect the selectivity. The roles of the pretreatment and of the presence of CO also were examined. A mechanism for the hydrogenation reaction is proposed. (c) 2008 Elsevier Inc. All rights reserved.