Epoxidation of ethylene over silver catalysts supported on α-alumina crystal carriers

New pure crystalline alpha-alumina carriers used in catalytic epoxidation were made of primary alpha-alumina crystal particles of 2-18 mum. The material was previously prepared by the calcination of transient alumina molecules in hydrogen chloride or chlorine-water vapor mixture at 1073-1673 K. The carriers had high purity, homogeneous pore distribution, and specific mean pore diameter in the range of 0.3-2.3 mum, which agreed with volume-based median pore diameter (VMPD). The pores comprised spaces or cavities surrounded by crystal planes of the primary particles. The Cs and Re-copromoted Ag catalysts supported on the alpha-alumina crystal carriers, in the epoxidation of ethylene without organic halides, showed good performances, i.e. high and very stable ethylene conversion and ethylene oxide selectivity. The best mean pore diameter of the alpha-alumina crystal carriers required for the epoxidation existed in the range of 0.5-1.2 mum. (C) 2002 Elsevier Science B.V. All rights reserved.