Effects of 1,2 dichloroethane addition on the optimal silver catalyst distribution in pellets for epoxidation of ethylene

The issue of optimal catalyst distribution was studied experimentally for the ethylene epoxidation reaction network on a Ag/alpha-Al2O3 catalyst in the presence of 1,2-dichloroethane (DCE). For a fixed amount of silver the influence of location and width of the catalytic layer on the conversion of ethylene, and on the selectivity and yield to ethylene oxide, was investigated for different concentrations of DCE (0-2 ppm) using a single-pellet reactor. Two levels of ethane in the feed (0 and 0.5 vol%) and a temperature range between 210 and 270 degrees C were studied. Depending an the experimental conditions, promotion, inhibition, and poisoning effects of DCE were observed. The catalyst distribution and the concentrations of DCE and ethane in the feed, which provide high selectivity and yield, were identified. XPS analysis was also conducted to determine the state and composition of the silver catalyst, both prior and subsequent to reaction. (C) 1998 Academic Press.