Surface science and the silver-catalyzed epoxidation of ethylene: an industrial perspective

Key surface science studies relating to the silver-catalyzed epoxidation of ethylene are reviewed from the perspective of industrial catalyst development. Fundamental studies using primarily Ag(111) and Ag(110) single crystals have provided evidence for the key role of atomic rather than molecular oxygen in both the epoxidation and combustion reactions. Model studies employing higher alkenes are also discussed as they reveal the importance of C-H bond reactivity in the combustion pathways. The influence of alkali and halide promoter species via electronic and geometric effects is discussed. Recent STM and in situ Raman studies of oxygen, chlorine and CO2 adsorption on Ag surfaces showing dynamic silver restructuring and the identification of reactive surface species are highlighted as an area that will further the understanding of the epoxidation reaction by providing key structural information. Such information would not only benefit computational modelling efforts, but could also lead to more rational catalyst development processes. (C) 1998 Elsevier Science B.V.