Silver Catalysts Supported on High Surface Area α‐Alumina: Effect of Carbohydrate Template Size and Heat Treatment on Phase Purity

Abstract

Abstractα‐Alumina is a non‐porous metal oxide with applications in ceramics and catalysis. Introducing pores into this material to create catalytically relevant surface area is challenging due to phase transitions over a wide temperature range. Current synthesis strategies involve hard templates such as synthetic polymers, e. g. polymethylmethacrylate (PMMA). Here, we compare cellulose and carbonized glucose as low‐cost and natural alternative templates for high surface area α‐alumina with a two‐step heating method. Quantitative XRD was used to methodically investigate alumina phase purity. Increasing the template size in the range of 220–1000 nm improved α‐alumina purity from 75 to 98 %, while maintaining high surface areas (21–29 m2 g−1). Phase purity increases substantially by prolonging the calcination time. The synthesized high surface area α‐alumina was studied as support for silver catalysts in the epoxidation of ethylene and allowed high silver loadings. Ethylene oxide selectivity increased with enhanced α‐alumina phase purity. Our 30 wt % silver catalyst on pure high surface area α‐alumina did not show loss in selectivity compared to a 15 wt % silver catalyst on commercial non‐porous α‐alumina. This shows the potential of carbohydrate templates, the importance of templating parameters and the benefits of pure high surface area α‐alumina as support for silver catalysts.