The effect of support calcination on carbon supported palladium catalysts for solvent-free benzyl alcohol oxidation

Abstract

Carbon is ubiquitous as a catalyst support used in a wide range of reactions. Various thermal and chemical approaches can tailor the physical properties of the support, such as the surface functionality, to control activity and selectivity. In this study, the effect of pretreatment of the carbon support, via calcination, is explored. A series of Pd/C catalysts prepared with increasing calcination temperature, and the final supported catalysts are compared to the untreated sample for their activity in the solvent free aerobic oxidation of benzyl alcohol. The increasing pretreatment temperature coincided with the increased removal of impurities such as sulfur, a higher active metal surface area and an increased acid oxygen functionality. The latter is proposed to dramatically affect metal dispersion resulting in an overall lower intrinsic activity of the catalysts. Interestingly, no effect on selectivity was found when catalysts were studied at iso-conversion. The role of the oxidative treatment was confirmed by comparison to an analogous treatment in nitrogen which had negligible impact on metal dispersion and intrinsic activity compared to the untreated standard material.