Carbon-supported PtSn Catalysts: Characterization and Catalytic Properties

Abstract

Carbon-supported PtSn catalysts were prepared by impregnation using a commercial activated carbon after purification and oxidation (H2O2, 20 v/v%) treatments. The support surface chemistry of the carbon after purification and the oxidized carbon, and successive impregnation or coimpregnation procedures were the variables investigated. The catalysts obtained were characterized using the following techniques: TPD and TPR experiments, H2 chemisorption, XPS and XAFS, and activity assessment in the following reactions: cyclohexane dehydrogenation (reaction insensitive to structure), cyclopentane hydrogenolysis (reaction sensitive to structure) and carvone hydrogenation, which allows analysis of the selectivity of PtSn catalysts (carvone contains one C=O group and two C=C bonds for hydrogenation). The objective of the study is to find any relationships between the preparation procedure and the support properties, the characteristics of the resulting catalysts, and the catalytic behavior. The porosity of the carbon support together with the surface oxidation determines the accessibility of reactants to the active sites. Unusual selectivity to alcohols was found. Addition of tin caused blocking and dilution of the platinum clusters. The carbon support also affected the selectivity either because of its electronic properties or because of the particular metal structures developed.