Studies of the interactions of H 2 and CO with [formula omitted] promoted with La 2O 3, CeO 2, Pr 6O 11, Nd 2O 3, and Sm 2O 3

Abstract

The interactions of H 2 and CO with Pd SiO 2 promoted with La 2O 3, CeO 2, Pr 6O 11, Nd 2O 3, and Sm 2O 3 have been investigated using temperature-programmed desorption and temperature-programmed surface reaction. Introduction of the promoter following the preparation of the Pd SiO 2 catalyst results in a partial coverage of the Pd particles by the oxide promoter. Upon reduction of the promoted catalysts, portions of the promoter in contact with Pd undergo reduction. The partially reduced rare earth oxide species covering the Pd particles reduce the amounts of H 2 and CO that can be adsorbed on the metal. The rare earth oxide moieties have a slight influence on the distribution of H 2 adstates but cause a significant change in the distribution of CO adstates. Decoration of Pd by rare earth oxide moieties also aids the dissociation of CO, and raises thereby the activity for CH 4 synthesis relative to that for Pd SiO 2 . The promoter also serves to increase the activity for CH 3OH synthesis and the formation of CO 2 via the water-gas shift reaction.