Studies of the interactions of H 2 and CO with [formula omitted] and TiO 2-promoted [formula omitted

Abstract

The interactions of H 2 and CO with Pd SiO 2 , Pd TiO 2 , and titania-promoted Pd SiO 2 have been investigated using temperature-programmed desorption and temperature-programmed surface reaction. In the presence of TiO 2, as a support or promoter, a portion of the TiO 2 is reduced to TiO x moieties which decorate the surfaces of the Pd particles. These species cause a suppression in chemisorption of H 2 and CO, the magnitude of which is a function of the catalyst reduction temperature. The TiO x moieties have little influence on distribution of H 2 adstates but cause a noticeable change in CO adstates. Decoration of Pd by TiO x moieties also aids the dissociation of CO, and raises thereby the activity for CH 4 synthesis relative to that for Pd SiO 2 .