Ag supported on meso-structured SiO2 with different morphologies for CO oxidation: On the inherent factors influencing the activity of Ag catalysts

Abstract

With the objective to prepare better CO oxidation catalysts and explore the inherent factors to determine the activity of supported Ag catalysts, KCC-1, SBA-15 and MCM-41, a series of mesoporous SiO2 with different morphologies, have been synthesized and used as supports for Ag to prepare catalysts (7% Ag/KCC-1, 7% Ag/SBA-15 and 7% Ag/MCM-41) for CO oxidation. It is found that the morphologies of the SiO2 supports influence the dispersion of the supported Ag species, thus resulting in catalysts with different Ag grain sizes and active metallic surface areas, as proved by XRD and H2 adsorption-desorption results. With fibrous KCC-1 silica spheres as the support, the mobilization and aggregation of the Ag particles can be effectively hindered by the open access surface mesopores. Therefore, compared with SBA-15 and MCM-41, Ag nanoparticles with much smaller grain sizes have been achieved, thus resulting in a catalyst with significantly improved activity. Furthermore, a linear relationship has been found between the differential CO oxidation rates and the Ag grain size. Therefore, it is concluded that the active Ag metal surface area is the determining factor for the activity of the silica supported Ag catalysts.