TPD and TPSR studies of formaldehyde adsorption and surface reaction activity over Ag/MCM-41 catalysts

The adsorption and surface reaction activity of formaldehyde were studied on the Ag/MCM-41 catalysts with different silver loadings by temperature-programmed desorption (TPD) and temperature-programmed surface reaction (TPSR) methods. It appeared that the silver loading had strong influence on the adsorption and surface reaction activity of HCHO. The addition of silver active species provided new adsorption site for the HCHO at low temperature, and its desorption temperature moved to lower temperature with the increase of silver loading to 8 wt%. With the further increase of silver loading, the desorption temperature of HCHO shifted to higher temperatures, which could be due to the aggregation of silver particles on the surface of the support. Moreover the quantity of adsorbed HCHO at higher silver loading (>8 wt%) changed inversely with the increase of silver content. TPSR experiments indicated that the surface reaction activity for HCHO oxidation was proportional with the adsorption performance of HCHO over Ag/MCM-41 catalysts with different silver loadings, and 8Ag/MCM-41 catalyst showed highest surface reaction activity for HCHO oxidation. Thus it is reasonable to suggest that an appropriate silver loading and particle dispersion would be essential to obtain high catalytic activity for HCHO oxidation at low temperatures.