CO oxidation over palladium-and sodium-promoted tin dioxide:catalyst characterization and temperature-programmed studies

摘要

One weight percentage PdO/SnO_2 and 0.1 wt.% Na-1 wt.% PdO/SnO_2 catalysts have been synthesized through a sol-gel route and these catalysts have been characterized by XRD,BET,SEM and temperature-programmed adsorption and desorption techniques with regard to their activity for the CO oxidation reaction.CO adsorption and CO-O_2 co-adsorption followed by O_2 TPD have been carried out to observe the role of sodium promotion on the catalytic activity.The catalytic activity of PdO/SnO_2 catalysts is suppressed by blockage of CO active sites by O_2 on co-adsorbed catalysts.Sodium-promoted catalysts possess increased affinity to oxygen and thus,exhibit superior activity upon CO-O_2 co-adsorption,but these catalysts have been observed to perform poorly upon consecutive adsorption of CO and O_2.The effect has been ascribed to enhanced interaction of sodium-promoted surfaces with CO hindering oxygen adsorption on CO precovered surface.