Abstract:
Roles of lanthana on silica supported palladium catalysts for ethanol decomposition over 2%Pd/Si02, 2%Pd/0.5%La2O3/SiO2, and 2%Pd/3%La203/Si02 were investigated. The reactions were carried out between 200 and 500℃ at an atmospheric pressure. Results from powder XRD and CO adsorption show that palladium dispersion over lanthana-modified silica was higher than that of unmodified one. Besides, the lanthana-modified silica catalysts are more active and selective for the ethanol decomposition than those of the unmodified ones at the temperature of 200-300℃. On the other hand, lower activity and selectivity were observed on lanthana-modified catalysts in the temperature range 400-500℃. The results suggest that the good Pd dispersion promoted by lanthana not only enhances the catalytic performance for the ethanol decomposition but also increases the active sites responsible for an ethanol dehydration, a side reaction which induces carbonaceous deposits and, thus, reduces the performance of the catalysts.
