Effect of isolated palladium atoms on the performance of PdAg/Al2O3 catalysts for the selective hydrogenation of acetylene
摘要
Egg-shell catalysts PdAg/Al2O3 with a molar ratio of Ag: Pd ranging from 0.5 to 10 were synthesized in order to study the gas-phase hydrogenation of acetylene. The results obtained by IR spectroscopy of adsorbed CO and transmission electron microscopy confirm the assumption that a catalyst with an equimolar ratio Ag: Pd = 1 contains a substitutional solid solution, while at a ratio of Ag: Pd = 10 single-atom Pd1 sites, isolated from each other by silver atoms are formed. The results presented in this work demonstrate that the transformation of the active sites from the substitutional solid solution structure to the single-atom arrangement entails a considerable increase in selectivity toward the formation of ethylene.