A XPS Study of Raney Copper-Neodymium Catalysts

The hydrogenolysis reaction of methyl formate was investigated over Raney Cu Nd and Raney Cu catalysts using synthetic gas （33%CO+H₂） and pure hydrogen.The X Photoelectron Spectroscopy （XPS） was used for the characterization of the Raney catalysts.The reaction results showed that addition of appropriate amount of neodynium can prominently raise the hydrogenolysis activities of Raney Cu Nd catalysts,and the activity under synthetic gas is slightly higher than that under pure H₂.It illustrated that Raney Cu Nd catalysts do not suffer from the presence of CO in the reaction gases.The results of XPS indicated that the surface copper of catalysts after reduction exists as Cu⁰;but some Cu⁰ was oxidized during the hydrogenolysis reaction,the surface copper mainly exists as Cu⁰ and Cu⁺ after reaction.The oxidation extent of copper varied with the gas atmosphere,and the percentage of Cu⁺ in CO+H₂ is higher than that in pure H₂.After reaction,owing to the addition of rare earth element neodymium,the surface Cu⁺ concentration of Raney Cu Nd catalysts is smaller than that of Raney Cu;consequently,it is proved that the oxidation speed of Cu⁰ was apparently slowed down and the concentration of Cu⁰ was maintained higher.This is the reason why Raney Cu Nd catalysts have higher activities of methyl formate hydrogenolysis.