Effects of Precursors on Preparation of Pd/α-alumina Catalyst for Synthesis of Dimethyl Oxalate

Abstract

The influence of two palladium precursors, PdCl2 and Pd(NO3)2, on the preparation of catalyst applied in the CO coupling reaction to synthesize dimethyl oxalate was studied. It is revealed that PdCl2 is much more difficult to decompose than Pd(NO3)2 during calcination, and for catalyst prepared from PdCl2, temperatures as high as 773 K are necessary to obtain surface Pd0, while for catalyst prepared from Pd(NO3)2, the corresponding temperature is 473 K. Furthermore, two palladium distributions across the pellet supports are illustrated. The eggshell palladium distribution resulting from using Pd(NO3)2 as precursor was proven more suitable for the present coupling reaction than the uniform palladium distribution obtained by using PdCl2. The results suggest that Pd(NO3)2 is superior to PdCl2 in preparing catalysts for the CO coupling reaction, and the active components on the support outer face have a more efficient utilization than that on the support inner face, which makes moderate reduction of Pd loadin...