Enhancing the activity of Pd/Zn–Al–O catalysts for esterification of CO to dimethyl oxalate via increasing oxygen defects by tuning the Zn/Al ratio

Abstract

Pd-Based heterogeneous catalysts possess excellent activity for direct esterification of CO to dimethyl oxalate (DMO), and lots of investigations have been conducted on the active component Pd. Nevertheless, there are few studies on the effect of the support structure on its catalytic performance. The cationic regulation of the spinel-like oxide Zn–Al–O support with a clear structure increased the activity of the catalyst from 48.4% to 63.7%. It was found that there are few oxygen defects in the pure support, but a large number of oxygen defects appear in the reduced catalyst, and their number is positively correlated with the Zn/Al ratio of the support. A large number of oxygen defects make the valence state of the active metal lower, which improves the activity of the catalyst. This work provides evidence revealing the favorable effect of the catalyst support on the direct esterification of CO to DMO.