Zr-Doped ZnO Microspheres for Highly Efficient and Stable Synthesis of Dimethyl Carbonate From Methanol

Zinc-based heterogeneous catalysts for the synthesis of dimethyl carbonate (DMC) suffer from unstable active sites and rapid deactivation during recycling. To address this issue, a series of zirconium-doped zinc oxide microspheres (ZnO@x%ZrO 2 ) were prepared. Among them, the optimal sample ZnO@5%ZrO 2 achieved a propylene carbonate (PC) conversion of 58.20%, a DMC selectivity of 89.90%, and a yield of 52.30%. Moreover, after five cycles, the selectivity of this catalyst decreased by only 4.10%, whereas undoped ZnO experienced a 15.70% drop in selectivity after just one use. Various characterization techniques (SEM, XRD, XPS, NH 3 -TPD, CO 2 -TPD, H 2 -TPR) revealed that high-valent Zr 4+ ions substituted Zn 2+ in the ZnO lattice, inducing a large number of oxygen vacancies to maintain charge balance and generating the required acid-base sites for the reaction. By tuning the zirconium loading, the electronic structure, vacancy concentration, and acid-base synergistic effects could be optimized, primarily dominated by moderate-strength basic sites complemented by acidic sites. This cooperative effect reduces the activation energy of the ester exchange reaction, significantly enhancing catalytic activity and excellent cycling stability. Graphical A Zr-doped ZnO microsphere catalyst was developed, in which Zr 4+ replaced Zn 2+ , resulting in a defect structure with abundant oxygen vacancies and the formation of a solid solution structure, which significantly enhanced the activity and stability of ZnO.