Activation of dimethyl carbonate on CeO2 surface: A combined experimental and theoretical study

Abstract

Dimethyl carbonate (DMC) has recently emerged as a green reagent that finds versatile applications in methoxycarbonylation, carbonylation, and methylation reactions due to its multiple functionalities. In order to optimize the activity/selectivity of DMC-mediated heterogeneous catalytic reaction, it is imperative to enhance the fundamental understanding of the activation of DMC on the catalyst surface. In this study, the chemistry of DMC on the CeO2(111) surface was investigated using in-situ infrared spectroscopy, temperature-programmed surface reaction, and density functional theory calculations. It is shown that DMC readily converts into adsorbed methoxycarbonyl and methoxy on CeO2(111) at near room temperature. Upon heating, methoxycarbonyl decomposes into methoxy and carbonyl; the formed carbonyl could react with the surface oxygen atom (OS) of CeO2(111) to form desorbed carbon dioxide (COOS), leaving a surface oxygen vacancy. The surface methoxy groups undergo intermolecular hydrogen transfer to form CH3OH and HCHO, which upon heating either desorb or dehydrogenate with OS to form adsorbed methoxy and formate (with OSH), respectively. Adsorbed formate could react with OS to form desorbed COOS at higher temperatures. These findings provide fundamental insights into the catalytic chemistry of DMC on CeO2(111) surface, which may prove informative for the CeO2-catalyzed DMC-mediated reactions.