We proposed a facilely synthesized catalyst CeO₂@[BMIm][HCO₃] ([BMIm][HCO₃]=1-butyl-3-methylimidazolium bicarbonate for the direct synthesis of dimethyl carbonate (DMC) from CO₂ and methanol as an alternative to present techniques that involve the stoichiometric use of hydrating agents, which presents environmental and toxicological challenges. This catalyst co-operatively capitalizes the unique properties of [BMIm][HCO₃] and CeO₂ nanoparticles to accelerate the reaction efficiently.

Abstract

As a crucial strategy towards a sustainable chemical industry, the direct synthesis of dimethyl carbonate (DMC) from renewable carbon dioxide (CO₂) and methanol (MeOH) is studied using CeO₂ nanoparticles modified with 1-butyl-3-methylimidazolium hydrogen carbonate ([BMIm][HCO₃]) devoid of stoichiometric dehydrating agents. The synthesized CeO₂@[BMIm][HCO₃] catalyst having high thermal stability harnesses the unique physicochemical properties of CeO₂ and the ionic liquid to exhibit a DMC yield of 10.4 % and a methanol conversion of 16.1 % at optimal conditions (pressure of CO₂=5 MPa; temperature=130 °C). The catalytic behavior of CeO₂@[BMIm][HCO₃] studied with a detailed XRD, XPS, CO₂ and NH₃-TPD, Raman spectroscopy, TGA, FTIR, SEM and TEM suggests that the synergy between the two catalytic components originating from an increased surface oxygen vacancies boosts the overall catalytic performance. After several recycling tests, the catalyst demonstrated no significant reduction in DMC yield and methanol conversion. This platform is an attractive approach to synthesize thermally stable nanoparticle@ionic liquid that retains and merges the physical attributes of both materials for producing useful bulk chemicals from readily available chemical resources.