Highly efficient synthesis of dimethyl carbonate from methanol and carbon dioxide using IL/DBU/SmOCl as a novel ternary catalytic system

•IL with DBU and SmOCl is used as ternary catalyst system for the synthesis of DMC.•This catalyst system increases DMC yield at optimum temperature.•Increase of DMC yield activates CO2 and methanol by IL/DBU and SmOCl, respectively.•Efficiency of the ternary catalyst system is tested by recycling.•Predicted mechanism of catalytic activity is described with 13C NMR experiment.

Excellent yield of dimethyl carbonate (DMC) was obtained by direct physical or chemical adsorption of carbon dioxide on [EmimOH][NTf2] ionic liquid (IL) in the presence of samarium oxychloride (SmOCl) and 1,8-diazabicyclo[2.2.2]undec-7-ene (DBU) as a super base. The novel ternary catalyst system consisting of [EmimOH][NTf2], DBU, and SmOCl was found to appreciably convert methanol (13.01%) to DMC with excellent selectivity (99.13%). The adsorption of CO2 on IL in the presence of DBU was analyzed by 13C experiment. Moreover, catalytic reactivity of SmOCl and OH-functional group was proved by a predictable mechanism. Various parameters such as reaction temperature, pressure, reaction time, and reusability of catalyst were investigated to maximize DMC yield.

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