Study on application of membrane reactor in direct synthesis DMC from CO2 and CH3OH over Cu–KF/MgSiO catalyst

Membrane catalytic reactor (MCR) combing catalytic reaction with membrane separating process has exhibited a promising pathway to improve reaction conversion and selectivity for its selective permeating products online or controlling the addition of key reactants. In this work, three types of supported membranes (i.e. silica inorganic membrane, polyimide-silica and polyimide-titania hybrid membranes) and copper catalyst supported on MgO–SiO2 composite substrate modified by KF were prepared, were used as MCRs materials and catalyst, respectively, for the direct synthesis of dimethyl carbonate (DMC) from carbon dioxide and methanol. The influences of operating conditions on the conversion of methanol and the selectivity to DMC were discussed. The results show that hybrid membranes have excellent thermal and hydrophilic properties and that water vapor diffusing through them obeyed surface flow mechanism. The reaction behaviors of MCR are higher than those of CCR with the conversion of methanol improved remarkably and the selectivity to DMC increase a few under proper reaction conditions. The catalytic reaction performances are controlled mainly by the characters of catalyst, and the incorporation of MCRs has not changed the reaction mechanism, which played the primary roles as the concentration distributors in the catalytic reaction system.