Mechanochemical synthesis of Cu2S bonded 2D-sulfonated organic polymers: continuous production of dimethyl carbonate (DMC) via preheating of reactants†
The vital need for an external dehydrating agent in high-yield production of dimethyl carbonate (DMC) has been circumvented via in situ formation of copper sulfide (Cu2S) bonded 2D-sulfonated organic polymers, Cu-SOPm and Cu-SOPs, by deploying single-step and solvent-assisted mechanochemical and solvothermal methods, respectively. Cu-SOPm exhibited excellent catalytic activity for the continuous production of DMC from carbon dioxide and methanol without using a dehydrating agent. The presence of a higher amount of sulfonic acid groups (–SO3H) is the key factor, which can adsorb the ensuing water during the reaction thus shifting reaction equilibrium in the forward direction; Cu-SOPs is relatively less active catalytically owing to a smaller amount of sulfonic groups. All the reactions are accomplished on a high-pressure fixed-bed flow reactor and the effects of various reaction parameters (flow rate, catalyst amount, system temperature and pressure) are investigated, especially the preheating of the CO2 and CH3OH mixture, which facilitated methanol conversion considerably, and afforded 42.8% yield of DMC with 100% selectivity. The preparation of the catalysts and formation of DMC were supported by a plausible mechanism wherein increased residence time and high reaction pressure always favored the methanol conversion. This study enables the continuous high-yield generation of DMC under flow conditions deploying preheating of substrates and concomitantly addressing the lingering problem for designing a built-in dehydrating capability in the catalyst.