Mechanochemical synthesis of Cu2S bonded 2D-sulfonated organic polymers: continuous production of dimethyl carbonate (DMC) via preheating of reactants

Abstract

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.