A DFT study on the reaction mechanism for dimethyl carbonate synthesis from methyl carbamate and methanol

Abstract

Using density functional theory, the reaction mechanism for dimethyl carbonate (DMC) synthesis from methyl carbamate (MC) and methanol (CH 3OH) with and without catalysts is investigated. And to investigate solvent effects, the reactions are simulated in CH 3OH solvent by using the conductor like solvent model (COSMO). In our calculation, the uncatalyzed MC methanolysis reaction is kinetically and thermodynamically unfavorable. However, it is obviously catalyzed by acid and base catalysts. By orbital energy calculation, MC methanolysis reaction is considered as the charge-controlled reaction. Thus, electrostatic potential fitted charges as reaction indicator is used to infer the activity of species after catalyst Zn(NH 3) 2(NCO) 2 initiation. And it is confirmed to be successful in reactivity prediction. The catalytic cycles involved the selected active species are proposed. By calculating activation energies, the catalytically active species is considered to be Zn(NH 3) 2(NCO)(NHCOOCH 3), which derives from the reaction of Zn(NH 3) 2(NCO) 2 with CH 3OH. The DMC synthesis from the catalytically active species and CH 3OH is favored, of which the reaction activation energy is effectively decreased.