Process intensification and optimization for efficient production of dimethyl carbonate through urea alcoholysis using low-cost anhydrous zinc acetate catalyst

Abstract

Anhydrous zinc acetate was used as a low-cost catalyst for the urea alcoholysis to produce dimethyl carbonate (DMC). Important operating variables including reaction time, temperature and catalyst amount were optimized using response surface methodology. Optimization was assessed through two different approaches. In the first approach, only DMC yield was maximized. N-methyl methyl carbamate (NMMC, the unfavorable byproduct) yield was minimized along with maximizing DMC yield in the second approach. Sobol sensitivity analysis uncovered that reaction temperature and the binary interaction of reaction temperature/catalyst amount were the most influential parameters on DMC yield with 57.01% and 29.17% impacts, respectively. Moreover, temperature and reaction time with 61.13% and 19.74% impacts were the most effective variables on NMMC yield. The multi-objective optimization results were more suitable for application in continuous production of DMC due to avoiding NMMC production. A modified continuous process was also proposed for DMC production. The main advantage of the preposed process was immediate extraction out of DMC from the reaction zone. To investigate the possible reaction mechanism, the Binding Energies (BEs) of the reactants were assessed using Density-Functional-Theory. Results illustrated that the highest BE values belong to the interaction of zinc with the nitrogen of methyl carbamate (MC).