Environmental assessment of dimethyl carbonate production: comparison of a novel electrosynthesis route utilizing CO2 with a commercial oxidative carbonylation process

Abstract

Life cycle assessment (LCA) has been used at an early design stage to evaluate the environmental sustainability of a novel process for synthesizing dimethyl carbonate (DMC) from waste CO2. The process involves an electrochemical reaction of CO2 and methanol in the presence of potassium methoxide and the ionic liquid 1-butyl-3-methylimidazolium bromide to produce DMC. Experimental data and process simulation have been combined to estimate the environmental impacts and compare them to the conventional commercial "Eni" process based on oxidative carbonylation of methanol. Eleven environmental impact categories have been assessed from "cradle to gate", including global warming potential (GWP), toxicity potentials, and resource depletion. For example, GWP of DMC produced in the electrochemical process ranges from 63.3 to 94.5 kg CO2 eq./kg DMC, depending on a process configuration. This is around 25 times higher than GWP of the commercial process estimated in this study at 3.2 kg CO2 eq./kg DMC. This is because of the low conversion achieved in the current design of the electrochemical process (0.7%), requiring high energy consumption in the separation process. The results suggest that the process yield must be increased to at least 20% to reduce the GWP to a level comparable with the commercial process. At this yield, the electrochemical process also becomes more sustainable than the commercial system for most other impacts considered. The study demonstrates how LCA can play a key role in the development of environmentally more sustainable processes during design by combining experimental data and process simulation at an early stage of technology development.