Sustainable Synthesis of Dimethyl- and Diethyl Carbonate from CO2 in Batch and Continuous Flow-Lessons from Thermodynamics and the Importance of Catalyst Stability

Matthew F O'Neill; Meenakshisundaram Sankar; Ulrich Hintermair

doi:10.1021/acssuschemeng.2c00291

Sustainable Synthesis of Dimethyl- and Diethyl Carbonate from CO₂ in Batch and Continuous Flow-Lessons from Thermodynamics and the Importance of Catalyst Stability

ACS Sustain Chem Eng. 2022 Apr 25;10(16):5243-5257. doi: 10.1021/acssuschemeng.2c00291. Epub 2022 Apr 12.

Authors

Matthew F O'Neill^{1

2}, Meenakshisundaram Sankar¹, Ulrich Hintermair²

Affiliations

¹ Cardiff Catalysis Institute, School of Chemistry, Cardiff University, Cardiff CF10 3AT, United Kingdom.
² Centre for Sustainable and Circular Technologies, University of Bath, Bath BA2 7AY, United Kingdom.

Abstract

Equilibrium conversions for the direct condensation of MeOH and EtOH with CO₂ to give dimethyl- and diethyl carbonate, respectively, have been calculated over a range of experimentally relevant conditions. The validity of these calculations has been verified in both batch and continuous flow experiments over a heterogeneous CeO₂ catalyst. Operating under optimized conditions of 140 °C and 200 bar CO₂, record productivities of 235 mmol/L·h DMC and 241 mmol/L·h DEC have been achieved using neat alcohol dissolved in a continuous flow of supercritical CO₂. Using our thermodynamic model, we show that to achieve maximum product yield, both dialkyl carbonates and water should be continuously removed from the reactor instead of the conventionally used strategy of removing water alone, which is much less efficient. Catalyst stability rather than activity emerges as the prime limiting factor and should thus become the focus of future catalyst development.