UC Berkeley

Electrosynthesis of ethanol from carbon dioxide (CO2) is a promising route to generate a sustainable fuel and a convenient feedstock for chemical manufacturing. While significant progress has been achieved in boosting the selectivity of CO2 to ethanol, the subsequent ethanol separation remains a bottleneck, which prevents leveraging the laboratory results into large-scale systems. Here we report vacuum membrane distillation as a method that efficiently concentrates dilute ethanol streams produced by CO2 electrolysis (CO2R), yielding up to ∼40 wt% ethanol in pure water. In our design considerations, we include previously underappreciated thermodynamic properties of the catholyte (salting-out effect) and propose strategies allowing a more precise estimation of energy inputs to the separation processes. Our work provides the basis for the detailed design of complex systems which integrate flow reactors and liquid separations and supports scaling of the systems previously considered not optimized for industrial use.