PNNL

Abstract

Here we coproduce two value-added chemicals, methanol and propylene glycol from CO2, H2 and propylene oxide for the first time using a heterogeneous Cu catalyst and an amine-based co-catalyst, achieving >80% selectivity. Compared to conventional CO2 hydrogenation to methanol, the coproduction approach improved the productivity of methanol by >five-fold. This integrated process can potentially achieve 100% carbon and hydrogen efficiency. A preliminary techno-economic analysis indicates that coproduction could reduce methanol costs by 30-60% relative to traditional gas-phase thermocatalytic conversion of CO2 to methanol process. In addition, the combined reaction is highly exothermic, allowing for waste heat recovery to generate electricity, which improves the overall thermal efficiency of the process by 23% compared to the conventional route. The estimated cradle-to-grave CO2 emissions for the coproduction approach are significantly lower than that of the conventional gas-phase CO2 hydrogenation to methanol (-45 vs +25 g CO2/MJ methanol combusted). This reduction is primarily attributed to (a) high atom and thermal efficiency and (b) displacement credits from the glycol co-production.