Designing bifunctional catalysts for the one-pot conversion of CO2 to sustainable marine transportation fuels

Abstract

Meeting ambitious net-zero targets will require the replacement of marine fossil fuels with sustainable alternatives such as dimethyl ether (DME). DME is non-toxic, can be fully produced via a circular carbon economy and can be rapidly deployed due to its compatibility with existing liquid petroleum gas infrastructure. One-pot production of DME from CO₂ via a methanol intermediate is achieved by combining redox and Brønsted or Lewis acid sites. Herein, we have synthesised, characterised and tested a variety of bifunctional CuZnO/silicoaluminophosphate catalysts for the one-pot production of DME. A range of synthetic approaches were employed to combine the redox and acidic functionalities in order to derive synthesis–structure–property correlations to guide the design of improved catalysts. We found that a CuZnO/SAPO-34 catalyst made via impregnation and drying can achieve 80% DME selectivity with no detectable toxic CO by-product formation. High acid site abundance resulted in extensive dehydration of the intermediate methanol, which increased localised water production, suppressing the CO-forming reverse water gas shift reaction and thus yielding exceptional DME selectivity that is amongst the highest in literature.