Reactive direct air capture of CO2 to C–C coupled products using multifunctional materials

Current direct air capture (DAC) approaches require a significant amount of energy for heating CO2-sorbed materials for regeneration and for compressing CO2 for transportation purposes. Rationally designing materials offering both capture and conversion functionalities could enable more energy and cost-efficient DAC and conversion. We have developed a single sorbent-catalytic (non-noble metal) material for the Integrated Direct Air Capture and CATalytic (iDAC-CAT) conversion of captured CO2 into value-added products. Solid sorbents are integrated with catalytic components to first capture CO2 from air. Subsequently, captured CO2, with renewable H2 co-feed is converted into olefins and paraffins. To the best of our knowledge, this is the first proof-of-concept demonstration for production of C2 products such as olefins from captured CO2. Among the different sorbent-catalytic materials studied, Fe/K2CO3/Al2O3 showed the best performance for integrated CO2 capture and conversion to C2 products. CO2 capture capacity of 8.2 wt% was achieved under optimized capture conditions at 25 °C, and a conversion of >70% to paraffins and olefins was achieved at 320–400 °C. The hydrogenation of captured CO2 was facilitated by the in situ formation of Fe3O4 and Fe5C2 species. The proximity between K and Fe was identified to be critical for producing C2 products from the captured CO2. The preliminary technoeconomic and life-cycle assessments suggest that the cost of the DAC can be considerably decreased by adopting the suggested iDAC-CAT technology, while renewable olefins could potentially be produced with negative greenhouse gases emissions.