Hydrogenation of CO2 on Fe-Based Catalysts: Preferred Route to Renewable Liquid Fuels

Catalytic hydrogenation of CO2 can be conducted either in one pot (CO2 hydrogenation) or in two stages (RWGS and CO hydrogenation). Its configuration consists of either three reactors in series with interim water removal (one-pot process) or CO2 separation and recycling (two-stage process) to reach high CO2 conversion. The two-stage process enables to reach optimal H2/CO and temperature in the hydrogenation reactor to yield higher productivity while minimizing production of the aqueous phase, which offset the advantages of the one-pot process. The techno-economic study determined that there is no apparent advantage in operating the hydrogenation reaction in one stage at current green hydrogen prices. The decision between the two routes should be based on catalyst stability and selectivity toward desired products. Blending 10% of liquid product from both processes with fossil fuels at current prices increases the fuel production cost by 30%, which can be offset by higher carbon pricing or equivalent incentives.