(693d) Adsorption Separation of CO2 and CO to Increase CO2 Conversion to CO for the Production of Synthetic Fuels

Efforts to reduce greenhouse gas (GHG) emissions from coal-fired power plants are focused primarily on carbon capture and sequestration (CCS) in which sequestration implies permanent disposal, usually underground. If widely implemented, carbon capture will result in availability of huge amounts of CO₂. Converting CO₂ to CO as an active precursor for synthetic fuel production via the Fischer Tropsch synthesis is proposed in this study as an alternative to CO₂ sequestration and disposal. This conversion can be achieved by the reverse water gas shift (RWGS) reaction, in which CO₂ reacts with hydrogen to produce CO and H₂O. For this method of reducing CO₂ emissions to be viable, maximum conversion of CO₂ to CO is imperative. Integration of an efficient separation system downstream of the RWGS reactor, and recycling of unreacted CO₂ to the reactor inlet, could achieve increased conversion. In this study, adsorption was examined as the primary separation mechanism to enable recycling of CO₂. Different adsorbents were investigated in terms of activity for pure gas (CO₂ and CO) adsorption. The best-performing candidates were then tested on a multi-component mixture simulating the RWGS reaction outlet stream for a flow-through system. The process characteristics (adsorption equilibrium and kinetics, selectivity, hydrothermal stability), as well as the effects of adsorption temperature and pressure were examined for various scenarios.