Monitoring Solid Oxide CO2 Capture Sorbents in Action

The separation, capture, and storage of CO2, the major greenhouse gas, from industrial gas streams has received considerable attention in recent years because of concerns about environmental effects of increasing CO2 concentration in the atmosphere. An emerging area of research utilizes reversible CO2 sorbents to increase conversion and rate of forward reactions for equilibrium‐controlled reactions (sorption‐enhanced reactions). Little fundamental information, however, is known about the nature of the sorbent surface sites, sorbent surface–CO2 complexes, and the CO2 adsorption/desorption mechanisms. The present study directly spectroscopically monitors Na2O/Al2O3 sorbent–CO2 surface complexes during adsorption/desorption with simultaneous analysis of desorbed CO2 gas, allowing establishment of molecular level structure–sorption relationships between individual surface carbonate complexes and the CO2 working capacity of sorbents at different temperatures. Tailorable, reversible solid oxide CO2 sorbents: Sodium‐doped Al2O3 solid oxide sorbents are synthesized and monitored in action, during CO2 capture, with operando IR spectroscopy. A structure–sorption relationship is established between sorbent–CO2 surface complexes and the sorbent working capacity. Surface Al2O3 hydroxyl groups are responsible for low temperature reversible adsorption while small carbonate nanoparticles are responsible for high temperature adsorption.