Synthesis and analysis of CO2 adsorbents based on cerium oxide

• CO2 adsorbents based on SiO2, Al2O3, ZrO2, and CeO2 were prepared and measured.
• CeO2-based adsorbent exhibited the largest CO2 adsorption capacity.
• CO2 adsorbed on CeO2 desorbed mainly from 323 K to 473 K.
• Bidentate carbonate and hydrogen carbonate were main species on CeO2.
• Desorption temperature of hydrogen carbonate species were the lowest.

In order to find materials suited for CO2 capture from exhaust gas, CO2 adsorbents based on single-metal oxide consisting of SiO2, Al2O3, ZrO2 and CeO2 were prepared and their CO2 chemical adsorption amounts were measured using CO2 pulse injection. In the CO2 adsorption measurement, the CeO2-based adsorbents exhibited the largest CO2 adsorption capacity. CO2 temperature programmed desorption (TPD) analysis revealed CO2 adsorbed on CeO2 desorbed mainly from 323 K to 473 K with its peak at 393 K, and relatively small amount of desorption continued to 723 K. To study CO2 adsorption and desorption mechanism, CO2 adsorbed on CeO2 and their temperature dependences were analyzed using in situ Fourier transform-infrared (FT-IR) spectroscopy. FT-IR peaks from four CO2 adsorbed species (monodentate carbonate, bidentate carbonate, polydentate carbonate, and hydrogen carbonate species) were identified. Bidentate carbonate and hydrogen carbonate were main species, and the latter desorbed at around 473 K, which was the lowest temperature among species observed. CO2 desorption temperature from other species were approximately 573 K (bidentate carbonate and monodentate carbonate) and 723 K (polydentate), and it was consistent with CO2 TPD analysis. This indicates that the formation of hydrogen carbonate species on CeO2 is a key process to decrease desorption temperature for CO2 capture.

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