High Selectivity Reactive Carbon Dioxide Capture over Zeolite Dual-Functional Materials

Reactive carbon dioxide capture (RCC) is a process where carbon dioxide (CO2) is captured from a mixed gas stream (such as air) and converted to products without first performing a separation step to concentrate the CO2. In this work, zeolite dual-functional materials (ZFMs) are introduced and evaluated for simulated RCC. The studied ZFMs feature high surface area, crystalline, microporous zeolite faujasite (FAU) as the support. Sodium oxide ("Na2O") is impregnated as an effective capture agent capable of scavenging low concentration CO2 (1,000 ppm). Exchanged and impregnated sodium on FAU chemisorbs CO2 as carbonates and bicarbonates but does not promote the conversion of sorbed CO2 to products when heated in hydrogen. The addition of Ru promotes the formation of formates, while the addition of Pt generates carbonyl surface species when heated in hydrogen. The active metal then promotes extremely high selectivity for CO2 hydrogenation to either methane on Ru catalyst (~150 degrees C) or carbon monoxide on Pt catalyst (~200 degrees C) when heated in reducing atmospheres.