Enhancing the CO<sub>2</sub> Adsorption Capacity of γ-Al<sub>2</sub>O<sub>3</sub> Supported Alkali and Alkaline-Earth Metals: Impacts of Dual Function Material (DFM) Preparation Methods
Chae Jeong-Potter, Monica Abdallah, Shruti Kota, Robert J. Farrauto
Abstract
The term “dual function material” (DFM) was coined by our research group for codispersed catalysts (e.g., Ru) and alkaline sorbents on the same high-surface-area carrier. These materials allow for combined CO2 capture and catalytic conversion, thus their dual functional nature. Herein, we report an additional, unexpected function; combining Ru with specific adsorbents and carriers substantially enhances CO2 capture capacity. Investigation of several Ru + sorbent/carrier formulations shows that the enhancement effect is not inherent with Ru but requires a specific combination of DFM components. Most surprisingly, significant enhancement of CO2 adsorption is retained during multiple cycles of adsorption in O2 and methanation, where RuOx species are present. Ru0 is known to adsorb CO2, as required for methanation, but the significant enhancement in the presence of RuOx indicates that Ru does not directly contribute to the adsorption mechanism. Instead, Ru allows for more efficient activation of adsorption sites on the alkaline sorbent via catalytic reduction during pretreatment. This is verified by greater adsorption capacity in materials with higher catalytic activity. These findings open up new pathways for designing materials with higher capture capacity than conventionally thought. Such materials can play a key role in mitigating the negative effects of climate change.