Low-Temperature Activated Direct Air Capture Methanation Using K-β″ Alumina

Abstract

400 ppm of CO 2 was captured with Ru/K 2 CO 3 on K-β″ alumina at 30 °C and was transformed into CH 4 successfully when the temperature was increased to 300 °C. K-β″ alumina was employed as the support material, and K + ions were designed to access Ru particles and induce the activation of adsorbed CO 2 . By the promotional effect, the K-β″ alumina-supported catalyst displayed a lower methanation temperature (120 °C) than the γ-Al 2 O 3 -supported one (150 °C). The K-β″ alumina-supported catalysts also exhibited high CH 4 selectivity (79%) and highly stable cyclic properties throughout the tests. Diffuse reflectance infrared Fourier transform spectroscopy revealed that K + in K-β″ alumina actively intervenes in the formation of intermediates (CO 3 2– and CO). The promotion in reactions will be due to σ → π K backdonation and can assist in their reactions to other intermediates (formate and carbonyl) at 120 °C. This implies that promotion of CH 4 intermediates’ formation was aided by the conduction of K + in K-β″ alumina.