Comparative study of binderless zeolites and carbon molecular sieves as adsorbents for CO₂ capture processes

CO2 capture from concentrated sources such as power plants will play an important role in reducing CO2 emissions, contributing to climate change mitigation. Adsorption technology has attracting scientific attention because it offers improved energy efficiency and reduced costs. Two of the most used families of adsorbents in the industry are zeolites and carbon-based adsorbents. This study compares the CO2 separation performance of two promising groups of adsorbents belonging to these families: binderless zeolites and carbon molecular sieves (CMSs). Five adsorption key performance indicators (KPIs), namely adsorption capacity, working capacity, regenerability, selectivity and adsorption selection parameter were obtained from the adsorption isotherms (CO2 and N2; measured at 0-10 bar and 283-323 K) and used to assess the potential of the adsorbents for CO2 capture processes. In general, the KPIs were better for binderless zeolites than for CMSs although CMSs had better regenerability. Zeolites 13XBL and 5ABL were selected as the most promising adsorbents and were tested in a laboratory column set-up for dynamic adsorption of a CO2/N2 mixture (15%/85% v/v), resembling a dry flue gas composition. Simulations of column adsorption experiments were then carried out combining an extended dual-site Langmuir (DSL) model for binary mixtures with Aspen Adsorption™. Binderless zeolite 13XBL showed a higher selectivity with a lower dependence on the pressure and temperature of adsorption, when compared to zeolite 5ABL. These results show that the 13XBL can be considered a good adsorbent for CO2/N2 separations.