Adsorbent screening for CO2/CO separation for applications in syngas production

Abstract

Single gas carbon dioxide (CO2) and carbon monoxide (CO) adsorption behaviour is investigated in detail with different adsorbents for the potential separation of syngas. In this study, 20 zeolites, 2 activated aluminas, 3 activated carbons, and 2 silica gels were investigated by determining pure gas isotherms of CO2 and CO at 30 °C. The results were compared to literature to determine which adsorbents would be the most promising for CO2 separation from syngas at this temperature. Since CO2 concentrations vary in syngas based on the method of production, different adsorbents were selected for purification and bulk separation of CO2 from a syngas mixture.The individual adsorption capacities of CO2 and CO were analysed separately using a gravimetric system, modelled, and then compared for all of the adsorbents studied. CO2 is shown to be more favourably adsorbed compared to CO, with CO2 having higher adsorption capacities and heats of adsorption for all adsorbent samples studied. High-density silica gel and H-Y type zeolites were found to be promising adsorbents for the bulk separation of CO2 from syngas due to the shape of their isotherms, large CO2 adsorption capacities, their favourable adsorption capacity ratios for CO2 over CO. For the purification of syngas, Na+ exchanged FAU structured zeolites with their high CO2 adsorption capacity at low pressures, and favourable CO2 over CO adsorption capacity ratios was found to be the most promising adsorbent.