Adsorption Separation of CO2 from CO in Syngas: Improving the Conversion of the Reverse Water Gas Shift Reaction

Abstract

In this research project, adsorption is considered for the separation of CO2 from CO for applications such as industrial syngas production and in particular to improve the conversion of the Reverse Water Gas Shift (RWGS) process. The use of adsorption technology for these applications requires an adsorbent that can effectively separate out CO2 from a gas mixture containing CO2, CO, and H2. However, adsorption of H2 is insignificant when compared to both CO2 and CO, with only CO2 and CO being the adsorbed species. The adsorption of CO2 and CO was investigated in this work for four major types of industrial adsorbents which include: activated aluminas, activated carbons, silica gels, and zeolites. Zeolites, with their ability to be fine tuned many parameters which may affect adsorption, were investigated in terms of the effect of the cations present, SiO2/Al2O3 ratios, and structure to determine how to optimize adsorption of CO2 while decreasing adsorption of CO. This will help to determine a promising adsorbent for this separation with focus on maximizing the selective adsorption of CO2 over CO. To investigate this separation three scientific experimental methods were used; gravimetric adsorption isotherm analysis, volumetric adsorption isotherm analysis, and packed bed adsorption desorption breakthrough analysis. Gravimetric and volumetric methods allow for testing the adsorbent with the individual species of CO2 and CO. This investigation will let us determine the pure component adsorption capacity, heats of adsorption, regenerability, and basic selectivity. Packed bed adsorption breakthrough experimentation was then carried out on promising adsorbents for the CO2 separation from a mixture of CO2, CO, and H2. These experiments used a gas mixture that would be comparable to that produced from the RWGS reaction to determine the multicomponent gas mixture behaviour for adsorption. Temperature swing adsorption (TSA) with a purge gas stream of H2 was then used to regenerate the adsorbent.