Catalytic COS formation on ion-exchanged LTA zeolites during adsorption

In this study, the catalytic reaction of H2S and CO2 to COS and H2O during the adsorptive treatment of a model natural gas on modified Linde type-A (LTA) zeolites is investigated. Breakthrough curves of all 4 components were measured at 25 degrees C in a fixed bed adsorber on eight NaA and CaNaA zeolites with different calcium exchange ratios. The COS breakthrough curves are discussed with regard to the properties of the materials in the exchange series (number of cations, cation position, cation type). The COS curves reveal that catalytic formation of COS occurs at cation positions II and III, whereas no COS formation occurs at position I. Ca2+-ions are more catalytically active than Na+-Ions due to their higher ionic charge. The quantities of COS formed prove that the reaction water plays a significant role in the termination of the reaction. The reaction water adsorbs on the catalytically active cations so that no further COS formation can occur. The feed water, on the other hand, mainly leads to a displacement of the previously adsorbed components (CO2, H2S, COS).