Ion-exchange modified zeolites X for selective adsorption desulfurization from Claus tail gas: Experimental and computational investigations

Zn, Co and Ag modified NaX zeolites were prepared by ion-exchange method and the post-synthesized samples were characterized using EDS, XRD, FT-IR, SEM and N2 adsorption. The selective adsorption performances for H2S and COS from Claus tail gas were evaluated in a fixed bed adsorption column. In addition, the underlying mechanism for H2S and COS adsorption on zeolites X was revealed by DFT computation. Among all the samples, AgX shows the most excellent adsorption performance, which shows the highest H2S and COS breakthrough adsorption capacities up to 1.53 mmol/g and 10.5 mol/g, respectively. The used AgX zeolite can also be regenerated by thermal treatment at 350 degrees C under air atmosphere. The DFT study indicates that the S-M bond between H2S or COS and metal ion can be formed during the adsorption process. Furthermore, the Ag-sulfide complex shows the strongest S-M interaction, hence, benefits the adsorption of H2S and COS on Ag-exchanged zeolite X.