(392f) Cation-Exchanged Zeolites As the Adsorbent for H2S: Quantum Chemical Calculations

To investigate the potentials of LiY, NaY, KY, CuY, AgY, Cu^IIY, Zn^IIY, and Ni^IIY zeolites as the adsorbent for hydrogen sulfide (H₂S) from Claus process tail gas, quantum chemical calculations based on density functional theory (DFT) were employed to study the adsorption properties of H₂S and other common impurities (CO, H₂O, N₂, and CO₂) using the zeolite cluster model that includes a six-membered ring. AgY was predicted to be the best adsorbent for H₂S, whereas CuY is subject to strong adsorption of CO, and alkali cation- and divalent cation- exchanged Y are subject to strong adsorption of H₂O. These results are in qualitative agreement with our experimental findings. 

To reveal the effect of the zeolite framework on the adsorption properties, simplified calculations that included only the adsorbate and only the cation were also carried. The same configuration for each adsorbate was found despite difference in cations and the presence of the zeolitic framework atoms. For LiY, NaY, and KY zeolites, the simplified calculations predict the same dominant adsorbates as the cluster calculations. However, for CuY and AgY, the simplified calculations fail to capture the strong adsorption of CO.