Hydrogen sulphide removal from biogas by zeolite adsorption: Part I. GCMC molecular simulations

In this work Grand Canonical Monte Carlo (GCMC) simulations have been used to study hydrogen sulfide (H2S) removal from biogas streams by different zeolites such as FAU (Faujasite, NaX and NaY), LTA (zeolite A (Lynde division, Union Carbide)) and MFI (Zeolite Socony Mobil – five). Additionally, quantum mechanics (QM) molecular simulations have been performed to obtain structures and partial charges of some sorbates. The computational procedure adopted has been validated by comparison with experimental data available for H2S removal in atmospheric environment by zeolite NaY. In order to obtain a priority list in terms of both H2S isotherms and adsorption selectivity, adsorption simulations for pure H2S at low pressures and for a prototype biogas mixture (i.e., CO2, CH4, and H2S) have been performed and compared. The adsorption mechanisms and competition for accessible adsorption sites in terms of thermodynamic behavior have been also examined. Overall, the results obtained in this work could be routinely applied to different case studies, thus yielding deeper qualitative and quantitative insights into adsorption pollutant removal processes in environmental fields.