Screening of zeolites for H2S adsorption in mixed gases: GCMC and DFT simulations

Abstract

Zeolites with high Si/Al ratio are widely used in industrial desulfurization process because of their stability and hydrophobicity as adsorbents. However, the method to design a practical zeolites and the kinetics of competitive adsorption in multicomponent systems still remain to be studied. The adsorption capacity of H2S in 36 all-silica zeolites with different accessible area and pore size was calculated by the Grand Canonical Monte Carlo (GCMC) method. Identical method was used to simulate the adsorption behavior of H2S in the 5 widely used all-silica zeolites (CHA, BEA, MFI, LTA, FAU). Further, the adsorption properties of H2S in metal-modified SSZ was investigated using the Density Functional Theory (DFT) method. The simulation results display that the zeolites with a pore size of 7–9 Å and a higher accessible area tend to exhibit efficient adsorption at 313 K and atmospheric pressure. For pure H2S component, CHA adsorbs most H2S molecules at atmospheric pressure while FAU are more attractive for removal of H2S at saturation pressure. FAU shows a strong preferential adsorption on H2S in the presence of CO, CO2, H2O and N2. In addition, the Co-SSZ obtained by doping Co on CHA is the most promising adsorbent in this research.