Preparation of green hydrophobic ZSM-5 zeolite and its toluene adsorption performance under high humidity conditions

Abstract

Considering the significant reduction in VOCs adsorption capacity of zeolites under high humidity conditions, this study employs an optimized liquid deposition method to hydrophobically modify ZSM-5 zeolite. The effects of deposition solvent and trimethylchlorosilane (TMCS) dosage on the hydrophobicity of ZSM-5 were evaluated using a series of characterization techniques, the adsorption performance for toluene was assessed at 80% relative humidity. The results showed that grafting Si–(CH₃)₃ using the eco-friendly solvent ethyl acetate (EA) significantly improved the adsorptive capacity of ZSM-5 for toluene. The modified ZSM-5, treated with 5 mL g⁻¹ TMCS and EA, exhibited superior dynamic adsorption capabilities, achieving breakthrough and saturation adsorption capacities of 64.09 mg g⁻¹ and 108.21 mg g⁻¹ for toluene, respectively. The ZSM-5-EA-5 material demonstrated robust thermal stability, retaining over 90% of its toluene adsorption capacity after five cycles of adsorption and desorption. Fourier transform infrared spectroscopy, in situ infrared spectroscopy, and density functional theory calculations indicate that after hydrophobic modification, the increased content of Si–(CH₃)₃ enhances the adsorption of toluene while reducing the adsorption of water, thereby improving the sieve's adsorptive efficiency for toluene.