Enhanced hydrophobic ZSM–5 with high capacity for toluene capture under high-humidity conditions

Abstract

Industrial volatile organic compounds (VOCs) have the characteristics of large displacement and high humidity. The problem of water resistance of the adsorbent in treating VOCs by adsorption method under high humidity conditions needs to be solved urgently. Herein, methyl triethoxysilane (CH3Si(C2H5O)3) and methyl trimethoxysilane (CH3Si(CH3O)3) are used for hydrophobic modification of ZSM-5, and its adsorption properties for toluene are studied under high-humidity conditions. Fourier infrared spectroscopy and X-ray photoelectron spectroscopy indicate that the hydrophobic groups –CH3 and –CH2– are successfully grafted onto the surface of the ZSM-5. The adsorption–desorption results of toluene show that the hydrophobicity of the modified ZSM-5 is remarkably improved, and the adsorption capacity for toluene is almost 6.5 times higher than that of original ZSM-5 at 80 % relative humidity. The mechanism of surface hydrophobicity modification of ZSM-5 was further investigated and found that the silicone hydroxyl group on the surface of the material reacted with the modifier to graft the hydrophobic group onto the surface of the material, which improved the hydrophobic property of the material. Moreover, the universality of the hydrophobic modification method has been proved feasible in commercial ZSM-5. Therefore, this work provides an important theory and reference for improving the hydrophobic properties of ZSM–5 molecular sieve.