Synthesis of high hydrophobicity USY zeolite with excellent VOCs adsorption performance under humid condition: Combined strategy of high temperature steam and acid treatment

Y Zeolite and its ultra-stabilized hierarchical derivative (USY) as absorbents have low adsorption capacity for VOCs under humid conditions thus limits their industrial applications. It is well known that high SiO2/Al2O3 ratio (SAR) can improve the hydrophobicity of zeolite, and the increase of pore volume can enhance the adsorption performance. In the present work, SAR and the pore size of CY were enlarged by oxalic acid-high temperature steam-citric acid treatment, as the framework aluminum in the zeolite was removed and maintaining its structural integrity. The surface morphology and structure of samples were characterized by XRD, BET, TEM, SEM and TG. 27Al MAS NMR, XPS and Pyridine infrared analysis the mechanism of aluminum removal from the CY framework. The dynamic adsorption properties of the samples were systematically investigated with toluene selected as representative volatile organic compounds. The hydrophobicity of the samples was investigated by static water adsorption, and the adsorption kinetics model of the samples were plotted to study their adsorption characteristics. N2 adsorption-desorption results showed that the modified CY material has larger surface area, wider pore size and larger microporous volume than the raw material. On the other hand, with the improved SiO2/Al2O3 ratio and hydrophobicity, the modified USY also exhibited excellent adsorption performance under humid conditions, with 4.2 times more capacity to adsorb toluene. Therefore, this method can provide effective adsorption of VOCs in humid environments.