Novel preparation of binder-free Y/ZSM-5 zeolite composites for VOCs adsorption

Abstract

• Shaped binder-free Y/ZSM-5 were prepared through gas–solid phase crystallization. • Steaming and acid treatment increased the SiO 2 /Al 2 O 3 ratios of Y/ZSM-5 composites. • Y/ZSM-5 composites exhibit mesopores and high adsorption capacities for VOCs. • Dealuminated Y/ZSM-5 exhibit pronounced hydrophobicity under humid conditions. Hydrophobic zeolites have been considered as effective adsorbents for capturing volatile organic compounds (VOCs). In this contribution, a series of binder-free Y/ZSM-5 zeolite composites were prepared through crystallization of shaped precursors by a vapor-phase transport (VPT) method. The obtained Y/ZSM-5 composites were dealuminated by steaming and hydrochloric acid (HCl). The presence of both ZSM-5 and Y zeolites was verified with XRD. FE-TEM was used to confirm the co-existence of lattice fringes of ZSM-5 and Y in the particles. The samples were also characterized by SEM, N 2 adsorption–desorption and ICP-OES. By selecting toluene (TOL), cyclohexane (CYH), butyl acetate (BAC), methyl ethyl ketone (MEK) and isopropanol (IPA) as representative VOCs of aromatics, alkanes, esters, ketones and alcohols, respectively, the dynamic adsorption performance and temperature-programmed desorption performance of the samples were systematically studied. The results showed that the zeolite composites had larger adsorption capacities for TOL, CYH and BAC than ZSM-5 due to larger surface area, wider pore diameter and higher micropore volume. On the other hand, the adsorption capacities of the composites for MEK and IPA were lower than ZSM-5, indicating that they are more suitable to adsorb larger molecules. The composites also exhibited excellent adsorption performance under humid conditions due to high SiO 2 /Al 2 O 3 ratios and hydrophobicity. By comparing the temperature corresponding to the maximum of the desorption peaks, it was found that the adsorbates were easier to desorb on the zeolite composites than on ZSM-5. Furthermore, the adsorbents have good regeneration ability due to high thermal stability and hydrothermal stability.