Adsorptive removal of toluene and dichloromethane from humid exhaust on MFI, BEA and FAU zeolites: An experimental and theoretical study

Toluene and dichloromethane are two kinds of frequently encountered VOC species derived from solvent usage, which severely threaten human health and the ecological environment. At the same time, they are valuable industrial resources that can be recovered. In this study, different types of zeolites with various topological structures, including FAU (NaX, USY), MFI (Silicalite-1) and BEA (Beta), were employed for adsorptive recovery of both VOCs. All adsorbents were characterized by means of X-ray diffraction, scanning electron microscopy, N-2 adsorption, and X-ray photoelectron spectroscopy. Static adsorption equilibrium and dynamic breakthrough experiments were conducted to determine the adsorption efficiency of VOCs from water vapor. An ab-initio theoretical calculation was carried out to discern and confirm the adsorption selectivity. Experimental results and theoretical simulations consistently showed that USY is the best candidate to selectively abate toluene, and Silicalite-1 is the best adsorbent to remove both toluene and dichloromethane from mixed exhaust. The supercage structure of USY and its high Si/Al ratio gives rise to strong affinity toward toluene compared to dichloromethane and water. The small-pore network of Silicalite-1 gives rise to good recovery of both toluene and dichloromethane. The results gained are important for more rational selection of adsorbents for complicated mixtures.