Experimental and Numerical Investigations on the Adsorption/Desorption Performance of Low-Concentration VOCs over H-ZSM-5 with Different SiO2/Al2O3 Ratios

A mechanistic study was presented on the effect of the SiO2/Al2O3 ratio (SAR) on the adsorption/desorption behaviors of low-concentration volatile organic compounds (VOCs) over H-ZSM-5. In this study, n-hexane, toluene, and ethyl acetate were used as the probe VOC molecules. And their adsorption isotherms on different H-ZSM-5 (SARs = 25, 130, 300, and 470) were collected at various temperatures (30, 40, and 50 °C). Results showed that high SARs were conducive to adsorption, but the desorption efficiency was imperfect. The dependence between an absorbent and VOCs was divergent. Higher adsorption capacity for toluene (87.54 mg·g–1) and ethyl acetate (150.74 mg·g–1) was achieved on H-ZSM-5(470), while H-ZSM-5(300) owned higher adsorption capacity for n-hexane (107.24 mg·g–1). Based on the adsorption isotherms and breakthrough curves, the equilibrium and kinetic parameters were obtained based on the Langmuir model. Then, a rigorous temperature swing desorption (TSA) model was established to predict the evolution of temperature and VOC concentration along the axial adsorption bed. And the simulation results of the TSA process agreed well with the experimental data.