Influence of physical structures and chemical modification on VOCs adsorption characteristics of molecular sieves

The adsorption method using molecular sieves as adsorbent is one of the effective ways to control the emission of volatile organic compounds (VOCs), while the unclear adsorption mechanism between different molecular sieves and VOCs blocks its industrial application. The effects of physical structure and chemical modification of molecular sieves on the adsorption of VOCs were studied by computer simulation and adsorption experiment. Grand Classical Monte Carlo (GCMC) simulation was employed to investigate the adsorption behaviors of VOCs in a variety of pure silica molecular sieves with different physical structures, including aldehydes, ketones and benzenes. Further, combined with density functional theory (DFT) calculations, the influences of chemical modification on the adsorption of VOCs were investigated. Finally, the theoretical results were verified through adsorption experiments. The results revealed that the molecular sieve topology, the pore diameter of the molecular sieve, and the molecular kinetic diameters of VOCs all markedly influenced the adsorption of VOCs. Pure silica molecular sieves exhibited considerable adsorption ability for polar adsorbates. For nonpolar adsorbates, the adsorption ability decreased as the molecular volume increased. The DFT results indicated that the adsorption of VOCs is stronger at Cu2+ site than [Cu-OH]+ site in modified MFI. The experimental results of toluene adsorption for MFI, BEA, and Y-type zeolites strongly supported the theoretical results.