Adsorptive Removal of Dichloromethane Vapor on FAU and MFI Zeolites: Si/Al Ratio Effect and Mechanism

Abstract

MFI zeolites (ZSM-5) with different Si/Al ratios were synthesized to assess their adsorptive removal of dichloromethane vapor, compared with FAU zeolites (NaX and NaY). All adsorbents were characterized by means of N2 adsorption, X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. The adsorption and desorption performance, water vapor tolerance, and regeneration ability were fully examined. FAU zeolites exhibited better equilibrium capacity than MFI zeolites, while MFI zeolites had superior dynamic capacity. The kinetic uptake of FAU zeolites was significantly depressed by low humidity levels in the mixture. Regardless of the type of zeolite, high Si content was not only beneficial to equilibrium adsorption but also helpful for water vapor resistance. ZSM-5 (200) (SiO2/Al2O3 = 200) with the highest Si/Al ratio was the best candidate in this study for removal of dichloromethane. In addition, it could be reused without a significant decrease in uptake after several regeneration cycles. With the aid of in situ diffuse reflectance Fourier transform infrared spectroscopy and density functional theory simulation, adsorbed dichloromethane was found to be in intimate contact with the pore window of FAU zeolites but was surrounded by the pore walls of MFI zeolites. Experimental and theoretical results were consistent with each other and indicated that MFI zeolites show better adsorptive selectivity of dichloromethane (DCM) over water than FAU.

A critical review on VOCs adsorption by different porous materials: Species, mechanisms and modification methods

“…5, zeolites including silicalite-1 (MFI-structure type), beta (*BEA-structure type), SSZ-23 (STT-structure type), and chabazite (CHA-structure type), have considerable potential as adsorbents for VOCs adsorption (Cosseron et al, 2013). MFI zeolites (ZSM-5) and FAU zeolites (NaX and NaY) with different Si/Al ratios were synthesized by Kang et al (2018). Their adsorptive removal of dichloromethane vapor at 30 ℃, 5000 ppm were assessed.…”

Core‐Shell Faujasite@Aqueous Miscible Organic‐Layered Double Hydroxides Composites with Tunable Acid/Base Properties for One‐Pot Synthesis of Ethyl trans‐α‐Cyanocinnamate

“…[ 15 ] In addition, to identify the location of acid sites in the zeolite structures, FT‐IR spectra of adsorbed collidine were obtained at 150 °C. Because the kinetic diameter of collidine is ≈0.74 nm, [ 37 ] which is slightly larger than the pore window of FAU (0.735 nm), [ 38 ] its adsorption would be limited on the outermost surface of a zeolite. Typically, the FTIR bands appeared in the range of 1632–1638 and 1616 cm −1 correspond to collidine adsorbed on Brønsted acid sites/Lewis acid sites, and silanol groups located on the external surface of a zeolite, respectively.…”

Synthesis of Zeolites from Coal Fly Ash for Removal of Harmful Gaseous Pollutants: A Review

“…Effectively controlling and reducing air pollution are important issues for scientists today. At present, the common methods for treating gas pollutants include adsorption (Kang et al, 2018), biodegradation (Zhu et al, 2013), direct combustion (Pan et al, 2018), and catalytic oxidation (Saqer et al, 2011); adsorption and catalytic oxidation are considered the two most effective methods. The adsorption method is widely used due to its advantages, including simple equipment, easy operation, convenient economy, and high efficiency, and its mechanism has been widely studied.…”