Adsorptive Removal of Dichloromethane Vapor on FAU and MFI Zeolites: Si/Al Ratio Effect and Mechanism
Adsorptive Removal of Dichloromethane Vapor on FAU and MFI Zeolites: Si/Al Ratio Effect and Mechanism
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FAU 和 MFI 沸石吸附去除二氯甲烷蒸气：Si/Al 比效应及机理
DOI：
10.1021/acs.jced.8b00174
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发表时间：
2018-06-01
期刊：
影响因子：
--
通讯作者：
Deng, Hua
中科院分区：
文献类型：
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作者：
Kang, Shunyu;Ma, Jinzhu;Deng, Hua
合成了不同硅铝比的MFI沸石（ZSM-5），并与FAU沸石（NaX和NaY）进行了比较，考察了它们对二氯甲烷蒸气的吸附去除效果。所有的吸附剂，其特征在于通过N-2吸附，X-射线衍射，X-射线光电子能谱，和扫描电子显微镜。考察了其吸附、脱附性能、耐水汽性能和再生能力。FAU分子筛的平衡容量优于MFI分子筛，而MFI分子筛具有优越的上级动态容量。FAU沸石的动力学吸收显着抑制低湿度水平的混合物。无论哪种沸石，高硅含量不仅有利于平衡吸附，而且有利于提高抗水汽能力。Si/Al比最高的ZSM-5（200）（SiO2/Al 2 O3 = 200）是本研究中去除二氯甲烷的最佳候选材料。此外，它可以重复使用，而不会显着减少吸收后，几个再生周期。借助原位漫反射傅里叶变换红外光谱和密度泛函理论模拟，发现吸附的二氯甲烷与FAU沸石的孔窗紧密接触，但被MFI沸石的孔壁包围。实验结果与理论计算结果一致，表明MFI分子筛对二氯甲烷的吸附选择性优于FAU分子筛。
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 N-2 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.