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The Leading Role of Association in Framework Modification of Highly Siliceous Zeolites with Adsorbed Methylamine
Author(s) -
Han AiJie,
Guo Juan,
Yu Hui,
Zeng Yu,
Huang YueFang,
He HeYong,
Long YingCai
Publication year - 2006
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200500389
Subject(s) - methylamine , zeolite , adsorption , chemistry , hydrogen bond , magic angle spinning , fourier transform infrared spectroscopy , microporous material , raman spectroscopy , inorganic chemistry , molecular sieve , methanol , desorption , dimethylamine , catalysis , chemical engineering , molecule , nuclear magnetic resonance spectroscopy , organic chemistry , physics , optics , engineering
Affinity index ( A T value), adsorption heat, X‐ray diffraction (XRD), and 13 C and 29 Si magic‐angle spinning (MAS) NMR, FTIR, and Raman spectroscopies were used to study the interaction of highly siliceous MFI‐, FAU‐, and FER‐type zeolites with adsorbed methylamine (MA). Compared with the data for methanol, the much higher A T values and adsorption heats, and significant changes in XRD patterns, 29 Si MAS NMR spectra, and FTIR spectra for the zeolites after adsorption of MA, revealed a strong hydrogen‐bonding interaction between the perfect framework of the zeolites and the adsorbed MAs. This interaction results from the fact that the H atom of the amine group attacks the [SiO] framework to form a SiO⋅⋅⋅H⋅⋅⋅N bond, which leads to the appearance of SiN bonds in the zeolites at 323 K. Therefore, the zeolite framework can be modified with MA under mild conditions. The highly siliceous MFI zeolite and the H‐ZSM‐5 zeolite with SiO 2 /Al 2 O 3 =31:1 were modified with MA and investigated by temperature‐programmed desorption of CO 2 . The modified zeolites exhibited greatly enhanced basic properties in comparison with those of the raw materials. The influence of defects in the zeolite on the adsorption and the interaction with MA is discussed.