The Leading Role of Association in Framework Modification of Highly Siliceous Zeolites with Adsorbed Methylamine

Abstract

Affinity index (AT value), adsorption heat, X-ray diffraction (XRD), and 13C and 29Si 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 AT values and adsorption heats, and significant changes in XRD patterns, 29Si 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 [Si-O] framework to form a Si-OHN bond, which leads to the appearance of Si-N 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 SiO2/Al2O3=31:1 were modified with MA and investigated by temperature-programmed desorption of CO2. 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.

Spectroscopic Signatures of Nitrogen-Substituted Zeolites

“…Strongly basic zeolites are attractive candidates, but such materials are notoriously difficult to make due to the strong inherent acidity of aluminosilicates. Several research groups have endeavored to produce strongly basic zeolites by treating zeolites with amines, − but to date there is little compelling evidence that nitrogen is incorporated into zeolite frameworks. Here, we detail synthesis, NMR spectroscopy, and calculations showing that nitrogen adds to both surface and interior oxygen while preserving the zeolite framework.…”

Long-Term Effectiveness, under a Mountain Environment, of a Novel Conservation Nanomaterial Applied on Limestone from a Roman Archaeological Site

“…On the other hand, as we previously reported [ 8 ], n-octylamine can also produce a silica nitridation [ 54 , 55 ]. In a previous paper, Han et al [ 55 ] investigated interactions between methylamine and zeolites.…”

“…On the other hand, as we previously reported [ 8 ], n-octylamine can also produce a silica nitridation [ 54 , 55 ]. In a previous paper, Han et al [ 55 ] investigated interactions between methylamine and zeolites. They concluded that the strong hydrogen bonding interaction results in the H atom of the amine group attacking the Si–O framework to form a Si–O...H...N bond, which leads to the formation of Si–N bonds in the zeolites.…”

Methylaminated Potassium Fulleride, (CH3NH2)K3C60: Towards Hyperexpanded Fulleride Lattices

“…Complementary fast (30 kHz) MAS 1 H NMR measurements confirmed the co-intercalation of CH 3 NH 2 in the fulleride salt (Figure S1). They showed the presence of a sharp resonance at 5.5 ppm, attributed to the −NH 2 protons and shifted downfield relative to that in uncoordinated CH 3 NH 2 (3.9 ppm), consistent with the expected cooordinative bonding to K + ions. Further resonances are also present at 3.4, 2.8, and 0.5 ppm and are attributed to the −CH 3 protons.…”