IR Study of H₂O Adsorbed on H-ZSM-5

Abstract

Adsorption of H2O on H-ZSM-5 was studied by FT-IR in the presence of gaseous H2O in the temperature range between 293 and 423 K. Conversion of monomeric hydrogen-bonded H2O to dimeric species was clearly observed in IR spectra measured at 373 K by increasing the equilibrium pressure of H2O. Polymeric water was also formed by further increase of H2O pressure at the expenses of dimeric species. The frequencies and the relative intensities of IR bands due to dimeric species agree with the quantum-chemical results for H5O2 + species.

Efficient removal of toluene and benzene in gas phase by the TiO2/Y-zeolite hybrid photocatalyst

“…Since a H 2 O molecule is polarized due to a high electronegativity of the O atom, H 2 O molecules interact more strongly with cationic surfaces than neutral or anionic surfaces [32,33]. In fact, some FTIR investigations 2 O (mmol/g) have already reported the existence of oxonium ions (H 3 O + or H 2 O 5 + ) adsorbed on the Brönsted acid sites of H-ZSM-5 or SAPO-34 [34][35][36][37] as well as H 2 O molecules directly interacting with the H + sites by hydrogen bondings [38]. These interpretations explain that the amount of H 2 O molecules adsorbed is closely related with the SiO 2 /Al 2 O 3 ratios of zeolites.…”

Quantum chemical calculation of infrared spectra of acidic groups in chabazite in the presence of water

“…During the last decade, adsorption of water on zeolites has been extensively studied both experimentally [1][2][3][4][5][6][7][8] and theoretically [9][10][11][12][13][14][15][16][17][18][19][20] in order to understand the nature of the interaction of basic molecules with the Brøn-sted sites in the zeolites. The reaction can be studied by infrared spectroscopy because the frequencies of the vibrations of the zeolite hydroxyl group will change upon interaction with the water molecule.…”

“…The reaction can be studied by infrared spectroscopy because the frequencies of the vibrations of the zeolite hydroxyl group will change upon interaction with the water molecule. When water is adsorbed on H-ZSM-5, [1][2][3][4][5][6]21 HY, 7 H-MOR, 4 or chabazite 22 a triplet of bands appears at 2872-3000, 2403-2515, and 1700 cm Ϫ1 , known also as an ABC triplet. This triplet is accompanied by two peaks at 3700 and 3550 cm Ϫ1 .…”

Redox Behavior of Nanostructured Molybdenum Oxide−Mesoporous Silica Hybrid Materials

“…However, the absorption band characteristic of the Mo-O at around a 640-cm -1 stretching mode was not observed in our spectra. 47,48 It can be summarized that various forms of mesoporous silica can be filled with MoO 3 while maintaining high porosity, high access to the pores, and access to the MoO 3 species. Consequently, we have studied now chemistry with this nano-MoO 3 in pores and investigated the effect of the different pore environments.…”