Infrared and Raman studies of ZSM-5 and silicalite-1 at room, liquid nitrogen and helium temperatures

New insight into the structure of dispersed titania by combining normal-mode analysis with experiment

“…Besides, there is a significant blue shift of about 11 cm −1 for the interphase Ti O Si with decreasing adaptation to the silica support, indicating the influence of the support material on the spectral position of the eigenmodes. These results are in good agreement with previous UV Raman data and DFT calculations, where the feature at 960 cm −1 has been assigned to an asymmetric stretching mode of the Ti O Si bridge[8,[23][24][25][26][27][28][29]. The two interphase modes at 940/951 cm −1 and 1036/1035 cm −1 differ by the degree to which the force constant f(Si O) Ti O Si contributes to these modes.…”

“…The normal-mode analysis identifies the Ti OH stretching vibration within the spectral window of 800-900 cm −1 (Model A: and asymmetric Ti O Si stretching modes [8,[23][24][25][26][27][28][29], respectively, whereas the Raman bands at around 1120 cm −1 and 1180 cm −1 have previously been assigned to LO/TO phonon modes of the silica support [31]. However, the deconvolution of the resonanceenhanced Raman data clearly identifies an additional band at 1045 cm −1 .…”

Hydrogen from Formic Acid via Its Selective Disproportionation over Nanodomain-Modified Zeolites

“…As reported in the literature, the intensities of the absorptions at 550, 800, and 1100 cm −1 decrease with increasing incorporation of Ge in the framework due to the slight changes in the T−O distances and T−O−T angles. 8,26,25 Calculated vibrational frequencies using 28T models (described in the Supporting Information) also provide support for this difference in absorptions, with an absorption at 1050 cm −1 found in the Na-ZSM-5 model shifted to 972 cm −1 in the Na-Ge-ZSM-5 model. Similarly, an absorption at 1100 cm −1 in Another absorption at 806 cm −1 can be assigned to Si−O−Si symmetric stretching vibration modes.…”

“…8,18,26,27 A well-defined absorption at 550 cm −1 can be attributed to the double-five-membered rings in the MFI structure. Additional evidence for Ge incorporation is an absorption at 1030 cm −1 (assigned to the Si−O−Ge asymmetric stretch 27 ), present in the Ge-ZSM-5 samples, whereas the samples without germanium have an absorption at 1100 cm −1 .…”

Characterization of aluminosilicate zeolites by UV Raman spectroscopy

“…It has been reported that the Si/Al ratio of zeolites strongly in¯uences the band position and band intensity of Raman spectra [4,48,49], but it is dicult to distinguish the species of Si±O±Si and Si±O±Al in Raman spectroscopy [48,49].…”