Comparative IR and 1H-MAS NMR study of adsorption of CD3CN on zeolite H-β: evidence of the presence of two families of bridged Brnsted sites

Abstract

The IR and 1H-MAS NMR spectroscopy of zeolite H-b in interaction with is described. Two families of strong CD 3 CN Si(OH)Al sites have been clearly distinguished : a Ðrst BrÊnsted family, characterized by an NMR signal at 4.4 ppm and an IR peak at 3614 cm-1 (isolated bridged hydroxys) and a second family, characterized by a broad band in the 3-7 ppm NMR range and in the 3600-3200 cm-1 IR range, due to bridged hydroxys which are perturbed by H-bond interactions with the zeolitic framework. This last family of hydroxys form weaker adducts with acetonitrile.

Nature, Environment and Quantification of Titanium Species in TiSiBEA Zeolites Investigated by XRD, NMR, DR UV–Vis and XPS

“…3), two main peaks are observed at 1.32 and 5.27 ppm due to protons of isolated and/or terminal SiO-H and H-bonded silanol groups at vacant T-atom sites, respectively, in line with earlier data on BEA [11,17,18], MFI [19,20], silicalite [21] and silica [22].…”

Complex Formation via Hydrogen bonding between Rhodamine B and Montmorillonite in Aqueous Solution

“…For MMT, the weak adsorption bands at 680 cm −1 , 841 cm −1 , 920 cm −1 and 1050 cm −1 are, Al-O stretching, O-H bending in Mg-Al-OH, O-H bending in Al-Al-OH and Si-O-Si stretching, respectively 35 . The band at 3623 cm −1 is ascribed to O-H stretching in Al-Si-OH 36 (Table S1). Surface aluminum ion is a strong Lewis acid and the edge hydroxyls are polarized as indicated by the pyridine adsorption study.

Figure 3Full IR spectra of RhB, MB, MMT, MMT/MB and MMT/RhB ( a ) and partial IR spectra (1200–1800 cm −1 ) showing residual bands after washing with water ( b ).

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Dealumination of HBEA zeolite by steaming and acid leaching: distribution of the various aluminic species and identification of the hydroxyl groups

“…Several authors have demonstrated the heterogeneity of the Brønsted site strength [15,16,23]. The presence of very strong Brønsted sites has also been noticed in several works [11,15,16,24].…”

“…The strongest Brønsted sites would be located in the well crystallized areas, the weakest in the areas of lower crystallinity [15]. Pazè et al [23] have identified weak Brønsted sites as bridging hydroxyls perturbed by H-bond interaction with the zeolite framework. These sites give a broad IR band in the 3600-3200 cm -1 range.…”