FT-IR characterization of silicated aluminas, active olefin skeletal isomerization catalysts

Characterization of Silica-Containing Aluminum Hydroxide and Oxide Aerogels

“…Surface silanols appear only for samples with at least 4% silica. In result in Brønsted acidity (11). This is also observed here and contrasts with what happens with silica-aluminas, any case, no Brønsted acidity appears.…”

Pure vs ultra-pure γ-alumina: A spectroscopic study and catalysis of ethanol conversion

“…3725 cm -1 appears to be more intense, relative to the others, in P than U. It has been reported that small amounts of silica on alumina produce a new OH stretching band just at 3725 cm -1 [32].…”

Modification by SiO2 of Alumina Support for Light Alkane Dehydrogenation Catalysts

“…SiOx-islands form additional porosity in the range of diameters 10-30 nm; the volume of these pores On the surface of the modified supports silica is distributed in the form of SiO x -fragments Si(OSi) 3 O and Si(OSi) 4 . This is indicated by the occurrence of the signals at −101 and −125 ppm on the 29 Si Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) spectra ( Figure 5) [18,[21][22][23][24].…”

“…The maximal temperature of ammonia desorption shifts to lower values ( Figure 7) indicating a decrease in strength of the acid sites. It is likely that the acid sites formed are hydroxyl groups bonded to the silicon atoms and the Lewis acid sites of various structures [21,24]. For example, Iengo et al [21] suggested, that the new It is likely that the acid sites formed are hydroxyl groups bonded to the silicon atoms and the Lewis acid sites of various structures [21,24].…”

“…It is likely that the acid sites formed are hydroxyl groups bonded to the silicon atoms and the Lewis acid sites of various structures [21,24]. For example, Iengo et al [21] suggested, that the new It is likely that the acid sites formed are hydroxyl groups bonded to the silicon atoms and the Lewis acid sites of various structures [21,24]. For example, Iengo et al [21] suggested, that the new acid sites are formed at the border of the SiO x -islands, where aluminum and silicon are arranged relative to each other in such a way, that the aluminum atoms are positively charged and partially neutralized by the negative charges of the silicates.…”