FTIR study of β-picoline and pyridine-3-carbaldehyde transformation on V–Ti–O catalysts. The effect of sulfate content on β-picoline oxidation into nicotinic acid

Effective hydrolysis of polysaccharides by activated attapulgite

“…In the spectra of ATP S, the band at 1200-1100 cm −1 is assigned to the asymmetrical stretching of sulphate groups, and the bands at 970 and 675 cm −1 are due to symmetrical stretching and asymmetrical bending modes of sulfate groups. 24 The above results show that some sulfate groups have been implanted on ATP by H 2 SO 4 activation. 25 Acid sites characterization It is well known that pyridine is a base probe molecular, and pyridine-FTIR has been well established as a useful technique for characterizing the acidic properties of samples.…”

“…The strong band at approximately 470 cm −1 is attributed to the O‐Si‐O bending mode of the SiO 4 tetrahedron, which is stable in the H 2 SO 4 activation process. In the spectra of ATPS, the band at 1200–1100 cm −1 is assigned to the asymmetrical stretching of sulphate groups, and the bands at 970 and 675 cm −1 are due to symmetrical stretching and asymmetrical bending modes of sulfate groups 24 . The above results show that some sulfate groups have been implanted on ATP by H 2 SO 4 activation 25 …”

“…The band at 1540 cm −1 on ATP‐S was also enhanced, and this is attributed to Brønsted acid sites, indicating that the acidic properties of Brønsted acid were augmented after H 2 SO 4 activation. According to Chesalov et al ., an increase of the SO 4 2− content results in the higher acidity of Brønsted acid sites, proving that the acid properties of ATP can be transformed by H 2 SO 4 activation 24,27,28 . Besides that, the band of Lewis acid sites at 1450 cm −1 also augmented after the modification, implying that the amount of Lewis acid sites also increased.…”

“…Those Lewis acid sites are supposed to come from the coordinatively unsaturated metal ions (i.e., Al 3+ ). 24,26 The band at 1540 cm −1 on ATP-S was also enhanced, and this is attributed to Brønsted acid sites, indicating that the acidic properties of Brønsted acid were augmented after H 2 SO 4 activation. According to Chesalov et al, an increase of the SO 4 2− content results in the higher acidity of Brønsted acid sites, proving that the acid properties of ATP can be transformed by H 2 SO 4 activation.…”

“…Both samples show a band at 1450 cm −1 that is attributed to the pyridine molecules binding with Lewis acid sites. Those Lewis acid sites are supposed to come from the coordinatively unsaturated metal ions (i.e., Al 3+ ) 24,26 . The band at 1540 cm −1 on ATP‐S was also enhanced, and this is attributed to Brønsted acid sites, indicating that the acidic properties of Brønsted acid were augmented after H 2 SO 4 activation.…”