Characterisation of acid-treated bentonite. Reactivity, FTIR study and 27Al MAS NMR

Acid-treated bentonite shows a catalytic activity towards decomposition of isopropanol due to overall acidity whereas the selectivity accounts for the nature of its acid sites. The examination of the IR spectra using different basic probes such as 2,6-dimethylpyridine, pyridine and CD₃CN shows the presence of various types of acid sites. The Lewis acid sites, considered to be the most abundant, are well characterised by pyridine and CD₃CN adsorption. In contrast, lutidine adsorption reveals both the existence of Brønsted acid sites and the presence of hydroxyl groups characteristic of beidellite. The potential site created by Al in tetrahedral layers is confirmed by using ²⁷Al MAS NMR.