IR and NMR studies of hierarchical material obtained by the treatment of zeolite Y by ammonia solution

Ammonia treatment of ultrastable zeolite Y has a great impact on its features. XRD showed a partial loss of crystallinity coupled with a loss of long-distance zeolite ordering. However, a typical short-range zeolite ordering, in the light of Si-29 NMR studies, was largely preserved. Al-22 MAS NMR spectra evidenced that most of Al was located in zeolitic tetrahedral positions, but some of them adopted a distorted configuration. Evolution of zeolites acidity was followed quantitatively by using IR. In particular, such studies revealed the presence of strongly acidic Si-OH-Al groups. IR studies suggest also heterogeneity of these OH groups. The heterogeneity of Si-OH-Al groups was a consequence of the less ordered structure of zeolites treated with ammonia solutions. It was also found that the treatment with ammonia solutions yields hierarchical material. The samples revealed promising catalytic properties in the liquid phase isomerization of et-pinene. Zeolites desilicated with ammonia may constitute an inexpensive route yielding viable hierarchical catalysts. (C) 2017 Elsevier B.V. All rights reserved.