Mesoporous Layered Aluminosilicates Prepared from Protozeolitic Nanoclusters: Synthesis and Physicochemical and Catalytic Properties

Abstract

Mesoporous layered aluminosilicates were prepared by a two-stage route using tetrapropylammonium hydroxide and hexadecylamine. First, aluminosilicate sols were prepared from very dilute solutions under mild conditions. Optically clear sols contained aluminosilicate nanoclusters of average size of 4–5 nm. 27Al NMR studies demonstrated that tumbling alone of small aluminosilicate nanoclusters due to Brownian motions removes effectively chemical shift anisotropy and dipolar interactions and narrows quadrupolar interactions; thus, magic angle spinning was not required for obtaining good-quality 27Al and also 29Si NMR spectra of the sols studied. Evolution of the quantitative 29Si NMR spectra in time provided an insight into the dynamical behavior of the sols. Second, sols with the Si/Al ratios of 12–70 were used for the preparation of X-ray amorphous aluminosilicate materials. The samples exhibited good sorption properties because of the presence of ca. 3 nm slit mesopores. They also contained Bronsted and Le...