Metakaolin as a reagent for the assembly of mesoporous aluminosilicates with hexagonal, cubic and wormhole framework structures from proto-faujasitic nanoclusters

Abstract

Metakaolin, formed through the thermal de-hydroxylation of kaolin clay, has been shown to be an effective reagent for the preparation of faujasitic zeolite nanoclusters for framework incorporation into hexagonal, cubic and wormhole aluminosilicate mesophases with Si/Al ratios in the range 5.6–1.6. Single tetrahedral aluminum sites with ²⁷Al NMR chemical shift of 60 ppm are observed for each mesostructure, which is indicative of the incorporation of the protozeolitic nanoclusters into the framework walls. Unlike aluminosilicate mesostructures assembled from conventional precursors, no framework de-alumination was observed for the mesostructures upon calcination at 550 °C. The results suggest that metakaolin is a promising low-cost precursor for the industrial scale production of high quality aluminosilicate mesophases.