Mesoporous aluminosilicates assembled from dissolved LTA zeolite and triblock copolymer in the presence of tetramethylammonium hydroxide

Abstract

Zeolite Na-A crystals dissolved in a HCl solution were used as a single-source of silicon and aluminum for the synthesis of mesoporous aluminosilicates via a template-assisted method with an organic base tetramethylammonium hydroxide (TMAOH). Amphiphilic triblock copolymer Pluronic F127 (EO 106PO 70EO 106) was used as template. Increasing the amount of TMAOH in the synthetic solution resulted in an increase in the aluminum content of the products. On the other hand, mesostructural periodicity was deteriorated with higher content of aluminum incorporated into the mesoporous framework. The samples with low Si/Al ratios less than 5 have wormhole-like pore structure, while the samples with Si/Al ratios more than 7 possess highly ordered mesoporous structure, a body-centered Im 3 m symmetry, with single crystal like morphology. The samples with Si/Al ratio of 7, which prepared at TMAOH molar concentration of 25 mM in the templating solution, possess BET surface area of 470 m 2/g, pore size of 6.4 nm, and pore volume of 0.56 cm 3/g. Aluminum atoms have successfully been incorporated in a tetra-coordinated position and remained stable even after calcination at 600 °C.