Crystallization behavior of zeolite beta with balanced incorporation of silicon and aluminum synthesized from alkali metal cation-free mixture

Zeolite beta with the SiO2/Al2O3 ratios ranging from 20 to 60 is synthesized from alkali metal cation-free aluminosilicate gel under basic condition. MTW-type zeolite is crystallized as an impurity phase at higher SiO2/Al2O3 ratios. The presence of sodium cations also induces the formation of impurity phases. The total amount of tetraethylammonium cations occluded in the crystals are related to the crystalline phases of the obtained products: that is, the amount of tetraethylammonium cations are the same in all of the zeolite beta products while smaller amounts are occluded in the MTW products. The SiO2/Al2O3 molar ratios of the obtained zeolites are almost the same as those of the initial mixtures, which is an unusual phenomenon in hydrothermally crystallized zeolite beta in hydroxide media, indicating balanced incorporation of silicon and aluminum. Since the reactivity of aluminum species strongly affects the incorporation of aluminum into the framework of zeolite beta, balance of yields of silicon and aluminum could be tuned. In other words, the SiO2/Al2O3 ratios could be adjusted by balancing the reactivity of aluminum and silicon sources. Acylation of 2-methoxynaphthalene with acetic anhydride is carried out as a test reaction. The zeolite beta synthesized from alkali metal cation-free gel shows a higher catalytic activity for acylation of 2-methoxynaphthalene than that synthesized with alkali metal cation. (C) 2008 Elsevier Inc. All rights reserved.