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Influence of TEA<inf>2</inf>O/SiO<inf>2</inf> ratio on the polymorph formation and crystallization of zeolite beta

Abstract:

Zeolite beta is formed by different proportions of polymorphs. The influence of the syntheses conditions on the polymorphs formation has not been systematically studied up to now. In the present work a detailed study of the effect of the variation of TEA2O/SiO2 on the synthesis of zeolite beta has been carried out, for different molar ratios: 0.15, 0.27, 0.50 and 0.75. TEA2O concentration affects the crystallization kinetics, crystal size and morphology, polymorph proportion, textural properties and Al content in the final products. TEA2O/SiO2 = 0.27, seems to be a threshold value below or above which the nucleation rate decreases. For this ratio nanosize beta was obtained with the highest content of polymorph A, highest surface area and micropore volume. Lower or higher TEA 2O/SiO2 ratios resulted in larger crystal size and higher content of polymorph B. The proportion of polymorphs obtained were in the range of 32%A-68%B to 51%A-49%B. © 2013 Elsevier B.V. All rights reserved.