Effect of agitation on the synthesis of zeolite beta and its synthesis mechanism in absence of alkali cations

Abstract

Zeolite beta was hydrothermally synthesized in the TEAOH–SiO 2–Al(0)–H 2O system in the absence of alkali cations. The effects of agitation under various TEAOH/SiO 2 molar ratios on the crystallization kinetics, particle size, particle size distribution, and framework SiO 2/Al 2O 3 of synthesized zeolite beta were studied. The as-synthesis and calcinated zeolites were characterized by XRD, TEM, N 2 adsorption. The effect of the agitation on the induction time, the particle size, and the framework SiO 2/Al 2O 3 ratio of the synthesized zeolites was more pronounced at high TEAOH/SiO 2 molar ratio (0.6) than at a low TEAOH/SiO 2 molar ratio (0.21 and 0.4). Under agitation, the induction time, the particle size, and the framework SiO 2/Al 2O 3 molar ratio of the zeolite greatly decreased with the increase of the TEAOH/SiO 2 ratio. While under the static state, the minimum induction time and the crystal particle size existed at TEAOH/SiO 2 ratio = 0.4, and the framework SiO 2/Al 2O 3 molar ratio of the zeolite increased with the increase of TEAOH/SiO 2 ratio. The crystallization proceeded via solution phase nucleation mechanism.