Synthesis of Ultrafine Zeolite NaY(II) - Effect of Complexing Agent

Ultrafine zeolite NaY was hydrothermally synthesized with silica sol and Al2(SO4)3 as silica and alumina sources, respectively, by adding complexing agent such as citrate, acetate or editate to synthesis batch. The effect of the amount of citrate on the crystallization rate, SiO2/Al2O3 ratio and crystal size of as-synthesized zeolite NaY was investigated. When the relatively lower amount of citrate [n(citrate) : n(Al2O3) [less-than or equal to] 2 : 1] was added, both the crystallization rate and the SiO2/Al2O3 ratio increased while the crystal size reduced obviously comparing with that in the absence of citrate. This indicates that the nucleation and crystallization of zeolite NaY was promoted by complexing agent. When the relatively higher amount of citrate [n (citrate) : n (Al2O3 > 2 : 1] was added, the above promotion effect diminished. The crystallization rate was found to reduce comparing with that in the absence of citrate, although the crystal size was still smaller than that in the later case. The optimum amount of citrate added to batch appears to be at the citrate : Al2O3 molar ratio of 1. 5 : 1. The similar promotion effect was also observed both for the addition of editate and acetate with the molar ratio of editate : Al2O3 and acetate : Al2O3 equal to 1. 5, respectively. The promotion effect of complexing agents to the nucleation and crystallization of zeolite NaY was related with their complexing ability to aluminum.