Synthesis of ultrafine zeolite NaY(I) - Effect of light rare earth ions additive
- 化学化工－已发表论文 
Ultrafine zeolite NaY was hydrothermally crystallized with silica sol and Al-2(SO4)(2) as source materials via optimizing synthesis conditions and adding light rare earth ions (Ln(3+)) to the synthesis batch. The crystallization performance of NaY could be affected by the aging time of nucleation Si-Al gel and the crystallization temperature of reaction Si-Al gel. With increasing the aging time (2-7 d) of nucleation gel, the crystallization rate of zeolite NaY increased whereas the average crystal size of zeolite NaY decreased. When elevating the crystallization temperature (363-383 K) of reaction gel, both the crystallization rate and the average crystal size of zeolite NaY increased. Nevertheless, the crystallization performance of zeolite NaY was more remarkably affected by the addition of Ln(3+) ions in the synthesis batch. The crystallization rate and the n (SiO2)/n(Al2O3) ratio obviously increased while the average crystal size greatly reduced when zeolite NaY was crystallized in the presence of Ln(3+) ions, comparing with that in the absence of Ln(3+) ions, It was found that, with the amount of the added Ln(3+) ions increasing, the average crystal size of zeolite NaY decreased followed by increasing, while the crystallization rate and the SiO2/Al2O3 ratio in framework changed in the opposite direction. The optimal amount of Ln(3+) additive appears to be in the range of n(Ln(3+)) : n(Al3+) = 0.05 : 1-0.1 : 1 in mole. In the case, the as-synthesized NaY zeolites had the smallest average crystal sizes (<100 nm), the highest n(SiO2)/n(Al2O3) ratio (>5.7) and the shortest crystallization time (<36 h), The role of the added Ln(3+) ions was proposed to be that there formed the micro-crystalline Ln(OH)(3) under the synthesis conditions, which may present additional area to initiate the nucleation of zeolite NaY.