超微NaY分子筛的合成(Ⅰ)──添加轻稀土离子的影响

Abstract

[中文文摘]导向剂的陈化时间和反应胶的晶化温度可以影响 Na Y分子筛的晶化行为 .随导向剂陈化时间的增加 ,Na Y分子筛的晶化速度加快 ,晶粒尺寸减小 ;随晶化温度的升高 ,Na Y分子筛的晶化速度加快 ,但晶粒尺寸增加 .而向合成体系中添加轻稀土离子 (L n3+)对 Na Y分子筛的晶化行为影响更为明显 .与未添加稀土离子时相比较 ,在一定的稀土离子添加量范围内 [n(L n3+) / n(Al3+) <0 .2 ],Na Y分子筛的晶化速度明显加快而晶粒尺寸显著减小 ,同时所合成出的 Na Y分子筛的 n(Si O2 ) / n(Al2 O3)比也有较大的提高 .添加稀土离子使合成体系中形成异晶晶种的 L n(OH) 3微晶 ,从而进一步引发 Na Y分子筛的成核.[英文文摘]Ultrafine zeolite NaY was hydrothermal ly cr ystallized w ith silica so l and Al2 ( SO4 ) 2 as source materials via optimizing synthesis condit ions and adding light rare earth ions( Ln3+ ) to the sy nthesis batch. T he crystallizatio n per formance of NaY could be affected by the ag ing time o f nucleation Si-Al g el and the crystallizat ion temperatur e o f react ion Si-Al gel. With increasing the aging t ime( 2—7 d) of nucleat io n g el , the cry stallizat ion rate of zeo lite NaY incr eased whereas the average cry stal size of zeolite NaY decreased. When elevat ing the crystal lization temperature ( 363—383 K ) of reaction gel, both the cry stallizat io n rate and the average cry stal size o f zeolite NaY increased. Nevertheless,the cry stallizat ion perfo rmance o f zeolite NaY was more remarkably affected by the addit ion o f Ln3+ions in the synthesis batch. T he crystallizat ion rate and the n ( SiO2 ) / n( Al2O3 ) ratio obv io usly increased w hile the average cr ystal size great ly reduced w hen zeo lite NaY was crystallized in the presence of Ln3+ ions, comparing with that in the absence of Ln3+ ions. It w as found that , with the amount of the added Ln3+ io ns increasing , the average cry stal size of zeolite NaY decreased fo llowed by incr easing , w hile the crystall izat ion rate and the SiO2 / Al2O3 rat io in fr amew or k chang ed in the o pposite direct io n. T he opt imal amount of Ln3+ additive appears to be in the rang e of n( Ln3+ ) ∶ n( Al3+ ) = 0. 05∶1—0. 1∶1 in mole. In the case, the as-synthesized NaY zeolites had the smallest aver ag e cr ystal sizes( < 100 nm) , the highest n( SiO2) / n( Al2O3 ) rat io ( > 5. 7) and the shortest cr ystallizat io n t ime( < 36 h) . T he role of the added Ln3+ ions was proposed to be that there formed the micro-cry stalline Ln( OH) 3 under the synthesis condit ions, w hich may present addit ional area to init iate the nucleat io n of zeolite NaY.