Ω型分子筛脱铝的核磁共振研究

在不同投料比（ＳｉＯ２／Ａｌ２Ｏ３＝１３．８，１９及２１）条件下，合成了三种Ω型分子筛原粉．对投料比为１３．８的原粉样品进行了四种不同方式的脱铝处理，即水热、ＳｉＣｌ４、ＥＤＴＡ和（ＮＨ４）２ＳｉＦ６处理，而形成了系列脱铝Ω型分子筛样品．对原粉及其脱铝样品进行了２９Ｓｉ和２７ＡｌＭＡＳＮＭＲ测试，确定出样品骨架硅铝比和铝在两种晶体学不等价Ｔ位上的占据比率，以探索四种脱铝方法的效果．实验结果与分析表明：在所有样品中，铝原子的占据具有择优Ｂ位的倾向；且铝在ＴＡ与ＴＢ位上的占据比率与合成条件有关；四种处理方式对Ω型分子筛的脱铝效果不尽相同．

NMR STUDIES ON DEALUMINATED ZEOLITE OMEGA

Parent samples of zeolite omega are synthesized with different ratio of silicon aluminium source (SiO2 / Al2O3 = 13.8, 19.0 and 21 .0, respectively). One of the parent samples (SiO2 / Al2O3 = 13.8)is then treated by thermal-steam, SiCl4, EDTA, (NH4)2SiF6 under different conditions.The series of treated samples are studies by NMR. The 27Al MAS NMR observations of the parent zeolite omega samples indicate that a preferenhal incorporation of the aluminium atoms in sites TS (located in the S6R) always occurred in our conditions of synthesis. The 29Si MAS NMR observations of the series dealuminated zeolite omega samples examine the dealuminating effects on the different condition of the thermal chemical treatmentS. There are experimental indications that in SiCl4 and EDTA-treated samples more TA (located in the S4R) Al atoms are removed from the framework of zeolite omega than TB Al atoms. However, the (NH4)2SiF6-treatment shows an opposite tendency.