Y型沸石脱铝机制和铝状态的NMR研究

NMR STUDIES ON DEALUMINATED Y ZEOLITES

对Ｙ型沸石原粉及几种不同脱铝样品进行了几种不同ＮＭＲ方法的测量，确定了不同处理过程的脱铝机制和骨架内外铝状态的变化，￣（２９）ＳｉＭＡＳＮＭＲ谱给出了骨架Ｓｉ、Ａｌ分布的信息，反映了不同方法处理样品其脱铝机制的差异，据此可以控制Ｙ沸石脱铝过程获得更高的硅铝比，￣（２７）ＡｌＭＡｓＮＭＲ谱、二维章动ＮＭＲ及￣１Ｈ－￣（２７）ＡｌＣＰ／ＭＡｓＮＭＲ测量表明：水热处理的Ｙ沸石中存在４种不同的铝状态。综合￣（２９）Ｓｉ和￣（２７）ＡｌＭＡＳＮＭＲ观测，可相当程度地推断Ｙ型沸石分子筛脱铝改性所发生的内部过程。

ealuminated Y zeolites after mild steaming and (NH_4)_2SiF_6 treatments were studiedby ^(29)Si ,^(27)Al MAS NMR, ^(27)Al-~1H cross polarization MAS NMR and 2D nutationNMR. ^(29)Si MAS NMR shows that the Si, Al framework distributions of ultrastableY zeolites and Y zeolites dealuminated by (NH_4)_2SiF_6 isomorphous substitution are dif-ferent, even if they have almost the same framework Si／Al ratio. The reason is due totheir different dealumination experience. Y zeolites with high Si／Al framework ratio canbe obtained by a coorperation of isomorphous substitution and hydrothermialdealumination . Based on ^(27)Al MAS NMR, ^(27)Al-~1H CP／MAS NMR and 2D nutation^(27)Al NMR observations, four aluminuous species, i.e. framework tetrahedral Al(Al^(FT)),distortcd framework tetrahedral Al(Al^(FDT)), penta - coordinated non framework Al(Al^(NFP))and non framework octahedral Al(Al^(NFO)), in dealununated Y zeolites are supposedSi／Al frame ratios of dealuminated Y zeolites determined by ^(27)Al MAS NMRsimulations are in good agreement with whose results of ^(29)Si MAS NMR