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Analysis of Dynamics and Molecular Design of Heteropolyacid catalysts by High Resolution Solid State NMR

高分辨率固体核磁共振分析杂多酸催化剂的动力学和分子设计

基本信息

批准号：
05403021
负责人：
MISONO Makoto
金额：
$ 24.96万
依托单位：
University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (A)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1995
项目状态：
已结题

项目摘要

"Pseudo-liquid" phase of heteropoly acids, in which reactant molecules are abosrbed into bulk of catalysts, is considered as unique 3-dimensional reaction field. It is noteworthy that proton and hetelopolyanion would contribute catalysis concertedly. In this study, dinamic behavior of adsorbed moelcules in pseudo-liquid phase of heteropolyaced and zeolite were elucidated mainly by high-resolution solid-state NMR experiments.In the pseudo-liquid phase of methanol-H_3PW_<12>O_<40> system, it was elucidated by ^<13>C,^1H,and ^<31>P solid-state NMR that protonated methanol monomerand dimer were formed stoichiometrically when absorbed amounts was varied form 1 molecule/anion to 6 molecules/anion. As for 1-6 molecules/anion, proton of heteropolyacid and hydroxy of methanol exchanged rapidly, while the nobility of methanol molecules was low. Above 6 molecule/anion, sharp peaks were observed by ^1H NMR,demonstrating rapid movement of methanol molecules in pseudo-liquid phase. This is a rare casein which ^1H NMR of solid gave sharp peaks. the significant increase of the mobility when absorbed amount was changed from 6 molecules/anion to 7 molecules/anion indicates high stabilities of protonated methanol monomer and dimer which were formed for 6 molecul/anion or below. On the other hand, only a part of adsorbed methanol was able to interact with proton on H-ZSM-5 at rt. This would be due to the different position of proton sites and acid strength distribution.In addition, methoxy groups, which would be and intermediate of dehydration reaction, were directly observed in pseudo-liquid phase heated up to 423 K by solid state NMR.

杂多酸的“伪液”相，即反应物分子被吸附到催化剂中，被认为是独特的三维反应领域。值得注意的是，质子和杂多阴离子对催化有协同作用。本研究主要通过高分辨固体核磁共振实验解释了吸附模型在杂多酸和沸石的伪液相中的动力学行为。在甲醇-H_3PW_&lt；12&gt；O_&lt；40&gt；体系的伪液相中，当吸附量从1个分子/阴离子到6个分子/阴离子时，通过^&lt；13&gt；C，^1H和^&lt；31&gt；P固体核磁共振确定了以化学计量比的方式形成质子化的甲醇单体和二聚体。对于1-6个分子/阴离子，杂多酸和甲醇羟基的质子交换较快，而甲醇分子的高贵程度较低。在6个分子/阴离子以上，核磁共振氢谱观察到尖锐的峰，表明甲醇分子在伪液相中运动迅速。这是一种罕见的酪蛋白，其固体的~1H核磁共振谱有尖锐的峰。当吸附量从6个分子/阴离子改变到7个分子/阴离子时，迁移率显著增加，表明在6个分子/阴离子或以下形成的质子化甲醇单体和二聚体具有很高的稳定性。另一方面，在RT条件下，只有一部分吸附的甲醇能够与H-ZSM-5上的质子相互作用。这可能是由于质子中心的位置和酸强度分布的不同所致。此外，固体核磁共振在加热到423K的伪液相中直接观察到脱水反应的中间产物甲氧基。