Dynamics of Pseudoliquid Phase of Heteropolyacids and Design of New Catalytic Reactions

本研究的目的是：(1)阐明假液相在催化中的行为；(2)揭示假液相中分子的活化状态；(3)利用杂多化合物的假液相构建新的催化反应体系。结果表明：(1)由于体中几乎所有质子都参与了醇类脱水的催化，因此伪液相具有较高的催化活性。此外，由于假液相的存在，对极性分子的反应具有独特的选择性。(2)利用红外光谱和固体核磁共振（NMR）分析了乙醇在H_3PW_<12>O_<40>的假液相中脱水的反应机理。质子化乙醇二聚体（乙醚的中间体）、质子化单体和乙氧基（乙烯的中间体）通过^<13>C固态核磁共振直接检测。(3)用x射线单晶衍射法测定了配合物[(C_5H_5N)_2H]_3PW_<12>O_<40>的晶体结构，其中吡啶分子成对形成(C_5H_5N)- h ^+-(NC_5H_5)阳离子。(4)通过伪液相，苯酚的液相烷基化活性大大提高。H_3PW_<12 bbb_ O_<40>比普通固体酸和H_2SO_4活性高。

The aims of this study are (i) to elucidate the pseudoliquid phase behavior in catalysis, (ii) to reveal the activated state of the molecules in pseudoliquid phase, and (iii) to construct the new catalytic reaction systems, utilizing the pseudoliquid phase of heteropoly compounds.The results are summarized as follows:(1) The pseudoliquid phase brought about the high catalytic activity for dehydration of alcohols, since nearly all protons in the bulk takes part in catalysis. In addition, unique selectivity for the reaction of polar molecules due to the pseudoliquid phase was obtained.(2) The reaction mechanism of dehydration of ethanol in the pseudoliquid phase of H_3PW_<12>O_<40> was elucidated by using IR and solid state NMR. Protonated ethanol dimer (intermediate for diethyl ether),protonated monomer, and ethoxy group (intermediate for ethylene) were directly detected by ^<13>C solid state NMR.(3) The crystal structure of the complex, [(C_5H_5N)_2H]_3PW_<12>O_<40> was determined by the single crystal X-ray diffraction method, where pyridine molecules are paired forming the (C_5H_5N)-H^+-(NC_5H_5) cation in the structure.(4) By the pseudoliquid phase, the activity of liquid-phase alkylation of phenol was greatly enhanced. H_3PW_<12>O_<40> was much more active than ordinary solid acids and H_2SO_4.