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

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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.