C-5. ベンゼンのヒドロキシル化反応に対する修飾ヘテロポリ酸塩を利用した触媒設計

概要

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Using selectively site-substituted vanadium (V) Keggin and Dawson heteropolytungstates (HPA), the catalytic activities for hydroxylation of benzene in the presence of 30% aqueous H_2O_2 were examined at room temperature under atmospheric pressure in a two liquid phase, aqueous and organic process. In particular, potassium salts of di- and tri-vanadium (V) substituted Keggin HPAs, α-1,2-PW_<10>V_2 and α-1,2,3-PW_9V_3,showed 0.81 and 8.69 catalytic turnovers for phenol production with excellent selectivity, respectively, for 48h reaction under the conditions : 0.1mmol catalyst, 1mL(11.3mmol) benzene, 2mL of acetonitrile and 2mL of 30% H_2O_2. The activity of tri-substituted, PW_9V_3,HPA was initially high, but it maximized after 48h and its structure completely decomposed, whereas that of di-substituted, PW_<10>V_2,HPA gradually increased and exceeded that of the PW_9V_3 after 120h. The polyoxoanion structure of the PW_<10>V_2 was maintained even after 576h. Their activities and stabilities as catalysts were compared with those of vanadium (V)-substituted Dawson HPAs (α-P_2W_<17>V and α-1,2,3-P_2W_<15>V_3), vanadium (V)-containing isopolyanions (IPA; VW_5 and V_<10>), the Milas reagent (V_2O_5 and aqueous H_2O_2), and the picolinato-vanadium (V) oxo peroxo complex.
神奈川大学の論文