Liquid-Phase Oxidation of Benzene to Phenol over V-Substituted Heteropolyacid Catalysts

Abstract

The liquid-phase oxidation of benzene was carried out in aqueous acetic acid solvent over V-substituted heteropolyacids (V−HPAs) using molecular O2 and ascorbic acid as the oxidant and reducing reagent, respectively. Phenol was exclusively obtained as the oxygenation product. The elimination of the V species from the V−HPA (Keggin structure) catalyst into the reaction solvent during the benzene oxidation reaction was largely inhibited by ion-exchanging the proton of the V−HPA catalyst with Cs+. The main active species were assumed to be the V species anchored in the HPA. The influences of the reaction temperature, the concentration of acetic acid in the aqueous solvent, and the reaction pressure on the yield of phenol were investigated to obtain the optimal reactions condition for phenol formation. The reuse of the V−HPA catalyst caused gradual deactivation for phenol formation, despite the retention of the structure of the V−HPA catalyst. The deactivation was suggested to be due to the reduction of the V species in the V−HPA catalyst on the basis of the diffuse reflection spectra of the used catalysts.

One-pot Hydrothermal Synthesis of Mesoporous V-SBA-16 with a Function of the pH of the Initial Gel and its Improved Catalytic Performance for Benzene Hydroxylation

“…Compounds of vanadium, due to their reactivity and remarkable stability, have been utilized as efficient catalysts for a variety of catalytic reactions [12][13][14][15][16], especially for the catalytic selective oxidation of benzene to phenol [17][18][19][20][21]. Recently, various vanadium containing mesoporous molecular sieves such as V-MCM-41 [22,23], V-MCM-48 [24] and V-SBA-15 [25,26] have been prepared by hydrothermal methods through different synthesis routes.…”

Synthesis and Characterization of V-HMS Employed for Catalytic Hydroxylation of Benzene

“…It was reported that H 2 O 2 can be stably present in the acidic medium as its selfdecomposition is inhibited [22,23]. Thus, the aqueous acetic acid solvent was chosen in this work.…”

Catalytic Hydroxylation of Benzene to Phenol with Hydrogen Peroxide over Cesium Salts of Keggin-type Heteropoly Acids

“…Yamaguchi et al reported the oxidation of benzene over the cesium salts of heteropoly acids (CsPMoV n , n＝1-3) using O 2 as oxidant. [28] Compared with the application of cesium salts of heteropoly acids as catalyst in acid reactions and gaseous phase oxidation reactions, their application in liquid phase oxidation reaction as water-tolerant catalysts was rare. [29][30][31] From the synthetic point of view, the typical procedure for preparation of cesium salts of HPAs are generally proceeded through a solution method by titrating the controlled amount of an aqueous solution of Cs 2 CO 3 into the aqueous solution of HPA.…”