The oxygen activated by the active vanadium species for the selective oxidation of benzene to phenol

2010

Catal Lett

The organic-inorganic hybrid catalyst L-MnPMoV was prepared simply by combining a schiff base Mn complex (L-Mn, L: N,N 0 -disalicylidene-1, 6-hexanediamine) with the Keggin-structured molybdovanadophosphoric heteropolyacid (PMoV). The proposed composition and structure of the catalyst were evidenced by TG, elemental analysis, FT-IR, and UV-Vis characterizations. Its catalytic performance was evaluated in the direct hydroxylation of benzene to phenol by molecular oxygen with ascorbic acid as the reducing agent. Various reaction parameters were changed to attain the optimal conditions. The hybrid catalyst has a formula [{Mn(C 20 H 22 N 2 O 2 )(Cl)} 2 (H 4 PMo 11 VO 40 )], with the two terminal oxygen atoms in the PMoV Keggin structure coordinately linked to the two Mn(III) ions in two L-Mn units, respectively. It exhibits a remarkably enhanced yield to phenol compared to the pure PMoV due to the synergy effect between the Schiff-base manganese complex and PMoV.

Section: Catalytic Performancementioning

confidence: 97%

Hydroxylation of Benzene to Phenol by Molecular Oxygen over an Organic–Inorganic Hybrid Catalyst: Schiff Base Manganese Complex Attached to Molybdovanadophosphoric Heteropolyacid

Zhou

2010

Catal Lett

“…Due to the high bond energy of the C-H bond (472.2 kJ mol -1 ) [37], benzene was difficult to be oxidatively hydroxylized to phenol. Many efforts have been made for the process, but the yield for phenol was not satisfactory so far [38,39]. In many reported catalysts systems, such as LaOx/HZSM-5 [40], PMoV 1 -b-CyDs [41], Cu/ZnO [42], etc., some co-reducing agent, such as ascorbic acid, was necessary to achieve the conversion of phenol.…”

Section: Resultsmentioning

confidence: 99%

Preparation of VO2(B) Nanoflake with Glycerol as Reductant Agent and its Catalytic Application in the Aerobic Oxidation of Benzene to Phenol

Chen

2011

Top Catal

Self Cite

“…Much effort has been made to produce phenol by hydroxylation of benzene with molecular oxygen under mild conditions. [11][12][13][14][15][16][17] However, the mechanism and the factors affecting the selectivity are still not clear for the hydroxylation of benzene to phenol in the liquid phase. With H 2 O 2 as the oxidant agent, C]O and the armchair conguration defects in the carbon catalyst were reported to have a positive effect on the yield of phenol.…”

Section: Introductionmentioning

confidence: 99%

V_xO_y@C catalyst prepared from biomass for hydroxylation of benzene to phenol with molecular oxygen

Shi

et al. 2017

RSC Adv.

A series of V x O y @C catalysts was prepared from different types of biomass and NH 4 VO 3 using a hydrothermal method. The prepared catalysts were characterized using a series of methods including XRD, SEM, FT-IR, SEM and XPS to investigate the mechanism of formation of the V x O y @C catalysts.Furthermore, the factors related to the selectivity of phenol and the mechanism of the hydroxylation of benzene to phenol were studied. It was found that the activity was related to the V species on the catalyst and the selectivity was related to the adsorption of phenol. IntroductionC-H bond activation is important in catalysis, especially the C-H bond of arenes. The C-H bond of benzene has a high binding energy of 473.1 kJ mol À1 at 298 K.1 The functionalization of benzene is vitally important for the green conversion of benzene to other chemicals such as the direct conversion of benzene to phenols, anilines, etc.2,3 However, functionalized benzene derivatives are thermodynamically and kinetically favorable to being further converted compared with benzene, 4,5 which makes the direct conversion of benzene to phenol or aniline a great challenge.The direct conversion of benzene to phenol has attracted much research interest for it is a greener route than the industrial three steps of the cumene process route.6-10 Direct conversion of benzene to phenol requires oxidant agents. Among the oxidant agents (such as H 2 O 2 , O 2 and N 2 O) for the hydroxylation of benzene to phenol, O 2 is believed to be the most conveniently available and low cost oxidant. Much effort has been made to produce phenol by hydroxylation of benzene with molecular oxygen under mild conditions. 11-17 However, the mechanism and the factors affecting the selectivity are still not clear for the hydroxylation of benzene to phenol in the liquid phase. With H 2 O 2 as the oxidant agent, C]O and the armchair conguration defects in the carbon catalyst were reported to have a positive effect on the yield of phenol.18-20 However, with molecular oxygen as the oxidant, research on the factors related to the selectivity is still rarely reported. As stated above, phenol is thermodynamically and kinetically more favourable to being further oxidized than benzene in the hydroxylation reaction of benzene to phenol, which makes the selectivity of phenol a challenge in this kind of continuous reaction.21 Therefore, elucidating the factors affecting the selectivity is vitally important for the direct conversion of benzene to phenol.Vanadium is the effective element for the hydroxylation of benzene to phenol with molecular oxygen as the oxidant. Various catalysts have been prepared to improve the yield and selectivity of phenol, including those with different species of vanadium oxide and supports.22-27 Recently, we have developed a V x O y @C catalyst prepared from sucrose and NH 4 VO 3 by a facile one-pot hydrothermal carbonization (HTC) method for the hydroxylation of benzene with molecular oxygen as the oxidant, 28 which exhibited good yield and selectivity of pheno...