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Ternary metal oxide catalysts for selective oxidation of benzene to phenol
Garun Tanarungsun,Worapon Kiatkittipong,Piyasan Praserthdam,Hiroshi Yamada,Tomohiko Tagawa,Suttichai Assabumrungrat 한국공업화학회 2008 Journal of Industrial and Engineering Chemistry Vol.14 No.5
This paper studied the liquid phase hydroxylation of benzene to phenol with hydrogen peroxide catalyzed by ternary metal oxide catalysts (Fe(III), V(V) and Cu(II)) supported on TiO2 at room temperature. The effects of V(V) and Cu(II) metal oxide loading were investigated. The catalysts were prepared by co-impregnation method and characterized by BET, XRD, XRF, SEM-EDX, NH3-TPD techniques. It was reported that the presence of V(V) and Cu(II) influenced the acid property on the catalyst. The increase of the metal loading increased the acidity of the catalyst. TiO2 loaded with Fe, Vand Cu of 5, 2.5 and 2.5 wt%, respectively offered the highest yield of phenol. Although the increase of the metal loading improved the yield of phenol, the TOF reduced due to the reduction of dispersion of the catalyst metal. The optimum condition for the system is a reaction time of 4 h, catalyst weight of 0.2 g, the H2O2:benzene molar ratio of 2 and 6.25 g of ascorbic acid per mole of benzene.
SuttichaiAssabumrungrat,Tomohiko Tagawa,Piyasan Praserthdam,Garun Tanarungsun,Worapon Kiatkittipong,Suttichai Assabumrungrat,Hiroshi Yamada 한국공업화학회 2007 Journal of Industrial and Engineering Chemistry Vol.13 No.3
of CHD (Eq. 3). In addi-tion, CHD can easily collapse to benzene when the Fe(II) content increased (Eq. 4) and also phenol can be further reacted with excess hydroxyl radicals to yield catechol, hydroquinone, and benzoquinone, resulting in the de-crease of selectivity.It is should be noted that ascorbic acid was highly solu-ble in the aqueous phase, but not in the organic phase. The addition of solvent was necessary to promote the re-action in this system by dissolving H2O2, ascorbic acid, and benzene into one phase. ConclusionThe liquid phase hydroxylation of benzene to phenol with hydrogen peroxide catalyzed by Fe(III)/TiO2 cata-lysts was investigated. The most suitable Fe(III) pre-cursor and %Fe(III) loading were iron(III) acetylaceto-nate and 5 wt%, respectively. Among the solvents stud-ied (acetone, dichloromethane, acetronitrile, pyridine, tert-butyl alcohol, 1-butyl alcohol, and ethyl alcohol), acetone showed the highest conversion and yield, but low selectivity. However, acetronitrile may be an attrac-tive solvent because of its high selectivity. Biphasic op-eration was not attractive compared to triphasic operation because of the dilution effect. Benzene conversion in-creased with increasing the amount of ascorbic acid; however, to much ascorbic acid retarded the yield im-provement because of lower phenol selectivity.AcknowledgmentFinancial support from the Thailand Research Fund and Commission on Higher Education are gratefully acknowledged.