One-step Hydroxylation Of Benzene Research Articles

One-Step Selective Hydroxylation of Benzene to Phenol with Hydrogen Peroxide Catalysed by Copper Complexes Incorporated into Mesoporous Silica-Alumina.

Benzene was hydroxylated with hydrogen peroxide (H2O2) in the presence of catalytic amounts of copper complexes in acetone to yield phenol at 298 K. At higher temperature, phenol was further hydroxylated with H2O2 by catalysis of copper complexes to yield p-benzoquinone. The kinetic study revealed that the rate was proportional to concentrations of benzene and H2O2, but to the square root of concentration of a copper(II) complex ([Cu(tmpa)]2+: tmpa = tris(2-pyridylmethyl)amine). The addition of a spin trapping reagent resulted in formation of a spin adduct of hydroperoxyl radical (HO2•), as observed by EPR spectroscopy, inhibiting phenol formation. HO2• produced by the reaction of [Cu(tmpa)]2+ with H2O2 acts as a chain carrier for the radical chain reactions for formation of phenol. When [Cu(tmpa)]2+ was incorporated into mesoporous silica-alumina (Al-MCM-41) by a cation exchange reaction, the selectivity to production of phenol was much enhanced by prevention of hydroxylation of phenol, which was not adsorbed to Al-MCM-41. The high durability with turnover number of 4320 for the hydroxylation of benzene to phenol with H2O2 was achieved using [Cu(tmpa)]2+ incorporated into Al-MCM-41 as an efficient and selective catalyst.

One-step hydroxylation of benzene to phenol i. gas-phase nitric acid oxidation over fe/mo/sio2

Abstract Among a group of silica coformed binary oxide catalysts, the Fe/Mo/SiO2 catalyst performed best for the selective gas-phase nitric acid oxidation of benzene to phenol. The dual functions exhibited by the catalyst, the formation of nitrobenzene and phenol, can be controlled by the atomic ratio of Mo/Fe and the oxidation temperature. With the atomic ratio of Mo/Fe = 2.3, nitrobenzene was selectively formed at the lower temperatures ( 400°C). With the ratio of Mo/Fe = 1.5, phenol was selectively formed at 350–475°C. With the ratio of Mo/Fe = 1.05, a mixture of phenol and nitrobenzene was produced at all temperatures. Blending of 1 mol-% nitrobenzene in benzene remarkably enhanced the phenol yield, and nitrobenzene functions as a promoter for the reaction.