Selective Hydroxylation Of C-H Bond On Benzene And Tetrahydropyrrole Rings Catalyzed By Metalltic Catalysts And Biocatalysts

Selective oxidation of hydrocarbons is a challenge in catalytic chemistry.It is academic and applicable significance to research about the direct hydroxylation of benzene to phenol. In the world, ninety percent of phenol is produced using the cumene method, which consists of three steps, produces acetone as a byproduct and pollute the environment seriously. For the high bond energy of the C-H bond, benzene is difficult to activate. In addition, the deep oxidation is easy to occur because phenol is more active than benzene. The direct hydroxylation of benzene to phenol is a challenges problem. One of the objects of this work is to research and develop the catalyst for hydroxylation of benzene to phenol with oxygen or hydrogen peroxide in liquid-phase.Firstly, isomorphously substituted iron zeolite beta catalysts with varied iron loading were successfully synthesized and characterized. A moderate conversion of 12% was obtained with Fe-beta catalyst of Si/Fe ratio 25 and a phenol selectivity of 100% with hydrogen peroxide as green oxidant. Fe-beta catalysts were found to be resistant to leaching and regained activity on calcination after the first cycle of reaction.Secondly, V-beta catalysts with two different precursors, namely vanadium acetylacetonate and ammonium vanadate, were successfully synthesized and characterized. V-beta catalysts prepared with vanadium acetylacetonate as the precursor was far more active than the other type of V-beta catalyst. A conversion of about 6.8% was achieved with V-beta catalyst of Si/V ratio 100, which was found to go up to 11% in the presence of 4mmol of the ascorbic acid reductant. Ascorbic acid was found to be the best reductant with sodium sulfite being a possible cheaper alternative. V-MCM-41 catalysts were synthesized and characterized with varied amounts of vanadium loading. The values obtained for catalytic activity and characterization are in good agreement with the literature values. Partial leaching of about 14% was observed in the V-beta catalysts whereas V-MCM-41 catalysts were very unstable and underwent 98% leaching.Thirdly, The homogeneous catalytic oxidation of benzene to phenol was carried out over Fe (II) acetate as catalyst and trifluoroacetic acid as co-catalyst. A benzene conversion of about 18% and a selectivity of 88% were achieved with the catalyst to substrate ratio at 1:450. The presence of trifluoroacetic acid in the catalytic system is necessary for conversion and increase in selectivity. Addition of hydrogen peroxide oxidant in one lot is comparatively more favorable than syringe pump addition in terms of conversion of benzene to phenol.Biological oxidation processes are very intersting because non-activated varbon atons can be oxidized directly by the use of microorganisms.In our experiment, we are developing a high-thoughput enantioselectivity assay that is generally applicable for enantioselective hydroxylation by the use of enantiopure isotopically labeled substrate droxylated with Sphingomonas sp. HXN-200.