Studies On The Catalysts For The Selective Hydroxylation Of Benzene Ring

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. The object of this work is to research and develop the catalyst for hydroxylation of benzene to phenol with oxygen in liquid-phase.First, the hydroxylation of benzene with hydrogen peroxide to phenol over clay and FSM-16 modified by metal was studied in this work. The results show that vanadium oxide is the most active element in the reaction. The catalyst of clay-supported vanadium oxides gives 14.1 % conversion of benzene and 94 % selectivity to phenol.Second, the manner to activate oxygen for the selective oxidation of benzene to phenol was studied in the work. The lower valence vanadium oxide, which could be obtained by reducing the vanadium oxide supported on alumina by hydrogen or ascorbic acid in advance, activate the dioxygen to generate the active oxygen species through the"reductive activation"process to realized the hydroxylation of benzene with oxygen to phenol. Characterization of the samplesshows the quadrivalence vanadium oxides is the active species in the reaction.At last, the catalysts of nano vanadium oxide mainly composed of quadrivalence vanadium species were developed in this work, based that the pentavalent vanadium species was reduced to quadrivalence vanadium species by amines in the process to produce the vanadium nanotube. Under different conditions, nano vanadium oxides which are various modalities were prepared. The catalyst VO-N-P-A gives 3.7% conversion of benzene, which is best performance. The results of the recycling experiment shows that the catalyst VO-C16-A could by reused.In addition, the FSM-16 modified by metal catalysing the hydroxylation of phenol to dihydroxybenzene was studied in this work. 27.8% conversion of phenol and 94% selectivity to dihydroxybenzene (n(catechol):n(hydroquinone)= 1.8:1) were realized over Fe-FSM-16, which performance is comparable with the well-known TS-1 catalyst.