Transition Metals Modified Sba-16 Molecular Sieve Benzene Direct Hydroxylation To Phenol

Abstract The direct one-step hydroxylation of benzene to phenol using environ- mentally safer and economical hydrogen peroxide or molecular oxygen as oxidant has been considered most probably way to substitute the multi-step so-called cumene process in industry, which attracts researchers to study and carry out the project insistently.In this dissertation, the SBA-16 molecular sieves catalysts modified by transition metal were prepared by facile impregnation method. The structure properties of samples were characterized by XRD, TEM and N2 adsorption-desorption, which reveal that the SBA-16 molecular sieves catalysts possess a large surface area, uniform pore size and 3-D cubic porestructure. The activity for hydroxylation of benzene was investigated under mild conditions using hydrogen peroxide as oxidant, and some reaction conditions were also optimized. The VOx/SBA-16 samples showed excellent catalytic activities for benzene hydroxylation. The phenol yields attain 13.8% and 18.68% in solvent systerm of acetonitrile and acetic acid, respectively, and both the selectivities of phenol are higher than 97%. The Cu/SBA-16 samples showed relative lower activities, the highest phenol yield was only 7.7%. However, the catalyst could retain more than 60% of initial activity after three runs of benzene hydroxylation. The surface active species were characterized with FT-IR,Raman,DRUV-vis,XPS,EPR and TPR measurements, which prove that highly dispersed CuO and VOx are main active species for benzene hydroxylation, CuO and V2O5 species with small particle size are beneficial to the reaction.Liquid benzene hydroxylation by molecular oxygen as oxidant was investigated in acetic acid solvent systerm over VOx/SBA-16 catalysts. It was found that the highest activity result was obtained under reaction condition: 100mg VOx/SBA-16(8 wt%) as catalyst, 2.1g ascorbic acid as reduced agent, oxygen pressure 1.5MPa, reaction temperature at 70℃, reaction time for 5h. The yield and selectivity of phenol is 18.7% and 75.4%, respectively.