The Preparation And Catalytic Performance Of Catalysts For Synthesis Of Phenol From Benzene-O₂

Phenol is a widely used chemical materials,which has important applications in industry,agriculture,medicine and other industries.At present,nearly 90%of the phenol is synthesized by the isopropylbenzene process,which has many disadvantages such as the long technological process,the production cost affected by the price of acetone,environmental pollution of the phenol contained waste water and so on.Therefore,the development of green preparation routes for phenol has become the research hotspot.Using oxygen as oxidant for directly oxidation benzene to produce phenol has the advantages of short reaction process,high atomic utilization rate,low cost,all meeting the requirments of green chemistry.Aerobic oxidation benzene to phenol has important theoretical and practical significance.In this thesis,the aerobic oxidation of benzene to phenol was studied.VO?acac?₂ was used as the active center of the catalyst while phytic acid was used as the carbon source.The vanadium-carbon catalyst V_xO_y/C was prepared by calcining method.The preparation conditions of the catalyst were optimized.Meanwhile,a series of catalysts including V_xO_y/AC?activated carbon?,V_xO_y/C₃N₄?carbon nitride?,V_xO_y/MWCNTS?multi-walled carbon nanotube?,V_xO_y/BENT?bentonite?were prepared by adding different carriers in the preparation process of the catalysts.The catalysts were characterized by XRD,FT-IR,SEM,XPS,Raman,ICP and N₂ adsorption/desorption.The catalytic performances of the vanadium-carbon catalysts were investigated by aerobic oxidation of benzene to phenol.The reaction conditions were optimized as follows:1.0 mL benzene,100 mg V_xO_y/C catalyst,0.4 g ascorbic acid,3.0 mL70%?V/V?acetic acid solution,3.0 MPa O₂,at 80?for 2 h.The selectivity and yield of phenol were 42.7%and 6.1%.With the V_xO_y/AC as catalyst,the selectivity and yield of phenol were improved to 77.0%and 10.9%,respectively.The titration experiment of H₂O₂ shows that the H₂O₂ was generated in the reaction.The mechanism of catalytic reaction was studied by controlling experiments.Generally,the synthesis of phenol by aerobic oxidation benzene requires the transition metal catalyst and reductant.In order to overcome these disadvantages,a series of QAPs catalysts were prepared with p-phenyl quinone and different amine sources,which were QAP-E?ethanediamine?,QAP-D?diaminopropane?,QAP-H?hexanediamine?,QAP-DB?diaminobenzene?and QAP-M?melamine?,respectively.The catalysts were characterized by XRD,FT-IR,SEM,XPS,EA and N₂ adsorption/desorption.The catalytic performances of the QAPs were investigated by aerobic oxidation of benzene to phenol without reductant.The reaction conditions were optimized as follows:0.5 ml benzene,100 mg QAP-E catalyst,0.4 g LiOAc,3.0 mL 70%?V/V?acetic acid solution,3.0 MPa O₂,at120?for 24 h.The yield of phenol was 13.1%.Using the QAP-D as catalyst,the yield of phenol could reach 15.9%,which reached the same level of metal catalyst.The possible mechanism of aerobic oxidation benzene to phenol without reductant was studied by control experiments and catalyst characterization of catalyst.