Research On Preparation And Catalytic Performance Of Pd/Manganese Oxide-carbon Microspheres Supports

Diphenyl carbonate?DPC?is an important intermediate in the preparation of thermoplastic engineering plastic polycarbonate?PC?.In industry,DPC were produced mainly by phosgene method and ester exchange method.Phosgene method does not meet the requirements of green chemistry and low-carbon economic development model due to the use of highly toxic phosgene raw materials.The ester exchange method had long process and was difficult to separate product.Therefore,it is necessary to develop new environmental friendly synthetic method.The phenol oxidative carbonylation method has the characteristics of simple process,low raw material cost,and no pollution.This method has become the main research direction at home and abroad,its core technology is the choice of active components of the catalyst and its carrier.In this work,glucose and other organic carbon sources were used to modify and prepare manganese oxide-carbon microsphere carriers,and then the palladium/manganese oxide-carbon microsphere catalyst were prepared to catalyze oxidative carbonylation of phenol to synthesize diphenyl carbonate.The specific research work includes:1.Hydrothermal synthesis of carbon microspheres using different organic carbon sources as precursors.2.Preparation of manganese oxide-carbon microsphere supports.The carbon microspheres were preliminarily loaded with manganese by impregnation method,and then the carbon microspheres were subjected to secondary manganese loading and surface control with potassium permanganate solution.3.Preparation of manganese oxide carbon microsphere palladium-supported catalyst from different carbon sources.The catalytic performances of different catalysts were investigated on the oxidative carbonylation of phenol to diphenyl carbonate.4.The reaction conditions and stability of catalyst were also investigated subsequentlyThe related research results are as follows:The carbon microspheres were prepared by hydrothermal method with glucose and sucrose as raw materials in different conditons.The influence of the type and concentration of carbon source,reaction time and other factors on the morphology of carbon microspheres was discussed.The particle size,morphology and chemical structure of different carbon microspheres were analyzed by EDS,SEM and FTIR.The results showed that the carbon microspheres from glucose were smaller with 400 nm uniform particle size,smooth surface and complete pherical structure.The carbon microspheres from sucrose were larger with 700 nm uniform particle size,rough and porous surface and complete spherical structure.Those carbon microspheres were mainly composed of C,H,and 30%oxygen elements.The manganese oxide carbon microspheres carriers were obtained by impregnation with 50%manganese nitrate solution and then modified with potassium permanganate.The corresponding palladium-loaded catalyst were prepared and applied to the synthesis of diphenyl carbonate by oxidative carbonylation of phenol.The catalytic performances were evaluated under different carbon microspheres carrier,reaction time,reaction temperature,reaction pressure.The results show that the carrier CM3 from glucose as the carbon source not only retained the complete spherical structure but also has the appropriate specific surface area.The corresponding palladium-loaded catalyst had good catalytic performance with yield of 12.34%and selectivity of 97.12%at a total reaction pressure of 5 MPa,reaction temperature of 70?and reaction time of 4 h.The carrier CM7 from sucrose retained complete spherical structure and had large specific surface area.The corresponding palladium-loaded catalyst had better catalytic performance with yield of14.26%and selectivity of 98.25%at a total reaction pressure of 5 MPa,reaction temperature of 70?and reaction time of 4 h.The reaction temperature,reaction pressure and reaction time had important influence on the yield of DPC.The optimum reaction conditions were reaction temperature 70?,total pressure 5 MPa?7%O₂?and reaction time 16 h.The yield of DPC could reach18.07%.