Synthesis Of Diphenyl Carbonate Over Metal Silicon Dioxide Composite Supported Pd Catalyst

Heterogeneous palladium catalysts supported on silica aerogels composite oxides demonstrate theoretical and practical values in oxidative carbonylation of phenol to diphenyl carbonate?DPC?for the chemical engineering.This heterogeneous catalysts are easy separated and the function of reoxidation additives.The most important researchs focus on the catalytic performance of the catalysts which are high activity,high selectivity and sustainability.The main catalyst of PdO species are easy reoxidated to be Pd⁰and sintered agglomeration in oxidative carbonylation reaction.The central issue is the selection and optimization of cocatalysts and carriers that help to improve the catalytic performance of the main active component.The physical structure and chemical properties of the carrier correlate with the catalytic activity of the catalyst.The carrier can react with more active species and reactants to improve mass transfer and heat transfer performance due to higher specific surface area and suitable pore volume.Silica aerogel has high specific surface area,high porosity,3D network structure and other characteristics,these excellent performance could limits the metal oxide grain size and disperse uniformly on carriers.The performance of composite silica aerogel supporters was studied for direct synthesis of DPC.The performance of catalysts are investigated the relationship between the carrier structure and the dispersion state of the metal particle.The carrier structure are modulated by preparation methods?component metal additives,roasting temperatures and surfactants modify ect.The following works has been done:?1?The pure silica aerogels obtain a larger specific surface aera and better catalytic activity by calcined at 500?.Active PdO species on the catalyst are more dispersed and PdO nanoparticles are uniform and small.?2?The silica aerogels are modifyed by CTAB,SDS,PEG,respectively.The Catalytic performance and carriers structure are investigated by X-ray diffraction?XRD?,transmission electron microscopy?TEM?,and N₂ adsorption and desorption?BET?characterization techniques.It show that the PEG-modified supports had larger specific surface area and pore volume,narrower pore size distribution and more Si-OH on the support surface.The CuO particles had the average particle size for 2.4 nm and dispersed uniofrmly on the catalyst which the yield of DPC was 16.47%.?3?The composite Ce-Mn silica aerogels were prepared by in-situ,precipitation and impregnation method,respectively.The cerium-manganese oxide in silica aerogel carriers prepared by impregnation were nano-size particles and those composite carriers remained intact pore due to spatial limitation effect.The carrier has better catalytic with the high metal content and high specific surface area(up to 509 m²/g^-1).The single pass yield of DPC reached 21.58%with selectivity above 99.27%under a total pressure of5 MPa at 75?for 6h.