Regulation Of Copper(?)-palladium(?) Relative Distirbution And Its Catalytic Evaluation Towards Ethanol Oxycarbonylation

Oxycarbonylation of alcohols,involving the insertion of CO and C-O bond formation,is one of the important ways to produce esters that has been widely used in the chemical industry.Among the esters,diethyl carbonate(DEC)has been widely applied in the synthesis of polycarbonates and the intermediates of pesticide medicine molecules such as antibiotic,phenobarbital and pyrethrin etc.The production of DEC by ethanol oxidative carbonylation is a promising method.However,the low catalytic efficiency and sintering of active center in industrial catalyst limit the development of ethanol oxycarbonylation.In this work,an uniformly-dispersed Cu(?)-Pd(?)coordinated with pyridine imine grafted on mesoporous silica has been developed for ethanol oxycarbonylation.The main work of this research displayed as follows:1.An uniformly-dispersed Cu(?)-Pd(?)coordinated with pyridine imine grafted on mesoporous silica has been prepared and applied in ethanol oxycarbonylation.Due to the electron donation of N ligand,the Cu centers presented Cu(?)and Cu(?)state,and the Pd centers presented Pd(?)and Pd(0)state.By regulating the coordination sequence of Cu(?)and Pd(?),the relative distribution of Cu-Pd center is regulated.It was found that the performance of ethanol oxycarbonylation increased with the increase of Cu-Pd pairs percentage.189 mg-g-1·h-1 ethanol space-time conversion with 85.4%diethyl carbonate selectivity was obtained at 56.7%Cu-Pd pairs,and catalytic performance was maintained within 24 hours.2.The formed Cu-Pd pair is beneficial to enhance Pd-Cu interaction,generating more Cu(?)centers.The performance of ethanol oxycarbonylation was enhanced with the increase of Cu(?)percentage.To figure out the role of Cu(?)center in ethanol and CO simultaneously activation,the operando FT-IR spectra of ethanol and adsorption were recorded.It was found that Cu(?)was beneficial to the simultaneous activation of ethanol and CO.Under high ethanol coverage,the activation of CO was significantly improved with more Cu(?)center.3.By regulating the ratio of Cu/Pd,relative distribution of Cu-Pd center was further regulated.Uniformly distribution of Cu-Pd is beneficial to increase the relative content of Cu(?).4.The relative content of Cu(?)was further regulated by in situ treatment with ethanol and CO.298 mg·g-1·h-1 ethanol space-time conversion with 85.1%diethyl carbonate selectivity was obtained when Cu(?)relative content increased to 87.9%.