Synthesis And Application Of Palladium Catalyst For CO And MN Coupling To Dimethyl Oxalate

In this paper,the crutial reaction for generating ethylene glycol by coal-MN coupling with CO to synthesizing DMO was taken as the target,and the synthesis conditions and reaction process conditions of Pd/α-Al₂O₃ catalyst were optimized.On account of the experimental study of kinetic characteristics,the intrinsic kinetic equation of the coupling reaction was established,which provided an application basis for the industrial application of the catalyst.Pd/α-Al₂O₃ catalyst was synthesized by liquid phase reduction and impregnation.The influences of synthesis elements on the physical and chemical characteristics and catalytic performance of the catalyst were found by TEM,ICP and single factor experiment.The optimal synthesis conditions were confirmed by characterization and assessment of catalyst property.The consequences indicate that as the rising of synthesis temperature,the particle size of nano-Pd increases at first and then decreases,and the particle size distribution tends to be uniform.With the increase of m（PVP）/m（Na₂Pd Cl₄）,the diameter of Pd nanoparticles expands at the beginning and then minishes,and the diameter is well-distributed.Pd/α-Al₂O₃ catalyst made by incipient-wetness impregnation method has uneven Pd nanoparticles distribution on the carrier,low actual load and poor catalytic performance.When Pd/α-Al₂O₃ catalyst is prepared by excessive impregnation method,the loss of Pd element is relatively small,and the nanoparticles have good dispersion and uniform distribution on the surface of alumina carrier,and the catalytic performance is also better.To sum up,when the synthesis condition is 130℃,the ratio of m（PVP）/m（Na₂Pd Cl₄）is 6,and the impregnation method is excessive impregnation,the catalyst has the best catalytic performance.Aiming at the optimized Pd/α-Al₂O₃ catalyst,the influences of main technological conditions on the chemical reaction process of coupling CO with MN to dimethyl oxalate was exported by single factor method.The optimum technological conditions of the chemical reaction were found by response surface experiment and response surface optimization analysis on account of experimental results.The results manifest that the optimum process conditions for the reaction of CO turning into dimethyl oxalate catalyzed by Pd/α-Al₂O₃catalyst are as follows:reaction temperature is 140.62℃,CO/MN is 1.83,and space velocity is 800 ml/（g·h）.Under the optimized conditions,the conversion rate of methyl nitrite as feed gas can reach 95.82%,and the selectivity of dimethyl oxalate as product can reach 95.58%,which is close to the prediction result of response surface methodology,indicating that the model determined by response surface methodology has good predictability.Based on Pd/α-Al₂O₃ catalyst,under the circumstance of atmospheric pressure,105～155℃and the mole fraction of CO and MN in the feed composition of 0.0511～0.1311 and 0.0316～0.1422 respectively,an experimental study on the kinetic characteristics of CO-MN coupling reaction was carried out,and the experimental data were searched and optimized by the method of interior point-fourth order-Runge Kutta,and a power-function kinetic rate equation matching well with the experimental data was established as follows...