Effect of additive Cu on performance of supported palladium catalyst for perfluoroolefin hydrogenation
Hydrofluorocarbons have excellent characteristics of environmental friendliness,low toxicity,high stability,and are widely used in many fields,especially in the refrigeration industry,which has attracted great attention.Hydrofluorocarbons usually need to be prepared by hydrogenation of fluorinated olefins.However,due to the strong electronegativity of fluorine atoms,it is difficult to activate perfluoroalkenes,leading to perfluoroalkene hydrogenation is a challenging problem.For the hydrogenation reaction of perfluoroalkenes,precious metal supported palladium catalysts are currently widely used internationally,with a large palladium loading capacity and high cost.In this work,a high activity and low loading palladium catalyst with only 0.1 wt％palladium content was prepared by impregnation method,and a series of copper promoted palladium catalysts were also prepared.The performance of different catalysts in the hydrogenation of hexafluoropropylene dimer were investigated on a micro fixed bed continuous reactor.The results showed that the 0.l wt％Pd catalyst also had good activity,the conversion of hexafluoropropylene dimer was 49.3％,and the selectivity of the target product was 97.6％.When 10wt％Cu promoter was used,the catalyst had the best activity,the conversion of hexafluoropropylene dimer was higher than 93.4％,and the selectivity of the target product could reach 98.6％.Through the characterization and analysis of XRD,H2-TPR,and XAFS technologies,it was found that the copper in the catalyst mainly existed in the form of Cu2O and Cu0.Cu2O could form a strong interaction with Pd,greatly reduced the reduction temperature of Cu2O in the catalyst through hydrogen overflow,and the hydrogen atoms overflowing from palladium could greatly improve the hydrogenation activity of hexafluoropropylene dimer.Therefore,this work provides a highly active,low-content and stable palladium-based catalyst for perfluoroolefin hydrogenation reaction and its preparation method,which provides a research direction for further design of efficient catalysts.
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