Study On Maleic Anhydride Hydrogenation Performance Of Y-doped ZrO₂ Supported Ni Catalyst

Maleic anhydride butylene diacid anhydride,short for maleic anhydride,is an important chemical raw material.Maleic anhydride can be synthesized by catalytic hydrogenation to succinic anhydride,gamma-butyrolactone,tetrahydrofuran,1,4-butanediol and a series of high value-added products.They are widely used in military industry,textile,pharmaceutical synthesis and food industry.Maleic anhydride molecule is a five-membered ring molecule consisting of a C=C and two C=O double bonds and a C-O-C functional group.Among them,C=C bond and two C=O bond conjugate each other,and the electron distribution in maleic anhydride molecule tends to be uniform.Therefore,it is difficult to selectively hydrogenate unsaturated functional groups in maleic anhydride molecule to achieve directional synthesis of downstream hydrogenation derivatives of maleic anhydride.Studying the structure-activity relationship of catalysts for maleic anhydride hydrogenation and discussing the hydrogenation mechanism of some functional groups in maleic anhydride molecule have important theoretical significance and practical application value for the research and development of high performance catalysts for maleic anhydride hydrogenation.In order to understand the mechanism of the effect of surface oxygen vacancies on hydrogenation of maleic anhydride over Ni-based catalysts supported on ZrO2.A series of ZrO2 supports with different surface structure and oxygen vacancy concentration were prepared.The catalysts supported on nickel were evaluated.The supports and catalysts were characterized by H2-TPR,H2-TPD,Raman and XPS.The effect of oxygen vacancy on selective hydrogenation of Ni/ZrO2 maleic anhydride was discussed.The main research contents are as follows:(1)ZrO2 supports with different Y2O3 doping amount were synthesized by hydrothermal method.The effects of Y2O3 doping amount on the hydrogenation of maleic anhydride over Ni catalyst supported on ZrO2 were investigated.The results show that the selectivity of succinic anhydride increases and that of ?-butyrolactone decreases with the increase of Y2O3 doping.The doping of Y2O3 reduces the catalytic activity of C=O hydrogenation and improves the selectivity of C=C bond hydrogenation.The main product of maleic anhydride hydrogenation is succinic anhydride.The characterization results show that Y2O3 doping has little effect on the hydrogen adsorption and activation ability of the catalyst.It is speculated that the effect of Y2O3 doping on the hydrogenation activity of catalyst C=O is that Y2O3 doping changes the surface structure of the catalyst and the interaction between metal and support,resulting in the formation of oxygen vacancies with different properties on the surface of the catalyst.(2)In order to understand the internal relationship among Y-doped ZrO2 catalyst,metal-support interaction,oxygen vacancy formation and properties,and maleic anhydride hydrogenation performance,the support and catalyst were further characterized by in situ FTIR,Raman,XPS and other characterization techniques.The results show that with the increase of Y2O3 doping,the concentration of low coordination oxygen ions and oxygen vacancies on the carrier surface increases.After loading nickel,the nickel species preferentially interact with low coordination oxygen ions and oxygen vacancies on the carrier surface,forming a Ni-O-Zr-like structure,resulting in the decrease of oxygen vacancy concentration on the carrier surface,resulting in the increase of the average charge density of oxygen vacancies and the formation of electron-rich oxygen vacancies.As a result,the ability of activating C=O decreased,the activity of C=O bond hydrogenation was significantly reduced,and the selectivity of C=C bond hydrogenation was improved.