Study The Catalytic Performance Of Ni-based Catalysts With Phyllosilicate As Precursor For The Hydrogenation Of Maleic Anhydride

Maleic anhydride?MA?has been regarded as a good feedstock since it can be produced at a low cost and on a large scale by partial oxidation of n-butane instead of benzene.Moreover,it is recently reported that MA can be obtained by oxidation of renewable biomass-derived chemical platforms such as biobutanol,5-hydromethylfurfural and furfural.Hydrogenation of maleic anhydride can produce a series of high value-added chemicals such as succinic anhydride?SA?,?-butyrolactone?GBL?and tetrahydrofuran?THF?,which are widely used in pesticides,machinery,military and plastics.The research on the hydrogenation of maleic anhydride to its downstream products has important theoretical significance and practical application value for expanding the coal chemical industry chain and promoting the extension of petrochemical industry and biomass furfural to the high and middle end.Several metal catalysts have been reported to be active in thehydrogenation of MA to SA or GBL,including noble metal catalysts and non-noble metal catalysts.Noble metal catalysts are highly active for MA hydrogenation but relatively expensive,high production cost and it is difficult to achieve application on a large scale.Non-noble metal catalysts are mainly Ni-based supported catalysts,which are cheap and low production cost.However,such catalysts suffer from low catalytic activity and poor stability.Hence,it would be highly desirable but more challenging to develop a novel Ni-based catalytic system with highly activity at low temperature and high selectivity and stability at high temperature for the hydrogenation of MA.Based on these understandings,a series of nickel phyllosilicate catalysts prepared by ammonia evaporation method were proposed for the hydrogenation of MA.We systematically studied the effect of Ni/Si molar ratio,doping promoters and their contents on the structure,properties and the catalytic performance of the catalysts for the hydrogenation of MA.And the structure-activity relationship of the catalyst was established.The main research contents are as follows:1.In view of the low catalytic activity and poor stability of Ni/SiO₂?Ni-IM?catalyst prepared by traditional impregnation method in MA hydrogenation process,the high efficiency and stable nickel phyllosilicate?Ni-PS?was designed and developed.The catalyst was applied to catalyze the hydrogenation of MA to SA under low temperature.Additionally,the catalytic performance of Ni-PS was compared with the Ni/SiO₂?Ni-IM?catalyst.The results show that the activity of Ni-PS catalyst is significantly higher than that of Ni-IM catalyst in hydrogenation of MA to SA under the low temperature of 80 °C as the presence of synergistic bewteen Ni⁰ and.L acid centers.The TOF value of Ni-PS is about three times than that of Ni-IM catalyst.Moreover,it was found that a lower activation energy was present for the hydrogenation of MA over Ni-PS catalyst by the kinetic studies.The value of Ea over Ni-PS was 1/4 of that over Ni-IM catalyst.2.The structure of the catalyst has a significant effect on its catalytic activity.Herein,the Ni/Si molar ratio was regulated to investigate its effect on the catalyst structure,properties and the catalytic performance of the catalyst for the hydrogenation of MA.The results indicated that the Ni/Si molar ratio has an important effect on the catalyst structure and catalytic activity.The active metal Ni⁰ in the catalyst increases linearly,while the L acid sites show the trend of a volcanic curve with increasing the Ni/Si molar ratio.When the Ni/Si molar ratio is 0.48,the catalyst possesses the largest content of L acid and exhibits an excellent low-temperature catalytic performance.The yield of succinic anhydride is up to 95.45% at 80 oC within 3 h.However,the catalyst possesses the maximum content of Ni⁰ and displays the highest catalytic activity for the hydrogenation of MA to GBL 200 oC when the Ni/Si molar ratio is 1.30.The yield of GBL reached 70% within 3h.3.In view of the understandings of above,a second metal Mo,Ce and Zn was intruduced into the nickel phyllosilicate to increase the number of metal Ni⁰ while maintained the L acid site on the catalyst surface.Under the synergistic effect of Ni⁰ and L acid,the catalytic activity of the catalyst was further improved in the hydrogenation of MA to GBL.The results demostrated that the doping of different promoters had a significant effect on the catalyst structure and catalytic performance.Compared with the undoped catalyst,the activity of the catalyst with doping Mo was significantly improved while the addition of Zn and Ce dramatically reduced its catalytic activity.Moreover,it was observed that the catalytic activity of the Mo-Ni-PS catalyst for the hydrogenation of MA to GBL increases firstly and then decreases with increasing the content of Mo.The catalyst with a 3% of Mo displays the highest activity at 160 oC,the yield of GBL was up to 27% within 3 h,which was twice of that wihtout doping.