Preparation And Catalytic Performance Of Carbon-coated Nickel-based Catalyst For The Liquid Phase Hydrogenation Of Maleic Anhydride

Maleic anhydride(MA)was the third-largest anhydride material.The hydrogenation of maleic anhydride(MA)can produce succinic anhydride(SA),?-butyrolactone(GBL),tetrahydrofuran(THF)and 1,4-butanediol(BDO).All these products are widely applied in the manufacturing of food additives,phmaceuticals,chemical industrial as a organic intermediate.The key of selective hydrogenation of maleic anhydride is the preparation of a highly active catalyst.Polyamide-amine(PAMAM)dendrimers have a large content of carbon and nitrogen components.Dendrimers have became a hot research topic in the related fileds because of its intrinsic properties,such as unique nanoscale cavity,suitable coordination,easily coated with metal ions,and favourable templation.Recently,carbon materials have been synthesized by hydrothermal method from glucose and they play a very important role in the industrial-production of heterogeneous catalysis due to the characteristics of unique controllable structure and easily doping.Thus,the synthesis of enviromental carbon based hydrogenation catalyst is a concerned problem.In this paper,we synthesized three types of nickel-based catalyst by using PAMAM as a template and carbon material as carrier.The resultant catalysts structure were characterized by XRD,TEM,FT-IR,Raman and H2-TPD.The influence of PAMAM polymerization degree and carbon support on the structure and hydrogenation activity were investigated.The main results and conclusions are as follows:1?A series of GX PAMAM-Ni(X=0.5,1.5,2.5,3.5)catalysts were prepared by chemical reduction method with PAMAM templates in aqueous solution.These particles were stabilized by carboxyl-terminated PAMAM and the hydrogenation performance of the catalysts were investigated.The results showed that GX PAMAM-Ni catalysts had the characteristics of amorphous alloys;With the increase of the degree of polymerization PAMAM,Ni particle size of GX PAMAM-Ni samples decreased,dispersion of Ni nanoparticles and the specific surface area increased gradually,the selectivity of?-butyrolactone also increased.Selectivity of y-butyrolactone can reached 99.8%when we used G3.5 PAMAM-Ni as catalyst.2?A series of CN-X Ni supported catalysts were prepared by using sodium borohydride as reduction agent which carbon support was prepared via hydrothermal method.the hydrogenation performance of the catalysts was investigated.The characterization and evaluation results showed that the carbon materials possessed amorphous and graphite structure;the main active was zero-valent Nickel after calcination.As the increased of the Ni content,Ni particle size of CN-X Ni samples were increased,and reaction conversion can reached 100%.Obviously,catalyst with suitable content of nickel was easy to the generation of succinic anhydride and high content catalyst was easy to the generation of y-butyrolactone.3?Using sodium borohydride reduction method as reduction agent and PAMAM as templates,a series of C-X Ni nickel-based catalysts were prepared by using carbon materials as carrier that was prepared via hydrothermal method.The characterization and evaluation results showed that carbon materials existed on the amorphous and graphite structure and the surface of the catalysts contained rich functional groups.Used PAMAM as templates,the nickel particles showed more highly dispersion compared with CN-X Ni nickel-based catalysts;When the load of nickel is less than 15%,the catalyst mainly exsits NiO,otherwise it exists with the form of NiO and Ni0.With the increase of the Ni content,the amount of active ingredient of C-X Ni samples increased.But hydrogen desorption amount of C-X Ni catalysts is less than the CN-X Ni catalysts with the same nickel content.In summary,catalyst with low content of nickel was easy to the generation of succinic anhydride and high content catalyst was easy to the generation of y-butyrolactone.