Preparation And Applicatio Of Nano-morphology Palladium/nano-array/foam Nickel Catalyst

The monolithic catalyst has the advantages of high catalytic efficiency and easy separation,enhanced mass and heat transfer peroformance,low bed pressure drop,resulting in an easy scale-up and decrease of operating cost.The current monolithic eatalyst also has the problems,such as high precious metal loading and uneven loading of the active component on the coating,which severely limits the development and application of the monolith catalyst.Therefore,developing new preparation technology of monolithic catalyst is of great significance.This work proposes a series of palladium-based monolithic catalysts with nano-morphology by introducing a Co3O4 nano-array on a Ni foam substrate by using the simplest impregnation-pyrolysis method.Effects of different concentrations of palladium chloride on the morphology of the catalyst were investigated by SEM,TEM,XPS,and ICP.The growth mechanism of,Pd/Co3O4/Ni foam was alos studied.The catalytic activity of the above catalyst was investigated by hydrogenation of α-methylstyrene(AMS)as a probe reaction.The main contents are as follows:(1)After introducing the Co3O4 nano-array into the substrate,the catalyst was preparated by using palladium chloride as the precursor of the active component.It is found that when the palladium chloride concentration was less than 15 mmol/L,PdC12 was not enough to form a regular microscopic structure and only highly dispersed Pd nanoparticles were formed.When the concentration was greater than 15 mmol/L,more and more flower-like PdC12 solutes were formed,leading to the formation of porous flower-like Pd nanocrystals having a skeleton width of 18 nm.(2)Based on the systematic analysis,it is found that the nano-structure of Co3O4 has three functions in the preparation of Pd/Co3O4/Ni foam:first,Co3O4 can cover the surface of the substrate to inhibit the replacement reaction between Pdluand Ni matrix;secondly,Co3O4 can increase the specific surface area of substrate to increase the adsorption amount of PdC12 adsorbed,thereby increasing the loading of Pd;third,C03O4 can control the crystallization process of PdC12 precursor after immersion drying,and obtain the flower-like morphology.Thus,a porous flower-like Pd catalyst was obtained after the calcination,which contributed to the high dispersion of the active component Pd.(3)In the stirred reactor,the prepared Pd0.51/Co3O4/Ni foam has better catalytic hydrogenation performance than Pd5.99/Ni foam and Ni foam and Co3O4/Ni foam which are not modified with nano array.For example,the catalytic reaction rate of AMS conversion by Pd0.51/Co3O4/Ni foam was 9.44 mmol·gPd-1·s-1 at 40℃ and hydrogen pressure 0.5 MPa.The reaction rate of pd5.99/Ni foam catalyst was only 0.324 mmol·gPd-1·s-1.The resutls strongly prove that the nano-microstructure modified monolithic catalyst can not only reduce the amount of precious metals,but also effectively increase the reaction rate of AMS hydrogenation.In addition,at 60℃ and hydrogen pressure of 0.5 MPa,the reaction rate of AMS hydrogenation by Pd0.51/Co3O4/N1 foam monolith catalyst can be further enhanced in the rotating packed bed(RPB)reactor,up to 19.8 mmol·gP0d-1·s-1.The prepared catalyst is suitable not only for a stirred tank reactor,but also for a RPB reactor.The preparation strategy of this nano-array modification by conventional impregnation calcination can provide reference for the design and preparation of monolith catalysts.