Preparation And Hydrogenation Performance Of Nickel-Based And Cobalt-Based Non-Noble Metal Hydrogenation Catalysts

With the development of human society,catalysis technology has been used to solve major hot issues such as environment,energy and health.Catalytic hydrogenation is a very important research direction in the field of catalysis.The corresponding amine compounds prepared by hydrogenation of nitro compounds and high value-added chemicals prepared by hydrogenation of biomass platform molecules are important intermediates of polymer products,agricultural chemicals and pharmaceutical chemicals.Catalysts play key role in catalytic technology.A series of noble metal catalysts show excellent catalytic performance in the above hydrogenation reaction,but their large-scale application is limited due to the scarcity of noble metal and high cost.Therefore,it is urgent to develop non-noble metal catalysts to replace noble metal catalysts in catalytic hydrogenation.Although non-noble metal catalysts have been widely studied and made great breakthroughs,there are still many problems and challenges.In this paper,the catalytic performance of Ni-based and Co-based non-noble metal catalysts were improved through modification of active component,modification of support and optimization of the interaction between metal and support.The prepared catalysts showed excellent catalytic performance in the hydrogenation of nitro compounds,guaiacol and furfural.A series of highly dispersed Ni-based bimetallic catalysts supported on activated carbon Ni-M/AC（M=Cu,Co,Fe or Zn）were prepared by impregnation and used for hydrogenation of 1-nitronaphthalene to produce 1-naphthalamine.The characterization results showed that the metal additives could inhibit the agglomeration of Ni nanoparticles and reduce the average size of Ni nanoparticles,thus exposing more catalytic active sites.In addition,the metal additives could promote the reduction of Ni O and increase the content of metal Ni on the catalyst surface.Among them,Zn promoter showed the best promoting effect.At the same time,the calcination and reduction temperature had a great influence on the structural properties of the catalysts,and the best reduction temperature was 350 ^oC.Therefore,Ni-Zn/AC-350 catalyst showed the best catalytic performance.Under the optimal reaction conditions,the yield of 1-naphthylamine reached 96.8%when DMF was used as the reaction solvent.And Ni-Zn/AC-350 catalyst presented good universality for the aromatic nitro compounds hydrogenation.Ti O₂-modified activated carbon supported Ni-based catalysts were prepared by impregnation and used for selective hydrogenation of m-chloronitrobenzene to m-chloraniline.Characterization results showed that a large number of oxygen-containing functional groups were generated on the surface of activated carbon during acid treatment,which was beneficial to Ti O₂dispersion.Ti O₂modification could increase the interaction between Ni nanoparticles and the support,so the agglomeration of Ni nanoparticles was inhibited to produce smaller Ni nanoparticles.In addition,there was a strong electron interaction between Ni and Ti O₂,and the electrons were transferred from the Ti³⁺to the metal Ni to form electron-rich Ni.Such electron-rich Ni could induce electron-rich hydrogen generation,which was conducive to a nucleophilic attack on-NO₂rather than an electrophilic attack on the C-Cl bond.In addition,the calcination temperature had a great effect on the crystal properties of Ti O₂.In this reaction system,the optimal calcination temperature for the support was 550 ^oC.Therefore,Ni/10%Ti O₂@OAC-550 catalyst showed the best catalytic performance.Under the optimal reaction conditions,99.0%m-chloraniline yield was obtained in ethanol solvent over Ni/10%Ti O₂@OAC-550.MCM-41 with high specific surface area was prepared by using sepiolite as silicon source.The prepared MCM-41 was modified by Sn/La and amino functional groups.A series of highly dispersed Ni-based catalysts were prepared by impregnation method using the modified MCM-41 as a support and used for selective hydrogenation of m-chloronitrobenzene to produce m-chloraniline.The characterization results showed that amino modification could prevent the agglomeration of Ni nanoparticles and reduce the average size of Ni nanoparticles,while Sn/La modification not only affected the morphology of Ni nanoparticles but also regulated the electronic structure of Ni nanoparticles.There was a strong electron interaction between Ni and Sn/La,and electrons transfered from Sn/La to Ni surface to form electron-rich Ni,which was conducive to the increase of catalytic activity.The DFT calculation results showed that the electron transfer from Sn/La species to Ni led to a downshift in d-band center of Ni,which was in favor of H desorption and hence promoted hydrogenation activity.In addition,chloronitrobenzene preferred the tilted adsorption orientation mode on the surface of Ni-Sn and Ni-La₂O₃to flat adsorption orientation.Moreover the C-Cl bond scission on Ni-Sn and Ni-La₂O₃were thermodynamically unfavorable in comparison with pure-phased Ni.Therefore,Ni/La MCM-41-NH₂catalyst showed excellent catalytic performance.Under the optimal reaction conditions,99.6%m-chloraniline yield was obtained in ethanol solvent over Ni/La MCM-41-NH₂.And the catalyst showed wide universality for hydrogenation of aromatic nitro compounds.A series of highly dispersed Ni-Fe alloy nanoparticles supported catalysts were prepared by calcination and reduction of hydrotalcite precursors.And the catalysts were used for the hydrodeoxygenation of guaiacol to produce cyclohexanol.The characterization results showed that there was a strong synergistic effect between Ni and Fe.The introduction of Fe species inhibited the sintering of Ni nanoparticles and promoted the reduction of Ni O.The electron interaction between Ni and Fe resulted in electron transfer from Fe to Ni to form electron-rich Ni,which facilitated the desorption of active H species on the surface of catalyst and promoted the hydrogenation activity of catalyst.In addition,the introduction of Mg species could increase the abasic sites on the catalyst surface,which was benificial to selective demethoxylation.The kinetic study indicated that the formation of Ni-Fe alloy could reduce the activation energy of aromatic ring hydrogenation,and the introduction of Mg species could decrease the activation energy of demethoxylation.Therefore,the Ni-Fe/Mg Al O_x-1 gave the highest cyclohexanol yield of 92.1%under the optimal reaction conditions.N-doped carbon encapsulated Co-Ni bimetallic catalysts were prepared by one-step pyrolysis of metal-organic framework materials and applied in the hydrogenation of furfural to furfuryl alcohol or cyclopentanone.The characterization results showed that there was a strong synergistic effect between Co and Ni,and the N doping significantly affected the structural properties of the catalysts,thus improving the catalytic performance.In addition,Lewis acid sites provided by metal oxides in catalysts not only promoted the formation of furfuryl alcohol by polarize the C=O bond via lone pair electrons on the oxygen atom,but also played an important role in the hydrogenation rearrangement of furfural to cyclopentanone.In addition,the solvent played an important role in the product distribution.Under the optimal reaction conditions,99.0%furfuryl alcohol yield was obtained in methanol solvent,while 92.5%cyclopentanone yield was obtained in water solvent over2Co-1Ni@NC-800.N-doped carbon encapsulated Co based catalysts with different N content were prepared by one-step pyrolysis of metal-organic framework materials and used for selective hydrogenation of furfural to furfuryl alcohol.The characterization results showed that the content of N in the catalysts could be effectively regulated by changing the amount of N ligand,and the work function of the catalysts could be increased by N-doping.At a high work function,the electron interaction between metal Co and N species could be enhanced,which would improve the catalytic activity of the catalyst.In addition,pyrolysis temperature was an important factor for the formation of encapsulated structure.When the pyrolysis temperature was 800 ^oC,the catalyst could form the structure of nitrogen-carbon encapsulated metal particles.And the formation of encapsulated structure could enhance the interaction between metal and support.As metal Co transfered electrons to pyridine N to form electron-rich nitrogen-carbon coating,the in-situ FT-IR adsorption characterization showed that electron-rich nitrogen-carbon coating could inhibit the adsorption of furan ring in furfural molecule and prevent the deep hydrogenation of furfural to tetrahydrofurfuryl alcohol.Under the optimal reaction conditions,99.3%furfuryl alcohol yield was obtained in water solvent over Co@NC-5-800.Trace Zn-doped nitrogen-carbon supported Co-based catalysts were prepared by one-step pyrolysis of metal-organic framework materials and used for selective hydrogenation of furfural to 2-methyltetrahydrofuran.The characterization results showed that Zn doping could promote the electron interaction between metal Co and the support,and enhance the hydrogen overflow phenomenon on the catalyst surface.DFT results showed that Zn doping promoted the activation of H₂,promoted the adsorption of furfural and 2-methylfuran on the catalyst,and reduced the energy barrier in breaking C-OH bond of furfuryl alcohol.In addition,in-situ FT-IR adsorption results showed that Zn doping could optimize the adsorption configuration of the substrate during the hydrogenation of furfural to 2-methyltetrahydrofuran.These could facilitate the hydrogenation of furfural to 2-methyltetrahydrofuran.Under the optimal reaction conditions,the yield of 2-methyltetrahydrofuran reached 93.8%in isopropanol solvent over Zn-Co/NC-1.