Preparation Of Nickel-based Catalysts And Their Performance In Phenyl Hydrogenation

Cyclohexane derivatives have wide applications in many fields,such as pharmaceutical intermediates,liquid crystal monomers,and plastic additives.Hydrogenation of the phenyl in benzene derivatives is the most important method for synthesizing cyclohexane derivatives,and a high-performance catalyst is the key factor for the efficient hydrogenation.Although precious metal catalysts showed excellent performance in this transformation,their limited reserves and high price restrict their applications.In contrast,nickel-based catalysts have attracted increasing attention due to their low cost and relatively high hydrogenation activity.However,nickel-based catalysts still suffer from the problems such as easy aggregation and relatively poor stability.To address these issues,in this study,a series of efficient and stable nickel-based catalysts were designed,prepared,and applied in the synthesis of cyclohexane derivatives by catalytic hydrogenation of phenyl in benzene derivatives.First,to solve the problem of low nickel species utilization in traditional hydrotalcite-derived nickel-based catalysts,a supported nickel-based catalyst was prepared by in-situ generation of Ti O₂ support during the hydrothermal synthesis of Ni Ti-LDH.The effect of the in-situ generated Ti O₂ support on the catalytic performance of catalysts was mainly investigated.This catalyst showed good catalytic activity and stability in the hydrogenation of dioctyl phthalate.Characterization results showed that the in-situ generated Ti O₂ support resulted in uniform dispersion of Ni particles,which could improve the utilization of nickel species.During the reduction of Ni Ti O_x/Ti O₂,strong metal-support interactions（SMSI）were formed between the Ti O₂ support and the metallic Ni particles.The SMSI suppressed the aggregation and loss of Ni particles in the Ni Ti O_x/Ti O₂-R,resulting in its good catalytic activity and stability.Second,in order to improve the efficiency of dioctyl phthalate hydrogenation,a series of nickel-based catalysts derived from Ni Ti Al-MMO was prepared by different methods,and their performances in dioctyl phthalate hydrogenation were investigated.It was found that the catalyst prepared by the hydrothermal method exhibited excellent activity and can be recycled9 times,which was significantly superior to the catalyst prepared by the coprecipitation method.The characterization results showed that the electron transfer from Ni to Ti between Ti₂O₃ and Ni⁰ in the Ni Ti Al-MMO-Ht-R catalyst can strengthen the interaction between Ni and the Ti Al-MMO support,which enabled its higher catalytic performance.Third,to further enhance the performance of the nickel-based catalyst and reduce the reaction conditions of dioctyl phthalate hydrogenation,an embedded nickel-based catalyst derived from Ni-USY was prepared using a"introduction first and reduction later"strategy.The impact rules of the embedded structure on the performance of the catalysts in the hydrogenation of dioctyl phthalate were investigated.The catalyst exhibited excellent activity and stability.Specifically,the catalyst can be stably recycled for 12 times with a yield of 98%for dioctyl hexahydro-phthalate.Characterization results showed that a special structure of Ni particles embedded in filamentous USY pyrolysis products has been formed in Ni-USY-R,which stabilizes and protects the Ni particles,thereby accounting for its excellent catalytic performance.Then,in order to prepare nickel-based catalysts with excellent catalytic performance,we loaded nickel species on silica by a hierarchical porous Ni-MOFs derivative method to prepare a supported nickel-based catalyst.The effect of calcination conditions on the structure and performance of the prepared nickel-based catalyst was emphatically investigated.This nickel-based catalyst showed excellent catalytic performance in the hydrogenation of phthalate esters.The characterization results showed that the nickel species were uniformly distributed in the Ni-MOFs structure,and certain interactions existed between Ni-MOFs and m Si O₂.Therefore,the Ni particles in the Ni-MOFs-m Si O₂（250）-R catalyst can maintain uniform dispersion and small particle size after high-temperature reduction,accounting for its excellent catalytic activity.Furthermore,the possible reason for the high stability of the catalyst was discussed.During the reduction of Ni-MOFs-m Si O₂（250）,Ni-MOFs were transformed into Ni particles with a surface wrapped by carbon material.Under the protection of the carbon material and its anchoring effect with m Si O₂ support,the loss and aggregation of Ni particles were prevented,so that the Ni-MOFs-m Si O₂（250）-R catalyst exhibited excellent stability.Finally,the application areas of the nickel-based catalysts were expanded to phenol hydrogenation.A series of nickel-based catalysts was prepared by an ammonia evaporation method using nanodiamond（ND）as support.The influence of support surface modification methods on the performance of the nickel-based catalysts was emphasisly studied.It was found that the Ni/OND-R with H₂O₂-treated ND as support showed higher activity and stability in the hydrogenation of phenol,compared with Ni/ND-R and Ni/NND-R,which used untreated ND and ND treated with high-temperature nitrogen atmosphere as supports,respectively.Characterization results showed that the H₂O₂ pretreatment changed the oxygen species on the surface of ND,thus enhancing the interaction between the support and Ni species,allowing the active metal Ni to anchor on OND with a smaller particle size,thereby improving its catalytic activity and stability.In conclusion,this study designed and prepared a series of nickel-based catalysts and investigated their catalytic performance in the hydrogenation of aromatic ring in benzene derivatives.By regulating the catalyst structure,preparation method,and electronic effects,the activity of the catalysts was significantly improved,allowing the reaction to proceed under relatively mild conditions.Simultaneously,the interaction between the active Ni sepcies and supports in the catalysts was enhanced,which markedly improved the stability of catalysts.This study provides feasible schemes for the green synthesis of cyclohexane derivatives and offers reliable references for the preparation of high-performance non-precious metal catalysts.