Preparation Of Two-dimensional Layered Metal Hydroxide Nickel-based Catalyst And Its Application In Hydrogenation Reaction

As a kind of important for hydrogenation or reduction catalyst,the nickel-based catalysts are difficult to obtain clean and highly dispersed samples by conventional methods due to its active metal properties.To solve the problem,this paper proposes and implements a new way to construct an ordered two-dimensional metal nanosheets directly as a catalyst or as a precursor to obtain a small-scale nickel catalyst without surfactant protection.By growing nickel-based nanosheets on Al₂O₃,nickel catalyst with 2.8 nm and clean surface can be obtained after thermal reduction treatment.For the hydrogenation of benzoic acid,the yield of cyclohexane carboxylic acid is as high as 98%,compared with the supported nickel-based catalyst of 5.0-8.0 nm prepared by the conventional impregnation method or deposition precipitation method（yield:28-40%）,its intrinsic activity（turnover frequency:TOF）increased by 15-40 times,and the strong metal-support interaction shows good catalytic stability.The kinetic measurement further indicates that the highly dispersed nickel catalyst derived from the two-dimensional nanosheets can significantly reduce the activation energy of the reaction.It is thus revealed that the reaction may be a structural sensitivity reaction on nickel-based catalysts.In addition,this paper also attempts to construct a two-dimensional layered double hydroxide（LDH）for the selective hydrogenation of citral.The sample can be transformed in situ into an Ag-[Ni（OH）₂]_x/LDH composite structure without pre-reduction treatment.Based on the interaction of the metal with this two-dimensional layered structure and the hydrogen spillover effect promoted by moderately acidic sites,that is,Ag produces highly mobile atomic hydrogen,which is migrated to the surface supporter to reduce nickel.It can significantly increase the selectivity of the catalyst for the hydrogenation of unsaturated aldehydes.These results indicate that the above-mentioned two-dimensional nanomaterials and application methods may be an effective way to obtain high-performance active transition metal catalysts,which deserves attention and development.