Performance Of Nickel-based Nanocatalysts For Hydrogenation Of Carbonyl Compounds

Catalytic hydrogenation was an important type of elementary reaction in the chemical industry.The products of carbonyl compounds hydrogenation are widely used in the preparation of fine chemicals,pharmaceutical intermediates and fragrances.Thus,Ni was selected as the active species for hydrogention due to its high catalytic activity and low price in this work.A series of supported Ni-based nanocatalysts was prepared by organic anion intercalation of hydrotalcite,modification of SBA-15 and bio-template assistance ofγ-Al₂O₃and evaluated in the catalytic hydrogenation of carbonyl compounds.Firstly,the organic ligand 2,4-dihydroxypyrimidine-5-carboxylic acid was complexed with Ni²⁺and inserted into the LDHs laminate by the calcination-reconstruction method.Ni-based nanocatalysts derived from hydrotalcite were calcined and reduced,and their catalytic performance in benzophenone hydrogenation was tested.Compared with the catalyst prepared by an impregnation method,this catalyst shows excellent catalytic performance.The conversion of benzophenone is up to 99.0%,the selectivity for benzyl alcohol is above 96.5%,and the catalyst can be stably recycled for 6 times.X-ray diffraction（XRD）and Fourier transform infrared spectroscopy（FT-IR）proved the insertion of anionic complexes in the laminate.Transmission electron microscopy（TEM）,temperature programmed reduction of hydrogen（H₂-TPR）and X-ray photoelectron spectroscopy（XPS）showed that the introduction of the ligand improved the dispersion of the active Ni in the catalyst and enhanced the activity.The interaction between Ni and the support enabled the catalyst to exhibit better catalytic activity and stability.Secondly,the Ni-based nanocatalyst Ni-Al₂O₃/SBA-15-X was prepared by an ammonia evaporation method using Al₂O₃ modified SBA-15 as the support,and the effect of the Al₂O₃amount on the catalyst performance was studied.The results showed that the Ni-Al₂O₃/SBA-15-30%catalyst showed excellent catalytic performance in the hydrogenation of methyl levulinate while the amount of Al₂O₃ was 30%.The conversion of methyl levulinate and the selectivity forγ-valerolactone were 97.4%and 90.0%,respectively.Furthermore,it can be recycled 6 times without significant loss of the initial activity.With the help of temperature-programmed desorption of ammonia（NH₃-TPD）and H₂-TPR,it was proven that the addition of Al₂O₃ can not only increase the acidity of the catalyst and increase the yield of theγ-valerolactone product,but also enhance the stability of the catalyst.Finally,a Ni-based nanocatalyst Ni/γ-Al₂O₃-G was prepared using glucose assisted synthesizedγ-Al₂O₃-G as support and evaluated in the hydrogenation of furfural.The conversion of furfural reached 99.6%and the selectivity for furfuryl alcohol was 97.1%under mild reaction conditions.Furthermore,there was no significant loss of initial activity after 4cycles of use.XRD and TEM proved that the Ni/γ-Al₂O₃-G catalyst prepared with the addition of glucose significantly increased its specific surface area,decreased the particle size of the active Ni of the catalyst and increased its dispersion.These characteristics provided more interaction sites for Ni with the support,resulting in the generatation of stronger metal-support interaction,and accounting for the excellent activity and good stability of this catalyst.