Preparation Of Nickel-based Nanocatalysts And Their Hydrogenation Performance For Carbonyl Compounds

In recent years,due to the increasingly serious environmental problems,green chemistry has become the research focus at home and abroad.Catalytic hydrogenation is the most effective way to replace traditional chemical reduction because it has atomic economy and meets the requirements of green chemistry and chemical industry.Hydrogenation of carbonyl compounds is an important process in the synthesis of drugs and fine chemicals.In this transformation,the catalytic performance of precious metal catalysts is excellent,but their high cost has limited their further applications.Therefore,a series of nickel-based nanocatalysts was prepared and tested in the hydrogenation of carbonyl compounds.Firstly,a series of NiB-x?x denotes as the molar ratio of hydrogelator:Ni?amorphous alloy was prepared using a hydrogelator,2,4-?3,4-dichlorobenzylidene?-D-sorbitol?DCBS?,and tested in the selective hydrogenation of benzophenone to benzhydrol.The Brunauer-Emmett-Teller?BET?,Transmission electron microscopy?TEM?and temperature-programmed desorption of hydrogen?H₂-TPD?results demonstrate that DCBS can self-assemble in water to form a three-dimensional network structure,which can inhibit the agglomeration of NiB particles and make them more dispersed.It results in larger surface area and more active Ni sites,which make it show excellent catalytic performance in carbonyl hydrogenation.Secondly,a novel nickel-based nanocatalyst was prepared by ammonia evaporation method?AE?using three-dimensional flower hydrotalcite as support.Its performance in the hydrogenation of benzophenone was then studied.Under the optimal reaction conditions,the conversion of benzophenone can reach above 98.0%and the selectivity of diphenylmethanol is 96.9%.Notably,the catalyst can be used stably for 9 runs without significant change in activity.TEM,H₂-chemisorption and H₂-TPD results demonstrate that the ammonia evaporation method can not only decrease the Ni particle size and improve the dispersion of Ni,but also effectively control the formation of the spinel structure of Mg-Ni-O.Finally,a nickel-aluminum composite metal oxide catalyst was in situ prepared by using nickel-based hydrotalcite as precursor and applied in the hydrogenation of levulinic acid.Under the optimal reaction conditions,the conversion of levulinic acid is 100.0%and the selectivity for?-valerolactone can reach 90.48%.The catalyst can be recycled for 6 times without significant loss of its activity.BET,TEM,H₂-chemisorption and H₂-TPD results demonstrate that the Ni nanoparticles prepared by the in situ method have small particle size,uniform distribution and relatively strong interaction between Ni and the support,which make the catalysts have high activity and stability.