Hydrogenation Of Benzoic Acid And Cinnamic Acid Over Nickel-based Nanocatalysts

The catalytic hydrogenation of unsaturated substrates for the manufacture of saturated or partially saturated products has attracted much attention in recent years.Pd-,Pt-,Ru-and Rh-based catalysts,have achieved good activity and stability.Although some of them have been applied,the high prices of noble metals have limited their further applications,making it desirable to design and prepare non-noble metal catalysts with high activity and stability.Thus,non-noble metal Ni with high activity and lower price was selected as the active species in this work.A series of nickel-based nanocatalysts was prepared and then evaluated their catalytic performance in the hydrogenation of benzoic acid and cinnamic acid.Firstly,the tannic acid modified amorphous NiB catalyst NiB-TA was prepared by a chemical reduction method.The hydrogenation of aromatic ring was studied using the selective hydrogenation of benzoic acid to cyclohexanic acid as model reaction.The obtained catalyst exhibited good activity in the selective hydrogenation of benzoic acid to cyclohexanic acid with the conversion and selectivity being 98.8% and 94.1% respectively.The results showed that the addition of tannic acid could improve the formation and dispersion of the acitve species,compared with the nickel boron amorphous alloy catalyst prepared by a traditional method.Thus,the activity of NiB-TA has significantly enhanced,compared with NiB.Then,in order to improve the stability of nickel-based catalysts,we prepared a series of supported nanocatalysts by optimizing the type of the supports and the preparation methods.The result showed that the catalyst Ni/mSiO2-AE,which was prepared by an ammonia-evaporation method,exhibited good stability in the selective hydrogenation of benzoic acid to cyclohexanic acid.It can be recycled four times without appreciable loss of its initial catalytic activity and selectivity.The reasons for the good performance of this catalyst were explained based on the results of XRD,TEM,H₂-TPR.Finally,the hydrogenation of C=C was studied using the selective hydrogenation of cinnamic acid to hydrocinnamic acid as model reaction.Considering the activity,stability and separation efficiency of the catalyst,we herein designed and prepared a novel NiB deposited LDH coated ferroferric oxide?Fe₃O₄@LDH@NiB?magnetic core-shell nanocomposite.It exhibited good activity in the selective hydrogenation of cinnamic acid to hydrocinnamic acid with the conversion and selectivity both approach to 100%.Notably,the obtained Fe3O4@LDH@NiB can be easily separated by an external magnetic field and recycled eleven times without appreciable loss of its initial catalytic activity,demonstrating good stability.