Preparation Of Hydrotalcite Nickel-Based Nanocatalysts For Phenol Hydrogenation

Ni-based nanocatalysts are widely applied in the catalytic hydrogenation of unsaturated compounds due to their high activity and low cost.However,the trend to agglomeration and sintering of nickel nanoparticles under severe reaction conditions resulted in a rapid deactivation of nickel-based nanocatalysts and affected their industrial applications.Therefore,preparation of highly active and stable nickel-based catalysts is a key issue in the current research on nickel-based nanocatalysts.On the other hand,hydrotalcite is considered to be a promising support due to its tunability between the main layer and the guest anion,as well as the confinement effect.Thus,a series of hydrotalcite Ni-based nanocatalysts was prepared and applied in phenol catalytic hydrogenation.Firstly,the hydrotalcite precursor NiAl-LDH was prepared by the urea coprecipitation method using natural pine pollen as a biological template.Then,it is calcined and reduced to prepare a hydrotalcite Ni-based nanocatalyst Ni2Al1 O.This catalyst exhibited excellent catalytic performance in phenol hydrogenation with conversion of phenol can reach 99% and selectivity for cyclohexanol is above 99%.Notably,it can be recycled 10 times with no significant decrease of its initial activity,much better than the catalyst without biological template.Fourier transform infrared,temperature programmed reduction of hydrogen and X-ray photoelectron spectroscopy demonstrated that the introduction of biological templates improves the dispersibility of the active component nickel and enhances the interaction between nickel nanoparticles and support,so that inhibits the agglomeration and loss of the active components during the reaction.Secondly,the precursor NiMgCo-LDH was prepared by the solvothermal method using metal organic framework MOFs(ZIF-67)as template,and a hollow Nickel-based nanocatalyst NiMgCoO-in situ(10)was obtained by calcination and reduction steps.The conversion of phenol is 99%,the selectivity for cyclohexanol is 99%.Furthermore,the catalyst can be recycled 6 times,showing good stability.The specific hollow structure and its relationship with the performance of the catalyst were confirmed by Brunauer-Emmett-Teller and Transmission electron microscopy.Finally,a ternary hydrotalcite nickel-based nanocatalyst NiXAlO was prepared by introducing a third metal(X=Ca,Mg and Zn)into the binary NiAl-LDH.The conversion of phenol is 99% and the selectivity for cyclohexanol is 99% over the prepared NiCaAlO nanocatalyst.Notably,the catalyst can maintain good activity after being recycled for 8 times,which is better than that of the binary nickel-based nanocatalyst,demonstrating its excellent catalytic performance.As proven by Brunauer-Emmett-Teller,Transmission electron microscopy and X-ray photoelectron spectroscopy,the introduction of Ca can significantly increase the specific surface area of the catalyst and improve the dispersibility of the active nickel.