Catalytic Transfer Hydrogenation Of Biomass-derived Oxygen-containing Compounds Over CePO₄-Ni₃P Catalysts

With the rapid development of modern society,the demand of fuel and energy is constantly increasing.Replacement of fossil energy with an environmentally friendly and renewable energy has become increasingly important.Biomass,the only renewable carbon source,has become the focus of great attention.The products of biomass hydrogenation and their derivatives are highly valuable platform molecules,which have found a wide range of applications in the sector of energy and fine chemicals.The traditional direct hydrogenation（DH）is usually conducted at elevated H2 pressures and high temperatures,which presents several problems,such as H₂ storage,safety and transportation.In recent years,catalytic transfer hydrogenation（CTH）has become a research hotspot that replaces traditional direct hydrogenation process in some cases.The difference between CTH and DH is that a liquid hydrogen donor is used in CTH reaction without the use of gaseous hydrogen,and the reaction conditions are much milder.In the present study,a series of CePO₄（x）-Ni₃P catalyst（x represents Ce/Ni molar ratio）was prepared by H₂-TPR method and characterized by means of XRD,XPS,TEM,NH₃-TPD,and TG-DSC.The catalytic transfer hydrogenation of phenol,levulinic acid and furfural were carried out using alcohols as the hydrogen donors.The influences of Ce/Ni molar ratio,structure of the hydrogen donor,solvent composition and reaction temperature on the catalytic performance were investigated.The results show that,in the CTH reactions of these three reactants,the catalytic performance of CePO₄（x）-Ni₃P was always superior to Ni₃P,which might be attributed to the improved dispersion of Ni₃P particles and the enhancement of acidity/basicity.The optimal catalyst for phenol CTH was CePO₄（0.2）-Ni₃P,while that for levulinic acid and furfural CTH was CePO₄（0.1）-Ni₃P.Among the hydrogen donors tested,isopropanol showed the highest activity,and secondary alcohols had better catalytic performance than primary alcohols.In the CTH reaction of furfural,adding water into the solution would produce cyclopentanol and cyclopentanone in the reaction.The activity of the CTH reaction strongly depended on the reaction temperature,and,on increasing the reaction temperature,the hydrogen donor dehydrogenates more quickly to provide a significant amount of active hydrogen atoms so as to accelerate the CTH reaction.Under the investigated experimental conditions,the transfer hydrogenation rection of phenol over CePO₄（0.2）-Ni₃P catalyst could be seen as a zero-order reaction and the calculated activation energy was about27.9 kJ/mol;the transfer hydrogenation rection of levulinic acid over CePO₄（0.1）-Ni₃P catalyst could be seen as a first-order reaction and the calculated activation energy was about 74.2kJ/mol.