Manipulation Of Co_yNi_2-yP Phosphide Alloy Catalysts With Y For Low-pressure Pydrogenation Transformation Of Biomass Platform Compounds In Water

The conversion of biomass platform compounds into biofuels and other chemicals is one of the key technologies to replace fossil raw materials for green carbon cycle and sustainable chemical production.In this dissertation,a series of Y-Co-Ni-P composite catalysts were developed by introducing Y into the process of modulation synthesis of Co-Ni binary metal phosphide alloy catalysts around the application of biomass platform compounds such as levulinic acid and furfural in aqueous phase hydrogenation conversion.The dependence law between the catalyst composition,structure and catalytic properties of the catalytic system was explored.The research contents are as follows:（1）A series of Co-Ni-P catalysts with different Co-Ni compositions were prepared by hydrothermal synthesis using metal nitrate as precursor and ammonium phosphate as P source.The structure of the obtained catalyst was characterized by ICP-OES/XRD/XPS/TEM as a Co_yNi_2-yP binary metal phosphide alloy.On this basis,Y was introduced to obtain a（YPO₄）_x/Co_yNi_2-yP composite catalyst with tunable molar composition（x,y:metal molar composition）,wherein x=0.1,0.2 or 0.3;y=0.5,1.0or 1.5.（2）The prepared Co_yNi_2-yP and（YPO₄）_x/Co_yNi_2-yP catalysts were used in the hydroconversion reaction of levulinic acid（LA）or furfural（FAL）in water,and it was found that the increase of Co composition in the binary metal phosphide alloy catalysts was beneficial to improve the catalytic activity,but the metal precipitation in water also increased leading to the decrease of catalyst stability.The optimized composition was Co_1.0Ni_1.0P;the introduction of Y to form the（YPO₄）_x/Co_yNi_2-yP structure was much more active than the Co_yNi_2-yP catalyst in low pressure hydrogenation;The optimized composition of（YPO₄）_0.2/Co_1.0Ni_1.0P was used for the stable and efficient conversion of levulinic acid toγ-valerolactone with a yield of 98.1%and selectivity close to 100%at 0.5 MPa hydrogen pressure,120°C for 2 h.Theγ-valerolactone yield was still 95.4%after 8 h of reaction by reducing the hydrogen pressure to 0.1 MPa.Under the conditions of 0.5 MPa hydrogen pressure,150°C and 6 h,the yield of cyclopentanone synthesized from furfural aqueous phase hydrogenation could reach 92.7%,and the yield of cyclopentanone could still reach 61.2%after 8 h by reducing the hydrogen pressure to 0.1 MPa.（3）H₂-TPD,NH₃-TPD and kinetic analyses showed that YPO₄ made a major contribution to the activation of H₂ over a catalyst with a controlled Co-Ni relative composition of 1:1 basis,which also provided additional Lewis acid sites.Kinetic tests showed that both reactants followed first-order kinetics,for hydroconversion over（YPO₄）_0.2/Co_1.0Ni_1.0P catalyst,with activation energies（Ea）of 42.3 k J/mol for levulinic acid and 75.9 k J/mol for furfural,with significantly lower activation energies relative to Co_1.0Ni_1.0P.These results suggest that the construction of Co_yNi_2-yP metal phosphide alloys in combination with Y modulation in the aqueous phase hydroconversion of biomass platform compounds is an effective way to obtain practical catalytic systems with low cost,stable and durable structures,excellent performance and mild operating conditions,which may provide a reference for the design of practical and efficient multiphase catalysts for biomass applications.