Preparation Of Furfural Hydrorearrangement Pd Catalysts And Study On Peformance Of Reaction

The hydrogenation rearrangement of furfural,a bioderived platform chemical,to produce cyclopentanone and cyclopentanol is a sustainable development strategy.Currently,Furfural hydrogenation rearrangement suffers from the non-selective adsorption of carbonyl groups,resulting in a declined selectivity toward the intermediate furfuryl alcohol;and the weak synergistic effect of the metal sites and acid sites in resultant catalysts,leading to the low activity for furfuryl alcohol hydrogenation rearrangement.The reaction pathway of the furfural hydrogenation as well as the product distribution can be controlled by modifying the structural properties of the support and metal-support interaction between the active components and the support,control of the furfural hydrogenation pathway and product distribution can be realized.In the present work,a series of Pd catalysts with specifical structure were prepared and applied into the furfural hydrogenation rearrangement.Combined with various characterizations,kinetic study and DFT calculations,the structure-performance relationship and intrinsic reaction mechanism were unambiguously elucidated,providing meaningful information for the development of Pd catalysts with the high performance in large-scale production.1.The construction of hierarchical catalysis structure and the study on hydrogenation mechanism of furfuralHerein,hierarchical catalytic structures with the spatial separation of Pd and acid sites were constructed by the multistep deposition strategy,wherein Pd was confined on defective CeO₂ nanoclusters,which were dispersed on high-surface-area SiO₂ with the strong acidity.The intimacy extent of Pd and acid sites in hierarchical catalytic structures of Pd/CeO₂/SiO₂ can be modulated by adjusting the CeO₂ content,which leads to the aqueous-phase hydrogenation of furfural following a unique treble-site mechanism.The perpendicular adsorption of furfural on enriched oxygen vacancies of Pd/CeO₂ contributes to the selective hydrogenation of the carbonyl group,and then the formed furfuryl alcohol undergoes the acid-catalyzed rearrangement of furan rings on SiO₂ through the cooperative effect of acid sites and hydrogen spillover to give cyclopentanone.Meanwhile,the asynchronous catalysis effectively hinders the furan ring hydrogenation to tetrahydrofurfuryl alcohol by spatially separating Pd from the SiO₂ surface.The superior catalytic performance is obtained on Pd/CeO₂/SiO₂-10 with furfural conversion of 93%and cyclopentanone selectivity of 84%.2.The preparation of hierarchical structure Pd/Co₃O₄/SiO₂ by electrostatic adsorption and the study on hydrogenation performance of furfuralPd/Co₃O₄/SiO₂-m-SEA with hierarchical catalytic structures were prepared by electrostatic adsorption.Pd can be selectively dispersed on the surface of Co₃O₄ by utillizing the difference of surface charge properties between Co₃O₄ and SiO₂ to realize spatially separating Pd from the SiO₂ surface.The intimacy extent of Pd and acid sites can be modulated by adjusting the Co₃O₄ content,which leads to the aqueous-phase hydrogenation of furfural following a unique treble-site mechanism.The perpendicular adsorption of furfural on enriched oxygen vacancies of Co₃O₄ contributes to the selective hydrogenation of the carbonyl group,and then the formed furfuryl alcohol undergoes the acid-catalyzed rearrangement of furan rings on SiO₂ through the cooperative effect of acid sites and hydrogen spillover to give cyclopentanone.Meanwhile,the asynchronous catalysis effectively hinders the furan ring hydrogenation to tetrahydrofurfuryl alcohol by spatially separating Pd from the SiO₂ surface.The superior catalytic performance is obtained on Pd/Co₃O₄/SiO₂-40-SEA with furfural conversion of 95%and cyclopentanone selectivity of 88%.3.The study of acid modified Pd/Co₃O₄ metal-support interaction strengthening furfural hydrogenation rearrangementDifferent concentrations of hydrochloric acid were used to treat Co₃O₄,and then Pd/Co₃O₄-H catalyst was prepared by simple Saturated impregnation method.It was found that acid treatment resulted in partial loss of Co₃O₄.but significantly increased the specific surface area of Co₃O₄,thus promoting Pd dispersion.The strong metalsupport interaction in Pd/Co₃O₄-H promotes the reduction of Co₃O₄ to metallic Co.Meanwhile,the d-band center away from the Fermi level derived from the increased electron density of metallic cobalt on the surface due to the electron transfer from Pd to neighboring Co atoms.Pd/Co₃O₄-6 with furfural conversion of 99%and cyclopentanone selectivity of 85%.The superior catalytic activity was attributed to the high dispersion of Pd and enhanced Pd-Co interaction which enhanced the catalytic hydrogenation activity of Co.On the other hand,with the increase of H coverage on Co surface,parallel adsorption configuration convert to perpendicular adsorption configuration of furfural,which is conducive to carbonyl hydrogenation to furfuryl alcohol intermediate.