Surface Morphology Control Of Hydrogen-Based Catalysts Based On Layer Double Hydroxide And Its Regulation On Selective Hydrogenation Of Furfural

Under the circumstances of exhaustion of fossil resources and environmental pollution,renewable resources become highly desirable to meet requirements of energy consumption and chemical production,among which biomass energy and biomass platform molecules have received considerable attention in recent years.Furfural is one of the most important biomass-derived chemical owing to its various highly-valued derivatives.For instance,furfural alcohol(FOL),half-hydrogenation product of furfural,has been widely used in manufacture of resin,lysine,vitamins and lubricating oils.Tetrahydrofurfuryl alcohol(THFOL),deep-hydrogenation product of furfural,is an important green solvent used in agriculture and printing industry.2-methylfuran(2-MF),a product obtained by hydrodeoxygenation of furfural,serves as an excellent biofuel with broad market prospects.However,the reaction pathway of furfural hydrogenation is rather complicated and how to obtain a high selectively toward a target product remains a conundrum.Although a great number of noble metal-based catalysts have been developed,they normally suffer from high cost or laborious preparation process.In a structure-sensitive reaction such as furfural hydrogenation,surface structure of catalysts imposes a crucial influence on reactant activation,reaction pathway and selectivity.The incorporation of the second metal can effectively separate active sites,thereby further protecting the furan ring and activating the hydroxyl group.The main research results are as follows:1.Preparation of FOL and THFOL by tuning exposed facet of metal NiIn this work,two NiAl-LDH precursors,with NO3-and C032-as interlayer anion respectively,were prepared firstly.Followed by a subsequent topological transformation process,we obtained two supported Ni nanocatalysts on MMO substrate(denoted as Ni/MMO-NO3 and Ni/MMO-CO3),which were used in the selectivity hydrogenation reaction of furfural.Notably,Ni/MMO-NO3 shows a high selectivity toward FOL(97%)while Ni/MMO-CO3 exhibits selectivity toward THFOL(99%)(Scheme 1).Structural characterizations based on XRD,HRTEM,EXAFS and in situ CO-DRIFTS show multi-facets exposure with abundant steps/edges for Ni/MMO-NO3 sample while a highly-exposed Ni(111)facet for Ni/MMO-CO3 sample.In situ FT-IR measurements and DFT calculations prove that activated adsorption of both C=O group and furan ring occurs on Ni(111)terrace of Ni/MMO-CO3,accounting for the overall hydrogenation of furfural and thus the production of THFOL.In contrast,furan ring has a rather weak interaction with the surface of Ni/MMO-NO3,and only C=O group undergoes linear activated adsorption on Ni surface,which results in a high selectivity to FOL.The surface fine structure of Ni nanoparticles tuned by LDHs precursors with different interlayer anions,imposes an extremely significant influence on adsorption configuration of furfural molecule and the resulting hydrogenation selectivity,which establishes a facile switch between two target products.2.Preparation of NiZn bimetallic catalyst and its catalytic hydrogenation of furfural to produce 2-MFBased on the above studies,it is known that Ni/MMO-NO3 plays an important role in the protection of furan rings.Thus we tried the preparation of a bimetallic catalyst for the hydrogenation of furfural to produce 2-methylfuran.A series of nitrate-intercalated NiZnAl hydrotalcites were prepared as catalyst precursors,followed by an in-situ reduction treatment to obtain supported NiZn bimetallic catalysts.By changing the relative proportion of Ni/Zn,two different alloy phases with unique geometries were obtained.The sample of Ni1Zn3/MMO shows the optimal catalytic performance toward furfural hydrogenation to 2-methylfuran,with a yield of 95%.HRTEM images demonstrate a β-alloy phase for Ni1Zn3/MMO.The Ni active sites are divided by Zn and therefore inhibit the activated adsorption of furan ring from hydrogenation.XPS results confirm an electron transfer between Ni and Zn,which facilitates the step of hydrodeoxygenation and the resulting high catalytic selectivity toward 2-methylfuran.