Construction Of Highly Efficient Catalyst For Hydrogenation Of Biomass Derived Platform Compounds And Their Catalytic Performance

As a renewable resource,biomass and its derivatives can be converted into various important liquid fuels and high-value chemicals.Levulinic acid（LA）,furfural（FAL）and 5-hydroxymethylfurfural（HMF）can be converted into various high value-added chemicals through green catalytic hydrogenation process.However,the existing catalyst systems have many disadvantages,such as hard preparation process,high cost,low catalytic efficiency,and difficult to recycle.Therefore,it is important to develop low-cost and highly active green catalysts for the hydrogenation of biomass platform compounds.The reaction efficiency of hydrogenation is related to the species and number of active sites on the catalyst surface and interface closely.According to the active sites required by hydrogenation reactions,it is challenging that achieve high selectivity towards products by increasing the number of active sites on the catalyst surface and interface.Based on this,in this paper,D-amino acid oxidase（DAAO）was to coordinate with Zr（Ⅳ）and Zn（Ⅱ）simultaneously in phosphate buffer solution（PBS）to prepare nanoflower-like material DAAO@Zn&HPO₄&Zr.The catalytic activity of DAAO@Zn&HPO₄&Zr for LA conversion toγ-valerolactone（GVL）was investigated.Neohesperidin（NES）derived from orange peel was used as ligand,and Zr-NES polymer with a large number of coordinatively unsaturated Zr sites（Zr-CUS）was prepared by adjusting the ratio of NES toZr.The selective hydrogenation of HMF to BHMF catalyzed by Zr-NES was investigated.Hollow polymer microspheres（h-PDMA）containing a large amount of carboxyl groups were used as organic ligands to synthesize Zr-coordinated hollow mesoporous polymer microspheres（h-PDMA&Zr）by domain-restricted coordination method.The catalytic activity of h-PDMA&Zr for FAL conversion to furfuryl alcohol（FOL）was investigated.The main contents and results are as follows:（1）DAAO@Zn&HPO₄&Zr was prepared at room temperature and without the use of any organic solvent.The nitrogenous groups of D-amino acid oxidase（DAAO）molecules and phosphate groups in PBS buffer were used to coordinate with Zr（Ⅳ）and Zn（Ⅱ）simultaneously Based on SEM,³¹PNMR,XRD,FTIR,XPS,BET TPD and py-FTIR characterization results,the effects of changing the molar ratio of Zr（Ⅳ）to Zn（Ⅱ）on the morphology,composition,basicity,Lewis acid and Br（?）nsted acid sites of DAAO@Zn&HPO₄&Zr were analyzed.The formation process of DAAO@Zn&HPO₄&Zr and coordination structure of～（Zn HPO₄）@DAAO@（Zr HPO₄）～were determined.DAAO@Zn&HPO₄&Zr had dual acid sites and basic sites.The coordinated N from DAAO and coordinated O from phosphate in DAAO@Zn&HPO₄&Zr were the Lewis base sites,and the coordinated Zn（Ⅱ）and Zr（Ⅳ）were the Lewis acid sites.The experimental results showed that when the initial molar ratio of Zr（Ⅳ）to Zn（Ⅱ）is 1:2,DAAO@Zn&HPO4&Zr-IC exhibited remarkable catalytic activity for catalytic transfer hydrogenation of levulinic acid（LA）toγ-valerolactone（GVL）,achieving the LA conversion of 99.8%and the GVL yield of 98.2%at 130°C within 2 h.Nanoflower-like structure and a larger average pore size facilitated the adsorption of LA onto DAAO@Zn&HPO4&Zr-IC,and promoted the interaction between LA and active sites.The formation of the～（Zn HPO₄）@DAAO@（Zr HPO₄）～coordination networks endows the coordinated Zr（Ⅳ）and Zn（Ⅱ）in DAAO@Zn&HPO4&Zr-IC with a relatively stronger Lewis acidity Therefore,DAAO@Zn&HPO4&Zr-IC can efficiently catalyze the conversion of LA to GVL.（2）The polymer Zr-NES with coordinatively unsaturated Zr sites（Zr-CUS）was prepared by using Neohesperidin（NES）derived from orange peel as an organic ligand under mild hydrothermal conditions.Based on SEM,XRD,FTIR,XPS,BET,TPD and py-FTIR characterization results,the coordination structure,composition and number of acid-base sites of Zr-NES were analyzed.The effects of different proportions of NES and Zr on the content of coordinatively unsaturated Zr sites（Zr-CUS）were analyzed by acid-base titration experiment.The results showed that due to the presence of coordinatively unsaturated Zr sites,Zr-NES had highly active Lewis acid sites,so it can efficiently catalyze the hydrogenation of HMF to prepare BHMF.The experimental results showed that:Zr-NES_0.1（molar ratio of NES/Zr OCl₂·8H₂O=0.1）exhibited the highest catalytic activity..When reacting at 120°C for 2 h,the conversion of HMF could reach 99.6%,the selectivity of BHMF was 99.4%,and the TOF was 8.5 h^-1.The kinetic experiment showed that the activation energy of HMF hydrogenation was 44.73 k J/mol.The catalytic activity of Zr-NES_0.1 did not decrease significantly after five cycles.In addition,BHMF can be further etherified to 5-[（1-methylethoxy）methyl]-2-furanmethanol（MEFA）with high selectivity by extending the reaction time.The study of reaction mechanism showed that hydrogen transfer fromα-C of isopropanol to BHMF.The reaction path of Zr-NES_0.1 catalytic hydrogenation is direct hydrogen transfer.（3）The hollow mesoporous polymer catalyst（h-p DMA&Zr）was constructed by domain-restricted coordination mode,which used the carboxyl rich hollow mesoporous polymer（h-p DMA）as an organic ligand.Fe₃O₄ was immobilized on the surface of h-p DMA&Zr by amide bond,to make it possess magnetic recovery property（mh-p DMA&Zr）.Based on SEM,XRD,FTIR,XPS,BET,TPD and py-FTIR characterization results,the coordination structure,composition,formation process and number of acid-base sites of Zr-NES were analyzed.h-p DMA&Zr had Lewis acid and basic sites.The Lewis acid sites were provided by Zr in C-O-Zr,and the basic sites were provided by O in C-O-Zr.The interaction between h-p DMA&Zr and substrate was analyzed by adsorption experiments and UV characterization.The catalytic activity of h-p DMA&Zr for the reduction of FAL to FOL was studied.The experimental results showed that:when reacting at 120°C for 2 h,the conversion of FAL could reach 99.8%,the the yield of FOL is 99.1%.The hollow mesoporous structure and the Zr⁴⁺-O^2-active sites well-distributed on the surface facilitate the interaction between substrate and catalyst,as well as mass transfer.The isotope labeling experiments showed that hydrogen was transferred fromα-C in isopropanol to FOL,and the hydrogenation of FAL catalyzed by h-p DMA&Zr was directly hydrogen transfer.mh-p DMA&Zr could be separated and recovered by external magnet after reaction.