Studies On The Selective Oxidation Of HMF To FDCA Over Supported Ruthenium Nanocatalysts

Pressures for an evolving sustainable society are calling for awareness upon chemistry science and for a need to develop smart technologies to convert lignocellulosic biomass,as an abundant and environmentally sound resource,into chemicals and fuels.The aerobic oxidation of 5-Hydroxymethylfurfural(HMF),a versatile bio-platform compound,to 2,5-furandicarboxylic acid(FDCA),a renewable plastic monomer,is regarded as one of the most attractive reactions in biorefinery.Achieving this reaction under green and mild conditions has attracted a lot of researchers.In this dissertation,Ru/HAP,Ru/MnXCe1OY and PtRu/HTn catalysts have been developed for the base-free aerobic oxidation of HMF to FDCA using water and oxygen/air as solvent and oxidant,repectively.The preparation of catalysts and the effects of reaction parameters have been investigated.Finally,the structure-activity relationship has been established based on catalysts characterizations and catalytic performances.In this dissertation,hydroxyapatite(HAP)support was obtained from commercial sources.Mn-Ce mixed oxides(MnXCe1OY)and hydrotalcite(HTn)supports were prepared by co-precipitation method.Ru/HAP and Ru/MnXCe1OY catalysts were prepared by immobilization of the PVP-stabilized colloidal Ru nanoparticles onto HAP and MnXCe1OY supports.PtRu/HTn catalysts were synthesized by the same protocol.The catalytic performance of the Ru/HAP catalyst was influenced mainly by HMF/Ru molar ratio.O2 pressure,reaction temperature and reaction time.When HMF/Ru molar ratio was of 25.100%conversion of HMF and 99.6%yield of FDCA were achieved at 120? and 1 MPa O2.Kinetic study revealed that the oxidation of HMF to FDCA followed a multistep pathway and the last step,i.e.?the oxidation of FFCA to FDCA,was found as the rate-determining step.ICP-MS,XRD,N2 isotherms,NH3/CO2-TPD,TEM and XPS were used to characterize the Ru/HAP catalyst.Well-dispersed uniform1y-small Ru0 nanoparticles and the acidic-basic sites on the surface of HAP support were essential to realize the base-free oxidation of HMF to FDCA.A minor decline in activity was observed after five cycles,which may be attributed to the partial oxidation of RuJ species,but the activity can be entirely recovered by a hydrogen reduction.The plausible reaction mechanism of aerobic oxidation of HMF over the Ru/HAP catalyst has been proposed based on the results of experiments and characterizationsThe catalytic performance of the Ru/MnXCe1OY catalysts was influenced by Mn/Ce molar ratios and reaction parameters(HMF/Ru molar ratio,O2 pressure,reaction temperature and reaction time).The Ru/Mn6Ce1Oy catalyst(HMF/Ru molar ratio is of 6)showed the best catalytic performance.?99%yield and 5.3molFDCA molRu-1 h-1 productivity of FDCA can be achieved over this catalyst.The reaction route and rate-determining step for oxidation of HMF to FDCA over the Ru/MnXCe1OY,catalysts were investigated by kinetic study.The Ru/MnXCe1OY catalysts were characterized by XRD,H2-TPR,O2-TPD,UV-Vis DRS,XPS and TEM technologies to reveal their properties.Well-dispersed Ru nanoparticles with a mean size of 4.4nm supported on the support were essential to achieve the oxidation of HMF to FDCA.The superior catalytic performance of the Ru/Mn6Ce1OY catalyst was mainly associated with(1)the strong metal-support interaction and(2)the synergistic effect between manganese and cerium oxides.The Ru/MnXCe1OY catalyst showed the highest surface concentrations in Mn4+and Ce3+ among the series,which,as a consequence,enhanced the availability and mobility of active oxvgen species.The Ru/MnXCe1OY catalyst was shown resistant to deactivation during eight recycling uses mainly due to a strong metal-support interaction between Ru nanoparticles and Mn.6Ce1OY supportThe catalytic performance of the PtRu/HTncatalysts was mainly influenced by Pt/Ru and Mg/Al molar ratio.When Pt/Ru and Mg/Al molar ratio were of 2 and 4,100%conversion of HMF and 99%yield of FDCA could be achieved at 100? and 0.2 MPa air after 24 h.Kinetic study revealed that the oxidation of HMF to FDCA over the Pt2Ru1/HT4 followed a tandem pathway and the last step,the oxidation of FFCA to FDCA,was the rate-determining step.During the kinetic controlled range,the activity of the catalyst was almost remained after five cycles.ICP-MS,N2 isotherms,XRD,CO2-TPD,XPS and TEM were used to characterize the properties of the PtRu alloy and morphology as well as basicity of HTn supports.Finally,structure-activity relationship has been established based on the results of experiments and characterizations.