| Synthes of fine chemicals with high-added value by renewable biomass resource is an effective way to alleviate the shortage of fossil energy.It is worth noticing that biodiesel is a kind of representative biofuel.However,with the rapid development of biodiesel industry,it has led to the excess of the main byproduct,glycerol,so it is urgent to convert it into chemicals with high value-added.Glycerol is a highly functionalized molecule which possesses three hydroxyl groups,thus making it a very potential platform compound that can be converted into a variety of high value-added chemicals via catalytic oxidation,such as glyceric acid and dioxyacetone.This method has attracted a wide range of attention due to the advantages of easily operation,separation and environmentally efficiency.However,catalytic oxidation of glycerol to obtain glyceric acid is related to the effective activation of the primary hydroxyl group and continuous oxidation of C-OH and C=O,as well as C-C cleavage.Therefore,it is nonnegligible challenge to develop an efficient method to effectively convert glycerol into glyceric acid.In terms of supported catalysts,the interfacial active sites play an essential role on modulating the reaction pathways.Therefore,the reasonable design of active sites that matches the reactant of a specific reaction is an effective method of promoting catalytic performance,which provides a new perspective for the catalysts aiming to realize the activition of carbon-oxygen bonds.This thesis aims at the enhancement of catalytic performance of selective oxidation of glycerol,which involves the activation of various carbon-oxygen bonds.It focuses on the precise control of electronic and coordinative structure at metal-support interface due to the tunable crystal structure and defect structure of reducible oxide support.Then investigate the mechanism of selective oxidation of glycerol,in order to reveals the matching degree between interfacial active sites and different adsorption mode of the reactant from the molecular level.Aiming at the issue that promoting the activity of Pt-based catalysts under alkali-free conditions,the strategy based on the tunable crystal facet of reducible oxide support is proposed to modulate the electronic and coordination structure of metal-support interface micro-area to strengthen the activation of C-OH bond.In view that the difficulty of controlling product distribution in the multi-step semi-continuous oxidation reaction,a method of using support interfaces containing different crystal planes to form a multicomponent metal-support interface is put foward to achieve continuous activation of C-O and C=O while inhibiting C-C cleavage,so as to obtain a new idea of high yield of the target product.With the purpose of the innovation of the glycerol oxidation process,a method based on the variation of defect structure at the support to modulate metal-support interface scales and anchoring active components is raised.The atomic-level interface is applied to realize the efficient conversion of glycerol under photo-assisted conditions and a new pathway to promote hydrogen generation by photocatalysis of water.(1)Aiming for the enhancement of catalytic activity of glycerol oxidation under base-free conditions,by utilizing supported AuPt/CeO2 catalyst as the research material,the construction of low coordinative metal-support interface was achieved and the strong metal-support interaction caused by the coordinated unsaturated structure of the support is revealed based on the exposure of specific crystal facet of CeO2 support.The exposed facet exerted significant effect on the electronic structure of interfacial active sites,thus effectively enhancing the intrinsic activity of glycerol oxidation.To be specific,using CeO2 with mainly exposed(200),(220)and(111)crystal planes were selected as the support to prepare a series of AuPt/CeO2(200),AuPt/CeO2(220)and AuPt/CeO2(111)interfaces.The study found that the different crystal faces exposed by the support had no obvious influence on the size of active component but will significantly change interaction strength with active component,thus regulating the electronic structure of the metal-carrier interface.Specifically,the CeO2 support promotes the transfer of electrons from the active component Pt to the CeO2,which generated Pt2+species at the interface and accompanying with the generation of oxygen vacancies VO.Because of the low-coordinated Ce6cO2c structure exposed by the CeO2(200)crystal plane has the strongest oxidizing ability which causes the most significant change in the electronic structure interfacial micro-area.The experimental results show that Pt2+-VO is the advantageous interface sites that can effectively promote the adsorption and activation of O2 molecules,which effectively enhanced the intrinsic activity of glycerol oxidation.Therefore,the AuPt/CeO2(200)interface exibited highest intrinsic activity with the TOF value of(937.8 h-1),which was significantly improved to 1.3 and 1.9 times compared with AuPt/CeO2(220)and AuPt/CeO2(111)catalysts,respectively.(2)Due to specific crystal facet could clearly affected interfacial electronic structure,the multicomponent metal-oxide interface is prepared by support interface containg different crystal faces of TiO2.Controllable regulation and discloses the mechanism for controlling product distribution in multi-step semi-continuous reactions.Specifically,the TiO2 with the exposure of(101),(110)crystal facet and TiO2 support containing a(101)/(110)interface was used as support respectively.Therfore,the series of single Pt/TiO2(101),Pt/TiO2(110)interfaces and multicomponent Pt/TiO2(101/110)interface were obtained,respectively,which were employed to reveal the interfacial effect on selective oxidation of glycerol.Combining with the results of FTIR and kinetic,it was found that the C=O bond of the intermediate glycerydehyde molecules were highly dissociated on Pt/(Ti-O-Ti)(101/110)coordinative unsaturated sites at the Pt/TiO2(101/110)interface in a bidentate form,thus achieving efficient transformation from glycerydehyde to glyceric acid.Moreover,since the Pt/(Ti-O-Ti)(101/110)site has a longer Ti-Ti distance,which effectively suppressed the further oxidation of target glyceric acid and C-C cleavage.Combining with the result of DFT calculation and kinetic experiments,the multicomponent Pt/TiO2(101/110)interface possessed the advantage of single Pt/TiO2(101)and Pt/TiO2(110)interfaces,which ensured the continous transform of intermediate glycerydehyde into glyceric acid.Furthermore,the consumption of glyceric acid is alleviated by inhibiting the C-C cleavage.Therefore,81.2%glycerol selectivity was achieved under when the conversion of glycerol reached 93.6%over Pt/TiO2(101/110)interface.(3)Aiming at the innovation of selective oxidation process of glycerol,the performance of a series of Pt/TiO2 catalysts which differed in interface scales under photo-assisted conditions as well as hydrogen generation reaction were evaluated.Based on the tunability of defective structures of oxide support,a large content of metal vacancies(VTi)was controllably constructed.Then a series of Pt/TiO2 catalysts with different size of active components including single atoms(Ptiso),atomic clusters(Ptcluster)and nanoparticles(PtNP)were obtained by changing the loading conditions,which resulted in the effective control of scales of metal-oxide interfaces.The investigation found that the atomic-level Ptiso/TiO2 interface could achieve a glycerol conversion of 90.6%and the glyceric acid selectivity of 70.3%at 60?,which were significantly higher than that of Ptcluster/TiO2 and PtNP/TiO2 interfaces.In addition,at the same time,the catalyst showed the largest amount of hydrogen generation.The experimental results showed that the distinct reason for the improvement of catalytic performance,which can be attributed to the adjustment of the semiconductor type and band gap by advantageous interfacial Pt4+-VTi active sites,which significantly increases the separation capacity of holes and electrons as well as the light absorption capacity.Due to the atomic-level interface possessed the largest amount of active of Pt4+-VTi sites,the interface effect was maximized.Finally,the highest activity of glycerol selective oxidation as well as hydrogen generation by photocatalysis of water was obtained. |
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