LDHs结构拓扑效应对强化生物质转化功能的MOx/金属界面影响机制研究

In view of the current social background of the fossil resources shortage, this project aims at the high-value directional conversion of glycerol, which is an important biomass platform compound. We intend to design a highly performed noble metal (Pd, Pt or Au)/transition oxides catalyst with MOx/metal interface structure, and study its catalytic mechanism in glycerol oxidation reaction. Based on the confinement effect of layered double hydroxides (LDHs), a precursor with highly dispersed transition metal cation and active metal complex will be constructed. On account of the structural topology effect, the number of interfacial sites will be increased along with the improved active metal dispersion. Meanwhile, the migration and dispersion as well as coating degree of MOx can be effectively controlled to avoid the excessive encapsulation of metal particles. Based on the tunability of LDHs, the laminate charge density and stack thickness will be regulated to realize the synergetic control of interface dispersion structure, coordination structure and electronic environment. Besides, the effects of surface properties and topological transition conditions of LDHs on the formation and evolution of interfacial structure will be revealed to clarify the catalytic mechanism of MOx/metal interface structure in glycerol oxidation. Based on the above new understanding, a series of glycerol oxidation catalyst with both high activity and selectivity will be designed and prepared through accurate building the interface sites which are well matched with adsorption and activation pattern for primary and secondary hydroxyl. The implementation of the project will build a new method for fabricating and regulating the MOx/metal interface structure and provide a new idea and approach for efficient conversion of biomass resources.

鉴于化石资源短缺的社会背景，本项目以生物质平台化合物甘油的高值转化为目标，以过渡金属氧化物负载的贵金属Pd、Pt和Au催化剂为研究对象，基于层状复合金属氢氧化物（LDHs）开展MOx/金属界面结构构筑及性能强化机制研究。利用LDHs层板及层间限域作用，构筑过渡金属阳离子及活性金属配合物均匀分散的前驱体，基于结构拓扑效应，在提高金属分散度以增加界面位点数量的同时，实现对MOx迁移和分散程度的控制；利用LDHs可调控性，通过层板电荷密度及堆叠程度的调节，进一步实现界面电子结构、分散结构及配位结构的协同控制；阐明LDHs结构拓扑效应对MOx/金属界面形成的影响规律及界面结构在甘油氧化中的作用机制；基于与伯/仲羟基吸附活化方式相匹配的界面位点的精准构筑，获得兼具高活性和选择性的甘油氧化催化剂。通过项目实施，将创制一种金属/载体界面结构构筑的新方法，并为生物质资源高效定向转化提供一种新的思路和途径。

项目组按照任务要求，围绕生物质资源甘油的热催化氧化过程，以过渡金属氧化物负载的贵金属催化剂为创新研究对象，开展了基于LDHs二维材料的反转式MOx/金属界面结构可控构筑及催化作用机制研究，获得了预期研究成果。以过渡金属阳离子及活性金属配合物均匀分散的LDHs纳米材料为前驱体，在特定气氛及温度下进行热处理，经结构拓扑转变获得了空间分布和电子结构可控的系列反转式MOx/金属（Pd、Pt、Au等）界面结构催化剂。采用原位IR、CO脉冲吸附、球差电镜、EXAFS等表征，对不同条件下获得的催化剂表界面结构进行了分析，并阐释了非配位饱和过渡金属氧化物簇MOx的拓扑形成机制及其在活性金属颗粒表面有限迁移的控制机制。重点围绕Pt、Au及AuPt合金催化剂，开展了甘油选择性氧化制甘油酸的性能研究，探究了MOx/金属界面电子结构和配位结构对催化活性、选择性及稳定性的影响。明晰了低配位MOx-金属界面位点对分子氧活化以中间产物甘油醛分子C=O键活化的促进作用，阐明了活性金属表面结构的变化对甘油醇羟基解离吸附的影响，揭示了界面处过渡金属原子的距离对抑制产物甘油酸断链的作用。最后通过MOx/金属界面作用的强化及其与表面位点的协同，提高了甘油氧化的活性、稳定性及其对单一产物甘油酸的选择性。通过项目研究，在ACS Catal.、Appl. Catal. B: Environ.、J. Catal.、AIChE. J.、Fundamental Research等期刊上发表学术论文8篇；基于创新性学术思想申请国家发明专利4项。