碳纳米管负载的铈基水滑石-纳米金催化剂的制备及其催化甘油氧化性能研究

Selective oxidation of biomass-derived polyols is one of the important pathways for their high-value utilization. In particular, rational design of heterogeneous catalysts plays key roles in the exploration of green and efficient catalysis technology. We will focus on the challenge that the Au catalysts are in low conversion and poor selectivity for the glycerol oxidation reaction in base-free medium. We plan to precisely synthesize ultrathin Ce-LDH nanosheets with highly distributed Ce element, and assemble them with carbon nanotubes (CNT) to form 3D supports with large surface areas. Meanwhile, the size, morphology and crystal phase of the gold nanocrystals on the support will be controlled. Consequently, a kind of Au/Ce-LDH/CNT catalysts with specific compositions in defined assembly ways will be designed and synthesized. And the problem of low catalytic activity and poor selectivity of the Au catalysts may be overcomed by taking the advantages of the tunable compositions of LDH nanosheets, the redox properties of Ce element, as well as the facet effect and phase effect of Au nanocrystals. Consequently, a kind of catalyst with high catalytic activity, high C3 product selectivity and high stability toward glycerol oxidation in base-free medium will be achieved. The research will benefit for the high-value utilization of biomass-derived polyols and the rational design of supported catalysts.

生物质基多元醇的选择性氧化是生物质资源高附加值利用的重要途径。其中，异相催化剂的理性设计是开发绿色、高效的催化工艺的关键。我们拟针对非碱性环境下金催化甘油氧化反应活性低、选择性不佳等问题，通过精准合成铈元素高度分散的水滑石（Ce-LDH）超薄纳米片，并将其与碳纳米管（CNT）组装形成具有三维大比表面积的载体，同时对载体上金纳米晶的尺寸、形貌、晶相等进行调控，设计合成具有可控组成、特定组装方式的Au/Ce-LDH/CNT催化剂，充分发挥水滑石纳米片灵活的调变性、铈元素的氧化还原特性以及金纳米晶的晶面与晶相效应，获得一类在非碱性环境下具有高催化活性、高C3产物选择性的甘油氧化催化剂。本项研究将为生物质基多元醇的高附加值利用以及负载型催化剂的理性设计提供指导作用。

本项目的研究目标是通过碳纳米管负载的铈基水滑石-纳米金催化剂的可控合成、催化性能、构效关系的研究，开发出具有高催化活性、高C3产物选择性、高稳定性的甘油氧化催化剂。我们建立了四种Ce-LDH及其CNT复合物的可控合成方法，实现了Ce元素均匀分布的水滑石超薄纳米片的合成及其与CNT的可控组装。并阐明了载体中稀土元素种类、尺寸、形貌、价态、氧空位、羟基，及其与Au/CNT的结合方式对Au催化甘油氧化反应活性、产物选择性、稳定性的的关系规律。在此基础上，成功地开发出Au/LREO、AuPt/LCeO、Au/MgAlCe、Au-CeO2/MgAl、Au/CuMgAl、Pt/LCeO/CNT、Pt-CeO2/CNT等七种高催化活性、高C3产物选择性、高稳定性的甘油氧化催化剂。此外，我们还将Au-CeO2/CNT、Pt-CeO2/CNT、Pt/FeNC催化剂用于电催化氧化甘油制C3产物的反应，其催化活性、产物选择性、稳定性均远优于M/CNT催化剂。发现Au/CeO2和Pd/CeO2催化剂对葡萄糖氧化制葡萄糖酸的反应展示出优异的催化活性和耐毒性。与MgAl-LDH相比，MgAlCe-LDH催化剂在甘油与碳酸二甲酯合成甘油碳酸酯反应中的催化活性大幅提升。. 本项目首次合成了尺寸均一的超薄LCeH纳米片，开发出富含介孔和氧空位的LCeH衍生纳米片负载贵金属催化剂。并用反相微乳液法合成了十二种LREH纳米薄片，揭示了镧系收缩对于LREH衍生纳米片负载金颗粒尺寸的影响规律及其催化作用机制。本项目研究对于稀土基水滑石催化材料的设计以及异相催化甘油氧化产业的工业化具有重要的指导意义。