CO氧化偶联制草酸二甲酯用Pd基多相催化剂的载体效应研究

Rich coal and shortage of oil and gas of China lead to that coal to ethylene glycol is an important alternative technology, which not only effectively relieve the conflict of ethylene glycol supply and demand, but also enhances the level of efficient and clean use of coal resources. CO oxidative coupling to dimethyl oxalate is the crucial step to realize the conversion of inorganic to organic in coal to ethylene glycol. Nano palladium based heterogeneous catalysts have been demonstrated to be active for CO oxidative coupling to dimethyl oxalate. Because of its structure-sensitive reaction, the activity, selectivity and stability of catalysts are strongly affected by the structure of support. However, the intrinsic nature of support effect on the catalytic performance is unclear so far. Based on the problem, we plan to control the electron structure of support by the doping of rare earth into support lattice, and regulate the exposed facet structure of support by the shape-controllable synthesis in this project. And then, we will reveal and confirm the inherent nature of relationship between the electron and exposed facet structure of support and the catalytic performance (activity, selectivity and stability) through varieties of physical and chemical characterization methods and theoretical simulation. We also intend to enhance the stability of catalysts by strengthen the electronic and faced interaction between the active metal components and support. Guided by the knowledge of support effect, high-performance and long-lived Pd based heterogeneous catalysts will be prepared, which lay a solid foundation for the development of a new generation of coal to ethylene glycol catalyst technology.

我国的资源特点是缺油、少气、煤炭资源相对丰富。因而发展煤制乙二醇技术，不仅可以有效缓解乙二醇突出的供需矛盾，还能提升煤炭资源高效转化利用水平。CO氧化偶联制草酸二甲酯是煤制乙二醇中实现无机物到有机物转化的关键步骤。Pd基多相催化剂已被证明是这一反应的活性催化剂。该反应是一个对催化剂载体结构敏感的反应，载体结构对催化剂的活性、选择性和稳定性影响很大。但是，该反应载体效应的结构本质至今仍不清楚。针对此问题，本项目拟通过对载体晶格进行稀土掺杂来调变载体的电子结构，以及可控制备不同形貌的载体来调控载体的晶面结构，然后通过物理化学表征和理论模拟等手段，揭示载体的电子结构和晶面结构与催化活性、选择性和稳定性之间的构效关系，加强活性金属组分与载体之间的电子和晶面相互作用，提升催化剂稳定性，有效制备高活性、高选择性、长寿命的Pd基多相催化剂，为开发新一代煤制乙二醇催化剂技术奠定坚实的基础。

本项目主要围绕煤制乙二醇CO氧化偶联制草酸二甲酯催化剂中Pd基多相催化剂的载体效应开展应用基础性研究，发现载体的比表面积和Lewis酸碱性是影响催化活性的两个重要因素，比表面积小和Lewis碱性强的载体适宜作为CO氧化偶联的催化剂载体。在此基础上开发了一系列新型、低贵金属负载量、高性能的Pd/MgO、Pd/MgAl-LDO-400、Pd/ZnO催化剂。在保持和强化催化活性的前提下，将贵金属Pd负载量从一代煤制乙二醇催化剂技术的2%降低到0.5%，将极大降低催化剂成本，节约大量贵金属。.该项目的研究取得了如下成果：.（1）Pd/MgO催化剂的制备及其性能研究.利用溶液法结合高温煅烧处理合成MgO纳米片载体，然后通过浸渍法制备Pd/MgO催化剂并对其进行CO氧化偶联制草酸二甲酯催化性能研究。结果表明合成的MgO载体是一种Lewis碱性很强纳米片结构，Pd纳米颗粒高度分散在MgO载体上，尺寸小且分布均一。此Pd/MgO催化剂在较低Pd负载量(0.5%)下表现出优异的CO氧化偶联催化性能。CO单程转化率可达65%，DMO选择性高达96%，稳定性超过100小时。.（2）Pd/MgAl-LDO催化剂的制备及其性能研究.通过水热法获得一种比表面积小、路易斯碱性强的MgAl-LDO-400载体，首次发现MgAl-LDO-400作为载体制备的Pd/MgAl-LDO-400催化剂应用于CO氧化偶联制草酸二甲酯反应中在较低Pd负载量(0.5%)下表现出优异的催化性能。更有趣的是发现镁铝水滑石前驱体(MgAl-LDHs)焙烧温度对CO氧化偶联催化性能影响很大。400度焙烧温度制备Pd/MgAl-LDO-400催化剂的催化活性要明显优越于600度焙烧温度制备Pd/MgAl-LDO-600催化剂。这活性的差异归因于MgAl-LDHs前驱体焙烧温度不同引起载体MgAl-LDO的路易斯碱性位点数量不同。.（3）Pd/ZnO催化剂的制备及其性能研究.通过简易水热法结合高温煅烧处理成功合成了多孔纤锌矿ZnO纳米片，并将多孔ZnO纳米片作为载体负载Pd催化剂应用于CO气相氧化偶联制草酸二甲酯反应中，发现Pd/ZnO纳米催化剂在较低Pd负载量（0.5%）下表现出优异的CO氧化偶联催化活性，CO单程转化率达66%，DMO选择性98%，其催化性能要远高于工业催化剂，具有潜在的工业应用价值。