Lechner Manuel, Güttel Robert, Streb Carsten
Institute of Inorganic Chemistry I, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany.
Dalton Trans. 2016 Nov 14;45(42):16716-16726. doi: 10.1039/c6dt03051c. Epub 2016 Sep 7.
Selective catalytic oxidation is one of the most widely used chemical processes. Ideally, highly active and selective catalysts are used in combination with molecular oxygen as oxidant, leading to clean, environmentally friendly process conditions. For homogeneous oxidation catalysis, molecular metal oxide anions, so-called polyoxometalates (POMs) are ideal prototypes which combine high reactivity and stability with chemical tunability on the molecular level. Typically, POM-mediated aerobic oxidations are biphasic, using gaseous O and liquid reaction mixtures. Therefore, the overall efficiency of the reaction is not only dependent on the chemical components, but requires chemical engineering insight to design reactors with optimized productivity. This Perspective shows that POM-mediated aerobic liquid-phase oxidations are ideal reactions to be carried out in microstructured flow reactors as they enable facile mass and energy transfer, provide large gas-liquid interfaces and can be easily upscaled. Recent advances in POM-mediated aerobic catalytic oxidations are therefore summarized with a focus on technological importance and mechanistic insight. The principles of reactor design are discussed from a chemical engineering point of view with a focus on homogeneous oxidation catalysis using O in microfluidic systems. Further, current limitations to catalytic activity are identified and future directions based on combined chemistry and chemical engineering approaches are discussed to show that this approach could lead to sustainable production methods in industrial chemistry based on alternative energy sources and chemical feedstocks.
选择性催化氧化是应用最为广泛的化学过程之一。理想情况下，高活性和高选择性的催化剂与分子氧作为氧化剂配合使用，可实现清洁、环保的工艺条件。对于均相氧化催化而言，分子金属氧化物阴离子，即所谓的多金属氧酸盐（POMs）是理想的原型，它们在分子水平上兼具高反应活性、稳定性和化学可调性。通常，POM介导的需氧氧化反应是双相的，使用气态氧气和液态反应混合物。因此，反应的整体效率不仅取决于化学成分，还需要化学工程方面的知识来设计具有最佳生产率的反应器。本文观点表明，POM介导的需氧液相氧化反应是在微结构化流动反应器中进行的理想反应，因为它们能够实现便捷的质量和能量传递，提供大的气液界面，并且易于放大。因此，本文总结了POM介导的需氧催化氧化的最新进展，重点关注其技术重要性和机理见解。从化学工程的角度讨论了反应器设计的原理，重点是在微流体系统中使用氧气的均相氧化催化。此外，确定了催化活性的当前限制，并讨论了基于化学与化学工程相结合方法的未来发展方向，以表明这种方法可能会导致基于替代能源和化学原料的工业化学可持续生产方法。
