Structure-reactivity relationships in MoO3-based catalysts for hydrodeoxygenation of lignin pyrolysis products

与人类营养无关的可再生资源以木质素为主要成分。它们作为化石资源的替代品正变得越来越重要。从木质素中提取的热解油含有20%-40%的结合氧，在进一步作价之前必须将其除去。这是通过与氢的催化反应(加氢脱氧，HDO)完成的，通常在气态热解产物冷凝后的液体中进行。然而，它们在离开热解反应器后直接在气相中的HDO将更具吸引力，因为这将使它们的缩合变得可有可无，并节省成本。与液态HDO相比，对气相中HDO的研究要少得多。此类研究应在本项目中使用具有不同结合氧(如苯酚、苯甲醚、愈创木酚)的木质素相关模型底物和以氧化钼为基础的催化剂进行。我们正在遵循一种综合的方法，包括合成不同目的掺杂的MoO_3催化剂，催化测试包括反应条件的优化，以及全面的光谱原位/操纵性研究，以得出反应路径。本项目的主要目的是阐明是否以及如何通过掺杂不同价态和还原程度的第二金属离子来控制木质素相关模型底物的气相HDO中的活性和选择性(如保持芳香键，防止甲烷释放)以及稳定性(如抗积炭性能)。

Renewable resources not relevant for human nutrition contain lignin as main component. They are gaining more and more importance as substitutes for fossil resources. Pyrolysis oil derived from lignin contains 20-40% of bound oxygen which must be removed before further valorization. This is done by catalytic reaction with hydrogen (hydrodeoxygenation, HDO), which in general is performed in liquid phase after condensation of the gaseous pyrolysis products. However, their HDO in the gas phase directly after leaving the pyrolysis reactor would be much more attractive, since this would make their condensation dispensable and save costs. In contrast to liquid phase HDO, there is much less research on HDO in the gas phase. Such investigations shall be performed in this project using lignin-relevant model substrates with differently bound oxygen (e. g. phenol, anisole, Guaiacol) and catalysts based on molybdenum oxide. We are following an integrated approach comprising synthesis of differently purposefully doped MoO3 catalysts, catalytic testing including optimization of reaction conditions as well as comprehensive spectroscopic in situ/operando studies to derive reaction pathways. It is the main aim of this project to elucidate if and how activity and selectivity (e. g. maintaining aromatic bonds, preventing liberation of methane) as well as stability (e. g. resistance against coke deposition) in gas phase HDO of lignin-relevant model substrates can be controlled through modification of redox and acid-base properties of MoO3 catalysts by doping with second metal ions of different valence state and reducibility.