Styrolsynthese an Eisenoxid-Katalysatoren: Vom einkristallinen Modellsystem im Ultrahochvakuum zum Realkatalysator im technischen Reaktor

该项目旨在开发一种方法来揭示金属氧化物催化剂的反应机制，并将这些见解从特高压条件下模型系统的基础表面科学研究转移到技术工艺条件下的多晶催化剂。正在研究的例子体系是乙苯在未促进或k促进的氧化铁上脱氢制苯乙烯。在第一个资助期获得的见解之后，可以为第二个资助期制定更具体的目标：-速率限制步骤被确定为从吸附的乙苯分子中提取氢，而不是最初认为的产物解吸。因此，需要精细的功能和动力学模型来正确描述表面反应。-相同成分的单晶模型催化剂和多晶粉末催化剂在催化行为方面具有相似的性质。“材料间隙”的存在是指在反应条件下，氧化物表面被与表面反应相关的致密碳质层覆盖。因此，有必要可重复地合成各自的顶层，通过表面科学技术对其进行表征，并从理论上确定其存在的稳定条件。在第二个资助期，我们将重点研究氧化和非氧化条件下未推广的FexOy系统。我们将修改和完善在第一次拨款期间开发的功能模型，并得出一致的动力学模型。动力学参数将直接由单晶样品的测量或基于分子和量子化学模型的理论考虑来确定。该模型将通过准技术条件下的实验进行验证，并将用于有关技术过程优化的探索性研究。在稍后的阶段，我们将考虑K提升系统作为开发系统的实际相关测试用例。

The project aims at developing a methodology for the unravelling of reaction mechanisms over metal oxide catalysts and the transfer of these insights from fundamental surface science studies on model systems under UHV conditions to the polycrystalline catalysts under technical process conditions. The example system under investigation is the dehydrogenation of ethylbenzene to styrene over unpromoted or K-promoted iron oxide. After the insights gained during the first grant period, more specific aims can be formulated for the second period: - The rate limiting step was identified to be the hydrogen abstraction from the adsorbed ethylbenzene molecule and not - as initially thought - product desorption. Hence, elaborate functional and kinetic models are needed for a proper description of the surface reactions. - Monocrystalline model catalysts and polycrystalline powder catalysts of the same composition feature analogue properties regarding their catalytic behaviour. A "materials gap" exists in the sense that under reaction conditions the oxide surface is covered by a dense carbonaceous layer which is relevant for the surface reactions. Therefore, it is necessary to reproducibly synthesise the respective top layer, to characterise it by means of surface science techniques and to theoretically determine stability conditions for its existence. During the second grant period we will concentrate on the unpromoted FexOy system under oxidative and nonoxidative conditions. We will revise and refine the functional models developed during the first grant period and derive consistent kinetic models. The kinetic parameters will be determined either directly from measurements over monocrystalline samples or from theoretical considerations based on molecular and quantum-chemical models. The model will be verified through experiments under quasi-technical conditions and will be employed for exploratory studies concerning the optimisation of the technical process. At a later stage we will consider the K promoted system as a practically relevant test case for the developed systematics.