Fundamental origins of different activity and time-on-stream stability of supported Mo-, W-, and Re-based materials in metathesis of ethylene and 2-butene to propene

一种有吸引力的用于丙烯生产的替代方案是乙烯和2-丁烯在负载的基于WOx、MoOx和ReOx的催化剂上的复分解。这些催化剂在不同的反应温度（分别为300°C、100 °C和室温）下操作，并且具有不同的丙烯选择性和运转时间稳定性。尽管WOx基催化剂的反应在工业上已经应用了几年，但其催化性能的差异是由催化剂的基本特征决定的，目前还不清楚。以前从丙烯开始的逆反应所获得的机理知识只能在有限的范围内应用，因为乙烯和2-丁烯的复分解被并行发生的2-丁烯的顺/反和2-/1-异构化反应所复杂化。本项目旨在缩小这些差距。它旨在理解（i）结构-反应性/选择性关系和（ii）阐明乙烯和2-丁烯复分解为丙烯的机理和动力学方面，以及2-丁烯异构化反应在明确支持的WOx，MoOx和ReOx物种上的作用。将稳态和瞬态动力学分析与空间和时间分辨的原位催化剂表征相结合，以建立各个反应步骤的动力学参数与固体性质之间的关系，并提高对失活行为的理解。研究结果将有助于在科学的基础上设计出更好的催化剂，并为复分解反应器的设计提供更好的操作策略。

An attractive alternative for on-purpose propene production is the metathesis of ethyleneand 2-butene over supported WOx-, MoOx-, and ReOx-based catalysts. These catalysts operateat different reaction temperatures (300°C, 10 0°C, and room temperature, respectively)and possess different propene selectivity and time-on-stream stability. It is still unclear whichfundamental catalyst features determine their different performance although the reactionover WOx-based catalysts is in practice in industry since several years. Previous mechanisticknowledge obtained for the reverse reaction starting from propene can be applied only toa limited extend, because the metathesis of ethylene and 2-butene is complicated by in paralleloccurring cis-/trans and 2-/1-isomerisation reactions of 2-butene. This project is proposedto close these gaps. It aims at understanding (i) structure-reactivity/selectivity relationshipsand (ii) elucidating mechanistic and kinetic aspects of ethylene and 2-butene metathesisto propene as well as the role of 2-butene isomerisation reactions over well-definedsupported WOx, MoOx, and ReOx species. A combination of steady-state and transient kineticanalysis with spatial- and time-resolved in-situ catalyst characterization will be appliedto establish relationships between kinetic parameters of individual reaction steps with solidstateproperties and to improve the understanding of the deactivation behavior. The resultswill ultimately enable to design better catalysts on scientific basis and to derive improvedoperating strategies for metathesis reactors.