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

乙烯和2-丁烯在负载型WOx、MoOx和reox催化剂上的复合反应是生产丙烯的一种有吸引力的替代方法。这些催化剂在不同的反应温度下（分别为300°C、10°C和室温），具有不同的丙烯选择性和流上时间稳定性。尽管基于wox的催化剂的反应已经在工业上实践了几年，但仍不清楚是哪些基本的催化剂特征决定了它们不同的性能。先前从丙烯开始的逆反应获得的力学知识只能在有限的范围内应用，因为乙烯和2-丁烯的复合反应由于平行发生的2-丁烯的顺/反和2-/1异构化反应而变得复杂。该项目旨在弥补这些差距。它旨在理解(i)结构-反应性/选择性关系；（ii）阐明乙烯和2-丁烯合成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。稳态和瞬态动力学分析与空间和时间分辨原位催化剂表征相结合，将应用于建立单个反应步骤的动力学参数与固态性质之间的关系，并提高对失活行为的理解。研究结果最终将有助于在科学的基础上设计更好的催化剂，并为复分解反应器提供改进的操作策略。

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.