美国麻省理工学院Romn-Leshkov, Yuriy团队报道了促进非均相烯烃复分解催化剂中活性位点的更新。相关研究成果发表在2023年5月17日出版的《自然》。

作为一种大规模烯烃相互转化的原子效率策略，非均相催化烯烃复分解在石化、聚合物和特种化学工业中有着商业应用。值得注意的是，乙烯和2-丁烯的热中性和高选择性交叉复分解为丙烯的专门生产提供了一条有吸引力的途径，以解决蒸汽裂解器中使用页岩气作为原料造成的C3短缺。然而，几十年来，关键的机理细节一直模糊不清，阻碍了工艺开发，并对相对于其他丙烯生产技术的经济可行性产生了不利影响。

该文中，通过对模型和工业WOx/SiO₂催化剂上丙烯复分解的严格动力学测量和光谱研究，确定了一个迄今未知的动态位点更新和衰变循环，该循环由涉及近端Brnsted酸性OH基团的质子转移介导，与经典Chauvin循环同时运行。研究人员展示了如何使用少量的助催化剂烯烃来操纵这个循环，以在250°C下将稳态丙烯复分解率大幅提高30倍，而助催化剂的消耗可以忽略不计。在MoOx/SiO₂催化剂上也观察到活性的增加和操作温度要求的显著降低，这表明该策略可能适用于其他反应，并可以解决与工业复分解过程相关的主要障碍。

附：英文原文

Title: Promoting active site renewal in heterogeneous olefin metathesis catalysts

Author: Gani, Terry Z. H., Berkson, Zachariah J., Zhu, Ran, Kang, Jong Hun, Di Iorio, John R., Chan, Ka Wing, Consoli, Daniel F., Shaikh, Sohel K., Copret, Christophe, Romn-Leshkov, Yuriy

Issue&Volume: 2023-05-17

Abstract: As an atom-efficient strategy for the large-scale interconversion of olefins, heterogeneously catalysed olefin metathesis sees commercial applications in the petrochemical, polymer and speciality chemical industries1. Notably, the thermoneutral and highly selective cross-metathesis of ethylene and 2-butenes1 offers an appealing route for the on-purpose production of propylene to address the C3 shortfall caused by using shale gas as a feedstock in steam crackers2,3. However, key mechanistic details have remained ambiguous for decades, hindering process development and adversely affecting economic viability4 relative to other propylene production technologies2,5. Here, from rigorous kinetic measurements and spectroscopic studies of propylene metathesis over model and industrial WOx/SiO2 catalysts, we identify a hitherto unknown dynamic site renewal and decay cycle, mediated by proton transfers involving proximal Brnsted acidic OH groups, which operates concurrently with the classical Chauvin cycle. We show how this cycle can be manipulated using small quantities of promoter olefins to drastically increase steady-state propylene metathesis rates by up to 30-fold at 250°C with negligible promoter consumption. The increase in activity and considerable reduction of operating temperature requirements were also observed on MoOx/SiO2 catalysts, showing that this strategy is possibly applicable to other reactions and can address major roadblocks associated with industrial metathesis processes.

DOI: 10.1038/s41586-023-05897-w

Source: https://www.nature.com/articles/s41586-023-05897-w