Olefin Metathesis Catalysis in Heterogeneous Systems

Olefin metathesis is a powerful carbon–carbon bond-forming reaction in which alkene fragments are reorganised via metal-alkylidene intermediates. In heterogeneous systems, active sites are typically isolated metal-oxide species dispersed on high-surface-area supports, such as silica, alumina or mixed oxides. These catalysts enable the production of light olefins (notably propene) and polymers, and offer advantages in terms of recyclability and process intensification compared with homogeneous analogues. Key challenges include the controlled generation of active alkylidene centres, maintenance of high dispersion to maximise site density, suppression of deactivation pathways (coke formation, sintering and leaching) and fine-tuning of support acidity and redox properties. Advances in synthesis methods, in situ spectroscopy and computational modelling have begun to unravel initiation mechanisms, reveal the role of surface functionalities and guide the design of more robust and selective solids.

Research from Nature Portfolio

Recent studies have elucidated the origins and mitigation of catalyst deactivation by coke in WO₃/SiO₂ metathesis systems. By physically mixing MgO with WO₃/SiO₂, researchers showed that the nature and temperature of coke species depend critically on support composition. At elevated temperatures (450 °C), metathesis activity predominates and coke deposits at higher temperatures, whereas at lower temperatures (300 °C) hard coke forms via butene dimerisation and isomerisation pathways. The introduction of MgO alters the reaction network and suppresses formation of intractable carbonaceous species, thereby prolonging catalyst life and reducing the frequency of regeneration cycles.

Olefin Metathesis Catalysis in Heterogeneous Systems publication trend

The graph below shows the total number of articles in olefin metathesis catalysis in heterogeneous systems across all publications each year (not limited to Nature Index journals).

Technical terms

Olefin metathesis: Redistribution of carbon–carbon double bonds in alkenes by metal-alkylidene intermediates.

Heterogeneous catalysis: Catalytic reactions in which the catalyst exists in a different phase (usually solid) from the reactants (gaseous or liquid).

Active site: The specific location on a catalyst surface, often an isolated metal-oxide or metal-alkylidene species, where substrate conversion occurs.

Carbene (alkylidene): A divalent carbon species bound to a metal centre, essential for the metathesis cycle.

Silanol: A surface hydroxyl group (Si–OH) on silica supports that can interact with metal-oxide species to facilitate activation and initialise catalytic cycles.

References

1. Propylene Metathesis over Molybdenum Silicate Microspheres with Dispersed Active Sites. ACS Catalysis (2023).
2. Propylene synthesis via isomerization–metathesis of 1-hexene and FCC olefins. Catalysis Science & Technology (2021).
3. Role of Surface Silanols in Active Site Formation during Olefin Metathesis over a WO x /SiO2 Catalyst: A Computational Perspective. The Journal of Physical Chemistry C (2024).