What is Flow Chemistry?
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Flow chemistry is a simple yet powerful technique: a chemical reaction is run in a continuously flowing stream, in opposition to a static volume contained in a vessel. Fluids containing the various reagents are pumped to join into a mixer and be submitted to different experimental conditions (such as heating, cooling, pressure etc.), in order to react.
The main advantage of this new concept is that molecules enter, react and leave the system hence avoiding sustained exposition to conditions that would eventually lead to side reactions, by-products or impurities formation, etc.
In terms of reactivity, the strength of flow chemistry originates from the mixing. At large scale, mixing becomes much more powerful and heat exchange surface much more favorable than in a batch operation.
Doubling reaction size multiplies the surface by only 4, but the volume by 8. This volume-surface ratio is specially critical when hot spots arise (low temperature reactions), or when build-up next to the vessel’s walls (high temperature reactions): temperature of the fluids is thus homogeneous.
Using silica-supported products in flow chemistry applications will ensure the following:
- Increase in R&D and manufacturing productivity
- Much higher reproducibility during scale-up because there is no issue of volume:surface ratio
- Precise control of mixing & temperature
- Minimal risk associated with hazardous reagents
- Separation of the catalyst from the products alleviates the need for any filtration (or further handling)
- SiliaBond, SiliaCat and SiliaMetS can be used without degradation
Importance of Flow Chemistry
Flow chemistry is a relatively new technique that is being used more and more for large scale manufacturing because it only requires a small investment but enables the production of large quantities in shorter time and less space.
The use of supported catalysts in flow chemistry is even more recent. Supported catalysts are available on different supports such as polymers, charcoal, alumina and silica. They offer many advantages over the traditional homogeneous catalysts, including ease of handling and purification.
Silica presents many advantages such as no swelling, good mechanical and thermal stability and ease of scalability. SiliCycle has developed innovative silica-based catalysts (SiliaCat), reagents (SiliaBond) and metal scavengers (SiliaMetS) that can be used in flow chemistry.