Date: 5 August 2021 | Category: News
Here we present our latest application note: “Application Note 71: Photochemistry – Process development and scale up to kilos/day” featuring Vapourtec 420 nm High Power LED”.
In this work, the ene-like reaction between singlet oxygen and citronellol was optimised and scaled up using a UV-150 photochemical reactor. A Gen-2 420 nm LED was initially used for reaction optimisation [1], and scaled up using a 420 nm High Power LED. By quadrupling the photonic load, a throughput of 1.4 kg/day was achieved.
When quantum yields are <1, radiant power determines throughput
In photochemistry, quantum yield (Φ) is a measurement of how efficient photons are being used in a reaction.
Reactions with Φ>1 (chain reactions), such as photochemical bromination, often involve the formation of radicals, prompting a cyclic process in which more radicals are formed, speeding up the reaction. In this case, the number of irradiated photons is not critical for the reaction’s throughput.
On the other hand, reactions with Φ<1 will not utilise all the photons effectively, requiring higher photonic flux for the reaction to proceed at an acceptable rate.
The versatility of the UV-150 photochemical reactor
The UV-150 photochemical reactor covers the widest range of wavelengths (from 220 to 600 nm). By offering low and medium pressure mercury lamps, as well as LEDs, our customers can use the UV-150 for polymer synthesis, photo-redox catalysis, or singlet oxygen formation.
Research Groups led by Prof. Dave MacMillan, Prof. Peter Seeberger, Prof. Cory Stephenson, Prof. Timothy Noël, Prof. Michael Oelgemöller, and Prof. Steven Ley (amongst others) have successfully demonstrated the potential to scale up these photocatalyzed reactions using continuous flow reactors.
Radiant power is usually the limiting “reagent” in the quest to increase the throughput in continuous flow photochemical reactions. To overcome this, in 2020, Vapourtec launched the High Power LED family, a drop-in replacement light source for the UV-150 that has more than triple the photon output compared with the standard lamp. With the same footprint, the UV-150 photochemical reactor cartridge can be can now deliver more photons per unit time.
Photochemical generation of singlet oxygen
Singlet oxygen (1O2) is a highly reactive oxidiser and can be photochemically generated using tetraphenylporphyrin (TPP) as photocatalyst. 1O2 can be used to oxidise alkenes into more added value products, peroxides or alcohols [1], [2]. The ene-like reaction of singlet oxygen with citronellol was used as example chemistry in this application note.
Duncan Guthrie, Vapourtec’s MD commented: “The UV-150 is our ever-evolving flagship reactor and, by developing new UV sources and new capabilities, we can extend the scope of it to new horizons. This application note demonstrates the efficacy of Vapourtec’s flow chemistry systems in process development. This ene-like reaction was optimised with our standard 420 nm LED, and with the optimised conditions, it was scaled up by using a High Power LED as the UV source, which has an irradiance power ~4 times that of our standard LED. We achieved a throughput of 1.4 kg/day, which extrapolates to more than half a tonne a year, which is impressive considering the small footprint of the UV-150.
References
[1] Vapourtec Ltd, “Application Note 43 – Singlet oxygen reaction in continuous flow, an example of an ene reaction,” 2017
[2] F. Lévesque and P. H. Seeberger, “Highly Efficient Continuous Flow Reactions Using Singlet Oxygen as a ‘Green’ Reagent,” Org. Lett., vol. 13, no. 19, pp. 5008–5011, Oct. 2011
To read more about the UV-150 click here
To read the application note featured in this article click here
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