Practical Ferrioxalate Actinometry for the Determination of Photon Fluxes in Production-Oriented Photoflow Reactors

• Bavo Vandekerckhove^a
• Nicola Piens^b
• Bert Metten^b
• Christian V. Stevens^a
• Thomas S. A. Heugebaert*^a

• ^aSynBioC Research Group, Department of Green Chemistry and Technology, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Ghent, Belgium
• ^bAjinomoto Bio-Pharma Services, Cooppallaan 91, 9230 Wetteren, Belgium

Accurate determination of the photon flux is of major importance to evaluate and characterize photochemical reactor setups. Knowing the photon flux ensures reproducible reactor operation and facilitates predictable scale-up. Over the past years, flow reactors have proven to be the key enabling technology for photochemistry to become relevant on production scales. This is mainly due to the mitigation of the limited penetration depth of photons in typical batch reactors. However, due to the practical drawbacks of the widely accepted standard for photon flux determination (ferrioxalate actinometry) concerning precipitation and gas formation at higher conversion, reliable actinometry in flow reactors is still challenging. In this paper, three practical approaches for the ferrioxalate-based determination of the photon flux are presented, which address these problems. These “dimmed emitter,” “segment-based,” and “time-resolved” methods thus allow photon flux determination in flow reactors with higher irradiated volumes and more powerful light sources, which is of utmost importance in the context of future scale-up.

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