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

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.