Impact of the diffusion limitation in microphotoreactors

Tristan Aillet (1) , Karine Loubiere (1) , Laurent Prat (1) , Odile Dechy-Cabaret (2)

1 LGC - Laboratoire de Génie Chimique
2 LCC - Laboratoire de chimie de coordination

This publication describes a model that aims (1) to predict the performances (conversion, photonic efficiency) of a photochemical reaction at the outlet of a microreactor. To achieve this, a set of equations that couple mass transport, radiative transfer, and kinetic equations is established and solved, considering (1) a two-dimensional geometry and (2) a simple monomolecular photoreaction A -> B-hv, where the species A and B are in competition for absorbing incident photons. The model is expressed using classical dimensionless numbers, such as the Damkohler I and II numbers, the absorbance, and the competitive absorption factor. The results show how and why, when competitive absorption exists, the occurrence of diffusion limitations (Da(II) > 1) can severely impact the conversion of the photochemical reaction and the photonic efficiency. Consequently, a diagram is proposed as a practical tool for selecting operating conditions subsequently avoiding these limitations.

Domaines: Chimie de coordination

Tristan Aillet, Karine Loubiere, Laurent Prat, Odile Dechy-Cabaret. Impact of the diffusion limitation in microphotoreactors. AIChE Journal, 2015, 61 (4), pp.1284-1299. ⟨10.1002/aic.14718⟩. ⟨hal-01910077⟩