The Extended Use of Actinometry in the Interpretation of Photochemical Reaction Engineering Data

Abstract

Actinometry is an old and useful method developed in the chemistry field to estimate the amount of photons entering and being absorbed in a reaction cell filled with a well-known reacting system. As it is usually used it is of reduced suitability for intrinsic kinetic studies aimed at scaling-up purposes. However, in photochemical reaction engineering analysis it can be of invaluable help if it is properly applied to accurately calculate the boundary condition that is needed to solve the radiative transfer equation in laboratory photochemical reactors dedicated to obtain intrinsic kinetic parameters. This contribution shows the way that actinometric measurements can be used as one of the most precise and simple methods to estimate the above mentioned boundary condition for both homogeneous and heterogeneous systems, an indispensable parameter to calculate with precise models based in the general radiation transport equation, the light distribution inside the reaction space. This local property is needed to formulate the initiation step of any photochemical reaction scheme when operation is made in the kinetic control regime. Consequently it will be always included in any properly developed complete reaction kinetic model. The proposed extended application is illustrated with one example employing a reactor used in photocatalytic reactions.