The Parallel-Series Kinetic Model Approximation

These experimental observations call for a different mechanism than that proposed by Okamoto et al. (1985a). This parallel-in-series mechanism considers both in-series reaction steps where OH groups are progressively incorporated in the phenol molecule and in the phenolic derived species, and parallel steps where the phenol molecule is being photo converted in oxidation steps of different strength. This parallel-series mechanism can be justified given the possible existence of a distribution of oxidation strengths of the photocatalytic sites. 

The proposed parallel-series mechanism is summarized in Figui e 5.2 and involves the following steps 

FIGURE 5.2. Pi oposed parallel-series reaction model based on the evolution of observable species on the liquid phase. Full anows represent experimentally supported steps, whereas broken anows represent possible steps, experimentally unconfirmed (Reprinted from Chem. En. Set, 59, M. Salaices, B. SeiTano and H.I. de Lasa, Photocatalytic conversion of phenoiic compounds in sliUTy reactors, 3-i5, Copyright 2004, with permission from Elsevier). 

The kinetic modeling of the photocatalytic conversion of phenol, involves important assumptions, 

Concerning assumption c) and d) they can be justified on the basis of the studies and obseivations of Okamoto et al. (1985b). 

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