Photocatalytic membrane reactors phase reaction

Tsuru T, Kan-no T, Yoshioka T and Asaeda M (2003), A photocatalytic membrane reactor for gas-phase reactions using porous titanium oxide membranes , Catal Today, 82,41-48. 

When a PMR equipped with a photocatalytic membrane with photoactive skin layer was appfied for gas phase reactions, an improvement in the efficiency of decomposition, compared to a conventional photocatalytic reactor with T1O2 film immobilized on a non-porous support, was observed (Tsuru et al., 2003). In the case of the photocatalytic reaction conducted in the PMR, all reactants permeate through the pores of the 1102 active layer, which results in more effective contact between the reactants and the photoactive I1O2 surface. Application of a membrane allows control of the residence time of the reactants, thus improving the reaction rate. Moreover, the transport of organic compounds to the IIO2 surface is enhanced by forced convection in addition to transport by diffusion, and a larger surface area could be utilized for the photocatalytic reaction when conducted in the PMR. 

There are two types of PMRs (i) PMRs with photocatalytic membranes, and (ii) PMRs with suspended photocatalysts. In the former, membrane fouling due to photocatalyst particles can be avoided and, moreover, the photocatalytic reaction can be conducted either in the feed or in the permeate. However, when the photocatalytic reaction takes place in an aqueous phase the efficiency of photodegradation is found to be lower than in case of the latter configuration. On the other hand, when gaseous phase reactions are considered, the reaction rate is found to be faster when using PMRs with suspended photocatalysts than when using reactors with photocatalysts fixed on a non-porous support. 

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