(8c) Photochemical Synthesis in a Microreaction System

Recently, microreaction systems have been successfully applied to a wide range of chemical transformations utilizing the features unique to microspace. However, only a small number of studies have been made so far on photochemical reactions conducted in microreactors. Thus we are investigating organic photoreactions in microreactors.

One can expect microreactors to exhibit some advantages on photoreactions, such as higher spatial illumination homogeneity, better light penetration through the entire reactor depth and larger illuminated surface area per unit volume in comparison to large-scale reactors. It was revealed that efficiency and selectivity of some photocycloaddition and asymmetric photosensitized reactions can be greatly enhanced in comparison to the results obtained in batch reaction systems by utilizing the features unique to microspace.

We have further developed a photocatalytic microreaction system by immobilizing a photocatalytic TiO2 layer on inner walls of microfabricated channels and photocatalytic alkylation of amines, water-splitting, and reduction of carbon dioxide processes were examined under multiphase flow condition. Though numerous attempts have been made on multiphase catalytic reactions, there are still difficulties on conduction the reactions due to the low reaction yield arising from very low efficiency of interaction and mass transfer between different phases. To produce high interfacial area between the phases, we introduced a sample solution and gas into a microchannel to form gas-liquid-solid multiphase flow. The model reactions proceeded quite rapidly with considerably large efficiencies under gas-liquid-solid multiphase flow condition as compared to those in batch reaction systems. The result may arise from very high efficiency of interaction and mass transfer between different phases in the microreaction system.

References

[1] Y. Matsushita, T. Ichimura, N. Ohba, S. Kumada, K. Sakeda, T. Suzuki, H.Tanibata, and T. Murata, Pure Appl. Chem., 79, 166-171 (2007).

[2] Y. Matsushita, A. Murata, T. Murata, H. Tanibata, T. Suzuki, T. Ichimura, Micro Total Analysis System 2007, 2, 1462-1464 (2007).

[3] Y. Matsushita, N. Ohba, S. Kumada, K. Sakeda, T. Suzuki, T. Ichimura,　Chem. Eng. J, 135, S303-308 (2008).

[4] Y. Matsushita, N. Ohba, T. Suzuki, T. Ichimura, Catalysis Today, 132, 153-158 (2008).