Recently, tremendous progress has been achieved in developing low-cost and efficient electrocatalysts for the chlorine evolution reaction (CER). However, the drawbacks of the DSA such as high cost, inferior selectivity and detrimental effects on the environment cannot meet the demand of modern industries. In the past half a century, the dimensionally stable anode (DSA) made of RuO2and TiO2coated on the Ti substrate is the most widely used catalytic electrode for chlorine oxidation. Photocatalytic oxidation of benzyl alcohol by molecular oxygen became quick when high-power LED irradiation was employed.Ĭhlorine gas is one of the most basic chemicals produced through electrolysis of brine solution and is a key raw material in many areas of industrial chemistry. We also applied flow technologies for photo-bromination and chlorination of C–H bonds. Photo-induced reductive 5-exo-dig radical cyclization and reduction of alkenyl halides proceeded smoothly, thanks to the combination of a photo flow reactor and low-pressure Hg lamp. Photo-redox-catalyzed alkene alkylation proceeded within a shortened reaction time when the same photo flow reactor and white LED were used instead of a batch reactor. We used a photo-flow set-up, consisting of stainless steel engraved microchannels covered by a quartz top (MiChS L-1) and a sodium lamp, for the isomerization of a fulleroid to PCBM. However, the energy profile of these reactions was improved further by the use of LED lights. Again the use of blacklight was successful. Then we examined Barton nitrite reaction using a photo flow reactor consisting of stainless-steel channels and a quartz glass top provided by DNS. We started with the flow update of traditional cycloaddition using Mikroglas Dwell device as a flow reactor and a compact light source, such as blacklight, instead of a high-pressure mercury lamp. In this article, we discuss how effective photo-induced organic reactions became when applied evolving photo flow technologies through our experiences over these two last decades. We found that the substrate contamination with water negatively influenced the performance of the C–H chlorination. At a higher conversion of ethylene carbonate such as 61%, the selectivity for monochlorinated ethylene carbonate over dichlorinated ethylene carbonate was 86%. Near-complete selectivity for single chlorination required the low conversion of ethylene carbonate such as 9%, which was controlled by limited introduction of chlorine gas. The partial irradiation of the flow channels also sufficed for the C–H chlorination, which is consistent with the requirement of photoirradiation for the purpose of radical initiation. Such short time of exposition sufficed the photo C–H chlorination. When ethylene carbonate was introduced to the reactor, the residence time was measured to be 15 or 30 s, depending on the slope of the reactor set at 15 or 5°, respectively. The setup employed sloped channels so as to make the liquid phase thinner, ensuring a high surface-to-volume ratio. A novel photoflow setup designed for a gas–liquid biphasic reaction turned out to be useful for the direct use of chlorine gas. We report the high-speed C–H chlorination of ethylene carbonate, which gives chloroethylene carbonate, a precursor to vinylene carbonate.
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