With the help of high-speed camera and micro particle image velocimetry (µ-PIV) techniques, it was identified that the increasing inert gas fraction resulted in more stable segmented flow with shorter liquid segments, favoring the reaction rate. The photocatalytic reaction performance was very sensitive to the gas-liquid-solid segmented flow conditions, which needed to be carefully tuned. The effects of various reaction parameters (temperature, light source power, catalyst content) in the continuous system were examined, and the reaction kinetic was found in first order. Compared with the batch reactor, the photocatalytic reaction rate was greatly improved in the microreactor, and the reaction time was shortened from 180 min of the batch to 7.5 min for near-full conversion of nitrobenzene. In this work, the gas-liquid-solid segmented flow was employed in the photocatalytic production of azo- compounds (azoxybenzene and azobenzene) from nitrobenzene using graphitic carbon nitride (g-C3N4) as solid catalyst. The increase of substrate concentration would lead to the addition reaction between styrene cationic intermediates with styrene, thereby decreasing the selectivity of 2-phenylethanol.ĭifficult handling the solid catalysts remains one of the pain points in the continuous flow photochemistry. The optimal photosensitizer concentration was 2 %. The maximum productivity of 2-phenylethanol was 0.122 mol/(L.h), which was 2.5 times higher than that obtained in test tube under the same reaction conditions and 34 times higher than that reported in previous literature. The continuous flow microreactor permitted to ensure more uniform light intensity and larger specific surface area, the reaction rate could thus be enhanced. The effects of light source shape, reaction temperature, substrate concentration and catalyst concentration on the reaction were investigated. The present work aims to intensify this reaction in continuous flow microreactor with comparison to traditional batch reactor. However, this reaction usually takes ten or even dozens of hours, facing the problem in scale up. The visible light catalyzed anti-Markovnikov hydration of styrene is a single-step reaction using non-toxic catalyst under mild conditions. The 2-phenylethanol production by traditional chemical methods requires multi-step reactions, in which harsh conditions such as high temperature or strong acid/base are required and undesired by-products are easily produced.
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