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An asymmetric Paternò–Büchi-type photoreaction between 2,3-dimethyl-2-butene and benzoylformic acid ester with a chiral menthyl auxiliary was studied in a continuous-flow microcapillary reactor. The fluorinated ethylene propylene (FEP) microcapillary reactor using normal one-layer flow mode gave oxetane products with better efficiency than the batch system. In addition, the slug flow mode in microcapillary reactor using inactive reagent, N2 gas or H2O, improved the reaction efficiency dramatically because of synergistic light dispersion, stirring and thin layer film effects. The reaction efficiencies under each condition were discussed as energy efficiencies calculated from reactors' parameters.

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Based on previous work studying complex microreactors, it was desired to further improve the mixing efficiency by varying the mixing unit design for fast liquid—liquid reactions. Different flow regimes were studied, including slug flow, parallel flow, and drop flow. The two-phase hydrolysis of 4-nitrophenyl acetate in sodium hydroxide solution was used to evaluate the overall volumetric mass transfer coefficients (K org a) as a function of the average rate of energy dissipation (ε) for each microreactor design and all flow regimes. The liquid—liquid systems investigated used n-butanol or toluene as the organic phase solvent and a 0.5-M NaOH aqueous solution. The use of surfactant was also investigated with the toluene—water system. All microreactor geometry designs were based on contraction—expansion repeating units with asymmetric obstacles to aid the breakup of slugs and desynchronize the recombination of split streams. The investigated designs were chosen to avoid the formation of the parallel flow regime, contrary to curvature-based mixing-unit designs. The microreactor design can then be optimized to reduce the ε required to reach drop flow, since K org a has been found to be constant at equal ε for a given solvent system in this flow regime, regardless of the reactor selection. Additionally, the “3/7th” scaleup rule was applied and confirmed with the LL-Triangle mixer. It was found that, for low interfacial-tension systems (i.e., n-butanol—water), the onset of drop flow occurred at a lower ε for the LL-Triangle mixer when compared with the Sickle or LL-Rhombus mixers.

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Journal 2012 , 179 , 330 – 337 . “ Direct carbonylation of nitrobenzene to phenylisocyanate using gas-liquid slug flow in microchannel ” Takebayashi , Y. , Sue , K. , Yoda , S. , Furuya , T. , Mae , K. Chemical

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] quantum dots (QDs) is also reported where nucleation, growth, and functionalization stages can be separated in a hydrodynamically controlled environment in supercritical ethanol and hexane, respectively. The use of a supercritical solvent [ 30 ] or slug

Open access