An efficient production of pyruvate by the oxidative dehydrogenation of lactate is achieved using a micro flow system based on gas−liquid slug flow. In this micro flow system, oxidizing agents and acetonitrile solutions of lactates and vanadium species are used, and lactate is converted into the corresponding pyruvate. For reasons of atom economy and enhanced mass transfer of oxygen into the liquid phase, due to internal circulation flow within slugs, molecular oxygen is the preferred agent. In a catalyst screening, vanadium oxytrichloride (VOCl3) gave the highest pyruvate yield. A continuous system is developed, consisting of the following two processes using T-shaped mixers: the mixing of an acetonitrile solution of lactate with that of VOCl3 and the injection of oxygen gas into the solution mixture. Compared with the conventional batch system, the oxidative dehydrogenation of lactate to the corresponding pyruvate proceeds more effectively using this micro flow system.

Catalytic oxidation of methacrolein (MAL)

a b s t r a c tThe use of a gas-liquid slug flow in a microreactor has several advantages such as a large surface area for contacting gas and liquid phases and circulation flow inside slugs. These advantages accelerate the mass transfer between the two phases, resulting in a high concentration of dissolved gas. The enhanced mass transfer is useful in carrying out liquid phase oxidation that uses oxygen gas as the oxidizing agent. The gas-liquid slug flow in a microreactor system is applied to the oxidation of ethyl lactate using an oxyvanadium species for producing ethyl pyruvate. The reactor system includes two T-shaped micromixers: one for mixing the substrate with a catalyst solution and the other for generating slug flow by the addition of oxygen. The oxidation reaction proceeds right after the slug flow is generated in the second mixer, because the substrate and the catalyst mix rapidly in the first micromixer. Moreover, a high concentration of dissolved oxygen due to improved mass transfer in slug flow increases the oxidation reaction rate. Therefore, compared to a batch reaction, the synthesis using slug flow provides high yields of ethyl pyruvate per unit time and achieves satisfactory productivity at the reaction temperature of 323 K, which is lower than that employed in conventional syntheses. The proposed system enables the production of ethyl pyruvate using a simple reactor setup with reduced energy consumption.

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