In organic syntheses, a desired product is often formed via unstable intermediates. The intermediates are changed into by-products in a quite short time. For increasing the selectivity of the desired product, it is required to react the intermediates with reactants immediately after the formation of the intermediates under precisely controlled temperature. To realize such reaction operation, we need a reactor realizing rapid mixing and heat transfer and short residence time. Microreactor has a high mass and heat transfer efficiency due to its large surface area to volume ratio. The miniaturization of a reactor also leads to a reduction of residence time in a reactor. These advantages offer an opportunity to satisfy these requirements.

In this context, we have developed a reactor for multi-step organic syntheses including the formation of intermediates with improved selectivity of desired products. We call this reactor “assembled reactor.” This reactor consists of mixing, residence time (reaction) and heat exchange units. Connection of these three units forms a module for a single reaction. Repeated joint of modules enables the reactor to be used in multi-step syntheses. We can flexibly replace the units or add units according to elementary reactions of a synthesis. This reactor is made of stainless steel (SUS316) and polyimide resin (CEPLA). The polyimide resin acts as heat insulator. The units made of the resin are embedded between the units having inlets of reactants to control feed temperatures of reactant fluid and reaction temperatures independently. The units are connected without tubing. This connection enables a short residence time between consecutive reactions. For using this reactor in industrial production with a high throughput, we designed the channel sizes to be on the order of several hundred micro meters.

We have examined the usefulness of the assembled reactor from the viewpoint of mixing and heat transfer rate. For the study of mixing performance, we used the Villermaux/Dushman reaction. For the study of heat transfer rate, we performed the heat exchange between hot water and cold water with temperature difference from 20–40 K.

The results showed that this reactor enables rapid mixing under the total flow rates of more than 30 mL/min and heat transfer efficiency of the order of 10 K per 10 ms under this range of temperature difference. Through this study, we have confirmed the effectiveness of the developed reactor for the use in industrial production. This reactor also contributes to design a reactor according to each elementary reaction. The example of multi-step synthesis using this reactor will be presented at the conference.