(8b) Modular Micro Reaction Plant for Photochemical Reactions

Micro reaction technology provides the unique possibility to perform chemical reactions in safe, economical and ecological way. The concept of such a micro chemical plant will be described. The used micro fluidic devices are made from glass, because of its ideal properties like chemical stability. For the same reason, all modules to run a glass micro reactor, e.g. pumps, valves, tubing, temperature-, pressure-sensors, analytical modules, and safety installations use materials with the same chemical stability. Glass for micro reactors is not only a perfect inert material, it also allows light transmission. It is therefore a perfect tool for photochemistry. Photochemical applications in actual production are well known. Usually, they are performed in a big vessel with a lamp hanging into the solution of the reaction components. Even though it is heavily stirred, the reaction time can reach several hours. The reason for this is, that the photons are absorbed by the solution within several 10 µm. Therefore, only a small portion of the reaction volume has the chance to see the light. The absorption length can be increased by diluting the solution, by working with lower concentrations. But this has in the end the same effect: the throughput per given time is low. Micro reactors can optimize the reaction by providing channels with a depth in the necessary range. Channel depths of several 10 µm allow all molecules to absorb photons. With this, the residence time to achieve a good yield of the reaction can be shortened. A laboratory plant will be demonstrated, which shows these advantages. As a light source a special lamp from Heraeus Noblelight has been used. If necessary, the reaction mixture can be send several times through a loop in front of the light source. A special IR-sensor allows to measure the status of the reaction, and will open a valve, when the expected conversion has been detected. With this procedure, the output and yield of the reaction can automatically be optimized. The first prototype of such a plant and the first results will be shown in the presentation. The authors would like to thank the German Ministry for Education and Research for funding parts of this work.