Within the scope of the Helmholtz Research Programs processes are investigated. Processes with several phases side by side are widespread in chemical engineering. Often conversion and selectivity are limited by mass transport. The challenge is to bring the reaction partners and possibly the catalysts in good contact and thereby use the reactor volume effectively. 

One method for process intensification is the generation of very thin films or fluid filaments. This can be achieved e. g. using microstructured instruments with distributed gas support or micromixers. An optimized feeding of the fluidic phases is essential for a success. 

Because the residence time in micromixers or microreactors often is very short, special techniques for monitoring of the reactions are needed. For this purpose, at IMVT laser Raman spectroscopy was applied and optimized. It allows the measurement of concentrations of chemical components in-situ, e. g. between two gas bubbles in a Taylor flow (picture).

The following gas-liquid reactions were investigated and characterized:

• Hydrogenation of nitrobenzene to aniline
  • This reaction was investigated as part of the Helmholtz Research Programs.
• Oxidation of toluene with air
  • Important for this process is, besides an intensive contacting of the phases, a good control of the residence time to avoid consecutive oxidations. The control of the residence time is an advantage of micro process engineering, too.
• Oxidation of hydrocarbons with oxygen
  • Examples are the oxidation of cyclohexane and the oxidation of isobutane, which was also investigated as part of the Helmholtz Energy Alliance. 
• Emulsions
  • Emulsions are investigated as method for contacting liquid-liquid systems. For a characterization of emulsions rheological methods are used. Furthermore, static and dynamic light scattering is applied for measuring particle sizes (see flex3 project).