Solid catalyzed hydrogenation in a Si/glass microreactor using supercritical CO2 as the reaction solvent

We present the use of supercritical CO2 (scCO2) as reaction solvent in a packed bed silicon/glass microreactor in case of the hydrogenation of cyclohexene as a model reaction. In situ phase studies in the continuous flow of the reaction mixture, hydrodynamic characterization and the influence of pressure and temperature on the reaction performance are discussed. The results are compared with the same reaction conducted in three phase gas–liquid–solid state and larger scale reactors using scCO2 as reaction solvent. The phase study experiments show a single phase flow behavior at 136 bar and 25 °C for a 90:5:5 molar mixture of CO2:C6H10:H2. At 50 °C compositions up to 87.8:2.4:9.8 show single phase flow. The reaction performance increases with increasing temperature where pressure variations show no significant change. The comparison with larger scale systems indicates an increase of about one order of magnitude in space time yield in the presented microreactor.

Schematic representation of the used microreactor (top) with its different functionalities for solid catalyzed hydrogenation in a Si/glass microreactor using supercritical CO2 as the reaction solvent.Micrographs (bottom) of the reaction mixture in the microfluidic channel using a 20× objective before and after the scCO2 injection at 136 bar and 50 °C. The substrate to hydrogen ratio was 1:2.Figure optionsDownload as PowerPoint slide