Raman-Spectroscopy for Measuring Chemical Reactions in Micro Reactors

Abstract

EXTENDED ABSTRACTMicro heat exchangers, micro mixers and micro reactors have gained importance in chemical, pharmaceutical and life sciences applications. Due to the large surface to volume ratio these devices provide efficient mass and heat transfer. This results in greater selectivity and higher yield for chemical reactions. The Institute for Micro Process Engineering is working on the development, manufacturing, and testing of micro channel devices mainly manufactured of stainless steel, where channel widths and depths lie in the range of 0.2 mm.In order to obtain a better understanding of the physical and chemical processes within such components and to optimize these devices it is necessary to get a look into these micro channels during a mixing process or a chemical reaction. For this purpose laser Raman spectroscopy can be applied. This method is very selective for individual chemical compounds and allows a spatial resolution better than 0.01 mm. Figure 1 shows the experimental setup. The light of an air cooled cw argon ion laser is focused by a microscope objective into a micro channel, measuring the Raman bands over its cross section at several distances from the mixing point. A spectrograph with a CCD-array detects the Raman light, which consists of lines that are characteristic for the chemical compounds flowing through the micro channels and can therefore be used to calculate their concentrations. Figure 1 -Experimental setup for Raman spectroscopy. Raman-SpectrumLaser Micro-Mixer Downloaded From: http://proceedings.asmedigitalcollection.asme.org/ on 03/28/2015 Terms of Use: http://asme.org/terms

Combined measurement of concentration distribution and velocity field of two components in a micromixing process

“…A commercial Raman microscope was used to monitor the concentration profiles during the synthesis of ethyl acetate within a micromixer, which consists of silicon and Pyrex (Fletcher et al 2003). Some more applications emerge in the literature dealing with this issue (Lee et al 2003;Leung et al 2005;Ewinger et al 2008). However, in these approaches only the spectral information or their temporal evolutions have been used.…”