In situ Raman spectroscopy to monitor the hydrolysis of acetal in microreactors

Abstract

In order to obtain a better understanding of the physical and chemical processes within micromixers or microreactors and to optimize these devices it is necessary to monitor the concentrations within the microchannels. To get chemical information, laser Raman spectroscopy can be used. This method is very selective for individual chemical compounds, allows a spatial resolution of 10 lm within fluids and a quantitative analysis. We examined the hydrolysis of the acetal 2,2-dimethoxypropane to acetone and methanol in the presence of hydrogen ions as catalyst. This reaction can be used to characterize micromixers. The aim of this work is the in situ monitoring of concentrations of acetal and its products, acetone and methanol, during the hydrolysis of acetal within a T-shaped micromixer with a channel width of 0.4 mm and a channel depth of 0.2 mm. In these experiments a continuous-wave argon ion laser was used as an excitation source. The laser radiation was coupled into a microscope and into the micromixer covered with a quartz plate. A special microscope objective was used. It allows the correction of optical aberrations resulting from quartz plates up to a thickness of 2 mm. Concentration profiles of acetal, methanol, and acetone were measured across the width of the microchannel.

Simultaneous In Situ Measurement of Oxygen Consumption and Product Formation during Oxidation of Cyclohexane

“…Der optische Versuchsaufbau basiert auf Arbeiten von Rinke et al [13] , und von Sauerstoff bei 1559 cm -1 während der Cyclohexanoxidation, bezogen auf den jeweiligen Referenzpunkt, für verschiedene mittlere Verweilzeiten dargestellt. Trotz der geringen Konzentrationen von < 2 % bei den geringen Umsätzen < 6 % sind die charakteristischen Peaks quantitativ auswertbar.…”

Development of an on-line Raman spectral analytical method for monitoring and endpoint determination of the Cornu Caprae Hircus hydrolysis process

“…Currently selected conventional offline amino acid analysis methods that use high‐performance liquid chromatography (HPLC) or an amino acid analyser are not suitable for process monitoring, mainly due to long intervals between sampling and obtaining analytical results caused by time‐consuming procedures. In recent years, in a variety of fields, the hydrolysis process has been studied and monitored by different spectroscopic sensors, including near‐infrared (NIR) spectroscopy, infrared (IR) spectroscopy, Raman spectroscopy, ultraviolet–visible (UV–Vis) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy and other spectroscopic sensors . In the TCM pharmaceutical industry, NIR spectroscopy‐based methods were developed by Wu et al .…”

Characterization of a Raman Spectroscopic and Holographic System for Gas‐Liquid Flows in Microchannels

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