Reaction Monitoring of Heterogeneously Catalyzed Hydrogenation of Imines by Coupled ATR-FTIR, UV/Vis, and Raman Spectroscopy

Autor: Navid Nemati, Angelika Brückner, Ursula Bentrup, Leif R. Knöpke, Angela Köckritz
Rok vydání: 2010
Předmět:
Zdroj: ChemCatChem. 2:273-280
ISSN: 1867-3899
1867-3880
DOI: 10.1002/cctc.200900273
Popis: Coupled ATR-FTIR, UV/Vis, and Raman spectroscopy has been introduced for the monitoring of liquid phase hydrogenation reactions under elevated H2 pressure by implementation of spectroscopic immersion probes into a modified autoclave reactor. The setup was successfully tested for the heterogeneously catalyzed hydrogenation of several imine substrates under H2 pressures up to 20 bar. The conversion of the imines could be analyzed by Raman spectroscopy and the product formation was observable by attenuated total reflectance FTIR spectroscopy (ATR-FTIR), which illustrates the benefits of coupling complementary spectroscopic methods. Separate spectroscopic investigations show that imines intensively interact with the phosphoric acid ester that is used as catalyst modifier, indicated by a shift of the original ν(CN) band of the imine to higher wavenumbers. UV/Vis spectroscopic investigations reveal a distinct shift of the absorption edge to a higher wavelength. Furthermore, the formation of adsorbates on the surface of used Pt/Al2O3 catalysts, resulting mainly from adsorbed imine, was detected by FTIR spectroscopic analysis. The potential of UV/Vis spectroscopy in transmission mode for analyzing the organic components was tested. Due to its high sensitivity at low concentrations this method offers an additional possibility for a quantitative in situ analysis of the reaction progress in real time.
Databáze: OpenAIRE
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