IngentaConnect Applicability of Fiber-Optic-Based Raman Probes for On-Line React...

Authors: Hamminga, Gerben M.¹; Mul, Guido¹; Moulijn, Jacob A.¹

Source: Applied Spectroscopy, Volume 61, Issue 5, Pages 94A-102A and 459-569 (May 2007) , pp. 470-478(9)

Publisher: Society for Applied Spectroscopy

Abstract:

This study evaluates the applicability of fiber-optic-based Raman probes for on-line reaction monitoring of high-pressure catalytic hydrogenation reactions in batch autoclaves. First, based on trends in the strong intensity of the 945 cm⁻¹ C-O-C vibration of 1,3-dioxolane, the effect of various experimental parameters on sensitivity was evaluated and can be summarized as follows: (1) above 500 rpm a linear increase in stirring speed induces a linear decrease in Raman intensity; (2) a linear increase in hydrogen pressure also leads to a linear decrease of the Raman signal; (3) linear temperature elevation exponentially decreases the Raman intensity; and (4) increasing the catalyst particle concentration results in a steep nonlinear decrease of the Raman signal. Light scattering by gas bubbles, or combined scattering and absorption by (black) catalyst particles, reducing the amount of light collected by the optical fiber probe, explain the observed experimental trends. Second, the sensitivity of Raman spectroscopy was directly compared with attenuated total reflection-Fourier transform infrared (ATR-FT-IR) spectroscopy in the analysis of three different hydrogenation reactions over a Cu-ZnO catalyst. From the applied target molecules, diethyl maleate hydrogenation could be very well analyzed by Raman spectroscopy due to the high Raman scattering efficiency of the C=C bond, while for analysis of the hydrogenation of γ-butyrolactone or 1-butanal, ATR-FT-IR is the technique of choice.

Keywords: RAMAN SPECTROSCOPY; ATTENUATED TOTAL REFLECTION; FOURIER TRANSFORM INFRARED SPECTROSCOPY; ATR-FT-IR SPECTROSCOPY; MULTIPLE TECHNIQUES; FIBER-OPTIC PROBE; HETEROGENEOUS LIQUID-PHASE CATALYSIS; HYDROGENATION; CU-ZNO; GAMMA-BUTYROLACTONE; DIETHYL MALEATE

Document Type: Research article

DOI: 10.1366/000370207780807768

Affiliations: 1: Reactor and Catalysis Engineering, Delft University of Technology, Julianalaan 136, 2628 BL, The Netherlands

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Applicability of Fiber-Optic-Based Raman Probes for On-Line Reaction Monitoring of High-Pressure Catalytic Hydrogenation Reactions