Oxidation of Ethanol by Hydrogen Peroxide in a Modular Microreactor System
M. Krauta, A.Nagelb, K. Schuberta
a) Institute for Micro Process Engineering
Karlsruhe Research Center
Hermann-von-Helmholtz-Platz 1
76344 Eggenstein-Leopoldshafen
Germany
b) Bayer AG
Process Technology/Reaction Engineering
51386 Leverkusen
Germany
Klaus.Schubert@IMVT.FZK.DE
WWW.FZK.DE/IMVT
Prepared for presentation at the 2002 AIChE Spring National Meeting (IMRET 6 - 6th International Conference on Microreaction Technology), March 10-14, New Orleans, LA
Proposed topic: TBa05: Poster Session Microreactors as Tools in Chemical Research
Abstract
The iron(III)-catalyzed oxidation of ethanol by hydrogen peroxide to acetic acid is a highly exothermic reaction that was intensively studied by Hafke [1]. This makes it an ideal test reaction for microstructured reactors. Experiments were performed in a newly built test stand planned for a throughput of up to 10 kg/h, temperatures of up to 180 °C, and pressures of up to 10 bar.
We developed a modular microreactor system for this chemical reaction, which is parametrically sensitive and strongly exothermic. The modules consist of a micromixer and microreactors. The reactors are built as cross-flow devices. The reaction passage consists of 169 channels with cross-sections of 150 µm x 200 µm and lengths of 6 cm. The other passage, through which the reaction heat is removed, has 1960 channels with cross-sections of 150 µm x 200 µm and lengths of 1.8 cm each. The modules are flanged together, as a result of which a small dead volume is obtained between the modules. This prevents an uncontrollable temperature rise in this space. The complete microreactor system is built up by combining the micromixer and four reactor modules. The temperatures can be adjusted for each of the modules individually.
In a typical experiment, 1.2 l/h ethanol and 3.1 l/h hydrogen peroxide solution (30%) plus 50 ml/h of an acidic aqueous solution of Fe(NO3)3 serving as a catalyst were fed into the microreactor system. The temperatures in the four reactor modules were adjusted to 70 °C, 105 °C, 105 °C, and 20 °C respectively. The yield was 99.3% acetic acid with a complete conversion of both ethanol and hydrogen peroxide, thereby generating about 3.8 kW of heat. The steady state was achieved and the temperature was kept within narrow boundaries for each of the modules.
Thus, it has been shown that a highly exothermic fast liquid phase reaction can be performed isothermally in microstructured reactors.
References:
[1] C. Hafke, PhD thesis, Universität Stuttgart 1972.
http://www.aiche.org/conferences/techprogram/paperdetail.asp?PaperID=365&DSN=spring02