American Chemical Society
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Kinetics of n‑Butanol Partial Oxidation to Butyraldehyde over Lanthanum–Transition Metal Perovskites

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journal contribution
posted on 2012-10-31, 00:00 authored by Bing-Shiun Jiang, Ray Chang, Yi-Chen Hou, Yu-Chuan Lin
Partial oxidation of butanol to butyraldehyde over a series of LaBO3 (B = Mn, Fe, and Co) perovskites was investigated in a continuous fixed-bed system under ambient pressure. Physicochemical properties of catalysts were characterized by X-ray diffraction, H2 temperature-programmed reduction, and temperature-programmed oxidation. LaMnO3 was more favorable to be reduced and reoxidized than LaFeO3 and LaCoO3. Catalytic results have indicated that all catalysts show similar butanol and oxygen conversions and over 90% butyraldehyde selectivities below 300 °C. Side reactions such as butanol or butyraldehyde combustion could be enhanced at high temperatures. To gain an in-depth understanding of perovskite’s chemistry involved, kinetic analysis has been carried out. Eight reaction pathways based on the Mars–van Krevelen redox cycle were proposed. These pathways have been lumped and associated with the Langmuir–Hinshelwood–Hougen–Watson formalism to derive a set of rate equations. Parameter estimation via nonlinear regression of derived rate equations has shown that surface reaction, evolving chemisorbed butanol and oxygen, is probably rate-determining. The estimated activation energy of LaMnO3 (15.0 kcal/mol) by assuming surface reaction as the rate-limiting step was the lowest among all perovskites. This can be ascribed to the better redox property of LaMnO3, thereby decreasing the energy barrier in butanol partial oxidation.