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

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.