Catalytic activity for methane flameless combustion and thermal stability of nano-sized lanthanum cobaltites doped with Ce, Pr and Tb
|Alexander Y. Kryukov 1, Anatoly V. Vishniakov 1, Lucio Forni 2, Cesare Oliva 2|
1. D.I.Mendeleyev University of Chemical Technology of Russia (MUCTR), Miusskaya sq. 9, Moscow 125047, Russian Federation
High surface area nano-sized catalysts with general formula La0.9M0.1CoO3 (M=Ce, Pr, Tb) were synthesised by a novel flame-spray-pyrolysis method, based on spraying a solution of the corresponding metals salts (acetates in the present case, dissolved in propionic acid), together with oxygen, in a nozzle burner, where the mixed oxides particles form, followed by collection of the latter by means of an electrostatic precipitator.
All the prepared samples possessed the LaCoO3 perovskite-like structure and consisted of 30-60 nm particles, lumped into larger (80-200 nm) agglomerates. Their surface area ranged from 45 to 60 m2/g. All of the catalysts showed a very high activity for the methane flameless combustion, attaining 100% conversion at a temperature Tf (temperature of full conversion) ranging between 495 and 515°C, depending on the nature of the M doping ions. The results of life-tests did not show any decreasing of catalytic activity after 50 h under reaction conditions at Tf. Thermal stability under high temperature exploitation was investigated by overheating the catalysts two times for 1h at 800°C in flowing reacting gas mixture (fast deactivation cycles) and then measuring again methane conversion at Tf. All the catalysts showed a more or less considerable decrease of activity, depending on chemical composition. For example, conversion after the second cycle decreased from 100% down to 80% for LaCoO3 and to 48% for La0.9Tb0.1CoO3. Taking into account the results of SEM analysis, this was attributed to sintering, connected with Gibbs instability of nano-sized materials.
Presentation: Poster at E-MRS Fall Meeting 2006, Symposium B, by Alexander Y. Kryukov
See On-line Journal of E-MRS Fall Meeting 2006
Submitted: 2006-05-10 11:24 Revised: 2009-06-07 00:44
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