COMBUSTION OF METHANE OVER LA0.66SR0.34NI0.3CO0.7O3 AND LA0.4SR0.6FE0.4CO0.6O3 PREPARED BY FREEZE-DRYING

A kinetic study of methane combustion at low temperatures (648 to 923 K) over La0.66Sr0.34Ni0.3Co0.7O3 and La0.4Sr0.6Fe0.4Co0.6O3 perovskites, both prepared by spray-freezing/freeze-drying, has been carried out to determine the kinetic parameters for simple models suitable for use in reactor design and in reactor performance evaluation. The two tested models, a simple first-order model r = k . P(CH4), and a two-term model r = (k1 + k2 p(O2)0.5) P(CH4) are related to the redox mechanism. The first-order model gave a good fit to the experimental data for La0.66Sr0.34Ni0.3Co0.7O3 and was found adequate also for La0.4Sr0.6Fe0.4Co0.6O3. However, in the case of the latter catalyst the experimental data were best described by a Mars-van Krevelen model. The activity of the two catalysts is very good and stable, but the nickel-based catalyst is more active.