Catalytic performance of La0.66Sr0.34Co0.2Fe0.8O3 perovskite in propane combustion: Effect of preparation and specific surface area

Abstract

Several compositions in a system of La1-x SrxCo1-y FeyO3-δ perovskites are known as very good electronic and ionic conductors, as well as excellent catalysts for hydrocarbon oxidation. In this study La0.66Sr0.34Co0.2Fe0.8O3 was selected as possibly the optimum composition. To assess the effect of preparation and calcination conditions on the activity in propane combustion, a series of different samples was prepared by a method based on slurry of reactive component precursors processed by freeze-drying. Three different materials were used as source of iron and the samples were aged at successively higher temperatures (1,153–1,343 K). The specific surface areas varied between 5.9 and 1 m2/g, depending on iron precursor and/or aging. The activity was determined in an integral U-shape reactor, typically for 1 and 2 vol% propane in air, with 1 g catalyst and 200 or 100 ml/min flowrate. Kinetics determined on the basis of a wider range of concentrations (1–4.3 vol% propane; 10 vol%-pure oxygen) for a selected, the least aged sample indicated that the propane catalytic combustion is best represented by a Mars van Krevelen model with 0.5 order in oxygen and the two kinetic constants having E app of 83 and 81 kJ/mol, respectively. For the aged samples, the pseudofirst order E app varied from 85 to 98 kJ/mol.