Towards practical application of lanthanum ferrite catalysts for NO reduction with H2

A series of perovskite-type catalysts (LaFeO3, La0.8Sr0.2FeO3, Pd/La0.8Sr0.2FeO3, La0.8Sr0.2Fe0.9Pd0.1O3, La0.7Sr0.2Ce0.1FeO3, Pd/La0.7Sr0.2Ce0.1FeO3 and La0.7Sr0.2Ce0.1Fe0.9Pd0.1O3) has been prepared by the solution combustion synthesis method and fully characterized by XRD, BET, FESEM and TPD/R analyses. The performance of these catalysts towards the NO reduction mechanism by H-2 has been evaluated in a temperature-programmed reaction apparatus (TPRe) in the absence and in the presence of oxygen. The catalysts have been studied in the 25-350 degrees C temperature range, and significant catalytic activities were measured at 150-250 degrees C. Among the catalysts screened, La0.8Sr0.2Fe0.9Pd0.1O3, showed the best performance. Hence, it was deposited directly over a ceramic honeycomb monolith by in situ SCS, tested in a lab-scale test rig, then submitted to the specific ageing protocol (thermal treatment at 500 degrees C for 96 h) in the presence of water vapour and sulfur dioxide, two potentially deactivating species present in diesel exhaust gases, and it showed a good compromise between satisfactory catalytic activity and stability. A mechanistic analysis is presented concerning the relationship between the observed activity and the reducibility of the B site, determined through TPR experiments. Some final conclusions are drawn on the perspective of the practical application of the investigated aftertreatment route for diesel exhaust gases. (C) 2009 Elsevier B.V. All rights reserved.