N2O decomposition over perovskite catalysts

Four perovskite catalysts LaBO3 (where B = Cr, Mn, Fe, and Co) were prepared via a highly exothermic and self-sustaining reaction, the so-called solution combustion synthesis (SCS), and characterized by means of X-ray diffraction, BET, field-emission scanning electron microscopy-energy-dispersive spectrometry, and H-2-temperature-programmed reduction (TPR) analyses. The performance of these catalysts toward the decomposition of N2O to N-2 and O-2 was evaluated in a temperature programmed reaction (TPRe) apparatus in the absence and the presence of different oxygen concentrations. Among the catalysts screened, LaCoO3 showed the best performance, with 50% conversion of N2O at 455 degrees C and 490 degrees C in the absence and presence of 5% of oxygen, respectively. The LaCoO3 catalyst was deposited by in situ SCS directly over a ceramic honeycomb monolith and then tested in a lab-scale test rig. The coated ceramic monolith gave 50% N2O conversion performance similar to that obtained on powder for GHSV values of industrial interest (10 000-30 000 h(-1)). The correlation between the observed oxygen inhibition and the proposed N2O decomposition mechanism as well as the relationship between the observed activity and the reducibility of the B site, determined from TPR experiments, is discussed.