N₂O Decomposition over Perovskite Catalysts

Four perovskite catalysts LaBO 3 (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 N 2 O 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, LaCoO 3 showed the best performance, with 50% conversion of N 2 O at 455 °C and 490 °C in the absence and presence of 5% of oxygen, respectively. The LaCoO 3 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% N 2 O 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 N 2 O decomposition mechanism as well as the relationship between the observed activity and the reducibility of the B site, determined from TPR experiments, is discussed.