Effect of neodymium in Co(Cu)‐Al mixed oxides on their physico‐chemical properties and activity in N2O decomposition

Cu-Al and Co-Al (M/Al = 0.8/0.2, molar ratio; M = Cu or Co) mixed metal oxides showed a moderate activity in N2O decomposition (deN2O) with full conversion at about 500-550 C. Addition of Nd modified the physico-chemical and catalytic properties of both Cu-Al and Co-Al materials, though an optimal Nd loading was required. The addition of 0.5 molar ratio of Nd in Cu0.8Al0.2 and Co0.8Al0.2 improved significantly their catalytic activity. In particular, the temperatures needed for full N2O conversion were 100 C lower than those of the bare materials. Furthermore, the most active Nd0.5Co0.8Al0.2 catalyst exhibited a stable 60% N2O conversion at 450 oC for 50 h in presence of NO (200 ppm), O2 (20,000 ppm) and H2O (2500 ppm). The enhancement in the activity of both Cu- and Co-containing materials was related to the formation of CuNd2O4 for Nd0.5Cu0.8Al0.2 and NdCoO3 for Nd0.5Co0.8Al0.2. The presence of CuNd2O4 or NdCoO3 accounted for changes in redox properties, e.g., easier reduction or faster release of oxygen, and in turn an increased catalyst activity in deN2O. The investigation of rare earth-based catalysts for deN2O are limited in the scientific literature, while a comprehensive understanding of the involved active species may facilitate a knowledge-based catalyst optimization.