Development of new catalysts for N2O-decomposition from adipic acid plant

Direct decomposition of NO was investigated using simulated and real industrial gas stream coming from an adipic acid plant. Two different kinds of catalysts were studied: (i) LaB1-xB'O-x(3) and CaB1-xCuO3 (B = Mn, Fe and B' = Cu, Ni) perovskites (PVKs) and (ii) supported PVKs (10 or 20 wt.%) on gamma-Al2O3 and CeO2-ZrO2. The structural modifications induced by the composition of PVK samples affect the catalytic performances: mixed oxide formation in CaMn0.7Cu0.3O3 samples allows to reach the highest values of N2O conversion while the effect of PVK phases is more controversial. The importance of copper on catalytic activities is confirmed by the investigation on CaMn1-xCuxO3 samples. The best results were obtained with a CaMn0.6Cu0.4O3 catalyst calcined at 700 degrees C for 5 h, in which the presence of copper maximises the Ca3CuMnO6 phase formation. The increase in Cu-content produces a large segregation of CuO despite PVK formation. The best catalyst was tested using industrial gas stream, showing good stability also in the presence of H2O and O-2 (8% v/v) after 1400 h on-stream. To increase surface area, Cu-containing PVKs were deposed on gamma-Al2O3 and CeO2-ZrO2, and this latter has been recognised as the best support. Indeed, the activity of the PVKs supported on ceria-zirconia is comparable to and even better than that of the bulk catalysts. A possible explanation regards the support contribution in terms of activity and/or promotion of O-2 mobility which enhances the overall activity of the catalyst. (c) 2006 Elsevier B.V. All rights reserved.