Pt-free sulphur resistant NOx traps

A thioresistant NOx trap based on CuO supported on sulphated zirconia mixed with a solid base is described. The rate of adsorption of NO at constant temperature and the amount of NO retained from a feed containing 750 ppm NO, 10% O-2 and 5% water in nitrogen were measured. On badly dispersed CuO, the capacity for NOx adsorption does not decrease but slightly increases in the presence of 25 ppm SO2 in the feed. By contrast, a well dispersed Cu catalyst is irreversibly poisoned. The surface nitrates can be decomposed in air at 623 K. In a mixture, Ar + 1% H-2, the nitrate is partly reduced to N-2 at about 630 K, even after operation in the presence Of SO2. The catalyst does not lose adsorption capacity after 10 cycles of adsorption-desorption and can be used in the temperature range 473-773 K. The resistance to SO2 depends also in part of the properties of the solid base. (C) 2004 Elsevier B.V. All rights reserved.