Pt-free sulphur resistant NOx traps

Abstract A thioresistant NO x 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 NO x adsorption does not decrease but slightly increases in the presence of 25 ppm SO 2 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 SO 2 . 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 SO 2 depends also in part of the properties of the solid base.