The reduction of NO with CO over Cu catalysts in the presence of excess oxygen was investigated.The samples were characterized by thermo-gravimetric analysis (TGA)

X-ray diffraction (XRD)

and temperature-programmed-reduction of H2(H2-TPR) and BET.Cu was supported on modified sepiolite by impregnation.The condition of sepiolite modification was chosen by orthogonal experiments.The acid-treatment can improve the special surface area of Cu/sepiolite greatly.The optimized conditions of sepiolite modification were as follows:the concentration of hydrochloric acid was 1.2 mol8226;L-1; the solid/liquid volume ratio was 1∶20;the soaking time was 20 h;and the soaking temperature was 333 K.The catalytic performance was studied under oxidizing conditions.The maximum conversion of NO was observed on the Cu/sepiolite loaded with 5%(mass)Cu.It shows a lowest light-off temperature of 518 K and reaches the maximum NO conversion of 90.3% at 653 K.Calcination above 873 K would cause irreversible folding in the structure of sepiolite.When the calcination temperature is about 673 K

the Cu/sepiolite shows a highest activity.The addition of rare-earth elements Ce and Sm can improve the activity of Cu/sepiolite greatly.And this improvement is not only related to the kind of additive but also to the ratio of them.The effect of the oxygen content and the GHSV (gas hourly space velocity) on the catalytic activities was also studied.The suitable working condition of Cu/sepiolite requires that 2.3% oxygen exists in the gas mixture and the space velocity does not exceed 16000 h-1.Under the same experimental conditions

the catalytic activity of Cu/sepiolite is better than Cu/ZSM-5.