Study On The Performance Of Cu/Sepiolite Catalyst For The Selective Catalytic Reduction

The natural sepiolite has been treated with hydrochloric acid and modified by ion-exchange method. Then a series of copper and silver catalysts were prepared by vacuum impregnation with the modified sepiolite as support and rare earth elements Cerium and Samarium as supplement catalysts. The catalytic activity for NOx reduction by CO was evaluated under lean burn conditions. Moreover, the means of XRD, TGA, IR, TPR and SEM etc. were used to characterize these catalysts and the factors affecting the activity of catalysts were discussed. It was found that the modified sepiolite was superior to the conventional support over performance. The support treated by acid has better performance than through the ion-exchange method. The best acid treat conditions were gained by orthogonal experiment: concentration of hydrochloric acid is 1.2 mol/L, volume of solid and liquid ratio is 1:20, treating time is 20h and treating temperature is 60℃.The whole performance of Cu/Sep is superior to Ag/Sep, and the former has good anti-water and thermal stable properties and catalytic activity under lean burn conditions. Cu/Sep catalyst (5%wt.) has the best activity over NOx reduction among the series of catalysts, whose light-off temperature (T50%) is the lowest, 245℃; and active temperature(T90%) is 320℃, also the lowest. The addition of rare earth elements Cerium and Samarium further increases the catalytic activity, and that the best activity was achieved when the Sm-Ce ratio is 1:4. It indicated that the increase of activity has relation not only to the elements added but also their ratios. There is some synergetic effect between the added elements.Ag/Sep with silver content 2%(wt.) has better activity, the highest conversion of NOx 80.94% was gained at 320℃. It showed that the activity of Ag/Sep is lower than that of Cu/Sep, well the loading of activity component is a little lower too.Oxygen concentration has much effect on the activity of catalysts. There is better catalytic activity of the catalyst when the oxygen concentration is lower than 3.8%(Vol.), and the best activity was gained when the concentration of oxygen is 2.2%(Vol.), so the catalyst has good adaption to the oxygen.