Synthesis, characterization and activity evaluation of Cu-based catalysts derived from layered double hydroxides (LDHs) for DeNOx reaction

Abstract

Catalytic filter for DeNOx reaction composed of practical ceramic filter and catalytic active component enables simultaneous removal of dusts and NOx and therefore is of great potential for industrial application. To find out catalytically active components for DeNOx reaction and concurrently which can be grown on ceramic filter by an in-situ method, the Cu-based catalysts derived from LDHs precursor with different promoters (Co, Ni, Zn, Mg) were synthesized. The results of catalytic activity evaluation showed Zn is the most suitable promoter. Then, the effect of the Cu/Zn ratio on the catalytic performance was examined. It was found that the (CuxZny)2Al-MMO with an Cu/Zn ratio of 4 exhibited the maximum NOx conversion of 80% at 240°C and a NH3/NO ratio of 0.8. The addition of Zn could weaken the catalytic oxidation of ammonia (NH3-SCO) and then improve turnover frequency (TOF) of NOx reduction per Cu atom. The characterizations of the TEM and H2-N2O titration to catalysts reveal that the addition of Zn helps the dispersity of CuO on the surface of the support. The H2-TPR results further demonstrates that the added Zn species facilitate the reducibility of CuO species at low temperature. At last, in-situ growth of Cu-Zn-Al-LDHs on a practical ceramic filter for DeNOx reaction was first successfully carried out and the resulted catalytic filter showed a reasonably high DeNOx activity and strong bonding strength between catalyst and filter.