Transition metals cobaltites spinel for depollution of NO x emissions using SCR technology

The catalytic performances of various transition metal (M = Cu, Mn, and Ni) cobaltites prepared by the nanocasting method were investigated for the selective catalytic reduction (SCR) of NO under lean burn conditions. KIT‐6 was used as a hard template in the nanocasting method for preparation of catalysts. The catalyst samples were characterized by various techniques such as XRD, low‐temperature N 2 physisorption, SEM‐EDS, and XPS. The catalysts were examined for the SCR of NO by NH 3 and H 2 ‐LPG in a packed bed tubular flow reactor under the following reaction conditions: 500 ppm NO, 8 % O 2 , (0.1 % NH 3 ) or (1000 ppm LPG, 1 % H 2 ) in Ar with 200 mg catalyst. The inlet and outlet gases of the reactor were analyzed by an Eco Physics CLD 62 chemiluminescence NO/NO x analyzer and online GC. NO and NO 2 measurements were done by an Eco Physics CLD 62 chemiluminescence NO/NO x analyzer. Two separate GCs equipped with Porapak Q/capillary columns and FID/ECD detectors were used to analyze the hydrocarbons/−N 2 O respectively. The addition of 1 % H 2 with LPG promoted NO reduction at a remarkably low temperature. It was found that the nature of the dispersed metal strongly affects the light‐off temperature (52 °C) and enhances NO conversion. The oxygen‐deficient MnCo 2 O 4 spinel structure enhanced NO reduction (87.1 %) at a lower temperature of 250 °C as compared to Cu and Ni cobaltites using H 2 ‐LPG‐SCR. The H 2 ‐LPG reductant showed the best de‐NO x activity and the order of catalyst activity followed the sequence: MnCo 2 O 4  > CuCo 2 O 4  > NiCo 2 O 4 .