Transition metals cobaltites spinel for depollution of NO_x emissions using SCR technology

Abstract

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 N2 physisorption, SEM‐EDS, and XPS. The catalysts were examined for the SCR of NO by NH3 and H2‐LPG in a packed bed tubular flow reactor under the following reaction conditions: 500 ppm NO, 8 % O2, (0.1 % NH3) or (1000 ppm LPG, 1 % H2) in Ar with 200 mg catalyst. The inlet and outlet gases of the reactor were analyzed by an Eco Physics CLD 62 chemiluminescence NO/NOx analyzer and online GC. NO and NO2 measurements were done by an Eco Physics CLD 62 chemiluminescence NO/NOx analyzer. Two separate GCs equipped with Porapak Q/capillary columns and FID/ECD detectors were used to analyze the hydrocarbons/−N2O respectively. The addition of 1 % H2 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 MnCo2O4 spinel structure enhanced NO reduction (87.1 %) at a lower temperature of 250 °C as compared to Cu and Ni cobaltites using H2‐LPG‐SCR. The H2‐LPG reductant showed the best de‐NOx activity and the order of catalyst activity followed the sequence: MnCo2O4 > CuCo2O4 > NiCo2O4.

Enhanced low‐temperature Selective Catalytic Reduction (SCR) of NOx by CuO‐CeO2‐MnOx/γ‐Al2O3 mixed oxide catalysts

“…When the lattice oxygen in the active component was exhausted, the denitrification efficiency can only be maintained at a lower level, and the denitrification efficiency of the catalyst showed an evident increase as the content of O 2 in the flue gas gradually increased. The reason behind this is that in addition to the adsorption of the catalyst, the active components and the O 2 adsorbed on the surface also engage in oxidizing NO to NO 2 , while the lattice oxygen consumed by the active components is constantly supplemented so that the reaction is sustained . Nevertheless, when the content of O 2 grows from 6 to 9 %, the denitration efficiency did not increase noticeably, which indicates that the content of O 2 is a necessary condition for the SCR denitration reaction but that it is not a favourable factor.…”

Hollow Cu2O@CoMn2O4 Nanoreactors for Electrochemical NO Reduction to NH3: Elucidating the Void‐Confinement Effects on Intermediates

“…[14,15] Nevertheless, the void-confinement effect of hollow nanoreactors on reaction intermediates still lacks experimental evidence. Meanwhile, compared with selective catalytic reduction (SCR) for NO removal, [16][17][18] electrochemical NO reduction to NH 3 (ENOR), a "one-stone-two -birds" strategy, is of significance in environmental remediation and energy storage. [19][20][21] Unfortunately, nanoreactors with hollow structures have never been reported for ENOR.…”