Tunable preparation of highly dispersed Ni x Mn-LDO catalysts derived from Ni x Mn-LDHs precursors and application in low-temperature NH3-SCR reactions.

A series of Ni x Mn bimixed metal oxides (Ni x Mn-LDO) were prepared via calcining Ni x Mn layered double hydroxides (Ni x Mn-LDHs) precursors at 400 °C and applied as catalysts in the selective catalytic reduction (SCR) of NO x with NH3. The DeNO x performance of catalysts was optimized by adjusting the Ni/Mn molar ratios of Ni x Mn-LDO precursors, in which Ni5Mn-LDO exhibited above 90% NO x conversion and N2 selectivity at a temperature zone of 180-360 °C. Besides, Ni5Mn-LDO possessed considerable SO2 & H2O resistance and outstanding stability. Multiple characterization techniques were used to analyze the physicochemical properties of the catalysts. The analysis results indicated that all catalysts had the same active species Ni6MnO8, while their particle sizes showed significant differences. Notably, the uniform distribution of active species particles in the Ni5Mn-LDO catalyst provided the rich surface acidity and suitable redox ability which were the primary causes for its desirable DeNO x property.

Fabrication of Highly Dispersed Cu-Based Oxides as Desirable NH3-SCR Catalysts via Employing CNTs To Decorate the CuAl-Layered Double Hydroxides.

In this study, three kinds of CuAl-LDO/CNT (LDO, layered double oxide) catalysts were prepared by the assembly of CNTs and CuAl-LDH (LDH, layered double hydroxides) as well as subsequently structural topological transformation. The effects of the assembly method on the surface structure property and the DeNOx performance of the prepared samples were systematically investigated. It was found that three CuAl-LDO/CNT catalysts showed preferable NH3-SCR catalytic performance compared with CuAl-LDO where the catalyst CuAl-LDO/CNTs(I) exhibited optimum NOx conversion (>80%) and N2 selectivity (>90%) within 180-300 °C. Such fine catalytic performance can be attributed to the proper surface acidity and redox ability of the catalyst, which might be correlated with the high dispersion of Cu-based active centers caused by the induced nucleation and effective separation action of LDH by carbon nanotubes. In addition, the outstanding H2O and SO2 resistance of the CuAl-LDO/CNTs(I) catalyst was also obtained because of the synergistic effect between CuAl-LDO and CNTs, which could greatly promote the activation and decomposition of ammonium sulfate at lower temperatures.