Low-cost Mn-Fe/SAPO-34 catalyst from natural ferromanganese ore and lithium-silicon-powder waste for efficient low-temperature NH3-SCR removal of NOx.

The development of low-temperature selective catalytic reduction of NOx with NH3 (NH3-SCR) catalysts is desirable but still challenging. Herein, a low-cost Mn-Fe/SAPO-34 catalyst was successfully synthesized using natural ferromanganese ore (FO) and industrial waste lithium-silicon-powder (LSP) by solid-state ion exchange (SSIE) method, and showed high NH3-SCR activity at low temperature range (150-200 °C) with high N2 selectivity. After loading FO, Mn-O and Fe-O bonds on Mn-Fe/SAPO-34 were weakened, which were beneficial to electron transfer and the oxidation-reduction cycle of SCR. The coexisting of Mn and Fe promoted the dispersion of Fe, resulted in high amounts of Oa, Mn4+ and Fe3+ which facilitated the adsorption and activization of NH3 over Mn-Fe/SAPO-34 catalyst. The Brønsted and Lewis acid sites participate in NH3-SCR, and the adsorbed nitrate species could quickly react with the adsorbed NH3 species via the Langmuir-Hinshelwood (L-H) mechanism. The Mn-Fe/SAPO-34 integrated the advantages of low-cost, resource saving and environment friendly, giving a low-carbon and sustainable choice for the industrial application of NOx abatement.

A novel CNTs functionalized CeO2/CNTs-GAC catalyst with high NO conversion and SO2 tolerance for low temperature selective catalytic reduction of NO by NH3.

Low-temperature selective catalytic reduction of NOx by NH3 (NH3-SCR) for diminishing SO2 poisoning remains an issue in flue gas denitrification (DeNOx). Herein, A novel CNTs functionalized low temperature NH3-SCR catalyst CeO2/CNTs-GAC was prepared, which showed high NO conversion activity (100% at 150 °C) and SO2 resistance. The addition of CNTs restrained SO2 adsorption but improved the selective adsorption of NO, which restricted the deposition of (NH4)2SO4 and/or Ce2(SO4)3, and resulted in high SO2 resistance. The addition of CNTs facilitated the diffusion and transportation of NH3 and NO, and the electron transfer on CeO2/CNTs-GAC, leading to higher content of Ce3+ and adsorbed O species on the CeO2/CNTs-GAC surface and promoted formation of surface-adsorbed oxygen OA. Therefore, CeO2/CNTs-GAC provided abundant NO adsorption and activation sites, facilitating "fast SCR" reaction and enhancing the NH3-SCR reaction. The proposed CeO2/CNTs-GAC catalyst exhibited higher NH3-SCR activity, N2 selectivity, catalytic durability and SO2 resistance than CeO2/GAC.

Low-temperature selective catalytic reduction of NO x with NH3 over an activated carbon-carbon nanotube composite material prepared by in situ method.

Ce-supported activated carbon-carbon nanotube composite (Ce/AC-CNTs) catalyst was prepared by in situ formation of CNTs on AC and then modified by Ce. This Ce/AC-CNTs catalyst was subsequently used for low-temperature selective catalytic reduction of NO x with NH3 (NH3-SCR). The NO conversion of Ce/AC-CNTs was 1.41 times higher than that of Ce/AC at 150 °C with good SO2 tolerance. The catalysts were analyzed by N2 physisorption, SEM, XRD, NH3-TPD, XPS, and Raman technologies. The results showed that the introduction of CNTs could form new mesopores and increase the amount of surface chemisorbed oxygen and acid sites, which all contribute to the high NH3-SCR activity.