Low-temperature selective catalytic reduction of NO over MnOx/CNTs catalysts

Promotional effects of nitrogen doping on catalytic performance over manganese-containing semi-coke catalysts for the NH3-SCR at low temperatures

A series of nitrogen-doped MnO_x/semi-coke catalysts were studied for low-temperature (LT) de-NO_x performance in the NH₃-SCR reaction. Changes in morphology, structure, and surface chemistry of the semi-coke catalysts were systematically investigated to analyze the promotional effects of nitrogen doping on catalytic performance. The catalytic activity of ASC-10U10 Mn was found to be enhanced significantly in a broad temperature range of 100-300 °C, improving 44.2 % at 150 °C-the largest jump in this temperature range-and reaching 94.5 % at 275 °C. Nitrogen doping results in aromatic pyridinic-N, pyrrolic-N, and quaternary-N; the unpaired electrons on these groups play a critical role in enhancing the adsorption and oxidation of NO. NH₃ adsorption is enhanced due to numerous diverse Lewis acid sites on ASC-10U10 Mn. The electron distribution of MnO_x/semi-coke catalysts and the electron mobility between manganese and oxygen species are improved by nitrogen doping. The resulting nitrate intermediates, especially bridging nitrates, can be reduced by NH₃ species at low temperatures. The increase in the number of oxygen vacancies improves oxidation of coordinated NH₃. In addition, DRIFTS results suggest that coordinated NH₃ and intermediate -NH₂ are much more active and make a considerable positive contribution to the LT SCR reaction.

Synthesis of MnO2-CuO-Fe2O3/CNTs catalysts: low-temperature SCR activity and formation mechanism

MnO₂-CuO-Fe₂O₃/CNTs catalysts, as a low-dimensional material, were fabricated by a mild redox strategy and used in denitration reactions. A formation mechanism of the catalysts was proposed. NO conversions of 4% MnO₂-CuO-Fe₂O₃/CNTs catalyst of 43.1-87.9% at 80-180 °C were achieved, which was ascribed to the generation of amorphous MnO₂, CuO and Fe₂O₃, and a high surface-oxygen (O_s) content.

Enhancing low-temperature SCR de-NOx and alkali metal poisoning resistance of a 3Mn10Fe/Ni catalyst by adding Co

Alkaline K poisoned and Co-modified catalysts were prepared using Fe and Mn as active components, nickel foam as a carrier, and Co as a trace additive.

A review of carbon-based and non-carbon-based catalyst supports for the selective catalytic reduction of nitric oxide

Various types of carbon-based and non-carbon-based catalyst supports for nitric oxide (NO) removal through selective catalytic reduction (SCR) with ammonia are examined in this review. A number of carbon-based materials, such as carbon nanotubes (CNTs), activated carbon (AC), and graphene (GR) and non-carbon-based materials, such as Zeolite Socony Mobil-5 (ZSM-5), TiO2, and Al2O3 supported materials, were identified as the most up-to-date and recently used catalysts for the removal of NO gas. The main focus of this review is the study of catalyst preparation methods, as this is highly correlated to the behaviour of NO removal. The general mechanisms involved in the system, the Langmuir-Hinshelwood or Eley-Riedeal mechanism, are also discussed. Characterisation analysis affecting the surface and chemical structure of the catalyst is also detailed in this work. Finally, a few major conclusions are drawn and future directions for work on the advancement of the SCR-NH3 catalyst are suggested.

Catalysts for the selective catalytic reduction of NOx with NH3 at low temperature

This review presents recent studies on low-temperature NH₃-SCR catalysts, particularly Mn-based oxides, V₂O₅/AC, and Cu-based small pore zeolites.

Fabrication of Mn–CeOx/CNTs catalysts by a redox method and their performance in low-temperature NO reduction with NH3

Highly active Mn–CeO_x/CNTs catalysts were first fabricated by a novel redox method, and a formation mechanism was proposed.