Removal of SO2and NOXUsing Microwave Swing Adsorption over Activated Carbon Carried Catalyst

A critical review on the technique and mechanism of microwave-based denitrification in flue gas

Microwave radiation has received extensive attention due to its significant thermal and non-thermal effects, and the development of MW-based denitrification in flue gas has become one of the most promising methods to avoid the defects of ammonia escape, high temperature and cost in traditional SCR. This review introduces the thermal and non-thermal effects of microwaves and divides MW-based denitrification methods into MW reduction and oxidation denitrification, systematically summarizes these denitrification methods, including MW discharge reduction, MW-induced catalytic reduction using active carbon, molecular sieves, metal oxides (transition metals, perovskites, etc.), MW-induced oxidation denitrification with and without additional oxidant, and discusses their removal pathway and mechanism. Finally, several research prospects and directions regarding the development of microwave-based denitrification methods are provided.

Diesel engine exhaust denitration using non-thermal plasma with activated carbon

A diesel engine de-NO_x system combining non-thermal plasma and activated carbon was set up. The de-NO_x efficiency reaches 91.8% and 92.5% for simulated gas and real exhaust gas, respectively. It has good potential to replace vanadium-based SCR.

Enhanced Oxygen Vacancies in a Two-Dimensional MnAl-Layered Double Oxide Prepared via Flash Nanoprecipitation Offers High Selective Catalytic Reduction of NOx with NH₃

A two-dimensional MnAl-layered double oxide (LDO) was obtained by flash nanoprecipitation method (FNP) and used for the selective catalytic reduction of NOx with NH₃. The MnAl-LDO (FNP) catalyst formed a particle size of 114.9 nm. Further characterization exhibited rich oxygen vacancies and strong redox property to promote the catalytic activity at low temperature. The MnAl-LDO (FNP) catalyst performed excellent NO conversion above 80% at the temperature range of 100⁻400 °C, and N₂ selectivity above 90% below 200 °C, with a gas hourly space velocity (GHSV) of 60,000 h-1, and a NO concentration of 500 ppm. The maximum NO conversion is 100% at 200 °C; when the temperature in 150⁻250 °C, the NO conversion can also reach 95%. The remarkable low-temperature catalytic performance of the MnAl-LDO (FNP) catalyst presented potential applications for controlling NO emissions on the account of the presentation of oxygen vacancies.

A comparative study on the Mn/TiO2-M(M = Sn, Zr or Al) Ox catalysts for NH3-SCR reaction at low temperature

A series of TiO₂-M(M = Sn, Zr or Al) O_x were prepared and manganese oxide (MnO_x) was supported on the carrier by the traditional impregnation method for low-temperature selective catalytic reduction (SCR) of NO_x with ammonia as a reductant. The obtained catalysts were characterized by XRD, BET, high-resolution transmission electron microscope (HRTEM), H₂-TPR, NH₃-TPD, X-ray photoelectron spectroscopy (XPS) and in situ Fourier-transform infrared (FT-IR) and their catalytic activities for NO_x reduction with NH₃ in the presence of SO₂ were investigated comparatively. The results showed that the highest NO_x conversion of over 90% could be obtained with the Mn/Ti-Sn catalyst at a wide range of temperature window of 150-270°C. The combination of characterization techniques, such as BET, XRD and HRTEM, revealed that manganese oxides were well dispersed on Ti-Sn. H₂-TPR suggested that Ti-Sn and Ti-Zr supports could enhance the reduction ability of catalysts. Accordingly, Mn/Ti-Al exhibited worse activity at low temperature. XPS results were in good agreement with H₂-TPR results, and Mn/Ti-Sn had more surface-reducible species of Mn⁴⁺ ions and more surface-adsorbed oxygen species, which was conducive to SCR reaction. The in situ FT-IR spectra of NH₃ adsorption indicated that all the modified catalysts had more Lewis acid sites and the amide species at 1506 cm^-1 had a certain influence on the catalytic reaction at low temperature. Mn/Ti-Zr showed a stronger resistance to SO₂ but Mn/Ti-Al was affected more adversely and all the catalysts could not be restored to the initial catalytic activity after stopping feeding SO₂. NH₃-TPD revealed that the total acid amount of the Mn/Ti-Sn sample was larger than other samples, which indicated that the Ti-Sn solid solution could provide more surface acid sites over the catalyst.

Catalytic oxidation of nitric oxide (NO) with carbonaceous materials

This paper reviewed recent progress in catalytic oxidation of nitric oxide (NO) over various carbonaceous materials, such as activated carbon, carbon nanofibers with the aim of NO abatement.