Selective Catalytic Reduction Of Nitrogen Monoxide Research Articles

Flue gas purification from NO using supported Cu–Mn and Cu–Mn–Nb catalysts synthesized by electroless metal deposition method

In the present work, granular fixed-bed catalysts with active Cu–Mn and Cu–Mn–Nb layers synthesized by electroless metal deposition method were prepared and tested for purification of a flue gas from nitrogen monoxide (NO) by CO. Lightweight expanded clay aggregate with i.d. of 2–4 mm and 8–10 mm was used as a substrate for deposition of the active layer. Elemental composition of the prepared catalytic layers was determined by means of inductively coupled plasma optical emission spectroscopy and energy-dispersive X-ray analysis. Field emission scanning electron microscopy and X-ray photoelectron spectroscopy were applied to investigate morphology of the active layers and the oxidation state of the main components (Mn, Cu and Nb), respectively. Additionally, X-ray diffraction analysis and energy-dispersive X-ray mapping were conducted to provide comprehensive information about the structure and dispersion of active components on the surface of the catalysts prepared. It was demonstrated that electroless metal deposition method allows preparation of a relatively uniform active layer with highly distributed active sites on the substrate surface, while the Cu0.012–Mn0.986Nb0.0012 active layer synthesized by electroless metal deposition can be successfully applied for selective catalytic reduction of NO with the use of CO as a reductant. The effective NO conversion (90–95%) was observed at temperatures of 300–400 °C and higher. X-ray photoelectron spectroscopy revealed that significant amount of Mn3+ and Mn4+ species and predominance of chemisorbed oxygen over the lattice oxygen should be responsible for NO conversion efficiency of the catalyst prepared.

Effects of SO2 on selective catalytic reduction of NO with NH3 over a TiO2 photocatalyst

The effect of SO2 gas was investigated on the activity of the photo-assisted selective catalytic reduction of nitrogen monoxide (NO) with ammonia (NH3) over a TiO2 photocatalyst in the presence of excess oxygen (photo-SCR). The introduction of SO2 (300 ppm) greatly decreased the activity of the photo-SCR at 373 K. The increment of the reaction temperature enhanced the resistance to SO2 gas, and at 553 K the conversion of NO was stable for at least 300 min of the reaction. X-ray diffraction, FTIR spectroscopy, thermogravimetry and differential thermal analysis, x-ray photoelectron spectroscopy (XPS), elemental analysis and N2 adsorption measurement revealed that the ammonium sulfate species were generated after the reaction. There was a strong negative correlation between the deposition amount of the ammonium sulfate species and the specific surface area. Based on the above relationship, we concluded that the deposition of the ammonium sulfate species decreased the specific surface area by plugging the pore structure of the catalyst, and the decrease of the specific surface area resulted in the deactivation of the catalyst.

Selective catalytic reduction of NO using acetone solvent vapors as the reducing agent over Cu2+ and/or Al3+ ions substituted MCM-41 catalysts

Selective catalytic reduction (SCR) of nitrogen monoxide (NO) using acetone solvent vapors as the reducing agent over mesoporous Cu–MCM-41, Al–MCM-41, Cu–Al–MCM-41 and CuO supported metal oxides such as CuO/Al2O3 and CuO/SiO2 was investigated in this study. The synthesized materials were characterized by using powder low-angle X-ray diffraction (XRD), N2 adsorption–desorption measurements, 27Al magic angle spinning-nuclear magnetic resonance spectroscopy (MAS-NMR), electron paramagnetic resonance spectroscopy (EPR) and inductively coupled plasma-mass spectrometer (ICP-MS) analysis. The presence of isolated Cu2+ ions and tetrahedrally coordinated Al3+ ions within the framework of Cu–Al–MCM-41 catalyst played a vital role in this deNOx reaction as confirmed by EPR and 27Al MAS-NMR spectroscopic studies, respectively. Among the various catalysts studied, bifunctional Cu–Al–MCM-41 was found to be the most effective catalyst for achieving maximum deNOx activity at lower temperatures of around 250–350°C. Besides, Cu–Al–MCM-41 catalyst also showed higher acetone oxidation than those of Cu–MCM-41, CuO/Al2O3 and CuO/SiO2 catalysts in the entire temperature range. For higher temperature of above 400°C, it was found that Cu–MCM-41 catalyst shows highest activity for the NO reduction but it shows less acetone incineration activity as compared to that of Cu–Al–MCM-41 catalyst. The study of simultaneous removal of NO and acetone solvent vapors using Cu–Al–MCM-41 and Cu–MCM-41 catalysts reveals the potential of using waste organic solvents from industry as the reducing agent of deNOx (SCR) process.