Selective catalytic reduction of NO with NH3 over sol-gel-derived CuO-CeO2-MnOx/γ-Al2O3 catalysts

Abstract

Granular CuO-CeO 2 -MnO x /γ-Al 2 O 3 catalysts were synthesized by the sol-gel method. The performance of the CuO-CeO 2 -MnO x /γ-Al 2 O 3 catalysts for the selective catalytic reduction (SCR) was studied in a fixed bed system. Preliminary tests were carried out to analyze the behavior of NH 3 and NO over catalyst in the presence of oxygen. The optimum temperature range for SCR over the CuO-CeO 2 -MnO x /γ-Al 2 O 3 catalysts is 300−400 . The catalysts maintain nearly 100% NO conversion at 350 ℃ . The ℃ NH 3 oxidation experiments show that both NO and N 2 O are produced gradually with the increase of temperature. The catalysts in this experiment have a stronger oxidation property on NH 3 , which improves the denitrification activity at low temperature. The over-oxidation of NH 3 at high temperature is the main cause leading to a decrease in the NO conversion. The NH 3 and NO desorption experiments show that NH 3 and NO can be adsorbed on CuO-CeO 2 -MnO x /γ-Al 2 O 3 granular catalysts. The transient response of NH 3 and NO indicates that the SCR reaction proceeds in accordance with the Eley-Rideal mechanism. The adsorbed NO has little influence on the denitrification activity in SCR process.

In situ FT-IR study of highly dispersed MnO x /SAPO-34 catalyst for low-temperature selective catalytic reduction of NO x by NH 3

“…6 and combined with the results of NO + O 2 co-adsorption experiments, the band at 1610 cm −1 was disappeared immediately after the NH 3 was introduced. It is worth noting that the band at 1610 cm −1 (bridged nitrate) [43] was disappeared very rapidly and the band at 1625 (bridged nitrate) [53] and 1525 cm −1 (bidentate nitrate) [21] was appeared simultaneously, which indicated that the specific chemical environment of the bridged nitrate species (1610 cm −1 ) might participate in the catalytic reaction. Furthermore, the intensity of the band at 1197 cm −1 ascribed to the bridged nitrate species was gradually weakened, and the intensity of the band at 1389 cm −1 (nitrate species) [18] was decreased slightly.…”

Manganese Oxides Supported on TiO2–Graphene Nanocomposite Catalysts for Selective Catalytic Reduction of NOX with NH3 at Low Temperature

“…The presence of manganese oxides with different valences resulted from the introduction of GE, which played an important role in improving the electron transfer and low-temperature SCR activity of MnO X /TiO 2 –0.8%GE catalysts. The redox properties of the catalyst were improved to effectively remove nitrogen oxides through the SCR reaction . XPS patterns of O 1s (Figure c) show that there are two kinds of surface oxygen for the sample, including lattice oxygen (denoted as O β ) and chemisorption oxygen (denoted as O α ).…”

“…Therefore, the result suggested that there was almost no NH 3 oxidation below 180 °C. Moreover, a high oxidation degree of NO favors high SCR activity, a finding that is widely accepted. In this reaction, NO 2 was thought to be one kind of important intermediate species, while its concentration decreased with the increase of temperature, which was opposite to that of the SCR reaction activity for this catalyst.…”

Design Strategies for P-Containing Fuels Adaptable CeO2–MoO3 Catalysts for DeNOx: Significance of Phosphorus Resistance and N2 Selectivity

“…In NH 3 –SCR reaction, it is believed that NH 3 is adsorbed to acid center and intermediates like NH 2 (on L acid site) − or NH 4 + (on B acid site) , formed, then they react with aerial NO and NO 2 to produce N 2 and H 2 O. N 2 selectivity in SCR reaction is affected significantly by the intermediates appearing in NH 3 oxidation. At low temperatures, the emergence of ammonia oxidation reactions would improve the SCR activity; whereas, the overoxidation of NH 3 at high temperatures, which leads to the formation of N 2 O and/or NO, is likely to be responsible for the decrease of both the NO x conversion and N 2 selectivity. Over CeO 2 catalyst, the drop of NO x conversion due to catalytic oxidization of NH 3 to NO at high temperatures has been confirmed by our research .…”