Involvement of NCO species in promotion effect of water vapor on propane-SCR over Co-MFI zeolite

High Zr-loaded SBA-15 cobalt catalyst for efficient NOx reduction in lean-burn exhaust

“…The formation of CO2 in the presence of water vapor was about 2 and 2.5 times more than those in the absence of the steam at 300 and 350 , respectively. These findings are in good agreement with previous reports [7,79]. Furthermore, the formation of organic nitroso or nitro species (R -NO, R -NO2) via gas phase or surface reaction has been evidenced as intermediate species in HC-SCR system [7,80,81].…”

“…These findings are in good agreement with previous reports [7,79]. Furthermore, the formation of organic nitroso or nitro species (R -NO, R -NO2) via gas phase or surface reaction has been evidenced as intermediate species in HC-SCR system [7,80,81]. Nitroso or nitro species are adsorbed as NCO and CN species through several reaction steps.…”

“…Nitroso or nitro species are adsorbed as NCO and CN species through several reaction steps. Ultimately, NCO and CN species can be converted to N2, CO2 and H2O through the following reaction pathways; (i) oxidation by NO2 gas in which the reaction rate might increase in the presence of water vapor , (ii) conversion to ammonia through hydrolysis by water vapor and then selective reduction of NO by the formed NH3 [7,82]. Thus, the presence of water vapor enhances the NO reduction to N2 irrespective to the reaction pathways.…”

“…Amongst, zeolite-supported cobalt catalyst has exhibited promising results in NO reduction with propane [7][8][9] that is the main component of unburned hydrocarbons in lean-burn gas, diesel and natural gas-fueled appliances exhausts [10][11][12][13]. Shichi et al [7] reported that Co-MFI zeolite catalyst had 30% and 80% NO conversion at 350 and 400 , respectively. In another report, 30% and 40% of NO conversion was observed over CoZSM-5 catalyst in the presence of propane at the same temperature range [8].…”

Improving the Activity of Rh/Al2O3 Catalyst for NO Reduction by Na Addition in the Presences of H2O and O2

“…The second region at 2,000-1,600 cm -1 attributed to the adsorption of NO on the active sites of Rh [36,[45][46][47][48]. The third region at 3,700-3,500 cm -1 assigned to the OH decomposed from H 2 O [36,49]. On the other hand, no significant adsorption bands at 2,210 cm -1 assigned to CO [45,46] was observed in the FTIR spectra of Rh/Al 2 O 3 catalysts.…”