The effect of oxygen concentration on the reduction of NO with propylene over CuO/γ-Al2O3 |
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Authors: | Yawu Chi Steven S. C. Chuang |
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Affiliation: | Department of Chemical Engineering, The University of Akron, Akron, OH 44325-3906, USA |
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Abstract: | The effect of oxygen concentration on the pulse and steady-state selective catalytic reduction (SCR) of NO with C3H6 over CuO/γ-Al2O3 has been studied by infrared spectroscopy (IR) coupled with mass spectroscopy studies. IR studies revealed that the pulse SCR occurred via (i) the oxidation of Cu0/Cu+ to Cu2+ by NO and O2, (ii) the co-adsorption of NO/NO2/O2 to produce Cu2+(NO3−)2, and (iii) the reaction of Cu2+(NO3−)2 with C3H6 to produce N2, CO2, and H2O. Increasing the O2/NO ratio from 25.0 to 83.4 promotes the formation of NO2 from gas phase oxidation of NO, resulting in a reactant mixture of NO/NO2/O2. This reactant mixture allows the formation of Cu2+(NO3−)2 and its reaction with the C3H6 to occur at a higher rate with a higher selectivity toward N2 than the low O2/NO flow. Both the high and low O2/NO steady-state SCR reactions follow the same pathway, proceeding via adsorbed C3H7---NO2, C3H7---ONO, CH3COO−, Cu0---CN, and Cu+---NCO intermediates toward N2, CO2, and H2O products. High O2 concentration in the high O2/NO SCR accelerates both the formation and destruction of adsorbates, resulting in their intensities similar to the low O2/NO SCR at 523–698 K. High O2 concentration in the reactant mixture resulted in a higher rate of destruction of the intermediates than low O2 concentration at temperatures above 723 K. |
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Keywords: | NO reduction O2 effect Reaction mechanism Propylene pulse NO/O2 adsorption Nitrate formation Selective catalytic reduction Infrared spectroscopy CuO/γ-Al2O3 |
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