Browsing by Subject "In Situ Ft-ir Spectroscopy"

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    FT-IR spectroscopic investigation of the effect of SO2 on the SCR of NOx with propene over ZrO2–Nb2O5 catalyst
    (Elsevier, 2011-11-01) Kantcheva, M.; Cayirtepe, I.; Naydenov, A.; Ivanov, G.
    The SO2 tolerance of a catalyst based on ZrO2–Nb2O5 solid solution (mole ratio ZrO2:Nb2O5 = 1:6) in the catalytic activity for NOx reduction with propene in excess oxygen has been studied. No loss in the C3H6-SCR activity was observed for 2 h after the addition of 56 ppm of SO2 to the reaction mixture. When the concentration of SO2 has been increased to 200 ppm (the so-called fast poisoning experiment) the activity of the catalyst decreased by 13% and remained unchanged for more than 5 h under these conditions. The effect of SO2 on the surface reaction of the SCR reactants has been investigated by in situ FT-IR spectroscopy and mechanism for the suppression of the catalytic activity at high concentration of the poison has been proposed.
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    In situ FT-IR spectroscopic investigation of gold supported on tungstated zirconia as catalyst for CO-SCR of NOx
    (Elsevier, 2012-09-15) Kantcheva, M.; Milanova, M.; Mametsheripov, S.
    The possibility for application of gold supported on tungstated zirconia as catalyst in the selective catalytic reduction of NOx with CO (CO-SCR) has been investigated by means of in situ FT-IR spectroscopy. Tungstated zirconia containing 18 wt% of WO3 was prepared by co-precipitation. Gold was deposited on zirconia and tungstated zirconia by cationic adsorption using [Au(en)2]Cl3 as a precursor (en = ethylenediamine). The FT-IR spectra obtained during the interaction of CO with NOx species adsorbed on the Au/ZrO2–WOx and Au/ZrO2 samples revealed the formation of surface isocyanates attached to the gold particles. The generation of Au–NCO species occurred atlow temperature (25–50 ◦C). The W-containing sample was characterized by higher activity in the ad-NOx + CO reaction than the Wfree one. It is shown that the nitrate species or adsorbed NO2 are essential for the generation of surface isocyanates and the oxidation of NO by oxygen is an important step. The obtained results suggest that Au catalysts supported on tungstated zirconia might be of interest for the selective reduction of NOx with CO at low temperatures.