4.8 Article

Selective catalytic reduction of NO by hydrogen (H2-SCR) on WON-promoted CezZr1-zO2 solids

期刊

APPLIED CATALYSIS B-ENVIRONMENTAL
卷 156, 期 -, 页码 72-83

出版社

ELSEVIER SCIENCE BV
DOI: 10.1016/j.apcatb.2014.03.008

关键词

Selective catalytic reduction; H-2-SCR; Surface acidity; NH3-TPD; Tungsten; NO-TPD; H-2/O-2-TPSR; UV-vis/DRS; Nitrogen oxides

资金

  1. Tekes
  2. Finnish Funding Agency for Technology and Innovation via the Cleen Ltd's Future Combustion Engine Power Plant (FCEP) programme
  3. Research Committee of the University of Cyprus

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The selective catalytic reduction of NOx by H-2 (H-2-SCR) under strongly oxidizing conditions (520 ppm NOx/1% H-2/5% O-2/10% CO2/He; NO:NO2-4:1-9:1) in the 150-600 degrees C range has been studied over 3 wt-% W-promoted Ce02-Zr02 solids (85 wt-% Ce02-15 wt-% Zr02 (CeZr), and 17 wt-% CeO2-83 wt-% Zr (ZrCe) synthesised by a proprietary method) for the first time. The highest NOx conversion (XN0, = 54%) was obtained on the W-ZrCe (Zr-rich) solid at 300 degrees C (GHSV of 51,000 h-1), whereas N2 -selectivity was in the 77-92%-range over both W-ZrCe (Zr-rich) and W-CeZr (Ce-rich) catalysts. Significantly higher integral specific rates (RNo, ja,mol NO m-2 mm-1) were estimated on the W-ZrCe (Zr-rich) catalyst compared to the W-CeZr (Ce-rich) one in the 250-350 degrees C range. The formation of adsorbed NO under 0.1% NO/10% 02/He gas treatment at 25 degrees C followed by H-2/O-2-TPSR experiments revealed that at least two different kinds of active NOx of low concentration (4-7 mu mol g(-1)) were formed on both catalysts, whereas other inactive (spectator) NOx species formed were of larger concentration (>160 ji,mol UV-vis/DRS studies revealed that deposition of 3 wt-% Won ZrCe (Zr-rich) mixed metal oxide following calcination at 600 degrees C resulted in the formation of both polymeric WOx and WO3 clusters, whereas on CeZr (Ce-rich) only the latter phase (W6+) was seen. Large differences in the concentration (p,mol m-2) and strength of surface acid sites between the W-CeZr and W-ZrCe solids were revealed after performing NH3-TPD and NH3-DRIFTS. These results were found to correlate with the specific H2-SCR rate (Ilmol m-2 min) obtained for the two solids. In particular, the surface acid sites on W-ZrCe and W-CeZr solids were found to be 5.96 and 2.76 mu mol m(-2), respectively, whereas the specific reaction rate was 0.14 and 0.046 mu mol m(-2) min at 300 and 250 degrees C, at which maximum rates were observed, respectively. (C) 2014 Elsevier B.V. All rights reserved.

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