NO direct decomposition on BaO/Y2O3 oxide catalyst was investigated and it was found that BaO supported on Y2O 3 or Sc2O3 is highly active to NO decomposition into N2. The highest N2 yield of ca.90% at 1123 K was achieved at 5 mol% BaO supported on Y2O3. On this catalyst, NO conversion decreases with increasing oxygen partial pressure, PO2, however reasonably high N2 yield (ca. 40%) was exhibited under co-feeding of 5% O2 and PO2 dependence is as small as -0.23. From NO-TPD results, large desorption peak of oxygen was observed around 773 K suggesting that weak adsorption strength of O2 on BaO/Y 2O3 catalyst. In case of NO, large NO desorption peak was also observed around 473 K and so NO adsorption was improved by loading BaO on Y2O3. In addition, part of NO desorbs as O2 and NO, and small amount of N2 desorbs at 773 K. This suggests that disproportional reaction of NO (3NO = N2 + NO3ad or NO = N2Oad + NO2ad) occurred and the surface of the catalyst was covered with nitrogen oxide species. In spite of small surface area of BaO/Y2O3 (1.1 m2/g), reasonably high N 2 yield (ca.30%) is shown at a high space velocity of 40,000 h -1.
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