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The study of NO X release on CeO 2 at low temperature during lean NO X trapping

The study of NO X release on CeO 2 at low temperature during lean NO X trapping. Student: Qingqing Zhang Tutor: Meiqing Shen School of Chemical Engineering and Technology, TJU 2011-04-13. Contents. Study of NO X Release on CeO 2. NO X conversion has a low point around 147℃.

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The study of NO X release on CeO 2 at low temperature during lean NO X trapping

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  1. The study of NOX release on CeO2 at low temperature during lean NOX trapping Student: Qingqing Zhang Tutor: Meiqing Shen School of Chemical Engineering and Technology, TJU 2011-04-13

  2. Contents

  3. Study of NOX Release on CeO2 • NOX conversion has a low point around 147℃. • Sample: aged-(PA+CeO2), 0.5g sample + 1.5g quartz. • Condition: absorb NOX at 100℃ about 500s, then increase the temperature with 10 ℃/min. NOX release Fig. 1 NOX conversion with temperature increasing. Gas composition: 120 ppm NO, 10% O2, 5% CO2, 6% H2O, and N2 as balance gas; the total flow rate was 1 L/min; The delay time at 100 ℃ is 500s.

  4. Study of NOX Release on CeO2 • The NOX trapping capacity of CeO2 around 150℃ is lower than other temperature, Fig. 2 NOX concentration of each sample. Fig. 3 NOX trapping capacity of CeO2 at different temperature (400s).

  5. Study of NOX Release on CeO2 • Bidentate nitrites on CeO2 decompose around 150℃ indicating NOX release at low temperature. Bidentate nitrites Bidentate nitrites Fig. 4 DRIFTS spectra collected at 100℃ Fig. 5 DRIFTS spectra collected at different temperature

  6. Inhibit NOX release • CeZr and Ba/CeO2 inhibit the NOX release at low temperature, however NOX trapping capacity of Ba/CeO2 is less than pure CeO2. Fig. 7 NOX trapping capacity of each sample at different temperature (400s). Fig. 6 NOX conversion of each sample with temperature increasing.

  7. Summary • NOX release is happened on purge CeO2 sample. Bidentate nitrites on the surface of CeO2 are not stable enough, it will decompose around 150℃. • CeZr and Ba/CeO2 inhibit the NOX release at low temperature. Ce6Zr4 present outstanding NOX trapping capacity in comparison with pure CeO2. However, Ba/CeO2 is worse.

  8. Further Research • Further Research: • NOX decomposition on the surface of Pt/Al2O3 and CeO2: • Change gas composition, e.g. NO, NO/O2, and detect the outlet concentration of NO and NO2; • Detect N2 through heat exchange. • The mechanism of nitrites/nitrates formed on the surfaces of CeO2 and CeZr (DRIFTS): • NOX adsorption at low temperature, e.g. 50℃; • Change gas composition, e.g. NO/O2, NO2, NO; • Decrease gas concentration, e.g. 50ppm NO; • Change sample composition, e.g. PA+CeZr, CeZr.

  9. Further Research • Further Research: • The reason of CeZr inhibiting NOX release: • Surface active [O] species: TPR, DRIFTS. • Heat of reaction (TGA/DSC): • NOX absorbs on the surface of CeO2 and CeZr; • NOX desorbs from the surface of CeO2 and CeZr. • The relationship of Ba and CeO2 on Ba/CeO2.

  10. Thank you

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