The Introduction of NSR and The Study of CeZr Inhibits the NO X Release

Student: Qingqing Zhang

Tutor: Meiqing Shen

Environmental Catalysis

School of chemical engineering and technology, TJU

2010.12.02

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Lean Rich (HC, CO, H2)

Noble Metal (Pt, Pd, Rh) Noble Metal (Pt, Pd, Rh)

The NOX storage-reduction (NSR) catalyst was developed for automotive lean-burn engines, and the NOX reduction phenomena were investigated by four steps.

NSR catalyst involve three components: Noble metal component: Pt, Rh, Pd; Storage component: alkali- or alkaline-earth species (Ba, K, Ce); Support material: Al2O3, ZrO2, CeO2, TiO2;

The typical NSR catalyst: Pt/Al2O3, Ba/Al2O3

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Support material

PM

Nitrates, nitrites

SM

NO+O2NO2

Support material

PM

Nitrates, nitrites

SM

NOX

Lean condition Rich condition

NO HC, H2, CO

N2, H2O CO2

The influences of temperature and gas(environment) for NSR:

Temperature: 350-400 ;℃ 1. noble metal;

2. storage component;

3. support component;

Exhaust gas composition:

1. Reduction gas: H2 > CO > HC;

2. H2O, CO2;

3. SO2;

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Every curve has a lowest point around 145 , and lowest NO℃ X conversion with respect to PA-Ce is smallest.

Bidentate nitrites on CeO2 decompose about 200 . ℃

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NOX release

Bidentate nitrites on CeO2

300 ℃

100 ℃

200 ℃

Fig. 1 NOX conversion of each sample withtemperature increasing.

Fig. 2 DRIFTS of CeO2 collected with temperature increasing.

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We test using CeZr to inhibit the NOX release at low temperature.

Every curve have a valley, while CeO2 shows the release phenomena obviously.

CeO2

From the Fig. 3, Ce8Zr2 shows a better NOX storage capacity than CeO2. Ce6Zr4 and ZrO2 adsorb less NOX than CeO2 at low temperature (< 120 ).℃More ZrO2 is not benefit for NOX storage.Ce8Zr2 can inhibit the NOX release to some extent.

Fig. 3 NOX conversion of CeZr samples withtemperature increasing.

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Nitrates and nitrites develop with time going on.

Fig. 4 DRIFTS of CeZr samples collected with temperature increasing. * B. Azambre, J. Phys. Chem. C 2009, 113, 13287-13299

Monodentate nitrites on ZrO2: 1462 v(N=O), 1160 v(N-O);Bidentate nitrites on CeZr: 1200-1185 v(N-O);Bidentate nitrites on CeO2: 1178 v(N-O);Bridged bidentate nitrates: 1610, 1220 vas(NO3

-) splitAround 1000 vs(NO3

-);Chelate biedntate nitrates: 1520, 1227 vas(NO3

-) split, 1030 vs(NO3

-) ;Bidentate nitrites on Al2O3: 1320;Bridged bidentate nitrates: 1660-1590, 1250-1240, 1060-1000.Bidentate nitrites

appear on each sample.

10Fig. 5 DRIFTS of CeZr collected with temperature increasing.

Bidentate nitrites on CeO2 decompose about 200 . ℃

* B. Azambre, J. Phys. Chem. C 2009, 113, 13287-13299

Bidentate nitrites

Bidentate nitrites

Bidentate nitrites

Monodentate nitrites on ZrO2: 1462 v(N=O), 1160 v(N-O);Bidentate nitrites on CeZr: 1200-1185 v(N-O);Bidentate nitrites on CeO2: 1178 v(N-O);Bridged bidentate nitrates: 1610, 1220 vas(NO3

-) splitAround 1000 vs(NO3

-);Chelate biedntate nitrates: 1520, 1227 vas(NO3

-) split, 1030 vs(NO3

-) ;Bidentate nitrites on Al2O3: 1320;Bridged bidentate nitrates: 1660-1590, 1250-1240, 1060-1000.Bidentate nitrites on CeO2

decompose about 200 ;℃CeZr does not inhibit the bidentate nitrites appearance and decomposition;

Conclusion From Fig. 3, Ce8Zr2 inhibits the NOX release at low temperature

obviously, however Ce8Zr2 does not inhibit the bidentate nitrites appearance and decomposition.

Issues need further addressing: Why dose Ce8Zr2 inhibit the NOX release?

How is it happened?

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