Abstract
NOx storage on Pt/Al2O3 and Pt/La-Al2O3 in the temperature range 80-160°C was investigated by means of microreactor and in situ DRIFTS experiments, to ascertain their suitability for passive NOx adsorber applications. Addition of 1wt% La to Al2O3 resulted in the creation of new NOx storage sites and improved NOx storage efficiency. However, according to TPD measurements, Pt/La-Al2O3 exhibited slightly lower NOx desorption efficiency below 250°C than Pt/Al2O3. During repeated NOx adsorption-desorption cycles, almost no benefit of La addition was observed after five cycles, due to the inability to regenerate the strong NOx storage sites associated with the La at 250°C. DRIFTS measurements indicated that during NOx-TPD, nitrites and weakly bound nitrate species were initially removed from the surface of Pt/Al2O3 and Pt/La-Al2O3. NOx desorption at higher temperatures (>250°C) was mainly associated with nitrate decomposition. DRIFTS measurements on Pt/Al2O3 revealed that NOx was mainly stored on the Al2O3 surface when oxidized Pt was present, although when a reductive re-treatment was applied NOx storage on reduced Pt sites became significant and total NOx storage efficiency was improved. However, compared to bare Al2O3, NOx desorption efficiency below 250°C significantly dropped when Pt was present, and was even lower after pre-reduction in H2. Overall, the Pt-Al without pre-reduction showed the highest amount of NOx desorption below 250°C.
Original language | English |
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Pages (from-to) | 283-292 |
Number of pages | 10 |
Journal | Applied Catalysis B: Environmental |
Volume | 170-171 |
DOIs | |
State | Published - Jul 1 2015 |
Bibliographical note
Publisher Copyright:© 2015 Elsevier B.V.
Keywords
- Adsorption
- Alumina
- Desorption
- Lanthanum
- Low temperature
- Passive nox adsorber
ASJC Scopus subject areas
- Catalysis
- General Environmental Science
- Process Chemistry and Technology