Relationship of Pt Particle Size with the NOx Storage Performance of Thermally Aged Pt/BaO/Al2O3 Lean NOx Trap Catalysts
Relationship between Pt particle size and NOx storage performance was investigated over a model Pt/BaO/Al2O3 and an enhanced lean NOx trap catalyst (LNT). These catalysts were treated at elevated temperature to mimic the effect of thermal aging encountered during the desulfation step in NOx trap catalyst regeneration. Combination of in situ time-resolved X-ray Diffraction (TR-XRD), DRIFT measurement after CO adsorption and TEM observation over the thermally aged samples clearly shows the sintering behavior of Pt crystalline as a function of time and temperature. Under elevated temperatures, the crystalline growth of Pt occurs within a short time (e.g. 1.5 hr) followed by the gradual increase with time. NOx storage reaction performed after successive thermal treatments of catalyst under oxygen and in situ XRD experiment have allowed us to correlate the NOx storage performance with phase change. Comparing the simple Pt-BaO/Al2O3 sample with the enhanced one which shows much less Pt sintering, it was confirmed that the Pt crystalline size plays a critical role in determining the NOx storage activity, in other words, the retention of the small Pt particles after thermal aging is crucial to maintain a higher activity. In conclusion, the prevention of Pt sintering when operated at elevated temperature must be a key factor to design the more durable LNT catalyst, thus potentially implying the practical importance for the improvement of the LNT technology.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 898102
- Report Number(s):
- PNNL-SA-49255; VT0401000; TRN: US200705%%412
- Journal Information:
- Industrial and Engineering Chemistry Research, 45(26):8815-8821, Journal Name: Industrial and Engineering Chemistry Research, 45(26):8815-8821
- Country of Publication:
- United States
- Language:
- English
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