Quantification of the in situ DRIFT spectra of Pt/K/γ-Al 2O3 NOx adsorber catalysts

Todd J. Toops; D. Barton Smith; William P. Partridge

doi:10.1016/j.apcatb.2004.10.021

Quantification of the in situ DRIFT spectra of Pt/K/γ-Al ₂O₃ NO_x adsorber catalysts

Todd J. Toops, D. Barton Smith, William P. Partridge

Applied Catalysis&Emissions Res. Group

Research output: Contribution to journal › Article › peer-review

95 Scopus citations

Abstract

A method to quantify DRIFT spectral features associated with the in situ adsorption of gases on a NO_x adsorber catalyst, Pt/K/Al ₂O₃, is described. To implement this method, the multicomponent catalyst is analysed with DRIFT and chemisorption to determine that under operating conditions the surface comprised a Pt phase, a pure γ-Al₂O₃ phase with associated hydroxyl groups at the surface, and an alkalized-Al₂O₃ phase where the surface -OH groups are replaced by -OK groups. Both DRIFTS and chemisorption experiments show that 93-97% of the potassium exists in this form. The phases have a fractional surface area of 1.1% for the 1.7 nm-sized Pt, 34% for pure Al ₂O₃ and 65% for the alkalized-Al₂O₃. NO₂ and CO₂ chemisorption at 250°C is implemented to determine the saturation uptake value, which is observed with DRIFTS at 250°C. Pt/Al₂O₃ adsorbs 0.087 μmol CO ₂/m²and 2.0 μmol NO₂/m², and Pt/K/Al₂O₃ adsorbs 2.0 μmol CO₂/m ²and 6.4 μmol NO₂/m². This method can be implemented to quantitatively monitor the formation of carboxylates and nitrates on Pt/K/Al₂O₃ during both lean and rich periods of the NO_x adsorber catalyst cycle.

Original language	English
Pages (from-to)	245-254
Number of pages	10
Journal	Applied Catalysis B: Environmental
Volume	58
Issue number	3-4
DOIs	https://doi.org/10.1016/j.apcatb.2004.10.021
State	Published - Jun 28 2005

Funding

This research was sponsored by the U.S. Department of Energy, Office of Transportation Technologies with Gurpreet Singh as the program manager. The authors thank Dr. Louis Powell of the Oak Ridge Y-12 National Security Complex for use of the MIDAC FTIR spectrometer. The contribution of Todd J. Toops was supported, in part, by an appointment to the Oak Ridge National Laboratory Postdoctoral Research Associates Program administered jointly by the Oak Ridge Institute for Science and Education and the Oak Ridge National Laboratory. Oak Ridge National Laboratory operates under DOE contract number DE-AC05-00OR22725 and is managed by UT-Battelle. EmeraChem LLC of Knoxville, TN is a catalyst and surface chemistry company with commercial experience in NO x adsorber catalysis.

Funders	Funder number
Oak Ridge National Laboratory
Office of Transportation Technologies
U.S. Department of Energy	DE-AC05-00OR22725
Oak Ridge National Laboratory
Oak Ridge Institute for Science and Education
UT-Battelle

Keywords

Chemisorption
Lean NO traps
NO adsorber catalysts
Potassium
Pt
Pt/K/AlO
Quantified DRIFTS
γ-AlO

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10.1016/j.apcatb.2004.10.021

Cite this

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title = "Quantification of the in situ DRIFT spectra of Pt/K/γ-Al 2O3 NOx adsorber catalysts",

abstract = "A method to quantify DRIFT spectral features associated with the in situ adsorption of gases on a NOx adsorber catalyst, Pt/K/Al 2O3, is described. To implement this method, the multicomponent catalyst is analysed with DRIFT and chemisorption to determine that under operating conditions the surface comprised a Pt phase, a pure γ-Al2O3 phase with associated hydroxyl groups at the surface, and an alkalized-Al2O3 phase where the surface -OH groups are replaced by -OK groups. Both DRIFTS and chemisorption experiments show that 93-97% of the potassium exists in this form. The phases have a fractional surface area of 1.1% for the 1.7 nm-sized Pt, 34% for pure Al 2O3 and 65% for the alkalized-Al2O3. NO2 and CO2 chemisorption at 250°C is implemented to determine the saturation uptake value, which is observed with DRIFTS at 250°C. Pt/Al2O3 adsorbs 0.087 μmol CO 2/m2and 2.0 μmol NO2/m2, and Pt/K/Al2O3 adsorbs 2.0 μmol CO2/m 2and 6.4 μmol NO2/m2. This method can be implemented to quantitatively monitor the formation of carboxylates and nitrates on Pt/K/Al2O3 during both lean and rich periods of the NOx adsorber catalyst cycle.",

keywords = "Chemisorption, Lean NO traps, NO adsorber catalysts, Potassium, Pt, Pt/K/AlO, Quantified DRIFTS, γ-AlO",

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AU - Toops, Todd J.

AU - Smith, D. Barton

AU - Partridge, William P.

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Y1 - 2005/6/28

N2 - A method to quantify DRIFT spectral features associated with the in situ adsorption of gases on a NOx adsorber catalyst, Pt/K/Al 2O3, is described. To implement this method, the multicomponent catalyst is analysed with DRIFT and chemisorption to determine that under operating conditions the surface comprised a Pt phase, a pure γ-Al2O3 phase with associated hydroxyl groups at the surface, and an alkalized-Al2O3 phase where the surface -OH groups are replaced by -OK groups. Both DRIFTS and chemisorption experiments show that 93-97% of the potassium exists in this form. The phases have a fractional surface area of 1.1% for the 1.7 nm-sized Pt, 34% for pure Al 2O3 and 65% for the alkalized-Al2O3. NO2 and CO2 chemisorption at 250°C is implemented to determine the saturation uptake value, which is observed with DRIFTS at 250°C. Pt/Al2O3 adsorbs 0.087 μmol CO 2/m2and 2.0 μmol NO2/m2, and Pt/K/Al2O3 adsorbs 2.0 μmol CO2/m 2and 6.4 μmol NO2/m2. This method can be implemented to quantitatively monitor the formation of carboxylates and nitrates on Pt/K/Al2O3 during both lean and rich periods of the NOx adsorber catalyst cycle.

AB - A method to quantify DRIFT spectral features associated with the in situ adsorption of gases on a NOx adsorber catalyst, Pt/K/Al 2O3, is described. To implement this method, the multicomponent catalyst is analysed with DRIFT and chemisorption to determine that under operating conditions the surface comprised a Pt phase, a pure γ-Al2O3 phase with associated hydroxyl groups at the surface, and an alkalized-Al2O3 phase where the surface -OH groups are replaced by -OK groups. Both DRIFTS and chemisorption experiments show that 93-97% of the potassium exists in this form. The phases have a fractional surface area of 1.1% for the 1.7 nm-sized Pt, 34% for pure Al 2O3 and 65% for the alkalized-Al2O3. NO2 and CO2 chemisorption at 250°C is implemented to determine the saturation uptake value, which is observed with DRIFTS at 250°C. Pt/Al2O3 adsorbs 0.087 μmol CO 2/m2and 2.0 μmol NO2/m2, and Pt/K/Al2O3 adsorbs 2.0 μmol CO2/m 2and 6.4 μmol NO2/m2. This method can be implemented to quantitatively monitor the formation of carboxylates and nitrates on Pt/K/Al2O3 during both lean and rich periods of the NOx adsorber catalyst cycle.

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