Sulfur-tolerant NOx storage traps: an infrared and thermodynamic study of the reactions of alkali and alkaline-earth metal sulfates

John Breen, M. Marella, C. Pistarino, J.R.H. Ross

Research output: Contribution to journalArticle

58 Citations (Scopus)

Abstract

The sulfur tolerance of a barium-containing NOx storage/reduction trap was investigated using infrared analysis. It was confirmed that barium carbonate could be replaced by barium sulfate by reaction with low concentrations of sulfur dioxide (50 ppm) in the presence of large concentrations of carbon dioxide (10%) at temperatures up to 700 degreesC. These sulfates could at least be partially removed by switching to hydrogen-rich conditions at elevated temperatures. Thermodynamic calculations were used to evaluate the effects of gas composition and temperature on the various reactions of barium sulfate and carbonate under oxidizing and reducing conditions. These calculations clearly showed that if, under a hydrogen-rich atmosphere, carbon dioxide is included as a reactant and barium carbonate as a product then barium sulfate can be removed by reaction with carbon dioxide at a much lower temperature than is possible by decomposition to barium oxide. It was also found that if hydrogen sulfide was included as a product of decomposition of barium sulfate instead of sulfur dioxide then the temperature of reaction could be significantly lowered. Similar calculations were conducted using a selection of other alkaline-earth and alkali metals. In this case calculations were simulated in a gas mixture containing carbon monoxide, hydrogen and carbon dioxide with partial pressures similar to those encountered in real exhausts during switches to rich conditions. The results indicated that there are metals such as lithium and strontium with less stable sulfates than barium, which may also possess sufficient NOx storage capacity to give sulfur-tolerant NOx traps.
Original languageEnglish
Pages (from-to)123-128
Number of pages6
JournalCatalysis Letters
Volume80
Issue number3-4
Publication statusPublished - Jun 2002

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Alkaline Earth Metals
Barium Sulfate
Alkaline earth metals
alkaline earth metals
Alkalies
Barium
Sulfur
Sulfates
barium
sulfates
alkalies
sulfur
Carbon Dioxide
traps
Thermodynamics
Infrared radiation
thermodynamics
Hydrogen
Sulfur Dioxide
carbon dioxide

Cite this

Breen, John ; Marella, M. ; Pistarino, C. ; Ross, J.R.H. / Sulfur-tolerant NOx storage traps: an infrared and thermodynamic study of the reactions of alkali and alkaline-earth metal sulfates. In: Catalysis Letters. 2002 ; Vol. 80, No. 3-4. pp. 123-128.
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Sulfur-tolerant NOx storage traps: an infrared and thermodynamic study of the reactions of alkali and alkaline-earth metal sulfates. / Breen, John; Marella, M.; Pistarino, C.; Ross, J.R.H.

In: Catalysis Letters, Vol. 80, No. 3-4, 06.2002, p. 123-128.

Research output: Contribution to journalArticle

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