Evaluation of sol‐gel processed BaO·nAl2O3 materials as NOx traps

Narula, Chaitanya K.; Nakouzi, Sabine R.; Wu, Ruowen; Goralski, Christian T.; Allard, Lawrence F.

doi:10.1002/aic.690470320

Cited by 11 publications

(5 citation statements)

References 16 publications

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“…Sung and Burk have suggested that the primary deactivation mechanism is the sintering of the Pt [24]. However, Ford researchers reported that sol-gel processed catalysts can withstand temperatures up to 900 • C [34]. Regardless of the mechanism, protocols that avoid such excursions should be followed.…”

Section: Discussionmentioning

confidence: 97%

NOX storage and reduction on a Pt/BaO/alumina monolithic storage catalyst

2004

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Section: Discussionmentioning

confidence: 97%

NOX storage and reduction on a Pt/BaO/alumina monolithic storage catalyst

2004

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“…The samples used in these experiments were prepared by impregnating of γ-Al 2 O 3 (Alfa Aesar) with aqueous solutions of Ba(NO 3 ) 2 (Alfa Aesar). The BaO loadings were chosen to be 20 wt%, a value reported by Narula, et al as providing optimal storage properties [10], and 5-wt%, a value below that required to form a monolayer on the γ-Al 2 O 3 [7]. After impregnation of the alumina with Ba(NO 3 ) 2 , the samples were dried in air at 373 K for 4 h to remove excess water and then calcined in air for 5 h to various temperatures to form different phases.…”

Section: Methodsmentioning

confidence: 99%

“…For example, Piacentini and coworkers recently reported that there are three types of BaO in Ba/Al 2 O 3 , with an amorphous type that forms above the monolayer BaO exhibiting the highest reactivity towards NO x [7]. Related to this question is that BaO and Al 2 O 3 will react at high temperatures to form an aluminate phase, BaAl 2 O 4 [8][9][10][11][12]. While some have indicated that the aluminate phase can act as a trap [9][10][11][12], the majority of trapping studies reported in the literature have been performed on materials that were calcined at temperatures that suggested the aluminate phase was being avoided [3,[13][14][15][16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%

An investigation of NOx storage on Pt–BaO–Al2O3

Gong

Luo

Gorte

2006

Applied Catalysis B: Environmental

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A series of samples containing 5-wt% or 20-wt% BaO on γ-Al 2 O 3 with different loadings of Pt were prepared and examined for their NO 2 adsorption properties using temperature programmed desorption (TPD), temperature programmed reduction (TPR), and x-ray diffraction (XRD). For calcination at 873 K or above, BaO/Al 2 O 3 formed BaAl 2 O 4. While carbonates were found to be unstable on the aluminate phase, NO 2 reacted with the aluminate to form bulk Ba(NO 3) 2 and Al 2 O 3 , even at room temperature. With BaO/Al 2 O 3 , reaction to form the nitrate required slightly higher temperatures because of the need to displace CO 2 ; however, pulsing NO 2 over pure Ba(CO 3) showed rapid reaction to form CO 2 and NO in the gas phase, along with Ba(NO 3) 2 , at 673 K. The decomposition temperature for Ba(NO 3) 2 shifted by more than 100 degrees when TPD was carried out in vacuum rather than in a carrier gas, showing that re-equilibration with the gas phase is important in the decomposition process. The addition of Pt had a minimal effect on the thermal stability of the nitrates but was essential for the reduction of the nitrate in H 2. Since a relatively small amount of Pt was sufficient to cause the complete reduction of the Ba(NO 3) 2 phase at temperatures below 400 K, it appears that the nitrates must be extremely mobile within the Ba-containing phase. Finally, trapping studies of NO 2 at 573 K, with or without 10% CO 2 in the gas phase, showed no measurable difference between BaO/Al 2 O 3 and BaAl 2 O 4 , with or without CO 2 .

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“…Matsumoto (2000) discussed adding TiO 2 and using a hexagonal monolith substrate to reduce the impact of sulfur poisoning. Narula et al (2001) found that sol–gel‐processed NOx traps have increased NOx trapping efficiency and respond better to high‐temperature regeneration than catalysts prepared through standard impregnation techniques. Theis et al (2003) found that the addition of rhodium reduces the amount of NOx released during the addition of the reductant.…”

Section: Introductionmentioning

confidence: 99%