Study of the effect of Ba loading for catalytic activity of Pt–Ba/Al2O3 model catalysts

Castoldi, L.; Nova, Isabella; Lietti, Luca; Forzatti, Pio

doi:10.1016/j.cattod.2004.05.006

Cited by 155 publications

(92 citation statements)

References 22 publications

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“…Since the 20%BaO/Al 2 O 3 sample has a longer complete NO x uptake time than the 8% loaded one, the amount of barium species around the Pt particles seems to determine the time period in which complete NO x uptake occurs. These interpretations are consistent with the recent report about the effect of BaO loading for catalytic activity of Pt/BaO/Al 2 O 3 catalysts published by Nova and coworkers [18]. These authors clearly show that the NO x uptake increased with BaO loading and they point out the importance of the intimate contact between Pt and the Ba-containing phase in the NO x storage process.…”

Section: Resultssupporting

confidence: 90%

NO x uptake mechanism on Pt/BaO/Al2O3 catalysts

et al. 2006

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The NO x adsorption mechanism on Pt/BaO/Al 2 O 3 catalysts was investigated by performing NO x storage/reduction cycles, NO 2 adsorption and NO + O 2 adsorption on 2%Pt=ðxÞBaO/Al 2 O 3 (x = 2, 8, and 20 wt%) catalysts. NO x uptake profiles on 2%Pt=20%BaO/Al 2 O 3 at 523 K show complete uptake behavior for almost 5 min, and then the NO x level starts gradually increasing with time and it reaches 75% of the inlet NO x concentration after 30 min time-on-stream. Although this catalyst shows fairly high NO x conversion at 523 K, only $2.4 wt% out of 20 wt% BaO is converted toBa(NO 3 Þ 2 . Adsorption studies by using NO 2 and NO + O 2 suggest two different NO x adsorption mechanisms. The NO 2 uptake profile on 2%Pt=20%BaO/Al 2 O 3 shows the absence of a complete NO x uptake period at the beginning of adsorption and the overall NO x uptake is controlled by the gassolid equilibrium between NO 2 and BaO/BaðNO 3 Þ 2 phase. When we use NO + O 2 , complete initial NO x uptake occurs and the time it takes to convert $4% of BaO to BaðNO 3 Þ 2 is independent of the NO concentration. These NO x uptake characteristics suggest that the NO + O 2 reaction on the surface of Pt particles produces NO 2 that is subsequently transferred to the neighboring BaO phase by spill over. At the beginning of the NO x uptake, this spill-over process is very fast and so it is able to provide complete NO x storage. However, the NO x uptake by this mechanism slows down as BaO in the vicinity of Pt particles are converted to BaðNO 3 Þ 2 . The formation of BaðNO 3 Þ 2 around the Pt particles results in the development of a diffusion barrier for NO 2 , and increases the probability of NO 2 desorption and consequently, the beginning of NO x slip. As NO x uptake by NO 2 spill-over mechanism slows down due to the diffusion barrier formation, the rate and extent of NO 2 uptake are determined by the diffusion rate of nitrate ions into the BaO bulk, which, in turn, is determined by the gas phase NO 2 concentration.

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Section: Resultssupporting

confidence: 90%

NO x uptake mechanism on Pt/BaO/Al2O3 catalysts

et al. 2006

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“…However, beyond that, the percentage of NO storage started to decreased, probably due to the diffusion limitations at higher loading. These data were in agreement with some of the literature (Bethke et al 1995;Castoldi et al 2004;Milt et al 2003a). The decrease in activity for the higher loading samples was also attributed to the dissolution of some amount of K(NO 3 ) during the impregnation process and caused higher K coverage of the Al 2 O 3 surface (Castoldi et al 2004;Dawody et al 2004 Matsumoto, 2004.…”

Section: Process Studiessupporting

confidence: 93%

“…These data were in agreement with some of the literature (Bethke et al 1995;Castoldi et al 2004;Milt et al 2003a). The decrease in activity for the higher loading samples was also attributed to the dissolution of some amount of K(NO 3 ) during the impregnation process and caused higher K coverage of the Al 2 O 3 surface (Castoldi et al 2004;Dawody et al 2004 Matsumoto, 2004. The combination of the Ba and K loading resulted in a catalyst capable of showing improvement in the catalytic activity compared to single metal loading, and may be attributed to some synergistical effects between these two metal oxides.…”

Section: Process Studiessupporting

confidence: 93%

Storage of Nitrous Oxide (NOx) in Diesel Engine Exhaust Gas using Alumina-Based Catalysts: Preparation, Characterization, and Testing

Alsobaai¹

2017

Jou. Eng. Res.

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This work investigated the nitrous oxide (NOx) storage process using alumina-based catalysts (K 2 O/Al 2 O 3 , CaO/Al 2 O 3, and BaO/Al 2 O 3 ). The feed was a synthetic exhaust gas containing 1,000 ppm of nitrogen monoxide (NO), 1,000 ppm i-C 4 H 10 , and an 8% O 2 and N 2 balance. The catalyst was carried out at temperatures between 250-450°C and a contact time of 20 minutes. It was found that NOx was effectively adsorbed in the presence of oxygen. The NOx storage capacity of K 2 O/Al 2 O 3 was higher than that of BaO/Al 2 O 3. The NOx storage capacity for K 2 O/Al 2 O 3 decreased with increasing temperature and achieved a maximum at 250°C. Potassium loading higher than 15% in the catalyst negatively affected the morphological properties. The combination of Ba and K loading in the catalyst led to an improvement in the catalytic activity compared to its single metal catalysts. As a conclusion, mixed metal oxide was a potential catalyst for de-NOx process in meeting the stringent diesel engine exhaust emissions regulations. The catalysts were characterized by a number of techniques and measurements, such as X-ray diffraction (XRD), electron affinity (EA), a scanning electron microscope (SEM), Brunner-Emmett-Teller (BET) to measure surface area, and pore volume and pore size distribution assessments.

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“…The NOx absorption by BaO requires oxidation of the thermal nitrogen oxide, [6][7][8][9][10] i.e., NO, which becomes converted to NO 2 on a platinum catalyst. [11][12][13] Conversely, following the release of NO 2 from BaO, the reduction to N 2 takes place on a rhodium catalyst. 14 We investigate the possible utilization of functionalized boron doped graphene in circumventing the above Pt/BaO/Rh catalyst system.…”

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confidence: 99%