NOx storage catalysts

Figure 10.10. Principle of operation of NOx storage catalyst. During lean combustion, NO is oxidized to NO2 and stored by BaO as barium nitrates. Once the getter is saturated, a short rich excursion of the air-fuel mixture...

Engstrom, P., Amberntsson, A., Skoglundh, M. et al. (1999) Sulphur Dioxide Interaction with NOx Storage Catalysts, Appl. Catal. B Environ., 22, L241. 

Gobel, U., Hoehne, J., Lox, E.S. et al. (1999) Durability Aspects of NOx Storage Catalysts for Direct Injection Gasoline Vehicles, SAE Technical Paper 99FL-103. 

Fekete N, Kemmler R, Voigtlaender D, Kmtzsch B, Zimmer E et al (1997) Evaluation of NOx storage catalysts for lean bum gasoline fueled passenger cars. SAE Technical Paper 970746, doi 10.4271/970746... 

The NOx storage catalyst usually contains noble metals for reduction and oxidation and a NOx storage compound (an alkaline earth compound) supported on alumina [2]. During lean-bum conditions, NOx is being stored in the catalyst. To regenerate the catalyst, short periods of rich conditions are employed during which the stored NOx is released and subsequently reduced on the noble metal surfaces. 

TPD measurements were performed for the NOx-storage catalyst with Pt-Rh/Ba0/Al203 and for samples without the storage medium (BaO) or noble metals, respectively. TPD experiments were performed by exposing pre-reduced and pre-oxidised catalysts, respectively, to either NO or NO2 at room temperature. 

Finally, the cross sensitivity to S02 was measured. High S02 concentrations do not occur under normal driving conditions with fuels available in Western Europe, North America, or Japan, but if we consider the fuels available in emerging markets or the exhaust composition during desulfuration of a NOx storage catalyst, S02 concentrations of more than 500 ppm can occur. The results in Fig. 7.16.5 d show a small cross sensitivity to S02. 

This spike is caused by the breakthrough of the rich gas components. Then the fuel combustion changes from a rich A/F ratio back to a lean A/F ratio, and loading of the NOx storage catalyst starts again. 

Koci P, Plat F, Stepanek J, BSrtovS , Marek M, Kubicek M, SchmeiBer V, Chatteijee D, Weibel M (2009) Global kinetic model for the regeneration of NOx storage catalyst with CO, H2 and C3H6 in the presence of CO2 and H2O. Catal. Today 147 257-264... 

Clayton RD, Harold MP, Balakotaiah V (2008) Selective catalytic reduction of NO by H2 in 02 on Pt/BaO/Al203 monolith NOx storage catalysts. Appl. Catal. B 81 161-181... 

Tuttlies, U., Schmeisser, V., and Eigenberger, G. (2004) A mechanistic simulation model for NOx storage catalyst dynamics. Chem. Eng. Sci., 59,4731-4738. 

Krishna, K. and Makkee, M. (2006). Soot Oxidation over NOx Storage Catalysts Activity and Deactivation, Catal Today, 114, pp. 48-56. 

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