Role of Support in Lean DeNO_xCatalysis

Abstract

FTIR and pulse thermal analysis were applied to investigate catalysts containing Pt (1 wt%)/Ba (17 wt%) supported on c-Al 2 O 3 , SiO 2 and ZrO 2 . The aim was to learn how the support material affects the thermal stability of barium carbonate and its activity in the reaction to bulk Ba(NO 3 ) 2 . The lower thermal stability of BaCO 3 in alumina supported samples was found to influence the formation of barium nitrate during the NO x storage process. Quantification of Ba(NO 3 ) 2 formed during NO x storage indicated that for alumina supported catalysts only ca. 30% of barium present in the sample is involved in the storage process. The low thermal stability found for alumina supported barium nitrite excludes its role in the formation of barium nitrate during interaction of NO x with the catalyst at 300°C. The studies indicate that c-Al 2 O 3 plays a major role in influencing the thermal stability of BaCO 3 and Ba(NO 3 ) 2 . This finding seems to be relevant for the higher activity of c-Al 2 O 3 -supported catalysts in NO x storage reduction reactions. KEY WORDS:Lean DeNO x ; BaCO 3 ; Ba(NO 3 ) 2 and Ba(NO 2 ) 2 thermal stability; pulse thermal analysis; role of the support in NO x storage.

Effect of Ceria on the Storage and Regeneration Behavior of a Model Lean NO x Trap Catalyst

“…4, NO x evolution was not detected below 300°C. This is in line with literature reports that thermal desorption of NO x does not occur below the temperature at which adsorption was performed [12][13][14]. Decomposition of the adsorbed NO x species commenced slightly above 300°C, as evidenced by the evolution of NO x , this process extending up to 500°C for both catalysts.…”

Effect of γ-Al2O3 substrate on NO2 interaction with supported BaO clusters

“…A similar cooperative effect was also found on the decarbonated BaCO 3 surface [9] -adsorption of a NO 2 pair causing desorption of one CO 2 molecule with an energy gain of 1.5 eV and complete decarbonation of the BaCO 3 surface (adsorption of two NO 2 pairs and desorption of two CO 2 molecules) resulted in an energy gain of 2.2 eV. Although most experimental studies focused on BaO supported on various oxide substrates and demonstrated that the nature of the support materials has strong influence on the sorption property of BaO toward NO x [10,11], previous theoretical studies utilizing either periodic supercells or molecular clusters of BaO were almost exclusively focused on the bulk BaO surface or unsupported BaO clusters [12][13][14][15]. In the present letter, we report our results of the density functional theory (DFT) study on the substrate effect of c-Al 2 O 3 on BaO clusters towards NO 2 adsorption.…”

Role and distribution of different Ba-containing phases in supported Pt–Ba NSR catalysts

“…Assuming that NO x species are stored as nitrates allowed to quantify the amount of NO stored by TPRD of NO x saturated catalysts and to derive the fraction of active Ba [9,24,26]. The NO x storage efficiency is presented in figure 4 in terms of fraction of Ba involved in the NO x storage process versus the total Ba loaded.…”

“…Al 2 O 3, CeO 2 , ZrO 2 , Ce-Zr-oxides and SiO 2 are widely used in the control of combustion pollutants [13][14][15][16][17][18][19][20][21] and in our studies we specifically addressed the comparison of these oxides as supports in Pt-Ba based NO x storage-reduction catalysts. Preliminary results on Pt-Ba catalysts supported on different oxides indicated different NO x storage behavior depending on the support [9].…”

“…Detailed characterization of Ba-containing species on the support indicated that, depending on their interaction with the support [9,10], they posses different stability and NO x storage efficiency [11,12]. Al 2 O 3, CeO 2 , ZrO 2 , Ce-Zr-oxides and SiO 2 are widely used in the control of combustion pollutants [13][14][15][16][17][18][19][20][21] and in our studies we specifically addressed the comparison of these oxides as supports in Pt-Ba based NO x storage-reduction catalysts.…”