Development of Synergic Mixed Metal Oxides for the Combined Catalytic-Absorptive Removal of Nitric Oxide from Diesel Exhaust

Document Type : Research Article


1 Discipline of Chemical Engineering, School of Engineering, Monash University Sunway Campus, Jalan Lagoon Selatan, 46150 Bandar Sunway, Selangor, MALAYSIA

2 School of Chemical Engineering, Engineering Campus, University Sains Malaysia, 14300, Nibong Tebal, Penang, MALAYSIA


The NO removal over oxide sorbents (K2O/Al2O3 , CaO/Al2O3 and BaO/Al2O3) at a loading of up to 25 wt.% was investigated using a synthetic diesel exhaust gas containing  1,000 ppm NO, 1000 ppm iso-butane (i-C4H10), 8% O2 and N2 balance. The reactor was operated  at 250 oC to 450 oC for the activity study. NO was effectively stored (removal efficiencies between 30-60 %) as nitrate under experimental conditions after surface oxidation to NO2; and the maximum removal efficiency decreased in the order of K2O/Al2O3 (55.4 %) > BaO/Al2O3 (39.0 %) > CaO/Al2O3 (37.0 %). K2O/Al2O3 had higher mobility; but loadings higher than 15 wt.% were detrimental to the morphological properties. Despite higher basicity, CaO/Al2O3 showed  lower removal efficiency of NO compared to BaO(10)/Al2O3 due to low catalytic NO2 formation activity. Unlike K2O(10)/Al2O3, BaO(10)/Al2O3 showed increasing NO removal between 350 oC and 450 oC. K2O(5)BaO(5)/Al2O3 resulted in better surface area and volume leading to about 65 % of NO removal. This was attributed to synergic effects between physicochemical, catalytic and NO removal properties of the components.The high performance of K2O(5)BaO(5)/Al2O3  wassuccessfully elucidated based on the characteristics of the sorbent.


Main Subjects

[1] Kabin K.S., Muncrief R.L., Harold M.P., NOx Storage and Reduction on a Pt/BaO/alumina Monolithic Storage Catalyst, Catal. Today, 96, p. 79 (2004).
[2] Centi G., Arena G.E., Perathoner S., Nanostructured Catalyst for NOx Storage-reduction and N2O Decomposition, J. Catal., 216, p. 443 (2003).
[3] Epling W.S., Parks J.E., Campbell G.C., Yezerets A., Currier N.W., Campbell L.E., Further Evidence of Multiple NOx Sorption Sites on NOx Storage/Reduction Catalysts, Catal. Today, 96, p. 21 (2004).
[4] Takahashi N., Shinjoh H., Ijima T., Suzuku T., Yamazaki K., Yokota K., Suzuki H., Miyoshi N., Matsumoto S., Tanizawa T., Tanaka T., Tateishi S., Kasahara K., The New Concept 3-Way Catalyst for Automotive Lean-burn Engine: NOx Storage and Reduction Catalyst, Catal. Today, 27, p. 63 (1996).
[5] Lietti L., Forzatti P., Nova I., Tronconi E., NOx Storage Reduction over Pt-Ba/γ-Al2O3 Catalyst, J. Catal., 204, p. 175 (2001).
[6] Milt V.G., Querini C.A., Miró E.E., Ulla M.A., Abatement of Diesel Exhaust Pollutants: NOx Adsorption on Co,Ba,K/CeO2 Catalyst, J. Catal., 220, p. 424 (2003).
[7] Su Y., Amiridis M.D., In Situ FTIR Studies of the Mechanism of NOx Storage and Reduction on Pt/Ba/Al2O3 Catalysts, Catal. Today, 96, p. 31 (2004).
[8] Piacentini M., Maciejewski M., Baiker A., NOx Storage-reduction Behavior of Pt-Ba/MO2 (MO2=SiO2, CeO2, ZrO2) Catalysts, Appl. Catal. B, 72, p. 105 (2006).
[9] Jimenez B.I.M., Lahougue A., Bazin P., Harle V., Blanchard G., Sassi A., Daturi M., Operando Systems for the Evaluation of the Catalytic Performance of NOx Storage and Reduction Materials, Catal. Today, 119, p. 73 (2007).
[10] Bethke K.A., Kung M.C., Yang B., Shah M., Alt D., Li C., Kung H.H., Metal Oxide Catalysts for Lean NOx Reduction, Catal. Today, 26, p. 169 (1995).
[11] Fridell E., Skoglundh M., Westerberg B., Johansson S., Smedler G., NOx Storage in Barium-containing Catalysts, J. Catal., 183, p. 196 (1999).
[12] Milt V.G., Pisarello M.L., Miró E.E., Querini C.A., Abatement of Diesel-exhaust Pollutants: NOx Storage and Soot Combustion K/La2O3 Catalysts, Appl. Catal. B, 41, p. 397 (2003).
[13] Despres J., Koebel M., Kröcher O., Elsener M., Wokaun A., Storage of NO2 on BaO/TiO2 and       the Influence of NO, Appl. Catal. B, 43, p. 389 (2003).
[14] Westerberg B., Fridell E., A Transient FTIR Study of Species Formed During NOx Storage in the Pt/BaO/Al2O3 System, J. Molec. Catal. A, 165, p. 249 (2001).
[15] Dawody J., Skonglundh M., Fridell E., The Effect of Metal Oxide Additives (WO3, MoO3, V2O5, Ga2O3) on the Oxidation of NO and SO2 over Pt/Al2O3 and Pt/BaO/Al2O3 Catalysts, J. Molec. Catal. A, 209, p. 215 (2004).
[16] Castoldi L., Nova I., Lietti L., Forzatti P., Study of the Effect of Ba Loading for Catalytic Activity of Pt–Ba/Al2O3 Model Catalysts, Catal. Today, 96, p. 43 (2004).
[17] Xiao J., Li X., Deng S., Wang F., Wang L., NOx Storage-reduction over Combined Catalyst Mn/Ba/Al2O3 and Pt/Ba/Al2O3, Catal. Comm., 8, p. 926 (2007).
[18] Sedlmair C., Seshan K., Lercher J.J., Elementary Steps of NOx Adsorption and Surface Reaction on    a Commercial Storage-reduction Catalyst, J. Catal., 214, p. 308 (2003).
[19] Halachev T., Antanasova P., Agudo A.L., Arias M.G., Ramirez J., Activity of P-Ni-W/Al2O3 Catalysts  with Varying Phosphorus Content in the Hydrogenation of Naphthalene, Appl. Catal. A, 136, p. 161 (1996).