Effect of barium loading on CuO x–CeO 2 catalysts: NO x storage capacity, NO oxidation ability and soot oxidation activity

Abstract

A series of Ba–Cu–Ce catalysts were prepared by loading different amounts of Ba(Ac) 2 on the sol–gel-synthesized CuO x –CeO 2 mixed oxides. The activities of the catalysts for soot oxidation were evaluated in 1000 ppm NO/10% O 2/N 2 under loose contact conditions. The catalysts were characterized by XRD, BET, H2-TPR, in situ-DRIFTS and NO-TPO measurements. When Ba loading is between 6 and 10 mol.% of Cu + Ce, the catalysts exhibit an onset temperature ( T i) as low as 376 °C. NO is oxidized at Cu x+ and Ce x+ sites and then stored on the adjacent Ba species in form of barium nitrate. Ba(NO 3) 3 begins to decompose, releasing abundant NO 2 at around 370 °C under the driving of soot as the reductant. The nitrate-derived NO 2 and the NO-derived NO 2 initiate the soot combustion over the Ba-modified catalysts with a significantly lowered T i. The ternary catalysts lose their NO x storage capacity after hydrothermally aged at 800 °C for 10 h due to the formation of BaCeO 3. However, Ba restrains the sintering of (Cu,Ce)O x , resulting in relatively more favorable redox properties and thus higher activity for NO oxidation. The barium-modified catalysts show lower onset temperatures (470–480 °C) of soot oxidation than pure CuCe (509 °C) after aging.