Properties of BaAl₂O₄ in the Simultaneous Removal of Soot and NO_x

Abstract

The catalytic activity of BaAl 2 O 4 in the simultaneous removal of soot and NO x was evaluated by Temperature Programmed Reaction (TPR). It was found that BaAl 2 O 4 could effectively catalyze the reaction of soot with NO x under various reaction conditions. Compared with non-catalytic combustion, ignition temperature, T ig , and maximum combustion temperature, T m , of soot decreased by more than 175°C and 240°C, respectively. Tight contact of soot with BaAl 2 O 4 , higher O 2 content and a lower flow rate of synthesized gases were beneficial to the catalytic reaction. It was confirmed by Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) analysis, that the reaction of soot with NO 2(ad) was the most important factor in simultaneous removal of soot and NO x , in which NO 2(ad) existed on BaAl 2 O 4 in the form of monodentate nitrate, bridged nitrate and ionic nitrate.

The Effect of Oxygen Concentration on the Reaction of NOx with Soot Over BaAl2O4

“…It was found that the activity of the catalyst was closely related to the O 2 concentration in the NO-containing stream [6][7][8]. In previous work by the current authors [1], it has been demonstrated that the activity of BaAl 2 O 4 is negligible and that N 2 O is not produced in the absence of oxygen. However, the activity and the N 2 O production level increase markedly under excess oxygen conditions.…”

“…2a), and the weak bands at 1385 and 1744 cm -1 are observed at the same time. These results suggest that the formation of nitrates is due to the oxidation of nitrites by lattice oxygen [1,15]. After feed- Figure 1.…”

“…As described in the preceding paper [1], Ba(NO 3 ) 2 and Al-(NO 3 ) 3 · 9 H 2 O were the starting materials used to synthesize BaAl 2 O 4 . The stoichiometric quantities of barium nitrate and alumina nitrate were dissolved in distilled water and then dried.…”

“…Diesel engines contribute a large part of the worldwide NO x and soot particulate emissions especially in the larger cities. Catalytic processes for the simultaneous reduction of the emissions from diesel exhausts have attracted much attention [1][2][3][4]. The process in which NO x and soot were removed simultaneously in an oxidizing atmosphere was first proposed by Yoshida et al [5].…”

“…It has been explained in literature that nitrates, which are easily produced on the catalyst surface in the presence of oxygen, result in BaAl 2 O 4 showing high activity [1]. As yet unresolved issues include the mechanisms by which O 2 exerts an influence on the selectivity of the products and on the adsorbates on BaAl 2 O 4 .…”