deNOx Performance and Reaction Mechanism of the Di-Air System

Reaction Mechanism Study of the Di-Air System and Selectivity and Reactivity of NO Reduction in Excess O2

“…The reactant and product(s) are recorded versus time (response) by a mass spectrometer, details of this set-up can be found elsewhere [19]. In the TAP experiments with 15 NO and 18 O 2 pulses: 1) the catalyst was firstly oxidised using an O 2 pulse train; 2) secondly, a pre-reduction step with C 3 H 6 pulses was performed until the effluent of the reactor remained constant.…”

“…Figure 1A showed the result of 15 NO pulses over C 3 H 6 reduced ceria at 560 °C. The discontinuities in Figure 1A was attributed to the refilling of the 15 NO buffer vessel in the TAP. From 0 to 5340 pulses ( Figure 1A), a full NO conversion was observed with 15 N 2 as the main product (hardly any CO was formed).…”

“…Compared to the current NSR system's narrow operating temperature window, caused by the requirement to store the NO x as nitrite/nitrate on the Ba component, the Di-Air system retains a high NO x conversion (above 80%) up to 800 o C at a high space velocity up to 1.2·10 5 l/l/h. They found that HC's injection was more effective in the NO x reduction in comparison to that of CO and H 2 [14,15]. The unique performance of the Di-Air system was attributed to the formation of stable isocyanate (CNO) and isocyanide (CN) intermediates on the catalyst surface as being evidenced by FTIR observations [16].…”

Next Generation Automotive DeNOx Catalysts: Ceria What Else?

“…Some of these hydrocarbons derived intermediates were presumed to convert to N ei- ther independently or by reacting with close-by NO , while some were converted to -CN and -NCO by hydrolysis and could be selectively reduced to NO . Upon hydrolysis of these intermediates, many by-products can be expected, and some have been observed in another type of NO abatement technology at relatively high NO conversion [52,53], like aldehydes (R-CHO), carboxylic acids (R-COOH), amines (R-NH ), oximes (R-CNOH), and hydroxylamine (NH OH). The proposed Di-Air reaction mechanism is shown in Figure 1.17.…”

Fundamental understanding of the Di-Air system (an alternative NO abatement technology). I: The difference in reductant pre-treatment of ceria

“…Recently, Bisaiji et al (Toyota company) developed the Di-Air system (Diesel DeNO x System by Adsorbed Intermediate Reductants). Short rich and lean time intervals are created by high frequency directly injecting hydrocarbons (diesel fuel injection) into the exhaust system upstream of a typical NSR catalyst (Pt/Rh/Ba/K/Ce/Al 2 O 3 ) [4,5]. The Di-Air system has shown promise to meet future NO x emission standards under realistic driving test conditions.…”