Diesel and lean-bum engines

The selective reduction of NO by hydrocarbons in oxygen rich atmosphere has been reported for zeolite-based catalysts, especially Cu-ZSM-5 solids (1), but their low thermal stability limits their use for treatment of emissions from Diesel and lean-bum engines. An... 

The catalytic reduction or decomposition of nitrogen oxides, particularly NO to N2, is very important from the viewpoint of environmental air pollution. The selective reduction by hydrocarbons in the presence of air has been extensively studied as a potential process in NO emission control for Diesel and lean-bum engines (see certain recent publications [61]). 

The NOx abatement in Diesel and lean-bum Otto engine exhaust gases is of special interest. The direct decomposition of NO into N2 and O2 (Eq. 10-10) is a dream reaction for catalyst researchers ... 

Lean-bum engine technologies such as gasoline direct injection and diesel engines can provide significant improvements in fuel efficiency and performance. 

NO removal (DeNO ) from diesel or lean-bum gasoline engines can be done by SCR by controlled dosing of ammonia to the exhaust line. As in many other applications, pressure vessels of liquid ammonia are too hazardous for cars and safe storage in solid form enables on-board transportation. Ammonia may also be stored on-board indirectly as an aqueous solution of urea (AdBlue ), but the storage density is three times lower and the chemical conversion of urea must take place before ammonia is available in the exhaust line (Elm0e et al., 2006). 

Selective catalytic reduction (SCR) of NO, by hydrocarbons is under investigation as an alternative NO, removal technology. NO reduction by NHj is presently the commercial state-of-the-art technology available for reducing NO, from stationary sources and from the exhausts of lean-bum gasoline and diesel engines. A number of catalysts for the selective reduction of NO by hydrocarbons have been examined in previous studies [1-18], Transition metal ion-exchang zeolite catalysts such as mordenite and ZSM-5 are the most effective SCR catalysts. 

The control of NOx emissions in lean-bum gasoline and diesel engines has become one of the most important challenges in environmental catalysis due to the difficulty of reducing nitrogen oxides in their typically humid, oxygen rich exhaust streams. Reduction with hydrocarbons is an attractive means of converting NO to N2 [1]. However, no industrially practical catalyst has been reported to date. 

Lean bum is a very old topic in engine research. The basics are well understood. Gains come mainly from pumping losses, which are those of the Diesel engine, and from thermodynamic advantages linked to the more favorable Cp/Cv ratio of air compared to a stoechiometric mixture. 

Due to the combined requirement for improving environmental protection and fuel efficiency, the development of lean-bum and Diesel engines for automobiles is linked to the availability of catalysts able of removing NOx froin oxygen-rich exliaust gas. Copper-zeolite has been proposed as a potential catalyst for NOx control in lean exliaust gas, selectively converting NOx 2 in the presence of hydrocarbons and excess O2 [1-2]. Most of the results reported have been obtained with laboratory reactors in experimental conditions rather different from... 

The goal of this paper is to represent a fifth direction of an intense research effort focused on electrochemical cells for the reduction of NOx gases due to the need to design an effective method for the purification of the exhaust gases from lean bum and diesel engines. 

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