NO reducing agent AUS 32 ("ADBlue") for SCR systems; Approved NO reducing agent AUS 32 ("ADBlue") - BB00.40-P-0352-00A

For diesel engines, direct diesel injection technology has developed to the point where it can nearly be called the standard technology. The very tough legislation now in place to regulate diesel engine exhaust emissions makes exhaust aftertreatment technology a must. That is why many of today's passenger car diesel engines are equipped with oxidation catalytic converters. Further exhaust aftertreatment systems will be needed for at least the heavier vehicles in the passenger car and light commercial vehicle categories in order to comply with the latest emissions regulations.

A range of systems are currently in development, and in some cases already in use, for reducing NO_x emissions. In heavy commercial vehicles  NO_x catalytic converters employing urea as the reducing agent provide a system for the highly selective reduction of nitrogen oxide emissions. Here, there is selective catalytic NO_x reduction in the presence of ammonia.

Standardization at international level is also in progress. Appropriate specifications are expected to be available in August 2006 under the designation of ISO 22241 Part 1 (requirements) and Part 2 (test procedure).

The urea/water solution introduced into the exhaust train is first converted into ammonia via an upstream reaction stage. In the subsequent catalytic reduction process, the ammonia breaks down most of the NO_x to nitrogen and water. Connecting an oxidation catalytic converter in series can further improve reactivity, since in this case NO is oxidized to the more easily converted NO₂ . However, this primary catalytic converter is sensitive to sulfur.

The urea-SCR process for exhaust aftertreatment is series production configuration in commercial vehicles. A detailed description of the quality of the reducing agent must form the basis for the universal, manufacturer-independent introduction of this technology and is essential for ensuring the long-term operation of the exhaust aftertreatment system. The reducing agent requirements have been published in standards DIN 70070 (requirements) and DIN V 70071 (test procedure).

This exhaust cleaning system is also under development for diesel cars, meaning that the importance of having a NOx removal agent of a suitable grade will increase in future.

Sheet 352.1 contains recommendations for suitable grades.