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In this project funded by the Bayerische Forschungsstiftung two fundamental investigations had been carried out: first a new N-rich liquid ammonia precursor solution based on guanidine salts had been completely characterized and secondly a new type of side-flow reactor for the controlled catalytic decomposition of aqueous NH₃ precursor to ammonia gas has been designed, applied and tested in a 3-liter passenger car diesel engine. Guanidine salts came into the focus due to the fact of a high nitrogen-content derivate of urea. Specially guanidinium formate has shown extraordinary solubility in water (more than 6 kg per 1 liter water at room temperature) and therefore a possible high ammonia potential per liter solution compared to the classical 32.5% aqueous urea solution (AUS32) standardized in ISO 22241 and known as DEF (diesel emission fluid), ARLA32 or AdBlue® .

The reduction of particulate emissions limits requires new strategies for the tuning of engines and exhaust after treatment systems. A non-blocking exhaust after treatment solution for HD vehicles to achieve the EuroIV emission limits has been developed which consists of a platinum oxidation catalyst and a stainless steel deposition structure with open channels for continuous soot storage and oxidation [1]. The significant advantages compared to standard particulate filters are caused by the open channel structure and characterized by a relatively low level of back pressure, selective separation of soot (EC) and penetrability for engine lubrication oil incineration ash. Extensive laboratory studies, including a screening of numerous promising deposition structure designs, led to a metal catalyst structure with microsphere coating. The processes dominating particle deposition could be determined, leading to a target-oriented optimization of the deposition structure.

The reduction of particulate emissions limits requires new tools for the tuning of engines and exhaust aftertreatment systems. Time-resolved monitoring of low soot emissions is a key feature for such developments. The paper describes an improved photoacoustic soot sensor, and presents its applications for the characterization of transient exhaust soot emissions before and after Diesel emission after-treatment systems. The detection limit of the unit is around 5 μg/m3 soot, which is two orders of magnitude better than conventional time-resolved transmission measurement. Additionally, a wide dynamic range of four orders of magnitude can be achieved without range switching. The photoacoustic signal is proportional to the soot mass, no significant cross-sensitivities to gaseous absorbers were detected.

A new type of catalyst for exhaust emission control of Diesel engines has been developed by a catalyst producer in cooperation with engine/heavy duty truck manufacturers. This so-called Sorption/Oxidation (“SO”)-catalyst is an extruded TiO2-type and works as a HC-trap as well as oxidation catalyst for hydrocarbons. In addition, a certain amount of particle matter was reduced, depending on type of engine, fuel sulfur content and test cycle. Due to its unique composition, i.e. oxides of titanium (80 wt %), tungsten and vanadium, the catalytic selectivity results in very low formation of sulfates as well as excellent resistance against sulfur compounds. The geometry of the catalyst prototypes corresponds to standard monoliths of 5,66″(144mm) in diameter and suitable lengths to be installed in standard mufflers. Since 1996, several buses and trucks have been equipped with SO-catalysts and are still in operation without problems.