Ulrich Dr. Göbel

Ir/H-ZSM-5 Catalysts in the Selective Reduction of NOx with Hydrocarbons

Three different Ir catalysts supported on H-ZSM-5 were prepared and tested for the selective catalytic reduction of NO under net oxidizing conditions using propene as reducing agent. The preparation of highly active Ir catalysts and the elaboration of a procedure for enhancing activity by on stream conditioning was targeted. Structural changes of the catalyst during conditioning were investigated by means of XRD, TEM and activity measurements. Under reaction conditions Ir was present as Ir0 and IrO2. The presence of Ir0 was essential for high DeNOx activity. The ratio of Ir0/Ir4+ was found to depend on the size of Ir-containing crystallites. Larger crystallites contained predominantly Ir0. Crystallite size and oxidation state of Ir have been identified to be crucial for the NO reduction behaviour of Ir/H-ZSM-5.

Die Abgasreinigung der FSI-Motoren von Volkswagen

Zur weiteren Absenkung des Kraftstoffverbrauchs ihrer Fahrzeugflotte hat sich die Volkswagen AG fur die Entwicklung eines Ottomotors mit Kraftstoffdirekteinspritzung entschieden. Um dieses neue Motorkonzept unter Einhaltung der EU-IV-Grenzwerte betreiben zu konnen, war die Entwicklung eines adaquaten Abgasnachbehandlungssystems notwendig, die im Rahmen einer intensiven Zusammenarbeit zwischen der Volkswagen AG und der dmc2 Degussa Metals Catalysts Cerdec AG realisiert wurde. Der folgende Artikel beschreibt das Abgasnachbehandlungssystem fur die FSI-Motoren von Volkswagen, dessen Integration im Fahrzeug, sowie die dafur wichtigen Entwicklungsrichtungen und -schwerpunkte.

Long-term durability of NOx aftertreatment systems for diesel engines

Lean NOx trap (LNT) systems are currently being improved in order to comply with the more stringent Tier 2 Bin 5 standards. Improving the LNT’s durability is key in this endeavour. The main two aging mechanisms that need to be addressed are thermal deactivation and poisoning with sulphur. The two processes are linked because sulphur poisoning indirectly leads to thermal deactivation through regular desulfations of the catalyst. Those sulphur removal procedures expose the catalyst to considerable thermal stress that reduces its long term performance. Umicore research activities on improved LNT systems and data recorded in durability tests demonstrate substantially improved performance and durability. The main strategies employed were a reduction in the required desulfation temperature of the LNT as well as improved engine control and desulfation strategies.