Reijo Lylykangas

NOx reduction by urea in the presence of NO2 on metal substrated SCR catalysts for heavy-duty vehicles

The emission limitations for heavy-duty vehicles are coming stricter between 2005 - 2008 in Europe, Japan and United States. In addition to engine, fuel and control modifications, efficient exhaust gas after treatments like oxidation/deNO x catalysts and particulate filters are needed. In mobile truck applications the system should operate at low (<300°C) and stand high temperatures (500-650°C) in transient driving conditions. Coated V 2 O 5 /TiO 2 -WO3 based SCR catalysts on thin metal foil substrates have been studied here in laboratory and engine experiments. The open-coating method enables the high volumetric amount of SCR catalyst evenly coated on high cell density substrates (e.g. 600 cpsi). A new washcoat composition with platinum loading has been used in pre-oxidation catalyst to reach the NO 2 concentrations, which initiate the SCR reaction clearly below 300°C. Dip-coated new catalyst structures with lower cell densities and mixing channel shapes improved the efficiencies in mass transfer controlled region. The coated mixer structure confirmed uniform urea hydrolysis and ammonia generation particularly at low temperatures. The NH 3 slip was cut down by the optimization of urea injection and a small post-oxidation catalyst. The combinations of different metallic catalysts match well into modular truck silencer structures.

Evaluation of High Cell Density Z-Flow Catalyst

A new type of metal supported catalyst for gasoline engines has been developed. The catalysts excellent conversion efficiency is based on the use of high cell densities. With the new Z-flow construction the substrate has been turned semi transversely to the flow direction. The substrate length has been shortened and the cross section area increased, thus ensuring pressure drop characteristics are kept competitive with conventional converter systems. In this work the theoretical background for the causes of pressure drop in the catalyst and advantages of high cell densities are presented. The catalyst function has been studied with differing cell densities up to 1600 cpsi. The performance of the new Z-flow catalyst has been compared with several commercially available ceramic catalysts. The results show that when employing high cell density catalysts in conjunction with the Z-flow converter construction, considerably smaller catalyst volumes and less precious metal amounts are required. (A) For the covering abstract see IRRD 858138.

Advanced Metallic Three-Way Catalysts with Optimized Washcoat Performance

The major challenge for future catalyst systems was to develop more thermally stable washcoats for close coupled operating conditions and for engines operating under high speed and load conditions. To design these future emission systems extensive research and development was undertaken to develop methods to disperse and stabilize the key catalytic materials for operation at much higher temperatures. The second priority was to design catalysts that are more effective under low exhaust temperature exhaust conditions and have improved oxygen storage properties in the washcoats. Incorporating new materials and modified preparation technology a new generation of metallic catalyst formulations emerged, those being trimetallic K6 (Pt:Pd:Rh) and bimetallic K7 (Pd+Pd:Rh). The target was to combine the best property of Pt:Rh (good NO{sub x} reduction) with that of the good HC oxidation activity of Pd and to ensure that precious metal/support interactions were positively maintained. Both K6 and K7 concepts contain special catalyst structures with optimized washcoat performance which can be employed either individually or combined in a single or double brick converter configuration. Improvement in light-off, thermal stability and transient performance with these new catalyst formulations has clearly been shown in both laboratory and vehicular testing.

PARTICLE OXIDATION CATALYST FOR HEAVY-DUTY DIESEL ENGINES

Today, most heavy-duty diesel vehicles do not require any exhaust gas after-treatment devices, as they already meet existing Euro 3 emission limits. The new requirements, Euro 4 and Euro 5 beginning in October 2005 and October 2008 respectively, will change the situation.