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Silicon carbide diesel particulate filter (DPF) is now recognized as the most effective and robust way to reduce not only the mass but also the number of emitted particles on diesel passenger cars. Widespread use of expensive catalytic platinum-containing coatings has contributed to increased harmful NO₂ emissions. A novel low-cost palladium-base metal coating, BMC-211, was developed which assists soot regeneration by oxygen transport and which actively removes NO₂ still having comparable passive and active soot regeneration properties. The novel coating was tested against a traditional commercial platinum coating on a modern series-produced car, on chassis dynamometer and on engine test bench.

Data on the release of vanadium and tungsten during operation from a vanadium-based Selective Catalytic Reduction catalyst and a newly developed product with advanced thermal stability are presented. The effect of the ammonia slip catalyst as a vanadium trap is highlighted and the implications of the vanadium and tungsten release are briefly discussed.

The Selective Catalytic Reduction (SCR) catalyst with ammonia as reducing agent plays a central role in today's exhaust after-treatment systems for heavy-duty vehicles and there is a wide selection of possible catalytic materials to use. In order to facilitate the design of future catalysts, several aspects of the materials must be evaluated both in steady-state and transient operation. To this end, this paper presents a methodology for comparing the dynamic properties of different catalysts using full-size engine testing. The studied characteristics include the ammonia storage capacity, the effect of starting with an empty catalyst, the transient response to temperature gradients and changes in the urea dosing level. The temperature response is of particular importance in transient operation, where temperature increases may lead to substantial ammonia slip. A vanadium catalyst is compared to a Cu-SAPO-34 catalyst, and they show significant differences in their dynamic response.

To reach the very strict Euro VI regulations of PM and NOx for heavy-duty trucks, it will be necessary to apply integrated catalytic solutions for removal of both PM and NOx. The most cost-effective solution would be to base the Euro VI system on Euro IV/V base engines, without EGR, and apply a high efficiency aftertreatment system, able to reduce the NOx from the common 7-8 g/kWh down to the Euro VI level at 0.4 g/kWh. The described system consists of a catalytic configuration, where the SCR catalyst is placed directly downstream of the diesel engine followed by an ammonia slip catalyst (ASC) and diesel injection over an oxidation catalyst (DOC) and a catalyzed diesel particulate filter (cDPF).

For trucks today, the diesel particulate filter (DPF) and SCR catalysts are combined in this sequential order in diesel exhaust systems with the drawback of insufficient temperature for the SCR catalyst during cold start and large volume. The problems can potentially be solved by integrating the SCR catalyst into the particulate filter as one multifunctional unit. For off-road and heavy-duty vehicles applications with fully managed passive NO2-soot regenerations, integration of V-based SCR formulations on the DPF (V-SCRonDPF) represents an attractive solution due to high sulfur resistance accompanied by low-temperature NOx conversion and improved fuel economy. Engine bench tests together with an NO2-active DOC show that it is possible to manage the NO2/NOx ratio so both a high NOx conversion and still a low soot balance point temperature is obtained. The soot balance point is almost unaffected by the fast SCR reaction when urea is introduced.

Today, the DPF and SCR catalysts are combined sequentially in diesel exhaust systems. However, such sequential system configuration has several drawbacks: 1) large volume; 2) insufficient temperature for the SCR catalyst during cold start when DPF is placed in front of SCR; and 3) unfavorable conditions for passive soot regeneration if SCR is placed upstream of the DPF. The problems can potentially be solved by integrating the SCR catalyst into the particulate filter as one multifunctional unit. The study indicates that SCRonDPF based on Cu-zeolite type as SCR material can achieve the NOx conversion levels close to flow-through SCR catalysts for LDV (Light Duty Vehicles) using forced regenerations. Forced soot regeneration solves potential sulfur poisoning.