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The integration of DeNOx functionality into wall flow filters for the after treatment of diesel engine exhaust gases is a field of technology to which many publications in the recent years have drawn their attention. To integrate the needed amount of catalyst, high porous substrate materials have been developed. A drawback of the high porosity levels of 60% and higher is a significant reduction in mechanical strength. The aim of this work is to provide a new solution based on a high porous SiC material which is treated by a dual layer coating. The first layer is a nanoparticle coating which enhances the mechanical strength of the substrate. It can also be used to improve the catalytic performance and to finally decrease the loading of the second coating layer which is the active catalyst for selective catalytic reduction (SCR) of NOx with ammonia.

The paper presents results illustrating the effect on Diesel particulate filters (DPF) in relation to rapeseed methyl ester (RME) and animal tallow methyl ester (TME) compared to Diesel (EN590). Measurements were performed in an engine test cell using a modern common rail light duty CI engine running at five different load points for more than 330 hours. Regulated and non-regulated gaseous emission such as NOx and NO2 were monitored before and after the DPF to characterize the catalytic activity. Detailed investigation was also carried out concerning the ash balance in relation to engine lubricant additives and fuel contribution. Results showed an increase in NO2 engine out emission when the engine was fueled with biodiesel. However, the balance point temperature for the catalyst was significantly decreased illustrating the opportunity to optimize the catalytic surface correspondingly with increasing amount of biodiesel being regulatory implemented.

This text is divided into two parts; the first part gives a short recapitulation of the development status of the electrochemical reactor for soot removal, while the second part gives a description of activities on electrochemical NOx reduction. The Electrochemical Reactor for filtration and continuous combustion of soot from diesel exhaust gas has been described earlier [1, 2]. The reactor size has been increased by stacking flat plate reactors, and full size test has been performed on a diesel engine in a test bench. The soot removal efficiency is better than 90%, but the efficiency for gas oxidation (conversion of carbon monoxide (CO) and hydrocarbons (CH)) is still low, of the order of 50%. The packing and mounting of the reactor is under development to avoid mechanical breakage by engine vibrations. This has improved the durability significantly, and on road vehicle test is under initiation.

A concept for an electrochemical reactor acting as a trap for the removal of soot particles from diesel exhaust gas has been developed and presented earlier [1]. Only small scale flat plate samples tested with synthetic exhaust gas was presented. Since then, the sample size has been increased, and test on a diesel engine in a test bench has been carried out. Various concepts for the establishment of a sufficient filtering surface and for the electrical connections have been tested, and the construction of a muffler with an electrochemical reactor installed has been initiated. This is to be on a passenger car for on-road test. The preliminary bench test indicates a soot removal efficiency of 75-90% with no accumulation of soot at the reactor, at temperatures above 250°C. A separate project has been started to evaluate the possibilities of lean NOx removal on a similar reactor. Results from this will be reported separately.

A new concept for a particulate trap for diesel engines has been developed. The trap is a combination of a ceramic wall-flow filter and an electrochemical reactor. When trapped in the filter, the soot particles are continuously converted to carbon dioxide by an electrochemical reaction. This reaction is activated by applying a small voltage to an electrochemical reactor, consisting of the walls of the filter element. The filter element is constructed as an electrochemical reactor with a ceramic, oxygen ion conducting electrolyte and ceramic or metallic electrodes which are both electronic conducting and catalytically active. By controlling the processing parameters of the materials, the porosity of the filter can be adjusted thus allowing the majority of the soot particles to penetrate into the filter unit and be collected at the electrode/electrolyte interface. Here the soot will be electrochemically converted to carbon dioxide, even at relatively low temperatures.