Nitrous oxide: New catalytic converter process cleans up efficiently

November 5, 2017 | 01:44
A compact chemical processing plant
A compact chemical processing plant
Nitrous oxide emissions from diesel vehicles are a hot topic for debate and scandal. Conventional catalytic converters which use urea only start working properly when the exhaust gas temperature reaches 150 ° C and this temperature may not be achieved under all conditions. Researchers at the Jülich Research institute together with the RWTH University of Aachen and industrial partners Ford, Deutz, Sasol, FEV, Umicore and Clariant are developing a new type of converter (the DeNOx project) that can remove nitrous oxide (NOx) almost completely without using any additives.

According to Dr. Jürgen Dornseiffer from the Jülich research institute if the project is successful and the technology is installed in all new diesel vehicles, the strict worldwide standards for nitrous oxide emissions from diesel vehicles could be met and air quality, especially in cities, will be decisively improved. "We are still at the beginning of our research but if everything goes to plan, we will have a prototype ready within three years. This technology will then be directly shared with our participating industrial partners and integrated into their new vehicle designs."
In addition to the researchers at Jülich several other well-known vehicle and catalytic converter manufacturers and suppliers are involved in this joint project. The project is sponsored by the German Federal Ministry of Education and Research (BMBF) and coordinated by RWTH Aachen University.

New novel material works its magic
Inspiration for the development of this novel material came from research into fuel cells. The base materials are also used in the production of ceramic high-temperature solid-oxide fuel cells (SOFC), which the Jülich research institute has already been successfully demonstrating in a long-term experiment in operation for more than ten years now. By changing the cathode material, a new type of NOx storage system is produced which can decompose the nitrous oxide in a continuous recirculatory process.

Construction of the new catalytic converter
In contrast to a conventional catalytic converter the various stages of exhaust gas purification are not arranged in separate units one behind the other. This new system integrates all the different functions directly into the single catalytic converter unit. In principle, this type of converter acts as a switchable chemical processing plant: The process starts with the storage of the nitrous oxide in the catalytic converter. Once a maximum level has been reached, a brief change of the motor operating conditions is sufficient to cause the new catalytic materials to convert the accumulated nitrous oxide into ammonia which is then stored.  The ammonia can now convert the nitrous oxide into harmless nitrogen very efficiently under normal driving conditions.
 
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