Highly efficient electrochemical removal of soot, hydrocarbons and NOx from diesel exhaust

Air pollution from Diesel engines in the form of soot (particles), NOx and unburned fuel (hydrocarbons) is an increasing problem in today s cities. To counter this, more efficient ways of cleaning Diesel exhausts are needed. Electrochemical gas purification is an attractive possibility. The idea behind the concept is to activate the reduction of NOx and the oxidation of soot and hydrocarbons by the use of an all solid state electrochemical cell based on an oxide ion conductor. The present project will develop a prototype filter unit to be tested on a real Diesel engine. Electrochemical gas purification has a number of advantages compared to traditional methods using selective catalytic reduction (SCR) of NOx and the removal of soot by the reaction with NO2. The removal of soot and nitrous gasses is achieved in a single unit, making it easier to fit into the existing exhaust system. With electrochemical gas purification no additives are needed, in contrast to SCR which relies on a reducing agent, typically urea. There are fewer emissions from an electrochemical filter, since the formation of nitrous oxide (N2O, a greenhouse gas) is avoided. Furthermore, use of electrochemical gas cleaning may lower the fuel consumption in comparison to the traditional filters. Finally, the use of noble metals makes the traditional methods expensive. The proposed project will address the key issues needed to bring the technology to a proof-of-concept state: New ceramic materials for the electrochemical reduction of NOx and the electro-chemical oxidation of soot and hydrocarbons will be developed. The design of a prototype filter will be optimized using modelling. The new materials and the design will be implemented in a prototype filter using inexpensive ceramic forming methods. Then the prototype filters will be tested in realistic conditions. In addition, the impact of the technology on society will also be evaluated