Ceramic papers as flexible structures for the development of novel diesel soot combustion catalysts

Abstract

Currently, the most adequate technology for the abatement of particles coming from diesel engines is the one that employs catalytic filters. This work proposes the preparation of catalytic ceramic papers to be employed in the development of new catalytic filters. To this end, the papermaking technique was employed. The resulting papers were flexible, easy to handle and presented suitable mechanical properties to resist the tests from a test bench in which they were placed inside a metal housing, at the exhaust pipe outlet of a Corsa 1.7 vehicle. These optimal mechanical properties were obtained through the incorporation of a suspension of CeO2 nanoparticles during the papermaking process. It was found that the nanoparticles covered the ceramic fibers completely and that their excess accumulated under the form of patches. In order to promote the filter continuous regeneration, once the ceramic papers were formed they were impregnated with a cobalt salt which, after a calcination stage, produced oxidic clusters in tight contact with the CeO2 nanoparticles. The papers thus obtained exhibited a maximum soot combustion temperature close to 400°C, being T50 = 376°C for the more active catalytic ceramic paper, in the presence of NO (1000 ppm) in the feed. Even though more tests are necessary to determine filtration efficiency, preliminary experiments carried out in the test bench proved that the ceramic papers properly resisted the high gas flow rates of fumes emitted by a real diesel engine (approximately 2 m3.min-1). From the TPO experiments performed on samples of catalytic ceramic papers taken from the test bench and in tight contact with the soot retained, it was possible to obtain a maximum soot combustion temperature equal to 428°C. It was also found that the presence of ceria aggregates caused the papers to deactivate to a lesser degree after being treated at 900°C.