Environ. Sci. Technol. 2006, 40, 5532-5537
PM0.1 Emissions during Diesel Trap Regeneration E. CAUDA, S. HERNANDEZ, D. FINO,* G. SARACCO, AND V. SPECCHIA Department of Materials Science and Chemical Engineering, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy
A nanostructured spinel-type oxide catalyst (CoCr2O4) prepared by solution combustion synthesis was developed and deposited over a SiC wall-flow trap for diesel particulate removal. Bench tests proved that, after soot loading, the developed trap enables a faster and more complete regeneration at 550 °C than a commercial Ptcatalyst based trap or a noncatalyzed trap. On the other hand, secondary nanoparticle emission occurs during the fast regeneration promoted by the CoCr2O4-catalyzed trap. This is a likely consequence of oxidative fragmentation of the trapped soot agglomerates. This problem can be resolved by performing a “mild” regeneration at lower temperatures (e.g., 450 °C).
Introduction There is increasing concern about the heath effects of particulate matter, PM, emitted from diesel engines for automotive applications. PM is suspected of causing acute and chronic damage to the pulmonary and the cardiovascular systems. Based on scientific proof, air pollution legislation in several countries classifies diesel soot as carcinogenic (1). Moreover, several health effects are associated with ultrafine particles with diameters below 100 nm (PM0.1) (2). Recent research has shown that these particles can penetrate the cell membranes, enter the blood, and even reach the brain (3). Furthermore, some investigations have indicated that particles can induce heritable mutations in mice (4). Pending EU regulations (Euro V, to be enforced before 2010) are expected to fix emission limits as low as 0.005 g/km for diesel particulate, a limit which could not be met without an after-treatment system. Currently, under Euro IV regulations (diesel particulate
