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This program examined the PAH emissions from two diesel engines representing state-of-the-art technology. One heavy-duty engine, a DDC Series 60, used in highway trucks, and one medium-duty engine, Navistar DTA-466, used in pick-up and delivery type vehicles. The medium-duty engine was tested for engine out emissions and with two different sized exhaust oxidation catalysts. Both of the catalysts were composed of a ceramic monolith coated with a palladium type catalyst. Both engines were tested according to the US EPA transient emissions test on a series of diesel fuels blended with varying aromatics and PAH contents to determine the impact of fuel quality on emissions. All diesel fuels had a low sulphur content (<0.05%) to minimize the formation of sulphate. The particulate matter was collected on teflon-coated filters, backed up with polyurethane foam filters to capture the vapour phase PAH.

The performance of two catalyst preparations, styled base and base/noble, were determined employing a simulated mining vehicle loading cycle. Such cycles are characterized by sufficiently high exhaust temperatures to cause auto-regeneration of the filter units when these catalyst preparations are employed. Such loading is exhibited in raining service by some moderate and most high production load-haul-dump vehicles plus some haulage trucks. These preparations were shown to be capable of depressing the nominal, ‘untreated’ steady-state minimum soot ignition temperature of approximately 500°C (932°F), to a range varying from 395°C to 424°C (743°F to 797°F). Results of gaseous constituent analyses, particulate determinations, polynuclear aromatic hydrocarbon sampling, catalytic sulphur conversion (SO2 to H2SO4) and Ames testing are presented for the two catalyst preparations studied.