Comparison of Particulate PAH Emissions for Diesel, Biodiesel and Cooking Oil using a Heavy Duty DI Diesel Engine

An investigation was conducted into particulate PAH emissions from a heavy duty DI diesel engine using; a typical diesel fuel, 100% methyl ester derived from waste cooking oils, and 100% rapeseed oil supplied as fresh cooking oil. This study quantifies the particulate PAH levels emitted at two steady state load conditions, with comparison of the oxidation catalyst efficiency for the main species identified. The engine used was a 6 cylinder, turbocharged, intercooled Perkins Phaser engine, with emission compliance of EURO 2. Particulate samples were also analysed for VOF and carbon content. Both biofuels resulted in reductions in the most abundant particulate PAH species, particularly at the lower load condition. Larger species such as Benzo(a)anthracene, chrysene, benzo(b)fluoranthene and benzo (k)fluoranthene were detectable for all fuels upstream of the catalyst but were oxidized to near or below detection limits downstream of the catalyst. The most abundant PAH detected were phenanthrene, fluoranthene and pyrene. The apparent catalyst efficiency for phenanthrene was low compared to other species, indicating that a mechanism of synthesis was counteracting the catalytic oxidation. Fluoranthene, was not present in the diesel fuel but was emitted in all particulate samples, indicating a pyrosynthesis route for this species.