Determination of VOC components in the exhaust of light vehicles fuelled with different biofuels
Résumé
The speciated exhaust emissions of VOCs in the C2-C19 range were measured on 4 Euro-4 certified vehicles (3 diesel and 1 gasoline) equipped with a catalytic converter, according to 5 real-world driving cycles. To determine the effects of blended fuels on the emission factors, several test fuels were used: gasoline, E10 (10% of ethanol, by volume), diesel, B5, B30 (5% and 30% of biodiesel or FAME) and HVO (pure Hydrotreated or Hydrogenated Vegetable Oil). These tests were performed on a chassis dynamometer with constant volume sampling (CVS). The sampling of compounds was made using dedicated Carbotrap and Tenax cartridges, analysed by GC-FID and GC-MS respectively. Carbonyl compounds were sampled on DNPH-coated cartridges and analysed by UVHPLC. The emission factors of individual pollutants were determined, especially of 1,3-butadiene, benzene, and formaldehyde, which are recognized as genotoxic carcinogens. Detailed speciation of the emissions shows changes with the composition of the biofuel in the levels of hydrocarbons, aromatic compounds and carbonyls present in diesel and gasoline engine exhaust gases. This evolution of the emission factors for the different compound families is compared to the results obtained in previous studies, where the influence of driving cycles, technology and type of fuels were evaluated (Caplain et al, 2006). In the framework of this study, the first results show that an addition of ethanol in the unleaded gasoline leads to a decrease of the emissions of aromatics especially of benzene and an increase of the 1,3-butadiene emission. An increase of aromatics emissions but no specific trend for carbonyl compounds emission factors was observed when partially substituting biodiesel to diesel. Pure HVO leads to higher carbonyl emissions than pure or substituted diesel fuel.
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