Abstract
Determination of hydrocarbons (HC) in the exhaust emissions of vehicles fueled with ethanol is a great analytical challenge. In this project a new method was implemented and optimized. A flex fuel vehicle (PROCONVE L6), using ethanol (E100) and gasoline (E22), was tested using the EPA-75 driving cycle (ABNT/NBR 6601). The exhaust was collected in Tedlar® bags and transferred to electropolished stainless steel canisters (Silonite®). The three exhaust phases (cold start, stabilized and hot start) and the dilution air of each phase were analyzed using thermal desorption heart-cutting multidimensional gas chromatography (MDGC). The analytical system consisted on a Agilent 7890A GC with a capillary flow technology (CFT) Deans Switch, two chromatographic columns (a DB-624 and a PoraPLOT Q-HT) and two detectors (a mass spectrometer and a flame ionization detector) without cryogenic trapping. HC emissions, Ozone Forming Potentials (OFP) and Maximum Incremental Reactivities (MIR) were determined:
Weighted emissions: 0,0042 ± 0,0006 g km-1 (Gasoline E22) and 0,0057 ± 0,0008 g km-1 (Ethanol E100); MIR: 3,6 ± 0,2 (Gasoline E22) and 5,7 ± 0,3 (Ethanol E100); OFP: 0,015 ± 0,001 g O3 km-1 (Gasoline E22) and 0,032 ± 0,005 g O3 km-1 (Ethanol E100).
These results were obtained using a new method developed in Brazil and can be useful for technical discussions about ozone forming potential using Brazilian vehicles and fuels. The method showed a performance compatible with international procedures used in Europe and the United States of America.