Hydrocarbon emissions in flex fuel vehicles using ethanol: Preliminary results using a method implemented in Brazil

Abstract

Vehicle emissions are the main source of hydrocarbons (HC) in many urban areas. However, the determination of HC in exhaust emissions of vehicles fueled with ethanol is a great challenge, from the analytical point of view, due to the interference of several contaminants. In this study, sampling and analytical methods were implemented and optimized. Contamination during sampling and interference of non-burned ethanol and carbonyl compounds were minimized through a rigorous sampling and analytical procedure. Two flex fuel vehicles, using 100% v/v hydrous ethanol (E100), were tested. Vehicle exhaust samples were collected during emission testing with EPA-75 drive cycle (according to ABNT/NBR 6601) for each of the three phases: cold start, stabilized and hot start. The exhaust was collected in Tedlar® bags and transferred to electropolished stainless steel canisters. HC (C2-C12) in samples were analyzed using thermal desorption and gas chromatography with a mass spectrometry detector. Ethene, ethyne and ethane represented approximately 95% of measured non-methane hydrocarbons (C2-C12). Aromatic compounds were considered negligible (<2%). Since speciated HC emission results are required to calculate MIR (maximum incremental reactivity) and OFP (ozone forming potential) factors, these results can be useful for technical discussions about the ozone formation in a Brazilian fuel scenario. To our knowledge, this was the first HC speciated analysis developed in Brazil using ethanol and Brazilian flex fuel vehicles.