An analysis of speciated hydrocarbons in hydrous ethanol (H100) and ethanol-gasoline blend (E22) for vehicle exhaust emissions

Abstract

Speciation and quantification of hydrocarbons (HC) in exhaust emissions are essential when making an evaluation of MIR (maximum incremental reactivity) and OFP (ozone forming potential) factors with different fuels. In Brazil, flex-fuel vehicles were launched in 2003 and can operate with H100 (100% hydrous ethanol, 4.0–4.9% vol/vol of water), commercial gasohol (gasoline blended with 18–27% vol/vol anhydrous ethanol) or any blend of these fuels. The main difficulties when conducting an analysis of HC with these fuels, are the presence of several contaminants, the interference of ethanol and relatively high concentrations of C2 species. In this study, a new analytical method was employed that was based on a heart-cutting gas chromatography approach. Two flex fuel vehicles, using H100 and E22 (22% v/v of anhydrous ethanol), were tested with the EPA-75 drive cycle (in accordance with the requirements of ABNT/NBR 6601) and HC (C2–C12) in the three gas exhaust phases (cold start, stabilized and hot start) were analyzed. In the case of the latest vehicle (PROCONVE L6, Tier 2 equivalent), with H100, the MIR and OFP values were 5.7 ± 0.3 and 0.032 ± 0.005 gO3 km−1, respectively. When fueled with E22, the MIR and OFP values were determined as 3.6 ± 0.2 and 0.015 ± 0.001 gO3 km−1, respectively. To the best of our knowledge, this was the first complete HC (C2–C12) speciated analysis conducted in Brazil using H100 and E22 (without any significant contamination with ethanol as fuel) and aided by heart-cutting gas chromatography.