BTEX emissions from flex fuel motorcycles

Abstract

Comparative studies were developed with regard to the criteria emissions of THC - total hydrocarbons, CO - carbon monoxide and NOx - nitrogen oxides, and BTEX (benzene, toluene, ethyl benzene and xylenes). Three four-stroke motorcycles were fuelled with E22 fuel (gasoline with 22% of ethanol). One flex fuel motorcycle was also fuelled with E100, 100% Hydrated Reference Ethanol, and with E61 (61% of ethanol). Criteria emissions were quantified using traditional measurement techniques based on the European Directive 97/24/EC (EURO protocol). To determine the BTEX emissions, gas chromatography coupled with mass spectrometry was employed. All motorcycles were equipped with a catalyst (TWC) used to reduce the amount of toxic emissions in the exhaust gases. To evaluate the performance of the catalyst, one motorcycle was tested with and without the device. One motorcycle was tested according to two different test protocols, namely, the ECE/TRANS/180 WMTC, also known as the Worldwide Motorcycle Test Cycle, and the EURO protocol. The main results were that toluene emissions were more prevalent than other aromatics. The tests with and without the catalyst showed that after the catalyst was employed the conversion efficiencies for benzene, toluene, ethyl benzene and xylene were 52.3%, 84.0%, 85.0%, and 86.0%, respectively. The results regarding the flex fuel motorcycle show that BTEX emissions decrease with an increase of ethanol in the mixture. Comparing the EURO and WMTC protocols, it was observed that the WMTC protocol generates lower emissions compared to the EURO protocol; however, NOx showed the opposite trend of BTEX.