Effects of different mixing ratios on emissions from passenger cars fueled with methanol/gasoline blends

Regulated and unregulated emissions from four passenger cars fueled with methanol/gasoline blends at different mixing ratios (M15, M20, M30, M50, M85 and M100) were tested over the New European Driving Cycle (NEDC). Volatile organic compounds (VOCs) were sampled by Tenax TA and analyzed by thermal desorption-gas chromatograph/mass spectrometer (TD-GC/MS). Carbonyls were trapped on dinitrophenylhydrazine (DNPH) cartridges and analyzed by high performance liquid chromatography (HPLC). The results showed that total emissions of VOCs and BTEX (benzene, toluene, ethylbenzene, p,m,o-xylene) from all vehicles fueled with methanol/gasoline blends were lower than those from vehicles fueled with only gasoline. Compared to the baseline, the use of M85 decreased BTEX emissions by 97.4%, while the use of M15 decreased it by 19.7%. At low-to-middle mixing ratios (M15, M20, M30 and M50), formaldehyde emissions showed a slight increase while those of high mixing ratios (M85 and M100) were three times compared with the baseline gasoline only. When the vehicles were retrofitted with new three-way catalytic converters (TWC), emissions of carbon monoxide (CO), total hydrocarbon (THC), and nitrogen oxides (NOx) were decreased by 24%-50%, 10%-35%, and 24%-58% respectively, compared with the cars using the original equipment manufacture (OEM) TWC. Using the new TWC, emissions of formaldehyde and BTEX were decreased, while those of other carbonyl increased. It is necessary that vehicles fueled with methanol/gasoline blends be retrofitted with a new TWC. In addition, the specific reactivity of emissions of vehicles fueled with M15 and retrofitted with the new TWC was reduced from 4.51 to 4.08 compared to the baseline vehicle. This indicates that the use of methanol/gasoline blend at a low mixing ratio may have lower effect on environment than gasoline.