Formaldehyde and Methanol Emissions from a Methanol/Gasoline-Fueled Spark-Ignition (SI) Engine

Abstract

With a three-cylinder spark-ignition (SI) engine, formaldehyde (HCHO) and methanol (CH3OH) emission characteristics as well as the three-way catalytic converter (TWC) conversion efficiency were investigated when it ran on gasoline, M10, M20, and M85 (gasoline blended with 10, 20, and 85% of methanol in volume), respectively. HCHO and CH3OH were detected by gas chromatography (GC) with a pulsed discharge helium ionization detector (PDHID). Experimental results show that HCHO emission increases with engine speed, while CH3OH emission from a methanol/gasoline blend-fueled engine decreases with it. HCHO emission from a gasoline-fueled engine varies in a “U” curve with the engine torque. The addition of 10% methanol in gasoline doubles the HCHO emission. The increasing methanol fraction greatly improves HCHO and CH3OH emission; their concentrations are both approximately linear to the amount of cyclically supplied fuel methanol. CH3OH can be totally removed by lightened-off TWC. However, the HCHO concentration may increase rather than decrease via the conversion of TWC at high engine speeds.

Effects of engine misfire on regulated, unregulated emissions from a methanol-fueled vehicle and its ozone forming potential

“…When the misfire rate was raised from 0% to 9%, exhaust temperature gauged near the catalyst inlet increased by about 100 K on average. As reported by Wei et al [24,40], the conversion efficiency for engine-out methanol promoted as the temperature of catalyst rose. However, it should be also noted that the conversion efficiency of unburned methanol in catalyst hardly changed with temperature after 500 K, so higher temperature of catalyst with the presence of engine misfire was unlikely to have any practical benefit.…”

Methanol as a fuel for internal combustion engines

“…A compound of concern is formaldehyde, HCHO. This plays an important role in photochemistry and is a human carcinogen [87]. Formaldehyde emissions have been reported to potentially be higher on methanol (-blends) than on gasoline [22], so could be a concern for methanol-fuelled vehicles as these emissions are not always regulated currently (they are limited in U.S. regulations for vehicle exhaust emissions).…”

“…Today, we know that FID measurements have a low relative sensitivity to oxygenated compounds and thus other methods, such as FTIR (Fourier transform infrared) should be used to measure HC levels in alcohol engines [88,89,90]. Wei et al point out that an FID has a very low response to formaldehyde, and use a fast chromatographic method with a pulsed discharge helium ionization detector instead [87]. Geng et al compare the FTIR method to gas chromatography (GC) and high performance liquid chromatography [91].…”

“…Whereas advantages in power density and efficiency are clear with the use of methanol, results concerning emissions are confusing. Wei et al [87] ran a small gasoline engine on gasoline, and various methanol blends (splash blended). They noted that engine-out emissions of unburned methanol primarily were a function of exhaust temperature, with no such emissions when exhaust temperatures were high.…”

Autoignition of methanol: Experiments and computations

“…The combustion of methanol in compression ignition engines in conjunction with diesel and diesel-like fuels has been extensively studied [4][5][6][7][8][9][10][11][12][13][14][15]. Similar combustion studies have also been conducted in spark ignition engines using gasoline and methanol fuels simultaneously [16][17][18][19][20]. Methanol has also been investigated in context with other advanced combustion concepts such as the homogeneous charge compression ignition engine [21][22][23][24][25][26][27][28].…”