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The use of methanol as a “clean fuel” appears to be a viable approach to reduce air pollution. However, concern has been expressed about potentially high formaldehyde emissions from stoichiometrically operated light-duty vehicles. This paper presents results from an emission test program conducted for the California Air Resources Board (CARB) and the South Coast Air Quality Management District (SCAQMD) to identify and evaluate advanced catalyst technology to reduce formaldehyde emissions without compromising regulated emission control. An earlier paper presented the results of evaluating eighteen different catalyst systems on a hybrid methanol-fueled test vehicle. (1)* This paper discusses the optimization of three of these catalyst systems on four current technology methanol-fueled vehicles. Emission measurements were conducted for formaldehyde, nonmethane organic gases (NMOG), methanol, carbon monoxide, and oxides of nitrogen emissions.

Two additive blends proposed for improving the flame luminosity in neat methanol fuel were investigated to determine the effect of these additives on the exhaust emissions in a dual-fueled Volkswagen Jetta. The two blends contained 4 percent toluene plus 2 percent indan in methanol and 5 percent cyclopentene plus 5 percent indan in methanol. Each blend was tested for regulated and unregulated emissions as well as a speciation of the exhaust hydrocarbons resulting from use of each fuel. The vehicle exhaust emissions from these two fuel blends were compared to the Coordinating Research Council Auto-Oil national average gasoline (RF-A), M100, and M85 blended from RF-A. Carter Maximum Incremental Reactivity Factors were applied to the speciated hydrocarbon emission results to determine the potential ozone formation for each fuel. Toxic emissions as defined in the 1990 Clean Air Act were also compared for each fuel.

Neat methanol fuel (M100) has many advantages for achieving low emission levels as an automotive fuel, but there are several items that require attention before this fuel can replace conventional fuels. One item involves the low flame luminosity of methanol. An extensive literature search and laboratory evaluation were conducted to identify potential additive candidates to improve the luminosity of a methanol flame. Potential compounds were screened based on their concentration, luminosity improvement, and duration of luminosity improvement during the burn. Three compounds were found to increase the flame luminosity for segments of the burn at relatively low concentrations: toluene, cyclopentene, and indan. In combination, these three compounds markedly improved the luminosity of methanol throughout the majority of the burn. The two combinations were 1) 4 percent toluene plus 2 percent indan and 2) 5 percent cyclopentene plus 5 percent indan in methanol.