Comparison of Exhaust Emissions from a Vehicle Fueled with Methanol-Containing Additives for Flame Luminosity 930220

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. Additive blends performed well when compared to M85 and M100 with minimal emissions impact observed for the regulated emissions.

THE CALIFORNIA AIR RESOURCES BOARD (CARB), the South Coast Air Quality Management District (SCAQMD), and the California Energy Commission (CEC) are supporting research and development on methanol as one potential strategy for achieving significant reductions in motor vehicle emissions.^{(1, 2, 3 and 4)}* Preliminary results have indicated that utilization of neat methanol (M100), rather than a mixture of 85 percent methanol and 15 percent gasoline (M85), provides an air quality benefit. However, safety and toxicity issues related to methanol use have prevented its wider acceptance as a clean motor fuel. During an extensive project for CARB, SCAQMD, and CEC, several potential additives were identified to improve the flame luminosity when added to neat methanol fuel.

This paper discusses additional work performed on a program for CARB to demonstrate additives to improve the safety-related properties of neat methanol fuel. In the first task of this program, a literature search of potential additives was performed, and a laboratory evaluation of candidate additives at low concentration was conducted to evaluate potential improvements in fuel lubricity, flame luminosity, and flammability limits.^(5-6) Two additive packages were selected for further evaluation in this task. One additive package contained 4 percent toluene plus 2 percent indan in methanol, and the second contained 5 percent cyclopentene plus 5 percent indan in methanol. As a subsequent step in this program, emission measurements (regulated exhaust emissions and a hydrocarbon speciation) were performed on the two additive blends in methanol to:

• Determine the emissions impact from toxic substances and regulated emissions compared to neat methanol (M100).
• Evaluate if the additives packages could reduce the reactive hydrocarbons by at least 50 percent compared to M85 (15 percent gasoline and 85 percent methanol).
• Determine the specific reactivities of the exhaust from the different fuels and additive blends.

The results of these experiments on exhaust emissions from the additive blends are discussed below.