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 Task 1 of an emission test program conducted for the California Air Resources Board (CARB) and the South Coast Air Quality Management District (SCAQMD) to identify advanced catalyst technology to reduce formaldehyde emissions without compromising regulated emission control.
A hybrid M90 test vehicle was used to evaluate 18 unaged catalyst systems for formaldehyde, methanol, gasoline derived hydrocarbon, organic material hydrocarbon equivalent mass, carbon monoxide, and oxides of nitrogen emissions. The vehicle was operated on a chassis dynamometer using the FTP driving cycle. Catalyst systems evaluated included electrically-heated, manifold, close-coupled, and underbody catalysts, as well as combinations of the above. Three catalyst systems were selected for further evaluation on current technology vehicles (both dedicated methanol- and flexible-fueled). Selections were made to achieve a variety of emission control systems that were effective in formaldehyde and regulated emission control. All three systems selected for additional evaluations gave average formaldehyde emission levels of less than 8 mg/mi.