This paper describes aldehyde and unburned fuel emissions (UBF) measurements made on several light-duty, methanol-fueled vehicles with developmental 2.5-L engines and production and three-way catalytic converters. Emissions data were obtained under both steady-state and Federal Test Procedure (FTP) driving-cycle conditions. The data were then compared to those from a similarly equipped production gasoline vehicle.
Before- and after-catalyst aldehyde and UBF emissions data are presented for three vehicle types as a function of equivalence ratio. In addition, aldehyde emission data for one of the methanol vehicles using a base-metal catalyst are discussed.
The steady-state tests showed that both before- and after-catalyst aldehyde and UBF emissions are minimized by vehicle operation at lean equivalence ratios. The data also showed that formaldehyde accounted for 98% of the total aldehydes from the methanol vehicles, and only 31-54% of the total aldehydes from the gasoline vehicle. In addition, the steady-state tests showed that a base-metal catalyst was as effective as the three-way catalyst in controlling aldehyde exhaust emissions from the methanol vehicles.
Under the Federal Test Procedure conditions, the methanol-fueled vehicles had aldehyde emissions ten times higher than, and unburned fuel emissions equal to those of the gasoline-fueled vehicle.