Characterization of Emissions from Methanol and Methanol/Gasoline Blended Fuels

Research was undertaken to characterize the potential differences in the chemical composition of precatalyst and postcatalyst exhaust gases from engines fueled with methanol/gasoline blends, (20/80 volume %-designated as M-20) pure alcohol and gasoline. Results were developed from both steady-state engine tests and transient CVS vehicle tests. A heated CVS system was developed for sampling emissions to minimize significant oxygenated hydrocarbon sample losses commonly encountered in the standard CVS sampling procedure. Gas chromatography/mass spectrometry(GC/MS) was used for characterizing the emissions. Minimal losses of methanol emissions were found using the described sampling and analysis system. The only significant qualitative differences observed in the hydrocarbon emissions generated by engines burning pure Indolene clear compared to the M-20 fuel was the significant presence of unburned methanol and in some cases traces of ethanol in the exhaust of the M-20 fueled vehicle. The Indolene clear and M-20 fuels did not produce significantly different quantities of total aldehyde emissions. Methanol comprised from 2 to 20 mole% of the total hydrocarbon emissions from using M-20, depending upon the operating conditions. Greater than 98 mole% of the hydrocarbon and oxygenated hydrocarbon emissions from an engine burning pure methanol were unburned methanol and aldehydes.