Laboratory and Vehicle Studies of Aldehyde Emissions from Alcohol Fuels

Abstract

<div class="htmlview paragraph">Laboratory and vehicle studies were carried out characterizing formaldehyde emissions from methanol fuels. Laboratory experiments focused on catalytic methanol oxidation activity and yield of formaldehyde as a function of temperature and feedgas composition. Pt and Pd catalysts gave the highest activity and lowest formaldehyde yield of a series of noble and base metal catalysts. Formaldehyde yields were lowest under stoichiometric or slightly rich conditions. Experiments carried out with thermally aged lead poisoned catalysts indicated at most about 5% conversion of methanol to formaldehyde, thus proving that catalytic partial oxidation of methanol is not a major source of tailpipe formaldehyde emissions. Nevertheless, FTP emission tests on a 3.0L FFV Taurus with production three-way converters showed significant mileage related increases in formaldehyde emissions from 14 mg/mile for a fresh catalyst (4,000 simulated miles) to 17 mg/mile for a 50,000 simulated mile catalyst and 30 mg/mile for a 100,000 mile in-use catalyst tested with 100,000 mile oxygen sensor. Additional laboratory experiments were carried out on a pulse flame combuster examining the effects of combustion temperature and air/fuel ratio on unburned methanol and formaldehyde emissions.</div>