Treatment of Vehicle Emissions from the Combustion of E85 and Gasoline with Catalyzed Hydrocarbon Traps

Ethanol has been gaining attention as a partial substitute in North American pump gasoline in amounts up to 85% ethanol and 15% gasoline, or what is commonly known as “E85”. The problems with E85 fuel for cold start emissions relative to gasoline fuel are the lower energy density and vapor pressure for combustion. Each contributes to excess E85 fuel injected during cold start for comparable combustion quality and drivability to gasoline. The excess emissions occur before the first three-way catalyst (TWC) converter is warmed-up and active for engine-out exhaust conversion. The treatment of non-methane organic gas (NMOG) emissions from the combustion of E85 and gasoline was evaluated using several different zeolite based hydrocarbon (HC) traps coated with different precious metal loadings and ratios. These catalyzed HC traps were evaluated in a flow reactor and also on a gasoline Partial Zero Emissions Vehicle (PZEV) with experimental flexible fuel capability. Fourier Transform Infra Red (FTIR) spectroscopy and other methods were used to analyze the alcohols, aldehydes and ketones necessary to quantify NMOG emissions. HC trap performance was quantified through measurement of adsorption and desorption of specific hydrocarbon species, and formation of CO₂ and partial combustion products. Temperature data was used to quantify where specific hydrocarbon species desorbed in relation to catalyst activation. The traps evaluated in the lab reactor all showed similar adsorption efficiencies, and the traps with platinum catalyst generated the most CO₂, but also the most acetaldehyde. The HC traps evaluated on the vehicle with E85 improved the weighted tailpipe emissions of NMOG from the base TWC results of 0.016 grams/mile down to 0.013 grams/mile. The results illustrate the challenges of adsorbing NMOG emissions, retaining it for conversion and achieving complete oxidation, with the overall system efficiency reflecting the combination of these efficiencies.