U. González

Impact of reformulated ethanol–gasoline blends on high-emitting vehicles

In-use vehicles which are high emitters (HEVs) make a large contribution to the emissions inventory. It is not known, however, whether HEVs share common emissions characteristics, and particularly the effect of ethanol blends. We study this by first examining laboratory measurements of exhaust and evaporative emissions on ethanol blends containing 21%, 26% and 30% aromatics, and a reference fuel formulated with methyl-tertiary butyl ether (MTBE). Switching from MTBE to ethanol fuels on HEVs shows no effect on the total emissions of regulated pollutants, but 1,3-butadiene emissions would increased substantially while the emissions of total carbonyls would not be affected except in the case of acetaldehyde, which would increase with EtOH. The ozone-forming potential of exhaust and evaporative emissions would be less using the EtOH blends and specific reactivity will not be incremented. Lowering the vapour pressure of the gasoline and increasing the proportions of alkylate and isomerate in the composition produces an ethanol-blended fuel with lower environmental impact both in normal vehicles and HEVs.

The effects of addition of co-solvents on the physicochemical properties of gasoline–methanol blended fuels

The scope of the work carried out is aimed to evaluate the effects of blending methanol in the gasoline pool, particularly octane number and Reid vapor pressure increase when methanol is substituting methyl-tertiary-butyl ether in the formulation of Regular and Premium base gasolines. Isopropyl alcohol and ethanol have been investigated and found to be a promising co-blending alcohol to be mixed in gasoline methanol blends. Isopropyl alcohol is most effective below 3 vol%. Ethanol has been found to be the most promising co-blending alcohol able to reduce the Reid vapor pressure increase by 1.4 psi even with concentrations in the range of 2 vol%. The addition of isopropyl alcohol to the methanol–gasoline blends has shown the ability of a ternary mixture to further reduce the Reid vapor pressure of the finished gasoline and, subject to availability and price of isopropyl alcohol, could be of interest in further formulation studies focused on maximizing the saving on finished gasoline cost by reducing the Reid vapor pressure of base gasoline and/or increasing the methanol content.

Performance and emissions of gasoline–dual alcohol blends in spark-ignited single cylinder engine:

Three alcohols (ethanol, methanol and isobutanol), two ethers (ethyl tert-butyl ether and methyl tert-butyl ether) and dimethyl carbonate were blended in a base fuel at 3.5 wt % oxygen. Two of the fuels were dual alcohol–gasoline blends with methanol/ethanol and methanol/isobutanol having the same added volume of each alcohol. The performance was analyzed on a single spark-ignited engine. Emissions of nitrogen oxides, carbon monoxide, unburned hydrocarbons and carbon dioxide were monitored online. The dual-alcohol blends present higher cooling effect, power and thermal efficiency as well as low combustion cyclic dispersion and fast combustion. Combustion effects due to the addition of oxygenates can be attributed to base gasoline dilution, for a given oxygen content. Also, dilution increases the hydrogen proportion, and this seems to have a strong relationship with the observed increases in combustion duration.