(463f) Dual-Alcohol Blending Effects on Gasoline Properties

A pure alcohol cannot provide the distillation temperature range required by spark ignition engines for smooth driveability. The front-end volatility in a distillation curve is of importance for cold start, engine warm-up, evaporative emissions, and vapor lock. Mid-range volatility is vital for warming up, acceleration, and cold weather performance. Finally, tail-end volatility is essential for running when the engine is hot, and it also indicates the propensity for combustion deposits and oil dilution. In addition, the high enthalpy of vaporization of alcohols is a prohibitive factor for good cold-start behavior. Therefore, both light and heavy hydrocarbon fractions of gasoline are needed to supply an ignitable mixture under these challenging conditions. In general, blends of gasoline with a single alcohol also have shortfalls. If lower alcohols (methanol and ethanol) are used, azeotropic behaviour due to the high polarity of these molecules, as well as their low calorific value, high enthalpy of vaporization and low stability would be problematic. If higher alcohols are used, achieving very low volatilities is challenging and can significantly limit the maximum volume that can be blended with gasoline. Thus, in order to increase the portion of bio-alcohols in the gasoline blend, another approach is needed. Using multi-alcohol-gasoline blends is an approach that might achieve a fuel with high portion of biofuel while meeting all standard specifications with no need for major changes in existing infrastructures and engines. Mixing a lower and a higher alcohol (e.g., ethanol and 1-butanol) in gasoline can provide a mixture that has the same vapor pressure as that of gasoline while reducing the evaporative emission on the fuel delivery system. However, other physicochemical and combustion related properties of dual alcohol– gasoline blends have not determined to fully characterize these fuel blends for a satisfactory performance in existing spark ignition engines. This presentation will describe the development of a database of all normal and cyclic C1-C10 alcohols and a procedure to downselect for a pair of alcohols that can be blended with gasoline in different target volumes from midrange (20 vol. %) to high range (40 vol. %). After selecting the desired pair of alcohols, a range of properties were measured to evaluate the fuel blends: distillation curve, calorific value, vapor pressure, vapor lock index, ignition quality, water tolerance and phase separation, density, and viscosity.