Octane Numbers of Ethanol− and Methanol−Gasoline Blends Estimated from Molar Concentrations
ABSTRACT When expressed using volumetric concentrations (as is industry practice), the addition of relatively small amounts of ethanol or methanol (e.g., 10% by volume) to gasoline appears to result in disproportionately large, nonlinear increases in research octane number (RON) and motor octane number (MON). As a result, volumetric “blending octane numbers” are of limited value for estimating the octane number of alcohol−gasoline blends because they vary with alcohol content and base gasoline composition. We show that RON and MON increases with alcohol content are approximately linear when expressed using molar concentrations. Moreover, molar-based blending octane numbers are effectively equal to the octane numbers of the pure alcohols for most base gasolines. A limited dependence on gasoline composition was observed, namely, greater-than-predicted octane numbers for ethanol−gasoline blends with unusually high isoparaffin content. We suggest that octane numbers of methanol−gasoline and ethanol−gasoline blends can be estimated conveniently and more accurately from their molar composition by linear interpolation between the octane numbers of the base gasoline and the pure alcohol.
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ABSTRACT: Research and Motor Octane Number (RON and MON, respectively) measurements were performed to assess a linear-by-mole computation method for octane number prediction based on pure compound values. Measurements demonstrated that a linear computation method is accurate for ternary mixtures of n-heptane, iso-octane and toluene, with a very high level of accuracy for RON, MON and sensitivity in the range of values of actual gasolines. The relation was further compared to alternative formulations from the literature to demonstrate its relevance and better accuracy despite its simple form. Such a relation is a key to define surrogates for gasoline when representativity for auto-ignition is looked after.Fuel 01/2014; 115:666-673. · 3.36 Impact Factor
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ABSTRACT: High energy prices, environmental issues and increasing importation of fossil fuels has provoked, in some countries, a reorientation of resources towards the development of biofuels that can partially substitute the consumption of fossil fuels. Ethanol is one of the biofuels more commonly used in the world; in the United States, Brazil and Australia gasoline blends that reach up to 85% Ethanol are commercialized. This work presents the results of a physicochemical characterization of commercial Mexican gasoline (Magna and Premium) and diesel blends with 10% vol. and 15% vol. anhydrous Ethanol. The analytical testing included: Research Octane Number, Motor Octane Number, Cetane Number, Reid Vapor Pressure, Distillation Curve and Heating Value. The stability of the blends was also evaluated. The theoretical emissions of CO2 were calculated based on the results of the physicochemical characterization. The ethanol-gasoline blends increased their Octane Number with respect to the commercial gasoline, while conserving an appropriate Distillation Index. The Cetane Number of the ethanol-diesel blends showed a substantial decrease, while the heating value of gasoline and diesel blends was negatively affected by the addition of ethanol. Nevertheless, taking into account the credits by the use of a renewable fuel, the use of the reformulated gasoline blends would imply a maximum theoretical reduction of 7.5% in CO2 emissions whereas in the case of ethanol-diesel blends it would represent a 9.2% decrease.Ingeniería Investigación y Tecnología. 07/2012; 13(3):293-306.