Effect of Fuel Additives on Gasoline Volatility

Oxygenated additives are added to base gasoline for such purposes as increase of Octane Number, improvement of engine performance and decease of exhaust emissions. In Iran, Methyl Tertiary Butyl Ether (MTBE) is used as an additive to the base gasoline. Due to destructive environmental effects of the said material, our country, the same as other developed countries, should seek to use a replacement for the said additive. The combination of the base gasoline and fuel additives has such limitations as increase of the quantity of volatility, the reid vapor pressure (RVP) and decrease of calorific value of the fuel obtained. In this research, Ethanol, Tertiary Butyl Alcohol (TBA) and Metyl Tertiary Butyl Ether in the volumetric ratios of 2.5, 5, 7.5, 10, 15 and 20 are blended with the base gasoline of Tehran Oil Refinery Company (TORC). The behavior of volatility of the obtained fuel has been investigated based on ASTM standards. The results obtained from the said investigation reveal that in case of use of Ethanol as a fuel additive, certain changes should be made in the formulation of base gasoline. The said combination has an undesirable effect on other characteristics of fuel such as Octane Number. Addition of Tertiary Butyl Alcohol to gasoline shall result in trivial increase of the reid vapor pressure. Consequently, there will be no need for replacement of light straight run gasoline (LSRG) compounds with heavier compounds in order to decrease the reid vapor pressure.