Impact of Simultaneous ETBE and Ethanol Addition on Motor Gasoline Properties

This study examines the impact of ETBE and ethanol addition on the main properties of motor gasoline. European Union mandates the use of biofuels in all transport fuels, according to the 2003/30/EC Directive. The addition of ethanol, a known octane enhancing component, in small proportions significantly increases the vapor pressure of the final gasoline, exceeding the maximum specification limits. ETBE (ethyl tert-butyl ether) is on the other hand an excellent but expensive octane enhancing component with beneficial impact on vapor pressure of the final gasoline. This paper examines the ability of ETBE to act as a stabilizer in gasoline - ethanol blends. Two gasoline samples with different chemical compositions and characteristics were prepared by blending basic refinery components. In each sample, ETBE was added in concentrations of 2, 4, and 6 % V/V respectively. In each of these ETBE - gasoline blends, ethanol was added in concentrations from 1 to 6 % V/V in 1% steps. The properties measured were composition, density, distillation characteristics, vapor pressure and octane numbers (RON and MON). In all cases, the addition of ETBE and ethanol had positive effect on octane numbers. The vapor pressure was increased due to ethanol addition, but the blends with ETBE had lower vapor pressures compared to the blends without ETBE. The higher the ETBE concentration, the lower the increase in vapor pressure of the final blend (0.4 to 2.7 kPa, depending on ETBE and ethanol content). Therefore, the use of ETBE as stabilizer can contribute to the introduction of bioethanol in motor gasoline, especially in the warmer EU countries of the Mediterranean Region.