Chapter 3 | Ethanol and Other Fuel Oxygenates

Fuel oxygenates are widely used in the United States and around the world for octane enhancement, air quality, and volume extension. As the significant health hazards of the use of tetra ethyl lead in fuel applications were confirmed, the demand for gasoline oxygenates increased. Many oxygenates are approved for use by the U. S. Environmental Protection Agency; the first oxygenated gasoline approval was the 1978 “gasohol” waiver. An oxygenate is defined under ASTM D02 specifications as an oxygen-containing, ashless, organic compound, such as an alcohol or ether, which can be used as a fuel or fuel supplement. The role oxygenates play has transformed from mandatory oxygen levels in gasoline in the 1990s, to reduce exhaust emissions and increase gasoline octane, to today's role continuing the octane increase combined with renewable energy strategies and reductions in greenhouse gases to address climate change goals. Nearly all gasoline in the United States contains an oxygenate. Ethanol is the primary oxygenate used in gasoline in the United States and around the world. Oxygenates, such as methyl tertiary butyl ether (MTBE), methanol, tertiary-amyl methyl ether (TAME), ethyl tertiary-butyl ether (ETBE), butanol, and diisopropyl ether (DIPE) are approved for use in the United States. This chapter focuses on ethanol and other oxygenates for use as blending components in fuel or for use as the primary fuel component for spark-ignition engines. This chapter summarizes the significance of the important physical and chemical characteristics of these oxygenates and the pertinent test methods for determining these properties. Information on the status of current research and government regulations is also included.