A Concise Background

Fuel oxygenates are oxygen-containing compounds (e.g., ethers and alcohols) that are added to gasoline either to boost the octane rating, to make the fuel burn cleaner by increas-ing the oxygen content, or to achieve a combination of both. The most commonly used oxygenates are methyl tertiary-butyl ether (MTBE) and ethanol. Other oxy-genates include ter-tiary-amyl methyl ether (TAME), ethyl tertiary-butyl ether (ETBE), diisopropyl ether (DIPE), tertiary-amyl ethyl ether (TAEE), tertiary-butyl alcohol (TBA), tertiary-amyl alcohol (TAA), and methanol. Some oxygenates have a long history of usage in gasoline. For example, ethanol has been used in automotive fuel blends since the 1930s. Ethers, and primarily MTBE, have been used increasingly since the late 1970s. Ini-tially, MTBE was used to boost the octane rating of mid- and high-grade gasoline and was present at concentrations of about 4 to 8 percent by volume. These fuels were transported, stored, and used nationwide. Amendments to the Clean Air Act in 1990 led to the implementation of the Oxygenated Fuel (Oxyfuel) and Refor-mulated Gasoline (RFG) programs in 1992 and 1995, respec-tively. While these programs stipulated a minimum oxygen content for gasoline sold in specific metropolitan areas to reduce air pollution, the choice of which oxygenate to use was ■ continued on page