Tetraethyl lead (TEL) is the major oxygenating additive of gasoline that has been used in the world in the recent past (Figure 1.2a). The U. S. scientist Thomas Midgley discovered the excellent properties of TEL in December 1921. One liter of TEL was enough to treat 1,150 liters of gasoline. Thus, the oil companies began the addition of this compound to the gasoline instead of ethanol. In the case of the latter, its use would have reduced the utilization of gasoline by 20 to 30% making the vehicles less oil dependent. Leaded gasoline has an average octane number of 89 (Nadim et al., 2001). However, some concerns were expressed in 1923 about the negative effect of TEL on human health. In particular, it was pointed out that each liter of consumed gasoline would emit 1 g of lead oxide. Later studies demonstrated the negative neurological effects of this compound, especially in children (Thomas and Kwong, 2001). It wasn’t until January 1996 that leaded gas­oline was banned in the United States. In Colombia, leaded gasoline is no longer produced. In fact, its import has been banned since 1994 (Ministerio del Medio Ambiente, 1994). Nevertheless, there exist some African and Mideast countries where leaded gasoline is still being used because of its low cost (Thomas and Kwong, 2001).

One of the ways of avoiding TEL usage is the modernization of refineries in order to elevate the production of aromatic and aliphatic hydrocarbons, but these modifications are costly. In addition, the augmentation in the concentration of aromatic compounds in the gasoline increases the risks related to the benzene exposition. Another option consists in the substitution of TEL with other less toxic compounds. Both options represent additional expenses in the refineries that explain why the phase-out of TEL utilization has been very slow in spite of hav­ing known its toxic properties for a number of years.