Although MTBE volatility is relatively low, the standards for reformulated gasoline in the developed countries are very exigent during summer in order to reduce the smog formation in the cities. This makes the RVP specifications for gasoline lower than the corresponding value for MTBE. For this reason, the employing of ethers with more branched carbon chains and lower volatilities has been explored. Precisely, the ethyl tert-butyl ether (ETBE), the second most utilized ether as an oxygenate, has an RVP less than MTBE and antiknocking properties slightly higher (see Table 1.1). ETBE is produced by the exothermic reaction between isobutene and ethanol. As in the case of MTBE production, this reaction requires ionic exchange resins as a catalyst (Ancillotti and Fattore, 1998). ETBE is produced mainly in the United States and Europe. The produc­tion of ETBE incorporates reactive distillation using acid ionic exchange res­ins (Thiel et al., 1997) or structured zeolites as packing materials (Oudshoorn et al., 1999). One substantial difference in ETBE production is that one of its feedstocks, ethanol, can be obtained from renewable resources like the bio­mass, which entails the integration of the petrochemical industry with the bio­technological sector. One example is the case of France where bioethanol has been produced from sugar beets since 1990. In this way, the ETBE obtained is partially renewable, which implies greater environmental benefits compared to MTBE whose production is totally from fossil origin. These benefits are repre­sented in a lower emission of greenhouse gases (N2O, CH4, and CO2), a lower contribution to the depletion of natural resources, and better air quality in the cities (less unburned hydrocarbons and formed formaldehyde, although more acetaldehyde produced). In fact, a 3.8% reduction in the amount of unburned hydrocarbons emitted and 17.6% decrease in benzene emissions has been noted in vehicles provided with catalyst employing gasoline blends with 15% (by vol­ume) ETBE (Poitrat, 1999). On the other hand, Spain also employs the ETBE as an oxygenate for its gasoline. In this case, the ETBE production has reached its maximum due to the availability of isobutene in the Spanish refineries (Espinal et al., 2005).

The solubility of ETBE in water is also relatively high compared to the remaining gasoline components (12.2 g/L). Like MTBE, ETBE can also be eas­ily transferred to groundwater from gasoline leakages from storage tanks, pipe­lines, or other distribution systems (Ancillotti and Fattore, 1998). The ETBE biodegradation under aerobic or anaerobic conditions has been researched to evaluate the potential for its decontamination (Kharoune et al., 2001).