Methyltertiarybutyl ether

One obvious use for isobutane in a synthetic fuels scenario is to dehydrogenate the isobutane to isobutylene, and react it with methanol (already manufactured on site) to produce methyltertiarybutyl ether (MTBE), which can then be used as an octane enhancer(l). This use is particularly attractive as there should be a ready market for the MTBE. If this choice was adopted, the remaining lpg fraction could be used to make other chemicals, or it could be recycled back through the plant. Care will be required in selecting other components from the lpg fraction as many of the obvious products from propene and butene are already in oversupply throughout the world. 

Ethers are relatively uncommon atmospheric pollutants, although the flammability hazard of diethyl ether vapor in an enclosed work space is well known. In addition to aliphatic ethers, such as dimethyl ether and diethyl ether, several alkenyl ethers, including vinylethyl ether, are produced by internal combustion engines. Methyltertiarybutyl ether, MTBE, became tiie octane booster of choice to replace tetraethyllead in gasoline. Because of its widespread distribution, MTBE has the potential to be an air pollutant, although its hazard is limited by its low vapor pressure. Largely because of its potential to contaminate water, MTBE was proposed for phaseout by both the state of California and the U.S. Environmental Protection Agency in 1999. Ethers are relatively unreactive and not as water-soluble as the lower alcohols or carboxylic acids. 

The 1990 U.S. Clean Air Act called for reformulating gasoline by adding more oxygenated compounds to reduce emissions of hydrocarbons and carbon monoxide. However, this measure has been rather controversial and as noted earlier in this chapter, questions have been raised regarding one of the major oxygenated additives, methyltertiarybutyl ether, MTBE, which has become a common water pollutant in some areas. 

Two common ethers are dietiiyl ether and methyltertiarybutyl elher (MTBE) shown below ... 

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