Methyl tert-butyl ether , octane booster

Methyl f erf-butyl ether (MTBE, C5H120), a substance used as an octane booster in gasoline, can be made by reaction of isobutylene (C4H8) with methanol (CH40). What is the percent yield of the reaction if 32.8 g of methyl tert-butyl ether is obtained from reaction of 26.3 g of isobutylene with sufficient methanol ... 

At present, glycerol alkyl ethers, especially GTBEs, are of particular interest, because the higher ethers (h-GTBEs) can be used as octane boosters in automotive fuels analogously to methyl tert-butyl ether (MTBE), but they do not exhibit the same environmental problems. Glycerol can be converted with isobutene [47-49] or with tert-butanol [50] to the desired fuel additives (Scheme 3.6). When using on tert-butanol, water is a by-product and must be removed. 

With TEL no longer avcdlable as an octane booster, chemists tried to find other compounds to replace it. Aromatic compounds were effective in enhancing the octane value, but they were discovered to be serious health hazards. Recently, methyl alcohol, tert-butyl alcohol, and methyl tert-butyl ether (MTBE) have been used 2is octane boosters. 

Catalytic Distillation Catalytic or reactive distillation is another example of the use of a hybrid reactor and combines catalysis and distillation in one column/reactor. Usually, we have a two-phase process with gas and liquid flowing in countercurrent mode. This requires special catalysts and packings, for example, monoliths, as in case of a fixed-bed flooding of the reactor would occur at high flow rates. In industry, catalytic distillation is already used for the production of MTBE (methyl tert-butyl ether), an important octane booster (Figure 4.10.77 DeGarmo, Parulekar, and Pinjala, 1992), cumene (DeGarmo, Parulekar, and Pinjala, 1992), and ethylbenzene (Podrebarac, Ng, and Rempel, 1997). 

Because the Williamson synthesis is an S 2 reaction, it is subject to all the usual constraints, as discussed in Section 11.2. Primary halides and tosylates work best because competitive E2 elimination can occur with more hindered substrates. Unsymmetrical ethers should therefore be synthesized by reaction between the more hindered alkoxide partner and less hindered halide partner rather than vice versa. For example, terf-butyl methyl ether, a substance used in the 1990s as an octane booster in gasoline, is best prepared by reaction of tert-butoxide ion. with iodomethane rather than by reaction of methoxide ion with 2-chloro-2-methylpropane. 

Small amounts of fert-butyl methyl ether are added to gasohne as an octane booster. The daily consumption of gasoline is so high that the demand for tert-butyl methyl ether exceeds our present capacity to produce it. 

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