Methyl f-Butyl Ether MTBE

Addition of methanol to isobutene to yield MTBE (80-110°C, 7-20 bar, ion exchange resin in the H+ form as the catalyst). 

Isobutene is present in refinery streams. Especially C4 fractions from catalytic cracking are used. Such streams consist mainly of n-butenes, isobutene and butadiene, and generally the butadiene is first removed by extraction. For the purpose of MTBE manufacture the amount of C4 (and C3) olefins in catalytic cracking can be enhanced by adding a few percent of the shape-selective, medium-pore zeolite ZSM-5 to the FCC catalyst (see Fig. 2.23), which is based on zeolite Y (large pore). Two routes lead from n-butane to isobutene (see Fig. 2.24) the isomerization/dehydrogenation pathway (upper route) is industrially practised. Finally, isobutene is also industrially obtained by dehydration of f-butyl alcohol, formed in the Halcon process (isobutane/propene to f-butyl alcohol/ propene oxide). The latter process has been mentioned as an alternative for the SMPO process (see Section 2.7). 

The main use of MTBE is as an octane booster in gasoline formulations. Table 2.1 (above) compares octane number and boiling points of some tertiary ethers and hydrocarbons. The volatility is another important property of gasoline components. In fact, the lower volatility of ETBE is an advantage with respect to MTBE. Another (smaller scale) application of MTBE is the synthesis of high purity isobutene by cracking MTBE over amorphous silica-alumina. This isobutene serves as a monomer for polyisobutene. 

MTBE is the fastest growing chemical of the last decade. Presently, over 11 million t/y capacity has been installed. Further growth is foreseen. Essentially the success of MTBE is founded (i) on its outstanding antiknock properties as a gasoline component, and (ii) its function as a key product in the C4 hydrocarbon processing within a refinery. 

The synthesis of MTBE is carried out in the liquid phase over a fixed bed of ion 

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Generally, dissolved aromatics may be found quite far from the origin of a spill, but entrained hydrocarbons may be found in water close to the petroleum source. Oxygenates such as methyl-f-butyl ether (MTBE) are even more water soluble than aromatics and are highly mobile in the environment. 

One method (EPA 8020) that is suitable for volatile aromatic compounds is often referred to as benzene-toluene-ethylbenzene-xylene analysis, although the method includes other volatile aromatics. The method is similar to most volatile organic gas chromatographic methods. Sample preparation and introduction is typically by purge-and-trap analysis (EPA 5030). Some oxygenates, such as methyl-f-butyl ether (MTBE), are also detected by a photoionization detector, as well as olefins, branched alkanes, and cycloalkanes. 

Initiating a remarkable series of papers in 2008-2009, Grubbs and Whited reported the formation of an Ir(I) carbene complex, 44, from the reaction of methyl f-butyl ether (MTBE) with Ozerov s (PNP)lrH2 (PNP = [N(2-P Pr2-4-Me-C6H3)2] ) and NBE [121-127]. C-H addition to (PNP)lr presumably occurs followed by... 

Various studies on the fate of the gasoline additive methyl-f-butyl ether (MTBE) have shown that it can be oxidized to t-butyl-formate (TBF) which happens particularly in the atmosphere ... 

Methyl f-Butyl Ether. MTBE is produced by reaction of isobutene and methanol on acid ion-exchange resins. The supply of isobutene, obtained from hydrocarbon cracking units or by dehydration of tert-butyl alcohol, is limited relative to that of methanol. The cost to produce MTBE from by-product isobutene has been estimated to be between 0.13 to 0.16/L ( 0.50—0.60/gal) (90). Direct production of isobutene by dehydrogenation of isobutane or isomerization of mixed butenes are expensive processes that have seen less commercial use in the United States. 

A newly developed isobutene recovery is based on its selective and quantitative etherification into methyl f-butyl ether (MTBE) by treatment of the C4 stream with methanol in the presence of a cation-exchange resin (e.g., Amberlyst 15), followed by catalytic splitting of the isolated ether [43-45]. MTBE was, and still is, primarily produced as a high-octane blending component for unleaded gazoline. 

Methyl f-butyl ether (MTBE) vapor pressure vs. 1/T... 

A typical pro cedure follows [167]. Freshly distilled, benzoic acid free, benzaldehyde (37.1 g = 0.35 mol), HCN (12.2 g = 0.45 mol and (J )-oxynitrilase (78 mg) were dissolved in 225 ml of methyl f-butyl ether (MTBE) and 250 ml of 50 mmol 1 citric acid buffer (pH 5.5) at 22 °C. After stirring for 20 min the MTBE layer was separated and the aqueous layer was extracted with 25 ml of MTBE. The combined organic layers were dried over MgSO4, filtered and concentrated under reduced pressure (200 mbar) using a water bath (30°C). Yield ... 

The first Hthiation and substitution of an allyUc amine to provide enantioen-riched products was reported in 1980 by Ahlbrect and coworkers [92,93]. Deprotonation of cinnamylamine 125 and substitution with electrophiles provided y-substituted enamines 126, which were hydrolyzed to the corresponding aldehydes. The aldehydes were isolated in good yield with high enantiomeric ratios when methyl f-butyl ether (MTBE) was used as the solvent (Scheme 39). 

The presence of antioxidants in eluents and extraction solvents Antioxidants can be readily oxidized electrochemically and generate high background currents or interfering broad peaks. Thus, eluents and extraction solvents containing such compounds should be either avoided or purified before use. For example, ethers, such as diethyl ether, diisopropyl ether, and tetrahydrofuran are likely to contain up to 0.1% (w/v) pyrogallol or quinol (hydroquinone) as stabilizer. If the stabilizer is removed, peroxides will form and their concentration will increase with time unless the solvent is stored under nitrogen. Not only do peroxides present a hazard from explosion, but they may also oxidize susceptible analytes. Methyl f-butyl ether (MTBE), on the other hand, is stable to oxidation. 

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