Alkyl tertiary butyl ethers

Other major components in gasoline come from catalytic reforming, alkylation and the addition of an oxygenated octane booster, methyl tertiary-butyl ether (MTB E). 

Cation-exchange resins are used as catalysts in the produdion of MTBE (methyl tertiary-butyl ether, 2-methoxy-2-methylpropane) and various other oxygenates and, lately, also in the dimerization of isobutene [30]. Other commercial applications of the cation-exchange resins indude dehydration of alcohols, alkylation of phenols, condensation readions, alkene hydration, purification of phenol, ester hydrolysis and other reactions [31]. The major producers of ion-exchange resins are Sybron Chemicals Incorporated [32] (Lewatit resins), Dow Chemical Company [33] (DOWEX resins), Purolite [28] (Purolite resins), and Rohm and Haas Company [27] (Amberlyst resins). 

Isobutylene is the most chemically reactive of the butylene isopiers. If the objective is just to get the isobutylene out of the C4 stream, it can be removed by reaction with methanol (CH3OH) to make MTBE (methyl tertiary butyl ether), by reaction with water to make TBA (tertiary butyl alcohol), by polymerization, or by solvent extraction. After that, butene-1 can be removed by selective adsorption or by distillation. That leaves the butene-2 components, together with iso- and normal butane, which are generally used as feed to an alkylation plant. 

In addition to its octane enhancement ability described above, ZSM-5 also increases the feed to alkylation, methyl tertiary butyl ether (MTBE) and tertiary amyl methyl ether (TAME) units. Since the products from all these processes contain high Research and Motor Octane components, ZSM-5 provides the refiner additional flexibility in his downstream processing whenever the need exists to increase overall gasoline pool octane. In addition, the overall refinery can be rebalanced to take... 

Application The Uhde Sleam Active Reforming STAR process produces (a) propylene as feedstock for polypropylene, propylene oxide, cumene, acrylonitrile or other propylene derivatives, and (b) butylenes as feedstock for methyl tertiary butyl ether (MTBE), alkylate, isooctane, polybutylenes or other butylene derivatives. 

Ethylene is the largest volume carbon-based chemical produced in the United States. Moreover, ethylene can be converted directly to transportable fuels (ethanol or high-octane gasoline) or high-volume petrochemicals, such as ethylene glycol. Similarly, methanol is a liquid and can be used directly as a turbine or transportation fuel. It can also be converted to MTBE (methyl tertiary butyl ether) by alkylation with isobutylene. Oxyhydrochlorination of methane includes production of methylchloride as an intermediate to the production of gasoline. 

Additives to petroleum products. They include alkyl lead additives (tetramethyl lead and trimethylethyl lead at m/z 253 and 223, dimethyldiethyl lead at miz 267 and 223, methyltriethyl lead at m/z 281 and 223, tetraethyl lead at 295 and 237) oxygenates including substances such as ethanol, methanol, methyl tertiary butyl ether (MTBE), ethyl tertiary butyl ether (ETBE), and tertiary amyl methyl ether (TAME) fuel dyes used for differentiation among fuel grades and antioxidant compounds added to fuels to retard auto oxidation ... 

The determination of fluorine in various liquid and gaseous hydrocarbons is vital at many points in the refining process primarily in any blend component that has been sourced fiom the hydrogen fluoride (HF) Alkylation Unit. Fluorinated compounds poison process catalysts therefore, it is essential that process feeds be as free of fluorine as possible. As an example, butane is used to produce methyl tertiary-butyl ether (MTBE). The butane must be fluorine free prior to butane isomerization to prevent the poisoning of the process catalyst, fri addition, any HF acid or its combustion products may be extremely destructive in any environment. Therefore, any finished hydrocarbon product or synthesized material that is utilized in the presence of sufficient heat (i.e., car engine), such as frel and lubricating oils, must be free of fluoride. 

Olefins, unlike paraffins, do not show significant gains in octane number with skeletal isomerization (see Table 14.2). As a result, olefin isomerization is not a useful octane boosting strategy. However, tertiary olefins (olefins with three alkyl substituents on the double bond), do react fairly readily with olefins to form ethers, which do have good octane numbers-for example, methyl tert-butyl ether (MTBE). 

A tertiary radical can be formed by elimination during AF of ter/-butyl methyl and ethyl ethers thus, isolation of the respective perfluoro-/erf-butyl ethers, e.g. 1, occurs in only 36 and 42% yield.28 Significant quantities of perfluoro(2-methylpropane) (2) are also isolated. The longer alkyl chains (ethyl and larger) appear to be slightly less prone to scission than the methyl group. Apparently, carbonyl fluoride is more readily eliminated than trifluoroacetyl fluoride, a phenomenon observed during AF of esters.29 Elimination becomes most serious in the special class of polyethers called ortho esters, e.g. 3-5.30 Cyclic ortho esters, acetals and ketals are much less affected than acyclics. 

This is a second-order reaction because methoxide ion is a strong base as well as a strong nucleophile. It attacks the alkyl halide faster than the halide can ionize to give a first-order reaction. No substitution product (methyl tert-butyl ether) is observed, however. The SN2 mechanism is blocked because the tertiary alkyl halide is too hindered. The observed product is 2-methylpropene, resulting from elimination of HBr and formation of a double bond. 

Other alkyl nitrates as well as ether nitrates and some nitroso compounds, have also been found to be effective cetane number improvers. However, they are not currently used commercially. Di-tertiary butyl peroxide has recently been introduced as a commercial cetane number improver. 

The reactivity of the aluminum-carbon bonds is greatly reduced in the 1 1 adducts, and this may be utilized in preparing particularly labile organoaluminum compounds which cannot be isolated in the free form. Thus tri-tert-alkyl alanes, such as tri-terf-butylalane, may be prepared as etherates from tertiary butyl lithium in diethylether (207) or from the corresponding magnesium tertiary alkyls (157, 159) ... 

The first reaction was found by Levy and Szwarc to be predominant when methyl radicals attacked isooctane. The second reaction is predominant, however, for aromatic hydrocarbons. The free radicals formed in the above two reactions will react with each other, with other free radicals, or with impurities. The affinity of the methyl radical to attack an aromatic increases in the following order benzene, diphenyl ether, pyridine, diphenyl, benzophenone, naphthalene, quinoline, phenanthrene, pyrene, and anthracene. The ability of free alkyl radicals to interact with isopropylbenzene and cyclohexene decreases in the following order methyl, ethyl, propyl, butyl, isopropyl, sec-butyl, and tertiary butyl. 

If the para- substituent group R- (above) is an alkyl group of about four or more carbon atoms (e.g. tertiary butyl, (CH3)3 C-), the product is soluble in oils otherwise in alcohols, ether-alcohols or alcohol/aromatic hydrocarbon mixtures. If the resin is made from a phenol blocked in the para-position, with a high formaldehyde level and using an alkaline catalyst, it will react when heated with un-saturatcd materials, such as drying oils or rosin to produce a modified phenolic resin. The mechanism is thought to be of the type ... 

The clear cleavage pattern emerges the tertiary alkyl group is converted more readily into the corresponding bromide than the secondary one, and the latter more readily than a primary group. Consequently, f-butyl-n-butyl ether gives exclusively f-butylbromide, whereas sec-butyl-n-butyl ether leads only to sec-butylbromide. Isobutyl-n-butyl ether yields predominantly n-butylbromide. 

Now let s use alkoxides to make ethers—the Williamson ether synthesis. Several modifications of the original procedure have made this venerable method quite useful, although there are some restrictions. The reaction works only for alkyl halides that are active in the Sn2 reaction. Therefore, tertiary halides cannot be used. They are too hindered to undergo the crucial Sn2 reaction. Sometimes there is an easy way around this problem, but sometimes there isn t. For example, tert-huXy methyl ether cannot be made from tert-hnty iodide and sodium methoxide, but it can be made from / r/-butoxide and methyl iodide (Fig. 7.106). However, there is no way to use the Williamson ether synthesis to make di-Z rZ-butyl ether. 

Similarly, glycol mono-/-alkyl ether can be hydrolyzed to obtain tertiary alcohols with strongly acidic cation-exchange resins. For example, ethyleneglycol mono-<-butyl ether gives <-butyl alcohol at 350 — 400 K. 

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