Atomization isohexanes

Table I gives the compositions of alkylates produced with various acidic catalysts. The product distribution is similar for a variety of acidic catalysts, both solid and liquid, and over a wide range of process conditions. Typically, alkylate is a mixture of methyl-branched alkanes with a high content of isooctanes. Almost all the compounds have tertiary carbon atoms only very few have quaternary carbon atoms or are non-branched. Alkylate contains not only the primary products, trimethylpentanes, but also dimethylhexanes, sometimes methylheptanes, and a considerable amount of isopentane, isohexanes, isoheptanes and hydrocarbons with nine or more carbon atoms. The complexity of the product illustrates that no simple and straightforward single-step mechanism is operative rather, the reaction involves a set of parallel and consecutive reaction steps, with the importance of the individual steps differing markedly from one catalyst to another. To arrive at this complex product distribution from two simple molecules such as isobutane and butene, reaction steps such as isomerization, oligomerization, (3-scission, and hydride transfer have to be involved.

Isomerization—A refining process which alters the fundamental arrangement of atoms in the molecule, Used to convert normal butane into isobutane, as alkylation process feedstock, and normal pentane and hexane into isopentane and isohexane, high-octane gasoline components,... 

Now in the prefix meth- Figure 7.20 od of naming things the molecule in Figure 6.12 (p. 119) would he called isohexane because there are six carhon atoms total and it s the first rearrangement you can create heyond having all six carbons in a row. In the lUPAC system the molecule in Figure 6.12 is called 2-methylpentane. The... 

Neohexane did not react when contacted with 2-butene at 10° in the presence of 100% sulfuric acid (McAllister el al., 12). Under similar conditions, alkylation of isohexane (a mixture of 2- and 3-methylpentane) yielded alkylate to the extent of 206% by weight of the 2-butene. It therefore appears that isoparaffins that contain tertiary carbon atoms are more susceptible to alkylation. 

The fast reaction is the reversible skeletal isomerization of normal hexane to isohexane. Isomerization reactions are an important building block in the production of high-octane gasoline, as the octane numbers of branched paraffins are substantially higher than those of normal paraffins with the same number of carbon atoms. The slow reaction is the hydrogenolysis (hydrocracking) of normal hexane to lower paraffins such as methane. This reaction is undesirable, as these light paraffins have a much lower economic value. 

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