Isobutane from //-butane

The skeletal isomerization of butane to isobutane is a typical reaction catalyzed by superacidity. Early in the history of this work, S04/Fe203, S04/Ti02, and S04/Zr02, were termed superacids owing to their ability to isomerize butane at room temperature or below [32, 37, 39] The formation of isobutane from butane, however, does not necessarily require superacidic strength. A bimolecular reaction pathway based on the intermediacy of butane is energetically lower than a monomolecular mechanism [129-133]. The monomolecular and bimolecular mechanisms are shown in Schemes 17.1 and 17.2, respectively, using pentane as a model. 

Each sample cylinder was analyzed, in order to assure their homogenity, using a Varian Vista 6000 Gas Chromatograph. When developing this technique we encountered the common G.C. problems separation of Ethane from Methane in the presence of 90% Methane, separation of Isobutane from Butane, Isopentane from Pentane and condensation of higher hydrocarbons (Hexane, Heptane) on intermediate lines before injection. 

A distillation column is to be used to separate isobutane from -butane. The column, which is equqjped with 100 sieve trays, has an inside diameter of 10 ft (120 in.) and a tangent-to-tangent length of 212 ft (2,544 in.). Operating conditions are 110 psia and 150 F at the bottom of the tower and 100 psia and... 

The C4H9 alkyl groups may be derived either from the unbranched carbon skele ton of butane or from the branched carbon skeleton of isobutane Those derived from butane are the butyl (n butyl) group and the 1 methylpropyl (sec butyl) group... 

There are other commercial processes available for the production of butylenes. However, these are site or manufacturer specific, eg, the Oxirane process for the production of propylene oxide the disproportionation of higher olefins and the oligomerisation of ethylene. Any of these processes can become an important source in the future. More recentiy, the Coastal Isobutane process began commercialisation to produce isobutylene from butanes for meeting the expected demand for methyl-/ rZ-butyl ether (40). 

Evaporative emissions from vehicle fuel systems have been found to be a complex mixture of aliphatic, olefinic, and aromatic hydrocarbons [20,24,33]. However, the fuel vapor has been shown to consist primarily of five light paraffins with normal boiling points below 50 °C propane, isobutane, n-butane, isopentane, and n-pentane [33]. These five hydrocarbons represent the more volatile components of gasoline, and they constitute from 70 to 80 per cent mass of the total fuel vapor [24,33]. 

Gasoline contains more than 250 components of a mixture of C4-C12 hydrocarbons, which varies in concentration from batch to batch. Some of these components are isobutane, n-butane. isopentane, n-pentane, 2,3-dimethylbutane, 3-methylpentane, n-hexane, 2,4-dimethylpentane, benzene, 2-methylhexane, 3-meth-ylhexane, 2,2,4-trimethylpentane, 2,3,4-trimethylpentane, 2,5-dimethylhexane, 2,4-dimethylhexane, toluene, 2,3-dimethylhexane. ethylbenzene, methylethylbenzenes, m-, p-, and o-xylene, trimeth- ylbenzenes, naphthalene, methylnaphthalenes, and dimethylnaph-thalenes... 

Hydrogenolysis of butane was performed using Pt and PtRh nanowires and particles/FSM-16 [23, 32] Table 15.6 summarizes the results. In this reaction, methane, ethane and propane were formed from hydrogenolysis of butane, and isobutane from isomerization (15.1) ... 

Products are fractionated in the deisobutanizer and debutanizer to separate isobutane and butane from alkylate HF-produced alkylate is fractionated in a similar manner... 

It is also clear that during periods of low surface ozone, chlorine atoms are a major reactant for hydrocarbons (e.g., Jobson et al., 1994 Solberg et al., 1996 Ariya et al., 1998). Figure 6.39, for example, shows the measured ratios of isobutane, n-butane, and propane during an ozone depletion event (Jobson et al., 1994). These particular pairs of hydrocarbons were chosen to differentiate chlorine atom chemistry from OH reactions. Thus isobutane and propane have similar rate constants for reaction with Cl but different rate constants for reaction with OH. If chlorine atoms are responsible for the loss of these organics, their ratio should remain relatively constant in the air mass, as indicated by the line marked Cl. Similarly, isobutane and n-butane have similar rate constants for removal by OH but different rate constants for reactions with... 

Under photo-stimulation, isoindolyloxyl radical (5) abstracts primary, secondary, or tertiary hydrogens from unactivated hydrocarbons including cyclohexane, isobutane, or / -butane (Scheme l).23 The nitroxide (5) traps the resultant carbon-centred radical (R ) and so afford the /V-alkoxyisoiiulolcs (6). Blank photolysis experiments with no added hydrocarbon have shown some unprecedented / -fragmentation of (5) to afford the nitrone (7). A number of C60 nitroxide derivatives have been synthesized and characterized by ESR spectroscopy which show features common to nitroxide radicals.24 Reaction of nitroxide and thionitroxide radicals with thiyl radicals have been observed, from which sulfinyl, sulfonyl, and sulfonyloxy radicals were generated.25 The diisopropyl nitroxide radical was generated in the reaction of lithium diisopropylamide with a-fluoroacetate esters.26... 

Only two alkanes have the molecular formula C4H10 butane and isobutane (2-methylpropane)— both of which give two monochlorides on free-radical chlorination. However, dehydrochlorination of one of the monochlorides derived from butane yields a mixture of alkenes. 

The magnitude of the deviations from Raoult s law increases with the difference in nature between the components. For instance, the normal propanol-water system (Fig. 1.3a) and the acetone-chloroform system (Fig. 1.36) show large activity coefficients, the highest being 13. On the other hand, the highest-activity coefficient in a mixture of isobutane-normal butane, which are similar to each other, is smaller than 1.1 (at about 100 psia). 

In a natural gasoline fractionation system there are usually six chemical species present in appreciable quantities methane, ethane, propane, isobutane, n-butane, and n-pentane. A mixture of these species is placed in a closed vessel from which all air has been removed. If the temperature and pressure are fixed so that both liquid and vapor phases exist at equilibrium, how many additional phase-rule variables must be chosen to fix the compositions of both phases ... 

Fig. 2.6 Formation of isobutane from n-butane by a dimerization-cracking mechanism involving branched C8+ intermediates...

Fig. 1. Temperature dependence of G-values of n-butane and isobutane from y-irradiation of E-P copolymer (o) n-butane ( ) isobutane CHjSH (a) n-butane, (a) isobutane (CjHjIjN ( ) n-butane, ( ) isobutane...

Figure 13.10. Composition and efficiency profiles in distillation of propane-isobutane-M-butane. Calculations and data from Ognisty and Sakata (1987).

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