Isopentane oxygenation

These are effective high-octane gasoline additive oxygenates. The conversion of isobutane into isopropyl, methyl ketone, or isopentane into isobutyl, methyl ketone is illustrative. In this reaction, no branched carboxylic acids (Koch products) are formed. 

Some isopentane is dehydrogenated to isoamylene and converted, by processes analogous to those which produce methyl /-butyl ether [1634-04-4] (MTBE) to /-amyl methyl ether [994-05-8] (TAME), which is used as a fuel octane enhancer like MTBE. The amount of TAME which the market can absorb depends mostly on its price relative to MTBE, ethyl /-butyl ether [637-92-3] (ETBE), and ethanol, the other important oxygenated fuel additives. 

GC-TEA Analysis. A Bendix model 2200 GC and Thermo Electron model 502 TEA were used. The GC injector temperature was 210 C. The TEA pyrolysis furnace was operated at 450 C and the cold trap was held at -150 C in isopentane slush. Oxygen flow to the ozonator was 20 cc/min and indicated pressure was 1.5 torr at a helium flow rate of 20 cc/min. TEA output was processed by a digital integrator (Spectra Physics System I). 

Photolysis studies of diazomethane/isopentane mixtures in the presence and absence of oxygen, gave a calculated figure of 15—20% triplet methylene 97). 

An alternative photoinduced pathway has been identified in the photolysis of the meso-ionic oxathiazolone (335). Irradiation in ethanol in the presence of oxygen yields ethyl phenylglyoxylate (340 65%), ethyl benzoate (3%), and benzonitrile (21%). The postulated intermediates (Fig. 5) have been spectroscopically identified by photolysis in ether-isopentane-ethanol-glass at 85°K. ... 

When a stream of oxygen containing 15% ozone was passed through a solution of isobutane in HSC F-SbFs-SOiClF solution held at —78°C, the colorless solution immediately turned brown in color. 1H and 13C NMR spectra of the resultant solution were consistent with the formation of the dimethylmethylcar-boxonium ion in 45% yield together with trace amounts of acetylium ion (CH3CO+). Further oxidation products (i.e., acetylium ion and C02) were reported to be observed in a number of reactions studied. Such secondary oxidation products, however, are not induced by ozone. Similar treatment of isopentane, 2,3-dimethylbutane, and 2,2,3-trimethylbutane resulted in formation of related carboxonium ions as the major products (Table 5.37). 

In the field of halogenation, the practical aspects of the work were stressed by a number of Russian workers. Thus, in 1940 and later Mamedaliev reported (215) on the chlorination of methane over cupric chloride, pumice, iron, or aluminum shavings. Yields of 75 to 80% of products ranging from methyl chloride to carbon tetrachloride with small amounts of hexachloroethane were obtained. Similar work on the continuous chlorination of hydrocarbons such as isopentane, unsaturated compounds, oxygenated compounds, and on the mechanism of chlorination has been reported by Russian researchers from time to time (180,248,366,367,389). 

The catalysts were evaluated by exposure to a simulated automobile exhaust gas stream composed of 0.2% isopentane, 2% carbon monoxide, 4% oxygen and a balance of nitrogen. The temperature required to oxidize the isopentane and carbon monoxide was used to compare catalyst performance. The chromium-promoted catalyst oxidized isopentane at the lowest temperature, and a mixed chromium/copper-promoted catalyst proved the most efficient for oxidizing carbon monoxide and isopentane. It is interesting to note that the test rig used a stationary engine with 21 pounds of catalyst. Although the catalyst was very effective it is difficult to envisage uranium oxide catalysts employed for emission control of mobile sources. 

With pure oxygen the effect of lead tetraethyl on gasoline is slight.43-oaCi 14a However, Lewis 130 found that isopentane heated with oxygen in a glass apparatus to a temperature below the ignition point was more resistant to oxidation by the addition of one per cent of lead tetraethyl. 

A somewhat different method has been employed for the diazomethane-isopentane system . The formation of pentenes is attributed to the disproportionation of pentyl radicals and, therefore, indicative of abstraction by triplet methylene. The assumption that all of the products eliminated by added oxygen arise through reactions involving triplet methylene leads to the expression... 

While the phosphorescence of solids is easily observed at room temperature, it is often impossible to observe the phosphorescence of solutions at room temperature apparently oxygen molecules, absorbing energy in collisions with the excited species involved, quench its phosphorescence. To avoid this, solutions are cooled in liquid nitrogen (77°K) and allowed to freeze such solutions are referred to as rigid solutions or glasses. Two organic solvents commonly used to prepare such solutions are ethanol and EPA, a mixture of ethyl ether, isopentane, and ethanol. 

Empirical C9H12O Formula (CH3)2CHC6H40H Properties Lt. yel. liq. or solid medicinal, creosote odor sol. in isopentane, toluene, ethanol, 10% NaOH, oxygenated soivs. insol. in water m.w. 136.19 dens. 1.012 m.p. 15-16 C b.p. 212-213... 

For nonpolar fluids [32, 33] (methane, ethane, propane, n-butane, w-pentane, n-hexane, n-heptane, n-octane, argon, oxygen, nitrogen, ethylene, isobutane, cyclohexane, sulfur hexafluoride, carbon monoxide, carbonyl sulfide, n-decane, hydrogen sulfide, isopentane, neopentane, isohexane, krypton, w-nonane, toluene. 

This paper aims at summarizing our researches on the pyrolyses, at about 500 C, of four other alkanes -ethane (6a), isobutane (6b), n-butane (6c) and isopentane (6d)- in the presence of small oxygen concentrations (0.01 up to several %) and at initial pressures between 10 and 100 mm Hg. In an attempt to reach the chemical and kinetic features of the reactions without interference arising from the products, these reactions were studied at low percentage of conversion. Some preliminary results obtained in these investigations have already been succinctly presented (5)... 

Here again, in the presence of small amounts of oxygen and as a consequence of the oxidation, we observe the formation of hydrogen peroxide (or water) and extra yields of the olefins which already appear in the decomposition reactions of the alkanes by loss of H, i.e. isobutene in isobutane pyrolysis, ethylene and n butenes in n-butane pyrolysis, ethylene, propene and isopentanes in isopentane pyrolysis (see Tables I, II and III). 

We made similar observations for the pyrolyses of isobutane> n-butane and of isopentane in the presence of oxygen traces. 

Figure 5 shows that oxygen is swiftly consumed in Vessels (1) and (2) where isopentane decomposition is initially accelerated by sharp contrast, oxygen is slowly consumed in Vessels (3) and... 

Let us recall that several stoichiometries are necessary to represent the primary decomposition of isobutane, n-butane and isopentane. The presence of oxygen makes oxidation reactions appear. If we only consider the decomposition reactions (the oxidation ones being set apart), we see that the addition of oxygen modifies the relative weights of the decomposition stoichiometries ... 

The pyrolysis of four alkanes (ethane, isobutane, n-butane and isopentane) was studied in the presence of small quantities of oxygen, at low extent of reaction. 

At last, in the cases of isobutane, n-butane and isopentane, the presence of oxygen increases the relative weight of the deme-thanation" reaction (with regard to the other decomposition reactions of the alkane). This indicates that the free-radical becomes less easily oxidized than other chain carriers of the alkane decomposition. 

Results obtained in an investigation of the pyrolyses of four alkanes (ethane, n-butane, isobutane and isopentane) in the presence of trace amounts of oxygen, at low extent of reaction and around 500 C, are reported. The organic products of the primary oxidation are mainly olefins. According to experimental conditions (particularly to wall conditions of the reaction vessel), oxygen accelerates or inhibits the alkane decomposition. Walls inhibit the oxygen consumption. These experimental facts are interpreted and compared with recent results in literature. 

The data in Table 4.6 show that catalyst activity increases with polymerization temperature from 1,150 g PE/g catalyst at 65 C to 5,100 g PE/g catalyst at 77.5°C. However, very importantly, the polyethylene molecular weight may be controlled over the range necessary for the manufactme of commercial grades of polyethylene for industrial appHcations, as shown by Melt Index (MI values from 4.1 to 0.6. Isopentane or isopentane containing 0.3 ppm oxygen was needed to produce the relatively higher molecular weight products. 

Different regio-selectivities are found in the sMMO-catalyzed hydroxylation of branched alkane. Sterically hindered tertiary carbon is not reactive. In the oxygenation of 2,3-dimethylpentane catalyzed by sMMO from M. capsulatus (Bath), 3,4-dimethyl-2-pentanol is the sole product as shown in eq. (6) The sMMO-catalyzed hydroxylation of isopentane occurs mainly at the primary carbons of the alkane (see Table 3). These different selectivities may depend on shape and size of the substrate binding site of sMMO. These reactivities are similar to the (o-hydroxylation of -alkane catalyzed by cytochrome P-450 [74]. 

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