Isobutane yields

The very small isobutane yields can not be attributed to the participation of Reaction 3 since the known rate constant data are inconsistent with this. Isobutane must come from some other reactions, as yet undefined. 

The isobutane yield was constant in both systems resulting in significantly higher iC /nC and iC /LPG volume ratios in the sulfur-free system. Although converting more of the feed, the sulfur-containing system produced significantly less C + C2 than the sulfur-free system. 

Isobutane Production. The importance of isobutane domestically prompted experimentation aimed at maximizing the isobutane yield. Indications had been obtained from Figures 2 and 3 and discussed previously that as the catalyst aged, isobutane yields increased (at the expense of propane). It appeared likely that processing at less severe conditions would be beneficial towards increasing isobutane yields. 

Figure 6. Product distribution in hydrocracking for maximum isobutane yields. 7,000 kPa (1,000 psig), 5 hydrogen-to-hydrocarbon mole ratio, 200 ppm sulfur in feed. 0.7 wt % Pd — 15 wt % Nir-SMM, sulfided.

In this processing to maximize Isobutane yields, a significant amount of C5+ normally liquid product remained (e.g. 40 vol % based on feed). The Iso-to-normal ratios from the C5 s and Cg s are presented In Figure 8. The same type relationship as previously shown In Figure 4 for LPG maximization resulted, e.g., a high lC5/nC5 ratio and a ICg/nCg ratio of 4-5 as compared to 1.4 for the feed. The results Indicated that this C5 total fraction should have a significantly higher octane number than the Cg" " feed. This was Indeed the case as the product Cj" " RON,... 

The reaction of isobutane with vinyl chloride in the presence of aluminum chloride yielded liquid isoparaffins and l,l-dichloro-3,3-dimethyl-butane (40% yield at —10° and 20% yield at 25°). t-Butyl was isolated in about 10% yield. The formation of the dichlorohexane instead of monochlorohexane may be explained as being due to the relative unreactivity of the primary chlorine atoms only a very small amount of the dichloride is reduced to monochloride by the reaction similar to step 3. In the case of the allyl chloride reaction, the dichloroheptane contains a secondary chlorine atom and reacts readily with isobutane, yielding raono-chloroheptane and <-butyl chloride. Under conditions which are such as bring about the reduction of a chlorine atom of the dichlorohexane, both chlorine atoms are replaced, and the product consists of isoparaffins and only a very small amount of monochlorohexane. 

Isobutane yields the isobutyl group by removal of a hydrogen from one of the methyl carbons. The t-butyl group is derived by removal of a hydrogen from the CH carbon. 

FIGURE 2.33 (a) and (b) Replacement of one of the hydrogens of butane with X yields two kinds of butyl derivatives, butyl—X and rec-butyl —X. (c) and (d) Replacement of hydrogen with X in isobutane yields two more butyl compounds, /cr/-butyl—X and isobutyl—X. 

Propylene oxide [75-56-9] is manufactured by either the chlorohydrin process or the peroxidation (coproduct) process. In the chlorohydrin process, chlorine, propylene, and water are combined to make propylene chlorohydrin, which then reacts with inorganic base to yield the oxide. The peroxidation process converts either isobutane or ethylbenzene direcdy to an alkyl hydroperoxide which then reacts with propylene to make propylene oxide, and /-butyl alcohol or methylbenzyl alcohol, respectively. Table 1 Hsts producers of propylene glycols in the United States. 

Autoxidation of alkanes generally promotes the formation of alkyl hydroperoxides, but d4-tert-huty peroxide has been obtained in >30% yield by the bromine-catalyzed oxidation of isobutane (66). In the presence of iodine, styrene also has been oxidized to the corresponding peroxide (44). 

Hydroperoxide Process. The hydroperoxide process to propylene oxide involves the basic steps of oxidation of an organic to its hydroperoxide, epoxidation of propylene with the hydroperoxide, purification of the propylene oxide, and conversion of the coproduct alcohol to a useful product for sale. Incorporated into the process are various purification, concentration, and recycle methods to maximize product yields and minimize operating expenses. Commercially, two processes are used. The coproducts are / fZ-butanol, which is converted to methyl tert-huty ether [1634-04-4] (MTBE), and 1-phenyl ethanol, converted to styrene [100-42-5]. The coproducts are produced in a weight ratio of 3—4 1 / fZ-butanol/propylene oxide and 2.4 1 styrene/propylene oxide, respectively. These processes use isobutane (see Hydrocarbons) and ethylbenzene (qv), respectively, to produce the hydroperoxide. Other processes have been proposed based on cyclohexane where aniline is the final coproduct, or on cumene (qv) where a-methyl styrene is the final coproduct. 

Alkylation of isobutylene and isobutane in the presence of an acidic catalyst yields isooctane. This reaction proceeds through the same mechanism as dimerization except that during the last step, a proton is transferred from a surrounding alkane instead of one being abstracted by a base. The cation thus formed bonds with the base. Alkylation of aromatics with butylenes is another addition reaction and follows the same general rules with regard to relative rates and product stmcture. Thus 1- and 2-butenes yield j -butyl derivatives and isobutylene yields tert-huty derivatives. 

A typical feed to a commercial process is a refinery stream or a steam cracker B—B stream (a stream from which butadiene has been removed by extraction and isobutylene by chemical reaction). The B—B stream is a mixture of 1-butene, 2-butene, butane, and isobutane. This feed is extracted with 75—85% sulfuric acid at 35—50°C to yield butyl hydrogen sulfate. This ester is diluted with water and stripped with steam to yield the alcohol. Both 1-butene and 2-butene give j -butyl alcohol. The sulfuric acid is generally concentrated and recycled (109) (see Butyl alcohols). 

Seasonal chances in gasoline sales and heating oil sales compel some modifications to be made in conversion level. Therefore, the conversion pattern of a given catalytic cracking unit can vary from season to season. In summer operations, for instance, higher yields of motor gasoline are desired, both from direct production of 5/430° FVT catalytic naphtha and also from conversion of butylenes and isobutane to alkylate. 

A singlet pair of <-butyl radicals produced by peroxide decomposition disproportionate to yield isobutane and isobutene [equation (41)]. Both products show E/A multiplet effects. 

Figure 4 shows the evolution of the initial conversion versus temperature at a space velocity of 0.03 h l. The equilibrium conversion of isobutane to isobutene is 100% in our conditions. An increase of the conversion with temperature up to 773-823 K is observed. When metals were added, we also noted a large increase in isobutane dehydrogenation. Table 2 gives initial isobutane conversions, isobutene selectivities and yields of the reaction at 823 K for the three tested samples. 

Model systems indicate that aldehydes may also be produced by the action of polyphenoloxidases on amino acids in the presence of catechin, all of which are present in coffee beans at some stage between green and roasted. For example, valine yields isobutanal, leucine yields isopentanal, and isoleucine yields 2-methyl-butanal.14 Some of these aldehydes probably undergo condensation reactions in the acidic medium of the roasted bean when moisture is present.15 Some dienals in green coffee beans have recently been identified as (E,E)-2,4- and (E,Z)-2,4-nonadienal and (E,E)-2,4- and (E,Z)-2,4-decadienal.18... 

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