Octanes, reaction

The relative importance of the two pathways is reflected in the ratio of the yields of the hydroxycar-bonyls compared to the carbonyl products with the same number of carbons as the parent compound as well as in the absolute yields of the latter products. Thus the carbonyl product yields decrease from 70% for the n-butane reaction to 0.7% for the n-octane reaction at the same time, the ratio of hydroxycarbonyl products to carbonyls increases from 0.14 to 50 (Kwok... 

Hence, we can assume that the DHC reaction rates remain proportional to the degree of conversion (the formal n-octane reaction order provided between 0 and 1). 

The n-octane reaction network consists of 383 elementary chemical steps (52 hydride shifts of the 1.2- and 36 of the 1.3-type, 24 methyl shifts, 96 PCP branching isomerizations, 15 iS-scissions, 75 protonations and 85 deprotonations) involving 14 octanes, 5 paraffinic and 9 olefinic cracking products, 49 octenes, 42 octyl carbenium ions and 6 carbenium ions with a smaller carbon number, disregarding the methyl- and primary carbenium ions, which are known to be less stable. There is, however, no need to consider 383 rate coefficients, since the elementary chemical steps belong to only 6 types when no distinction is made between 1.2 and 1.3 hydride shifts. Yet, since the values of rate coefficients depend upon the structure of the reactant and the product, the true number of parameters depends upon the detail of the structure accounted for in the modeling. 

Alkylation combines lower-molecular-weight saturated and unsaturated hydrocarbons (alkanes and alkenes) to produce high-octane gasoline and other hydrocarbon products. Conventional paraffin-olefin (alkane-alkene) alkylation is an acid-catalyzed reaction, such as combining isobutylene and isobutane to isooctane. 

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. 

Facile reaction of a carbon nucleophile with an olefinic bond of COD is the first example of carbon-carbon bond formation by means of Pd. COD forms a stable complex with PdCl2. When this complex 192 is treated with malonate or acetoacetate in ether under heterogeneous conditions at room temperature in the presence of Na2C03, a facile carbopalladation takes place to give the new complex 193, formed by the introduction of malonate to COD. The complex has TT-olefin and cr-Pd bonds. By the treatment of the new complex 193 with a base, the malonate carbanion attacks the cr-Pd—C bond, affording the bicy-clo[6.1,0]-nonane 194. The complex also reacts with another molecule of malonate which attacks the rr-olefin bond to give the bicyclo[3.3.0]octane 195 by a transannulation reaction[l2.191]. The formation of 194 involves the novel cyclopropanation reaction of alkenes by nucleophilic attack of two carbanions. 

The principal class of reactions in the FCC process converts high boiling, low octane normal paraffins to lower boiling, higher octane olefins, naphthenes (cycloparaffins), and aromatics. FCC naphtha is almost always fractionated into two or three streams. Typical properties are shown in Table 5. Properties of specific streams depend on the catalyst, design and operating conditions of the unit, and the cmde properties. 

Isomerization. Isomerization is a catalytic process which converts normal paraffins to isoparaffins. The feed is usually light virgin naphtha and the catalyst platinum on an alumina or zeoflte base. Octanes may be increased by over 30 numbers when normal pentane and normal hexane are isomerized. Another beneficial reaction that occurs is that any benzene in the feed is converted to cyclohexane. Although isomerization produces high quahty blendstocks, it is also used to produce feeds for alkylation and etherification processes. Normal butane, which is generally in excess in the refinery slate because of RVP concerns, can be isomerized and then converted to alkylate or to methyl tert-huty ether (MTBE) with a small increase in octane and a large decrease in RVP. 

Mixtures of CO—H2 produced from hydrocarbons, as shown in the first two of these reactions, ate called synthesis gas. Synthesis gas is a commercial intermediate from which a wide variety of chemicals are produced. A principal, and frequendy the only source of hydrogen used in refineries is a by-product of the catalytic reforming process for making octane-contributing components for gasoline (see Gasoline and OTHER MOTOR fuels), eg. 

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