Pentanes-hexanes isomerization

Butane isomerization and pentane-hexane isomerization are the two most important isomerization processes. Isobutane is utilized primarily as alkylate feedstock. Isopentanes and isohexanes have become valuable high-octane blending components in gasoline. 

Penex [Pentane and hexane isomerization] A process for converting n-pentane and n-hexane and their mixtures into branched-chain pentanes and hexanes of higher octane number by catalytic isomerization. The catalyst is similar to the Butamer catalyst. The product is used in high-octane gasoline. First commercialized by UOP in 1958. More than 75 units were operating as of 1996. 

Table 12.3 Zeolitic pentane and hexane isomerization catalysts. 

The mechanism and kinetics of pentane, hexane, and cyclohexane isomerization over Pd-H-mordenite have been extensively investigated by Bryant (6), Hopper (21), and Beecher (20). They assume a conventional dual function mechanism as described earlier. Bryant (6) pointed out that H-mordenite itself has a high activity for pentane isomerization and that impregnation of a noble metal does not change the rate of the isomerization reaction. This exceptional activity of mordenite has since been reported by Benesi (14) and Minachev (7) as well. In Mina-chev s paper the reaction mechanism of n-pentane isomerization over H-mordenite is discussed in some detail. The rate of reaction is inversely proportional to the hydrogen pressure, and it is concluded that the reaction proceeds according to the following scheme ... 

The SZNbPt catalyst shows a higher isomerization selectivity and activity for all hydrocarbons. While n-pentane and n-hexane isomerization selectivity is very similar on both catalysts, important differences occur with n-heptane. When comparing both catalysts at the same conversion level (60%), SZNbPt shows a higher selectivity (— 5096) than the conventional sulfated zirconia ( 30%). However, the isomerization selectivity of n-heptane SZNbPt is still too low when the temperature is increased to achieve high C5-C6 isomerization yields. 

I. M. Keen The slide data were given to show that mordenite-based catalysts are more active than their Y-type counterparts for isomerizing C5 and Cg paraffins. The feedstock used in this comparison was a commercial pentane/hexane blend, containing some isoparaffins. The C5 and Ce isomerization levels in this instance are defined as the percent weight of i-C and 2,2-dimethylbutane (2,2-DMB) in the respective total C5 and Cq fractions. On this basis, the C5 and Ce isomerization conversion levels in the feedstock were ca. 35 and 2 wt %, respectively. 

Isomerization (Evering, 1954) Pentane Hexane Iso-pentane 2-mcthyl pentane Sublimation Sublimation... 

Related alkanes such as pentanes, hexanes and heptanes isomerize by similar pathways with increasing tendency towards cracking (i.e. C—C bond cleavage). 

Pentane/hexane (CsCe) isomerization processes increase the octane of light gasoline. In a typical unit, dried, hydrotreated feed is mixed with a small amount of organic chloride and recycled hydrogen, then heated to reaction temperature. 

In isomerizing butane with aluminum chloride, only a small amount of catalyst-hydrocarbon complex is formed, but pentane and especially hexane produce more complex. Both pentane and hexane tend to crack during treatment and this is the cause of the extensive side reactions. The formation of sludge is inhibited in pentane isomerization by the use of 0.3 to 1.3 weight per cent benzene, and in hexane isomerization, hydrogen is used as an inhibitor. 

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. 

Initially, aluminum chloride was the catalyst used to isomerize butane, pentane, and hexane. Siace then, supported metal catalysts have been developed for use ia high temperature processes that operate at 370—480°C and 2070—5170 kPa (300—750 psi), whereas aluminum chloride and hydrogen chloride are universally used for the low temperature processes. 

An industrial example of a eonseeutive reversible reaetion is the eatalytie isomerization reaetions of n-hexane to 2-methyl pentane and 3-methyl pentane and is represented as ... 

Microwave activation of alkane transformations was studied in detail by Roussy et al., who summarized their results in several papers [2, 28, 29, 79]. Isomerization of hexane, 2-methylpentane, 2-methyl-2-pentene, and hydrogenolysis of methylcydo-pentane have been investigated, and the diversity of possible effects has been specified [2]. The course of 2-methylpentane isomerization on a 0.3% Pt/Al203 catalyst depended on the mode of heating - the distribution of hexane products was different... 

Isomerate A continuous hydrocarbon isomerization process for converting pentanes and hexanes to highly branched isomers. Developed by the Pure Oil Company, a division of the Union Oil Company of California. The catalyst, unlike those used in most such processes, does not contain a noble metal. 

Isomerization (Figure 4.15) converts n-butane, n-pentane and n-hexane into then-respective isoparaffins of substantially higher octane number. The straight-chain... 

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