Isomerization of hexanes

Isomer Distributions in Initial Products from Hydrogenolysis of Methylcyclopentane and from Isomerization of Hexanes over Platinum Catalysts ... 

Proportions of Isotopically Labeled Products from Isomerization of Hexanes over 0.2% Platinum /Alumina Catalyst at 273°C ... 

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... 

In this paper, the results of the isomerization of hexane, heptane and octane over a Mo2C-oxygen-modified-catalyst, a Mo03-carbon-modified catalyst and a Pt//l-zeolite catalyst, at atmospheric pressure, are presented. Also, the results for a conventional Pt/Al203 catalyst are presented for the isomerization of hexane. Then, the effect of pressure on the isomerization of heptane and octane over the molybdenum catalysts and the Pt//l-zeolite catalyst is shown. Finally, the ability of the molybdenum catalysts to catalyse the isomerization reaction at high conversion with high selectivity even with hydrocarbons larger than hexane is demonstrated this is not possible over the Pt catalysts. The differences between the catalysts are discussed in terms of the reaction mechanisms. 

Fig. 67. Effect of Pd content on activities for isomerization of hexane catalyzed by PdrH3-2,PW 12O40. (From Ref. 378.)...

Hydrogenolysis of Methylcyclopentane and Isomerization of Hexanes. Comparison Between Calculated and Observed Distributions a... 

In tlie hydrogenolysis of methylcyclopentane, and the isomerization of hexanes, striking differences in initial product distributions on dispersed (0.2% 14-AI2O3) and concentrated (10% Pt-Al203) catalysts were ascribed to the occurrence of 2.0 and 20.0 nm crystallites, which promoted the cyclic mechanism or the bond shift + cyclic mechanisms, respectively. The possible roles of support acidity or secondary reactions were debated, for example ref. 182, which also lists earlier references. 

The hydrocracking and isomerization of hexane over de-aluminated mordenites were investigated with detailed product analyses. The hydroisomerization and hydrocracking of pentane over various exchanged mordenite catalysts were studied by Gray and Cobb. The cracked products consisted of relatively more propane and butanes over the smallest cation form (Be-mordenite) and relatively more methane for the largest cation form (Ba-mordenite), indicating a selectivity effect. The catalysts used in commercial processes for the hydroisomerization... 

Chick, Katzer, and Gates varied the Pd content of Pd/H-mordenite catalysts for the reaction of hexane at 523 K. They found the rate of cracking decreased sharply as the Pd content increased to about 0.7 wt %, whereas the rate of isomerization increased with Pd content. The rate of catalyst deactivation increased with the rate of cracking and the associated deposition of coke in the pore mouths. H-mordenite and CaY zeolites loaded with various transition metals were testedfor the isomerization of hexane and pentane. 

The first approach to the cyclic mechanism of isomerization was the finding that the interconversion of n-hexane and methylpentanes takes place under the conditions where the nonselective mechanism of hydrogenolysis (Mechanism A) is the only one operating that is, on 0.2% Pt/AljOj (32). The identical product distributions in isomerization of hexanes and hydrogenolysis of methylcyclopentane suggested that both reactions involve a common intermediate with a methylcyclopentane structure. It was then proposed that the species responsible for dehydrocyclization of hexanes are a,j8, -triadsorbed species involving a single metal atom (55) (Scheme 40). 

R-AgTP exhibits a catalytic activity for the isomerization of hexane only in the presence of hydrogen. 

The activities of R-AgTP for the isomerization of hexane reversibly with hydrogen pressure, llius, the catalytic activity disappears when hydrogen is eliminated from the gas phase and reappears upon reintroducing hydrogen. 

The preparation of sulphated zirconia designed for catalyst supports was studied by Boutonnet et al. . Zirconia prepared in microemulsion showed a pure tetragonal structure compared with zirconia prepared by an impregnation -precipitation procedure which also contained monoclinic phase. Platinum-promoted sulphated zirconia catalysts were prepared both in anionic and non-ionic microemulsions. Furthermore, the catalytic activity and selectivity for the isomerization of hexanes were tested. The catalysts produced by the microemulsion method showed a higher selectivity towards isomers but a lower activity when compared to catalysts prepared by impregnation technique. More recently, a study of zirconia synthesis from micro and macroemulsion systems has been conducted . Spherical ZrOa particles ranging from tens of nanometers to a few micrometers were produced. 

The side reactions occurring during the isomerization of hexanes have no effect on the chemical equilibrium. This is shown in Table XXXII. 

Commercial Methods for Isomerization of Hexane Refer to section III, 5b. 

The first reactions performed with inert alumina supported platinum in a flow reactor were done by the group of Gault [4] in 1963. Studies directed to understanding the mechanism of isomerization of hexanes on platinum catalysts started with... 

Szabo. C. Nascimento. P. Deeker, S. Meehanism for isomerization of -hexane over sulfated zireonia Role of 43. hydrogen. Chem. Commun. 1999. 1819-1820. 

A superacid polymer catalyst was obtained by binding aluminium chloride to sulfonated, macroporous co(polystyrene-DVB) (Magnotta et u/., 1976 Magnotta and Gates, 1977a,b). The catalyst was active in bringing about cracking and isomerization of -hexane at 357 C at atmospheric pressure. 

Some attempts have been made to prepare solid superacids by combining AlCb with solid cocatalysts. A complex of AICI3 with crosslinked polystyrene sulfonic acid was prepared and its catalystic activity examined in alkanes reactions. nie catalyst showed activity to catalyze cracking and isomerization of hexane at 353 K. 

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