Isomerization of n-pentane

For the isomerization of n-pentane in a hydrogen atmosphere a proposed rate equation at 372 C is... 

Garin and Gault 82) reported a hydrogen order of - 3.4 for position isomerization of n-pentane over alumina-supported platinum between 240° and 300°C. They concluded therefore that a surface species that lost 3-4 hydrogen atoms would cyclize. It is not clear to what extent this discrepancy (cf. 77 and 82) may be attributed to different experimental conditions, to different catalysts, or actually to different mechanisms that is, C5 cyclization with participation of unsaturated intermediates. 

A study of the kinetics of isomerization of n-pentane at 372°C. over a platinum on alumina catalyst (0.3% platinum) has been reported by Sinfelt et al. (S4). The rate measurements were made in a flow system at low conversion levels (4-18%). The n-pentane was passed over the catalyst in the presence of hydrogen at total pressures ranging from 7.7 to 27.7 atm. and at hydrogen to n-pentane ratios varying from 1.4 to 18. Over this range of conditions the rate was found to be independent of total pressure and to increase with increasing n-pentane to hydrogen ratio (Fig. 4). The rate data were correlated by an expression of the form... 

In order to follow the catalytic recovering produced by the burning of coke, partially regenerated catalyst samples were submitted to standard reaction tests for benzene hydrogenation (metallic function) and normal pentane isomerization (acid function). Benzene hydrogenation was done at 423 K, 0.1 MPa, WHSV = 2 h 1, and molar ratio H2/Bz = 20. 200 mg of catalyst were loaded, which was reduced at 533 K with H2 for 2 h before the test. The isomerization of n-pentane was performed at 773 K, 0.1 MPa, WHSV = 2 h 1 and molar ratio H n = 6. 200 mg of catalyst were loaded, and were reduced with hydrogen at 773 K for 2 h before the test. 

Abstract. Tungstated zirconia catalysts are stable and highly selective catalytic materials for the isomerization of alkanes when promoted by platinum and a transition metal oxide and when dihydrogen is present in the feed. Physical properties and the catalytic performance of these solids for the isomerization of n-pentane are discussed. 

We review here a standard synthesis of unpromoted and promoted WZ catalysts, and their physical characteristics as related to their catalytic performance in the isomerization of n-pentane to isopentane. 

Analysis of such a correlation may reveal the significant variables and interactions, and may suggest some model, say of the L-H type, that could be analyzed in more detail by a regression process. The variables X, could be various parameters of heterogeneous processes as well as concentrations. An application of this method to isomerization of n-pentane is given by Kittrel and Erjavec (Ind. Eng. Chem. Proc. Des. Dev., 7, 321 [1968]). 

The discussion to this point has emphasized kinetics of catalytic reactions on a uniform surface where only one type of active site participates in the reaction. Bifunctional catalysts operate by utilizing two different types of catalytic sites on the same solid. For example, hydrocarbon reforming reactions that are used to upgrade motor fuels are catalyzed by platinum particles supported on acidified alumina. Extensive research revealed that the metallic function of Pt/Al203 catalyzes hydrogenation/dehydrogenation of hydrocarbons, whereas the acidic function of the support facilitates skeletal isomerization of alkenes. The isomerization of n-pentane (N) to isopentane (I) is used to illustrate the kinetic sequence associated with a bifunctional Pt/Al203 catalyst ... 

Sinfelt, Hurwitz, and Rohrer (1960) proposed essentially the following reaction scheme for the isomerization of n-pentane (nCs) to z-pentane (zCs) on a Pt/alumina catalyst ... 

A. E. Hirschler (Sun Oil Co., Marcus Hook, Pa. 19061) You report on one of your slides that at 300°C the extent of isomerization of n-pentane was 65% vs. 15% for n-hexane. Usually, n-hexane is more readily isomerized, or more extensively isomerized, than n-pentane. How do you account for the reverse situation which you have reported and the magnitude of the difference between C5 and Ce paraffins (The subject shde is not included in the paper.)... 

As an example of catalytic reforming we shall consider the isomerization of n-pentane to i-pentane ... 

Figure 2. Isomerization of n-pentane on R-hybrid catalysts containing various zeolites. V/F=5.0 g-cat h mol-1, n-C, 10 kPa, Hi, 90kPa, Pt/Si02 zeolite=l 4.

Figure 4 shows that the relative activity for n-pentane Isomerization drops linearly with the amount of carbon deposited on the acid function of the catalyst. This is so because isomerization of n-pentane is a typical bifunctional reaction controlled by the acid function of the catalyst. Hydrocracking to propane shows... 

Fig. 13. Particle size effect in isomerization of n-pentane-2- C contribution of cyclic mechanism.

In this paper, pyridine adsorption was utilized to investigate the hydrogen spillover phenomenon from metal to acidic centers of zeolite by observing hydrogenation of chemisorbed pyridine on B or L acid sites of USY zeolite using hybrid catalyst composed of USY zeolite and Pt/SiOo. To give insight into spill-over process in the hybrid catalyst system, isomerization of n-pentane, which is one of the typical add catalyzed reaction, was also studied. 

In the first systematic study of the isomerization of n-pentane it was found that freshly sublimed aluminum chloride does not catalyze the isomerization of n-pentane even on refluxing for several days (Glasebrook, Phillips, and Lovell, 29). When, however, a small amount of water, alkyl... 

It has been shown that the isomerization of n-pentane in the presence of aluminum chloride or aluminum bromide containing catalysts was accompanied by side reactions, characterized by the formation of butanes and tarry material. These side reactions can be inhibited by the use of hydrogen or organic additives. 

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