Isomerization of pentanes

To illustrate how a bifunctional catalyst operates, we discuss the kinetic scheme of the isomerization of pentane [R.A. van Santen and J.W. Niemantsverdriet, Chemical Kinetics and Catalysis (1995), Plenum, New York]. The first step is the dehydrogenation of the alkane on the metal ... 

The use of a labeled molecule is the only exact way to determine quantitatively the contribution of the 5C complexes to the overall isomerization. However, a rough estimate of it can, in favorable cases, also be made by comparing the isomerization of pentane (3C only) and hexane (both 3C and 5C complexes are possible) on the same catalyst and under the same conditions. For Pt and Pt/Cu alloys both methods have led to the same conclusions (188). 

Tn commercial petroleum refining, isomerization of light paraffins has been A applied for many years. Until recently the scope of the process was limited, however, and its main application was isomerization of butane as feed preparation for alkylation processes. Generally, except for a few specific cases, no commercial justification could be found for isomerization of pentane and hexane fractions since in most cases the quality requirements for motor gasoline could be met by alternative processing routes and by addition of various additives, such as lead tetraalkyls, to improve fuel burning characteristics. 

AICI3-Metal Sulfates. Room temperature isomerization of pentane has been carried out with a series of mixtures containing aluminum chloride with sulfates of metals such... 

The Lewis acid (AICI3) and Bronsted acid (HCI) catalyzed isomerization of pentane to a more highly branched product would form 2,3-dimethylpropane ... 

The isomerization of pentane was carried out with a series of mixtures containing aluminum chloride or bromide with sulfates of metals such as Ti, Fe, Ni, Cu, Al, and others the most effective catalyst was an equimolar mixture of AlBr3 and Ti2(S04)3 with a conversion of 86% and a selectivity to isopentane of 99% at room temperature (50, 51). In the vapor phase conversion, however, the main product was isobutane. 

The AIC13-CuS04 mixture was more thoroughly investigated (52). The catalytic activity of the mixtures for the isomerization of pentane was found to be proportional to the amount of CuS04 and also to the specific surface area of the CuS04 used. The acidity was estimated to be - 14.52 < Ho < — 13.75. It was concluded that the active species were located on the surface of the CuS04. 

The catalytic isomerization of -pentane was carried out in a once-through fixed bed flow reactor using helium as a carrier gas, at a standard temperature of 523 K in the absence and presence of dihydrogen in the feed. Characteristic rate and selectivity data are compared in Table 2 for WZ and PtWZ.21,35... 

As crude oil becomes more costly to recover from the ground, isomerization of pentane and hexanes can be expected to increase in prominence. Isomerization is the best way to raise the octane number of these low-boiling components of gasoline without loss in yield. Hydrocarbons with less than six carbons in the longest straight chain do not lend themselves to cyclization and conversion to high-octane aromatics. 

During the past two decades, the isomerization of pentanes and hexanes has very often been used as a test reaction in the study of particle size or alloying effects. In these studies, the product distribution, and especially the percentage of cyclic molecules (cyclopentane or methylcyclopentane), have often been used for estimating the contribution of the cyclic mechanism. 

The activities of noble-metal-impregnated synthetic clays for the isomerization of pentane are compared in Table I. Pd-NiSMM in its protonic form has been pre-reduced at 350 °C. 

Effect of Organic Additives upon ike Isomerization of Pentane... 

What operating temperature is required to attain 90% conversion of CO under these conditions if the reactor inlet composition is 1% CO, 10% O2, and the remainder inert. Neglect volume changes of the reaction. Sinfelt, Burwitz and Rohrer [J.B. Sinfelt, S. Hurwitz and J.C. Rohrer, J. Phys. Chem., 64, 892 (I960)] report the following rate equation for the isomerization of -pentane in a hydrogen atmosphere. 

For example, a value of -3.5 for the order versus hydrogen, found for cyclic type isomerization of pentane and hexanes [12, 26, 52] would mean that the reactive species is obtained by rupturing at least seven carbon-hydrogen bonds. Since it is difficult to imagine first that species such as [C5H5]ids or [CsH ] could react further to give isomer products and secondly to find a parallel with any surface organometaUic complex [53], another approach has been taken. 

The nucleophilic nature of the alkanes is also shown by the influence of the acidity level on their solubility. Torek and coworkers have investigated the variation of the composition of the catalytic phase as a function of SbFs concentration in isomerization of pentane in HFiSbFs. 

Similarly, isomerization of pentane and 2-methylbutane over a number of SbF5-treated metal oxides has been investigated. The Ti02 Zr02 SbF5 system was the most reactive and, at the maximum conversion, the selectivity for skeletal isomerization was found to be ca 100% . 

As discussed in A Word About... Petroleum, Gasoline, and Octane Number on p. 103, isomerization is often used to convert one alkane to a more substituted alkane. Suggest the highly branched product obtained from the isomerization of pentane using a mixture of AICI3 and HCl over an alumina catalyst. Provide the correct lUPAC name for the product. 

The regression is generally nonlinear, and in the second case the computations are even more complicated because the equation is implicit in x. Peterson and Lapidus [1965] used the integral method with nonlinear regression on Franckaerts and Froment s data and found excellent agreement, as shown by Table 2.6.2-1. A further illustration of such agreement is based on Hosten and Froment s data on the isomerization of / pentane [1971] as analyzed by Froment and Mezaki [1970]. 

Skeletal isomerization of paraffins such as butane, pentane, etc. is not catalyzed even by 100% H2SO4. It was found, however, that Zr02 S04 , Ti02 — S04 , and Fe203 — S04 " catalyzed the skeletal isomerization of butane at 293 — 323 K, the main products being isobutane. The activity of the solid superacids is lowered as the reaction proceeds probably due to coke formation. To prevent the catalyst from its deactivation, a catalyst on which a small amount of Pt, Ni etc. was added was developed. Over a Pt — Z1O2 — S04 catalyst, no deactivation was observed for more than 100 h for the skeletal isomerization of pentane at 413 K under 20 kg/cm of hydrogen pressure. 

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