Hydrocracking of paraffins

It should be noted that many practically important catalytic transformations (such as isomerization of or hydrocracking of paraffins), which are presumed to proceed via consecutive mechanisms, are performed on multifunctional catalysts, with which the coupling of reactions in the sense just discussed may not necessarily occur. The problem of the selectivity of some models of polystep reactions on these catalysts has been discussed in detail by Weisz (56). 

Hydrodewaxing Selective hydrocracking of paraffins from oil fractions or products to prevent wax precipitation (negative influence on cold flow properties) ... 

Robert B. Anderson. Iron catalysts apparently do not isomerize hydrocarbons however, there is little experimental evidence besides the products of the Fischer-Tropsch synthesis. In hydrocracking of paraffins on nickel and cobalt catalysts the isomerization does not occur. 

Fig. 24. Typical examples of rearrangements of carbon-carbon bonds in isomerization and hydrocracking of paraffins over an ideal and bifunctional large-pore zeolite catalyst (297).

Baltanas, M. A., and G. F. Froment, Computer generation of reaction networks and calculation of product distributions in the hydroisomerization and hydrocracking of paraffins on Pt-containing bifunctional catalysts, Comput. Chem. Eng., 9. 71-81 (1985). 

M. Niwa, K. Kawashima, and Y. Murakami, A Shape-Selective Platinum-Loaded Mordenite Catalyst for the Hydrocracking of Paraffins by the Chemical Vapour Deposition of Silicon Alkoxide. J. Chem. Soc., Faraday Trans. 1, 1985, 81, 2757-2761. 

Hydrocracking of paraffins and naphthenes to lighter saturated paraffins. 

Schweitzer, J. M., Galtier, P., and Schweich, D., A single events kinetic model for the hydrocracking of paraffins in a three-phase reactor, Chem. Eng. Sci. 54(13-14), 2441-2452 (1999). 

The mechanism for hydrocracking of paraffins with a strongly acidic catalyst containing a mild hydrogenation component is generally believed... 

On the other hand, R-exchanged zeolites have also been used in combination with a metal function, for carrying out the isomerization and hydrocracking of paraffins and cycloalkanes. This is the case for isomerization of n-hexane to isohexane and 2,2-dimethyl-butane (Rabo et al. 1961) the isomerization of n-undecane to mixed Ci 1 isomers at 275°C on Pt/Ce-Y zeolite (Weitkamp et al. 1985) the isomerization of c (7o-exo-tricyclo[5.2.1.02,6]-decane or exo-tricyclo[6.2.1.02,7]-undecane into adamantane or 1-methyladamantane, respectively, on R-Y at 150-270°C (Lau and Maier 1987) the isomerization of tetrahydrodicyclopentadiene into adamantane on Re-Y in a H2/HC1 atmosphere at 250°C (Honna et al. 1986) or the double bond relocation of 2-alkyl acrolein into fran.j-2-methyl-2-alkenals over Ce,B-ZSM-5 (Fisher et al. 1986). Recently, it has been reported that Ce-promoted Pd/ZSM-5 is an active and selective catalyst in the dehydroisomerization of a-limonene to / -cymene (Weyrich et al. 1997). 

Mechanisms of hydrocracking of paraffins have been studied extensively (27-33). A carbonium ion mechanism is usually proposed similar to the mechanisms previously proposed for catalytic cracking except that hydrogenation and hydroisomerization are superimposed. The paraffins are first dehydrogenated to an olefin, then are adsorbed as a cation on an acidic site, isomer-ized to the preferred tertiary configuration, and undergoes beta scission. Virtually no methane and ethane are formed. The reaction becomes more selective for isoparaffin production as the temperature is decreased. 

Hydrocracking of Paraffins. An additional acid-catalyzed paraffin reaction is cracking to lighter products, thus removing them from the liquid product. Octane is improved through the removal of low octane paraffinic species from the liquid product by their conversion to gaseous, lower molecular weight paraffins. 

Hydrocracking of paraffins, including long alkyl side chains Figure 12 shows how these reactions might convert 2-butylnapthalene into propane, butane and toluene. 

Baltanas M.A. and Froment G.F. (1985) Computer Generation of Reaction Networks and Calculation of Product Distribution in the Hydroisomerization and Hydrocracking of Paraffins on Pt-Containing Bi-ftmctional Catalysts , Comp. Chem. Eng. 9, 1, 71-81. 

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