Shell naphthene isomerization process

Essential features of the Shell naphthene isomerization process (24) are outlined in Figure 26. Although the contactor principle employed in the other liquid-phase Shell processes is used, the catalyst is handled in the form of hydrocarbon complex. A carefully fractionated and dried concentrate of dimethylcyclopentanes is preheated to 200°F., and about 0.1% of anhydrous hydrogen chloride is added. The feed is joined by a stream of catalyst complex and charged to the reactor under a gauge... 

The naphthene isomerization process has been applied also to the conversion of meth-ylcyclopentane to cyclohexane for subsequent dehydrogenation to benzene. Shell s Wilmington, Calif., refinery has been operating commercial equipment on this basis since March 1950 (18). 

Naphthene Isomerization. In addition to the paraffin isomerization processes, naphthene isomerization also proved useful during the war in connection with the manufacture of toluene. In the Shell dehydrogenation process for the manufacture of toluene, good yields depend upon increasing the methylcyclohexane content of the feed by isomerization of dimethylcyclopentanes. This process was employed commercially at one refinery in the Midwest and one on the Pacific Coast. 

The operating conditions for the three processes are very similar— only temperatures are somewhat dissimilar. The Shell Development system, employing a modified Friedel-Crafts system, operates at a lower temperature—150°-210°F vs. 250°-400°F for the other two processes. However, the equilibrium effects of the temperature differences are minimized as shown by the similarity in n-C4 and n-C5 yields shown in Table VI. Unleaded octane numbers for C5/C6 isomerate, obtained from a pure C5/C6 straight-run fraction, could not be found in the literature for the Shell process. However, pilot unit operations charging laboratory blends of n-C5, n-C6, and C6 naphthenes have been reported (26, 45). In the Shell process the use of antimony trichloride and hydrogen has considerably reduced the amount of side reactions for a Friedel-Crafts system so that the yield for this process is quite close to the yield structure for the other two processes. 

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