Cycloparaffins, hydrocracking

Catalytic Reforming. Worldwide, approximately 30% of commercial benzene is produced by catalytic reforming, a process ia which aromatic molecules are produced from the dehydrogenation of cycloparaffins, dehydroisomerization of alkyl cyclopentanes, and the cycHzation and subsequent dehydrogenation of paraffins (36). The feed to the catalytic reformer may be a straight-mn, hydrocracked, or thermally cracked naphtha fraction ia the... 

Of the main reactions, aromatization takes place most readily and proceeds ca 7 times as fast as the dehydroisomerization reaction and ca 20 times as fast as the dehydrocyclization. Hence, feeds richest in cycloparaffins are most easily reformed. Hydrocracking to yield paraffins having a lower boiling point than feedstock proceeds at about the same rate as dehydrocyclization. 

Under more severe conditions, Pd or Pt-H-mordenite hydrocracks both paraffins and cycloparaffins, again being more active than the corresponding Y-type zeolite catalyst. We have found that n-Cc and n-Cj are converted essentially to C3 and i-C, whereas n-Cio gives i-C and i-Cs primarily. Although n-Ce and n-Cio paraflBns are hydrocracked more rapidly than the corresponding cycloparafiins (cyclohexane and decalin), with binary mixtures of paraffin and the corresponding cycloparaffin, the latter are removed preferentially (4, 24, 25). 

Figure 7. Product distribution from hydrocracking C12 cycloparaffins...

For hydrocarbon reactions, metals (particularly platinum and its alloys) are frequently applied to acidic supports to catalyse hydrogen transfers. Thus platinum on a chlorinated alumina support accelerates the acid catalysed isomerization of n-alkanes (at about 150°C). In hydrocracking, the metal catalyses hydrogenation of heavy aromatic and polyaromatic components the resulting cycloparaffins (cycloalkanes) undergo zeolitic cracking, with... 

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