Hydrocarbon reactions paraffins, dehydrocyclization

The hydrocarbon-type analysis of the Platformate discussed above was based on the product having an octane number of 92.9 (F-l plus 3 ml. of tetraethyllead per gallon). The aromatic content (based on charge) increases continually with increased severity. At the two highest severities, the aromatic yield (based on the charge) is in excess of the total naphthenes and aromatics present in the charge. This indicates the participation of the dehydrocyclization reaction of paraffins to form aromatics. 

Supported chromia catalysts have a wide range of applications such as hydrogenation and dehydrogenation reactions of hydrocarbons, the dehydrocyclization of paraffins, dehydroisomerization of paraffins, olefins, and naphthenes, and the polymerization of olefins [1-3]. In order to improve the activity and selectivity, characterization of some critical parameters for both fresh and spent catalysts is necessary. 

A special case is the dehydrocyclization of paraffins—a complicated reaction similar to the previous one. Aromatic hydrocarbons are formed in it by way of dehydrogenation of the intermediate six-membered rings... 

Lately, dehydrocyclization has been extended to the closing of five and six-membered rings in paraffins with the formation of cyclo-pentanc hydrocarbons (151, 152). For the mechanism of these reactions see Section I,D. 

Cyclization—The conversion of aliphatic hydrocarbons containing six or more carbon atoms in a chain to the corresponding aromatic hydrocarbon is known as dehydrocyclization. The reaction sequence is believed to involve dehydrogenation of a paraffin to an olefin followed by ring closure and subsequent dehydrogenation of the ring compound to an aromatic. In many cases, isomerization (see 18) reactions also take place. 

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