Dehydrocyclization, carbon complexes

Dehydrocyclization, 30 35-43, 31 23 see also Cyclization acyclic alkanes, 30 3 7C-adsorbed olefins, 30 35-36, 38-39 of alkylaromatics, see specific compounds alkyl-substituted benzenes, 30 65 carbene-alkyl insertion mechanism, 30 37 carbon complexes, 32 179-182 catalytic, 26 384 C—C bond formation, 30 210 Q mechanism, 29 279-283 comparison of rates, 28 300-306 dehydrogenation, 30 35-36 of hexanes over platintim films, 23 43-46 hydrogenolysis and, 23 103 -hydrogenolysis mechanism, 25 150-158 iridium supported catalyst, 30 42 mechanisms, 30 38-39, 42-43 metal-catalyzed, 28 293-319 n-hexane, 29 284, 286 palladium, 30 36 pathways, 30 40 platinum, 30 40 rate, 30 36-37, 39... 

Reactions of molecules with labeled carbon (13C, UC). Gault and his co-workers pioneered (see, for review, 157) the use of 13C-labeled molecules in experiments by which the operation of adsorbed complexes with either three or five C atoms involved could be tested (see below). 14C has been repeatedly used in problems concerning the dehydrocyclization and aromatization reactions (157,163-166). The authors (163-166) in their research combined the use of labeled molecules with the third method, the study of archetype molecules. 

Carbon deposition blocks the valleys rather than the summits, which relatively enhances formation of 3C complexes and relatively suppresses formation of 2C complex. Moreover, carbon -covered surface has a lower concentration of hydrogen and this relatively promotes isomerization and, with higher hydrocarbons—dehydrocyclization. 

Naphtha is a complex mixture of con unds, mainly paraffins, naphthenes, and aromatics, generally containing 6-10 carbon atoms. Several different types of reaction take place in the reforming process. Two of the most in ortant classes of reaction are dehydrogenation and dehydrocyclization, examples of which are given by the following reactions. 

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