Stability olefin isomerization over

This reaction probably involves the participation of more than two carbon atoms and the extension of a delocalized n-electron system. The results are readily explained by the unequal stabilities of the two possible intermediates, involving carbene formation on the methyl group and on the alkyl group, respectively (Scheme 74). In the first case, demethylation easily occurs by metallocarbyne formation, while in the second case, stabilization by carbene-olefin isomerization (very fast compared to hydrocracking) prevents dealkylation. However, when the a-carbon atom in the alkyl group cannot dehydrogenate to give a metallocarbene, as for 1-methyl-1-terf-butylcyclohexane, dealkylation prevails over demethylation. 

The demonstrated performance of ZSM-5 in over 35 cracking units is reviewed. The main features of ZSM-5 are its high activity and stability, favorable selectivity, metals tolerance and flexibility, particularly when used as an additive catalyst. ZSM-5 cracks and isomerizes low octane components in the naphtha produced by the faujasite cracking catalyst. As a result and olefins are produced and gasoline compositional changes occur which explain its increased research and motor octanes. A model was developed which predicts ZSM-5 performance in an FCC unit. 

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