Bronsted acid sites, reactions catalyzed hydrocarbons

It is generally admitted that skeletal transformations of hydrocarbons are catalyzed by protonic sites only. Indeed good correlations were obtained between the concentration of Bronsted acid sites and the rate of various reactions, e g. cumene dealkylation, xylene isomerization, toluene and ethylbenzene disproportionation and n-hexane cracking10 12 On the other hand, it was never demonstrated that isolated Lewis acid sites could be active for these reactions. However, it is well known that Lewis acid sites located in the vicinity of protonic sites can increase the strength (hence the activity) of these latter sites, this effect being comparable to the one observed in the formation of superacid solutions. Protonic sites are also active for non skeletal transformations of hydrocarbons e g. cis trans and double bond shift isomerization of alkenes and for many transformations of functional compounds e.g. rearrangement of functionalized saturated systems, of arenes, electrophilic substitution of arenes and heteroarenes (alkylation, acylation, nitration, etc ), hydration and dehydration etc. However, many of these transformations are more complex with simultaneously reactions on the acid and on the base sites of the solid... 

IV. Reactions Catalyzed by Bronsted Acid Sites The MTO Process and Oligomerization of Unsaturated Hydrocarbons... 

Subsequent hydride transfer and metal catalyzed dehydrogenation steps lead to benzene. Qualitatively, the hydrocarbon conversion over bifunctional catalysts can thus be described as a reaction network using two types of sites. The reactions taking place on the Bronsted sites are similar to those in liquid acids, as described in the first part of this paper a second group of reactions takes place on the metal sites these steps are identical with those observed on the same metal in the absence of acid sites. Mills et al. devised a simple model... 

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