Superacids immobilized

Superacids Immobilized on Solid Supports. The considerable success of Magic Acid and related superacids in solution chemistry and interest to extend the scope and utility of acid-catalyzed reactions, particularly hydrocarbon transformations, logically led to the attempts to adopt this chemistry to solid systems allowing heterogeneous catalytic processes. 

Ways have been found to immobilize and/or to bind superacidic catalysts to an otherwise inert solid support. Several types are described in this section. 

Data for the use of alcohols as alkylating agents in superacids are scarce. A study of the alkylation of phenol and naphthols with ferf-butyl alcohol has shown198 that triflic acid adsorbed on aminopropyl-modified silica is the most selective to yield monoalkylated products compared to solid acids (triflates immobilized in silica). 

Although much effort was devoted to the immobilization of superacids, the major drawback in these catalysts was their short lifetime and ease of deactivation. Although initial conversions were high, the catalysts totally deactivated after a long period on stream. The immobilized superacids were not stable enough for the catalytic process, and metal halides were leached out by the feed from the graphite layers reduction of metals in the superacids was also easily brought about [23, 29]. 

Ionic polymerizations catalyzed by immobilized complexes, in particular Lewis acids on polymer supports, so-called solid superacids, are now extensively developed. A variety of cationic catalyst (protonic and Lewis acids), their combinations (complexes) and complexes with different supports are summarized in a review [111] (Table 12-9). 

Immobilized superacids Superacids (both Bronsted and Lewis types) bound to inert supports such as graphite, fluorinated graphite, etc. 

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