Porous Polymers as Catalysts

Cation- and anion-exchange resins are widely applied as catalysts, when reactions can be carried out at temperatures lower than 423 K [161-171], Cation-exchange resins in acid forms have Bronsted acid sites and when exchanged with metallic cations contain Lewis acid sites, while anion exchange resins forms base species to carry out base-catalyzed reactions [169], The principles previously described in this chapter for these sites in other catalysts, can be applied for the catalytic action of these polymers. 

The pioneer work in this field was carried out on polystyrene-supported acid catalysts [161]. Thereafter, several works on the use of sulfonic, strong acidic cation exchangers as acid catalysts were reported for alkylation, hydration, etherification, esterification, cleavage of ether bonds, dehydration, and aldol condensation [162,168-171], Besides, industrial applications of these materials were evaluated with reactions related to the chemistry of alkenes, that is, alkylation, isomerization, oligomerization, and acylation. [163,169], Also, Nation, an acid resin which has an acid strength equivalent to concentrated sulfuric acid, can be applied as an acid catalyst. It is used for the alkylation of aromatics with olefins in the liquid or gas phases and other reactions however, due to its low surface area, the Nation resin has relatively low catalytic activity in gas-phase reactions or liquid-phase processes where a nonpolar reactant or solvent is employed [166], 

McNaught and A. Wilkinson, IUPAC Compendium of Chemical Terminology (2nd edition), Royal Society of Chemistry, Cambridge, UK, 1997. 

Guerasimov, V. Dreving, E. Eriomin, A. Kiseliov, V. Lebedev, G. Pacehnkov, and Ashliguin, Curso de Fisica Quimica, Tomo II, Editorial MIR, Moscow, 1971. 

Shriver and RW. Atkins, Inorganic Chemistry (3rd edition), W.H. Freeman Co., New York, 1999. 

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