Cation-exchange resins bifunctional

The condensation of resorcinol, chloroacetic add, and formaldehyde in alkaline medium gives a bifunctional cation-exchange resin containing —COOH and —OH groups . The condensation of salicylic add with formaldehyde in add medium followed by treatment with phenol in alkaline medium also gives a bifiinctional resin which is suitable for separation and purification of proteins . A bifunctional cation-... 

Styrene. The condensation of furfural with styrene in presence of zinc chloride followed by sulfonation with sulfuric acid yields a bifunctional cation-exchange resin (SFS) containing —SO3H and —COOH groups The resin has a total capacity of 4.2 meq/g and a sal-splitting capacity of 3.1 meq/g and can be used up to 100 °C without any appreciable fall in capacity In column operation the bed volume of the resin has been observed to be constant in a series of cycles carried out, indicating the stability of the resin in different regenerant and influent solutions. 

A bifunctional cation exchange resin carrying strongly acidic (sulfonic) and weakly acidic (carboxylic) groups was introduced in the mid-1960s but was to never merit a sustained commercial viability, and has since been discontinued. Undoubtedly, the acrylic and styrene copolymers with divinylbenzene form the basis of most commercially manufactured cation exchange resins available today. 

Fig. 4 Schematic representation of bifunctional polysiloxane catalysts and ionically modified polystyrene cation exchange resins.

Comparison data were presented, that demonstrate the use of the polysiloxane material as an advantageous substitute for organic cation exchange resins, sulfuric acid, p-toluene sulfonic acid and acidic zeolites. It is demonstrated, that materials like 1 and 2 are cost-efficient and reliable catalysts in esterification, alkylation, and condensation, whereas use of the bifunctional catalyst 3 gives excellent conversions in hydrogenolysis reactions in general. 

S.D. Alexandratos, M.A. Strand, D.R. Quillen and A.J. Walder, Synthesis and characteristics of bifunctional phosphinic acid resins, Macromolecules, 1985, 18, 829 R.H. Selzer and D.G. Howery, Phosphoric acid ester cation-exchange resins. 1. Synthesis and preliminary characterization, Macromolecules, 1986, 19, 2673 Phos-phonic acid ester cation-exchange resins. 2. Physicochemical characterization, ibid. 1986, 19, 2974. 

Copolymerization of styrene with small amounts of bifunctional monomers such as divinylbenzene is used for the synthesis of networks. The polymerization technique of choice is bead polymerization. Polymer porosity can be controlled by the addition of polystyrene, which can be extracted after polymerization has been completed. Sulfonation of such networks yields cation-exchange resins anion-exchange resins can be synthesized... 

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