Polystyrene sulfonic acid beads

Aromatic electrophilic substitution is used commercially to produce styrene polymers with ion-exchange properties by the incorporation of sulfonic acid or quaternary ammonium groups [Brydson, 1999 Lucas et al., 1980 Miller et al., 1963]. Crosslinked styrene-divinyl-benzene copolymers are used as the starting polymer to obtain insoluble final products, usually in the form of beads and also membranes. The use of polystyrene itself would yield soluble ion-exchange products. An anion-exchange product is obtained by chloromethylation followed by reaction with a tertiary amine (Eq. 9-38) while sulfonation yields a cation-exchange product (Eq. 9-39) ... 

The sulfonated polystyrene beads can be used as a cation exchange resin. For example, if the sulfonated resin is treated with sodium hydroxide, the sodium salt of each of the sulfonic acid groups is formed. This resin can then be employed to exchange sodium cations for other cations in an aqueous solution. 

Sodium softeners are used to treated RO influent water to remove soluble hardness (calcium, magnesium, barium, and strontium) that can form scale on RO membranes. Once known as sodium zeolite softeners, zeolites have been replaced with synthetic plastic resin beads. For sodium softeners, these resin beads are strongly acidic cation (SAC) polystyrene resin in the sodium form. The active group is benzene sulfonic acid, in the sodium, not free acid, form. Figure 8.12 shows styrene-divinylbenzene gel cation resin. Equation 8.4 shows the softening reaction for calcium exchange ... 

Sevenich and Fritz [9] published a comprehensive study of metal cation selectivity with resins of a more modern type. The studies were made on a column packed with a 12% cross-linked polystyrene-divinylbenzene resin 12-15 mm in diameter and with an exchange capacity of 6.1 pequiv/g. The resins were prepared by rapid sulfonation so that the sulfonic acid groups are concentrated on the outer perimeter of the resin beads [10]. 

Moyer et al. [8] performed a systematic study of the impregnation of a macrocycle, tetrathia-l4-crown-4 (TT14CA), onto polystyrene-divinylbe-nzene sulfonic acid (PS-DVB) strong-acid resin beads to obtain an SIR for extraction of Cu(II) from sulfuric acid. Four different impregnation procedures were tested, as can be seen in Fig. 4. In their study the effects of different parameters, such as the organic solvent used and hydration steps, were tested in order to improve the copper extraction ability. 

Paul et al. (25) observed that for polymer volume fractions less than 0.8, the functional dependence of the diffusion coefficients on the polymer volume fraction was, generally, in accordance with Equation 40. Muhr and Blanshard (26) provide additional supporting data on different polymers than those reported by Paul et al, Roucls and Ekerdt (27) measured the diffusion of cyclic hydrocarbons in benzene-swollen polystyrene beads their diffusion coefficients satisfy the general form of Equation 40. The effective dlffuslvltles of organic substrates in crossllnked polystyrene reported by Marconi and Ford (17) also follow trends predicted in Equation 40. In the absence of experimental data, it appears that Equation 40 provides a reasonable, and the simplest, means to estimate D for use in detailed modeling or in estimation methods such as Equation 38. Equation 40 was used by Dooley et al. (11) in their study of substrate diffusion and reaction in a macroreticular sulfonic acid resin which involved vapor phase reactants. 

Styrene-DVB copolymer beads are sulfonated to produce the most widely used strong-acid type cation-exchange resins. To make them, the copolymer precursor beads are dispersed in about 10 times their weight of concentrated sulfuric acid and heated slowly to 150°C. The sulfonic acid group is normally introduced into the para position. Though the reaction is very simple in principle, it involves delicate operations and close control of parameters in order to achieve beads of suitable structure and durability. A fully mono-sulfonated, polystyrene has a theoretical ion content of 5.1 equivalents/kg (dry) but many commercial resins have about 4.4-S.2 eq/kg. Amberlite IR-120, Dowex-50, Nalcite HCR, Permutit Q, Duolite C-20 and C-25, and Lewatit S-100 are resins of this type. 

Additives used in final products Fillers calcium carbonate, calcium hydroxide, calcium oxide, carbon black, polymeric beads, polystyrene particles, zinc oxide Plasticizers 1-isobutyrate benzyl phthalate, 2,2,4-tri-methyl-1,3-pentanediol, alkyl sulfonic acid esters of phenol and/or cresol, benzyl butyl phthalate, chlorinated paraffins, hydrogenated perphenyl, isooctyl benzyl phthalate Curatives metal peroxides, oxy salts (e.g., dioxides of lead, manganese, calcium, etc.) ... 

The monomer 4-styrenesulfonic acid was prepared by dehydrohalogenation of -bromoethjibenzene—sulfonyl chloride. The potassium salt can be polymerized in aqueous solution (222). The sulfonation of cross-linked polystyrene beads is being carried out in industry with concentrated sulfuric acid. 

Insoluble polystyrene crosslinked with divinylbenzene can easily be converted by sulfonation to a usable ion exchanger. For this purpose a mixture of 0.2 g of silver sulfate and 150 ml of concentrated sulfuric acid are heated to 80-90 °C in a 500 ml threenecked flask fitted with stirrer, reflux condenser, and thermometer. 20 g of a bead polymer of styrene and divinylbenzene (see Example 3-41) are then introduced with stirring the temperature climbs spontaneously to 100-105 °C.The mixture is maintained at 100 C for 3 h,then cooled to room temperature and allowed to stand for some hours. Next the contents of the flask are poured into a 11 conical flask that contains about 500 ml of 50% sulfuric acid. After cooling, the mixture is diluted with distilled water, and the gold-brown colored beads are filtered off on a sintered glass filter and washed copiously with water. 

The acidity of these resins, however, increases significantly by treating them with Lewis acid halides. Gates and co-workers151 153 have prepared a superacid catalyst from AICI3 and beads of macroporous, sulfonated polystyrene-divinylbenzene. The... 

The resins are prepared first by copolymerizing styrene (ST) and divinylbenzene (DVB), resulting in a cross-linked polystyrene. Usually, they are produced in the form of spherical beads. These beads are sulfonated with sulfuric acid for anionic resins and methylated with chloromethyl ether followed by quatemization with trimethylamine for cationic resins. Two types of resins exist gel and microporous. The microporous beads are used to remove ionic substances quickly while the gel-type beads are used for sustaining drug release over a long period of time. 

As with MTBE, acidic resins are the catalysts employed in the industrial practice for ETBE synthesis standard products, made from different manufacturers in the form of spherical beads (e.g., Rohm and Haas, Bayer, Purolite, Dow), have similar characteristics - a macroporous structure, polystyrene-divinylbenzene, functionalized with sulfonic groups (active sites 5.2 eq H per kg). 

The basic mechanism of separation of carbohydrates is by ligand exchange chromatography but is quite similar to ion-exclusion chromatography described earlier in this chapter for weak organic and inorganic acids. The column contains fully sulfonated polystyrene polymer beads cross-linked with polydivinylbenzene. The polymers are fully hydrated and contain occluded water within the gel polymer matrix, just as in ion-exclusion polymer beads. Analytes partition between the occluded water within the bead matrix and the mobile phase. Water is most often used as the mobile phase and the detection method is most often refractive index. 

FFF Rolgl ren latex beads Viruses Prgejns SDS-protein complex Sulfonated polystyrenes N oj crylic acids... 

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