Commercial ion-exchange resins

The percent ring substitution (% RS) of the polymer with active sites affects catalytic activity. Polystyrenes with < 25 % RS with lipophilic quarternary onium ions are swollen in triphase mixtures almost entirely by the organic phase. Water reduces the activity of anions by hydrogen bonding. In most triphase nucleophilic displacement reactions onium ion catalysts with <25% RS are highly active, and those with >40% RS, such as most commercial ion exchange resins, are much less active. However, low % RS is not critical for the reactions of hydroxide ion with active methylene compounds, as commericial ion exchange resins work well in alkylation of active nitriles. 

The data in Table 7 obtained with equimolar amounts of the polymeric catalysts and the 2-naphthoxide ion should be more reliable because all of the reactive anion is contained within the polymer. These conditions (expts 7-9) gave 100 % O-alkylation, indicating that the active site environment of the polystyrene-bound tri-n-butylphos-phonium ion/naphthoxide ion pair or aggregate is aprotic even with the 60%RS polymer. However, the common benzyltrimethylammonium ion found in commercial ion exchange resins is more hydrophilic, giving both C- and O-alkylation (expts 10 and 11 of Table 7). 

Cicero, C.M., Herman, C.A., Workman, P., Poole, K., Erich, D., Harden, J., Commercial Ion Exchange Resin Vitrification in Borosilicate Glass, Rep. WSRC-MS- 98-00392, Westinghouse Savannah River Co., Aiken, SC (1998)... 

In ion exchange, the aqueous phase ions are replaced with H and OH ions. If the aqueous phase ions are in equilibrium with the adsorbed ions, their removal from the aqueous phase causes desorption of the adsorbed ions to maintain the equilibrium until all of the adsorbed ions have been removed. In practice, this removal is quantitative (2-5). Ion exchange is rapid and easily carried out however, commercial ion exchange resins contain leachable polyelectrolytes which adsorb on latex particle surfaces these polyelectrolytes can be removed only by an arduous purification process (2-5). 

The empirical formula of a commercial ion-exchange resin is C8H7S03Na. The resin can be used to soften water according to the reaction provided. Expressed in moles Ca2+ taken up per gram resin used, what would be the maximum uptake of Ca2+ ... 

Defluoridation processes can be classified into four main groups Adsorption methods, in these methods sorbents such as bone charcoal, activated alumina and clay are used in column or batch systems. Ion-exchange methods, these methods require expensive commercial ion-exchange resins. Coprecipitation and... 

Ion exchange processes function by replacing undesirable ions of a liquid with ions such as H+ or OH from a solid material in which the ions are sufficiently mobile, usually some synthetic resin. Eventually the resin becomes exhausted and may be regenerated by contact with a small amount of solution with a high content of the desired ion. Resins can be tailored to have selective affinities for particular kinds of ions, for instance, mercury, boron, ferrous iron, or copper in the presence of iron. Physical properties of some commercial ion exchange resins are listed in Table 15.4 together with their ion exchange capacities. The most commonly used sizes are -20 + 50 mesh (0.8-0.3 mm) and -40 -h 80 mesh (0.4-0.18 mm). 

The total exchange capacity is usually determined by titrating the resin with a solution of acid or base to a specific end point. This type of information is readily available fi om the manufacturers of commercial ion exchange resins. 

Table 16. Pressure Drop for Commercial Ion Exchange Resins...

Choice of Support. The most commonly used organic support is polystyrene (cross-linked with DVB) in its microp-orous (1-2% cross-linking) form, although it has also been used in its macroporous and popcorn form (Ford et al, 1982 Shan et al.,1989). Various other polymeric catalysts have been used like polyvinylpyridine resins, commercial ion-exchange resins (Arrad and Sasson, 1989), modified dextran anion exchangers (Kise et al, 1981), and macroporous glycidyl methacrylate-ethylene dimethacrylate resins (Hradil and Svec,... 

Arrad, 0., and Y. Sasson, Commercial Ion Exchange Resins as Catalysts in Solid-Solid-Liquid Reactions, J. Org. Chem., 54, 4493 (1989). 

The label on a bottle of commercial ion exchange resin generally contains the following information strongly acidic, sulfonic acid, Na, 20-50 mesh, medium porosity or 8X, 4.4 meq/g min dry. What does this mean ... 

Wu cl al. [42. 46 reported the amount of imbibed solvent, volume ratio and porosity for 12 kinds of ion-exchange resins for seven kinds of solvents (dichloromcihane. chloroform, 1.2-dichlorocthane. bcn cnc. toluene, chlorobcn/cnc and water) when Ig of the resin was placed into 25 cm of the pure solvent. The experimental results for the commercial ion-exchange resin are as follows (i) The amounts v>f the imbibed solvent for the aromatic solvents (benzene, toluene, and chlorobenzene) were larger than those for halide aliphatic solvents (dichioromethanc. chloroform. 1.2-dichloroethanc) since the resin was of the styrene type. The sequence of the imbibed amount for the aromatic solvents is benzene toluene > chlorobenzene, (ii) The imbibed amounts of water and organic solvent were around I g and... 

Figure 7. Performance of batch reactor (a.d) resin = O.bOOg recycle fixed-bed reactor (b.c)resin 2.000g SV-l.5mPmin. (c.O SV=7.5mPmin. for commercial ion-exchange resin (IRA-9(K))arKJ lab-produced resin ( macro CL -4%. RS 40 o). T=20. lOOOrpm. CVIhOII-0.05bmol.

Ion-exchange polymers. The above described perbromlde reagent can be obtained somewhat more easily the treatment of a commercial Ion exchange resin (Amberlyst A-26, bromide form) with molecular bromine In CCI4 (65) according to the method of Bonglnl et al. (Equation 12). Aside from the bromlnatlon of olefins. 

Commercial ion-exchange resin beads are produced in a suspension polymerization, in which small droplets of monomer are dispersed in water and radical initiators in the monomer start the polymerization. This method can not be used for our intended catalyst preparation because it is not possible to stir a suspension in the pores of a carrier. The particles from suspension polymerization are too big for our purposes. 

---