Anion-exchange particles

The two-phase epoxidation of alkenes by hydrogen peroxide in water-dichloromethane system, catalysed by manganese(III)-porphyrin, is strongly accelerated by addition of catalytic amounts of a carboxylic acid and lipophilic imidazole or pyridine axial ligand365,366. Manganese(III)-porphyrin bound to colloidal anion-exchange particles is more active in the selective epoxidation of styrene by aqueous hypochlorite than the same catalyst in aqueous solution367. 

Fig. 3-22. Raster electron micrograph of a 5-pm anion exchange particle.

In the column equilibration step the column packed with solid anion-exchange particles (designated as Res-Cl ) is washed continuously with the NaOH eluent to convert the ion exchanger completely to the -OH form. 

Figure 4,9. Different types of polymer particles for liquid chromatography. Macroporous polymer (A), surface functionalized porous polymer for cation-exchange chromatography (B) and electrostatically agglomerated anion-exchange particle (C).

Figure 33.B Scanning electron micrograph of a nanobead-agglomerated anion-exchange particle.

Anion-exchange stationary phases described in Section 3.4.1.4 are based on colloidal anion-exchange particles (the so-called nanobeads or latex particles) that are electrostatically bound to the surface of nonporous surface-sulfonated or sur-face-carboxylated PS/DVB and EVB/DVB copolymer beads. This approach to stationary-phase design provides a number of advantages including the following ... 

Fig. 3-8. Schematic representation of an anion exchange particle in separator columns such as the lonPac ASM.

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