Preparation of high capacity chloroethylated strong base anion exchange resin using NO x

Abstract

Suspension polymerization of styrene and divinylbenzene has been carried out in the presence of gelatin as stabilizer to form macroporous polystyrene divinylbenzene resin (PS–DVB). In order to prepare surface chloroethylated macroporous PS–DVB resin, it is nitrated (resin 2) using a mixture of NO and NO2 gases (called NO x ), is reduced to amine groups (resin 3), further reacted with dichloroethane, then quarternized (resin 6) using trimethyl amine. Simple material balance demonstrates that all NO x reacted show up as exchanging sites of resin 6 and this resin has at least three exchanging sites on every repeat unit. We have examined the effect of duration of nitration on the exchange capacity of resin 6 and it was found that it first increased with increase in the duration of nitration, reaching a broad maxima of 4.8 meq/g of wet resin with 69% moisture (or capacity of 15.5 meq/g of dry resin) for about 5 hr of nitration and when nitration is continued for a longer time there is a fall due to polymer degradation. This is to be compared with the commercial chloride form of strong base anion exchange resin, which has the exchange capacity of 1.68 meq/g of wet resin with 43.53% moisture (or capacity of 2.97 meq/g of dry resin). In order to assess the solvation ability of the chloroethylated resin, we evolved a three-stage drying procedure and showed that it holds moisture differently. On a dry gram basis, the chloroethylated resin is about five times superior compared to available commercial resin.