PREPARATION OF ULTRA-PURE SUCCINONITRILE BY COUNTERCURRENT DISTILLATION FOR CRYSTAL GROWTH

We developed the purification method to produce ultra-pure succinonitrile by multiple countercurrent distillations. The distillation column used was 25 mm in diameter and 110 cm in the packed height with Heli-Pak® packing (0·05” × 0·10” × 0·10”, packing factor+ 960). Typical operational conditions of each stage are as follows: condenser temperature 65 °C, reboiler temperature 160 °C, head pressure 50 m Torr or below, and reflux ratio of 60:1. As the number of distillation stages increases, the maximum temperature of the freezing curve increases and the freezing curves become flat. Triple point of our sample, which is obtained after eight distillation stages, is not appreciably different from that of a standard NIST specimen. The purity of the SCN prepared in our experiments is estimated at 99·99992% which corresponds to a melting range (T1, – Ts) of 1·2 mK. To ensure the purity of our purified SCN for the purpose of crystal growth, the growth rate and the tip radius of dendrite were measured at various su...