GB707145A - Dehydrating fluorochloromethanes by distillation - Google Patents

Abstract

Moist difluorodichloromethane or moist mono-fluorotrichloromethane is dehydrated by distilling the moist compounds in a fractionating column at a gauge pressure in the range of 35 to 160 pounds per square inch in the case of the difluoro-compound or of 0 to 25 p.s.i. in the case of the monofluro-compound, condensing the vapours and allowing the condensate to separate into an upper aqueous layer and a lower non-aqueous layer, returning the non-aqueous layer to the column as reflux, and withdrawing the dried fluorochloromethane from the boiler of the column. In order to prevent droplets of water passing into the lower liquid layer a filter of wire wool, contained in a metal wire basket, is disposed beneath the liquid interface. Difluorodichloromethane containing 140 p.p.m. of water was charged into the boiler of a packed fractionating column (equivalent to 12 theoretical plates), and heated at 35 DEG C. under a pressure of 110 p.s.i.g. The vapours from the top of the column were condensed, and the condensate was passed to a separator containing a filter of wire wool. The water layer was removed from the system, and the CF2 Cl2 layer was returned to the column as reflux. When the water content of the material in the boiler was less than 10 p.p.m., continuous withdrawal of the dried product therefrom was commenced, and CF2 Cl2 vapour containing 0.2 per cent. water was introduced continuously into the condenser at such a rate as to maintain steady the level of the liquid in the boiler.