Patent ID: 6488817
Filing Date: 2002-12-03
Classification: C07C,Y10S

Abstract:
A process for the purification of difluorometane from a mixture of difluoromethane (HFC-32) and dichlorodifluoromethane (CFC-12), said process comprising:(a) distilling a first mixture of HFC-32 and CFC-12 at a first pressure below 40 psia in a first distillation step to produce a first distillate and a first bottoms, said first distillate being enriched with CFC-12 and said first bottoms being enriched with HFC-32; and (b) distilling the first distillate at a second pressure of about 50 to about 400 psia in a second distillation step to produce a second distillate and a second bottoms, said first distillate having a second mixture of HFC-32 and CFC-12 at said second pressure, the pressure difference between the first and second distillation steps is sufficient to result in a change in composition of an azeotrope of CFC-12 and HFC-32 of at least 10 wt %, said second distillate being enriched with HFC-32, and said second bottoms being enriched with CFC-12; (c) recovering purified HFC-32 from said first bottoms; and (d) one of either feeding said second distillate to said first distillation step or recovering HFC-32 from said second distillate.