Isolation of tetrafluoroethylene and hexafluoropropene from the pyrolyzates of chlorodifluoromethane

Claim 1

A PROCESS FOR THE ISOLATION AND RECOVERY OF SUBSTANTIALLY PURE TETRAFLUOROETHYLENE AND HEXAFLUORORPROPENE FROM CHLORODIFLUOROMETHANE PYROLYZATES WHICH COMPRISES (A) WASHING A PYROLYZATE FORMED UPON THE PYROLYSIS OF CHLORODIFLUOROMETHANE AND CONTAINING TETRAFLUOROETHYLENE, HEXAFLUOROPROPENE, UNREACTED CHLORODIFLUOROMETHANE, AND OTHER COMPONENTS, WITH WATER TO REMOVE ANY WATER-SOLUBLE ACIDS WHICH WERE CONCURRENTLY FORMED DURING THE PYROLYSIS REACTION AND WHICH REMAIN IN THE PYROLYZATE; (B) SUBJECTING THE WATER-WASHED PYROLYZATE TO FRACTIONAL DISTILLATION TO SEPARATE THE PYROLYZATE INTO (I) A FIRST DISTILLATE CONTAINING PART OF THE TETRAFLUOROETHYLENE AND SUBSTANTIALLY ALL OF THE LOW BOILING COMPONENTS OF THE PYROLYZATE, AND (II) A FIRST DISTILLATION RESIDUE; (C) CONTACTING THE FIRST DISTILLATE WITH A POLAR ORGANIC SOLVENT OF THE GROUP CONSISTING OF METHANOL, ETHANOL, ISOPROPANOL, ACETONE, AND DIMETHYLFORMAMIDE AT A TEMPERATURE IN THE RANGE FROM ABOUT -40*C. TO ABOUT 10*C. TO DISSOLVE BY ABSORPTION SUBSTANTIALLY ALL OF THE LOW BOILING COMPONENTS FROM THE FIRST DISTILLATE IN THE POLAR ORGANIC SOLVENT WHILE LEAVING UNDISSOLVED SUBSTANTIALLY ALL OF THE TETRAFLUOROETHYLENE CONTAINED IN THE FIRST DISTILLATE; (D) COMBINING THE TETRAFLUOROETHYLENE REMAINING UNDISSOLVED FROM THE SOLVENT ABSORPTION OF THE FIRST DISTILLATE WITH THE FIRST DISTILLATION RESIDUE AND THEN SUBJECTING THE RESULTANT MIXTURE TO FRACTIONAL DISTILLATION TO SEPARATE IT INTO (I) A SECOND DISTILLATE CONSISTING ESSENTIALLY OF SUBSTANTIALLY PURE TETRAFLUOROETHYLENE, THEREBY ISOLATING SUBSTANTIALLY PURE TETRAFLUOROETHYLENE FROM THE PYROLYZATE, AND (II) A SECOND DISTILLATION RESIDUE; AND RECOVERING THE RESULTANT SUBSTANTIALLY PURE TETRAFLUOROETHYLENE; (E) SUBJECTING THE SECOND DISTILLATION RESIDUE TO FRACTIONAL DISTILLATION TO SEPARATE IT INTO (I) A THIRD DISTILLATE CONSISTING ESSENTIALLY OF HEXAFLUOROPROPENE AND CHLORODIFLUOROMETHANE, AND (II) A THIRD DISTILLATION RESIDUE; (F) CONTACTING THE THIRD DISTILLATE WITH A POLAR ORGANIC SOLVENT OF THE GROUP CONSISTING OF METHANOL, ETHANOL, ISOPROPANOL, ACETONE, AND DIMETHYLFORMAMIDE TO DISSOLVE BY ABSORPTION SUBSTANTIALLY ALL OF THE CHLORODIFLUOROMETHANE FROM THE THIRD DISTILLATE IN THE POLAR ORGANIC SOLVENT WHILE LEAVING UNDISOLVED SUBSTANTIALLY PURE HEXAFLUOROPROPENE, THEREBY ISOLATING SUBSTANTIALLY PURE HEXAFLUOROPROPENE FROM THE PYROLYZATE, AND RECOVERING THE RESULTANT SUBSTANTIALLY PURE HEXAFLUOROPROPENE; AND (G) RECOVERING THE CHLORODIFLUOROMETHANE REMAINING IN THE POLAR ORGANIC SOLVENT EMPLOYED IN THE SOLVENT ABSORPTION OF THE THIRD DISTILLATE.