METHOD FOR PREPARING HEXAFLUOROBUTADIENE AND 1,2-DICHLOROHEXAFLUOROCYCLOBUTANE Russian patent published in 2005 - IPC

FIELD: organic chemistry, chemical technology.

SUBSTANCE: invention relates to methods for preparing fluoro-containing monomers and methods for preparing halogen-containing cyclic compounds, namely: to preparing hexafluorobutadiene and 1,2-dichlorohexafluorocyclobutane (C₄Cl₂F₆-cyclo). Method for preparing hexafluorobutadiene is carried out by pyrolysis of chlorotrifluoroethylene followed by dechlorination of 1,2-dichlorohexafluorobutene-3 in the presence of zinc in a solvent. The parent chlorotrifluoroethylene is subjected for pyrolysis at temperature from 505°C to 600°C for 0.5-15 s. Prepared pyrolysate is condensed at temperature from 0°C to -10°C and then condensate is rectified to isolate fraction boiling at 59.0-59.5°C and containing 1,2-dichlorohexafluorocyclobutane (C₄F₆Cl₂). Fraction boiling at 63.5-64°C and containing 1,2-dichlorohexafluorobutene-3 is subjected for dechlorination in polar solvent medium at temperature 37-50°C. Compounds not condensed at the condensation stage are recovered to pyrolysis. Method provides carrying out pyrolysis of chlorotrofluoroethylene with conversion 50-70% and to obtain hexafluorobutadiene and 1,2-dichlorohexafluorocyclobutane simultaneously. Method exhibits technological effectiveness and involves essentially 3 main stages only.

EFFECT: improved preparing method.

2 cl, 2 tbl