| 摘要 |
Tetrafluoroethylene and hexafluoropropylene are produced by pyrolysing crude or pure chlorodifluoromethane at a temperature of 700 to 900 DEG C. and a pressure of 0.1 to 2 atmospheres for a time of 0.1 to 10 seconds to obtain a conversion (as defined in the Specification) of the chlorodifluoromethane to pyrolysis products of between 86% and 94%. The reaction is preferably carried out at a chlorodifluoromethane pressure of 0.5 to 1.2 atmospheres, the partial pressure being varied for example by dilution of the chlorodifluoromethane with nitrogen, helium or carbon dioxide. The process is preferably carried out in a tubular reactor through which the starting materials are caused to flow, the temperature in the reactor preferably increasing in the direction of flow of the chlorodifluoromethane. Octafluorocyclobutane may also be formed during the pyrolysis and, together with unreacted chlorodifluoromethane, may be separated from the reaction products and recycled, the pyrolysis of octafluorocyclobutane producing tetrafluoroethylene and hexafluoropropylene. The pyrolysis products may be separated by fractional distillation or by extractive distillation in the presence of hydrocarbons or chlorinated hydrocarbons. Numerous examples and comparative examples are given. Specification 481,405 and U.S.A. Specification 2,758,138 are referred to. |
