Process for perfluorocyclobutane purification
AssigneeE. I. Du Pont de Nemours and Company
InventorV. N. Malikarjuna
Life of this patent
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Abstract
A process is disclosed for obtaining octafluorocyclobutane of increased purity from a mixture comprising (a) octafluorocyclobutane and (b) at least one halocarbon impurity which is difficult to separate from octafluorocyclobutane by distillation (e.g., azeotropes of octafluorocyclobutane with such halocarbons). The process involves (1) contacting the mixture with a catalyst in the vapor phase in the presence HCl and/or HF at a temperature sufficient to react component (b) impurity with HCl and/or HF to provide a product mixture comprising halogenated product which is more easily separated from octafluorocyclobutane by distillation than the unreacted impurity; and (2) separating halogenated product obtained in (1) from octafluorocyclobutane by distillation.
Claims10
A process for obtaining octafluorocyclobutane of increased purity from a mixture comprising (a) octafluorocyclobutane and (b) at least one halocarbon impurity which is difficult to separate from octafluorocyclobutane by distillation, comprising:
- (1) contacting the mixture with a catalyst in the vapor phase in the presence of at least one hydrogen halide selected from the group consisting of HCl and HF at a temperature sufficient to react component (b) impurity with said hydrogen halide to provide a product mixture comprising halogenated product which is more easily separated from octafluorocyclobutane by distillation than the unreacted impurity;
- and
- (2) separating halogenated product obtained in (1) from octafluorocyclobutane by distillation.
A process for increasing the purity of octafluorocyclobutane from a mixture comprising (a) octafluorocyclobutane and (b) at least one halocarbon impurity which is difficult to separate from octafluorocyclobutane by distillation which is produced during the manufacture of tetrafluoroethylene, octafluorocyclobutane and optionally hexafluoropropylene by the pyrolysis of chlorodifluoromethane or mixtures of chlorodifluoromethane and chlorotetrafluoroethane, characterized by:
- (1) contacting the mixture with a catalyst in the vapor phase in the presence of at least one hydrogen halide selected from the group consisting of HCl and HF at a temperature sufficient to react component (b) impurity with said hydrogen halide to provide a product mixture comprising halogenated product which is more easily separated from octafluorocyclobutane by distillation than the unreacted impurity;
- and
- (2) separating halogenated product obtained in (1) from octafluorocyclobutane by distillation.
A method of obtaining essentially pure octafluorocyclobutane and essentially pure C2HF5 from an azeotrope or azeotrope-like mixture of octafluorocyclobutane and C2HClF4, comprising:
- (1) contacting the mixture with a catalyst in the vapor phase in the presence of HF at a temperature sufficient to react C2HClF4 with HF to provide a product mixture comprising C2HF5;
- (2) separating C2HF5 from the product mixture by distillation and removing azeotropically combined HF therefrom;
- and
- (3) separating essentially pure octafluorocyclobutane from the product mixture by distillation.
Dependencies are inferred from the claim text.