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US 4,062,929 AGranted
Production of hydrogen fluoride
AssigneeFitzwilton Limited
InventorsWilliam Henry Thompson, Ralph Eric Worthington, David John Stamper
Life of this patent
Estimating the term…
Abstract
Hydrogen fluoride is produced from hydrofluosilicic acid. The hydrofluosilicic acid is reacted with ammonia. An aqueous solution of ammonium fluoride thus produced is fed with partly recycled alkali metal fluoride to a continuously operated reactor where a bifluoride of the alkali metal is formed in aqueous solution. Reaction mixture is continuously withdrawn and solid alkali metal bifluoride crystallized therefrom. The mother liquor is recycled to the reactor. The solid alkali metal bifluoride is decomposed by heat to produce hydrogen fluoride and solid alkali metal fluoride. The alkali metal fluoride is recycled to the reactor.
Claims11
A process for the production of the hydrogen fluoride from hydrofluosilicic acid comprising the following steps:
- a. reacting ammonia with hydrofluosilicic acid to produce an aqueous solution of ammonium fluoride and a precipitate of silica, and separating said silica from said aqueous solution of ammonium fluoride;
- b. feeding said aqueous solution of ammonium fluoride obtained in step (a) with an alkali metal fluoride, at least partly recycled from step (e), to a continuously operated reactor, wherein said ammonium fluoride and said alkali metal fluoride react to form a bifluoride of said alkali metal in aqueous solution;
- c. continuously withdrawing reaction mixture from said reactor in step (b), crystallising therefrom a solid product comprising alkali metal bifluoride substantially free from ammonium fluoride, and recycling the mother liquor to said reactor in step (b), the mother liquor comprising a solution of ammonium fluoride, alkali metal fluoride and alkali metal bifluoride thereby obtaining substantially complete conversion of the ammonium fluoride fed to said reactor in step (b) from step (a);
- d. drying said solid alkali metal bifluoride obtained in step (c) and decomposing at least part of it by heat to produce substantially pure hydrogen fluoride gas and solid alkali metal fluoride;
- and
- e. recycling said alkali metal fluoride produced in step (d), together with undecomposed alkali metal bifluoride from step (d), to the reactor in step (b).
3 more elements
A process for the production of hydrogen fluoride from hydrofluosilicic acid comprising the following steps:
- a. reacting ammonia with hydrofluosilicic acid to produce an aqueous solution of ammonium fluoride and a precipitate of silica, and separating said silica from said aqueous solution of ammonium fluoride;
- b. feeding said solution of ammonium fluoride obtained in step (a), and an aqueous mother liquor solution obtained in steps (c) and (d) to a continuously operated reactor, wherein said ammonium fluoride and said potassium fluoride react to form potassium bifluoride in aqueous solution;
- c. continuously withdrawing reaction mixture from said reactor in step (b), crystallising therefrom a solid product comprising potassium bifluoride and separating from the mother liquor said solid product substantially free from ammonium fluoride, and recycling the mother liquor to said reactor in step (b), the mother liquor comprising a solution of ammonium fluoride, alkali metal fluoride and alkali metal bifluoride, thereby obtaining substantially complete conversion of the ammonium fluoride fed to said reactor in step (b) from step (a);
- d. mixing at least part of said solid potassium bifluoride obtained at step (c) with sodium fluoride recycled from step (f), in the presence of water in a reactor to form solid sodium bifluoride and an aqueous solution of potassium fluoride, separating said solid sodium bifluoride from the mother liquor, and recycling said mother liquor to said reactor at step (b);
- e. drying said solid sodium bifluoride from step (d) and decomposing at least part of it by heat to produce substantially pure hydrogen fluoride gas and solid sodium fluoride;
- and
- f. recycling said solid sodium fluoride produced at step (e), together with undecomposed sodium bifluoride from step (e), to said reactor at step (d).
4 more elements
A process for the production of the hydrogen fluoride from hydrofluosilicic acid comprising the following steps:
- a. reacting ammonium with hydrofluosilicic acid to produce an aqueous solution of ammonium fluoride and a precipitate of silica, and separating said silica from said aqueous solution of ammonium fluoride;
- b. feeding said aqueous solution of ammonium fluoride obtained in step (a) with a potassium fluoride, at least partly recycled from step (e), to a continuously operated reactor, wherein said ammonium fluoride and said potassium fluoride react to form a potassium bifluoride in aqueous solution;
- c. continuously withdrawing reaction mixture from said reactor in step (b) crystallising therefrom a solid product comprising potassium bifluoride substantially free from ammonium fluoride, and recycling the mother liquor to said reactor in step (b), the mother liquor comprising a solution of ammonium fluoridie, alkali metal metal fluoride and alkali metal bifluoride, thereby obtaining substantially complete conversion of the ammonium fluoride fed to said reactor in step (b) from step (a);
- d. drying said solid potassium bifluoride obtained in step (c) and decomposing at least part of it by heat to produce substantially pure hydrogen fluoride gas and solid potassium fluoride;
- and
- e. recycling said potassium fluoride produced in step (d), together with undecomposed potassium bifluoride from step (d), to the reactor in step (b).
3 more elements
Dependencies are inferred from the claim text.