US3914398A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for making anhydrous hydrogen fluoride from fluosilicic acid
Assignee: EIDP Inc
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Filing: 1974-12-16
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Granted: 1975-10-21
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Expires: 1994-12-16
Abstract
Abstract Anhydrous hydrogen fluoride is recovered from fluosilicic acid by a process comprising the steps of (1) contacting aqueous fluosilicic acid with an excess of ammonia to produce an aqueous solution of ammonium fluoride which is subsequently recovered, (2) heating the ammonium fluoride solution to remove ammonia and water and to produce liquid ammonium bifluoride; (3) contacting the ammonium bifluoride with sufficient sulfuric acid to produce ammonium bisulfate and hydrogen fluoride and recovering both products; (4) burning the ammonium bisulfate at a temperature of about 850* to 1200*C. to produce a gaseous mixture containing sulfur dioxide; (5) contacting the sulfur dioxide with oxygen in the presence of a catalyst to make sulfur trioxide; (6) contacting the sulfur trioxide with water to produce sulfuric acid; and (7) recycling the sulfuric acid to step (3). Hydrogen fluoride is recovered in step (3) as an anhydrous gas.
Inventors
- 👤 Carl Raymond Faust
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 08:47
CPC Classifications
C; C01; C01B; C01B17/00; C01B17/69; C01B17/74; C01B17/745; C01B7/00; C01B7/19; C01B7/191; C01B7/193; C01B7/194
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
142 words
A PROCESS FOR PRODUCING ANHYDROUS HYDROGEN FLUORIDE FROM FLUOSILICIC ACID COMPRISING THE STEPS OF (1) CONTACTING AN AQUEOUS SOLUTION OF FLUOSILICIC ACID WITH AMMONIA PRODUCE AN AQUEOUS SOLUTION OF AMMONIUM FLUORIDE AND RECOVERING SAID AMMONIUM FLUORIDE SOLUTION, SAID AMMONIA BEING PRESENT IN EXCESS OF THE AMOUNT REQUIRED TO REACT WITH ALL OF SAID FLUOSILICIC ACID, (2) HEATING SAID AMMONIUM FLUORIDE SOLUTION TO REMOVE AMMONIA AND WATER AND TO PRODUCE LIQUID AMMONIUM BIFLUORIDE, (3) CONTACTING SAID AMMONIUM BIFLUORIDE WITH SULFURIC ACID TO PRODUCE AMMONIUM BISULFATE AND HYDROGEN FLUORIDE AND RECOVERING AMMONIUM BISULFATE AND ANHYDROUS HYDROGEN FLUORIDE, (4) BURNING THE AMMONIUM BISULFATE AT A TEMPERATURE OF FROM ABOUT 850* TO 1200*C. TO PRODUCE A GASEOUS MIXTURE CONTAINING SULFUR DIOXIDE, 5) CONTACTING THE SULFUR DIOXIDE WITH OXYGEN IN THE PRESENCE OF A CATALYST TO FORM SULFUR TRIOXIDE, (6) CONTACTING THE SULFUR TRIOXIDE WITH WATER TO
Claim 2
Dependent Claim
142 words
A PROCESS FOR PRODUCING ANHYDROUS HYDROGEN FLUORIDE FROM FLUOSILICIC ACID COMPRISING THE STEPS OF (1) CONTACTING AN AQUEOUS SOLUTION OF FLUOSILICIC ACID WITH AMMONIA PRODUCE AN AQUEOUS SOLUTION OF AMMONIUM FLUORIDE AND RECOVERING SAID AMMONIUM FLUORIDE SOLUTION, SAID AMMONIA BEING PRESENT IN EXCESS OF THE AMOUNT REQUIRED TO REACT WITH ALL OF SAID FLUOSILICIC ACID, (2) HEATING SAID AMMONIUM FLUORIDE SOLUTION TO REMOVE AMMONIA AND WATER AND TO PRODUCE LIQUID AMMONIUM BIFLUORIDE, (3) CONTACTING SAID AMMONIUM BIFLUORIDE WITH SULFURIC ACID TO PRODUCE AMMONIUM BISULFATE AND HYDROGEN FLUORIDE AND RECOVERING AMMONIUM BISULFATE AND ANHYDROUS HYDROGEN FLUORIDE, (4) BURNING THE AMMONIUM BISULFATE AT A TEMPERATURE OF FROM ABOUT 850* TO 1200*C. TO PRODUCE A GASEOUS MIXTURE CONTAINING SULFUR DIOXIDE, 5) CONTACTING THE SULFUR DIOXIDE WITH OXYGEN IN THE PRESENCE OF A CATALYST TO FORM SULFUR TRIOXIDE, (6) CONTACTING THE SULFUR TRIOXIDE WITH WATER TO
Claim 3
Dependent Claim
24 words
The process of claim 1 where in step (4) ammonium bisulfate is contacted with oxygen at a temperature of from about 950* to 1050*C.
Claim 4
Dependent Claim
15 words
The process of claim 2 wherein ammonia from step (2) is recycled to step (1).
Claim 5
Dependent Claim
21 words
The process of claim 3 wherein the ammonium bisulfate from step (3) is treated with silica to remove fluorine values therefrom.
Claim 6
Dependent Claim
17 words
The process of claim 4 wherein anhydrous hydrogen fluoride is recovered in step (3) by fractional distillation.
Claim 7
Dependent Claim
53 words
The process of claim 1 where in step 2 first ammonia and water are removed by heating the aqueous solution of ammonium fluoride to a temperature of from about 140* to 150*C. and then the remaining solution is heated to a temperature of from about 175* to 185*C. to produce liquid ammonium bifluoride.
Claim 8
Dependent Claim
24 words
The process of claim 6 where in step (4) ammonium bisulfate is contacted with oxygen at a temperature of from about 950* to 1050*C.
Claim 9
Dependent Claim
15 words
The process of claim 7 wherein ammonia from step (2) is recycled to step (1).
Claim 10
Dependent Claim
21 words
The process of claim 8 wherein the ammonium bisulfate from step (3) is treated with silica to remove fluorine values therefrom.
Claim 11
Dependent Claim
17 words
The process of claim 9 wherein anhydrous hydrogen fluoride is recovered in step (3) by fractional distillation.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-10-20 | 1979-04-21 | 1979-10-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-10-20 | 1983-04-21 | 1983-10-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-10-20 | 1987-04-21 | 1987-10-21 | $7700.00 | Window Closed / Lapsed |