Patent US4010240A successfully refreshed from Google Patents.
US4010240A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for the regeneration of sulfuric acid
Assignee: Hoechst AG
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Filing: 1974-06-12
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Granted: 1977-03-01
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Expires: 1994-06-12
Abstract
Abstract Contaminated sulfuric acid which may contain water, organic compounds and inorganic salts is converted to almost pure concentrated sulfuric acid by passing the acid through a Pauling plant and distilling the concentrated contaminated acid. Addition of nitric acid improves the decomposition of organic compounds and ammonium salts of the contaminated acid.
Inventors
- 👤 Helmold von Plessen
- 👤 Eberhard Fischer
- 👤 Siegfried Schiessler
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 22:05
CPC Classifications
C; C01; C01B; C01B17/00; C01B17/69; C01B17/90; C01B17/88
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
165 words
A two-step process for the continuous regeneration of contaminated aqueous 65 to 95% sulfuric acid to obtain essentially pure 95 to 98% sulfuric acid, which comprises adding to said contaminated sulfuric acid a hexavalent chromium compound as a corrosion inhibitor and in a first step continuously feeding said contaminated 65 to 95% sulfuric acid containing metal salt contaminants and a small amount of up to 4% by weight organic impurities, calculated as carbon, to a cast iron dephlegmator mounted on an external heated vessel containing concentrated boiling sulfuric acid at atmospheric pressure, removing overhead water vapor and volatile organic contaminants, continuously withdrawing as a bottoms product 95 to 98% concentrated contaminated acid and continuously feeding the withdrawn acid, in a second step, to a cast iron distillation unit in which boiling concentrated sulfuric acid is maintained, continuously removing and recovering overhead essentially pure 95 to 98% concentrated sulfuric acid and withdrawing and removing from the distillation step nonvolatile metal salt contaminants as a bottoms product.
Claim 2
Dependent Claim
165 words
A two-step process for the continuous regeneration of contaminated aqueous 65 to 95% sulfuric acid to obtain essentially pure 95 to 98% sulfuric acid, which comprises adding to said contaminated sulfuric acid a hexavalent chromium compound as a corrosion inhibitor and in a first step continuously feeding said contaminated 65 to 95% sulfuric acid containing metal salt contaminants and a small amount of up to 4% by weight organic impurities, calculated as carbon, to a cast iron dephlegmator mounted on an external heated vessel containing concentrated boiling sulfuric acid at atmospheric pressure, removing overhead water vapor and volatile organic contaminants, continuously withdrawing as a bottoms product 95 to 98% concentrated contaminated acid and continuously feeding the withdrawn acid, in a second step, to a cast iron distillation unit in which boiling concentrated sulfuric acid is maintained, continuously removing and recovering overhead essentially pure 95 to 98% concentrated sulfuric acid and withdrawing and removing from the distillation step nonvolatile metal salt contaminants as a bottoms product.
Claim 3
Dependent Claim
22 words
The process of claim 1 which comprises addinng 0.1 to 5 weight % nitric acid to the feed to the first step.
Claim 4
Dependent Claim
23 words
The process of claim 1 which comprises adding 0.1 to 5 weight % of nitric acid to the feed to the second step.
Claim 5
Dependent Claim
29 words
The process of claim 1 which comprises adding to the contaminated sulfuric acid feed to the first or second step an inorganic compound of positive tri- and/or pentavalent nitrogen.
Claim 6
Dependent Claim
31 words
The process of claim 1 which comprises adding to the first or second step a sufficient amount of inorganic compounds of positive tri- and/or pentavalent nitrogen to decompose ammonium ions present.
Claim 7
Dependent Claim
30 words
The process of claim 1 wherein the contaminants are members selected from the group consisting of aromatic mono carboxylic acids, aromatic polycarboxylic acids, and ions of light and heavy metals.
Claim 8
Dependent Claim
40 words
The process of claim 1 wherein volatile organic contaminants are removed overhead with water vapor in the first step, and heavy metal salts are precipitated in the bottoms product of the first step and are removed from the bottoms product.
Claim 9
Dependent Claim
38 words
The process of claim 1 wherein heavy metal sulfates are precipitated in the bottoms product of the second step and are separated therefrom, and soluble light metal sulfates are removed with the concentrated contaminated sulfuric acid bottoms product.
Claim 10
Dependent Claim
20 words
The process of claim 1 wherein the corrosion inhibitor is Na 2 Cr 2 O 7 . 2H 2 O.
Claim 11
Dependent Claim
35 words
The process of claim 9 wherein during the second step the corrosion inhibitor is separated by distillation from essentially pure concentrated sulfuric acid distillate product and remains with the contaminated concentrated sulfuric acid bottoms product.
References Cited (Backward Citations)
DE299774C
Cited
US1545498A
Cited
US1795995A
Cited
DE651048C
Cited
US2049517A
Cited
GB483821A
Cited
US2134909A
Cited
US2313910A
Cited
DK66665C
Cited
US2513131A
Cited
US2837474A
Cited
US2863780A
Cited
US2981643A
Cited
GB910313A
Cited
DE1143492B
Cited
US3294650A
Cited
US3415754A
Cited
US3713786A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-02-29 | 1980-08-30 | 1981-03-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-02-29 | 1984-08-30 | 1985-03-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-02-29 | 1988-08-30 | 1989-03-01 | $7700.00 | Window Closed / Lapsed |