Patent US3919404A successfully refreshed from Google Patents.
US3919404A
Expired / Lapsed
US
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Hydrothermal process for preparation of alpha iron oxide crystals
Assignee: Dow Chemical Co
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Filing: 1974-06-28
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Granted: 1975-11-11
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Expires: 1994-06-28
Abstract
Abstract Elongated, polycrystalline particles of alpha iron oxide, characterized by an open, porous structure and consisting of hematite microcrystallites containing from 2 to 4 percent of sulfate are prepared by the reaction of lithium hydroxide and ferric sulfate in weakly acidic to neutral aqueous solution under at least autogenous pressures at temperatures in the range of 150*-350*C. The particles are readily converted to gamma iron oxide of good magnetic properties and also have utility as pigments and catalysts.
Inventors
- 👤 Henry Nelson Beck
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 15:45
CPC Classifications
B; B82; B82Y; B82Y30/00; B01; B01J; B01J23/00; B01J23/70; B01J23/74; B01J23/745; C; C01; C01G; C01G49/00; C01G49/02; C01G49/06; G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70626; G11B5/70642; G11B5/70652; G11B5/70663; G11B5/70678; G11B5/70684; G11B5/70689; C01P; C01P2002/00; C01P2002/60; C01P2004/00; C01P2004/10; C01P2004/54; C01P2004/60; C01P2004/61; C01P2004/62; C01P2004/64; C01P2006/00; C01P2006/42
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
129 words
A PROCESS FOR PREPARAING ELONGATED HEMATITE PARTICLES COMPRISING: A. PROVIDING A MIXTURE CONSISTING ESSENTIALLY OF FERRIC SULFATE, WATER AND LITHIUM HYDROXIDE IN WHICH THE CONCENTRATION OF IRON SULFATE IS ABOUT 0.2 TO ABOUT 2.0 MOLAR, THE ATOMIC RATIO OF IRON TO LITHIUM IS FROM ABOUT 0.7 TO ABOUT 1.5 AND THE TOTAL CONTENT OF PHOSPHATE, MOLYBDENUM AND TUNGSTEN IS LESS THAN 0.001 MOLAR; B. HEATING SAIS MIXTURE TO A TEMPERATURE WITHIN THE RANGE OF ABOUT 150*C. TO ABOUT 350*C. AT A RATE OF FROM ABOUT 1*/MINUTE TO ABOUT 38*/MINUTE; C. MAINTAINING THE MIXTURE AT SAIS TEMPERATURE UNDER AT LEAST AUTOGENOUS PRESSURE FOR A TIME PERIOD FROM ABOUT 1 MINUTE TO ABOUT 80 HOURS; D. COOLING THE MIXTURE WHILE AVOIDING THE FORMATION OF JAROSITES; AND E. RECOVERING THE RESULTANT PARTICLES.
Claim 2
Dependent Claim
129 words
A PROCESS FOR PREPARAING ELONGATED HEMATITE PARTICLES COMPRISING: A. PROVIDING A MIXTURE CONSISTING ESSENTIALLY OF FERRIC SULFATE, WATER AND LITHIUM HYDROXIDE IN WHICH THE CONCENTRATION OF IRON SULFATE IS ABOUT 0.2 TO ABOUT 2.0 MOLAR, THE ATOMIC RATIO OF IRON TO LITHIUM IS FROM ABOUT 0.7 TO ABOUT 1.5 AND THE TOTAL CONTENT OF PHOSPHATE, MOLYBDENUM AND TUNGSTEN IS LESS THAN 0.001 MOLAR; B. HEATING SAIS MIXTURE TO A TEMPERATURE WITHIN THE RANGE OF ABOUT 150*C. TO ABOUT 350*C. AT A RATE OF FROM ABOUT 1*/MINUTE TO ABOUT 38*/MINUTE; C. MAINTAINING THE MIXTURE AT SAIS TEMPERATURE UNDER AT LEAST AUTOGENOUS PRESSURE FOR A TIME PERIOD FROM ABOUT 1 MINUTE TO ABOUT 80 HOURS; D. COOLING THE MIXTURE WHILE AVOIDING THE FORMATION OF JAROSITES; AND E. RECOVERING THE RESULTANT PARTICLES.
Claim 3
Dependent Claim
53 words
The process of claim 1 in which the concentration of ferric sulfate is from about 0.4 to about 0.6 molar, the lithium to iron atomic ratio is from about 0.9 to about 1.2 and the total content of phosphate, molybdenum, tungsten, vanadium, antimony, chromium, arsenic, copper and titanium is less than 0.001 molar.
Claim 4
Dependent Claim
71 words
The process of claim 1 in which the mixture is heated at a rate of from about 3*/minute to about 12*/minute to a reaction temperature of from about 240*C. to about 260*C., is maintained at said reaction temperature for a period of from about 1- 3/4 to about 2- 1/4 hours and is cooled at a rate of not more than 1*/minute until a temperature of 125*C. or less is reached.
Claim 5
Dependent Claim
57 words
The process of claim 1 in which the concentration of iron sulfate is about 0.5 molar, the concentration of LiOH is about 1.0 molar and the mixture is maintained at a temperature of about 250*C. for about 2 hours and then cooled at a rate less than 3*/minute until a temperature of 150* or less is reached.
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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) | 1978-11-10 | 1979-05-12 | 1979-11-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-11-10 | 1983-05-12 | 1983-11-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-11-10 | 1987-05-12 | 1987-11-11 | $7700.00 | Window Closed / Lapsed |