US3923591A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Prehydrolysis and digestion of fibrous lignocellulosic material
Assignee: Process Evaluation and Development Corp
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Filing: 1974-02-21
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Granted: 1975-12-02
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Expires: 1994-02-21
Abstract
Abstract Process for chemically pulping lignocellulosic materials with aqueous digestion medium having a pH of 8.5 to 11.5 and containing water, alkali metal bisulfite, sodium carbonate and alkali metal hydroxide. The lignocellulosic material may be prehydrolyzed at a pH of 4.6 prior to pulping with the alkaline digestion medium to increase yield.
Inventors
- 👤 Eduardo Joel Villavicencio
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 17:03
CPC Classifications
D; D21; D21C; D21C3/00; D21C3/02; D21C3/022
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
126 words
A METHOD FOR THE PRODUCTION OF CELLULOSIC PULP FROM FIBROUS LIGNOCELLULOSIC MATERIAL COMPRISING PREHYDROLIZING SAID LIGNOCELLULOSE MATERIAL AT A PH OF ABOUT 4.0 TO 6.0 IN THE PRESENCE OF ABOUT 70 TO 100 WEIGHT PERCENT MOISTURE B THE DRY WEIGHT OF SAID MATERIAL, DIGESTING THE PREHYDROLIZED MATERIAL WITH A SODIUM CARBONATE BUFFERED AQUEOUS DIGESTION SOLUTION HAVING A PH OF 8.5 TO 11.5 AND A SODIUM OXIDE CONTENT OF ABOUT 10 TO 14 PERCENT BY WEIGHT, SAID AQUEOUS DIGESTION SOLUTION CONSISTING ESSENTIALLY OF ABOUT 1.1 TO 3 MOLES OF SODIUM BESULFITE PER MOLE OF SODIUM HYDROXIDE WHEREBY DURING DIGESTION THE PH REMAINS ABOVE ABOUT 8.5 AND SAID SODIUM BISULFITE AND SODIUM HYDROXIDE PENETRATE SAID FIBROUS LIGNOCELLULOSE MATERIAL, REACT TO FORM SODIUM SULFITE, AND DIGEST SAID LIGNOCELLULOSE MATERIAL.
Claim 2
Independent Claim
126 words
A METHOD FOR THE PRODUCTION OF CELLULOSIC PULP FROM FIBROUS LIGNOCELLULOSIC MATERIAL COMPRISING PREHYDROLIZING SAID LIGNOCELLULOSE MATERIAL AT A PH OF ABOUT 4.0 TO 6.0 IN THE PRESENCE OF ABOUT 70 TO 100 WEIGHT PERCENT MOISTURE B THE DRY WEIGHT OF SAID MATERIAL, DIGESTING THE PREHYDROLIZED MATERIAL WITH A SODIUM CARBONATE BUFFERED AQUEOUS DIGESTION SOLUTION HAVING A PH OF 8.5 TO 11.5 AND A SODIUM OXIDE CONTENT OF ABOUT 10 TO 14 PERCENT BY WEIGHT, SAID AQUEOUS DIGESTION SOLUTION CONSISTING ESSENTIALLY OF ABOUT 1.1 TO 3 MOLES OF SODIUM BESULFITE PER MOLE OF SODIUM HYDROXIDE WHEREBY DURING DIGESTION THE PH REMAINS ABOVE ABOUT 8.5 AND SAID SODIUM BISULFITE AND SODIUM HYDROXIDE PENETRATE SAID FIBROUS LIGNOCELLULOSE MATERIAL, REACT TO FORM SODIUM SULFITE, AND DIGEST SAID LIGNOCELLULOSE MATERIAL.
Claim 3
Dependent Claim
24 words
A method as defined in claim 1 wherein the weight ratio of fibrous lignocellulose material to digestion solution is about 1: 2 to 1:6.
Claim 4
Dependent Claim
21 words
A method as defined in claim 1 in which the total equivalent alkali metal oxide concentration is about 12 weight percent.
Claim 5
Dependent Claim
47 words
A method as defined in claim 2 in which the prehydrolysis and digestion is conducted at steam gauge pressures of from about 75 to about 150 pounds per square inch and about 320*F to about 390*F for a period of from about 5 to about 30 minutes.
Claim 6
Dependent Claim
44 words
A method as defined in claim 4 in which the lignocellulosic material is depithed sugarcane bygasse and the digestion solution has a pH of at least about 10.0 whereby the brightness of the resultant unbleached pulp is at least about 35 percent G. E.
Claim 7
Dependent Claim
22 words
A method as defined in claim 2 wherein said digestion solution contains 1.5 moles of sodium bisulfite per mole of sodium hydroxide.
Claim 8
Dependent Claim
27 words
A method as defined in claim 2 wherein said digestion solution has a pH of about 10 and a sodium oxide content of about 12 weight percent.
References Cited (Backward Citations)
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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) | 1978-12-01 | 1979-06-02 | 1979-12-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-12-01 | 1983-06-02 | 1983-12-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-12-01 | 1987-06-02 | 1987-12-02 | $7700.00 | Window Closed / Lapsed |