Patent US3862218A successfully refreshed from Google Patents.
US3862218A
Expired / Lapsed
US
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Purification of terephthalic acid by thermal treatment
Assignee: Celanese Corp
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Filing: 1971-09-07
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Granted: 1975-01-21
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Expires: 1991-09-07
Abstract
Abstract A process for purifying terephthalic acid (TPA) by heating the TPA and a liquid medium to above 325*C while maintaining a liquid phase except when the critical temperature is exceeded. The heated mixture is then cooled allowing the TPA to crystallize. The heating is preferably carried to a temperature such that no TPA remains in the solid phase. Catalysts may be used.
Inventors
- 👤 Adin L Stautzenberger
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 06:04
CPC Classifications
C; C07; C07C; C07C51/00; C07C51/42; C07C51/43
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
20 words
The process of claim 1 wherein the heating is continued until none of the terephthalic acid remains as a solid.
Claim 2
Dependent Claim
36 words
The process of claim 1 wherein the crude terephthalic acid is present in amounts of from about 3 to 95 percent by weight based on the combined weight of crude terephthalic acid and inert, liquid medium.
Claim 3
Dependent Claim
16 words
The process of claim 1 wherein the temperature of heating is from about 325*C to 440*C.
Claim 4
Dependent Claim
20 words
The process of claim 1 wherein said crude terephthalic acid has been produced by the oxidation of p-xylene with air.
Claim 5
Dependent Claim
16 words
The process of claim 1 wherein the heating above 325*C is for at least 2 minutes.
Claim 6
Dependent Claim
93 words
The process of claim 1 wherein said heating is continued for a period of time such that the recovered, purified terephthalic acid contains less impurities than that obtained in a simple recrystallization process wherein the crude terephthalic acid and inert liquid medium are heated to a temperature sufficient to dissolve the crude terephthalic acid followed by cooling the resulting solution to recrystallize the terephthalic acid, and wherein said inert liquid medium has a boiling point of at least 20*C and a melting point of less than about 200*C and comprises an organic medium.
Claim 7
Dependent Claim
80 words
The process of claim 7 wherein the terephthalic acid is present in amounts of from about 5 to 50 percent by weight based on the combined weight of crude terephthalic acid and inert liquid medium and wherein said inert liquid medium comprises from about 0 to 75 percent by weight water and from about 25 to 100 percent of a member selected from the group consisting of C5+ hydrocarbons, C2+ halohydrocarbons, carboxylic acids, hydrocarbon ethers, halohydrocarbon ethers, and mixtures thereof.
Claim 8
Dependent Claim
25 words
The process of claim 8 wherein said heating is at least to a temperature such that none of the terephthalic acid exists as a solid.
Claim 9
Dependent Claim
18 words
The process of claim 9 wherein the heating is at a temperature of from about 340* to 420*C.
Claim 10
Dependent Claim
32 words
The process of claim 10 wherein the inert liquid medium comprises from 0 to 15 percent by weight of water and from 85-100 percent by weight of a C2-C4 aliphatic carboxylic acid.
Claim 11
Dependent Claim
82 words
The process of claim 7 wherein the crude terephthalic acid is present in amounts of from about 50 to 95 percent by weight based on the combined weight of crude terephthalic acid and inert liquid medium and wherein said inert liquid medium comprises from about 10 to 100 percent by weight of water and 0 to 90 percent by weight of a member selected from the group consisting of C5+ hydrocarbons, C2+ halohydrocarbons, carboxylic acids, hydrocarbon ethers, halohydrocarbon ethers, and mixtures thereof.
Claim 12
Dependent Claim
20 words
The process of claim 12 wherein the heating is continued until none of the terephthalic acid remains as a solid.
Claim 13
Dependent Claim
16 words
The process of claim 13 wherein the heating is to a temperature of 340* to 420*C.
Claim 14
Dependent Claim
33 words
The process of claim 13 wherein said liquid medium consists essentially of from 10 to 100 percent by weight of water and 0 to 90 percent by weight of an aliphatic carboxylic acid.
Claim 15
Independent Claim
121 words
A METHOD FOR IMPROVING THE PURITY OF A CRUDE TEREPHTHALIC ACID PRODUCED BY THE LIQUID-PHASE OXIDIATION OF P-XYLENE WITH AN OXYGEN-CONTAINING GAS AND CONTAINING IMPURITIES COMPRISING 4-CARBOXYBENZALDEHYDE, WHICH METHOD COMPRISES: A. HEATING CRUDE TEREPHTHALIC ACID, AN INERT LIQUID MEDIUM, AND A CATALYST CONSISTING ESSENTIALLY OF AN ALKALI METAL SALT OF A CARBOXYLIC ACID OR AN INORGANIC ACID TO A TEMPERATURE OF AT LEAST 325*C, SAID TEMPERATURE BEING ONE AT WHICH NO MORE THAN ABOUT 50 PERCENT OF THE TEREPHTHALIC ACID REMAINS AS A SOLID, THE PRESSURE BEING SUFFICIENT TO MAINTAIN A LIQUID PHASE AT TEMPERATURE BELOW THE CRITICAL TEMPERATURE, B. COOLING THE TEREPHTHALIC ACID LIQUID MEDIUM SO AS TO CRYSTALLIZE TEREPHTHALIC ACID AND C. RECOVERING THE THUS CRYSTALLIZED, PURIFIED TEREPHTHALIC ACID.
Claim 16
Dependent Claim
17 words
The process of claim 16 wherein the catalyst is an alkali metal salt of a carboxylic acid.
Claim 17
Dependent Claim
11 words
The method of claim 16 wherein the catalyst is sodium acetate.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-01-20 | 1978-07-22 | 1979-01-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-01-20 | 1982-07-22 | 1983-01-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-01-20 | 1986-07-22 | 1987-01-21 | $7700.00 | Window Closed / Lapsed |