Patent US4416798A successfully refreshed from Google Patents.
US4036854A
Expired / Lapsed
US
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Method for preparing coumarin
Assignee: Dow Chemical Co
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Filing: 1976-04-26
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Granted: 1977-07-19
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Expires: 1996-04-26
Abstract
Abstract A filter having a peripheral skirt extending above and below the filter element, provides a gaseous cushion which prevents clogging the filter. The peripheral edges of the filter may have means for preventing entry of solid in the narrow space between the skirt wall and the filter edge. The filter can be part of an entry or exit port in the base of a crystallizer in which crystals are formed, washed, melted and filtered in a single unit. A reactor containing the novel filter is also useful for carrying reactions using heterogeneous catalysts and reactions in which an initially homogeneous catalyst becomes nonhomogeneous during the reaction.
Inventors
- 👤 Kuo Yuan Chang
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 00:02
CPC Classifications
C; C07; C07D; C07D311/00; C07D311/02; C07D311/04; C07D311/06; C07D311/08; C07D311/10
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
130 words
A method of preparing coumarin by reacting salicylaldehyde, 1 to about 4 moles of acetic anhydride per mole of salicylaldehyde and an alkali metal acetate wherein the molar concentration of the alkali metal acetate is at or below the concentration of salicylaldehyde in the reaction, said reaction being conducted at temperatures up to 200° C for between about 2 and about 10 hours, the improvement comprising draining the liquid contents of the reactor through a filter medium located at the base of the reactor while passing an inert gaseous medium through said filter, to thereby retain the crystalline alkali metal acetate in the reactor, adding salicylaldehyde and acetic anhydride to the reactor and repeating the conversion thereof to coumarin without prior removal of the alkali metal acetate from the reactor.
Claim 2
Independent Claim
130 words
A method of preparing coumarin by reacting salicylaldehyde, 1 to about 4 moles of acetic anhydride per mole of salicylaldehyde and an alkali metal acetate wherein the molar concentration of the alkali metal acetate is at or below the concentration of salicylaldehyde in the reaction, said reaction being conducted at temperatures up to 200° C for between about 2 and about 10 hours, the improvement comprising draining the liquid contents of the reactor through a filter medium located at the base of the reactor while passing an inert gaseous medium through said filter, to thereby retain the crystalline alkali metal acetate in the reactor, adding salicylaldehyde and acetic anhydride to the reactor and repeating the conversion thereof to coumarin without prior removal of the alkali metal acetate from the reactor.
Claim 3
Dependent Claim
14 words
The method of claim 1 in which the alkali metal acetate is sodium acetate.
Claim 4
Dependent Claim
21 words
The method of claim 1 in which the acetic anhydride is added incrementally and acetic acid is distilled during the reaction.
Claim 5
Dependent Claim
59 words
The method of claim 3 in which a ratio of 100 parts by weight of sodium acetate, 244 parts by weight of salicylaldehyde and 204 parts by weight acetic anhydride is initially charged to the reactor and an additional 800 parts by weight of acetic anhydride are added incrementally during the reaction at a temperature of about 175° C.
References Cited (Backward Citations)
US3631067A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-07-18 | 1981-01-17 | 1981-07-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-07-18 | 1985-01-17 | 1985-07-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-07-18 | 1989-01-17 | 1989-07-19 | $7700.00 | Window Closed / Lapsed |