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Method for preparing pyrogallic acid with glyoxaline as gallic acid decarboxylation catalyst

A technology of pyrogallic acid and gallic acid, which is applied in chemical instruments and methods, preparation of organic compounds, physical/chemical process catalysts, etc., can solve the problems of high cost and complicated process, and achieve low cost, simple process and high reaction rate. The effect of low temperature

Inactive Publication Date: 2009-07-08
NANJING FORESTRY UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Using NaOH-K 2 CO 3 It can be used as a catalyst, but purification methods such as crystallization and recrystallization are required, the process is complicated and the cost is high
No other high-efficiency decarboxylation catalysts have been reported

Method used

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  • Method for preparing pyrogallic acid with glyoxaline as gallic acid decarboxylation catalyst

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0015] Weigh 200g of gallic acid raw material with 1 molecule of crystal water, place it in a petri dish, and dry it for 3 hours at a system pressure of 4.0kPa and a temperature of 100°C. The amount of dried material is 181.1g. Weigh 30.0 g (0.176 mol) of dried gallic acid, add it into a 100-mL three-necked flask equipped with a stirrer, a thermometer and a condenser, add 3.0 g of imidazole (purity is 99.0%), and gradually heat to 145 ~150°C, the color of the material gradually changes from white to gray, and then to dark gray, and the material gradually changes from solid powder to molten, and a large amount of CO2 gas escapes at the same time. Insulation reaction until no bubble escapes, sampling and detection by TLC (silica gel plate chromatography, 10% FeCl 3 The aqueous solution is used as the developer, and the developer is V (acetone): V (60-90°C petroleum ether) = 1.5: 1, add 2-3 drops of glacial acetic acid to eliminate the tailing phenomenon). Vacuumize the reaction...

Embodiment 2

[0017] Weigh 100.0 g (0.587 mol) of dried gallic acid, add it into a 250-mL three-necked flask equipped with a stirrer, a thermometer and a condenser, add 8.0 g of imidazole (purity is 99.0%), and gradually heat to 145 ~150°C, the color of the material gradually changes from white to gray, and then to dark gray, and the material gradually changes from solid powder to molten, and there is a large amount of CO 2 Gas escapes. Insulate the reaction until no bubbles escape, take a sample and use TLC detection (silica gel plate chromatography, 10% FeCl3 aqueous solution as the color developer, the developer is V (acetone): V (60 ~ 90 ° C petroleum ether) = 1.5: 1 , add 2 to 3 drops of glacial acetic acid to eliminate tailing phenomenon). Vacuumize the reaction system until the pressure of the system is 2.67kPa, and gradually raise the temperature to 160°C. At this time, a white sublimation product, pyrogallic acid, escapes. Keep this temperature until no sublimation product escapes...

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Abstract

The invention provides a method for preparing pyrogallol by taking imidazole as a gallic acid decarboxylation catalyst. The method comprises the following steps that: anhydrous gallic acid and imidazole solids are stirred, mixed and progressively heated under normal pressure; materials are melted, and a large amount of CO2 gas escapes at the same time; reaction temperature is kept between 145 and 150 DEG C till no bubble escapes from a reaction product and till the reaction product is detected to contain no gallic acid raw material through TLC; the reaction product is progressively heated to between 155 and 160 DEG C under reduced pressure (system pressure is between 2.0 and 2.67 kPa) so as to allow flores to escape, and the temperature is kept till no flores escapes; and the flores is ground, so a pyrogallol product is obtained. The method has the advantages of low decarboxylation temperature, high reaction speed, simple process, cheap catalyst, good catalytic effect, low catalyst alkalinity, few byproducts, high boiling point of catalyst, products quality assurance, high pyrogallol yield and capability of obtaining the high-purity product with no post-treatment.

Description

technical field [0001] The invention relates to a method for preparing pyrogallic acid, in particular to a method for preparing pyrogallic acid by using imidazole as a gallic acid decarboxylation catalyst. It belongs to the technical field of pyrogallic acid preparation. Background technique [0002] The preparation of pyrogallic acid mainly includes chemical synthesis method, biosynthesis method, gallic acid decarboxylation method and tannin or its initial raw materials (such as gallnut powder, tara powder, tea leaf powder, etc.) and other preparation methods. [0003] Among them, pyrogallic acid is prepared by chemical synthesis using 7,8-dihydroxy-2,4-diphenyl-[1,4-benzopyranol] as raw material, and acetophenone is removed under the action of alkali to obtain Pyrogallic acid. 1-(2,3,4-trimethoxyphenyl)-cyclohex-1-ene was used as raw material, heated to 210°C under the action of aniline hydrochloride to obtain 40% pyrogallic acid, and HBr As a catalyst, 16% pyrogallic a...

Claims

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Application Information

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IPC IPC(8): C07C39/10C07C37/50B01J31/02
Inventor 王石发杨杨谷文刘兵敖汪伟
Owner NANJING FORESTRY UNIV
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