CN1119314C - Process for preparing salicylic acid by solvent method - Google Patents
Process for preparing salicylic acid by solvent method Download PDFInfo
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- CN1119314C CN1119314C CN00123036A CN00123036A CN1119314C CN 1119314 C CN1119314 C CN 1119314C CN 00123036 A CN00123036 A CN 00123036A CN 00123036 A CN00123036 A CN 00123036A CN 1119314 C CN1119314 C CN 1119314C
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Abstract
The present invention relates to new technology for preparing salicylic acid by a solvent method, which comprises the steps: after phenol is neutralized with sodium hydroxide, the prepared sodium phenolate salt solution containing water is dewatered in vacuum in a C8H17OH organic solvent under the conditions of the vacuum degree of 0 to 0.1MPa and the temperature of 40 to 140 DEG C; the dewatered sodium phenolate salt is homogeneous transparent liquid; after the moisture measurement is qualified, excessive carbon dioxide is introduced for carboxylation reaction, the reaction pressure is from 0 to 0.8MPa, and the temperature is from 110 to 190 DEG C; after the reaction is completed, the temperature is lowered under the condition of nitrogen gas, water is added, and the separated organic solvent containing phenol is recovered and used; the separated water phase is acidified to prepare salicylic acid with the content of 99.56 %. The technology has the advantages of short reaction time, good selectivity, high total recovery rate, little investment and obvious effect, and no waste water, waste gas or waste slag basically exists. The present invention is suitable for mass continuous industrial preparation.
Description
The present invention belongs to the field of salicylic acid producing technology with phenol, sodium hydroxide, carbon dioxide, sulfuric acid, etc. as material. In particular to a method for preparing salicylic acid by dehydrating in the presence of an organic solvent, dissolving the dehydrated sodium phenolate and the organic solvent into a uniform and transparent liquid and carrying out carboxylation reaction on the liquid and carbon dioxide.
The salicylic acid is mainly used in the industries of medicine, pesticide, dye and the like, and the traditional Koble-Skhmitt solid phase carboxylation method is still adopted to produce the salicylic acid at home and abroad before the invention is made. The method has the disadvantages that the phenol sodium salt is dehydrated into dry powder which is easy to burn and explode. The reaction is a gas-solid reaction, the contact of the reaction is poor, the partial overheating is easy, the p-hydroxybenzoic acid is easy to generate, the product is difficult to refine, and the sublimation-grade salicylic acid can be obtained only by using special vacuum sublimation equipment.
In recent years, the solvent process for the preparation of salicylic acid has been reported (C, A, Vol121990), which uses alkylbenzene C6H6-nRn(R is low-carbon alkyl, n is 1-4) is solvent, the alkali metal salt of phenol reacts with carbon dioxide to prepare salicylic acid, the sodium salt of phenol is insoluble in alkylbenzene, the reaction is gas-liquid-solid three-phase reaction, the reaction effect is poor, the process flow is long, and the industrial production is difficult.
The invention aims to provide a novel process for preparing salicylic acid by a solvent method, which adopts an organic solvent with good intermiscibility with sodium phenolate to ensure that reaction liquid is uniform and transparent liquid, and removes water in the sodium phenolate to directionally produce the salicylic acid.
The object of the invention is achieved by the following technical measures.
The technological process for preparing salicylic acid is shown in the attached drawing. A process for preparing salicylic acid by solvent method includes such steps as adding the sodium phenolate containing water to octanol as organic solvent, vacuum dewatering to obtain transparent liquid, introducing carbon dioxide, gas-liquid phase carboxylating reaction to obtain sodium salicylate, and acidifying. In the reaction process, the weight ratio of the organic solvent to the phenol is preferably selected to be within the range of 4-10: 1.
In addition, in the process, the molar ratio of phenol to sodium hydroxide is 1: 1.0-1.05, and the concentration of the adopted sodium hydroxide aqueous solution can be 30-50%.
The process is carried out under vacuum degree of 0-0.1Mpa and temperature of 40-140 deg.C. When the water content in the sodium salt of phenol is less than 0.3 percent, the dehydration is stopped. At this time, excess carbon dioxide may be introduced into the liquid phase to perform carboxylation reaction at a reaction pressure of 0-0.8Mpa and a temperature of 100-190 ℃. And stopping introducing the carbon dioxide after the reaction is finished to generate the salicylic acid sodium salt. Then, cooling, adding water and standing under the protection of nitrogen, and acidifying the separated water phase to obtain the high-purity salicylic acid with the content of more than 99.55%. And recycling the separated organic solvent containing phenol.
The reaction equation for preparing salicylic acid in the invention is as follows:
1. to produce phenol sodium salt:
phenol is a weak acid which reacts readily with alkali to form sodium phenolate and water
2. And (3) carboxylation reaction:
the alkali metal salts of phenol readily undergo carboxylation with carbon dioxide to form sodium hydroxybenzoate, and different alkali metals or hydroxybenzoic acids formed at different temperatures. The reason why the present invention can orient the production of sodium ortho-hydroxybenzoate (salicylate) is that the presence of the above organic solvent results in a homogeneous solution for carboxylation. The reaction equation is as follows:
because the hydrogen on the hydroxyl in the molecule of the sodium salicylate is acidic, the sodium salicylate reacts with sodium phenolate to generate disodium salicylate:
obtaining a reaction formula (3) from the reaction formulas (1) + (2):
as can be seen from the reaction formula (3): the theoretical yield of salicylic acid from phenol is up to 50%, but carboxylation under pressure inhibits the formation of the disodium salt.
3. And (3) acidification reaction:
4. side reaction:
water and carbon dioxide react to form carbonic acid:
because of H2CO3Acid strength: pka1＝10，Pka210.2, and C6H5The hydrogen acidity strength at the hydroxyl group in (OH) is Pka ═ 10, so the sodium salt of phenol reacts readily with carbonic acid to form phenol and sodium bicarbonate:
from the reaction equation: no water exists in the reaction system, otherwise, the phenol sodium salt is reduced into phenol, carboxylation cannot occur, and salicylic acid cannot be generated. The key problem of the process is how to completely remove the water in the sodium phenolate. The traditional Kolbe-Skhmitt method uses excessive phenol for dehydration to finally obtain dry powder of sodium phenolate, the water content of the dry powder is difficult to control in the production process, water is difficult to remove completely, local overheating and explosion are easy to occur, the reaction effect is poor, p-hydroxybenzoic acid is easy to generate, black spots exist in the product, and high-quality salicylic acid is difficult to obtain.
The invention selects an organic solvent with good effect, which is dissolved with sodium phenolate to form uniform transparent liquid, and the organic solvent is dehydrated in liquid phase, with good effect, and can dehydrate water in a reaction system to 0.02-0.3%. Carboxylation in liquid phase has high reaction selectivity, can directionally generate salicylic acid,and can recycle the solvent easily. The whole reaction process has no local overheating, the carboxylation reaction is a gas-liquid two-phase reaction, the traditional solid phase reaction is replaced by a liquid phase reaction, the carboxylation reaction speed is high, the selectivity is good, the total yield is high, and the solvent is easy to recover and reuse. The reaction process is a sealed circulation system, basically has no pollution, and is a new method suitable for industrial continuous production of salicylic acid.
Compared with the prior art, the invention has the following advantages:
1 the reaction system is easy to dehydrate,
2 the dehydrated phenol sodium salt is homogeneous transparent liquid,
3 the water content is 0.02-0.3%.
The 4 carboxylation reaction is a gas-liquid two-phase reaction, the reaction speed is high, and the reaction time is 4-6 hours.
5 has good reaction selectivity, can directionally generate salicylic acid and basically has no p-hydroxybenzoic acid.
The 6-carboxylation reaction can be carried out under normal pressure or under pressure.
The solvent 7 is easy to recover, phenol and the solvent are recycled together in the reaction process, and the total recovery rate of the reaction is high and is more than 95 percent.
8, the product quality is high, the product meets the pharmaceutical grade standard, and the content is 99.56 percent.
9 the process is simple, safe in production, low in production cost, short in reaction time and suitable for large-scale continuous production.
The process can adopt closed cycle production, the phenol is recycled, no discharge is generated, andthree wastes are basically not generated.
Salicylic acid product analysis
Project of the invention in the United states of China
The content of salicylic acid is more than 99.599.5-101 and more than 99.5
Phenol content%<0.100.03
Chloride%<0.014<0.0100.002
Ignition residue%<0.10<0.05<0.10.007
Heavy metal (pb)%<0.001<0.002<0.0020.001
Sulfate%<0.020<0.0200.01
Melting point range of 158-161158-161158.4-160.9
The invention will be further described in detail with reference to the following examples:
FIG. 1 is a schematic view of the production process of the present invention.
The first embodiment is as follows:
in a 5000 ml four-hole glass reaction bottle with a stirrer and a moisture separator, 235 g (2.5 g molecule) of phenol is firstly added under the protection of nitrogen, 40 percent NaOH 285 g (2.75 molecule) is slowly added with stirring, and then octanol (C) is added8H17OH)1900 g, controlling vacuum degree at 0.08Mpa, heating to 73 deg.C, discharging water, sampling at 136 deg.C for analysis, water content of 0.02%, free phenol content of 0.0802% (chromatographic analysis), cooling to 100 deg.C, introducingQuantitative dried CO2Carboxylation reaction is carried out, the reaction temperature is 185 ℃, the reaction time is 5 hours, the reaction is stopped, 1500 ml of distilled water is added to dissolve the salicylic acid sodium salt when the temperature is reduced to 100 ℃, water phase and oil phase are separated after standing, the oil phase is recycled, the water phase is decolored and acidified by 30 percent of sulfuric acid, the acid addition is stopped when the PH is 2, the temperature is reduced and filtration is carried out, crude salicylic acid (the content is 97.5 percent) is obtained, and 185 g of salicylic acid is obtained by recrystallization with water, the content is 99.83 percent (liquid chromatography analysis). The single-pass yield is: 53.9%, total yield based on phenol consumed was 96%.
Example two:
firstly, 1.4 kg of phenol is added into a mixer, 19.9 kg of octanol which is a solvent is recovered, wherein 1.887 kg of phenol (20.07 g of molecules) is added based on 0.487 kg of phenol, and 40 percent of NaOH2.05 kg (20.05 g of molecules) is added under stirringMolecular), putting into a 30-liter stainless steel reaction kettle under the protection of nitrogen, stirring and heating, controlling the vacuum degree to be 0.09Mpa, and beginning to discharge water when the temperature reaches 58 ℃. Samples were taken for analysis when the temperature rose to 136 ℃: the content of phenol is 0.01 percent, the content of water is 0.12 percent, the materials are cooled to 110 ℃, and CO of 0.4-0.6 Mpa is mixed under stirring2After being dried, the mixture is introduced into a reaction kettle for carboxylation reaction at the reaction temperature of 185 ℃, and when CO absorbed by the reaction is reacted2When the amount meets the requirement and sampling analysis is qualified, cooling to 100 ℃ in the presence of nitrogen, adding 10 kilograms of water, stirring for five minutes, standing, and separating out a water phase and an oil phase, wherein the refining method of the water phase is the same as that of the first embodiment. 0.927 kg of salicylic acid with the content of 99.56 percent is obtained, the once-through yield is 49.1 percent, and the total yield of the salicylic acid is 94 percent according to the consumed phenol.
Claims (7)
1. A process for preparing salicylic acid by solvent method includes such steps as adding the sodium phenolate containing water to octanol as organic solvent, vacuum dewatering to obtain transparent liquid, introducing carbon dioxide, gas-liquid phase carboxylating reaction to obtain sodium salicylate, and acidifying.
2. The process according to claim 1, wherein the weight ratio of the organic solvent to phenol is 4-10: 1.
3. The process as claimed in claim 1, wherein the molar ratio of phenol to sodium hydroxide is 1: 1.0-1.05, and the concentration of the aqueous sodium hydroxide solution is 30-50%.
4. The process according to claim 1 or 2, characterized in that after the organic solvent is added, the process is carried out under vacuum at a vacuum degree of 0-0.1Mpa and a temperature of 40-140 ℃, and the dehydration is terminated when the water content in the phenol sodium salt is less than 0.3%.
5. The process as claimed in claim 4, wherein the carboxylation reaction of dehydrated sodium phenolate with excessive carbon dioxide is carried out at a reaction pressure of 0-0.8MPa and a temperature of 100-190 ℃ to produce sodium salicylate, and then the introduction of carbon dioxide is stopped.
6. The process as claimed in claim 1 or 5, wherein the carboxylation reaction is carried out by cooling, adding water, standing under nitrogen protection, and acidifying theseparated water phase to obtain salicylic acid.
7. The process according to claim 6, wherein the organic solvent containing phenol separated by standing after the carboxylation reaction is reused.
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| CN00123036A CN1119314C (en) | 2000-09-25 | 2000-09-25 | Process for preparing salicylic acid by solvent method |
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| CN00123036A CN1119314C (en) | 2000-09-25 | 2000-09-25 | Process for preparing salicylic acid by solvent method |
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| CN1289760A CN1289760A (en) | 2001-04-04 |
| CN1119314C true CN1119314C (en) | 2003-08-27 |
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Families Citing this family (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100355719C (en) * | 2004-06-04 | 2007-12-19 | 北京清华紫光英力化工技术有限责任公司 | Salicylic acid preparing process |
| CN102584539A (en) * | 2011-01-06 | 2012-07-18 | 萍乡市飞虎炭黑有限公司 | Phenol sodium salt treatment method and device |
| CN102690195B (en) * | 2012-03-06 | 2015-02-18 | 江苏添鑫生物工程有限公司 | Para-hydroxybenzoic acid continuous production technique by liquid-phase method |
| CN103073394B (en) * | 2013-02-01 | 2015-07-29 | 河北敬业化工股份有限公司 | A kind of method of being produced phenol by salicylic acid sublimation residue |
| CN105878118A (en) * | 2016-05-21 | 2016-08-24 | 广州丹奇日用化工厂有限公司 | Method for extracting cedrela sinensis extract from cedrela sinensis leaves and application of method |
| CN107963963A (en) * | 2017-12-06 | 2018-04-27 | 江西省隆南药化有限公司 | A kind of preparation method of septichen |
| CN110041189A (en) * | 2019-04-28 | 2019-07-23 | 东南大学 | It is a kind of to prepare salicylic technique using microchannel continuous flow reactor |
| CN113416137B (en) * | 2021-06-22 | 2024-01-02 | 宁夏万香源生物科技有限公司 | Preparation method of benzyl salicylate |
| CN113336638A (en) * | 2021-06-22 | 2021-09-03 | 宁夏万香源生物科技有限公司 | Efficient synthesis method of salicylic acid |
| CN114345285B (en) * | 2022-01-12 | 2023-09-08 | 青岛科技大学 | Continuous production process of sodium salicylate solution |
| CN115010599B (en) * | 2022-06-13 | 2024-01-09 | 扬州大学 | Method for separating and refining salicylic acid from sodium salicylate acidified material |
| CN114805060A (en) * | 2022-06-13 | 2022-07-29 | 扬州大学 | Preparation method of potassium parahydroxybenzoate |
| CN116267989B (en) * | 2022-09-09 | 2024-05-07 | 兰州大学 | Nanometer iron antibacterial agent for fusarium trilineum |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1034362A (en) * | 1988-01-23 | 1989-08-02 | 株式会社上野制药应用研究所 | The preparation method of aromatic hydroxycarboxylic acid |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1034362A (en) * | 1988-01-23 | 1989-08-02 | 株式会社上野制药应用研究所 | The preparation method of aromatic hydroxycarboxylic acid |
Non-Patent Citations (1)
| Title |
|---|
| 辽宁化工，第3期 1994-01-01 曹广宏，水杨酸的合成及其应用 * |
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