The method of purification of adipic acid by recrystallization

 

(57) Abstract:

The invention relates to a method of purification of adipic acid, which is used to obtain a polyamide. The method consists in the crystallization or recrystallization of adipic acid with a minimum purity of 95%, containing traces of metals, at least one carboxylic acid with a melting point below 20oC. Purification could be accomplished in the presence of carbon monoxide or strong proton acid. The method allows to achieve maximum purification efficiency close to 100%. 9 C. p. F.-ly, 3 tables.

The present invention relates to a method of purification of adipic acid by crystallization or recrystallization in at least one carboxylic acid.

Adipic acid is one of the two main substances used to obtain polyamide 6-6. The use of polyamide 6-6 requires very high purity, and the purity must be already inherent in his predecessors, in particular adipic acid.

According to the method of producing adipic acid, contained impurities diverse in nature.

Patent FR-A-901841 describes how to separate the various dicarboxylic acids perakis Pinova acid, succinic acid.

However, the method does not describe the separation from the metallic impurities contained in the purified adipic acid.

Closest to the invention is a method for the crystallization of adipic acid in at least one carboxylic acid having a melting temperature below the 20oC, in particular, acetic acid (SU 282166 A, 14.09.70).

The difference between the claimed process is that recrystallization is subjected to adipic acid with a minimum purity of 95%.

This method can be applied to adipic acid obtained in various ways. One of the impurities that create the most noise and sometimes the most costly presents traces of catalyst used in the preparation of adipic acid.

However, in the following description, a method is considered in terms of its application in respect of adipic acid, obtained by double hydroxycarbonylmethyl butadiene or oxidation of cyclohexane.

In the first hydroxycarbonylmethyl butadiene get the mixture pentenoic acids, mainly 3-pontenova acid. In the second hydroxycarbonylmethyl,train containing some amount of 2-methyl-glutaric acid, 2-ethyl-succinic acid, and other compounds obtained already in the first reaction hydroxycarbonylmethyl-valerolactone, normal partenavia acid, methylbutanoate acid. It also contains traces of catalyst used in the second reaction hydroxycarbonylmethyl, often iridium and/or rhodium.

Direct oxidation of cyclohexane to adipic acid is usually carried out in the presence of cobalt, and in this way obtain adipic acid contains traces of cobalt catalyst.

Since adipic acid is poorly soluble in water in a cold condition and much better hot, this solvent is usually used for crystallization of the specified acid.

However, given the ever-increasing demands on the purity of adipic acid, in particular, in regard to trace metals, single or even repeated recrystallization is often not enough.

In addition to the interference caused by the presence of traces of metals in the various uses of adipic acid, the cost of certain catalysts, such as iridium or rhodium, given the large amount of adipic acid production, dictates BA.

The present invention is an improved method of crystallization or recrystallization of adipic acid, characterized in that the specified crystallization or recrystallization is carried out in at least one carboxylic acid with a melting point below 20oC.

Carboxylic acids used in the present method are, in particular, aliphatic saturated or containing one unsaturated ethylene communication carboxylic acid.

Preferably a linear or branched monocarboxylic acid having from 2 to 6 carbon atoms.

As non-limiting examples of such monocarboxylic acids can be called acetic acid, propionic acid, butane acid, pentane acid, hexanoic acid, partenavia acid.

Preference is given to acetic acid and pentanoyl acids, acetic acid because of its availability and its use in the synthesis of adipic acid from cyclohexane and pentanoyl acids because they are intermediate compounds in the adipic acid production of butadiene.

The purity of the recrystallized thus adipic acid can b is laroda may be, at least partially, the atmosphere, in which is placed the solution in the reactor crystallization or recrystallization (or sky reactor), or to create in the specified reactor pressure above atmospheric.

In practice, working at an absolute pressure from 0 bar (preferably, not less than 0,5 bar) up to 50 bar carbon monoxide, while the upper bound is not strict, but dictated the use of industrial equipment, the cost of which should not be very high.

Adipic acid, which is subjected to recrystallization under this method, is usually adipic acid, past one or more steps of purification, in particular, by crystallization from water, refining or distillation and having a minimum purity of about 95%.

Typically, the purity adipic acid, which is subjected to recrystallization method according to the invention, is from 95 to 99.95%.

Recrystallization is that the purified adipic acid is dissolved in a minimum amount of aliphatic carboxylic acid at a high temperature, i.e., usually at a temperature of from 80oC to 250oC, possibly in the atmosphere or under at least chochlate solution, perhaps, after priming solution crystals of pure adipic acid.

Usually use this amount of carboxylic acid to obtain a saturated solution of adipic acid at the selected temperature. For example, if 90oC a saturated solution of 3-pentenol acid contains about 33 wt%. adipic acid.

The content of the catalyst in the adipic acid can also be reduced by performing recrystallization in the presence of a strong proton acid.

Under the strong proton acid in this text mean inorganic proton acid with a pKa less than 1.

As examples of such a strong proton acids can be called idiscovered acid, Hydrobromic acid, hydrochloric acid, nitric acid, sulfuric acid.

The number of strong proton acid can be from 0 mol to 100 mol per 1 mol of the metal catalyst contained in the adipic acid. Preferably the amount of the proton acid is from 0 mol (preferably from 1 mol to 50 mol per 1 mol of the metal-catalyst.

In the method according to the invention also includes the crystallization of adipic acid from its containing reaction anilinium partenopei acid, water and carbon monoxide. This reaction mixture can be mixed with carboxylic acid, in the presence or absence used in the reaction of hydroxycarbonate of carbon monoxide and the temperature of this mixture is maintained within the range of from 80oC to 250oC, as described above for the recrystallization.

Crystallization can also be carried out in the reactor hydroxycarbonylmethyl, allowing to cool the reaction mixture, preferably under pressure of carbon monoxide. This option can be used, in particular, when hydroxycarbonylmethyl spend carboxylic acid or when it is done in 3-pentenol acid with incomplete metamorphosis last.

If the reaction hydroxycarbonylmethyl carried out in the presence of carbon monoxide, usually do not want to add this link for crystallization, but this possibility is not excluded.

Also, if the promoter used in the reaction of hydroxycarbonate is itestosterone acid or Hydrobromic acid, adding a strong proton acid may not be required. However, if you wish you can add a number of strong proton acid included in the reaction mixture. It is also possible, as and when the cross is reverent.

The recrystallization of adipic acid according to the invention can be performed several times to further reduce the metal content of the catalyst. It is also possible after crystallization or recrystallization according to the invention to carry out one or more times a recrystallization in water.

The following examples are a clear demonstration of the invention.

EXAMPLE 1

In a glass ampoule is injected with 5.2 g of adipic acid, and 31.2 ág Co (0,0006% weight. in relation to the weight of adipic acid and 7.5 ml of acetic acid. Adipic acid was obtained by direct oxidation of cyclohexane in the presence of acetate Co and purified by recrystallization in water. It does not contain organic impurities in measurable amounts.

Open the ampoule was placed in an autoclave with a capacity of 125 ml, and the autoclave closed.

Create a cold atmosphere of nitrogen (about 1 bar).

Heated to 185oC and maintain this temperature for approximately 30 minutes.

After cooling and venting the autoclave with nitrogen, filtered adipic acid autoclave and washed with acetic acid (few ml).

Filtered adipic acid washed 2x5 m is usilina Cabinet (60oC). Determine the amount of cobalt contained in the final adipic acid, using a plasma induction and mass spectrometric analysis (IPC/Masse). This amount is 0,00008% weight. Co.

EXAMPLE 2

Act as in example 1, using the same load and the same operating conditions, but added to the reaction mixture used 10 molar equivalents of HCl per 1 molar equivalent of Co contained in the adipic acid.

After the same processing as in example 1, to obtain the final dry adipic acid, containing 0,000009% weight. Co.

EXAMPLES 3-8

Act as in example 1 and under the same operating conditions, but added to the reaction mixture used HI (molar ratio HI/Ir, as indicated in table 1), using 3-pontenova acid (RA) as a solvent for recrystallization and using adipic acid (AdOH) containing iridium. Adipic acid was obtained by hydroxycarbonylmethyl 3-pentenol acid in the presence of a catalyst based on Ir and purified by recrystallization in water. It does not contain organic impurities in measurable amounts.

After recrystallization adipic acid washed 3-p is tx2">

Table 1 presents the conditions in which examples were carried out (Tr = temperature), as well as initial and final content of Ir (Ir primary and Ir nite), expressed in μg per g used adipic acid.

EXAMPLES 9-12

Act as in examples 3-8, but use adipic acid (AdOH) containing rhodium. Adipic acid was obtained by hydroxycarbonylmethyl 3-pentenol acid in the presence of a catalyst based on rhodium and purified by recrystallization in water. It does not contain organic impurities in measurable amounts.

After recrystallization adipic acid washed 3-pentenol acid, which is saturated adipic acid, then with water, saturated adipic acid.

Table 2 presents the conditions in which examples were carried out (Tp = temperature), as well as initial and final content of Rh (Rh primary and Rh end), expressed in μg per g of adipic acid.

EXAMPLE 13

In example 13 repeat the recrystallization described in examples 3-8 using recrystallized adipic acid, obtained in example 7.

Table 3 presents the conditions in which he was made an example of, as well as starting ANICELY EXPERIENCE 1

Conduct recrystallization in water adipic acid obtained by hydroxycarbonylmethyl 3-pentenol acid in the presence of iridium and HI. This adipic acid have been already subjected to crystallization and still contains 0,00022 % iridium.

The recrystallization is conducted in the usual way by dissolving at approximately 95oC adipic acid in a minimum amount of water, then gradually cooling the resulting solution, then filtered and finally, washing the filtered adipic acid 2x5 ml of water and 3x8 ml of water.

Dried adipic acid over night in an oven (60oC). Determine the amount of iridium contained in the final adipic acid. It is 0,00022% weight. Ir. Thus, failed to reduce the amount of iridium in the adipic acid.

EXAMPLE 14

Exercise hydroxycarbonylmethyl 3-pentenol acid with the following downloads:

77,7 g 3-pentenol acid

at 88.1 mg [IrCl (COD)]

169,6 mg aqueous solution of 57 wt% HI

5.7 g of water with continuous injection.

The pressure of carbon monoxide at the reaction temperature (185oC) support at the level of 22 bar and stop the reaction after 1 hour 05 minutes

annoy adipic acid. Then, by chromatography in gaseous phase and liquid chromatography with high resolution connections filtrate determine the degree of conversion of 3-pentenol acid (56.6 per cent).

Crystallized thus adipic acid contains 0,000122% iridium.

This adipic acid is recrystallized from 3-pentenol acid in an atmosphere of carbon monoxide (bubble circulation).

After recrystallization adipic acid washed 3-pentenol acid, which is saturated adipic acid, then with water, saturated adipic acid.

The content of iridium in recrystallized and dried adipic acid is 0,00002% weight.

Received adipic acid has a purity of nearly 100%, that is certainly higher than 95%.

1. The method of purification of adipic acid by recrystallization or crystallization in at least one carboxylic acid with a melting point below 20o, Characterized in that the purification is subjected to adipic acid with a minimum purity of 95%, containing traces of metals.

2. The method according to p. 1, wherein the carboxylic acid is chosen from aliphatic, saturated or containing one of new acids, having from 2 to 6 carbon atoms.

3. The method according to PP. 1 and 2, characterized in that the carboxylic acid is chosen from acetic acid, propionic acid, butane acid, pentanoic acid, hexanoic acid, pentenoic acids.

4. The method according to any of paragraphs. 1-3, characterized in that the crystallization or recrystallization is carried out in the presence of carbon monoxide.

5. The method according to p. 4, characterized in that the carbon monoxide is at least partially, the atmosphere, in which is placed the solution in the reactor crystallization or recrystallization, or creates the specified reactor pressure above atmospheric.

6. The method according to PP. 4 and 5, characterized in that it is carried out at an absolute pressure of from 0.5 to 50 bar carbon monoxide.

7. The method according to any of paragraphs. 1-6, characterized in that the purity adipic acid, which is subjected to recrystallization or crystallization ranging from 95 to 99.95%.

8. The method according to any of paragraphs. 1-7, characterized in that the recrystallization or crystallization was carried out in the presence of a strong proton acid.

9. The method according to p. 8, wherein the strong protonic acid is selected from idiscovered kilopascal according to any one of paragraphs. 1-9, characterized in that the number of strong proton acid is from 0 to 100 mol per 1 mol of the metal catalyst contained in adipic acid, preferably from 0 to 50 mol per 1 mol of the metal-catalyst.

 

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SUBSTANCE: invention relates to adipic acid crystals and treatment thereof to achieve minimum crystal caking. Crystals are prepared by crystallization of adipic acid from aqueous medium or between treating it with aqueous solution. Crystals are then subjected to ripening stage, that is crystals are held at temperature between 10 and 80°C until content of exchangeable water in crystals falls below 100 ppm, while using an appropriate means to maintain ambient absolute humidity at a level of 20 g/m3. Renewal of ambient medium is accomplished by flushing crystal mass with dry air flow having required absolute humidity. Means to maintain or to lower absolute humidity contains moisture-absorption device placed in a chamber. Content of exchangeable water in crystals is measured for 300 g of adipic acid crystals, which are enclosed in tightly sealed container preliminarily flushed with dry air and containing 2 g of moisture absorbing substance. In chamber, temperature between 5 and 25°C is maintained for 24 h. Content of water will be the same as amount of water absorbed by absorbing substance per 1 g crystals. Total content of water exceeds content of exchangeable water by at least 20 ppm.

EFFECT: minimized caking of crystals and improved flowability.

13 cl, 5 ex

FIELD: organic chemistry, chemical technology.

SUBSTANCE: invention relates to the improved method for isolating crystalline terephthalic acid comprising less 150 mas. p. p. per million (ppm) of p-toluic acid with respect to weight of terephthalic acid. Method involves the following steps: (1) preparing a solution containing from 10 to 35 wt.-% of dissolved terephthalic acid wherein from 150 to 1100 ppm of p-toluic acid is dissolved with respect to mass of terephthalic acid at temperature from 260°C to 320°C and under pressure providing maintaining the solution in liquid phase; (2) charge of solution from step (1) to crystallization zone comprising multitude amount of associated crystallizers wherein the solution is subjected for cooling at evaporation at the controlled rate by the moderate pressure and temperature reducing resulting to crystallization of terephthalic acid and wherein the solution pressure at the end of crystallization zone is equal to atmosphere pressure or lower; (3) condensation of solvent evaporated from crystallizers and recovering the condensed solution to the crystallization zone to place of descending flow from crystallizer wherein solvent is removed by evaporation, and (4) isolation of solid crystalline terephthalic acid comprising less 150 ppm of p-toluic acid with respect to the terephthalic acid mass by separation of the phase liquid-solid substance under atmosphere pressure. The advantage of method is preparing the end product in improved crystalline form and carrying out the process under atmosphere pressure or pressure near to atmosphere pressure.

EFFECT: improved method of crystallization.

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EFFECT: the invention ensures production of the target product in the improved crystalline form.

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FIELD: chemistry.

SUBSTANCE: invention pertains to the perfection of the method of regulating quantities of dissolved iron in liquid streams during the process of obtaining aromatic carboxylic acids or in the process of cleaning technical aromatic carboxylic acids, characterised by that, to at least, part of the liquid stream for regulating the quantity of dissolved iron in it, at least one peroxide with formula R1-O-O-R2 is added. Here R1 and R2 can be the same or different. They represent hydrogen or a hydrocarbon group, in quantities sufficient for precipitation of the dissolved iron from the liquid. The invention also relates to the perfection of the method of obtaining an aromatic carboxylic acid, through the following stages: A) contacting the crude aromatic material which can be oxidised, with molecular oxygen in the presence of an oxidising catalyst, containing at least, one metal with atomic number from 21 to 82, and a solvent in the form of C2-C5 aliphatic carboxylic acid in a liquid phase reaction mixture in a reactor under conditions of oxidation with formation of a solid product. The product contains technical aromatic carboxylic acid, liquid, containing a solvent and water, and an off-gas, containing water vapour and vapour of the solvent; B) separation of the solid product, containing technical aromatic carboxylic acid from the liquid; C) distillation of at least part of the off gas in a distillation column, equipped with reflux, for separating vapour of the solvent from water vapour. A liquid then forms, containing the solvent, and in the upper distillation cut, containing water vapour; D) returning of at least, part of the liquid from stage B into the reactor; E) dissolution of at least, part of the separated solid product, containing technical aromatic carboxylic acid, in a solvent from the cleaning stage with obtaining of a liquid solution of the cleaning stage; F) contacting the solution from the cleaning stage with hydrogen in the presence of a hydrogenation catalyst and under hydrogenation conditions, sufficient for formation of a solution, containing cleaned aromatic carboxylic acid, and liquid, containing a cleaning solvent; G) separation of the cleaned aromatic carboxylic acid from the solution, containing the cleaning solvent, which is obtained from stage E, with obtaining of solid cleaned aromatic carboxylic acid and a stock solution from the cleaning stage; H) retuning of at least, part of the stock solution from the cleaning stage, to at least, one of the stages B and E; I) addition of at least, one peroxide with formula R1-O-O-R2, where R1 and R2 can be the same or different, and represent hydrogen or a hydrocarbon group, in a liquid from at least one of the other stages, or obtained as a result from at least one of these stages, to which the peroxide is added, in a quantity sufficient for precipitation of iron from the liquid.

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EFFECT: obtaining mixture of carboxylic acid/diol.

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FIELD: chemistry.

SUBSTANCE: method of separating multi-atom alcohols, for instance, neopentylglycol and sodium formiate, includes evaporation and cooling of reaction mixture, addition of organic solvent, crystallisation of sodium formiate, separation of sodium formiate from saturated solution of multi-atom alcohol, for instance, by filtration, and crystallisation of multi-atom alcohol. Reaction mixture is evaporated until two liquid layers are formed, which are separated into light phase - water-multi-atom alcohol and heavy phase -water-salt, separated water-salt fraction of solution is cooled until sodium formiate contained in it in form of cryslallohydrate is crystallised, sodium formiate crystals are separated, and remaining mother-solution is returned to process head, to evaporation stage, then separated light phase - water-multi-atom alcohol is additionally evaporated until 70% of contained in it sodium formiate is crystallised, then cooled to 25-30°C and subjected to processing with organic solvent from line of single-atom saturated alcohols, for instance, methane, for removal of remaining admixtures, with further crystallisation of multi-atom alcohol from remaining mother-solution.

EFFECT: reduction of amount of used organic solvent, elimination of high-temperature stage of extraction, preservation of yield of pure target products.

2 cl, 2 dwg, 1 ex

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