The method of purification of adipic acid in water

 

(57) Abstract:

The invention relates to a method of purification by crystallization or recrystallization in water adipic acid, which is one of the main substances used to obtain polyamide 6-6, which contains traces of catalyst, with a minimum purity specified adipic acid is at least 95%, and the specified crystallization or recrystallization is carried out in the presence of a strong proton acid and/or in the presence of carbon monoxide. The number of strong proton acid is preferably from 1 to 50 mol per 1 mol of the metal catalyst. 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. Such crystallization or recrystallization allows you to lower the levels of trace metal catalysts in adipic acid. 6 C.p. f-crystals, 1 table.

The present invention relates to a method of purification of adipic acid in water.

Adipic acid is one of the two main substances used to obtain polyamide 6-6. For what about the predecessors, in particular adipic acid.

According to the method of producing adipic acid contained impurities are heterogeneous. This method can be used to clean adipic acid obtained in various ways. One of the impurities that create the most noise and sometimes the most costly represents the traces of the catalyst used in the preparation of adipic acid.

A known method of purification of adipic acid by crystallization and recrystallization from water in the presence of a strong proton acid, in particular sulfuric (SU, 394354 And 22.08.78). However, this method relates to the purification of adipic acid from organic impurities and it does not provide for the recrystallization in the presence of a strong acid and removal of metallic impurities.

Source of information EN 94010123 does not apply to the cleaning of adipic acid, and relates to the regeneration of the catalyst from the mother liquor adipic acid production. Another object, another task and therefore a means of achieving this task. It is written that this method can find application in the adipic acid production. But the claimed technical solution does not apply to polcenigo have suggested to use the method on this document to remove small amounts of metal compounds from pure adipic acid. This document discloses only that it's possible to keep most of metals (catalyst) in solution using acid.

In the following description, the method is more specifically considered in terms of its application to 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, the object of which are partenavia acid obtained in the first reaction, get adipic acid, containing some methyl-2-glutaric acid, ethyl-2-succinic acid, and other compounds produced in the first reaction hydroxycarbonylmethyl, such as gamma 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 carried out usually in the presence of cobalt, and in this way obtain adipic acid with the cold and a little better - in the hot, the solvent usually used for crystallization of the specified acid.

However, given the ever-increasing demands on the purity adipic acid, especially in regard to trace metals, one or even multiple crystallization in water is often not enough.

In addition to interference, which can create 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, causing the need for the fullest possible retrieval within economically viable industrial way.

The present invention is an improved method of crystallization or recrystallization of adipic acid in water, characterized in that the specified crystallization or recrystallization is carried out in the presence of a strong proton acid and/or in the presence of carbon monoxide.

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

As examples of such a strong proton acids can name the strong acid.

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

Carbon monoxide may be at least partially (preferably at least 0.5 bar absolute.) 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 higher than atmospheric.

In practice, operate in this way at an absolute pressure of from 0 to 50 bar carbon monoxide, while the upper bound is not strict, but dictated the use of industrial equipment, the cost is not too high. Preferably an absolute pressure of carbon monoxide is from 1 to 50 bar.

Adipic acid, which is subjected to recrystallization of the present invention, is usually adipic acid, have already held one or more stages of the cleaning processing, in particular, by the method of crystallization in water, refining or distillation and having a minimum purity about the t 95% to 99.95%.

Recrystallization is that the purified adipic acid dissolved in the minimum amount of water in hot form, i.e., at a temperature usually between 80oWith up to 250oWith the presence of a strong proton acid and/or in the atmosphere or under, at least, partial pressure of carbon monoxide, then crystallized dissolved adipic acid by cooling the solution possible after priming solution crystals of pure adipic acid.

Usually use this amount of water to obtain a saturated solution of adipic acid at the selected temperature. For example, if 80oA saturated solution contains about 40% weight. adipic acid.

The method according to the invention also includes the crystallization of adipic acid from its containing reaction mixtures.

So you can, for example, to crystallize adipic acid from the mixture obtained by hydroxycarbonylmethyl partenopei acid, water and carbon monoxide. This reaction mixture can be mixed with water in the presence of a strong proton acid and/or at least partial atmosphere or under at least the partial pressure of carbon monoxide, temperature recip is I.

The promoter used in the reaction of hydroxycarbonate may be itestosterone acid or Hydrobromic acid, adding a strong proton acid may not be necessary. However, if you wish you can add a number of strong proton acid present in the reaction mixture.

Similarly, because the reaction hydroxycarbonylmethyl carried out in the presence of carbon monoxide, is not necessary to add this link for crystallization, but this possibility is not excluded. It is also possible, as in the case of recrystallization of adipic acid, to act in the absence of carbon monoxide, cleaning the atmosphere mixes for hydroxycarbonylmethyl before crystallization.

The following examples are a clear demonstration of the invention.

Example 1

In a glass ampoule is placed 5,16 g of adipic acid, containing by 31.0 µg (0,0006% weight. in relation to the weight of adipic acid and 7.5 ml of water. Adipic acid was obtained by direct oxidation of cyclohexane in the presence of acetate and purified by recrystallization in water. It does not contain organic impurities in defined quantities.

Open the ampoule was placed in an autoclave arr).

Heated to 185oC and maintain this temperature for about 30 minutes

After cooling and venting the autoclave with nitrogen, filtered adipic acid autoclave and washed with several ml of water.

Filtered adipic acid washed with 25 ml of water, then 38 ml of water.

Adipic acid is dried overnight in a drying Cabinet (60oC). Determine the amount of cobalt present in the final adipic acid, using a plasma induction and in conjunction with mass spectrometric analysis (IPS/Masse). Define 0,000012% weight. With.

Example 2

Act the same way as in example 1, using a total of 5.21 g of the same sample adipic acid, 31,12 mcg With (0,0006% weight. in relation to the weight of adipic acid), 7.5 ml of water and 1 ml 96,7 mg model HC1 in 50 ml of water. The molar ratio model HC1/With is 10.

Conditions are the same as in example 1, but the atmosphere is replaced by nitrogen atmosphere (1 bar absolute.).

After washing and drying determine the amount of cobalt contained in the final adipic acid. It is 0,00009% weight.

Examples 3-7

Act as in example 1, using adipic acid containing iridium. Hell the iridium and purified by recrystallization in water.

It does not contain organic impurities in measurable amounts.

Table 1 shows 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/g of adipic acid (AdOH).

Example 8

In a glass vessel equipped with fridge at him and with a device for heating and cooling impose 5,44 g adipinate acid containing 0,00095% Rh, 7.5 g of water and an aqueous solution of HI (molar ratio HI/Rh contained in the adipic acid = 10). 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 defined quantities.

In cold water creates a nitrogen atmosphere (about 1 bar). Heated to 90oC and maintain this temperature for about 30 minutes After cooling is filtered adipic acid and washed with 25 ml of water, saturated adipic acid.

Dried adipic acid over night in an oven (60oC). Determine the amount of the rhodium contained in the final adipic acid. It is 0,00054% Annoy hydroxycarbonylmethyl 3-pentenol acid in the presence of iridium and HI. This adipic acid has already passed crystallization and still contains 0,00022% iridium.

The recrystallization is conducted in the usual way by dissolving in approximately 95oWith adipic acid in a minimum amount of water, then gradually cooling the resulting solution, and then filtering and finally, washing the filtered adipic acid, 25 ml of water and 38 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. Therefore, failed to reduce the content of iridium in adipic acid.

1. The method of purification by crystallization or recrystallization in water adipic acid containing traces of catalyst, characterized in that the minimum purity specified adipic acid is at least 95%, and the specified crystallization or recrystallization is carried out in the presence of a strong proton acid and/or in the presence of carbon monoxide.

2. The method according to p. 1, wherein the strong protonic acid is chosen from iodine-hydrogen acid, Hydrobromic acid, chloride-hydrogen acid, nitric acid, setulae from 0 to 100 mol per 1 mol of the metal-catalyst, contained in adipic acid, preferably from 1 to 50 mol per 1 mol of the metal-catalyst.

4. The method according to any of paragraphs. 1-3, 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.

5. The method according to any of paragraphs. 1-4, characterized in that it is carried out at an absolute pressure of from 0 to 50 bar carbon monoxide.

6. The method according to any of paragraphs. 1-4, characterized in that it is carried out at an absolute pressure of from 1 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 is from 95 to 99.95%.

 

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FIELD: crystal growing.

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.

3 cl, 1 dwg, 1 tbl, 2 ex

FIELD: chemical industry; methods of production of the purified crystalline terephthalic acid.

SUBSTANCE: the invention is pertaining to the improved method of production and separation of the crystalline terephthalic acid containing less than 150 mass ppm of the p-toluene acid in terms of the mass of the terephthalic acid. The method provides for the following stages: (1) loading of (i) para- xylene, (ii) the water reactionary acetic-acidic medium containing the resolved in it components of the oxidation catalyst, and (iii) the gas containing oxygen fed under pressure in the first zone of oxidation, in which the liquid-phase exothermal oxidization of the para-xylene takes place, in which the temperature and the pressure inside the first being under pressure reactor of the oxidization are maintained at from 150°С up to 180°С and from 3.5 up to 13 absolute bars; (2) removal from the reactor upper part of the steam containing the evaporated reactionary acetic-acidic medium and the gas depleted by the oxygen including carbon dioxide, the inertial components and less than 9 volumetric percents of oxygen in terms of the non-condensable components of the steam; (3) removal from the lower part of the first reactor of the oxidized product including (i) the solid and dissolved terephthalic acid and (ii) the products of the non-complete oxidation and (ii) the water reactionary acetic-acidic medium containing the dissolved oxidation catalyst; (4) loading of (i) the oxidized product from the stage (3) and (ii) the gas containing oxygen, into the second being under pressure zone of the oxidation in which the liquid-phase exothermal oxidization of the products of the non-complete oxidization takes place; at that the temperature and the pressure in the second being under pressure reactor of the oxidization are maintained from 185°С up to 230°С and from 4.5 up to 18.3 absolute bar; (5) removal from the upper part of the second steam reactor containing the evaporated water reactionary acetic-acidic medium and gas depleted by the oxygen, including carbon dioxide, the inertial components and less, than 5 volumetric percents of oxygen in terms of the non-condensable components of the steam; (6) removal from the lower part of the second reactor of the second oxidized product including (i) the solid and dissolved terephthalic acid and the products of the non-complete oxidation and (ii) the water reactionary acetic-acidic medium containing the dissolved oxidation catalyst; (7) separation of the terephthalic acid from (ii) the water reactionary acetic-acidic medium of the stage (6) for production the terephthalic acid containing less than 900 mass ppm of 4- carboxybenzaldehyde and the p-toluene acid; (8) dissolution of the terephthalic acid gained at the stage (7) in the water for formation of the solution containing from 10 up to 35 mass % of the dissolved terephthalic acid containing less than 900 mass ppm of the 4- carboxybenzaldehyde and the p-toluene acid in respect to the mass of the present terephthalic acid at the temperature from 260°С up to 320°С and the pressure sufficient for maintaining the solution in the liquid phase and introduction of the solution in contact with hydrogen at presence of the catalytic agent of hydrogenation with production of the solution of the hydrogenated product; (9) loading of the solution of the stage (8) into the crystallization zone including the set of the connected in series crystallizers, in which the solution is subjected to the evaporating cooling with the controlled velocity using the significant drop of the temperature and the pressure for initiation of the crystallization process of the terephthalic acid, at the pressure of the solution in the end of the zone of the crystallization is atmospheric or below; (10) conduct condensation of the dissolvent evaporated from the crystallizers and guide the condensed dissolvent back into the zone of the crystallization by feeding the part of the condensed dissolvent in the line of removal of the product of the crystallizer, from which the dissolvent is removed in the form of the vapor; and (11) conduct separation of the solid crystalline terephthalic acid containing less than 150 mass ppm of the p-toluene acid in terms of the mass of the terephthalic acid by separation of the solid material from the liquid under the atmospheric pressure. The method allows to obtain the target product in the improved crystalline form.

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

8 cl, 3 tbl, 2 dwg, 3 ex

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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19 cl, 1 dwg, 6 ex, 4 tbl

FIELD: chemistry.

SUBSTANCE: invention relates to an improved method, by which the carboxylic acid/diol mixture, that is suitable as the initial substance for the manufacture of polyester, obtained from the decolourised solution of carboxylic acid without actually isolating the solid dry carboxylic acid. More specifically, the invention relates to the method of manufacturing a mixture of carboxylic acid/diol, where the said method includes the addition of diol to the decolourised solution of carboxylic acid, which includes carboxylic acid and water, in the zone of the reactor etherification, where diol is located at a temperature sufficient for evaporating part of the water in order to become the basic suspending liquid with the formation of the specified carboxylic acid/diol mixture; where the said carboxylic acid and diol enter into a reaction in the zone of etherification with the formation of a flow of a complex hydroxyalkyl ether. The invention also relates to the following variants of the method: the method of manufacture of the carboxylic acid/diol mixture, where the said method includes the following stages: (a) mixing of the powder of damp carboxylic acid with water in the zone for mixing with the formation of the solution of damp carboxylic acid; where the said carboxylic acid is selected from the group, which includes terephthalic acid, isophthatic acid, naphthalenedicarboxylic acid and their mixtures; (b) discolourisation of aforesaid solution of damp carboxylic acid in the zone for reaction obtaining the decolourised solution of carboxylic acid; (c) not necessarily, instantaneous evaporation of the said decolourised solution of carboxylic acid in the zone of instantaneous evaporation for the removal of part of the water from the decolourised solution of carboxylic acid; and (d) addition of diol to the decolourised solution of carboxylic acid in the zone of the reactor of the etherification, where the said diol is located at a temperature, sufficient for the evaporation of part of the water in order to become the basic suspending liquid with the formation of the carboxylic acid/diol mixture; where the aforesaid carboxylic acid and diol then enter the zone of etherification with the formation of the flow of complex hydroxyalkyl ether; and relates to the method of manufacture of carboxylic acid/diol, where the said method includes the following stages: (a) the mixing of the powder of damp carboxylic acid with water in the zone for mixing with the formation of the solution of carboxylic acid; (b) discolourisation of the said solution of damp carboxylic acid in the reactor core with the formation of the decolourised solution of carboxylic acid; (c) crystallisation of the said decolourised solution of carboxylic acid in the zone of crystallisation with the formation of an aqueous suspension; and (d) removal of part of the contaminated water in the aforesaid aqueous solution and addition of diol into the zone of the removal of liquid with the obtaining of the said carboxylic acid/diol mixture, where diol is located at a temperature sufficient for evaporating part of the contaminated water from the said aqueous suspension in order to become the basic suspending liquid.

EFFECT: obtaining mixture of carboxylic acid/diol.

29 cl, 4 dwg

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