Adipinic acid crystallisation plant

FIELD: process engineering.

SUBSTANCE: invention relates to chemistry. Proposed plant comprises crystallisation reservoir furnished with adipinic acid mixers, coolers and/or concentrators Note here that, at least, a part of the walls of said coolers and/or concentrators in contact with adipinic acid solution is made from material selected from austenitic stainless steels of AISI 310L-grade compliance with AISI (USA) nomenclature of European nomenclature XlCrNi25-21 (1.4335).

EFFECT: reduced "lining" effect and deterioration of plant surface

7 cl, 2 tbl

 

The invention relates to an apparatus for the crystallization of adipic acid.

Adipic acid is an important chemical compound used as a raw material for the synthesis of many compounds. So, adipic acid is an important intermediate compound for the synthesis of polyamides and more particularly RA 6.6., and also for the production of polyesters, polyurethanes. Adipic acid is also used as an additive in a number of other applications, for example when receiving plasticizers.

Adipic acid is synthesized mainly from cyclohexane by oxidation of the latter in a mixture of cyclohexanone/cyclohexanol with subsequent oxidation with nitric acid the mixture to adipic acid.

Several methods of oxidation of cyclohexane to cyclohexanone/cyclohexanol carried out with different catalysts.

Nitric oxidation of a mixture of cyclohexanol/cyclohexanone is carried out in the presence of a metal catalyst, with adipic acid extract and purify mainly consistent cristallization.

It was also suggested that the direct oxidation of cyclohexane to adipic acid with oxygen or air in the presence of metal catalysts and solvent, such as acetic acid. In these methods, the adipic acid was extracted mainly the form of an aqueous solution.

Regardless of the method of synthesis of adipic acid to produce connections suitable for the above applications, it is necessary to subject him to treatment. Used mainly cleaning methods contain stage of crystallization, usually consisting in concentrating and/or cooling of a solution of adipic acid to obtain pure crystals of adipic acid.

These crystallization primarily in the mold of the big sizes. Installation for crystallization can contain multiple crystallizers connected in series, or a device that has multiple compartments, allowing you to clean continuously, or more crystallizers operating in accordance with a periodic way.

Molds are supplied mainly by the means for mixing, means for cooling and/or concentrating the solution. These latter means may consist of a device provided in contact with the solution, and in which circulates a fluid coolant, when funds allow to evaporate the solution, in particular by providing moderate pressure.

Means for cooling and/or concentrating the solution can consist of several devices used individually or in combination, such as a double shell in the article is the NCA of the mold, items containing means to circulate a fluid coolant, which is in solution, or an external circuit solution, which includes the heat exchanger. This list means for cooling and/or concentration of a solution is given for information only and are not restrictive.

For the proper functioning of the mould and maintain its performance, it is necessary to control certain operating parameters and, more specifically, the parameters affecting the contamination of the mold by deposits of crystallized adipic acid on the walls of the installation. This phenomenon, called "facing", depends on the nature of the material and surface condition of the walls. More specifically, it contributes to the emergence of the temperature difference between the solution and the walls that are in contact with the solution. Indeed, if this temperature difference is higher than the critical value depending on concentration and temperature of the solution, the speed of circulation of the solution in the mold, from the nature of the material and surface condition of the wall, is the deposition of adipic acid is attached to the wall.

Deposition of adipic acid is also observed regardless of the temperature differences on the walls with poor surface conditions, in particular, in the case of Krista the implementation by concentrating the solution by creating a moderate pressure in the mould.

For definitions of terms acceptable to the functioning of the mould, it is necessary to periodically stop the method for removing deposits of adipic acid on the walls of the heat exchanger or on the walls of the mould.

In addition, the sudden detachment of deposits in the process of adipic acid production can lead to mechanical damage, and even cause changes in the quality of adipic acid.

To limit this phenomenon facing the inner wall of the mold and the wall of the device for cooling and/or concentrating the solution is polished to obtain a minimally rough surface. These polished surfaces can also be cleaned and washed using conventional treatment technologies used in the field of metal surface treatment.

However, the surface condition of the walls may deteriorate rapidly under the action of chemical corrosion, in particular, when the crystallization of adipic acid occurs from solutions obtained by nitric oxidation of mixtures of cyclohexanone/cyclohexanol. Indeed, these solutions are acidic and contain significant amounts of nitric acid and/or nitrate ions.

To limit the phenomenon of facing and possible deterioration of the surface of the mold and the walls of heat exchangers often carry Aut austenitic stainless steel type AISI 304L. However, these phenomena are facing and corrosion still occurs. The use of material of this type is not possible to eliminate or reduce stop installation to troubleshoot lining.

Thus, at the present time, there is a need for materials or devices, allowing it to maintain the correct state of the surface and limit the impact of corrosion to reduce or eliminate the phenomenon lining.

To solve this problem the present invention proposes to use for the production of walls in contact with a solution of adipic acid, a material selected from special grades of stainless steel.

To this end, the invention proposes to install or crystallizer for crystallization of adipic acid, containing tank or the mold, means for agitation and a means for cooling and/or concentrating the solution of adipic acid, characterized in that at least part of the walls in contact with a solution of adipic acid and part of the tank or the mold and/or means for concentrating and/or cooling of the solution, made of austenitic stainless steel type AISI 310L in accordance with the nomenclature of the AISI (USA).

Austenitic stainless steel type AISI 310L also indicate XlCrNi25-21 (1.4335) according to the European nomenclature.

In accordance with one feature of the invention the means for cooling and/or concentrating the solution of adipic acid consist of devices that are in contact with the solution. More specifically, devices in which the fluid circulates coolant, can preferably be used for the cooling solution. According to the invention the walls of these devices for cooling in contact with a solution of adipic acid, made of austenitic stainless steel type AISI 310L. In another embodiment, the method of crystallization of adipic acid with the concentration of the solution by evaporation by creating a moderate pressure in the installation part of the installation, such as the inner walls of the mold, for example, are made of austenitic stainless steel type AISI 310L.

In accordance with another characteristic of the invention, the surface or wall, made of austenitic stainless steel type AISI 310L, grind before you install them in the mould. This grinding can be accomplished by any known means using physical and/or chemical methods to reduce surface roughness.

For information, and without limitation, the surface roughness, measured by a method defined in the standards NF EN ISO 3274 and NF EN ISO 4288, is preferably less than 0.3 microns.

Means for having hladiny and/or concentration of a solution of adipic acid can be different, such as coils, plates with a double wall, where circulating fluids or the like.

The mould according to the invention is suitable, in particular, for the crystallization of adipic acid from solutions that emerge from the stage of oxidation of the mixture of cyclohexanone/cyclohexanol with nitric acid.

The examples given below solely for the information, illustrate the invention.

A pilot test to determine the corrosion resistance and changes the state of the surface of products made from different grades of stainless steel were carried out in the following order:

Samples in the form of a parallelepiped of size 50×30 mm, the surface of which was polished to its original roughness Ra is less than 0.1 μm, immersed in the environment, obtained by oxidation with nitric acid a mixture of cyclohexanone/cyclohexanol containing the weight concentration of adipic acid 24% and nitric acid in amount of about 28 wt.%.

The temperature of the solution support 90°C at atmospheric pressure and stirred during the entire period of immersion. After 400 hours since the beginning of the dive, determine the state of the sample surface and the loss of thickness. These samples again immersed for another 400 hours in the same environment. Solution update before each new dive.

Test samples made from two grades of stainless steel:

Education is the EC 1: steel type AISI 304L

Sample 2: steel type AISI 310L

The composition of these steels are given in table I

Table I
The composition of the metal304L310L
wt. -%
0,0150,017
S0,0020,006
P0,0250,019
Si0,2480,14
Mn1,6900,593
Cr18,41024,29
Ni10,48021,62
Mo0,125MX 0.317
Cu0,0690,167
N--
Febal.bal.
(bal. means up to 100%)

The results are shown in table II:

Table II
Sample12
Originalroughness Ra (μm)<0,1<0,1
the loss of thickness (µm/AP)00
400 hoursroughness Ra (μm)0,5<0,1
the loss of thickness (µm/AP)90<5
800 hoursroughness Ra (μm)1,90,2
the loss of thickness (µm/AP)130<20
1200 hoursroughness Ra (μm)2,80,2
the loss of thickness (µm/AP)130<5
1600 hoursroughness Ra (μm)4,10,3
the loss of thickness (µm/AP)230<20
2000 hoursroughness Ra (μm)the 4.70,3
the loss of thickness (µm/AP)90<5
2400 hoursroughness Ra (μm)the 4.70,3
the loss of thickness (µm/AP)140<5

The above results show that the roughness of the sample 2 according to the invention varies very little over time compared with the measured Shirokov what lead when using steel type 304L (sample 1). This feature illustrates the fact that the use of steel type 310L according to the invention allows to maintain over time a good surface condition in the reaction conditions in question, and, therefore, to limit the phenomenon lining.

Moreover, the above results show that the corrosion resistance (loss of thickness) steel type 310L in the environment, obtained by oxidation with nitric acid a mixture of cyclohexanone/cyclohexanol (invention), has increased.

1. Installation for the crystallization of adipic acid, containing a reservoir for crystallization, equipped with means for stirring, means for cooling and/or concentrating the solution of adipic acid, characterized in that at least part of the walls of the vessel for crystallization and/or means for cooling and/or concentrating in contact with a solution of adipic acid, made from a material selected from austenitic stainless steels of type AISI 310L in accordance with the nomenclature A1SI (USA) or XlCrNi25-21 (1.4335) in accordance with the European nomenclature.

2. Installation according to claim 1, characterized in that the solution of adipic acid is a solution obtained by oxidation of a mixture of cyclohexanone/cyclohexanol with nitric acid.

3. Installation according to any one of claims 1, 2, characterized in that it includes a device for cooling of the solution, providing for circulation of a fluid coolant, and these devices are made of austenitic stainless steel type AISI 310L.

4. Installation according to any one of claims 1 to 2, characterized in that at least the inner part of the walls of the vessel for crystallization is made of austenitic stainless steel type AISI 310L.

5. Installation according to any one of claims 1 to 2, characterized in that the concentration of the solution is achieved by creating a moderate pressure in the vessel for crystallization.

6. Installation according to claim 1, characterized in that the surface of the walls of the device according to the invention, made of austenitic stainless steel type AISI 310L is polished.

7. Installation according to claim 6, characterized in that the polished surface is made of austenitic stainless steel type AISI 310L, have a roughness less than 0.3 μm, measured according to the method specified in the standards NF EN ISO 3274 and NF EN ISO 4288.



 

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FIELD: chemistry.

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20 cl, 2 ex, 2 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to a carboxylic acid synthesis method. The invention specifically relates to a method for synthesis of carboxylic acids through oxidation of a hydrocarbon with oxygen or an oxygen-containing gas, and more specifically to oxidation of cyclohexane to adipinic acid. According to the invention, the method involves a step for oxidising the hydrocarbon and at least one step for extracting the formed dicarboxylic acids from the reaction medium and, in known cases, return unconverted hydrocarbon and oxidation by-products such as ketones and alcohols which may be formed to the reaction. The disclosed method also includes a step for conversion, separation or extraction of α,ω-hydroxycarboxylic compounds formed during oxidation. This step for conversion, separation or extraction of α,ω-hydroxycarboxylic compounds involves oxidation of medium containing the said compounds in order to convert them to dibasic acids.

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3 cl, 7 ex, 1 tbl

FIELD: chemistry.

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13 cl, 5 dwg, 11 ex

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16 cl, 5 ex

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13 cl, 5 ex

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8 cl, 11 tbl, 26 ex

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16 cl, 1 ex

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112 cl, 30 dwg, 4 tbl

FIELD: chemistry.

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EFFECT: high efficiency of production and purification, simple process.

2 cl, 1 dwg, 1 tbl, 11 ex

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing potassium acetate by reacting potassium hydroxide with aqueous acetic acid solution and subsequent steps for treating the obtained potassium acetate. The method involves filtration treatment of the obtained potassium acetate solution, evaporation of the filtrate at 105-115°C, cooling to 55-65°C and vacuum crystallisation. The method is characterised by that the starting products used are crystalline potassium hydroxide and 40-60% acetic acid, which is added to potassium hydroxide in 30-35% stoichiometric excess and while keeping temperature of the reaction mass at 80-90°C, and that the potassium acetate crystals formed after the vacuum crystallisation step are further centrifuged at 500-2000 rpm and then vacuum dried at 145-155°C.

EFFECT: method enables to obtain a highly pure product with minimal content of heavy metal impurities.

1 cl, 2 tbl, 11 ex

FIELD: chemistry.

SUBSTANCE: method of separating acrylic and benzoic acid contained in a gas mixture of products of partial oxidation into acrylic acid, during which acrylic and benzoic acid are first converted to a liquid phase from which, using a thermal separation technique, components with lower boiling point than benzoic and acrylic acid are then separated and acrylic acid is then separated from the remaining liquid phase by crystallisation. The method does not require energy consuming separation techniques. There is basically no fusion of benzoic acid into a crystal during crystallisation, which forms the basis of marked efficiency of the procedure according to the disclosed method.

EFFECT: less energy consuming separation technique.

22 cl, 1 ex, 1 tbl

FIELD: chemistry.

SUBSTANCE: invention relates to improved methods of producing aromatic carboxylic acids, involving bringing material containing at least one initial substituted aromatic hydrocarbon, where the substitutes are oxidisable to carboxylic acid groups, with oxygen gas in a liquid-phase oxidation reaction mixture containing a monocarboxylic acid as a solvent and water, in the presence of a catalyst composition containing at least one heavy metal, which is effective for catalysing oxidation of the substituted aromatic hydrocarbon to an aromatic carboxylic acid, in a reaction section at high temperature and pressure, effective for keeping the liquid-phase oxidation reaction mixture in a liquid state and forming an aromatic carboxylic acid, and impurities containing by-products of oxidation of the initial aromatic hydrocarbon, which are dissolved or suspended in the liquid-phase oxidation reaction mixture, and a high-pressure vapour phase containing a solvent - monocarboxylic acid, water and small amounts of the initial aromatic hydrocarbon and by-products; transferring the high-pressure vapour phase from the reaction section into a separation section sprinkled by a liquid reflux containing water and capable of almost completely separating the solvent - monocarboxylic acid and water in the high-pressure vapour phase to form a liquid rich in solvent - monocarboxylic acid and depleted of water, high-pressure gas containing water vapour; transferring the high-pressure gas containing water vapour from the separation section without processing to remove organic impurities into a condensation section and condensation of the high-pressure gas to form a liquid condensate containing water and exhaust gas from the condensation section under pressure, containing non-condensed high-pressure gas components, transferred into the condensation section; removal from the condensation section of a liquid condensate containing water and suitable for use without further processing as at least one liquid containing water in a method of purifying aromatic carboxylic acids; and feeding the liquid condensate containing water removed from the condensation section during purification of aromatic carboxylic acids in which at least one step includes: (a) preparing a purification reaction solution containing an aromatic carboxylic acid and impurities which are dissolved or suspended in a liquid containing water; (b) bringing the purification reaction solution containing aromatic carboxylic acid and impurities in the liquid containing water, at high temperature and pressure, into contact with hydrogen in the presence of a hydrogenation catalyst to form a liquid purification reaction mixture; (c) separating the solid purified product containing carboxylic acid from the liquid purification reaction mixture containing aromatic carboxylic acid and impurities in the liquid containing water; and (d) using at least one liquid containing water to wash the obtained purified solid aromatic carboxylic acid separated from the liquid purification reaction mixture containing aromatic carboxylic acid, impurities and the liquid containing water; such that the liquid containing water on at least one step of the purification method contains a liquid condensate containing water and which needs processing to remove organic impurities.

EFFECT: invention also relates to apparatus for producing aromatic carboxylic acids.

44 cl, 2 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to an improved method of drying aromatic carboxylic acid, involving drying of aromatic carboxylic acid precipitate using a fluidised bed drier, where the precipitate is fed into the drier at a rate of 50 kg/h or higher, and a drying gas at temperature 80-160°C is fed into the drier with reduced speed of 0.3-1 m/s, so that content of liquid in the precipitate is equal to or less than 14 wt %; as well as to an improved method of obtaining dry aromatic carboxylic acid, involving continuous drying of aromatic carboxylic acid precipitate using a fluidised bed drier to obtain ready aromatic carboxylic acid, where the precipitate is fed into the drier at a rate of 50 kg/h or higher, and drying gas at temperature 80-160°C is fed into the drier at reduced speed of 0.3-1 m/s so that content of liquid in the precipitate is equal to or less than 14 wt %. The aim of the invention is to develop a method of drying aromatic carboxylic acid and a method of drying aromatic carboxylic acid, each method solving problems associated with use of a fluidised bed drier, such as clogging by crystals or aromatic carboxylic acid crystals sticking in the drier, and low efficiency of the drier.

EFFECT: ensuring stable operation of a fluidised bed drier.

8 cl, 5 dwg, 1 tbl, 3 ex

FIELD: chemistry.

SUBSTANCE: invention relates to an improved method of recovering energy during production of aromatic carboxylic acids via liquid phase oxidation of aromatic hydrocarbons wherein vapour containing reaction solvent and water forms in the top part of the reactor, and the method comprises the following steps: a) high efficiency separation of the vapour from the top part of the reactor to form at least a high-pressure gas stream containing water and organic impurities; b) recovering heat of the high-pressure gas stream via heat exchange with a heat sink, where a condensate forms, said condensate containing approximately 20-60 wt % water, present in the high-pressure gas stream, and high-pressure exhaust gas containing approximately 40-80 wt % water present in the high-pressure gas stream, remains uncondensed and temperature or pressure of the heat sink increases; and c) expansion of the high-pressure exhaust gas which is uncondensed at step (b), containing approximately 40-80 wt % water, present in the high-pressure gas stream, in order to recover energy of the high-pressure exhaust gas in form of work; and d) directing the heat sink, whose temperature and pressure increases at step (c), to another step of the method for heating or using outside the method. The invention also relates to a method of producing aromatic carboxylic acids with energy recovery and a device for recovering energy.

EFFECT: invention significantly lowers power consumption during production of aromatic carboxylic acids.

16 cl, 3 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing isophthalic acid and other by-products - terephthalic and benzoic acid, based on oxidation of a mixture of xylene isomers and monoalkylbenzenes contained therein with an oxygen-containing gas in the medium of acetic acid in the presence of a catalyst which contains heavy metal salts and halides at high temperature and pressure to a defined degree of conversion of said isomer mixtures to isophthalic acid and by-products, followed by purification and separation of isophthalic acid and by-products via re-crystallisation in a solvent, wherein said oxidation process is carried out in two steps with increasing concentration of the Co-Mn catalyst on the steps, promoted by halides in form of HBr in equimolar ratio to metals in the range of 800-1200 ppm at temperature 150-200°C and discrete stepwise reduction of pressure in the range of 1.8-1.2 MPa with pressure drop gradient between steps of 0.2-0.6 MPa; purification and separation of the mixture of isophthalic and by-product benzene-carboxylic acids is carried out in two steps by extracting impurities via re-crystallisation in acetic acid at temperature 140-230°C at the first step followed by extraction of the purified binary system of isophthalic and terephthalic acid and separation thereof at the second step via dissolution in water at temperature 220-230°C and stepwise selective crystallisation and extraction of terephthalic acid at temperature 180-195°C, and isophthalic acid at temperature 60-100°C.

EFFECT: improved quality of isophthalic acid and by-products and high efficiency of the synthesis process.

10 cl, 12 ex, 3 tbl

FIELD: chemistry.

SUBSTANCE: method of extracting acrylic acid from a liquid phase uses acrylic acid as the main component and desired product and methacrolein as the by-product, where the liquid phase used is obtained via at least one fuzzy separation from a gaseous mixture of products of gas-phase partial oxidation on a heterogeneous catalyst of at least one tri-carbon precursor of acrylic acid, where the liquid phase is crystallised with enriched acrylic acid in the formed crystallised product and methacrolein in the residual liquid phase.

EFFECT: method enables efficient separation of methacrolein from acrylic acid.

14 cl, 1 ex, 1 tbl

FIELD: chemistry.

SUBSTANCE: present invention refers to the method for preparation of aloe-emodin, and rein or diacerein used for treatment of the diseases concerned with anomalous dystrophy of connective tissues. The method for preparation of aloe-emodin includes oxidation of aloin dissolved in the polyatomic alcohol with oxygen-containing gas in the presence of acid. The method for preparation of rein or diacerein includes the following stages: a) oxidation of aloin dissolved in the polyatomic alcohol with oxygen-containing gas in the presence of acid to aloe-emodin; b) oxidation of aloe-emodin with chrome-free oxidising media to rein; c) purification of the rein obtained on the stage b) and d) optional acetylation of the rein obtained on the stage c) with acetylation agent to diacerein. The claimed method allows obtaining of aloe-emodin with good yield and purity level without using of toxic or harmful substances and complicated purification methods.

EFFECT: claimed method allows also diacerein obtaining without using of hexavalent; chrome as oxidiser and without complicated purification methods.

17 cl, 1 tbl, 5 ex

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