Method of preparing adipic acid crystals and thus obtained crystals

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

 

The present invention relates to a method for producing crystals of adipic acid, and the resulting crystals.

It is, in particular, relates to a method for processing crystals of adipic acid, obtained after crystallization to obtain crystals with minimal caking during storage.

Adipic acid is an important intermediate product, in particular in the field of polymers and mainly of polyamide and in the synthesis of polyurethanes. She also finds other uses as additives, for example, in detergent compositions.

Adipic acid is usually produced by oxidation of a mixture of cyclohexanone/cyclohexanol with nitric acid in the presence of oxidation catalysts, such as vanadium and copper.

Adipic acid is isolated and then purified by successive stages of crystallization. The crystallization is usually conducted in the aquatic environment.

When carrying out these steps adipic acid is separated, in particular, formed from other dicarboxylic acids such as glutaric, and succinic acid.

Crystals of adipic acid, obtained after crystallization, typically have an elongated shape and may have an uneven surface.

After washing and drying these crystals is usually stored in barrels, bags or containers large R is smera and can be delivered to the places of their use, for example, equipment for production of polyamide or hexamethylenediisocyanate.

During storage and transportation is sliianie, i.e. bonding of multiple crystals between them. This phenomenon creates a difficulty, as it greatly reduces the flowability of adipic acid during boot crystals on the installation, for example, to obtain polyamides.

In the patent US 5471001 proposed an original method for the crystallization of adipic acid using ultrasound. The obtained crystals have better flowability and lower "caking during storage and transport.

In the application for French patent 2795721 also proposed a method of processing crystals for modification of their surface, in order to reduce the ability to caking.

However, in these methods, you must use these types of treatments, which require significant investment and may result in a reduction of the yield of adipic acid.

One of the objectives of the present invention is to develop a method of obtaining crystals of adipinic acid, which would have minimal caking during storage and good flowability during loading or unloading of containers or containers in which they are contained.

Thus, the first object of the present invention are crystals of adipic acid obtained is haunted by crystallization or processed in the aquatic environment, and which can be stored for a long period of time in containers or in containers that are sealed against moisture environment, without the risk of caking, agglomerating or gluing crystals. When using the crystals adipinic acid according to the invention are exempt containers for storage or for transportation of crystals. This greatly facilitates the use of adipic acid.

In accordance with the invention, the crystals of adipic acid are characterized in that the content of the exchange of water in them is less than or equal to 100 ppm, preferably less than 50 h/million

Under exchange water see the water contained in the crystals, which migrates to the surface of the crystals during storage. Crystals of adipic acid may also contain water, called "enabled" water, which is formed by incorporating a certain amount of crystallization solution in which crystal formation or processing. This water is usually not an exchange, i.e. it does not migrate to the surface of the granulate in the absence of external influences.

Another feature of the crystals according to the invention is that the total water content in the granulate must be greater than the content of the exchange of water for at least 20 hours per million, Preferably, the difference is the t of about 30 ppm to 2000 ppm, mostly from 50 to 1000 h/million

The amount of water exchange in the mass of crystals is determined by the following method:

The analyzed powder or crystals with a mass in the amount of 300 g was placed in a hermetically sealed container with high tightness to the environment. Container capacity is 500 ml Over the analyzed powder or crystals, or they put a substance that absorbs moisture, which are crystals of silica gel (about 2 g). Specified absorbent substance is placed in a watch glass to avoid any contact between different substances. Analyzed products and absorbent substance is kept in a tightly closed container for 24 hours under ambient temperature and pressure, i.e. at atmospheric pressure and at a temperature of from about 5°to 25°C.

After 24 hours, weighed absorbent substance. Correction of the difference in weight of the exercise by the difference between the mass obtained in idle experience, which is carried out in parallel under the conditions described above, but in which any of the analyzed powder or crystals in the container is not placed.

The true difference in mass, i.e. the difference after correction is taken as the number of exchange of water contained in the analyzed powder or crystals and will is placed an absorbent substance. It is expressed in parts per million (ppm) relative to the mass of powder or crystals placed in the container.

The total water content in the crystals is determined by the following method.

The analysis is performed in the cell DSC7 company Perkin-Elmer in the following operating conditions:

- the speed of temperature rise 5°C/min

the sample holder: aluminum capsule in the frame

the sample for analysis: approximately 20 mg

- lowering the temperature to -50°With its subsequent increase to 25°C.

The observed endothermic peak at a temperature rise occurs at a temperature of 0°and corresponds to the transition of the solid/water contained in the crystals. The measured enthalpy difference count in the total water content. The total water content expressed in parts per million relative to the mass of crystals.

Another object of the present invention is a method of obtaining crystals of adipic acid, having the specified properties.

This method lies in the fact that the crystals of adipic acid, obtained by crystallization, is subjected to maturation. Specified maturation is that the crystals are maintained at a temperature in the range from 10°C to 80°C in an atmosphere with an absolute humidity of less than 20 g in one normal cubic meter, within the time required on the I removal of at least the greater part of the exchange of water, contained in the crystals. In other words, the ripening determine thus to get the content of the exchange of water in the crystals less than 100 ppm, preferably less than 50 ppm, as described above.

In the method according to the invention uses funds to maintain the absolute humidity of the environment in which keep the crystals at the level of less than 20 grams per normal cubic meter of gas, for example air. Absolute humidity is supported at the level less than 10 g per normal cubic meter of air. Such means are, for example, means to absorb moisture, such as hygroscopic substances, such as silica gels, or the use of dry gas such as dry air, which periodically or continuously updated.

Alternatively, the implementation stage of maturation, in accordance with the invention can result, for example, storing crystals in the container with the blowing of the upper part of the container by the flow of dry air or a flow of dry air through the mass of crystals. In the specified last embodiment of the invention, crystals can form a stationary layer, through which passes a flow of air, or "pseudocyesis layer, if the flow rate of air is sufficient to cause the crystals in motion.

The stage of maturation Chris who allow can also be made by placing them in an unpressurized container, that is, at least, allowing the moisture contained in the crystals to evaporate into the atmosphere surrounding the container, or, more preferably, allowing only the evaporation of moisture on the outside of the container and preventing the penetration of moisture into the specified container.

Containers can be placed either in a closed chamber having an atmosphere with a controlled relatively low absolute moisture content, with the aim of exchange evaporation of water contained in the crystals or in the outdoor camera with updating atmosphere, so that it had a fairly low value absolute humidity, with the aim of evaporation of water exchange.

Estestvenno that it is possible to combine these different ways of carrying out the invention without going beyond the borders of the present invention.

In addition, the description of the various embodiments ripening stages are provided solely to illustrate and not limit the present invention.

Crystals of adipic acid, treated according to the method of the invention are usually obtained by crystallization from an aqueous solution of adipic acid.

In addition, methods of producing adipic acid usually contain a purification step of adipic acid, which is the crystallization of the acid from the water. This crystallization can be carried out in ODI is or several successive stages of crystallization.

Adipic acid, isolated by filtration or by centrifugation, has the form of crystals with more or less significant size and irregular shape. The size distribution of the crystals can be both wide and narrow.

Crystals can also be subjected to one or more washings with water. Finally, the crystals are dried, then stored in containers or containers for transportation or loading at the place of their use.

In accordance with the method according to the invention, the crystals of adipic acid, after drying, is subjected to the above-described stage of ripening. However, the dried crystals can be stored and be subjected to a stage of maturation before they are Packed in shipping containers. Stage of maturation can also be carried out during transport of these crystals with the use of appropriate containers, for example containers, sealed against external moisture, but providing the evaporation of water exchange, or containers that maintain an atmosphere with a low absolute humidity. In accordance with a preferred embodiment of the invention the stage of maturation of the crystals is carried out before their packaging for transportation, while this package is used in sealed containers to avoid moisture.

For this reason it is Italy adipic acid, obtained in the method according to the invention have good flowability and very low caking that allows you to easily release the containers, facilitating control of the flow of crystals of adipic acid on a different setup where they are used.

Thus, it is possible to store and transport these products for a long time and in an uncontrolled atmospheric conditions.

The invention is illustrated in the examples for clarification.

Example 1

6-liter container placed 4 kg of adipic acid in the form of crystals with an average size of 450 microns with the content of the exchange of water, defined in accordance with the described methodology, about 150 h/million Above the layer of crystals placed in a watch glass with 5 g of desiccant (silica gel). The container tightly closed. After 24 hours of maturation at room temperature (20-25° (C) observe that various processed parties are good, i.e. after storage in a closed vessel for several weeks no sticking of the crystals are not installed. The content of the exchange of water treated crystals, determined using the above test, is less than 10 ppm, and the total water content is 900 h/million

Comparative example 2

Study storage adip the new acid, not subjected to any maturation in the above-described airtight container, identifies numerous sticking of the crystals between them, which prevent easy extraction of crystals from the container during storage.

Example 3

1.4 kg of adipic acid in the form of crystals with an average size of 330 μm and a content of the exchange of water of 150 ppm, determined by the method described above, is placed in a closed glass column (diameter 75 mm, height 1 m). After standing for several hours the crystals stick together, and the column cannot be released by the natural precipitation of crystals.

Contained in the column, the product was incubated for about 15 hours in the column and then subjected to several minutes fluidization using dry air. After keeping the specified processed acid in an airtight container for storage in a few weeks no sticking of the crystals is not installed. The content of the exchange of water determined by the method described above, is less than 10 ppm, and the total water content is 920 h/million

Example 4

500 kg of crystals of adipic acid with an average size of 420 μm and the content of the exchange of water 130 ppm, which is determined by the above method, fill a leaky bag (woven material) and leave at room the Oh temperature (12-25° C) and normal pressure (relative humidity outside is changed depending on a temperature in the range from 40 to 50%) [specify values of absolute humidity].

The humidity sensors placed on the product, allow to monitor the relative moisture content within the product. After several hours of storage sets the balance between the absolute humidity outside and the absolute humidity inside the bag. In these storage conditions no sticking of the crystals is not installed. The content of the exchange of water in these crystals is less than 20 ppm, and the total water content is 910 h/million

In contrast, storage in airtight bags at the same temperature and humidity leads to significant agglomeration. The analysis of the content of the exchange of water in these crystals shows that it has not changed.

Example 5

Holding maturation and removal of metabolic water (blow dry gas) from the same batch of crystals of adipic acid with an average size of 320 μm and the initial content of 120 ppm water exchange carried out according to methodology described in the present description.

20 tons of crystals of adipic acid with an average size of 320 μm and the content of the exchange of water 120 ppm is poured into the container with bag, hard permeable to moisture in gases (less than 1 g/m3). The upper part is of ontainer (with a size of 20 m 2) blow dry gas (400 normal cubic meters per hour) for 10 days. After the termination of the specified processing and closing of the bag product is not deformed, and the container can easily be free (at least for an hour) after two months of transportation. Absolute humidity during transportation is less than 10 g/m3the content of the exchange of water in the crystals at the outlet of the reservoir is less than 10 ppm, and the total water content is 890 h/million

1. Crystals of adipic acid, characterized in that the content of the exchange of water is less than 100 ppm, and the content of the exchange water is determined based on 300 g of crystals of adipic acid, which is placed in a hermetically sealed container, purged with dry air, with 2 g of a water absorbing substance, maintaining the temperature in the container for 24 h in the interval from 5°to 25°and the water content will be equal to the amount of water absorbed absorbent substance, per 1 g of the crystals, as well as the that the total water content exceeds the content of the exchange of water for at least 20 h/million

2. The crystals according to claim 1, characterized in that the content of the exchange of water is less than 50 h/million

3. The crystals according to any one of claims 1 and 2, characterized in that the difference between total water content and content of the exchange of water the leaves from 30 ppm to 2000 h/million

4. The method of producing crystals of adipic acid according to any one of claims 1 to 3, characterized in that the crystals of adipic acid, obtained by crystallization from aqueous medium or treated with an aqueous solution, is subjected to a maturing stage, which is that the crystals are maintained at a temperature in the range from 10°C to 80°C for the time necessary to ensure that the content of the exchange of water in the crystals was less than 100 ppm, in the presence of means to maintain the absolute humidity of the environment around the crystals at the level of less than 20 grams per normal cubic meter.

5. The method according to claim 4, characterized in that the crystals are placed in the chamber together with means to reduce or maintain the absolute humidity environment inside the chamber at the level of less than 20 grams per normal cubic meter per period of time sufficient to obtain a constant absolute humidity content in the above environment.

6. The method according to claim 5, characterized in that the means to maintain or reduce the absolute humidity of the specified environment is a means of permanent or periodic updates of the environment of the crystals to exchange on Wednesday, with an absolute humidity of less than 20 grams per normal cubic meter.

7. The method according to claim 6, characterized in that the flow of dry air is passed through the mass of crystals.

8. JV the property according to claim 7, characterized in that the gas is dry air.

9. The method according to claim 5, characterized in that the means to maintain or reduce the absolute humidity environment contains a device for absorption of the specified moisture, placed in the chamber.

10. The method according to claim 9, characterized in that the device for absorbing moisture contains a compound absorbing moisture.

11. The method according to any of claims 4 to 10, characterized in that the means to reduce or maintain the absolute humidity contains the update tool environment and device for absorption of moisture.

12. The method according to any of claims 4 to 10, characterized in that the chamber containing the crystals, includes container, removes the moisture from the inside out and removes the moisture from the outside in.

13. The method according to any of claims 4 to 10, characterized in that the stage of ripening is carried out before packaging crystals of adipic acid in containers for storage and transportation, impervious to moisture of the surrounding air.



 

Same patents:

FIELD: industrial organic synthesis.

SUBSTANCE: invention relates to improved method for production of carboxylic acids and polyacids via liquid-phase oxidation of cyclohexane with molecular oxygen in presence of catalyst: lipophilic acidic organic compound with solubility in water below 10 wt % at 10-30°C, which forms with cyclohexane at least one homogenous liquid phase. Molar ratio of lipophilic acid to catalyst-forming metal lies within a range of 7.0 to 1300. Lipophilic acid is selected from group consisting of 2-ethylhexanoic, decanoic, undecanoic, stearic acids and permethylated derivatives thereof, alkyl(preferably tert-butyl-type)substituted 2-octadecylsuccinic, 2,5-di-tert-butylbenzoic. 4-tert-butylbenzoic, 4-octylbenzoic, tert-butylhydro-o-phthalic, naphthenic, and anthracenic acids, fatty acids, and substituted phthalic acid derivatives.

EFFECT: simplified separation and recycling of oxidation intermediates and catalyst as compared to methods wherein acetic acid is used as solvent.

8 cl, 11 tbl, 26 ex

The invention relates to an improved method for the oxidation of cyclic hydrocarbons, alcohols and/or ketones to carboxylic acids with oxygen or oxygen-containing gas

The invention relates to an improved method of processing the reaction mixture obtained by direct oxidation of cyclohexane to adipic acid, in liquid phase, in a solvent and in the presence of dissolved in the reaction medium, catalyst, including decantation two liquid phases: upper non-polar phase containing mainly unreacted cyclohexane, and the lower polar phase containing mainly solvent, adipic acid and the resulting acid, the catalyst and other reaction products and unreacted hydrocarbons, distillation of the lower polar phase or, if necessary, the entire reaction mixture with obtaining, on the one hand, distillate, containing, at least a part of the most volatile compounds such as unreacted cyclohexane, the solvent, the intermediate reaction products and water, and, on the other hand, residue from distillation, containing adipic acid and the resulting carboxylic acid, the catalyst, and the method includes a step of adding to the residue after distillation of the organic solvent in which adipic acid has a solubility less than or equal to 15 wt

The invention relates to an improved method of isolation and purification of adipic acid, used for the production of polyamide-6,6 or polyurethanes, which consists in treating the reaction mixture obtained by direct oxidation of cyclohexane to adipic acid by molecular oxygen in an organic solvent and in the presence of a catalyst, removing by-products from the reaction mixture and the adipic acid by crystallization, and before adipic acid from the reaction environment carry out consistently the following operations: the decantation of the two phases of the reaction medium with the formation of the upper organic the cyclohexane phase, containing mainly cyclohexane, and the lower phase, containing mainly the solvent, the resulting dicarboxylic acid, the catalyst and other reaction products and unreacted cyclohexane; distillation bottom phase to separate, on the one hand, distillate containing at least a part of the most volatile compounds, such as organic solvent, water and unreacted cyclohexane, cyclohexanone, cyclohexanol, complex cyclohexylamine esters and possibly lactones, and, with the pin acid from residue from distillation by means of crystallization and thus obtained crude adipic acid is subjected in aqueous solution purification by hydrogenation and/or oxidation with subsequent crystallization and recrystallization of the purified adipic acid in water

The invention relates to an improved method for producing crystals of adipic acid used in the production of polymers, for example, to obtain a polyamide or polyurethanes
The invention relates to an improved method of direct oxidation of hydrocarbon selected from cycloalkanes, the cycle which contains from 5 to 12 carbon atoms to carboxylic acid using oxygen or oxygen-containing gas in the liquid phase in a solvent selected from the proton polar and aprotic solvents, in the presence of a catalyst soluble in the reaction medium, the catalyst contains at least one soluble compound of cobalt, and at least one soluble chromium compound, and the molar ratio between chromium and cobalt in the catalyst is from 0.001 to 100, preferably from 0.01 to 10
The invention relates to an improved method of liquid-phase oxidation of cycloalkanes, cycloalkanones and/or cycloalkanones to carboxylic acids, in particular cyclohexane to adipic acid used to obtain the polyamide 6-6
The invention relates to a method of producing crystallization dicarboxylic acids from a solution containing not less than one organic dicarboxylic acid, by adding to the solution until crystallization or during crystallization, at least one anionic polyelectrolyte with a molecular weight of at least 2,000, preferably from 100000 to 500000, in the amount of from 0.01 to 200 h

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 invention relates to an improved method of reducing the content of 4-carboxybenzene in the production of terephthalic or 3-carboxymethylthio in the production of isophthalic acid, comprising: (a) dissolving crude terephthalic acid or crude isophthalic acid in a solvent at a temperature of from 50 to 250With obtaining a solution; (b) crystallization of the purified acid from this solution by reducing the temperature and/or pressure; (C) the Department specified crystallized terephthalic acid or isophthalic acid from the solution; (d) adding an oxidant to the reactor oxidation carboxyanhydride for oxidation specified filtered solution of stage (C), leading to the transformation of 4-carboxybenzene or 3-carboxymethylthio in terephthalic acid or isophthalic acid; (e) evaporating the solvent from this solution from step (d); (f) cooling the concentrated solution from step (e) for crystallization additional quantities of purified terephthalic acid or isophthalic acid and filtering the specified slurry and recycling the most part, the mother liquor from step (f) in the devices is

The invention relates to an improved method of processing the reaction mixture obtained by direct oxidation of cyclohexane to adipic acid, in liquid phase, in a solvent and in the presence of dissolved in the reaction medium, catalyst, including decantation two liquid phases: upper non-polar phase containing mainly unreacted cyclohexane, and the lower polar phase containing mainly solvent, adipic acid and the resulting acid, the catalyst and other reaction products and unreacted hydrocarbons, distillation of the lower polar phase or, if necessary, the entire reaction mixture with obtaining, on the one hand, distillate, containing, at least a part of the most volatile compounds such as unreacted cyclohexane, the solvent, the intermediate reaction products and water, and, on the other hand, residue from distillation, containing adipic acid and the resulting carboxylic acid, the catalyst, and the method includes a step of adding to the residue after distillation of the organic solvent in which adipic acid has a solubility less than or equal to 15 wt

The invention relates to an improved method of isolation and purification of adipic acid, used for the production of polyamide-6,6 or polyurethanes, which consists in treating the reaction mixture obtained by direct oxidation of cyclohexane to adipic acid by molecular oxygen in an organic solvent and in the presence of a catalyst, removing by-products from the reaction mixture and the adipic acid by crystallization, and before adipic acid from the reaction environment carry out consistently the following operations: the decantation of the two phases of the reaction medium with the formation of the upper organic the cyclohexane phase, containing mainly cyclohexane, and the lower phase, containing mainly the solvent, the resulting dicarboxylic acid, the catalyst and other reaction products and unreacted cyclohexane; distillation bottom phase to separate, on the one hand, distillate containing at least a part of the most volatile compounds, such as organic solvent, water and unreacted cyclohexane, cyclohexanone, cyclohexanol, complex cyclohexylamine esters and possibly lactones, and, with the pin acid from residue from distillation by means of crystallization and thus obtained crude adipic acid is subjected in aqueous solution purification by hydrogenation and/or oxidation with subsequent crystallization and recrystallization of the purified adipic acid in water

The invention relates to an improved process for the preparation of terephthalic and isophthalic acids

The invention relates to an improved method for producing isophthalic acid used in copolymerization ways of producing fibers, films, plastic bottles and structures made of polyester resin, which consists in the oxidation of metaxalone in the reaction solvent to obtain a liquid dispersion

The invention relates to chemical technology of obtaining low molecular weight aliphatic acids, which are valuable raw materials for the chemical, petrochemical and forestry industry

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 invention relates to a method of purification of adipic acid, which is used to obtain polyamide

The invention relates to a technology for technical formate sodium from aqueous solution technical Chlorella, which is a waste product of chloroform
The invention relates to a method of catalytic hydroxycarbonylmethyl pentenoic acid to adipic acid

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

Up!