Methods of drying aromatic carboxylic acid and methods of obtaining dry aromatic carboxylic acid

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

 

The technical FIELD TO WHICH the INVENTION RELATES.

The present invention relates to a method of drying aromatic carboxylic acids and methods of producing dry aromatic carboxylic acid.

The LEVEL of TECHNOLOGY

Aromatic carboxylic acids are used, for example, as raw materials for synthesis of the polyester and they are usually obtained by oxidation of alkylaromatic compounds.

The stage of obtaining terephthalic acid as a typical example, aromatic carboxylic acids, are explained below.

To obtain the crude terephthalic acid is generally used method, is shown in figure 1. First used as raw material of p-xylene B are oxidized in a solvent consisting of acetic acid, A, in the oxidation reactor 1 with obtaining the crude terephthalic acid. The liquid reaction mixture is usually subjected to crystallization in the crystallizer 2 accessing primary suspension C, containing crude terephthalic acid. This primary suspension C is introduced into the separator the liquid and solid phases 3 and is divided into separated mother liquor D and the wet sediment that is, This wet precipitate E dried in the dryer 4 with obtaining, as a result, crystals of crude terephthalic acid F.

To obtain terephthalic acid of high purity from crude terephthalic acid used method, is shown in Figure 2. First raw Tere is traveling acid, obtained using the above method of producing a crude terephthalic acid, mixed with water b in the vessel for mixing 21 with the receipt of the initial suspension c. This initial suspension c is pumped by a pump 22 and then heated by the heater 23 to complete dissolution. The resulting solution d to restore the hydrogen in the hydrogenation reactor 24 with recovery, as a result, 4-carboxybenzene, which is a typical impurity in the crude terephthalic acid, p-Truelove acid, which is soluble in water. Received the restored e liquid is subjected to cooling in the open air in the mold 25 with the crystallization of the resulting terephthalic acid with obtaining suspension f. This suspension f separated in the separator the liquid and solid phases 26 and the separated mother liquor j and wet sediment (g. This wet precipitate g dried in the dryer 27 with obtaining, as a result, crystals of terephthalic acid of high purity h. Other aromatic carboxylic acids are also obtained by almost the same as the manufacturing steps.

As the dryer 4 and dryers 27 for drying wet precipitation of the aromatic carboxylic acid is often used tubular dryer with steam-heated drum dryer). Tubular dryer with steam heating is a device to the / establishment, which includes a rotating cylinder, equipped with a heat exchanger tube, and in which the substance is dried with heat transferred to the steam passing through the pipe. This device has advantages, manifested, for example, that one can easily solve the problems of the deviations of the liquid content in sediment input due to regulation time. However, the problem is that this device has a very large sizes. Recently there was an increase in the size and capacity of facilities for the production of aromatic carboxylic acids. In accordance with this trend, also increased the size of the tubular dryer with steam heating, and increased its cost and the cost of maintenance. Therefore, a method of drying, which would use less expensive dryer with smaller sizes.

For example, as such a method of drying has been proposed a method that uses a fluidized bed dryer, (patent document 1). However, on the basis of the conducted research, the authors of the present invention have come to the conclusion that when replacing this production stage tube dryer with steam to heat the fluidized bed dryer crystals of the aromatic carboxylic acid adhering to the walls of the dryer fluidized bed, and this leads to the clogging of the nozzle feed suchilin the gas and reduce drying efficiency, and may lead to stoppage of equipment.

Patent document 1: JP-A-2004-315431

Description of the INVENTION

The PROBLEM solved by the INVENTION

The aim of the invention is the development of methods of drying aromatic carboxylic acids and methods of obtaining dry aromatic carboxylic acid, which is solved each of the problems associated with the use of dryers, fluidized bed, such as the adherence of the crystals of the aromatic carboxylic acid in the dryer, and problems, including clogging of the nozzle of the supply of the drying gas, the decrease in the efficiency of drying and stopping equipment, and which results in stable operation of the dryer fluidized bed.

Resolving PROBLEMS

To achieve this goal, the authors of the present invention conducted in-depth research. As a result, they found that these problems occur during operation of the dryer, can be solved by regulating the characteristics of the sediment aromatic carboxylic acid, subjected to drying. And, as a result, it was established the present invention.

Namely, the invention relates to a method of drying an aromatic carboxylic acid, which comprises drying the precipitate aromatic carboxylic acid using the dryer fluidized bed, characterized in that subject pre is sustained fashion to regulate the characteristics of the sludge, in the result, the contents of the liquid in it is 14% by mass or below.

In addition, the invention relates to a method of drying in which drying is carried out in continuous mode.

In addition, the invention relates to a method of drying, in which any residue of the aromatic carboxylic acid is introduced into a fluidized bed dryer at 50 kg/hour or more.

In addition, the invention relates to a drying method in which a drying gas is fed into the fluidized bed dryer at reduced speed from 0.2 to 1 m/sec.

In addition, the invention relates to a method of drying in which drying gas is supplied into the fluidized bed dryer has a temperature of 80-160°C.

In addition, the invention relates to a drying method in which a suspension containing aromatic carboxylic acid is subjected to separation in the system solid-liquid under pressure to get the sediment aromatic carboxylic acid and the precipitate is subjected to instant drying, resulting regulate liquid content in the sediment to 14% by weight or below.

In another aspect the invention relates to a method of drying an aromatic carboxylic acid, which comprises drying the precipitate aromatic carboxylic acid using the dryer fluidized bed, characterized in that they are subjected to ex-ante regulation'hara the indices of sediment, resulting value of flowability sediment is 2000 MJ or below.

In another aspect the invention relates to a method of drying an aromatic carboxylic acid, characterized in that the suspension containing the aromatic carboxylic acid is subjected to separation in the system solid-liquid under pressure to get the sediment aromatic carboxylic acid, the precipitate is subjected to instant drying and then dried sludge using drying and fluidized bed.

In another aspect the invention relates to a method for dry aromatic carboxylic acid, which comprises drying the precipitate aromatic carboxylic acid using the dryer fluidized bed with getting ready aromatic carboxylic acids, characterized in that they are subjected to ex-ante regulation characteristics of the sediment, resulting in fluid content in the sediment is 14% by mass or below.

In addition, the invention relates to a method for, in which drying is carried out in continuous mode.

In addition, the invention relates to a method for, in which any residue of the aromatic carboxylic acid is fed to the fluidized bed dryer at a speed of 50 kg/hour or higher.

In addition, the invention relates to a method for producing, in which the drying gas is fed into the dryer the fluidized bed at the present rate of 0.2-1 m/sec.

In addition, the invention relates to a method for producing, in which the drying gas, which is fed to the fluidized bed dryer has a temperature of 80-160°C.

In addition, the invention relates to the production method, in which a suspension containing aromatic carboxylic acid is subjected to separation in the system solid-liquid under pressure to get the sediment aromatic carboxylic acid and the precipitate is subjected to instant drying with regulation in the liquid content in the sediment to 14% by weight or below.

In addition, the invention relates to a method for, which additionally includes the stage of oxidation of alkylaromatic compounds in a solvent to obtain a suspension of the crude aromatic carboxylic acid, and separating the suspension system, the solid-liquid obtaining sediment aromatic carboxylic acid.

In addition, the invention relates to a method for which further includes recovering the crude aromatic carboxylic acid in a solvent containing water, followed by crystallization of the aromatic carboxylic acid from the obtained liquid reaction mixture to obtain a suspension, and separating the suspension system, the solid-liquid obtaining sediment aromatic carboxylic acid is you.

In yet another additional aspect of the invention relates to a method for dry aromatic carboxylic acid, which comprises drying the precipitate aromatic carboxylic acid using the dryer fluidized bed with getting ready aromatic carboxylic acids, characterized in that they are subjected to ex-ante regulation characteristics of the sediment, resulting in a value of flowability is 2000 MJ or below.

In yet another additional aspect of the invention relates to a method for producing a dry, aromatic carboxylic acids, characterized in that the suspension containing the aromatic carboxylic acid is subjected to separation in the system solid-liquid under pressure to get the sediment aromatic carboxylic acid residue is subjected instant drying and then dried sludge using drying and fluidized bed with getting ready aromatic carboxylic acid.

Advantages of the INVENTION

According to the invention can be suggested ways of drying aromatic carboxylic acids and methods for producing dry aromatic carboxylic acid, which resolves the problems associated with the use of dryers, fluidized bed, such as the adherence of the crystals of the aromatic carboxylic acid in the dryer, and arising in connection with these the violation, including clogging of the nozzle of the supply of the drying gas, the decrease in the efficiency of drying and stopping equipment, and, as a result, achieved stable operation of the dryer fluidized bed. In addition, the fluidized bed dryer can be basically used as a replacement for tubular dryer with steam heating. Therefore, can be achieved by reducing the size of the installation and reducing installation costs and costs of maintenance.

BRIEF DESCRIPTION of DRAWINGS

Figure 1 shows a block diagram illustrating an example of the traditional way obtain a crude terephthalic acid.

Figure 2 shows a block diagram illustrating an example of conventional method of producing terephthalic acid of high purity.

Figure 3 shows a block diagram illustrating one variant of the method of obtaining the crude terephthalic acid according to the invention.

Figure 4 shows a block diagram illustrating one variant of the method of obtaining terephthalic acid of high purity according to the invention.

Figure 5 is a diagram illustrating used in the examples of the fluidized bed dryer.

DESCRIPTION LEGEND

1, 11: reactor oxidation

2, 12: mould

3, 13: separator liquid and solid phases

4: dryer

14: stage regulated the I characteristics of sediment

15: fluidized bed dryer

16: cyclone

17: scrubber

18: a device for the purification of gas

A, A': acetic acid

B, B': p-xylene

C, C': suspension

D, D': separated mother liquor

E, E': the wet sediment

F': sediment with low liquid content

F, G': crystals of crude terephthalic acid
H': drying gas

I': the exhaust gas from the dryer fluidized bed

J': solid

K': coming out of the cyclone gas

L': lessons suspension

M': coming out of the scrubber gas

N': circulating gas

21, 31: vessel for mixing

22, 32: pump

23, 33: heater

24, 34: reactor hydrogenation

25, 35: mold

26, 36: separator liquid and solid phases

27: dryer

27: dryer

37: stage regulation characteristics of sediment

38: fluidized bed dryer

39: cyclone

40: scrubber

41: a device for the purification of gas

a, a': crude terephthalic acid

b, b': water

c, c': the original suspension

d, d': solution

e, e': remove liquid

f, f': suspension

g, g': the wet sediment

h': sediment with low liquid content

h, i': crystals of terephthalic acid of high purity

j, j': separated mother liquor

k': drying gas

l': off-gas from the dryer fluidized bed

m': solid

n': the emergent and the cyclone gas

q': lessons suspension

p': coming out of the scrubber gas

r': circulating gas

51: fluidized bed dryer

52: heater

53: cyclone

54: blower

61: hose precipitate terephthalic acid

62: fitting conclusion crystals of terephthalic acid

63: fitting the supply of the drying gas

64: the fitting conclusion of the drying gas from the drying fluidized bed

65: a fitting conclusion to the exhaust gas from the cyclone

66: the hole for extracting solids

67: steam pipe for indirect heating

The PREFERRED embodiment of the INVENTION

The following is a detailed description of the invention.

In the first embodiment of the invention, before drying the sludge in a fluidized bed dryer and regulate the characteristics of the sludge so that the liquid content in the sediment was 14% by weight or below. Namely, when applied at the appropriate stage of the production of aromatic carboxylic acids dryer fluidized bed govern the characteristics of the sludge so that the liquid content in the sediment was low. The result is prevented adhesion of the crystals of the aromatic carboxylic acid to the inner wall of the dryer.

The fluidized bed dryer is a device, in which the input material is crushed into powder and is also pseudogout using a drying gas. The use of dryers fluidized bed for drying sludge aromatic carboxylic acid has the advantage that as a result of crushing into a powder fluidization and contact sediment aromatic carboxylic acid with gas high efficiency mixing, and sediment can be uniformly dried. Another advantage is that due to the direct contact of sludge with gas is also achieved high efficiency of heat transfer and can be achieved through reduced energy costs. However, it was found that even when an appropriate stage of the production of aromatic carboxylic acids used only a fluidized bed dryer, there are cases when there is unsatisfactory grinding into powder or fluidization of the crystals of the aromatic carboxylic acid in a fluidized bed dryer, and the crystals stick to the inner wall. When the crystals stick in large quantities, there is a probability that can be hammered fitting supply of the drying gas, which reduces drying efficiency.

As a result of research conducted by the authors of the present invention, it was found that when the amount of liquid contained in Vadimom upsetting aromatic carboxylic what islote, reduced to 14% by mass or less, can be reduced consumed by the dryer energy and can be prevented adhesion of the crystals of the aromatic carboxylic acid to the inner wall of the dryer.

In the second embodiment of the invention, before the precipitate is dried in a fluidized bed dryer, is subjected to the regulation characteristics of the sediment, resulting in a value of flowability of the aromatic carboxylic acid is 2000 MJ or less.

The value of flowability means the amount of energy required for fluidization of the powder. The lower the value, the powder is more loose. Conversely, the higher the value, the powder is less bulk. Usually the value of flowability can be determined by using a rheometer for powders by the method in which powder spirally moving the blade, and integrate the force applied to the blades during the movement. The value of flowability expressed in units of amount of work, resulting from the integration.

Preliminary regulation flowability of sediment to the amount of 2,000 MJ or below means that the characteristics of the sediment aromatic carboxylic acids supplied to the fluidized bed dryer at an appropriate stage of manufacture of aromatic carboxylic acids, regulate so, th is would he be, at least to some extent loose. The result can be prevented adhesion of the crystals of the aromatic carboxylic acid to the inner wall of the dryer.

In the third embodiment of the invention the precipitated aromatic carboxylic acid is dried with the dryer fluidized bed, and this residue is a residue obtained by dividing a suspension containing an aromatic carboxylic acid under pressure in the system solid-liquid obtaining sediment aromatic carboxylic acid, and then by instant drying this precipitate. Namely, the separation of suspensions containing aromatic carboxylic acid in the system, the solid-liquid under pressure and then instant drying characteristics of the sludge is pre-adjusted so that it had a low liquid content and low value of flowability. In the result, it is possible to prevent adhesion of the crystals of the aromatic carboxylic acid to the inner wall of the dryer.

The type of aromatic carboxylic acids to which the invention is applicable is not specifically limited. Their examples include o-phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid (benzotriazolyl acid), 2,6 - or 2,7-naphthaleneboronic acid and 4,4'-biphenyldiol the OIC acid. Preferably the application of the invention in the production of isophthalic acid, terephthalic acid, trimellitic acid and naphthaleneboronic acid. Particularly preferred application of the invention in the manufacture of terephthalic acid.

The question of how it was obtained a residue of an aromatic carboxylic acid, the invention is not specifically limited. Solid aromatic carboxylic acid may precipitate obtained by the oxidation of alkylaromatic compounds in a solvent to obtain a suspension of the crude aromatic carboxylic acid and separation of the suspension system, the solid-liquid. Alternatively, the solid aromatic carboxylic acid may be a residue obtained by reduction of crude aromatic carboxylic acid in a solvent containing water, followed by crystallization of the aromatic carboxylic acid from the obtained liquid reaction mixture to obtain a suspension and separation of this suspension system, the solid-liquid. The residue of aromatic carboxylic acids, obtained by the separation in the separator the liquid and solid phases, typically has a liquid content of 15-20% by weight. This sediment has a value of flowability usually from 2000 to 3000 MJ MJ.

Examples of alkylaromatic compounds used as cheese which I for aromatic carboxylic acid, include di - and trialkylated, di - and trialkylated and di - and trialkylsilanes. Their preferred examples include o-xylene, m-xylene, p-xylene, o-, m-, or p-diisopropylbenzene, trimethylbenzene, 2,6 - or 2,7-dimethylnaphthalene, 2,6-aminobutiramida naphthalene and 4,4'-dimethylbiphenyl. Used as raw material alkylaromatic compound may contain one or more partially oxidized alkylaromatic compounds, or may consist only of one or more partially oxidized alkylaromatic compounds.

Each of the partially oxidized alkylaromatic compounds is any of the above alkylaromatic compounds in which the alkyl group was oxidized to the aldehyde group, acyl group, carboxyl group, hydroxyalkyl group and other groups, but which were not oxidized in the desired aromatic carboxylic acid. Their examples include 3-methylbenzaldehyde, 4-methylbenzaldehyde, m-Truelove acid, p-Truelove acid, 3-formylbenzoate acid, 4-formylbenzoate acid and 2-methyl-6-formylation.

They can be used individually or as mixtures of two or more.

Preferred of all these above alkylaromatic compounds are m-xylene and p-xylene. Particularly preferred is p-xylene. If use is of p-xylene as alkylaromatic compounds examples of partially oxidized alkylaromatic compounds include 4-carboxybenzene (hereinafter referred to as "CBA").

This alkylaromatic compound are oxidized in a solvent in the presence of a catalyst to obtain, as a result, an aromatic carboxylic acid. Used solvent is a solvent which does not interact chemically with the alkylaromatic compound or aromatic carboxylic acid. Preferably, the solvent was measured at atmospheric pressure the boiling temperature from 400°C to 200°C, more preferably from 50°C to 180°C, most preferably from 60°C to 150°C. Using a solvent having a boiling point at atmospheric pressure in this range, makes it easy to transport and to extract at each stage not only the reaction medium, and then facilitates the operation of removal of the liquid and drying. In addition, preferably, measured at atmospheric pressure the heat of evaporation of the solvent was 300 kcal/kg or less, more preferably 200 kcal/kg or less, most preferably 150 kcal/kg or less. There is no limit on the amount of the lower limit of the heat of vaporization. Usually, however, the heat of evaporation of the solvent is 50 kcal/kg or more, preferably 70 ADC is/kg or more. Can usually be used a solvent comprising as a main component, carboxylic acid, preferably acetic acid.

The catalyst used in the oxidation reaction, can be any of the known catalysts. However, it is preferable to use cobalt, manganese and bromine. Examples of the compounds include cobalt cobalt acetate, cobalt naphthenate and cobalt bromide. Preferred of them is cobalt acetate. Examples of compounds of manganese include manganese acetate, manganese naphthenate and manganese bromide. Preferred of them is manganese acetate. Examples of compounds of bromine include hydrogen bromide, sodium bromide, cobalt bromide, manganese bromide and bromate. Preferred of them is hydrogen bromide. These compounds can be used in combination. In the solvent, acetic acid may be present other ingredients metals. For example, when the ingredient sodium is present in an amount of from 1 ppm to 100 ppm, it helps to prevent deposition of ingredient manganese and, in addition, improves the transmittance of the obtained terephthalic acid.

The amount of catalyst may be as follows. The number of ingredients used cobalt is usually from 100 mass ppm to 2000 mass ppm of the mass of the process is Italia, preferably from 200 mass ppm to 1000 mass ppm by weight of solvent based on the amount of cobalt metal. The number of ingredients used manganese is usually from 1 mass ppm to 1000 wt. ppm, preferably from 5 mass ppm to 500 wt. ppm. The number of ingredients used bromine is usually from 400 ppm to 2000 ppm. To accelerate the reaction in combination with the catalyst may be used soukissian.

The temperature used for the oxidation reaction, is not specifically limited. However, typically use a temperature not lower than the boiling point of the solvent at atmospheric pressure. Preferably, the temperature was 50°C or higher, more preferably 100°C or higher, more preferably 130°C. or higher. When using the temperature above the lower limit increases catalytic activity and increases output. On the other hand, it is preferable that the reaction temperature was 350°C or below, more preferably to 300°C or lower, more preferably 250°C or below. When using temperatures below the upper limit, the less likely the occurrence of side reactions and decomposition, which increases output.

Typically, the reaction pressure used atmospheric pressure (about 0.1 MPa) or higher, and preferably, it status is ulala 0.2 MPa or higher, more preferably 0.5 MPa or higher, more preferably 1 MPa or higher. When using a pressure above the lower limit can be used in higher temperature, which leads to increased catalytic activity and increase output. On the other hand, usually the reaction pressure is 22 MPa or lower, preferably, it was 20 MPa or lower, more preferably 10 MPa or lower, more preferably 5 MPa or lower, most preferably 3 MPa or lower. When using a pressure below the upper limit is less than the probability of occurrence of side reactions and decomposition, which increases output.

The resulting slurry containing crystals of the crude aromatic carboxylic acid, is subjected to separation in the system solid-liquid receiving, as a result, sediment aromatic carboxylic acid.

Crude aromatic carboxylic acid restores in solvent a transformation, as a result, the intermediate compounds in water-soluble ingredient. As a result, the crystals of the aromatic carboxylic acid of high purity. As a solvent water is most commonly used. The resulting slurry containing crystals of the aromatic carboxylic acid of high purity, is subjected to separation in the system solid-liquid floor with the rising sediment aromatic carboxylic acid.

Crystals of the aromatic carboxylic acid, which deliver a quality product, usually require drying before the liquid content of 0.1 mass% or below. Therefore the residue of an aromatic carboxylic acid, obtained by separation in the system solid-liquid, should be directed to the step of drying and dried. In the first embodiment of the invention, the liquid content in the aromatic carboxylic acid is reduced in advance to 14% by weight or below to prevent sticking of the crystals of the aromatic carboxylic acid in a fluidized bed dryer. Preferably, the liquid content in the aromatic carboxylic acid is reduced to 13% by mass or lower, more preferably 10 mass% or below, most preferably up to 8% by mass or lower. The lower the liquid content in the sediment, the less likely it is that the crystals of the aromatic carboxylic acid will stick in the fluidized bed dryer. However, it is undesirable to excessively lower the liquid content as a significant reduction of the liquid content before submitting it in the dryer requires a significant expenditure. Usually regulate the fluid content in the sediment up to 3% by mass or higher, preferably 5% by mass or higher.

The term "fluid" in the invention means ve is ichino, expressed in mass ratio W1/W2, where W1 is the mass of the liquid (e.g. water or organic solvent)contained in the sediment aromatic carboxylic acid, and W2 is the weight of solids contained in the sludge aromatic carboxylic acid. The main component of solids are usually crystals of the aromatic carboxylic acid. Normal is the following technique. First, determine the mass of sediment (W1 + W2), which is a mixture of liquid and solids. Then the precipitate is heated, for example, in an oven to evaporate and remove liquid substances and determine the mass of the remaining solids (W2). As a result, can be computed the value of W1 and fluid content. When the precipitate, which is heated at atmospheric pressure (about 1 ATM) and at a temperature below the boiling point of the liquid and not higher than the temperature of sublimation of aromatic carboxylic acids (for example, at 150°C), does not undergo the change in mass for 3 minutes or more, consider that the evaporation of liquid left over. When the liquid is water, the liquid content in the sediment can be determined more easily by determining the water content in the sludge by the method of Fisher.

In the second embodiment of the invention to prevent sticking of the crystals of the aromatic carboxylic to the slots in the fluidized bed dryer the amount of the flowability of sediment aromatic carboxylic acid pre-reduce to 2000 MJ or less. In the characteristics of the sludge is adjusted so that it was at least somewhat loose. As a result, can be prevented adhesion of the crystals of the aromatic carboxylic acid to the inner wall of the dryer. Preferably, the amount of the flowability of sediment regulated so that it was 1900 MJ or below, more preferably 1800 MJ or less, even more preferably 1700 MJ or less. On the other hand, a significant decrease in flowability before applying sludge in the dryer requires a high cost. Therefore, it is undesirable to excessively reduce the amount of flowability. Preferably, the amount of the flowability of sediment regulated so that it was 1000 MJ or higher, more preferably 1200 MJ or higher, even more preferably 1400 MJ or higher, most preferably 1500 MJ or higher.

The value of flowability of sediment usually increases with increasing liquid content. Dry aromatic carboxylic acids by liquid content of 0.1% by mass or below a value of flowability usually 1200-1300 MJ, while the aromatic carboxylic acid with the liquid content of 20% by weight have a size flowability about 3000 MJ. As a result of research conducted by the inventors, it was found that the point at which there is a sharp change in the value si is uchesti, corresponds to the liquid content in the range of 10-20% by weight. Suppose that the position of this point depends on different factors for a particular precipitation, including the distribution of particle diameter, particle shape, surface condition of the particles (e.g., charge), and other factors.

Next explains how the sludge drying aromatic carboxylic acid using the dryer fluidized bed. The fluidized bed dryer is a device that enter the drying gas to evaporate the liquid, which is present in the sediment aromatic carboxylic acid, and, as a result, the strip is dried sludge.

Mode dryers fluidized bed in the invention are not specifically limited. Can be used either dryer periodic actions, or dryer continuous action. However, it should be noted that for the dryers fluidized bed continuous action is characterized by the occurrence of sticking, and as they have continuously served the residue of an aromatic carboxylic acid having the phenomenon of adhesion leads to significant negative consequences such as a decrease in the efficiency of drying and stop the installation. Therefore, the invention is very useful in case of applying it to the dryer fluidized bed continuous action. Type dryer with psav origanum layer is also not specifically limited. For example, there may be used a fluidized bed dryer described in the patent document JP-A-2004-315431.

The rate at which sediment aromatic carboxylic acid is fed to the fluidized bed dryer is not limited. However, it should be borne in mind. When sediment is served at low speed, adhesion occurs to a lesser extent, even when the liquid content in the sediment is relatively high. When sediment is served at a higher speed, adhesion occurs to a significant extent. Therefore, the invention is very useful when it is used for drying, in which the precipitate is served with a speed of 50 kg/h (kg / h) or higher. Preferably, the feed rate was more than 150 kg per hour or higher, more preferably 250 kg/HR or more, most preferably 1000 kg/HR or more. Despite the fact that the rate of sediment supply is not limited, unless it does not exceed the capacity of the dryer fluidized bed, usually this speed is 400 tons/hour or lower, preferably 200 tons/hour or lower, more preferably 150 tons/hour or lower, more preferably 100 tons/hour or lower.

Preferably, the residence time of sediment aromatic carboxylic acid in a fluidized bed dryer was in and the interval from 15 minutes to 150 minutes. The residence time of the precipitate depends on the size of the dryer feed rate of sediment, temperature, and flow rate of the drying gas, liquid content or the amount of the flowability of sediment and other factors. However, from the viewpoint of high efficiency drying of the crystals of the aromatic carboxylic acid and reducing the amount of fluid in them up to 0.1% by weight or below, preferably, the residence time was 15 minutes or more. More preferably, the residence time was 30 minutes or more, even more preferably 45 minutes or more. On the other hand, from the viewpoint of reducing production costs and improving productivity, it is preferable that the residence time was small. It is desirable that the residence time was 150 minutes or less, more preferably 90 minutes or less, even more preferably 75 minutes or less.

The temperature of the sediment measured at the inlet of the fluidized bed dryer is not specifically limited. However, it is usually the temperature is about 70-100°C.

Examples of the liquid substance contained in the sediment of the aromatic carboxylic acid include water or used in the manufacture of the solvent acetic acid. However, the liquid substance is not specifically limited. The drying gas is gas that is used for the ablation and removal of this liquid substance, is contained in the sediment aromatic carboxylic acid, and who has that kind of humidity, which does not cause dew condensation at the temperature of the dryer. For example, preferred is a gas with a dew point of -40°C or below. From the point of view of prevention of dew condensation, it is desirable that the drying gas was supplied in an amount which corresponds to the quantity of liquid substances carried away by the gas.

Care should be taken not to cause condensation of dew, as the number present in the drying gas liquids is large at the top facing the gas stream in the fluidized bed dryer, lower than the incoming stream. In the case when the drying gas use gas with a dew point of -40°C, it is desirable that the amount of the drying gas was 100-1000 m3more preferably 300-800 m3under normal conditions per tonne of aromatic carboxylic acids contained in the sediment aromatic carboxylic acid. The term "normal conditions" means a temperature of 0°C and pressure 1 ATM.

It is desirable that shows the speed of the drying gas fed to the fluidized bed dryer was in the range of 0.2-1 m/s in the calculation for normal conditions. The term "speed" refers to a value obtained by dividing the volumetric flow rate of the drying gas to the square of the cross is about the section of the dryer fluidized bed, and it is usually expressed in the form of speed under normal conditions (0°C, 1 ATM). The regulation provides the velocity of the drying gas to 0.2 m/sec or above has advantages, which are to increase the efficiency of contact of the gas/solid and improving drying efficiency. More preferably, given the speed of the drying gas was 0.25 m/sec or higher, more preferably 0.3 m/sec or higher. On the other hand, the regulation provides speed drying gas to 1 m/sec or below has the advantage that less dissolved particles of aromatic carboxylic acids. The destroyed particles are fine particles which can be displayed together with the outgoing gas and which lead to technological problems. In addition, when using such a speed, can be reduced the number of circulating substances in the cyclone, which will be described later. More preferably, given the speed of the drying gas was 0.85 m/sec or lower, even more preferably 0.7 m/sec or below.

Believe that the destruction of the particles affects the linear speed of ejection of the gas in the hole for the discharge of the drying gas, formed in the lower part of the dryer fluidized bed. Preferably, the linear velocity of the emission gas regulation is ovali so, so it was 2 m/sec or higher, although it select the interval depends on the ratio of hole size for ejection to the diameter of the column. Regulation of the linear velocity of the gas release until this value has the advantage of ease of powder flow, which increases the efficiency of drying and, in addition, prevents clogging of the holes for the discharge of gas. More preferably, the linear velocity of the gas release was 2.5 m/sec or higher, more preferably 3 m/sec or higher. Preferably, the linear speed of ejection of the gas was adjusted so that it was 75 m/sec or lower. This gives the advantage that less destruction of particles of aromatic carboxylic acids. In addition, there may be a reduced number of circulating substances in the cyclone, which will be described later. More preferably, the linear velocity of the gas release was 50 m/sec or lower, even more preferably 35 m/sec or below.

The drying gas supplied to the fluidized bed dryer, has any desired temperature. However, from the point of view of increasing the drying efficiency, it is desirable that the gas temperature was 80°C or higher. More preferably, the gas temperature was 90°C or higher. The higher the temperature of the drying gas, the higher the efficiency with which the loud. For example, when as a heat source for heating the drying gas use steam or hot oil, the gas temperature can be raised to approximately 160°C or 320°C, respectively. When escaping gas from the heating furnace is used as a heat source, the temperature of the drying gas can be increased to about 850°C. However, from a cost perspective, as a heat source, it is preferable to use pairs (for example, a vapor pressure of about 6 kg/cm2). It is desirable that the temperature of the drying gas was 160°C or below.

The output from the dryer crystals of the aromatic carboxylic acids before they reach the entrance to the bunker, usually cooled to a temperature of 80°C or below with the help of the pipeline with the shirt (the pipe is double-walled, water-cooled). This is because a flexible container bags have heat resistance to a temperature of about 80°C. when the temperature at the outlet of the dryer is too high, it is necessary to increase the length of the pipeline with the shirt, and this leads to higher, not lower costs. In addition, from this point of view it is desirable that the temperature of the drying gas was 160°C or below, more preferably 140°C or lower, more preferably 120°C or below.

It is desirable that the drying gas was the process gas is an inert gas, or a mixture of such gases. The term "inert gas" refers to gas that does not react with an aromatic carboxylic acid. Examples of inert gas include nitrogen, air, and noble gases. Under the process gas means any gas which is formed at the stage described above to obtain a crude aromatic carboxylic acid of alkylaromatic compounds, the stage of preparation of aromatic carboxylic acid of high purity from a crude aromatic carboxylic acid and subsequent stages. Examples of technology include gas exhaust gas, which is generated by the oxidation of p-xylene with air in the stage of obtaining terephthalic acid, and the gas resulting from processing the exhaust gas. Using the process gas has the advantage that the availability of this gas in large quantities at low cost and no need for a separate gas.

The drying gas, which was used for drying sludge aromatic carboxylic acid in a fluidized bed dryer, contains vaporized liquid substance and excreted as waste gas dryer from the dryer fluidized bed through the fitting conclusion of the drying gas.

Preferably, the temperature of the gas measured in the fitting conclusion of the drying gas was 80°C-160 is C. When the number exposed to the sludge treatment is small, and the residence time of sediment is relatively large, then the temperature of the gas in the nozzle conclusion of the drying gas was not significantly different from the gas temperature in the nozzle feed. More preferably, the temperature of the gas in the nozzle conclusion of the drying gas was 80-145°C. Preferably, the liquid content in the drying gas, which is determined in the fitting conclusion of the drying gas was regulated so that it was 5-30% by weight. When the liquid content in the drying gas in the nozzle conclusion of the drying gas adjust to a low value, an aromatic carboxylic acid becomes quite dry. When the liquid content in the drying gas at the outlet of the drying gas to regulate high values can be achieved by reducing production costs. More preferably, the liquid content in the drying gas is regulated so that it was 8% by mass or higher, and more preferably 25 mass% or below.

The liquid content in the drying gas in the nozzle conclusion of the drying gas can be regulated, for example, by increasing or decreasing the flow rate of the drying gas.

It should be noted that when the dryer fluidized bed, in some cases, depending on such factors as to icesto supplied drying gas, given the velocity of the gas in the apparatus and conditions of fluidization, the exhaust gas may contain not only the evaporated liquid substance, but also a solid substance composed of crystals of the aromatic carboxylic acid. Ablation of these crystals leads to lower total output. It is therefore desirable to maximize the crystals.

Preferably, in order to separate the solid matter contained in the exhaust gas dryer fluidized bed, from gaseous substances used such a device for extracting solids, as, for example, a cyclone, and the extracted solid was returned to the fluidized bed dryer. When using cyclone particulate matter contained in exhaust gas can be collected by a centrifugal force and is separated by sedimentation from the gaseous substances, i.e. from coming out of the cyclone gas.

Preferably, the invention additionally includes the stage at which at least part of the exhaust from the dryer fluidized bed gas directed into the cyclone and separated into solid and gaseous ingredient and the solid is returned to the fluidized bed dryer. Preferably, the ratio of the circulation of the cyclone regulated so that it was 0,15-0,7. A high rate of circulation oznacza is t, what is present in the dried powder is in a state of energetic flow. Therefore, the higher the ratio of circulation, the shorter the period of time required for drying. Preferably, the ratio of circulation was 0.15 or higher, more preferably 0.2 or higher. On the other hand, too high circulation ratios lead to increased production costs. Therefore, it is preferable that the ratio of circulation was 0.7 or below, more preferably 0.6 or below.

The ratio of the circulation of the cyclone can be determined by dividing circulating through the cyclone amount of substance (the amount of solids extracted using cyclone (kg/h)) on the amount of sediment supplied to the fluidized bed dryer (kg/h).

Other methods of extracting solids include a method in which the used scrubber for processing exhaust gas by washing, for example, acetic acid, resulting in a solid substance contained in the exhaust gas is extracted in the form of a suspension. The remaining gaseous output in the form of a flue gas scrubber.

Preferably, obtained in the cyclone coming out of the cyclone gas is then subjected to processing in the scrubber by washing with acetic acid and extracting, as a result, in the form of suspensionbridge substances, which was not recovered in the cyclone and remained in coming out of the cyclone gas. Such operation is desirable, as the aromatic carboxylic acid can be extracted more fully with increased output.

The extracted slurry may, for example, be directed into the container for mixing and reused as raw material for the reaction. Alternatively, the extracted slurry may be directed to the separator liquid and solid phases and used as a liquid for washing the precipitate. In any case, it is desirable that the extracted solid was returned at any stage of the preparation of aromatic carboxylic acid.

On the other hand, leaving the scrubber, the gas contains liquids which hit him in the fluidized bed dryer and scrubber. It is desirable that the liquids were removed from this coming out of the scrubber gas by means of a device for the purification of gas, and the resulting purified gas returned to the stage, as this operation can reduce the amount of discharged gas, which is removed from the system. For example, leaving the scrubber, the gas is treated so that it had the humidity and temperature, which satisfy the same requirements as in the case of drying gas when it is used in the fluidized bed dryer, and part of the gas or the entire processed is thus gas is used as the circulating gas together with the drying gas. This method is desirable from the point of view of environmental protection and reduce production costs.

The dried crystals thus aromatic carboxylic acids typically have a liquid content of about 0.1% by weight or below. It is desirable that the temperature of the crystals of the aromatic carboxylic acid obtained in the fluidized bed dryer was 70°C or higher. The reason is that this temperature is effective to increase the rate of evaporation and increasing the amount of evaporated liquid substances and to achieve the appropriate degree of drying. More preferably, the crystal temperature was 80°C or higher, more preferably 90°C or higher. On the other hand, it is desirable that the temperature of the crystals of the aromatic carboxylic acid was 100°C or below. This temperature has the advantage that, for example, sufficient cooling is supplied by a jacket pipe of smaller length, or for cooling, there is no need to use fitted shirt pipeline.

In the fluidized bed dryer residue of an aromatic carboxylic acid is subjected to fluidization using a drying gas with achievement by increasing the effective area of the drying contained in the sediment aromatic carboxylic key is lots of liquid substance (for example, water) is evaporated by surface evaporation. Therefore, the temperature of the aromatic carboxylic acid can be maintained at 100°C or below.

Next explains how regulation of the liquid content in the sediment of aromatic carboxylic acids to 14% by weight or below in the first embodiment of the invention.

Ways to reduce the liquid content in the sediment of aromatic carboxylic acids to 14% by weight or lower in the invention are not specifically limited. Their examples include: (i) a method in which a suspension containing aromatic carboxylic acid is subjected to separation in the system solid-liquid under pressure to get the sediment aromatic carboxylic acid, and the residue is subjected to instant drying; (ii) the way in which the residue of an aromatic carboxylic acid pre-dried with a heater; and (iii) the manner in which the crystals of the aromatic carboxylic acids, which have already been subjected to drying, mixing with the sediment aromatic carboxylic acid. Preferred of these, from the viewpoint of ease of control, reduce the machine size and simplicity of the method, is the method (i). Next will be explained each method.

(i) a Method in which a suspension containing aromatic carboxylic acid is subjected to separation in the system, the solid-fluid the industry under pressure to get the sediment aromatic carboxylic acid, and the residue is subjected to instant drying:

Instant drying is a drying method, which is applied to the draught of an aromatic carboxylic acid, the pressure is suddenly reduced, resulting in evaporation of suspended liquid. In this way the separation in the system, the solid-fluid is conducted under pressure, i.e. at a pressure above atmospheric pressure (0.1 MPa), and the resulting precipitate the aromatic carboxylic acid is extracted while maintaining the elevated pressure and then send it into a zone of lower pressure. As a result, released internal energy, and contained in the Deposit of the liquid evaporates, the result can be reduced fluid content in the sediment.

When applying this method in a method of producing aromatic carboxylic acids, in which the reaction of the oxidation of alkylaromatic compounds and the reduction of intermediate compounds is carried out under pressure at a high temperature and then carry out the separation in the system solid-liquid and drying, the slurry may be subjected to separation in the system solid-liquid while maintaining the same values of pressure and temperature used in the oxidation reaction, and then can be carried out instant drying. Therefore, the advantage concludes what I have to reduce the liquid content in the sediment at no additional cost.

Separation in the system solid-liquid can be carried out at any pressure above atmospheric pressure. However, it is preferable that the pressure for separation in the system solid-liquid was 0.11 MPa or higher, more preferably of 0.21 MPa or higher, even more preferably at 0.31 MPa or higher. The higher the pressure relatively lower limit, the higher the effect is achieved at the subsequent instant drying, and the more can be reduced fluid content. Preferably, the pressure was 22 MPa or lower, more preferably 12 MPa or lower, more preferably 7 MPa or lower, most preferably 5 MPa or lower, most preferably 3 MPa or lower. The lower pressure relative to the upper limit, the more one achieves the advantage of ease of adjustment of instantaneous drying and in achieving the reduction of the cost of the equipment. When this method is used in a method of producing an aromatic carboxylic acid, it is preferable that the pressure for separation in the system solid-liquid regulated so that it is not higher than the pressure used in the oxidation of alkylaromatic compounds.

The temperature used for the separation in the system of the firm in the society-liquid not specifically limited. However, it is preferable that the temperature was 50°C or higher, more preferably 100°C or higher, more preferably 130°C. or higher. The higher the temperature is relatively lower limit, the higher the effect is achieved at the subsequent instant drying, and the more can be reduced fluid content. On the other hand, it is preferable that the temperature for the separation in the system solid-liquid was 350°C or below, more preferably to 300°C or lower, more preferably 250°C or below. The lower temperature relative to the upper limit, the more one achieves the advantage of lowering the cost of the equipment. When this method is used in a method of producing an aromatic carboxylic acid, it is preferable that the temperature for the separation in the system solid-liquid regulated so that it was not higher than the temperature used in the oxidation of alkylaromatic compounds.

Examples of apparatus for use in separation of the suspension system, the solid-fluid under pressure include dewatering sump separator with a solid rotor and a rotary filter press.

The separated precipitate is usually stored in the camera, with almost exactly zegavlena, as in the separator the liquid and solid phases, and its output, in accordance with need, with the exhaust valve and is directed at the regulation of the amount of sediment in the tank for powder having a lower pressure. As a result of such discharge with valve sludge under pressure in the chamber, in an environment of lower pressure, the boiling temperature being in the sediment of the liquid decreases. Located in lees liquid evaporates due to physical warmth due to the resulting difference in the boiling point.

The amount of sediment stored in the camera, and the frequency of its output through the exhaust valve is not specifically limited. The camera can always be precipitate, or she may not be blank. By the way, while maintaining the pressure in the chamber is higher than in the tank for powder, the valve may be always open. However, it is preferable to periodically open/close the valve, as it is important to ensure the sealing gas. The amount of sludge present in the cell, can be measured indirectly or directly without any specific limitations. Typically, to determine the position of the surface of the sediment used detector contact type or distance measuring device that uses light or sound wave. The camera may be equipped with only one vypusk the m valve or two or more exhaust valves. Examples of valves include ball valve, double valve, rotary valve, flap valve, gate and spindle valve. The camera can be designed so that it can continuously output the sediment by using two or more valves and control the time of opening of each valve.

Preferably, the pressure difference at the instant drying (pressure difference between the separator and the area with low pressure) was 0.01 MPa or more, more preferably of 0.11 MPa or more, even more preferably of 0.21 MPa or more. The greater the pressure difference relative to the lower limit, the more effective is instant drying and can largely be reduced fluid content. Preferably, the pressure difference was 22 MPa or less, more preferably 12 MPa or less, more preferably 7 MPa or less. The smaller the pressure difference relative to the upper limit, the greater is achieved the advantage of ease of adjustment of instantaneous drying and reducing the cost of equipment.

Preferably, the difference between the temperature of the sediment instant before drying and after drying (the difference between the temperature of the sludge in the separator and the temperature of the sludge in the area of low pressure) was 5°C or more, valueproposition - 10°C or more, even more preferably 20°C or more. The greater the temperature difference relative to the lower limit, the more effective is instant drying and can largely be reduced fluid content. Preferably, the temperature difference was 250°C or less, more preferably 200°C. or less, more preferably 170°C. less Than the temperature difference relative to the upper limit, the more one achieves the advantage of lowering the cost of the equipment.

As an instant dryers can be used dryer described, for example, in the patent document JP-A-2002-336687.

Preferably, the reduction of fluid in the sediment aromatic carboxylic acid in the instant drying was 3% by mass or more, more preferably 6% by mass or more, more preferably 9% by mass or more. However, it is preferable that the reduction of the liquid content was 15% by mass or less, more preferably 12 mass% or less. By the way, when the reduction is 3% by weight, this means, for example, that the liquid content decreased from 15 mass% to 12 mass%.

In addition to the regulation reduction of the liquid content by changing the pressure or temperature, it can easily regulate the sterile by increasing or reducing the rate of supply of sediment.

Stage instantaneous drying can be carried out anywhere in the technological scheme between phase separation in the system solid-liquid and stage drying with the dryer fluidized bed. Phase separation in the system solid-liquid phase instantaneous drying may be carried out sequentially. Alternatively, the stage instantaneous drying can be carried out before the fitting of the input sludge dryers fluidized bed.

(ii) the Way in which any residue of the aromatic carboxylic acid is subjected to preliminary drying with heater:

In this method, a heater (heating device) installed before the dryer, and the liquid contained in the sediment aromatic carboxylic acid is removed by evaporation with achievement, as a result, reduce the liquid content in the sediment. The type of heater is not specifically limited, provided that it can achieve the goal. From the point of view of efficiency, it is preferable that the steam formed as a side product during the preparation of aromatic carboxylic acid, was used as a heat source for the heater.

The temperature to which the sludge must be heated with the heater, usually can be any temperature not lower than the temperature of Kipen is I contained in the Deposit of liquid.

However, it should be noted that too high temperature may cause decomposition or sublimation of aromatic carboxylic acids. Therefore, usually the precipitate is heated to a temperature lower than the temperature of decomposition and sublimation of aromatic carboxylic acids. The heating time may be appropriately determined based on the liquid content in the feed sludge, the desired final liquid content in the sediments, the desired reduction of the liquid content in the sediment, and other factors. Preferably, the heating time was chosen after the contents of the liquid in the sludge.

Preferably, to reduce the liquid content in the sediment of aromatic carboxylic acids by this method was 3% by mass or more, more preferably 6% by mass or more, more preferably 9% by mass or more. However, it is preferable that the reduction of the liquid content was 15% by mass or less, more preferably 12 mass% or less. By the way, when the reduction is 3% by weight, this means, for example, that the liquid content decreased from 15 mass% to 12 mass%.

(iii) the Manner in which the crystals of the aromatic carboxylic acids, which have already been subjected to drying, mixing with the sediment aromatic carboxylic acids:

In ecompose crystals of the aromatic carboxylic acid, which have already been subjected to drying and has a low content of liquid mixed with solid aromatic carboxylic acid having a high liquid content, with achievement, as a result, low liquid content in the mixture as a whole. Added to the mixture of crystals of the aromatic carboxylic acid can be any acid crystals that have the desired low content of liquid. However, it is preferable from the point of view of economy to use dry crystals of the aromatic carboxylic acid, obtained as a commercial product at ordinary stages of the preparation of aromatic carboxylic acids. It is preferable that the content of the liquid added to the mixture of crystals of the aromatic carboxylic acid was 0.12% by weight or below, more preferably of 0.10% by mass or lower. The number added to the mixture of crystals of the aromatic carboxylic acid can be suitably selected based on the content of the liquid in the feed sludge, the desired final liquid content in the sediments, the desired reduction of the liquid content in the sediment, and other factors.

Preferably, to reduce the liquid content in the sediment of aromatic carboxylic acids by using this method was 3% by mass or more, more preferably 6% is about weight or more, even more preferably 9% by mass or more. However, it is preferable that the reduction of the liquid content was 15% by mass or less, more preferably 12 mass% or less. By the way, when the reduction is 3% by weight, this means, for example, that the liquid content decreased from 15 mass% to 12 mass%.

For regulating the amount of the flowability of sediment aromatic carboxylic acid of up to 2000 MJ or below in the second embodiment of the present invention may be used the same methods as the methods used to adjust the liquid content up to 14% by weight or below in the first embodiment.

As to the third variant embodiment of the invention, there can be used the same way (i) in the first embodiment.

Although the methods of the invention are used in methods of preparation of aromatic carboxylic acids, it is preferable to apply these methods in a method of producing terephthalic acid.

For example, the methods applicable at the stage of drying in the method of obtaining the crude terephthalic acid which comprises oxidizing p-xylene in a solvent to obtain a slurry of crude terephthalic acid, separation of the suspension system, the solid-liquid obtaining a precipitate of terephthalic acid and drying the precipitate. In addition, methods of application which we are at the stage of drying in a method of producing terephthalic acid of high purity, which includes the recovery of crude terephthalic acid in a solvent containing water, followed by crystallization of terephthalic acid from a liquid reaction mixture to obtain a suspension, the separation of the suspension system, the solid-liquid obtaining a precipitate of terephthalic acid and drying the precipitate.

Next, with reference to Figure 3 explains an example in which the invention is used in the method of obtaining the crude terephthalic acid.

In a solvent comprising acetic acid A', oxidize 95% or more p-xylene B' in the presence of a catalyst containing cobalt, manganese and bromine in continuous feed to the oxidation reactor 11 gas containing molecular oxygen. Although it can be used only one oxidation reactor 11, it is preferable to use two or more series-connected reactors oxidation 11 for carrying out oxidation reactions in two or more stages. Conditions typically include a temperature of 100-250°C and a pressure of 0.2 to 5 MPa. The reaction time of the oxidation (mean residence time) is typically 30-300 minutes.

From the oxidation reactor 11 yields a suspension of terephthalic acid C, consisting of crystals of terephthalic acid and solvent. Although the condition of the reaction mixture obtained in the reaction are not specifically limited, the reaction mixture called a suspension, to which Yes it consists of two phases, which are the solid phase and the liquid phase consists of three phases, which are gas, liquid and solid phase. Terephthalic acid is obtained in the form of solids, preferably in the form of crystals, and get a suspension containing at least a solid connection and the solvent. Part of the terephthalic acid may be dissolved in the reaction medium.

Next, the suspension is optionally cooled in the mold 12 under reduced pressure for an additional deposition of crystals containing terephthalic acid as a main component. Although it may be used only one mold 12, it is preferable to use two or more serially connected molds 12 for carrying out the crystallization in two or more stages. However, when at a later stage carry out the separation in the system solid-liquid under pressure, it is desirable not to carry out the crystallization in the crystallizer.

Suspension C' is introduced into the separator the liquid and solid phases 13 and divided into separated mother liquor D' and the wet sediment E'. This sediment has a liquid content of 50 mass% or below, preferably 30 mass% or below, more preferably 20 mass% or less, most preferably 15 mass% or lower. The following explains the method of separation of suspension C is the system solid-liquid by means of a separator liquid and solid phases 13. Separation in the system solid-liquid usually involves phase separation in the system solid-liquid phase washing, and these stages can, individually, to be held in the respective apparatuses. However, these two stages can be carried out simultaneously in the same apparatus (apparatus for the separation in the system solid-liquid and washing). Examples of such apparatus include dewatering sump separator with a solid rotor, rotary vacuum filter, horizontal belt filter and a rotary filter press. Are preferred apparatus in which the separation in the system solid-liquid can be carried out under pressure, such as dewatering sump separator with a solid rotor and a rotary filter press.

When there is a probability that the submission received wet sludge E', as he is, in a fluidized bed dryer 15 may cause such a violation, as adhesion, as is the case when the wet sediment E' has a high content of liquid or high value properties, then the wet sediment E' serves on stage regulation characteristics of the sludge 14. Thus obtained precipitate terephthalic acid F' is a low fluid content or lower the amount of flowability. The residue is F' with the shat using the dryer fluidized bed 15 with obtaining crystals of crude terephthalic acid G'. Under regulation characteristics of sediment 14 may apply the methods described above. The preferred method is instant drying.

Next, the precipitate terephthalic acid F' is dried in a fluidized bed dryer 15. In the fluidized bed dryer 15 liquid substance that was contained in the Deposit of terephthalic acid F'is evaporated and removed by the drying gas H'. Acetic acid is the main component of the liquid substance contained in the sediment of terephthalic acid F'. The drying gas H' contains a liquid substance that is vaporized and removed from the precipitate of terephthalic acid, and excreted from the dryer fluidized bed 15 in the form of exhaust from the dryer gas I'. Before it can thus deduce that the exhaust from the dryer fluidized bed gas I' treated in the cyclone 16 for separating solids (crystals of terephthalic acid)contained in the exhaust gas I', from gaseous substances. This is a recoverable solid J' directed to the fluidized bed dryer 15. The gaseous substance is output as the output from the cyclone gas K'.

In addition, the exhaust from the dryer fluidized bed gas I' and/or output from the cyclone gas K' it is desirable to clean with acetic acid in the scrubber 17 to extract the contained solid substances is in the form of the extracted suspension of L1. The gaseous substance is output as the output of the scrubber gas M1.

Extracted, thus obtained a suspension of L' can be sent to the oxidation reactor 11 and dissolved in acetic acid A' together with p-xylene B'. More preferably, the extracted suspension L' was sent to the separator liquid and solid phases 13 and used for washing the wet sludge E'. On the other hand, it is desirable that the output of the scrubber gas M' subjected to the processing using the device for the purification of gas 18 for removal of liquid substances and, as a result, obtaining the circulating gas N'with the same humidity and temperature as the drying gas H', and part or all of the gas N' returned into the fluidized bed dryer 15.

Next, with reference to Figure 4 explains an example in which the invention is used in a method of producing terephthalic acid of high purity.

First, in the vessel for mixing 31 crude terephthalic acid a' is mixed with water b' with the receipt of the initial suspension c'. This initial suspension c' is pumped by a pump 32 and then heated by the heater 33 to complete dissolution. The resulting solution d' are in contact with hydrogen in the hydrogenation reactor 34 to restore oxidized intermediate compounds contained in the crude terephthalic acid, and thus purify cyrogenically acid. The oxidized intermediate compounds are intermediate compounds formed in the oxidation of p-xylene to clean terephthalic acid, main component is a 4-carboxybenzene. Substance formed during the restoration of this intermediate compound is p-tolarova acid. As the hydrogenation catalyst is usually used, a catalyst containing an element of Groups 8-10 of the Periodic system of elements, such as iron, ruthenium, osmium, cobalt, rhodium, iridium, Nickel, palladium or platinum.

From the recovered liquid e', the resulting clean, carry out the deposition of crystals of terephthalic acid with obtaining, as a result, suspension f'. In this operation, the recovered liquid e' in the mold 35 is cooled optional under reduced pressure to accelerate the deposition of crystals of terephthalic acid. Although it may be used only one mold 35, it is preferable to use two or more serially connected crystallizers 35 for carrying out the crystallization in two or more stages. Since the oxidized intermediate compounds were recovered in the hydrogenation reactor 34 in well water-soluble ingredients, then precipitated at this stage, the crystals of terephthalic acid have a high purity. For the further increase of purity, it is desirable to use the temperature of deposition of 120-180°C. However, when, at a subsequent stage should be a separation in the system solid-liquid under pressure, it is desirable not to carry out the crystallization in the crystallizer.

Suspension f' is introduced into the separator the liquid and solid phases with 36 receiving the separated mother liquor j' and wet sediment (g'. Separation in the system solid-liquid usually involves phase separation in the system solid-liquid phase washing, and these stages can, individually, to be held in the respective apparatuses. However, these two stages can be carried out simultaneously in the same apparatus (apparatus for the separation in the system solid-liquid and washing). Examples of such apparatus include dewatering sump separator with a solid rotor, rotary vacuum filter, horizontal belt filter and a rotary filter press. Are preferred apparatus in which the separation in the system solid-liquid can be carried out under pressure, such as dewatering sump separator with a solid rotor and a rotary filter press.

When there is a probability that the submission received wet sediment (g', as he is, in a fluidized bed dryer 38 may cause such a violation, as adhesion, as is the case when the wet precipitate g' has a high content of liquid or high value of flowability, then the wet sediment (g' serves on stage regulation characteristics of sediment 37. Thus obtained precipitate terephthalic acid h' is reduced liquid content or lower the amount of flowability. The residue is h' is dried with the dryer fluidized bed 38 of obtaining crystals of terephthalic acid of high purity i'. Under state regulation 37 sediment can apply the methods described above. The preferred method is instant drying.

Next, the precipitate terephthalic acid h' is dried in a fluidized bed dryer 38. In the fluidized bed dryer 38 liquid substance that was contained in the Deposit of terephthalic acid h', evaporated and removed by the drying gas k'. Water is the main component of the liquid substance contained in the sediment of terephthalic acid h'. The drying gas k' contains a liquid substance that is vaporized and removed from the precipitate of terephthalic acid, and excreted from the dryer fluidized bed 38 in the form of exhaust from the dryer gas l'. Before the gas thus deduce that the exhaust from the dryer fluidized bed gas l' processed in the cyclone 39 for separating solids (crystals of terephthalic acid)contained in the exhaust gas l', from gaseous substances. It is extracted solid material m' is sent to drying is the fluidized bed 38. Gaseous output as coming from the cyclone gas n'.

In addition, the exhaust from the dryer fluidized bed gas l' and/or output from the cyclone gas n' it is desirable to clean with water in the scrubber 40 to extract the contained solids in the form of the extracted suspension q'. Gaseous output as leaving the gas scrubber p'.

Extracted, thus obtained suspension q' can be directed into the container for mixing 31 and dissolved in water b' together with the crude terephthalic acid a'. More preferably, the extracted suspension q' was sent to the separator liquid and solid phases 36 and used for washing the wet sludge g'. On the other hand, it is desirable that leaving the scrubber gas p' subjected to the processing using the device for the purification of gas 41 for removal of liquid substances and, as a result, obtaining the circulating gas r'having the same humidity and temperature as the drying gas k', and part or all of the gas r' returned into the fluidized bed dryer 38.

Hereinafter the invention will be explained in more detail using examples. However, in no case should not assume that these examples limit the invention.

<Method for determination of water content by the method of Fisher>

Took a sample of sediment or crystals t is refshalevej acid were placed in a flask made of polypropylene, and the flask was sealed. This sample was immediately subjected to analysis by using the analyzer water by Fisher (table automatic analyzer for volumetric titration type K-F-100 Mitsubishi Chemical Corp.). The determination was carried out under conditions which were selected automatically when the sample was placed in an automatic analyzer.

<Method of determining the amount of the flowability>

The amount of the flowability was determined as follows.

Measuring device: rheometer for powders (FT-4, the company Sysmex Corp.)

Measuring conditions:

In room conditions (temperature 25°C; humidity 60%) 160 ml of the analyzed sample was placed in a cylinder made of borosilicate glass with an inner diameter of 50 mm Twisted the blade diameter of 48 mm was moved up/down by rotation and spiral (-5°) moved in the sample. Installed the circumferential speed of the end portion of the blade 100 mm/sec. When preparing to measure the blade is rotated in the reverse direction in the sample to homogenize the sample. As a result, guaranteeing reproducible concentration condition.

Continuously measured the force in the axial direction (vertical load) and a rotational force (torque)applied to the blades, and their values are integrated. Received, as a result, the amount of work (energy) was taken as a measure of flowability.

The EXAMPLE 1

<obtaining a precipitate of terephthalic acid of high purity>

Used production equipment with a capacity of terephthalic acid 36 tons/hour. P-xylene and acetic acid is continuously fed into the reactor liquid-phase oxidation. At the same time in the reactor was filed cobalt acetate, manganese acetate and hydrogen bromide as a catalyst for oxidation reaction at a temperature of 197°C and a pressure of 1.45 MPa. As the oxidizing gas for the reaction of the oxidation of used air. Then, the resulting suspension is withdrawn from the reactor liquid-phase oxidation was continuously applied to additional low-temperature reactor oxidation, and the oxidation reaction is optionally carried out at a temperature of 190°C and a pressure of 1.3 MPa. As the oxidizing gas for carrying out this reaction the oxidation of used air.

The suspension obtained in additional low-temperature oxidation reactor, continuously introduced in an intermediate tank for processing, forming three stages of processing. They spent crystallization from deposition of crystals of crude terephthalic acid. Then the suspension was subjected to separation in the system solid-liquid at atmospheric pressure (about 1 ATM) to obtain the wet sludge. The obtained wet sediment had a liquid content of 15.0% by m the SSE.

This wet precipitate was dried under atmospheric pressure (about 1 ATM) using a drum dryer using steam as a heat source (tube dryer with steam heating). In a tubular dryer with steam heating passed steam with a pressure of 0.6 MPa and carry out its circulation through the pipeline, and using steam heat wet sediment. The liquid held by the crystals of crude terephthalic acid, as a result, evaporates. The vaporized liquid is discharged from the system using an inert gas, continuously passing through the dryer. The outlet temperature of the dryer is 140°C. Obtained in the dryer crystals of crude terephthalic acid are liquid content of 0.10% by mass.

Then, the result of the above crude terephthalic acid and the water are continuously fed into the hydrogenation reactor and the spent reaction recovery at a temperature of 290°C and a pressure of 8.6 MPa. As a reducing gas for the reaction of recovery used hydrogen.

Obtained in the hydrogenation reactor, the suspension is continuously fed into an intermediate tank for processing, forming a five-speed processing. Spent in them crystallization to precipitate crystals of terephthalic acid. Then the suspension was subjected to separation in the system solid-liquid at atmospheric pressure (about 1 ATM) is getting wet sediment. The obtained wet sediment had a liquid content of 15.0% by mass.

This wet precipitate was dried under atmospheric pressure (about 1 ATM) using a drum dryer using steam as a heat source (tube dryer with steam heating). In a tubular dryer with steam heating passed steam with a pressure of 0.6 MPa and carry out its circulation through the tubing and is heated wet sediment using steam. The liquid held by the crystals of crude terephthalic acid, as a result, evaporates. The vaporized liquid is discharged from the system using an inert gas, continuously passing through the dryer. The outlet temperature of the dryer is 140°C. Obtained in the dryer crystals of crude terephthalic acid are liquid content of 0.10% by mass.

To the obtained in the previous phase of the crystals of terephthalic acid of high purity was added a given amount of water with obtaining, as a result, the precipitate terephthalic acid of high purity with a water content of 14% by weight. This sediment was determined value of flowability and, as a result, it was found that the magnitude of the flow properties of the sediment were in the range of 1500-1700 MJ.

<Drying using a dryer fluidized bed>

The precipitate terephthalic acid of high purity with a water content of 14% by weight, obtained in the above example, receiving the Oia terephthalic acid, dried using a dryer fluidized bed 51 (inner diameter 300 mm; the area of the fluidized bed 0.24 m2), shown in figure 5.

The precipitate of terephthalic acid was injected through the hose precipitate terephthalic acid 61 dryer fluidized bed 51, and a drying gas heated with the heater 52, was injected through the nozzle supply drying gas 63. The precipitate was constantly in contact with the drying gas in the regime of fluidization with obtaining, as a result, the dry sludge. The crystals of terephthalic acid produced from the fitting conclusion 62, was analyzed for water content analyzer Fisher. (The atmosphere in the fluidized bed dryer had a dry bulb temperature of 32°C and the temperature of the wet bulb temperature of 25.5°C.) Sludge fed into the fluidized bed dryer 51 at a speed of 200 kg/hour. As the drying gas used dry nitrogen with a dew point of -40°C. or below. This drying gas was applied at 100°C. so as to obtain a given velocity in the fluidized bed dryer 0.3 m/sec (under normal conditions). Steam with a temperature of 151°C. was passed through the steam line 67 for indirect heating in the dryer 51.

The exhaust from the dryer fluidized bed gas containing vaporized and remote water from the precipitate of terephthalic acid, is brought out through the nozzle of the gas outlet 64 dryer with pseud the liquefied layer 51. In some cases, this exhaust gas contains as solid crystals of terephthalic acid. Therefore, the exhaust gas subjected to the processing using the cyclone 53 to separate it into solid and gaseous ingredient. The solid is returned to the fluidized bed dryer 51 through the hole to extract solids 66. Separated gaseous ingredient taken out through a fitting conclusion 65 to the gas outlet of the cyclone and out of the system by blower 54. The ratio of the circulation of the cyclone regulated so that its value was in the range of 0.3 to 0.5.

Dryer continuously in operation for 1 hour. As a result, there was no sticking of the crystals of terephthalic acid, and the mode of fluidization was satisfactory. The crystals of terephthalic acid, collected on the nozzle output 62, had a temperature in the range of 80-100°C and the water content (water content at the outlet) of 0.11% by weight.

[Comparative example 1]

In the example of obtaining terephthalic acid of example 1 was changed to the amount of water that is added to the obtained crystals of terephthalic acid of high purity, obtaining a precipitate of terephthalic acid of high purity with a water content of 15% by mass.

The precipitate terephthalic acid of high purity, which had a water content of 15% is the mass was dried. Used the same conditions as in example 1, except that the sediment was introduced into the fluidized bed dryer 51 at a speed of 240 kg/h to regulate the number of crystals of terephthalic acid produced from the fitting conclusion 62, to almost the same values as in example 1.

Was carried out in continuous operation for approximately 1 hour. As a result, the crystals of terephthalic acid began to stick immediately after the start of drying. It is allowed to work only for 15 minutes, then stopped the flow of sediment terephthalic acid, and subjected to the dryer dynamic shock to remove the crystals of terephthalic acid adhering to the inner wall of the dryer. The crystals of terephthalic acid, collected on the nozzle output 62, had a temperature in the range of 80-100°C. was Determined in their water content, and found that it is about 0.14% by weight.

[Comparative example 2]

In the example of obtaining terephthalic acid of example 1 was changed to the amount of water that is added to the obtained crystals of terephthalic acid of high purity, obtaining a precipitate of terephthalic acid of high purity with a water content of 20% by weight. Determined the size of the flowability of this sediment, and found that it is about 3000 MJ.

Was undertaken drying the obtained precipitate of tereta the eve acid of high purity with a water content of 20% by weight under the same conditions, as in example 1. Immediately after the beginning of the introduction of sediment inside the dryer fluidized bed mode of fluidization of the sediment never installed, and drying would become impossible. Therefore, the experiment was stopped after approximately 15 minutes after the start.

Table 1
The water content in sediment input (wt.%)The temperature of the drying gas inlet (°C)Given the speed of drying gas (m/sec)The content of the water (wt.%)Results
201000,3-Poor (not achieved fluidization)
151000,30,14Bad (sticking)
141000,30,11Good adhesion does not occur)

EXAMPLE 2

Crude terephthalic acid was obtained as in example receipt if the EPA 1. The resulting crude terephthalic acid and the water are continuously fed into the hydrogenation reactor and the spent reaction recovery at a temperature of 290°C and a pressure of 8.6 MPa for the conversion of 4-carboxybenzene contained in the crude terephthalic acid, p-Truelove acid. As a reducing gas for the reaction of recovery used hydrogen.

Obtained in the hydrogenation reactor, the suspension was subjected to separation in the system solid-liquid at high pressure 0,4-0,8 MPa division of suspension to precipitate terephthalic acid (water content of 15% by weight) and the mother liquor. Then, the precipitate of terephthalic acid was injected under the conditions of high pressure in the separator flash evaporation, where the sediment was placed in an environment at atmospheric pressure (about 0.1 MPa) for instant drying. As a result, received a residue of terephthalic acid with a water content of 10% by weight. Determined the size of the flowability of this sediment, and found that it is in the range of 1500-1700 MJ.

The precipitate is continuously fed into the fluidized bed dryer 51, shown in Figure 5, and subjected to drying. The residue was applied at a speed of 200 kg/hour, and the residence time of the sludge was adjusted so that it was 45-60 minutes. The temperature of the sediment on the hose reg is laravale so, to 110-120°C. Dry nitrogen gas having a temperature of 100°C, was used as drying gas and submit it so that, as a result, its linear speed measured at the nozzle output gas was $ 3.75 to 7.5 m/sec, and the velocity in the fluidized bed dryer was 0.3-0.6 m/sec (under normal conditions). The ratio of the circulation of the cyclone regulated so that he was 0.3 to 0.5. The outlet gas temperature was 90-110°C, and the liquid content in the exhaust gas was 14-18% by mass.

The dryer has worked continuously for about 1 hour. As a result, there was no sticking of the crystals of terephthalic acid, and the mode of fluidization was satisfactory. The crystals of terephthalic acid, collected at the outlet 62, had a temperature in the range of 80-90°C. was Determined by the water content in them, and it was found that the water content is 0.1% by mass.

EXAMPLE 3

Example 2 reduced the feed rate of sludge in the separator of the instant evaporation of receiving, as a result, the precipitate of terephthalic acid with a water content of 5% by weight. Determined the size of the flowability of this sediment, and found that it is in the range of 1500-1700 MJ.

The precipitate was dried in the same manner as in example 2. The dryer has worked continuously for about 1 hour. In d is the query result, there was no sticking of the crystals of terephthalic acid, and the mode of fluidization was satisfactory. The crystals of terephthalic acid, collected on the nozzle output 62, had a temperature in the range of 80-90°C. was Determined by the water content in them, and it was found that it is 0.1% by mass.

Although the invention has been described in detail with reference to specific variations in its implementation, for the specialist in this area it is obvious that it can be made various changes and modifications without deviating from the essence and scope of the invention.

This application is based on patent application Japan, issued on June 13, 2006(Application No 2006-163694), the content of which is given here as references.

INDUSTRIAL APPLICABILITY

According to the invention can be suggested ways of drying aromatic carboxylic acids and methods for producing dry aromatic carboxylic acid, which resolves the problems associated with the use of dryers, fluidized bed, such as the adherence of the crystals of the aromatic carboxylic acid in the dryer, and emerging, as a result, violations, including clogging of the nozzle of the supply of the drying gas, the decrease in the efficiency of drying and stop the machine, which results in stable operation of the dryer fluidized bed. In addition to t the th, the fluidized bed dryer can be used in practice as a replacement for tubular dryer with steam heating. Therefore, can be achieved by reducing the size of the apparatus and reducing the cost of equipment and cost of its maintenance. Therefore, the invention is of great importance for the industry.

1. The method of drying aromatic carboxylic acids, which includes the continuous drying of sludge aromatic carboxylic acid using the dryer fluidized bed, characterized in that the sludge is introduced into the dryer at a speed of 50 kg/h or higher, and a drying gas having a temperature of 80-160°C., is fed into the dryer at the present rate of 0.3-1 m/s, so that the liquid content in the sediment was 14% by weight or below.

2. The method of drying an aromatic carboxylic acid according to claim 1, in which a suspension containing aromatic carboxylic acid is subjected to separation in the system solid-liquid under pressure which is above atmospheric pressure, to obtain the sediment aromatic carboxylic acid, and the precipitate is subjected to instant drying at a pressure below the pressure used in the separation system, the solid-liquid so that the liquid content in the sediment was 14% by weight or below.

3. The method of drying aromatic carboxylic acid p is 1, characterized in that they are subjected to ex-ante regulation characteristics of the sediment, so that it had a value of flowability 2000 MJ or less, measured using the rheometer for powders as the amount of work.

4. The method of obtaining dry aromatic carboxylic acids, which includes the continuous drying of sludge aromatic carboxylic acid using the dryer fluidized bed with getting ready aromatic carboxylic acids, characterized in that the sludge is introduced into the dryer at a speed of 50 kg/h or higher, and a drying gas having a temperature of 80-160°C., is fed into the dryer at the present rate of 0.3-1 m/s, so that the liquid content in the sediment was 14% by weight or below.

5. The method of obtaining dry aromatic carboxylic acid according to claim 4, which additionally includes the stage of exposure to the suspension containing aromatic carboxylic acid, the separation in the system solid-liquid under pressure which is above atmospheric pressure, to obtain the precipitate of aromatic carboxylic acids, and exposure to sediment instant drying at a pressure below the pressure used in the separation system, the solid-liquid so that the liquid content in the sediment was 14% by weight or below, to the stage of continuous sludge drying using a dryer with psevdoozhizhennykh.

6. The method of obtaining dry aromatic carboxylic acid according to claim 4, which additionally includes the stage of oxidation of alkylaromatic compounds in a solvent to obtain a suspension of the crude aromatic carboxylic acid, and separating the suspension system, the solid-liquid obtaining sediment aromatic carboxylic acids, to the stage of continuous sludge drying using a dryer fluidized bed.

7. The method of obtaining dry aromatic carboxylic acid according to claim 4 which further includes recovering the crude aromatic carboxylic acid in a solvent containing water, followed by crystallization of the aromatic carboxylic acid from the obtained liquid reaction mixture to obtain a suspension, and separating the suspension system, the solid-liquid obtaining sediment aromatic carboxylic acids, to the stage of continuous sludge drying using a dryer fluidized bed.

8. The method of obtaining dry aromatic carboxylic acid according to claim 4, which includes drying the precipitate aromatic carboxylic acid using the dryer fluidized bed with getting ready aromatic carboxylic acids, characterized in that they are subjected to ex-ante regulation characteristics of the sediment, so that he had deliciosamente 2000 MJ or below, measured by using a rheometer for powders as the amount of work.



 

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FIELD: chemistry.

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

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FIELD: chemistry.

SUBSTANCE: invention relates to an improved method of purifying carboxylic acid from a mixture which contains one or more carboxylic acids selected from a group consisting of terephthalic acid, isophthalic acid, orthophthalic acid and their mixtures, and also contains one or more substances selected from a group consisting of carboxybenzaldehyde, toluic acid and xylene. The method involves: bringing the mixture into contact with a selective solvent for crystallisation at temperature and in a period of time sufficient for formation of a suspension of a complex salt of carboxylic acid with the selective solvent for crystallisation without complete dissolution of the complex salt of carboxylic acid; extraction of the complex salt and decomposition of the complex salt in the selective solvent for crystallisation in order to obtain free carboxylic acid. The mixture containing unpurified carboxylic acid is brought into contact with the selective solvent for crystallisation in order to form a suspension of a complex salt of carboxylic acid with the selective solvent for crystallisation. The complex salt is extracted and, if desired, processed for extraction of free carboxylic acid.

EFFECT: methods are especially suitable for purifying aromatic dibasic carboxylic acids such as terephthalic acid, and also enables reduction of the degree of contamination of phthalic acids with carboxybenzaldehyde isomers.

22 cl, 3 tbl, 1 dwg, 3 ex

FIELD: chemistry.

SUBSTANCE: method of obtaining product - purified carboxylic acid, includes: (a) oxidation of aromatic initial materials in primary oxidation zone with formation of raw carboxylic acid suspension; where raw carboxylic acid suspension contains terephthalic acid; where said oxidation is carried out at temperature within the range from 120°C to 200°C; (b) withdrawal of admixtures from raw suspension of carboxylic acid, removed at temperature from 140°C to 170°C from stage of oxidation of paraxylol in primary oxidation zone and containing terephthalic acid, catalyst, acetic acid and admixtures, realised in zone of solid products and liquid separation with formation of mother liquid flow and product in form of suspension; where part of said catalyst in said suspension of raw carboxylic acid is removed in said mother liquid flow; and where into said zone of solid products and liquid separation optionally additional solvent is added; (c) oxidation of said product in form of suspension in zone of further oxidation with formation of product of further oxidation; where said oxidation is carried out at temperature within the range from 190°C to 280°C; and where said oxidation takes place in said zone of further oxidation at temperature higher than in said primary oxidation zone; (d) crystallisation of said product of further oxidation in crystallisation zone with formation of crystallised product in form of suspension; (e) cooling of said crystallised product in form of suspension in cooling zone with formation of cooled suspension of purified carboxylic acid; and (i) filtration and optionally drying of said cooled suspension of purified carboxylic acid in filtration and drying zone in order to remove part of solvent from said cooled suspension of carboxylic acid with obtaining of said product - purified carboxylic acid.

EFFECT: purified carboxylic acid with nice colour and low level of admixtures, without using stages of purification like hydration.

8 cl, 1 tbl, 1 dwg, 1 ex

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

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.

EFFECT: controlled reduction of the formation of suspension of iron oxide during production of technical aromatic acid.

19 cl, 1 dwg, 6 ex, 4 tbl

FIELD: carbon materials and hydrogenation-dehydrogenation catalysts.

SUBSTANCE: invention relates to improved crude terephthalic acid purification process via catalyzed hydrogenating additional treatment effected on catalyst material, which contains at least one hydrogenation metal deposited on carbonaceous support, namely plane-shaped carbonaceous fibers in the form of woven, knitted, tricot, and/or felt mixture or in the form of parallel fibers or ribbons, plane-shaped material having at least two opposite edges, by means of which catalyst material is secured in reactor so ensuring stability of its shape. Catalyst can also be monolithic and contain at least one catalyst material, from which at least one is hydrogenation metal deposited on carbonaceous fibers and at least one non-catalyst material and, bound to it, supporting or backbone member. Invention also relates to monolithic catalyst serving to purify crude terephthalic acid, comprising at least one catalyst material, which contains at least one hydrogenation metal deposited on carbonaceous fibers and at least one, bound to it, supporting or backbone member, which mechanically supports catalyst material and holds it in monolithic state.

EFFECT: increased mechanical strength and abrasion resistance.

8 cl, 4 ex

FIELD: industrial production of methacrylic acids at reduced amount of industrial wastes.

SUBSTANCE: proposed method is performed by catalytic oxidation of propane, propylene or isobutylene in vapor phase at separation of final product and forming of high-boiling mixture as by-product which contains (according to Michaels addition) water, alcohol or methacrylic acid added to methacrylic group. By-product is decomposed in thermal decomposition reactor at simultaneous distillation of decomposition products in distilling column from which methacrylic acid is taken in form of distillate. Flow of liquid decomposition residue is forced for peripheral direction by means of mixing blades before withdrawal from reactor. Peripheral direction is obtained with the aid of liquid fed from the outside of decomposition reactor; to this end use is made of initial high-boiling material or flow of liquid discharged from decomposition reactor. If necessary, etherification stage is performed through interaction with alcohol for obtaining methecrylic ester. Decomposition of by-product formed at obtaining methacrylic acid by oxidation of propylene or isobutylene or at obtaining methacrylic acid by interaction of acid with alcohol by alcohol through introduction of by-product into thermal decomposition reactor provided with distilling column which has plates made in form of disks and toroids for simultaneous decomposition and distillation. Plant proposed for realization of this method includes thermal decomposition reactor and distilling column, level meters and lines for discharge of liquid containing easily polymerized compounds. Level indicator mounted at area of accumulation of liquid shows pressure differential. Line for detecting the side of high pressure of this level meter is connected with accumulated liquid discharge line.

EFFECT: updated technology; increased yield of target products.

38 cl, 14 dwg, 2 tbl, ex

FIELD: chemical technology.

SUBSTANCE: invention relates to technology for synthesis of acetic acid by the cabonylation reaction of methanol with carbon monoxide. Method involves preparing the productive flow in the reaction section containing acetic acid, acetaldehyde, water and other impurities. In the cleansing treatment the reaction products are subjected for treatment wherein acetaldehyde impurities are oxidized to either acetic acid after its isolation and recovered to the reaction zone or to carbon dioxide and water that removed from the system. As result, method provides excluding the negative effect of acetaldehyde at step for separation of the reaction products. Oxygen, air or their mixtures, ozone, carbon peroxide or peracetic acid are used as oxidant. As possible variants of the method, the productive flow is fed to distillation column wherein flow of light products or heavy products are isolated under condition that each of these flow involves acetic acid, acetaldehyde and water. Then "light" or "heavy" flow is subjected for oxidation as said above to reduce the concentration of acetaldehyde. As a variant of the method the flow of heavy products can be treated by extraction with water followed by oxidation of acetaldehyde-containing aqueous phase. Invention provides improvement of method due to exclusion of the necessity of purification of the end product from acetaldehyde impurity.

EFFECT: improved treatment method.

20 cl, 3 tbl, 35 ex

FIELD: chemistry.

SUBSTANCE: invention relates to a method of increasing utilisation factor of silver during adsorption and removal of decyl iodide from acetic acid which contains decyl iodide as an impurity, by passing acetic acid through a packed layer of a cation-exchange resin at temperature 50°C or lower, where the cation-exchange resin is a macroporous-type polystyrene resin with average particle size ranging from 0.3 to 0.6 mm and average pore size from 15 to 28 nm, and where the resin has sulpho groups, and silver occupies 40-60% of the active sites of sulpho groups.

EFFECT: high utilisation factor of silver during adsorption and removal of decyl iodide from acetic acid.

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