JP3864563B2 - Method for producing high purity terephthalic acid - Google Patents

Description

【００３８】
表１の結果より、粉末ＣＴＡと一部の水を混練して５５〜７５重量％、特に６０〜７０重量％濃度の予混合物を形成し、これを残部の水と混合してスラリーを形成することにより、気泡および浮遊ＣＴＡが少なく、均質化したスラリーが得られることがわかる。
【図面の簡単な説明】
【図１】実施形態の高純度テレフタル酸の製造方法を示すフローシートである。
【図２】混練装置の断面図である。
【符号の説明】
１ 粉末ＣＴＡ
２ａ、２ｂ、２ｃ、２ｄ 水
３ 混練装置
４ 予混合物
５ スラリー調製槽
６ ＣＴＡ水溶液
７ 水素
８ 水素添加反応器
９ 反応液
１０ 晶析槽
１１ スラリー
１２ 固液分離装置
１３ａ、１３ｂ 分離液
１４ 結晶
１５ 乾燥機
１６ ＰＴＡ
２１ 回転軸
２２ 回転円板
２３ ＣＴＡ供給路
２４ 間隙
２５ 隔板
２６、２７ ガイド板
２８ 抵抗路
２９ 水供給路
３０ ケーシング[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing high-purity terephthalic acid (hereinafter sometimes referred to as PTA) by subjecting crude terephthalic acid (hereinafter sometimes referred to as CTA) obtained by liquid phase oxidation of para-xylene to hydrogenation treatment. is there.
[0002]
[Prior art]
When para-xylene is oxidized in the liquid phase with a molecular oxygen-containing gas, it contains 4-carboxybenzaldehyde (hereinafter sometimes referred to as 4-CBA) as a main impurity in addition to terephthalic acid (hereinafter sometimes referred to as TA). CTA generates. However, since the production of polyester fiber requires PTA as a raw material, it is necessary to purify the CTA.
[0003]
As a method for producing PTA, a method in which CTA is subjected to a hydrogenation treatment in the presence of a hydrogenation catalyst is known (for example, JP-A-4-66553). In this method, PTA is produced by reducing 4-CBA to water-soluble p-toluic acid at low temperature by hydrogenation, and separating p-toluic acid from terephthalic acid by crystallization, solid-liquid separation, or the like.
[0004]
The hydrogenation treatment is performed by forming a solid catalyst fixed layer in the reactor and supplying hydrogen while passing an aqueous CTA solution through the catalyst layer. In this case, the CTA aqueous solution is prepared by forming a slurry in which CTA powder is dispersed in water and heating it to dissolve CTA in water. In order to perform the reaction efficiently at this time, it is required to form a slurry having a concentration corresponding to the solubility of terephthalic acid during heating.
[0005]
In conventional CTA slurrying, water and powder CTA are generally introduced into a water slurry preparation tank having a rotary stirring blade and stirred to form a slurry. This method is a method in which powder CTA is dispersed in water by continuously supplying water and powder CTA while stirring the liquid filling the slurry preparation tank.
[0006]
However, since powder CTA does not have high affinity with water, it may be dispersed in a state containing bubbles, and separation of bubbles is difficult. In the state containing bubbles, the powder CTA flows in a lump, does not dissolve even when heated, flows into the hydrogenation reactor as a lump, and is trapped in the hydrogenation catalyst layer, causing clogging.
[0007]
In order to prevent this, conventionally, the amount of powder CTA to be dispersed in water is reduced, and by forming a low-concentration water slurry, the amount of CTA containing bubbles and agglomerated is reduced. It can be dissolved. However, when a low concentration slurry is supplied, there is a problem that the efficiency of the hydrogenation reaction is lowered.
[0008]
[Problems to be solved by the invention]
The object of the present invention is to promote the separation of bubbles to uniformly disperse the powder CTA, to form a high-concentration water slurry, to efficiently perform the hydrogenation reaction, and thereby to efficiently produce PTA. It is to propose a method for producing high purity terephthalic acid.
[0009]
[Means for Solving the Problems]
The present invention is the following method for producing high-purity terephthalic acid.
(1) Crude terephthalic acid obtained by liquid phase oxidation of para-xylene is mixed with water to form a slurry, and this slurry is heated to form a crude terephthalic acid solution, which is then hydrogenated in the presence of a hydrogenation catalyst. Then, in the method for producing high-purity terephthalic acid, powdered crude terephthalic acid and a part of water are premixed in a kneading apparatus to form a premixture having a concentration of 55 to 75% by weight, A method for producing high-purity terephthalic acid, comprising mixing with water to form a slurry and performing a hydrogenation treatment.
(2) The method according to (1) above, wherein the premixing is performed with a continuous kneader.
(3) Premixing with a rotating disk-type kneading device that mixes water while feeding powder CTA in the radial direction by a rotating disk arranged in the horizontal direction and moves the mixture through a narrow zigzag resistance path to homogenize the mixture. The method according to (1) above, wherein
[0010]
In the present invention, crude terephthalic acid (CTA) to be subjected to hydrogenation treatment is crude terephthalic acid obtained by liquid phase oxidation of paraxylene. Such terephthalic acid generally contains about 0.1 to 0.4% by weight of 4-CBA as a main impurity.
[0011]
The liquid phase oxidation of para-xylene is performed using a solvent and a catalyst. Examples of the solvent in the liquid phase oxidation of para-xylene include fatty acids such as acetic acid, propionic acid, n-butyric acid, isobutyric acid, n-valeric acid, trimethylacetic acid, caproic acid, and a mixture of these with water. Among these, acetic acid or acetic acid containing water as described later is preferable.
[0012]
The liquid phase oxidation catalyst for para-xylene is generally a heavy metal compound and / or a bromine-containing compound, and the former is nickel, cobalt, iron, chromium, manganese, etc. Used in a form that dissolves in the reaction system. In a preferred embodiment, a cobalt compound, a manganese compound and a bromine compound are used. The amount of the cobalt compound used is usually 10 to 10,000 ppm, preferably 100 to 3000 ppm as cobalt with respect to the solvent. Further, the manganese compound has an atomic ratio of manganese to cobalt of 0.001 to 2, and similarly the bromine compound has an atomic ratio of cobalt of 0.1 to 5.
[0013]
The liquid phase oxidation of para-xylene is performed using a molecular oxygen-containing gas. As such an oxygen-containing gas, oxygen diluted with an inert gas is usually used. For example, air or oxygen-enriched air is used. The temperature of the oxidation reaction is usually 150 to 270 ° C., preferably 170 to 220 ° C., and the pressure is at least the pressure at which the mixture can maintain a liquid phase at the reaction temperature, and usually 0.5 to 4 MPa (gauge pressure). . Furthermore, although the reaction time depends on the size of the apparatus, the residence time is usually about 20 minutes to 180 minutes. The water concentration in the reaction system is usually 3 to 30% by weight, preferably 5 to 15% by weight.
[0014]
CTA obtained by the above liquid phase oxidation reaction is introduced into a reactor, and hydrogenation treatment is performed in the presence of a hydrogenation catalyst to produce PTA. In this case, CTA separated from the mother liquid in the liquid phase oxidation reaction The resulting water slurry is heated and pressurized, introduced into the reactor as an aqueous terephthalic acid solution, and subjected to hydrogenation treatment. In general, the CTA concentration of the slurry is 10 to 40% by weight, preferably 20 to 30% by weight, but it is preferable that the concentration corresponds to the solubility during heating and pressurization.
[0015]
In the present invention, in order to form this slurry, powder CTA and a part of water are premixed by a kneader to form a premixture having a concentration of 55 to 75% by weight, preferably 60 to 70% by weight. By mixing the remaining water with the mixture, the powder CTA is uniformly dispersed to form a slurry with less bubbles and lumps.
[0016]
Premixing of the powder CTA and a part of water is performed by a kneading apparatus. The kneading apparatus is an apparatus for kneading the powder CTA in the presence of water, and a general kneading apparatus can be used. As such a kneading device, the container rotating type is a ball mill type; the container fixing type is a horizontal axis rotating blade type, a roll type, a screw type, a disk type, and a vertical axis rotating type blade type, wheel type, high speed A flow type, a rotating disk type, a rigid type; a vibration mill or the like can be mentioned as a container vibration type, but a continuous type is preferable.
[0017]
As a particularly preferable kneading apparatus, rotating disk-shaped mixing is performed by mixing water while feeding powder CTA in a radial direction by a rotating disk arranged in a horizontal direction, and moving the mixture through a narrow zigzag resistance path to homogenize the mixture. Equipment.
[0018]
Bubbles adhering to the powder CTA by mixing the powder CTA and a part of water so that the powder CTA concentration is 55 to 75% by weight, preferably 60 to 70% by weight in such a kneader. And the powdered CTA and water are uniformly mixed to form a homogenized premix.
[0019]
Since the premixture thus obtained is in a state where air bubbles are removed and water and CTA are uniformly mixed, the powder CTA is uniformly dispersed by introducing it into the slurry preparation tank together with the remaining water and stirring and mixing. A homogenized slurry is formed. As the mixing means in this case, those conventionally used for adjusting the slurry, such as a mixing tank having a rotary stirring blade, can be used.
[0020]
The CTA concentration of the slurry at this time is as described above. In this case, since bubbles in the premix are removed and the lump is reduced, dissolution is easy even if the slurry concentration is increased. The concentration can be close to solubility.
[0021]
The slurry thus obtained is heated to dissolve CTA to form a terephthalic acid solution, which is introduced into a reactor and subjected to a hydrogenation treatment. The shape, structure, etc. of the reactor for performing the hydrogenation treatment are not limited as long as the reactor is filled with a catalyst and hydrogen can be supplied in contact with the CTA aqueous solution.
[0022]
As a preferable reactor, a solid catalyst is filled to form a fixed layer, and an introduction path and an outlet path are provided so that a CTA aqueous solution can be passed therethrough, and a hydrogen supply path is provided so that hydrogen can be supplied. Those are preferred. The CTA solution may be an upward flow, but it is preferable that the introduction path communicates with the upper part of the reactor and the outlet path communicates with the lower part so that the downward flowing liquid flows. It is preferable to contact.
[0023]
As the hydrogenation catalyst, those conventionally used can be used. For example, palladium, ruthenium, rhodium, osmium, iridium, platinum, platinum black, palladium black, iron, cobalt-nickel, etc. are used. A solid catalyst in which these are supported on an adsorbent carrier such as activated carbon so that they can be formed is preferable.
[0024]
In the hydrogenation treatment, in a steady state, the water slurry of CTA is heated and pressurized to a temperature of 230 ° C. or higher, preferably 240 to 300 ° C., a pressure of 1 to 11 MPa, preferably 3 to 9 MPa (gauge pressure) to dissolve terephthalic acid. While supplying the resulting CTA aqueous solution to the reactor and passing it through the catalyst layer, hydrogen gas was fed at a flow rate of 1.5 times mol or more, preferably 2 times mol or more of 4-CBA in the crude terephthalic acid aqueous solution. Supply and perform hydrogenation. The reaction temperature of hydrogenation is 230 ° C. or higher, preferably 255 to 300 ° C., the pressure is 1 to 11 MPa, preferably 3 to 9 MPa (gauge pressure), and the hydrogen partial pressure is 0.05 MPa or higher, preferably about 0.05 to 2 MPa. It is said.
[0025]
Since 4-CBA in CTA is reduced to water-soluble p-toluic acid by the hydrogenation treatment, it is crystallized at 300 ° C. or lower, preferably 100 to 280 ° C. Separation of p-toluic acid gives purified terephthalic acid. This purified terephthalic acid is re-slurried into a slurry, and foreign substances adhering to the crystals are transferred to the water side, followed by solid-liquid separation and drying to produce high-purity terephthalic acid (PTA).
[0026]
【The invention's effect】
According to the present invention, the powder CTA and a part of water are kneaded to form a premix, and this mixture is mixed with the remaining water to form a slurry. The powder CTA is uniformly dispersed to form a high-concentration water slurry, and the hydrogenation reaction is efficiently carried out, whereby PTA can be produced efficiently.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a flow sheet showing a method for producing high-purity terephthalic acid according to an embodiment.
[0028]
In FIG. 1, high-purity terephthalic acid (PTA) is produced by first supplying powdered terephthalic acid (CTA) 1 together with a part of water 2a to a kneading device 3 and premixing the mixture, thereby preliminarily having a concentration of 55 to 75% by weight. The mixture 4 is formed, and this is supplied to the slurry preparation tank 5 together with other water 2b. If necessary, other water (make-up water) 2c is further supplied and stirred to form a slurry. This slurry is heated and pressurized to dissolve CTA, and the CTA aqueous solution 6 and hydrogen 7 are supplied to the hydrogenation reactor 8 to perform a hydrogenation treatment. The reaction solution 9 subjected to the hydrogenation treatment is decompressed, cooled, and introduced into the crystallization tank 10 for crystallization.
[0029]
The produced slurry 11 is introduced into a solid-liquid separator 12 to perform solid-liquid separation. The solid-liquid separation is usually performed in a plurality of stages, and the first-stage separation liquid 13a is discharged as waste water. In the second-stage solid-liquid separation, water (washing water) 2d is supplied to reslurry and solid-liquid separation is performed. The separation liquid 13b circulates as water 2a and 2b.
The separated crystals 14 are dried in a drier 15 to produce high purity terephthalic acid (PTA) 16.
[0030]
FIG. 2 is a cross-sectional view of the kneading device 3, in which a vertical axis rotating disk-type kneading device is used. The kneading apparatus 3 has a CTA supply passage 23 opened to face the central portion of a rotating disk 22 arranged in a horizontal direction rotated by a vertical rotating shaft 21, and rotates around an end portion thereof via an annular gap 24. A donut-like partition plate 25 whose peripheral portion is thick is provided substantially parallel to the circular plate 22, and a zigzag-shaped resistance path 28 is provided between the peripheral portions of the guide plates 26 and 27 that cover these peripheral portions from below and above. Is formed. 29 is a water supply path provided so as to surround the CTA supply path 23, and 30 is a casing.
[0031]
In the kneading apparatus 3, when the powder CTA 1 is supplied from the CTA supply path 23 and the water 2 a is supplied from the water supply path 29 while rotating the rotating disk 22 by the rotating shaft 21, the powder CTA 1 that has exited from the CTA supply path 23 rotates. It collides with the disk 22 and flows radially and mixed with water exiting from the gap 24 and flows spirally in the peripheral direction, mixed with water flowing from the upper side of the partition plate 25 and flows in a zigzag manner through the resistance path 28, As a result, the powder CTA and water are premixed, bubbles are separated, and the powder CTA and water are uniformly mixed to form a homogeneous premix 4.
[0032]
The homogenized premix 4 is stirred and mixed with the water 2b and 2c in the slurry preparation tank 5, so that the powder CTA is homogeneously dispersed in water without being agglomerated to form a homogenized slurry. . For this reason, even if the CTA concentration of the slurry is increased, it can be dissolved almost completely when heated and pressurized to obtain a uniform TA aqueous solution, and the reaction efficiency of the hydrogenation treatment in the hydrogenation reactor 8 can be increased.
[0033]
In the above example, a rotating disk type is used as the kneading apparatus, but other types may be used. Further, the solid-liquid separated crystal 14 in the solid-liquid separation device 12 is dried as it is, but water is added to the separated crystal 14 to form a re-water slurry, and the re-water slurry is purified again by solid-liquid separation and purification. Also good.
[0034]
【Example】
Examples of the present invention will be described below.
[0035]
Reference example 1
Into the slurry preparation tank 5 of FIG. 1 having a rotary blade type stirrer, 200 kg powder CTA and 800 kg water were stirred and mixed to form a 20 wt% slurry, which was allowed to stand for 30 minutes and the state of phase separation was observed.
[0036]
Examples 1 and 2, Reference Examples 2 and 3
The powder CTA and a part of water are introduced into the rotating disk kneader 3 shown in FIG. 2 and kneaded, and the premix and the remaining water are introduced into the slurry preparation tank 5 of FIG. A 20% by weight slurry was prepared by stirring and mixing, and the separation state after standing for 30 minutes was similarly observed.
The results are shown in Table 1.
[0037]
[Table 1]

[0038]
From the results shown in Table 1, powder CTA and a part of water are kneaded to form a premix of 55 to 75% by weight, particularly 60 to 70% by weight, and this is mixed with the remaining water to form a slurry. Thus, it can be seen that a homogenized slurry is obtained with less bubbles and floating CTA.
[Brief description of the drawings]
FIG. 1 is a flow sheet showing a method for producing high-purity terephthalic acid according to an embodiment.
FIG. 2 is a cross-sectional view of a kneading apparatus.
[Explanation of symbols]
1 Powder CTA
2a, 2b, 2c, 2d Water 3 Kneading device 4 Premix 5 Slurry preparation tank 6 CTA aqueous solution 7 Hydrogen 8 Hydrogenation reactor 9 Reaction liquid 10 Crystallization tank 11 Slurry 12 Solid-liquid separator 13a, 13b Separation liquid 14 Crystal 15 Dryer 16 PTA
21 Rotating shaft 22 Rotating disc 23 CTA supply path 24 Gap 25 Separating plates 26 and 27 Guide plate 28 Resistance path 29 Water supply path 30 Casing

Claims (3)

Crude terephthalic acid obtained by liquid phase oxidation of para-xylene is mixed with water to form a slurry, and this slurry is heated to form a crude terephthalic acid solution, and hydrogenated in the presence of a hydrogenation catalyst, In a method for producing high-purity terephthalic acid, powdered crude terephthalic acid and a part of water are premixed in a kneader to form a premixture having a concentration of 55 to 75% by weight, and this premixture is mixed with the remaining water. Forming a slurry, and performing a hydrogenation process, a method for producing high-purity terephthalic acid. The method according to claim 1, wherein the premixing is carried out in a continuous kneader. Requests to premix in a rotating disk kneading device that mixes water while feeding powder CTA in the radial direction by a rotating disk arranged in the horizontal direction and moves the mixture through a narrow zigzag resistance path to homogenize the mixture. Item 2. The method according to Item 1.

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