WO2018051775A1 - 高純度テレフタル酸の製造方法 - Google Patents
高純度テレフタル酸の製造方法 Download PDFInfo
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- WO2018051775A1 WO2018051775A1 PCT/JP2017/030795 JP2017030795W WO2018051775A1 WO 2018051775 A1 WO2018051775 A1 WO 2018051775A1 JP 2017030795 W JP2017030795 W JP 2017030795W WO 2018051775 A1 WO2018051775 A1 WO 2018051775A1
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/16—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/16—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation
- C07C51/21—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen
- C07C51/255—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of compounds containing six-membered aromatic rings without ring-splitting
- C07C51/265—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of compounds containing six-membered aromatic rings without ring-splitting having alkyl side chains which are oxidised to carboxyl groups
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/42—Separation; Purification; Stabilisation; Use of additives
- C07C51/47—Separation; Purification; Stabilisation; Use of additives by solid-liquid treatment; by chemisorption
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D9/00—Crystallisation
- B01D9/0059—General arrangements of crystallisation plant, e.g. flow sheets
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/42—Separation; Purification; Stabilisation; Use of additives
- C07C51/43—Separation; Purification; Stabilisation; Use of additives by change of the physical state, e.g. crystallisation
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/42—Separation; Purification; Stabilisation; Use of additives
- C07C51/487—Separation; Purification; Stabilisation; Use of additives by treatment giving rise to chemical modification
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C63/00—Compounds having carboxyl groups bound to a carbon atoms of six-membered aromatic rings
- C07C63/14—Monocyclic dicarboxylic acids
- C07C63/15—Monocyclic dicarboxylic acids all carboxyl groups bound to carbon atoms of the six-membered aromatic ring
- C07C63/26—1,4 - Benzenedicarboxylic acid
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D9/00—Crystallisation
- B01D2009/0086—Processes or apparatus therefor
- B01D2009/009—Separation of organic compounds by selective or extractive crystallisation with the aid of auxiliary substances forming complex or molecular compounds, e.g. with ureum, thioureum or metal salts
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/16—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation
- C07C51/21—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen
- C07C51/215—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of saturated hydrocarbyl groups
Definitions
- the present invention relates to a method for producing high-purity terephthalic acid.
- Terephthalic acid is produced by a liquid phase oxidation reaction of a p-phenylene compound such as p-alkylbenzene represented by p-xylene.
- a catalyst such as cobalt or manganese is used with acetic acid as a solvent, or a catalyst obtained by adding a promoter such as a bromine compound or acetaldehyde to a catalyst such as cobalt or manganese is used.
- this liquid phase oxidation reaction uses acetic acid as a solvent, and the resulting crude terephthalic acid slurry contains 4-carboxybenzaldehyde (hereinafter also referred to as 4CBA), p-toluic acid (hereinafter also referred to as p-TOL), Many impurities such as benzoic acid and other various coloring impurities are contained.
- 4CBA 4-carboxybenzaldehyde
- p-TOL p-toluic acid
- impurities such as benzoic acid and other various coloring impurities are contained.
- the above impurities are also mixed in the crude terephthalic acid obtained by separation from the crude terephthalic acid slurry, and obtaining a high-purity terephthalic acid requires a considerably high level of purification technology.
- the crude terephthalic acid is dissolved in acetic acid, water, or a mixed solvent thereof at high temperature and high pressure, and catalytic hydrogenation, decarbonylation, oxidation, recrystallization, Alternatively, various methods such as a high temperature immersion treatment in a slurry state in which a part of terephthalic acid crystals are dissolved are known. Regardless of which purification method is used, it is necessary to finally separate the terephthalic acid crystals from the mother liquor.
- oxide intermediates such as 4CBA, p-TOL, and benzoic acid or coloring-causing substances present as impurities in the slurry obtained by purifying crude terephthalic acid are dissolved in the slurry mother liquor at high temperatures.
- these impurities come into the terephthalic acid crystals, making it difficult to obtain high-purity terephthalic acid. .
- Centrifugation is the most commonly used method for separating mother liquor from a slurry containing terephthalic acid crystals. Centrifugation is a method in which a slurry solution is introduced into a basket that rotates at high speed, the mother liquor overflows from the top, and the crystals are guided to the bottom. It is known that the centrifuge method involves some difficulties in continuous operation at high temperature and high pressure due to structural and functional limitations of the centrifuge.
- Patent Document 1 discloses a mother liquor replacement device in which a lateral shelf having a plurality of holes is provided therein, and when such a structure is not provided, channeling of fluid in the device or It is described that the efficiency of substitution is reduced by backmixing.
- Patent Document 2 describes that the replacement performance is improved by providing a shelf that forms a slope in the apparatus.
- Patent Document 3 a terephthalic acid slurry is introduced from the upper part of the tower and a dispersion medium for substitution is introduced from the lower part of the tower, and the terephthalic acid crystals that settle in the tower and the substitution dispersion medium that rises in the tower are countercurrently flowed.
- a stirrer is provided at the lower part of the tower, and the terephthalic acid content in the slurry in the lower region is higher than the terephthalic acid content in the slurry in the intermediate region, A simple dispersion medium replacement device that does not require a shelf is described.
- Patent Document 4 discloses that a crude terephthalic acid is dissolved in water and reduced in contact with hydrogen in the presence of a platinum group metal catalyst. Is described as a slurry, and the crystals in the slurry are separated by a solid-liquid separator to obtain purified terephthalic acid.
- the moisture content of the dehydrated cake of terephthalic acid obtained by solid-liquid separation in this process is 15 to 20% by mass, and when drying using a fluidized bed dryer, flash drying or heater It is disclosed that a step of reducing the water content of terephthalic acid to 14% by mass or less is necessary by a method such as predrying according to No.
- Patent Document 4 various solid-liquid separation methods such as a screen bowl centrifuge, a rotary vacuum filter, and a horizontal belt filter were tried. However, the moisture content was reduced to 14% by mass or less only by solid-liquid separation. It is disclosed that it is difficult to do.
- terephthalic acid is reacted with ethylene glycol or the like and used mainly as a raw material for polyester. If the particle size of the terephthalic acid exceeds 200 ⁇ m, the particle size of the terephthalic acid tends to remain as an unreacted component. As a result, it is necessary to increase the reaction time, thereby increasing the amount of by-products. Arise.
- Patent Document 5 discloses a method in which the ratio of the particle size exceeding 210 ⁇ m is made 10% by mass or less.
- crude terephthalic acid is dissolved in an aqueous medium, subjected to catalytic hydrogenation treatment with a platinum group metal catalyst, and crystallized by cooling in stages in a multistage crystallization tank connected in series.
- the ratio of the particle size exceeding 210 ⁇ m is made 10 mass% or less.
- Japanese Patent Laid-Open No. 57-053431 Japanese Unexamined Patent Publication No. 55-087744 JP-A-8-231465 JP 2009-203163
- An object of the present invention is to perform crystallization after catalytic hydrogenation treatment of a crude terephthalic acid-containing liquid obtained by liquid phase oxidation, and further convert the terephthalic acid crystal slurry into purified terephthalic acid slurry with clean water using a mother liquor replacement device.
- the mother liquor substitution is performed efficiently, and the heating load during the drying step of the purified terephthalic acid cake after solid-liquid separation is reduced.
- An object of the present invention is to provide a method for producing high-purity terephthalic acid which is small and exhibits good behavior as a raw material for polyester.
- the present inventors have effectively performed mother liquor replacement by operating the crystallization step and the mother liquor replacement step after the catalytic hydrogenation treatment of the crude terephthalic acid-containing liquid under specific conditions.
- the inventors have found a method for producing high-purity terephthalic acid that has a small heating load when drying a purified terephthalic acid cake after solid-liquid separation and exhibits good behavior as a polyester raw material, and has completed the present invention.
- the present invention is as follows. [1] The following steps (a) to (e); (A) a step of obtaining a crude terephthalic acid crystal by liquid phase oxidation of a p-phenylene compound; (B) a step of catalytic hydrogenation after dissolving the crude terephthalic acid crystals in water; (C) Step of reducing the pressure of the reaction solution after the catalytic hydrogenation stepwise using two or more crystallization tanks, lowering the temperature to crystallize terephthalic acid to obtain a terephthalic acid slurry, (D) The terephthalic acid slurry is introduced into the upper part of the mother liquor displacement tower, and the terephthalic acid crystals are brought into contact with the rising flow of substitution water introduced from the bottom of the mother liquor displacement tower while allowing the terephthalic acid crystals to settle in the tower.
- a method for producing high-purity terephthalic acid comprising: The amount of the crystal to be subjected to the catalytic hydrogenation treatment is Q [ton / hr], the residence time of the first crystallization tank of the two or more crystallization tanks is T 1 [hr], and When the cross-sectional area is A [m 2 ], the following conditions (1) to (3); (1) 0.07 ⁇ T 1 ⁇ 0.5 (2) 0.3 ⁇ A / Q ⁇ 0.8 (3) 0.035 ⁇ T 1 ⁇ A / Q ⁇ 0.25 A method for producing high-purity terephthalic acid that satisfies all requirements.
- the present embodiment a mode for carrying out the present invention (hereinafter simply referred to as “the present embodiment”) will be described in detail.
- the following embodiments are examples for explaining the present invention, and are not intended to limit the present invention to the following contents.
- the present invention can be implemented with appropriate modifications within the scope of the gist thereof.
- the method for producing high-purity terephthalic acid of this embodiment is as follows: The following steps (a) to (e); (A) a step of obtaining a crude terephthalic acid crystal by liquid phase oxidation of a p-phenylene compound; (B) a step of catalytic hydrogenation after dissolving the crude terephthalic acid crystals in water; (C) Step of reducing the pressure of the reaction solution after the catalytic hydrogenation stepwise using two or more crystallization tanks, lowering the temperature to crystallize terephthalic acid to obtain a terephthalic acid slurry, (D) The terephthalic acid slurry is introduced into the upper part of the mother liquor displacement tower, and the terephthalic acid crystals are brought into contact with the rising flow of substitution water introduced from the bottom of the mother liquor displacement tower while allowing the terephthalic acid crystals to settle in the tower.
- Extracting from the bottom of the tower as a slurry with the replacement water (E) a step of solid-liquid separation of the slurry extracted from the bottom of the tower into water and terephthalic acid crystals, and drying the separated terephthalic acid crystals; including.
- the amount of crystals to be subjected to the catalytic hydrogenation treatment is Q [ton / hr], and the first crystallization tank of the two or more crystallization tanks.
- T 1 [hr] is the residence time and A [m 2 ] is the cross-sectional area of the mother liquor displacement column, the following conditions (1) to (3): (1) 0.07 ⁇ T 1 ⁇ 0.5 (2) 0.3 ⁇ A / Q ⁇ 0.8 (3) 0.035 ⁇ T 1 ⁇ A / Q ⁇ 0.25 Satisfy all of the above.
- the high purity terephthalic acid in the production method of the present embodiment refers to terephthalic acid purified through the above steps (a) to (e) (hereinafter also referred to as purified terephthalic acid).
- the form of the purified terephthalic acid in this embodiment is preferably a crystal.
- Step (a) is a step of obtaining crude terephthalic acid crystals by liquid phase oxidation of a p-phenylene compound.
- Step (a) is preferably a step of obtaining crude terephthalic acid crystals by separating the reaction mother liquor from the crude terephthalic acid slurry obtained by subjecting the p-phenylene compound to liquid phase oxidation and then dropping the pressure and lowering the temperature.
- the p-phenylene compound in this embodiment has two carboxyl groups or oxidizable substituents that generate carboxyl groups by liquid-phase air oxidation on phenyl, and the two carboxyl groups or oxidizable substituents are It is the positional relationship of the para position.
- the oxidizable substituent include a methyl group, an ethyl group, a propyl group, an isopropyl group, an aldehyde group, and an acetyl group.
- the two substituents on the phenyl may be the same or different.
- the oxidizing agent used for liquid phase oxidation is oxygen or air, and is not limited to either, but in acetic acid solution in the presence of cobalt and manganese catalysts and bromide compound promoters. In the case of oxidation, air is sufficient. Moreover, when oxidizing in acetic acid solution in presence of a cobalt catalyst, it is preferable to use oxygen.
- cobalt and manganese catalysts are used as the catalyst, it is preferable to use a bromide compound in combination.
- the bromide compound is generally considered to function as a cocatalyst, and as the bromide compound, for example, hydrogen bromide and sodium bromide are preferable.
- acetaldehyde, methyl ethyl ketone, etc. together as a promoter.
- Crude terephthalic acid crystals obtained by a liquid phase oxidation reaction in an acetic acid solution usually contain many impurities including 4CBA, and the value of OD340, which is an index of whiteness, is not at a level that can be used directly as a polymer raw material.
- OD340 there is no particular upper limit for OD340.
- Step (b) is a step in which the crude terephthalic acid crystal is subjected to catalytic hydrogenation.
- the step (b) is preferably a step in which the crude terephthalic acid crystal is dissolved in water at high temperature and high pressure and then subjected to catalytic hydrogenation.
- the crude terephthalic acid crystal is mixed with water and subjected to a catalytic hydrotreating process.
- This catalytic hydrogenation treatment is carried out under high temperature and high pressure conditions because it is carried out in a solution state.
- the catalytic hydrogenation treatment is to perform a catalytic hydrogenation reaction.
- the temperature of the catalytic hydrogenation reaction is preferably 260 ° C. or higher, more preferably 270 to 300 ° C.
- the concentration of crude terephthalic acid in the solution is preferably 10 to 40% by mass.
- the pressure of the catalytic hydrogenation reaction is not particularly limited as long as it is sufficient for the terephthalic acid-containing treatment liquid to maintain a liquid phase and can maintain a hydrogen partial pressure suitable for the catalytic hydrogenation reaction. It is preferably ⁇ 10 MPa.
- the group 8 noble metal is preferably palladium, platinum, ruthenium or rhodium, more preferably palladium or platinum. In addition, it is not always necessary to use these metals alone, and two or more kinds may be used in combination as necessary.
- the catalyst is preferably supported on a carrier from the viewpoint of maintaining long-term activity.
- a carrier a porous material is usually used, and a carbon-based carrier is preferable in terms of material.
- the carbon-based carrier include activated carbon and coconut shell charcoal, and coconut shell charcoal is preferable.
- the amount of the catalyst supported on the carrier is not particularly limited because the effect of the catalyst is obtained even in a trace amount, but is preferably about 0.1 to 0.5% by mass from the viewpoint of maintaining long-term activity.
- the amount of hydrogen in the catalytic hydrogenation treatment is preferably twice or more moles relative to 4CBA contained in the crude terephthalic acid solution.
- the time for the catalytic hydrogenation treatment may be a time sufficient for the hydrogenation reaction to proceed, and is usually 1 to 60 minutes, preferably 2 to 20 minutes. Usually, the catalytic hydrotreatment is carried out continuously.
- the crude terephthalic acid solution after the catalytic hydrogenation treatment was made of sintered titanium, other sintered metals, or carbon particles, for example, to prevent contamination of fine powders caused by wear of activated carbon used as a catalyst support. It is preferable to filter with a filter.
- Step (c) is a step of obtaining a terephthalic acid slurry by crystallizing terephthalic acid by gradually reducing the pressure and lowering the temperature of the reaction solution after the catalytic hydrogenation using two or more crystallization tanks.
- the reaction solution after the catalytic hydrogenation is introduced into two or more stages of crystallization tanks connected in series, and the temperature is lowered to 120 to 200 ° C. by flash evaporation of water, and the terephthalic acid crystals are reduced. Crystallizes to obtain a terephthalic acid crystal slurry.
- the number of crystallization tanks connected in series affects the average particle size and particle size distribution of purified terephthalic acid crystals.
- a terephthalic acid crystal having a moderate average particle size and a narrow particle size distribution has a small heating load during drying and exhibits good behavior as a raw material for polyester.
- the larger the number of crystallization tanks the more the amount of impurities in the crystal can be reduced. Even if the number of stages of the crystallization tank is 7 or more, the effect of reducing impurities is reduced. Therefore, the number of stages of the crystallization tank is preferably 2 to 6, more preferably 3 to 5.
- the temperature and residence time of each crystallization tank also affect the average particle size and particle size distribution of purified terephthalic acid crystals and the amount of impurities in the crystals.
- the temperature and residence time of the first stage crystallization tank have a large effect on the average grain size of crystals.
- the temperature of the first crystallization tank is preferably 230 to 270 ° C., more preferably 240 to 260 ° C. By setting the temperature of the first crystallization tank to 230 to 270 ° C., it is possible to obtain a purified terephthalic acid crystal with a small heating load during drying and a small amount of impurities.
- the residence time in the first crystallization tank (hereinafter sometimes referred to as T 1 ) is 0.07 to 0.5 hr (hereinafter also referred to as condition (1)), preferably 0.08. Is 0.4 hr, more preferably 0.1 to 0.3 hr.
- the average particle diameter of the residence time is long enough purified terephthalic acid crystals tend to increase, by a T 1 and 0.07 ⁇ 0.5 hr, having an appropriate average particle diameter, heat load during drying is small
- purified terephthalic acid crystals exhibiting good behavior as a raw material for polyester can be obtained.
- the residence time in the second and subsequent crystallization tanks is preferably 0.08 to 0.5 hr, more preferably 0.1 to 0.4 hr.
- Second (sometimes hereinafter referred to T 2) residence time crystalliser also for impact on the average particle size and particle size distribution of crystals is large, the residence time of the sum of the residence time of the first crystallizer T 1 + T 2 [hr] is preferably 0.15 to 0.7 hr.
- the temperature of the second and subsequent crystallization tanks is preferably lowered stepwise so that the final crystallization tank temperature is 120 to 200 ° C., specifically 20 to 20 The temperature is preferably lowered by 40 ° C.
- step (d) the terephthalic acid crystal slurry is introduced into the upper part of the mother liquor displacement tower, and the terephthalic acid crystals are brought into contact with the rising flow of substitution water introduced from the bottom of the mother liquor displacement tower while being settled in the tower, This is a step of extracting the terephthalic acid crystals from the bottom of the tower as a slurry with the replacement water (hereinafter also referred to as “mother liquor replacement step”).
- the temperature of the terephthalic acid crystal slurry introduced into the upper part of the mother liquor displacement tower is preferably 120 to 200 ° C, more preferably 130 to 180 ° C, and further preferably 140 to 170 ° C.
- the temperature of the terephthalic acid crystal slurry is preferably 120 to 200 ° C, more preferably 130 to 180 ° C, and further preferably 140 to 170 ° C.
- mother liquor replacement step the mother liquor containing a large amount of impurities in the supplied terephthalic acid crystal slurry (hereinafter also referred to as “raw slurry”) is replaced with fresh water.
- the apparatus used in the mother liquor replacement step namely, “mother liquor replacement tower” is roughly divided into a tower upper part, a tower bottom part, and a tower intermediate part.
- the upper part of the tower has an introduction part of a raw slurry made of a mother liquor containing terephthalic acid crystals.
- the introduction portion of the raw slurry may be opened in the inner wall of the tower upper part, but it is preferable that the raw slurry is extended and opened in the upper part of the tower from the viewpoint of improving the dispersion of crystals.
- the opening tip of the raw slurry introduction part may be installed downward, and the opening tip may be provided with a mechanism for promoting the dispersion of crystals such as a dispersion plate.
- the upper part of the tower is further provided with a mother liquor outlet, from which the mother liquor containing almost no terephthalic acid crystals is extracted and led to a predetermined treatment tank.
- the middle part of the tower does not need to be provided with a structure such as a shelf that obstructs the movement of the terephthalic acid crystals that settle by gravity.
- the tower bottom part includes a replacement water supply part, an extraction port for the purified terephthalic acid slurry substituted with the replacement water, an adjustment part for the replacement water supply flow rate and the replacement slurry extraction flow rate, and a stirring device for the slurry in the tower bottom part.
- the position of the extraction port of the purified terephthalic acid slurry substituted with substitution water is preferably closer to the lower part of the tower bottom because the slurry has a high specific gravity.
- the size of the mother liquor displacement tower can be appropriately changed depending on the amount of terephthalic acid crystals to be treated.
- the inner diameter of the tower middle part is defined as Q [ton / hr] for the amount of terephthalic acid crystals to be subjected to catalytic hydrogenation treatment, and A [m 2 ] for the cross-sectional area of the mother liquor replacement tower, 0.3 ⁇ A / Q ⁇ 0.8 (Hereinafter also referred to as condition (2)).
- the inner diameter of the middle part of the tower is 0.35 ⁇ A / Q ⁇ 0.6
- the inner diameter is preferably such that
- the inner diameter is such that A / Q is smaller than 0.3, separation between the mother liquor and the terephthalic acid crystal becomes insufficient, and the amount of impurities in the purified terephthalic acid increases. In some cases, terephthalic acid crystals flow out from the mother liquor extraction portion at the top of the tower.
- the inner diameter is such that A / Q is greater than 0.8, the amount of impurities in the purified terephthalic acid increases because the amount of the mother liquor mixed into the bottom of the column increases due to the large column cross-sectional area.
- the diameter of the tower upper part and the tower bottom may be the same as that of the middle part of the tower, but can be larger.
- the height of the column is preferably such that the supplied terephthalic acid crystals are dispersed throughout the column. Specifically, the distance from the raw slurry introduction part to the column bottom is 1 with respect to the column inner diameter. It is preferable to set the height to be about 3 times.
- the mother liquor displacement effect in the mother liquor displacement column is affected not only by the inner diameter of the column but also by the average particle size and particle size distribution of the terephthalic acid crystals to be treated. Therefore, displacement effect of the mother liquor varies by residence time T 1 of the average particle diameter is large and the influence of the particle size distribution first crystallizer of the terephthalic acid crystals.
- T 1 ⁇ A / Q satisfies the condition of the following formula (also referred to as condition (3)). 0.035 ⁇ T 1 ⁇ A / Q ⁇ 0.25
- T 1 ⁇ A / Q preferably satisfies the following condition. 0.04 ⁇ T 1 ⁇ A / Q ⁇ 0.2
- T 1 ⁇ A / Q satisfies the following condition. 0.045 ⁇ T 1 ⁇ A / Q ⁇ 0.15
- T 1 ⁇ A / Q By setting T 1 ⁇ A / Q to 0.035 to 0.25, a high mother liquor replacement effect can be obtained.
- T 1 ⁇ A / Q is less than 0.035, the replacement effect of the mother liquor is reduced.
- T 1 ⁇ A / Q is greater than 0.25, the replacement effect of the mother liquor is reduced and the size is excessive. Crystallization tank and mother liquor replacement tower are required.
- the terephthalic acid slurry introduced from the top of the tower forms a high slurry concentration layer at the bottom of the mother liquor replacement tower by sedimentation by gravity, and a high slurry concentration layer and a low slurry concentration region where terephthalic acid crystals settle by gravity.
- An interface is formed between the two.
- the slurry layer at the bottom of the column is preferably given fluidity by a stirrer in order to prevent crystal solidification and blockage. If stirring is performed more than necessary, the concentration of the impurities to be replaced is uniformly stirred and the replacement efficiency is remarkably lowered. Therefore, it is preferable that the stirring be performed so as not to impair the fluidity of the slurry layer.
- the power of the stirrer is preferably 0.05 to 1.0 kWh / m 3 and more preferably 0.1 to 0.8 kWh / m 3 as the power per unit volume of the slurry layer at the bottom of the tower. 0.2 to 0.7 kWh / m 3 is more preferable.
- the mother liquor is mainly extracted from the top of the tower along with the upward flow of replacement water introduced from the bottom of the tower.
- the fine crystals in the supplied terephthalic acid slurry are not settled but rise with an upward flow, and are extracted from the top of the column together with the mother liquor.
- high-purity terephthalic acid produced through a mother liquor replacement device has a small proportion of small particle diameters of 53 ⁇ m or less and a particularly small proportion of fine particle diameters of 38 ⁇ m or less.
- the crystallization step is to satisfy the condition (1) to (3), the proportion of these small particle size crystals Can be further reduced, and high-purity terephthalic acid in which crystals having a small particle size of less than 53 ⁇ m are 15% or less and crystals having a fine particle size of less than 38 ⁇ m are 7% or less can be obtained.
- the crystal grain size ratio indicates a ratio obtained by classification by sieving of crystals.
- the linear velocity of the ascending liquid flow in the middle portion of the mother liquor displacement tower is preferably 0.2 to 1.5 m / hr (based on the empty column), more preferably 0.5 to 1.0 m / hr. . If the linear velocity is too low, the mother liquor and terephthalic acid crystals are not sufficiently separated, and the amount of impurities in the purified terephthalic acid increases. On the other hand, if the linear velocity is too low, the number of fine crystals of terephthalic acid rising with the mother liquor extracted from the top of the column decreases. On the other hand, if the linear velocity is too high, there is a disadvantage that the amount of replacement water used increases.
- the linear velocity of the ascending liquid flow of the replacement water can be calculated from the balance of the water of the replacement water supply amount and the slurry extracted from the bottom of the tower.
- the pressure of the mother liquor replacement tower is a pressure that can maintain at least the temperature of the raw slurry and the replacement water. Although there is no restriction on the operation of the upper limit of the pressure, operating at an excessive pressure causes an increase in equipment cost because it is necessary to increase the pressure resistance of the substitution tower.
- the pressure in the mother liquor displacement column is preferably 0.1 to 2 MPa (gauge pressure), more preferably 0.2 to 1.5 MPa.
- Step (e) is a step of solid-liquid separating the slurry extracted from the tower bottom into water and terephthalic acid crystals and drying the separated terephthalic acid crystals.
- the slurry extracted from the bottom of the mother liquor replacement tower is separated into terephthalic acid crystals and water by a solid-liquid separator such as a rotary vacuum filter.
- the terephthalic acid crystal obtained by solid-liquid separation is obtained as a cake, and the water content of the cake after solid-liquid separation is 12 to 13% by mass. That is, according to the manufacturing method of the present embodiment, the moisture content of the cake can be easily reduced to 15% by mass or less only by the solid-liquid separation process.
- the moisture content of the cake is low, it is possible to suppress energy consumption in the subsequent drying process.
- a steam tube dryer or the like that is commonly used for terephthalic acid production can be used.
- the water content of the terephthalic acid cake is low, so the separated cake is directly used in a fluidized bed dryer. And can be dried.
- the high-purity terephthalic acid produced in this embodiment has a narrow particle size distribution, the proportion of crystals having a particle size of less than 53 ⁇ m is reduced to 15% or less, and crystals having a particle size of 212 ⁇ m or more are also reduced to 15% or less.
- One of the embodiments is a high purity in which the median diameter is 100 to 130 ⁇ m, the crystal having a particle size of less than 53 ⁇ m is 15% by mass or less, and the crystal having a particle size of 212 ⁇ m or more is 15% by mass or less with respect to the total crystal mass.
- Terephthalic acid is a high purity in which the median diameter is 100 to 130 ⁇ m, the crystal having a particle size of less than 53 ⁇ m is 15% by mass or less, and the crystal having a particle size of 212 ⁇ m or more is 15% by mass or less with respect to the total crystal mass.
- a high-purity terephthalic acid having a median diameter of 100 to 130 ⁇ m, 15% by mass or less of crystals having a particle size of 53 ⁇ m or less, and 15% by mass or less of crystals having a particle size of 212 ⁇ m or less with respect to the mass of all crystals is It can manufacture with the manufacturing method of a form.
- the proportion of crystals having a particle size of 212 ⁇ m or more in the high purity terephthalic acid of this embodiment is preferably 12% or less.
- the proportion of crystals having a particle size of less than 38 ⁇ m is preferably 7% or less.
- the crystal having a particle size of 212 ⁇ m or more is 15% by mass or less, a good behavior as a polyester raw material can be exhibited. Moreover, when the crystal
- Mother liquor replacement rate (%) (Amount of benzoic acid contained in the mother liquor extracted from the mother liquor outlet at the top of the tower) / (Amount of benzoic acid contained as impurities in the crude terephthalic acid slurry) ⁇ 100
- the terephthalic acid content (% by mass) in the mother liquor discharged from the upper part of the mother liquor replacement tower was calculated from the crystal weight obtained by filtering the mother liquor cooled to room temperature.
- Example 1 A liquid phase oxidation reaction of p-xylene was carried out in an acetic acid solution using a cobalt and manganese catalyst and a bromide compound co-catalyst, followed by crystallization and cooling, and the precipitated crude terephthalic acid crystals were separated.
- the obtained crude terephthalic acid was mixed with water and dissolved by heating, and the hydrogenation reaction tank 1 in FIG. 1 was used for catalytic hydrogenation reaction at 281 ° C., and the terephthalic acid solution as the reaction solution was crystallized.
- the first crystallization tank of tank 2 It is sent to the first crystallization tank of tank 2 at a flow rate of 126 tons per hour (the terephthalic acid content is 24.8% by mass and the terephthalic acid crystal treatment amount Q is 31.3 ton per hour) to form a 250 ° C. crystallization slurry. It was. At this time, the slurry residence time in the 1st crystallization tank calculated from the liquid level of the 1st crystallization tank was 0.12 hr. The 250 ° C. crystallization slurry was continuously supplied to the second crystallization tank at 230 ° C. via a transfer pipe at a flow rate of 114 tons per hour (the terephthalic acid content was 27.4% by mass).
- the slurry residence time in the second crystallization tank was 0.20 hr. Furthermore, it was continuously supplied to a third crystallization tank at about 195 ° C. at a flow rate of 111 tons (the terephthalic acid content was 28.2% by mass). Further, it was continuously supplied to a fourth crystallization tank at 165 ° C. at a flow rate of 104 tons (the terephthalic acid content was 30.1% by mass). The slurry residence time in the third crystallization tank and the fourth crystallization tank was both 0.20 hr.
- a 165 ° C. terephthalic acid slurry obtained from the fourth crystallization tank is converted into a mother liquor replacement tower 4 having a tower inner diameter of 4 m and a tower cross-sectional area of 12.6 m 2 by using a raw slurry supply pump 3. And introduced at a flow rate of 100 tons per hour (the terephthalic acid content is 31.3% by mass).
- Replacement water at 100 ° C. was introduced into the mother liquor replacement tower 4 at a flow rate of 66 tons per hour by the replacement water supply pump 8 through the replacement water inlet 9.
- the introduced terephthalic acid slurry forms a terephthalic acid crystal deposition layer b having a high slurry concentration at the bottom of the mother liquor displacement column 4 by sedimentation due to gravity, and is an interface with a portion having a low slurry concentration (also referred to as an upper surface of the deposition layer).
- A) was formed.
- the purified terephthalic acid slurry was extracted at a flow rate of 92 tons per hour (the terephthalic acid content was 33.9% by mass) from the purified terephthalic acid slurry extraction port 7 at the bottom of the mother liquor displacement column 4.
- a terephthalic acid slurry having a temperature of 110 ° C. was extracted from the purified terephthalic acid slurry extraction port 7 and sent to the crystallization tank 10 to generate a slurry of 100 ° C.
- the obtained slurry was sent to a rotary vacuum filter at a flow rate of 95 tons per hour (the terephthalic acid content was 32.8% by mass), and was separated from water.
- the wet cake of purified terephthalic acid before being sent to the drying process was sampled.
- the sampled wet cake was dried at 120 ° C. for 9 hours with a dryer substituted with nitrogen, and the moisture content was calculated from the weight before and after drying. It was 12.4 mass% as a result of calculating the moisture content in a wet cake as a mass percentage.
- Example 1 The dried purified terephthalic acid crystals obtained in Example 1 were sieved and classified using a robot shifter manufactured by Seishin Enterprise.
- crystallization below 38 micrometers is 5.18 mass%.
- the median diameter was 116 ⁇ m.
- Table 1 shows the operating conditions, the mother liquor replacement rate, the terephthalic acid concentration in the mother liquor outlet, the moisture content of the vacuum filter wet cake, and the dry crystal particle size distribution of Example 1.
- Examples 2 to 5, Comparative Examples 1 to 3 Crude terephthalic acid was purified using the apparatus used in Example 1. By adjusting the terephthalic acid treatment amount Q and the liquid levels of the first and second crystallization tanks, the crystallization tank residence times T1, T2, A / Q, and T 1 ⁇ A / Q are changed. Driving was performed. The flow rate of the crude terephthalic acid refining water and the replacement water flow rate is proportional to the terephthalic acid treatment amount Q so that the slurry concentration is the same as in Example 1, and the slurry flow rate of each part is also equal to the terephthalic acid treatment amount Q. Adjusted together.
- Example 1 shows the operating conditions, the mother liquor substitution rate, the terephthalic acid concentration in the mother liquor outlet, the moisture content of the wet cake, and the particle size distribution of the dried crystals in each example and comparative example.
- Example 4 In the apparatus used in Example 1, the crude terephthalic acid was purified by supplying the slurry of the fourth crystallization tank directly to the crystallization tank 10 without using the mother liquor replacement tower. The operation was carried out with the temperature of each part being the same as in Example 1 except that the temperature of the fourth crystallization tank was 155 ° C., and the residence time of each crystallization tank being the same as in Example 2. Table 1 shows the operating conditions, the mother liquor replacement rate, the terephthalic acid concentration in the mother liquor outlet, the moisture content of the wet cake, and the particle size distribution of the dried crystals.
- Comparative Example 1 In Comparative Example 1 in which the amount of terephthalic acid treatment Q is large and A / Q is too small, the mother liquor replacement rate is significantly reduced. In Comparative Example 2 the residence time T 1 in the first crystallizer is too small, decrease in the mother liquor substitution rate is observed with the crystal grain size decreases. In Comparative Example 3 in which T 1 ⁇ A / Q is excessively small, the crystal grain size is reduced and the mother liquor substitution rate is greatly deteriorated as compared with Example 4 in which the amount of terephthalic acid treatment Q is equivalent. In Comparative Example 4 in which the mother liquor replacement column is not used, the ratio of fine crystals of less than 53 ⁇ m and less than 38 ⁇ m is high, and the moisture content of the wet cake of the solid-liquid separator is high.
- the production method of the present invention has industrial applicability in the field of terephthalic acid production.
- the terephthalic acid of this invention can be used as a raw material of polyester, and has industrial applicability in polyester manufacture.
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Abstract
Description
しかしながら、この液相酸化反応は酢酸を溶媒とし、得られた粗テレフタル酸スラリーには4-カルボキシベンズアルデヒド(以下、4CBAとも記載する。)、パラトルイル酸(以下、p-TOLとも記載する。)、安息香酸等の不純物、あるいはその他にも種々の着色性不純物が多く含まれる。そして粗テレフタル酸スラリーから分離して得られた粗テレフタル酸にも、上記の不純物が混入しており、高純度のテレフタル酸を得ることはかなり高度の精製技術を必要とする。
[1]
以下の工程(a)~(e);
(a)p-フェニレン化合物を液相酸化することにより粗テレフタル酸結晶を得る工程、
(b)前記粗テレフタル酸結晶を水に溶解させた後、接触水素化処理する工程、
(c)前記接触水素化後の反応液を2段以上の晶析槽を用いて段階的に落圧、降温してテレフタル酸を晶析させてテレフタル酸スラリーを得る工程、
(d)前記テレフタル酸スラリーを母液置換塔の上部に導入し、テレフタル酸結晶を塔内で沈降させながら母液置換塔の塔底部から導入された置換水の上昇流と接触させ、前記テレフタル酸結晶を前記置換水とのスラリーとして塔底部より抜き出す工程、
(e)前記塔底部より抜き出したスラリーを、水とテレフタル酸結晶とに固液分離し、分離したテレフタル酸結晶を乾燥させる工程、
を含む、高純度テレフタル酸の製造方法であって、
前記接触水素化処理を行う結晶の処理量をQ[ton/hr]、前記2段以上の晶析槽の1段目の晶析槽の滞留時間をT1[hr]、前記母液置換塔の断面積をA[m2]とするとき、下記の条件(1)~(3);
(1)0.07≦T1≦0.5
(2)0.3≦A/Q≦0.8
(3)0.035≦T1×A/Q≦0.25
を全て満たす、高純度テレフタル酸の製造方法。
[2]
前記2段以上の晶析槽の段数が、3~5段である、[1]記載の製造方法。
[3]
メジアン径が、100~130μmであり、
粒径53μm未満の結晶が、15%以下であり、
粒径212μm以上の結晶が、15%以下である、
高純度テレフタル酸。
[4]
粒径38μm未満の結晶が、7%以下である、[3]記載の高純度テレフタル酸。
以下の工程(a)~(e);
(a)p-フェニレン化合物を液相酸化することにより粗テレフタル酸結晶を得る工程、
(b)前記粗テレフタル酸結晶を水に溶解させた後、接触水素化処理する工程、
(c)前記接触水素化後の反応液を2段以上の晶析槽を用いて段階的に落圧、降温してテレフタル酸を晶析させてテレフタル酸スラリーを得る工程、
(d)前記テレフタル酸スラリーを母液置換塔の上部に導入し、テレフタル酸結晶を塔内で沈降させながら母液置換塔の塔底部から導入された置換水の上昇流と接触させ、前記テレフタル酸結晶を前記置換水とのスラリーとして塔底部より抜き出す工程、
(e)前記塔底部より抜き出したスラリーを、水とテレフタル酸結晶とに固液分離し、分離したテレフタル酸結晶を乾燥させる工程、
を含む。
また、本実施形態の高純度テレフタル酸の製造方法は、前記接触水素化処理を行う結晶の処理量をQ[ton/hr]、前記2段以上の晶析槽の1段目の晶析槽の滞留時間をT1[hr]、前記母液置換塔の断面積をA[m2]とするとき、下記の条件(1)~(3);
(1)0.07≦T1≦0.5
(2)0.3≦A/Q≦0.8
(3)0.035≦T1×A/Q≦0.25
を全て満たす。
工程(a)は、p-フェニレン化合物を液相酸化することにより粗テレフタル酸結晶を得る工程である。
工程(a)は、好ましくは、p-フェニレン化合物を液相酸化した後、落圧、降温して得られる粗テレフタル酸スラリーから反応母液を分離することにより粗テレフタル酸結晶を得る工程である。
該被酸化性置換基としては、例えば、メチル基、エチル基、プロピル基、イソプロピル基、アルデヒド基、アセチル基等が例示される。フェニル上の2つの置換基は、互いに同一であっても、異なっていてもよい。
触媒としてコバルト触媒を使用する場合は、促進剤として、アセトアルデヒド、メチルエチルケトン等を併用することが好ましい。
工程(b)は、前記粗テレフタル酸結晶を接触水素化処理する工程である。
工程(b)は、好ましくは、前記粗テレフタル酸結晶を、高温、高圧下で水に溶解させた後、接触水素化処理する工程である。
接触水素化反応の温度は、好ましくは260℃以上であり、より好ましくは270~300℃である。
溶液中の粗テレフタル酸の濃度は、好ましくは10~40質量%である。
接触水素化反応の圧力は、テレフタル酸含有処理液が液相を維持するに充分であり、且つ、接触水素化反応に適切な水素分圧を保持できる圧力であれば特に制限されず、通常6~10MPaであることが好ましい。
工程(c)は、前記接触水素化後の反応液を2段以上の晶析槽を用いて段階的に落圧、降温してテレフタル酸を晶析させてテレフタル酸スラリーを得る工程である。
前記接触水素化後の反応液は、直列に連結された2段以上の晶析槽へ導入され、段階的に落圧することで、水分のフラッシュ蒸発によって120~200℃まで降温され、テレフタル酸結晶が晶析し、テレフタル酸結晶スラリーが得られる。
また、第1晶析槽の滞留時間(以下、T1と記載する場合がある)は、0.07~0.5hrであり(以下、条件(1)ともいう。)、好ましくは0.08~0.4hrであり、より好ましくは0.1~0.3hrである。滞留時間が長いほど精製テレフタル酸結晶の平均粒径が大きくなる傾向にあり、T1を0.07~0.5hrとすることにより、適度な平均粒径を持ち、乾燥時の加熱負荷が小さく、かつ、ポリエステルの原料として良好な挙動を示す精製テレフタル酸結晶が得られる。
工程(d)は、前記テレフタル酸結晶スラリーを母液置換塔の上部に導入し、テレフタル酸結晶を塔内で沈降させながら母液置換塔の塔底部から導入された置換水の上昇流と接触させ、前記テレフタル酸結晶を前記置換水とのスラリーとして塔底部より抜き出す工程(以下、「母液置換工程」ともいう。)である。
母液置換工程に用いられる装置(即ち「母液置換塔」)は、大きく分けて塔上部、塔底部および塔中間部からなる。
塔上部は、テレフタル酸結晶を含有する母液からなる原スラリーの導入部を有する。原スラリーの導入部は、塔上部内壁に開口していてもよいが、結晶の分散を良好にする観点から、塔上部内に延びて開口していることが好ましい。さらに、原スラリー導入部の開口先端部は下向きに設置されていてもよく、また、開口先端部に分散板等の結晶の分散を促進する機構を備えていてもよい。塔上部は母液排出口をさらに備え、母液排出口からはテレフタル酸結晶をほとんど含まない母液が抜き出され、所定の処理槽に導かれる。
塔中間部は、重力で沈降するテレフタル酸結晶の動きを阻害するような棚段等の構造物を設ける必要はない。
塔底部は、置換水供給部と、置換水で置換された精製テレフタル酸スラリーの抜き出し口、置換水供給流量および置換スラリー抜き出し流量の調節部、並びに塔底部内スラリーの攪拌装置を備えている。置換水で置換された精製テレフタル酸スラリーの抜き出し口の位置は、スラリーが高比重であるため、塔底部の下方に近い方が好ましい。
0.3≦A/Q≦0.8
となる(以下、条件(2)ともいう。)ような内径にすることが必要である。さらに、塔中間部の内径は、
0.35≦A/Q≦0.6
となるような内径にするのが好ましい。
塔上部や塔底部の径は、塔中間部と同程度の径であればよいが、より大きな径とすることもできる。
また、塔の高さは、供給したテレフタル酸結晶が塔内全体に分散する高さにすることが好ましく、具体的には原スラリー導入部から塔底までの距離が、塔内径に対して1~3倍となるような高さにすることが好ましい。
0.035≦T1×A/Q≦0.25
0.04≦T1×A/Q≦0.2
0.045≦T1×A/Q≦0.15
塔上部から導かれたテレフタル酸スラリーは、重力による沈降により、母液置換塔底部にスラリー濃度が高い層を成し、高スラリー濃度の層と、テレフタル酸結晶が重力で沈降する低スラリー濃度の領域との間に界面が形成される。
塔底部のスラリー層は結晶の固結や閉塞を防ぐために攪拌装置によって流動性を与えることが好ましい。必要以上に撹拌を行なうと、置換すべき不純物の濃度も均一に撹拌されて置換効率が著しく低下するため、スラリー層の流動性が損なわれない程度の適度な撹拌が好ましい。攪拌機の動力としては、塔底部のスラリー層の単位体積あたりの動力として0.05~1.0kWh/m3であることが好ましく、0.1~0.8kWh/m3であることがより好ましく、0.2~0.7kWh/m3であることがさらに好ましい。
前記晶析工程の第1晶析相の滞留時間T1と母液置換塔の断面積が、前記条件(1)~(3)を満たすようにすることにより、これらの小粒径の結晶の割合をさらに低減することが可能になり、53μm未満の小粒径の結晶が15%以下、38μm未満の微細粒径の結晶が7%以下である高純度テレフタル酸を得ることができる。なお、本願において結晶の粒径割合は、結晶の篩分けによる分級で得られた割合を示している。
ここで、置換水の上昇液流の線速度は、置換水供給量と塔底からの抜き出しスラリーとの水のバランスから計算することができる。
工程(e)は、前記塔底部より抜き出したスラリーを水とテレフタル酸結晶に固液分離し、分離したテレフタル酸結晶を乾燥させる工程である。
母液置換塔底部より抜き出したスラリーは、ロータリーバキュームフィルター等の固液分離装置でテレフタル酸結晶と水に分離する。固液分離により得られるテレフタル酸結晶は、ケーキとして得られ、固液分離後のケーキの含水率は12~13質量%である。すなわち、本実施形態の製造方法により、固液分離工程のみで容易にケーキの含水率を15質量%以下にすることができる。ケーキの含水率が低いことで、続く乾燥工程におけるエネルギー消費量を抑えることが可能である。次の乾燥工程では、テレフタル酸製造に通常用いられるスチームチューブドライヤー等を使用することができ、さらに、テレフタル酸ケーキの含水率が低いことで、分離後のケーキを直接、流動層乾燥機を用いて乾燥することが可能である。
本実施形態の一つは、メジアン径が100~130μmであり、全結晶の質量に対し、53μm未満の結晶が15質量%以下であり、粒径212μm以上の結晶が15質量%以下の高純度テレフタル酸である。メジアン径が100~130μmであり、全結晶の質量に対し、粒径53μm以下の結晶が15質量%以下であり、粒径212μm以上の結晶が15質量%以下の高純度テレフタル酸は、本実施形態の製造方法により製造することができる。
本実施形態の高純度テレフタル酸における粒径212μm以上の結晶の割合は、好ましくは12%以下である。
本実施形態の高純度テレフタル酸は、粒径38μm未満の結晶の割合が7%以下であることが好ましい。
粒径212μm以上の結晶が15質量%以下であることにより、ポリエステルの原料として良好な挙動を示すことができる。
また、53μm未満の結晶が15質量%以下であることにより、固液分離して乾燥する際の加熱負荷を小さくすることができる。
母液置換率(%)=(塔上部の母液排出口より抜き出された母液中に含まれる安息香酸量)/(粗テレフタル酸スラリー中に不純物として含まれる安息香酸量)×100
また、母液置換塔上部から排出される母液中のテレフタル酸含有量(質量%)は、常温まで冷却した母液をフィルターで濾過して得られる結晶重量から算出した。
コバルトおよびマンガン触媒と臭化化合物の助触媒を用いて、酢酸溶液中でp-キシレンの液相酸化反応を行った後、晶析して冷却し、析出した粗テレフタル酸結晶を分離した。得られた粗テレフタル酸を水と混合して加熱溶解し、図1の水素添加反応槽1を用いて281℃で接触水素化反応を行い、該反応液であるテレフタル酸の溶液を、晶析槽2の第1晶析槽に毎時126トンの流量(テレフタル酸含有量は24.8質量%でテレフタル酸結晶処理量Qは毎時31.3ton)で送り、250℃の晶析スラリーを生成させた。この時、第1晶析槽の液面から計算される第1晶析槽におけるスラリー滞留時間は0.12hrであった。この250℃の晶析スラリーを、移送配管を介して230℃の第2晶析槽に毎時114トンの流量で連続的に供給した(テレフタル酸含有量は27.4質量%)。この時、第2晶析槽におけるスラリー滞留時間は0.20hrであった。さらに、約195℃の第3晶析槽に毎時111トンの流量で連続的に供給した(テレフタル酸含有量は28.2質量%)。さらに、165℃の第4晶析槽に毎時104トンの流量で連続的に供給した(テレフタル酸含有量は30.1質量%)。なお、第3晶析槽および第4晶析槽におけるスラリー滞留時間は、共に0.20hrであった。
実施例1の運転条件、母液置換率、母液排出口中のテレフタル酸濃度、バキュームフィルターのウェットケーキの含水率、乾燥結晶の粒径分布を表1に示す。
実施例1で使用した装置を用いて粗テレフタル酸の精製を行なった。テレフタル酸処理量Q、および第1晶析槽、第2晶析槽の液面を調節して、晶析槽滞留時間T1、T2、A/Q、T1×A/Qを変えて装置の運転を行なった。なお、粗テレフタル酸精製用の水および置換水の流量は、スラリー濃度が実施例1と同じになるようにテレフタル酸処理量Qに比例した流量とし、各部のスラリー流量もテレフタル酸処理量Qに合わせて調節した。また、水素添加反応槽、各晶析槽および母液置換塔の温度、および第3晶析槽、第4晶析槽の滞留時間は、実施例1と同じにして運転を行なった。
各実施例、比較例の運転条件、母液置換率、母液排出口中のテレフタル酸濃度、ウェットケーキの含水率、乾燥結晶の粒径分布を表1に示す。
実施例1で使用した装置において、母液置換塔を用いずに第4晶析槽のスラリーを晶析槽10に直接供給する方法で粗テレフタル酸の精製を行なった。第4晶析槽の温度を155℃とした以外は、各部の温度は実施例1と同じとし、各晶析槽の滞留時間は実施例2と同じとして運転を行なった。
運転条件、母液置換率、母液排出口中のテレフタル酸濃度、ウェットケーキの含水率、乾燥結晶の粒径分布を表1に示す。
2:晶析槽
3:原スラリー供給ポンプ
4:母液置換塔
5:原スラリー導入ノズル
6:母液排出口
7:精製テレフタル酸スラリー抜き出し口
8:置換水供給ポンプ
9:置換水導入口
10:晶析槽
a:堆積層上面
b:テレフタル酸結晶の堆積層
Claims (4)
- 以下の工程(a)~(e);
(a)p-フェニレン化合物を液相酸化することにより粗テレフタル酸結晶を得る工程、
(b)前記粗テレフタル酸結晶を水に溶解させた後、接触水素化処理する工程、
(c)前記接触水素化後の反応液を2段以上の晶析槽を用いて段階的に落圧、降温してテレフタル酸を晶析させてテレフタル酸スラリーを得る工程、
(d)前記テレフタル酸スラリーを母液置換塔の上部に導入し、テレフタル酸結晶を塔内で沈降させながら母液置換塔の塔底部から導入された置換水の上昇流と接触させ、前記テレフタル酸結晶を前記置換水とのスラリーとして塔底部より抜き出す工程、
(e)前記塔底部より抜き出したスラリーを、水とテレフタル酸結晶とに固液分離し、分離したテレフタル酸結晶を乾燥させる工程、
を含む、高純度テレフタル酸の製造方法であって、
前記接触水素化処理を行う結晶の処理量をQ[ton/hr]、前記2段以上の晶析槽の1段目の晶析槽の滞留時間をT1[hr]、前記母液置換塔の断面積をA[m2]とするとき、下記の条件(1)~(3);
(1)0.07≦T1≦0.5
(2)0.3≦A/Q≦0.8
(3)0.035≦T1×A/Q≦0.25
を全て満たす、高純度テレフタル酸の製造方法。 - 前記2段以上の晶析槽の段数が、3~5段である、請求項1記載の製造方法。
- メジアン径が、100~130μmであり、
粒径53μm未満の結晶が、15%以下であり、
粒径212μm以上の結晶が、15%以下である、
高純度テレフタル酸。 - 粒径38μm未満の結晶が、7%以下である、請求項3記載の高純度テレフタル酸。
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