CN113831234A - Method for recovering high-purity terephthalic acid from printing and dyeing white mud through hydrothermal process - Google Patents
Method for recovering high-purity terephthalic acid from printing and dyeing white mud through hydrothermal process Download PDFInfo
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- KKEYFWRCBNTPAC-UHFFFAOYSA-N Terephthalic acid Chemical compound OC(=O)C1=CC=C(C(O)=O)C=C1 KKEYFWRCBNTPAC-UHFFFAOYSA-N 0.000 title claims abstract description 166
- 238000004043 dyeing Methods 0.000 title claims abstract description 64
- 238000001027 hydrothermal synthesis Methods 0.000 title claims abstract description 45
- 238000000034 method Methods 0.000 title claims abstract description 43
- 239000012065 filter cake Substances 0.000 claims abstract description 54
- 239000000047 product Substances 0.000 claims abstract description 53
- 238000005406 washing Methods 0.000 claims abstract description 45
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 41
- 239000007788 liquid Substances 0.000 claims abstract description 29
- 238000000926 separation method Methods 0.000 claims abstract description 28
- 239000002253 acid Substances 0.000 claims abstract description 26
- 238000001035 drying Methods 0.000 claims abstract description 20
- 239000007787 solid Substances 0.000 claims abstract description 20
- 239000004094 surface-active agent Substances 0.000 claims abstract description 13
- 238000011084 recovery Methods 0.000 claims abstract description 9
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 28
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 claims description 27
- 239000007795 chemical reaction product Substances 0.000 claims description 17
- 229940051841 polyoxyethylene ether Drugs 0.000 claims description 17
- 229920000056 polyoxyethylene ether Polymers 0.000 claims description 17
- 239000006185 dispersion Substances 0.000 claims description 10
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 8
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims description 7
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 claims description 6
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 4
- 229910017604 nitric acid Inorganic materials 0.000 claims description 4
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 3
- 238000011049 filling Methods 0.000 claims description 3
- 239000005020 polyethylene terephthalate Substances 0.000 claims description 3
- -1 polyethylene terephthalate Polymers 0.000 claims description 2
- 229920000139 polyethylene terephthalate Polymers 0.000 claims description 2
- 238000003825 pressing Methods 0.000 claims description 2
- 239000000203 mixture Substances 0.000 abstract description 14
- 239000003513 alkali Substances 0.000 abstract description 10
- 229920000728 polyester Polymers 0.000 abstract description 8
- 239000012535 impurity Substances 0.000 abstract description 5
- 230000015572 biosynthetic process Effects 0.000 abstract description 4
- 238000003786 synthesis reaction Methods 0.000 abstract description 4
- 238000010335 hydrothermal treatment Methods 0.000 abstract description 3
- 238000004064 recycling Methods 0.000 abstract description 3
- 239000004014 plasticizer Substances 0.000 abstract description 2
- 239000002910 solid waste Substances 0.000 abstract description 2
- 239000004753 textile Substances 0.000 abstract description 2
- 235000008733 Citrus aurantifolia Nutrition 0.000 abstract 2
- 235000011941 Tilia x europaea Nutrition 0.000 abstract 2
- 239000004571 lime Substances 0.000 abstract 2
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 45
- 235000011121 sodium hydroxide Nutrition 0.000 description 15
- 238000004458 analytical method Methods 0.000 description 12
- 230000000052 comparative effect Effects 0.000 description 11
- 239000013078 crystal Substances 0.000 description 7
- LLLVZDVNHNWSDS-UHFFFAOYSA-N 4-methylidene-3,5-dioxabicyclo[5.2.2]undeca-1(9),7,10-triene-2,6-dione Chemical compound C1(C2=CC=C(C(=O)OC(=C)O1)C=C2)=O LLLVZDVNHNWSDS-UHFFFAOYSA-N 0.000 description 6
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 description 6
- 239000004744 fabric Substances 0.000 description 6
- 150000003504 terephthalic acids Chemical class 0.000 description 4
- 239000002351 wastewater Substances 0.000 description 4
- 239000003795 chemical substances by application Substances 0.000 description 3
- 239000000835 fiber Substances 0.000 description 3
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- 238000005554 pickling Methods 0.000 description 3
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 238000003916 acid precipitation Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000000701 coagulant Substances 0.000 description 2
- 238000004128 high performance liquid chromatography Methods 0.000 description 2
- 239000003960 organic solvent Substances 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 238000001953 recrystallisation Methods 0.000 description 2
- 239000010802 sludge Substances 0.000 description 2
- 238000001228 spectrum Methods 0.000 description 2
- 239000013585 weight reducing agent Substances 0.000 description 2
- 229920004934 Dacron® Polymers 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 238000009529 body temperature measurement Methods 0.000 description 1
- 238000005345 coagulation Methods 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 239000006260 foam Substances 0.000 description 1
- 238000005187 foaming Methods 0.000 description 1
- 239000002932 luster Substances 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 238000011946 reduction process Methods 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
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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
-
- 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
- C07C51/47—Separation; Purification; Stabilisation; Use of additives by solid-liquid treatment; by chemisorption
-
- 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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- Chemical & Material Sciences (AREA)
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- Oil, Petroleum & Natural Gas (AREA)
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Abstract
The invention discloses a method for recovering high-purity terephthalic acid from printing and dyeing white mud through hydrothermal treatment, and belongs to the technical field of solid waste recycling in the textile printing and dyeing industry. The recovery method of the invention comprises the following steps: washing the alkali-reduced lime mud by using a dilute acid solution containing a surfactant, and then carrying out solid-liquid separation to obtain a lime mud filter cake; dispersing the white mud filter cake in water, adjusting the pH value, and placing the mixture in a hydrothermal kettle for hydrothermal reaction; carrying out solid-liquid separation on the hydrothermal product and washing the obtained filter cake by using a proper amount of pure water; and carrying out solid-liquid separation again, taking out the solid and drying to obtain the high-purity terephthalic acid. The impurity content of the pure terephthalic acid recovered and prepared by the method is lower than 1.5%, the average grain size is larger than 145 mu m, and the pure terephthalic acid can be recycled for polyester synthesis or plasticizer synthesis, so that the printing and dyeing white mud can be recycled economically and effectively.
Description
Technical Field
The invention relates to a method for recovering high-purity terephthalic acid from printing and dyeing white mud through hydrothermal treatment, and belongs to the technical field of solid waste recycling in the textile printing and dyeing industry.
Background
The dyeing white mud (alkali weight reduction white mud) mainly comes from an alkali weight reduction process in the dyeing process of the dacron chemical fiber fabric. The alkali decrement process is an important link of the printing and dyeing production of the polyester fabric and is also a key production link. The polyester fiber is hydrolyzed to make the fabric light and the fiber diameter thin through treating the polyester fabric with high temperature and stronger caustic soda solution, thereby making the fabric soft in hand feeling and soft in luster. The decrement rate of the polyester fabric is generally 5-20%, the waste enters the wastewater in the form of terephthalic acid, ethylene glycol and polyester oligomer, and grey-white materialized sludge is formed in the processes of acidification-coagulation and the like of alkali decrement wastewater.
The printing white mud contains terephthalic acid as a main component, but cannot be directly used due to impurities such as polyester oligomer and coagulant. The method effectively recovers the high-purity terephthalic acid from the printing and dyeing white mud, reduces the printing and dyeing sludge, can utilize the terephthalic acid as resources, and has double benefits of environment and economy. At present, the methods for recovering terephthalic acid from printing and dyeing white mud mainly comprise three methods, namely a precipitation washing method, an alkali dissolution-acid precipitation method and a recrystallization method. The precipitation washing method and the alkali dissolution-acid precipitation method are relatively simple and easy to implement, but can not remove some ethylene terephthalate oligomers with the properties close to those of terephthalic acid, so that the product quality is uneven, and the water consumption and the waste water generation amount are large. The recrystallization method can obtain terephthalic acid with larger crystal grains and higher purity, but the process needs to use organic solvents such as dimethylformamide and the like, is relatively complex and is easy to cause secondary pollution.
Disclosure of Invention
The technical problem solved by the invention is as follows: the prior method for recovering the terephthalic acid in the printing and dyeing white mud has the problems that some ethylene terephthalate oligomers with the property close to that of the terephthalic acid cannot be removed, the product purity is not high, the water consumption and the waste water generation amount are large, secondary pollution is easily caused by using organic solvents such as dimethylformamide and the like, and the like.
In order to solve the technical problem, the invention provides a method for recovering high-purity terephthalic acid from printing and dyeing white mud through hydrothermal reaction, which comprises the following steps:
step 1: washing the printing and dyeing white mud by using a dilute acid solution containing a surfactant, and then carrying out solid-liquid separation to obtain a white mud filter cake;
step 2: dispersing the white mud filter cake obtained in the step 1 into water to obtain a white mud dispersion liquid, adjusting the pH value, and placing the white mud dispersion liquid into a hydrothermal kettle for hydrothermal reaction to obtain a hydrothermal reaction product;
and step 3: performing solid-liquid separation on the hydrothermal product obtained in the step 2, and dispersing and washing a filter cake by using pure water to obtain a washed product dispersion liquid;
and 4, step 4: carrying out solid-liquid separation on the product dispersion liquid obtained in the step 3 again, and drying the solid to obtain high-purity terephthalic acid;
the components of the printing and dyeing white mud comprise terephthalic acid, ethylene glycol, polyethylene terephthalate oligomer, oil, acid and polyaluminium chloride.
Preferably, the diluted acid solution in the step 1 is at least one of sulfuric acid, hydrochloric acid and nitric acid, the concentration of the diluted acid solution is 0.5-2 mol/L, and the using amount of the diluted acid solution is 1-5 times of the volume of the white mud.
Preferably, the surfactant in the step 1 is alcohol ether acid-resistant surfactant such as fatty alcohol-polyoxyethylene ether, and the concentration of the surfactant is 0.05-0.2 mol/L.
Preferably, the solid-to-liquid ratio of the white mud dispersion liquid in the step 2 is 1: 5-9 g/mL.
Preferably, the pH value in the step 2 is 6.5-7.5.
Preferably, the temperature of the hydrothermal reaction in the step 2 is 150-180 ℃ and the time is 12-24 h.
Preferably, the filling degree of the hydrothermal kettle in the step 2 is 60-80%.
Preferably, the volume of the pure water for washing in the step 3 is 5-10 times of the volume of the filter cake.
Preferably, the solid-liquid separation mode in the steps 3 and 4 is centrifugal separation or mechanical filter pressing.
Preferably, the drying temperature in the step 4 is 60-80 ℃.
The principle of the invention is as follows:
the printing and dyeing white mud contains a large amount of terephthalic acid and ethylene glycol, and also contains incompletely hydrolyzed ethylene terephthalate oligomer, oil, acid, polyaluminium chloride and other conventional coagulants. The invention utilizes the characteristic that terephthalic acid is insoluble in dilute acid and substances such as ethylene glycol, polyaluminium chloride and the like are easily soluble, and dilute acid is used for washing to separate impurities such as ethylene glycol, polyaluminium chloride and the like which are easily soluble in acid in the white mud from the terephthalic acid solid; the surfactant in the dilute acid can simultaneously emulsify the oil agent contained in the white mud, and the alcohol ether acid-resistant surfactant can effectively emulsify the oil agent and simultaneously avoid generating a large amount of foam and secondary pollution such as phosphorus, nitrogen and the like; then, the characteristics that ester bond hydrolysis is facilitated under a high-temperature condition and crystal growth is facilitated under a hydrothermal condition are utilized, the complete hydrolysis of oligomers in the white mud is promoted and the growth of terephthalic acid crystals is strengthened through a hydrothermal method under a neutral condition; finally, the high-purity terephthalic acid is obtained through solid-liquid separation and drying.
Compared with the prior art, the invention has the following beneficial effects:
1. on the basis of preliminarily washing off impurities such as ethylene glycol, oil solution, polyaluminium chloride and the like by using dilute acid containing a surfactant, the high-temperature environment of a hydrothermal method is utilized to promote the incompletely hydrolyzed ethylene terephthalate oligomer in the white mud to further generate terephthalic acid and ethylene glycol, and meanwhile, the growth of terephthalic acid crystals is enhanced by utilizing the high-temperature and high-pressure condition of the hydrothermal method, so that the efficiency of recovering the terephthalic acid from the alkali-reduced white mud and the purity of a terephthalic acid product are remarkably improved;
2. the impurity content of the pure terephthalic acid recovered and prepared by the method is lower than 1.5%, the average grain size is larger than 145 mu m, and the pure terephthalic acid can be recycled for polyester synthesis or plasticizer synthesis, so that the printing and dyeing white mud can be recycled economically and effectively.
Drawings
FIG. 1 is an X-ray diffraction spectrum of a terephthalic acid product (example 1) and a corresponding standard card.
Detailed Description
In order to make the invention more comprehensible, preferred embodiments are described in detail below.
Example 1
A process for hydrothermal recovery of high purity terephthalic acid from a printing and dyeing white mud comprising:
taking 10g of printing and dyeing white mud, washing the printing and dyeing white mud by using 30mL of 0.5mol/L sulfuric acid solution (containing 0.05mol/L fatty alcohol-polyoxyethylene ether), and performing centrifugal separation to obtain a white mud filter cake; dispersing the white mud filter cake into 50mL of pure water, adjusting the pH to 7.0 by using sodium hydroxide, and placing the mixture into a hydrothermal kettle with the capacity of 80mL for hydrothermal reaction (150 ℃, 12 hours) to obtain a hydrothermal reaction product; and centrifugally separating the hydrothermal product, dispersing and washing a filter cake by using a proper amount of pure water, centrifugally separating again, taking the solid, and drying to obtain the terephthalic acid product.
Example 2
A process for hydrothermal recovery of high purity terephthalic acid from a printing and dyeing white mud comprising:
taking 10g of printing and dyeing white mud, washing the printing and dyeing white mud by using 30mL of hydrochloric acid solution with the concentration of 1.5mol/L (containing 0.05mol/L fatty alcohol-polyoxyethylene ether), and performing centrifugal separation to obtain a white mud filter cake; dispersing the white mud filter cake into 50mL of pure water, adjusting the pH to 7.0 by using sodium hydroxide, and placing the mixture into a hydrothermal kettle with the capacity of 80mL for hydrothermal reaction (150 ℃, 12 hours) to obtain a hydrothermal reaction product; and centrifugally separating the hydrothermal product, dispersing and washing a filter cake by using a proper amount of pure water, centrifugally separating again, taking the solid, and drying to obtain the terephthalic acid product.
Example 3
A process for hydrothermal recovery of high purity terephthalic acid from a printing and dyeing white mud comprising:
taking 10g of printing and dyeing white mud, washing the printing and dyeing white mud by using 30mL of nitric acid solution with the concentration of 1.0mol/L (containing 0.05mol/L fatty alcohol-polyoxyethylene ether), and performing centrifugal separation to obtain a white mud filter cake; dispersing the white mud filter cake into 50mL of pure water, adjusting the pH to 7.0 by using sodium hydroxide, and placing the mixture into a hydrothermal kettle with the capacity of 80mL for hydrothermal reaction (150 ℃, 12 hours) to obtain a hydrothermal reaction product; and centrifugally separating the hydrothermal product, dispersing and washing a filter cake by using a proper amount of pure water, centrifugally separating again, taking the solid, and drying to obtain the terephthalic acid product.
Comparative example 1
Taking 10g of printing and dyeing white mud, washing with 30mL of pure water (containing 0.05mol/L fatty alcohol-polyoxyethylene ether), and performing centrifugal separation to obtain a white mud filter cake; dispersing the white mud filter cake into 50mL of pure water, adjusting the pH to 7.0 by using sodium hydroxide, and placing the mixture into a hydrothermal kettle with the capacity of 80mL for hydrothermal reaction (150 ℃, 12 hours) to obtain a hydrothermal reaction product; and centrifugally separating the hydrothermal product, dispersing and washing a filter cake by using a proper amount of pure water, centrifugally separating again, taking the solid, and drying to obtain the terephthalic acid product.
The results of the analyses of the terephthalic acids obtained in examples 1, 2 and 3 and comparative example 1 are shown in Table 1, and the specific analysis methods are as follows:
(1) purity: determination by high performance liquid chromatography (Wanghao, Feifei Shuishuan, Chan, Li Zuoqing. high performance liquid chromatography determines terephthalic acid content [ J ] in secondary PTA 2008,21(1):16-17,38.)
(2) Average particle size: determination by means of a laser particle sizer (GB/T30921.6-2016 Industrial Purified Terephthalic Acid (PTA) test method part 6: determination of particle size distribution);
(3) yield:
yield-quality of the solid produced x purity/white mud quality.
TABLE 1 analysis of the product index of terephthalic acid in different pickling processes
As can be seen from table 1, in the case of fixing hydrothermal conditions and other preparation conditions, acid washing is a key step for improving the purity and yield of terephthalic acid products, and dilute acid solutions such as sulfuric acid, hydrochloric acid, nitric acid and the like are used for washing alkali-reduced white mud to primarily remove substances such as ethylene glycol, polyaluminum chloride and the like which are easily dissolved in the acid solution in the white mud, so that the terephthalic acid can be stably maintained in the white mud solids due to insolubility, and the dilute acid washing is helpful for improving the purity and yield of recycling the terephthalic acid from the alkali-reduced white mud.
Example 4
A process for hydrothermal recovery of high purity terephthalic acid from a printing and dyeing white mud comprising:
taking 10g of Indonesia white mud, washing with 30mL of 0.5mol/L sulfuric acid solution (containing 0.1mol/L fatty alcohol-polyoxyethylene ether), and performing centrifugal separation to obtain a white mud filter cake; dispersing the white mud filter cake into 50mL of pure water, adjusting the pH to 7.0 by using sodium hydroxide, and placing the mixture into a hydrothermal kettle with the capacity of 80mL for hydrothermal reaction (150 ℃, 12 hours) to obtain a hydrothermal reaction product; and centrifugally separating the hydrothermal product, dispersing and washing a filter cake by using a proper amount of pure water, centrifugally separating again, taking the solid, and drying to obtain the terephthalic acid product.
Comparative example 2
Taking 10g of printing and dyeing white mud, washing the printing and dyeing white mud by using 30mL of sulfuric acid solution with the concentration of 0.5mol/L (without fatty alcohol-polyoxyethylene ether), and performing centrifugal separation to obtain a white mud filter cake; dispersing the white mud filter cake into 50mL of pure water, adjusting the pH to 7.0 by using sodium hydroxide, and placing the mixture into a hydrothermal kettle with the capacity of 80mL for hydrothermal reaction (150 ℃, 12 hours) to obtain a hydrothermal reaction product; and centrifugally separating the hydrothermal product, dispersing and washing a filter cake by using a proper amount of pure water, centrifugally separating again, taking the solid, and drying to obtain the terephthalic acid product.
Comparative example 3
Taking 10g of printing and dyeing white mud, washing the printing and dyeing white mud by using 30mL of 0.5mol/L sulfuric acid solution (containing 0.5mol/L fatty alcohol-polyoxyethylene ether), and performing centrifugal separation to obtain a white mud filter cake; dispersing the white mud filter cake into 50mL of pure water, adjusting the pH to 7.0 by using sodium hydroxide, and placing the mixture into a hydrothermal kettle with the capacity of 80mL for hydrothermal reaction (150 ℃, 12 hours) to obtain a hydrothermal reaction product; and centrifugally separating the hydrothermal product, dispersing and washing a filter cake by using a proper amount of pure water, centrifugally separating again, taking the solid, and drying to obtain the terephthalic acid product.
The results of the analyses of the terephthalic acids obtained in example 4 and comparative examples 2 and 3 are shown in Table 2, and the analytical methods were the same as those described above.
TABLE 2 analysis of the product index of terephthalic acid in different pickling processes
As can be seen from Table 2, the use of the non-foaming acid-resistant fatty alcohol-polyoxyethylene ether for removing the oil agent from the white mud during the pickling process can significantly improve the purity and yield of the product. However, the use of an excessive amount of surfactant tends to affect the growth of terephthalic acid crystals, resulting in poor crystallization of the product.
Example 5
A process for hydrothermal recovery of high purity terephthalic acid from a printing and dyeing white mud comprising:
taking 10g of printing and dyeing white mud, washing the printing and dyeing white mud by using 30mL of 0.5mol/L sulfuric acid solution (containing 0.05mol/L fatty alcohol-polyoxyethylene ether), and performing centrifugal separation to obtain a white mud filter cake; dispersing the white mud filter cake into 90mL of pure water, adjusting the pH to 7.0 by using sodium hydroxide, and placing the mixture into a hydrothermal kettle with the capacity of 150mL for hydrothermal reaction (at 150 ℃, for 12 hours) to obtain a hydrothermal reaction product; and centrifugally separating the hydrothermal product, dispersing and washing a filter cake by using a proper amount of pure water, centrifugally separating again, taking the solid, and drying to obtain the terephthalic acid product.
Comparative example 4
Taking 10g of printing and dyeing white mud, washing the printing and dyeing white mud by using 30mL of 0.5mol/L sulfuric acid solution (containing 0.05mol/L fatty alcohol-polyoxyethylene ether), and performing centrifugal separation to obtain a white mud filter cake; dispersing the white mud filter cake into 10mL of pure water, adjusting the pH to 7.0 by using sodium hydroxide, and placing the mixture into a hydrothermal kettle with the capacity of 15mL for hydrothermal reaction (150 ℃, 12 hours) to obtain a hydrothermal reaction product; and centrifugally separating the hydrothermal product, dispersing and washing a filter cake by using a proper amount of pure water, centrifugally separating again, taking the solid, and drying to obtain the terephthalic acid product.
Comparative example 5
Taking 10g of printing and dyeing white mud, washing the printing and dyeing white mud by using 30mL of 0.5mol/L sulfuric acid solution (containing 0.05mol/L fatty alcohol-polyoxyethylene ether), and performing centrifugal separation to obtain a white mud filter cake; dispersing the white mud filter cake into 150mL of pure water, adjusting the pH to 7.0 by using sodium hydroxide, and placing the white mud filter cake into a hydrothermal kettle with the capacity of 250mL for hydrothermal reaction (150 ℃, 12 hours) to obtain a hydrothermal reaction product; and centrifugally separating the hydrothermal product, dispersing and washing a filter cake by using a proper amount of pure water, centrifugally separating again, taking the solid, and drying to obtain the terephthalic acid product.
The results of the analyses of the terephthalic acids obtained in example 5 and comparative examples 4 and 5 are shown in Table 3, and the analytical methods were the same as those described above.
TABLE 3 analysis of terephthalic acid product index at different solid-to-liquid ratios
As can be seen from Table 3, under the conditions of fixed acid washing and other preparation conditions, the solid-liquid ratio is a key step influencing the purity and yield of the terephthalic acid product, when the hydrothermal solid-liquid ratio is greater than 1:5, the filling degree is kept within the range of 60-66.7%, the high-purity terephthalic acid product can be obtained, and the yield is kept above 70%. The proper solid-to-liquid ratio can promote the complete hydrolysis of the low ethylene terephthalate polymer to raise the product purity and yield and strengthen the crystal growth of terephthalic acid. On the other hand, although the excessive solid-liquid ratio does not affect the purity and yield of the product, the corresponding water consumption is excessive, which is not beneficial to saving water in production.
Example 6
A process for hydrothermal recovery of high purity terephthalic acid from a printing and dyeing white mud comprising:
taking 10g of printing and dyeing white mud, washing the printing and dyeing white mud by using 30mL of 0.5mol/L sulfuric acid solution (containing 0.05mol/L fatty alcohol-polyoxyethylene ether), and performing centrifugal separation to obtain a white mud filter cake; dispersing the white mud filter cake into 50mL of pure water, adjusting the pH to 7.0 by using sodium hydroxide, and placing the mixture into a hydrothermal kettle with the capacity of 150mL for hydrothermal reaction (180 ℃, 12 hours) to obtain a hydrothermal reaction product; and centrifugally separating the hydrothermal product, dispersing and washing a filter cake by using a proper amount of pure water, centrifugally separating again, taking the solid, and drying to obtain the terephthalic acid product.
Example 7
A process for hydrothermal recovery of high purity terephthalic acid from a printing and dyeing white mud comprising:
taking 10g of printing and dyeing white mud, washing the printing and dyeing white mud by using 30mL of 0.5mol/L sulfuric acid solution (containing 0.05mol/L fatty alcohol-polyoxyethylene ether), and performing centrifugal separation to obtain a white mud filter cake; dispersing the white mud filter cake into 50mL of pure water, adjusting the pH to 7.0 by using sodium hydroxide, and placing the mixture into a hydrothermal kettle with the capacity of 150mL for hydrothermal reaction (at 150 ℃, for 24 hours) to obtain a hydrothermal reaction product; and centrifugally separating the hydrothermal product, dispersing and washing a filter cake by using a proper amount of pure water, centrifugally separating again, taking the solid, and drying to obtain the terephthalic acid product.
Comparative example 6
Taking 10g of printing and dyeing white mud, washing the printing and dyeing white mud by using 30mL of 0.5mol/L sulfuric acid solution (containing 0.05mol/L fatty alcohol-polyoxyethylene ether), and performing centrifugal separation to obtain a white mud filter cake; dispersing the white mud filter cake into 50mL of pure water, adjusting the pH to 7.0 by using sodium hydroxide, and placing the mixture into a hydrothermal kettle with the capacity of 150mL for hydrothermal reaction (120 ℃, 24 hours) to obtain a hydrothermal reaction product; and centrifugally separating the hydrothermal product, dispersing and washing a filter cake by using a proper amount of pure water, centrifugally separating again, taking the solid, and drying to obtain the terephthalic acid product.
Comparative example 7
Taking 10g of printing and dyeing white mud, washing the printing and dyeing white mud by using 30mL of 0.5mol/L sulfuric acid solution (containing 0.05mol/L fatty alcohol-polyoxyethylene ether), and performing centrifugal separation to obtain a white mud filter cake; dispersing the white mud filter cake into 50mL of pure water, adjusting the pH to 7.0 by using sodium hydroxide, and placing the mixture into a hydrothermal kettle with the capacity of 150mL for hydrothermal reaction (at 150 ℃, for 6 hours) to obtain a hydrothermal reaction product; and centrifugally separating the hydrothermal product, dispersing and washing a filter cake by using a proper amount of pure water, centrifugally separating again, taking the solid, and drying to obtain the terephthalic acid product.
The results of the analyses of the terephthalic acids obtained in examples 6 and 7 and comparative examples 6 and 7 are shown in Table 4, and the analytical methods were the same as those described above.
TABLE 4 terephthalic acid product index analysis under different hydrothermal conditions
As can be seen from Table 4, the temperature measurement time of the hydrothermal treatment is also very critical under the conditions of fixed acid washing and other preparation conditions, and when the temperature of the hydrothermal reaction is 150-180 ℃ and the reaction time is 12-24 hours, a high-purity terephthalic acid product can be obtained, and the yield is kept above 75%. The proper hydrothermal temperature can ensure that the ethylene terephthalate oligomer is completely hydrolyzed to improve the purity and yield of the product and promote the crystal growth of the terephthalic acid.
FIG. 1 shows the X-ray diffraction spectrum of a terephthalic acid product (example 1) and a corresponding standard card, and it can be seen that the method for recovering terephthalic acid by hydrothermal method of the present invention can obtain a terephthalic acid product with high crystallinity and good purity from printing and dyeing white mud.
While the invention has been described with respect to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.
Claims (10)
1. A method for recovering high-purity terephthalic acid from printing and dyeing white mud through hydrothermal process is characterized by comprising the following steps:
step 1: washing the printing and dyeing white mud by using a dilute acid solution containing a surfactant, and then carrying out solid-liquid separation to obtain a white mud filter cake;
step 2: dispersing the white mud filter cake obtained in the step 1 into water to obtain a white mud dispersion liquid, adjusting the pH value, and placing the white mud dispersion liquid into a hydrothermal kettle for hydrothermal reaction to obtain a hydrothermal reaction product;
and step 3: carrying out solid-liquid separation on the hydrothermal reaction product obtained in the step 2, and dispersing and washing a filter cake by using pure water to obtain a washed product dispersion liquid;
and 4, step 4: carrying out solid-liquid separation on the product dispersion liquid obtained in the step 3 again, and drying the solid to obtain high-purity terephthalic acid;
the components of the printing and dyeing white mud comprise terephthalic acid, ethylene glycol, polyethylene terephthalate oligomer, oil, acid and polyaluminium chloride.
2. The method for hydrothermally recovering high-purity terephthalic acid from printing and dyeing white mud according to claim 1, wherein the dilute acid solution in the step 1 is at least one of sulfuric acid, hydrochloric acid and nitric acid, and the concentration of the dilute acid solution is 0.5-2 mol/L and is 1-5 times of the volume of the white mud.
3. The method for hydrothermal recovery of high-purity terephthalic acid from printing and dyeing white mud according to claim 1, wherein the surfactant in the step 1 is alcohol ether acid-resistant surfactant such as fatty alcohol-polyoxyethylene ether, and the concentration of the surfactant is 0.05-0.2 mol/L.
4. The method for hydrothermally recovering high-purity terephthalic acid from printing and dyeing white mud according to claim 1, wherein the solid-to-liquid ratio of the white mud dispersion liquid in the step 2 is 1: 5-9 g/mL.
5. The method for hydrothermally recovering high-purity terephthalic acid from printing and dyeing white mud according to claim 1, wherein the pH in the step 2 is 6.5-7.5.
6. The method for hydrothermally recovering high-purity terephthalic acid from printing and dyeing white mud according to claim 1, wherein the temperature of the hydrothermal reaction in the step 2 is 150-180 ℃ and the time is 12-24 hours.
7. The method for hydrothermally recovering high-purity terephthalic acid from printing and dyeing white mud according to claim 1, wherein the filling degree of the hydrothermal kettle in the step 2 is 60-80%.
8. The method for hydrothermally recovering high-purity terephthalic acid from printing and dyeing white mud according to claim 1, wherein the volume of pure washing water in the step 3 is 5-10 times of the volume of the filter cake.
9. The method for hydrothermally recovering high-purity terephthalic acid from dyeing white mud according to claim 1, wherein the solid-liquid separation in steps 3 and 4 is centrifugal separation or mechanical filter pressing.
10. The method for hydrothermally recovering high-purity terephthalic acid from printing and dyeing white mud according to claim 1, wherein the drying temperature in the step 4 is 60-80 ℃.
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4355175A (en) * | 1981-04-06 | 1982-10-19 | Pusztaszeri Stephen F | Method for recovery of terephthalic acid from polyester scrap |
| CN105585475A (en) * | 2015-08-06 | 2016-05-18 | 绍兴汉青环保科技有限公司 | Printing and dyeing white mud resource utilizing method |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4355175A (en) * | 1981-04-06 | 1982-10-19 | Pusztaszeri Stephen F | Method for recovery of terephthalic acid from polyester scrap |
| CN105585475A (en) * | 2015-08-06 | 2016-05-18 | 绍兴汉青环保科技有限公司 | Printing and dyeing white mud resource utilizing method |
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