CN113214078A - Method for recycling and preparing dioctyl terephthalate by utilizing terephthalic acid production waste - Google Patents
Method for recycling and preparing dioctyl terephthalate by utilizing terephthalic acid production waste Download PDFInfo
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- CN113214078A CN113214078A CN202110576910.4A CN202110576910A CN113214078A CN 113214078 A CN113214078 A CN 113214078A CN 202110576910 A CN202110576910 A CN 202110576910A CN 113214078 A CN113214078 A CN 113214078A
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- terephthalic acid
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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 117
- 239000002699 waste material Substances 0.000 title claims abstract description 38
- 238000000034 method Methods 0.000 title claims abstract description 22
- OEIWPNWSDYFMIL-UHFFFAOYSA-N dioctyl benzene-1,4-dicarboxylate Chemical compound CCCCCCCCOC(=O)C1=CC=C(C(=O)OCCCCCCCC)C=C1 OEIWPNWSDYFMIL-UHFFFAOYSA-N 0.000 title claims abstract description 21
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 21
- 238000004064 recycling Methods 0.000 title claims abstract description 18
- 238000005886 esterification reaction Methods 0.000 claims abstract description 38
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 24
- 238000006386 neutralization reaction Methods 0.000 claims abstract description 23
- 238000005406 washing Methods 0.000 claims abstract description 21
- 238000001914 filtration Methods 0.000 claims abstract description 18
- BWDBEAQIHAEVLV-UHFFFAOYSA-N 6-methylheptan-1-ol Chemical compound CC(C)CCCCCO BWDBEAQIHAEVLV-UHFFFAOYSA-N 0.000 claims abstract description 9
- 238000001179 sorption measurement Methods 0.000 claims abstract description 8
- 239000000126 substance Substances 0.000 claims abstract description 7
- 238000002425 crystallisation Methods 0.000 claims abstract description 3
- 230000008025 crystallization Effects 0.000 claims abstract description 3
- 238000003756 stirring Methods 0.000 claims description 37
- 239000000463 material Substances 0.000 claims description 33
- 238000001816 cooling Methods 0.000 claims description 16
- 229910001220 stainless steel Inorganic materials 0.000 claims description 16
- 239000010935 stainless steel Substances 0.000 claims description 16
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims description 15
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 15
- 238000010438 heat treatment Methods 0.000 claims description 15
- 150000002148 esters Chemical class 0.000 claims description 13
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 12
- 238000003825 pressing Methods 0.000 claims description 12
- 239000007788 liquid Substances 0.000 claims description 11
- 239000000047 product Substances 0.000 claims description 11
- 239000013078 crystal Substances 0.000 claims description 10
- 239000000706 filtrate Substances 0.000 claims description 10
- 239000007787 solid Substances 0.000 claims description 10
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 9
- 230000032050 esterification Effects 0.000 claims description 8
- 239000003054 catalyst Substances 0.000 claims description 7
- -1 titanium metal compound Chemical class 0.000 claims description 7
- 239000003963 antioxidant agent Substances 0.000 claims description 6
- 230000003078 antioxidant effect Effects 0.000 claims description 6
- 239000003795 chemical substances by application Substances 0.000 claims description 6
- 229910000029 sodium carbonate Inorganic materials 0.000 claims description 6
- 238000006243 chemical reaction Methods 0.000 claims description 5
- 239000008367 deionised water Substances 0.000 claims description 5
- 229910021641 deionized water Inorganic materials 0.000 claims description 5
- 239000012535 impurity Substances 0.000 claims description 5
- 238000000967 suction filtration Methods 0.000 claims description 5
- 239000000203 mixture Substances 0.000 claims description 4
- 239000010936 titanium Substances 0.000 claims description 4
- 229910052719 titanium Inorganic materials 0.000 claims description 4
- VXUYXOFXAQZZMF-UHFFFAOYSA-N titanium(IV) isopropoxide Chemical compound CC(C)O[Ti](OC(C)C)(OC(C)C)OC(C)C VXUYXOFXAQZZMF-UHFFFAOYSA-N 0.000 claims description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 3
- 239000003513 alkali Substances 0.000 claims description 3
- 230000003472 neutralizing effect Effects 0.000 claims description 3
- 239000005995 Aluminium silicate Substances 0.000 claims description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 2
- 235000012211 aluminium silicate Nutrition 0.000 claims description 2
- YHWCPXVTRSHPNY-UHFFFAOYSA-N butan-1-olate;titanium(4+) Chemical compound [Ti+4].CCCC[O-].CCCC[O-].CCCC[O-].CCCC[O-] YHWCPXVTRSHPNY-UHFFFAOYSA-N 0.000 claims description 2
- 238000013329 compounding Methods 0.000 claims description 2
- NLYAJNPCOHFWQQ-UHFFFAOYSA-N kaolin Chemical compound O.O.O=[Al]O[Si](=O)O[Si](=O)O[Al]=O NLYAJNPCOHFWQQ-UHFFFAOYSA-N 0.000 claims description 2
- 150000007522 mineralic acids Chemical class 0.000 claims description 2
- 238000002156 mixing Methods 0.000 claims description 2
- 238000011085 pressure filtration Methods 0.000 claims description 2
- 239000002351 wastewater Substances 0.000 claims description 2
- 230000008901 benefit Effects 0.000 abstract description 4
- 239000002994 raw material Substances 0.000 abstract description 4
- 238000005516 engineering process Methods 0.000 abstract description 2
- 238000004090 dissolution Methods 0.000 abstract 1
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 6
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 6
- 239000004014 plasticizer Substances 0.000 description 6
- KWSLGOVYXMQPPX-UHFFFAOYSA-N 5-[3-(trifluoromethyl)phenyl]-2h-tetrazole Chemical group FC(F)(F)C1=CC=CC(C2=NNN=N2)=C1 KWSLGOVYXMQPPX-UHFFFAOYSA-N 0.000 description 4
- 239000002253 acid Substances 0.000 description 4
- 229910001379 sodium hypophosphite Inorganic materials 0.000 description 4
- 238000004458 analytical method Methods 0.000 description 3
- 230000005587 bubbling Effects 0.000 description 3
- 238000007599 discharging Methods 0.000 description 3
- 239000012263 liquid product Substances 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- 238000007670 refining Methods 0.000 description 3
- 238000005070 sampling Methods 0.000 description 3
- 239000000654 additive Substances 0.000 description 2
- 230000032798 delamination Effects 0.000 description 2
- 229920001971 elastomer Polymers 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 239000003973 paint Substances 0.000 description 2
- 239000004033 plastic Substances 0.000 description 2
- 229920003023 plastic Polymers 0.000 description 2
- 239000005060 rubber Substances 0.000 description 2
- 229920000459 Nitrile rubber Polymers 0.000 description 1
- 239000005062 Polybutadiene Substances 0.000 description 1
- CLBRCZAHAHECKY-UHFFFAOYSA-N [Co].[Pt] Chemical compound [Co].[Pt] CLBRCZAHAHECKY-UHFFFAOYSA-N 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- UHOVQNZJYSORNB-UHFFFAOYSA-N benzene Substances C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000005034 decoration Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010292 electrical insulation Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 239000000314 lubricant Substances 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 231100000252 nontoxic Toxicity 0.000 description 1
- 230000003000 nontoxic effect Effects 0.000 description 1
- 229920001084 poly(chloroprene) Polymers 0.000 description 1
- 229920002857 polybutadiene Polymers 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
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-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C67/00—Preparation of carboxylic acid esters
- C07C67/08—Preparation of carboxylic acid esters by reacting carboxylic acids or symmetrical anhydrides with the hydroxy or O-metal group of organic compounds
-
- 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
- C07C67/00—Preparation of carboxylic acid esters
- C07C67/48—Separation; Purification; Stabilisation; Use of additives
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention belongs to the field of chemical industry, and particularly relates to a technology for recycling terephthalic acid waste, and provides a method for recycling and preparing dioctyl terephthalate by utilizing terephthalic acid production waste. The method adopts terephthalic acid waste and isooctyl alcohol as main raw materials, and the method comprises the specific operation processes of dissolution, filtration, neutralization and crystallization, washing, esterification reaction, negative pressure dealcoholization, addition and subtraction neutralization, water washing, steam stripping, adsorption decoloration and filtration. The invention has the advantages of simple production process, high safety, low production cost, stable product quality and the like, and simultaneously achieves the purposes of high recycling and changing waste into valuable.
Description
Technical Field
The invention belongs to the field of chemical industry, in particular relates to a technology for recycling terephthalic acid waste, and mainly aims at the plasticizer industry to provide a method for recycling and preparing dioctyl terephthalate by utilizing terephthalic acid production waste.
Background
The plasticizer is an essential additive in the plastic industry, and is added to increase the plasticity and the fluidity and ensure the flexibility of a finished product when processing high polymers such as plastics, rubber, paint and the like, wherein the dioctyl terephthalate is a plasticizer with excellent performance, is a nontoxic green environment-friendly non-o-benzene plasticizer, has good cold resistance, heat resistance, extraction resistance, electrical insulation property and low-temperature flexibility, and has small volatility and high plasticizing efficiency. The plasticizer is widely applied to softeners of rubbers such as nitrile rubber, chloroprene rubber, ternary butadiene rubber and the like, is an ideal plasticizer for producing cable materials with the temperature of 70 ℃ and other PVC products requiring volatilization resistance, and can also be applied to lubricants and additives of paint coatings of high-grade furniture and interior decoration.
The prior industrial production method mainly takes an esterification synthesis process as a main raw material, and adopts raw materials of terephthalic acid and isooctanol for esterification reaction, wherein the main raw material of terephthalic acid generates a large amount of terephthalic acid waste every year in the production process due to equipment failure maintenance, ground scattering and the like, and direct landfill not only seriously affects the environment, but also wastes resources, but also has the difficulties of low recovery rate, complex process and the like in the prior treatment. Therefore, the aim of recycling waste materials is fulfilled by comprehensively recycling the terephthalic acid through technical innovation, and the recovered terephthalic acid is used for preparing the dioctyl terephthalate product, so that the environment is protected, the production cost is reduced, the economic benefit of an enterprise is improved, and the market competitiveness of the product is enhanced.
Disclosure of Invention
The invention mainly aims at the defects of high treatment difficulty, complex process and the like in the prior art, and provides a novel process and a novel method for preparing dioctyl terephthalate by recycling waste materials in the PTA production process, so that the purposes of high recycling and changing waste into valuable are achieved during treatment.
The technical scheme is as follows:
a method for preparing dioctyl terephthalate by recycling terephthalic acid production waste is characterized by comprising the following steps:
1. dissolving: adding pure water into a stainless steel kettle with a stirrer, putting terephthalic acid waste into a reaction kettle, starting stirring, slowly heating to 55-65 ℃, then dropwise adding a sodium hydroxide solution, stopping dropwise adding when the pH value reaches 10-12, continuously stirring for 1-2 hours, and completely dissolving the terephthalic acid waste.
2. And (3) filter pressing: and (3) after the terephthalic acid waste is completely dissolved, carrying out pressure filtration while the terephthalic acid waste is hot, and removing insoluble solid mechanical impurities to obtain a filtrate.
3. Neutralization and crystallization: and transferring the obtained filtrate into a neutralization kettle, starting stirring, slowly dropwise adding inorganic acid to perform neutralization reaction, stopping dropwise adding when the pH value reaches 6.8-7.0, cooling to 25-35 ℃, crystallizing, and performing filter pressing to obtain crude terephthalic acid crystals.
4. Washing: putting the crude terephthalic acid crystal obtained by filter pressing into a stainless steel kettle with stirring, adding 50% acetic acid solution, starting stirring, washing for 0.5-1 hour at normal temperature and normal pressure, and then carrying out suction filtration to obtain the fine terephthalic acid.
5. Esterification reaction: and (3) putting the obtained purified terephthalic acid and isooctyl alcohol into an esterification reaction kettle with stirring and pressure resistance according to the mol ratio of 1: 2-2.5, and adding an esterification catalyst and an antioxidant. Starting stirring and slowly heating to 210-230 ℃ for esterification reaction to obtain crude ester.
6. Dealcoholizing: after the esterification reaction is finished, starting a vacuum pump to remove alcohol through negative pressure, so that part of the residual isooctyl alcohol can be fully removed.
7. Neutralizing: cooling the materials in the esterification reaction kettle, transferring the crude ester of the materials into a neutralization kettle, and adding sodium carbonate alkali liquor for neutralization.
8. Washing with water: then, deionized water was added to carry out 2 water washing operations.
9. Stripping: then stripping is carried out under the condition of negative pressure, and excessive residual alcohol and part of low-boiling substances are removed.
10. And (3) adsorption and decoloration: adding inorganic filtering agent, and adsorbing and decolorizing.
11. And (3) filtering: filtering the material by a filter to separate solid from liquid to obtain the dioctyl terephthalate product
In the invention, the terephthalic acid waste comprises pond materials, ground materials, pipeline materials and waste water generated in the production process of the terephthalic acid.
The esterification catalyst is a compound titanium metal compound, and the compound titanium metal compound is prepared by mixing and compounding 20-30% by weight of tetrabutyl titanate and 70-80% by weight of tetraisopropyl titanate.
The antioxidant is sodium hypophosphite,
the alkali used for neutralization is sodium carbonate solution with the content of 4 percent.
The inorganic filter-adsorbing agent is a porous adsorbing material, and the component is a mixture of active carbon, diatomite and kaolin according to the mass ratio of 2: 0.5.
The invention has the advantages of
The invention provides a method for recycling and preparing dioctyl terephthalate by utilizing terephthalic acid production waste, which has the advantages of simple production process, high safety, low production cost and stable product quality, and simultaneously achieves the purpose of changing waste into valuable.
Drawings
FIG. 1 is a schematic flow chart of the production process of the method for preparing dioctyl terephthalate by recycling terephthalic acid production waste, wherein: 1. dissolving, 2, filtering, 3, neutralizing and crystallizing, 4, washing, 5, esterifying, 6, dealcoholizing under negative pressure, 7, adding or reducing neutralization, 8, washing, 9, stripping, 10, adsorbing and decoloring, 11, filtering, 12 and obtaining a finished product.
Detailed Description
The preparation process of the present invention is further illustrated by the following examples.
Example 1
Adding 2000L of pure water into a 10000L stainless steel kettle with a stirrer, putting 6000kg of terephthalic acid waste into a reaction kettle, starting stirring, slowly heating to 65 ℃, then dropwise adding a sodium hydroxide solution, stopping dropwise adding when the pH value reaches 10, continuously stirring for 1.5 hours, filtering while hot after the terephthalic acid waste is completely dissolved, and removing insoluble solid mechanical impurities to obtain a filtrate.
Transferring the obtained filtrate into a neutralization kettle, starting stirring, slowly dripping 28% hydrochloric acid for neutralization reaction, stopping dripping when the pH value reaches 7, cooling to 30 ℃, crystallizing, and performing filter pressing to obtain crude terephthalic acid crystals.
Putting 2800kg of crude terephthalic acid crystals obtained by filter pressing into a 5000L stainless steel kettle with a stirrer, adding 2000L of 50% acetic acid solution, starting the stirrer, washing for 1 hour at normal temperature and normal pressure, and then carrying out suction filtration to obtain the purified terephthalic acid.
5200kg of isooctanol, 2200kg of purified terephthalic acid, 6kg of esterification catalyst compound titanium compound and 8kg of antioxidant sodium hypophosphite are respectively put into a 10000L stainless steel esterification reaction kettle with stirring and pressure resistance, the temperature is raised by heating and kept at 215-225 ℃, the pressure is 0.06-0.18 MPa, after 5 hours of esterification reaction, a small amount of nitrogen is introduced into the materials in the esterification reaction kettle for bubbling, and meanwhile, sampling is carried out for analysis, and when the acid value reaches less than 0.4mgKOH/g, the esterification reaction is finished.
After the esterification reaction is finished, the heating device is firstly closed, then the vacuum pump is started, and then the micro-negative pressure dealcoholization is carried out, so that part of excessive alcohol is fully removed. Cooling the materials in the esterification reaction kettle, when the temperature of the materials is reduced to 65 ℃, transferring the crude ester of the materials into a stainless steel refining kettle, firstly adding a sodium carbonate solution with the content of 4% for neutralization, starting stirring for 30 minutes, standing for 15 minutes, and discharging water in the crude ester liquid of the materials after layering; then 50L of deionized water is added for water washing, after stirring is started for 20 minutes, the mixture is kept still for 15 minutes, water in the material crude ester liquid is drained after delamination, and the water washing operation is repeated again. And then heating to 165 ℃ and carrying out steam stripping under the condition of negative pressure to remove residual alcohol and part of low-boiling-point substances, finally cooling to 80 ℃, adding an inorganic filtering and adsorbing agent, starting stirring for 30 minutes, carrying out adsorption decoloration treatment, continuing cooling to 35 ℃, and filtering by using a filter to separate solid from liquid to obtain a liquid product dioctyl terephthalate.
Example 2
Adding 1800L of pure water into a 10000L stainless steel kettle with a stirrer, putting 5800kg of terephthalic acid waste into a reaction kettle, starting stirring, slowly heating to 60 ℃, then dropwise adding a sodium hydroxide solution, stopping dropwise adding when the pH value reaches 11, continuously stirring for 1.2 hours, completely dissolving the terephthalic acid waste, filtering while hot, and removing insoluble solid mechanical impurities to obtain a filtrate.
Transferring the obtained filtrate into a neutralization kettle, starting stirring, slowly dripping 28% hydrochloric acid for neutralization reaction, stopping dripping when the pH value reaches 6.8, cooling to 32 ℃, crystallizing, and performing filter pressing to obtain crude terephthalic acid crystals.
Putting 2500kg of crude terephthalic acid crystals obtained by filter pressing into a 5000L stainless steel kettle with a stirrer, adding 2000L of 50% acetic acid solution, starting stirring, washing for 1 hour at normal temperature and normal pressure, and then carrying out suction filtration to obtain the purified terephthalic acid.
Respectively adding 5000kg of isooctanol, 2300kg of purified terephthalic acid, 5.5kg of esterification catalyst compound titanium compound and 7.5kg of antioxidant sodium hypophosphite into a 10000L stainless steel esterification reaction kettle with stirring and pressure resistance, heating and maintaining at 215-225 ℃ under the pressure of 0.06-0.18 MPa, introducing a small amount of nitrogen into the materials in the esterification reaction kettle for bubbling after 5 hours of esterification reaction, sampling for analysis, and finishing the esterification reaction when the acid value is less than 0.4 mgKOH/g.
After the esterification reaction is finished, the heating device is firstly closed, then the vacuum pump is started, and then the micro-negative pressure dealcoholization is carried out, so that part of excessive alcohol is fully removed. Cooling the materials in the esterification reaction kettle, when the temperature of the materials is reduced to 65 ℃, transferring the crude ester of the materials into a stainless steel refining kettle, firstly adding a sodium carbonate solution with the content of 4% for neutralization, starting stirring for 30 minutes, standing for 15 minutes, and discharging water in the crude ester liquid of the materials after layering; then adding 100L of deionized water for washing, starting stirring for 20 minutes, standing for 15 minutes, draining water in the material crude ester liquid after layering, and repeating the washing operation once again. And then heating to 165 ℃ and carrying out steam stripping under the condition of negative pressure to remove residual alcohol and part of low-boiling-point substances, finally cooling to 80 ℃, adding an inorganic filtering and adsorbing agent, starting stirring for 30 minutes, carrying out adsorption decoloration treatment, continuing cooling to 35 ℃, and filtering by using a filter to separate solid from liquid to obtain a liquid product dioctyl terephthalate.
Example 3
1900L of pure water is added into a 10000L stainless steel kettle with a stirrer, 6100kg of terephthalic acid waste is put into a reaction kettle, the stirring is started, the temperature is slowly heated to 58 ℃, then sodium hydroxide solution is dripped, when the PH reaches 12, the dripping is stopped, the stirring is continued for 2 hours, the terephthalic acid waste is filtered when the terephthalic acid waste is completely dissolved, and insoluble solid mechanical impurities are removed to obtain filtrate.
Transferring the obtained filtrate into a neutralization kettle, starting stirring, slowly dripping 28% hydrochloric acid for neutralization reaction, stopping dripping when the pH value reaches 6.9, cooling to 35 ℃, crystallizing, and performing filter pressing to obtain crude terephthalic acid crystals.
Putting 3000kg of crude terephthalic acid crystals obtained by filter pressing into a 5000L stainless steel kettle with a stirrer, adding 2000L of 50% acetic acid solution, starting stirring, washing for 1 hour at normal temperature and normal pressure, and then carrying out suction filtration to obtain the purified terephthalic acid.
Respectively adding 5400kg of isooctanol, 2300kg of purified terephthalic acid, 6.5kg of esterification catalyst compound titanium compound and 9kg of antioxidant sodium hypophosphite into a 10000L stainless steel esterification reaction kettle with stirring and pressure resistance, heating and maintaining at 215-225 ℃ under the pressure of 0.06-0.18 MPa, introducing a small amount of nitrogen into the materials in the esterification reaction kettle for bubbling after 5 hours of esterification reaction, sampling for analysis, and finishing the esterification reaction when the acid value is less than 0.4 mgKOH/g.
After the esterification reaction is finished, the heating device is firstly closed, then the vacuum pump is started, and then the micro-negative pressure dealcoholization is carried out, so that part of excessive alcohol is fully removed. Cooling the materials in the esterification reaction kettle, when the temperature of the materials is reduced to 65 ℃, transferring the crude ester of the materials into a stainless steel refining kettle, firstly adding a sodium carbonate solution with the content of 4% for neutralization, starting stirring for 30 minutes, standing for 15 minutes, and discharging water in the crude ester liquid of the materials after layering; then 50L of deionized water is added for water washing, after stirring is started for 20 minutes, the mixture is kept still for 15 minutes, water in the material crude ester liquid is drained after delamination, and the water washing operation is repeated again. And then heating to 165 ℃ and carrying out steam stripping under the condition of negative pressure to remove residual alcohol and part of low-boiling-point substances, finally cooling to 80 ℃, adding an inorganic filtering and adsorbing agent, starting stirring for 30 minutes, carrying out adsorption decoloration treatment, continuing cooling to 35 ℃, and filtering by using a filter to separate solid from liquid to obtain a liquid product dioctyl terephthalate.
The performance index test result of the prepared dioctyl terephthalate is shown in the following table, and the quality indexes of the dioctyl terephthalate all reach the grade standard of HG/T2423-2008 superior products.
| Serial number | Name of item | Superior product | Detecting a value |
| 1 | Appearance of the product | Transparent, clear and no suspended matter | Transparent, clear and no suspended matter |
| 2 | Purity (%) | ≥99 | 99.3 |
| 3 | Density (g/cm)3,20℃) | 0.981-0.986 | 0.984 |
| 4 | Moisture (%) | ≤0.1 | 0.03 |
| 5 | Flash Point (. degree.C.) | ≥210 | 215 |
| 6 | Color number (platinum-cobalt) | ≤50 | 30 |
| 7 | Acid value (mgKOH/g) | ≤0.02 | 0.015 |
| 8 | Volume resistivity (omega. cm) | ≥2×1012 | 3×1012 |
The invention provides a thought and a method, and a plurality of methods and ways for realizing the technical scheme are provided, and the above description is only the preferred embodiment of the invention. It should be noted that, for those skilled in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should be considered as within the scope of the present invention, and each component which is not specified in the present embodiment can be implemented by using the prior art.
Claims (4)
1. A method for preparing crude dioctyl terephthalate by recycling terephthalic acid production waste is characterized by comprising the following steps:
(1) dissolving: adding pure water into a stainless steel kettle with a stirrer, putting the terephthalic acid waste into a reaction kettle, starting stirring, slowly heating to 55-65 ℃, then dropwise adding a sodium hydroxide solution, stopping dropwise adding when the pH value reaches 10-12, continuously stirring for 1-2 hours, and completely dissolving the terephthalic acid waste;
(2) and (3) filter pressing: after the terephthalic acid waste is completely dissolved, carrying out pressure filtration while the terephthalic acid waste is hot, and removing insoluble solid mechanical impurities to obtain a filtrate;
(2) neutralization and crystallization: transferring the obtained filtrate into a neutralization kettle, starting stirring, slowly dropwise adding inorganic acid to perform neutralization reaction, stopping dropwise adding when the pH value reaches 6.8-7.0, cooling to 25-35 ℃, crystallizing, and performing filter pressing to obtain crude terephthalic acid crystals;
(3) washing: putting the crude terephthalic acid crystals obtained by filter pressing into a stainless steel kettle with stirring, adding 50% acetic acid solution, starting stirring, washing for 0.5-1 hour at normal temperature and normal pressure, and then carrying out suction filtration to obtain refined terephthalic acid;
(4) esterification reaction: putting the obtained purified terephthalic acid and isooctyl alcohol into an esterification reaction kettle with stirring and pressure resistance according to the molar ratio of 1: 2-2.5, and adding an esterification catalyst and an antioxidant; starting stirring and slowly heating to 210-230 ℃ for esterification reaction to prepare crude ester;
(5) dealcoholizing: after the esterification reaction is finished, starting a vacuum pump to perform dealcoholization through negative pressure, so that part of the residual isooctyl alcohol can be fully removed;
(6) neutralizing: cooling the materials in the esterification reaction kettle, transferring the crude ester of the materials into a neutralization kettle, and adding sodium carbonate alkali liquor for neutralization;
(7) washing with water: then adding deionized water to carry out washing operation for 2 times;
(8) stripping: then, carrying out steam stripping under the condition of negative pressure to remove excessive residual alcohol and part of low-boiling-point substances;
(9) and (3) adsorption and decoloration: adding inorganic filtering agent, and then carrying out adsorption decoloration treatment;
(11) and (3) filtering: filtering the material by a filter to separate solid from liquid to obtain the dioctyl terephthalate product.
2. The method for recycling and preparing crude dioctyl terephthalate from terephthalic acid production waste according to claim 1, wherein the terephthalic acid waste comprises pond material, ground material, pipeline material and waste water generated in the terephthalic acid production process.
3. The method for recycling and preparing crude dioctyl terephthalate from terephthalic acid production waste according to claim 1, wherein the esterification catalyst is a complex titanium metal compound, and the complex titanium metal compound is prepared by mixing and compounding 20-30% by weight of tetrabutyl titanate and 70-80% by weight of tetraisopropyl titanate.
4. The method for recycling and preparing crude dioctyl terephthalate from terephthalic acid production waste according to claim 1, wherein the inorganic filter is a porous adsorption material, and the component is a mixture of activated carbon, diatomite and kaolin according to a mass ratio of 2: 0.5.
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