CN114276238A

CN114276238A - Preparation method of diisooctyl terephthalate

Info

Publication number: CN114276238A
Application number: CN202210017085.9A
Authority: CN
Inventors: 岳军臣; 曹迎东; 王金鸽; 刘同友
Original assignee: Jining Changxing Plastic Additive Co ltd
Current assignee: Jining Changxing Plastic Additive Co ltd
Priority date: 2022-01-07
Filing date: 2022-01-07
Publication date: 2022-04-05

Abstract

A preparation method of diisooctyl terephthalate belongs to the technical field of plasticizer preparation, and is characterized by comprising the following steps: 1) primary esterification; 2) carrying out secondary esterification; 3) distilling; 4) neutralizing; 5) and (5) filtering and the like. The method can greatly shorten the time required by primary esterification and greatly improve the production efficiency through secondary esterification; in addition, excessive octanol forms azeotropy with ethylene glycol generated in the reaction, the ethylene glycol can be removed directly in an esterification kettle, and the ethylene glycol can be separated through water washing and standing layering, so that the octanol is convenient to recycle.

Description

Preparation method of diisooctyl terephthalate

Technical Field

The invention relates to a preparation method of diisooctyl terephthalate, belonging to the technical field of plasticizer preparation.

Background

Diisooctyl terephthalate (DOTP) is a novel plasticizer for polyvinyl chloride developed in recent years, and has the advantages of high insulation, low volatility, heat resistance, cold resistance, extraction resistance, good flexibility, good compatibility with PVC resin and the like.

The synthesis method of DOTP mainly comprises the following technical routes:

1) terephthaloyl chloride process: the terephthalic acid is used for preparing terephthalyl chloride, and then the terephthalyl chloride and isooctyl alcohol are heated under the action of catalysts such as sodium carbonate and the like to prepare the terephthalic acid.

2) Terephthalic acid process: is prepared by esterifying terephthalic acid and isooctyl alcohol under the action of concentrated sulfuric acid or p-toluenesulfonic acid, tetrabutyl titanate and other catalysts.

3) Dimethyl terephthalate process: dimethyl terephthalate is subjected to ester exchange under the action of catalysts such as titanium, manganese, cobalt and the like to produce DOYTP.

4) Polyethylene terephthalate process: polyester chips, waste polyester yarns and leftover materials are used as raw materials, and isooctanol or ethylene glycol is subjected to ester exchange through an explanation method to produce DOTP. The chemical equation is as follows:

chinese patent publication No. CN1135479A discloses a method for producing terephthalic acid diester and ethylene glycol from polyester waste, in which polyethylene terephthalate and monohydric alcohol with carbon number greater than 6 and boiling range greater than 150 ℃ are subjected to ester exchange degradation reaction under the action of catalyst, and ethylene glycol is added into the reaction system continuously at a certain speed to make ethylene glycol quickly escape from the reaction system, and the reaction is quick and thorough without the need of special separator to separate from monohydric alcohol, and the reaction degree can be controlled, the produced terephthalic acid diester can be used as plasticizer, and ethylene glycol can be used as important chemical raw material.

Chinese patent publication No. CN101531594A discloses a method for preparing high-purity terephthalic acid diester from polyethylene terephthalate waste, which comprises using polyethylene terephthalate (PET) waste and aliphatic saturated unit alcohol in the presence of oxalate catalyst, and performing alcoholysis reaction, transesterification reaction, and purification processes to obtain high-purity terephthalic acid diester. The prepared terephthalic acid diester can be used as a plasticizer. According to the method of the present invention, since the PET waste is used as a starting material, the negative effects of the PET waste on the environment can be reduced, the consumption of petrochemical raw materials can be reduced, and the production cost of the terephthalic acid diester can be reduced.

Disclosure of Invention

The invention provides a preparation method of diisooctyl terephthalate, which has the advantages of shortening the preparation time and improving the production efficiency mainly through secondary esterification.

The invention specifically adopts the technical scheme that:

a preparation method of diisooctyl terephthalate is characterized by comprising the following steps:

1) first esterification

1.1) preheating PET and excessive octanol to 150 ℃ of 120-plus, adding the PET and the excessive octanol into an esterification kettle, raising the temperature to 180 ℃ of 170-plus under the vacuum degree of-0.08 to-0.98 MPa, then adding a catalyst, and continuing the esterification reaction at 180 ℃ of 170-plus until the esterification conversion rate is 70-80%; wherein the catalyst is a titanium catalyst, and the dosage of the catalyst is 0.01 to 0.4 percent of the weight of PET;

the present invention can employ a titanium-based catalyst suitable in the art, which is readily available on the market, such as tetrabutyl titanate.

1.2) heating to 190-200 ℃, decompressing and dealcoholizing, and removing excessive octanol and generated glycol to a first temporary storage tank;

2) second esterification

2.1) adding the unreacted PET into a secondary esterification kettle every 4-5 batches in the step 1), heating to 180 ℃ at the vacuum degree of-0.08-0.98 MPa, then adding a catalyst, and continuing the esterification reaction at 180 ℃ below 170 ℃ until the conversion rate is 100 percent;

2.2) heating to 190-200 ℃, decompressing and dealcoholizing, and removing excessive octanol and generated glycol to a first temporary storage tank;

3) distillation

Transferring the materials obtained in the steps 1) and 2) to a distillation kettle, controlling the liquid phase temperature of the distillation kettle to be 255-265 ℃, controlling the vacuum degree to be more than or equal to-0.098 Mpa, and removing octanol through reduced pressure distillation;

4) neutralization

Transferring the material in the step 3) to a neutralization kettle, adding a decolorizing agent, decolorizing for 1-2 hours, and then neutralizing and washing with NaOH aqueous solution until the acid value is less than or equal to 0.02;

5) filtration

Transferring the material obtained in the step 4) to a filter tank, and performing filter pressing to remove a decolorizing agent filter cake, wherein the filtrate is the product of the invention.

In the industrial preparation of diisooctyl terephthalate, the time required for complete transesterification is very long, usually in a single charge of 10 tons, and, as far as the Applicant is aware, the transesterification time in the industrial process is generally from 24 to 48 hours, depending on the charge.

The invention can greatly shorten the time required by primary esterification and greatly improve the production efficiency through secondary esterification.

Wherein, the material dosage in the steps 1) and 2) is preferably PET: octanol: catalyst 1: 2-2.5: 0.01 to 0.4 percent. The amount is preferably based on: firstly, ensuring that octanol is excessive, and secondly, ensuring that the excessive octanol forms azeotropy with ethylene glycol generated in the reaction, and directly removing the ethylene glycol in an esterification kettle.

Wherein, the octanol and the ethylene glycol removed in the step 1.2) can be separated out through water washing, standing and layering in the first temporary storage tank, so that the octanol can be conveniently recycled.

Wherein the decoloring agent adopted in the step 4) is a mixture of diatomite, sulfuric acid and hydrogen peroxide.

Compared with the prior art, the invention has the advantages that:

1) the invention is particularly improved aiming at the industrial-grade method for preparing DOTP by a terephthalic acid dihydric alcohol ester method, and the method greatly shortens the time required by primary esterification and greatly improves the production efficiency by mainly carrying out secondary esterification;

2) excessive octanol and glycol generated in the reaction form azeotropy, the glycol can be removed directly in the esterification kettle, and the glycol can be separated by water washing and standing layering, so that the octanol is convenient to recycle.

Detailed Description

Best mode for carrying out the invention

The method comprises the following steps: first esterification

The feeding ratio is as follows: 9 tons of PET waste (the PET content is 80-90%), 18-20 tons of octanol and 0.027 ton of catalyst.

In the above-mentioned material-feeding ratio, if new octanol is adopted, the lower limit value can be adopted for feeding, and if recovered octanol is added, the upper limit value can be adopted for feeding.

Preheating the materials to the temperature of 150 ℃.,. sub.120-;

step two: second esterification

Step two is substantially the same as step one except that: 1) the adopted PET raw material is the unreacted material residue in the step one; 2) and reducing the pressure to remove the alcohol after the PET conversion rate is 100 percent.

The first and second decompression dealcoholization steps can basically remove the produced glycol, and the separated alcohol mixture can be washed and layered in the second temporary storage tank, so that the octanol can be conveniently separated and recycled.

Step three: distillation

Transferring the materials obtained in the first step and the second step to a distillation kettle, controlling the liquid phase temperature of the distillation kettle to be 255-265 ℃, controlling the vacuum degree to be more than or equal to-0.098 Mpa, and removing octanol through reduced pressure distillation;

step four: neutralization

Transferring the materials in the third step to a neutralization kettle, adding a decolorizing agent, decolorizing for 1-2 hours, and then neutralizing and washing with NaOH aqueous solution until the acid value is less than or equal to 0.02;

wherein, the decolorizing agent is a mixture of diatomite, sulfuric acid and hydrogen peroxide, wherein about 10 kg of sulfuric acid and 200 kg of hydrogen peroxide are added, and the diatomite is prepared by adopting a process amount.

5) Filtration

Transferring the material obtained in the step four to a filter tank, and performing filter pressing to remove a decolorizing agent filter cake, wherein the filtrate is the product of the invention.

Claims

1. A preparation method of diisooctyl terephthalate is characterized by comprising the following steps:

1) first esterification

2) second esterification

3) distillation

4) neutralization

Transferring the material in the step 3) to a neutralization kettle, adding a decolorizing agent, decolorizing for 1-2 hours, then neutralizing with NaOH aqueous solution, and washing with water until the acid value is less than or equal to 0.02;

5) filtration

2. The method for preparing diisooctyl terephthalate according to claim 1, wherein the amount of the materials used in the steps 1) and 2) is PET: octanol: catalyst 1: 2-2.5: 0.01 to 0.4 percent.

3. The method of claim 1, wherein the octanol and ethylene glycol removed in step 1.2) are separated from the ethylene glycol by washing with water and standing in a first holding tank.

4. The method of claim 1, wherein the decolorizing agent used in step 4) is a mixture of diatomaceous earth, sulfuric acid, and hydrogen peroxide.