阅读说明：本技术 一种pta氧化残渣生产增塑剂的生产工艺 (Production process for producing plasticizer from PTA oxidation residues ) 是由 沈福昌 沈建东 沈世金 张利 于 2021-01-20 设计创作，主要内容包括：本发明公开了一种PTA氧化残渣生产增塑剂的生产工艺,包括S1：酯化：将酯化反应器内加入PTA氧化残渣、辛醇和催化剂加热酯化,过滤后得到酯化液；S2：精馏：酯化液经两级精馏分离出粗苯甲酸辛酯和对苯二甲酸二辛酯以及偏苯三酸三辛酯；分离出的粗苯甲酸辛酯与混合多元醇进行酯交换反应；所述酯化步骤使用辛醇做冷却液。本发明在采用PTA氧化残渣生产对苯二甲酸二辛酯增塑剂剂的同时,还能生产苯甲酸辛酯和少量偏苯三甲酸三辛酯,加强了原料的利用效率,节约了能源,增加了成品收获,扩大了效益,采用辛醇作为冷却液,在酯化的同时冷凝,节约了冷凝器设备维护的成本,冷却效果好,转化热效率高。(The invention discloses a production process for producing a plasticizer from PTA oxidation residues, which comprises the following steps of S1: esterification: adding PTA oxidation residue, octanol and a catalyst into an esterification reactor, heating for esterification, and filtering to obtain an esterification solution; s2: and (3) rectification: separating out crude octyl benzoate, dioctyl terephthalate and trioctyl trimellitate from the esterification solution by two-stage rectification; carrying out ester exchange reaction on the separated crude octyl benzoate and mixed polyol; and in the esterification step, octanol is used as a cooling liquid. The invention can produce dioctyl terephthalate plasticizer and small amount of trioctyl trimellitate while adopting PTA oxidation residue to produce dioctyl terephthalate plasticizer, thereby enhancing the utilization efficiency of raw materials, saving energy, increasing the yield of finished products, enlarging the benefit, adopting octanol as cooling liquid, condensing while esterifying, saving the maintenance cost of condenser equipment, having good cooling effect and high conversion thermal efficiency.)

1. A production process for producing a plasticizer from PTA oxidation residues is characterized by comprising the following steps:

s1: esterification: adding PTA oxidation residue, octanol and a catalyst into an esterification reactor, heating for esterification, and filtering to obtain an esterification solution;

s2: and (3) rectification: after two-stage rectification of the esterification solution, crude octyl benzoate, crude dioctyl terephthalate and crude trioctyl trimellitate are obtained through condensation separation; performing ester exchange reaction on the crude octyl benzoate and mixed polyol to obtain benzoic acid polyol ester;

s3: removing impurities: respectively and sequentially neutralizing, washing, stripping, adsorbing and decoloring the crude trioctyl trimellitate and the crude dioctyl terephthalate, and filtering to remove impurities;

and in the esterification step, octanol is used as cooling liquid.

2. The process of claim 1 for producing plasticizer from PTA oxidation residue, wherein: the esterification step adopts octanol as cooling liquid and comprises the following steps: and (3) metering octanol through a flowmeter, pumping the octanol into a condenser to serve as a cooling medium, and introducing the heated cooling medium into the reactor to serve as a reactant.

3. The process of claim 1 for producing plasticizer from PTA oxidation residue, wherein: in step S1, the dehydration treatment is performed before esterification of PTA oxidation residues, and the specific steps are as follows: and (3) putting the PTA oxidation residue into a heating kettle for heating, and removing the separated water phase to treat wastewater.

4. The process of claim 1 for producing plasticizer from PTA oxidation residue, wherein: in step S1, the adding amount ratio of PTA oxidation residue, octanol and catalyst is: 1:2.001:0.0345, and the heating temperature is 180-220 ℃; and (3) end point of esterification reaction: the acid value is reduced to be below 0.5; and (3) introducing gas during esterification into a condenser for condensation, standing and layering the condensed liquid, and adding the octanol at the upper layer into the esterification reactor for recycling.

5. The process of claim 1 for producing plasticizer from PTA oxidation residue, wherein: in the step S2, the evaporation phase of the first-stage rectification is condensed to obtain crude octyl benzoate; adding mixed polyol and zinc acetate into the crude octyl benzoate to perform ester exchange reaction to obtain an ester exchange product, wherein the feeding proportion of the mixed polyol to the crude octyl benzoate is as follows: 1:4.5, the input amount of zinc acetate is 0.1 percent of the total mass, and the temperature is as follows: 220 ℃; rectifying and condensing the ester exchange product to obtain a finished product of the benzoic acid polyol ester.

6. The process of claim 5 for producing plasticizer from PTA oxidation residue, wherein: the mixed polyol is a mixture of diethylene glycol and dipropylene glycol.

7. The process of claim 5 for producing plasticizer from PTA oxidation residue, wherein: in the rectification step, the crude octyl benzoate is used as cooling liquid for recycling.

8. The process of claim 1 for producing plasticizer from PTA oxidation residue, wherein: and in the step S3, adding liquid alkali into the crude dioctyl terephthalate for neutralization until the pH value is 7.5-8, standing for layering after neutralization, adding pure water into the upper oil phase for washing, standing for layering after washing, inputting steam into the upper oil phase for steam stripping, and adsorbing and filtering by adopting activated carbon and diatomite in sequence after steam stripping to obtain a dioctyl terephthalate finished product.

9. The process of claim 1 for producing plasticizer from PTA oxidation residue, wherein: and in the step S3, adding liquid alkali into the crude trioctyl trimellitate to neutralize until the pH value is 7.5-8, standing and layering after neutralization, adding pure water into the upper oil phase for washing, standing and layering after washing, and adsorbing and filtering the upper oil phase by sequentially adopting activated carbon and diatomite to obtain a trioctyl trimellitate finished product.

Technical Field

The invention relates to the field of chemical waste treatment, in particular to a production process for producing a plasticizer by using PTA oxidation residues.

Background

Terephthalic acid is one of important organic raw materials, the demand of the terephthalic acid is gradually increased along with the development of society, the most important method for producing PTA at present is to oxidize paraxylene at high temperature to obtain the terephthalic acid, a large amount of oxidation residues are generated in the oxidation process, the amount of the residues accounts for 0.5-1% of the PTA capacity, the components in the PTA oxidation residues are very complex, and the main components are benzoic acid, terephthalic acid, phthalic acid, isophthalic acid and other aromatic acids. The conventional method is to discharge after direct treatment, which causes resource waste, and the existing treatment methods have low production efficiency, single reaction product and low raw material utilization rate, so that a production process for producing the plasticizer by using the PTA oxidation residue, which has high utilization rate and saves resources, is needed to be designed.

Disclosure of Invention

The invention aims to provide a production process for producing a plasticizer by using PTA oxidation residues, which has high utilization rate and saves resources.

The technical scheme for realizing the purpose of the invention is as follows: a production process for producing a plasticizer from PTA oxidation residues comprises the following steps:

s1: esterification: adding PTA oxidation residue, octanol and a catalyst into an esterification reactor, heating for esterification, and filtering to obtain an esterification solution;

s2: and (3) rectification: separating out crude octyl benzoate, crude dioctyl terephthalate and crude trioctyl trimellitate from the esterification solution by two-stage rectification; carrying out ester exchange reaction on the crude octyl benzoate to obtain a finished product of the benzoic acid polyol ester;

s3: removing impurities: respectively and sequentially neutralizing, washing, stripping, adsorbing and decoloring the crude trioctyl trimellitate and the crude dioctyl terephthalate, and filtering to remove impurities;

the catalyst adopts tetrabutyl titanate.

In step S1, the dehydration treatment is performed before esterification of PTA oxidation residues, and the specific steps are as follows: and (3) putting the PTA oxidation residue into a heating kettle for heating, and removing the separated water phase to treat wastewater.

The adding amount proportion of PTA oxidation residue, octanol and catalyst is as follows: 1:2.001:0.0345, and the heating temperature is 180-220 ℃; and (3) end point of esterification reaction: the acid value is reduced to be below 0.5; and (3) introducing gas during esterification into a condenser for condensation, standing and layering the condensed liquid, and adding the octanol at the upper layer into the esterification reactor for recycling.

And in the esterification step and the rectification step, octanol is adopted as a cooling liquid, the esterification tower top is condensed by a condenser and then enters a pure water separator, the octanol returns to the tower top after separation, the cooled octanol returns to the tower top at about 40 ℃, is heated to 184 ℃ after returning to the tower and is vaporized and refluxed with water, and the energy is wasted due to cyclic reciprocation. And after the water is vaporized by the traditional condenser, calcium and magnesium ions in the water can form scale, so that the condenser is polluted. In order to solve the problems, a pump is used for metering octanol into a condenser through a flowmeter to serve as a cooling medium, and the method has the advantages that the octanol and alcohol steam are cooled and heat exchanged in the condenser, so that the octanol is heated to about 140 ℃ and enters an esterification tower, the heat energy is saved, and the problem of scaling of the condenser is solved.

And dealcoholizing the esterified liquid after esterification, and refluxing the dealcoholized octanol and octanol generated by steam stripping together to the esterification step to participate in the reaction.

Condensing the evaporation phase of the first-stage rectification to obtain crude octyl benzoate; adding mixed polyol and zinc acetate into the crude octyl benzoate to perform ester exchange reaction to obtain an ester exchange product, wherein the feeding proportion of the mixed polyol to the crude octyl benzoate is as follows: 1:4.5, the input amount of zinc acetate is 0.1 percent of the total mass, and the temperature is as follows: 220 ℃; rectifying and condensing the ester exchange product to obtain a finished product of the benzoic acid polyol ester. Collecting and condensing the evaporated gas during the ester exchange reaction, standing and layering the condensate, taking octanol at the upper layer, conveying the octanol to an esterification reactor for recycling, and recycling crude octyl benzoate used as a cooling liquid by the condenser. The vacuum degree of the top of the rectification column is 0.15kpa, the temperature of the bottom of the rectification column is 220 ℃, the temperature of the top of the rectification column is 120 ℃, and the reflux ratio is 5:1, evaporating excessive octyl benzoate, wherein the temperature of a tower kettle is 240 ℃, the temperature of a tower top is 200 ℃, and the reflux ratio is as follows: 1:1, distilling out the benzoic acid polyol ester, and recycling the crude octyl benzoate used as cooling liquid by the condenser, thereby saving heat energy and solving the problem of condenser scaling. The mixed polyol is a mixture of diethylene glycol and dipropylene glycol.

When the octyl benzoate is extracted, the vacuum degree at the top of the tower is 0.15kpa, the temperature at the bottom of the tower is 250 ℃, the temperature at the top of the tower is 120 ℃, and the reflux extraction ratio is 5: 1. When the dioctyl terephthalate is extracted, the vacuum degree at the top of the tower is 0.15kpa, the temperature at the bottom of the tower is 250-255 ℃, the temperature at the top of the tower is 220-230 ℃, and the reflux ratio is 1: 1. When the trioctyl trimellitate is extracted, the vacuum degree at the top of the tower is 0.15kpa, the temperature at the bottom of the tower is 265 ℃, the temperature at the top of the tower is 235-240 ℃, and the trioctyl trimellitate is fully extracted without reflux.

The rectification adopts a vacuum unit, preferably a three-stage Roots unit combination, the unit has high efficiency, does not retain low-boiling-point substances, is more suitable for distillation in high vacuum degree, and operates very stably.

And burning residues in the second-stage rectifying still to obtain cobalt salt, manganese salt and bromine salt.

The rectification is carried out under the condition of negative pressure, the vacuum degree is 0.15kpa, the reaction time is shortened, the reaction temperature is reduced, and the conversion rate is improved.

And in the step S3, adding liquid alkali into the crude dioctyl terephthalate for neutralization until the pH value is 7.5-8, standing for layering after neutralization, adding pure water into the upper oil phase for washing, standing for layering after washing, inputting steam into the upper oil phase for steam stripping, and adsorbing and filtering by adopting activated carbon and diatomite in sequence after steam stripping to obtain a dioctyl terephthalate finished product. The alkali liquor adopts sodium hydroxide solution.

And in the step S3, adding liquid alkali into the crude trioctyl trimellitate to neutralize until the pH value is 7.5-8, standing and layering after neutralization, adding pure water into the upper oil phase for washing, standing and layering after washing, and adsorbing and filtering the upper oil phase by sequentially adopting activated carbon and diatomite to obtain a trioctyl trimellitate finished product.

By adopting the technical scheme, the invention has the following beneficial effects:

(1) the invention can produce dioctyl terephthalate plasticizer and small amount of trioctyl trimellitate while adopting PTA oxidation residue to produce dioctyl terephthalate plasticizer, thereby enhancing the utilization efficiency of raw materials, saving energy, increasing the yield of finished products, enlarging the benefit, and simultaneously adopting octanol as cooling liquid to condense during reaction, saving the maintenance cost of condenser equipment, having good cooling effect and high conversion thermal efficiency.

(2) The method carries out dehydration pretreatment before esterification reaction, removes liquid in PTA oxidation residues, reduces COD value, and reduces reaction difficulty and production cost.

(3) The octanol evaporated by the method is recycled, so that the octanol consumption is reduced, and the cost is saved.

(4) In the rectification step, octyl benzoate is adopted as cooling liquid for cyclic utilization, so that the maintenance cost of condenser equipment is further saved, the cooling effect is good, and the conversion heat efficiency is high.

(5) The octyl benzoate is subjected to ester exchange reaction, and then rectified and condensed to obtain a finished product of the polyol benzoate, so that the utilization rate is improved, the product diversity is increased, the production line income is enlarged, and the waste emission is reduced.

(6) The cobalt salt, the manganese salt and the bromine salt obtained from the second-stage rectifying still residue can be used as industrial production raw materials, so that the yield of the product evaluation line is increased, and the utilization rate of the raw materials is improved.

Drawings

In order that the present disclosure may be more readily and clearly understood, reference is now made to the following detailed description of the present disclosure taken in conjunction with the accompanying drawings, in which

FIG. 1 is a block flow diagram of the present invention.

Detailed Description

Referring to fig. 1, the present application provides a production process for producing plasticizer from PTA oxidation residues, which solves the problems of large yield and low utilization rate of PTA oxidation residues in the prior art, and the general concept is as follows: comprises the following steps

S1: esterification: adding PTA oxidation residue, octanol and a catalyst into an esterification reactor, heating for esterification, and filtering to obtain an esterification solution;

s2: and (3) rectification: separating out crude octyl benzoate, crude dioctyl terephthalate and crude trioctyl trimellitate from the esterification solution by two-stage rectification; carrying out ester exchange reaction on the crude octyl benzoate to obtain a finished product of the benzoic acid polyol ester;

s3: removing impurities: respectively and sequentially neutralizing, washing, stripping, adsorbing and decoloring the crude trioctyl trimellitate and the crude dioctyl terephthalate, and filtering to remove impurities;

the catalyst adopts tetrabutyl titanate.

In step S1, the dehydration treatment is performed before esterification of PTA oxidation residues, and the specific steps are as follows: and (3) putting the PTA oxidation residue into a heating kettle for heating, and removing the separated water phase to treat wastewater.

The adding amount proportion of PTA oxidation residue, octanol and catalyst is as follows: 1:2.001:0.0345, and the heating temperature is 180-220 ℃; and (3) end point of esterification reaction: the acid value is reduced to be below 0.5; and (3) introducing gas during esterification into a condenser for condensation, standing and layering the condensed liquid, and adding the octanol at the upper layer into the esterification reactor for recycling.

And in the esterification step and the rectification step, octanol is adopted as a cooling liquid, the esterification tower top is condensed by a condenser and then enters a pure water separator, the octanol returns to the tower top after separation, the cooled octanol returns to the tower top at about 40 ℃, is heated to 184 ℃ after returning to the tower and is vaporized and refluxed with water, and the energy is wasted due to cyclic reciprocation. And after the condenser vaporizes the water, calcium and magnesium ions in the water can form scale, and the condenser is polluted. In order to solve the problems, a pump is used for metering octanol into a condenser through a flowmeter to serve as a cooling medium, and the method has the advantages that the octanol and alcohol steam are cooled and heat exchanged in the condenser, so that the octanol enters an esterification tower at the temperature of about 140 ℃, heat energy is saved, and the problem of scaling of the condenser is solved.

And dealcoholizing the esterified liquid after esterification, and refluxing the dealcoholized octanol and octanol generated by steam stripping together to the esterification step to participate in the reaction.

Condensing the evaporation phase of the first-stage rectification to obtain crude octyl benzoate; adding mixed polyol and zinc acetate into the crude octyl benzoate to perform ester exchange reaction to obtain an ester exchange product, wherein the feeding proportion of the mixed polyol to the crude octyl benzoate is as follows: 1:4.5, the input amount of zinc acetate is 0.1 percent of the total mass, and the temperature is as follows: 220 ℃; rectifying and condensing the ester exchange product to obtain a finished product of the benzoic acid polyol ester. Collecting and condensing the evaporated gas during the ester exchange reaction, standing and layering the condensate, taking octanol at the upper layer, conveying the octanol to an esterification reactor for recycling, and recycling crude octyl benzoate used as a cooling liquid by the condenser. The vacuum degree of the top of the rectification column is 0.15kpa, the temperature of the bottom of the rectification column is 220 ℃, the temperature of the top of the rectification column is 120 ℃, and the reflux ratio is 5:1, evaporating excessive octyl benzoate, wherein the temperature of a tower kettle is 240 ℃, the temperature of a tower top is 200 ℃, and the reflux ratio is as follows: 1:1, distilling out the benzoic acid polyol ester, and recycling the crude octyl benzoate used as cooling liquid by the condenser, thereby saving heat energy and solving the problem of condenser scaling. The mixed polyol is a mixture of diethylene glycol and dipropylene glycol.

When the octyl benzoate is extracted, the vacuum degree at the top of the tower is 0.15kpa, the temperature at the bottom of the tower is 250 ℃, the temperature at the top of the tower is 120 ℃, and the reflux extraction ratio is 5: 1. When the dioctyl terephthalate is extracted, the vacuum degree at the top of the tower is 0.15kpa, the temperature at the bottom of the tower is 250-255 ℃, the temperature at the top of the tower is 220-230 ℃, and the reflux ratio is 1: 1. When the trioctyl trimellitate is extracted, the vacuum degree at the top of the tower is 0.15kpa, the temperature at the bottom of the tower is 265 ℃, the temperature at the top of the tower is 235-240 ℃, and the trioctyl trimellitate is fully extracted without reflux. The rectification adopts a vacuum unit, preferably a three-stage Roots unit combination, the unit has high efficiency, does not retain low-boiling-point substances, is more suitable for distillation in high vacuum degree, and operates very stably.

And burning residues in the second-stage rectifying still to obtain cobalt salt, manganese salt and bromine salt.

The rectification is carried out under the condition of negative pressure, the vacuum degree is 0.15kpa, the reaction time is shortened, the reaction temperature is reduced, and the conversion rate is improved.

And in the step S3, adding liquid alkali into the crude dioctyl terephthalate for neutralization until the pH value is 7.5-8, standing for layering after neutralization, adding pure water into the upper oil phase for washing, standing for layering after washing, inputting steam into the upper oil phase for steam stripping, and adsorbing and filtering by adopting activated carbon and diatomite in sequence after steam stripping to obtain a dioctyl terephthalate finished product.

And adding the crude trioctyl trimellitate into liquid alkali to neutralize until the pH value is 7.5-8, standing and layering after neutralization, taking the upper oil phase, adding pure water for washing, standing and layering after washing, taking the upper oil phase, and sequentially adopting activated carbon and diatomite for adsorption and filtration to obtain a trioctyl trimellitate finished product. The alkali liquor adopts sodium hydroxide solution.

The reaction equation for the process design is as follows:

the reaction equation is as follows:

C₈H₆O₄+2C₈H₁₈O→C₂₄H₃₈O₂+2H₂O

phthalic acid, octanol and dioctyl phthalate mixed water

C₉H₆O₆+3C₈H₁₈O→C₃₃H₃₆O₄+3H₂O

Trimellitic acid octanol Trimellitic acid trioctyl ester water

2C₇H₆O₂+C₄H₁₀O₂→C₁₈H₁₈O₅+2H₂O

Diethylene glycol dibenzoate water

2C₇H₆O₂+C₆H₁₄O₃→C₂₀H₂₂O₅+2H₂O

Dipropylene glycol dibenzoate benzoate water

The technical solution of the present application is further explained below with reference to different embodiments.

Sampling, and taking dry base PTA oxidation residue available in the market for component analysis, wherein specific data of each kg of components are shown in the following table:

table 1 dry basis PTA oxidation residue per kg component content for each manufacturer.

Unit: g

(example 1)

1000g (dry basis) of Jiaxing tung Kun PTA oxidation residue is taken and added into a reactor, 2001g of octanol is added, and heating and stirring are started. When the temperature of the materials rises to 184 ℃, adding 3.45g of tetrabutyl titanate catalyst, refluxing octanol at the moment and carrying water, waiting until the temperature in the kettle rises to about 220 ℃ and no water drops are extracted, regarding as the end point of the esterification reaction, and when the acid value of the esterification liquid is detected to be below 0.5, finishing the esterification reaction. And when the temperature of the esterification liquid is reduced to 90 ℃, filtering to obtain transparent esterification liquid, and starting to enter the rectification step.

Pouring the transparent esterification liquid into a rectifying tower kettle, heating the tower kettle when the vacuum of the tower top reaches 0.15kpa, starting to extract excessive octanol when the temperature of the tower top rises and stabilizes at about 43 ℃, and starting to collect octyl benzoate obtained by the reaction when the temperature of the tower top rises and stabilizes at about 120 ℃ after the octanol is extracted. The amount of octyl benzoate obtained was 688.7g (loss of material during the process: 3.3g), and the transesterification was started.

Pouring the obtained octyl benzoate into a reactor, adding 153g of polyhydric alcohol and 1g of zinc acetate, heating and stirring, and taking the reaction as the end point when the temperature reaches about 220 ℃ and no octanol is extracted.

The amount of product formed per kg of oxidation residue on a dry basis and the amount consumed are shown in Table 2.

(example 2)

1000g (dry basis) of oxidized residue of PTA in east Asian Shanghai is taken and added into a reactor, 2001g of octanol is added, and heating and stirring are started. When the temperature of the materials rises to 184 ℃, adding 3.45g of tetrabutyl titanate catalyst, refluxing octanol at the moment and carrying water, waiting until the temperature in the kettle rises to about 220 ℃ and no water drops are extracted, regarding as the end point of the esterification reaction, and when the acid value of the esterification liquid is detected to be below 0.5, finishing the esterification reaction. And when the temperature of the esterification liquid is reduced to 90 ℃, filtering to obtain transparent esterification liquid, and starting to enter the rectification step.

Pouring the transparent esterification liquid into a rectifying tower kettle, heating the tower kettle when the vacuum of the tower top reaches 0.15kpa, starting to extract excessive octanol when the temperature of the tower top rises and stabilizes at about 43 ℃, and starting to collect octyl benzoate obtained by the reaction when the temperature of the tower top rises and stabilizes at about 120 ℃ after the octanol is extracted. The amount of octyl benzoate obtained was 593.2g (loss of material in the course of the process was 2.8g), and the transesterification was started.

Pouring the obtained octyl benzoate into a reactor, adding 132g of polyhydric alcohol and 1g of zinc acetate, heating and stirring, and taking the reaction as the end point when the temperature reaches about 220 ℃ and no octanol is extracted.

The reaction equation is as follows:

the amount of product formed per kg of oxidation residue on a dry basis and the amount consumed are shown in Table 2.

(example 3)

1000g (dry basis) of oxidized residue of Jiangyin Helan PTA is taken and added into a reactor, 2001g of octanol is added, and heating and stirring are started. When the temperature of the materials rises to 184 ℃, adding 3.45g of tetrabutyl titanate catalyst, refluxing octanol at the moment and carrying water, waiting until the temperature in the kettle rises to about 220 ℃ and no water drops are extracted, regarding as the end point of the esterification reaction, and when the acid value of the esterification liquid is detected to be below 0.5, finishing the esterification reaction. And when the temperature of the esterification liquid is reduced to 90 ℃, filtering to obtain transparent esterification liquid, and starting to enter the rectification step.

Pouring the transparent esterification liquid into a rectifying tower kettle, heating the tower kettle when the vacuum of the tower top reaches 0.15kpa, starting to extract excessive octanol when the temperature of the tower top rises and stabilizes at about 43 ℃, and starting to collect octyl benzoate obtained by the reaction when the temperature of the tower top rises and stabilizes at about 120 ℃ after the octanol is extracted. The amount of octyl benzoate obtained was 632.1g (loss of material in the course of the process was 2.9g), and the transesterification was started.

Pouring the obtained octyl benzoate into a reactor, adding 141g of polyhydric alcohol and 1g of zinc acetate, heating and stirring, and taking the reaction as the end point when the temperature reaches about 220 ℃ and no octanol is extracted.

The amount of product formed per kg of oxidation residue on a dry basis and the amount consumed are shown in Table 2.

(example 4)

1000g (dry basis) of PTA oxidation residue is added into Sichuan energy, 2001g of octanol is added, and heating and stirring are started. When the temperature of the materials rises to 184 ℃, adding 3.45g of tetrabutyl titanate catalyst, refluxing octanol at the moment and carrying water, waiting until the temperature in the kettle rises to about 220 ℃ and no water drops are extracted, regarding as the end point of the esterification reaction, and when the acid value of the esterification liquid is detected to be below 0.5, finishing the esterification reaction. And when the temperature of the esterification liquid is reduced to 90 ℃, filtering to obtain transparent esterification liquid, and starting to enter the rectification step.

Pouring the transparent esterification liquid into a rectifying tower kettle, heating the tower kettle when the vacuum of the tower top reaches 0.15kpa, starting to extract excessive octanol when the temperature of the tower top rises and stabilizes at about 43 ℃, and starting to collect octyl benzoate obtained by the reaction when the temperature of the tower top rises and stabilizes at about 120 ℃ after the octanol is extracted. The amount of octyl benzoate obtained was 650.9g (loss of material during the process: 3.1g), and the transesterification was started.

Pouring the obtained octyl benzoate into a reactor, adding 145g of polyalcohol and 1g of zinc acetate, heating and stirring, and taking the reaction as the end point when the temperature reaches about 220 ℃ and no octanol is extracted.

The amount of product formed per kg of oxidation residue on a dry basis and the amount consumed are shown in Table 2.

Table 2 production and consumption of 1kg oxidation residue on a dry basis in the example:

manufacturer of the product	Benzoic acid polyester	Terephthalic acid dioctyl ester	Trimellitic acid trioctyl ester	Octanol (I)	Mixed polyols
						Jiaxing tung queen tree	450	900	150	648	153
Shanghai Yadong	388	860	75	620	132
						River yin sea lun	413	840	100	605	141
All-weather can throw	425	880	150	634	145

Unit: g

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.