System and method for polyester recycling co-producing bis(2-hydroxyethyl) terephthalate and 1,4-cyclohexanedimethanol

Abstract

The present invention relates to the field of organic synthesis, and in particular to a system and method for polyester recycling co-producing bis(2-hydroxyethyl) terephthalate and 1,4-cyclohexanedimethanol. The system, in the direction of feed, sequentially comprises a polyester alcoholysis system, a solid filtration system, a solvent recovery system, and a diethyl terephthalate purification system, as well as a bis(2-hydroxyethyl) terephthalate preparation system and a 1,4-cyclohexanedimethanol preparation system, each connected to the diethyl terephthalate purification system. The present invention, by optimizing the process route for polyester recycling co-producing bis(2-hydroxyethyl) terephthalate and 1,4-cyclohexanedimethanol, first degrades a polyester into an intermediate product diethyl terephthalate, and then prepares bis(2-hydroxyethyl) terephthalate and 1,4-cyclohexanedimethanol from the diethyl terephthalate. In this way, two degradation products can be obtained simultaneously, especially addressing the current issue of the high production cost of 1,4-cyclohexanedimethanol, reducing the cost of polyester recycling, and making it more suitable for industrial application.

Description

System and method for polyester recovery co-production of bis-hydroxyethyl terephthalate and 1,4-cyclohexanedimethanol TECHNICAL FIELD

[0001] The present application relates to the field of organic synthesis, in particular to a system and method for polyester recovery co-production of bis-hydroxyethyl terephthalate and 1,4-cyclohexanedimethanol. BACKGROUND

[0002] Polyester is one of the most commonly used polymers at present, which is mainly used for preparing fibers, films and bottles, etc. According to statistics, since 2003, the global polyester production capacity has expanded at an average annual rate of about 9%, and the polyester production capacity in China reached 29 million tons in 2010, becoming the world's largest producer and consumer of polyester. Due to the increasing social demand, the global polyester production is growing rapidly, and most of the polyester products are disposable consumer goods, which leads to the generation of a large amount of polyester waste. Waste polyester materials are not easily degraded by air or microorganisms in a short period of time due to their strong chemical inertness, which causes great pressure on the protection of the ecological environment. Therefore, there are many related researches on the degradation of waste polyester materials at home and abroad, but the intermediate product bis-hydroxyethyl terephthalate obtained by alcoholysis of waste polyester materials has no direct application in the market, which leads to the fact that the existing various recovery methods cannot meet the industrial application.

[0003] CN117430506A discloses a method for degrading and recycling polyester. The method mixes polyester, solvent and catalyst, and then heats and reacts to degrade the polyester into bis-hydroxyethyl terephthalate. The catalyst is an ionic liquid functionalized magnetic nanoparticle, and the solvent is a binary organic alcohol (specifically, any one of ethylene glycol, propylene glycol, butylene glycol and pentanediol). However, the polyester degradation product obtained by the method is only bis-hydroxyethyl terephthalate, and the catalyst used for degradation needs to be specially prepared. The degradation process is complicated, a large number of reagents are needed, the overall economic value is poor, and it is not suitable for large-scale industrial application. TECHNICAL PROBLEM

[0004] Therefore, how to reduce the cost of polyester recovery and obtain a higher value recovery product is a technical problem to be solved. TECHNICAL SOLUTION

[0005] To solve the above technical problems, the present application provides a system and method for polyester recovery co-production of bis-hydroxyethyl terephthalate and 1,4-cyclohexanedimethanol. The system and method can solve the problems of high cost of polyester recovery and single recovery product by optimizing the process route of polyester recovery co-production of bis-hydroxyethyl terephthalate and 1,4-cyclohexanedimethanol.

[0006] The application provides a polyester recovery system for co-production of terephthalic acid bishydroxyethyl ester and 1,4-cyclohexane dimethanol, which comprises, in sequence in the feeding direction, a polyester alcoholysis system, a solid filtering system, a solvent recovery system, a diethyl terephthalate refining system, and a terephthalic acid bishydroxyethyl ester preparation system and a 1,4-cyclohexane dimethanol preparation system connected to the diethyl terephthalate refining system respectively, wherein,

[0007] The polyester alcoholysis system comprises a depolymerization reactor.

[0008] The solid filtering system comprises, in sequence in the feeding direction, a centrifuge and a filter.

[0009] The solvent recovery system comprises an ethanol recovery tower.

[0010] The diethyl terephthalate refining system comprises, in sequence in the feeding direction, a diethyl terephthalate distillation tower and a diethyl terephthalate crystallizer.

[0011] The terephthalic acid bishydroxyethyl ester preparation system comprises, in sequence in the feeding direction, an ester exchange reactor, a terephthalic acid bishydroxyethyl ester crystallizer and an ethylene glycol recovery tower.

[0012] The 1,4-cyclohexane dimethanol preparation system comprises, in sequence in the feeding direction, a benzene ring hydrogenation reactor, a diethyl 1,4-cyclohexane dicarboxylate gas-liquid separator, an ester group hydrogenation reactor and a 1,4-cyclohexane dimethanol gas-liquid separator.

[0013] Further, the depolymerization reactor is used for depolymerization of the polyester to obtain a depolymerization solution, which is continuously fed into the centrifuge.

[0014] Further, an electric agitator is arranged in the depolymerization reactor, which is used for stirring the material.

[0015] Further, the centrifuge is used for centrifugation of the depolymerization solution to obtain a depolymerization centrifugation solution, which is continuously fed into the filter.

[0016] Further, the filter is used for filtration of the depolymerization centrifugation solution to obtain a depolymerization filtration solution, which is continuously fed into the ethanol recovery tower.

[0017] Further, the ethanol recovery tower is used for recovery of ethanol in the depolymerization filtration solution to obtain crude diethyl terephthalate, which is continuously fed into the diethyl terephthalate distillation tower.

[0018] Further, the crude terephthalic acid diethyl ester rectification tower is used for rectifying the crude terephthalic acid diethyl ester to obtain rectified terephthalic acid diethyl ester, which continues to enter the terephthalic acid diethyl ester crystallizer.

[0019] Further, the terephthalic acid diethyl ester crystallizer is used for crystallizing the rectified terephthalic acid diethyl ester to obtain terephthalic acid diethyl ester crystals, which continue to enter the ester exchange reactor or the benzene ring hydrogenation reactor.

[0020] Further, the ester exchange reactor is used for subjecting the terephthalic acid diethyl ester crystals to ester exchange reaction to obtain crude bis-hydroxyethyl terephthalate, which continues to enter the bis-hydroxyethyl terephthalate crystallizer.

[0021] Further, the bis-hydroxyethyl terephthalate crystallizer is used for crystallizing the crude bis-hydroxyethyl terephthalate to obtain bis-hydroxyethyl terephthalate crystals, and the filtrate after crystallization continues to enter the ethylene glycol recovery tower.

[0022] Further, the ethylene glycol recovery tower is used for recovering ethylene glycol in the filtrate.

[0023] Further, the benzene ring hydrogenation reactor is used for subjecting the terephthalic acid diethyl ester crystals to benzene ring hydrogenation reaction to obtain crude 1,4-cyclohexane dimethyl ester, which continues to enter the 1,4-cyclohexane dimethyl ester gas-liquid separator.

[0024] Further, the 1,4-cyclohexane dimethyl ester gas-liquid separator is used for recovering hydrogen in the crude 1,4-cyclohexane dimethyl ester to obtain refined 1,4-cyclohexane dimethyl ester, which continues to enter the ester group hydrogenation reactor.

[0025] Further, the ester group hydrogenation reactor is used for subjecting the refined 1,4-cyclohexane dimethyl ester to ester group hydrogenation reaction to obtain crude 1,4-cyclohexane dimethyl alcohol, which continues to enter the 1,4-cyclohexane dimethyl alcohol gas-liquid separator.

[0026] Further, the 1,4-cyclohexane dimethyl alcohol gas-liquid separator is used for recovering hydrogen in the crude 1,4-cyclohexane dimethyl alcohol to obtain refined 1,4-cyclohexane dimethyl alcohol.

[0027] The present application provides a method for recovering polyester to co-produce bis-hydroxyethyl terephthalate and 1,4-cyclohexanedimethanol, which comprises: a polyester alcoholysis method, a solid filtration method, a solvent recovery method, a diethyl terephthalate refining method, a bis-hydroxyethyl terephthalate preparation method and a 1,4-cyclohexanedimethanol preparation method.

[0028] Further, in the polyester alcoholysis method, the following steps are included:

[0029] Step 1.1: the polyester, anhydrous ethanol and a depolymerization catalyst are subjected to the depolymerization reaction in the depolymerization reactor to obtain the depolymerization solution.

[0030] Further, in the solid filtration method, the following steps are included in sequence:

[0031] Step 2.1: the depolymerization solution is subjected to centrifugal treatment in the centrifuge to obtain the depolymerization centrifugal solution;

[0032] Step 2.2: the depolymerization centrifugal solution is subjected to filtration treatment in the filter to obtain the depolymerization filtrate.

[0033] Further, in the solvent recovery method, the following steps are included:

[0034] Step 3.1: the depolymerization filtrate is subjected to ethanol recovery treatment in the ethanol recovery tower to obtain the crude diethyl terephthalate, and the recovered ethanol is returned to the depolymerization reactor through a pipeline.

[0035] Further, in the diethyl terephthalate refining method, the following steps are included in sequence:

[0036] Step 4.1: the crude diethyl terephthalate is subjected to rectification treatment in the diethyl terephthalate rectification tower to obtain the rectified diethyl terephthalate;

[0037] Step 4.2: the rectified diethyl terephthalate is subjected to crystallization treatment in the diethyl terephthalate crystallizer to obtain the diethyl terephthalate crystal.

[0038] Further, in the bis-hydroxyethyl terephthalate preparation method, the following steps are included in sequence:

[0039] Step 5.1: the diethyl terephthalate crystal, ethylene glycol and an ester exchange catalyst are subjected to the ester exchange reaction in the ester exchange reactor to obtain the crude bis-hydroxyethyl terephthalate;

[0040] Step 5.2: the crude bis-hydroxyethyl terephthalate is subjected to crystallization treatment in the bis-hydroxyethyl terephthalate crystallizer to obtain the bis-hydroxyethyl terephthalate crystal.

[0041] Step 5.3: The filtrate after the crystallization treatment is subjected to a recovery ethylene glycol treatment in the ethylene glycol recovery column, and the recovered ethylene glycol is returned to the ester exchange reactor through a pipeline.

[0042] Further, in the 1,4-cyclohexanedimethanol preparation method, the following steps are sequentially included:

[0043] Step 6.1: The diethyl terephthalate crystals, hydrogen, and a benzene ring hydrogenation catalyst are subjected to the benzene ring hydrogenation reaction in the benzene ring hydrogenation reactor to obtain the crude diethyl 1,4-cyclohexanedicarboxylate;

[0044] Step 6.2: The crude diethyl 1,4-cyclohexanedicarboxylate is subjected to a recovery hydrogen treatment in the diethyl 1,4-cyclohexanedicarboxylate gas-liquid separator to obtain the refined diethyl 1,4-cyclohexanedicarboxylate, and the recovered hydrogen is returned to the benzene ring hydrogenation reactor through a pipeline;

[0045] Step 6.3: The refined diethyl 1,4-cyclohexanedicarboxylate, hydrogen, and an ester group hydrogenation catalyst are subjected to the ester group hydrogenation reaction in the ester group hydrogenation reactor to obtain the crude 1,4-cyclohexanedimethanol;

[0046] Step 6.4: The crude 1,4-cyclohexanedimethanol is subjected to a recovery hydrogen treatment in the 1,4-cyclohexanedimethanol gas-liquid separator to obtain the refined 1,4-cyclohexanedimethanol, and the recovered hydrogen is returned to the ester group hydrogenation reactor through a pipeline.

[0047] Further, in the step 1.1, the polyester is one or a mixture of both of polyethylene terephthalate and polyethylene terephthalate-1,4-cyclohexanedimethanol.

[0048] Further, in the step 1.1, the mass ratio of the polyester to the anhydrous ethanol is 1: (5-8).

[0049] Further, in the step 1.1, the depolymerization catalyst is one of zinc acetate, manganese acetate, sodium hydroxide, or sulfuric acid, and the amount of the depolymerization catalyst is 2-5% of the total mass of the polyester, based on the total mass of the polyester.

[0050] Further, in the step 1.1, the temperature of the depolymerization reactor is 170-230°C, and the time of the depolymerization reaction is 1-3h.

[0051] Further, in the step 1.1, the pressure of the depolymerization reactor is 1.5-1.8 MPa.

[0052] Further, in the step 1.1, the depolymerization rate of the polyester is 95-99%.

[0053] Further, in the step 3.1, the temperature of the ethanol recovery column is 70-100℃.

[0054] Further, in the step 4.1, the temperature of the diethyl terephthalate rectification column is 160-200℃.

[0055] Further, in the step 4.1, the pressure of the diethyl terephthalate rectification column is 1-5 MPa.

[0056] Further, in the step 4.2, the crystallization treatment of the rectified diethyl terephthalate is performed using anhydrous ethanol, and the mass ratio of the rectified diethyl terephthalate to the anhydrous ethanol is 1: (0.5-1).

[0057] Further, in the step 4.2, the temperature of the crystallization treatment is 0-10℃.

[0058] Further, in the step 4.2, the purity of the diethyl terephthalate crystal is 99.9%.

[0059] Further, in the step 5.1, the mass ratio of the diethyl terephthalate crystal to the ethylene glycol is 1: (1-5).

[0060] Further, in the step 5.1, the transesterification catalyst is one of calcium oxide, titanium dioxide, aluminum oxide, or vanadium oxide, and the amount of the transesterification catalyst is 2-5% of the mass of the diethyl terephthalate crystal, based on the mass of the diethyl terephthalate crystal.

[0061] Further, in the step 5.1, the initial temperature of the transesterification reactor is 140-190℃, the initial reaction time is 1-3h, and then the temperature of the transesterification reactor is increased to 180-240℃, and the reaction is continued for 1-3h.

[0062] Further, in the step 5.1, the pressure of the transesterification reactor is (-0.002)-0.006 MPa.

[0063] Further, in the step 5.2, the crystallization treatment of the crude bis-hydroxyethyl terephthalate is performed using ethylene glycol, and the mass ratio of the crude bis-hydroxyethyl terephthalate to the ethylene glycol is 1: (1-3).

[0064] Further, in the step 5.2, the temperature of the bis-hydroxyethyl terephthalate crystallizer is 10-20℃.

[0065] Further, in the step 5.2, the yield of the bis-hydroxyethyl terephthalate crystal is 89-91%.

[0066] Further, in the step 5.3, the temperature of the ethylene glycol recovery tower is 90-110°C.

[0067] Further, in the step 6.1, the amount of hydrogen is used to maintain the pressure of the benzene ring hydrogenation reactor at 3-6 MPa.

[0068] Further, in the step 6.1, the benzene ring hydrogenation catalyst is one of a Ni / Al2O3 catalyst, a Pd / Al2O3 catalyst, a Pd / C catalyst, or a Ru-Pd / C catalyst, and the amount of the benzene ring hydrogenation catalyst is 0.1-0.5% of the mass of the bis-hydroxyethyl terephthalate crystal, based on the mass of the bis-hydroxyethyl terephthalate crystal.

[0069] Further, in the step 6.1, the temperature of the benzene ring hydrogenation reactor is 120-180°C.

[0070] Further, in the step 6.2, the temperature of the 1,4-cyclohexanedicarboxylic acid diethyl ester gas-liquid separator is 300-350°C.

[0071] Further, in the step 6.2, the pressure of the 1,4-cyclohexanedicarboxylic acid diethyl ester gas-liquid separator is 1-5 MPa.

[0072] Further, in the step 6.3, the amount of hydrogen is used to maintain the pressure of the ester group hydrogenation reactor at 8-12 MPa.

[0073] Further, in the step 6.3, the ester group hydrogenation catalyst is a copper-chromium-aluminum catalyst, and the amount of the copper-chromium-aluminum catalyst is 0.1-0.5% of the mass of the refined 1,4-cyclohexanedicarboxylic acid diethyl ester, based on the mass of the refined 1,4-cyclohexanedicarboxylic acid diethyl ester.

[0074] Further, in the step 6.3, the temperature of the ester group hydrogenation reactor is 180-230°C.

[0075] Further, in the step 6.4, the temperature of the 1,4-cyclohexanedimethanol gas-liquid separator is 300-350°C.

[0076] Further, in the step 6.4, the pressure of the 1,4-cyclohexanedimethanol gas-liquid separator is 1-5 MPa.

[0077] Further, in the step 6.4, the yield of the refined 1,4-cyclohexanedimethanol is 92-95%. Advantages

[0078] 1, the prior art generally adopts the method of directly degrading polyester into bis-hydroxyethyl terephthalate, however, this method can only obtain one degradation product, and the degradation process is complicated, and sometimes the catalyst used for degradation also needs special preparation, so the prior art is poor in economy; and the present application unexpectedly optimizes the process route of polyester recovery and co-production of bis-hydroxyethyl terephthalate and 1,4-cyclohexanedimethanol by adopting an unexpected recovery system and method, first degrading polyester into intermediate product diethyl terephthalate, and then preparing bis-hydroxyethyl terephthalate and 1,4-cyclohexanedimethanol from the diethyl terephthalate, so that two degradation products can be obtained at the same time, and especially the problem of high cost of preparing 1,4-cyclohexanedimethanol is solved, so that the present application unexpectedly optimizes the process route of polyester recovery and co-production of bis-hydroxyethyl terephthalate and 1,4-cyclohexanedimethanol, reduces the cost of polyester recovery, and makes it more suitable for industrial application.

[0079] 2, the present application is beneficial to resource recycling and sustainable development of society by degrading and recycling waste polyester.

[0080] 3, the present application is beneficial to ecological environment protection by degrading and treating waste polyester. BRIEF DESCRIPTION OF DRAWINGS

[0081] Fig. 1 is a system flow chart of the present application of polyester recovery and co-production of bis-hydroxyethyl terephthalate and 1,4-cyclohexanedimethanol,

[0082] 1-polyester alcoholysis system; 2-solid filter system; 3-solvent recovery system; 4-diethyl terephthalate refining system; 5-bis-hydroxyethyl terephthalate preparation system; 6-1,4-cyclohexanedimethanol preparation system; 1-1-depolymerization reactor; 2-1-centrifuge; 2-2-filter; 3-1-ethanol recovery column; 4-1-diethyl terephthalate distillation column; 4-2-diethyl terephthalate crystallizer; 5-1-ester exchange reactor; 5-2-bis-hydroxyethyl terephthalate crystallizer; 5-3-ethylene glycol recovery column; 6-1-benzene ring hydrogenation reactor; 6-2-1,4-cyclohexanedimethanol gas-liquid separator; 6-3-ester group hydrogenation reactor; 6-4-1,4-cyclohexanedimethanol gas-liquid separator. Best mode of the present application

[0083] A system of polyester recovery and co-production of bis-hydroxyethyl terephthalate and 1,4-cyclohexanedimethanol, the system sequentially comprises, in the feeding direction:

[0084] Polyester alcoholysis system 1, solid filter system 2, solvent recovery system 3, diethyl terephthalate refining system 4, and bis-hydroxyethyl terephthalate preparation system 5 and 1,4-cyclohexane dimethanol preparation system 6 connected to the diethyl terephthalate refining system 4, respectively, wherein, as shown in Figure 1, the polyester alcoholysis system 1 comprises a depolymerization reactor 1-1; the solid filter system 2 comprises a centrifuge 2-1 and a filter 2-2 in sequence in the feeding direction; the solvent recovery system 3 comprises an ethanol recovery column 3-1; the diethyl terephthalate refining system 4 comprises a diethyl terephthalate distillation column 4-1 and a diethyl terephthalate crystallizer 4-2 in sequence in the feeding direction; the bis-hydroxyethyl terephthalate preparation system 5 comprises an ester exchange reactor 5-1, a bis-hydroxyethyl terephthalate crystallizer 5-2, and an ethylene glycol recovery column 5-3 in sequence in the feeding direction; and the 1,4-cyclohexane dimethanol preparation system 6 comprises a benzene ring hydrogenation reactor 6-1, a diethyl 1,4-cyclohexane dicarboxylate gas-liquid separator 6-2, an ester group hydrogenation reactor 6-3, and a 1,4-cyclohexane dimethanol gas-liquid separator 6-4 in sequence in the feeding direction.

[0085] The polyester enters the depolymerization reactor 1-1, and an electric agitator is arranged in the depolymerization reactor 1-1, to obtain a depolymerization solution. The depolymerization solution continues to enter the centrifuge 2-1, to obtain a depolymerization centrifugal solution, which continues to enter the filter 2-2, to obtain a depolymerization filtered solution, which continues to enter the ethanol recovery column 3-1, to obtain crude diethyl terephthalate. The crude diethyl terephthalate continues to enter the diethyl terephthalate distillation column 4-1, to obtain refined diethyl terephthalate, which continues to enter the diethyl terephthalate crystallizer 4-2, to obtain diethyl terephthalate crystals.

[0086] Part of the diethyl terephthalate crystals enter the ester exchange reactor 5-1, to obtain crude bis-hydroxyethyl terephthalate, which continues to enter the bis-hydroxyethyl terephthalate crystallizer 5-2, to obtain bis-hydroxyethyl terephthalate crystals, and the filtrate after the crystallization process continues to enter the ethylene glycol recovery column 5-3.

[0087] The other part of the diethyl terephthalate crystals enter the benzene ring hydrogenation reactor 6-1, to obtain crude diethyl 1,4-cyclohexane dicarboxylate, which continues to enter the diethyl 1,4-cyclohexane dicarboxylate gas-liquid separator 6-2, to obtain refined diethyl 1,4-cyclohexane dicarboxylate. The refined diethyl 1,4-cyclohexane dicarboxylate continues to enter the ester group hydrogenation reactor 6-3, to obtain crude 1,4-cyclohexane dimethanol, which continues to enter the 1,4-cyclohexane dimethanol gas-liquid separator 6-4, to obtain refined 1,4-cyclohexane dimethanol. Embodiment of the present application

[0088] Example 1

[0089] A polyester recycling system for co-producing terephthalic acid bishydroxyethyl ester and 1,4-cyclohexane dimethanol, the system comprising in sequence in the feeding direction:

[0090] a polyester alcoholysis system 1, a solid filtering system 2, a solvent recovery system 3, a diethyl terephthalate refining system 4, and a terephthalic acid bishydroxyethyl ester preparation system 5 and a 1,4-cyclohexane dimethanol preparation system 6 connected to the diethyl terephthalate refining system 4 respectively, wherein, as shown in Fig. 1, the polyester alcoholysis system 1 comprises a depolymerization reactor 1-1; the solid filtering system 2 comprises in sequence in the feeding direction a centrifuge 2-1 and a filter 2-2; the solvent recovery system 3 comprises an ethanol recovery column 3-1; the diethyl terephthalate refining system 4 comprises in sequence in the feeding direction a diethyl terephthalate distillation column 4-1 and a diethyl terephthalate crystallizer 4-2; the terephthalic acid bishydroxyethyl ester preparation system 5 comprises in sequence in the feeding direction an ester exchange reactor 5-1, a terephthalic acid bishydroxyethyl ester crystallizer 5-2 and an ethylene glycol recovery column 5-3; the 1,4-cyclohexane dimethanol preparation system 6 comprises in sequence in the feeding direction a benzene ring hydrogenation reactor 6-1, a diethyl 1,4-cyclohexane dicarboxylate gas-liquid separator 6-2, an ester group hydrogenation reactor 6-3 and a 1,4-cyclohexane dimethanol gas-liquid separator 6-4.

[0091] Polyester enters the depolymerization reactor 1-1, and an electric agitator is also arranged in the depolymerization reactor 1-1 to obtain a depolymerization solution. The depolymerization solution continues to enter the centrifuge 2-1 to obtain a depolymerization centrifugal liquid, which continues to enter the filter 2-2 to obtain a depolymerization filtered liquid, which continues to enter the ethanol recovery column 3-1 to obtain crude diethyl terephthalate. The crude diethyl terephthalate continues to enter the diethyl terephthalate distillation column 4-1 to obtain distilled diethyl terephthalate, which continues to enter the diethyl terephthalate crystallizer 4-2 to obtain diethyl terephthalate crystals.

[0092] Part of the diethyl terephthalate crystals enter the ester exchange reactor 5-1 to obtain crude terephthalic acid bishydroxyethyl ester, which continues to enter the terephthalic acid bishydroxyethyl ester crystallizer 5-2 to obtain terephthalic acid bishydroxyethyl ester crystals, and the filtrate after crystallization continues to enter the ethylene glycol recovery column 5-3.

[0093] Another part of the diethyl terephthalate crystals enters the benzene ring hydrogenation reactor 6-1 to obtain crude diethyl 1,4-cyclohexanedicarboxylate, and the crude diethyl 1,4-cyclohexanedicarboxylate continues to enter the diethyl 1,4-cyclohexanedicarboxylate gas-liquid separator 6-2 to obtain refined diethyl 1,4-cyclohexanedicarboxylate. The refined diethyl 1,4-cyclohexanedicarboxylate continues to enter the ester group hydrogenation reactor 6-3 to obtain crude 1,4-cyclohexanedimethanol, and the crude 1,4-cyclohexanedimethanol continues to enter the 1,4-cyclohexanedimethanol gas-liquid separator 6-4 to obtain refined 1,4-cyclohexanedimethanol. Example 2

[0094] A method for recovering polyester to co-produce bis-hydroxyethyl terephthalate and 1,4-cyclohexanedimethanol, comprising the following steps:

[0095] Step 1: polyester alcoholysis: taking polyester 10 kg, anhydrous ethanol 50 kg and depolymerization catalyst zinc acetate 0.3 kg in the depolymerization reactor 1-1 to carry out depolymerization reaction to obtain a depolymerization solution, the temperature of the depolymerization reactor 1-1 is 170°C, the pressure is 1.5 MPa, the depolymerization reaction time is 1 h, and the depolymerization rate of the polyester is 95%.

[0096] Step 2: solid filtration: taking the depolymerization solution obtained in step 1 to carry out centrifugal treatment in the centrifuge 2-1 to obtain a depolymerization centrifugal liquid, and the depolymerization centrifugal liquid is filtered in the filter 2-2 to obtain a depolymerization filtrate.

[0097] Step 3: solvent recovery: taking the depolymerization filtrate obtained in step 2 to carry out anhydrous ethanol recovery treatment in the ethanol recovery tower 3-1 to obtain crude diethyl terephthalate, and the temperature of the ethanol recovery tower 3-1 is 70°C. The recovered anhydrous ethanol returns to the depolymerization reactor 1-1 through a pipeline to continue to participate in the depolymerization reaction as a solvent.

[0098] Step 4: diethyl terephthalate refining: taking the crude diethyl terephthalate obtained in step 3 to carry out rectification treatment in the diethyl terephthalate rectification tower 4-1 to obtain rectified diethyl terephthalate, and the temperature of the diethyl terephthalate rectification tower 4-1 is 180°C and the pressure is 1 MPa. Then, taking 5 kg of the rectified diethyl terephthalate and 4 kg of anhydrous ethanol in the diethyl terephthalate crystallizer 4-2 to carry out crystallization treatment at a temperature of 0°C to obtain diethyl terephthalate crystals with a purity of 99.9%.

[0099] Step 5: Preparation of bis-hydroxyethyl terephthalate: The crude bis-hydroxyethyl terephthalate obtained in step 4 was taken and subjected to crystallization in a bis-hydroxyethyl terephthalate crystallizer 5-2 along with ethylene glycol 0.5 kg at a temperature of 15°C to obtain bis-hydroxyethyl terephthalate crystals with a yield of 89%. The filtrate obtained after the crystallization was subjected to ethylene glycol recovery in an ethylene glycol recovery column 5-3 at a temperature of 90°C. The recovered ethylene glycol was returned to the transesterification reactor 5-1 through a pipe to continue as a solvent in the transesterification reaction.

[0100] Step 5: Preparation of bis-hydroxyethyl terephthalate: The crude bis-hydroxyethyl terephthalate obtained in step 4 was taken and subjected to crystallization in a bis-hydroxyethyl terephthalate crystallizer 5-2 along with ethylene glycol 0.5 kg at a temperature of 15°C to obtain bis-hydroxyethyl terephthalate crystals with a yield of 89%. The filtrate obtained after the crystallization was subjected to ethylene glycol recovery in an ethylene glycol recovery column 5-3 at a temperature of 90°C. The recovered ethylene glycol was returned to the transesterification reactor 5-1 through a pipe to continue as a solvent in the transesterification reaction.

[0101] Step 6: Preparation of 1,4-cyclohexanedimethanol: The crude 1,4-cyclohexanedimethanol obtained in step 4 was taken and subjected to hydrogen recovery in a 1,4-cyclohexanedimethanol gas-liquid separator 6-4 at a temperature of 300°C and a pressure of 5 MPa to obtain purified 1,4-cyclohexanedimethanol with a yield of 92%. The recovered hydrogen was returned to the ester group hydrogenation reactor 6-3 through a pipe to continue in the ester group hydrogenation reaction.

[0102] Step 6: Preparation of 1,4-cyclohexanedimethanol: The crude 1,4-cyclohexanedimethanol obtained in step 4 was taken and subjected to hydrogen recovery in a 1,4-cyclohexanedimethanol gas-liquid separator 6-4 at a temperature of 300°C and a pressure of 5 MPa to obtain purified 1,4-cyclohexanedimethanol with a yield of 92%. The recovered hydrogen was returned to the ester group hydrogenation reactor 6-3 through a pipe to continue in the ester group hydrogenation reaction. Example 3

[0103] A method for recovering polyester co-producing bis-hydroxyethyl terephthalate and 1,4-cyclohexanedimethanol, comprising the steps of:

[0104] Step 1: Polyesters alcoholysis: Take the polyester 10 kg, anhydrous ethanol 60 kg and depolymerization catalyst zinc acetate 0.2 kg in the depolymerization reactor 1-1 to carry out the depolymerization reaction, and obtain the depolymerization solution, the temperature of the depolymerization reactor 1-1 is 200 ℃, the pressure is 1.6 MPa, the time of the depolymerization reaction is 2 h, and the depolymerization rate of the polyester is 96%.

[0105] Step 2: Solid filtration: Take the depolymerization solution obtained in step 1 to carry out centrifugal treatment in the centrifuge 2-1, and obtain the depolymerization centrifugal liquid, which is filtered in the filter 2-2 to obtain the depolymerization filtrate.

[0106] Step 3: Solvent recovery: Take the depolymerization filtrate obtained in step 2 to carry out anhydrous ethanol recovery treatment in the ethanol recovery tower 3-1, and obtain crude diethyl terephthalate, the temperature of the ethanol recovery tower 3-1 is 90 ℃, and the recovered anhydrous ethanol returns to the depolymerization reactor 1-1 through the pipeline to continue to participate in the depolymerization reaction as the solvent.

[0107] Step 4: Diethyl terephthalate refining: Take the crude diethyl terephthalate obtained in step 3 to carry out distillation treatment in the diethyl terephthalate distillation tower 4-1, and obtain distilled diethyl terephthalate, the temperature of the diethyl terephthalate distillation tower 4-1 is 200 ℃, and the pressure is 3 MPa, then take 5 kg of the distilled diethyl terephthalate and 2.5 kg of anhydrous ethanol to carry out crystallization treatment in the diethyl terephthalate crystallizer 4-2, and obtain diethyl terephthalate crystals with a purity of 99.9% at a crystallization temperature of 4 ℃.

[0108] Step 5: Preparation of bis-hydroxyethyl terephthalate: Take 1 kg of the diethyl terephthalate crystals obtained in step 4, 3 kg of ethylene glycol and 35 g of ester exchange catalyst alumina in the ester exchange reactor 5-1 to carry out ester exchange reaction, and obtain crude bis-hydroxyethyl terephthalate, the initial temperature of the ester exchange reactor 5-1 is 190 ℃, the initial reaction time is 3 h, then the ester exchange reactor 5-1 is heated to 240 ℃, and the reaction continues for 2 h, and the pressure of the ester exchange reactor 5-1 is 0.002 MPa.

[0109] Then take 0.5 kg of the crude bis-hydroxyethyl terephthalate and 1 kg of ethylene glycol to carry out crystallization treatment in the bis-hydroxyethyl terephthalate crystallizer 5-2, and obtain bis-hydroxyethyl terephthalate crystals with a yield of 91% at a crystallization temperature of 10 ℃, and the filtrate after crystallization is treated by recovering ethylene glycol in the ethylene glycol recovery tower 5-3, the temperature of the ethylene glycol recovery tower 5-3 is 100 ℃, and the recovered ethylene glycol returns to the ester exchange reactor 5-1 through the pipeline to continue to participate in the ester exchange reaction as the solvent.

[0110] Step 6: 1,4-Cyclohexanedimethanol preparation: The diethyl terephthalate crystals obtained in step 4, hydrogen and benzene ring hydrogenation catalyst Pd / Al2O3 3 g were taken in benzene ring hydrogenation reactor 6-1 to carry out benzene ring hydrogenation reaction to obtain crude diethyl 1,4-cyclohexanedimethylate, the temperature of the benzene ring hydrogenation reactor 6-1 was 150°C, and the pressure was 3 MPa. Then the crude diethyl 1,4-cyclohexanedimethylate was taken to 1,4-cyclohexanedimethylate gas-liquid separator 6-2 to carry out hydrogen recovery treatment to obtain refined diethyl 1,4-cyclohexanedimethylate, the temperature of the 1,4-cyclohexanedimethylate gas-liquid separator 6-2 was 350°C, and the pressure was 5 MPa, and the recovered hydrogen was returned to the benzene ring hydrogenation reactor 6-1 through a pipeline to continue to participate in the benzene ring hydrogenation reaction.

[0111] The refined diethyl 1,4-cyclohexanedimethylate 0.5 kg, hydrogen and ester group hydrogenation catalyst copper chromium aluminum 1 g were taken in ester group hydrogenation reactor 6-3 to carry out ester group hydrogenation reaction to obtain crude 1,4-cyclohexanedimethanol, the temperature of the ester group hydrogenation reactor 6-3 was 230°C, and the pressure was 10 MPa. Then the crude 1,4-cyclohexanedimethanol was taken to 1,4-cyclohexanedimethyl alcohol gas-liquid separator 6-4 to carry out hydrogen recovery treatment to obtain refined 1,4-cyclohexanedimethyl alcohol with a yield of 94%, the temperature of the 1,4-cyclohexanedimethyl alcohol gas-liquid separator 6-4 was 300°C, and the pressure was 1 MPa, and the recovered hydrogen was returned to the ester group hydrogenation reactor 6-3 through a pipeline to continue to participate in the ester group hydrogenation reaction. Example 4

[0112] A method for recovering polyester to co-produce bis-hydroxyethyl terephthalate and 1,4-cyclohexanedimethanol, comprising the following steps:

[0113] Step 1: Polyester alcoholysis: The polyester 10 kg, anhydrous ethanol 80 kg and depolymerization catalyst manganese acetate 0.5 kg were taken in depolymerization reactor 1-1 to carry out depolymerization reaction to obtain a depolymerization solution, the temperature of the depolymerization reactor 1-1 was 230°C, the pressure was 1.8 MPa, the time of the depolymerization reaction was 3 h, and the depolymerization rate of the polyester was 99%.

[0114] Step 2: Solid filtration: The depolymerization solution obtained in step 1 was taken in centrifuge 2-1 to carry out centrifugal treatment to obtain a depolymerization centrifugal liquid, and the depolymerization centrifugal liquid was taken in filter 2-2 to carry out filtration treatment to obtain a depolymerization filtrate.

[0115] Step 3: Solvent recovery: The depolymerization filtrate obtained in step 2 was taken in ethanol recovery tower 3-1 to carry out ethanol recovery treatment to obtain crude diethyl terephthalate, the temperature of the ethanol recovery tower 3-1 was 100°C, and the recovered anhydrous ethanol was returned to the depolymerization reactor 1-1 through a pipeline to continue to participate in the depolymerization reaction as a solvent.

[0116] Step 4: Purification of diethyl terephthalate: The crude diethyl terephthalate obtained in Step 3 was first subjected to purification in a diethyl terephthalate distillation column 4-1 at a temperature of 160°C and a pressure of 5 MPa to obtain purified diethyl terephthalate. Then, 5 kg of the purified diethyl terephthalate and 5 kg of anhydrous ethanol were subjected to crystallization in a diethyl terephthalate crystallizer 4-2 at a temperature of 5°C to obtain diethyl terephthalate crystals having a purity of 99.9%.

[0117] Step 5: Preparation of bis-hydroxyethyl terephthalate: 1 kg of the diethyl terephthalate crystals obtained in Step 4, 5 kg of ethylene glycol, and 50 g of an ester exchange catalyst titanium dioxide were subjected to ester exchange reaction in an ester exchange reactor 5-1 at an initial temperature of 170°C for 3 h, and then the ester exchange reactor 5-1 was heated to 180°C for an additional 1 h at a pressure of 0.006 MPa to obtain crude bis-hydroxyethyl terephthalate.

[0118] Then, 0.5 kg of the crude bis-hydroxyethyl terephthalate and 1.5 kg of ethylene glycol were subjected to crystallization in a bis-hydroxyethyl terephthalate crystallizer 5-2 at a temperature of 20°C to obtain bis-hydroxyethyl terephthalate crystals at a yield of 90%. The filtrate after the crystallization was subjected to ethylene glycol recovery in an ethylene glycol recovery column 5-3 at a temperature of 110°C, and the recovered ethylene glycol was returned to the ester exchange reactor 5-1 through a pipe to participate in the ester exchange reaction as a solvent.

[0119] Step 6: Preparation of 1,4-cyclohexanedimethanol: 1 kg of the diethyl terephthalate crystals obtained in Step 4, hydrogen gas, and a benzene ring hydrogenation catalyst Pd / C 5 g were subjected to benzene ring hydrogenation reaction in a benzene ring hydrogenation reactor 6-1 at a temperature of 180°C and a pressure of 6 MPa to obtain crude 1,4-cyclohexanedimethanol diethyl ester. Then, the crude 1,4-cyclohexanedimethanol diethyl ester was subjected to hydrogen recovery in a 1,4-cyclohexanedimethanol diethyl ester gas-liquid separator 6-2 at a temperature of 300°C and a pressure of 3 MPa to obtain purified 1,4-cyclohexanedimethanol diethyl ester. The recovered hydrogen gas was returned to the benzene ring hydrogenation reactor 6-1 through a pipe to participate in the benzene ring hydrogenation reaction.

[0120] The refined 1,4-cyclohexane dimethyl ester 0.5 kg, hydrogen and ester group hydrogenation catalyst copper chromium aluminum 2.5 g are taken in the ester group hydrogenation reactor 6-3 to carry out ester group hydrogenation reaction, to obtain crude 1,4-cyclohexane dimethyl alcohol, the temperature of the ester group hydrogenation reactor 6-3 is 180 DEG C, and the pressure is 12 MPa. Then the crude 1,4-cyclohexane dimethyl alcohol is taken in the 1,4-cyclohexane dimethyl alcohol gas-liquid separator 6-4 to carry out hydrogen recovery treatment, to obtain refined 1,4-cyclohexane dimethyl alcohol with a yield of 95%, the temperature of the 1,4-cyclohexane dimethyl alcohol gas-liquid separator 6-4 is 350 DEG C, and the pressure is 2 MPa, and the recovered hydrogen is returned to the ester group hydrogenation reactor 6-3 through a pipeline to continue to participate in the ester group hydrogenation reaction. Industrial applicability

[0121] The present application unexpectedly optimizes the process route of polyester recovery co-production of bis-hydroxyethyl terephthalate and 1,4-cyclohexane dimethyl alcohol by adopting an unexpected recovery system and method, first degrading polyester into intermediate product diethyl terephthalate, then preparing bis-hydroxyethyl terephthalate and 1,4-cyclohexane dimethyl alcohol from the diethyl terephthalate, so that two degradation products can be obtained at the same time, especially solving the problem of high cost of 1,4-cyclohexane dimethyl alcohol preparation at present, thus the present application unexpectedly optimizes the process route of polyester recovery co-production of bis-hydroxyethyl terephthalate and 1,4-cyclohexane dimethyl alcohol, reduces the cost of polyester recovery, and makes it more suitable for industrial application.

Claims

1. A system for the recovery of a polyester co-producing terephthalic acid bis-hydroxyethylester and 1,4-cyclohexane dimethanol, characterized in that, The system sequentially comprises, in the feeding direction: a polyester alcoholysis system (1), a solid filtering system (2), a solvent recovery system (3), a diethyl terephthalate refining system (4), and a bis-hydroxyethyl terephthalate preparation system (5) and a 1,4-cyclohexane dimethanol preparation system (6) connected to the diethyl terephthalate refining system (4) respectively, wherein, The polyester alcoholysis system (1) comprises: a depolymerization reactor (1-1); The solid filtering system (2) sequentially comprises, in the feeding direction: a centrifuge (2-1), a filter (2-2); The solvent recovery system (3) comprises: an ethanol recovery tower (3-1); The diethyl terephthalate refining system (4) sequentially comprises, in the feeding direction: a diethyl terephthalate rectifying tower (4-1), a diethyl terephthalate crystallizer (4-2); The bis-hydroxyethyl terephthalate preparation system (5) sequentially comprises, in the feeding direction: an ester exchange reactor (5-1), a bis-hydroxyethyl terephthalate crystallizer (5-2), an ethylene glycol recovery tower (5-3); The 1,4-cyclohexane dimethanol preparation system (6) sequentially comprises, in the feeding direction: a benzene ring hydrogenation reactor (6-1), a diethyl 1,4-cyclohexane dicarboxylate gas-liquid separator (6-2), an ester group hydrogenation reactor (6-3), a 1,4-cyclohexane dimethanol gas-liquid separator (6-4).

2. The system of claim 1, wherein, The depolymerization reactor (1-1) is used for making the polyester undergo a depolymerization reaction to obtain a depolymerization solution, which continues to enter the centrifuge (2-1).

3. The system of claim 2, wherein, The centrifuge (2-1) is used for centrifuging the depolymerization solution to obtain a depolymerization centrifugal liquid, which continues to enter the filter (2-2); The filter (2-2) is used for filtering the depolymerization centrifugal liquid to obtain a depolymerization filtered liquid, which continues to enter the ethanol recovery tower (3-1); The ethanol recovery tower (3-1) is used for recovering ethanol in the depolymerization filtered liquid to obtain crude diethyl terephthalate, which continues to enter the diethyl terephthalate rectifying tower (4-1).

4. The system of claim 3, wherein, The diethyl terephthalate rectifying tower (4-1) is used for rectifying the crude diethyl terephthalate to obtain rectified diethyl terephthalate, which continues to enter the diethyl terephthalate crystallizer (4-2); The diethyl terephthalate crystallizer (4-2) is used for crystallizing the rectified diethyl terephthalate to obtain diethyl terephthalate crystals, which continue to enter the ester exchange reactor (5-1) or the benzene ring hydrogenation reactor (6-1).

5. The system of claim 4, wherein, The ester exchange reactor (5-1) is used for making the diethyl terephthalate crystals undergo an ester exchange reaction to obtain crude bis-hydroxyethyl terephthalate, which continues to enter the bis-hydroxyethyl terephthalate crystallizer (5-2); The terephthalic acid bishydroxyethyl ester crystallizer (5-2) is used for crystallizing the crude terephthalic acid bishydroxyethyl ester to obtain terephthalic acid bishydroxyethyl ester crystals, and the filtrate after the crystallization treatment continues to enter the ethylene glycol recovery tower (5-3).

6. The system of claim 4, wherein, The benzene ring hydrogenation reactor (6-1) is used for subjecting the terephthalic acid diethyl ester crystals to benzene ring hydrogenation reaction to obtain crude 1,4-cyclohexane dicarboxylic acid diethyl ester, and the crude 1,4-cyclohexane dicarboxylic acid diethyl ester continues to enter the 1,4-cyclohexane dicarboxylic acid diethyl ester gas-liquid separator (6-2).

7. The system of claim 6, wherein, The 1,4-cyclohexane dicarboxylic acid diethyl ester gas-liquid separator (6-2) is used for recovering hydrogen in the crude 1,4-cyclohexane dicarboxylic acid diethyl ester to obtain refined 1,4-cyclohexane dicarboxylic acid diethyl ester, and the refined 1,4-cyclohexane dicarboxylic acid diethyl ester continues to enter the ester group hydrogenation reactor (6-3).

8. The system of claim 7, wherein, The ester group hydrogenation reactor (6-3) is used for subjecting the refined 1,4-cyclohexane dicarboxylic acid diethyl ester to ester group hydrogenation reaction to obtain crude 1,4-cyclohexane dimethanol, and the crude 1,4-cyclohexane dimethanol continues to enter the 1,4-cyclohexane dimethanol gas-liquid separator (6-4).

9. The system of claim 8, wherein, The 1,4-cyclohexane dimethanol gas-liquid separator (6-4) is used for recovering hydrogen in the crude 1,4-cyclohexane dimethanol to obtain refined 1,4-cyclohexane dimethanol.

10. A process for the recovery of polyester co-producing bis-hydroxyethyleter terephthalate and 1,4-cyclohexane dimethanol using the system according to any one of claims 1 to 9, characterized in that, The method comprises a polyester alcoholysis method, a solid filtration method, a solvent recovery method, a terephthalic acid diethyl ester refining method, a terephthalic acid bishydroxyethyl ester preparation method, and a 1,4-cyclohexane dimethanol preparation method.

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