System and method for preparing 1,4-cyclohexanedimethanol from recycled polyester

Abstract

The present invention relates to the field of organic synthesis, and in particular to a system and method for preparing 1,4-cyclohexanedimethanol from recycled polyester. The system sequentially comprises, in a feed direction, a polyester alcoholysis system, an alcoholysis solution impurity removal system, a solvent recovery system, a diethyl terephthalate purification system, and a 1,4-cyclohexanedimethanol preparation system. In the present invention, by optimizing the process route for preparing 1,4-cyclohexanedimethanol from recycled polyester, the polyester is first degraded to an intermediate product diethyl terephthalate, and then 1,4-cyclohexanedimethanol is prepared from the diethyl terephthalate. In this way, the problem of waste polyester recycling is solved, and 1,4-cyclohexanedimethanol having high economic value is prepared at a low cost, and the problems of high preparation cost and high preparation difficulty of 1,4-cyclohexanedimethanol are solved, so that the present invention is more suitable for industrial application.

Description

System and method for preparing 1,4-cyclohexanedimethanol by recycling polyester TECHNICAL FIELD

[0001] The present application relates to the field of organic synthesis, and particularly relates to a system and method for preparing 1,4-cyclohexanedimethanol by recycling polyester. BACKGROUND

[0002] Polyester is one of the most commonly used polymers at present, and 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 strong chemical inertness, which causes great pressure on the protection of the ecological environment, and therefore there are many related researches on the degradation of waste polyester materials at home and abroad. However, the intermediate product diethyl terephthalate obtained by alcoholysis of waste polyester materials has no direct application in the market, so that the existing various recycling methods cannot meet the industrial application.

[0003] CN103687834A discloses a method for preparing 1,4-cyclohexanedimethanol by ester exchange and two-step hydrogenation of terephthalic acid. Terephthalic acid is first ester-exchanged with methanol to generate dimethyl terephthalate, a one-stage hydrogenation reaction is carried out to generate 1,4-cyclohexanedicarboxylic acid dimethyl ester by reacting dimethyl terephthalate with hydrogen under the action of a Pd-based catalyst, and a two-stage hydrogenation reaction is carried out to generate 1,4-cyclohexanedimethanol by reacting 1,4-cyclohexanedicarboxylic acid dimethyl ester with hydrogen under the action of a Cu-based catalyst. The methanol generated in the reaction process is recycled to the ester exchange reaction. The two-stage hydrogenation reaction adopts high-pressure operation, the absolute pressure is 10-40 MPa, the temperature is 180-300 DEG C, and the liquid space velocity is 0.5-5 / h. In addition, the by-products such as terephthalic acid monomethyl ester of the one-stage hydrogenation have an influence on the activity of the Cu-based catalyst, and therefore the preparation method has problems of high raw material cost and harsh operation conditions. TECHNICAL PROBLEM

[0004] Therefore, how to reduce the preparation cost and difficulty of 1,4-cyclohexanedimethanol is a technical problem to be solved. TECHNICAL SOLUTION

[0005] To solve the above technical problems, the present application provides a polyester recycling system and method for preparing 1,4-cyclohexanedimethanol, which can solve the problems of high cost and great difficulty in preparing 1,4-cyclohexanedimethanol by optimizing the process route of polyester recycling for preparing 1,4-cyclohexanedimethanol.

[0006] The present application provides a polyester recycling system for preparing 1,4-cyclohexanedimethanol, which comprises, in sequence in the feeding direction: a polyester alcoholysis system, an alcoholysis solution impurity removal system, a solvent recovery system, a diethyl terephthalate refining system, and a 1,4-cyclohexanedimethanol preparation system, wherein,

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

[0008] The alcoholysis solution impurity removal system comprises, in sequence in the feeding direction: a centrifuge, a plate-and-frame filter.

[0009] The solvent recovery system comprises, in sequence in the feeding direction: a flash tank, a falling film evaporator.

[0010] The diethyl terephthalate refining system comprises, in sequence in the feeding direction: a diethyl terephthalate rectification tower, a diethyl terephthalate ion adsorption column, and a diethyl terephthalate crystallizer.

[0011] The 1,4-cyclohexanedimethanol preparation system comprises, in sequence in the feeding direction: a benzene ring hydrogenation reactor, a 1,4-cyclohexanedicarboxylic acid diethyl ester gas-liquid separator, an ester group hydrogenation reactor, and a 1,4-cyclohexanedimethanol gas-liquid separator.

[0012] Further, the depolymerization reactor is used for subjecting the polyester to a depolymerization reaction to obtain a depolymerization solution, which continues to enter the centrifuge.

[0013] Further, the depolymerization reactor is further provided with an electric agitator, which is used for stirring the material.

[0014] Further, the centrifuge is used for centrifuging the depolymerization solution to obtain a depolymerization centrifuged solution, which continues to enter the plate-and-frame filter.

[0015] Further, the plate-and-frame filter is used for filtering the depolymerization centrifuged solution to obtain a depolymerization filtered solution, which continues to enter the flash tank.

[0016] Further, the flash tank is used for recovering ethanol in the depolymerization filtered solution to obtain primary evaporation diethyl terephthalate, which continues to enter the falling film evaporator.

[0017] Further, the falling film evaporator is used for recovering ethanol in the primary evaporated diethyl terephthalate to obtain secondary evaporated diethyl terephthalate, which continues to enter the diethyl terephthalate rectification tower.

[0018] Further, the diethyl terephthalate rectification tower is used for rectifying the secondary evaporated diethyl terephthalate to obtain rectified diethyl terephthalate, which continues to enter the diethyl terephthalate ion adsorption column.

[0019] Further, the diethyl terephthalate ion adsorption column is used for adsorbing and removing metal ions in the rectified diethyl terephthalate to obtain impurity-removed diethyl terephthalate, which continues to enter the diethyl terephthalate crystallizer.

[0020] Further, the diethyl terephthalate crystallizer is used for crystallizing the impurity-removed diethyl terephthalate to obtain diethyl terephthalate crystals, which continue to enter the benzene ring hydrogenation reactor.

[0021] Further, the benzene ring hydrogenation reactor is used for subjecting the diethyl terephthalate crystals to benzene ring hydrogenation reaction to obtain crude diethyl 1,4-cyclohexanedicarboxylate, which continues to enter the diethyl 1,4-cyclohexanedicarboxylate gas-liquid separator.

[0022] Further, the diethyl 1,4-cyclohexanedicarboxylate gas-liquid separator is used for recovering hydrogen in the crude diethyl 1,4-cyclohexanedicarboxylate to obtain refined diethyl 1,4-cyclohexanedicarboxylate, which continues to enter the ester group hydrogenation reactor.

[0023] Further, the ester group hydrogenation reactor is used for subjecting the refined diethyl 1,4-cyclohexanedicarboxylate to ester group hydrogenation reaction to obtain crude 1,4-cyclohexanedimethanol, which continues to enter the 1,4-cyclohexanedimethanol gas-liquid separator.

[0024] Further, the 1,4-cyclohexanedimethanol gas-liquid separator is used for recovering hydrogen in the crude 1,4-cyclohexanedimethanol to obtain refined 1,4-cyclohexanedimethanol.

[0025] The present application provides a method for preparing 1,4-cyclohexanedimethanol by recycling polyester, which comprises a polyester alcoholysis method, an impurity removal method for alcoholysis liquid, a solvent recovery method, a diethyl terephthalate refining method, and a 1,4-cyclohexanedimethanol preparation method.

[0026] Further, in the polyester alcoholysis method, comprising the following steps:

[0027] Step 1.1: the polyester, anhydrous ethanol and depolymerization catalyst are subjected to the depolymerization reaction in the depolymerization reactor to obtain the depolymerization solution.

[0028] Further, in the alcoholysis solution impurity removal method, comprising the following steps in sequence:

[0029] Step 2.1: the depolymerization solution is subjected to centrifugal treatment in the centrifuge to obtain the depolymerization centrifugal solution;

[0030] Step 2.2: the depolymerization centrifugal solution is subjected to filtration treatment in the plate-and-frame filter to obtain the depolymerization filtrate.

[0031] Further, in the solvent recovery method, comprising the following steps in sequence:

[0032] Step 3.1: the depolymerization filtrate is subjected to recovered ethanol treatment in the flash tank to obtain the primary evaporated diethyl terephthalate, and the recovered ethanol is returned to the depolymerization reactor through a pipeline;

[0033] Step 3.2: the primary evaporated diethyl terephthalate is subjected to recovered ethanol treatment in the falling-film evaporator to obtain the secondary evaporated diethyl terephthalate, and the recovered ethanol is returned to the depolymerization reactor through a pipeline.

[0034] Further, in the diethyl terephthalate refining method, comprising the following steps in sequence:

[0035] Step 4.1: the secondary evaporated diethyl terephthalate is subjected to rectification treatment in the diethyl terephthalate rectification column to obtain the rectified diethyl terephthalate;

[0036] Step 4.2: the rectified diethyl terephthalate is subjected to adsorption and metal ion removal treatment in the diethyl terephthalate ion adsorption column to obtain the impurity-removed diethyl terephthalate;

[0037] Step 4.3: the impurity-removed diethyl terephthalate is subjected to crystallization treatment in the diethyl terephthalate crystallizer to obtain the diethyl terephthalate crystal.

[0038] Further, in the 1,4-cyclohexanedimethanol preparation method, comprising the following steps in sequence:

[0039] Step 5.1: the benzene ring hydrogenation reaction is performed on the benzene ring hydrogenation catalyst, the diethyl terephthalate crystals, hydrogen gas and benzene in the benzene ring hydrogenation reactor, to obtain the crude diethyl 1,4-cyclohexanedicarboxylate;

[0040] Step 5.2: the crude diethyl 1,4-cyclohexanedicarboxylate is subjected to the recovered hydrogen treatment in the diethyl 1,4-cyclohexanedicarboxylate gas-liquid separator, to obtain the refined diethyl 1,4-cyclohexanedicarboxylate, and the recovered hydrogen gas is returned to the benzene ring hydrogenation reactor through a pipeline;

[0041] Step 5.3: the ester group hydrogenation reaction is performed on the ester group hydrogenation catalyst, the refined diethyl 1,4-cyclohexanedicarboxylate, hydrogen gas and benzene in the ester group hydrogenation reactor, to obtain the crude 1,4-cyclohexanediol;

[0042] Step 5.4: the crude 1,4-cyclohexanediol is subjected to the recovered hydrogen treatment in the 1,4-cyclohexanediol gas-liquid separator, to obtain the refined 1,4-cyclohexanediol, and the recovered hydrogen gas is returned to the ester group hydrogenation reactor through a pipeline.

[0043] Further, in the step 1.1, the polyester is one or a mixture of both of polyethylene terephthalate and polyethylene terephthalate-1,4-cyclohexanediol.

[0044] Further, in the step 1.1, the mass ratio of the polyester to the anhydrous ethanol is 1: (6-10).

[0045] 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.

[0046] Further, in the step 1.1, the temperature of the depolymerization reactor is 190-250°C, and the time of the depolymerization reaction is 1-3h.

[0047] Further, in the step 1.1, the pressure of the depolymerization reactor is 2-2.5MPa.

[0048] Further, in the step 1.1, the depolymerization rate of the polyester is 96-99%.

[0049] Further, in the step 3.1, the temperature of the flash tank is 90-120°C.

[0050] Further, in the step 3.1, the pressure of the flash tank is 1-4MPa.

[0051] Further, in the step 3.2, the temperature of the falling film evaporator is 120-150℃.

[0052] Further, in the step 3.2, the pressure of the falling film evaporator is 2-6 MPa.

[0053] Further, in the step 4.1, the temperature of the diethyl terephthalate rectification tower is 180-210℃.

[0054] Further, in the step 4.1, the pressure of the diethyl terephthalate rectification tower is 1-5 MPa.

[0055] Further, in the step 4.3, the impure diethyl terephthalate is subjected to a crystallization treatment using anhydrous ethanol, and the mass ratio of the impure diethyl terephthalate to the anhydrous ethanol is 1: (1-2).

[0056] Further, in the step 4.3, the temperature of the crystallization treatment is 0-10℃.

[0057] Further, in the step 4.3, the purity of the diethyl terephthalate crystal is 99.9%.

[0058] Further, in the step 5.1, the amount of the hydrogen gas is used to maintain the pressure of the benzene ring hydrogenation reactor at 3-6 MPa.

[0059] Further, in the step 5.1, 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 0.5-1% of the mass of the diethyl terephthalate crystal, based on the mass of the diethyl terephthalate crystal.

[0060] Further, in the step 5.1, the temperature of the benzene ring hydrogenation reactor is 140-200℃.

[0061] Further, in the step 5.2, the temperature of the 1,4-cyclohexane dicarboxylic acid diethyl ester gas-liquid separator is 300-350℃.

[0062] Further, in the step 5.2, the pressure of the 1,4-cyclohexane dicarboxylic acid diethyl ester gas-liquid separator is 1-5 MPa.

[0063] Further, in the step 5.3, the amount of the hydrogen gas is used to maintain the pressure of the ester group hydrogenation reactor at 8-12 MPa.

[0064] Further, in the step 5.3, the ester group hydrogenation catalyst is copper chromium aluminum catalyst, and the amount of the ester group hydrogenation catalyst is 0.2-1% of the mass of the refined 1,4-cyclohexanedicarboxylic acid diethyl ester.

[0065] Further, in the step 5.3, the temperature of the ester group hydrogenation reactor is 200-250℃.

[0066] Further, in the step 5.4, the temperature of the 1,4-cyclohexanediol gas-liquid separator is 300-350℃.

[0067] Further, in the step 5.4, the pressure of the 1,4-cyclohexanediol gas-liquid separator is 1-5MPa.

[0068] Further, in the step 5.4, the yield of the refined 1,4-cyclohexanediol is 94-98%. Beneficial effects

[0069] 1、The prior art generally adopts a method of preparing 1,4-cyclohexanediol by ester exchange and two-step hydrogenation of terephthalic acid, but this method has high preparation cost and harsh operating conditions, so the prior art has poor economy; and the present application unexpectedly optimizes the process route of polyester recovery and preparation of 1,4-cyclohexanediol by using an unexpected preparation system and method, which first degrades the polyester to an intermediate product of diethyl terephthalate, and then prepares 1,4-cyclohexanediol from diethyl terephthalate, so that the problem of waste polyester recovery is solved, and 1,4-cyclohexanediol with high economic value is prepared at a lower cost, so that the present application unexpectedly optimizes the process route of polyester recovery and preparation of 1,4-cyclohexanediol, and can solve the problems of high cost and difficulty in preparation of 1,4-cyclohexanediol, making it more suitable for industrial application.

[0070] 2、The present application recovers waste polyester after degradation, which is beneficial to resource recycling and sustainable development of society.

[0071] 3、The present application reduces waste polyester pollution by degrading waste polyester, which is beneficial to ecological environment protection. BRIEF DESCRIPTION OF DRAWINGS

[0072] Fig. 1 is a system flow chart of the present application for polyester recovery and preparation of 1,4-cyclohexanediol,

[0073] 1-polyester alcoholysis system; 2-alcoholysis solution impurity removal system; 3-solvent recovery system; 4-diethyl terephthalate refining system; 5-1,4-cyclohexane dimethanol preparation system; 1-1-depolymerization reactor; 2-1-centrifuge; 2-2-plate and frame filter; 3-1-flash tank; 3-2-falling film evaporator; 4-1-diethyl terephthalate distillation column; 4-2-diethyl terephthalate ion adsorption column; 4-3-diethyl terephthalate crystallizer; 5-1-benzene ring hydrogenation reactor; 5-2-1,4-cyclohexane dicarboxylic acid diethyl ester gas-liquid separator; 5-3-ester group hydrogenation reactor; 5-4-1,4-cyclohexane dimethanol gas-liquid separator. Best mode of the present application

[0074] A system for preparing 1,4-cyclohexane dimethanol from polyester recovery, the system sequentially comprises, in the feeding direction:

[0075] The polyester alcoholysis system 1, the alcoholysis solution impurity removal system 2, the solvent recovery system 3, the diethyl terephthalate refining system 4 and the 1,4-cyclohexane dimethanol preparation system 5, wherein, as shown in FIG. 1, the polyester alcoholysis system 1 comprises a depolymerization reactor 1-1; the alcoholysis solution impurity removal system 2 sequentially comprises, in the feeding direction, a centrifuge 2-1 and a plate and frame filter 2-2; the solvent recovery system 3 sequentially comprises, in the feeding direction, a flash tank 3-1 and a falling film evaporator 3-2; the diethyl terephthalate refining system 4 sequentially comprises, in the feeding direction, a diethyl terephthalate distillation column 4-1, a diethyl terephthalate ion adsorption column 4-2 and a diethyl terephthalate crystallizer 4-3; and the 1,4-cyclohexane dimethanol preparation system 5 sequentially comprises, in the feeding direction, a benzene ring hydrogenation reactor 5-1, a 1,4-cyclohexane dicarboxylic acid diethyl ester gas-liquid separator 5-2, an ester group hydrogenation reactor 5-3 and a 1,4-cyclohexane dimethanol gas-liquid separator 5-4.

[0076] The polyester enters the depolymerization reactor 1-1, and an electric agitator is further 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 plate and frame filter 2-2 to obtain a depolymerization filtered solution. The depolymerization filtered solution continues to enter the flash tank 3-1 to obtain first evaporated diethyl terephthalate, which continues to enter the falling film evaporator 3-2 to obtain second evaporated diethyl terephthalate. The second evaporated diethyl terephthalate continues to enter the diethyl terephthalate distillation column 4-1 to obtain refined diethyl terephthalate, which continues to enter the diethyl terephthalate ion adsorption column 4-2 to obtain impurity-removed diethyl terephthalate, which continues to enter the diethyl terephthalate crystallizer 4-3 to obtain diethyl terephthalate crystals.

[0077] The terephthalic acid diethyl ester crystals continue to enter the benzene ring hydrogenation reactor 5-1 to obtain crude 1,4-cyclohexane diethyl ester, and the crude 1,4-cyclohexane diethyl ester continues to enter the 1,4-cyclohexane diethyl ester gas-liquid separator 5-2 to obtain refined 1,4-cyclohexane diethyl ester. The refined 1,4-cyclohexane diethyl ester continues to enter the ester group hydrogenation reactor 5-3 to obtain crude 1,4-cyclohexane dimethyl alcohol, and the crude 1,4-cyclohexane dimethyl alcohol continues to enter the 1,4-cyclohexane dimethyl alcohol gas-liquid separator 5-4 to obtain refined 1,4-cyclohexane dimethyl alcohol. Embodiments of the present application

[0078] Example 1

[0079] A system for recycling polyester to prepare 1,4-cyclohexane dimethyl alcohol, the system sequentially comprises, in the feeding direction:

[0080] The polyester alcoholysis system 1, the alcoholysis liquid impurity removal system 2, the solvent recovery system 3, the terephthalic acid diethyl ester refining system 4 and the 1,4-cyclohexane dimethyl alcohol preparation system 5, wherein, as shown in FIG. 1, the polyester alcoholysis system 1 comprises a depolymerization reactor 1-1; the alcoholysis liquid impurity removal system 2 sequentially comprises, in the feeding direction, a centrifuge 2-1 and a plate-and-frame filter 2-2; the solvent recovery system 3 sequentially comprises, in the feeding direction, a flash tank 3-1 and a falling film evaporator 3-2; the terephthalic acid diethyl ester refining system 4 sequentially comprises, in the feeding direction, a terephthalic acid diethyl ester rectification tower 4-1, a terephthalic acid diethyl ester ion adsorption column 4-2 and a terephthalic acid diethyl ester crystallizer 4-3; and the 1,4-cyclohexane dimethyl alcohol preparation system 5 sequentially comprises, in the feeding direction, a benzene ring hydrogenation reactor 5-1, a 1,4-cyclohexane diethyl ester gas-liquid separator 5-2, an ester group hydrogenation reactor 5-3 and a 1,4-cyclohexane dimethyl alcohol gas-liquid separator 5-4.

[0081] The polyester enters the depolymerization reactor 1-1, and at the same time, the depolymerization reactor 1-1 is also provided with an electric agitator 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 plate-and-frame filter 2-2 to obtain a depolymerization filtered liquid. The depolymerization filtered liquid continues to enter the flash tank 3-1 to obtain first evaporated terephthalic acid diethyl ester, which continues to enter the falling film evaporator 3-2 to obtain second evaporated terephthalic acid diethyl ester. The second evaporated terephthalic acid diethyl ester continues to enter the terephthalic acid diethyl ester rectification tower 4-1 to obtain rectified terephthalic acid diethyl ester, which continues to enter the terephthalic acid diethyl ester ion adsorption column 4-2 to obtain impurity-removed terephthalic acid diethyl ester, which continues to enter the terephthalic acid diethyl ester crystallizer 4-3 to obtain terephthalic acid diethyl ester crystals.

[0082] The terephthalic acid diethyl ester crystals continue to enter the benzene ring hydrogenation reactor 5-1 to obtain crude 1,4-cyclohexane diethyl ester, and the crude 1,4-cyclohexane diethyl ester continues to enter the 1,4-cyclohexane diethyl ester gas-liquid separator 5-2 to obtain refined 1,4-cyclohexane diethyl ester. The refined 1,4-cyclohexane diethyl ester continues to enter the ester group hydrogenation reactor 5-3 to obtain crude 1,4-cyclohexane dimethyl alcohol, and the crude 1,4-cyclohexane dimethyl alcohol continues to enter the 1,4-cyclohexane dimethyl alcohol gas-liquid separator 5-4 to obtain refined 1,4-cyclohexane dimethyl alcohol. Embodiment

[0083] A method for recycling polyester to prepare 1,4-cyclohexane dimethyl alcohol, comprising the following steps:

[0084] Step 1: polyester alcoholysis: take 10 kg of polyester, 60 kg of anhydrous ethanol and 200 g of depolymerization catalyst in a depolymerization reactor 1-1 to carry out a depolymerization reaction to obtain a depolymerization solution, the temperature of the depolymerization reactor 1-1 is 190°C, the pressure is 2 MPa, the time of the depolymerization reaction is 3 h, and the depolymerization rate of the polyester is 96%.

[0085] Step 2: solid filtration: take the depolymerization solution obtained in step 1 to carry out centrifugal treatment in a centrifuge 2-1 to obtain a depolymerization centrifugal liquid, and the depolymerization centrifugal liquid is filtered in a plate and frame filter 2-2 to obtain a depolymerization filtrate.

[0086] Step 3: solvent recovery: take the depolymerization filtrate obtained in step 2 to carry out anhydrous ethanol recovery treatment in a flash tank 3-1 to obtain once evaporated terephthalic acid diethyl ester, the temperature of the flash tank 3-1 is 90°C, the pressure is 1 MPa, and 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.

[0087] Take the once evaporated terephthalic acid diethyl ester to carry out anhydrous ethanol recovery treatment in a falling film evaporator 3-2 to obtain twice evaporated terephthalic acid diethyl ester, the temperature of the falling film evaporator 3-2 is 130°C, the pressure is 2 MPa, and 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.

[0088] Step 4: Purification of diethyl terephthalate: The diethyl terephthalate obtained from step 3 is first subjected to purification treatment in a diethyl terephthalate rectification column 4-1, to obtain purified diethyl terephthalate, at a temperature of 200°C and a pressure of 1 MPa. The purified diethyl terephthalate is then subjected to metal ion removal treatment by adsorption in an ion adsorption column, to obtain impurity-removed diethyl terephthalate. Finally, the impurity-removed diethyl terephthalate 5 kg and anhydrous ethanol 5 kg are subjected to crystallization treatment in a diethyl terephthalate crystallizer 4-3, at a temperature of 0°C, to obtain diethyl terephthalate crystals with a purity of 99.9%.

[0089] Step 5: Preparation of 1,4-cyclohexanedimethanol: The diethyl terephthalate crystals obtained from step 4, hydrogen gas, and a benzene ring hydrogenation catalyst Pd / Al2O 3 5 g are subjected to benzene ring hydrogenation reaction in a benzene ring hydrogenation reactor 5-1, to obtain crude diethyl 1,4-cyclohexanediacetate, at a temperature of 170°C and a pressure of 5 MPa. The crude diethyl 1,4-cyclohexanediacetate is then subjected to hydrogen recovery treatment in a diethyl 1,4-cyclohexanediacetate gas-liquid separator 5-2, to obtain purified diethyl 1,4-cyclohexanediacetate, at a temperature of 300°C and a pressure of 1 MPa. The recovered hydrogen gas is returned to the benzene ring hydrogenation reactor 5-1 through a pipeline to continue participating in the benzene ring hydrogenation reaction.

[0090] The purified diethyl 1,4-cyclohexanediacetate 0.5 kg, hydrogen gas, and an ester group hydrogenation catalyst copper chromium aluminum 5 g are subjected to ester group hydrogenation reaction in an ester group hydrogenation reactor 5-3, to obtain crude 1,4-cyclohexanedimethanol, at a temperature of 230°C and a pressure of 8 MPa. The crude 1,4-cyclohexanedimethanol is then subjected to hydrogen recovery treatment in a 1,4-cyclohexanedimethanol gas-liquid separator 5-4, to obtain purified 1,4-cyclohexanedimethanol with a yield of 98%, at a temperature of 300°C and a pressure of 1 MPa. The recovered hydrogen gas is returned to the ester group hydrogenation reactor 5-3 through a pipeline to continue participating in the ester group hydrogenation reaction. Embodiment

[0091] A method for preparing 1,4-cyclohexanedimethanol by recycling polyester, comprising the following steps:

[0092] Step 1: Alcoholysis of polyester: The polyester 10 kg, anhydrous ethanol 80 kg, and a depolymerization catalyst 300 g are subjected to depolymerization reaction in a depolymerization reactor 1-1, to obtain a depolymerization solution, at a temperature of 250°C and a pressure of 2 MPa, for a reaction time of 1 h. The depolymerization rate of the polyester is 99%.

[0093] Step 2: solid filtration: the depolymerization solution obtained in step 1 is subjected to centrifugal treatment in centrifuge 2-1 to obtain a depolymerization centrifugal liquid, and the depolymerization centrifugal liquid is subjected to filtration treatment in plate and frame filter 2-2 to obtain a depolymerization filtrate.

[0094] Step 3: solvent recovery: the depolymerization filtrate obtained in step 2 is subjected to ethanol recovery treatment in flash tank 3-1 to obtain first evaporated diethyl terephthalate, the temperature of flash tank 3-1 is 105°C, and the pressure is 2 MPa, and the recovered anhydrous ethanol is returned to depolymerization reactor 1-1 through a pipeline to continue to participate in the depolymerization reaction as a solvent.

[0095] The first evaporated diethyl terephthalate is subjected to ethanol recovery treatment in falling film evaporator 3-2 to obtain second evaporated diethyl terephthalate, the temperature of falling film evaporator 3-2 is 150°C, and the pressure is 4 MPa, and the recovered anhydrous ethanol is returned to depolymerization reactor 1-1 through a pipeline to continue to participate in the depolymerization reaction as a solvent.

[0096] Step 4: diethyl terephthalate refining: the second evaporated diethyl terephthalate obtained in step 3 is subjected to rectification treatment in diethyl terephthalate rectification column 4-1 to obtain rectified diethyl terephthalate, the temperature of diethyl terephthalate rectification column 4-1 is 180°C, and the pressure is 3 MPa, then the rectified diethyl terephthalate is subjected to metal ion removal treatment by adsorption in an ion adsorption column to obtain impurity-removed diethyl terephthalate, and finally 5 kg of impurity-removed diethyl terephthalate and 8 kg of anhydrous ethanol are subjected to crystallization treatment in a diethyl terephthalate crystallizer 4-3 at a temperature of 5°C to obtain diethyl terephthalate crystals with a purity of 99.9%.

[0097] Step 5: 1,4-cyclohexanedimethanol preparation: 1 kg of diethyl terephthalate crystals, hydrogen gas, and benzene ring hydrogenation catalyst Pd / Al2O 3 5g obtained in step 4 are subjected to benzene ring hydrogenation reaction in benzene ring hydrogenation reactor 5-1 to obtain crude 1,4-cyclohexanedimethanol, the temperature of benzene ring hydrogenation reactor 5-1 is 140°C, and the pressure is 3 MPa. Then the crude 1,4-cyclohexanedimethanol is subjected to hydrogen recovery treatment in 1,4-cyclohexanedimethanol gas-liquid separator 5-2 to obtain refined 1,4-cyclohexanedimethanol, the temperature of 1,4-cyclohexanedimethanol gas-liquid separator 5-2 is 330°C, and the pressure is 3 MPa, and the recovered hydrogen gas is returned to benzene ring hydrogenation reactor 5-1 through a pipeline to continue to participate in the benzene ring hydrogenation reaction.

[0098] Take refined 1,4-cyclohexane dimethyl ester 0.5 kg, hydrogen and ester base hydrogenation catalyst copper chromium aluminum 1 g in ester base hydrogenation reactor 5-3 to carry out ester base hydrogenation reaction, to obtain crude 1,4-cyclohexane dimethyl alcohol, the temperature of ester base hydrogenation reactor 5-3 is 200 DEG C, the pressure is 10 MPa. Then take crude 1,4-cyclohexane dimethyl alcohol in 1,4-cyclohexane dimethyl alcohol gas-liquid separator 5-4 to carry out hydrogen recovery treatment, to obtain refined 1,4-cyclohexane dimethyl alcohol with a yield of 97%, the temperature of 1,4-cyclohexane dimethyl alcohol gas-liquid separator 5-4 is 350 DEG C, the pressure is 3 MPa, and the recovered hydrogen is returned to ester base hydrogenation reactor 5-3 through a pipeline to continue to participate in ester base hydrogenation reaction. Example

[0099] A method for preparing 1,4-cyclohexane dimethyl alcohol by polyester recovery, comprising the following steps:

[0100] Step 1: polyester alcoholysis: take polyester 10 kg, anhydrous ethanol 100 kg and depolymerization catalyst 500 g in depolymerization reactor 1-1 to carry out depolymerization reaction, to obtain a depolymerization solution, the temperature of depolymerization reactor 1-1 is 220 DEG C, the pressure is 2.5 MPa, the time of depolymerization reaction is 2 h, and the depolymerization rate of polyester is 98%.

[0101] Step 2: solid filtration: take the depolymerization solution obtained in step 1 to carry out centrifugal treatment in centrifuge 2-1, to obtain a depolymerization centrifugal liquid, and the depolymerization centrifugal liquid is filtered in plate and frame filter 2-2, to obtain a depolymerization filtrate.

[0102] Step 3: solvent recovery: take the depolymerization filtrate obtained in step 2 to carry out ethanol recovery treatment in flash tank 3-1, to obtain first evaporation terephthalic acid diethyl ester, the temperature of flash tank 3-1 is 120 DEG C, the pressure is 4 MPa, and the recovered anhydrous ethanol is returned to depolymerization reactor 1-1 through a pipeline to continue to participate in depolymerization reaction as a solvent.

[0103] Take the first evaporation terephthalic acid diethyl ester to carry out ethanol recovery treatment in falling film evaporator 3-2, to obtain second evaporation terephthalic acid diethyl ester, the temperature of falling film evaporator 3-2 is 120 DEG C, the pressure is 6 MPa, and the recovered anhydrous ethanol is returned to depolymerization reactor 1-1 through a pipeline to continue to participate in depolymerization reaction as a solvent.

[0104] Step 4: Diethyl terephthalate purification: The diethyl terephthalate obtained from step 3 was first subjected to rectification treatment in a diethyl terephthalate rectification column 4-1 to obtain rectified diethyl terephthalate, the temperature of the diethyl terephthalate rectification column 4-1 was 210°C, and the pressure was 5 MPa. Then, the rectified diethyl terephthalate was subjected to ion adsorption column treatment to remove metal ions to obtain impurity-removed diethyl terephthalate. Finally, 5 kg of the impurity-removed diethyl terephthalate and 10 kg of anhydrous ethanol were subjected to crystallization treatment in a diethyl terephthalate crystallizer 4-3 at a temperature of 10°C to obtain diethyl terephthalate crystals with a purity of 99.9%.

[0105] Step 5: 1,4-Cyclohexanedimethanol preparation: 1 kg of the diethyl terephthalate crystals obtained from step 4, hydrogen gas, and a benzene ring hydrogenation catalyst Ni / Al2O 3 10g were subjected to benzene ring hydrogenation reaction in a benzene ring hydrogenation reactor 5-1 to obtain crude diethyl 1,4-cyclohexanediacetate, the temperature of the benzene ring hydrogenation reactor 5-1 was 200°C, and the pressure was 6 MPa. Then, the crude diethyl 1,4-cyclohexanediacetate was subjected to hydrogen recovery treatment in a diethyl 1,4-cyclohexanediacetate gas-liquid separator 5-2 to obtain refined diethyl 1,4-cyclohexanediacetate, the temperature of the diethyl 1,4-cyclohexanediacetate gas-liquid separator 5-2 was 350°C, and the pressure was 5 MPa, and the recovered hydrogen gas was returned to the benzene ring hydrogenation reactor 5-1 through a pipeline to continue participating in the benzene ring hydrogenation reaction.

[0106] The refined diethyl 1,4-cyclohexanediacetate 0.5 kg, hydrogen gas, and an ester group hydrogenation catalyst copper chromium aluminum 3 g were subjected to ester group hydrogenation reaction in an ester group hydrogenation reactor 5-3 to obtain crude 1,4-cyclohexanedimethanol, the temperature of the ester group hydrogenation reactor 5-3 was 250°C, and the pressure was 12 MPa. Then, the crude 1,4-cyclohexanedimethanol was subjected to hydrogen recovery treatment in a 1,4-cyclohexanedimethanol gas-liquid separator 5-4 to obtain refined 1,4-cyclohexanedimethanol with a yield of 94%, the temperature of the 1,4-cyclohexanedimethanol gas-liquid separator 5-4 was 330°C, and the pressure was 5 MPa, and the recovered hydrogen gas was returned to the ester group hydrogenation reactor 5-3 through a pipeline to continue participating in the ester group hydrogenation reaction. Industrial applicability

[0107] The present application solves the problem of waste polyester recovery by adopting an unexpected preparation system and method, and then makes polyester degrade into intermediate product terephthalic acid diethyl ester, and then prepares 1,4-cyclohexane dimethanol from terephthalic acid diethyl ester, so that the problem of waste polyester recovery is solved, and 1,4-cyclohexane dimethanol with high economic value is prepared at low cost, therefore, the present application unexpectedly optimizes the process route of polyester recovery and preparation of 1,4-cyclohexane dimethanol, and can solve the problems of high cost and great difficulty in preparation of 1,4-cyclohexane dimethanol, so that it is more suitable for industrial application.

Claims

1. A system for the recovery of a polyester to produce 1,4-cyclohexanedimethanol, characterized in that, The system sequentially comprises, in the feeding direction: a polyester alcoholysis system (1), an alcoholysis solution impurity removal system (2), a solvent recovery system (3), a diethyl terephthalate refining system (4), and a 1,4-cyclohexane dimethanol preparation system (5), wherein, The polyester alcoholysis system (1) comprises: a depolymerization reactor (1-1); The alcoholysis solution impurity removal system (2) sequentially comprises, in the feeding direction: a centrifuge (2-1), a plate-and-frame filter (2-2); The solvent recovery system (3) sequentially comprises, in the feeding direction: a flash tank (3-1), a falling film evaporator (3-2); The diethyl terephthalate refining system (4) sequentially comprises, in the feeding direction: a diethyl terephthalate rectification tower (4-1), a diethyl terephthalate ion adsorption column (4-2), a diethyl terephthalate crystallizer (4-3); The 1,4-cyclohexane dimethanol preparation system (5) sequentially comprises, in the feeding direction: a benzene ring hydrogenation reactor (5-1), a 1,4-cyclohexane diethyl ester gas-liquid separator (5-2), an ester group hydrogenation reactor (5-3), a 1,4-cyclohexane dimethanol gas-liquid separator (5-4).

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 centrifuged solution, which continues to enter the plate-and-frame filter (2-2); The plate-and-frame filter (2-2) is used for filtering the depolymerization centrifuged solution to obtain a depolymerization filtered solution, which continues to enter the flash tank (3-1).

4. The system of claim 3, wherein, The flash tank (3-1) is used for recovering ethanol in the depolymerization filtered solution to obtain primary evaporated diethyl terephthalate, which continues to enter the falling film evaporator (3-2); The falling film evaporator (3-2) is used for recovering ethanol in the primary evaporated diethyl terephthalate to obtain secondary evaporated diethyl terephthalate, which continues to enter the diethyl terephthalate rectification tower (4-1).

5. The system of claim 4, wherein, The diethyl terephthalate rectification tower (4-1) is used for rectifying the secondary evaporated diethyl terephthalate to obtain rectified diethyl terephthalate, which continues to enter the diethyl terephthalate ion adsorption column (4-2); The diethyl terephthalate ion adsorption column (4-2) is used for adsorbing and removing metal ions in the rectified diethyl terephthalate to obtain impurity-removed diethyl terephthalate, which continues to enter the diethyl terephthalate crystallizer (4-3); The diethyl terephthalate crystallizer (4-3) is used for crystallizing the impurity-removed diethyl terephthalate to obtain diethyl terephthalate crystals, which continue to enter the benzene ring hydrogenation reactor (5-1).

6. The system of claim 5, wherein, The benzene ring hydrogenation reactor (5-1) is used for benzene ring hydrogenation reaction of the terephthalic acid diethyl ester crystals, to obtain crude 1,4-cyclohexane dicarboxylic acid diethyl ester, which continues to enter the 1,4-cyclohexane dicarboxylic acid diethyl ester gas-liquid separator (5-2).

7. The system of claim 6, wherein, The 1,4-cyclohexane dicarboxylic acid diethyl ester gas-liquid separator (5-2) 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, which continues to enter the ester group hydrogenation reactor (5-3).

8. The system of claim 7, wherein, The ester group hydrogenation reactor (5-3) is used for ester group hydrogenation reaction of the refined 1,4-cyclohexane dicarboxylic acid diethyl ester, to obtain crude 1,4-cyclohexane dimethanol, which continues to enter the 1,4-cyclohexane dimethanol gas-liquid separator (5-4).

9. The system of claim 8, wherein, The 1,4-cyclohexane dimethanol gas-liquid separator (5-4) is used for recovering hydrogen in the crude 1,4-cyclohexane dimethanol, to obtain refined 1,4-cyclohexane dimethanol.

10. A process for the production of 1,4-cyclohexanedimethanol using the system according to any one of claims 1 to 9, characterized in that The method comprises: a polyester alcoholysis method, an alcoholysis liquid impurity removal method, a solvent recovery method, a terephthalic acid diethyl ester refining method, and a 1,4-cyclohexane dimethanol preparation method.

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