A 1,4-cyclohexanedimethanol production system and method

Abstract

The invention discloses a 1,4-cyclohexanedimethanol production system and method, the production system comprises a first-stage hydrogenation reaction unit, a first-stage separation unit, a second-stage hydrogenation reaction unit and a second-stage separation unit connected in sequence; the first-stage separation unit outlet is also connected to the first-stage hydrogenation reaction unit inlet; the first-stage hydrogenation reaction unit is used to dissolve DMT in DMCD and mix it with hydrogen for preheating, and then perform a first-stage hydrogenation reaction to generate a first-stage mixed product; the first-stage separation unit is used to separate the first-stage mixed product to obtain a first part of DMCD and a second part of DMCD, and the first part of DMCD is sent to the second-stage hydrogenation reaction unit, and the second part of DMCD is sent to the first-stage hydrogenation reaction unit as a solvent for DMT; the second-stage hydrogenation reaction unit is used to mix the first part of DMCD with hydrogen for preheating, and then perform a second-stage hydrogenation reaction to generate a second-stage mixed product; the second-stage separation unit is used to separate the second-stage mixed product to obtain 1,4-cyclohexanedimethanol. The production system has a simple process, strong operability and low production cost.

Description

Technical Field

[0001] The invention relates to a system and method for producing 1,4-cyclohexanedimethanol. Background Art

[0002] 1,4-cyclohexanedimethanol (CHDM) is one of the important raw materials for high-performance, new environmentally friendly engineering plastics and packaging materials, and is also an important industrial raw material for polyester production. PETG copolyester chips produced by using CHDM as a monomer to partially replace ethylene glycol and polymerize with terephthalic acid are high-end special polyesters. Their products are highly transparent and have excellent impact resistance. They are particularly suitable for molding thick-walled transparent products. They have excellent processing and molding properties and can be designed in any shape according to the designer's intention. They can be widely used in sheet materials, high-performance shrink films, bottles and profiles, cosmetic packaging and other markets. At the same time, they have excellent secondary processing properties and can be modified by conventional machining.

[0003] At present, CHDM industrial production is mainly prepared by two-step hydrogenation reaction using dimethyl phthalate DMT as raw material: the first step is to dissolve DMT in ester and hydrogenate the benzene ring to obtain dimethyl cyclohexanedicarboxylate DMCD, and the second step is to hydrogenate the ester group of DMCD to generate CHDM. The two-step reaction uses precious metal-supported catalysts and copper-based catalysts respectively. However, the existing CHDM production process has a high freezing point of the main materials, the process pipeline is easy to condense and block, and the uneven distribution of gas and liquid phases in the hydrogenation reactor causes local hot spots, which affects the catalyst life and product purity. The device cannot operate stably for a long period of time, and the operating energy and material consumption is high. Summary of the invention

[0004] In view of the defects of the prior art, the present invention provides a 1,4-cyclohexanedimethanol production system and method to at least partially solve the problems existing in the prior art, and the scheme is as follows:

[0005] In a first aspect, the present invention relates to a 1,4-cyclohexanedimethanol production system, comprising a first-stage hydrogenation reaction unit, a first-stage separation unit, a second-stage hydrogenation reaction unit and a second-stage separation unit connected in sequence;

[0006] The outlet of the first separation unit is also connected to the inlet of the first hydrogenation reaction unit;

[0007] The one-stage hydrogenation reaction unit is used to dissolve DMT in DMCD and mix it with hydrogen for preheating, and then perform a one-stage hydrogenation reaction to generate a one-stage mixed product;

[0008] The first separation unit is used to separate the first mixed product to obtain a first part of DMCD and a second part of DMCD, and the first part of DMCD is sent to the second hydrogenation reaction unit, and the second part of DMCD is sent to the first hydrogenation reaction unit as a solvent for DMT;

[0009] The two-stage hydrogenation reaction unit is used to mix the first part of DMCD with hydrogen and preheat it, and then perform a two-stage hydrogenation reaction to generate a two-stage mixed product;

[0010] The two-stage separation unit is used to separate the two-stage mixed products to obtain 1,4-cyclohexanedimethanol.

[0011] In one or some optional embodiments, the first stage hydrogenation reaction unit includes a hydrogenation reactor I, and a distributor I is provided in the hydrogenation reactor I, and the distributor I is used to evenly distribute the reactants in the hydrogenation reactor I.

[0012] In one or some optional embodiments, the first stage hydrogenation reaction unit further includes a DMCD storage tank I, a DMT raw material warehouse, and a DMT dissolution tank;

[0013] The DMCD storage tank I and the DMT raw material warehouse are both connected to the DMT dissolution tank. The second part of DMCD is sent to the DMCD storage tank I, mixed with the DMT from the DMT raw material warehouse, and then sent to the DMT dissolution tank.

[0014] In one or some optional embodiments, the one-stage hydrogenation reaction unit further includes a DMT feed pump, a DMCD heater, a DMT preheater, and a one-stage mixed raw material preheater;

[0015] The DMT raw material bin, the DMT dissolving tank, the DMT feed pump, the DMT preheater, the first stage mixed raw material preheater, and the hydrogenation reactor I are connected in sequence; the DMCD heater is arranged between the DMCD storage tank I and the DMT dissolving tank.

[0016] In one or some optional embodiments, the first separation unit includes a first high-temperature separation tank, a first low-temperature separation tank, a DMCD storage tank II, a distillation tower I, a distillation tower II, and a tower top reflux pump II connected in sequence;

[0017] The first stage high temperature separation tank is also connected to the DMCD storage tank II;

[0018] The tower top reflux pump II is connected to the DMCD storage tank I.

[0019] In one or some optional embodiments, the first separation unit further includes a tower top reflux pump I, a tower top reflux tank I, an aftercooler I, a tower top reflux tank II, an aftercooler II, and a heavy ester cooler;

[0020] The top outlet of the distillation tower I is connected to the top reflux tank I and the top reflux pump I in sequence; the top reflux tank I is provided with the aftercooler I; the bottom outlet of the distillation tower II is connected to the heavy ester cooler; the top outlet of the distillation tower II is connected to the top reflux tank II and the top reflux pump II in sequence; the top reflux tank II is provided with the aftercooler II.

[0021] In one or some optional embodiments, the two-stage hydrogenation reaction unit includes a hydrogenation reactor II; the hydrogenation reactor II is provided with a distributor II, and the distributor II is used to evenly distribute the reactants in the hydrogenation reactor II.

[0022] In one or some optional embodiments, the two-stage hydrogenation reaction unit further includes a DMCD preheater and a two-stage mixed raw material preheater connected to each other;

[0023] The DMCD preheater is connected to the DMCD storage tank I.

[0024] In one or some optional embodiments, the second-stage separation unit includes a second-stage high-temperature separation tank, a second-stage low-temperature separation tank, a CHDM storage tank, a distillation tower III, and a distillation tower IV connected in sequence;

[0025] The second-stage high-temperature separation tank is also connected to the CHDM storage tank.

[0026] In one or some optional embodiments, the second-stage separation unit further includes a tower top reflux tank III, an aftercooler III, a tower top reflux pump III, an aftercooler IV, a tower top reflux tank IV, a tower top reflux pump IV, and a heavy alcohol cooler;

[0027] The top outlet of the distillation tower III is connected to the top reflux tank III and the top reflux pump III in sequence; the top reflux tank III is provided with the aftercooler III; the bottom outlet of the distillation tower IV is connected to the heavy alcohol cooler; the top outlet of the distillation tower IV is connected to the top reflux tank IV and the top reflux pump IV in sequence; the top reflux tank IV is provided with the aftercooler IV.

[0028] In one or some optional embodiments, the first-stage mixed product and the second-stage mixed product also include hydrogen.

[0029] In one or some optional embodiments, the production system further includes a hydrogen recovery unit for recovering hydrogen from the first-stage mixed product and the second-stage mixed product.

[0030] In one or some optional embodiments, the hydrogen recovery unit includes a circulating hydrogen compressor I, a circulating hydrogen compressor II, a hydrogen recovery device and a hydrogen compressor;

[0031] The circulating hydrogen compressor I is arranged between the first-stage low-temperature separation tank and the DMT preheater; the circulating hydrogen compressor II is arranged between the second-stage low-temperature separation tank and the DMCD preheater; the inlet of the hydrogen recovery device is respectively connected to the first-stage low-temperature separation tank and the second-stage low-temperature separation tank; the outlet of the hydrogen recovery device is connected to the inlet of the hydrogen compressor; the outlet of the hydrogen compressor is respectively connected to the DMT preheater and the DMCD preheater.

[0032] In one or some optional embodiments, the production system further includes a vacuum unit; and a negative pressure separation environment is provided for the first-stage separation unit and the second-stage separation unit by vacuuming the first-stage separation unit and the second-stage separation unit.

[0033] In one or some optional embodiments, the vacuum unit includes a gas-liquid separator and a vacuum device;

[0034] The gas-liquid separator is connected to the aftercooler I, the aftercooler II, the aftercooler III, and the aftercooler IV respectively; the vacuum pumping device is connected to the gas-liquid separator.

[0035] In one or some optional embodiments, the reaction conditions of the hydrogenation reactor I are: operating pressure 5-12 MPaG, operating temperature 130-250°C, mass ratio of hydrogen to DMT raw material 80-300, mass space velocity 0.1-0.5h -1 .

[0036] In one or some optional embodiments, the reaction conditions of the hydrogenation reactor II are: operating pressure 5-12 MPaG, operating temperature 200-280°C, mass ratio of hydrogen to DMCD 100-250, mass space velocity 0.05-0.3 h -1 .

[0037] In a second aspect, the present invention relates to a method for producing 1,4-cyclohexanedimethanol, the method comprising:

[0038] 1) dissolving DMT in DMCD, mixing with hydrogen and preheating, and then performing a hydrogenation reaction to obtain a mixed reaction product containing DMCD;

[0039] 2) separating the mixed reaction product obtained in step 1) to obtain DMCD;

[0040] 3) mixing the DMCD obtained in step 2) with hydrogen and preheating it, and then performing a hydrogenation reaction to obtain a mixed reaction product containing 1,4-cyclohexanedimethanol;

[0041] 4) Separating the mixed reaction product obtained in step 3) to obtain 1,4-cyclohexanedimethanol.

[0042] In one or some optional embodiments, the method further comprises:

[0043] 5) Separating the unreacted hydrogen in step 1) and step 3) and recycling it.

[0044] The present invention connects a separation unit outlet with a hydrogenation reaction unit inlet, so that the second part of DMCD generated by the hydrogenation reaction is mixed with DMT for heat exchange, thereby preheating the DMT, effectively preventing the high freezing point DMT from blocking the reaction system channel, thereby reducing the consumption of DMT and increasing the service life of the production system. The 1,4-cyclohexanedimethanol production system provided by the present invention has a simple process flow, strong operability and low production cost.

[0045] The present invention ensures uniform distribution of feed in the hydrogenation reactor by arranging a distributor in the hydrogenation reactor, thereby improving the conversion rate of the reaction and the yield of the product.

[0046] The present invention reduces the consumption of hydrogen and reduces the emission of waste gas by arranging a hydrogen recovery unit.

[0047] The invention separates the reaction products by a vacuum distillation method, thereby reducing the heat consumption of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is a schematic diagram of the connection relationship of the 1,4-cyclohexanedimethanol production system provided by the present invention;

[0049] Figure 2 It is a schematic diagram of the device structure of the 1,4-cyclohexanedimethanol production system provided by the present invention.

[0050] Among them: 1. DMT raw material warehouse; 2. DMT dissolving tank; 3. DMT feed pump; 4. DMCD storage tank Ⅰ; 5. DMCD heater; 6. DMT preheater; 7. One-stage mixed raw material preheater; 8. Hydrogenation reactor Ⅰ; 9. One-stage high-temperature separation tank; 10. DMCD storage tank Ⅱ; 11. One-stage low-temperature separation tank; 12. Circulating hydrogen compressor Ⅰ; 13. Distillation tower Ⅰ; 14. Top reflux pump Ⅰ; 15. Top reflux tank Ⅰ; 16. Aftercooler Ⅰ; 17. Hydrogen compressor; 18. Gas-liquid separator; 19. Distillation tower Ⅱ; 20. Top reflux tank Ⅱ; 21. 1. Top reflux pump II; 22. Aftercooler II; 23. Heavy ester cooler; 24. Hydrogenation reactor II; 25. DMCD preheater; 26. Second-stage mixed raw material preheater; 27. Second-stage high-temperature separation tank; 28. CHDM storage tank; 29. ​​Second-stage low-temperature separation tank; 30. Circulating hydrogen compressor II; 31. Distillation tower III; 32. Top reflux tank III; 33. Aftercooler III; 34. Top reflux pump III; 35. Distillation tower IV; 36. Aftercooler IV; 37. Top reflux tank IV; 38. Top reflux pump IV; 39. Heavy alcohol cooler; 40. Hydrogen recovery device; 41. Vacuum extraction device. DETAILED DESCRIPTION

[0051] The following is a detailed description of the embodiments of the present invention: The embodiments of the present invention are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and processes are given, but the protection scope of the present invention is not limited to the following embodiments. The process parameters for which specific conditions are not specified in the following embodiments are generally based on conventional conditions.

[0052] The endpoints and any values ​​of the ranges disclosed in the present invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in the present invention.

[0053] After implementing relevant technical solutions with reference to patent documents CN1058959C, CN201110134923.2, CN106518608A and CN109942372A, the inventors found that the pipelines were easily clogged, the device could not operate stably for a long period of time, the operating energy and material consumption was high, and the product purity was not ideal.

[0054] The inventors made the present invention after further research and development. The present invention alleviates the problem of high-freezing-point DMT clogging pipelines and reactors by preheating the raw material mixture, reduces operating energy and material consumption, and obtains a product CHDM with an ideal yield.

[0055] In the embodiments of the present invention, unless otherwise specified, the “connection” is connection through a pipeline.

[0056] In the embodiments of the present invention, the distributor used can refer to patents CN21322089U and CN21322090U.

[0057] The embodiment of the present invention provides a 1,4-cyclohexanedimethanol production system, referring to Figure 1 The production system comprises a first-stage hydrogenation reaction unit, a first-stage separation unit, a second-stage hydrogenation reaction unit and a second-stage separation unit connected in sequence; the first-stage separation unit outlet is also connected to the first-stage hydrogenation reaction unit inlet;

[0058] S1 one-stage hydrogenation reaction unit: used to dissolve DMT in DMCD and mix it with hydrogen for preheating, and then conduct a one-stage hydrogenation reaction to generate a mixed product;

[0059] S2 first stage separation unit: used to separate the first stage mixed product to obtain the first part of DMCD and the second part of DMCD, the first part of DMCD is sent to the second stage hydrogenation reaction unit, and the second part of DMCD is sent to the first stage hydrogenation reaction unit as a solvent for DMT;

[0060] S3 two-stage hydrogenation reaction unit: used to mix the first part of DMCD with hydrogen and preheat it, and then perform a two-stage hydrogenation reaction to generate a two-stage mixed product;

[0061] S4 two-stage separation unit: used to separate the two-stage mixed products to obtain 1,4-cyclohexanedimethanol.

[0062] The mixed product generated by the first hydrogenation reaction has a high heat content due to the heat released by the reaction. The second part of DMCD separated by the first separation unit also has a high heat content. The outlet of the first separation unit is connected to the inlet of the first hydrogenation reaction unit, and the second part of DMCD is mixed with DMT and hydrogen to preheat the DMT and hydrogen. The heat released by the first hydrogenation reaction is fully utilized, which reduces the heat consumption of the production system. At the same time, it avoids solid precipitation caused by the mixing of cold hydrogen and DMT, effectively preventing the problem of high freezing point DMT clogging the pipeline, thereby reducing the consumption of DMT and increasing the service life of the production system.

[0063] In the embodiment of the present invention, the above-mentioned one-stage hydrogenation reaction unit includes a hydrogenation reactor Ⅰ8, and a distributor Ⅰ is provided in the hydrogenation reactor Ⅰ8. The distributor Ⅰ is used to evenly distribute the reactants in the hydrogenation reactor Ⅰ8.

[0064] By adding a distributor I in the hydrogenation reactor I8, it is ensured that DMT, DMCD and hydrogen can enter the hydrogenation reactor I8 in a continuous and dispersed state, are uniformly mixed in the upper part of the hydrogenation reactor I8, and can react after uniformly contacting with the catalyst, thereby avoiding uneven distribution of reactants in the bed of the hydrogenation reactor I8 affecting the catalytic efficiency or causing over-temperature deactivation, thereby maximizing the performance and production efficiency of the first-stage hydrogenation reaction, that is, maximizing the conversion rate of the reaction and the yield of the product.

[0065] In a specific embodiment, the hydrogenation reactor I8 may be a trickle bed reactor.

[0066] In a specific embodiment, the catalyst may be a metal composite catalyst containing Rh and Pt.

[0067] In a specific embodiment, the reaction conditions of the hydrogenation reactor I8 are: operating pressure 5-12 MPaG, operating temperature 130-250°C, mass ratio of hydrogen to DMT raw material 80-300, mass space velocity 0.1-0.5h -1 .

[0068] In an embodiment of the present invention, the one-stage hydrogenation reaction unit also includes a DMCD storage tank Ⅰ4, a DMT raw material warehouse 1, and a DMT dissolution tank 2; the DMCD storage tank Ⅰ4 and the DMT raw material warehouse 1 are both connected to the DMT dissolution tank 2, and the second part of DMCD is sent to the DMCD storage tank Ⅰ4, mixed with the DMT from the DMT raw material warehouse 1, and then sent to the DMT dissolution tank 2.

[0069] In an embodiment of the present invention, the one-stage hydrogenation reaction unit also includes a DMT feed pump 3, a DMCD heater 5, a DMT preheater 6, and a one-stage mixed raw material preheater 7; the DMT raw material warehouse 1, the DMT dissolution tank 2, the DMT feed pump 3, the DMT preheater 6, the one-stage mixed raw material preheater 7, and the hydrogenation reactor Ⅰ8 are connected in sequence; the DMCD heater 5 is arranged between the DMCD storage tank Ⅰ4 and the DMT dissolution tank 2.

[0070] The DMCD from the DMCD storage tank Ⅰ4 is heated by the DMCD heater 5, sent to the DMT dissolution tank 2, mixed with the DMT raw material bin 1, sent to the DMT preheater 6 by the DMT feed pump 3 for preheating, and then mixed with hydrogen, preheated by a first-stage mixed raw material preheater 7, and then sent to the hydrogenation reactor Ⅰ8 for a first-stage hydrogenation reaction to generate a first-stage mixed product.

[0071] In a specific embodiment, the DMCD heater 5, the DMT preheater 6, and the first-stage mixed raw material preheater 7 can be turned on or off according to the actual production temperature.

[0072] In an embodiment of the present invention, the above-mentioned first-stage separation unit includes a first-stage high-temperature separation tank 9, a first-stage low-temperature separation tank 11, a DMCD storage tank II 10, a distillation tower I 13, a distillation tower II 19, and a top reflux pump II 21 connected in sequence; the first-stage high-temperature separation tank 9 is also connected to the DMCD storage tank II 10; the top reflux pump II 21 is connected to the DMCD storage tank I 4.

[0073] In the implementation of the present invention, the first-stage separation unit also includes a top reflux pump Ⅰ14, a top reflux tank Ⅰ15, an aftercooler Ⅰ16, a top reflux tank Ⅱ20, an aftercooler Ⅱ22, and a heavy ester cooler 23; the top outlet of the distillation tower Ⅰ13 is connected to the top reflux tank Ⅰ15 and the top reflux pump Ⅰ14 in sequence; the top reflux tank Ⅰ15 is provided with an aftercooler Ⅰ16; the bottom outlet of the distillation tower Ⅱ19 is connected to the heavy ester cooler 23; the top outlet of the distillation tower Ⅱ19 is connected to the top reflux tank Ⅱ20 and the top reflux pump Ⅱ21 in sequence; the top reflux tank Ⅱ20 is provided with an aftercooler Ⅱ22.

[0074] The mixed product obtained from the first stage hydrogenation reaction unit is separated by a first stage high temperature separation tank 9 and a first stage low temperature separation tank 11, and the mixture obtained at the bottom of the tank enters the DMCD storage tank II 10, and then is distilled and separated by a distillation tower I 13. The mixture at the top of the distillation tower I 13 is sent to the top reflux tank I 15, cooled by the aftercooler I 16, and then refluxed to the top reflux tank I 15, and then the light ester by-product is transported out by the top reflux pump I 14; the mixture at the bottom of the distillation tower I 13 is sent to the distillation tower I 13. Tower II 19 performs distillation separation, and the bottom product of the distillation tower I 13 is sent to the heavy ester cooler 23 for cooling to obtain a heavy ester by-product; the product obtained at the top of the distillation tower I 13 is sent to the external top reflux tank II 20, cooled by the aftercooler II 22, and refluxed to the top reflux tank II 20, and then sent to the DMCD storage tank I 4 by the top reflux pump II 21, the first part of the DMCD is sent to the second-stage hydrogenation reaction unit, and the second part of the DMCD is sent to the first-stage hydrogenation reaction unit as a solvent for DMT.

[0075] In the embodiment of the present invention, the two-stage hydrogenation reaction unit comprises a hydrogenation reactor II 24 ; the hydrogenation reactor II 24 is provided with a distributor II, and the distributor II is used to evenly distribute the reactants in the hydrogenation reactor II 24 .

[0076] In the implementation of the present invention, the two-stage hydrogenation reaction unit further includes a DMCD preheater 25 and a two-stage mixed raw material preheater 26 connected to each other; the DMCD preheater 25 is connected to the DMCD storage tank Ⅰ4.

[0077] The first part of DMCD is heated in the DMCD preheater 25 and mixed with hydrogen. After being mixed and preheated in the second-stage mixed raw material preheater 26, it is sent to the hydrogenation reactor II 24 for hydrogenation reaction to generate a second-stage mixed product.

[0078] In a specific embodiment, the DMCD preheater 25 and the second-stage mixed raw material preheater 26 can be opened or closed according to the actual production temperature.

[0079] By adding a distributor II to the hydrogenation reactor II 24, it is ensured that DMCD and hydrogen can enter the hydrogenation reactor II 24 in a continuous and dispersed state, are uniformly mixed in the upper part of the hydrogenation reactor II 24, and can react after uniformly contacting with the catalyst, thereby avoiding uneven distribution of reactants in the bed of the hydrogenation reactor II 24 affecting the catalytic efficiency or causing over-temperature deactivation, thereby maximizing the performance and production efficiency of the first-stage hydrogenation reaction, that is, maximizing the conversion rate of the reaction and the yield of the product.

[0080] In a specific embodiment, the hydrogenation reactor II 24 may be a trickle bed reactor.

[0081] In a specific embodiment, the catalyst may be a copper-based catalyst.

[0082] In a specific embodiment, the reaction conditions of the hydrogenation reactor II 24 are: operating pressure 5-12 MPaG, operating temperature 200-280°C, mass ratio of hydrogen to DMCD 100-250, mass space velocity 0.05-0.3 h -1 .

[0083] In the embodiment of the present invention, the above-mentioned two-stage separation unit includes a second-stage high-temperature separation tank 27, a second-stage low-temperature separation tank 29, a CHDM storage tank 28, a distillation tower III 31, and a distillation tower IV 35 connected in sequence; the second-stage high-temperature separation tank 27 is also connected to the CHDM storage tank 28.

[0084] In an embodiment of the present invention, the two-stage separation unit also includes a top reflux tank III32, an aftercooler III33, a top reflux pump III34, an aftercooler IV36, a top reflux tank IV37, a top reflux pump IV38, and a heavy alcohol cooler 39; the top outlet of the distillation tower III31 is connected to the top reflux tank III32 and the top reflux pump III34 in sequence; the top reflux tank III32 is provided with an aftercooler III33; the bottom outlet of the distillation tower IV35 is connected to the heavy alcohol cooler 39; the top outlet of the distillation tower IV35 is connected to the top reflux tank IV37 and the top reflux pump IV38 in sequence; the top reflux tank IV37 is provided with an aftercooler IV36.

[0085] The second-stage mixed product generated by the second-stage hydrogenation reaction unit is separated by the second-stage high-temperature separation tank 27 and the second-stage low-temperature separation tank 29, and the mixture obtained at the bottom of the tank enters the CHDM storage tank 28, and is then distilled and separated by the distillation tower III 31. The mixture at the top of the distillation tower III 31 is sent to the top reflux tank III 32, cooled by the aftercooler III 33, and refluxed to the top reflux tank III 32, and then the light alcohol by-product is transported out by the top reflux pump III 34; the mixture at the bottom of the distillation tower III 31 is sent to the distillation tower IV 35 for distillation and separation, and the bottom product of the distillation tower IV 35 is sent to the heavy alcohol cooler 39 for cooling to obtain the heavy alcohol by-product; the product obtained at the top of the distillation tower IV 35 is sent to the external top reflux tank IV 37, cooled by the aftercooler IV 36, and refluxed to the top reflux tank IV 37, and then the final product CHDM is transported out by the top reflux pump IV 38.

[0086] In an embodiment of the present invention, the production system further includes a hydrogen recovery unit for recovering hydrogen from the first-stage mixed product and the second-stage mixed product. The hydrogen recovery unit includes a circulating hydrogen compressor I12, a circulating hydrogen compressor II30, a hydrogen recovery device 40 and a hydrogen compressor 17; the circulating hydrogen compressor I12 is arranged between the first-stage low-temperature separation tank 11 and the DMT preheater 6; the circulating hydrogen compressor II30 is arranged between the second-stage low-temperature separation tank 29 and the DMCD preheater 25; the inlet of the hydrogen recovery device 40 is respectively connected to the first-stage low-temperature separation tank 11 and the second-stage low-temperature separation tank 29; the outlet of the hydrogen recovery device 40 is connected to the inlet of the hydrogen compressor 17; the outlet of the hydrogen compressor 17 is respectively connected to the DMT preheater 6 and the DMCD preheater 25.

[0087] Through the above arrangement, it is convenient to compress the hydrogen-rich gas separated by the first low-temperature separation tank 11 and mix it with DMT for a first hydrogenation reaction, and it is convenient to compress the hydrogen-rich gas separated by the second low-temperature separation tank 29 and mix it with DMCD for a second hydrogenation reaction.

[0088] In a specific embodiment, the hydrogen recovery device 40 can adopt PSA pressure swing adsorption method or membrane separation method, and PSA pressure swing adsorption method is preferably used.

[0089] In a specific embodiment, the production system can transport new hydrogen to the production system through the hydrogen compressor 17 to supplement the hydrogen lost in the production process.

[0090] In an embodiment of the present invention, the production system also includes a vacuum unit; by vacuuming the above-mentioned first-stage separation unit and the second-stage separation unit, a negative pressure separation environment is provided for the above-mentioned first-stage separation unit and the second-stage separation unit, and the reaction products are separated by a vacuum distillation method, which can effectively reduce the heat consumption of the production system.

[0091] In an embodiment of the present invention, the vacuum unit includes a gas-liquid separator 18 and a vacuum device 41 ; the gas-liquid separator 18 is respectively connected to the aftercooler I 16 , aftercooler II 22 , aftercooler III 33 , and aftercooler IV 36 ; the vacuum device 41 is connected to the gas-liquid separator 18 .

[0092] In a specific embodiment, the vacuum extraction device 41 may adopt a vacuum pump method or a steam injection method, and preferably adopts a vacuum pump method.

[0093] Reference Figure 2 The process flow of the 1,4-cyclohexanedimethanol production method in the embodiment of the present invention is as follows:

[0094] (1) One-stage hydrogenation reaction: The DMT solid raw material is mixed and dissolved with the high-temperature circulating DMCD, mixed with hydrogen and preheated, and then sent to the hydrogenation reactor I8. The mixed raw material and hydrogen are uniformly mixed in the distributor at the top of the reactor, and then contacted with the catalyst in the bed to carry out hydrogenation reaction, thereby obtaining the product light component ester, DMCD and heavy component ester.

[0095] (2) One-stage separation reaction: The product is separated from the hydrogen after cooling and sent to a distillation tower for distillation separation under vacuum conditions. There are two distillation towers to separate the light component ester, DMCD and heavy component ester. The light and heavy component esters are used as by-products, and DMCD is sent to the DMCD hydrogenation reactor. The separated hydrogen enters the circulating hydrogen compressor for recycling, and the discharged gas enters the hydrogen recovery device 40 for recovery.

[0096] (3) Second stage hydrogenation reaction: DMCD is mixed with hydrogen and preheated, and then sent to hydrogenation reactor II 24. The mixed raw materials and hydrogen are uniformly mixed in a distributor at the top of the reactor and then contacted with the catalyst in the bed to carry out hydrogenation reaction, thereby obtaining light alcohol component, CHDM and heavy alcohol component products.

[0097] (4) Second stage separation reaction: The product is separated from the hydrogen after cooling and sent to a distillation tower for distillation separation under vacuum conditions. There are two distillation towers to separate the light alcohol component, CHDM and heavy alcohol component. CHDM is the final product, and the light and heavy alcohol components are by-products. The separated hydrogen enters the circulating hydrogen compressor for recycling, and the discharged gas enters the hydrogen recovery device 40 for recovery.

[0098] Examples 1 to 20

[0099] The above-mentioned 1,4-cyclohexanedimethanol production system was adopted, and with reference to the above-mentioned 1,4-cyclohexanedimethanol production method, different reaction conditions were set to carry out Examples 1 to 20 to produce 1,4-cyclohexanedimethanol, and the conversion rate and selectivity of the raw materials during the production reaction were tested and analyzed. The reaction conditions and reaction analysis results of the first-stage hydrogenation reaction unit in Examples 1 to 20 are shown in Table 1, and the reaction conditions and reaction analysis results of the second-stage hydrogenation reaction unit in Examples 1 to 20 are shown in Table 2.

[0100] Table 1 One-stage hydrogenation reaction conditions and reaction analysis results

[0101]

[0102] Table 2 Second stage hydrogenation reaction conditions and reaction analysis results

[0103]

[0104] From analysis of Table 1 and Table 2, it can be seen that the 1,4-cyclohexanedimethanol production method and system provided by the present invention achieves a higher raw material conversion rate and selectivity when producing 1,4-cyclohexanedimethanol.

[0105] Examples 21 to 23

[0106] According to Examples 1 to 20 in Tables 1 and 2, the energy consumption of the production system, the conversion rate of the reaction and the yield of the product during the production reaction were comprehensively considered, and after the reaction conditions were optimized, the above-mentioned 1,4-cyclohexanedimethanol production system was also used, and with reference to the above-mentioned 1,4-cyclohexanedimethanol production method, Examples 21 to 23 were carried out to produce 1,4-cyclohexanedimethanol, and the consumption of raw material DMT in the production process of Examples 21 to 23 and the total energy consumption of the production system were tested. The reaction conditions of the first-stage hydrogenation reaction and the second-stage hydrogenation reaction, the consumption of raw material DMT, and the total energy consumption of the production system in Examples 21 to 23 are shown in Table 3.

[0107] Table 3

[0108]

[0109] From the analysis of Table 3, it can be seen that the 1,4-cyclohexanedimethanol production method and system provided by the present invention achieves lower raw material DMT consumption and total system energy consumption in the process of producing 1,4-cyclohexanedimethanol.

[0110] Although the specific embodiments of the present invention have been described in detail, it will be understood by those skilled in the art. According to all the teachings disclosed, various modifications and replacements can be made to those details, and these changes are all within the protection scope of the present invention. The full scope of the present invention is given by the attached claims and any equivalents thereof.

Claims

1. A method for producing 1,4-cyclohexanedimethanol, characterized in that: The method is run on the following production system: The 1,4-cyclohexanedimethanol production system comprises a first-stage hydrogenation reaction unit, a first-stage separation unit, a second-stage hydrogenation reaction unit and a second-stage separation unit connected in sequence; An outlet of a separation unit is connected to an inlet of a hydrogenation reaction unit; The one-stage hydrogenation reaction unit is used to dissolve DMT in DMCD and mix it with hydrogen for preheating, and then perform a one-stage hydrogenation reaction to generate a one-stage mixed product; The first separation unit is used to separate the first mixed product to obtain a first part of DMCD and a second part of DMCD, and the first part of DMCD is sent to the second hydrogenation reaction unit, and the second part of DMCD is sent to the first hydrogenation reaction unit as a solvent for DMT; The two-stage hydrogenation reaction unit is used to mix the first part of DMCD with hydrogen and preheat it, and then perform a two-stage hydrogenation reaction to generate a two-stage mixed product; The two-stage separation unit is used to separate the two-stage mixed products to obtain 1,4-cyclohexanedimethanol; The one-stage hydrogenation reaction unit comprises a hydrogenation reactor I, wherein the hydrogenation reactor I is provided with a distributor I, and the distributor I is used to evenly distribute the reactants in the hydrogenation reactor I; The two-stage hydrogenation reaction unit includes a hydrogenation reactor II; The hydrogenation reactor II is provided with a distributor II, and the distributor II is used to evenly distribute the reactants in the hydrogenation reactor II; The method comprises: 1) The first stage hydrogenation reaction unit dissolves DMT in DMCD, mixes with hydrogen and preheats the mixture, and then performs a hydrogenation reaction to obtain a mixed reaction product containing DMCD; 2) separating the mixed reaction product obtained in step 1) to obtain DMCD; 3) The two-stage hydrogenation reaction unit is used to mix the DMCD obtained in step 2) with hydrogen and preheat it, and then perform a hydrogenation reaction to obtain a mixed reaction product containing 1,4-cyclohexanedimethanol; 4) separating the mixed reaction product obtained in step 3) to obtain 1,4-cyclohexanedimethanol; The reaction conditions of the hydrogenation reactor I are: using a metal composite catalyst containing Rh and Pt, an operating pressure of 12 MPa, an operating temperature of 120°C, a molar ratio of hydrogen to DMT raw material of 300, and a mass space velocity of 0.1 h -1 ; The reaction conditions of the hydrogenation reactor II are: using a copper-based catalyst, operating pressure 12 MPa, operating temperature 180°C, molar ratio of hydrogen to DMCD 300, mass space velocity 0.05 h -1 ; The first stage hydrogenation reaction unit also includes a DMCD storage tank I, a DMT raw material warehouse, and a DMT dissolution tank; The DMCD storage tank I and the DMT raw material warehouse are both connected to the DMT dissolution tank. The second part of DMCD is sent to the DMCD storage tank I, mixed with the DMT from the DMT raw material warehouse, and then sent to the DMT dissolution tank.

2. The production method according to claim 1, characterized in that The one-stage hydrogenation reaction unit also includes a DMT feed pump, a DMCD heater, a DMT preheater, and a one-stage mixed raw material preheater; The DMT raw material bin, the DMT dissolving tank, the DMT feed pump, the DMT preheater, the first stage mixed raw material preheater, and the hydrogenation reactor I are connected in sequence; the DMCD heater is arranged between the DMCD storage tank I and the DMT dissolving tank.

3. The production method according to claim 1, characterized in that The first stage separation unit comprises a first stage high temperature separation tank, a first stage low temperature separation tank, a DMCD storage tank II, a distillation tower I, a distillation tower II, and a tower top reflux pump II which are connected in sequence; The first stage high temperature separation tank is also connected to the DMCD storage tank II; The tower top reflux pump II is connected to the DMCD storage tank I.

4. The production method according to claim 3, characterized in that The first stage separation unit further comprises a tower top reflux pump I, a tower top reflux tank I, an aftercooler I, a tower top reflux tank II, an aftercooler II, and a heavy ester cooler; The distillation tower I is connected to the top reflux tank I and the top reflux pump I in sequence through the top outlet; the top reflux tank I is provided with the aftercooler I; the distillation tower II is connected to the heavy ester cooler through the bottom outlet; the distillation tower II is connected to the top reflux tank II and the top reflux pump II in sequence through the top outlet; the top reflux tank II is provided with the aftercooler II.

5. The production method according to claim 1, characterized in that The first-stage mixed product and the second-stage mixed product also include hydrogen; the production system also includes a hydrogen recovery unit for recovering the hydrogen in the first-stage mixed product and the second-stage mixed product.

6. The production method according to claim 1, characterized in that The production system further comprises a vacuum unit; by vacuuming the first-stage separation unit and the second-stage separation unit, a negative pressure separation environment is provided for the first-stage separation unit and the second-stage separation unit.

7. The production method according to claim 1, characterized in that The method further comprises: 5) Separate the unreacted hydrogen in step 1) and step 3) and recycle it.

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