Method and device for removing heavy components from cyclohexanol

Abstract

The invention relates to the technical field of chemical engineering, in particular to a method and a device for removing heavy components from cyclohexanol. Comprising the following steps: a, rectifying a cyclohexanol-containing material from a cyclohexene hydration reaction to obtain a first solution containing cyclohexanol and heavy components in a tower kettle; b, carrying out heavy component removal operation on the first solution to obtain a third solution containing a catalyst and heavy components, a first gas phase and a second gas phase; and c, rectifying the first gas phase and the second gas phase to obtain a fourth solution subjected to heavy component removal, namely cyclohexanol subjected to heavy component removal. The entrained catalyst and heavy components are removed together, and the fluidity required by the catalyst waste liquid is maintained by using the heavy components, so that the loss of cyclohexanol is reduced.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, and in particular to a method and apparatus for removing heavy components from cyclohexanol. Background Technology

[0002] Cyclohexanol is mainly used to produce cyclohexanone, adipic acid, plasticizers, surfactants, and as an industrial solvent. The cyclohexene hydration method has the advantages of lower production costs and a cleaner process, making it the primary technology for cyclohexanol production. The cyclohexene hydration process for cyclohexanol production includes units such as hydration reaction, cyclohexanol separation, two-stage concentration and evaporation with catalyst, and cyclohexanol purification.

[0003] Under conditions of 110–130 °C and 0.4–0.6 MPaG, cyclohexene hydrates with water in the presence of a hydration catalyst to form cyclohexanol. The conversion rate of cyclohexene is approximately 10%, and the selectivity of cyclohexanol is approximately 99%. The amount of byproducts from the cyclohexene hydration reaction is small, but the composition of the byproducts is quite complex. The light components include methylcyclopentene and methylcyclopentanol, while the heavy components include cyclohexylcyclohexene isomers and dicyclohexyl ether (boiling point approximately 242.5 °C). Cyclohexylcyclohexene isomers refer to dimers of cyclohexene, mainly including 3-cyclohexylcyclohexene (boiling point approximately 230.4 °C), 1-cyclohexylcyclohexene (boiling point approximately 234.2 °C), and cyclohexylenedicyclohexane (boiling point approximately 237.6 °C). In addition to the cyclohexylcyclohexene isomers and dicyclohexyl ethers mentioned above, the heavy components in cyclohexanol production also include various components with boiling points higher than cyclohexanol (approximately 160.8℃). For details, please refer to "Component Analysis of Bottom Waste Liquid from Cyclohexanol Distillation Columns" in *Henan Chemical Industry*, Vol. 33, No. 1, 2016; these will not be elaborated upon here. HG / T 4121-2009 *Industrial Cyclohexanol* requires that the heavy component content of premium-grade cyclohexanol not exceed 0.2 wt%. Furthermore, entrained hydrated catalyst particles that separate from the vaporized cyclohexanol can also be considered heavy components, which need to be removed or separated during cyclohexanol production.

[0004] like Figure 1 As shown, Chinese patent CN103649029A discloses a method for refining cyclohexanol via a side stream (see appendix of the patent). Figure 1 The method shown is to discharge from pipeline 15) to reduce the weight content of the heavy component cyclohexylcyclohexene isomer in the cyclohexanol product to less than 500 ppm. The boiling point difference between cyclohexanol and the cyclohexylcyclohexene isomer is large, allowing for good separation even with only one theoretical plate. The heavy component is separated through the appendix of this patent. Figure 1Pipeline 14 is shown as the outlet. In actual production, this heavy component contains approximately 15% dicyclohexyl ether and about 80% cyclohexanol. In the cyclohexanol refining system disclosed in Chinese Patent CN212025228U, the bottom material of the cyclohexanol separation tower is concentrated by an optimized first and second evaporator before entering the cyclohexanol distillation tower, and then discharged as waste liquid. The pressure of the two evaporators is basically equal, and it contains a large amount of heavy components that need to be removed later. In the high-purity cyclohexanol purification system and method disclosed in Chinese Patent CN108440241A, the hydrated catalyst slurry and heavy components such as cyclohexylcyclohexene isomers are discharged separately. The cyclohexanol product can be further reduced by discharging it through a side stream in the rectification section. It is claimed that the purity of cyclohexanol can reach 99.8%–99.98% wt.

[0005] To maintain the fluidity of the catalyst waste liquid and prevent clogging of the evaporation equipment, approximately 70% cyclohexanol is entrained in the catalyst waste liquid. The cyclohexanol content in the waste liquid fluctuates greatly depending on the discharge frequency. Therefore, in existing technologies, a large amount of cyclohexanol is entrained in both the catalyst waste liquid and the discharge of heavy components, affecting the yield of the cyclohexanol unit. Summary of the Invention

[0006] To address the aforementioned technical problems, the present invention provides the following technical solutions.

[0007] A method for removing heavy components from cyclohexanol includes the following steps:

[0008] a. The cyclohexanol-containing material from the cyclohexene hydration reaction is distilled, and a first solution containing cyclohexanol and heavy components is obtained from the bottom of the column;

[0009] b. Perform a weight removal operation on the first solution to obtain a third solution containing heavy components, as well as a first gas phase and a second gas phase;

[0010] c. The first gas phase and the second gas phase are subjected to distillation, and a fourth solution after weight removal is obtained in the bottom of the column. The fourth solution is cyclohexanol after the removal of heavy components.

[0011] In the above-described method for removing heavy components from cyclohexanol, in step b, the heavy component removal operation includes heating and separating the first solution to obtain the first gas phase and the second solution containing the heavy components, and then distilling the second solution to obtain the second gas phase and the third solution.

[0012] In the above-described method for removing heavy components from cyclohexanol, the pressure of the first gas phase is higher than the pressure of the second gas phase; the pressure of the second gas phase is 50-80 kPaA.

[0013] In the above-described method for removing heavy components from cyclohexanol, the distillation in the heavy component removal operation is a stripping process.

[0014] In the above-described method for removing heavy components from cyclohexanol, the first gas phase and / or the second gas phase are defoamed; the first gas phase and / or the second gas phase are condensed and / or cooled before subsequent distillation, and the condensate is transported to the subsequent distillation.

[0015] In the above-described method for removing heavy components from cyclohexanol, the fourth solution is distilled to obtain cyclohexanol with the heavy components removed in the stripping section of the distillation column.

[0016] An apparatus for removing heavy components from cyclohexanol includes a cyclohexanol separation tower, a heavy component removal system, a cyclohexanol distillation tower, and a feed pipeline for conveying cyclohexene hydration products. The outlet of the feed pipeline is connected to the inlet of the cyclohexanol separation tower. The liquid phase outlet of the bottom of the cyclohexanol separation tower is connected to the heavy component removal system via a pipeline. The first gas phase outlet of the heavy component removal system is connected to the first inlet of the cyclohexanol distillation tower via a pipeline. The second gas phase outlet of the heavy component removal system is connected to the second inlet of the cyclohexanol distillation tower via a pipeline. The liquid phase outlet of the heavy component removal system is connected to a pipeline for conveying a third solution.

[0017] In the above-mentioned apparatus for removing heavy components from cyclohexanol, the heavy component removal system includes a separator and a cyclohexanol heavy component removal tower. The cyclohexanol heavy component removal tower is equipped with a reboiler. The liquid phase outlet of the separator is connected to the top inlet of the cyclohexanol heavy component removal tower via a pipeline. A pipeline for conveying the first gas phase is connected to the gas phase outlet of the separator. A pipeline for conveying the second gas phase is connected to the top gas phase outlet of the cyclohexanol heavy component removal tower. A pipeline for conveying the third solution is connected to the bottom outlet of the cyclohexanol heavy component removal tower.

[0018] In the above-mentioned apparatus for removing heavy components from cyclohexanol, a heavy component delivery pump is installed on the pipeline for delivering the third solution, and the inlet of the reboiler of the heavy component removal tower is connected to the outlet of the heavy component delivery pump via a pipeline.

[0019] In the aforementioned apparatus for removing heavy components from cyclohexanol, a first condenser is installed on the pipeline conveying the first gas phase, and the first condenser is equipped with a non-condensable gas discharge port. A second condenser is installed on the pipeline conveying the second gas phase, and the second condenser is also equipped with a non-condensable gas discharge port. The reboiler of the cyclohexanol distillation column is connected to a cyclohexanol light component removal column.

[0020] Compared with existing technologies, the advantages of this invention are:

[0021] 1. The entrained catalyst is removed together with the heavy components, and the heavy components are used to maintain the required fluidity of the catalyst waste liquid, thereby reducing the loss of cyclohexanol.

[0022] 2. By using a staged gasification and concentration method with high pressure followed by low pressure, a lower pressure is used when the concentration of catalyst and heavy components is high to increase the gasification effect of cyclohexene and reduce the difficulty of removing heavy components.

[0023] 3. The condensation heat of the first gas phase and / or the second gas phase can be used as a heat source to heat the parts of the device that need to be heated, thus saving energy and reducing consumption.

[0024] 4. Before cyclohexanol distillation, heavy components are removed, eliminating the need for side-stream desiccation to obtain superior cyclohexanol, significantly reducing the design and operation difficulty of the cyclohexanol distillation column.

[0025] 5. Combining it with the side-stream discharge debinding method can produce higher quality cyclohexanol products. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the existing cyclohexanol separation process;

[0027] Figure 2 This is a flowchart illustrating the present invention;

[0028] Figure 3 This is another schematic diagram of the process of the present invention;

[0029] Figure 4 This is another schematic diagram of the process of the present invention;

[0030] In the diagram: 1. Cyclohexanol separation tower; 2. Separator; 3. Cyclohexanol de-heavy tower; 4. Cyclohexanol distillation tower; 5. Cyclohexanol de-light tower; 7. Feed line for conveying cyclohexene hydration products; 8. First condenser; 9. Second condenser; 30. De-heavy system; 31. De-heavy tower reboiler; 32. Heavy component transfer pump; 81. First condensate pump; 91. Second condensate pump. Detailed Implementation

[0031] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Knowledge related to distillation and liquid-liquid extraction should be well-known in the field of chemical engineering. Alternatively, one can refer to Volume 3, "Chemical Unit Processes," of the *Petrochemical Engineering Design Handbook* (edited by Wang Songhan, published by Chemical Industry Press in 2001, hereinafter referred to as the *Handbook*). In this text, "wt%" indicates "weight percentage."

[0032] Example 1

[0033] This embodiment provides a method and apparatus for removing heavy components from cyclohexanol.

[0034] like Figure 2As shown, an apparatus for removing heavy components from cyclohexanol includes a cyclohexanol separation tower 1, a heavy component removal system 30, a cyclohexanol distillation tower 4, and a feed line 7 for conveying cyclohexene hydration products. The outlet of the feed line 7 is connected to the inlet of the cyclohexanol separation tower 1. The liquid phase outlet of the bottom of the cyclohexanol separation tower 1 is connected to the heavy component removal system 30 via a pipeline. The first gas phase outlet of the heavy component removal system 30 is connected to the first inlet of the cyclohexanol distillation tower 4 via a pipeline. The second gas phase outlet of the heavy component removal system 30 is connected to the second inlet of the cyclohexanol distillation tower 4 via a pipeline. The liquid phase outlet of the heavy component removal system 30 is connected to a pipeline for conveying a third solution.

[0035] Specifically, such as Figure 4 As shown, the deweighting system 30 includes a separator 2, a cyclohexanol deweighting tower 3, a deweighting tower reboiler 31, and a heavy component transfer pump 32. The outlet of the feed pipeline 7 is connected to the inlet of the cyclohexanol separator 1. The bottom liquid outlet of the cyclohexanol separator 1 is connected to the inlet of the separator 2 via a pipeline. The gas outlet of the separator 2 is the first gas outlet of the deweighting system 30, which is connected to the first inlet A of the cyclohexanol distillation tower 4 via a pipeline. The liquid outlet of the separator 2 is connected to the top inlet of the cyclohexanol deweighting tower 3 via a pipeline. The top gas outlet of the cyclohexanol deweighting tower 3 is the second gas outlet of the deweighting system 30, which is connected to the second inlet B of the cyclohexanol distillation tower 4 via a pipeline. The bottom outlet of the cyclohexanol deweighting tower 3 is the liquid outlet of the deweighting system 30, which is connected to a pipeline for conveying a third solution. The inlet of the deweighting tower reboiler 31 is connected to the outlet of the heavy component transfer pump 32 via a pipeline. To prevent entrained catalyst from causing blockage, the cyclohexanol deweighting tower 3 preferably uses anti-blockage tower internals, such as anti-blockage random packing or sieve tray towers.

[0036] In a preferred embodiment, a first condenser 8 is installed on the pipeline transporting the first gas phase, and the first condenser 8 is equipped with a non-condensable gas discharge port. A second condenser 9 is installed on the pipeline transporting the second gas phase, and the second condenser 9 is also equipped with a non-condensable gas discharge port. The outlet of the first gas phase is connected to the first inlet A of the cyclohexanol distillation column 4 via pipelines through the first condenser 8 and the first condensate pump 81. The second condenser 9 is connected to the second inlet B of the cyclohexanol distillation column 4 via pipelines through the second condensate pump 91.

[0037] The specific method for removing heavy components from cyclohexanol is as follows:

[0038] a. The cyclohexanol-containing material from the cyclohexene hydration reaction is distilled, and the first solution I containing cyclohexanol and heavy components is obtained from the bottom of the column;

[0039] b. The first solution I is subjected to a deweighting operation to obtain a third solution III containing heavy components, as well as a first gas phase X and a second gas phase XI, wherein the first gas phase X and the second gas phase XI are substantially free of catalyst and heavy components;

[0040] c. The first gas phase X and the second gas phase XI are subjected to distillation, and the fourth solution IV after the heavy components are removed is obtained in the bottom of the column. The fourth solution IV is cyclohexanol after the heavy components have been removed.

[0041] The above-mentioned deweighting operation includes heating and separating the first solution I to obtain the first gas phase X and the second solution II containing heavy components, and then distilling the second solution II to obtain the second gas phase XI and the third solution III.

[0042] The pressure of the first gas phase is higher than the pressure of the second gas phase; the pressure of the second gas phase is 50-80 kPaA.

[0043] The distillation in the de-weighting operation is stripping, that is, the distillation column only includes the stripping section and not the rectification section, and the feed enters from the top of the column. For details, please refer to the "Handbook".

[0044] The first gas phase and / or the second gas phase are defoamed; the first gas phase and / or the second gas phase are condensed and / or cooled before subsequent distillation, and the condensate is transported to the subsequent distillation.

[0045] In a preferred embodiment, the fourth solution is subjected to distillation to obtain cyclohexanol with heavy components removed in the stripping section of the distillation column, thereby further improving the purity of the cyclohexanol.

[0046] Specifically, the material containing about 10 wt% cyclohexanol from the cyclohexene hydration reaction is distilled in cyclohexanol separation tower 1 at an operating pressure of 40 kPaA. Light components such as methylcyclopentene are obtained at the top of the tower, and a first solution I containing about 75 wt% cyclohexanol is obtained at the bottom of the tower, which contains about 0.4 wt% heavy components and trace amounts of catalyst.

[0047] Separator 2 is used to achieve gas-liquid separation. Those skilled in the art can choose appropriate equipment, such as a batch evaporator. In this embodiment, separator 2 is a gas-liquid separation tank with a heater. A demister is installed at the top of the separation tank. Under a pressure of 100 kPaA, the first solution I is heated to 145°C. The content of heavy components relative to cyclohexanol in the obtained first gas phase X is approximately 0.15 wt%. The operating pressure of the cyclohexanol de-heavy tower 3 is 80 kPaA. A demister is installed at the top of the cyclohexanol de-heavy tower, and the tower bottom temperature is around 160°C. The content of heavy components relative to cyclohexanol in the obtained second gas phase XI is approximately 0.16 wt%. The cyclohexanol content in the third solution III is approximately 65 wt%, containing approximately 4 wt% catalyst. The pressure of the first gas phase X is equal to the operating pressure of separator 2 (100 kPaA), and the pressure of the second gas phase XI is equal to the operating pressure of the cyclohexanol de-heavy tower 3 (80 kPaA).

[0048] The first gas phase X directly enters the cyclohexanol distillation column 4, and the second gas phase XI is condensed and cooled in the second condenser 9. The non-condensable gas is discharged to the cyclohexanol separation column 1, and the condensate is sent to the cyclohexanol distillation column 4. The operating pressure of the cyclohexanol distillation column 4 is 80 kPaA. Light components such as cyclohexene are obtained at the top of the column, and the fourth solution IV obtained at the bottom of the column contains about 99.2 wt% cyclohexanol and about 0.16 wt% heavy components.

[0049] Examples 2-4

[0050] Examples 2-4 provide a method and apparatus for removing heavy components from cyclohexanol, which have the same structure and working principle as Example 1, except for the operating pressure of the cyclohexanol removal tower 3.

[0051]

[0052]

[0053] The pressure in the table is the operating pressure of the cyclohexanol de-heavy tower 3, the cyclohexanol content is the cyclohexanol content in the third solution III, and the fluidity is the visual judgment of the third solution III.

[0054] As the operating pressure of the cyclohexanol deweighting tower 3 gradually decreases, the cyclohexanol content in the third solution III also gradually decreases. In Example 4, the amount of cyclohexanol entrained in the third solution III is already relatively small; based on the entrainment amount of the hydrated catalyst, the catalyst content in the third solution III at this point is approximately 8 wt%. In contrast, the catalyst slurry concentration in the cyclohexene hydration reactor during production is 18–22%, maintaining good fluidity through stirring.

[0055] Cyclohexanol in the third solution III can be further recovered by setting up a negative pressure evaporation device. A thin film evaporator is preferred. The recovered cyclohexanol containing heavy components is returned to the cyclohexanol deweighting tower 3 for deweighting. The thin film evaporator is a relatively common device in related fields.

[0056] Example 5

[0057] This embodiment provides a method and apparatus for removing heavy components from cyclohexanol, which are basically the same as the apparatus and method provided in Embodiment 1, except that:

[0058] The device is based on Example 1, such as Figure 3 As shown, a cyclohexanol light phase removal tower 5 is set up, and the liquid phase outlet of the bottom of the cyclohexanol distillation tower 4 is connected to the cyclohexanol light phase removal tower 5.

[0059] The specific method is to set up a cyclohexanol light component removal tower 5 with an operating pressure of 90 kPaA, and feed the fourth solution IV from the middle of the cyclohexanol light component removal tower 5. Light components such as methylcyclopentanol are obtained at the top of the tower, and cyclohexanol product with a heavy component content of 0.02 wt% is obtained in the side stream of the stripping section.

[0060] The specific embodiments described herein are merely illustrative examples of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention.

Claims

1. A process for the removal of heavy constituents from cyclohexanol, characterized in that, The process comprises the following steps: a. subjecting the cyclohexanol-containing material from the hydration of cyclohexene to rectification, to obtain a first solution containing cyclohexanol and heavy components from the column bottom; b. subjecting the first solution to a heavy component removal operation to obtain a third solution containing heavy components, and a first gas phase and a second gas phase; c. subjecting the first gas phase and the second gas phase to rectification to obtain a fourth solution from the column bottom after the heavy component removal operation, which is the cyclohexanol from which the heavy components have been removed.

2. The method for removing heavy components from cyclohexanol according to claim 1, characterized in that, In step b, the heavy component removal operation comprises subjecting the first solution to a heating separation to obtain the first gas phase and a second solution containing heavy components, and subjecting the second solution to rectification to obtain the second gas phase and the third solution.

3. The process of claim 2 wherein the process is conducted at a temperature of from about 100°C to about 200°C. The pressure of the first gas phase is higher than that of the second gas phase; the pressure of the second gas phase is 50-80 kPaA.

4. The process of claim 2, wherein the process is carried out at a temperature of from about 20°C to about 60°C. The rectification in the heavy component removal operation is stripping.

5. The process of claim 1 wherein, The first gas phase and / or the second gas phase are subjected to defoaming; the first gas phase and / or the second gas phase are subjected to condensation and / or cooling before subsequent rectification, and the condensate is transported to the subsequent rectification.

6. The process of claim 1 wherein, The fourth solution is subjected to rectification to obtain the cyclohexanol from which the heavy components have been removed from the stripping section of the rectification column.

7. An apparatus for use in the process for removing heavy components from cyclohexanol according to any one of claims 1 to 6, characterized in that The process comprises a cyclohexanol separation column (1), a heavy component removal system (30), a cyclohexanol rectification column (4), and a feed pipeline (7) for transporting the hydration product of cyclohexene, the outlet of the feed pipeline (7) being connected to the inlet of the cyclohexanol separation column (1), the liquid phase outlet of the column bottom of the cyclohexanol separation column (1) being connected to the heavy component removal system (30) through a pipeline, the first gas phase outlet of the heavy component removal system (30) being connected to the first inlet of the cyclohexanol rectification column (4) through a pipeline, the second gas phase outlet of the heavy component removal system (30) being connected to the second inlet of the cyclohexanol rectification column (4) through a pipeline, and the liquid phase outlet of the heavy component removal system (30) being connected to the pipeline for transporting the third solution.

8. The apparatus of claim 7, wherein, The heavy component removal system (30) comprises a separator (2) and a cyclohexanol heavy component removal column (3), the cyclohexanol heavy component removal column (3) being provided with a heavy component removal column reboiler (31), the liquid phase outlet of the separator (2) being connected to the top inlet of the cyclohexanol heavy component removal column (3) through a pipeline, the pipeline for transporting the first gas phase being connected to the gas phase outlet of the separator (2), the pipeline for transporting the second gas phase being connected to the overhead gas phase outlet of the cyclohexanol heavy component removal column (3), and the pipeline for transporting the third solution being connected to the column bottom liquid phase outlet of the cyclohexanol heavy component removal column (3).

9. The apparatus of claim 8, wherein, A heavy component transport pump (32) is arranged on the pipeline for transporting the third solution, and the inlet of the heavy component removal column reboiler (31) is connected to the outlet of the heavy component transport pump (32) through a pipeline.

10. The apparatus of claim 8, wherein, A first condenser (8) is arranged on the pipeline for transporting the first gas phase, and the first condenser (8) is provided with a non-condensable gas discharge port; a second condenser (9) is arranged on the pipeline for transporting the second gas phase, and the second condenser (9) is provided with a non-condensable gas discharge port; and the column bottom liquid phase outlet of the cyclohexanol rectification column (4) is connected to a cyclohexanol light component removal column (5).

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