A method for separating cyclohexanol and phenol by extractive distillation

Abstract

The application provides a method for separating cyclohexanol and phenol by extractive rectification, relates to the field of chemical separation technology, and selects alcohol solvents such as ethylene glycol as extractants for extractive rectification, changes the relative volatility among components, effectively overcomes the defect that the conventional rectification technology is difficult to separate due to the highest azeotropic point of cyclohexanol and phenol, and can obtain cyclohexanol and phenol products with high purity and high yield. The purity of the cyclohexanol product is greater than or equal to 99.5 wt%, the purity of the phenol product is greater than or equal to 99.95 wt%, and the product yield is greater than or equal to 98%. The separation process is simple and efficient, the solvent can be recycled, and the method has good economic benefits and application prospect.

Description

Technical Field

[0001] This invention relates to the field of chemical separation technology, specifically to a method for separating cyclohexanol and phenol by extractive distillation. Background Technology

[0002] Cyclohexanol is an important industrial raw material, mainly used as a solvent in the fields of synthetic rubber, synthetic resin, coatings and paints. It is also an important raw material for the production of caprolactam and adipic acid.

[0003] Currently, the main methods for producing cyclohexanol include cyclohexane oxidation, cyclohexene hydration, and phenol hydrogenation. Cyclohexane oxidation uses cyclohexane as a raw material and oxidizes it with air or oxygen to obtain cyclohexanol. This method has disadvantages such as complex process flow, high energy consumption, and serious environmental pollution. Cyclohexene hydration uses cyclohexene as a raw material and reacts it with water in the presence of a catalyst to produce cyclohexanol. This method has advantages such as safety and environmental friendliness, but its conversion rate is low, approximately 8-12%. For many years, researchers have been dedicated to improving the conversion rate of the cyclohexene hydration reaction to increase production efficiency. Because cyclohexene has very low solubility in water (only 0.02 wt% at 25°C), the cyclohexene hydration reaction is significantly limited. Japanese patents JP-A-62-120333 and JP-A-62-126141 propose adding phenol as an auxiliary agent to the hydration reaction, which can effectively improve the conversion rate of cyclohexanol. However, due to the high azeotropic point between cyclohexanol and phenol, separation using conventional distillation methods is difficult, limiting its application. The phenol hydrogenation method, using phenol as a raw material and hydrogenating it under the action of a catalyst to produce cyclohexanol, was the earliest industrialized method for producing cyclohexanol. However, due to the shortage and high price of phenol, it was gradually surpassed by other methods.

[0004] In recent years, with the advancement of the global "dual carbon" strategy, in order to improve the competitiveness and sustainable development capabilities of the industry, domestic enterprises have accelerated the pace of industrial upgrading and transformation, and a number of integrated refining and chemical enterprises have emerged, broadening the sources of phenol and making the phenol-to-cyclohexanol process increasingly economical and competitive in the market.

[0005] However, the efficient and economical separation of cyclohexanol and phenol is a technical problem that urgently needs to be solved. Summary of the Invention

[0006] In view of the problems existing in the prior art, the present invention provides a method for extractive distillation to separate cyclohexanol and phenol. Ethylene glycol and other alcohol solvents are used as extractants for extractive distillation, which changes the relative volatility between the components. This effectively overcomes the drawback of conventional distillation techniques being difficult to separate cyclohexanol and phenol due to their highest azeotropic points. The method can obtain high-purity and high-yield cyclohexanol and phenol products, with a purity of ≥99.5 wt% for cyclohexanol and ≥99.95 wt% for phenol, and a product yield of ≥98%. The separation process is simple and efficient, and the solvent is recycled, resulting in good economic benefits and application prospects.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] The purpose of this invention is to provide a method for extractive distillation to separate cyclohexanol and phenol, the method comprising the following steps:

[0009] A mixture of cyclohexanol and phenol is fed into the middle section of an extractive distillation column. The lean solvent from the solvent recovery column is fed into the upper section of the extractive distillation column. The cyclohexanol product is collected from the top of the column, and the rich solvent from the bottom of the column is fed into the middle section of the solvent recovery column.

[0010] The solvent recovery tower separates phenol from the solvent. Phenol product is collected from the top of the tower, and the lean solvent is collected from the bottom of the tower and exchanged with the mixed raw material for heat. After being cooled by a cooler, it is recycled to the upper part of the extractive distillation tower.

[0011] The solvent is any one or a combination of at least two of the following: ethylene glycol, 1,3-propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-octanediol, diethylene glycol, or triethylene glycol.

[0012] The method described in this invention uses alcohol solvents such as ethylene glycol as extractants for extractive distillation, which changes the relative volatility between components. This effectively overcomes the drawback of conventional distillation techniques, which make separation difficult due to the highest azeotropic point of cyclohexanol and phenol. The method can obtain high-purity and high-yield cyclohexanol and phenol products, with a purity of ≥99.5 wt% for cyclohexanol and ≥99.95 wt% for phenol, and a product yield of ≥98%. The separation process is simple and efficient, and the solvent can be recycled, resulting in good economic benefits and application prospects.

[0013] It should be noted that in this invention, the cyclohexanol and phenol in the mixed raw materials can be mixed in any proportion, and there are no excessive restrictions.

[0014] As a preferred embodiment of the present invention, the temperature of the lean solvent entering the upper part of the extractive distillation column is 25-120°C, for example, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, or 120°C, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0015] As a preferred embodiment of the present invention, the solvent / raw material mass ratio of the lean solvent entering the upper part of the extractive distillation column is 0.1 to 10, for example, 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5 or 10, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0016] As a preferred embodiment of the present invention, the operating conditions of the extractive distillation column are as follows: the number of theoretical plates is 10 to 70, for example, 10, 20, 30, 40, 50, 60, or 70, etc.; the operating pressure at the top of the column is -0.04 to -0.099 MPa(G), for example, -0.04 MPa(G), -0.045 MPa(G), -0.05 MPa(G), -0.055 MPa(G), -0.06 MPa(G), -0.065 MPa(G), -0.07 MPa(G), -0.075 MPa(G), -0.08 MPa(G), - The pressure is 0.085MPa(G), -0.09MPa(G), or -0.099MPa(G), etc., and the reboiler operating temperature is 100 to 250℃, such as 100℃, 130℃, 150℃, 180℃, 200℃, 220℃, or 250℃, etc., and the reflux ratio is 0.1 to 10, such as 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, or 10, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0017] As a preferred embodiment of the present invention, the feed position of the lean solvent into the extractive distillation column is the 2nd to 15th theoretical plates below the top of the column, and above the feed position of the mixed raw materials.

[0018] As a preferred embodiment of the present invention, the operating conditions of the solvent recovery tower are as follows: the number of theoretical plates is 10 to 60, for example, 10, 20, 30, 40, 50, or 60, and the operating pressure at the top of the tower is -0.03 to -0.0998 MPa(G), for example, -0.035 MPa(G), -0.04 MPa(G), -0.045 MPa(G), -0.05 MPa(G), -0.055 MPa(G), -0.06 MPa(G), -0.065 MPa(G), -0.07 MPa(G), -0.075 MPa(G), or -0.08 MPa. (G), -0.085MPa(G), -0.09MPa(G) or -0.098MPa(G), etc., with a reboiler operating temperature of 100 to 250℃, such as 100℃, 130℃, 150℃, 180℃, 200℃, 220℃ or 250℃, etc., and a reflux ratio of 0.1 to 10, such as 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5 or 10, etc., but not limited to the listed values, other unlisted values ​​within the above range are also applicable.

[0019] As a preferred embodiment of the present invention, the purity of the cyclohexanol product is ≥99.5wt%, and the purity of the phenol product is ≥99.95wt%.

[0020] As a preferred technical solution of the present invention, the method for separating cyclohexanol and phenol by extraction distillation is a continuous process.

[0021] As a preferred embodiment of the present invention, before exchanging heat with the mixed raw materials, a portion of the lean solvent is continuously discharged. The continuous discharge amount of the lean solvent is 0.1 to 20 wt% of the total circulating solvent, for example, 0.1 wt%, 0.5 wt%, 1 wt%, 3 wt%, 5 wt%, 7 wt%, 10 wt%, 12 wt%, 15 wt%, 18 wt%, or 20 wt%, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0022] It should be noted that in this invention, due to long-term operation at high temperature, the solvent may coke or deteriorate. It is necessary to continuously discharge part of the solvent according to the actual operating conditions, and control the continuous discharge amount to be 0.1 to 20 wt% of the total circulating solvent. Alternatively, intermittent complete discharge and regeneration can be carried out according to the actual operating conditions. Those skilled in the art can make reasonable choices.

[0023] As a preferred embodiment of the present invention, before the lean solvent exchanges heat with the mixed raw materials, fresh solvent is added to replenish it. The amount of fresh solvent added is 0.1 to 20 wt% of the total circulating solvent, for example, 0.1 wt%, 0.5 wt%, 1 wt%, 3 wt%, 5 wt%, 7 wt%, 10 wt%, 12 wt%, 15 wt%, 18 wt%, or 20 wt%, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0024] It should be noted that, in this invention, due to the long-term operation at high temperature, some solvent will be lost during the extraction and distillation process. Fresh solvent needs to be replenished according to the actual operating conditions, and the replenishment amount should be controlled to be 0.1 to 20 wt% of the total circulating solvent to ensure good extraction effect of the extractant.

[0025] Compared with existing technical solutions, the present invention has at least the following beneficial effects:

[0026] (1) The method for separating cyclohexanol and phenol by extractive distillation of the present invention uses alcohol solvents such as ethylene glycol as extractants for extractive distillation, which changes the relative volatility between the components and effectively overcomes the defect that the highest azeotropic point of cyclohexanol and phenol makes it difficult to separate them by conventional distillation techniques.

[0027] (2) The method for separating cyclohexanol and phenol by extraction distillation described in this invention can obtain cyclohexanol and phenol products with high purity and high yield. The purity of the cyclohexanol product is ≥99.5wt%, the purity of the phenol product is ≥99.95wt%, and the product yield is ≥98%.

[0028] (3) The method for separating cyclohexanol and phenol by extraction distillation described in this invention is simple and efficient in separation process, has a wide range of solvent sources and can be recycled, and has a simple regeneration process, which has good economic benefits and application prospects. Attached Figure Description

[0029] Figure 1 This is a process flow diagram of the extraction and distillation method for separating cyclohexanol and phenol according to a specific embodiment of the present invention;

[0030] In the diagram: C-101 is the extractive distillation column, C-102 is the solvent recovery column, E-101 is the feed preheater, E-102 is the extractive distillation column condenser, E-103 is the extractive distillation column reboiler, E-104 is the solvent recovery column condenser, E-105 is the solvent recovery column reboiler, E-106 is the cooler, P-101 is the extractive distillation column reflux pump, P-102 is the extractive distillation column bottom liquid pump, P-103 is the solvent recovery column reflux pump, and P-104 is the solvent recovery column bottom liquid pump.

[0031] In the diagram, 1 represents the mixed feedstock of cyclohexanol and phenol; 2 represents the vapor phase at the top of the extractive distillation column; 3 represents the reflux at the top of the extractive distillation column; 4 represents the top product from the extractive distillation column; 5 represents the bottom liquid from the extractive distillation column; 6 represents the bottom liquid circulation from the extractive distillation column; 7 represents the feed to the solvent recovery column; 8 represents the vapor phase at the top of the solvent recovery column; 9 represents the reflux at the top of the solvent recovery column; 10 represents the top product from the solvent recovery column; 11 represents the bottom liquid from the solvent recovery column; 12 represents the bottom liquid circulation from the solvent recovery column; 13 represents the lean solvent circulating feed; 14 represents the replenishment of fresh solvent; and 15 represents the lean solvent discharge. Detailed Implementation

[0032] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0033] To better illustrate the present invention and facilitate understanding of its technical solutions, typical but non-limiting embodiments of the present invention are as follows:

[0034] This invention provides a specific embodiment, and the process flow diagram of the method for separating cyclohexanol and phenol by extractive distillation is shown below. Figure 1 As shown, the method includes the following steps:

[0035] A mixture of cyclohexanol and phenol feedstock 1 is fed into the middle of extractive distillation column C-101. Lean solvent from solvent recovery column C-102 is fed into the upper part of extractive distillation column C-101. The vapor phase 2 at the top of the extractive distillation column is first condensed by extractive distillation column condenser E-102, and then pressurized by extractive distillation column reflux pump P-101. Part of it is used as extractive distillation column reflux 3, and the other part is used as extractive distillation column top product 4, that is, cyclohexanol product is collected at the top of the column. The liquid at the bottom of the extractive distillation column 5 is first reboiled by extractive distillation column reboiler E-103, and then pressurized by extractive distillation column bottom liquid pump P-102. Part of it is used as extractive distillation column bottom liquid circulation 6, and the other part is used as solvent recovery column feed 7. That is, the rich solvent at the bottom of extractive distillation column C-101 is fed into the middle of solvent recovery column C-102.

[0036] The solvent recovery tower C-102 separates phenol from the solvent. The gas phase 8 at the top of the solvent recovery tower is condensed by the solvent recovery tower condenser E-104 and then pressurized by the solvent recovery tower reflux pump P-103. Part of it is used as the solvent recovery tower top reflux 9, and the other part is used as the solvent recovery tower top product 10, i.e., the phenol product is collected at the top of the tower. The liquid at the bottom of the solvent recovery tower 11 is first reboiled by the solvent recovery tower reboiler E-105 and then pressurized by the solvent recovery tower bottom liquid pump P-104. Part of it is used as the solvent recovery tower bottom liquid circulation 12, and the other part is used as the lean solvent circulation feed 13. It first exchanges heat with the mixed raw material 1 of cyclohexanol and phenol through the raw material preheater E-101, and then is cooled by the cooler E-106 before entering the upper part of the extractive distillation tower C-101 for recycling. Moreover, before entering the raw material preheater E-101, the lean solvent circulation feed 13 will also remove part of the lean solvent for discharge 15 and replenish fresh solvent 14.

[0037] The solvent is any one or a combination of at least two of the following: ethylene glycol, 1,3-propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-octanediol, diethylene glycol, or triethylene glycol.

[0038] Example 1

[0039] This embodiment provides a method for extractive distillation to separate cyclohexanol and phenol, the method comprising the following steps:

[0040] A mixture of cyclohexanol and phenol is fed into the middle section of an extractive distillation column. The lean solvent from the solvent recovery column is fed into the upper section of the extractive distillation column. The cyclohexanol product is collected from the top of the column, and the rich solvent from the bottom of the column is fed into the middle section of the solvent recovery column.

[0041] The solvent recovery tower separates phenol from the solvent. Phenol product is collected from the top of the tower, and the lean solvent is collected from the bottom of the tower and exchanged with the mixed raw material for heat. After being cooled by a cooler, it is recycled to the upper part of the extractive distillation tower.

[0042] In the mixed feedstock of cyclohexanol and phenol, the mass percentage of cyclohexanol is 50 wt% and the mass percentage of phenol is 50 wt%; the solvent is 1,4-butanediol; the temperature of the lean solvent entering the upper part of the extractive distillation column is 60°C; the solvent / feed mass ratio of the lean solvent entering the upper part of the extractive distillation column is 0.8.

[0043] The operating conditions of the extractive distillation column are as follows: 38 theoretical plates, the feed position of the mixed raw material is the 17th theoretical plate, the feed position of the lean solvent is the 10th theoretical plate, the operating pressure at the top of the column is -0.086 MPa(G), the operating temperature at the bottom of the column is 170℃, and the reflux ratio is 2; the operating conditions of the solvent recovery column are as follows: 38 theoretical plates, the feed position of the rich solvent is the 19th theoretical plate, the operating pressure at the top of the column is -0.09 MPa(G), the operating temperature at the bottom of the column is 170℃, and the reflux ratio is 2.5.

[0044] The method described in this embodiment can obtain high-purity and high-yield cyclohexanol and phenol products. The purity of the cyclohexanol product is 99.5 wt%, and the yield of the cyclohexanol product is 99.0%. The purity of the phenol product is 99.95 wt%, and the yield of the phenol product is 98.9%.

[0045] Compared to the method described in Example 1, Examples 2 to 6 respectively provide a method for extractive distillation to separate cyclohexanol and phenol, and the relevant process parameters, product purity and yield results of Examples 1 to 6 are summarized in Table 1.

[0046] Table 1

[0047]

[0048]

[0049] Comparative Examples 1 and 2 respectively provide a conventional distillation method for separating cyclohexanol and phenol. The mixed feedstock of cyclohexanol and phenol is fed into the middle of a conventional distillation column. The cyclohexanol product is collected from the top of the column, and the phenol product is collected from the bottom of the column. The specific process parameters, product purity and yield results are summarized in Table 2.

[0050] Table 2

[0051]

[0052] As can be seen from Table 2, due to the highest azeotropic point between cyclohexanol and phenol, conventional distillation techniques are difficult to separate them, resulting in low purity, low yield, or even inability to separate the cyclohexanol and phenol products.

[0053] In summary, the extractive distillation method for separating cyclohexanol and phenol described in this invention uses alcohol solvents such as ethylene glycol as extractants, thereby altering the relative volatility between the components. This effectively overcomes the drawback of conventional distillation techniques, which struggle to separate cyclohexanol and phenol due to their shared azeotropic point. The method yields high-purity and high-yield cyclohexanol and phenol products, with a purity of ≥99.5 wt% for cyclohexanol and ≥99.95 wt% for phenol, and a product yield of ≥98%. The separation process is simple and efficient, the solvent is recycled, and the regeneration process is straightforward, demonstrating good economic benefits and promising application prospects.

[0054] The present invention has been illustrated with the above embodiments to illustrate its detailed structural features. However, the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0055] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0056] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable way without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0057] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for separating cyclohexanol and phenol by extractive distillation, characterized in that, The method includes the following steps: A mixture of cyclohexanol and phenol is fed into the middle section of an extractive distillation column. The lean solvent from the solvent recovery column is fed into the upper section of the extractive distillation column. The cyclohexanol product is collected from the top of the column, and the rich solvent from the bottom of the column is fed into the middle section of the solvent recovery column. The solvent recovery tower separates phenol from the solvent. Phenol product is collected from the top of the tower, and the lean solvent is collected from the bottom of the tower and exchanged with the mixed raw material for heat. After being cooled by a cooler, it is recycled to the upper part of the extractive distillation tower. The solvent is any one or a combination of at least two of the following: ethylene glycol, 1,3-propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-octanediol, diethylene glycol, or triethylene glycol. The operating conditions of the extractive distillation column are as follows: theoretical plate number of 10 to 70, column top operating pressure of -0.04 to -0.099 MPa(G), column bottom operating temperature of 100 to 250℃, and reflux ratio of 0.1 to 10. The operating conditions of the solvent recovery tower are as follows: theoretical plate number of 10 to 60, tower top operating pressure of -0.03 to -0.0998 MPa(G), tower bottom operating temperature of 100 to 250℃, and reflux ratio of 0.1 to 10.

2. The method for separating cyclohexanol and phenol by extractive distillation according to claim 1, characterized in that, The temperature of the lean solvent entering the upper part of the extractive distillation column is 25–120°C.

3. The method for separating cyclohexanol and phenol by extractive distillation according to claim 1, characterized in that, The solvent / feed mass ratio of the lean solvent entering the upper part of the extractive distillation column is 0.1 to 10.

4. The method for separating cyclohexanol and phenol by extractive distillation according to claim 1, characterized in that, The lean solvent enters the extractive distillation column at the 2nd to 15th theoretical plates below the top of the column, and is located above the feed position of the mixed raw material.

5. The method for separating cyclohexanol and phenol by extractive distillation according to claim 1, characterized in that, The purity of the cyclohexanol product is ≥99.5 wt%, and the purity of the phenol product is ≥99.95 wt%.

6. The method for separating cyclohexanol and phenol by extractive distillation according to claim 1, characterized in that, The method for separating cyclohexanol and phenol by extraction distillation is a continuous process.

7. The method for separating cyclohexanol and phenol by extractive distillation according to claim 6, characterized in that, Before exchanging heat with the mixed raw materials, a portion of the lean solvent is continuously discharged, and the continuous discharge amount of the lean solvent is 0.1 to 20 wt% of the total circulating solvent.

8. The method for separating cyclohexanol and phenol by extractive distillation according to claim 1, characterized in that, Before exchanging heat with the mixed raw materials, the lean solvent is replenished with fresh solvent, and the amount of fresh solvent added is 0.1 to 20 wt% of the total circulating solvent.

Images