Method for separating cyclohexane, cyclohexanone and cyclohexanol

Abstract

The invention relates to a method for separating cyclohexane, cyclohexanol and cyclohexanone. According to the method disclosed by the invention, a selective solvent and a cyclohexane oxidation product are in countercurrent contact in an extraction tower, so that an extraction phase obtained from a tower kettle of the extraction tower sequentially passes through a stripping tower and a solvent recovery tower to obtain a mixture of cyclohexanol and cyclohexanone, and meanwhile, an extraction solvent is further purified through rectification of a solvent rectification tower and flash evaporation of a solvent regeneration tank. The purity of the cyclohexanol and cyclohexanone mixture obtained through the method is higher than 99%, the mass yield is higher than 95%, a caustic soda solution does not need to be added in the separation process, and emission of three wastes and environmental pollution are avoided; impurities in the circulating solvent are further separated, so that the stability of the circulating solvent is improved, and the device can run for a long period.

Description

Technical Field

[0001] The present disclosure relates to the field of fine chemicals, and in particular to a method for separating cyclohexane from cyclohexanone and cyclohexanol. Background Art

[0002] In the cyclohexane oxidation process for producing cyclohexanone, the oxidation step in the cyclohexane oxidation unit produces a product primarily composed of cyclohexyl hydroperoxide. After alkaline treatment and separation, the oxidation liquid yields an organic phase primarily composed of cyclohexane, cyclohexanol, and cyclohexanone. The traditional process uses a triple-effect distillation-saponification-extraction-drying process to separate the cyclohexanol and cyclohexanone from the organic phase, yielding a 98% alcohol-ketone mixture that feeds the cyclohexanone refining unit. The addition of caustic soda during the saponification process causes polycondensation of the cyclohexanol and cyclohexanone. Discharge of the waste caustic soda results in loss of both cyclohexanol and cyclohexanone, resulting in a final yield of only 90%. Furthermore, incineration of the waste caustic soda also results in the emission of three wastes and environmental pollution. Therefore, adopting a new process for separating cyclohexanone from cyclohexanone is of great significance. In addition, in the organic phase obtained by cyclohexane oxidation-alkali decomposition-waste alkali liquid separation, in addition to cyclohexanol and cyclohexanone, unconverted cyclohexane accounts for the vast majority. In addition, it also contains a small amount of aldehydes, ketones, acids, alcohols, esters and other hundreds of oxygen-containing compound impurities. The presence of impurities affects the quality of the circulating solvent, and over time, affects the stability of the device operation.

[0003] Patent CN101505844A discloses a method for separating alcohols from cycloalkanes, ketones from cycloalkanes, and alcohol-ketones from cycloalkanes using ionic liquid extraction. The alcohol-ketones are cyclohexanol, cyclohexanone, cyclododecanol, or cyclododecanone, and the cycloalkanes are cyclohexane or cyclododecane. This method does not address the separation of oxygenate impurities in cyclohexane oxidation products. Summary of the Invention

[0004] The purpose of the present disclosure is to provide a method for separating cyclohexane from cyclohexanol and cyclohexanone, wherein the purity of the cyclohexanol and cyclohexanone mixture obtained by the method is higher than 99% and the mass yield is higher than 95%.

[0005] In order to achieve the above object, the present disclosure provides a method for separating cyclohexane from cyclohexanol and cyclohexanone, the method comprising the following steps:

[0006] (a) allowing the material to be separated to enter an extraction tower, contact it with an extraction solvent in countercurrent from bottom to top, obtain raffinate oil from the top of the tower, and obtain a first rich solvent from the bottom of the tower; allowing the raffinate oil to enter a water washing tower for water washing to obtain wash water and washed raffinate oil containing cyclohexane;

[0007] (b) allowing the first rich solvent to enter a stripping tower for stripping, obtaining a light component containing cyclohexane from the top of the stripping tower, and obtaining a second rich solvent from the bottom of the stripping tower; allowing the second rich solvent to enter a solvent recovery tower for distillation, obtaining a separated product containing cyclohexanone and cyclohexanol from the top of the solvent recovery tower, and obtaining a first lean solvent from the bottom of the solvent recovery tower;

[0008] (c) returning a portion of the first lean solvent to the extraction column and allowing the remainder of the first lean solvent to enter a solvent purification unit to remove impurities;

[0009] The solvent purification unit comprises a solvent distillation tower and a solvent regeneration tank; the substance to be separated is the organic phase obtained by separating the oxidation liquid of the cyclohexane oxidation unit after alkali treatment.

[0010] Optionally, the material to be separated comprises, by mass fraction, 3% to 8% of cyclohexanol and cyclohexanone, 91.5% to 96.9% of cyclohexane and 0.1% to 0.5% of impurities; the impurities comprise one or more of alcohols, aldehydes, ketones, acids and esters.

[0011] Optionally, the extraction solvent is selected from an organic solvent with a boiling point of 300° C. or above; and the extraction solvent contains 0.1% to 10% by mass of water.

[0012] Optionally, the extraction solvent is selected from alcohol solvents with a carbon number of 6 to 14. Preferably, the extraction solvent is tetraethylene glycol and / or pentaethylene glycol.

[0013] Optionally, the method comprises: returning the washed raffinate oil from the water scrubber to the cyclohexane oxidation unit;

[0014] The light component containing cyclohexane from the stripping tower is cooled and then enters a reflux tank for phase separation to obtain an aqueous phase and a first oil phase containing cyclohexane. The aqueous phase is returned to the water washing tower, a portion of the first oil phase is returned to the stripping tower, and another portion of the first oil phase is returned to the cyclohexane oxidation unit.

[0015] Optionally, in step (a), the mass ratio of the extraction solvent to the object to be separated is 0.5 to 2:1; the inlet temperature of the extraction solvent to the tower is 40°C to 80°C, the inlet temperature of the object to be separated to the tower is 40°C to 80°C, and the number of theoretical plates of the extraction tower is 5 to 15.

[0016] Optionally, in step (b), in the stripping tower, the absolute pressure at the top of the stripping tower is 0.1 MPa to 0.2 MPa, the reflux ratio is 0.1 to 1, and the bottom temperature is 120° C. to 160° C.;

[0017] In the solvent recovery tower, the absolute pressure at the top of the solvent recovery tower is 0.01 MPa to 0.06 MPa, the reflux ratio is 0.1 to 1, and the tower bottom temperature is 150° C. to 190° C.

[0018] Optionally, the method further includes:

[0019] The washed water from the water scrubber enters a water stripping tower for stripping to obtain wash water and solvent-enriched water; the wash water is returned to the water scrubber, a portion of the solvent-enriched water is returned to the stripping tower, and the remaining portion of the solvent-enriched water enters the solvent regeneration tank;

[0020] The remaining portion of the first lean solvent from the solvent recovery tower enters the solvent distillation tower for distillation, and the first impurities are obtained from the top of the tower, and the second lean solvent is obtained from the bottom of the tower; the second lean solvent enters the solvent regeneration tank for flash evaporation, and a flash gas phase is obtained from the top of the solvent regeneration tank. The flash gas phase is returned to the solvent recovery tower, and the second impurities are discharged from the bottom of the solvent regeneration tank.

[0021] Optionally, the mass of the first lean solvent entering the solvent distillation tower accounts for 0.1% to 5% of the total mass of the first lean solvent.

[0022] Optionally, the absolute pressure at the top of the solvent distillation tower is 0.001 MPa to 0.01 MPa, the bottom temperature is 190 to 230° C., the reflux ratio is 2 to 10, and the number of theoretical plates is 40 to 80;

[0023] The absolute pressure of the solvent regeneration tank is 0.001 MPa to 0.01 MPa, and the temperature is 200° C. to 250° C.

[0024] Optionally, the mass ratio of the enriched solvent water entering the solvent regeneration tank to the mass ratio of the second lean solvent entering the solvent regeneration tank is 2 to 4:1.

[0025] Through the above technical solution, the present invention achieves a mixture of cyclohexanol and cyclohexanone by bringing the selective solvent and the product to be separated into countercurrent contact within an extraction tower, passing the extract phase obtained from the extraction tower kettle sequentially through a stripping tower and a solvent recovery tower. Simultaneously, the extraction solvent is further purified by distillation in a solvent distillation tower and flash evaporation in a solvent regeneration tank to separate impurities from the circulating solvent. The cyclohexanol and cyclohexanone mixture obtained by the disclosed method has a purity exceeding 99% and a mass yield exceeding 95%. The addition of caustic soda solution during the separation process avoids the discharge of three wastes and environmental pollution. This further improves the stability of the circulating solvent, enabling the device to operate over a long period of time.

[0026] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following detailed description, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings:

[0028] Figure 1 It is a schematic flow chart of the separation process in Example 1 of the present disclosure.

[0029] Figure 2 It is a schematic flow chart of the separation process in Comparative Example 1 of the present disclosure.

[0030] Description of Reference Numerals

[0031] 1: Feedstock inlet; 2: Solvent inlet; 3: Raffinate; 4: First rich solvent; 5: A portion of the oil phase; 6: Another portion of the oil phase; 7: Water phase; 8: Second rich solvent; 9: Separate; 10: The remainder of the first lean solvent; 11: First impurity; 12: Second lean solvent; 13: Raffinate after washing; 14: Wash water; 15: Wash water; 16: A portion of the enriched solvent water; 17: The remainder of the enriched solvent water; 18: Flash gas phase;

[0032] 101: extraction tower; 102: stripping tower; 103: water washing tower; 104: solvent recovery tower; 105: solvent distillation tower; 106: water stripping tower; 107: solvent regeneration tank. DETAILED DESCRIPTION

[0033] The following describes the specific embodiments of the present disclosure in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure and are not intended to limit the present disclosure.

[0034] The present disclosure provides a method for separating cyclohexane, cyclohexanol and cyclohexanone, the method comprising the following steps:

[0035] (a) allowing the material to be separated to enter an extraction tower, contact it with an extraction solvent in countercurrent from bottom to top, obtain raffinate oil from the top of the tower, and obtain a first rich solvent from the bottom of the tower; allowing the raffinate oil to enter a water washing tower for water washing to obtain wash water and washed raffinate oil containing cyclohexane;

[0036] (b) allowing the first rich solvent to enter a stripping tower for stripping, obtaining a light component containing cyclohexane from the top of the stripping tower, and obtaining a second rich solvent from the bottom of the stripping tower; allowing the second rich solvent to enter a solvent recovery tower for distillation, obtaining a separated product containing cyclohexanone and cyclohexanol from the top of the solvent recovery tower, and obtaining a first lean solvent from the bottom of the solvent recovery tower;

[0037] (c) returning a portion of the first lean solvent to the extraction column and allowing the remainder of the first lean solvent to enter a solvent purification unit to remove impurities;

[0038] The solvent purification unit comprises a solvent distillation tower and a solvent regeneration tank; the substance to be separated is the organic phase obtained by separating the oxidation liquid of the cyclohexane oxidation unit after alkali treatment.

[0039] The present invention involves countercurrently contacting a selective solvent with the product to be separated within an extraction tower, passing the extract phase from the extraction tower kettle sequentially through a stripping tower and a solvent recovery tower to produce a mixture of cyclohexanol and cyclohexanone. Simultaneously, the extraction solvent is further purified by distillation in a solvent distillation tower and flash evaporation in a solvent regeneration tank to separate impurities from the circulating solvent. The resulting cyclohexanol and cyclohexanone mixture has a purity exceeding 99% and a mass yield exceeding 95%. The separation process eliminates the need for caustic soda solution, preventing the discharge of three wastes and environmental pollution. This further improves the stability of the circulating solvent, enabling the device to operate over a long period of time.

[0040] According to the present disclosure, the oxidizing liquid is subjected to alkaline decomposition and then separated by water washing to obtain an organic phase mainly containing cyclohexane, cyclohexanol and cyclohexanone. By mass fraction, the substances to be separated include 3% to 8% of cyclohexanol and cyclohexanone, 91.5% to 96.9% of cyclohexane and 0.1% to 0.5% of impurities, and the impurities include one or more of alcohols, aldehydes, ketones, acids and esters. The inventors of this application found that compared with cyclohexane, cyclohexanone and cyclohexanol have stronger polarity, and a liquid-liquid extraction process can be used to separate cyclohexanone, cyclohexanol and cyclohexane. Since the organic phase also contains 0.1% to 0.3% of various impurities such as aldehydes, ketones, alcohols, acids, esters, etc., and the boiling point of these impurities usually does not exceed 300°C, an extractant with a boiling point higher than 300°C can be selected, and a solvent distillation tower is added to separate the solvent and impurities through precise distillation under high vacuum conditions, ensuring the quality of the circulating solvent and the long-term operation of the device.

[0041] According to one embodiment of the present disclosure, the extraction solvent is selected from an organic solvent with a boiling point of 300°C or higher; the extraction solvent contains 0.1% to 10% water by mass. In one embodiment, the extraction solvent is selected from an alcohol solvent having 6 to 14 carbon atoms, preferably tetraethylene glycol and / or pentaethylene glycol. This embodiment improves the selectivity of the extraction solvent and increases the purity of the cyclohexanol and cyclohexanone mixture.

[0042] According to one embodiment of the present disclosure, the method includes: returning the washed raffinate oil to the cyclohexane oxidation unit to allow the cyclohexane therein to continue to react.

[0043] According to one embodiment of the present disclosure, the method includes: passing the cyclohexane-containing light fraction from the stripping column into a reflux drum for phase separation to produce an aqueous phase and an oil phase containing cyclohexane; returning the aqueous phase to the water scrubber; returning a portion of the oil phase to the stripping column; and returning another portion of the oil phase to the cyclohexane oxidation unit. This embodiment is conducive to improving the mass yield of the cyclohexanol and cyclohexanone mixture.

[0044] According to one embodiment of the present disclosure, in step (a), the mass ratio of the extraction solvent to the substance to be separated is 0.5 to 2:1, preferably 1.0 to 1.8:1; the extraction solvent is introduced into the tower at a temperature of 40°C to 80°C, preferably 40 to 60°C; the substance to be separated is introduced into the tower at a temperature of 40°C to 80°C, preferably 40 to 60°C; and the extraction tower has a theoretical plate number of 5 to 15, preferably 7 to 14. The above embodiment is conducive to improving the mass yield of the cyclohexanol and cyclohexanone mixture.

[0045] According to one embodiment of the present disclosure, in step (b), in the stripping tower, the absolute pressure at the top of the stripping tower is 0.1 MPa to 0.2 MPa, preferably 0.1 MPa to 0.15 MPa; the reflux ratio is 0.1 to 1, preferably 0.3 to 0.8; the bottom temperature is 120° C. to 160° C., preferably 130 to 150° C.; and the number of theoretical plates is 15 to 25, preferably 15 to 20. The above embodiment is conducive to improving the mass yield of the cyclohexanol and cyclohexanone mixture.

[0046] According to one embodiment of the present disclosure, in step (b), in the solvent recovery tower, the absolute pressure at the top of the solvent recovery tower is 0.01 MPa to 0.06 MPa, preferably 0.02 MPa to 0.05 MPa; the reflux ratio is 0.1 to 1, preferably 0.2 to 0.6:1; the bottom temperature is 150° C. to 190° C., preferably 160° C. to 190° C.; and the number of theoretical plates is 15 to 25, preferably 15 to 20. The above embodiment is conducive to improving the mass yield of the cyclohexanol and cyclohexanone mixture.

[0047] According to one embodiment of the present disclosure, in order to further recover the extraction solvent and reuse the washing water, the method further includes: allowing the washed water from the bottom of the water washing tower to enter a water stripping tower for stripping to obtain washing water and enriched solvent water; returning the washing water to the water washing tower, returning a portion of the enriched solvent water to the stripping tower, and allowing the rest of the enriched solvent water to enter the solvent regeneration tank.

[0048] According to one embodiment of the present disclosure, the method further includes: passing the remaining portion of the first lean solvent from the solvent recovery tower into the solvent distillation tower for distillation, obtaining a first impurity containing primarily alcohols, aldehydes, ketones, and acids at the top of the tower, and obtaining a second lean solvent at the bottom of the tower; passing the second lean solvent into the solvent regeneration tank for flash evaporation, obtaining a flash vapor phase from the top of the solvent regeneration tank, returning the flash vapor phase to the solvent recovery tower, and discharging a second impurity containing primarily heavy alcohols and esters from the bottom of the solvent regeneration tank. The above embodiment is conducive to improving the purity of cyclohexanol and cyclohexanone, further enhancing the quality of the circulating solvent.

[0049] According to one embodiment of the present disclosure, the mass of the first lean solvent entering the solvent distillation tower accounts for 0.1% to 5%, preferably 0.5% to 3%, of the total mass of the first lean solvent. The above embodiment is conducive to improving the purity of cyclohexanol and cyclohexanone, and further improving the quality of the circulating solvent.

[0050] According to one embodiment of the present disclosure, the absolute pressure at the top of the solvent distillation tower is 0.001 MPa to 0.01 MPa, preferably 0.003 to 0.009 MPa; the bottom temperature is 190 to 230°C, preferably 200 to 220°C; the reflux ratio is 2 to 10, preferably 3 to 6; the number of theoretical plates is 40 to 80, preferably 50 to 70; the absolute pressure of the solvent regeneration tank is 0.001 MPa to 0.01 MPa, preferably 0.001 to 0.005 MPa, and the temperature is 200 to 250°C, preferably 210 to 240°C. The above embodiment is conducive to improving the purity of cyclohexanol and cyclohexanone, and further improving the quality of the circulating solvent.

[0051] According to one embodiment of the present disclosure, the mass ratio of the enriched solvent water entering the solvent regeneration tank to the second lean solvent entering the solvent regeneration tank is 2 to 4:1. This embodiment is conducive to improving the purity of cyclohexanol and cyclohexanone, and further enhancing the quality of the circulating solvent.

[0052] The present disclosure is further illustrated by the following examples, but the present disclosure is not limited thereto. Unless otherwise specified, the remaining chemical reagents used in the examples are commercially available products.

[0053] Example 1

[0054] like Figure 1As shown, the material to be separated enters the extraction tower 101 through the raw material inlet 1, and the extraction solvent enters the extraction tower 101 through the solvent inlet 2. After the material to be separated contacts the extraction solvent in countercurrent from bottom to top, a raffinate oil 3 mainly containing cyclohexane is obtained from the top of the extraction tower 101, and a first rich solvent 4 is obtained from the bottom of the tower; the raffinate oil 3 enters the water washing tower 103 for water washing to remove water-soluble impurities in the recovered cyclohexane, thereby obtaining washed water 14 and washed raffinate oil 13 containing cyclohexane; and the washed raffinate oil 13 is returned to the cyclohexane oxidation unit;

[0055] The first rich solvent 4 is passed into a stripping tower 102 for steam stripping separation to remove a small amount of cyclohexane in the first rich solvent. A light component containing cyclohexane is obtained from the top of the stripping tower 102. The light component containing cyclohexane is cooled and passed into a reflux tank 108 for phase separation to obtain an aqueous phase 7 and an oil phase containing cyclohexane. The aqueous phase 7 is returned to a water scrubber 103 for recycling, a portion of the oil phase 5 is returned to the stripping tower, and another portion of the oil phase 6 is returned to the cyclohexane oxidation unit. A second rich solvent 8 is obtained from the bottom of the stripping tower. The second rich solvent 8 is passed into a solvent recovery tower 104 for distillation to separate cyclohexanol and cyclohexanone from the extraction solvent. A separated product 9 containing cyclohexanone and cyclohexanol is obtained from the top of the solvent recovery tower 104. The first lean solvent is obtained from the bottom of the solvent recovery tower 104.

[0056] The washed water 14 from the water scrubber is passed to the water stripping tower 106 for stripping to recover a small amount of extraction solvent contained in the washed water, thereby obtaining wash water 15 and solvent-enriched water. The wash water 15 is returned to the water scrubber 103 for recycling, a portion of the solvent-enriched water 16 is returned to the stripping tower for further recycling, and the remaining portion 17 of the solvent-enriched water is passed to the solvent regeneration tank 107.

[0057] A portion of the first lean solvent is returned to the extraction tower 101, and the remaining portion 10 of the first lean solvent is entered into the solvent distillation tower 105 for distillation to purify part of the extraction solvent, and a first impurity 11 mainly containing alcohols, aldehydes, ketones and acids is obtained from the top of the solvent distillation tower, and a second lean solvent 12 is obtained from the bottom of the tower; the second lean solvent 12 is entered into the solvent regeneration tank 107 for flash evaporation, and a flash gas phase 18 is obtained from the top of the solvent regeneration tank 107. The flash gas phase 18 is returned to the solvent recovery tower 104, and a second impurity mainly containing heavy component alcohols and esters is discharged from the bottom of the solvent regeneration tank 107.

[0058] according to Figure 1The process for separating cyclohexanone and cyclohexanol is described. The product to be separated is the organic phase obtained by separating the oxidation liquid from the cyclohexane oxidation unit after alkaline treatment. The composition of the product to be separated is shown in Table 1. The extraction solvent is tetraethylene glycol containing 1% water by mass. The first lean solvent entering the solvent distillation column accounts for 1% of the total mass of the first lean solvent. The main operating conditions of each column are shown in Table 2. The composition of the separated cyclohexanol and cyclohexanone mixture is shown in Table 3. The mass yield of the cyclohexanol and cyclohexanone mixture is 96.1%. The separation device can operate smoothly for at least three months.

[0059] Example 2

[0060] The method of Example 2 is the same as that of Example 1, except that the extraction solvent is pentaethylene glycol containing 5% water. The first lean solvent entering the solvent distillation column accounts for 3% of the total mass of the first lean solvent. The main operating conditions of each column are shown in Table 2. The composition of the separated cyclohexanol and cyclohexanone mixture is shown in Table 3. The mass yield of the cyclohexanol and cyclohexanone mixture is 97.4%.

[0061] Example 3

[0062] The method of Example 3 is the same as that of Example 1, except that the operating conditions of the stripping tower and the solvent recovery tower are different. The specific operating conditions are shown in Table 2. The composition of the separated cyclohexanol and cyclohexanone mixture is shown in Table 3. The mass yield of the cyclohexanol and cyclohexanone mixture is 95.2%.

[0063] Example 4

[0064] The method of Example 4 is the same as that of Example 1, except for the absolute pressure and reflux ratio at the top of the solvent distillation column. Specific operating conditions are shown in Table 2. The composition of the separated cyclohexanol and cyclohexanone mixture is shown in Table 3. The mass yield of the cyclohexanol and cyclohexanone mixture is 95.7%.

[0065] Example 5

[0066] The method of Example 5 is the same as that of Example 1, except that the mass ratio of the enriched solvent water entering the solvent regeneration tank to the mass ratio of the second lean solvent entering the solvent regeneration tank is 5. Specific operating conditions are shown in Table 2. The composition of the separated cyclohexanol and cyclohexanone mixture is shown in Table 3. The mass yield of the cyclohexanol and cyclohexanone mixture is 96.5%.

[0067] Example 6

[0068] The method of Example 6 is the same as that of Example 1, differing only in that the extraction solvent is tetraethylene glycol, which does not contain water. The main operating conditions of each column are shown in Table 2. The composition of the separated cyclohexanol and cyclohexanone mixture is shown in Table 3. The mass yield of the cyclohexanol and cyclohexanone mixture is 96.8%.

[0069] Comparative Example 1

[0070] This comparative example is as follows Figure 2 The process shown here separates cyclohexanol and cyclohexanone. The raw materials are the same as in Example 1, and the solvent is 1-ethyl-3-methylimidazolium hydrogen sulfate. 1) With the extraction column operating at 1 MPa and a temperature of 130-135°C, a cyclohexane-KA oil mixed solution is fed from the lower side of the extraction tube at a flow rate of 10 kg / h. An ionic liquid 1-ethyl-3-methylimidazolium hydrogen sulfate solution at 130°C is introduced into the extraction column from the top of the column, with the mass ratio of the ionic liquid to the cyclohexane-KA oil mixture being controlled at 1:2. The ionic liquid and the cyclohexane-KA oil mixed solution are countercurrently extracted, resulting in a raffinate phase of light liquid cyclohexane at the top of the column and an ionic liquid-KA oil mixed phase at the bottom of the column. 2) The raffinate phase is condensed to room temperature at the top of the column, and the cyclohexane solution is recovered. 3) The flash column was operated at a pressure of 0.02 MPa. The extract phase at the bottom of the extraction column was passed into the flash column. The extract phase, a mixed solution of ionic liquid and KA oil at 130-135°C, was introduced into the flash column through a pipeline from the middle of the flash column. The liquid pressure rapidly dropped from 1 MPa to 0.02 MPa, causing the KA oil to reach its saturated vapor pressure and vaporize. The KA oil solution was condensed at the top of the column in a condenser and recovered. The composition of the separated cyclohexanol and cyclohexanone mixture is shown in Table 3. The mass yield of the cyclohexanol and cyclohexanone mixture was 92.7%.

[0071] Comparative Example 2

[0072] In this comparative example, cyclohexanol and cyclohexanone were separated using a triple-effect distillation-saponification-extraction-drying process developed by DSM of the Netherlands. The raw materials were the same as those in Example 1. 80,000 kg of cyclohexane was added to an oxidation reactor. The temperature was controlled at 155°C to 165°C and the pressure was controlled at 900 kPa to 1300 kPa. Without the addition of a catalyst, the cyclohexane was partially oxidized in the liquid phase by molecular oxygen in the air. The conversion of cyclohexane was approximately 4.5 mol%. The composition of the separated cyclohexanol and cyclohexanone mixture is shown in Table 3. The mass yield of the cyclohexanol and cyclohexanone mixture was 90.1%.

[0073] Table 1 Composition of the substances to be separated

[0074]

[0075] Table 2 Main operating conditions

[0076]

[0077]

[0078] Table 3 Product composition

[0079]

[0080] According to the data in Table 3, the mass yield of the cyclohexanol and cyclohexanone mixture obtained by the method of the present invention is higher than 95%, and the purity of the cyclohexanol and cyclohexanone is higher than 99%. By comparing Example 1 with Example 3, it can be seen that within the operating conditions of the stripping tower and solvent recovery tower of the present invention, the purity and mass yield of the cyclohexanol and cyclohexanone obtained by the present invention are higher. By comparing Example 1 with Example 4, it can be seen that within the operating conditions of the solvent distillation tower of the present invention, the purity and mass yield of the cyclohexanol and cyclohexanone obtained by the present invention are higher. By comparing Example 1 with Example 5, it can be seen that within the mass ratio of the enriched solvent water entering the solvent regeneration tank of the present invention to the mass ratio of the second lean solvent entering the solvent regeneration tank of the present invention, the purity of the cyclohexanol and cyclohexanone obtained by the present invention is higher. By comparing Example 1 with Example 6, it can be seen that within the mass fraction range of water in the extraction solvent of the present invention, the purity of the cyclohexanol and cyclohexanone obtained by the present invention is higher.

[0081] By comparing Example 1 with Comparative Example 1, it can be seen that in Comparative Example 1, since there is no effective method for removing polar impurities in the raw materials, the solvent deteriorates seriously, and the extraction and separation effect decreases significantly after continuous circulation for one week.

[0082] By comparing Example 1 with Comparative Example 2, it can be seen that although Comparative Example 2 uses a traditional three-effect distillation-saponification-extraction-drying process, it can effectively remove various impurities from the raw materials. However, due to the certain solubility of cyclohexanol and cyclohexanone in water, its mass yield is far inferior to that of the present invention. Because the cyclohexanone-cyclohexanol mixture is further separated from impurities in the subsequent refining unit by light and heavy removal towers, and the cyclohexanol dehydrogenation unit converts cyclohexanol into cyclohexanone, the slightly higher impurity content in the cyclohexanone-cyclohexanol mixture obtained in Example 1 does not affect the purity of the cyclohexanone product, and the yield is significantly improved.

[0083] The preferred embodiments of the present disclosure are described in detail above in conjunction with the accompanying drawings. However, the present disclosure is not limited to the specific details of the above embodiments. Within the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the scope of protection of the present disclosure.

[0084] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0085] In addition, the various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A method for separating cyclohexane, cyclohexanol and cyclohexanone, characterized in that: The method comprises the following steps: (a) allowing the material to be separated to enter an extraction tower, contact it with an extraction solvent in countercurrent from bottom to top, obtain raffinate oil from the top of the tower, and obtain a first rich solvent from the bottom of the tower; allowing the raffinate oil to enter a water washing tower for water washing to obtain wash water and washed raffinate oil containing cyclohexane; (b) allowing the first rich solvent to enter a stripping tower for stripping, obtaining a light component containing cyclohexane from the top of the stripping tower, and obtaining a second rich solvent from the bottom of the stripping tower; allowing the second rich solvent to enter a solvent recovery tower for distillation, obtaining a separated product containing cyclohexanone and cyclohexanol from the top of the solvent recovery tower, and obtaining a first lean solvent from the bottom of the solvent recovery tower; (c) returning a portion of the first lean solvent to the extraction column and allowing the remainder of the first lean solvent to enter a solvent purification unit to remove impurities; The solvent purification unit comprises a solvent distillation tower and a solvent regeneration tank; the substance to be separated is the organic phase obtained by separating the oxidation liquid of the cyclohexane oxidation unit after alkali treatment.

2. The method according to claim 1, wherein Calculated by mass, the substance to be separated includes 3% to 8% of cyclohexanol and cyclohexanone, 91.5% to 96.9% of cyclohexane and 0.1% to 0.5% of impurities; the impurities include one or more of alcohols, aldehydes, ketones, acids and esters.

3. The method according to claim 1, wherein The extraction solvent is selected from organic solvents with a boiling point of 300° C. or higher; the extraction solvent contains 0.1% to 10% by mass of water.

4. The method according to claim 1, wherein The extraction solvent is selected from alcohol solvents with a carbon number of 6 to 14. Preferably, the extraction solvent is tetraethylene glycol and / or pentaethylene glycol.

5. The method according to claim 1, wherein The method comprises: returning the washed raffinate oil from the water scrubber to a cyclohexane oxidation unit; The light component containing cyclohexane from the stripping tower is cooled and then enters a reflux tank for phase separation to obtain an aqueous phase and a first oil phase containing cyclohexane. The aqueous phase is returned to the water washing tower, a portion of the first oil phase is returned to the stripping tower, and another portion of the first oil phase is returned to the cyclohexane oxidation unit.

6. The method according to claim 1, wherein In step (a), the mass ratio of the extraction solvent to the substance to be separated is 0.5 to 2:1; the inlet temperature of the extraction solvent to the tower is 40°C to 80°C, the inlet temperature of the substance to be separated to the tower is 40°C to 80°C, and the number of theoretical plates of the extraction tower is 5 to 15.

7. The method according to claim 1, wherein In step (b), in the stripping tower, the absolute pressure at the top of the stripping tower is 0.1 MPa to 0.2 MPa, the reflux ratio is 0.1 to 1, and the bottom temperature is 120° C. to 160° C.; In the solvent recovery tower, the absolute pressure at the top of the solvent recovery tower is 0.01 MPa to 0.06 MPa, the reflux ratio is 0.1 to 1, and the tower bottom temperature is 150° C. to 190° C.

8. The method according to claim 1, wherein The method further comprises: The washed water from the water scrubber enters a water stripping tower for stripping to obtain wash water and solvent-enriched water; the wash water is returned to the water scrubber, a portion of the solvent-enriched water is returned to the stripping tower, and the remaining portion of the solvent-enriched water enters the solvent regeneration tank; The remaining portion of the first lean solvent from the solvent recovery tower enters the solvent distillation tower for distillation, and the first impurities are obtained from the top of the tower, and the second lean solvent is obtained from the bottom of the tower; the second lean solvent enters the solvent regeneration tank for flash evaporation, and a flash gas phase is obtained from the top of the solvent regeneration tank. The flash gas phase is returned to the solvent recovery tower, and the second impurities are discharged from the bottom of the solvent regeneration tank.

9. The method according to claim 8, wherein The mass of the first lean solvent entering the solvent distillation tower accounts for 0.1% to 5% of the total mass of the first lean solvent.

10. The method according to claim 8, wherein The absolute pressure at the top of the solvent distillation tower is 0.001 MPa to 0.01 MPa, the bottom temperature is 190 to 230° C., the reflux ratio is 2 to 10, and the number of theoretical plates is 40 to 80; The absolute pressure of the solvent regeneration tank is 0.001 MPa to 0.01 MPa, and the temperature is 200° C. to 250° C.

11. The method according to claim 8, wherein The mass ratio of the enriched solvent water entering the solvent regeneration tank to the second lean solvent entering the solvent regeneration tank is 2 to 4:1.

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