Method for separating cyclohexane oxidation product

Abstract

The invention relates to a method for separating a cyclohexane oxidation product, the purity of a cyclohexanol and cyclohexanone mixture obtained by 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 three-waste discharge and environmental pollution are avoided; the stability of the circulating solvent is further improved, so that the device can operate 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 oxidation products. Background Art

[0002] Cyclohexanone is an important organic chemical raw material and an intermediate in the production of caprolactam and adipic acid. Currently, the industrial production of cyclohexanone primarily utilizes the cyclohexane oxidation process. The oxidation step in the cyclohexane oxidation unit produces an oxidation liquid primarily composed of cyclohexyl hydroperoxide. After alkali treatment and separation, the oxidation liquid yields an organic phase primarily composed of cyclohexane, cyclohexanol, and cyclohexanone. The conventional 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, the adoption of a new process for separating cyclohexanol and cyclohexanone is of great significance. In addition, the organic phase obtained from cyclohexane oxidation-alkaline decomposition-waste alkali separation contains, in addition to cyclohexanol and cyclohexanone, unconverted cyclohexane, which accounts for the vast majority. It also contains small amounts of aldehydes, ketones, acids, alcohols, esters, and hundreds of other oxygen-containing compound impurities. These impurities are also highly polar, with a wide boiling point distribution, and easily accumulate in the solvent, affecting the long-term operation of the device. Conventional methods for purifying solvents, such as vacuum distillation, cannot remove impurities whose boiling points overlap with those of the solvent; and stripping is only suitable for removing non-polar or weakly polar impurities. Therefore, polar impurities such as aldehydes, ketones, alcohols, and acids with boiling points between 200°C and 300°C are difficult to separate from the solvent by conventional distillation.

[0003] CN110078582A discloses a cyclohexane separation device for the production of cyclohexanone and cyclohexanol, comprising a first distillation column, a second distillation column, a reboiler, a reflux drum, a cooler, and a compressor. This method uses clean electrical energy to drive the compressor, mechanically compressing the overhead vapor to raise its temperature and serving as a heat source for the bottom of the column. This method improves upon the existing triple-effect distillation process and does not address the issue of increasing the yield of cyclohexanol and cyclohexanone. Summary of the Invention

[0004] The purpose of the present disclosure is to provide a method for separating cyclohexane oxidation products, wherein the purity of the obtained cyclohexanol and cyclohexanone mixture is higher than 99%, the mass yield is higher than 95%, and no caustic soda solution needs to be added during the separation process, thereby avoiding the discharge of three wastes and pollution of the environment.

[0005] In order to achieve the above object, the present disclosure provides a method for separating cyclohexane oxidation products, 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 extraction 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 and a first impurity 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 tower, passing the remaining portion of the first lean solvent into a solvent regeneration unit to remove impurities, and returning the regenerated extraction solvent to the extraction tower;

[0009] The solvent regeneration unit comprises a cationic resin module, an anionic resin module and a solvent regeneration tank; the object 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, wherein the impurities comprise one or more of aldehydes, ketones, alcohols, acids and esters.

[0011] Optionally, the extraction solvent is selected from an organic solvent with a boiling point of 200-300° C.; the molecules of the extraction solvent contain one or more of O, N and S; and the extraction solvent contains 0.1% to 2.0% by mass of water.

[0012] Optionally, the extraction solvent is selected from one of sulfolane, N-methylpyrrolidone and N-formylmorpholine; preferably, the extraction solvent is sulfolane.

[0013] Optionally, the post-wash raffinate oil from the water washing tower is returned to the cyclohexane oxidation unit; the post-wash water from the water washing tower enters a water stripping tower for stripping to obtain an aqueous phase and an oil phase containing cyclohexane; the aqueous phase is returned to the water washing tower, and the oil phase is returned to the stripping tower.

[0014] 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.

[0015] Optionally, in step (b), the absolute pressure at the top of the stripping tower is 0.1 MPa to 0.2 MPa; 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 bottom temperature is 140° C. to 180° C.

[0016] Optionally, in step (c), the first lean solvent entering the solvent regeneration unit accounts for 0.1% to 15% of the total mass of the first lean solvent, preferably 1 to 10%.

[0017] Optionally, the method further includes:

[0018] The remaining portion of the first lean solvent from the solvent recovery tower is sequentially processed through a cationic resin module and an anionic resin module to obtain a second lean solvent; a portion of the second lean solvent is returned to the extraction tower, and the remaining portion of the second lean solvent enters a solvent regeneration tank for flash evaporation to obtain a flash gas phase, which is then returned to the solvent recovery tower.

[0019] Optionally, the cationic resin module is filled with a strong acid styrene resin, and the particle size of the resin is 0.2 mm to 1.5 mm; the temperature of the cationic resin module is 30° C. to 80° C., and the apparent flow velocity is 0.5 m / h to 6.0 m / h.

[0020] Optionally, the anion resin module is filled with weakly alkaline styrene resin, and the particle size of the resin is 0.2 mm to 1.5 mm; the temperature of the anion resin module is 25° C. to 60° C., and the superficial flow rate is 0.5 m / h to 6.0 m / h.

[0021] Optionally, the second lean solvent entering the solvent regeneration tank accounts for 0.1% to 3% of the total mass of the first lean solvent; the absolute pressure of the solvent regeneration tank is 0.001 MPa to 0.01 MPa, and the temperature is 160° C. to 180° C.

[0022] Through the above technical solution, the present invention produces a mixture of cyclohexanol and cyclohexanone by bringing a selective solvent and a cyclohexane oxidation product into countercurrent contact within an extraction column. The extract phase obtained from the extraction column kettle is sequentially passed through a stripping column and a solvent recovery column. Simultaneously, the extraction solvent is further regenerated through cationic resin catalysis, anionic resin adjustment of the solvent system, and flash evaporation in a solvent regeneration tank, further separating polar 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. The stability of the circulating solvent is further improved, enabling the device to operate over a long period of time.

[0023] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] 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:

[0025] Figure 1 It is a schematic flow chart of the separation process in Example 1 of the present disclosure.

[0026] Figure 2 It is a schematic flow chart of the separation process in Comparative Example 1 of the present disclosure.

[0027] Description of Reference Numerals

[0028] 1: feedstock inlet; 2: extraction solvent inlet; 3: raffinate; 4: first rich solvent; 5: raffinate after washing; 6: water after washing; 7: aqueous phase; 8: oil phase; 9: light components; 10: second rich solvent; 11: separated material containing cyclohexanone and cyclohexanol; 12: remaining portion of the first lean solvent; 13: part of the first lean solvent; 14: part of the second lean solvent; 15: remaining portion of the second lean solvent; 16: flash gas phase;

[0029] 101: extraction tower; 102: stripping tower; 103: water washing tower; 104: water stripping tower; 105: solvent recovery tower; 106: cation resin module; 107: anion resin module; 108: solvent regeneration tank. DETAILED DESCRIPTION

[0030] 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.

[0031] The present disclosure provides a method for separating cyclohexane oxidation products, the method comprising the following steps:

[0032] (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 extraction 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;

[0033] (b) allowing the first rich solvent to enter a stripping tower for stripping, obtaining a light component containing cyclohexane and a first impurity 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;

[0034] (c) returning a portion of the first lean solvent to the extraction tower, passing the remaining portion of the first lean solvent into a solvent regeneration unit to remove impurities, and returning the regenerated extraction solvent to the extraction tower;

[0035] The solvent regeneration unit comprises a cationic resin module, an anionic resin module and a solvent regeneration tank; the object to be separated is the organic phase obtained by separating the oxidation liquid of the cyclohexane oxidation unit after alkali treatment.

[0036] The present invention involves countercurrently contacting a selective solvent with a cyclohexane oxidation product within an extraction column, passing the extract phase from the extraction column kettle sequentially through a stripping column and a solvent recovery column to produce a mixture of cyclohexanol and cyclohexanone. Simultaneously, the extraction solvent is further regenerated through catalysis with a cationic resin, pH adjustment with an anionic resin, and a solvent regeneration tank to further separate polar 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, thus avoiding 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.

[0037] In the present disclosure, the cyclohexane oxidation product refers to the organic phase obtained by separating the oxidation liquid of the cyclohexane oxidation unit after alkali treatment.

[0038] According to the present disclosure, the oxidation liquid undergoes alkaline decomposition followed by oil-water separation to yield an organic phase primarily containing cyclohexane, cyclohexanol, and cyclohexanone. By mass, the fraction to be separated comprises 3% to 8% cyclohexanol and cyclohexanone, 91.5% to 96.9% cyclohexane, and 0.1% to 0.5% impurities. These impurities include one or more of aldehydes, ketones, alcohols, and esters. The inventors discovered that cyclohexanol and cyclohexanone are more polar than cyclohexane and, based on the principle of like dissolves like, can be separated by liquid-liquid extraction with polar solvents. Compared to extractants such as sulfolane, aldehydes, ketones, alcohols, and acids have relatively poor chemical stability. Strongly acidic cationic resins can catalyze the conversion of aldehydes, ketones, alcohols, and acids in the cyclohexane oxidation product into weakly polar compounds. These weakly polar compounds are returned to the extraction column and extracted into the raffinate oil by the cyclohexane in the feedstock. Treatment with the cationic resin significantly reduces the pH of the solvent, which is then adjusted to approximately 7 by treatment with a weakly basic anionic resin. At the same time, in order to ensure the pH value of the circulating solvent, organic base can be injected into the solvent system, and the salt and other residues generated by the acid are discharged from the bottom of the solvent regeneration tank.

[0039] According to one embodiment of the present disclosure, the extraction solvent is selected from an organic solvent with a boiling point of 200-300°C; the extraction solvent contains one or more of O, N, and S in its molecules; and the extraction solvent contains 0.1% to 2.0% water by mass. In a further embodiment, the extraction solvent is selected from one of sulfolane, N-methylpyrrolidone, and N-formylmorpholine; preferably, the extraction solvent is sulfolane. The above embodiment is conducive to improving the selectivity of the extraction solvent and increasing the purity of the cyclohexanol and cyclohexanone mixture.

[0040] According to one embodiment of the present disclosure, the post-wash raffinate oil from the water scrubber is returned to the cyclohexane oxidation unit to allow the cyclohexane therein to continue to react; the post-wash water from the water scrubber is passed to a water stripping tower for stripping to produce an aqueous phase and an oil phase containing cyclohexane; the aqueous phase is returned to the water scrubber, and the oil phase is returned to the stripping tower. This embodiment facilitates the recovery of the extraction solvent and the wash water, thereby improving the mass yield of the cyclohexanol and cyclohexanone mixture.

[0041] According to one embodiment of the present disclosure, in step (a), in the extraction tower, the mass ratio of the substances to be separated is 0.5 to 2:1, preferably 0.8 to 1.5:1, the temperature is 40°C to 80°C, preferably 40 to 60°C, the inlet temperature of the substances to be separated is 40°C to 80°C, preferably 40 to 60°C, and the number of theoretical plates of the extraction tower is 5 to 15, preferably 7 to 14. The above embodiment is conducive to improving the mass yield of the cyclohexanol and cyclohexanone mixture.

[0042] According to one embodiment of the present disclosure, in step (b), 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; in the solvent recovery tower, the absolute pressure at the top is 0.01 MPa to 0.06 MPa, preferably 0.02 MPa to 0.05 MPa; the reflux ratio is 0.1 to 1:1, preferably 0.2 to 0.6:1, and the bottom temperature is 140° C. to 180° C., preferably 160° C. to 180° C. The above embodiment is conducive to improving the mass yield of the cyclohexanol and cyclohexanone mixture.

[0043] According to one embodiment of the present disclosure, in step (c), the first lean solvent entering the solvent regeneration unit accounts for 0.1% to 15% of the total mass of the first lean solvent, preferably 1% to 10%. This embodiment is beneficial for improving the purity of cyclohexanol and cyclohexanone, further separating impurities in the circulating solvent, improving the stability of the circulating solvent, and enabling long-term operation of the device.

[0044] According to one embodiment of the present disclosure, the method further includes:

[0045] The remaining portion of the first lean solvent from the solvent recovery tower is processed in turn through a cationic resin module and an anionic resin module to obtain a second lean solvent; a portion of the second lean solvent is returned to the extraction tower, and the remaining portion of the second lean solvent enters a solvent regeneration tank for flash evaporation to obtain a flash vapor phase, which is returned to the solvent recovery tower, and impurities mainly containing heavy alcohols and ketones are discharged from the bottom of the solvent regeneration tank. The cationic resin catalyzes the aldehydes, ketones, alcohols, and acids in the separated material to produce weakly polar compounds. These weakly polar compounds are returned to the extraction tower with cyclohexane and extracted into the raffinate oil by the cyclohexane in the raw material; the pH value of the solvent is adjusted to about 7 by a weakly basic anionic resin to improve the stability of the circulating solvent and avoid corrosion of equipment. The above embodiment is conducive to improving the purity of cyclohexanol and cyclohexanone, further separating impurities in the circulating solvent, improving the stability of the circulating solvent, and enabling the device to operate for a long period of time.

[0046] According to one embodiment of the present disclosure, the cationic resin module is loaded with a strong acid styrene resin having a particle size of 0.2 mm to 1.5 mm. The temperature of the cationic resin module is 30°C to 80°C, and the superficial flow rate is 0.5 m / h to 6.0 m / h. In one embodiment, the strong acid styrene resin is selected from a macroporous strong acid styrene-SO3H type, and the resin processing capacity is 20 to 160 g sulfolane / g resin.

[0047] According to one embodiment of the present disclosure, the anion resin module is loaded with a weakly basic styrene resin, and the particle size of the resin is 0.2 mm to 1.5 mm; the temperature of the anion resin module is 25°C to 60°C, and the apparent flow rate is 0.5 m / h to 6.0 m / h. In one embodiment, the anion resin is selected from a macroporous basic anion resin, preferably a macroporous weakly basic anion resin, and more preferably a macroporous weakly basic styrene resin, for example, it can be selected from a weakly basic macroporous styrene-NH2 type or -N(CH3) type resin. Before use and during regeneration, the weakly basic anion resin must be soaked in water for 8 to 15 hours, and then a dilute alkaline solution of 1 to 5 times the volume of the resin must be passed through the resin to convert the resin into the hydroxide type.

[0048] According to one embodiment of the present disclosure, the second lean solvent entering the solvent regeneration tank accounts for 0.1% to 3% of the total mass of the first lean solvent, preferably 0.5 to 2%; the absolute pressure of the solvent regeneration tank is 0.001 MPa to 0.01 MPa, preferably 0.001 MPa to 0.005 MPa, and the temperature is 160°C to 180°C, preferably 170 to 180°C.

[0049] 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.

[0050] Example 1

[0051] Example 1 According to Figure 1 The process shown is to separate cyclohexanol and cyclohexanone from the cyclohexane oxidation product. Figure 1 As shown, the material to be separated enters the middle and lower part of the extraction tower 101 from the raw material inlet 1, and the extraction solvent enters the upper part of the extraction tower 101 from the extraction 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, and obtains washed water 6 and washed raffinate oil 5 containing cyclohexane and a small amount of impurities; the washed raffinate oil 5 is returned to the cyclohexane oxidation unit; the washed water 6 enters the water stripping tower 104 for stripping to recover a small amount of extraction solvent in the washed water, and obtains an aqueous phase 7 and an oil phase 8 containing cyclohexane; the aqueous phase 7 is returned to the water washing tower 103 for recycling, and the oil phase 8 is returned to the stripping tower 102 for continued stripping;

[0052] The first rich solvent 4 is passed into a stripping tower 102 for separation to remove a small amount of cyclohexane and impurities with lower boiling points from the first rich solvent. A solution containing cyclohexane and light component impurities 9 is obtained from the top of the stripping tower 102, and a second rich solvent 10 is obtained from the bottom of the stripping tower 102. The second rich solvent 10 is passed into a solvent recovery tower 105 for distillation to separate cyclohexanol and cyclohexanone from the extraction solvent. A separated product 11 containing cyclohexanone and cyclohexanol is obtained from the top of the solvent recovery tower 105, and a first lean solvent is obtained from the bottom of the solvent recovery tower 105.

[0053] A portion of the first lean solvent 13 from the solvent recovery tower is returned to the extraction tower 101, and the remaining portion 12 of the first lean solvent is sequentially treated through the cationic resin module 106 and the anionic resin module 107 to remove impurities such as aldehydes, ketones, alcohols and acids to obtain a second lean solvent; a portion 14 of the second lean solvent is returned to the extraction tower 101, and the remaining portion 15 of the second lean solvent enters the solvent regeneration tank 108 for flash evaporation to obtain a flash vapor phase 16, which is returned to the solvent recovery tower 105 for recycling, and impurities discharged from the bottom of the solvent regeneration tank 108 are mainly mechanical impurities, impurities with a boiling point higher than 300°C, and a very small amount of solvent autopolymers generated due to high temperature.

[0054] The product to be separated is the organic phase obtained by cyclohexane oxidation and alkaline decomposition. The composition of the product to be separated is shown in Table 1. The solvent is 1% water-containing sulfolane. The first lean solvent entering the solvent regeneration unit accounts for 10% of the total mass of the first lean solvent, and the second lean solvent entering the solvent regeneration tank accounts for 1% of the total mass of the first lean solvent. The cationic resin module is loaded with a styrene-SO3H type cationic resin with a particle size of 0.8 mm. The anionic resin module is loaded with a styrene-N(CH3) type anionic resin pretreated with a dilute NaOH solution with a particle size of 0.8 mm. The main operating conditions of each tower 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 3 months.

[0055] Example 2

[0056] The separation process of Example 2 is the same as that of Example 1. The extraction solvent used in Example 2 is a composite solvent composed of 3-methylsulfone, N-methylpyrrolidone and water, and the mass ratio of the three is 90:8:2. The first lean solvent entering the solvent regeneration unit accounts for 8% of the total mass of the first lean solvent, and the second lean solvent entering the solvent regeneration tank accounts for 1% of the total mass of the first lean solvent. The cationic resin module is filled with styrene-SO3H type cationic resin, and the anionic resin module is filled with styrene-NH2 type anionic resin pretreated with dilute NaOH solution. The main operating conditions of each tower are shown in Table 2. The composition of the separated cyclohexanol and cyclohexanone mixture product is shown in Table 3, and the mass yield of the cyclohexanol and cyclohexanone mixture is 96.2%.

[0057] Example 3

[0058] The method of this example is the same as that of Example 1, differing only in the reflux ratio between the top of the stripping column and the solvent recovery column, and in the operating conditions. Specific operating conditions are shown in Table 2. The composition of the separated cyclohexanol and cyclohexanone mixture is shown in Table 3. Due to the excessively low pressure at the top of the solvent recovery column, the solvent in the cyclohexanol and cyclohexanone mixture was not completely separated, resulting in a decrease in purity. Furthermore, due to the excessively low pressure at the top of the stripping column, the mass yield dropped to 95.9%.

[0059] Example 4

[0060] The method of this embodiment is the same as that of Example 1, except that the first lean solvent entering the solvent regeneration unit accounts for 0.1% of the total mass of the first lean solvent. The composition of the separated cyclohexanol and cyclohexanone mixture is shown in Table 3. Due to the low amount of solvent regeneration, the impurity content in the lean solvent increased, the purity of the cyclohexanol and cyclohexanone mixture decreased, and the mass yield was 95.1%.

[0061] Example 5

[0062] The method of this example was the same as that of Example 1, differing only in that the cationic resin module was loaded with the weakly polar macroporous adsorption resin AB-8, with a particle size of 0.8 mm. The composition of the separated cyclohexanol and cyclohexanone mixture is shown in Table 3. Because the AB-8 resin was unable to effectively remove polar impurities in the lean solvent, affecting the separation efficiency of the lean solvent, the mass yield of the cyclohexanol and cyclohexanone mixture was 95.0%.

[0063] Comparative Example 1

[0064] This comparative example is as follows Figure 2 The process shown separates cyclohexanol and cyclohexanone. The products to be separated are the same as those in Example 1, and the solvent is 1-ethyl-3-methylimidazolium hydrogen sulfate. 1) With the extraction tower operating at 1 MPa and a tower 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 tower from the top of the tower, 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 light liquid cyclohexane at the top of the tower and an ionic liquid-KA oil mixed phase at the bottom of the tower. 2) The raffinate light liquid is condensed to room temperature at the top of the tower, 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%.

[0065] Comparative Example 2

[0066] 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 materials to be separated were the same as those in Example 1. In an oxidation reactor, 80,000 kg of cyclohexane was added. The temperature was controlled at 155°C to 165°C and the pressure was controlled at 900 kPa to 1300 kPa. No catalyst was added. The cyclohexane was partially oxidized in the liquid phase by molecular oxygen in the air. The conversion rate 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%.

[0067] Table 1 Composition of the substances to be separated

[0068]

[0069] Table 2 Main operating conditions

[0070]

[0071]

[0072] Table 3 Product composition

[0073]

[0074] According to the data in Table 3, the purity of the cyclohexanol and cyclohexanone mixture obtained by the method of the present invention is higher than 99%, and the mass yield is higher than 95%. There is no need to add caustic soda solution during the separation process, which avoids the discharge of three wastes and pollution of the environment. At the same time, the circulating solvent is purified and regenerated, so that the properties of the circulating solvent are stable and the device can operate for a long period of time. By comparing Example 1 with Example 3, it can be seen that within the operating conditions of the stripping tower and the solvent recovery tower of the present invention, the purity and mass yield of cyclohexanol and cyclohexanone are higher. By comparing Example 1 with Example 4, it can be seen that within the mass range of the first lean solvent entering the solvent regeneration unit of the present invention, the purity and mass yield of the obtained cyclohexanol and cyclohexanone mixture are higher. By comparing Example 1 with Example 5, it can be seen that within the range of the cationic resin of the present invention, the purity and mass yield of the obtained cyclohexanol and cyclohexanone mixture are higher.

[0075] By comparing Example 1 with Comparative Example 1, it can be seen that in Comparative Example 1, due to the lack of an effective method for removing polar impurities from the raw materials, the solvent deteriorates severely, and the extraction and separation effect decreases significantly after one week of continuous recycling. The mass yield of the cyclohexanol and cyclohexanone mixture is much lower than that of the present application.

[0076] By comparing Example 1 and Comparative Example 2, it can be seen that although Comparative Example 2 can better remove various impurities in the raw materials using traditional processes, its mass yield is far lower than that of the present application due to the solubility of cyclohexanol and cyclohexanone in water.

[0077] 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.

[0078] 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.

[0079] 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 oxidation products, 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 extraction 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 and a first impurity 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 tower, passing the remaining portion of the first lean solvent into a solvent regeneration unit to remove impurities, and returning the regenerated extraction solvent to the extraction tower; The solvent regeneration unit comprises a cationic resin module, an anionic resin module and a solvent regeneration tank; the object 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, and the impurities include one or more of aldehydes, ketones, alcohols, acids and esters.

3. The method according to claim 1, wherein The extraction solvent is selected from an organic solvent with a boiling point of 200 to 300° C.; the molecules of the extraction solvent contain one or more of O, N and S; and the extraction solvent contains 0.1% to 2.0% by mass of water.

4. The method according to claim 3, wherein: The extraction solvent is selected from one of sulfolane, N-methylpyrrolidone and N-formylmorpholine; preferably, the extraction solvent is sulfolane.

5. The method according to claim 1, wherein The washed raffinate oil from the water washing tower is returned to the cyclohexane oxidation unit; the washed water from the water washing tower enters the water stripping tower for stripping to obtain a water phase and an oil phase containing cyclohexane; the water phase is returned to the water washing tower, and the oil phase is returned to the stripping tower.

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), the absolute pressure at the top of the stripping tower is 0.1 MPa to 0.2 MPa; 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 bottom temperature is 140° C. to 180° C.

8. The method according to claim 1, wherein In step (c), the first lean solvent entering the solvent regeneration unit accounts for 0.1% to 15% of the total mass of the first lean solvent, preferably 1% to 10%.

9. The method according to claim 1, wherein The method further comprises: The remaining portion of the first lean solvent from the solvent recovery tower is sequentially processed through a cationic resin module and an anionic resin module to obtain a second lean solvent; a portion of the second lean solvent is returned to the extraction tower, and the remaining portion of the second lean solvent enters a solvent regeneration tank for flash evaporation to obtain a flash gas phase, which is then returned to the solvent recovery tower.

10. The method according to claim 9, wherein: The cationic resin module is filled with a strong acid styrene resin, and the particle size of the resin is 0.2 mm to 1.5 mm; the temperature of the cationic resin module is 30° C. to 80° C., and the superficial flow rate is 0.5 m / h to 6.0 m / h.

11. The method according to claim 9, wherein The anion resin module is filled with weakly alkaline styrene resin, and the particle size of the resin is 0.2mm-1.5mm; the temperature of the anion resin module is 25°C-60°C, and the apparent flow rate is 0.5m / h-6.0m / h.

12. The method according to claim 9, wherein The second lean solvent entering the solvent regeneration tank accounts for 0.1% to 3% of the total mass of the first lean solvent; the absolute pressure of the solvent regeneration tank is 0.001 MPa to 0.01 MPa, and the temperature is 160° C. to 180° C.

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