Method for separating cyclohexanol and cyclohexanone from cyclohexane

Abstract

The present disclosure relates to a process for separating cyclohexanol and cyclohexanone from cyclohexane. According to the method, aldehyde, ketone, alcohol, acid, ester and other impurities are separated in a targeted mode according to the polarity and boiling point of the extraction solvent, the stability of the circulating solvent is further improved, a device can operate for a long period, the purity of the cyclohexanol and cyclohexanone mixture obtained through the method is higher than 99%, the mass yield is higher than 95%, and the method is suitable for industrial production. No caustic soda solution is added in the separation process, so that emission of three wastes and environmental pollution are avoided.

Description

Technical Field

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

[0002] Currently, there are three main industrial processes for the synthesis and production of cyclohexanone, one of which is 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 traditional process uses a triple-effect distillation-saponification-extraction-drying process to separate the cyclohexanol and cyclohexanone from the organic phase, resulting in 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 the separation of cyclohexanol and cyclohexanone is of great significance. In addition, in the organic phase obtained by cyclohexane oxidation-alkaline 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 hundreds of other oxygen-containing compound impurities. These impurities have a wide boiling point distribution and large differences in polarity. Although the content is low, since the boiling point of most extractants is between 200°C and 300°C, there is a certain overlap with the boiling point of impurities and they cannot be removed by conventional distillation. Therefore, they are easily accumulated in the solvent, affecting long-term operation.

[0003] CN113004113A discloses a method for separating cyclohexane from KA oil (primarily composed of cyclohexanol and cyclohexanone) using an ionic liquid as an extractant. The ionic liquid and the extractant are continuously introduced into an extraction tower in a mass ratio of 1 to 3. Continuous extraction is carried out at a temperature of 100 to 200°C and a pressure of 0.1 to 2.0 MPa, either countercurrently or concurrently. The extracted phase is a mixed solution of KA oil and ionic liquid, and the raffinate is cyclohexane. The extracted phase is introduced into a flash tower, where it undergoes flash evaporation, yielding a high-purity KA oil product at the top. The ionic liquid at the bottom of the flash tower is then introduced into the extraction tower for repeated recycling. This method does not address whether oxygen-containing impurities in the raw materials might accumulate in the ionic liquid, thereby affecting the long-term use of the solvent. Furthermore, the extraction temperature is higher than the boiling point of cyclohexane, and gaseous cyclohexane may be present in the extraction tower. This does not constitute traditional liquid-liquid two-phase separation. Summary of the Invention

[0004] The purpose of the present disclosure is to provide a method for separating cyclohexanol and cyclohexanone from cyclohexane, 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 cyclohexanol and cyclohexanone from cyclohexane, 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 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 lean solvent from the bottom of the solvent recovery tower;

[0008] (c) allowing a portion of the lean solvent and the washed water from the water scrubber to enter a solvent purification unit for purification to obtain purified water, purified solvent, and impurity components; and returning the remaining portion of the lean solvent and the purified solvent to the extraction tower;

[0009] The solvent purification unit includes one or more of a water washing and stripping module, an adsorption module, a membrane separation module and a flash evaporation module; 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; 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° C. to 300° C., and the molecules of the extraction solvent contain one or more of O, N, and S; the extraction solvent contains 0.1% to 2.0% by mass of water;

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

[0013] Optionally, the raffinate oil from the water scrubber is returned to the cyclohexane oxidation unit;

[0014] A portion of the purified water from the solvent purification unit is returned to the water scrubber, and the remaining portion of the purified water enters a water stripping tower for stripping to obtain an aqueous phase and an oil phase containing an extraction solvent. The aqueous phase is returned to the water scrubber, and the oil phase is returned to the solvent recovery tower.

[0015] Optionally, in step (a), the mass ratio of the extraction solvent to the object to be separated is 0.5:1 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), the absolute pressure at the top of the stripping tower is 0.1 MPa to 0.2 MPa; in the solvent recovery tower, the absolute pressure at the top 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.

[0017] Optionally, in step (c), the mass ratio of the washed water to the lean solvent entering the solvent purification unit is 0.25 to 1.5:1; and the lean solvent entering the solvent purification unit accounts for 0.1% to 15% of the total mass of the lean solvent.

[0018] Optionally, the solvent purification unit includes a water washing and stripping module, an adsorption module, a membrane separation module and a flash evaporation module in sequence;

[0019] The method comprises:

[0020] The washed water and a portion of the lean solvent from the water washing tower enter the water washing and stripping module to contact with a stripping agent, perform water washing, stripping and phase separation, and obtain a stripping agent containing a second impurity and a first aqueous solvent;

[0021] allowing the first aqueous solvent to enter the adsorption module to separate the third impurity to obtain a second aqueous solvent;

[0022] The second aqueous solvent is allowed to enter the membrane separation module to obtain the purified water and the purified solvent; a portion of the purified solvent is returned to the extraction tower, and the remaining portion of the purified solvent is allowed to enter the flash evaporation module for flash evaporation to obtain a tank bottom liquid containing a fourth impurity and a flash gas phase, and the flash gas phase is returned to the bottom of the solvent recovery tower.

[0023] Optionally, in the water washing and stripping module, the mass ratio of the stripping agent to the lean solvent is 0.3 to 1:1; the stripping agent is an alkane with a carbon number of 3 to 8, preferably cyclohexane; the operating temperature of the water washing and stripping is 25°C to 60°C, and the theoretical number of stages is 1 to 5.

[0024] Optionally, in the adsorption module, the adsorbent is a macroporous resin or silica gel, preferably a styrene-based macroporous resin; and the temperature of the adsorption module is 25°C to 50°C.

[0025] Optionally, in the membrane separation module, the separation membrane is a molecular sieve pervaporation membrane, and the carrier is a hollow fiber tubular carrier; the permeate side pressure is below 0.5 kPa, and the temperature is 40° C. to 100° C.

[0026] Optionally, the mass of the purified solvent entering the flash evaporation module accounts for 0.1% to 1.0% of the total mass of the lean solvent; in the flash evaporation module, the absolute pressure is 0.001 MPa to 0.01 MPa, and the temperature is 160° C. to 180° C.

[0027] Through the above technical solution, the present invention obtains a mixture of cyclohexanol and cyclohexanone by allowing the selective solvent and the substance to be separated to contact each other in countercurrent within an extraction tower, and passing the extract phase obtained from the extraction tower kettle through a stripping tower and a solvent recovery tower in sequence. At the same time, the extraction solvent is subjected to water washing, stripping, adsorption separation, membrane separation, and flash evaporation to further purify the circulating solvent. The method disclosed herein can selectively separate impurities such as aldehydes, ketones, alcohols, acids, and esters based on the polarity and boiling point of the extraction solvent, thereby improving the stability of the circulating solvent and enabling the device to operate for a long period of time. The purity of the cyclohexanol and cyclohexanone mixture obtained by the method disclosed herein is higher than 99%, and the mass yield is higher than 95%. No caustic soda solution needs to be added during the separation process, thereby avoiding the discharge of three wastes and pollution of the environment.

[0028] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] 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:

[0030] Figure 1 It is a schematic flow chart of the separation process in Example 1 of the present disclosure.

[0031] Figure 2 It is a schematic diagram of the process of the purification unit in Example 1 of the present disclosure.

[0032] Figure 3 It is a schematic flow chart of the separation process in Comparative Example 1 of the present disclosure.

[0033] Description of Reference Numerals

[0034] 1: Feedstock inlet; 2: Extraction solvent inlet; 3: Raffinate; 4: First rich solvent; 5: Raffinate after washing; 6: Wash water; 7: Light components; 8: Second rich solvent; 9: Separate; 10: Remaining portion of lean solvent; 11: Portion of lean solvent; 12: Flash gas phase; 13: Portion of purified water; 14: Remaining portion of purified water; 15: Aqueous phase; 16: Oil phase; 17: Pipeline; 18: Stripping agent inlet; 19: Stripping agent containing Class II impurities; 20: First aqueous solvent; 21: Second aqueous solvent; 22: Purified water; 23: Remaining portion of purified solvent; 24: Portion of purified solvent;

[0035] 101: Liquid-liquid extraction tower; 102: Water washing tower; 103: Stripping tower; 104: Solvent recovery tower; 105: Solvent purification unit; 106: Water stripping tower; 107: Water washing and stripping module; 108: Adsorption module; 109: Membrane separation module; 110: Solvent regeneration tank. DETAILED DESCRIPTION

[0036] 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.

[0037] The present disclosure provides a method for separating cyclohexanol and cyclohexanone from cyclohexane, the method comprising the following steps:

[0038] (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;

[0039] (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 lean solvent from the bottom of the solvent recovery tower;

[0040] (c) allowing a portion of the lean solvent and the washed water from the water scrubber to enter a solvent purification unit for purification to obtain purified water, purified solvent, and impurity components; and returning the remaining portion of the lean solvent and the purified solvent to the extraction tower;

[0041] The solvent purification unit includes one or more of a water washing and stripping module, an adsorption module, a membrane separation module and a flash evaporation module; the object to be separated is the organic phase obtained by separating the oxidation liquid of the cyclohexane oxidation unit after alkali treatment.

[0042] The present invention allows a selective solvent and a substance to be separated to contact each other in countercurrent within an extraction tower, and passes the extract phase obtained from the extraction tower kettle through a stripping tower and a solvent recovery tower in sequence to obtain a mixture of cyclohexanol and cyclohexanone. Simultaneously, the extraction solvent is subjected to water washing, stripping, adsorption separation, membrane separation, and flash evaporation to further purify the circulating extraction solvent. The method disclosed herein selectively separates impurities such as aldehydes, ketones, alcohols, acids, and esters based on the polarity and boiling point of the extraction solvent, further improving the stability of the circulating solvent and enabling the device to operate over a long period of time. Furthermore, the purity of the cyclohexanol and cyclohexanone mixture obtained by the method disclosed herein is greater than 99%, and the mass yield is greater than 95%. No caustic soda solution needs to be added during the separation process, thereby avoiding the discharge of three wastes and pollution of the environment.

[0043] According to the present disclosure, the oxidation 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 to-be-separated substances include 3% to 8% of cyclohexanol and cyclohexanone, 91.5% to 96.9% of cyclohexane, and 0.1% to 0.5% of impurities. The inventors of the present application discovered that the impurities in cyclohexane can be divided into four categories based on polarity and boiling point: Class I impurities are light impurities with a boiling point below 200°C, such as hexanal and heptanone; Class II impurities are weakly polar impurities with a boiling point between 200°C and 300°C, such as cyclohexyl hexanoate and cyclohexenylcyclohexanone; Class III impurities are polar impurities with a boiling point between 200°C and 300°C, such as cyclohexanediol and 4-hydroxycyclohexanone; and Class IV impurities are heavy impurities with a boiling point above 300°C, such as cyclohexanetriol and dicyclohexyl adipate. Class I impurities can be separated from the solvent by distillation, Class II impurities can be separated from the solvent by water washing-non-polar compound stripping, Class III impurities can be separated from the solvent by selective adsorption, and Class IV impurities can be separated from the solvent by reduced pressure flash evaporation. The present invention designs a solvent purification unit for the separation of cyclohexanol and cyclohexanone, which can include one or more of a water washing stripping module, an adsorption module, a membrane separation module, and a flash evaporation module. In practical applications, the various modules of the purification unit can be set according to the content of different types of impurities in the object to be separated, and the arrangement order between the modules can be optimized to ensure the quality of the circulating solvent. For example, if there are no Class IV impurities in the object to be separated, a flash evaporation module may not be provided in the solvent purification unit.

[0044] According to one embodiment of the present disclosure, the extraction solvent is selected from an organic solvent with a boiling point of 200°C to 300°C, the molecules of the extraction solvent contain one or more of O, N, and S, the extraction solvent contains 0.1% to 2.0% water by mass, and the extraction solvent is selected from one of sulfolane, N-methylpyrrolidone, and N-formylmorpholine, preferably sulfolane. This embodiment is conducive to improving the selectivity of the extraction solvent and increasing the purity of cyclohexanol and cyclohexanone.

[0045] According to one embodiment of the present disclosure, the method includes: returning the washed raffinate oil from the water washing tower to the cyclohexane oxidation unit to allow the cyclohexane therein to continue to react.

[0046] According to one embodiment of the present disclosure, the method includes: returning a portion of the purified water from the solvent purification unit to the water washing tower, allowing the remaining portion of the purified water to enter a water stripping tower for stripping to obtain an aqueous phase and an oil phase containing an extraction solvent, returning the aqueous phase to the water washing tower, and returning the oil phase to the solvent recovery tower.

[0047] 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 0.8 to 1.5:1; the extraction solvent is introduced into the tower at a temperature of 40°C to 80°C, preferably 40°C to 60°C; the substance to be separated is introduced into the tower at a temperature of 40°C to 80°C, preferably 40°C 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 cyclohexanol and cyclohexanone.

[0048] 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; 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 1:1, preferably 0.2 to 0.6:1, and the bottom temperature of the solvent recovery tower is 140° C. to 180° C., preferably 160° C. to 180° C. The above embodiment is conducive to improving the mass yield of cyclohexanol and cyclohexanone.

[0049] According to one embodiment of the present disclosure, in step (c), the mass ratio of the wash water to the lean solvent entering the solvent purification unit is 0.25 to 1.5:1, preferably 0.25 to 1:1; and the lean solvent entering the solvent purification unit accounts for 0.1% to 15% of the total mass of the lean solvent. This embodiment is conducive to improving the purity of the cyclohexanol and cyclohexanone mixture.

[0050] According to one embodiment of the present disclosure, the solvent purification unit comprises a water washing and stripping module, an adsorption module, a membrane separation module and a flash evaporation module in sequence;

[0051] The method comprises:

[0052] The washed water and a portion of the lean solvent enter the water washing and stripping module to contact with the stripping agent, perform water washing and stripping and phase separation, and obtain the stripping agent containing weakly polar esters and ketones as second impurities and the first aqueous solvent;

[0053] allowing the first aqueous solvent to enter the adsorption module to separate highly polar alcohols and ketones as third impurities, thereby obtaining a second aqueous solvent;

[0054] The second aqueous solvent enters the membrane separation module to produce the purified water and the purified solvent. A portion of the purified solvent is returned to the extraction tower, and the remainder is flashed in the flash evaporation module to produce a bottoms liquid containing recombinant alcohols and esters as fourth impurities and a flash vapor phase. The flash vapor phase is returned to the bottom of the solvent recovery tower. This embodiment improves the purity of the cyclohexanol and cyclohexanone mixture, further separates impurities from the circulating solvent, enhances the stability of the circulating solvent, and enables long-term operation of the device.

[0055] According to one embodiment of the present disclosure, in the water-wash stripping module, the mass ratio of the stripping agent to the lean solvent is 0.3 to 1:1, preferably 0.5 to 0.8:1; the stripping agent is an alkane with 3 to 8 carbon atoms, preferably cyclohexane; the operating temperature of the water-wash stripping is 25°C to 60°C, preferably 30°C to 50°C, and the theoretical stage is 1 to 5. The above embodiment is conducive to improving the purity of the cyclohexanol and cyclohexanone mixture, further separating impurities in the circulating solvent, improving the stability of the circulating solvent, and enabling the long-term operation of the device.

[0056] According to one embodiment of the present disclosure, in the adsorption module, the adsorbent is a macroporous resin or silica gel, preferably a styrene-based macroporous resin, and more preferably a styrene-based ion exchange resin; the resin particle diameter can be 0.2 to 1.5 mm, preferably 0.4 to 1.2 mm; the resin processing capacity is 20 to 200 g of sulfolane / g of resin, the apparent flow rate of the first aqueous solvent entering the resin loading equipment is 0.5 m / h to 6.0 m / h; and the temperature of the adsorption module is 25°C to 50°C, preferably 30°C to 45°C. The above embodiment is conducive to improving the purity of the cyclohexanol and cyclohexanone mixture, 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.

[0057] According to one embodiment of the present disclosure, in the membrane separation module, the separation membrane is a molecular sieve pervaporation membrane, the support is a hollow fiber tubular support, preferably an yttrium-stabilized zirconia hollow fiber tubular support; the molecular sieve membrane includes one or more of NaA, ZMS-5, NaY, T, and CHA types, preferably T and / or CHA types; the permeate side pressure is below 0.5 kPa, and the temperature is 40°C to 100°C, preferably 70°C to 100°C. The above embodiment is conducive to improving the purity of the cyclohexanol and cyclohexanone mixture, 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.

[0058] According to one embodiment of the present disclosure, the mass of the purified solvent entering the flash evaporation module accounts for 0.1% to 1.0%, preferably 0.1% to 0.8%, of the total mass of the purified solvent; in the flash evaporation module, the absolute pressure 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° C. to 180° C. The above embodiment is conducive to improving the purity of the cyclohexanol and cyclohexanone mixture, further separating impurities in the circulating solvent, improving the stability of the circulating solvent, and enabling the long-term operation of the device.

[0059] 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.

[0060] Example 1

[0061] This embodiment 1 uses Figure 1 The process shown is to separate cyclohexanol and cyclohexanone from cyclohexane using Figure 2 Purify the solvent. Figure 1 In the process, the material to be separated enters the liquid-liquid extraction tower 101 through the raw material inlet 1, and the extraction solvent enters the liquid-liquid extraction tower 101 through the extraction solvent inlet 2. After the two are in countercurrent contact, a raffinate oil 3 mainly containing cyclohexane is obtained at the top of the tower, and a first rich solvent 4 is obtained at the bottom of the tower; the raffinate oil 3 enters the water washing tower 102 for water washing to remove water-soluble impurities in the recovered cyclohexane, thereby obtaining washed water 6 and washed raffinate oil 5 containing cyclohexane, and the washed raffinate oil 5 is returned to the cyclohexane oxidation unit;

[0062] The first rich solvent 4 is passed into a stripping tower 103 to remove a small amount of cyclohexane and Class I impurities such as low-boiling aldehydes and ketones from the first rich solvent. A light component 7 containing cyclohexane and low-boiling hexanal, which are Class I impurities, is obtained from the top of the stripping tower 103. 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. A lean solvent is obtained from the bottom of the solvent recovery tower 104.

[0063] A portion 11 of the lean solvent from the solvent recovery tower and the washed water 6 from the water scrubber are fed into the solvent purification unit 105 for purification to improve the quality of the circulating extraction solvent and obtain purified water 22, purified solvent 24 and impurity components; the remaining portion 10 of the lean solvent and the purified solvent 24 are returned to the extraction tower 101 for recycling; a portion 13 of the purified water is returned to the water scrubber 102, and the remaining portion 14 of the purified water is fed into the water stripping tower 106 for stripping to recover a small amount of extraction solvent in the purified water to obtain an aqueous phase 15 and an oil phase 16 containing the extraction solvent; the aqueous phase 15 is returned to the water scrubber 102 for recycling, and the oil phase 16 is returned to the solvent recovery tower 104.

[0064] Figure 2 In the embodiment 1, the solvent purification unit includes a water washing and stripping module, an adsorption module, a membrane separation module and a flash evaporation module. A portion of the lean solvent 11 from the solvent recovery tower is mixed with the washed water 6 and then enters the water washing and stripping module 107 through the pipeline 17. The stripping agent cyclohexane enters the water washing and stripping module 107 from the stripping agent inlet 18 for water washing, stripping and phase separation to obtain a first aqueous solvent 20 and a stripping agent 19 containing cyclohexenylcyclohexanone, a Class II impurity. The cyclohexane can be further distilled to obtain cyclohexane for recycling. The Class II impurity discharge device is used. The first aqueous solvent 20 enters the adsorption module 108 to separate the Class III impurity cyclohexanediol and discharge the device to obtain a second aqueous solvent 21; the second aqueous solvent 21 enters the membrane separation module 109 to obtain purified water 22 and a purified solvent. A portion 24 of the purified solvent is returned to the extraction tower, and the remaining portion 23 enters the solvent regeneration tank 110 (flash evaporation module) for flash evaporation. The flash gas phase 12 obtained at the top of the tank enters the solvent recovery tower 104, and the Class IV impurity dicyclohexyl adipate is obtained at the bottom of the tank and is discharged.

[0065] Example 1: Hexanal, cyclohexenylcyclohexanone, cyclohexanediol, and dicyclohexyl adipate were used as representatives of Class I to IV impurities, respectively, to prepare an organic phase (to be separated) obtained by simulating the oxidation and alkaline decomposition of cyclohexane. The composition of the separated product is shown in Table 1. The extraction solvent was 1% water-containing sulfolane. The lean solvent entering the solvent purification unit accounted for 10% of the total lean solvent mass, and the purified solvent entering the solvent regeneration tank accounted for 1% of the total lean solvent mass. A styrene-divinylbenzene polymer ion exchange resin was selected as the adsorbent in the adsorption module. In the membrane separation module, a T-type molecular sieve membrane was selected, and an yttrium-stabilized zirconia hollow fiber tubular support was selected as the support. 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 was 96.1%, and the separation device could operate smoothly for at least 3 months.

[0066] Example 2

[0067] The process of Example 2 is the same as that of Example 1, except that the solvent purification unit of Example 2 does not include a flash evaporation module, and the remaining process is used to purify the solvent.

[0068] Example 2 Heptanone, cyclohexyl isovalerate, and 4-hydroxycyclohexanone are respectively used as representatives of Class I to III impurities to prepare an organic phase (to be separated) obtained by simulating cyclohexane oxidation-alkali decomposition. The composition of the to be separated is shown in Table 1, and the extraction solvent is 1wt% sulfolane containing water. The solvent entering the solvent purification unit accounts for 8% of the total mass of the lean solvent. In the adsorption module, a styrene-divinylbenzene polymer ion exchange resin is selected as the adsorbent. In the membrane separation module, a T-type molecular sieve membrane is selected, and an yttrium-stabilized zirconia hollow fiber tubular carrier is selected as the carrier. 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. The mass yield of the cyclohexanol and cyclohexanone mixture is 96.2%.

[0069] Example 3

[0070] The method of Example 3 is the same as that of Example 1, except that the operating conditions of the stripping column and the top of the solvent recovery column are different, as shown in Table 2. The composition of the separated cyclohexanol and cyclohexanone mixture is shown in Table 3. The purity of the cyclohexanol and cyclohexanone mixture has decreased, and the mass yield is 95.7%.

[0071] Example 4

[0072] The method of Example 4 was the same as that of Example 1, except that the mass ratio of the wash water to the lean solvent entering the solvent purification unit was 0.1:1. The operating conditions were detailed 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 was 95.2%.

[0073] Example 5

[0074] The method of Example 5 is the same as that of Example 1, except that the purified solvent entering the flash evaporation module accounts for 0.05% of the total mass of the lean solvent. The 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%.

[0075] Comparative Example 1

[0076] This comparative example is as follows Figure 3The 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 pressure at 1 MPa and the tower temperature at 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 a temperature of 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 operating pressure of the flash tower was 0.02 MPa. The extract phase at the bottom of the extraction tower was passed into the flash tower. The extract phase was a mixed solution of ionic liquid and KA oil at 130-135°C. It was introduced into the flash tower through a pipeline from the middle of the flash tower. The liquid pressure was rapidly reduced from 1 MPa to 0.02 MPa. The KA oil reached its saturated vapor pressure and vaporized. The cyclohexanol and cyclohexanone mixture separated by condensation in a condenser at the top of the tower was shown in Table 3. The mass yield of the cyclohexanol and cyclohexanone mixture was 92.7%.

[0077] Comparative Example 2

[0078] 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. 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%.

[0079] Table 1 Composition of the substances to be separated

[0080]

[0081] Table 2 Main operating conditions

[0082]

[0083]

[0084] Table 3 Mass yield and product composition of the separated cyclohexanol and cyclohexanone mixture

[0085]

[0086]

[0087] 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%. 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 the cyclohexanol and cyclohexanone obtained are higher. By comparing Example 1 with Example 4, it can be seen that within the mass ratio of the post-wash water to the lean solvent of the present invention, the purity and mass yield of the cyclohexanol and cyclohexanone mixture obtained are higher. By comparing Example 1 with Example 5, it can be seen that within the total mass ratio of the purified solvent to the lean solvent of the present invention, the purity and mass yield of the cyclohexanol and cyclohexanone mixture obtained are higher.

[0088] By comparing Example 1 with Comparative Example 1, it can be seen that since Comparative Example 1 does not have an effective method for removing polar impurities in the substance to be separated, the solvent deteriorates severely, and the extraction and separation effect decreases significantly after continuous circulation for one week. The mass yield of the cyclohexanol and cyclohexanone mixture is lower than that of the method disclosed in the present invention, and the purity is also much lower than that of the present invention.

[0089] By comparing Example 1 with Comparative Example 2, it can be seen that Comparative Example 2 can better remove various impurities in the raw materials using traditional processes, but since cyclohexanol and cyclohexanone have a certain solubility in water, its mass yield is far less than that of the present disclosure.

[0090] 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.

[0091] 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.

[0092] 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 cyclohexanol and cyclohexanone from cyclohexane, 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 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 lean solvent from the bottom of the solvent recovery tower; (c) allowing a portion of the lean solvent and the washed water from the water scrubber to enter a solvent purification unit for purification to obtain purified water, purified solvent, and impurity components; and returning the remaining portion of the lean solvent and the purified solvent to the extraction tower; The solvent purification unit includes one or more of a water washing and stripping module, an adsorption module, a membrane separation module and a flash evaporation module; 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; 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° C. to 300° C., and the molecules of the extraction solvent contain one or more of O, N, and S; the extraction solvent contains 0.1% to 2.0% by mass of water; The extraction solvent is selected from one of sulfolane, N-methylpyrrolidone and N-formylmorpholine; preferably sulfolane.

4. The method according to claim 1, wherein The method comprises: returning the washed raffinate oil from the water scrubber to a cyclohexane oxidation unit; A portion of the purified water from the solvent purification unit is returned to the water scrubber, and the remaining portion of the purified water enters a water stripping tower for stripping to obtain an aqueous phase and an oil phase containing an extraction solvent. The aqueous phase is returned to the water scrubber, and the oil phase is returned to the solvent recovery tower.

5. The method according to claim 1, wherein In step (a), the mass ratio of the extraction solvent to the substance to be separated is 0.5:1 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.

6. 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; in the solvent recovery tower, the absolute pressure at the top 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.

7. The method according to claim 1, wherein In step (c), the mass ratio of the washed water to the lean solvent entering the solvent purification unit is 0.25-1.5:1; and the lean solvent entering the solvent purification unit accounts for 0.1%-15% of the total mass of the lean solvent.

8. The method according to claim 1, wherein The solvent purification unit includes a water washing and stripping module, an adsorption module, a membrane separation module and a flash evaporation module in sequence; The method comprises: The washed water and a portion of the lean solvent from the water washing tower enter the water washing and stripping module to contact with a stripping agent, perform water washing, stripping and phase separation, and obtain a stripping agent containing a second impurity and a first aqueous solvent; allowing the first aqueous solvent to enter the adsorption module to separate the third impurity to obtain a second aqueous solvent; The second aqueous solvent is allowed to enter the membrane separation module to obtain the purified water and the purified solvent; a portion of the purified solvent is returned to the extraction tower, and the remaining portion of the purified solvent is allowed to enter the flash evaporation module for flash evaporation to obtain a tank bottom liquid containing a fourth impurity and a flash gas phase, and the flash gas phase is returned to the bottom of the solvent recovery tower.

9. The method according to claim 8, wherein In the water washing and stripping module, the mass ratio of the stripping agent to the lean solvent is 0.3 to 1:1; the stripping agent is an alkane with a carbon number of 3 to 8, preferably cyclohexane; the operating temperature of the water washing and stripping is 25° C. to 60° C., and the theoretical stage number is 1 to 5.

10. The method according to claim 8, wherein In the adsorption module, the adsorbent is a macroporous resin or silica gel, preferably a styrene-based macroporous resin; and the temperature of the adsorption module is 25° C. to 50° C.

11. The method according to claim 8, wherein In the membrane separation module, the separation membrane is a molecular sieve pervaporation membrane, and the carrier is a hollow fiber tubular carrier; the permeate side pressure is below 0.5 kPa, and the temperature is 40° C. to 100° C.

12. The method according to claim 8, wherein The mass of the purified solvent entering the flash evaporation module accounts for 0.1% to 1.0% of the total mass of the lean solvent; in the flash evaporation module, the absolute pressure is 0.001 MPa to 0.01 MPa, and the temperature is 160° C. to 180° C.

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