A separation method, separation system and application of a cyclohexyl phenyl oxidation product

Abstract

This invention relates to a method, system, and application for separating cyclohexylbenzene oxidation products. It primarily addresses the problem of residual cyclohexylbenzene accumulating during the extractive distillation separation process in the existing cyclohexylbenzene oxidation and decomposition technology for producing phenol-cyclohexanone, leading to reduced extractant efficiency and necessitating the addition of extractant purification equipment. This invention experimentally discovers for the first time that cyclohexylbenzene and polyol extractants form a heterogeneous low-boiling-point azeotrope. By adding a liquid-phase sidestream extraction and liquid-liquid separation device to the solvent recovery and stripping section, the cyclohexylbenzene-extractant azeotrope can be extracted. After cooling and phase separation, the lighter phase, mainly containing cyclohexylbenzene, is discharged, while the heavier phase, mainly containing extractant, is recycled. This extractant recycling technology effectively solves the problem and can be used in cyclohexylbenzene production phenol-cyclohexanone plants.

Description

Technical Field

[0001] This invention belongs to the field of separation and purification technology, specifically relating to a method, separation system and application for separating cyclohexylbenzene oxidation products. Background Technology

[0002] The oxidation of cyclohexylbenzene (CHB) and the decomposition of cyclohexylbenzene hydroperoxide (1-CHBHP) acid are characterized by numerous byproducts, multiple isomers, and azeotropes during the separation process, making it difficult to achieve efficient separation using conventional distillation.

[0003] It is well known that phenol and cyclohexanone can be co-produced via a variation of the Hock method, wherein cyclohexylbenzene is oxidized to yield cyclohexylbenzene hydroperoxide and the hydroperoxide is decomposed in the presence of an acid catalyst to the desired phenol and cyclohexanone. While various methods are available for the preparation of cyclohexylbenzene, a preferred route is disclosed in U.S. Patent 6,037,513, which discloses the preparation of cyclohexylbenzene by contacting benzene with hydrogen in the presence of a bifunctional catalyst comprising a molecular sieve of the MCM-22 group and at least one hydride metal selected from palladium, ruthenium, nickel, cobalt, and mixtures thereof. This patent also discloses that the resulting cyclohexylbenzene can be oxidized to the corresponding hydroperoxide, which is then decomposed in approximately equimolar amounts to the desired phenol and cyclohexanone byproducts.

[0004] However, besides the Hock process, other methods for preparing phenol from cyclohexylbenzene have many problems. One problem is that phenol and cyclohexanone form an azeotrope in the product, with an azeotropic composition of 28 wt% cyclohexanone: 72 wt% phenol. Therefore, although some high-purity cyclohexanone can be recovered from the product of US patent 6,037,513 by simple distillation, the preparation of high-purity phenol requires a different separation method. A convenient method is extractive distillation. This method uses a solvent with lower volatility than the lowest volatile component in the mixture to be separated, miscible with the mixture and its components, and not forming an azeotrope with the mixture or any of its components. The solvent interacts differently with the azeotropic mixture components, thereby causing a change in their relative volatility. This allows the new three-part system to be separated in a simple one or more distillation apparatuses. The highest volatile initial component is separated as the top product, while the bottom product contains the solvent and the lower volatile component. This bottom product can also be easily separated because the solvent does not form an azeotrope with the lower volatile component.

[0005] Various solvents have been proposed over the years for separating azeotropic phenol systems. For example, for the phenol-cyclohexanone system, US Patent 2,265,939 discusses the use of diols and glycols as solvents. This patent records the reaction of ethylene glycol with cyclohexanone to form a ketal co-distilled with cyclohexanone, and the recovery of the cyclohexanone and ethylene glycol from the reaction must be carried out by hydrolysis. The patent further mentions that, to avoid the reaction between cyclohexanone and the solvent, a larger molecule should be used, which provides a greater atomic spacing between the two hydroxyl groups of the diol or glycol (e.g., diethylene glycol).

[0006] US Patent 5,334,774 discusses the use of diethylene glycol for the separation of phenol and sec-butylbenzene azeotropic systems. In US Patent 4,230,638, a mixture of sulfolane / diethylene glycol and a non-oxygenated hydrocarbon was proposed as a solvent in a liquid-liquid extraction system to separate cyclohexylbenzene from phenol and cyclohexanone. However, while sulfolane has excellent solvent qualities for this separation, it is not preferred due to its high reactivity with oxygen, requires vacuum pressure, and air ingress is unavoidable in any distillation method using sulfolane as a solvent, leading to the formation of acids and other harmful degradation products. Diols and glycols are preferred because they are more resistant to undesirable side reactions with oxygen. According to the disclosure of the present invention, it has now been found that diols and glycols with hydroxyl groups attached to non-adjacent carbon atoms can react with cyclohexanone to form, under certain conditions, a class of previously undisclosed hemiketals and enol-ether condensation products. Specifically, we found that large acyclic hemiacetals are formed, and under certain conditions, dehydrated products (enol-ethers) of their cyclic olefins / ethers are also formed, which can affect the separation of phenol and cyclohexanone. This fact and the understanding of the properties of these new compounds are important for the proper design and operation of extractive distillation systems that typically use such large diols and glycols (especially diethylene glycol) as solvents to separate phenol and cyclohexanone.

[0007] Chinese patent CN106008153A reports a method for separating a mixture containing cyclohexanone and phenol, in which a solid-phase alkaline material, such as an alkaline ion exchange resin, is used to remove acid and / or sulfur from the mixture prior to separation. This method results in a low amount of contaminants, such as cyclic ethers, within the cyclohexanone and / or phenol products. Since phenol and cyclohexanone form an azeotrope, complete separation of phenol and cyclohexanone can be achieved solely with the aid of an extractive distillation solvent to obtain two pure products. It has been found that the presence of sulfur and / or acid in the feed within a distillation column (including, but not limited to, extractive distillation columns) can significantly hinder efficient separation and / or operation of the distillation column, resulting in unwanted contaminants in one or both of the cyclohexanone and phenol products. Effluent from the pyrolysis step typically contains phenol, cyclohexanone, acid catalysts, cyclohexylbenzene, and additional contaminants that can be produced as byproducts of the oxidation and / or pyrolysis steps. To obtain pure phenol and cyclohexanone, the cracking effluent is typically first treated in the liquid phase under operating conditions with a basic material, such as an amine (e.g., pentane-1,5-diamine, hexane-1,6-diamine, hexane-1,5-diamine, 2-methylpentane-1,5-diamine, ethylenediamine, diethylenetriamine, triethylenetetramine, propylenediamine, and the like), to neutralize at least a portion of the acid catalyst. The neutralized cracking effluent is then separated, for example, by a distillation column. Since phenol and cyclohexanone form an azeotrope, complete separation of phenol and cyclohexanone to obtain both pure products can be achieved solely with the aid of an extractive distillation solvent. It has been found that the presence of sulfur and / or acid in the feed within a distillation column (including, but not limited to, extractive distillation columns) can significantly hinder efficient separation and / or operation of the distillation column, resulting in unwanted contaminants in one or both of the cyclohexanone and phenol products.

[0008] Chinese patent CN103097329A reports that the production of phenol from cyclohexylbenzene also generates various contaminants that are difficult to separate from the desired product. However, the nature of these contaminants and the separation involved are significantly different from those involved in the conventional Hock process for the production of phenol and acetone. For example, the hydrogenation alkylation of benzene produces, among other things, significant amounts of cyclohexane and smaller amounts of methylcyclopentane, cyclohexene, phenylcyclohexene, and phenylcyclohexyldiene. Similarly, the oxidation of cyclohexylbenzene typically produces peroxides different from those produced in the Hock process, such as the desired cyclohexyl-1-phenyl-1-hydroperoxide (CHBHP), and undesirable byproduct hydroperoxides, such as cyclohexyl-1-phenyl-2-hydroperoxide, cyclohexyl-1-phenyl-3-hydroperoxide, and cyclohexyl-1-phenyl-4-hydroperoxide. Finally, the cracking of these different hydroperoxides produces a variety of contaminant substances as undesirable hydroperoxide products and desirable CHBHP undesirable byproducts, which are not generated by the chemistry and technology of the Hock process.

[0009] Chinese patent CN104030892A discloses a process flow for the oxidation-decomposition of CHB to produce phenol and cyclohexanone. The decomposition products after neutralization are fed into a first distillation column for separation. This column discharges three streams: 1) a high-boiling-point component containing neutralizing agent organic amine salts, C12 oxides, and similar substances, discharged from the bottom of the column and sent to a processing station; 2) a side stream containing a high concentration of CHB, collected from the middle of the column, processed, and recycled back to the feed hydrogenation reactor; 3) a top stream containing phenol, cyclohexanone, and water, fed into a second fractionation column. The second fractionation column is a light component removal column; the aqueous light component removed from the top is sent to the processing station, while the bottom stream containing phenol and cyclohexanone is sent to a third fractionation column. The third fractionation column is an extractive distillation column, where a composite solvent containing diethylene glycol and hemiketal is added as an extractant to disrupt the azeotropic reaction between phenol and cyclohexanone, achieving their separation. Crude cyclohexanone is obtained from the top of the third fractionation column and enters the fourth fractionation column for purification. High-purity cyclohexanone product and phenol and extraction solvent from the bottom stream of the third fractionation column enter the fifth fractionation column. The fifth fractionation column separates phenol and the extractant. The extractant discharged from the bottom of the fifth fractionation column is recycled back to the extraction column. Crude phenol is obtained from the top of the fifth fractionation column and continues to be purified in the sixth fractionation column. High-purity phenol is obtained from the top of the sixth fractionation column, and the bottom stream is recycled back to the first rectification column or sent to the processing station. The first distillation column contains phenol, cyclohexanone, and water at the top, maintained at 80-150°C; the intermediate effluent is cyclohexylbenzene, and the bottom contains at least 80 wt% amine salts, maintained at 180-300°C; the absolute pressure is below 100 kPa. The second distillation column contains water at the top, maintained at 40-100°C; the bottom contains phenol and cyclohexanone, maintained at 80-180°C; the absolute pressure is below 100 kPa. The third distillation column (extractive distillation column) contains at least 60 wt% cyclohexanone at the top, maintained at 50-150°C; the bottom contains phenol and extractant, maintained at 120-220°C; the absolute pressure is below 100 kPa; the extractant feed point is higher than... Feed locations: Fourth distillation column (purifying crude cyclohexanone): at least 90 wt% cyclohexanone at the top, 150-250℃; heavy components at the bottom, 120-300℃; absolute pressure above 100 kPa; Fifth distillation column (recovering extractant): at least 60 wt% phenol at the top, 80-180℃; extractant at the bottom, 120-250℃; absolute pressure below 100 kPa; Sixth distillation column (purifying crude phenol): at least 90 wt% phenol at the top, 120-250℃; heavy components at the bottom, 150-300℃; absolute pressure above 100 kPa.

[0010] Through the above process, the top of the first fractionation column yields a small amount of cyclohexylbenzene. After separation in the second, third, and fifth fractionation columns, cyclohexylbenzene becomes the second heaviest or heaviest component in the system (excluding oligomers and other polymers). This cyclic accumulation reduces the extraction efficiency of the extractant, necessitating periodic discharge of the extractant for fuel or post-treatment. This requires the addition of new distillation columns and other equipment to purify the extractant, leading to increased equipment investment or raw material costs. Furthermore, none of the above patents consider that glycols are heat-sensitive substances; at a certain temperature, they begin to decompose, generating other substances such as dehydration to form olefins, or intermolecular etherification to form ethers while simultaneously dehydrating. Strict control of the separation temperature, especially the column bottom temperature, is required to prevent the extractant from becoming ineffective during dehydration. Summary of the Invention

[0011] Existing technologies for the oxidation and decomposition of cyclohexylbenzene to produce phenol-cyclohexanone suffer from the problem of residual cyclohexylbenzene accumulating during the extractive distillation separation process in the phenol-cyclohexanone azeotropic system, leading to reduced extraction efficiency and necessitating the addition of extractant purification equipment. This invention provides a method and system for separating the cyclohexylbenzene oxidation products to address this issue. By adding a liquid-phase side stream extraction and liquid-liquid separation device to the solvent recovery and stripping section, the cyclohexylbenzene-extractant azeotrope can be extracted, cooled, and separated to obtain cyclohexylbenzene, achieving effective separation of the components.

[0012] One objective of this invention is to provide a method for separating cyclohexylbenzene oxidation products, comprising: mixing the cyclohexylbenzene oxidation products and an extractant, and then performing extractive distillation and solvent recovery to obtain phenol, cyclohexanone, cyclohexylbenzene, and the extractant. The solvent recovery includes: collecting the cyclohexylbenzene-extractant azeotrope and then cooling and separating the phases to obtain a light phase containing cyclohexylbenzene and a heavy phase containing the extractant. Preferably, the separation method specifically includes the following steps:

[0013] 1) The cyclohexylbenzene oxidation product and the extractant were extracted and distilled in an extractive distillation column to obtain a top stream and a bottom stream containing cyclohexanone.

[0014] 2) The column bottom stream is separated by a solvent recovery column to obtain a column top stream containing phenol, a column bottom stream containing extractant, and a side stream of cyclohexylbenzene-extractant azeotrope;

[0015] 3) The cyclohexylbenzene-extractant azeotrope is cooled and separated to obtain a light phase containing cyclohexylbenzene and a heavy phase containing the extractant.

[0016] According to a specific embodiment of the present invention, in the method for separating the cyclohexylbenzene oxidation products:

[0017] The cyclohexylbenzene oxidation product comprises phenol, cyclohexanone, and cyclohexylbenzene. Preferably, based on 100 wt% of the cyclohexylbenzene oxidation product, the content of phenol is 45-75 wt%, the content of cyclohexanone is 24-50 wt%, and the content of cyclohexylbenzene is ≤5 wt%.

[0018] In the prior art, the oxidation products of cyclohexylbenzene contain multiple components such as phenol and cyclohexanone. After preliminary separation, a mixture mainly containing phenol, cyclohexanone, and a small amount of cyclohexylbenzene is obtained. The separation method of the present invention is preferably designed for the separation of this mixture mainly containing phenol, cyclohexanone, and a small amount of cyclohexylbenzene, for example, as described in Chinese Patent CN104030892A. Figure 1 B-type logistics 209.

[0019] According to a specific embodiment of the present invention, the extractant is selected from polyol compounds, preferably from at least one of diethylene glycol and triethylene glycol; the mass ratio of the extractant to the cyclohexylbenzene oxidation product is 1:(1-6), preferably 1:(1.2-4).

[0020] According to a specific embodiment of the present invention:

[0021] In step 1), the temperature of the bottom of the extractive distillation column shall not exceed 165°C, and preferably be 150-165°C.

[0022] The temperature of the solvent recovery tower bottom in step 2) shall not exceed 165°C, preferably 160-165°C.

[0023] Since the extractants diethylene glycol and triethylene glycol are both heat-sensitive substances, they will decompose when the temperature reaches 165℃. Therefore, the operating temperature of the bottom of the extractive distillation column should not exceed 165℃, and the operating temperature of the bottom of the solvent recovery column should also not exceed 165℃.

[0024] According to a specific embodiment of the present invention, in the method for separating the cyclohexylbenzene oxidation products:

[0025] The side-stream cyclohexylbenzene-extractant azeotrope is located above the solvent recovery tower, and its operating temperature is lower than the tower bottom temperature. The cyclohexylbenzene-extractant azeotrope is collected by controlling appropriate operating conditions of the side-stream. Preferably, the conditions for collecting the cyclohexylbenzene-extractant azeotrope by the side-stream are: pressure of 1-10 kPa and temperature of 95-150°C; more preferably, pressure of 2-6 kPa and temperature of 105-135°C.

[0026] The extractant-containing bottom stream obtained in step 2) is recycled to the extractive distillation column;

[0027] In step 3), the cyclohexylbenzene-extractant azeotrope is cooled at a temperature of 30–60°C, preferably 40–60°C. The lower the temperature, the lower the mutual solubility of the two components, the better the phase separation effect of the cyclohexylbenzene-extractant azeotrope, the lower the extractant content in the light phase, and the lower the cyclohexylbenzene content in the heavy phase.

[0028] The cyclohexylbenzene-containing light phase obtained in step 3) is optionally washed with water; water washing can remove water-soluble components (such as extractants) and can be recycled and reused.

[0029] The heavy phase containing the extractant obtained in step 3) is recycled to the solvent recovery tower.

[0030] According to a specific embodiment of the present invention:

[0031] The bottom material containing the extractant obtained in step 2) is circulated to the extractive distillation column after being cooled by heat exchange; preferably, the cooling temperature is above 40°C, more preferably 40-60°C;

[0032] The position where the heavy phase extractant obtained in step 3) is circulated to the solvent recovery tower is below the position of the cyclohexylbenzene-extractant azeotrope taken out by the side stream; preferably 1 to 5 theoretical plates below the position of the cyclohexylbenzene-extractant azeotrope taken out by the side stream, more preferably 2 to 4 theoretical plates.

[0033] The location of the extracted cyclohexylbenzene-extractant azeotrope is 1 to 8 theoretical plates below the feed position of the solvent recovery tower, preferably 1 to 5 theoretical plates.

[0034] The second objective of this invention is to provide a cyclohexylbenzene oxidation product separation system for implementing the above-mentioned separation method, comprising: an extractive distillation column, a solvent recovery column, and a liquid-liquid separation tank connected in sequence by pipelines; the material outlet at the bottom of the extractive distillation column is connected to the solvent recovery column by a pipeline; a liquid-liquid outlet is provided on the side of the solvent recovery column and connected to the liquid-liquid separation tank by a pipeline; the bottom of the liquid-liquid separation tank is provided with a cyclohexylbenzene light phase stream outlet and an extractant heavy phase stream outlet, wherein the extractant heavy phase stream outlet circulates the extractant heavy phase stream to the solvent recovery column by a pipeline.

[0035] According to a specific embodiment of the present invention, the extractive distillation column and the solvent recovery column are independently equipped with reboilers. Preferably, the reboilers are independently selected from either a forced circulation reboiler or a falling film reboiler. Since the extractants diethylene glycol and triethylene glycol are both heat-sensitive substances, they decompose at 165°C, resulting in the generation of byproducts. These byproducts reduce the extraction efficiency of the extractant. Simultaneously, coking and carbon deposition occur in the high-temperature zone of the reboiler wall, leading to increased thermal resistance of the heat exchanger and decreased heat exchange efficiency. Based on the advantages of falling film reboilers—low surface temperature, short material residence time, and low process-side pressure—forced circulation reboilers or falling film reboilers are preferred for the extractive distillation column and the solvent recovery column. This reduces the occurrence of thermal degradation of the extractant and ensures the extractant efficiency.

[0036] According to a specific embodiment of the present invention, in the extractive distillation column:

[0037] The extractive distillation column comprises 30 to 60 theoretical plates, preferably 35 to 55 theoretical plates;

[0038] The extractive distillation column is equipped with a cyclohexanone-containing material outlet at the top, and the material at the bottom of the column enters a solvent recovery column for processing.

[0039] The extractive distillation column comprises, from top to bottom, a rectification section, an extraction section, and a stripping section. An extractant inlet is provided between the rectification section and the extraction section, and a cyclohexylbenzene oxidation product inlet is provided between the extraction section and the stripping section.

[0040] The cyclohexanone stream obtained from the extractive distillation column can be purified using common purification methods in the art to obtain qualified products. For example, the distillation process commonly used in the prior art can be referred to the purification method disclosed in "Optimization of Cyclohexanone Distillation Process" (Chemical Industry and Engineering Progress, Vol. 36 Supplement, 2017, pp. 548-552).

[0041] According to a specific embodiment of the present invention, in the solvent recovery tower:

[0042] The solvent recovery tower comprises 10 to 40 theoretical plates, preferably 15 to 35 theoretical plates;

[0043] The bottom material outlet of the solvent recovery tower is connected to a circulating extractant cooler via a pipeline, which is used to cool the recovered extractant and circulate it back to the extractant feed pipeline. Preferably, the cooling temperature of the circulating extractant cooler is above 40°C, and more preferably 40-60°C.

[0044] A cooler is also provided between the solvent recovery tower and the liquid-liquid separation tank. Preferably, the cooling temperature of the cooler is 30-60°C, and more preferably 40-60°C.

[0045] The solvent recovery tower's stripping section is equipped with a side-stream liquid-liquid outlet connected to a liquid-liquid separator via a pipeline. Preferably, the side-stream liquid-liquid outlet is located 1 to 8 theoretical plates below the feed position of the solvent recovery tower, more preferably 1 to 5 theoretical plates.

[0046] The location where the extractant heavy phase stream is circulated to the solvent recovery tower is 1 to 5 theoretical plates below the side-stream liquid-liquid outlet, preferably 2 to 4 theoretical plates;

[0047] The top of the solvent recovery tower is the phenol material outlet. The obtained phenol stream can be refined into qualified products using common refining methods in the field, such as the refining methods disclosed in "A Review of High-Purity Phenol Refining Processes" (Chemical Industry and Engineering Progress, No. 2, 1999) and "A Review of Phenol Refining Methods" (Chemical Industry and Engineering Progress, No. 5, 1992).

[0048] According to a specific embodiment of the present invention, the sidestream liquid phase of the solvent recovery tower is cooled and separated into light and heavy phase streams. The light phase mainly contains cyclohexylbenzene and is collected externally, while the cyclohexylbenzene content in the heavy phase is significantly reduced. The treatment method for the light phase can be determined according to the scale of the equipment. If the scale is large and there is recovery value, the light phase can be treated by controlling the water washing temperature and performing water washing and phase separation to recover phenol and cyclohexylbenzene, taking advantage of the property that phenol is soluble in hot water and cyclohexylbenzene is insoluble in water. If the amount is small, it can be sent to an incinerator for treatment. The heavy phase mainly contains the extractant diethylene glycol or triethylene glycol and is returned to the solvent recovery tower. Through the above design, cyclohexylbenzene in the circulating extractant no longer accumulates in the circulation. In addition, the reboiler adopts a forced circulation reboiler and a falling film reboiler, which can reduce the occurrence of thermal degradation of the extractant and ensure the efficiency of the extractant. The position of the heavy phase stream of the extractant circulating to the solvent recovery tower is 1 to 5 theoretical plates below the sidestream liquid outlet, preferably 2 to 4 theoretical plates.

[0049] The third objective of this invention is the separation method of cyclohexylbenzene oxidation products according to the first objective of this invention, or the application of the separation system of cyclohexylbenzene oxidation products according to the second objective of this invention in the separation of components of cyclohexylbenzene oxidation products.

[0050] This invention relates to a method for separating cyclohexylbenzene oxidation products. Specifically, it involves using a polyol extractant within an extractive distillation column to separate the products from the oxidation and acidolysis reactions of cyclohexylbenzene, which contain phenol, cyclohexanone, and trace amounts of cyclohexylbenzene. During the research process, the inventors discovered that cyclohexylbenzene has a negative effect on extractive distillation; the higher the concentration, the worse the extractive distillation effect. First, experiments verified the cyclohexanone-phenol azeotropic composition and temperature. Molecular simulations predicted that the polyol extractant and cyclohexylbenzene would form a heterogeneous low-boiling-point azeotrope. Thermodynamic experiments were conducted for the first time to discover that cyclohexylbenzene and the polyol extractant would form a heterogeneous low-boiling-point azeotrope. Based on this, a technical solution was developed that involves collecting the cyclohexylbenzene-extractant azeotrope from the side stream of the solvent recovery and stripping section, cooling and separating the phases. The lighter phase, mainly containing cyclohexylbenzene, is discharged, while the heavier phase, mainly containing the extractant, is recycled. This solution effectively solves the problem and can be used in cyclohexylbenzene production plants for phenol-cyclohexanone.

[0051] The beneficial effects of this invention are:

[0052] The liquid phase from the side stream of the solvent recovery tower is cooled and separated. The light phase, which mainly contains cyclohexylbenzene, is collected externally, while the cyclohexylbenzene content in the heavy phase is significantly reduced. The heavy phase, which mainly contains polyol extractants, is returned to the solvent recovery tower. Through the above design, cyclohexylbenzene in the circulating extractant no longer accumulates. In addition, the reboiler adopts a forced circulation reboiler and a falling film reboiler, which can reduce the occurrence of thermal degradation of the extractant and ensure the efficiency of the extractant. Attached Figure Description

[0053] Figure 1 This is a flowchart illustrating the method described in this invention.

[0054] Explanation of reference numerals in the attached diagram: C1—Extractive distillation column, C2—Solvent recovery column, E1—Cooler, D1—Liquid-liquid separator, E2—Circulating extractant cooler, Stream 1—Mainly contains phenol, cyclohexanone, and a small amount of cyclohexylbenzene (CHB), Stream 2—Supplemental extractant, Stream 3—Extractant feed to extractive distillation column C1, Stream 4—Crude cyclohexanone product, Stream 5—Boiler liquid from extractive distillation column C1, Stream 6—Crude phenol product, Stream 7—Liquid phase effluent from solvent recovery column C2, Stream 8—Cooling liquid from solvent recovery column C2, Stream 9—Light phase from liquid-liquid separator D1, Stream 10—Heavy phase from liquid-liquid separator D1, returned to solvent recovery column C2, Stream 11—Boiler liquid from solvent recovery column C2, Stream 12—Cooled circulating extractant.

[0055] Figure 2 This is a distillation residue curve of the phenol-CHB-DEG ternary system in this invention. From... Figure 2 As can be seen, in the presence of CHB, CHB and DEG will form a low-boiling-point azeotrope, and the side stream sample is a mixture of CHB and DEG.

[0056] Figure 3 shows the effect curves of different cyclohexylbenzene concentrations on the extraction performance of the extractant in this invention. Figure 3A The curves show the effect of phenol concentration (0–100%) on volatility in liquid-phase systems. Figure 3B for Figure 3A Figure 3 is an enlarged graph showing the phenol concentration curves in the liquid phase from 60% to 100%, where the horizontal axis (x1') represents the phenol concentration in the liquid phase and the vertical axis represents the relative volatility of the system. As can be seen from Figure 3, under the same extractant concentration, the presence of cyclohexylbenzene reduces the extractant's extraction performance, and this effect intensifies with increasing cyclohexylbenzene concentration in the mixture. Therefore, cyclohexylbenzene must be removed from the extractant during separation.

[0057] Figure 4 is the equilibrium phase diagram of the cyclohexylbenzene + DEG binary gas-liquid (VLLE) in this invention. Figure 4A The diagram shows the binary vapor-liquid equilibrium phase diagram of cyclohexylbenzene + DEG under a pressure of 1 kPa. Figure 4B Figure 4 shows the binary gas-liquid equilibrium phase diagram of cyclohexylbenzene + DEG under a pressure of 10 kPa. The horizontal axis represents the gas-liquid phase composition of cyclohexylbenzene (1), and the vertical axis represents the temperature. As can be seen from Figure 4, the cyclohexylbenzene phase in the liquid-liquid phase separation contains almost no DEG extractant. Therefore, cyclohexylbenzene in the extractant can be removed through liquid-liquid phase separation, thereby maintaining the extraction performance of the extractant. From the VLLE curve, the CHB-DEG azeotrope is a heterogeneous azeotrope. After liquid-liquid phase separation, the light phase contains a very small amount of DEG, and the heavy phase contains a small amount of CHB.

[0058] Figure 5 This is a diagram showing the distribution of solvent recovery tower trays, temperature, and liquid phase composition in this invention. Figure 5 As can be seen, the CHB liquid concentration is highest near the side stream extraction point, and then decreases until it approaches 0, meaning that the CHB content in the extractant extracted from the bottom of the column is close to 0. Detailed Implementation

[0059] The present invention will now be described in detail with reference to the accompanying drawings. However, it should be noted that the scope of protection of the present invention is not limited thereto, but is determined by the claims in the appendix.

[0060] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0061] When this specification uses the prefixes “known to those skilled in the art,” “prior art,” or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those commonly used in the art at the time of this application, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0062] In the context of this specification, except where expressly stated, any matters or issues not mentioned herein shall apply directly to those known in the art without any modification. Furthermore, any implementation described herein may be freely combined with one or more other implementations described herein, and any resulting technical solutions or concepts shall be considered part of the original disclosure or original record of this invention, and should not be regarded as new content not disclosed or anticipated herein, unless those skilled in the art consider such combination to be clearly unreasonable.

[0063] Unless otherwise specified, all percentages, parts, ratios, etc. mentioned in this specification are based on weight, unless being based on weight would not be in accordance with the common understanding of those skilled in the art.

[0064] Unless otherwise specified, all pressures mentioned in this manual are absolute pressures.

[0065] In the embodiments of the present invention, the content of each component was determined by GC-MS gas chromatography-mass spectrometry.

[0066] The present invention will be further described below through specific embodiments.

[0067] Figure 1 This is a schematic diagram of the separation system for the cyclohexylbenzene oxidation products described in this invention.

[0068] Figure 1 In the process flow diagram, C1 is the extractive distillation column, C2 is the solvent recovery column, E1 is the cooler, D1 is the liquid-liquid separator, and E2 is the circulating extractant cooler. Flow 1 mainly contains phenol, cyclohexanone, and a small amount of cyclohexylbenzene (CHB). Flow 2 is the supplementary extractant. Flow 3 is the extractant feed to extractive distillation column C1. Flow 4 is the crude cyclohexanone product. Flow 5 is the bottom liquid of extractive distillation column C1. Flow 6 is the crude phenol product. Flow 7 is the liquid phase output from solvent recovery column C2. Flow 8 is the coolant from the liquid phase output of solvent recovery column C2. Flow 9 is the light phase from liquid-liquid separator D1. Flow 10 is the heavy phase from liquid-liquid separator D1, returned to solvent recovery column C2. Flow 11 is the bottom liquid from solvent recovery column C2. Flow 12 is the cooled circulating extractant.

[0069] The specific steps are as follows:

[0070] Stream 1, mainly containing phenol, cyclohexanone, and a small amount of cyclohexylbenzene (CHB), is fed from the bottom of extractive distillation column C1. Stream 1 uses stream 209 from Chinese patent CN104030892A. The supplementary extractant stream 2 and the cooled recycled extractant stream 12 are mixed and used as the extractant feed for extractive distillation column C1. Stream 3 is fed from the top of column C1. The section above stream 3 is the rectification section, the section between stream 3 and stream 1 is the extraction section, and the section below stream 1 is the stripping section. Crude cyclohexanone product stream 4 is obtained at the top of extractive distillation column C1, and the bottom of the column is the bottom liquid stream 5, which mainly contains phenol, extractant, and... CHB, stream 5, enters solvent recovery tower C2 for separation to obtain crude phenol product stream 6 at the top of the tower. A CHB-rich mixture of CHB and DEG is collected from the side stream of solvent recovery tower C2 and cooled to 40-60°C through circulating extractant cooler E1. Cooling liquid stream 8 enters liquid-liquid separator D1 for liquid-liquid phase separation, resulting in light phase stream 9 which is separated from the system. Heavy phase stream 10 from liquid-liquid separator D1 returns to solvent recovery tower C2, with the return position below the side stream collection position. Liquid stream 11 from the bottom of solvent recovery tower C2 is cooled to 40-60°C through heat exchange and E2. The cooled circulating extractant stream 12 is then recycled to C1.

[0071] Regarding the heat utilization and thermal integration of 11, and 9 containing CHB, a small amount of phenol and DEG, both can be treated using conventional methods according to actual needs. For example, 9 can be separated and recovered by water washing. This invention will not elaborate on these points here, but any extensions made based on these methods are within the scope of this invention.

[0072]

Example 1

[0073] like Figure 1As shown, stream 1, mainly containing phenol, cyclohexanone, and a small amount of cyclohexylbenzene (CHB), is fed from the bottom of extractive distillation column C1. Stream 1 is stream 209 as described in Chinese patent CN104030892B. The supplementary extractant stream 2 (DEG) and the cooled recycled extractant stream 12 are mixed and fed as extractant stream 3 into extractive distillation column C1 from the top. The section above stream 3 is the rectification section, the section between stream 3 and stream 1 is the extraction section, and the section below stream 1 is the stripping section. The temperature of the extractive distillation column is 160℃. Crude cyclohexanone product stream 4 is obtained at the top of extractive distillation column C1, and the bottom liquid stream 5 of extractive distillation column C1 mainly contains phenol. Extractant and CHB, stream 5 enters solvent recovery tower C2 for separation to obtain crude phenol product stream 6. The temperature of the solvent recovery tower is 160℃. The side stream 7 of solvent recovery tower C2 collects a CHB- and DEG mixture rich in CHB, which is cooled to 55℃ by cooler E1. Cooling liquid stream 8 enters liquid-liquid separator D1 for liquid-liquid phase separation. Light phase stream 9 of liquid-liquid separator D1 is separated from the system. Heavy phase stream 10 of liquid-liquid separator D1 returns to solvent recovery tower C2. The return position is below the side stream collection position. After the bottom liquid stream 11 of solvent recovery tower C2 is cooled to 55℃ by heat exchanger and cooler E2, the cooled circulating extractant stream 12 is recycled to C1.

[0074] Material 1 feed composition: 70% phenol, 28% cyclohexanone, 1% cyclohexylbenzene (CHB), and 1% other components; Flow 3 to Flow 1 mass ratio: 1.5:1; Extractive distillation column C1 has 46 theoretical plates (counting from top to bottom), with Material 1 fed onto the 37th theoretical plate and Flow 3 fed onto the 15th theoretical plate; Solvent recovery column C2 has 30 theoretical plates (counting from top to bottom), with Material 5 fed onto the 18th theoretical plate and Flow 7 collected from the 21st theoretical plate at a temperature of 116.5℃ and a pressure of 3kPa; Flow 10 is fed onto the 24th theoretical plate; Flow 4 has a cyclohexanone purity of 99.75%, Flow 6 has a phenol purity of 99.75%, cyclohexanone recovery rate is 99.71%, and phenol recovery rate is 99.89%. The crude cyclohexanone product from Flow 4 and the crude phenol product from Flow 6 are purified to obtain qualified products. The mass flow rate of the side stream from feed 7 is 3:100 with that of feed 1. The CHB contents in feeds 7, 9, and 10 are 34.2%, 95.1%, and 7.25%, respectively. The CHB content in the circulating extractant of feed 11 is less than 1 ppm. The mass ratio of feed 9 to feed 7 is 0.31:1. With 1% CHB in the feed, it is collected via the side stream liquid phase, reducing the CHB concentration in the circulating extractant to below 1 ppm, thus eliminating the impact of CHB accumulation on the extraction performance of the extractant.

[0075] The bottom temperature of extractive distillation column C1 is 152℃, and the bottom temperature of solvent recovery column C2 is 164℃.

[0076]

Example 2

[0077] The separation method is the same as in [Example 1], except that:

[0078] The extractant used is DEG. Feed 1 contains 69% phenol, 28% cyclohexanone, 2% cyclohexylbenzene (CHB), and 1% other components by mass. The mass ratio of feed 3 to feed 1 is 1.5:1. The extractive distillation column C1 has 46 theoretical plates (counting from top to bottom), with feed 1 fed onto the 37th theoretical plate and feed 3 fed onto the 15th theoretical plate. The solvent recovery column C2 has 30 theoretical plates (counting from top to bottom), with feed 5 fed onto the... The feed was placed on the 18th theoretical plate. Stream 7 exited from the 21st theoretical plate, with a temperature of 119.0℃ and a pressure of 3.4 kPa. Stream 10 was fed from the 24th theoretical plate. Stream 4 had a cyclohexanone purity of 99.71%, and Stream 6 had a phenol purity of 99.72%. The recovery rates of cyclohexanone and phenol were 99.70% and 99.92%, respectively. The crude cyclohexanone from Stream 4 and the crude phenol from Stream 6 were purified to obtain qualified products. The mass flow rate of the side stream from Stream 7 was 5:100 of that of Stream 1. The CHB contents in Streams 7, 9, and 10 were 39.7%, 99.24%, and 4.11%, respectively. The CHB content in the circulating extractant of Stream 11 was less than 1 ppm. The mass ratio of Stream 9 to Stream 7 was 0.374:1. 2% CHB in the feed is extracted via a side-stream liquid phase, reducing the CHB concentration in the circulating extractant to below 1 ppm, thus eliminating the impact of CHB accumulation on the extraction performance of the extractant, which may even lead to its disappearance.

[0079] The bottom temperature of extractive distillation column C1 is 152℃, and the bottom temperature of solvent recovery column C2 is 164℃.

[0080]

Example 3

[0081] The separation method is the same as in [Example 1], except that:

[0082] The extractant used is DEG. Feed 1 contains 69% phenol, 28% cyclohexanone, 2% cyclohexylbenzene (CHB), and 1% other components by mass. The mass ratio of feed 3 to feed 1 is 1.5:1. The extractive distillation column C1 has 46 theoretical plates (counting from top to bottom), with feed 1 fed onto the 37th theoretical plate and feed 3 fed onto the 15th theoretical plate. The solvent recovery column C2 has 30 theoretical plates (counting from top to bottom), with feed 5 fed onto the... The feed was placed on the 18th theoretical plate. Stream 7 exited from the 21st theoretical plate, with a temperature of 121.0℃ and a pressure of 3.8 kPa. Stream 10 was fed from the 24th theoretical plate. Stream 4 had a cyclohexanone purity of 99.71%, and Stream 6 had a phenol purity of 99.72%. The recovery rates of cyclohexanone and phenol were 99.69% and 99.94%, respectively. The crude cyclohexanone from Stream 4 and the crude phenol from Stream 6 were purified to obtain qualified products. The mass flow rate of the side stream from Stream 7 was 4:100 of that of Stream 1. The CHB contents in Streams 7, 9, and 10 were 48.6%, 99.25%, and 4.10%, respectively. The CHB content in the circulating extractant of Stream 11 was less than 1 ppm. The mass ratio of Stream 9 to Stream 7 was 0.468:1. 2% CHB in the feed is extracted via a side-stream liquid phase, reducing the CHB concentration in the circulating extractant to below 1 ppm, thus eliminating the impact of CHB accumulation on the extraction performance of the extractant, which may even lead to its disappearance.

[0083] The bottom temperature of extractive distillation column C1 was 151.6℃, and the bottom temperature of solvent recovery column C2 was 164.2℃.

[0084]

Example 4

[0085] The separation method is the same as in [Example 1], except that:

[0086] The extractant used is DEG. Feed 1 contains 69% phenol, 28% cyclohexanone, 2% cyclohexylbenzene (CHB), and 1% other components by mass. The mass ratio of feed 3 to feed 1 is 1.5:1. The extractive distillation column C1 has 46 theoretical plates (counting from top to bottom), with feed 1 fed onto the 37th theoretical plate and feed 3 fed onto the 15th theoretical plate. The solvent recovery column C2 has 30 theoretical plates (counting from top to bottom), with feed 5 fed onto the... The feed position is set at the 18th theoretical plate. Flow 7 exits at the 19th theoretical plate, with a temperature of 121.0℃ and a pressure of 3.8 kPa. Flow 10 is fed at the 22nd theoretical plate. Flow 4 has a cyclohexanone purity of 99.73%, and Flow 6 has a phenol purity of 99.71%. The recovery rates of cyclohexanone and phenol are 99.69% and 99.93%, respectively. Crude cyclohexanone from Flow 4 and crude phenol from Flow 6 are purified to obtain qualified products. The mass flow rate of the side stream from Flow 7 is 4:100 of that of Flow 1. The CHB contents in Flow 7, Flow 9, and Flow 10 are 48.6%, 98.72%, and 4.47%, respectively. The CHB content in the circulating extractant of Flow 11 is less than 1 ppm. The mass ratio of Flow 9 to Flow 7 is 0.468:1. 2% CHB in the feed is extracted via a side-stream liquid phase, reducing the CHB concentration in the circulating extractant to below 1 ppm, thus eliminating the impact of CHB accumulation on the extraction performance of the extractant, which may even lead to its disappearance.

[0087] The bottom temperature of extractive distillation column C1 was 151.6℃, and the bottom temperature of solvent recovery column C2 was 164.2℃.

[0088]

Example 5

[0089] The separation method is the same as in [Example 1], except that:

[0090] The extractant used is TEG. Because TEG has a higher boiling point than DEG, high pressure drop is required in both columns, and the pressure drop should be as low as possible, especially in the solvent recovery column. The bottom operating pressure needs to be controlled below 3 kPa, and the bottom temperature needs to be kept below 165℃. The feed composition of material 1 is 69% phenol, 28% cyclohexanone, 2% cyclohexylbenzene (CHB), and 1% other components. The mass ratio of material 3 to material 1 is 1.45:1. The C1 extractive distillation column has 46 theoretical plates (counting from top to bottom). Material 1 is fed onto the 37th theoretical plate, and material 3 is fed onto the... The solvent recovery tower (C2) has 30 theoretical plates (counting from top to bottom), with 15 theoretical plates for feed 5 and feed 7 collected from the 20th theoretical plate. Feed 7 has a collection temperature of 106.5℃ and a pressure of 2.3 kPa. Feed 10 has the 24th theoretical plate. Feed 4 has a cyclohexanone purity of 99.52%, and feed 6 has a phenol purity of 99.60%. Cyclohexanone recovery rate is 99.50%, and phenol recovery rate is 99.80%. The crude cyclohexanone from feed 4 and the crude phenol from feed 6 are purified to obtain qualified products. The mass flow rate of feed 7 (side stream) is 4:100 with that of feed 1. The CHB contents in feeds 7, 9, and 10 are 49.4%, 99.78%, and 5.44%, respectively. The CHB content in the circulating extractant of feed 11 is less than 1 ppm. The mass ratio of feed 9 to feed 7 is 0.466:1. 2% CHB in the feed is extracted via a side-stream liquid phase, reducing the CHB concentration in the circulating extractant to below 1 ppm, thus eliminating the impact of CHB accumulation on the extraction performance of the extractant, which may even lead to its disappearance.

[0091] The bottom temperature of extractive distillation column C1 was 156.9℃, and the bottom temperature of solvent recovery column C2 was 163.6℃.

[0092]

Example 6

[0093] The separation method is the same as in [Example 1], except that:

[0094] The extractant used is DEG. Feed 1 contains 48% phenol, 49% cyclohexanone, 2% cyclohexylbenzene (CHB), and 1% other components by mass. The mass ratio of feed 3 to feed 1 is 1.5:1. The extractive distillation column C1 has 46 theoretical plates (counting from top to bottom), with feed 1 fed onto the 37th theoretical plate and feed 3 fed onto the 15th theoretical plate. The solvent recovery column C2 has 30 theoretical plates (counting from top to bottom), with feed 5 fed onto the... The feed was placed on the 18th theoretical plate. Stream 7 exited from the 21st theoretical plate at a temperature of 122.6℃ and a pressure of 3.9 kPa. Stream 10 was fed from the 24th theoretical plate. Stream 4 had a cyclohexanone purity of 99.85%, and Stream 6 had a phenol purity of 99.57%. The recovery rates of cyclohexanone and phenol were 99.80% and 99.99%, respectively. The crude cyclohexanone from Stream 4 and the crude phenol from Stream 6 were purified to obtain qualified products. The mass flow rate of the side stream from Stream 7 was 3.6:100 compared to Stream 1. The CHB contents in Streams 7, 9, and 10 were 54.43%, 99.50%, and 3.92%, respectively. The CHB content in the circulating extractant of Stream 11 was less than 1 ppm. The mass ratio of Stream 9 to Stream 7 was 0.527:1. 2% CHB in the feed is extracted via a side-stream liquid phase, reducing the CHB concentration in the circulating extractant to below 1 ppm, thus eliminating the impact of CHB accumulation on the extraction performance of the extractant, which may even lead to its disappearance.

[0095] The bottom temperature of extractive distillation column C1 was 156.3℃, and the bottom temperature of solvent recovery column C2 was 164.2℃.

[0096] Table 2 presents the liquid-phase equilibrium data for the cyclohexylbenzene + DEG binary liquid.

[0097] Table 2 Boiling points and azeotropic points of system components

[0098]

[0099] Table 3 shows the mass content of CHB and DEG in the feed and in the resulting light and heavy phase components.

[0100] Table 3

[0101] Feeding Light phase Reappearance CHB 0.6687 0.9985 0.0493 DEG 0.3313 0.0014 0.9507

[0102] As can be seen from the table above, the CHB-DEG mixture is collected from the side stream of the solvent recovery tower. After phase separation by cooling liquid, the light phase contains almost no DEG, while the CHB concentration in the heavy phase is significantly reduced.

[0103] Comparative Example 1

[0104] The conditions are the same as in Example 1, except that no side-stream extraction is set up, and no CHB removal device such as a de-weighting tower is set up, which causes CHB to accumulate in the system. According to simulation calculations and experimental data, as long as CHB is present, the extraction efficiency of DEG decreases, such as when the CHB molar concentration is 0.01 mol%. When the CHB molar concentration reaches 0.30%, the relative volatility decreases very severely, and the extraction efficiency drops significantly.

Claims

1. A method for separating cyclohexylbenzene oxidation products, comprising the following steps: 1) The cyclohexylbenzene oxidation product and the extractant are extracted and distilled in an extractive distillation column to obtain a top stream and a bottom stream containing cyclohexanone; the extractant is selected from at least one of diethylene glycol and triethylene glycol; 2) The column bottom stream is separated by the solvent recovery column to obtain the column top stream containing phenol, the column bottom stream containing extractant, and the cyclohexylbenzene-extractant azeotrope collected by the side stream; the location of the collected cyclohexylbenzene-extractant azeotrope is 1 to 8 theoretical plates below the feed position of the solvent recovery column; 3) The cyclohexylbenzene-extractant azeotrope was cooled and separated to obtain a light phase containing cyclohexylbenzene and a heavy phase containing the extractant; The cyclohexylbenzene oxidation product comprises phenol, cyclohexanone, and cyclohexylbenzene. Based on 100 wt% of the cyclohexylbenzene oxidation product, the content of phenol is 45-75 wt%, the content of cyclohexanone is 24-50 wt%, and the content of cyclohexylbenzene is ≤5 wt%.

2. The separation method according to claim 1, characterized in that, The mass ratio of the extractant to the cyclohexylbenzene oxidation product is 1:(1~6).

3. The separation method according to claim 2, characterized in that, The mass ratio of the extractant to the cyclohexylbenzene oxidation product is 1:(1.2~4).

4. The separation method according to claim 1, characterized in that, In step 1), the temperature of the reboiler of the extractive distillation column shall not exceed 165°C; and / or, In step 2), the temperature of the solvent recovery tower reboiler shall not exceed 165°C; and / or, The conditions for the side-stream extraction of the cyclohexylbenzene-extractant azeotrope are: pressure of 1~10 kPa and temperature of 95~150℃; and / or, The extractant-containing bottom stream obtained in step 2) is recycled to the extractive distillation column; and / or, In step 3), the cyclohexylbenzene-extractant azeotrope undergoes phase separation at a temperature of 30-60°C; and / or, The cyclohexylbenzene-containing light phase obtained in step 3) is optionally washed with water; and / or, The heavy phase containing the extractant obtained in step 3) is recycled to the solvent recovery tower.

5. The separation method according to claim 4, characterized in that, In step 1), the temperature of the reboiler of the extractive distillation column is 150~165℃; and / or, In step 2), the temperature of the solvent recovery tower reboiler is 160~165℃; and / or, The conditions for the side-stream extraction of the cyclohexylbenzene-extractant azeotrope are: pressure of 2~6 kPa and temperature of 105~135℃; and / or, In step 3), the cyclohexylbenzene-extractant azeotrope undergoes phase separation at a temperature of 40~60℃.

6. The separation method according to claim 5, characterized in that, The extractant-containing reboiler stream obtained in step 2) is circulated back to the extractive distillation column after being cooled by a heat exchanger; and / or, The position of the heavy phase stream containing extractant obtained in step 3) that is circulated to the solvent recovery tower is below the position of the cyclohexylbenzene-extractant azeotrope extracted by the side stream.

7. The separation method according to claim 6, characterized in that, The extractant-containing reboiler stream obtained in step 2) is circulated back to the extractive distillation column after being cooled by a heat exchanger, with a cooling temperature above 40°C; and / or, The location of the heavy phase stream containing extractant obtained in step 3) that is circulated to the solvent recovery tower is 1 to 5 theoretical plates below the location of the cyclohexylbenzene-extractant azeotrope extracted by the side stream.

8. The separation method according to claim 7, characterized in that, The extractant-containing reboiler stream obtained in step 2) is circulated back to the extractive distillation column after being cooled by a heat exchanger at a temperature of 40-60°C; and / or, The position of the heavy phase stream containing extractant obtained in step 3) that is circulated to the solvent recovery tower is 2 to 4 theoretical plates below the position of the cyclohexylbenzene-extractant azeotrope extracted by the side stream.

9. The separation method according to claim 1, characterized in that, The location of the extracted cyclohexylbenzene-extractant azeotrope is 1 to 5 theoretical plates below the feed position of the solvent recovery tower.

10. A cyclohexylbenzene oxidation product separation system for implementing the separation method according to any one of claims 1 to 9, comprising: An extractive distillation column, a solvent recovery column, and a liquid-liquid separator are connected in sequence by pipelines. The material outlet at the bottom of the extractive distillation column is connected to the solvent recovery column by a pipeline. A liquid-liquid outlet is provided on the side of the solvent recovery column and is connected to the liquid-liquid separator by a pipeline. The liquid-liquid separator has a cyclohexylbenzene light phase stream outlet and an extractant heavy phase stream outlet at the bottom. The extractant heavy phase stream outlet circulates the extractant heavy phase stream to the solvent recovery column by a pipeline. The side liquid-liquid outlet is located 1 to 8 theoretical plates below the feed position of the solvent recovery column.

11. The separation system according to claim 10, characterized in that, The extractive distillation column and the solvent recovery column are each equipped with a reboiler, which is independently selected from either a forced circulation reboiler or a falling film reboiler.

12. The separation system according to claim 10, characterized in that, The extractive distillation column comprises 30-60 theoretical plates; and / or, The extraction distillation column is equipped with an outlet for cyclohexanone-containing material at its top.

13. The separation system according to claim 12, characterized in that, The extractive distillation column comprises 35 to 55 theoretical plates.

14. The separation system according to claim 10, characterized in that, The solvent recovery tower comprises 10 to 40 theoretical plates; and / or, The bottom material outlet of the solvent recovery tower is connected by a pipeline to a circulating extractant cooler; and / or, The solvent recovery tower's stripping section is equipped with a side-stream liquid-liquid outlet connected by a pipeline to a liquid-liquid separator; and / or, A cooler is also installed between the solvent recovery tower and the liquid-liquid separation tank.

15. The separation system according to claim 14, characterized in that, The solvent recovery tower comprises 15 to 35 theoretical plates.

16. The separation system according to claim 14, characterized in that, The cooling temperature of the circulating extractant cooler is above 40°C; and / or, The cooling temperature of the cooler between the solvent recovery tower and the liquid-liquid separation tank is 30~60℃; and / or, The location where the heavy phase extractant is circulated to the solvent recovery tower is 1 to 5 theoretical plates below the side liquid-liquid outlet.

17. The separation system according to claim 16, characterized in that, The cooling temperature of the circulating extractant cooler is 40~60℃; and / or, The cooling temperature of the cooler between the solvent recovery tower and the liquid-liquid separation tank is 40~60℃; and / or, The side-stream liquid outlet is located 1-5 theoretical plates below the feed position of the solvent recovery tower; and / or, The location where the heavy phase extractant is circulated to the solvent recovery tower is 2 to 4 theoretical plates below the side liquid-liquid outlet.

18. The method for separating cyclohexylbenzene oxidation products according to any one of claims 1 to 9, or the system for separating cyclohexylbenzene oxidation products according to any one of claims 10 to 17, is used in the separation of components of cyclohexylbenzene oxidation products, wherein the cyclohexylbenzene oxidation products comprise phenol, cyclohexanone, and cyclohexylbenzene, and based on 100 wt% of the cyclohexylbenzene oxidation products, the content of phenol is 45-75 wt%, the content of cyclohexanone is 24-50 wt%, and the content of cyclohexylbenzene is ≤5 wt%.

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