Process and device for recovering cyclohexene hydration catalyst

Abstract

The invention relates to the technical field of chemical engineering, in particular to a recovery process and device of a cyclohexene hydration catalyst. The method comprises the processes of flash evaporation, extraction, separation and the like, an entrained hydration catalyst is separated from flash evaporation gas in the flash evaporation process and is separated from flash evaporation liquid in the extraction process, cyclohexanol separation is carried out on the flash evaporation gas and the flash evaporation liquid after the catalyst is separated in the separation process, and a catalyst aqueous solution is returned to a hydration reaction unit for recycling. According to the device and the method, the liquid-phase material needing to be subjected to catalyst recovery is concentrated and cooled, the treatment efficiency is improved, high-temperature sensible heat is effectively transferred to a subsequent rectification separation unit in a latent heat gasification mode, energy conservation and consumption reduction are facilitated, and the cyclohexanol yield of the device can also be improved.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, and in particular to a process and apparatus for recovering cyclohexene hydration catalysts. Background Technology

[0002] Cyclohexanol is mainly used to produce cyclohexanone, adipic acid, plasticizers, surfactants, and as an industrial solvent. The cyclohexene hydration method has the advantages of lower production costs and a cleaner process, making it the primary technology for cyclohexanol production. The cyclohexene hydration process for cyclohexanol production includes units such as hydration reaction, cyclohexanol separation, two-stage concentration and evaporation with catalyst, and cyclohexanol purification.

[0003] Cyclohexene hydration is an acid-catalyzed reaction; sulfuric acid, ion exchange resins, and zeolite catalysts can all hydrate cyclohexene to cyclohexanol. Currently, the commonly used hydration catalyst in industrial production is ZSM-5 zeolite molecular sieve, which consists of powdered particles with a particle size generally below 5 μm. Under temperature and pressure conditions of 110–130℃ and 0.4–0.6 MPaG, cyclohexene hydrates with water to cyclohexanol in the presence of ZSM-5, with a cyclohexene conversion rate of approximately 10% and a cyclohexanol selectivity of approximately 99%. In actual production, a small amount of hydrated catalyst may be carried over to the reactor outlet. For example, the article "Analysis of the Causes of Catalyst Loss in Cyclohexanol Units" published in *Chemical Technology*, Vol. 12, No. 3, 2004, described and studied the type of hydration reactor and the amount of catalyst carried over in the oil phase discharge, which will not be elaborated upon here.

[0004] The hydrated catalyst carried out by the reaction oil phase is collected from the bottom of the cyclohexanol separation tower along with the cyclohexanol feedstock. If not removed, it will enter the subsequent cyclohexanol refining process. During refining, due to the higher temperature in the tower bottom and the gradual concentration of the material, the entrained catalyst particles precipitate and adhere to the tower, heat exchanger, and pipelines, accumulating and causing blockages, ultimately severely affecting the normal operation of the unit. Furthermore, the entrained catalyst, still active, can cause adverse side reactions within the system, such as the dehydration of cyclohexanol to cyclohexene and the isomerization of cyclohexene to methylcyclopentene. A common removal method is to set up a two-stage catalyst concentration and evaporation system before cyclohexanol refining. The vaporization of cyclohexanol and other components separates the catalyst solid particles, which are discharged as waste liquid. To maintain the fluidity of the waste liquid and prevent blockage of the evaporation equipment, a large amount of cyclohexanol is also entrained in the waste liquid. Taking a 200,000-ton-per-year cyclohexanol unit as an example, the annual consumption of hydrated catalyst exceeds 50 tons.

[0005] Devices and processes for treating entrained hydrated catalysts are a hot research topic in the field of cyclohexanol production. The most direct method for removing solids from a liquid is filtration. As disclosed in Chinese patents CN102180772A, CN215610593U, CN216826129U, and CN217568658U, filtration devices are used to separate the hydrated catalyst, and most of these also consider returning the filtered catalyst to the hydration reaction for reuse through backwashing. Another method, as disclosed in Chinese patents CN102180772A, CN108440241A, and CN110302557A, involves installing a liquid-liquid phase separator between the hydration reactor and the cyclohexanol separation tower. This separator utilizes free water carried out by the reactants or added water for liquid-liquid phase separation. Based on the density and hydrophilicity of the hydrated catalyst, a portion of the catalyst is carried out from the aqueous phase and returned to the hydration reactor, while the resulting oil phase enters the cyclohexanol separation tower.

[0006] The catalyst entrained in the cyclohexanol material exists in a suspended state and needs to be in full contact with the aqueous phase to be transferred to the aqueous phase. The existing technology cannot achieve a good catalyst separation effect with the free water or a small amount of water added. At the same time, adding too much water will increase the amount of cyclohexanol entrained in the aqueous phase.

[0007] In the prior art, all cyclohexanol mixtures entering the cyclohexanol separation tower need to pass through a liquid-liquid phase separator and / or filtration device. Due to the limitation of the hydration reaction conversion rate, the weight content of cyclohexene in the cyclohexanol mixture can be as high as 90%, while the weight content of the hydration catalyst is only 20-50 ppm. The efficiency of filtration and liquid-liquid phase separation is low, and the hydration catalyst cannot be effectively separated and recovered. Summary of the Invention

[0008] To address the aforementioned technical problems, the present invention provides the following technical solutions.

[0009] A process for recovering cyclohexene hydration catalyst includes the following steps:

[0010] a. Flash evaporation: The cyclohexanol-containing material from the cyclohexene hydration reaction is flashed to obtain flash vapor and flash liquid;

[0011] b. Extraction: In at least one extraction device, water is used as the extractant to extract the flash liquid described in step a, to obtain an extract phase and a raffinate phase;

[0012] c. Separation: The flash gas from step a and the raffinate from step b are sent to the cyclohexanol separation unit, and the extract phase from step b is sent to the hydration reaction unit.

[0013] In the above-mentioned recovery process of cyclohexene hydration catalyst, the extraction equipment in step b is at least one of packed extraction tower, sieve plate extraction tower and spray extraction tower, and the operating pressure of flash evaporation in step a is 30-100 kPaA.

[0014] In the above-mentioned recovery process of cyclohexene hydration catalyst, during the extraction operation in step b, the extractant is a continuous phase and the flash liquid is a dispersed phase.

[0015] In the above-mentioned recovery process of cyclohexene hydration catalyst, the extraction equipment is a packed extraction tower, and the flash evaporation operation pressure in step a is 40-60 kPaA.

[0016] In the above-mentioned recovery process of cyclohexene hydration catalyst, the flash gas in step a is defoamed and then sent to the cyclohexanol separation unit.

[0017] In the above-mentioned recovery process of cyclohexene hydration catalyst, before step b, all or part of the flash liquid in step a is heated and flashed to further concentrate the flash liquid.

[0018] In the above-mentioned recovery process of cyclohexene hydration catalyst, the mass flow rate of the extractant added in step b is less than 5% of the mass flow rate of the flash liquid added.

[0019] An apparatus for recovering cyclohexene hydration catalyst includes a flash tank, an extractor, a cyclohexanol separation tower, a feed line for conveying cyclohexene hydration products, and an extractant line. The outlet of the feed line is connected to the inlet of the flash tank, the outlet of the extractant line is connected to the upper inlet of the extractor, the liquid phase outlet of the flash tank is connected to the lower inlet of the extractor via a pipeline, the gas phase outlet of the flash tank is connected to the first inlet of the cyclohexanol separation tower via a pipeline, and the upper outlet of the extractor is connected to the second inlet of the cyclohexanol separation tower via a pipeline.

[0020] In the above-described apparatus, the second inlet of the cyclohexanol separation tower is positioned higher than the first inlet.

[0021] In the above-described apparatus, a delivery pump is installed on the connecting pipeline between the liquid phase outlet of the flash tank and the lower inlet of the extractor, and a branch pipeline is installed on the connecting pipeline between the liquid phase outlet of the flash tank and the lower inlet of the extractor. The outlet of the branch pipeline is connected to the flash tank, and a heater is installed on the branch pipeline.

[0022] Compared with existing technologies, the advantages of this invention are:

[0023] 1. This invention concentrates liquid materials that require catalyst recovery, thereby improving processing efficiency.

[0024] 2. Without external cooling, the temperature of the material requiring catalyst recovery is reduced to below 80℃, while the high sensible heat of the reactants is effectively utilized, thus improving the efficiency of heat utilization.

[0025] 3. Extraction at lower temperatures can reduce the amount of cyclohexanol dissolved in water and increase the yield of cyclohexanol in the apparatus. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of the device provided by the present invention;

[0027] Figure 2 This is another schematic diagram of the device provided by the invention;

[0028] In the diagram: 1. Hydration reactor; 2. Flash tank; 3. Extractor; 4. Cyclohexanol separation tower; 5. Feed line; 9. Extractant line; 25. Transfer pump; 26. Heater. Detailed Implementation

[0029] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Knowledge related to distillation and liquid-liquid extraction should be well-known in the field of chemical engineering. Alternatively, one can refer to Volume 3, "Chemical Unit Processes," of the *Petrochemical Engineering Design Handbook* (edited by Wang Songhan, published by Chemical Industry Press in 2001, hereinafter referred to as the *Handbook*). In this text, "wt%" indicates "weight percentage."

[0030] Example 1

[0031] This embodiment provides a device for recovering cyclohexene hydration catalyst, such as... Figure 1 As shown, the system includes a flash tank 2, an extractor 3, a cyclohexanol separation tower 4, a feed line 5 for conveying cyclohexene hydration products, and an extractant line 9. The outlet of the feed line 5 is connected to the inlet of the flash tank 2, the outlet of the extractant line 9 is connected to the upper inlet of the extractor 3, the liquid phase outlet of the flash tank 2 is connected to the lower inlet of the extractor 3 via a pipeline, the gas phase outlet of the flash tank 2 is connected to the first inlet A of the cyclohexanol separation tower 4 via a pipeline, and the upper outlet of the extractor 3 is connected to the second inlet B of the cyclohexanol separation tower 4 via a pipeline.

[0032] The bottom of the cyclohexanol separation column 4 is connected to a bottom pump 45. The top of the cyclohexanol separation column 4 is connected to a reflux tank 42 and a reflux pump 43 in sequence via a condenser 41. The reflux pump 43 is connected to the upper part of the cyclohexanol separation column 4. A reboiler 44 is provided at the bottom of the cyclohexanol separation column 4.

[0033] The second inlet B of the cyclohexanol separation tower 4 is positioned higher than the first inlet A. The flash gas after flash evaporation contains cyclohexanol, which is preferably separated in the cyclohexanol separation tower. The pressure inside the flash tank is maintained by the pressure within the cyclohexanol separation tower, thus eliminating the need for a separate vacuum system in the flash tank. During flash evaporation, the flash gas carries a certain amount of heavy components, and the flash liquid also carries a certain amount of light components. Positioning the second inlet B of the cyclohexanol separation tower 4 higher than the first inlet A allows for the separation of light and heavy components through mass transfer within the tower.

[0034] The inlet of feed line 5 is connected to the oil phase outlet of the second hydration reactor. Feed line 5 and flash tank 2 are externally insulated. A pressure gauge is installed in the upper gas phase region of flash tank 2 to measure the pressure inside the tank, and a thermometer is installed in the lower liquid phase region to measure the liquid temperature after flashing. A level gauge is also installed to measure the liquid level inside the flash tank. Extractor 3 is equipped with an interface gauge for measuring the separation of the oil and water phases.

[0035] A delivery pump 25 is installed on the connecting pipeline between the liquid phase outlet of the flash tank 2 and the lower inlet of the extractor 3. This pump is used to pressurize and deliver the liquid phase material in the flash tank 2, so as to maintain a stable liquid level in the flash tank and keep the extractor 3 under sufficient pressure.

[0036] The working principle of this embodiment is as follows:

[0037] a) The cyclohexanol-containing material from the cyclohexene hydration reaction is flash-distilled to obtain flash vapor and flash liquid. The oil phase exiting the hydration reactor is a liquid phase containing cyclohexanol at approximately 120°C. Cooling it to 60°C would release a large amount of heat, wasting the sensible heat of the material and consuming a large amount of cooling water. Flash distillation transfers this sensible heat to the subsequent cyclohexanol separation unit via the latent heat of the flash vapor, improving heat utilization. The oil phase exiting the hydration reactor contains a small amount of catalyst, which cannot be vaporized during flash distillation and remains entrained in the liquid. Although the liquid volume decreases before and after flash distillation, the total amount of entrained catalyst remains essentially unchanged. Therefore, flash distillation is a concentration process for the catalyst, which is highly beneficial for subsequent catalyst separation.

[0038] b. In at least one extraction device, water is used as the extractant to extract the flash liquid described in step a, yielding an extractant phase and a raffinate phase. The catalyst entrained in the flash liquid will enter the aqueous phase upon sufficient contact with it. Since the density of water as the extractant is greater than that of the flash liquid, the extractant enters from the upper inlet of the extraction device and exits from the lower outlet. The extractant phase exiting from the lower outlet contains the catalyst extracted from the oil phase, thus separating the catalyst from the flash liquid.

[0039] c. The flash vapor from step a and the raffinate from step b are sent to the cyclohexanol separation unit, and the extract phase from step b is sent to the hydration reaction unit. Sending the flash vapor to the cyclohexanol separation unit can transfer the sensible heat of cooling in step a, improving heat utilization. Sending the catalyst-containing extract phase after separation from the flash liquid in step b to the hydration reaction unit can recover this part of the catalyst, reducing the consumption of hydrated catalyst.

[0040] The entrained catalyst is separated from the flash gas in step a and from the flash liquid in step b. The separated catalyst is then recovered and reused in step c. Simultaneously with the separation of the catalyst from the flash gas and flash liquid, the high-temperature sensible heat is effectively transferred to the subsequent distillation separation unit via the latent heat of vaporization, contributing to energy conservation and emission reduction.

[0041] The extraction equipment in step b is at least one of a packed extraction tower, a sieve plate extraction tower, and a spray extraction tower. The flash evaporation operating pressure in step a is 30–100 kPaA. Preferably, the extraction equipment is a packed extraction tower, and the flash evaporation operating pressure in step a is 40–60 kPaA. During the extraction operation, the extractant is the continuous phase, and the flash liquid is the dispersed phase. After the extraction operation stabilizes, the added mass flow rate of the extractant is less than 5% of the added mass flow rate of the flash liquid.

[0042] Preferably, the flash gas in step a is defoamed before being sent to the cyclohexanol separation unit. The flash gas may contain small amounts of droplets or catalyst; therefore, defoaming is preferred to prevent catalyst entrainment into the subsequent distillation system. The demister can be located outside or inside the flash tank. When the amount of catalyst entrained in the flash gas is small, it is preferable to install the demister inside the flash tank.

[0043] Example 2

[0044] This embodiment is basically the same as embodiment 1 in structure and working principle, the difference being that, Figure 2 As shown, a branch line is provided on the connecting pipeline between the liquid phase outlet of the flash tank 2 and the lower inlet of the extractor 3. The outlet of the branch line is connected to the flash tank 2, and a heater 26 is provided on the branch line. The heater 26 heats the flash liquid and then returns it to the flash tank 2 for flash evaporation again after heating.

[0045] The function of heater 26 is to heat and flash-evaporate all or part of the flash liquid in step a before step b, thereby further concentrating the flash liquid. In the extraction operation, the key to extracting the catalyst entrained in the oil phase is sufficient contact between the catalyst and the aqueous phase. The concentrated flash liquid is more efficient at separating the catalyst during the extraction operation.

[0046] Example 3

[0047] This embodiment provides a process for recovering cyclohexene hydration catalyst, using the apparatus provided in Example 1.

[0048] The specific process involves the following steps:

[0049] a. Flash Evaporation: The cyclohexanol-containing material from the cyclohexene hydration reaction is flash-evaporated to obtain flash vapor I and flash liquid II. The oil phase material from the hydration reactor is a high-temperature liquid at 110–130℃ and 0.4–0.6 MPaG, containing a small amount of hydrated catalyst, and is essentially saturated. Flash evaporation will occur after depressurization. If it is cooled directly to 60℃ without flash evaporation, a large amount of heat will be released, wasting the sensible heat of the material and consuming a large amount of cooling water. Flash evaporation can "transfer" this sensible heat to the subsequent cyclohexanol separation unit through the latent heat of the flash vapor, improving heat utilization. The oil phase from the hydration reactor contains a small amount of catalyst, which cannot be vaporized during flash evaporation and will continue to be entrained in the liquid. The amount of liquid before and after flash evaporation decreases, but the total amount of entrained catalyst remains essentially unchanged. Therefore, flash evaporation is a concentration process for the catalyst, which is very beneficial for subsequent catalyst separation.

[0050] b. Extraction: In at least one extraction device, water is used as the extractant to extract the flash liquid II obtained in step a, yielding extractant phase IV and raffinate phase III. The catalyst entrained in the flash liquid will enter the aqueous phase upon sufficient contact with it. Since the density of water as the extractant is greater than that of the flash liquid, the extractant enters from the upper inlet of the extraction device and exits from the lower outlet. The extractant phase exiting from the lower outlet contains the catalyst extracted from the oil phase, thus separating the catalyst from the flash liquid.

[0051] c. Separation: The raffinate phase III from step b is sent to the cyclohexanol separation unit for cyclohexanol separation. The extract phase IV from step b is sent to the hydration reaction unit, meaning the separated catalyst re-enters the hydration reaction. The flash vapor I from step a, also containing cyclohexanol, is sent to the cyclohexanol separation unit. Sending flash vapor I to the cyclohexanol separation unit allows for the transfer of the sensible heat from the cooling process in step a, improving heat utilization. Sending the catalyst-containing extract phase, separated from the flash liquid in step b, to the hydration reaction unit allows for the recovery of this portion of the catalyst, reducing the consumption of hydrated catalyst.

[0052] Specifically, an externally insulated flash tank 2 is installed. The vapor outlet of flash tank 2 is connected to a vacuum system with a condenser, so the condensed liquid does not return. A pressure gauge is installed in the upper vapor region of flash tank 2 to measure the pressure inside the flash tank, and a thermometer is installed in the lower liquid region to measure the liquid temperature inside the flash tank. A level gauge is also installed to measure the liquid level inside the flash tank. The material in the feed line 5 and the liquid phase materials such as flash liquid II are metered by a flow meter. The installed transfer pump 25 pressurizes and transports the liquid phase material in flash tank 2, maintaining a stable liquid level inside flash tank 2 while keeping the extractor 3 under sufficient pressure.

[0053] The pressure in flash tank 2 is maintained at 50 kPa using a vacuum system. Then, the material from the hydration reaction feed line 5 is pressurized and heated to 120°C before being fed into flash tank 2. The cyclohexene and cyclohexanol contents in the material transported by feed line 5 are approximately 87 wt% and 10 wt%, respectively. After the system parameters such as temperature, pressure, liquid level, and flow rate stabilize, the temperature of flash tank 2 is 60°C, and the concentration ratio is 0.68. The concentration ratio is defined here as the ratio of the flow rate of flash liquid II to the flow rate in feed line 5.

[0054] Concentration ratio = Liquid weight before flash evaporation / Liquid weight after flash evaporation

[0055] With the total amount of entrained catalyst remaining unchanged, the amount of liquid to be treated is reduced by 32% (1-0.68=0.32), and the concentration of entrained catalyst is increased by 47% (1 / 0.68-1=0.47), which is more conducive to the removal of catalyst by methods such as filtration and extraction.

[0056] A packed extraction tower is set up as extractor 3, using metal flat ring packing. Water, as the extractant, is transported in pipeline 9. During the extraction operation, the aqueous phase, being the extractant phase, has a higher density and enters from the upper inlet of extractor 3, exiting from the lower outlet. The flash liquid, as the raffinate phase, enters from the lower inlet of extractor 3 and exits from the upper outlet. An interface meter is installed above the upper inlet of extractor 3 to measure the separation of the oil and aqueous phases. Its location above the upper inlet is to accommodate the operation mode where the extractant is the continuous phase and the flash liquid is the dispersed phase; details can be found in the manual, and will not be elaborated here.

[0057] Before introducing flash liquid II into extractor 3, water is first introduced through extractant line 9 until extractor 3 is full. Then, the extraction rates of raffinate phase III and extractant phase IV are adjusted to stabilize the interface of the interface meter. A portion of flash liquid II and raffinate phase III is collected for measuring the entrained catalyst. The method for measuring the entrained catalyst content is as follows: after the sample is cooled, it is weighed, filtered using a suction funnel and filter paper, then vacuum dried and weighed again. The catalyst content is calculated by the difference between the previous and subsequent weighings. The catalyst content in the obtained flash liquid II is 0.005 wt%, and the catalyst content in raffinate phase III is close to 0. The reason for the close proximity to 0 may be due to limitations of the measurement method, or the sufficient amount of packing material and extractant in the extractor in this embodiment.

[0058] After the extraction operation is completed, the catalyst contained in the water used as the extraction phase can be directly returned to the hydration reaction unit, where the catalyst can be reused. The returned water can be used as makeup water for the hydration reaction itself, or it can be returned to the hydration catalyst regeneration unit to be regenerated together with other catalysts and reused.

[0059] Examples 4-8

[0060] The working principle of Examples 4-8 is basically the same as that of Example 3, the difference being the pressure of the flash tank 2.

[0061] Pressure,kPaA Temperature, °C Concentration ratio Example 4 100 80 0.78 Example 5 80 73 0.75 Example 6 60 64 0.70 Example 7 40 54 0.65 Example 8 30 46 0.61

[0062] The temperatures and pressures in the table are those of flash tank 2.

[0063] Example 9

[0064] This embodiment provides a process for recovering cyclohexene hydration catalyst, using the apparatus provided in Example 2. The process is basically the same as that in Example 3, except that:

[0065] a. Flash evaporation of cyclohexanol-containing materials from the hydration reaction of cyclohexene yields flash vapor I and flash liquid II;

[0066] b. In at least one extraction device, water is used as the extractant to extract the flash liquid II obtained in step a, to obtain extract phase IV and raffinate phase III;

[0067] c. Send the raffinate phase III from step b to the cyclohexanol separation unit, send the extract phase IV from step b to the hydration reaction unit, and send the flash gas I from step a to the cyclohexanol separation unit.

[0068] Before proceeding to step b, all or part of the flash liquid from step a above is heated and flash-evaporated to further concentrate the flash liquid. Specifically, the flash liquid II from Example 3 is collected. After stopping the feed line 5, the collected flash liquid II is pressurized and heated to 70°C before being sent to flash tank 2. Other settings are the same as in Example 3. After the parameters such as temperature, pressure, liquid level, and flow rate in the system stabilize, the temperature is 61°C and the concentration ratio is 0.95.

[0069] It should be noted that this embodiment is a further concentration of the flash liquid based on embodiment 3. Combining the concentration ratio of 0.68 in embodiment 3 with the amount of material transported in feed line 5, the total concentration ratio of embodiment 3 and embodiment 3 is 0.68*0.95=0.65.

[0070] Examples 10-11

[0071] The working principle of Examples 10-11 is basically the same as that of Example 9, except that the heating temperature of flash liquid II is different.

[0072] Heating temperature, ℃ Flash temperature, ℃ Concentration ratio Total Concentration Ratio Example 10 90 62 0.85 0.58 Example 11 110 63 0.72 0.49

[0073] The temperature and pressure in the table are the temperature and pressure of flash tank 2, and the total concentration ratio = concentration ratio * 0.68.

[0074] Example 12

[0075] This embodiment is based on Embodiment 3, and studies the ratio of the added flow rate of the extractant to the added flow rate of the flash liquid during the extraction operation in step b.

[0076] When liquid cyclohexene is mixed with water, it separates into an oil phase (light phase) and an aqueous phase (heavy phase), with some mutual dissolution; that is, trace amounts of water dissolve in the oil phase, and trace amounts of cyclohexene dissolve in the aqueous phase. Liquid cyclohexanol exhibits similar properties to water, but its degree of mutual dissolution is much greater than that of cyclohexene and water. This degree of mutual dissolution varies with temperature, generally increasing with higher temperatures. The table below shows the solubility of cyclohexene or cyclohexanol in the aqueous phase at temperatures ranging from 30 to 130°C.

[0077] Water content 30℃ 50℃ 110℃ 130℃ Cyclohexene, wt% 0.02％ 0.01％ 0.04％ 0.59％ Cyclohexanol, wt% 3.61％ 3.09％ 3.98％ 5.01％

[0078] In Examples 4-8, the temperature after flash evaporation, between 45 and 80°C, is a suitable temperature for the extraction operation. The extraction operation is preferably carried out at a temperature close to the flash liquid temperature to prevent excessive temperature difference from affecting stratification and flow within the extractor, and also to minimize heat loss.

[0079] The amount of water added as the extractant should not be too large. After extraction, approximately 1-5 wt% of cyclohexanol will remain dissolved in the aqueous phase. A second extraction using cyclohexene stream can back-extract the dissolved cyclohexanol from the water, reducing the cyclohexanol content in the water to less than 0.1%. However, the recovery process after this operation is complex. Considering the catalyst entrainment and the solubility of cyclohexanol in the aqueous phase, it is preferable that the weight of water entering the extraction operation is less than 10% of the weight of the flash liquid entering the extraction operation. More preferably, the weight of water entering the extraction operation is less than 5% of the weight of the flash liquid entering the extraction operation, at which point it is economical to avoid further cyclohexene back-extraction.

[0080] When the amount of water added is limited, in order to give the catalyst entrained in the flash liquid more opportunities to come into contact with the aqueous phase, the extraction operation is preferably carried out in a packed extraction tower, and it is preferable to use the aqueous phase as the continuous phase and the flash liquid as the dispersed phase.

[0081] In step b, the added mass flow rate of the extractant is less than 5% of the added mass flow rate of the flash liquid, which is the addition flow rate ratio after the extraction operation has stabilized. To achieve an operation mode where the extractant is the continuous phase and the flash liquid is the dispersed phase, more extractant needs to be added to the extraction column at the beginning. Simultaneously, to maintain long-term extraction operation, the amount of water added as extractant cannot be infinitely small, as the flash liquid will dissolve and carry away some water. The minimum amount of water added is related to the temperature of the extraction operation, as well as the specific type and size of the extraction column and the composition of the flash liquid.

[0082] In actual operation, the amount of water added should be sufficient to ensure interface stability in the extractor. The table below shows the dissolved water content in cyclohexene or cyclohexanol at different temperatures, which can be used as a reference when adjusting the amount of water added.

[0083] Water content 30℃ 50℃ 110℃ 130℃ In cyclohexene, wt% 0.06％ 0.12％ 0.35％ 0.69％ In cyclohexanol, wt% 11.5％ 10.9％ 14.5％ 19.1％

[0084] The data in the table in this embodiment comes from research results from Fuzhou University, specifically Biyu Wang, Xiuxiu Ge, Huidong Zheng, Ting Qiu, Yanxiang Wu, J. Chem. Eng. Data, 2010, 55, 2529-2531 Liquid-Liquid Equilibrium for the System Water+Cyclohexene+Cyclohexanol over the Temperature Range of (303.2 to 403.2) K. When the temperature gradually decreases from 130℃, the solubility of cyclohexanol in water and the solubility of water in cyclohexanol both decrease first and then increase, with the solubility of cyclohexanol in water reaching its minimum at approximately 50–70℃.

[0085] A certain amount of the filtrate from flash liquid II in Example 3 was filtered through a suction funnel and filter paper. After weighing, 5% water by weight of the filtrate was added, and the mixture was stirred thoroughly and allowed to stand. The lower layer of liquid was then measured using a refractometer, and the cyclohexanol content was calculated to be approximately 2 wt%. The discrepancy with the data in the previous table is due to the room temperature being around 25°C, and the influence of other components in flash liquid II being factored into the cyclohexanol content.

[0086] The specific embodiments described herein are merely illustrative examples of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention.

Claims

1. A process for the recovery of a cyclohexene hydration catalyst, characterized in that, The process comprises the following steps: a. Flashing: the cyclohexanol-containing material from the hydration reaction of cyclohexene is flashed to obtain flash gas and flash liquid; b. Extraction: the flash liquid in step a is extracted with water as the extractant in at least one extraction device to obtain an extract phase and a raffinate phase; c. Separation: the flash gas in step a and the raffinate phase in step b are sent to a cyclohexanol separation unit, and the extract phase in step b is sent to a hydration reaction unit.

2. The process for the recovery of cyclohexene hydration catalyst according to claim 1, characterized in that, The extraction device in step b is at least one of a packed extraction column, a sieve plate extraction column and a spray extraction column, and the operating pressure of the flashing in step a is 30-100 kPaA.

3. The process for the recovery of cyclohexene hydration catalyst according to claim 2, characterized in that, In the extraction operation in step b, the extractant is the continuous phase and the flash liquid is the dispersed phase.

4. The process for recovering cyclohexene hydration catalyst according to claim 2, characterized in that, The extraction device is a packed extraction column, and the operating pressure of the flashing in step a is 40-60 kPaA.

5. The process for recovering cyclohexene hydration catalyst according to claim 1, characterized in that, The flash gas in step a is subjected to defoaming treatment before being sent to the cyclohexanol separation unit.

6. The process for recovering a cyclohexene hydration catalyst according to claim 1, characterized in that, Before step b, all or part of the flash liquid in step a is subjected to heating flashing, and the flash liquid is further concentrated.

7. The process for recovering cyclohexene hydration catalyst according to claim 1, characterized in that, In step b, the mass flow rate of the extractant added is less than 5% of the mass flow rate of the flash liquid added.

8. An apparatus for the recovery process of the catalyst for the hydration of cyclohexene according to any one of claims 1 to 7, characterized in that, The process comprises a flash tank (2), an extractor (3), a cyclohexanol separation column (4), a feed line (5) for transporting the hydration product of cyclohexene, and an extractant line (9), the outlet of the feed line (5) is connected to the inlet of the flash tank (2), the outlet of the extractant line (9) is connected to the upper inlet of the extractor (3), the liquid phase outlet of the flash tank (2) is connected to the lower inlet of the extractor (3) through a pipeline, the gas phase outlet of the flash tank (2) is connected to the first inlet (A) of the cyclohexanol separation column (4) through a pipeline, and the upper outlet of the extractor (3) is connected to the second inlet (B) of the cyclohexanol separation column (4) through a pipeline.

9. The apparatus of claim 8, wherein, The second inlet (B) of the cyclohexanol separation column (4) is higher than the first inlet (A).

10. The apparatus of claim 8, wherein, A delivery pump (25) is arranged on the pipeline connecting the liquid phase outlet of the flash tank (2) to the lower inlet of the extractor (3), a branch pipeline is arranged on the pipeline connecting the liquid phase outlet of the flash tank (2) to the lower inlet of the extractor (3), the outlet of the branch pipeline is connected to the flash tank (2), and a heater (26) is arranged on the branch pipeline.

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