Method and device for preparing cyclopentanone by dehydrogenating cyclopentanol

Abstract

The invention relates to the technical field of reactive distillation, in particular to a method and device for preparing cyclopentanone through cyclopentanol dehydrogenation, and the method for preparing cyclopentanone through cyclopentanol dehydrogenation comprises the following steps: S1, cyclopentanol is added into a reaction kettle of a distillation reactor, water is added into the reaction kettle of the distillation reactor, and the reaction kettle of the distillation reactor is heated to 60-80 DEG C; heating to generate mixed steam of cyclopentanol and water; s2, carrying out dehydrogenation reaction on the mixed steam obtained in the step S1 through a catalyst, stripping and condensing in a rectification part of a rectification reactor, and carrying out gas-liquid separation to obtain an oil-water mixed liquid phase; s3, carrying out oil-water separation on the liquid phase obtained in the step S2 to respectively obtain a water phase and an oil phase; the extracted oil phase is cyclopentanone. The method and the device for preparing cyclopentanone by dehydrogenating cyclopentanol are improved, the reaction energy consumption is reduced, the conversion rate and the reaction stability are improved, side reactions are reduced, the service life of the catalyst is ensured, and the operation error-tolerant rate is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of reactive distillation, in particular to a method and device for preparing cyclopentanone by dehydrogenation of cyclopentanol. BACKGROUND

[0002] Cyclopentanone is an important chemical intermediate, which is widely used in the fields of medicine, pesticide, perfume and polymer material. At present, cyclopentanone is mainly prepared by dehydrogenation of cyclopentanol in industry. However, the traditional process has problems such as high energy consumption, low conversion rate, many by-products and fast activity decline of catalyst.

[0003] Cui Jinling et al. found in the research on catalytic process for preparing cyclopentanone by gas phase dehydrogenation of cyclopentanol that the reaction temperature for preparing cyclopentanone by gas phase catalytic dehydrogenation on the self-made catalyst (Ni-Cu-A / Al2O3-SiO2) is 140-150℃, the liquid hourly space velocity is 1-1.5h-1, the conversion rate of cyclopentanol is more than 75%, and the selectivity of cyclopentanone is more than 98%. -1 Guo Shizhuo et al. recorded in the preparation of cyclopentanone by catalytic dehydrogenation of cyclopentanol that the intrinsic kinetics for preparing cyclopentanone by dehydrogenation of cyclopentanol with Raney nickel as catalyst was studied. In a tank reactor, when the reaction temperature is more than 124℃, the stirring speed is greater than 50r / min, and the catalyst amount is 10% of the mass of the reaction material, the conversion rate of cyclopentanol is more than 17% after 2h of reaction, and the selectivity of cyclopentanone is close to 100%. In the reaction distillation, the ideal liquid hourly space velocity is less than 0.49h-1, the reflux ratio is 4:1, and the activity and selectivity of the catalyst remain basically unchanged after 200h of operation. -1

[0004] At present, the main production method of cyclopentanone is reaction distillation, which has high thermal efficiency, low energy consumption, and can improve the conversion rate and selectivity. However, the existing ordinary reaction distillation still has some problems. That is, the reaction kettle is in a strong heating state, the side reactions increase, and the reaction raw materials are also easy to be quickly deactivated due to high temperature. The catalyst and reaction raw materials are both in the reaction kettle. In order to ensure the continuous reaction, a part of the kettle liquid needs to be discharged at a certain interval to reduce the concentration of by-product, at this time, the catalyst is also easy to be lost.

[0005] Therefore, the inventors have made research and exploration on the basis and improved the method and device for preparing cyclopentanone by dehydrogenation of cyclopentanol. SUMMARY

[0006] In order to solve the above technical problems, the present application provides a method and device for preparing cyclopentanone by dehydrogenation of cyclopentanol, which improves the method and device for preparing cyclopentanone by dehydrogenation of cyclopentanol, improves the conversion rate and reaction stability, reduces the occurrence of side reactions, ensures the service life of the catalyst and improves the operation fault tolerance.

[0007] ​The technical scheme adopted by the present application for solving the technical problem is:

[0008] A method for preparing cyclopentanone by dehydrogenation of cyclopentanol, comprising the following steps:

[0009] A method for preparing cyclopentanone by dehydrogenation of cyclopentanol, comprising the following steps:

[0010] Step S1: cyclopentanol is added to a rectification reactor, and water is added to the reaction kettle of the rectification reactor to generate mixed vapor of cyclopentanol and water by heating; wherein the volume ratio of cyclopentanol to water is 1.5-3:1;

[0011] Step S2: the mixed vapor of cyclopentanol and water obtained in step S1 is subjected to dehydrogenation reaction by a catalyst to obtain post-reaction vapor; the post-reaction vapor is subjected to rectification, condensation and gas-liquid separation in the rectification part of the rectification reactor to obtain oil-water mixed liquid phase;

[0012] Step S3: the liquid phase obtained in step S2 is subjected to oil-water separation to obtain water phase and oil phase respectively; wherein the water phase is returned to step S1 for adding water to the rectification reactor, and the oil phase obtained is cyclopentanone.

[0013] Further, it further comprises step S4: the oil phase obtained in step S3 is fed from the middle part of the column body of the rectification column, relatively pure cyclopentanone is obtained at the bottom of the column, and the vapor at the top of the column is condensed and then repeated step S3.

[0014] Further, a homogenizing solvent which is soluble with cyclopentanone and water is further added to the reaction kettle of the rectification reactor.

[0015] Further, the homogenizing solvent is an organic solvent with a boiling point between 170℃ and 250℃, which does not react with cyclopentanone and water and does not azeotrope with cyclopentanone and water.

[0016] Further, the volume ratio of cyclopentanone to homogenizing solvent in the reaction kettle of the rectification reactor is 1:1-1.5.

[0017] Further, the homogenizing solvent is ethylene glycol butyl ether.

[0018] Further, the pressure in the reaction kettle of the rectification reactor is 0.05-0.1 MPa of gauge pressure.

[0019] Further, the catalyst is a supported nickel catalyst, and the carrier of the catalyst is alumina.

[0020] A device for preparing cyclopentanone by dehydrogenation of cyclopentanol, comprising:

[0021] The rectification reactor comprises a reaction kettle and a column body connected above the reaction kettle, a feed pipe and a reboiler are connected to the reaction kettle; the column body comprises a packing section and a rectification section, the packing section is located at the lower end of the rectification section, the packing section is filled with catalyst, the rectification section is arranged with trays, a downcomer communicating with the reaction kettle is arranged on the lowermost tray of the rectification section, so that the liquid phase at the lower end of the rectification section bypasses the packing section containing catalyst and directly enters the reaction kettle, and a condenser-refluxer assembly is arranged at the upper end of the rectification section, the condenser-refluxer assembly is provided with a gas-liquid separator, and the gas-liquid separator is provided with a gas phase outlet pipe, a reflux pipe and a liquid phase outlet pipe.

[0022] The oil-water separator is provided with an inlet communicating with the liquid phase outlet pipe, an oil phase outlet pipe and a water phase outlet pipe; wherein the water phase outlet pipe communicates with the reaction kettle.

[0023] Further, the rectification column is further provided with an inlet communicating with the oil phase outlet pipe of the oil-water separator, and a top outlet pipe communicating with the inlet of the oil-water separator and a kettle pipe outlet pipe.

[0024] Compared with the prior art, the beneficial effects of the present application are:

[0025] 1. The present application utilizes gas phase reaction, and the catalyst is not in the reaction kettle, the reaction kettle is only a container for heating and gasification, the catalyst does not receive direct heating, the generation of by-products is reduced, and the service life is prolonged; at the same time, even if the temperature control is unstable during production, the reaction rate will not change greatly due to heating temperature, and the operation fault tolerance is improved.

[0026] 2. The present application utilizes the azeotropic characteristics of cyclopentanol and water, introduces water to reduce the boiling point of the product, and can save more energy compared with the existing gas phase dehydrogenation reaction process.

[0027] 3. The present application separates the catalyst from a large amount of reaction raw materials, and there is less cyclopentanone in the vapor and water vapor as a diluent gas, which can inhibit the occurrence of side reactions compared with liquid phase dehydrogenation reaction and gas phase dehydrogenation reaction without water, and improve the conversion rate. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a process flow chart of the present application;

[0029] Figure 2 is a structure schematic diagram of the device for preparing cyclopentanone by dehydrogenation of cyclopentanol according to the present application.

[0030] The attached diagram is labeled as follows: 1. Reactor; 2. Tower body; 3. Feed line; 4. Reboiler; 5. Packed section; 6. Rectifying section; 7. Tray; 8. Downcomer; 9. Reflux condenser assembly; 10. Gas-liquid separator; 11. Gas phase outlet pipe; 12. Reflux pipe; 13. Liquid phase outlet pipe; 14. Oil-water separator; 15. Oil phase outlet pipe; 16. Aqueous phase outlet pipe; 17. Distillation column; 18. Top outlet pipe; 19. Bottom pipe. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be noted that, unless otherwise specified, the raw materials and equipment used in this embodiment are conventional; for example, cyclopentanol is a commercially available product, water is deionized water, and the distillation column is existing laboratory pilot-scale or small-scale equipment.

[0032] The technical solution of the present invention is as follows:

[0033] like Figure 1 As shown: A method for the dehydrogenation of cyclopentanol to cyclopentanone includes the following steps:

[0034] Step S1: Add cyclopentanol to the distillation reactor and add water to the reaction vessel of the distillation reactor, and heat to generate a mixed vapor of cyclopentanol and water; wherein the volume ratio of cyclopentanol to water is 1.5-3:1;

[0035] Step S2: The cyclopentanol and water mixture vapor obtained in step S1 is dehydrogenated by a catalyst to obtain post-reaction vapor; the post-reaction vapor is processed in the rectification section of the rectification reactor, the high-boiling-point material enriched at the bottom is returned to the reactor of step S1, and the low-boiling-point material enriched at the top is condensed and then separated into gas and liquid to obtain an oil-water mixture liquid phase.

[0036] Step S3: Separate the liquid phase obtained in step S2 into an oil phase and an oil phase; the water phase is returned to step S1 to add water to the distillation reactor, and the extracted oil phase is cyclopentanone.

[0037] The purpose of adding water is to form an azeotrope with cyclopentanol (azeotropic point 96.3℃, cyclopentanol content in vapor 42% vol%). Firstly, water has a lower boiling point than cyclopentanol (140.8℃), reducing the energy required to generate vapor. Secondly, water also forms an azeotrope with cyclopentanone (azeotropic point 92.8℃, cyclopentanone content in vapor 22% vol%), and the azeotropic temperature of water with cyclopentanone is lower than that of water with cyclopentanol. This means water can act as a carrier while preventing cyclopentanol from accumulating at the top of the column. Furthermore, the presence of water vapor can dilute the hydrogen gas, reducing operational risks.

[0038] The amount of water added in the mixture is less than the amount of cyclopentanol because the dehydrogenation reaction is an endothermic reaction, which requires a higher reaction system temperature to have a higher conversion rate. Therefore, a smaller amount of water can ensure that the temperature in the reaction kettle is higher than the boiling point of water, which promotes the gasification of water in a higher proportion to adapt to the reaction endothermicity and to carry cyclopentanone with water, thereby avoiding the problem of steam liquefaction inside the catalyst during the reaction process due to heat absorption.

[0039] Because cyclopentanol is viscous and only slightly soluble in water, during the reaction process, vapor instability may occur due to oil-water separation. In order to prevent unnecessary reaction fluctuations, a homogenizing solvent dissolved in water is also added to the reaction kettle of the rectification reactor. The homogenizing solvent needs to be non-reactive with cyclopentanol and water and non-azeotropic with cyclopentanol and water, and needs to be soluble with both water and cyclopentanol, to promote the generation of a uniform phase in the reaction kettle and promote the stable operation of the reaction system. Therefore, the homogenizing solvent is preferably an organic solvent with a boiling point between 170-250°C. In this embodiment, the homogenizing solvent is ethylene glycol butyl ether.

[0040] Preferably, the volume ratio of cyclopentanol to homogenizing solvent in the reaction kettle of the rectification reactor is 1:1-1.5.

[0041] In this embodiment, the pressure in the reaction kettle of the rectification reactor is 0.05-0.1 MPa of gauge pressure, which requires lower energy consumption for micro-positive pressure and is beneficial to maintaining the stability of the reaction and reducing the risk of air mixing in the reactor.

[0042] The catalyst is a supported nickel catalyst, and when the catalyst is used as a filler, the amount of supported nickel catalyst used is 500g. The carrier of the catalyst is alumina. Although Raney nickel is better for conventional reactions, the catalyst is used as a filler in this application, so the supported catalyst is better. The loading of nickel is 3%-5% of the weight of the carrier. Because the supported nickel catalyst needs to form a filler column, the amount used is relatively large, so the amount of nickel used is not much different from the amount used when pure Raney nickel is used.

[0043] The cyclopentanone obtained only by oil-water separation still contains a small amount of water, so an additional step of rectifying the cyclopentanone is added, i.e. step S4: the oil phase obtained in step S3 is fed from the middle part of the column body of the rectification column, and relatively pure cyclopentanone is obtained at the bottom of the column. The vapor at the top of the column is condensed and separated from the liquid phase component separated by the gas-liquid separator, which can be returned to the oil-water separator for separation.

[0044] The implementation of the present application relies on a self-made reactor. Because the process used in the present application is not suitable for conventional reaction rectification experimental equipment, the inventors have adjusted the existing experimental equipment, i.e. adjusting the lower end of the rectification section to a filler section for storing the catalyst for gas phase reaction, and the liquid phase in the tray part bypasses the filler section directly back to the reaction kettle through a downcomer. The specific structure is as follows:

[0045] As shown in Figure 2 A device for preparing cyclopentanone by dehydrogenation of cyclopentanol, comprising:

[0046] A rectifying reactor, which comprises a reaction kettle 1 and a column body 2 connected above the reaction kettle 1, a feed pipe 3 and a reboiler 4 are connected to the reaction kettle 1; the column body 2 comprises a packing section 5 and a rectifying section 6, wherein the packing section 5 is filled with catalyst, 30 trays 7 are arranged on the rectifying section 6, a downcomer 8 communicating with the reaction kettle 1 is arranged on the lowest tray 7 of the rectifying section 6, the downcomer 8 directly communicates with the reaction kettle 1 through the catalyst column in the packing section 5, so that the liquid phase at the lower end of the rectifying section 6 directly enters the reaction kettle 1 without passing through the packing section 5 containing catalyst, a condenser-refluxer assembly 9 is arranged at the upper end of the rectifying section 6, the condenser-refluxer assembly 9 is provided with a gas-liquid separator 10, the gas-liquid separator 10 has a gas phase outlet pipe 11, a reflux pipe 12 and a liquid phase outlet pipe 13;

[0047] An oil-water separator 14, which has a feed inlet communicating with the liquid phase outlet pipe 13, an oil phase outlet pipe 15 and a water phase outlet pipe 16; wherein the water phase outlet pipe 16 communicates with the reaction kettle 1.

[0048] When necessary, the device for preparing cyclopentanone by dehydrogenation of cyclopentanol further comprises a rectifying column 17, the feed inlet of the rectifying column 17 communicates with the oil phase outlet pipe 15 of the oil-water separator 14, a column top outlet pipe 18 is connected to the feed inlet of the oil-water separator 14, and a column bottom pipe 19 is used to collect cyclopentanone.

[0049] Example 1:

[0050] The air in the rectifying reactor is replaced by nitrogen, then 250 ml of ethylene glycol butyl ether, 250 ml of cyclopentanol and 150 ml of water are added to the reaction kettle 1, and heated to 137℃, at this time the mixed vapor of cyclopentanol and water passes upward through the catalyst for dehydrogenation reaction, after the reaction, the vapor is enriched in the rectifying section 6, the mixed vapor of cyclopentanone with lower boiling point and water and hydrogen gas are condensed in the condenser-refluxer assembly 9, and then separated into hydrogen gas and liquid phase through the gas-liquid separator 10, the hydrogen gas is discharged, the liquid phase is subjected to full reflux in the rectifying section 6, the cyclopentanol with higher boiling point directly returns to the reaction kettle 1 through the downcomer 8, the temperature in the reaction kettle 1 gradually decreases, when the temperature in the reaction kettle 1 decreases to below 130℃, the liquid phase is collected, the reflux ratio is 4, and the cyclopentanol and water are added dropwise, the liquid level in the reaction kettle 1 is kept unchanged, the collected liquid phase is subjected to oil-water separation, the water phase is used to add water to the reaction kettle 1, and the oil phase is cyclopentanone.

[0051] After the reaction is stable, the temperature in the reactor is 108-109°C. Real-time detection by gas chromatography (GC) and verification by mass spectrometry (MS) show that the oil phase contains 98.46wt% cyclopentanone, 1.32wt% water, 0.15wt% cyclopentanol and 0.07wt% other impurities.

[0052] Example 2:

[0053] The air in the rectification reactor is replaced with nitrogen, and then 250ml of ethylene glycol butyl ether, 200ml of cyclopentanol and 100ml of water are added to the reactor 1. The mixture is heated to 137°C, at which time the mixed vapor of cyclopentanol and water passes upward through the catalyst for dehydrogenation. After the reaction, the vapor is enriched in the rectification section 6. The mixed vapor of cyclopentanone and water with hydrogen is condensed in the condenser assembly 9, and the hydrogen and liquid phase are separated in the gas-liquid separator 10. The hydrogen is discharged, and the liquid phase is returned to the reactor 1 through the downcomer under full reflux in the rectification section 6. The temperature in the reactor 1 gradually decreases, and when the temperature in the reactor 1 drops below 130°C, the liquid phase is collected. The reflux ratio is 2.5, and the addition of cyclopentanol and water is started. The liquid level in the reactor 1 is kept constant, and the collected liquid phase is subjected to oil-water separation. The water phase is used to add water to the reactor 1, and the oil phase is cyclopentanone.

[0054] After the reaction is stable, the temperature in the reactor is 110-112°C. Real-time detection by gas chromatography (GC) and verification by mass spectrometry (MS) show that the oil phase contains 97.88wt% cyclopentanone, 1.87wt% water, 0.19wt% cyclopentanol and 0.06wt% other impurities.

[0055] Example 3:

[0056] This example is based on the rectification of the oil phase in Example 2. Real-time detection by gas chromatography (GC) and verification by mass spectrometry (MS) show that the collected cyclopentanone contains 99.37wt% cyclopentanone, 0.38wt% water, 0.19wt% cyclopentanol and 0.06wt% other impurities.

[0057] Example 4:

[0058] This example is based on the operation of Example 3 for 120h. The composition of the material in the reactor is as follows:

[0059] Ethylene glycol butyl ether 42.94wt%, cyclopentanol 38.24wt%, water 17.90wt%, cyclopentanone 0.81wt% and other impurities 0.11wt%; the coking of the catalyst in the packing section is only 7.78% (thermogravimetric method).

[0060] Comparative Example:

[0061] The comparative example is carried out on a conventional reactive distillation unit, the catalyst is added into the reactor, 250 ml of ethylene glycol butyl ether (as diluent) and 250 ml of cyclopentanol are added into the reactor, the catalyst is Raney nickel, the catalyst dosage is 25 g, the stirring speed is 50 r / min, the temperature in the reactor is 142℃ after the unit is running stably, and cyclopentanol is collected at the top of the column;

[0062] The composition of the material in the reactor is detected as follows:

[0063] Ethylene glycol butyl ether 49.53 wt%, cyclopentanol 42.41 wt%, cyclopentanone 7.74%, and other impurities 0.32%; the catalyst coking is 11.53% (thermogravimetric method).

[0064] It should be understood that the specific examples described herein are merely used to explain the present application, and are not used to limit the present application.

Claims

1. A method for dehydrogenating cyclopentanol to cyclopentanone, characterized by, The method comprises the following steps: Step S1: adding cyclopentanol into a reaction kettle (1) of a rectification reactor, and adding water into the reaction kettle (1) of the rectification reactor to generate mixed vapor of cyclopentanol and water by heating; wherein the volume ratio of cyclopentanol to water is 1.5-3:1; Step S2: subjecting the mixed vapor of cyclopentanol and water obtained in step S1 to dehydrogenation reaction by a catalyst to obtain post-reaction vapor; subjecting the post-reaction vapor to rectification, condensation and gas-liquid separation in a rectification part of the rectification reactor to obtain liquid phase of oil-water mixture; Step S3: subjecting the liquid phase obtained in step S2 to oil-water separation to obtain water phase and oil phase respectively; wherein the water phase is returned to step S1 for adding water into the rectification reactor, and the oil phase is the cyclopentanone.

2. The process for the dehydrogenation of cyclopentanol to cyclopentanone according to claim 1, characterized in that, The method further comprises step S4: feeding the oil phase obtained in step S3 from the middle part of the tower body of a rectification tower, obtaining relatively pure cyclopentanone at the bottom of the tower, and repeatedly performing step S3 after condensation of the vapor at the top of the tower.

3. The process for the dehydrogenation of cyclopentanol to cyclopentanone according to claim 1, characterized in that, The reaction kettle (1) of the rectification reactor further comprises a homogenizing solvent which is soluble with cyclopentanone and water.

4. The process for the dehydrogenation of cyclopentanol to cyclopentanone according to claim 3, characterized in that, The homogenizing solvent is an organic solvent with a boiling point of 170-250°C, and does not react with cyclopentanol and water or form azeotrope with cyclopentanol and water.

5. The process for the dehydrogenation of cyclopentanol to cyclopentanone according to claim 3, characterized in that, The volume ratio of cyclopentanol to the homogenizing solvent in the reaction kettle (1) of the rectification reactor is 1:1-1.

5.

6. The process for the dehydrogenation of cyclopentanol to cyclopentanone according to claim 3, characterized in that, The homogenizing solvent is ethylene glycol butyl ether.

7. The process for the dehydrogenation of cyclopentanol to cyclopentanone according to claim 1, characterized in that, The pressure in the reaction kettle (1) of the rectification reactor is 0.05-0.1 MPa.

8. The process for dehydrogenation of cyclopentanol to cyclopentanone according to claim 1, characterized by, The catalyst is a supported nickel catalyst, and the carrier of the catalyst is alumina.

9. A device for the dehydrogenation of cyclopentanol to cyclopentanone for carrying out the method for the dehydrogenation of cyclopentanol to cyclopentanone according to any one of claims 1 to 8, characterized in that The method comprises: The rectification reactor comprises a reaction kettle (1) and a tower body (2) connected above the reaction kettle (1), the reaction kettle (1) is connected with a feeding pipeline (3) and a reboiler (4); the tower body (2) comprises a packing section (5) and a rectification section (6), the packing section (5) is located at the lower end of the rectification section (6), the packing section (5) is filled with a catalyst, the rectification section (6) is arranged with a tray (7), the tray (7) at the lowermost end of the rectification section (6) is provided with a downcomer (8) connected with the reaction kettle (1), so that the liquid phase at the lower end of the rectification section (6) bypasses the packing section (5) containing the catalyst and directly enters the reaction kettle (1), the upper end of the rectification section (6) is provided with a condenser-refluxer assembly (9), the condenser-refluxer assembly (9) is provided with a gas-liquid separator (10), and the gas-liquid separator (10) is provided with a gas phase outlet pipe (11), a reflux pipe (12) and a liquid phase outlet pipe (13); The oil-water separator (14) is provided with a feeding inlet connected with the liquid phase outlet pipe (13), an oil phase outlet pipe (15) and a water phase outlet pipe (16); wherein the water phase outlet pipe (16) is connected with the reaction kettle (1).

10. The apparatus for dehydrogenation of cyclopentanol to cyclopentanone according to claim 9, characterized in that, The method further comprises a rectification tower (17), the feeding inlet of the rectification tower (17) is connected with the oil phase outlet pipe (15) of the oil-water separator (14), a tower top outlet pipeline (18) is connected with the feeding inlet of the oil-water separator (14), and a tower kettle pipeline (19) is used to take out cyclopentanone.

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