High-selectivity cyclohexanol preparation system and preparation method

Abstract

The invention provides a system for preparing cyclohexanol with high selectivity and a preparation method, the system comprises a hydrogenation reactor, the bottom of the hydrogenation reactor is provided with a plurality of reinforced reactors, the reinforced reactors are connected through a plurality of channels, and the middle upper part of the hydrogenation reactor is provided with a multi-stage fixed reaction bed; the hydrogenation reactor is connected with the separation device and the rectification device. The system can realize the combined proceeding of hydrogenation reaction and hydration reaction; meanwhile, benzene and cyclohexene can be recycled, and a reinforced reaction unit is combined, so that the reaction efficiency is improved, and the selectivity of cyclohexanol is improved.

Description

Technical Field

[0001] The invention relates to the field of chemical engineering and process technology, and in particular to a system and method for preparing cyclohexanol with high selectivity. Background Art

[0002] Cyclohexanol is an important organic compound with a wide range of uses. It is a key raw material for producing a variety of chemical products, mainly including adipic acid, hexamethylenediamine, cyclohexanone, etc. Cyclohexanol can also be used as an organic solvent and plasticizer, etc., and has a wide range of uses. The existing cyclohexanol preparation processes mainly include phenol hydrogenation, cyclohexane oxidation, and cyclohexene hydration. Among them, the raw material price of the phenol hydrogenation method is high and the cost is relatively large; the cyclohexane oxidation method has low selectivity, low conversion rate, and poor safety. The present invention adopts micro-interface enhanced benzene hydrogenation hydration to produce cyclohexanol, and combines benzene hydrogenation to produce cyclohexene with cyclohexene hydration to produce cyclohexanol, which can make the selectivity of the generated cyclohexanol reach 99%, achieving the goal of saving costs and improving product selectivity. In the existing benzene hydrogenation reactor, hydrogen gas enters the reactor after bubbling through the bottom distributor to complete the initial distribution. The bubble diameter is too large, the interfacial area of ​​the gas-liquid two phases is too small, and the bubbles initially distributed are easy to aggregate and become larger during the rising process, resulting in low gas-liquid mass transfer efficiency and reaction rate.

[0003] In view of this, the present invention is proposed. Summary of the invention

[0004] The object of the present invention is to provide a highly selective system for preparing cyclohexanol, which can realize the combined hydrogenation reaction and hydration reaction; at the same time, benzene and cyclohexene can be recycled, and at the same time, combined with an enhanced reaction unit, the reaction efficiency is improved and the selectivity of cyclohexanol is improved.

[0005] The second object of the present invention is to provide a highly selective method for preparing cyclohexanol, which can effectively improve the reaction efficiency, save the cost of the reaction, and better improve the selectivity of the product. In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted: The invention provides a system for preparing cyclohexanol with high selectivity, comprising: a hydrogenation reactor, a plurality of enhanced reactors are arranged at the bottom of the hydrogenation reactor, the enhanced reactors are connected by a plurality of channels, a multi-stage fixed reaction bed is arranged at the middle and upper part of the hydrogenation reactor; the hydrogenation reactor is connected with a separation device and a distillation device.

[0006] In the present invention, a plurality of enhanced reactors are provided in the hydrogenation reactor, and the number of enhanced reactors can be set according to actual needs, and the enhanced reactors provided are all pneumatic enhanced reactors, so as to convert the reactants involved in the reaction into microbubbles. At the same time, a channel is provided between each enhanced reactor, and the channel between two enhanced reactors can be vertically connected to each other, or can be set to a non-parallel type, and the channel can be arbitrarily set according to needs. The channel can make the reactants involved in the reaction more concentrated, so that the reactants involved in the reaction can be mixed more efficiently, and the reaction rate is increased exponentially.

[0007] In the present invention, the reaction bed can be a fixed reaction bed, or a suspended bed or slurry bed reactor can be selected to replace the fixed reaction bed according to the size of the catalyst. After the hydrogenation reaction, the separation device and the distillation device can better separate the substances and recycle the reaction materials.

[0008] Preferably, as a further specific implementation, a diffusion tube is provided between the enhanced reactor and the multi-stage fixed reaction bed, and the inclination angle of the tube wall of the diffusion tube is 4°-5°.

[0009] When the catalyst is placed in a fixed bed for reaction, there is no need to set up an additional separation device to separate the catalyst from the reactants; at the same time, the diffuser provided can further concentrate the reactants, which is more conducive to improving the reaction efficiency. The inclination angle of the diffuser wall is set to 4°-5°. If the inclination angle is too small, the diffuser is almost vertical, which cannot play a good role in deceleration and sufficient mixing between the reactants; and if the inclination angle is too large, it is bound to shorten the distance between the diffuser and the enhanced reactor, thereby shortening the reaction distance. Therefore, when the inclination angle of the diffuser wall is set to 4°-5°, it is beneficial to reduce the rate of reactants entering the fixed bed, so that the reactants can fully contact with the catalyst, reduce the occurrence of side reactions, and improve the reaction efficiency.

[0010] Preferably, as a further specific embodiment, the separation device comprises a gas-liquid separation tower, two separators are arranged inside the gas-liquid separation tower, and an inlet is arranged between the two separators, and the gas-liquid separation tower is directly connected to the hydrogenation reactor through the inlet.

[0011] In the present invention, the hydrogen separated from the top of the gas-liquid separation tower is recycled through the hydrogenation reactor, and the liquid material enters the hydration reactor through a circulation pump for hydration reaction, thereby realizing the recycling of the material. An inlet is provided between the two separators to ensure the separation of the gas-liquid two phases, and the separation effect of a single separator will be reduced. At the same time, the separation tower can separate the hydrogen in the product, and the hydrogen can enter the reaction system again, realizing the reuse of the hydrogen.

[0012] Preferably, as a further specific embodiment, the separation device includes a hydration reactor, and the gas-liquid separation tower is directly connected to the hydration reactor through a circulation pump; a plurality of enhanced reactors are provided at the bottom of the hydration reactor, and the enhanced reactors are connected by a plurality of channels, and a plurality of fixed reaction beds are provided in the middle and upper part of the hydration reactor.

[0013] The settings inside the hydration reactor are basically consistent with the structure inside the hydrogenation reactor, so that after the materials enter the hydration reactor, the reaction materials flow from bottom to top, and by strengthening the setting of the reaction unit and pipelines, the efficiency of the hydration reaction is improved and the occurrence of side reactions is reduced.

[0014] Preferably, as a further specific embodiment, the separation device further comprises an oil-water separation tank, and the oil-water separation tank is used to connect the gas-liquid separation tower and the distillation device; a pipeline is provided at the bottom of the oil-water separation tank to connect with the upstream of the circulation pump.

[0015] Preferably, as a further specific embodiment, the distillation device includes a distillation tower a and a distillation tower b, and the tops of the distillation tower a and the distillation tower b are both connected in parallel with condensers, and the bottoms are both connected in parallel with reboilers; the condenser connected in parallel with the distillation tower b is connected to the liquid inlet arranged at the bottom of the hydrogenation reactor, and the reboiler connected in parallel with the distillation tower b is connected to the upstream of the circulation pump.

[0016] The setting of water-oil separation tank and multiple distillation towers can better separate cyclohexanol, cyclohexene, cyclohexane and benzene. Single distillation cannot separate the above substances at one time, or it may lead to incomplete separation, thereby reducing the purity of the product. Preferably, as a further specific implementation, the top of the gas-liquid separation tower is provided with an outlet, which is connected to the gas inlet of the hydrogenation reactor through a pipeline.

[0017] The present invention also provides a method for preparing cyclohexanol using the system for preparing cyclohexanol with high selectivity, comprising the following steps: Mixing benzene, hydrogen and water, hydrogenating and separating at a reaction pressure of 4.0Mpa-5.0Mpa and a reaction temperature of 130°C-145°C to generate cyclohexene; The cyclohexene is subjected to a hydration reaction at a reaction pressure of 0.5 MPa to 0.6 MPa and a reaction temperature of 115° C. to 120° C. to generate cyclohexanol; The cyclohexanol is separated into water and oil, and the oil phase is distilled to obtain the cyclohexanol.

[0018] Preferably, as a further specific implementation, the molar ratio of benzene:hydrogen:water=6:5:3.

[0019] In the hydration reaction, it is necessary to ensure that there is an excess of water. In the reaction of benzene with hydrogen, it is necessary to ensure that there is an excess of benzene to ensure the conversion rate of cyclohexene produced by the hydrogenation reaction. If there is an excess of hydrogen, cyclohexane will be produced after the hydrogenation reaction.

[0020] Preferably, as a further specific embodiment, the catalyst used in the hydrogenation reaction is a ruthenium-zinc catalyst; the catalyst used in the hydration reaction is a crystalline molecular sieve catalyst SiO 2 / Al 2 O 3 .

[0021] The above-mentioned crystalline molecular sieve has a large specific surface area and a relatively stable structure, and can make the reactants contact with it more fully during the reaction process, so that the reactants can react more fully, thereby improving the conversion effect of the reactants.

[0022] Compared with the prior art, the present invention has the following beneficial effects: The hydrogenation reactor of the present invention adopts a fixed bed reactor, and the catalyst adopts a ruthenium-zinc catalyst; the hydration reactor adopts a fixed bed reactor, and the catalyst adopts a crystalline molecular sieve catalyst SiO 2 / Al 2 O 3 If the catalyst particles used are small, a suspended bed or slurry bed reactor can be used instead of a fixed bed reactor. This can effectively save costs, speed up the reaction rate, and recycle the reaction materials, saving costs; there are fewer side reactions, and the selectivity of cyclohexanol is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings: Figure 1 : Schematic diagram of an enhanced device for the highly selective preparation of cyclohexanol.

[0024] The symbols in the accompanying drawings are: 1. Hydrogen inlet; 2. Benzene and oxygen-free water inlet; 3. Hydrogenation reactor; 4. Gas-liquid separation tower; 5. Hydration reactor; 6. Oil-water separation tank; 7. Distillation tower a; 8. Distillation tower b; 9. Reboiler; 10. Cyclohexane outlet; 11. Fixed reaction bed; 12. Fixed reaction bed; 13. Enhanced reactor; 14. Enhanced reactor; 15. Separator; 16. Separator; 17. Fixed reaction bed; 18. Fixed reaction bed; 19. Enhanced reactor; 20. Enhanced reactor; 21. Circulation pump; 22. Condenser; 23. Condenser; 24. Reboiler; 25. Channel; 26. Diffuser; 27. Channel. DETAILED DESCRIPTION

[0025] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0026] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0027] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0028] In order to more clearly explain the technical solution of the present invention, it is described in the form of specific embodiments below.

[0029] Example 1 like Figure 1The connection mode shown. In the present invention, a hydrogenation reactor 3 is provided, and an enhanced reactor 14 and an enhanced reactor 13 are provided at the bottom of the hydrogenation reactor 3. The enhanced reactor 14 and the enhanced reactor 13 are both pneumatic enhanced reaction devices, and the two are connected by a channel 25. A fixed reaction bed 12 and a fixed reaction bed 13 are provided at the upper part of the hydrogenation reactor 3, and a ruthenium-zinc catalyst is laid in the above-mentioned fixed reaction beds. A diffusion pipe 26 is provided on the enhanced reactor 13 to connect with the fixed reaction bed 12, and the inclination angle of the tube wall of the diffusion pipe 26 is 4°-5°. A hydrogen inlet 14 is provided at a position corresponding to the enhanced reactor 14 in the hydrogenation reactor 3, and a benzene and oxygen-free water inlet 2 is provided at the bottom of the hydrogenation reactor 3.

[0030] The hydrogenation reactor 3 is connected to the gas-liquid separation tower 4, and the gas-liquid separation tower is provided with a separator 15 and a separator 16. A pipeline is provided on the top of the hydrogenation reactor 3, one end of the pipeline is connected to the hydrogenation reactor 3, and the other end is connected to the gas-liquid separation tower 4, and the position connected to the gas-liquid separation tower 4 is set between the separator 15 and the separator 16. In addition, a pipeline is provided on the top of the gas-liquid separation tower 4, and the pipeline is also connected to the pipeline of the hydrogen inlet 1.

[0031] The lower part of the gas-liquid separation tower 4 is provided with a pipeline, which is connected to the bottom of the hydration reactor 5 through a circulation pump 21. The bottom of the hydration reactor 5 is provided with an enhanced reactor 19 and an enhanced reactor 20, both of which are pneumatic enhanced reactors, and a channel 27 is provided between the enhanced reactor 19 and the enhanced reactor 20. The top of the hydration reactor 5 is provided with a fixed reaction bed 17 and a fixed reaction bed 18. The top of the hydration reactor 5 is provided with a pipeline outlet connected to the oil-water separation tank 6. The bottom of the oil-water separation tank 6 is provided with a pipeline outlet, which is connected to the upstream of the pipeline where the circulation pump 21 is located.

[0032] The oil-water separation tank 6 is connected to the distillation tower a7 and the distillation tower b8 in sequence, wherein the tops of the distillation tower a7 and the distillation tower b8 are respectively connected in parallel with the condenser 22 and the condenser 23, and the bottoms are respectively connected in parallel with the reboiler 9 and the reboiler 24, wherein the middle of the distillation tower b8 is also provided with a cyclohexane outlet. The reboiler 24 is also provided with a pipeline connected to the benzene and oxygen-free water inlet 2, and the condenser 23 is provided with a pipeline connected to the upstream of the pipeline where the circulating pump 21 is located.

[0033] Working Mode: The ruthenium-zinc catalyst is loaded into the fixed bed 12 and the fixed bed 11 of the hydrogenation reactor 3, and benzene, hydrogen and water are introduced into the enhanced reactor 14 through the hydrogen inlet 1 and the benzene and oxygen-free water inlet 2 in a molar ratio of 6:5:3. The reactants enter the enhanced reactor 13 through the channel 25 therebetween, and then pass through the diffusion tube 26 to react with the ruthenium-zinc catalyst loaded in the fixed bed 12 and the fixed bed 11 at a reaction pressure of 4.0Mpa-5.0Mpa and a reaction temperature of 130°C-145°C to produce cyclohexene.

[0034] The generated cyclohexene flows from the top of the hydrogenation reactor 3 into the gas-liquid separation tower 4, and the separated hydrogen enters the hydrogenation reactor 3 through the pipeline at the top of the gas-liquid separation tower 4 for recycling. The liquid material passes through the pipeline set at the bottom of the gas-liquid separation tower 4 and enters the hydration reactor 5 through the circulation pump 21. The fixed reaction bed 17 and the fixed reaction bed 18 in the hydration reactor 5 are fixed with a crystalline molecular sieve catalyst SiO 2 / Al 2 O 3 The liquid material enters from the bottom of the hydration reaction tower 5, moves upward continuously, is initially crushed by the enhanced reactor 20, and enters the enhanced reactor 19 through the channel 27, forms a micro-interface system, and then continues to move upward. The cyclohexene hydration reaction is carried out to produce cyclohexanol at a reaction pressure of 0.5Mpa-0.6Mpa and a reaction temperature of 115℃-120℃ through the catalysts set in the fixed reaction beds 18 and 19. Since the reaction required for the hydration reaction is slightly gentle, there is no need to set up an additional diffusion tube to enhance the reaction during the reaction.

[0035] The material after hydration reaction enters the oil-water separation tank 6 from the hydration reactor 5 and is left to stand for separation. Water flows out of the oil-water separation tank 6 and is passed through a pipeline into the hydration reactor 5 for recycling. The oil phase is passed into a distillation tower for distillation separation.

[0036] The oil phase is distilled twice in the distillation separation tower a7 and the distillation separation tower b8, and cyclohexanol is obtained after the initial distillation in the distillation separation tower a7; after the remaining oil phase enters the distillation separation tower b8, the separated cyclohexene can be recycled into the hydration reactor 5 through the upstream pipeline where the circulation pump 21 is located, and the separated benzene can be recycled into the reaction system through the benzene and oxygen-free water inlet 2. During the reaction process, the reboiler 9 and the reboiler 24 can vaporize the oil phase again, which is beneficial to reducing energy consumption and reusing energy; the condenser 22 and the condenser 23 can quickly convert the vaporized oil phase into a liquid phase and can dissipate heat from the system in a timely manner.

[0037] Example 2 10kg / h of hydrogen is passed into the hydrogenation reactor 3, and the feed temperature is controlled at 30℃-40℃. 469kg / h of benzene and 54kg / h of oxygen-free water are passed into the hydrogenation reactor 3 from the bottom, and the feed temperature is controlled at about 40℃. The fixed reaction bed in the hydrogenation reactor 3 is equipped with a ruthenium-zinc catalyst, the reaction pressure is 4.0Mpa, and the reaction temperature is 130℃. The reacted materials flow from bottom to top in the hydrogenation reactor 3, and flow into the gas-liquid separation tower 4 from the top of the tower. The separated hydrogen is passed into the hydrogenation reactor for recycling to obtain 222kg / h of cyclohexene. Cyclohexene is passed into the bottom of the hydration reactor 5 for hydration reaction. The fixed bed of the hydration reactor 5 is equipped with a crystalline molecular sieve catalyst SiO 2 / Al 2 O 3 The reaction pressure is 0.5Mpa, the reaction temperature is 115°C, the reacted materials flow from bottom to top in the hydration reactor 5, flow into the oil-water separation tank 6 from the top of the tower, stand and separate, water flows out from the bottom of the tank, and is passed into the hydration reactor 5 for recycling, the oil phase is passed into the distillation tower a7 and the distillation tower b8 for distillation separation, the separated benzene is passed into the hydrogenation reactor 3 for recycling, and the cyclohexene is passed into the hydration reactor 5 for recycling, to obtain 29kg / h of cyclohexanol, and the selectivity reaches 99%.

[0038] Example 3 10kg / h of hydrogen is passed into the hydrogenation reactor 3, and the feed temperature is controlled at 30℃-40℃. 469kg / h of benzene and 54kg / h of oxygen-free water are passed into the hydrogenation reactor 3 from the bottom, and the feed temperature is controlled at about 40℃. The fixed reaction bed in the hydrogenation reactor 3 is equipped with a ruthenium-zinc catalyst, the reaction pressure is 4.0Mpa, and the reaction temperature is 150℃. The reacted materials flow from bottom to top in the hydrogenation reactor 3, and flow into the gas-liquid separation tower 4 from the top of the tower. The separated hydrogen is passed into the hydrogenation reactor for recycling to obtain 227kg / h of cyclohexene. Cyclohexene is passed into the bottom of the hydration reactor for hydration reaction. The fixed bed of the hydration reactor 5 is equipped with a crystalline molecular sieve catalyst SiO 2 / Al 2 O 3 The reaction pressure is 0.5Mpa, the reaction temperature is 120°C, the reacted materials flow from bottom to top in the hydration reactor 5, flow into the oil-water separation tank 6 from the top of the tower, stand and separate, water flows out from the bottom of the tank, and is passed into the hydration reactor 5 for recycling, the oil phase is passed into the distillation tower a7 and the distillation tower b8 for distillation separation, the separated benzene is passed into the hydrogenation reactor 3 for recycling, and the cyclohexene is passed into the hydration reactor 5 for recycling, to obtain 31kg / h of cyclohexanol, and the selectivity reaches 99%.

[0039] Example 4 20kg / h of hydrogen is passed into the hydrogenation reactor 3, and the feed temperature is controlled at 30℃-40℃. 938kg / h of benzene and 108kg / h of oxygen-free water are passed into the hydrogenation reactor 3 from the bottom, and the feed temperature is controlled at about 40℃. The fixed reaction bed in the hydrogenation reactor 3 is equipped with a ruthenium-zinc catalyst, the reaction pressure is 4.0Mpa, and the reaction temperature is 130℃. The reacted materials flow from bottom to top in the hydrogenation reactor 3, and flow into the gas-liquid separation tower 4 from the top of the tower. The separated hydrogen is passed into the hydrogenation reactor for recycling to obtain 443kg / h of cyclohexene. Cyclohexene is passed into the bottom of the hydration reactor for hydration reaction. The fixed bed of the hydration reactor 5 is equipped with a crystalline molecular sieve catalyst SiO 2 / Al 2 O 3 The reaction pressure is 0.5Mpa, the reaction temperature is 115°C, the reacted materials flow from bottom to top in the hydration reactor 5, flow into the oil-water separation tank 6 from the top of the tower, stand and separate, water flows out from the bottom of the tank, and is passed into the hydration reactor 5 for recycling, the oil phase is passed into the distillation tower a7 and the distillation tower b8 for distillation separation, the separated benzene is passed into the hydrogenation reactor 3 for recycling, and the cyclohexene is passed into the hydration reactor 5 for recycling, to obtain 59kg / h of cyclohexanol, and the selectivity reaches 99%.

[0040] Example 5 20kg / h of hydrogen is passed into the hydrogenation reactor 3, and the feed temperature is controlled at 30℃-40℃. 938kg / h of benzene and 108kg / h of oxygen-free water are passed into the hydrogenation reactor 3 from the bottom, and the feed temperature is controlled at about 40℃. The fixed reaction bed in the hydrogenation reactor 3 is equipped with a ruthenium-zinc catalyst, the reaction pressure is 4.0Mpa, and the reaction temperature is 150℃. The reacted materials flow from bottom to top in the hydrogenation reactor 3, and flow into the gas-liquid separation tower 4 from the top of the tower. The separated hydrogen is passed into the hydrogenation reactor for recycling to obtain 454kg / h of cyclohexene. Cyclohexene is passed into the bottom of the hydration reactor for hydration reaction. The fixed bed of the hydration reactor 5 is equipped with a crystalline molecular sieve catalyst SiO 2 / Al 2 O 3 The reaction pressure is 0.5Mpa, the reaction temperature is 120°C, the reacted materials flow from bottom to top in the hydration reactor 5, flow into the oil-water separation tank 6 from the top of the tower, stand and separate, water flows out from the bottom of the tank, and is passed into the hydration reactor 5 for recycling, the oil phase is passed into the distillation tower a7 and the distillation tower b8 for distillation separation, the separated benzene is passed into the hydrogenation reactor 3 for recycling, and the cyclohexene is passed into the hydration reactor 5 for recycling, to obtain 62kg / h of cyclohexanol, and the selectivity reaches 99%.

[0041] Comparative Example 1 The specific implementation method is consistent with Example 2, except that the micro-interface strengthening unit of the hydrogenation reactor and the hydration reactor is removed. After the hydrogenation reaction, gas-liquid separation is performed to obtain 141 kg / h of cyclohexene, which is introduced into the hydration reactor for reaction to obtain 15 kg / h of cyclohexanol with a selectivity of 80%.

[0042] Comparative Example 2 The specific implementation method is consistent with Example 3, except that the micro-interface strengthening unit of the hydrogenation reactor and the hydration reactor is removed. After the hydrogenation reaction, gas-liquid separation is performed to obtain 283 kg / h of cyclohexene, which is introduced into the hydration reactor for reaction to obtain 30 kg / h of cyclohexanol with a selectivity of 82%.

[0043] Based on the above data, the following conclusions can be drawn: Increasing the reaction temperature of the hydrogenation reaction can increase the solubility of benzene in water, while the solubility of cyclohexene is less affected by temperature. Therefore, increasing the temperature can increase the reaction rate of benzene hydrogenation and improve the conversion rate of benzene, but it will reduce the selectivity of cyclohexene. At the same time, increasing the temperature will reduce the solubility of hydrogen in the catalyst system, weaken the adsorption effect on the catalyst surface, and too high a reaction temperature will accelerate the growth of the catalyst grains and accelerate the aging of the catalyst. Therefore, the reaction temperature should be controlled at 130℃-145℃.

[0044] The cyclohexene hydration reaction is a reversible exothermic reaction, and the reaction temperature is one of the more important factors affecting the cyclohexene hydration reaction. If the reaction temperature is too high, the balance is favorable to the reverse reaction, and if the temperature is too low, the reaction rate is too slow, and the yield is too low within a certain reaction time. Therefore, the reaction temperature should be controlled at 115℃-120℃.

[0045] The use of the micro-interface strengthening unit can greatly improve the selectivity of cyclohexanol in the hydration reaction and has a significant effect on reaction strengthening.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A system for preparing cyclohexanol with high selectivity, characterized in that: include: A hydrogenation reactor, wherein a plurality of enhanced reactors are arranged at the bottom of the hydrogenation reactor, the enhanced reactors are connected by a plurality of channels, a multi-stage fixed reaction bed is arranged at the middle and upper part of the hydrogenation reactor; the hydrogenation reactor is connected with a separation device and a distillation device.

2. The system for preparing cyclohexanol with high selectivity according to claim 1, characterized in that: A diffusion tube is provided between the enhanced reactor and the multi-stage fixed reaction bed, and the inclination angle of the tube wall of the diffusion tube is 4°-5°.

3. The system for preparing cyclohexanol with high selectivity according to claim 1, characterized in that: The separation device comprises a gas-liquid separation tower, two separators are arranged inside the gas-liquid separation tower, and an inlet is arranged between the two separators. The gas-liquid separation tower is directly connected to the hydrogenation reactor through the inlet.

4. The system for preparing cyclohexanol with high selectivity according to claim 3, characterized in that: The separation device comprises a hydration reactor, and the gas-liquid separation tower is directly connected to the hydration reactor via a circulation pump; a plurality of enhanced reactors are arranged at the bottom of the hydration reactor, the enhanced reactors are connected via a plurality of channels, and a plurality of fixed reaction beds are arranged in the middle and upper part of the hydration reactor.

5. The system for preparing cyclohexanol with high selectivity according to claim 4, characterized in that: The separation device further comprises an oil-water separation tank, which is used to connect the gas-liquid separation tower and the distillation device; a pipeline is provided at the bottom of the oil-water separation tank to connect with the upstream of the circulation pump.

6. The system for preparing cyclohexanol with high selectivity according to claim 4, characterized in that: The distillation device includes a distillation tower a and a distillation tower b, and the tops of the distillation tower a and the distillation tower b are both connected in parallel with condensers, and the bottoms are both connected in parallel with reboilers; the condenser connected in parallel with the distillation tower b is connected to the liquid inlet arranged at the bottom of the hydrogenation reactor, and the reboiler connected in parallel with the distillation tower b is connected to the upstream of the circulation pump.

7. The system for preparing cyclohexanol with high selectivity according to claim 2, characterized in that: The top of the gas-liquid separation tower is provided with an outlet, which is connected to the gas inlet of the hydrogenation reactor through a pipeline.

8. A method for preparing cyclohexanol using a system for preparing cyclohexanol with high selectivity as claimed in any one of claims 1 to 7, characterized in that: The steps include: Mixing benzene, hydrogen and water, hydrogenating and separating at a reaction pressure of 4.0Mpa-5.0Mpa and a reaction temperature of 130°C-145°C to generate cyclohexene; The cyclohexene is subjected to a hydration reaction at a reaction pressure of 0.5 MPa to 0.6 MPa and a reaction temperature of 115° C. to 120° C. to generate cyclohexanol; The cyclohexanol is separated into water and oil, and the oil phase is distilled to obtain the cyclohexanol.

9. The method for preparing cyclohexanol according to claim 8, characterized in that: The molar ratio of benzene:hydrogen:water=6:5:

3.

10. The method for preparing cyclohexanol according to claim 8, characterized in that: The catalyst used in the hydrogenation reaction is a ruthenium-zinc catalyst; the catalyst used in the hydration reaction is a crystalline molecular sieve catalyst SiO2 / Al2O3.

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