Method for preparing alcohol by low-energy consumption liquid phase hydrogenation of enal

Abstract

The application discloses a kind of low energy consumption enal liquid phase hydrogenation preparation alcohol method: enal raw material, hydrogen raw material occurs in the catalyst fixed bed of liquid phase hydrogenation reactor once liquid phase hydrogenation reaction, generates corresponding alcohol crude product;Part of alcohol crude product is mixed after condensation cooling with part of uncondensed alcohol crude product, enal raw material, and returns to the catalyst fixed bed of liquid phase hydrogenation reactor, both complete hydrogenation reactor raw material inlet temperature regulation and realize the cyclic hydrogenation of part of crude alcohol;The rest of alcohol crude product and hydrogen raw material are sent into the catalyst fixed bed of central core pipe and occur secondary liquid phase hydrogenation reaction, generate corresponding alcohol crude product;Alcohol crude product and unreacted gas phase are separated into two phases in gas-liquid separator respectively.The application is combined by "annular catalyst fixed bed once liquid phase hydrogenation+core pipe secondary liquid phase hydrogenation", control pressure 2.5-2.9MPa, temperature 110-120 DEG C, hydrogen oil ratio 2.0-2.05:1, energy consumption is reduced while realizing the improvement of enal hydrogenation total conversion rate.

Description

Technical Field

[0001] This invention relates to a technology for preparing alcohols by liquid-phase hydrogenation of aldehydes, and more specifically, to a low-energy-consumption method for preparing alcohols by liquid-phase hydrogenation of aldehydes. Background Technology

[0002] The hydrogenation process for preparing alcohols from aldehydes is mainly divided into two technical routes: gas-phase hydrogenation and liquid-phase hydrogenation. However, both have significant energy consumption and efficiency bottlenecks. The gas-phase hydrogenation process requires the complete vaporization of the raw material aldehyde. Chinese patent CN101172958A uses a gas-phase hydrogenation temperature between 180-220℃, which not only requires equipment such as a feed vaporizer and a high-temperature heater, but also requires a circulating compressor to maintain hydrogen circulation. This results in high system energy consumption, large equipment investment, and the easy generation of heavy components under high temperature conditions, which reduces the yield of the target alcohol.

[0003] While liquid-phase hydrogenation overcomes some of the drawbacks of gas-phase hydrogenation by eliminating the need for a raw material vaporization step and simplifying the equipment process, offering significant advantages in investment and operating costs compared to gas-phase hydrogenation, it still has technical shortcomings: Firstly, the reaction temperature is relatively high. Patent CN120829338A uses a liquid-phase hydrogenation reaction temperature of 165-175℃, which not only increases energy consumption but also accelerates catalyst sintering and deactivation, shortening its lifespan and increasing the operating costs associated with frequent catalyst replacements. Secondly, hydrogen utilization is low. Patent C... N108101728 uses a liquid-phase hydrogenation process with a hydrogen-to-oil ratio (molar ratio) range of (5-15):1. In actual operation, a high hydrogen-to-oil ratio is often required to ensure conversion rate, which leads to a large surplus of hydrogen. This not only increases raw material consumption but also requires a hydrogen recovery system to handle unreacted hydrogen, further increasing system energy consumption. Thirdly, it has not completely eliminated the need for compression equipment. Some liquid-phase hydrogenation processes still require compressors to assist in the circulation of unreacted hydrogen and raw materials, failing to completely eliminate the dependence on compression equipment, thus limiting the space for energy consumption optimization.

[0004] To address the technical problems of high reaction temperature, excessive hydrogen-to-oil ratio, and reliance on compression equipment in existing alkenal liquid-phase hydrogenation processes for alcohol production, which result in high energy consumption and raw material costs, there is an urgent need to develop a process for alkenal liquid-phase hydrogenation for alcohol production with lower energy consumption and higher hydrogen utilization rate, in order to further reduce the operating costs of the equipment and improve the economic efficiency and competitiveness of the process. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention proposes a low-energy-consumption method for preparing alcohols from aldehydes via liquid-phase hydrogenation. This invention uses a liquid-phase hydrogenation reactor as the core equipment, employing a combined process of "primary liquid-phase hydrogenation in a fixed-bed ring catalyst + secondary liquid-phase hydrogenation in a core tube." The liquid-phase hydrogenation reaction pressure for aldehydes is 2.5-2.9 MPa, the temperature is controlled at 110-120℃, and the hydrogen-to-oil ratio is controlled at 2.0-2.05:1 (molar ratio). Simultaneously, a portion of the hydrogenation product is recycled to the core tube in the reactor center for a secondary hydrogenation reaction. This reduces energy consumption while increasing the overall conversion rate of aldehyde hydrogenation. Furthermore, compared to existing gas-phase hydrogenation and conventional liquid-phase hydrogenation technologies, this invention, while maintaining the same conversion rate of aldehyde hydrogenation, achieves a high yield of the target alcohol, good product color, low unsaturation, and significantly reduces process energy consumption.

[0006] The objective of this invention can be achieved through the following technical solutions.

[0007] A low-energy-consumption method for preparing alcohols from enal via liquid-phase hydrogenation, comprising a liquid-phase hydrogenation reactor as the core reaction device, wherein a central core tube is coaxially arranged inside the liquid-phase hydrogenation reactor, and a distributor, a first ceramic ball layer, a catalyst fixed bed, a second ceramic ball layer, and a grid plate are arranged sequentially from top to bottom inside the central core tube and the annulus between the central core tube and the liquid-phase hydrogenation reactor; the method specifically includes the following steps: Step S1: Primary liquid-phase hydrogenation reaction The alkenal and hydrogen feedstocks are fed into the top of the liquid phase hydrogenation reactor through the alkenal feedstock feed pipe and the hydrogen feedstock feed pipe, respectively. After being mixed evenly by the distributor between the liquid phase hydrogenation reactor and the central core pipe, the feedstocks undergo a liquid phase hydrogenation reaction in the catalyst fixed bed at the bottom to generate the corresponding crude alcohol product, which finally falls into the bottom of the liquid phase hydrogenation reactor. Step S2: Temperature regulation of the primary reaction products and secondary liquid-phase hydrogenation reaction The crude alcohol product after a single liquid-phase hydrogenation reaction is pressurized by a circulating pump and then divided into two streams: The first batch of crude alcohol products is fed into the circulating cooler for condensation and cooling via the crude product reflux condensation feed pipe. The cooled crude alcohol products are mixed with some uncondensed crude alcohol products. This mixture is then mixed again with the alkenal feedstock and returned to the top of the liquid phase hydrogenation reactor. It then re-enters the annular catalyst fixed bed between the liquid phase hydrogenation reactor and the central core tube, thus completing both temperature control and circulating hydrogenation. The second batch of crude alcohol product and hydrogen feedstock are simultaneously transported to the top of the central core tube for mixing. After being evenly distributed by the distributor in the central core tube, a secondary liquid-phase hydrogenation reaction occurs in the catalyst fixed bed in the central core tube to generate the corresponding crude alcohol product. The crude alcohol product falls into the bottom of the liquid-phase hydrogenation reactor. Step S3: Separation of unreacted gas phase and hydrogenation products A small amount of hydrogen and other gaseous components that did not participate in the liquid-phase hydrogenation reaction in the liquid-phase hydrogenation reactor are transported to the gas-liquid separator. At the same time, the crude alcohol product at the bottom of the liquid-phase hydrogenation reactor is also transported to the gas-liquid separator to complete the separation of the gas and liquid phases. The liquid phase separated by the gas-liquid separator is sent to the crude product storage tank for storage, and the gas phase separated by the gas-liquid separator is sent to the shell-and-tube cooler for condensation. The condensed liquid phase is returned to the gas-liquid separator, and the condensed gas is introduced into the high-pressure flare tower for compliant discharge.

[0008] Further, in step S1, the molar ratio of hydrogen feedstock and alkenal feedstock is 2.0~2.05:1, and they are fed into the top of the liquid phase hydrogenation reactor through the hydrogen feedstock feed pipe and the alkenal feedstock feed pipe, respectively.

[0009] Furthermore, the hydrogen inlet and acrylaldehyde inlet at the top of the liquid-phase hydrogenation reactor are respectively connected to a hydrogen feed pipe and an acrylaldehyde feed pipe; the bottom reflux outlet of the liquid-phase hydrogenation reactor is connected to the inlet of the circulating pump through a crude product reflux pipe; the outlet of the circulating pump is connected to the crude product inlet of the circulating cooler and the top reflux inlet of the central core tube through a crude product reflux condensation feed pipe and a crude product uncondensation reflux bypass pipe, respectively; the top hydrogen inlet of the central core tube is connected to the hydrogen feed pipe; the crude product outlet of the circulating cooler is connected to the acrylaldehyde feed pipe through a crude product reflux condensation outlet pipe; and a crude product uncondensation reflux bypass manifold is connected between the crude product reflux condensation outlet pipe and the crude product uncondensation reflux bypass pipe.

[0010] Furthermore, the lower gas phase outlet and bottom outlet of the liquid phase hydrogenation reactor are connected to the gas-liquid separator inlet through the unreacted gas phase outlet pipe and the crude product outlet pipe, respectively. The bottom outlet of the gas-liquid separator is connected to the crude product storage tank through the liquid phase crude product outlet pipe. The top outlet and upper reflux inlet of the gas-liquid separator are connected to the shell-and-tube cooler through the gas phase outlet pipe and the gas-liquid separator reflux pipe, respectively. The shell-and-tube cooler is connected to the high-pressure flare tower through the flare tower delivery pipe.

[0011] Furthermore, the circulating cooler uses condensate as the heat exchange medium, which generates low-pressure steam after exchanging heat with the crude alcohol product; through the load adjustment of the circulating cooler, the maximum temperature of the liquid phase hydrogenation reactor in the initial stage is kept stable at 110-120℃, and the maximum temperature in the final stage is controlled at 120-130℃.

[0012] Compared with the prior art, the beneficial effects of the technical solution of the present invention are as follows: This invention feeds olefin feedstock into a liquid-phase hydrogenation reactor and achieves efficient hydrogenation conversion of the olefin feedstock through a combined process of "primary liquid-phase hydrogenation in a fixed-bed ring catalyst + secondary liquid-phase hydrogenation in the core tube," producing the corresponding crude alcohol product. A portion of the crude alcohol product obtained from hydrogenation is recycled to the central core tube of the hydrogenation reactor for a secondary hydrogenation reaction, further improving the overall conversion rate of olefin hydrogenation, reaching over 99.8%. A portion of the crude alcohol product obtained from hydrogenation is condensed and cooled in a circulating cooler, mixed with the uncondensed crude alcohol product, and then mixed again with the olefin feedstock before returning to the top of the liquid-phase hydrogenation reactor. This process achieves both temperature control and cyclic hydrogenation, improving hydrogen utilization.

[0013] The raw material of this invention is liquid alkenyl alcohol. Through circulating cooling, the maximum temperature of the liquid-phase hydrogenation reactor in the initial stage can be stably maintained at a low temperature of 110-120℃, and the maximum temperature in the final stage can be controlled at 120-130℃. This ensures the conversion efficiency and selectivity in the initial stage of the reaction, adapts to the decay law of hydrogenation catalyst activity over time, reduces energy consumption, effectively slows down the deactivation rate of the catalyst, and extends the catalyst's lifespan. This invention can directly use condensate as the cooling medium. Since the crude alcohol product has a low temperature, the energy consumption required for the circulating cooling process is significantly reduced. Compared with gas-phase hydrogenation technology, this invention does not require a raw material vaporizer, and the cooling energy consumption of the hydrogenated product is significantly reduced, solving the technical pain point of high energy consumption in gas-phase hydrogenation processes.

[0014] In this invention, the molar ratio of alkenyl to hydrogen feedstock is 2.0~2.05:1. Precise hydrogen-to-oil ratio control eliminates the need for a hydrogen circulation and compression system, reducing equipment investment and simplifying system operation, further optimizing process energy consumption. The deviation of this molar ratio from the theoretical stoichiometric ratio of 2.0 is ≤0.5%. This parameter selection ensures a hydrogenation reaction conversion rate ≥99.8% without requiring an additional circulation and compression system to handle redundant hydrogen, significantly reducing process energy consumption and equipment investment costs. Attached Figure Description

[0015] Figure 1 This is a schematic diagram illustrating the process principle of the low-energy-consumption liquid-phase hydrogenation method for preparing alcohols from aldehydes according to the present invention.

[0016] Figure reference numerals: 1 Liquid phase hydrogenation reactor; 2 Circulating pump; 3 Circulating cooler; 4 Gas-liquid separator; 5 Shell-and-tube cooler; 6 Alkenal feed pipe; 7 Crude product reflux pipe; 8 Crude product reflux condenser feed pipe; 9 Crude product uncondensed reflux bypass pipe; 10 Crude product uncondensed reflux bypass manifold; 11 Crude product reflux condenser discharge pipe; 12 Central core pipe; 13 Crude product storage tank; 14 Crude product discharge pipe; 15 Hydrogen feed pipe; 16 Second ceramic ball layer; 17 Unreacted gas phase discharge pipe; 18 Gas phase discharge pipe of gas-liquid separator; 19 Gas-liquid separator reflux pipe; 20 Liquid phase crude product discharge pipe; 21 Flare tower conveying pipe; 22 Grating plate; 23 First ceramic ball layer; 24 Catalyst fixed bed; 25 Distributor; 26 Baffle. Detailed Implementation

[0017] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings.

[0018] like Figure 1 As shown, the low-energy-consumption liquid-phase hydrogenation method for preparing alcohols from aldehydes according to the present invention includes a liquid-phase hydrogenation reactor 1. A central core tube 12 is coaxially arranged inside the liquid-phase hydrogenation reactor 1. Inside the central core tube 12 and in the annulus between it and the liquid-phase hydrogenation reactor 1, a distributor 25, a first ceramic ball layer 23, a catalyst fixed bed 24, a second ceramic ball layer 16, and a grid plate 22 are arranged sequentially from top to bottom. The central core tube 12 is a tubular structure with a closed top and an open bottom. The top of the central core tube 12 has a reflux inlet and a hydrogen inlet, and the lower part slopes towards the bottom outlet of the liquid-phase hydrogenation reactor 1. A baffle 26 is provided at the bottom of the liquid-phase hydrogenation reactor 1, dividing the bottom of the reactor 1 into a crude product reflux liquid area and a crude product discharge area. The reflux outlet and discharge outlet at the bottom of the liquid-phase hydrogenation reactor 1 are located in the crude product reflux liquid area and the crude product discharge area, respectively.

[0019] Each alkenyl inlet at the top of the liquid-phase hydrogenation reactor 1 is connected to the alkenyl feed pipe 6, and the hydrogen inlet at the top of the liquid-phase hydrogenation reactor 1 is connected to the hydrogen feed pipe 15. The bottom reflux outlet of the liquid-phase hydrogenation reactor 1 is connected to the inlet of the circulating pump 2 through the crude product reflux pipe 7. The outlet of the circulating pump 2 is connected to the crude product inlet of the circulating cooler 3 and the top reflux inlet of the central core pipe 12 through the crude product reflux condensation feed pipe 8 and the crude product uncondensed reflux bypass pipe 9, respectively. The top hydrogen inlet of the central core pipe 12 is connected to the hydrogen feed pipe 15. The crude product outlet of the circulating cooler 3 is connected to the alkenyl feed pipe 6 through the crude product reflux condensation outlet pipe 11. The crude product uncondensed reflux bypass pipe 10 connects the crude product reflux condensation outlet pipe 11 and the crude product uncondensed reflux bypass pipe 9. The circulating cooler 3 is also connected to a cooling medium inlet pipe and a cooling medium outlet pipe. The circulating cooler 3 uses condensate as a heat exchange medium. After exchanging heat with the crude alcohol product, it generates low-pressure steam, thereby realizing the recovery and utilization of reaction heat.

[0020] The lower gas phase outlet and bottom outlet of the liquid phase hydrogenation reactor 1 are connected to the inlet of the gas-liquid separator 4 through the unreacted gas phase outlet pipe 17 and the crude product outlet pipe 14, respectively. The bottom outlet of the gas-liquid separator 4 is connected to the crude product storage tank 13 through the liquid phase crude product outlet pipe 20. The top outlet and upper reflux inlet of the gas-liquid separator 4 are connected to the shell-side inlet and shell-side bottom outlet of the shell-and-tube cooler 5 through the gas phase outlet pipe 18 and the reflux pipe 19, respectively. The shell-side top outlet of the shell-and-tube cooler 5 is connected to the high-pressure flare tower through the flare tower delivery pipe 21. The tube-side inlet and tube-side outlet of the shell-and-tube cooler 5 are connected to the cooling water inlet pipe WC and the cooling water return pipe WCR, respectively, for conveying the cooling medium.

[0021] In the above-described process, flow valves can be installed on each pipeline as needed. The circulating pump 2, circulating cooler 3, crude product reflux pipe 7, crude product reflux condensate feed pipe 8, crude product non-condensate reflux bypass pipe 9, crude product non-condensate reflux bypass junction pipe 10, and crude product reflux condensate discharge pipe 11 constitute the circulating cooling system of the present invention, through which the heat of hydrogenation reaction can be removed.

[0022] This invention discloses a low-energy-consumption method for preparing alcohols from enaldehydes via liquid-phase hydrogenation. The method utilizes a liquid-phase hydrogenation reactor 1 as the core reaction equipment. Enaldehyde feedstock is fed into the reactor 1, and a combined process of "primary liquid-phase hydrogenation in a fixed-bed ring catalyst + secondary liquid-phase hydrogenation in the core tube" is employed to achieve efficient hydrogenation conversion of the enaldehyde feedstock into the corresponding alcohol product. The method specifically includes the following steps: Step S1: Primary liquid-phase hydrogenation reaction The alkenal raw material and hydrogen raw material are fed into the top of the liquid phase hydrogenation reactor 1 through the alkenal raw material feed pipe 6 and the hydrogen raw material feed pipe 15, respectively. After being mixed evenly by the distributor 25 between the liquid phase hydrogenation reactor 1 and the central core pipe 12, the raw materials enter the annular catalyst fixed bed 24 through the first ceramic ball layer 23 at the bottom. Under the action of the hydrogenation catalyst, a liquid phase hydrogenation reaction occurs to generate the corresponding crude alcohol product. The crude alcohol product falls into the bottom of the liquid phase hydrogenation reactor 1 after passing through the second ceramic ball layer 16 and the grid plate 22.

[0023] In the liquid-phase hydrogenation reaction, the hydrogen-to-oil ratio is the molar ratio of hydrogen to alkenal feedstock. Specifically, the hydrogen feedstock and alkenal feedstock can be fed into the top of the liquid-phase hydrogenation reactor 1 through the hydrogen feedstock inlet pipe 15 and the alkenal feedstock inlet pipe 6, respectively. The molar ratio of hydrogen feedstock to alkenal feedstock is 2.0~2.05:1. The deviation of this molar ratio from the theoretical stoichiometric ratio of 2.0 is ≤0.5%. This parameter selection can ensure that the hydrogenation reaction conversion rate is ≥99.8% and eliminate the need to add a circulating compression system to handle redundant hydrogen, thus significantly reducing process energy consumption and equipment investment costs.

[0024] This step, through the regulation of the circulating cooling system (i.e., the load adjustment of the circulating cooler 3), ensures that the highest temperature of the liquid phase hydrogenation reactor in the initial stage is stably maintained at 110-120℃, and the highest temperature in the final stage is controlled at 120-130℃, thus ensuring the conversion efficiency and selectivity in the initial stage of the reaction and adapting to the decay law of hydrogenation catalyst activity with the running time.

[0025] Step S2: Temperature regulation of the primary reaction products and secondary liquid-phase hydrogenation reaction The crude alcohol product after the first liquid-phase hydrogenation reaction enters the crude product reflux pipe 7, and after being pressurized and sent out by the circulation pump 2, it is divided into two streams: The first batch of crude alcohol product is fed into the circulating cooler 3 for condensation and cooling via the crude product reflux condenser feed pipe 8. The cooled crude alcohol product flows out through the crude product reflux condenser outlet pipe 11 and mixes with the uncondensed crude alcohol product in the uncondensed reflux bypass manifold 10. This mixture is then mixed again with the alkenal raw material in the alkenal raw material feed pipe 6 and returns to the top of the liquid phase hydrogenation reactor 1. It then re-enters the annular catalyst fixed bed 24 between the liquid phase hydrogenation reactor 1 and the central core pipe 12, thus completing both temperature control and circulating hydrogenation.

[0026] The second crude alcohol product, after passing through the uncondensed crude product reflux bypass pipe 9, is simultaneously transported to the top of the central core pipe 12 along with the hydrogen feedstock from the hydrogen feedstock 15. After being evenly distributed by the distributor 25 within the central core pipe 12, it enters the catalyst fixed bed 24 within the central core pipe 26 through the first ceramic ball layer 23 at its bottom. Under the action of the hydrogenation catalyst, a secondary liquid-phase hydrogenation reaction occurs to generate the corresponding crude alcohol product. This crude alcohol product then passes through the second ceramic ball layer 16 within the central core pipe 12 and, guided by the flow guide baffle 26, falls into the crude product discharge area at the bottom of the liquid-phase hydrogenation reactor 1.

[0027] By adjusting the flow ratio of the two channels, the temperature rise fluctuation range of the material entering the liquid phase hydrogenation reactor 1 can be precisely controlled within 10~20℃. This avoids both excessively high temperatures leading to deactivation of the hydrogenation catalyst and decreased product selectivity, and excessively low temperatures causing insufficient hydrogenation reaction rate, effectively ensuring hydrogenation efficiency and product quality stability.

[0028] Step S3: Separation of unreacted gas phase and hydrogenation products A small amount of hydrogen and other gaseous components that did not participate in the liquid-phase hydrogenation reaction in the liquid-phase hydrogenation reactor 1 enter the gas-liquid separator 4 through the unreacted gas phase discharge pipe 17. At the same time, the crude alcohol product at the bottom of the liquid-phase hydrogenation reactor 1 is sent to the gas-liquid separator 4 through the crude product discharge pipe 14, thus completing the gas-liquid two-phase separation.

[0029] The gas phase components separated by the gas-liquid separator 4 are sent to the shell-and-tube cooler 5 for condensation through the gas phase discharge pipe 18 of the gas-liquid separator. The condensed gas is introduced into the high-pressure flare tower for compliant discharge through the flare tower delivery pipe 21, while the condensed liquid phase flows back to the gas-liquid separator 4.

[0030] The liquid phase components separated by the gas-liquid separator 4 are transported to the crude product storage tank 13 via the crude product discharge pipe 20 to provide raw materials for subsequent refining processes.

[0031] The raw materials for this invention are octenal, 2-propylheptenal, and other enaldehydes. If the enaldehyde raw material is octenal, hydrogenation will produce octanol; if the enaldehyde raw material is 2-propylheptenal, hydrogenation will produce 2-propylheptanol (2-PH). This invention can improve the hydrogenation conversion rate of enaldehydes to over 99.8% through two liquid-phase hydrogenation processes.

[0032] Example 1 The specific process of the low-energy-consumption liquid-phase hydrogenation method for preparing alcohols from enal in this embodiment is as follows: Step S1: Octenal and hydrogen feedstock are fed into the top of the liquid-phase hydrogenation reactor 1 at a molar ratio of 2.0:1 via octenal feedstock inlet 6 and hydrogen feedstock inlet 15, respectively. After being uniformly mixed by the distributor 25 between the liquid-phase hydrogenation reactor 1 and the central core tube 12, the feedstock enters the annular catalyst fixed bed 24 through the first ceramic ball layer 23 at its bottom. Under the action of the hydrogenation catalyst, a primary liquid-phase hydrogenation reaction occurs to produce crude octanol. This step is controlled by a circulating cooling system to maintain the reaction pressure of the liquid-phase hydrogenation reactor 1 at 2.5 MPa, the initial maximum temperature at 110℃, and the final maximum temperature at 120℃, ensuring the conversion efficiency and selectivity in the initial stage of the reaction.

[0033] Step 2: The crude octanol product after the first liquid-phase hydrogenation reaction enters the crude product reflux pipe 7, and after being pressurized by the circulation pump 2, it is divided into two streams: The first crude octanol product is fed into the circulating cooler 3 for condensation and cooling via the crude product reflux condenser feed pipe 8. The cooled crude octanol product flows out through the crude product reflux condenser outlet pipe 11 and mixes with the uncondensed crude octanol product in the uncondensed reflux bypass manifold 10. This mixture is then mixed again with the octenal in the enal feed pipe 6 and returns to the top of the liquid phase hydrogenation reactor 1, re-entering the annular catalyst fixed bed 24 between the liquid phase hydrogenation reactor 1 and the central core pipe 12, thus completing both temperature control and circulating hydrogenation.

[0034] The second crude octanol product, after passing through the uncondensed crude product reflux bypass pipe 9, is simultaneously transported to the top of the central core pipe 12 along with the hydrogen feedstock from the hydrogen feedstock pipe 15. After being evenly distributed by the distributor 25 inside the central core pipe 12, it enters the catalyst fixed bed 24 inside the central core pipe 26 through the first ceramic ball layer 23 at its bottom. Under the action of the hydrogenation catalyst, a secondary liquid-phase hydrogenation reaction occurs to generate crude octanol product. This crude octanol product then passes through the second ceramic ball layer 16 inside the central core pipe 12 and falls into the crude product discharge area at the bottom of the liquid-phase hydrogenation reactor 1 under the guidance of the flow guide baffle 26.

[0035] Step S3: A small amount of hydrogen and other gaseous components that did not participate in the liquid-phase hydrogenation reaction in the liquid-phase hydrogenation reactor 1 enter the gas-liquid separator 4 through the unreacted gas phase discharge pipe 17. At the same time, the crude octanol product at the bottom of the liquid-phase hydrogenation reactor 1 is sent to the gas-liquid separator 4 through the crude product discharge pipe 14, thus completing the gas-liquid two-phase separation.

[0036] The gas phase components separated by the gas-liquid separator 4 are sent to the shell-and-tube cooler 5 for condensation through the gas phase discharge pipe 18 of the gas-liquid separator. The condensed gas is introduced into the high-pressure flare tower for compliant discharge through the flare tower delivery pipe 21, while the condensed liquid phase flows back to the gas-liquid separator 4.

[0037] The liquid phase components separated by the gas-liquid separator 4 are transported to the crude product storage tank 13 via the crude product discharge pipe 20 to provide raw materials for subsequent refining processes.

[0038] Example 2 Example 2 is similar to Example 1, except that octenal feedstock and hydrogen feedstock are fed into the top of liquid-phase hydrogenation reactor 1 at a molar ratio of 2.05:1 through octenal feedstock inlet 6 and hydrogen feedstock inlet 15, respectively. The reaction pressure in liquid-phase hydrogenation reactor 1 is controlled at 2.9 MPa, the maximum temperature under initial conditions is stably maintained at 120°C, and the maximum temperature under final conditions is controlled at 130°C. All other conditions and processes are the same as in Example 1.

[0039] The liquid-phase hydrogenation method described in this embodiment ensures high conversion rates of aldehydes and olefins, while also achieving high yields of the target alcohol, good product color, and low unsaturation. Furthermore, it consumes less energy compared to traditional gas-phase hydrogenation and other liquid-phase hydrogenation methods.

[0040] Taking the production of 1 ton of octanol by liquid-phase hydrogenation of octenal as an example, the energy consumption data of the present invention and gas-phase hydrogenation are compared in Table 1.

[0041] Table 1

[0042] Energy prices: Electricity price is 0.7 yuan / kWh, and steam price is 220 yuan / ton. This calculation is based on the lower value of the energy-saving index range, resulting in a saving of 377.5 yuan per ton of octanol produced.

[0043] Taking the production of 1 ton of octanol by liquid-phase hydrogenation of octenal as an example, Table 2 compares the energy consumption data of this invention with other liquid-phase hydrogenation methods.

[0044] Table 2

[0045] Energy prices: Electricity price is 0.7 yuan / kWh, steam price is 220 yuan / ton, and cooling water price is 0.25 yuan / ton. This calculation is based on the lower value of the energy saving index range, and the production of one ton of octanol saves 40.6 yuan.

[0046] Example 3 Example 3 is similar to Example 1, except that the octenal feedstock is replaced with 2-propylheptenal feedstock, which, after hydrogenation, produces 2-propylheptanol (2-PH). 2-propylheptenal and hydrogen feedstock are fed into the top of the liquid-phase hydrogenation reactor 1 at a molar ratio of 2.03:1 via the octenal feedstock inlet 6 and the hydrogen feedstock inlet 15, respectively. The feed pressure of the liquid-phase hydrogenation reactor 1 is controlled at 2.7 MPa, the initial maximum temperature is maintained at 115°C, and the final maximum temperature is controlled at 125°C. All other conditions and processes are the same as in Example 1.

[0047] The liquid-phase hydrogenation method described in this embodiment ensures high conversion rates of aldehydes and olefins, while also achieving high yields of the target alcohol, fewer byproducts, good product color, and low unsaturation. Furthermore, it consumes less energy compared to traditional gas-phase hydrogenation and other liquid-phase hydrogenation methods.

[0048] Taking the production of 1 ton of 2-propylheptanol by liquid-phase hydrogenation of 2-propylheptenal as an example, the energy consumption data of the present invention and gas-phase hydrogenation are compared in Table 3.

[0049] Table 3

[0050] Energy prices: Electricity price is 0.7 yuan / kWh, and steam price is 220 yuan / ton. This calculation is based on the lower value of the energy-saving index range, and the production of one ton of 2-propylheptanol saves 408.3 yuan.

[0051] Taking the production of 1 ton of 2-propylheptanol by liquid-phase hydrogenation of 2-propylheptenal as an example, the energy consumption data of this invention and other liquid-phase hydrogenation methods are compared in Table 4.

[0052] Table 4

[0053] Energy prices: Electricity price is 0.7 yuan / kWh, and steam price is 220 yuan / ton. This calculation is based on the lower value of the energy-saving index range, and the production of one ton of 2-propylheptanol saves 57.5 yuan.

[0054] Although the functions and working processes of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific functions and working processes described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims, and all of these are within the protection scope of the present invention.

Claims

1. A method for preparing alcohols by liquid-phase hydrogenation of alkenes with low energy consumption, characterized in that, This method uses a liquid-phase hydrogenation reactor (1) as the core reaction equipment. A central core tube (12) is coaxially arranged inside the liquid-phase hydrogenation reactor (1). Inside the central core tube (12) and in the annulus between it and the liquid-phase hydrogenation reactor (1), a distributor (25), a first ceramic ball layer (23), a catalyst fixed bed (24), a second ceramic ball layer (16), and a grid plate (22) are arranged sequentially from top to bottom. The method specifically includes the following steps: Step S1: Primary liquid-phase hydrogenation reaction The alkenal raw material and hydrogen raw material are fed into the top of the liquid phase hydrogenation reactor (1) through the alkenal raw material feed pipe (6) and the hydrogen raw material feed pipe (15), respectively. After the raw materials are mixed evenly by the distributor (25) between the liquid phase hydrogenation reactor (1) and the central core pipe (12), a liquid phase hydrogenation reaction is carried out in the catalyst fixed bed (24) at its lower end to generate the corresponding crude alcohol product, which finally falls into the bottom of the liquid phase hydrogenation reactor (1). Step S2: Temperature regulation of the primary reaction products and secondary liquid-phase hydrogenation reaction The crude alcohol product after a single liquid-phase hydrogenation reaction is pressurized and sent out via a circulating pump (2) and then divided into two streams: The first crude alcohol product is fed into the circulating cooler (3) through the crude product reflux condenser feed pipe (8) for condensation and cooling. The cooled crude alcohol product is mixed with some uncondensed crude alcohol product. After the mixture is mixed with the alkenyl raw material again, it returns to the top of the liquid phase hydrogenation reactor (1) and re-enters the annular catalyst fixed bed (24) between the liquid phase hydrogenation reactor (1) and the central core tube (12), thus completing both temperature control and circulating hydrogenation. The second-path crude alcohol product and hydrogen feedstock are simultaneously transported to the top of the central core tube (12) for mixing. After being evenly distributed by the distributor (25) in the central core tube (12), a secondary liquid-phase hydrogenation reaction occurs in the catalyst fixed bed (24) in the central core tube (26) to generate the corresponding crude alcohol product. The crude alcohol product falls into the bottom of the liquid-phase hydrogenation reactor (1). Step S3: Separation of unreacted gas phase and hydrogenation products A small amount of hydrogen and other gaseous components that did not participate in the liquid phase hydrogenation reaction in the liquid phase hydrogenation reactor (1) are transported to the gas-liquid separator (4). At the same time, the crude alcohol product at the bottom of the liquid phase hydrogenation reactor (1) is transported to the gas-liquid separator (4) to complete the separation of the gas and liquid phases. The liquid phase separated by the gas-liquid separator (4) is sent to the crude product storage tank (13) for storage. The gas phase separated by the gas-liquid separator (4) is sent to the shell-and-tube cooler (5) for condensation. The condensed liquid phase is returned to the gas-liquid separator (4), and the condensed gas is introduced into the high-pressure flare tower for compliant discharge.

2. The method for preparing alcohols by low-energy-consumption liquid-phase hydrogenation of alkenes according to claim 1, characterized in that, The molar ratio of hydrogen feedstock to aldehyde feedstock in step S1 is 2.0~2.05:1, and the feedstock is fed into the top of the liquid phase hydrogenation reactor (1) through the hydrogen feedstock feed pipe (15) and the aldehyde feedstock feed pipe (6), respectively.

3. The method for preparing alcohols by low-energy-consumption liquid-phase hydrogenation of alkenes according to claim 1, characterized in that, The hydrogen inlet and alkenal inlet at the top of the liquid-phase hydrogenation reactor (1) are respectively connected to the hydrogen feed pipe (15) and the alkenal feed pipe (6); the bottom reflux outlet of the liquid-phase hydrogenation reactor (1) is connected to the inlet of the circulating pump (2) through the crude product reflux pipe (7); the outlet of the circulating pump (2) is connected to the crude product inlet of the circulating cooler (3) and the top reflux inlet of the central core pipe (12) through the crude product reflux condensation feed pipe (8) and the crude product uncondensed reflux bypass pipe (9); the top hydrogen inlet of the central core pipe (12) is connected to the hydrogen feed pipe (15); the crude product outlet of the circulating cooler (3) is connected to the alkenal feed pipe (6) through the crude product reflux condensation outlet pipe (11); and the crude product uncondensed reflux bypass pipe (9) is connected to the crude product uncondensed reflux bypass manifold pipe (10).

4. The method for preparing alcohols by low-energy-consumption liquid-phase hydrogenation of alkenes according to claim 1, characterized in that, The lower gas phase outlet and bottom outlet of the liquid phase hydrogenation reactor (1) are connected to the inlet of the gas-liquid separator (4) through the unreacted gas phase outlet pipe (17) and the crude product outlet pipe (14), respectively. The bottom outlet of the gas-liquid separator (4) is connected to the crude product storage tank (13) through the liquid phase crude product outlet pipe (20). The top outlet and upper reflux inlet of the gas-liquid separator (4) are connected to the shell-and-tube cooler (5) through the gas phase outlet pipe (18) and the reflux pipe (19) of the gas-liquid separator, respectively. The shell-and-tube cooler (5) is connected to the high-pressure flare tower through the flare tower delivery pipe (21).

5. The method for preparing alcohols by low-energy-consumption liquid-phase hydrogenation of alkenes according to claim 3, characterized in that, The circulating cooler (3) uses condensate as the heat exchange medium and generates low-pressure steam after exchanging heat with crude alcohol products. By adjusting the load of the circulating cooler (3), the maximum temperature of the liquid phase hydrogenation reactor in the initial stage is controlled to be stably maintained at 110-120℃, and the maximum temperature in the final stage is controlled at 120-130℃.

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