Method and system for continuously producing 1, 4-cyclohexanedimethanol

Abstract

The invention relates to a method and a system for continuously producing 1, 4-cyclohexanedimethanol, and belongs to the technical field of preparation of 1, 4-cyclohexanedimethanol. The problems of high raw material price, expensive catalyst, low production efficiency, harsh reaction conditions and the like in the existing 1, 4-cyclohexanedimethanol production process are solved. The method comprises the following steps: chloridizing p-xylene to prepare p-xylylene dichloride, hydrolyzing the p-xylylene dichloride to prepare terephthalyl alcohol, and hydrogenating the terephthalyl alcohol to prepare the 1, 4-cyclohexanedimethanol. The method takes p-xylene as a raw material, and is high in production efficiency, good in product quality, green, environment-friendly and low in energy consumption.

Description

Technical Field

[0001] This invention belongs to the field of 1,4-cyclohexanediethanol (CHDM) preparation technology, specifically relating to a method and system for the continuous production of 1,4-cyclohexanediethanol, and particularly relating to a method and system for the efficient, green and continuous production of 1,4-cyclohexanediethanol using p-xylene (PX) as raw material and employing three reaction units based on chlorination, hydrolysis and hydrogenation. Background Technology

[0002] 1,4-Cyclohexanediethanol is a novel polyester monomer. Polymerization with dimethyl terephthalate (DMT) yields poly(1,4-cyclohexanediethanol) terephthalate (PCT polyester); polymerization with terephthalic acid (PTA) and ethylene glycol (EG) yields polyethylene terephthalate-1,4-cyclohexanediethanol (PETG polyester). PCT polyester is a high-temperature resistant, semi-crystalline thermoplastic with excellent mechanical properties and good dimensional stability, and has been widely used in the automotive and consumer electronics industries in recent years. PETG polyester is a transparent, amorphous copolyester with high transparency, low-temperature toughness, and easy processability, making it a benchmark material for environmentally friendly engineering plastics.

[0003] Currently, CHDM is mainly produced industrially from DMT via a two-step hydrogenation process. DMT is a downstream product of PTA, primarily obtained through the esterification reaction of PTA and methanol. In 1959, Eastman Chemical Company in the United States first achieved the industrial application of the two-step hydrogenation of DMT to produce CHDM. The synthetic route is as follows: Figure 1 As shown, the process first involves hydrogenation to produce dimethyl 1,4-cyclohexanedicarboxylate (DMCD), followed by a second-stage hydrogenation to produce CHDM. According to US Patent US3334149, the first-stage hydrogenation uses a Pd-based catalyst, and the second-stage hydrogenation uses a Cu-based catalyst. The reaction temperature is 150-275℃, and the hydrogen pressure is 20-40 MPa. Although the production process conditions are extremely demanding, the two-step hydrogenation of terephthalic acid esters to produce CHDM is currently the only industrially applied technology, and Eastman Chemical Company remains the world's largest producer of CHDM.

[0004] Some patents have improved the catalysts and production methods in the two-stage hydrogenation process mentioned above. For the first-stage benzene ring hydrogenation process, Chinese invention patent CN1689698A discloses a Pd-based catalyst. The catalyst includes an additive and a support. The support is alumina. The additive contains two components: the first additive is silicon dioxide, and the second additive is Ru. The weight percentage of metallic Pd is 0.5-2%, the weight percentage of the first additive silicon dioxide is 0.01-0.5%, and the weight percentage of the second additive Ru is 0.01-0.5%. Under reaction temperatures of 150-350℃ and hydrogen pressures of 4-6 MPa, the DMT conversion rate is 95-99%, and the selectivity of DMCD is 94-98%. However, this reaction system requires a large amount of ethyl acetate solvent, resulting in low production efficiency and high production and separation rates. Chinese invention patent CN108947842A discloses a method for preparing DMCD by hydrogenation of DMT catalyzed by a Ru-Re bimetallic catalyst. The total loading of ruthenium-rhenium bimetals is 0.3-5%. Under conditions of hydrogen pressure 2-5 MPa, reaction temperature 30-120℃, and reaction time 1-3 hours, the conversion rate of DMT can reach 97.91%, and the selectivity of DMCD can reach 99.88%. However, compared to DMT, this method uses ethyl acetate at a mass ratio of 40:1 as a solvent, and the reaction is batch-progressive, with a DMT to catalyst weight ratio of only 4:1, resulting in lower reaction efficiency.

[0005] For the second-stage ester hydrogenation process, Cu-based catalysts are mainly used. Chinese invention patent CN1223631A discloses a method for the continuous hydrogenation of DMCD to CHDM in the presence of a catalyst containing Cu and Cr. The reaction is carried out at a temperature of 220-280℃ and a hydrogen pressure of 18.5-30 MPa, achieving a CHDM selectivity of over 97%. However, this method requires the use of a toxic Cr component as the catalyst and necessitates high-pressure conditions, resulting in high investment and operating costs. Chinese invention patent CN116943665A discloses a method for the continuous hydrogenation of DMCD to CHDM catalyzed by a Cu-based catalyst, in which one or more components selected from manganese, zinc, aluminum, magnesium, nickel, tin, chromium, and iron are used as promoters. The liquid hourly space velocity is 0.095 h⁻¹. -1 Under reaction conditions of 220℃ and hydrogen pressure of 4MPa, the yield of CHDM reached 95.6%. However, due to the low liquid hourly space velocity in this method, the production efficiency was low.

[0006] Chinese invention patent application CN107805183A discloses a one-pot method for preparing CHDM from DMT hydrogenation. This method involves mixing two catalysts, one containing Cu and the other Ni, and adding them together with a methanol solution of DMT to a reactor. Although it is a one-pot method, it still involves two-stage hydrogenation. The first stage of hydrogenation is carried out at 200°C and a hydrogen pressure of 4 MPa, and the second stage is carried out at 240°C and a hydrogen pressure of 8 MPa, achieving a CHDM yield of 92%. Chinese invention patent application CN113248346A also discloses a method for directly hydrogenating CHDM from DMT. This method uses a mixture of two catalysts, one containing Pd and the other Cu, for catalytic reaction, achieving a yield of 91% under conditions of 250°C, a hydrogen pressure of 3 MPa, and a reaction time of 3 hours. Compared to the two-step hydrogenation method, both of these methods, while using the same catalyst for both stages of the reaction, result in a lower CHDM yield. Furthermore, both inventions are batch reactions, leading to long reaction times and low production efficiency.

[0007] In summary, while the two-step hydrogenation process for producing CHDM from DMT is currently the main industrially used method, it suffers from numerous problems, including high DMT synthesis costs, expensive catalysts, low production efficiency, and demanding reaction conditions. These issues directly lead to high CHDM production costs and market prices. Summary of the Invention

[0008] The technical problem to be solved by this invention is to address the numerous problems existing in the current CHDM production process, such as high raw material prices, expensive catalysts, low production efficiency, and harsh reaction conditions. This invention provides a method and system for the continuous production of CHDM using inexpensive chemical product paraxylene (PX) as raw material and employing three reaction units based on chlorination, hydrolysis, and hydrogenation. This continuous CHDM production method and system has high production efficiency, good product quality, is environmentally friendly, and has low energy consumption.

[0009] The present invention solves the above-mentioned technical problems by adopting the following technical solution.

[0010] In a first aspect, the present invention provides a method for the continuous production of 1,4-cyclohexanediethanol, comprising: Step 1: P-xylene is mixed with liquid chlorine and chlorinated under ultraviolet light at 50-150°C using a eutectic ionic liquid as a catalyst. The resulting reaction product (mainly containing PXDC and unreacted PX, as well as byproducts such as p-methylbenzyl chloride (PMBC) and 1-(dichloromethyl)-4-toluene (PMDCMB)) is filtered. The filter cake (mainly PXDC and heavy components) is melted, and the light components are removed first, followed by the heavy components, to obtain p-dichlorobenzyl chloride (PXDC). The eutectic ionic liquid is composed of hydrogen bond acceptors and hydrogen bond donors in a molar ratio of 1:2 to 10:1; Step 2: Mix the p-dichlorobenzyl prepared in Step 1 with an alkaline solution and carry out a hydrolysis reaction at 100-200℃ and 0.5-1MPa. The resulting reaction product (mainly containing BDM, unreacted PXDC and water, as well as alkali and chloride salts) is cooled and then extracted with an extractant. The extractant is first removed from the extract phase, and then the light and heavy components are removed sequentially to obtain terephthalic acid (BDM). Step 3: Using a heterogeneous hydrogenation catalyst, the terephthalic acid diethanol prepared in step 2 is hydrogenated with hydrogen at 100-200℃ and 1-6MPa. The resulting reaction product (mainly containing CHDM, water, and byproducts such as PX and 4-methyl-1-cyclohexaneethanol (MCHM)) is first dehydrogenated, and then the light and heavy components are removed sequentially to obtain 1,4-cyclohexanediethanol (CHDM).

[0011] Preferably, the method for continuous production of 1,4-cyclohexanediethanol includes: Step 1: p-xylene and liquid chlorine are fed into a chlorination reactor. Under ultraviolet light irradiation, the reaction is carried out using a eutectic ionic liquid as a catalyst. The resulting hydrogen chloride and chlorine gas are discharged. The reaction product is sent to a filter for filtration. The filtrate (mainly containing catalyst, unreacted PX, and reaction products PMBC, PMDCMB, etc.) is discharged. The filter cake is sent to a melting tank, heated and melted, and then sent to a chlorination light component removal tower. The resulting light component is discharged. The bottom liquid of the tower (mainly PXDC and heavy components) is sent to a chlorination heavy component removal tower to remove the heavy components. p-dichlorobenzyl is obtained by side stream. Step 2: benzyl dichlorotrichloro and alkaline solution are fed into a hydrolysis reactor for hydrolysis. After cooling, the reaction product is fed into an extraction tower for extraction. The raffinate is discharged. The extract phase is first sent to an extractant recovery tower to recover the extractant, and then sent to a hydrolysis delighting tower. The light component is discharged from the top of the tower. The bottom liquid of the tower is sent to a hydrolysis deheavy tower. The bottom liquid of the tower is discharged. The gas phase is sent to the hydrolysis product tower from the top of the tower, and terephthalic acid is obtained by side stream. Step 3: Terephthalic acid and hydrogen are fed into a hydrogenation reactor, where a heterogeneous hydrogenation catalyst is used for the hydrogenation reaction. The resulting reaction products are sent to a gas-liquid separator for separation. The resulting gas phase is discharged from the top of the separator, while the resulting hydrogenation product is sent from the bottom of the separator to a hydrogenation light component removal tower. The resulting light components (water, PX, MCHM, 4-methylbenzyl alcohol (MBA), etc.) are discharged from the top of the tower. The resulting bottom liquid is sent to a hydrogenation heavy component removal tower, where the resulting gas phase is discharged from the top of the tower. The resulting bottom liquid is sent to a hydrogenation product tower, and 1,4-cyclohexanediethanol is collected from the side stream.

[0012] More preferably, in step one, after the p-xylene is buffered in a PX buffer tank, it is pumped into the first mixer. After the liquid chlorine is buffered in a liquid chlorine buffer tank, it is pumped into the first mixer. The PX and liquid chlorine are mixed in the first mixer and then fed into the chlorination reactor for reaction. The filtrate is sent into the PX buffer tank. The light component obtained from the chlorination light component removal tower is discharged from the top of the tower, condensed in the first condenser, and first enters the first storage tank. Then, part of it is returned to the chlorination light component removal tower by four pumps, and the other part is sent into the PX buffer tank. More preferably, in step one, the reaction temperature in the chlorination reactor is controlled at 50-150°C by an external heat exchanger; More preferably, in step one, the filter cake is buffered in a silo and then conveyed into a melting tank. More preferably, in step one, after the filter cake is heated and melted, it is sent into the chlorination removal tower by three pumps; More preferably, in step one, a portion of the bottom liquid obtained from the chlorination light-removal tower is returned to the chlorination light-removal tower after being reboiled in the first reboiler, and the other portion is sent to the chlorination heavy-removal tower via five pumps. More preferably, in step one, the top temperature of the chlorination tower is 125-135°C, the top pressure is 1-2 kPa, and the bottom temperature is 155-165°C. More preferably, in step one, the gas phase obtained from the chlorination de-heavy phase tower is condensed from the top of the tower by the second condenser and then enters the second storage tank. A portion of the gas phase is then returned to the chlorination de-heavy phase tower by six pumps, while the other portion is discharged. More preferably, in step one, a portion of the bottom liquid obtained from the chlorination de-heavy tower is returned to the chlorination de-heavy tower after being reboiled in the second reboiler, while the other portion is discharged. More preferably, in step one, the top temperature of the chlorination de-heavyweight tower is 155-165℃, the top pressure is 1-2kPa, and the bottom temperature is 240-260℃. More preferably, in step two, the benzyl dichloroisocyanurate is buffered in a PXDC buffer tank and then fed into the hydrolysis reactor via pump seven, while the alkali solution is buffered in an alkali solution buffer tank and then fed into the hydrolysis reactor via pump eight. More preferably, in step two, the reaction product is fed into a cooler via nine pumps and then fed into an extraction tower. More preferably, in step two, the extractant used in the extraction is fed from the extractant buffer tank into the extraction tower via pump ten. The raffinate phase is discharged from the top of the extraction tower and fed into the wastewater stripping tower via pump eleven. The resulting gas phase is condensed in the third condenser and then sent back to the extractant buffer tank. Part of the resulting bottom liquid is reboiled in the third reboiler and then returned to the wastewater stripping tower, while the other part is discharged. The extractant phase is fed into the extractant recovery tower via pump twelve. The resulting gas phase is condensed in the third condenser and then sent back to the extractant buffer tank. Part of the resulting bottom liquid is reboiled in the fourth reboiler and then returned to the extractant recovery tower, while the other part is fed into the hydrolysis delighting tower via pump thirteen. More preferably, in step two, a portion of the bottom liquid obtained from the hydrolysis light column is returned to the hydrolysis light column after being reboiled by the fifth reboiler, and the other portion is sent to the hydrolysis heavy column by the fifteenth pump. The light component obtained from the hydrolysis light column is condensed from the top of the column by the fourth condenser and first enters the third storage tank. Then, a portion is returned to the hydrolysis light column by the fourteenth pump, and the other portion is discharged. More preferably, in step two, the temperature at the top of the hydrolysis light tower is 120-130℃, the pressure is 0.5-1.5kPa, and the temperature at the bottom of the tower is 160-180℃. More preferably, in step two, part of the bottom liquid obtained from the hydrolysis decomposition tower is returned to the hydrolysis decomposition tower after being reboiled by the sixth reboiler, and the other part is discharged. The gas phase obtained from the hydrolysis decomposition tower is condensed from the top of the tower by the fifth condenser and first enters the fourth storage tank. Then, part of it is returned to the hydrolysis decomposition tower by the sixteenth pump, and the other part is sent to the hydrolysis product tower by the seventeenth pump. More preferably, in step two, the temperature at the top of the hydrolysis decompression tower is 135-145℃, the pressure is 0.5-1.5kPa, and the temperature at the bottom of the tower is 300-320℃. More preferably, in step two, a portion of the bottom liquid of the hydrolysis product tower is returned to the hydrolysis product tower after being reboiled by the seventh reboiler, and the other portion is discharged. The gas phase obtained from the hydrolysis product tower is condensed from the top of the tower by the sixth condenser and first enters the fifth storage tank. Then, a portion is returned to the hydrolysis product tower by the seventeenth pump, and the other portion is discharged. More preferably, in step two, the top temperature of the hydrolysis product tower is 125-140℃, the pressure is 0.5-1.5kPa, and the bottom temperature is 300-325℃. More preferably, in step three, terephthalic acid is buffered in a BDM buffer tank and then pumped into the second mixer by the nineteenth pump. Hydrogen is buffered in a hydrogen buffer tank and then pumped into the second mixer. After terephthalic acid and hydrogen are mixed in the second mixer, the resulting mixed gas first exchanges heat with the reaction products of the hydrogenation reactor in the first heat exchanger and then is heated in the heater. Then it is sent to the hydrogenation reactor for reaction. The resulting reaction products first exchange heat with the mixed gas in the first heat exchanger and then exchange heat with cold water in the second heat exchanger. Finally, it is sent to the gas-liquid separator. The gas phase obtained from the gas-liquid separator is discharged from the top of the tank and compressed to 1.8-2 MPa by the compressor and sent to the hydrogen buffer tank for recycling. More preferably, in step three, the temperature of the reaction product entering the gas-liquid separator is controlled at 100-120°C; More preferably, in step three, the hydrogenation product obtained from the gas-liquid separator is pumped from the bottom of the tank into the hydrodelight removal tower via twenty pumps. More preferably, in step three, a portion of the bottom liquid obtained from the hydrodelighting column is returned to the hydrodelighting column after being reboiled in the eighth reboiler, and the other portion is sent to the hydrodeheavy column by pump twenty-two. The light component obtained from the hydrodelighting column is condensed from the top of the column by the seventh condenser and first enters the sixth storage tank, a portion of which is discharged and another portion enters the twenty-first pump, a portion of which is returned to the hydrodelighting column and the other portion is discharged. More preferably, in step three, the top temperature of the hydrotreating column is 20-40°C, the pressure is 1-3 kPa, and the bottom temperature is 180-200°C. More preferably, in step three, part of the bottom liquid obtained from the hydrodeweighting tower is returned to the hydrodeweighting tower after being reboiled by the ninth reboiler, and the other part is discharged. The gas phase obtained from the hydrodeweighting tower is condensed from the top of the tower by the eighth condenser and first enters the seventh storage tank, and then enters the twenty-third pump. Part of it is returned to the hydrodeweighting tower, and the other part is sent to the hydrogenation product tower by the twenty-fourth pump. More preferably, in step three, the top temperature of the hydrodeweighting tower is 165-195℃, the pressure is 1-3kPa, and the bottom temperature is 240-280℃. More preferably, in step three, a portion of the bottom liquid obtained from the hydrogenation product tower is returned to the hydrogenation product tower after being reboiled by the tenth reboiler, and the other portion is discharged. The gas phase obtained from the hydrogenation product tower is condensed from the top of the tower by the ninth condenser and first enters the eighth storage tank, then enters the twenty-fifth pump, a portion of which is returned to the hydrogenation product tower and the other portion is discharged. More preferably, in step three, the top temperature of the hydrogenation product tower is 135-145℃, the pressure is 1-3kPa, and the bottom temperature is 240-280℃.

[0013] Preferably, in step one, the hydrogen bond acceptor is one of tetrabutylammonium bromide, tetrabutylammonium chloride, choline chloride, and tetraoctylammonium chloride, and the hydrogen bond donor is one of urea, ethylene glycol, glycerol, lactic acid, imidazole, ethanolamine, diethanolamine, and triethanolamine.

[0014] Preferably, in step one, the amount of the eutectic ionic liquid catalyst is 0.3 wt.%-5 wt.% of the amount of p-xylene.

[0015] Preferably, in step one, the molar ratio of liquid chlorine to p-xylene is 1:1 to 5:1.

[0016] Preferably, in step one, the chlorination reaction takes 0.5-2 hours.

[0017] Preferably, in step one, the temperature of the filter is controlled at 55-65℃.

[0018] Preferably, in step one, the temperature at which the filter cake is heated and melted is 80-120℃.

[0019] Preferably, in step two, the alkaline solution is a NaOH aqueous solution or a KOH aqueous solution with a mass concentration of 10-40%.

[0020] Preferably, in step two, the mass of the alkaline solution is 1-5 times the mass of benzyl dichloroisocyanurate.

[0021] Preferably, in step two, the hydrolysis reaction takes 0.5-3 hours.

[0022] Preferably, in step two, the reaction product is cooled to below 30°C.

[0023] Preferably, in step two, the extractant is one of dichloromethane, chloroform, 1,2-dichloroethane, chlorobenzene, chlorotoluene, p-dichlorobenzene, o-dichlorobenzene, dibromomethane, and bromobenzene, and the mass of the extractant is 0.5-2 times the mass of p-dichlorobenzene.

[0024] Preferably, in step three, the molar ratio of hydrogen to terephthalic acid is 3-10:1.

[0025] Preferably, in step three, the heterogeneous hydrogenation catalyst is composed of a support and an active component supported on the support. The support is one of ZrO2, ZnO, SiO2, Al2O3, SiO2-Al2O3, CeO2, and MgO. The active component is one of Ru, Pd, Pt, Rh, Ni, Co, and Cu. The mass content of the active component is 0.5-10%, and the mass content of the support is 90-99.5%.

[0026] Preferably, in step three, the mass hourly space velocity (MSV) of the hydrogenation reaction is 1-10 h⁻¹. -1 .

[0027] In a second aspect, the present invention also provides a system for the continuous production of 1,4-cyclohexanediethanol, comprising a chlorination unit, a hydrolysis unit and a hydrogenation unit; The chlorination unit includes a chlorination reactor; A filter located downstream of the chlorination reactor and connected to the chlorination reactor via a pipeline; A melting tank located downstream of the filter and connected to the filter via a pipe; A chlorination tower for removing light components is located downstream of the melting tank and connected to the melting tank via a pipeline; A chlorination tower for removing heavy metals is located downstream of the chlorination tower for removing light metals and is connected to the chlorination tower for removing light metals via a pipeline; The hydrolysis unit includes a hydrolysis reactor; An extraction tower located downstream of the hydrolysis reactor and connected to the hydrolysis reactor via a pipeline; An extractant recovery tower is located downstream of the extraction tower and connected to the extraction tower via a pipeline; A hydrolysis light tower is located downstream of the extractant recovery tower and connected to the extractant recovery tower via a pipeline; A water decomposition heavy tower is located downstream of the water decomposition light tower and connected to the water decomposition light tower via a pipeline; A hydrolysis product tower located downstream of the hydrolysis decomposition tower and connected to the hydrolysis decomposition tower via a pipeline; The hydrogenation unit includes a hydrogenation reactor; A gas-liquid separator located downstream of the hydrogenation reactor and connected to the hydrogenation reactor via a pipeline; A hydrotreating tower located downstream of a gas-liquid separator and connected to the gas-liquid separator via a pipeline; A hydrotreating heavy tower located downstream of the hydrotreating light tower and connected to the hydrotreating light tower via a pipeline; The hydrogenation product tower is located downstream of the hydrodeweighting tower and is connected to the hydrodeweighting tower via a pipeline.

[0028] Preferably, the chlorination unit further includes a PX buffer tank, a liquid chlorine buffer tank, a first mixer, a first condenser, a first storage tank, and four pumps; the outlet of the PX buffer tank is connected to the inlet of the first mixer via a pipeline, and a pump is installed on the pipeline connecting the PX buffer tank and the first mixer; the inlet of the PX buffer tank is connected to the filtrate outlet of the filter via a pipeline, and is also connected to the PX feed pipeline; the inlet of the liquid chlorine buffer tank is connected to the liquid chlorine feed pipeline, and the outlet of the liquid chlorine buffer tank is connected to the first mixer via a pipeline. The feed inlet of the first condenser is connected to the light component outlet of the chlorination stripping tower via a pipeline, and two pumps are installed on the pipeline connecting the liquid chlorine buffer tank and the first mixer; the outlet of the first mixer is connected to the feed inlet of the chlorination reactor via a pipeline; the feed inlet of the first condenser is connected to the light component outlet of the chlorination stripping tower via a pipeline, the outlet of the first condenser is connected to the feed inlet of the first storage tank via a pipeline, the outlet of the first storage tank is connected to the feed inlet of the four pumps via a pipeline, and the outlets of the four pumps are connected to the top of the chlorination stripping tower and the feed inlet of the PX buffer tank via pipelines respectively.

[0029] Preferably, the chlorination unit further includes an external heat exchanger disposed outside the chlorination reactor.

[0030] Preferably, in the chlorination unit, a silo and a conveyor are sequentially installed along the pipeline connecting the filter and the melting tank from upstream to downstream.

[0031] Preferably, in the chlorination unit, three pumps are installed on the pipeline connecting the melting tank and the chlorination stripping tower.

[0032] Preferably, in the chlorination unit, a first reboiler is provided outside the chlorination light-removal tower, and five pumps are provided on the pipeline connecting the chlorination light-removal tower and the chlorination heavy-light-removal tower.

[0033] Preferably, in the chlorination unit, a second reboiler is provided outside the heavy and light chlorination tower.

[0034] Preferably, the chlorination unit further includes a second condenser, a second storage tank, and a sixth pump. The inlet of the second condenser is connected to the gas phase outlet of the chlorination de-heavy tower via a pipeline. The outlet of the second condenser is connected to the inlet of the second storage tank via a pipeline. The outlet of the second storage tank is connected to the inlet of the sixth pump via a pipeline. The outlet of the sixth pump is connected to the top of the chlorination de-heavy tower via a pipeline and is also connected to the gas phase outlet pipeline of the chlorination de-heavy tower.

[0035] Preferably, the hydrolysis reactor further includes a PXDC buffer tank and an alkali buffer tank. The inlet of the PXDC buffer tank is connected to a PXDC feed pipeline, and the outlet of the PXDC buffer tank is connected to the inlet of the hydrolysis reactor via a pipeline. Seven pumps are installed on the pipeline connecting the PXDC buffer tank and the hydrolysis reactor. The inlet of the alkali buffer tank is connected to an alkali feed pipeline, and the outlet of the alkali buffer tank is connected to the inlet of the hydrolysis reactor via a pipeline. Eight pumps are installed on the pipeline connecting the alkali buffer tank and the hydrolysis reactor.

[0036] Preferably, in the hydrolysis unit, nine pumps and a cooler are sequentially installed on the pipeline connecting the hydrolysis reactor and the extraction tower from upstream to downstream.

[0037] Preferably, the hydrolysis unit further includes an extractant buffer tank, a wastewater stripping tower, and a third condenser. The outlet of the extractant buffer tank is connected to the inlet of the extraction tower via a pipeline, and ten pumps are installed on the pipeline connecting the extractant buffer tank and the extraction tower. The inlet of the extractant buffer tank is connected to the extractant feed pipeline and to the outlet of the third condenser via a pipeline. The inlet of the third condenser is connected to the gas phase outlet of the wastewater stripping tower and the gas phase outlet of the extractant recovery tower via pipelines respectively. The inlet of the wastewater stripping tower is connected to the gas phase outlet of the extraction tower, and eleven pumps are installed on the pipeline connecting the extraction tower and the wastewater stripping tower. A third reboiler is installed outside the wastewater stripping tower.

[0038] Preferably, in the hydrolysis unit, twelve pumps are installed on the pipeline connecting the extraction tower and the extractant recovery tower.

[0039] Preferably, in the hydrolysis unit, a fourth reboiler is provided outside the extractant recovery tower, and thirteen pumps are provided on the pipeline connecting the extractant recovery tower and the hydrolysis delight tower.

[0040] Preferably, in the hydrolysis unit, a fifth reboiler is provided outside the hydrolysis light tower, and fifteen pumps are provided on the pipeline connecting the hydrolysis light tower and the hydrolysis heavy tower.

[0041] Preferably, the hydrolysis unit further includes a fourth condenser, a third storage tank, and a fourteenth pump. The inlet of the fourth condenser is connected to the gas phase outlet of the hydrolysis light tower via a pipeline. The outlet of the fourth condenser is connected to the inlet of the third storage tank via a pipeline. The outlet of the third storage tank is connected to the inlet of the fourteenth pump via a pipeline. The outlet of the fourteenth pump is connected to the top of the hydrolysis light tower via a pipeline and is also connected to the gas phase outlet pipeline of the hydrolysis light tower.

[0042] Preferably, in the hydrolysis unit, a sixth reboiler is provided outside the hydrolysis decomposition tower.

[0043] Preferably, the hydrolysis unit further includes a fifth condenser, a fourth storage tank, and sixteen pumps. The inlet of the fifth condenser is connected to the gas phase outlet of the hydrolysis deweighting tower via a pipeline. The outlet of the fifth condenser is connected to the inlet of the fourth storage tank via a pipeline. The outlet of the fourth storage tank is connected to the inlet of the sixteen pumps via a pipeline. The outlet of the sixteen pumps is connected to the top of the hydrolysis deweighting tower and the inlet of the hydrolysis product tower via pipelines, respectively. Seventeen pumps are provided on the pipeline connecting the hydrolysis deweighting tower and the hydrolysis product tower.

[0044] Preferably, in the hydrolysis unit, a seventh reboiler is provided outside the hydrolysis decomposition tower.

[0045] Preferably, the hydrolysis unit further includes a sixth condenser, a fifth storage tank, and an eighteenth pump. The inlet of the sixth condenser is connected to the gas phase outlet of the hydrolysis product tower via a pipeline. The outlet of the sixth condenser is connected to the inlet of the fifth storage tank via a pipeline. The outlet of the fifth storage tank is connected to the inlet of the eighteenth pump via a pipeline. The outlet of the eighteenth pump is connected to the top of the hydrolysis product tower via a pipeline and is also connected to the gas phase outlet pipeline of the hydrolysis product tower.

[0046] Preferably, the hydrogenation unit further includes a BDM buffer tank, a hydrogen buffer tank, a second mixer, a second heat exchanger, a first heat exchanger, a heater, and a compressor; the inlet of the BDM buffer tank is connected to the BDM feed pipeline, and the outlet of the BDM buffer tank is connected to the inlet of the second mixer via a pipeline, and nineteen pumps are installed on the pipeline connecting the BDM buffer tank and the second mixer; the inlet of the hydrogen buffer tank is connected to the hydrogen feed pipeline, and the outlet of the hydrogen buffer tank is connected to the inlet of the second mixer via a pipeline; the outlet of the second mixer is connected to the first inlet of the first heater via a pipeline; the first heater... The first discharge port is connected to the inlet of the heater via a pipeline. The discharge port of the heater is connected to the inlet of the hydrogenation reactor via a pipeline. The second inlet of the first heat exchanger is connected to the discharge port of the hydrogenation reactor via a pipeline. The second discharge port of the first heat exchanger is connected to the first inlet of the second heat exchanger. The first discharge port of the second heat exchanger is connected to the inlet of the gas-liquid separator via a pipeline. The second inlet and second discharge port of the second heat exchanger are connected to the cold water inlet pipe and the hot water outlet pipe, respectively. The inlet of the compressor is connected to the gas phase discharge port of the gas-liquid separator via a pipeline. The discharge port of the compressor is connected to the inlet of the hydrogen buffer tank via a pipeline.

[0047] Preferably, in the hydrogenation unit, twenty pumps are installed on the pipeline connecting the gas-liquid separator and the hydrogenation delight tower.

[0048] Preferably, in the hydrogenation unit, an eighth reboiler is provided outside the hydrogenation light removal tower, and twenty-two pumps are provided on the pipeline connecting the hydrogenation light removal tower and the hydrogenation heavy removal tower.

[0049] Preferably, the hydrogenation unit further includes a seventh condenser, a sixth storage tank, and a twenty-one pump. The inlet of the seventh condenser is connected to the gas phase outlet of the hydrotreating tower via a pipeline. The outlet of the seventh condenser is connected to the inlet of the sixth storage tank via a pipeline. The outlet of the sixth storage tank is connected to the inlet of the twenty-one pump via a pipeline and is also connected to the outlet pipeline of the sixth storage tank. The outlet of the twenty-one pump is connected to the top of the hydrotreating tower via a pipeline and is also connected to the gas phase outlet pipeline of the hydrotreating tower.

[0050] Preferably, in the hydrogenation unit, a ninth reboiler is provided outside the hydrogenation deweighting tower.

[0051] Preferably, the hydrogenation unit further includes an eighth condenser, a seventh storage tank, and twenty-three pumps. The inlet of the eighth condenser is connected to the gas phase outlet of the hydrodeweighting tower via a pipeline. The outlet of the eighth condenser is connected to the inlet of the seventh storage tank via a pipeline. The outlet of the seventh storage tank is connected to the inlet of the twenty-three pumps via a pipeline. The outlet of the twenty-three pumps is connected to the top of the hydrodeweighting tower and the inlet of the hydrogenation product tower via pipelines, respectively. Twenty-four pumps are installed on the pipeline connecting the hydrodeweighting tower and the hydrogenation product tower.

[0052] Preferably, in the hydrogenation unit, a tenth reboiler is provided outside the hydrogenation product tower.

[0053] Preferably, the hydrogenation unit further includes a ninth condenser, an eighth storage tank, and a twenty-five pump. The inlet of the ninth condenser is connected to the gas phase outlet of the hydrogenation product tower via a pipeline. The outlet of the ninth condenser is connected to the inlet of the eighth storage tank via a pipeline. The outlet of the eighth storage tank is connected to the inlet of the twenty-five pump via a pipeline. The outlet of the twenty-five pump is connected to the top of the hydrogenation product tower via a pipeline and is also connected to the gas phase outlet pipeline of the hydrogenation product tower.

[0054] The principle of this invention is as follows: PX is an important aromatic compound in the petrochemical industry chain, and compared to DMT, it has the advantages of being widely available and inexpensive. For example... Figure 2 As shown, this invention achieves continuous production of CHDM based on the preparation of PXDC by PX chlorination, the preparation of BDM by PXDC hydrolysis, and the preparation of CHDM by BDM hydrogenation.

[0055] In the chlorination unit, the eutectic ionic liquid catalyst used has extremely high catalytic efficiency, which can rapidly convert PX under mild reaction conditions and achieve a PXDC selectivity of over 95%, enabling continuous production. Some components that are relatively lighter than PXDC can be recycled back to the chlorination reactor to continue reacting and generating PXDC.

[0056] In the hydrolysis unit, a continuous process is adopted, which enables continuous production of BDM, greatly improving production efficiency. Moreover, the reaction conditions are mild and the energy consumption is low.

[0057] In the hydrogenation unit, a heterogeneous hydrogenation catalyst is used, eliminating the problem of catalyst-product separation during the reaction and significantly reducing production energy consumption. Compared to the traditional CHDM production method, this hydrogenation unit only involves one hydrogenation process, with mild reaction conditions, making it environmentally friendly, and achieving high product yield and production efficiency. Furthermore, the hydrogenation unit of this invention can also achieve heat exchange between the feed hydrogen and the reaction products, thus contributing to energy conservation and consumption reduction.

[0058] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The method and system for continuous production of 1,4-cyclohexanediethanol provided by the present invention uses PX as raw material and prepares CHDM products through a process route of chlorination, hydrolysis and hydrogenation. This is different from the traditional process of preparing CHDM from DMT through two-step hydrogenation in terms of raw materials and process route.

[0059] 2. The method and system for continuous production of 1,4-cyclohexanediethanol provided by the present invention uses PX as a raw material to prepare CHDM. PX is an important aromatic compound in the petrochemical industry chain. Compared with the existing technology that uses DMT as a raw material, it has the advantages of wide availability and low price, which can significantly reduce production costs.

[0060] 3. The method and system for continuous production of 1,4-cyclohexanediethanol provided by the present invention are based on a three-step process and technology of PX chlorination to prepare PXDC, PXDC hydrolysis to prepare BDM, and BDM hydrogenation to prepare CHDM. This method and technology realizes the continuous production of CHDM and has higher production efficiency compared with the existing two-step hydrogenation process.

[0061] 4. The method and system for continuous production of 1,4-cyclohexanediethanol provided by this invention includes three completely different process routes: chlorination, hydrolysis, and hydrogenation. The chlorination and hydrolysis stages do not require harsh reaction conditions of high temperature and high pressure, and the final hydrogenation stage only involves the hydrogenation of the benzene ring. Compared with the two-stage hydrogenation process of DMT to prepare CHDM, which has harsh reaction conditions and high equipment requirements, this invention only has a single hydrogenation process, and the reaction conditions are mild and environmentally friendly.

[0062] 5. The method and system for continuous production of 1,4-cyclohexanediethanol provided by this invention can use the by-product industrial salt sodium chloride or potassium chloride (product of the wastewater stripping tower) as a basic raw material for the production of sodium hydroxide or potassium hydroxide.

[0063] 6. The method and system for continuous production of 1,4-cyclohexanediethanol provided by the present invention uses a low-cost and high-efficiency heterogeneous catalyst in the PX chlorination section, which can simultaneously obtain high conversion rate and high PXDC selectivity, and the catalyst cost and production cost are lower. Attached Figure Description

[0064] Figure 1 This is a schematic diagram of the existing synthetic route for preparing CHDM using two-step hydrogenation of DMT; Figure 2 This is a schematic diagram of the synthetic route for preparing CHDM using PX as a raw material in this invention; Figure 3 This is a process flow diagram of the chlorination unit in the method for continuous production of 1,4-cyclohexanediethanol of the present invention. Figure 4This is a process flow diagram of the hydrolysis unit of the method for continuous production of 1,4-cyclohexanediethanol of the present invention; Figure 5 This is a process flow diagram of the hydrogenation unit in the method for continuous production of 1,4-cyclohexanediethanol of the present invention. In the diagram, 1. PX buffer tank, 2. Pump 1, 3. Liquid chlorine buffer tank, 4. Pump 2, 5. First mixer, 6. Chlorination reactor, 7. External heat exchanger, 8. Filter, 9. Silo, 10. Conveyor, 11. Melting tank, 12. Pump 3, 13. Chlorination light-light removal tower, 14. First condenser, 15. First storage tank, 16. Pump 4, 17. First reboiler, 18. Pump 5, 19. Chlorination heavy-light removal tower, 20. Second condenser, 21. Second storage tank, 22. Pump 6, 23. Second reboiler, 24. 25. PXDC Buffer Tank, 26. Seven Pumps, 27. Alkali Buffer Tank, 28. Eight Pumps, 29. Hydrolysis Reactor, 30. Nine Pumps, 31. Cooler, 32. Extraction Tower, 33. Extractant Buffer Tank, 34. Ten Pumps, 35. Eleven Pumps, 36. Wastewater Stripping Tower, 37. Third Reboiler, 38. Third Condenser, 39. Twelfth Pump, 40. Extractant Recovery Tower, 41. Fourth Reboiler, 42. Thirteenth Pump, 43. Hydrolysis Delighting Tower, 44. Fifth Reboiler, 45. Fourth Condenser, 46. Third Storage Tank Storage tank, 46. Pump 14, 47. Pump 15, 48. Hydrolysis decomposition tower, 49. Sixth reboiler, 50. Fifth condenser, 51. Fourth storage tank, 52. Pump 16, 53. Pump 17, 54. Hydrolysis product tower, 55. Seventh reboiler, 56. Sixth condenser, 57. Fifth storage tank, 58. Pump 18, 59. BDM buffer tank, 60. Pump 19, 61. Hydrogen buffer tank, 62. Second mixer, 63. Second heat exchanger, 64. First heat exchanger, 65. Heater, 66. Hydrogenation tank Reactor, 67. Gas-liquid separator, 68. Compressor, 69. Pump 20, 70. Hydrotreating light component removal tower, 71. Eighth reboiler, 72. Seventh condenser, 73. Sixth storage tank, 74. Pump 21, 75. Pump 22, 76. Hydrotreating heavy component removal tower, 77. Ninth reboiler, 78. Eighth condenser, 79. Seventh storage tank, 80. Pump 23, 81. Pump 24, 82. Hydrotreating product tower, 83. Tenth reboiler, 84. Ninth condenser, 85. Eighth storage tank, 86. Pump 25. Detailed Implementation

[0065] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to embodiments.

[0066] In the following embodiments, various processes and methods not described in detail are conventional methods known in the art. Unless otherwise specified, the materials, reagents, apparatus, instruments, equipment, etc., used in the following embodiments are commercially available.

[0067] Example 1 The continuous production method for CHDM, with an annual output of 70,000 tons, involves the following steps: Step 1, Chlorination Reaction Unit p-xylene, after being buffered in PX buffer tank 1, is fed into the first mixer 5 via pump 2. Liquid chlorine, after being buffered in liquid chlorine buffer tank 3, is fed into the first mixer 5 via pump 4. PX (10617 kg / h) and liquid chlorine (14181 kg / h) are mixed in the first mixer 5 and then fed into the chlorination reactor 6 at 46°C and 0.2 MPa pressure. Under ultraviolet light irradiation, the reaction is carried out using a eutectic ionic liquid as a catalyst for a residence time of 1 hour. The reaction temperature in the chlorination reactor 6 is controlled at 60°C by an external heat exchanger 7. The resulting hydrogen chloride and chlorine gas are discharged from the top of the chlorination reactor 6. The reaction products (mainly containing PXDC and unreacted PX, and also byproducts such as p-methylbenzyl chloride (PMBC) and 1-(dichloromethyl)-4-toluene (PMDCMB)) are discharged and fed to filter 8 at the bottom of the tower. The temperature of filter 8 is controlled at 60℃. The filtrate (mainly containing catalyst, unreacted PX, and reaction products such as PMBC and PMDCMB) is buffered in PX buffer tank 1 and then returned to chlorination reactor 6 via pump 2 and first mixer 5 to react further with liquid chlorine. The filter cake (flow rate of 17125 kg / h) (mainly PXDC) is produced. After being buffered in silo 9, the C and heavy components are conveyed to melting tank 11 via conveyor 10. After melting at 105°C, they are sent to chlorination stripping tower 13 via three pumps 12. The resulting light components are discharged from the top of the tower, condensed in the first condenser 14, and then enter the first storage tank 15. Part of the condensate is then returned to chlorination stripping tower 13 via four pumps 16, while the other part is buffered in PX buffer tank 1 and then returned to chlorination reactor 6 via one pump 2 and the first mixer 5 to react further with liquid chlorine. The bottom liquid obtained from chlorination stripping tower 13 (flow rate of 13433 kg / h) mainly consists of PXDC and heavy components. Part of the liquid is returned to the chlorination removal tower 13 after reboiling in the first reboiler 17, and the other part is sent to the chlorination removal tower 19 via the fifth pump 18. The gas phase obtained from the chlorination removal tower 19 is condensed from the top of the tower by the second condenser 20 and then enters the second storage tank 21. After that, part of the gas phase is returned to the chlorination removal tower 19 via the sixth pump 22, and the other part is discharged. Part of the bottom liquid obtained from the chlorination removal tower 19 is returned to the chlorination removal tower 19 after reboiling in the second reboiler 23, and the other part is discharged. PXDC is obtained by side stream with a mass flow rate of 16770 kg / h. The PXDC yield in the chlorination unit is 95.8%. The eutectic ionic liquid used was a mixture of tetrabutylammonium bromide and triethanolamine in a molar ratio of 1:1, with a total mass of 212 kg. The top temperature of the chlorination removal tower 13 is 130°C, the top pressure is 1 kPa, and the bottom temperature is 159°C. The top temperature of the chlorination de-heavyweight column 19 is 157°C, the top pressure is 1 kPa, and the bottom temperature is 249°C.

[0068] Step 2, Hydrolysis reaction unit After being buffered in a PXDC (16770 kg / h) buffer tank 24, p-dichlorobenzyl is fed into the hydrolysis reactor 28 via pump 25. The alkali solution (35864 kg / h) is buffered in an alkali solution buffer tank 26 and then fed into the hydrolysis reactor 28 via pump 27. The hydrolysis reaction is carried out at 150°C and 0.8 MPa for 1 hour. The resulting reaction products (mainly containing BDM, unreacted PXDC, water, and NaOH and NaCl) are cooled to 30°C in a cooler 30 via pump 29 and then fed from the bottom of the tower into the extraction tower 31. Dichloromethane is used as the extractant, and the extractant flow rate (21233 kg / h) is drawn from the extractant... The buffer tank 32 is fed into the extraction tower 31 via pump 33. The raffinate (mainly containing water, NaOH, NaCl, and a small amount of dichloromethane) is discharged from the top of the extraction tower 31 and sent to the wastewater stripping tower 35 via pump 34. The resulting gas phase is condensed by the third condenser 37 and then sent to the extractant buffer tank 32. Part of the bottom liquid is reboiled by the third reboiler 36 and returned to the wastewater stripping tower 35, while the other part is discharged. The extract phase is fed into the extractant recovery tower 39 via pump 38. The resulting gas phase is condensed by the third condenser 37 and then sent to the extractant buffer tank 32. Part of the bottom liquid is reboiled by the fourth reboiler 40 and then returned to the extractant recovery tower. 39. Another portion is sent to the hydrolysis light column 42 via pump 13 41. The bottom liquid obtained from the hydrolysis light column 42 (mainly BDM and heavy components) is partially returned to the hydrolysis light column 42 after being reboiled by the fifth reboiler 43, and the other portion is sent to the hydrolysis heavy column 48 via pump 15 47. The light component obtained from the hydrolysis light column 42 is condensed from the top of the column by the fourth condenser 44 and first enters the third storage tank 45. Then, part of it is returned to the hydrolysis light column 42 via pump 14 46, and the other part is discharged. The bottom liquid obtained from the hydrolysis heavy column 48 is partially returned to the hydrolysis heavy column 48 after being reboiled by the sixth reboiler 49, and the other part is discharged. The gas phase obtained from the hydrolysis heavy column 48 is sent from the top of the column by the first reboiler 43 44 45 46 47 48 ... After condensation in condenser 50, the product first enters storage tank 51, then is partially returned to hydrolysis deweighting tower 48 via pump 16, and the other part is sent to hydrolysis product tower 54 via pump 17. Part of the bottom liquid (heavy components) of hydrolysis product tower 54 is reboiled in reboiler 55 and returned to hydrolysis product tower 54, while the other part is discharged. The gas phase obtained from hydrolysis product tower 54 is condensed in condenser 56 at the top of the tower and first enters storage tank 57, then is partially returned to hydrolysis product tower 54 via pump 17, while the other part is discharged. BDM product is obtained from the side stream of hydrolysis product tower 54, with a production rate of 12960 kg / h. The yield of BDM in the hydrolysis unit is 98%. The alkaline solution is a 20% (w / w) NaOH aqueous solution; The temperature at the top of the hydrolysis light tower 42 is 126℃, the pressure is 1kPa, and the temperature at the bottom is 170℃. The temperature at the top of the hydrolysis decompression tower 48 is 140℃, the pressure is 1.1kPa, and the temperature at the bottom is 315℃. The hydrolysis product tower 54 has a top temperature of 128°C, a pressure of 1 kPa, and a bottom temperature of 318°C.

[0069] Step 3, Hydrogenation Reaction Unit After being buffered in BDM buffer tank 59, terephthalic acid is fed into the second mixer 62 via the nineteenth pump 60. Hydrogen is buffered in hydrogen buffer tank 61 and then fed into the second mixer 62. Terephthalic acid (12960 kg / h) and hydrogen (693 kg / h) are mixed in the second mixer 62. The resulting mixture first exchanges heat with the reaction products of the hydrogenation reactor 66 via the first heat exchanger 64, then is heated to 120°C by the heater 65, and then fed into the hydrogenation reactor 66. The reaction is carried out at 150°C and 3 MPa pressure using Ru / ZrO2 as a catalyst (Ru content of 2% by mass, ZrO2 content of 98% by mass) at a mass hourly space velocity (H₂Sv) of 2 h⁻¹. -1The reaction products obtained (mainly containing CHDM and water, and also containing byproducts such as PX and 4-methyl-1-cyclohexanemethanol (MCHM)) are first heated to 127°C with the mixed gas in the first heat exchanger 64, and then heated to 115°C with cold water in the second heat exchanger 63. Finally, they are sent to the gas-liquid separator 67. The gas phase obtained from the gas-liquid separator 67 is discharged from the top of the tank, compressed to 2MPa by the compressor 68, and sent to the hydrogen buffer tank 61 for recycling. The hydrogenation product obtained from tank 7 is fed from the bottom of the tank into the hydrodelighting tower 70 via pump 69. Part of the bottom liquid from the hydrodelighting tower 70 is returned to the hydrodelighting tower 70 after reboiling in the eighth reboiler 71, while the other part is fed into the hydrodeheavy tower 76 via pump 72. The light components (water, PX, MCHM, etc.) obtained from the hydrodelighting tower 70 are condensed from the top of the tower by the seventh condenser 72 and first enter the sixth storage tank 73. Part of the condensate is discharged, and the other part enters the twenty-first pump 74. The liquid from the bottom of the hydrotreating tower 76 is returned to the light-weight removal tower 70, and the other part is discharged. The liquid from the bottom of the hydrotreating tower 76 is reboiled in the ninth reboiler 77 and returned to the hydrotreating tower 76, while the other part is discharged. The gas phase from the top of the hydrotreating tower 76 is condensed in the eighth condenser 78 and first enters the seventh storage tank 79, then enters the twenty-third pump 80. Part of the gas phase is returned to the hydrotreating tower 76, and the other part is sent to the hydrogenation product tower 82 via the twenty-fourth pump 81. The liquid from the bottom of the hydrogenation product tower 82 is reboiled in the tenth reboiler 83 and returned to the hydrogenation product tower 82, while the other part is discharged. The gas phase from the top of the hydrogenation product tower 82 is condensed in the ninth condenser 84 and first enters the eighth storage tank 85, then enters the twenty-fifth pump 86. Part of the gas phase is returned to the hydrogenation product tower 82, and the other part is discharged. CHDM is collected from the side stream at a flow rate of 13415 kg / h. In the hydrogenation unit, the yield of CHDM is 99.2%, and the purity of the CHDM product is greater than 99.9%. The top temperature of the hydrotreating light component removal column 70 is 25°C, the pressure is 2 kPa, and the bottom temperature is 187°C. The temperature at the top of the hydrodeweight removal tower 76 is 170℃, the pressure is 2kPa, and the temperature at the bottom is 257℃. The hydrogenation product tower 82 has a top temperature of 138°C, a pressure of 1.5 kPa, and a bottom temperature of 278°C.

[0070] Example 2 Except for replacing the alkali solution in the hydrolysis unit with a 20% NaOH aqueous solution and replacing the catalyst in the hydrogenation unit with a Pt / Al2O3 catalyst (the active component Pt and the support Al2O3 have mass contents of 2% and 98%, respectively), everything else is the same as in Example 1. The yields of each reaction unit are shown in Table 1.

[0071] Example 3 Except for replacing the catalyst in the chlorination unit with tetrabutylammonium bromide and triethanolamine with choline chloride and ethylene glycol (molar ratio 1:1) and the extractant in the hydrolysis unit with dichloromethane and 1,2-dichloroethane, the other steps were the same as in Example 1. The yields of each reaction unit are shown in Table 1.

[0072] Example 4 Except for replacing the catalyst in the chlorination unit with tetrabutylammonium bromide and triethanolamine in a molar ratio of 1:1, and replacing the catalyst in the hydrogenation unit with a Ni / Al2O3 catalyst (with the active component Ni and the support Al2O3 having mass contents of 10% and 90%, respectively), the other steps are the same as in Example 1. The yields of each reaction unit are shown in Table 1.

[0073] Example 5 Except for replacing the catalyst in the chlorination unit with tetrabutylammonium bromide and triethanolamine in a molar ratio of 1:1, and replacing the extractant in the hydrolysis unit with dichloromethane in a chlorobenzene, the other steps are the same as in Example 1. The yields of each reaction unit are shown in Table 1.

[0074] Example 6 Except for changing the temperature of chlorination reactor 6 in the chlorination unit from 60°C to 80°C, the temperature of hydrolysis reactor 28 in the hydrolysis unit from 150°C to 120°C, and the temperature of hydrogenation reactor 66 in the hydrogenation unit from 150°C to 170°C, everything else is the same as in Example 1. The yields of each reaction unit are shown in Table 1.

[0075] Table 1. Yields of each reaction unit in Examples 1-6

[0076] Table 1 illustrates that, using PX as raw material, CHDM products with a purity greater than 99.9% can be continuously produced through three reaction units: chlorination, hydrolysis, and hydrogenation. Under optimal conditions, the product yields of each of the three reaction units are greater than 95%, and the overall CHDM yield is greater than 90%. Compared to traditional processes, the method of this invention offers higher production efficiency while significantly reducing raw material costs, and also provides milder reaction conditions, resulting in lower energy consumption and production costs.

[0077] It is evident that this invention is a new green and environmentally friendly process that differs from traditional production methods and processes, and has the advantages of low cost and low energy consumption.

[0078] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the embodiments. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all embodiments here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for continuous production of 1,4-cyclohexanediethanol, characterized in that, include: Step 1: Mix p-xylene with liquid chlorine, use a eutectic ionic liquid as a catalyst, and carry out a chlorination reaction at 50-150℃ under ultraviolet light irradiation. After filtering the reaction product, melt the filter cake, remove the light components first, and then remove the heavy components to obtain p-dichlorobenzyl. The eutectic ionic liquid is composed of hydrogen bond acceptors and hydrogen bond donors in a molar ratio of 1:2 to 10:1; Step 2: Mix the p-dichlorobenzyl prepared in Step 1 with an alkaline solution and carry out a hydrolysis reaction at 100-200℃ and 0.5-1MPa. After cooling, the reaction product is extracted with an extractant. The extractant is removed from the extract phase first, and then the light and heavy components are removed in sequence to obtain terephthalic acid. Step 3: Using a heterogeneous hydrogenation catalyst, the terephthalic acid diethanol prepared in step 2 is hydrogenated with hydrogen at 100-200℃ and 1-6MPa. The resulting reaction product is first dehydrogenated, and then the light and heavy components are removed sequentially to obtain 1,4-cyclohexanediethanol.

2. The method for continuous production of 1,4-cyclohexanediethanol according to claim 1, characterized in that, Step 1: p-xylene and liquid chlorine are fed into chlorination reactor (6). Under ultraviolet light irradiation, the reaction is carried out with a eutectic ionic liquid as a catalyst. The resulting hydrogen chloride and chlorine gas are discharged. The reaction product is sent to filter (8) for filtration. The filtrate is discharged and the filter cake is sent to melting tank (11). After heating and melting, it is sent to chlorination light component removal tower (13). The resulting light component is discharged and the bottom liquid of the tower is sent to chlorination heavy component removal tower (19) to remove heavy component. p-dichlorobenzyl is obtained by side stream. Step 2: benzyl dichlorotrichloro and alkaline solution are fed into hydrolysis reactor (28) for hydrolysis reaction. After the reaction product is cooled, it is sent to extraction tower (31) for extraction. The raffinate phase is discharged. The extract phase is first sent to extractant recovery tower (39) to recover the extractant, and then sent to hydrolysis light desulfurization tower (42). The light component is discharged from the top of the tower. The bottom liquid of the tower is sent to hydrolysis heavy desulfurization tower (48). The bottom liquid of the tower is discharged. The gas phase is sent from the top of the tower to hydrolysis product tower (54). Terephthalic acid is obtained by side stream. Step 3: Terephthalic acid and hydrogen are fed into the hydrogenation reactor (66) and a heterogeneous hydrogenation catalyst is used for hydrogenation reaction. The resulting reaction product is sent to the gas-liquid separator (67) for separation. The resulting gas phase is discharged from the top of the separator, and the resulting hydrogenation product is sent from the bottom of the separator to the hydrogenation light component removal tower (70). The resulting light component is discharged from the top of the tower, and the resulting bottom liquid is sent to the hydrogenation heavy component removal tower (76). The resulting gas phase is discharged from the top of the tower, and the resulting bottom liquid is sent to the hydrogenation product tower (82). 1,4-cyclohexanediethanol is collected from the side stream.

3. The method for continuous production of 1,4-cyclohexanediethanol according to claim 2, characterized in that, In step one, one or more of the following characteristics are present: After being buffered in the PX buffer tank (1), p-xylene is sent to the first mixer (5) via a pump (2). After being buffered in the liquid chlorine buffer tank (3), liquid chlorine is sent to the first mixer (5) via a pump (4). PX and liquid chlorine are mixed in the first mixer (5) and then sent to the chlorination reactor (6) for reaction. The filtrate is sent to the PX buffer tank (1). The light components obtained from the chlorination light removal tower (13) are discharged from the top of the tower, condensed by the first condenser (14), and first enter the first storage tank (15). Then, a portion is returned to the chlorination light removal tower (13) via a pump (16), and the other portion is sent to the PX buffer tank (1). The reaction temperature in the chlorination reactor (6) is controlled at 50-150℃ by an external heat exchanger (7); The filter cake is buffered in the silo (9) and then sent to the melting tank (11) by the conveyor (10). After the filter cake is heated and melted, it is sent to the chlorination removal tower (13) via three pumps (12). Part of the bottom liquid obtained from the chlorination light removal tower (13) is returned to the chlorination light removal tower (13) after being reboiled by the first reboiler (17), and the other part is sent to the chlorination heavy removal tower (19) by five pumps (18). The top temperature of the chlorination removal tower (13) is 125-135℃, the top pressure is 1-2kPa, and the bottom temperature is 155-165℃. The gas phase obtained from the chlorination de-heavy column (19) is condensed from the top of the column by the second condenser (20) and then enters the second storage tank (21). After that, part of it is returned to the chlorination de-heavy column (19) by the six pumps (22), and the other part is discharged. Part of the bottom liquid obtained from the chlorination de-heavy column (19) is returned to the chlorination de-heavy column (19) after being reboiled in the second reboiler (23), and the other part is discharged. The temperature at the top of the chlorination de-heavy column (19) is 155-165℃, the pressure at the top is 1-2kPa, and the temperature at the bottom is 240-260℃.

4. The method for continuous production of 1,4-cyclohexanediethanol according to claim 2, characterized in that, In step two, one or more of the following characteristics are present: After being buffered in the PXDC buffer tank (24), the dichlorobenzyl is sent to the hydrolysis reactor (28) via the seventh pump (25). After being buffered in the alkaline buffer tank (26), the alkaline solution is sent to the hydrolysis reactor (28) via the eighth pump (27). The reaction product is fed into a cooler (30) via nine pumps (29) and then fed into an extraction tower (31) after cooling. The extractant used in the extraction is fed from the extractant buffer tank (32) into the extraction tower (31) via ten pumps (33). The raffinate phase is discharged from the top of the extraction tower (31) and sent to the wastewater stripping tower (35) via eleven pumps (34). The resulting gas phase is condensed by the third condenser (37) and then sent back to the extractant buffer tank (32). Part of the resulting bottom liquid is reboiled by the third reboiler (36) and then returned to the wastewater stripping tower (35), while the other part is discharged. The extractant phase is fed into the extractant recovery tower (39) via twelve pumps (38). The resulting gas phase is condensed by the third condenser (37) and then sent back to the extractant buffer tank (32). Part of the resulting bottom liquid is reboiled by the fourth reboiler (40) and then returned to the extractant recovery tower (39), while the other part is sent to the hydrolysis delighting tower (42) via thirteen pumps (41). Part of the liquid obtained from the hydrolysis light column (42) is returned to the hydrolysis light column (42) after being reboiled in the fifth reboiler (43), and the other part is sent to the hydrolysis heavy column (48) by the fifteenth pump (47). The light component obtained from the hydrolysis light column (42) is condensed from the top of the column by the fourth condenser (44) and first enters the third storage tank (45). Then, part of it is returned to the hydrolysis light column (42) by the fourteenth pump (46), and the other part is discharged. The temperature at the top of the hydrolysis light tower (42) is 120-130℃, the pressure is 0.5-1.5kPa, and the temperature at the bottom is 160-180℃. Part of the liquid obtained from the hydrolysis de-weighting tower (48) is returned to the hydrolysis de-weighting tower (48) after being reboiled in the sixth reboiler (49), and the other part is discharged. The gas phase obtained from the hydrolysis de-weighting tower (48) is condensed from the top of the tower by the fifth condenser (50) and first enters the fourth storage tank (51). Then, part of it is returned to the hydrolysis de-weighting tower (48) by the sixteenth pump (52), and the other part is sent to the hydrolysis product tower (54) by the seventeenth pump (53). The temperature at the top of the hydrolysis decompression tower (48) is 135-145℃, the pressure is 0.5-1.5kPa, and the temperature at the bottom is 300-320℃. A portion of the liquid in the bottom of the hydrolysis product tower (54) is returned to the hydrolysis product tower (54) after being reboiled by the seventh reboiler (55), while the other portion is discharged. The gas phase obtained from the hydrolysis product tower (54) is condensed from the top of the tower by the sixth condenser (56) and then enters the fifth storage tank (57). A portion of the gas phase is returned to the hydrolysis product tower (54) by the seventeenth pump (58), while the other portion is discharged. The top temperature of the hydrolysis product tower (54) is 125-140℃, the pressure is 0.5-1.5kPa, and the bottom temperature is 300-325℃.

5. The method for continuous production of 1,4-cyclohexanediethanol according to claim 1, characterized in that, Step 3: Possess one or more of the following characteristics: After being buffered in the BDM buffer tank (59), terephthalic acid is sent to the second mixer (62) by the nineteenth pump (60). After being buffered in the hydrogen buffer tank (61), hydrogen is sent to the second mixer (62). After being mixed in the second mixer (62), the resulting mixed gas is first sent to the heater (65) for heating after exchanging heat with the reaction products of the hydrogenation reactor (66) through the first heat exchanger (64), and then sent to the hydrogenation reactor (66) for reaction. The resulting reaction products are first sent to the mixed gas for heat exchange with the first heat exchanger (64), and then sent to the second heat exchanger (63) for heat exchange with cold water. Finally, they are sent to the gas-liquid separator (67). The gas phase obtained from the gas-liquid separator (67) is discharged from the top of the tank and compressed to 1.8-2 MPa by the compressor (68) and sent to the hydrogen buffer tank (61) for recycling. The hydrogenation product obtained from the gas-liquid separator (67) is sent from the bottom of the tank to the hydrodelight tower (70) via twenty pumps (69). Part of the bottom liquid obtained from the hydrodelighting column (70) is returned to the hydrodelighting column (70) after being reboiled in the eighth reboiler (71), and the other part is sent to the hydrodeheavy column (76) by pump twenty-two (75). The light components obtained from the hydrodelighting column (70) are condensed from the top of the column by the seventh condenser (72) and first enter the sixth storage tank (73). Part of the light components are discharged and the other part enters the twenty-first pump (74). Part of the light components are returned to the hydrodelighting column (70) and the other part is discharged. The top temperature of the hydrotreating light-light-removal tower (70) is 20-40℃, the pressure is 1-3kPa, and the bottom temperature is 180-200℃. Part of the bottom liquid obtained from the hydrodeweighting tower (76) is returned to the hydrodeweighting tower (76) after being reboiled in the ninth reboiler (77), and the other part is discharged. The gas phase obtained from the hydrodeweighting tower (76) is condensed from the top of the tower by the eighth condenser (78) and first enters the seventh storage tank (79), and then enters the twenty-third pump (80). Part of it is returned to the hydrodeweighting tower (76), and the other part is sent to the hydrodeweighting product tower (82) by the twenty-fourth pump (81). The top temperature of the hydrogenation deweight removal tower (76) is 165-195℃, the pressure is 1-3kPa, and the bottom temperature is 240-280℃. Part of the bottom liquid obtained from the hydrogenation product tower (82) is returned to the hydrogenation product tower (82) after being reboiled in the tenth reboiler (83), and the other part is discharged. The gas phase obtained from the hydrogenation product tower (82) is condensed from the top of the tower by the ninth condenser (84) and then enters the eighth storage tank (85), and then enters the twenty-fifth pump (86). Part of it is returned to the hydrogenation product tower (82), and the other part is discharged. The hydrogenation product tower (82) has a top temperature of 135-145℃, a pressure of 1-3kPa, and a bottom temperature of 240-280℃.

6. The method for continuous production of 1,4-cyclohexanediethanol according to claim 1, characterized in that, In step one, one or more of the following characteristics are present: The hydrogen bond acceptor is one of tetrabutylammonium bromide, tetrabutylammonium chloride, choline chloride, and tetraoctylammonium chloride, and the hydrogen bond donor is one of urea, ethylene glycol, glycerol, lactic acid, imidazole, ethanolamine, diethanolamine, and triethanolamine. The amount of the eutectic ionic liquid catalyst used is 0.3 wt.%-5 wt.% of the amount of p-xylene. The molar ratio of liquid chlorine to p-xylene is 1:1 to 5:1; The chlorination reaction takes 0.5-2 hours; The temperature of the filter is controlled at 55-65℃; The filter cake is heated and melted at a temperature of 80-120℃.

7. The method for continuous production of 1,4-cyclohexanediethanol according to claim 1, characterized in that, In step two, one or more of the following characteristics are present: The alkaline solution is a NaOH aqueous solution or a KOH aqueous solution with a mass concentration of 10-40%; The mass of the alkaline solution is 1-5 times the mass of benzyl dichloroisocyanurate; The hydrolysis reaction takes 0.5-3 hours; The reaction products were cooled to below 30°C; The extractant is one of dichloromethane, chloroform, 1,2-dichloroethane, chlorobenzene, chlorotoluene, p-dichlorobenzene, o-dichlorobenzene, dibromomethane, and bromobenzene, and the mass of the extractant is 0.5-2 times the mass of p-dichlorobenzene.

8. The method for continuous production of 1,4-cyclohexanediethanol according to claim 1, characterized in that, In step three, one or more of the following characteristics are present: The molar ratio of hydrogen to terephthalic acid is 3-10:1; The heterogeneous hydrogenation catalyst consists of a support and an active component supported on the support. The support is one of ZrO2, ZnO, SiO2, Al2O3, SiO2-Al2O3, CeO2, and MgO. The active component is one of Ru, Pd, Pt, Rh, Ni, Co, and Cu. The mass content of the active component is 0.5-10%, and the mass content of the support is 90-99.5%. The mass hourly space velocity of the hydrogenation reaction is 1-10 h⁻¹. -1 .

9. A system suitable for the method of continuous production of 1,4-cyclohexanediethanol according to any one of claims 1-8, characterized in that, It includes chlorination units, hydrolysis units, and hydrogenation units; The chlorination unit includes a chlorination reactor (6); A filter (8) is installed downstream of the chlorination reactor (6) and connected to the chlorination reactor (6) via a pipe. A melting tank (11) is located downstream of the filter (8) and connected to the filter (8) via a pipe. A chlorination removal tower (13) is located downstream of the melting tank (11) and connected to the melting tank (11) via a pipeline. A chlorination tower (15) is located downstream of the chlorination tower (13) and connected to the chlorination tower (13) via a pipeline. The hydrolysis unit includes a hydrolysis reactor (28); An extraction tower (31) is located downstream of the hydrolysis reactor (28) and connected to the hydrolysis reactor (28) via a pipeline. An extractant recovery tower (39) is located downstream of the extraction tower (31) and connected to the extraction tower (31) via a pipeline. A hydrolysis light tower (42) is located downstream of the extractant recovery tower (39) and connected to the extractant recovery tower (39) via a pipeline. A water-decomposing heavy tower (48) is located downstream of the water-decomposing light tower (42) and connected to the water-decomposing light tower (42) via a pipe. A hydrolysis product tower (54) is located downstream of the hydrolysis decomposition tower (48) and connected to the hydrolysis decomposition tower (48) via a pipeline. The hydrogenation unit includes a hydrogenation reactor (66); A gas-liquid separator (67) is located downstream of the hydrogenation reactor (66) and is connected to the hydrogenation reactor (66) via a pipeline. Hydrotreating tower (70) is located downstream of gas-liquid separator (67) and connected to gas-liquid separator (67) via a pipeline. A hydrode-heavy tower (76) is located downstream of the hydrode-light tower (70) and connected to the hydrode-light tower (70) via a pipeline. Hydrogenation product tower (82) is located downstream of the hydrodeweighting tower (76) and is connected to the hydrodeweighting tower (76) via a pipeline.

10. The system according to claim 9, characterized in that, It possesses one or more of the following characteristics: The chlorination unit also includes a PX buffer tank (1), a liquid chlorine buffer tank (3), a first mixer (5), a first condenser (14), a first storage tank (15), and four pumps (16). The outlet of the PX buffer tank (1) is connected to the inlet of the first mixer (5) through a pipe, and a pump (2) is installed on the pipe connecting the PX buffer tank (1) and the first mixer (5). The inlet of the PX buffer tank (1) is connected to the filtrate outlet of the filter (8) through a pipe, and is also connected to the PX feed line. The inlet of the liquid chlorine buffer tank (3) is connected to the liquid chlorine feed line, and the outlet of the liquid chlorine buffer tank (3) is connected to the inlet of the first mixer (5) through a pipe. The feed inlet is connected, and two pumps (4) are installed on the pipeline connecting the liquid chlorine buffer tank (3) and the first mixer (5); the outlet of the first mixer (5) is connected to the feed inlet of the chlorination reactor (6) through a pipeline; the feed inlet of the first condenser (14) is connected to the light component outlet of the chlorination light removal tower (13) through a pipeline, the outlet of the first condenser (14) is connected to the feed inlet of the first storage tank (15) through a pipeline, the outlet of the first storage tank (15) is connected to the feed inlet of the four pumps (16) through a pipeline, and the outlet of the four pumps (16) is connected to the top of the chlorination light removal tower (13) and the feed inlet of the PX buffer tank (1) through pipelines respectively; The chlorination unit also includes an external heat exchanger (7) disposed outside the chlorination reactor (6). In the chlorination unit, a silo (9) and a conveyor (10) are sequentially installed along the pipeline connecting the filter (8) and the melting tank (11) from upstream to downstream. In the chlorination unit, three pumps (12) are installed on the pipeline connecting the melting tank (11) and the chlorination light removal tower (13). In the chlorination unit, a first reboiler (17) is provided outside the chlorination light removal tower (13), and five pumps (18) are provided on the pipeline connecting the chlorination light removal tower (13) and the chlorination heavy light tower (19). In the chlorination unit, a second reboiler (23) is provided outside the heavy and light chlorination tower (19). The chlorination unit also includes a second condenser (20), a second storage tank (21), and a six-pump (22). The inlet of the second condenser (20) is connected to the gas phase outlet of the chlorination de-heavy tower (19) through a pipeline. The outlet of the second condenser (20) is connected to the inlet of the second storage tank (21) through a pipeline. The outlet of the second storage tank (21) is connected to the inlet of the six-pump (22) through a pipeline. The outlet of the six-pump (22) is connected to the top of the chlorination de-heavy tower (19) through a pipeline and is also connected to the gas phase outlet pipeline of the chlorination de-heavy tower. The hydrolysis reactor (28) also includes a PXDC buffer tank (24) and an alkali buffer tank (26). The inlet of the PXDC buffer tank (24) is connected to the PXDC feed pipeline, and the outlet of the PXDC buffer tank (24) is connected to the inlet of the hydrolysis reactor (28) through a pipeline. Seven pumps (25) are provided on the pipeline connecting the PXDC buffer tank (24) and the hydrolysis reactor (28). The inlet of the alkali buffer tank (26) is connected to the alkali feed pipeline, and the outlet of the alkali buffer tank (26) is connected to the inlet of the hydrolysis reactor (28) through a pipeline. Eight pumps (27) are provided on the pipeline connecting the alkali buffer tank (26) and the hydrolysis reactor (28). In the hydrolysis unit, nine pumps (29) and a cooler (30) are sequentially installed on the pipeline connecting the hydrolysis reactor (28) and the extraction tower (31) from upstream to downstream. The hydrolysis unit also includes an extractant buffer tank (32), a wastewater stripping tower (35), and a third condenser (37). The outlet of the extractant buffer tank (32) is connected to the inlet of the extraction tower (31) via a pipeline, and a ten-pump pump (33) is installed on the pipeline connecting the extractant buffer tank (32) and the extraction tower (31). The inlet of the extractant buffer tank (32) is connected to the extractant feed pipeline and is connected to the third condenser (37) via a pipeline. The outlet is connected, and the inlet of the third condenser (37) is connected to the gas phase outlet of the wastewater stripping tower (35) and the gas phase outlet of the extractant recovery tower (39) through pipelines respectively. The inlet of the wastewater stripping tower (35) is connected to the gas phase outlet of the extraction tower (31). Eleven pumps (34) are provided on the pipeline connecting the extraction tower (31) and the wastewater stripping tower (35). A third reboiler (36) is provided outside the wastewater stripping tower (35). In the hydrolysis unit, twelve pumps (38) are installed on the pipeline connecting the extraction tower (31) and the extractant recovery tower (39). In the hydrolysis unit, a fourth reboiler (40) is provided outside the extractant recovery tower (39), and a thirteen pump (41) is provided on the pipeline connecting the extractant recovery tower (39) and the hydrolysis delight tower (42). In the hydrolysis unit, a fifth reboiler (43) is provided outside the hydrolysis light tower (42), and fifteen pumps (47) are provided on the pipeline connecting the hydrolysis light tower (42) and the hydrolysis heavy tower (48). The hydrolysis unit also includes a fourth condenser (44), a third storage tank (45), and a fourteenth pump (46). The inlet of the fourth condenser (44) is connected to the gas phase outlet of the hydrolysis light tower (42) through a pipeline. The outlet of the fourth condenser (44) is connected to the inlet of the third storage tank (45) through a pipeline. The outlet of the third storage tank (45) is connected to the inlet of the fourteenth pump (46) through a pipeline. The outlet of the fourteenth pump (46) is connected to the top of the hydrolysis light tower (42) through a pipeline and is also connected to the gas phase outlet pipeline of the hydrolysis light tower. In the hydrolysis unit, a sixth reboiler (49) is provided outside the hydrolysis decomposition tower (48). The hydrolysis unit also includes a fifth condenser (50), a fourth storage tank (51), and sixteen pumps (52). The inlet of the fifth condenser (50) is connected to the gas phase outlet of the hydrolysis deweighting tower (48) through a pipe. The outlet of the fifth condenser (50) is connected to the inlet of the fourth storage tank (51) through a pipe. The outlet of the fourth storage tank (51) is connected to the inlet of the sixteen pumps (52) through a pipe. The outlet of the sixteen pumps (52) is connected to the top of the hydrolysis deweighting tower (48) and the inlet of the hydrolysis product tower (54) through pipes respectively. Seventeen pumps (53) are provided on the pipe connecting the hydrolysis deweighting tower (48) and the hydrolysis product tower (54). In the hydrolysis unit, a seventh reboiler (55) is provided outside the hydrolysis decomposition tower (48). The hydrolysis unit also includes a sixth condenser (56), a fifth storage tank (57), and an eighteenth pump (58). The inlet of the sixth condenser (56) is connected to the gas phase outlet of the hydrolysis product tower (54) through a pipeline. The outlet of the sixth condenser (56) is connected to the inlet of the fifth storage tank (57) through a pipeline. The outlet of the fifth storage tank (57) is connected to the inlet of the eighteenth pump (58) through a pipeline. The outlet of the eighteenth pump (58) is connected to the top of the hydrolysis product tower (54) through a pipeline and is also connected to the gas phase outlet pipeline of the hydrolysis product tower. The hydrogenation unit further includes a BDM buffer tank (59), a hydrogen buffer tank (61), a second mixer (62), a second heat exchanger (63), a first heat exchanger (64), a heater (65), and a compressor (68); the inlet of the BDM buffer tank (59) is connected to the BDM feed pipeline, and the outlet of the BDM buffer tank (59) is connected to the inlet of the second mixer (62) through a pipeline. Nineteen pumps (60) are installed on the pipeline connecting the BDM buffer tank (59) and the second mixer (62). The inlet of the hydrogen buffer tank (61) is connected to the hydrogen feed pipeline, and the outlet of the hydrogen buffer tank (61) is connected to the inlet of the second mixer (62) through a pipeline. The outlet of the second mixer (62) is connected to the first inlet of the first heater (64) through a pipeline. The first outlet of the heater (64) is connected to the inlet of the heater (65) through a pipe. The outlet of the heater (65) is connected to the inlet of the hydrogenation reactor (66) through a pipe. The second inlet of the first heat exchanger (64) is connected to the outlet of the hydrogenation reactor (66) through a pipe. The second outlet of the first heat exchanger (64) is connected to the first inlet of the second heat exchanger (63). The first outlet of the second heat exchanger (63) is connected to the inlet of the gas-liquid separator (67) through a pipe. The second inlet and second outlet of the second heat exchanger (63) are connected to the cold water inlet pipe and the hot water outlet pipe, respectively. The inlet of the compressor (68) is connected to the gas phase outlet of the gas-liquid separator (67) through a pipe. The outlet of the compressor (68) is connected to the inlet of the hydrogen buffer tank (61) through a pipe. In the hydrogenation unit, twenty pumps (69) are installed on the pipeline connecting the gas-liquid separator (67) and the hydrogenation light removal tower (70). In the hydrogenation unit, an eighth reboiler (71) is provided outside the hydrogenation light removal tower (70), and twenty-two pumps (75) are provided on the pipeline connecting the hydrogenation light removal tower (70) and the hydrogenation heavy removal tower (76). The hydrogenation unit also includes a seventh condenser (72), a sixth storage tank (73), and a twenty-one pump (74). The inlet of the seventh condenser (72) is connected to the gas phase outlet of the hydrodelighting tower (70) through a pipeline. The outlet of the seventh condenser (72) is connected to the inlet of the sixth storage tank (73) through a pipeline. The outlet of the sixth storage tank (73) is connected to the inlet of the twenty-one pump (74) through a pipeline and is also connected to the outlet pipeline of the sixth storage tank. The outlet of the twenty-one pump (74) is connected to the top of the hydrodelighting tower (70) through a pipeline and is also connected to the gas phase outlet pipeline of the hydrodelighting tower. In the hydrogenation unit, a ninth reboiler (77) is provided outside the hydrogenation deweight tower (76). The hydrogenation unit also includes an eighth condenser (78), a seventh storage tank (79), and twenty-three pumps (80). The inlet of the eighth condenser (78) is connected to the gas phase outlet of the hydrodeweighting tower (76) through a pipeline. The outlet of the eighth condenser (78) is connected to the inlet of the seventh storage tank (79) through a pipeline. The outlet of the seventh storage tank (79) is connected to the inlet of the twenty-three pumps (80) through a pipeline. The outlet of the twenty-three pumps (80) is connected to the top of the hydrodeweighting tower (76) and the inlet of the hydrogenation product tower (54) through pipelines respectively. Twenty-four pumps (81) are provided on the pipeline connecting the hydrodeweighting tower (76) and the hydrogenation product tower (82). In the hydrogenation unit, a tenth reboiler (83) is provided outside the hydrogenation product tower (82). The hydrogenation unit also includes a ninth condenser (84), an eighth storage tank (85), and a twenty-five pump (86). The inlet of the ninth condenser (84) is connected to the gas phase outlet of the hydrogenation product tower (54) through a pipeline. The outlet of the ninth condenser (84) is connected to the inlet of the eighth storage tank (85) through a pipeline. The outlet of the eighth storage tank (85) is connected to the inlet of the twenty-five pump (86) through a pipeline. The outlet of the twenty-five pump (86) is connected to the top of the hydrogenation product tower (82) through a pipeline and is also connected to the gas phase outlet pipeline of the hydrogenation product tower.

Images