System and method for preparing dimethyl 1, 4-cyclohexanedicarboxylate

Abstract

The invention provides a system and a method for preparing dimethyl 1, 4-cyclohexane dicarboxylate. The system comprises a first feeding pipeline, a second feeding pipeline and a hydrogenation reactor, the first feeding pipeline is communicated with the hydrogenation reactor through the bottom of the hydrogenation reactor; a reinforced mass transfer device is arranged in the hydrogenation reactor, microbubble outlets are formed in the upper end and the lower end of the reinforced mass transfer device, and the number of the microbubble outlets in the upper end is smaller than that of the microbubble outlets in the lower end; the second feeding pipeline is connected with the enhanced mass transfer device; the hydrogenation reactor is a slurry bed reactor, a material outlet of the hydrogenation reactor is higher than the reinforced mass transfer device in the vertical direction, and the material outlet is lower than the liquid level in the hydrogenation reactor in the vertical direction; a baffle is arranged in the hydrogenation reactor close to the material outlet, and the top of the baffle is located between the material outlet and the liquid level of the hydrogenation reactor in the vertical direction; the bottoms of the baffles are obliquely arranged close to the side wall of the hydrogenation reactor. The system can effectively increase the phase boundary mass transfer area of the gas phase and the liquid phase.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of dimethyl 1,4 - cyclohexanedicarboxylate, and in particular, to a system and a method for preparing dimethyl 1,4 - cyclohexanedicarboxylate. Background Art

[0002] Dimethyl 1,4 - cyclohexanedicarboxylate is an important chemical intermediate. It can be used as a raw material for polyester resins to produce high - performance fibers, films, and engineering plastics. It is also an intermediate for the preparation of 1,4 - cyclohexanedimethanol, which has extremely high application value and is an excellent monomer for producing high - value - added polyester materials. In the coatings and resin industries, dimethyl 1,4 - cyclohexanedicarboxylate, as a modifier and solvent, can enhance the adhesion, weather resistance, and gloss of coatings, and is widely used in fields such as architectural coatings, automotive coatings, and wood coatings. In addition, dimethyl 1,4 - cyclohexanedicarboxylate also plays a key role in resin production, being able to improve the toughness and chemical resistance of resins and being suitable for the production of products such as plastic modification, adhesives, and sealants. Dimethyl 1,4 - cyclohexanedicarboxylate can also be used as an intermediate for synthetic fragrances to manufacture various types of floral, fruity, and woody fragrances. These fragrances are widely used in fields such as daily chemicals, food, and cosmetics, providing consumers with a rich choice of aromas.

[0003] Dimethyl 1,4 - cyclohexanedicarboxylate is mainly prepared by hydrogenating dimethyl terephthalate. In the existing hydrogenation reactor, hydrogen gas enters the reactor through a bottom distributor for initial distribution by bubbling. The bubble diameter is relatively large, the phase - boundary area between the gas and liquid phases is relatively small, and the initially distributed bubbles are prone to coalescence and enlargement during the upward process, resulting in low gas - liquid mass transfer efficiency and reaction rate.

[0004] In view of this, the present invention is specifically proposed. Summary of the Invention

[0005] The first object of the present invention is to provide a system for preparing dimethyl 1,4 - cyclohexanedicarboxylate. By using a slurry - bed reactor for hydrogenation reaction and arranging a mass - transfer intensifier in the hydrogenation reactor, the phase - boundary mass - transfer area between the gas and liquid phases can be effectively increased, thereby contributing to increasing the gas - liquid mass transfer efficiency and reaction rate.

[0006] The second object of the present invention is to provide a method for preparing dimethyl 1,4 - cyclohexanedicarboxylate. This method uses the above - mentioned system to prepare dimethyl 1,4 - cyclohexanedicarboxylate, with high preparation efficiency and capable of realizing the high - efficient production of dimethyl 1,4 - cyclohexanedicarboxylate.

[0007] In order to achieve the above objects of the present invention, the following technical solutions are specifically adopted: The present invention provides a system for preparing dimethyl 1,4 - cyclohexanedicarboxylate, comprising: a first feed pipeline, a second feed pipeline, and a hydrogenation reactor; The first feed pipeline is used to transport dimethyl terephthalate, methanol, and a solid catalyst, and the first feed pipeline communicates with the hydrogenation reactor via the bottom of the hydrogenation reactor; The second feed pipeline is used to transport hydrogen. An enhanced mass transfer device is arranged in the hydrogenation reactor. Microbubble outlets are arranged at both the upper and lower ends of the enhanced mass transfer device, and the number of microbubble outlets at the upper end is less than that at the lower end; the second feed pipeline is connected to the enhanced mass transfer device; The hydrogenation reactor is a slurry bed reactor. The material outlet of the hydrogenation reactor is higher than the enhanced mass transfer device in the vertical direction and lower than the liquid level in the hydrogenation reactor in the vertical direction; A baffle is arranged in the hydrogenation reactor near the material outlet. The top of the baffle is located between the material outlet and the liquid level of the hydrogenation reactor in the vertical direction; the bottom of the baffle is inclined in the direction close to the side wall of the hydrogenation reactor, and there is a gap between the bottom of the baffle and the side wall of the hydrogenation reactor; a settling tank is formed between the baffle and the side wall where the material outlet is located.

[0008] In the above solution, dimethyl terephthalate, methanol, and a solid catalyst are mixed in the first feed pipeline. This method can make the solid catalyst evenly distributed in the hydrogenation reactor, which helps to better play the catalytic role; by using a slurry bed reactor as the hydrogenation reactor, the hydrogenation reaction catalyst can be replaced in real time during the production process. Thus, the problem of stopping the vehicle to replace the catalyst in the prior art is solved; by arranging an enhanced mass transfer device in the hydrogenation reactor, hydrogen can be dispersed and broken into microbubbles in the micron level, so as to increase the gas - liquid mass transfer area and the gas - liquid mass transfer efficiency, and further help to increase the reaction rate. Moreover, this method can reduce the requirements for temperature and pressure of the hydrogenation reaction to a certain extent, thus helping to reduce the reaction energy consumption; the enhanced mass transfer device of this solution adopts a flared structure with more outlets at one end and fewer outlets at the other end, so that the output microbubbles can be more reasonably distributed in the hydrogenation reactor and the mixing of the solid catalyst in the liquid phase can be enhanced; by arranging a baffle near the material outlet in the hydrogenation reactor, an internal settling tank can be formed between the baffle and the side wall of the hydrogenation reactor. The reaction liquid in the hydrogenation reactor flows into this settling tank for sedimentation. The supernatant is output through the material outlet, and the lower turbid liquid flows back into the hydrogenation reactor through the bottom of the settling tank to continue participating in the reaction. Thus, the purity of the product output through the material outlet and the utilization rate of the catalyst can be improved, which helps to save costs.

[0009] Preferably, the number of the mass transfer intensifiers is two, and the second feed pipeline is respectively connected to the two mass transfer intensifiers; one of the two mass transfer intensifiers is located above the other mass transfer intensifier in the vertical direction, and the two mass transfer intensifiers are staggeredly arranged in the vertical direction.

[0010] In the above solution, the two mass transfer intensifiers are staggeredly arranged in the vertical direction, so that the lower outlet of the upper mass transfer intensifier and the upper outlet of the lower mass transfer intensifier are staggered with each other. This arrangement can avoid the collision of two microbubble flows and cause liquid dead zones, and can use the microbubbles ejected by the two mass transfer intensifiers to stir the reaction liquid in the hydrogenation reactor. On the one hand, this can make the microbubbles evenly distributed, further increase the mass transfer area and the contact area between reaction raw materials, and improve the reaction efficiency. On the other hand, it can ensure the uniform distribution of the catalyst in the reaction liquid by stirring the reaction liquid, and ensure the catalytic effect of the catalyst, which helps to further improve the reaction efficiency of the hydrogenation reaction.

[0011] Preferably, the system further includes a first circulation pipeline; the inlet and outlet of the first circulation pipeline are both connected to the side wall of the hydrogenation reactor, and the inlet of the first circulation pipeline is located below the two mass transfer intensifiers in the vertical direction, and the outlet of the first circulation pipeline is located above the two mass transfer intensifiers.

[0012] In the above solution, by setting the first circulation pipeline, the solid catalyst deposited at the bottom of the hydrogenation reactor can be pumped into the upper middle part of the hydrogenation reactor via the first circulation pipeline, so that the solid catalyst can continue to participate in the reaction; and this way can play a role in stirring the reaction liquid at the bottom of the hydrogenation reactor in the vertical direction, and prevent the deposition of solid catalyst to a certain extent; in short, by setting the first circulation pipeline, the catalytic effect and utilization rate of the solid catalyst can be improved.

[0013] Preferably, the system further includes a second circulation pipeline; the inlet and outlet of the second circulation pipeline are both connected to the side wall of the hydrogenation reactor, and the inlet of the second circulation pipeline is lower than the bottom of the baffle in the vertical direction, and the outlet of the second circulation pipeline is located between the two mass transfer intensifiers in the vertical direction.

[0014] In the above solution, the lower turbid liquid settled at the bottom of the sedimentation tank can be directly input between the two mass transfer intensifiers via the second circulation pipeline, and is uniformly dispersed by the stirring of the microbubble flow of the two mass transfer intensifiers, which helps to further improve the utilization rate and catalytic effect of the catalyst.

[0015] Preferably, a plurality of partition plates are arranged in the hydrogenation reactor, the plurality of partition plates are arranged staggeredly, and the plurality of partition plates are all located between the baffle plate and the mass transfer intensifier in the vertical direction. Preferably, the partition plates are arranged obliquely downward in a direction away from the side wall of the hydrogenation reactor. By arranging a plurality of partition plates staggeredly, the flow velocity of the upper reaction liquid can be reduced, the sedimentation of the solid catalyst in the reaction liquid can be promoted, and thus the purity of the product output from the material outlet can be reduced. In a further solution, by arranging the partition plates obliquely downward, the sedimented solid catalyst can flow back into the reaction liquid below along the partition plates, avoiding the accumulation of the sedimented solid catalyst on the partition plates.

[0016] Preferably, a ring-shaped agitator is arranged at the bottom of the hydrogenation reactor; the ring-shaped agitator includes a ring-shaped pipe and a plurality of nozzles arranged in an array below the ring-shaped pipe; the plurality of nozzles are arranged obliquely downward; the first feed pipeline is connected to the ring-shaped pipe. The plurality of nozzles of the ring-shaped agitator spray the solid-liquid mixture in the first feed pipeline into the hydrogenation reactor, which can play a role in disturbing and stirring the reaction liquid in the hydrogenation reactor. On the one hand, it is beneficial to quickly mix the solid-liquid mixture with the reaction liquid and make the solid catalyst evenly distributed; on the other hand, it can avoid the deposition of the solid catalyst at the bottom of the hydrogenation reactor by stirring the reaction liquid at the bottom of the hydrogenation reactor, thereby further promoting the uniform distribution of the solid catalyst in the reaction liquid; at the same time, the ring-shaped agitator mainly stirs the reaction liquid at the bottom of the hydrogenation reactor in the horizontal direction, while the first circulation pipeline mainly plays a stirring role in the vertical direction, and the combination of the two can further improve the uniform distribution degree of the solid catalyst.

[0017] Preferably, the system further includes a sedimentation tank and a filter, the material outlet is connected to the sedimentation tank, the lower turbid liquid outlet of the sedimentation tank is connected to the filter, and the filter residue outlet of the filter is connected to the first feed pipeline; preferably, the number of filters is two, and the two filters are arranged in parallel. The reacted material enters the sedimentation tank through the material outlet, undergoes sedimentation in the sedimentation tank, and the lower turbid liquid therein enters the filter for filtration and separation, and the separated solid catalyst returns to the first feed pipeline through the filter residue outlet. In a further solution, the number of filters is set to two, and the two filters can adopt an open-close application mode to avoid stopping the vehicle due to cleaning the filter, which helps to increase the production efficiency.

[0018] Preferably, an arc-shaped filter cloth is provided inside the filter; the arc-shaped filter cloth divides the inner chamber of the filter into a filtration chamber and a filtrate chamber, and the filter residue outlet of the filter is arranged on the side wall of the filtration chamber; preferably, a guiding plate is provided at the inlet of the filter, and the guiding plate extends obliquely downward along the direction close to the arc-shaped filter cloth. In this solution, the filter cloth of the filter adopts a 1 / 4 circular arc design, which is more conducive to the recovery of solid catalysts and can effectively prevent the solid catalysts from clogging on the filter cloth; in a further solution, a guiding plate is provided inside the filter, and the guiding plate can play a guiding and buffering role, which can avoid the direct impact of the lower turbid liquid entering the filter on the arc-shaped filter cloth and ensure the filtration effect of the arc-shaped filter cloth.

[0019] Preferably, the system further includes a first distillation column and a second distillation column. The supernatant outlet of the sedimentation tank and the filtrate outlet of the filter are both connected to the first distillation column; the bottom outlet of the first distillation column is connected to the second distillation column, and the top outlet is connected to the first feed pipeline; the top outlet of the second distillation column is used to output the product, and the bottom outlet is connected to the first feed pipeline. The supernatant obtained from the sedimentation tank and the filtrate obtained from the filter enter the first distillation column for distillation. The methanol distilled from the top of the first distillation column returns to the first feed pipeline, and the bottom material flows into the second distillation column; the target product dimethyl 1,4-cyclohexanedicarboxylate is produced at the top of the second distillation column, and dimethyl terephthalate is produced at the bottom and input into the first feed pipeline to continue to participate in the reaction. This solution can effectively improve the product purity through two distillation treatments.

[0020] Those skilled in the art can understand that the enhanced mass transfer device used in the present invention has been embodied in the inventor's prior patents, such as patents with application numbers CN201610641119.6, CN201610641251.7, CN201710766435.0, CN106187660A, CN105903425A, CN205833127U and CN207581700U. The prior patent CN201610641119.6 describes in detail the specific product structure and working principle of the micron bubble generator (i.e., bubble breaker). The application document states that "the micron bubble generator includes a main body and a secondary crushing member, a cavity is provided in the main body, an inlet connected to the cavity is provided on the main body, the first and second opposite ends of the cavity are open, wherein the cross-sectional area of ​​the cavity decreases from the middle of the cavity to the first and second ends of the cavity; the secondary crushing member is provided at at least one of the first and second ends of the cavity, a part of the secondary crushing member is provided in the cavity, and an annular channel is formed between the secondary crushing member and the through holes open at both ends of the cavity. The micron bubble generator also includes an air inlet pipe and a liquid inlet pipe." From the specific structure disclosed in the application document, it can be known that its specific working principle is: the liquid enters the micron bubble generator tangentially through the liquid inlet pipe, rotates at ultra-high speed and cuts the gas, so that the gas bubbles are broken into micron-level microbubbles, thereby increasing the mass transfer area between the liquid phase and the gas phase, and the micron bubble generator in the patent is a pneumatic bubble breaker.

[0021] In addition, the prior patent 201610641251.7 records that the primary bubble breaker has a circulating liquid inlet, a circulating gas inlet and a gas-liquid mixture outlet, and the secondary bubble breaker connects the feed port with the gas-liquid mixture outlet, indicating that the bubble breaker requires gas-liquid mixture to enter. In addition, it can be seen from the following figures that the primary bubble breaker mainly uses circulating liquid as power, so the primary bubble breaker actually belongs to a hydraulic enhanced reactor, and the secondary bubble breaker simultaneously passes the gas-liquid mixture into an elliptical rotating ball for rotation, thereby achieving bubble breaking during the rotation process, so the secondary bubble breaker actually belongs to a gas-liquid linkage bubble breaker. In fact, whether it is a hydraulic bubble breaker or a gas-liquid linkage bubble breaker, it is a specific form of bubble breaker. However, the enhanced mass transfer device adopted by the present invention is not limited to the above-mentioned forms. The specific structure of the bubble breaker recorded in the prior patent is only one of the forms that can be adopted by the present invention.

[0022] In addition, it is recorded in the prior patent 201710766435.0 that "the principle of the bubble breaker is to achieve gas mutual collision by means of high-speed jet flow"; moreover, the prior patent CN106187660 also has relevant records on the specific structure of the bubble breaker. Specifically, see paragraphs

[0031] -

[0041] in the specification and the attached drawings. It elaborates in detail on the specific working principle of the bubble breaker S-2. The top of the bubble breaker is the liquid-phase inlet, and the side is the gas-phase inlet. The liquid phase entering from the top provides the entrainment power, thereby achieving the effect of being crushed into ultrafine bubbles. It can also be seen from the attached drawings that the bubble breaker has a conical structure, with the diameter of the upper part larger than that of the lower part, which is also to enable the liquid phase to better provide the entrainment power.

[0023] Since in the initial stage of the prior patent application, the bubble breaker had just been developed, it was early named the microbubble generator (CN201610641119.6), etc. With continuous technological improvement, it was later renamed the bubble breaker. Now, the mass transfer intensifier in the present invention is equivalent to the previous microbubble generator, microinterface generator, etc., only with different names. In summary, the mass transfer intensifiers of the present invention themselves all belong to the prior art.

[0024] The present invention also provides a method for preparing dimethyl 1,4-cyclohexanedicarboxylate. This method uses the system of any of the above embodiments to prepare dimethyl 1,4-cyclohexanedicarboxylate.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Dimethyl terephthalate, methanol and a solid catalyst are mixed in the first feed pipeline. This way can make the solid catalyst evenly distributed in the hydrogenation reactor, which helps to better play the catalytic role; 2. By using a slurry bed reactor as the hydrogenation reactor, the hydrogenation reaction catalyst can be replaced in real time during the production process. Thus, the problem of needing to stop the machine to replace the catalyst in the prior art is solved; 3. By arranging a mass transfer intensifier in the hydrogenation reactor, hydrogen can be dispersed and broken into microbubbles at the micron level, thereby increasing the gas-liquid mass transfer area, enhancing the gas-liquid mass transfer efficiency, and further helping to increase the reaction rate. And this way can, to a certain extent, reduce the requirements for temperature and pressure in the hydrogenation reaction, thus helping to reduce the reaction energy consumption; 4. The mass transfer intensifier of this solution adopts a flared structure with more outlets at one end and fewer outlets at the other end, which can make the output microbubbles more reasonably distributed in the hydrogenation reactor; 5. By arranging a baffle near the material outlet in the hydrogenation reactor, an internal settling tank can be formed between the baffle and the side wall of the hydrogenation reactor. The reaction liquid in the hydrogenation reactor flows into this settling tank for sedimentation. The supernatant is output through the material outlet, and the lower turbid liquid flows back into the hydrogenation reactor through the bottom of the settling tank to continue participating in the reaction. Thus, the purity of the product output from the material outlet and the utilization rate of the catalyst can be improved, which helps to save costs. Description of the Drawings

[0026] By reading the detailed description of the preferred embodiments below, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present invention. Moreover, throughout the drawings, the same reference numerals are used to represent the same components. In the drawings: Figure 1 A schematic diagram showing the system for preparing dimethyl 1,4 - cyclohexanedicarboxylate according to Embodiment 1 of the present invention; Figure 2 A schematic diagram showing the structure of the annular agitator according to Embodiment 1 of the present invention; Figure 3 A schematic diagram showing the structure of the filter according to Embodiment 1 of the present invention.

[0027] In the figure: 1, hydrogenation reactor; 2, partition board; 3, mass transfer intensifier; 4, second feed pipeline; 5, first circulation pipeline; 6, annular agitator; 601, annular pipe; 602, nozzle; 7, first feed pipeline; 8, baffle; 9, second circulation pipeline; 10, sedimentation tank; 11, filter; 12, first distillation column; 13, second distillation column; 14, arc - shaped filter cloth; 15, guiding plate. Detailed Embodiments

[0028] The technical solutions of the present invention will be clearly and completely described below in conjunction with the drawings and specific embodiments. However, those skilled in the art will understand that the following described embodiments are some embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present invention. Those not specified in the embodiments are carried out under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments not specified by the manufacturer are all conventional products that can be obtained through commercial purchase.

[0029] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0030] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0031] In order to more clearly illustrate the technical solutions in the present invention, the following will be described in the form of specific embodiments.

[0032] Embodiment 1 With reference to Figures 1 - 3 , this embodiment provides a system for preparing dimethyl 1,4 - cyclohexanedicarboxylate. The system includes: a first feed pipeline 7, a second feed pipeline 4, and a hydrogenation reactor 1; the first feed pipeline 7 is used to transport dimethyl terephthalate, methanol, and a solid catalyst, and the first feed pipeline 7 communicates with the hydrogenation reactor 1 through the bottom of the hydrogenation reactor 1; the second feed pipeline 4 is used to transport hydrogen, and an enhanced mass transfer device 3 is arranged in the hydrogenation reactor 1. Microbubble outlets are arranged at both the upper and lower ends of the enhanced mass transfer device 3, and the number of microbubble outlets at the upper end is less than that at the lower end; the second feed pipeline 4 is connected to the enhanced mass transfer device 3; the hydrogenation reactor 1 is a slurry bed reactor, and the material outlet of the hydrogenation reactor 1 is higher than the enhanced mass transfer device 3 in the vertical direction and lower than the liquid level in the hydrogenation reactor 1 in the vertical direction; a baffle 8 is arranged near the material outlet in the hydrogenation reactor 1, and the top of the baffle 8 is located between the material outlet and the liquid level of the hydrogenation reactor 1 in the vertical direction; the bottom of the baffle 8 is inclined along the direction close to the side wall of the hydrogenation reactor 1, and there is a gap between the bottom of the baffle 8 and the side wall of the hydrogenation reactor 1; a sedimentation tank is formed between the baffle 8 and the side wall where the material outlet is located.

[0033] In the solution of this embodiment, dimethyl terephthalate, methanol and a solid catalyst can be pre-mixed and then input into the hydrogenation reactor 1 via the first feed pipeline 7. The solid catalyst can be a powdery ruthenium-rhenium catalyst, which can be prepared by the equal-volume impregnation method. The total loading of ruthenium and rhenium bimetals is 0.3%-5%, and the carrier is one of activated carbon, carbon black, carbon nanotubes, and carbon nanofibers.

[0034] It can be understood that in order to ensure the flow of materials in each pipeline, a water pump can be set on the pipeline, which will not be elaborated here.

[0035] According to the above description, the number of microbubble outlets at the upper end of the mass transfer intensifier 3 adopted in this embodiment is less than the number of microbubble outlets at the lower end. In this embodiment, the vertical length ratio of the mass transfer intensifier 3 is 5:2.

[0036] In this embodiment, a settling tank is formed between the baffle 8 and the side wall where the material outlet is located. The volume of the settling tank can be 1 / 20 - 1 / 10 of the volume of the hydrogenation reactor 1, the height is 1 / 5 - 3 / 5 of the height of the hydrogenation reactor 1, the width is 1 / 10 - 1 / 5 of the hydrogenation reactor 1, and the height of the lower turbid liquid is 1 / 10 - 1 / 5 of the height of the tank.

[0037] As Figure 1 shown, in this embodiment, the number of mass transfer intensifiers 3 is two, and the second feed pipeline 4 is respectively connected to the two mass transfer intensifiers 3; one of the two mass transfer intensifiers 3 is located above the other mass transfer intensifier 3 in the vertical direction, and the two mass transfer intensifiers 3 are staggered in the vertical direction. The lower outlet of the upper mass transfer intensifier 3 can output a microbubble flow downward, and the upper outlet of the lower mass transfer intensifier 3 can output a microbubble flow upward. Since the two microbubble flows are staggered in the vertical direction, a counterclockwise stirring force can be generated between the two mass transfer intensifiers 3 by the two microbubble flows.

[0038] Continue to refer to Figure 1 , in this embodiment, the system further includes a first circulation pipeline 5; both the inlet and outlet of the first circulation pipeline 5 are connected to the side wall of the hydrogenation reactor 1, and the inlet of the first circulation pipeline 5 is located below the two mass transfer intensifiers 3 in the vertical direction (that is, it is below the lower mass transfer intensifier 3 among the two mass transfer intensifiers 3), and the outlet of the first circulation pipeline 5 is located above the two mass transfer intensifiers 3 (that is, it is above the upper mass transfer intensifier 3 among the two mass transfer intensifiers 3). The reaction liquid at the bottom of the hydrogenation reactor 1 is pumped into the upper part of the two mass transfer intensifiers 3 via the first circulation pipeline 5.

[0039] Continue to refer to Figure 1, in this embodiment, the system further includes a second circulation pipeline 9; both the inlet and the outlet of the second circulation pipeline 9 are connected to the side wall of the hydrogenation reactor 1, and the inlet of the second circulation pipeline 9 is vertically lower than the bottom of the baffle 8, and the outlet of the second circulation pipeline 9 is vertically located between the two mass transfer intensifiers 3. The lower turbid liquid settled in the sedimentation tank is pumped into the space between the two mass transfer intensifiers 3 via the second circulation pipeline 9.

[0040] Continue to refer to Figure 1 , a plurality of partition plates 2 are arranged in the hydrogenation reactor 1, the plurality of partition plates 2 are arranged staggeredly, and the plurality of partition plates 2 are all located between the baffle 8 and the mass transfer intensifier 3 in the vertical direction. In this embodiment, the partition plate 2 is inclined downward in a direction away from the side wall of the hydrogenation reactor 1.

[0041] Refer to in combination Figure 1 、 2 , a ring-shaped agitator 6 is arranged at the bottom of the hydrogenation reactor 1; the ring-shaped agitator 6 includes a ring-shaped pipe 601 and a plurality of nozzles 602 arranged in an array below the ring-shaped pipe 601; the plurality of nozzles 602 are inclined downward; the first feed pipeline 7 is connected to the ring-shaped pipe 601.

[0042] In Figure 1 , the inlet of the first circulation pipeline 5 is located above the ring-shaped agitator 6, and the outlet is located below the partition plate 2. The inlet of the second circulation pipeline 9 is located above the partition plate 2.

[0043] In this embodiment, as Figure 1 shown, the system further includes a sedimentation tank 10, a filter 11, a first rectification column 12 and a second rectification column 13. The material outlet is connected to the sedimentation tank 10, the lower turbid liquid outlet of the sedimentation tank 10 is connected to the filter 11, and the filter residue outlet of the filter 11 is connected to the first feed pipeline 7; the supernatant outlet of the sedimentation tank 10 and the filtrate outlet of the filter 11 are both connected to the first rectification column 12; the bottom outlet of the first rectification column 12 is connected to the second rectification column 13, and the top outlet is connected to the first feed pipeline 7; the top outlet of the second rectification column 13 is used to output the product, and the bottom outlet is connected to the first feed pipeline 7. The reacted material enters the sedimentation tank 10 via the material outlet, is precipitated in the sedimentation tank 10, and the lower turbid liquid therein enters the filter 11 for filtration separation. The separated solid catalyst returns to the first feed pipeline 7 via the filter residue outlet. The supernatant obtained from the sedimentation tank 10 and the filtrate obtained from the filter 11 enter the first rectification column 12 for rectification. The methanol rectified from the top of the first rectification column 12 returns to the first feed pipeline 7, and the bottom material flows into the second rectification column 13; the target product dimethyl 1,4-cyclohexanedicarboxylate is produced at the top of the second rectification column 13, and dimethyl terephthalate is produced at the bottom and is input into the first feed pipeline 7 to continue to participate in the reaction.

[0044] In this embodiment, the number of filters 11 is two, and the two filters 11 are arranged in parallel. During actual use, the two filters 11 can adopt an on-off application mode to avoid stopping the machine for cleaning the filters 11, which helps to increase production efficiency.

[0045] Refer to Figure 3 , in this embodiment, an arc-shaped filter cloth 14 is arranged inside the filter 11; the arc-shaped filter cloth 14 divides the inner chamber of the filter 11 into a filtration chamber and a filtrate chamber, and the filter residue outlet of the filter 11 is arranged on the side wall of the filtration chamber; a guiding plate 15 is arranged at the inlet of the filter 11, and the guiding plate 15 extends obliquely downward along the direction close to the arc-shaped filter cloth 14. In this embodiment, the filter cloth of the filter 11 adopts a 1 / 4 circular arc design.

[0046] This embodiment also provides a method for preparing dimethyl 1,4-cyclohexanedicarboxylate. This method uses the above system to prepare dimethyl 1,4-cyclohexanedicarboxylate.

[0047] The specific steps of this method are as follows: First, load the powdered ruthenium-rhenium catalyst into the hydrogenation reactor 1, and introduce dimethyl terephthalate (dissolved in methanol) and hydrogen into the microinterface intensification unit of the hydrogenation reactor 1 at a molar ratio of 1:4 to form a microinterface system, and react at a reaction pressure of 1.0 MPa - 3.0 MPa and a reaction temperature of 30 °C - 100 °C for 1 - 2 hours to generate dimethyl 1,4-cyclohexanedicarboxylate. During the reaction, the powdered ruthenium-rhenium catalyst can be mixed into the first feed pipeline 7 as needed to supplement the catalyst in real time. The reacted material flows upward in the hydrogenation reactor 1 and flows into the sedimentation tank 10 from the top of the tower for sedimentation. The supernatant flows into the first distillation column 12, and the lower turbid liquid is separated by filtration. The filtered solid catalyst is returned to the hydrogenation reactor 1 for recycling, and the filtrate flows into the first distillation column 12. The methanol produced at the top of the first distillation column 12 is introduced into the hydrogenation reactor 1 for recycling, and the bottom material of the column is introduced into the second distillation column 13. The target product dimethyl 1,4-cyclohexanedicarboxylate is produced at the top of the second distillation column 13, and dimethyl terephthalate produced at the bottom of the column is introduced into the hydrogenation reactor 1 for recycling.

[0048] In this embodiment, the specific process for preparing dimethyl 1,4 - cyclohexanedicarboxylate is as follows: 1.0 kg / h of hydrogen is introduced into the enhanced mass transfer device of the hydrogenation reactor, and the feed temperature is controlled at about 40 °C. 24.3 kg / h of dimethyl terephthalate and 100.0 kg / h of methanol are introduced into the hydrogenation reactor via the first feed pipeline, and the feed temperature is controlled at about 30 °C. The slurry bed of the hydrogenation reactor is filled with powdered ruthenium - rhenium catalyst, the reaction pressure is 3.0 Mpa, and the reaction temperature is 100 °C. During the reaction, the catalyst can be replenished in real - time through the first feed pipeline. The reacted material flows upward in the hydrogenation reactor, flows into the sedimentation tank from the top of the tower for sedimentation, the supernatant flows into the first distillation column, the lower turbid liquid is separated by filtration, the filtered solid catalyst is returned to the hydrogenation reactor for recycling, and the filtrate flows into the first distillation column. The methanol produced at the top of the first distillation column is introduced into the hydrogenation reactor for recycling, and the bottom material of the column is introduced into the second distillation column. The target product, dimethyl 1,4 - cyclohexanedicarboxylate, is produced at the top of the second distillation column, and the dimethyl terephthalate produced at the bottom is introduced into the hydrogenation reactor for recycling. After the reaction, 24.2 kg / h of the target product, dimethyl 1,4 - cyclohexanedicarboxylate, is obtained, and the selectivity reaches 99.7%.

[0049] Example 2 The system used in this example is the same as that in Example 1. The specific process for preparing dimethyl 1,4 - cyclohexanedicarboxylate in this example is as follows: 1.0 kg / h of hydrogen is introduced into the micro - interface intensification unit of the hydrogenation reactor, and the feed temperature is controlled at about 40 °C. 24.3 kg / h of dimethyl terephthalate and 100.0 kg / h of methanol are introduced into the hydrogenation reactor from the bottom, and the feed temperature is controlled at about 30 °C. The slurry bed of the hydrogenation reactor is filled with powdered ruthenium - rhenium catalyst, the reaction pressure is 3.0 Mpa, and the reaction temperature is 65 °C. During the reaction, the catalyst can be replenished in real - time through the first feed pipeline. The reacted material flows upward in the hydrogenation reactor, flows into the sedimentation tank from the top of the tower for sedimentation, the supernatant flows into the first distillation column, the lower turbid liquid is separated by filtration, the filtered solid catalyst is returned to the hydrogenation reactor for recycling, and the filtrate flows into the first distillation column. The methanol produced at the top of the first distillation column is introduced into the hydrogenation reactor for recycling, and the bottom material of the column is introduced into the second distillation column. The target product, dimethyl 1,4 - cyclohexanedicarboxylate, is produced at the top of the second distillation column, and the dimethyl terephthalate produced at the bottom is introduced into the hydrogenation reactor for recycling. After the reaction, 23.7 kg / h of the target product, dimethyl 1,4 - cyclohexanedicarboxylate, is obtained, and the selectivity reaches 98.8%.

[0050] Example 3 The system used in this example is the same as that in Example 1. The specific process for preparing dimethyl 1,4-cyclohexanedicarboxylate in this example is as follows: 1.0 kg / h of hydrogen is introduced into the microinterface intensification unit of the hydrogenation reactor, and the feed temperature is controlled at about 40 °C. 24.3 kg / h of dimethyl terephthalate and 100.0 kg / h of methanol are introduced into the hydrogenation reactor from the bottom, and the feed temperature is controlled at about 30 °C. The slurry bed of the hydrogenation reactor is filled with powdered ruthenium-rhenium catalyst, the reaction pressure is 3.0 Mpa, and the reaction temperature is 30 °C. During the reaction, the catalyst can be replenished in real time through the first feed pipeline. The reacted material flows upward in the hydrogenation reactor, flows into the sedimentation tank from the top of the tower for sedimentation, the supernatant flows into the first distillation column, the lower turbid liquid is separated by filtration, the filtered solid catalyst is returned to the hydrogenation reactor for recycling, and the filtrate flows into the first distillation column. The methanol produced at the top of the first distillation column is introduced into the hydrogenation reactor for recycling, and the bottom material is introduced into the second distillation column. The target product, dimethyl 1,4-cyclohexanedicarboxylate, is produced at the top of the second distillation column, and dimethyl terephthalate produced at the bottom is introduced into the hydrogenation reactor for recycling. After the reaction, 21.5 kg / h of the target product, dimethyl 1,4-cyclohexanedicarboxylate, is obtained, and the selectivity reaches 95.5%.

[0051] Example 4 The system used in this example is the same as that in Example 1. The specific process for preparing dimethyl 1,4-cyclohexanedicarboxylate in this example is as follows: 1.0 kg / h of hydrogen is introduced into the microinterface intensification unit of the hydrogenation reactor, and the feed temperature is controlled at about 40 °C. 24.3 kg / h of dimethyl terephthalate and 100.0 kg / h of methanol are introduced into the hydrogenation reactor from the bottom, and the feed temperature is controlled at about 30 °C. The slurry bed of the hydrogenation reactor is filled with powdered ruthenium-rhenium catalyst, the reaction pressure is 2.0 Mpa, and the reaction temperature is 100 °C. During the reaction, the catalyst can be replenished in real time through the first feed pipeline. The reacted material flows upward in the hydrogenation reactor, flows into the sedimentation tank from the top of the tower for sedimentation, the supernatant flows into the first distillation column, the lower turbid liquid is separated by filtration, the filtered solid catalyst is returned to the hydrogenation reactor for recycling, and the filtrate flows into the first distillation column. The methanol produced at the top of the first distillation column is introduced into the hydrogenation reactor for recycling, and the bottom material is introduced into the second distillation column. The target product, dimethyl 1,4-cyclohexanedicarboxylate, is produced at the top of the second distillation column, and dimethyl terephthalate produced at the bottom is introduced into the hydrogenation reactor for recycling. After the reaction, 23.8 kg / h of the target product, dimethyl 1,4-cyclohexanedicarboxylate, is obtained, and the selectivity reaches 99.1%.

[0052] Example 5 The system used in this example is the same as that in Example 1. The specific process for preparing dimethyl 1,4-cyclohexanedicarboxylate in this example is as follows: 1.0 kg / h of hydrogen is introduced into the microinterface intensification unit of the hydrogenation reactor, and the feed temperature is controlled at about 40 °C. 24.3 kg / h of dimethyl terephthalate and 100.0 kg / h of methanol are introduced into the hydrogenation reactor from the bottom, and the feed temperature is controlled at about 30 °C. The slurry bed of the hydrogenation reactor is filled with powdered ruthenium-rhenium catalyst, the reaction pressure is 1.0 Mpa, and the reaction temperature is 100 °C. During the reaction, the catalyst can be replenished in real time through the first feed pipeline. The reacted material flows upward in the hydrogenation reactor and flows into the sedimentation tank from the top of the tower for sedimentation. The supernatant flows into the first distillation column, and the lower turbid liquid is separated by filtration. The filtered solid catalyst is returned to the hydrogenation reactor for recycling, and the filtrate flows into the first distillation column. The methanol produced at the top of the first distillation column is introduced into the hydrogenation reactor for recycling, and the bottom material of the column is introduced into the second distillation column. The target product, dimethyl 1,4-cyclohexanedicarboxylate, is produced at the top of the second distillation column, and dimethyl terephthalate produced at the bottom is introduced into the hydrogenation reactor for recycling. After the reaction, 23.1 kg / h of the target product, dimethyl 1,4-cyclohexanedicarboxylate, is obtained, and the selectivity reaches 97.6%.

[0053] Example 6 The difference between this example and Example 1 is only that no annular agitator is installed in the hydrogenation reactor, and the material in the first feed pipeline directly flows into the hydrogenation reactor through the bottom of the hydrogenation reactor. After the hydrogenation reaction, 23.1 kg / h of the target product, dimethyl 1,4-cyclohexanedicarboxylate, is obtained through distillation separation, and the selectivity is 98.5%.

[0054] Example 7 The difference between this example and Example 1 is only that one of the two mass transfer intensifiers is located directly above the other mass transfer intensifier in the vertical direction, and at this time, the lower outlet of the upper mass transfer intensifier is opposite to the upper outlet of the lower mass transfer intensifier. After the hydrogenation reaction, 20.3 kg / h of the target product, dimethyl 1,4-cyclohexanedicarboxylate, is obtained through distillation separation, and the selectivity is 94.3%.

[0055] Comparative Example 1 The difference between this example and Example 1 is only that no mass transfer intensifier is installed in the hydrogenation reactor. After the hydrogenation reaction, 15.1 kg / h of the target product, dimethyl 1,4-cyclohexanedicarboxylate, is obtained through distillation separation, and the selectivity is 75.5%.

[0056] Comparative Example 2 The difference between the system in this example and that in Example 1 is that no mass transfer intensifier is installed in the hydrogenation reactor. The specific process for preparing dimethyl 1,4-cyclohexanedicarboxylate in this example is as follows: 1.0 kg / h of hydrogen is introduced into the hydrogenation reactor (removing the micro-interface intensification unit), and the feed temperature is controlled at about 40°C. 24.3 kg / h of dimethyl terephthalate and 100.0 kg / h of methanol are introduced into the hydrogenation reactor from the bottom, and the feed temperature is controlled at about 30°C. The slurry bed of the hydrogenation reactor is filled with powdered ruthenium-rhenium catalyst, the reaction pressure is 5.0 Mpa, and the reaction temperature is 130°C. During the reaction, the catalyst can be replenished in real time through the first feed pipeline. The reacted material flows upward in the hydrogenation reactor and flows into the sedimentation tank from the top of the tower for sedimentation. The supernatant flows into the first distillation column, and the lower turbid liquid is separated by filtration. The filtered solid catalyst is returned to the hydrogenation reactor for recycling, and the filtrate flows into the first distillation column. The methanol produced at the top of the first distillation column is introduced into the hydrogenation reactor for recycling, and the bottom material of the column is introduced into the second distillation column. The target product, dimethyl 1,4-cyclohexanedicarboxylate, is produced at the top of the second distillation column, and dimethyl terephthalate produced at the bottom is introduced into the hydrogenation reactor for recycling. After the reaction, 17.5 kg / h of the target product, dimethyl 1,4-cyclohexanedicarboxylate, is obtained, and the selectivity reaches 82.3%.

[0057] According to Examples 1-7, it can be seen that the system of the present invention has high yield and high selectivity in the preparation of dimethyl 1,4-cyclohexanedicarboxylate. And based on the data of Examples 1-5 and Comparative Examples 1-2, the following conclusions can be drawn: Increasing the reaction temperature in the hydrogenation reaction can increase the solubility of dimethyl terephthalate in methanol. Therefore, increasing the temperature can increase the reaction rate of the hydrogenation of dimethyl terephthalate and improve the conversion rate of dimethyl terephthalate. However, increasing the temperature will cause a decrease in the solubility of hydrogen in the catalyst system, weaken the adsorption effect on the catalyst surface, and if the reaction temperature is too high, it will accelerate the growth of the catalyst crystals and accelerate the aging of the catalyst. Therefore, the reaction temperature should be controlled at 30°C - 100°C. The reaction conditions are relatively mild, which can effectively reduce energy consumption.

[0058] Comparing Example 1 and Example 6, it can be seen that the product yield and selectivity of Example 1 are both better than those of Example 6. This may be because the annular agitator in Example 1 can stir the bottom of the hydrogenation reactor, promote the uniform distribution of the catalyst, avoid catalyst sedimentation, thereby improving the catalytic effect of the catalyst, and further improving the product yield and selectivity.

[0059] Comparing Comparative Example 1 and Example 7, it can be seen that both the product yield and selectivity of Example 1 are better than those of Example 7. This may be because the outlets of the two mass transfer intensifiers in Example 7 are opposite to each other, resulting in a dead zone of the reaction liquid. In Example 1, the reaction liquid is agitated by staggering the outlets of the two mass transfer intensifiers. Therefore, the distribution uniformity of the catalyst and microbubbles in the reaction liquid in the hydrogenation reactor in Example 1 is better, and the reaction rate is fast, which leads to better yield and selectivity than those in Example 7.

[0060] Comparing Example 1, Comparative Example 1 and Comparative Example 2, it can be seen that both the product yield and selectivity in Example 1 are better than those in Comparative Example 1 and Comparative Example 2. This shows that by setting the mass transfer intensifier in the present invention, the interfacial mass transfer area between raw materials is increased, and the reaction rate is improved. This also proves that the use of the mass transfer intensifier can greatly improve the selectivity of dimethyl 1,4-cyclohexanedicarboxylate in the hydrogenation reaction, and has a significant effect on reaction intensification.

[0061] In summary, the system of the present invention can effectively increase the interfacial mass transfer area between gas-liquid phases by using a slurry bed reactor for hydrogenation reaction and setting a mass transfer intensifier in the hydrogenation reactor, thereby helping to increase the gas-liquid mass transfer efficiency and reaction rate.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A system for preparing dimethyl 1,4-cyclohexanedicarboxylate, characterized in that: include: A first feed pipeline, a second feed pipeline and a hydrogenation reactor; The first feed pipeline is used to transport dimethyl terephthalate, methanol and a solid catalyst, and the first feed pipeline is connected to the hydrogenation reactor via the bottom of the hydrogenation reactor; The second feed pipeline is used to transport hydrogen. An enhanced mass transfer device is provided in the hydrogenation reactor. Microbubble outlets are provided at both the upper and lower ends of the enhanced mass transfer device, and the number of microbubble outlets at the upper end is less than the number of microbubble outlets at the lower end. The second feed pipeline is connected to the enhanced mass transfer device. The hydrogenation reactor is a slurry bed reactor, the material outlet of the hydrogenation reactor is higher than the enhanced mass transfer device in the vertical direction, and the material outlet is lower than the liquid level in the hydrogenation reactor in the vertical direction; A baffle is arranged near the material outlet in the hydrogenation reactor, and the top of the baffle is located between the material outlet and the liquid surface of the hydrogenation reactor in the vertical direction; the bottom of the baffle is inclined in the direction close to the side wall of the hydrogenation reactor, and there is a gap between the bottom of the baffle and the side wall of the hydrogenation reactor; a sedimentation tank is formed between the baffle and the side wall where the material outlet is located.

2. The system according to claim 1, characterized in that There are two enhanced mass transferors, and the second feed pipeline is connected to the two enhanced mass transferors respectively; one of the two enhanced mass transferors is located above the other enhanced mass transferor in the vertical direction, and the two enhanced mass transferors are staggered in the vertical direction.

3. The system according to claim 2, characterized in that It also includes a first circulation pipeline; the inlet and outlet of the first circulation pipeline are both connected to the side wall of the hydrogenation reactor, and the inlet of the first circulation pipeline is located below the two enhanced mass transferors in the vertical direction, and the outlet of the first circulation pipeline is located above the two enhanced mass transferors.

4. The system according to claim 2, characterized in that It also includes a second circulation pipeline; the inlet and outlet of the second circulation pipeline are both connected to the side wall of the hydrogenation reactor, and the inlet of the second circulation pipeline is lower than the bottom of the baffle in the vertical direction, and the outlet of the second circulation pipeline is located between the two enhanced mass transfer devices in the vertical direction.

5. The system according to any one of claims 1 to 4, characterized in that: A plurality of partitions are arranged in the hydrogenation reactor, the plurality of partitions are arranged in a staggered manner, and the plurality of partitions are located between the baffle and the enhanced mass transfer device along the vertical direction.

6. The system according to any one of claims 1 to 4, characterized in that: An annular perturbator is arranged at the bottom of the hydrogenation reactor; the annular perturbator comprises an annular tube and a plurality of nozzles arranged in an array below the annular tube; the plurality of nozzles are arranged tilted downward; and the first feed pipeline is connected to the annular tube.

7. The system according to any one of claims 1 to 4, characterized in that: It also includes a sedimentation tank and a filter, wherein the material outlet is connected to the sedimentation tank, the lower turbid liquid outlet of the sedimentation tank is connected to the filter, and the filter residue outlet of the filter is connected to the first feed pipeline; Preferably, there are two filters, and the two filters are arranged in parallel.

8. The system according to claim 7, characterized in that The filter is provided with an arc-shaped filter cloth; the arc-shaped filter cloth divides the inner chamber of the filter into a filter chamber and a filtrate chamber, and the filter residue outlet of the filter is provided on the side wall of the filter chamber; Preferably, a guide plate is provided at the inlet of the filter, and the guide plate is extended obliquely downward in a direction close to the arc-shaped filter cloth.

9. The system according to claim 7, characterized in that It also includes a first distillation tower and a second distillation tower, the supernatant outlet of the sedimentation tank and the filtrate outlet of the filter are both connected to the first distillation tower; the bottom outlet of the first distillation tower is connected to the second distillation tower, and the top outlet is connected to the first feed pipeline; the top outlet of the second distillation tower is used to output products, and the bottom outlet is connected to the first feed pipeline.

10. A method for preparing dimethyl 1,4-cyclohexanedicarboxylate, characterized in that: Dimethyl 1,4-cyclohexanedicarboxylate is prepared using the system described in any one of claims 1 to 9.

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