Preparation method of high-purity trans-4-propionyl cyclohexylbenzene

Abstract

The invention discloses a preparation method of high-purity trans-4-propionyl cyclohexylbenzene, and belongs to the technical field of preparation of liquid crystal materials. According to the method, on the basis of dynamic cooperation of three-section gradient temperature control, seed crystal fractional addition and intermittent stirring, crystal growth is induced through ultralow-temperature circulating crystallization and precise temperature control in a single petroleum ether solvent system; and the continuous operation of low-temperature solid-liquid separation and vacuum drying is realized by combining a suction filtration and drying all-in-one machine designed in a matched manner. According to the method, the product purity and the yield stability are remarkably improved, high-purity crystals are obtained at a time, the problems that in a traditional process, impurity separation is not thorough, energy consumption is high and batch fluctuation is large are solved, meanwhile, the industrial mass production requirement is met, and a green and efficient high-purity preparation path is provided for liquid crystal intermediates.

Description

Technical Field

[0001] The present invention relates to the technical field of organic compound crystallization technology and liquid crystal material preparation, and particularly relates to a method for preparing a key raw material of a liquid crystal intermediate, trans-4-(4-n-propylcyclohexyl)phenol, and specifically relates to a method for preparing high-purity trans-4-propionylcyclohexylbenzene. Background Art

[0002] Trans-4-propionylcyclohexylbenzene (3OP), a core intermediate in the synthesis of liquid crystal materials, has a purity that directly determines the performance of downstream products. Currently, the industry uses a one-step synthesis method involving propionyl chloride, cyclohexene, and benzene catalyzed by aluminum trichloride. The resulting crude product contains significantly insufficient effective 3OP and is contaminated with various cis-isomers, unreacted raw materials, and polysubstituted byproducts. Direct use of this low-purity crude product in subsequent reactions not only results in low raw material utilization and increased energy consumption, but can also cause equipment failure due to impurity deposition.

[0003] Although the existing ultra-low temperature recrystallization process can achieve partial purification, it still has defects that need to be improved: first, the process parameters are overly dependent on operating experience, and the solvent ratio and seed control lack quantitative standards, resulting in poor product yield stability; second, the traditional mixed solvent system has problems such as low crystallization efficiency and loose crystal structure, making it difficult to achieve efficient separation of impurities; third, conventional temperature control technology cannot accurately maintain the ultra-low temperature crystallization environment required for 3OP, resulting in frequent occurrence of impurities wrapped in crystals.

[0004] Although existing technologies have improved purification effects through solvent combination optimization, they have failed to break through the synergistic technical barriers of staged seed induction, temperature gradient control and dynamic stirring strategies. In addition, the separation and drying steps involved in the process need to be carried out on different equipment, resulting in more complicated material transportation and separation and dehydration operations, further reducing production efficiency.

[0005] In response to the problems of incomplete impurity separation, insufficient process controllability, high energy consumption and material loss in existing technologies, a high-purity trans-4-propionylcyclohexylbenzene preparation technology that integrates three-stage gradient temperature control, stepwise addition of seed crystals, and filtration and drying is urgently needed to be developed. Summary of the Invention

[0006] The present invention aims to address the technical issues of low yield, insufficient purity, high energy consumption, and poor batch stability in existing trans-4-propionylcyclohexylbenzene preparation processes. This invention provides a data-driven collaborative optimization method for ultra-low-temperature recrystallization. This method, through the dynamic coupling of fractionated seed addition, gradient temperature control, and intermittent stirring, enables the efficient preparation of high-purity trans-4-propionylcyclohexylbenzene crystals (≥85.0%). This method reduces energy consumption and is suitable for 50-500 kg industrial production, thereby promoting the upgrading of green manufacturing technology for liquid crystal intermediates. A second object of the present invention is to design an integrated filtration and drying machine in conjunction with the improved process, further improving production efficiency.

[0007] To achieve the above object, the present invention provides the following technical solution: a method for preparing high-purity trans-4-propionylcyclohexylbenzene, comprising the following steps: a) Solvent mixing: Mix crude trans-4-propionylcyclohexylbenzene with petroleum ether in a volume ratio of 1:0.6-1.5 and stir until completely dissolved to form a homogeneous solution; b) Ultra-low temperature pre-crystallization: The solution obtained in step a) is cooled to -25°C ± 2°C at a rate of 1°C / min, seed crystals are added in batches, and stirring is started. The amount of seed crystals added is 2.5-10% of the quality of the crude trans-4-propionylcyclohexylbenzene. The temperature is further cooled to -40°C ± 2°C and maintained for 50-60 minutes. c) Gradient pre-crystallization strengthening: Stage 1: Heat to -25°C ± 1°C at a rate of 0.5°C / min, stir under anchor mode for 20 minutes at a stirring speed of 100 rpm ± 10 rpm; cool to -35°C ± 1°C at a rate of 1°C / min, stir under anchor mode for 20 minutes at a stirring speed of 100 rpm ± 10 rpm; repeat the above operation for a total of 5 temperature rise and fall operations; The second stage: cool down to -40℃±1℃ at a rate of 1℃ / min and hold for 50-60min. Start anchor stirring for 2min every 10min at a stirring speed of 100rpm±10rpm, for a total of 5 intermittent stirrings. d) Low-temperature solid-liquid separation: Filter at -10°C ± 2°C with a filtration pressure of -0.08 MPa to -0.1 MPa for 10 min or less. Rinse the filter cake three times with petroleum ether pre-cooled to -10°C. The amount of eluent used for each wash is 30% to 50% of the quality of the crude trans-4-propionylcyclohexylbenzene. e) Vacuum drying: Dry the filter cake for 4 hours under the conditions of -0.09 MPa vacuum, 25°C ± 2°C, nitrogen protection, and humidity ≤ 10% RH to obtain trans-4-propionylcyclohexylbenzene crystals with a purity of ≥ 85.0%.

[0008] As a further embodiment of the present invention: in step a), the petroleum ether is a reagent-grade solvent with a distillation range of 90°C to 120°C; when the purity of the crude trans-4-propionylcyclohexylbenzene is less than 60%, it is required to be pre-treated by water washing, and the treatment steps are: mixing the crude product with deionized water in a mass ratio of 1:3, shaking for 10 minutes, and then separating the layers, and removing the solvent from the organic phase under reduced pressure until the moisture content is ≤0.5wt%.

[0009] As a further embodiment of the present invention, in step b), the seed crystal is prepared by dissolving pure trans-4-propionylcyclohexylbenzene in petroleum ether at a volume ratio of 1:2 and recrystallizing at -20°C to -25°C; the pure trans-4-propionylcyclohexylbenzene has a purity of ≥90% and a particle size of 50 to 100 μm; the solvent consists solely of petroleum ether and has a boiling range of 90°C to 120°C; The seed crystals are added in batches in step b): the seed crystals are added in three equal amounts, with a total addition amount of 2.5% to 10% of the quality of the crude trans-4-propionylcyclohexylbenzene, and each addition is 5 minutes apart; the stirring adopts an anchor stirrer with a speed of 100 rpm ± 10 rpm and a stirring power of 0.5 to 1.5 kw / m³.

[0010] As a further solution of the present invention: steps d) and e) are performed using a suction filtration and drying integrated machine, which includes a first reaction box, a connecting pipe fixedly connected to the bottom end of the first reaction box, a second reaction box fixedly connected to the bottom end of the connecting pipe, a discharge port fixedly connected to the bottom end of the second reaction box, the first reaction box performs a suction filtration operation through a suction filtration mechanism, and the second reaction box performs a drying operation through a drying mechanism.

[0011] As a further solution of the present invention: the filtration mechanism includes a suction bottle, the suction bottle is arranged in the inner cavity of the first reaction box, the bottom end of the suction bottle is fixedly connected to the drainage pipe, one side of the suction bottle is fixedly connected to the first suction pipe, the outer wall of the drainage pipe is provided with a valve, the drainage pipe and the first suction pipe extend to the outside of the first reaction box, the top of the suction bottle is fixedly connected to the connecting seat, the inner wall of the connecting seat is fixedly connected to the connecting block, the outer wall of the connecting block is fixedly connected to the filter plate, a movable cylinder is provided above the connecting seat, the top of the movable cylinder is fixedly connected to the movable tube, the movable tube is slidably connected to the first reaction box, the top of the movable tube is fixedly connected to the hopper, the outer wall of the movable tube is fixedly connected to the horizontal plate, the top of the first reaction box is installed with a first motor, the output end of the first motor is connected to the first threaded rod, and the first threaded rod passes through the horizontal plate.

[0012] As a further solution of the present invention: the drying mechanism includes a second motor, the second motor is installed on one side of the first reaction box, the output end of the second motor is connected to the second threaded rod, the interior of the connecting tube is slidably connected to a shielding frame extending from the connecting tube, the second threaded rod passes through the shielding frame, the outer wall of the shielding frame is fixedly connected to a pushing frame extending to the inner cavity of the first reaction box, the outer wall of the shielding frame is provided with a through hole, the outer wall of one side of the second reaction box is fixedly connected to a second exhaust pipe and an air inlet pipe, the bottom end of the inner wall of the second reaction box is fixed at the top of the discharge port It is connected to a square frame, and a constant temperature electric heater is provided on the inner wall of the square frame; a rotating plate is rotatably connected to the interior of the square frame, and a baffle is rotatably connected to the inner wall of the discharge port, and one end of the rotating plate and the baffle are fixedly connected to a spur gear, and the discharge port and the interior of the square frame are slidably connected to a gear rod, and a third motor is installed on the outer wall of one side of the discharge port, and the output end of the third motor is connected to a third threaded rod, and the third threaded rod passes through the gear rod, and the spur gear is in contact with the gear rod, and the top of the gear rod is fixedly connected to a partition 615, and the partition extends to the inner cavity of the air intake pipe.

[0013] As a further solution of the present invention: the inner wall of the movable cylinder is in contact with the outer wall of the filter plate, the outer wall of the movable cylinder is in contact with the inner wall of the connecting seat, the inner and outer walls of the movable cylinder are both provided with sealing rings, and the outer wall of the horizontal plate is provided with a first threaded hole, and the first threaded hole matches the first threaded rod.

[0014] As a further solution of the present invention: a second threaded hole is formed on the outer wall of the shielding frame, and the second threaded hole matches the second threaded rod.

[0015] As a further solution of the present invention: the gear rod is L-shaped and a third threaded hole is provided at the bottom end of the lower horizontal rod, the third threaded hole matches the third threaded rod, and a tooth groove is provided on the outer wall of the upper vertical rod of the gear rod, and the tooth groove is engaged with the spur gear.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. The method for preparing high-purity trans-4-propionylcyclohexylbenzene described herein significantly improves purification efficiency and crystal quality. By dynamically synergizing gradient temperature control in a cyclic operation between -40°C and -25°C with intermittent anchor stirring, the method can purify crude trans-4-propionylcyclohexylbenzene with an initial content of 60% to over 85.0% in a single step, achieving a 76.6% yield, an absolute improvement of 14.2 percentage points over the conventional process (yield of 62.4%). This method meets the 24-month storage stability requirement for liquid crystal materials, completely resolving the technical bottleneck of conventional processes that require multiple purification steps and are prone to degradation after storage.

[0017] 2. The method for preparing high-purity trans-4-propionylcyclohexylbenzene described in this invention achieves breakthroughs in industrial adaptability and production economics. Its flexible processing capacity of 50-500 kg seamlessly adapts to the GLR series crystallizers (50-1000 L). Precision temperature control of ±1°C is precisely matched to a stirring power of 0.5-1.5 kW / m³. Three equal additions of seed crystals (5-minute intervals) avoid localized oversaturation and reduce impurity inclusion. Batch-to-batch purity variation is ≤1.5% (RSD = 0.8%), and yield fluctuation standard deviation is ≤1.2%, exceeding the industry fluctuation threshold of 5%.

[0018] 3. Green environmental protection and industrial chain synergistic optimization produce high-purity products (≥85.0%). MSDS-certified petroleum ether solvent is used throughout the process, and VOCs emissions are <10mg / m³.

[0019] 4. A suction filtration and drying integrated machine is designed in conjunction with the improved process. The equipment is equipped with a suction filtration mechanism and a drying mechanism. The movable cylinder is displaced and inserted into the inner wall of the connecting seat. The filter plate enters the inner cavity of the movable cylinder. A cavity is formed between the movable cylinder and the filter plate. The prepared solution in step c) is poured into the cavity. The first exhaust pipe extracts the air in the suction bottle, thereby performing a suction filtration operation. After completion, the liquid in the suction bottle can be discharged through the drain pipe by opening the valve; after completing the filtration, the first motor is started to drive the movable cylinder to move to the top of the connecting seat. At this time, the filter cake is located on the top of the filter plate, and then petroleum ether pre-cooled to -10°C can be poured into the hopper and poured onto the filter cake through the movable pipe; the filter cake falls to the top of the rotating plate for drying operation, which is convenient for realizing integrated suction filtration and drying operations in one device, reducing the transportation links and equipment space, and further improving work efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a structural diagram of the suction filtration and drying integrated machine of the present invention; Figure 2 This is a schematic diagram of the internal structure of the first reaction box of the suction filtration and drying integrated machine of the present invention; Figure 3 This is a schematic diagram of the internal structure of the suction filtration bottle of the suction filtration and drying integrated machine of the present invention; Figure 4 This is a schematic diagram of the internal structure of the second reaction box of the suction filtration and drying integrated machine of the present invention; Figure 5 This is a structural schematic diagram of the shielding frame of the suction filtration and drying integrated machine of the present invention; Figure 6 This is a schematic diagram of the installation of the gear rod of the suction filtration and drying machine of the present invention; Figure 7 This is a schematic structural diagram of the gear rod of the suction filtration and drying integrated machine of the present invention.

[0021] In the figure: 1, first reaction box; 2, connecting pipe; 3, second reaction box; 4, discharge port; 5, filtration mechanism; 501, filtration bottle; 502, connecting seat; 503, drain pipe; 504, valve; 505, first air extraction pipe; 506, hopper; 507, movable pipe; 508, movable cylinder; 509, horizontal plate; 510, first motor; 511, first threaded rod; 512, connecting block; 513, Filter plate; 6. Drying mechanism; 601. Second motor; 602. Second threaded rod; 603. Shielding frame; 604. Pushing frame; 605. Through hole; 606. Second exhaust pipe; 607. Inlet pipe; 608. Square frame; 609. Rotating plate; 610. Baffle; 611. Spur gear; 612. Third motor; 613. Third threaded rod; 614. Gear rod; 615. Partition; 7. Sealing ring. DETAILED DESCRIPTION

[0022] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0023] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and should not be understood as indicating or implying relative importance. In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", and "set" should be understood in a broad sense, for example, they can be fixedly connected, detachably connected, or connected in one piece; they can be mechanically connected or electrically connected; they can be directly connected, or indirectly connected through an intermediate medium, or they can be internal connections between two components. 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 circumstances. The following describes an embodiment of the present invention based on its overall structure. Example 1

[0024] a) Solvent mixing: Mix 20 g of 58.2% pure 3OP crude product with 20 mL of petroleum ether in a 1:1 volume ratio and stir until completely dissolved to form a homogeneous solution; b) Ultra-low temperature pre-crystallization: The solution obtained in step a) was cooled to -25°C ± 2°C at a rate of 1°C / min, and seed crystals were added in batches. The seed crystals were added in equal amounts in three batches with stirring. The total addition amount was 1 g (5% of the crude product quality). Each addition was separated by 5 minutes. The stirring was carried out using an anchor stirrer at a speed of 100 rpm ± 10 rpm and a stirring power of 0.5 kW / m³. The temperature was further cooled to -40°C ± 2°C and maintained for 60 minutes. c) Gradient pre-crystallization strengthening: Stage 1: Cycle the following procedure five times: heat to -25°C ± 1°C at a rate of 0.5°C / min, stir under anchor mode for 20 min at a stirring speed of 100 rpm ± 10 rpm; cool to -35°C ± 1°C at a rate of 1°C / min, stir under anchor mode for 20 min at a stirring speed of 100 rpm ± 10 rpm; The second stage: cool down to -40℃±1℃ at a rate of 1℃ / min and hold for 60min. Start anchor stirring for 2min every 10min at a stirring speed of 100rpm±10rpm, for a total of 5 intermittent stirrings. d) Low-temperature solid-liquid separation: Filter at -10°C ± 2°C with a filtration pressure of -0.08 MPa to -0.1 MPa for 10 min or less. Rinse the filter cake three times with petroleum ether precooled to -10°C. The amount of eluent used for each wash is 50% of the crude trans-4-propionylcyclohexylbenzene (10 g). e) Vacuum drying: The filter cake was dried for 4 h under the conditions of -0.09 MPa vacuum, 25°C ± 2°C, nitrogen protection, and humidity ≤ 10% RH to obtain 10.15 g of the product with a purity of 87.8% and a percent yield of 76.6%.

[0025] Please refer to Figures 1 to 3, steps d) and e) are operated by a suction filtration and drying integrated machine, which includes a first reaction box 1, the bottom end of the first reaction box 1 is fixedly connected to a connecting pipe 2, the bottom end of the connecting pipe 2 is fixedly connected to a second reaction box 3, the bottom end of the second reaction box 3 is fixedly connected to a discharge port 4, the first reaction box 1 performs a suction filtration operation through a suction filtration mechanism 5, and the second reaction box 3 performs a drying operation through a drying mechanism 6, the suction filtration mechanism 5 includes a suction filtration bottle 501, the suction filtration bottle 501 is arranged in the inner cavity of the first reaction box 1, the bottom end of the suction filtration bottle 501 is fixedly connected to a drain pipe 503, one side of the suction filtration bottle 501 is fixedly connected to a first air extraction pipe 505, the outer wall of the drain pipe 503 is installed with a valve 504, the drain pipe 503 and the first An exhaust pipe 505 extends to the outside of the first reaction box 1, the top of the suction bottle 501 is fixedly connected to the connecting seat 502, the inner wall of the connecting seat 502 is fixedly connected to the connecting block 512, the outer wall of the connecting block 512 is fixedly connected to the filter plate 513, a movable cylinder 508 is provided above the connecting seat 502, the top of the movable cylinder 508 is fixedly connected to the movable tube 507, the movable tube 507 is slidingly connected to the first reaction box 1, the top of the movable tube 507 is fixedly connected to the hopper 506, the outer wall of the movable tube 507 is fixedly connected to the horizontal plate 509, the top of the first reaction box 1 is installed with a first motor 510, the output end of the first motor 510 is connected to the first threaded rod 511, and the first threaded rod 511 passes through the horizontal plate 509.

[0026] In this embodiment, when performing suction filtration, the first motor 510 is started, and the operation of the first motor 510 drives the first threaded rod 511 to rotate, and the rotation of the first threaded rod 511 drives the horizontal plate 509 to move, and the displacement of the horizontal plate 509 drives the hopper 506, the movable tube 507 and the movable cylinder 508 to move synchronously, and the movable cylinder 508 moves and inserts into the inner wall of the connecting seat 502, and the filter plate 513 enters the inner cavity of the movable cylinder 508, and a cavity is formed between the movable cylinder 508 and the filter plate 513, and the solution prepared in step c) is poured into the hopper 506, enters the cavity through the movable tube 507, and the first exhaust pipe 505 extracts the air in the suction bottle 501, thereby performing the filtration operation. After completion, the valve 504 can be opened to discharge the liquid in the suction bottle 501 through the drain pipe 503; after completion of the filtration, the first motor 510 is started to drive the movable cylinder 508 to move to the top of the connecting seat 502. At this time, the filter cake is located at the top of the filter plate 513, and then the petroleum ether pre-cooled to -10°C can be poured into the hopper 506 and poured onto the filter cake through the movable tube 507.

[0027] Please refer to Figures 4 to 7The drying mechanism 6 includes a second motor 601, which is installed on one side of the first reaction box 1. The output end of the second motor 601 is connected to a second threaded rod 602. The interior of the connecting tube 2 is slidably connected to a shielding frame 603 extending from the connecting tube 2. The second threaded rod 602 passes through the shielding frame 603. The outer wall of the shielding frame 603 is fixedly connected to a pushing frame 604 extending to the inner cavity of the first reaction box 1. A through hole 605 is provided on the outer wall of the shielding frame 603. A second exhaust pipe 606 and an air inlet pipe 607 are fixedly connected to the outer wall of one side of the second reaction box 3. The bottom end of the inner wall of the second reaction box 3 is located at the top of the discharge port 4 and is fixedly connected to a square frame 608. The inner wall of the square frame 608 is provided with a constant temperature electric heater; the interior of the square frame 608 is rotatably connected to a rotating plate 609, the inner wall of the discharge port 4 is rotatably connected to a baffle 610, one end of the rotating plate 609 and the baffle 610 are fixedly connected to a spur gear 611, the discharge port 4 and the interior of the square frame 608 are slidably connected to a gear rod 614, a third motor 612 is installed on the outer wall of one side of the discharge port 4, the output end of the third motor 612 is connected to a third threaded rod 613, the third threaded rod 613 passes through the gear rod 614, the spur gear 611 is in contact with the gear rod 614, the top of the gear rod 614 is fixedly connected to a partition 615, and the partition 615 extends to the inner cavity of the air inlet pipe 607.

[0028] In this embodiment: after the filter cake is rinsed, the second motor 601 is started, and the second motor 601 drives the second threaded rod 602 to rotate, and the second threaded rod 602 rotates to drive the shielding frame 603 to move, and the displacement of the shielding frame 603 drives the pushing frame 604 to move, and the pushing frame 604 moves to contact the filter cake, pushing the filter cake to move out of the filter plate 513 and fall into the connecting pipe 2. At this time, the displacement of the shielding frame 603 drives the through hole 605 to move into the inner cavity of the connecting pipe 2, and the connecting pipe 2 is opened. The filter cake enters the second reaction box 3 through the connecting pipe 2 and falls to the top of the rotating plate 609; then the second motor 601 is operated to drive the shielding frame 603 to reset, and the connecting pipe 2 is closed; the second exhaust pipe 606 extracts the gas in the second reaction box 3 to form a vacuum degree of -0.09 MPa, and the constant temperature electric heater arranged on the inner wall of the square frame 608 is in operation, so that the filter cake can be dried for 4 hours under the condition of temperature 25℃±2℃. After drying is completed, the third motor 612 is started, and the operation of the third motor 612 drives the third threaded rod 613 to rotate, and the rotation of the third threaded rod 613 drives the gear rod 614 to displace, and the displacement of the gear rod 614 drives the spur gear 611 to rotate, and the rotation of the spur gear 611 drives the rotating plate 609 and the baffle 610 to rotate synchronously, and the rotating plate 609 rotates to cause the material to fall, and the rotation of the baffle 610 drives the discharge port 4 to open, and the material falls through the discharge port 4. At the same time, the displacement of the gear rod 614 drives the partition 615 to displace, and the air inlet pipe 607 is opened, and nitrogen enters the second reaction box 3 through the air inlet pipe 607 to prevent outside air from entering the second reaction box 3 through the discharge port 4, so as to facilitate integrated filtration and drying operations.

[0029] Please refer to Figures 1 to 3 The inner wall of the movable cylinder 508 fits with the outer wall of the filter plate 513, and the outer wall of the movable cylinder 508 fits with the inner wall of the connecting seat 502. The inner and outer walls of the movable cylinder 508 are both provided with sealing rings 7. The outer wall of the horizontal plate 509 is provided with a first threaded hole, and the first threaded hole matches the first threaded rod 511.

[0030] In this embodiment: the operation of the first motor 510 drives the first threaded rod 511 to rotate, the rotation of the first threaded rod 511 drives the horizontal plate 509 to displace, the displacement of the horizontal plate 509 drives the hopper 506, the movable tube 507 and the movable cylinder 508 to displace synchronously, the movable cylinder 508 is displaced and inserted into the inner wall of the connecting seat 502, the filter plate 513 enters the inner cavity of the movable cylinder 508, and a cavity is formed between the movable cylinder 508 and the filter plate 513, and the sealing ring 7 is used to improve the sealing between the movable cylinder 508 and the connecting seat 502 and the filter plate 513 respectively.

[0031] Please refer to Figures 4 to 7 A second threaded hole is formed on the outer wall of the shielding frame 603 , and the second threaded hole matches the second threaded rod 602 .

[0032] In this embodiment, the second motor 601 drives the second threaded rod 602 to rotate, the rotation of the second threaded rod 602 drives the shielding frame 603 to move, and the displacement of the shielding frame 603 drives the pushing frame 604 to move.

[0033] Please refer to Figures 4 to 7 The gear rod 614 is L-shaped and a third threaded hole is opened at the bottom end of the lower horizontal rod, and the third threaded hole matches the third threaded rod 613. The outer wall of the upper vertical rod of the gear rod 614 is provided with a tooth groove, which meshes with the spur gear 611.

[0034] In this embodiment, the third motor 612 drives the third threaded rod 613 to rotate, the rotation of the third threaded rod 613 drives the gear rod 614 to move, the displacement of the gear rod 614 drives the spur gear 611 to rotate, and the rotation of the spur gear 611 drives the rotating plate 609 and the baffle 610 to rotate synchronously. Example 2

[0035] a) Solvent mixing: Take 500 kg of 58.5% purity 3OP crude product from the workshop and mix it with 400 L of petroleum ether (volume ratio 1:0.8) and stir until it is completely dissolved to form a homogeneous solution; b) Ultra-low temperature pre-crystallization: The solution obtained in step a) was cooled to -25°C ± 2°C at a rate of 1°C / min, and seed crystals were added in batches. The seed crystals were added in three equal amounts with stirring. The total addition amount was 5% of the crude product quality (25 kg). Each addition was separated by 5 minutes. The stirring was carried out using an anchor stirrer with a speed of 100 rpm ± 10 rpm and a stirring power of 1.2 kW / m³. The temperature was further cooled to -40°C ± 2°C and maintained for 60 minutes. c) Gradient pre-crystallization strengthening: Stage 1: Cycle the following procedure five times: heat to -25°C ± 1°C at a rate of 0.5°C / min, stir under anchor mode for 20 min at a stirring speed of 100 rpm ± 10 rpm; cool to -35°C ± 1°C at a rate of 1°C / min, stir under anchor mode for 20 min at a stirring speed of 100 rpm ± 10 rpm; The second stage: cool down to -40℃±1℃ at a rate of 1℃ / min and hold for 60min. Start anchor stirring for 2min every 10min at a stirring speed of 100rpm±10rpm, for a total of 5 intermittent stirrings. d) Low-temperature solid-liquid separation: Filter at -10°C ± 2°C with a filtration pressure of -0.1 MPa for 10 min or less. Rinse the filter cake three times with petroleum ether pre-cooled to -10°C. The amount of eluent used each time is 40% (200 kg) of the crude trans-4-propionylcyclohexylbenzene. e) Vacuum drying: The filter cake was dried for 4 h under the conditions of -0.09 MPa vacuum, 25°C ± 2°C, nitrogen protection, and humidity ≤ 10% RH to obtain a product with a purity of 86.7% and a yield of 75.3%.

[0036] The equipment used is the same as that in Example 1 and will not be described in detail here. Example 3

[0037] a) Solvent mixing: 20 g of 60.0% pure 3OP crude product was mixed with 12 mL of petroleum ether in a volume ratio of 1:0.6 and stirred until completely dissolved to form a homogeneous solution; b) Ultra-low temperature pre-crystallization: The solution obtained in step a) was cooled to -25°C ± 2°C at a rate of 1°C / min, and seed crystals were added in batches. The seed crystals were added in three equal amounts, with a total addition amount of 5% of the crude product quality (1g), and each addition was done at an interval of 5 minutes. The stirring was carried out using an anchor stirrer with a speed of 100 rpm ± 10 rpm and a stirring power of 1.5 kW / m³. The temperature was further cooled to -40°C ± 2°C and maintained for 60 minutes. c) Gradient pre-crystallization strengthening: Stage 1: Cycle the following procedure five times: heat to -25°C ± 1°C at a rate of 0.5°C / min, stir under anchor mode for 20 min at a stirring speed of 100 rpm ± 10 rpm; cool to -35°C ± 1°C at a rate of 1°C / min, stir under anchor mode for 20 min at a stirring speed of 100 rpm ± 10 rpm; The second stage: cool down to -40℃±1℃ at a rate of 1℃ / min and hold for 60min. Start anchor stirring for 2min every 10min at a stirring speed of 100rpm±10rpm, for a total of 5 intermittent stirrings. d) Low-temperature solid-liquid separation: Filter at -10°C ± 2°C with a filtration pressure of -0.08 MPa to -0.1 MPa for 10 min or less. Rinse the filter cake three times with petroleum ether pre-cooled to -10°C. The amount of eluent used for each wash is 30% (6 g) of the crude trans-4-propionylcyclohexylbenzene. e) Vacuum drying: The filter cake was dried for 4 h under the conditions of -0.09 MPa vacuum, 25°C ± 2°C, nitrogen protection, and humidity ≤ 10% RH to obtain 8.92 g of the product with a purity of 85.6% and a percent yield of 70.5%.

[0038] The equipment used is the same as that in Example 1 and will not be described in detail here. Example 4

[0039] a) Solvent mixing: same as step a) in Example 1; b) Ultra-low temperature pre-crystallization: same as step b) in Example 1; c) Gradient pre-crystallization strengthening: same as step c) in Example 1; d) Low temperature solid-liquid separation: The filtration mechanism in the filtration and drying machine ( Figure 2 ) and elution with petroleum ether pre-cooled to -10°C (refrigerated for 30 minutes). Filtration was performed using a filtration and drying machine at -10°C ± 2°C. Filtration pressures were set at -0.08 MPa, -0.09 MPa, and -0.10 MPa for testing. The filter cake surface temperature was monitored throughout the process.

[0040] When the pressure was -0.08 MPa, the filtration time was 7.8 min and the filter cake was intact; When the pressure was -0.09 MPa, the filtration time was 5.2 min and the filter cake was intact; When the pressure is -0.10 MPa, the filtration time is 4.5 min and the filter cake is intact; There is no freezing phenomenon in petroleum ether, and the surface temperature of the filter cake is monitored to be ≤-8℃.

[0041] e) Vacuum drying: same as step e) in Example 1. Example 5

[0042] a) Solvent mixing: Mix 20 g of 58.2% pure 3OP crude product with 20 mL of petroleum ether in a 1:1 volume ratio and stir until completely dissolved to form a homogeneous solution; b) Ultra-low temperature pre-crystallization: The solution obtained in step a) was cooled to -25°C ± 2°C at a rate of 1°C / min, and seed crystals were added in batches. The seed crystals were added in three equal amounts, with a total addition amount of 2.5% of the crude product quality (0.5g), with an interval of 5 minutes between each addition. The stirring was carried out using an anchor stirrer at a speed of 100 rpm ± 10 rpm and a stirring power of 1 kW / m³. The temperature was further cooled to -40°C ± 2°C and maintained for 60 minutes. c) Gradient pre-crystallization strengthening: Stage 1: Cycle the following procedure five times: heat to -25°C ± 1°C at a rate of 0.5°C / min, stir under anchor mode for 20 min at a stirring speed of 100 rpm ± 10 rpm; cool to -35°C ± 1°C at a rate of 1°C / min, stir under anchor mode for 20 min at a stirring speed of 100 rpm ± 10 rpm; The second stage: cool down to -40℃±1℃ at a rate of 1℃ / min and hold for 60min. Start anchor stirring for 2min every 10min at a stirring speed of 100rpm±10rpm, for a total of 5 intermittent stirrings. d) Low-temperature solid-liquid separation: Filter at -10°C ± 2°C with a filtration pressure of -0.08 MPa to -0.1 MPa for 10 min or less. Rinse the filter cake three times with petroleum ether precooled to -10°C. The amount of eluent used for each wash is 50% of the crude trans-4-propionylcyclohexylbenzene (10 g). e) Vacuum drying: The filter cake was dried for 4 h under the conditions of -0.09 MPa vacuum, 25°C ± 2°C, nitrogen protection, and humidity ≤ 10% RH to obtain 9.25 g of the product with a purity of 85.1% and a yield of 72.3%.

[0043] The equipment used is the same as that in Example 1 and will not be described in detail here. Example 6

[0044] a) Solvent mixing: Mix 20 g of 58.2% pure 3OP crude product with 20 mL of petroleum ether in a 1:1 volume ratio and stir until completely dissolved to form a homogeneous solution; b) Ultra-low temperature pre-crystallization: The solution obtained in step a) was cooled to -25°C ± 2°C at a rate of 1°C / min, and seed crystals were added in batches. The seed crystals were added in three equal amounts, with a total addition amount of 10% of the crude product quality (2.0g), and each addition was done at an interval of 5 minutes. The stirring was carried out using an anchor stirrer at a speed of 100 rpm ± 10 rpm and a stirring power of 0.5-1.5 kW / m³. The temperature was further cooled to -40°C ± 2°C and maintained for 60 minutes. c) Gradient pre-crystallization strengthening: Stage 1: Cycle the following procedure five times: heat to -25°C ± 1°C at a rate of 0.5°C / min, stir under anchor mode for 20 min at a stirring speed of 100 rpm ± 10 rpm; cool to -35°C ± 1°C at a rate of 1°C / min, stir under anchor mode for 20 min at a stirring speed of 100 rpm ± 10 rpm; The second stage: cool down to -40℃±1℃ at a rate of 1℃ / min and hold for 60min. Start anchor stirring for 2min every 10min at a stirring speed of 100rpm±10rpm, for a total of 5 intermittent stirrings. d) Low-temperature solid-liquid separation: Filter at -10°C ± 2°C with a filtration pressure of -0.08 MPa to -0.1 MPa for 10 min or less. Rinse the filter cake three times with petroleum ether precooled to -10°C. The amount of eluent used for each wash is 50% of the crude trans-4-propionylcyclohexylbenzene (10 g). e) Vacuum drying: The filter cake was dried for 4 h under the conditions of -0.09 MPa vacuum, 25°C ± 2°C, nitrogen protection, and humidity ≤ 10% RH to obtain 10.12 g of the product with a purity of 86.9% and a percent yield of 74.8%.

[0045] The equipment used is the same as that in Example 1 and will not be described in detail here. Example 7

[0046] a) Solvent mixing: Mix 20 g of 58.2% pure 3OP crude product with 30 mL of petroleum ether in a volume ratio of 1:1.5 and stir until completely dissolved to form a homogeneous solution; b) Ultra-low temperature pre-crystallization: The solution obtained in step a) was cooled to -25°C ± 2°C at a rate of 1°C / min, and seed crystals were added in batches. The seed crystals were added in three equal amounts, with a total addition amount of 5% of the crude product quality (1g), and each addition was done at an interval of 5 minutes. The stirring was carried out using an anchor stirrer at a speed of 100 rpm ± 10 rpm and a stirring power of 0.5-1.5 kW / m³. The temperature was further cooled to -40°C ± 2°C and maintained for 60 minutes. c) Gradient pre-crystallization strengthening: Stage 1: Cycle the following procedure five times: heat to -25°C ± 1°C at a rate of 0.5°C / min, stir under anchor mode for 20 min at a stirring speed of 100 rpm ± 10 rpm; cool to -35°C ± 1°C at a rate of 1°C / min, stir under anchor mode for 20 min at a stirring speed of 100 rpm ± 10 rpm; The second stage: cool down to -40℃±1℃ at a rate of 1℃ / min and hold for 60min. Start anchor stirring for 2min every 10min at a stirring speed of 100rpm±10rpm, for a total of 5 intermittent stirrings. d) Low-temperature solid-liquid separation: Filter at -10°C ± 2°C with a filtration pressure of -0.08 MPa to -0.1 MPa for 10 min or less. Rinse the filter cake three times with petroleum ether precooled to -10°C. The amount of eluent used for each wash is 50% of the crude trans-4-propionylcyclohexylbenzene (10 g). e) Vacuum drying: The filter cake was dried for 4 h under the conditions of -0.09 MPa vacuum, 25°C ± 2°C, nitrogen protection, and humidity ≤ 10% RH to obtain 8.92 g of the product with a purity of 85.3% and a percent yield of 71.6%.

[0047] The equipment used is the same as that in Example 1 and will not be described in detail here. Comparative Example 1: Adding Seed Crystals at Once

[0048] a) Solvent mixing: Mix 20 g of 58.2% pure 3OP crude product with 20 mL of petroleum ether in a volume ratio of 1:1 and stir until completely dissolved to form a homogeneous solution; b) Ultra-low temperature pre-crystallization: Cool the solution obtained in step a) to -25°C ± 2°C at a rate of 1°C / min, add seed crystals at once, with the total addition amount being 5% of the crude product quality (1 g); continue cooling to -40°C ± 2°C and hold for 60 min; c) Gradient pre-crystallization strengthening: Stage 1: Cycle the following procedure five times: heat to -25°C ± 1°C at a rate of 0.5°C / min, stir under anchor mode for 20 min at a stirring speed of 100 rpm ± 10 rpm; cool to -35°C ± 1°C at a rate of 1°C / min, stir under anchor mode for 20 min at a stirring speed of 100 rpm ± 10 rpm; The second stage: cool down to -40℃±1℃ at a rate of 1℃ / min and hold for 60min. Start anchor stirring for 2min every 10min at a stirring speed of 100rpm±10rpm, for a total of 5 intermittent stirrings. d) Low-temperature solid-liquid separation: Filter at -10°C ± 2°C with a filtration pressure of -0.08 MPa to -0.1 MPa for 10 min or less. Rinse the filter cake three times with petroleum ether precooled to -10°C. The amount of eluent used for each wash is 50% of the crude trans-4-propionylcyclohexylbenzene (10 g). e) Vacuum drying: The filter cake was dried for 4 h under the conditions of -0.09 MPa vacuum, 25°C ± 2°C, nitrogen protection, and humidity ≤ 10% RH to obtain a product with a purity of 83.9% and a yield of 68.1%.

[0049] The equipment used is the same as that in Example 1 and will not be described in detail here. Comparative Example 2: Traditional mixed solvent process

[0050] a) Solvent mixing: Take 20g of 60% pure workshop 3OP crude product and dissolve it in 20ml of petroleum ether / isopropanol (1:1) mixed solvent, stirring until completely dissolved to form a homogeneous solution; b) Ultra-low temperature pre-crystallization: without adding seed crystals, the solution was directly frozen to -40°C and kept for 12 hours; c) Gradient pre-crystallization strengthening: not performed; d) Low-temperature solid-liquid separation: filtration at 25°C ± 2°C (other parameters are the same as in Example 1); e) Vacuum drying: same as step e) in Example 1.

[0051] The product purity is 78.8%, the yield is 62.4%, and the solid content is 77.9%. Comparative Example 3: Direct ultra-low temperature freezing crystallization process

[0052] a) Solvent mixing: same as step a) in Example 1; b) Ultra-low temperature pre-crystallization: without adding seed crystals, the solution was directly frozen to -40°C and kept for 12 hours; c) Gradient pre-crystallization strengthening: not performed; d) Low-temperature solid-liquid separation: same as step d) in Example 1; e) Vacuum drying: same as step e) in Example 1.

[0053] After drying, 7.74 g of product was obtained with a purity of 85.2% and a yield of 55.0%. Comparative Example 4: Seedless Process

[0054] a) Solvent mixing: same as step a) in Example 1; b) Ultra-low temperature pre-crystallization: without adding seed crystals, the solution was directly frozen to -40°C and kept for 12 hours; c) Gradient pre-crystallization strengthening: same as step c) in Example 1; d) Low-temperature solid-liquid separation: same as step d) in Example 1; e) Vacuum drying: same as step e) in Example 1.

[0055] The product purity is 79.1% and the yield is 62.6%. Performance Testing

[0056] The trans-4-propionylcyclohexylbenzene (3OP) crystals prepared in Examples 1 to 7 and Comparative Examples 1 to 4 were subjected to product purity analysis, percentage yield calculation, temperature control accuracy monitoring, intermittent stirring efficiency, low-temperature filtration performance, and vacuum drying efficiency testing as follows: 1. Product purity analysis: High performance liquid chromatography (HPLC, Agilent 1260 Infinity II, C18 column 4.6 × 250 mm, mobile phase methanol:water = 85:15 (v / v), flow rate 1.0 mL / min, column temperature 30°C, detection wavelength 254 nm); Calculation: Main peak area normalization method, purity = (target peak area / total peak area) × 100%.

[0057] 2. Calculation of percent yield: Yield = (mass of crystals after drying × purity measured by HPLC) / (mass of crude material × initial purity of crude product) × 100%.

[0058] 3. Temperature control accuracy monitoring: A multi-channel temperature recorder (Fluke 2680A) collects temperature data in real time during the gradient cycle phase (-40°C ↔ -25°C ↔ -35°C) and calculates the ±1°C deviation compliance rate.

[0059] 4. Intermittent stirring efficiency: Laser particle size analyzer (Malvern Mastersizer 3000) was used to compare the particle size distribution consistency of seed crystals (50-100 μm) and product crystals.

[0060] 5. Low-temperature filtration performance: Filtration time: A pressure sensor (-0.10MPa to -0.08MPa) records the time required to reach the specified vacuum level; Filter cake temperature stability: An infrared thermal imager (FLIR T540) monitors the filter cake surface temperature difference during the elution process (required to be ≤±2°C).

[0061] 6. Vacuum drying efficiency: An online moisture analyzer (Mettler Toledo C30S) was used to monitor the drying endpoint (humidity ≤ 10% RH) and the time to reach the target was recorded.

[0062] The above performance test results are shown in Table 1 below: Table 1: Trans-4-propionylcyclohexylbenzene preparation process performance test results

[0063] In summary, the present invention systematically breaks through the bottleneck of the traditional purification process of trans-4-propionylcyclohexylbenzene through the dynamic coordination of three-stage gradient temperature control cycle, fractional addition of crystal seeds and intermittent stirring, combined with integrated filtration and drying equipment, and achieves efficient preparation of high-purity crystals (≥85.0%), overcoming the technical difficulties of multiple purifications, yield fluctuations and high energy consumption; industrial adaptability is significantly improved, and the flexible processing capacity design seamlessly matches 50-500kg production. The improvement of batch stability is achieved by quantifying process parameters. At the same time, a single petroleum ether solvent system and continuous equipment integration are used throughout the process, which reduces VOCs emissions and material transportation losses, providing a new green, stable and low-cost manufacturing path for liquid crystal intermediates.

[0064] The above is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field, within the technical scope disclosed by the present invention, can make equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention, which should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing high-purity trans-4-propionylcyclohexylbenzene, characterized in that: The following steps are involved: a) Solvent mixing: Mix crude trans-4-propionylcyclohexylbenzene with petroleum ether in a volume ratio of 1:(0.6-1.5) and stir until completely dissolved to form a homogeneous solution; b) Ultra-low temperature pre-crystallization: The solution obtained in step a) was cooled to -25°C ± 2°C at a rate of 1°C / min, seed crystals were added in batches with stirring, the total amount added being 2.5-10 wt% of the crude trans-4-propionylcyclohexylbenzene, and the temperature was further cooled to -40°C ± 2°C and maintained for 50-60 min; c) Gradient pre-crystallization strengthening: Stage 1: Cycle the following procedure five times: heat to -25°C ± 1°C at a rate of 0.5°C / min, stir under anchor mode for 20 min at a stirring speed of 100 rpm ± 10 rpm; cool to -35°C ± 1°C at a rate of 1°C / min, stir under anchor mode for 20 min at a stirring speed of 100 rpm ± 10 rpm; The second stage: cool down to -40℃±1℃ at a rate of 1℃ / min and hold for 50-60min. Start anchor stirring for 2min every 10min at a stirring speed of 100rpm±10rpm, for a total of 5 intermittent stirrings. d) Low-temperature solid-liquid separation: Filter at -10°C ± 2°C with a filtration pressure of -0.08 MPa to -0.1 MPa for 10 min or less. Rinse the filter cake three times with petroleum ether pre-cooled to -10°C. The amount of eluent used for each wash is 30% to 50% of the quality of the crude trans-4-propionylcyclohexylbenzene. e) Vacuum drying: Dry the filter cake for 4 hours under the conditions of -0.09 MPa vacuum, 25°C ± 2°C, nitrogen protection, and humidity ≤ 10% RH to obtain trans-4-propionylcyclohexylbenzene crystals with a purity of ≥ 85.0%.

2. The method for preparing high-purity trans-4-propionylcyclohexylbenzene according to claim 1, wherein: In the step a), the petroleum ether is a reagent-grade solvent with a distillation range of 90° C. to 120° C.; when the purity of the crude trans-4-propionylcyclohexylbenzene is less than 60%, it is required to be pre-treated by water washing, and the treatment steps are: mixing the crude product with deionized water in a mass ratio of 1:3, shaking for 10 minutes, and then separating the layers, and removing the solvent from the organic phase under reduced pressure until the moisture content is ≤0.5wt%.

3. The method for preparing high-purity trans-4-propionylcyclohexylbenzene according to claim 1 or 2, wherein: In step b), the seed crystal is prepared by dissolving pure trans-4-propionylcyclohexylbenzene in petroleum ether at a volume ratio of 1:2 and recrystallizing at -20°C to -25°C; the pure trans-4-propionylcyclohexylbenzene has a purity of ≥90% and a particle size of 50 to 100 μm; the solvent consists solely of petroleum ether and has a boiling range of 90°C to 120°C; The seed crystals are added in batches in step b): the seed crystals are added in equal amounts in 3 times, with a total addition amount of 2.5% to 10% of the crude trans-4-propionylcyclohexylbenzene quality, and each addition is 5 minutes apart; the stirring adopts an anchor stirrer with a speed of 100 rpm ± 10 rpm and a stirring power of 0.5 to 1.5 kw / m 3 .

4. The method for preparing high-purity trans-4-propionylcyclohexylbenzene according to claim 1, wherein Steps d) and e) are performed using a suction filtration and drying integrated machine, which comprises a first reaction box (1), the bottom end of the first reaction box (1) is fixedly connected to a connecting pipe (2), the bottom end of the connecting pipe (2) is fixedly connected to a second reaction box (3), the bottom end of the second reaction box (3) is fixedly connected to a discharge port (4), the first reaction box (1) performs a suction filtration operation through a suction filtration mechanism (5), and the second reaction box (3) performs a drying operation through a drying mechanism (6).

5. The method for preparing high-purity trans-4-propionylcyclohexylbenzene according to claim 4, wherein: The filtration mechanism (5) includes a filtration bottle (501), the filtration bottle (501) is arranged in the inner cavity of the first reaction box (1), the bottom end of the filtration bottle (501) is fixedly connected to a drain pipe (503), one side of the filtration bottle (501) is fixedly connected to a first air extraction pipe (505), the outer wall of the drain pipe (503) is installed with a valve (504), the drain pipe (503) and the first air extraction pipe (505) extend to the outside of the first reaction box (1), the top end of the filtration bottle (501) is fixedly connected to a connecting seat (502), the inner wall of the connecting seat (502) is fixedly connected to a connecting block (512), and the connecting block (512) is fixedly connected to the inner wall of the connecting seat (502). 12) is fixedly connected to the outer wall of the filter plate (513), a movable cylinder (508) is provided above the connecting seat (502), the top of the movable cylinder (508) is fixedly connected to the movable tube (507), the movable tube (507) is slidably connected to the first reaction box (1), the top of the movable tube (507) is fixedly connected to the hopper (506), the outer wall of the movable tube (507) is fixedly connected to the horizontal plate (509), the top of the first reaction box (1) is installed with a first motor (510), the output end of the first motor (510) is connected to a first threaded rod (511), and the first threaded rod (511) passes through the horizontal plate (509).

6. The method for preparing high-purity trans-4-propionylcyclohexylbenzene according to claim 5, wherein: The drying mechanism (6) includes a second motor (601), which is installed on one side of the first reaction box (1). The output end of the second motor (601) is connected to a second threaded rod (602). The interior of the connecting tube (2) is slidably connected to a shielding frame (603) extending from the connecting tube (2). The second threaded rod (602) passes through the shielding frame (603). The outer wall of the shielding frame (603) is fixedly connected to a pushing frame (604) extending to the inner cavity of the first reaction box (1). A through hole (605) is provided on the outer wall of the shielding frame (603). A second exhaust pipe (606) and an air inlet pipe (607) are fixedly connected to the outer wall of one side of the second reaction box (3). The bottom end of the inner wall of the second reaction box (3) is located at the top of the discharge port (4) and is fixedly connected to a square frame (608). The square frame The interior of (608) is rotatably connected to a rotating plate (609), and a constant temperature electric heater is provided on the inner wall of the square frame (608); the inner wall of the discharge port (4) is rotatably connected to a baffle (610), and one end of the rotating plate (609) and the baffle (610) are fixedly connected to a spur gear (611), and the discharge port (4) and the interior of the square frame (608) are slidably connected to a gear rod (614), and a third motor (612) is installed on the outer wall of one side of the discharge port (4), and the output end of the third motor (612) is connected to a third threaded rod (613), and the third threaded rod (613) passes through the gear rod (614), and the spur gear (611) contacts the gear rod (614), and the top end of the gear rod (614) is fixedly connected to a partition (615), and the partition (615) extends to the inner cavity of the air inlet pipe (607).

7. The method for preparing high-purity trans-4-propionylcyclohexylbenzene according to claim 5, wherein: The inner wall of the movable cylinder (508) is in contact with the outer wall of the filter plate (513), and the outer wall of the movable cylinder (508) is in contact with the inner wall of the connecting seat (502). The inner and outer walls of the movable cylinder (508) are both provided with sealing rings (7). The outer wall of the transverse plate (509) is provided with a first threaded hole, and the first threaded hole matches the first threaded rod (511).

8. The method for preparing high-purity trans-4-propionylcyclohexylbenzene according to claim 6, wherein: A second threaded hole is provided on the outer wall of the shielding frame (603), and the second threaded hole matches the second threaded rod (602).

9. The method for preparing high-purity trans-4-propionylcyclohexylbenzene according to claim 6, wherein: The gear rod (614) is L-shaped and a third threaded hole is provided at the bottom end of the lower horizontal rod, the third threaded hole matches the third threaded rod (613), and a tooth groove is provided on the outer wall of the upper vertical rod of the gear rod (614), and the tooth groove is engaged with the spur gear (611).

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