Steady-state material conveying method for the hydrogenation process of dimethyl 1,4-cyclohexanedicarboxylate.

Abstract

This invention belongs to the field of material transportation technology for the hydrogenation process of dimethyl 1,4-cyclohexanedicarboxylate (DMT), and discloses a steady-state material transportation method for the DMT hydrogenation process. DMT is pumped into a dissolving vessel via a feed pump, followed by the addition of lumpy dimethyl terephthalate (DTPB) through a silo. The dissolved material is then transported to a feeding vessel via pipelines and a material transfer pump. The dissolving vessel, material transport pipelines, and feeding vessel are all heated by a heat transfer medium, and the overall temperature is maintained at 100–150°C. Simultaneously, samples are taken at the outlet of the dissolving vessel to analyze the DMT / DMCD solution content and solid content. DMT concentration in the DMCD solution is 10–30 wt%. After the solid content meets the standard, the DMT / DMCD solution is pumped to the DMT feeding vessel using a material transfer pump. This method ensures stable transportation without material agglomeration and also offers advantages such as simple operation, safety, reliability, and strong adaptability.

Description

Technical Field

[0001] This invention belongs to the field of logistics transportation technology for the hydrogenation process of 1,4-cyclohexanedicarboxylate. Specifically, this invention relates to a steady-state material transportation method for easily clogging logistics, especially for the hydrogenation process of 1,4-cyclohexanedicarboxylate. Background Technology

[0002] 1,4-Cyclohexanedimethanol (CHDM), also known as 1,4-di(hydroxymethyl)cyclohexane, has CAS registry number 105-08-8. At room temperature, 99% pure CHDM is a white, waxy solid, while 90% hydrate is a colorless, transparent, or slightly turbid liquid. Its molecular formula is C8H₂O. 16 O2, with a molecular weight of 144.21, has two isomers: cis and trans.

[0003]

[0004] The industrial product is a mixture of cis and trans isomers, with the trans structure being more symmetrical, exhibiting high lattice energy and a regular structure. Therefore, the product has a high melting point and good heat resistance. The cis isomer has a melting point of 43℃, and the trans isomer has a melting point of 70℃. The mixture's melting point range is 40–60℃, boiling point range is 284℃–286℃, ignition point is 302℃, flash point is 169℃ (closed) and 167℃ (open), viscosity is 877 cP [MPa·S] (measured by SK at 50℃), density is 1.02–1.05 g / ml (measured at 25℃), and refractive index is 1.4893. It is miscible with water and alcohols, soluble in ketones, and almost insoluble in aliphatic hydrocarbons and diethyl ether. The intermediate product, dimethyl 1,4-cyclohexanedicarboxylate (DMCD), has a freezing point of 14 / 71℃.

[0005] In the industrial CHDM process, a two-step hydrogenation process using dimethyl terephthalate (DMT) is primarily employed. This two-stage hydrogenation is designed in two ways: fixed-bed gas-phase catalytic hydrogenation and high-pressure autoclave liquid-phase catalytic hydrogenation. The fixed-bed process offers advantages such as high production efficiency, simple catalyst-product separation, easy process control, and low energy consumption and operating costs, making it a more ideal industrial production technology. Since both DMT and DMC, the main raw materials for CHDM, are easily condensable, the technology for controlling condensation and blockage during the reaction process has a significant impact on the successful conduct of the hydrogenation reaction.

[0006] Patent 202011348630.X discloses a method for continuous production of CHDM, comprising a batching system, a continuous reaction system, and a solid-liquid separator connected in series. The continuous reaction system includes a first tower reactor and a second tower reactor connected in series. The batching system includes a DMT dissolving vessel and a DMT feed tank. The DMT dissolving vessel, DMT feed tank, and first tower reactor are connected in series. Solid DMT and DMC returned from the solid-liquid separator are mixed and dissolved in the DMT dissolving vessel. After the DMT is dissolved, it enters the DMT feed tank and is then piped into the first tower reactor. This method does not adequately consider the uneven dissolution of feedstock and the requirements for adjusting feedstock concentration under industrial conditions. It is difficult to achieve long-term uniform delivery of the reaction feedstock, easily leading to frequent changes in the composition of the output, which in turn affects downstream continuous hydrogenation operations. Summary of the Invention

[0007] To overcome the shortcomings of existing technologies, this invention provides a steady-state material conveying method for the hydrogenation process of dimethyl 1,4-cyclohexanedicarboxylate. Specifically, it relates to a material conveying method that achieves steady-state continuous material conveying in the hydrogenation process of dimethyl 1,4-cyclohexanedicarboxylate through a two-stage dissolution-feeding reactor connected in series. This method can achieve stable conveying without material agglomeration and also has the advantages of simple operation, safety, reliability, and strong adaptability.

[0008] The above-mentioned objective of this invention is achieved through the following technical solution:

[0009] A steady-state material conveying method for the hydrogenation process of 1,4-cyclohexanedicarboxylate (DMCD) involves pumping DMCD into a dissolving vessel via a feed pump, followed by adding lumpy dimethyl terephthalate (DMT) into the dissolving vessel via a silo. The dissolved material is then transported to a feeding vessel via pipelines and a material transfer pump. The dissolving vessel, material conveying pipelines, and feeding vessel are all heated by a heat transfer medium, and the overall temperature is maintained at 100-150°C. Simultaneously, samples are taken at the outlet of the dissolving vessel to analyze the DMT / DMCD solution content and solid content. The DMT concentration in the DMCD solution is 10-30 wt%. Once the solid content meets the standard, the DMT / DMCD solution is pumped to the DMT feeding vessel using a material transfer pump.

[0010] The system used in the above method includes a feeding device, a dissolving vessel connected in series, and a feeding vessel. The bottom of the dissolving vessel is connected to the feeding vessel via a material conveying pipeline, and a material conveying pump is installed on the material conveying pipeline. The dissolving vessel is externally connected to DMCD raw material inlet pipelines and DMT raw material inlet pipelines. Heating devices are installed outside the dissolving vessel, the material conveying pipeline, and the feeding vessel. Temperature sensors are installed at the outlet end of the dissolving vessel, the front, middle, and end ends of the material conveying pipeline, and the inlet end of the feeding vessel. A branch detection pipeline is also connected to the bottom of the dissolving vessel, and a butterfly valve is installed on the detection pipeline. The branch detection pipeline is used to monitor the content and solid content of the dissolved DMT / DMCD solution at any time. The entire system ensures sealing performance.

[0011] The bottom of the feeding vessel is connected to the DMT hydrogenation reaction system via a pipeline (this is existing technology and is not specifically limited). A feeding pump and a flow meter are installed on the pipeline.

[0012] The heating device is not specifically limited and can be set according to the specific conditions of the heat medium and operating conditions; existing equipment that meets the operating conditions is acceptable. The heat medium is preferably water or steam.

[0013] The dissolving vessel and the feeding vessel are also equipped with a vessel top heat exchanger, which uses low-pressure steam as a heat source. During the dissolving process, pay attention to the DMT sublimation crystallization site as seen in the sight glass on the top of the vessel. If the situation is serious, promptly connect low-pressure steam to the vessel top heat exchanger to melt the crystallized material.

[0014] Furthermore, both the dissolving vessel and the feeding vessel are equipped with sight glasses on the top for observing whether DMT has sublimated and crystallized.

[0015] Furthermore, the dissolving vessel and the feeding vessel are preferably equipped with full jacketed heating systems. The temperature after heating is 100–150°C.

[0016] Furthermore, a feeding device is installed before the dissolving tank to crush the lumpy raw materials to 10-20 mesh. This feeding device uniformly crushes the DMT lumpy raw materials and then feeds them into the dissolving tank.

[0017] Furthermore, the top of the dissolving vessel is also equipped with an absorption tank for absorbing sublimated DMCD. The absorption tank and the dissolving vessel are connected by a closed pipeline. The outlet of the absorption tank is connected to the inlet of the dissolving vessel. The absorption tank is also equipped with a cooling mechanism to cool the DMCD in the absorption tank and then return it to the dissolving vessel.

[0018] Furthermore, a stirring rod is installed inside the dissolving vessel, and the top of the stirring rod is connected to a motor, which is located at the top of the dissolving vessel.

[0019] Furthermore, a stirring rod is installed inside the feeding vessel, and the top of the stirring rod is connected to a motor, which is located at the top of the feeding vessel.

[0020] Furthermore, the motor is a servo motor, and there is no limitation on a specific model, as long as it can drive the stirring rod to move.

[0021] Furthermore, butterfly valves, pressure sensors, and temperature sensors are installed on both the DMCD raw material feed line and the DMT raw material feed line.

[0022] Furthermore, the bottom of the stirring rod is provided with a double Z-shaped stirring element, which makes the stirring more thorough.

[0023] Furthermore, butterfly valves are also installed on the material conveying pipeline.

[0024] The system is also equipped with a PLC control system. The motor, flow meter, temperature sensor, pressure sensor, butterfly valve, heating device, material conveying pump, and feed pump are all connected to the PLC control system. There is no restriction on a specific model, as long as the working function is realized.

[0025] The dissolved homogeneous flow dynamics can be used for subsequent mixing and hydrogenation of feedstocks, and samples are taken periodically for gas chromatography to detect the DMT and DMCD content.

[0026] The advantages of this invention compared to the prior art are:

[0027] This invention provides a steady-state material conveying method for the hydrogenation process of dimethyl 1,4-cyclohexanedicarboxylate (DMT). This method achieves steady-state continuous material conveying in the DMT hydrogenation process through a dual-reactor system (dissolution-feeding). This invention can achieve stable conveying under flexible adjustment of raw material concentration, without material precipitation or blockage. It has advantages such as simple operation, safety, reliability, and strong adaptability. Furthermore, this method is suitable for the dissolution hydrogenation of DMT with different raw material sizes, such as lumps or powders, improving adaptability to raw materials. Attached Figure Description

[0028] Figure 1 This is a simplified flowchart of the system of the present invention.

[0029] In the diagram: 1. Dissolving vessel, 2. Feeding vessel, 3. Absorption tank. Detailed Implementation

[0030] The present invention is described in detail below through specific embodiments, but this does not limit the scope of protection of the present invention. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can all be obtained commercially.

[0031] Example 1

[0032] A steady-state material conveying method for the hydrogenation process of 1,4-cyclohexanedicarboxylate (DMCD) involves pumping DMCD into a dissolving vessel via a feed pump, followed by adding lumpy dimethyl terephthalate (DMT) into the dissolving vessel via a silo. The dissolved material is then transported to a feeding vessel via pipelines and a material transfer pump. The dissolving vessel, material conveying pipelines, and feeding vessel are all heated by a heat transfer medium, and the overall temperature is maintained at 150°C. Simultaneously, samples are taken at the outlet of the dissolving vessel to analyze the DMT / DMCD solution content and solid content. Once the solid content reaches 10%, the DMT / DMCD solution is pumped to the DMT feeding vessel using a material transfer pump.

[0033] The system used in the above method includes a dissolving vessel and a feeding vessel connected in series. The bottom of the dissolving vessel is connected to the feeding vessel via a material conveying pipeline, and a material conveying pump is installed on the material conveying pipeline. The dissolving vessel is externally connected to DMCD raw material inlet pipelines and DMT raw material inlet pipelines. Heating devices are installed on the dissolving vessel, the material conveying pipelines, and the feeding vessel. Temperature sensors are installed at the outlet end of the dissolving vessel, the front, middle, and end ends of the material conveying pipeline, and the inlet end of the feeding vessel. A branch detection pipeline is also connected to the bottom of the dissolving vessel, and a butterfly valve is installed on the detection pipeline. The branch detection pipeline is used to monitor the content and solid content of the dissolved DMT / DMCD solution at any time. The entire system ensures sealing performance.

[0034] The bottom of the feeding vessel is connected to the DMT hydrogenation reaction system via a pipeline (this is existing technology and is not specifically limited). A feeding pump and a flow meter are installed on the pipeline.

[0035] The heating device is not specifically limited and can be set according to the specific conditions of the heat medium and operating conditions; existing equipment that meets the operating conditions is acceptable. The heat medium is preferably water or steam.

[0036] The dissolving vessel and the feeding vessel are also equipped with a vessel top heat exchanger, which uses low-pressure steam as a heat source. During the dissolving process, pay attention to the DMT sublimation crystallization site as seen in the sight glass on the top of the vessel. If the situation is serious, promptly connect low-pressure steam to the vessel top heat exchanger to melt the crystallized material.

[0037] Both the dissolving vessel and the feeding vessel are equipped with sight glasses on the top for observing whether DMT has sublimated and crystallized.

[0038] The dissolving vessel and feeding vessel are preferably equipped with full jacketed heating. The temperature after heating should not be less than 100-150℃.

[0039] A stirring rod is installed inside the dissolving vessel, and the top of the stirring rod is connected to a motor, which is located at the top of the dissolving vessel.

[0040] A stirring rod is installed inside the feeding vessel, and the top of the stirring rod is connected to a motor, which is located on the top of the feeding vessel.

[0041] The motor is a servo motor, and there is no restriction on a specific model. It is sufficient to drive the stirring rod to move.

[0042] Butterfly valves, pressure sensors, and temperature sensors are installed on both the DMCD raw material feed line and the DMT raw material feed line.

[0043] The bottom of the stirring rod is equipped with a double Z-shaped stirring element, which makes the stirring more thorough.

[0044] Butterfly valves are also installed on the material conveying pipeline.

[0045] The system is also equipped with a PLC control system. The motor, flow meter, temperature sensor, pressure sensor, butterfly valve, heating device, material conveying pump, and feed pump are all connected to the PLC control system. There is no restriction on a specific model, as long as the working function is realized.

[0046] The dissolved homogeneous flow dynamics can be used for subsequent mixing and hydrogenation of feedstocks, and samples are taken periodically for gas chromatography to detect the DMT and DMCD content.

[0047] DMT solid raw material is continuously added to the dissolving vessel from the DMT silo via a DMT weighing sensor and the DMT feed pipe. DMCD is also added to the DMT dissolving vessel. Under stirring, the DMT solid dissolves rapidly in the high-temperature DMCD solution. Low temperatures can easily cause DMT solid to precipitate. Excessively high temperatures can cause DMT to sublimate and condense on the pipe walls, clogging the pipes.

[0048] The dissolved DMT and DMCD solutions are pumped to the DMT feed vessel via a material transfer pump. The liquid collected from the bottom of the DMT feed vessel is pressurized by the DMT feed pump and then pumped to the DMT hydrogenation reaction section. The feed rate is a crucial parameter for production control. If the feed rate is too low, it can easily cause a rapid drop in reaction temperature and pressure, leading to safety accidents. Therefore, the feed rate should be closely monitored.

[0049] Example 2

[0050] The concentration of DMT in the DMCD solution was limited to 10 wt%, and other parameters were the same as in Example 1, with a dissolution time of 1 min.

[0051] Example 3

[0052] The concentration of DMT in the DMCD solution was limited to 20 wt%, and other parameters were the same as in Example 1, with a dissolution time of 2 min.

[0053] Example 4

[0054] The concentration of DMT in the DMCD solution was limited to 30 wt%, and other parameters were the same as in Example 1, with a dissolution time of 3 min.

[0055] Comparative Example 1

[0056] The overall temperature was maintained at 100°C, and everything else was the same as in Example 2. The dissolution time was 8 minutes and 20 seconds.

[0057] Comparative Example 2

[0058] The overall temperature was maintained at 100°C, and everything else was the same as in Example 3. The dissolution time was 10 minutes and 30 seconds.

[0059] Comparative Example 3

[0060] The overall temperature was maintained at 100°C, and everything else was the same as in Example 4; the substance did not dissolve.

[0061] Comparative Example 4

[0062] The overall temperature was maintained at 140°C, and everything else was the same as in Example 2. The dissolution time was 4 minutes and 30 seconds.

[0063] Comparative Example 5

[0064] The overall temperature was maintained at 140°C, and everything else was the same as in Example 3. The dissolution time was 6 minutes and 15 seconds.

[0065] Comparative Example 6

[0066] The overall temperature was maintained at 140°C, and everything else was the same as in Example 4. The dissolution time was 9 minutes and 20 seconds.

[0067] Comparative Example 7

[0068] The dissolving vessel and feeding vessel were fully jacketed and heated to 170°C. Other aspects were the same as in Example 2, with visible DMT sublimations.

[0069] Comparative Example 8

[0070] The dissolving vessel and the feeding vessel are fully jacketed and heated to 90°C. Everything else is the same as in Example 2, but no dissolution occurs.

[0071] The embodiments described above are merely preferred embodiments of the present invention, and not all feasible embodiments of the present invention. Any obvious modifications made by those skilled in the art without departing from the principles and spirit of the present invention should be considered to be included within the scope of protection of the claims of the present invention.

Claims

1. A material steady state transfer process for 1,4-cyclohexanedicarboxylic acid dimethyl ester hydrogenation process characterized by, The dimethyl 1,4-cyclohexanedicarboxylate is pumped into the dissolving kettle by the feeding pump, then the blocky dimethyl terephthalate is added into the dissolving kettle through the stock bin, the dissolved material is transported to the feed kettle through the pipeline and the material conveying pump, the dissolving kettle, the material conveying pipeline and the feed kettle are all heated by the heat medium, and the overall temperature is kept at 100-150℃, at the same time, the DMT / DMCD solution content and the solid content at the outlet of the dissolving kettle are sampled and analyzed, when the DMT concentration in the DMCD solution is 10-30 wt%, and the solid content reaches 10%, the DMT / DMCD solution is transported to the DMT feed kettle by the material conveying pump; The system used in the method comprises a discharging device, a dissolving kettle and a feed kettle connected in series; the bottom of the dissolving kettle is connected with the feed kettle through a material conveying pipeline, and a material conveying pump is arranged on the material conveying pipeline, and the dissolving kettle is externally connected with a DMCD raw material feeding pipeline and a DMT raw material feeding pipeline; heating devices are arranged outside the dissolving kettle, the material conveying pipeline and the feed kettle, and temperature sensors are arranged at the outlet end of the dissolving kettle, the front end, the middle end and the tail end of the material conveying pipeline and the inlet end of the feed kettle, and a branch detection pipeline is further connected to the bottom of the dissolving kettle, and a butterfly valve is arranged on the detection pipeline; the branch detection pipeline is used to inspect the DMT / DMCD solution content and the solid content at any time; The dissolving kettle and the feed kettle are provided with full-jacket heating; the temperature after heating is 100-150℃.

2. The material steady state transfer process for 1,4 cyclohexane dimethanolate dimethyl ester hydrogenation process as claimed in claim 1 wherein, The top of the dissolving kettle and the top of the feed kettle are further provided with kettle top heat exchangers, and the kettle top heat exchangers take low-pressure steam as the heat source.

3. The material steady state transfer process for 1,4 cyclohexane dimethanolate dimethyl ester hydrogenation process as claimed in claim 1, wherein, The top of the dissolving kettle and the top of the feed kettle are both provided with kettle top sight glasses for observing whether the DMT sublimates and crystallizes.

4. The material steady state transfer process for 1,4 cyclohexane dimethanol dimethyl ester hydrogenation process as claimed in claim 1 wherein, A stirring rod is arranged in the dissolving kettle, and the top of the stirring rod is connected with a motor, and the motor is arranged at the top of the dissolving kettle.

5. The material steady state transfer process for 1,4 cyclohexane dimethanol hydrolysis process as claimed in claim 1, wherein, A stirring rod is arranged in the feed kettle, and the top of the stirring rod is connected with a motor, and the motor is arranged at the top of the feed kettle.

6. The material steady state conveying process for 1,4 cyclohexane dimethanolate dimethyl ester hydrogenation process as claimed in claim 1, wherein, Butterfly valves, pressure sensors and temperature sensors are arranged on the DMCD raw material feeding pipeline and the DMT raw material feeding pipeline.

7. The material steady state conveying process for 1,4 cyclohexane dimethanolate dimethyl ester hydrogenation process as claimed in claim 1, wherein, A butterfly valve is further arranged on the material conveying pipeline.

8. The material steady state conveying process for 1,4-cyclohexanedicarboxylic acid dimethyl ester hydrogenation process according to any one of claims 1 to 7, characterized in that, A discharging device is arranged in front of the dissolving kettle, and the blocky raw material is crushed to 10-20 meshes; the discharging device uniformly crushes the DMT blocky raw material and then puts it into the dissolving kettle.

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