Device and process method for producing trimellitic anhydride through continuous liquid-phase oxidation of unsym-trimethylbenzene

Abstract

The invention relates to a device and a process method for producing trimellitic anhydride by continuous liquid-phase oxidation of unsym-trimethylbenzene. The device comprises an oxidation reaction tower, a DTB crystallizer, a horizontal screw centrifuge, an anhydride forming tower and a rectifying tower which are connected in sequence, the oxidation reaction tower is provided with N feed ports and N gas inlets, wherein N is greater than or equal to 3; 2N distributors are arranged in the cavity of the oxidation reaction tower; and the distributor is respectively connected with the feeding hole and the air inlet. The whole technological process is simple, the equipment investment is low, the automation degree is high, the product yield is high, the quality is good, the overall energy utilization efficiency is high, and part of problems existing in an intermittent process are solved.

Description

Technical Field

[0001] This application relates to an apparatus and process for the continuous liquid-phase oxidation of pseudotrimethylbenzene to produce pseudotriic anhydride, belonging to the field of chemical production technology. Background Technology

[0002] Trimericic anhydride, scientifically known as 1,2,4-phenyltricarboxylic anhydride, is also called trimellitic anhydride. Its molecular formula is C9H4O5. It appears as white flakes. Its melting point is 168℃, and its boiling point is 390℃. It is soluble in hot water, acetone, 2-acetone, dimethylformamide, ethyl acetate, and cyclohexanone. It is soluble in anhydrous ethanol and reacts with it; it is slightly soluble in carbon tetrachloride and toluene. Trimericic anhydride can be used to manufacture polyester resins and polyimide resins, water-soluble polyester resins, water-soluble polyurethane resins, plasticizers and water-soluble amino alkyd resins, epoxy resin curing agents, as well as high-grade aviation lubricants, power capacitor impregnating oils, granular binders, sizing agents, smoke suppressants, instant binders, and TOTM, etc.

[0003] Currently, the main production process for trimellitic anhydride employs the batch oxidation method. This batch process involves first dissolving the raw material, trimellitene, in acetic acid, and then oxidizing it to produce trimellitic acid. The resulting trimellitic acid mixture with the solvent is then directly added to a crystallization reactor. The solvent and water are first evaporated by heating, and then the temperature is raised to remove an intramolecular water molecule, yielding crude trimellitic anhydride. This crude product is then subjected to a batch distillation process to finally obtain the finished trimellitic anhydride product. The main problems with this method are long reaction time, incomplete reaction, many by-products, unstable quality, and low product yield. During batch production, the reactor needs to frequently change pressure and temperature conditions, which leads to equipment fatigue and shortened service life. The oxidation step has a risk of explosion due to the possibility of entering the explosion limit range with each temperature and pressure increase, resulting in low safety. The trimellitic anhydride produced by the batch method has poor quality, unstable quality, and severe material decomposition. The batch crystallization method uses a heating evaporation deacidification process to evaporate acetic acid and water, while catalysts such as cobalt and manganese are retained in the crude trimellitic anhydride, which increases catalyst consumption and decomposition of trimellitic anhydride in subsequent processes.

[0004] In addition, domestically, there are also stepwise oxidation and stirred multi-stage continuous oxidation processes, which have the advantage of achieving continuous production of local processes, such as patent publication number: CN1594302A. However, stirred tank reactors have high investment costs, are prone to leakage and damage of dynamic sealing components, have insufficient gas-liquid separation in the oxidation reactor effluent, and poor heat exchange efficiency in the condenser. Furthermore, continuous operation cannot be temperature-controlled, which is not conducive to crystal growth and results in poor crystallization. The mother liquor with incomplete crystallization must be recycled to achieve the purpose of crystallization separation, and the inlet of each crystallizer is prone to blockage. In the above methods, the purification of crude trimellitic anhydride is carried out by single-tower batch or continuous distillation. Since crude trimellitic anhydride contains complex impurities, a simple distillation alone cannot produce a high-purity product. To ensure product quality, it is necessary to collect more light and heavy components and perform multiple distillations, which leads to a decrease in purification yield and an increase in energy consumption. Summary of the Invention

[0005] To address the problem of incomplete crystallization of the mother liquor leading to blockage of the crystallizer outlet in existing trimellitic anhydride preparation processes, a method for producing trimellitic anhydride using a continuous liquid-phase oxidation process of trimellitylene is provided. This method offers advantages such as stable reaction, continuous production capability, high product quality, and high energy efficiency.

[0006] In one aspect, the present invention provides an apparatus for the continuous liquid-phase oxidation of pseudotrimethylbenzene to produce pseudotriglyceride.

[0007] The apparatus comprises an oxidation reaction tower, a DTB crystallizer, a horizontal screw centrifuge, an anhydride formation tower, and a distillation tower connected in sequence.

[0008] The oxidation reaction tower is provided with N feed inlets and N air inlets, where N≥3;

[0009] The oxidation reaction tower is equipped with 2N distributors inside its cavity;

[0010] The distributor is connected to the feed inlet and the air inlet respectively.

[0011] Optionally, the device further includes a cooler;

[0012] The oxidation reaction tower is provided with a gas phase outlet I at the top, and the gas phase outlet I is connected to a cooler;

[0013] The bottom of the oxidation reaction tower is provided with a discharge port I, which is connected to the DTB crystallizer via a discharge pump.

[0014] Optionally, the cooler outlet is connected to a gas-liquid separator, and the gas phase outlet II at the top of the gas-liquid separator is connected to an air compressor;

[0015] The gas-liquid separator is also provided with a liquid phase outlet, and the side wall at the bottom of the oxidation reaction tower is also provided with a liquid phase inlet, and the liquid phase outlet is connected to the liquid phase inlet.

[0016] Optionally, the height-to-diameter ratio of the oxidation reaction tower is 8 to 14:1.

[0017] Optionally, N can be 3 to 5.

[0018] Optionally, the DTB crystallizer is externally equipped with a circulating pump and a heater connected in series;

[0019] The lower part of the DTB crystallizer is connected to a precipitating column;

[0020] The DTB crystallizer is equipped with a flow guide tube and a cylindrical baffle.

[0021] Optionally, a settlement zone is provided around the cylindrical baffle;

[0022] The lower part of the analysis column is provided with a discharge port II, which is connected to the horizontal screw centrifuge via a discharge pump.

[0023] Optionally, the horizontal screw centrifuge is provided with a liquid discharge port and a slag discharge port;

[0024] The drain outlet is connected to the DTB crystallizer;

[0025] The slag discharge port is connected to the anhydride formation tower.

[0026] Optionally, the anhydride-forming tower is provided with multiple layers of packing.

[0027] The anhydride-forming tower has a partial anhydride outlet in the middle that is connected to the distillation tower.

[0028] The bottom of the anhydride-forming tower is provided with a heavy component outlet I;

[0029] The height-to-diameter ratio of the anhydride-forming tower is 1 to 3:1.

[0030] Optionally, the distillation column is provided with a discharge port III at the top, and the discharge port III is connected in sequence to the condenser I and the anhydride storage tank;

[0031] The distillation column reboiler is connected to a reboiler and a heavy component outlet II.

[0032] Optionally, the apparatus further includes an acetic acid recovery tower.

[0033] The top of the DTB crystallizer is also provided with a gas phase outlet III, which is connected to the acetic acid recovery tower.

[0034] The top of the anhydride formation tower is also provided with a gas phase outlet IV, which is connected to the acetic acid recovery tower.

[0035] The acetic acid recovery tower is provided with a discharge port at the top, and the discharge port is connected in sequence to a condenser II and a reflux tank.

[0036] The return tank is connected to a wastewater treatment unit;

[0037] The acetic acid recovery tower is provided with an acetic acid recovery outlet at the bottom, which is connected to an acetic acid storage tank.

[0038] In another aspect, the present invention provides a process for producing triglyceride through continuous liquid-phase oxidation of pseudotrimethylbenzene. The raw materials containing pseudotrimethylbenzene, acetic acid, and a cobalt-manganese-bromine ternary catalyst are mixed with air in an oxidation reaction tower to undergo an oxidation reaction and obtain a reaction product. The reaction product is then passed sequentially through a DTB crystallizer, a horizontal screw centrifuge, an anhydride formation tower, and a distillation tower to undergo crystallization, filtration, and anhydride formation in sequence to obtain the triglyceride.

[0039] Optionally, the molar ratio of pseudotrimethylbenzene to acetic acid is 1:1 to 25, and the molar ratio of pseudotrimethylbenzene to oxygen in the air is 1:10 to 50.

[0040] The cobalt-manganese-bromine ternary catalyst is a mixture of cobalt acetate, manganese acetate and tetrabromoethane;

[0041] The mass ratio of the mixture containing pseudotrimethylbenzene and acetic acid to cobalt acetate, manganese acetate, and tetrabromoethane is 1:0.001~0.01:0.001~0.01:0.0001~0.008.

[0042] Optionally, the oxygen volume content in the air is 18-22%.

[0043] Optionally, the reaction conditions for the oxidation reaction are as follows:

[0044] The pressure of the oxidation reaction is 1–4 MPa;

[0045] The oxidation reaction is carried out at a temperature of 100–320°C.

[0046] Optionally, the raw material feed flow rate is 0.5–10 m³ / h. 3 / h;

[0047] The air feed flow rate is 25–1000 m³ / h. 3 / h.

[0048] Optionally, the moisture content of the solid material, including trimellitic acid, is reduced to 10% to 50% by the horizontal screw centrifuge.

[0049] Optionally, the anhydride formation is carried out in an anhydride formation tower;

[0050] The conditions for anhydride formation are as follows:

[0051] The anhydride-forming pressure is 0.3–0.8 MPa, and the anhydride-forming temperature is 240–280 °C.

[0052] In this invention, the oxidation process is continuous. Trimethylbenzene is first oxidized to trimellitic acid and trimellitic acid, then to trimellitic acid. Due to the internal structure of the oxidation tower and the influence of the discharge, the materials within the tower may be unevenly mixed. This invention employs a feed distributor to ensure relatively uniform distribution of the materials within the reactor, minimizing excessive mixing between intermediate and final products. In the initial stage of the reaction, the heat release is high, allowing the process to proceed at a lower temperature without the need for heat exchange equipment. In the middle stage, the reaction continues to release heat, requiring the removal of some of the heat. In the later stage, the heat release is lower, necessitating the provision of sufficient heat to maintain the reaction temperature.

[0053] The reaction solution enters a DTB-type crystallizer. A separation column is connected to the bottom of the crystallizer. The crystallizer contains a guide tube and cylindrical baffles. During operation, the solution is continuously added to the bottom of the circulation pipe, mixing with the mother liquor containing small crystals, and then pumped to the heater. The heated solution flows into the crystallizer near the bottom of the guide tube and is propelled to the liquid surface by a slowly rotating propeller. The solution evaporates and cools at the liquid surface, reaching a supersaturated state. Some of the solute deposits on the surface of the suspended particles, causing crystal growth. There is a settling zone outside the annular baffles. In this zone, large particles settle, while small particles enter the circulation pipe with the mother liquor and dissolve upon heating. The crystals enter the separation column at the bottom of the crystallizer. To ensure the crystallized product has a uniform particle size, some of the mother liquor from the settling zone is added to the bottom of the separation column. Utilizing hydraulic classification, small particles return to the crystallizer with the liquid flow, while the crystallized product exits from the bottom of the separation column and enters a horizontal screw centrifuge.

[0054] The crystallized slurry enters a horizontal screw centrifuge. Inside the centrifuge, the drum and screw rotate at high speed in the same direction with a certain differential speed. The material is continuously introduced into the inner cylinder of the conveying screw through the feed pipe, and after acceleration, it enters the drum. Under the action of centrifugal force, the heavier solid phase is deposited on the drum wall to form a sludge layer. The conveying screw continuously pushes the deposited solid phase to the conical end of the drum and discharges it from the machine through the sludge discharge port. The lighter liquid phase forms an inner liquid ring, which continuously overflows from the large end of the drum and is discharged from the machine through the liquid discharge port. The horizontal screw centrifuge can continuously feed, separate, wash, and discharge at full speed, thereby achieving the continuous separation of crystallized trimellitic acid and mother liquor.

[0055] The centrifuged solid material enters the anhydride-forming tower, where the temperature is raised to melt trimellitic acid, and the residual acetic acid and water in the wet material are evaporated. The acetic acid and water vapor leave through the gas phase outlet. The material continues to remove one molecule of water in the packing of the anhydride-forming tower to obtain crude trimellitic anhydride. After purification in the purification tower, the finished trimellitic anhydride is obtained. The heavy components are discharged from the heavy components outlet at the bottom of the purification tower.

[0056] A further improvement of this invention is that the oxidation tower has a relatively simple structure, low cost, and saves investment costs; the crystallizer and centrifuge are independent devices with mature technology, and multiple units can be arranged in parallel, which is convenient for maintenance and has low technical risk; when using continuous air-liquid phase oxidation, the molar ratio of pseudotrimethylbenzene to acetic acid is 1:1 to 25, and the molar ratio of pseudotrimethylbenzene to oxygen in the air is 1:10 to 50; the cobalt-manganese-bromine ternary catalyst is a mixture of cobalt acetate, manganese acetate, and tetrabromoethane, and the mass ratio of the pseudotrimethylbenzene and acetic acid mixture to the catalyst cobalt acetate, manganese acetate, and tetrabromoethane is 1:0.001 to 0.01:0.001 to 0.01:0.0001 to 0.008, the oxidation reaction temperature is 100 to 320°C, and the absolute pressure is 1 to 4 MPa. By adopting the above material ratios and reaction conditions, the amount of catalyst used can be reduced, and the equipment requirements are relatively low, saving investment costs. Furthermore, to improve environmental performance, the air used is a gas with an oxygen volume content of 18-22%. The oxygen content of the exhaust gas after the reaction is reduced, and it can be mixed with fresh air in a certain proportion for recycling, improving oxygen utilization and reducing waste gas emissions.

[0057] The beneficial effects that this application can produce include:

[0058] 1) The process method provided in this application has a simple overall process flow and requires relatively few equipment, thus saving investment.

[0059] 2) In the process method provided in this application, the materials in the oxidation tower are mixed evenly, and each reaction section can achieve a high reaction efficiency.

[0060] 3) In the process method provided in this application, oxidation, crystallization, centrifugation and anhydride formation are completed continuously, which can shorten the reaction time, reduce the generation of reaction by-products, and have relatively low material and energy consumption, thereby improving yield and product quality. Attached Figure Description

[0061] Figure 1 This is a flowchart illustrating the continuous liquid-phase oxidation of pseudotrimethylbenzene to produce trimethylamine anhydride, as described in this application.

[0062] List of components and reference numerals:

[0063] #1: Batching tank; #2: Oxidation reaction tower; #3: Cooler; #4: Gas-liquid separator; #5: DTB crystallizer; #6: Heater; #7: Horizontal screw centrifuge; #8: Anhydride formation tower; #9: Refining tower; #10: Condenser; #11: Partial anhydride storage tank; #12: Reboiler; #13: Acetic acid recovery tower; #14: Condenser; #15: Reflux tank; #16: Acetic acid recovery tower reboiler. Detailed Implementation

[0064] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0065] Unless otherwise specified, the raw materials and catalysts used in the embodiments of this application were all purchased commercially.

[0066] In the embodiments of this application, the conversion rate, selectivity, yield, and purity are calculated as follows:

[0067] In the embodiments of this application, the conversion rate, selectivity, and yield are all calculated based on the molar amount of the raw material:

[0068] Conversion rate = Molar amount of reactants / Total molar amount of reactants;

[0069] Selectivity = Molar amount of reactant converted to the target product / Molar amount of reactant participating in the reaction;

[0070] Yield = Molar amount of raw material converted into target product / Total molar amount of raw material.

[0071] A method for producing trimellitic anhydride via continuous liquid-phase oxidation of trimellitene uses trimellitene and air as raw materials, acetic acid as solvent, and a cobalt-manganese-bromine ternary catalyst. Trimericic acid is generated through an aromatic side-chain oxidation reaction, followed by continuous crystallization, filtration, and anhydride formation processes to obtain trimellitic anhydride. The specific process is as follows: Figure 1 As shown.

[0072] Pseudotrimethylbenzene raw material and acetic acid solvent are added to mixing tank #1 in a certain proportion. The mixing tank is connected to the inlet via a feed pump.

[0073] The oxidation reaction is carried out in oxidation reaction tower #2. The oxidation reaction tower has at least three feed inlets and at least three gas inlets from top to bottom. The top of the oxidation tower is provided with a gas phase outlet I and connected to a cooler #3. The cooler outlet is connected to a gas-liquid separator #4. The oxidation tail gas is discharged from the gas phase outlet II at the top of the gas-liquid separator. When the oxygen concentration in the tail gas is high, it can be recycled. The bottom of the gas-liquid separator flows back to the upper part of the oxidation reaction tower #1. The bottom of the oxidation tower is provided with a discharge outlet I, which is connected to the DTB crystallizer #5 via a discharge pump.

[0074] The reaction solution enters DTB-type crystallizer #5. A precipitating column is connected to the bottom of the crystallizer, which contains a guide tube and cylindrical baffles. During operation, the feed solution is continuously added to the lower part of the circulation pipe, where it mixes with the mother liquor containing small crystals and is then pumped to heater #6. The heated solution flows into the crystallizer near the bottom of the guide tube and is then propelled to the liquid surface by a slowly rotating propeller along the guide tube. The solution evaporates and cools at the liquid surface, reaching a supersaturated state. Crystallizer #5 has a gas phase outlet III at the top; the distilled acetic acid enters acetic acid recovery tower #13. Some of the solute deposits on the surface of the suspended particles, causing crystal growth. There is a settling zone outside the annular baffle. Large particles settle in this zone, while smaller particles are carried by the mother liquor into the circulation pipe and dissolved by heat. Crystals enter the eluent column at the bottom of the crystallizer. To ensure the crystallized product has a uniform particle size, some of the mother liquor from the settling zone is added to the bottom of the eluent column. Utilizing hydraulic classification, small particles return to the crystallizer with the liquid flow. The crystallized product exits from the discharge port II at the bottom of the eluent column and enters the horizontal screw centrifuge #7. The crystallized slurry enters the horizontal screw centrifuge #7, where the drum and screw rotate at a certain differential speed in the same direction at high speed. The material is continuously introduced into the inner cylinder of the conveying screw through the feed pipe, accelerated, and then enters the drum. Under the action of the centrifugal force field, heavier solids deposit on the drum wall, forming a sludge layer. The conveying screw continuously pushes the deposited solids to the conical end of the drum, where they are discharged from the machine through the sludge discharge port. The lighter liquid phase forms an inner liquid ring, continuously overflowing from the large end of the drum and exiting through the drain port. The solvent containing trimellitic acid returns to the DTB crystallizer #5 from the drain port. The horizontal screw centrifuge can continuously feed, separate, wash, and discharge at full speed, thus achieving the continuous separation of the crystallized trimellitic acid and the mother liquor.

[0075] The centrifuged solid material enters the anhydride-forming tower #8, where the temperature is raised to melt trimellitic acid and evaporate the residual acetic acid and water from the wet material. The acetic acid and water vapor leave through the gas phase outlet IV. The material continues to remove one molecule of water in the packing of the anhydride-forming tower to obtain crude trimellitic anhydride. After purification in the refining tower #9, the finished trimellitic anhydride is obtained. The heavy components are discharged from the heavy components outlet II at the bottom of the refining tower. The top discharge of the distillation tower is connected to the condenser #10 and the trimellitic anhydride storage tank #11. The discharge of the trimellitic anhydride storage tank is sent to the slicing unit. The reboiler #12 of the distillation tower is heated by heat transfer oil.

[0076] Acetic acid recovery tower #13 has an acetic acid recovery outlet at the bottom. The recovered acetic acid is returned to the acetic acid storage tank for recycling. The discharge port IV at the top of the acetic acid recovery tower is connected to condenser #14 and reflux tank #15. Process wastewater is sent to the sewage treatment unit.

[0077] When using continuous air-liquid phase oxidation, the molar ratio of pseudotrimethylbenzene to acetic acid is 1:1–25, and the molar ratio of pseudotrimethylbenzene to oxygen in the air is 1:10–50. The cobalt-manganese-bromine ternary catalyst is a mixture of cobalt acetate, manganese acetate, and tetrabromoethane. The mass ratio of the pseudotrimethylbenzene and acetic acid mixture to the catalyst (cobalt acetate, manganese acetate, and tetrabromoethane) is 1:0.001–0.01:0.001–0.01:0.0001–0.008. The oxidation reaction temperature is 100–320℃, and the absolute pressure is 1–4 MPa. Using the above material ratios and reaction conditions can reduce the amount of catalyst used and has relatively lower equipment requirements, thus saving investment costs.

[0078] Air is a gas with an oxygen content of 18-22% by volume. The oxygen content of the exhaust gas after the reaction is reduced, and it can be mixed with fresh air in a certain proportion for recycling, thereby improving oxygen utilization and reducing exhaust emissions.

[0079] To reduce impurities, the trimellitic acid is melted by heating inside the anhydride formation tower, and residual acetic acid and water in the wet material are evaporated. The acetic acid and water vapor leave through the vapor outlet IV. The material further undergoes one-molecule water removal within the packing of the anhydride formation tower. The pressure inside the anhydride formation tower is 0.3–0.8 MPa, and the temperature is 240–280 °C. Reliable anhydride formation is ensured by timely discharge of acetic acid and water. Furthermore, the height-to-diameter ratio of the anhydride formation tower is 1–3:1.

[0080] To protect the equipment during shutdown, the oxidation tower, crystallizer, centrifuge, anhydride formation tower, and other equipment are equipped with protective gas inlets. When maintenance, cleaning, or shutdown is required, nitrogen or inert gas is introduced into the unit through these protective gas inlets to protect the equipment and pipelines from oxidation and ensure the safety of the system.

[0081] The following are production examples:

[0082] Example 1

[0083] 1000 kg of pseudotrimethylbenzene and 3200 kg of acetic acid were added to batching tank #1 using a transfer pump. Then, 2.5 kg of cobalt acetate catalyst, 2.5 kg of manganese acetate catalyst, and 2 kg of tetrabromoethane accelerator were added to the batching tank. The stirring was started to mix the materials evenly. Batching tank #1 was heated with hot water and maintained at 75°C. The mixed material was then fed through a feed pump at a rate of 0.8 m³ / h. 3 Feed is introduced into oxidation reaction tower #2 at a flow rate of / h. Feeding is stopped when the level gauge in oxidation reaction tower #2 shows 30% liquid level. Compressed air is then introduced into oxidation reaction tower #2 until the pressure reaches 1.2MPa. The heat transfer oil in oxidation reaction tower #2 is then turned on to heat the material inside the tower to 150℃, initiating the oxidation reaction. When the oxygen content detector at the top of the oxidation tower shows an increase in the oxygen content in the vent gas, the feed pump is restarted at a flow rate of 0.8m³ / h. 3A continuous feed rate of [amount] h is introduced into the reaction tower. The compressed air flow rate is adjusted to maintain the oxygen content in the vent gas at approximately 15%, achieving dynamic equilibrium. The pressure inside the reactor is maintained at approximately 2 MPa, and the temperature at 220°C. The reacted material is pumped to DTB crystallizer #5. The crystallizer is maintained at 125°C via an external circulating heater #6, which evaporates some of the solvent and generates crystals. The crystallized slurry is sent to a horizontal screw centrifuge #7 for solid-liquid separation. The solid material enters the anhydride-forming tower #8, where it is dehydrated and deacidified under conditions of 0.3 MPa and 240℃ to obtain crude trimellitic anhydride. This crude trimellitic anhydride is then fed into a distillation tower #9, where the temperature is maintained above 220℃ for vacuum distillation. The product, trimellitic anhydride with a purity of 96.5%–99%, is collected from the top of tower #9. The finished trimellitic anhydride from the refining tower continuously enters the trimellitic anhydride storage tank #11, where the temperature is maintained at 180℃. The material in storage tank #11 is continuously fed into a slicer for slicing or granulation to obtain 1200 kg of finished trimellitic anhydride. The total conversion rate is 91%, the total selectivity is 84%, and the yield reaches 75%. The waste residue generated at the bottom of distillation tower #9 is discharged in one go after distillation. Acetic acid and water vapor generated during production are sent to an acetic acid recovery tower, where the recovered acetic acid is recycled.

[0084] The above description is merely an embodiment of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. An apparatus for the continuous liquid-phase oxidation of pseudotrimethylbenzene to produce pseudotriglyceride, characterized in that, The apparatus comprises an oxidation reaction tower, a DTB crystallizer, a horizontal screw centrifuge, an anhydride formation tower, and a distillation tower connected in sequence. The oxidation reaction tower is provided with N feed inlets and N air inlets, where N≥3; The oxidation reaction tower is equipped with 2N distributors inside its cavity; The distributor is connected to the feed inlet and the air inlet respectively.

2. The apparatus according to claim 1, characterized in that, The device also includes a cooler; The oxidation reaction tower is provided with a gas phase outlet I at the top, and the gas phase outlet I is connected to a cooler; The bottom of the oxidation reaction tower is provided with a discharge port I, which is connected to the DTB crystallizer via a discharge pump; Preferably, the outlet of the cooler is connected to a gas-liquid separator, and the gas phase outlet II at the top of the gas-liquid separator is connected to an air compressor; The gas-liquid separator is also provided with a liquid phase outlet, and the side wall at the bottom of the oxidation reaction tower is also provided with a liquid phase inlet, and the liquid phase outlet is connected to the liquid phase inlet; Preferably, the height-to-diameter ratio of the oxidation reaction tower is 8 to 14:1; N is 3 to 5.

3. The apparatus according to claim 1, characterized in that, The external part of the DTB crystallizer is equipped with a circulating pump and a heater connected in series; The lower part of the DTB crystallizer is connected to a precipitating column; The DTB crystallizer is equipped with a flow guide tube and a cylindrical baffle. Preferably, a settling zone is provided around the cylindrical baffle; The lower part of the analysis column is provided with a discharge port II, which is connected to the horizontal screw centrifuge via a discharge pump.

4. The apparatus according to claim 1, characterized in that, The horizontal screw centrifuge is equipped with a liquid discharge port and a slag discharge port; The drain outlet is connected to the DTB crystallizer; The slag discharge port is connected to the anhydride formation tower.

5. The apparatus according to claim 1, characterized in that, The anhydride-forming tower is equipped with multiple layers of packing material. The anhydride-forming tower has a partial anhydride outlet in the middle that is connected to the distillation tower. The bottom of the anhydride-forming tower is provided with a heavy component outlet I; The height-to-diameter ratio of the anhydride-forming tower is 1 to 3:

1.

6. The apparatus according to claim 1, characterized in that, The distillation column is provided with a discharge port III at the top, and the discharge port III is connected in sequence to the condenser I and the anhydride storage tank; The distillation column reboiler is connected to a reboiler and a heavy component outlet II; Preferably, the apparatus further includes an acetic acid recovery tower. The top of the DTB crystallizer is also provided with a gas phase outlet III, which is connected to the acetic acid recovery tower. The top of the anhydride formation tower is also provided with a gas phase outlet IV, which is connected to the acetic acid recovery tower. The acetic acid recovery tower is provided with a discharge port IV at the top, and the discharge port IV is connected in sequence to a condenser II and a reflux tank. The return tank is connected to a wastewater treatment unit; The acetic acid recovery tower is provided with an acetic acid recovery outlet at the bottom, which is connected to an acetic acid storage tank.

7. A process for producing trimethylolpropionate from pseudotrimethylolpropionate by continuous liquid-phase oxidation, characterized in that, The process method uses the apparatus described in any one of claims 1 to 6, containing raw materials of pseudotrimethylbenzene, acetic acid, and a cobalt-manganese-bromine ternary catalyst, which are mixed with air in an oxidation reaction tower to undergo an oxidation reaction and obtain reaction products. The reaction products are then passed sequentially through a DTB crystallizer, a horizontal screw centrifuge, an anhydride formation tower, and a distillation tower to undergo crystallization, filtration, and anhydride formation to obtain the pseudotrimethylbenzene anhydride.

8. The process method according to claim 6, characterized in that, The molar ratio of the pseudotrimethylbenzene to acetic acid is 1:1 to 25, and the molar ratio of the pseudotrimethylbenzene to oxygen in the air is 1:10 to 50. The cobalt-manganese-bromine ternary catalyst is a mixture of cobalt acetate, manganese acetate and tetrabromoethane; The mass ratio of the mixture containing pseudotrimethylbenzene and acetic acid to cobalt acetate, manganese acetate, and tetrabromoethane is 1:0.001~0.01:0.001~0.01:0.0001~0.008; Preferably, the oxygen volume content in the air is 18-22%.

9. The process method according to claim 6, characterized in that, The reaction conditions for the oxidation reaction are as follows: The pressure of the oxidation reaction is 1–4 MPa; The oxidation reaction is carried out at a temperature of 100–320°C. Preferably, the raw material feed flow rate is 0.5–10 m³ / h. 3 / h; The air feed flow rate is 25–1000 m³ / h. 3 / h.

10. The process method according to claim 6, characterized in that, The moisture content of solid materials, including trimellitic acid, is reduced to 10%–50% by the horizontal screw centrifuge. Preferably, the anhydride formation is carried out in an anhydride formation tower; The conditions for anhydride formation are as follows: The anhydride-forming pressure is 0.3–0.8 MPa, and the anhydride-forming temperature is 240–280 °C.

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