System for synthesizing 2, 6-naphthalic acid

Abstract

The utility model provides a 2, 6 naphthalic acid system. The system provided by the utility model comprises an oxidation reactor, an inorganic membrane component and an external circulation heat exchanger which are connected in sequence. According to the utility model, the inorganic membrane component is coupled with the mechanical stirring oxidation reactor and is matched with external circulation heat removal, so that the continuous reaction process is realized, meanwhile, mother liquor is directly recycled without being separated, the influence of a rear system is small, the yield of 2, 6-naphthalic acid is high, the consumption of solvent combustion is low, the energy consumption of oxidation product concentration is low, and the device can be used for industrial production of 2, 6-naphthalic acid.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the field of chemical technology, more particularly to a system for synthesizing 2,6-naphthalene dicarboxylic acid. BACKGROUND

[0002] Poly 2,6-naphthalene dicarboxylic acid ethylene glycol ester can be widely used in film, filling container, engineering plastic, sound and light carrier and fiber fields instead of PET, has broad potential market, and is a new type of thermoplastic polyester material with great development prospect.

[0003] 2,6-naphthalene dicarboxylic acid (2,6-NDA) is an intermediate for synthesizing PEN, and its synthesis routes include: methanol alkylation of naphthalene and beta-methyl naphthalene, multi-methyl benzene alkylation, toluoylation, xylene alkylation and m-xylene acylation. Limited by the source of raw materials and the complexity of the process, the synthesis of 2,6-naphthalene dicarboxylic acid currently mainly stays in the small test research stage and small-scale industrial production.

[0004] At present, 2,6-DIPN is mostly synthesized into 2,6-NDA by intermittent or semi-continuous method. 2,6-DIPN is fed by intermittent or semi-continuous method, which belongs to intermittent reaction, and the production efficiency is low. The reaction mother liquor can be recovered and utilized only after being separated and purified, and the process is complex. 2,6-DIPN is a strong exothermic reaction, and if the heat is not removed in time, not only the yield of 2,6-naphthalene dicarboxylic acid will decrease, but also the solvent acetic acid will be accelerated to burn. At present, mechanical stirring kettle with built-in coil or jacket is mostly used for heat removal. This reaction mode is difficult to produce in large scale. With the production process, the reaction temperature will gradually increase, causing the yield of 2,6-NDA to decrease and the loss of solvent acetic acid to increase. In addition, in order to ensure the high yield of 2,6-NDA and control the generation of by-products, the proportion of catalyst in the reaction liquid is relatively high, which causes the subsequent recovery of 2,6-NDA to be difficult, the separation loss to increase, and the normal operation of the subsequent system to be affected. The concentration process of 2,6-NDA mostly uses multi-stage concentration crystallization, which not only has a complex process, but also needs to evaporate the solvent acetic acid in the concentration process, and the energy consumption is high. UTILITY MODEL CONTENT

[0005] In view of the problems of discontinuous reaction process, long-term operation reaction temperature rising, 2,6-naphthalene dicarboxylic acid yield reduction, high energy consumption of oxidation product concentration process and reaction mother liquor unable to be directly recycled in the prior art, the utility model provides a system for synthesizing 2,6-naphthalene dicarboxylic acid.The system provided by the utility model realizes the continuous reaction process on the one hand, and the reaction product is directly recycled after passing through the membrane assembly, and the reaction realizes the concentration of 2,6-naphthalene dicarboxylic acid; on the other hand, the reaction heat is efficiently removed through external circulation heat exchange, the problems of reaction temperature rising, solvent acetic acid combustion consumption increasing and 2,6-naphthalene dicarboxylic acid yield reduction with the prolongation of production time are avoided, the system has little influence, and can be used for 2,6-naphthalene dicarboxylic acid industrial production.

[0006] Specifically, the utility model provides a system for synthesizing 2,6-naphthalene dicarboxylic acid, which comprises an oxidation reactor, an inorganic membrane assembly and an external circulation heat exchanger connected in sequence.

[0007] In some embodiments, the oxidation reactor is provided with a gas phase outlet, a liquid phase outlet and a liquid phase inlet, the inorganic membrane assembly comprises a shell and an inorganic membrane tube arranged in the shell, the shell is provided with an inlet, a shell side outlet, a tube side outlet and a backflushing nitrogen gas port,

[0008] The liquid phase outlet of the oxidation reactor is connected with the inlet of the inorganic membrane assembly; the shell side outlet of the inorganic membrane assembly is connected with the inlet of the external circulation heat exchanger, and the outlet of the external circulation heat exchanger is connected with the liquid phase inlet of the oxidation reactor.

[0009] In the reaction process of preparing 2,6-NDA from 2,6-DIPN, in order to improve the 2,6-NDA yield and reduce the generation of by-products and impurities, the catalyst dosage needs to be increased. It is found in the production process that with the increase of the catalyst dosage, the reactor heat exchange effect gradually deteriorates over time, the reaction temperature slowly increases, and the 2,6-NDA yield gradually decreases, and the reaction performance of each batch is slightly different. At the same time, acetic acid is often used as a solvent in the prior art, and high solvent ratio causes high energy consumption in separation. In order to facilitate the subsequent separation of reaction products, 3-stage or more crystallization separation is often used to increase the 2,6-NDA concentration, and the post-treatment system often has problems such as blockage, which affects normal production.

[0010] The utility model discloses a kind of inorganic membrane assemblies and mechanical stirring oxidation reaction kettle coupling, while cooperating with external circulation heat removal, reaction kettle high pressure is as the power of membrane assembly cross-flow filtration, realizes continuous in reaction process, improves reaction efficiency, and equivalent production scale reactor size is greatly reduced.

[0011] In some embodiments, a liquid phase inlet is used for feeding circulating liquid and 2,6-naphthalene dicarboxylic acid.

[0012] In some embodiments, the material of the inorganic membrane tube is selected from one or more of TiO2, Al2O3 and ZrO2.

[0013] In some embodiments, the pore size of the inorganic membrane tube is 0.1 μm-10 μm, for example, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm or any value therebetween. In some embodiments, the pore size of the inorganic membrane tube is 1 μm-8 μm. In some embodiments, the pore size of the inorganic membrane tube is 2 μm-5 μm.

[0014] In some embodiments, the flux of the inorganic membrane tube is 100 L·h -1 ·m -2 -2000 L·h -1 ·m -2 , for example, 200 L·h -1 ·m -2 , 300 L·h -1 ·m -2 , 400 L·h -1 ·m -2 , 500 L·h -1 ·m -2 , 600 L·h -1 ·m -2 , 700 L·h -1 ·m -2 , 800 L·h -1 ·m -2 , 900 L·h -1 ·m -2 , 1000 L·h -1 ·m -2 , 1100 L·h -1 ·m -2 , 1200 L·h-1 ·m -2 1300L·h -1 ·m -2 1400L·h -1 ·m -2 1500L·h -1 ·m -2 1600L·h -1 ·m -2 1700L·h -1 ·m -2 1800L·h -1 ·m -2 1900L·h -1 ·m -2 Or any value in between. In some embodiments, the flux of the inorganic membrane tube is 200 L·h. -1 ·m -2 -1500L·h -1 ·m -2 .

[0015] In some embodiments, the transmembrane pressure differential of the inorganic membrane tube is 0.1 MPa-0.5 MPa, for example, 0.15 MPa, 0.2 MPa, 0.25 MPa, 0.3 MPa, 0.35 MPa, 0.4 MPa, 0.45 MPa, or any value between them. In some embodiments, the transmembrane pressure differential of the inorganic membrane tube is 0.2 MPa-0.3 MPa. In some embodiments, a mechanical stirring device is provided in the oxidation reactor. In some embodiments, a gas distribution device is provided in the oxidation reactor for dispersing air introduced from the bottom of the oxidation reactor. In some embodiments, the gas distribution device is selected from a gas distributor.

[0016] In some embodiments, a heat exchange jacket is provided on the outside of the oxidation reactor.

[0017] In some embodiments, the oxidation reactor does not have a coil heat exchanger inside.

[0018] In some embodiments, a buffer unit is further provided between the inorganic membrane module and the external circulation heat exchanger. The buffer unit includes a circulating liquid buffer tank and a circulation pump. The circulating liquid buffer tank is used to store the liquid phase material discharged from the shell side of the inorganic membrane module, and the circulation pump is used to pass the buffered liquid phase material into the external circulation reactor.

[0019] In some embodiments, the shell-side outlet of the inorganic membrane module is connected to the inlet of the circulating liquid buffer tank, the outlet of the circulating liquid buffer tank is connected to the inlet of the circulating pump, and the outlet of the circulating pump is connected to the inlet of the external circulating heat exchanger.

[0020] In some embodiments, the system further includes a tail gas cooler and a tail gas condenser connected in sequence, with the gas phase outlet of the oxidation reactor connected to the inlet of the tail gas cooler for condensing and separating the gas phase material discharged from the top of the oxidation reactor.

[0021] In some embodiments, a liquid separator is provided at the bottom of the exhaust gas condenser for collecting condensate.

[0022] In some embodiments, the exhaust gas cooler and exhaust gas condenser are located above the oxidation reactor so that the condensate returns to the oxidation reactor by gravity.

[0023] In some embodiments, the system further includes an aging device, with the tube-side outlet of the inorganic membrane module connected to the aging device.

[0024] In some embodiments, the reaction system further includes an aging device, with the tube-side outlet of the inorganic membrane module connected to the aging device.

[0025] Compared with existing technologies, this invention couples an inorganic membrane module with a mechanically stirred oxidation reactor and uses external circulation for heat removal, achieving continuous processing. Simultaneously, it concentrates 2,6-naphthalenedicarboxylic acid, solving the problem of system temperature rise due to decreased heat removal capacity over time. Furthermore, the mother liquor can be directly recycled without separation, minimizing impact on downstream systems. It achieves high 2,6-naphthalenedicarboxylic acid yield, low acetic acid combustion consumption, and low energy consumption for oxidation product concentration, making it suitable for industrial production of 2,6-naphthalenedicarboxylic acid. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the system for synthesizing 2,6-naphthalenedicarboxylic acid according to the present invention;

[0027] Figure 1 In the diagram, 1 is the oxidation reactor, 2 is the inorganic membrane module, 3 is the aging vessel, 4 is the tail gas cooler, 5 is the tail gas condenser, 6 is the circulating liquid buffer tank, 7 is the circulating pump, and 8 is the external circulating heat exchanger.

[0028] a is the feed for 2,6-naphthalenedicarboxylic acid, b is air, c is recycled acetic acid, d is oxidation tail gas, e-1 is the feed for refrigerant, and e-2 is the discharge for refrigerant.

[0029] Figure 2 This is a schematic diagram of the inorganic membrane component in the system for synthesizing 2,6-naphthalenedicarboxylic acid according to this invention.

[0030] Figure 2 In the diagram, 2-1 represents the shell, 2-2 represents the ceramic membrane tube, and f represents nitrogen gas. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to embodiments and accompanying drawings. The specific embodiments described herein are for illustrative purposes only and are not intended to constitute any limitation on the present utility model. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of this disclosure. Such structures and techniques have also been described in many publications.

[0032] This invention provides a system for synthesizing 2,6-naphthalenedicarboxylic acid, specifically as follows: Figure 1 and Figure 2 As shown, it includes an oxidation reactor 1, an inorganic membrane module 2, an aging vessel 3, a tail gas cooler 4, a tail gas condenser 5, a circulating liquid buffer tank 6, a circulating pump 7, and an external circulating heat exchanger 8 connected in sequence.

[0033] The oxidation reactor 1 is provided with a liquid phase inlet for introducing circulating liquid (circulating acetic acid c) and 2,6-naphthalenedicarboxylic acid feed a, a gas phase inlet for introducing air b, a gas phase outlet for discharging oxidation tail gas d, and a liquid phase outlet. The inorganic membrane module 2 includes a shell 2-1 and a ceramic membrane tube 2-2 disposed in the shell. The shell is provided with an inlet, a shell-side outlet, a tube-side outlet, and a backflushing nitrogen port f.

[0034] In this reactor, the liquid phase outlet of oxidation reactor 1 is connected to the inlet of inorganic membrane module 2. The shell-side outlet of inorganic membrane module is connected to circulating liquid buffer tank 6. Circulating liquid buffer tank 6 is connected to circulating pump 7, and circulating pump 7 is connected to the inlet of external circulating heat exchanger 8. The outlet of external circulating heat exchanger 8 is connected to the liquid phase inlet of oxidation reactor 1. Circulating liquid buffer tank 6 is used to store the liquid phase material discharged from the bottom of oxidation reactor. Circulating pump 7 is used to introduce the buffered liquid phase material into external circulating reactor 8.

[0035] Refrigerant feed e-1 enters the external circulation heat exchanger 8 and exchanges heat with the buffered liquid phase material before being discharged as refrigerant discharge e-2;

[0036] The gas phase outlet of the oxidation reactor 1 is connected to the tail gas cooler 4, and the tail gas cooler 4 is connected to the tail gas condenser 5. The tail gas condenser 5 is provided with a liquid separator at the bottom for collecting condensate. The collected condensate can be directly returned to the oxidation reactor 1 by gravity.

[0037] The tube-side outlet of the inorganic membrane module is connected to the aging vessel 3.

[0038] In addition, in this invention, an air distributor is installed at the bottom of the oxidation reactor 1 to uniformly distribute the feed air and ensure that the air is in full contact with the solvent and 2,6-NIPN. The distributor needs to be protected against clogging. A high-efficiency mechanical stirring device is installed inside the reactor, including a jacket as a supplementary means of heat dissipation. No other internal components such as coils are installed.

[0039] In this invention, the inorganic membrane modules 2 operate in parallel, with one in operation and one on standby. A backwashing mechanism is also provided for membrane regeneration after the membrane flux decreases.

[0040] In this invention, the aging vessel 3 is equipped with a pressure control system.

[0041] In this utility model, the inorganic membrane module is as follows: Figure 2 As shown, it includes a housing 2-1 and a ceramic membrane tube 2-2.

[0042] In this invention, the housing 2-1 of the inorganic membrane module is also provided with a backflushing nitrogen port for passing nitrogen f. The backflushing nitrogen port is connected to high-pressure nitrogen. After the inorganic membrane module is switched off, the high-pressure nitrogen is turned on for backflushing.

[0043] In this invention, the ceramic membrane tube 2-2 is made of one or more of TiO2, Al2O3 and ZrO2.

[0044] In this invention, the pore size of the inorganic membrane tube is 0.1 μm-10 μm, for example, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, or any value between them. In some embodiments, the pore size of the inorganic membrane tube is 1 μm-8 μm. In some embodiments, the pore size of the inorganic membrane tube is 2 μm-5 μm.

[0045] In some embodiments, the flux of the inorganic membrane tube is 100 L·h. -1 ·m -2 -2000L·h -1 ·m -2 For example, 200 L·h -1 ·m -2 300L·h -1 ·m -2 400L·h -1 ·m -2 500L·h -1 ·m -2 600L·h -1 ·m -2 700L·h-1 ·m -2 800L·h -1 ·m -2 900L·h -1 ·m -2 1000L·h -1 ·m -2 1100L·h -1 ·m -2 1200L·h -1 ·m -2 1300L·h -1 ·m -2 1400L·h -1 ·m -2 1500L·h -1 ·m -2 1600L·h -1 ·m -2 1700L·h -1 ·m -2 1800L·h -1 ·m -2 1900L·h -1 ·m -2 Or any value in between. In some embodiments, the pure water flux of the inorganic membrane tube is 200 L·h. -1 ·m -2 -1500L·h -1 ·m -2 .

[0046] The present invention will be further illustrated below through examples. To facilitate comparison of process technology effects, the catalyst used in the examples and comparative examples is a homogeneous metal catalyst containing Co-Mn-Br-K, with the molar ratio of Co / Mn / Br / K in the catalyst being 1.2 / 1 / 2.5 / 6.3. The mass ratio of catalyst to 2,6-DIPN is 1.21, and the catalyst is contained in circulating acetic acid.

[0047] The present invention will be described in detail below through embodiments.

[0048] Example 1

[0049] A 100-ton / year 2,6-naphthalenedicarboxylic acid production unit operates continuously for 8000 hours using the following process:

[0050] a) 2,6-Diisopropylnaphthalene, acetic acid solvent, and Co-Mn-Br-K homogeneous metal catalyst are introduced into oxidation reactor 1;

[0051] b) Air b enters oxidation reactor 1 from the bottom, wherein an air distributor is provided at the bottom of oxidation reactor 1;

[0052] c) Air and 2,6-diisopropylnaphthalene undergo an oxidation reaction in oxidation reactor 1 in the presence of a Co-Mn-Br-K catalyst to produce naphthalic acid, water, carbon monoxide, carbon dioxide, etc. Acetic acid undergoes a partial combustion reaction to produce water, carbon monoxide, and carbon dioxide, resulting in a reaction liquid solid phase material and a reaction gas phase material.

[0053] d) The gas phase generated in the oxidation reactor 1 passes through the tail gas cooler 4 and the tail gas condenser 5 in sequence. The tail gas condenser 5 is equipped with a liquid separator at the bottom to collect and condense acetic acid. The condensed acetic acid returns directly to the oxidation reactor 1 from the liquid separator by gravity. The oxidation tail gas e is discharged to the outside for centralized treatment.

[0054] e) The liquid-solid phase material generated in the oxidation reactor 1 enters the inorganic membrane module 2 from the bottom. The liquid on the shell side of the inorganic membrane module enters the circulating liquid buffer tank 6 through the pressure regulating valve. A circulating pump 7 is installed at the bottom of the circulating liquid buffer tank 6. The circulating liquid (circulating acetic acid) c returns to the oxidation reactor 1 through the external circulating heat exchanger 8. The material temperature at the tube side outlet of the external circulating heat exchanger is controlled by the flow rate of the shell-side refrigerant (e-1 and e-2). The circulating liquid includes acetic acid and supplemented Co-Mn-Br-K catalyst.

[0055] f) The liquid-solid phase of the inorganic membrane module 2 is discharged from the tube side to the aging reactor 3.

[0056] The feed rate of 2,6-DIPN is 14 kg / h. After mixing with circulating acetic acid containing the catalyst, the weight ratio of acetic acid to 2,6-DIPN is 6.76. The ratio of air volume feed rate to 2,6-DIPN mass is 80 (L / h) / kg.

[0057] A homogeneous metal salt catalyst containing Co-Mn-Br-K was used, with a catalyst / 2,6-DIPN mass ratio of 1.21 and a Co / Mn / Br / K molar ratio of 1.2 / 1 / 2.5 / 6.3. Some of the initial catalyst in the reactor was carried away by the subsequent discharge; this was addressed by replenishing the catalyst in the circulating acetic acid to ensure a constant catalyst-to-2,6-diisopropylnaphthalene ratio throughout the reaction process. In other words, the catalyst quantity was the sum of the initial catalyst and the catalyst in the circulating acetic acid.

[0058] The reaction temperature in the oxidation reactor is 185℃, the reaction pressure is 2.75MPa, and the liquid hourly space velocity (LISH, where the catalyst is dissolved in the solvent under reaction conditions, is the combined space velocity of all liquid phase materials) is 0.25 h⁻¹. -1 .

[0059] The inorganic membrane module uses an Al2O3 inorganic microfiltration membrane with a pore size of 5 micrometers, a transmembrane pressure differential of 0.3 MPa, and a membrane flux of 900 L·h. -1 ·m -2 .

[0060] The mass concentration of 2,6-naphthalenedicarboxylic acid in the aging vessel was 40%, the external circulation ratio (the ratio of the circulation volume of solvent-rich circulating material III to the flow rate of solid phase material I in the reaction liquid) was 0.75, and the external circulation volume (the circulation volume of circulating acetic acid after separation by the membrane module) was 93.8 kg / h.

[0061] According to GB / T 2589-2020 "General Rules for Calculation of Comprehensive Energy Consumption", the final concentration energy consumption is 5.2 kg standard oil / ton of 2,6-naphthalenedicarboxylic acid, the acetic acid combustion consumption is 50 kg / ton of 2,6-naphthalenedicarboxylic acid, the required membrane area is 0.1 m2, and the material consumption of 2,6-diisopropylnaphthalene in the reaction part is 1.12 tons / ton of 2,6-naphthalenedicarboxylic acid.

[0062] Example 2

[0063] The only difference from Example 1 is that the membrane module has a pore size of 1 micrometer and a membrane flux of 200 L·h. -1 ·m -2 .

[0064] Calculations show that the energy consumption for concentration is 5.2 kg of standard oil per ton of 2,6-naphthalenedicarboxylic acid, and the energy consumption for acetic acid combustion is 50 kg per ton of 2,6-naphthalenedicarboxylic acid. The required membrane area is 0.45 m². 2 The reaction section of 2,6-diisopropylnaphthalene consumes 1.12 tons / ton of 2,6-naphthalenedicarboxylic acid.

[0065] Example 3

[0066] The only difference from Example 1 is that the membrane module has a pore size of 10 micrometers, a cross-membrane pressure difference of 0.2 MPa, and a membrane flux of 1450 L·h. -1 ·m -2 .

[0067] Calculations show that the energy consumption for concentration is 4.9 kg of standard oil per ton of 2,6-naphthalenedicarboxylic acid, and the energy consumption for acetic acid combustion is 52 kg per ton of 2,6-naphthalenedicarboxylic acid. The required membrane area is 0.06 m². 2 The reaction section consumes 1.12 tons of 2,6-diisopropylnaphthalene per ton of 2,6-naphthalenedicarboxylic acid. The mother liquor circulation affects the subsequent system operation, and the unit needs to be shut down and thoroughly cleaned every 60 days.

[0068] Example 4

[0069] The only difference from Example 1 is that the aging vessel contains 60% 2,6-naphthalenedicarboxylic acid, has an external circulation ratio of 0.9, uses a ZrO2 membrane module with a pore size of 50 nm, a transmembrane pressure differential of 1.0 MPa, and a membrane flux of 150 L·h. -1 ·m -2 The external circulation volume is 188 kg / h.

[0070] Calculations show that the energy consumption for concentration is 20.3 kg of standard oil per ton of 2,6-naphthalenedicarboxylic acid, and the energy consumption for acetic acid combustion is 65 catties per ton of 2,6-naphthalenedicarboxylic acid. The required membrane area is 1.19 m². 2 The reaction section of 2,6-diisopropylnaphthalene consumes 1.12 tons / ton of 2,6-naphthalenedicarboxylic acid.

[0071] Example 5

[0072] The only difference from Example 1 is that the 2,6-naphthalenedicarboxylic acid concentration in the aging vessel is 30%, the external circulation ratio is 0.5, a TiO2 membrane module with a pore size of 8 nm is used, the transmembrane pressure difference is 1.0 MPa, and the membrane flux is 50 L·h. -1 ·m -2 The external circulation volume is 62.5 kg / h.

[0073] Calculations show that the energy consumption for concentration is 18.5 kg of standard oil per ton of 2,6-naphthalenedicarboxylic acid, and the energy consumption for acetic acid combustion is 46 catties per ton of 2,6-naphthalenedicarboxylic acid. The required membrane area is 0.61 m². 2 The reaction section of 2,6-diisopropylnaphthalene consumes 1.12 tons / ton of 2,6-naphthalenedicarboxylic acid.

[0074] Example 6

[0075] The only difference from Example 1 is that the membrane module has a pore size of 2 micrometers, the 2,6-naphthalenedicarboxylic acid concentration in the aging vessel is 60%, the external circulation ratio is 0.9, and the membrane flux is 650 L·h. -1 ·m -2 .

[0076] Calculations show that the energy consumption for concentration is 4.9 kg of standard oil per ton of 2,6-naphthalenedicarboxylic acid, and the energy consumption for acetic acid combustion is 48 kg per ton of 2,6-naphthalenedicarboxylic acid. The required membrane area is 0.12 m². 2 The reaction section of 2,6-diisopropylnaphthalene consumes 1.12 tons / ton of 2,6-naphthalenedicarboxylic acid.

[0077] Comparative Example 1

[0078] The only difference from Example 1 is that the liquid-solid phase generated in the oxidation reactor 1 undergoes external circulation heat exchange before being separated by the inorganic membrane module.

[0079] Specifically:

[0080] a)-d): Same as in Example 1;

[0081] e) The liquid-solid phase material generated in oxidation reactor 1 enters the inorganic membrane module 2 from the bottom after passing through the external circulation heat exchanger 8, and the rest is the same as in Example 1. The shell-side liquid (acetic acid-rich circulating material III) of inorganic membrane module 2 returns to oxidation reactor 1 through the pressure regulating valve;

[0082] f) The liquid-solid phase discharge (liquid-solid phase material IV rich in 2,6-naphthalenedicarboxylic acid) from the tube side of the inorganic membrane module 2 is discharged into the aging vessel 3.

[0083] The heat exchange efficiency of the external heat exchanger decreases, and the reaction temperature gradually rises to 185-200℃. The device needs to be cleaned every 10 days.

[0084] Calculations show that the energy consumption for concentration is 5.2 kg of standard oil per ton of 2,6-naphthalenedicarboxylic acid, and the energy consumption for acetic acid combustion is 50-60 kg per ton of 2,6-naphthalenedicarboxylic acid. The required membrane area is 0.15 m². 2 The reaction section of 2,6-diisopropylnaphthalene consumes 1.12-1.18 tons / ton of 2,6-naphthalenedicarboxylic acid.

[0085] Comparative Example 2

[0086] A 100-ton / year 2,6-naphthalenedicarboxylic acid production unit operates intermittently for 300 days per year, producing one batch per day. The unit needs to be cleaned every 10 days, with a cleaning time of 1 day.

[0087] It adopts a mechanically stirred tank with an internal and external coil, and uses heat transfer oil for heat dissipation.

[0088] A homogeneous metal acetate catalyst containing Co-Mn-Br-K was used, with a catalyst / 2,6-DIPN mass ratio of 1.21 and a Co / Mn / Br / K molar ratio of 1.2 / 1 / 2.5 / 6.3.

[0089] 2,6-Diisopropylnaphthalene is fed in batches of 436 kg at a reaction temperature of 170°C at a feed rate of 2.42 kg / min for 3 hours, followed by aging for 1 hour at a reaction temperature of 185–200°C and a reaction pressure of 2.76 MPa.

[0090] After the reaction product is flash evaporated to atmospheric pressure, it is concentrated by three-stage crystallization to a mass concentration of 40% for 2,6-naphthalenedicarboxylic acid. The mother liquor is recycled after post-treatment such as solvent recovery and catalyst recovery.

[0091] Calculations show that the energy consumption for concentration is 25.3 kg of standard oil per ton of 2,6-naphthalenedicarboxylic acid, the energy consumption for acetic acid combustion is 61.2 kg per ton of 2,6-naphthalenedicarboxylic acid, and the energy consumption for the reaction section of 2,6-diisopropylnaphthalene is 1.18 tons per ton of 2,6-naphthalenedicarboxylic acid.

[0092] Comparative Example 3

[0093] A 100-ton / year 2,6-naphthalenedicarboxylic acid production unit operates intermittently for 300 days per year, producing one batch per day. The unit needs to be cleaned every 20 days, with a cleaning time of 1 day.

[0094] A mechanically stirred vessel with external circulation for heat dissipation is used.

[0095] A homogeneous metal acetate catalyst containing Co-Mn-Br-K was used, with a catalyst / 2,6-DIPN mass ratio of 1.21 and a Co / Mn / Br / K molar ratio of 1.2 / 1 / 2.5 / 6.3.

[0096] 2,6-Diisopropylnaphthalene is fed in batches of 404 kg at a reaction temperature of 170°C at a feed rate of 2.24 kg / min for 3 hours, followed by aging for 1 hour at a reaction temperature of 185–198°C and a reaction pressure of 2.76 MPa.

[0097] After the reaction product is flash evaporated to atmospheric pressure, it is concentrated by three-stage crystallization to a mass concentration of 40% for 2,6-naphthalenedicarboxylic acid. The mother liquor is recycled after post-treatment such as solvent recovery and catalyst recovery.

[0098] Calculations show that the energy consumption for concentration is 25.3 kg of standard oil per ton of 2,6-naphthalenedicarboxylic acid, the energy consumption for acetic acid combustion is 59 kg per ton of 2,6-naphthalenedicarboxylic acid, and the energy consumption for the reaction section of 2,6-diisopropylnaphthalene is 1.15 tons per ton of 2,6-naphthalenedicarboxylic acid.

[0099] The preferred embodiments of this utility model have been described in detail above; however, this utility model is not limited thereto. Within the scope of the technical concept of this utility model, various simple modifications can be made to the technical solution of this utility model, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed by this utility model and are all within the protection scope of this utility model.

Claims

1. A system for synthesizing 2,6-naphthalenedicarboxylic acid, characterized in that, The system includes an oxidation reactor, an inorganic membrane module, and an external circulation heat exchanger connected in sequence. The oxidation reactor is provided with a gas phase outlet, a liquid phase outlet, a liquid phase inlet, and a gas phase inlet. The inorganic membrane module includes a shell and an inorganic membrane tube disposed within the shell. The shell is provided with an inlet, a shell-side outlet, a tube-side outlet, and a backflushing nitrogen port. The liquid phase outlet of the oxidation reactor is connected to the inlet of the inorganic membrane module; the shell-side outlet of the inorganic membrane module is connected to the inlet of the external circulation heat exchanger, and the outlet of the external circulation heat exchanger is connected to the liquid phase inlet of the oxidation reactor.

2. The system according to claim 1, characterized in that, The inorganic membrane tube is made of one of TiO2, Al2O3, and ZrO2; and / or The inorganic membrane tube has a pore size of 0.1 μm-10 μm; and / or The flux of the inorganic membrane tube is 100 L·h -1 ·m -2 -2000L·h -1 ·m -2 .

3. The system according to claim 1, characterized in that, The inorganic membrane tube has a pore size of 2μm-5μm; and / or The flux of the inorganic membrane tube is 200 L·h -1 ·m -2 -1500L·h -1 ·m -2 .

4. The system according to claim 1, characterized in that, The oxidation reactor is equipped with a mechanical stirring device and a gas distribution device; and / or The oxidation reactor is equipped with a heat exchange jacket on the outside, but no heat exchange device is installed inside the oxidation reactor.

5. The system according to claim 1, characterized in that, A buffer unit is also provided between the inorganic membrane module and the external circulation heat exchanger. The buffer unit includes a circulating liquid buffer tank and a circulation pump. The circulating liquid buffer tank is used to store the liquid phase material discharged from the shell side of the inorganic membrane module, and the circulation pump is used to pass the buffered liquid phase material into the external circulation reactor.

6. The system according to claim 5, characterized in that, The shell-side outlet of the inorganic membrane module is connected to the inlet of the circulating liquid buffer tank, the outlet of the circulating liquid buffer tank is connected to the inlet of the circulating pump, and the outlet of the circulating pump is connected to the inlet of the external circulating heat exchanger.

7. The system according to any one of claims 1-6, characterized in that, It also includes a tail gas cooler and a tail gas condenser connected in sequence. The gas phase outlet of the oxidation reactor is connected to the inlet of the tail gas cooler for condensing and separating the gas phase material discharged from the top of the oxidation reactor.

8. The system according to claim 7, characterized in that, The bottom of the exhaust gas condenser is equipped with a liquid distribution bag for collecting condensate, and / or The exhaust gas cooler and exhaust gas condenser are located at the top of the oxidation reactor so that the condensate returns to the oxidation reactor by gravity.

9. The system according to any one of claims 1-6, characterized in that, It also includes an aging device, with the tube-side outlet of the inorganic membrane module connected to the aging device.

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