CN114471404A

CN114471404A - Micro-interface preparation system and preparation method of trimellitic acid

Info

Publication number: CN114471404A
Application number: CN202210060161.4A
Authority: CN
Inventors: 张志炳; 孙海宁; 周政; 张锋; 李磊; 孟为民; 杨高东; 杨国强; 刘甲
Original assignee: Nanjing Institute of Microinterface Technology Co Ltd
Current assignee: Nanjing Institute of Microinterface Technology Co Ltd
Priority date: 2022-01-19
Filing date: 2022-01-19
Publication date: 2022-05-13

Abstract

The invention provides a micro-interface preparation system and a preparation method of trimellitic acid, which comprise the following steps: a reactor; a first micro-interface generator is arranged in the reactor, a reactant branch for introducing the pseudocumene and an air branch for introducing air are sequentially connected to the side wall of the reactor from top to bottom, and the air branch penetrates through the side wall of the reactor and is connected with the first micro-interface generator; a second micro-interface generator is arranged above the first micro-interface generator, the first micro-interface generator is positioned below the liquid level in the reactor, and the second micro-interface generator is positioned above the liquid level in the reactor; the bottom of the second micro-interface generator is provided with a diffusion tube, and the bottom of the diffusion tube is connected with the first micro-interface generator; the micro-interface preparation system of trimellitic acid has the advantages of low reaction temperature and pressure, high raw material conversion rate and high product yield, and is worthy of wide popularization and application.

Description

Micro-interface preparation system and preparation method of trimellitic acid

Technical Field

The invention relates to the technical field of preparation of trimellitic acid, and particularly relates to a micro-interface preparation system and a micro-interface preparation method of trimellitic acid.

Background

Trimellitic acid is an important chemical product and has wide application and prospect in the fields of resin, plasticizer, dye, adhesive and the like. Trimellitic anhydride can be obtained through further dehydration, and is an important fine chemical raw material and mainly used for producing high-quality TMA plasticizers, temperature-resistant polyimide insulating paint, high-grade powder coating, resin curing agents, modified alkyd resin and the like.

At present, the production method of trimellitic acid mainly comprises 4 methods of a pseudocumene liquid-phase air oxidation method, a pseudocumene gas-phase air oxidation method, a meta-xylene formaldehyde liquid-phase air oxidation method and a pseudocumene liquid-phase nitric acid oxidation method, wherein the pseudocumene liquid-phase air oxidation process of Amoco company is used for the leading position. The method takes pseudocumene as a raw material, adopts air as an oxidant and takes cobalt acetate and manganese acetate as catalysts to carry out oxidation reaction at the temperature of 220 ℃ and 240 ℃ and under the pressure of 2.0-2.5 MPa. The high temperature and high pressure reaction conditions increase the energy consumption and the danger of the reaction. On the other hand, a bubble tower type reactor is adopted in China mostly without a stirrer, gas enters the reactor and contacts with liquid after passing through a gas distributor, the reaction rate is slow, the oxygen utilization rate is less than 80%, and the oxygen content which is seriously out of standard increases the deflagration risk of the reaction.

Disclosure of Invention

The first purpose of the invention is to provide a micro-interface preparation system of trimellitic acid, which disperses and crushes mixed gas into micron-sized micro-bubbles through a first micro-interface generator arranged in a reactor, improves the phase boundary mass transfer area between the trimellitic acid and air, improves the reaction rate, reduces the retention time of raw materials in the reactor, and thus reduces the occurrence of side reactions; meanwhile, the reaction energy consumption can be effectively reduced, and the reaction conversion rate can be improved.

The second purpose of the invention is to provide a preparation method adopting the system, the method is simple and convenient to operate, and by applying the system, the reaction energy consumption is reduced, and the single-pass conversion rate of the raw material and the yield of trimellitic acid are improved.

In order to achieve the above purpose of the present invention, the following technical solutions are adopted:

the invention provides a micro-interface preparation system of trimellitic acid, which comprises the following steps: a reactor; a first micro-interface generator is arranged in the reactor, a reactant branch for introducing the pseudocumene and an air branch for introducing air are sequentially connected to the side wall of the reactor from top to bottom, and the air branch penetrates through the side wall of the reactor and is connected with the first micro-interface generator;

a second micro-interface generator is arranged above the first micro-interface generator, the first micro-interface generator is positioned below the liquid level in the reactor, and the second micro-interface generator is positioned above the liquid level in the reactor; the bottom of the second micro-interface generator is provided with a diffusion tube, and the bottom of the diffusion tube is connected with the first micro-interface generator;

a material circulating pipeline is arranged on one side of the reactor, an inlet of the material circulating pipeline is connected with the side wall of the reactor, and an outlet of the material circulating pipeline is connected with the second micro-interface generator; and a heat exchanger is arranged on the material circulating pipeline.

In the prior art, the preparation of the trimellitic acid generally adopts a pseudocumene liquid-phase air oxidation process, wherein air is adopted as an oxidant, cobalt acetate and manganese acetate are adopted as catalysts, and oxidation reaction is carried out at the temperature of 220-. The high temperature and high pressure reaction conditions increase the energy consumption and the danger of the reaction. In addition, gas enters the reactor and directly contacts with liquid after passing through a gas distributor, the reaction rate is slow, the oxygen utilization rate is less than 80%, and the oxygen content which is seriously out of standard increases the deflagration risk of the reaction.

In order to solve the technical problems, the invention provides a micro-interface preparation system of trimellitic acid, which has a simple overall structure, can disperse and crush air into micro bubbles at the micron level and then mix the micro bubbles with trimellitic acid to form a gas-liquid emulsion by arranging a first micro-interface generator in a reactor, increases the gas-liquid mass transfer area among reactants, improves the reaction efficiency, and simultaneously can reduce the temperature and pressure required by the reaction and improve the production safety; the second micro-interface generator is arranged above the liquid level in the reactor, so that unreacted air can be trapped, the air can continuously participate in the reaction, the conversion rate of oxygen in the air is improved, the reaction deflagration is prevented, and the reaction safety is improved.

Preferably, a plurality of layers of grid plates are arranged above the first micro-interface generator, the plurality of layers of grid plates are arranged in a staggered mode, and the grid plates are positioned below the liquid level in the reactor; and the inlet of the material circulating pipeline is positioned among the plurality of layers of grid plates along the vertical direction.

Preferably, the side wall of the reactor is provided with a material outlet, and the material outlet is positioned between the liquid level in the reactor and the grid plate along the vertical direction.

Preferably, the first micro-interface generator is a pneumatic micro-interface generator, and the second micro-interface generator is a hydraulic micro-interface generator.

Preferably, the top of the reactor is connected with a multifunctional tower, a circulating spray device is arranged in the multifunctional tower, a circulating spray pipeline is arranged on one side of the multifunctional tower, the inlet of the circulating spray pipeline is connected with the bottom of the multifunctional tower, the outlet of the circulating spray pipeline is respectively connected with the circulating spray device and the reactor, one part of circulating liquid in the circulating spray pipeline returns to the multifunctional tower through the circulating spray device, and the other part of circulating liquid returns to the reactor to continuously participate in the reaction.

Preferably, a wire mesh is arranged in the multifunctional tower and is positioned below the circulating spraying device.

Preferably, the top of the multifunctional tower is connected with a tail gas treatment pipeline, and a tail gas treatment device is arranged on the tail gas treatment pipeline.

Preferably, a partial condenser and a pressure reducing valve are arranged between the top of the reactor and the multifunctional column, after the reactor at the top of the reactor is condensed by the partial condenser, the condensed liquid-phase component flows back to the reactor, and the uncondensed gas-phase component enters the multifunctional column through the pressure reducing valve.

The reactor is internally provided with a first micro-interface generator and a second micro-interface generator, wherein the first micro-interface generator is mainly used for dispersing and crushing air into micro-bubbles, so that the phase boundary mass transfer area between the air and the pseudocumene is effectively increased, and the reaction efficiency is improved; the second micro-interface generator is arranged above the liquid level and is connected with a material circulating pipeline, liquid in the reactor is input into the second micro-interface generator by the material circulating pipeline, unreacted air at the top of the reactor is sucked into the second micro-interface generator through a negative pressure port on the second micro-interface generator, and the unreacted air is dispersed and broken into bubbles and then continuously reacts with the pseudocumene, so that the air utilization rate is improved, the risk of deflagration in the reaction process is prevented, and the reaction safety is improved.

In the invention, the outlet of the second micro-interface generator is connected with the first micro-interface generator through the diffusion pipe, the two micro-interface generators need to be combined into a whole and are not arranged independently, and the two micro-interface generators are combined to form the hybrid micro-interface unit SBBS, so that the application effect of the independent micro-interface generator is improved. On one hand, collision flow can be formed between the first micro-interface generator and the second micro-interface generator, and bubbles are further dispersed and crushed; on the other hand, when the first micro interface generator is internally blocked, the bubble flow of the second micro interface generator can flush the inside of the first micro interface generator, so that the blockage is prevented. And set up like this and can also improve fixed effect, play the supporting effect to the second micro-interface generator through the pipeline between first micro-interface generator and the second micro-interface generator. The space in the reaction tower is narrower itself, if the setting of micro-interface generator too disperse and also can influence the normal work of reaction tower, the design also shortens each micro-interface generator's distance for holistic structure in addition, strengthens the cooperation ability each other between each part, through the broken bubble collision impact back each other of micro-interface to improve dispersion crushing effect.

In addition, the positions of the reactant branches and the air branches cannot be randomly arranged, and the reactant branches are required to be arranged above the air branches. The reactant flows from top to bottom, the unreacted air flows from bottom to top, and the reactant introduced through the reactant branch is continuously contacted and reacted with the unreacted air, so that the conversion rate of oxygen in the air is improved, and the deflagration risk caused by the exceeding of the oxygen content is prevented.

According to the preparation system, the multilayer grid plate is arranged above the first micro-interface generator, the liquid flow is slowed down through the blocking effect of the multilayer grid plate, the fully mixed flow is changed into the plug flow, the liquid flow at the upper part is prevented from back mixing, the separation of gas and liquid is facilitated, meanwhile, the undissolved catalyst particles are favorably settled, and the use efficiency of the catalyst is improved.

The top of the reactor is connected with a multifunctional tower, the multifunctional tower is arranged for improving the recycling effect of the tail gas, and a circulating spray device is arranged in the multifunctional tower, so that the liquid is sprayed and dropped from the top to realize the sufficient contact between gas and liquid phases, the content of organic matters in a gas phase is reduced, and the tail gas is favorably discharged after reaching the standard; the arrangement of the silk screen is used for reducing floating foam in the spraying liquid and improving the contact efficiency between the gas phase and the liquid phase. In addition, the outlet of the circulating spray pipeline is also connected with the reactor, which is used for sending the reactant in the tail gas back to the reactor for continuous reaction, thereby improving the utilization rate of the raw materials and saving the cost.

It will be appreciated by those skilled in the art that the micro-interfacial generators used in the present invention are embodied in the inventor's prior patents, such as patent applications CN201610641119.6, CN201610641251.7, CN201710766435.0, CN106187660, CN105903425A, CN109437390A, CN205833127U and CN 207581700U. The detailed structure and operation principle of the micro bubble generator (i.e. micro interface generator) is described in detail in the prior patent CN201610641119.6, which describes that "the micro bubble generator comprises a body and a secondary crushing member, wherein the body is provided with a cavity, the body is provided with an inlet communicated with the cavity, the opposite first end and second end of the cavity are both open, and the cross-sectional area of the cavity decreases from the middle of the cavity to the first end and second end of the cavity; the secondary crushing member is disposed at least one of the first end and the second end of the cavity, a portion of the secondary crushing member is disposed within the cavity, and an annular passage is formed between the secondary crushing member and the through holes open at both ends of the cavity. The micron bubble generator also comprises an air inlet pipe and a liquid inlet pipe. "the specific working principle of the structure disclosed in the application document is as follows: liquid enters the micro-bubble generator tangentially through the liquid inlet pipe, and gas is rotated at a super high speed and cut to break gas bubbles into micro-bubbles at a micron level, so that the mass transfer area between a liquid phase and a gas phase is increased, and the micro-bubble generator in the patent belongs to a pneumatic micro-interface generator.

In addition, the first patent 201610641251.7 describes that the primary bubble breaker has a circulation liquid inlet, a circulation gas inlet and a gas-liquid mixture outlet, and the secondary bubble breaker communicates the feed inlet with the gas-liquid mixture outlet, which indicates that the bubble breakers all need to be mixed with gas and liquid, and in addition, as can be seen from the following drawings, the primary bubble breaker mainly uses the circulation liquid as power, so that the primary bubble breaker belongs to a hydraulic micro-interface generator, and the secondary bubble breaker simultaneously introduces the gas-liquid mixture into an elliptical rotating ball for rotation, thereby realizing bubble breaking in the rotating process, so that the secondary bubble breaker actually belongs to a gas-liquid linkage micro-interface generator. In fact, the micro-interface generator is a specific form of the micro-interface generator, whether it is a hydraulic micro-interface generator or a gas-liquid linkage micro-interface generator, however, the micro-interface generator adopted in the present invention is not limited to the above forms, and the specific structure of the bubble breaker described in the prior patent is only one of the forms that the micro-interface generator of the present invention can adopt. Furthermore, the prior patent 201710766435.0 states that the principle of the bubble breaker is that high-speed jet flows are used to achieve mutual collision of gases, and also states that the bubble breaker can be used in a micro-interface strengthening reactor to verify the correlation between the bubble breaker and the micro-interface generator; moreover, in the prior patent CN106187660, there is a related description on the specific structure of the bubble breaker, see paragraphs [0031] to [0041] in the specification, and the accompanying drawings, which illustrate the specific working principle of the bubble breaker S-2 in detail, the top of the bubble breaker is a liquid phase inlet, and the side of the bubble breaker is a gas phase inlet, and the liquid phase coming from the top provides the entrainment power, so as to achieve the effect of breaking into ultra-fine bubbles, and in the accompanying drawings, the bubble breaker is also seen to be of a tapered structure, and the diameter of the upper part is larger than that of the lower part, and also for better providing the entrainment power for the liquid phase.

Since the micro-interface generator was just developed in the early stage of the prior patent application, the micro-interface generator was named as a micro-bubble generator (CN201610641119.6), a bubble breaker (201710766435.0) and the like in the early stage, and is named as a micro-interface generator in the later stage along with the continuous technical improvement, and the micro-interface generator in the present invention is equivalent to the micro-bubble generator, the bubble breaker and the like in the prior art, and has different names. In summary, the micro-interface generator of the present invention belongs to the prior art.

Preferably, the preparation system still includes flash tank, first rectifying column and second rectifying column, the material export with the flash tank links to each other, flash tank bottom export with first rectifying column links to each other, first rectifying column bottom export with the second rectifying column links to each other, the crude product that obtains of reaction in the reactor passes through the flash tank flash distillation first rectifying column with the second rectifying column is extracted after the purification.

Preferably, the flash tank and the top of the first rectifying tower are both connected with the reactor. And a product extraction pipeline is arranged at the top of the second rectifying tower, and the bottom of the second rectifying tower is connected with the reactor. And the bottom of the second rectifying tower is also connected with a slag discharge pipeline.

The flash tank mainly removes most acetic acid in the crude product, the acetic acid returns to the reactor through a branch at the top of the flash tank, the conversion rate of the raw material is improved, and the purified crude product continuously enters the first rectifying tower;

the pressure in the first rectifying tower is negative pressure or normal pressure, and the pseudocumene and a small part of acetic acid in the crude product are mainly removed, the pseudocumene and the acetic acid return to the reactor through a branch at the top of the first rectifying tower, so that the conversion rate of the raw materials is improved, and the purified crude product continuously enters a second rectifying tower;

the pressure in the second rectifying tower is negative pressure or normal pressure, the catalyst and other high boiling point and solid impurities in the crude product are mainly removed, the cobalt acetate and manganese acetate catalyst returns to the reactor through the bottom of the second rectifying tower, the loss of the catalyst is reduced, and meanwhile, the bottom is periodically subjected to slag discharge. And the final trimellitic acid product is extracted through a product extraction pipeline at the top of the second rectifying tower.

The invention also provides a micro-interface preparation method of trimellitic acid, which adopts the preparation system to prepare trimellitic acid; the method comprises the following steps:

air is crushed into micro bubbles with micron level through a micro interface, and then the micro bubbles are mixed with the pseudocumene to react under the catalytic action of a catalyst to generate the pseudocumene acid.

Preferably, the reaction temperature is 0.1-0.5MPa, and the reaction pressure is 120-160 ℃.

Preferably, the catalyst is cobalt acetate and manganese acetate.

The preparation method has high preparation efficiency, can effectively improve the conversion rate of reactants and the yield of products, greatly reduces the temperature and the pressure required by the reaction, and obviously reduces the cost.

Compared with the prior art, the invention has the beneficial effects that:

(1) the micro-interface preparation system of trimellitic acid adopts the first micro-interface strengthening reactor and the second micro-interface generator to be matched for use, increases the gas/liquid phase interface area of oxygen and trimellitic acid in the air, greatly reduces the reaction temperature to 160 ℃, the operation pressure to 0.1-0.5MPa and improves the oxygen utilization rate to more than 95 percent;

(2) by arranging the plurality of layers of grid plates, the flow of liquid is slowed down, the sedimentation of undissolved catalyst particles is facilitated, the retention time of gas in a liquid phase is prolonged, and the reaction efficiency is improved;

(3) the flash tank, the first rectifying tower, the second rectifying tower and the circulating spray pipeline are respectively provided with a branch which flows back to the reactor, so that the acetic acid, the pseudocumene, the cobalt acetate and the manganese acetate catalyst are returned to the reactor, and the utilization rate of the raw materials and the catalyst is improved; meanwhile, the gas-liquid two phases are fully contacted by adopting a circulating spraying device, the content of organic matters in the gas phase is reduced, and the tail gas emission reaching the standard is facilitated.

Drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:

FIG. 1 is a schematic structural diagram of a system for preparing trimellitic acid by a micro-interface, provided in example 1 of the present invention;

FIG. 2 is a schematic structural view of a reactor provided in example 4 of the present invention;

FIG. 3 is a schematic diagram showing the structure of a reactor provided in comparative example 2 of the present invention.

Wherein:

10-a reactor; 101-a first micro-interface generator;

102-air branch; 103-reactant branch;

104-a diffuser tube; 105-a grid;

106-a second micro-interface generator; 107-material circulation line;

108-a heat exchanger; 109-material outlet;

20-a flash tank; 30-a first rectification column;

40-a second rectification column; 401-product take-off line;

402-a slag discharge pipeline; 50-a multifunctional tower;

501-silk screen; 502-circulating spray devices;

503-circulating spraying pipeline; 60-fractional condenser;

70-a pressure relief valve; 80-tail gas treatment device.

Detailed Description

The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and the detailed description, but those skilled in the art will understand that the following described embodiments are some, not all, of the embodiments of the present invention, and are only used for illustrating the present invention, and should not be construed as limiting the scope of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in a specific case to those of ordinary skill in the art.

In order to more clearly illustrate the technical solution of the present invention, the following description is made in the form of specific embodiments.

Example 1

Referring to fig. 1, this embodiment provides a system for preparing trimellitic acid by micro-interface, which includes: a reactor 10; a first micro-interface generator 101 is arranged in the reactor 10, a reactant branch 103 for introducing pseudocumene and an air branch 102 for introducing air are sequentially connected to the side wall of the reactor 10 from top to bottom, and the air branch 102 penetrates through the side wall of the reactor 10 and is connected with the first micro-interface generator 101;

a second micro-interface generator 106 is arranged above the first micro-interface generator 101, the two micro-interface generators are positioned on the same straight line along the vertical direction, the first micro-interface generator 101 is positioned below the liquid level in the reactor 10, and the second micro-interface generator 106 is positioned above the liquid level in the reactor 10; the bottom of the second micro-interface generator 106 is provided with a diffusion tube 104, and the bottom of the diffusion tube 104 is connected with the first micro-interface generator 101; in this embodiment, the reactor 10 is a slurry bed reactor 10, the first micro-interface generator 101 is a pneumatic micro-interface generator, and the second micro-interface generator 106 is a hydraulic micro-interface generator.

A material circulation pipeline 107 is arranged on one side of the reactor 10, an inlet of the material circulation pipeline 107 is connected with the side wall of the reactor 10, and an outlet of the material circulation pipeline 107 is connected with the second micro-interface generator 106; the material circulation line 107 is provided with a heat exchanger 108. During reaction, the material circulation pipeline 107 pumps the material into the second micro-interface generator 106, the material flows and sucks the air at the top of the reactor 10 into the material through the negative pressure port on the second micro-interface generator 106, so that the unreacted air continues to react, and the conversion rate of the raw material gas is improved.

Wherein, a plurality of layers of grid plates 105 are arranged above the first micro interface generator 101, the plurality of layers of grid plates 105 are arranged in a staggered manner, and the grid plates 105 are positioned below the liquid level in the reactor 10; the inlet of the material circulation line 107 is located between the multiple louver plates 105 in the vertical direction.

In this embodiment, a multi-function column 50 is connected to the top of the reactor 10, a partial condenser 60 and a pressure reducing valve 70 are disposed between the top of the reactor 10 and the multi-function column 50, the condensed liquid phase component flows back to the reactor 10 after the reactor 10 at the top of the reactor 10 is condensed by the partial condenser 60, and the uncondensed gas phase component enters the multi-function column 50 through the pressure reducing valve 70.

Wherein, a circulating spray device 502 is arranged in the multifunctional tower 50, a circulating spray pipeline 503 is arranged at one side of the multifunctional tower 50, an inlet of the circulating spray pipeline 503 is connected with the bottom of the multifunctional tower 50, an outlet of the circulating spray pipeline 503 is respectively connected with the circulating spray device 502 and the reactor 10, one part of circulating liquid in the circulating spray pipeline 503 returns to the multifunctional tower 50 through the circulating spray device 502, and the other part returns to the reactor 10 to continuously participate in the reaction. A wire mesh 501 is arranged in the multifunctional tower 50, and the wire mesh 501 is positioned below the circulating spray device 502. The top of the multifunctional tower 50 is connected with a tail gas treatment pipeline, and a tail gas treatment device 80 is arranged on the tail gas treatment pipeline.

With continued reference to FIG. 1, the side wall of the reactor 10 is provided with a material outlet 109, the material outlet 109 being vertically positioned between the liquid surface in the reactor 10 and the baffle 105. The preparation system of this embodiment further includes a flash tank 20, a first rectifying tower 30 and a second rectifying tower 40, the material outlet 109 is connected to the flash tank 20, the bottom outlet of the flash tank 20 is connected to the first rectifying tower 30, the bottom outlet of the first rectifying tower 30 is connected to the second rectifying tower 40, and the crude product obtained by the reaction in the reactor 10 is obtained after the flash evaporation in the flash tank, the purification in the first rectifying tower 30 and the purification in the second rectifying tower 40.

To promote the conversion of the feedstock, the flash tank 20 and the top of the first rectification column 30 are connected to the reactor 10. The second rectifying tower 40 is provided with a product withdrawal line 401 at the top and is connected to the reactor 10 at the bottom. The bottom of the second rectifying tower 40 is also connected with a slag discharge pipeline 402.

During the reaction process, the flash tank 20 mainly removes most of the acetic acid in the crude product, the acetic acid returns to the reactor 10 through the branch at the top of the flash tank 20, the conversion rate of the raw material is improved, and the purified crude product continuously enters the first rectifying tower 30;

the pressure in the first rectifying tower 30 is negative pressure or normal pressure, and the pseudocumene and a small part of acetic acid in the crude product are mainly removed, the pseudocumene and the acetic acid return to the reactor 10 through a branch at the top of the first rectifying tower 30, so that the conversion rate of the raw materials is improved, and the purified crude product continuously enters the second rectifying tower 40;

the pressure in the second rectifying tower 40 is negative pressure or normal pressure, which mainly removes the catalyst and other high boiling point and solid impurities in the crude product, the cobalt acetate and manganese acetate catalyst returns to the reactor 10 through the bottom of the second rectifying tower 40, thus reducing the loss of the catalyst and simultaneously discharging slag periodically at the bottom. The final trimellitic acid product is extracted through a product extraction pipeline 401 at the top of the second rectifying tower 40.

During reaction, air and pseudocumene are introduced into the reactor 10, the air is dispersed into microbubbles by the first micro-interface generator 101 and then mixed with the pseudocumene to form a gas-liquid emulsion, the gas-liquid emulsion reacts under the participation of a catalyst, and a reaction product is purified by the flash tank 20, the first rectifying tower 30 and the second rectifying tower 40 to obtain a product pseudocumene acid. The pressure in the reactor 10 was 0.3MPa and the temperature was 142 ℃.

Example 2

This example differs from example 1 only in the reaction temperature and pressure, which is 120 ℃ and 0.1 MPa.

Example 3

This example differs from example 1 only in the reaction temperature and pressure, which is 160 ℃ and 0.5 MPa.

Example 4

The difference between this example and example 1 is that the first micro-interface generator and the second micro-interface generator are not aligned in this example, as shown in fig. 2.

Comparative example 1

The difference between this example and example 1 is that the second micro-interface generator is a pneumatic micro-interface generator and is arranged below the liquid level in the reactor.

Comparative example 2

This example differs from example 1 in that in this example, instead of using a micro-interfacial generator, a high shear device is used to treat the gas-liquid feedstock, with both the reactant and air side streams passing directly into the high shear device. The high shear device may be a high shear device 40 as described in the examples of patent application No. 201080033116.5, and may be configured as shown in figure 3.

Examples of the experiments

Trimellitic acid was prepared using the preparation systems of examples 1-3 and comparative example 1, respectively, wherein: the flow rate of the pseudocumene is 2500kg/h, and the flow rate of the air is 800m³The volume ratio of the solvent acetic acid to the pseudocumene is 4: 1, the weight ratio of the pseudocumene to the cobalt acetate to the manganese acetate is 100: 1: 1. the reaction results are shown in the following table:

TABLE 1

	Pseudocumene conversion	Trimellitic acid yield	Utilization rate of oxygen in air
				Example 1	96.2％	95.5％	97.4％
Example 2	94.7％	93.8％	96.4％
				Example 3	95.8％	95.1％	96.9％
Example 4	95.3％	94.7％	97.0％
				Comparative example 1	93.1％	91.9％	89.2％
Comparative example 2	90.4％	88.7％	68.3％

As can be seen from the above table, the preparation system of this example still has good raw material conversion rate and product yield at a lower temperature and pressure, and it can be seen that the preparation system of this example has low reaction energy consumption and good preparation effect.

Among them, the conversion rate of oxygen in air of comparative example 1 is lower than that of example 1 because comparative example 1 does not effectively trap air at the top of the reactor even though it uses a mode of connecting two micro-interface generators, and it can be seen that this example improves the conversion rate of raw materials by setting the type and arrangement of the micro-interface generators.

In a word, compared with the prior art, the micro-interface preparation system of trimellitic acid has the advantages of low reaction temperature and pressure, high raw material conversion rate and high product yield, and is worthy of wide popularization and application.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A system for preparing trimellitic acid through a micro interface is characterized by comprising the following components: a reactor; a first micro-interface generator is arranged in the reactor, a reactant branch for introducing the pseudocumene and an air branch for introducing air are sequentially connected to the side wall of the reactor from top to bottom, and the air branch penetrates through the side wall of the reactor and is connected with the first micro-interface generator;

a second micro-interface generator is arranged above the first micro-interface generator, the first micro-interface generator is positioned below the liquid level in the reactor, and the second micro-interface generator is positioned above the liquid level in the reactor; the bottom of the second micro-interface generator is provided with a diffusion pipe, and the bottom of the diffusion pipe is connected with the first micro-interface generator;

2. The preparation system of claim 1, wherein a plurality of layers of grid plates are arranged above the first micro-interface generator, wherein the plurality of layers of grid plates are arranged in a staggered manner and are positioned below the liquid level in the reactor; and the inlet of the material circulating pipeline is positioned among the plurality of layers of grid plates along the vertical direction.

3. A production system according to claim 2, wherein the side wall of the reactor is provided with a material outlet which is located between the liquid level in the reactor and the grid in the vertical direction.

4. The system of claim 1, wherein the first micro-interface generator is a pneumatic micro-interface generator and the second micro-interface generator is a hydraulic micro-interface generator.

5. The preparation system of claim 1, wherein a multifunctional tower is connected to the top of the reactor, a circulating spray device is arranged in the multifunctional tower, a circulating spray pipeline is arranged on one side of the multifunctional tower, an inlet of the circulating spray pipeline is connected with the bottom of the multifunctional tower, an outlet of the circulating spray pipeline is respectively connected with the circulating spray device and the reactor, a part of circulating liquid in the circulating spray pipeline returns to the multifunctional tower through the circulating spray device, and the other part of circulating liquid returns to the reactor to continuously participate in the reaction.

6. The production system of claim 5, wherein a wire mesh is disposed within the multipurpose tower, the wire mesh being positioned below the circulating spray device.

7. The preparation system of claim 5, wherein a tail gas treatment pipeline is connected to the top of the multifunctional tower, and a tail gas treatment device is arranged on the tail gas treatment pipeline.

8. The production system according to claim 5, wherein a partial condenser and a pressure reducing valve are provided between the top of the reactor and the multifunctional column, and after the reactor at the top of the reactor is condensed by the partial condenser, the condensed liquid-phase component flows back into the reactor, and the uncondensed gas-phase component enters the multifunctional column through the pressure reducing valve.

9. A production method for producing trimellitic acid using the production system according to any one of claims 1 to 8, comprising the steps of:

10. The method as claimed in claim 9, wherein the reaction temperature is 0.1-0.5MPa and the reaction pressure is 120-160 ℃; preferably, the catalyst is cobalt acetate and manganese acetate.