阅读说明：本技术 一种使用微通道反应器连续化工业生产对苯二甲醛的工艺 (Process for continuously and industrially producing terephthalaldehyde by using microchannel reactor ) 是由 周坤 何强 赵建坤 谢学友 胡才勇 王康杨 于 2020-06-15 设计创作，主要内容包括：本发明涉及对苯二甲醛制备技术领域,尤其是一种使用微通道反应器连续化工业生产对苯二甲醛的工艺,所述的微通道反应器包括多组依次连通的反应芯片,所述反应芯片包括一次叠层的外面板一、反应通道一、反应通道二、反应通道三和外面板二,其对苯二甲醛生产步骤为：粉碎、配料、合成反应、冷却结晶、压滤一、碳酸钠溶液洗涤、压滤二、二次水洗、压滤、离心分离、干燥、包装入库,本发明大大提高了乌洛托品法生产对苯二甲醛的收率,且由于连续流生产和较快的反应速率,生产效率也得到了极高的提升。(The invention relates to the technical field of preparation of terephthalaldehyde, in particular to a process for continuously and industrially producing terephthalaldehyde by using a microchannel reactor, wherein the microchannel reactor comprises a plurality of groups of reaction chips which are sequentially communicated, each reaction chip comprises an outer panel I, a reaction channel II, a reaction channel III and an outer panel II which are laminated at one time, and the production steps of the terephthalaldehyde are as follows: the method has the advantages that the yield of terephthalaldehyde produced by a urotropine method is greatly improved, and the production efficiency is also extremely improved due to continuous flow production and faster reaction rate.)

1. A process for continuously and industrially producing terephthalaldehyde by using a microchannel reactor is characterized by comprising the following steps of: the microchannel reactor comprises a plurality of groups of reaction chips which are sequentially communicated, wherein each reaction chip comprises an outer panel I, a reaction channel II, a reaction channel III and an outer panel II which are laminated at one time, reaction cavities communicated between the outer panel I and the outer panel II are sealed at two ends, an input channel communicated with the reaction cavities is arranged on the outer panel I, an output channel communicated with the reaction cavities is arranged on the outer panel II, the output channel of one reaction chip between two adjacent reaction chips is communicated with the input channel of the other reaction chip, and the reaction chips are communicated in series at one time by adopting the connection mode;

the method for producing terephthalaldehyde comprises the following steps:

(1) crushing: conveying the chlorinated mixture of p-xylene to a pulverizer for pulverization;

(2) preparing materials: adding the crushed chlorinated mixture of p-xylene and toluene into a stirring tank, preheating the materials to a preset temperature through a high-low temperature circulating device, and carrying out stirring and high-speed shearing treatment to dissolve and uniformly disperse the materials in liquid;

(3) and (3) synthesis reaction: preheating a microchannel reactor to a preset temperature through a high-low temperature circulating device, then respectively pumping raw material liquid into an inlet of the microchannel reactor, controlling the feeding rate of a pump to ensure the proportion of each raw material liquid when entering the reactor, reacting the raw material liquid through a plurality of microchannel reactor units, controlling the temperature and the pressure of the microreactor in the reaction process to ensure uniform and stable reaction, strictly controlling the residence time of reactants in the microchannel reactor, generating a product of the reactants within the reaction time of 20-60 seconds, and discharging a reaction system in time;

(4) cooling and crystallizing: the material in the microchannel reactor is discharged and cooled for crystallization after reacting for a period of time, the material liquid at the discharge port of the microchannel reactor is a crude product solution of the DI intermediate, the material after the reaction is cooled to 60-70 ℃ by a disc condenser and then conveyed into a crystallization tank for crystallization, the crystallized material is subjected to filter pressing and separation, and the uncondensed gas is discharged;

(5) pressure filtration I: after the materials led out from the crystallization tank are subjected to filter pressing by a filter press, mother liquor is kept stand and separated, toluene is reused in a reaction tank, wastewater enters micro-reaction water treatment equipment for treatment, and raw materials are added in proportion according to the concentration of the unreacted raw materials in the mother liquor to carry out secondary reaction; the solid is a DI intermediate crude product, and the toluene is discharged periodically;

(6) washing with a sodium carbonate solution: putting the crude product collected by filter pressing into a reaction tank, adding a saturated sodium carbonate solution with the amount of 3 times of that of the crude product, washing, and then carrying out filter pressing to transfer carboxylic acid in the crude product into liquid;

(7) and (2) filter pressing II: after the materials washed by the sodium carbonate solution are subjected to filter pressing by a filter press, solid-liquid separation is carried out, the solid enters the next working procedure, and the liquid is recycled for three times and then enters micro-reaction water treatment equipment for treatment;

(8) secondary water washing and filter pressing: and putting the solid collected by filter pressing into a reaction tank, adding a certain amount of water for washing, and then carrying out filter pressing. Repeating the process for 2 times, feeding the solid after filter pressing into the next working procedure, and feeding the wastewater W1-3 and W1-4 into a micro-reaction water treatment device for treatment;

(9) centrifugal separation: and carrying out centrifugal operation on the filter-pressed solid by using the inertial centrifugal force of a centrifugal machine to realize the separation of the solid and the liquid. The solid enters the next working procedure, and the wastewater W1-5 is sent to a micro-reaction water treatment device for treatment;

(10) and (3) drying: drying the centrifugally separated materials by a dryer, packaging and warehousing.

2. The process for continuously and industrially producing terephthalaldehyde by using a microchannel reactor according to claim 1, wherein: in the step (1), waste gas G1-1 is generated in the crushing process;

in the step (4), waste gas G1-2 is generated in the condensation and crystallization process;

in the step (5), wastewater W1-1 is generated in the first filter pressing process;

in the step (7), wastewater W1-2 is generated in the second filter pressing process;

in the step (10), the drying process generates exhaust gas G1-3;

the generated waste gas and waste water are collected and treated in a centralized way.

3. The process for continuously and industrially producing terephthalaldehyde by using a microchannel reactor according to claim 1, wherein: according to step (2), the material is preheated to 50 ℃ by a high-low temperature circulating device.

4. The process for continuously and industrially producing terephthalaldehyde by using a microchannel reactor according to claim 1, wherein: according to the step (3), the microchannel reactor is preheated to the temperature of 110-145 ℃ by the high-low temperature circulating device, and the pressure in the microchannel reactor is controlled to be 13-20 MPa.

5. The process for continuously and industrially producing terephthalaldehyde by using a microchannel reactor according to claim 1, wherein: according to the step (10), the materials are dried for 24 hours at 80 ℃ by a dryer and then packaged and stored.

Technical Field

The invention relates to the technical field of preparation of terephthalaldehyde, in particular to a process for continuously and industrially producing terephthalaldehyde by using a microchannel reactor.

Background

With the development and application of E R series fluorescent whitening agents, the consumption of terephthalaldehyde is continuously increased, thereby attracting many chemical companies to carry out intensive research on the manufacturing technology of the products. Many synthetic methods are reported, such as: air oxidation of p-xylene, i.e. halogenation (bromination or chlorination) and hydrolysis or oxidative hydrolysis of p-xylene; reduction of terephthalic acid (or ester); p-phthaloyl chloride is reduced; reducing and hydrolyzing terephthalonitrile; oxidizing terephthalyl alcohol; electrolytic oxidation or reduction; carbon monoxide and hydrogen, etc. are added to dibromobenzene under high pressure in the presence of n-tributylamine and triphenylphosphine, palladium bromide.

In view of process condition requirements, production economic benefits and raw material sources, the prior process for producing terephthalaldehyde mostly adopts the steps of firstly halogenating (brominating or chloridizing) paraxylene, and then hydrolyzing or oxidatively hydrolyzing the paraxylene;

the yield of the halogenation process in the first step of the process is close to quantitative; there are thus two different approaches, mainly in the second hydrolysis or oxidative hydrolysis process. One method is to use dilute nitric acid for oxidation and hydrolysis, vanadium pentoxide is used as a catalyst, the yield is 75.6%, the dilute nitric acid has serious loss to the traditional equipment, and the process wastewater contains a large amount of heavy metal ions and seriously pollutes the water body; the other method is to use urotropine and water to replace dilute nitric acid and vanadium pentoxide, and the process has light equipment loss but the product yield is 42.7 percent. Since the use of urotropin as a reactant involves somley reaction, the reaction process cannot be precisely controlled in a conventional reaction vessel, and thus the yield is low.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a process for continuously and industrially producing terephthalaldehyde by using a microchannel reactor.

In order to achieve the purpose, the invention provides the following technical scheme: a process for continuously and industrially producing terephthalaldehyde by using a microchannel reactor, wherein the microchannel reactor comprises a plurality of groups of reaction chips which are sequentially communicated, each reaction chip comprises an outer panel I, a reaction channel II, a reaction channel III and an outer panel II which are laminated at one time, the two ends of a reaction cavity communicated between the outer panel I and the outer panel II are sealed, an input channel communicated with the reaction cavity is arranged on the outer panel I, an output channel communicated with the reaction cavity is arranged on the outer panel II, the output channel of one reaction chip between two adjacent reaction chips is communicated with the input channel of the other reaction chip, and the reaction chips are communicated in series at one time by adopting the connection mode;

the method for producing terephthalaldehyde comprises the following steps:

(1) crushing: conveying the chlorinated mixture of p-xylene to a pulverizer for pulverization;

(2) preparing materials: adding the crushed chlorinated mixture of p-xylene and toluene into a stirring tank, preheating the materials to a preset temperature through a high-low temperature circulating device, and carrying out stirring and high-speed shearing treatment to dissolve and uniformly disperse the materials in liquid;

(3) and (3) synthesis reaction: preheating a microchannel reactor to a preset temperature through a high-low temperature circulating device, then respectively pumping raw material liquid into an inlet of the microchannel reactor, controlling the feeding rate of a pump to ensure the proportion of each raw material liquid when entering the reactor, reacting the raw material liquid through a plurality of microchannel reactor units, controlling the temperature and the pressure of the microreactor in the reaction process to ensure uniform and stable reaction, strictly controlling the residence time of reactants in the microchannel reactor, generating a product of the reactants within the reaction time of 20-60 seconds, and discharging a reaction system in time;

(4) cooling and crystallizing: the material in the microchannel reactor is discharged and cooled for crystallization after reacting for a period of time, the material liquid at the discharge port of the microchannel reactor is a crude product solution of the DI intermediate, the material after the reaction is cooled to 60-70 ℃ by a disc condenser and then conveyed into a crystallization tank for crystallization, the crystallized material is subjected to filter pressing and separation, and the uncondensed gas is discharged;

(5) pressure filtration I: after the materials led out from the crystallization tank are subjected to filter pressing by a filter press, mother liquor is kept stand and separated, toluene is reused in a reaction tank, wastewater enters micro-reaction water treatment equipment for treatment, and raw materials are added in proportion according to the concentration of the unreacted raw materials in the mother liquor to carry out secondary reaction; the solid is a DI intermediate crude product, and the toluene is discharged periodically;

(6) washing with a sodium carbonate solution: putting the crude product collected by filter pressing into a reaction tank, adding a saturated sodium carbonate solution with the amount of 3 times of that of the crude product, washing, and then carrying out filter pressing to transfer carboxylic acid in the crude product into liquid;

(7) and (2) filter pressing II: after the materials washed by the sodium carbonate solution are subjected to filter pressing by a filter press, solid-liquid separation is carried out, the solid enters the next working procedure, and the liquid is recycled for three times and then enters micro-reaction water treatment equipment for treatment;

(8) secondary water washing and filter pressing: and putting the solid collected by filter pressing into a reaction tank, adding a certain amount of water for washing, and then carrying out filter pressing. Repeating the process for 2 times, feeding the solid after filter pressing into the next working procedure, and feeding the wastewater W1-3 and W1-4 into a micro-reaction water treatment device for treatment;

(9) centrifugal separation: and carrying out centrifugal operation on the filter-pressed solid by using the inertial centrifugal force of a centrifugal machine to realize the separation of the solid and the liquid. The solid enters the next working procedure, and the wastewater W1-5 is sent to a micro-reaction water treatment device for treatment;

(10) and (3) drying: drying the centrifugally separated materials by a dryer, packaging and warehousing.

Preferably, in the step (1), waste gas G1-1 is generated in the crushing process;

in the step (4), waste gas G1-2 is generated in the condensation and crystallization process;

in the step (5), wastewater W1-1 is generated in the first filter pressing process;

in the step (7), wastewater W1-2 is generated in the second filter pressing process;

in the step (10), the drying process generates exhaust gas G1-3;

the generated waste gas and waste water are collected and treated in a centralized way.

Preferably, according to step (2), the material is preheated to 50 ℃ by means of a high-low temperature circulation device.

Preferably, according to the step (3), the pressure in the microchannel reactor is controlled to be 13-20MPa by preheating the microchannel reactor to 110-145 ℃ through the high-low temperature circulating device.

Preferably, according to the step (10), the material is dried for 24 hours at 80 ℃ by a dryer and then packaged and warehoused. .

Compared with the prior art, the invention has the beneficial effects that: the invention uses the microchannel reactor to replace the traditional reaction kettle, carries out hydrolysis reaction in the microchannel reactor, adopts halogenated mixture of p-xylene and urotropine as raw materials, takes toluene as solvent of the halogenated mixture, uses a high-pressure pump to continuously convey materials to the microchannel reactor, utilizes the advantages of mass transfer, heat transfer and the like of the microchannel reactor to accurately control the reaction process, accurately controls the reaction temperature, the raw material proportion and the reaction time, has safe and reliable reaction operation, greatly reduces side reactions, and even completely eliminates the side reactions. The yield of terephthalaldehyde produced by the urotropine method is greatly improved, and the production efficiency is also extremely improved due to continuous flow production and higher reaction rate.

Drawings

FIG. 1 is a first outer panel of a reaction chip according to the present invention;

FIG. 2 shows a first reaction channel of the reaction chip of the present invention;

FIG. 3 shows a second reaction channel of the reaction chip of the present invention;

FIG. 4 shows a third reaction channel of the reaction chip of the present invention;

FIG. 5 is a second outer panel of the reaction chip of the present invention;

FIG. 6 is a schematic diagram of a microchannel reactor according to the present invention;

FIG. 7 is a process flow diagram of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. 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 reason for the low yield of the classical Sommelet reaction is mainly based on the problems that exist in the reaction scheme:

firstly, the method comprises the following steps: in the traditional Sommelet reaction process, after a benzyl halide compound and hexamethylenetetramine react to generate a quaternary ammonium salt, three intermediates are obtained in the following hydrolysis process: benzylamine cation, benzylamine and methylene Schiff base are difficult to be converted into aldehyde under the condition that only urotropine is added, even if the p H value is adjusted to be within the range of 3-6. The further reaction of the methylene Schiff base is converted from quaternary ammonium salt to methylene Schiff base, and simultaneously, nitrogen-containing compounds are generated, and the traditional mechanism is not clearly explained, so that no good measure is taken to inhibit the side reaction. Furthermore, this should be an equilibrium reaction, where the transition from methylene schiff base to benzylidene schiff base is accompanied by the transfer of protons. The process takes place with an acid of a certain acidity, otherwise the equilibrium reaction is carried out at a high temperature, but the temperature is too high, some aldehydes are decomposed, or some other side reactions are generated. In the classical Sommelet reaction, because the hydrolysis of quaternary ammonium salt is carried out by taking aqueous solution of acetic acid as solvent, the migration of proton has certain constraint, and no measure is taken to change the balance, so that the conversion of quaternary ammonium salt of benzyl halide into methylene Schiff base is incomplete.

Secondly, the method comprises the following steps: the rearrangement process from the conversion of methyleneschiff base to benzylidene schiff base is not described clearly, so that there is no reasonable inhibition to prevent side reactions. The process needs to undergo 1, 3-hydrogen migration, is thermodynamically allowable, needs a certain temperature, and in a proper temperature range, proton migration frequently occurs, and the conversion of the methylene Schiff base into the benzylidene Schiff base is more thorough. In general, isomers under thermodynamic control are unstable, and aryl groups bind to the double bond in the molecule rather than to the position of the double bond in the molecule, for which reason benzylene Schiff base is more stable than methylene Schiff base under thermodynamic conditions, and its binding energy is attributed to its free energy. In the classical Sommelet reaction, the reaction is not complete and yields are not high because the reaction is carried out in acidic water, the temperature required for rearrangement is not reached.

Thirdly, the method comprises the following steps: the traditional Sommelet reaction mostly adopts a 'one-pot' method to synthesize corresponding aromatic aldehyde, because in the classical Sommelet reaction, the heating time is very critical when the aldehyde is generated in the third step, some side reactions can occur along with the prolonging of the reaction time, the yield and the purity of the aldehyde can be obviously reduced, and the quaternary ammonium salt generated by the benzyl halide compound is easy to hydrolyze into nitrogen-containing compounds such as benzylamine, so-called Delepine reaction is generated, especially for polyhalomethyl aromatic hydrocarbon, the classical Sommelet reaction is just performed in a medium with water, and the hydrolysis reaction is accelerated due to the rising of the temperature.

Therefore, after the microchannel reactor is used as a reaction control unit, according to the reaction process, trace terephthalaldehyde is immediately conveyed out of the reaction system once generated, so that the reaction balance is favorably moved to the generation direction of the terephthalaldehyde, and the reaction materials are timely moved out of the reaction system before side reaction occurs. Thereby achieving the effect of improving the yield, the yield of the final product reaches 60 percent, and the yield is improved by nearly 17 points compared with the yield of the traditional reaction kettle. And the efficiency of continuous production is greatly improved. Compared with the traditional reaction kettle which produces the same amount of terephthalaldehyde, the reaction time is shortened to 1/6.

Referring to fig. 1 to 7, the present invention provides a technical solution: a process for continuously and industrially producing terephthalaldehyde by using a microchannel reactor, wherein the microchannel reactor comprises a plurality of groups of reaction chips which are sequentially communicated, each reaction chip comprises an outer panel I, a reaction channel II, a reaction channel III and an outer panel II which are laminated at one time, the two ends of a reaction cavity communicated between the outer panel I and the outer panel II are sealed, an input channel communicated with the reaction cavity is arranged on the outer panel I, an output channel communicated with the reaction cavity is arranged on the outer panel II, the output channel of one reaction chip between two adjacent reaction chips is communicated with the input channel of the other reaction chip, and the reaction chips are communicated in series at one time by adopting the connection mode;

the reaction channel I, the reaction channel II and the reaction channel III are reaction chip plates, a plurality of reaction channels are uniformly arranged on the reaction chip plates, the reaction channels on each reaction chip plate are communicated in a penetrating manner, then clamping and sealing are carried out through the outer panel I and the outer panel II, and double-input and double-output channels are arranged on the outer panel I and the outer panel II.

The microchannel reactor has the advantages of high mass transfer and heat transfer efficiency, accurate control of reaction temperature, raw material proportion and reaction time, safe and reliable reaction operation, great reduction, even complete elimination of side reaction, improved reaction yield and shortened reaction time;

the microchannel reactor can replace the traditional reaction kettle, can replace the traditional backward process, can realize continuous production, has higher product yield than the traditional product and is easy for large-scale production;

the microchannel reaction chip has better mass transfer and heat transfer efficiency, the cavity type of the I-shaped line is convenient for collision mixing of reactants in the cavity, the 316L stainless steel material is convenient for external heating control, and the laser welding technology ensures that the inside of the reaction chip can bear the pressure of 40 Mpa.

The microchannel reaction unit and the five reaction chips are connected to form a unit, and the microchannel reactor is assembled in the form of the reaction unit, so that the microchannel reactor is convenient to overhaul, install and replace in the production process.

The method for producing terephthalaldehyde comprises the following steps:

(1) crushing: conveying the chlorinated mixture of p-xylene to a pulverizer for pulverization;

(2) preparing materials: adding the crushed chlorinated mixture of p-xylene and toluene into a stirring tank, preheating the materials to a preset temperature through a high-low temperature circulating device, and carrying out stirring and high-speed shearing treatment to dissolve and uniformly disperse the materials in liquid;

(3) and (3) synthesis reaction: preheating a microchannel reactor to a preset temperature through a high-low temperature circulating device, then respectively pumping raw material liquid into an inlet of the microchannel reactor, controlling the feeding rate of a pump to ensure the proportion of each raw material liquid when entering the reactor, reacting the raw material liquid through a plurality of microchannel reactor units, controlling the temperature and the pressure of the microreactor in the reaction process to ensure uniform and stable reaction, strictly controlling the residence time of reactants in the microchannel reactor, generating a product of the reactants within the reaction time of 20-60 seconds, and discharging a reaction system in time;

(4) cooling and crystallizing: the material in the microchannel reactor is discharged and cooled for crystallization after reacting for a period of time, the material liquid at the discharge port of the microchannel reactor is a crude product solution of the DI intermediate, the material after the reaction is cooled to 60-70 ℃ by a disc condenser and then conveyed into a crystallization tank for crystallization, the crystallized material is subjected to filter pressing and separation, and the uncondensed gas is discharged;

(5) pressure filtration I: after the materials led out from the crystallization tank are subjected to filter pressing by a filter press, mother liquor is kept stand and separated, toluene is reused in a reaction tank, wastewater enters micro-reaction water treatment equipment for treatment, and raw materials are added in proportion according to the concentration of the unreacted raw materials in the mother liquor to carry out secondary reaction; the solid is a DI intermediate crude product, and the toluene is discharged periodically;

(6) washing with a sodium carbonate solution: putting the crude product collected by filter pressing into a reaction tank, adding a saturated sodium carbonate solution with the amount of 3 times of that of the crude product, washing, and then carrying out filter pressing to transfer carboxylic acid in the crude product into liquid;

(7) and (2) filter pressing II: after the materials washed by the sodium carbonate solution are subjected to filter pressing by a filter press, solid-liquid separation is carried out, the solid enters the next working procedure, and the liquid is recycled for three times and then enters micro-reaction water treatment equipment for treatment;

(8) secondary water washing and filter pressing: and putting the solid collected by filter pressing into a reaction tank, adding a certain amount of water for washing, and then carrying out filter pressing. Repeating the process for 2 times, feeding the solid after filter pressing into the next working procedure, and feeding the wastewater W1-3 and W1-4 into a micro-reaction water treatment device for treatment;

(9) centrifugal separation: and carrying out centrifugal operation on the filter-pressed solid by using the inertial centrifugal force of a centrifugal machine to realize the separation of the solid and the liquid. The solid enters the next working procedure, and the wastewater W1-5 is sent to a micro-reaction water treatment device for treatment;

(10) and (3) drying: drying the centrifugally separated materials by a dryer, packaging and warehousing.

In the step (1), waste gas G1-1 is generated in the crushing process;

in the step (4), waste gas G1-2 is generated in the condensation and crystallization process;

in the step (5), wastewater W1-1 is generated in the first filter pressing process;

in the step (7), wastewater W1-2 is generated in the second filter pressing process;

in the step (10), the drying process generates exhaust gas G1-3;

the generated waste gas and waste water are collected and treated in a centralized way.

According to step (2), the material is preheated to 50 ℃ by a high-low temperature circulating device.

According to the step (3), the microchannel reactor is preheated to the temperature of 110-145 ℃ by the high-low temperature circulating device, and the pressure in the microchannel reactor is controlled to be 13-20 MPa.

According to the step (10), the materials are dried for 24 hours at 80 ℃ by a dryer and then packaged and stored.

Toluene replaces water as the solvent, is convenient for the transport of material in the microchannel, and toluene can prevent the material to the jam of microchannel after dissolving the chlorination material as the solvent, and is immiscible with water, the separation of being convenient for.

According to the above description, in the specific implementation process, the project process flow and the contamination node are shown in fig. 7:

(1) pulverizing

The chlorinated mixture of paraxylene is sent to a pulverizer for pulverization. Exhaust gas G1-1 is generated during the pulverization process.

(2) Ingredients

Adding 400kg of the chlorinated mixture of p-xylene and 1200kg of toluene after crushing into a stirring tank, preheating the materials to 50 ℃ through a high-low temperature circulating device, and carrying out stirring and high-speed shearing treatment to enable the materials to be dissolved and uniformly dispersed in liquid.

1200kg of water and 560kg of urotropine are added into a stirring tank, the materials are preheated to 50 ℃ by a high-low temperature circulating device, and stirring and high-speed shearing treatment are carried out, so that the materials are dissolved and uniformly dispersed in the liquid.

(3) Synthesis reaction

The microchannel reactor was preheated to 135 ℃ by a high low temperature circulating device. Respectively pumping the raw material liquid into double inlets of the microchannel reactor. The feed rates of the two pumps were controlled to ensure the ratio of each feed solution entering the reactor. The raw material liquid is reacted through a plurality of microchannel reactor units, and the temperature (135 ℃) and the pressure (15MPa) of the microreactor are controlled in the reaction process, so that the uniform and stable reaction is ensured. The residence time of the reactants in the microchannel reactor is strictly controlled, the reactants can generate products within the reaction time of 20-60 seconds, and the reaction system needs to be discharged in time.

(4) Cooling crystallization

And discharging materials after the materials in the microreactor react for a period of time, cooling and crystallizing. And the feed liquid at the discharge port of the microchannel reactor is the crude product solution of the DI intermediate. And cooling the reacted materials to 60-70 ℃ through a disc condenser, then conveying the cooled materials into a crystallization tank for crystallization, and performing filter pressing separation on the crystallized materials. And discharging uncondensed gas. This process produces exhaust gas G1-2.

(5) Filter pressing

And (3) after the material led out from the crystallization tank is subjected to pressure filtration by a filter press, standing and separating mother liquor, reusing the toluene in the reaction tank, and treating wastewater by micro-reaction water treatment equipment. Adding raw materials in proportion according to the concentration of the unreacted raw materials in the mother solution to carry out secondary reaction; the solid is the crude DI intermediate. The toluene is discharged periodically, and the process generates waste water W1-1.

(6) Sodium carbonate solution washing

And putting the crude product collected by filter pressing into a reaction tank, adding a saturated sodium carbonate solution with the amount of 3 times of that of the crude product, washing, and then carrying out filter pressing to transfer carboxylic acid in the crude product into liquid.

(7) Filter pressing

And (3) carrying out solid-liquid separation on the materials washed by the sodium carbonate solution after filter pressing by a filter press. The solid enters the next working procedure, and the liquid enters micro-reaction water treatment equipment for treatment after being recycled for three times. This process produces waste water W1-2.

(8)2 times of water washing and filter pressing

And putting the solid collected by filter pressing into a reaction tank, adding a certain amount of water for washing, and then carrying out filter pressing. This process was repeated 2 times. And (3) feeding the solid after filter pressing into the next working procedure, and feeding the wastewater W1-3 and the wastewater W1-4 into a micro-reaction water treatment device for treatment.

(9) Centrifugal separation

And carrying out centrifugal operation on the filter-pressed solid by using the inertial centrifugal force of a centrifugal machine to realize the separation of the solid and the liquid. The solid enters the next working procedure, and the wastewater W1-5 is sent to a micro-reaction water treatment device for treatment.

(10) Drying

Drying the centrifuged material at 80 ℃ for 24h by a dryer, packaging and warehousing. Exhaust gas G1-3 is generated during the drying process.

According to the technical scheme, a chlorinated mixture of p-xylene is crushed and homogenized and then enters the microreactor through the metering pump, and the prepared urotropine and the like also enter the microreactor through the metering pump to perform synthetic reaction. And carrying out solid-liquid separation on the materials after the reaction is finished. And drying and packaging the solid after solid-liquid separation to obtain a finished product.

The reaction equation is as follows:

the conversion rate of dichloro-p-xylene is 86.68 percent, and the yield of terephthalaldehyde is 47.60 percent

The conversion rate of trichloro-p-xylene is 88.20 percent, and the yield of terephthalaldehyde is 56.41 percent

The conversion rate of tetrachloro-p-xylene is 87.43 percent, and the yield of terephthalaldehyde is 66.95 percent

The conversion rate of the terephthalaldehyde is 87.43 percent, and the yield of the terephthalic acid is 7.12 percent

NH₃+HCl→NH₄Cl

And (3) total reaction:

the conversion of terephthalic acid was 94.86% and the yield was 120%.

Alternatives can be made with other alternative reactants in practice:

alternative one:

ethanol was used as a solvent instead of toluene. The ethanol is cheap and easy to obtain, the use amount of the ethanol is less than that of the toluene, and the ethanol is used for replacing the toluene, so that part of the production cost can be reduced.

(1) Pulverizing

The chlorinated mixture of paraxylene is sent to a pulverizer for pulverization. Exhaust gas G1-1 is generated during the pulverization process.

(2) Ingredients

Adding 400kg of the chlorinated mixture of p-xylene and 700kg of ethanol into a stirring tank, preheating the materials to 50 ℃ through a high-low temperature circulating device, and carrying out stirring and high-speed shearing treatment to dissolve the materials and uniformly disperse the materials in liquid.

1200kg of water and 560kg of urotropine are added into a stirring tank, the materials are preheated to 50 ℃ by a high-low temperature circulating device, and stirring and high-speed shearing treatment are carried out, so that the materials are dissolved and uniformly dispersed in the liquid.

(3) Synthesis reaction

The microchannel reactor was preheated to 135 ℃ by a high low temperature circulating device. Respectively pumping the raw material liquid into double inlets of the microchannel reactor. The feed rates of the two pumps were controlled to ensure the ratio of each feed solution entering the reactor. The raw material liquid is reacted through a plurality of microchannel reactor units, and the temperature (135 ℃) and the pressure (15MPa) of the microreactor are controlled in the reaction process, so that the uniform and stable reaction is ensured. The residence time of the reactants in the microchannel reactor is strictly controlled, the reactants can generate products within the reaction time of 20-60 seconds, and the reaction system needs to be discharged in time.

(4) Cooling crystallization

And discharging materials after the materials in the microreactor react for a period of time, cooling and crystallizing. And the feed liquid at the discharge port of the microchannel reactor is the crude product solution of the DI intermediate. And cooling the reacted materials to 60-70 ℃ through a disc condenser, then conveying the cooled materials into a crystallization tank for crystallization, and performing filter pressing separation on the crystallized materials. And discharging uncondensed gas. This process produces exhaust gas G1-2.

(5) Filter pressing

And (3) after the material led out from the crystallization tank is subjected to pressure filtration by a filter press, standing and separating mother liquor, reusing the toluene in the reaction tank, and treating wastewater by micro-reaction water treatment equipment. Adding raw materials in proportion according to the concentration of the unreacted raw materials in the mother solution to carry out secondary reaction; the solid is the crude DI intermediate. The toluene is discharged periodically, and the process generates waste water W1-1.

(6) Sodium carbonate solution washing

And putting the crude product collected by filter pressing into a reaction tank, adding a saturated sodium carbonate solution with the amount of 3 times of that of the crude product, washing, and then carrying out filter pressing to transfer carboxylic acid in the crude product into liquid.

(7) Filter pressing

And (3) carrying out solid-liquid separation on the materials washed by the sodium carbonate solution after filter pressing by a filter press. The solid enters the next working procedure, and the liquid enters micro-reaction water treatment equipment for treatment after being recycled for three times. This process produces waste water W1-2.

(8)2 times of water washing and filter pressing

And putting the solid collected by filter pressing into a reaction tank, adding a certain amount of water for washing, and then carrying out filter pressing. This process was repeated 2 times. And (3) feeding the solid after filter pressing into the next working procedure, and feeding the wastewater W1-3 and the wastewater W1-4 into a micro-reaction water treatment device for treatment.

(9) Centrifugal separation

And carrying out centrifugal operation on the filter-pressed solid by using the inertial centrifugal force of a centrifugal machine to realize the separation of the solid and the liquid. The solid enters the next working procedure, and the wastewater W1-5 is sent to a micro-reaction water treatment device for treatment.

(10) Drying

Drying the centrifuged material at 80 ℃ for 24h by a dryer, packaging and warehousing. Exhaust gas G1-3 is generated during the drying process.

Alternative scheme two:

the reaction temperature is reduced, the reaction pressure is increased, and the reaction time can be shortened.

(1) Pulverizing

The chlorinated mixture of paraxylene is sent to a pulverizer for pulverization. Exhaust gas G1-1 is generated during the pulverization process.

(2) Ingredients

Adding 400kg of the chlorinated mixture of p-xylene and 1200kg of toluene after crushing into a stirring tank, preheating the materials to 50 ℃ through a high-low temperature circulating device, and carrying out stirring and high-speed shearing treatment to enable the materials to be dissolved and uniformly dispersed in liquid.

1200kg of water and 560kg of urotropine are added into a stirring tank, the materials are preheated to 50 ℃ by a high-low temperature circulating device, and stirring and high-speed shearing treatment are carried out, so that the materials are dissolved and uniformly dispersed in the liquid.

(3) Synthesis reaction

The microchannel reactor was preheated to 115 ℃ by a high low temperature circulating device. Respectively pumping the raw material liquid into double inlets of the microchannel reactor. The feed rates of the two pumps were controlled to ensure the ratio of each feed solution entering the reactor. The raw material liquid is reacted through a plurality of microchannel reactor units, and the temperature (115 ℃) and the pressure (18MPa) of the microreactor are controlled in the reaction process, so that the uniform and stable reaction is ensured. The residence time of the reactants in the microchannel reactor is strictly controlled, the reactants can generate products within the reaction time of 20-40 seconds, and the reaction system needs to be discharged in time.

(4) Cooling crystallization

And discharging materials after the materials in the microreactor react for a period of time, cooling and crystallizing. And the feed liquid at the discharge port of the microchannel reactor is the crude product solution of the DI intermediate. And cooling the reacted materials to 60-70 ℃ through a disc condenser, then conveying the cooled materials into a crystallization tank for crystallization, and performing filter pressing separation on the crystallized materials. And discharging uncondensed gas. This process produces exhaust gas G1-2.

(5) Filter pressing

And (3) after the material led out from the crystallization tank is subjected to pressure filtration by a filter press, standing and separating mother liquor, reusing the toluene in the reaction tank, and treating wastewater by micro-reaction water treatment equipment. Adding raw materials in proportion according to the concentration of the unreacted raw materials in the mother solution to carry out secondary reaction; the solid is the crude DI intermediate. The toluene is discharged periodically, and the process generates waste water W1-1.

(6) Sodium carbonate solution washing

And putting the crude product collected by filter pressing into a reaction tank, adding a saturated sodium carbonate solution with the amount of 3 times of that of the crude product, washing, and then carrying out filter pressing to transfer carboxylic acid in the crude product into liquid.

(7) Filter pressing

And (3) carrying out solid-liquid separation on the materials washed by the sodium carbonate solution after filter pressing by a filter press. The solid enters the next working procedure, and the liquid enters micro-reaction water treatment equipment for treatment after being recycled for three times. This process produces waste water W1-2.

(8)2 times of water washing and filter pressing

And putting the solid collected by filter pressing into a reaction tank, adding a certain amount of water for washing, and then carrying out filter pressing. This process was repeated 2 times. And (3) feeding the solid after filter pressing into the next working procedure, and feeding the wastewater W1-3 and the wastewater W1-4 into a micro-reaction water treatment device for treatment.

(9) Centrifugal separation

And carrying out centrifugal operation on the filter-pressed solid by using the inertial centrifugal force of a centrifugal machine to realize the separation of the solid and the liquid. The solid enters the next working procedure, and the wastewater W1-5 is sent to a micro-reaction water treatment device for treatment.

(10) Drying

Drying the centrifuged material at 80 ℃ for 24h by a dryer, packaging and warehousing. Exhaust gas G1-3 is generated during the drying process.

The ethanol replaces toluene as a solvent, so that the production cost is reduced, and the production cost can be reduced due to low price and less dosage of the ethanol

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.