CN113429295B - Method for preparing m-phenylenediamine based on continuous catalytic hydrogenation of fixed-bed microreactor - Google Patents

Abstract

The invention discloses a method for preparing m-phenylenediamine by continuous catalytic hydrogenation based on a fixed bed microreactor, which comprises the following steps: (1) Dinitrochlorobenzene is used as a raw material, and is dissolved in a solvent to be used as a substrate solution to be hydrogenated; the dinitrochlorobenzene is at least one of 2,4-dinitrochlorobenzene, 2,6-dinitrochlorobenzene and 3,5-dinitrochlorobenzene; (2) Mixing a substrate solution to be hydrogenated and hydrogen in a micro mixer to form a gas-liquid mixture with a good gas-liquid micro dispersion state, and then reacting in a micro packed bed reactor filled with a solid particle catalyst; the reaction temperature is 40-160 ℃, and the pressure is 1-5 MPa; the retention time of the gas-liquid mixture in the micro packed bed reactor is 10-120 s; (3) And (3) carrying out gas-liquid separation on the gas-liquid mixture obtained after the reaction is finished, and enabling the liquid product to enter a subsequent separation and purification system.

Description

Method for preparing m-phenylenediamine based on continuous catalytic hydrogenation of fixed-bed microreactor

technical field

The invention relates to the technical field of preparing m-phenylenediamine, in particular to a method for preparing m-phenylenediamine based on continuous catalytic hydrogenation of a fixed-bed microreactor.

Background technique

M-phenylenediamine is an important organic chemical raw material and intermediate, which is widely used in the dye industry in the synthesis of azo dyes, fur dyes, reactive dyes and sulfur dye intermediates, and can also be used to prepare hair dyes, Color developer, petroleum additives and cement coagulant and other materials. M-phenylenediamine can also be synthesized with phthaloyl chloride to prepare high-temperature-resistant aromatic polyamide resin and flame-retardant fiber, which are used in special fields such as national defense and aerospace. At present, the synthesis methods of m-phenylenediamine mainly include iron powder reduction method, electrolytic reduction method and catalytic hydrogenation method. Although the iron powder reduction method has a simple process, it will produce a large amount of iron sludge and wastewater containing aromatic amines that are difficult to handle, and the product quality is poor and the yield is low; the electrolytic reduction method has high cost and complicated equipment, and does not have the conditions for large-scale production; therefore At present, m-phenylenediamine is synthesized by catalytic hydrogenation production process at home and abroad.

During the preparation of nitrochlorobenzene, more meta-oil will be produced, that is, a mixture composed of p-nitrochlorobenzene, o-nitrochlorobenzene, and m-nitrochlorobenzene. Among them, o-nitrochlorobenzene can be obtained by rectification However, the difference between the boiling points of m-nitrochlorobenzene and p-nitrochlorobenzene is only 2°C, so it is difficult to separate, so the industry uses nitrochlorobenzene meta-oil to further nitrate to prepare 2,4-dinitrochlorobenzene Benzene, 2,6-dinitrochlorobenzene, 3,5-dinitrochlorobenzene, but the application value of dinitrochlorobenzene is low and it is difficult to store in large quantities. CN110128278A discloses a method of using 2,4-dinitrochlorobenzene as a raw material to synthesize m-phenylenediamine by hydrogenation in a batch reactor. The method uses noble metal palladium carbon as a catalyst, and an alkaline substance as an acid-binding agent. The hydrogenation reaction is completed after 4-5 hours at a temperature of 80-100° C. and a pressure of 0.8-1.5 MPa. The by-products obtained from the reaction are less, the yield is higher, and the development needs of the clean process are met. However, there are following defects in the preparation of m-phenylenediamine by hydrogenation of dinitrochlorobenzene in a hydrogenation kettle: the catalytic hydrogenation reaction of dinitrochlorobenzene is a typical gas-liquid-solid three-phase reaction, and when reacting in a batch kettle, In order to ensure the full contact between the three phases and the full progress of the hydrogenation reaction, high pressure and long reaction time are usually required, and the reaction efficiency is low. At the same time, the low mass transfer and reaction efficiency will lead to azo compounds and non-dechlorination The generation of by-products further affects the purity of the product, the post-treatment process is complicated, and 5% to 10% of the catalyst needs to be added after each reaction, which greatly increases the production cost.

Compared with the batch reactor, the microreactor has enhanced mass transfer and heat transfer performance, which greatly improves the production efficiency, and the liquid holding capacity in the microreactor is low, which has the advantage of intrinsic safety. Its application in the field of organic synthesis can realize the continuous reaction process, precisely control the reaction time, suppress side reactions, and improve the yield and selectivity of the reaction. Therefore, the development of a continuous synthesis of m-phenylenediamine by catalytic hydrogenation based on microreactor technology can improve the safety of the reaction system, simplify the process flow, improve product quality, and reduce the discharge of three wastes, which has extremely important economic, safety and environmental values. .

Contents of the invention

Aiming at the deficiencies in this field, the present invention provides a method for preparing m-phenylenediamine based on continuous catalytic hydrogenation of a fixed-bed microreactor, successfully converting dinitrochlorobenzene with high risk and low added value It is m-phenylenediamine with high added value, and compared with the traditional batch reactor, it has good mass and heat transfer performance, continuous operation, precise control of reaction conditions, small footprint, easy to scale up, intrinsically safe, green and environmental protection, etc. advantage. The method has the advantages of simple technological process, high economic benefit, short reaction cycle, high purity of the obtained product, and less content of azo by-products and non-dechlorinated by-products.

A method for preparing m-phenylenediamine based on fixed-bed microreactor continuous catalytic hydrogenation, comprising steps:

(1) taking dinitrochlorobenzene as a raw material, it is dissolved in a solvent as the substrate solution to be hydrogenated;

The dinitrochlorobenzene is at least one of 2,4-dinitrochlorobenzene, 2,6-dinitrochlorobenzene, and 3,5-dinitrochlorobenzene;

(2) Mix the substrate solution to be hydrogenated with hydrogen into a micro-mixer to form a gas-liquid mixture with a good gas-liquid microdispersion state, and then enter a micro-packed bed reactor filled with a solid particle catalyst to carry out reaction;

The temperature of the reaction is 40-160° C., and the pressure is 1-5 MPa;

The residence time of the gas-liquid mixture in the micro-packed bed reactor is 10-120s;

(3) After the reaction, the gas-liquid mixture obtained is subjected to gas-liquid separation, and the liquid product enters the subsequent separation and purification system.

The concept and technical route of the present invention are as follows: 1. Mix the substrate solution to be hydrogenated containing dinitrochlorobenzene and hydrogen in a micro-mixer to form a gas-liquid mixture with a good gas-liquid microdispersion state; 2. The obtained gas-liquid mixture enters the micro-packed bed reactor filled with solid particle catalyst for reaction, the catalyst will not be carried out by the reaction liquid, the product is still a gas-liquid mixture, and there is no need to separate the solid particle catalyst; 3. Micro-packed bed reactor The required reaction temperature is low, which can effectively reduce the generation of azo compounds, and can still obtain extremely high yield and purity of the target product at a reaction temperature as low as 70° C., and the yield of m-phenylenediamine can reach 98.7%.

On the basis of the above-mentioned concept and technical route, for the gas-liquid mixture and the fixed-bed microreactor, the present invention further optimizes and controls the corresponding reaction temperature, reaction pressure and gas-liquid mixture in the fixed-bed microreactor equipped with catalyst. Within the residence time, to achieve maximum reaction efficiency and product yield, purity. In the method of the present invention, during the catalytic hydrogenation reaction process in the fixed-bed microreactor, m-phenylenediamine with a high yield can be obtained in a short time at a reaction temperature as low as 70°C. On the premise of maintaining high reaction efficiency Significantly reduces energy consumption.

The method of the invention utilizes the high-efficiency mass transfer performance of the micro-packed bed reactor filled with solid particle catalysts, and effectively suppresses the azo by-products and non-dechlorinated by-products by strengthening the gas-liquid-solid mass transfer in the hydrogenation reaction process generation, and the reaction residence time is reduced from several hours required by the reactor to less than 2 minutes; at the same time, through the good control of the reaction residence time distribution, reaction temperature and reaction pressure, the reaction conversion rate and product purity are significantly improved, and the obtained reaction The conversion rate is close to 100%, and the highest yield of m-phenylenediamine can reach 99.4%. The method can effectively solve the problems of low production efficiency, poor product purity and complicated device operation in the hydrogenation kettle process, realize continuous automatic operation of the reaction process, and have the advantages of high yield and good safety.

In step (1), the solvent is preferably at least one of methanol, ethanol, propanol, isopropanol, tetrahydrofuran, and pyridine.

The concentration of dinitrochlorobenzene in the substrate solution to be hydrogenated affects the reaction conversion rate and product purity. In the method system of the present invention, in step (1), the mass concentration of the dinitrochlorobenzene in the solvent is preferably 2wt%-20wt%, more preferably 5wt%-10wt%.

In step (2), the micro-mixer preferably includes one of a membrane dispersion reactor, a micro-sieve reactor, and a T-type reactor, and can also be other micro-reactors that can realize the uniform mixing of the gas-liquid system of the present invention .

As a preference, in step (2), the temperature of the reaction is 50-100° C., and the pressure is 2-3.5 MPa;

The residence time of the gas-liquid mixture in the micro-packed bed reactor is 30-100s. The reaction temperature required by the present invention is lower, and still has extremely high reaction efficiency, product yield and purity at low reaction temperature and short reaction time.

In step (2), the molar ratio of dinitrochlorobenzene to hydrogen in the substrate solution to be hydrogenated is preferably 1:7.5-16, more preferably 1:8-12.

In the conventional technical solution of forming a suspension between the catalyst and the reaction liquid, the subsequent step of separation and recovery of the catalyst is involved. If the size of the catalyst is too small, it will lead to problems such as incomplete separation of the catalyst and the reaction product and difficulty in recovery. However, the present invention adopts a fixed-bed microreactor, which does not involve the subsequent separation process of the catalyst and the reaction product, so the size of the catalyst can be made smaller, and the reaction efficiency, product yield and purity are higher. As a preference, in step (2), the size of the solid particle catalyst is 50-1000 microns, which can cooperate with the above-mentioned reaction temperature, reaction pressure, residence time and other parameters of the catalytic hydrogenation process, and cooperate to further improve the reaction rate. Efficiency, product yield and purity.

In step (2), the solid particle catalyst is preferably at least one of palladium carbon catalyst, platinum carbon catalyst and ruthenium carbon catalyst.

In the method for preparing m-phenylenediamine based on fixed-bed microreactor continuous catalytic hydrogenation of the present invention, in step (1), the acid-binding agent may not be added to the substrate solution to be hydrogenated, or an acid-binding agent may be added.

In a preferred example, in step (1) of the method, an acid-binding agent is also added to the solution of the substrate to be hydrogenated.

The molar ratio of the acid-binding agent to dinitrochlorobenzene is preferably 1-2:1, more preferably 1.2-1.6:1.

The acid-binding agent preferably includes at least one of sodium acetate, sodium carbonate, sodium bicarbonate, potassium bicarbonate, and triethylamine.

In step (3), the yield of m-phenylenediamine in the gas-liquid mixture obtained after the reaction is not less than 98.3 wt%.

In step (3), the gas obtained from gas-liquid separation contains hydrogen, which can enter the tail gas treatment system and be recycled, such as being used in step (2) to mix with the substrate solution to be hydrogenated.

Compared with the prior art, the present invention has main advantages including:

1) Before and after the catalytic hydrogenation reaction, the transported material is always only a gas-liquid mixture. In the process of continuous synthesis of m-phenylenediamine by catalytic hydrogenation, a specific noble metal catalyst is used, and the gas-liquid-solid contact area in the fixed-bed microreactor is large, which promotes the occurrence of dechlorination reaction.

2) The mass and heat transfer efficiency of the fixed-bed microreactor is high, which can avoid catalyst deactivation caused by severe heat release.

3) The reaction temperature required by the fixed-bed microreactor is lower, which can effectively reduce the generation of azo by-products.

4) The reaction time is precisely and controllable, which suppresses the generation of azo compounds and ensures the complete dechlorination reaction, and the yield of m-phenylenediamine can reach more than 98.3%.

5) The reactor has small volume and high safety.

Description of drawings

Fig. 1 is a kind of schematic flow sheet of the method for preparing m-phenylenediamine based on fixed-bed microreactor continuous catalytic hydrogenation of the present invention;

In the figure: 1-micro-mixer; 2-micro-packed bed reactor filled with solid particle catalyst; 3-gas-liquid separation tank.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. The operating methods not indicated in the following examples are generally in accordance with conventional conditions, or in accordance with the conditions suggested by the manufacturer.

A kind of method for preparing m-phenylenediamine based on the continuous catalytic hydrogenation of fixed-bed microreactor of the present invention comprises steps:

(1) taking dinitrochlorobenzene as a raw material, dissolving it in a solvent as the substrate solution to be hydrogenated, i.e. dinitrochlorobenzene solution;

The dinitrochlorobenzene is at least one of 2,4-dinitrochlorobenzene, 2,6-dinitrochlorobenzene, and 3,5-dinitrochlorobenzene;

(2) The dinitrochlorobenzene solution and hydrogen are mixed in the micro-mixer 1 to form a gas-liquid mixture with a good gas-liquid microdispersion state, and then enter the micro-packed bed reactor 2 filled with solid particle catalysts react in

The temperature of the reaction is 40-160° C., and the pressure is 1-5 MPa;

The residence time of the gas-liquid mixture in the micro-packed bed reactor is 10-120s;

(3) The gas-liquid mixture obtained after the reaction is separated into gas-liquid in the gas-liquid separation tank 3, the gas containing hydrogen can enter the tail gas treatment system, and the liquid product containing m-phenylenediamine can enter the subsequent separation and purification system.

Example 1

Carry out experiment according to the method of the present invention, configure the ethanol solution of 2,4-dinitrochlorobenzene, concentration is 10wt%, the mol ratio of control hydrogen and 2,4-dinitrochlorobenzene is 10:1; Solution and hydrogen are in Mix in the entrance T-type micro-mixer, the gas-liquid mixture that forms passes through the micro-reactor that is packed with palladium-carbon catalyst (catalyst size 50 microns), setting reaction temperature is 90 ℃, reaction pressure 2.5MPa, residence time is 80s, in micro-reactor The reaction product was collected at the outlet of the reactor, and the obtained product was analyzed. The conversion rate of the obtained 2,4-dinitrochlorobenzene was 100%, the yield of m-phenylenediamine was 98.3%, and the azo species was 1.2%. Chlorine substances are 0.4%.

Example 2

Carry out experiment according to the method of the present invention, configure the methanol solution of 2,6-dinitrochlorobenzene, concentration is 5wt%, add triethylamine according to molar ratio 1:1.2, control hydrogen and 2,6-dinitrochlorobenzene The molar ratio is 8:1; the solution and hydrogen are mixed in the inlet membrane dispersion micro-mixer, and the formed gas-liquid mixture passes through the micro-reactor filled with platinum-carbon catalyst (catalyst size 200 microns), and the reaction temperature is set at 70°C, and the reaction The pressure is 2.0MPa, the residence time is 70s, the reaction product is collected at the outlet of the microreactor, and the resulting product is analyzed. The conversion rate of the obtained 2,6-dinitrochlorobenzene is 100%, and the yield of m-phenylenediamine is 98.7%. , 0.84% for azo substances, and 0.23% for non-dechlorinated substances.

Example 3

Carry out experiment according to the method of the present invention, configure the tetrahydrofuran solution of 3,5-dinitrochlorobenzene, concentration is 15wt%, add sodium bicarbonate according to molar ratio 1:1.5, control hydrogen and 3,5-dinitrochlorobenzene The molar ratio is 11:1; the solution and hydrogen are mixed in the inlet micro-mesh micro-mixer, and the gas-liquid mixture formed passes through the micro-reactor filled with palladium-carbon catalyst (catalyst size 800 microns), and the reaction temperature is set to 120 ° C. The reaction pressure is 3.0MPa, the residence time is 50s, the reaction product is collected at the outlet of the microreactor, and the resulting product is analyzed. The conversion rate of the obtained 3,5-dinitrochlorobenzene is 100%, and the yield of m-phenylenediamine is 99.4 %, azo substances are 0.14%, and non-dechlorinated substances are 0.33%.

Example 4

Carry out experiment according to the method of the present invention, configure the methanol solution of 2,4-dinitrochlorobenzene, concentration is 10wt%, add potassium bicarbonate according to molar ratio 1:1.4, control hydrogen and 2,4-dinitrochlorobenzene The molar ratio is 11:1; the solution and hydrogen are mixed in the inlet T-type micro-mixer, and the formed gas-liquid mixture passes through a micro-reactor filled with a platinum-carbon catalyst (catalyst size 1000 microns), and the reaction temperature is set at 100°C. The pressure is 4.0MPa, the residence time is 70s, the reaction product is collected at the outlet of the microreactor, and the resulting product is analyzed. The conversion rate of the obtained 2,4-dinitrochlorobenzene is 100%, and the yield of m-phenylenediamine is 99.0%. , 0.64% for azo substances, and 0.27% for non-dechlorinated substances.

Example 5

Carry out experiment according to the method of the present invention, configure the methanol solution of 2,4-dinitrochlorobenzene, concentration is 10wt%, the mol ratio of control hydrogen and 2,4-dinitrochlorobenzene is 10:1; Solution and hydrogen are in Mix in the inlet T-type micro-mixer, the formed gas-liquid mixture passes through the micro-reactor that is packed with ruthenium carbon catalyst (catalyst size 200 microns), setting reaction temperature is 100 ℃, reaction pressure 3.0MPa, residence time is 80s, in micro-reactor The reaction product was collected at the outlet of the reactor, and the obtained product was analyzed. The conversion rate of the obtained 2,4-dinitrochlorobenzene was 100%, the yield of m-phenylenediamine was 98.4%, and the azo species was 0.82%. Chlorine substances are 0.57%.

Example 6

Carry out experiment according to the inventive method, configure the isopropanol solution of 2,6-dinitrochlorobenzene, concentration is 12wt%, the mol ratio of control hydrogen and 2,6-dinitrochlorobenzene is 10:1; Solution and Hydrogen is mixed in the inlet T-type micro-mixer, and the formed gas-liquid mixture passes through the micro-reactor filled with platinum-carbon catalyst (catalyst size 500 microns), the reaction temperature is set at 90°C, the reaction pressure is 3.5MPa, and the residence time is 90s. The reaction product was collected at the outlet of the microreactor, and the resulting product was analyzed. The conversion rate of the obtained 2,6-dinitrochlorobenzene was 100%, the yield of m-phenylenediamine was 98.8%, and the azo species was 0.32%. The non-dechlorinated substance was 0.87%.

Example 7

Carry out experiment according to the method of the present invention, configure the methanol solution of 2,4-dinitrochlorobenzene, concentration is 10wt%, add sodium bicarbonate according to molar ratio 1:1.5, control hydrogen and 2,4-dinitrochlorobenzene The molar ratio is 10:1; the solution and hydrogen are mixed in the inlet membrane dispersion micro-mixer, and the formed gas-liquid mixture passes through a micro-reactor filled with a platinum-carbon catalyst (catalyst size 800 microns), and the reaction temperature is set at 80°C, and the reaction The pressure is 3.0MPa, the residence time is 70s, the reaction product is collected at the outlet of the microreactor, and the resulting product is analyzed. The conversion rate of the obtained 2,4-dinitrochlorobenzene is 100%, and the yield of m-phenylenediamine is 98.8%. , 0.82% for azo substances, and 0.17% for non-dechlorinated substances.

Example 8

Carry out experiment according to the method of the present invention, configure the methanol solution of 3,5-dinitrochlorobenzene, concentration is 10wt%, add potassium bicarbonate according to molar ratio 1:1.4, control hydrogen and 3,5-dinitrochlorobenzene The molar ratio is 10:1; the solution and hydrogen are mixed in the inlet membrane dispersion micro-mixer, and the gas-liquid mixture formed passes through the micro-reactor filled with palladium-carbon catalyst (catalyst size 200 microns), and the reaction temperature is set to 90°C, and the reaction The pressure is 3.0MPa, the residence time is 80s, the reaction product is collected at the outlet of the microreactor, and the obtained product is analyzed. The conversion rate of the obtained 3,5-dinitrochlorobenzene is 100%, and the yield of m-phenylenediamine is 98.5%. , 0.92% for azo substances, and 0.34% for non-dechlorinated substances.

In addition, it should be understood that after reading the above description of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

Claims (1)

1. A method for preparing m-phenylenediamine by continuous catalytic hydrogenation based on a fixed bed microreactor is characterized by comprising the following steps:

(1) Dinitrochlorobenzene is taken as a raw material, and is dissolved in a solvent methanol to be used as a substrate solution to be hydrogenated; the mass concentration of the dinitrochlorobenzene in the solvent is 5wt%;

the dinitrochlorobenzene is 2,6-dinitrochlorobenzene;

adding an acid-binding agent triethylamine into the substrate solution to be hydrogenated;

the molar ratio of the acid-binding agent to the dinitrochlorobenzene is 1.2;

(2) The substrate solution to be hydrogenated and hydrogen enter a micro mixer to be mixed to form a gas-liquid mixture with a good gas-liquid micro dispersion state, and then the gas-liquid mixture enters a micro packed bed reactor filled with a solid particle catalyst to react;

the reaction temperature is 70 ℃, and the pressure is 2MPa;

the molar ratio of the dinitrochlorobenzene to the hydrogen in the substrate solution to be hydrogenated is 1:8;

the micro mixer is a membrane dispersion micro mixer;

the solid particle catalyst is a platinum carbon catalyst, and the size of the solid particle catalyst is 200 microns;

the residence time of the gas-liquid mixture in the micro packed bed reactor is 70s;

(3) After the reaction is finished, the gas-liquid mixture is subjected to gas-liquid separation, the liquid product enters a subsequent separation and purification system, the conversion rate of 2,6-dinitrochlorobenzene is 100%, the yield of m-phenylenediamine is 98.7%, the yield of azo substances is 0.84%, and the content of dechlorinated substances is 0.23%.

Images