A method and apparatus for continuous preparation of p-aminoazobenzene

Abstract

The present invention relates to the technical field of chemical synthesis, and in particular to a method and device for continuously preparing p-aminoazobenzene, wherein the method for preparing p-aminoazobenzene is as follows: using nitrosyl chloride as a starting material, dripping water into nitrosyl chloride for reaction, and obtaining a diazo liquid containing nitrous acid and hydrogen chloride after the reaction is completed; controlling the reaction temperature, the diazo liquid and aniline undergo a diazo coupling reaction to obtain a diazo coupling reaction liquid having an intermediate product 1,3-diphenyltriazene; heating and stirring the diazo coupling reaction liquid to perform a rearrangement reaction to obtain an aniline solution of p-aminoazobenzene; alkali washing the aniline solution of p-aminoazobenzene to neutrality, and then post-processing to obtain a p-aminoazobenzene product. The method for preparing p-aminoazobenzene according to the present invention has a small amount of three wastes, green and easy-to-obtain raw materials, and high product yield and product purity.

Description

Technical Field

[0001] The invention relates to a method and equipment for continuously preparing p-aminoazobenzene, belonging to the technical field of chemical synthesis. Background Art

[0002] p-Aminoazobenzene, also known as 4-aminoazobenzene, is a common azo dye, also known as methyl orange. Because its organic molecules contain azo groups and have strong dye properties, it is widely used in dyeing textiles, leather, printing inks and other fields. In practical applications, the demand for reagent-grade p-aminoazobenzene is extremely high. Therefore, it is very necessary to develop an efficient, environmentally friendly and intrinsically safe continuous production method for p-aminoazobenzene.

[0003] At present, the synthesis method of p-aminoazobenzene is mainly the diazo coupling method. The main route is to use aniline as the starting raw material, hydrochloric acid and sodium nitrite as diazo reagents, and then couple aniline and diazo intermediates to generate 1,3-diphenyltriazene through diazo reaction, and then rearrange it under aniline and acidic conditions. The existing method uses hydrochloric acid and nitrous acid as diazo reagents, and the reaction uses water as solvent. Although the raw materials are easy to obtain and the process is mature, a large amount of hydrochloric acid participating in the reaction will not only produce waste acid and cause serious corrosion to the equipment; and the reaction using water as a solvent will produce a large amount of wastewater, which is complicated to post-process and seriously pollutes the environment. Therefore, it is very important to find an environmentally friendly solvent to produce p-aminoazobenzene.

[0004] Chinese patent application CN116003292A discloses a method for synthesizing aminoazobenzene by diazo-coupling reaction using substituted aniline as raw material and alcohol as solvent, which reduces the generation of three wastes to a certain extent. However, the diazo-coupling reaction process is generally characterized by heat release, and the heat cannot be removed in time, which will lead to a greater risk of loss of control during the process.

[0005] Chinese patent application CN102731320A discloses a method for absorbing nitrogen oxide tail gas with aniline as a raw material to produce p-phenylenediamine as a by-product. Aniline reacts with nitrogen oxide to form a diazonium salt, and the diazonium salt and unreacted aniline are converted into p-aminoazobenzene. The method has high atomic utilization and generates little waste. However, the synthesis equipment used in the method is a spray tower, which consumes a lot of power for liquid spraying, and there is a lot of mist entrainment in the outlet gas. The gas in the equipment is seriously back-mixed, resulting in low gas-liquid reaction efficiency.

[0006] Chinese patent application CN217140329U discloses a device for safely preparing p-aminoazobenzene. The device adopts a tank body with a conical bottom tank, a constant pressure liquid adder, etc. to prepare p-aminoazobenzene, which solves the problems of waste liquid separation and smooth material outflow, and prevents toxic gas from polluting the environment and harming the operator. However, with the traditional tank as the reaction site, the diazo coupling is an exothermic reaction, and the heat transfer and mass transfer are insufficient, which will cause the local temperature in the reactor to be too high or too low, which is not conducive to mass transfer and heat transfer during the reaction process, and will reduce the reaction efficiency to varying degrees. Based on the above problems existing in the prior art, it is very necessary to find a device and method for producing p-aminoazobenzene with intrinsic safety and high efficiency. Summary of the invention

[0007] The present invention aims at the deficiencies in the prior art and provides a method and equipment for continuously preparing p-aminoazobenzene, so as to solve the problems of serious pollution, low mass transfer efficiency and low product yield in the production of p-aminoazobenzene in the prior art and equipment.

[0008] The technical solution of the present invention to solve the above technical problem is as follows: a method for continuously preparing p-aminoazobenzene, wherein the method for preparing p-aminoazobenzene is:

[0009] S1. Preparation of diazo solution:

[0010] Using nitrosyl chloride as a starting material, water is added dropwise to nitrosyl chloride to react, and after the reaction is completed, a diazo liquid containing nitrous acid and hydrogen chloride is obtained;

[0011] S2, diazo coupling reaction:

[0012] Controlling the reaction temperature, the diazo liquid and aniline undergo a diazo coupling reaction to obtain a diazo coupling reaction liquid having an intermediate product of 1,3-diphenyltriazene;

[0013] S3, azotization reaction:

[0014] The diazo coupling reaction solution is heated and stirred to perform a rearrangement reaction to obtain an aniline solution of p-aminoazobenzene;

[0015] S4, alkali washing and post-treatment:

[0016] The p-aminoazobenzene aniline solution is alkali washed to neutrality and then post-treated to obtain a p-aminoazobenzene product.

[0017] Furthermore, in step S1, the molar ratio of nitrosyl chloride to water is 1:(1-1.5).

[0018] Furthermore, the reaction temperature of step S1 is 5-25°C.

[0019] Furthermore, in step S1, the dropping speed of water to nitrosyl chloride is 1-3 mL / min.

[0020] Furthermore, the molar ratio of aniline in step S2 to nitrosyl chloride in step S1 is (2.24-6.00):1.

[0021] Furthermore, the reaction temperature of step S2 is 25-50° C., and the reaction time is 0.5-2.5 h.

[0022] Furthermore, the reaction temperature of step S3 is 60-100° C., and the reaction time is 0.5-3.0 h.

[0023] Furthermore, in step S4, the post-treatment operation is: after the alkali washing treatment, the aqueous phase is separated and removed, and the organic phase is distilled to collect aniline and obtain the p-aminoazobenzene product.

[0024] Furthermore, the distillation temperature is 85-100° C., the pressure is 25-50 mmHg, the condensation temperature is less than 40° C., the distilled substance is the recovered aniline, and the remaining substance in the distillation tank is dried to obtain the p-aminoazobenzene product.

[0025] The present invention also discloses a device for continuously preparing p-aminoazobenzene, which comprises an aniline storage tank, a nitrosyl chloride storage tank, a heating and stirring tank, an alkali washing tank, a distillation tank, a product collecting tank, and a microchannel reactor;

[0026] The aniline storage tank is communicated with the main channel feed port of the microchannel reactor through a pipeline, the nitrosyl chloride storage tank is communicated with the branch channel feed port of the microchannel reactor, the discharge port of the microchannel reactor is communicated with the feed port of the heating and stirring tank, the discharge port of the heating and stirring tank is communicated with the feed port of the alkali washing tank, the discharge port of the alkali washing tank is communicated with the feed port of the distillation tank, a condenser is provided at the upper end of the distillation tank, the discharge port of the condenser is communicated with the aniline storage tank, and the discharge port at the lower end of the distillation tank is communicated with the product collection tank;

[0027] The diazo liquid is prepared in the nitrosyl chloride storage tank; the diazo coupling reaction is carried out in the microchannel reactor; the azotization reaction is carried out in the heating and stirring tank; and the post-processing operation is carried out in the distillation tank.

[0028] The beneficial effects of the present invention are:

[0029] The method and device for continuously preparing p-aminoazobenzene of the present invention use nitrosyl chloride, water and aniline as raw materials, generate 1,3-diphenyltriazene through diazotization coupling in a microchannel reactor, and then perform azotization reaction to generate p-aminoazobenzene. After the aniline solution of p-aminoazobenzene is neutralized and washed with alkaline water, pure p-aminoazobenzene is obtained by distillation. Aniline used as a solvent is recovered and recycled during distillation. Compared with the traditional production method of p-aminoazobenzene, the method of the present invention has less three wastes, green and easy-to-obtain raw materials, and high product yield and product purity. Moreover, in the whole preparation process, the intermediate does not need to be purified, thereby greatly simplifying the preparation process.

[0030] The invention uses nitrosyl chloride and water to prepare a diazo liquid, generates nitrous acid and hydrochloric acid at the same time, can generate the diazo liquid and ensure the occurrence of a diazo coupling reaction under an acidic condition, greatly reduces the use of additional acid, reduces the cost of raw materials for adding inorganic acid, and thus reduces the generation of waste salt and waste acid water; water and nitrosyl chloride mixed liquid are used as a diazo reagent, the raw materials are easily available and environmentally friendly, the preparation of the diazo liquid is simple, and the time of the diazo coupling reaction can be greatly reduced.

[0031] In addition, since the reaction involved in the present invention is exothermic, and the microchannel is small in size and has fast heat transfer, the safety hazards caused by the difficulty in controlling the reaction temperature and the risk of thermal runaway are avoided. The explosion energy is far smaller than that of traditional kettle reactions, and it has the advantages of high safety, high gas-liquid mass transfer efficiency, and high degree of automation. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of the equipment for continuously preparing p-aminoazobenzene according to the present invention;

[0033] In the figure, 1. Aniline storage tank; 2. Nitrosyl chloride storage tank; 3. Heating and stirring tank; 4. Alkaline washing tank; 5. Distillation tank; 6. Product collection tank; 7. Microchannel reactor. DETAILED DESCRIPTION

[0034] The specific implementation of the present invention is described in detail below. The present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used are only for describing specific embodiments and are not intended to limit the present invention.

[0036] A method for continuously preparing p-aminoazobenzene, the method for preparing p-aminoazobenzene is:

[0037] S1. Preparation of diazo solution:

[0038] ;

[0039] Using nitrosyl chloride as a starting material, water is added dropwise to nitrosyl chloride to react, and after the reaction is completed, a diazo liquid containing nitrous acid and hydrogen chloride is obtained;

[0040] S2, diazo coupling reaction:

[0041] The reaction route of the diazo coupling reaction is:

[0042] (1) Nitrosation:

[0043] ;

[0044] (2) Coupling reaction:

[0045] ;

[0046] Controlling the reaction temperature, the diazo liquid and aniline undergo a diazo coupling reaction to obtain a diazo coupling reaction liquid having an intermediate product of 1,3-diphenyltriazene;

[0047] S3, azotization reaction:

[0048] The reaction route of azotization reaction is:

[0049] ;

[0050] The diazo coupling reaction solution is heated and stirred to perform a rearrangement reaction to obtain an aniline solution of p-aminoazobenzene;

[0051] S4, alkali washing and post-treatment:

[0052] The p-aminoazobenzene aniline solution is alkali washed to neutrality and then post-treated to obtain a p-aminoazobenzene product.

[0053] Specifically, in step S1, the molar ratio of nitrosyl chloride to water is 1:(1-1.5).

[0054] Specifically, the reaction temperature of step S1 is 5-25°C.

[0055] Preferably, the reaction temperature of step S1 is 10-20°C.

[0056] Specifically, in step S1, the dropping speed when water is added dropwise to nitrosyl chloride is 1-3 mL / min.

[0057] Specifically, the molar ratio of aniline in step S2 to nitrosyl chloride in step S1 is (2.24-6.00):1.

[0058] Specifically, the reaction temperature of step S2 is 25-50° C., and the reaction time is 0.5-2.5 h.

[0059] Preferably, the reaction temperature of step S2 is 30-40° C., and the reaction time is 0.5-1.5 h.

[0060] Specifically, the reaction temperature of step S3 is 60-100° C., and the reaction time is 0.5-3.0 h.

[0061] Preferably, the reaction temperature of step S3 is 70-80° C., and the reaction time is 0.5-2.0 h.

[0062] More specifically, in step S3, the half speed of the azotization reaction is 600-1000 rpm, preferably 800-900 rpm.

[0063] Specifically, in step S4, the post-treatment operation is: after alkali washing, the aqueous phase is separated and removed, and the organic phase is distilled to collect aniline and obtain p-aminoazobenzene product.

[0064] More specifically, in step S4, the alkali washing temperature is 25-40° C., the pH of the solution after alkali washing is 7-8, and the aqueous phase is separated by standing.

[0065] More specifically, the alkali used in alkali washing is an inorganic alkali, which is selected from sodium hydroxide, potassium hydroxide or sodium carbonate; preferably sodium hydroxide.

[0066] Specifically, the distillation temperature is 85-100° C., the pressure is 25-50 mmHg, the condensation temperature is less than 40° C., the distilled substance is the recovered aniline, and the remaining substance in the distillation tank is dried to obtain the p-aminoazobenzene product.

[0067] like Figure 1 As shown, a device for continuously preparing p-aminoazobenzene comprises an aniline storage tank 1, a nitrosyl chloride storage tank 2, a heating and stirring tank 3, an alkali washing tank 4, a distillation tank 5, a product collecting tank 6; and a microchannel reactor 7;

[0068] The aniline storage tank 1 is communicated with the main channel feed port of the microchannel reactor 7 through a pipeline, the nitrosyl chloride storage tank 2 is communicated with the branch channel feed port of the microchannel reactor 7, the discharge port of the microchannel reactor 7 is communicated with the feed port of the heating and stirring tank 3, the discharge port of the heating and stirring tank 3 is communicated with the feed port of the alkali washing tank 4, the discharge port of the alkali washing tank 4 is communicated with the feed port of the distillation tank 5, a condenser is provided at the upper end of the distillation tank 5, the discharge port of the condenser is communicated with the aniline storage tank 1, and the lower end discharge port of the distillation tank 5 is communicated with the product collection tank 6;

[0069] The diazo liquid is prepared in the nitrosyl chloride storage tank 2; the diazo coupling reaction is carried out in the microchannel reactor; the azotization reaction is carried out in the heating and stirring tank 3; and the post-processing operation is carried out in the distillation tank 5.

[0070] More specifically, the heating and stirring tank 3, the alkali washing tank 4 and the distillation tank 5 are all provided with jackets, and heat-conducting medium flows through the jackets; materials are transferred between various production units through pumps.

[0071] use Figure 1 The equipment is used to prepare p-aminoazobenzene, and the specific examples involved are as follows:

[0072] Example 1

[0073] A method for continuously preparing p-aminoazobenzene comprises the following steps:

[0074] (1) Preparation of diazo liquid: Add 66 kg of nitrosyl chloride into a nitrous chloride storage tank, add 19 kg of water dropwise at a dropping rate of 2 mL / min, and stir at a rate of 500 r / min. During the preparation of the diazo liquid, control the temperature in the system at 25 °C.

[0075] (2) Diazo coupling reaction: The diazo liquid and aniline were introduced into the main channel and branch channel of the microchannel through a pump. The aniline addition rate was 279.381 kg / h, and the diazo liquid introduction rate was 83.47 kg / h. The reaction temperature was maintained at 35°C and the reaction time was 1 h to obtain a diazo coupling liquid in which the molar ratio of aniline to nitrosyl chloride was 3:1.

[0076] (3) Azo reaction: The diazo coupling liquid enters the heating stirring tank through the outlet of the microchannel reactor and the inlet of the heating stirring tank. The temperature of the heating stirring tank is maintained at 90°C, the stirring speed is 800 rpm, and the azo reaction is stirred for 1 hour to obtain an azo reaction liquid.

[0077] (4) Alkali washing: The rearranged material is pumped into the alkali washing tank through the inlet for neutralization. That is, the azotization reaction liquid is allowed to stand and then 40 kg of inorganic base NaOH is added to ensure that the solution is neutral or weakly alkaline. The temperature is maintained at 35 °C for alkali washing, and the water phase is discharged from the bottom of the alkali washing tank.

[0078] (5) Aniline recovery: The reaction liquid after alkali washing is pumped to a distillation tank. The temperature of the distillation tank is maintained at 85°C and the pressure is maintained at 50 mmHg. Aniline is converted into gas and evaporated from the gas outlet. It is condensed into a 40°C liquid by a condenser and returned to the aniline storage tank through the liquid outlet for reuse. The remaining liquid in the distillation tank is p-aminoazobenzene, with a gas phase purity of 99.0% and a yield of 89%.

[0079] Example 2

[0080] A method for continuously preparing p-aminoazobenzene comprises the following steps:

[0081] (1) Preparation of diazo liquid: Add 43.86 kg of nitrosyl chloride into a nitrous chloride storage tank, add 12.06 kg of water dropwise at a dropping rate of 1 mL / min, and stir at a rate of 500 r / min. During the preparation of the diazo liquid, the temperature in the system was controlled at 15 °C.

[0082] (2) Diazo coupling reaction: The diazo liquid and aniline were introduced into the main channel and branch channel of the microchannel through a pump. The amount of aniline added was 139.69 kg / h, and the amount of diazo liquid introduced was 27.965 kg / h. The reaction temperature was maintained at 40°C and the reaction time was 0.5 h to obtain a diazo coupling liquid in which the molar ratio of aniline to nitrosyl chloride was 2.24:1.

[0083] (3) Azo reaction: The diazo coupling liquid enters the heating stirring tank through the outlet of the microchannel reactor and the inlet of the heating stirring tank. The temperature of the heating stirring tank is maintained at 80°C, the stirring speed is 1000 rpm, and the azo reaction is stirred for 0.5 h to obtain an azo reaction liquid.

[0084] (4) Alkali washing: The rearranged material is pumped into the alkali washing tank through the inlet of the alkali washing tank for neutralization. That is, after the azotization reaction liquid is allowed to stand, 18.23 kg of inorganic base NaOH is added, and the temperature is maintained at 40°C for alkali washing operation. The water phase is discharged from the bottom of the alkali washing tank.

[0085] (5) Aniline recovery: The reaction liquid after alkali washing is pumped to a distillation tank. The temperature of the distillation tank is maintained at 90°C and the pressure is maintained at 40 mmHg. Aniline is converted into gas and evaporated from the gas outlet. It is condensed into a 40°C liquid by a condenser and returned to the aniline storage tank through the liquid outlet for reuse. The remaining liquid in the distillation tank is p-aminoazobenzene, with a gas phase purity of 99.1% and a yield of 95.5%.

[0086] Example 3

[0087] A method for continuously preparing p-aminoazobenzene comprises the following steps:

[0088] (1) Preparation of diazo liquid: Add 98.2 kg of nitrosyl chloride into a nitrous chloride storage tank, and add 27 g of water dropwise at a rate of 3 mL / min. During the preparation of the diazo liquid, the temperature in the system is controlled at 20°C.

[0089] (2) Diazo coupling reaction: The diazo liquid and aniline were introduced into the main channel and branch channel of the microchannel through a pump. The amount of aniline added was 419.07 kg / h, and the amount of diazo liquid introduced was 187.82 kg / h. The reaction temperature was maintained at 50°C and the reaction time was 1.5 h to obtain a diazo coupling liquid in which the molar ratio of aniline to nitrosyl chloride was 3:1.

[0090] (3) Azo reaction: The diazo coupling liquid enters the heating stirring tank through the outlet of the microchannel reactor and the inlet of the heating stirring tank. The temperature of the heating stirring tank is maintained at 100° C. The stirring speed is 800 rpm. The azo reaction is stirred for 1.5 h to obtain an azo reaction liquid.

[0091] (4) Alkali washing: The rearranged material is pumped into the alkali washing tank through the inlet of the alkali washing tank for neutralization. That is, after the azotization reaction liquid is allowed to stand, 54.70 kg of inorganic base NaOH is added, and the temperature is maintained at 50°C for alkali washing operation. The water phase is discharged from the bottom of the alkali washing tank.

[0092] (5) Aniline recovery: The reaction liquid after alkali washing is pumped to a distillation tank. The temperature of the distillation tank is maintained at 95°C and the pressure is maintained at 30 mmHg. Aniline is converted into gas and evaporated from the gas outlet. It is condensed into a 40°C liquid by a condenser and returned to the aniline storage tank through the liquid outlet for reuse. The remaining liquid in the distillation tank is p-aminoazobenzene, with a gas phase purity of 99.0% and a yield of 87%.

[0093] Example 4

[0094] A method for continuously preparing p-aminoazobenzene comprises the following steps:

[0095] (1) Preparation of diazo liquid: Add 32.73 kg of nitrosyl chloride into a nitrous chloride storage tank, and add 9 kg of water dropwise at a rate of 1.5 mL / min. During the preparation of the diazo liquid, the temperature in the system is controlled at 25 °C.

[0096] (2) Diazo coupling reaction: The diazo liquid and aniline were introduced into the main channel and branch channel of the microchannel through a pump. The amount of aniline added was 139.69 kg / h, and the amount of diazo liquid introduced was 20.87 kg / h. The reaction temperature was maintained at 45°C and the reaction time was 0.5 h to obtain a diazo coupling liquid in which the molar ratio of aniline to nitrosyl chloride was 3:1.

[0097] (3) Azo reaction: The diazo coupling liquid enters the heating stirring tank through the outlet of the microchannel reactor and the inlet of the heating stirring tank. The temperature of the heating stirring tank is maintained at 95°C, the stirring speed is 800 rpm, and the azo reaction is stirred for 1 hour to obtain an azo reaction liquid.

[0098] (4) Alkali washing: The rearranged material is pumped into the alkali washing tank through the inlet of the alkali washing tank for neutralization. That is, after the azotization reaction liquid is allowed to stand, 9.1 g of inorganic base NaOH is added, and the temperature is maintained at 35°C for alkali washing operation. The water phase is discharged from the bottom of the alkali washing tank.

[0099] (5) Aniline recovery: The reaction liquid after alkali washing is pumped to a distillation tank. The temperature of the distillation tank is maintained at 100°C and the pressure is maintained at 30 mmHg. Aniline is converted into gas and evaporated from the gas outlet. It is condensed into a 40°C liquid by a condenser and returned to the aniline storage tank through the liquid outlet for reuse. The remaining liquid in the distillation tank is p-aminoazobenzene, with a gas phase purity of 99.0% and a yield of 94.2%.

[0100] Example 5

[0101] A method for continuously preparing p-aminoazobenzene comprises the following steps:

[0102] (1) Preparation of diazo liquid: Add 98.2 kg of nitrosyl chloride into a nitrous chloride storage tank, and add 40.5 g of water dropwise at a rate of 2 mL / min. During the preparation of the diazo liquid, the temperature in the system is controlled at 20°C.

[0103] (2) Diazo coupling reaction: The diazo liquid and aniline were introduced into the main channel and branch channel of the microchannel through a pump. The amount of aniline added was 838.17 kg / h, and the amount of diazo liquid introduced was 187.82 kg / h. The reaction temperature was maintained at 25 °C and the reaction time was 2.5 h to obtain a diazo coupling liquid in which the molar ratio of aniline to nitrosyl chloride was 6:1.

[0104] (3) Azo reaction: The diazo coupling liquid enters the heating stirring tank through the outlet of the microchannel reactor and the inlet of the heating stirring tank. The temperature of the heating stirring tank is maintained at 60°C, the stirring speed is 1000 rpm, and the azo reaction is stirred for 3.0 h to obtain an azo reaction liquid.

[0105] (4) Alkali washing: The rearranged material is pumped into the alkali washing tank through the inlet of the alkali washing tank for neutralization. That is, after the azotization reaction liquid is allowed to stand, 54.70 kg of inorganic base NaOH is added, and the temperature is maintained at 50°C for alkali washing operation. The water phase is discharged from the bottom of the alkali washing tank.

[0106] (5) Aniline recovery: The reaction liquid after alkali washing is pumped to a distillation tank. The temperature of the distillation tank is maintained at 95°C and the pressure is maintained at 30 mmHg. Aniline is converted into gas and evaporated from the gas outlet. It is condensed into a 40°C liquid by a condenser and returned to the aniline storage tank through the liquid outlet for reuse. The remaining liquid in the distillation tank is p-aminoazobenzene, with a gas phase purity of 99.0% and a yield of 87%.

[0107] Comparative Example 1

[0108] p-Aminoazobenzene was prepared by the same method as in Example 1, except that the water addition rate was increased in step (1), and in this comparative example 1, the water addition rate was 10 mL / min. Other process conditions were the same as in Example 1.

[0109] The gas phase purity of p-aminoazobenzene in Comparative Example 1 was 92.0%, and the yield was 71%.

[0110] From the comparison of the data of Comparative Example 1 and Example 1, it can be seen that if the dripping speed of water is increased, the yield and purity of the target product p-aminoazobenzene will decrease. This is because if the dripping speed of water in step (1) is too fast, a large amount of nitrogen oxide gas and hydrogen chloride gas will overflow from the reaction system, which will reduce the concentration of the diazo liquid, thereby affecting the subsequent reaction process and ultimately causing the yield and purity of the target product p-aminoazobenzene to decrease.

[0111] Comparative Example 2

[0112] p-Aminoazobenzene was prepared by the same method as in Example 1, except that the reaction temperature of step (1) was increased. In this comparative example 2, the temperature in the system during the preparation of the diazo solution in step (1) was controlled at 40° C. (higher than the temperature specified in the present invention).

[0113] The gas phase purity of p-aminoazobenzene in this comparative example 2 is 93.5%, and the yield is 70%.

[0114] From the comparison of the data of Comparative Example 2 and Example 1, it can be seen that if the dripping speed of water is increased, the yield and purity of the target product p-aminoazobenzene will decrease. This is because if the reaction temperature in step (1) is too high, a large amount of nitrous acid generated by the reaction will be decomposed into gas, causing a sudden increase in the pressure in the system. The aniline in the subsequent azotization reaction cannot absorb the gas in time, thereby affecting the subsequent reaction process, and ultimately causing the yield and purity of the target product p-aminoazobenzene to decrease.

[0115] Comparative Example 3

[0116] p-Aminoazobenzene was prepared by the same method as in Example 1, except that the proportion of aniline added in step (2) was reduced. In this comparative example 3, the molar ratio of aniline to nitrosyl chloride was 1.3:1.

[0117] In this comparative example 3, the gas phase purity of p-aminoazobenzene is 90%, and the yield is 73%.

[0118] From the comparison of the data of Comparative Example 3 and Example 1, it can be seen that if the amount of aniline added is reduced, the yield and purity of the target product p-aminoazobenzene will decrease, because aniline not only acts as a reactant but also as a solvent in the entire reaction process. The reduction in the amount of aniline added is not conducive to the stability and dissolution of the product p-aminoazobenzene, and the obtained product will precipitate in the form of a solid; on the other hand, the reduction in the amount of aniline added will also cause an increase in by-products, ultimately affecting the mass transfer and heat transfer effects, resulting in a decrease in the yield and purity of the target product p-aminoazobenzene.

[0119] Comparative Example 4

[0120] p-Aminoazobenzene was prepared by the same method as in Example 1, except that the reaction temperature in step (2) was increased. In this comparative example 4, the reaction temperature in step (2) was 90° C. (higher than the temperature specified in the present invention).

[0121] The gas phase purity of p-aminoazobenzene in Comparative Example 4 is 92%, and the yield is 75%.

[0122] From the comparison of the data of Comparative Example 4 and Example 1, it can be seen that if the reaction temperature of the diazo coupling reaction in step (2) is appropriately increased, the appropriate increase in the reaction temperature is beneficial to the diazo coupling reaction of aniline, especially it can reduce the content of o-aminoazobenzene in the rearrangement reaction and increase the proportion of p-aminoazobenzene in the product. If the temperature is further increased, the side reactions increase, the amount of by-products biphenyl and diphenylamine increases, and finally the yield and purity of the target product p-aminoazobenzene decrease.

[0123] Comparative Example 5

[0124] p-Aminoazobenzene was prepared by the same method as in Example 1, except that the reaction temperature in step (3) was increased. In this comparative example 5, the reaction temperature in step (2) was 120° C. (higher than the temperature specified in the present invention).

[0125] The gas phase purity of p-aminoazobenzene in Comparative Example 5 is 87%, and the yield is 71%.

[0126] From the comparison of the data of Comparative Example 5 and Example 1, it can be seen that if the reaction temperature of the azotization reaction in step (3) is appropriately increased, the rearrangement rate of triazene azotization can be significantly increased, thereby increasing the yield of p-aminoazobenzene. Continuing to increase the rearrangement temperature has no significant effect on the rearrangement rate, but will cause an increase in energy consumption and the possibility of an increase in side reactions, ultimately affecting the yield and purity of the target product p-aminoazobenzene.

[0127] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are exhaustively listed. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0128] For those skilled in the art, several modifications and improvements may be made without departing from the concept of the present invention, all of which belong to the protection scope of the present invention. The protection scope of the present invention shall be based on the attached claims.

Claims

1. A method for continuously preparing p-aminoazobenzene, characterized in that: The method for preparing p-aminoazobenzene is: S1. Preparation of diazo solution: Using nitrosyl chloride as a starting material, water is added dropwise to nitrosyl chloride to react, and after the reaction is completed, a diazo liquid containing nitrous acid and hydrogen chloride is obtained; S2, diazo coupling reaction: Controlling the reaction temperature, the diazo liquid and aniline undergo a diazo coupling reaction to obtain a diazo coupling reaction liquid having an intermediate product of 1,3-diphenyltriazene; S3, azotization reaction: The diazo coupling reaction solution is heated and stirred to perform a rearrangement reaction to obtain an aniline solution of p-aminoazobenzene; S4, alkali washing and post-treatment: The p-aminoazobenzene aniline solution is subjected to alkali washing to neutrality, and then subjected to post-treatment to obtain a p-aminoazobenzene product; The reaction temperature of step S1 is 5-25°C; In step S1, the dropping speed of water to nitrosyl chloride is 1-3 mL / min; The molar ratio of aniline in step S2 to nitrosyl chloride in step S1 is (2.24-6.00): 1; The reaction temperature of step S2 is 25-50°C; In step S4, the post-treatment operation is: after alkali washing, the aqueous phase is separated and removed, and the organic phase is distilled to collect aniline and obtain p-aminoazobenzene product.

2. A method for continuously preparing p-aminoazobenzene according to claim 1, characterized in that: In step S1, the molar ratio of nitrosyl chloride to water is 1:(1-1.5).

3. A method for continuously preparing p-aminoazobenzene according to claim 1, characterized in that: The reaction time of step S2 is 0.5-2.5h.

4. A method for continuously preparing p-aminoazobenzene according to claim 1, characterized in that: The reaction temperature of step S3 is 60-100° C., and the reaction time is 0.5-3.0 h.

5. A method for continuously preparing p-aminoazobenzene according to claim 1, characterized in that: The distillation temperature is 85-100° C., the pressure is 25-50 mmHg, the condensation temperature is less than 40° C. The distilled substance is the recovered aniline, and the remaining substance in the distillation tank is dried to obtain the p-aminoazobenzene product.

6. An apparatus for continuously preparing p-aminoazobenzene, characterized in that: The equipment for continuously preparing p-aminoazobenzene comprises an aniline storage tank, a nitrosyl chloride storage tank, a heating and stirring tank, an alkali washing tank, a distillation tank, a product collecting tank; and a microchannel reactor; The aniline storage tank is communicated with the main channel feed port of the microchannel reactor through a pipeline, the nitrosyl chloride storage tank is communicated with the branch channel feed port of the microchannel reactor, the discharge port of the microchannel reactor is communicated with the feed port of the heating and stirring tank, the discharge port of the heating and stirring tank is communicated with the feed port of the alkali washing tank, the discharge port of the alkali washing tank is communicated with the feed port of the distillation tank, a condenser is provided at the upper end of the distillation tank, the discharge port of the condenser is communicated with the aniline storage tank, and the discharge port at the lower end of the distillation tank is communicated with the product collection tank; The diazo liquid is prepared in the nitrosyl chloride storage tank; the diazo coupling reaction is carried out in the microchannel reactor; the azotization reaction is carried out in the heating and stirring tank; and the post-processing operation is carried out in the distillation tank.

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