1. A preparation method of RT base by condensation and reflux is characterized in that: the method for preparing RT base by using aniline and nitrobenzene as raw materials and organic base as a condensation catalyst comprises the following steps: mixing aniline and organic alkali and then dehydrating; step two: and mixing the dehydrated material with nitrobenzene, performing condensation reaction on the sprayed and dispersed material in a reaction tower, condensing and refluxing the gas phase of the condensation reaction into a tower kettle, and reducing the condensed liquid after the reaction to prepare the RT base.

2. The method of claim 1, wherein: the organic alkali is aqueous solution of tetramethyl ammonium hydroxide or aqueous solution of tetraethyl ammonium hydroxide.

3. The method of claim 2, wherein: the concentration of the aqueous solution of tetramethylammonium hydroxide or the aqueous solution of tetraethylammonium hydroxide is 5-45%.

4. The production method according to claim 1, 2 or 3, characterized in that: the molar ratio of aniline to organic base is 3: 1-20: 1.

5. The method of claim 1, wherein: the dehydration temperature in the first step is 50-90 ℃, and the vacuum degree is 0.080-0.099 MPa.

6. The method of claim 1, wherein: and (3) after dehydration in the first step, the water content in the material is 5-35%.

7. The method of claim 1, wherein: the molar ratio of the addition amount of nitrobenzene to the organic base is 0.2: 1-1.1: 1.

8. The method of claim 1, wherein: the temperature of the secondary condensation reaction in the step is 60-90 ℃, and the vacuum degree is 0.080-0.099 MPa.

9. The method of claim 1, wherein: the temperature of gas phase condensation in the secondary condensation reaction is 45-65 ℃, and the vacuum degree is 0.080-0.099 MPa.

10. The method of claim 1, wherein: the condenser is arranged at the top of the reaction tower.

Background

RT base (p-aminodiphenylamine) is widely applied to the fields of rubber auxiliaries, dyes, textile, printing, pharmaceutical industry and the like, and is mainly used for producing rubber antioxidants IPPD, 6PPD and the like.

At present, the domestic RT base production capacity is 200kt/a, and the RT base production method is mainly used for producing 6 PPD. With the development of the rubber industry, the demand of rubber antioxidants is steadily increasing.

The RT base producing process includes condensation of nitrobenzene and aniline as material in the presence of organic base catalyst to produce 4-nitrosodiphenylamine and 4-nitrodiphenylamine, and hydrogenation reduction of the condensed liquid to obtain RT base. The nitrobenzene method process has the characteristics of less three wastes, high product yield, good quality and the like, is a green production process, and has obvious advantages compared with other preparation methods.

The production of RT base by the nitrobenzene method can generate impurities such as 2-aminodiphenylamine, phenazine and the like, and particularly the boiling points of the two substances are close to that of the RT base, so that the rectification of the RT base is difficult, and the quality of the RT base is influenced.

At present, RT base research mainly comprises the steps of optimizing a nitrobenzene method RT base process, improving the recovery efficiency of a phase transfer catalyst, reducing energy consumption and material consumption, inhibiting the generation of byproducts, improving the purity of RT base and the like.

The condensation reaction in the production of RT base is mainly carried out by adopting a kettle type continuous condensation process, but the materials in the kettle type process kettle can generate a back mixing phenomenon, the back mixing can cause the selectivity of a target product of the reaction to be reduced, impurities such as azobenzene, phenazine, o (sub) nitrodiphenylamine and the like in a condensation liquid can influence the purity of a finished product of the RT base, and the azobenzene can be reduced into aniline, but the energy consumption and the material consumption of the RT base production can be increased. Meanwhile, the condensation liquid is conveyed from the reaction kettle to the condensation liquid storage tank and then continues to react to generate other impurities, which inevitably affects the product yield and increases the rectification difficulty.

Disclosure of Invention

The invention aims to solve the problems and provide a RT base condensation method, namely a RT base preparation method adopting condensation and reflux.

The invention is realized by the following modes: the preparation method of the RT base by condensation and reflux is characterized by comprising the following steps: the method for preparing RT base by using aniline and nitrobenzene as raw materials and organic base as a condensation catalyst comprises the following steps: mixing aniline and organic alkali and then dehydrating; step two: and mixing the dehydrated material with nitrobenzene, performing condensation reaction on the sprayed and dispersed material in a reaction tower, condensing and refluxing the gas phase of the condensation reaction into a tower kettle, and reducing the condensed liquid after the reaction to prepare the RT base.

Typically, the organic base is an aqueous solution of tetramethylammonium hydroxide or tetraethylammonium hydroxide.

The concentration of the aqueous solution of tetramethylammonium hydroxide or the aqueous solution of tetraethylammonium hydroxide is 5-45%.

The molar ratio of the aniline to the organic base is 3: 1-20: 1.

The dehydration temperature in the first step is 50-90 ℃, and the vacuum degree is 0.080-0.099 MPa.

And 5% -35% of water content in the dehydrated material in the first step.

The molar ratio of the addition amount of the nitrobenzene to the organic alkali is 0.2: 1-1.1: 1.

The temperature of the secondary condensation reaction in the step is 60-90 ℃, and the vacuum degree is 0.080-0.099 MPa.

The temperature of gas phase condensation in the secondary condensation reaction is 45-65 ℃, and the vacuum degree is 0.080-0.099 MPa.

In the method, the condenser is arranged at the top of the reaction tower.

According to the method, aniline and organic alkali are mixed, then part of water in the organic alkali is removed through azeotropic distillation, the aniline and nitrobenzene are mixed, the mixed material is conveyed to a reaction tower with a sprayer, the sprayed and dispersed material is subjected to condensation reaction in the reaction tower, the condensation process is a dehydration process, the removed aniline water is condensed and refluxed to enter a reaction tower kettle, and in the whole process, the material moves forward in a horizontal pushing mode, so that the problems of reduction of raw material conversion rate and target product selectivity caused by back mixing in a kettle type process are solved, meanwhile, the condensed and refluxed aniline water enters the condensation liquid, the temperature of the condensation liquid is reduced, the water content in the condensation liquid is increased, the aim of slowing down the continuous proceeding of the condensation reaction is fulfilled, the occurrence of side reactions after the condensation is finished is reduced, and the selectivity of the condensation reaction is improved.

The invention adopts a tower type condensation process, and has the advantages of simplifying production flow, reducing the investment of reaction equipment, improving production efficiency and the like. The conversion rate of nitrobenzene is more than or equal to 99 percent, the selectivity of phenazine is less than or equal to 0.05 percent, and the selectivity of 2-aminodiphenylamine is less than or equal to 0.10 percent.

Drawings

FIG. 1 is a schematic flow chart of a method according to an embodiment of the present invention.

Detailed Description

The present invention will be described in detail below with reference to examples and the accompanying drawings.

The following example method refers to the scheme of figure 1.

Example 1

150 parts of aniline and 120 parts of 25% tetramethylammonium hydroxide are mixed and dehydrated, the dehydration temperature is 70 ℃, the dehydration vacuum degree is 0.090MPa, and the water content in the dehydrated material is 16.42%. Mixing the materials with 40 parts of nitrobenzene, spraying and dispersing the mixture, putting the mixture into a tower reactor for condensation reaction at the reaction temperature of 65 ℃ and the vacuum degree of 0.092MPa, condensing and refluxing the aniline and water evaporated by condensation to a tower kettle through a tower top condenser at the condensation temperature of 55 ℃, obtaining 200 parts of condensation liquid and 10 parts of condensation tail gas, wherein the mass percentage content of the nitrobenzene in the analysis condensation liquid is 0.06%, and the mass percentage content of the nitrobenzene in the condensation tail gas is 0.75%. Adding 80 parts of methanol into the obtained condensation liquid, and reducing to obtain 280 parts of reduced liquid, wherein the mass percent of the phenazine is 0.009%, and the mass percent of the 2-aminodiphenylamine is 0.013%. The conversion rate of nitrobenzene is 99.1 percent, the selectivity of phenazine is 0.045 percent, and the selectivity of 2-aminodiphenylamine is 0.050 percent.

Example 2

200 parts of aniline and 120 parts of 25% tetramethyl ammonium hydroxide are mixed and dehydrated, the dehydration temperature is 65 ℃, the dehydration vacuum degree is 0.093MPa, and the water content in the dehydrated material is 12.44%. Mixing the materials with 40 parts of nitrobenzene, spraying and dispersing the mixture, putting the mixture into a tower reactor for condensation reaction at the reaction temperature of 80 ℃ and the vacuum degree of 0.092MPa, condensing and refluxing the aniline and water evaporated by condensation to a tower kettle through a tower top condenser at the condensation temperature of 55 ℃, obtaining 249 parts of condensation liquid and 11 parts of condensation tail gas, and analyzing the mass percentage content of the nitrobenzene in the condensation liquid to be 0.011 percent. Adding 80 parts of methanol into the obtained condensation liquid, and reducing to obtain 330 parts of reduced liquid, wherein the mass percent of the phenazine is 0.009%, and the mass percent of the 2-aminodiphenylamine is 0.013%. The conversion rate of nitrobenzene is calculated to be 99.1 percent, the selectivity of phenazine is 0.049 percent, and the selectivity of 2-aminodiphenylamine is 0.073 percent.

Example 3

600 parts of aniline and 1000 parts of 5% tetramethyl ammonium hydroxide are mixed and dehydrated, the dehydration temperature is 65 ℃, the dehydration vacuum degree is 0.093MPa, and the water content in the dehydrated material is 25.30%. Mixing the materials with 40 parts of nitrobenzene, spraying and dispersing the mixture, putting the mixture into a tower reactor for condensation reaction at the reaction temperature of 70 ℃ and the vacuum degree of 0.092MPa, condensing and refluxing the aniline and water evaporated by condensation to a tower kettle through a tower top condenser at the condensation temperature of 55 ℃, wherein the obtained condensation liquid is 325 parts, the condensation tail gas is 15 parts, and the mass percentage content of the nitrobenzene in the analysis condensation liquid is 0.005%. Adding 80 parts of methanol into the obtained condensation liquid, and reducing to obtain 406 parts of reduced liquid, wherein the mass percent of the phenazine is 0.009%, and the mass percent of the 2-aminodiphenylamine is 0.010%. The conversion rate of nitrobenzene is calculated to be 99.2 percent, the selectivity of phenazine is 0.025 percent, and the selectivity of 2-aminodiphenylamine is 0.034 percent.

Example 4

150 parts of aniline and 120 parts of 40% tetramethylammonium hydroxide are mixed and dehydrated, the dehydration temperature is 65 ℃, the dehydration vacuum degree is 0.091MPa, and the water content in the dehydrated material is 16.94%. Mixing the materials with 20 parts of nitrobenzene, spraying and dispersing the mixture, putting the mixture into a tower reactor for condensation reaction at the reaction temperature of 65 ℃ and the vacuum degree of 0.092MPa, condensing and refluxing the aniline and water evaporated by condensation to a tower kettle through a tower top condenser at the condensation temperature of 45 ℃, obtaining 200 parts of condensation liquid, 5 parts of condensation tail gas, and analyzing the mass percentage content of the nitrobenzene in the condensation liquid to be 0.005 percent. Adding 100 parts of methanol into the obtained condensation liquid, and reducing to obtain 300 parts of a reducing liquid, wherein the mass percent of the phenazine is 0.004%, and the mass percent of the 2-aminodiphenylamine is 0.005%. The conversion rate of nitrobenzene is calculated to be 99.2 percent, the selectivity of phenazine is 0.012 percent, and the selectivity of 2-aminodiphenylamine is 0.019 percent.

Example 5

150 parts of aniline and 120 parts of 40% tetramethylammonium hydroxide are mixed and dehydrated, the dehydration temperature is 65 ℃, the dehydration vacuum degree is 0.091MPa, and the water content in the dehydrated material is 16.94%. Mixing the materials with 70 parts of nitrobenzene, spraying and dispersing the mixture, putting the mixture into a tower reactor for condensation reaction at the reaction temperature of 68 ℃ and the vacuum degree of 0.092MPa, condensing and refluxing the aniline and water evaporated by condensation to a tower kettle through a tower top condenser at the condensation temperature of 55 ℃, obtaining 265 parts of condensation liquid and 5 parts of condensation tail gas, and analyzing the mass percentage content of the nitrobenzene in the condensation liquid to be 0.002%. And adding 100 parts of methanol into the obtained condensation liquid, and reducing to obtain 366 parts of reduced liquid, wherein the mass percent of the phenazine is 0.0049%, and the mass percent of the 2-aminodiphenylamine is 0.006%. The conversion rate of nitrobenzene is calculated to be 99.2 percent, the selectivity of phenazine is 0.012 percent, and the selectivity of 2-aminodiphenylamine is 0.019 percent.

Example 6

350 parts of aniline and 650 parts of tetraethyl ammonium hydroxide with the content of 15 percent are mixed and dehydrated, the dehydration temperature is 75 ℃, the dehydration vacuum degree is 0.089MPa, and the water content in the dehydrated material is 25.20 percent. Mixing the materials with 40 parts of nitrobenzene, spraying and dispersing the mixture, feeding the mixture into a tower reactor for condensation reaction at the reaction temperature of 68 ℃ and the vacuum degree of 0.092MPa, condensing and refluxing the aniline and water evaporated by condensation to a tower kettle through a condenser at the top of the tower at the condensation temperature of 50 ℃, wherein the obtained condensation liquid is 300 parts, the condensation tail gas is 10 parts, and the mass percentage content of the nitrobenzene in the condensation liquid is analyzed to be 0.004%. Adding 100 parts of methanol into the obtained condensation liquid, and reducing to obtain 401 parts of a reducing liquid, wherein the mass percent of the phenazine is 0.005%, and the mass percent of the 2-aminodiphenylamine is 0.06%. The conversion rate of nitrobenzene is calculated to be 99.2 percent, the selectivity of phenazine is calculated to be 0.014 percent, and the selectivity of 2-aminodiphenylamine is calculated to be 0.019 percent.

Example 7

150 parts of aniline and 150 parts of tetraethylammonium hydroxide with the content of 20 percent are mixed and dehydrated, the dehydration temperature is 75 ℃, the dehydration vacuum degree is 0.091MPa, and the water content in the dehydrated material is 26.80 percent. Mixing the materials with 27 parts of nitrobenzene, spraying and dispersing the mixture, putting the mixture into a tower reactor for condensation reaction at the reaction temperature of 65 ℃ and the vacuum degree of 0.092MPa, condensing and refluxing the aniline and water evaporated by condensation to a tower kettle through a tower top condenser at the condensation temperature of 50 ℃, obtaining 207 parts of condensation liquid, 15 parts of condensation tail gas, and analyzing the mass percentage content of the nitrobenzene in the condensation liquid to be 0.005 percent. And adding 100 parts of methanol into the condensation liquid to reduce, thereby obtaining 308 parts of reduced liquid, wherein the mass percent of the phenazine is 0.006 percent, and the mass percent of the 2-aminodiphenylamine is 0.006 percent. The conversion rate of nitrobenzene is 99.2 percent, the selectivity of phenazine is 0.017 percent and the selectivity of 2-aminodiphenylamine is 0.020 percent by calculation.