Method for preparing RT base condensation liquid through falling film reaction

Abstract

The invention discloses a method for preparing an RT base condensation liquid through a falling film reaction, which comprises the following steps: mixing aniline, organic alkali and nitrobenzene, and carrying out vacuum dehydration condensation in a multi-stage serial falling film reactor to prepare 4-nitrosodiphenylamine and 4-nitrodiphenylamine condensation liquid. Compared with a conventional kettle type continuous process, the method has the advantages that the RT base condensation liquid is prepared by adopting the falling film reaction, the reaction time is shortened from about 4 hours to within 0.5 hour, the reaction time is greatly shortened, and the energy consumption is reduced. By adopting the preparation method provided by the invention, the conversion rate of nitrobenzene is greater than or equal to 87%, and the selectivity of 4-(nitrodiphenylamine) is greater than or equal to 90%.

Description

Technical Field

[0001] The invention belongs to the field of fine chemicals, and in particular relates to a method for preparing RT base condensation liquid by falling film reaction. Background Art

[0002] RT base, chemical name is p-aminodiphenylamine, can be used in rubber additives, dyes, textiles, printing and pharmaceutical industries, etc. It is mainly used to produce p-phenylenediamine rubber antioxidants 6PPD, 4010NA, etc. The global production capacity of RT base is about 225kt / a. The main foreign manufacturers are: Flexner of the United States, Lanxess of Germany, Aquifer of the Czech Republic, etc., and the development of p-aminodiphenylamine abroad is very unbalanced. There is a considerable supply gap in South Korea, Japan, India, Russia, Vietnam and other countries. The export prospect of p-aminodiphenylamine in my country is very optimistic.

[0003] The nitrobenzene method is the latest industrial synthesis process for p-aminodiphenylamine in the world. It is a clean and green process. In the process of producing RT base (p-aminodiphenylamine) by the nitrobenzene method, the condensation process adopts a kettle process. Aniline, nitrobenzene and catalyst quaternary ammonium base react under vacuum conditions to obtain 4-nitrodiphenylamine and 4-nitrosodiphenylamine. The reaction process is as follows:

[0004] (1) Aniline dehydrates with organic base to generate aniline anion

[0005]

[0006] The dehydration of aniline with organic base to produce aniline anion is the prerequisite for the condensation of aniline with nitrobenzene to produce 4-nitrosocyanate.

[0007] (2) Aniline anion reacts with nitrobenzene to form a complex

[0008]

[0009] The formation of the complex is the key to the overall selectivity of the target products 4-nitrosodiphenylamine and 4-nitrodiphenylamine.

[0010] (3) Rearrangement and hydrolysis

[0011]

[0012] The complex undergoes molecular rearrangement and hydrolysis to obtain 4-nitrosodiphenylamine, or reacts with nitrobenzene and then rearranges and hydrolyzes to obtain 4-nitrodiphenylamine. During the rearrangement, one molecule of water is released, and during the hydrolysis, one molecule of water is consumed, and tetramethylammonium hydroxide is released. From step (1) to step (3), tetramethylammonium hydroxide completes the catalytic condensation process.

[0013] (4) 4-(Sub)Nitrodiphenylamine is hydrogenated to give RT base, and azobenzene is reduced to aniline

[0014]

[0015] At present, in the production of RT base using the nitrobenzene method, the preparation process of the condensation liquid mainly adopts a continuous kettle process. As the reaction proceeds, a large amount of material circulates in the condensation reactor for dehydration and condensation reaction, and the material remixing rate is high and the residence time is long.

[0016] A falling film reactor is a reaction device that disperses the material along the wall of a falling film tube through a distributor to form a thin film, thereby reacting on the tube wall. The concept is to maximize the material required to achieve reaction conditions.

[0017] Therefore, studying a method for preparing RT base condensation solution by falling film reaction is of great significance for the industrial synthesis of p-aminodiphenylamine. Summary of the invention

[0018] Purpose of the invention: The purpose of the present invention is to provide a method for preparing RT base condensation liquid by falling film reaction in view of the shortcomings of the prior art. Compared with the conventional kettle continuous process, the present invention adopts falling film reaction to prepare RT base condensation liquid, and the reaction time is reduced from about 4 hours to less than 0.5 hours, which greatly shortens the reaction time and reduces energy consumption.

[0019] Technical solution: The purpose of the present invention is achieved through the following technical solution:

[0020] The invention provides a method for preparing RT base condensation liquid by falling film reaction, which is characterized in that aniline, an organic base and nitrobenzene are mixed and introduced into a multi-stage series falling film reactor for vacuum dehydration condensation to prepare 4-nitrosodiphenylamine and 4-nitrodiphenylamine condensation liquid.

[0021] Preferably, the falling film reactor is a falling film reactor with 5 to 8 stages connected in series.

[0022] Falling film reactors are mainly suitable for liquid phase reactions, especially for reactions that require the removal of volatile substances (such as water, methanol, ammonia, etc.). The liquid material to be reacted forms a thin film (0.2-3mm) on the inner wall of the falling film reactor, and heat is quickly transferred through the tube wall. The water generated by the reaction is quickly vaporized and detached from the tube wall. The material remaining on the tube wall reacts quickly because the reaction conditions are met. Falling film reaction is a type of interfacial reaction. When a falling film reactor is used for reaction, the proportion of materials that meet the reaction conditions in the reactor is much higher than that of traditional kettle reactors and tubular reactors. In theory, it only takes a few seconds to achieve the effect of several hours of reaction in traditional reactors.

[0023] Preferably, the falling film tube of the falling film reactor is a single tube, or a tube array formed by multiple falling film tubes.

[0024] Furthermore, the present invention improves the internal structure of the existing falling film reactor and designs a new falling film reactor, which uses the existing control means to achieve the falling film reaction. Figure 1 As shown, it is a double-layer structure. The tube-side material is the reaction material, and the shell-side is the heat medium. The emulsified material is sprayed into the falling film tube through an atomizing nozzle or diverted to the inner wall of the falling film tube through a liquid separator to form a film. The film-formed material flows from top to bottom along the falling film tube due to gravity and surface tension until the entire reaction process is completed.

[0025] Preferably, the organic base is an aqueous solution of tetramethylammonium hydroxide with a concentration of 5 to 45 wt %.

[0026] More preferably, the molar ratio of the organic base to nitrobenzene is 0.80:1 to 1.2:1.

[0027] Preferably, the molar ratio of aniline to nitrobenzene is 3:1 to 8:1.

[0028] Preferably, the dehydration condensation temperature is 60-85°C.

[0029] Preferably, the vacuum degree of the dehydration condensation is 0.080-0.099 MPa.

[0030] Preferably, the gaseous material produced by dehydration condensation is condensed and then enters the aniline water tank; the liquid material is mixed and then enters the next falling film reactor for vacuum dehydration condensation; the above operation is repeated until a condensation liquid that meets the requirements is obtained.

[0031] The present invention also provides a specific preferred embodiment, the method for preparing RT base condensation liquid by falling film reaction comprises the following steps:

[0032] (1) Mixing aniline, nitrobenzene and an organic base;

[0033] (2) emulsifying the mixed materials by stirring to form a pseudo-homogeneous phase;

[0034] (3) The emulsified material is input into a falling film reactor, and the material is evenly distributed on the inner wall of the falling film tube, and flows from the inlet at the upper part of the tube to the outlet at the lower part of the tube by gravity to obtain a condensation liquid, and the gas phase generated during the condensation process is condensed to recover aniline water;

[0035] (4) Analyze the material composition of the condensation liquid in step (3). If the condensation liquid meets the production requirements, the condensation liquid is transferred to the condensation liquid storage tank; otherwise, repeat steps (2) and (3) until the condensation reaction meets the production requirements. Beneficial effects:

[0036] In step (3), the emulsified material is pumped into a falling film reactor for dehydration and condensation, sprayed into the falling film reactor by a nozzle or overflowed into the falling film reactor by a separatory plate, and the material forms a film on the inner wall of the reactor for condensation reaction at a temperature of 60-85° C. and a vacuum degree of 0.080-0.099 MPa. The condensation liquid is then sent to the next falling film reaction until the condensation liquid is qualified; the aniline water produced by the dehydration and condensation is condensed and collected in an aniline water tank for recycling.

[0037] Beneficial effects:

[0038] The present invention provides a method for preparing RT base condensation liquid by falling film reaction. Compared with the conventional kettle continuous process, the present invention adopts falling film reaction to prepare RT base condensation liquid, and the reaction time is reduced from about 4 hours to less than 0.5 hours, which greatly shortens the reaction time and reduces energy consumption. By adopting the preparation method of the present invention, the conversion rate of nitrobenzene is ≥87%, and the selectivity of 4-(sub)nitrosodiphenylamine is ≥90%. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A schematic diagram of the structure of a falling film reactor used in an embodiment of the present invention;

[0040] Among them, 1-vacuum upper port; 2-sprinkler; 3-liquid film; 4-heat medium;

[0041] Figure 2 The present invention is a process flow chart for preparing RT base condensation solution by falling film reaction. DETAILED DESCRIPTION

[0042] The technical solution of the present invention is described in detail below through specific embodiments, but the protection scope of the present invention is not limited to the embodiments.

[0043] The structure of the falling film reactor used in the embodiment of the present invention is as follows Figure 1 As shown, it is a double-layer structure, where 1-vacuum upper port; 2-sprinkler; 3-liquid film; 4-heat medium. The tube side material is the reaction material, and the shell side is the heat medium 4. The reactor is evacuated to vacuum through the vacuum upper port 1. The temperature in the reactor is controlled by heating the heat medium 4 in the shell side. The emulsified material is sprayed onto the liquid film 3 on the inner wall of the falling film tube through the atomizing nozzle 2 to form a film. The film-formed material flows from top to bottom along the falling film tube due to gravity and surface tension until the entire reaction process is completed.

[0044] The process flow of preparing RT base condensation liquid by falling film reaction of the present invention is shown in Figure 2 .

[0045] Example 1

[0046] Aniline, 25 wt% tetramethylammonium hydroxide aqueous solution and nitrobenzene are added to a mixing kettle in a molar ratio of 5:1:1, and stirred evenly. The mixed materials are added to a 6-stage falling film reactor in series with a metering pump. The inner diameter of the falling film tube in the falling film reactor is 50 mm and the tube length is 3000 mm. Each stage of the falling film reactor is connected by a static mixer. The falling film reactor is heated by a water bath with a water bath temperature of 80°C. The vacuum degree in the falling film reactor is 0.092 MPa. The flow rate of the material in a single falling film tube is 20 mL / min, and the residence time of the material in the falling film reaction device is 15 min.

[0047] The composition of the materials in the condensation liquid was analyzed by HPLC, and the following calculations were made: the conversion of nitrobenzene was 96.68%, the total selectivity of 4-nitrosodiphenylamine and 4-nitrodiphenylamine was 91.34%, and the selectivity of phenazine was 2.17%.

[0048] Example 2

[0049] Aniline, 25 wt% tetramethylammonium hydroxide aqueous solution and nitrobenzene are added to a mixing kettle in a molar ratio of 8:1:1 and stirred evenly. The mixed materials are added to a 6-stage falling film reactor in series with a metering pump. The inner diameter of the falling film tube in the falling film reactor is 50 mm and the tube length is 3000 mm. Each stage of the falling film reactor is connected by a static mixer. The falling film reactor is heated by a water bath with a water bath temperature of 80°C. The vacuum degree in the falling film reactor is 0.092 MPa. The flow rate of the material in a single falling film tube is 30 mL / min, and the residence time of the material in the falling film reaction device is 13 min.

[0050] The composition of the materials in the condensation liquid was analyzed by HPLC, and the following calculations were made: the conversion of nitrobenzene was 97.28%, the total selectivity of 4-nitrosodiphenylamine and 4-nitrodiphenylamine was 92.09%, and the selectivity of phenazine was 1.98%.

[0051] Example 3

[0052] Aniline, 25 wt% tetramethylammonium hydroxide aqueous solution and nitrobenzene are added to a mixing kettle in a molar ratio of 5:1:1, and stirred evenly. The mixed materials are added to a 5-stage falling film reactor in series with a metering pump. The inner diameter of the falling film tube in the falling film reactor is 50 mm, and the tube length is 2000 mm. Each stage of the falling film reactor is connected by a static mixer. The falling film reactor is heated by a water bath with a water bath temperature of 85°C. The vacuum degree in the falling film reactor is 0.085 MPa. The flow rate of the material in a single falling film tube is 30 mL / min, and the residence time of the material in the falling film reaction device is 11 min.

[0053] The composition of the materials in the condensation liquid was analyzed by HPLC, and the following calculations were made: the conversion of nitrobenzene was 96.37%, the total selectivity of 4-nitrosodiphenylamine and 4-nitrodiphenylamine was 90.12%, and the selectivity of phenazine was 3.15%.

[0054] Example 4

[0055] Aniline, 5wt% tetramethylammonium hydroxide aqueous solution and nitrobenzene are added to a mixing kettle in a molar ratio of 4:1:1.2 and stirred evenly. The mixed materials are added to an 8-stage falling film reactor in series with a metering pump. The inner diameter of the falling film tube in the falling film reactor is 50mm and the tube length is 4000mm. Each stage of the falling film reactor is connected by a static mixer. The falling film reactor is heated by a water bath with a water bath temperature of 85°C. The vacuum degree in the falling film reactor is 0.097MPa. The flow rate of the material in a single falling film tube is 20mL / min, and the residence time of the material in the falling film reaction device is 15min.

[0056] The composition of the materials in the condensation liquid was analyzed by HPLC, and the following calculations were made: the conversion of nitrobenzene was 98.12%, the total selectivity of 4-nitrosodiphenylamine and 4-nitrodiphenylamine was 90.48%, and the selectivity of phenazine was 0.94%.

[0057] Example 5

[0058] Aniline, 45 wt% tetramethylammonium hydroxide aqueous solution and nitrobenzene are added to a mixing kettle in a molar ratio of 5:1:1, stirred evenly at 65°C, and the mixed materials are added to a 5-stage falling film reactor in series with a metering pump. The inner diameter of the falling film tube in the falling film reactor is 50 mm and the tube length is 3000 mm. Each stage of the falling film reactor is connected by a static mixer. The falling film reactor is heated by a water bath with a water bath temperature of 75°C. The vacuum degree in the falling film reactor is 0.095 MPa. The flow rate of the material in a single falling film tube is 30 mL / min, and the residence time of the material in the falling film reaction device is 10 min.

[0059] The composition of the materials in the condensation liquid was analyzed by HPLC, and the following were calculated: nitrobenzene conversion was 97.59%, the total selectivity of 4-nitrosodiphenylamine and 4-nitrodiphenylamine was 93.26%, and the selectivity of phenazine was 1.56%.

[0060] Example 6

[0061] Aniline, 25wt% tetramethylammonium hydroxide aqueous solution and nitrobenzene are added to a mixing kettle in a molar ratio of 6:1.2:1 and stirred evenly. The mixed materials are added to a 6-stage falling film reactor in series with a metering pump. The inner diameter of the falling film tube in the falling film reactor is 50mm and the tube length is 3000mm. Each stage of the falling film reactor is connected by a static mixer. The falling film reactor is heated by a water bath with a water bath temperature of 80°C. The vacuum degree in the falling film reactor is 0.095MPa. The flow rate of the material in a single falling film tube is 20mL / min, and the residence time of the material in the falling film reaction device is 12min.

[0062] The composition of the materials in the condensation liquid was analyzed by HPLC, and the following was calculated: the conversion of nitrobenzene was 87.41%, the total selectivity of 4-nitrosodiphenylamine and 4-nitrodiphenylamine was 93.10%, and the selectivity of phenazine was 1.43%.

[0063] Example 7

[0064] Aniline, 40 wt% tetramethylammonium hydroxide aqueous solution and nitrobenzene are added to a mixing kettle in a molar ratio of 5:1:1, and stirred evenly. The mixed materials are added to an 8-stage falling film reactor in series with a metering pump. The inner diameter of the falling film tube in the falling film reactor is 50 mm, and the tube length is 5000 mm. Each stage of the falling film reactor is connected by a static mixer. The falling film reactor is heated by a water bath with a water bath temperature of 80°C. The vacuum degree in the falling film reactor is 0.098 MPa. The flow rate of the material in a single falling film tube is 30 mL / min, and the residence time of the material in the falling film reaction device is 17 min.

[0065] The composition of the materials in the condensation liquid was analyzed by HPLC, and the following were calculated: nitrobenzene conversion was 95.03%, the total selectivity of 4-nitrosodiphenylamine and 4-nitrodiphenylamine was 92.10%, and the selectivity of phenazine was 0.94%.

[0066] As described above, although the present invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the present invention itself. Various changes in form and details may be made without departing from the spirit and scope of the present invention as defined in the appended claims.

Claims

1. A method for preparing RT base condensation solution by falling film reaction, characterized in that: Aniline, organic base and nitrobenzene are mixed and placed into a multi-stage falling film reactor for vacuum dehydration condensation to prepare 4-nitrosodiphenylamine and 4-nitrodiphenylamine condensation liquid.

2. The method for preparing RT base condensation solution by falling film reaction according to claim 1, characterized in that: The falling film tube of the falling film reactor is a single tube or a tube array formed by multiple falling film tubes.

3. The method for preparing RT base condensation solution by falling film reaction according to claim 1, characterized in that: The organic base is an aqueous solution of tetramethylammonium hydroxide, and its concentration is 5-45 wt %.

4. The method for preparing RT base condensation solution by falling film reaction according to claim 3, characterized in that: The molar ratio of the organic base to nitrobenzene is 0.80:1 to 1.2:

1.

5. The method for preparing RT base condensation solution by falling film reaction according to claim 1, characterized in that: The molar ratio of aniline to nitrobenzene is 3:1 to 8:

1.

6. The method for preparing RT base condensation solution by falling film reaction according to claim 1, characterized in that: The temperature of the dehydration condensation is 60-85°C.

7. The method for preparing RT base condensation solution by falling film reaction according to claim 1, characterized in that: The vacuum degree of the dehydration condensation is 0.080-0.099 MPa.

8. The method for preparing RT base condensation solution by falling film reaction according to claim 1, characterized in that: The gaseous material produced by dehydration condensation is condensed and enters the aniline water tank; the liquid material is mixed and then enters the next falling film reactor for vacuum dehydration condensation; the above operation is repeated until a condensation liquid that meets the requirements is obtained.

9. The method for preparing RT base condensation solution by falling film reaction according to claim 1, characterized in that: The following steps are involved: (1) Mixing aniline, nitrobenzene and an organic base; (2) emulsifying the mixed materials by stirring to form a pseudo-homogeneous phase; (3) The emulsified material is input into a falling film reactor, and the material is evenly distributed on the inner wall of the falling film tube, and flows from the inlet at the upper part of the tube to the outlet at the lower part of the tube by gravity to obtain a condensation liquid, and the gas phase generated during the condensation process is condensed to recover aniline water; (4) Analyze the material composition of the condensation liquid in step (3). If the condensation liquid meets the production requirements, the condensation liquid is transferred to the condensation liquid storage tank; otherwise, repeat steps (2) and (3) until the condensation reaction meets the production requirements.

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