Process for preparing RT base condensation liquid through falling film reaction

Abstract

The invention discloses a process for preparing RT base condensation liquid through falling film reaction, which comprises the following steps: mixing aniline and organic alkali, and carrying out vacuum dehydration and concentration in a falling film reactor; and mixing the concentrated material with nitrobenzene, and carrying out dehydration condensation in a next-stage falling film reactor to prepare 4-nitrosodiphenylamine and 4-nitrodiphenylamine condensation liquid. According to the invention, aniline and organic alkali enter a falling film reactor for co-dehydration, and the co-dehydrated material is mixed with nitrobenzene for dehydration condensation to prepare the RT base condensation liquid. According to the process, the water content in a condensation reaction system is remarkably reduced, and the condensation reaction is facilitated, so that the condensation reaction time is remarkably shortened, the stage number of the condensation reaction is favorably reduced, and the equipment investment is reduced.

Description

Technical Field

[0001] The invention belongs to the field of fine chemicals, and in particular relates to a process 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] In addition, during the preparation of RT base condensation solution, after aniline, organic base and nitrobenzene are mixed and enter the condensation reactor, water will also be produced during the condensation reaction because the organic base contains a large amount of water, which hinders the formation of tetramethylamine aniline salt, resulting in a low content of aniline anions in the reaction system, affecting the reaction rate. In an environment with high water content, side reactions will also increase.

[0017] 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.

[0018] Therefore, in order to reduce the influence of water in the condensation reaction system on the reaction, it is necessary to develop a new process for preparing RT base condensation solution by falling film reaction. Summary of the invention

[0019] Purpose of the invention: The purpose of the present invention is to provide a process for preparing RT base condensation liquid by falling film reaction in view of the shortcomings of the prior art. The process of the present invention can significantly reduce the water content in the condensation reaction system, which is conducive to reducing the order of the condensation reaction and reducing equipment investment.

[0020] Technical solution: The purpose of the present invention is achieved through the following technical solution:

[0021] The invention provides a process for preparing RT base condensation liquid by falling film reaction, comprising the steps of mixing aniline and an organic base, and entering a falling film reactor for vacuum dehydration and concentration; mixing the concentrated material with nitrobenzene, and then entering a next-stage falling film reactor for dehydration and condensation to prepare 4-nitrosodiphenylamine and 4-nitrodiphenylamine condensation liquid.

[0022] In the process of preparing the RT base condensation liquid, the present invention utilizes the principle that the organic base reacts with aniline to generate tetramethylamine aniline salt and aniline and water form an azeotrope, and pre-dehydrates the organic base, which can significantly reduce the water content in the condensation reaction system, is beneficial to the condensation reaction, and thus significantly reduces the condensation reaction time, is beneficial to reducing the order of the condensation reaction, and reduces equipment investment.

[0023] Preferably, the organic base is an aqueous solution of tetramethylammonium hydroxide with a concentration of 5 to 45 wt %.

[0024] Preferably, the molar ratio of the organic base to nitrobenzene is 0.80:1 to 1.2:1.

[0025] Preferably, the molar ratio of aniline to nitrobenzene is 3:1 to 8:1.

[0026] Preferably, the falling film tube of the falling film reactor is a single tube, or a tube array formed by multiple falling film tubes.

[0027] The present invention uses a multi-stage falling film reactor, which can be a three-stage falling film reactor connected in series, or a four-stage or five-stage falling film reactor connected in series.

[0028] 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.

[0029] Preferably, the falling film tube of the falling film reactor is a single tube, or a tube array formed by multiple falling film tubes.

[0030] 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 mixed and 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.

[0031] Preferably, the temperature of the dehydration and concentration is 60-80° C., and the vacuum degree of the dehydration and concentration is 0.080-0.099 MPa.

[0032] Preferably, the temperature of the dehydration condensation is 60-85° C., and the vacuum degree of the dehydration condensation is 0.080-0.099 MPa.

[0033] Preferably, the gaseous material produced by the 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.

[0034] The present invention also provides a specific preferred embodiment, the process for preparing RT base condensation liquid by falling film reaction comprises the following steps:

[0035] (1) mixing aniline and an organic base, and emulsifying them in a stirred tank to obtain a mixed material;

[0036] (2) The emulsified mixture is pumped into a falling film reactor for dehydration and concentration at a temperature of 60-80° C. and a vacuum degree of 0.080-0.099 MPa to generate tetramethylamine aniline salt;

[0037] (3) mixing the dehydrated tetramethylamine aniline salt with nitrobenzene and entering the next-stage falling film reactor to carry out a vacuum dehydration condensation reaction at a temperature of 60-85° C. and a vacuum degree of 0.080-0.099 MPa, and condensing the gas phase generated during the condensation process to recover aniline water;

[0038] The material is evenly distributed on the inner wall of the falling film tube and flows from the upper inlet of the tube to the lower outlet of the tube by gravity to obtain the condensation liquid.

[0039] (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, the condensation liquid is transferred to the next falling film reactor for condensation reaction until the condensation reaction meets the production requirements.

[0040] Further preferably, in step (2), the mixed material is sprayed into the falling film reactor by a nozzle or overflows into the falling film reactor by a separatory plate, and the material forms a film on the inner wall of the reactor for dehydration.

[0041] The aniline water produced by dehydration condensation is condensed and collected in an aniline water tank for recycling.

[0042] Beneficial effects:

[0043] The present invention provides a process for preparing RT base condensation liquid by falling film reaction, wherein aniline and nitrobenzene are used as raw materials and an organic base is used as a catalyst. Aniline and the organic base are firstly introduced into a falling film reactor for co-dehydration, and the co-dehydrated materials are then mixed with nitrobenzene for dehydration and condensation to prepare RT base condensation liquid. The process of the present invention significantly reduces the water content in the condensation reaction system, is conducive to the condensation reaction, thereby significantly reducing the condensation reaction time, is conducive to reducing the order of the condensation reaction, and reduces equipment investment. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 A schematic diagram of the structure of a falling film reactor used in an embodiment of the present invention;

[0045] Among them, 1-vacuum outlet; 2-nozzle; 3-liquid film; 4-heat medium.

[0046] Figure 2The present invention is a process flow chart for preparing RT base condensation solution by falling film reaction. DETAILED DESCRIPTION

[0047] 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.

[0048] 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, wherein 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 emulsified material is sprayed onto the inner wall of the falling film tube through the atomizing nozzle 2 to form a film. The film-forming material flows from top to bottom along the falling film tube due to gravity and surface tension until the entire reaction process is completed.

[0049] The process flow of preparing RT base condensation liquid by falling film reaction of the present invention is shown in Figure 2 .

[0050] Example 1

[0051] Aniline and 25wt% tetramethylammonium hydroxide aqueous solution are added to the mixing kettle at a molar ratio of 5:1, stirred evenly, and the mixed materials are added to the primary falling film reactor with a metering pump. The inner diameter of the falling film tube in the falling film reactor is 50mm, the tube length is 3000mm, the falling film reactor is heated by a water bath, the water bath temperature is 70℃, the vacuum degree in the falling film reactor is 0.092MPa, and the flow rate of the material in a single falling film tube is 20mL / min. The material concentrated by the primary falling film reactor is mixed with nitrobenzene, the molar ratio of nitrobenzene to organic base is 1:1, and enters the secondary, tertiary, and quaternary falling film reactors in turn. The inner diameter of the falling film tube in the falling film reactor is 50mm, the tube length is 3000mm, the falling film reactor is heated by a water bath, the water bath temperature is 80℃, the vacuum degree in the falling film reactor is 0.092MPa, and the flow rate of the material in a single falling film tube is 20mL / min. The residence time of the material in the falling film reaction device is 10min.

[0052] The composition of the materials in the condensation liquid was analyzed by HPLC, and the following calculations were made: the conversion of nitrobenzene was 97.23%, the total selectivity of 4-nitrosodiphenylamine and 4-nitrodiphenylamine was 93.69%, and the selectivity of phenazine was 1.23%.

[0053] Example 2

[0054] Aniline and 5wt% tetramethylammonium hydroxide aqueous solution are added to the mixing kettle in a molar ratio of 8:1, stirred evenly, and the mixed materials are added to the primary falling film reactor with a metering pump. The inner diameter of the falling film tube in the falling film reactor is 50mm, the tube length is 3000mm, the falling film reactor is heated by a water bath, the water bath temperature is 70℃, the vacuum degree in the falling film reactor is 0.092MPa, and the flow rate of the material in a single falling film tube is 20mL / min. The material concentrated by the primary falling film reactor is mixed with nitrobenzene, the molar ratio of nitrobenzene to organic base is 1:1, and enters the secondary, tertiary, and quaternary falling film reactors in turn. The inner diameter of the falling film tube in the falling film reactor is 50mm, the tube length is 3000mm, the falling film reactor is heated by a water bath, the water bath temperature is 80℃, the vacuum degree in the falling film reactor is 0.092MPa, and the flow rate of the material in a single falling film tube is 20mL / min. The residence time of the material in the falling film reaction device is 10min.

[0055] The composition of the materials in the condensation liquid was analyzed by HPLC, and the following calculations were made: the conversion of nitrobenzene was 98.05%, the total selectivity of 4-nitrosodiphenylamine and 4-nitrodiphenylamine was 94.51%, and the selectivity of phenazine was 0.97%.

[0056] Example 3

[0057] Aniline and 25wt% tetramethylammonium hydroxide aqueous solution are added to the mixing kettle at a molar ratio of 5:1, stirred evenly, and the mixed materials are added to the primary falling film reactor with a metering pump. The inner diameter of the falling film tube in the falling film reactor is 50mm, the tube length is 3000mm, the falling film reactor is heated by a water bath, the water bath temperature is 70℃, the vacuum degree in the falling film reactor is 0.092MPa, and the flow rate of the material in a single falling film tube is 20mL / min. The material concentrated by the primary falling film reactor is mixed with nitrobenzene, the molar ratio of nitrobenzene to organic base is 1:1, and enters the secondary and tertiary falling film reactors in turn. The inner diameter of the falling film tube in the falling film reactor is 50mm, the tube length is 3000mm, the falling film reactor is heated by a water bath, the water bath temperature is 85℃, the vacuum degree in the falling film reactor is 0.092MPa, and the flow rate of the material in a single falling film tube is 20mL / min. The residence time of the material in the falling film reaction device is 8min.

[0058] The composition of the materials in the condensation liquid was analyzed by HPLC, and the following were calculated: nitrobenzene conversion was 97.69%, the total selectivity of 4-nitrosodiphenylamine and 4-nitrodiphenylamine was 92.58%, and the selectivity of phenazine was 1.49%.

[0059] Example 4

[0060] Aniline and 25wt% tetramethylammonium hydroxide aqueous solution are added to the mixing kettle in a molar ratio of 3:1, stirred evenly, and the mixed materials are added to the primary falling film reactor with a metering pump. The inner diameter of the falling film tube in the falling film reactor is 50mm, the tube length is 3000mm, the falling film reactor is heated by a water bath, the water bath temperature is 65℃, the vacuum degree in the falling film reactor is 0.095MPa, and the flow rate of the material in a single falling film tube is 20mL / min. The material concentrated by the primary falling film reactor is mixed with nitrobenzene, the molar ratio of nitrobenzene to organic base is 1:1.2, and enters the secondary and tertiary falling film reactors in turn. The inner diameter of the falling film tube in the falling film reactor is 50mm, the tube length is 3000mm, the falling film reactor is heated by a water bath, the water bath temperature is 85℃, the vacuum degree in the falling film reactor is 0.085MPa, and the flow rate of the material in a single falling film tube is 20mL / min. The residence time of the material in the falling film reaction device is 8min.

[0061] The composition of the materials in the condensation liquid was analyzed by HPLC, and the following were calculated: nitrobenzene conversion was 98.19%, the total selectivity of 4-nitrosodiphenylamine and 4-nitrodiphenylamine was 93.07%, and the selectivity of phenazine was 1.57%.

[0062] Example 5

[0063] Aniline and 45wt% tetramethylammonium hydroxide aqueous solution are added to the mixing kettle at a molar ratio of 5:1, stirred evenly, and the mixed materials are added to the primary falling film reactor with a metering pump. The inner diameter of the falling film tube in the falling film reactor is 50mm, the tube length is 3000mm, the falling film reactor is heated by a water bath, the water bath temperature is 60℃, the vacuum degree in the falling film reactor is 0.090MPa, and the flow rate of the material in a single falling film tube is 20mL / min. The material concentrated by the primary falling film reactor is mixed with nitrobenzene, the molar ratio of nitrobenzene to organic base is 1.2:1, and enters the secondary and tertiary falling film reactors in turn. The inner diameter of the falling film tube in the falling film reactor is 50mm, the tube length is 3000mm, the falling film reactor is heated by a water bath, the water bath temperature is 80℃, the vacuum degree in the falling film reactor is 0.090MPa, and the flow rate of the material in a single falling film tube is 20mL / min. The residence time of the material in the falling film reaction device is 8min.

[0064] The composition of the materials in the condensation liquid was analyzed by HPLC, and the following calculations were made: the conversion of nitrobenzene was 83.14%, the total selectivity of 4-nitrosodiphenylamine and 4-nitrodiphenylamine was 94.20%, and the selectivity of phenazine was 1.07%.

[0065] Example 6

[0066] Aniline and 25wt% tetramethylammonium hydroxide aqueous solution are added to the mixing kettle at a molar ratio of 5:1, stirred evenly, and the mixed materials are added to the primary falling film reactor with a metering pump. The inner diameter of the falling film tube in the falling film reactor is 50mm, the tube length is 3000mm, the falling film reactor is heated by a water bath, the water bath temperature is 70℃, the vacuum degree in the falling film reactor is 0.088MPa, and the flow rate of the material in a single falling film tube is 20mL / min. The material concentrated by the primary falling film reactor is mixed with nitrobenzene, the molar ratio of nitrobenzene to organic base is 1:1, and enters the secondary, tertiary, and quaternary falling film reactors in turn. The inner diameter of the falling film tube in the falling film reactor is 50mm, the tube length is 3000mm, the falling film reactor is heated by a water bath, the water bath temperature is 75℃, the vacuum degree in the falling film reactor is 0.095MPa, and the flow rate of the material in a single falling film tube is 20mL / min. The residence time of the material in the falling film reaction device is 10min.

[0067] The composition of the materials in the condensation liquid was analyzed by HPLC, and the following calculations were made: the conversion of nitrobenzene was 96.71%, the total selectivity of 4-nitrosodiphenylamine and 4-nitrodiphenylamine was 94.12%, and the selectivity of phenazine was 0.97%.

[0068] Example 7

[0069] Aniline and 35wt% tetramethylammonium hydroxide aqueous solution are added to the mixing kettle at a molar ratio of 5:1, stirred evenly, and the mixed materials are added to the first-level falling film reactor with a metering pump. The inner diameter of the falling film tube in the falling film reactor is 50mm, the tube length is 3000mm, the falling film reactor is heated by a water bath, the water bath temperature is 75℃, the vacuum degree in the falling film reactor is 0.090MPa, and the flow rate of the material in a single falling film tube is 20mL / min. The material concentrated by the first-level falling film reactor is mixed with nitrobenzene, and the molar ratio of nitrobenzene to organic base is 1:1, and enters the second, third, fourth, and fifth falling film reactors in turn. The inner diameter of the falling film tube in the falling film reactor is 50mm, the tube length is 3000mm, the falling film reactor is heated by a water bath, the water bath temperature is 80℃, the vacuum degree in the falling film reactor is 0.093MPa, and the flow rate of the material in a single falling film tube is 20mL / min. The residence time of the material in the falling film reaction device is 13min.

[0070] The composition of the materials in the condensation liquid was analyzed by HPLC, and the following calculations were made: the conversion of nitrobenzene was 96.82%, the total selectivity of 4-nitrosodiphenylamine and 4-nitrodiphenylamine was 94.18%, and the selectivity of phenazine was 0.82%.

[0071] 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 process for preparing RT base condensation liquid by falling film reaction, characterized in that: Aniline and organic base are mixed and sent into a falling film reactor for vacuum dehydration and concentration; the concentrated material is mixed with nitrobenzene and then sent into the next falling film reactor for dehydration and condensation to prepare 4-nitrosodiphenylamine and 4-nitrodiphenylamine condensation liquid.

2. The process 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 %.

3. The process for preparing RT base condensation liquid by falling film reaction according to any one of claims 1 or 2, characterized in that: The molar ratio of the organic base to nitrobenzene is 0.80:1 to 1.2:

1.

4. The process 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.

5. The process for preparing RT base condensation liquid 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.

6. The process for preparing RT base condensation liquid by falling film reaction according to claim 1, characterized in that: The temperature of the dehydration and concentration is 60-80° C., and the vacuum degree of the dehydration and concentration is 0.080-0.099 MPa.

7. The process for preparing RT base condensation liquid by falling film reaction according to claim 1, characterized in that: The temperature of the dehydration condensation is 60-85° C., and the vacuum degree of the dehydration condensation is 0.080-0.099 MPa.

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

9. The process for preparing RT base condensation liquid by falling film reaction according to claim 1, characterized in that: The following steps are involved: (1) mixing aniline and an organic base to obtain a mixed material; (2) dehydrating and concentrating the mixed material through a falling film reactor to generate tetramethylamine aniline salt; (3) mixing tetramethylamine aniline salt with nitrobenzene and then entering into a falling film reactor at the next stage to carry out a vacuum dehydration condensation reaction, and decondensing the gas phase generated in the condensation process 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, the condensation liquid is transferred to the next falling film reactor for condensation reaction until the condensation reaction meets the production requirements.

10. The process for preparing RT base condensation liquid by falling film reaction according to claim 9, characterized in that: In step (2), the mixed material is sprayed into the falling film reactor by a nozzle or overflows into the falling film reactor by a liquid separator, and the material forms a film on the inner wall of the reactor for dehydration.

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