A method for the segmental condensation of aniline-nitrobenzene
By adding aniline and catalyst in stages through a two-stage continuous condensation reaction system, the problem of catalyst decomposition was solved, the reaction efficiency and safety were improved, the generation of by-products was reduced, and the service life of the hydrogenation catalyst was extended.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-09-12
- Publication Date
- 2026-03-27
AI Technical Summary
In the existing aniline-nitrobenzene condensation reaction, the condensation catalyst tetramethylammonium hydroxide decomposes severely under reduced pressure, leading to increased catalyst consumption and the generation of the toxic byproduct trimethylamine, which affects the reaction efficiency and subsequent catalytic hydrogenation reaction.
A two-stage continuous condensation reaction system using multiple reactors is employed, with aniline and condensation catalyst added in stages to increase the effective residence time of reactants within the system, inhibit catalyst decomposition, and reduce the generation of byproducts.
It significantly reduces catalyst consumption, decreases trimethylamine formation, improves reaction efficiency, enhances reaction performance, strengthens process safety and economy, and extends the lifespan of hydrogenation catalysts.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the field of rubber antioxidant intermediate p-aminodiphenylamine production, and particularly relates to a method for segment condensation reaction of aniline and nitrobenzene. BACKGROUND
[0002] The synthesis reaction of p-phenylenediamine rubber antioxidant key intermediate p-aminodiphenylamine (RT-Perse) is carried out in two steps: first, aniline and nitrobenzene are subjected to condensation reaction in the presence of a condensation catalyst to generate a condensation liquid containing p-nitrodiphenylamine and p-nitrosodiphenylamine; and then the condensation liquid is subjected to catalytic hydrogenation reaction to synthesize p-aminodiphenylamine. Among them, the condensation reaction of aniline and nitrobenzene is a key reaction step for preparing p-aminodiphenylamine.
[0003] The condensation reaction mechanism of aniline and nitrobenzene is that aniline and a basic condensation catalyst are first dehydrated to form an aniline ion, and then the aniline ion reacts with nitrobenzene as a nucleophilic reagent to generate 4-nitrodiphenylamine and 4-nitrosodiphenylamine. The catalyst used in the condensation reaction is mainly a quaternary amine base catalyst, among which tetramethylammonium hydroxide is the most commonly used. The theoretical reaction molar ratio of the condensation catalyst to aniline and nitrobenzene is 1:1, but in actual production, the addition amount of the condensation catalyst is slightly excessive compared to that of nitrobenzene, and the addition amount of aniline is several times that of nitrobenzene.
[0004] In the existing production process reported at present, whether adopting batch or continuous reaction form, or adopting any type of reactor, aniline, condensation catalyst and nitrobenzene are all added into the reaction system at once according to a certain proportion, and the dehydration condensation reaction is carried out under reduced pressure. Since the added condensation catalyst is usually 20%-30% tetramethylammonium hydroxide aqueous solution, the dehydration process under reduced pressure is relatively slow, so the process of combining aniline with tetramethylammonium hydroxide to form an aniline ion cannot be completed quickly, and a large amount of tetramethylammonium hydroxide which fails to participate in the reaction in time will decompose under the condition of reduced pressure reaction, thereby increasing the consumption of the condensation catalyst and the excess amount of nitrobenzene.
[0005] The decomposition of tetramethylammonium hydroxide generates trimethylamine, which is a toxic, flammable and fishy-smelling gas, and is one of the eight malodorous gases listed in the Malodorous Pollutant Discharge Standard, and cannot be directly discharged, which is also the reason why a series of complex tail gas treatment processes such as acid absorption and catalytic oxidation are required in the existing process.
[0006] In addition, the decomposition products of tetramethylammonium hydroxide also react with the reactants to generate a series of by-products such as N-methylaniline and N,N-dimethylaniline, which not only affect the quality of the condensation liquid, but also adversely affect the subsequent catalytic hydrogenation reaction. Therefore, it is of great significance for the production of RT-pesticides to develop a process method that can effectively control the decomposition consumption of the condensation catalyst and improve the condensation reaction efficiency SUMMARY
[0007] In order to make up for the shortcomings of the prior art, the present application provides a method for aniline-nitrophenol acid condensation reaction, which can effectively control the decomposition consumption of the condensation catalyst and improve the condensation reaction efficiency.
[0008] The present application is realized by the following technical solutions:
[0009] A method for aniline-nitrobenzene staged condensation reaction adopts a continuous condensation reaction form of a reaction kettle combination, and a plurality of reaction kettles are divided into two groups according to reaction requirements to form a two-stage reaction system, and specifically includes the following steps:
[0010] (1) Nitrobenzene, part of aniline and part of condensation catalyst are added to the first-stage reaction system, stirring is started, and dehydration reaction is carried out under heating and reduced pressure, and then the liquid is sent to the second-stage reaction system;
[0011] (2) The remaining aniline and condensation catalyst are added to the first reaction kettle of the second-stage reaction system, mixed with the liquid from the first-stage reaction system to continue the reaction, the temperature and vacuum degree are controlled, and a certain reaction time is maintained;
[0012] (3) The liquid reacted by the second-stage reaction system is transported to a condensation liquid storage tank, and is prepared to be sent to a hydrogenation section for catalytic hydrogenation reduction.
[0013] The present inventors have found through summarizing the existing aniline-nitrobenzene condensation reaction process technology that, regardless of whether an intermittent or continuous reaction form is adopted, and regardless of what type of reactor is used, aniline, condensation catalyst and nitrobenzene are all added to the reaction system at one time, and the slow process of dehydration combination of aniline and condensation catalyst to form aniline ions is ignored, and a large amount of aniline and condensation catalyst cannot quickly react and continuously stays in the system.
[0014] The present inventors have found through a large number of creative comparative verification experiments in the long-term research on aniline-nitrobenzene condensation reaction that quaternary ammonium base condensation catalysts will be decomposed more severely under the conditions of reduced pressure and heating in the reaction system for a long time, which is an important reason for the generation of trimethylamine, the increase of catalyst consumption and the initiation of condensation side reactions (generation of N-methylaniline and N,N-dimethylaniline).
[0015] The present application creatively develops a two-stage continuous condensation reaction process to specifically overcome the above problems, and the specific operation principle is as follows: a two-stage continuous reaction system is composed of multiple condensation reaction kettles in series and parallel combination, the condensation catalyst and aniline are proportionally distributed and respectively added into the two-stage reaction system according to the reaction characteristics, the storage amount of the condensation catalyst in the system at the initial stage of the reaction is reduced, the combination efficiency of aniline and the condensation catalyst and the condensation reaction efficiency of aniline ions and nitrobenzene are improved, and the decomposition of the condensation catalyst is inhibited. In addition, the segmented feeding reaction mode also improves the utilization rate of the reaction system, prolongs the effective residence time of the reaction materials in the reaction system, and improves the reaction effect.
[0016] The more preferred technical scheme of the present application is as follows:
[0017] The total number of the reaction kettles is 3-6, wherein the first-stage reaction system has 2-3 reaction kettles, and the second-stage reaction system has 1-3 reaction kettles.
[0018] Further preferably, in the first-stage reaction system, the reaction kettles are in series or parallel combination; when the number of the reaction kettles in the second-stage reaction system is more than or equal to 2, the reaction kettles are in series.
[0019] More preferably, in the first-stage reaction system, when the reaction kettles are in series, the nitrobenzene, aniline and condensation catalyst are all added into the first reaction kettle, and the liquid is sequentially flowed to the next reaction kettle after reaction in the kettle; when the reaction kettles are in parallel, the nitrobenzene, aniline and condensation catalyst are evenly distributed and added into each reaction kettle, and the liquid is collected and flowed into the second-stage reaction system after reaction in each reaction kettle.
[0020] In the second-stage reaction system, when the number of the reaction kettles is equal to or more than 2, the aniline and condensation catalyst are both added into the first reaction kettle.
[0021] Still more preferably, in the condensation reaction, the total mass ratio of the raw material aniline to nitrobenzene is 4-8, and the total molar ratio of the condensation catalyst to nitrobenzene is 1.05-1.5.
[0022] In step (1), the addition ratio of the aniline and condensation catalyst is 70-95% of the total addition amount; the reaction temperature is controlled to be 60-70℃, the pressure is controlled to be -0.09KPa to -0.065KPa, and the reaction time is 0.5-5h.
[0023] The condensation catalyst is tetramethylammonium hydroxide, and the addition form of the condensation catalyst is a tetramethylammonium hydroxide aqueous solution with a mass fraction of 20-35%.
[0024] In step (2), the feeding ratio of aniline and condensation catalyst is 5-30% of the total feeding amount, the reaction temperature is controlled at 65-80 DEG C, the pressure is controlled at -0.095 KPa to -0.07 KPa, and the reaction time is 0.5-5 h.
[0025] In step (3), the residual mass concentration of nitrobenzene in the condensation liquid after reaction is less than 0.1%.
[0026] The beneficial effects of the present application mainly include:
[0027] The two-stage continuous reaction system is formed by adopting the combined form of multiple condensation reaction kettles in series or parallel, the condensation catalyst and aniline are proportionally distributed and respectively fed into the two-stage reaction system according to the reaction characteristics, the accumulation and decomposition of the condensation catalyst in the reaction process are significantly inhibited, and the effective residence time of the reaction materials in the reaction system is improved.
[0028] The present application can effectively reduce the consumption of condensation catalyst, inhibit the occurrence of condensation side reactions, especially reduce the generation of N-methylaniline and N,N-dimethylaniline, reduce the generation of trimethylamine waste gas, and significantly increase the safety and economy of the process. DETAILED DESCRIPTION
[0029] In order to enable the personnel in the technical field to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below.
[0030] Example 1: A segmented condensation reaction method of aniline-nitrobenzene
[0031] The continuous condensation reaction form of 4 reaction kettles is adopted, the 4 reaction kettles are divided into two groups according to the reaction needs to form a two-stage reaction system, wherein the first-stage reaction system has 2 reaction kettles and adopts a series combination form, the second-stage reaction system also has 2 reaction kettles and also adopts a series combination form, and the specific steps include the following steps:
[0032] (1) 100 kg of nitrobenzene, 320 kg of aniline and 260.8 kg of 25% tetramethylammonium hydroxide aqueous solution are fed into the first reaction kettle in the first-stage reaction system, stirring is started, temperature is raised, and dehydration reaction is carried out under reduced pressure, the liquid flows to the next reaction kettle after staying and reacting in the first kettle, the temperature of the first-stage reaction system is controlled at 65 DEG C, the pressure is controlled at -0.085 MPa, the material stays and reacts in the stage for 2 h, and then is sent to the second-stage reaction system;
[0033] (2) adding 80 kg of aniline and 65.2 kg of a 25% mass concentration tetramethylammonium hydroxide aqueous solution into the first reactor of the second-stage reaction system, and mixing the solution with the feed liquid from the first-stage reaction system to continue the reaction, the feed liquid flows to the next reactor after being reacted in the first reactor, the temperature of the second-stage reaction system is controlled at 75°C, the pressure is controlled at -0.09 MPa, and the residence time of the material in the second-stage reaction system is 1.5 h;
[0034] (3) the feed liquid reacted in the second-stage reaction system is transported to a condensation liquid storage tank, and 574 kg of condensation liquid is obtained in total, which is ready to be sent to a hydrogenation section for catalytic hydrogenation reduction.
[0035] The aniline-containing aqueous phase discharged under reduced pressure in the condensation reaction process is condensed and collected, and 244 kg of aqueous phase is obtained in total; the tail gas generated in the condensation reaction process is completely absorbed by a hydrochloric acid solution.
[0036] The condensation reaction feed liquid and the aniline aqueous phase are sampled respectively, and analyzed by high performance liquid chromatography-external standard method. The analysis results show that the residual amount of nitrobenzene in the condensation liquid is 0.041%, the content of N-methylaniline is 0.011%, and the content of N,N-dimethylaniline is 0.003%; the nitrobenzene, N-methylaniline and N,N-dimethylaniline in the aniline aqueous phase are not detected. It is calculated that the reaction conversion rate of nitrobenzene is 99.76%, and the selectivity of the by-products N-methylaniline and N,N-dimethylaniline is 0.014% and 0.003% respectively (based on aniline). By measuring the content of trimethylamine hydrochloride in the hydrochloric acid absorption liquid, it is calculated that the decomposition rate of tetramethylammonium hydroxide in the reaction process is 0.012%.
[0037] The high performance liquid chromatography analysis method involved in the above example is as follows: mobile phase: methanol 0.56 mL / min, water 0.24 mL / min; detection wavelength: 254 nm; chromatographic column: VP-ODS C18 column (250 mm x 4.6 mm 5 μm).
[0038] Example 2: aniline-nitrobenzene segmented condensation reaction method
[0039] A continuous condensation reaction form of 4 reactors is used, the 4 reactors are divided into two groups according to the reaction needs, and constitute a two-stage reaction system, wherein the first-stage reaction system has 2 reactors, which are combined in parallel; the second-stage reaction system has 2 reactors, which are combined in series, and specifically includes the following steps:
[0040] (1) 100 kg of nitrobenzene, 320 kg of aniline and 260.8 kg of a 25% mass concentration tetramethylammonium hydroxide aqueous solution were evenly divided into two portions, which were added into two parallel reaction kettles in the first-stage reaction system, and stirring was started, and temperature was raised and vacuum dehydration reaction was carried out, the temperature and pressure of the reaction system were controlled in the same way as in Example 1, and the residence time of the material in the first-stage reaction system was 2 h, and then the material was collected and sent to the second-stage reaction system;
[0041] (2) The operation of the second-stage reaction system was the same as in Example 1.
[0042] (3) The material liquid after the reaction in the second-stage reaction system was transported to a condensation liquid storage tank, and 587 kg of condensation liquid was obtained, which was ready to be sent to the hydrogenation section for catalytic hydrogenation reduction.
[0043] The aniline-containing aqueous phase removed by vacuum dehydration in the condensation reaction process was condensed and collected, and 232 kg of aqueous phase was obtained; the tail gas generated in the condensation reaction process was completely absorbed by hydrochloric acid solution.
[0044] The condensation reaction material liquid and the aniline aqueous phase were sampled and analyzed by high performance liquid chromatography-external standard method. The analysis results showed that the residual amount of nitrobenzene in the condensation liquid was 0.038%, the content of N-methylaniline was 0.009%, and the content of N,N-dimethylaniline was 0.002%; the content of nitrobenzene in the aniline aqueous phase was 0.014%, and N-methylaniline and N,N-dimethylaniline were not detected. It was calculated that the reaction conversion rate of nitrobenzene was 99.74%, and the selectivity of by-products N-methylaniline and N,N-dimethylaniline was 0.011% and 0.002% respectively (based on aniline). By measuring the content of trimethylamine hydrochloride in the hydrochloric acid absorption liquid, it was calculated that the decomposition rate of tetramethylammonium hydroxide in the reaction process was 0.014%.
[0045] The high performance liquid chromatography analysis method involved in the above examples is the same as in Example 1.
[0046] Example 3: Aniline-nitrobenzene segmented condensation reaction method
[0047] A continuous condensation reaction form of 3 reaction kettles was used, and the 3 reaction kettles were divided into two groups according to the reaction needs, forming a two-stage reaction system, wherein the first-stage reaction system had 2 reaction kettles combined in series, and the second-stage reaction system had 1 reaction kettle, which specifically included the following steps:
[0048] (1) Put 100 kg of nitrobenzene, 420 kg of aniline and 282.8 kg of a tetramethylammonium hydroxide aqueous solution with a mass concentration of 22% into the first reactor in the first-stage reaction system, and the liquid flows into the next reactor after staying in the first reactor for reaction. The temperature of the first-stage reaction system is controlled at 70°C, the pressure is controlled at -0.088 MPa, and the residence time of the material in the first-stage reaction system is 2.5 h. Then, the material is sent to the second-stage reaction system.
[0049] (2) Put 180 kg of aniline and 121.2 kg of a tetramethylammonium hydroxide aqueous solution with a mass concentration of 22% into the first reactor in the second-stage reaction system, and mix the liquid with the liquid from the first-stage reaction system for continuous reaction. The temperature of the reaction system is controlled at 78°C, the pressure is controlled at -0.093 MPa, and the residence time of the material in the second-stage reaction system is 1 h.
[0050] (3) The liquid reacted in the second-stage reaction system is transported to a condensation liquid storage tank, and 825 kg of condensation liquid is obtained, which is ready to be sent to the hydrogenation section for catalytic hydrogenation reduction.
[0051] The aniline-containing aqueous phase discharged under reduced pressure in the condensation reaction process is condensed and collected, and 271 kg of aqueous phase is obtained. The tail gas generated in the condensation reaction process is completely absorbed by a hydrochloric acid solution.
[0052] The condensation reaction liquid and the aniline aqueous phase are sampled and analyzed by high performance liquid chromatography-external standard method. The analysis results show that the residual amount of nitrobenzene in the condensation liquid is 0.023%, the content of N-methylaniline is 0.008%, and N,N-dimethylaniline is not detected; the content of nitrobenzene in the aniline aqueous phase is 0.011%, and N-methylaniline and N,N-dimethylaniline are not detected. It is calculated that the reaction conversion rate of nitrobenzene is 99.78%, and the selectivity of the byproduct N-methylaniline is 0.011% (based on aniline). By measuring the content of trimethylamine hydrochloride in the hydrochloric acid absorption liquid, it is calculated that the decomposition rate of tetramethylammonium hydroxide in the reaction process is 0.019%.
[0053] The high performance liquid chromatography analysis method involved in the above example is the same as that in Example 1.
[0054] Example 4: A segmented condensation reaction method of aniline-nitrobenzene
[0055] A continuous condensation reaction form of three reactors is used, and the three reactors are divided into two groups according to the reaction needs to form a two-stage reaction system. The first-stage reaction system has two reactors combined in parallel, and the second-stage reaction system has one reactor, which specifically includes the following steps:
[0056] (1) 100 kg of nitrobenzene, 420 kg of aniline and 282.8 kg of a 22% mass concentration tetramethylammonium hydroxide aqueous solution were evenly divided into two portions, which were added into two parallel reaction kettles in the first-stage reaction system, and stirring was started, and temperature was raised and dehydration reaction was carried out under reduced pressure. The temperature and pressure control of the first-stage reaction system was completely consistent with that of Example 3. The residence time of the material in the first-stage reaction system was 2.5 h, and then the material was collected and sent to the second-stage reaction system.
[0057] (2) The operation of the second-stage reaction system was completely consistent with that of Example 3.
[0058] (3) The material liquid after the reaction in the second-stage reaction system was transported to a condensation liquid storage tank, and a total of 812 kg of condensation liquid was obtained, which was ready to be sent to the hydrogenation section for catalytic hydrogenation reduction.
[0059] The aniline-containing aqueous phase discharged under reduced pressure during the condensation reaction was collected by condensation, and a total of 285 kg of aqueous phase was obtained. The tail gas generated during the condensation reaction was completely absorbed by a hydrochloric acid solution.
[0060] The condensation reaction material liquid and the aniline aqueous phase were sampled and analyzed by high performance liquid chromatography-external standard method. The analysis results showed that the residual amount of nitrobenzene in the condensation liquid was 0.026%, the content of N-methylaniline was 0.022%, and N,N-dimethylaniline was not detected; the content of nitrobenzene in the aniline aqueous phase was 0.010%, and N-methylaniline and N,N-dimethylaniline were not detected. It was calculated that the reaction conversion rate of nitrobenzene was 99.76%, and the selectivity of the by-product N-methylaniline was 0.012% (based on aniline). By measuring the content of trimethylamine hydrochloride in the hydrochloric acid absorption liquid, it was calculated that the decomposition rate of tetramethylammonium hydroxide during the reaction was 0.023%.
[0061] The high performance liquid chromatography analysis method involved in the above examples is the same as that of Example 1.
[0062] Example 5 (Comparative Example 1):
[0063] The same reactor form as that of Example 1 was used, i.e., a reaction system formed by four reaction kettles connected in series, which specifically included the following steps:
[0064] 100 kg of nitrobenzene, 400 kg of aniline and 326 kg of a 25% mass concentration tetramethylammonium hydroxide aqueous solution were added into the first reaction kettle, stirring was started, and temperature was raised and dehydration reaction was carried out under reduced pressure. The material liquid flowed into the next reaction kettle in turn after the reaction in the kettle.
[0065] The temperature of the first and second reactors is controlled at 65°C, the pressure is controlled at -0.085 MPa, and the residence time of the material in the first and second reactors is 2 h; the temperature of the third and fourth reactors is controlled at 75°C, the pressure is controlled at -0.09 MPa, and the residence time of the material in the third and fourth reactors is 1.5 h.
[0066] After the reaction is completed, the material is transported to a condensation liquid storage tank, and a total of 584 kg of condensation liquid is obtained, which is ready to be sent to a hydrogenation section for catalytic hydrogenation reduction.
[0067] The aniline-containing water phase that is removed by vacuum during the condensation reaction is condensed and collected, and a total of 238 kg of water phase is obtained; the tail gas generated during the condensation reaction is completely absorbed by a hydrochloric acid solution.
[0068] The condensation reaction material and the aniline water phase are sampled and analyzed by high performance liquid chromatography-external standard method. The analysis results show that the residual amount of nitrobenzene in the condensation liquid is 0.435%, the content of N-methylaniline is 0.122%, and the content of N,N-dimethylaniline is 0.029%; the contents of nitrobenzene, N-methylaniline and N,N-dimethylaniline in the aniline water phase are all not detected. It is calculated that the reaction conversion rate of nitrobenzene is 97.43%, and the selectivities of the by-products N-methylaniline and N,N-dimethylaniline are 0.155% and 0.033% respectively (based on aniline). By measuring the content of trimethylamine hydrochloride in the hydrochloric acid absorption liquid, it is calculated that the decomposition rate of tetramethylammonium hydroxide in the reaction process is 0.320%.
[0069] The high performance liquid chromatography analysis method involved in the above examples is the same as that in Example 1.
[0070] Example 6 (Comparative Example 2):
[0071] The condensation reactor in the above example is in the form of a single reactor, which specifically includes the following steps:
[0072] 100 kg of nitrobenzene, 400 kg of aniline and 326 kg of tetramethylammonium hydroxide aqueous solution with a mass concentration of 25% are added to the reactor, stirring is started, and dehydration reaction is carried out under heating and reduced pressure, the reaction temperature is controlled at 75°C, the pressure is controlled at -0.90 MPa, and the residence time of the material in the reactor is 3.5 h.
[0073] After the reaction is completed, the material is transported to a condensation liquid storage tank, and a total of 595 kg of condensation liquid is obtained, which is ready to be sent to a hydrogenation section for catalytic hydrogenation reduction.
[0074] The aniline-containing water phase that is removed by vacuum during the condensation reaction is condensed and collected, and a total of 224 kg of water phase is obtained; the tail gas generated during the condensation reaction is completely absorbed by a hydrochloric acid solution.
[0075] The condensation reaction liquid and the aniline aqueous phase were sampled respectively, and analyzed by using high performance liquid chromatography-external standard method. The analysis results show that the residual amount of nitrobenzene in the condensation liquid is 0.615%, the content of N-methylaniline is 0.235%, and the content of N,N-dimethylaniline is 0.038%; the contents of nitrobenzene, N-methylaniline and N,N-dimethylaniline in the aniline aqueous phase are all not detected. It is calculated that the reaction conversion rate of nitrobenzene is 96.07%, and the selectivities of the by-products N-methylaniline and N,N-dimethylaniline are 0.304% and 0.043% respectively (based on aniline). By measuring the content of trimethylamine hydrochloride in the hydrochloric acid absorption liquid, it is calculated that the decomposition rate of tetramethylammonium hydroxide in the reaction process is 0.475%.
[0076] The high performance liquid chromatography analysis method involved in the above examples is the same as that in Example 1.
[0077] Example 7 (Comparative Example 3):
[0078] The same reactor form as that in Example 6 is used, i.e. a single reaction kettle, which specifically comprises the following steps:
[0079] 100 kg of nitrobenzene, 600 kg of aniline and 404 kg of tetramethylammonium hydroxide aqueous solution with a mass concentration of 22% are all added into the reaction kettle, stirring is started, and the reaction is carried out under the conditions of temperature control at 75°C and pressure control at -0.90 MPa, and the residence time of the materials in the kettle is 5 h.
[0080] After the reaction is completed, the liquid is transported to a condensation liquid storage tank, and a total of 806 kg of condensation liquid is obtained, which is ready to be sent to a hydrogenation section for catalytic hydrogenation reduction.
[0081] The aniline-containing aqueous phase discharged under reduced pressure in the condensation reaction process is collected by condensation, and a total of 288 kg of aqueous phase is obtained; the tail gas generated in the condensation reaction process is completely absorbed by a hydrochloric acid solution.
[0082] The condensation reaction liquid and the aniline aqueous phase are sampled respectively, and analyzed by using high performance liquid chromatography-external standard method. The analysis results show that the residual amount of nitrobenzene in the condensation liquid is 0.465%, the content of N-methylaniline is 0.267%, and the content of N,N-dimethylaniline is 0.045%; the contents of nitrobenzene, N-methylaniline and N,N-dimethylaniline in the aniline aqueous phase are all not detected. It is calculated that the reaction conversion rate of nitrobenzene is 96.15%, and the selectivities of the by-products N-methylaniline and N,N-dimethylaniline are 0.312% and 0.046% respectively (based on aniline). By measuring the content of trimethylamine hydrochloride in the hydrochloric acid absorption liquid, it is calculated that the decomposition rate of tetramethylammonium hydroxide in the reaction process is 0.592%.
[0083] The high performance liquid chromatography analysis method involved in the above examples is the same as that of Example 1.
[0084] Example 8: Condensation liquid catalytic hydrogenation reaction verification experiment 1
[0085] The condensation liquids prepared in Examples 1, 5, 6, and 7 are used as raw liquid, respectively, and are denoted as S1, S5, S6, and S7. The hydrogenation reaction of different condensation liquids is evaluated under the same catalytic hydrogenation reaction conditions.
[0086] The specific catalytic hydrogenation reaction operation is as follows: 400 g of condensation liquid, 160 g of methanol, and 10 g of Raney nickel catalyst are added to a 1 L 316L stainless steel high-pressure reactor equipped with an internal filter, and the reactor is replaced with nitrogen for 4 times and then hydrogen is introduced until the reaction pressure is reached. The reaction temperature is controlled at 75-80°C, the reaction hydrogen pressure is 1.4-1.6 MPa, and the stirring speed is 600 rpm. The reaction is considered to be completed when there is no hydrogen absorption. After the reaction is completed, the liquid is filtered and discharged, and the catalyst remains in the reactor. The reaction liquid and solvent are added again, and the reaction is carried out again after nitrogen replacement. The catalyst is evaluated by the above operation, and the influence of different condensation raw liquids on the stability of the hydrogenation catalyst is evaluated. The hydrogenation liquid is analyzed by the high performance liquid chromatography analysis method in Example 1, and the total conversion rate x of 4-nitrodiphenylamine and 4-nitrosodiphenylamine is calculated.
[0087]
[0088] From the above analysis results, it can be seen that the condensation liquids S1 and S5 prepared by Examples 1 and 5 are used as hydrogenation raw liquid, and the catalyst is continuously used for 10 times, the reaction time changes little, and 4-nitrodiphenylamine and 4-nitrosodiphenylamine can be completely converted, which shows that the stability of the catalyst is good when S1 and S5 are used as hydrogenation raw liquid. As a comparison, when the condensation liquids S6 and S7 prepared by Examples 6 and 7 are used as hydrogenation raw liquid, the catalyst is continuously used for 10 times, the reaction time is significantly prolonged with the increase of the number of catalyst use, and 4-nitrodiphenylamine and 4-nitrosodiphenylamine cannot be completely converted from the 4th use experiment, and the residual amount gradually increases, which shows that the catalyst activity is obviously deteriorated. Therefore, it can be preliminarily judged that the condensation liquid prepared by the step-by-step condensation reaction scheme has no adverse effect on the subsequent hydrogenation reaction, while the condensation liquid prepared by the traditional condensation reaction method has a certain degree of adverse effect on the subsequent hydrogenation reaction.
[0089] Example 9: Condensation liquid catalytic hydrogenation reaction verification experiment 2
[0090] The reagent grade aniline, 4-nitro diphenylamine, 4-nitroso diphenylamine, tetramethyl ammonium hydroxide are used to prepare the simulated condensation liquid, the specific formula is as follows: 10 kg of aniline, 2 kg of 4-nitro diphenylamine, 0.4 kg of 4-nitroso diphenylamine, 1 kg of tetramethyl ammonium hydroxide. The simulated condensation liquid is marked as S0. 5 kg of S0 is taken, and 0.5% and 0.05% of N-methyl aniline and N,N-dimethyl aniline are added, which is marked as SN.
[0091] S0 and SN are used as raw material liquid respectively, and the hydrogenation reaction conditions are evaluated under the same catalytic hydrogenation reaction conditions. The specific catalytic hydrogenation reaction operation is the same as that in Example 8. The hydrogenation liquid is analyzed by the high performance liquid chromatography analysis method in Example 1, and the total conversion rate x of the raw materials 4-nitro diphenylamine and 4-nitroso diphenylamine is calculated, and the results are as follows.
[0092]
[0093] From the above analysis results, it can be seen that when S0 is used as the hydrogenation raw material liquid, the catalyst is continuously used for 10 times, and the reaction time does not change significantly, and the 4-nitro diphenylamine and 4-nitroso diphenylamine can be completely converted, which shows that the stability of the catalyst is good. As a comparison, when SN is used as the hydrogenation raw material liquid, the catalyst is continuously used for 10 times, and the reaction time is significantly prolonged with the increase of the catalyst use times, and the 4-nitro diphenylamine and 4-nitroso diphenylamine cannot be completely converted from the second use experiment, and the residual amount gradually increases, which shows that the catalyst activity is obviously deteriorated. Therefore, it can be verified that N-methyl aniline and N,N-dimethyl aniline in the condensation liquid have an adverse effect on the hydrogenation reaction, and are the main reason for the deterioration of the catalyst activity. Therefore, it can be shown that the condensation liquid prepared by the segmented condensation reaction scheme has low content of impurities such as N-methyl aniline and N,N-dimethyl aniline, which can effectively prolong the service life of the hydrogenation catalyst.
[0094] Obviously, the above described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should belong to the protection scope of the present application.
Claims
1. A method for a segmental condensation reaction of aniline-nitrobenzene, characterized in that: The reaction employs a continuous condensation reaction using a combination of reactors. Several reactors are divided into two groups according to reaction requirements, forming a two-stage reaction system. The specific steps include: (1) Nitrobenzene, some aniline and some condensation catalyst are added to the first stage reaction system, stirring is started, the temperature is increased and the dehydration reaction is carried out under reduced pressure, and then the liquid is sent to the second stage reaction system. The ratio of aniline to condensation catalyst is 70-95% of the total dosage; the reaction temperature is controlled at 60-70℃, the pressure is controlled at -0.09KPa to -0.065KPa, and the reaction time is 0.5-5h. The condensation catalyst is tetramethylammonium hydroxide; (2) Add the remaining aniline and condensation catalyst to the first reactor of the second stage reaction system, mix with the feed liquid from the first stage reaction system and continue the reaction; The ratio of aniline to condensation catalyst is 5-30% of the total dosage. The reaction temperature is controlled at 65-80℃, the pressure is controlled at -0.095KPa to -0.07KPa, and the reaction time is 0.5-5h. (3) The liquid material after the reaction in the second stage reaction system is transported to the condensate storage tank, ready to be sent to the hydrogenation section for catalytic hydrogenation reduction; The mass concentration of nitrobenzene in the condensation solution after the reaction is completed is less than 0.1%.
2. The method for the aniline-nitrobenzene segmental condensation reaction as described in claim 1, characterized in that: The total number of reactor units is 3-6, of which 2-3 are in the first stage reaction system and 1-3 are in the second stage reaction system.
3. The method for the aniline-nitrobenzene segmental condensation reaction as described in claim 1 or 2, characterized in that: In the first stage of the reaction system, the reactors are connected in series or in parallel; in the second stage of the reaction system, when there are two or more reactors, the reactors are connected in series.
4. The method for the aniline-nitrobenzene segmental condensation reaction as described in claim 1, characterized in that: In the condensation reaction, the total mass ratio of aniline to nitrobenzene is 4-8, and the total molar ratio of condensation catalyst to nitrobenzene is 1.05-1.
5.
5. The method for the aniline-nitrobenzene segmental condensation reaction as described in claim 1, characterized in that: In step (1), the condensation catalyst is added in the form of a tetramethylammonium hydroxide aqueous solution with a mass fraction of 20-35%.
6. The method for the aniline-nitrobenzene segmental condensation reaction as described in claim 3, characterized in that: In the first stage reaction system, when the reactors are connected in series, nitrobenzene, aniline, and condensation catalyst are all added to the first reactor. After the liquid reacts in the reactor, it flows sequentially to the next reactor. When the reactors are connected in parallel, nitrobenzene, aniline, and condensation catalyst are evenly distributed and added to each reactor. After the liquid reacts in each reactor, it is collected and flows into the second stage reaction system.
7. The method for the aniline-nitrobenzene segmental condensation reaction as described in claim 1, characterized in that: In step (2), when the number of reactors in the second stage reaction system is equal to or greater than 2, aniline and condensation catalyst are both added to the first reactor.
Citation Information
Patent Citations
Device and process for producing 4-aminodiphenylamine by catalytic hydrogenation
CN103864626A