Continuous diazotization process and device for dye preparation

Abstract

The invention relates to a continuous diazotization process for dye, and belongs to the field of chemical engineering. The method comprises the following steps: mixing and pulping a diazo component and sulfuric acid, pumping into a material preparation kettle, sequentially feeding into a reactor I and a reactor II together with a nitrosyl sulfuric acid solution according to a certain proportion, reacting, feeding one part of effluent of the reactor I into the reactor II, continuing reacting, and finally feeding into a product receiving kettle, and the other part enters a cooler to be cooled, is mixed with diazonium components, namely sulfate and nitrous acid sulfuric acid, and returns to the reaction system through a circulating pump. According to the technical scheme provided by the invention, the intrinsic safety of diazotization reaction is greatly improved, automatic control is adopted in the whole process, different acidity, acid amount and temperature are adopted according to different diazonium components, the stability of diazonium salt is ensured, the reaction speed is ensured to be in a proper range, slurry is homogenized and emulsified by an emulsification pump without layering, and the stability of the diazonium salt is ensured. And meanwhile, the reaction speed is increased, and the purpose of continuous diazotization is achieved.

Description

Technical Field

[0001] The invention relates to the field of chemical industry, and more specifically to a continuous diazotization process and device for dye preparation. Background Art

[0002] The diazotization process is a reaction in which primary amines react with nitrous acid at low temperature to generate diazonium salts, such as aliphatic, aromatic and heterocyclic primary amines. The process involving diazotization is the diazotization process. Although the diazotization reaction is an ancient reaction, its products are important reagents and intermediates for organic synthesis and are widely used in fine chemical fields such as biomedicine. More than half of organic synthetic dyes are synthesized by the diazotization process.

[0003] Usually, the diazotizing agent is prepared temporarily by reacting sodium nitrite with hydrochloric acid. In addition to hydrochloric acid, inorganic acids such as sulfuric acid, perchloric acid and fluoroboric acid can also be used. Aliphatic diazonium salts are very unstable and can spontaneously decompose rapidly even at low temperatures, while aromatic diazonium salts are relatively stable.

[0004] Typical diazotization processes include the cis-addition method, the copper sulfate catalyst method, the salting-out method, and the nitrosylsulfuric acid method. The nitrosylsulfuric acid method replaces sodium nitrite with nitrosylsulfuric acid and is mainly used for the diazo reaction of disperse dyes, which can reduce costs and improve product quality. The dye industry often uses 2-cyano-4-nitroaniline, 2-cyano-4-nitro-6-bromoaniline, 2,4-dinitro-6-bromoaniline, 2,6-dibromo-4-nitroaniline and 2,4-dinitro-6-chloroaniline as diazo components and terminal amino-containing ether-containing coupling components to form monoazo disperse dyes through diazotization and coupling. For example, 2,4-dinitro-6-chloroaniline can be used as a raw material to prepare blue disperse dyes.

[0005] In the batch production of Blue 79, the diazotization reaction uses 2,4-dinitro-6-chloroaniline as the diazo component, concentrated sulfuric acid and nitrosyl sulfuric acid are first mixed, and 2,4-dinitro-6-chloroaniline powder is slowly added to carry out the diazotization reaction. The diazotization reaction is a liquid-solid reaction, and the reaction is greatly affected by liquid-solid mass transfer. Due to the high density and viscosity of the mixed liquid of concentrated sulfuric acid and nitrosyl sulfuric acid, 2,4-dinitro-6-chloroaniline powder is not easy to disperse evenly, and it is easy to form small agglomerates, the slurry is uneven, and the reaction speed is slow, so the reaction time is long, about 3~4h, and at the same time, due to the large heat release of the reaction, in order to maintain the appropriate temperature, a long feeding time is required, about 4~6h, so each batch operation takes about 7~10h, the efficiency is low, the temperature changes significantly during the feeding process, it is difficult to control, and the reaction risk is high. Summary of the invention

[0006] In view of the problems existing in the prior art, the object of the present invention is to provide a continuous diazotization process and device for dyes with fast reaction speed, stable reaction, intrinsic safety and uniform slurry.

[0007] To solve the above problems, the present invention adopts the following technical solutions.

[0008] A continuous diazotization process for dyes, comprising the following steps: S1: premix the diazo component and sulfuric acid in a batching kettle according to the mass ratio, and circulate the mixing in the batching kettle up and down, mix into a uniform diazo component sulfate slurry through beating and emulsification, and then pump it into the preparation kettle; S2: Add the prepared diazonium salt solution (diazo liquid) in advance as the base material into the reactor 1, start the circulation pump and cooling system, and set the interlocking temperature; S3: According to the molar ratio of the diazo component to nitrosyl sulfuric acid in the diazo component sulfate, the diazo component sulfate and nitrosyl sulfuric acid are pumped into the system through respective metering pumps for diazotization reaction, and the mixed solution passes through the reactor 1 and then splits, with one part entering the reactor 2 for final reaction to obtain the desired product and entering the product receiving kettle, and the other part entering the cooler for cooling and mixing with the diazo component sulfate and nitrosyl sulfuric acid and then entering the reactor 1 through the circulation pump to realize circulation; S4: The temperature of the reaction liquid in the reactor (reactor 1 / reactor 2) is controlled at 20-40°C. Different reaction temperatures are selected according to different diazonium salts, and the temperature is controlled using frozen brine.

[0009] Furthermore, in the step S1, 40-98% sulfuric acid is selected as the sulfuric acid, and different acidities are selected according to different diazo components. For example, when the diazo component is 6-chloro-2,4-dinitroaniline, 98% concentrated sulfuric acid can be used; when 4-nitroaniline is selected, 60% sulfuric acid is used.

[0010] Furthermore, in step S1, the mass ratio of the diazo component to sulfuric acid is 1:0.8-4, and different amounts of acid are selected according to different diazo components.

[0011] Furthermore, in the step S2, the molar ratio of the diazo component to nitrosyl sulfuric acid is 1:0.95-1.1.

[0012] Furthermore, the reaction solution is cooled and mixed with the diazo component sulfate and nitrosyl sulfuric acid and then returned to the reaction system to keep the system temperature stable. The system uses low-temperature frozen brine as a cooling medium.

[0013] Furthermore, the diazonium salt solution before pulping and emulsification into the emulsification pump in step S1 needs to be filtered before entering the emulsification pump, and after one round of emulsification cycle, it is pumped into the preparation kettle.

[0014] Furthermore, the reaction time of the mixed solution in the reactor 1 in step S3 is about 0.9 h, and the reaction time of the mixed solution in the reactor 2 in step S3 is about 0.2 h.

[0015] Furthermore, in step S3, the reaction time of the mixed solution in reactor one is 0.5 to 1.5 h, and in step S5, the reaction time of the mixed solution in reactor two is 0.1 to 0.5 h.

[0016] A continuous diazotization device for dye preparation, comprising a batching kettle, a material preparation kettle, a reactor 1, a cooler, a reactor 2 and a product receiving kettle arranged in the order of a diazotization reaction; The batching kettle is used for mixing and preparing the diazo component sulfate, and the discharge end of the batching kettle is connected to the feed end of the pump; The discharge end of the material preparation kettle is connected to a precision metering pump, and the feed end of the material preparation kettle is connected to the discharge end of the pump; The discharge end of the precision metering pump 1 is also mixed with a precision metering pump 2, and the precision metering pump 2 is used to introduce nitrosyl sulfuric acid; The discharge ends of precision metering pump 1 and precision metering pump 2 are connected to reactor 1 through the feed end of the circulation pump, one end of reactor 1 is connected to the feed end of the circulation pump through a cooler, and the other end is connected to the feed end of reactor 2, and the discharge end of reactor 2 is connected to the product receiving kettle.

[0017] Furthermore, the reactor 1 uses low-temperature frozen brine to control the temperature through jacket heat exchange, the reactor 2 uses jacket heat exchange to control the temperature, and the cooler uses tube heat exchange to cool down, and the system temperature is controlled to be 20-40°C, preferably 25-30°C.

[0018] Furthermore, in the step S2, the circulation pump is activated during the filling of the diazo liquid to promote gas discharge.

[0019] Furthermore, the first reactor is a loop reactor, and the second reactor is a tower reactor, and the liquid-solid reaction is completed by connecting the two reactors in series.

[0020] Furthermore, the circulation flow rate of the circulation pump is 10-17 times the total flow rate of the precision metering pump 1 and the precision metering pump 2.

[0021] Furthermore, when it is necessary to reduce the system resistance, the temperature can be increased to reduce the viscosity of the feed liquid.

[0022] Furthermore, when it is necessary to reduce the system resistance, the injection speed of the loop reactor nozzle can be reduced.

[0023] Compared with the prior art, the advantages of the present invention are: (1) The present invention adopts a loop reactor and a tower reactor in series, which greatly reduces the total residence time, i.e., the reaction time, and greatly improves the intrinsic safety of the diazotization reaction. The whole process adopts automatic control, and different acidities, acid amounts, and temperatures are used for the reaction according to different diazo components, which not only ensures the stability of the diazonium salt, but also ensures that the reaction speed is within an appropriate range. The slurry is homogenized and emulsified by an emulsifying pump, the slurry is not stratified, the fluidity is improved, and it is not easy to form small particles. At the same time, the reaction speed is accelerated to achieve the purpose of continuous diazotization; (2) The present invention mixes 6-chloro-2,4-dinitroaniline and sulfuric acid in a ratio required for the reaction, and performs pulping and emulsification for a short time, so that the slurry is pre-pulped and emulsified uniformly, the slurry is not separated for a long time, and the fluidity of the slurry is improved; (3) The slurry used in the present invention reacts with nitrosyl sulfuric acid, and the reaction rate is significantly accelerated; (4) The diazo liquid used in the present invention is stable and can be stored for a long time and repeatedly used at a certain temperature without obvious side reactions. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is the continuous diazotization flow chart of the present invention; DETAILED DESCRIPTION

[0025] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0026] Embodiment 1:

[0027] See also Figure 1 , a continuous diazotization process for dyes, comprising the following steps: S1. 404 kg of 6-chloro-2,4-dinitroaniline as a diazo component and 505 kg of 98% concentrated sulfuric acid are emulsified in a batching kettle to form hexachlorosulfate, and the hexachlorosulfate is circulated by a pump to be more fully emulsified; S2. adding hexachlorosulfate to the preparation kettle; S3. Pour the prepared diazo solution into the reactor 1, start the circulation pump halfway through the diazo solution filling process to promote gas discharge, and keep the circulation flow rate stable at 10-14m³ / h; S4. Use two precision metering pumps to deliver the slurry, namely precision metering pump 1 and precision metering pump 2. First, start precision metering pump 2 to deliver nitrosyl sulfuric acid, with a flow rate of 310L / h, and then start precision metering pump 1 to deliver hexachlorosulfate. The control coefficient of the two is 1:2.06; The mixed liquid enters reactor one through a circulation pump. After a preliminary reaction of about 0.9 hours, the reaction liquid is discharged from the top of reactor one and returns to the feed end of the circulation pump through a cooler for continuous circulation. The mixed liquid enters reactor two and is further reacted for about 0.2 hours before being discharged from the top of reactor two. The two reactors are connected in series to complete the liquid-solid reaction. Reactor one uses low-temperature frozen brine to control the temperature through jacket heat exchange, and reactor two uses jacket heat exchange to control the temperature, and the system temperature is 25-30°C.

[0028] Embodiment 2:

[0029] S1. 550 kg of 2,6-dibromo-4-nitroaniline as a diazo component and 825 kg of 98% concentrated sulfuric acid are emulsified in a batching kettle to form dibromosulfate, and the dibromosulfate is circulated by a pump to be more fully emulsified; S2. Add dibromosulfate to the preparation kettle; S3. Pour the prepared diazo solution into the reactor 1, start the circulation pump halfway through the diazo solution filling process to promote gas discharge, and stabilize the circulation flow rate at 13-18m³ / h; S4. Use two precision metering pumps to transport the slurry, namely precision metering pump 1 and precision metering pump 2. First, start precision metering pump 2 to transport nitrosyl sulfuric acid, with a flow rate of 310L / h, and then start precision metering pump 1 to transport dibromosulfate. The control coefficient of the two is 1:2.95; The mixed liquid enters reactor one through a circulation pump. After a preliminary reaction of about 0.7 hours, the reaction liquid is discharged from the top of reactor one and returns to the feed end of the circulation pump through a cooler for continuous circulation. The mixed liquid enters reactor two and is further reacted for about 0.17 hours before being discharged from the top of reactor two. The two reactors are connected in series to complete the liquid-solid reaction. Reactor one uses low-temperature frozen brine to control the temperature through jacket heat exchange, and reactor two uses jacket heat exchange to control the temperature, and the system temperature is 25-30°C.

[0030] Embodiment 3:

[0031] S1. 487 kg of 6-bromo-2,4-dinitroaniline as a diazo component and 633 kg of 98% concentrated sulfuric acid are emulsified in a batching kettle to form hexabromosulfate, and the hexabromosulfate is circulated by a pump to be more fully emulsified; S2. Hexabromosulfate is added into the preparation kettle; S3. Pour the prepared diazo solution into the reactor 1, start the circulation pump halfway through the diazo solution filling process to promote gas discharge, and keep the circulation flow rate stable at 10-14m³ / h; S4. Use two precision metering pumps to deliver the slurry, namely precision metering pump 1 and precision metering pump 2. First, start precision metering pump 2 to deliver nitrosyl sulfuric acid, with a flow rate of 310L / h, and then start precision metering pump 1 to deliver hexabromosulfate. The control coefficient of the two is 1:2.23; The mixed liquid enters reactor one through a circulation pump. After a preliminary reaction of about 0.85 hours, the reaction liquid is discharged from the top of reactor one and returns to the feed end of the circulation pump through a cooler for continuous circulation. The mixed liquid enters reactor two and is discharged from the top of reactor two after further reaction of about 0.2 hours. The two reactors are connected in series to complete the liquid-solid reaction. Reactor one uses low-temperature frozen brine to control the temperature through jacket heat exchange, and reactor two uses jacket heat exchange to control the temperature. The system temperature is 25-30°C.

[0032] Embodiment 4:

[0033] S1. 256 kg of 4-nitroaniline as a diazo component and 427 kg of 60% sulfuric acid are emulsified in a batching kettle to form nitrosulfate, and the nitrosulfate is more fully emulsified by circulating the pump; S2. adding nitrosulfate to the preparation kettle; S3. Pour the prepared diazo solution into the reactor 1, start the circulation pump halfway through the diazo solution filling process to promote gas discharge, and keep the circulation flow rate stable at 10-14m³ / h; S4. Use two precision metering pumps to transport the slurry, namely precision metering pump 1 and precision metering pump 2. First, start precision metering pump 2 to transport nitrosyl sulfuric acid, with a flow rate of 350L / h, and then start precision metering pump 1 to transport para-nitrosulfate. The control coefficient of the two is 1:1.85; The mixed liquid enters reactor one through a circulation pump. After a preliminary reaction of about 0.6 hours, the reaction liquid is discharged from the top of reactor one and returns to the feed end of the circulation pump through a cooler for continuous circulation. The mixed liquid enters reactor two and is discharged from the top of reactor two after further reaction of about 0.1 hours. The two reactors are connected in series to complete the liquid-solid reaction. Reactor one uses low-temperature frozen brine to control the temperature through jacket heat exchange, and reactor two uses jacket heat exchange to control the temperature. The system temperature is 20-25°C.

[0034] Embodiment 5:

[0035] S1. 338 kg of 2,4-dinitroaniline as a diazo component and 525 kg of 90% sulfuric acid are emulsified in a batching kettle to form dinitrosulfate, and the dinitrosulfate is circulated by a pump to be more fully emulsified; S2. Add dinitrosulfate to the preparation kettle; S3. Pour the prepared diazo solution into the reactor 1, start the circulation pump halfway through the diazo solution filling process to promote gas discharge, and keep the circulation flow rate stable at 10-14m³ / h; S4. Use two precision metering pumps to transport the slurry, namely precision metering pump 1 and precision metering pump 2. First, start precision metering pump 2 to transport nitrosyl sulfuric acid, with a flow rate of 280L / h, and then start precision metering pump 1 to transport dinitrosulfate. The control coefficient of the two is 1:2.18; The mixed liquid enters reactor one through a circulation pump. After a preliminary reaction of about 0.9 hours, the reaction liquid is discharged from the top of reactor one and returns to the feed end of the circulation pump through a cooler for continuous circulation. The mixed liquid enters reactor two and is discharged from the top of reactor two after further reaction of about 0.2 hours. The two reactors are connected in series to complete the liquid-solid reaction. Reactor one uses low-temperature frozen brine to control the temperature through jacket heat exchange, and reactor two uses jacket heat exchange to control the temperature. The system temperature is 20-25°C.

[0036] Embodiment 6:

[0037] S1. 320 kg of 2-chloro-4-nitroaniline as a diazo component and 961 kg of 98% concentrated sulfuric acid are emulsified in a batching kettle to form o-chlorosulfate, and the o-chlorosulfate is more fully emulsified by circulating a pump; S2. o-chlorosulfate is added to the preparation kettle; S3. Pour the prepared diazo solution into the reactor 1, start the circulation pump halfway to promote gas discharge, and keep the circulation flow rate stable at 10-14m 3 / h; S4. Use two precision metering pumps to transport the slurry, namely precision metering pump 1 and precision metering pump 2. First, start precision metering pump 2 to transport nitrosyl sulfuric acid, with a flow rate of 290L / h, and then start precision metering pump 1 to transport o-chlorosulfate. The control coefficient of the two is 1:2.3; The mixed liquid enters reactor one through a circulation pump. After a preliminary reaction of about 0.9 hours, the reaction liquid is discharged from the top of reactor one and returns to the feed end of the circulation pump through a cooler for continuous circulation. The mixed liquid enters reactor two and is further reacted for about 0.2 hours before being discharged from the top of reactor two. The two reactors are connected in series to complete the liquid-solid reaction. Reactor one uses low-temperature frozen brine to control the temperature through jacket heat exchange, and reactor two uses jacket heat exchange to control the temperature, and the system temperature is 25-30°C.

[0038] Embodiment 7:

[0039] S1. 384 kg of 2,6-chloro-4-nitroaniline as a diazo component and 461 kg of 98% concentrated sulfuric acid are emulsified in a batching kettle to form dichlorosulfate, and the dichlorosulfate is more fully emulsified by circulating a pump; S2. adding dichlorosulfate to the preparation kettle; S3. Pour the prepared diazo solution into the reactor 1, start the circulation pump halfway through the diazo solution filling process to promote gas discharge, and keep the circulation flow rate stable at 10-14m³ / h; S4. Use two precision metering pumps to transport the slurry, namely precision metering pump 1 and precision metering pump 2. First, start precision metering pump 2 to transport nitrosyl sulfuric acid, with a flow rate of 310L / h, and then start precision metering pump 1 to transport dichlorosulfate. The control coefficient of the two is 1:2.07; The mixed liquid enters reactor one through a circulation pump. After a preliminary reaction of about 0.9 hours, the reaction liquid is discharged from the top of reactor one and returns to the feed end of the circulation pump through a cooler for continuous circulation. The mixed liquid enters reactor two and is further reacted for about 0.2 hours before being discharged from the top of reactor two. The two reactors are connected in series to complete the liquid-solid reaction. Reactor one uses low-temperature frozen brine to control the temperature through jacket heat exchange, and reactor two uses jacket heat exchange to control the temperature, and the system temperature is 25-30°C.

Claims

1. A continuous diazotization process for dye preparation, characterized in that: The following steps are involved: S1: The diazo component and sulfuric acid are mixed by beating and emulsifying according to the mass ratio to form the diazo component sulfate, which is premixed in a batching kettle, and the mixing is circulated up and down inside the batching kettle, and then pumped into the preparation kettle; S2: Add the prepared diazonium salt solution as the base material into the reactor 1, start the circulation pump and cooling system, and set the interlocking temperature; S3: According to the molar ratio of the diazo component to nitrosyl sulfuric acid in the diazo component sulfate, the diazo component sulfate and nitrosyl sulfuric acid are pumped into the system through respective metering pumps for diazotization reaction, and the mixed solution passes through the reactor 1 and then splits, with one part entering the reactor 2 for final reaction to obtain the desired product, and the other part entering the cooler for cooling, mixing with the diazo component sulfate and nitrosyl sulfuric acid, and then entering the reactor 1 through the circulation pump to realize circulation; S4: The temperature of the reaction solution in the reactor is controlled at 20-40°C using refrigerated brine.

2. A continuous diazotization process for dye preparation according to claim 1, characterized in that: In the step S1, 40-98% sulfuric acid is selected as the sulfuric acid.

3. A continuous diazotization process for dye preparation according to claim 1, characterized in that: In the step S1, the mass ratio of the diazo component to sulfuric acid is 1:0.8-4.

4. A continuous diazotization process for dye preparation according to claim 1, characterized in that: In the step S2, the molar ratio of the diazo component to nitrosyl sulfuric acid is 1:0.95-1.

1.

5. A continuous diazotization process for dye preparation according to claim 1, characterized in that: After cooling, the reaction liquid is mixed with the diazo component sulfate and nitrosyl sulfuric acid and then returned to the reaction system to keep the system temperature stable. The system uses low-temperature frozen brine as a cooling medium.

6. A continuous diazotization process for dye preparation according to claim 1, characterized in that: The reaction time of the mixed solution in the reactor 1 in step S3 is 0.5 to 1.5 h, and the reaction time of the mixed solution in the reactor 2 in step S5 is 0.1 to 0.5 h.

7. A continuous diazotization device for dye preparation, characterized in that: It includes a batching kettle, a material preparation kettle, a reactor 1, a cooler, a reactor 2 and a product receiving kettle arranged in the order of before and after the diazotization reaction; The batching kettle is used for mixing and preparing the diazo component sulfate, and the discharge end of the batching kettle is connected to the feed end of the pump; The discharge end of the material preparation kettle is connected to a precision metering pump; The discharge end of the precision metering pump 1 is also mixed with a precision metering pump 2, and the precision metering pump 2 is used to introduce nitrosyl sulfuric acid; The discharge ends of precision metering pump 1 and precision metering pump 2 are connected to reactor 1 through the feed end of the circulation pump, one end of reactor 1 is connected to the feed end of the circulation pump through a cooler, and the other end is connected to the feed end of reactor 2, and the discharge end of reactor 2 is connected to the product receiving kettle.

8. A continuous diazotization device for dye preparation according to claim 2, characterized in that: The reactor 1 uses low-temperature frozen brine to control the temperature through jacket heat exchange, the reactor 2 uses jacket heat exchange to control the temperature, and the cooler uses tube heat exchange to reduce the temperature, so that the system temperature is 20-40°C.

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