Method and device for preparing CLT acid through pipeline type continuous catalytic hydrogenation reduction

Abstract

The invention discloses a method and a device for preparing CLT acid through pipeline type continuous catalytic hydrogenation reduction. According to the method, catalytic hydrogenation reduction reaction is carried out in the device. According to the method, equipment such as a five-stage static tubular mixer, a gas-liquid separation tank and a reduction liquid temporary storage tank is adopted, so that efficient hydrogenation reduction of the CLT acid nitride is realized. In the reaction process, hydrogen is proportionally introduced by stages through a grading mixer, the hydrogen pressure is controlled to be 0.8-1.0 MPa, and the reaction temperature is controlled to be 70-80 DEG C. The used platinum-carbon catalyst is not recycled and recycled after being filtered and recycled, so that the loss of precious metal platinum is effectively reduced. Through the method, the reduction efficiency of CLT acid is remarkably improved, the generation amount of byproducts and dechlorination products is low, and the nitro conversion rate reaches 99.90% or above. The method has the advantages of small equipment volume, short reaction time, high reaction stability and selectivity, and low catalyst cost.

Description

Technical Field

[0001] The invention relates to the field of organic chemical synthesis, and in particular to a method and a device for preparing CLT acid by pipeline continuous catalytic hydrogenation reduction. Background Art

[0002] CLT acid, also known as 2-amino-4-methyl-5-chlorobenzenesulfonic acid, is an important organic pigment intermediate, widely used in the manufacture of a variety of red organic pigments, such as Golden Red C, Rubber Red LG and Lithol Red, etc. These pigments are widely used in the coloring of inks, paints, coatings, plastics and rubber, so CLT acid occupies an important position in the chemical industry.

[0003] At present, the toluene sulfonation method is usually used for the synthesis of CLT acid at home and abroad. This process includes sulfonation, chlorination, nitration, reduction, acid precipitation, filter pressing and drying. Among them, the reduction process of CLT acid is the key step in the entire synthesis process. At present, there are mainly the following reduction processes in industrial production: iron powder reduction process, kettle continuous catalytic hydrogenation reduction process, loop injection continuous catalytic hydrogenation reduction process and fixed bed continuous catalytic hydrogenation reduction process. The following is a specific analysis of the above reduction processes:

[0004] Iron powder reduction process: Iron powder reduction is the earliest reduction method used. A large amount of iron powder is consumed during the reaction process, and a large amount of iron mud is produced during the reduction process, which brings environmental pollution problems. In addition, this process is not only labor-intensive, but also has a large amount of waste gas emissions and low production efficiency, which is difficult to meet the needs of modern industry for environmental protection and efficient production.

[0005] Kettle-type continuous catalytic hydrogenation reduction process: Kettle-type continuous catalytic hydrogenation reduction process uses water-phase hydrogenation reaction. Although it can carry out hydrogenation reaction at a lower temperature, the long residence time of the material in the kettle reactor can easily lead to catalyst pore blockage. Especially when using precious metal catalysts, the precious metal loss in the catalyst is serious, which increases the production cost. In addition, when using catalysts such as Raney nickel, the reaction activity is too high, which can easily lead to the dechlorination reaction of CLT acid products, resulting in a decrease in product purity and yield, which further limits the large-scale industrial application of this process.

[0006] Loop injection continuous catalytic hydrogenation reduction process: This process uses loop injection to carry out catalytic hydrogenation reduction reaction. Although it can reduce the material residence time and reduce the problem of catalyst loss compared to the kettle process, it also faces the problem of catalyst deactivation in the water phase system. This process still has problems with catalyst recycling and stability. Especially in the long-term reaction process, the stability of the precious metal catalyst is difficult to ensure, resulting in large fluctuations in the quality of the reaction product.

[0007] Fixed-bed continuous catalytic hydrogenation reduction process: Granular catalysts in fixed-bed reactors are commonly used in the industry for continuous hydrogenation reduction processes. However, due to the relatively low purity of CLT acid nitro materials, fixed-bed catalysts are easily poisoned and ineffective, especially sensitive to the impurity content in the materials, making the production process difficult to control. In addition, the fixed-bed process requires high raw material purity and stability, so it is not suitable for industrial continuous production of CLT acid.

[0008] In summary, based on the above deficiencies in the prior art, the existing reduction process has problems such as insufficient catalyst activity and stability, long reaction time, serious loss of catalyst precious metals, many reaction by-products, and serious dechlorination, making it difficult to achieve efficient production of CLT acid. Especially in large-scale industrial production, the instability of the process and the high cost of the catalyst seriously restrict its application. Summary of the invention

[0009] One of the technical problems to be solved by the present invention is to provide a pipeline-type continuous catalytic hydrogenation reduction device for preparing CLT acid, so as to solve the problems of discontinuous operation, serious catalyst loss, low reaction efficiency, high production cost, etc. existing in conventional devices in the prior art, and solve the problems that the existing kettle reactor has unstable reaction and a large amount of by-products due to the long-term residence of materials and uneven stirring, and the pore size of the precious metal catalyst is easily blocked, resulting in catalyst failure and loss, which leads to increased costs.

[0010] In order to solve the above technical problems, the present invention provides a pipeline continuous catalytic hydrogenation reduction device for preparing CLT acid, the device comprising a CLT acid nitrate metering pump, a catalyst metering pump, a multi-stage static pipeline mixer, a gas-liquid separation tank, and a reducing liquid temporary storage tank;

[0011] The inlet of the CLT acid nitrate metering pump is connected to the CLT acid nitrate storage tank, and the outlet is connected to the inlet of the multi-stage static pipeline mixer;

[0012] The inlet of the catalyst metering pump is connected to the catalyst storage tank, and the outlet is connected to the inlet of the multi-stage static pipeline mixer;

[0013] The multi-stage static pipeline mixer comprises at least three stages of connected tubular mixers, and each stage of the tubular mixer is provided with a hydrogen input pipeline for introducing hydrogen into the mixer in stages;

[0014] The inlet of the gas-liquid separation tank is connected to the outlet of the multi-stage static pipeline mixer, and is used to separate the gas phase and the liquid phase in the reaction product, and the gas-liquid separation tank is provided with a gas phase outlet and a liquid phase outlet;

[0015] The inlet of the reducing liquid temporary storage tank is connected to the liquid phase outlet of the gas-liquid separation tank.

[0016] Compared with the prior art, the present invention discloses a pipeline-type continuous catalytic hydrogenation reduction device for preparing CLT acid, which has the following advantages: the kettle reactor in the prior art is changed into a multi-stage static pipeline mixer: the direct technical principle is that the continuous-flow multi-stage tubular mixer can achieve uniform reaction conditions, no back-mixing, no retentate, short material residence time, and ensure the stability and efficiency of the reaction process. The direct technical effect is to reduce the generation of by-products, stabilize the product quality, avoid local overheating or overcooling in the reactor, and improve the reaction selectivity. By combining these features, the high efficiency and stability of the production process are achieved, and by reasonably controlling the reaction temperature and pressure, it is ensured that the high-purity CLT acid product is finally obtained; and the disposable catalyst in the prior art is changed into a catalyst recovery system: in the present invention, the platinum carbon catalyst used is recovered by the filter and then regenerated and recycled, and the catalyst is separated by the high-efficiency filter to prevent the loss of the catalyst, which significantly reduces the consumption cost of the catalyst and avoids the loss of precious metals. Through this design, the economic benefits of the device can be further improved.

[0017] The adoption of the above technical solution can significantly improve the continuity, stability and selectivity of the reaction, achieve reaction uniformity through a multi-stage static pipeline mixer, control the phased entry of hydrogen, avoid local excessive hydrogen supply leading to side reactions, thereby improving hydrogen utilization and enhancing reaction selectivity, while greatly reducing the generation of by-products such as dechlorination products. This setting not only reduces energy consumption, but also optimizes the overall efficiency of the reaction, meeting production needs.

[0018] As a preferred solution, the device also includes a filter pump and a filter, the outlet of the reducing liquid temporary storage tank is connected to the inlet of the filter pump, the outlet of the filter pump is connected to a filter, and the filter is used to separate the catalyst in the reducing liquid; a discharge regulating valve is provided at the bottom of the gas-liquid separation tank.

[0019] Compared with the prior art, the above technical solution can achieve efficient recovery of the catalyst, separate the reusable catalyst through the filter, and prevent the loss of the catalyst, thereby reducing the cost of catalyst use, extending the production cycle, and reducing the consumption of precious metals.

[0020] As a preferred solution, the multi-stage static pipeline mixer includes a five-stage static tubular mixer, and the static tubular mixer is a SK type or SV type static tubular mixer with an inner diameter of DN40-DN50 and a height of 3-5 meters; and each stage of the tubular mixer is provided with a jacket cooling system, and the jacket cooling system is used to pass cooling water into the tubular mixer, thereby controlling the reaction temperature of each stage of the tubular mixer.

[0021] Compared with the existing technology, the above technical solution can accurately control the reaction temperature, prevent overheating of the reaction, maintain the reaction temperature at 70-80°C through the cooling water jacket, ensure the best reaction efficiency, avoid catalyst deactivation due to high temperature, and improve the stability of the reaction and the purity of the product.

[0022] As a preferred solution, the reducing liquid temporary storage tank is also provided with a nitrogen sealing system for displacing the air in the tank and reducing the contact between the material and oxygen.

[0023] Compared with the prior art, the above technical solution can prevent oxygen from contacting the reactants, thereby reducing the occurrence of oxidation side reactions, isolating oxygen through nitrogen, ensuring the stability and safety of the reactants, and reducing the generation of by-products.

[0024] Another technical problem to be solved by the present invention is a method for preparing CLT acid by pipeline continuous catalytic hydrogenation reduction, so as to solve the problems of low reaction efficiency, serious catalyst loss and large number of by-products in the conventional methods in the prior art.

[0025] The present invention also provides a method for preparing CLT acid by pipeline continuous catalytic hydrogenation reduction, which is implemented by the above-mentioned device and comprises the following steps:

[0026] S1: The reaction system is gas-replaced, and then hot water is pumped into the reaction system through a CLT acid nitrate metering pump;

[0027] S2: starting the catalyst metering pump to inject a portion of the platinum-carbon catalyst aqueous solution into the reaction system after the treatment in step S1, and further introducing hydrogen into the reaction system through the hydrogen input pipeline on the tubular mixer;

[0028] S3: simultaneously start the CLT acid nitrate metering pump and the catalyst metering pump, pump CLT acid nitrate and platinum carbon catalyst aqueous solution into the reaction system in proportion, wherein the flow rate of the platinum carbon catalyst aqueous solution is 3-7% of the flow rate of the CLT acid nitrate; and introduce hydrogen in stages through the hydrogen input pipeline below each level of tubular mixer; and control the reaction temperature of each level of tubular mixer to be 70-80°C;

[0029] S4: After the liquid level in the gas-liquid separation tank reaches the set height after the treatment in step S3, the discharge regulating valve at the bottom of the gas-liquid separation tank is opened to put the reduced liquid at the bottom that has been reacted into the reduced liquid temporary storage tank, further control the liquid level in the gas-liquid separation tank, and control the pressure of the gas-liquid separation tank between 0.8-1.0MPa;

[0030] S5: After filtering the reducing liquid in the reducing liquid temporary storage tank in step S4, the filtrate is passed into the reducing liquid temporary storage tank. The catalyst recovered after filtering can be recycled and reused in the reaction.

[0031] Compared with the prior art, the present invention provides a method for preparing CLT acid by pipeline continuous catalytic hydrogenation reduction, which has the following advantages: in step S1, the reaction environment in the system is ensured to be pure by gas replacement, and side reactions caused by oxygen are avoided, thereby improving the safety and efficiency of the reaction; in step S2, a platinum carbon catalyst and an initial amount of hydrogen are introduced into the system to ensure that the reaction can proceed smoothly. Compared with the problem of catalyst deactivation in the prior art, this step ensures the uniformity of the reaction environment by accurately controlling the amount of catalyst and hydrogen added, ensures the stability of the initial reaction by introducing an appropriate amount of hydrogen, prevents uneven reactions caused by excessive hydrogen supply, improves catalytic efficiency, and ensures the controllability of reaction conditions; in step S3, hydrogen is introduced in stages to ensure the reasonable distribution of hydrogen in different reaction stages, prevents excessive hydrogen from affecting the uniformity of the reaction, ensures the efficiency and uniformity of the reaction, and ultimately improves the purity of the product. In step S4, when the liquid level in the gas-liquid separator reaches the set height, the discharge regulating valve at the bottom is automatically opened to ensure that the reduced liquid that has completed the reaction can be quickly discharged to the reduced liquid temporary storage tank. This design ensures the efficient operation of the system through liquid level monitoring and automatic valve control. Compared with the prior art, this method prevents the liquid level from being too high or too low from interfering with the reaction process by precise liquid level control, ensures the continuity of the reaction, reduces the intermittent operation, and improves production efficiency. In addition, by pressure control, the pressure in the gas-liquid separator is always maintained within the stable range of 0.8-1.0MPa, ensuring the effective separation of gas and liquid, avoiding the instability of the reaction, and improving the safety and reaction efficiency of the entire system. In step S5, after gas-liquid separation, the reduced liquid is transmitted to the filtration system to separate the platinum carbon catalyst in the reduced liquid, and then the catalyst is recovered and recycled. Compared with the problem of high catalyst loss in the prior art, effective filtration and catalyst recovery and regeneration can greatly reduce the loss of platinum-carbon catalysts, reduce production costs, and reduce waste generation, making the entire reaction process more environmentally friendly and economical.

[0032] The method of the present application solves the common problems of catalyst deactivation, uneven reaction, and low hydrogen utilization rate in the prior art by optimizing the operating conditions of each step in the reaction process, further improving production efficiency and product quality, ensuring the purity of the reaction environment through gas replacement, controlling the uniformity and efficiency of the reaction through staged hydrogen supply, ensuring the continuity and safety of the reaction through automatic control of liquid level and pressure, and reducing catalyst loss and cost through catalyst recovery and regeneration, ultimately achieving efficient, stable, and economical production results.

[0033] As a preferred solution, the CLT acid nitrate is an aqueous solution with a content of 25-30%, and the chemical formula of the reaction process of steps S1-S5 is as follows:

[0034] Wherein, Pt / C catalyst is platinum-carbon catalyst.

[0035] As a preferred solution, in step S1, the gas replacement includes: replacing air in the entire reaction system with nitrogen twice, and then replacing nitrogen twice with hydrogen; pumping hot water into the reaction system through the CLT acid nitrate metering pump includes: pumping 70°C hot water into the multi-stage static pipeline mixer with the CLT acid nitrate metering pump until the liquid level in the gas-liquid separation tank shows 0.2 meters.

[0036] Compared with the prior art, the above technical solution can significantly improve the safety and stability of the reaction process. The direct technical principle is to replace air with nitrogen to effectively remove oxygen in the system, thereby preventing oxygen from participating in the reaction and causing dangerous side reactions. In addition, hydrogen further replaces nitrogen to ensure that only the required gas components are retained in the reaction system. This operation not only provides a purer and inert environment for subsequent hydrogenation reactions, but also reduces the possibility of oxidation reactions, improves the controllability of the reaction, avoids unnecessary oxidation reactions, thereby improving the safety of the reaction, avoiding a decrease in product purity, and ensuring the efficiency of the reaction and the consistency of the product; by ensuring the purity of the reaction environment, it can greatly reduce safety hazards, reduce the generation of by-products, and ultimately improve the purity and reaction efficiency of the product. In addition, pumping in 70°C hot water also preheats the system, avoids the problem of thermal inhomogeneity during cold start, helps maintain temperature control of the reaction, and ensures that there is enough liquid level in the gas-liquid separation tank to promote stable operation of subsequent reactions.

[0037] As a preferred solution, in step S2, the portion of the platinum-carbon catalyst aqueous solution is 5% of the total amount of the platinum-carbon catalyst aqueous solution, and the condition for introducing hydrogen is: introducing hydrogen until the hydrogen pressure in the system reaches 0.8 MPa.

[0038] Compared with the prior art, the above technical solution can ensure the stability of the reaction start-up by controlling the amount of catalyst and the amount of hydrogen added. By adding 5% platinum carbon catalyst aqueous solution to the reaction system, the catalytic process can be pre-activated, so that the initial hydrogenation reaction can be carried out stably under the conditions of low catalyst amount and appropriate amount of hydrogen; the introduction of hydrogen to a pressure of 0.8MPa can ensure that the hydrogen molecules are in full contact with the catalyst surface, ensuring the speed of the reaction without causing uneven local reactions due to excessive hydrogen; by strictly controlling the initial amount of catalyst and hydrogen, the deactivation of the catalyst and the fluctuation of reaction conditions are avoided, ensuring the uniformity and stability of the initial reaction; the catalytic efficiency of the reaction is greatly improved, avoiding uneven reactions or overreactions caused by excessive hydrogen. By accurately controlling the hydrogen pressure and the amount of catalyst, the smooth start-up of the reaction can be ensured, and the foundation for the stable progress of subsequent reactions is laid, effectively improving the reaction yield and the overall stability of the reaction.

[0039] As a preferred solution, in step S3, the number of the multi-stage static tubular mixers is 5, and the step of introducing hydrogen in stages through the hydrogen input pipeline below each stage of the tubular mixer includes: introducing hydrogen into the system through the hydrogen input pipeline below the 1st to 4th stage static tubular mixers, controlling the hydrogen introduction amounts of the 1st, 2nd, 3rd and 4th stages to be 50%, 30%, 15% and 5% of the total flow rate, respectively, and maintaining the hydrogen pressure at 0.8-1.0Mpa.

[0040] Compared with the prior art, the above technical solution is adopted. In step S3, hydrogen is gradually introduced into static mixers of different levels in stages and proportions to ensure the reasonable distribution of hydrogen in different reaction stages. The amount of hydrogen introduced into each mixer is precisely controlled (50% in the first stage, 30% in the second stage, 15% in the third stage, and 5% in the fourth stage). This segmented hydrogen supply design ensures the effective use of hydrogen and avoids the supply of excessive hydrogen affecting the uniformity of the reaction, thereby ensuring the reaction efficiency of each stage. This not only ensures the full contact between hydrogen and reactants and avoids the waste of hydrogen, but also further improves the purity of the final product and the overall efficiency of the reaction.

[0041] As a preferred solution, step S4 specifically includes: when the liquid level in the gas-liquid separation tank reaches a set height of 1 meter, the discharge regulating valve at the bottom of the gas-liquid separation tank is automatically opened, and the reducing liquid at the bottom that has completed the reaction is placed in the reducing liquid temporary storage tank, and the liquid level of the gas-liquid separation tank is further controlled between 1-1.2 meters, and the pressure of the gas-liquid separation tank is controlled between 0.8-1.0MPa through the tail gas pressure regulating valve at the top of the gas-liquid separation tank.

[0042] Compared with the prior art, the above technical solution can significantly improve the automation and precise control capabilities of the reaction process. By automatically monitoring and adjusting the liquid level and pressure of the gas-liquid separation tank, it can ensure that the liquid level in the gas-liquid separation tank is maintained within the optimal working range (1-1.2 meters), which is not only beneficial to the stability of the subsequent liquid treatment process, but also can prevent uneven reactions or equipment instability caused by too low or too high liquid levels. In addition, the tail gas pressure regulating valve is used to maintain the pressure in the tank between 0.8-1.0MPa, which can ensure the balance of hydrogen supply and reaction system, thereby improving reaction efficiency and uniformity. Through this automated liquid level and pressure control, the reaction system can be maintained in a stable operating state, avoiding changes in reaction conditions caused by liquid level or pressure fluctuations, thereby significantly improving the overall stability and efficiency of the reaction. The system's automated control not only reduces human intervention and operational errors, but also ensures the continued stability and controllability of reaction conditions by reasonably adjusting the liquid level and pressure of the gas-liquid separation tank, and reduces the impact of reaction fluctuations on the quality of the final product, ensuring the efficiency and consistency of the catalytic hydrogenation reaction; it avoids the problems of uneven reaction rate and decreased product purity caused by factors such as insufficient gas-liquid separation and pressure fluctuations in the reaction. This design not only optimizes the operating efficiency of the equipment, but also ensures the continued stability of the reaction system by precisely controlling the key parameters of the gas-liquid separation tank, further synergistically improving the quality and purity of the final product. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a schematic structural diagram of a pipeline-type continuous catalytic hydrogenation reduction device for preparing CLT acid according to the present invention;

[0044] Figure 1 In: 1. CLT acid nitrate metering pump; 2. Catalyst metering pump; 3. Multi-stage static pipeline mixer; 4. Gas-liquid separation tank; 5. Reduction liquid temporary storage tank; 6. Filter pump; 7. Filter; 8. Discharge regulating valve; 9. Jacket cooling system; 10. Nitrogen sealing system; 11. Hydrogen input pipeline;

[0045] Figure 2 It is a reaction process diagram of preparing CLT acid by pipeline continuous catalytic hydrogenation reduction of the present invention. DETAILED DESCRIPTION

[0046] First, those skilled in the art should understand that these implementations are only used to explain the technical principles of the embodiments of the present application, and are not intended to limit the protection scope of the embodiments of the present application. Those skilled in the art can make adjustments to them as needed to adapt to specific application scenarios.

[0047] The present invention provides a pipeline-type continuous catalytic hydrogenation reduction device for preparing CLT acid, such as Figure 1 As shown, Figure 1 The present invention discloses a pipeline-type continuous catalytic hydrogenation reduction device for preparing CLT acid and a reaction flow chart; the device comprises a CLT acid nitrate metering pump 1, a catalyst metering pump 2, a multi-stage static pipeline mixer 3, a gas-liquid separation tank 4, a reducing liquid temporary storage tank 5, a filter pump 6 and a filter 7;

[0048] The inlet of the CLT acid nitrate metering pump 1 is connected to the CLT acid nitrate storage tank, and the outlet is connected to the inlet of the multi-stage static pipeline mixer 3;

[0049] The inlet of the catalyst metering pump 2 is connected to the catalyst storage tank, and the outlet is connected to the inlet of the multi-stage static pipeline mixer 3;

[0050] The multi-stage static pipeline mixer 3 includes at least three stages of connected tubular mixers, and each stage of the tubular mixer is provided with a hydrogen input pipeline 11 for introducing hydrogen into the mixer in stages;

[0051] The inlet of the gas-liquid separation tank 4 is connected to the outlet of the multi-stage static pipeline mixer 3, and is used to separate the gas phase and the liquid phase in the reaction product, and the gas-liquid separation tank 4 is provided with a gas phase outlet and a liquid phase outlet;

[0052] The inlet of the reducing liquid temporary storage tank 5 is connected to the liquid phase outlet of the gas-liquid separation tank 4 .

[0053] As a preferred solution, the device also includes a filter pump 6 and a filter 7, the outlet of the reducing liquid temporary storage tank 5 is connected to the inlet of the filter pump 6, and the outlet of the filter pump 6 is connected to a filter 7, and the filter 7 is used to separate the catalyst in the reducing liquid; a discharge regulating valve 8 is provided at the bottom of the gas-liquid separation tank 4.

[0054] As a preferred solution, the multi-stage static pipeline mixer 3 includes a five-stage static tubular mixer, and the static tubular mixer is an SK type or SV type static tubular mixer; and each stage of the tubular mixer is provided with a jacket cooling system 9, and the jacket cooling system 9 is used to pass cooling water into the tubular mixer, thereby controlling the reaction temperature of each stage of the tubular mixer.

[0055] As a preferred solution, the reducing liquid temporary storage tank 5 is also provided with a nitrogen sealing system 10 for displacing the air in the tank and reducing the contact between the material and oxygen.

[0056] The present invention also provides a pipeline continuous catalytic hydrogenation reduction method for preparing CLT acid, the reaction process is as follows Figure 2 As shown, the method is implemented by the above-mentioned device, and the method includes the following steps:

[0057] S1: Perform gas replacement on the reaction system, and then pump hot water into the reaction system through CLT acid nitrate metering pump 1;

[0058] S2: starting the catalyst metering pump 2, injecting a portion of the platinum-carbon catalyst aqueous solution into the reaction system after the treatment in step S1, and further introducing hydrogen into the reaction system through the hydrogen input pipeline 11 on the tubular mixer;

[0059] S3: simultaneously start the CLT acid nitrate metering pump 1 and the catalyst metering pump 2, and pump CLT acid nitrate and platinum carbon catalyst aqueous solution into the reaction system in proportion, wherein the flow rate of the platinum carbon catalyst aqueous solution is 3-7% of the flow rate of the CLT acid nitrate; and introduce hydrogen in stages through the hydrogen input pipeline 11 below each level of tubular mixer; and control the reaction temperature of each level of tubular mixer to be 70-80°C;

[0060] S4: After the liquid level in the gas-liquid separation tank 4 reaches the set height after the treatment in step S3, the discharge regulating valve 8 at the bottom of the gas-liquid separation tank 4 is opened to put the reduced liquid at the bottom that has been reacted into the reduced liquid temporary storage tank 5, and the liquid level in the gas-liquid separation tank 4 is further controlled, and the pressure of the gas-liquid separation tank 4 is controlled to be between 0.8-1.0MPa;

[0061] S5: After filtering the reducing liquid in the reducing liquid temporary storage tank 5 in step S4, the filtrate is passed into the reducing liquid temporary storage tank 5. The catalyst recovered after filtering can be reused in the reaction after regeneration cycle.

[0062] Compared with the prior art, the pipeline continuous catalytic hydrogenation reduction method for preparing CLT acid of the present invention has the following significant beneficial effects:

[0063] 1. When the method is used for continuous hydrogenation, continuous feeding and continuous discharging to prepare CLT acid by catalytic hydrogenation reduction, the equipment volume is small, the material residence time is short, there is no backmixing of materials, the reaction stability is good, the content of dechlorination products in the reaction products is low, the selectivity is high, the by-products are small, the content of residual main nitro products is also low, and the nitro conversion rate is as high as 99.90% or more;

[0064] 2. The platinum-carbon catalyst used is not recycled internally, which ensures the activity and catalytic ability of the catalyst during the catalytic hydrogenation process and effectively controls the stability of the reaction; since the catalyst is not recycled internally, the loss of platinum metal in the platinum-carbon catalyst can be effectively reduced, greatly reducing the cost of using the platinum-carbon catalyst.

[0065] As a preferred solution, the chemical formula of the reaction process of steps S1-S5 is as follows:

[0066] Wherein, Pt / C catalyst is platinum-carbon catalyst.

[0067] As a preferred solution, in step S1, the gas replacement includes: replacing air twice with nitrogen in the entire reaction system, and then replacing nitrogen twice with hydrogen; pumping hot water into the reaction system through the CLT acid nitrate metering pump 1 includes: pumping 70°C hot water into the multi-stage static pipeline mixer 3 with the CLT acid nitrate metering pump 1 until the liquid level in the gas-liquid separation tank 4 shows 0.2 meters.

[0068] As a preferred solution, in step S2, the portion of the platinum-carbon catalyst aqueous solution is 5% of the total amount of the platinum-carbon catalyst aqueous solution, and the condition for introducing hydrogen is: introducing hydrogen until the hydrogen pressure in the system reaches 0.8 MPa.

[0069] As a preferred solution, in step S3, the number of the multi-stage static tubular mixers is 5, and the step of introducing hydrogen in stages through the hydrogen input pipeline 11 below each stage of the tubular mixer includes: introducing hydrogen into the system through the hydrogen input pipeline 11 below the 1st to 4th stage static tubular mixers, controlling the hydrogen introduction amounts of the 1st, 2nd, 3rd and 4th stages to be 50%, 30%, 15% and 5% of the total flow rate, respectively, and maintaining the hydrogen pressure at 0.8-1.0Mpa.

[0070] As a preferred solution, step S4 specifically includes: when the liquid level in the gas-liquid separation tank 4 reaches a set height of 1 meter, the discharge regulating valve 8 at the bottom of the gas-liquid separation tank 4 is automatically opened, and the reducing liquid at the bottom that has completed the reaction is placed in the reducing liquid temporary storage tank 5, and the liquid level of the gas-liquid separation tank 4 is further controlled between 1-1.2 meters, and the pressure of the gas-liquid separation tank 4 is controlled between 0.8-1.0 MPa through the tail gas pressure regulating valve at the top of the gas-liquid separation tank 4.

[0071] The following provides specific embodiments in combination with the above technical solution to further illustrate the above technical solution of the present invention:

[0072] Example 1

[0073] Example 1 provides a method and apparatus for preparing CLT acid by pipeline continuous catalytic hydrogenation reduction.

[0074] The device comprises a CLT acid nitrate metering pump 1, a catalyst metering pump 2, a multi-stage static pipeline mixer 3, a gas-liquid separation tank 4, a reducing liquid temporary storage tank 5, a filter pump 6 and a filter 7; the inlet of the CLT acid nitrate metering pump 1 is connected to the CLT acid nitrate storage tank, and the outlet is connected to the inlet of the multi-stage static pipeline mixer 3; the inlet of the catalyst metering pump 2 is connected to the catalyst storage tank, and the outlet is connected to the inlet of the multi-stage static pipeline mixer 3; the multi-stage static pipeline mixer 3 comprises at least three stages of tubular mixers, and each stage of the tubular mixer is provided with a hydrogen input pipeline 11 for stepwise mixing. hydrogen is introduced into the mixer in the first stage; the inlet of the gas-liquid separation tank 4 is connected to the outlet of the multi-stage static pipeline mixer 3, and is used to separate the gas phase and the liquid phase in the reaction product, and the gas-liquid separation tank 4 is provided with a gas phase outlet and a liquid phase outlet; the inlet of the reducing liquid temporary storage tank 5 is connected to the liquid phase outlet of the gas-liquid separation tank 4, and the reducing liquid temporary storage tank 5 is also provided with a nitrogen sealing system 10, which is used to expel the air in the tank and reduce the contact between the material and oxygen; the outlet of the reducing liquid temporary storage tank 5 is also connected to the inlet of a filter pump 6, and the outlet of the filter pump 6 is connected to a filter 7, and the filter 7 is used to separate the catalyst in the reducing liquid.

[0075] The multi-stage static pipeline mixer 3 includes a five-stage static tubular mixer, and the static tubular mixer is an SK type or SV type static tubular mixer, which uses a five-stage SK type static tubular mixer with an inner diameter of DN40 and a length of 4 meters for continuous catalytic hydrogenation reduction to prepare CLT acid. A jacket cooling system 9 is provided on each stage of the tubular mixer, and the jacket cooling system 9 is used to pass cooling water into the tubular mixer, thereby controlling the reaction temperature of each stage of the tubular mixer.

[0076] The method specifically comprises the following steps:

[0077] S1: First replace the air in the entire reaction system with nitrogen twice, then replace the nitrogen with hydrogen twice, and then use the CLT acid nitrate metering pump 1 to pump 70°C hot water into the five-stage SK type static tube mixer until the liquid level in the gas-liquid separation tank 4 shows 0.2 meters. Put the nitrogen sealing system 10 in the reduction liquid temporary storage tank 5 into operation, and automatically control the micro positive pressure to 1-2KPa.

[0078] S2: Start the catalyst metering pump 2 to pump a 5% concentration of platinum carbon catalyst (3% platinum content) aqueous solution into the system until the liquid level in the gas-liquid separation tank 4 rises to 0.3 meters.

[0079] S3: hydrogen is charged into the system through the hydrogen pipeline below the first-stage static mixer until the hydrogen pressure in the gas-liquid separation tank 4 reaches 0.8 MPa.

[0080] Start the CLT acid nitrate metering pump 1 and the catalyst aqueous solution metering pump, pump the CLT acid nitrate aqueous solution with a concentration of 25% at a flow rate of 3m3 / h, pump the platinum carbon catalyst (platinum content 3%) aqueous solution with a concentration of 5% at a flow rate of 0.15m3 / h, and control the catalyst aqueous solution flow rate to be about 5% of the CLT acid nitrate aqueous solution flow rate; at the same time, hydrogen is introduced into the system through the hydrogen pipeline below the 1-4 level static mixer to maintain the hydrogen pressure in the gas-liquid separation tank 4 at 0.8-1.0MPa. When hydrogen is introduced below the 1-4 level static mixer, the total hydrogen flow rate is controlled to be 50%, 30%, 15% and 5%, respectively, and the total hydrogen flow rate is controlled to be 300-350Nm3 / h; cooling water is introduced into the jacket of the 1-5 level static mixer to control the reaction temperature at each level to be between 70-75°C.

[0081] S4: When the liquid level in the gas-liquid separation tank 4 reaches 1 meter, the discharge regulating valve 8 at the bottom of the gas-liquid separation tank 4 is automatically opened, and the reduced liquid at the bottom that has completed the reaction is placed in the reduced liquid temporary storage tank 5, and the liquid level of the gas-liquid separation tank 4 is controlled between 1-1.2 meters. The tail gas pressure regulating valve at the top of the gas-liquid separation tank 4 is used to control the pressure of the gas-liquid separation tank 4 to be between 0.8-1.0 MPa.

[0082] S5: When the liquid level in the reducing liquid temporary storage tank 5 reaches a height of 2 meters, the filter pump 6 is started to pump the reducing liquid containing the catalyst into the filter 7 for filtration, and the filtrate is sent to the reducing liquid temporary storage tank 5. The recovered catalyst is regenerated and recycled. The filter pump 6 is interlocked with the liquid level in the reducing liquid temporary storage tank 5 to automatically control the high and low liquid levels.

[0083] The above-mentioned method of continuously introducing hydrogen, continuously feeding and continuously discharging is adopted to carry out catalytic hydrogenation reduction to prepare CLT acid aqueous solution.

[0084] During the experimental reaction, samples were taken from the reducing liquid temporary storage tank 5 at regular intervals to detect the nitro conversion rate and conduct liquid chromatography analysis. The specific experimental data are shown in Table 1:

[0085] Table 1: Sampling and analysis results of reducing liquid temporary storage tank 5 in Example 1:

[0086]

[0087] Example 2

[0088] Example 2 provides a method and apparatus for preparing CLT acid by pipeline continuous catalytic hydrogenation reduction.

[0089] The device comprises a CLT acid nitrate metering pump 1, a catalyst metering pump 2, a multi-stage static pipeline mixer 3, a gas-liquid separation tank 4, a reducing liquid temporary storage tank 5, a filter pump 6 and a filter 7; the inlet of the CLT acid nitrate metering pump 1 is connected to the CLT acid nitrate storage tank, and the outlet is connected to the inlet of the multi-stage static pipeline mixer 3; the inlet of the catalyst metering pump 2 is connected to the catalyst storage tank, and the outlet is connected to the inlet of the multi-stage static pipeline mixer 3; the multi-stage static pipeline mixer 3 comprises at least three stages of tubular mixers, and each stage of the tubular mixer is provided with a hydrogen input pipeline 11 for stepwise mixing. hydrogen is introduced into the mixer in the first stage; the inlet of the gas-liquid separation tank 4 is connected to the outlet of the multi-stage static pipeline mixer 3, and is used to separate the gas phase and the liquid phase in the reaction product, and the gas-liquid separation tank 4 is provided with a gas phase outlet and a liquid phase outlet; the inlet of the reducing liquid temporary storage tank 5 is connected to the liquid phase outlet of the gas-liquid separation tank 4, and the reducing liquid temporary storage tank 5 is also provided with a nitrogen sealing system 10, which is used to expel the air in the tank and reduce the contact between the material and oxygen; the outlet of the reducing liquid temporary storage tank 5 is also connected to the inlet of a filter pump 6, and the outlet of the filter pump 6 is connected to a filter 7, and the filter 7 is used to separate the catalyst in the reducing liquid.

[0090] The multi-stage static pipeline mixer 3 includes a five-stage static tubular mixer, and the static tubular mixer is an SK type or SV type static tubular mixer, which uses a five-stage SV type static tubular mixer with an inner diameter of DN50 and a length of 5 meters for continuous catalytic hydrogenation reduction to prepare CLT acid; and each stage of the tubular mixer is provided with a jacket cooling system 9, and the jacket cooling system 9 is used to pass cooling water into the tubular mixer, thereby controlling the reaction temperature of each stage of the tubular mixer.

[0091] The method specifically comprises the following steps:

[0092] S1: First replace the air in the entire reaction system with nitrogen twice, then replace the nitrogen with hydrogen twice, and then use the CLT acid nitrate metering pump 1 to pump 70°C hot water into the five-stage SK type static tube mixer until the liquid level in the gas-liquid separation tank 4 shows 0.2 meters. Put the nitrogen sealing system 10 in the reduction liquid temporary storage tank 5 into operation, and automatically control the micro positive pressure to 1-2KPa.

[0093] S2: Start the catalyst metering pump 2 to pump a 5% concentration of platinum carbon catalyst (3% platinum content) aqueous solution into the system until the liquid level in the gas-liquid separation tank 4 rises to 0.3 meters.

[0094] S3: Hydrogen is charged into the system through the hydrogen pipeline below the first-stage static mixer until the hydrogen pressure in the gas-liquid separation tank 4 reaches 0.8 MPa.

[0095] Start the CLT acid nitrate metering pump 1 and the catalyst aqueous solution metering pump, pump the CLT acid nitrate aqueous solution with a concentration of 25% at a flow rate of 5m3 / h, pump the platinum carbon catalyst (platinum content 3%) aqueous solution with a concentration of 5% at a flow rate of 0.25m3 / h, and control the catalyst aqueous solution flow rate to be about 5% of the CLT acid nitrate aqueous solution flow rate; at the same time, hydrogen is introduced into the system through the hydrogen pipeline below the 1-4 level static mixer to maintain the hydrogen pressure in the gas-liquid separation tank 4 at 0.8-1.0MPa. When hydrogen is introduced below the 1-4 level static mixer, the total hydrogen flow rate is controlled to be 50%, 30%, 15% and 5%, respectively, and the total hydrogen flow rate is controlled to be 500-550Nm3 / h; cooling water is introduced into the jacket of the 1-5 level static mixer to control the reaction temperature at each level to be between 70-75°C.

[0096] S4: When the liquid level in the gas-liquid separation tank 4 reaches 1 meter, the discharge regulating valve 8 at the bottom of the gas-liquid separation tank 4 is automatically opened, and the reduced liquid at the bottom that has completed the reaction is placed in the reduced liquid temporary storage tank 5, and the liquid level of the gas-liquid separation tank 4 is controlled between 1-1.2 meters. The tail gas pressure regulating valve at the top of the gas-liquid separation tank 4 is used to control the pressure of the gas-liquid separation tank 4 to be between 0.8-1.0 MPa.

[0097] S5: When the liquid level in the reducing liquid temporary storage tank 5 reaches a height of 2 meters, the filter pump 6 is started to pump the reducing liquid containing the catalyst into the filter 7 for filtration, and the filtrate is sent to the reducing liquid temporary storage tank 5. The recovered catalyst is regenerated and recycled. The filter pump 6 is interlocked with the liquid level in the reducing liquid temporary storage tank 5 to automatically control the high and low liquid levels.

[0098] The above-mentioned method of continuously introducing hydrogen, continuously feeding and continuously discharging is adopted to carry out catalytic hydrogenation reduction to prepare CLT acid aqueous solution.

[0099] During the experimental reaction, samples were taken from the reducing liquid temporary storage tank 5 at regular intervals to detect the nitro conversion rate and conduct liquid chromatography analysis. The specific experimental data are shown in Table 2:

[0100] Table 2: Sampling and analysis results of the reducing liquid temporary storage tank in Example 2:

[0101]

[0102] Through Example 1, Example 2 and the data in the table, it is further proved that the present invention provides a method for preparing CLT acid by pipeline continuous catalytic hydrogenation reduction, and has significant process improvements and technical advantages.

[0103] It can be seen from the experimental data that the continuous catalytic hydrogenation process of the present invention shows excellent effects in terms of catalyst activity, hydrogen utilization rate and reaction stability. The experimental data show that during the reaction process, the nitro conversion rate is stably maintained at more than 99.9%, and the dechlorination product content is as low as about 0.1%, which proves that the method can not only efficiently carry out nitro conversion, but also effectively avoid the occurrence of side reactions, thereby improving the purity of CLT acid; secondly, the pipeline reactor used in the present invention is combined with the design of a static mixer to achieve full mixing of reactants and hydrogen, greatly improving the uniformity and efficiency of the reaction. This multi-stage tubular mixer's segmented hydrogen introduction technology can reasonably control the hydrogen supply in each reaction stage, prevent the problem of excessive or insufficient hydrogen, and ensure the smooth progress of the reaction. In addition, the data in the table also show that by controlling key parameters such as reaction temperature, hydrogen pressure, and catalyst dosage, the reaction time can be significantly shortened, energy consumption can be further reduced, and the economy of the process can be improved. This optimization not only reduces the amount of catalyst used and hydrogen consumption, but also effectively reduces the loss of precious metal platinum, greatly reducing production costs. The continuous hydrogenation and continuous discharging technologies in the embodiments also verify that the present invention has a high level of automation and process stability, especially the automated control design in the gas-liquid separation system, which effectively avoids the influence of liquid level fluctuations on reaction efficiency and product quality, and enables the entire production process to be carried out in a highly controllable state.

[0104] In general, Example 1, Example 2 and experimental data clearly prove that the method for preparing CLT acid by pipeline continuous catalytic hydrogenation reduction provided by the present invention has the advantages of high efficiency, safety and economy, improves the nitro conversion rate, reduces the generation of by-products, and greatly reduces the production cost by optimizing the process conditions. It has great industrial application prospects and solves the technical problems existing in the background technology.

[0105] In the description of the embodiments of the present application, it should be noted that in the description of the present application, terms such as "inside" and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings. This is only for the convenience of description, and does not indicate or imply that the device or component must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present application.

[0106] In the description of the present application, the description with reference to the terms "one embodiment", "some embodiments", "in the present embodiment", "specific example", or "some examples" etc. means that the specific features, mechanisms, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, mechanisms, materials or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0107] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A pipeline-type continuous catalytic hydrogenation reduction device for preparing CLT acid, characterized in that: The device comprises a CLT acid nitrate metering pump (1), a catalyst metering pump (2), a multi-stage static pipeline mixer (3), a gas-liquid separation tank (4), and a reducing liquid temporary storage tank (5); The inlet of the CLT acid nitrate metering pump (1) is connected to the CLT acid nitrate storage tank, and the outlet is connected to the inlet of the multi-stage static pipeline mixer (3); The inlet of the catalyst metering pump (2) is connected to the catalyst storage tank, and the outlet is connected to the inlet of the multi-stage static pipeline mixer (3); The multi-stage static pipeline mixer (3) comprises at least three stages of connected tubular mixers, and each stage of the tubular mixer is provided with a hydrogen input pipeline (11) for introducing hydrogen into the mixer in stages; The inlet of the gas-liquid separation tank (4) is connected to the outlet of the multi-stage static pipeline mixer (3) for separating the gas phase and the liquid phase in the reaction product, and the gas-liquid separation tank (4) is provided with a gas phase outlet and a liquid phase outlet; The inlet of the reducing liquid temporary storage tank (5) is connected to the liquid phase outlet of the gas-liquid separation tank (4).

2. The pipeline continuous catalytic hydrogenation reduction device for preparing CLT acid according to claim 1, characterized in that: The device further comprises a filter pump (6) and a filter (7); the outlet of the reducing liquid temporary storage tank (5) is connected to the inlet of the filter pump (6); the outlet of the filter pump (6) is connected to the filter (7); the filter (7) is used to separate the catalyst in the reducing liquid; and a discharge regulating valve (8) is arranged at the bottom of the gas-liquid separation tank (4).

3. The pipeline continuous catalytic hydrogenation reduction device for preparing CLT acid according to claim 1, characterized in that: The multi-stage static pipeline mixer (3) includes five stages of static tubular mixers, and the static tubular mixers are SK-type or SV-type static tubular mixers, with an inner diameter of DN40-DN50 and a height of 3-5 meters; and each stage of the tubular mixer is provided with a jacket cooling system (9), and the jacket cooling system (9) is used to pass cooling water into the tubular mixer, thereby controlling the reaction temperature of each stage of the tubular mixer.

4. The pipeline continuous catalytic hydrogenation reduction device for preparing CLT acid according to claim 1, characterized in that: The reducing liquid temporary storage tank (5) is also provided with a nitrogen sealing system (10) for displacing the air in the tank and reducing the contact between the material and oxygen.

5. A method for preparing CLT acid by pipeline continuous catalytic hydrogenation reduction, characterized in that: The method is implemented by the device according to any one of claims 1 to 4, and the method comprises the following steps: S1: The reaction system is gas-replaced, and then hot water is pumped into the reaction system through a CLT acid nitrate metering pump (1); S2: starting the catalyst metering pump (2) to inject a portion of the platinum-carbon catalyst aqueous solution into the reaction system after the treatment in step S1, and further introducing hydrogen into the reaction system through the hydrogen input pipeline (11) on the tubular mixer; S3: simultaneously start the CLT acid nitrate metering pump (1) and the catalyst metering pump (2), and pump CLT acid nitrate and platinum carbon catalyst aqueous solution into the reaction system, wherein the flow rate of the platinum carbon catalyst aqueous solution is 3-7% of the flow rate of the CLT acid nitrate; and introduce hydrogen through the hydrogen input pipeline (11) below each level of tubular mixer; and control the reaction temperature of each level of tubular mixer to be 70-80°C; S4: After the liquid level in the gas-liquid separation tank (4) reaches a set height after the treatment in step S3, the discharge regulating valve (8) at the bottom of the gas-liquid separation tank (4) is opened, and the reduced liquid at the bottom that has completed the reaction is placed in the reduced liquid temporary storage tank (5), and the liquid level in the gas-liquid separation tank (4) is further controlled, and the pressure of the gas-liquid separation tank (4) is controlled to be between 0.8-1.0 MPa; S5: After filtering the reducing liquid in the reducing liquid temporary storage tank (5), the filtrate is passed into the reducing liquid temporary storage tank (5).

6. The method for preparing CLT acid by pipeline continuous catalytic hydrogenation reduction according to claim 5, characterized in that: The catalyst aqueous solution is a 5% aqueous solution prepared with a platinum carbon catalyst having a platinum content of 2.5-3%, and the CLT acid nitrate is an aqueous solution having a content of 25-30%. The chemical formula of the reaction process of steps S1-S5 is as follows: Wherein, Pt / C catalyst is platinum-carbon catalyst.

7. The method for preparing CLT acid by pipeline continuous catalytic hydrogenation reduction according to claim 5, characterized in that: In the step S1, the gas replacement includes: replacing air twice with nitrogen in the entire reaction system, and then replacing nitrogen twice with hydrogen; pumping hot water into the reaction system through the CLT acid nitrate metering pump (1) includes: pumping 70° C. hot water into the multi-stage static pipeline mixer (3) through the CLT acid nitrate metering pump (1) until the liquid level in the gas-liquid separation tank (4) shows 0.2 meters.

8. The method for preparing CLT acid by pipeline continuous catalytic hydrogenation reduction according to claim 5, characterized in that: In the step S2, the portion of the platinum-carbon catalyst aqueous solution is 5% of the total amount of the platinum-carbon catalyst aqueous solution, and the condition for introducing hydrogen is: introducing hydrogen until the hydrogen pressure in the system reaches 0.8 MPa.

9. The method for preparing CLT acid by pipeline continuous catalytic hydrogenation reduction according to claim 5, characterized in that: In the step S3, the number of the multi-stage static tubular mixers is 5, and the introducing of hydrogen through the hydrogen input pipeline (11) below each stage of the tubular mixers comprises: introducing hydrogen into the reaction system through the hydrogen input pipeline (11) below the 1st to 4th stage static tubular mixers, controlling the hydrogen introduction amounts of the 1st stage, the 2nd stage, the 3rd stage, and the 4th stage to be 50%, 30%, 15%, and 5% of the total flow rate, respectively, and maintaining the hydrogen pressure at 0.8-1.0Mpa.

10. The method for preparing CLT acid by pipeline continuous catalytic hydrogenation reduction according to claim 5, characterized in that: The step S4 specifically comprises: when the liquid level in the gas-liquid separation tank (4) reaches a set height of 1 meter, the discharge regulating valve (8) at the bottom of the gas-liquid separation tank (4) is automatically opened, and the reduced liquid at the bottom that has completed the reaction is placed in the reduced liquid temporary storage tank (5), and the liquid level of the gas-liquid separation tank (4) is further controlled to be between 1 and 1.2 meters, and the pressure of the gas-liquid separation tank (4) is controlled to be between 0.8 and 1.0 MPa through the tail gas pressure regulating valve at the top of the gas-liquid separation tank (4).

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