Reaction equipment for preparing benzyl pyridinium nicotinate and preparation process of benzyl pyridinium nicotinate

Abstract

The invention relates to the technical field of chemical synthesis, in particular to reaction equipment for preparing benzyl pyridinium nicotinate and a preparation process of the benzyl pyridinium nicotinate. The reaction equipment for preparing the benzyl pyridinium nicotinate comprises a heat preservation shell, a reaction kettle, a temperature control device and a temperature control device, and an installation space is formed in the heat preservation shell; the mixing cavity is arranged at the top of the mounting space, a feeding pipe is arranged at the top in the mixing cavity, and a discharging opening is formed in the bottom; the mixed reaction module comprises a feeding cavity, a mixed reaction pipe and a discharging cavity; the mixed reaction tube comprises a detection unit, a mixing unit and a verification unit; the collecting cavity is arranged below the mixing reaction pipe, is used for collecting and conveying the mixed liquid conveyed by the mixing reaction pipe, and is communicated with the mixing cavity and / or the feeding cavity through a conveying pipeline; and the bidirectional stirring mechanism is arranged in the mixing cavity and the collecting cavity. Under the condition that no catalyst is adopted, side reactions can be effectively inhibited, generation of by-products is reduced, the displacement and deep plating capacity is effectively improved, and the industrial value is good.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical synthesis, and in particular to a reaction device for preparing benzylnicotinate iodide and a preparation process thereof. Background Art

[0002] Benzylpyridinium 3-carboxylate (BPC), a core brightener in cyanide-free zinc plating, has become a key material driving technological upgrades in the industry thanks to its exceptional brightening and leveling properties. It precisely regulates the deposition behavior of metal ions during the electroplating process, significantly improving the leveling of the coating and achieving a mirror-like gloss, effectively enhancing the product's appearance and corrosion resistance.

[0003] At present, the preparation of BPC is mainly achieved through the chemical reaction of nicotinic acid, benzyl chloride and sodium hydroxide. The main synthesis reaction is: C6H5NO2+C7H7Cl+NaOH→C 13 H 11 NO2 + +NaCl+H2O, the specific equation is as follows Figure 1 shown.

[0004] The main reaction will produce multiple side reactions. The main one is that when the pH is low, benzyl chloride is hydrolyzed to form benzyl alcohol: C7H7Cl+H2O→C7H7OH+HCl. The specific equation is as follows: Figure 2 As shown; or benzyl alcohol dehydrates and couples at high temperature to form dibenzyl ether: 2C7H7OH→C6H5CH2-O-C6H5CH2+H2O, the specific equation is as follows Figure 3 When the pH is high, benzyl chloride is easily hydrolyzed to form benzyl alcohol: C6H5CH2Cl+NaOH→C6H5CH2OH+NaCl, or undergoes elimination reaction to form styrene: C6H5CH2Cl+2NaOH→C6H5=CH2+NaCl+H2O.

[0005] In order to suppress side reactions and improve product purity, the market currently mainly uses a mixture of K2CO3 or Na2CO3 and quaternary ammonium salts as a composite catalyst, and introduces a buffer to shorten the entire reaction time and increase purity.

[0006] However, the catalyst components introduced into the reaction system, such as quaternary ammonium salts, may react with metal ions (such as Zn 2+) form complexes, altering its deposition behavior and leading to uneven metal deposition rates. This can result in uneven coating thickness or localized "burning" and can affect the coating crystallization process, potentially leading to coarse crystals or a loose coating. Furthermore, the introduction of catalysts not only affects the coating's appearance but also contaminates the plating solution during continued use, affecting its long-term stability, increasing the difficulty of process control, and increasing the difficulty of wastewater treatment. Quaternary ammonium salts can also decompose in strong alkalis, forming colored polymers or oxidation products that darken the solution.

[0007] As mentioned above, the conventional synthesis of benzylnicotinate onium salts utilizes a composite catalyst and buffer. However, this approach results in catalyst residue in the resulting benzylnicotinate onium salt, which can affect the coating quality during the zinc plating process. Without a catalyst, existing reaction equipment provides relatively crude reaction control, unable to precisely control the pH and temperature of different regions. The only option is to drip a conditioning solution through a feed mechanism and then disperse it into the mixed solution using a stirring device. As the primary reaction proceeds, numerous side reactions occur, resulting in an excessive number of byproducts, ultimately affecting product yield.

[0008] Furthermore, at high temperatures, benzylnicotinate not only undergoes a side reaction involving the dehydration coupling of benzyl alcohol to form dibenzyl ether, but also undergoes the elimination reaction of benzyl chloride to form styrene. When the system temperature is >90°C and alkaline conditions are present, benzyl chloride readily forms benzyl alcohol, with the hydrolysis rate increasing 5-8 times with every 10°C increase in temperature. Furthermore, the elimination reaction to form styrene is evident at temperatures >100°C, with trace amounts already occurring above 80°C. Inadequate stirring during the dropwise addition of benzyl chloride or during the initial reaction phase can lead to excessive concentrations of benzyl chloride in certain areas, resulting in a localized, intense reaction and a sharp rise in temperature. Conventional reactors rely on a single stirring device to maintain uniform mixing during both the addition and reaction. However, this can cause laminar flow due to centrifugal forces or create dead spots at the edges, leading to uneven material distribution and the inability to dissipate accumulated reaction heat, ultimately rendering the reaction conditions inoperable.

[0009] Therefore, it is urgent to develop a reaction equipment that can carry out large-scale continuous production by precisely controlling parameters such as the reaction liquid temperature and pH value during the reaction process, thereby obtaining high-purity benzylnicotinate ion salt without introducing a catalyst. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to provide a reaction device for preparing benzyl nicotinate onium salt, so as to solve the problem that the existing benzyl nicotinate onium salt preparation process requires the introduction of a composite catalyst, which affects the coating during subsequent use.

[0011] In order to solve the above technical problems, the technical solution adopted by the present invention is: a reaction device for preparing benzyl nicotinate iodine salt, comprising: A heat-insulating shell with an interior installation space; The mixing chamber is arranged at the top of the installation space, and is provided with a feed pipe at the top and a discharge port at the bottom; The mixing reaction module includes a feed chamber, a mixing reaction tube and a discharge chamber. The mixing reaction tubes are arranged in a ring shape and are arranged below the feed chamber. The feed chamber is connected to the discharge port through a connecting pipe. The feed chamber is provided with a distribution port corresponding to the mixing reaction tube. The mixed liquid in the feed chamber flows through the mixing reaction tube and enters the discharge chamber. The discharge chamber is connected to the feed chamber through a delivery pipe. The mixing reaction tube includes at least one group of detection units, a mixing unit and a verification unit. The detection unit is used to detect the pH value of the solution entering the mixing unit. The side wall of the mixing unit is provided with a regulating pipe, which is connected to the regulating liquid delivery pipe. The regulating liquid delivery pipe delivers the regulating liquid to the mixing reaction tube according to the signal sent by the detection unit. The verification unit is arranged below the mixing unit and is used to detect the change in the transmittance of the liquid flowing through the verification unit. The collecting chamber is arranged below the mixing reaction tube, and is used to collect and transport the mixed liquid transported from the mixing reaction tube, and is connected to the mixing chamber and / or the feeding chamber through the transport pipeline; The bidirectional stirring mechanism is arranged inside the mixing cavity and the collecting cavity, and is used to fully stir the liquid in the mixing cavity and the collecting cavity.

[0012] In one embodiment, the detection unit is disposed on the top of the mixing unit, and a pH meter and a temperature sensor are embedded in the side wall of the detection unit.

[0013] In one embodiment, the detection unit, the mixing unit and the verification unit are covered with segmented heat exchange rings, and the heat exchange rings adjust the heat exchange temperature according to the signals from the detection unit and / or the verification unit.

[0014] In one embodiment, the verification unit includes a cylinder, a fixed sleeve, a transparent window, a laser and a receiver. A pair of fitting grooves are provided on the side wall of the cylinder, and the transparent window is arranged in the fitting grooves; the fixed sleeve is arranged on the cylinder, and two irradiation holes are provided on the fixed sleeve. The irradiation holes extend from the fixed sleeve to the corresponding transparent window, and the laser and receiver are respectively arranged in the irradiation holes.

[0015] In one embodiment, the diameter of the mixing unit is first reduced and then increased to form a Venturi structure, and the regulating pipeline is connected to the smallest diameter point of the mixing unit.

[0016] In one embodiment, heat exchange loops are provided on the outer walls of the mixing chamber and the collecting chamber.

[0017] In one embodiment, a circulation pump and a delivery pump are provided on the delivery pipeline. The circulation pump circulates the mixed liquid in the mixing reaction module, and the delivery pump pumps the mixed liquid in the collecting chamber to the mixing chamber or the feeding chamber.

[0018] In one embodiment, the bidirectional stirring mechanism includes a driving motor, a gear frame, a driving bevel gear, a first bevel gear and a second bevel gear, a hollow rotating shaft and a driven shaft. The driving bevel gear, the first bevel gear and the second bevel gear are arranged on the gear frame, the driving bevel gear is connected to the output end of the driving motor, the first bevel gear and the second bevel gear are meshed with the driving bevel gear and are respectively arranged on the upper and lower sides of the driving bevel gear, the hollow rotating shaft is connected to the second bevel gear, the driven shaft is connected to the first bevel gear and passes through the axis of the hollow rotating shaft and extends downward, the driving motor causes the hollow rotating shaft and the driven shaft to rotate in opposite directions, and stirring paddles are provided at the ends of the hollow rotating shaft and the driven shaft.

[0019] A process for preparing benzylnicotinate onium salt, using any of the above-described reaction equipment for preparing benzylnicotinate onium salt, comprises the following steps: Adding a sodium hydroxide solution to a reaction device for preparing benzyl nicotinate onium salt, dissolving nicotinic acid in the sodium hydroxide solution, then dropwise adding benzyl chloride at 70° C. to 75° C., stirring thoroughly during the dropwise addition, and then sequentially carrying out the first, second, and third stage reactions to obtain benzyl nicotinate onium salt; The first stage is to react at a pH value of 6.5-6.8 for 35-50 minutes, the second stage is to react at a pH value uniformly increased from 6.8 to 7.3 for 45-60 minutes, and the third stage is to react at a pH value of 7.4±0.1 for 25-35 minutes. The reaction temperature for the first stage is 70°C-75°C, and the reaction temperatures for the second and third stages are 75°C-80°C.

[0020] In one embodiment, the molar ratio of nicotinic acid, sodium hydroxide, and benzyl chloride is 1.01-1.05:1.01-1.05:1.

[0021] In one embodiment, the concentration of the sodium hydroxide solution is 5% to 40% by mass, and the concentration of the sodium hydroxide solution used in the pH adjustment process is 5% to 15%. Preferably, the concentration of the sodium hydroxide solution is 22%.

[0022] In one embodiment, the ratio of the addition rate of the sodium hydroxide solution in the first stage to the addition rate of the sodium hydroxide solution in the second stage is 2-3:1.

[0023] In one embodiment, the first stage, the second stage and the third stage are circulated in the mixing reaction module respectively, and the different reaction stages are circulated from the mixing reaction module to the collecting chamber and then to the mixing chamber when alternating.

[0024] The beneficial effects of the present invention are: 1. The reaction equipment for preparing benzylnicotinate onium salt provided by the present invention forms a reaction chamber for collecting, dispersing, and then collecting again through a mixing chamber, a mixing reaction module, and a collecting chamber. While enabling mass production, the reaction at different stages can be finely controlled within the mixing reaction module, significantly improving reaction efficiency and shortening reaction time. At the same time, it can inhibit the occurrence of side reactions, resulting in a low content of by-products in the obtained benzylnicotinate onium salt, effectively increasing its travel depth in galvanizing applications, and having good industrial application value.

[0025] 2. The present invention uses a mixing chamber with a bidirectional stirring mechanism to disperse the feed in time when the material is added. The bidirectional stirring mechanism causes the material to form turbulence in the mixing chamber, so that the overall components of the mixed liquid formed after stirring are evenly distributed, avoiding the situation where the local concentration is too high. In addition, the mixed reaction module used in the present invention disperses the mixed liquid into multiple mixed reaction tubes through the feed chamber and then flows into the collection chamber, so that the mixed liquid circulates in the mixed reaction module, thereby avoiding the inability to disperse the heat accumulated in the local reaction, thereby effectively suppressing the occurrence of side reactions.

[0026] 3. The preparation process provided by the present invention has strict pH control requirements for the first, second, and third stages of the benzylnicotinate iodide reaction process. Conventional reactors typically rely on a feed pipe to control the overall pH value when adding a regulating solution. This results in a delayed overall regulation process and a lack of actual feedback. Therefore, conventional reactors are unable to achieve the pH control requirements of the present invention. The present invention, however, incorporates a detection unit within the mixing reaction tube. This detection unit detects the pH value of the mixed solution at different stages within the mixing reaction tube, transmitting the signal in real time to a regulating solution delivery pipe. This pipe then delivers the regulating solution to the reaction tube based on the actual pH of the mixed solution, thereby ensuring that the pH of the mixed solution meets the requirements and that parameter adjustment is accurate.

[0027] 4. The overall appearance of benzyl nicotinate iodide varies from light yellow to dark brown depending on the concentration and content of by-products. During the reaction process, if excessive by-products are generated due to local temperature or pH fluctuations, dark brown or dark brown substances will appear in the final product, seriously affecting product quality. The present invention disperses the reaction solution through a mixed reaction module and detects and adjusts the pH value during the reaction process through a detection unit. Although it can suppress side reactions, due to the large number of side reactions of benzyl nicotinate iodide, the overall process is affected by the combined effects of various factors such as stirring, temperature, and pH. At the same time, different factors have different degrees of influence in different reaction processes. The detection unit can only reflect a part of the reaction environment. The operator still cannot directly obtain the actual effect after adjusting the pH value or the degree of dispersion, and the overall reaction process cannot be effectively monitored. If the reaction conditions are compared based on the quality of the final product, not only will the initial cost be high and waste products will easily be generated, but due to factors such as control deviation, it will be difficult for the operator to find the point where the problem occurs. Therefore, the present invention uses a verification unit to illuminate the reaction liquid. When the dark brown or dark brown substance disperses through the verification unit, it absorbs a greater amount of light emitted by the laser than a normal mixture, resulting in a significant decrease in light intensity received by the receiver. The intensity changes detected by the verification unit provide real-time visibility into byproduct formation during the reaction, directly confirming whether byproducts are being formed. This allows for direct verification of the effectiveness of parameter adjustments during the reaction, providing real-time feedback to operators and effectively controlling the reaction environment.

[0028] During specific control, when a significant drop in light intensity is detected in the verification unit, the corresponding mixed reaction tube can automatically lower the corresponding reaction temperature or pH value according to the settings, thereby inhibiting the progress of side reactions. If the verification unit continues to be abnormal or multiple mixed reaction tubes are abnormal, the delivery path of the reaction liquid can be adjusted through the delivery pipeline so that the reaction liquid converges to the collection chamber for re-stirring before being input into the mixed reaction module. An alarm signal will be sent to the operator to indicate that the overall process is abnormal and prompt manual intervention, so that the entire equipment can automatically perform dynamic balance of the reaction process and promptly remind manual intervention and adjustment when major abnormalities occur. Not only can the reaction process be adjusted in a timely manner, but it can also remind manual intervention when major abnormalities occur, thereby ensuring the quality of the final product.

[0029] 5. The reaction equipment for preparing benzylnicotinate onium salt provided by the present invention can combine data from the detection unit and the verification unit in real time to promptly control the reaction parameters and provide intuitive feedback on the adjustment effect, making the overall reaction process more controllable. This allows the formation of by-products to be precisely suppressed without the introduction of a catalyst, effectively improving the reaction yield and purity of benzylnicotinate onium salt.

[0030] 6. The present invention provides a process for preparing benzylnicotinate onium salt by precisely controlling the pH and temperature at three stages using the benzylnicotinate onium salt preparation equipment. This allows for real-time adjustments to the reaction process based on actual conditions, and timely feedback is obtained for further adjustments to ensure the normal progress of the main reaction. This process effectively suppresses side reactions and reduces the formation of byproducts without the use of a catalyst, thus possessing excellent industrial value.

[0031] Other features and beneficial effects of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purposes and other beneficial effects of the present invention can be achieved and obtained by the structures and / or components specified in the description and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is the main reaction equation for the synthesis of benzyl nicotinate; Figure 2 The equation for the hydrolysis of benzyl chloride to form benzyl alcohol is given; Figure 3 The equation for the dehydration coupling of benzyl alcohol to form dibenzyl ether; Figure 4 is a three-dimensional schematic diagram of an embodiment of the present invention; Figure 5 for Figure 4 A top view of Figure 6 for Figure 5 Cross-section at AA; Figure 7 for Figure 6 A partial enlarged view of point B in the middle; Figure 8 for Figure 4 Exploded view of; Figure 9 This is an exploded view of a unit group of a mixing reaction tube in one embodiment of the present invention; Figure 10 This is a cross-sectional view of a unit group of a mixing reaction tube in one embodiment of the present invention; Figure 11 A cross-sectional view of a unit group of a mixing reaction tube in another embodiment of the present invention; Figure 12 This is a physical comparison diagram of Example 1 of the present invention and Comparative Examples 1 and 2.

[0033] Description of labels: 1. Insulation shell; 2. Mixing chamber; 21. Feed pipe; 22. Discharge port; 3. Mixing reaction module; 31. Feed chamber; 311. Connecting pipe; 312. Distribution port; 32. Mixing reaction tube; 321. Detection unit; 3211. pH meter; 3212. Temperature sensor; 322. Mixing unit; 323. Verification unit; 3231. Cylinder; 3232. Fixing sleeve; 3233. Transparent window; 3234. Laser ; 3235, receiver; 324, heat exchange ring sleeve; 33, discharge cavity; 34, regulating pipeline; 35, regulating liquid delivery pipe; 4, collecting cavity; 5, delivery pipeline; 51, circulation pump; 52, delivery pump; 6, two-way stirring mechanism; 61, driving motor; 62, gear rack; 63, driving bevel gear; 64, first bevel gear; 65, second bevel gear; 66, hollow rotating shaft; 67, driven shaft; 68, stirring paddle; 7, heat exchange ring pipe. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments; the technical features designed in different implementation modes of the present invention described below can be combined with each other as long as they do not conflict with each other; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0035] In the description of the present invention, it should be noted that all terms used in the present invention (including technical terms and scientific terms) have the same meanings as those generally understood by ordinary technicians in the field to which the present invention belongs, and should not be understood as limiting the present invention; it should be further understood that the terms used in the present invention should be understood to have the same meanings as these terms in the context of this specification and the relevant field, and should not be understood in an idealized or overly formal sense, unless explicitly defined as such in the present invention.

[0036] like Figures 4-11 As shown, a reaction device for preparing benzyl nicotinate iodine salt comprises: The heat-insulating shell 1 has an installation space inside; The mixing chamber 2 is arranged at the top of the installation space, and is provided with a feed pipe 21 at the top and a discharge port 22 at the bottom; The mixing reaction module 3 includes a feed chamber 31, a mixing reaction tube 32 and a discharge chamber 33. The mixing reaction tube 32 is arranged in a ring shape and is arranged below the feed chamber 31. The feed chamber 31 is connected to the discharge port 22 through a connecting pipe 311. The feed chamber 31 is provided with a distribution port 312 corresponding to the mixing reaction tube 32. The mixed liquid in the feed chamber 31 flows through the mixing reaction tube 32 and enters the discharge chamber 33. The discharge chamber 33 is connected to the feed chamber 31 through the conveying pipe 5. At least one group of detection units 321, mixing units 322 and verification units 323, the detection unit 321 is used to detect the pH value of the solution entering the mixing unit 322, the side wall of the mixing unit 322 is provided with a regulating pipeline 34, the regulating pipeline 34 is connected to the regulating liquid delivery pipe 35, and the regulating liquid delivery pipe 35 delivers the regulating liquid to the mixing reaction tube 32 according to the signal sent by the detection unit 321; the verification unit 323 is set below the mixing unit 322, and is used to detect the transmittance change of the liquid flowing through the verification unit 323.

[0037] The collecting chamber 4 is arranged below the mixing reaction tube 32 and is used to collect and transport the mixed liquid transported by the mixing reaction tube 32. It is connected to the mixing chamber 2 and the feeding chamber 31 separately through the transport pipeline 5; or the collecting chamber 4 is connected to the mixing chamber 2 and the feeding chamber 31 at the same time through the transport pipeline 5; The bidirectional stirring mechanism 6 is arranged inside the mixing cavity 2 and the collecting cavity 4 and is used to fully stir the liquid in the mixing cavity 2 and the collecting cavity 4 .

[0038] Specifically, one detection unit 321 , one mixing unit 322 , and one verification unit 323 in the mixed reaction tube 32 are sequentially connected to form one unit group.

[0039] Specifically, the regulating solution is 15% sodium hydroxide solution.

[0040] Specifically, the collecting chamber 4 outputs the mixed liquid to the outside through the delivery pipeline 5.

[0041] Preferably, each mixing reaction tube 32 is composed of at least three groups of detection units 321, mixing units 322, and verification units 323. This arrangement ensures that the mixed liquid has sufficient detection, adjustment, and reaction time during a single passage through the mixing reaction tube 32. Those skilled in the art can adjust the length of the mixing reaction tube 32, the number of groups of each unit, and the number of mixing reaction tubes 32 according to production volume, and are not specifically limited.

[0042] Preferably, a solenoid valve is provided on the distribution port 312. During actual operation, the operator can control the mixed liquid to enter a specific mixing reaction tube 32 or shield a specific mixing reaction tube 32 through the solenoid valve on the distribution port 312, thereby improving the overall adjustability.

[0043] Specifically, a solenoid valve is provided on the regulating pipeline 34 , and the solenoid valve can adjust the opening according to the signal transmitted from the detection unit 321 , thereby controlling the amount of the regulating liquid added and ensuring the accuracy of pH value control.

[0044] Specifically, the actual transmittance range can be adjusted by those skilled in the art according to the concentration of the target product and is not specifically limited.

[0045] Preferably, the middle part of the discharge cavity 33 is provided with a bidirectional stirring mechanism 6 corresponding to the collecting cavity 4 to avoid the installation space.

[0046] In this embodiment, the detection unit 321 is disposed on the top of the mixing unit 322 , and a pH meter 3211 and a temperature sensor 3212 are embedded in the side wall of the detection unit 321 .

[0047] Preferably, to ensure detection accuracy and prevent detection failure due to abnormalities in the pH meter 3211 and temperature sensor 3212, two pH meters 3211 and two temperature sensors 3212 are provided in each detection unit 321. This arrangement allows the pH meters 3211 and temperature sensors 3212 in each detection unit 321 to be compared with each other, thereby improving detection accuracy. Furthermore, the solenoid valve on the regulating liquid delivery pipe 35 can be adjusted based on the average values ​​of the pH meter 3211 and temperature sensor 3212, thereby ensuring regulation accuracy.

[0048] Reaction temperature is an important parameter in the synthesis process of benzylnicotinate. In order to achieve precise temperature control, in this embodiment, the detection unit 321, the mixing unit 322, and the verification unit 323 are equipped with segmented heat exchange rings 324. The heat exchange rings 324 in different positions adjust the heat exchange temperature based on the signals from the detection unit 321 or the verification unit 323, or the entire device adjusts the heat exchange temperature based on the signals from the detection unit 321 and the verification unit 323.

[0049] Specifically, a semiconductor refrigeration plate is provided in the heat exchange ring sleeve 324. When the semiconductor refrigeration plate receives a signal from the detection unit 321 or the verification unit 323 indicating that the temperature is too high or a large number of side reactions have occurred, it cools down the reaction liquid, thereby ensuring that the temperature of the reaction liquid does not exceed the limit value.

[0050] Preferably, the temperature of the heat exchange ring sleeve 324 corresponding to the detection unit 321 is adjusted according to the mixed liquid temperature measured by the detection unit 321, and the heat exchange ring sleeve 324 on the verification unit 323 and the mixing unit 322 is initially the same as the temperature of the heat exchange ring sleeve 324 corresponding to the detection unit 321. When the verification unit 323 detects that the transmittance fluctuates out of the range, the temperature of the heat exchange ring sleeve 324 on this group and the next group of verification units 323 and the mixing unit 322 is reduced or cooled until the transmittance returns to the normal range.

[0051] In this embodiment, the verification unit 323 includes a cylindrical body 3231, a fixing sleeve 3232, a transparent window 3233, a laser 3234, and a receiver 3235. The sidewall of the cylindrical body 3231 is provided with a pair of engaging grooves, within which the transparent window 3233 is disposed. The fixing sleeve 3232 is mounted on the cylindrical body 3231 and has two illumination holes extending from the fixing sleeve 3232 to the corresponding transparent windows 3233. The laser 3234 and the receiver 3235 are respectively disposed within the illumination holes. Specifically, the fixing sleeve 3232 is provided with an escape groove corresponding to the transparent window 3233, allowing the transparent window 3233 to partially fit within the fixing sleeve 3232, thereby allowing the laser 3234 and the receiver 3235 to abut against the transparent window 3233, thereby ensuring that the relative positions of the laser 3234 and the receiver 3235 remain unchanged.

[0052] Preferably, the inner diameter of the verification unit 323 gradually expands from its connection with the other units to the transparent window 3233, with the ratio of the maximum inner diameter of the verification unit 323 to the maximum inner diameter of the mixing unit 322 being 1.2 to 3:1. That is, the internal cavity structure of the verification unit 323 exhibits an overall structure that first expands and then contracts. This arrangement decelerates the mixed liquid entering the verification unit 323 from the mixing unit 322, while also fully rupturing any bubbles in the mixed liquid, effectively preventing bubbles from interfering with transmittance testing.

[0053] Preferably, the laser wavelength emitted by laser 3234 is 400-700 nm. More preferably, the laser wavelength emitted by laser 3234 is 400-450 nm or 500-700 nm. Preferably, laser 3234 simultaneously emits lasers of different wavelengths, and by simultaneously detecting the intensity attenuation of multiple lasers, precise reaction byproduct detection can be achieved.

[0054] To ensure that the regulating liquid is fully mixed with the mixed liquid in the pipeline after being added, in this embodiment, the diameter of the mixing unit 322 first decreases and then increases, forming a Venturi structure, and the regulating pipeline 34 is connected to the smallest diameter point of the mixing unit 322. That is, the mixing unit 322 adopts a Venturi structure, and the diameter of the mixing unit 322 first decreases and then increases. When the mixed liquid flows through the mixing unit 322, the regulating liquid enters the mixing unit 322 through the throat of the Venturi structure. The high-speed flowing mixed liquid impacts the regulating liquid, ensuring that the regulating liquid and the mixed liquid are fully mixed.

[0055] In order to ensure the temperature of the entire reaction process and avoid excessive local heating of the mixed liquid in direct contact with the heat exchange tube, in this embodiment, the outer walls of the mixing chamber 2 and the collecting chamber 4 are provided with a heat exchange loop 7. The heat exchange loop 7 arranged on the outside conducts heat to the liquid in the mixing chamber 2 and the collecting chamber 4, ensuring the reaction temperature while suppressing the occurrence of side reactions. At the same time, the heat exchange loop 7 cooperates with the heat exchange ring sleeve 324 of the mixed reaction module 3, so that the entire device has a segmented temperature control capability and enhances the adjustable capability of the device. Specifically, the temperature of the heat exchange medium in the heat exchange loop 7 is slightly lower than the initial set temperature, avoiding a sharp rise in temperature when adding reactants, resulting in a temperature exceeding the range. Furthermore, the heat exchange loop 7 is provided with a reserve heat exchange tube that can be connected to different heat exchange media. When the temperature is too high and needs to be cooled, the reserve heat exchange tube can be activated to cool the reaction liquid in time, thereby ensuring the control effect.

[0056] In this embodiment, a circulation pump 51 and a delivery pump 52 are provided on the delivery pipeline 5. The circulation pump 51 circulates the mixed liquid in the mixing reaction module 3, and the delivery pump 52 pumps the mixed liquid in the collecting chamber 4 to the mixing chamber 2 or the feeding chamber 31. This arrangement enables the entire device to have a small cycle within the reaction stage and a large cycle across stages, or it can be realized as needed that the mixed liquid in the mixing reaction module 3 enters the collecting chamber 4 for sufficient stirring and then continues to enter the mixing reaction module 3 for reaction, thereby improving the adjustable capacity of the device. Specifically, a solenoid valve is provided on the delivery pipeline 5, and technicians control the path of the mixed liquid by switching the solenoid valves at different positions.

[0057] Preferably, a control valve is provided between the mixing reaction tube 32 and the discharge chamber 33. The control valve enables the operator to control whether different mixing reaction tubes 32 are connected to the discharge chamber 33. When the verification unit 323 detects a large amount of by-products in a single mixing reaction tube 32, while adjusting the reaction parameters, the valves of other mixing reaction tubes 32 can be closed, and the by-products can be discharged separately before continuing the reaction cycle to avoid the generated by-products affecting the judgment of the verification unit 323 within the cycle.

[0058] Preferably, a control module is also included, which is electrically connected to the mixing reaction module 3, the two-way stirring mechanism 6 and the solenoid valve in the conveying pipeline 5 or the regulating pipeline 34, so that the operator can obtain real-time data feedback and adjust the reaction process.

[0059] In this embodiment, the bidirectional stirring mechanism 6 includes a driving motor 61, a gear frame 62, a driving bevel gear 63, a first bevel gear 64 and a second bevel gear 65, a hollow rotating shaft 66 and a driven shaft 67. The driving bevel gear 63, the first bevel gear 64 and the second bevel gear 65 are arranged on the gear frame 62. The driving bevel gear 63 is connected to the output end of the driving motor 61. The first bevel gear 64 and the second bevel gear 65 are meshed with the driving bevel gear 63 and are respectively arranged on the upper and lower sides of the driving bevel gear 63. The hollow rotating shaft 66 is connected to the second bevel gear 65. The driven shaft 67 is connected to the first bevel gear 64 and passes through the axis of the hollow rotating shaft 66 and extends downward. The driving motor 61 causes the hollow rotating shaft 66 and the driven shaft 67 to rotate in opposite directions. The ends of the hollow rotating shaft 66 and the driven shaft 67 are provided with stirring paddles 68.

[0060] In this embodiment, the mixing chamber 2 and the collecting chamber 4 adopt a structure with a cylindrical upper part and a conical lower part. The bidirectional stirring mechanism 6 includes two stirring paddles 68 of a driving motor 61, which stir in the cylindrical area and the conical area respectively. The diameter of the stirring paddle 68 in the cylindrical area is larger than that of the stirring paddle 68 in the conical area.

[0061] The following examples are based on the reaction equipment for preparing benzylnicotinate iodide provided by the present invention. During the preparation, the first, second, and third stages are circulated in the mixing reaction module 3, and the different reaction stages are circulated from the mixing reaction module 3 to the collecting chamber 4 and then to the mixing chamber 2.

[0062] Example 1 366.6 g of sodium hydroxide solution (22% by mass) was added to a reaction apparatus for preparing benzylnicotinate onium salt, 250 g of nicotinic acid was dissolved in the sodium hydroxide solution, and then 250 g of benzyl chloride was added dropwise at 70° C. with sufficient stirring during the addition process. Then, the first, second, and third stage reactions were sequentially carried out to obtain benzylnicotinate onium salt. The first stage was carried out at 70°C and a pH value range of 6.5-6.8 for 40 minutes. The second stage was carried out at 75°C and a pH value uniformly increased from 6.8 to 7.2 for 50 minutes. The third stage was carried out at 78±0.5°C and a pH value of 7.4±0.1 for 30 minutes. The pH was adjusted with 15% NaOH solution.

[0063] After the reaction is completed, benzyl nicotinate is obtained in the form of a light yellow liquid with a product content of 48.4% (HPLC).

[0064] Example 2 732.0 g of a sodium hydroxide solution (22% by mass) was added to a reaction apparatus for preparing benzylnicotinate onium salt, 500 g of nicotinic acid was dissolved in the sodium hydroxide solution, and then 500 g of benzyl chloride was added dropwise at 70° C. with sufficient stirring during the addition process. Then, the first, second, and third stage reactions were sequentially carried out to obtain benzylnicotinate onium salt. The first stage was carried out at 70°C and a pH value range of 6.5-6.8 for 40 minutes. The second stage was carried out at 75°C and a pH value uniformly increased from 6.8 to 7.2 for 50 minutes. The third stage was carried out at 78±0.5°C and a pH value of 7.4±0.1 for 30 minutes. The pH was adjusted with 15% NaOH solution.

[0065] After the reaction is completed, benzyl nicotinate is obtained in the form of a light yellow liquid with a product content of 48.3% (HPLC).

[0066] Example 3 In a reaction apparatus for preparing benzylnicotinate onium salt, 3657.1 g of a sodium hydroxide solution (22% by mass) was added, 2500 g of nicotinic acid was dissolved in the sodium hydroxide solution, and then 2500 g of benzyl chloride was added dropwise at 70° C. with sufficient stirring during the addition process. Then, the first, second, and third stage reactions were sequentially carried out to obtain benzylnicotinate onium salt. The first stage was carried out at 70°C and a pH value ranging from 6.5 to 6.8 for 40 minutes. The second stage was carried out at 75°C and a pH value uniformly increased from 6.8 to 7.3 for 50 minutes. The third stage was carried out at 78±0.5°C and a pH value of 7.4±0.1 for 30 minutes. The pH was adjusted with 15% NaOH solution.

[0067] After the reaction is completed, benzyl nicotinate is obtained as a light yellow liquid with a product content of 48.5% (HPLC).

[0068] Comparative Example 1 To the reaction apparatus for preparing benzyl nicotinate iodide, add 366.6 g of sodium hydroxide solution (22% by mass), dissolve 250 g of nicotinic acid in the sodium hydroxide solution, and then add 250 g of benzyl chloride dropwise at 70°C with sufficient stirring. The reaction was carried out at 75°C and a pH of 7.4±0.1 for 2 h.

[0069] After the reaction is completed, benzyl nicotinate is obtained, which is a light brown liquid with a product content of 40.2% (HPLC).

[0070] Comparative Example 2 Add 366.6g of sodium hydroxide solution (mass fraction 22%) to a conventional reactor, dissolve 250g of nicotinic acid in the sodium hydroxide solution, adjust the pH to 7.4, and then add 250g of benzyl chloride dropwise at 75°C. Stir thoroughly during the addition process, and then react at 75°C for 2h.

[0071] After the reaction is completed, benzyl nicotinate is obtained as a dark brown liquid with a product content of 38.4% (HPLC).

[0072] The actual product comparison diagram of Example 1, Comparative Example 1 and Comparative Example 2 is as follows Figure 12 As shown, Figure 12 From left to right in the figure are the final products of Example 1, Comparative Example 1 and Comparative Example 2. A 500 ml Hull cell test and a throwing power test were performed on Example 1 and Comparative Example 2. The specific results are shown in Table 1.

[0073] Table 1 Experimental data and results

[0074] It should be noted that the specific parameters or some commonly used reagents in the above embodiments are specific embodiments or preferred embodiments under the concept of the present invention, and are not intended to limit the present invention; those skilled in the art can make adaptive adjustments within the concept and protection scope of the present invention.

[0075] In addition, unless otherwise specified, the raw materials used may be conventional commercial products in the art, or may be prepared by conventional methods in the art.

[0076] In addition, those skilled in the art should understand that, although there are many problems in the prior art, each embodiment or technical solution of the present invention may be improved in only one or several aspects, without having to simultaneously solve all the technical problems listed in the prior art or background art. Those skilled in the art should understand that any content not mentioned in a claim should not be construed as limiting the claim.

[0077] Although terms such as thermal insulation shell and mixing chamber are frequently used in this document, the possibility of using other terms is not excluded. These terms are used only to more conveniently describe and explain the essence of the present invention; interpreting them as any additional limitations is contrary to the spirit of the present invention. The terms "first" and "second" (if any) in the description and claims of the embodiments of the present invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A reaction device for preparing benzylnicotinate, characterized in that: include: A heat-insulating shell (1) having an installation space therein; A mixing cavity (2) is provided at the top of the installation space, and is provided with a feed pipe (21) at the top and a discharge port (22) at the bottom; A mixing reaction module (3) comprises a feed cavity (31), a mixing reaction tube (32) and a discharge cavity (33), wherein the mixing reaction tube (32) is arranged in a ring shape and is arranged below the feed cavity (31), the feed cavity (31) is connected to the discharge port (22) through a connecting pipe (311), the feed cavity (31) is provided with a distribution port (312) corresponding to the mixing reaction tube (32), the mixed liquid in the feed cavity (31) flows through the mixing reaction tube (32) and enters the discharge cavity (33), and the discharge cavity (33) is connected to the feed cavity (31) through a conveying pipe (5); the mixing reaction tube (32) includes at least one detection unit (321), a mixing unit (322) and a verification unit (323), wherein the detection unit (321) is used to detect the pH value of the solution entering the mixing unit (322), and a regulating pipeline (34) is provided on the side wall of the mixing unit (322), wherein the regulating pipeline (34) is connected to the regulating liquid delivery pipe (35), and the regulating liquid delivery pipe (35) delivers the regulating liquid to the mixing reaction tube (32) according to the signal sent by the detection unit (321); the verification unit (323) is arranged below the mixing unit (322) and is used to detect the change in the transmittance of the liquid flowing through the verification unit (323); a collecting chamber (4), arranged below the mixing reaction tube (32), for collecting and conveying the mixed liquid conveyed from the mixing reaction tube (32), and communicating with the mixing chamber (2) and / or the feeding chamber (31) via the conveying pipeline (5); A bidirectional stirring mechanism (6) is arranged inside the mixing cavity (2) and the collecting cavity (4) and is used to fully stir the liquid in the mixing cavity (2) and the collecting cavity (4).

2. The reaction equipment for preparing benzylnicotinate according to claim 1, characterized in that: The detection unit (321) is arranged on the top of the mixing unit (322), and a pH meter (3211) and a temperature sensor (3212) are embedded in the side wall of the detection unit (321).

3. The reaction equipment for preparing benzylnicotinate according to claim 2, characterized in that: The detection unit (321), the mixing unit (322), and the verification unit (323) are sleeved with heat exchange rings (324) arranged in sections, and the heat exchange rings (324) adjust the heat exchange temperature according to the signals of the detection unit (321) and / or the verification unit (323).

4. The reaction equipment for preparing benzylnicotinate according to claim 1, characterized in that: The verification unit (323) comprises a cylinder (3231), a fixing sleeve (3232), a transparent window (3233), a laser (3234) and a receiver (3235); a pair of interlocking grooves are provided on the side wall of the cylinder (3231); the transparent window (3233) is arranged in the interlocking grooves; the fixing sleeve (3232) is sleeved on the cylinder (3231); two irradiation holes are provided on the fixing sleeve (3232); the irradiation holes extend from the fixing sleeve (3232) to the corresponding transparent window (3233); the laser (3234) and the receiver (3235) are respectively arranged in the irradiation holes.

5. The reaction equipment for preparing benzylnicotinate according to claim 1, characterized in that: The diameter of the mixing unit (322) first decreases and then increases, forming a Venturi structure, and the regulating pipeline (34) is connected to the smallest diameter point of the mixing unit (322).

6. The reaction equipment for preparing benzylnicotinate according to claim 1, characterized in that: Heat exchange loops (7) are provided on the outer walls of the mixing cavity (2) and the collecting cavity (4).

7. The reaction equipment for preparing benzylnicotinate according to claim 1, characterized in that: The delivery pipeline (5) is provided with a circulation pump (51) and a delivery pump (52), wherein the circulation pump (51) circulates the mixed liquid in the mixed reaction module (3), and the delivery pump (52) pumps the mixed liquid in the collecting cavity (4) to the mixing cavity (2) or the feeding cavity (31).

8. The reaction equipment for preparing benzylnicotinate according to claim 1, characterized in that: The bidirectional stirring mechanism (6) comprises a driving motor (61), a gear frame (62), a driving bevel gear (63), a first bevel gear (64), a second bevel gear (65), a hollow rotating shaft (66), and a driven shaft (67). The driving bevel gear (63), the first bevel gear (64), and the second bevel gear (65) are arranged on the gear frame (62). The driving bevel gear (63) is connected to the output end of the driving motor (61). The first bevel gear (64) and the second bevel gear (65) are connected to the output end of the driving motor (61). The driving bevel gear (63) is meshed and respectively arranged on the upper and lower sides of the driving bevel gear (63), the hollow rotating shaft (66) is connected to the second bevel gear (65), the driven shaft (67) is connected to the first bevel gear (64) and passes through the axis of the hollow rotating shaft (66) and extends downward, the driving motor (61) causes the hollow rotating shaft (66) and the driven shaft (67) to rotate in opposite directions, and the ends of the hollow rotating shaft (66) and the driven shaft (67) are both provided with stirring paddles (68).

9. A process for preparing benzylnicotinate onium salt, using the reaction equipment for preparing benzylnicotinate onium salt according to any one of claims 1 to 8, characterized in that: The preparation steps are as follows: Adding a sodium hydroxide solution to the reaction equipment for preparing the benzylnicotinate onium salt, dissolving nicotinic acid in the sodium hydroxide solution, then dropwise adding benzyl chloride at 70° C. to 75° C., stirring thoroughly during the dropwise addition process, and then sequentially carrying out the first, second, and third stage reactions to obtain the benzylnicotinate onium salt; The first stage reacts at a pH value of 6.5-6.8 for 35-50 minutes, the second stage reacts at a pH value uniformly increased from 6.8 to 7.2-7.3 for 45-60 minutes, and the third stage reacts at a pH value of 7.4±0.1 for 25-35 minutes; the reaction temperature of the first stage is 70°C-75°C, and the reaction temperatures of the second and third stages are 75°C-80°C.

10. The process for preparing benzylnicotinate according to claim 9, wherein: The molar ratio of the nicotinic acid, sodium hydroxide and benzyl chloride is 1.01-1.05:1.01-1.05:1.

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