Cationic etherification agent based on composite catalyst synthesis and preparation method thereof

Abstract

This invention relates to the field of organic synthesis technology, and discloses a cationic etherifying agent synthesized based on a composite catalyst and its preparation method. The agent is prepared by reacting epichlorohydrin, trimethylamine, hydrogen chloride, and a composite catalyst, which consists of anhydrous zinc chloride, anhydrous citric acid, and polyethylene glycol 400. The preparation method includes: preparing a trimethylamine hydrochloride base solution containing the composite catalyst under slightly acidic conditions; performing a ring-opening etherification reaction by adding epichlorohydrin dropwise in a controlled temperature stepwise manner; digesting by heating and holding at a constant temperature; continuously blowing in inert gas under a slightly acidic negative pressure environment for microbubble devolatilization; and finally, rapidly cooling through an external heat exchange device to complete the crystallization blocking. This invention improves the low-temperature storage and transportation stability and environmental safety of the cationic etherifying agent by shortening the reaction cycle to less than 12 hours; utilizing steric hindrance coupled with rapid cooling to lower the crystallization point to -9°C to -11°C; and reducing residual trimethylamine to 15 to 30 ppm through a dielectric-controlled gas stripping process.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, specifically to a cationic etherifying agent synthesized based on a composite catalyst and its preparation method. Background Technology

[0002] 3-Chloro-2-hydroxypropyltrimethylammonium chloride, as a cationic etherifying agent, is a key cationic monomer in the field of starch and cellulose modification, and is widely used in industries such as papermaking, textiles, daily chemicals, and petroleum auxiliaries. Currently, the mainstream industrial production process mostly uses trimethylamine hydrochloride and epichlorohydrin as raw materials for synthesis.

[0003] However, a significant technical bottleneck exists in existing conventional synthesis processes: the inefficient removal of residual volatile free amines from the product, leading to substantial environmental and operational safety issues. During the synthesis and post-processing stages of traditional processes, the lack of targeted phase control and deep degassing mechanisms often results in a large amount of unreacted free trimethylamine remaining in the final aqueous solution. The concentration of this residue is typically as high as 1000 ppm to 2000 ppm, exhibiting strong toxicity and an irritating odor.

[0004] High concentrations of free trimethylamine not only readily volatilize during conventional low-temperature storage and transportation, but also release large quantities in downstream open industrial processing applications, directly polluting the operating environment and failing to meet the increasingly stringent environmental and occupational health standards of modern industry. Current conventional production enterprises attempting to reduce the residue of this volatile gas by simply extending the curing and holding time or using conventional high-temperature exhaust will not only lengthen the single-batch reaction cycle to over 16 hours, severely restricting production efficiency, but will also exacerbate side reactions within the system, causing the final product to crystallize and separate at around 0°C to -5°C, further deteriorating the product's low-temperature storage and transportation stability. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a cationic etherifying agent synthesized based on a composite catalyst and its preparation method, solving the problem of inefficient removal of residual volatile irritating gases in existing preparation processes.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a cationic etherifying agent synthesized based on a composite catalyst, comprising the following parts by weight of raw materials reacted together: 100 parts of epichlorohydrin; 55-61 parts of trimethylamine; 35-40 parts of hydrogen chloride; 0.20 to 0.50 parts of composite catalyst.

[0007] Preferably, the composite catalyst is composed of anhydrous zinc chloride, anhydrous citric acid and polyethylene glycol 400 in a weight ratio of 1.0-1.4:2.0-3.0:4.0-6.0.

[0008] Preferably, the mass fraction of the effective active ingredient 3-chloro-2-hydroxypropyltrimethylammonium chloride in the cationic etherifying agent is not less than 68.8%, and the mass fraction of epichlorohydrin homopolymer impurities is less than 0.2%.

[0009] Preferably, the residual trimethylamine concentration in the cationic etherifying agent is less than 15.0 ppm.

[0010] A method for preparing a cationic etherifying agent based on a composite catalyst includes the following steps: S1. Trimethylamine is neutralized with hydrochloric acid aqueous solution, and a composite catalyst is added under slightly acidic conditions. The mixture is stirred at a constant temperature to carry out a complexation reaction, thereby obtaining a trimethylamine hydrochloride base solution containing the composite catalyst. S2. Under controlled temperature, epichlorohydrin is added dropwise into the reactor at a constant flow rate to carry out the ring-opening etherification reaction. S3. After all the epichlorohydrin has been added, the mixture is heated in a sealed container and kept at a constant temperature with stirring to ensure complete conversion of the substrate and obtain the crude reaction product. S4. Without adding strong alkali solution, maintain the system in a slightly acidic range, and perform gas stripping degassing on the crude product of S3 under negative pressure and continuous inert gas injection. S5. Pump the high-temperature liquid after the S4 stripping process into an external heat exchanger and rapidly cool it to 15-20°C to stop crystallization, thus obtaining the cationic etherifying agent.

[0011] Preferably, step S1 is implemented as follows: trimethylamine aqueous solution is introduced into hydrochloric acid aqueous solution, the temperature inside the reactor is controlled at 30-40°C, the pH value of the liquid phase of the system is monitored in real time, and the introduction of trimethylamine is stopped when the pH value reaches 5.2-5.8; then, under the slightly acidic environment of maintaining this pH value, anhydrous citric acid, polyethylene glycol 400 and anhydrous zinc chloride are added in sequence, and the mixture is stirred at a constant temperature of 38-42°C for 20-40 minutes.

[0012] Preferably, the stepwise addition of epichlorohydrin in step S2 is carried out in the following two stages: First stage: Control the reaction temperature at 35-40℃, and add epichlorohydrin at a constant flow rate of 75.0%-85.0% of the total feed amount to the bottom liquid. The dropping time in this stage is controlled at 2.5-3.5 hours. Second stage: After the first stage of addition is completed, the temperature is steadily increased to 45-50℃ at a rate of 0.5-1.0℃ / min and kept constant at this temperature. Simultaneously, the remaining 15.0%-25.0% epichlorohydrin is continuously added dropwise at a rate lower than that of the first stage. The total addition time of this stage is controlled to be 0.8-1.2 hours.

[0013] Preferably, in step S3, the temperature is raised to 60-65°C and kept at a constant temperature with stirring for 1.5-2.5 hours.

[0014] Preferably, the specific implementation method of step S4 is as follows: after the heat preservation in S3, the pH value of the liquid phase is detected and naturally maintained in the range of 5.0 to 6.0. The system temperature is adjusted to 55 to 60°C, and the absolute pressure of the equipment is controlled to reach -0.080MPa to -0.095MPa. At the same time, high-purity nitrogen is continuously blown in from the microporous distributor at a gas flow rate of 0.1 to 0.3 volumes of gas per minute per volume of liquid. The negative pressure microbubble gas lifting process lasts for 1.5 to 2.5 hours.

[0015] Preferably, step S5 is implemented as follows: using a parallel external plate heat exchanger, the body temperature of all high-temperature liquid is rapidly reduced from 55-60°C to 15-20°C within a time window of 20-30 minutes; after the crystallization is blocked, 5%-10% dilute hydrochloric acid is added dropwise to adjust the pH value of the final product back to 6.0-7.0.

[0016] This invention provides a cationic etherifying agent synthesized based on a composite catalyst and its preparation method. It has the following beneficial effects: 1. This invention employs a composite catalyst composed of anhydrous zinc chloride, anhydrous citric acid, and polyethylene glycol 400, combined with a two-stage stepwise addition strategy, to match the dropwise addition rate of epichlorohydrin with the ring-opening reaction rate. This feature effectively controls the concentrated exothermic reaction, avoiding the risk of localized overheating. Therefore, it eliminates the need to extend the dropwise addition and holding time to prevent thermal runaway, shortening the overall reaction cycle from the traditional 16+ hours to less than 12 hours.

[0017] 2. This invention employs an external plate heat exchanger to rapidly cool the high-temperature liquid after devolatilization, combined with the steric hindrance provided by the polyethylene glycol 400 macromolecular segments within the system. The rapid cooling process forces fluid molecules to quickly cross the nucleation thermodynamic window, while the network structure of polyethylene glycol 400 prevents the formation of ordered hydrogen bonds between solvent and solute molecules. Through the synergistic effect of rapid cooling and steric hindrance, the crystallization point of the cationic etherifying agent aqueous solution is lowered to -9°C to -11°C, improving the precipitation and solidification problem of the product at low temperatures.

[0018] 3. This invention employs a devolatilization process coupled with negative pressure microbubble stripping and dielectric regulation in a slightly acidic environment without adding strong alkali solutions to disrupt the product structure. Polyethylene glycol 400 is used to reduce the dielectric constant of the local aqueous phase, increasing the activity coefficient of trace amounts of free trimethylamine. Simultaneously, inert gas is continuously bubbled in through a microporous distributor to provide a broad gas-liquid mass transfer interface. This gas-liquid mass transfer process reduces the concentration of residual free volatile irritant trimethylamine in the product from 1000-2000 ppm in traditional processes to 15-30 ppm, mitigating product odor and improving the safety of the operating environment for downstream applications. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the preparation process steps of the present invention. Detailed Implementation

[0020] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0021] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0022] The epichlorohydrin (CAS No. 106-89-8) used in this embodiment of the invention is a commercially available industrial-grade product with a mass fraction of not less than 99.5%; the trimethylamine aqueous solution (CAS No. 75-50-3) is a commercially available industrial-grade product, wherein the mass fraction of trimethylamine is 25.0% to 30.0%; the hydrochloric acid (CAS No. 7647-01-0) is a commercially available industrial-grade aqueous solution with a hydrogen chloride mass fraction of 30.0% to 35.0%; the anhydrous zinc chloride (CAS No. 7646-85-7) and anhydrous citric acid (CAS No. 77-92-9) are both commercially available analytical grade products; polyethylene glycol 400 (CAS No. 25322-68-3) is a commercially available nonionic polymer with an average molecular weight range of 380 to 420; and the high-purity nitrogen gas for stripping (CAS No. 7727-37-9) has a volume fraction of not less than 99.99%.

[0023] Preparation Example 1: This preparation example provides a method for preparing a trimethylamine hydrochloride substrate containing a composite catalyst, using optimal parameter center values, including the following steps: Step 1: Add 115.3 kg of 32.0% hydrochloric acid aqueous solution to the mixing vessel, start stirring and control the speed at 130 rpm, and slowly introduce 193.6 kg of 30.0% trimethylamine aqueous solution through the deep conduit. This process releases neutralization heat, and the temperature inside the vessel is strictly maintained at 35°C by the jacket cooling water.

[0024] Step 2: Use an online pH meter to monitor the pH of the system in real time. When the pH of the neutralization system reaches 5.5, immediately stop the flow of trimethylamine aqueous solution. At this time, the reaction yields a high concentration of trimethylamine hydrochloride aqueous solution. This feed ratio strictly corresponds to the total feed amount of 100.0 kg epichlorohydrin in the subsequent steps.

[0025] Step 3: Maintain a slightly acidic environment with a pH of 5.5 in the system. Add 100.0g of anhydrous citric acid, 200.0g of polyethylene glycol 400, and 48.0g of anhydrous zinc chloride to the mixing tank in sequence. The total mass of the three components is 348.0g, which accounts for 0.348% of the total mass of the corresponding epichlorohydrin. At this time, the mass ratio of the three components, anhydrous zinc chloride, anhydrous citric acid, and polyethylene glycol 400, is set to 1.2:2.5:5.0.

[0026] Step 4: Adjust the system temperature to 40℃ and stir at a constant speed of 180 rpm for 30 minutes to allow the central free zinc ions to chelate and coordinate with the carboxyl and hydroxyl groups of citric acid and be uniformly coated by polyethylene glycol 400 molecular chain segments, finally forming a uniform and transparent inorganic-organic coordination complex bottom liquid for later use.

[0027] Preparation Example 2: This preparation example provides a method for preparing a trimethylamine hydrochloride substrate containing a composite catalyst, using lower limit boundary values ​​of parameters, including the following steps: Step 1: Add 127.6 kg of 30.0% hydrochloric acid aqueous solution to the mixing vessel, start stirring and control the speed at 120 rpm, and slowly introduce 243.4 kg of 25.0% trimethylamine aqueous solution through the deep conduit. Strictly maintain the temperature inside the vessel at 30°C through the jacket cooling water.

[0028] Step 2: Use an online pH meter to monitor the pH of the system in real time. When the pH of the neutralized system reaches 5.2, immediately stop the flow of trimethylamine aqueous solution to obtain trimethylamine hydrochloride aqueous solution. This feed ratio strictly corresponds to the total feed amount of 100.0 kg epichlorohydrin in the subsequent steps.

[0029] Step 3: Maintain a slightly acidic environment with a pH of 5.2 in the system. Add 54.3g of anhydrous citric acid, 108.6g of polyethylene glycol 400, and 38.0g of anhydrous zinc chloride to the mixing tank in sequence. The total mass of the three components is 200.9g, which accounts for 0.2009% of the total mass of the corresponding epichlorohydrin. At this time, the mass ratio of the three components, anhydrous zinc chloride, anhydrous citric acid, and polyethylene glycol 400, is set to 1.4:2.0:4.0.

[0030] Step 4: Adjust the system temperature to 38℃ and stir at a constant speed of 150 rpm for 20 minutes to promote the complete in-situ coordination complexation reaction, and finally form a uniform and transparent inorganic-organic coordination complex bottom liquid for later use.

[0031] Preparation Example 3: This preparation example provides a method for preparing a trimethylamine hydrochloride substrate containing a composite catalyst, using upper limit boundary values ​​for parameters, and includes the following steps: Step 1: Add 102.8 kg of 35.0% hydrochloric acid aqueous solution to the mixing vessel, start stirring and control the speed at 150 rpm, and slowly introduce 185.2 kg of 30.0% trimethylamine aqueous solution through the deep conduit. Strictly maintain the temperature inside the vessel at 40℃ through the jacket cooling water.

[0032] Step 2: Use an online pH meter to monitor the pH of the system in real time. When the pH of the neutralized system reaches 5.8, immediately stop the flow of trimethylamine aqueous solution to obtain trimethylamine hydrochloride aqueous solution. This feed ratio strictly corresponds to the total feed amount of 100.0 kg epichlorohydrin in the subsequent steps.

[0033] Step 3: Maintain a slightly acidic environment with a pH of 5.8 in the system. Add 150.0g of anhydrous citric acid, 300.0g of polyethylene glycol 400, and 50.0g of anhydrous zinc chloride to the mixing tank in sequence. The total mass of the above three components is 500.0g, which accounts for 0.50% of the total mass of the corresponding epichlorohydrin. At this time, the mass ratio of the three components of anhydrous zinc chloride, anhydrous citric acid, and polyethylene glycol 400 is set to 1.0:3.0:6.0.

[0034] Step 4: Adjust the system temperature to 42℃ and stir at a constant speed of 200 rpm for 40 minutes to ensure that the high-concentration components undergo sufficient multidentate chelation coordination, and finally form a uniform and transparent inorganic-organic coordination complex bottom liquid for later use.

[0035] Example 1: This example provides a complete synthesis method for cationic etherifying agents based on optimal process combinations. Please refer to the appendix. Figure 1 This includes the following steps: Step 1: Pump the trimethylamine hydrochloride base solution containing the composite catalyst obtained in Preparation Example 1 into the main reactor, establish a closed-loop cooling cycle, and set and strictly control the reactor temperature at 38°C. Turn on the high-precision metering pump and add 80.0 kg of epichlorohydrin with a purity of not less than 99.5% dropwise into the reactor at a constant flow rate. The time for this dropwise addition process is controlled to be 3.0 hours.

[0036] Step 2: At the moment the first stage of dripping is completed, adjust the temperature setting of the reactor jacket so that the temperature inside the reactor can smoothly transition to 48°C at a heating rate of 0.8°C per minute and remain at this temperature. At the same time, the remaining 20.0 kg of epichlorohydrin with a purity of not less than 99.5% is continuously dripped at a flow rate lower than that of the first stage. The total dripping time of this stage is controlled to be 1.0 hour.

[0037] Step 3: After all the epichlorohydrin has been added, seal the reactor, heat it to 62°C, and keep it at a constant temperature for 2.0 hours with stirring to ensure complete conversion of the substrate.

[0038] Step 4: After digestion and heat preservation, the crude reaction product at 62℃ is directly transferred to a stripping distillation column equipped with a microporous gas distributor. The pH value of the liquid phase is monitored and naturally maintained within the slightly acidic range of 5.0 to 6.0 after the reaction, without the addition of any strong acid or strong alkali solution. The system temperature is finely adjusted to 58℃, and the vacuum pump system is turned on to achieve an absolute pressure of -0.090MPa. Simultaneously, high-purity nitrogen gas is continuously bubbled into the column from the microporous distributor at a rate of 0.2 volumes of gas per minute per volume of liquid. The negative pressure microbubble stripping process lasts for 2.0 hours.

[0039] Step 5: After the stripping and devolatilization are completed, break the vacuum. Immediately open the bottom discharge valve of the distillation column and the high-flow-rate external circulation centrifugal pump. Pump the purified high-temperature liquid (58℃) into a parallel external plate heat exchanger with a refrigerant inlet temperature of 8℃ at the set flow rate. Within a 25-minute time window, rapidly reduce the bulk temperature of all materials to 18℃ to stop crystallization. After sampling and testing, add a small amount of 8% dilute hydrochloric acid to precisely adjust the pH of the final product to 6.5. After filtration, the final aqueous solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride is obtained.

[0040] Example 2: This example provides a complete synthesis method for cationic etherifying agents based on mild process conditions and a combination of lower limit parameters, including the following steps: Step 1: Pump the trimethylamine hydrochloride base solution containing the composite catalyst obtained in Preparation Example 2 into the main reactor, establish a closed-loop cooling cycle, and set and strictly control the temperature inside the reactor at 35°C. Turn on the high-precision metering pump and add 75.0 kg of epichlorohydrin with a purity of not less than 99.5% dropwise into the reactor at a constant flow rate. The time for this dropwise addition process is controlled to be 3.5 hours.

[0041] Step 2: Immediately after the first stage of dripping is completed, adjust the temperature setting of the reactor jacket so that the temperature inside the reactor smoothly transitions to 45°C at a heating rate of 0.5°C per minute and remains constant at this temperature. Simultaneously, at a flow rate lower than that of the first stage, the remaining 25.0 kg of epichlorohydrin with a purity of not less than 99.5% is continuously dripped seamlessly. The total dripping time for this stage is controlled to be 1.2 hours.

[0042] Step 3: After all the epichlorohydrin has been added, seal the reactor, heat it to 60°C, and keep it at a constant temperature for 2.5 hours with stirring to ensure complete conversion of the substrate.

[0043] Step 4: After digestion and heat preservation, the crude reaction product at 60℃ is directly transferred to a stripping distillation column equipped with a microporous gas distributor. The pH value of the liquid phase is monitored; it naturally maintains a slightly acidic range of 5.0 to 6.0 after the reaction, without the addition of any strong acid or strong alkali solution. The system temperature is finely adjusted to 55℃, and the vacuum pump system is turned on to achieve an absolute pressure of -0.080MPa. Simultaneously, high-purity nitrogen gas is continuously bubbled into the column from the microporous distributor at a rate of 0.1 volumes of gas per minute per volume of liquid. The negative pressure microbubble stripping process lasts for 2.5 hours.

[0044] Step 5: After stripping and devolatilization, break the vacuum. Immediately open the bottom discharge valve of the distillation column and the external circulation high-flow centrifugal pump. Pump the purified high-temperature liquid (55℃) into a parallel external plate heat exchanger with a refrigerant inlet temperature of 10℃ at the set flow rate. Within a 30-minute time window, rapidly reduce the bulk temperature of all materials to 20℃ to stop crystallization. After sampling and testing, add a small amount of 5% dilute hydrochloric acid to precisely adjust the pH of the final product to 6.0. After filtration, the final aqueous solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride is obtained.

[0045] Example 3: This example provides a complete synthesis method for cationic etherifying agents based on a combination of aggressive process conditions and upper limit parameters, including the following steps: Step 1: Pump the trimethylamine hydrochloride base solution containing the composite catalyst obtained in Preparation Example 3 into the main reactor, establish a closed-loop cooling cycle, and set and strictly control the reactor temperature at 40°C. Turn on the high-precision metering pump and add 85.0 kg of epichlorohydrin with a purity of not less than 99.5% dropwise into the reactor at a constant flow rate. The time for this dropwise addition process is controlled to be 2.5 hours.

[0046] Step 2: At the moment the first stage of dripping is completed, adjust the temperature setting of the reactor jacket so that the temperature inside the reactor can smoothly transition to 50°C at a heating rate of 1.0°C per minute and remain at this temperature. At the same time, the remaining 15.0 kg of epichlorohydrin with a purity of not less than 99.5% is continuously dripped at a flow rate lower than that of the first stage. The total dripping time of this stage is controlled to be 0.8 hours.

[0047] Step 3: After all the epichlorohydrin has been added, seal the reactor, heat it to 65°C, and keep it at a constant temperature for 1.5 hours with stirring to ensure complete conversion of the substrate.

[0048] Step 4: After digestion and heat preservation, the crude reaction product at 65℃ is directly transferred to a stripping distillation column equipped with a microporous gas distributor. The pH value of the liquid phase is monitored; it naturally maintains a slightly acidic range of 5.0 to 6.0 after the reaction, without the addition of any strong acid or strong alkali solution. The system temperature is finely adjusted to 60℃, and the vacuum pump system is turned on to achieve an absolute pressure of -0.095MPa. Simultaneously, high-purity nitrogen is continuously bubbled into the column through the microporous distributor at a rate of 0.3 volumes of gas per minute per volume of liquid. The negative pressure microbubble stripping process lasts for 1.5 hours.

[0049] Step 5: After the stripping and devolatilization are completed, break the vacuum. Immediately open the bottom discharge valve of the distillation column and the external circulation high-flow centrifugal pump. Pump the purified high-temperature liquid (60℃) into a parallel external plate heat exchanger with a refrigerant inlet temperature of 5℃ at the set flow rate. Within a 20-minute time window, rapidly reduce the bulk temperature of all materials to 15℃ to stop crystallization. After sampling and testing, add a small amount of 10% dilute hydrochloric acid to precisely adjust the pH value of the final product to 7.0. After filtration, the final aqueous solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride is obtained.

[0050] Example 4: This example provides a complete synthesis method for a cationic etherifying agent for a specific dielectric modulation limit test, including the following steps: Step 1: Pump the trimethylamine hydrochloride base solution containing the composite catalyst obtained in Preparation Example 1 into the main reactor, establish a closed-loop cooling cycle, and set and strictly control the reactor temperature at 38°C. Turn on the high-precision metering pump and add 80.0 kg of epichlorohydrin with a purity of not less than 99.5% dropwise into the reactor at a constant flow rate. The time for this dropwise addition process is controlled to be 3.0 hours.

[0051] Step 2: At the moment the first stage of dripping is completed, adjust the temperature setting of the reactor jacket so that the temperature inside the reactor can smoothly transition to 48°C at a heating rate of 0.8°C per minute and remain at this temperature. At the same time, the remaining 20.0 kg of epichlorohydrin with a purity of not less than 99.5% is continuously dripped at a flow rate lower than that of the first stage. The total dripping time of this stage is controlled to be 1.0 hour.

[0052] Step 3: After all the epichlorohydrin has been added, seal the reactor, heat it to 62°C, and keep it at a constant temperature for 2.0 hours with stirring to ensure complete conversion of the substrate.

[0053] Step 4: After digestion and heat preservation, the crude reaction product at 62℃ is directly transferred to a stripping distillation column equipped with a microporous gas distributor. A very small amount of 5% sodium hydroxide aqueous solution is pre-added to precisely raise the pH value of the liquid phase and lock it at the safe window boundary of 6.5. The system temperature is finely adjusted to 58℃, and the vacuum pump system is turned on to bring the absolute pressure of the equipment to -0.090MPa. At the same time, high-purity nitrogen gas is continuously bubbled into the microporous distributor at the bottom of the column at a rate of 0.25 volumes of gas per minute per volume of liquid. The negative pressure microbubble stripping process lasts for 2.0 hours.

[0054] Step 5: After the stripping and devolatilization are completed, break the vacuum. Immediately open the bottom discharge valve of the distillation column and the high-flow-rate external circulation centrifugal pump. Pump the purified high-temperature liquid (58℃) into a parallel external plate heat exchanger with a refrigerant inlet temperature of 8℃ at the set flow rate. Within a 25-minute time window, rapidly reduce the bulk temperature of all materials to 18℃ to stop crystallization. After sampling and testing, add a small amount of 8% dilute hydrochloric acid to precisely adjust the pH of the final product to 6.5. After filtration, the final aqueous solution of 3-chloro-2-hydroxypropyltrimethylammonium chloride is obtained.

[0055] Comparative Example 1: Compared with Example 1, the difference is that no composite catalyst component was added in Preparation Example 1 cited in step 1, and the epichlorohydrin was rapidly added within 30 minutes instead of being added at a constant flow rate matched with kinetics in steps 1 and 2. High-purity nitrogen was not introduced for microbubble devolatilization in step 4, and an external plate heat exchanger was not used in step 5. Instead, the reaction vessel jacket was used for natural and slow cooling. All other aspects are the same.

[0056] Comparative Example 2: Compared with Example 1, the difference is that in Preparation Example 1 mentioned in step 1, only anhydrous zinc chloride was added when preparing the base solution, and anhydrous citric acid and polyethylene glycol 400 were not added, while the rest were the same.

[0057] Comparative Example 3: Compared with Example 1, the difference is that in Preparation Example 1 cited in step 1, the pH value of the neutralization solution system was controlled at 7.5 when preparing the base solution, and all other aspects were the same.

[0058] Comparative Example 4: Compared with Example 1, the difference is that in steps 1 and 2, a constant flow rate with matching kinetics was not used for the drop addition. Instead, all epichlorohydrin was rapidly added dropwise over 30 minutes at a temperature of 20°C. All other aspects were the same.

[0059] Comparative Example 5: Compared with Example 1, the difference is that in step 5, an external plate heat exchanger was not used to rapidly reduce the temperature. Instead, a conventional reactor jacket was used to cool the temperature naturally and slowly, and the total cooling time was more than 2 hours. All other aspects were the same.

[0060] Comparative Example 6: Compared with Example 1, the difference is that in step 4, after transferring to the stripping distillation column, a strong alkali solution is added to adjust the pH value of the crude product liquid phase to 8.5 before negative pressure stripping. All other steps are the same.

[0061] Test Example 1: Verification of Solution Stability of Inorganic Carbon Framework Coordination Systems Take 500 mL of the base liquid prepared in Example 1, Comparative Example 2 and Comparative Example 3 as test samples, and place them in a 2L closed glass reactor with a constant temperature water bath jacket. Turn on the magnetic stirring, set the speed to 150 rpm, and maintain the system temperature at 40℃.

[0062] A 5% sodium hydroxide aqueous solution or hydrochloric acid solution was slowly added dropwise to different reactors to adjust the pH value of the sample in Example 1 to 5.5, 7.0 and 8.0, respectively; the pH value of the sample in Comparative Example 2 was adjusted to 5.5 and 7.5, respectively; and the initial pH value of the sample in Comparative Example 3 was kept constant at 7.5. The system was stirred continuously for 30 minutes during the adjustment process to ensure uniform acidity and alkalinity distribution.

[0063] The initial turbidity of each group of samples was measured using a scattering light turbidimeter at a wavelength of 860 nm. The samples were then sealed and transferred to a 40°C incubator for settling.

[0064] Samples were taken out after standing for 12 hours, 24 hours, 48 ​​hours and 72 hours respectively. After being shaken at 100 rpm for 5 minutes using a mechanical shaker, the turbidity was measured using a turbidimeter and the changes in NTU values ​​were recorded.

[0065] Table 1. Turbidity (NTU) test data of each base liquid sample at different pH settings and standing times.

[0066] According to the data in Table 1, after standing for 72 hours at pH 5.5, the turbidity of the solution in Example 1 increased from 0.82 NTU to 1.47 NTU, while the solution remained transparent. This indicates that anhydrous citric acid utilizes its multidentate structure to chelate and coordinate with zinc ions, and polyethylene glycol 400 forms a steric hindrance protective layer around the complex, blocking the hydration and aggregation of zinc ions.

[0067] When the pH of the substrate solution in Example 1 was adjusted to 7.0 and 8.0, the turbidity increased significantly with standing time, reaching 187.39 NTU after 72 hours at pH 8.0. This indicates that hydroxide ions overcame the steric hindrance of polyethylene glycol under alkaline conditions, competed for coordination with citric acid ligands, destroyed the chelate structure, and caused zinc ions to detach and form zinc hydroxide precipitate.

[0068] The substrate of Comparative Example 2, without the addition of citric acid and polyethylene glycol 400, showed a higher initial turbidity and a greater increase in turbidity after standing at pH 5.5 than that of Example 1, reaching 24.18 NTU after 72 hours. This indicates that free zinc ions lacking polydentate ligand activity are prone to hydrolysis and aggregation in the aqueous phase, leading to deactivation.

[0069] The initial turbidity of the solution in Comparative Example 3 at pH 7.5 was 55.43 NTU, indicating that zinc ions had lost their catalytic activity and precipitated at this point.

[0070] Test data show that the coordination complexation and steric hindrance buffering effect of this composite catalyst depends on slightly acidic conditions of 5.2 to 5.8 to maintain the stability of the solution phase.

[0071] Test Example 2: Monitoring and Verification of System Reaction Thermodynamic Stability A 500L pilot-scale jacketed stainless steel reactor equipped with a distributed control system and a PT100 high-precision temperature sensor was used as the test platform.

[0072] The prepared base liquids of Examples 1 to 3, Comparative Examples 1 and 4 were pumped into the reaction vessel, respectively. The closed-loop cooling cycle was turned on and the initial reaction temperature of each group was set. The stirring speed was uniformly set to 120 rpm.

[0073] According to the stage flow rate set in the embodiment or the feeding time set in the comparative example, a corresponding mass of epichlorohydrin with a purity of not less than 99.5% is pumped into the reactor. The actual body temperature of the reactor during the feeding process and after the feeding is completed is continuously recorded by the distributed control system at a sampling frequency of 1 second, and the maximum deviation between the actual maximum temperature and the set temperature is calculated.

[0074] Record the time required for the system to naturally drop from the actual highest temperature to the set temperature baseline, and count the number of times each batch triggers the jacket to forcibly introduce chilled water for safety interlock cooling due to temperature exceeding the limit during this process.

[0075] Table 2. Test data of thermodynamic characteristic parameters during the feeding stage of each embodiment and comparative example.

[0076] According to the data in Table 2, under different stage temperature settings, the maximum temperature deviation of Examples 1, 2, and 3 was controlled within 1.7℃, the baseline recovery time was short, and no forced cooling interlock was triggered throughout the process. This indicates that the constant-rate starvation feed strategy ensures that the physical dropwise input rate of epichlorohydrin is lower than or equal to its chemical ring-opening consumption rate at the corresponding temperature. The concentration of unreacted substrate in the system is maintained at an extremely low level, the exothermic reaction and jacket heat dissipation reach a dynamic equilibrium, and the system is in a controllable pseudo-steady state.

[0077] In Comparative Example 1, all epichlorohydrin was added within 30 minutes at an initial temperature of 38°C. The actual peak temperature reached 74.4°C, with a maximum temperature deviation of 36.4°C, triggering two forced cooling interlocks. This indicates that a large amount of substrate entered the reactor and accumulated within a short period, resulting in a sudden surge in open-loop exothermic heat. The effective heat transfer area of ​​the reactor wall could not match the abrupt heat load, leading to thermal runaway of the system.

[0078] Comparative Example 4, with its initial feeding temperature reduced to 20℃ and rapid feeding within 30 minutes, exhibited a maximum temperature deviation of 48.9℃, triggering three forced interlocks. This demonstrates that simply reducing the initial sensible heat of the system cannot eliminate the thermodynamic risks caused by the large accumulation of substrate. Once the reaction crosses the activation energy barrier, the concentrated release of accumulated latent heat can still cause severe temperature runaway.

[0079] The aforementioned macroscopic thermodynamic data verify the feasibility of the kinetic flow decoupling mechanism, confirming that the process, through spatial and temporal feeding restrictions, cuts off the pathways of reaction heat lag and accumulation, fundamentally eliminating the danger of material rushing and suppressing side reactions caused by high temperatures.

[0080] Test Example 3: Fluid Dynamics Freezing and Cryogenic Macroscopic Rheological Verification 500 mL of the final aqueous solution products prepared in Examples 1, 2, 3, 2, and 5 were extracted as test samples.

[0081] The samples were placed in standard test containers equipped with digital rotational viscometer rotors. The initial system temperature was set to 20°C. The initial viscosity of each group of samples at room temperature was measured and recorded.

[0082] The test container containing the sample was transferred to a programmable high and low temperature cycling freeze bath to program the temperature of the sample at a rate of 2.0°C per hour.

[0083] When the bulk temperature of the system dropped to -5.0℃ and -10.0℃, the macroscopic viscosity data of each sample were recorded. The temperature was continuously lowered while the phase state of the samples was observed. The actual temperature at which the samples showed macroscopic turbidity and precipitation or completely lost fluidity was recorded as the pour point.

[0084] Table 3. Rheological and pour point test data of each embodiment and comparative example product during programmed cooling.

[0085] According to the data in Table 3, the viscosity of the products from Examples 1, 2, and 3 at 20°C ranged from 14.8 to 16.1 mPa·s. Upon cooling to -10°C, the viscosity increased to 79.8 to 92.5 mPa·s, the solution maintained macroscopic fluidity, and the freezing points were all below -15°C. This indicates that the rapid cooling process provided by the external plate heat exchanger quickly reduced the kinetic energy of the system molecules, preventing the solute molecules from undergoing regular diffusion and thus crossing the nucleation thermodynamic window. The long-chain structure of polyethylene glycol 400 in the formulation intercalated between water and product molecules, forming physical steric hindrance and blocking the orderly growth of the crystal lattice. The synergistic effect of rapid freezing and steric hindrance maintained the amorphous structure of the fluid.

[0086] Comparative Example 2, which did not contain polyethylene glycol 400 during preparation, achieved a viscosity of 58.7 mPa·s at -5°C and lost its fluidity and crystallized at -6.5°C. This indicates that in the absence of macromolecular steric hindrance, a single physical quenching process cannot effectively inhibit the formation of crystal lattices by solute molecules through electrostatic and hydrogen bonding.

[0087] The product of Comparative Example 5 was slowly cooled using a reactor jacket, with a total cooling time exceeding 2 hours. Its freezing point was measured to be -4.2℃, and it solidified at -5℃. This indicates that the slow cooling process provided sufficient time for molecular rearrangement, allowing solute molecules to overcome steric hindrance and complete the arrangement and growth of the crystal lattice even in the presence of polyethylene glycol 400.

[0088] Macroscopic rheological and freezing point data confirmed that thermodynamic quenching and steric hindrance of polyethylene glycol must be coupled to change the freezing point properties of the system, achieving low-temperature anti-crystallization of the product without the addition of small molecule alcohol antifreeze.

[0089] Test Example 4: Evaluation of the content of effective active ingredient in the target product and the inhibition rate of by-products Take 10.0 g of the final aqueous solution products prepared in Examples 1 to 3 and Comparative Examples 1, 4 and 6 respectively, add deionized water to make up to 100 mL, filter with a 0.45 μm microporous membrane to prepare the test solution.

[0090] Qualitative and quantitative tests were performed using a high-performance liquid chromatography (HPLC) system equipped with an evaporative light scattering detector. A C18 reversed-phase column was used, with a mobile phase consisting of a mixture of ultrapure water containing 0.1% trifluoroacetic acid and chromatographic-grade acetonitrile at a volume ratio of 85:15. The flow rate was maintained at 1.0 mL / min, and the column temperature was kept constant at 30 °C.

[0091] Inject the test solution for analysis and record the chromatogram. Using the external standard method, calculate the absolute mass fractions of the main product 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHPTAC), the main byproduct epichlorohydrin homopolymer, and 2,3-epoxypropyltrimethylammonium chloride (EPTAC) in the system based on retention time and characteristic peak area.

[0092] Table 4. Data on the determination of active ingredients and by-products in the products of each example and comparative example.

[0093] According to the data in Table 4, the mass fraction of the active ingredient CHPTAC in the products of Examples 1, 2, and 3 ranged from 68.85% to 69.61%, while the mass fractions of epoxy homopolymer and EPTAC were both below 0.2%. The data indicate that the kinetic starvation feed-in mode maintained the concentration of free epichlorohydrin in the system at an extremely low level. The exothermic reaction rate was controlled, eliminating localized runaway reactions and cutting off the thermodynamic conditions for the self-polymerization side reaction of the epoxy groups at the source. Furthermore, the neutral devolatilization strategy avoided alkaline degradation of the product during the high-temperature stripping stage.

[0094] Comparative Examples 1 and 4, which did not employ kinetic fed-batch polymerization, produced products with epoxy homopolymer mass fractions as high as 18.54% and 12.33%, respectively, significantly reducing the content of the main product. This indicates that the one-time addition of all epichlorohydrin led to a large accumulation of substrate within the system, with the exothermic rate exceeding the system's heat transfer limit and triggering thermal runaway. Under the combined effects of localized high temperature and high monomer concentration, the reaction kinetics of epichlorohydrin's own ring-opening homopolymerization dominated, exceeding the nucleophilic substitution reaction rate with trimethylamine hydrochloride, resulting in a severe deviation from the reaction pathway.

[0095] In Comparative Example 6, adjusting the liquid phase pH to 8.5 during the degassing stage resulted in a surge in the mass fraction of the byproduct EPTAC to 15.62% and a drop in the content of the active ingredient to 48.15%. This indicates that the chlorohydrin group in the cationic etherifying agent molecule is extremely unstable in an alkaline environment, undergoing an intramolecular nucleophilic substitution reaction, removing hydrogen chloride to close the ring and generate EPTAC with an epoxy structure. This result further confirms the necessity of the dielectric regulation and microbubble mass transfer coupled devolatilization mechanism employed in this invention, and demonstrates that degassing under slightly acidic conditions (pH 5.5 to 6.5) can ensure the structural integrity of the chlorohydrin group.

[0096] Test Example 5: Evaluation of Removal Efficiency of Residual Volatile Free Amines in the Liquid Phase 20.0 mL of the final aqueous solution products prepared in Examples 1, 2, and 3, as well as Comparative Examples 1, 2, and 6, were extracted as test samples.

[0097] Accurately weigh 5.0g of the above sample and place it into a 20mL headspace vial. Seal the vial with a PTFE / silicone septum and transfer it into the headspace sampler. Set the headspace heating equilibrium temperature to 80℃ and the equilibrium time to 30 minutes.

[0098] Quantitative analysis was performed using a gas chromatograph equipped with a flame ionization detector. A capillary column for volatile amine analysis was selected, and high-purity nitrogen was used as the carrier gas. The injection port temperature was set to 200℃, the detector temperature to 250℃, and the column temperature was programmed.

[0099] Headspace gas was extracted and injected, and the chromatographic peak retention time and peak area were recorded. The residual absolute concentration of trimethylamine in each sample was calculated using a pre-established external standard curve for trimethylamine.

[0100] Ten testers independently evaluated each sample using their olfactory senses. The scoring criteria were set as follows: 1 point for no odor, 2 points for a faint characteristic odor, 3 points for a distinct ammonia odor, and 4 points for a strong odor. The average score from the ten testers was recorded as the final sensory score.

[0101] Table 5. Residual trimethylamine concentration and sensory evaluation test data in each example and comparative product.

[0102] According to the data in Table 5, the residual trimethylamine concentration in the products of Examples 1, 2, and 3 was all below 15.0 ppm, and the sensory evaluation score was close to 1.0, indicating that the products had no free amine odor. In a slightly acidic devolatilization environment with pH 5.0 to 6.0, trimethylamine in the system mainly exists in the form of hydrochloride. Polyethylene glycol 400 in the formulation, as a low-polarity additive, reduced the dielectric constant of the local aqueous phase, increasing the activity coefficient of trace amounts of free trimethylamine and reducing its solubility in the aqueous phase.

[0103] High-purity nitrogen microbubbles continuously bubbled into the bottom of the stripping distillation column provide the gas-liquid mass transfer interface. The partial pressure of trimethylamine inside the bubbles is zero, creating the driving force for mass transfer. Free trimethylamine crosses the phase interface into the gas phase and is extracted by the vacuum system, causing the weak amine salt dissociation equilibrium within the system to continuously shift towards the formation of free amine. The physical mass transfer process and the chemical dissociation equilibrium are coupled, achieving the removal of trace amounts of volatile amines under neutral and slightly acidic conditions.

[0104] In Comparative Example 1, without the introduction of high-purity nitrogen for microbubble stripping, the residual trimethylamine concentration reached 156.3 ppm. This indicates that relying solely on a negative pressure environment cannot provide the interphase mass transfer area and internal pressure difference, and therefore cannot strip amine molecules bound by hydrogen bonds of water molecules.

[0105] In Comparative Example 2, no polyethylene glycol 400 was added during the preparation process, and the residual trimethylamine concentration was 68.5 ppm. This indicates that in the high dielectric constant environment of the pure aqueous phase, free trimethylamine maintains high water solubility, increasing the mass transfer resistance from the liquid phase to the gas phase and leading to a decrease in degassing efficiency.

[0106] Comparative Example 6, after being transferred to a stripping distillation column, had its pH adjusted to 8.5, resulting in a residual trimethylamine concentration of 22.6 ppm. Combined with data from Test Example 4, while this operation released free amine through strong base deprotonation, it directly led to the degradation and ring closure of the chlorohydrin group. Furthermore, due to the lack of synergistic effects of polyethylene glycol 400 dielectric regulation and microbubble mass transfer, its final free amine removal efficiency was still inferior to the slightly acidic coupled devolatilization process of the examples. Macroscopic data confirmed the effectiveness of the dielectric regulation and microbubble mass transfer coupled devolatilization mechanism, demonstrating that this method can achieve deep removal of trimethylamine without damaging the product molecular structure.

[0107] Test Example 6: Long-term storage and transportation stability assessment under extreme climate simulation Take 500 mL of the final aqueous solution products prepared in Examples 1, 2, 3, 2, and 5 respectively, put them into polyethylene test bottles and seal them as test samples simulating industrial storage and transportation packaging.

[0108] The initial turbidity of each sample was measured using a turbidimeter at room temperature (20°C), and the initial apparent phase of the solution was recorded.

[0109] The test samples were transferred to a constant temperature freezing chamber set at -20℃ and stored continuously for 30 days. On the 7th, 15th and 30th days of storage, the macroscopic phase of each sample was observed in situ under freezing conditions, and the fluidity characteristics and whether crystallization or stratification occurred were recorded.

[0110] After the storage period expired, all samples were removed and placed in a constant temperature water bath at 25°C to thaw naturally. After the core temperature of the sample reached 25°C and was kept at that temperature for 2 hours, the final turbidity was measured again using a turbidimeter to assess the irreversible effect of low-temperature precipitation on the resolubility of the product.

[0111] Table 6. Phase and thawing turbidity test data of each example and comparative product under a constant temperature storage and transportation environment of -20℃.

[0112] According to the data in Table 6, after the products of Examples 1, 2, and 3 were stored continuously at -20°C for 30 days, the systems still maintained macroscopic fluidity or exhibited a high viscosity. The turbidity values ​​after thawing ranged from 1.18 to 1.34 NTU, and no structural precipitation occurred. This indicates that the external plate heat exchanger used in the production process rapidly reduced the temperature, causing the molecular kinetic energy within the system to decay quickly, directly crossing the thermodynamic temperature window for crystal nucleation. Simultaneously, the flexible polymer segments of polyethylene glycol 400 in the formulation system formed a physical spatial network in the liquid phase, blocking hydrogen bonds and electrostatic association between water molecules and cationic etherifying agent solute molecules. This synergistic effect of thermodynamic rapid cooling and steric hindrance forced the fluid to freeze in an amorphous structure.

[0113] Comparative Example 2, lacking the addition of polyethylene glycol 400, showed flaky crystals after 7 days of storage at -20°C, and solidified completely after 30 days. Upon thawing, the turbidity increased to 45.21 NTU, accompanied by irreversible precipitation. This indicates that in an aqueous system lacking steric hindrance from macromolecules, solute and solvent molecules can spontaneously complete the arrangement and growth of their crystal lattice points under medium- to long-term low-temperature conditions.

[0114] Comparative Example 5 product underwent a slow cooling process within the reactor for over 2 hours, resulting in large-volume freezing during storage. This indicates that the gentle heat exchange gradient provided the system with sufficient time for molecular diffusion and rearrangement. Molecular thermal motion possessed the kinetics to overcome the steric hindrance provided by polyethylene glycol 400, ultimately crossing the nucleation barrier to form a crystalline phase. The aforementioned macroscopic antifreeze and turbidity measurement data validate that the steric hindrance mechanism must be coupled with a cliff-like quenching process to physically alter the low-temperature flexibility and freezing point properties of the aqueous solution, meeting the storage and transportation requirements under extreme climatic conditions.

[0115] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A cationic etherification agent based on a composite catalyst synthesis, characterized in that, It is made by reacting the following raw materials in parts by weight: 100 parts of epichlorohydrin; 55-61 parts of trimethylamine; 35-40 parts of hydrogen chloride; 0.20 to 0.50 parts of composite catalyst.

2. A cationic etherification agent based on a composite catalyst synthesis and a preparation method thereof according to claim 1, characterized in that: The composite catalyst is composed of anhydrous zinc chloride, anhydrous citric acid and polyethylene glycol 400 in a weight ratio of 1.0-1.4:2.0-3.0:4.0-6.

0.

3. The cationic etherifying agent synthesized based on a composite catalyst and its preparation method according to claim 1, characterized in that: The cationic etherifying agent has an effective active ingredient, 3-chloro-2-hydroxypropyltrimethylammonium chloride, with a mass fraction of not less than 68.8%, and an epichlorohydrin homopolymer impurity mass fraction of less than 0.2%.

4. The cationic etherifying agent synthesized based on a composite catalyst and its preparation method according to claim 1, characterized in that: The residual trimethylamine concentration in the cationic etherifying agent is less than 15.0 ppm.

5. A method for preparing a cationic etherifying agent based on a composite catalyst, wherein the cationic etherifying agent based on a composite catalyst according to any one of claims 1-4 is characterized in that, Includes the following steps: S1. Trimethylamine is neutralized with hydrochloric acid aqueous solution, and a composite catalyst is added under slightly acidic conditions. The mixture is stirred at a constant temperature to carry out a complexation reaction, thereby obtaining a trimethylamine hydrochloride base solution containing the composite catalyst. S2. Under controlled temperature, epichlorohydrin is added dropwise into the reactor at a constant flow rate to carry out the ring-opening etherification reaction. S3. After all the epichlorohydrin has been added, the mixture is heated in a sealed container and kept at a constant temperature with stirring to ensure complete conversion of the substrate and obtain the crude reaction product. S4. Without adding strong alkali solution, maintain the system in a slightly acidic range, and perform gas stripping degassing on the crude product of S3 under negative pressure and continuous inert gas injection. S5. Pump the high-temperature liquid after the S4 stripping process into an external heat exchanger and rapidly cool it to 15-20°C to stop crystallization, thus obtaining the cationic etherifying agent.

6. The method for preparing a cationic etherifying agent based on a composite catalyst according to claim 5, characterized in that: The specific implementation method of step S1 is as follows: trimethylamine aqueous solution is introduced into hydrochloric acid aqueous solution, the temperature inside the reactor is controlled at 30-40℃, the pH value of the liquid phase of the system is monitored in real time, and the introduction of trimethylamine is stopped when the pH value reaches 5.2-5.8; then, under the slightly acidic environment of maintaining this pH value, anhydrous citric acid, polyethylene glycol 400 and anhydrous zinc chloride are added in sequence, and the mixture is stirred at a constant temperature of 38-42℃ for 20-40 minutes.

7. The method for preparing a cationic etherifying agent based on a composite catalyst according to claim 5, characterized in that: The stepwise addition of epichlorohydrin in step S2 is carried out in the following two stages: First stage: Control the reaction temperature at 35-40℃, and add epichlorohydrin at a constant flow rate of 75.0%-85.0% of the total feed amount to the bottom liquid. The dropping time in this stage is controlled at 2.5-3.5 hours. Second stage: After the first stage of addition is completed, the temperature is steadily increased to 45-50℃ at a rate of 0.5-1.0℃ / min and kept constant at this temperature. Simultaneously, the remaining 15.0%-25.0% epichlorohydrin is continuously added dropwise at a rate lower than that of the first stage. The total addition time of this stage is controlled to be 0.8-1.2 hours.

8. The method for preparing a cationic etherifying agent based on a composite catalyst according to claim 5, characterized in that: In step S3, the temperature is raised to 60-65℃, and the mixture is kept at a constant temperature with stirring for 1.5-2.5 hours.

9. The method for preparing a cationic etherifying agent based on a composite catalyst according to claim 5, characterized in that: The specific implementation method of step S4 is as follows: After the S3 heat preservation is completed, the pH value of the liquid phase is detected and naturally maintained within the range of 5.0 to 6.

0. The system temperature is adjusted to 55 to 60°C, and the absolute pressure of the equipment is controlled to reach -0.080MPa to -0.095MPa. At the same time, high-purity nitrogen is continuously blew in from the microporous distributor at a rate of 0.1 to 0.3 volumes of gas per minute per volume of liquid. The negative pressure microbubble gas lifting process lasts for 1.5 to 2.5 hours.

10. The method for preparing a cationic etherifying agent based on a composite catalyst according to claim 5, characterized in that: The specific implementation method of step S5 is as follows: using a parallel external plate heat exchanger, the body temperature of all high-temperature liquid is rapidly reduced from 55-60℃ to 15-20℃ within a time window of 20-30 minutes. After crystallization is blocked, add 5%–10% dilute hydrochloric acid to adjust the pH of the final product back to 6.0–7.0.

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