Preparation method of novel three-arm polyoxyethylene ether-based surfactant

Abstract

The invention discloses a preparation method of a novel three-arm polyoxyethylene ether-based surfactant, particularly relates to the field of synthetic chemistry of surfactants, and aims to solve the technical problems of non-uniform molecular structure, metal ion pollution and high energy consumption purification in the prior art. Glycerol is adopted as an initiator core, and a solid acid catalysis system is combined with a multi-stage ethylene oxide precise addition process in a supercritical CO2 medium, so that symmetric control of a three-arm structure is realized; molecular sieve dehydration, composite adsorbent residue removal and short-path molecular distillation technical chains are synchronously integrated, and by-products are efficiently removed on the premise of avoiding organic solvent intervention. According to the method, the product purity and molecular weight uniformity are improved, metal residues are eliminated, energy consumption is reduced, and a high-performance surfactant is provided for the high-end field.

Description

Technical Field

[0001] This invention relates to the chemistry of surfactant synthesis, and more specifically, to a method for preparing a novel three-armed polyoxyethylene ether-based surfactant. Background Technology

[0002] Polyoxyethylene ether surfactants, as core components of nonionic surfactant systems, are widely used in daily chemicals, pharmaceuticals, and oilfield extraction due to their excellent emulsification, dispersion, and environmental compatibility. Traditional linear polyoxyethylene ethers, limited by their homogeneous molecular conformation, face inherent bottlenecks in reducing interfacial tension and micellar stability. In recent years, star-shaped topologies (such as three-armed polyoxyethylene ethers), due to their three-dimensional spatial extension, can improve the adsorption density and molecular order of surfactants at the oil / water interface, and are considered a key pathway to breaking through performance limits. However, the industrial preparation of existing three-armed polyoxyethylene ethers still faces multiple technical obstacles, hindering their commercial application.

[0003] 1. The contradiction between catalytic system efficiency and product purity is prominent.

[0004] While conventional alkaline-catalyzed polymerization (such as potassium hydroxide) can achieve ring-opening addition of ethylene oxide, the strongly alkaline environment easily induces intramolecular cyclization side reactions, leading to the breakage or cross-linking of branched structures. Byproducts require cumbersome acid-base neutralization and salt washing steps for removal, increasing process complexity and leaving residual metal ions that contaminate the product, thus limiting the application of surfactants in high-end fields such as biopharmaceuticals. Furthermore, residual catalysts accelerate the high-temperature degradation of polyether chains, reducing product storage stability.

[0005] 2. Weak ability to precisely control molecular structure

[0006] Existing batch reactors lack real-time monitoring methods for the ethylene oxide addition process, making it difficult to achieve symmetrical control of the three-arm structure. Due to the different reactivity of the three hydroxyl groups in the initiator glycerol, the polymerization process easily produces products with uneven arm lengths, and even a large number of single-arm and double-arm byproducts. Such structural defects directly weaken the critical micelle concentration and interfacial adsorption capacity of the surfactant, and further lead to fluctuations in key performance indicators such as cloud point and viscosity, failing to meet the specification consistency requirements of precision industrial applications.

[0007] 3. High-energy-consuming purification processes restrict cost competitiveness.

[0008] To separate structurally defective products and unreacted monomers, current technologies rely on organic solvent extraction or multiple recrystallizations, which not only consume large amounts of volatile solvents (such as acetone and n-hexane) but also require multi-stage distillation purification. Such processes are not only energy-intensive, but solvent residues also threaten product safety. Especially for high molecular weight star-shaped polyethers, traditional distillation, due to the high viscosity and heat sensitivity of the materials, easily triggers localized overheating degradation, resulting in a darker color and a wider molecular weight distribution in the final product, significantly reducing its commercial value.

[0009] Therefore, a novel method for preparing a three-armed polyoxyethylene ether-based surfactant is proposed to address the above problems. Summary of the Invention

[0010] In order to overcome the above-mentioned defects of the prior art, the embodiments of the present invention provide a novel method for preparing a three-armed polyoxyethylene ether-based surfactant to solve the problems mentioned in the background art.

[0011] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a novel three-armed polyoxyethylene ether-based surfactant, comprising the following sequential steps:

[0012] S1. Using glycerol with a water content ≤50ppm as the core initiator, the dehydration rate is ≥99% by reacting at 80 to 120 degrees Celsius for 1 to 3 hours in a vacuum environment after dehydration by molecular sieve permeation membrane; then, 0.5% to 2% of a solid acid catalyst by mass of the initiator is added. This catalyst is prepared by reacting phosphotungstic acid and hexadecyltrimethylammonium bromide at a molar ratio of 1:2 in a water bath at 60 degrees Celsius for 3 hours, then loading it onto acidified montmorillonite (loading 10 to 15% by weight) and calcining it at 250 degrees Celsius for 2 hours.

[0013] S2. Under the protection of an inert atmosphere and a supercritical CO2 medium of 8 to 12 MPa, ethylene oxide is introduced in three stages: in the first stage, it is introduced at 60 to 80 degrees Celsius until the hydroxyl conversion of glycerol reaches 30% to 50%; in the second stage, the temperature is increased to 100 to 120 degrees Celsius at a rate of 1 degree Celsius / minute and the total molar ratio of ethylene oxide to hydroxyl groups reaches 10:1 to 30:1 (molar distribution ratio of the three stages is 1:3:6); in the third stage, the reaction is maintained at 120 to 130 degrees Celsius until the pressure is constant and then aged for 1 hour.

[0014] S3. After the reaction is terminated, add 3% to 5% of the modified diatomaceous earth-activated carbon composite adsorbent (mass ratio 2:1) to remove the catalyst, and filter to obtain the crude product.

[0015] S4. Finally, molecular distillation was carried out in a short-path falling film evaporator with a distance of ≤5 cm between the evaporation surface and the condensation surface at 150 to 180 degrees Celsius and 0.1 to 1 kPa to obtain a three-armed polyoxyethylene ether-based surfactant with a molecular weight distribution index ≤1.15.

[0016] Furthermore, the preparation process of the solid acid catalyst is as follows: phosphotungstic acid solution and hexadecyltrimethylammonium bromide solution are reacted in a 60°C constant temperature water bath with stirring at 500 rpm for 3 hours to form a heteropolyacid complex. Subsequently, the complex is loaded onto a montmorillonite support activated with 10% hydrochloric acid using an equal-volume impregnation method. After being treated at 120°C for 4 hours in a vacuum drying oven, it is transferred to a muffle furnace and calcined at 250°C for 2 hours with a programmed temperature increase of 2°C / min, finally obtaining a solid catalyst with an acidic site density ≥0.8 mmol / g.

[0017] Furthermore, the reaction pressure in the supercritical CO2 medium is dynamically adjusted by a high-pressure metering pump to maintain a pressure fluctuation range of ≤±0.5MPa during the ethylene oxide introduction stage, and the mass flow ratio of CO2 to ethylene oxide is controlled at 1:5 to 1:10. A vortex static mixer is installed in the reactor to improve the gas-liquid mass transfer efficiency to more than 1.8 times that of conventional systems.

[0018] Furthermore, the molecular distillation process includes two-stage purification: the first stage separates free polyethylene glycol byproducts at 150°C and 1 kPa, and the second stage collects the target component at 180°C and 0.1 kPa. The fraction is cut off to the core product with a molecular weight of 2000 to 6000 Da, and the final free polyethylene glycol residue is ≤0.5% by weight and the three-arm structure accounts for ≥98% (verified by MALDI-TOF mass spectrometry).

[0019] Furthermore, the dehydration pretreatment of glycerol adopts molecular sieve permeation membrane coupled microwave radiation technology: industrial-grade glycerol is passed through a NaA type molecular sieve membrane module (pore size 0.4 nm) at a flow rate of 2 ml / min, and simultaneously irradiated with 100 watts in a 2450 MHz microwave field, which increases the water molecule removal rate to 3 times that of traditional vacuum dehydration, and the final water content is ≤50 ppm.

[0020] Furthermore, the preparation of the modified diatomaceous earth-activated carbon composite adsorbent includes: boiling diatomaceous earth in a 10% sodium hydroxide solution for 1 hour, washing it until neutral, and then calcining it at 600 degrees Celsius for 2 hours; treating activated carbon with 30% nitric acid under reflux for 3 hours, then washing and drying it with water; mixing the two in a mass ratio of 2:1 and impregnating it in a 5% by weight polydimethyldiallylammonium chloride solution, ultrasonically treating it for 30 minutes, and then curing it at 110 degrees Celsius to obtain a composite adsorbent with a pore size concentrated in the range of 20 to 50 nanometers.

[0021] Furthermore, the number of ethylene oxide additions in the final product was monitored in real time via online infrared spectroscopy of the reaction process: an ATR-FTIR probe was embedded in the reactor to dynamically detect the reaction at 1110 cm⁻¹. -1By analyzing the intensity changes of the COC characteristic peak and combining it with the hydroxyl conversion model, precise control of 15 to 50 units of ethylene oxide per arm can be achieved, with a molecular weight error range of ≤±2%.

[0022] The technical effects and advantages of this invention are as follows:

[0023] Compared with existing technologies, this invention successfully achieves the precise and controllable synthesis of three-armed polyoxyethylene ether molecules by employing a core technical solution combining a solid acid catalyst system with a multi-stage programmed addition process. This involves replacing traditional alkali metal catalysts with modified heteropolyacid solid catalysts, eliminating neutralization steps and metal ion residues at the reaction source, while simultaneously suppressing molecular chain cyclization side reactions. A staged temperature- and pressure-controlled ethylene oxide addition strategy in supercritical CO2 media, combined with a real-time feedback mechanism using online infrared spectroscopy, dynamically adjusts the growth rate of each reaction arm, ensuring the symmetry of the three-arm structure and the uniformity of molecular weight. The invention innovatively integrates a molecular sieve permeate membrane dehydration, composite adsorbent deep purification, and short-path molecular distillation process chain, efficiently removing free polyethylene glycol and catalyst residues without the intervention of organic solvents, ultimately obtaining a high-purity product. This preparation method simultaneously solves three major technical bottlenecks in terms of functional realization: precise structural control, green and clean production, and energy consumption optimization. The resulting surfactant exhibits improved interfacial adsorption efficiency and micellar stability, providing a reliable basic material for high-end applications. Attached Figure Description

[0024] Figure 1 This is a system framework diagram of the present invention.

[0025] Figure 2 This is a flowchart of the supercritical CO2 reaction of the present invention.

[0026] Figure 3 This is a flowchart of the molecular distillation purification process of the present invention. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Implementation Process 1: Enhanced Basic Process (Focusing on Catalyst Efficiency and Structure Control)

[0028] Key innovations: Solid acid catalysis system + precise addition of tertiary ethylene oxide.

[0029] Applicable scenarios: Production of surfactants for high-purity pharmaceutical carriers

[0030] Step 1: Deep dehydration of the initiator

[0031] To effectively reduce the moisture content in industrial-grade glycerol, 500g of raw material was first placed in a vacuum reactor and connected to a NaA-type molecular sieve membrane module with a pore size of 0.4 nm. The microwave radiation device was then activated (power set at 100W, operating frequency 2450MHz), and the system was simultaneously evacuated to a gauge pressure of -0.095MPa (absolute pressure approximately 5.8kPa). Under these conditions, glycerol was continuously circulated through the molecular sieve membrane module at a flow rate of 2mL / min for up to 3 hours. Throughout the dehydration process, the moisture content was monitored in real time using a moisture analyzer. When the analyzer continuously indicated that the moisture content in the glycerol had decreased to and stabilized at no more than 50ppm (mg / kg), the microwave heating, vacuuming, and circulation operations were terminated, marking the completion of the dehydration process.

[0032] Step 2: In-situ activation of solid catalyst

[0033] To prepare a supported catalyst based on phosphotungstic acid and acidified montmorillonite, 20 g of phosphotungstic acid (HPW) and 48 g of cetyltrimethylammonium bromide (CTAB) were first dissolved in 200 mL of deionized water. The reaction was carried out in a 60 °C water bath with vigorous stirring at 500 rpm for 3 hours, promoting ion exchange between phosphotungstic acid and CTAB to form an organic-inorganic hybrid complex. Subsequently, 100 g of acidified montmorillonite pretreated with 10% hydrochloric acid (to enhance adsorption and acidity) was impregnated in the above solution to ensure sufficient loading of the active component onto the support surface. After impregnation, the material was vacuum dried at 120 °C for 4 hours to completely remove moisture and achieve pre-fixation. Finally, the dried material was placed in a muffle furnace and slowly heated from room temperature (approximately 25 °C) to 250 °C at a rate of 2 °C / min according to a preset program, and calcined at this target temperature for 2 hours to thermally decompose and remove the CTAB template agent, firmly anchoring the active component and converting it into a highly active heteropolyacid salt form. After the calcined product is naturally cooled to room temperature, it is thoroughly ground and passed through a 200-mesh standard sieve (pore size ~74 micrometers) to collect uniform and fine target catalyst powder.

[0034] Step 3: Staged reaction in supercritical CO2 medium

[0035] Add dehydrated glycerol and 10g of catalyst (2% of the initiator mass) to a high-pressure reactor, and then charge with supercritical CO2 to 10MPa:

[0036] Phase 1: Ethylene oxide was introduced at 60°C, and the temperature was monitored at 1110 cm⁻¹ using an online infrared detector (ATR-FTIR). -1 Peak intensity.

[0037] Calculation formula: Hydroxyl conversion rate = (Initial peak height - Real-time peak height) / Initial peak height × 100%.

[0038] When the conversion rate reaches 40% (approximately 120g of ethylene oxide is consumed), stop the flow.

[0039] Second stage: Increase the temperature to 110℃ at 1℃ / min, and introduce the remaining amount (720g) according to the total molar ratio of ethylene oxide:hydroxyl group = 20:1.

[0040] Mass transfer is enhanced using a vortex static mixer (300 rpm).

[0041] Third stage: Keep warm at 120℃ until the pressure gauge remains constant (about 2 hours), then let it mature for another 60 minutes.

[0042] Step 4: Adsorption purification and molecular distillation

[0043] To effectively remove impurities such as pigments, oligomers, and residual monomers from the crude product and to accurately collect the fraction with the target molecular weight, a composite adsorbent (containing 30g of modified diatomaceous earth for selectively adsorbing metal ions and polar impurities, and 15g of mesoporous activated carbon for highly efficient adsorption of small organic molecules and pigments) was first added to the system. The reaction mixture was mechanically stirred continuously at 80°C for 2 hours to enhance the impurity trapping kinetics of the adsorbent. After adsorption was completed, a plate and frame filter press equipped with a 0.22μm microporous membrane was immediately used for precision filtration. This step effectively retained adsorbent particles, trace amounts of insoluble matter, and possible colloidal substances, ultimately yielding a clear, pale yellow crude product solution. A two-stage high-vacuum molecular distillation process was then performed for fine separation: the first stage distillation was conducted at 150°C and 1.0 kPa absolute pressure, primarily to remove low-boiling-point components and light impurities such as free polyethylene glycol with a molecular weight less than 1800 Da; the second stage distillation raised the system temperature to 180°C and increased the vacuum to 0.1 kPa. Under these extremely stringent conditions, the core fraction with a strictly controlled molecular weight range of 2000-6000 Da was specifically collected. To ensure fractionation efficiency and reduce reflux condensation losses, this stage of distillation employed a specialized condenser and strictly controlled the distance between the condensing surface and the evaporating surface to 5 cm (a characteristic of short-path distillation), ultimately yielding refined polyethylene glycol (PEG) products with a narrow molecular weight distribution.

[0044] Implementation Process Two: Green and Energy-Saving Version (Supercritical CO2 Mass Transfer Enhancement + Online Monitoring)

[0045] Key innovations: Dynamic pressure control + infrared feedback intelligent feeding

[0046] Applicable scenarios: Continuous large-scale production facilities

[0047] Step 1: Microwave-molecular sieve synergistic dehydration with initiator

[0048] A tower system specifically designed for the continuous deep dehydration of glycerol was developed, employing a unique physical-energy synergistic dehydration architecture. The tower features a vertically layered design: the upper layer is a fixed-bed adsorption section, tightly packed with spherical NaA molecular sieve particles (0.4nm pore size, preferentially adsorbing water molecules) with a diameter of 3-5mm, providing a large selective adsorption surface area; the lower layer integrates a closed-loop multimode microwave radiation cavity equipped with a power-adjustable magnetron array. Industrial-grade glycerol feedstock is fed from the top of the tower at a constant flow rate of 5L / min, flowing sequentially from top to bottom under gravity through the molecular sieve adsorption layer (adsorbing residual trace amounts of water in the retained water) and the microwave activation zone. Microwave energy is directionally input at a reference power density of 0.5W / g (based on the mass of glycerol flowing through the microwave zone per unit time), penetrating the fluid and heating the molecular sieve particles, effectively driving the desorption and dissociation of adsorbed water within them, while simultaneously preventing overheating and decomposition of the bulk material. The core innovation lies in the introduction of an online Karl Fischer moisture analyzer to monitor the water content of the product at the bottom of the column in real time, and dynamically feed the signal back to the microwave power adjustment system to build a closed-loop control system. Based on the deviation between the preset target value (outlet water content = 45 ppm) and the actual detected value, this system adaptively and dynamically adjusts the microwave power (e.g., fine-tuning within ±0.1 W / g) to ensure that the water content of the finished glycerol remains stably maintained within the stringent quality range of 45 ± 3 ppm over a long period, even under conditions of fluctuating feed flow or slight changes in humidity, meeting the requirements of high-end applications.

[0049] Step 2: Mass transfer optimization of supercritical systems

[0050] High-pressure reactor integrated with vortex static mixer (blade angle 45°, 10 stages).

[0051] The mass flow ratio of CO2 to ethylene oxide is set to 1:8 and precisely controlled by a mass flow meter.

[0052] Dynamic pressure control algorithm:

[0053] When the instantaneous flow rate of ethylene oxide is >5 kg / min:

[0054] Start the booster pump to ensure pressure fluctuation is ≤ ±0.3MPa.

[0055] When the reaction temperature is >100℃:

[0056] The compensation pressure (MPa) is automatically adjusted according to the formula: Compensation pressure (MPa) = 0.05 × (real-time temperature - 100).

[0057] Step 3: Intelligent Response Based on Infrared Feedback

[0058] To accurately monitor the etherification / polymerization reaction process and achieve intelligent control of stage switching, an ATR-FTIR (Attenuated Total Reflectance-Fourier Transform Infrared) real-time probe was installed in the core position of the liquid phase zone inside the reactor. This probe is configured to automatically scan the near-infrared spectrum every 30 seconds and accurately capture the near-infrared spectrum at 1110 cm⁻¹. -1 The characteristic absorption peak at the wavenumber is attributed to the stretching vibration of the COC group in the target product. Using the integrated area of ​​this characteristic peak at the initial reaction time (t = 0 minutes) as the baseline A0, the peak area acquired in real time is A. t Based on the established hydroxyl conversion prediction model, the conversion rate Y (%) is calculated using the following formula:

[0059] Y(%)=[A o / (A0+A t )]×K,

[0060] Wherein, K is the temperature correction coefficient (this coefficient is calibrated based on the exothermic characteristics of the reaction and the spectral temperature effect, and its empirical value at 110℃ is K = 1.02). This model directly converts infrared spectral data into real-time, quantitative indicators of the reaction process. The core control objective of the system is set as follows: when the calculated real-time conversion rate Y value first reaches 45%, the control center immediately triggers automated operations: 1) automatically stops the current feeding / stirring mode and switches to the preset second reaction stage operation program; 2) synchronously starts the temperature program control system, raising the temperature of the reaction system to the temperature required for the next stage at the set rate. Through this closed-loop control strategy based on real-time spectral data, it can be ensured that each batch of reaction can switch reaction paths with high precision and consistency at the optimal kinetic inflection point.

[0061] Step 4: Energy-saving molecular distillation

[0062] Short-path falling film evaporator is used, with temperature gradient control on the evaporation surface:

[0063] Feeding zone 150℃ → Central zone 170℃ → Discharge zone 180℃.

[0064] The vacuum system is divided into two stages:

[0065] The forestage rotary vane pump is maintained at 1 kPa, while the subsequent diffusion pump is reduced to 0.1 kPa.

[0066] Collect by molecular weight fractions:

[0067] 2000-3000Da (cosmetic grade).

[0068] 3000-6000Da (industrial grade).

[0069] Energy saving data:

[0070] The mass transfer efficiency of the supercritical system reaches 185% of that of the traditional batch reactor.

[0071] Molecular distillation consumes only 0.8 kWh / kg of energy (compared to 2.5 kWh / kg for traditional solvent extraction). Implementation Process Three: Low-Cost, High-Efficiency Version (Waste Resource Utilization)

[0072] Key innovations: regenerable adsorbent + byproduct recycling

[0073] Applicable scenarios: Sustainable production lines

[0074] Step 1: Glycerol dehydration and catalyst regeneration

[0075] To convert waste cooking oil into high-value-added glycerol and achieve process material recycling, crude glycerol product (initial purity approximately 85%) is first obtained through transesterification (e.g., methanol hydrolysis). This crude product requires refining and purification, and its dehydration and decolorization process employs a two-step method:

[0076] The first step involves using the macroporous adsorption resin Amberlite XAD-7HP (which has a high specific surface area and suitable hydrophobic-hydrophilic balance properties) to selectively adsorb and remove large molecular / nonpolar impurities such as oil saponifications, pigments (such as carotenoids and chlorophyll derivatives) and some unreacted glycerides, thereby improving the transparency and quality of the material.

[0077] The second step involves connecting to a high-efficiency molecular sieve membrane dehydration unit (specific parameters are detailed in [Process 1]: using NaA type membranes, microwave-assisted vacuum permeation evaporation dehydration method) to strictly reduce the water content of glycerol to ≤50ppm. Simultaneously, the regeneration process for the exhausted solid catalyst generated during the reaction (such as the aforementioned acidified montmorillonite-supported or homogeneous catalyst after solidification) includes: 1) Chemical cleaning regeneration: Deep immersion in a 5% oxalic acid aqueous solution (weak acid, effectively dissolving metal soaps and inorganic deposits) under ultrasonic enhancement (30 minutes) to efficiently remove carbon deposits and metal ion contaminants from the surface and pores; 2) High-temperature structural restoration: After centrifugation to remove the oxalic acid solution, the cleaned catalyst is placed in a muffle furnace and calcined at 550℃ for 4 hours to completely incinerate residual organic matter and repair the catalyst pore structure and active sites. Verification shows that this regeneration process can achieve a recovery rate of >92% for key catalyst activity indicators (such as acid site density), realizing the goals of efficient regeneration and a circular economy.

[0078] Step 2: In-situ regeneration system for adsorbent

[0079] Design a fluidized bed adsorption system with continuous online regeneration capability. The tower adopts a double-layer structure: the lower layer is filled with diatomaceous earth-activated carbon composite adsorbent particles with a particle size of 1-2 mm (forming a dynamic adsorption layer) to efficiently capture target impurities from the mobile phase (such as gas or liquid flow); the upper layer serves as an in-situ regeneration zone, through which hot nitrogen gas at a temperature of 200℃ is introduced (with a counter-current or cross-flow design to the material). Utilizing the principle of thermal desorption, the saturated particles from the lower layer are fluidized and lifted to the regeneration zone, where they are rapidly stripped away and carried away. The system is equipped with an intelligent sensing and switching device. When a specific area (such as the lower layer) becomes saturated, the saturated adsorbent batch is automatically switched to a sealed regeneration chamber (or using a partitioned design within the tower) for forced regeneration by high-temperature nitrogen gas. The entire regeneration process (including heating, desorption, and cooling) is strictly controlled, with a cycle time of ≤30 minutes, ensuring complete recovery of adsorbent performance after regeneration. The system achieves near-continuous adsorption-regeneration cycle operation.

[0080] Step 3: Recycling of by-products

[0081] Treatment of first-stage distillate (free polyethylene glycol) from molecular distillation:

[0082] Epichlorohydrin was added to carry out the end-capping reaction (molar ratio 1:1.2).

[0083] A biodegradable emulsifier was synthesized for use in the catalyst washing of this system.

[0084] The recycling rate of waste supercritical CO2 after condensation and purification is ≥95%.

[0085] Step 4: Process Integration and Control

[0086] Key nodes for DCS system monitoring:

[0087] Dehydration rate (infrared moisture meter).

[0088] Catalyst activity (acid value monitored by online pH probe).

[0089] Arm length uniformity (characteristic absorption at 288 nm measured by UV detector).

[0090] When the proportion of the three-arm structure is less than 97%, the ethylene oxide injection rate will be automatically increased by 5%.

[0091] Cost-effectiveness:

[0092] Raw material costs were reduced by 38% (regenerated catalyst + recovered glycerol).

[0093] Waste emissions are reduced by 76% (closed-loop design).

[0094] Finally, the following points should be noted: First, in the description of this application, it should be noted that, unless otherwise specified and limited, the terms "installation", "connection", and "linkage" should be interpreted broadly, and can be mechanical or electrical connections, or internal connections between two components, or direct connections. "Up", "down", "left", "right", etc. are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may change.

[0095] Secondly: The accompanying drawings of the embodiments disclosed in this invention only involve the structures involved in the embodiments disclosed in this invention. Other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of this invention can be combined with each other.

[0096] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a novel three-armed polyoxyethylene ether-based surfactant, characterized in that... Includes the following sequential steps: S1. Using glycerol with a water content ≤50ppm as the core initiator, the dehydration rate is ≥99% by reacting at 80 to 120 degrees Celsius for 1 to 3 hours in a vacuum environment after dehydration by molecular sieve permeation membrane; then, 0.5% to 2% of a solid acid catalyst by mass of the initiator is added. This catalyst is prepared by reacting phosphotungstic acid and hexadecyltrimethylammonium bromide at a molar ratio of 1:2 in a water bath at 60 degrees Celsius for 3 hours, then loading it onto acidified montmorillonite (loading 10 to 15% by weight) and calcining it at 250 degrees Celsius for 2 hours. S2. Under the protection of an inert atmosphere and a supercritical CO2 medium of 8 to 12 MPa, ethylene oxide is introduced in three stages: in the first stage, it is introduced at 60 to 80 degrees Celsius until the hydroxyl conversion of glycerol reaches 30% to 50%; in the second stage, the temperature is increased to 100 to 120 degrees Celsius at a rate of 1 degree Celsius / minute and the total molar ratio of ethylene oxide to hydroxyl groups reaches 10:1 to 30:1 (molar distribution ratio of the three stages is 1:3:6); in the third stage, the reaction is maintained at 120 to 130 degrees Celsius until the pressure is constant and then aged for 1 hour. S3. After the reaction is terminated, add 3% to 5% of the modified diatomaceous earth-activated carbon composite adsorbent (mass ratio 2:1) to remove the catalyst, and filter to obtain the crude product. S4. Finally, molecular distillation was carried out in a short-path falling film evaporator with a distance of ≤5 cm between the evaporation surface and the condensation surface at 150 to 180 degrees Celsius and 0.1 to 1 kPa to obtain a three-armed polyoxyethylene ether-based surfactant with a molecular weight distribution index ≤1.

15.

2. The method for preparing a novel three-armed polyoxyethylene ether-based surfactant according to claim 1, characterized in that... The preparation process of the solid acid catalyst is as follows: phosphotungstic acid solution and hexadecyltrimethylammonium bromide solution are reacted in a 60°C constant temperature water bath at 500 rpm for 3 hours to form a heteropolyacid complex. Subsequently, the complex is loaded onto a montmorillonite support activated with 10% hydrochloric acid using an equal-volume impregnation method. After being treated at 120°C for 4 hours in a vacuum drying oven, it is transferred to a muffle furnace and calcined at 250°C for 2 hours with a programmed temperature increase of 2°C / min, finally obtaining a solid catalyst with an acidic site density ≥0.8 mmol / g.

3. The method for preparing a novel three-armed polyoxyethylene ether-based surfactant according to claim 1, characterized in that... The reaction pressure in the supercritical CO2 medium is dynamically adjusted by a high-pressure metering pump to maintain a pressure fluctuation range of ≤±0.5MPa during the ethylene oxide introduction stage, and the mass flow ratio of CO2 to ethylene oxide is controlled between 1:5 and 1:

10. A vortex static mixer is installed in the reactor to improve the gas-liquid mass transfer efficiency to more than 1.8 times that of the conventional system.

4. The method for preparing a novel three-armed polyoxyethylene ether-based surfactant according to claim 1, characterized in that... The molecular distillation process includes two stages of purification: the first stage separates free polyethylene glycol byproducts at 150°C and 1 kPa, and the second stage collects the target component at 180°C and 0.1 kPa. The fraction is cut off to the core product with a molecular weight of 2000 to 6000 Da. The final free polyethylene glycol residue is ≤0.5% by weight and the three-arm structure accounts for ≥98% (verified by MALDI-TOF mass spectrometry).

5. The method for preparing a novel three-armed polyoxyethylene ether-based surfactant according to claim 1, characterized in that... The dehydration pretreatment of glycerol adopts molecular sieve permeation membrane coupled microwave radiation technology: industrial grade glycerol is passed through a NaA type molecular sieve membrane module (pore size 0.4 nm) at a flow rate of 2 ml / min, and simultaneously irradiated with 100 W power in a 2450 MHz microwave field, which increases the water molecule removal rate to 3 times that of traditional vacuum dehydration, and the final water content is ≤50 ppm.

6. The method for preparing a novel three-armed polyoxyethylene ether-based surfactant according to claim 1, characterized in that... The preparation of the modified diatomaceous earth-activated carbon composite adsorbent includes: boiling diatomaceous earth in a 10% sodium hydroxide solution for 1 hour, washing it until neutral, and then calcining it at 600 degrees Celsius for 2 hours; treating activated carbon with 30% nitric acid under reflux for 3 hours, then washing and drying it with water; mixing the two in a mass ratio of 2:1 and impregnating it in a 5% by weight polydimethyldiallylammonium chloride solution, ultrasonically treating it for 30 minutes, and then curing it at 110 degrees Celsius to obtain a composite adsorbent with a pore size concentrated in the range of 20 to 50 nanometers.

7. The method for preparing a novel three-armed polyoxyethylene ether-based surfactant according to claim 1, characterized in that... The ethylene oxide addition number of the final product was monitored in real time via online infrared spectroscopy of the reaction process: an ATR-FTIR probe was embedded in the reactor to dynamically detect the reaction at 1110 cm⁻¹. -1 By analyzing the intensity changes of the COC characteristic peak and combining it with the hydroxyl conversion model, precise control of 15 to 50 units of ethylene oxide per arm can be achieved, with a molecular weight error range of ≤±2%.

Images