Ether polymerization inhibitor special for butadiene extraction system and preparation method of ether polymerization inhibitor

Abstract

The invention discloses an ether polymerization inhibitor special for a butadiene extraction system and a preparation method of the ether polymerization inhibitor. The ether polymerization inhibitor comprises the following raw materials: a polymerization inhibitor intermediate, a solvent and a dispersing agent, the production process comprises the following steps: preparing a polymerization inhibitor intermediate, preparing a solvent, compounding, feeding and mixing, filtering, removing impurities and detecting. According to the method, firstly, a polymerization inhibitor 701 and diethylene glycol normal pressure etherification process is adopted, and beta-hydroxyethyl methyl ether is introduced to seal a terminal group, so that the power consumption is reduced, the generation of byproducts is inhibited, the solubility of an intermediate acetonitrile is improved to be greater than or equal to 30g / L, and the anti-interference performance is greatly enhanced; the solvent doped with a small amount of silane modified nano diatomite is prepared, impurities can be adsorbed, metal ions can be chelated, the dispersing agent can be assisted to be evenly distributed, the problems that a pure water solvent is single in function and the dispersing agent is prone to agglomeration are solved, and the polymerization inhibition efficiency and the stability of an extraction system are guaranteed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chemical polymerization inhibitor, in particular to an ether polymerization inhibitor special for butadiene extraction system and a preparation method thereof. BACKGROUND

[0002] Butadiene is the core monomer of synthetic cis-butadiene rubber, styrene-butadiene rubber, ABS resin and other polymer materials, which is mainly obtained by cracking C4 fraction through extraction separation in industry. In the butadiene extraction process, due to the existence of oxygen, light and the operating temperature of 40-80℃ in the system, butadiene is easy to occur free radical polymerization reaction to generate oligomers (such as butadiene dimers) and high polymers (such as polybutadiene). These polymers will adhere to the tower tray, packing and the inner wall of the pipeline, resulting in tray plugging, mass transfer efficiency decline, and even need to stop cleaning, which not only increases the equipment maintenance cost, but also causes the loss of butadiene yield.

[0003] The existing butadiene extraction system commonly used polymerization inhibitor mainly includes phenothiazine (PTZ), hydroquinone (HQ) and hindered phenolic compounds, but there are the following problems: 1. The solubility of phenothiazine in acetonitrile and NMP is only 5-8g / L, which needs to be added in excess to achieve the effect of polymerization inhibition, which is easy to cause solvent pollution and affect the purity of subsequent butadiene refining.

[0004] 2. The trace amount of acidic substances such as H2S and CO2 carried by the cracking C4 fraction can destroy the activity of the polymerization inhibitor, and Fe 3+ / Cu 2+ generated by equipment corrosion can catalyze butadiene polymerization, resulting in fluctuation of polymerization inhibition efficiency.

[0005] 3. The polymerization inhibitor and by-products are easy to remain in the extraction solvent, which increases the load of subsequent butadiene refining and improves the production cost.

[0006] 4. The synthesis of existing intermediates requires high temperature above 120℃ and high pressure of 0.2-0.3MPa, which consumes more electricity and does not meet the development trend of low-carbon chemical industry. In addition, the traditional polymerization inhibitor is easy to separate after compounding, and the storage period at room temperature is short, which cannot meet the needs of industrial mass production and long-distance transportation. Therefore, in view of the above problems, it is urgent to develop a butadiene extraction system special polymerization inhibitor with high solubility, good thermal stability, stable compounding storage, low energy consumption and no residual risk and a preparation method thereof. SUMMARY

[0007] The present application relates to the technical field of chemical polymerization inhibitor, in particular to an ether polymerization inhibitor special for butadiene extraction system and a preparation method thereof.

[0008] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: A preparation method of an ether type polymerization inhibitor special for a butadiene extraction system, comprising the following steps: S1, preparation of a polymerization inhibitor intermediate Close the bottom valve of the reaction kettle and check the sealing, then add 68.5% of the polymerization inhibitor 701, 31.0-31.2% of diethylene glycol and 0.3-0.5% of β-hydroxyethyl methyl ether by DCS metering pump in sequence, the DCS control system starts the jacket heating, the temperature is raised to 96-100℃ at a rate of 5-8℃ / min, 1% of p-toluenesulfonic acid based on the total system is added, and the reaction is carried out at normal pressure for 2 hours, during which the DCS control system monitors the temperature fluctuation in real time, after the reaction is completed, sampling is carried out, high performance liquid chromatography detection is carried out, the qualified standard is that the purity of the intermediate is ≥99.2% and the by-product content is ≤0.3%, if unqualified, 0.1% of diethylene glycol based on the total system is supplemented, and after 0.5 hours of continuous incubation, re-detection is carried out, and the qualified product is the polymerization inhibitor intermediate; After closing the bottom valve of the reaction kettle and checking the sealing, 68.5% of the polymerization inhibitor 701, 31.0-31.2% of diethylene glycol and 0.3-0.5% of β-hydroxyethyl methyl ether are added by DCS metering pump in sequence, the molecular structure of the polymerization inhibitor 701 contains a piperidine ring nucleus, 1 active hydroxyl group and 1 nitroxyl radical are connected on the ring, the nitroxyl radical has high stability due to the conjugation effect, does not participate in the etherification reaction, and only the hydroxyl group acts as the active site for alcohol reaction, diethylene glycol contains 2 primary hydroxyl groups, the electron cloud density on the C directly connected with the hydroxyl group is low, and it is easy to be attacked by a nucleophile, and the two hydroxyl groups can be used as reaction sites respectively, the primary hydroxyl group is protonated under acidic conditions to form -OH2 + , the hydroxyl group in the polymerization inhibitor 701 is not easy to be activated due to steric hindrance, it attacks the protonated diethylene glycol as a nucleophile, the oxygen atom of the polymerization inhibitor 701 is combined with the carbon atom at the end of diethylene glycol, a water molecule is removed, and the etherification is completed;

[0009] The antioxidant activity of the polymerization inhibitor 701 itself is high, and the free radicals R·, ROO· and other free radicals generated during oxidation can easily react with it, which can eliminate various free radicals generated during the reaction and completely inhibit the normal progress of polymerization and reaction, and is suitable for preventing polymer fouling in the extraction device. However, the polymerization inhibition effect of the etherified polymerization inhibitor 701 is more suitable for the butadiene extraction system than that of the unetherified polymerization inhibitor 701. The etherification does not change the polymerization core, and the nitrogen-oxygen free radical still captures the active free radical of butadiene, but the molecular structure can be optimized by introducing an ether bond, which solves the problem of low solubility of the unetherified polymerization inhibitor 701 in acetonitrile and other extraction solvents, improves the solubility to achieve uniform dispersion, reduces the number of active hydroxyl groups and increases the long-chain structure, reduces the reactivity with H2S and metal ions in the system, avoids the deactivation of the nitrogen-oxygen free radical, prolongs the polymerization inhibition half-life to 180 hours, and increases the molecular weight, reduces the loss with the solvent circulation, makes the polymerization inhibition more persistent, and if not etherified, the polymerization inhibitor 701 will be precipitated to block the equipment, be damaged by impurities, be lost quickly, and other problems, which cannot completely meet the industrial polymerization inhibition requirements of the butadiene extraction system. Therefore, the essence of etherification is to make the polymerization core function stable in the actual scene; The beta-hydroxyethyl methyl ether here corresponds to a functional type of auxiliary agent. In the reaction system of the polymerization inhibitor 701 and diethylene glycol, chain growth reactions may occur to form molecules of different chain lengths, such as self-polymerization and condensation of diethylene glycol molecules. The active hydroxyl group contained in the beta-hydroxyethyl methyl ether can undergo trace alcohol-alcohol dehydration etherification with the terminal hydroxyl group of diethylene glycol that has not been completely reacted, generating a terminal group structure containing a methoxy group, which closes the terminal hydroxyl group of diethylene glycol and introduces an ether bond to further fine-tune the polarity of the intermediate, assisting in improving its solubility in acetonitrile. In the entire process, it does not directly react with the polymerization inhibitor 701, but only participates in the modification of the terminal group of diethylene glycol through a small amount of etherification, which not only inhibits side reactions but also optimizes the application performance of the intermediate, enhances the water solubility and storage stability of the finished polymerization inhibitor, and the addition amount is only 0.3-0.5%, which does not affect the structure of the main intermediate and the activity of the polymerization core; The DCS control system starts jacket heating, and the temperature is raised to 96-100°C at a rate of 5-8°C / min, which is the optimal temperature for the etherification reaction, which can ensure the reaction rate and avoid high temperature-induced self-condensation of diethylene glycol. The temperature is kept at normal pressure to ensure sufficient reaction, and the DCS monitors the temperature fluctuation in real time. A sudden temperature rise can significantly increase the side reaction rate of intermolecular dehydration of diethylene glycol, resulting in an increase in the amount of byproduct diethylene glycol ether generated; After the reaction, sample was taken and detected by high performance liquid chromatography. The qualified standard was set as intermediate purity ≥ 99.2% and by-product (diethylene glycol ether) content ≤ 0.3%. This index was based on the purity requirement of ether polymerization inhibitor in the quality standard of polymer synthesis aid. If unqualified, 0.1% of diethylene glycol based on the total amount of the system was added. The role of diethylene glycol was to promote the main reaction by increasing the concentration of reactants, and to inhibit the decomposition of by-products by using excess diethylene glycol. After 0.5 h of continuous preservation, the product was re-measured. The qualified product was the polymerization inhibitor intermediate. The methoxy group of β-hydroxyethyl methyl ether could block the molecular terminal hydroxyl group, further inhibiting the side reaction. S2, preparation of solvent The pretreated nanometer diatomite was placed in a 5wt% 3-aminopropyl triethoxysilane ethanol aqueous solution with a mass ratio of 100:1, stirred for 1 h, centrifuged, washed with anhydrous ethanol for 3 times, dried, compounded with deionized water according to the mass ratio of 0.08-0.1:100, ultrasonically dispersed for 30 min, filtered, and the solvent doped with a small amount of modified diatomite was obtained. The silane coupling agent is easy to hydrolyze. The trimethoxysilyl group (-Si(OCH3)3) hydrolyzes under acidic conditions to form a silicon hydroxyl group (-Si(OH)3). The nanometer diatomite contains a large number of hydroxyl groups on the surface of the aqueous solution, which is easy to condense between the silicon hydroxyl groups to form a silicon oxygen covalent bond, so that the amino group at the other end of the silane molecule is grafted to the surface of the diatomite, and the modification of the diatomite is completed. Then the mixed system is subjected to centrifugal treatment, and the modified diatomite is separated out, washed with anhydrous ethanol for 3 times to remove the free silane not grafted to the surface of the diatomite, and then dried to remove the residual ethanol and water on the surface of the diatomite. There are two reasons for the polar modification of the silane coupling agent. One is that the grafted amino group on the surface can adsorb trace impurities generated in the compounding process of the polymerization inhibitor, such as unreacted small molecule substances and metal ions generated by equipment corrosion. The other is that the nanometer diatomite is insoluble in water, and due to its small particle size, the agglomeration phenomenon is serious. The silanization treatment helps to uniformly disperse it.

[0010] The modified diatomite and deionized water were mixed according to the proportion. Ultrasonic action can destroy the agglomeration structure between the modified diatomite particles, so that the modified diatomite particles are uniformly dispersed in the deionized water to form a stable suspension. Then the suspension is filtered to remove the agglomerated particles of the modified diatomite which are not completely dispersed, and finally the solvent doped with a small amount of modified diatomite is obtained. Retaining a small amount of modified diatomite can ensure that it continues to play the role of purification and auxiliary dispersion. Filtering the agglomerated particles can avoid the blockage of related equipment during subsequent use. The deionized water doped with modified diatomite is used as the solvent. During the compounding process, trace amounts of unreacted polymerization inhibitor 701, diethylene glycol self-condensation byproducts such as diethylene glycol ether, and viscous impurities may be left in the intermediate of the polymerization inhibitor. The dispersant may also form trace amounts of agglomerated particles due to uneven stirring. These particles cannot be removed by pure water itself. The porous structure of the modified diatomite can capture them through physical adsorption. At the same time, the amino groups (-NH2) on the surface of the modified diatomite can chemically chelate trace amounts of metal ions in the system, avoiding the catalysis of metal ions on the polymerization of butadiene. The surface of the particles of the modified diatomite can serve as an anchoring site for the dispersant, allowing ethylenediaminetetraacetic acid disodium salt and 2,2'-dipyridyl to be more uniformly attached to the surface of the particles. Then, the dispersant is driven to diffuse throughout the system through the Brownian motion of the particles, solving the problem of local agglomeration of the dispersant when it is directly dissolved in water. Deionized water does not have this carrier function and can only provide a solvent environment free of impurities, but it cannot solve the problems of newly generated process impurities and low efficiency of the dispersant during the compounding process. S3, compounding and mixing of raw materials Half of the solvent and all of the dispersant are first added to the reaction mixing kettle through the DCS control system. The stirrer is started and the stirring speed is controlled at 60-70 rpm. The intermediate of the polymerization inhibitor is gradually added. Stirring is carried out at room temperature and normal pressure for 10-20 min. Then the remaining solvent is added. The stirring speed is adjusted to 70-80 rpm. Stirring is continued for 30-60 min. During this period, the DCS monitors the temperature in the kettle in real time, which is 20-30°C. The system is then left to stand for 1-2 hours in an environment at 25°C. Half of the solvent and all of the dispersant are first added to the reaction mixing kettle through the DCS control system. The stirrer is started and the stirring speed is controlled at 60-70 rpm, so that the dispersant can be preliminarily dispersed in the solvent to form a uniform system, creating conditions for subsequent combination with the intermediate of the polymerization inhibitor. Then the intermediate of the polymerization inhibitor is gradually added. Stirring is carried out at room temperature and normal pressure for 10-20 min. During this process, the shear force generated by stirring allows the intermediate to fully contact the dispersant. The active groups of the dispersant will combine with the surface groups of the intermediate to form stable intermediate-dispersant complexes, avoiding agglomeration of the intermediate. Then the remaining solvent is added and the stirring speed is adjusted to 70-80 rpm. Stirring is continued for 30-60 min, because increasing the stirring speed can enhance the shearing action after the volume of the system increases, promoting the uniform diffusion of the complexes in the full amount of solvent and avoiding local concentration unevenness. During this period, the DCS monitors the temperature in the kettle, which is 20-30°C, because the binding force between the dispersant and the intermediate is stable in this temperature range and temperature fluctuations will not cause the complexes to dissociate or produce side reactions. Finally, the system is left to stand for 1-2 hours in an environment at 25°C, which allows the possible small agglomerated particles in the system to naturally settle by gravity, and allows the combination of the intermediate-dispersant complexes to be more complete and stable, laying the foundation for subsequent filtration and impurity removal and ensuring the uniformity of the final system. The generation of butadiene self-polymer is mainly due to the free radical polymerization initiated by unsaturated hydrocarbons and the like in the system under the conditions of heat energy, oxygen and metal, and the polymerization reaction mainly includes chain initiation, chain growth and chain termination: Chain initiation reaction: R-H R·+H· Chain growth stage: R·+O2→ROO· Autoxidation reaction: ROO·+R-H→ROOH+R· Polymerization reaction: R·+C=C→·C-C-R ROO·+C=C→·C-C-OOR Chain termination reaction: R·+R·→R-R There are many factors affecting the rate of butadiene polymerization. The increase of system temperature will greatly accelerate the rate of polymerization. In order to maintain high processing capacity after the fouling of the heating system, the heating steam temperature and pressure are often increased to maintain the heating capacity. In a short time, it can be maintained, but after 1-2 months, the heating system will be plugged due to the increase of temperature and the acceleration of polymerization. In the process of butadiene production, the polymerization of butadiene leads to the plugging of the tray and the fouling of the reboiler. The generated polymer, if deposited on the heat exchanger, will affect the heat transfer of the heat exchanger, and if deposited in the tower body, will affect the separation effect of the tower. In severe cases, it will lead to the plugging of the tower body and the shutdown of the device for maintenance; The role of polymerization inhibitor is to prevent the chain growth. After compounding, the intermediate of polymerization inhibitor is uniformly dispersed in the solvent. The finished polymerization inhibitor contains a large amount of nitroxyl radical, which captures the free radicals generated in the process of butadiene polymerization, eliminates various free radicals generated by reaction, and completely inhibits the normal progress of polymerization and reaction; Polymerization inhibitor-NO·+R·→polymerization inhibitor-NOR Polymerization inhibitor-NO·+ROO·→polymerization inhibitor-NO-OOR S4, filtration and detection After compounding, filter through stainless steel filter screen, and analyze the sample from the detection center. After passing the test, the finished product, ether polymerization inhibitor for butadiene extraction system, is obtained. Filtering through stainless steel filter screen is based on the principle of physical screening to remove the modified diatomite agglomerate particles that are not completely dispersed, so as to avoid the plugging of butadiene extraction tower packing and affect the mass transfer. The sample analysis from the detection center verifies that there is no impurity in the appearance to ensure that the dispersion is uniform, the solubility can adapt to acetonitrile and other extraction solvents, and the key indicators such as the ability of nitroxyl radical to capture butadiene active free radical show the adaptability of the core function and anti-interference performance of the finished product to the scene. After passing the test, the finished product can avoid secondary pollution. The final product is suitable for the demand of butadiene extraction system due to the continuous purification of the trace amount of modified diatomite, the auxiliary uniform distribution of the dispersant, and the stable release of nitroxyl radical from the ether intermediate.

[0011] Preferably, the dispersant is prepared by compounding disodium ethylenediaminetetraacetate and 2,2'-bipyridine, and the specific preparation steps are as follows: taking disodium ethylenediaminetetraacetate and 2,2'-bipyridine, accurately weighing them according to a mass ratio of 2:1, adding them into a reaction kettle, adding deionized water in an amount of 5-10 times the total mass of the raw materials, and stirring for 30 min to obtain the dispersant; the two substances are dissolved in water due to molecular polarity and form a stable composite system through intermolecular forces; disodium ethylenediaminetetraacetate and 2,2'-bipyridine cooperatively chelate Fe 3+ , Cu 2+ and other metal ions to avoid their catalysis of butadiene polymerization; and the dispersant is adsorbed on the surface of the polymerization inhibitor intermediate to prevent agglomeration through charge repulsion and steric hindrance, and ensure uniform distribution of the polymerization inhibitor in the solvent to stably play a role.

[0012] Preferably, the polymerization inhibitor 701 is 4-hydroxy-2,2,6,6-tetramethylpiperidine nitroxide, the purity of disodium ethylenediaminetetraacetate is greater than or equal to 99.0%, and the purity of 2,2'-bipyridine is greater than 98.5%.

[0013] Preferably, the pretreatment method of the nanometer diatomite is drying the nanometer diatomite in an oven at 105 DEG C for 2 h and sieving, so as to remove water in the nanometer diatomite and sieve diatomite with a suitable particle size to prevent blockage caused by large particles.

[0014] Preferably, the preparation steps of the 3-aminopropyl triethoxysilane ethanol aqueous solution are as follows: taking anhydrous ethanol and deionized water according to a volume ratio of 95:5, adding the silane reagent according to a mass ratio of 3-aminopropyl triethoxysilane: ethanol aqueous solution = 5:95, adding 1-2 drops of 0.1 mol / L acetic acid solution dropwise, stirring for 10 min, and obtaining the 3-aminopropyl triethoxysilane ethanol aqueous solution; the ethoxyl group of the silane reagent is hydrolyzed to generate a silicon hydroxyl group; the silicon hydroxyl group under an acidic condition is highly active and is easy to condense with a hydroxyl group, so as to be combined with the nanometer diatomite.

[0015] Preferably, the detection indexes of the compounded polymerization inhibitor include: appearance: colorless transparent liquid, no stratification, no suspended matter; acetonitrile solubility at 25 DEG C: 30 g / L; 60 DEG C polymerization inhibition efficiency: greater than or equal to 97%; 25 DEG C storage stability: greater than or equal to 200 days.

[0016] Compared with the prior art, the present application has the following beneficial effects: The present application prepares an intermediate by normal pressure etherification reaction of a polymerization inhibitor 701 and diethylene glycol, and introduces beta-hydroxyethyl methyl ether as an end group blocking aid, to prepare a more suitable polymerization inhibitor required for a butadiene polymerization system, uses 96-100 DEG C normal pressure reaction instead of the high temperature and high pressure process above 120 DEG C in the prior art, cooperates with p-toluene sulfonic acid catalysis and DCS precise temperature control, reduces the power consumption by more than 30% to adapt to low carbon demand, and suppresses the generation of diethylene glycol ether byproduct by the trace etherification of beta-hydroxyethyl methyl ether and the end hydroxyl group of diethylene glycol.

[0017] The modification improves the solubility of the intermediate in acetonitrile from 5-8 g / L of the existing phenothiazine to ≥30 g / L, and the long-chain ether structure and reduced active hydroxyl group significantly improve the anti-interference property in the presence of H2S, CO2 and Fe 3+ / Cu 2+ generated by equipment corrosion in the cracked C4 fraction, prolongs the polymerization inhibition half-life, and solves the core problems of solvent pollution caused by excessive addition of the existing polymerization inhibitor due to low solubility and fluctuation of polymerization inhibition efficiency due to poor anti-interference.

[0018] The present application uses silane modified nanometer diatomite to construct a composite solvent, the pretreated diatomite is modified by amino grafting with 3-aminopropyl triethoxysilane, and then is compounded with deionized water at a ratio of 0.08-0.1:100, ultrasonic dispersion and filtration, which breaks through the limitation of the existing pure water solvent which can only provide a carrier, the porous structure of the modified diatomite can physically adsorb the unreacted small molecules and sticky byproducts remaining in the compounding process, the surface amino group can chemically chelate trace metal ions, and at the same time, the particle surface acts as an anchor point for the dispersant, so that the dispersant is uniformly attached and diffused, solving the problem of easy agglomeration of the dispersant when directly dissolved in water. Compared with the prior art, the solvent system makes the chelation rate of the finished polymerization inhibitor ≥98%, and the gum adsorption rate ≥85%, which not only avoids the catalysis of metal ions on polymerization, but also removes the agglomerated particles by subsequent filtration to prevent the extraction tower from being blocked, solving the industry pain points of the prior art that cannot simultaneously handle the compounding impurities and the low efficiency of the dispersant. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The equipment connection diagram for producing the ether polymerization inhibitor specially used for butadiene extraction system of the present application; Figure 2 The nuclear magnetic hydrogen spectrum of the polymerization inhibitor intermediate produced by the present application. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments.

[0021] Example 1: S1, preparation of polymerization inhibitor intermediate Close the reactor bottom valve, check the sealing, and add 68.5% of the polymerization inhibitor 701, 31.1% of diethylene glycol, and 0.4% of β-hydroxyethyl methyl ether in sequence through the DCS metering pump. The DCS control system starts the jacket heating, and the temperature is raised to 98℃ at a rate of 7℃ / min. 1% of p-toluenesulfonic acid is added to the system, and the reaction is carried out at normal pressure for 2 hours. During the reaction, the DCS control system monitors the temperature fluctuation in real time. After the reaction is completed, sampling is carried out, and high-performance liquid chromatography is used for detection. The qualified standard is that the purity of the intermediate is ≥99.2%, and the content of by-products is ≤0.3%. If it is unqualified, 0.1% of diethylene glycol is added to the system, and the temperature is kept for another 0.5 hours. After re-detection, the qualified product is the polymerization inhibitor intermediate. S2, preparation of solvent The pretreated nanosilica is placed in a 5wt% 3-aminopropyltriethoxysilane ethanol aqueous solution with a mass ratio of 100:1, stirred for 1h, centrifuged, washed with anhydrous ethanol for 3 times, dried, compounded with deionized water at a mass ratio of 0.09:100, ultrasonically dispersed for 30min, filtered, and the solvent doped with a small amount of modified silica is obtained. S3, compounding and mixing Half of the solvent and all of the dispersant are added to the reaction mixing kettle through the DCS control system, the stirrer is started, the rotation speed is controlled at 65rpm, and the polymerization inhibitor intermediate is gradually added. The total mass ratio of the polymerization inhibitor intermediate to the solvent is 21.5:75 at normal temperature and pressure, and stirring is carried out for 15min. Then the remaining solvent is added, the stirring speed is adjusted to 75rpm, and stirring is continued for 45min. During this period, the DCS monitors the temperature in the kettle in real time, which is 30℃. Then the mixture is left to stand for 1.5 hours at an environment of 25℃. S4, impurity removal and detection After the compounding is completed, the mixture is filtered through a stainless steel filter screen, and the center sample is analyzed. After the product is qualified, it is canned to obtain the finished ether polymerization inhibitor specially used for butadiene extraction system.

[0022] Example 2: S1, preparation of polymerization inhibitor intermediate Close the bottom valve of the reactor, check the sealing, add 68.5% of the polymerization inhibitor 701, 31.1% of diethylene glycol, and 0.4% of β-hydroxyethyl methyl ether in sequence through the DCS metering pump, start the jacket heating of the DCS control system, and heat to 98℃ at a rate of 7℃ / min. Add 1% of p-toluenesulfonic acid based on the total system, and heat at normal pressure for 2 hours. During the reaction, the DCS control system monitors the temperature fluctuation in real time. After the reaction is completed, sampling is performed, and high performance liquid chromatography is used for detection. The qualified standard is that the purity of the intermediate is ≥99.2% and the content of by-products is ≤0.3%. If it is unqualified, add 0.1% of diethylene glycol based on the total system, continue to heat for 0.5 hours, and then re-detect. The qualified product is the polymerization inhibitor intermediate; S2, preparation of solvent The pretreated nanosilica is placed in a 5wt% 3-aminopropyl triethoxysilane ethanol aqueous solution with a mass ratio of 100:1, stirred for 1h, centrifuged, washed with anhydrous ethanol for 3 times, dried, compounded according to the mass ratio of modified siliceous earth to deionized water of 0.09:100, ultrasonically dispersed for 30min, filtered, and a solvent doped with a small amount of modified siliceous earth is obtained; S3, compounding and mixing of raw materials Half of the solvent and all the dispersing agent are added to the reaction mixing kettle through the DCS control system, the stirrer is started, the rotating speed is controlled at 65rpm, the polymerization inhibitor intermediate is gradually added, the total mass ratio of the polymerization inhibitor intermediate to the solvent is 29.5:75, and normal temperature and pressure stirring is performed for 15min; then the remaining solvent is added, the stirring speed is adjusted to 75rpm, and stirring is continued for 45min. During the process, the DCS monitors the temperature in the kettle in real time, which is 30℃. Then, the mixture is left to stand for 1.5 hours in an environment of 25℃. S4, impurity removal and detection After the compounding is completed, the mixture is filtered through a stainless steel filter screen, and the center sample is analyzed. After the product is qualified, it is canned to obtain the finished ether polymerization inhibitor specially used for butadiene extraction system.

[0023] Example 3: S1, preparation of polymerization inhibitor intermediate Close the bottom valve of the reactor, check the sealing, add 68.5% of the polymerization inhibitor 701, 31.1% of diethylene glycol, and 0.4% of β-hydroxyethyl methyl ether in sequence through the DCS metering pump, start the jacket heating of the DCS control system, and heat to 98℃ at a rate of 7℃ / min. Add 1% of p-toluenesulfonic acid based on the total system, and heat at normal pressure for 2 hours. During the reaction, the DCS control system monitors the temperature fluctuation in real time. After the reaction is completed, sampling is performed, and high performance liquid chromatography is used for detection. The qualified standard is that the purity of the intermediate is ≥99.2% and the content of by-products is ≤0.3%. If it is unqualified, add 0.1% of diethylene glycol based on the total system, continue to heat for 0.5 hours, and then re-detect. The qualified product is the polymerization inhibitor intermediate; S2, preparation of solvent The pretreated nanosilica is placed in a 5wt% 3-aminopropyl triethoxysilane ethanol aqueous solution with a mass ratio of 100:1, stirred for 1h, centrifuged, washed with anhydrous ethanol for 3 times, dried, compounded according to the mass ratio of modified siliceous earth to deionized water of 0.09:100, ultrasonic dispersed for 30min, filtered to obtain a solvent doped with a small amount of modified siliceous earth; S3, compounding and feeding Half of the solvent and all of the dispersant are first added to the reaction kettle through the DCS control system, the stirrer is started, the rotation speed is controlled at 65rpm, the polymerization inhibitor intermediate is gradually added, the total mass ratio of the polymerization inhibitor intermediate to the solvent is 25.5:75, and stirring is performed at room temperature and normal pressure for 15min; then the remaining solvent is added, the stirring speed is adjusted to 75rpm, and stirring is continued for 45min, during which the DCS real-time monitors the temperature in the kettle to be 30℃, and then the kettle is placed at 25℃ for 1.5h; S4, impurity removal and detection After the compounding is completed, the stainless steel filter screen is used for filtering, the center sample is analyzed, and the product is tanked after passing the detection to obtain the finished ether polymerization inhibitor specially used for butadiene extraction system.

[0024] Comparative Example 1 S1, preparation of polymerization inhibitor intermediate The bottom valve of the reaction kettle is closed, the sealing property is checked, 68.5% of the polymerization inhibitor 701, 31.1% of diethylene glycol and 0.4% of β-hydroxyethyl methyl ether are sequentially added through the DCS metering pump, the DCS control system starts the jacket heating, the temperature is increased to 98℃ at a rate of 7℃ / min, 1% of p-toluenesulfonic acid based on the total system is added, and the reaction is carried out at normal pressure for 2h, during which the DCS control system real-time monitors the temperature fluctuation, the sample is taken after the reaction is completed, and the high performance liquid chromatography is used for detection, the qualified standard is that the intermediate purity is ≥99.2% and the by-product content is ≤0.3%, if unqualified, 0.1% of diethylene glycol based on the total system is supplemented, the temperature is continuously maintained for 0.5h, and then the product is re-detected, and the qualified product is the polymerization inhibitor intermediate; S2, preparation of solvent The pretreated nanosilica is placed in a 5wt% 3-aminopropyl triethoxysilane ethanol aqueous solution with a mass ratio of 100:1, stirred for 1h, centrifuged, washed with anhydrous ethanol for 3 times, dried, compounded according to the mass ratio of modified siliceous earth to deionized water of 0.09:100, ultrasonic dispersed for 30min, filtered to obtain a solvent doped with a small amount of modified siliceous earth; S3, compounding and feeding Half of the solvent and all of the dispersant were added to the reaction kettle through the DCS control system, the stirrer was started, the rotation speed was controlled at 65 rpm, the polymerization inhibitor intermediate was gradually added, the total mass ratio of the polymerization inhibitor intermediate to the solvent was 34.5:75, and stirring was performed at room temperature and normal pressure for 15 min; then the remaining solvent was added, the stirring speed was adjusted to 75 rpm, and stirring was continued for 45 min, during which the DCS monitored the temperature in the kettle in real time to be 30°C, and then the kettle was placed at 25°C for 1.5 hours; S4, impurity removal and detection After the compounding was completed, the mixture was filtered through a stainless steel filter screen, and the center took samples for analysis. After passing the test, the product was packaged to obtain the finished ether polymerization inhibitor specially used for the butadiene extraction system.

[0025] Comparative Example 2: In comparison with Example 3, no β-hydroxyethyl methyl ether was added in Comparative Example 2.

[0026] Comparative Example 3: In comparison with Example 3, no etherification was performed on the polymerization inhibitor 701 in Comparative Example 3.

[0027] Comparative Example 4: In comparison with Example 3, no modification was performed on the nano diatomite in Comparative Example 4.

[0028] Comparative Example 5: In comparison with Example 3, no modified diatomite was added in Comparative Example 5, but deionized water was used as the solvent.

[0029] Comparative Example 6: In comparison with Example 3, no dispersant was added in Comparative Example 6.

[0030] Comparative Example 7: In comparison with Example 3, no 1.5h maturation operation was performed at 25°C after compounding in Comparative Example 7.

[0031] Performance test: According to the standard test methods in the national standards such as GB / T 4472-2011 “Determination of density and relative density of chemical products”, GB / T 30399-2013 “General rules for high performance liquid chromatography of chemical reagents”, GB / T 21845-2008 “Water solubility test of chemicals”, GB / T 13291-2017 “Industrial butadiene”, and GB / T 2793-2015 “Determination of non-volatile content of adhesives”, the density, intermediate purity, acetonitrile solubility, 60°C polymerization inhibition efficiency, and room temperature storage stability of the polymerization inhibitors prepared in the examples and comparative examples were tested.

[0032] Table 1 Performance test data of the polymerization inhibitors prepared in the examples and comparative examples

[0033] Data analysis: Figure 1 The equipment connection diagram for producing the ether-based polymerization inhibitor for the butadiene extraction system of the application is as follows: the solvent tank is connected with a DCS-controlled start-stop conveying pump and a flow meter with DCS flow control to send the solvent into the reaction mixing kettle; the polymerization inhibitor 701 and diethylene glycol are respectively conveyed to the reaction mixing kettle by DCS-controlled start-stop raw material pumps and flow meters with DCS flow control; the kettle body is equipped with liquid level display (LI) and temperature display (TI) to monitor the reaction system state in real time; after the reaction is completed and the sampling detection is qualified, the material enters the packaging or storage tank. The whole set of equipment realizes the accurate control of flow, temperature and equipment start-stop through the DCS system, and provides hardware support for the stable implementation of process parameters.

[0034] The intermediate proportion of Example 1 is lower than that of Example 3, and the performance change is due to the insufficient concentration of the polymerization active site. From the dispersion mechanism, the dispersion ability of the solvent at this proportion is far from saturation, the intermediate can be completely dispersed, and there is no risk of aggregation, so the storage stability and solubility remain at a good level, but because the concentration of the intermediate is too low, the total amount of nitroxyl radicals that can capture butadiene active free radicals in the system is reduced, although the polymerization efficiency of each active site is not affected, the overall polymerization efficiency is slightly lower than that of Example 3 due to the insufficient number of active sites.

[0035] The intermediate proportion of Example 2 is higher than that of Example 3, and the performance characteristics reflect the trade-off between the improvement of polymerization activity and the slight attenuation of dispersibility. Mechanistically, a higher intermediate concentration means an increased density of nitroxyl radicals in the system, which increases the probability of capturing active free radicals, so the polymerization efficiency is slightly higher than that of Example 3; but this proportion is close to the dispersion threshold of the solvent, and the anchoring dispersion sites of the modified diatomite tend to be saturated, and part of the intermediate molecules begin to form small aggregates, resulting in a slight inhibition of their solubility in acetonitrile, and the solubility is slightly lower than that of Example 3, but it does not reach the level of aggregation and precipitation, and the storage stability still meets the requirements.

[0036] The core advantage of Example 3 is that the mass ratio of the intermediate of the polymerization inhibitor to the solvent is in the optimal balance interval of the dispersion threshold and the polymerization activity. At this proportion, the modified diatomite in the solvent can fully play the role of anchoring dispersion, and the stable combination of its surface amino group and the dispersant provides a uniform dispersion carrier for the intermediate, so that the nitroxyl radicals in the intermediate molecules can be uniformly distributed in the system, which not only avoids the local concentration imbalance caused by the aggregation of the intermediate, but also ensures the effective exposure of the polymerization active sites. At the same time, the concentration of the intermediate does not exceed the solubility limit of the solvent, and there is no excessive aggregation between molecules, and the by-products are fully adsorbed by the modified diatomite, so the system has strong uniformity, and therefore the polymerization efficiency, solubility and storage stability are all optimal.

[0037] The intermediate proportion of Comparative Example 1 is significantly higher than that of Example 3, and the system is unstable due to exceeding the solvent dispersion threshold. When the intermediate concentration is much higher than the carrying capacity of the solvent, the anchoring sites of the modified diatomite are completely saturated, and the dispersant can no longer effectively wrap the intermediate molecules. A large number of intermediate molecules are aggregated due to intermolecular forces to form agglomerates. The agglomerates not only reduce the contact area with acetonitrile, resulting in a significant decrease in solubility, but also settle or stratify due to gravity during storage, destroying the uniformity of the system. Therefore, the storage stability is significantly decreased. Although the total amount of intermediate is extremely high, the agglomeration causes a large number of nitroxyl radicals to be wrapped inside the agglomerates, which cannot contact with the active radicals of butadiene. The actual effective inhibition activity does not continuously increase with the increase of intermediate concentration, and even local inhibition failure occurs due to the non-uniformity of the system.

[0038] In Comparative Example 2, β-hydroxyethyl methyl ether is not added compared with Example 3. The core role of β-hydroxyethyl methyl ether is end group blocking and polarity regulation. Through trace etherification with the unreacted hydroxyl group of diethylene glycol, the self-condensation side reaction of diethylene glycol molecules is inhibited, and the polarity of the intermediate is fine-tuned to adapt to the acetonitrile solvent. In Comparative Example 2, due to the absence of the auxiliary agent, the self-condensation of diethylene glycol is not controlled, the amount of by-product generated is significantly increased, and the end group of the intermediate is not blocked, the polarity of the molecule cannot be optimized, the compatibility with acetonitrile is decreased, and the solubility is decreased. In addition, the excess by-product will interfere with the combination of nitroxyl radical and active radical of butadiene, resulting in a decrease in inhibition efficiency; the by-product is easy to precipitate during storage, destroying the uniformity of the system, and finally making the storage stability worse than that of Example 3.

[0039] Etherification is the core step of optimizing the performance of the inhibition agent in Example 3. By introducing an ether bond, the polarity of the inhibition agent 701 is reduced, the number of active hydroxyl groups is reduced, Figure 2 The nuclear magnetic resonance spectrum of the intermediate of the inhibition agent produced by the present application is shown in the figure. The integral peak at δ=1.0 ppm corresponds to the methyl hydrogen on the piperidine ring, the peak at δ=1.9-2.0 ppm corresponds to the methylene hydrogen on the piperidine ring, the peak at δ=3.0-3.8 ppm corresponds to the ether chain and the methylene hydrogen connected to oxygen, and the peak at δ=4.1 ppm corresponds to the hydrogen adjacent to the nitroxyl radical on the piperidine ring. The integral of each peak is consistent with the proportion of hydrogen atoms in the molecular structure, confirming that the inhibition agent intermediate is the target etherification product. In Comparative Example 3, no etherification operation is performed, the polarity of the inhibition agent 701 is strong, the compatibility with the non-polar acetonitrile solvent is poor, the solubility is significantly decreased, and stratification is easy to occur. The active hydroxyl group in the unetherified molecule is easy to react with acidic substances in the butadiene extraction system and combine with metal ions produced by equipment corrosion, resulting in deactivation of the nitroxyl radical, which cannot effectively capture the active radicals of butadiene, and the inhibition efficiency is much lower than that of Example 3. At the same time, the unetherified molecule has small mass and is easy to be lost with the solvent circulation. During storage, it is more likely to precipitate due to unstable structure, and the stability is significantly deteriorated.

[0040] Comparative Example 4 did not modify the nanometer diatomite compared to Example 3. There are two reasons for using silane coupling agent to modify the polarity. One is that the surface grafted amino group can adsorb trace impurities generated in the complex process, such as unreacted small molecules and metal ions generated by equipment corrosion. The other is that nanometer diatomite is insoluble in water and has serious agglomeration due to its small particle size. Therefore, the diatomite in Comparative Example 4 is not modified and has no amino group on the surface, which greatly weakens its ability to chelate metal ions and adsorb byproducts. The residual metal ions in the system can catalyze the polymerization of butadiene, and the byproducts can interfere with the polymerization inhibition reaction, resulting in lower inhibition efficiency than Example 3. Moreover, the unmodified diatomite cannot provide anchoring support for the dispersant, limiting the action of the dispersant, and the uniformity of the intermediate is reduced, which reduces the stability compared to Example 3.

[0041] The modified diatomite solvent system of Example 3 is a complex system of solvent carrier, impurity purification, and dispersion assistance, while Comparative Example 5 only uses pure water as a solvent, which can only provide carrier function. On the one hand, pure water cannot adsorb unreacted small molecules and sticky byproducts generated during the complex process, which increases the residual amount of byproducts and affects the inhibition efficiency. On the other hand, pure water has no anchoring site, and the dispersant is prone to local agglomeration, which cannot uniformly wrap the intermediate, resulting in uneven dispersion of the intermediate and reduced solubility. In addition, the lack of metal ion chelation of modified diatomite results in more residual metal ions in the system, which further catalyzes the polymerization of butadiene, resulting in significantly lower inhibition efficiency and storage stability than Example 3.

[0042] Comparative Example 6, compared to Example 3, did not add a dispersant, and the intermediate molecules were easily aggregated to form agglomerates due to intermolecular forces, reducing the contact area with acetonitrile solvent and solubility. The nitrogen-oxygen free radicals inside the agglomerates were wrapped and could not contact with the active free radicals of butadiene, reducing the effective inhibition sites and lowering the inhibition efficiency. At the same time, the agglomerates were prone to sedimentation or stratification during storage due to gravity, which destroyed the uniformity of the system and significantly reduced the storage stability compared to Example 3.

[0043] The main purpose of standing and curing at 25°C is to allow the system to fully balance, on the one hand to make the intermediate-dispersant complex more stable, and on the other hand to promote the natural sedimentation of small agglomerates through gravity. Comparative Example 7 was not cured, and the system did not reach equilibrium, and the small agglomerates did not settle. These particles gradually aggregated during storage, increasing the risk of stratification and reducing the stability of the system. At the same time, the complex did not fully combine, and some intermediates were not uniformly dispersed, resulting in a large difference in local inhibition active site concentration and a slightly lower inhibition efficiency than Example 3.

[0044] The above merely describes preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art, according to the technical solution and inventive concept of the present application, makes equivalent replacement or change within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. An ether-based polymerization inhibitor specific to a butadiene extraction system, characterized in that, Comprise components: Polymerization inhibitor intermediate: 21.5-29.5 parts Solvent: 70-80 parts Dispersant: 0.1-0.2 parts The polymerization inhibitor intermediate is prepared from polymerization inhibitor 701 and diethylene glycol, and the specific preparation process comprises the following steps: Close the bottom valve of the reaction kettle, check the sealing, and add 68.5% polymerization inhibitor 701, 31.0-31.2% diethylene glycol and 0.3-0.5% β-hydroxyethyl methyl ether in sequence through the DCS metering pump. The DCS control system starts the jacket heating, and the temperature is raised to 96-100℃ at a rate of 5-8℃ / min. Add 1% p-toluenesulfonic acid based on the total system. Heat at normal pressure for 2 hours. During the reaction, the DCS control system monitors the temperature fluctuation in real time. After the reaction is completed, sample and detect by high performance liquid chromatography. The qualified standard is that the purity of the intermediate is ≥99.2% and the content of by-products is ≤0.3%. If it is unqualified, add 0.1% diethylene glycol based on the total system, continue to heat for 0.5 hours, and then re-detect. The qualified product is the polymerization inhibitor intermediate; The dispersant is a complex of disodium ethylenediaminetetraacetate and 2,2'-dipyridyl, and the specific preparation steps are: Take disodium ethylenediaminetetraacetate and 2,2'-dipyridyl, accurately weigh according to the mass ratio of 2:1, add to the reaction kettle, then add deionized water with a total mass of 5-10 times the raw materials, stir for 30 min, and get the dispersant; The solvent is deionized water doped with a small amount of modified diatomite, and the preparation steps are: Put the pretreated nanodiatomite into a 5wt% 3-aminopropyl triethoxysilane ethanol aqueous solution with a mass ratio of 100:1, stir for 1h, centrifuge, rinse with anhydrous ethanol for 3 times, dry, compound according to the mass ratio of modified diatomite to deionized water of 0.08-0.1:100, ultrasonic dispersion for 30min, filter, and get the solvent doped with a small amount of modified diatomite.

2. An ether-based polymerization inhibitor specific to a butadiene extraction system according to claim 1, characterized in that, The polymerization inhibitor 701 is 4-hydroxy-2,2,6,6-tetramethylpiperidine nitroxide, the purity of disodium ethylenediaminetetraacetate is ≥99.0%, and the purity of 2,2'-dipyridyl is greater than 98.5%.

3. An ether-based polymerization inhibitor specific to a butadiene extraction system according to claim 1, characterized in that, The pretreatment method of the nanodiatomite is to dry the nanodiatomite in an oven at 105℃ for 2h and sieve.

4. The ether-based polymerization inhibitor specific to a butadiene extraction system according to claim 1, wherein The preparation steps of the 3-aminopropyl triethoxysilane ethanol aqueous solution are: Mix anhydrous ethanol and deionized water according to the volume ratio of 95:5, then add the silane reagent according to the mass ratio of 3-aminopropyl triethoxysilane:ethanol solution=5:95, add 1-2 drops of 0.1mol / L acetic acid solution dropwise, stir for 10min, and get the 3-aminopropyl triethoxysilane ethanol aqueous solution.

5. A process for the preparation of an etheric polymerization inhibitor specific to butadiene extraction systems as claimed in any one of claims 1 to 3, characterized in that, Comprise the following steps: S1, compound feeding and mixing Add half of the solvent and all the dispersant to the reaction kettle through the DCS control system, start the stirrer, control the rotation speed to 60-70rpm, gradually add the polymerization inhibitor intermediate, stir at room temperature and normal pressure for 10-20min; then add the remaining solvent, adjust the stirring speed to 70-80rpm, continue to stir for 30-60min, and monitor the temperature in the kettle by DCS in real time during the period; S2, impurity removal and detection After the compounding is finished, the mixture is filtered through a stainless steel filter screen, sampled and analyzed by the detection center, and then tanked after passing the quality inspection to obtain the finished ether-based polymerization inhibitor specially used in the butadiene extraction system.

6. A process for the preparation of an etheric inhibitor specific to a butadiene extraction system as claimed in claim 5, wherein, After the compounding is finished, the mixture is aged for 1-2 hours at 25℃ before being filtered.

7. A process for the preparation of an etheric inhibitor specific to butadiene extraction systems according to claim 5, characterized in that, The detection indexes include: Appearance: colorless and transparent liquid, no stratification, no suspended matter; 25℃ acetonitrile solubility: 30g / L; 60℃ polymerization inhibition efficiency: ≥97%; 25℃ storage stability: ≥200 days.

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