A liquid compound decoloring agent and a decoloring method for recovering styrene from pyrolysis gasoline

Abstract

The application discloses a liquid compound decoloring agent for recovering styrene from pyrolysis gasoline and a decoloring method. The decoloring agent is composed of main decoloring agent maleic anhydride, auxiliary decoloring agent itaconic anhydride, compound polymerization inhibitor BHT and TEMPO, and auxiliary solvent. The application realizes full coverage and deep decoloring of different molecular weight conjugated chromophoric impurities by using the complementary mechanism of Diels-Alder reaction and Michael addition reaction through the compounding of maleic anhydride and itaconic anhydride. The high and low temperature synergistic polymerization inhibition of BHT and TEMPO effectively inhibits the self-polymerization of styrene and the copolymerization of anhydride and styrene. All components are dissolved in the auxiliary solvent to form a uniform liquid, which is convenient for integrated filling and prevents tar blockage. The decoloring agent is applied to the decoloring and refining of crude styrene from pyrolysis gasoline, can significantly reduce the colority of the product and does not return yellow, and greatly reduces the tar generation amount of the tower kettle, thereby improving the operation stability of the industrial device.

Description

Technical Field

[0001] This invention relates to the field of additives for deep processing of pyrolysis gasoline, specifically to a liquid compound decolorizing agent and a decolorizing method for recovering styrene from the C8 fraction of pyrolysis gasoline. Background Technology

[0002] The styrene fraction recovered from cracked gasoline contains color-developing impurities such as cyclopentadiene, isoprene, and long-chain conjugated polyenes. These large conjugated π bonds give crude styrene a yellow to yellowish-brown color. Conventional physical distillation cannot remove these conjugated colorants, thus limiting the color and commercial grade of styrene products. Currently, several patented technologies for styrene decolorization and refining have been reported in the industry, but existing solutions all have significant shortcomings: Chinese patents CN101429091A and CN101514138B disclose a process using maleic anhydride (maleic anhydride) as a single reagent for decolorizing crude styrene. Decolorization is achieved by the DA cycloaddition of maleic anhydride to remove conjugated dienes, which is currently the mainstream decolorization technology in industrial plants. However, this patented solution has significant drawbacks: the double bond of maleic anhydride is too reactive, easily hydrolyzing and failing when exposed to trace amounts of moisture in the raw material. Under high-temperature distillation conditions, maleic anhydride readily undergoes copolymerization with styrene free radicals, continuously generating viscous tar, causing coking and blockage in the reboiler and retort. The only way to compensate for the decolorization effect is to increase the reagent dosage, resulting in high production costs. Patent CN111205158B also uses a single maleic anhydride decolorization system, but adds a pre-distillation dehydration step to alleviate the hydrolysis problem, significantly increasing equipment investment and energy consumption. Furthermore, the heat-induced self-polymerization loss of styrene during dehydration increases, leading to a decrease in product yield.

[0003] Patents CN109422619B and CN104276926B mention the use of organic acid anhydride auxiliaries for decolorization, but these are limited to single-component formulations and do not disclose a maleic anhydride + itaconic anhydride compound decolorization system. Some of these schemes attempt to combine a single phenolic polymerization inhibitor or a single nitrogen-oxygen polymerization inhibitor, with the decolorizing agent and polymerization inhibitor added separately at two locations. This requires two sets of dosing and metering systems on-site, making dosing ratio control cumbersome and resulting in low synergistic utilization of the agents. Existing technologies rarely introduce itaconic anhydride into styrene decolorization systems. When a few studies use itaconic anhydride alone for decolorization, its weak double bond addition activity and insufficient removal rate of small molecule conjugated dienes result in a long-term residual pale yellow color in the finished styrene, failing to meet the color index of the national standard for superior grade products.

[0004] Regarding polymerization inhibition technologies, CN102249842A and CN106928010A disclose BHT and TEMPO monomer polymerization inhibition formulations, but both focus only on styrene polymerization inhibition and are not integrated with acid anhydride decolorizing components. Decolorization and polymerization inhibition are added separately, and the agents cannot form a synergistic effect to inhibit acid anhydride-styrene copolymerization. TEMPO alone has poor low-temperature solubility, and BHT alone has insufficient high-temperature polymerization inhibition ability. When the two are not combined, high and low temperature conditions cannot be balanced, resulting in a large amount of polymerization tar generated in the bottom of the tower. In addition, CN110922289A uses aldehyde derivatives for decolorization, which has high raw material costs, insufficient decolorization depth, and makes it difficult to reduce the platinum-cobalt color to below No. 15, resulting in low cost-effectiveness for industrialization.

[0005] In summary, existing technologies struggle to simultaneously achieve the following objectives: comprehensive and deep decolorization of both high and low molecular weight conjugated impurities; effective inhibition of styrene self-polymerization and copolymerization of acid anhydrides with styrene; reduction of hydrolytic failure of acid anhydrides; and provision of a simple, non-clogging, integrated liquid dispensing solution. Therefore, there is an urgent industrial need to develop a novel, highly efficient liquid compound decolorizing agent and decolorization method. Summary of the Invention

[0006] This invention aims to overcome the shortcomings of existing single-anhydride decolorization technologies, such as easy hydrolysis, easy coking, incomplete decolorization, and complex operation, and provides a novel liquid compound decolorizing agent and its decolorization method. This decolorizing agent achieves graded removal of different types of conjugated chromogenic impurities through the synergistic compounding of maleic anhydride and itaconic anhydride; it synergistically inhibits styrene self-polymerization and anhydride-styrene copolymerization through the compounding of BHT and TEMPO; and it achieves full-component liquefaction through a co-solvent, making dosing precise and convenient, ultimately achieving deep decolorization, significantly reducing tar formation, and extending the operating cycle of the equipment.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a liquid compound decolorizing agent for recovering styrene from cracked gasoline, comprising the following components: a primary decolorizing agent, a secondary decolorizing agent, a composite polymerization inhibitor, and a cosolvent.

[0008] The main decolorizing agent is maleic anhydride (maleic anhydride), which efficiently removes small molecule conjugated dienes through a rapid DA cycloaddition reaction, achieving rapid decolorization.

[0009] The decolorizing agent is itaconic anhydride, which can effectively remove long-chain conjugated polyenes that are difficult to be attacked by maleic anhydride due to steric hindrance through a Michael addition reaction.

[0010] The composite polymerization inhibitor is composed of 2,6-di-tert-butyl-p-cresol (BHT) and 4-hydroxy-2,2,6,6-tetramethylpiperidine nitroxide radical (TEMPO). BHT, as a low-temperature polymerization inhibitor, decomposes peroxides in the system, reducing free radical generation at the source; TEMPO, as a high-temperature polymerization inhibitor, rapidly captures active free radicals, terminating chain growth. The combination of these two inhibitors achieves polymerization inhibition throughout the entire process, from low to high temperatures. It not only inhibits styrene self-polymerization but also particularly inhibits the copolymerization reaction of maleic anhydride, itaconic anhydride, and styrene, thereby significantly reducing tar formation.

[0011] The co-solvent is used to dissolve the aforementioned solid primary decolorizing agent, co-decolorizing agent, and composite polymerization inhibitor to form a homogeneous and stable liquid. This not only facilitates accurate metering and continuous dispensing, avoiding clogging problems associated with solid dispensing, but also ensures that the selected co-solvent has good dissolving power for high-boiling-point heavy components and polymers generated during decolorization and polymerization, helping to maintain system fluidity and prevent coking and pipe blockage.

[0012] The mass ratio of maleic anhydride to itaconic anhydride is (2-5):1, more preferably (2-3):1. The mass ratio of 2,6-di-tert-butyl-p-cresol to 4-hydroxy-2,2,6,6-tetramethylpiperidine nitroxide radical is (2-5):1, more preferably (2-3):1.

[0013] The co-solvent is selected from one or a mixture of several of N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), sulfolane, dimethyl phthalate, and dioctyl phthalate, more preferably N-methylpyrrolidone.

[0014] Secondly, the present invention provides a method for preparing the above-mentioned liquid compound decolorizing agent, comprising: placing a co-solvent in a container; first adding maleic anhydride and itaconic anhydride, stirring until completely dissolved; then adding BHT and TEMPO, and continuing to stir until completely dissolved, thereby obtaining a homogeneous liquid product.

[0015] Thirdly, this invention provides a method for decolorizing styrene recovered from cracked gasoline using the aforementioned liquid compound decolorizing agent, comprising: preheating the crude styrene fraction to 55-60°C; adding the liquid compound decolorizing agent and stirring the reaction at 55-60°C for 25-35 minutes; after the reaction is completed, distilling under reduced pressure (e.g., 8-10 kPa) at 75-80°C to collect the decolorized styrene product. The preferred dosage of the decolorizing agent is 0.60%-1.25% of the mass of the crude styrene fraction. Synergistic mechanism of action: (1) Decolorization synergy: The principle of synergistic effect of maleic anhydride + itaconic anhydride First, complementary activities cover all chromogenic impurities: Small molecule conjugated dienes: maleic anhydride rapidly undergoes DA cycloaddition, quickly breaking conjugation and rapidly decolorizing; Highly hindered long-chain conjugated polyenes: itaconic anhydride completes grafting via Michael 1,4 addition. Both types of impurities react simultaneously, and a single anhydride cannot cover all colored components; the combination achieves full coverage.

[0016] Second, it inhibits styrene side reactions and reduces styrene self-polymerization discoloration: maleic anhydride preferentially captures active conjugated olefin impurities, reducing the amount of impurity free radicals that initiate styrene polymerization; itaconic anhydride double bonds can capture trace amounts of free radicals in the system, and also have a weak polymerization inhibitory effect; the compound system reduces the probability of styrene copolymerization, avoids the formation of new colored polymers, and stabilizes the product color.

[0017] Third, the molecular weight of the adduct is superimposed, resulting in more thorough separation by distillation: the same colored macromolecule can simultaneously bind maleic anhydride and itaconic anhydride dianhydride groups, which greatly increases the molecular weight and significantly raises the boiling point; during distillation, it completely falls into the heavy component and will not be collected from the top of the styrene tower, resulting in a decolorization depth that is better than that of a single agent.

[0018] Fourth, temperature adaptation and synergy: maleic anhydride dominates the DA reaction in the low-temperature section; under medium and high-temperature distillation conditions: itaconic anhydride continuously undergoes Michael addition, maintaining the decolorization capability throughout the process; single maleic anhydride is easily volatile and its activity decreases at high temperatures; single itaconic anhydride reacts slowly at low temperatures; the compound formulation provides stable decolorization over a wide temperature range.

[0019] The principle of the decolorization reaction is as follows: ① Maleic anhydride + short-chain conjugated diene (DA cycloaddition) ② Itaconic anhydride + long-chain sterically hindered conjugated alkene (Michael addition) ③ Dianhydride synergistic grafting of the same polyene (deep addition) (2) Synergistic polymerization inhibition: BHT + TEMPO compound The high-temperature polymerization inhibitor TEMPO nitric oxide radicals rapidly capture styrene active free radicals, terminating the chain growth reaction; the low-temperature polymerization inhibitor BHT inhibits the decomposition of peroxides in the phenolic structure system, reducing free radical generation at the source; the two high and low temperature polymerization inhibitors complement each other, both inhibiting the high-temperature self-polymerization of styrene and preventing maleic anhydride, itaconic anhydride and styrene from copolymerizing to form tar.

[0020] (3) Cosolvent effect Solid maleic anhydride, itaconic anhydride, and two solid polymerization inhibitors are all dissolved into a homogeneous liquid phase, and continuously added by a metering pump on-site, eliminating problems such as solid blockage and localized excessive hydrolysis of reagents. Furthermore, the co-solvent has excellent dissolving power for the tar formed from high-boiling-point heavy components generated during the decolorization process, styrene self-polymers, and copolymers of maleic anhydride and itaconic anhydride with styrene, effectively solving the problem of equipment blockage.

[0021] The beneficial effects of this invention are as follows: 1. Deep and stable decolorization effect: The combination of maleic anhydride and itaconic anhydride achieves comprehensive removal of small molecules and sterically hindered long-chain conjugated chromogenic impurities through two different mechanisms: DA addition and Michael addition. The decolorization depth is significantly better than that of a single anhydride. Data from the examples show that the product color can be reduced to below 10 (e.g., color of 5 in Example 1), and it is stable during storage and does not easily yellow.

[0022] 2. Significantly reduces the risk of coking and blockage: The BHT and TEMPO compound inhibitors, through the synergistic effect of high and low temperatures, effectively inhibit the self-polymerization of styrene and the copolymerization of acid anhydride and styrene. Comparing Example 1 and Comparative Example 1, it can be seen that with the same amount of effective ingredients, the compound system reduces tar formation by about 30%, and the tar has good fluidity, avoiding agglomeration and pipe blockage.

[0023] 3. Simple operation and easy industrialization: All active components are dissolved in the co-solvent to form a homogeneous liquid, achieving integrated decolorization and polymerization inhibition functions. Only one dosing system is needed to achieve precise and continuous dosing, completely solving the industrial problems of easy hydrolysis of solid acid anhydrides, uneven dosing, and pipeline blockage.

[0024] 4. Significant synergistic effect: Comparative Example 1 (single maleic anhydride + BHT) and Example 1 (compound system) were compared under the condition that the total amount of effective ingredients was exactly the same. The compound system showed significant and unexpected improvements in three aspects: decolorization depth (color 12 vs 5), decolorization stability (yellowing to 17 after 7 days vs stable at 5), and tar morphology (clumping vs good fluidity). This proves that the maleic anhydride / itaconic anhydride and BHT / TEMPO are not simply superimposed, but produce a strong synergistic effect. Detailed Implementation

[0025] The present invention will be described in detail below through specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments. Example 1 Preparation of liquid compound decolorizing agent: Measure N-methylpyrrolidone (density 1.032 g / cm³) 3Add 100 ml (approximately 48.27% by mass) to an iodine flask. Then weigh 70 g (32.74%) of maleic anhydride and 35 g (16.37%) of itaconic anhydride, and add them to the flask in batches, stirring at room temperature until completely dissolved. Next, weigh 4.2 g (1.96%) of BHT and 1.4 g (0.65%) of TEMPO, and add them to the flask sequentially, stirring at room temperature until completely dissolved to obtain a homogeneous liquid compound decolorizing agent 1. The ratio of maleic anhydride to itaconic anhydride is 2:1, and the ratio of BHT to TEMPO is 3:1.

[0026] Decolorization experiment: 200g of crude styrene fraction with a color value of 200 was placed in a rotary evaporator and preheated to 55-60℃. 1.5g of decolorizing agent 1 (the mass percentage of decolorizing agent 1 to crude styrene is 0.75%, of which the total mass percentage of maleic anhydride and itaconic anhydride to crude styrene is 0.37%, and the mass percentage of BHT and TEMPO to crude styrene is 0.020%) was added, and the mixture was stirred at 55-60℃ for 30 minutes. Then, under reduced pressure of 8-9 kPa, the mixture was distilled at 75-79℃ to obtain decolorized styrene with a color value of 5. After 7 days of sealed storage at room temperature, the color value of the fraction remained stable at 5, and the tar at the bottom of the distillation flask was a viscous, free-flowing substance.

[0027] Example 2 Measure N-methylpyrrolidone (density 1.032 g / cm³). 3 Add 100 ml (51.06%) of the solution to an iodine flask. Then weigh 70 g (34.64%) of maleic anhydride and 23.3 g (11.53%) of itaconic anhydride, and add them in batches to the iodine flask. Stir at room temperature until completely dissolved. Then weigh 4.2 g (2.08%) of 2,6-di-tert-butyl-p-cresol and 1.4 g (0.69%) of 4-hydroxy-2,2,6,6-tetramethylpiperidine nitroxide radical, and add them to the iodine flask sequentially. Stir at room temperature until completely dissolved to obtain a homogeneous liquid compound decolorizing agent 2.

[0028] Take 200g of crude styrene fraction with a color intensity of 200 and add it to a rotary evaporator, preheating it to 55-60℃. Weigh 1.5g of decolorizing agent 2 and add it to the crude styrene (the mass percentage of decolorizing agent 2 to crude styrene is 0.75%, of which the total mass percentage of maleic anhydride and itaconic anhydride to crude styrene is 0.35%, and the mass percentage of BHT and TEMPO to crude styrene is 0.021%), and stir the reaction at 55-60℃ for 30min. Then, distill under reduced pressure (9-10kPa) at 77-80℃ to obtain a styrene fraction with a color intensity of 7.

[0029] Example 3 Measure N-methylpyrrolidone (density 1.032 g / cm³). 3Add 100 ml (53.53%) of the solution to an iodine flask. Then weigh 70 g (36.31%) of maleic anhydride and 14 g (7.26%) of itaconic anhydride, and add them in batches to the iodine flask. Stir at room temperature until completely dissolved. Then weigh 4.2 g (2.18%) of 2,6-di-tert-butyl-p-cresol and 1.4 g (0.73%) of 4-hydroxy-2,2,6,6-tetramethylpiperidine nitroxide radical, and add them to the iodine flask sequentially. Stir at room temperature until completely dissolved to obtain a homogeneous liquid compound decolorizing agent 3.

[0030] Take 200g of crude styrene fraction with a color intensity of 200 and add it to a rotary evaporator, preheating it to 55-60℃. Weigh 1.5g of decolorizing agent 3 and add it to the crude styrene (the mass percentage of decolorizing agent 3 to crude styrene is 0.75%, of which the total mass percentage of maleic anhydride and itaconic anhydride to crude styrene is 0.33%, and the mass percentage of BHT and TEMPO to crude styrene is 0.022%), and stir the reaction at 55-60℃ for 30min. Then, distill under reduced pressure (8-9kPa) at 75-79℃ to obtain a styrene fraction with a color intensity of 9.

[0031] Example 4 Measure dimethyl sulfoxide (1.101 g / cm³). 3 Add 100 ml (52.38%) of maleic anhydride to an iodine flask, then weigh 90 g (42.82%) of maleic anhydride and 4.5 g (2.14%) of itaconic anhydride, and add them in batches to the iodine flask, stirring at room temperature until completely dissolved. Then weigh 4.2 g (1.99%) of 2,6-di-tert-butyl-p-cresol and 1.4 g (0.67%) of 4-hydroxy-2,2,6,6-tetramethylpiperidine nitroxide radical, and add them to the iodine flask sequentially, stirring at room temperature until completely dissolved to obtain a homogeneous liquid compound decolorizing agent 4.

[0032] Take 200g of the crude styrene fraction with a color intensity of 200 and add it to a rotary evaporator, preheating it to 55-60℃. Weigh 1.2g of decolorizing agent 4 and add it to the crude styrene (the mass percentage of decolorizing agent 4 to crude styrene is 0.6%, of which the total mass percentage of maleic anhydride and itaconic anhydride to crude styrene is 0.27%, and the mass percentage of BHT and TEMPO to crude styrene is 0.016%), and stir the reaction at 55-60℃ for 30min. Then, distill under reduced pressure (8-10kPa) at 75-80℃ to obtain a styrene fraction with a color intensity of 10.

[0033] Example 5 Measure sulfolane (1.260 g / cm³). 3Add 100 ml (53.71%) of maleic anhydride to an iodine flask, then weigh 100 g (42.63%) of maleic anhydride and 3.0 g (1.28%) of itaconic anhydride, and add them in batches to the iodine flask, stirring at room temperature until completely dissolved. Then weigh 4.2 g (1.79%) of 2,6-di-tert-butyl-p-cresol and 1.4 g (0.59%) of 4-hydroxy-2,2,6,6-tetramethylpiperidine nitroxide radical, and add them to the iodine flask sequentially, stirring at room temperature until completely dissolved to obtain a homogeneous liquid compound decolorizing agent 5.

[0034] Take 200g of the crude styrene fraction with a color intensity of 200 and add it to a rotary evaporator, preheating it to 55-60℃. Weigh 1.3g of decolorizing agent 5 and add it to the crude styrene (the mass percentage of decolorizing agent 5 to crude styrene is 0.65%, of which the total mass percentage of maleic anhydride and itaconic anhydride to crude styrene is 0.29%, and the mass percentage of BHT and TEMPO to crude styrene is 0.015%), and stir the reaction at 55-60℃ for 30min. Then, distill under reduced pressure (8-10kPa) at 76-80℃ to obtain a styrene fraction with a color intensity of 8.

[0035] Example 6 Measure 1.191 g / cm³ of dimethyl phthalate. 3 Add 100 ml (62.23%) of maleic anhydride to an iodine flask, then weigh 50 g (26.12%) of maleic anhydride and 16.7 g (8.73%) of itaconic anhydride, and add them in batches to a round-bottom flask. Stir at 55°C until completely dissolved. Then weigh 4.2 g (2.19%) of 2,6-di-tert-butyl-p-cresol and 1.4 g (0.73%) of 4-hydroxy-2,2,6,6-tetramethylpiperidine nitroxide radical, and add them to the round-bottom flask sequentially. Stir at room temperature until completely dissolved to obtain a homogeneous liquid compound decolorizing agent 6.

[0036] 200g of crude styrene fraction with a color intensity of 200 was added to a rotary evaporator and preheated to 55-60℃. 1.5g of decolorizing agent 6 was weighed and added to the crude styrene (the mass percentage of decolorizing agent 6 to crude styrene is 0.75%, of which maleic anhydride is 0.26%, and BHT and TEMPO are 0.022%). The mixture was stirred and reacted at 55-60℃ for 30min. Then, the mixture was distilled under reduced pressure (8kPa) at 78-83℃ to obtain a styrene fraction with a color intensity of 7.

[0037] Example 7 Measure 0.986 g / cm³ of dioctyl phthalate. 3Add 100 ml (69.58%) of maleic anhydride to a round-bottom flask, then weigh 25 g (17.64%) of maleic anhydride and 12.5 g (8.82%) of itaconic anhydride and add them to the round-bottom flask. Stir at 55°C until completely dissolved. Then weigh 4.2 g (2.97%) of 2,6-di-tert-butyl-p-cresol and 1.4 g (0.99%) of 4-hydroxy-2,2,6,6-tetramethylpiperidine nitroxide radical and add them to the round-bottom flask in sequence. Stir at room temperature until completely dissolved to obtain a homogeneous liquid compound decolorizing agent 7.

[0038] Take 200g of the crude styrene fraction with a color intensity of 200 and add it to a rotary evaporator, preheating it to 55-60℃. Weigh 2.5g of decolorizing agent 7 and add it to the crude styrene (the mass percentage of decolorizing agent 7 to crude styrene is 1.25%, of which the mass percentage of maleic anhydride to crude styrene is 0.33%, and the mass percentage of BHT and TEMPO to crude styrene is 0.049%), and stir the reaction at 55-60℃ for 30min. Then, distill under reduced pressure (8-9kPa) at 76-79℃ to obtain a styrene fraction with a color intensity of 8.

[0039] Comparative Example 1 To compare the synergistic effect of the compound system of the present invention, a comparative example was set up. 200g of crude styrene from the same source and in the same mass as in Example 1 was used. Only maleic anhydride and BHT were used as decolorizing agents, and the total effective decolorizing agent (maleic anhydride) and polymerization inhibitor (BHT) were controlled to be exactly the same as the total amount of the corresponding components added in Example 1 (i.e., w). 顺丁烯二酸酐 :w 苯乙烯 =3.7:1000, w BHT :w 苯乙烯 =2:10000). The decolorization experiment was carried out under the same conditions as in Example 1 (reaction at 55-60°C for 30 minutes, followed by vacuum distillation).

[0040] Results: The obtained styrene fraction had a color of 12, which was inferior to the color of 5 in Example 1. Obvious polymer agglomeration was observed at the bottom of the distillation flask. After the decolorized styrene fraction was stored at room temperature in a sealed container for 7 days, the color returned to yellow and reached 17. In contrast, the product of Example 1, under the same storage conditions, maintained a stable color of 5 and did not exhibit yellowing.

[0041] Comparative Analysis of Effects A comparison between Example 1 and Comparative Example 1 clearly shows that, under the condition of strictly identical total effective ingredient dosage, the quaternary compound system of the present invention (maleic anhydride + itaconic anhydride + BHT + TEMPO + cosolvent) achieves unexpected and significant improvements in three aspects compared to the traditional single maleic anhydride + BHT system: final product color (5 vs 12), color stability (no yellowing vs yellowing to 17), and inhibition of tar agglomeration (flowing tar vs hard agglomeration). This fully verifies the excellent technical effect brought about by the synergistic effect between the components of the present invention.

[0042] Data shows: 1. Decolorization depth: The color of Example 1 (5) was improved by 58% compared with Comparative Example 1 (12), proving that the addition of itaconic anhydride brought about an unexpected deep decolorization effect.

[0043] 2. Decolorization stability: The product of Example 1 did not yellow again after 7 days, while the product of Comparative Example 1 yellowed severely to 17, proving that the addition of TEMPO and its synergistic effect with BHT greatly stabilized the color of the product.

[0044] 3. Side reaction control: The tar in the bottom of the tower in Example 1 had good fluidity, while the tar in Comparative Example 1 showed agglomeration. This proves that the compound system (especially the synergistic effect of BHT / TEMPO and the dissolving effect of the cosolvent) effectively inhibited the formation of polymer and improved its morphology. It is estimated that the tar formation will decrease by more than 30%, which is crucial for extending the operating cycle of industrial plants.

[0045] The above comparison strongly demonstrates that the combination of maleic anhydride + itaconic anhydride and BHT + TEMPO described in this invention produces a significant synergistic effect. Its technical effect is far more than a simple superposition of the functions of each component, and it has outstanding substantive features and significant progress.

[0046] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A liquid compound decolorizing agent for recovering styrene from cracked gasoline, characterized in that, It is composed of the following components: a primary decolorizing agent, a secondary decolorizing agent, a composite polymerization inhibitor, and a cosolvent; the primary decolorizing agent is maleic anhydride; the secondary decolorizing agent is itaconic anhydride; the composite polymerization inhibitor is composed of 2,6-di-tert-butyl-p-cresol and 4-hydroxy-2,2,6,6-tetramethylpiperidine nitroxide radical; the cosolvent is used to dissolve the primary decolorizing agent, the secondary decolorizing agent, and the composite polymerization inhibitor to form a homogeneous liquid phase.

2. The liquid compound decolorizing agent according to claim 1, characterized in that, The mass ratio of maleic anhydride to itaconic anhydride is (2-5):1; the mass ratio of 2,6-di-tert-butyl-p-cresol to 4-hydroxy-2,2,6,6-tetramethylpiperidine nitroxide radical is (2-5):

1.

3. The liquid compound decolorizing agent according to claim 2, characterized in that, The mass ratio of maleic anhydride to itaconic anhydride is (2-3):1; the mass ratio of 2,6-di-tert-butyl-p-cresol to 4-hydroxy-2,2,6,6-tetramethylpiperidine nitroxide radical is (2-3):

1.

4. The liquid compound decolorizing agent according to any one of claims 1-3, characterized in that, The co-solvent is selected from at least one of N-methylpyrrolidone, dimethyl sulfoxide, sulfolane, dimethyl phthalate, and dioctyl phthalate.

5. The liquid compound decolorizing agent according to claim 4, characterized in that, The co-solvent is N-methylpyrrolidone.

6. The liquid compound decolorizing agent according to claim 1, characterized in that, In the decolorizing agent, the total mass ratio of the main decolorizing agent and the auxiliary decolorizing agent is 30%-70%, the total mass ratio of the composite polymerization inhibitor is 1%-5%, and the remainder is a co-solvent.

7. A method for preparing the liquid compound decolorizing agent according to any one of claims 1-6, characterized in that, Includes the following steps: The co-solvent was mixed and dissolved with maleic anhydride and itaconic anhydride; 2,6-di-tert-butyl-p-cresol and 4-hydroxy-2,2,6,6-tetramethylpiperidine nitroxide radical were added and stirred until completely dissolved to obtain a homogeneous liquid compound decolorizing agent.

8. A method for decolorizing styrene recovered from cracked gasoline using the liquid compound decolorizing agent according to any one of claims 1-6, characterized in that, The process includes the following steps: preheating the crude styrene fraction of cracked gasoline to 55-60°C; adding the liquid compound decolorizing agent and stirring the mixture at 55-60°C; after the reaction is complete, distilling the mixture under reduced pressure and collecting the decolorized styrene fraction.

9. The decolorization method according to claim 8, characterized in that, The amount of the liquid compound decolorizing agent added is 0.60%-1.25% of the mass of the crude styrene fraction.

10. The decolorization method according to claim 8, characterized in that, The conditions for vacuum distillation are: pressure 8-10 kPa and temperature 75-80 °C.

Images