Method for improving stability of maleic anhydride

Abstract

This invention relates to the field of maleic anhydride production technology, specifically to a method for improving the stability of maleic anhydride. The method includes adding a stabilizer to the maleic anhydride, comprising organotin / organoantimony compounds, organotin compounds and / or organoantimony compounds, acyl halides, metal oxides, antioxidants, and polymerization inhibitors; the stabilizer comprises: 105-5050 parts by weight of organotin / organoantimony compounds, 10-5080 parts by weight of acyl halides, 105-5030 parts by weight of metal oxides, 10-50 parts by weight of antioxidants, and 105-5040 parts by weight of polymerization inhibitors. After adding the stabilizer, the color number of maleic anhydride stabilizes within 25 after being kept at 140℃ for 2 hours, which meets the requirements of GB / T 3676-2020. At the same time, the color number of maleic anhydride after being stored at 60℃ for 90 days is within 35. The color numbers of maleic anhydride all meet the requirements of GB / T 3676-2020, which can meet the needs of producing high-quality maleic anhydride products and is suitable for the industrial production of maleic anhydride products.

Description

Technical Field

[0001] This invention relates to the field of maleic anhydride production technology, and more specifically to a method for improving the stability of maleic anhydride. Background Technology

[0002] Maleic anhydride, also known as maleic anhydride or maleic anhydride (MA), is an important organic chemical raw material. It is the world's third largest source of acid anhydrides after acetic anhydride and phthalic anhydride, and its downstream products have a wide range of development and application prospects. Maleic anhydride is widely used in the synthesis of unsaturated resins, lubricant additives, pharmaceuticals, food additives, 1,4-butanediol (BDO), γ-butyrolactone (GBL), tetrahydrofuran (THF), and a series of other important organic and fine chemicals.

[0003] The core of maleic anhydride production technology lies in the high-temperature exothermic, gas-solid phase catalytic oxidation reaction between raw materials and air in a fixed-bed reactor. Currently, the global production process for maleic anhydride is mainly based on the n-butane oxidation method, which uses n-butane as a raw material and undergoes a gas-phase oxidation reaction under the action of a vanadium-phosphorus catalyst to produce crude maleic anhydride. After refining, the crude maleic anhydride product is refined to obtain essentially colorless maleic anhydride. Through research and communication with research institutes and downstream customers, it has been confirmed that the market demand for maleic anhydride is substantial and has broad prospects. High-end resin crafts, in particular, have a high demand and stringent requirements for high-quality maleic anhydride. However, during the storage, sales, and processing of maleic anhydride, it often yellows, causing the product's color grade to rise, directly affecting the appearance quality of downstream products.

[0004] The discoloration of maleic anhydride is a complex, multi-reaction chemical process, related to its reactive nature, the variety of impurities in the product, and the complexity of the chemical reactions. During maleic anhydride production, byproducts such as maleic acid, fumaric acid, citric acid, butyl acetate, and acrylic acid are also produced. Although refined, small amounts of these impurities still remain in the maleic anhydride. The proportion of products stored and sold in liquid form at 60-70℃ is gradually increasing, but this temperature condition intensifies reactions such as self-polymerization, polymerization with impurities, and oxidation of maleic anhydride. Impurities from polymerization or oxidation further affect the color of maleic anhydride. Currently, some maleic anhydride manufacturers add certain reagents to maleic anhydride to slow down the increase in color. Research on high-temperature heat stabilizers for maleic anhydride is limited. Among the reported maleic anhydride stabilizers, phthaloyl chloride is the main component (CN110437061A, CN114133365A). While these stabilizers have achieved some effectiveness, phthaloyl chloride is a liquid at room temperature and pressure and is highly irritating. Its compounding, use, and storage all require specific conditions. Products with stabilizers primarily composed of phthaloyl chloride are prone to vaporization and odor upon heating, impacting downstream manufacturers. In other words, existing maleic anhydride stabilizers offer poor protection for maleic anhydride under high temperatures or long-term storage, still easily leading to yellowing and reduced quality. Furthermore, maleic anhydride production capacity has expanded rapidly in recent years, with domestic effective capacity currently reaching 2.85 million tons. Downstream customers have increasingly higher requirements for maleic anhydride performance indicators, including color, making competition in maleic anhydride quality increasingly fierce. Therefore, continuously seeking more effective, lower-cost, and environmentally friendly combinations or systems of maleic anhydride color stabilizing additives, considering its physicochemical properties, storage and transportation methods, and trace impurities, is crucial for improving the stability of maleic anhydride and enhancing its competitiveness. Summary of the Invention

[0005] To address the current issues of poor high-temperature stability and yellowing during long-term storage of maleic anhydride, this invention provides a method to improve the stability of maleic anhydride. This involves adding a stabilizer to the refined maleic anhydride product and stirring. This method effectively improves the high-temperature and long-term storage stability of maleic anhydride, reducing its color during subsequent heating treatments or storage, and meeting the needs of downstream customers for high-quality maleic anhydride.

[0006] To achieve the above objectives, the first aspect of the present invention provides a method for improving the stability of maleic anhydride, wherein the method comprises adding a stabilizer including organotin compounds and / or organoantimony compounds, acyl halide compounds, metal oxides, antioxidants, and polymerization inhibitors to maleic anhydride;

[0007] The stabilizer comprises: 5-50 parts by weight of organotin compounds and / or organoantimony compounds, 10-80 parts by weight of acyl halides, 5-30 parts by weight of metal oxides, 10-50 parts by weight of antioxidants, and 5-40 parts by weight of polymerization inhibitors.

[0008] Many factors contribute to the discoloration of maleic anhydride. These include unavoidable byproducts and impurities during the preparation process, impurities arising from polymerization at higher temperatures, and oxidation reactions. While there are conventional solutions for each factor—for example, adding heat stabilizers to mitigate or eliminate the adverse effects of high temperatures, adding polymerization inhibitors to prevent polymerization, and adding antioxidants to prevent oxidation—the interrelationships and interactions among these factors complicate the cause of maleic anhydride discoloration. Simply using a combination of conventional stabilizing components such as heat stabilizers, polymerization inhibitors, and antioxidants is insufficient to effectively solve the problem.

[0009] Through extensive research, the inventors of this application discovered that using organotin compounds and / or organoantimony compounds, along with acyl halides, as stabilizers can achieve better stabilization of maleic anhydride. Organotin compounds and / or organoantimony compounds possess thermal stability and UV absorption resistance; upon heating or exposure to light, they are the first to absorb heat and react to form stable complexes, inhibiting the formation of unstable conjugated polyenes. This protects maleic anhydride from the effects of high temperatures or light exposure, delaying yellowing under high-temperature conditions and long-term storage. Acyl halides, with electrophilic functional groups such as carbonyl groups, are more reactive than maleic anhydride. Their addition to maleic anhydride, under high-temperature conditions or long-term storage, allows them to undergo oxidation reactions before maleic anhydride or react with maleic acid and acrylic acid impurities in maleic anhydride, thus improving the high-temperature stability of maleic anhydride. Furthermore, the addition of oxidants and polymerization inhibitors further suppresses oxidation and polymerization reactions in maleic anhydride. Based on the combined use of the above four components, the introduction of metal oxides can further enhance the stabilizing effect of the stabilizer by coupling with organotin compounds and / or organoantimony compounds, antioxidants, and polymerization inhibitors. This not only improves the stabilizing effect of the stabilizer but also protects and stabilizes maleic anhydride or other components in the stabilizer, thus extending the service life of other components. This allows the stabilizer to function stably for a long time, significantly delaying the yellowing phenomenon of maleic anhydride under high temperature conditions and long-term storage, and significantly improving the quality of maleic anhydride and the appearance quality of downstream products.

[0010] The stabilizer used in this invention is made from low-cost, readily available, safe, and environmentally friendly raw materials. The method for improving stability in this invention is simple and easy to implement, and suitable for the industrial production of maleic anhydride.

[0011] In this invention, when the amounts of each component in the stabilizer are relatively similar, the effect on improving the stability of maleic anhydride is better.

[0012] According to a preferred embodiment of the present invention, the stabilizer comprises: 15-25 parts by weight of organotin compounds and / or organoantimony compounds, 15-30 parts by weight of acyl halide compounds, 10-25 parts by weight of metal oxides, 15-25 parts by weight of antioxidants, and 10-20 parts by weight of polymerization inhibitors.

[0013] In some embodiments of the present invention, the yellowing phenomenon of maleic anhydride under high temperature conditions and long-term storage is significantly delayed, so that the high temperature color number of maleic anhydride is no greater than 25 and the long-term storage color number of maleic anhydride is no greater than 35, which significantly improves the high temperature stability of maleic anhydride and the appearance quality of downstream products.

[0014] In this invention, the high-temperature color number of maleic anhydride is tested according to the requirements of GB / T 3676-2020, section 4.8, determination of melting color after heating, to determine the color number of maleic anhydride after heating and to determine the high-temperature stability of maleic anhydride; the long-term storage color number of maleic anhydride is tested according to the requirements of GB / T 3676-2020, section 4.4, determination of melting color, to determine the color number of maleic anhydride after long-term storage and to determine the long-term storage stability of maleic anhydride.

[0015] According to a preferred embodiment of the present invention, the organotin compound and / or organoantimony compound includes at least one selected from dimethyltin dilaurate, tris(isooctyl mercaptoacetate)antimony, di-n-octyltin maleate, dioctyltin dimercaptoacetate, and tetraphenyltin.

[0016] According to a preferred embodiment of the present invention, the organotin compound and / or organoantimony compound includes any two of dimethyltin dilaurate, antimony tris(isooctyl mercaptoacetate), di-n-octyltin maleate, dioctyltin dimercaptoacetate, and tetraphenyltin.

[0017] According to a particularly preferred embodiment of the present invention, the organotin compound and / or organoantimony compound comprises a mixture of antimony tris(isooctyl mercaptoacetate) and di-n-octyltin maleate.

[0018] According to a more preferred embodiment of the present invention, the weight ratio of the tris(isooctyl mercaptoacetate) antimony to di-n-octyltin maleate is 1-5:1, more preferably 2-3:1.

[0019] In some embodiments of the present invention, the acyl halide compound includes at least one of o-acetylsalicylic acid chloride, diethyl chloromaleate, valerate bromide, and 3-phenylacryloyl chloride.

[0020] According to a preferred embodiment of the present invention, the acyl halide compound includes any two of o-acetylsalicylic acid chloride, diethyl chloromaleate, valerate bromide, and 3-phenylacryloyl chloride.

[0021] According to a particularly preferred embodiment of the present invention, the acyl halide compound includes diethyl chloromaleate and acetylsalicylic acid chloride.

[0022] According to a more preferred embodiment of the present invention, the weight ratio of diethyl chloromaleate to acetylsalicylic acid chloride is 1:0.2-1, more preferably 1:0.3-0.5.

[0023] In some embodiments of the present invention, the metal oxide includes at least one of zinc oxide, aluminum oxide, and magnesium oxide.

[0024] According to a preferred embodiment of the present invention, the metal oxide includes any two of zinc oxide, aluminum oxide and magnesium oxide.

[0025] According to a particularly preferred embodiment of the present invention, the metal oxide is a mixture of zinc oxide and aluminum oxide.

[0026] According to a more preferred embodiment of the present invention, the weight ratio of the zinc oxide to the aluminum oxide mixture is 0.5-5.5:1, more preferably 2-3:1. In some embodiments of the present invention, the antioxidant includes at least one selected from stearoylbenzoylmethane, 3,5-di-tert-butylsalicylic acid, and di[3-(1,1-dimethylethyl)-4-hydroxy-5-methylphenylpropionic acid]polyethylene glycol.

[0027] According to a preferred embodiment of the present invention, the antioxidant comprises any two of stearoylbenzoylmethane, 3,5-di-tert-butylsalicylic acid and di[3-(1,1-dimethylethyl)-4-hydroxy-5-methylphenylpropionic acid]polyethylene glycol.

[0028] According to a particularly preferred embodiment of the present invention, the antioxidant comprises stearoylbenzoylmethane and di[3-(1,1-dimethylethyl)-4-hydroxy-5-methylphenylpropionic acid]polyethylene glycol.

[0029] According to a more preferred embodiment of the present invention, the weight ratio of stearoylbenzoylmethane to di[3-(1,1-dimethylethyl)-4-hydroxy-5-methylphenylpropionic acid]polyethylene glycol is 1-6:1, more preferably 2-3.5:1.

[0030] In some embodiments of the present invention, the polymerization inhibitor comprises at least one of 2,5-ditert-octylhydroquinone, p-tert-butylcatechol, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxy radical and 4,4-dichlorodiphenyl sulfone.

[0031] According to a preferred embodiment of the present invention, the polymerization inhibitor comprises any two of 2,5-ditert-octylhydroquinone, p-tert-butylcatechol, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxy radical and 4,4-dichlorodiphenyl sulfone.

[0032] According to a particularly preferred embodiment of the present invention, the polymerization inhibitor comprises 2,5-ditert-octylhydroquinone and p-tert-butylcatechol.

[0033] According to a more preferred embodiment of the present invention, the weight ratio of 2,5-ditert-octylhydroquinone to p-tert-butylcatechol is 0.5-5:1, more preferably 1.5-3:1.

[0034] According to a preferred embodiment of the present invention, the amount of maleic anhydride stabilizer added is 3-25 ppm, preferably 5-15 ppm. In this invention, ppm is a concentration expressed as parts per million (ppm) of the weight of the added component to the weight of maleic anhydride, also known as parts per million concentration. Using the aforementioned embodiment can significantly improve the stability of maleic anhydride, delay yellowing under high temperature conditions and long-term storage, and significantly improve the quality of maleic anhydride and the appearance quality of downstream products. In particular, when the amount of maleic anhydride stabilizer added is 5-15 ppm, it can further improve the stability of maleic anhydride, significantly delay yellowing under high temperature conditions and long-term storage, ensuring that the high-temperature color number of maleic anhydride is no greater than 25 and the long-term storage color number is no greater than 35, thus better improving the quality of maleic anhydride and the appearance quality of downstream products.

[0035] This invention does not impose any particular limitations on the mixing time or method of the maleic anhydride and stabilizer, as long as the refined maleic anhydride and stabilizer are thoroughly and uniformly mixed. According to a preferred embodiment of the invention, the mixing time is greater than or equal to 0.5 hours, preferably 1-3 hours. And / or, the mixing is performed using a reflux method. By employing the aforementioned embodiments, the maleic anhydride and stabilizer can be mixed more uniformly, effectively improving the high-temperature stability of maleic anhydride, delaying yellowing under high-temperature conditions and long-term storage, thereby improving the quality of maleic anhydride and the appearance quality of downstream products.

[0036] Furthermore, when the method for improving the stability of maleic anhydride provided in this application is applied to a pilot-scale production of hundreds of tons, the results are basically equivalent to those of small-scale laboratory experiments, which meets the needs of large-scale production.

[0037] Beneficial effects of the present invention

[0038] This application comprehensively considers factors that may cause maleic anhydride discoloration. By preferentially reacting with impurities and suppressing the effects of heating and light, it delays the oxidation of maleic anhydride and prevents side reactions such as self-polymerization and free radical chain polymerization. Combined with the coupling effect of metal oxides on other components in the stabilizer, it effectively improves the stabilizing effect of the stabilizer on maleic anhydride, delays the yellowing phenomenon of maleic anhydride under high temperature conditions and long-term storage, and ensures that the color number of maleic anhydride after adding the stabilizer is stable within 25 after being kept at 140℃ for 2 hours, which meets the requirements of GB / T 3676-2020. At the same time, the color number of maleic anhydride after being stored at 65℃ for 90 days is within 35, and the color number of maleic anhydride meets the requirements of GB / T 3676-2020. It can meet the needs of producing high-quality maleic anhydride and is suitable for the industrial production of maleic anhydride. Detailed Implementation

[0039] In the following examples, the color of the maleic anhydride sample was determined by visually comparing it with a platinum-cobalt color standard or by using a VISTA benchtop colorimeter after the maleic anhydride sample was kept at a preset temperature for a preset time. The maleic anhydride sample was refined maleic anhydride produced by Ningbo Dafeng Jiangning New Material Technology Co., Ltd.; dioctyltin maleate and dimethyltin dilaurate were commercially available products from Quzhou Jianhua Dongxu Additives Co., Ltd. (purity ≥ 98%); antimony tris(mercaptoacetate isooctyl)antimony, dioctyltin dimercaptoacetate, and tetraphenyltin were commercially available products from BASF (purity ≥ 98%); zinc oxide and aluminum oxide were also used. Magnesium oxide is a commercially available product from Wuxi Yasheng Chemical Co., Ltd. (analytical grade); o-acetylsalicylic acid chloride, diethyl chloromaleate, valeryl bromide, 3-phenylacryloyl chloride, stearoylbenzoylmethane, 3,5-di-tert-butylsalicylic acid, and di[3-(1,1-dimethylethyl)-4-hydroxy-5-methylphenylpropionic acid]polyethylene glycol, 2,5-ditert-octylhydroquinone, p-tert-butylcatechol, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxy radical, and 4,4-dichlorodiphenyl sulfone are commercially available products from Aladdin Company (purity ≥98%).

[0040] The color number testing method and testing standard refer to the national standard GB / T 3676-2020.

[0041] To demonstrate the effectiveness of the stabilizer of this invention, high-temperature stability tests (140°C for 2 hours) and long-term storage stability tests (65°C, 0-90 days) of maleic anhydride were conducted.

[0042] The high-temperature stability test method is as follows: Take 500 mL of the company's refined maleic anhydride (without additives), add an appropriate amount of the stabilizer of this invention, take 50 mL of the maleic anhydride sample with the added stabilizer, seal it, transfer it to a digester, and set the temperature to 140℃ for 2 hours. The detection method is as follows: After adding the stabilizer of this invention, visually compare it with the platinum-cobalt color standard or use a VISTA benchtop colorimeter to determine the color of the maleic anhydride sample; after holding it at the preset temperature for a preset time, visually compare it with the platinum-cobalt color standard again or use a VISTA benchtop colorimeter to determine the color of the maleic anhydride sample.

[0043] The long-term storage stability test method is as follows: Take 500 mL of the company's refined maleic anhydride (without additives), add an appropriate amount of the maleic anhydride stabilizer of this invention, seal the maleic anhydride sample, transfer it to an oven, and heat it at 65℃ for 90 days. On days 0 (the current day), 7, 14, 21, 28, 60, and 90, take 50 mL of the sample, transfer it to a digester, and heat it at 140℃ for 2 hours. The detection method is as follows: After adding the stabilizer of this invention, visually compare the sample with the platinum-cobalt color standard or use a VISTA benchtop colorimeter to determine the color of the maleic anhydride sample; after heat treatment at a preset temperature for a preset time, again visually compare the sample with the platinum-cobalt color standard or use a VISTA benchtop colorimeter to determine the color of the maleic anhydride sample.

[0044] Example 1

[0045] The stabilizer comprises the following raw materials in parts by weight: 20 parts by weight of organotin compounds and / or organoantimony compounds, 20 parts by weight of acyl halides, 20 parts by weight of metal oxides, 20 parts by weight of antioxidants, and 20 parts by weight of polymerization inhibitors.

[0046] Among them, the organotin compounds and / or organoantimony compounds are antimony tris(thiocarboxylate) and di-n-octyltin maleate in a mass ratio of 2:1; the acyl halogen compounds are diethyl chloromaleate and acetylsalicylic acid chloride in a mass ratio of 2:1; the metal oxides are zinc oxide and aluminum oxide in a mass ratio of 2:1; the antioxidant is stearoylbenzoylmethane and di[3-(1,1-dimethylethyl)-4-hydroxy-5-methylphenylpropionic acid]polyethylene glycol in a weight ratio of 2:1; and the polymerization inhibitor is 2,5-ditert-octylhydroquinone and p-tert-butylcatechol in a weight ratio of 2:1.

[0047] The preparation and use method of the stabilizer in this embodiment includes the following steps:

[0048] At room temperature, 2 mg of organotin compounds and / or organoantimony compounds, 2 mg of acyl halide compounds, 2 mg of metal oxides, 2 mg of antioxidants, and 2 mg of polymerization inhibitors are mixed to obtain a stabilizer. The stabilizer is added to the feed port of the intermediate tank for the purified maleic anhydride at a dosage of 6 ppm by mass of maleic anhydride. The maleic anhydride and stabilizer are thoroughly mixed using a reflux pump, with a reflux mixing time of 2 hours.

[0049] Example 2

[0050] The stabilizer comprises the following raw materials in parts by weight: 25 parts by weight of organotin compounds and / or organoantimony compounds, 25 parts by weight of acyl halides, 15 parts by weight of metal oxides, 20 parts by weight of antioxidants, and 15 parts by weight of polymerization inhibitors.

[0051] Among them, the organotin / organoantimony compound is a mixture of tris(mercaptoacetate isooctyl)antimony and di-n-octyltin maleate in a mass ratio of 3:1; the acyl halide compound is a mixture of diethyl chloromaleate and acetylsalicylic acid chloride in a mass ratio of 3:1; the metal oxide is a mixture of zinc oxide and aluminum oxide in a mass ratio of 3:1; the antioxidant is a mixture of stearoylbenzoylmethane and di[3-(1,1-dimethylethyl)-4-hydroxy-5-methylphenylpropionic acid]polyethylene glycol in a weight ratio of 3:1; and the polymerization inhibitor is a mixture of 2,5-ditert-octylhydroquinone and p-tert-butylcatechol in a weight ratio of 3:1.

[0052] The preparation and use method of the stabilizer in this embodiment includes the following steps:

[0053] A stabilizer was prepared by mixing 2.5 mg of organotin compounds and / or organoantimony compounds, 2.5 mg of acyl halide compounds, 1.5 mg of metal oxides, 2.0 mg of antioxidants, and 1.5 mg of polymerization inhibitors at room temperature. The stabilizer was added to the feed port of the intermediate tank containing the purified maleic anhydride at a dosage of 6 ppm by mass of maleic anhydride. The maleic anhydride and stabilizer were thoroughly mixed using a reflux pump for 2 hours.

[0054] Example 3

[0055] The method is the same as in Example 1, except that in the preparation and use of the stabilizer, the amount of stabilizer added is 4 ppm of maleic anhydride by mass.

[0056] Example 4

[0057] The method is the same as in Example 1, except that in the preparation and use of the stabilizer, the amount of stabilizer added is 14 ppm of maleic anhydride by mass.

[0058] Example 5

[0059] The method is the same as in Example 1, except that in the preparation and use of the stabilizer, the amount of stabilizer added is 17 ppm of maleic anhydride by mass.

[0060] Example 6

[0061] The method is the same as in Example 1, except that in the preparation and use of the stabilizer, the amount of stabilizer added is 25 ppm of maleic anhydride by mass.

[0062] Comparative Example 1

[0063] The method is the same as in Example 1, except that the maleic anhydride stabilizer is a commercially available stabilizer, including the following raw materials in the following weight ratios: 20 parts by weight of phenyl phthalate, 20 parts by weight of 2,4-dihydroxybenzophenone, 20 parts by weight of hexamethylphosphoric triamine, 20 parts by weight of 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol, and 20 parts by weight of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxy free radical;

[0064] Specifically, it includes: 2 mg of phenyl oxobenzoate, 2,4-dihydroxybenzophenone, 2 mg of hexamethylphosphoric triamine, 2 mg of 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol, and 2 mg of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxy radical.

[0065] Example 7

[0066] The method of Example 1 is different except that the stabilizer comprises the following raw materials in the following weight ratios: 50 parts by weight of organotin compounds and / or organoantimony compounds, 10 parts by weight of acyl halides, 15 parts by weight of metal oxides, 10 parts by weight of antioxidants, and 15 parts by weight of polymerization inhibitors.

[0067] Example 8

[0068] The method of Example 1 is different except that the stabilizer comprises the following raw materials in the following weight ratios: 10 parts by weight of organotin compounds and / or organoantimony compounds, 15 parts by weight of acyl halides, 50 parts by weight of metal oxides, 15 parts by weight of antioxidants, and 10 parts by weight of polymerization inhibitors.

[0069] Example 9

[0070] The method of Example 1 is different except that the stabilizer comprises the following raw materials in the following weight ratios: 15 parts by weight of organotin compounds and / or organoantimony compounds, 50 parts by weight of acyl halides, 10 parts by weight of metal oxides, 15 parts by weight of antioxidants, and 10 parts by weight of polymerization inhibitors.

[0071] Example 10

[0072] The method of Example 1 is different except that the stabilizer comprises the following raw materials in the following weight ratios: 10 parts by weight of organotin compounds and / or organoantimony compounds, 15 parts by weight of acyl halides, 10 parts by weight of metal oxides, 50 parts by weight of antioxidants, and 15 parts by weight of polymerization inhibitors.

[0073] Example 11

[0074] The method of Example 1 is different except that the stabilizer comprises the following raw materials in the following weight ratios: 15 parts by weight of organotin compounds and / or organoantimony compounds, 10 parts by weight of acyl halides, 15 parts by weight of metal oxides, 10 parts by weight of antioxidants, and 50 parts by weight of polymerization inhibitors.

[0075] Example 12

[0076] The method is the same as in Example 1, except that the organotin compounds and / or organoantimony compounds are tris(thiocarboxylate) antimony and di-n-octyltin maleate mixed in a mass ratio of 1:1; the acyl halogen compounds are diethyl chloromaleate and acetylsalicylic acid chloride mixed in a mass ratio of 4:1; the metal oxides are zinc oxide and aluminum oxide mixed in a mass ratio of 1:1; the antioxidant is stearoylbenzoylmethane and di[3-(1,1-dimethylethyl)-4-hydroxy-5-methylphenylpropionic acid]polyethylene glycol mixed in a weight ratio of 4:1; and the polymerization inhibitor is 2,5-ditert-octylhydroquinone and p-tert-butylcatechol mixed in a weight ratio of 5:1.

[0077] Example 13

[0078] The method is the same as in Example 1, except that the organotin compound and / or organoantimony compound is tris(isooctyl mercaptoacetate)antimony, the acyl halide compound is diethyl chloromaleate, the metal oxide is zinc oxide, the antioxidant is stearoylbenzoylmethane, and the polymerization inhibitor is 2,5-ditert-octylhydroquinone.

[0079] Example 14

[0080] The method is the same as in Example 1, except that the organotin compound and / or organoantimony compound is di-n-octyltin maleate, the acyl halide compound is acetylsalicylic acid chloride, the metal oxide is aluminum oxide, the antioxidant is di[3-(1,1-dimethylethyl)-4-hydroxy-5-methylphenylpropionic acid]polyethylene glycol, and the polymerization inhibitor is p-tert-butylcatechol.

[0081] Example 15

[0082] The method is the same as in Example 1, except that the reflux mixing time is 0.5 h in the preparation and use of the stabilizer.

[0083] Example 16

[0084] The method is the same as in Example 1, except that the reflux mixing time is 5 hours in the preparation and use of the stabilizer.

[0085] Comparative Example 2

[0086] The method of Example 1 is different except that the stabilizer comprises the following raw materials in the following weight ratios: 1 part by weight of organotin compound and / or organoantimony compound, 1 part by weight of acyl halide compound, 1 part by weight of metal oxide, 1 part by weight of antioxidant, and 96 parts by weight of polymerization inhibitor.

[0087] Comparative Example 3

[0088] The method of Example 1 is different except that the stabilizer comprises the following raw materials in the following weight ratios: 96 parts by weight of organotin compounds and / or organoantimony compounds, 1 part by weight of acyl halide compounds, 1 part by weight of metal oxides, 1 part by weight of antioxidants, and 1 part by weight of polymerization inhibitors.

[0089] Comparative Example 4

[0090] The method of Example 1 is different except that the stabilizer comprises the following raw materials in the following weight ratios: 1 part by weight of organotin compound and / or organoantimony compound, 96 parts by weight of acyl halide compound, 1 part by weight of metal oxide, 1 part by weight of antioxidant, and 1 part by weight of polymerization inhibitor.

[0091] Comparative Example 5

[0092] The method of Example 1 is different except that the stabilizer comprises the following raw materials in the following weight ratios: 1 part by weight of organotin compound and / or organoantimony compound, 1 part by weight of acyl halide compound, 96 parts by weight of metal oxide, 1 part by weight of antioxidant, and 1 part by weight of polymerization inhibitor.

[0093] Comparative Example 6

[0094] The method of Example 1 is different except that the stabilizer comprises the following raw materials in the following weight ratios: 1 part by weight of organotin compound and / or organoantimony compound, 1 part by weight of acyl halide compound, 1 part by weight of metal oxide, 96 parts by weight of antioxidant, and 1 part by weight of polymerization inhibitor.

[0095] Comparative Example 7

[0096] The method of Example 1 is different except that the stabilizer comprises the following raw materials in the following weight ratios: 25 parts by weight of organotin compounds and / or organoantimony compounds, 25 parts by weight of acyl halides, 25 parts by weight of metal oxides, 25 parts by weight of antioxidants, and 0 parts by weight of polymerization inhibitors.

[0097] Comparative Example 8

[0098] The method of Example 1 is different except that the stabilizer comprises the following raw materials in the following weight ratios: 0 parts by weight of organotin compounds and / or organoantimony compounds, 25 parts by weight of acyl halide compounds, 25 parts by weight of metal oxides, 25 parts by weight of antioxidants, and 25 parts by weight of polymerization inhibitors.

[0099] Comparative Example 9

[0100] The method of Example 1 is different except that the stabilizer comprises the following raw materials in the following weight ratios: 25 parts by weight of organotin compounds and / or organoantimony compounds, 0 parts by weight of acyl halide compounds, 25 parts by weight of metal oxides, 25 parts by weight of antioxidants, and 25 parts by weight of polymerization inhibitors.

[0101] Comparative Example 10

[0102] The method of Example 1 is different except that the stabilizer comprises the following raw materials in the following weight ratios: 25 parts by weight of organotin compounds and / or organoantimony compounds, 25 parts by weight of acyl halides, 0 parts by weight of metal oxides, 25 parts by weight of antioxidants, and 25 parts by weight of polymerization inhibitors.

[0103] Comparative Example 11

[0104] The method of Example 1 is different except that the stabilizer comprises the following raw materials in the following weight ratios: 25 parts by weight of organotin compounds and / or organoantimony compounds, 25 parts by weight of acyl halides, 25 parts by weight of metal oxides, 0 parts by weight of antioxidants, and 25 parts by weight of polymerization inhibitors.

[0105] Experimental Example 1

[0106] Taking maleic anhydride as an example, the stabilizers of Examples 1-16 and Comparative Examples 1-11 of the present invention were used to conduct a high-temperature stability test (140°C, 2h). The color number of maleic anhydride after heating was determined and the high-temperature stability of maleic anhydride was determined in accordance with GB / T 3676-2020.

[0107] Blank control group: Take 500 mL of purified maleic anhydride, and the amount of stabilizer added is 0 ppm;

[0108] Examples 1-16 and Comparative Examples 1-11 were added according to the specific formulation and amount of stabilizer described in the examples. All maleic anhydride used was from the same production batch of our company. The experimental results are shown in Table 1.

[0109] Table 1. High-temperature properties analysis of maleic anhydride in Examples 1-16, Comparative Examples 1-11, and the blank control group.

[0110]

[0111]

[0112] As shown in Table 1, the method for improving the stability of maleic anhydride provided by this invention, after heating the maleic anhydride with added stabilizer to 140°C and holding it for 2 hours, can reduce the color number of the maleic anhydride to below 25, fully meeting the requirements for industrial applications. In comparison, Comparative Example 1, which involves adding commonly used industrial stabilizers to maleic anhydride, shows a final color number of 92.5 after heating to 140°C and holding for 2 hours. Therefore, it is clear that the method provided by this invention has a significantly better effect on improving the stability of maleic anhydride.

[0113] As can be seen from Examples 1 and 4-6, more stabilizer is not necessarily better; the effect is better when the amount added is 5-15 ppm.

[0114] As can be seen from Examples 1 and 7-11, when the amounts of various raw material components in Example 1 are the same, the effect of improving the high-temperature stability of maleic anhydride is better than when one of the raw materials accounts for 50%.

[0115] Examples 12-14 illustrate the effect of the selection of stabilizer raw materials on high-temperature stability. If the ratio of raw materials is not optimal or the component has only a single composition, the average final color number of maleic anhydride after heating to 140°C and holding for 2 hours is higher than 24; however, the overall color number is lower than 25, which meets the requirements of production and industry.

[0116] Examples 1, 15, and 16 show the effect of different reflux mixing times. When the reflux time is short, the stabilizer cannot be effectively and uniformly dispersed in maleic anhydride, and cannot play a good role in protecting the stability of maleic anhydride, resulting in slightly poor high-temperature stability.

[0117] Comparative Examples 2-6 show cases where a certain component of the stabilizer constitutes the majority, resulting in poor high-temperature stabilization. After heating to 140℃ and holding for 2 hours, the average final color number of maleic anhydride was greater than 100, and in some cases even reached 155.8.

[0118] The comparison between Example 1 and Comparative Examples 7-11 shows that the absence of any component in the stabilizer will greatly reduce the high-temperature stability of maleic anhydride. This indicates that there is a synergistic effect among the components. Only when the five components interact and couple can they exert the maximum effect of improving the stability of maleic anhydride. It also further illustrates that the stabilizer used in this invention is a holistic formulation, and each component is indispensable.

[0119] Therefore, the method for improving the stability of maleic anhydride provided by the present invention has the characteristics of long stabilization time and good stabilization effect. It can effectively improve the high-temperature stability of maleic anhydride, reduce the high-temperature color number of maleic anhydride, effectively delay the yellowing phenomenon of maleic anhydride under high-temperature conditions, and improve the quality of maleic anhydride and the appearance quality of downstream products.

[0120] Experiment Example 2

[0121] Taking maleic anhydride as an example, long-term storage tests (65°C, 0-90 days) were conducted using the stabilizers of Examples 1-16 and Comparative Examples 1-11 of the present invention. The color number of maleic anhydride after long-term storage was determined and the stability of maleic anhydride during long-term storage was determined in accordance with GB / T 3676-2020.

[0122] Blank control group: Take 500 mL of purified maleic anhydride, and the amount of stabilizer added is 0 ppm;

[0123] Examples 1-16 and Comparative Examples 1-11 were added according to the specific formulation and amount of stabilizer described in the examples. All maleic anhydride used was from the same production batch of our company. The experimental results are shown in Table 2.

[0124] Table 2. Long-term storage performance of maleic anhydride in Examples 1-16, Comparative Examples 1-11, and the blank control group.

[0125]

[0126]

[0127] Table 2 shows that, using the method for improving the stability of maleic anhydride provided by this invention, after storing the maleic anhydride with added stabilizer at 65°C for 90 days, the color number of the maleic anhydride is below 35, fully meeting the requirements for industrial applications. In contrast, Comparative Example 1, which involves adding commonly used industrial stabilizers to maleic anhydride, shows a final color number of 88.7 after storing at 65°C for 90 days. Therefore, it is clear that the method provided by this invention has a significantly better effect on improving the stability of maleic anhydride.

[0128] As can be seen from Examples 1 and 4-6, more stabilizer is not necessarily better; the effect is better when the amount added is 5-15 ppm.

[0129] As can be seen from Examples 1 and 7-11, when the amounts of various raw material components in Example 1 are the same, the effect of improving the storage stability of maleic anhydride is better than when one of the raw materials accounts for 50%.

[0130] Examples 12-14 illustrate the impact of the selection of stabilizer raw materials on storage stability. If the ratio of raw materials is not optimal, or if the component has only a single composition, the average final color number of maleic anhydride after 90 days of storage at 65°C is higher than 30; however, the overall color number is lower than 34, which meets the requirements of production and industry.

[0131] Examples 1, 15, and 16 show the effect of different reflux mixing times. When the reflux time is short, the stabilizer cannot be effectively and uniformly dispersed in maleic anhydride, and cannot play a good role in protecting the stability of maleic anhydride, resulting in slightly poor storage stability.

[0132] Comparative Examples 2-6 show cases where a certain component of the stabilizer constitutes the majority, resulting in poor storage stability. After storage at 65°C for 90 days, the average final color number of maleic anhydride was greater than 68, and in some cases even reached 87.3.

[0133] The comparison between Example 1 and Comparative Examples 7-11 shows that the absence of any component in the stabilizer will greatly reduce the storage stability of maleic anhydride. This indicates that there is a synergistic effect among the components. Only when the five components interact and couple can they exert the maximum effect of improving the stability of maleic anhydride. It also further illustrates that the stabilizer used in this invention is a holistic formulation, and each component is indispensable.

[0134] Therefore, the method for improving the stability of maleic anhydride provided by the present invention has the characteristics of long stabilization time and good stabilization effect. It can effectively improve the storage stability of maleic anhydride, reduce the color number of maleic anhydride during long-term storage, effectively delay the yellowing phenomenon of maleic anhydride under long-term storage conditions, and improve the quality of maleic anhydride and the appearance quality of downstream products.

[0135] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for improving the stability of maleic anhydride, characterized in that, The method includes adding a stabilizer to maleic anhydride, including organotin compounds and / or organoantimony compounds, acyl halide compounds, metal oxides, antioxidants, and polymerization inhibitors; The stabilizer comprises: 5-50 parts by weight of organotin compounds and / or organoantimony compounds, 10-80 parts by weight of acyl halides, 5-30 parts by weight of metal oxides, 10-50 parts by weight of antioxidants, and 5-40 parts by weight of polymerization inhibitors.

2. The method according to claim 1, characterized in that, The stabilizer comprises: 15-25 parts by weight of organotin compounds and / or organoantimony compounds, 15-30 parts by weight of acyl halide compounds, 10-25 parts by weight of metal oxides, 15-25 parts by weight of antioxidants, and 10-20 parts by weight of polymerization inhibitors.

3. The method according to claim 1 or 2, characterized in that, The organotin compounds and / or organoantimony compounds include at least one of dimethyltin dilaurate, antimony tris(isooctyl mercaptoacetate), di-n-octyltin maleate, dioctyltin dimercaptoacetate, and tetraphenyltin. Preferably, the organotin compounds and / or organoantimony compounds include any two of dimethyltin dilaurate, tris(isooctyl mercaptoacetate)antimony, di-n-octyltin maleate, dioctyltin dimercaptoacetate, and tetraphenyltin.

4. The method according to any one of claims 1-3, characterized in that, The acyl halide compounds include at least one of o-acetylsalicylic acid chloride, diethyl chloromaleate, valeryl bromide and 3-phenylacryloyl chloride; Preferably, the acyl halide compound includes any two of o-acetylsalicylic acid chloride, diethyl chloromaleate, valerate bromide, and 3-phenylacryloyl chloride.

5. The method according to any one of claims 1-4, characterized in that, The metal oxide includes at least one of zinc oxide, aluminum oxide and magnesium oxide; Preferably, the metal oxide includes any two of zinc oxide, aluminum oxide, and magnesium oxide.

6. The method according to any one of claims 1-5, characterized in that, The antioxidant includes at least one of stearoylbenzoylmethane, 3,5-di-tert-butylsalicylic acid and di[3-(1,1-dimethylethyl)-4-hydroxy-5-methylphenylpropionic acid]polyethylene glycol; Preferably, the antioxidant comprises stearoylbenzoylmethane, 3,5-di-tert-butylsalicylic acid, and di-... Any two of the following: [3-(1,1-dimethylethyl)-4-hydroxy-5-methylphenylpropionic acid]polyethylene glycol.

7. The method according to any one of claims 1-6, characterized in that, The polymerization inhibitor includes at least one of 2,5-ditert-octylhydroquinone, p-tert-butylcatechol, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxygen radical and 4,4-dichlorodiphenyl sulfone. Preferably, the polymerization inhibitor comprises any two of 2,5-ditert-octylhydroquinone, p-tert-butylcatechol, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxy radical, and 4,4-dichlorodiphenyl sulfone.

8. The method according to any one of claims 1-7, characterized in that, The amount of stabilizer added to maleic anhydride is 3-25 ppm, preferably 5-15 ppm.

9. The method according to any one of claims 1-8, characterized in that, After the stabilizer is added to maleic anhydride, the mixing time should be no less than 0.5 h, preferably 1-3 h.

10. The method according to any one of claims 1-9, characterized in that, After the stabilizer is added to the maleic anhydride, it is mixed by circulating reflux.

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