Method for improving utilization rate of maleic anhydride

Abstract

The invention discloses a method for improving the utilization rate of maleic anhydride, and belongs to the technical field of chemical engineering. The method comprises the following steps: carrying out a ring-opening esterification reaction on a maleic anhydride material containing heavy components and alcohols in a vacuum rectifying tower, separating to obtain maleic anhydride without the heavy components at the tower top, and obtaining maleic acid monoester containing the heavy components at the tower kettle; and cooling the maleic acid monoester containing the heavy components, and carrying out solid-liquid separation to obtain liquid-phase maleic acid monoester and solid-phase heavy components. According to the method, alcohol and maleic anhydride materials containing heavy components are subjected to ring-opening esterification in a reactive distillation manner to produce maleic acid monoester. Based on the fact that the boiling points of maleic monoester and heavy components are higher than that of maleic anhydride, maleic monoester and heavy components can be extracted from a tower kettle, and maleic anhydride without heavy components can be obtained from the tower top. After cooling, the maleic acid monoester is liquid, the heavy component is solid, and the maleic acid monoester can be recycled through solid-liquid separation. The obtained maleic acid monoester can be sold out or further utilized, so that the loss of maleic anhydride is reduced, and the economic benefit is improved.

Description

Technical Field

[0001] The invention relates to the technical field of chemical industry, in particular to a method for improving the utilization rate of maleic anhydride. Background Art

[0002] Maleic anhydride is also known as maleic anhydride and 2,5-furandione. It is the third largest anhydride in the world after phthalic anhydride and acetic anhydride. Maleic anhydride has a strong pungent odor, is soluble in ethanol, ether and acetone, and is difficult to dissolve in petroleum ether and carbon tetrachloride. It is a colorless needle-shaped or flaky crystal. Maleic anhydride is mainly used as a raw material for the production of γ-butyrolactone, 1,4-butanediol, tetrahydrofuran, succinic acid, unsaturated polyester resin, alkyd resin, etc., as well as in the fields of medicine and pesticides.

[0003] Maleic anhydride will generate acetic acid, acrylic acid, tar and other impurities during the production process. Acrylic acid is very active and can easily self-polymerize to generate low molecular weight polymers in the downstream separation process. Although the content of tar and acrylic acid oligomers as heavy components is very low, they are enough to seriously affect the product quality of maleic anhydride (purity, color value, thermal stability, etc.), so they must be removed.

[0004] However, due to the low content of heavy components and the limitation of separation accuracy, the heavy components removed during the maleic anhydride refining process generally contain 60-80% maleic anhydride. Since this material is difficult to utilize, most of the current devices use incineration as a treatment method, which not only wastes materials and reduces the operating efficiency of the device, but also increases carbon emissions. Summary of the invention

[0005] The object of the present invention is to provide a method for improving the utilization rate of maleic anhydride to solve or improve the above technical problems.

[0006] This application can be implemented as follows:

[0007] In a first aspect, the present application provides a method for improving the utilization rate of maleic anhydride, which comprises the following steps: subjecting maleic anhydride materials containing heavy components to a ring-opening esterification reaction with alcohols in a vacuum distillation tower, followed by separation, obtaining maleic anhydride from which the heavy components have been removed at the top of the tower, and obtaining maleic acid monoester containing the heavy components at the bottom of the tower;

[0008] The maleic acid monoester containing the heavy component is cooled until the maleic acid monoester is liquid, and the solid and liquid are separated to obtain the maleic acid monoester in liquid phase and the heavy component in solid phase.

[0009] In an optional embodiment, the alcohol is an alcohol having 1 to 6 carbon atoms and containing one hydroxyl group.

[0010] In an alternative embodiment, the alcohol includes at least one of methanol, ethanol, isopropanol, n-butanol, sec-butanol, 2-pentanol and 2-hexanol.

[0011] In an optional embodiment, the mass ratio of the maleic anhydride material containing the heavy component to the alcohol is 50:1 to 300:1.

[0012] In an optional embodiment, the top operating pressure of the vacuum distillation tower is 1-20 KPa absolute pressure.

[0013] In an optional embodiment, the top operating temperature of the vacuum distillation tower is 70-150°C.

[0014] In an optional embodiment, the maleic anhydride material containing heavy components is first mixed with alcohols and then introduced into a vacuum distillation tower.

[0015] In an optional embodiment, the maleic anhydride material containing heavy components and the alcohols are independently introduced into the vacuum distillation tower.

[0016] In an optional embodiment, the temperature is reduced to 30-50°C.

[0017] In an optional embodiment, the solid-liquid separation method includes centrifugal separation or filtration separation.

[0018] The beneficial effects of this application include:

[0019] The present application uses a reactive distillation method to introduce alcohols into the refining process of maleic anhydride containing heavy components, and alcohols and maleic anhydride undergo ring-opening esterification to produce maleic acid monoesters during the refining process. Since maleic acid monoesters and heavy components have higher boiling points than maleic anhydride, they can be extracted from the tower bottom, and maleic anhydride with heavy components removed can be obtained at the top of the tower. After cooling, maleic acid monoesters are liquid, while heavy components are solid. By utilizing the difference in melting points between the two, the material extracted from the tower bottom can be cooled and then recovered by simple solid-liquid separation to recover maleic acid monoesters. The obtained maleic acid monoesters can be sold or enter the downstream supporting device of maleic anhydride for further use, thereby greatly reducing the loss of maleic anhydride and improving the economic benefits of the operation of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 A first process schematic diagram of the method for improving maleic anhydride utilization provided in the present application;

[0022] Figure 2 A second process schematic diagram of the method for improving maleic anhydride utilization provided in this application. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0024] The method for improving the utilization rate of maleic anhydride provided in the present application is described in detail below.

[0025] The present application proposes a method for improving the utilization rate of maleic anhydride, which comprises the following steps: subjecting maleic anhydride materials containing heavy components to a ring-opening esterification reaction with alcohols in a vacuum distillation tower, followed by separation, obtaining maleic anhydride with the heavy components removed at the top of the tower, and obtaining maleic acid monoester containing the heavy components at the bottom of the tower.

[0026] By introducing alcohols into the refining process of maleic anhydride containing heavy components, alcohols and maleic anhydride undergo ring-opening esterification during the refining process to obtain maleic acid monoester. Maleic acid monoester and heavy components have higher boiling points than maleic anhydride, so they can be extracted from the bottom of the tower, while maleic anhydride with heavy components removed can be obtained at the top of the tower.

[0027] In the present application, the alcohol used may be an alcohol containing one hydroxyl group and having 1 to 6 carbon atoms. That is, the alcohol used may have 1, 2, 3, 4, 5 or 6 carbon atoms.

[0028] In some optional embodiments, the alcohol used may illustratively include at least one of methanol, ethanol, isopropanol, n-butanol, sec-butanol, 2-pentanol and 2-hexanol.

[0029] For reference, the amount of maleic anhydride material containing heavy components used in this application is excessive, so as to ensure that the alcohol is completely reacted with it to form maleic acid monoester.

[0030] Illustratively, the mass ratio of maleic anhydride material containing heavy components to alcohols can be 50:1 to 300:1, such as 50:1, 80:1, 100:1, 120:1, 150:1, 180:1, 200:1, 220:1, 250:1, 280:1 or 300:1, or any other value within the range of 50:1 to 300:1.

[0031] In some embodiments, the maleic anhydride material containing heavy components and the alcohols are separately introduced into the vacuum distillation tower. Specifically, the maleic anhydride material containing heavy components and the alcohols removed can be independently introduced into the vacuum distillation tower from different feed ports (e.g. Figure 1 ), and can also enter the vacuum distillation tower from the same feed inlet; in other embodiments, the maleic anhydride material containing the heavy component is first mixed with the alcohol and then passed into the vacuum distillation tower (such as Figure 2 ).

[0032] In some embodiments, the vacuum distillation process is a continuous operation; in other embodiments, the vacuum distillation process is a batch operation.

[0033] In the present application, the top operating pressure of the vacuum distillation tower can be an absolute pressure of 1-20 KPa, such as 1 KPa, 2 KPa, 5 KPa, 8 KPa, 10 KPa, 12 KPa, 15 KPa, 18 KPa or 20 KPa, etc., or it can be any other value within the range of 1-20 KPa.

[0034] The top operating temperature of the vacuum distillation tower can be 70-150°C, such as 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C or 150°C, or any other value within the range of 70-150°C.

[0035] It should be noted that, according to different reaction raw materials, the operating pressure and operating temperature used are determined to meet the requirements of the ring-opening esterification reaction.

[0036] Furthermore, the temperature of the maleic acid monoester containing the heavy components is reduced until the maleic acid monoester is in liquid form, and solid-liquid separation is performed to obtain liquid phase maleic acid monoester and solid phase heavy components.

[0037] As a reference, the temperature is lowered to 30-50°C, such as 30°C, 35°C, 40°C, 45°C or 50°C, etc. Lowering the temperature to this range can ensure that the maleic acid monoester is liquid and the heavy component is still solid.

[0038] For example, the solid-liquid separation method may include centrifugal separation or filtration separation.

[0039] As mentioned above, at room temperature, maleic acid monoester is liquid, while recombinant fraction is solid. By taking advantage of the difference in melting points between the two, maleic acid monoester can be effectively recovered through simple filtration or centrifugal separation. The recovered maleic acid monoester can be sold or used in the downstream supporting equipment of maleic anhydride for further utilization, which is beneficial to greatly reduce the loss of maleic anhydride and improve the economic benefits of the operation of the equipment.

[0040] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0041] Example 1

[0042] This embodiment provides a method for improving the utilization rate of maleic anhydride. Figure 1 , which comprises the following steps:

[0043] S1: The maleic anhydride material containing heavy components and methanol are fed into a vacuum distillation tower at a mass ratio of 300:1 through different feed ports to perform a continuous ring-opening esterification reaction. After the reaction is completed, maleic anhydride with heavy components removed is obtained at the top of the tower, and maleic acid monoester containing heavy components is obtained at the bottom of the tower.

[0044] The feed rate of the maleic anhydride material containing heavy components into the vacuum distillation tower is 1000 kg / h, the content of heavy components in the maleic anhydride material containing heavy components is 0.079 wt%, the top operating pressure of the vacuum distillation tower is 10 KPa absolute pressure, and the top operating temperature is 128°C. Under this operating temperature and pressure, methanol completely undergoes a ring-opening esterification reaction with maleic anhydride to generate maleic acid monoester. The amount of maleic anhydride (referred to as refined maleic anhydride) obtained at the top of the tower after the heavy components are removed is 988.89 kg / h.

[0045] S2: Cool the maleic acid monoester containing the heavy components to 40°C and filter to obtain the maleic acid monoester in the liquid phase and the heavy components in the solid phase. Due to the separation accuracy, part of the maleic anhydride will fall into the bottom of the tower. After cooling, part of the maleic anhydride will dissolve in the maleic acid monoester and part will solidify with the heavy components.

[0046] The amount of maleic acid monoester containing maleic anhydride obtained was 13.55 kg / h, and the amount of heavy components containing maleic anhydride was 0.90 kg / h.

[0047] Example 2

[0048] This embodiment provides a method for improving the utilization rate of maleic anhydride, such as Figure 2 As shown, it includes the following steps:

[0049] S1: The maleic anhydride material containing heavy components is mixed with ethanol at a mass ratio of 200:1, and then the mixture is passed into a vacuum distillation tower for continuous ring-opening esterification reaction. After the reaction is completed, maleic anhydride with heavy components removed is obtained at the top of the tower, and maleic acid monoester containing heavy components is obtained in the bottom of the tower.

[0050] The feed rate of the maleic anhydride material containing heavy components into the vacuum distillation tower is 1000 kg / h, the content of the heavy components in the maleic anhydride material containing heavy components is 0.079 wt%, the top operating pressure of the vacuum distillation tower is 20 KPa absolute pressure, and the top operating temperature is 148°C. Under this operating temperature and pressure, ethanol completely undergoes a ring-opening esterification reaction with maleic anhydride to generate maleic acid monoester. The amount of maleic anhydride (referred to as refined maleic anhydride) obtained at the top of the tower after the heavy components are removed is 988.43 kg / h.

[0051] S2: Cool the maleic acid monoester containing the heavy components to 40°C and centrifuge to obtain the maleic acid monoester in the liquid phase and the heavy components in the solid phase. Due to the separation accuracy, part of the maleic anhydride will fall into the bottom of the tower. After cooling, part of the maleic anhydride will dissolve in the maleic acid monoester and part will solidify with the heavy components.

[0052] The amount of maleic acid monoester containing maleic anhydride obtained was 15.66 kg / h, and the amount of heavy components containing maleic anhydride was 0.92 kg / h.

[0053] Example 3

[0054] The present embodiment provides a method for improving the utilization rate of maleic anhydride, which comprises the following steps:

[0055] S1: The maleic anhydride material containing heavy components is mixed with isopropanol at a mass ratio of 150:1, and then the mixture is passed into a vacuum distillation tower for continuous ring-opening esterification reaction. After the reaction is completed, maleic anhydride with heavy components removed is obtained at the top of the tower, and maleic acid monoester containing heavy components is obtained in the bottom of the tower.

[0056] The feed rate of the maleic anhydride material containing heavy components into the vacuum distillation tower is 1000 kg / h, the content of heavy components in the maleic anhydride material containing heavy components is 0.079 wt%, the operating pressure at the top of the vacuum distillation tower is 5 KPa absolute pressure, and the operating temperature at the top of the tower is 110° C. Under this operating temperature and pressure, isopropanol completely undergoes a ring-opening esterification reaction with maleic anhydride to generate maleic acid monoester. The amount of maleic anhydride (referred to as refined maleic anhydride) obtained at the top of the tower after the heavy components are removed is 988.15 kg / h.

[0057] S2: Cool the maleic acid monoester containing the heavy components to 40°C and filter to obtain the maleic acid monoester in the liquid phase and the heavy components in the solid phase. Due to the separation accuracy, part of the maleic anhydride will fall into the bottom of the tower. After cooling, part of the maleic anhydride will dissolve in the maleic acid monoester and part will solidify with the heavy components.

[0058] The amount of maleic acid monoester containing maleic anhydride obtained was 17.57 kg / h, and the amount of heavy components containing maleic anhydride was 0.96 kg / h.

[0059] Example 4

[0060] The present embodiment provides a method for improving the utilization rate of maleic anhydride, which comprises the following steps:

[0061] S1: The maleic anhydride material containing heavy components is mixed with n-butanol at a mass ratio of 127:1, and then the mixture is passed into a vacuum distillation tower for continuous ring-opening esterification reaction. After the reaction is completed, maleic anhydride with heavy components removed is obtained at the top of the tower, and maleic acid monoester containing heavy components is obtained in the bottom of the tower.

[0062] The feed rate of the maleic anhydride material containing heavy components into the vacuum distillation tower is 1000 kg / h, the content of the heavy components in the maleic anhydride material containing heavy components is 0.079 wt%, the top operating pressure of the vacuum distillation tower is 15 KPa absolute pressure, and the top operating temperature is 140° C. Under this operating temperature and pressure, n-butanol completely undergoes a ring-opening esterification reaction with maleic anhydride to generate maleic acid monoester. The amount of maleic anhydride (referred to as refined maleic anhydride) obtained at the top of the tower after the heavy components are removed is 988.66 kg / h.

[0063] S2: Cool the maleic acid monoester containing the heavy components to 40°C and filter to obtain the maleic acid monoester in the liquid phase and the heavy components in the solid phase. Due to the separation accuracy, part of the maleic anhydride will fall into the bottom of the tower. After cooling, part of the maleic anhydride will dissolve in the maleic acid monoester and part will solidify with the heavy components.

[0064] The amount of maleic acid monoester containing maleic anhydride obtained was 18.31 kg / h, and the amount of heavy components containing maleic anhydride was 0.91 kg / h.

[0065] Example 5

[0066] The present embodiment provides a method for improving the utilization rate of maleic anhydride, which comprises the following steps:

[0067] S1: The maleic anhydride material containing heavy components is mixed with sec-butyl alcohol at a mass ratio of 80:1, and then the mixture is passed into a vacuum distillation tower for continuous ring-opening esterification reaction. After the reaction is completed, maleic anhydride with heavy components removed is obtained at the top of the tower, and maleic acid monoester containing heavy components is obtained in the bottom of the tower.

[0068] The feed rate of the maleic anhydride material containing heavy components into the vacuum distillation tower is 1000 kg / h, the content of heavy components in the maleic anhydride material containing heavy components is 0.079 wt%, the operating pressure at the top of the vacuum distillation tower is 7 KPa absolute pressure, and the operating temperature at the top of the tower is 120° C. Under this operating temperature and pressure, the secondary butanol completely undergoes a ring-opening esterification reaction with maleic anhydride to generate maleic acid monoester. The amount of maleic anhydride (referred to as refined maleic anhydride) obtained at the top of the tower after the heavy components are removed is 982.56 kg / h.

[0069] S2: Cool the maleic acid monoester containing the heavy components to 40°C and filter to obtain the maleic acid monoester in the liquid phase and the heavy components in the solid phase. Due to the separation accuracy, part of the maleic anhydride will fall into the bottom of the tower. After cooling, part of the maleic anhydride will dissolve in the maleic acid monoester and part will solidify with the heavy components.

[0070] The amount of maleic acid monoester containing maleic anhydride obtained was 29.07 kg / h, and the amount of heavy components containing maleic anhydride was 0.89 kg / h.

[0071] Example 6

[0072] The present embodiment provides a method for improving the utilization rate of maleic anhydride, which comprises the following steps:

[0073] S1: The maleic anhydride material containing heavy components is mixed with 2-pentanol at a mass ratio of 70:1, and then the mixture is passed into a vacuum distillation tower to perform a continuous ring-opening esterification reaction. After the reaction is completed, maleic anhydride with heavy components removed is obtained at the top of the tower, and maleic acid monoester containing heavy components is obtained in the bottom of the tower.

[0074] The feed rate of the maleic anhydride material containing heavy components into the vacuum distillation tower is 1000 kg / h, the content of the heavy components in the maleic anhydride material containing heavy components is 0.079 wt%, the operating pressure at the top of the vacuum distillation tower is 7 KPa absolute pressure, and the operating temperature at the top of the tower is 120° C. Under this operating temperature and pressure, 2-pentanol completely undergoes a ring-opening esterification reaction with maleic anhydride to generate maleic acid monoester. The amount of maleic anhydride (referred to as refined maleic anhydride) obtained at the top of the tower after the heavy components are removed is 983.16 kg / h.

[0075] S2: Cool the maleic acid monoester containing the heavy components to 40°C and filter to obtain the maleic acid monoester in the liquid phase and the heavy components in the solid phase. Due to the separation accuracy, part of the maleic anhydride will fall into the bottom of the tower. After cooling, part of the maleic anhydride will dissolve in the maleic acid monoester and part will solidify with the heavy components.

[0076] The amount of maleic acid monoester containing maleic anhydride obtained was 30.22 kg / h, and the amount of heavy components containing maleic anhydride was 0.93 kg / h.

[0077] Example 7

[0078] The present embodiment provides a method for improving the utilization rate of maleic anhydride, which comprises the following steps:

[0079] S1: The maleic anhydride material containing heavy components is mixed with 2-hexanol at a mass ratio of 50:1, and then the mixture is passed into a vacuum distillation tower to perform a continuous ring-opening esterification reaction. After the reaction is completed, maleic anhydride with heavy components removed is obtained at the top of the tower, and maleic acid monoester containing heavy components is obtained in the bottom of the tower.

[0080] The feed rate of maleic anhydride containing heavy components into the vacuum distillation tower is 1000 kg / h, the operating pressure at the top of the vacuum distillation tower is 7 KPa absolute pressure, and the operating temperature at the top of the tower is 120°C. Under this operating temperature and pressure, 2-hexanol completely undergoes a ring-opening esterification reaction with maleic anhydride to form maleic acid monoester. The amount of maleic anhydride (referred to as refined maleic anhydride) obtained at the top of the tower after the heavy components are removed is 979.81 kg / h.

[0081] S2: Cool the maleic acid monoester containing the heavy components to 40°C and filter to obtain the maleic acid monoester in the liquid phase and the heavy components in the solid phase. Due to the separation accuracy, part of the maleic anhydride will fall into the bottom of the tower. After cooling, part of the maleic anhydride will dissolve in the maleic acid monoester and part will solidify with the heavy components.

[0082] The amount of maleic acid monoester containing maleic anhydride obtained was 39.24 kg / h, and the amount of heavy components containing maleic anhydride was 0.97 kg / h.

[0083] Comparative Example

[0084] In this comparative example, maleic anhydride containing heavy components is subjected to vacuum distillation according to the existing process, but no alcohol is added, and refined maleic anhydride is obtained at the top of the tower, and heavy components containing maleic anhydride are obtained in the bottom of the tower. The heavy components containing maleic anhydride are also incinerated according to the existing process. The difference between this comparative example and the embodiment is that no alcohol is added, so there is no corresponding cooling and solid-liquid separation process. In the above process, the feed amount of maleic anhydride material containing heavy components is 1000kg / h, the content of heavy components in the maleic anhydride material containing heavy components is 0.079wt%, and the discharged maleic anhydride containing heavy components is 3.95kg / h. The content of heavy components in the maleic anhydride containing heavy components material is 20%, and the content of maleic anhydride is 80%. Therefore, the maleic anhydride lost is 3.16kg / h, and the refined maleic anhydride obtained at the top of the tower is 996.05kg / h.

[0085] The industrial values ​​of the above-mentioned Examples 1-7 and the comparative examples are compared and summarized as shown in Tables 1 and 2.

[0086] Table 1 Comparison results

[0087]

[0088]

[0089] Table 2 Comparison results

[0090] Example 4 Example 5 Example 6 Example 7 NO. project n-Butanol Sec-Butanol 2-Pentanol 2-Hexanol 1 Maleic anhydride feed amount containing heavy components, kg / h 1000 1000 1000 1000 2 Heavy component content, wt% 0.079％ 0.079％ 0.079％ 0.079％ 3 Discharged heavy components containing maleic anhydride, kg / h - - - - 3.1 Heavy component, kg / h - - - - 3.2 Maleic anhydride, kg / h - - - - 4 Refined maleic anhydride obtained from the top of the tower, kg / h 988.66 982.56 983.16 979.81 5 Mass ratio of maleic anhydride and alcohols containing heavy components 127 80 70 50 6 Maleic acid monoester containing maleic anhydride obtained by solid-liquid separation, kg / h 18.31 29.07 30.22 39.24 6.1 Maleic acid monoester,kg / h 18.30 29.05 30.19 39.22 6.2 Maleic anhydride, kg / h 0.01 0.02 0.02 0.03 7 Heavy components containing maleic anhydride obtained by solid-liquid separation, kg / h 0.91 0.89 0.93 0.97 7.1 Heavy component, kg / h 0.79 0.79 0.79 0.79 7.2 Maleic anhydride, kg / h 0.12 0.10 0.14 0.18 8 Maleic anhydride loss corresponding to 150,000 tons / year maleic anhydride production capacity, t / a 18 15 21 28

[0091] It can be seen from Table 1 and Table 2 that, according to the existing process used in the comparative example, based on the maleic anhydride production capacity of 150,000 tons / year and the maleic anhydride price of 8,000 yuan / ton, the existing process loses 476 tons of maleic anhydride per year, causing an economic loss of 3.81 million yuan. After adopting the method of the present invention, the maleic anhydride loss is 15-28 tons / year, and the economic loss is 120,000-220,000 yuan / year, which greatly reduces the loss of maleic anhydride and improves the economic benefits.

[0092] After adopting the process provided by the present application, the loss of maleic anhydride is greatly reduced, and part of the maleic anhydride reacts with alcohols to generate maleic acid monoesters with higher economic value (market price varies from 12,000 to 20,000 yuan / ton). Although the maleic acid monoester contains a small amount of maleic anhydride, the maleic acid monoester content is high, more than 99%, so it does not affect its downstream applications after sales. Therefore, the maleic acid monoester containing maleic anhydride can be sold externally, or it can be processed into a downstream device supporting the maleic anhydride device to obtain products with higher economic value (such as maleic anhydride esterification and hydrogenation to produce butanediol, γ-butyrolactone device). Therefore, the scheme provided by the present application can improve the recovery rate and utilization rate of maleic anhydride in the maleic anhydride production device without changing the main process flow of the existing maleic anhydride production device, reduce the emission of heavy components containing maleic anhydride, and improve the efficiency of the device.

[0093] In summary, the present application converts maleic anhydride in the discharged heavy component into maleic acid monoester, utilizes the difference in melting points between maleic acid monoester and heavy component, and utilizes simple solid-liquid separation to recover maleic acid monoester. Maleic acid monoester and heavy component have higher boiling points than maleic anhydride, and are extracted from the bottom of the tower; maleic anhydride with the heavy component removed is extracted from the top of the tower. The heavy component / maleic acid monoester extracted from the bottom of the tower is cooled to a certain temperature, and then solid-liquid separation is performed to obtain the heavy component and maleic acid monoester with higher value, thereby improving the utilization rate of maleic anhydride, greatly reducing the loss of maleic anhydride, and improving the economic benefits of the operation of the device.

[0094] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for improving the utilization rate of maleic anhydride, characterized in that: The following steps are involved: The maleic anhydride material containing heavy components and alcohol undergo a ring-opening esterification reaction in a vacuum distillation tower, followed by separation, obtaining maleic anhydride free of heavy components at the top of the tower, and obtaining maleic acid monoester containing heavy components at the bottom of the tower; The maleic acid monoester containing the heavy components is cooled until the maleic acid monoester is liquid, and the solid and liquid are separated to obtain the maleic acid monoester in liquid phase and the heavy components in solid phase.

2. The method according to claim 1, characterized in that The alcohol is an alcohol having 1 to 6 carbon atoms and containing one hydroxyl group.

3. The method according to claim 2, characterized in that The alcohol includes at least one of methanol, ethanol, isopropanol, n-butanol, sec-butanol, 2-pentanol and 2-hexanol.

4. The method according to any one of claims 1 to 3, characterized in that: The mass ratio of the maleic anhydride material containing heavy components to the alcohols is 50:1 to 300:

1.

5. The method according to claim 4, characterized in that The top operating pressure of the vacuum distillation tower is an absolute pressure of 1-20 KPa.

6. The method according to claim 4, characterized in that The top operating temperature of the vacuum distillation tower is 70-150°C.

7. The method according to claim 1, characterized in that The maleic anhydride material containing heavy components is first mixed with the alcohols and then introduced into a vacuum distillation tower.

8. The method according to claim 1, characterized in that The maleic anhydride material containing heavy components and the alcohols are independently introduced into a vacuum distillation tower.

9. The method according to claim 1, characterized in that: Cool down to 30-50℃.

10. The method according to claim 1, characterized in that Methods for solid-liquid separation include centrifugal separation or filtration separation.

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