A succinic anhydride and a method for preparing the same

Abstract

This invention relates to succinic anhydride and its preparation method, belonging to the field of synthetic technology. The succinic anhydride has a purity ≥99.85%, is free of tetrahydrofuran, and the remainder consists of impurities; these impurities include γ-butyrolactone (≤0.12%) and 1,4-butanediol (≤0.05%). Its preparation includes the following steps: maleic anhydride solution and hydrogen are introduced into a reactor containing a supported catalyst for reaction, followed by separation and purification to obtain succinic anhydride; the catalyst preparation includes the following steps: S1, asphalt and molybdenum disulfide are heat-treated to obtain a porous carbon / molybdenum disulfide support; S2, a nickel precursor, a copper precursor, and a hydrophobic compound are dispersed in water to obtain a mixed solution; S3, the porous carbon / molybdenum disulfide support is impregnated in the mixed solution, and then aged, dried, and thermally reduced to obtain the supported catalyst. This reaction is stable over a long period and can be used to prepare biodegradable polyesters such as polybutylene succinate or polybutylene adipate.

Description

Technical Field

[0001] This invention belongs to the field of synthetic technology, and particularly relates to a succinic anhydride and its preparation method. Background Technology

[0002] Succinic anhydride is an important organic synthesis intermediate and fine chemical raw material, widely used in food, surfactants, coatings, pharmaceuticals, plastics, and other fields. Currently, the industrial methods for preparing succinic anhydride include the succinic acid dehydration method and the maleic anhydride catalytic hydrogenation method. The succinic acid dehydration method has a small production scale and lower product quality; the maleic anhydride catalytic hydrogenation method has the advantages of simple process, convenient operation, and high product purity with few impurities, making it the most efficient production process.

[0003] Maleic anhydride contains one C=C bond and two C=O bonds. Under certain catalytic conditions, selective hydrogenation of the C=C bond can prepare succinic anhydride; however, deep hydrogenation sequentially produces γ-butyrolactone and tetrahydrofuran. Therefore, deep hydrogenation reduces the selectivity of succinic anhydride. Thus, controlling the hydrogenation reaction to proceed only to the C=C bond hydrogenation stage is crucial for the preparation of succinic anhydride from maleic anhydride. Furthermore, the catalytic hydrogenation system for maleic anhydride is acidic; systems intolerant to acid generally lead to poisoning of the active site, hindering long-term production.

[0004] Patents US1541210A and EP0691335A select palladium, a precious metal, as the active center. Although the hydrogenation selectivity is high, the amount of precious metal used accounts for 3.0%-10.0% of the total weight of the catalyst, which greatly increases the production cost and makes it difficult to achieve industrialization.

[0005] Therefore, how to prepare high-purity succinic anhydride through low-cost, targeted, and highly selective hydrogenation remains an urgent problem to be solved and has significant industrial value. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a succinic anhydride and its preparation method. The method employs a high-strength molybdenum disulfide / porous carbon support, which avoids the loss of non-precious metal nickel and copper catalytic centers into the product under pressurized hydrogenation conditions, thus preventing a gradual decrease in catalyst activity and ensuring long-cycle production. Furthermore, the hydrophobic compound allows for rapid desorption of the hydrogenated product from the catalyst surface. The degree of hydrogenation of maleic anhydride's C=C bonds and its two C=O bonds can be controlled by adjusting the reaction pressure and temperature, thereby obtaining the target product.

[0007] The first objective of this invention is to provide a succinic anhydride with a purity ≥99.85%, free of tetrahydrofuran, with the remainder being impurities; said impurities include γ-butyrolactone, with a content ≤0.12%, and 1,4-butanediol, with a content ≤0.05%.

[0008] The second objective of this invention is to provide succinic anhydride and its preparation method, wherein maleic anhydride solution and hydrogen are introduced into a reactor containing a supported catalyst to carry out a reaction, and then succinic anhydride is obtained by separation and purification.

[0009] The preparation method of the supported catalyst includes the following steps:

[0010] S1. Heat treatment of asphalt and molybdenum disulfide yields a porous carbon / molybdenum disulfide support.

[0011] S2. Disperse the nickel precursor, copper precursor, and hydrophobic compound in water to obtain a mixed solution; the structural formula of the hydrophobic compound is as follows: n≥6;

[0012] S3. The porous carbon / molybdenum disulfide support described in S1 is impregnated in the mixed solution described in S2, and then aged, dried and thermally reduced to obtain the supported catalyst.

[0013] In one embodiment of the present invention, in S1, the mass ratio of the asphalt to molybdenum disulfide is 1:5-5:1; the molybdenum disulfide has a 5-20 layer nanosheet structure.

[0014] In one embodiment of the present invention, in S1, the heat treatment is performed by heating at 200°C-400°C for 3-8 hours in an oxygen atmosphere.

[0015] In one embodiment of the present invention, in S2, the nickel precursor is selected from one or more of nickel chloride, nickel nitrate, nickel sulfate, basic nickel carbonate, nickel acetylacetone, nickel oxalate, nickel acetate, nickel citrate, nickel hypophosphite, nickel phosphate, and nickel formate; the copper precursor is selected from one or more of copper chloride, copper nitrate, and copper sulfate.

[0016] In one embodiment of the present invention, in S3, the aging temperature is 50℃-80℃ and the time is 12h-16h; the drying temperature is 100℃-150℃ and the time is 10h-14h; the thermal reduction treatment is carried out in a hydrogen atmosphere, with the temperature increased to 160℃-200℃ at a rate of 10℃ / h-20℃ / h, and the reduction is carried out for 6h-10h.

[0017] In one embodiment of the present invention, the supported catalyst has a nickel loading of 30wt%-60wt%, a copper loading of 5wt%-10wt%, and a hydrophobic compound loading of 0.01wt%-0.2wt%; the porous carbon / molybdenum disulfide support has a pore volume of 0.2mL / g-0.7mL / g, a particle size of 3mm-5mm, and a bulk density of 750kg / m³. 3 -1100kg / m 3The clusters have a length of 80nm-150nm, a width of 30nm-100nm, and a thickness of 10nm-30nm; the clusters are active centers composed of nickel, copper, and hydrophobic compounds supported on porous carbon / molybdenum disulfide supports.

[0018] In one embodiment of the present invention, the maleic anhydride solution has a mass fraction of 5wt%-30wt%; the solvent of the maleic anhydride solution is selected from one or more of tetrahydrofuran, γ-butyrolactone, diethyl ether, ethyl acetate, ethyl formate and methyl acetate; preferably, the solvent of the maleic anhydride solution is selected from tetrahydrofuran and / or γ-butyrolactone.

[0019] In one embodiment of the present invention, the reaction pressure is 1 MPa-10 MPa, the temperature is 25°C-100°C, and the space velocity is 0.6 hr. -1 -6.0hr -1 .

[0020] Preferably, the reaction pressure is 1 MPa-3 MPa and the temperature is 40℃-70℃.

[0021] In one embodiment of the present invention, the flow rate ratio of the maleic anhydride solution to hydrogen is (0.1-5):(0.1-100).

[0022] The porous carbon / molybdenum disulfide support of this invention, due to the layered structure of molybdenum disulfide, allows the asphalt to extend along the layered voids during high-temperature treatment. Subsequently, under certain temperatures, processes such as dehydration and removal of organic matter result in a layered carbon structure that firmly bonds with molybdenum disulfide, creating numerous porous channels that facilitate the dispersion of active metal components. Simultaneously, this composite support structure naturally possesses high mechanical strength, easily achieving a particle strength of ≥450 N / cm, which is difficult to achieve with traditional alumina particles; the mechanical strength of commercial catalyst support alumina particles typically reaches 100 N / cm.

[0023] The technical solution of the present invention has the following advantages compared with the prior art:

[0024] (1) The supported catalyst described in this invention has a strength of over 450 N / cm, and the metal is not easily lost during the reaction, which plays a key role in the synthesis of high-purity succinic anhydride.

[0025] (2) The supported catalyst described in this invention uses nickel / copper non-precious metals as the catalytic center and porous carbon / molybdenum disulfide as the support. The nickel / copper non-precious metals are uniformly dispersed and loaded in the ordered porous carbon / molybdenum disulfide support. The porous carbon / molybdenum disulfide support has certain hydrogenation activity, which can promote the improvement of reaction activity, thereby reducing the reaction temperature, improving the reaction selectivity, and thus improving the purity of the product.

[0026] (3) The supported catalyst described in this invention uses hydrophobic compounds as additives. After surface treatment with hydrophobic compounds, the surface of the supported catalyst has fewer adsorption C=O bond sites, which can make the product succinic anhydride desorb from the surface of the supported catalyst as soon as possible. On the one hand, it can accelerate the reaction rate, and on the other hand, it can avoid further reaction of the product on the catalyst surface, thereby achieving a maleic anhydride reaction conversion rate of up to 99.95% and a product purity of over 99.85%. It can also operate stably for a long period of time and can be used to prepare biodegradable polyesters such as polybutylene succinate or polybutylene adipate. Detailed Implementation

[0027] The present invention will be further described below with reference to specific embodiments, so that those skilled in the art can better understand and implement the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. It should be understood that the specific embodiments are only used to explain the present invention, but the embodiments are not intended to limit the present invention.

[0028] In this invention, unless otherwise stated, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0029] In this invention, unless otherwise stated, the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0030] In this invention, unless otherwise specified, the experimental methods used in the embodiments of this invention are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0031] In this invention, unless otherwise stated, the molybdenum disulfide used in the embodiments of this invention is a 5-20 layer nanosheet structure.

[0032] Example 1

[0033] The succinic anhydride and its preparation method in this embodiment specifically include the following steps:

[0034] S1. Preparation of supported catalysts

[0035] S11. Preparation of porous carbon / molybdenum disulfide carrier: Asphalt and molybdenum disulfide were mixed at a mass ratio of 1:1 and heat-treated at 300℃ for 4 hours under oxygen conditions to obtain a pore volume of 0.5 mL / g, a particle size of 5 mm, and a bulk density of 850 kg / m³. 3 Porous carbon / molybdenum disulfide support;

[0036] S12. Preparation of mixed solution: Weigh 50.00g basic nickel carbonate, 9.16g copper nitrate, 159.5mL of 5mol / L dilute nitric acid solution, 0.30g sodium dodecyl sulfonate and 500.00g deionized water, and stir at 45℃ until all solids are dissolved to obtain a mixed solution;

[0037] S13. Preparation of supported catalyst: A porous carbon / molybdenum disulfide support was impregnated in a mixed solution. Under stirring, it was first aged at 60°C for 14 h, then dried at 120°C for 12 h, and finally packed into a tube. The temperature was increased to 200°C for 6 h under hydrogen conditions at a heating rate of 20°C / h to obtain a supported catalyst with a cluster length of about 125 nm, a width of about 86 nm, and a thickness of about 18 nm.

[0038] Preparation of S2 and succinic anhydride

[0039] S21. Preparation of maleic anhydride solution: Dissolve maleic anhydride in tetrahydrofuran to obtain a maleic anhydride solution with a mass fraction of 5 wt%.

[0040] S22. Preparation of succinic anhydride: Maleic anhydride solution and hydrogen gas were mixed at flow rates of 0.5 mL / min and 50 mL / min, respectively, and continuously introduced into a 50 mL hydrogenation tubular reactor containing a supported catalyst. The reaction temperature was 70 °C, the reaction pressure was 1.9 MPa(A), and the space velocity was 0.6 hr. -1 The product is then continuously fed into a distillation column for separation and purification at a temperature of 140°C and a pressure of 50 kPa (A) to obtain the product.

[0041] Example 2

[0042] The process is basically the same as in Example 1, except that in the preparation of the supported catalyst, basic nickel carbonate is replaced with nickel nitrate.

[0043] Example 3

[0044] The process is basically the same as in Example 1, except that copper nitrate is replaced with copper chloride in the preparation of the supported catalyst.

[0045] Example 4

[0046] The process is basically the same as in Example 1, except that in the preparation of succinic anhydride, the 5 wt% maleic anhydride solution is replaced with a 10 wt% maleic anhydride solution.

[0047] Example 5

[0048] The process is basically the same as in Example 1, except that in the preparation of succinic anhydride, the solvent tetrahydrofuran in the maleic anhydride solution is replaced with the solvent γ-butyrolactone; and the separation and purification conditions are changed from a separation temperature of 140°C and a separation pressure of 50 kPa (A) to a separation temperature of 160°C and a separation pressure of 10 kPa (A).

[0049] Comparative Example 1

[0050] The process is basically the same as in Example 1, except that copper nitrate is not added during the preparation of the supported catalyst.

[0051] Comparative Example 2

[0052] The process is basically the same as in Example 1, except that sodium dodecyl sulfonate is not added during the preparation of the supported catalyst.

[0053] Comparative Example 3

[0054] The process is basically the same as in Example 1, except that copper nitrate and sodium dodecyl sulfonate are not added during the preparation of the supported catalyst.

[0055] Comparative Example 4

[0056] The process is basically the same as in Example 1, except that molybdenum disulfide is not added during the preparation of the supported catalyst.

[0057] Test Example 1

[0058] The supported catalysts of Examples 1-5 and Comparative Example 4 were tested for strength according to the HG / T 2782 standard, and the results are shown in Table 1:

[0059] Table 1

[0060] Sample Strength (N / cm) Example 1 450.6 Example 2 455.5 Example 3 455.8 Example 4 450.6 Example 5 450.6 Comparative Example 4 203.6

[0061] As shown in Table 1, the supported catalyst prepared in the examples has a strength exceeding 450 N / cm. By combining high-strength molybdenum disulfide with porous carbon, the strength of the supported catalyst can be significantly improved. This avoids the problem of non-precious metal nickel and copper catalytic centers being lost into the product under pressurized hydrogenation conditions, thus preventing a gradual decrease in catalyst activity and ensuring long-cycle production.

[0062] Test Example 2

[0063] The purity and impurity content of the products from Examples 1-5 and Comparative Examples 1-4 were tested by gas chromatography. The gas chromatography column was HP-5 (30m × 320μm × 0.25μm), with an FID detector. The column temperature conditions were: initial temperature 60℃, first-order termination temperature 90℃, heating rate 15℃ / min, hold for 2 min, second-order termination temperature 230℃, heating rate 10℃ / min, injection port temperature 260℃, split ratio 100:1, injection volume 0.2μL, hydrogen flow rate 30mL / min, and nitrogen flow rate 25mL / min. Standard curves for maleic anhydride, succinic anhydride, tetrahydrofuran, γ-butyrolactone, and 1,4-butanediol were established using acetone as solvent. The conversion rate (%) and selectivity (%) of maleic anhydride after 1000 h of continuous hydrogenation experiments are shown in Table 2.

[0064] Table 2

[0065] Sample maleic anhydride Succinic anhydride Tetrahydrofuran γ-Butyrolactone 1,4-Butanediol Example 1 - 99.92 - 0.08 - Example 2 - 99.90 - 0.10 - Example 3 - 99.88 - 0.12 - Example 4 0.05 99.90 0.05 Example 5 - 99.85 0.10 0.05 Comparative Example 1 - 99.40 0.50 0.10 Comparative Example 2 5.00 95.00 Comparative Example 3 3.60 94.40 2.00 Comparative Example 4 20.00 80.00 - - -

[0066] As can be seen from Table 2, the succinic anhydride prepared in the examples has a purity ≥99.85%, a maleic anhydride residual content ≤0.05%, and a γ-butyrolactone content ≤0.15%, indicating that the method of the present invention can prepare high-purity succinic anhydride.

[0067] Test Example 3

[0068] The products (succinic anhydride) of Examples 1-5 and Comparative Examples 1-4 were evaluated by polymerization experiments. The specific polymerization steps are as follows: 200.0 g of succinic anhydride and 252.0 g of 1,4-butanediol were added to a 1000 mL three-necked flask and esterified at 180 °C. The esterification was completed when the system no longer distilled water. Then, 0.39 g of tetrabutyl titanate catalyst was added and the pre-condensation reaction was carried out at 230 °C and 2.5 kPa (A) for 2 h. Finally, the polymer product was prepared by high vacuum condensation reaction at 230 °C and 100 Pa (A) for 3 h. Melt index and color value tests were performed on the polymer products. The melt index was tested using a melt indexer at a test temperature of 190℃ and a test pressure of 2160g, in accordance with GB / T 3682-2000. The color was tested using the CIE 1976 L*a*b* color system test, in accordance with the provisions of 5.5.2 in GB / T14190-2008. The results are shown in Table 3.

[0069] Table 3

[0070]

[0071] As can be seen from Table 3, the high-purity succinic anhydride prepared by the method of the present invention can be used to prepare polybutylene succinate polyester material with high viscosity (melt index < 10 g / 10 min) and bright white color (L value > 80, b value < 7).

[0072] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing succinic anhydride, characterized in that, A maleic anhydride solution and hydrogen gas are introduced into a reactor containing a supported catalyst to carry out the reaction, and then succinic anhydride is obtained by separation and purification; the supported catalyst has a nickel loading of 30wt%-60wt%, a copper loading of 5wt%-10wt%, and a hydrophobic compound loading of 0.01wt%-0.2wt%. The preparation method of the supported catalyst includes the following steps: S1. Heat treatment of asphalt and molybdenum disulfide yields a porous carbon / molybdenum disulfide support. S2. Disperse the nickel precursor, copper precursor, and hydrophobic compound in water to obtain a mixed solution; the hydrophobic compound is sodium dodecyl sulfonate. S3. The porous carbon / molybdenum disulfide support described in S1 is impregnated in the mixed solution described in S2, and then aged, dried and thermally reduced to obtain the supported catalyst.

2. The method for preparing succinic anhydride according to claim 1, characterized in that, In S1, the mass ratio of the asphalt to molybdenum disulfide is 1:5-5:1; the molybdenum disulfide has a 5-20 layer nanosheet structure.

3. The method for preparing succinic anhydride according to claim 1, characterized in that, In S1, the heat treatment is performed by heating at 200°C-400°C for 3-8 hours in an oxygen atmosphere.

4. The method for preparing succinic anhydride according to claim 1, characterized in that, In S2, the nickel precursor is selected from one or more of nickel chloride, nickel nitrate, nickel sulfate, basic nickel carbonate, nickel acetylacetone, nickel oxalate, nickel acetate, nickel citrate, nickel hypophosphite, nickel phosphate, and nickel formate; the copper precursor is selected from one or more of copper chloride, copper nitrate, and copper sulfate.

5. The method for preparing succinic anhydride according to claim 1, characterized in that, In S3, the aging temperature is 50℃-80℃ and the time is 12h-16h; the drying temperature is 100℃-150℃ and the time is 10h-14h; the thermal reduction treatment is carried out in a hydrogen atmosphere, with the temperature increased to 160℃-200℃ at a rate of 10℃ / h-20℃ / h, and the reduction is carried out for 6h-10h.

6. The method for preparing succinic anhydride according to claim 1, characterized in that, The porous carbon / molybdenum disulfide support has a pore volume of 0.2 mL / g-0.7 mL / g, a particle size of 3 mm-5 mm, and a bulk density of 750 kg / m³. 3 -1100kg / m 3 The clusters have a length of 80nm-150nm, a width of 30nm-100nm, and a thickness of 10nm-30nm.

7. The method for preparing succinic anhydride according to claim 1, characterized in that, The maleic anhydride solution has a mass fraction of 5wt%-30wt%; the solvent of the maleic anhydride solution is selected from one or more of tetrahydrofuran, γ-butyrolactone, diethyl ether, ethyl acetate, ethyl formate and methyl acetate.

8. The method for preparing succinic anhydride according to claim 1, characterized in that, The reaction was carried out at a pressure of 1 MPa-10 MPa, a temperature of 25°C-100°C, and a space velocity of 0.6 hr. -1 -6.0hr -1 .

9. The method for preparing succinic anhydride according to claim 1, characterized in that, The flow rate ratio of the maleic anhydride solution to hydrogen is (0.1-5):(0.1-100).

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