Method for preparing succinic acid through catalytic hydrogenation of maleic anhydride and system and catalyst applied to method

Abstract

The invention discloses a method for preparing succinic acid through catalytic hydrogenation of maleic anhydride and a system and a catalyst applied to the method, and the method comprises the following steps: firstly hydrolyzing maleic anhydride into maleic acid, then carrying out catalytic hydrogenation reaction in the presence of hydrogen and the catalyst, carrying out gas-liquid separation after the reaction, and cooling and crystallizing the obtained liquid phase to obtain the succinic acid. Centrifugally separating to obtain crystal mush, and drying a solid phase obtained by centrifugally separating the crystal mush to obtain succinic acid; a catalyst in the catalytic hydrogenation reaction is a Ni-Pt hydrogenation catalyst. The Ni-Pt hydrogenation catalyst which is high in activity, stable in performance and suitable in surface property is adopted as the selective hydrogenation catalyst for maleic anhydride water-phase hydrogenation acid resistance, succinic acid is produced through a maleic anhydride water-phase hydrogenation one-step method, and the selectivity of succinic acid is 100%; the method has the characteristics of low cost, simple process flow and easiness in large-scale production; the method has technical advancement, economic benefit and industrial application development prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of new material chemical synthesis, and specifically relates to a method for catalytic hydrogenation of maleic anhydride to prepare succinic acid, and a system and a catalyst for its application. Background Art

[0002] Succinic acid, also known as amber acid, is the main material of the biodegradable plastic PBS. In the global environment of plastic restriction / banning, PBS can be used alone as a thermoplastic product, and its biodegradability can reach 100% (with properties similar to polypropylene), or it can be used to produce other products, with great market potential. Correspondingly, the annual demand for succinic acid has reached more than ten million tons, but the production of PBS materials is currently restricted by the production capacity of succinic acid. Approximately 620 kg of succinic acid is required to produce 1000 kg of PBS, and 850 kg of maleic anhydride is required to produce 1000 kg of succinic acid. Due to the application of the n-butane oxidation method, the annual production capacity of maleic anhydride in China has reached more than 7.5 million tons, reducing the production cost, while the annual production capacity of succinic acid is less than 30,000 tons. Compared with the electrolysis method or fermentation method for producing succinic acid with excessively high production costs, the production method of catalytic hydrogenation of maleic anhydride to prepare succinic acid has received wide attention.

[0003] Currently, there are mainly the following two process routes for the catalytic hydrogenation method of maleic anhydride: one is the melting method, in which the catalyst is added to molten maleic anhydride, and maleic anhydride is catalytically hydrogenated under solvent-free conditions to produce succinic anhydride under a certain pressure. The other is the solvent method, in which maleic anhydride in an organic solvent is hydrogenated under the action of a catalyst to obtain succinic anhydride. The succinic anhydride prepared by this method has a high yield and high purity, and is more commonly used in global production.

[0004] For the solvent method, the most crucial is the selection of the catalyst and the solvent. How to regulate the surface properties and structural characteristics of the catalyst to make the prepared catalyst have high hydrogenation activity for C=C in the maleic anhydride molecule, while suppressing the hydrogenation activity of C=O, is the primary problem faced in the large-scale production of the directional synthesis of succinic acid by maleic anhydride hydrogenation.

[0005] The hydrogenation of maleic anhydride to produce succinic acid is a highly exothermic reaction, which easily causes the local temperature of the hydrogenation sites on the catalyst surface to be too high during the reaction process, leading to the polymerization and coking of organic substances on the catalyst surface and reducing the catalyst activity. There are also problems such as many by-products in the hydrogenation of maleic anhydride in an organic solvent to produce succinic acid, and the complex separation and purification of succinic acid produced by hydrolysis and high costs.

[0006] CN25517302A discloses a method for preparing succinic acid by hydrolysis and hydrogenation of maleic anhydride. This method uses a highly active bimetallic Pd-Pt catalyst as the selective hydrogenation catalyst for acid-resistant hydrogenation of maleic anhydride in aqueous phase, and realizes effective heat transfer through regulation of microscopic and macroscopic structures, enabling succinic acid to rapidly desorb from the catalyst surface, greatly improving the selectivity, achieving continuous production of succinic acid by hydrogenation of maleic anhydride in aqueous phase. Meanwhile, a low-boiling solvent is added during the reaction process, and the latent heat of the low-boiling solvent is utilized to ensure the stable operation of the reaction, which is beneficial to removing the reaction heat on the catalyst surface and is also beneficial to the crystallization and purification of succinic acid.

[0007] However, the catalyst selected in this method is not suitable for application and popularization. Firstly, palladium is a rare and precious metal with scarce reserves on the earth, and its mining and smelting are relatively difficult. At the same time, it is an indispensable key material in high-tech fields such as aviation, aerospace, navigation, ordnance, and nuclear energy, as well as the automotive manufacturing industry. Therefore, the material is scarce and the price is expensive. Secondly, a solvent is added during the reaction process, and the latent heat of the solvent is utilized to ensure the stable operation of the reaction. Although it is beneficial to removing the reaction heat on the catalyst surface, there are major problems in the treatment of the solvent in the later stage of the reaction. Summary of the Invention

[0008] To solve the above problems in the prior art, the present invention provides a method for catalytic hydrogenation of maleic anhydride to prepare succinic acid, as well as a system and a catalyst for its application, which ensure the stable operation of the reaction, ensure the purity of succinic acid crystallization, have low cost, simple process, and are easy to scale up production by selecting a suitable catalyst for hydrogenation of maleic anhydride in aqueous phase.

[0009] The technical solution adopted by the present invention is as follows:

[0010] In the first aspect of the present invention, there is provided a method for catalytic hydrogenation of maleic anhydride to prepare succinic acid, comprising the following steps:

[0011] Maleic anhydride is first hydrolyzed to maleic acid, and then, in the presence of hydrogen and a catalyst, a catalytic hydrogenation reaction is carried out. After the reaction, gas-liquid separation is carried out. The obtained liquid phase is cooled and crystallized, and then centrifuged to obtain a crystal slurry. The solid phase obtained after centrifuging the crystal slurry is dried to obtain succinic acid;

[0012] The catalyst in the catalytic hydrogenation reaction is a Ni-Pt hydrogenation catalyst.

[0013] Furthermore, the Ni-Pt hydrogenation catalyst is a supported catalyst, and the carrier of the Ni-Pt hydrogenation catalyst is spherical carbon microspheres, spherical activated carbon or water-resistant activated carbon; wherein, the mass loading of the metal is 0.3-1%, and the Ni / Pt molar ratio is 6-10.

[0014] Furthermore, the particle diameter of the Ni-Pt hydrogenation catalyst is 1.5 mm, the pore volume ≥ 0.4 mL / g, and the specific surface area ≥ 600 m2 / g, the radial strength ≥ 50 N / cm, and the bulk ratio is 0.45 - 0.55 g / mL.

[0015] Further, the preparation steps of the Ni-Pt hydrogenation catalyst are as follows: First, dissolve the prepared nickel salt and platinum salt with a specific metal molar ratio in a polyol solution to obtain a metal sol, and then coat the metal sol on the carrier by the spin coating method or the dip impregnation method to obtain the catalyst.

[0016] Further, the platinum salt is selected from one or more of Pt(acac)2, K2PtCl6, and H2PtCl6;

[0017] The nickel salt is selected from one or two of Ni(acac)2 and NiCl2;

[0018] The polyol is selected from one or several of ethylene glycol, glycerol, 1,2-propanediol, and 1,3-propanetriol.

[0019] Further, in the catalytic hydrogenation reaction of maleic acid, the reaction temperature is 70 - 150 °C, the reaction pressure is 1.0 - 5.0 MPa, and the liquid hourly space velocity is 0.3 - 0.4 h -1 , and the molar ratio of hydrogen to maleic acid, that is, the hydrogen-acid molar ratio is (2 - 5):1.

[0020] Further, in the hydrolysis reaction of maleic anhydride, the hydrolysis temperature is 60 - 70 °C, the hydrolysis time is 2 - 3 h, and the mass concentration of maleic anhydride is 15 - 25%.

[0021] The second aspect of the present invention is to provide a system for catalytic hydrogenation of maleic anhydride to prepare succinic acid. The system includes a hydrolysis tank, a static mixer, a hydrogenation reaction tower, a gas-liquid separator, a crystallization separation tank, a centrifuge, a dryer, and a product collection tank connected in sequence through pipelines;

[0022] It also includes a supplementary hydrogen compressor connected to the static mixer, a recycle hydrogen compressor arranged between the gas-liquid separator and the static mixer, and a heat exchanger arranged between the static mixer and the hydrogenation reaction tower.

[0023] Further, the top of the hydrolysis tank is provided with an aqueous phase inlet and a maleic anhydride inlet, and the centrifuge is provided with a liquid phase outlet and is connected to the aqueous phase inlet of the hydrolysis tank.

[0024] The third aspect of the present invention is to provide a Ni-Pt hydrogenation catalyst applied to the method for catalytic hydrogenation of maleic anhydride to prepare succinic acid as described above.

[0025] The beneficial effects of the present invention are as follows:

[0026] 1. The technical solution of the present invention adopts a Ni-Pt hydrogenation catalyst with high activity, stable performance and suitable surface properties as an acid-resistant selective hydrogenation catalyst for aqueous phase hydrogenation of maleic anhydride, which not only realizes the one-step production of succinic acid by aqueous phase hydrogenation of maleic anhydride, but also achieves a conversion rate of maleic acid of 90-100%, and a selectivity of succinic acid of 100%, and has the characteristics of low cost, simple process flow, and easy large-scale production.

[0027] 2. The technical solution of the present invention improves the anti-carbon deposition performance of the Ni-Pt hydrogenation catalyst during the reaction process by selecting a specific molar ratio of Ni-Pt hydrogenation catalyst without adding a solvent, thereby improving the stability of the catalyst, extending its service life, and reducing the frequency of catalyst replacement, while effectively avoiding the problem of subsequent solvent treatment.

[0028] 3. The technical solution of the present invention adopts a continuous feeding method, which has the characteristics of mild reaction conditions, simple process flow, high product yield, good product quality, large-scale production, small investment, low production cost and energy consumption. It not only has technological advancement and economic benefits, but also has the development prospect of industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a system for preparing succinic acid by catalytic hydrogenation of maleic anhydride.

[0030] In the figure:

[0031] 1-hydrolysis tank; 2-static mixer; 3-hydrogenation reaction tower; 4-gas-liquid separator; 5-crystallization separation tank; 6-centrifuge; 7-dryer; 8-product collection tank; 9-supplementary hydrogen compressor; 10-circulating hydrogen compressor; 11-heat exchanger.

[0032] MAH-maleic anhydride; DW-water; LPS-low pressure steam, LPC-low pressure steam condensate. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is described clearly and in detail below through specific embodiments in conjunction with the accompanying drawings. It should be understood that the following embodiments are only part of the embodiments of the present invention and are not intended to limit the scope of the present invention.

[0034] Example 1. Preparation of Ni-Pt hydrogenation catalyst a

[0035] Pt(acac)2 and Ni(acac)2 with a prepared Ni / Pt molar ratio of 8 were dissolved in ethylene glycol solution, and NaOH was added to adjust the solution pH>11. The solution was aged for 12 hours and then heated to 80°C for 3 hours to prepare a metal sol.

[0036] First, dry the carbon microsphere support with a diameter of 4 mm. Then, spin-spray the metal sol (Ni / Pt molar ratio is 8) on the carbon microsphere support, and control the thickness of the metal shell layer by controlling the spraying amount. After washing and heating and drying in an inert atmosphere, Ni-Pt catalyst a is formed, and the mass loading of the metal is 0.6%.

[0037] Example 2. Preparation of Ni-Pt hydrogenation catalyst b

[0038] Dissolve the prepared K2PtCl6 and NiCl2 with a Ni / Pt molar ratio of 6 in a glycerol solution, then add NaOH to adjust the solution pH>11. After the solution is aged for 12 h, heat it to 80 °C and keep it for 3 h to prepare the metal sol.

[0039] First, dry the spherical activated carbon support with a diameter of 6 mm. Then, spin-spray the metal sol (Ni / Pt molar ratio is 6) on the spherical activated carbon support, and control the thickness of the metal shell layer by controlling the spraying amount. After washing and heating and drying in an inert atmosphere, Ni-Pt catalyst b is formed, and the mass loading of the metal is 1%.

[0040] Example 3. Preparation of Ni-Pt hydrogenation catalyst c

[0041] Dissolve the prepared H2PtCl6 and NiCl2 with a Ni / Pt molar ratio of 7 in a 1,2-propanediol solution, then add NaOH to adjust the solution pH>11. After the solution is aged for 12 h, heat it to 80 °C and keep it for 3 h to prepare the metal sol.

[0042] First, dry the spherical activated carbon support with a diameter of 2 mm. Then, spin-spray the metal sol (Ni / Pt molar ratio is 7) on the spherical activated carbon support, and control the thickness of the metal shell layer by controlling the spraying amount. After washing and heating and drying in an inert atmosphere, Ni-Pt catalyst c is formed, and the mass loading of the metal is 0.8%.

[0043] Example 4. Preparation of Ni-Pt hydrogenation catalyst d

[0044] Dissolve the prepared Pt(acac)2 and Ni(acac)2 with a Ni / Pt molar ratio of 10 in a 1,3-glycerol solution, then add NaOH to adjust the solution pH>11. After the solution is aged for 12 h, heat it to 80 °C and keep it for 3 h to prepare the metal sol.

[0045] Using 200-mesh water-resistant activated carbon as the carrier, which does not require pretreatment, the carrier is immersed in the metal sol (Ni / Pt molar ratio is 10) by the dip-coating method. After repeated washing, drying, and impregnation to reach the appropriate loading, the catalyst is reduced in H2 at 300 °C for 2 h to obtain the Ni-Pt bimetallic hydrogenation catalyst d, and the mass loading of the metal is 0.3%.

[0046] The catalysts a - d prepared in Examples 1 - 4 are in strip shape, with a particle diameter of 1.5 mm, a pore volume ≥ 0.4 mL / g, a specific surface area ≥ 600 m 2 / g, a radial strength ≥ 50 N / cm, and a bulk density of 0.45 - 0.55 g / mL.

[0047] Comparative Example 1

[0048] This example is basically the same as Comparative Example 1, except that the Ni / Pt molar ratio in the metal sol is 3, and finally the Ni-Pt hydrogenation catalyst e is obtained.

[0049] Comparative Example 2

[0050] This example is basically the same as Comparative Example 1, except that the Ni / Pt molar ratio in the metal sol is 15, and finally the Ni-Pt hydrogenation catalyst f is obtained.

[0051] Comparative Examples 3 - 4

[0052] Comparative Examples 3 - 4 are basically the same as Example 1, except that Al2O3 and SiO2 are used to replace the platinum salt respectively to prepare sols with Ni / Al and Ni / Si molar ratios of 8, and finally the Ni-Al hydrogenation catalyst and Ni-Si hydrogenation catalyst are obtained.

[0053] Example 5. A system for catalytic hydrogenation of maleic anhydride to succinic acid

[0054] A system for catalytic hydrogenation of maleic anhydride to succinic acid, as Figure 1 shown, the system includes a hydrolysis tank 1, a static mixer 2, a hydrogenation reaction tower 3, a gas-liquid separator 4, a crystallization separation tank 5, a centrifuge 6, a dryer 7, and a product collection tank 8 connected in sequence through pipelines; it also includes a make-up hydrogen compressor 9 connected to the static mixer 2, a recycle hydrogen compressor 10 arranged between the gas-liquid separator 4 and the static mixer 2, and a heat exchanger 11 arranged between the static mixer 2 and the hydrogenation reaction tower 3.

[0055] Furthermore, the top of the hydrolysis tank 1 is provided with an aqueous phase inlet and a maleic anhydride inlet, and the centrifuge 6 is provided with a liquid phase outlet and is connected to the aqueous phase inlet of the hydrolysis tank 1.

[0056] The process flow of the system for preparing succinic acid by catalytic hydrogenation of maleic anhydride is as follows:

[0057] First, maleic anhydride and water are mixed in a hydrolysis tank 1 in a certain proportion and then hydrolyzed. After hydrolysis, it is pumped to a static mixer 2 to be mixed with hydrogen from a make-up hydrogen compressor 9 and a recycle hydrogen compressor 10, and then heated by a heat exchanger 11 and sent into a hydrogenation reaction tower 3 filled with a Ni-Pt hydrogenation catalyst for catalytic hydrogenation; after the reaction ends, the reaction liquid is sent to a gas-liquid separator 4 for gas-liquid separation. The temperature of the gas-liquid separation tank 4 is controlled at 60 - 65 °C to prevent the precipitation and blockage of succinic acid. The hydrogen separated is sent into the static mixer 2 by the recycle hydrogen compressor 10 for recycling. The separated liquid phase is pumped into a crystallization separation tank 5. The temperature during the crystallization process is 15 - 25 °C. The generated crystal slurry is sent to a centrifuge 6 for liquid-solid separation. After the separated liquid phase removes trace impurity metals, it is sent into the hydrolysis tank 1 for recycling. The separated solid phase enters a dryer 7. The temperature of the dryer 7 needs to be less than 150 °C. After drying, succinic acid with a purity greater than 99.5% is obtained and sent into a product collection tank 8.

[0058] Example 6. Influence of the catalyst on the hydrogenation of maleic acid

[0059] In the system for preparing succinic acid by catalytic hydrogenation of maleic anhydride described in Example 5, the Ni-Pt hydrogenation catalysts a - d prepared in Examples 1 - 4 above, the Ni-Pt hydrogenation catalysts e - f prepared in Comparative Examples 1 - 4, a Ni-Al hydrogenation catalyst, and a Ni-Si hydrogenation catalyst are respectively used to catalyze the hydrogenation reaction of maleic acid, and the influence of different catalysts on the hydrogenation of maleic acid is studied. The specific catalytic effects are shown in Table 1 below.

[0060] Reaction conditions: hydrolysis temperature is 65 °C, hydrolysis time is 3 h, mass concentration of maleic anhydride is 25%; reaction temperature for catalytic hydrogenation is 75 °C, reaction pressure is 1.5 MPa, and liquid volume hourly space velocity is 0.4 h -1 。

[0061] Table 1

[0062]

[0063] From the results in Table 1 above, it can be seen that the catalytic effects of the Ni-Pt hydrogenation catalysts a - f are significantly better than those of the Ni-Al hydrogenation catalyst and the Ni-Si hydrogenation catalyst. Among them, under the catalysis of the Ni-Pt hydrogenation catalysts a - d, the conversion rate of maleic acid can reach more than 98%, and the selectivity of succinic acid is 100%.

[0064] Example 7. Stability of the Ni-Pt catalyst

[0065] In this example, the stability of the Ni-Pt hydrogenation catalyst a prepared in the above Example 1, the Ni-Pt hydrogenation catalysts e, f, Ni-Al hydrogenation catalyst, and Ni-Si hydrogenation catalyst prepared in Comparative Examples 1-4 was studied.

[0066] In the system for catalytic hydrogenation of maleic anhydride to succinic acid described in Example 5, the above hydrogenation catalysts were respectively used to catalyze the hydrogenation reaction of maleic acid. The reaction temperature was 130 °C, the reaction pressure was 3 MPa, the liquid volume hourly space velocity was 0.3 h -1 , the molar ratio of hydrogen to acid was 3, the concentration of maleic anhydride was 25%, the feeding mode was downward feeding, and the reaction results are shown in Table 2 below.

[0067] Table 2

[0068]

[0069] From the results in Table 2 above, it can be seen that the Ni-Pt hydrogenation catalyst of the present invention can maintain stable performance within 2500 hours during the catalytic hydrogenation of maleic anhydride to succinic acid. The conversion rate of maleic acid is above 95%, and the selectivity of succinic acid is as high as 100%, which is beneficial to continuous industrial production. In addition, too high or too low Ni / Pt molar ratio of the Ni-Pt hydrogenation catalyst is not conducive to maintaining its stability.

[0070] At the same time, the catalytic performance and stability of the Ni-Pt hydrogenation catalyst of the present invention are significantly superior to those of the Ni-Al hydrogenation catalyst and the Ni-Si hydrogenation catalyst. Although the activity of the Ni-Al hydrogenation catalyst is higher than that of the Ni-Si hydrogenation catalyst, its acid resistance is poor. After only 14 hours of reaction, the catalytic performance of the Ni-Si hydrogenation catalyst has decreased significantly, the selectivity of succinic acid is as low as 31%, the content of by-products has increased greatly, and a large amount of the catalyst has dissolved.

[0071] Example 8. Selection of maleic anhydride hydrolysis reaction conditions

[0072] The main influencing factors in the maleic anhydride hydrolysis stage include the mass fraction of maleic anhydride, hydrolysis temperature, and hydrolysis time. The following is to study the effects of different mass fractions of maleic anhydride, hydrolysis temperature, and hydrolysis time on the hydrolysis rate of maleic anhydride, select suitable hydrolysis reaction conditions, and the detection results are shown in Table 3 below.

[0073] Table 3

[0074]

[0075] From the results in Table 3, it can be seen that when the hydrolysis temperature is 60-70 °C, the hydrolysis time is 2-3 h, and the mass concentration of maleic anhydride is 15-25%, the hydrolysis rate of maleic anhydride is greater than 99%.

[0076] Example 9. Influence of Hydrogenation Reaction Conditions on the Hydrogenation Performance of Maleic Acid

[0077] In this example, the Ni-Pt hydrogenation catalyst a prepared in Example 1 above was used as the selective hydrogenation catalyst to study the influence of different hydrogenation reaction conditions on the hydrogenation performance of maleic acid. The specific catalytic effects are shown in Table 4 below.

[0078] Hydrolysis reaction conditions: hydrolysis temperature is 65 °C, hydrolysis time is 3 h, and the mass concentration of maleic anhydride is 25%.

[0079] Table 4

[0080]

[0081]

[0082] As can be seen from Table 4 above, when the Ni-Pt hydrogenation catalyst is used as the selective hydrogenation catalyst in the catalytic hydrogenation reaction of maleic acid, the reaction temperature is 70 - 150 °C, the reaction pressure is 1.0 - 5.0 MPa, the liquid volume space velocity is 0.3 - 0.4 h -1 , and the molar ratio of hydrogen to acid is (2 - 5):1, the conversion rate of maleic acid can reach 90 - 100%, and the selectivity of succinic acid is 100%.

[0083] The technical solution of the present invention has been described in detail above, aiming to enable those skilled in the art to understand the content of the present invention and implement it. However, the protection scope of this application cannot be limited accordingly. Any equivalent changes, substitutions, or modifications made according to the spirit and essence of this application should be covered by the protection scope of this application.

Claims

1. A method for preparing succinic acid by catalytic hydrogenation of maleic anhydride, characterized in that, It includes the following steps: Maleic anhydride is first hydrolyzed into maleic acid, and then catalytic hydrogenation reaction is carried out in the presence of hydrogen and a catalyst. After the reaction, gas-liquid separation is carried out. The obtained liquid phase is cooled and crystallized, and then centrifugally separated to obtain a crystal slurry. The solid phase obtained after centrifugal separation of the crystal slurry is dried to obtain succinic acid; The catalyst in the catalytic hydrogenation reaction is a Ni-Pt hydrogenation catalyst.

2. The method for preparing succinic acid by catalytic hydrogenation of maleic anhydride according to claim 1, wherein The Ni-Pt hydrogenation catalyst is a supported catalyst, and the carrier of the Ni-Pt hydrogenation catalyst is spherical carbon microspheres, spherical activated carbon or water-resistant activated carbon; wherein, the mass loading of the metal is 0.3-1%, and the Ni / Pt molar ratio is 6-10.

3. The method for preparing succinic acid by catalytic hydrogenation of maleic anhydride according to claim 1, characterized in that, The particle diameter of the Ni-Pt hydrogenation catalyst is 1.5 mm, the pore volume is ≥ 0.4 mL / g, the specific surface area is ≥ 600 m 2 / g, the radial strength is ≥ 50 N / cm, and the bulk density is 0.45 - 0.55 g / mL.

4. The method for preparing succinic acid by catalytic hydrogenation of maleic anhydride according to claim 1, characterized in that, The preparation steps of the Ni-Pt hydrogenation catalyst are as follows: First, nickel salts and platinum salts with a specific metal molar ratio are dissolved in a polyol solution to prepare a metal sol, and then the metal sol is coated on the carrier by a rotary spraying method or a dip coating method to obtain a Ni-Pt hydrogenation catalyst.

5. The method for preparing succinic acid by catalytic hydrogenation of maleic anhydride according to claim 4, wherein, The platinum salt is selected from one or more of Pt(acac)2, K2PtCl6 and H2PtCl6; The nickel salt is selected from one or two of Ni(acac)2 and NiCl2; The polyol is one or several of ethylene glycol, glycerol, 1,2-propanediol and 1,3-propanetriol.

6. The method for preparing succinic acid by catalytic hydrogenation of maleic anhydride according to claim 1, characterized in that, In the catalytic hydrogenation reaction of maleic acid, the reaction temperature is 70 to 150 °C, the reaction pressure is 1.0 to 5.0 MPa, and the liquid hourly space velocity is 0.3 to 0.4 h -1 , and the molar ratio of hydrogen to acid is (2 to 5):

1.

7. The method for preparing succinic acid by catalytic hydrogenation of maleic anhydride according to claim 1, characterized in that, In the hydrolysis reaction of maleic anhydride, the hydrolysis temperature is 60-70 °C, the hydrolysis time is 2-3 h, and the mass concentration of maleic anhydride is 15-25%.

8. A system for preparing succinic acid by catalytic hydrogenation of maleic anhydride, characterized in that, For the method for catalytic hydrogenation of maleic anhydride to prepare succinic acid according to any one of claims 1-7 above, the system includes a hydrolysis tank, a static mixer, a hydrogenation reaction tower, a gas-liquid separator, a crystallization separation tank, a centrifuge, a dryer and a product collection tank connected in sequence through pipelines; It also includes a supplementary hydrogen compressor connected to the static mixer, a recycle hydrogen compressor arranged between the gas-liquid separator and the static mixer, and a heat exchanger arranged between the static mixer and the hydrogenation reaction tower.

9. A Ni-Pt hydrogenation catalyst, characterized in that, Applied to the method for catalytic hydrogenation of maleic anhydride to prepare succinic acid according to any one of claims 1-7 above.

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