Method for preparing succinic acid and co-producing gamma-butyrolactone through maleic anhydride hydrogenation

Abstract

The invention discloses a method for preparing gamma-butyrolactone and coproducing succinic acid through maleic anhydride hydrogenation. The invention relates to a method for producing gamma-butyrolactone and succinic acid by using maleic anhydride as a raw material through solvent-free direct catalytic hydrogenation, which is carried out in three units and comprises the following specific steps: directly hydrogenating a maleic anhydride solution, and separating to obtain high-purity gamma-butyrolactone and succinic acid products through the procedures of hydrolysis, recrystallization, extraction, rectification and the like. According to the method, the conversion rate of the raw material maleic anhydride can reach 99.9% or above, the selectivity of succinic anhydride and gamma-butyrolactone is 100%, excessive hydrogenation byproducts are avoided, the separation energy consumption is reduced, and the technological process is simplified. And the extraction agent, the extraction raffinate and the recrystallization mother liquor are all recycled, so that the energy consumption is reduced, and the equipment cost and the production cost are greatly saved. Meanwhile, the method has the advantages that the generation proportion of the gamma-butyrolactone and the succinic acid can be adjusted by changing hydrogenation reaction conditions, and the complex and changeable market requirements can be flexibly met.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical organic synthesis, and specifically relates to a new method for preparing succinic acid and co-producing gamma-butyrolactone by catalytic hydrogenation using maleic anhydride as a raw material. Background Art

[0002] Succinic acid and γ-butyrolactone (GBL) are both important organic chemical raw materials, which are widely used in the synthesis of pharmaceutical intermediates and other fine chemical products. Succinic acid is promoted and applied by the biodegradable plastic polybutylene succinate (PBS), and γ-butyrolactone is a special solvent with high conductivity. Driven by the rapid development of new energy vehicles and lithium battery industries, the demand for these two products has increased dramatically, and the planned and under-construction production capacity has grown explosively. However, the current production technology of such products is difficult, the process is complex, and the energy consumption is high.

[0003] The industrial methods for producing succinic acid include electrochemical method, biological fermentation method and maleic anhydride catalytic hydrogenation method. The early electrochemical method was more common, but it had high power consumption, easy corrosion of electrodes, easy damage of ion membranes, small electrolytic cell monomers, and was extremely unfavorable for large-scale production. Post-biological methods have gradually developed, but the efficiency of producing succinic acid by bio-based fermentation is low, there are many by-products, separation is more complicated, quality is easily affected, and the synthesis cost is high. At present, maleic anhydride catalytic hydrogenation has become the most widely used industrial method for synthesizing succinic acid. It not only has a high conversion rate and good product quality, but also has extremely advantageous raw materials.

[0004] The main methods for producing γ-butyrolactone are 1,4-butanediol dehydrogenation and maleic anhydride hydrogenation. 1,4-butanediol dehydrogenation is a traditional method for producing GBL, and the process is relatively mature. Its liquid phase hydrogenation catalyst is easily deactivated, the equipment is severely corroded, and the gas phase hydrogenation method has many problems such as complex reaction process and harsh conditions. Maleic anhydride hydrogenation methods include direct hydrogenation and esterification hydrogenation. The esterification hydrogenation method introduces alcohol, has many by-products, and a complex process flow. In comparison, the direct catalytic hydrogenation route is shorter and more economical.

[0005] Patent CN114181038B discloses a technology for the joint production of succinic anhydride and 1,4-butanediol. Since tetrahydrofuran, a deep hydrogenation product, is produced during the hydrogenation of maleic anhydride, the refining unit uses four towers for continuous distillation to achieve the separation and refining of the target product γ-butyrolactone and succinic anhydride. When the light removal tower is under a tower pressure of 10-60KPa, the tower top temperature is 120-180°C, and the tower bottom temperature is 200-250°C, γ-butyrolactone is separated from succinic anhydride, and a heavy removal tower is subsequently added to distill and purify succinic anhydride, but the purity of succinic anhydride is less than 97.3%. The entire process is cumbersome and lengthy, the equipment investment is large, and the production cost is high.

[0006] Patent CN114917897 has developed a method for producing γ-butyrolactone and succinic anhydride, and its hydrogenation catalyst has both the carbon-carbon hydrogenation performance of maleic anhydride and the carbonyl hydrogenation dehydration performance of succinic anhydride. The catalyst can effectively control the degree of hydrogenation, but the water released by the reaction will react with the incompletely converted succinic anhydride to generate succinic acid, and the process uses solvent hydrogenation with a solvent content of 50%-90%. The solvent content is large, and the hydrogenation product is a mixture of γ-butyrolactone, succinic anhydride, succinic acid and solvent. The energy consumption in the product separation and refining process is high, and the economic efficiency is not good.

[0007] Therefore, in the existing maleic anhydride hydrogenation process technology, the products are diverse with different degrees of hydrogenation, but most of them are single products or mixed products. According to the existing technology, when maleic anhydride is catalytically hydrogenated to produce γ-butyrolactone, a variety of over-hydrogenation products will be generated. There is a technology for the co-production of γ-butyrolactone and succinic anhydride. If succinic acid is produced, γ-butyrolactone and succinic anhydride need to be separated by high-temperature distillation, and then hydrolyzed to obtain succinic acid. The boiling points of the two substances are relatively high (γ-butyrolactone: 206°C, succinic anhydride: 261°C), and the succinic acid with a higher boiling point in the product needs to be dehydrated and then distilled or directly discharged as a heavy component. The refining process is long and consumes a lot of energy. At the same time, succinic anhydride is a heat-sensitive material, and the quality of the product is easily affected by high-temperature heating. If it is possible to complete the production of succinic acid and γ-butyrolactone by hydrogenation of maleic anhydride under mild conditions, and adjust the ratio of the two according to market demand, it will have better economic and social benefits.

[0008] The present invention provides a method for producing succinic acid and γ-butyrolactone by direct catalytic hydrogenation without solvent using maleic anhydride as raw material. Through a short process of maleic anhydride hydrogenation hydrolysis and then extraction, the separation of two high-boiling point and heat-sensitive substances, succinic acid and γ-butyrolactone, at low temperature is achieved, energy consumption is greatly reduced, and high-quality succinic acid products are finally obtained. By adjusting reaction parameters such as temperature and pressure, the output ratio of succinic acid and γ-butyrolactone can also be adjusted, and flexible changes can be made to cope with complex and changeable market demands, making the product more competitive. Summary of the invention

[0009] The object of the present invention is to provide a method for preparing succinic acid and γ-butyrolactone by hydrogenating maleic anhydride. The method is a method for jointly producing succinic acid and γ-butyrolactone, which solves the problems of complicated and lengthy traditional process flow and high energy consumption.

[0010] The object of the present invention is achieved as follows: A method for preparing succinic acid and γ-butyrolactone by hydrogenating maleic anhydride, characterized in that maleic anhydride is used as a raw material for solvent-free direct catalytic hydrogenation, which is divided into three units: Ⅰ. Maleic anhydride hydrogenation unit: including maleic anhydride hydrogenation device and gas-liquid separation device The melted liquid maleic anhydride enters from the top of the hydrogenation device, the hydrogenation device is filled with a catalyst, hydrogen is introduced into the bottom of the reaction device, and the gas and liquid are in countercurrent contact to carry out hydrogenation reaction; the reaction is divided into two stages, in the first stage, maleic anhydride is hydrogenated under low temperature and low pressure conditions to generate succinic anhydride, and the temperature and pressure are increased after the reaction is complete, and in the second stage, it is hydrogenated to generate γ-butyrolactone and water, and the water generated by the reaction reacts with succinic anhydride to generate succinic acid; the hydrogen pressure in the first stage is 2-3MPa, the reaction temperature is 130-140°C, and the reaction time is 3-4h, and the hydrogen pressure in the second stage is 5-6MPa, the reaction temperature is 180-220°C, and the reaction time is 5-6h; During the hydrogenation process, after the gas and liquid come into countercurrent contact, the gas phase enters the gas-liquid separation device through the gas outlet at the top of the tower. The hydrogen separated by the gas-liquid separation device is continuously sent to the bottom of the hydrogenation reaction device to participate in the reaction together with the fresh hydrogen. After the hydrogenation reaction is completed, the liquid phase directly enters the heat exchanger for cooling and is then sent to the hydrolysis device; Ⅱ. Succinic acid refining unit: including hydrolysis device, crystallization device and recrystallization device; The mixed liquid product after the second-stage hydrogenation reaction is cooled by a heat exchanger and then enters a hydrolysis device for hydrolysis, and the remaining succinic anhydride in the mixed material is completely hydrolyzed into succinic acid; The liquid phase after complete hydrolysis enters the crystallizer for cooling and crystallization; in the crystallizer, succinic acid is cooled and crystallized to separate, and the remaining liquid phase is a mixed solution of succinic acid, water, and γ-butyrolactone; the precipitated succinic acid crystals are sent to the recrystallization device again for purification; In the recrystallization device, water is used as the recrystallization solvent. The crude succinic acid product is recrystallized to obtain a high-quality succinic acid product, and the remaining dilute acid aqueous solution is sent to the hydrolysis device for reuse; III. γ-butyrolactone refining unit: including extraction device, solvent recovery tower and γ-butyrolactone distillation tower; The remaining solution after the succinic acid is separated out from the crystallizer is transported to the extraction device, and liquid-liquid extraction is performed with an extractant. After sufficient extraction, the mixed solution in the extraction device is divided into two layers, one layer is a succinic acid aqueous solution, and the other layer is γ-butyrolactone and the extractant. The mixed solution of γ-butyrolactone and the extractant is transported to a solvent recovery tower, and the succinic acid aqueous solution is returned to the hydrolysis device for recycling; The top products of the solvent recovery tower are extractant and water, which are cooled and separated and then circulated to the extraction tower to be recycled and used as extractant; the bottom of the tower is γ-butyrolactone and a small amount of high-boiling point polymer, which are transported into the γ-butyrolactone distillation tower through the bottom outlet; in the γ-butyrolactone distillation tower, after sufficient contact between gas and liquid, high-purity γ-butyrolactone is produced from the top of the tower and sent to the product tank area, and heavy component impurities are produced from the bottom of the tower and sent to the heavy oil tank area.

[0011] The object of the present invention can also be achieved as follows: in step II, the crude product after hydrogenation is cooled by a heat exchanger before hydrolysis, and the temperature after cooling is 60-140°C, preferably 80-120°C; the hydrolysis temperature is 50-90°C, preferably 60-80°C.

[0012] In the step II, the crude product after hydrogenation is cooled by a heat exchanger before hydrolysis, and the temperature after cooling is 80-120°C; the hydrolysis temperature is 60-80°C.

[0013] In the step II, in the hydrolysis device, the mass ratio of water to the mixed solution entering the hydrolysis device is 0.1 to 2:1.

[0014] In step II, the temperature of the crystallizer is 10-40°C, preferably 20-30°C.

[0015] In step II, the temperature of the crystallizer is 20-30°C.

[0016] In step II, the mass ratio of fresh water to crude succinic acid in the recrystallization device is 1-10:1. After the succinic acid enters the device, the water temperature rises to 50-90°C, preferably 70-80°C; after the succinic acid is completely dissolved, the temperature drops to 10-40°C, preferably 20-30°C.

[0017] In step II, the mass ratio of fresh water to crude succinic acid in the recrystallization device is 1-10:1, and the water temperature rises to 70-80° C. after the succinic acid enters the device; the temperature drops to 20-30° C. after the succinic acid is completely dissolved.

[0018] In the step III, the extractant is one or more of dichloromethane, chloroform, benzene, xylene, 1,2-dichloroethane, etc.; the ratio of the extractant to the liquid phase remaining after crystallization is 0.05 to 3:1, and the extraction time is 30 minutes to 2 hours.

[0019] In the step III, the solvent recovery tower is an atmospheric distillation tower with a reflux ratio of 1 to 2, a tower top temperature of 40 to 120°C, and a tower bottom temperature of 100 to 160°C.

[0020] In step III, the γ-butyrolactone distillation tower is a negative pressure distillation tower with a top pressure of 20 to 60 KPa, preferably 30 to 50 KPa; a top temperature of 150 to 200°C, preferably 160 to 180°C; a reflux ratio of 1 to 3, preferably 2; and a bottom temperature of 200 to 260°C, preferably 200 to 240°C.

[0021] In the step III, the γ-butyrolactone distillation tower is a negative pressure distillation tower, with a top pressure of 30-50 KPa, a top temperature of 160-180° C., a reflux ratio of 2, and a bottom temperature of 200-240° C.

[0022] The catalyst used in the hydrogenation device is a multi-element nickel catalyst with SiO2, Al2O3, TiO2 or activated carbon as a carrier and two or more transition elements of copper, zinc, cobalt, manganese and lanthanum, cerium, praseodymium, and neodymium as active components.

[0023] The catalyst used in the hydrogenation device is a Ni-Cu / SiO2 two-component catalyst, a Ni-Cu-Zn / Al2O3 catalyst, a Ni-Cu / Al2O3 catalyst, a Ni-Co-Ce / Al2O3 or a Ni-Co / Al2O3 two-component catalyst.

[0024] The hydrogenation device is a special equipment for maleic anhydride hydrogenation, including a power component, a reaction component and a protection component, and is characterized in that the reaction component structure is a closed reactor composed of a reactor cover and a reactor body, the reactor cover is provided with a vent, a stirrer is provided in the reactor body, and the lower stirring shaft of the stirrer is connected to the stirring shaft of the power component through a coupling; the paddles of the stirrer are installed on the lower stirring shaft in three sections, and the paddles are of a porous structure; a reaction jacket is provided outside the reactor body, and the reaction jacket is filled with heat medium steam or heat transfer oil in the reaction temperature rising and temperature control stage. When the reaction temperature exceeds the critical dangerous temperature, a solenoid valve is used to introduce a refrigerant to cool down the reaction to achieve a safe temperature control effect.

[0025] The three-stage paddle of the agitator has different air inlet sizes on each paddle. The design requirement is that, based on the rated maleic anhydride feed amount, by calculating the pressure exerted by maleic anhydride on the air inlet, each layer of the paddle can maintain balance and stability during operation, thereby promoting the stable reaction of the system.

[0026] The paddles of the stirrer are provided with catalyst filters, the pore size of which is less than or equal to 5 μm, so as to prevent small catalyst particles from entering the paddles and the shaft and causing mechanical wear.

[0027] The power assembly includes an outer rotor, an inner rotor, an inner bearing ceramic, and a stirring shaft. The outer rotor and the inner rotor are both made of multiple groups of tile-shaped rare earth permanent magnet materials. The outer rotor uses magnetic force to transmit the power of the motor to the inner rotor through a sealing cover, and then the power is transmitted to the stirring shaft by the inner rotor, thereby realizing magnetic drive without contact torque transmission. The inner rotor is sealed in the reactor sealing system by the sealing cover, and static sealing is achieved by relying on the sealing cover.

[0028] The lower support end bearing of the stirring shaft of the power assembly adopts a labyrinth seal structure.

[0029] The power assembly, the motor and the reducer adopt a direct connection structure.

[0030] The power assembly is electronically controlled with a frequency of 0-60 Hz.

[0031] The protection components include a pressure gauge, a safety manhole, a lifting lug and a blind plate. The pressure gauge is connected to a parameter interface of a control panel to monitor the pressure in the kettle in real time.

[0032] The present invention has the following beneficial effects: (1) Only one set of process equipment is required to produce two high value-added chemicals, succinic acid and γ-butyrolactone. The conversion rate of maleic anhydride can reach more than 99%. The hydrogenation product has a simple composition and few by-products. In the second stage hydrogenation, the hydrogenation product is γ-butyrolactone, and an equal mole of water is produced at the same time. Water and unreacted succinic anhydride can produce succinic acid. Therefore, the conversion rate of succinic anhydride is not required to be close to 100%. The output ratio of the two can be adjusted by changing the conditions of the catalytic hydrogenation reaction, which can flexibly adapt to complex and changing market demands.

[0033] (2) The traditional production of succinic acid and γ-butyrolactone products adopts the distillation method, which has a cumbersome process flow. In addition, the separation degree of succinic anhydride and γ-butyrolactone by distillation is low, making them difficult to separate. They are also prone to discoloration under long-term high temperature, resulting in unqualified product quality. The present invention adopts the extraction method, which avoids the occurrence of these problems and can also greatly reduce energy consumption.

[0034] (3) Compared with the traditional product refining, the residual liquid phase, extractant and residual extraction liquid after recrystallization are all recycled, which greatly improves the product yield and makes full use of energy, reducing environmental pollution.

[0035] (4) The special equipment for hydrogenation device of the present invention can quickly balance and release the energy released in the reaction process when the amount of maleic anhydride added is large and the catalyst activity is high. Its characteristics are reflected in: 1) The blades are arranged in three sections on the stirring shaft. According to the rated amount of maleic anhydride added, the size of the air inlet of each section of the blade is different. By calculating the pressure generated by maleic anhydride on the air inlet, each layer of the blade can maintain balance and stability during operation, thereby promoting the stable reaction of the system. The stirring blade is a porous structure, which allows the gas to better contact with the liquid maleic anhydride as the blade moves, thereby achieving a faster reaction rate. 2) A reaction jacket is added outside the reactor, and a water inlet and a water outlet are set. During the reaction, low-pressure steam is introduced to keep the temperature, and the valve is cut off when the temperature is over-temperature, and cooling water is introduced to cool down to ensure the safety of the reaction. 3) According to the current situation that the catalyst particles used are small, a catalyst filter is arranged on the blade, and its pore size is less than or equal to 5μm, which can prevent small catalyst particles from entering the blade and the shaft to cause mechanical wear, thereby protecting the equipment. 4) The power assembly uses multiple groups of tile-shaped rare earth permanent magnet materials to form an inner rotating body and an outer rotating body, and uses magnetic force to transmit power through the sealing cover. The inner rotating body is sealed in the reactor sealing system by the sealing cover and rotates synchronously with the outer rotating body. The equipment relies on the sealing cover to achieve static sealing. Due to the use of static sealing, it achieves high pressure resistance, zero leakage and no pollution. At the same time, magnetic drive belongs to non-contact torque transmission, which can effectively avoid overload, vibration and other phenomena, and effectively protect the equipment. 5) The structural design adopts the direct connection method between the motor and the reducer and the power assembly. The whole machine has a compact and reasonable structure, a large stirring torque, stable and reliable operation, and low vibration and noise. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a process flow chart for the co-production of γ-butyrolactone and succinic acid in Example 2 of the present invention.

[0037] Ⅰ. Maleic anhydride hydrogenation unit, Ⅱ. Succinic acid refining unit, Ⅲ. γ-butyrolactone refining unit.

[0038] Markings in the figure: a, hydrogenation reaction unit, b, gas-liquid separation unit, c, heat exchanger, d, hydrolysis unit, e, crystallizer, f, recrystallization unit, g, extraction unit, h, solvent recovery tower, j, γ-butyrolactone distillation tower.

[0039] Figure 2 This is a schematic diagram of the structure of special equipment for hydrogenation reaction unit.

[0040] Figure 3 This is a schematic diagram of the power component structure of the special equipment for the hydrogenation reaction unit.

[0041] Markings in the figure: Power assembly 1: including outer rotating body 11, inner rotating body 12, cooling water joint 13, inner bearing ceramic 14, stirring shaft 15; Reaction assembly 2: including kettle cover 21, coupling 22, lower stirring shaft 23, cooling pipe 24, paddle 25, kettle body 26, reaction jacket 27, vent 28; Protection component 3: includes a pressure gauge 31, a safety manhole 32, a lifting lug 33, and a blind plate 34. DETAILED DESCRIPTION Example 1

[0042] The molten liquid maleic anhydride enters from the top of the hydrogenation device (a), which is filled with a Ni-Cu / SiO2 two-component catalyst. Hydrogen is introduced into the bottom of the reaction device (a), and the gas and liquid are contacted in countercurrent to carry out the hydrogenation reaction. The conditions for the first stage hydrogenation reaction are: hydrogen pressure 2.0MPa, reaction temperature 140℃, reaction time 3h, temperature and pressure increase after the reaction, and the conditions for the second stage hydrogenation reaction are hydrogen pressure 6MPa, reaction temperature 190℃, and reaction time 5h. After the reaction, the γ-butyrolactone content was 20.08%, succinic anhydride 65.86%, and succinic acid 13.33%.

[0043] During the hydrogenation process, the gas phase enters the gas-liquid separation device (b) through the gas outlet at the top of the tower after the gas-liquid countercurrent contact. The hydrogen separated by the gas-liquid separation device is continuously sent to the bottom of the hydrogenation reaction device to participate in the reaction with fresh hydrogen. After the hydrogenation reaction is completed, the separated γ-butyrolactone, succinic anhydride, and succinic acid mixed product is cooled to 110°C by a heat exchanger and then transported to the hydrolysis device (d).

[0044] In the hydrolysis device, the mass ratio of water to the mixed material entering the hydrolysis device is 1:1, and the hydrolysis temperature is 80° C. After the hydrolysis is complete, the mixed solution of succinic acid and γ-butyrolactone enters the crystallizer (e).

[0045] The temperature of the crystallizer (e) is 25°C. After saturated precipitation of succinic acid, it is sent to the recrystallization device (f) for recrystallization and purification. The remaining low-concentration succinic acid aqueous solution and gamma-butyrolactone in the crystallizer are sent to the extraction device (g).

[0046] In the recrystallization device (f), the mass ratio of fresh water to crude succinic acid product is 2:1. After succinic acid is completely dissolved in the recrystallization device at a water temperature of 70°C, it is stirred and cooled to 25°C to crystallize. After crystallization and drying, high-quality succinic acid is obtained. The remaining dilute acid aqueous solution is sent to the hydrolysis device (d) for reuse.

[0047] The extractant in the extraction device (g) is dichloromethane, which enters from the top of the extraction tower, and the liquid phase separated from the solid-liquid separation in the crystallizer enters from the bottom of the tower. The extraction time is 30 minutes, and the ratio of the extractant to the mixed solution is 1:6. After the extraction is completed, the upper layer of the succinic acid aqueous solution is pumped into the hydrolysis device for recycling, and the lower layer of the extractant and γ-butyrolactone enter the solvent recovery tower (h).

[0048] In the solvent recovery tower, dichloromethane and water are produced at the top of the tower, which are returned to the extraction tower for recycling after cooling, and γ-butyrolactone and a small amount of high-boiling polymer are separated in the bottom of the tower. The liquid phase in the bottom of the tower is transported to the γ-butyrolactone distillation tower (j). The operating pressure of the solvent recovery tower is atmospheric pressure, the top temperature is 40°C, the reflux ratio is 2, and the bottom temperature is 100°C.

[0049] In the γ-butyrolactone distillation tower, high-purity γ-butyrolactone products are taken out from the top, cooled and transported to the product tank area, and heavy components are taken out from the bottom of the tower and sent to the outside for treatment. The pressure of the γ-butyrolactone distillation tower is 50kPa, the top temperature is 180℃, the reflux ratio is 2, and the bottom temperature is 240℃. Example 2

[0050] Succinic acid and γ-butyrolactone were synthesized from molten liquid maleic anhydride, with the same steps as in Example 1, and a catalyst with a carrier of Ni-Cu-Zn / Al2O3 was installed in the hydrogenation device. The first stage hydrogenation reaction conditions were: hydrogen pressure of 3.0 MPa, reaction temperature of 130°C, reaction time of 3 hours, and temperature and pressure were increased after the reaction. The second stage hydrogenation reaction conditions were: hydrogen pressure of 5 MPa, reaction temperature of 200°C, and reaction time of 5 hours. After the reaction, the content of γ-butyrolactone was 34.33%, succinic anhydride was 37.48%, and succinic acid was 27.29%.

[0051] After hydrogenation, the temperature is cooled to 100℃ by the heat exchanger and then transported to the hydrolysis device. The mass ratio of water to the mixed material entering the hydrolysis device is 1:1. After entering the crystallizer, the temperature drops to 20℃, and the mass ratio of fresh water added to the recrystallization device to the crude succinic acid product is 2:1. Succinic acid is completely dissolved in the recrystallization device at a water temperature of 70℃ and then stirred and cooled to 20℃ for crystallization. The extraction solvent in the extraction device is 1,2-dichloroethane, the ratio of the extractant to the mixed solution is 1:3, and the extraction time is 1h. The operating pressure of the solvent recovery tower is atmospheric pressure, the top temperature is 90℃, the reflux ratio is 2, and the bottom temperature is 140℃. The pressure of the γ-butyrolactone distillation tower is 45kPa, the top temperature is 170℃, the reflux ratio is 2, and the bottom temperature is 220℃. Example 3

[0052] Succinic acid and γ-butyrolactone were synthesized from molten liquid maleic anhydride, with the same steps as in Example 1. The hydrogenation device was equipped with a Ni-Cu / Al2O3 catalyst as a carrier. The first stage hydrogenation reaction conditions were: hydrogen pressure of 2.5 MPa, reaction temperature of 140°C, reaction time of 4 hours, and temperature and pressure were increased after the reaction. The second stage hydrogenation reaction conditions were: hydrogen pressure of 6 MPa, reaction temperature of 210°C, and reaction time of 6 hours. After the reaction, the γ-butyrolactone content was 49.19%, succinic anhydride 26.88%, and succinic acid 23.23%.

[0053] After hydrogenation, the temperature is cooled to 90℃ by the heat exchanger and then transported to the hydrolysis unit. The mass ratio of water to the mixed material entering the hydrolysis unit is 1:1. The temperature after entering the crystallizer is 25℃, and the mass ratio of fresh water added to the crude succinic acid product entering the recrystallization unit is 7:4. Succinic acid is completely dissolved in the recrystallization unit at a water temperature of 80℃ and then stirred and cooled to 25℃ for crystallization. The extraction solvent in the extraction tower is benzene, the ratio of the extractant to the mixed solution is 3:2, and the extraction time is 30min. The liquid phase separated in the crystallizer enters from the top of the tower, and benzene enters from the bottom. After being fully mixed and evenly layered, the extractant and water at the top of the tower enter the solvent recovery tower, and the succinic acid aqueous solution in the bottom of the tower is returned to the hydrolysis unit for recycling. The operating pressure of the solvent recovery tower is normal pressure, the top temperature is 85℃, the reflux ratio is 2, and the bottom temperature is 130℃. The pressure of the γ-butyrolactone distillation tower is 40 kPa, the top temperature is 170°C, the reflux ratio is 2, and the bottom temperature is 220°C. Example 4

[0054] Succinic acid and γ-butyrolactone were synthesized from molten liquid maleic anhydride, with the same steps as in Example 1, and a Ni-Co-Ce / Al2O3 catalyst as the carrier was installed in the hydrogenation device. The first-stage hydrogenation reaction conditions were: hydrogen pressure of 3.0 MPa, reaction temperature of 130°C, reaction time of 4 hours, and temperature and pressure were increased after the reaction. The second-stage hydrogenation reaction conditions were: hydrogen pressure of 5 MPa, reaction temperature of 220°C, and reaction time of 6 hours. After the reaction, the γ-butyrolactone content was 67.81%, succinic anhydride was 14.83%, and succinic acid was 16.51%.

[0055] After hydrogenation, the temperature is cooled to 80℃ by the heat exchanger and then transported to the hydrolysis device. The mass ratio of water to the mixed material entering the hydrolysis device is 1:4. The temperature after entering the crystallizer is 30℃, and the mass ratio of fresh water added to the recrystallization device to the crude succinic acid product is 5:3. Succinic acid is completely dissolved in the recrystallization device at a water temperature of 80℃ and then stirred and cooled to 30℃ for crystallization. The extraction solvent in the extraction device is chloroform, the ratio of the extractant to the mixed solution is 1:1, and the extraction time is 1.5h. The operating pressure of the solvent recovery tower is atmospheric pressure, the top temperature is 70℃, the reflux ratio is 1, and the bottom temperature is 120℃. The pressure of the γ-butyrolactone distillation tower is 30kPa, the top temperature is 160℃, the reflux ratio is 2, and the bottom temperature is 200℃. Example 5

[0056] When only succinic acid is produced, the process is as follows: The molten liquid maleic anhydride is transported to a hydrogenation reaction device (1). The catalyst in the hydrogenation device is a two-component catalyst with a carrier of Ni-Co / Al2O3. Hydrogen is introduced into the catalyst. After the catalyst contacts and reacts completely under certain reaction conditions, the catalyst enters a gas-liquid separation device (2). The reaction conditions are: hydrogen pressure 2.5MPa, reaction temperature 140°C, and reaction time 4h. After the reaction is completed, the maleic anhydride conversion rate is 99.9% and the succinic anhydride selectivity is 99.98%.

[0057] The hydrogen separated by the gas-liquid separation device (3) is recycled and enters the hydrogenation device together with fresh hydrogen to participate in the reaction. The liquid phase after the hydrogenation is cooled to 120° C. by a heat exchanger and then transported to the hydrolysis device (4).

[0058] In the hydrolysis unit, succinic anhydride is completely hydrolyzed into succinic acid, and the mass ratio of water to hydrogenation reaction liquid is 3:2. After the hydrolysis is complete, the solution is sent to the crystallizer (5).

[0059] In the crystallizer (5), succinic acid is cooled and saturated and precipitated. The temperature of the crystallizer is 20°C. After succinic acid is saturated and precipitated, the precipitated crystals are sent to the recrystallizer (6). The low-concentration succinic acid aqueous solution remaining in the crystallizer (5) can be reused as a hydrolyzate.

[0060] In the recrystallization device (6), succinic acid is completely dissolved in the recrystallization device at a water temperature of 80°C and then stirred and cooled to 20°C for crystallization. The product quality is further improved, and high-quality succinic acid is obtained after crystallization and drying.

[0061] The results of each embodiment are shown in Table 1:

[0062] From the above examples, it can be seen that under different catalysts and reaction conditions, the co-production of succinic acid and γ-butyrolactone is achieved, and the product proportion can be adjusted. The purity of succinic acid refined by this process is ≥99.8%, and the purity of γ-butyrolactone is ≥99.5%. After the remaining dilute acid aqueous solution and the residual extraction liquid after recrystallization are recycled and reused multiple times, the total yield of succinic acid and γ-butyrolactone will be greatly improved.

[0063] In the hydrogenation process, maleic anhydride is added in large amounts, and the catalyst is highly active. The hydrogenation reaction is a highly exothermic reaction, so it is necessary to balance and release the energy released during the reaction. Based on this, the present invention designs a special device for hydrogenation, which adopts a three-stage (or three-stage) blade structure. According to the rated maleic anhydride addition amount, the air inlet size of each stage of the blade is different. By calculating the pressure generated by maleic anhydride on the air inlet, each layer of the blade can maintain balance and stability during operation, thereby promoting the stable reaction of the system and ensuring the stability of hydrogenation at all depths in the kettle. A jacket is added to the outer layer of the reactor, and a water inlet and a water outlet are set. During the reaction, low-pressure steam is introduced for heat preservation, and when the temperature is over-temperature, the valve is cut off to introduce cooling water for cooling to ensure the safety of the reaction. According to the conditions of the existing catalyst, the present invention is provided with a catalyst filter on the blade, and its pore size is <= 5μm, which can prevent small catalyst particles from entering the blade and the shaft to cause mechanical wear, thereby protecting the equipment.

[0064] Figure 2 , Figure 3 The structure diagram of the special equipment for hydrogenation of maleic anhydride includes a power assembly 1 (also called a magnetic seal stirring assembly), a reaction assembly 2, and a protection assembly 3. The magnetic seal stirring assembly includes an outer rotating body 11, an inner rotating body 12, a cooling water joint 13, an inner bearing ceramic 14, and a stirring shaft 15. The reaction assembly includes a kettle cover 21, a coupling 22, a lower stirring shaft 23, a cooling pipe 24, a paddle 25, a kettle body 26, a reaction jacket 27, and a vent 28. The protection assembly 3 includes a pressure gauge 31, a safety manhole 32, a lifting lug 33, and a blind plate 34. The magnetic sealing stirring assembly is controlled by an electric control with a frequency of 0-60Hz. The kettle cover 21 is provided with three air holes for ventilation 28, which are mainly used for introducing nitrogen and hydrogen and connecting the vent pipe. The lifting lug 33 is used to fix the equipment on the steel platform to protect the stability of the equipment. The paddle 25 of the stirrer is a porous structure, which is more conducive to the dispersion of gas in the liquid. There are four external flange ports on the reaction jacket 27, which can realize the control of reaction insulation and the connection of the solenoid valve to control the coolant. When the reaction temperature exceeds the set dangerous value, the cut-off valve controls the addition of coolant for forced circulation to reduce the temperature in the reactor and avoid over-temperature accidents.

[0065] The reaction assembly structure is a closed reaction kettle composed of a kettle cover 21 and a kettle body 26. The kettle cover 21 is provided with a vent 28. The kettle body 26 is provided with a stirrer. The lower stirring shaft 23 of the stirrer is connected to the stirring shaft 15 of the power assembly through a coupling 22. The paddle 25 of the stirrer is installed on the lower stirring shaft 23 in three sections. The paddle 25 is a porous structure. A reaction jacket 27 is provided outside the kettle body 26. The reaction jacket 27 is filled with heat medium steam or heat transfer oil during the reaction temperature rise and temperature control stage. When the reaction temperature exceeds the critical dangerous temperature, the solenoid valve is used to cool down the reaction medium to achieve the effect of safe temperature control. The three-section paddle 25 of the stirrer has different air inlet sizes. The design requirement is that, according to the rated maleic anhydride feed amount, by calculating the pressure generated by maleic anhydride on the air inlet, each layer of the paddle can maintain balance and stability during operation, thereby promoting the stable reaction of the system. The impeller 25 of the agitator is provided with a catalyst filter, the pore size of which is less than or equal to 5 μm, to prevent small catalyst particles from entering the impeller and the shaft and causing mechanical wear.

[0066] The power assembly includes an outer rotor 11, an inner rotor 12, an inner bearing ceramic 14, and a stirring shaft 15. The outer rotor 11 and the inner rotor 12 are both made of multiple sets of tile-shaped rare earth permanent magnet materials. The outer rotor 11 uses magnetic force to transmit the power of the motor to the inner rotor 12 through the sealing cover, and then the inner rotor 12 transmits it to the stirring shaft 15, realizing magnetic drive without contact torque transmission; the inner rotor 12 is sealed in the reactor sealing system by the sealing cover, and static sealing is achieved by the sealing cover. The lower support end bearing of the stirring shaft 15 of the power assembly adopts a labyrinth seal structure. The power assembly adopts a direct connection structure with the motor and the reducer. The power assembly is controlled by an electronic control with a frequency of 0-60Hz.

[0067] The protection assembly includes a pressure gauge 31, a safety manhole 32, a lifting lug 33 and a blind plate 34. The pressure gauge 31 is connected to the parameter interface of the control panel to monitor the pressure in the kettle in real time.

[0068] The working process is as follows: the maleic anhydride raw material is transported to the reactor through a metering pump through a pipeline, the catalyst in the required proportion is added through the safety manhole 32, the nitrogen is replaced 3 times through the nitrogen inlet and outlet, and then the hydrogen is replaced 3 times through the hydrogen inlet and outlet, steam is introduced into the reaction jacket 27 to heat the reaction system, and after reaching the target temperature, the magnetic sealing stirring component 1 is started, and after setting the corresponding frequency of 50 HZ, hydrogen is introduced to the set pressure to start the reaction; after a period of reaction according to the process requirements, the reaction liquid is transported to the next process after sampling and analysis. During this period, the relevant parameters of the protection component 3 are monitored through the control panel and necessary adjustments are made according to the situation. Because the catalyst used in the new process of direct catalytic hydrogenation of maleic anhydride without solvent is a small granular catalyst with a d<50μm, a catalyst filter with a pore size of <=5μm is set on the blade to prevent small catalyst particles from entering the blade and shaft to cause mechanical wear, thereby protecting the equipment.

[0069] The pressure gauge 31 on the reactor is connected to the parameter interface of the control panel to monitor the pressure in the reactor in real time to prevent overpressure accidents. There are emergency shut-off valves and bypasses on the air inlet pipeline on the reactor. When the temperature or pressure in the equipment exceeds the limit, the solenoid valve works to control the stop of the continued entry of hydrogen and the external control reaction to achieve safer use. At the same time, there are four external flange ports on the reaction jacket, which can realize the left and right of the reaction insulation and connect the solenoid valve to control the coolant. When the reaction temperature exceeds the set dangerous value, the shut-off valve controls the addition of coolant for forced circulation to reduce the temperature in the reactor and avoid overheating accidents.

[0070] The present invention realizes a conversion rate of maleic anhydride as high as 99.9% or more, and the selectivity of succinic anhydride and γ-butyrolactone is 100%, no excessive hydrogenation byproducts are generated, separation energy consumption is reduced, and the process flow is simplified. The extractant, the residual extraction liquid, and the recrystallization mother liquor are all recycled, which reduces energy consumption and greatly saves equipment cost and production cost. At the same time, the advantages of the present invention can also adjust the generation ratio of γ-butyrolactone and succinic acid by changing the hydrogenation reaction conditions, and flexibly adapt to complex and changeable market demands.

[0071] The protection scope of the present invention is not limited to the above-mentioned implementation modes. The above-mentioned embodiments are only partial examples of the present invention and do not limit the protection scope of the present invention. Any modification and equivalent replacement made by using the same process route as the above-mentioned embodiments shall fall within the protection scope of the present invention.

Claims

1. A method for preparing succinic acid and γ-butyrolactone by hydrogenating maleic anhydride, characterized in that: Solvent-free direct catalytic hydrogenation of maleic anhydride is carried out in three units: Ⅰ. Maleic anhydride hydrogenation unit: including maleic anhydride hydrogenation device and gas-liquid separation device; The melted liquid maleic anhydride enters from the top of the hydrogenation device, the hydrogenation device is filled with a catalyst, hydrogen is introduced into the bottom of the reaction device, and the gas and liquid are in countercurrent contact to carry out a hydrogenation reaction; the reaction is divided into two stages, in the first stage, maleic anhydride is hydrogenated under low temperature and low pressure conditions to generate succinic anhydride, and the temperature and pressure are increased after the reaction is complete, and in the second stage, it is hydrogenated to generate γ-butyrolactone and water, and the water generated by the reaction reacts with succinic anhydride to generate succinic acid; the hydrogen pressure in the first stage is 2-3 MPa, the reaction temperature is 130-140°C, and the reaction time is 3-4h, and the hydrogen pressure in the second stage is 5-6 MPa, the reaction temperature is 180-220°C, and the reaction time is 5-6h; During the hydrogenation process, after the gas and liquid come into countercurrent contact, the gas phase enters the gas-liquid separation device through the gas outlet at the top of the tower. The hydrogen separated by the gas-liquid separation device is continuously sent to the bottom of the hydrogenation reaction device to participate in the reaction together with the fresh hydrogen. After the hydrogenation reaction is completed, the liquid phase directly enters the heat exchanger for cooling and is then sent to the hydrolysis device; Ⅱ. Succinic acid refining unit: including hydrolysis device, crystallization device and recrystallization device; The mixed liquid product after the second-stage hydrogenation reaction is cooled by a heat exchanger and then enters a hydrolysis device for hydrolysis, and the remaining succinic anhydride in the mixed material is completely hydrolyzed into succinic acid; The liquid phase after complete hydrolysis enters the crystallizer for cooling and crystallization; in the crystallizer, succinic acid is cooled and crystallized to separate, and the remaining liquid phase is a mixed solution of succinic acid, water, and γ-butyrolactone; the precipitated succinic acid crystals are sent to the recrystallization device again for purification; In the recrystallization device, water is used as the recrystallization solvent. The crude succinic acid product is recrystallized to obtain a high-quality succinic acid product, and the remaining dilute acid aqueous solution is sent to the hydrolysis device for reuse; III. γ-butyrolactone refining unit: including extraction device, solvent recovery tower and γ-butyrolactone distillation tower; The remaining solution after the succinic acid is separated out from the crystallizer is transported to the extraction device, and liquid-liquid extraction is performed with an extractant. After sufficient extraction, the mixed solution in the extraction device is divided into two layers, one layer is a succinic acid aqueous solution, and the other layer is γ-butyrolactone and the extractant. The mixed solution of γ-butyrolactone and the extractant is transported to a solvent recovery tower, and the succinic acid aqueous solution is returned to the hydrolysis device for recycling; The top products of the solvent recovery tower are extractant and water, which are cooled and separated and then circulated to the extraction tower to be recycled and used as extractant; the bottom of the tower is γ-butyrolactone and a small amount of high-boiling point polymer, which are transported into the γ-butyrolactone distillation tower through the bottom outlet; in the γ-butyrolactone distillation tower, after sufficient contact between gas and liquid, high-purity γ-butyrolactone is produced from the top of the tower and sent to the product tank area, and heavy component impurities are produced from the bottom of the tower and sent to the heavy oil tank area.

2. The method for preparing succinic acid and γ-butyrolactone by hydrogenating maleic anhydride according to claim 1, characterized in that: In the step II, the crude product after hydrogenation is cooled by a heat exchanger before hydrolysis, the temperature after cooling is 60-140°C, and the hydrolysis temperature is 50-90°C.

3. The method for preparing succinic acid and γ-butyrolactone by hydrogenating maleic anhydride according to claim 2, characterized in that: In the step II, the crude product after hydrogenation is cooled by a heat exchanger before hydrolysis, and the temperature after cooling is 80-120°C; the hydrolysis temperature is 60-80°C.

4. The method for preparing succinic acid and γ-butyrolactone by hydrogenating maleic anhydride according to claim 1, 2 or 3, characterized in that: In the step II, in the hydrolysis device, the mass ratio of water to the mixed solution entering the hydrolysis device is 0.1 to 2:

1.

5. The method for preparing succinic acid and γ-butyrolactone by hydrogenating maleic anhydride according to claim 1, characterized in that: In step II, the temperature of the crystallizer is 10-40°C.

6. The method for preparing succinic acid and γ-butyrolactone by hydrogenating maleic anhydride according to claim 5, characterized in that: In step II, the temperature of the crystallizer is 20-30°C.

7. The method for preparing succinic acid and γ-butyrolactone by hydrogenating maleic anhydride according to claim 1, 2 or 3, characterized in that: In step II, the temperature of the crystallizer is 10-40°C.

8. The method for preparing succinic acid and γ-butyrolactone by hydrogenating maleic anhydride according to claim 1, characterized in that: In step II, the mass ratio of fresh water to crude succinic acid in the recrystallization device is 1-10:1, and the water temperature rises to 50-90° C. after the succinic acid enters the device; the temperature drops to 10-40° C. after the succinic acid is completely dissolved.

9. The method for preparing succinic acid and γ-butyrolactone by hydrogenating maleic anhydride according to claim 8, characterized in that: In step II, the mass ratio of fresh water to crude succinic acid in the recrystallization device is 1-10:1, and the water temperature rises to 70-80° C. after the succinic acid enters the device; the temperature drops to 20-30° C. after the succinic acid is completely dissolved.

10. The method for preparing succinic acid and γ-butyrolactone by hydrogenating maleic anhydride according to claim 1, characterized in that: In the step III, the extractant is one or more of dichloromethane, chloroform, benzene, xylene, 1,2-dichloroethane, etc.; the ratio of the extractant to the liquid phase remaining after crystallization is 0.05 to 3:1, and the extraction time is 30 minutes to 2 hours.

11. The method for preparing succinic acid and γ-butyrolactone by hydrogenating maleic anhydride according to claim 1 or 10, characterized in that: In the step III, the solvent recovery tower is an atmospheric distillation tower with a reflux ratio of 1 to 2, a tower top temperature of 40 to 120°C, and a tower bottom temperature of 100 to 160°C.

12. The method for preparing succinic acid and γ-butyrolactone by hydrogenating maleic anhydride according to claim 1 or 10, characterized in that: In the step III, the γ-butyrolactone distillation tower is a negative pressure distillation tower, with a top pressure of 20 to 60 KPa, a top temperature of 150 to 200° C., a reflux ratio of 1 to 3, and a bottom temperature of 200 to 260° C.

13. The method for preparing succinic acid and γ-butyrolactone by hydrogenating maleic anhydride according to claim 12, characterized in that: In the step III, the γ-butyrolactone distillation tower is a negative pressure distillation tower, with a top pressure of 30-50 KPa, a top temperature of 160-180° C., a reflux ratio of 2, and a bottom temperature of 200-240° C.

14. The method for preparing succinic acid and γ-butyrolactone by hydrogenating maleic anhydride according to claim 1, characterized in that: The catalyst used in the hydrogenation device is a multi-element nickel catalyst with SiO2, Al2O3, TiO2 or activated carbon as a carrier and two or more transition elements of copper, zinc, cobalt, manganese and lanthanum, cerium, praseodymium, and neodymium as active components.

15. The method for preparing succinic acid and γ-butyrolactone by hydrogenating maleic anhydride according to claim 14, characterized in that: The catalyst used in the hydrogenation device is a Ni-Cu / SiO2 two-component catalyst, a Ni-Cu-Zn / Al2O3 catalyst, a Ni-Cu / Al2O3 catalyst, a Ni-Co-Ce / Al2O3 or a Ni-Co / Al2O3 two-component catalyst.

16. A method for preparing succinic acid and γ-butyrolactone by hydrogenating maleic anhydride, characterized in that: The hydrogenation device is a special equipment for maleic anhydride hydrogenation, including a power component, a reaction component and a protection component, and is characterized in that the reaction component structure is a closed reactor composed of a reactor cover and a reactor body, the reactor cover is provided with a vent, a stirrer is provided in the reactor body, and the lower stirring shaft of the stirrer is connected to the stirring shaft of the power component through a coupling; the paddles of the stirrer are installed on the lower stirring shaft in three sections, and the paddles are of a porous structure; a reaction jacket is provided outside the reactor body, and the reaction jacket is filled with heat medium steam or heat transfer oil in the reaction temperature rising and temperature control stage. When the reaction temperature exceeds the critical dangerous temperature, a solenoid valve is used to introduce a refrigerant to cool down the reaction to achieve a safe temperature control effect.

17. The method for preparing succinic acid and γ-butyrolactone by hydrogenating maleic anhydride according to claim 16, characterized in that: The three-stage paddle of the agitator has different air inlet sizes on each paddle. The design requirement is that, based on the rated maleic anhydride feed amount, by calculating the pressure exerted by maleic anhydride on the air inlet, each layer of the paddle can maintain balance and stability during operation, thereby promoting the stable reaction of the system.

18. The method for preparing succinic acid and γ-butyrolactone by hydrogenating maleic anhydride according to claim 17, characterized in that: The paddles of the stirrer are provided with catalyst filters, the pore size of which is less than or equal to 5 μm, so as to prevent small catalyst particles from entering the paddles and the shaft and causing mechanical wear.

19. The method for preparing succinic acid and γ-butyrolactone by hydrogenating maleic anhydride according to claim 17, characterized in that: The power assembly includes an outer rotor, an inner rotor, an inner bearing ceramic, and a stirring shaft. The outer rotor and the inner rotor are both made of multiple groups of tile-shaped rare earth permanent magnet materials. The outer rotor uses magnetic force to transmit the power of the motor to the inner rotor through a sealing cover, and then the power is transmitted to the stirring shaft by the inner rotor, thereby realizing magnetic drive without contact torque transmission. The inner rotor is sealed in the reactor sealing system by the sealing cover, and static sealing is achieved by relying on the sealing cover.

20. The method for preparing succinic acid and γ-butyrolactone by hydrogenating maleic anhydride according to claim 19, characterized in that: The lower support end bearing of the stirring shaft of the power assembly adopts a labyrinth seal structure.

21. The method for preparing succinic acid and γ-butyrolactone by hydrogenating maleic anhydride according to claim 19, characterized in that: The power assembly, the motor and the reducer adopt a direct connection structure.

22. The method for preparing succinic acid and γ-butyrolactone by hydrogenating maleic anhydride according to claim 19, characterized in that: The power assembly is electronically controlled with a frequency of 0-60 Hz.

23. The method for preparing succinic acid and γ-butyrolactone by hydrogenating maleic anhydride according to claim 16, characterized in that: The protection components include a pressure gauge, a safety manhole, a lifting lug and a blind plate. The pressure gauge is connected to a parameter interface of a control panel to monitor the pressure in the kettle in real time.

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