Process for the production of succinic acid and system for the production of succinic acid

Abstract

The present application relates to a kind of maleic anhydride as raw material, system and method for producing succinic acid by hydrogenation.The present application uses two-stage hydrogenation reactor, maleic anhydride solution is divided into two materials, one is mixed with the liquid phase material of two-stage reaction part, then enters the first hydrogenation reactor from the upper part of the reactor, the other is mixed with the liquid phase material of first-stage reaction, then enters the second hydrogenation reactor from the upper part of the reactor, after two-stage hydrogenation reaction, maleic anhydride is completely converted into succinic anhydride, then after light removal, heavy removal, hydrolysis-crystallization, the succinic acid product meeting the requirements is obtained.The method of the present application can effectively remove the heat released during reaction, operation is flexible, easy to control, and the utilization rate of catalyst is high, at the same time, the concentration of maleic anhydride in the incoming maleic anhydride solution can not be too low, which reduces the amount of solvent used, and reduces the energy consumption of subsequent solvent recovery.The process and method of the present application have the characteristics of simple process, low investment, strong applicability and easy control.

Description

TECHNICAL FIELD

[0001] The present application relates to a liquid phase hydrogenation reaction process of maleic anhydride, further relates to a process and method for producing succinic acid by hydrogenation of maleic anhydride, more particularly includes a method for preparing succinic acid and a system for preparing succinic acid. BACKGROUND

[0002] Succinic acid, commonly known as succinic acid, is a colorless crystal with a relative density of 1.572 (25 / 4℃), a melting point of 188℃, and a decomposition temperature of 235℃. It is soluble in water, ethanol, and diethyl ether, but insoluble in carbon disulfide and carbon tetrachloride. It is a common natural organic acid widely found in humans, animals, plants, and microorganisms. Succinic acid is an important organic chemical raw material and intermediate, widely used in the synthesis of plastics, rubber, medicine, food, paint, and other industries. The current global annual production of succinic acid is only 30-50 thousand tons, and due to its potential as a monomer for producing biodegradable polymers, its market demand is likely to grow to the million-ton level.

[0003] The main production methods of succinic acid are biological fermentation, electrolytic reduction, and maleic anhydride catalytic hydrogenation. Currently, there are more than ten succinic acid production enterprises in China, most of which use electrolytic reduction process, and the production scale is not large. In addition, the electrolytic reduction process has many problems to be solved, such as high power consumption, severe electrode corrosion, difficult electrolytic tank maintenance, and not suitable for large-scale production. The domestic fermentation method for preparing succinic acid started late, the process is complicated, the wastewater discharge is large, the production and separation cost is high, and it has not been applied to actual production. Industrially, succinic acid is mainly prepared by hydrogenation of petroleum-based maleic anhydride (maleic acid or fumaric acid), and the catalyst used is nickel or noble metal, with a reaction temperature of about 130-140℃.

[0004] In the process of preparing succinic acid by hydrogenation and hydrolysis of maleic anhydride, the preparation of succinic anhydride by hydrogenation of maleic anhydride is the first section, and the hydrolysis of succinic anhydride to succinic acid is the second section. However, the hydrogenation of maleic anhydride to succinic anhydride is a strong exothermic reaction (ΔH = -128 kJ / mol), and the reaction temperature of the catalyst bed is difficult to control. Therefore, it is urgent to develop a maleic anhydride hydrogenation reaction process to effectively remove the heat released during the reaction.

[0005] CN101735182A discloses a process for continuous production of succinic anhydride by hydrogenation of maleic anhydride. By a certain split ratio, part of the reaction liquid is fed into a rectification tower to obtain product succinic anhydride and solvent, and the remaining liquid is mixed with maleic anhydride solution and then fed into the reactor. The reduction of maleic anhydride concentration by returning the liquid can achieve the effect of heat removal, but the liquid product returned contains impurities generated by the reaction, and the long-term accumulation of impurities through the catalyst bed can easily lead to the deactivation of supported nickel catalyst, reducing the service life of the catalyst.

[0006] US2245404(A) discloses a method for removing the heat of reaction of maleic anhydride hydrogenation by using built-in heat exchange tubes to control the temperature rise of the catalyst bed. The heat removal tubes cannot remove the reaction heat uniformly, and also affect the distribution of the reaction liquid in the reactor, thereby affecting the reaction performance of the catalyst. Therefore, this method is not suitable for removing the reaction heat of a large-scale reaction device. SUMMARY

[0007] The present application is to solve the problems in the prior art, such as large heat release of maleic anhydride hydrogenation, difficult heat removal, large production process investment, high energy consumption, etc. A new process and method for continuously producing succinic acid from maleic anhydride hydrogenation are provided, which has the characteristics of easy removal of reaction heat, low investment and low energy consumption.

[0008] The present application provides the following method:

[0009] (1) The maleic anhydride solution is divided into two streams, one of which is mixed with part of the liquid phase material of the second reaction and then enters the first hydrogenation reactor from the upper part of the reactor, and the other is mixed with the liquid phase material of the first reaction and then enters the second hydrogenation reactor from the upper part of the reactor.

[0010] (2) The circulating hydrogen gas is mixed with the fresh hydrogen gas supplement and then enters the first hydrogenation reactor from the top of the reactor to react with the maleic anhydride, converting all / partial maleic anhydride hydrogenation reaction to succinic anhydride.

[0011] (3) The first hydrogenation product is first cooled by a cooler, then separated by a gas-liquid separator, and the gas phase is all introduced into the second hydrogenation reactor from the top, and the liquid phase is mixed with part of the maleic anhydride solution and then introduced into the second hydrogenation reactor from the upper part of the reactor to react with hydrogen gas, converting all maleic anhydride to succinic anhydride.

[0012] (4) The second hydrogenation reaction product is separated by gas-liquid separation, the gas phase is cooled to the reaction temperature by heat exchange and then circulated to step (2) to be mixed with the fresh hydrogen gas supplement and then introduced into the first hydrogenation reactor from the top. Part of the liquid phase is removed to a light removal tower, and part is cooled and then mixed with the maleic anhydride solution and introduced into the first hydrogenation reactor from the upper part of the reactor.

[0013] (5) After the second hydrogenation product is separated by gas-liquid separation, part of the liquid phase is introduced into a light removal tower, the light components are removed from the top and sent outside the area, and the tower bottom material is sent to a heavy removal tower.

[0014] (6) Succinic anhydride is removed from the side line of the heavy removal tower, the solvent components are removed from the top, and the heavy components such as polymers are removed from the tower bottom.

[0015] (7) The succinic anhydride is sent to a hydrolysis system to obtain succinic acid product through hydrolysis-drying operation.

[0016] The present application provides a method for preparing succinic acid, which comprises:

[0017] (1) The maleic anhydride solution is divided into two streams, wherein one stream is mixed with the liquid phase material of the cooled or uncooled part of the second-stage hydrogenation reaction, and then enters the first-stage hydrogenation reactor from the upper liquid phase feed port of the first-stage hydrogenation reactor to contact with hydrogen for hydrogenation, and the hydrogen enters the first-stage hydrogenation reactor from the top gas phase inlet of the first-stage hydrogenation reactor;

[0018] (2) The first stage hydrogenation product is sequentially cooled and gas-liquid separated, and the gas phase of the gas-liquid separation is all fed into the second stage hydrogenation reactor from the gas phase feed port at the top of the second stage hydrogenation reactor. The liquid phase of the gas-liquid separation is mixed with another stream of maleic anhydride solution and then fed into the second stage hydrogenation reactor from the liquid phase feed port at the top of the second stage hydrogenation reactor to react with hydrogen, thereby converting all maleic anhydride into succinic anhydride through hydrogenation reaction;

[0019] (3) The second-stage hydrogenation product is subjected to gas-liquid separation to obtain a gas phase and a liquid phase material of the second-stage hydrogenation reaction, and part of the liquid phase material of the second-stage hydrogenation reaction is returned to step (1), and part or all of the gas phase of the second-stage hydrogenation product is optionally used as circulating hydrogen;

[0020] (4) The liquid phase material of the remaining two-stage hydrogenation reaction is sent to a light removal tower, the light components are extracted from the top of the light removal tower, and the bottom material is sent to a heavy removal tower;

[0021] (5) Succinic anhydride is taken out from the side line of the deweighting tower, the solvent is taken out from the top of the tower, and the heavy components including polymers are taken out from the bottom of the tower;

[0022] (6) Succinic anhydride is sent to the hydrolysis system, where it is hydrolyzed, separated, and dried to obtain succinic acid.

[0023] Preferably, the operating pressure of the lightness removal tower is 0.5-20 KPa, preferably 6-15 KPa; the operating temperature is 30-150° C., preferably 80-130° C.; and the theoretical plate number is 10-80.

[0024] Preferably, the operating pressure of the deweighting tower is 0.5-20 KPa, preferably 3-15 KPa; the operating temperature is 30-150° C., preferably 100-130° C.; and the number of theoretical plates is 10-80.

[0025] Preferably, the hydrogen feedstock in step (1) is a mixed hydrogen feedstock of recycled hydrogen and supplementary hydrogen.

[0026] Preferably, the liquid phase material of the second-stage hydrogenation reaction in step (1) is a cooled material.

[0027] Preferably, the liquid phase material of the second-stage hydrogenation reaction in step (1) is cooled to 30-80°C, preferably cooled to 40-60°C.

[0028] Preferably, in step (2), the operating conditions of the second-stage hydrogenation reactor include: a temperature of 30-100℃, preferably 40-80℃; and / or a pressure of 0.1-10 MPa, preferably 0.5-5 MPa; and / or a space velocity of 0.5-5 h -1 .

[0029] Preferably, in step (1), the maleic anhydride solution is a mixture of maleic anhydride and a solvent, and the solvent is one or more of acetic anhydride, γ-butyrolactone, dioxane, tetrahydrofuran, aromatic hydrocarbon, ethyl acetate, tetracarboxylic acid ester, ethanol, isopropanol, hexane, cyclohexane, propylene oxide, ketone and ether.

[0030] Preferably, the concentration of maleic anhydride in the maleic anhydride solution is 1-90 wt%, preferably 10-40 wt%.

[0031] Preferably, the proportion of each of the two streams is 5-95 wt%, and preferably the proportion of one stream is 20-50 wt% and the proportion of the other stream is 50-80 wt%.

[0032] Preferably, the molar ratio of the total amount of hydrogen to the total maleic anhydride in the maleic anhydride solution is 5-100, preferably 10-40.

[0033] Preferably, the operating conditions of the first-stage hydrogenation reactor include: a temperature of 30-100℃, preferably 40-80℃; and / or a reaction pressure of 0.1-10 MPa, preferably 0.5-5 MPa; and / or a space velocity of 0.5-5 h -1 .

[0034] Preferably, 20-90 wt% of the liquid-phase material of the second-stage hydrogenation reaction is returned to step (1) as raw material, and the rest is sent to the light-removing column.

[0035] Preferably, 0.5-2 wt% of the gas-phase material of the second-stage hydrogenation reaction is produced as fuel gas, and the rest is used as the circulating hydrogen.

[0036] The present application provides a preparation system of succinic acid, which comprises:

[0037] a first-stage hydrogenation reactor, which comprises a top gas-phase feed port, an upper liquid-phase feed port and a bottom discharge port; and a first-stage reaction product cooler and a first-stage gas-liquid separator connected in series at the end of the bottom discharge port of the first-stage hydrogenation reactor;

[0038] a second-stage hydrogenation reactor, which is in series communication with the first-stage gas-liquid separator, and comprises a top gas-phase feed port and an upper liquid-phase feed port and a bottom discharge port;

[0039] a liquid phase feedstock supply line, the liquid phase feedstock supply line being in communication with both the upper liquid phase feed inlet of the first stage hydrogenation reactor and the upper liquid phase feed inlet of the second stage hydrogenation reactor;

[0040] a second stage gas-liquid separator, the second stage gas-liquid separator being in serial communication with the second stage hydrogenation reactor bottom outlet;

[0041] the second stage gas-liquid separator being in serial communication with the second stage hydrogenation reactor bottom outlet;

[0042] a light component removal column for removing light components from the liquid phase product from the second stage gas-liquid separator;

[0043] a heavy component removal column for removing solvent to obtain succinic anhydride;

[0044] a hydrolysis system for hydrolyzing succinic anhydride from the heavy component removal column to prepare succinic acid.

[0045] Preferably, the feed inlet of the light component removal column is in communication with the liquid phase outlet of the second stage gas-liquid separator, and the light component removal column is provided with a top outlet and a column bottom outlet.

[0046] Preferably, the feed inlet of the heavy component removal column is in communication with the column bottom outlet of the light component removal column, and the heavy component removal column is provided with a top outlet, a bottom outlet and a side draw outlet.

[0047] Preferably, the feed inlet of the hydrolysis system is in communication with the side draw outlet of the heavy component removal column.

[0048] Preferably, the top gas phase outlet of the first stage gas-liquid separator is in communication with the top gas phase feed inlet of the second stage hydrogenation reactor via a line.

[0049] Preferably, the bottom liquid phase outlet of the first stage gas-liquid separator is in communication with the upper liquid phase feed inlet of the second stage hydrogenation reactor via a line.

[0050] Preferably, the top gas phase outlet of the second stage gas-liquid separator is in communication with the top gas phase feed inlet of the first stage hydrogenation reactor via a line.

[0051] Preferably, the bottom liquid phase outlet of the second stage gas-liquid separator is in communication with the upper liquid phase feed inlet of the first stage hydrogenation reactor and the feed inlet of the light component removal column each via a line.

[0052] Preferably, a circulating material cooler is provided on the line for communication between the bottom liquid phase outlet of the second stage gas-liquid separator and the upper liquid phase feed inlet of the first stage hydrogenation reactor.

[0053] Preferably, a circulating gas cooler is provided on the line for communication between the top gas phase outlet of the second stage gas-liquid separator and the top gas phase feed inlet of the first stage hydrogenation reactor.

[0054] Preferably, a second-stage cooler and a third gas-liquid separator are arranged in series at the top gas phase outlet end of the second-stage gas-liquid separator, and the gas phase outlet of the third gas-liquid separator is communicated with the top gas phase feed inlet of the first-stage hydrogenation reactor through a pipeline; the bottom liquid phase outlet of the third gas-liquid separator is communicated with the liquid phase feed inlet of the second-stage gas-liquid separator.

[0055] Preferably, the system further comprises a distributor for distributing the liquid phase raw material into two streams for supplying the first-stage hydrogenation reactor and the second-stage hydrogenation reactor as needed.

[0056] The process and method of the present application have the following characteristics:

[0057] The present application can effectively remove the heat released in the reaction, is flexible in operation, easy to control, has good gas-liquid-solid contact, high effective utilization rate of catalyst, and low investment. By using the method of the present application, the concentration of maleic anhydride in the incoming maleic anhydride solution can be not too low, thereby reducing the solvent usage amount and reducing the energy consumption of subsequent solvent recovery. The present application has mild reaction operating conditions and low reaction bed temperature, which is beneficial to improve the selectivity of the catalyst and prolong the service life of the catalyst. By using the method of the present application, through the combined operation of the light removal column and the heavy removal column, the product purity of succinic anhydride is high, and at the same time, the purity of succinic acid obtained by hydrolysis is good, the process is simple, and easy to operate and control. BRIEF DESCRIPTION OF DRAWINGS

[0058] Figure 1 is a flow diagram of a method for continuously producing succinic acid by hydrogenation of maleic anhydride according to the present application.

[0059] BRIEF DESCRIPTION OF DRAWINGS

[0060] 1 distributor; 2 first-stage hydrogenation reactor;

[0061] 3 first-stage reaction product cooler; 4 first-stage gas-liquid separator;

[0062] 5 second-stage hydrogenation reactor; 6 second-stage gas-liquid separator;

[0063] 7 circulating material cooler; 8 circulating gas cooler;

[0064] 9 light removal column; 10 heavy removal column; 11 hydrolysis system;

[0065] 21 maleic anhydride solution; 22 supplemental hydrogen; 23 light component;

[0066] 24 byproduct; 25 heavy component;

[0067] 26 succinic anhydride; 27 succinic acid. DETAILED DESCRIPTION

[0068] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as the exact dimensions are not critical to the invention. Any numeric range recited is intended to include all values from the lower value to the upper value, inclusive of both values, and to also include any value approximately or about the value in the range, Rounding errors or errors resulting from truncation of a value to a different number of significant digits can be expected in the values given and the invention is intended to cover such values. Numeric ranges include endpoints.

[0069] As shown in Figure 1 The present invention provides a method for preparing succinic acid, which comprises:

[0070] (1) The succinic anhydride solution 21 is divided into two streams by the distributor 1, one of which is mixed with part of the liquid phase material from the second stage hydrogenation reaction, and then enters the first stage hydrogenation reactor from the upper liquid phase inlet of the first stage hydrogenation reactor 2, and is contacted with hydrogen gas to carry out hydrogenation, and the hydrogen gas enters the first stage hydrogenation reactor from the top gas phase inlet of the first stage hydrogenation reactor;

[0071] (2) The first stage hydrogenation product enters the first stage reaction product cooler 3 and the first stage gas-liquid separator 4 in turn to carry out cooling, temperature reduction, gas-liquid separation, and the gas phase from the gas-liquid separation enters the second stage hydrogenation reactor 5 from the top gas phase inlet of the second stage hydrogenation reactor, and the liquid phase from the gas-liquid separation is mixed with the other stream of succinic anhydride solution, and then enters the second stage hydrogenation reactor 5 from the upper liquid phase inlet of the second stage hydrogenation reactor, and reacts with hydrogen gas to convert all succinic anhydride into succinic anhydride;

[0072] (3) The second stage hydrogenation product enters the second stage gas-liquid separator 6 to carry out gas-liquid separation to obtain the gas phase and the liquid phase material from the second stage hydrogenation reaction, part of the liquid phase material from the second stage hydrogenation reaction is returned to step (1), and optionally part or all of the gas phase of the second stage hydrogenation product is used as recycle hydrogen gas;

[0073] (4) The remaining liquid phase material from the second stage hydrogenation reaction is sent to the light component removal column 9, the light components are collected from the top of the light component removal column, and the column bottom material is sent to the heavy component removal column 10;

[0074] (5) Succinic anhydride is collected from the side line of the heavy component removal column 10, solvent is collected from the top of the heavy component removal column, and heavy components including polymers are collected from the column bottom;

[0075] (6) The succinic anhydride 26 is sent to the hydrolysis system 11, and succinic acid is obtained through hydrolysis, separation, and drying.

[0076] The application can effectively remove the heat released by reaction, has flexible operation, easy control of gas-liquid-solid contact, high effective utilization of catalyst and low investment. The method of the application can be used to process the succinic anhydride solution with a low succinic anhydride concentration, thereby reducing the solvent usage and lowering the energy consumption of subsequent solvent recovery. The application has mild reaction operation conditions and low bed temperature, which is beneficial to improve the selectivity of catalyst and prolong the service life of catalyst. The method of the application can be used to combine the light-removing column and the heavy-removing column to obtain the succinic anhydride product with high purity, and the succinic acid product obtained by hydrolysis has high purity, simple process and easy operation control.

[0077] According to the preferred embodiment of the application, the light component 23 is discharged from the top of the light-removing column 9; the material in the column bottom of the light-removing column 9 is introduced into the heavy-removing column 10, the byproduct 24 is discharged from the top of the heavy-removing column 10, the heavy component 25 is discharged from the column bottom, and the succinic anhydride 26 is taken out from the side line to be introduced into the hydrolysis system 11 to be hydrolyzed and crystallized to obtain the succinic acid 27.

[0078] In the application, the light component refers to hydrogen dissolved in the liquid phase, a small amount of solvent such as γ-butyrolactone and tetrahydrofuran, etc.

[0079] In the application, the purpose of the light-removing column is to remove hydrogen, a small amount of solvent such as γ-butyrolactone and tetrahydrofuran, etc., and there is no special requirement for the setting and operation conditions thereof, as long as the purpose of the application can be achieved.

[0080] In the application, the purpose of the heavy-removing column is to remove the solvent from the top and the heavy component generated by polymerization from the column bottom, and the succinic anhydride meeting the requirements is taken out from the side line, and there is no special requirement for the setting and operation conditions thereof, as long as the purpose of the application can be achieved.

[0081] In the application, the purpose of the hydrolysis system is to prepare succinic acid by hydrolyzing succinic anhydride, and there is no special requirement for the setting and operation conditions thereof, as long as the purpose of the application can be achieved. For example, the succinic acid is generally prepared by hydrolyzing and crystallizing in the hydrolysis unit. For example, the hydrolysis unit generally includes a hydrolysis kettle, a centrifugal separation unit and a drying unit to obtain the succinic acid product after hydrolysis, centrifugal separation and drying.

[0082] The application has no special requirement for the operation conditions of the dehydrocarbon column, according to the preferred embodiment of the application, the operation pressure of the light-removing column is 0.5-20 KPa, preferably 6-15 KPa; the operation temperature is 30-150℃, preferably 80-130℃; and the theoretical plate number is 10-80.

[0083] The application has no special requirement for the operation conditions of the heavy-removing column, according to the preferred embodiment of the application, the operation pressure of the heavy-removing column is 0.5-20 KPa, preferably 3-15 KPa; the operation temperature is 30-150℃, preferably 100-130℃; and the theoretical plate number is 10-80.

[0084] According to a preferred embodiment of the present application, the hydrogen raw material of step (1) is a mixed hydrogen raw material of the circulating hydrogen and the supplemental hydrogen 22.

[0085] According to a preferred embodiment of the present application, the liquid material of the two-stage hydrogenation reaction of step (1) is a cooled material.

[0086] According to a preferred embodiment of the present application, the liquid material of the two-stage hydrogenation reaction of step (1) is a material cooled to 30-80℃, preferably 40-60℃.

[0087] According to a preferred embodiment of the present application, in step (2), the operating conditions of the two-stage hydrogenation reactor include: temperature of 30-100℃, preferably 40-80℃, for example 40℃, 41℃, 42℃, 43℃, 44℃, 45℃, 46℃, 47℃, 48℃, 49℃, 50℃, and the like, each of which is applicable to the present application; and / or pressure of 0.1-10MPa, preferably 0.5-5MPa; and / or space velocity of 0.5-5h -1 .

[0088] The present application does not have special requirements for the maleic anhydride solution. According to a preferred embodiment of the present application, in step (1), the maleic anhydride solution is a mixture of maleic anhydride and a solvent, which can be a commonly used solvent, for example one or more of acetic anhydride, γ-butyrolactone, dioxane, tetrahydrofuran, aromatic hydrocarbon, ethyl acetate, tetracarbon diacid ester, ethanol, isopropyl alcohol, hexane, cyclohexane, propylene oxide, ketone and ether.

[0089] According to a preferred embodiment of the present application, the concentration of maleic anhydride in the maleic anhydride solution is 1-90wt%, preferably 10-40wt%. With the method of the present application, the concentration of maleic anhydride in the incoming maleic anhydride solution can not be too low, which reduces the amount of solvent used and reduces the energy consumption of subsequent solvent recovery.

[0090] According to a preferred embodiment of the present application, the proportion of each of the one stream and the other stream is 5-95wt%, wherein the proportion of the one stream is preferably 20-50wt% and the proportion of the other stream is 50-80wt%.

[0091] According to a preferred embodiment of the present application, the molar ratio of the total hydrogen amount to the total maleic anhydride in the maleic anhydride solution is 5-100, preferably 10-40.

[0092] According to the preferred embodiment of the present application, the operating conditions of the first hydrogenation reactor include: temperature of 30-100℃, preferably 40-80℃, for example 40℃, 41℃, 42℃, 43℃, 44℃, 45℃, 46℃, 47℃, 48℃, 49℃, 50℃, and the like, in sequence, each of which is applicable to the present application; and / or reaction pressure of 0.1-10MPa, preferably 0.5-5MPa; and / or space velocity of 0.5-5h -1 .

[0093] According to the preferred embodiment of the present application, 20-90wt% of the liquid-phase material of the second hydrogenation reaction is returned to step (1) as raw material, and the rest is sent to the light-removing column. In this way, the heat released by the reaction can be effectively removed, and the effective utilization rate of the catalyst is improved.

[0094] According to the preferred embodiment of the present application, 0.5-2wt% of the gas-phase material of the second hydrogenation reaction is recovered as fuel gas, and the rest is used as the circulating hydrogen. In this way, the heat released by the reaction can be effectively removed, and the effective utilization rate of the catalyst is improved.

[0095] The present application provides a preparation system of succinic acid, which comprises:

[0096] a first hydrogenation reactor 2, which comprises a top gas-phase feed port, an upper liquid-phase feed port and a bottom discharge port; and a first reaction product cooler 3 and a first gas-liquid separator 4 connected in sequence at the end of the bottom discharge port of the first hydrogenation reactor 2;

[0097] a second hydrogenation reactor 5, which is connected in series with the first gas-liquid separator 4, and comprises a top gas-phase feed port and an upper liquid-phase feed port and a bottom discharge port;

[0098] a liquid-phase raw material supply pipeline, which is connected with the upper liquid-phase feed port of the first hydrogenation reactor 2 and the upper liquid-phase feed port of the second hydrogenation reactor 5;

[0099] a second gas-liquid separator 6, which is connected in series with the bottom discharge port of the second hydrogenation reactor 5;

[0100] the second gas-liquid separator 6 is connected in series with the bottom discharge port of the second hydrogenation reactor 5;

[0101] a light-removing column 9, which is used for removing light components in the liquid-phase product from the second gas-liquid separator;

[0102] a heavy-removing column 10, which is used for removing solvent to obtain succinic anhydride;

[0103] A hydrolysis system 11 is used to hydrolyze succinic anhydride from the heavy-removing column 10 to produce succinic acid. The system of the present application can effectively remove the heat released from the reaction and improve the effective utilization of the catalyst.

[0104] According to the preferred embodiment of the present application, the feed inlet of the light-removing column 9 is communicated with the liquid phase outlet of the two-stage gas-liquid separator 6, and the light-removing column 9 is provided with a top outlet and a column bottom outlet.

[0105] According to the preferred embodiment of the present application, the feed inlet of the heavy-removing column 10 is communicated with the column bottom outlet of the light-removing column 9, and the heavy-removing column 10 is provided with a top outlet, a bottom outlet and a side outlet.

[0106] According to the preferred embodiment of the present application, the feed inlet of the hydrolysis system 11 is communicated with the side outlet of the heavy-removing column 10.

[0107] According to the preferred embodiment of the present application, the top gas phase outlet of the one-stage gas-liquid separator is communicated with the top gas phase inlet of the two-stage hydrogenation reactor through a pipeline. Thus, the heat released from the reaction can be effectively removed, and the effective utilization of the catalyst is improved.

[0108] According to the preferred embodiment of the present application, the bottom liquid phase outlet of the one-stage gas-liquid separator is communicated with the upper liquid phase inlet of the two-stage hydrogenation reactor through a pipeline. Thus, the heat released from the reaction can be effectively removed, and the effective utilization of the catalyst is improved.

[0109] According to the preferred embodiment of the present application, the top gas phase outlet of the two-stage gas-liquid separator is communicated with the top gas phase inlet of the one-stage hydrogenation reactor through a pipeline. Thus, the heat released from the reaction can be effectively removed, and the effective utilization of the catalyst is improved.

[0110] According to the preferred embodiment of the present application, the bottom liquid phase outlet of the two-stage gas-liquid separator is communicated with the upper liquid phase inlet of the one-stage hydrogenation reactor and the feed inlet of the light-removing column through respective pipelines. The system of the present application can effectively remove the heat released from the reaction, and improve the effective utilization of the catalyst.

[0111] According to the preferred embodiment of the present application, a circulating material cooler 7 is preferably arranged on the pipeline communicating the bottom liquid phase outlet of the two-stage gas-liquid separator with the upper liquid phase inlet of the one-stage hydrogenation reactor. The system of the present application can effectively remove the heat released from the reaction, and improve the effective utilization of the catalyst.

[0112] According to the preferred embodiment of the present application, a circulating gas cooler 8 is preferably arranged on the pipeline communicating the top gas phase outlet of the two-stage gas-liquid separator with the top gas phase inlet of the one-stage hydrogenation reactor. Thus, the heat released from the reaction can be effectively removed, and the effective utilization of the catalyst is improved.

[0113] According to the preferred embodiment of the present application, a two-stage cooler and a third gas-liquid separator are preferably arranged in series at the top gas phase outlet end of the two-stage gas-liquid separator, the gas phase outlet of the third gas-liquid separator is communicated with the top gas phase feed inlet of the first-stage hydrogenation reactor through a pipeline; and the bottom liquid phase outlet of the third gas-liquid separator is communicated with the liquid phase feed inlet of the two-stage gas-liquid separator. Thus, the heat released during the reaction can be effectively removed, and the effective utilization rate of the catalyst is improved.

[0114] According to the preferred embodiment of the present application, the system further comprises a distributor 1 for distributing the liquid phase raw material into two streams to supply the first-stage hydrogenation reactor and the two-stage hydrogenation reactor as needed. Thus, the heat released during the reaction can be effectively removed, and the effective utilization rate of the catalyst is improved.

[0115] In the present application, after the first-stage hydrogenation product is subjected to gas-liquid separation, the gas phase is all introduced into the two-stage hydrogenation reactor from the top, and the liquid phase is mixed with part of the maleic anhydride solution and then introduced into the hydrogenation reactor from the upper part of the reactor. After the two-stage hydrogenation reaction, the maleic anhydride is all converted into succinic anhydride.

[0116] In the present application, the catalysts for the first-stage hydrogenation reactor and the two-stage hydrogenation reactor are not limited, and conventional maleic anhydride hydrogenation catalysts can be used, such as the catalysts described in Chinese Patent CN202011118431.X and Chinese Patent CN202011120495.3.

[0117] In the present application, when the gas phase and the liquid phase of each reactor enter the first-stage reactor and the two-stage reactor, they can optionally pass through a distributor before contacting the catalyst.

[0118] In the present application, after the two-stage hydrogenation reaction product is subjected to gas-liquid separation, the gas phase material can be further cooled, and the cooling temperature is preferably 30-80°C. The cooled material is then subjected to a further gas-liquid separation, the gas phase is recycled as recycled hydrogen, and the liquid phase is returned to the previous gas-liquid separator.

[0119] In the present application, after the two-stage hydrogenation product is subjected to gas-liquid separation, about 0.5%-2% of the material in the gas phase is preferably vented, and the remaining gas phase is cooled and then recycled to the first-stage hydrogenation reactor, mixed with fresh hydrogen, and then introduced into the first-stage hydrogenation reactor.

[0120] In the present application, after the liquid phase of the two-stage hydrogenation product is subjected to gas-liquid separation, 10%-80% (by weight) of the liquid phase is preferably sent to a light-removing tower, and the remaining liquid phase reaction product is first cooled to 40-80°C by a cooler and then mixed with a maleic anhydride solution before being introduced into the first-stage hydrogenation reactor for recycling.

[0121] In the present application, succinic anhydride is preferably collected from the stripping section of the heavy-removing tower.

[0122] In the present application, the hydrolysis system includes but is not limited to hydrolysis kettle, crystallizer, centrifugal separator, dryer, mother liquor tank, and required heat exchanger, pump, tank, etc. Succinic anhydride is mixed with circulating mother liquor and fresh purified water to enter the hydrolysis kettle to obtain nearly saturated succinic acid aqueous solution, which enters the vacuum cooling crystallizer to obtain succinic acid solid, and then the mother liquor is separated from the succinic acid solid by centrifuge, the mother liquor is recycled back to the hydrolysis kettle, and the succinic acid solid enters the dryer to obtain succinic acid solid product. The operating pressure of the hydrolysis kettle is preferably 0.001-0.2 MPa, and the operating temperature is preferably 40-150℃. The equipment form and operating conditions of the vacuum cooling crystallizer and the dryer are not limited, and the person skilled in the art determines them according to professional knowledge and existing technology.

[0123] The process described in the present application can also include pumps, heat exchangers, tanks, compressors, etc. in addition to the equipment listed in the drawings, which are set up by the person skilled in the art according to needs and professional common sense.

[0124] The method of the present application has the following characteristics:

[0125] (1) The present application divides the maleic anhydride solution into two streams, which are mixed with different materials and then enter two hydrogenation reactors, so that the content of maleic anhydride entering the reactor is reduced, the heat released by the reaction can be effectively removed, the operation is flexible and easy to control.

[0126] (2) Using the method of the present application, the concentration of maleic anhydride in the incoming maleic anhydride solution can not be too low, which reduces the amount of solvent used and reduces the energy consumption of subsequent solvent recovery.

[0127] (3) After the first stage reaction, the present application cools and separates the gas and liquid phases, and the gas phase enters the second stage reactor, which can effectively remove the heat generated by the second stage reaction.

[0128] (4) The present application sets up a gas-liquid separation after the first stage reactor, and the gas and liquid phases enter the reactor respectively, and can be selected by a distribution device, so that the materials entering the reactor are more fully contacted, the gas-liquid-solid contact is good, the effective utilization rate of the catalyst is high, and the investment is saved.

[0129] (5) The reaction operating conditions of the present application are mild, which can be reacted at about 40℃, greatly reducing the severity of the reaction, lowering the reaction bed temperature, and being beneficial to improving the selectivity of the catalyst and prolonging the service life of the catalyst.

[0130] (6) Using the method of the present application, through the combined operation of the light removal tower and the heavy removal tower, the succinic anhydride product has high purity, and at the same time, the succinic acid product obtained by hydrolysis has good purity, the process is simple, and easy to operate and control.

[0131] The present application will be described in detail below in conjunction with specific drawings and examples. It is necessary to point out here that the following examples are only used to further illustrate the present application and cannot be understood as limiting the protection scope of the present application. Some non-essential improvements and adjustments to the present application made by those skilled in the art based on the content of the present application still fall within the protection scope of the present application.

[0132] The following examples use the following catalyst:

[0133] Chinese patent application CN202011118431.X - Example 1

[0134] (1) 50.00 g of basic nickel carbonate (nickel content 45 wt.%, 9.16 g of Cu(NO3)2·3H2O, 49.91 g of ethylenediaminetetraacetic acid, 500 g of deionized water, and 100 g of 25 wt.% ammonia water are mixed, and ammonia gas is introduced to adjust the pH value of the solution to 10.5, and the solution is stirred at 45°C until all the solids are dissolved to obtain a nickel-copper ammonia complex solution;

[0135] (2) 458.31 g of silica sol is mixed with the nickel-copper ammonia complex solution obtained in step (1) to obtain a mixed solution;

[0136] (3) The mixed solution is aged at a temperature of 60°C for 14 h under stirring, and then dried at 120°C for 12 h to obtain a catalyst precursor;

[0137] (4) The catalyst precursor is saturatedly impregnated with a cerium nitrate solution containing 11.41 g of Ce(NO3)3·6H2O to obtain a matrix catalyst;

[0138] (5) The matrix catalyst is dried at 115°C for 12 h, and then calcined at 400°C for 4 h to form a catalyst S1.

[0139] Based on the total weight of the catalyst S1, the catalyst S1 contains 19 wt.% of NiO, 2 wt.% of CuO, 3 wt.% of CeO2, and 76 wt.% of SiO2.

[0140] CN202011120495.3 - Example 1

[0141] (1) 10.90 g of Ni(NO3)3·6H2O and 5.04 g of Ce(NO3)3·6H2O cerium are dissolved in water and diluted to 50.0 ml, and then 50 g of carrier SiO2 (specific surface area 300 m2 / g, water absorption 1.0 mL / g) is impregnated in the mixed solution of nickel nitrate-cerium nitrate, stirred uniformly, and aged for 4 hours, then dried at 120°C for 12 hours, and finally calcined at 450°C in air for 4 hours to obtain a composite oxide carrier E;

[0142] (2) The composite oxide support E was added to 100 ml of a ruthenium metal solution having an exothermic Ru content of 0.02 g / L. Under stirring conditions, 25% ammonia water was added dropwise, and the pH value of the solution was adjusted and maintained at 9.55°C. After reacting for 6 hours, the solution was filtered, dried at 110°C for 12 hours, and finally calcined in air at 500°C for 4 hours to obtain the finished catalyst S1.

[0143] The catalyst S1 contains: based on the mass of the catalyst carrier SiO2, the mass fraction of Ni in the catalyst is 7% of the carrier mass, the mass fraction of CeO2 is 4% of the carrier mass, and the mass fraction of Ru is 0.4% of the carrier mass.

[0144] Example 1

[0145] use Figure 1 A method for continuously producing succinic acid by hydrogenating maleic anhydride is shown. The solvent used is γ-butyrolactone. The maleic anhydride solution contains 10% maleic anhydride by weight. The maleic anhydride solution is split into two streams at a ratio of 50% and 50% by weight. One stream is mixed with the recycled product of the second-stage hydrogenation reaction and then enters the first-stage hydrogenation reactor from the top of the reactor. The other stream is mixed with the product of the first-stage hydrogenation reaction and then enters the second-stage hydrogenation reactor from the top of the reactor. The molar ratio of the total amount of recycled hydrogen and replenished fresh hydrogen to the total amount of maleic anhydride in the incoming maleic anhydride solution is 10.

[0146] In the first stage hydrogenation reactor, the space velocity of the first stage hydrogenation reactor is 2.5h -1 The reaction temperature is 40℃ and the reaction pressure is 1.5MPa. The product of the first stage hydrogenation reaction is cooled to 40℃. After gas-liquid separation, the gas phase enters the second stage hydrogenation reactor from the top of the reactor. The liquid phase is mixed with maleic anhydride solution and then enters the second stage hydrogenation reactor from the top of the reactor. The space velocity of the second stage hydrogenation reactor is 1h -1 The reaction temperature was 42°C and the reaction pressure was 1.3 MPa. After the second-stage hydrogenation reaction product passed through the gas-liquid separator, 1 volume percent of the gas phase was extracted to remove the fuel gas. The remaining gas phase was fed into the first-stage hydrogenation reactor together with fresh hydrogen. After the gas-liquid separation, 65 weight percent of the liquid phase was fed to the light removal tower, heavy removal tower, and hydrolysis system. The 35 weight percent liquid phase was heat-exchanged to 40°C, mixed with the maleic anhydride solution, and then fed into the first-stage hydrogenation reactor.

[0147] The catalysts loaded in the first and second stage reactors are both Ni active component catalysts, see CN202011118431.X-Example 1 for details.

[0148] After two-stage reaction, the total conversion rate of maleic anhydride is 99.3%, and the total selectivity of succinic anhydride is 99.5%.

[0149] The light removal tower had 26 theoretical plates, a top pressure of 10 kPa, and an operating temperature of 100° C. The heavy removal tower had 25 theoretical plates, a top pressure of 3 kPa, and an operating temperature of 105° C. The purity of the obtained succinic anhydride was 99.9%.

[0150] The hydrolysis system's hydrolysis kettle operates at a pressure of 0.12 MPa and a temperature of 80°C. Succinic acid is obtained after centrifugal separation and drying. The purity of the succinic acid product is 99.9%.

[0151] Example 2

[0152] use Figure 1 A method for continuously producing succinic acid from maleic anhydride is described. Hexane is used as the solvent. The maleic anhydride solution contains 25% maleic anhydride by weight. The maleic anhydride solution is divided into two streams, 40% by weight and 60% by weight. The 40% maleic anhydride solution is mixed with the product of the second-stage hydrogenation reaction and then enters the first-stage hydrogenation reactor from the top of the reactor. The 60% maleic anhydride solution is mixed with the product of the first-stage hydrogenation reaction and then enters the second-stage hydrogenation reactor from the top of the reactor. The molar ratio of the total amount of recycled hydrogen and replenished fresh hydrogen to the total maleic anhydride in the incoming maleic anhydride solution is 40.

[0153] In the first stage hydrogenation reactor, the space velocity of the first stage hydrogenation reactor is 3h -1 The reaction temperature is 40°C and the reaction pressure is 1.7 MPa. The first stage hydrogenation reaction product is cooled to 42°C. After gas-liquid separation, the gas phase enters the second stage hydrogenation reactor from the top of the reactor. The liquid phase is mixed with part of the maleic anhydride solution and then enters the second stage hydrogenation reactor. The space velocity of the second stage hydrogenation reactor is 0.8h -1 , reaction temperature 45°C, reaction pressure 1.5MPa. After the second-stage hydrogenation reaction product passes through the gas-liquid separator, the gas phase is cooled to 40°C again, and then passed through the gas-liquid separator. The gas phase and the fresh hydrogen are sent to the first-stage hydrogenation reactor. 50% by weight of the liquid phase of the gas-liquid separator is sent to the lightness removal tower, heavyness removal tower and hydrolysis system. 50% by weight of the liquid phase is returned to the first-stage hydrogenation reactor, mixed with part of the maleic anhydride solution, and then heat exchanged to 40°C before entering the first-stage hydrogenation reactor.

[0154] The catalysts loaded in the first and second stage reactors are both Ni active component catalysts, see CN202011120495.3-Example 1 for details.

[0155] After two-stage reaction, the total conversion rate of maleic anhydride is 99.78%, and the total selectivity of succinic anhydride is 99.1%.

[0156] The light removal tower had a theoretical plate number of 30, a top pressure of 6 kPa, and an operating temperature of 80° C. The heavy removal tower had a theoretical plate number of 35, a top pressure of 8 kPa, and an operating temperature of 100° C. The purity of the obtained succinic anhydride was 99.9%.

[0157] The hydrolysis system's hydrolysis kettle operates at a pressure of 0.17 MPa and a temperature of 85°C. Succinic acid is obtained after centrifugal separation and drying. The purity of the succinic acid product is 99.85%.

[0158] Example 3

[0159] use Figure 1 A method for continuously producing succinic acid from maleic anhydride is described. The solvent used is dioxane. The maleic anhydride solution contains 18% maleic anhydride by weight. The maleic anhydride solution is divided into two streams, 20% by weight and 80% by weight. The 20% maleic anhydride solution is mixed with the product of the second-stage hydrogenation reaction and then enters the first-stage hydrogenation reactor from the top of the reactor. The 80% maleic anhydride solution is mixed with the product of the first-stage hydrogenation reaction and then enters the second-stage hydrogenation reactor from the top of the reactor. The molar ratio of the total amount of recycled hydrogen and replenished fresh hydrogen to the total maleic anhydride in the incoming maleic anhydride solution is 30.

[0160] In the first stage hydrogenation reactor, the space velocity of the first stage hydrogenation reactor is 1.8h -1 The reaction temperature is 40°C and the reaction pressure is 1.3 MPa. The first stage hydrogenation reaction product is cooled to 45°C. After gas-liquid separation, the gas phase enters the second stage hydrogenation reactor from the top of the reactor. The liquid phase is mixed with part of the maleic anhydride solution and then enters the second stage hydrogenation reactor. The space velocity of the second stage hydrogenation reactor is 1.2h -1 The reaction temperature is 48°C and the reaction pressure is 1.2 MPa. After the second-stage hydrogenation reaction product passes through the gas-liquid separator, the gas phase is sent to the first-stage hydrogenation reactor together with the replenished fresh hydrogen. 60% by weight of the liquid phase is sent to the light removal tower, heavy removal tower and hydrolysis system. 40% by weight of the liquid phase is returned to the first-stage hydrogenation reactor, mixed with the maleic anhydride solution, and then heat exchanged to the reaction temperature before entering the first-stage hydrogenation reactor.

[0161] The catalysts loaded in the first and second stage reactors are both Ni active component catalysts, see CN202011118431.X-Example 1 for details.

[0162] After two-stage reaction, the total conversion rate of maleic anhydride is 99.5%, and the total selectivity of succinic anhydride is 99.6%.

[0163] The light removal tower had 20 theoretical plates, a top pressure of 15 kPa, and an operating temperature of 110° C. The heavy removal tower had 25 theoretical plates, a top pressure of 15 kPa, and an operating temperature of 115° C. The purity of the obtained succinic anhydride was 99.9%.

[0164] The hydrolysis system operates at a pressure of 0.1 MPa and a temperature of 70°C. The succinic acid product is obtained after centrifugal separation and drying. The purity of the succinic acid product is 99.9%.

[0165] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including that each technical feature is combined in any other suitable manner. These simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A method for preparing succinic acid, characterized in that: The method includes: (1) The maleic anhydride solution is divided into two streams, wherein one stream is mixed with a portion of the liquid phase material of the second-stage hydrogenation reaction that has been cooled to 30-80°C, and then enters the first-stage hydrogenation reactor from the upper liquid phase feed port of the first-stage hydrogenation reactor to contact with hydrogen for hydrogenation, and the hydrogen enters the first-stage hydrogenation reactor from the top gas phase inlet of the first-stage hydrogenation reactor; (2) The first stage hydrogenation product is sequentially cooled and gas-liquid separated, and the gas phase of the gas-liquid separation is all fed into the second stage hydrogenation reactor from the gas phase feed port at the top of the second stage hydrogenation reactor. The liquid phase of the gas-liquid separation is mixed with another stream of maleic anhydride solution and then fed into the second stage hydrogenation reactor from the liquid phase feed port at the top of the second stage hydrogenation reactor to react with hydrogen, thereby converting all maleic anhydride into succinic anhydride through hydrogenation reaction; (3) The second-stage hydrogenation product is subjected to gas-liquid separation to obtain a gas phase and a liquid phase material of the second-stage hydrogenation reaction, and part of the liquid phase material of the second-stage hydrogenation reaction is returned to step (1), and part or all of the gas phase of the second-stage hydrogenation product is optionally used as circulating hydrogen; (4) The liquid phase material of the remaining two-stage hydrogenation reaction is sent to a light removal tower, the light components are extracted from the top of the light removal tower, and the bottom material is sent to a heavy removal tower; (5) Succinic anhydride is taken out from the side line of the deweighting tower, the solvent is taken out from the top of the tower, and the heavy components including polymers are taken out from the bottom of the tower; (6) Succinic anhydride is sent to the hydrolysis system, where it is hydrolyzed, separated, and dried to obtain succinic acid; The maleic anhydride concentration of the maleic anhydride solution is 1 to 90 weight %; The molar ratio of the total amount of hydrogen to the total amount of maleic anhydride in the maleic anhydride solution is 5 to 100.

2. The method according to claim 1, wherein The lightness removal tower has an operating pressure of 0.5 to 20 kPa, an operating temperature of 30 to 150°C, and a theoretical plate number of 10 to 80; and / or The operating pressure of the deweighting tower is 0.5-20KPa; the operating temperature is 30-150°C; and the theoretical plate number is 10-80.

3. The method according to claim 2, wherein: The operating pressure of the lightness removal tower is 6-15KPa; the operating temperature is 80-130°C; and / or The operating pressure of the deweighting tower is 3~15KPa; the operating temperature is 100-130℃.

4. The method according to claim 1, wherein The hydrogen raw material in step (1) is a mixed hydrogen raw material of circulating hydrogen and supplementary hydrogen.

5. The method according to claim 4, wherein The liquid phase material of the second-stage hydrogenation reaction in step (1) is a material cooled to 40-60°C.

6. The method according to claim 1, wherein In step (2), the operating conditions of the second-stage hydrogenation reactor include: temperature of 30-100°C; and / or pressure of 0.1-10 MPa; and / or space velocity of 0.5-5h -1 .

7. The method according to claim 1, wherein In step (2), the operating conditions of the second-stage hydrogenation reactor include: a temperature of 40-80° C.; and / or a pressure of 0.5-5 MPa.

8. The method according to claim 1, wherein In step (1), The maleic anhydride solution is a mixture of maleic anhydride and a solvent, wherein the solvent is one or more of acetic anhydride, γ-butyrolactone, dioxane, tetrahydrofuran, aromatic hydrocarbons, ethyl acetate, tetracarbonyl dibasic acid esters, ethanol, isopropanol, hexane, cyclohexane, propylene oxide, ketones and ethers; and / or The maleic anhydride concentration of the maleic anhydride solution is 10 to 40% by weight; and / or The proportion of one strand and the other strand is 5 to 95% by weight respectively; and / or The molar ratio of the total amount of hydrogen to the total amount of maleic anhydride in the maleic anhydride solution is 10 to 40; and / or The operating conditions of the first stage hydrogenation reactor include: temperature of 30-100°C; and / or reaction pressure of 0.1-10 MPa; and / or space velocity of 0.5-5h -1 .

9. The method according to claim 1, wherein In step (1), One share accounts for 20-50% by weight, and the other share accounts for 50-80% by weight; and / or The operating conditions of the first-stage hydrogenation reactor include: a temperature of 40-80° C.; and / or a reaction pressure of 0.5-5 MPa.

10. The method according to any one of claims 1 to 9, wherein: 20-90 wt% of the liquid phase material from the second stage hydrogenation reaction is returned to step (1) for use as a raw material, and the rest is sent to a light removal tower; 0.5 to 2 weight percent of the gaseous material in the second-stage hydrogenation reaction is extracted as fuel gas, and the rest is used as the circulating hydrogen.

11. A system for preparing succinic acid, characterized in that: The system includes: A first-stage hydrogenation reactor (2), the first-stage hydrogenation reactor (2) comprising a top gas phase feed port, an upper liquid phase feed port and a bottom discharge port; and a first-stage reaction product cooler (3) and a first-stage gas-liquid separator (4) sequentially connected in series to the bottom discharge port end of the first-stage hydrogenation reactor (2); A second-stage hydrogenation reactor (5), the second-stage hydrogenation reactor (5) is connected in series with the first-stage gas-liquid separator (4), and the second-stage hydrogenation reactor (5) comprises a top gas phase feed port, an upper liquid phase feed port, and a bottom discharge port; a liquid-phase raw material supply pipeline, the liquid-phase raw material supply pipeline being connected to both the upper liquid-phase feed port of the first-stage hydrogenation reactor (2) and the upper liquid-phase feed port of the second-stage hydrogenation reactor (5); A second-stage gas-liquid separator (6), wherein the second-stage gas-liquid separator (6) is connected in series with the bottom discharge port of the second-stage hydrogenation reactor (5); The second-stage gas-liquid separator (6) is connected in series with the bottom discharge port of the second-stage hydrogenation reactor (5); A light-removal tower (9) is used to remove light components from the liquid phase product from the second-stage gas-liquid separator; a deweighting tower (10) for removing the solvent to obtain succinic anhydride; The hydrolysis system (11) is used to hydrolyze succinic anhydride from the deweighting tower (10) to prepare succinic acid.

12. The preparation system according to claim 11, wherein: The feed port of the light-removal tower (9) is communicated with the liquid phase discharge port of the second-stage gas-liquid separator (6), and the light-removal tower (9) is provided with a top outlet and a tower bottom discharge port; The feed port of the de-weighting tower (10) is connected to the discharge port of the bottom of the de-weighting tower (9), and the de-weighting tower (10) is provided with a top outlet, a bottom outlet and a side line outlet; The feed port of the hydrolysis system (11) is communicated with the side line outlet of the deweighting tower (10).

13. The preparation system according to claim 11, wherein: The top gas phase outlet of the first stage gas-liquid separator is connected to the top gas phase feed port of the second stage hydrogenation reactor via a pipeline; and / or The bottom liquid phase outlet of the first stage gas-liquid separator is connected to the upper liquid phase feed port of the second stage hydrogenation reactor via a pipeline; and / or The top gas phase outlet of the second-stage gas-liquid separator is connected to the top gas phase feed port of the first-stage hydrogenation reactor through a pipeline; and / or The bottom liquid phase outlet of the second-stage gas-liquid separator is connected to the upper liquid phase feed port of the first-stage hydrogenation reactor and the feed port of the lightness removal tower through pipelines.

14. The preparation system according to claim 13, wherein: A circulating material cooler (7) is provided on the connecting pipeline between the bottom liquid phase outlet of the second-stage gas-liquid separator and the upper liquid phase feed port of the first-stage hydrogenation reactor; A circulating gas cooler (8) is provided on the connecting pipeline between the top gas phase outlet of the second-stage gas-liquid separator and the top gas phase feed port of the first-stage hydrogenation reactor.

15. The preparation system according to any one of claims 11 to 14, wherein: The system also includes a distributor for distributing the liquid raw material into two streams according to needs to supply the first-stage hydrogenation reactor and the second-stage hydrogenation reactor.

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