Method and apparatus for the combined production of succinic acid by hydrocarbon ejection cycle stepwise oxidation and hydrogenation

Abstract

This invention relates to a method and apparatus for the combined production of succinic acid through a hydrocarbon ejector cycle of stepwise oxidation and hydrogenation. The method includes a method for preparing maleic anhydride, which involves reacting a mixture of air, n-butane, water vapor, and an inert gas to obtain a maleic anhydride mixture. The apparatus includes a reaction unit, an ejector device, and a compressed air unit. The gas inlet of the reaction unit is connected to the outlet of the ejector device. The compressed air unit and a hydrocarbon gas source are respectively connected to the jet inlet of the ejector device. The jet inlet of the ejector device is connected to a water vapor source. This invention solves the problems of low product yield, complex equipment structure, high cost, poor safety and reliability, and significant pollution emissions in existing maleic anhydride and succinic acid production processes.

Description

Technical Field

[0001] This invention belongs to the field of succinic acid preparation technology, specifically relating to a method and apparatus for the combined production of succinic acid by hydrocarbon ejection cycle stepwise oxidation and hydrogenation. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] There are several methods for producing succinic acid, the main ones that are currently industrialized include: electrolytic reduction, maleic anhydride catalytic hydrogenation, and bio-fermentation. In existing processes for producing succinic acid by maleic anhydride hydrogenation, maleic anhydride is typically produced in a maleic anhydride production unit, and then the maleic anhydride or maleic acid is hydrogenated to produce succinic acid.

[0004] The catalytic hydrogenation of maleic anhydride has advantages such as high conversion rate, high product purity, no obvious side reactions, and environmental friendliness, making it the most widely used industrial method for synthesizing succinic acid. There are currently two main routes for the catalytic hydrogenation of maleic anhydride to produce succinic acid: catalytic hydrogenation to succinic anhydride under organic solvent or solvent-free (molten) conditions, followed by hydrolysis of the succinic anhydride to succinic acid, i.e., the non-aqueous phase method; and the aqueous phase method, which first generates maleic acid under aqueous conditions, followed by hydrogenation to succinic acid under supported noble metal catalyst conditions, i.e., the aqueous phase method.

[0005] Existing production processes for maleic acid and maleic anhydride include fixed-bed, fluidized-bed, and moving-bed methods, each with its own characteristics. Among them, the tubular fixed-bed method with molten salt cooling has the best overall performance and is the most widely used.

[0006] The reaction for producing maleic anhydride from n-butane is a strongly exothermic reaction. The target product is maleic anhydride, and the main byproduct is maleic acid. Other byproducts include methane, carbon monoxide, carbon dioxide, ethane, butene, and unoxidized n-butane. Typically, the heat of the partial oxidation reaction combined with the heat generated during byproduct processing is used to produce steam for energy output.

[0007] The reason for producing maleic acid as a byproduct in existing maleic anhydride processes is that it alleviates the conflict between product yield and energy consumption, maximizing economic benefits. However, the addition of a maleic acid recovery and refining unit increases the investment and operating costs of existing maleic anhydride units.

[0008] The existing fixed-bed maleic anhydride process uses a molten salt system for heat removal, controlling the reaction temperature and outputting heat energy. An excess of air is used to keep the air-butane mixture away from the deflagration limit.

[0009] In existing tubular fixed-bed maleic anhydride reaction systems, the length of the tubes in medium to large-sized tubular molten salt deheating reactors can reach over 6 meters, with tens of thousands of tubes densely arranged. Heat exchange relies on the flow of molten salt between the tubes, resulting in a complex structure, high cost, and poor reliability. The tubes are susceptible to corrosion and leakage, allowing molten salt to enter the catalyst bed, damaging the catalyst and causing significant losses.

[0010] When a mixture of preheated air and n-butane enters the catalyst bed in the tube-and-tube pipeline, an exothermic reaction begins. Current methods to keep the air-butane mixture away from the deflagration limit involve using a large amount of excess air and a small amount of n-butane, thus keeping the mixture away from the space deflagration limit at high temperatures. However, within the reaction tube, as the gas mixture flows forward, the amount of partial oxidation products increases, as do the contents of dry gas and low-boiling-point combustible components, leading to a rise in temperature and an increased tendency for deflagration. Within the reaction tube, oxygen is always in excess, ensuring that the conditions for gas-phase combustion and deflagration are always present. The tendency for gas-phase combustion and deflagration increases with increasing tube length and diameter, and with an increase in the number of reaction tubes, the non-uniformity of the molten salt flow field increases, further increasing the tendency for overheating and deflagration. Under these reaction and cooling processes, hot spots easily form within the catalyst bed, and more hot spots easily appear near these hot spots, generating more deflagration, which in turn generates even more hot spots. Therefore, the inventors believe that the production capacity of maleic anhydride using the existing tubular reactor with molten salt deheating will be limited, deflagration is difficult to avoid, the deflagration area is prone to overheating, the overheated area is prone to deflagration, and the temperature control of the reactor catalyst bed is difficult.

[0011] Studies have shown that excessive oxidation of maleic anhydride due to further contact with gaseous oxygen and adsorbed oxygen is the main reason for the decrease in maleic anhydride yield. Because a large excess air coefficient is used to control deflagration, the oxygen concentration is high both inside and outside the catalyst bed of the existing fixed bed, including the outlet heat exchanger and even the trapping device, resulting in over-oxidation. This limits the choice of trapping method and further reduces the maleic anhydride yield.

[0012] The inventors discovered that in the existing maleic anhydride fixed-bed process, the method of controlling deflagration with excess air presents an insurmountable contradiction in terms of controlling peroxidation, improving selectivity, and increasing conversion rate.

[0013] In the existing fixed-bed anhydride homogenization process, a large amount of compressed air is required, resulting in high power consumption. At the same time, a large amount of exhaust gas is discharged, and the cost of post-treatment equipment is high, resulting in high operating costs and environmental pollution.

[0014] In existing maleic anhydride production facilities, maleic anhydride is usually the main product. To improve product yield and the economic efficiency of the facility, maleic acid is generally required as a byproduct. The production of maleic acid byproducts requires large amounts of water or solvents. Furthermore, in the aqueous phase hydrogenation process of maleic anhydride to produce succinic acid, maleic anhydride needs to be hydrolyzed into maleic acid, followed by hydrogenation of the maleic acid in an aqueous solution. The refining process from n-butane to succinic acid involves repeated dehydration and water addition processes, high investment costs, high energy consumption, and significant pollution. Summary of the Invention

[0015] To address the problems existing in the prior art, the purpose of this invention is to provide a method and apparatus for the combined production of succinic acid through hydrocarbon ejection cycle stepwise oxidation and hydrogenation. A composite heat removal method, consisting of gas circulation heat removal and high-pressure steam tubular fixed-bed heat removal, is used, eliminating the need for a molten salt heat removal system and thus solving the problems associated with molten salt systems.

[0016] To solve the above technical problems, the technical solution of the present invention is as follows:

[0017] In the first aspect, a method for producing succinic acid by a combination of hydrocarbon ejection cycle stepwise oxidation and hydrogenation, the method including a method for preparing maleic anhydride, wherein the maleic anhydride is prepared by mixing air, n-butane, water vapor and inert gas and reacting them to obtain a mixture of maleic anhydride.

[0018] Adding water vapor and inert gas reduces the concentrations of n-butane and oxygen in the mixed gas, especially the oxygen concentration, which significantly reduces the peroxidation reaction and increases the yield of maleic anhydride.

[0019] During the reaction, water vapor absorbs the heat energy to form high-temperature, high-pressure steam, combining two heat dissipation methods—heat removal from the reactor and heat energy output—to control the reaction temperature and prevent explosions. Simultaneously, the addition of water vapor reduces the oxygen concentration in the reactants, preventing deflagration.

[0020] The role of inert gas is to reduce the oxygen concentration of the reactants, prevent deflagration, and absorb the heat of reaction.

[0021] This invention absorbs maleic anhydride from the reaction products in the form of maleic acid aqueous solution, and allows and requires that the reaction products contain a high water vapor content.

[0022] Secondly, the apparatus for the combined production of succinic acid by hydrocarbon ejection cycle stepwise oxidation and hydrogenation includes: a reaction unit, an ejector unit, and a compressed air unit. The gas inlet of the reaction unit is connected to the outlet of the ejector unit. The compressed air unit and the hydrocarbon gas source are respectively connected to the jet inlet of the ejector unit. The jet inlet of the ejector unit is connected to a steam source. The ejector unit of the reaction unit is also included.

[0023] The reaction apparatus provides the site for the reaction. An ejector device is used to introduce air into the reaction apparatus, and high-temperature, high-pressure steam is used as the ejector power to increase the pressure and temperature of the fresh compressed air.

[0024] One or more technical solutions of the present invention have the following beneficial effects:

[0025] This invention employs a combined process of partial oxidation of n-butane to produce maleic anhydride, hydrolysis of maleic anhydride to produce maleic acid, and hydrogenation treatment of maleic acid aqueous solution to produce succinic acid. It combines a tail gas complete oxidation treatment exothermic method with a combined heat removal method of gas circulation cooling and tubular steam heat removal, and a method of recycling unreacted n-butane and insufficiently oxidized products. This solves the problems of low product yield, complex equipment structure, high cost, poor safety and reliability, and large emissions pollution in existing maleic anhydride and succinic acid production processes.

[0026] This invention produces succinic acid by hydrogenating an aqueous solution of maleic acid. The organic matter in the wastewater from this process is mainly succinic acid, which is easily biodegradable and has low treatment costs. Existing maleic anhydride production facilities produce wastewater containing mainly maleic acid, resulting in high treatment costs. This invention, through the hydrogenation treatment of the maleic acid aqueous solution, simultaneously reduces the difficulty of treating the organic wastewater from the entire plant. Attached Figure Description

[0027] The accompanying drawings, which form part of this invention, are used to provide a further understanding of this application. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0028] Figure 1 A structural diagram of an apparatus for the combined production of succinic acid by stepwise oxidation and hydrogenation of hydrocarbons via a hydrocarbon ejector cycle;

[0029] Among them, 1. Raw material hydrocarbon unit, 2. Heat exchange and separation unit, 3. Reaction unit, 4. Ejector unit, 5. Compressed air unit, 6. Thermal energy unit, 7. Boiler, 8. Water supply unit, 9. Hydrogenation unit, 10. Water treatment unit, 11. Concentration and crystallization unit. Detailed Implementation

[0030] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0031] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0032] Industrial-grade n-butane primarily originates from mixed C4 fractions. The main components of these mixed C4 fractions include n-butane, isobutane, n-butene, isobutene, butadiene, propane, and pentane, and are mainly used as chemical feedstocks and fuels. Isobutane, n-butene, isobutene, and butadiene are frequently extracted for use as chemical feedstocks. The remaining mixed C4 feedstock, with n-butane as the main component, is often used to blend liquefied petroleum gas (LPG) for use as fuel in thermoelectric plants. This component is also used in the production of maleic anhydride. In this invention, the maleic anhydride feedstock of the mixed C4 fraction with n-butane as the main component is simply referred to as n-butane.

[0033] Succinic acid, also known as succinic acid, has a molecular weight of 118.09, a melting point of 188℃, a boiling point of 235℃, and a density of 1.572. At room temperature, it is a colorless or white solid with an acidic odor. It is an important organic chemical raw material and intermediate, widely found in humans, animals, plants, and microorganisms. It was first obtained in 1546 by boiling amber. Its main applications are in pharmaceuticals, pesticides, food, synthetic plastics, rubber, protective coatings, dyes, and other industries. Besides these applications, succinic acid can also be used to derive many downstream products, such as 1,4-butanediol, tetrahydrofuran, γ-butyrolactone, and methylpyrrolidone. Succinic acid can serve as a major raw material for biodegradable plastics such as aliphatic diacid diol polyesters, and with the guidance and development direction of global and national environmental protection and biodegradability policies, it faces enormous market opportunities.

[0034] In the first aspect, a method for producing succinic acid by a combination of hydrocarbon ejection cycle stepwise oxidation and hydrogenation, the method including a method for preparing maleic anhydride, wherein the maleic anhydride is prepared by mixing air, n-butane, water vapor and inert gas and reacting them to obtain a mixture of maleic anhydride.

[0035] Adding water vapor and inert gas reduces the concentrations of n-butane and oxygen in the mixed gas, especially the oxygen concentration, which significantly reduces the peroxidation reaction and increases the yield of maleic anhydride.

[0036] During the reaction, water vapor absorbs the heat energy to form high-temperature, high-pressure steam, combining two heat dissipation methods—heat removal from the reactor and heat energy output—to control the reaction temperature and prevent explosions. Simultaneously, the addition of water vapor reduces the oxygen concentration in the reactants, preventing deflagration.

[0037] The role of inert gas is to reduce the oxygen concentration of the reactants, prevent deflagration, and absorb the heat of reaction.

[0038] This solves the problem of gas-phase combustion in the later part of the long reaction tube.

[0039] In some embodiments of the present invention, the inert gas is one or more of inert gases such as carbon dioxide, nitrogen, and argon; preferably one or two of carbon dioxide and nitrogen; more preferably carbon dioxide. Selecting carbon dioxide as the inert gas component with its high specific heat allows for better absorption of reaction heat and control of the catalyst bed temperature in the reactor. Carbon dioxide and water vapor have good anti-detonation effects, require small amounts, and result in a higher proportion of maleic anhydride in the product compared to existing processes, facilitating the separation of maleic anhydride from the product.

[0040] In some embodiments of the present invention, the maleic anhydride mixture is condensed and then mixed with condensate to obtain an aqueous solution of maleic acid, which is then subjected to a hydrogenation reaction to obtain succinic acid.

[0041] The maleic anhydride mixture contains maleic anhydride gas, water vapor, inert gas, unreacted n-butane, and under-oxidized hydrocarbons. Upon condensation, the maleic anhydride, with the highest boiling point, liquefies and separates. Simultaneously, some water vapor condenses to form condensate. The maleic anhydride and condensate mix, and the maleic anhydride hydrolyzes to give maleic acid, forming an aqueous maleic acid solution. The maleic acid solution undergoes a hydrogenation reaction to yield succinic acid.

[0042] Succinic acid can be further separated and purified by hydrogenation and cooling crystallization to produce high-quality derivatives, such as succinic anhydride and butanediol.

[0043] Succinic acid can be further hydrogenated to produce butanediol, and succinic acid and butanediol can be further synthesized into biodegradable plastics.

[0044] This invention addresses the market demand for butanediol succinate in the biodegradable plastics market. Succinic acid, produced by hydrogenating maleic acid aqueous solution, is the main intermediate chemical product of this device. Maleic anhydride, a product of partial oxidation of hydrocarbons, is completely absorbed by maleic acid aqueous solution to become maleic acid aqueous solution. This solves the problems of existing maleic anhydride devices, which use maleic anhydride as the main product and maleic acid as a by-product, requiring two sets of collection and purification devices, resulting in high equipment cost and high energy consumption.

[0045] This invention uses maleic acid aqueous solution as the product of the oxidation reaction. The advantages of hydrogenating and refining maleic acid aqueous solution to produce succinic acid include, but are not limited to, a simplified hydrocarbon oxidation product recovery device, direct hydrogenation and refining of maleic acid aqueous solution, and simultaneous completion of hydrogenation and refining processes. Direct hydrogenation and refining of maleic acid aqueous solution avoids repeated dehydration and water addition processes, avoids the handling, packaging, storage and transportation of solid materials, and makes succinic acid-containing wastewater easier to biodegrade and treat compared to maleic acid-containing wastewater, thus reducing wastewater treatment costs.

[0046] In the apparatus of this invention, high-temperature and high-pressure water vapor and n-butane vapor serve as the driving fluids of the ejector system, ejecting inert gases and other circulating gases. The inert gases include water vapor and carbon dioxide generated during the reaction, unreacted n-butane, nitrogen, etc.

[0047] In some embodiments of the present invention, the volume ratio of water vapor, air, and inert gas in the reactants can vary within a certain range, for example: 1-5:1-2:1-10; preferably 1:1:1. The ratio of n-butane to oxygen in the mixed gas is close to the equivalence ratio of partial oxidation. The present invention uses air as the oxidant with an equivalence ratio close to that of hydrocarbon partial oxidation, and water vapor and inert gas as stabilizers, thus solving the problems of large compressed air processing capacity, high power consumption, large exhaust gas emissions, and serious pollution in existing processes.

[0048] Secondly, the apparatus for the combined production of succinic acid by hydrocarbon ejection cycle stepwise oxidation and hydrogenation includes: a reaction unit, an ejector unit, and a compressed air unit. The gas inlet of the reaction unit is connected to the outlet of the ejector unit. The compressed air unit and the hydrocarbon gas source are respectively connected to the jet inlet of the ejector unit. The jet inlet of the ejector unit is connected to a steam source. The ejector unit of the reaction unit is also included.

[0049] The reaction apparatus provides the site for the reaction. An ejector device is used to introduce air into the reaction apparatus, and high-temperature, high-pressure steam is used as the ejector power to increase the pressure and temperature of the fresh compressed air.

[0050] This invention utilizes steam for heat removal and product endothermy, thus solving the corrosion and leakage problems associated with existing molten salt heat removal systems. It also addresses the issue of deflagration in the latter half of the tubular reaction structure as the tubes grow longer.

[0051] In some embodiments of the present invention, a heat exchange separation device is also included, wherein the product outlet of the reaction device is connected to the reaction gas inlet of the heat exchange separation device, and the reaction gas outlet of the heat exchange separation device is connected to the ejector device.

[0052] The gaseous products from the reaction unit enter a heat exchanger for cooling, separating maleic anhydride from the gas. The remaining gaseous products include carbon dioxide, nitrogen, water vapor, a small amount of unreacted n-butane, and under-oxidized hydrocarbons. A portion of the remaining gaseous products enters the reaction unit through the gas outlet of the heat exchanger for further reaction. These gaseous products are then injected back into the reactor inlet using hydrocarbon vapor and water vapor to mix with fresh air, and then re-enter the catalyst bed in the reactor for further reaction. This allows the unreacted n-butane and under-oxidized products to further react to form maleic anhydride, increasing the conversion rate of n-butane and reducing the amount of exhaust gas.

[0053] The presence of inert gas in the circulating material reduces the oxygen concentration in both reactants and products, lowering the probability of over-oxidation and preventing deflagration. This resolves the contradiction between conversion rate and selectivity in existing reaction systems and reduces the likelihood of deflagration.

[0054] In some embodiments of the present invention, the heat exchange separation device has a tubular heat exchange structure, the inlet of the tubular heat exchange structure is connected to a hydrocarbon source and a water source respectively, the water vapor outlet of the tubular heat exchange structure is connected to a reaction device, and the hydrocarbon vapor outlet of the tubular heat exchange structure is connected to the jet inlet of the ejector device.

[0055] In some embodiments of the present invention, the reaction apparatus is a tubular fixed-bed structure. The gas inlet of the heat exchange tubes of the tubular fixed-bed structure is connected to the steam outlet of the heat exchange separation device, and the gas outlet of the heat exchange tubes is connected to the ejector device. When the material mixture passes through the catalyst bed, the raw hydrocarbon is oxidized, releasing heat of reaction, which is absorbed by the reaction products and the catalyst bed, and simultaneously transferred to the steam through the tubes. The combined heat removal method of gas circulation cooling and tube-based steam heat removal lowers the temperature during the reaction process and improves safety. A radial fixed-bed reactor is preferred, as radial fixed-bed reactors have lower operating resistance, further reducing the power consumption of the reactants.

[0056] In some embodiments of the present invention, a boiler is also included. The reaction gas outlet of the heat exchanger separation device is connected to the combustion gas inlet of the boiler, the gas outlet of the heat exchanger tubes of the reaction device is connected to the heat exchange inlet of the boiler, and the heat exchange outlet ejector of the boiler is connected. The product gas after heat exchange in the heat exchanger separation device includes carbon dioxide, water vapor, nitrogen, methane, ethane, etc., a portion of which is sent to the boiler for complete combustion and discharge, releasing heat. The water vapor in the heat exchanger tubes of the reaction device enters the boiler for further heating, further increasing the water vapor temperature and outputting high-quality heat energy. The heated water vapor enters the ejector, increasing the temperature of the reactants and having an endothermic effect in the reaction. A portion of the heat-exchanged product gas discharged from the heat exchanger separation device is sent to the ejector for reaction, and the inert circulating gases such as carbon dioxide, nitrogen, and water vapor contained therein continue to be added as inert gases to the reaction mixture to lower the reaction temperature.

[0057] In some embodiments of the present invention, a heat energy utilization device is also included, and the combustion gas outlet of the boiler is connected to the heat energy utilization device. A portion of the heat-exchange product gas discharged from the heat exchange separation device undergoes complete combustion and heat exchange again, ensuring full utilization of the heat, before being discharged.

[0058] In some embodiments of the present invention, a hydrogenation device, a water treatment device, a concentration and crystallization device are also included. The liquid outlet of the heat exchange separation device is connected to the hydrogenation device, the wastewater outlet of the hydrogenation device is connected to the water treatment device, and the product outlet of the hydrogenation device is connected to the concentration and crystallization device.

[0059] A method for producing succinic acid using a hydrocarbon ejector cycle stepwise oxidation and hydrogenation combined process.

[0060] High-pressure liquid hydrocarbon feedstock from feedstock hydrocarbon unit 1 enters heat exchange separation unit 2, where it absorbs heat from the product and vaporizes into superheated hydrocarbon vapor. This vapor is then mixed with high-temperature, high-pressure steam from boiler 7 via ejector device 4. Compressed air from compressed air unit 5 and inert circulating gas from heat exchange separation unit 2 are then ejected to form a homogeneous mixture, which enters the catalyst bed in reaction unit 3 for reaction. The reaction products then enter heat exchange separation unit 2, where they are cooled by steam and feedstock hydrocarbons, and the heat energy is transferred to the steam input from water supply unit 8. The high-temperature, high-pressure steam is further heated by boiler 7 and then divided into two streams: one stream is output through heat energy unit 6, and the other stream enters ejector device 4 as a motive fluid. The product, maleic anhydride, condenses and deposits at the bottom, dissolves in water to form maleic acid aqueous solution, and is discharged into maleic acid hydrogenation unit 9 for hydrogenation and hydrogenation refining separation processes. Subsequently, the generated wastewater enters water treatment unit 10, and the succinic acid aqueous solution enters succinic acid concentration and crystallization unit 11 to complete the concentration or crystallization process.

[0061] The wastewater from the hydrogenation process is the wastewater from the hydrogenation of maleic acid. The concentration of maleic acid is low, resulting in low treatment costs. The waste gas generated during hydrogenation, concentration, and crystallization can be treated in boiler 7 before being discharged.

[0062] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An apparatus for the combined production of succinic acid by hydrocarbon ejector cycle stepwise oxidation and hydrogenation, characterized in that: include: The reaction apparatus, ejector device, and compressed air device are connected. The gas inlet of the reaction apparatus is connected to the outlet of the ejector device. The compressed air device and the hydrocarbon gas source are respectively connected to the jet inlet of the ejector device. The jet inlet of the ejector device is connected to the water vapor source. The ejector device of the reaction apparatus. The apparatus for the combined production of succinic acid by hydrocarbon ejection cycle stepwise oxidation and hydrogenation also includes a heat exchange separation unit. The product outlet of the reaction unit is connected to the reaction gas inlet of the heat exchange separation unit, and the reaction gas outlet of the heat exchange separation unit is connected to the ejection unit.

2. A method for producing succinic acid by combining hydrocarbon ejector cycle stepwise oxidation and hydrogenation, using the apparatus for producing succinic acid by combining hydrocarbon ejector cycle stepwise oxidation and hydrogenation as described in claim 1, characterized in that: The method includes a method for preparing maleic anhydride, wherein the maleic anhydride is prepared by mixing air, n-butane, water vapor and inert gas and reacting them to obtain a mixture of maleic anhydride.

3. The method for producing succinic acid by combined hydrocarbon ejection cycle stepwise oxidation and hydrogenation as described in claim 2, characterized in that: The inert gas is one or more of carbon dioxide, nitrogen, and argon.

4. The method for producing succinic acid by combined hydrocarbon ejection cycle stepwise oxidation and hydrogenation as described in claim 2, characterized in that: The inert gas is one or both of carbon dioxide and nitrogen.

5. The method for producing succinic acid by combined hydrocarbon ejection cycle stepwise oxidation and hydrogenation as described in claim 2, characterized in that: The inert gas is carbon dioxide.

6. The method for producing succinic acid by combined hydrocarbon ejection cycle stepwise oxidation and hydrogenation as described in claim 2, characterized in that: After condensation, the maleic anhydride mixture is mixed with condensate to obtain an aqueous solution of maleic acid, which is then subjected to a hydrogenation reaction to obtain succinic acid.

7. The method for producing succinic acid by combined hydrocarbon ejection cycle stepwise oxidation and hydrogenation as described in claim 2, characterized in that: The volume ratio of water vapor, air, n-butane, and inert gas is 1-5:1-2:1-10.

8. The method for producing succinic acid by combined hydrocarbon ejection cycle stepwise oxidation and hydrogenation as described in claim 2, characterized in that: The volume ratio of water vapor, air, n-butane, and inert gas is 1:1:

1.

9. The apparatus for the combined production of succinic acid by hydrocarbon ejection cycle stepwise oxidation and hydrogenation as described in claim 1, characterized in that: The heat exchange separation device has a shell-and-tube heat exchange structure. The inlet of the shell-and-tube heat exchange structure is connected to the hydrocarbon source and the water source respectively. The water vapor outlet of the shell-and-tube heat exchange structure is connected to the reaction device. The hydrocarbon vapor outlet of the shell-and-tube heat exchange structure is connected to the jet inlet of the ejector device.

10. The apparatus for the combined production of succinic acid by hydrocarbon ejection cycle stepwise oxidation and hydrogenation as described in claim 9, characterized in that: The reaction device is a tubular fixed bed structure. The gas inlet of the heat exchange tubes of the tubular fixed bed structure is connected to the steam outlet of the heat exchange separation device, and the gas outlet of the heat exchange tubes of the tubular fixed bed structure is connected to the ejector device.

11. The apparatus for the combined production of succinic acid by hydrocarbon ejection cycle stepwise oxidation and hydrogenation as described in claim 10, characterized in that: It also includes a boiler, the reaction gas outlet of the heat exchanger and separator is connected to the combustion gas inlet of the boiler, the gas outlet of the heat exchanger tubes of the reaction unit is connected to the heat exchange inlet of the boiler, and the heat exchange outlet of the boiler is connected to the ejector device.

12. The apparatus for the combined production of succinic acid by hydrocarbon ejector cycle stepwise oxidation and hydrogenation as described in claim 1, characterized in that: It also includes a heat energy utilization device, and the boiler's combustion gas outlet is connected to the heat energy utilization device; Alternatively, it may also include a hydrogenation unit, a water treatment unit, a concentration and crystallization unit, with the liquid outlet of the heat exchange separation unit connected to the hydrogenation unit, the wastewater outlet of the hydrogenation unit connected to the water treatment unit, and the product outlet of the hydrogenation unit connected to the concentration and crystallization unit.

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