Method for hydrogenating maleic anhydride and method for producing succinic acid containing the same

Abstract

The present invention relates to a method for producing succinic anhydride by maleic anhydride hydrogenation, comprising the steps of: (1) feeding maleic anhydride solution and hydrogen feedstock through an upper liquid phase feed port and an upper gas phase feed port of the first-stage hydrogenation reactor into a first-stage hydrogenation reactor to carry out a first-stage hydrogenation reaction and obtain a first-stage hydrogenation product; (2) feeding the first-stage hydrogenation product into a second-stage hydrogenation reactor to carry out a second-stage hydrogenation reaction and obtain a second-stage hydrogenation product, and optionally, feeding the first-stage hydrogenation product into a second-stage hydrogenation reactor to carry out a second-stage hydrogenation reaction and obtain a second-stage hydrogenation product, and optionally, (3) subjecting the second-stage hydrogenation product to a second-stage gas-liquid separation to obtain a first-stage gas phase and a first-stage liquid phase, and then feeding the first-stage gas phase and the first-stage liquid phase from an upper gas phase feed port and an upper liquid phase feed port of a second-stage hydrogenation reactor, respectively; and (4) subjecting the second-stage hydrogenation product to a second-stage gas-liquid separation to obtain a second-stage gas phase and a second-stage liquid phase, returning a portion of the second-stage liquid phase to step (1) to mix with the maleic anhydride solution to carry out the first-stage hydrogenation reaction, and optionally using a portion or all of the second-stage gas phase as recycled hydrogen. The present invention also relates to a method for producing succinic acid including such a method, a liquid phase hydrogenation reaction system, and a system for producing succinic acid including such a system.

Description

Detailed Description of the Invention

[0001] [Technical field] The present invention relates to a method for producing succinic anhydride by hydrogenation of maleic anhydride. The present invention also relates to a method for producing succinic acid comprising such a method. The present invention further relates to a liquid phase hydrogenation reaction system and a system for producing succinic acid comprising such a system. [Background technology] Succinic acid (C4H6O4) is a colorless or white odorless solid with an acidic taste. Succinic acid can react with bases, undergo reactions such as esterification and reduction, and can be dehydrated by heating to produce succinic anhydride, which can undergo nucleophilic substitution reactions in which hydroxyls are replaced by halogen atoms, amine compounds, acyl groups, etc. Succinic anhydride is an important fine chemical product and an organic synthesis intermediate. Succinic acid and its derivatives are useful platform chemicals and are widely used in the production of polymers, fuel additives, inks, cosmetics, and food and pharmaceutical additives. Succinic acid is an important monomer in the production of polybutylene succinate (PBS). With the rise of degradable plastic PBS resin worldwide, the production of succinic acid has attracted more and more widespread attention, with huge market potential and broad development prospects.

[0002] The processes for producing succinic acid mainly include microbial fermentation, electrochemical synthesis and maleic anhydride catalytic hydrogenation. The process of preparing succinic acid by microbial fermentation is cumbersome, produces a large amount of wastewater, and has high production and separation costs. The process of preparing succinic acid by electrochemical synthesis cannot achieve a high conversion rate, consumes a lot of electricity, is difficult to maintain the electrolytic cell, has serious electrode corrosion, and produces a large amount of wastewater, so it is not suitable for large-scale production. The catalytic hydrogenation process is to hydrogenate maleic anhydride or maleic acid under the action of a catalyst to produce succinic anhydride, which is then hydrolyzed to obtain succinic acid. This process for producing succinic acid has the advantages of high conversion rate, high product purity, no obvious side reactions, and environmental friendliness. It is the most widely used synthesis process of succinic acid in the industry at present.

[0003] Succinic anhydride is an important organic synthesis intermediate and fine chemical raw material. It can undergo hydrolysis, alcoholysis, esterification, halogenation, acylation and other reactions, and is widely used in the fields of medicine, pesticides, food, petrochemicals, building materials, synthetic resins, dyes and other fields. At present, there are few manufacturers producing succinic anhydride in the world, and the production volume is not large, but succinic anhydride is widely used, so there is a shortage of succinic anhydride around the world. The companies producing succinic anhydride in China are small in scale and the production volume is small, so it is far from meeting the domestic demand for succinic anhydride. In particular, high-purity succinic anhydride is almost entirely dependent on imports.

[0004] According to the source of raw materials, the main processes for preparing succinic anhydride include maleic anhydride hydrogenation process, succinic acid dehydration process, acetylene carbonylation process, etc. The current industrial production process is mainly maleic anhydride hydrogenation process and succinic acid dehydration process.

[0005] The succinic acid dehydration step is the first step in producing succinic anhydride, which requires obtaining the raw material succinic acid and dehydrating it under certain conditions. The source of succinic acid is scarce, and it is mainly produced by catalytic hydrogenation or electrolysis of maleic anhydride, so the production cost is high. As can be seen from the synthesis route, the dehydration of succinic acid to prepare succinic anhydride is the reverse reaction of the hydrolysis of succinic anhydride, while succinic anhydride can be easily hydrolyzed to produce succinic acid, so this process has no prospect of development in terms of both the rationality of the process route and the economics.

[0006] At present, most of the world's succinic anhydride production adopts the maleic anhydride hydrogenation process. Maleic anhydride is directly hydrogenated in an organic solvent to produce succinic anhydride. This process has a high conversion rate and yield, no obvious side reactions, and high product purity. However, the reaction of hydrogenating maleic anhydride to produce succinic anhydride is a strong exothermic reaction (ΔH=-128kJ / mol), so the adiabatic temperature rise of the reaction is large, and organic matter is easily polymerized and coked on the catalyst surface, resulting in a decrease in catalytic activity. At the same time, the accumulation of reaction heat makes it easy for the temperature of the catalyst layer to rise sharply, resulting in a temperature runaway phenomenon. Therefore, how to effectively reduce the heat released by the reaction is the focus and difficulty of the maleic anhydride hydrogenation process.

[0007] CN103570650A discloses a process for continuously producing succinic anhydride through the hydrogenation of maleic anhydride and co-producing succinic acid. A two-stage hydrogenation reactor is used. At the outlet of the primary hydrogenation reactor, after heat exchange of the raw material, part of the reaction liquid enters the secondary hydrogenation reactor, and the remaining reaction liquid is mixed with the raw material maleic anhydride solution and enters the primary hydrogenation reactor again. Although this process can achieve a certain reaction heat removal effect, the raw material at the outlet of the primary reactor still contains a certain amount of maleic anhydride, so when this raw material is recycled to the inlet of the primary reactor, the amount of maleic anhydride entering the primary reactor is not significantly reduced, and the amount of heat released by the reaction in the primary reactor is also not significantly reduced, so there is a great pressure in terms of reaction heat removal of the reactor.

[0008] CN107253938A discloses a production process for preparing high-purity succinic anhydride through the direct hydrogenation of maleic anhydride. The direct hydrogenation of maleic anhydride adopts a fixed bed for hydrogenation, hydrogen is recycled, and a small amount of hydrogen is only added as an auxiliary, the molar ratio of hydrogen to maleic anhydride is 800-1000, and hydrogen is added through four stages of cold hydrogen, so that maleic anhydride can react fully in the process of dropping from above, reducing the production of other heavy components such as butyrolactone, and then said maleic anhydride can fully participate in the reaction, and the main components of the reaction product are succinic anhydride, maleic anhydride and butyrolactone. This process can achieve a certain reaction heat removal effect, but because the amount of circulating hydrogen is relatively large, the energy consumption of the compressor for circulating hydrogen is relatively large, while the amount of hydrogen entering the reactor is large, and the volume of the reactor needs to be correspondingly increased, resulting in increased investment and increased energy consumption.

[0009] Therefore, there is an urgent need to develop a maleic anhydride hydrogenation reaction process that can effectively remove the heat released by the reaction and at the same time solve the current problems of the excessively high ratio of hydrogen to anhydride, high investment and high energy consumption.

[0010] The production process of maleic anhydride is mainly divided into benzene oxidation process and n-butane oxidation process according to the raw material route. With the development of large-scale intensification of maleic anhydride production, the post-treatment of maleic anhydride tends to adopt more and more solvent adsorption and desorption technology. Representative solvent adsorption and desorption processes include Huntsman process, Conser process, and ALMA process. The first two use dibutyl phthalate (DBP) as the solvent, and the last one uses diisobutyl hexahydrophthalate (DIBP) as the solvent. In any process, the crude maleic anhydride after absorption and desorption needs to be distilled and rectified many times before the rectified maleic anhydride product can be obtained, and multiple separation towers are operated under reduced pressure, which results in large capital investment, complicated process, and long process.

[0011] In addition, since the absorption solvent used for the production of maleic anhydride is different from the solvent used for the maleic anhydride hydrogenation reaction, the existing maleic anhydride production process and maleic anhydride hydrogenation reaction process cannot be combined, and they are two independent processes. Since different solvents are used in the process of producing maleic anhydride and the process of producing succinic anhydride, the solvent desorption, rectification, and recycling occur twice, and the product separation and purification also occur twice. Two independent sets of solvent separation and recovery, as well as product separation and rectification systems are required. Therefore, the existing process route has problems such as long process, large investment, high energy consumption, large loss of raw materials and auxiliary materials, and high operation costs. For companies with C4 resources or benzene resources, it is urgent to optimize and improve the succinic acid production process using butane or benzene as raw materials.

[0012] Therefore, there is still a need for a process and system for producing succinic anhydride by hydrogenating maleic anhydride, which can effectively remove the reaction heat and reduce the molar ratio of hydrogen to maleic anhydride, and a process and system for producing succinic acid by combining the process and system for producing succinic anhydride by hydrogenating maleic anhydride.In addition, there is still a need for an improved process and system for producing succinic acid, which can effectively integrate the step of producing maleic anhydride and the step of hydrogenating maleic anhydride to produce succinic anhydride, realize continuous production of succinic acid, and simplify the separation operation of maleic anhydride.

[0013] In order to solve many problems in the prior art, such as high heat generation, difficult heat removal, high molar ratio of hydrogen to maleic anhydride, high investment in the production process, high energy consumption, etc., in the hydrogenation reaction process and system for the hydrogenation reaction of maleic anhydride to succinic anhydride, the object of the present invention is to provide a process and system for producing succinic anhydride by the hydrogenation reaction of maleic anhydride, which has the characteristics of easy removal of reaction heat, low molar ratio of hydrogen to maleic anhydride, low investment, low energy consumption, and can achieve the desired maleic anhydride conversion rate and succinic anhydride selectivity.

[0014] Another object of the present invention is to provide a method and system for producing succinic acid, including a method and system for producing succinic anhydride by hydrogenating maleic anhydride, which can achieve the above-mentioned effects such as easy removal of reaction heat, a low molar ratio of hydrogen to maleic anhydride, and ability to produce succinic acid having desired quality.

[0015] Another object of the present invention is to provide a process and system for producing succinic acid through a full process using butane / benzene as raw material, which simplifies and improves the maleic anhydride separation operation process, realizes that the absorption solvent used for producing maleic anhydride and the solvent for maleic anhydride hydrogenation reaction are the same and are mutually applicable, and can obtain succinic acid with desired quality, and has the characteristics of simple process, low investment, strong applicability, easy control, etc. This process and system realizes the combined use of maleic anhydride separation process and maleic anhydride hydrogenation process.

[0016] The object of the present invention is achieved by one or more of the following aspects.

[0017] In a first aspect, the present invention provides a process for producing succinic anhydride by hydrogenation of maleic anhydride, the process comprising the steps of: (1) feeding a maleic anhydride solution and a hydrogen source into a first-stage hydrogenation reactor through an upper liquid phase feed port and an upper gas phase feed port of the first-stage hydrogenation reactor, respectively, to carry out a first-stage hydrogenation reaction and obtain a first-stage hydrogenation product; (2) supplying the first-stage hydrogenation product to a second-stage hydrogenation reactor for a second-stage hydrogenation reaction to obtain a second-stage hydrogenation product, optionally subjecting the first-stage hydrogenation product to a first-stage gas-liquid separation before entering the second-stage hydrogenation reactor to obtain a first-stage gas phase and a first-stage liquid phase, and then supplying the first-stage gas phase and the first-stage liquid phase from an upper gas phase supply port and an upper liquid phase supply port of the second-stage hydrogenation reactor, respectively; and (3) subjecting the second-stage hydrogenation product to a second-stage gas-liquid separation to obtain a second-stage gas phase and a second-stage liquid phase, returning a portion of the second-stage liquid phase to step (1) for mixing with the maleic anhydride solution and subjecting it to the first-stage hydrogenation reaction, and optionally using a portion or all of the second-stage gas phase as recycled hydrogen.

[0018] In a second aspect, the present invention provides a process for producing succinic acid comprising the hydrogenation process of maleic anhydride according to the present invention.

[0019] In a third aspect, the present invention provides a liquid phase hydrogenation reaction system comprising: a first stage hydrogenation reactor having an upper vapor phase feed port, an upper liquid phase feed port, and a lower exhaust port; a first-stage hydrogenation reaction product cooler and a first-stage gas-liquid separator, which are sequentially connected in series to the lower discharge port of the first-stage hydrogenation reactor; a second stage hydrogenation reactor connected in series with the first stage gas-liquid separator, the second stage hydrogenation reactor having an upper gas phase feed port, an upper liquid phase feed port, and a lower discharge port; a second stage gas-liquid separator connected in series with the lower discharge port of the second stage hydrogenation reactor; and a liquid phase feedstock supply pipeline connected to an upper liquid phase supply port of the first stage hydrogenation reactor, and optionally connected to an upper liquid phase supply port of the second stage hydrogenation reactor;

[0020] In a fourth aspect, the present invention provides a system for producing succinic acid from butane and / or benzene comprising a liquid phase hydrogenation reaction system according to the present invention as a maleic anhydride hydrogenation reaction unit.

[0021] In a fifth aspect, the present invention provides the use of a liquid phase hydrogenation reaction system according to the present invention in a succinic acid production system.

[0022] The technical solution of the present invention has at least the following advantages: By adopting the process of the present invention, the heat removal method of maleic anhydride hydrogenation is improved, the heat generated by the hydrogenation of maleic anhydride can be effectively removed, the ratio of hydrogen to anhydride in the system is reduced, the investment is reduced, and the desired maleic anhydride conversion rate and succinic anhydride selectivity are obtained;The maleic anhydride concentration in the maleic anhydride solution does not need to be too low, so the amount of solvent used is reduced, and the energy consumption of the subsequent solvent recovery is reduced;In the present invention, after the first-stage hydrogenation reaction, after cooling and gas-liquid separation, the gas phase is all fed to the second-stage reactor, which is conducive to effectively removing the reaction heat generated by the second-stage hydrogenation reaction;The operating conditions of the reaction of the present invention are mild, and the reactor can be operated at 40°C, which greatly reduces the severity of the reaction, and the temperature rise of the reaction bed is low, which is conducive to improving the selectivity of the catalyst and extending the life of the catalyst; The maleic anhydride solution is divided into several streams, e.g., two or three streams, each mixed with different raw materials, and the mixture is fed into various, e.g., two or three hydrogenation reactors, so that under the same throughput, the amount of maleic anhydride entering the first-stage reactor is reduced, so that the heat released by the reaction can be effectively controlled, and the operation is flexible and easy to control; The maleic anhydride separation unit of the present invention is simpler than the conventional process and saves equipment investment; the solvent used in the maleic anhydride separation unit is the same as the solvent used in maleic anhydride hydrogenation and can be a by-product generated in the process itself, and the solvent is recycled and does not need to be purchased, so that low investment, independent process and strong practicality can be realized; the maleic anhydride separation unit can be operated without vacuum, which not only saves equipment investment but also saves energy consumption; the maleic anhydride separation unit can adjust the operating conditions such as absorbent at any time according to the solution concentration or solvent required for the subsequent maleic anhydride hydrogenation reaction, so as to realize the controllable operation of the whole process in the industry; the maleic anhydride separation unit can effectively remove substances that are prone to side reactions, which is beneficial to the production of succinic anhydride; The succinic anhydride separation unit of the present invention is easy to operate and control; The succinic acid production step of the present invention has the characteristics of simple process, low investment, strong applicability, easy control, etc., and realizes the combined use of maleic anhydride separation process, maleic anhydride hydrogenation process and succinic anhydride separation process, so as to obtain the desired overall yield and quality of succinic acid. Description of the drawings FIG. 1 is a schematic diagram of a maleic anhydride hydrogenation process according to one embodiment of the present invention.

[0023] FIG. 2 is a schematic diagram of a maleic anhydride hydrogenation process according to another embodiment of the present invention.

[0024] FIG. 3 is a schematic diagram of a maleic anhydride hydrogenation process according to yet another embodiment of the present invention.

[0025] FIG. 4 is a schematic diagram of a process for producing succinic acid from butane / benzene in accordance with one embodiment of the present invention.

[0026] FIG. 5 is a schematic diagram of a process for producing succinic acid from butane / benzene in accordance with another embodiment of the present invention. Detailed Description of the Invention The range endpoints and any values ​​disclosed herein are not intended to be limited to the exact range or value, but rather should be understood to include values ​​close to such ranges or values. For numerical ranges, the endpoints of each range, the individual point values, can be combined with each other to obtain one or more new numerical ranges, which are considered to be specifically disclosed herein.

[0027] The present invention will be described in detail below with reference to specific figures and examples. Hereinafter, it should be pointed out that the following examples are only used to further illustrate the present invention, and cannot be understood as limiting the scope of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art according to the content of the present invention still fall within the protection scope of the present invention. Maleic Anhydride Hydrogenation Process The present invention provides a process for the production of succinic anhydride by hydrogenation of maleic anhydride, comprising the steps of: (1) feeding a maleic anhydride solution and a hydrogen source into a first-stage hydrogenation reactor through an upper liquid phase feed port and an upper gas phase feed port of the first-stage hydrogenation reactor, respectively, to carry out a first-stage hydrogenation reaction and obtain a first-stage hydrogenation product; (2) supplying the first-stage hydrogenation product to a second-stage hydrogenation reactor for a second-stage hydrogenation reaction to obtain a second-stage hydrogenation product, optionally subjecting the first-stage hydrogenation product to a first-stage gas-liquid separation before entering the second-stage hydrogenation reactor to obtain a first-stage gas phase and a first-stage liquid phase, and then supplying the first-stage gas phase and the first-stage liquid phase from an upper gas phase supply port and an upper liquid phase supply port of the second-stage hydrogenation reactor, respectively; and (3) subjecting the second-stage hydrogenation product to a second-stage gas-liquid separation to obtain a second-stage gas phase and a second-stage liquid phase, returning a portion of the second-stage liquid phase to step (1) and mixing it with the maleic anhydride solution to the first-stage hydrogenation reaction, and optionally using a portion or all of the second-stage gas phase as recycled hydrogen.

[0028] In the present invention, there is no special requirement for the composition of the maleic anhydride solution. According to a preferred embodiment of the present invention, in step (1), the maleic anhydride solution is a mixture of maleic anhydride and a solvent, and the type of the solvent can be, for example, a commonly used solvent, and the solvent is one or more of acetic anhydride, γ-butyrolactone, dioxane, tetrahydrofuran, aromatic hydrocarbon, ethyl acetate, C4 dibasic acid ester, ethanol, isopropanol, hexane, cyclohexane, propylene oxide, ketone and ether.

[0029] In general, increasing the maleic anhydride concentration in the raw material solution improves the productivity of the reactor, but the hydrogenation site on the catalyst surface is likely to reach an extremely high temperature, which tends to cause sintering of the catalytically active components or polymerization and coking of organic matter. By using the process of the present invention, a part of the second stage liquid phase (substantially free of maleic anhydride) is returned to step (1), which has the effect of diluting the maleic anhydride solution and reducing heat generation, so that it is not necessary to reduce the maleic anhydride concentration in the inflowing maleic anhydride solution too much, and the amount of solvent used is reduced, thereby reducing the energy consumption for subsequent solvent recovery. According to a preferred embodiment of the present invention, the maleic anhydride solution has a maleic anhydride concentration of 1 to 90% by weight, preferably 5 to 40% by weight, more preferably 10 to 40% by weight.

[0030] In the prior art, hydrogen is used to remove the reaction heat. However, the large amount of hydrogen provided by the high ratio of hydrogen to maleic anhydride (i.e., hydrogen / anhydride ratio) causes deep hydrogenation of succinic anhydride, producing by-products such as γ-butyrolactone, and greatly increasing the energy consumption of the hydrogen compressor. In the present invention, the reaction heat is effectively reduced by recycling a part of the second-stage liquid phase to the first-stage hydrogenation reactor, thereby achieving a significant reduction in the hydrogen / anhydride ratio. According to a preferred embodiment of the present invention, the molar ratio of the total amount of hydrogen to the total amount of maleic anhydride in the maleic anhydride solution is 5-100, preferably 5-60, more preferably 10-40, for example 15-35 or 20-30. Here, a low hydrogen / anhydride ratio can be used to indicate the efficient removal of reaction heat.

[0031] In the present invention, the hydrogen raw material can be fresh hydrogen or recycled hydrogen. According to a preferred embodiment of the present invention, the hydrogen raw material in step (1) is a mixed hydrogen gas of the recycled hydrogen and auxiliary hydrogen in step (3), so that the reaction heat can be effectively removed and the catalyst efficiency can be improved.

[0032] According to a preferred embodiment of the present invention, in step (1), the operating conditions of the first-stage hydrogenation reactor have no special requirements and can be conventional operating conditions, for example: a temperature of 30-100°C, preferably 40-80°C, for example, 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C, 50°C, etc., each reaction temperature is suitable for the present invention; and / or a reaction pressure of 0.1-10 MPa, preferably 0.5-5 MPa; and / or a reaction time of 0.5-8 h. -1 , preferably 0.5 to 5 hours -1 , e.g. 1, 2, 3, 4h -1 is the spatial velocity.

[0033] According to the present invention, in step (1), the maleic anhydride solution as the raw material is mixed with a part of the liquid phase raw material from the second-stage hydrogenation reaction in step (3), and then this mixture is supplied to the first-stage hydrogenation reactor from the liquid phase supply port of the first-stage hydrogenation reactor and contacted with hydrogen to carry out the hydrogenation reaction.

[0034] In step (1), the maleic anhydride solution can be divided into several streams, such as two or three streams, which can then be mixed with different feedstocks before entering various hydrogenation reactors, such as two or three, to reduce the amount of maleic anhydride entering the reactors and reduce the heat released in each reactor. The operation is flexible and easy to control. In one embodiment, the maleic anhydride solution can be divided into at least two streams, the first stream being mixed with a portion of the second stage liquid phase recycled in step (3) before entering the first stage hydrogenation reactor to carry out the first stage hydrogenation reaction, and the second stream being mixed with the second stage hydrogenation reactor to carry out the second stage hydrogenation reaction. For example, the second stream can be mixed with the first stage hydrogenation product or the first stage liquid phase (if first stage gas-liquid separation is performed) and used for the second stage hydrogenation reaction.

[0035] According to a preferred embodiment of the present invention, the first and second streams are each 5-95% by weight based on the raw maleic anhydride solution, more preferably, the first stream is 20-60% by weight, for example, 20-50% by weight, and the second stream is 40-80% by weight, for example, 50-80% by weight. As a result, the amount of heat released from each reactor can be reduced, which is very beneficial for heat removal and improves reaction efficiency.

[0036] According to a preferred embodiment of the present invention, in step (2), the operating conditions of the second-stage hydrogenation reactor have no special requirements and can be conventional operating conditions, for example, a temperature of 30-100°C, preferably 40-80°C, for example, 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 46°C, 47°C, 48°C, 49°C, 50°C, etc., each reaction temperature is suitable for the present invention; and / or a pressure of 0.1-10 MPa, preferably 0.5-5 MPa; and / or a reaction time of 0.5-8 h. -1 , preferably 0.5 to 5 hours -1 , e.g. 1, 2, 3, 4h -1 is the spatial velocity.

[0037] The present invention is mainly in the process design.There is no limitation on the hydrogenation catalyst, for example, the catalyst supported in the first hydrogenation reactor and the second hydrogenation reactor can be any maleic anhydride hydrogenation catalyst, for example, the catalysts described in Chinese patent applications CN114433100(A) and CN114433127(A) can be used.

[0038] According to a preferred embodiment of the invention, as the gas and liquid phases enter the first and second stage hydrogenation reactors, they optionally pass through a distributor and then contact the catalyst.

[0039] In the present invention, after the first-stage reactor, a gas-liquid separation can be arranged as necessary, and the gas phase and liquid phase enter the hydrogenation reactor respectively, preferably through a distributor, so that the raw 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 cost is low.

[0040] According to one embodiment of the present invention, in step (2), the first-stage hydrogenation product is subjected to first-stage gas-liquid separation to obtain a first-stage gas phase and a first-stage liquid phase, and the first-stage gas phase and the first-stage liquid phase are fed to a second-stage hydrogenation reactor through an upper gas phase feed port and an upper liquid phase feed port of the second-stage hydrogenation reactor, respectively, to carry out the second-stage hydrogenation reaction, and obtain the second-stage hydrogenation product.

[0041] According to a preferred embodiment of the present invention, in step (2), the first-stage hydrogenation product can be cooled before carrying out the first-stage gas-liquid separation.

[0042] According to a preferred embodiment of the present invention, in step (3), a part of the second-stage liquid phase feed can be cooled and converted into a cooled feed before being mixed with the maleic anhydride solution, so that the reaction heat can be effectively removed and the catalyst efficiency can be improved. Preferably, the part of the second-stage liquid phase feed is a feed cooled to 30-80°C, preferably 40-60°C.

[0043] According to a preferred embodiment of the present invention, in step (3), 20-90 wt%, preferably 30-70 wt%, of the second-stage liquid phase feedstock is returned to step (1) for use as a feedstock, and the remainder of the second-stage liquid phase is sent to a downstream separation system, such as a succinic anhydride separation unit, as a liquid phase product, so that heat can be effectively removed and reaction efficiency can be improved.

[0044] According to a preferred embodiment of the present invention, 0.5 to 2 wt % of the second-stage gaseous phase raw material of the second-stage hydrogenation reaction is extracted as fuel gas, and the remainder of the second-stage gaseous phase is used as circulating hydrogen. Preferably, 0.5 to 2 wt % of the second-stage gaseous phase is extracted as fuel gas, and the remainder of the second-stage gaseous phase is cooled and recycled to the first-stage hydrogenation reactor, and is mixed with fresh hydrogen as an auxiliary before entering the first-stage hydrogenation reactor.

[0045] According to a preferred embodiment of the present invention, a part or all of the second-stage gas phase obtained by gas-liquid separation of the second-stage hydrogenation product is recycled to the first-stage hydrogenation reactor and used as circulating hydrogen, and the remainder is used as vent gas, and a part of the second-stage liquid phase feedstock obtained by gas-liquid separation of the second-stage hydrogenation product is recycled to the first-stage hydrogenation reactor and used as feedstock.

[0046] According to a preferred embodiment of the present invention, the process further includes the steps of cooling the second-stage gas phase obtained by gas-liquid separation of the second-stage hydrogenation product in step (3), followed by a third-stage gas-liquid separation to obtain a third gas phase and a third liquid phase, using a part or all of the third gas phase as circulating hydrogen to be mixed with auxiliary hydrogen as a hydrogen feedstock for the first-stage hydrogenation reactor, and optionally returning the third liquid phase to the second-stage gas-liquid separator to perform second-stage gas-liquid separation. The second-stage gas phase obtained by gas-liquid separation of the second-stage hydrogenation product is preferably cooled to a temperature of 30-80°C through a heat exchanger, which can effectively remove heat and improve catalyst efficiency.

[0047] According to a preferred embodiment of the present invention, after gas-liquid separation of the second-stage hydrogenation reaction product, the second-stage gas phase feedstock can be cooled through a heat exchanger, and the cooling temperature is preferably 30 to 80°C. The cooled feedstock is further subjected to gas-liquid separation, and the obtained gas phase is recycled to step (1), and the obtained liquid phase is returned to the previous gas-liquid separator.

[0048] In a specific embodiment of the present invention, the maleic anhydride hydrogenation process comprises carrying out a two-stage hydrogenation reaction, (1) dividing the maleic anhydride solution into two streams, mixing the first stream with a part of the cooled or uncooled second-stage liquid phase feedstock, and then feeding the mixture into the first-stage hydrogenation reactor through the upper liquid phase feed port of the first-stage hydrogenation reactor to contact the hydrogenation feedstock for hydrogenation reaction, and feeding the hydrogenation feedstock into the first-stage hydrogenation reactor through the upper gas phase feed port of the first-stage hydrogenation reactor; (2) subjecting the first-stage hydrogenation product to cooling and first-stage gas-liquid separation in sequence to obtain the first-stage gas phase and the first-stage liquid phase, feeding all of the first-stage gas phase to the second-stage hydrogenation reactor through the upper gas phase feed port of the second-stage hydrogenation reactor, mixing the first-stage liquid phase with a second stream of the maleic anhydride solution, and then feeding the mixture to the second-stage hydrogenation reactor through the upper liquid phase feed port of the second-stage reactor to react with hydrogen, and converting all of the maleic anhydride to succinic anhydride by the hydrogenation reaction; and (3) subjecting the second-stage hydrogenation product to second-stage gas-liquid separation to obtain a second-stage gas phase and a second-stage liquid phase, recycling a portion of the second-stage liquid phase to step (1) and mixing them, and optionally using all or a portion of the second-stage gas phase as circulating hydrogen.

[0049] In a preferred maleic anhydride hydrogenation process of the present invention, maleic anhydride is used as a raw material for hydrogenation to produce succinic anhydride. The maleic anhydride solution is divided into at least two streams, the first stream is mixed with a part of the second-stage liquid phase raw material from the second-stage hydrogenation reaction and then fed to the first-stage hydrogenation reactor from the top of the first-stage hydrogenation reactor, and the second stream is mixed with the first-stage liquid phase raw material from the first-stage hydrogenation reaction and then fed to the second-stage hydrogenation reactor from the top of the second-stage hydrogenation reactor. After the two-stage hydrogenation reaction, all the maleic anhydride is converted to succinic anhydride. In the present invention, the maleic anhydride solution is divided into at least two streams, each mixed with a different raw material and then fed into two hydrogenation reactors, so that the amount of maleic anhydride entering the reactors is reduced, the heat released in each reactor is reduced, and the operation is flexible and easy to control. At the same time, the maleic anhydride concentration in the inflowing maleic anhydride solution does not need to be too low, and the amount of solvent used is reduced, so the energy consumption for subsequent solvent recovery is reduced. The present invention has the characteristics of simple process, low investment, strong applicability, easy control, etc.

[0050] The maleic anhydride hydrogenation process of the present invention has good gas-liquid-solid contact, high catalyst utilization rate, and low investment. The reaction operating conditions are mild, the reaction can be carried out at about 40°C, and the temperature rise of the reaction bed is low. Compared with the prior art, the reaction temperature is significantly reduced, the catalyst selectivity is improved, and the catalyst life is extended. [Succinic acid production process] The present invention provides a process for the production of succinic acid, including the maleic anhydride hydrogenation process according to the present invention, which easily removes the heat of reaction, has a low molar ratio of hydrogen to maleic anhydride, and provides succinic acid of desired quality and yield.

[0051] The present invention also provides a process for producing succinic acid, which includes a maleic anhydride separation process and a maleic anhydride hydrogenation process, preferably a process for producing succinic acid, which includes a maleic anhydride hydrogenation process according to the present invention. In the maleic anhydride separation process, a mixture containing maleic anhydride is fed to a maleic anhydride separation unit equipped with an absorption tower and a rectification tower, and absorbed and rectified to obtain a maleic anhydride solution. In this way, the present invention simplifies and improves the maleic anhydride separation step, reduces energy consumption and investment, and improves the yield of succinic anhydride. In addition, by the combined operation of the maleic anhydride separation process and the maleic anhydride hydrogenation process, the absorption solvent for producing maleic anhydride can be used as the raw material for maleic anhydride hydrogenation to produce succinic anhydride, which is helpful in constructing a whole process production process.

[0052] In a specific embodiment of the present invention, a process for producing succinic acid from butane and / or benzene comprises the following steps: 1) subjecting butane and / or benzene and an oxygen-containing gas to an oxidation reaction in an oxidation reaction unit to obtain an oxidation reaction product; 2) supplying the oxidation reaction product to a maleic anhydride separation unit including an absorption tower and a rectification tower to obtain a maleic anhydride solution through absorption and rectification; 3) feeding the maleic anhydride solution into a maleic anhydride hydrogenation reaction unit to carry out maleic anhydride hydrogenation reaction, preferably maleic anhydride hydrogenation reaction according to the present invention, to obtain a hydrogenation product; 4) sending the unrecycled second-stage liquid phase from the second-stage hydrogenation reaction to a succinic anhydride separation unit to separate succinic anhydride and a solvent; optionally returning the separated solvent to step (2) and recycling it as an absorbent in the absorption tower; optionally using the separated solvent to dilute the maleic anhydride solution from the maleic anhydride separation unit, and then sending it to the maleic anhydride hydrogenation reaction unit; 5) feeding the succinic anhydride to a succinic anhydride hydrolysis unit for hydrolysis and crystallization to obtain succinic acid product.

[0053] In the present invention, there is no special requirement for the oxygen-containing gas. In the present invention, any oxygen-containing gas commonly used for oxidation can be used, for example, air and / or oxygen can be used.

[0054] The process of the present invention specifically comprises the following steps: 1) feeding butane / benzene and air to an oxidation reaction unit; 2) feeding the oxidation reaction product to a maleic anhydride separation unit for absorption and rectification to obtain a maleic anhydride solution; 3) feeding the maleic anhydride solution into a maleic anhydride hydrogenation reaction unit; 4) passing the non-recycled second stage liquid phase of the hydrogenation product through a succinic anhydride separation unit to obtain succinic anhydride and solvent products, and recycling the separated solvent back to step (2); 5) feeding the separated succinic anhydride to a hydrolysis unit for hydrolysis and crystallization to obtain succinic acid product.

[0055] According to the present invention, in step 1), butane / benzene and oxygen-containing gas such as air are supplied to the oxidation reaction unit. The design and operation conditions of the oxidation reaction unit are not particularly limited and can be determined by those skilled in the art according to their professional knowledge and prior art, for example, the operation temperature of the oxidation reaction unit is 400-450°C, the operation pressure is 0.1-0.3MPag, and the reaction heat is removed by a molten salt cooler and a gas cooler.

[0056] According to the present invention, in step 2), the maleic anhydride separation unit mainly includes an absorption tower, a rectification tower, and other devices, such as heat exchangers, pumps, tanks, pipelines, etc., which are determined by those skilled in the art according to the situation and the prior art. The maleic anhydride separation unit can be operated without vacuum. The oxidation reaction product after heat exchange and cooling is fed to the absorption tower from the bottom of the absorption tower, the solvent is fed to the absorption tower from the top of the absorption tower, the raw material from the top of the absorption tower is sent to the outside of the boundary area, and the rich solvent obtained in the absorption tower kettle is fed to the rectification tower. The raw material at the top of the rectification tower is withdrawn and sent to the outside of the boundary area, and the raw material in the tower kettle is sent to the maleic anhydride hydrogenation reaction unit. The rectification tower can remove water, acetic acid, acrylic acid and other substances by rectification, reduce the generation of maleic acid from maleic anhydride, and increase the yield of succinic anhydride.

[0057] According to the present invention, optionally, in the rectification tower of step 2), the feedstock from the top of the tower can be withdrawn and sent to outside the boundary region, the mixture of maleic anhydride and solvent can be withdrawn from the side of the tower and sent to the maleic anhydride hydrogenation reaction unit, and the feedstock in the tower pot can be sent to the solvent purification unit.

[0058] According to the present invention, in step 2), the operating pressure of the absorption tower is 0.0-1.0 MPa g, for example, 0.0-0.8 MPa g, the operating temperature is 40-120° C., for example, 60-100° C., and the number of theoretical plates is 5-50, for example, 15-35.

[0059] According to the present invention, in step 2), the operation pressure of the rectification column is 0.0 to 1.0 MPa g, for example, 0.0 to 0.8 MPa g, the operation temperature is 40 to 150° C., for example, 60 to 120° C., and the number of theoretical plates is 5 to 100, for example, 15 to 80.

[0060] According to the invention, in step 2), it is preferred to replenish the absorber with fresh absorbent which is fed to the top of the absorber column.

[0061] According to the present invention, in step 2), the absorbent is preferably a solvent required for maleic anhydride hydrogenation reaction, such as one or more mixed solvents selected from the group consisting of γ-butyrolactone, dibutyl phthalate, diisobutyl hexahydrophthalate, tetrahydrofuran, aromatic hydrocarbons, ethyl acetate, C4 dibasic acid esters, ethanol, isopropanol, hexane, cyclohexane, propylene oxide, benzene, xylene, chlorobenzene, dichlorobenzene, dioxane, and some ketones and ether solvents, etc., preferably γ-butyrolactone, dioxane and tetrahydrofuran.

[0062] According to the present invention, in step 2), the ratio of the absorbent to the solvent of maleic anhydride is not particularly limited and can be determined by a person skilled in the art according to his / her professional knowledge and prior art. Preferably, the ratio of the absorbent to the oxidation reactant is 0.1-5.

[0063] According to the present invention, optionally, in step 2), a part of the raw material from the absorption tower is cooled to 30-80° C. and then returned to the absorption tower, and the remainder is sent to the rectification tower.

[0064] According to the present invention, optionally, in step 2), the feed from the top of the absorption tower is cooled to 20-50°C through a heat exchanger, and then passes through a gas-liquid separator, and the gas phase is sent out of the boundary region and the liquid phase is sent to the rectification tower.

[0065] According to a preferred embodiment of the present invention, in the maleic anhydride separation unit, the operating conditions of the absorption tower include a pressure of 0.0 to 1.0MPa, a temperature of 40 to 120°C, and a theoretical plate number of 5 to 50; and the absorbent is one or more mixed solvents selected from the group consisting of γ-butyrolactone, dibutyl phthalate, diisobutyl hexahydrophthalate, tetrahydrofuran, aromatic hydrocarbons, ethyl acetate, C4 dibasic acid esters, ethanol, isopropanol, hexane, cyclohexane, propylene oxide, benzene, xylene, chlorobenzene, dichlorobenzene, dioxane, ketones, and ethers, and is preferably γ-butyrolactone, dioxane, and / or tetrahydrofuran.

[0066] In step 3) of the process for producing succinic acid according to the present invention, the maleic anhydride hydrogenation reaction unit and the maleic anhydride hydrogenation reaction process are not particularly limited and can be determined by those skilled in the art according to their professional knowledge and prior art. According to a preferred embodiment of the present invention, the maleic anhydride hydrogenation reaction in step 3) is the maleic anhydride hydrogenation process according to the present invention described above.

[0067] According to a specific embodiment of the present invention, the hydrogenation reaction of step 3) in the step of producing succinic acid comprises the following steps: (1) feeding the maleic anhydride aqueous solution and the hydrogen source into the first-stage hydrogenation reactor through an upper liquid phase feed port and an upper gas phase feed port of the first-stage hydrogenation reactor, respectively, to carry out a first-stage hydrogenation reaction and obtain a first-stage hydrogenation product; (2) supplying the first-stage hydrogenation product to a second-stage hydrogenation reactor for a second-stage hydrogenation reaction to obtain a second-stage hydrogenation product; optionally, before entering the second-stage hydrogenation reactor, subjecting the first-stage hydrogenation product to a first-stage gas-liquid separation to obtain a first-stage gas phase and a first-stage liquid phase, and then supplying the first-stage gas phase and the first-stage liquid phase from an upper gas phase supply port and an upper liquid phase supply port of the second-stage hydrogenation reactor, respectively; and (3) subjecting the second hydrogenation product to a second stage gas-liquid separation to obtain a second stage gas phase and a second stage liquid phase, returning a portion of the second stage liquid phase to step (1) for mixing with the maleic anhydride solution for the first stage hydrogenation reaction, and optionally using a portion or all of the second stage gas phase as recycled hydrogen; (4) sending the remainder of the second-stage liquid phase feed to the succinic anhydride separation unit;

[0068] According to a preferred embodiment of the present invention, the hydrogenation reaction of step 3) in the process for producing succinic acid comprises the following steps: (1) dividing the maleic anhydride solution into two streams, mixing the first stream with a part of the second-stage liquid phase feedstock that is cooled or uncooled, and then feeding the mixture into the first-stage hydrogenation reactor through an upper liquid phase feed port of the first-stage hydrogenation reactor to contact with the hydrogen feedstock for the hydrogenation reaction; (2) sequentially subjecting the first-stage hydrogenation product to cooling and first-stage gas-liquid separation to obtain the first-stage gas phase and the first-stage liquid phase, feeding all of the first-stage gas to the second-stage hydrogenation reactor through the upper gas phase feed port of the second-stage hydrogenation reactor, mixing the first-stage liquid phase with a second stream of maleic anhydride solution, and then feeding the mixture to the second-stage hydrogenation reactor through the upper liquid phase feed port of the second-stage reactor to convert all of the maleic anhydride to succinic anhydride by a hydrogenation reaction; and (3) subjecting the second-stage hydrogenation product to a second-stage gas-liquid separation to obtain a second-stage gas phase and a second-stage liquid phase, recycling a portion of the second-stage liquid phase to step (1) for mixing, and optionally using all or a portion of the second-stage gas phase as circulating hydrogen; (4) sending the remainder of the second-stage liquid phase feed to the succinic anhydride separation unit;

[0069] According to a preferred embodiment of the present invention, 20-90 wt% of the second-stage liquid phase feed from the second-stage hydrogenation reaction is returned to step (1) for use as feed, and the remainder of the second-stage liquid phase is sent to the light-removal tower of the succinic anhydride separation unit. The maleic anhydride hydrogenation process of the present invention is used to obtain succinic anhydride product by the joint operation of the light-removal tower and the heavy-removal tower. The process is simple, easy to operate and control, and the succinic anhydride product is of high purity.

[0070] According to a preferred embodiment of the present invention, preferably, 10-80% by weight of the second-stage liquid phase from the second-stage hydrogenation product after gas-liquid separation is sent to a light-end removal tower, and the remainder of the second-stage liquid phase is first cooled to 40-80°C by a cooler, and then mixed with the maleic anhydride solution and fed to the first-stage hydrogenation reactor for recycling.

[0071] According to a preferred embodiment of the present invention, in step (2), the operation conditions of the first-stage hydrogenation reactor are: temperature 30-100°C, preferably 40-80°C; reaction pressure 0.1-10 MPa, preferably 0.5-5 MPa; space velocity 0.5-8 h -1 , preferably 0.5 to 5 hours -1 This includes being.

[0072] According to a preferred embodiment of the present invention, in step (2), the operation conditions of the second-stage hydrogenation reactor are: temperature 30 to 100°C, preferably 40 to 80°C; reaction pressure 0.1 to 10 MPa, preferably 0.5 to 5 MPa; space velocity 0.5 to 8 h -1 , preferably 0.5 to 5 hours -1 This includes being.

[0073] According to the present invention, in step 4), the succinic anhydride separation unit mainly includes a light-removal tower and a heavy-removal tower, the raw material from the maleic anhydride hydrogenation reaction unit is fed to the light-removal tower, the raw material from the light-removal tower's kettle is fed to the heavy-removal tower, the solvent is withdrawn from the top of the heavy-removal tower, succinic anhydride is withdrawn from the side line of the tower, and the heavy component is withdrawn from the kettle.

[0074] According to the present invention, optionally, in step 4), the succinic anhydride separation unit further comprises a solvent recovery tower. The raw material from the maleic anhydride hydrogenation reaction unit is sent to the light removal tower, the raw material from the light removal tower's kettle is sent to the solvent recovery tower, the solvent is withdrawn from the top of the solvent recovery tower, the raw material from the solvent recovery tower's kettle is sent to the heavy removal tower, succinic anhydride is withdrawn from the top of the heavy removal tower, and heavy components are withdrawn from the kettle of the heavy removal tower. In this way, the yield and purity of succinic anhydride can be improved.

[0075] According to a preferred embodiment of the present invention, in step 4), the succinic anhydride separation unit comprises a light-end removal tower and a heavy-end removal tower connected in series. The remainder of the second-stage liquid phase feed from the maleic anhydride hydrogenation reaction unit is supplied to the light-end removal tower, the feed from the bottom of the light-end removal tower is supplied to the heavy-end removal tower, the solvent is withdrawn from the top of the heavy-end removal tower, the succinic anhydride is withdrawn from the side line of the tower, and the heavy components are withdrawn from the bottom. Preferably, the succinic anhydride separation unit comprises a light-end removal tower, a solvent recovery tower, and a heavy-end removal tower connected in series. The remainder of the second stage liquid phase feed from the maleic anhydride hydrogenation reaction unit is supplied to the light removal tower, the feed from the bottom of the light removal tower is supplied to the solvent recovery tower, heavy components are withdrawn from the bottom of the solvent recovery tower and supplied to the heavy removal tower, and the succinic anhydride is withdrawn from the top of the heavy removal tower.

[0076] According to a preferred embodiment of the present invention, light components are discharged from the top of the light removal tower, a raw material from the tower pot of the light removal tower is supplied to the heavy removal tower, by-products are discharged from the top of the heavy removal tower, heavy components are discharged from the tower pot, and the succinic anhydride is withdrawn from a side line.

[0077] In the present invention, the light components refer to dissolved hydrogen and small amounts of solvents such as γ-butyrolactone and tetrahydrofuran.

[0078] In the present invention, the purpose of the light-end removal tower is to remove hydrogen and small amounts of solvents such as γ-butyrolactone, tetrahydrofuran, etc. There are no special requirements for its arrangement and operating conditions as long as the object of the present invention can be achieved.

[0079] In the present invention, the purpose of the heavy component removal tower is to remove the solvent from the top of the tower, remove the heavy components produced by polymerization from the tower tank, and extract the succinic anhydride that satisfies the requirements from the side line. There are no special requirements for the arrangement and operating conditions as long as the object of the present invention can be achieved.

[0080] In the present invention, there is no special requirement for the operating conditions of the light removal tower, and all commonly used operating conditions of the light removal tower are applicable to the present invention. In the present invention, preferably in step 4), the operating pressure of the light removal tower is 0.5 to 20 KPa, preferably 6 to 15 KPa, the operating temperature is 30 to 150°C, preferably 80 to 130°C, and the number of theoretical plates is 10 to 80, preferably 20 to 60.

[0081] In the present invention, there are no special requirements for the operating conditions of the heavy-removal tower, and all commonly used operating conditions of the heavy-removal tower are applicable to the present invention. In the present invention, preferably in step 4), the operating pressure of the heavy-removal tower is 0.5 to 20 KPa, preferably 3 to 15 KPa, the operating temperature is 30 to 250°C, for example 30 to 150°C, preferably 100 to 130°C, for example 50 to 250°C, preferably 100 to 200°C, and the number of theoretical plates is 10 to 80, preferably 20 to 60.

[0082] According to the present invention, in step 4), the operating pressure of the solvent recovery column 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, preferably 20-60.

[0083] According to the invention, it is preferred that in step 4) the separated solvent needs to be heat exchanged up to the absorption temperature and recycled to the absorption tower of step 2).

[0084] According to the present invention, in step 5), the hydrolysis unit is not particularly limited in the present invention and can be determined by those skilled in the art according to their professional knowledge and conventional techniques, for example, hot water is used for hydrolysis, the hydrolysis temperature is 50-95°C, and the hydrolysis pressure is 0.1-0.3 MPa. [Liquid phase hydrogenation reaction system] The present invention provides a liquid phase hydrogenation reaction system, comprising: a first stage hydrogenation reactor including an upper vapor phase feed port, an upper liquid phase feed port, and a lower discharge port; a first-stage hydrogenation reaction product cooler and a first-stage gas-liquid separator, sequentially connected in series to the lower discharge port of the first-stage hydrogenation reactor; a second stage hydrogenation reactor connected in series with the first stage gas-liquid separator, the second stage hydrogenation reactor having an upper gas phase feed port, an upper liquid phase feed port, and a lower discharge port; a second stage gas-liquid separator connected in series with the lower discharge port of the second stage hydrogenation reactor; and a liquid phase feedstock supply pipeline connected to an upper liquid phase supply port of the first stage hydrogenation reactor, and optionally connected to an upper liquid phase supply port of the second stage hydrogenation reactor;

[0085] In one embodiment of the present invention, the liquid phase feedstock supply pipeline is connected to the upper liquid phase supply port of the first stage hydrogenation reactor. Preferably, the liquid phase feedstock supply pipeline is connected to both the upper liquid phase supply port of the first stage hydrogenation reactor and the upper liquid phase supply port of the second stage hydrogenation reactor.

[0086] In one embodiment of the present invention, the upper gas phase discharge port of the first-stage gas-liquid separator is connected to the upper gas phase supply port of the second-stage hydrogenation reactor through a pipeline, so that the upper gas phase of the first-stage gas-liquid separator can enter the second-stage hydrogenation reactor through the upper gas phase supply port.

[0087] In one embodiment of the present invention, the lower liquid phase discharge port of the first-stage gas-liquid separator is connected to the upper liquid phase supply port of the second-stage hydrogenation reactor through a pipeline, so that the lower liquid phase of the first-stage gas-liquid separator can enter the second-stage hydrogenation reactor through the upper liquid phase supply port.

[0088] In one embodiment of the present invention, the upper gas phase discharge port of the second-stage gas-liquid separator is connected to the upper gas phase supply port of the first-stage hydrogenation reactor through a pipeline, so that the upper gas phase of the second-stage gas-liquid separator can return to the first-stage hydrogenation reactor through the upper gas phase supply port.

[0089] In one embodiment of the present invention, the lower liquid phase discharge port of the second stage gas-liquid separator is connected to the upper liquid phase supply port of the first stage hydrogenation reactor through a pipeline, so that the lower liquid phase of the second stage gas-liquid separator can return to the first stage hydrogenation reactor through the upper liquid phase supply port.

[0090] In one embodiment of the present invention, it is preferred to arrange a circulating feed cooler on the connecting pipeline between the lower liquid phase discharge port of the second-stage gas-liquid separator and the upper liquid phase supply port of the first-stage hydrogenation reactor.

[0091] In one embodiment of the present invention, it is preferred to arrange a circulating gas cooler on the connecting pipeline between the upper gas phase discharge port of the second-stage gas-liquid separator and the upper gas phase supply port of the first-stage hydrogenation reactor.

[0092] In an embodiment of the present invention, it is preferable to arrange a second-stage cooler and a third gas-liquid separator in series at the upper gas phase discharge port of the second-stage gas-liquid separator. The gas phase discharge port of the third gas-liquid separator is connected to the upper gas phase supply port of the first-stage hydrogenation reactor through a pipeline, and the lower liquid phase discharge port of the third gas-liquid separator is connected to the liquid phase supply port of the second-stage gas-liquid separator. Therefore, the gas phase of the third gas-liquid separator can return to the first-stage hydrogenation reactor from the upper gas phase supply port, and the lower liquid phase of the third gas-liquid separator can return to the liquid phase supply port of the second-stage gas-liquid separator to perform gas-liquid separation again. It is preferable to arrange a circulation gas cooler on the connecting pipeline between the gas phase discharge port of the third gas-liquid separator and the upper gas phase supply port of the first-stage hydrogenation reactor.

[0093] In one embodiment of the invention, the system further comprises a distributor for splitting the liquid phase feed into two streams as needed to feed the first stage and second stage hydrogenation reactors.

[0094] In an embodiment of the present invention, optionally, the first-stage hydrogenation reactor and the second-stage hydrogenation reactor are equipped with a raw material dispenser at the top, and the gas phase and the liquid phase enter the first-stage hydrogenation reactor and the second-stage hydrogenation reactor, pass through the dispenser, and then contact and react with the catalyst.

[0095] In the present invention, in addition to the special configurations of the present invention, such as the devices shown in the drawings, devices such as pumps, heat exchangers, tanks, compressors, etc. may be included as necessary, and will be arranged by a person skilled in the art using his or her specialized knowledge as necessary.

[0096] The liquid phase hydrogenation reaction system of the present invention can improve catalyst efficiency, improve catalyst conversion rate, and effectively remove reaction heat, and is suitable for various hydrogenation reactions that require heat removal and improved catalyst efficiency. The liquid phase hydrogenation reaction system of the present invention is particularly suitable for maleic anhydride hydrogenation reactions, such as the maleic anhydride hydrogenation process of the present invention.

[0097] For example, the raw material of the liquid phase hydrogenation reaction system of the present invention is divided into two streams, which respectively enter into different stages of the reactor, and a cooler and a gas-liquid separator are arranged after the first stage hydrogenation reactor, and the resulting gas phase and liquid phase respectively enter into the second stage hydrogenation reactor, which can improve the catalytic efficiency and effectively remove the heat released by the reaction, and is flexible in operation and easy to control.

[0098] The present invention provides the use of the liquid phase hydrogenation reaction system according to the present invention in a maleic anhydride hydrogenation process.

[0099] The present invention provides the use of the liquid phase hydrogenation reaction system according to the present invention in a succinic acid production system. [Succinic acid production system] The present invention provides a system for producing succinic acid from butane and / or benzene, comprising, as a maleic anhydride hydrogenation reaction unit, the liquid phase hydrogenation reaction system according to the present invention.

[0100] The present invention also provides a system for producing succinic acid from butane and / or benzene, comprising a maleic anhydride separation unit and a maleic anhydride hydrogenation reaction unit, preferably comprising the liquid-phase hydrogenation reaction system according to the present invention as the maleic anhydride hydrogenation reaction unit, the maleic anhydride separation unit comprising an absorption tower and a fractionation tower.

[0101] In a specific embodiment of the present invention, a system for producing succinic acid from butane and / or benzene includes an oxidation reaction unit, a maleic anhydride separation unit having an absorption tower and a rectification tower connected in series, a maleic anhydride hydrogenation reaction unit, a succinic anhydride separation unit, and a succinic anhydride hydrolysis unit, which are connected in series along a flow direction of the feedstock; Butane and / or benzene undergo an oxidation reaction with an oxygen-containing gas in the oxidation reaction unit, and are supplied to the maleic anhydride separation unit for absorption and rectification to obtain a maleic anhydride solution; the maleic anhydride solution is supplied to the maleic anhydride hydrogenation reaction unit for hydrogenation to obtain a hydrogenated product; the hydrogenated product is supplied to the succinic anhydride separation unit to separate succinic anhydride and a solvent; and the succinic anhydride is supplied to the succinic anhydride hydrolysis unit for hydrolysis and crystallization to obtain a succinic acid product.

[0102] In the present invention, there are no special requirements for the oxidation reaction unit, the succinic anhydride separation unit, the succinic anhydride hydrolysis unit, etc. Those skilled in the art can judge and select according to their own techniques.

[0103] The present invention has no special requirements for the maleic anhydride hydrogenation reaction unit, which can be determined by those skilled in the art according to their professional knowledge and prior art. According to a preferred embodiment of the present invention, the maleic anhydride hydrogenation reaction unit is the liquid-phase hydrogenation reaction system according to the present invention described above.

[0104] According to a specific embodiment of the present invention, the maleic anhydride hydrogenation reaction unit comprises: a first-stage hydrogenation reactor, a first-stage reaction product cooler and a first-stage gas-liquid separator, which are connected in series along the flow direction of the raw material; a second-stage hydrogenation reactor, which is connected to a gas phase discharge port of the first-stage gas-liquid separator through an upper gas phase supply port and to a liquid phase discharge port of the first-stage gas-liquid separator through an upper liquid phase supply port; and a second-stage gas-liquid separator, which is connected in series to the second-stage hydrogenation reactor; a liquid phase feed pipeline connected to an upper liquid phase feed port of said first stage hydrogenation reactor, and optionally to an upper liquid phase feed port of said second stage hydrogenation reactor;

[0105] In a specific embodiment of the present invention, The succinic anhydride separation unit comprises a light-ends removal column and a heavy-ends removal column connected in series, the feed port of the lights removal column is connected to the liquid phase discharge port of the second stage gas-liquid separator, the lights removal column having a top discharge port and a bottom discharge port; and a feed port of the heavies removal column is connected to a bottom discharge port of the lights removal column, the heavies removal column having an upper discharge port, a lower discharge port and a side discharge port; or the succinic anhydride separation unit comprising a lights removal column, a solvent recovery column and a heavies removal column connected in series; the feed port of the lights removal column is connected to the liquid phase discharge port of the second stage gas-liquid separator, the lights removal column having a top discharge port and a bottom discharge port; The feed port of the solvent recovery column is connected to the bottom discharge port of the lights removal column, and the solvent recovery column has an overhead discharge port and a bottom discharge port; and The feed port of the heavies removal column is connected to a bottom discharge port of the solvent recovery column, and the heavies removal column has a bottom discharge port and an overhead discharge port.

[0106] Exemplary embodiments of the invention will now be described in more detail with reference to the drawings.

[0107] 1 to 3 exemplarily illustrate schematic diagrams of a maleic anhydride hydrogenation process according to the present invention and a liquid-phase hydrogenation reaction system applied thereto.

[0108] In Figures 1, 2 and 3, 1: distributor, 2: first stage hydrogenation reactor, 3: first stage hydrogenation reaction product cooler, 4: first stage gas-liquid separator, 5: second stage hydrogenation reactor, 6: second stage gas-liquid separator, 7: circulating feed cooler, 11: second stage cooler, 12: third gas-liquid separator, 16: circulating gas cooler, 21: maleic anhydride solution, 15: liquid phase product, 22: auxiliary hydrogen.

[0109] As shown in FIG. 1, in an exemplary embodiment of the present invention, the maleic anhydride hydrogenation process includes the following steps: (1) mixing the maleic anhydride aqueous solution 21 with a part of the second-stage liquid phase feedstock from the second-stage hydrogenation reaction that has been cooled or uncooled (cooled by the circulating feedstock cooler 7), supplying the mixture to the first-stage hydrogenation reactor 2 from the upper liquid phase feedstock supply port of the first-stage hydrogenation reactor 2, contacting the mixture with hydrogen (including auxiliary hydrogen 22 and circulating hydrogen) to carry out a hydrogenation reaction, and supplying the hydrogen (including auxiliary hydrogen 22 and circulating hydrogen) to the first-stage hydrogenation reactor 2 from the upper gas phase supply port of the first-stage hydrogenation reactor 2; (2) sequentially supplying the first-stage hydrogenation reaction product to the first-stage hydrogenation reaction product cooler 3 for cooling, and supplying the first-stage gas-liquid separator 4 for first-stage gas-liquid separation to obtain a first-stage gas phase and a first-stage liquid phase, supplying all of the first-stage gas phase to the second-stage hydrogenation reactor 5 through the upper gas phase supply port of the second-stage hydrogenation reactor 5, and supplying the first-stage liquid phase to the second-stage hydrogenation reactor 5 through the upper liquid phase supply port of the second-stage hydrogenation reactor 5 for reacting with hydrogen, thereby converting all of the maleic anhydride into succinic anhydride by hydrogenation; (3) supplying the second-stage hydrogenation product to a second-stage gas-liquid separator 6 for second-stage gas-liquid separation to obtain a second-stage gas phase from the second-stage hydrogenation reaction described in step (1), a portion of the second-stage liquid phase feedstock, and a liquid phase product 15, and optionally using a portion or all of the second-stage gas phase as recycled hydrogen.

[0110] As shown in FIGS. 2-3, in an exemplary embodiment of the present invention, the maleic anhydride hydrogenation process includes the following steps: (1) splitting the maleic anhydride solution 21 into two streams through a distributor 1, mixing the first stream with a part of the second-stage liquid phase feed from the second-stage hydrogenation reaction, either cooled or uncooled (cooled in a circulating feed cooler 7), and then feeding the mixture to the first-stage hydrogenation reactor 2 through an upper liquid phase feed port of the first-stage hydrogenation reactor 2, and hydrogenating the mixture by contacting with hydrogen (including auxiliary hydrogen 22 and circulating hydrogen), wherein the hydrogen (including auxiliary hydrogen 22 and circulating hydrogen) is fed to the first-stage hydrogenation reactor 2 through an upper vapor phase feed port of the first-stage hydrogenation reactor 2; (2) sequentially supplying the first-stage hydrogenation product to the first-stage hydrogenation product cooler 3 for cooling and the first-stage gas-liquid separator 4 for first-stage gas-liquid separation to obtain a first-stage gas phase and a first-stage liquid phase, supplying all of the first-stage gas phase to the second-stage hydrogenation reactor 5 through the upper gas phase supply port of the second-stage hydrogenation reactor 5, mixing the first-stage liquid phase with a second stream of maleic anhydride solution, and supplying the mixture to the second-stage hydrogenation reactor 6 through the upper liquid phase supply port of the second-stage hydrogenation reactor 5 for reacting with hydrogen, thereby converting all of the maleic anhydride into succinic anhydride by hydrogenation; (3) feeding the second-stage hydrogenation product to a second-stage gas-liquid separator 6 for second-stage gas-liquid separation to obtain a second-stage gas phase and a portion of the second-stage liquid phase feedstock from the second-stage hydrogenation reaction described in step (1) and a liquid phase product 15, and optionally using a portion or all of the second-stage gas phase as recycle hydrogen (as shown in FIG. 2); or The second-stage gas phase obtained by the second-stage gas-liquid separation of the second-stage hydrogenation product is supplied to the second-stage cooler 11 for cooling, and then supplied to the third gas-liquid separator 12 for third-stage gas-liquid separation to obtain a third gas phase and a third liquid phase, and a part or all of the third gas phase is mixed with auxiliary hydrogen 22 as circulating hydrogen, and then returned to the first-stage hydrogenation reactor 2, and optionally the third gas phase is returned to the second-stage gas-liquid separator 6 for gas-liquid separation (shown in FIG. 3). The second-stage gas phase obtained by the second-stage gas-liquid separation of the second-stage hydrogenation product is preferably cooled to a temperature of 30 to 80° C. in the second-stage cooler 11, which can effectively remove heat and improve catalyst efficiency.

[0111] As shown in FIGS. 1-3, in an exemplary embodiment of the present invention, a liquid phase hydrogenation reaction system includes: a first-stage hydrogenation reactor 2, a first-stage hydrogenation reaction product cooler 3 and a first-stage gas-liquid separator 4, which are connected in series along the direction of material flow; a second-stage hydrogenation reactor 5, which is connected to a gas phase discharge port of the first-stage gas-liquid separator 4 via a gas phase supply port and to a liquid phase discharge port of the first-stage gas-liquid separator 4 via a liquid phase supply port; and a second-stage gas-liquid separator 6, which is connected in series to the second-stage hydrogenation reactor 5; A liquid phase raw material supply pipeline connected to the liquid phase supply port of the first stage hydrogenation reactor 2; or a liquid phase raw material supply pipeline connected to both the liquid phase supply port of the first-stage hydrogenation reactor 2 and the liquid phase supply port of the second-stage hydrogenation reactor 5;

[0112] As shown in Figures 1 to 3, in the liquid phase hydrogenation reaction system, the first-stage reaction product cooler 3 and the first-stage gas-liquid separator 4 are sequentially connected in series to the lower discharge port of the first-stage hydrogenation reactor 2.

[0113] As shown in FIGS. 1 to 3, in the liquid phase hydrogenation reaction system, the second-stage gas-liquid separator 6 is connected in series to the lower discharge port of the second-stage hydrogenation reactor 5.

[0114] As shown in FIGS. 1 to 3, in the liquid phase hydrogenation reaction system, the first-stage hydrogenation reactor 2 has an upper gas phase supply port, an upper liquid phase supply port, and a lower discharge port.

[0115] As shown in FIGS. 1 to 3, in the liquid phase hydrogenation reaction system, the second-stage hydrogenation reactor 5 has an upper gas phase supply port, an upper liquid phase supply port, and a lower discharge port.

[0116] As shown in Figures 1 to 3, in the liquid phase hydrogenation reaction system, the upper gas phase discharge port of the first stage gas-liquid separator 4 is connected to the upper gas phase supply port of the second stage hydrogenation reactor 5 via a pipeline.

[0117] As shown in Figures 1 to 3, in the liquid phase hydrogenation reaction system, the lower gas phase discharge port of the first stage gas-liquid separator 4 is connected to the upper liquid phase supply port of the second stage hydrogenation reactor 5 via a pipeline.

[0118] As shown in Figures 1 to 3, in the liquid phase hydrogenation reaction system, the upper gas phase discharge port of the second stage gas-liquid separator 6 is connected to the upper gas phase supply port of the first stage hydrogenation reactor 2 via a pipeline.

[0119] As shown in Figures 1 to 3, in the liquid phase hydrogenation reaction system, the lower liquid phase discharge port of the second stage gas-liquid separator 6 is connected to the upper liquid phase supply port of the first stage hydrogenation reactor 2 via a pipeline.

[0120] As shown in Figures 1 to 3, a circulating feed cooler 7 is preferably provided on the connecting pipeline between the lower liquid phase discharge port of the second-stage gas-liquid separator 6 and the upper liquid phase supply port of the first-stage hydrogenation reactor 2.

[0121] As shown in Figures 1 to 3, a circulating gas cooler 16 is preferably provided on the connecting pipeline between the upper gas phase discharge port of the second-stage gas-liquid separator 6 and the upper gas phase supply port of the first-stage hydrogenation reactor 2.

[0122] As shown in FIG. 2-3, the liquid-phase hydrogenation reaction system further includes a distributor 1, which is used to distribute the liquid-phase feedstock into two streams as needed to be supplied to the first-stage hydrogenation reactor 2 and the second-stage hydrogenation reactor 5.

[0123] As shown in FIG. 3, a second-stage cooler 11 and a third gas-liquid separator 12 are sequentially arranged in series at the end of the upper gas phase discharge port of the second-stage gas-liquid separator 6, the gas phase discharge port of the third gas-liquid separator 12 is connected to the upper gas phase supply port of the first-stage hydrogenation reactor 2 via a pipeline, and the lower liquid phase discharge port of the third gas-liquid separator 12 is connected to the liquid phase supply port of the second-stage gas-liquid separator 6.

[0124] As shown in FIG. 3, a circulating gas cooler 16 is provided on the connecting pipeline between the gas phase discharge port of the third gas-liquid separator 12 and the upper gas phase supply port of the first-stage hydrogenation reactor 2.

[0125] 4-5 are schematic diagrams of a succinic acid production process according to the present invention and a succinic acid production system applied thereto.

[0126] In Figures 4 and 5, 8: light-end removal column, 9: heavy-end removal column, 10: solvent recovery column, 13: absorption column, and 14: fractionator.

[0127] As shown in FIGS. 4-5, in an exemplary embodiment of the present invention, a process for producing succinic acid from butane and / or benzene includes the following steps: 1) subjecting butane and / or benzene and air to an oxidation reaction in an oxidation reaction unit to obtain an oxidation reaction product; 2) supplying the oxidation reaction product to the absorption tower (13), supplying an absorbent from the top of the absorption tower to the absorption tower (13) for absorption, supplying the rich solvent obtained in the absorption tower pot to the fractionation tower (14) for fractionation, and sending the fractionation tower pot feed to a maleic anhydride hydrogenation reaction unit; 3) carrying out a hydrogenation reaction in the maleic anhydride hydrogenation reaction unit to obtain a hydrogenation product (shown in Figures 1 to 3); 4) feeding the hydrogenation product to the lights removal column (8), withdrawing light components from the top of the lights removal column (8), feeding the bottom feed of the lights removal column (8) to the heavies removal column (9), withdrawing solvent from the top of the heavies removal column (9) for recycling as absorbent back to the absorption column (13), withdrawing succinic anhydride from a side line of the heavies removal column (9), withdrawing heavy components from the bottom feed of the heavies removal column (9) (as shown in FIG. 4), and optionally using the solvent withdrawn from the heavies removal column (9) to dilute the maleic anhydride solution from the maleic anhydride separation unit (not shown); or supplying the hydrogenated product to a light removal column (8), withdrawing light components from the top of the light removal column (8), supplying the bottom feed of the light removal column (8) to the solvent recovery column (10), withdrawing the solvent from the top of the solvent recovery column (10) and returning it to the absorption column (13) to recycle it as an absorbent; withdrawing heavy components from the bottom feed of the solvent recovery column (10), supplying it to the heavy removal column (9), withdrawing succinic anhydride from the top of the heavy removal column (9) (as shown in FIG. 5), and optionally diluting the maleic anhydride solution from a maleic anhydride separation unit (not shown) with the solvent withdrawn from the solvent recovery column (10); 5) feeding the succinic anhydride to a succinic anhydride hydrolysis unit for hydrolysis and crystallization to obtain succinic acid product.

[0128] As shown in FIG. 2, in an exemplary embodiment of the present invention, the maleic anhydride hydrogenation reaction in step 3) of the process for producing succinic acid from butane and / or benzene includes the following steps: (1) splitting maleic anhydride solution 21 into two streams through distributor 1, mixing the first stream with a part of the cooled or uncooled liquid phase feed from the second stage hydrogenation reaction, and then feeding the mixture to first stage hydrogenation reactor 2 through the upper liquid phase feed port of first stage hydrogenation reactor 2 for hydrogenation by contacting with hydrogen, and hydrogen being fed to first stage hydrogenation reactor 2 through the upper gas phase feed port of said first stage hydrogenation reactor 2; (2) sequentially supplying the first-stage hydrogenation product to the first-stage hydrogenation product cooler 3 for cooling, supplying the first-stage gas-liquid separator 4 for first-stage gas-liquid separation, supplying all of the first-stage gas phase from the gas-liquid separation to the second-stage hydrogenation reactor 5 through the upper gas phase supply port of the second-stage hydrogenation reactor 5, mixing the first-stage liquid phase from the gas-liquid separation with a second stream, and supplying the mixture to the second-stage hydrogenation reactor 5 through the upper liquid phase supply port of the second-stage hydrogenation reactor 5 for reacting with hydrogen, thereby converting all of the maleic anhydride into succinic anhydride through the hydrogenation reaction; (3) subjecting the second-stage hydrogenation product to a second-stage gas-liquid separation to obtain a second-stage gas phase and a second-stage liquid phase, returning a portion of the liquid phase feed from the second-stage hydrogenation reaction to step (3), and optionally using a portion or all of the gas phase of the second-stage hydrogenation product as recycle hydrogen; (4) sending the remaining liquid phase feed from the second-stage hydrogenation reaction to the lights removal column (8), withdrawing light components from the top of the lights removal column (8), and sending the bottom feed of the lights removal column (8) to the heavy removal column (9); (5) A step of withdrawing succinic anhydride from the side line of the heavy end removal column (9), withdrawing by-products containing solvents such as γ-butyrolactone from the top of the column, and withdrawing heavy components containing polymers from the column bottom.

[0129] As shown in FIGS. 4-5, in an exemplary embodiment of the present invention, a system for producing succinic acid from butane and / or benzene includes: an oxidation reaction unit, a maleic anhydride separation unit in which an absorption tower (13) and a rectification tower (14) are connected in series, a maleic anhydride hydrogenation reaction unit, a succinic anhydride separation unit, and a succinic anhydride hydrolysis unit are connected in series along the flow direction of the raw material; Butane and / or benzene are oxidized with oxygen in the oxidation reaction unit, and then fed to the maleic anhydride separation unit for absorption and rectification to obtain a maleic anhydride solution; the maleic anhydride solution is fed to the maleic anhydride hydrogenation reaction unit for hydrogenation to obtain a hydrogenated product; the hydrogenated product is fed to the succinic anhydride separation unit for separation into succinic anhydride and a solvent; the succinic anhydride is fed to the succinic anhydride hydrolysis unit for hydrolysis and crystallization to obtain a succinic acid product.

[0130] As shown in Figure 4, the succinic anhydride separation unit includes: a light removal column (8) and a heavy removal column (9) connected in series; the feed port of the light removal column (8) is connected to the liquid phase discharge port of the second stage gas-liquid separator, and the light removal column (8) has a top discharge port and a bottom discharge port; the feed port of the heavy removal column (9) is connected to the bottom discharge port of the light removal column (8), and the heavy removal column (8) has a top discharge port, a bottom discharge port, and a side line withdrawal port.

[0131] As shown in Figure 5, the succinic anhydride separation unit includes a light removal tower (8), a solvent recovery tower (10) and a heavy removal tower (9) connected in series. The feed port of the light removal tower (8) is connected to the liquid phase discharge port of the second stage gas-liquid separator, and the light removal tower (8) is provided with a top discharge port and a pot discharge port; the feed port of the solvent recovery tower (10) is connected to the pot discharge port of the light removal tower (8), and the solvent recovery tower (10) is provided with a tower discharge port and a pot discharge port; the feed port of the heavy removal tower (9) is connected to the pot discharge port of the solvent recovery tower (10), and the heavy removal tower (9) is provided with a pot discharge port and a top discharge port. [Example] In the examples below, the following catalysts are used: [Hydrogenation catalyst S1] With reference to the preparation process of the hydrotreating catalyst described in Preparation Example 1 of the applicant's patent application CN114433100(A), the hydrogenation catalyst S1 was prepared according to the following procedure: (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% aqueous ammonia solution were weighed out, mixed, and the pH value of the solution was adjusted to 10.5 by introducing ammonia gas. The mixture was stirred at 45°C until all the solids were dissolved, to obtain a nickel-copper ammonia complex solution; (2) 458.31 g of silica sol is weighed out and mixed with the nickel-cuprammonium complex solution obtained in step (1) to obtain a mixed solution; (3) The mixture is aged at 60°C for 14 hours under stirring, and then dried at 120°C for 12 hours to obtain a catalyst precursor; (4) saturating the catalyst precursor with a cerium nitrate solution containing 11.41 g of Ce(NO3)3·6H2O to obtain a matrix catalyst; (5) The matrix catalyst is dried at 115° C. for 12 hours, then calcined at 400° C. for 4 hours and molded to obtain catalyst S1.

[0132] Based on the total weight of the catalyst S1, the catalyst S1 contained 19 wt. % NiO, 2 wt. % CuO, 3 wt. % CeO2, and 76 wt. % SiO2. [Hydrogenation catalyst S2] With reference to the preparation process of the hydrogenation catalyst described in Example 1 of the applicant's patent application CN114433127(A), the hydrogenation catalyst S2 was prepared according to the following procedure: (1) Weigh out 10.90 g of Ni(NO3)3·6H2O and 5.04 g of Ce(NO3)3·6H2O, dissolve them in water to make 50.0 ml, and place them on 50 g of SiO2 carrier (specific surface area 300 m 2 / g, water absorption rate 1.0mL / g) is immersed in a nickel nitrate-cerium nitrate mixed solution, stirred uniformly, and then left for aging for 4 hours, then oven-dried at 120°C for 12 hours, and finally calcined in air at 450°C for 4 hours to obtain composite oxide support E; (2) The composite oxide support E is added to 100 ml of a ruthenium metal solution having a Ru content of 0.02 g / L, and while stirring, an aqueous ammonia solution having a mass concentration of 25% is added dropwise to adjust the pH value of the solution and maintain it at pH 9. The solution is reacted at 55°C for 6 hours, filtered, and then oven-dried at 110°C for 12 hours. Finally, the catalyst is calcined in air at 500°C for 4 hours to obtain a completed catalyst S2.

[0133] In the catalyst S2, the mass fraction of Ni in the catalyst was 7% of the support mass, the mass fraction of CeO2 was 4% of the support mass, and the mass fraction of Ru was 0.4% of the support mass, based on the mass of the catalyst support SiO2. Example 1 According to the present invention, a maleic anhydride hydrogenation reaction was carried out. γ-butyrolactone was used as a solvent, and the content of maleic anhydride in the maleic anhydride solution was 10% by weight. This maleic anhydride solution was mixed with a part of the second-stage liquid phase feedstock recycled from the second-stage hydrogenation reaction, and fed to the first-stage hydrogenation reactor from the upper liquid phase feed port of the reactor. The molar ratio of the total amount of recycled hydrogen and supplemental fresh hydrogen to the total amount of maleic anhydride in the maleic anhydride solution fed was 12.

[0134] The space velocity of the first stage hydrogenation reactor is 2.5 h -1 The reaction temperature was 40°C and the reaction pressure was 1.5MPa. The first-stage hydrogenation reaction product was cooled to 40°C. After the first-stage gas-liquid separation, the entire amount of the first-stage gas phase and the entire amount of the first-stage liquid phase were fed to a second-stage hydrogenation reactor from the upper gas phase feed port and the upper liquid phase feed port of the reactor, respectively. The space velocity of the second-stage hydrogenation reactor was 1h -1 The reaction temperature was 45°C and the reaction pressure was 1.3MPa. After the second-stage hydrogenation reaction product was subjected to second-stage gas-liquid separation, 1% by volume of the second-stage gas phase was extracted and vented, and the remaining gas phase was sent to the first-stage hydrogenation reactor together with supplementary new hydrogen, 65% by weight of the second-stage liquid phase after the gas-liquid separation was sent to a subsequent separation system (such as a light-end removal tower), and 35% by weight of the liquid phase was heat-exchanged to 40°C and mixed with a maleic anhydride solution, and then supplied to the first-stage hydrogenation reactor.

[0135] The catalysts loaded into the first-stage hydrogenation reactor and the second-stage hydrogenation reactor were both hydrogenation catalyst S1 (a catalyst containing Ni as an active component).

[0136] After the second stage hydrogenation, the overall conversion of maleic anhydride was 99.91%, and the overall selectivity to succinic anhydride was 99.85%. Example 2 According to the present invention, maleic anhydride hydrogenation reaction was carried out. γ-butyrolactone was used as a solvent, and the content of maleic anhydride in the maleic anhydride solution was 10 wt%. The maleic anhydride solution was divided into two streams according to a ratio of 50 wt%, and the first stream (50 wt% of the maleic anhydride solution) was mixed with a part of the second-stage liquid-phase feedstock recycled from the second-stage hydrogenation reaction, and then fed to the first-stage hydrogenation reactor from the upper liquid-phase feed port of the first-stage hydrogenation reactor. The second stream (50 wt% maleic anhydride solution) was mixed with the first-stage liquid-phase product from the first-stage hydrogenation reaction, and then fed to the second-stage hydrogenation reactor from the upper liquid-phase feed port of the second-stage hydrogenation reactor. The molar ratio of the total hydrogen amount of the circulating hydrogen and the supplementary fresh hydrogen to the total maleic anhydride in the fed maleic anhydride solution was 10.

[0137] The space velocity of the first stage hydrogenation reactor is 2.5 h -1 The reaction temperature was 40°C and the reaction pressure was 1.5 MPa. The hydrogenation reaction product was cooled to 40°C. After the first-stage gas-liquid separation, the first-stage gas phase was entirely fed to the second-stage hydrogenation reactor through the upper gas phase feed port of the second-stage hydrogenation reactor, and the first-stage liquid phase was mixed with a second stream of maleic anhydride solution and then fed to the second-stage hydrogenation reactor through the upper liquid phase feed port of the second-stage hydrogenation reactor. The space velocity of the second-stage hydrogenation reactor was 1 h -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 second-stage gas-liquid separator, the second-stage gas phase was cooled to 40° C. and sent to the first-stage hydrogenation reactor together with supplementary fresh hydrogen, and 65% by weight of the second-stage liquid phase after gas-liquid separation was sent to a subsequent separation device (such as a light-ends removal tower), and 35% by weight of the liquid phase was heat-exchanged to 40° C., mixed with the first stream of maleic anhydride solution, and then sent to the first-stage hydrogenation reactor.

[0138] The catalysts loaded into the first-stage hydrogenation reactor and the second-stage hydrogenation reactor were both hydrogenation catalyst S1 (a catalyst containing Ni as an active component).

[0139] After the two-stage hydrogenation reaction, the total conversion of maleic anhydride was 99.91%, and the total selectivity of succinic anhydride was 99.83%. Example 3 According to the present invention, the hydrogenation reaction of maleic anhydride was carried out. Dioxane was used as a solvent, and the content of maleic anhydride in the maleic anhydride solution was 18 wt%. The maleic anhydride solution was divided into two streams according to the ratio of 20 wt% and 80 wt%, and the first stream (20 wt% of the maleic anhydride solution) was mixed with a part of the second-stage liquid phase feedstock recycled from the second-stage hydrogenation reaction and fed to the first-stage hydrogenation reactor from the upper liquid phase feed port of the first-stage hydrogenation reactor. The second stream (80 wt% of the maleic anhydride solution) was mixed with the first-stage liquid phase product from the first-stage hydrogenation reaction, and then fed to the second-stage hydrogenation reactor from the upper liquid phase feed port of the second-stage hydrogenation reactor. The molar ratio of the total hydrogen amount of the circulating hydrogen and the supplementary fresh hydrogen to the total maleic anhydride in the maleic anhydride aqueous solution fed was 30.

[0140] The space velocity of the first stage hydrogenation reactor is 1.8 h -1 The reaction temperature was 40° C. and the reaction pressure was 1.3 MPa. The first-stage hydrogenation reaction product was cooled to 45° C. After the first-stage gas-liquid separation, the first-stage gas phase was entirely fed to the second-stage hydrogenation reactor through the upper gas phase feed port of the second-stage hydrogenation reactor, and the first-stage liquid phase was mixed with a second stream of maleic anhydride solution and then fed to the second-stage hydrogenation reactor through the upper liquid phase feed port of the second-stage hydrogenation reactor. The space velocity of the second-stage hydrogenation reactor was 1.2 h -1 The reaction temperature was 48° C. and the reaction pressure was 1.2 MPa. The second-stage hydrogenation reaction product passed through the second-stage gas-liquid separator, and the second-stage gas phase was sent to the first-stage hydrogenation reactor together with supplementary fresh hydrogen, and 60 wt % of the second-stage liquid phase after the gas-liquid separation was sent to a subsequent separation system (such as a light-ends removal tower), and 40 wt % of the liquid phase was heat-exchanged to 40° C. and mixed with the first stream of maleic anhydride solution, and then fed to the first-stage hydrogenation reactor.

[0141] The catalysts loaded into the first-stage hydrogenation reactor and the second-stage hydrogenation reactor were both hydrogenation catalyst S1 (a catalyst containing Ni as an active component).

[0142] After the two-stage hydrogenation reaction, the total conversion of maleic anhydride was 99.83%, and the total selectivity of succinic anhydride was 99.85%. Example 4 According to the present invention, maleic anhydride hydrogenation reaction was carried out. Hexane was used as a solvent, and the content of maleic anhydride in the maleic anhydride solution was 25 wt%. The maleic anhydride solution was divided into two streams according to the ratio of 40 wt% and 60 wt%, and the first stream (40 wt% of the maleic anhydride solution) was mixed with a part of the second-stage liquid phase raw material recycled from the second-stage hydrogenation reaction and fed to the first-stage hydrogenation reactor from the upper liquid phase feed port of the first-stage hydrogenation reactor. The second stream (60 wt% of the maleic anhydride solution) was mixed with the first-stage liquid phase product from the first-stage hydrogenation reaction, and then fed to the second-stage hydrogenation reactor from the upper liquid phase feed port of the second-stage hydrogenation reactor. The molar ratio of the total hydrogen amount of the circulating hydrogen and the auxiliary fresh hydrogen to the total maleic anhydride in the maleic anhydride aqueous solution fed was 40.

[0143] The space velocity of the first stage hydrogenation reactor is 3h -1 The reaction temperature was 40°C and the reaction pressure was 1.7MPa. The first-stage hydrogenation reaction product was cooled to 42°C. After the first-stage gas-liquid separation, the first-stage gas phase was entirely fed to the second-stage hydrogenation reactor through the upper gas phase feed port of the second-stage hydrogenation reactor, and the first-stage liquid phase was mixed with the second stream of maleic anhydride solution and then fed to the second-stage hydrogenation reactor through the upper liquid phase feed port of the second-stage hydrogenation reactor. The space velocity of the second-stage hydrogenation reactor was 0.8h -1, the reaction temperature was 45°C, and the reaction pressure was 1.5MPa. After the second-stage hydrogenation reaction product passed through the second-stage gas-liquid separator, the gas phase was further cooled to 40°C and passed through the third gas-liquid separator, and the resulting gas phase was sent to the first-stage hydrogenation reactor together with auxiliary fresh hydrogen; 50% by weight of the liquid phase in the second-stage liquid phase from the second-stage gas-liquid separator was sent to a subsequent separation system (such as a light-ends removal tower), and 50% by weight of the liquid phase was heat-exchanged to 40°C, mixed with the first stream of maleic anhydride solution, and fed to the first-stage hydrogenation reactor.

[0144] The catalysts loaded into the first-stage hydrogenation reactor and the second-stage hydrogenation reactor were both hydrogenation catalyst S2 (a catalyst containing Ni as an active component).

[0145] After the two-stage hydrogenation reaction, the overall conversion of maleic anhydride was 99.89%, and the overall selectivity to succinic anhydride was 99.78%. Comparative Example 1 The maleic anhydride hydrogenation reaction of Example 1 was used. γ-butyrolactone was used as the solvent, and the maleic anhydride content in the maleic anhydride solution was 10 wt %. The difference was that the liquid phase feed from the second-stage hydrogenation reaction product was all sent to the subsequent separation unit and was not recycled to be mixed with the maleic anhydride solution.

[0146] The space velocity of the first stage hydrogenation reactor is 2.5 h -1 The reaction temperature was 40°C and the reaction pressure was 1.5 MPa. The first-stage hydrogenation reaction product was cooled to 40°C. After the first-stage gas-liquid separation, the entire first-stage gas phase and the entire first-stage liquid phase were fed to the second-stage hydrogenation reactor from the upper gas phase feed port and the upper liquid phase feed port, respectively. The space velocity of the second-stage hydrogenation reactor was 1 h -1 The reaction temperature was 45°C and the reaction pressure was 1.3MPa. After the second-stage hydrogenation reaction product underwent second-stage gas-liquid separation, 1% by volume of the second-stage gas phase was extracted and vented, and the remainder of the gas phase was sent to the first-stage hydrogenation reactor together with supplementary fresh hydrogen, and the second-stage liquid phase after gas-liquid separation was entirely sent to the subsequent separation unit (such as a light-ends removal tower).

[0147] The catalysts loaded into the first-stage hydrogenation reactor and the second-stage hydrogenation reactor were both hydrogenation catalyst S1 (a catalyst containing Ni as an active component).

[0148] After the two-stage hydrogenation reaction, the overall conversion of maleic anhydride was 99.91%, and the overall selectivity to succinic anhydride was 99.85%.

[0149] In Comparative Example 1, in order to make the outlet temperature of the hydrogenation reactor the same as that in the Examples, the molar ratio of the total hydrogen amount of the recycled hydrogen and the supplemental fresh hydrogen to the total maleic anhydride in the incoming maleic anhydride solution had to be increased by at least 78%, and the ratio of hydrogen to anhydride was greatly increased. The energy consumption was greatly increased, and considering only the energy consumption of the recycled hydrogen compressor, the energy consumption of this compressor increased by 84.8%. Comparative Example 2 The maleic anhydride hydrogenation reaction of Example 2 was used. γ-butyrolactone was used as the solvent, the maleic anhydride content in the maleic anhydride solution was 10 wt%, and the maleic anhydride solution was divided into two streams according to the ratio of 50 wt% and 50 wt%. The difference is that the liquid phase feed from the second-stage hydrogenation reaction product was all sent to the subsequent separation unit (such as the light-ends removal tower) and was not recycled to mix with the first stream of maleic anhydride solution.

[0150] After the second stage hydrogenation, the overall conversion of maleic anhydride was 99.91%, and the overall selectivity for succinic anhydride was 99.83%.

[0151] In Comparative Example 2, in order to make the hydrogenation reactor outlet temperature the same as that in the Example, the molar ratio of the total hydrogen amount of the recycled hydrogen and the supplemental fresh hydrogen to the total maleic anhydride in the inflowing maleic anhydride solution had to be increased by at least 79%, and the ratio of hydrogen to anhydride increased significantly. The energy consumption increased significantly, and when only the energy consumption of the recycled hydrogen compressor was considered, the energy consumption of this compressor increased by 84.0%. Comparative Example 3 The maleic anhydride hydrogenation reaction of Example 3 was used. Dioxane was used as the solvent, the maleic anhydride content in the maleic anhydride solution was 18 wt%, and the maleic anhydride solution was divided into two streams according to the ratio of 20 wt% and 80 wt%. The difference is that the liquid phase feed from the second stage hydrogenation reaction product was all sent to the subsequent separation device (such as the light-removal tower) and was not recycled to mix with the first stream of the maleic anhydride solution.

[0152] After the two-stage hydrogenation reaction, the overall conversion of maleic anhydride was 99.83%, and the overall selectivity to succinic anhydride was 99.85%.

[0153] In Comparative Example 3, in order to make the outlet temperature of the hydrogenation reactor the same as in the Examples, the molar ratio of the total hydrogen amount (the recycled hydrogen and the supplemental fresh hydrogen) to the total maleic anhydride in the incoming maleic anhydride solution had to be increased by at least 120%, and the ratio of hydrogen to anhydride was greatly increased. The energy consumption was greatly increased, and considering only the energy consumption of the recycled hydrogen compressor, the energy consumption of this compressor increased by 168.4%. Comparative Example 4 The maleic anhydride hydrogenation reaction of Example 4 was used, except that hexane was used as the solvent, the maleic anhydride content in the maleic anhydride solution was 25 wt%, and the maleic anhydride solution was divided into two streams according to the ratio of 40 wt% and 60 wt%, and the liquid phase feed from the second-stage hydrogenation reaction product was all sent to the subsequent separation device (such as the light-ends removal tower) and was not recycled to mix with the first stream of maleic anhydride solution.

[0154] After the second stage hydrogenation, the overall conversion of maleic anhydride was 99.83%, and the overall selectivity for succinic anhydride was 99.85%.

[0155] In Comparative Example 4, in order to make the outlet temperature of the hydrogenation reactor the same as that in the Examples, the molar ratio of the total hydrogen amount of the recycled hydrogen and the supplemental fresh hydrogen to the total maleic anhydride in the incoming maleic anhydride solution had to be increased by at least 125%, and the ratio of hydrogen to anhydride was greatly increased. The energy consumption was greatly increased, and considering only the energy consumption of the recycled hydrogen compressor, the energy consumption of this compressor increased by 171.7%.

[0156] In Comparative Examples 1-4, when the liquid phase feedstock from the second-stage hydrogenation reaction product was not recycled and all of it was fed to the subsequent separation unit, the heat released in the hydrogenation reactor could not be effectively removed when the same low ratio of hydrogen to anhydride as in Examples 1-4 was used, and the reactor outlet temperature was much higher than that in the Examples. From the comparison between the above Examples and Comparative Examples, it can be seen that the present invention can effectively remove the reaction heat by partially recycling the liquid phase feedstock from the second-stage hydrogenation reaction product, reduce the hydrogen / anhydride molar ratio, which is the total amount of recycled hydrogen and supplementary new hydrogen relative to the total maleic anhydride in the inflowing maleic anhydride solution, reduce energy consumption, and achieve the desired maleic anhydride conversion rate and succinic anhydride selectivity. Example 5 According to the present invention, succinic acid was produced using butane as a raw material.

[0157] Butane and air were mixed and fed to the oxidation reaction unit. The oxidation reaction temperature was 420°C and the reaction pressure was 0.2MPag. The oxidation reaction product was fed to the absorption tower of the maleic anhydride separation unit, entered from the kettle of the absorption tower, and used γ-butyrolactone as a solvent and entered the absorption tower from the top of the absorption tower. The absorption tower had a total of 18 theoretical plates, an operating temperature of 75°C and an operating pressure of 0.06MPag. Tail gas was withdrawn from the top of the absorption tower, and the rich solvent in the kettle was fed to the rectification tower. The rectification tower had a total of 20 theoretical plates, an operating temperature of 95°C and an operating pressure of 0.003MPag. Light components were withdrawn from the top of the rectification tower, and the feed in the kettle was a maleic anhydride solution with a maleic anhydride content of 35% by weight. It was diluted to obtain a maleic anhydride solution having a maleic anhydride content of 10 wt%, which was sent to the maleic anhydride hydrogenation reaction unit.

[0158] Said maleic anhydride hydrogenation reaction unit adopts a two-stage hydrogenation reactor, and carries out maleic anhydride hydrogenation reaction according to the process of Example 1. After two-stage hydrogenation reaction, the total conversion rate of maleic anhydride is 99.91%, and the total selectivity of succinic anhydride is 99.85%.

[0159] The liquid phase raw material from the maleic anhydride hydrogenation reaction unit was supplied to the succinic anhydride separation unit. First, the liquid phase raw material passed through the light removal tower to separate light components from the tower top, and the raw material from the tower pot was sent to the heavy removal tower. γ-butyrolactone was extracted from the top of the heavy removal tower, and a part of the γ-butyrolactone was returned to the absorption tower of the maleic anhydride separation unit for recycling. The maleic anhydride solution with a maleic anhydride content of 35% by weight from the maleic anhydride separation unit was diluted with the remaining γ-butyrolactone as a solvent, and mixed to obtain a maleic anhydride solution with a maleic anhydride content of 10% by weight, which then entered the hydrogenation reactor. Heavy components were extracted from the tower pot of the heavy removal tower, and succinic anhydride was extracted from a side line and sent to the succinic anhydride hydrolysis unit.

[0160] The theoretical number of plates in the light removal tower was 26, the pressure at the top was 10 KPa, and the operating temperature was 100° C. The theoretical number of plates in the heavy removal tower was 25, the pressure at the top was 3 KPa, and the operating temperature was 105° C. The purity of the obtained succinic anhydride was 99.9%.

[0161] The operating pressure of the hydrolysis vessel of the succinic anhydride hydrolysis unit is 0.12MPa, and the operating temperature is 80°C. After centrifugation and drying, succinic acid product is obtained. The purity of the succinic acid product is 99.9%. Example 6 According to the present invention, succinic acid was produced using butane as a raw material.

[0162] The oxidation reaction and maleic anhydride separation were carried out according to the steps of Example 5 to obtain a maleic anhydride solution with a maleic anhydride content of 10 wt %. γ-butyrolactone was used as the solvent.

[0163] The maleic anhydride hydrogenation reactor adopts a two-stage hydrogenation reactor, and carries out maleic anhydride hydrogenation according to the process of Example 2. After the two-stage hydrogenation, the total conversion rate of maleic anhydride is 99.91%, and the total selectivity of succinic anhydride is 99.83%.

[0164] After separation and hydrolysis, the succinic acid product was obtained with a purity of 99.9%. Example 7 According to the present invention, succinic acid was produced using butane as a raw material.

[0165] Using dioxane as an absorbent, the oxidation reaction and maleic anhydride separation were carried out according to the process of Example 5 to obtain a maleic anhydride solution having a maleic anhydride content of 18 wt%.

[0166] The maleic anhydride hydrogenation reaction unit adopts a two-stage hydrogenation reactor, and carries out maleic anhydride hydrogenation reaction according to the process of Example 3. After the two-stage hydrogenation reaction, the total conversion rate of maleic anhydride is 99.83%, and the total selectivity of succinic anhydride is 99.85%.

[0167] After separation and hydrolysis, the succinic acid product was obtained with a purity of 99.9%. Example 8 According to the present invention, succinic acid was produced using butane as a raw material.

[0168] Hexane was used as absorbent, and the oxidation reaction and maleic anhydride separation were carried out according to the process of Example 5 to obtain a maleic anhydride solution with a maleic anhydride content of 25 wt%, and the solvent was hexane.

[0169] The maleic anhydride hydrogenation reaction unit adopts a two-stage hydrogenation reactor, and carries out maleic anhydride hydrogenation reaction according to the process of Example 4. After the two-stage hydrogenation reaction, the total conversion rate of maleic anhydride is 99.89%, and the total selectivity of succinic anhydride is 99.78%.

[0170] After separation and hydrolysis, the succinic acid product was obtained with a purity of 99.9%. Comparative Example 5 According to the prior art, succinic acid was produced using butane as a raw material.

[0171] Butane and air were mixed and fed to the oxidation reaction unit. The oxidation reaction temperature was 420°C and the reaction pressure was 0.2MPag. The oxidation reaction product was fed to the absorption tower of the maleic anhydride separation unit, fed from the kettle of the absorption tower, and used dibutyl phthalate as an absorbent, fed to the absorption tower from the top of the absorption tower. The absorption tower had a total of 20 theoretical plates, an operating temperature of 90°C, and an operating pressure of 0.06MPag. Tail gas was withdrawn from the top of the absorption tower and sent to the outside of the boundary region, and the rich solvent in the top kettle was fed to the stripping tower. The stripping tower had a total of 25 theoretical plates, an operating temperature of 142°C, and an operating pressure of 12KPa. The feedstock at the top of the stripping tower was sent to the light component tower, and the feedstock in the stripping tower kettle was sent to the absorption tower for recycling. The light components column had a total of 20 theoretical plates, an operating temperature of 40° C., and an operating pressure of 10 KPa. The feed from the top of the light components column was sent to the outside of the boundary region, and the feed in the kettle was sent to the product fractionator. The product fractionator had a total of 25 plates, an operating temperature of 132° C., and an operating pressure of 10 KPa. The maleic anhydride product was withdrawn from the upper side of the product fractionator and sent to the maleic anhydride hydrogenation reaction unit, and the feed in the kettle was heat-exchanged to 50° C. and returned to the absorption column for recycling.

[0172] The operation conditions of the maleic anhydride hydrogenation reaction unit were the same as those in Example 5, except that γ-butyrolactone / dioxane had to be introduced from outside as the solvent. After the two-stage hydrogenation reaction, the total conversion of the maleic anhydride was 99.50%, and the total selectivity of the succinic anhydride was 99%.

[0173] The succinic anhydride separation unit and hydrolysis unit were the same as in Example 5. The purity of the succinic acid product was 99.5%. In the maleic anhydride separation unit, compared with Comparative Example 5, Example 5 had two fewer tower devices, saving at least four heat exchangers, eight pumps and other auxiliary devices. In addition, the maleic anhydride separation unit in Example 5 was operated at a pressure above normal pressure, while the tower devices other than the absorption tower in Comparative Example 5 were operated under reduced pressure. Therefore, Example 5 could save capital investment compared with Comparative Example 5. In addition, when the maleic anhydride separation unit was analyzed from the viewpoint of energy consumption, compared with Comparative Example 5, Example 5 could reduce energy consumption by about 35%, which was equivalent to a saving of about 68 kg standard oil / ton C4.

[0174] It can be seen that in the prior art process, the operation of the maleic anhydride separation unit is complicated, and additional absorbents and solvents need to be introduced, which increases the process cost and energy consumption.In contrast, the maleic anhydride separation unit of the present invention has a simple process flow, which can save equipment investment and save energy consumption.

[0175] In addition, the succinic acid production process of the present invention establishes a full-step production process, realizes the combined use of maleic anhydride separation step and maleic anhydride hydrogenation step, and can obtain high-purity succinic acid product. The above is a detailed description of the preferred embodiment of the present invention, but the present invention is not limited thereto. Within the technical spirit of the present invention, many simple modifications can be made to the technical solution of the present invention, including combining various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as the contents disclosed by the present invention and belong to the protection scope of the present invention. [Explanation of symbols]

[0176] 8:Light removal tower 9:Heavy removal tower 10: Solvent recovery tower 13: Absorption tower 14: Rectification [Brief description of the drawings]

[0177] [Figure 1] FIG. 1 is a schematic diagram of a maleic anhydride hydrogenation process according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram of a maleic anhydride hydrogenation process according to another embodiment of the present invention. [Diagram 3] FIG. 3 is a schematic diagram of a maleic anhydride hydrogenation process according to yet another embodiment of the present invention. [Figure 4] FIG. 4 is a schematic diagram of a process for producing succinic acid from butane / benzene in accordance with one embodiment of the present invention. [Diagram 5] FIG. 5 is a schematic diagram of a process for producing succinic acid from butane / benzene in accordance with another embodiment of the present invention.

Claims

1. 1. A process for producing succinic anhydride by hydrogenation of maleic anhydride, comprising the steps of: (1) feeding a maleic anhydride solution and a hydrogen source into a first-stage hydrogenation reactor through an upper liquid-phase feed port and an upper vapor-phase feed port of the first-stage hydrogenation reactor, respectively, to carry out a first-stage hydrogenation reaction and obtain a first-stage hydrogenation product; (2) supplying the first-stage hydrogenation product to a second-stage hydrogenation reactor to carry out a second-stage hydrogenation reaction to obtain a second-stage hydrogenation product, optionally subjecting the first-stage hydrogenation product to first-stage gas-liquid separation before entering the second-stage hydrogenation reactor to obtain a first-stage gas phase and a first-stage liquid phase, and then supplying the first-stage gas phase and the first-stage liquid phase from an upper gas phase supply port and an upper liquid phase supply port of the second-stage hydrogenation reactor, respectively; and (3) subjecting the second-stage hydrogenation product to second-stage gas-liquid separation to obtain a second-stage gas phase and a second-stage liquid phase, returning a portion of the second-stage liquid phase to step (1) and mixing it with the maleic anhydride solution to subject it to the first-stage hydrogenation reaction, and optionally using a portion or all of the second-stage gas phase as recycled hydrogen.

2. In step (1), the maleic anhydride solution is a mixture of maleic anhydride and a solvent, the solvent being one or more of acetic anhydride, gamma-butyrolactone, dioxane, tetrahydrofuran, aromatic hydrocarbons, ethyl acetate, C4 dibasic acid esters, ethanol, isopropanol, hexane, cyclohexane, propylene oxide, ketones, and ethers; and / or the maleic anhydride solution has a maleic anhydride concentration of 1 to 90% by weight; and / or 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; and / or The operation conditions of the first-stage hydrogenation reactor are a temperature of 30 to 100°C; and / or a reaction pressure of 0.1 to 10 MPa; and / or a space velocity of 0.5 to 8 h －１ and / or 2. The method of claim 1, wherein the hydrogen source is a mixed hydrogen gas of the recycled hydrogen and auxiliary hydrogen in step (3).

3. In step (1), the maleic anhydride solution is divided into at least two streams, a first stream is mixed with a portion of the second-stage liquid phase in step (3) to carry out the first-stage hydrogenation reaction, and a second stream is used in the second-stage hydrogenation reaction; 3. The method of claim 1, wherein the first stream and the second stream are each 5 to 95 wt % of the maleic anhydride solution.

4. In step (2), The operating conditions of the second-stage hydrogenation reactor are a temperature of 30 to 100°C; and / or a pressure of 0.1 to 10 MPa; and / or a space velocity of 0.5 to 5 h －１ and / or 3. The process of claim 1 or 2, wherein the first-stage hydrogenation product is cooled prior to the first-stage vapor-liquid separation.

5. In step (3), a portion of the second stage liquid phase is cooled before being mixed; and / or 20 to 90 wt. % of the second-stage liquid phase is returned to step (1) for use as feedstock, with the remainder being sent as liquid phase product to a subsequent separation system; and / or 3. The method according to claim 1, wherein 0.5 to 2 wt. % of the second stage vapor phase is withdrawn as fuel gas, and the remainder is used as recycle hydrogen.

6. In step (3), after cooling the second-stage gas phase, perform third-stage gas-liquid separation to obtain a third gas phase and a third liquid phase, and use a part or all of the third gas phase as circulating hydrogen to be mixed with auxiliary hydrogen as a hydrogen source for the first-stage hydrogenation reactor; 3. The method of claim 1 or 2, optionally further comprising returning the third liquid phase to the second stage gas-liquid separator for second stage gas-liquid separation.

7. (1) dividing the maleic anhydride solution into two streams, mixing the first stream with the cooled or uncooled portion of the second-stage liquid phase, and then supplying this mixture to the first-stage hydrogenation reactor through the upper liquid-phase supply port of the first-stage hydrogenation reactor to contact with the hydrogen feedstock for hydrogenation reaction, and supplying the hydrogen feedstock to the first-stage hydrogenation reactor through the upper vapor-phase supply port of the first-stage hydrogenation reactor; (2) subjecting the first-stage hydrogenation product to cooling and first-stage gas-liquid separation in sequence to obtain the first-stage gas phase and the first-stage liquid phase; feeding the entire first-stage gas phase to the second-stage hydrogenation reactor through the upper gas phase feed port of the second-stage hydrogenation reactor; mixing the first-stage liquid phase with a second stream; and then feeding the mixture to the second-stage hydrogenation reactor through the upper liquid phase feed port of the second-stage reactor to react with hydrogen; (3) The method according to claim 1 or 2, wherein the second-stage hydrogenation product is subjected to second-stage gas-liquid separation to obtain a second-stage gas phase and a second-stage liquid phase, a portion of the second-stage liquid phase is recycled to step (1) and mixed therewith, and optionally a portion or all of the second-stage gas phase is used as recycled hydrogen.

8. 3. A method for producing succinic acid, comprising the step of producing succinic anhydride by hydrogenation of maleic anhydride according to claim 1 or 2.

9. A method for producing succinic acid, comprising the method for producing succinic anhydride by hydrogenation of maleic anhydride according to claim 1 or 2, comprising: (1) subjecting butane and / or benzene and an oxygen-containing gas to an oxidation reaction in an oxidation reaction unit to obtain an oxidation reaction product; (2) supplying the oxidation reaction product to a maleic anhydride separation unit including an absorption tower and a rectification tower, and obtaining a maleic anhydride solution through absorption and rectification; (3) feeding the maleic anhydride solution into a maleic anhydride hydrogenation reaction unit to carry out the hydrogenation reaction according to claim 1 or 2; (4) feeding the second-stage liquid phase not recycled from the second-stage hydrogenation reaction to a succinic anhydride separation unit to separate it into succinic anhydride and a solvent; optionally returning the separated solvent to step (2) for recycling as an absorbent; (5) feeding the succinic anhydride to a succinic anhydride hydrolysis unit for hydrolysis and crystallization to obtain a succinic acid product.

10. In the maleic anhydride separation unit, The operating conditions of the absorption tower include a pressure of 0.0 to 1.0 MPag, a temperature of 40 to 120°C, and a theoretical plate number of 5 to 50; The absorbent is one or a mixed solvent of two or more selected from the group consisting of γ-butyrolactone, dibutyl phthalate, diisobutyl hexahydrophthalate, tetrahydrofuran, aromatic hydrocarbons, ethyl acetate, C4 dibasic acid esters, ethanol, isopropanol, hexane, cyclohexane, propylene oxide, benzene, xylene, chlorobenzene, dichlorobenzene, dioxane, ketones, and ethers; 10. The method according to claim 9, wherein the operating conditions of the rectification column include a pressure of 0.0 to 1.0 MPag, a temperature of 40 to 150°C, and a theoretical plate number of 5 to 100.

11. In step (2), A portion of the feed from the absorber kettle is cooled to 30-80°C and returned to the absorber, and the remainder is sent to the fractionator; and / or The method according to claim 9, wherein the feedstock from the top of the absorption tower is cooled to 20 to 50°C via a heat exchanger and then passes through a gas-liquid separator, and the gas phase is sent to a boundary region outside and the liquid phase is sent to the rectification tower.

12. In step (4), 10. The method of claim 9, wherein the succinic anhydride separation unit comprises a lights removal column and a heavies removal column connected in series, the remainder of the second-stage liquid phase from the second-stage hydrogenation reaction is supplied to the lights removal column, a feedstock from the bottom of the lights removal column is supplied to the heavy components removal column, the solvent is withdrawn from the top of the heavy components removal column, the succinic anhydride is withdrawn from a side line of the column, and heavy components are withdrawn from the bottom of the column.

13. The method described in claim 9, wherein in step (4), the succinic anhydride separation unit comprises a light-end removal tower, a solvent recovery tower, and a heavy-end removal tower connected in series, the remainder of the second-stage liquid phase from the second-stage hydrogenation reaction is supplied to the light-end removal tower, raw material from the tank of the light-end removal tower is supplied to the solvent recovery tower, heavy components are extracted from the tank of the solvent recovery tower and supplied to the heavy-end removal tower, and succinic anhydride is extracted from the top of the heavy-end removal tower.

14. The operating conditions of the lights removal column include a pressure of 0.5 to 20 KPa, a temperature of 30 to 150°C, and a theoretical plate count of 10 to 80; and / or The operating conditions of the heavy end removal column are a pressure of 0.5 to 20 KPa, a temperature of 30 to 250°C, and a theoretical plate number of 10 to 80, and / or 13. The method of claim 12, wherein the operating conditions of the solvent recovery column include a pressure of 0.5 to 20 KPa, a temperature of 30 to 150°C, and a theoretical plate number of 10 to 80.

15. A liquid phase hydrogenation reaction system comprising: a first-stage hydrogenation reactor having an upper vapor phase feed port, an upper liquid phase feed port, and a lower discharge port; a first-stage hydrogenation reaction product cooler and a first-stage gas-liquid separator connected in series to the lower discharge port of the first-stage hydrogenation reactor; a second-stage hydrogenation reactor connected in series with the first-stage gas-liquid separator, the second-stage hydrogenation reactor having an upper vapor-phase feed port, an upper liquid-phase feed port, and a lower discharge port; a second-stage gas-liquid separator connected in series with the lower discharge port of the second-stage hydrogenation reactor; and a liquid phase feed pipeline connected to an upper liquid phase feed port of said first stage hydrogenation reactor and optionally connected to an upper liquid phase feed port of said second stage hydrogenation reactor;

16. The upper vapor phase discharge port of the first-stage gas-liquid separator is connected to the upper vapor phase supply port of the second-stage hydrogenation reactor via a pipeline; and / or The lower liquid phase discharge port of the first-stage gas-liquid separator is connected to the upper liquid phase supply port of the second-stage hydrogenation reactor via a pipeline; and / or the upper vapor phase discharge port of the second-stage gas-liquid separator is connected to the upper vapor phase supply port of the first-stage hydrogenation reactor via a pipeline; and / or 16. The hydrogenation reaction system according to claim 15, wherein the lower liquid phase discharge port of the second-stage gas-liquid separator is connected to the upper liquid phase supply port of the first-stage hydrogenation reactor via a pipeline.

17. a distributor for dividing the liquid phase feed into two streams as needed to feed the first-stage hydrogenation reactor and the second-stage hydrogenation reactor; and / or the second-stage cooler and the third gas-liquid separator are arranged in series in the upper gas-phase discharge port of the second-stage gas-liquid separator, the gas-phase discharge port of the third gas-liquid separator being connected to the upper gas-phase supply port of the first-stage hydrogenation reactor via a pipeline, and the lower liquid-phase discharge port of the third gas-liquid separator being connected to the liquid-phase supply port of the second-stage gas-liquid separator; The hydrogenation reaction system according to claim 15.

18. A system for producing succinic acid, comprising a liquid phase hydrogenation reaction system according to any one of claims 15 to 17 as a maleic anhydride hydrogenation reaction unit.

19. The method comprises: an oxidation reaction unit, a maleic anhydride separation unit having an absorption tower and a rectification tower connected in series, the maleic anhydride hydrogenation reaction unit, a succinic anhydride separation unit, and a succinic anhydride hydrolysis unit, which are connected in series along the flow direction of the raw material; 19. The system according to claim 18, characterized in that butane and / or benzene are oxidized with an oxygen-containing gas in the oxidation reaction unit, and then supplied to the maleic anhydride separation unit for absorption and rectification to obtain a maleic anhydride solution; the maleic anhydride solution is supplied to the maleic anhydride hydrogenation reaction unit for hydrogenation to obtain a hydrogenated product; the hydrogenated product is supplied to the succinic anhydride separation unit for separation into succinic anhydride and a solvent; and the succinic anhydride is supplied to the succinic anhydride hydrolysis unit for hydrolysis and crystallization to obtain a succinic acid product.

20. the succinic anhydride separation unit comprises a lights removal column and a heavy ends removal column connected in series; The feed port of the light-end removal column is connected to the liquid-phase discharge port of the second-stage gas-liquid separator, and the light-end removal column has a column top discharge port and a column bottom discharge port; the feed port of the heavy-ends removal column is connected to the column bottom discharge port of the light-ends removal column, and the heavy-ends removal column has a column top discharge port, a bottom discharge port, and a side line withdrawal port; or the succinic anhydride separation unit comprises a lights removal column, a solvent recovery column, and a heavy ends removal column connected in series; The feed port of the light-ends removal column is connected to the liquid-phase discharge port of the second-stage gas-liquid separator, and the light-ends removal column has a column top discharge port and a column bottom discharge port; The feed port of the solvent recovery tower is connected to the bottom discharge port of the lights removal tower, and the solvent recovery tower has a top discharge port and a bottom discharge port; and 20. The system of claim 19, wherein the feed port of the heavies removal column is connected to a bottom discharge port of the solvent recovery column, and the heavies removal column comprises a bottom discharge port and an overhead discharge port.

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