Liquid-phase hydrogenation reaction system and application thereof and maleic anhydride hydrogenation method

Abstract

The application provides a liquid-phase hydrogenation reaction system and application thereof and a maleic anhydride hydrogenation method, which comprises a first hydrogenation reactor, a first hydrogenation reactor product cooler and a first gas-liquid separator connected in series at the bottom discharge port of the first hydrogenation reactor, a second hydrogenation reactor connected in series with the first gas-liquid separator, the second hydrogenation reactor comprising a top gas-phase feed port, an upper liquid-phase feed port and a bottom discharge port, a second gas-liquid separator connected in series with the bottom discharge port of the second hydrogenation reactor, and a liquid-phase raw material supply pipeline connected with the upper liquid-phase feed port of the first hydrogenation reactor and the upper liquid-phase feed port of the second hydrogenation reactor. The application can improve the catalytic efficiency, effectively remove the heat generated in the reaction, and is flexible and easy to control.

Description

Technical Field

[0001] This invention relates to a liquid-phase hydrogenation reaction system and its application, as well as a method for hydrogenating maleic anhydride. Background Technology

[0002] Succinic anhydride is an important organic synthesis intermediate and fine chemical raw material. It can undergo hydrolysis, alcoholysis, esterification, halogenation, and acylation reactions, and is widely used in pharmaceuticals, pesticides, food, petrochemicals, building materials, synthetic resins, and dyes. Currently, there are relatively few manufacturers producing succinic anhydride worldwide, and the output is small, while the applications of succinic anhydride are very extensive, resulting in a global supply shortage. In my country, succinic anhydride production enterprises are small in scale and have low output, far from meeting domestic demand, especially for high-purity succinic anhydride, which is almost entirely dependent on imports.

[0003] Based on the source of raw materials, the main methods for preparing succinic anhydride include the maleic anhydride method, the succinic acid dehydration method, and the acetylene carbonylation method. Currently, the main industrial production methods are the maleic anhydride method and the succinic acid dehydration method.

[0004] The succinic acid dehydration method, which requires first obtaining succinic acid as a raw material and then dehydrating it under certain conditions, is the earliest method for producing succinic anhydride. However, due to the limited sources of succinic acid, primarily relying on the catalytic hydrogenation or electrolysis of maleic anhydride, production costs are high. Furthermore, from a synthetic route perspective, the dehydration of succinic acid to produce succinic anhydride is the reverse reaction of succinic anhydride hydrolysis, and succinic anhydride readily hydrolyzes to form succinic acid. Therefore, this method lacks development prospects both in terms of process rationality and economics.

[0005] Currently, most succinic anhydride production worldwide utilizes the maleic anhydride hydrogenation method. This method involves directly hydrogenating maleic anhydride in an organic solvent to produce succinic anhydride, resulting in high conversion rates, yields, minimal side reactions, and good product purity. However, the hydrogenation of maleic anhydride to succinic anhydride is a strongly exothermic reaction (ΔH = -128 kJ / mol), leading to a large adiabatic temperature rise. This can easily cause organic matter to polymerize and coke on the catalyst surface, reducing catalyst activity. Furthermore, it can cause a rapid increase in catalyst bed temperature, resulting in runaway reactions. Therefore, effectively reducing the exothermic reaction is a key challenge and a crucial aspect of the maleic anhydride hydrogenation process.

[0006] CN103570650A discloses a process for the continuous production of succinic anhydride and co-production of succinic acid via maleic anhydride hydrogenation. This process employs a two-stage hydrogenation reactor. At the outlet of the first-stage hydrogenation reactor, after heat exchange, a portion of the reaction solution enters the second-stage hydrogenation reactor. The remaining reaction solution is mixed with the raw maleic anhydride solution and then re-enters the first-stage hydrogenation reactor. This method aims to achieve heat removal; however, because the material at the outlet of the first-stage reactor still contains a certain amount of maleic anhydride, and this material is recycled back to the inlet of the first-stage reactor, the reduction in the amount of maleic anhydride entering the first-stage reactor is not significant. Therefore, the heat removal effect of this reactor is limited.

[0007] CN105801536A discloses a method for preparing succinic anhydride by liquid-phase selective hydrogenation of maleic anhydride. This method employs a two-stage reactor connected in series, using hydrogen for heat removal. Hydrogen is introduced into both the first and second stage reactors. The first stage reactor reacts at a low temperature of 40-80℃, while the second stage reactor reacts at 60-120℃. After reducing the heat of reaction, the hydrogen is separated by a gas-liquid separator and then recycled. The molar ratio of recycled hydrogen to maleic anhydride is 30-200:1. This method achieves a certain degree of heat removal. However, due to the large volume of recycled hydrogen, the energy consumption of the recycled hydrogen compressor is relatively high. Furthermore, the large amount of hydrogen entering the reactor necessitates a larger reactor volume, leading to increased investment and energy consumption.

[0008] Therefore, there is an urgent need to develop a maleic anhydride hydrogenation reaction process to effectively remove the heat released by the reaction, while solving problems such as large investment and high energy consumption. Summary of the Invention

[0009] To address the problems of high exothermic reaction rates, difficult heat removal, large investment, and high energy consumption in existing hydrogenation reaction systems, such as the hydrogenation of maleic anhydride to succinic anhydride, a new liquid-phase hydrogenation reaction system and method are proposed. This system and method feature easy heat removal, low investment, and low energy consumption.

[0010] According to a first aspect of the present invention, the present invention provides a liquid-phase hydrogenation reaction system, the system comprising: a hydrogenation reactor, the hydrogenation reactor comprising a top gas phase inlet, an upper liquid phase inlet and a bottom outlet; and a reaction product cooler and a gas-liquid separator connected in series at the bottom outlet end of the hydrogenation reactor.

[0011] The two-stage hydrogenation reactor is connected in series with the first-stage gas-liquid separator. The two-stage hydrogenation reactor includes a top gas phase inlet, an upper liquid phase inlet, and a bottom outlet.

[0012] A two-stage gas-liquid separator is connected in series with the bottom outlet of the two-stage hydrogenation reactor.

[0013] The liquid feedstock supply pipeline is connected to both the upper liquid feed inlet of the first-stage hydrogenation reactor and the upper liquid feed inlet of the second-stage hydrogenation reactor.

[0014] According to a second aspect of the present invention, the present invention provides the application of the hydrogenation reaction system described herein in the hydrogenation reaction of maleic anhydride.

[0015] According to a third aspect of the present invention, a method for hydrogenating maleic anhydride is provided, the method comprising a two-stage hydrogenation reaction.

[0016] (1) The maleic anhydride solution is divided into two streams of material. One stream is mixed with the liquid phase material of the second stage hydrogenation reaction, which is either cooled or uncooled, and then enters the first stage hydrogenation reactor from the liquid phase feed port at the top of the first stage hydrogenation reactor to contact with hydrogen for hydrogenation. The hydrogen enters the first stage hydrogenation reactor from the gas phase inlet at the top of the first stage hydrogenation reactor.

[0017] (2) The hydrogenation product of the first stage is cooled down and separated into gas and liquid. All the gas phase separated into gas phase enters the second stage hydrogenation reactor from the top gas phase feed port of the second stage hydrogenation reactor. The liquid phase separated into gas and liquid phase is mixed with another maleic anhydride solution and then enters the second stage hydrogenation reactor from the upper liquid phase feed port of the second stage reactor to react with hydrogen and convert all the maleic anhydride hydrogenation reaction into succinic anhydride.

[0018] (3) The two-stage hydrogenation product is separated into gas and liquid phases to obtain gas phase and liquid phase material from the two-stage hydrogenation reaction described in step (1). Optionally, part or all of the gas phase can be used as recycled hydrogen.

[0019] In the hydrogenation reaction system of the present invention, the raw materials are divided into two streams and enter each stage reactor respectively. After the first stage reactor, cooling and gas-liquid separation are set up so that the gas phase and liquid phase enter the second stage hydrogenation reactor respectively. This can improve the catalytic efficiency, effectively remove the heat released by the reaction, and make the operation flexible and easy to control.

[0020] The system of the present invention, when applied to the maleic anhydride hydrogenation reaction process and method, has the following characteristics:

[0021] (1) In this invention, the maleic anhydride solution is divided into two streams, which are then mixed with different materials and fed into two hydrogenation reactors. This reduces the maleic anhydride content entering the reactors, effectively removing the heat released by the reaction. The operation is flexible and easy to control.

[0022] (2) By using the method of the present invention, the concentration of maleic anhydride in the incoming maleic anhydride solution does not need to be too low, which reduces the amount of solvent used and reduces the energy consumption of subsequent solvent recovery.

[0023] (3) After the first stage reaction, the gas phase is cooled and separated into gas and liquid phases, and then all the gas phase enters the second stage reactor, which is beneficial to effectively remove the heat of reaction generated in the second stage reaction.

[0024] (5) The reaction operation conditions of the present invention are mild and the temperature rise of the reaction bed is low, which is beneficial to improving catalyst selectivity and extending catalyst life.

[0025] The method of this invention uses maleic anhydride as a raw material to produce succinic anhydride through hydrogenation. The maleic anhydride solution is divided into two streams. One stream is mixed with a portion of the liquid phase material from the second-stage reaction and then enters the first-stage hydrogenation reactor from the top of the reactor. The other stream of maleic anhydride solution is mixed with the liquid phase material from the first-stage reaction and then enters the second-stage hydrogenation reactor from the top of the reactor. Through the two-stage hydrogenation reaction, all maleic anhydride is converted into succinic anhydride. By dividing the maleic anhydride solution into two streams and mixing them with different materials before entering two hydrogenation reactors, the maleic anhydride content entering the reactor is reduced, which effectively removes the heat released by the reaction. The operation is flexible and easy to control. At the same time, the concentration of maleic anhydride in the incoming maleic anhydride solution does not need to be too low, reducing solvent usage and lowering the energy consumption for subsequent solvent recovery. This invention features a simple process, low investment, strong applicability, and ease of control. Attached Figure Description

[0026] Figure 1 This is a schematic flowchart of a maleic anhydride hydrogenation method according to one embodiment of the present invention.

[0027] Figure 2 This is a schematic flowchart of a maleic anhydride hydrogenation method according to another embodiment of the present invention.

[0028] Explanation of reference numerals in the attached figures

[0029] 1. Distributor; 2. First-stage hydrogenation reactor;

[0030] 3. A first-stage reaction product cooler; 4. A gas-liquid separator A;

[0031] 5. Two-stage hydrogenation reactor; 6. Gas-liquid separator B;

[0032] 7. Circulating material cooler; 8. Cooler;

[0033] 9. Gas-liquid separator C; 11. Maleic anhydride solution;

[0034] 12. Reaction products; 13. Add hydrogen gas. Detailed Implementation

[0035] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0036] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0037] In addition to the special features of this invention as shown in the accompanying drawings, pumps, heat exchangers, tanks, compressors, and other equipment may also be included as needed, as can be provided by those skilled in the art based on their needs and professional knowledge.

[0038] This invention provides a liquid-phase hydrogenation reaction system, the system comprising:

[0039] A hydrogenation reactor, comprising a top gas phase inlet, an upper liquid phase inlet, and a bottom outlet; and a reaction product cooler and a gas-liquid separator connected in series at the bottom outlet of the hydrogenation reactor.

[0040] The two-stage hydrogenation reactor is connected in series with the first-stage gas-liquid separator. The two-stage hydrogenation reactor includes a top gas phase inlet, an upper liquid phase inlet, and a bottom outlet.

[0041] A two-stage gas-liquid separator is connected in series with the bottom outlet of the two-stage hydrogenation reactor.

[0042] The liquid feedstock supply pipeline is connected to both the upper liquid feed inlet of the first-stage hydrogenation reactor and the upper liquid feed inlet of the second-stage hydrogenation reactor.

[0043] In the hydrogenation reaction system of the present invention, the raw materials are divided into two streams and enter each stage reactor respectively. After the first stage reactor, cooling and gas-liquid separation are set up so that the gas phase and liquid phase enter the second stage hydrogenation reactor respectively. This can improve the catalytic efficiency, effectively remove the heat released by the reaction, and make the operation flexible and easy to control.

[0044] According to a preferred embodiment of the present invention, the top gas phase outlet of the first-stage gas-liquid separator is connected to the top gas phase inlet of the second-stage hydrogenation reactor via a pipeline. Thus, the top gas phase of the first-stage gas-liquid separator can enter the second-stage hydrogenation reactor from the top.

[0045] According to a preferred embodiment of the present invention, the bottom liquid phase outlet of the first-stage gas-liquid separator is connected to the upper liquid phase inlet of the second-stage hydrogenation reactor via a pipeline. Thus, the bottom liquid phase of the first-stage gas-liquid separator can enter the second-stage hydrogenation reactor from the top.

[0046] According to a preferred embodiment of the present invention, the top gas phase outlet of the two-stage gas-liquid separator is connected to the top gas phase inlet of the first-stage hydrogenation reactor via a pipeline. Thus, the top gas phase of the two-stage gas-liquid separator can be returned from the top and enter the first-stage hydrogenation reactor.

[0047] According to a preferred embodiment of the present invention, the bottom liquid phase outlet of the two-stage gas-liquid separator is connected to the upper liquid phase inlet of the first-stage hydrogenation reactor via a pipeline. Thus, the bottom liquid phase of the two-stage gas-liquid separator can enter the first-stage hydrogenation reactor from the top.

[0048] According to a preferred embodiment of the present invention, a circulating material cooler is preferably provided on the connecting pipeline between the bottom liquid phase outlet of the two-stage gas-liquid separator and the upper liquid phase inlet of the first-stage hydrogenation reactor.

[0049] According to a preferred embodiment of the present invention, a second-stage cooler and a third gas-liquid separator are preferably connected in series at the top gas phase outlet of the second-stage gas-liquid separator. The gas phase outlet of the third gas-liquid separator is connected to the top gas phase inlet of the first-stage hydrogenation reactor via a pipeline; the bottom liquid phase outlet of the third gas-liquid separator is connected to the liquid phase inlet of the second-stage gas-liquid separator. Thus, the gas phase from the third gas-liquid separator can return from the top into the first-stage hydrogenation reactor, and the bottom liquid phase from the third gas-liquid separator can return to the liquid phase inlet of the second-stage gas-liquid separator for re-separation.

[0050] According to a preferred embodiment of the present invention, the system further includes: a distributor for distributing the liquid phase feedstock into two streams as needed to supply the first-stage hydrogenation reactor and the second-stage hydrogenation reactor.

[0051] According to a preferred embodiment of the present invention, optionally, the first-stage hydrogenation reactor and the second-stage hydrogenation reactor are provided with a feed distributor at the top. After the gas phase and liquid phase enter the first-stage reactor and the second-stage reactor, they come into contact with the catalyst to react.

[0052] The hydrogenation reaction system of this invention can enhance catalytic efficiency, improve catalytic conversion rate, and effectively remove reaction heat, making it suitable for various hydrogenation reactions requiring heat removal and enhanced catalytic efficiency. The system of this invention is particularly suitable for the hydrogenation reaction of maleic anhydride.

[0053] This invention provides the application of the hydrogenation reaction system described herein in the hydrogenation reaction of maleic anhydride.

[0054] This invention provides a method for hydrogenating maleic anhydride, the method comprising a two-stage hydrogenation reaction.

[0055] (1) The maleic anhydride solution is divided into two streams of material. One stream is mixed with the liquid phase material of the second stage hydrogenation reaction, which is either cooled or uncooled, and then enters the first stage hydrogenation reactor from the liquid phase feed port at the top of the first stage hydrogenation reactor to contact with hydrogen for hydrogenation. The hydrogen enters the first stage hydrogenation reactor from the gas phase inlet at the top of the first stage hydrogenation reactor.

[0056] (2) The hydrogenation product of the first stage is cooled down and separated into gas and liquid. All the gas phase separated into gas phase enters the second stage hydrogenation reactor from the top gas phase feed port of the second stage hydrogenation reactor. The liquid phase separated into gas and liquid phase is mixed with another maleic anhydride solution and then enters the second stage hydrogenation reactor from the upper liquid phase feed port of the second stage reactor to react with hydrogen and convert all the maleic anhydride hydrogenation reaction into succinic anhydride.

[0057] (3) The two-stage hydrogenation product is separated into gas and liquid phases to obtain gas phase and liquid phase material from the two-stage hydrogenation reaction described in step (1). Optionally, part or all of the gas phase can be used as recycled hydrogen.

[0058] The maleic anhydride hydrogenation reaction method of the present invention has the following characteristics:

[0059] (1) In this invention, the maleic anhydride solution is divided into two streams, which are then mixed with different materials and fed into two hydrogenation reactors. This reduces the maleic anhydride content entering the reactors, effectively removing the heat released by the reaction. The operation is flexible and easy to control.

[0060] (2) By using the method of the present invention, the concentration of maleic anhydride in the incoming maleic anhydride solution does not need to be too low, which reduces the amount of solvent used and reduces the energy consumption of subsequent solvent recovery.

[0061] (3) After the first stage reaction, the gas phase is cooled and separated into gas and liquid phases, and then all the gas phase enters the second stage reactor, which is beneficial to effectively remove the heat of reaction generated in the second stage reaction.

[0062] (5) The reaction operation conditions of the present invention are mild and the temperature rise of the reaction bed is low, which is beneficial to improving catalyst selectivity and extending catalyst life.

[0063] According to a preferred embodiment of the present invention, the hydrogen feedstock in step (1) is a mixed hydrogen feedstock consisting of recycled hydrogen and supplementary hydrogen. This effectively removes heat and improves catalytic efficiency.

[0064] According to a preferred embodiment of the present invention, the liquid phase material in the two-stage hydrogenation reaction in step (1) is a cooled material. This effectively removes heat and improves catalytic efficiency.

[0065] According to a preferred embodiment of the present invention, the liquid phase material in the two-stage hydrogenation reaction in step (1) is cooled to 30–80°C, preferably to 40–60°C. This effectively removes heat and improves catalytic efficiency.

[0066] According to a preferred embodiment of the present invention, the method further includes:

[0067] The gas phase obtained from the gas-liquid separation of the second-stage hydrogenation product is cooled and then subjected to a third gas-liquid separation. Part or all of the resulting gas phase is mixed with the recycled hydrogen and supplementary hydrogen as the hydrogen feedstock for the first-stage hydrogenation reactor. Optionally, the resulting liquid phase is returned to the second-stage gas-liquid separator for further gas-liquid separation. Preferably, the temperature at which the gas phase obtained from the gas-liquid separation of the second-stage hydrogenation product is cooled is 30–80°C. This effectively removes heat and improves catalytic efficiency.

[0068] This invention does not have any special requirements for the maleic anhydride solution. According to a preferred embodiment of this invention, in step (1), the maleic anhydride solution is a mixture of maleic anhydride and a solvent. The solvent can be a commonly used solvent. For this invention, the solvent is preferably one or more of acetic anhydride, γ-butyrolactone, dioxane, tetrahydrofuran, aromatic hydrocarbons, ethyl acetate, tetracarbon diester, ethanol, isopropanol, hexane, cyclohexane, propylene oxide, ketones and ethers.

[0069] According to a preferred embodiment of the present invention, the maleic anhydride concentration of the maleic anhydride solution is 1-90% by weight, preferably 10-40% by weight. Using the method of the present invention, the concentration of maleic anhydride in the incoming maleic anhydride solution does not need to be too low, reducing the amount of solvent used and thus reducing the energy consumption for subsequent solvent recovery.

[0070] According to a preferred embodiment of the present invention, the proportions of one component and the other component are each 5-95% by weight; preferably, the content of one component is 20-50% by weight, and the content of the other component is 50-80% by weight. This can effectively remove heat and improve reaction efficiency.

[0071] According to a preferred embodiment of the present invention, the molar ratio of total hydrogen to total maleic anhydride in the maleic anhydride solution is 5 to 100, preferably 10 to 40.

[0072] According to a preferred embodiment of the present invention, the operating conditions of the first-stage hydrogenation reactor are not particularly required and can be conventional operating conditions, such as: a temperature of 30-100℃, preferably 40-80℃, for example 40℃, 41℃, 42℃, 43℃, 44℃, 45℃, 46℃, 47℃, 48℃, 49℃, 50℃, etc., and so on, all reaction temperatures are applicable to the present invention; and / or a reaction pressure of 0.1-10MPa, preferably 0.5-5MPa; and / or a space velocity of 0.5-5h. -1 .

[0073] According to a preferred embodiment of the present invention, in step (2), the operating conditions of the two-stage hydrogenation reactor are not particularly required and can be conventional operating conditions, such as: a temperature of 30-100℃, preferably 40-80℃, for example 40℃, 41℃, 42℃, 43℃, 44℃, 45℃, 46℃, 47℃, 48℃, 49℃, 50℃, etc., and so on, and each reaction temperature is applicable to the present invention; and / or a pressure of 0.1-10MPa, preferably 0.5-5MPa.

[0074] According to a preferred embodiment of the present invention, in step (2), the airspeed is 0.5-5 h. -1 .

[0075] According to a preferred embodiment of the present invention, 20-90% by weight, preferably 30-70% by weight, of the liquid phase material from the two-stage hydrogenation reaction is returned to step (1) as a raw material, and the remainder is sent to a subsequent separation system as a liquid phase product. This effectively removes heat and improves reaction efficiency.

[0076] According to a preferred embodiment of the present invention, 0.5 to 2% by weight of the gaseous material from the two-stage hydrogenation reaction is extracted as fuel gas, and the remainder is used as the recycled hydrogen.

[0077] The method of this invention uses maleic anhydride as a raw material to produce succinic anhydride through hydrogenation. The maleic anhydride solution is divided into two streams. One stream is mixed with a portion of the liquid phase material from the second-stage reaction and then enters the first-stage hydrogenation reactor from the top of the reactor. The other stream of maleic anhydride solution is mixed with the liquid phase material from the first-stage reaction and then enters the second-stage hydrogenation reactor from the top of the reactor. Through the two-stage hydrogenation reaction, all maleic anhydride is converted into succinic anhydride. By dividing the maleic anhydride solution into two streams and mixing them with different materials before entering two hydrogenation reactors, the maleic anhydride content entering the reactor is reduced, which effectively removes the heat released by the reaction. The operation is flexible and easy to control. At the same time, the concentration of maleic anhydride in the incoming maleic anhydride solution does not need to be too low, reducing solvent usage and lowering the energy consumption for subsequent solvent recovery. This invention features a simple process, low investment, strong applicability, and ease of control.

[0078] The main focus of this invention is on process design. The catalyst used in hydrogenation reactors, such as a single-stage hydrogenation reactor and a two-stage hydrogenation reactor, is not limited and any hydrogenation catalyst can be used, such as the catalysts described in Chinese patent applications 202011118431.X and CN202011120495.3.

[0079] According to a preferred embodiment of the present invention, the following examples employ... Figure 1 or Figure 2 The process shown is as follows.

[0080] Figure 1 and Figure 2 The method of this invention comprises: 1. Distributor; 2. First-stage hydrogenation reactor; 3. First-stage reaction product cooler; 4. First-stage gas-liquid separator; 5. Second-stage hydrogenation reactor; 6. Second-stage gas-liquid separator; 7. Circulating material cooler; 8. Second-stage cooler; 9. Third-stage gas-liquid separator; 11. Maleic anhydride solution; 12. Liquid phase product; 13. Supplementary hydrogen.

[0081] (1) The maleic anhydride solution 11 is divided into two streams by the distributor 1. One stream is mixed with the liquid phase material of the second stage hydrogenation reaction (cooling is carried out in the circulating material cooler 7) which is cooled or not cooled. Then, it enters the first stage hydrogenation reactor 2 from the liquid phase inlet at the top of the first stage hydrogenation reactor 2 and contacts hydrogen (containing supplementary hydrogen 13 and circulating hydrogen) for hydrogenation. The hydrogen (containing supplementary hydrogen 13 and circulating hydrogen) enters the first stage hydrogenation reactor 2 from the gas phase inlet at the top of the first stage hydrogenation reactor 2.

[0082] (2) The hydrogenation product of the first stage enters the first stage reaction product cooler 3 for cooling and temperature reduction. The gas-liquid separator 4 separates the gas and liquid phases. All the gas phases separated by the gas-liquid separation enter the second stage hydrogenation reactor 5 from the top gas phase feed port. The liquid phases separated by the gas-liquid separation are mixed with another stream of maleic anhydride solution and then enter the second stage hydrogenation reactor from the upper liquid phase feed port of the second stage reactor to react with hydrogen and convert all the maleic anhydride hydrogenation reaction into succinic anhydride.

[0083] (3) The second-stage hydrogenation product enters the second-stage gas-liquid separator 6 for gas-liquid separation to obtain the gas phase and the liquid phase material of the second-stage hydrogenation reaction in step (1) and the liquid phase product 12. Optionally, part or all of the gas phase can be used as recycled hydrogen.

[0084] Alternatively, the second-stage hydrogenation product can be cooled in a second-stage cooler 8 and then enter a third gas-liquid separator 9 for gas-liquid separation. Part or all of the resulting gas phase is mixed with the recycled hydrogen 13 as the hydrogen feedstock for the first-stage hydrogenation reactor. Optionally, the resulting liquid phase is returned to the second-stage gas-liquid separator 6 for further gas-liquid separation. Preferably, the gas phase obtained from the gas-liquid separation of the second-stage hydrogenation product is cooled in the second-stage cooler 8 at a temperature of 30–80°C. This effectively removes heat and improves catalytic efficiency.

[0085] This invention divides the maleic anhydride solution into two streams, which are then mixed with different materials and fed into two hydrogenation reactors. This reduces the maleic anhydride content entering the reactors, effectively removing the heat released by the reaction. The operation is flexible and easy to control.

[0086] Using the method of the present invention, the concentration of maleic anhydride in the incoming maleic anhydride solution does not need to be too low, which reduces the amount of solvent used and reduces the energy consumption of subsequent solvent recovery.

[0087] In this invention, after the first stage of reaction, the gas phase is cooled and separated into gas and liquid phases, and then all the gas phase enters the second stage reactor, which helps to effectively remove the heat of reaction generated in the second stage reaction.

[0088] This invention incorporates a gas-liquid separator after the primary reactor stage, allowing the gas and liquid phases to enter the hydrogenation reactor separately. Optionally, a distribution device can be used to ensure more thorough contact between the materials entering the reactor, resulting in better gas-liquid-solid contact, higher catalyst utilization, and lower investment.

[0089] The reaction conditions of this invention are mild, with the reaction occurring at around 40°C. The temperature rise of the reaction bed is low, which is significantly lower than the reaction temperature of existing technologies. This is beneficial for improving catalyst selectivity and extending catalyst life.

[0090] The following examples use the following catalysts:

[0091] Chinese patent application CN202011118431.X - Example 1

[0092] (1) Weigh 50.00g of basic nickel carbonate (nickel content 45% by weight), 9.16g of Cu(NO3)2·3H2O, 49.91g of ethylenediaminetetraacetic acid, 500g of deionized water and 100g of 25% by weight ammonia water, mix them together, and pass ammonia gas through them to adjust the pH of the solution to 10.5. Stir at 45℃ until all solids dissolve to obtain a solution of nickel-copper-ammonia complex.

[0093] (2) Weigh 458.31g of silica sol and mix it with the nickel-copper ammonia complex solution obtained in step (1) to obtain a mixture;

[0094] (3) The mixture was aged at 60°C for 14 hours under stirring, and then dried at 120°C for 12 hours to obtain the catalyst precursor.

[0095] (4) The catalyst precursor was saturated with a cerium nitrate solution containing 11.41 g of Ce(NO3)3·6H2O to obtain the matrix catalyst;

[0096] (5) The matrix catalyst is dried at 115°C for 12 hours and then calcined at 400°C for 4 hours to obtain catalyst S1.

[0097] Based on the total weight of the catalyst S1, the catalyst S1 contains: 19% by weight NiO, 2% by weight CuO, 3% by weight CeO2 and 76% by weight SiO2.

[0098] Chinese patent application CN202011120495.3 - Example 1

[0099] (1) Weigh 10.90g of Ni(NO3)3·6H2O and 5.04g of Ce(NO3)3·6H2O, dissolve them in water and make up to 50.0ml. Then, 50g of carrier SiO2 (specific surface area 300m2 / g, water absorption rate 1.0mL / g) is immersed in a nickel nitrate-cerium nitrate mixed solution, stirred evenly, and allowed to stand for aging for 4 hours. Then, it is dried at 120℃ for 12 hours and finally calcined in air at 450℃ for 4 hours to obtain composite oxide carrier E.

[0100] (2) The composite oxide support E was added to 100 ml of an exothermic Ru metal solution with a Ru content of 0.02 g / L. Under stirring conditions, 25% ammonia water was added dropwise to adjust the pH value of the solution and maintain it at 9. After reacting at 55°C for 6 hours, the solution was filtered, dried at 110°C for 12 hours, and finally calcined in air at 500°C for 4 hours to obtain the finished catalyst S1.

[0101] The catalyst S1 contains, based on the mass of the catalyst support SiO2, Ni in the catalyst is 7% of the mass of the support, CeO2 is 4% of the mass of the support, and Ru is 0.4% of the mass of the support.

[0102] Example 1

[0103] use Figure 1 The method for hydrogenating maleic anhydride shown uses γ-butyrolactone as the solvent. The maleic anhydride solution contains 10% by weight of maleic anhydride. This maleic anhydride solution is divided into two streams at a ratio of 50% by weight and 50% by weight. One stream is mixed with the liquid phase material from the recycled second-stage hydrogenation reaction and then enters the first-stage hydrogenation reactor through the liquid phase inlet at the top of the reactor. The other stream is mixed with the liquid phase product from the first-stage hydrogenation reaction and then enters the second-stage hydrogenation reactor through the liquid phase inlet at the top of the second-stage reactor. The molar ratio of the total amount of recycled hydrogen and replenished fresh hydrogen to the total maleic anhydride in the incoming maleic anhydride solution is 10.

[0104] In a single-stage hydrogenation reactor, the space velocity is 2.5 h⁻¹. -1 The reaction temperature was 40℃, and the reaction pressure was 1.5MPa. After cooling the products of the first-stage hydrogenation reaction to 40℃ and separating the gas and liquid phases, the gas phase entered the second-stage hydrogenation reactor entirely through the top gas phase inlet. The liquid phase, after mixing with another maleic anhydride solution, entered the second-stage hydrogenation reactor through the upper liquid phase inlet. The space velocity (SHV) of the second-stage hydrogenation reactor was 1 h⁻¹. -1The reaction temperature was 42℃ and the reaction pressure was 1.3MPa. After the products of the second-stage hydrogenation reaction passed through a gas-liquid separator, the gas phase was cooled to 40℃ and then sent into the first-stage hydrogenation reactor along with the replenished fresh hydrogen. 65% by weight of the liquid phase was sent to the subsequent separation system, and 35% by weight of the liquid phase was returned to the first-stage hydrogenation reactor, mixed with another maleic anhydride solution, and then heated to 40℃ before entering the first-stage hydrogenation reactor.

[0105] The catalysts packed in the first and second stage hydrogenation reactors are all Ni active component catalysts, as detailed in CN202011118431.X-Example 1.

[0106] After two stages of reaction, the total conversion rate of maleic anhydride was 99.2%, and the total selectivity of succinic anhydride was 99.3%.

[0107] Example 2

[0108] use Figure 2 The method for hydrogenating maleic anhydride shown uses hexane as the solvent. The maleic anhydride solution contains 25% maleic anhydride by weight. This maleic anhydride solution is divided into two streams in a ratio of 40% by weight and 60% by weight. The 40% by weight maleic anhydride solution is mixed with the liquid phase material from the second-stage hydrogenation reaction and then enters the first-stage hydrogenation reactor through the liquid phase inlet at the top of the reactor. The 60% by weight maleic anhydride solution is mixed with the liquid phase product from the first-stage hydrogenation reaction and then enters the second-stage hydrogenation reactor through the liquid phase inlet at the top of the reactor. The molar ratio of the total amount of recycled hydrogen and replenished fresh hydrogen to the total maleic anhydride in the incoming maleic anhydride solution is 40.

[0109] In a single-stage hydrogenation reactor, the space velocity (SPV) is 3 h⁻¹. -1 The reaction temperature was 40℃, and the reaction pressure was 1.7MPa. The products of the first-stage hydrogenation reaction were cooled to 42℃, and after gas-liquid separation, the gas phase entered the second-stage hydrogenation reactor from the top gas phase inlet. The liquid phase mixed with another maleic anhydride solution and then entered the second-stage hydrogenation reactor. The space velocity in the second-stage hydrogenation reactor was 0.8 h⁻¹. -1 The reaction temperature is 45℃ and the reaction pressure is 1.5MPa. After the product of the second-stage hydrogenation reaction passes through a gas-liquid separator, the gas phase is cooled again to 40℃ and then passes through a gas-liquid separator. The gas phase, along with the replenished fresh hydrogen, is sent into the first-stage hydrogenation reactor. 50% by weight of the liquid phase from gas-liquid separator B is sent to the light phase removal tower, and another 50% by weight of the liquid phase is returned to the first-stage hydrogenation reactor. After mixing with some maleic anhydride solution, the mixture is heated to 40℃ and then enters the first-stage hydrogenation reactor.

[0110] The catalysts packed in the first and second stage hydrogenation reactors are all Ni active component catalysts, as detailed in CN202011120495.3-Example 1.

[0111] After two stages of reaction, the total conversion rate of maleic anhydride was 99.5%, and the total selectivity of succinic anhydride was 99.7%.

[0112] Example 3

[0113] use Figure 1 The method for hydrogenating maleic anhydride shown uses dioxane as the solvent. The maleic anhydride solution contains 18% by weight. This maleic anhydride solution is divided into two streams in a ratio of 20% by weight and 80% by weight. The 20% by weight maleic anhydride solution is mixed with the liquid phase product of the second-stage hydrogenation reaction and then enters the first-stage hydrogenation reactor from the top of the first-stage reactor. The 80% by weight maleic anhydride solution is mixed with the liquid phase product of the first-stage hydrogenation reaction and then enters the second-stage hydrogenation reactor from the liquid phase inlet at the top of the first-stage reactor. The molar ratio of the total amount of circulating hydrogen and replenished fresh hydrogen to the total maleic anhydride in the incoming maleic anhydride solution is 30.

[0114] In a single-stage hydrogenation reactor, the space velocity is 1.8 h⁻¹. -1 The reaction temperature was 40℃, and the reaction pressure was 1.3MPa. The products of the first-stage hydrogenation reaction were cooled to 45℃, and after gas-liquid separation, the gas phase entered the second-stage hydrogenation reactor from the top gas phase inlet. The liquid phase, after mixing with another portion of the maleic anhydride solution, entered the second-stage hydrogenation reactor. The space velocity in the second-stage hydrogenation reactor was 1.2 h⁻¹. -1 The reaction temperature is 48℃ and the reaction pressure is 1.2MPa. After the two-stage hydrogenation reaction products pass through the gas-liquid separator, the gas phase is sent to the first-stage hydrogenation reactor along with the replenished fresh hydrogen. 60% of the liquid phase is sent to the subsequent separation system, and 40% of the liquid phase is returned to the first-stage hydrogenation reactor. After being mixed with maleic anhydride solution, the mixture is heated to the reaction temperature and then enters the first-stage hydrogenation reactor.

[0115] The catalysts packed in the first and second stage hydrogenation reactors are all Ni active component catalysts, as detailed in CN202011118431.X-Example 1.

[0116] After two stages of reaction, the total conversion rate of maleic anhydride was 99.0%, and the total selectivity of succinic anhydride was 99.5%.

[0117] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A process for the hydrogenation of maleic anhydride, characterized in that, This method involves a two-stage hydrogenation reaction. (1) The maleic anhydride solution is divided into two streams of material, one stream having a content of 20-50% by weight and the other stream having a content of 50-80% by weight. One stream is mixed with the liquid phase material of the second stage hydrogenation reaction after being cooled to 30-80°C, and then enters the first stage hydrogenation reactor from the liquid phase inlet at the top of the first stage hydrogenation reactor to contact with hydrogen for hydrogenation. The hydrogen enters the first stage hydrogenation reactor from the gas phase inlet at the top of the first stage hydrogenation reactor. (2) The hydrogenation products of the first stage are cooled down and separated into gas and liquid. The gas phase of the gas-liquid separation enters the second stage hydrogenation reactor from the top gas phase feed port of the second stage hydrogenation reactor. The liquid phase of the gas-liquid separation is mixed with another maleic anhydride solution and then enters the second stage hydrogenation reactor from the upper liquid phase feed port of the second stage reactor to react with hydrogen and convert all the maleic anhydride hydrogenation reaction into succinic anhydride. (3) The two-stage hydrogenation product is subjected to gas-liquid separation to obtain a gas phase and a liquid phase material from the two-stage hydrogenation reaction described in step (1). The gas phase obtained from the gas-liquid separation of the two-stage hydrogenation product is cooled to a temperature of 30~80℃. Part or all of the gas phase is used as recycled hydrogen. 20-90% by weight of the liquid phase material from the two-stage hydrogenation reaction is returned to step (1) as a raw material, and the remainder is sent to the subsequent separation system as a liquid phase product. The maleic anhydride concentration of the maleic anhydride solution is 1-90% by weight. The molar ratio of total hydrogen to total maleic anhydride in the maleic anhydride solution is 5-100.

2. The method according to claim 1, wherein, The hydrogen feedstock in step (1) is a mixture of recycled hydrogen and supplementary hydrogen.

3. The method according to claim 1, wherein, The liquid phase material in the two-stage hydrogenation reaction described in step (1) is a material cooled to 40~60℃.

4. The method of any of claims 1-3, wherein, The method also includes: The gas phase obtained by gas-liquid separation of the second-stage hydrogenation product is cooled and then subjected to a third gas-liquid separation. Part or all of the obtained gas phase is mixed with the circulating hydrogen and supplementary hydrogen as the hydrogen feedstock for the first-stage hydrogenation reactor. Optionally, the obtained liquid phase is returned to the second-stage gas-liquid separator for gas-liquid separation.

5. The method of any of claims 1-3, wherein, In step (1), The maleic anhydride solution is a mixture of maleic anhydride and a solvent, wherein the solvent is one or more selected from acetic anhydride, γ-butyrolactone, dioxane, tetrahydrofuran, aromatic hydrocarbons, ethyl acetate, tetracarbon diesters, ethanol, isopropanol, hexane, cyclohexane, propylene oxide, ketones, and ethers; and / or The operating conditions of the first hydrogenation reactor include: a temperature of 30-100℃; and / or a reaction pressure of 0.1-10 MPa; and / or a space velocity of 0.5-5 h -1 .

6. The method of claim 5, wherein, In step (1), The maleic anhydride concentration of the maleic anhydride solution is 10-40% by weight.

7. The method of claim 5, wherein, In step (1), The molar ratio of total hydrogen to total maleic anhydride in the maleic anhydride solution is 10~40.

8. The method of claim 5, wherein, In step (1), The operating conditions for a single-stage hydrogenation reactor include a temperature of 40-80℃.

9. The method according to claim 5, wherein, In step (1), The operating conditions for a single-stage hydrogenation reactor include a reaction pressure of 0.5-5 MPa.

10. The method of any one of claims 1-3, wherein, In step (2), the operating conditions of the two-stage hydrogenation reactor include: Temperature: 30-100℃; and / or pressure: 0.1-10MPa; and / or space velocity: 0.5-5h. -1 .

11. The method of claim 10, wherein, In step (2), The operating conditions for the two-stage hydrogenation reactor include a temperature of 40-80℃.

12. The method of claim 10, wherein, In step (2), The operating conditions for the two-stage hydrogenation reactor include a pressure of 0.5-5 MPa.

13. The method of any one of claims 1-3, wherein, 30-70% by weight of the liquid phase material from the second-stage hydrogenation reaction is returned to step (1) as a raw material, and the remainder is sent to the subsequent separation system as a liquid phase product. 0.5-2% by weight of the gaseous material from the second-stage hydrogenation reaction is extracted as fuel gas, and the remainder is used as the recycled hydrogen.

14. The method according to any one of claims 1-3, wherein, This method is carried out in a liquid-phase hydrogenation reaction system, which includes: A hydrogenation reactor, comprising a top gas phase inlet, an upper liquid phase inlet, and a bottom outlet; and a reaction product cooler and a gas-liquid separator connected in series at the bottom outlet of the hydrogenation reactor. The two-stage hydrogenation reactor is connected in series with the first-stage gas-liquid separator. The two-stage hydrogenation reactor includes a top gas phase inlet, an upper liquid phase inlet, and a bottom outlet. A two-stage gas-liquid separator is connected in series with the bottom outlet of the two-stage hydrogenation reactor. A circulating material cooler is installed on the connecting pipeline between the bottom liquid phase outlet of the two-stage gas-liquid separator and the upper liquid phase inlet of the first-stage hydrogenation reactor. The liquid feedstock supply pipeline is connected to both the upper liquid feed inlet of the first-stage hydrogenation reactor and the upper liquid feed inlet of the second-stage hydrogenation reactor.

15. The hydrogenation reaction system according to claim 14, The top gas phase outlet of the first-stage gas-liquid separator is connected to the top gas phase inlet of the second-stage hydrogenation reactor via a pipeline; and / or The bottom liquid phase outlet of the first-stage gas-liquid separator is connected to the upper liquid phase inlet of the second-stage hydrogenation reactor via a pipeline; and / or The top gas phase outlet of the two-stage gas-liquid separator is connected to the top gas phase inlet of the first-stage hydrogenation reactor via a pipeline; and / or The bottom liquid phase outlet of the two-stage gas-liquid separator is connected to the upper liquid phase inlet of the first-stage hydrogenation reactor via a pipeline.

16. The hydrogenation reaction system according to claim 14, A second-stage cooler and a third gas-liquid separator are connected in series at the top gas phase outlet of the second-stage gas-liquid separator. The gas phase outlet of the third gas-liquid separator is connected to the top gas phase inlet of the first-stage hydrogenation reactor via a pipeline. The bottom liquid phase outlet of the third gas-liquid separator is connected to the liquid phase inlet of the second-stage gas-liquid separator.

17. The hydrogenation reaction system of claim 14, further comprising: A distributor is used to distribute liquid feedstock into two streams as needed for supplying the first-stage hydrogenation reactor and the second-stage hydrogenation reactor.

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