A reaction process for preparing succinic anhydride

Abstract

The application discloses a reaction process for preparing succinic anhydride, and comprises the following contents: (1) mixing uniformly a maleic anhydride solution and hydrogen to obtain mixed feed I, feeding the mixed feed I into an up-flow fixed bed reactor A, and performing a first hydrogenation reaction to obtain a first hydrogenation reaction product; (2) after heat removal, mixing uniformly the first hydrogenation reaction product with supplemental hydrogen to obtain mixed feed II, feeding the mixed feed II into an up-flow fixed bed reactor B, and performing a second hydrogenation reaction to obtain a second hydrogenation reaction product; and (3) after heat removal, performing gas-liquid separation on the second hydrogenation reaction product, recycling a part of a liquid phase, and feeding the other part of the liquid phase into a subsequent product fractionation unit. By adjusting the hydrogen feeding ratio of the reactor A / B and the micro-bubble content, the maleic anhydride hydrogenation reaction conversion rate and selectivity can be kept high during the preparation of succinic anhydride, and all catalysts in the reaction system can be simultaneously deactivated, so that the total operation period of the device is greatly prolonged, and the economy of the industrial device is improved.

Description

Technical Field

[0001] This invention belongs to the field of biodegradable material production technology, and specifically relates to a reaction process for preparing succinic anhydride. Background Technology

[0002] Currently, the main production methods of succinic anhydride are succinic acid dehydration, bio-fermentation, and maleic anhydride catalytic hydrogenation. Among them, maleic anhydride hydrogenation is the method with the highest conversion rate and product yield of succinic anhydride, and is most suitable for large-scale industrialization. However, the production of succinic anhydride by maleic anhydride hydrogenation has not yet been industrialized on a large scale. The main problems at present are as follows: (1) The reaction of maleic anhydride hydrogenation to prepare succinic anhydride is a strongly exothermic reaction (ΔH=128kJ / mol). Conventional trickle bed hydrogenation and conventional liquid phase hydrogenation cannot remove the heat of reaction in time, making it impossible to control the temperature of the reaction process. (1) Problems such as local hot spots in the catalyst bed, serious side reactions, catalyst coking and caking; (2) In the later stage of the maleic anhydride hydrogenation reaction, due to the low concentration of maleic anhydride, the contact mass transfer rate between hydrogen and maleic anhydride is very low. It takes a very long residence time to reach a conversion rate of more than 99%, which also increases the side reactions; (3) Generally, the maleic anhydride hydrogenation reaction adopts two-stage reactors in series, which makes the reaction rate of the first reactor and the reaction rate and temperature rise of the second reactor different. This causes the catalysts of the two reactors to be unable to be deactivated synchronously, affecting the total operating cycle and economy of the device.

[0003] CN103570650A proposes a process for the continuous production of succinic anhydride and succinic acid from maleic anhydride via hydrogenation. This method employs a two-stage hydrogenation reactor. The first-stage reactor is a fixed-bed reactor where hydrogen and the reaction liquid flow from bottom to top. The second-stage reactor is a trickle-bed reactor where both hydrogen and the reaction liquid flow from top to bottom, utilizing external circulation to remove heat and control the average operating temperature of the entire reactor, ensuring temperature uniformity. However, the first-stage reactor uses a co-current upward flow of hydrogen and the reaction liquid. Due to the high exothermic nature of the maleic anhydride hydrogenation reaction, conventional techniques cannot guarantee uniform mixing and distribution of materials, thus failing to ensure uniform reaction and address localized hot spots. Furthermore, the second-stage reactor uses a co-current downward flow of a trickle-bed reactor, which further hinders the timely removal of reaction heat and the resolution of localized hot spots.

[0004] CN 105801536B proposes a method for preparing succinic anhydride by liquid-phase selective hydrogenation of maleic anhydride. The liquid-phase hydrogenation reaction employs a two-stage low-temperature, low-pressure reaction process using two reactors: a primary reactor and a secondary reactor, connected in series. Maleic anhydride, solvent, and hydrogen enter the primary reactor for partial catalytic selective hydrogenation. After the reaction, the remaining maleic anhydride, the generated succinic anhydride, and the solvent mixture enter the secondary reactor for complete catalytic selective hydrogenation. The product from the secondary reactor is then subjected to gas-liquid separation and distillation to obtain the succinic anhydride product. However, this method uses a two-stage reactor with liquid-phase hydrogenation of the reaction liquid. Due to the high exothermic nature of the maleic anhydride hydrogenation reaction, conventional liquid-phase hydrogenation mixing and reaction techniques cannot guarantee uniform mixing and distribution of the materials, nor can they ensure uniform reaction or address localized hot spots.

[0005] In summary, there are few existing patents related to the production technology of maleic anhydride hydrogenation to succinic anhydride, and most of them focus on catalyst preparation and reaction process. Solving the problem of concentrated exothermic reaction, ensuring high conversion rate and selectivity, and synchronous catalyst deactivation during the hydrogenation reaction of maleic anhydride are of great significance for the long-term and efficient operation of succinic anhydride production plants. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention discloses a reaction process for preparing succinic anhydride. This invention deeply couples the hydrogen feed ratio (K) and microbubble content of the upflow fixed-bed series reactors A / B in the maleic anhydride hydrogenation reaction process with the early / late stages and the entire reaction process. This ensures that the maleic anhydride hydrogenation reaction maintains a consistently high conversion rate and selectivity during the succinic anhydride preparation process. Simultaneously, it enables the synchronous deactivation of all catalysts within the reaction system, significantly extending the overall operating cycle of the equipment and improving the economic efficiency of the industrial plant.

[0007] The reaction process for preparing succinic anhydride according to the present invention includes the following:

[0008] (1) The mixed feed I obtained by uniformly mixing maleic anhydride solution and hydrogen gas is fed into an upflow fixed bed reactor A to carry out the first hydrogenation reaction and obtain the first hydrogenation reaction product;

[0009] (2) After the first hydrogenation reaction product is heated, it is mixed with supplementary hydrogen to obtain mixed feed II, which enters the upflow fixed bed reactor B to carry out the second hydrogenation reaction and obtain the second hydrogenation reaction product.

[0010] (3) After the second hydrogenation reaction product is heated, it undergoes gas-liquid separation. Part of the liquid phase is recycled, and the other part enters the subsequent product fractionation unit; wherein, the flow rates (Nm) of hydrogen from the upflow fixed-bed reactor A in step (1) and the supplementary hydrogen from the upflow fixed-bed reactor B in step (2) are... 3 The ratio K of / h is 1:10 to 10:1.

[0011] In the method of the present invention, the maleic anhydride content in the maleic anhydride solution is 0.03-0.3 g / mL, preferably 0.05-0.15 g / mL, and the solvent used for the maleic anhydride solution is one or more of benzene, toluene, xylene, acetone, tetrahydrofuran, γ-butyrolactone, methyl acetone, cyclohexanone, ethyl acetate, diethyl succinate, or ethylene glycol monomethyl ether.

[0012] In the method of the present invention, the hydrogen gas used can generally be hydrogen gas with a purity greater than 90 (v)%, and preferably 99.9% pure hydrogen.

[0013] In the method of this invention, in the mixture I, hydrogen gas is uniformly dispersed in the maleic anhydride solution, and the hydrogen bubbles are mainly of millimeter size (diameter d1 is generally 0.01-20 mm), that is, ≥70% of the hydrogen bubbles are millimeter size, and the remainder are nanometer or micrometer size. The mixing process can generally employ one or more combinations of static mixers, jet mixers, mechanical shear mixers, and impact mixers. Since the process in the upflow fixed-bed reactor A is in the early stage of the reaction, the maleic anhydride concentration is relatively high, and the chemical hydrogen consumption and mass transfer driving force are relatively large. When hydrogen gas is introduced into the reactor to undergo a hydrogenation reaction, breaking the hydrogen gas into bubbles mainly of millimeter size ensures a sufficiently high reaction rate. The method for determining the bubble size and content used in this paper is as follows: A transparent reactor is used, and a mixture of maleic anhydride solution and hydrogen gas is introduced into it in a certain proportion. Under stable flow conditions, a microfluidic high-frequency camera is used to photograph any area inside the reactor. After magnification, the bubble size within the photographed area is measured, the proportion of various bubble types is calculated, and the average value of multiple area photographs is taken as the final calculation result. The early stage of the reaction, as described in this article, refers to the stage in which the concentration of maleic anhydride in the maleic anhydride solution in the reactor is greater than or equal to the concentration of succinic anhydride, while the later stage of the reaction refers to the stage in which the concentration of maleic anhydride in the maleic anhydride solution in the reactor is less than the concentration of succinic anhydride.

[0014] In the method of this invention, the first hydrogenation reaction conditions are as follows: reaction temperature of 40–200°C, preferably 50–150°C; reaction pressure of 0.5–10.0 MPa, preferably 1–5.0 MPa; and liquid hourly space velocity of 0.5–15.0 h⁻¹. -1 Preferably 3.0–8.0h -1 Hydrogen (Nm³) in upflow fixed-bed reactor A 3 / h) and maleic anhydride solution (m 3The volumetric flow rate ratio ( / h) is 5:1 to 100:1, preferably 10:1 to 60:1.

[0015] In the method of this invention, in the mixture II, hydrogen is uniformly mixed and dispersed in the first hydrogenation product. The mixing process employs equipment capable of generating a large number of microbubbles, such as one or more combinations of dissolved gas pumps, colloid mills, microporous plate nano / micro hydrogen dispersion components, microbubble generators, ceramic membrane nano / micro hydrogen dispersion components, metal membrane nano / micro hydrogen dispersion components, microchannel mixers, Venturi injectors, high-speed shearing equipment, etc. The hydrogen bubbles can all be nano / micron sized (diameter d2 is generally 10nm to 1000μm), or mainly nano / micron sized (diameter d2 is generally 10nm to 1000μm), that is, ≥70% of the hydrogen bubbles are nano / micron sized, and the remainder are millimeter sized. Here, the process in the upflow fixed-bed reactor B is in the later stage of the reaction, with a relatively low maleic anhydride concentration, chemical hydrogen consumption, and mass transfer driving force. When hydrogen is introduced into the reactor for a hydrogenation reaction, it is necessary to break the hydrogen into bubbles with predominantly nanometer-micron dimensions to significantly increase the gas-liquid contact area and enhance mass transfer during the reaction process, thereby ensuring a high mass transfer reaction rate, high conversion rate, and high selectivity. In the method of this invention, the second hydrogenation reaction conditions are: reaction temperature of 40–200℃, preferably 50–150℃; reaction pressure of 0.5–10.0 MPa, preferably 1–5.0 MPa; and liquid hourly space velocity of 0.1–8.0 h⁻¹. -1 Preferably 0.5–3.0 h -1 Hydrogen (Nm³) in upflow fixed-bed reactor B 3 / h) and maleic anhydride feedstock in upflow fixed-bed reactor A (m 3 The ratio of volumetric flow rate ( / h) is 1:1 to 60:1, preferably 5:1 to 40:1.

[0016] In the method of the present invention, one or more catalyst beds may be set in the upflow fixed bed reactors A and B as needed. The catalyst can generally be a catalyst with hydrogenation function commonly used in the field of maleic anhydride hydrogenation reaction, preferably a supported nickel-based catalyst. The catalyst support can be one or more of SiO2, Al2O3, SiO2-Al2O3, TiO2, activated carbon or molecular sieve, etc. The catalyst shape can be one of spherical, strip-shaped, clover-shaped or toothed spherical, etc., preferably spherical or toothed spherical catalyst.

[0017] In the method of this invention, the maleic anhydride conversion rate of the first hydrogenation reaction is generally 41%–99%, and the conversion rate of maleic anhydride in the initial stage of the reaction is generally 71%–99%, while the conversion rate in the final stage of the reaction is generally 41%–70%. The maleic anhydride conversion rate of the second hydrogenation reaction is generally 1%–40%, and the conversion rate in the initial stage of the reaction is generally 1%–20%, while the conversion rate in the final stage of the reaction is generally 21%–40%. The initial and final stages of the reaction described herein are defined based on the total operating cycle of the catalyst. The initial stage refers to the stage where the reactor inlet temperature meets the maleic anhydride conversion requirement. The final stage refers to the stage where, with the extension of the reaction time and the decrease in catalyst activity, the reactor inlet temperature no longer meets the maleic anhydride conversion requirement, and the reactor inlet temperature needs to be increased to meet the maleic anhydride conversion requirement. The total operating cycle of the catalyst is reached when the reactor inlet temperature reaches its upper limit.

[0018] This invention, during the total operating cycle of the catalyst, on the one hand, gradually changes the hydrogen ratio (K) in reactors A and B, causing the maleic anhydride conversion rate in reactor A to gradually decrease and the maleic anhydride conversion rate in reactor B to gradually increase. This transfers the hydrogenation reaction conversion rate from the first reactor to the second reactor, balancing the reaction conversion rate and catalyst activity in both reactors, ensuring that the catalysts in both reactors reach the end of the reaction and deactivate simultaneously. On the other hand, as the maleic anhydride hydrogenation reaction conversion rate shifts, the material residence time in reactor B gradually shortens. To ensure the reaction conversion rate, as the hydrogen feed rate in reactor B gradually increases, the proportion of hydrogen broken into nanobubbles gradually increases, significantly enhancing and ensuring the mass transfer reaction rate and conversion rate of the second hydrogenation reaction.

[0019] In the method of the present invention, the first circulating material recycled back to the upflow fixed bed reactor A accounts for 15wt% to 90wt%, preferably 30wt% to 80wt%, of the fresh feed (maleic anhydride solution) of the upflow reactor A; the second circulating material recycled back to the upflow reactor B accounts for 0 to 80wt%, preferably 0 to 40wt%, of the fresh feed of the upflow reactor B.

[0020] The existing reaction process for preparing succinic anhydride has the following main problems: (1) The reaction for preparing succinic anhydride by hydrogenation of maleic anhydride is a strongly exothermic reaction. Conventional trickle bed hydrogenation and conventional liquid phase hydrogenation cannot remove the heat of reaction in time, which can easily cause local hot spots in the catalyst bed, serious side reactions, catalyst coking and caking, etc. (2) In the later stage of the maleic anhydride hydrogenation reaction, due to the low concentration of maleic anhydride, the contact mass transfer rate between hydrogen and maleic anhydride is very low. In particular, a very long residence time is required to achieve a conversion rate of more than 99%, which is also an important reason for the increase of side reactions and low selectivity. (3) Generally, the maleic anhydride hydrogenation reaction adopts a two-stage hydrogenation reactor series process, which makes the reaction rate of the first reactor and the reaction rate of the second reactor, as well as the catalyst deactivation rate, different. This causes the catalysts of the two reactors to be deactivated synchronously, affecting the overall operating cycle and economy of the device.

[0021] This invention system, by controlling the hydrogen feed ratio (K) and microbubble content of the upflow fixed-bed series reactors A and B in the maleic anhydride hydrogenation reaction to prepare succinic anhydride, deeply couples with the early and late stages of the maleic anhydride hydrogenation reaction and the entire reaction process. This ensures that the maleic anhydride hydrogenation reaction maintains a high conversion rate (≥99.8%) and selectivity (≥98.5%) throughout the succinic anhydride preparation process. Simultaneously, it achieves synchronous deactivation of all catalysts within the reaction system, significantly extending the overall operating cycle of the unit and improving the economic efficiency of the industrial plant. Here, the system addresses the significant difference in reaction rates between the early and late stages of the maleic anhydride hydrogenation reaction. Specifically, the early stage has a relatively high maleic anhydride concentration, a relatively fast reaction rate, and a relatively large mass transfer driving force, while the late stage has a relatively low maleic anhydride concentration, a relatively slow reaction rate, and a relatively small mass transfer driving force. This results in two main issues: firstly, the required residence time differs between the early and late stages, with a longer residence time required to achieve a conversion rate of ≥99% in the late stage, leading to more side reactions and lower selectivity; secondly, the catalyst deactivation rates are inconsistent between the early and late stages, meaning the catalyst deactivation within the reaction system is asynchronous. Therefore, this invention sets up a two-stage series continuous hydrogenation reactor, so that the hydrogenation reaction is mainly concentrated in the upflow hydrogenation reactor A in the early stage of the reaction, and then the hydrogenation reaction is transferred to the upflow hydrogenation reactor B as the reaction proceeds, until the catalysts in the two reactors are deactivated simultaneously. During this process, the transfer of the hydrogenation reaction is controlled by the hydrogen supply and the proportion of microbubbles is controlled to achieve the purpose of high conversion rate and selectivity of hydrogenation reaction. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a reaction process for preparing succinic anhydride according to the present invention.

[0023] Wherein, 1 is maleic anhydride solution, 2 is first hydrogen gas, 3 is supplementary hydrogen gas, 4 is mixer A, 5 is upflow fixed bed reactor A, 6 is ceramic ball, 7 is catalyst bed, 8 is first hydrogenation reaction product, 9 is heat extraction device A, 10 is liquid feed to upflow fixed bed reactor B, 11 is upflow fixed bed reactor B, 12 is mixer B, 13 is catalyst bed, 14 is second hydrogenation reaction product, 15 is heat extraction device B, 16 is gas-liquid separator feed, 17 is gas-liquid separator, 18 is separated gas, 19 is separated liquid phase hydrogenation product, 20 is liquid phase product entering the fractionation unit, 21 is circulation pump, 22 is circulating material entering upflow fixed bed reactor B, and 23 is circulating material entering upflow fixed bed reactor A. Detailed Implementation

[0024] The present invention will now be described in detail with reference to the accompanying drawings and embodiments, but this does not limit the scope of the invention.

[0025] With attachment Figure 1 The following is an example illustrating the application process of a reaction method for preparing succinic anhydride according to the present invention: First, maleic anhydride solution 1, recycled material 23, and first hydrogen gas 2 are mixed evenly in mixer A4 to obtain mixed feed I, which enters an upflow fixed-bed hydrogenation reactor A5. After being evenly distributed again by ceramic balls 6, an upflow hydrogenation reaction occurs from bottom to top in the catalyst bed 7, yielding the first hydrogenation reaction product 9. After leaving the upflow fixed-bed hydrogenation reactor A5, the product is heated by heat extraction device A9, and then enters an upflow fixed-bed reactor B11 with recycled material 22 and supplementary hydrogen gas 3. The product is first evenly mixed by mixer B12 to obtain mixed feed II, while the supplementary hydrogen gas is broken into nano / micron bubbles, and then enters the catalyst bed 13 to undergo an upflow hydrogenation reaction from bottom to top, yielding the first hydrogenation reaction product 14. After leaving the upflow fixed-bed hydrogenation reactor B11, the product is heated by heat extraction device B14. Heat is extracted from 15 and then enters the gas-liquid separator 17. The gas 18 after gas-liquid separation is led out of the reaction system, and the separated liquid product 18 is divided into two paths. One path enters the subsequent separation unit, and the other path is circulated back to the reaction system via the circulation pump 21.

[0026] The method of this invention was applied to the process of hydrogenating maleic anhydride to succinic anhydride. Both the maleic anhydride feedstock and the γ-butyrolactone solvent were commercially available, and their specific properties are shown in Tables 1 and 2, respectively. The catalyst properties are shown in Table 3.

[0027] Table 1 Properties of maleic anhydride raw materials

[0028]

[0029] Table 2. Solvent properties of γ-butyrolactone

[0030]

[0031] Table 3 Physicochemical properties of catalysts

[0032]

[0033] Comparative Example 1

[0034] A conventional fixed-bed hydrogenation process is employed, using an upflow fixed-bed hydrogenation reactor A and a downflow fixed-bed hydrogenation reactor B connected in series. Maleic anhydride undergoes hydrogenation in the first hydrogenation reactor A and the second hydrogenation reactor B sequentially. First, the maleic anhydride feedstock is dissolved in γ-butyrolactone solvent and mixed thoroughly to prepare a maleic anhydride solution. After being heated to the reactor inlet temperature, the solution is mixed with hydrogen gas and enters from the bottom of the upflow hydrogenation reactor A, undergoing hydrogenation from bottom to top through the catalyst bed. The resulting hydrogenated product is then heated again and mixed with supplemental hydrogen gas before entering from the top of the downflow hydrogenation reactor A, undergoing hydrogenation from top to bottom through the catalyst bed. After the hydrogenation reaction is complete, the product leaves the reactor and undergoes gas-liquid separation in a separator. Part of the separated material is recycled, while the other part enters the separation unit.

[0035] The operating conditions for the first hydrogenation reactor A are as follows:

[0036] The reaction temperature is 50℃~150℃;

[0037] The reaction pressure is 6.0–6.5 MPaG;

[0038] Reactor height-to-diameter ratio: 2.5

[0039] Volumetric hourly space velocity: 3.0 h -1

[0040] maleic anhydride concentration: 12 g / mL

[0041] Hydrogen (Nm 3 / h) and fresh ingredients (m 3 The volume ratio of the solution (a solution of maleic anhydride dissolved in γ-butyrolactone solvent) is 300:1.

[0042] The mass ratio of reaction products entering the primary reactor cycle to fresh feedstock is 30%.

[0043] The operating conditions for the second hydrogenation reactor B are as follows:

[0044] The reaction temperature is 50℃~150℃;

[0045] The reaction pressure is 6.0–6.5 MPaG;

[0046] Volumetric hourly space velocity: 1.0 h -1 ;

[0047] Reactor height-to-diameter ratio: 2.5;

[0048] Note: The effluent from the first reactor is heated and then enters the second reactor. No more hydrogen is added to the inlet of the second reactor, nor is any recycled material introduced again.

[0049] Under these reaction conditions, maleic anhydride and γ-butyrolactone solvents listed in Tables 1 and 2 were used as raw materials and continuously fed into the first hydrogenation reactor A and the second hydrogenation reactor B to obtain hydrogenated products. The reaction results are shown in Table 4.

[0050] Comparative Example 2

[0051] A conventional fixed-bed hydrogenation process is employed, using two upflow fixed-bed hydrogenation reactors, A and B, connected in series. Maleic anhydride undergoes hydrogenation sequentially in reactors A and B. First, the maleic anhydride feedstock is dissolved in γ-butyrolactone solvent and mixed thoroughly to prepare a maleic anhydride solution. After being heated to the reactor inlet temperature, this solution is mixed with hydrogen and enters from the bottom of reactor A, undergoing hydrogenation from bottom to top through the catalyst bed. The resulting hydrogenated product is then heated again and mixed with supplemental hydrogen before entering from the bottom of reactor B, undergoing hydrogenation from bottom to top through the catalyst bed. After hydrogenation, the product exits the reactor and undergoes gas-liquid separation in a separator. Part of the separated liquid phase is recycled, while the other part enters the separation unit. The separated gaseous phase is compressed by a circulating hydrogen compressor and reused.

[0052] The operating conditions for the first hydrogenation reactor A are as follows:

[0053] The reaction temperature is 50℃~150℃;

[0054] The reaction pressure is 6.0–6.5 MPaG;

[0055] Reactor height-to-diameter ratio: 2.5

[0056] Volumetric hourly space velocity: 3.0 h -1

[0057] maleic anhydride concentration: 12 g / mL

[0058] Hydrogen (Nm 3 / h) and fresh ingredients (m 3 The volume ratio of the solution (a solution of maleic anhydride dissolved in γ-butyrolactone solvent) is 100:1.

[0059] The mass ratio of reaction products entering the primary reactor cycle to fresh feedstock is 30%.

[0060] The operating conditions for the second hydrogenation reactor B are as follows:

[0061] The reaction temperature is 50℃~150℃;

[0062] The reaction pressure is 6.0–6.5 MPaG;

[0063] Volumetric hourly space velocity: 1.0 h -1 ;

[0064] Reactor height-to-diameter ratio: 2.5;

[0065] Replenish hydrogen (Nm 3 / h) and fresh ingredients (m) 3 The volume ratio of the solution (a solution of maleic anhydride dissolved in γ-butyrolactone solvent) is 400:1.

[0066] Note: The effluent from the first reactor is heated and then enters the second reactor. No more circulating material is introduced into the inlet of the second reactor.

[0067] Under these reaction conditions, maleic anhydride and γ-butyrolactone solvents listed in Tables 1 and 2 were used as raw materials and continuously fed into the first hydrogenation reactor A and the second hydrogenation reactor B to obtain hydrogenated products. The reaction results are shown in Table 4.

[0068] Example 1

[0069] Using the process of this invention, the maleic anhydride hydrogenation reaction zone is equipped with two upflow fixed-bed hydrogenation reactors, A and B. First, a pre-prepared 15% maleic anhydride (γ-butyrolactone solvent) solution and hydrogen are mixed uniformly using a conventional SV-type static mixer to form mixed feed I, which enters upflow fixed-bed hydrogenation reactor A for the first hydrogenation reaction, yielding the first hydrogenation reaction product. The first hydrogenation reaction product, after being heated, is mixed uniformly with supplementary hydrogen to obtain mixed feed II, which enters upflow fixed-bed hydrogenation reactor B for the second hydrogenation reaction, yielding the second hydrogenation reaction product. Here, the first hydrogenation reaction product and supplementary hydrogen are mixed using a Venturi mixer, that is, the hydrogen is dispersed into nano- and micron-sized bubbles before being mixed with the first hydrogenation reaction product, forming a liquid phase containing nano- and micron-sized bubbles, which enters upflow fixed-bed hydrogenation reactor B. The second hydrogenation reaction product, after being heated, undergoes gas-liquid separation; part of the liquid phase is recycled, and the other part enters the subsequent product fractionation unit.

[0070] The operating conditions for upflow fixed-bed hydrogenation reactor A are as follows:

[0071] The reaction temperature is 50℃~150℃;

[0072] The reaction pressure is 4.0–4.5 MPaG;

[0073] Reactor height-to-diameter ratio: 2.5

[0074] Volumetric hourly space velocity: 6.0 h -1

[0075] maleic anhydride concentration: 15 g / mL

[0076] Hydrogen (Nm 3 / h) and fresh ingredients (m 3 The volume ratio of the solution (a solution of maleic anhydride dissolved in γ-butyrolactone solvent) is 60:1.

[0077] The mass ratio of the reaction product entering reactor A in circulation to the fresh feed is 30%.

[0078] In the upflow fixed-bed hydrogenation reactor A, maleic anhydride solution and hydrogen are mixed using a conventional SV-type static mixer. It was determined that the bubble size in the mixed material is entirely within the range of 1 to 20 mm in diameter.

[0079] The operating conditions for the upflow fixed-bed hydrogenation reactor B are as follows:

[0080] The reaction temperature is 50℃~150℃;

[0081] The reaction pressure is 4.0–4.5 MPaG;

[0082] Reactor height-to-diameter ratio: 2.5

[0083] Volumetric hourly space velocity: 1.5h -1

[0084] Replenish hydrogen (Nm 3 / h) and fresh feed (m) in upflow fixed-bed reactor A 3 The volumetric flow rate ratio (sum of maleic anhydride and solvent) is 6:1.

[0085] The mass ratio of the reaction product entering reactor B in circulation to the fresh feed is 20%.

[0086] In the upflow fixed-bed hydrogenation reactor B, the first hydrogenation product and the supplementary hydrogen are mixed in a gas-liquid mixture using a Venturi mixer. After mixing in this mixer, about 72% of the bubbles in the mixture have a diameter of 50μm to 1000μm, and the remaining about 28% of the bubbles are in the millimeter range.

[0087] Hydrogen feed rate of upflow fixed-bed reactor A and the make-up hydrogen feed rate of upflow fixed-bed reactor B (Nm³) 3 The ratio K of / h is 10:1.

[0088] Under these reaction conditions, maleic anhydride and γ-butyrolactone solvents listed in Tables 1 and 2 were used as raw materials and continuously fed into upflow fixed-bed hydrogenation reactors A and B to obtain hydrogenated products. The reaction results are shown in Table 4.

[0089] Example 2

[0090] Using the method of this invention, the maleic anhydride hydrogenation reaction zone is equipped with two upflow fixed-bed hydrogenation reactors, A and B. First, a pre-prepared 15% maleic anhydride (γ-butyrolactone solvent) solution and hydrogen are mixed uniformly using a conventional SV-type static mixer to form mixed feed I, which enters upflow fixed-bed hydrogenation reactor A for the first hydrogenation reaction, yielding the first hydrogenation reaction product. The first hydrogenation reaction product is then heated and mixed uniformly with supplementary hydrogen to obtain mixed feed II, which enters upflow fixed-bed hydrogenation reactor B for the second hydrogenation reaction, yielding the second hydrogenation reaction product. Here, the first hydrogenation reaction product and supplementary hydrogen are mixed using a cyclone shear-type bubble generator, and the resulting liquid phase containing nano- and micron-sized bubbles enters upflow fixed-bed hydrogenation reactor B. The second hydrogenation reaction product is heated and then subjected to gas-liquid separation; part of the liquid phase is recycled, and the other part enters the subsequent product fractionation unit.

[0091] The operating conditions for upflow fixed-bed hydrogenation reactor A are as follows:

[0092] The reaction temperature is 50℃~150℃;

[0093] The reaction pressure is 4.0–4.5 MPaG;

[0094] Reactor height-to-diameter ratio: 4.0

[0095] Volumetric hourly space velocity: 5.0 h -1

[0096] maleic anhydride concentration: 15 g / mL

[0097] Hydrogen (Nm 3 / h) and fresh ingredients (m 3 The volume ratio of the solution (a solution of maleic anhydride dissolved in γ-butyrolactone solvent) is 30:1.

[0098] The mass ratio of the reaction product entering reactor A in circulation to the fresh feed is 40%.

[0099] In the upflow fixed-bed hydrogenation reactor A, maleic anhydride solution and hydrogen are mixed using a conventional SV-type static mixer. It was determined that the bubble size in the mixture is entirely within the range of 1 to 20 mm in diameter.

[0100] The operating conditions for the upflow fixed-bed hydrogenation reactor B are as follows:

[0101] The reaction temperature is 50℃~150℃;

[0102] The reaction pressure is 4.0–4.5 MPaG;

[0103] Reactor height-to-diameter ratio: 2.0

[0104] Volumetric hourly space velocity: 1.7 h -1

[0105] Replenish hydrogen (Nm 3 / h) and fresh feed (m) in upflow fixed-bed reactor A 3 The volumetric flow rate ratio (sum of maleic anhydride and solvent) is 30:1.

[0106] The mass ratio of the reaction product entering reactor B in circulation to the fresh feed is 25%.

[0107] In the upflow fixed-bed hydrogenation reactor B, the first hydrogenation product and the supplementary hydrogen are mixed using a swirling shear-type bubble generator based on the shear principle. According to the measurement, about 86% of the bubbles in the total bubbles of the mixture have a diameter range of 50μm to 1000μm, and the remaining about 14% of the bubbles are in the millimeter range.

[0108] Hydrogen feed rate of upflow fixed-bed reactor A and the make-up hydrogen feed rate of upflow fixed-bed reactor B (Nm³) 3 The ratio K of / h is 1:1.

[0109] Under these reaction conditions, maleic anhydride and γ-butyrolactone solvents listed in Tables 1 and 2 were used as raw materials and continuously fed into upflow fixed-bed hydrogenation reactors A and B to obtain hydrogenated products. The reaction results are shown in Table 4.

[0110] Example 3

[0111] Using the method of this invention, two upflow fixed-bed hydrogenation reactors, A and B, are set up in the maleic anhydride hydrogenation reaction zone. First, a pre-prepared 15% maleic anhydride (γ-butyrolactone solvent) solution is mixed evenly with hydrogen to form mixed feed I, which enters upflow fixed-bed hydrogenation reactor A for the first hydrogenation reaction, yielding the first hydrogenation reaction product. The first hydrogenation reaction product, after being heated, is mixed evenly with supplementary hydrogen using a Venturi mixer to obtain mixed feed II, which enters upflow fixed-bed reactor B for the second hydrogenation reaction, yielding the second hydrogenation reaction product. Here, the first hydrogenation reaction product is mixed with supplementary hydrogen using a ceramic membrane mixer, that is, the hydrogen is dispersed into nano- and micron-sized bubbles before being mixed with the first hydrogenation reaction product, forming a liquid phase containing nano- and micron-sized bubbles, which enters upflow fixed-bed hydrogenation reactor B. The second hydrogenation reaction product, after being heated, undergoes gas-liquid separation; part of the liquid phase is recycled, and the other part enters the subsequent product fractionation unit.

[0112] The operating conditions for upflow fixed-bed hydrogenation reactor A are as follows:

[0113] The reaction temperature is 50℃~150℃;

[0114] The reaction pressure is 4.0–4.5 MPaG;

[0115] Reactor height-to-diameter ratio: 6.0

[0116] Volumetric hourly space velocity: 4.0 h -1

[0117] maleic anhydride concentration: 15 g / mL

[0118] Hydrogen (Nm 3 / h) and fresh ingredients (m 3 The volume ratio of the solution (a solution of maleic anhydride dissolved in γ-butyrolactone solvent) is 25:1.

[0119] The mass ratio of the reaction product entering reactor A in circulation to the fresh feed is 30%.

[0120] In the upflow fixed-bed hydrogenation reactor A, maleic anhydride solution and hydrogen are mixed using a Venturi injector. After mixing by this injector, 87% of the bubbles in the material are in the range of diameter 1 to 20 mm, and the remaining 13% are micron-sized bubbles.

[0121] The operating conditions for the upflow fixed-bed hydrogenation reactor B are as follows:

[0122] The reaction temperature is 50℃~150℃;

[0123] The reaction pressure is 4.0–4.5 MPaG;

[0124] Reactor height-to-diameter ratio: 2.0

[0125] Volumetric hourly space velocity: 1.8h -1

[0126] Replenish hydrogen (Nm 3 / h) and fresh feed (m) in upflow fixed-bed reactor A 3 The volumetric flow rate ratio (sum of maleic anhydride and solvent) is 50:1.

[0127] The mass ratio of the reaction product entering reactor B in circulation to the fresh feed is 30%.

[0128] In the upflow fixed-bed hydrogenation reactor B, the first hydrogenation product and the supplementary hydrogen are mixed using a ceramic membrane mixer based on the microporous dispersion principle. After mixing by this mixer, about 95% of the bubbles are in the range of 50μm to 1000μm in diameter, and the remaining about 5% are in the millimeter range.

[0129] Hydrogen feed rate of upflow fixed-bed reactor A and the make-up hydrogen feed rate of upflow fixed-bed reactor B (Nm³) 3 The ratio K ( / h) is 0.5:1.

[0130] Under these reaction conditions, maleic anhydride and γ-butyrolactone solvents listed in Tables 1 and 2 were used as raw materials and continuously fed into upflow fixed-bed hydrogenation reactors A and B to obtain hydrogenated products. The reaction results are shown in Table 4.

[0131] Table 4 Reaction Results

[0132]

[0133] Note: Total running time is the sum of the running time in the initial and final stages of the reaction. The running is terminated when the total conversion rate drops below 99.8% and the total selectivity drops below 95%.

[0134] From the above comparative examples and embodiments, it can be seen that: (1) When using conventional trickle bed and conventional liquid phase hydrogenation for maleic anhydride hydrogenation reaction, the reaction is uneven, the reaction efficiency is low, and it is easy to cause problems such as local hot spots in the catalyst bed and many side reactions. On the one hand, it affects the total running time of the catalyst, and on the other hand, it also affects the selectivity of the catalyst; (2) In the conventional technology, the maleic anhydride hydrogenation reaction is based on the low concentration of maleic anhydride in the later stage of the reaction, which leads to a very low contact mass transfer rate between hydrogen and maleic anhydride. It takes a very long residence time to reach a conversion rate of more than 99%, which is also one of the reasons for the increase of side reactions; (3) In the conventional technology, when two-stage reactors are connected in series, the reaction rate of the first reactor and the reaction rate, temperature rise and catalyst deactivation rate of the second reactor are different, which causes the catalysts of the two reactors to be unable to deactivate synchronously, affecting the total operating cycle and economy of the device. Therefore, this invention employs a two-stage series continuous hydrogenation reactor. In the early stages of the reaction, the hydrogenation reaction is primarily concentrated in the upflow fixed-bed hydrogenation reactor A. As the reaction progresses, the hydrogenation reaction shifts to the upflow hydrogenation reactor B until the catalysts in both reactors are simultaneously deactivated. During this process, the transfer of the hydrogenation reaction is controlled by regulating the hydrogen feed rate. The proportion of microbubbles in both reactors is coordinated to ensure the conversion rate (≥99.8%) and selectivity (≥98.5%) of the maleic anhydride hydrogenation reaction. Furthermore, the simultaneous deactivation of the catalysts in reactors A and B significantly extends the overall operating cycle of the unit and improves the economic efficiency of the industrial plant.

Claims

1. A reaction process for preparing succinic anhydride, comprising the following steps: (1) mixing maleic anhydride solution and hydrogen gas to obtain a mixed feed I, which is then fed into an upflow fixed-bed reactor A for a first hydrogenation reaction to obtain a first hydrogenation reaction product; (2) after heat removal, the first hydrogenation reaction product is mixed with supplementary hydrogen gas to obtain a mixed feed II, which is then fed into an upflow fixed-bed reactor B for a second hydrogenation reaction to obtain a second hydrogenation reaction product; (3) after heat removal, the second hydrogenation reaction product undergoes gas-liquid separation, with a portion of the liquid phase recycled and the other portion entering a subsequent product fractionation unit; wherein, In step (1), the hydrogen gas from the upflow fixed-bed reactor A and the supplementary hydrogen gas from the upflow fixed-bed reactor B in step (2) are in the form of Nm³. 3 The ratio K of the flow rate per hour is 1:10 to 10:1; in the mixed feed I, hydrogen is uniformly dispersed in the maleic anhydride solution, wherein ≥70% of the hydrogen bubbles are in the millimeter range; in the upflow fixed-bed reactor A, hydrogen is distributed in Nm³. 3 / h and maleic anhydride solution in m 3 The ratio of the volumetric flow rate per hour is 5:1 to 100:1; in the mixed feed II, hydrogen is uniformly mixed and dispersed in the first hydrogenation reaction product, wherein ≥70% of the hydrogen bubbles are nano-micron in size; in the upflow fixed-bed reactor B, hydrogen is distributed in nanometers... 3 / h meter and the maleic anhydride solution in the upflow fixed-bed reactor A at m 3 The ratio of the volumetric flow rate to the flow rate is 5:1 to 40:

1.

2. The reaction process according to claim 1, characterized in that: The maleic anhydride solution contains 0.03–0.3 g / mL of maleic anhydride; the solvent used for the maleic anhydride solution is one or more of benzene, toluene, xylene, acetone, tetrahydrofuran, γ-butyrolactone, cyclohexanone, ethyl acetate, diethyl succinate, or ethylene glycol monomethyl ether.

3. The reaction process according to claim 1, characterized in that: The first hydrogenation reaction conditions are: reaction temperature 40–200℃, reaction pressure 0.5–10.0 MPa, and liquid hourly space velocity 0.5–15.0 h⁻¹. -1 .

4. The reaction process according to claim 1, characterized in that: Hydrogen gas in upflow fixed-bed reactor A is in the form of Nm³ 3 / h and maleic anhydride solution in m 3 The ratio of the volumetric flow rate to the flow rate is 10:1 to 60:

1.

5. The reaction process according to claim 1, characterized in that: The second hydrogenation reaction conditions are: reaction temperature 40–200℃, reaction pressure 0.5–10.0 MPa, and liquid hourly space velocity 0.1–8.0 h⁻¹. -1 .

6. The reaction process according to claim 1, characterized in that: Upflow fixed-bed reactors A and B employ catalysts with hydrogenation capabilities, and one or more catalyst beds are set up as needed.

7. The reaction process according to claim 1, characterized in that: The maleic anhydride conversion rate of the first hydrogenation reaction is 41%–99%, with 71%–99% in the initial stage and 41%–70% in the final stage. The maleic anhydride conversion rate of the second hydrogenation reaction is 1%–40%, with 1%–20% in the initial stage and 21%–40% in the final stage. The initial and final stages of the reaction are defined according to the total catalyst operating cycle. The initial stage refers to the stage where the reactor inlet temperature meets the maleic anhydride conversion requirements. The final stage refers to the stage where, as the reaction time increases and the catalyst activity decreases, the reactor inlet temperature no longer meets the maleic anhydride conversion requirements, and the reactor inlet temperature needs to be increased to meet the requirements. The total catalyst operating cycle is reached when the reactor inlet temperature reaches its upper limit.

8. The reaction process according to claim 1, characterized in that: The first circulating material returned to the upflow fixed-bed reactor A accounts for 15 wt% to 90 wt% of the maleic anhydride solution in the upflow fixed-bed reactor A; the second circulating material returned to the upflow fixed-bed reactor B accounts for 0 to 80 wt% of the maleic anhydride solution in the upflow fixed-bed reactor B.

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