Method for preparing succinic anhydride by liquid phase hydrogenation of maleic anhydride

Abstract

The application provides a method for preparing succinic anhydride by liquid-phase hydrogenation of maleic anhydride, which uses a maleic anhydride solution as a raw material, and adopts a series type one-stage hydrogenation reactor and a two-stage hydrogenation reactor for reaction, wherein the molar ratio of hydrogen gas entering the one-stage hydrogenation reactor to the maleic anhydride feed is 0.5-0.8:1, and the total molar ratio of hydrogen gas entering the one-stage hydrogenation reactor and the two-stage hydrogenation reactor to the maleic anhydride feed of the one-stage reactor is 1.0-1.6:1. The application realizes the preparation of succinic anhydride from maleic anhydride by two-stage hydrogenation, controls the hydrogen gas addition amount of the one-stage hydrogenation and the two-stage hydrogenation through precise control, controls the reaction conversion rate of maleic anhydride, especially the one-stage hydrogenation, effectively controls the reaction heat release, makes the hydrogenation reaction run for a long period, and stabilizes the maleic anhydride conversion rate and the succinic anhydride selectivity both above 99%. Meanwhile, liquid material circulation is not needed for heat removal, energy consumption is reduced, and the process operation difficulty is reduced.

Description

Technical Field

[0001] This invention relates to a method for preparing succinic anhydride by hydrogenation of maleic anhydride, specifically a method for the stepwise controlled preparation of succinic anhydride by liquid-phase hydrogenation of maleic anhydride. Background Technology

[0002] Succinic acid, also known as succinic acid, is a common natural organic acid with the molecular formula C4H6O4 and a molecular weight of 118.09. It is a colorless triclinic or monoclinic crystal, flammable, and has a density of 1.572 g / cm³. 3 Succinic acid (25°C), melting point 188°C, boiling point 235°C, soluble in water, ethanol, and ether, insoluble in carbon disulfide and carbon tetrachloride, is commonly used as an important organic chemical raw material and intermediate, and is widely used in food, medicine, agriculture, and chemical industries. As a polymer monomer, succinic acid can be used to synthesize biodegradable plastics such as PBS (polybutylene succinate) and PHS (polyhexyl succinate). Among them, PBS is currently recognized worldwide as the best-performing fully biodegradable plastic, capable of 100% degradation under natural conditions.

[0003] The main methods for producing succinic acid are bio-fermentation, electroreduction, and catalytic hydrogenation. Catalytic hydrogenation is currently the most commonly used method for industrial production of PBS, characterized by mature technology, simple processes and equipment, high yield, high product purity, no significant side reactions, and environmental friendliness, making it suitable for industrial scale-up.

[0004] In the process of preparing succinic acid by catalytic hydrogenation hydrolysis, the hydrogenation of maleic anhydride to prepare succinic anhydride is the first step, and the hydrolysis of succinic anhydride to succinic acid is the second step. The first step is the key step, which determines the final quality of succinic acid.

[0005] CN106861702A discloses a catalyst for the direct synthesis of succinic acid from maleic anhydride via aqueous-phase hydrogenation, its preparation method, and its application. The catalyst uses alumina as a support and supports a carbon-coated nickel-copper catalyst. The hydrogenation reaction is carried out using an aqueous maleic anhydride solution as raw material in a fixed-bed or high-pressure reactor. In the fixed-bed hydrogenation reaction: the concentration of the maleic anhydride aqueous solution is 8-30 wt%, the reaction temperature is 60-140℃, the hydrogen pressure is 2-6 MPa, and the liquid hourly space velocity is 1-6 h⁻¹. -1In the high-pressure reactor hydrogenation reaction: the concentration of maleic anhydride aqueous solution is 8-30 wt%, the reaction temperature is 60-140℃, the hydrogen pressure is 2-6 MPa, the catalyst dosage is 0.01-0.05 g (catalyst) / g (maleic anhydride), the reaction time is 1-6 h, the maleic anhydride conversion rate is >99%, and the selectivity is 100%. This process uses maleic anhydride aqueous solution for hydrogenation, and the reaction solution is highly acidic, thus placing high demands on the materials used in the reaction apparatus. Furthermore, the acidic conditions can corrode the catalyst, leading to catalyst deactivation, and can also cause succinic acid precipitation that can block the reaction channels, resulting in shutdown.

[0006] CN112661625A discloses a process for preparing succinic acid, which involves using maleic anhydride as a raw material and directly hydrogenating it in a slurry bed under the action of a microsphere catalyst to produce succinic anhydride, followed by hydrolysis to produce succinic acid. Maleic anhydride hydrogenation is a strongly exothermic reaction, making the reaction temperature difficult to control and prone to runaway reactions or the generation of large amounts of byproducts.

[0007] CN111689849A discloses a novel two-stage liquid-phase hydrogenation method for producing succinic acid. The feedstock is an aqueous solution with a maleic acid content of 5% by mass, and the feedstock temperature is controlled at 30°C. The uniformly mixed material is fed into the first-stage reaction bed from the top and flows downwards through the catalyst for pre-hydrogenation. The inlet temperature of the first stage is 30°C, the reaction pressure is 0.5 MPa, and the mass hourly space velocity (HHSV) is 0.2 h⁻¹. -1 The hydrogen feedstock volume ratio is 100, and the first-stage outlet temperature is 50℃. The material exiting the first reaction bed undergoes heat exchange and then enters the second reaction bed from the top, flowing downwards through the catalyst for the main hydrogenation reaction. The second-stage inlet temperature is 40℃, the reaction pressure is 0.5 MPa, and the mass hourly space velocity (WHSV) is 0.2 h⁻¹. -1 With a hydrogen feedstock volume ratio of 100 and a second-stage outlet temperature of 50°C, both the conversion rate of maleic acid and the selectivity of succinic acid reached 100%. However, in a trickle bed, the reactants are prone to flow deviation, causing local overheating and affecting the selectivity of succinic acid. Furthermore, the hydrogenation of maleic acid aqueous solution results in a highly acidic reaction solution, placing high demands on the materials used in the reaction apparatus. The acidic conditions also corrode the catalyst, leading to catalyst deactivation, and the precipitation of succinic acid can block the reaction channels, causing shutdowns. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a method for preparing succinic anhydride by liquid-phase hydrogenation of maleic anhydride. By controlling the first-stage and second-stage hydrogenation reactions in stages, the exothermic reaction can be controlled, thereby enabling long-term continuous production of succinic anhydride. The operation process is simple and can simultaneously achieve stable and high maleic anhydride conversion and succinic anhydride selectivity.

[0009] The technical objective of this invention is achieved through the following technical solution: This invention provides a method for preparing succinic anhydride by liquid-phase hydrogenation of maleic anhydride. The method uses maleic anhydride solution as raw material and employs a series-connected single-stage and two-stage hydrogenation reactors. The molar ratio (hydrogen-to-anhydride ratio) of hydrogen entering the single-stage hydrogenation reactor to the feed maleic anhydride is 0.5-0.8:1, preferably 0.6-0.7:1. The total molar ratio of hydrogen entering the single-stage and two-stage hydrogenation reactors to the feed maleic anhydride in the single-stage reactor is 1.0-1.6:1, preferably 1.1-1.4:1.

[0010] Furthermore, the molar ratio of hydrogen entering the second-stage hydrogenation reactor to maleic anhydride fed into the first-stage hydrogenation reactor is 0.2-0.7:1, preferably 0.3-0.5:1.

[0011] Furthermore, the catalyst loading (volume) of the first-stage hydrogenation reactor is V1, and the catalyst loading (volume) of the second-stage hydrogenation reactor is V2, with V1:V2 = 1:1.5-1:10, preferably 1:2-1:5. Neither the first-stage nor the second-stage hydrogenation reactor has an external cooling device.

[0012] Furthermore, the volume hourly space velocity (VHSV) of the liquid material entering the first-stage hydrogenation reactor relative to the catalyst is 3 h⁻¹. -1 -7h -1 4h preferred -1 -6h -1 .

[0013] Furthermore, the volume hourly space velocity (VHSV) of the liquid feedstock relative to the catalyst entering the second-stage hydrogenation reactor is 0.5 h⁻¹. -1 -10h -1 1 hour preferred -1 -6h -1 .

[0014] Furthermore, the hydrogen gas and maleic anhydride solution are thoroughly mixed before being introduced into the hydrogenation reactor; preferably, the mixing is carried out through a membrane tube distributor.

[0015] Furthermore, the membrane tube dispenser is made of 316L stainless steel or ceramic material, and is covered with nano- to micron-sized pores, which can effectively disperse hydrogen gas into tiny bubbles.

[0016] Furthermore, the concentration of maleic anhydride in the maleic anhydride solution is 5%-50% by weight, preferably 10%-20%; the solvent is γ-butyrolactone.

[0017] Furthermore, the temperature of the materials entering the first-stage hydrogenation reactor and the second-stage hydrogenation reactor is 30-80℃, preferably 40-70℃.

[0018] Furthermore, the reaction pressure in the first-stage hydrogenation reactor and the second-stage hydrogenation reactor is 0.5MPa-6MPa, preferably 2-4MPa.

[0019] Furthermore, the catalyst used in the hydrogenation reaction is well known to those skilled in the art. Specifically, it is an acid-resistant support supporting a catalyst in which at least one of Ni, Pt, Pd, Ir, Ru, and Rh is used as the active component. A reduction treatment is performed before use.

[0020] Furthermore, a gas-liquid separation device is connected between the first-stage hydrogenation reactor and the second-stage hydrogenation reactor to separate the hydrogen from the first-stage hydrogenation reaction product and recover hydrogen. The hydrogen can be selectively recycled and used to continue to participate in the reaction with fresh hydrogen. The separated liquid material enters the second-stage hydrogenation reactor.

[0021] Furthermore, the discharge of the second-stage hydrogenation reactor is connected to a gas-liquid separation device, which is used to separate the hydrogen from the second-stage hydrogenation reaction product and recover hydrogen. The hydrogen can be selectively used as recycled hydrogen to continue to participate in the reaction with fresh hydrogen, and the separated liquid material is discharged as the product.

[0022] This invention has the following advantages: (1) This invention uses a two-stage hydrogenation process to prepare succinic anhydride from maleic anhydride. By precisely controlling the amount of hydrogen added in the first and second stages of hydrogenation, the reaction conversion rate of maleic anhydride, especially in the first stage, is controlled, effectively controlling the exothermic reaction and enabling the hydrogenation reaction to operate for a long period. The conversion rate of maleic anhydride and the selectivity of succinic anhydride are both stable at over 99%. At the same time, there is no need to circulate liquid materials for heat extraction, which reduces energy consumption and simplifies the process operation.

[0023] (2) The present invention uses a membrane tube distributor to achieve full mixing of liquid materials and hydrogen. Based on precise control of hydrogen, hydrogen participates in the reaction more fully (the molar ratio of maleic anhydride and hydrogen is close to the theoretical molar ratio), thus achieving precise control of the reaction conversion rate. Detailed Implementation

[0024] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the invention, but do not limit the invention in any way.

[0025] The composition of the materials was analyzed by gas chromatography using an Agilent 7890A gas chromatograph with an HP-INNOWAX column (30m × 0.32mm × 0.25μm) and a flame ionization detector. Qualitative analysis was performed using the standard sample retention time comparison method, and quantification was performed using the normalization method for butyrolactone, maleic anhydride, and succinic anhydride.

[0026] The gas chromatograph was used for the determination under the following conditions: column temperature: initial temperature 80℃, held for 5 min, then increased to 200℃ at a rate of 12℃ / min; vaporization temperature: 250℃; detection temperature: 250℃; nitrogen 3 ml / min, hydrogen 40 ml / min, air 400 ml / min; injection volume 0.2 μL; split ratio 60:1.

[0027] Example 1 The preparation of succinic anhydride by liquid-phase hydrogenation of maleic anhydride was carried out using a series of two hydrogenation reactors: a primary hydrogenation reactor and a secondary hydrogenation reactor. The catalyst used was an alumina-supported catalyst with Ni as the active component (30 wt% nickel oxide). The primary hydrogenation reactor was loaded with a catalyst volume of VL, and the secondary hydrogenation reactor was loaded with a catalyst volume of 3VL. A 10% (w / w) maleic anhydride-butyrolactone solution was prepared as the reactant. After heat exchange in a heat exchanger to a temperature of 55°C, the reactant was mixed with hydrogen gas at a hydrogen:maleic anhydride molar ratio of 0.6:1 in a membrane distributor before entering the primary hydrogenation reactor. The liquid hourly space velocity (LHSV) of the maleic anhydride solution relative to the catalyst was 4 h⁻¹. -1 The reaction pressure is 3 MPa.

[0028] The feed from the first-stage hydrogenation reactor is connected to a first-stage gas-liquid separator. Once a certain liquid level is reached in the first-stage separator, the reactants are heated to 55°C via a heat exchanger. After mixing with hydrogen in a membrane distributor, the mixture enters the second-stage hydrogenation reactor. The molar ratio of hydrogen used in this stage to maleic anhydride feed from the first-stage reactor is 0.5:1, and the total molar ratio of hydrogen from both stages to the total maleic anhydride is 1.1:1. The liquid hourly space velocity (LHSV) of the maleic anhydride solution relative to the catalyst is 1 h⁻¹. -1 The reaction pressure is 3 MPa. The discharge from the two-stage hydrogenation reactor is connected to a two-stage gas-liquid separator to produce succinic anhydride.

[0029] After the system stabilized, the maleic anhydride conversion rate was 99.81% and the succinic anhydride selectivity was 98.42%.

[0030] Example 2 Similar to Implementation 1, except that the molar ratio of hydrogen used in the two-stage hydrogenation reactor to maleic anhydride fed into the first-stage hydrogenation reactor is 0.7:1, and the molar ratio of hydrogen used in both stages to total maleic anhydride is 1.3:1.

[0031] After the system stabilized, the maleic anhydride conversion rate was 99.86% and the succinic anhydride selectivity was 98.21%.

[0032] Example 3 Similar to Implementation 1, except that the molar ratio of hydrogen to maleic anhydride in the first-stage hydrogenation reactor is 0.8:1, the molar ratio of hydrogen to maleic anhydride in the second-stage hydrogenation reactor is 0.7:1, and the molar ratio of hydrogen in both stages to total maleic anhydride is 1.5:1.

[0033] After the system stabilized, the maleic anhydride conversion rate was 99.87% and the succinic anhydride selectivity was 98.02%.

[0034] Example 4 Similar to Embodiment 1, except that the molar ratio of hydrogen to maleic anhydride in the first-stage hydrogenation reactor is 0.7:1, the molar ratio of hydrogen to maleic anhydride in the second-stage hydrogenation reactor is 0.4:1, and the molar ratio of hydrogen in both stages to total maleic anhydride is 1.1:1.

[0035] After the system stabilized, the maleic anhydride conversion rate was 99.85% and the succinic anhydride selectivity was 99.40%.

[0036] Example 5 Similar to Implementation 1, except that a 20% maleic anhydride-butyrolactone solution is prepared as the reactant.

[0037] After the system stabilized, the maleic anhydride conversion rate was 98.57% and the succinic anhydride selectivity was 98.40%.

[0038] Comparative Example 1 The preparation of succinic anhydride by liquid-phase hydrogenation of maleic anhydride was carried out using a series of single-stage and two-stage hydrogenation reactors. The catalyst was the same as in Example 1. The catalyst volume of the single-stage hydrogenation reactor was VL, and the catalyst volume of the two-stage hydrogenation reactor was 3VL. A 10% (w / w) maleic anhydride-butyrolactone solution was prepared as the reactant. After heat exchange in a heat exchanger, the temperature of the reactant reached 55°C. It was then mixed with hydrogen in a membrane tube distributor at a hydrogen:maleic anhydride molar ratio of 1.4:1 and entered the single-stage hydrogenation reactor. The liquid hourly space velocity (LHSV) of the maleic anhydride solution relative to the catalyst was 4 h⁻¹. -1 The reaction pressure is 3 MPa.

[0039] The feed from the first-stage hydrogenation reactor is connected to a first-stage gas-liquid separator. Once a certain liquid level is reached in the first-stage separator, the reactants are heated to 55°C via a heat exchanger. After mixing with hydrogen in a membrane distributor, the mixture enters the second-stage hydrogenation reactor. The molar ratio of hydrogen used in this stage to maleic anhydride feed from the first-stage reactor is 1.4:1, and the molar ratio of hydrogen from both stages to total maleic anhydride is 2.8:1. The liquid hourly space velocity (LHSV) of the maleic anhydride solution relative to the catalyst is 1 h⁻¹. -1 The reaction pressure is 3 MPa. The discharge from the two-stage hydrogenation reactor is connected to a two-stage gas-liquid separator to produce succinic anhydride.

[0040] Due to excessive hydrogenation, the selectivity of succinic anhydride decreases, and the water generated in the system causes maleic anhydride and succinic anhydride to hydrolyze, clogging the system.

[0041] Comparative Example 2 The preparation of succinic anhydride by liquid-phase hydrogenation of maleic anhydride was carried out using a series of single-stage and two-stage hydrogenation reactors. The catalyst was the same as in Example 1. The catalyst volume of the single-stage hydrogenation reactor was VL, and the catalyst volume of the two-stage hydrogenation reactor was VL. A 10% (w / w) maleic anhydride-butyrolactone solution was prepared as the reactant. After heat exchange in a heat exchanger, the temperature of the reactant reached 55°C. It was then mixed with hydrogen in a membrane tube distributor at a hydrogen:maleic anhydride molar ratio of 0.6:1 and entered the single-stage hydrogenation reactor. The liquid hourly space velocity (LHSV) of the maleic anhydride solution relative to the catalyst was 2 h⁻¹. -1 The reaction pressure is 3 MPa.

[0042] The feed from the first-stage hydrogenation reactor is connected to a first-stage gas-liquid separator. Once a certain liquid level is reached in the first-stage separator, the reactants are heated to 55°C via a heat exchanger. After mixing with hydrogen in a membrane distributor, the mixture enters the second-stage hydrogenation reactor. The molar ratio of hydrogen in this stage to maleic anhydride feed to the first-stage reactor is 0.5:1, and the molar ratio of hydrogen in the second stage to total maleic anhydride is 1.1:1. The liquid hourly space velocity (LHSV) of the maleic anhydride solution relative to the catalyst is 4 h⁻¹. -1 The reaction pressure is 3 MPa. The discharge from the two-stage hydrogenation reactor is connected to a two-stage gas-liquid separator to produce succinic anhydride.

[0043] With this catalyst loading method, the heat of the first-stage hydrogenation reactor cannot be controlled, requiring additional auxiliary heat exchange.

[0044] Comparative Example 3 The preparation of succinic anhydride by liquid-phase hydrogenation of maleic anhydride was carried out using a series of single-stage and two-stage hydrogenation reactors. The catalyst was the same as in Example 1. The catalyst volume of the single-stage hydrogenation reactor was VL, and the catalyst volume of the two-stage hydrogenation reactor was 3VL. A 10% (w / w) maleic anhydride-butyrolactone solution was prepared as the reactant. After heat exchange in a heat exchanger, the temperature of the reactant reached 55°C. It was then mixed with hydrogen in a membrane tube distributor at a hydrogen:maleic anhydride molar ratio of 0.4:1 and entered the single-stage hydrogenation reactor. The liquid hourly space velocity (LHSV) of the maleic anhydride solution relative to the catalyst was 4 h⁻¹. -1 The reaction pressure is 3 MPa.

[0045] The feed from the first-stage hydrogenation reactor is connected to a first-stage gas-liquid separator. Once a certain liquid level is reached in the first-stage separator, the reactants are heated to 55°C via a heat exchanger. After mixing with hydrogen in a membrane distributor, the mixture enters the second-stage hydrogenation reactor. The molar ratio of hydrogen in this stage to maleic anhydride feed to the first-stage reactor is 0.8:1, and the molar ratio of hydrogen in the second stage to total maleic anhydride is 1.2:1. The liquid hourly space velocity (LHSV) of the maleic anhydride solution relative to the catalyst is 1 h⁻¹. -1 The reaction pressure is 3 MPa. The discharge from the two-stage hydrogenation reactor is connected to a two-stage gas-liquid separator to produce succinic anhydride.

[0046] At this hydrogen-maleic anhydride molar ratio, the heat in the two-stage hydrogenation reactor cannot be controlled, requiring additional auxiliary heat exchange.

Claims

1. A method for preparing succinic anhydride by liquid-phase hydrogenation of maleic anhydride, characterized in that, Using maleic anhydride solution as raw material, a series of single-stage and two-stage hydrogenation reactors are used for the reaction. The molar ratio of hydrogen gas entering the single-stage hydrogenation reactor to the feed maleic anhydride is 0.5-0.8:1, and the molar ratio of total hydrogen gas entering the single-stage and two-stage hydrogenation reactors to the feed maleic anhydride in the single-stage reactor is 1.0-1.6:

1. The catalyst loading amount in the single-stage hydrogenation reactor is V1, and the catalyst loading amount in the two-stage hydrogenation reactor is V2, with V1:V2=1:1.5-1:

10. The method does not require heat extraction from the circulating liquid material, and the first-stage and second-stage hydrogenation reactors do not have external cooling devices.

2. The method according to claim 1, characterized in that, The molar ratio of hydrogen to maleic anhydride entering the first-stage hydrogenation reactor is 0.6-0.7:1, and the molar ratio of total hydrogen entering the first-stage and second-stage hydrogenation reactors to maleic anhydride in the first-stage reactor is 1.1-1.4:

1.

3. The method according to claim 1, characterized in that, The molar ratio of hydrogen entering the second-stage hydrogenation reactor to maleic anhydride fed into the first-stage hydrogenation reactor is 0.2-0.7:

1.

4. The method according to claim 3, characterized in that, The molar ratio of hydrogen entering the second-stage hydrogenation reactor to maleic anhydride fed into the first-stage hydrogenation reactor is 0.3-0.5:

1.

5. The method according to claim 1, characterized in that, The catalyst loading ratio of the first-stage hydrogenation reactor to the second-stage hydrogenation reactor is V1:V2 = 1:2-1:

5.

6. The method according to claim 1, characterized in that, The volume hourly space velocity (VHSV) of the liquid feedstock relative to the catalyst entering the first-stage hydrogenation reactor is 3 h⁻¹. -1 -7h -1 .

7. The method according to claim 6, characterized in that, The volume hourly space velocity (VHSV) of the liquid feedstock relative to the catalyst entering the first-stage hydrogenation reactor is 4 h⁻¹. -1 -6h -1 .

8. The method according to claim 1, characterized in that, The hydrogen gas and maleic anhydride solution are first thoroughly mixed through a membrane tube distributor before being introduced into the hydrogenation reactor.

9. The method according to claim 8, characterized in that, The membrane tube dispenser is made of 316L stainless steel or ceramic and is covered with nano- to micron-sized pores.

10. The method according to claim 1, characterized in that, The maleic anhydride solution contains 5%-50% maleic anhydride by weight, and the solvent is γ-butyrolactone.

11. The method according to claim 1, characterized in that, The temperature of the material entering the first-stage hydrogenation reactor and the second-stage hydrogenation reactor is 30-80℃, and the reaction pressure inside the first-stage hydrogenation reactor and the second-stage hydrogenation reactor is 0.5MPa-6MPa.

12. The method according to claim 1, characterized in that, A gas-liquid separator is connected between the first-stage hydrogenation reactor and the second-stage hydrogenation reactor. This separator separates the hydrogen from the first-stage hydrogenation reaction product to recover hydrogen. The recovered hydrogen can be selectively recycled and mixed with fresh hydrogen to continue the reaction. The separated liquid material enters the second-stage hydrogenation reactor. The outlet of the second-stage hydrogenation reactor is connected to the gas-liquid separator to further separate the hydrogen from the second-stage hydrogenation reaction product. This recycled hydrogen can be selectively recycled and mixed with fresh hydrogen to continue the reaction. The separated liquid material is discharged as the final product.