Preparation method and system of adipic acid

Abstract

The invention provides a preparation method and system of adipic acid. The method comprises the following steps: (1) contacting cyclohexane with a hydrogen peroxide solution to obtain a material a; (2) settling the material a to obtain supernate; and (3) carrying out oxidation reaction on the supernate and O2-containing gas to obtain an adipic acid-containing product material b. The method is simple, efficient, green and environment-friendly, and the obtained adipic acid provides an excellent raw material for polyester production.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, specifically to a method and system for preparing adipic acid. Background Technology

[0002] Adipic acid and its derivatives are extremely important commercial aliphatic dicarboxylic organic acids that can undergo condensation polymerization to form high molecular weight compounds. They play a vital role in chemical production, organic synthesis, pharmaceuticals, and lubricant manufacturing. Specifically, adipic acid can be used to synthesize nylon 66 and produce polyurethane; it can also be used as a food acidifier to maintain the freshness and stability of food; furthermore, it can be used in the production of fragrances and dyes.

[0003] In traditional industry, the production of adipic acid initially used benzene as a raw material to produce cyclohexene, cyclohexane, and phenol, which were then further oxidized to obtain KA oil and adipic acid. Therefore, the production methods of adipic acid are mainly divided into the following three types according to the raw materials: cyclohexane oxidation method, cyclohexene oxidation method, and phenol method.

[0004] Cyclohexane, being a rigid ring, presents significant challenges in oxidative ring-opening, especially when using air as an oxidant due to its poor oxidizing properties. Not only is reaction initiation difficult, but once initiated, the free radical reaction chain is hard to control, easily generating various byproducts and impurities, making it difficult to improve the selectivity of the target product, adipic acid. While using hydrogen peroxide directly as an oxidant can improve reaction efficiency, it decomposes easily at high temperatures, resulting in low utilization. Furthermore, cyclohexane is prone to explosion, increasing production costs and significantly reducing system safety.

[0005] Therefore, the conversion efficiency of direct cyclohexane feeding in existing technologies is not high. It usually requires high reaction temperature and long reaction time, and a large amount of cyclohexane recycling is used to increase the yield of adipic acid. The separation of impurity byproducts generated in the reaction is difficult, the separation energy consumption is high, and the atom economy is poor. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method and system for preparing adipic acid. This method is simple, efficient, and environmentally friendly, and the resulting adipic acid provides an excellent raw material for polyester production.

[0007] In a first aspect, the present invention provides a method for preparing adipic acid, comprising:

[0008] (1) Cyclohexane was contacted with hydrogen peroxide solution to obtain material a;

[0009] (2) The material a is allowed to settle to obtain the supernatant;

[0010] (3) The supernatant is reacted with O2 gas to obtain product b containing adipic acid.

[0011] The inventors of this application unexpectedly discovered that by first pre-activating cyclohexane with hydrogen peroxide solution, and then oxidizing the pre-activated cyclohexane with O2 gas, the reaction rate is greatly accelerated, while the impurity content in the product is greatly reduced, thereby improving the yield and selectivity of adipic acid.

[0012] In some embodiments, the mass concentration of H2O2 in the hydrogen peroxide solution is 25-45%, for example, 25%, 28%, 31%, 34%, 37%, 40%, 43% or any value between them.

[0013] In some embodiments, the mass ratio of the hydrogen peroxide solution to cyclohexane is (1:2)-(2:1), for example, 1:2, 0.8:1, 1:1, 1.5:1, 2:1.

[0014] In some embodiments, the temperature of the contact is 10-80°C, for example 15°C, 25°C, 35°C, 45°C, 55°C, 65°C, 75°C or any value between them.

[0015] In some embodiments, the temperature of the contact is 30-50°C.

[0016] In some implementations, the contact time is 10-120 min, for example 20 min, 40 min, 60 min, 80 min, 100 min, 120 min or any value between them.

[0017] In some implementations, the contact time is 15-60 minutes.

[0018] In some embodiments, the settling temperature is 15-25°C, for example 17°C, 19°C, 21°C, 23°C, 25°C or any value between them.

[0019] In some embodiments, the oxidation reaction is carried out in the presence of a catalyst and a solvent.

[0020] In some embodiments, the solvent is selected from acetic acid.

[0021] In some embodiments, the catalyst is selected from metal salt catalysts.

[0022] In some embodiments, the metal element in the metal salt catalyst is selected from one or more of copper, manganese, or chromium.

[0023] In some embodiments, the metal salt is an acetate of a metal element.

[0024] In some embodiments, the catalyst is a mixture of copper acetate, manganese acetate, and cobalt acetate.

[0025] In some embodiments, the mass ratio of copper, manganese, and cobalt in the catalyst is (5-10):(1-5):1, for example, 5:1-5:1, 6:1-5:1, 7:1-5:1, 8:1-5:1, 9:1-5:1, 10:1-5:1, 5-10:1:1, 5-10:2:1, 5-10:3:1, 5-10:4:1, 5-10:5:1, or any value thereof.

[0026] In some embodiments, the mass ratio of copper, manganese and cobalt in the catalyst is 8:3:1.

[0027] In some embodiments, the oxidation reaction includes the following steps:

[0028] S1, the catalyst and solvent are mixed to obtain a catalyst solution;

[0029] S2, the catalyst solution, supernatant and O2-containing gas are subjected to an oxidation reaction.

[0030] In some embodiments, the mass ratio of the catalyst solution to the supernatant is (1.5-8):1, for example, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1 or any value between them.

[0031] In some embodiments, the mass concentration of the catalyst in the catalyst solution is 0.05-5%, for example, 0.05%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or any value between them.

[0032] In some embodiments, the mass ratio of the O2-containing gas to the supernatant is (5-15):1, for example, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1 or any value between them.

[0033] In some embodiments, the volume content of O2 in the O2-containing gas is 10-25%, for example, 10%, 13%, 16%, 19%, 21%, 24% or any value between them.

[0034] In some embodiments, the oxidation reaction is carried out at a temperature of 85-110°C; for example, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C or any value between them.

[0035] In some embodiments, the pressure of the oxidation reaction is 1.5-5 MPa; for example, 1.5 MPa, 2 MPa, 2.5 MPa, 3 MPa, 3.5 MPa, 4 MPa, 4.5 MPa, 5 MPa or any value between them.

[0036] In some embodiments, the oxidation reaction time is 0.5-2 h, for example 0.5 h, 0.7 h, 0.9 h, 1.1 h, 1.3 h, 1.5 h, 1.7 h, 1.9 h or any value between them.

[0037] In some implementations, according to Figure 1 The process shown describes the preparation method of adipic acid, which includes:

[0038] 1) Cyclohexane from the cyclohexane feed tank flows into the mixing contactor through the cyclohexane feed pipe, and hydrogen peroxide solution from the hydrogen peroxide solution tank is fed into the mixing contactor through the hydrogen peroxide solution feed pipe to obtain material a;

[0039] 2) The mixed material a is fed into a settling tank through the material a discharge pipe for settling, resulting in an upper liquid and a lower liquid; the lower liquid flows out through the lower liquid discharge pipe.

[0040] The supernatant flows into the reactor through the supernatant feed pipe, and the O2-containing gas flows into the reactor through the O2-containing gas feed pipe; the catalyst solution in the catalyst tank flows into the reactor through the catalyst solution feed pipe, and the oxidation reaction takes place in the reactor to obtain product b containing adipic acid.

[0041] 3) Product material b containing adipic acid flows into the discharge tank, and the tail gas after the oxidation reaction is discharged.

[0042] In a second aspect, the present invention provides a system for preparing adipic acid, which is used in the method for preparing adipic acid described in the first aspect of the present invention, the system comprising:

[0043] Cyclohexane feedstock tank;

[0044] hydrogen peroxide solution tank;

[0045] A mixing contactor connected to the cyclohexane feedstock tank and the hydrogen peroxide solution tank; to bring the cyclohexane and the hydrogen peroxide solution into contact to obtain material a;

[0046] A settling device connected to the mixing contactor is used to allow material a to settle and obtain supernatant;

[0047] A reactor connected to the settling tank is used to oxidize the supernatant with O2 gas to obtain product material b containing adipic acid.

[0048] In some embodiments, the system further includes a catalyst tank connected to the reactor so that the oxidation reaction is carried out in the presence of a catalyst solution.

[0049] In some embodiments, the system further includes a discharge tank connected to the reactor to receive material b.

[0050] In some embodiments, the mixing contactor is a jacketed stirring vessel.

[0051] In some embodiments, heat transfer oil is circulated through the jacket layer of the jacketed stirred tank.

[0052] In some implementations, the flow rates of cyclohexane and hydrogen peroxide solution are controlled by a pump.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] (1) In this invention, the reaction activity of cyclohexane is significantly improved after contact treatment with hydrogen peroxide solution, the reaction rate of cyclohexane with O2 gas is significantly accelerated, the impurity content is greatly reduced, and the yield and selectivity of adipic acid are improved.

[0055] (2) The system equipment of the present invention has low investment and simple operation process, and can be used in the continuous industrial production of cyclohexane oxidation to prepare adipic acid. Attached Figure Description

[0056] Figure 1 This is a flowchart illustrating Embodiment 1 of the present invention;

[0057] Explanation of reference numerals in the attached figures:

[0058] 1. Cyclohexane feed tank; 2. Hydrogen peroxide solution tank; 3. Cyclohexane feed pipe; 4. Hydrogen peroxide solution feed pipe; 5. Mixing contactor; 6. Material A discharge pipe; 7. Settler; 8. Supernatant discharge pipe; 9. Substrate discharge pipe; 10. Reactor; 11. O2-containing gas feed pipe; 12. Tail gas; 13. Discharge tank; 14. Catalyst tank; 15. Catalyst solution feed pipe. Detailed Implementation

[0059] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments and accompanying drawings. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way.

[0060] 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.

[0061] Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art. Unless otherwise specified, the reagents used in the following embodiments are conventional biochemical reagents; the raw materials, instruments, and equipment used in the following embodiments can all be obtained commercially or by existing methods; unless otherwise specified, the reagent dosages are those used in routine experimental operations; unless otherwise specified, the experimental methods are conventional methods.

[0062] The gas chromatograph used in this invention is an Agilent 7890 with an HP5 column.

[0063] The liquid chromatography used in this invention employs an Agilent 1260 column and a C18 column.

[0064] In this embodiment of the invention, the O2-containing gas is air with an O2 content of 21% (by volume).

[0065] In the following examples and comparative examples, the Co-Mn-Cu catalyst solution contains 0.01 wt% Co, 0.03 wt% Mn, and 0.08 wt% Cu, all of which are acetates, and the remaining solvent is acetic acid.

[0066] The feedstock cyclohexane is calculated based on a flow rate of 100 g / h. The selectivity of adipic acid is calculated as follows:

[0067] Adipic acid selectivity = (Moles of adipic acid produced in the reaction / Moles of cyclohexane consumed in the reaction) * 100%. The yield of adipic acid is calculated as follows:

[0068] Adipic acid yield = (Molar amount of adipic acid produced in the reaction) / (Molar amount of cyclohexane in the feed) * 100%

[0069] Example 1 (contact of 30wt% hydrogen peroxide aqueous solution with cyclohexane)

[0070] Example 1 uses air oxidation of cyclohexane with an O2 content of 21% by volume to prepare adipic acid.

[0071] I) Such as Figure 1As shown, cyclohexane from cyclohexane feed tank 1 enters mixing contactor 5 from the top via cyclohexane feed pipe 3, and hydrogen peroxide solution from hydrogen peroxide solution tank 2 enters mixing contactor 5 from the top via hydrogen peroxide solution feed pipe 4. The hydrogen peroxide solution and cyclohexane contact in mixing contactor 5 to obtain material a. After contact, material a enters settling tank 7 from material a discharge pipe 6. The flow rate of raw cyclohexane is 100 g / h, the flow rate of 30 wt% hydrogen peroxide solution is 100 g / h, the contact time is 30 min, and the contact temperature is 40℃.

[0072] II) The supernatant after sedimentation enters the reactor 10 through the supernatant outlet pipe 8, and the lower layer liquid is discharged through the lower layer liquid outlet pipe 9. The flow rate of the supernatant is 100g / h, and the sedimentation temperature is 20℃.

[0073] III) The catalyst and solvent are combined in the catalyst tank 14 to form a catalyst solution, which is then added to the reactor 10 through the catalyst solution feed pipe 15 at a flow rate of 400 g / h.

[0074] IV) Introduce O2-containing gas (air) with an O2 content of 21% by volume into reactor 10 through O2-containing gas feed pipe 11, and heat the reactor to the reaction temperature of 95°C, the reaction pressure of 2MPa, and the flow rate of O2-containing gas (air) of 500g / h.

[0075] V) O2-containing gas under working pressure is continuously fed into reactor 10 for contact for 1.5 hours;

[0076] VI) Stop feeding to end the reaction and obtain product material b containing adipic acid; the synthetic liquid containing adipic acid flows into the discharge tank 13, and the tail gas 12 after the oxidation reaction is discharged.

[0077] The concentration of cyclohexane in the synthesis liquid discharged from tank 13 was analyzed by gas chromatography to calculate the cyclohexane consumption, and the concentration of adipic acid was analyzed by liquid chromatography to calculate the adipic acid production. Combined with the cyclohexane feed rate, the adipic acid yield and selectivity were calculated to be 85.9% and 98.1%, respectively.

[0078] Example 2-11

[0079] The steps are the same as in Example 1, and the operating conditions are shown in Table 1.

[0080] Comparative Example 1 (without hydrogen peroxide activation)

[0081] Comparative Example 1: Adipic acid was prepared by oxidizing cyclohexane with an O2-containing gas (air) containing 21% by volume of O2.

[0082] I) Cyclohexane enters the reactor without adding hydrogen peroxide solution;

[0083] II) The flow rate of cyclohexane is 100 g / h, and the temperature is 20 °C;

[0084] III) Add the catalyst and solvent solution to the reactor at a flow rate of 400 g / h.

[0085] IV) Air containing 21% by volume of O2 is introduced into the reactor, and the reactor is heated to a reaction temperature of 95°C, a reaction pressure of 2MPa, and an air flow rate of 500g / h.

[0086] V) O2-containing gas at the working pressure is continuously fed into the reactor for contact for 1.5 hours;

[0087] VI) Stop feeding to end the reaction.

[0088] The cyclohexane consumption was calculated by analyzing the concentration of cyclohexane in the synthesis solution using gas chromatography, and the adipic acid production was calculated by analyzing the concentration of adipic acid in the solution using liquid chromatography. Combined with the cyclohexane feed rate, the adipic acid yield and selectivity were calculated to be 19.6% and 81.3%, respectively.

[0089] Comparative Example 2 (using hydrogen peroxide as the oxidant instead of O2 gas)

[0090] Comparative Example 2: Preparation of adipic acid by oxidation of cyclohexane with hydrogen peroxide solution.

[0091] I) Cyclohexane enters the mixing contactor, and hydrogen peroxide solution enters the mixing contactor to contact with the cyclohexane. The mixed liquid after contact enters the reactor. The flow rate of cyclohexane is 100 g / h, the flow rate of 30 wt% hydrogen peroxide solution is 100 g / h, the contact time is 30 min, and the contact temperature is 40℃.

[0092] II) The flow rate of the mixed liquid is 200 g / h, and the temperature is 20℃;

[0093] III) Add the catalyst and solvent solution to the reactor at a flow rate of 400 g / h.

[0094] IV) Do not introduce O2 gas, and heat the reactor to the reaction temperature of 95°C and the reaction pressure of 2 MPa;

[0095] V) The mixed liquid under working pressure is continuously fed into the reactor for contact for 1.5 hours;

[0096] VI) Stop feeding to end the reaction.

[0097] The cyclohexane consumption was calculated by analyzing the concentration of cyclohexane in the synthesis solution using gas chromatography, and the adipic acid production was calculated by analyzing the concentration of adipic acid in the solution using liquid chromatography. Combined with the cyclohexane feed rate, the adipic acid yield and selectivity were calculated to be 6.9% and 63.2%, respectively.

[0098] Table 1

[0099]

[0100]

[0101] The O2 concentration in the O2-containing gas in Table 1 is expressed as a volume percentage.

[0102] As can be seen from Table 1, the yield and selectivity of adipic acid prepared from cyclohexane after pretreatment with hydrogen peroxide solution are higher.

[0103] As can be seen from the comparison between Example 1 and Comparative Example 1, when hydrogen peroxide solution is not used for pretreatment and activation (Comparative Example 1), the yield and selectivity of adipic acid decrease significantly.

[0104] As can be seen from the comparison between Example 1 and Comparative Example 2, when hydrogen peroxide solution is used as an oxidant for the oxidation reaction, the yield and selectivity of adipic acid will also decrease significantly.

[0105] 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 method for preparing adipic acid, comprising: (1) Cyclohexane was contacted with hydrogen peroxide solution to obtain material a; (2) The material a is allowed to settle to obtain the supernatant; (3) The supernatant is reacted with O2 gas to obtain product b containing adipic acid.

2. The preparation method according to claim 1, characterized in that, The mass concentration of H2O2 in the hydrogen peroxide aqueous solution is 25-45%; and / or The mass ratio of the hydrogen peroxide solution to cyclohexane is (1:2)-(2:1).

3. The preparation method according to claim 1 or 2, characterized in that, The contact temperature is 10-80℃, preferably 30-50℃; and / or The contact time is 10-120 min, preferably 15-60 min; and / or The settling temperature is 15-25℃.

4. The preparation method according to any one of claims 1-3, characterized in that, The oxidation reaction is carried out in the presence of a catalyst and a solvent; Preferably, the solvent is selected from acetic acid.

5. The preparation method according to claim 4, characterized in that, The catalyst is selected from metal salt catalysts; Preferably, the metal element in the metal salt catalyst is selected from one or more of copper, manganese, or cobalt; Preferably, the metal salt is an acetate of a metal element; Preferably, the catalyst is a mixture of copper acetate, manganese acetate and cobalt acetate; Preferably, the mass ratio of copper, manganese and cobalt in the catalyst is (5-10):(1-5):

1.

6. The preparation method according to any one of claims 1-5, characterized in that, The oxidation reaction includes the following steps: S1, the catalyst and solvent are mixed to obtain a catalyst solution; S2, the catalyst solution, supernatant and O2-containing gas are subjected to an oxidation reaction; Preferably, the mass ratio of the catalyst solution to the supernatant is (1.5-8):1; and / or The mass concentration of the catalyst in the catalyst solution is 0.05-5%.

7. The preparation method according to any one of claims 1-6, characterized in that, The mass ratio of the O2-containing gas to the supernatant is (5-15):1; and / or The volume content of O2 in the O2-containing gas is 10-25%.

8. The preparation method according to any one of claims 1-7, characterized in that, The oxidation reaction is carried out at a temperature of 85-110°C; and / or The oxidation reaction is carried out at a pressure of 1.5-5 MPa; and / or The oxidation reaction time is 0.5-2 hours.

9. A system for preparing adipic acid, used in the method for preparing adipic acid according to any one of claims 1-8, said system comprising: Cyclohexane feedstock tank; hydrogen peroxide solution tank; A mixing contactor connected to the cyclohexane feedstock tank and the hydrogen peroxide solution tank; To bring cyclohexane into contact with hydrogen peroxide solution, material a is obtained; A settling device connected to the mixing contactor is used to allow material a to settle and obtain supernatant; A reactor connected to the settling tank is used to oxidize the supernatant with O2 gas to obtain product material b containing adipic acid.

10. The system according to claim 9, characterized in that, The system also includes a catalyst tank connected to the reactor, so that the oxidation reaction is carried out in the presence of a catalyst solution; Preferably, the system further includes a discharge tank connected to the reactor to receive material b.

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