A method for preparing 1,6-hexanediol from 1,3-butadiene

Abstract

The invention discloses a method for preparing adipic acid by hydroformylation and oxidation of butadiene in series in a one-pot process. The method is a one-pot process in which an intermediate product containing 1,6-adipaldehyde can be directly oxidized without separating adipaldehyde to directly prepare 1,6-adipic acid. The method according to the present invention realizes the one-pot synthesis method of the present invention by rationally selecting different solvents and catalysts. The method has mild conditions, simple operation, cheap and easily available raw materials, no catalyst is required for the oxidation process, and is easy to industrialize. The method also has few by-products and is easy to industrially separate. The method can prepare 1,6-adipic acid with high selectivity.

Description

Technical Field

[0001] The present invention belongs to the fields of catalysis and fine chemicals, and specifically relates to a method for preparing 1,6-hexanedioic acid (hereinafter referred to as adipic acid) from 1,3-butadiene (hereinafter referred to as butadiene). Background Art

[0002] 1,6-Adipic acid (ADA, hereinafter referred to as adipic acid) is a very important organic chemical raw material, mainly used in the production of nylon fibers and polyurethanes. It can also be used in food additives, pharmaceutical intermediates, pesticides, lubricants, plasticizers, flavor and fragrance control agents, adhesives, coatings, and dyes. With the development of my country's economy, the demand for adipic acid in various industries is also growing rapidly. For example, the automotive industry, the home appliance industry, and road and bridge construction have all stimulated the growth of demand for adipic acid production. Therefore, the market prospects for adipic acid are very broad. DuPont in the United States began industrial production in 1973, and my country began large-scale production in the 1970s. Adipic acid products already have mature production processes. Currently, there are four main methods for the production of adipic acid: the phenol method, the butadiene method, the cyclohexane method, and the cyclohexene method.

[0003] The phenol process involves hydrogenating phenol over the catalytic action of Ni-Al₂O₃ to produce cyclohexanol, which is then further dehydrogenated to produce cyclohexanone, which is then oxidized to produce adipic acid. Its main advantages are low energy consumption, high economic efficiency, high-purity adipic acid, and relatively mature production technology. However, limited phenol resources can increase the production cost of adipic acid. The butadiene process, developed by BASF in Germany, uses butadiene as the raw material, undergoes two carbonylation reactions, and is then hydrolyzed to produce adipic acid. The entire process requires five steps. The raw material, butadiene, is also relatively inexpensive, making it economically viable. However, this process is relatively complex, with multiple steps, low product yield, and a high number of byproducts. The reaction conditions are stringent, and it is currently still in the research stage and not yet suitable for large-scale industrial production. The cyclohexane process uses benzene as the raw material, which is hydrogenated to produce cyclohexane. Cyclohexane reacts with air to produce a mixture of cyclohexanol and cyclohexanone (referred to as KA oil). This alcohol-ketone mixture can be used to produce adipic acid. The advantages of this method are relatively mature production technology and high conversion rates. Currently, over 90% of global production is produced using this method. However, its disadvantages include high energy consumption, large investment, and a complex production process. It also generates large amounts of waste gas and wastewater, causing significant damage to the ecological environment. The cyclohexene method uses benzene as a raw material, hydrogenating it at a specific temperature and pressure to produce cyclohexene, which is then hydrated to produce cyclohexanol, and finally oxidized with nitric acid to produce adipic acid. This method is a significant improvement over production using cyclohexane, offering significant advantages in terms of raw material consumption, product purity, yield, and environmental protection. However, because nitric acid is used as the oxidant, waste gas emissions are unavoidable, which still causes some damage to the ecological environment.

[0004] In summary, the phenol, cyclohexane, and cyclohexene processes all use benzene as a raw material, sharing similar technical approaches. However, they all present challenges in terms of cost, energy consumption, investment, and production process. Environmental issues are particularly prominent, and with the current increasing emphasis on environmental protection, greening processes is inevitable. While the butadiene process is relatively the most environmentally friendly, it also suffers from technical drawbacks and is not yet suitable for industrial production.

[0005] A novel method for producing 1,6-adipaldehyde (hereinafter referred to as adipaldehyde) from butadiene via dihydroformylation, followed by oxidation to adipic acid, is proposed. This method offers low raw material costs, mild reaction conditions, and minimal equipment requirements. Currently, this method has been little studied, primarily due to the lack of mature research into the process for producing adipaldehyde through the first step of butadiene dihydroformylation. To address this issue, and drawing on previous research experience, the inventors of this application have previously developed a one-pot dual-ligand tandem relay-catalyzed butadiene hydroformylation to produce adipaldehyde and n-valeraldehyde (CN116041155A). The product distribution of the butadiene hydroformylation reaction under the combined action of the dual ligands is n-valeraldehyde (selectivity 25%-38%) and adipaldehyde (selectivity 55%-70%, l / b = 6-12). The process has a maximum selectivity of nearly 70% for adipaldehyde, laying the foundation for the development of a process for preparing adipic acid using butadiene as raw material. However, if adipaldehyde is to be oxidized to produce adipic acid, the product adipaldehyde needs to be separated and then further reacted, which limits the economic efficiency of the reaction. Summary of the Invention

[0006] In response to the problems existing in the current process for preparing adipic acid, the present invention develops a new one-pot method for preparing adipic acid by serially catalyzing the hydroformylation of butadiene with two ligands in a one-pot process to produce adipic dialdehyde and n-valeraldehyde based on the previously developed strategy of a one-pot dual-ligand serial relay catalysis of butadiene hydroformylation to produce adipic dialdehyde and n-valeraldehyde. This method is a one-pot process that can directly oxidize the intermediate product containing adipic dialdehyde without isolating the adipic dialdehyde to directly prepare adipic acid.

[0007] According to one aspect of the present invention, an object of the present invention is to provide a novel method for preparing 1,6-hexanediol from butadiene in a one-pot process, the method being as follows:

[0008] Under the protection of an inert atmosphere, butadiene, the first Rh(acac)(CO)2, the ligand Lx and the first solvent are added to an autoclave, the autoclave is sealed, and a synthesis gas of 6-10 MPa H2 and CO is introduced for the first time, wherein the volume ratio of H2 to CO is 1:1, and the reaction is carried out at 60-120°C for 5-15 hours; after cooling to room temperature, the autoclave is opened under the protection of an inert atmosphere, and then the second Rh(acac)(CO)2 and the ligand Biphephos are added, the autoclave is sealed, and 0 .5-6MPa H2 and CO synthesis gas, wherein the volume ratio of H2 to CO is 1:3, react at 60-100°C for 5-20 hours; cool to room temperature, add a second solvent under inert atmosphere protection, seal the autoclave, introduce oxidizing gas to replace the atmosphere in the autoclave, maintain the gas pressure in the autoclave at 0.1MPa-10MPa, then stir at room temperature-100°C for 1 hour-48 hours, cool to room temperature, and purify and separate the product 1,6-hexanediol by column chromatography, precipitation method or crystallization method.

[0009] The structures of the ligands Lx and Biphephos are as follows:

[0010]

[0011] Preferably, the inert atmosphere is a nitrogen or argon atmosphere.

[0012] Preferably, the first solvent is selected from toluene and xylene, preferably toluene.

[0013] Preferably, the synthesis gas of H2 and CO introduced for the first time is 8 MPa.

[0014] Preferably, the reaction temperature of the synthesis gas of H2 and CO introduced for the first time is 80°C.

[0015] Preferably, the reaction time of the first introduction of H2 and CO synthesis gas is 12 hours.

[0016] Preferably, the synthesis gas of H2 and CO introduced for the second time is 0.5-4 MPa, more preferably 1 MPa.

[0017] Preferably, the second solvent is a polar solvent, selected from at least one of methanol, ethanol, isopropanol, formic acid, acetic acid, propionic acid, acetonitrile, N,N-dimethylformamide, N-methylpyrrolidone, ether, tetrahydrofuran and dioxane, preferably formic acid, acetic acid, tetrahydrofuran and methanol.

[0018] Preferably, based on the molar amount of the raw material butadiene, the amount of the first Rh(acac)(CO)2 used is 0.01-0.3 mol%, more preferably 0.05-0.2 mol%, and most preferably 0.1 mol%.

[0019] Preferably, based on the molar amount of the raw material butadiene, the amount of the ligand Lx is 0.01-0.3 mol%, more preferably 0.05-0.2 mol%, most preferably 0.12 mol%.

[0020] Preferably, the molar ratio of the ligand Lx to the first Rh(acac)(CO)2 is 0.5:1-2.0:1, preferably 0.8:1-1.6:1, and more preferably 1.2:1.

[0021] Preferably, based on the molar amount of the raw material butadiene, the amount of the second Rh(acac)(CO)2 used is 0.1-0.6 mol%, more preferably 0.1-0.4 mol%, and most preferably 0.2 mol%.

[0022] Preferably, based on the molar amount of the raw material butadiene, the amount of the ligand Biphephos used is 0.1-0.8 mol%, more preferably 0.2-0.6 mol%, and most preferably 0.4 mol%.

[0023] Preferably, the molar ratio of the ligand Biphephos to the second Rh(acac)(CO)2 is 0.5:1-2.0:1, preferably 0.8:1-1.6:1, and more preferably 1.2:1.

[0024] Preferably, the oxidizing gas is selected from oxygen, an oxygen-nitrogen mixture, or an oxygen-argon mixture.

[0025] Preferably, the pressure of the oxidizing gas is preferably 0.1 MPa-2 MPa.

[0026] Preferably, the oxidation reaction temperature is 25-80°C, preferably 40-60°C.

[0027] Preferably, the oxidation reaction time is 6 hours to 36 hours, preferably 10 hours to 24 hours.

[0028] Preferably, the stirring speed is 500 rpm to 1500 rpm.

[0029] Beneficial effects

[0030] The present invention develops a novel one-pot method for preparing 1,6-adipic acid by serially reacting butadiene hydroformylation and oxidation. The one-pot synthesis method of the present invention is achieved by rationally selecting different solvents and catalysts. The method has mild conditions, simple operation, cheap and readily available raw materials, and no catalyst is required in the oxidation process, which is convenient for industrial application. The method also has few by-products and is convenient for industrial separation. The method can prepare 1,6-adipic acid with high selectivity. DETAILED DESCRIPTION

[0031] The present invention will be described in detail below. Before describing, it should be understood that the terms used in this specification and the appended claims should not be interpreted as limited to the general meaning and dictionary meaning, but should be interpreted according to the meaning and concept corresponding to the technical aspects of the present invention on the basis of the principle that allows the inventor to appropriately define the terms for the best interpretation. Therefore, the descriptions presented here are merely preferred examples for illustrative purposes and are not intended to limit the scope of the present invention. It should be understood that other equivalents or improvements can be obtained therefrom without departing from the spirit and scope of the present invention.

[0032] The following examples are merely examples of embodiments of the present invention and do not constitute any limitation thereto. Those skilled in the art will appreciate that modifications without departing from the spirit and scope of the present invention fall within the scope of protection of the present invention. Unless otherwise specified, the reagents and instruments used in the following examples are commercially available products.

[0033] Hereinafter, preferred embodiments of the present disclosure will be described in detail. Prior to the description, it should be understood that the terms used in the specification and the appended claims should not be construed as limited to their general and dictionary meanings, but rather should be interpreted based on the meanings and concepts corresponding to the technical aspects of the present invention, based on the principle of allowing the inventor to appropriately define the terms for the best interpretation. Therefore, the description herein is merely a preferred example for illustrative purposes and is not intended to limit the scope of the present invention. It should be understood that other equivalent implementations and modifications may be made without departing from the spirit and scope of the present invention.

[0034] As used herein, the terms "comprise," "include," "have," "contain," or any similar terms are open-ended transitional phrases that are intended to encompass non-exclusive inclusions. For example, a composition or article containing multiple elements is not limited to the elements listed herein, but may also include other elements not expressly listed but generally inherent to the composition or article. In addition, unless expressly stated to the contrary, the term "or" refers to an inclusive "or" rather than an exclusive "or." For example, any of the following situations satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), and both A and B are true (or exist). In addition, as used herein, the terms "comprise," "include," "have," and "contain" should be interpreted as specifically disclosing and encompassing closed or semi-closed transitional phrases such as "consisting of" and "consisting essentially of."

[0035] Throughout this document, all features or conditions defined as numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered to encompass and specifically disclose all possible subranges and individual values within those ranges, particularly integer values. For example, a description of a range "1 to 8" should be considered to specifically disclose all possible subranges such as 1 to 7, 2 to 8, 2 to 6, 3 to 6, 4 to 8, 3 to 8, and so forth, particularly those defined by all integer values, and should be considered to specifically disclose individual values within those ranges such as 1, 2, 3, 4, 5, 6, 7, and 8. Unless otherwise indicated, the foregoing interpretation applies to all of the present disclosure, regardless of whether the ranges are comprehensive or not.

[0036] If a quantity or other value or parameter is expressed as a range, a preferred range, or a series of upper and lower limits, it should be understood that all ranges consisting of any upper limit or preferred value of the range and any lower limit or preferred value of the range have been specifically disclosed herein, regardless of whether these ranges are disclosed separately. In addition, when a numerical range is mentioned herein, unless otherwise specified, the range should include its endpoints and all integers and fractions within the range.

[0037] In this document, numerical values should be understood to have the accuracy of the number of significant digits of the numerical value, provided that the purpose of the invention can be achieved. For example, the number 40.0 should be understood to cover the range from 39.50 to 40.49.

[0038] In the method according to the present invention, the preparation of adipaldehyde is achieved by adding Rh(acac)(CO)2 twice and selecting ligands Lx and Biphephos respectively, and then the second solvent, oxidizing gas, etc. are directly added to continue the reaction without separating the product to prepare 1,6-hexanediol.

[0039] The second solvent is a polar solvent. Selecting a polar solvent can help increase the solubility of oxygen. It is particularly advantageous that the polar solvent is a solvent containing active hydrogen, such as an alcohol, an acid, or a heterocyclic solvent, preferably at least one selected from methanol, ethanol, isopropanol, formic acid, acetic acid, propionic acid, acetonitrile, N,N-dimethylformamide, N-methylpyrrolidone, diethyl ether, tetrahydrofuran, and dioxane, preferably formic acid, acetic acid, tetrahydrofuran, and methanol.

[0040] The analysis method is as follows:

[0041] After the reaction, the temperature was cooled to room temperature to fully release the gas. Decane was added as an internal standard. Gas chromatography analysis was performed using a Shimadzu Nexis GC-2030 equipped with a flame ionization detector (FID) and an SH-Rtx-5 capillary column (30 m, 0.25 mm ID, 0.25 μm film thickness), using nitrogen as the carrier gas. A three-step temperature program was as follows: hold at 35°C for 8 min, then increase to 90°C at a rate of 20°C / min, hold for 3 min, and finally increase to 250°C at a rate of 30°C / min, hold for 5 min.

[0042] Examples 1-5: Effects of different solvents

[0043] Under nitrogen protection, 0.04mmol Rh(CO)2(acac) and 0.048mmol ligand Lx were added to an autoclave, followed by 40mL toluene and 40mmol butadiene. The autoclave was sealed, 8MPa synthesis gas (H2 / CO=1:1) was introduced, and the reaction was stirred at 80°C for 12 hours. Cooled to room temperature, 0.008mmol Rh(CO)2(acac) and 0.016mmol ligand Biphephos were added, 1MPa mixed gas (H2:CO=1:3) was introduced, and the reaction was stirred at 70°C for 15 hours. Cooled to room temperature, 40mL of the second solvent was added, the autoclave was sealed, 1MPa mixed gas (O2 / N2=1:3) was introduced, and the reaction was stirred at 60°C for 12 hours. The product can be separated by conventional methods, such as column chromatography, precipitation or crystallization. The gas phase results are shown in Table 1 below:

[0044] Table 1

[0045] Example Second solvent 1,6-Hexanedioic acid selectivity Example 1 Toluene 25％ Example 2 Methanol 51％ Example 3 Acetic acid 67％ Example 4 Acetonitrile 53％ Example 5 Tetrahydrofuran 58％

[0046] Examples 3, 6-7: Effects of different times

[0047] The same procedures as in Example 1 were followed except that 40 mL of acetic acid (the second solvent) was added, the autoclave was sealed, a 1 MPa mixed gas (O2 / N2 = 1:3) was introduced, and the reaction was stirred at 60°C for a period of time. The gas phase results are shown in Table 2 below:

[0048] Table 2

[0049] Example time 1,6-Hexanedioic acid selectivity Example 6 4 hours 45％ Example 7 8 hours 60％ Example 3 12 hours 67％

[0050] Examples 3, 8-9: Effect of Temperature

[0051] The same procedures as in Example 1 were followed except that 40 mL of acetic acid (the second solvent) was added, the autoclave was sealed, a 1 MPa mixed gas (O2 / N2 = 1:3) was introduced, and the reaction was stirred at a constant temperature for 12 hours. The gas phase results are shown in Table 3 below:

[0052] Table 3

[0053]

[0054]

[0055] Examples 3, 10-11: Effects of Different Pressures

[0056] The same procedures as in Example 1 were followed, except that 40 mL of acetic acid (the second solvent) was added, the autoclave was sealed, a mixed gas (O2 / N2 = 1:3) at a certain pressure was introduced, and the reaction was stirred at 60°C for 12 hours. The gas phase results are shown in Table 4 below:

[0057] Table 4

[0058] Example pressure 1,6-Hexanedioic acid selectivity Example 10 0.5MPa 54％ Example 3 1MPa 67％ Example 11 2MPa 67％

[0059] Examples 3, 12-13: Effect of Mixed Gas Ratio

[0060] The same procedures as in Example 1 were followed except that 40 mL of acetic acid (second solvent) was added, the autoclave was sealed, a 1 MPa mixed gas was introduced, and the reaction was stirred at 60° C. for 12 hours. The gas phase results are shown in Table 5 below:

[0061] Table 5

[0062] Example <![CDATA[O2 / N2]]> 1,6-Hexanedioic acid selectivity Example 12 1:0 67％ Example 3 1:3 67％ Example 13 1:10 61％

[0063] Examples 14-18: Effects of other conditions

[0064] The same procedures as in Example 1 were followed except that 40 mL of acetic acid (the second solvent) was added, the autoclave was sealed, 0.1 MPa of oxygen was introduced, and the reaction was stirred at a certain temperature for a certain time. The gas phase results are shown in Table 6 below:

[0065] Table 6

[0066]

[0067]

[0068] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A novel method for preparing 1,6-hexanediol from butadiene in one pot, the method comprising: Under the protection of an inert atmosphere, butadiene, the first Rh(acac)(CO)2, the ligand Lx and the first solvent are added to an autoclave, the autoclave is sealed, and a synthesis gas of 6-10 MPa H2 and CO is introduced for the first time, wherein the volume ratio of H2 to CO is 1:1, and the reaction is carried out at 60-120°C for 5-15 hours; after cooling to room temperature, the autoclave is opened under the protection of an inert atmosphere, and then the second Rh(acac)(CO)2 and the ligand Biphephos are added, the autoclave is sealed, and 0 .5-6MPa H2 and CO synthesis gas, wherein the volume ratio of H2 to CO is 1:3, reacting at 60-100°C for 5-20 hours; cooling to room temperature, adding a second solvent under inert atmosphere, sealing the autoclave, introducing an oxidizing gas to replace the atmosphere in the autoclave, maintaining the gas pressure in the autoclave at 0.1MPa-10MPa, then stirring at room temperature-100°C for 6 hours-36 hours, cooling to room temperature, and purifying and isolating the product 1,6-hexanedioic acid by column chromatography, precipitation method or crystallization method; The first solvent is selected from toluene and xylene; The second solvent is a polar solvent selected from at least one of methanol, ethanol, isopropanol, formic acid, acetic acid, propionic acid, acetonitrile, N,N-dimethylformamide, N-methylpyrrolidone, diethyl ether, tetrahydrofuran and dioxane; The structures of the ligands Lx and Biphephos are as follows:

2. The method for preparing 1,6-hexanediol from butadiene in one pot according to claim 1, characterized in that: The inert atmosphere is nitrogen or argon atmosphere; The first solvent is toluene; The first injection of H2 and CO synthesis gas is 8MPa; The reaction temperature of the first introduction of H2 and CO synthesis gas is 80°C; The reaction time of the first introduction of H2 and CO synthesis gas is 12 hours.

3. The method for preparing 1,6-hexanediol from butadiene in one pot according to claim 1, characterized in that: The synthesis gas of H2 and CO introduced for the second time is 0.5-4MPa.

4. The method for preparing 1,6-adipic acid from butadiene in one pot according to claim 3, characterized in that: The synthesis gas of H2 and CO introduced for the second time has a pressure of 1 MPa.

5. The method for preparing 1,6-adipic acid from butadiene in one pot according to claim 1, characterized in that: The second solvent is selected from the group consisting of formic acid, acetic acid, tetrahydrofuran and methanol.

6. The method for preparing 1,6-adipic acid from butadiene in one pot according to claim 1, characterized in that: Based on the molar amount of the raw material butadiene, the amount of the first Rh(acac)(CO)2 used is 0.01-0.3 mol%.

7. The one-pot method for preparing 1,6-adipic acid from butadiene according to claim 6, characterized in that: Based on the molar amount of the raw material butadiene, the amount of the first Rh(acac)(CO)2 used is 0.05-0.2 mol%.

8. The method for preparing 1,6-hexanediol from butadiene in one pot according to claim 7, characterized in that: Based on the molar amount of the raw material butadiene, the amount of the first Rh(acac)(CO)2 used was 0.1 mol%.

9. The one-pot method for preparing 1,6-adipic acid from butadiene according to claim 1, characterized in that: Based on the molar amount of raw material butadiene, the amount of ligand Lx used is 0.01-0.3 mol%.

10. The one-pot method for preparing 1,6-adipic acid from butadiene according to claim 9, characterized in that: Based on the molar amount of raw material butadiene, the amount of ligand Lx used is 0.05-0.2 mol%.

11. The one-pot method for preparing 1,6-adipic acid from butadiene according to claim 10, characterized in that: Based on the molar amount of the raw material butadiene, the amount of the ligand Lx used was 0.12 mol%.

12. The method for preparing 1,6-adipic acid from butadiene in one pot according to claim 1, characterized in that: The molar ratio of the ligand Lx to the first Rh(acac)(CO)2 is 0.5:1-2.0:

1.

13. The method for preparing 1,6-adipic acid from butadiene in one pot according to claim 12, characterized in that: The molar ratio of the ligand Lx to the first Rh(acac)(CO)2 is 0.8:1-1.6:

1.

14. The one-pot method for preparing 1,6-adipic acid from butadiene according to claim 13, characterized in that: The molar ratio of the ligand Lx to the first Rh(acac)(CO)2 is 1.2:

1.

15. The one-pot method for preparing 1,6-adipic acid from butadiene according to claim 1, characterized in that: Based on the molar amount of the raw material butadiene, the amount of the second Rh(acac)(CO)2 used is 0.1-0.6 mol%.

16. The method for preparing 1,6-adipic acid from butadiene in one pot according to claim 15, characterized in that: Based on the molar amount of the raw material butadiene, the amount of the second Rh(acac)(CO)2 used is 0.1-0.4 mol%.

17. The one-pot method for preparing 1,6-adipic acid from butadiene according to claim 16, characterized in that: Based on the molar amount of the raw material butadiene, the amount of the second Rh(acac)(CO)2 used was 0.2 mol%.

18. The one-pot method for preparing 1,6-adipic acid from butadiene according to claim 1, characterized in that: Based on the molar amount of the raw material butadiene, the amount of the ligand Biphephos used is 0.1-0.8 mol%.

19. The one-pot method for preparing 1,6-adipic acid from butadiene according to claim 18, characterized in that: Based on the molar amount of the raw material butadiene, the amount of the ligand Biphephos used is 0.2-0.6 mol%.

20. The one-pot method for preparing 1,6-adipic acid from butadiene according to claim 19, characterized in that: Based on the molar amount of the raw material butadiene, the amount of the ligand Biphephos used was 0.4 mol%.

21. The one-pot method for preparing 1,6-adipic acid from butadiene according to claim 1, characterized in that: The molar ratio of the ligand Biphephos to the second Rh(acac)(CO)2 is 0.5:1-2.0:

1.

22. The one-pot method for preparing 1,6-adipic acid from butadiene according to claim 21, characterized in that: The molar ratio of the ligand Biphephos to the second Rh(acac)(CO)2 is 0.8:1-1.6:

1.

23. The one-pot method for preparing 1,6-adipic acid from butadiene according to claim 12, characterized in that: The molar ratio of the ligand Biphephos to the second Rh(acac)(CO)2 is 1.2:

1.

24. The one-pot method for preparing 1,6-adipic acid from butadiene according to claim 1, characterized in that: The oxidizing gas is selected from oxygen, oxygen-nitrogen mixture or oxygen-argon mixture; The pressure of the oxidizing gas is 0.1MPa-2MPa; The oxidation reaction temperature is 25-80°C; The oxidation reaction time is 10 hours to 24 hours; The stirring speed is 500 rpm to 1500 rpm.

25. The one-pot method for preparing 1,6-adipic acid from butadiene according to claim 24, characterized in that: The oxidation reaction temperature is 40-60°C.

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