A catalyst for isomerization of branched unsaturated fatty nitrile and its preparation method and use

Abstract

The present invention discloses a catalyst for isomerizing branched unsaturated fatty nitriles to linear products. The catalyst comprises P5DP-X, a phosphorus ligand 1, and zero-valent metal Ni. P5DP-X is a pillar aromatic phosphite derivative, the structure of which is represented by the following general formula I. The present invention also discloses a preparation method and uses of the catalyst. The catalyst according to the present invention has stable properties, good tolerance to certain humidity and oxygen levels, is easy to access and feed, simplifies industrial operation processes, can highly selectively convert 2M3BN to 3PN, and can further reduce the load on 2M3BN separation equipment in existing industrial plants. The recycling process has minimal losses, good activity retention, and significant economic benefits. #imgabs0#

Description

Technical Field

[0001] The present invention belongs to the technical field of organic chemistry and chemical engineering, and specifically relates to providing a catalyst for isomerizing branched unsaturated fatty nitriles into linear products and a preparation method thereof, as well as use of the catalyst in catalyzing the isomerization of 2M3BN into 3PN. Background Art

[0002] The hydrocyanation of 1,3-butadiene to produce adiponitrile (ADN) has important industrial application value. The process developed by DuPont mainly includes the following steps:

[0003]

[0004] The above process is a homogeneous nickel(0)-catalyzed olefin hydrocyanation reaction. The process can be divided into three main steps. In the first step, hydrocyanic acid reacts with 1,3-butadiene in the presence of NiL4 (L = phosphorus ligand) catalyst to produce 3-pentenenitrile (3PN) and 2-methyl-3-butenenitrile (2M3BN). In the second step, a Lewis acid auxiliary is added to the NiL4 catalyst to achieve the isomerization of 2M3BN to 3PN. Finally, in the third step, under the synergistic action of the NiL4 catalyst and the Lewis acid auxiliary, 3PN isomerizes to 4-pentenenitrile (4PN), while HCN is selectively added to 4PN to obtain the target product ADN.

[0005] During the first hydrocyanation step, the ratio of the products 3PN and 2M3BN can reach 1.5 to 2:1. The isomerization of 2M3BN also produces a series of side reactions, such as the formation of 2-methyl-2-butenenitrile (2M2BN) and 2-pentenenitrile (2PN). The presence of 2M2BN and 2PN can cause catalyst deactivation, generate dicyanonic acid precipitates, and clog the reaction equipment. Therefore, highly selectively isomerizing 2M3BN to 3PN while suppressing side reactions is a key factor in improving yield, reducing costs, and protecting catalyst activity.

[0006] At present, the catalysts used in the prior art, whether they are phosphorus-containing monodentate ligands or multidentate ligands, are often single phosphine ligand catalysts, such as CN1169143A, CN1914157A, and CN1875025A. However, the catalytic performance of these catalysts is still not ideal, so there is still a need to develop new catalysts to improve the yield. Summary of the Invention

[0007] In order to effectively improve the problems existing in the above-mentioned prior art, the present invention provides a catalyst for the isomerization of branched unsaturated fatty nitriles to linear products and a preparation method thereof, as well as the use of the catalyst in catalyzing the isomerization of 2M3BN to 3PN. The catalyst can effectively improve the selectivity and yield.

[0008] According to one aspect of the present invention, an object of the present invention is to provide a catalyst for isomerizing branched unsaturated fatty nitriles to linear products, the catalyst comprising components P5DP-X, phosphorus ligand 1 and zero-valent metal Ni, wherein the molar ratio of P5DP-X:phosphorus ligand 1:Ni(0) is 1:2-20:0.5-5, preferably 1:2-10:1-4, and more preferably 1:6:2.

[0009] The P5DP-X is a pillararene phosphite derivative, and its structure is shown in the following general formula I:

[0010]

[0011] As shown in the general formula I, P5DP-X consists of two parts, a pillar aromatic hydrocarbon part and a phosphorus-containing substituent part, wherein the pillar aromatic hydrocarbon part is a methoxy-substituted pillar [5] aromatic hydrocarbon, and the phosphorus-containing substituent part is a structure of -OP(X)2, wherein X is selected from one of o-methylphenoxy, m-methylphenoxy, p-methylphenoxy, o-ethylphenoxy, m-ethylphenoxy, p-ethylphenoxy, p-isopropylphenoxy, p-tert-butylphenoxy, 2,4-di-tert-butylphenoxy, o-phenylphenoxy, p-phenylphenoxy, 1-naphthyloxy, 2-naphthyloxy, 2,6-dimethylphenoxy, and 2,4,6-trimethylphenoxy.

[0012] Preferably, X is o-methylphenoxy, m-methylphenoxy, p-methylphenoxy, p-tert-butylphenoxy, or p-phenylphenoxy.

[0013] Preferably, the phosphorus ligand 1 is one of triethyl phosphite, triphenyl phosphite, tri-p-cresyl phosphite, tri-m-cresyl phosphite, tri-o-cresyl phosphite, and tri-p-tert-butylphenyl phosphite.

[0014] Preferably, the catalyst is represented by the general formula II:

[0015]

[0016]

[0017] in, is the structural formula of the P5DP-X, and L is the phosphorus ligand 1.

[0018] According to another aspect of the present invention, another object of the present invention is to provide a method for preparing the catalyst, which is carried out as follows: P5DP-X and nickel powder are added to an organic solvent and mixed, reacted at a certain temperature, and then phosphorus ligand 1 is added, the reaction is continued for a period of time, filtered to remove insoluble matter, and the filter cake is washed with the same organic solvent. The filtrate is combined and concentrated to obtain the target catalyst.

[0019] Preferably, the reaction temperature is 95-160°C, preferably 120-140°C.

[0020] Preferably, the reaction time of P5DP-X and nickel powder is 1-4 hours, preferably 1-3 hours; and the reaction time after adding phosphorus ligand 1 is 2-10 hours, preferably 4-8 hours.

[0021] Preferably, the organic solvent is one or more of 3PN, 2M3BN, a mixture of 3PN and 2M3BN, xylene, toluene, dimethylformamide, diethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, and sulfolane, preferably 3PN, 2M3BN, or a mixture of 3PN and 2M3BN. The amount of the organic solvent used is 2-5 times the mass of P5DP-X.

[0022] According to another aspect of the present invention, another object of the present invention is to provide a use of the catalyst in catalyzing the isomerization of branched unsaturated fatty nitriles to linear products. Preferably, the use is the use of the catalyst in catalyzing the isomerization of 2M3BN to 3PN.

[0023] According to another aspect of the present invention, another main object of the present invention is to provide a method for isomerization of branched unsaturated fatty nitrile, the method comprising: in a reactor, mixing a substrate containing 2M3BN, the catalyst according to the present invention, a phosphorus ligand 2, and a Lewis acid to form a reaction system, reacting at a certain temperature and pressure, and separating unreacted 2M3BN and 3PN by distillation after the reaction reaches an end point. The remaining bottom liquid is mainly a catalyst solution, which is taken out and recycled.

[0024] The substrate containing 2M3BN is a mixture of 2M3BN, 3PN and 2M3BN, wherein the source of 2M3BN can be 2M3BN, a by-product generated by the primary hydrocyanation of butadiene, or commercially available 2M3BN.

[0025] The phosphorus ligand 2 is one or more of triethyl phosphite, triphenyl phosphite, tri-p-cresyl phosphite, tri-m-cresyl phosphite, and tri-o-cresyl phosphite.

[0026] The Lewis acid is one of aluminum chloride, zinc chloride, triphenylboron, ferric chloride, copper chloride, ferric sulfate, nickel sulfate, nickel chloride, and cobalt acetate, preferably zinc chloride.

[0027] The mass ratio of the substrate containing 2M3BN, the catalyst, the phosphorus ligand 2, and the Lewis acid is 30-1000:2:5-100:1-50, preferably 350-400:2:10:2.

[0028] The above reaction system contains a solvent or does not contain a solvent. The solvents that can be selected include one or more of 2M3BN itself, xylene, toluene, dimethylformamide, diethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, and cyclobutane sulfonate. From the perspective of cost and ease of operation, 2M3BN or a mixture of 3PN and 2M3BN is preferably used as the reaction substrate and solvent.

[0029] The reaction temperature is 40 to 200°C, preferably 90 to 110°C.

[0030] The reaction time is 2-10 hours, preferably 4-8 hours.

[0031] Beneficial effects

[0032] 1. The catalyst according to the present invention can convert 2M3BN into 3PN with high selectivity. Compared with the current industrial method, the selectivity can be improved by 10-15%.

[0033] 2. Compared with the current industrial method, which requires the distillation and purification of 2M3BN generated by a single hydrocyanation process before isomerization, this solution can increase the 3PN content in situ and reduce 2M3BN. Therefore, it can further reduce the load of 2M3BN separation equipment in existing industrial devices.

[0034] 3. The loss in the recycling process is small, the activity is well maintained, and there are obvious economic benefits.

[0035] 4. The catalyst has stable properties and good tolerance to certain humidity and oxygen content. It is easy to use and feed, simplifying the industrial operation process.

[0036] 5. The pillar aromatics in the catalyst of the present invention are stable, easily available, and the raw materials used in production are common products in petrochemical and coal chemical industries, eliminating the bottleneck of raw materials and making it suitable for large-scale production. DETAILED DESCRIPTION

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] Example 1: Preparation of ligand P5DP-X, wherein X is m-methoxy

[0043] The source of the fully methylated column [5] aromatic hydrocarbons was purchased from a reagent company or was self-made, referring to the methods described in the literature such as Euro.J.Org.Chem., 2013, 6(15), 2961–2975.

[0044] The first step is to place a stirring magnet in a 1000mL round-bottom flask, add 400mL of dichloromethane, add the permethylated column [5] aromatic hydrocarbon (15.0g, 20.0mmol), and stir thoroughly until completely dissolved. Then add cerium ammonium nitrate (22g, 40.0mmol) and add 10mL of water. The mixture is stirred at room temperature for 30 minutes. After the reaction is completed, 200mL of deionized water is added to the system to quench the reaction. The organic layer is separated, and the organic phase is washed 3 times with saturated brine and deionized water, and then concentrated and desolventized to obtain a dark red solid (11.0g). The crude product is directly used in the next reaction without purification.

[0045] Second step, in a 1000mL round-bottom flask, a magnet is placed, a constant pressure dropping funnel and a nitrogen protection device are placed, the crude product obtained in the previous step is dissolved in 200mL of dichloromethane and added to the flask in a disposable manner, and a solution of 200mL of water of sodium hyposulfite (20g, 115mmol) is added to the constant pressure dropping funnel. The system is replaced with nitrogen three times, then stirring is opened, and sodium hyposulfite is slowly dripped into the reaction flask, and the reaction temperature is controlled by the control of the dropping rate. The temperature of the reaction system is maintained to be less than 35°C throughout the entire process. After the addition is complete, it can be observed that the red solution becomes colorless, and stirring is continued at room temperature for 2 hours. Separate the liquid, and the organic phase is washed with water three times. After the organic phase is desolvated, freeze-dried and dehydrated to obtain a light yellow solid (12.0g), and the crude product is directly used in the next step reaction.

[0046] The third step is to place a 1000mL round-bottom flask in an ice bath with a tetrafluoroborate magnet, a thermometer, and a constant pressure dropping funnel. Add 50mL of cyclohexane solution of bis(meta-cresyl)phosphinoyl chloride (14g) to the constant pressure dropping funnel. Add the crude product obtained in the previous step to the reaction flask, add 200mL of anhydrous cyclohexane and 4.0g of freshly distilled triethylamine, and stir thoroughly. The system is replaced with nitrogen. When the system is cooled to -5°C, slowly drop bis(meta-cresyl)phosphinoyl chloride into the reaction flask. Pay attention to control the reaction temperature and keep the temperature at -5°C. After the addition is completed, slowly warm it to room temperature, filter the salt generated by the reaction, wash the filter cake three times with cyclohexane, combine the filtrate, concentrate and desolventize to obtain a light yellow amorphous solid (10.0g, yield%). ESI-MS: 1211.4 ([M+H]+), 1H-NMR (400MHz, CDCl3, 298K) δ (ppm): 6.97 (s, 4H), 6.87 (s, 2H), 6.80 (d, 4H), 6.74 (s, 2H), 6.70 (s, 2H), 6.67-6.63 (m, 8H),6.55(s,2H),5.92(s,2H),3.92–3.71(m,10H),3.69(d,6H),3.57(s,6H),3.38(s,6H),3.30(s,6H),2.26(s,12H).

[0047] The prepared catalyst was analyzed by elemental analysis and nuclear magnetic resonance analysis, and its basic structure is as follows:

[0048]

[0049] in, This is a simplified structural formula of P5DP-X.

[0050] Examples 2 to 5

[0051] Except for using different X substituents, the preparation method is the same as that of Example 1, as summarized in Table 1.

[0052] Example 6: Preparation of a catalyst containing P5DP-X

[0053] A 1000 mL round-bottom flask equipped with a mechanical stirrer, thermometer, reflux condenser, and nitrogen atmosphere was added to the flask. 121.1 g of the P5DP-X ligand prepared in Example 1, 12.0 g of nickel powder, and 360 g of 3PN were added. The atmosphere was purged with nitrogen, stirring was initiated, and an oil bath was added. The temperature was raised to 130°C and the reaction stirred for 2 hours. Subsequently, 211.2 g of tris-m-cresol phosphite (P(Om-Cresol)3) was added. The reaction was maintained at the same temperature and stirring was continued for 6 hours. Heating was stopped, the mixture was cooled to 60-80°C, and the unreacted nickel powder was filtered off while hot. The resulting homogeneous solution containing the catalyst was directly used in the rearrangement reaction of 2M3BN. Calculations indicate that 48.87 g of catalyst is present per 100 g of this catalyst-containing solution.

[0054] Examples 7 to 12:

[0055] The catalyst was prepared according to the same preparation method as Example 6 except for the different amounts of ligand added and phosphorus ligand used. The specific feed ratio and catalyst content are shown in Table 2.

[0056] Example 13: Isomerization of 2M3BN

[0057] A 500 mL round-bottom flask was equipped with a magnet, reflux condenser, and thermometer. A 200 g mixture of 2M3BN and 3PN was added as the reaction substrate. GC analysis revealed 72% 2M3BN and 26% 3PN, with the remainder being impurities. Subsequently, 5.0 g of P(Om-Cresol)3 and 1.0 g of anhydrous zinc chloride were added to the reaction solution. Finally, 2.06 g of the catalyst from Example 6, containing 48.87% by weight, was added. The atmosphere was purged with nitrogen, an oil bath was started, the system temperature was raised to 100°C, and the reaction was continued for 240 minutes. Sampling was performed and analyzed. After achieving the desired reaction temperature, the reaction solution was subjected to vacuum distillation to remove the original and generated 3PN, residual 2M3BN, and impurities such as 2PN and 2M2BN. The remaining bottom liquid was recycled. The analytical results are shown in Table 4.

[0058] Examples 14 to 19:

[0059] Except that the feeding ratio is in accordance with Table 3, the same method as Example 13 was followed. The analysis results are shown in Table 4.

[0060] Example 20: Stability test of P5DP-X

[0061] The catalyst prepared in Example 6 was placed in an environment of 65°C, 21% oxygen content, and 55% humidity for 4 hours. The catalyst was then used for the isomerization of 2M3BN using the same procedures as in Example 13. The analytical results are shown in Table 3.

[0062] Example 21: Recycling of catalyst system

[0063] After distilling off 3PN, 2M3BN, and other substances from Example 13, the remaining bottom liquid was re-added with the substrate (the same as that used in Example 13). The procedure of Example 13 was repeated, and the resulting catalyst was placed in an environment of 65°C, 21% oxygen content, and 55% humidity for 4 hours. The catalyst was then used in the isomerization of 2M3BN using the same procedure as in Example 13, repeated six times. The analytical results are shown in Table 5.

[0064] Comparative Example 1: Isomerization of 2M3BN with P(Om-cresol)3 Catalyst

[0065] The catalyst used is abbreviated as NiL4, where L is P(Om-cresol)3, i.e., does not contain a P5DP-X ligand structure, and is a 75% (wt) 3PN solution. The remaining operating methods are the same as those in Example 13. The feed ratios are shown in Table 3, and the analysis results are shown in Table 4.

[0066] Comparative Example 2: Comparison of Stability of Catalysts Containing P(Om-cresol)3

[0067] NiL4 in Comparative Example 1, i.e., without the P5DP-X ligand structure, was used, and the operation method was the same as in Example 20. Activity was then determined. The specific operation was referenced to Example 13. The feeding ratio is shown in Table 3, and the analysis results are shown in Table 4.

[0068] Table 1

[0069] name X Substituent Appearance Product mass (g) Yield % Example 1 m-Cresol Light yellow solid 10.01 41.29 Example 2 p-Cresol Light yellow solid 97.10 40.12 Example 3 o-Cresol Light yellow solid 10.54 43.50 Example 4 4-tert-Butylphenol White solid 10.56 38.27 Example 5 p-phenylphenol Light yellow solid 9.83 33.65

[0070] Table 2

[0071]

[0072] Table 3

[0073]

[0074] Table 4

[0075]

[0076] Table 5

[0077]

[0078] 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 catalyst for isomerizing branched unsaturated fatty nitrile to linear products, the catalyst being represented by general formula II: in, is the structural formula of P5DP-X, L is phosphorus ligand 1; The catalyst comprises components P5DP-X, phosphorus ligand 1 and zero-valent metal Ni, wherein the molar ratio of P5DP-X:phosphorus ligand 1:Ni(0) is 1:2-20:0.5-5; The P5DP-X is a pillararene phosphite derivative, and its structure is shown in the following general formula I: As shown in the general formula I, P5DP-X consists of two parts, a pillar aromatic hydrocarbon part and a phosphorus-containing substituent part, wherein the pillar aromatic hydrocarbon part is a methoxy-substituted pillar [5] aromatic hydrocarbon, and the phosphorus-containing substituent part is a structure of -OP(X)2, wherein X is selected from one of o-methylphenoxy, m-methylphenoxy, p-methylphenoxy, o-ethylphenoxy, m-ethylphenoxy, p-ethylphenoxy, p-isopropylphenoxy, p-tert-butylphenoxy, 2,4-di-tert-butylphenoxy, o-phenylphenoxy, p-phenylphenoxy, 1-naphthyloxy, 2-naphthyloxy, 2,6-dimethylphenoxy, and 2,4,6-trimethylphenoxy; The phosphorus ligand 1 is one of triethyl phosphite, triphenyl phosphite, tri-p-cresyl phosphite, tri-m-cresyl phosphite, tri-o-cresyl phosphite, and tri-p-tert-butylphenyl phosphite.

2. The catalyst according to claim 1, characterized in that The molar ratio of P5DP-X:phosphorus ligand 1:Ni(0) in the catalyst is 1:2-10:1-4.

3. The catalyst according to claim 1, characterized in that The molar ratio of P5DP-X:phosphorus ligand 1:Ni(0) in the catalyst is 1:6:

2.

4. The catalyst according to claim 1, characterized in that The X is o-methylphenoxy, m-methylphenoxy, p-methylphenoxy, p-tert-butylphenoxy or p-phenylphenoxy.

5. A method for preparing a catalyst according to any one of claims 1 to 4, comprising adding P5DP-X and nickel powder to an organic solvent, mixing them, and reacting them at a certain temperature. Then, phosphorus ligand 1 is added, the reaction is continued for a period of time, and the mixture is filtered to remove insoluble matter. The filter cake is washed with the same organic solvent, the filtrates are combined, and the mixture is concentrated to obtain the target catalyst.

6. The preparation method according to claim 5, characterized in that The reaction temperature is 95-160°C.

7. The preparation method according to claim 6, characterized in that The reaction temperature is 120-140°C.

8. The preparation method according to claim 5, characterized in that The reaction time of P5DP-X and nickel powder is 1-4 hours; the reaction time after adding phosphorus ligand 1 is continued for 2-10 hours.

9. The preparation method according to claim 8, characterized in that The reaction time of P5DP-X and nickel powder is 1-3 hours; the reaction time after adding phosphorus ligand 1 is continued for 4-8 hours.

10. The preparation method according to claim 5, characterized in that The organic solvent is one or more of 3PN, 2M3BN, a mixture of 3PN and 2M3BN, xylene, toluene, dimethylformamide, diethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, and sulfolane; the amount of the organic solvent is 2-5 times the mass of P5DP-X.

11. The preparation method according to claim 10, characterized in that: The organic solvent is selected from 3PN, 2M3BN, and a mixture of 3PN and 2M3BN.

12. Use of the catalyst according to any one of claims 1 to 4 in catalyzing the isomerization of branched unsaturated fatty nitriles to linear products.

13. The use according to claim 12, characterized in that The use is the use of the catalyst in catalyzing the isomerization of 2M3BN to 3PN.

14. A method for isomerizing branched unsaturated fatty nitrile, comprising: In a reactor, a substrate containing 2M3BN, a catalyst according to any one of claims 1 to 4, a phosphorus ligand 2, and a Lewis acid are mixed to form a reaction system, and the reaction is carried out at a certain temperature and pressure. After the reaction reaches an end point, unreacted 2M3BN and 3PN are separated by distillation, and the remaining bottom liquid is mainly a catalyst solution, which is taken out and recycled; The substrate containing 2M3BN is a mixture of 2M3BN, 3PN and 2M3BN, wherein the source of 2M3BN is the by-product 2M3BN generated by the primary hydrocyanation of butadiene, or commercially available 2M3BN; The phosphorus ligand 2 is one or more of triethyl phosphite, triphenyl phosphite, tri-p-cresyl phosphite, tri-m-cresyl phosphite, and tri-o-cresyl phosphite; The Lewis acid is one of aluminum chloride, zinc chloride, triphenylboron, ferric chloride, copper chloride, ferric sulfate, nickel sulfate, nickel chloride, and cobalt acetate.

15. The isomerization method according to claim 14, characterized in that: The Lewis acid is zinc chloride.

16. The isomerization method according to claim 14, characterized in that: The mass ratio of the substrate containing 2M3BN, the catalyst, the phosphorus ligand 2, and the Lewis acid is 30-1000:2:5-100:1-50.

17. The isomerization method according to claim 16, characterized in that: The mass ratio of the substrate containing 2M3BN, the catalyst, the phosphorus ligand 2, and the Lewis acid is 350-400:2:10:

2.

18. The isomerization method according to claim 14, characterized in that: The reaction system contains a solvent or does not contain a solvent. The selected solvents include one or more of 2M3BN itself, xylene, toluene, dimethylformamide, diethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, and cyclobutane sulfone.

19. The isomerization method according to claim 18, characterized in that The solvent is 2M3BN, or a mixture of 3PN and 2M3BN.

20. The isomerization method according to claim 14, characterized in that The reaction temperature is 40-200°C.

21. The isomerization method according to claim 20, characterized in that The reaction temperature is 90-110°C.

22. The isomerization method according to claim 14, characterized in that: The reaction time is 2-10 hours.

23. The isomerization method according to claim 14, characterized in that The reaction time is 4-8 hours.

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