Diphosphine ligand and preparation method thereof, catalyst composition for hydrogen esterification reaction, and preparation method of organic carboxylic ester

Abstract

The invention relates to the field of catalysts for hydrogen esterification reaction, and discloses a diphosphine ligand and a preparation method thereof, a catalyst composition for hydrogen esterification reaction, and a preparation method of organic carboxylic ester. The ligand has a structure as shown in a formula (I). In the formula (I), R1 and R2 are respectively and independently selected from one of methyl, ethyl, phenyl, tertiary butyl and diethylamino, and X is selected from one of-CH2-and-O-. The diphosphine ligand provided by the invention has the advantages of simple and easily available raw materials, simple and convenient synthesis method and the like, and the diphosphine ligand has excellent catalytic activity, high reaction conversion rate, high selectivity, high product yield, low production cost and higher economical efficiency and industrial application value when being used in the reaction for synthesizing organic carboxylic ester through olefin hydrogen esterification. # imgabs0 #

Description

Technical Field

[0001] The present invention relates to the field of catalysts for hydroesterification reactions, and in particular to a diphosphine ligand and a preparation method thereof, a catalyst composition for hydroesterification reactions, and a preparation method for organic carboxylic acid esters. Background Art

[0002] Organic carboxylic acid esters are an important class of organic substances, which are widely used in the fields of fine chemical products, medicine, pesticides, food additives, fragrances, coatings, paints, etc. For example, isononanoic acid esters are widely used in the cosmetics industry and feed as solvents and additives. In addition, isononanoic acid esters are also important chemical intermediates. Isononanoic acid esters can be hydrolyzed to produce isononanoic acid, which is also an important organic chemical raw material with good solubility, stability and low temperature performance. It is widely used in different fields such as coatings, lubricants, dyes and plastics.

[0003] Olefin hydroesterification is a process in which olefins, carbon monoxide and alcohols react in one step under the action of metal compounds / phosphine ligands to synthesize organic carboxylic acid esters and their derivatives with one more carbon atom than olefins. At present, the catalyst systems reported for olefin hydroesterification are mainly Rh-P, Pd-P, or Co-N catalytic systems, and the catalytic reactions include homogeneous catalysis and heterogeneous catalysis. Among them, the Pd-P catalytic system has become the most widely studied catalytic system in olefin hydroesterification due to its mild reaction conditions, excellent catalytic performance, and good substrate universality.

[0004] In the hydroesterification reaction of olefins catalyzed by the Pd-P catalytic system, the research and development of ligands plays a key role. The ligands have an important influence on the activity of the hydroesterification reaction and the selectivity of the product. At present, the phosphine ligands reported in the research mainly include monophosphine ligands and diphosphine ligands, as well as triphosphine ligands and tetraphosphine ligands that are gradually developed later. Although these ligands have high catalytic reaction activity, they are extremely unstable in the air, and the current phosphine ligands have complex synthesis methods, high costs, and poor catalytic activity. Therefore, it is urgent to develop olefin hydroesterification reaction ligands with good stability, simple synthesis methods and excellent catalytic performance. Summary of the invention

[0005] The purpose of the present invention is to overcome the problems of complex ligand synthesis method and poor catalytic activity in the olefin hydroesterification reaction catalyst in the prior art.

[0006] In order to achieve the above object, the first aspect of the present invention provides a diphosphine ligand having a structure shown in formula (I):

[0007]

[0008] Wherein, in formula (I),

[0009] R1 and R2 are each independently selected from one of methyl, ethyl, phenyl, tert-butyl and diethylamino, and X is selected from one of -CH2- and -O-.

[0010] The second aspect of the present invention provides a method for preparing the diphosphine ligand described in the first aspect, the method comprising the following steps: in the presence of a protective atmosphere,

[0011] S1: in the presence of a solvent, bringing the compound represented by formula (II) into first contact with a metal organic lithium compound to obtain an intermediate product;

[0012] S2: contacting the intermediate product with compound PClR1R2 for a second time to obtain a diphosphine ligand represented by formula (I);

[0013]

[0014] In formula (II) and compound PClR1R2, the definitions of X, R1, and R2 are the same as those of X, R1, and R2 in the first aspect.

[0015] The third aspect of the present invention provides a catalyst composition for olefin hydroesterification reaction, wherein the catalyst composition contains a metal palladium compound, a diphosphine ligand and an acidic substance;

[0016] The diphosphine ligand is the diphosphine ligand described in the first aspect.

[0017] A fourth aspect of the present invention provides a method for preparing an organic carboxylic acid ester, the method comprising:

[0018] In the presence of an organic solvent, olefins, fatty alcohols, carbon monoxide, and a catalyst composition are subjected to a hydroesterification reaction to generate an organic carboxylic acid ester;

[0019] The catalyst composition is the catalyst composition for olefin hydroesterification reaction described in the third aspect.

[0020] The diphosphine ligand provided by the present invention is used in a catalyst composition for a hydroesterification reaction, has high catalytic activity and good stability, and can improve product yield. At the same time, the diphosphine ligand has a simple preparation method, low production cost, and good application prospects.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] The diphosphine ligand provided by the present invention has the advantages of simple and readily available raw materials, a simple synthesis method, and the like. The diphosphine ligand has excellent catalytic activity in the reaction of olefin hydroesterification to synthesize organic carboxylic acid esters, high reaction conversion rate and selectivity, high product yield, low production cost, and high economic value and industrial application value. DETAILED DESCRIPTION

[0023] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0024] Unless stated otherwise, the following terms used herein have the following meanings.

[0025] In the present invention, “C 2-18 The term "olefin" refers to an olefin having a total carbon atom count of 2 to 18, such as ethylene, propylene, 1-butene, isobutylene, pentene, hexene, heptene, 1-octene, 2-octene, diisobutylene, triisobutylene, and the like.

[0026] “C 1-4 The term "fatty alcohol" refers to a fatty alcohol having 1 to 4 carbon atoms, such as methanol, ethanol, 1-propanol, isopropanol, 1-butanol, 2-butanol, isobutanol, etc.

[0027] As mentioned above, the first aspect of the present invention provides a diphosphine ligand having a structure shown in formula (I):

[0028]

[0029] Wherein, in formula (I),

[0030] R1 and R2 are each independently selected from one of methyl, ethyl, phenyl, tert-butyl and diethylamino, and X is selected from one of -CH2- and -O-.

[0031] Preferably, in formula (I), R1 and R2 are tert-butyl groups, and X is selected from one of -CH2- and -O-. The inventors have found that under the preferred conditions, the obtained diphosphine ligand has better catalytic activity when used in a catalyst composition for hydroesterification reaction.

[0032] As mentioned above, the second aspect of the present invention provides a method for preparing the diphosphine ligand described in the first aspect, the method comprising: in the presence of a protective atmosphere,

[0033] S1: in the presence of a solvent, bringing the compound represented by formula (II) into first contact with a metal organic lithium compound to obtain an intermediate product;

[0034] S2: contacting the intermediate product with compound PClR1R2 for a second time to obtain a diphosphine ligand represented by formula (I);

[0035]

[0036] In formula (II) and compound PClR1R2, the definitions of X, R1, and R2 are the same as those of X, R1, and R2 in the first aspect.

[0037] Preferably, the conditions for the first contact include: temperature of -78°C to 50°C, and reaction time of 20-120 min; the conditions for the second contact include: temperature of -78°C to 100°C, and reaction time of 1-6 h.

[0038] More preferably, the conditions for the first contact include: temperature of -20°C to 50°C, and reaction time of 20-60 min; the conditions for the second contact include: temperature of 0-50°C, and reaction time of 1-3 h.

[0039] Preferably, the metal organic lithium compound is at least one selected from methyl lithium, ethyl lithium, n-butyl lithium, tert-butyl lithium, lithium diisopropylamide, pentyl lithium, and phenyl lithium.

[0040] Preferably, the molar ratio of the compound represented by formula (II), the metal organic lithium compound and the compound PClR1R2 is 1:1.5-3:1.5-3.

[0041] Preferably, the protective atmosphere is argon.

[0042] Preferably, the amount of the solvent used is 1-10 L relative to 1 mol of the metal organic lithium compound.

[0043] Preferably, the solvent is selected from at least one of chloroform, dichloromethane, 1,2-dichloroethane, ether, tetrahydrofuran, methyl tert-butyl ether, 2-methyltetrahydrofuran, cyclopentane, n-pentane, n-hexane, cyclohexane and n-heptane.

[0044] Preferably, the method further comprises: quenching the second contacted material with a saturated aqueous ammonium chloride solution, and then sequentially performing separation, water washing, rotary evaporation, and column chromatography to obtain the diphosphine ligand represented by formula (I).

[0045] The compound represented by formula (II) described in the present invention can be synthesized or purchased according to the technical means known in the art; the present invention has no particular limitation on this.

[0046] As mentioned above, the third aspect of the present invention provides a catalyst composition for olefin hydroesterification reaction, the catalyst composition contains a metal palladium compound, a diphosphine ligand and an acidic substance;

[0047] The diphosphine ligand is the diphosphine ligand described in the first aspect.

[0048] Preferably, the metal palladium compound is selected from at least one of palladium acetate, palladium chloride, bis(triphenylphosphine)palladium dichloride, bis(acetonitrile)palladium dichloride, (1,5-cyclooctadiene)palladium dichloride, allylpalladium chloride, tetrakis(triphenylphosphine)palladium, palladium acetylacetonate, bis(dibenzylideneacetone)palladium, and tris(dibenzylideneacetone)dipalladium.

[0049] More preferably, the metal palladium compound is selected from at least one of palladium acetate, palladium chloride, allylpalladium chloride and palladium acetylacetonate.

[0050] Preferably, the molar ratio of the metal palladium compound to the diphosphine ligand calculated as palladium element is 1:0.1-200; preferably 1:1-100.

[0051] Preferably, the molar ratio of the metal palladium compound to the diphosphine ligand, calculated as palladium element, is 1:1 to 10. The inventors have found that in this preferred case, the reaction efficiency of the catalyst composition is more conducive to improving the conversion rate of the reactants.

[0052] Preferably, the acidic substance is selected from at least one of perchloric acid, sulfuric acid, phosphoric acid, hydrochloric acid, formic acid, acetic acid, oxalic acid, methanesulfonic acid, trifluoromethanesulfonic acid, tert-butanesulfonic acid, p-toluenesulfonic acid, 2-hydroxy-propane-2-sulfonic acid, 2,4,6-trimethylbenzenesulfonic acid and dodecylsulfonic acid.

[0053] Preferably, the molar ratio of the acidic substance to the metallic palladium compound calculated as palladium element is 0.1-100:1, preferably 5-80:1.

[0054] The present invention has no special requirements for the preparation method of the catalyst composition for olefin hydroesterification reaction, and those skilled in the art can adopt conventional methods in the art. Exemplarily, the various components in the catalyst composition are mixed.

[0055] Compared with the existing hydroesterification catalysts, the catalyst composition for olefin hydroesterification provided by the present invention not only improves the reaction efficiency and reduces the cost, but also increases the yield of the product, and has higher practical value.

[0056] As mentioned above, the fourth aspect of the present invention provides a method for preparing an organic carboxylic acid ester, the method comprising:

[0057] In the presence of an organic solvent, olefins, fatty alcohols, carbon monoxide, and a catalyst composition are subjected to a hydroesterification reaction to generate an organic carboxylic acid ester;

[0058] The catalyst composition is the catalyst composition for olefin hydroesterification reaction described in the third aspect.

[0059] Preferably, the conditions of the hydroesterification reaction include: reaction pressure of 1-20 MPa, reaction temperature of 50-160° C., and reaction time of 2-30 h.

[0060] More preferably, the conditions of the hydroesterification reaction include: reaction pressure of 2-10 MPa, reaction temperature of 70-130° C., and reaction time of 4-20 h.

[0061] Preferably, the molar ratio of the catalyst composition to the olefin, calculated as palladium element, is 0.00001-0.05:1.

[0062] More preferably, the molar ratio of the catalyst composition to the olefin, calculated as palladium element, is 0.0002-0.02: 1. The inventors have found that in this preferred case, the yield of the organic carboxylic acid ester is higher.

[0063] Preferably, the olefin is C 2-18 Olefins; preferably C 2-12 More preferably, the olefin is isobutylene and / or diisobutylene.

[0064] Preferably, the fatty alcohol is C 1-4 More preferably, the fatty alcohol is methanol and / or ethanol.

[0065] Preferably, the organic solvent is at least one of aliphatic alcohol, dioxane, tetrahydrofuran, ethylene glycol dimethyl ether, acetonitrile, ethyl acetate, butyl acetate, benzene, toluene, anisole, xylene, dichloromethane, chloroform and chloroform.

[0066] In the present invention, when the organic solvent for the hydroesterification reaction is a fatty alcohol, the fatty alcohol is both a reactant and a reaction solvent. Preferably, the molar ratio of the olefin to the fatty alcohol is 1:3-50. When the organic solvent for the hydroesterification reaction is an organic solvent other than a fatty alcohol, the molar ratio of the olefin to the fatty alcohol is 1:1-10.

[0067] The present invention will be described in detail below through preparation examples and test examples. In the following preparation examples and test examples, unless otherwise specified, all raw materials used are commercially available.

[0068] In the following preparation examples and embodiments, room temperature refers to a temperature condition that does not require additional heating or cooling.

[0069] The analytical instruments and methods used in the embodiments are as follows:

[0070] 400 MHz NMR spectrometer: instrument manufacturer BRUKER, model Ascend 400;

[0071] Gas chromatography-mass spectrometry: Agilent 5977B-7820A;

[0072] Gas chromatograph: Agilent 7820A;

[0073] Gas chromatography column: 0.2mm (ID) × 50m (L) capillary column, detector FID, vaporization chamber temperature 300℃, column box temperature 60℃, detector temperature 300℃, argon flow rate 0.5mL / min, hydrogen flow rate 30mL / min, air flow rate 400mL / min, injection volume 0.2μL. The conversion rate of olefins and the selectivity of products were calculated using the area normalization method. Heating program: preheat to column temperature 60℃, hold for 5min, increase from 60℃ to 260℃ at a rate of 10℃ / min, and hold for 10min.

[0074] Preparation Example 1: Preparation of diphosphine ligand A

[0075] The diphosphine ligand A was prepared according to the following synthetic route:

[0076]

[0077] (1) Preparation of 4,5-dibromo-9-fluorenone: At room temperature, 0.1 mol of 2,2',6,6'-tetrabromobiphenyl was added to a 1000 mL three-necked flask, and the flask was evacuated and filled with argon. This process was repeated three times. 300 mL of anhydrous tetrahydrofuran (THF) was added as a solvent in the argon atmosphere. The three-necked flask was then placed in a dry ice acetone bath, and 0.205 mol of a 1.6 mol / L n-butyllithium solution in n-hexane was slowly added dropwise. After the addition was complete, the temperature was raised to 0°C and the reaction was allowed to proceed for 0.5 h. The temperature was then lowered to -78°C using a dry ice acetone bath, and a 0.105 mol THF solution (150 mL) of methyl chloroformate was added to the flask. After the addition was complete, the temperature was raised to room temperature and reacted for 2 hours. A saturated aqueous solution of ammonium chloride was then added to the flask to quench the reaction. The mixture was separated and washed with water. The solvent was evaporated on a rotary evaporator and separated by column chromatography to obtain the product 4,5-dibromo-9-fluorenone (30.2 g).

[0078] (2) Preparation of 4,5-dibromo-9-fluorene: Add all 4,5-dibromo-9-fluorenone (30.2 g) into a 1000 mL three-necked flask, add 300 mL toluene as solvent, add 100 mL of hydrazine hydrate (0.1 mol) in ethanol, and then add 1.5 g of Raney nickel. After electromagnetic stirring, heat to reflux reaction in an oil bath. After two hours of reaction, monitor the completion of the reaction. Filter the reaction solution to remove the catalyst, and evaporate the filtrate to dryness on a rotary evaporator to obtain the product 4,5-dibromo-9-fluorene (28.6 g).

[0079] (3) Preparation of diphosphine ligand A: At room temperature, 28.6 g of 4,5-dibromo-9-fluorene was added to a 1000 mL three-necked flask, and the process was repeated three times. 300 mL of dry THF was added as a solvent in an argon atmosphere. The three-necked flask was then placed in a dry ice acetone bath and 0.18 mol of n-butyl lithium in n-hexane solution (1.6 mol / L) was slowly added dropwise. After the addition was complete, the temperature was raised to 0°C and reacted for 0.5 h. The temperature was then lowered to -78°C using a dry ice acetone bath. 0.18 mol of di-tert-butylphosphine chloride was added to the flask. After the addition was complete, the temperature was naturally raised to room temperature and reacted for 2 hours. Saturated aqueous ammonium chloride was added to the flask to quench the reaction. The mixture was separated and washed with water. The solvent was evaporated on a rotary evaporator and separated by column chromatography to obtain the product diphosphine ligand A (36 g).

[0080] The diphosphine ligand A prepared in the above preparation example was characterized by NMR, and the results were as follows: 1 H NMR (400MHz, CDCl3): δ = 4.12 (s, 2H), 7.33 (d, 2H), 7.16 (d, 2H), 7.06 (t, 2H), 1.06 (s, 36H); 13 C NMR (400MHz, CDCl3): δ=138.1, 142.5, 37.1, 137.9, 124.0, 130.6, 127.5, 31.0, 27.9.

[0081] Preparation Example 2: Preparation of diphosphine ligand B

[0082] The diphosphine ligand B was prepared according to the following synthetic route:

[0083]

[0084] At room temperature, 0.1 mol of 1,9-dibromodibenzofuran was added to a 1000 mL three-necked flask, and the mixture was evacuated and filled with argon gas, which was repeated three times. 300 mL of dry THF was added as a solvent in an argon atmosphere, and then the three-necked flask was placed in a dry ice acetone bath, and 0.20 mol of n-butyl lithium in n-hexane solution (1.6 mol / L) was slowly added dropwise. After the addition was completed, the temperature was raised to 0°C and reacted for 0.5 h, and then the temperature was lowered to -78°C using a dry ice acetone bath. 0.20 mol of di-tert-butylphosphine chloride was added to the flask. After the addition was completed, the temperature was naturally raised to room temperature and reacted for 2 hours. A saturated aqueous ammonium chloride solution was added to the flask to quench the reaction, and the mixture was washed with water after separation. The solvent was evaporated on a rotary evaporator, and the product diphosphine ligand B (36.8 g) was obtained by column chromatography.

[0085] The diphosphine ligand B prepared in the above preparation example was characterized by NMR, and the results were as follows: 1H NMR (400MHz, CDCl3): δ=7.59 (d, 2H), 7.38 (t, 2H), 7.36 (d, 2H), 1.06 (s, 36H); 13 C NMR (400MHz, CDCl3): δ=150.9, 110.5, 124.1, 124.8, 131.6, 118.2, 31.0, 27.9.

[0086] Example 1

[0087] In a 200mL autoclave, catalyst composition M1 (containing 0.03mmol acetylacetonate palladium, 0.12mmol diphosphorus ligand A, 0.24mmol p-toluenesulfonic acid), anhydrous methanol (900mmol), isobutylene (30mmol) were added in sequence, the autoclave was sealed, the autoclave was replaced with carbon monoxide for 3 times, and then carbon monoxide was charged until the pressure of the autoclave was 4.0MPa, the reaction temperature was controlled by a temperature controller to rise to 100°C, and the hydroesterification reaction was carried out for 12 hours to obtain methyl isovalerate product. After cooling to room temperature, the gas was slowly released, the autoclave was unloaded, and the methyl isovalerate product obtained by the reaction was qualitatively analyzed by gas chromatography-mass spectrometry, and quantitatively analyzed by gas chromatography, and the specific results are shown in Table 1.

[0088] Example 2

[0089] The hydroesterification reaction was carried out in a similar manner to Example 1, except that the catalyst composition M2 contained 0.03 mmol of palladium acetylacetonate, 0.12 mmol of diphosphorus ligand B, and 0.36 mmol of p-toluenesulfonic acid;

[0090] The remaining steps are the same as in Example 1. The specific results of product analysis are shown in Table 1.

[0091] Example 3

[0092] The hydroesterification reaction was carried out in a similar manner to Example 1, except that the catalyst composition M3 contained 0.03 mmol of palladium acetate, 0.12 mmol of diphosphorus ligand B, and 0.30 mmol of p-toluenesulfonic acid; the amount of anhydrous methanol was 1200 mmol; and the reaction temperature was controlled by a temperature controller to rise to 90°C;

[0093] The remaining steps are the same as in Example 1. The specific results of product analysis are shown in Table 1.

[0094] Example 4

[0095] The hydroesterification reaction was carried out in a similar manner to Example 1, except that the catalyst composition M4 contained 0.03 mmol of palladium acetate, 0.12 mmol of diphosphorus ligand A, and 0.60 mmol of p-toluenesulfonic acid; the amount of anhydrous methanol was 1200 mmol; and the reaction temperature was controlled by a temperature controller to rise to 90° C.;

[0096] The remaining steps are the same as in Example 1. The specific results of product analysis are shown in Table 1.

[0097] Example 5

[0098] In a 200mL autoclave, catalyst composition M5 (containing 0.06mmol acetylacetonate palladium, 0.24mmol diphosphorus ligand A, 0.60mmol p-toluenesulfonic acid), anhydrous methanol (900mmol), diisobutylene (30mmol) were added in sequence, the autoclave was sealed, the autoclave was replaced with carbon monoxide for 3 times, and then carbon monoxide was filled until the pressure of the autoclave was 4.0MPa, the reaction temperature was controlled by a temperature controller to rise to 100°C, and the hydroesterification reaction was carried out for 12 hours. After cooling to room temperature, the gas was slowly released, the autoclave was unloaded, and the methyl isononanoate obtained by the reaction was qualitatively analyzed by gas chromatography-mass spectrometry, and quantitatively analyzed by gas chromatography, and the specific results are shown in Table 1.

[0099] Example 6

[0100] The hydroesterification reaction was carried out in a similar manner to that of Example 5, except that the amount of anhydrous methanol used was 1200 mmol, the amount of diisobutylene used was 30 mmol, carbon monoxide was charged until the pressure of the reactor reached 6.0 MPa, the reaction temperature was controlled by a temperature controller to rise to 120° C., and the hydroesterification reaction was carried out for 20 hours;

[0101] The remaining steps are the same as in Example 5. The specific results of product analysis are shown in Table 1.

[0102] Comparative Example 1

[0103] The method of Example 1 was used to carry out the hydroesterification reaction, except that the composition of the catalyst composition was different. In this comparative example, the catalyst composition DM1 contained 0.03 mmol of palladium acetylacetonate, 0.12 mmol of 1,1'-binaphthyl-2,2'-bisdiphenylphosphine, and 0.24 mmol of p-toluenesulfonic acid.

[0104] The remaining steps are the same as in Example 1. The specific results of product analysis are shown in Table 1.

[0105] Comparative Example 2

[0106] The method of Example 3 was used to carry out the hydroesterification reaction, except that the composition of the catalyst composition was different. In this comparative example, the catalyst composition DM2 contained 0.03 mmol of palladium acetate, 0.12 mmol of 4,5-bis(diphenylphosphine)-9,9-dimethylxanthene, and 0.30 mmol of p-toluenesulfonic acid;

[0107] The remaining steps are the same as in Example 3. The specific results of product analysis are shown in Table 1.

[0108] Table 1

[0109]

[0110]

[0111] It can be seen from the above results that compared with catalyst composition DM1 and catalyst composition DM2, the catalyst formed by the diphosphine ligand and the metal palladium compound provided by the present invention is used in the hydroesterification reaction, has a higher conversion rate and selectivity, a high product yield, a low production cost, and has a higher economic value and industrial application value.

[0112] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A diphosphine ligand, characterized in that: The ligand has a structure shown in formula (I): Wherein, in formula (I), R1 and R2 are each independently selected from a methyl group, an ethyl group, a phenyl group, a tert-butyl group, and a diethylamino group. X is selected from -CH2- and -O-.

2. The diphosphine ligand according to claim 1, characterized in that In formula (I), R1 and R2 are tert-butyl groups, and X is selected from one of -CH2- and -O-.

3. A method for preparing the diphosphine ligand according to claim 1 or 2, characterized in that: The method comprises the following steps: in the presence of a protective atmosphere, S1: in the presence of a solvent, bringing the compound represented by formula (II) into first contact with a metal organic lithium compound to obtain an intermediate product; S2: contacting the intermediate product with compound PClR1R2 for a second time to obtain a diphosphine ligand represented by formula (I); Wherein, in formula (II) and compound PClR1R2, the definitions of X, R1, and R2 are the same as those of X, R1, and R2 in claim 1 or 2; Preferably, the conditions for the first contact include: temperature of -78°C to 50°C, reaction time of 20-120 min; the conditions for the second contact include: temperature of -78°C to 100°C, time of 1-6 h; the metal organic lithium compound is selected from at least one of methyl lithium, ethyl lithium, n-butyl lithium, tert-butyl lithium, diisopropylamine lithium, pentyl lithium, and phenyl lithium.

4. A catalyst composition for olefin hydroesterification reaction, characterized in that: The catalyst composition contains a metal palladium compound, a diphosphine ligand and an acidic substance; The diphosphine ligand is the diphosphine ligand according to claim 1 or 2.

5. The catalyst composition according to claim 4, characterized in that The metal palladium compound is selected from at least one of palladium acetate, palladium chloride, bis(triphenylphosphine)palladium dichloride, bis(acetonitrile)palladium dichloride, (1,5-cyclooctadiene)palladium dichloride, allylpalladium chloride, tetrakis(triphenylphosphine)palladium, palladium acetylacetonate, bis(dibenzylideneacetone)palladium, and tris(dibenzylideneacetone)dipalladium; Preferably, the metal palladium compound is selected from at least one of palladium acetate, palladium chloride, allyl palladium chloride, and palladium acetylacetonate; Preferably, the molar ratio of the metallic palladium compound to the diphosphine ligand calculated as palladium element is 1:0.1-200, preferably 1:1-10.

6. The catalyst composition according to claim 4 or 5, characterized in that The acidic substance is at least one selected from perchloric acid, sulfuric acid, phosphoric acid, hydrochloric acid, formic acid, acetic acid, oxalic acid, methanesulfonic acid, trifluoromethanesulfonic acid, tert-butanesulfonic acid, p-toluenesulfonic acid, 2-hydroxy-propane-2-sulfonic acid, 2,4,6-trimethylbenzenesulfonic acid and dodecylsulfonic acid; Preferably, the molar ratio of the acidic substance to the metallic palladium compound calculated as palladium element is 0.1-100:1, preferably 5-80:

1.

7. A method for preparing an organic carboxylic acid ester, characterized in that: The method includes: In the presence of an organic solvent, olefins, fatty alcohols, carbon monoxide, and a catalyst composition are subjected to a hydroesterification reaction to generate an organic carboxylic acid ester; The catalyst composition is the catalyst composition for olefin hydroesterification reaction as described in any one of claims 4 to 6.

8. The method according to claim 7, characterized in that The conditions of the hydroesterification reaction include: reaction pressure of 1-20 MPa, reaction temperature of 50-160° C., and reaction time of 2-30 h; Preferably, the conditions for the hydroesterification reaction include: reaction pressure of 2-10 MPa, reaction temperature of 70-130° C., and reaction time of 4-20 h.

9. The method according to claim 7 or 8, characterized in that: The molar ratio of the catalyst composition to the olefin, calculated on the basis of palladium element, is 0.00001-0.05:

1.

10. The method according to any one of claims 7 to 9, characterized in that: The olefin is C 2-18 Olefins; preferably C 2-12 Olefins, preferably isobutylene and / or diisobutylene; The organic solvent is at least one of aliphatic alcohol, dioxane, tetrahydrofuran, ethylene glycol dimethyl ether, acetonitrile, ethyl acetate, butyl acetate, benzene, toluene, anisole, xylene, dichloromethane, chloroform and chloroform; The fatty alcohol is C 1-4 A fatty alcohol, preferably methanol and / or ethanol; The molar ratio of the olefin to the fatty alcohol is 1:3-50.

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