Diphosphine ligand modified rhodium catalyst as well as preparation method and application thereof

Abstract

The invention provides a diphosphine ligand modified rhodium catalyst as well as a preparation method and application thereof, and relates to the technical field of catalysts. The rhodium catalyst modified by the diphosphine ligand comprises an active metal component and a diphosphine ligand subjected to antioxidant modification treatment, the active metal component is Rh, and the diphosphine ligand is one or more of 2, 2 '-bis (diphenylphosphine) biphenyl, 1, 1'-binaphthyl-2, 2 '-diphenylphosphine, 4, 5-bis (diphenylphosphine-9, 9-dimethyl xanthene or (S)-DTBM-SEGPHOS. A large-steric-hindrance diphosphine ligand is selected to inhibit generation of side reactions and improve selectivity of glycolaldehyde through steric hindrance, coordination configurations of formaldehyde and CO are limited through a stereo effect, linear insertion of a C-C bond is promoted to generate glycolaldehyde, the diphosphine ligand subjected to antioxidant modification treatment can further enhance oxidation resistance of a ligand framework, and the selectivity of glycolaldehyde is improved. The thermal stability is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and more specifically, to a rhodium catalyst modified with a bisphosphine ligand, its preparation method and application. Background Art

[0002] Glycolaldehyde (HOCH2CHO) is an important chemical raw material, which is widely used in the fields of pharmaceuticals, fragrances and biobased materials. The ribose formed by its reaction with acrolein is a very important molecule in the origin of life. Glycolaldehyde can also be hydrogenated to produce the important chemical raw material ethylene glycol. In the food industry, glycolaldehyde can act as a good browning reagent and is an excellent browning promoter for food coloring, seasonings, flavors, etc.

[0003] The hydroformylation of formaldehyde is an important route for the production of glycolaldehyde and also an important intermediate step for the direct synthesis of ethylene glycol from syngas. The catalysts for the hydroformylation of formaldehyde reported so far are mainly Co-based, Ru-based and Rh-based homogeneous catalysts. Among them, the Rh catalyst has been widely studied due to its best activity. In 1977, Monsanto reported in patent EP0002908A that the hydroformylation of formaldehyde can be achieved under relatively mild conditions using bis(triphenylphosphine)rhodium(I) chloride carbonyl.

[0004] The existing rhodium catalysts modified with bisphosphine ligands have problems of poor thermal stability and poor selectivity. At high temperatures (for example, above 150 °C), the existing bisphosphine ligands are easily oxidized or decomposed, and by-products (ethylene glycol, formic acid, paraformaldehyde, etc.) are easily generated, resulting in the aggregation and inactivation of rhodium metal. Therefore, it is very necessary to develop a hydroformylation catalyst for formaldehyde with high thermal stability and high selectivity. Summary of the Invention

[0005] In order to solve the above problems, the present application provides a rhodium catalyst modified with a bisphosphine ligand, which solves the problems of poor thermal stability and poor selectivity of the existing hydroformylation catalysts for formaldehyde.

[0006] In the first aspect of the present application, a rhodium catalyst modified with a bisphosphine ligand is provided. The rhodium catalyst modified with a bisphosphine ligand includes an active metal component and a bisphosphine ligand subjected to antioxidant modification treatment. The active metal component is Rh, and the bisphosphine ligand is one or more of 2,2'-bis(diphenylphosphino)biphenyl (abbreviation: BIPHEP), 1,1'-binaphthalene-2,2'-bis(diphenylphosphine) (abbreviation: BINAP), 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (abbreviation: Xantphos) or (S)-DTBM-SEGPHOS.

[0007] Specifically, the structural formula of (S)-DTBM-SEGPHOS is , In the present invention, a bulky phosphine ligand is selected to suppress the generation of side reactions through steric hindrance and improve the selectivity of glycolaldehyde. The bulky group can protect the rhodium metal center through a steric shielding effect, reduce the deactivation caused by metal aggregation or excessive coordination with reactants at high temperatures, and limit the coordination configuration of formaldehyde and CO through a steric effect, promoting the linear insertion of the C-C bond to generate glycolaldehyde instead of the branched-chain insertion to form formate or condensation by-products. Moreover, the phosphine ligand treated by antioxidant modification can further enhance the oxidation resistance of the ligand backbone, reduce the oxidative decomposition of the phosphine group (P-C bond) at high temperatures, and further improve the thermal stability.

[0008] Optionally, the active metal component accounts for 0.1-5 wt% of the total mass of the rhodium catalyst modified with the phosphine ligand. Optionally, the active metal component accounts for 0.1 wt%, 0.2 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt% or any value and range therebetween of the total mass of the rhodium catalyst modified with the phosphine ligand.

[0009] Optionally, the preparation method of the phosphine ligand treated by antioxidant modification includes the following steps: S1: Under an inert atmosphere, dissolve the phosphine ligand in an anhydrous solvent, and then add n-butyllithium (n-BuLi) to generate a dilithiated intermediate. Optionally, the inert atmosphere can be nitrogen or argon.

[0010] S2: Dissolve pentafluorophenyl bromide (C6F5Br) in an anhydrous solvent, and then add it to the dilithiated intermediate solution obtained in step S1 for reaction. After extraction, concentration under reduced pressure, and purification in sequence, a phosphine ligand treated by antioxidant modification is obtained.

[0011] After introducing a fluoroaromatic ring onto the phosphine ligand treated by antioxidant modification, the high bond energy of the C-F bond (~485 kJ / mol) can significantly enhance the oxidation resistance of the ligand backbone, reduce the oxidative decomposition of the phosphine group (P-C bond) at high temperatures. The hydrophobicity of the fluoroaromatic ring can reduce the attack of water molecules on the rhodium metal center. At the same time, the rigid structure of the fluoroaromatic ring can inhibit molecular vibration at high temperatures and delay thermal degradation. In addition, during the production of glycolaldehyde by the hydroformylation of formaldehyde, the strong electron-withdrawing effect of the fluoroaromatic ring can reduce the electron density of the rhodium center, weaken the π-backbonding orbital feedback of CO, thereby accelerating the CO insertion step and inhibiting excessive hydrogenation, reducing the production of by-products, and improving the selectivity of glycolaldehyde.

[0012] Optionally, the molar ratio of the phosphine ligand, n-butyllithium, and pentafluorophenyl bromide is 1:(2-4):(2-4). Optionally, the molar ratio of the phosphine ligand, n-butyllithium, and C6F5Br is 1:(2-3):(2-3).

[0013] Optionally, the anhydrous solvent can be anhydrous tetrahydrofuran.

[0014] Optionally, the method for preparing the antioxidant-modified diphosphine ligand further comprises the following steps: S01: Dissolve the diphosphine ligand, bis(pinacolato)diboron (B2pin2), and a palladium catalyst in a solvent, and react at a certain temperature to obtain a mono-borate-esterified diphosphine ligand; S02: Dissolve the mono-borate-esterified diphosphine ligand, 4-(trifluoromethyl)phenylboronic acid (4-CF3-phenylboronic acid), a strong base, and a palladium catalyst in a solvent, and react at a certain temperature to obtain a diphosphine ligand-CF3.

[0015] Before introducing the fluoroaromatic ring, introducing a -CF3 group onto one aromatic ring of the diphosphine ligand through Suzuki coupling first, and then performing a fluorination reaction on the other aromatic ring using a strong nucleophile (n-BuLi) can ensure the normal progress of the subsequent fluorination reaction. At the same time, introducing an electron-withdrawing group -CF3 onto the diphosphine ligand using 4-(trifluoromethyl)phenylboronic acid can reduce the electron density of the Rh metal center, slow down over-hydrogenation, further slow down the formation of by-products, and improve the selectivity of glycolaldehyde.

[0016] Optionally, the molar ratio of the diphosphine ligand to bis(pinacolato)diboron is 1:(1.5 - 4). Optionally, the molar ratio of the diphosphine ligand to bis(pinacolato)diboron is 1:(2 - 3).

[0017] Optionally, the molar ratio of the mono-borate-esterified diphosphine ligand, 4-CF3-phenylboronic acid, and the strong base is 1:(1.2 - 3):(4 - 6). Optionally, the molar ratio of the mono-borate-esterified diphosphine ligand, 4-CF3-phenylboronic acid, and the strong base is 1:(2 - 3):(4 - 5).

[0018] Optionally, the palladium catalyst is one or more of palladium acetate, tetrakis(triphenylphosphine)palladium, and dichloro-bis(triphenylphosphine)palladium.

[0019] Optionally, the strong base is one or more of sodium hydroxide, potassium hydroxide, potassium carbonate, and cesium carbonate.

[0020] Optionally, in step S01, the certain temperature is 70 - 120 °C. Optionally, in step S01, the certain temperature is 80 - 110 °C.

[0021] Optionally, in step S02, the certain temperature is 90 - 120 °C. Optionally, in step S02, the certain temperature is 110 - 120 °C.

[0022] Optionally, it further includes a mesoporous material. For example, the mesoporous material can be one or more of MCM-41, SBA-15, SiO2, and CMK-3. To improve the cyclic stability of the catalyst, the rhodium catalyst modified with a bisphosphine ligand can be immobilized on the mesoporous material.

[0023] The second aspect of the present application provides a preparation method of a rhodium catalyst modified with a bisphosphine ligand, including the following steps: Add a rhodium precursor to an organic reagent to prepare a rhodium solution with a certain concentration, then add an antioxidant-modified bisphosphine ligand, stir in an inert gas atmosphere, and then successively perform centrifugation, washing, and drying treatments to obtain a rhodium catalyst modified with a bisphosphine ligand.

[0024] Optionally, the rhodium precursor is one of Rh(acac)(CO)2, RhCl3, HRh(PPh3)2Cl, Rh(PPh3)3Cl, and HRh(PPh3)3.

[0025] Optionally, the rhodium solution with a certain concentration is a rhodium solution with a concentration of 5-15 mmol / L.

[0026] Optionally, the organic reagent is one of methanol, ethanol, acetonitrile, N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, and acetylacetone.

[0027] The third aspect of the present application provides an application of a rhodium catalyst modified with a bisphosphine ligand in the hydroformylation reaction of formaldehyde.

[0028] Optionally, in the hydroformylation reaction of formaldehyde, the raw materials are a mixed gas of formaldehyde, CO, and H2, the molar ratio of CO to H2 is 1:(1-4), the reaction temperature is 100-250 °C, and the reaction pressure is 5-10 MPa.

[0029] Compared with the prior art, the present invention has at least one of the following beneficial effects: (1) The rhodium catalyst modified with a bisphosphine ligand of the present invention suppresses the generation of side reactions and improves the selectivity of glycolaldehyde through steric hindrance by selecting a bisphosphine ligand with a large steric hindrance, and restricts the coordination configuration of formaldehyde and CO through the steric effect, promoting the linear insertion of the C-C bond to generate glycolaldehyde. Moreover, the bisphosphine ligand treated with antioxidant modification can further enhance the oxidation resistance of the ligand skeleton and improve the thermal stability.

[0030] (2) After introducing a fluoroaromatic ring on the bisphosphine ligand treated with antioxidant modification of the present invention, the oxidation resistance of the ligand skeleton can be enhanced and the thermal stability can be improved. In addition, during the production of glycolaldehyde by the hydroformylation reaction of formaldehyde, the strong electron-withdrawing effect of the fluoroaromatic ring can reduce the electron density of the rhodium center, weaken the π-backbonding orbital feedback effect of CO, thereby accelerating the CO insertion step and suppressing over-hydrogenation, reducing the production of by-products, and improving the selectivity of glycolaldehyde.

[0031] (3) Before the fluorination reaction of the present invention, a -CF3 group is introduced onto one aromatic ring of the bisphosphine ligand through Suzuki coupling first, which can reduce the electron density of the Rh metal center, slow down the over-hydrogenation, and further slow down the formation of by-products to improve the selectivity of glycolaldehyde. Specific Embodiments

[0032] For a clearer explanation of the overall concept of the present invention, it will be described in detail by way of examples below.

[0033] Many specific details are set forth in the following description in order to fully understand the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0034] Example 1 In an exemplary embodiment of the present invention, the preparation method of the rhodium catalyst modified with bisphosphine ligand comprises the following steps: S1: Under a nitrogen atmosphere, dissolve 651 g of BINAP (1 mol) in 5 L of anhydrous THF, cool to -78 °C, and then slowly dropwise add 1.96 L of 1.6 M n-BuLi (3.136 mol), and stir for 30 min to generate a dilithiated intermediate.

[0035] S2: Dropwise add 775 g of C6F5Br (3.138 mol), slowly warm up to room temperature, stir for 12 h, then add 1 L of saturated ammonium chloride to quench the reaction, extract with ethyl acetate, combine the organic phases, concentrate under reduced pressure, and then purify by silica gel column chromatography to obtain BINAP-(C6F5)2. The reaction general formulas involved in steps S1 and S2 are shown as follows: BINAP + C6F5Br + n-BuLi → BINAP-(C6F5)2 + LiBr + C4H 10 S3: Dissolve 2.03 g of RhCl3 (0.0097 mol) in 970 mL of anhydrous ethanol to prepare a rhodium solution of 10 mmol / L, then add 997 g of BINAP-(C6F5)2 to the rhodium solution, stir at room temperature for 6 h under a nitrogen atmosphere, introduce H2 for 2 hours for reduction reaction, and then successively carry out centrifugation, washing, and drying treatments to obtain the rhodium catalyst modified with bisphosphine ligand, and Rh accounts for 0.1 wt% in the total mass of the rhodium catalyst modified with bisphosphine ligand.

[0036] Example 2 In an exemplary embodiment of the present invention, the preparation method of the rhodium catalyst modified with bisphosphine ligand comprises the following steps: S1: Under a nitrogen atmosphere, dissolve 631.3 g of BINAP in 5 L of anhydrous THF, cool to -78 °C, and then slowly add dropwise 1.267 L of 1.6 M n-BuLi (2.028 mol). Stir for 30 min to form a dilithiated intermediate.

[0037] S2: Add dropwise 751.3 g of C6F5Br (3.042 mol), slowly warm up to room temperature, stir for 12 h, then add 1 L of saturated ammonium chloride to quench the reaction. Extract with ethyl acetate, combine the organic phases, concentrate under reduced pressure, and then purify by silica gel column chromatography to obtain BINAP-(C6F5)3. The reaction general formula involved in steps S1 and S2 is as follows: BINAP + C6F5Br + n-BuLi → BINAP-(C6F5)3 + LiBr + C4H 10 S3: Dissolve 75.5 g of Rh(acac)(CO)2 (0.2915 mol) in 19.43 L of anhydrous tetrahydrofuran to prepare a rhodium solution of 15 mmol / L. Then add 970 g of BINAP-(C6F5)3 to the rhodium solution, stir at room temperature for 8 h under a nitrogen atmosphere, and then successively perform centrifugation, washing, and drying treatments to obtain a rhodium catalyst modified with a diphosphine ligand. Rh accounts for 3 wt% in the total mass of the rhodium catalyst modified with the diphosphine ligand.

[0038] Example 3 In an exemplary embodiment of the present invention, the preparation method of the rhodium catalyst modified with a diphosphine ligand includes the following steps: S1: Under a nitrogen atmosphere, dissolve 325.5 g of BINAP in 3 L of anhydrous tetrahydrofuran, cool to -78 °C, and then slowly add dropwise 654 mL of 1.6 M n-BuLi (1.046 mol). Stir for 30 min to form a dilithiated intermediate.

[0039] S2: Add dropwise 258.3 g of C6F5Br (1.046 mol), slowly warm up to room temperature, stir for 12 h, then add 500 ml of saturated ammonium chloride to quench the reaction. Extract with ethyl acetate, combine the organic phases, concentrate under reduced pressure, and then purify by silica gel column chromatography to obtain BINAP-(C6F5)2. The reaction general formula involved in steps S1 and S2 is as follows: BINAP + C6F5Br + n-BuLi → BINAP-(C6F5)2 + LiBr + C4H 10 S3: Dissolve 453.3 g of Rh(PPh3)3Cl (0.485 mol) in 48.5 L of methanol to prepare a rhodium solution with a concentration of 10 mmol / L. Then add 546.7 g of BINAP-(C6F5)2 to the rhodium solution, stir at room temperature for 12 h under a nitrogen atmosphere, and then successively perform centrifugation, washing, and vacuum drying to obtain a rhodium catalyst modified with a diphosphine ligand. Rh accounts for 5 wt% in the total mass of the rhodium catalyst modified with the diphosphine ligand.

[0040] Example 4 In an exemplary embodiment of the present invention, the preparation method of the rhodium catalyst modified with a diphosphine ligand includes the following steps: S1: Under a nitrogen atmosphere, dissolve 277.4 g of BIPHEP in 3 L of anhydrous tetrahydrofuran, cool to -78 °C, and then slowly dropwise add 595 mL of 1.6 M n-BuLi (0.952 mol), and stir for 30 min to generate a dilithiated intermediate.

[0041] S2: Dropwise add 235.2 g of C6F5Br (0.952 mol), slowly warm up to room temperature, stir for 12 h, then add 500 ml of saturated ammonium chloride to quench the reaction, extract with ethyl acetate, combine the organic phases, concentrate under reduced pressure, and then purify by silica gel column chromatography (petroleum ether / ethyl acetate volume ratio 10:1) to obtain BIPHEP-(C6F5)2. The reaction general formulas involved in steps S1 and S2 are shown as follows: BIPHEP + n-BuLi + C6F5Br → BIPHEP-(C6F5)2 + LiBr + C4H 10 S3: Dissolve 123.6 g of rhodium dicarbonyl acetylacetonate Rh(PPh3)3Cl (0.477 mol) in 47.7 L of anhydrous N,N-dimethylformamide to prepare a rhodium solution with a concentration of 10 mmol / L. Then add 722.4 g of BIPHEP-(C6F5)2 to the rhodium solution, heat to 50 °C and stir for 10 h under a nitrogen atmosphere, and then successively perform centrifugation, washing, and vacuum drying to obtain 1 kg of a rhodium catalyst modified with a diphosphine ligand. Rh accounts for 5 wt% in the total mass of the rhodium catalyst modified with the diphosphine ligand.

[0042] Example 5 In an exemplary embodiment of the present invention, the preparation method of the rhodium catalyst modified with a diphosphine ligand includes the following steps: S1: Under a nitrogen atmosphere, dissolve 282.5 g of Xantphos in 3 L of anhydrous tetrahydrofuran, cool to -78 °C, and then slowly dropwise add 555 mL of 1.6 M n-BuLi (0.888 mol), and stir for 30 min to generate a dilithiated intermediate.

[0043] S2: Add 219.3 g of C6F5Br (0.888 mol), slowly warm up to room temperature, stir for 12 h, then add 500 ml of saturated ammonium chloride to quench the reaction, extract with ethyl acetate, combine the organic phases, concentrate under reduced pressure, and then purify by silica gel column chromatography (petroleum ether / ethyl acetate volume ratio 10:1) to obtain Xantphos-(C6F5)2. The reaction general formulas involved in Steps S1 and S2 are as follows: Xantphos + n-BuLi + C6F5Br → Xantphos-(C6F5)2 + LiBr + C4H 10 S3: Dissolve 123.5 g of rhodium(III) acetylacetonate tris(triphenylphosphine) Rh(PPh3)3Cl (0.477 mol) in 47.7 L of anhydrous N,N-dimethylformamide to prepare a rhodium solution of 10 mmol / L, then add 717.5 g of Xantphos-(C6F5)2 to the rhodium solution, heat to 50 °C and stir for 10 h under a nitrogen atmosphere, and then successively perform centrifugation, washing, and vacuum drying treatments to obtain 1 kg of a rhodium catalyst modified with a diphosphine ligand, and Rh accounts for 5 wt% in the total mass of the rhodium catalyst modified with the diphosphine ligand.

[0044] Example 6 In an exemplary embodiment of the present invention, the preparation method of the rhodium catalyst modified with a diphosphine ligand includes the following steps: S01: Dissolve 138.2 g of BINAP (0.22 mol) and 112.9 g of bis(pinacolato)diboron (B2pin2) (0.44 mol) in 2 L of toluene, add 8.05 g of Pd(dppf)Cl2, and reflux at 110 °C for 12 hours to obtain a mono-borylated diphosphine ligand.

[0045] S02: Then add 88.8 g of 4-CF3-phenylboronic acid (0.43 mol) and 35.5 g of NaOH (dissolved in 0.5 L of water), continue to reflux for 24 hours, separate the liquid, wash the organic phase with saturated brine, dry, concentrate under reduced pressure, and purify by column chromatography to obtain BINAP-CF3.

[0046] S1: Under a nitrogen atmosphere, dissolve 179.9 g of BINAP-CF3 in 1.5 L of anhydrous tetrahydrofuran, cool to -78 °C, and then slowly add dropwise 278 mL of 1.6 M n-BuLi (0.444 mol), stir for 30 min to generate a dilithiated intermediate.

[0047] S2: Add 109.6 g of C6F5Br (0.444 mol), slowly warm up to room temperature, stir for 12 h, then add 500 ml of saturated ammonium chloride to quench the reaction, extract with ethyl acetate, combine the organic phases, concentrate under reduced pressure, and then purify by silica gel column chromatography to obtain BINAP-CF3-(C6F5)2.

[0048] S3: Dissolve 238.1 g of Rh(PPh3)3Cl (0.255 mol) in 25.5 L of anhydrous methanol to prepare a rhodium solution with a concentration of 10 mmol / L. Then add 761.9 g of BINAP-CF3-(C6F5)2 to the rhodium solution, stir at room temperature for 12 h under a nitrogen atmosphere, and then successively perform centrifugation, washing, and vacuum drying to obtain a rhodium catalyst modified with a diphosphine ligand. Rh accounts for 5 wt% in the total mass of the rhodium catalyst modified with the diphosphine ligand.

[0049] Example 7 S01: Dissolve 283.0 g of BIPHEP and 370.3 g of B2pin2 in 3 L of toluene, add 17.8 g of Pd(dppf)Cl2, and reflux at 110 °C for 12 h to obtain a mono-borylated diphosphine ligand.

[0050] S02: Then add 291.6 g of 4-CF3-phenylboronic acid and 633.5 g of cesium carbonate (dissolved in 0.75 L of water), continue to reflux for 24 h, separate the layers, wash the organic phase with saturated brine, dry, concentrate under reduced pressure, and purify by column chromatography to obtain BIPHEP-CF3.

[0051] S1: Under a nitrogen atmosphere, dissolve 316 g of BIPHEP-CF3 in 2 L of anhydrous tetrahydrofuran, cool to -78 °C, and then slowly add 607.5 mL of 1.6 M n-BuLi (0.972 mol), stir for 30 min to generate a dilithiated intermediate.

[0052] S2: Add 240 g of C6F5Br (0.972 mol), slowly warm up to room temperature, stir for 12 h, then add 500 ml of saturated ammonium chloride to quench the reaction, extract with ethyl acetate, combine the organic phases, concentrate under reduced pressure, and then purify by silica gel column chromatography to obtain BIPHEP-CF3-(C6F5)2.

[0053] S3: Dissolve 454 g of Rh(PPh3)3Cl (0.486 mol) in 48.6 L of anhydrous methanol to prepare a rhodium solution with a concentration of 10 mmol / L. Then add 546 g of BIPHEP-CF3-(C6F5)2 to the rhodium solution, stir at room temperature for 20 h under a nitrogen atmosphere, and then successively perform centrifugation, washing, and vacuum drying treatments to obtain a rhodium catalyst modified with a bisphosphine ligand. Rh accounts for 5 wt% in the total mass of the rhodium catalyst modified with the bisphosphine ligand.

[0054] Example 8 On the basis of Example 7, the main difference is that the bisphosphine ligand BIPHEP is replaced by Xantphos, and the other steps are similar to those in Example 7.

[0055] Example 9 On the basis of Example 1, the main difference is that the active metal component accounts for 0.05 wt% in the total mass of the rhodium catalyst modified with the bisphosphine ligand.

[0056] Comparative Example 1 On the basis of Example 1, the main difference is that the bisphosphine ligand is not subjected to antioxidant modification treatment.

[0057] Comparative Example 2 On the basis of Example 1, the main difference is that the bisphosphine ligand is bis(diphenylphosphino)methane.

[0058] Test Example: Apply the catalysts prepared in the above examples and comparative examples to the hydroformylation reaction of formaldehyde: Add the catalysts prepared in the examples and comparative examples to a reaction kettle, add the solvent DMF, then pump in an aqueous formaldehyde solution (concentration 40%), introduce a CO and H2 mixed gas, with a molar ratio of CO to H2 of 1:2, a reaction temperature of 240 °C, a reaction pressure of 5 MPa, and a stirring speed of 800 rpm. After the product is cooled, it is analyzed by gas chromatography, and the results are shown in Table 1.

[0059] Table 1

[0060] As shown in Table 1, when the rhodium catalyst modified with the bisphosphine ligand prepared by the present invention is applied to the production of glycolaldehyde by hydroformylation of formaldehyde, at high temperatures (above 200 °C), the conversion rate of formaldehyde is not less than 40%, and the selectivity of glycolaldehyde is not less than 35%. It is proved that the rhodium catalyst modified with the bisphosphine ligand has good high-temperature stability and high selectivity.

[0061] Compared with Example 1, the main difference in Comparative Example 1 is that the bisphosphine ligand is not subjected to antioxidant modification treatment. At high temperatures, the bisphosphine ligand undergoes oxidation and decomposition, resulting in the aggregation and inactivation of rhodium metal.

[0062] The above are only embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the scope of the claims of the present invention.

Claims

1. A rhodium catalyst modified with a diphosphine ligand, characterized in that, The rhodium catalyst modified with a bisphosphine ligand comprises an active metal component and a bisphosphine ligand subjected to antioxidant modification treatment. The active metal component is Rh, and the bisphosphine ligand is one or more of 2,2'-bis(diphenylphosphino)biphenyl, 1,1'-binaphthalene-2,2'-bis(diphenylphosphine), 4,5-bis(diphenylphosphino)-9,9-dimethyloxanthrene, or (S)-DTBM-SEGPHOS.

2. The rhodium catalyst modified with a diphosphine ligand according to claim 1, characterized in that, The active metal component accounts for 0.1-5 wt% of the total mass of the rhodium catalyst modified with a bisphosphine ligand.

3. The rhodium catalyst modified with a diphosphine ligand according to claim 1, characterized in that, The preparation method of the bisphosphine ligand subjected to antioxidant modification treatment comprises the following steps: S1: Under an inert atmosphere, dissolve the bisphosphine ligand in an anhydrous solvent, and then add n-butyllithium to generate a dilithiated intermediate. S2: Dissolve pentafluorophenyl bromide in an anhydrous solvent, and then add it to the dilithiated intermediate solution obtained in step S1 for reaction. After extraction, concentration under reduced pressure, and purification in sequence, a bisphosphine ligand subjected to antioxidant modification treatment is obtained.

4. The rhodium catalyst modified with a diphosphine ligand according to claim 3, characterized in that, The molar ratio of the bisphosphine ligand, n-butyllithium, and pentafluorophenyl bromide is 1:(2-4):(2-4).

5. The rhodium catalyst modified with a diphosphine ligand according to claim 3, wherein The preparation method of the bisphosphine ligand subjected to antioxidant modification treatment further comprises the following steps: S01: Dissolve the bisphosphine ligand, bis(pinacolato)diboron, and a palladium catalyst in a solvent, and react at a certain temperature to obtain a mono-borylated bisphosphine ligand. S02: Dissolve the mono-borylated bisphosphine ligand, 4-CF3-phenylboronic acid, a strong base, and a palladium catalyst in a solvent, and react at a certain temperature to obtain a bisphosphine ligand-CF3.

6. The rhodium catalyst modified with a diphosphine ligand according to claim 5, wherein The molar ratio of the bisphosphine ligand to bis(pinacolato)diboron is 1:(1.5-4); and / or the molar ratio of the mono-borylated bisphosphine ligand, 4-CF3-phenylboronic acid, and the strong base is 1:(1.2-3):(4-6).

7. The rhodium catalyst modified with a diphosphine ligand according to claim 5, wherein The palladium catalyst is one or more of palladium acetate, tetrakis(triphenylphosphine)palladium, and dichloro-bis(triphenylphosphine)palladium; and / or the strong base is one or more of sodium hydroxide, potassium hydroxide, potassium carbonate, and cesium carbonate.

8. A method for preparing a rhodium catalyst modified with a diphosphine ligand according to any one of claims 1-7, characterized in that, The preparation method comprises the following steps: Add a rhodium precursor to an organic reagent to prepare a rhodium solution with a certain concentration, then add a bisphosphine ligand subjected to antioxidant modification treatment, stir under an inert gas atmosphere, and then successively perform centrifugation, washing, and drying treatments to obtain a rhodium catalyst modified with a bisphosphine ligand.

9. The preparation method according to claim 8, characterized in that, The rhodium precursor is one of Rh(acac)(CO)2, RhCl3, HRh(PPh3)2Cl, Rh(PPh3)3Cl, and HRh(PPh3)3.

10. Use of a rhodium catalyst modified with a bisphosphine ligand according to any one of claims 1-7 in the hydroformylation reaction of formaldehyde.

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