Preparation of rhodium-based catalysts embedded in bisphosphine polymers and their application in the hydroformylation of olefins using CO2 as a carbonyl source

Abstract

This invention discloses the preparation of a rhodium-based catalyst embedded in a bisphosphine polymer and its application in the hydroformylation of olefins using CO2 as a carbonyl source, belonging to the field of catalytic materials technology. The catalytic material prepared by this invention exhibits good catalytic activity, chemoselectivity, and catalyst stability in the hydroformylation of olefins using CO2 as a carbonyl source, efficiently converting aromatic and aliphatic olefins with different functional groups into aldehydes with yields of 58%–89%. In the prepared catalytic material, the abundant and dispersed phosphine ligands and bisphosphine ligands within the catalyst mesopores promote the high activity and high stability of the catalyst. In summary, this invention provides a new industrial technology for the preparation of aldehydes from the hydroformylation of olefins using CO2 as a carbonyl source.

Description

Technical Field

[0001] This invention belongs to the field of catalytic materials technology, and particularly relates to a rhodium-based catalyst embedded in a bisphosphine polymer and its application in the hydroformylation reaction of olefins with CO2 as the carbonyl source. Background Technology

[0002] With the increasingly severe environmental damage caused by excessive CO2 emissions, the efficient utilization of CO2 and its conversion into high-value-added chemicals and energy-related products has attracted widespread attention. In CO2 utilization, using CO2 as a carbonyl source to replace toxic and flammable CO in carbonylation reactions opens up new avenues for obtaining carbonyl-containing compounds. Furthermore, since CO2 is much cheaper than CO, it will provide a low-cost method for synthesizing high-value-added carbonyl-containing chemicals.

[0003] Hydroformylation is the most important industrial application of carbonylation, and it is the most widely used and largest-scale carbonylation reaction in the chemical industry. Hydroformylation can easily convert olefins to aldehydes with 100% atom economy. The resulting aldehyde, as a versatile chemical intermediate, can be further derivatized into various fine chemicals such as alcohols, acids, acetals, amines, and internal alkenes through hydrogenation, oxidation, aldol condensation, reductive amination, and the Wittig reaction. However, as a widely used reaction in industry, the commonly used carbonyl source CO has the disadvantages of being flammable and toxic, which is detrimental to large-scale industrial production. Therefore, it is essential to develop a highly efficient olefin hydroformylation catalytic system to replace CO with CO2.

[0004] Currently, catalytic technologies for hydroformylation reactions using CO2 as a carbonyl source mainly focus on homogeneous catalytic systems. However, existing homogeneous catalytic systems still suffer from problems such as difficulty in effectively recovering and reusing catalysts and a limited range of applicable substrates. For heterogeneous systems, although some reports have been published in in-depth research, there are still shortcomings in controlling the chemoselectivity and substrate universality (e.g., the applicability of aromatic olefins in CO2-involved heterogeneous olefin catalytic systems).

[0005] Therefore, there is an urgent need to develop a new type of highly efficient heterogeneous catalytic material that can improve the activity and substrate versatility of hydroformylation reactions using CO2 as a carbonyl source, while also being able to be effectively recycled. Summary of the Invention

[0006] The purpose of this invention is to provide a rhodium-based catalyst embedded in a bisphosphine polymer and its preparation method.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] The preparation of rhodium-based catalysts embedded with bisphosphine ligand polymers includes the following steps:

[0009] 1) Under an inert atmosphere, the vinyl-functionalized bisphosphine ligand and the rhodium source were co-dissolved in a first organic solvent and stirred at 20~80℃ for 1~4h to obtain the coordination product;

[0010] 2) The aforementioned coordination product, vinyl-functionalized comonomer, and free radical initiator are co-dissolved in a second organic solvent and polymerized at 40-100°C for 20-25 h. After washing and vacuum drying, a rhodium-based catalyst embedded with aryl bisphosphine ligand polymer is obtained.

[0011] The vinyl-functionalized bisphosphine ligand has the following structure:

[0012] ,

[0013] Where n is a natural number between 1 and 5.

[0014] The rhodium source is rhodium trichloride trihydrate, triphenylphosphine rhodium chloride, dichloro(pentamethylcyclopentadienyl)rhodium(III) dimer, (1,5-cyclooctadiene)rhodium(I) dimer, rhodium acetate, rhodium acetylacetone, rhodium acetylacetone dicarbonyl, rhodium acetylacetone (1,5-cyclooctadiene) rhodium, triphenylmonophosphine acetylacetone carbonyl rhodium(I), or tri(triphenylmonophosphine) carbonyl hydride or tetra(triphenylphosphine) hydride rhodium(I).

[0015] The molar ratio of the vinyl-functionalized bisphosphine ligand to the rhodium source is (3~60):1.

[0016] The vinyl-functionalized comonomer is any one of the following three structures:

[0017] , or .

[0018] The free radical initiator is one of azobisisobutyronitrile, hydrogen peroxide, ammonium persulfate, potassium persulfate, benzoyl peroxide, or methyl ethyl ketone peroxide.

[0019] The molar ratio of the vinyl-functionalized comonomer to the rhodium source is (10~100):1, and the molar ratio of the vinyl-functionalized comonomer to the free radical initiator is (10~150):1.

[0020] The first organic solvent and the second organic solvent are independently one or more of ethanol, 1,4-dioxane, tetrahydrofuran, ethylene glycol dimethyl ether, ethyl acetate, N,N-dimethylformamide, dimethyl sulfoxide, n-hexane, toluene, anisole, dichloromethane, and chloroform.

[0021] The rhodium-based catalyst embedded in the bisphosphine ligand polymer prepared by the above method includes a bisphosphine ligand polymer and a metallic rhodium active component embedded in the bisphosphine ligand polymer backbone; the metallic rhodium active component forms a coordination configuration with the bisphosphine ligand.

[0022] Another object of the present invention is to provide the application of the above-mentioned rhodium-based catalyst embedded with bisphosphine ligand polymer in the hydroformylation reaction of olefins using CO2 as a carbonyl source. Specifically, under liquid-phase conditions, olefins and CO2 / H2 undergo a hydroformylation reaction under the catalysis of the above-mentioned catalyst to produce an aldehyde with one more carbon atom than the olefin.

[0023] In summary, this invention uses vinyl-functionalized bisphosphine ligands as monomers, pre-coordinates the bisphosphine ligands with active metal rhodium, and then performs free radical polymerization of the coordination product with vinyl-functionalized comonomers, embedding the rhodium metal in the bisphosphine ligand polymer in one step. The prepared catalytic material belongs to the polymer heterogeneous catalyst category. The abundant but dispersed phosphine ligands and bisphosphine ligands within the catalyst mesopores enhance the catalytic activity of the material, prevent the loss of active metal, and greatly improve the stability of the catalyst. Data shows that the catalytic material prepared by this invention exhibits excellent reaction performance (activity, chemoselectivity, substrate universality, and catalyst reusability), effectively converting aromatic and aliphatic olefins with different functional groups into aldehydes via hydroformylation with CO2 as the carbonyl source, with a maximum yield of up to 89%. Furthermore, compared with existing hydroformylation reaction systems using CO2 as the carbonyl source, the polymer catalytic material prepared by this invention has superior catalytic performance and better substrate universality, and the preparation method is simple. Attached Figure Description

[0024] Figure 1 The image shows the BET characterization of catalyst A in Example 1.

[0025] Figure 2 The image shows the TGA characterization of catalyst A in Example 1.

[0026] Figure 3 The images show the HR-TEM and EDX maps of catalyst A in Example 1. Detailed Implementation

[0027] The present invention will be further explained and described below with reference to specific embodiments.

[0028] The structures of the vinyl-functionalized bisphosphine ligands used in Examples 1-8 are as follows:

[0029] .

[0030] The structures of the vinyl-functionalized comonomers used in Examples 1-8 are as follows:

[0031] .

[0032] The above-mentioned methods for synthesizing phosphine ligands L1-L7 are described in the literature ( Org. Chem. Front. 2019, 6 (16), 2964-2967; J. Am. Chem. Soc. 2015, 137 (15), 5204-5209.; Chem. Commun. 2022, 58,8093-8096; J. Am. Chem. Soc. 2013, 135 (22), 8357-8362.).

[0033] Example 1

[0034] Preparation of rhodium-based catalyst embedded in bisphosphine ligand polymer: Under an argon atmosphere, L1 (74 mg, 0.147 mmol) and rhodium acetylacetone dicarbonyl (6.4 mg, 0.05 mmol) were dissolved in 10 mL of tetrahydrofuran and stirred at room temperature for 2 h to obtain a coordination product. Under an inert atmosphere, the coordination product, L5 (480 mg, 1.41 mmol), and the free radical initiator azobisisobutyronitrile (16.4 mg, 0.1 mmol) were added to 10 mL of tetrahydrofuran. The resulting reaction solution was transferred to a hydrothermal reactor and stirred at room temperature for 0.5 h. Then, it was heated to 100 °C in a forced-air drying oven and allowed to stand for 24 h. After the polymerization reaction was completed, the resulting pale yellow solid was filtered, washed with tetrahydrofuran (20 mL × 3), and dried under vacuum at 60 °C for 12 h to obtain a rhodium-based catalyst material embedded in bisphosphine ligand polymer, denoted as catalyst A.

[0035] Example 2

[0036] The only difference from Example 1 is that 76 mg of bisphosphine ligand L2 was weighed out instead of 74 mg of L1, and the rest was the same as in Example 1. The resulting bisphosphine ligand polymer was used to encapsulate a rhodium-based catalytic material, which was denoted as catalyst B.

[0037] Example 3

[0038] The only difference from Example 1 is that 78 mg of bisphosphine ligand L3 was weighed out to replace L1, and the rest was the same as in Example 1. The resulting bisphosphine ligand polymer was used to encapsulate a rhodium-based catalyst material, which was denoted as catalyst C.

[0039] Example 4

[0040] The only difference from Example 1 is that 72 mg of bisphosphine ligand L4 was weighed to replace L1, and the rest was the same as in Example 1. The resulting bisphosphine ligand polymer was used to encapsulate a rhodium-based catalyst material, which was denoted as catalyst D.

[0041] Example 5

[0042] The only difference from Example 1 is that 500 mg L6 was weighed instead of 480 mg L5, and the rest is the same as in Example 1. The resulting bisphosphine ligand polymer is used to encapsulate the rhodium-based catalyst material, which is denoted as catalyst E.

[0043] Example 6

[0044] The only difference from Example 1 is that 460 mg L7 was used instead of 480 mg L5, the stirring temperature during the coordination process was 60°C, and the time was 1 h. The rest was the same as in Example 1. The resulting bisphosphine ligand polymer was used to encapsulate the rhodium-based catalyst material, which was denoted as catalyst F.

[0045] Example 7

[0046] The only difference from Example 1 is that triphenylphosphine rhodium chloride is used instead of acetylacetone dicarbonyl rhodium as the active metal, and hydrogen peroxide is used instead of azobisisobutyronitrile as the free radical initiator. The rest is the same as in Example 1. The resulting bisphosphine ligand polymer encapsulates the rhodium-based catalytic material, which is denoted as catalyst G.

[0047] Example 8

[0048] The only difference from Example 1 is that rhodium chloride trihydrate, substituted for rhodium dicarbonyl chloride, is used as the active metal. During the polymerization process, the hydrothermal reactor is heated to 140°C in a forced-air drying oven and allowed to stand for 18 hours. The rest is the same as in Example 1. The resulting bisphosphine ligand polymer is used to embed rhodium-based catalyst material in situ, which is denoted as catalyst H.

[0049] The structural characterization and performance evaluation are as follows.

[0050] Structural characterization

[0051] 1. BET representation

[0052] The structural characteristics of catalyst A in Example 1 were evaluated at 77 K using a nitrogen adsorption isotherm, which showed a reversible type IV adsorption isotherm, indicating the presence of a hierarchical porous structure. According to quenched solid density functional theory (QSDFT), the pore size is mainly distributed in the range of 0.5–34 nm, which is beneficial for the encapsulation of Rh species and the diffusion of substances during the reaction.

[0053] 2. TGA characterization

[0054] TG analysis curves show that catalyst A in Example 1 exhibits excellent thermal stability at 420°C. oC loses only 3.7% of its weight at high temperatures, indicating that the catalyst has a stable chemical structure and good application potential.

[0055] 3. Characterization using HR-TEM and EDX maps

[0056] TEM images showed that catalyst A in Example 1 was porous and amorphous. Furthermore, no Rh nanoparticles were detected in the HRTEM images, indicating that Rh species were highly dispersed in the polymer. Additionally, EDX images showed a uniform distribution of C, P, and Rh elements on catalyst A in Example 1, with the presence of Rh elements indicating the formation of isolated Rh species encapsulated within the polymer.

[0057] Performance Evaluation

[0058] 1. Catalytic performance

[0059] The catalysts prepared in Examples 1-8 above were used in the hydroformylation of styrene with CO2 as the carbonyl source to illustrate the catalytic performance of different catalysts in the hydroformylation of styrene with CO2 as the carbonyl source.

[0060] 60 mg of the catalyst prepared above was added to a 100 mL reactor, along with 104 mg (1 mmol) of styrene and 4 mL of N-methylpyrrolidone. The reactor was sealed and the air in the system was replaced three times with CO2 gas until the pressure reached 3 MPa. Then, H2 was added until the pressure reached 4 MPa. The reactor was then heated to 110 °C and reacted for 24 h. After the reaction, the reactor was cooled to room temperature, and n-hexadecane was added as an internal standard. The reaction solution was analyzed by gas chromatography using an HP-7890N equipped with an HP-5 capillary column and an FID detector. The catalytic performance data of different catalysts are shown in Table 1.

[0061] Table 1 Catalytic performance of different catalysts in Examples 1-8

[0062]

[0063] As shown in Table 1, the catalyst provided by this invention has good catalytic performance for the hydroformylation of olefins with CO2 as the carbonyl source.

[0064] 2. Cyclic stability

[0065] Taking catalyst A prepared in Example 1 as an example, the reusability of the rhodium-based catalyst embedded with bisphosphine ligand polymer in the catalytic hydroformylation reaction of styrene is illustrated.

[0066] 60 mg of the catalyst prepared above was added to a 100 mL reactor, along with 104 mg (1 mmol) of styrene and 4 mL of N-methylpyrrolidone. The reactor was sealed and the air in the system was replaced three times with CO2 gas until the pressure reached 3 MPa. Then, H2 was added until the pressure reached 4 MPa. The temperature was then raised to 110 °C and the reaction proceeded for 24 h. After the reaction, the reactor was cooled to room temperature, and the solid catalyst was separated by centrifugation and washed three times each with tetrahydrofuran, water, methanol, and diethyl ether. The catalyst was then dried in a vacuum drying oven at 60 °C for 12 h and reused. Hexadecane was added to the reaction solution as an internal standard, and the analysis was performed using an HP-7890N gas chromatograph equipped with an HP-5 capillary column and an FID detector. Reaction data for catalyst reuse are shown in Table 2.

[0067] Table 2. Reusability of catalyst A in Example 1

[0068]

[0069] As can be seen from Table 2, the catalyst prepared by this invention can be reused at least eight times, and its catalytic activity can still be maintained at a high level.

[0070] 3. Adaptability

[0071] Taking catalyst A prepared in Example 1 as an example, the catalytic performance of the rhodium-based catalyst embedded with bisphosphine ligand polymer in the hydroformylation of different olefins is illustrated. The reaction process is identical to that of styrene, except that 1 mmol of a different olefin substrate is used instead of 1 mmol of styrene. The structures are shown in Table 3 below.

[0072] Table 3 Catalytic performance of catalyst A in different olefin hydroformylation reactions in Example 1

[0073]

[0074]

[0075]

[0076] As can be seen from Table 3, the catalytic materials prepared in this invention exhibit excellent catalytic activity and good applicability when applied to the hydroformylation reactions of different olefins with CO2 as the carbonyl source.

[0077] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a rhodium-based catalyst embedded in a bisphosphine polymer, characterized in that, Includes the following steps: 1) Under an inert atmosphere, the vinyl-functionalized bisphosphine ligand and the rhodium source were co-dissolved in a first organic solvent and stirred at 20~80℃ for 1~4h to obtain the coordination product; The vinyl-functionalized bisphosphine ligand has the following structure: ， Where n is a natural number between 1 and 5; 2) The aforementioned coordination product, vinyl-functionalized comonomer, and free radical initiator were co-dissolved in a second organic solvent and polymerized at 40-100°C for 20-25 h. After washing and vacuum drying, a rhodium-based catalyst embedded in an aryl bisphosphine ligand polymer was obtained. The vinyl-functionalized comonomer is any one of the following three structures: , or .

2. The method for preparing the rhodium-based catalyst embedded in the bisphosphine ligand polymer as described in claim 1, characterized in that, The rhodium source is rhodium trichloride trihydrate, triphenylphosphine rhodium chloride, dichloro(pentamethylcyclopentadienyl)rhodium(III) dimer, (1,5-cyclooctadiene)rhodium(I) dimer, rhodium acetate, rhodium acetylacetone, rhodium acetylacetone dicarbonyl, rhodium acetylacetone (1,5-cyclooctadiene) rhodium, triphenylmonophosphine acetylacetone carbonyl rhodium(I), or tri(triphenylmonophosphine) carbonyl hydride or tetra(triphenylphosphine) hydride rhodium(I).

3. The method for preparing the rhodium-based catalyst embedded in the bisphosphine ligand polymer as described in claim 1, characterized in that, The molar ratio of the vinyl-functionalized bisphosphine ligand to the rhodium source is (3~60):

1.

4. The method for preparing the rhodium-based catalyst embedded in the bisphosphine ligand polymer as described in claim 1, characterized in that, The free radical initiator is one of azobisisobutyronitrile, hydrogen peroxide, ammonium persulfate, potassium persulfate, benzoyl peroxide, or methyl ethyl ketone peroxide.

5. The method for preparing the rhodium-based catalyst embedded in the bisphosphine ligand polymer as described in claim 1, characterized in that, The molar ratio of the vinyl-functionalized comonomer to the rhodium source is (10~100):1, and the molar ratio of the vinyl-functionalized comonomer to the free radical initiator is (10~100):

1.

6. The method for preparing the rhodium-based catalyst embedded in the bisphosphine ligand polymer as described in claim 1, characterized in that, The first organic solvent and the second organic solvent are independently one or more of ethanol, 1,4-dioxane, tetrahydrofuran, ethylene glycol dimethyl ether, ethyl acetate, N,N-dimethylformamide, dimethyl sulfoxide, n-hexane, toluene, anisole, dichloromethane, and chloroform.

7. A rhodium-based catalyst embedded in a bisphosphine ligand polymer prepared by any one of claims 1-6.

8. The application of the rhodium-based catalyst embedded in the bisphosphine ligand polymer prepared by any one of claims 1-6 in the hydroformylation reaction of olefins with CO2 as the carbonyl source.

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