Composite rhodium catalyst as well as preparation method and application thereof

Abstract

The invention provides a composite rhodium catalyst and a preparation method and application thereof, and the preparation method comprises the following steps: (1) mixing a rhodium source, a phosphine ligand source and a first solvent, and carrying out a first reaction to obtain a phosphine rhodium complex; and (2) mixing the phosphine rhodium complex, the MOF-808 metal organic framework material and a second solvent to obtain a composite solution, and carrying out a second reaction on the composite solution to obtain the composite rhodium catalyst. The synthesis method of the composite rhodium catalyst is easy to operate, easy to implement and high in efficiency, the prepared catalyst can be suitable for hydroformylation reaction of styrene derivatives such as p-methoxystyrene, p-methylstyrene and halogenated styrene, the catalyst is good in stability, and after the catalyst is recycled for 6 times, the yield is high, and the yield is high. The substrate conversion rate, the product selectivity and the catalyst structure are basically kept unchanged.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of heterogeneous catalysts, and relates to a composite rhodium catalyst, a preparation method thereof and an application thereof. Background Art

[0002] The hydroformylation reaction of olefins is one of the most important homogeneous catalytic industrial processes, with an annual production scale exceeding 10 million tons. It refers to the process in which carbon monoxide and hydrogen (commonly known as syngas) react with olefins to form a mixture of branched aldehydes or / and linear aldehydes, accompanied by the occurrence of isomerization, hydrogenation by-products, etc. As is well known, aldehydes can be further derived into a variety of alcohols, acids, acetals, amines and internal olefins through hydrogenation, oxidation, reductive amination and Wittig reactions. Among them, linear aldehydes are raw materials and intermediates for bulk chemicals such as detergents and plasticizers, while branched aldehydes are raw materials and intermediates for fine chemicals such as cosmetics and pharmaceuticals. Due to the difficulty in separating linear aldehydes from branched aldehydes, it is required that the catalysts used have high activity, high chemo-selectivity and high regioselectivity. Currently, the main catalysts used in industrial hydroformylation are homogeneous catalysts based on rhodium and cobalt. Moreover, since the phosphine rhodium complex has mild reaction conditions and excellent performance, it has become the catalyst with the highest proportion used in industry since 1995. A large number of studies have shown that by regulating the electronic effect and steric effect of phosphine ligands, the chemo-selectivity and regioselectivity of the hydroformylation reaction can be greatly improved. However, homogeneous catalysts face problems such as complex process operations, difficult recovery and reuse, and easy loss of expensive rhodium. Therefore, it is very urgent to develop a heterogeneous catalyst with high activity, high chemo- and regioselectivity and high stability.

[0003] CN118751265A discloses an Rh-Co-C composite catalyst of a doped Rh ZIF-67-derived carbon material for catalyzing the hydroformylation of diisobutene to prepare isononanal, but the diisobutene substrate has no regioselectivity requirement and cannot meet the general applicability requirements of industrial substrates.

[0004] CN118652166A uses zeolite molecular sieves to confine and encapsulate rhodium or cobalt single atoms, and regulates the steric hindrance of single atoms by introducing different types of alkali metals for the selective catalytic hydroformylation reaction of propylene to synthesize n-butyraldehyde, but the required reaction pressure exceeds 6 MPa and the reaction conditions are relatively harsh.

[0005] CN118616095A discloses a catalyst with relatively high hydroformylation activity and selectivity (TOF value 1359h -1, a catalyst with an aldehyde selectivity of 99.5% and a n / i ratio of 9.5), its preparation method and application. The heterogeneous catalyst uses a porous organic polymer formed by polymerizing various monodentate or bidentate phosphine ligands containing olefin groups as a carrier. By introducing substances containing S and N into the carrier skeleton, the coordination mode of the active metal center Rh is optimized and regulated, enhancing its catalytic activity and n-butyraldehyde selectivity in the hydroformylation reaction of propylene. However, the synthesis steps of the porous organic polymer carrier are complex, and the cost of monodentate or bidentate phosphine monomers containing olefin groups is high.

[0006] The above-mentioned solutions have reported various types of heterogeneous catalysts and modification methods. However, hydroformylation is still limited to harsh reaction temperatures / pressures, low chemical / regioselectivity, and stability, and there is also a lack of in-depth understanding of the three-dimensional geometric structure of the catalyst active sites. Therefore, there is an urgent need to develop heterogeneous catalysts with high activity, high selectivity, and high stability to study their catalysis of different types of hydroformylation. Summary of the Invention

[0007] The purpose of the present invention is to provide a composite rhodium catalyst, its preparation method and application. The synthesis method of the composite rhodium catalyst of the present invention is easy to operate, easy to implement, and highly efficient. The prepared catalyst can be applied to the hydroformylation reaction of styrene derivatives, such as p-methoxystyrene, p-methylstyrene, halogenated styrene, etc. The catalyst has good stability. After being recycled 6 times, its substrate conversion rate, product selectivity, and catalyst structure basically remain unchanged.

[0008] To achieve the purpose of this invention, the present invention adopts the following technical solutions:

[0009] In the first aspect, the present invention provides a preparation method of a composite rhodium catalyst. The preparation method includes the following steps:

[0010] (1) Mix a rhodium source, a phosphine ligand source, and a first solvent, and obtain a phosphine rhodium complex through a first reaction;

[0011] (2) Mix the phosphine rhodium complex, the MOF-808 metal-organic framework material, and a second solvent to obtain a composite solution, and perform a second reaction on the composite solution to obtain the composite rhodium catalyst.

[0012] The present invention first prepares a phosphine rhodium complex, and then grafts the phosphine rhodium complex with MOF-808 through ligand exchange to form a composite rhodium catalyst. Based on the defective zirconium nodes in MOF-808, the phosphine rhodium complex is grafted onto it to fix a single Rh site in the confined cavity. The composite rhodium catalyst has good catalytic stability and also shows high chemical selectivity and regioselectivity in the reaction of catalyzing the hydroformylation of styrene to synthesize 2-phenylpropanal.

[0013] The method of the present invention can also be applied to the grafting heterogenization of noble metals such as palladium, platinum, ruthenium, iridium, etc. with corresponding types of phosphine ligands on metal-organic framework materials.

[0014] Preferably, the rhodium source in step (1) includes rhodium acetylacetonate dicarbonyl.

[0015] Preferably, the phosphine ligand source in step (1) includes 4-diphenylphosphinobenzoic acid.

[0016] Preferably, the molar ratio of the rhodium source to the phosphine ligand source in step (1) is 1:(4 - 6), for example: 1:4, 1:4.5, 1:5, 1:5.5 or 1:6, etc. It is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0017] Preferably, the first solvent in step (1) includes dichloromethane.

[0018] Preferably, the mixing method in step (1) includes: separately mixing the rhodium source, the phosphine ligand source with the first solvent to obtain a rhodium source solution and a phosphine ligand source solution, and dropping the phosphine ligand source solution into the rhodium source solution.

[0019] Preferably, the mass concentration of the rhodium source solution is 10 g / L - 20 g / L, for example: 10 g / L, 12 g / L, 15 g / L, 18 g / L or 20 g / L, etc. It is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0020] Preferably, the mass concentration of the phosphine ligand source solution is 80 g / L - 100 g / L, for example: 80 g / L, 85 g / L, 90 g / L, 95 g / L or 100 g / L, etc. It is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0021] Preferably, the temperature of the first reaction in step (1) is 30°C - 40°C, for example: 30°C, 32°C, 35°C, 38°C or 40°C, etc. It is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0022] Preferably, the time of the first reaction in step (1) is 3 h - 5 h, for example: 3 h, 3.5 h, 4 h, 4.5 h or 5 h, etc. It is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0023] Preferably, after the first reaction in step (1), under stirring conditions, anhydrous ether is added to the system, and after centrifugation, a yellow solid is obtained. The yellow solid is washed and dried to obtain the phosphine-rhodium complex.

[0024] Preferably, the detergent for washing includes anhydrous ethyl ether.

[0025] Preferably, the MOF-808 metal-organic framework material in step (2) is prepared by the following method:

[0026] Mix a zirconium source solution with a regulator to obtain a mixed solution, mix the mixed solution with a trimesic acid solution, carry out a hydrothermal reaction, and after cooling and solid-liquid separation, obtain the MOF-808 metal-organic framework material.

[0027] Preferably, the solvents of the zirconium source solution and the trimesic acid solution are independently N,N-dimethylformamide.

[0028] Preferably, the zirconium source in the zirconium source solution includes zirconium oxychloride octahydrate.

[0029] Preferably, the mass concentration of the zirconium source solution is 50 g / L to 80 g / L, for example: 50 g / L, 55 g / L, 60 g / L, 70 g / L or 80 g / L, etc., not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0030] Preferably, the mass concentration of the trimesic acid solution is 10 g / L to 20 g / L, for example: 10 g / L, 12 g / L, 15 g / L, 18 g / L or 20 g / L, etc., not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0031] Preferably, the molar ratio of the zirconium source in the zirconium source solution to the trimesic acid in the trimesic acid solution is (2.5 to 3.5):1, for example: 2.5:1, 2.8:1, 3:1, 3.2:1 or 3.5:1, etc., not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0032] Preferably, the regulator includes formic acid and / or acetic acid.

[0033] Preferably, the volume ratio of the zirconium source solution to the regulator is 1:(1.5 to 2.5), for example: 1.5:1, 1.8:1, 2:1, 2.2:1 or 2.5:1, etc., not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0034] Preferably, the temperature of the hydrothermal reaction is 80°C to 120°C, for example: 80°C, 90°C, 100°C, 110°C or 120°C, etc., not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0035] Preferably, the hydrothermal reaction time is 15 h to 20 h, for example: 15 h, 16 h, 17 h, 18 h, 19 h or 20 h, etc. It is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0036] Preferably, the mass ratio of the phosphine-rhodium complex to the MOF-808 metal-organic framework material in step (2) is 1:(3 - 4), for example: 1:3, 1:3.2, 1:3.5, 1:3.8 or 1:4, etc. It is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0037] Preferably, the second solvent includes dichloromethane.

[0038] Preferably, the mass concentration of the composite solution is 25 g / L to 30 g / L, for example: 25 g / L, 26 g / L, 27 g / L, 28 g / L, 29 g / L or 30 g / L, etc.

[0039] Preferably, the temperature of the second reaction in step (2) is 30 °C to 40 °C, for example: 30 °C, 32 °C, 35 °C, 38 °C or 40 °C, etc. It is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0040] Preferably, the time of the second reaction in step (2) is 70 h to 75 h, for example: 70 h, 71 h, 72 h, 73 h, 74 h or 75 h, etc. It is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0041] Preferably, stirring is carried out during the second reaction in step (2).

[0042] Preferably, the stirring speed is 800 rpm to 1200 rpm, for example: 800 rpm, 900 rpm, 1000 rpm, 1100 rpm or 1200 rpm, etc. It is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0043] Preferably, solid-liquid separation and washing treatments are carried out after the second reaction in step (2).

[0044] In a second aspect, the present invention provides a composite rhodium catalyst, and the composite rhodium catalyst is prepared by the preparation method as described in the first aspect.

[0045] In a third aspect, the present invention provides an application of the composite rhodium catalyst as described in the second aspect, and the composite rhodium catalyst is used for catalyzing the olefin formylation reaction.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] (1) The synthesis method of the composite rhodium catalyst of the present invention is easy to operate, easy to implement, and highly efficient. The prepared catalyst can be applied to the hydroformylation reaction of styrene derivatives, such as p-methoxystyrene, p-methylstyrene, halogenated styrene, etc. The catalyst has good stability. After being recycled 6 times, its substrate conversion rate, product selectivity, and catalyst structure basically remain unchanged.

[0048] (2) The composite rhodium catalyst of the present invention shows a conversion rate of 99.6% of styrene, an aldehyde chemoselectivity of 99.5%, a regioselectivity of 94.9% of 2-phenylpropanal (B / L 20.63), and good reusability in 6 runs under mild reaction conditions, far superior to the reported heterogeneous catalysts. Description of the Drawings

[0049] Figure 1 It is a transmission electron microscope image of the MOF-808 metal-organic framework material synthesized in Example 1.

[0050] Figure 2 It is a transmission electron microscope image of the composite rhodium catalyst prepared in Example 1.

[0051] Figure 3 It is a high-angle annular dark-field scanning transmission electron microscope image with low magnification of the composite rhodium catalyst prepared in Example 1.

[0052] Figure 4 It is a high-angle annular dark-field scanning transmission electron microscope image and element distribution map of the composite rhodium catalyst prepared in Example 1.

[0053] Figure 5 It is a transmission electron microscope image of the composite rhodium catalyst described in Example 1 after the hydroformylation catalytic reaction of styrene.

[0054] Figure 6 It is an XRD pattern of the MOF-808 metal-organic framework material synthesized in Example 1.

[0055] Figure 7 It is an XRD pattern of the composite rhodium catalyst prepared in Example 1.

[0056] Figure 8 It is an XRD pattern of the composite rhodium catalyst described in Example 1 after the hydroformylation catalytic reaction of styrene.

[0057] Figure 9 It is an FTIR pattern of the MOF-808 metal-organic framework material synthesized in Example 1.

[0058] Figure 10 It is an FTIR pattern of the composite rhodium catalyst prepared in Example 1.

[0059] Figure 11 It is the FTIR graph of the composite rhodium catalyst described in Example 1 after the hydroformylation catalytic reaction of styrene.

[0060] Figure 12 It is the CO-DRIFT spectrum of the composite rhodium catalyst prepared in Example 1.

[0061] Figure 13 It is the CO-DRIFT spectrum of the composite rhodium catalyst described in Example 1 after the hydroformylation catalytic reaction of styrene.

[0062] Figure 14 It is the 31 P solid-state NMR spectrum of the composite rhodium catalyst prepared in Example 1.

[0063] Figure 15 It is the catalytic stability graph of the composite rhodium catalyst prepared in Example 1 at 60 °C. Specific implementation mode

[0064] The technical solution of the present invention will be further described below through specific implementation modes. Those skilled in the art should understand that the described embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0065] Example 1

[0066] This example provides a composite rhodium catalyst, and the preparation method of the composite rhodium catalyst is as follows:

[0067] (1) Dissolve 30.96 mg of rhodium acetylacetonate dicarbonyl in 2 mL of dichloromethane (DCM), and stir vigorously at room temperature; at the same time, ultrasonically disperse 183.75 mg of 4-diphenylphosphinobenzoic acid in 2 mL of dichloromethane (the molar ratio of the rhodium source to the phosphine ligand source is 1:5), and slowly add it dropwise to the above-mentioned dichloromethane solution of rhodium acetylacetonate dicarbonyl and react at 35 °C for 4 h. Cool to room temperature, add a large amount of anhydrous ether under vigorous stirring, centrifuge to obtain a yellow solid, and wash it three times with anhydrous ether. Finally, dry Rh-bi-4DPPB in a vacuum oven at 80 °C for 24 h;

[0068] (2) Dissolve 642 mg of zirconium oxychloride octahydrate in 10 mL of N,N-dimethylformamide (DMF). Meanwhile, dissolve 140 mg of trimesic acid in 10 mL of N,N-dimethylformamide (the molar ratio of zirconium oxychloride octahydrate to trimesic acid is 3:1). After ultrasonic treatment, add 20 mL of formic acid (the volume ratio of the zirconium source solution to the regulator is 1:2) to the N,N-dimethylformamide solution of zirconium oxychloride octahydrate. Then, mix the two solutions and transfer them into a hydrothermal reactor, and react in an oven at 100 °C for 18 h. After cooling to room temperature, centrifuge to obtain a white solid, and wash it three times with N,N-dimethylformamide and acetone in sequence. Finally, dry the obtained MOF-808 metal-organic framework material in a vacuum oven at 80 °C for 24 h. Weigh 30.6 mg of Rh-bi-4DPPB and 105.24 mg of MOF-808 (the mass ratio is 1:3.44), disperse them in 5 mL of dichloromethane, and vigorously stir the solution at 35 °C for 72 h. Centrifuge to obtain a yellow solid, then wash it three times with dichloromethane, and dry it in a vacuum oven at 80 °C for 24 h to obtain the composite rhodium catalyst.

[0069] Example 2

[0070] This example provides a composite rhodium catalyst, and the preparation method of the composite rhodium catalyst is as follows:

[0071] (1) Dissolve 30.96 mg of rhodium(II) acetylacetonate dicarbonyl in 2 mL of dichloromethane (DCM), and vigorously stir at room temperature. Meanwhile, ultrasonically disperse 147 mg of 4-diphenylphosphinobenzoic acid in 2 mL of dichloromethane (the molar ratio of the rhodium source to the phosphine ligand source is 1:4), and slowly add it dropwise to the dichloromethane solution of rhodium(II) acetylacetonate dicarbonyl, and react at 30 °C for 5 h. After cooling to room temperature, add a large amount of anhydrous ether under vigorous stirring, centrifuge to obtain a yellow solid, and wash it three times with anhydrous ether. Finally, dry Rh-bi-4DPPB in a vacuum oven at 80 °C for 24 h;

[0072] (2) Dissolve 535 mg of zirconium oxychloride octahydrate in 10 mL of N,N-dimethylformamide (DMF). Meanwhile, dissolve 140 mg of trimesic acid in 10 mL of N,N-dimethylformamide (the molar ratio of zirconium oxychloride octahydrate to trimesic acid is 2.5:1). After ultrasonic treatment, add 15 mL of formic acid (the volume ratio of the zirconium source solution to the regulator is 1:1.5) to the N,N-dimethylformamide solution of zirconium oxychloride octahydrate. Then, mix the two solutions and transfer them into a hydrothermal reactor, and react in an oven at 80 °C for 20 h. After cooling to room temperature, centrifuge to obtain a white solid, and wash it three times with N,N-dimethylformamide and acetone in turn. Finally, dry the obtained MOF-808 metal-organic framework material in a vacuum oven at 80 °C for 24 h. Weigh 30.6 mg of Rh-bi-4DPPB and 91.8 mg of MOF-808 (mass ratio is 1:3), disperse them in 5 mL of dichloromethane, and vigorously stir the solution at 30 °C for 75 h. Centrifuge to obtain a yellow solid, then wash it three times with dichloromethane, and dry it in a vacuum oven at 80 °C for 24 h to obtain the composite rhodium catalyst.

[0073] Example 3

[0074] This example provides a composite rhodium catalyst, and the preparation method of the composite rhodium catalyst is as follows:

[0075] (1) Dissolve 30.96 mg of rhodium acetylacetonate dicarbonyl in 2 mL of dichloromethane (DCM), and vigorously stir at room temperature. Meanwhile, ultrasonically disperse 220.5 mg of 4-diphenylphosphinobenzoic acid in 2 mL of dichloromethane (the molar ratio of the rhodium source to the phosphine ligand source is 1:6), and slowly add it dropwise to the dichloromethane solution of rhodium acetylacetonate dicarbonyl, and react at 40 °C for 3 h. After cooling to room temperature, add a large amount of anhydrous ether under vigorous stirring, centrifuge to obtain a yellow solid, and wash it three times with anhydrous ether. Finally, dry Rh-bi-4DPPB in a vacuum oven at 80 °C for 24 h;

[0076] (2) Dissolve 749 mg of zirconium oxychloride octahydrate in 10 mL of N,N-dimethylformamide (DMF). Meanwhile, dissolve 140 mg of trimesic acid in 10 mL of N,N-dimethylformamide (the molar ratio of zirconium oxychloride octahydrate to trimesic acid is 3.5:1). After ultrasonic treatment, add 25 mL of formic acid (the volume ratio of the zirconium source solution to the regulator is 1:2.5) to the N,N-dimethylformamide solution of zirconium oxychloride octahydrate. Then, mix the two solutions and transfer them into a hydrothermal reactor, and react in an oven at 80 °C for 20 h. After cooling to room temperature, centrifuge to obtain a white solid, and wash it three times each with N,N-dimethylformamide and acetone. Finally, dry the obtained MOF-808 metal-organic framework material in a vacuum oven at 80 °C for 24 h. Weigh 30.6 mg of Rh-bi-4DPPB and 122.4 mg of MOF-808 (mass ratio is 1:4), disperse them in 5 mL of dichloromethane, and vigorously stir the solution at 40 °C for 70 h. Centrifuge to obtain a yellow solid, then wash it three times with dichloromethane, and dry it in a vacuum oven at 80 °C for 24 h to obtain the composite rhodium catalyst.

[0077] Example 4

[0078] The difference between this example and Example 1 is only that the molar ratio of the rhodium source to the phosphine ligand source in step (1) is 1:3, and other conditions and parameters are exactly the same as those in Example 1.

[0079] Example 5

[0080] The difference between this example and Example 1 is only that the molar ratio of the rhodium source to the phosphine ligand source in step (1) is 1:7, and other conditions and parameters are exactly the same as those in Example 1.

[0081] Example 6

[0082] The difference between this example and Example 1 is only that the molar ratio of zirconium oxychloride octahydrate to trimesic acid in step (2) is 2:1, and other conditions and parameters are exactly the same as those in Example 1.

[0083] Example 7

[0084] The difference between this example and Example 1 is only that the molar ratio of zirconium oxychloride octahydrate to trimesic acid in step (2) is 4:1, and other conditions and parameters are exactly the same as those in Example 1.

[0085] Example 8

[0086] The difference between this example and Example 1 is only that the volume ratio of the zirconium source solution to formic acid in step (2) is 1:1, and other conditions and parameters are exactly the same as those in Example 1.

[0087] Example 9

[0088] The difference between this example and Example 1 is only that the volume ratio of the zirconium source solution to formic acid described in step (2) is 1:3, and other conditions and parameters are exactly the same as those in Example 1.

[0089] Example 10

[0090] The difference between this example and Example 1 is only that the mass ratio of Rh-bi-4DPPB to MOF-808 described in step (2) is 1:2, and other conditions and parameters are exactly the same as those in Example 1.

[0091] Example 11

[0092] The difference between this example and Example 1 is only that the mass ratio of Rh-bi-4DPPB to MOF-808 described in step (2) is 1:5, and other conditions and parameters are exactly the same as those in Example 1.

[0093] Example 12

[0094] The difference between this example and Example 1 is only that in step (1), 4-diphenylphosphinobenzoic acid is replaced with 3-diphenylphosphinobenzoic acid, and other conditions and parameters are exactly the same as those in Example 1.

[0095] Example 13

[0096] The difference between this example and Example 1 is only that in step (1), 4-diphenylphosphinobenzoic acid is replaced with 2-diphenylphosphinobenzoic acid, and other conditions and parameters are exactly the same as those in Example 1.

[0097] Comparative Example 1

[0098] In this comparative example, Rh-bi-4DPPB and MOF-808 are directly physically mixed in a solid phase according to a mass ratio of 1:3.44.

[0099] Comparative Example 2

[0100] In this comparative example, Rh(CO)(acac)PPh 3 and MOF-808 are directly physically mixed in a solid phase according to a mass ratio of 1:3.44.

[0101] Comparative Example 3

[0102] In this comparative example, Rh(CO)(acac)PPh 3 and MOF-808 are directly compounded according to a mass ratio of 1:3.44 by using the solvent-ligand exchange method.

[0103] Performance test:

[0104] Disperse 30 mg of the catalyst in 3 mL of toluene, then add 0.5 mmol of styrene. After mixing the above solution evenly, transfer it to a 50 mL stainless steel autoclave with a polytetrafluoroethylene liner. Then introduce hydrogen gas and displace the air 5 times to remove the air in the autoclave. Hydrogen and carbon monoxide are introduced as reaction gases in the catalytic reaction, and the mixing ratio is controlled at 1:1. The total pressure is controlled at 3 MPa, the reaction temperature is 60 °C, the magnetic stirring speed is 600 revolutions per minute, and the reaction time is 6 h. After the reaction, the solid catalyst is separated by centrifugation. The obtained reaction solution is filtered through an organic filter membrane (0.22 μm) and then analyzed by gas chromatography (Shimadzu GC-2014C, Japan). Among them, the B / L value is the ratio of 2-phenylpropanal to 3-phenylpropanal. The catalytic test results are shown in Table 1:

[0105] Table 1

[0106]

[0107]

[0108] As can be seen from Table 1, from Examples 1-11, it can be obtained that the conversion rate of styrene catalyzed by the composite rhodium catalyst of the present invention can reach more than 90.1%, the aldehyde selectivity can reach more than 90.5%, and the B / L can reach more than 9.82. By adjusting the raw material ratio and preparation conditions of the composite rhodium catalyst, the conversion rate of styrene catalyzed by the prepared composite rhodium catalyst can reach more than 99.4%, the aldehyde selectivity can reach more than 99.2%, and the B / L can reach more than 18.32.

[0109] From the comparison between Example 1 and Examples 4-5, it can be obtained that during the preparation process of the composite rhodium catalyst of the present invention, the molar ratio of the rhodium source to the phosphine ligand source will affect its performance. Controlling the molar ratio of the rhodium source to the phosphine ligand source at 1:(4-6) results in better performance of the prepared composite rhodium catalyst. If the addition amount of the phosphine ligand source is too large, the activity of the composite catalyst will become poor. If the addition amount of the phosphine ligand source is too small, the chemoselectivity of the aldehyde of the composite catalyst will decrease.

[0110] From the comparison between Example 1 and Examples 6-7, it can be obtained that during the preparation process of the composite rhodium catalyst of the present invention, the molar ratio of the zirconium source to trimesic acid will affect its performance. Controlling the molar ratio of the zirconium source to trimesic acid at (2.5-3.5):1 results in better performance of the prepared composite rhodium catalyst. If the addition amount of trimesic acid is too large, the activity of the composite catalyst will become poor. If the addition amount of trimesic acid is too small, the chemoselectivity of the aldehyde of the composite catalyst will decrease.

[0111] Comparing Example 1 with Examples 8-9, it can be seen that in the preparation process of the composite rhodium catalyst of the present invention, the molar ratio of the volume ratio of the zirconium source solution to formic acid (modulator) will affect its performance. Controlling the volume ratio of the zirconium source solution to the modulator at 1:(1.5-2.5) results in better performance of the prepared composite rhodium catalyst. If the addition amount of the modulator is too large, the chemical selectivity of aldehyde and the regioselectivity of branched-chain aldehyde of the composite catalyst will decrease. If the addition amount of the modulator is too small, the activity of the composite catalyst will deteriorate.

[0112] Comparing Example 1 with Examples 10-11, it can be seen that in the preparation process of the composite rhodium catalyst of the present invention, the mass ratio of the phosphine rhodium complex to MOF-808 will affect its performance. Controlling the mass ratio of the phosphine rhodium complex to MOF-808 at 1:(3-4) results in better performance of the prepared composite rhodium catalyst. If the addition amount of MOF-808 is too large, the activity of the composite catalyst will deteriorate. If the addition amount of MOF-808 is too small, the chemical selectivity of aldehyde and the regioselectivity of branched-chain aldehyde of the composite catalyst will decrease.

[0113] Comparing Example 1 with Examples 12-13, it can be seen that the composite rhodium catalyst of the present invention grafts MOF-808 and Rh-bi-DPPB through ligand exchange, and constructs a P-Rh-P bite angle through the nodes and defects at different positions of MOF-808. Rh-bi-4DPPB, Rh-bi-3DPPB and Rh-bi-2DPPB can form P-Rh-P bite angles with different angles as precursors. Among them, MOF-808-(Rh-bi-4DPPB) can form the largest P-Rh-P bite angle, and has the best activity, chemical selectivity and regioselectivity.

[0114] Comparing Example 1 with Comparative Example 1, it can be seen that MOF-808 has a unique structure with a small ligand pore diameter and a large cavity, which can confine Rh-bi-4DPPB in the cavity and improve the chemical selectivity and regioselectivity of the composite catalyst through steric hindrance effect. In the physical mixture, Rh-bi-4DPPB can only be adsorbed on the surface, which cannot achieve this purpose and has poor stability.

[0115] Comparing Example 1 with Comparative Example 2, Rh(CO)(acac)PPh 3 Physically mixing with MOF-808 can only form a surface adsorption structure and is not compounded with the MOF-808 carrier. Therefore, the ligand does not have the ability of flexible adaptive coordination, and the regioselectivity cannot be effectively adjusted.

[0116] Comparing Example 1 with Comparative Example 3, Rh(CO)(acac)PPh is obtained by the solvent ligand exchange method 3Confined in the cavity of MOF-808, the regioselectivity can be improved to a certain extent through steric hindrance effects, but a reasonable structure cannot be optimized to further enhance the regioselectivity, and it also affects the chemoselectivity to a certain extent.

[0117] Take 30 mg of the catalyst prepared in Example 1 and disperse it in 3 mL of toluene. Then add 0.5 mmol of styrene, and after mixing the above solution evenly, transfer it to a 50 mL stainless steel autoclave with a PTFE liner. Then introduce hydrogen and displace 5 times to remove the air in the autoclave. In the catalytic reaction, hydrogen and carbon monoxide are introduced as reaction gases, and the mixing ratio is controlled at 1:1. The total pressure is controlled at 3 MPa, the reaction temperature is 60 °C, the magnetic stirring speed is 600 rpm, and the reaction time is 6 h. After the reaction, the solid catalyst is separated by centrifugation, and the obtained reaction solution is filtered through an organic filter membrane (0.22 μm) and then subjected to a general test using gas chromatography (Shimadzu GC-2014C in Japan). The B / L value is the ratio of branched-chain aldehyde to straight-chain aldehyde, and the test results are shown in Table 2:

[0118] Table 2

[0119]

[0120]

[0121] As can be seen from Table 2, in the hydroformylation reaction of styrene derivatives catalyzed by the composite rhodium catalyst of the present invention, the catalysts all exhibit high activity, chemoselectivity and regioselectivity.

[0122] During the preparation process of the composite rhodium catalyst described in Example 1, the transmission electron microscopy image of the synthesized MOF-808 metal-organic framework material is as Figure 1 shown, the transmission electron microscopy image of the composite rhodium catalyst is as Figure 2 shown, the low-magnification high-angle annular dark-field scanning transmission electron microscopy image of the composite rhodium catalyst is as Figure 3 shown, the high-angle annular dark-field scanning transmission electron microscopy image and the element distribution map of the composite rhodium catalyst are as Figure 4 shown. It can be seen from Figures 1-4 that MOF-808 has an octahedral morphology with uniform size distribution and an average size of 200 nanometers. After post-modification grafting, the morphology and size of the obtained catalyst MOF-808(Rh-bi-4DPPB) remain unchanged, and the Rh single sites are evenly distributed without obvious Rh aggregates. The transmission electron microscopy image of the composite rhodium catalyst described in Example 1 after the styrene hydroformylation catalytic reaction is as Figure 5 shown. It can be seen from Figure 5 that after the styrene hydroformylation catalytic reaction, the distribution and size of the Rh single sites basically remain unchanged without agglomeration.

[0123] The MOF-808 prepared in Example 1, the composite rhodium catalyst, and the composite rhodium catalyst after the hydroformylation catalysis reaction of styrene were characterized by an X-ray diffractometer (Rigaku D / MAX-TTRIII). The obtained XRD patterns are respectively as Figure 6 , Figure 7 and Figure 8 shown. It can be seen from Figures 6-8 that the MOF-808 synthesized in the present invention has a good crystal structure. After the subsequent synthesis of MOF-808(Rh-bi-4DPPB), the crystal structure remains unchanged and there is no characteristic peak of metallic Rh. After the hydroformylation catalysis reaction of styrene, the crystal structure of the catalyst remains unchanged.

[0124] The prepared MOF-808, the composite rhodium catalyst, and the composite rhodium catalyst after the hydroformylation catalysis reaction of styrene were characterized by a Fourier transform infrared spectrometer (Thermo Scientific Nicolet IS50). The obtained FTIR spectra are respectively as Figure 9 , Figure 10 and Figure 11 shown. It can be seen from Figures 9-11 that the characteristic peaks of MOF-808(Rh-bi-4DPPB) are consistent with those of the MOF-808 support, indicating that the structure of MOF-808 is maintained during the post-modification process. At the same time, the peak at 1967 cm -1 is the asymmetric stretching vibration peak of Rh-CO. After the hydroformylation catalysis reaction of styrene, the framework structure of the catalyst remains unchanged.

[0125] The Rh single sites of the composite rhodium catalyst prepared in Example 1 and the composite rhodium catalyst after the hydroformylation catalysis reaction of styrene were characterized by diffuse reflectance Fourier transform infrared spectroscopy (DRIFT) using carbon monoxide (CO) as a probe molecule. The obtained CO-DRIFT spectra are as Figures 12-13 shown. It can be seen from Figures 12-13 that the characteristic doublet indicates that the Rh in the catalyst is dispersed at the atomic level single sites, while the peaks at 2070 cm -1 and 2000 cm -1 correspond to the symmetric stretching and asymmetric stretching of CO respectively, indicating the existence of Rh(CO) 2 species. There are CO adsorption doublets in the MOF-808(Rh-bi-4DPPB) after the hydroformylation catalysis reaction of styrene, indicating that the single-site Rh can still be well maintained without agglomeration.

[0126] The catalyst material prepared in Example 1 was characterized using a solid-state nuclear magnetic resonance spectrometer (Bruker Avance Neo 400 WB), and the 31 31P solid-state NMR spectrum is as shown in Figure 14 ... It can be seen from Figure 14 that a chemical shift of 36.6 ppm indicates that P in MOF-808 (Rh-bi-4DPPB) is coordinated with the Rh single site. Combining the data of inductively coupled plasma optical emission spectrometer (ICP-OES), P:Rh = 2 (molar ratio) and the Rh loading is 1.0 wt%, indicating that a P-Rh-P coordination structure is formed in the catalyst.

[0127] The catalytic stability diagram of the composite rhodium catalyst prepared in Example 1 at 60 °C is as shown in Figure 15 ... It can be seen from Figure 15 that after 6 cyclic experiments, the conversion rate of styrene and the regioselectivity of 2-phenylpropanal remain unchanged, and the morphology and crystal structure of the catalyst can be maintained, indicating that the catalyst has excellent stability.

[0128] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for preparing a composite rhodium catalyst, characterized in that, The preparation method comprises the following steps: (1) mixing a rhodium source, a phosphine ligand source and a first solvent, and obtaining a phosphine-rhodium complex through a first reaction; (2) Mixing the phosphine-rhodium complex, the MOF-808 metal organic framework material and a second solvent to obtain a composite solution, and subjecting the composite solution to a second reaction to obtain the composite rhodium catalyst.

2. The preparation method according to claim 1, characterized in that The rhodium source in step (1) comprises rhodium dicarbonyl acetylacetonate; Preferably, the phosphine ligand source in step (1) comprises 4-diphenylphosphinobenzoic acid; Preferably, the molar ratio of the rhodium source to the phosphine ligand source in step (1) is 1:(4-6); Preferably, in step (1), the first solvent comprises dichloromethane.

3. The preparation method according to claim 1 or 2, characterized in that: The mixing method in step (1) includes: mixing the rhodium source, the phosphine ligand source and the first solvent respectively to obtain a rhodium source solution and a phosphine ligand source solution, and adding the phosphine ligand source dropwise into the rhodium source solution; Preferably, the mass concentration of the rhodium source solution is 10 g / L to 20 g / L; Preferably, the mass concentration of the phosphine ligand source solution is 80 g / L to 100 g / L.

4. The preparation method according to any one of claims 1 to 3, characterized in that: Step (1) The temperature of the first reaction is 30°C to 40°C; Preferably, the first reaction time in step (1) is 3 h to 5 h; Preferably, after the first reaction in step (1), anhydrous ether is added to the system under stirring, and the mixture is centrifuged to obtain a yellow solid, which is then washed and dried to obtain a phosphine-rhodium complex; Preferably, the washing detergent comprises anhydrous ether.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The MOF-808 metal organic framework material in step (2) is prepared by the following method: The zirconium source solution is mixed with the regulator to obtain a mixed solution, the mixed solution is mixed with a trimesic acid solution, a hydrothermal reaction is carried out, and the MOF-808 metal organic framework material is obtained through cooling and solid-liquid separation.

6. The preparation method according to claim 5, characterized in that: The solvents of the zirconium source solution and the trimesic acid solution are independently N,N-dimethylformamide; Preferably, the zirconium source in the zirconium source solution comprises zirconium oxychloride octahydrate; Preferably, the mass concentration of the zirconium source solution is 50 g / L to 80 g / L; Preferably, the mass concentration of the trimesic acid solution is 10 g / L to 20 g / L; Preferably, the molar ratio of the zirconium source in the zirconium source solution to the trimesic acid in the trimesic acid solution is (2.5-3.5):1; Preferably, the conditioning agent comprises formic acid and / or acetic acid; Preferably, the volume ratio of the zirconium source solution to the regulator is 1:(1.5-2.5); Preferably, the temperature of the hydrothermal reaction is 80°C to 120°C; Preferably, the hydrothermal reaction time is 15 h to 20 h.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The mass ratio of the phosphine-rhodium complex to the MOF-808 metal organic framework material in step (2) is 1:(3-4); Preferably, the second solvent comprises dichloromethane; Preferably, the mass concentration of the composite solution is 25 g / L to 30 g / L.

8. The preparation method according to any one of claims 1 to 7, characterized in that: Step (2) The temperature of the second reaction is 30°C to 40°C; Preferably, the time of the second reaction in step (2) is 70h to 75h; Preferably, stirring is performed during the second reaction in step (2); Preferably, the stirring speed is 800 rpm to 1200 rpm; Preferably, in step (2), the second reaction is followed by solid-liquid separation and washing.

9. A composite rhodium catalyst, characterized in that The composite rhodium catalyst is prepared by the preparation method according to any one of claims 1 to 8.

10. An application of the composite rhodium catalyst as claimed in claim 9, characterized in that: The composite rhodium catalyst is used for catalyzing olefin formylation reaction.

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