A cobalt-rhodium bimetallic catalyst, a preparation method and application thereof

Abstract

The application discloses a cobalt-rhodium bimetallic catalyst and a preparation method and application thereof, and the method comprises the following steps: mixing a cobalt precursor compound and a phosphine ligand to obtain a first mixture, heating and reacting the first mixture in a carbon monoxide atmosphere to prepare a cobalt ion complex, mixing the cobalt ion complex and a rhodium precursor compound to obtain a second mixture, and heating and reacting the second mixture in a first synthesis gas atmosphere composed of hydrogen and carbon monoxide to prepare the cobalt-rhodium bimetallic catalyst. According to the application, the cobalt ion complex is prepared by mixing the cobalt precursor compound and the phosphine ligand, and then the cobalt ion complex and the rhodium precursor compound are pre-activated, so that the energy barrier of a rate-determining step can be effectively reduced, less rhodium component can be used to ensure that a high reaction rate can still be maintained under mild conditions, the dependence on the noble metal rhodium can be significantly reduced, and the production cost of a hydroformylation reaction can be greatly reduced while the high activity of the catalyst is maintained.

Description

Technical Field

[0001] This invention relates to the field of olefin hydroformylation technology, specifically to a cobalt-rhodium bimetallic catalyst and its preparation method, as well as the application of the catalyst in olefin hydroformylation reactions. Background Technology

[0002] The hydroformylation of olefins is one of the most important homogeneous catalytic processes in industry. This reaction, carried out under the action of a catalyst, involves the reaction of olefins with syngas composed of carbon monoxide and hydrogen to produce aldehydes, which have one more carbon atom than the feedstock olefins. Currently, the global annual production of chemicals produced through hydroformylation exceeds 20 million tons, playing a crucial role in the synthesis of plasticizers, alcohols, surfactants, solvents, and various fine chemicals.

[0003] In the development of hydroformylation catalytic systems, cobalt-based catalysts were developed earlier and play an important role in the conversion of long-chain olefins. However, traditional cobalt-based catalysts have significant drawbacks in industrial applications. For example, at lower carbon monoxide partial pressures, HCo(CO)4 easily loses its coordinating carbonyl group and decomposes to form the dimer Co2(CO)8, which further transforms into inactive polynuclear cobalt clusters or even metallic cobalt, leading to a sharp decline in catalytic activity. Furthermore, in industrial applications, cobalt-based catalysts typically require higher syngas pressures, such as 8–12 MPa, significantly increasing equipment investment and energy costs. Currently, the mainstream process for olefin hydroformylation uses phosphine-ligand-modified rhodium catalysts to achieve efficient conversion of olefins to aldehydes or alcohols in homogeneous or heterogeneous systems. However, rhodium metal is expensive and scarce, and its high cost significantly impacts the economic efficiency of industrial hydroformylation production.

[0004] Given the limitations of individual single-metal catalysts, the rhodium-cobalt bimetallic catalyst system has emerged. This system leverages the synergistic effect between the metals to achieve complementary advantages and offset each other's disadvantages, thereby reducing the cost of hydroformylation and improving product selectivity and conversion rate. Patent CN117797872A discloses a rhodium-cobalt bimetallic catalyst system using a rhodium and cobalt metal compound in a molar ratio of 1:(1~10), combined with a phosphine ligand to form the catalyst system, aiming to improve the selectivity of the hydroformylation reaction. Patent CN118788390A also discloses a cobalt-rhodium bimetallic catalyst, which uses a phosphine ligand, cobalt source compound, and rhodium source compound in a molar ratio of (1~2):1:1 to accelerate the overall hydroformylation reaction of highly branched olefins and improve product selectivity.

[0005] However, existing rhodium-cobalt bimetallic catalyst systems are typically mixtures of two metal compounds and phosphine ligands. While this reduces the amount of rhodium compound used to some extent, the amount remains relatively high. Furthermore, existing catalyst systems suffer from deactivation and decomposition of active catalyst species and easy loss of rhodium compounds during high-temperature reaction and separation. This allows the catalyst system to achieve high conversion rates and ideal selectivity in the initial stages of production, but as reaction time increases and the catalyst system is recycled more frequently, the conversion rate and selectivity of hydroformylation rapidly decline. This necessitates the replenishment of phosphine ligands and catalyst to maintain high conversion rates and ideal selectivity, making the production process and equipment more complex and resulting in high production costs. Summary of the Invention

[0006] One objective of this invention is to provide a method for preparing a cobalt-rhodium bimetallic catalyst. This method involves reacting a cobalt precursor compound with a phosphine ligand to form a cobalt ion complex, and then reacting the cobalt ion complex with a rhodium precursor compound to obtain the cobalt-rhodium bimetallic catalyst. This method not only features a simple preparation process and mild reaction conditions, but also effectively improves the conversion rate and selectivity of the hydroformylation reaction. Furthermore, this preparation method significantly reduces the amount of rhodium precursor compound used in the cobalt-rhodium bimetallic catalyst, and the prepared cobalt-rhodium bimetallic catalyst retains high conversion rate and selectivity even after several cycles, thereby significantly reducing the cost of the hydroformylation reaction.

[0007] This invention is achieved through the following technical solution:

[0008] A method for preparing a cobalt-rhodium bimetallic catalyst includes the following steps:

[0009] S1: Mix cobalt precursor compound and phosphine ligand to obtain a first mixture, and heat the first mixture under a carbon monoxide atmosphere to obtain a cobalt ion complex;

[0010] S2: The cobalt ion complex and the rhodium precursor compound are mixed to obtain a second mixture. The second mixture is heated and reacted under a first synthesis gas atmosphere composed of hydrogen and carbon monoxide to obtain a cobalt-rhodium bimetallic catalyst.

[0011] The phosphine ligand has the structure shown in Formula I:

[0012] Formula I: ;

[0013] In Formula I, the group R can be selected from H, halogen, sulfonic acid group, C1~C6 alkyl group, C1~C6 haloalkyl group, C1~C6 alkoxy group, C1~C6 alkylyl group, C1~C6 ester group, and nitrile group.

[0014] In this technical solution, the preparation of the cobalt-rhodium bimetallic catalyst includes two steps: the first step is to prepare a cobalt ion complex based on a cobalt precursor compound and a phosphine ligand; the second step is to prepare the cobalt-rhodium bimetallic catalyst based on the pre-activation of the cobalt ion complex and the rhodium precursor compound.

[0015] Specifically, in step S1, the cobalt precursor compound and phosphine ligand are dissolved in a first solvent to obtain a first mixture. The first solvent is preferably methanol; in one or more embodiments, toluene, acetonitrile, xylene, etc., may also be used. To achieve the reaction of the first mixture under a carbon monoxide atmosphere, in some embodiments, the air inside the reaction vessel can be replaced with carbon monoxide at room temperature. After replacement, carbon monoxide is introduced into the reaction vessel until the desired pressure, such as 2.0 MPa, is reached. Next, the first mixture is heated and stirred under a carbon monoxide atmosphere to react and obtain a cobalt ion complex.

[0016] In step S2, the cobalt ion complex and the rhodium precursor compound are dissolved in a second solvent to obtain a second mixture. The second solvent is preferably tetrahydrofuran. In one or more embodiments, the second solvent may also be dichloromethane, N,N-dimethylformamide, 1,2-dichloroethane, anisole, toluene, diethyl ether, tetrahydrofuran, xylene, trimethylbenzene, 1,4-dioxane, chloroform, acetonitrile, etc. To enable the second mixture to react under a syngas atmosphere, in some embodiments, the air in the reaction vessel can be replaced with syngas at room temperature. After replacement, syngas is introduced into the reaction vessel until the desired pressure is reached, for example, 3.0 MPa. Subsequently, the second mixture is heated and stirred under a syngas atmosphere to pre-activate and obtain the cobalt-rhodium bimetallic catalyst.

[0017] In this technical solution, the phosphine ligand adopted is a type of 2,2'-bipyridine skeleton bisphosphine ligand BiPyPhos disclosed by the inventors' team in CN114656501B. The cobalt atoms in the cobalt precursor compound can coordinate with BiPyPhos, forming a stable chelate ring structure using its bisphosphine sites. This structure generates excellent stabilization through a strong chelation effect, enabling the prepared cobalt ion complex to effectively resist loss caused by high-temperature decomposition and oxidation during flash evaporation separation. This overcomes the problem of insufficient stability of cobalt ion complexes in traditional cobalt-rhodium bimetallic catalysts.

[0018] Further mechanistic analysis revealed that the pyridine nitrogen atom in the cobalt ion complex, which does not participate in cobalt coordination, possesses dual catalytic functions: this nitrogen atom not only serves as an additional coordination site to coordinate with rhodium, constructing a bimetallic active center; but more importantly, it acts as an intramolecular proton shuttle, playing a key role in the catalytic cycle. Specifically, this nitrogen atom, with its lone pair electrons and tunable proton affinity, can reversibly capture and release protons (H+). + This property is crucial in reactions involving hydrogen activation, such as hydroformylation, because it facilitates the heterolytic cleavage of the hydrogen molecule (H2), releasing the proton (H2). + ) is directionally transferred to the olefin substrate and promotes the transfer of negative hydrogen (H) - The hydrogen is transferred to the metal center, thereby significantly reducing the energy barrier for hydrogen activation. This mechanism not only improves the overall reaction rate and avoids the formation of an inert state by direct heterolytic cleavage of H2 in the noble metal center, but also effectively suppresses side reactions by optimizing the proton transfer pathway, ultimately playing a key role in improving catalytic efficiency and product selectivity.

[0019] In this technical solution, by preparing a cobalt ion complex with a cobalt precursor compound and a phosphine ligand, and then pre-activating the cobalt ion complex with a rhodium precursor compound, the energy barrier of the rate-determining step can be effectively reduced. Using less rhodium component can ensure that a high reaction rate can still be maintained under mild conditions. Thus, while maintaining high catalyst activity, the dependence on the precious metal rhodium can be significantly reduced, and the production cost of the hydroformylation reaction can be greatly reduced.

[0020] Meanwhile, the cobalt ion complex of the prepared cobalt-rhodium bimetallic catalyst has a chelated ring structure. Under the protection of the multi-coordination effect of phosphine nitrogen atoms, it can effectively avoid the problem of loss of cobalt due to flash evaporation separation and the formation of multi-carbonyl hydrides. Furthermore, it can operate stably without the need for additional ligand protection, significantly reducing the loss and decomposition of cobalt components. This allows the cobalt-rhodium bimetallic catalyst to be used for extended periods and multiple cycles without a significant decrease in catalytic activity, greatly reducing the amount of cobalt-rhodium bimetallic catalyst used and further lowering the production cost of the hydroformylation reaction. Moreover, the bimetallic active center constructed by the cobalt-rhodium bimetallic catalyst effectively enhances its catalytic activity, enabling it to achieve high conversion rates and selectivity even in the more challenging branched olefin hydroformylation reaction, demonstrating broad application value.

[0021] Further, the molar ratio of cobalt in the cobalt ion complex to rhodium in the rhodium precursor compound is 1:(100~1000). In the cobalt-rhodium bimetallic system, the introduction of cobalt can regulate the electron density of rhodium, thereby enhancing its activation ability for carbon monoxide and hydrogen, and improving the catalyst's resistance to deactivation, while the highly efficient catalytic properties of rhodium can be fully utilized at low loading. In this technical solution, the bimetallic active center is constructed by coordinating the pyridine nitrogen atom that does not participate in cobalt coordination with rhodium in the cobalt ion complex, and the nitrogen atom is used as an intramolecular proton shuttle to play a core role in the catalytic cycle, achieving dual catalytic function, thereby significantly reducing the proportion of rhodium content while ensuring catalytic activity. In some preferred embodiments, the molar ratio of cobalt in the cobalt ion complex to rhodium in the rhodium precursor compound is 1:(100~1000). In a more preferred embodiment, the molar ratio of cobalt to rhodium is 1:(500~800).

[0022] Further, the molar ratio of the cobalt precursor compound to the phosphine ligand is 1:(1~3). This molar ratio affects the formation of the cobalt ion complex and the number of pyridine nitrogen atoms that do not participate in cobalt coordination. Preferably, in this technical solution, the molar ratio of the cobalt precursor compound to the phosphine ligand is 1:(1~3). More preferably, the molar ratio of the cobalt precursor compound to the phosphine ligand is 1:(1~2).

[0023] As a preferred cobalt precursor compound in this invention, the cobalt precursor compound is selected from at least one of Co(acac)3, Co(hfac)2, Co(dpm)2, Co2(CO)8, HCo(CO)(TPP)3, [Co(cod)Cl]2, CoCl2, and Co(acac)2. In some preferred embodiments, the cobalt precursor compound is selected from Co2(CO)8, HCo(CO)(TPP)3, Co(acac)2, and Co(acac)3. More preferably, the cobalt precursor compound is selected from Co2(CO)8.

[0024] As a preferred rhodium precursor compound in this invention, the rhodium precursor compound is selected from Rh(acac)(CH2=CH2)2, [RhCl(CH2=CH2)2]2, Rh(cod)2BF4, HRh(CO)(TPP)3, [Rh(cod)Cl]2. At least one of [RhCl(CO)2]2 or Rh(acac)(CO)2. In some preferred embodiments, the rhodium precursor compound is selected from Rh(CO)(acac)2, HRh(CO)(TPP)3, Rh(cod)2BF4, and more preferably, the rhodium precursor compound is selected from Rh(CO)(acac)2.

[0025] Furthermore, the group R of the phosphorus ligand can be selected from H, trifluoromethyl, methyl, ethyl, methoxy, bromine, or sulfonic acid group.

[0026] Further, in step S1, the first mixture is reacted in carbon monoxide at 1.5~4.0 MPa at 95~115 °C to obtain the cobalt ion complex; in step S2, the second mixture is stirred in a first syngas at 1.0~5.0 MPa at 90~120 °C to obtain the cobalt-rhodium bimetallic catalyst. In a partially preferred embodiment, the first mixture is reacted in carbon monoxide at 2.0~3.0 MPa at 100~110 °C to obtain the cobalt ion complex. In a partially preferred embodiment, the second mixture is stirred in a first syngas at 2.0~4.0 MPa at 100~115 °C to obtain the cobalt-rhodium bimetallic catalyst.

[0027] Another objective of this invention is to provide a cobalt-rhodium bimetallic catalyst, which is prepared using any of the aforementioned methods for preparing cobalt-rhodium bimetallic catalysts. This cobalt-rhodium bimetallic catalyst replaces the traditional high-loading method with trace amounts of rhodium, directly and significantly reducing the cost of precious metals. Simultaneously, the cobalt-rhodium bimetallic catalyst fully utilizes the coordination saturation characteristic of Co(BiPyPhos) without requiring additional ligands, thereby further saving ligand costs. Moreover, this cobalt-rhodium bimetallic catalyst does not sacrifice performance; it precisely controls the electronic properties of the cobalt center through P-N dual coordination and the synergistic effect of the bimetallic compounds, maintaining high catalytic activity for multi-substituted branched olefins such as diisobutylene and triisobutylene.

[0028] Another object of the present invention is to provide the application of any of the aforementioned cobalt-rhodium bimetallic catalysts in the hydroformylation reaction of olefins, the application comprising the following steps:

[0029] A mixture of olefin substrate and cobalt-rhodium bimetallic catalyst is obtained. The mixture is subjected to hydroformylation reaction in a second synthesis gas atmosphere composed of hydrogen and carbon monoxide at a reaction temperature of 80-120°C and a reaction pressure of 2.0-5.0 MPa. After the reaction is completed, the hydroformylation reaction product and the catalyst solution are separated.

[0030] In one or more embodiments, the molar ratio of cobalt to the olefin substrate is 1:(200~500), and the molar ratio of rhodium to the olefin substrate is 1:(20000~55000). The catalytic system composed of the cobalt-rhodium bimetallic catalyst can significantly reduce the amount of catalyst used while ensuring catalytic activity, thereby reducing the production cost of the hydroformylation reaction.

[0031] In one or more embodiments, the volume ratio of CO to H2 in the second synthesis gas is 1.0 to 2.0:1. The reaction pressure is 2.0 to 3.0 MPa, and the reaction temperature is 85 to 100°C.

[0032] Furthermore, the cobalt-rhodium bimetallic catalyst can be recycled multiple times. In some preferred embodiments, the catalyst solution is stirred in a first synthesis gas at 1.0~5.0 MPa at 90~120 °C to obtain a catalyst solution to be recycled. The catalyst solution to be recycled is used as the cobalt-rhodium bimetallic catalyst for the next round of hydroformylation reaction and is mixed with the olefin substrate to obtain the mixture.

[0033] In this technical solution, after obtaining the catalyst solution through flash evaporation, the high stability of the cobalt-rhodium bimetallic catalyst ensures that the cobalt, rhodium, and phosphine ligands are not easily lost at high temperatures. Therefore, the catalyst solution can be re-activated using the reaction conditions in step S2, and then used for the next hydroformylation reaction, thereby significantly reducing the production cost of the hydroformylation reaction. In some preferred embodiments, the cobalt-rhodium bimetallic catalyst can repeatedly catalyze the olefin substrate reaction more than 10 times, and the olefin conversion rate of each cycle is greater than 75%, and the aldehyde selectivity of the product is greater than 90%.

[0034] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0035] 1. This invention prepares a cobalt ion complex by combining a cobalt precursor compound with a phosphine ligand, and then pre-activates the cobalt ion complex with a rhodium precursor compound. This effectively reduces the energy barrier of the rate-determining step, and allows for the maintenance of a high reaction rate under mild conditions with less rhodium component. This significantly reduces the dependence on the precious metal rhodium while maintaining high catalyst activity, thereby greatly reducing the production cost of the hydroformylation reaction.

[0036] 2. The cobalt ion complex of the cobalt-rhodium bimetallic catalyst of the present invention has a chelated ring structure. Under the protection of the multi-coordination effect of phosphine nitrogen atoms, it can effectively avoid the problem of loss of cobalt by flash separation and formation of multi-carbonyl hydride. Moreover, it can operate stably without the protection of additional ligands, which greatly reduces the loss and decomposition of cobalt components. This allows the cobalt-rhodium bimetallic catalyst to be used for a long time and many times without significant decrease in catalytic activity, greatly reducing the amount of cobalt-rhodium bimetallic catalyst used and further reducing the production cost of hydroformylation reaction.

[0037] 3. The bimetallic active center constructed by the cobalt-rhodium bimetallic catalyst of the present invention can effectively enhance its catalytic activity, enabling it to achieve high conversion and selectivity even when applied to the hydroformylation reaction of branched olefins, which is a difficult reaction, and thus has broad application value.

[0038] 4. By optimizing the molar ratio of cobalt and rhodium in the cobalt-rhodium bimetallic catalyst, this invention can further reduce the amount of rhodium precursor compound used while ensuring catalytic activity, thereby further reducing production costs.

[0039] 5. When the cobalt-rhodium bimetallic catalyst of the present invention is used for the hydroformylation reaction of branched olefins, it can be recycled more than 10 times after pre-activation, and the olefin conversion rate of each cycle is greater than 75% and the aldehyde selectivity of the product is greater than 90%. Attached Figure Description

[0040] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0041] Figure 1 This is a flowchart of the preparation method in a specific embodiment of the present invention;

[0042] Figure 2 The phosphorus nuclear magnetic resonance spectrum of the cobalt ion complex Co(BiPyPhos) in Example 1 of this invention;

[0043] Figure 3 The 1H NMR spectrum of the cobalt ion complex Co(BiPyPhos) in Example 1 of this invention;

[0044] Figure 4 This is an analytical diagram of the single-crystal structure of the cobalt ion complex Co(BiPyPhos) in Example 1 of the present invention;

[0045] Figure 5 This is the GC spectrum of the diisobutylene reaction solution in a specific embodiment of the present invention;

[0046] Figure 6 This is the GC spectrum of the triisobutylene reaction solution in a specific embodiment of the present invention;

[0047] Figure 7 This is the GC spectrum of the tetrapropylene reaction solution in a specific embodiment of the present invention;

[0048] Figure 8 This is the GC spectrum of the 2-ethylhexene reaction solution in a specific embodiment of the present invention;

[0049] Figure 9 This is the GC spectrum of the 2-butyloctene reaction solution in a specific embodiment of the present invention. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0051] All raw materials used in this invention are not particularly limited in their source; they can be purchased commercially or prepared using conventional methods well-known to those skilled in the art. The purity of all raw materials used in this invention is not particularly limited; however, analytical grade or conventional purity requirements in the field of hydroformylation are preferred. All raw materials used in this invention have designations and abbreviations that are conventional in the art, and each designation and abbreviation is clearly defined within its relevant application. Those skilled in the art can obtain these materials from commercial sources or prepare them using conventional methods based on the designation, abbreviation, and corresponding application.

[0052] The present invention does not impose any particular restrictions on the expression of the substituents, and all expressions are well known to those skilled in the art. Based on common sense, those skilled in the art can correctly understand their meaning according to their expression.

[0053] In this application, the phosphine ligand BiPyPhos is a type of 2,2'-bipyridine skeleton bisphosphine ligand disclosed by the inventors in patent CN114656501B, which has the structure shown in Formula I:

[0054] Formula I: ;

[0055] In Formula I, the group R can be selected from H, halogen, sulfonic acid group, C1~C6 alkyl group, C1~C6 haloalkyl group, C1~C6 alkoxy group, C1~C6 alkylyl group, C1~C6 ester group, and nitrile group.

[0056] In some preferred embodiments, the group R may be selected from H, halogen, sulfonic acid group, C1-C6 alkyl group, C1-C6 haloalkyl group, and C1-C6 alkoxy group. In more preferred embodiments, the group R may be selected from H, trifluoromethyl, methyl, ethyl, methoxy, bromine, or sulfonic acid group.

[0057] The cobalt-rhodium bimetallic catalysts prepared based on the aforementioned phosphine ligand BiPyPhos all exhibit good performance, with even better results when the group R is selected from H, trifluoromethyl, or methyl. Therefore, for simplicity, in the following embodiments, the phosphine ligand BiPyPhos uses a 2,2'-bipyridine skeleton bisphosphine ligand with group R of H as shown in Formula II. However, those skilled in the art should understand that cobalt-rhodium bimetallic catalysts prepared based on 2,2'-bipyridine skeleton bisphosphine ligands with other groups R should also be included within the scope of protection of this invention.

[0058] Formula II: .

[0059] I. Preparation of Cobalt-Rhodium Bimetallic Catalysts

[0060]

Example 1

[0061] S1: A high-pressure reactor was loaded with Co2(CO)8 (0.1 mmol), phosphine ligand BiPyPhos (0.1 mmol), and methanol (2.0 mL). The reactor was purged three times with carbon monoxide at room temperature, and then purged with 4 MPa of carbon monoxide. The reaction was heated and stirred at 105°C for 4 hours. The reactor was then cooled to room temperature and the pressure was released, yielding an orange solid product. This solid was washed with anhydrous diethyl ether (3 × 5 mL) and dried under high vacuum to obtain the cobalt ion complex Co(BiPyPhos).

[0062] S2: Rh(CO)(acac)2 and Co(BiPyPhos) were dissolved in tetrahydrofuran (THF) at a molar ratio of Rh:Co = 1:750 to obtain a mixture. The mixture was stirred at 110°C for 5.0 h in 3.0 MPa syngas (H2:CO = 1.1:1) to obtain the pre-synthesized cobalt-rhodium bimetallic catalyst C1.

[0063] Figure 2 and Figure 3 The NMR spectrum of the cobalt ion complex Co(BiPyPhos) is shown below.

[0064] 31 P{ 1 H} NMR NMR (162 MHz, DMSO-d6) δ 59.82 ppm.

[0065] 1 H NMR (400 MHz, DMSO-d6) δ 8.87 – 6.41 (m, 26H), 5.22 (s, 2H), 4.71 (s, 2H).

[0066] Figure 4 The single-crystal structure of the cobalt ion complex Co(BiPyPhos) is shown. As can be seen from the analytical diagram, after cobalt coordinates with the phosphine ligand BiPyPhos, a stable chelate ring structure is formed using its biphosphine sites. This chelate ring structure provides excellent stabilization through a strong chelation effect, enabling the cobalt ion complex to effectively resist loss caused by high-temperature decomposition and oxidation during flash evaporation separation, thus overcoming the key problem of insufficient stability in traditional cobalt-phosphine complexes.

[0067]

Example 2

[0068] In this embodiment, the preparation method is the same as in Example 1, except that in step S2, Rh(CO)(acac)2 and Co(BiPyPhos) are dissolved in tetrahydrofuran (THF) at a molar ratio of Rh:Co=1:100 to obtain a mixture. The mixture is stirred at 110°C for 5.0 h under 3.0 MPa syngas to obtain cobalt-rhodium bimetallic catalyst C2.

[0069]

Example 3

[0070] In this embodiment, the preparation method is the same as in Example 1, except that in step S2, Rh(CO)(acac)2 and Co(BiPyPhos) are dissolved in THF at a molar ratio of Rh:Co=1:250 to obtain a mixture. The mixture is stirred at 110°C for 5.0 h under 3.0 MPa syngas to obtain cobalt-rhodium bimetallic catalyst C3.

[0071]

Example 4

[0072] In this embodiment, the preparation method is the same as in Example 1, except that in step S2, Rh(CO)(acac)2 and Co(BiPyPhos) are dissolved in THF at a molar ratio of Rh:Co=1:500 to obtain a mixture. The mixture is stirred at 110°C for 5.0 h under 3.0 MPa syngas to obtain the cobalt-rhodium bimetallic catalyst C4.

[0073]

Example 5

[0074] In this embodiment, the preparation method is the same as in Example 1, except that in step S2, Rh(CO)(acac)2 and Co(BiPyPhos) are dissolved in THF at a molar ratio of Rh:Co=1:800 to obtain a mixture. The mixture is stirred at 110°C for 5.0 h under 3.0 MPa syngas to obtain cobalt-rhodium bimetallic catalyst C5.

[0075]

Example 6

[0076] In this embodiment, the preparation method is the same as in Example 1, except that in step S2, Rh(CO)(acac)2 and Co(BiPyPhos) are dissolved in THF at a molar ratio of Rh:Co=1:1000 to obtain a mixture. The mixture is stirred at 110°C for 5.0 h under 3.0 MPa syngas to obtain the cobalt-rhodium bimetallic catalyst C6.

[0077]

Example 7

[0078] In this embodiment, the preparation method is the same as in Example 1. The difference is that in step S1, Co(acac)2 is used to replace Co2(CO)8, and the cobalt ion complex Co(BiPyPhos) is prepared by reacting with BiPyPhos. Finally, it is pre-activated with Rh(CO)(acac)2 to obtain the cobalt-rhodium bimetallic catalyst C7.

[0079]

Example 8

[0080] In this embodiment, the preparation method is the same as in Example 1. The difference is that in step S1, HCo(CO)(TPP)3 is used to replace Co2(CO)8, and the cobalt ion complex Co(BiPyPhos) is prepared by reacting with BiPyPhos. Finally, it is pre-activated with Rh(CO)(acac)2 to obtain the cobalt-rhodium bimetallic catalyst C8.

[0081]

Example 9

[0082] In this embodiment, the preparation method is the same as in Example 1, except that in step S1, the molar ratio of Co2(CO)8 to BiPyPhos is 1:2 to obtain the cobalt-rhodium bimetallic catalyst C9.

[0083]

Example 10

[0084] In this embodiment, the preparation method is the same as in Example 1, except that in step S1, the molar ratio of Co2(CO)8 to BiPyPhos is 1:3 to obtain the cobalt-rhodium bimetallic catalyst C10.

[0085]

Example 11

[0086] In this embodiment, the preparation method is the same as in Example 1, except that in step S2, the rhodium precursor compound is replaced by HRh(CO)(TPP)3 to obtain the cobalt-rhodium bimetallic catalyst C11.

[0087]

Example 12

[0088] In this embodiment, the preparation method is the same as in Example 1, except that in step S2, the rhodium precursor compound is replaced by Rh(cod)2BF4 to obtain the cobalt-rhodium bimetallic catalyst C12.

[0089] In some embodiments, the cobalt precursor compound may also be Co(hfac)2, Co(dpm)2, [Co(cod)Cl]2, CoCl2 or Co(acac)3; wherein cod is 1,4-cyclooctadiene, acac is acetylacetone, hfac is a deprotonated anionic ligand of hexafluoroacetylacetone, and dpm is a deprotonated anionic ligand of di-tert-valeratemethane.

[0090] In some embodiments, the rhodium precursor compound may also be Rh(acac)(CH2=CH2)2, [RhCl(CH2=CH2)2]2, [Rh(cod)Cl]2. Or [RhCl(CO)2]2, where, It is a pentamethylcyclopentadiene anion.

[0091] II. Performance Testing of Cobalt-Rhodium Bimetallic Catalysts

[0092] In performance testing, after the hydroformylation reaction was completed, the components of the reaction solution were analyzed using GC. The instrument used for GC was an Agilent Technologies 8860 gas chromatograph, and the analysis software was a ChemStation chromatography workstation. The GC test conditions were as follows:

[0093] 1) Chromatographic column: HP-5 30m×0.32mm×0.25μm flexible quartz capillary column, using split injection with a split ratio of 100:1;

[0094] 2) Column temperature: Initial temperature 60 ℃, hold for 5 min, then increase to 300 ℃ at a rate of 15 ℃ / min and hold for 7 min;

[0095] 3) Average linear velocity of carrier gas (high-purity N2): 18 cm / s;

[0096] 4) Hydrogen flow rate: 30 mL / min;

[0097] 5) Airflow rate: 320 mL / min;

[0098] 6) Flow rate of tail gas (high-purity N2): 10 mL / min;

[0099] 7) Vaporization chamber temperature: 280 ℃;

[0100] 8) Detector temperature: 300 ℃;

[0101] 9) Injection volume: 0.4 μL.

[0102]

Example 13

[0103] In this embodiment, the catalytic activity of the cobalt-rhodium bimetallic catalyst C1 prepared in Example 1 in the hydroformylation reaction of isobutylene was tested. Comparative Example 1 was the cobalt ion complex Co(BiPyPhos) prepared in Example 1, and Comparative Example 2 was Rh(CO)(acac)2.

[0104] Specifically, 30 mL of diisobutylene was mixed with 3.0 mmol of comparative example 1, 4.0 μmol of comparative example 2, or 30 mL of cobalt-rhodium bimetallic catalyst C1. The mixture was placed in a high-pressure reactor equipped with a magnetic stirrer, and the air inside the reactor was replaced with syngas at 3.0 MPa (CO to H2 volume ratio of 1.1:1). The reaction was carried out at 95 °C for 3 h. After the reaction was completed, the composition of the reaction solution was analyzed by GC. The reaction results are shown in Table 1.

[0105] Table 1:

[0106]

[0107] It is evident that the cobalt-rhodium bimetallic catalyst C1 exhibits significantly higher reactivity than Co(BiPyPhos) alone. In contrast, using only the rhodium precursor Rh(CO)(acac)2 as a catalyst results in similarly low catalytic activity under the same conditions. This suggests that the cobalt-rhodium bimetallic catalyst system constructed in this application possesses a significant activity advantage compared to single rhodium or cobalt metals.

[0108]

Example 14

[0109] In the hydroformylation of olefins, branched olefins are generally more difficult to react than straight-chain terminal olefins. In this example, the catalytic performance of the cobalt-rhodium bimetallic catalyst C1 in the hydroformylation of various branched olefins was tested. The specific experimental steps are as follows:

[0110] 30 mL of different olefin substrates and 30 mL of cobalt-rhodium bimetallic catalyst C1 were mixed. The mixture was placed in a high-pressure reactor equipped with a magnetic stirrer. The air in the reactor was replaced with syngas (CO and H2 volume ratio of 1.1:1) at 3.0 MPa. The reaction was carried out at 95 °C for 3 h. After the reaction, the composition of the reaction solution was analyzed by GC. The GC spectra of the reaction solutions corresponding to each olefin substrate are shown below. Figures 5 to 9 As shown in the figure. The reaction results are shown in Table 2:

[0111] Table 2:

[0112]

[0113] In Table 2, diisobutylene is obtained by dimerization of isobutylene, triisobutylene is obtained by trimerization of isobutylene, tetrapropylene is obtained by tetramerization of propylene, 2-ethylhexene is obtained by dimerization of butene, and 2-butyloctene is obtained by dimerization of hexene.

[0114] As shown in Table 2, the cobalt-rhodium bimetallic catalyst C1 not only achieves high conversion and selectivity in the hydroformylation of diisobutylene, but also achieves a conversion rate of over 98% in the hydroformylation of 2-ethylhexene and 2-butyloctene. Even when used for the hydroformylation of triisobutylene or tetrapropylene, which are very difficult to hydroformylate, the cobalt-rhodium bimetallic catalyst C1 still achieves good conversion and excellent aldehyde selectivity, indicating that the cobalt-rhodium bimetallic catalyst of this application has strong versatility.

[0115]

Example 15

[0116] In this embodiment, the effect of different cobalt-rhodium ratios (Rh:Co) on the catalytic activity of the cobalt-rhodium bimetallic catalyst was tested.

[0117] Specifically, 30 mL of diisobutylene was mixed with 30 mL of each of the following cobalt-rhodium bimetallic catalysts: C1, C2, C3, C4, C5, and C6. The mixtures were placed in a high-pressure reactor equipped with a magnetic stirrer. Syngas was introduced at 3.0 MPa (CO to H2 volume ratio of 1.1:1) to replace the air in the reactor. The reaction was carried out at 95 °C for 3 h. After the reaction, the components of the reaction solution were analyzed by GC. The reaction results are shown in Table 3.

[0118] Table 3:

[0119]

[0120] As shown in Table 3, when the molar ratio of cobalt-rhodium bimetallic catalyst Rh:Co is in the range of 1:(100~1000), diisobutylene can achieve excellent selectivity. The conversion rate first gradually increases and then gradually decreases as the Rh content decreases. When Rh:Co=1:(500~1000), a conversion rate of over 70% can be achieved, while when Rh:Co=1:750, a conversion rate of 82.94% is reached.

[0121] Therefore, this application demonstrates that by preparing Co(BiPyPhos) from a cobalt precursor compound and a phosphine ligand, and then pre-activating Co(BiPyPhos) with a rhodium precursor compound to obtain a cobalt-rhodium bimetallic catalyst, the method can significantly reduce the amount of rhodium precursor compound used in the catalytic system compared to existing technologies, while achieving high conversion and selectivity, thereby effectively reducing the production cost of the hydroformylation reaction.

[0122]

Example 16

[0123] In this embodiment, the effects of different cobalt precursor compounds on the catalytic performance of the cobalt-rhodium bimetallic catalyst were compared. The hydroformylation reaction of diisobutylene was used for testing. Specifically, 30 mL of diisobutylene was mixed with 30 mL of cobalt-rhodium bimetallic catalyst C1, C7, or C8. The mixture was placed in a high-pressure reactor equipped with a magnetic stirrer, and the air inside the reactor was replaced with syngas at 3.0 MPa (CO to H2 volume ratio of 1.1:1). The reaction was carried out at 95 °C for 3 h. After the reaction, the composition of the reaction solution was analyzed by GC. The reaction results are shown in Table 4.

[0124] Table 4:

[0125]

[0126] As shown in Table 4, all three cobalt-rhodium bimetallic catalysts achieved excellent selectivity after changing the cobalt precursor compound. Catalysts C7 or C8, obtained by replacing Co2(CO)8 with Co(acac)2 or HCo(CO)(TPP)3, exhibited almost the same catalytic activity as catalyst C1. However, when HCo(CO)(TPP)3 was used as the cobalt precursor compound, the conversion rate after activation with the rhodium precursor compound decreased slightly. This may be due to its stable coordination-saturated structure leading to a high energy barrier for the formation of active species, and its large steric hindrance and strong electron-donating effect hindering reactant coordination and CO dissociation. Therefore, in some preferred embodiments, Co2(CO)8 is used as the cobalt precursor.

[0127]

Example 17

[0128] In this embodiment, the stability of the cobalt-rhodium bimetallic catalyst C1 was tested through ten cycles of reaction. Specifically:

[0129] (1) Mix 30 mL of diisobutylene with 30 mL of cobalt-rhodium bimetallic catalyst C1, place the mixture in a high-pressure reactor with magnetic stirring, replace the air in the reactor with syngas, and fill with 3.0 MPa of syngas (the volume ratio of CO to H2 is 1.1:1). React at 95 °C for 3 h. After the reaction is completed, the catalyst and product are separated by flash evaporation.

[0130] (2) The catalyst concentrate obtained in step (1) is used as the catalyst for the new round. The catalyst for the new round needs to be stirred at 110°C for 5.0 h in syngas (hydrogen and carbon monoxide) at 3.0 MPa to obtain the pre-activated cobalt-rhodium bimetallic catalyst. Step (1) is repeated until it is repeated 10 times. Table 5 shows the experimental data of the cobalt-rhodium bimetallic catalyst C1 after 10 cycles:

[0131] Table 5:

[0132]

[0133] Table 5 shows that after 10 cycles, the catalytic activity of the cobalt-rhodium bimetallic catalyst C1 remained relatively stable, with no significant activity loss. The cobalt concentration in the flash-separated fraction was less than 1 ppm. The continuous decrease in isononanal / alcohol selectivity during the cycle was due to the continuous generation of heavy components during catalyst use. Therefore, the cobalt-rhodium bimetallic catalyst C1 exhibits excellent stability, maintaining high conversion and selectivity even after prolonged use and multiple cycles, thus significantly reducing the production cost of olefin hydroformylation.

[0134] The terms "first," "second," etc., used herein (e.g., first mixture, second mixture, etc.) are merely for clarity of description and are not intended to restrict any order or emphasize importance. Furthermore, the term "link" used herein, unless otherwise specified, can refer to a direct link or an indirect link via other groups.

[0135] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a cobalt-rhodium bimetallic catalyst, characterized in that, Includes the following steps: S1: Mix cobalt precursor compound and phosphine ligand to obtain a first mixture, and heat the first mixture under a carbon monoxide atmosphere to obtain a cobalt ion complex; S2: The cobalt ion complex and the rhodium precursor compound are mixed to obtain a second mixture. The second mixture is heated and reacted under a first synthesis gas atmosphere composed of hydrogen and carbon monoxide to obtain a cobalt-rhodium bimetallic catalyst. The phosphine ligand has the structure shown in Formula I: Formula I: ; In Formula I, the group R can be selected from H, halogen, sulfonic acid group, C1~C6 alkyl group, C1~C6 haloalkyl group, C1~C6 alkoxy group, C1~C6 alkylyl group, C1~C6 ester group, and nitrile group.

2. The method for preparing a cobalt-rhodium bimetallic catalyst according to claim 1, characterized in that, The molar ratio of cobalt in the cobalt ion complex to rhodium in the rhodium precursor compound is 1:(100~1000).

3. The method for preparing a cobalt-rhodium bimetallic catalyst according to claim 1, characterized in that, The molar ratio of the cobalt precursor compound to the phosphine ligand is 1:(1~3).

4. The method for preparing a cobalt-rhodium bimetallic catalyst according to claim 1, characterized in that, The cobalt precursor compound is selected from at least one of Co(acac)3, Co(hfac)2, Co(dpm)2, Co2(CO)8, HCo(CO)(TPP)3, [Co(cod)Cl]2, CoCl2, and Co(acac)2.

5. The method for preparing a cobalt-rhodium bimetallic catalyst according to claim 1, characterized in that, The rhodium precursor compound is selected from Rh(acac)(CH2=CH2)2, [RhCl(CH2=CH2)2]2, Rh(cod)2BF4, HRh(CO)(TPP)3, [Rh(cod)Cl]2. At least one of [RhCl(CO)2]2 or Rh(acac)(CO)2.

6. The method for preparing a cobalt-rhodium bimetallic catalyst according to claim 1, characterized in that, The group R can be selected from H, trifluoromethyl, methyl, ethyl, methoxy, bromine, or sulfonic acid group.

7. A method for preparing a cobalt-rhodium bimetallic catalyst according to any one of claims 1 to 6, characterized in that, In step S1, the first mixture is reacted in carbon monoxide at 1.5~4.0 MPa at 95~115 °C to obtain the cobalt ion complex; In step S2, the second mixture is stirred in a first synthesis gas at 1.0~5.0 MPa at 90~120 °C to obtain the cobalt-rhodium bimetallic catalyst.

8. A cobalt-rhodium bimetallic catalyst, characterized in that, It was prepared using the method described in any one of claims 1 to 7.

9. The application of cobalt-rhodium bimetallic catalysts in the hydroformylation of olefins, characterized in that, The cobalt-rhodium bimetallic catalyst is the cobalt-rhodium bimetallic catalyst described in claim 8, and the application... Includes the following steps: A mixture of olefin substrate and cobalt-rhodium bimetallic catalyst is obtained. The mixture is subjected to hydroformylation reaction in a second synthesis gas atmosphere composed of hydrogen and carbon monoxide at a reaction temperature of 80-120°C and a reaction pressure of 2.0-5.0 MPa. After the reaction is completed, the hydroformylation reaction product and the catalyst solution are separated.

10. The application according to claim 9, characterized in that, It also includes the following steps: The catalyst solution is stirred in a first synthesis gas at 1.0~5.0 MPa at 90~120 °C to obtain a catalyst solution to be recycled. The catalyst solution to be recycled is used as the cobalt-rhodium bimetallic catalyst for the next round of hydroformylation reaction and is mixed with the olefin substrate to obtain the mixture.

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