Preparation method of rhodium cluster catalyst and olefin hydroformylation catalyzed by rhodium cluster catalyst

Abstract

The invention discloses a preparation method of a rhodium cluster catalyst and a method for catalyzing olefin hydroformylation by using the rhodium cluster catalyst. The preparation method comprises the following steps: firstly, synthesizing a monomer material CTP-6-CHO; then, a certain amount of CTP-6-CHO and p-phenylenediamine are subjected to a self-assembly reaction, and an organic framework material QTD-COF is prepared; then, the prepared QTD-COF is roasted in an Ar atmosphere, and an N and P double-doped carbon-based material (P-NC) is prepared; finally, the P-NC is used as a carrier material, RhCl3. 3H2O is impregnated and adsorbed, high-temperature reduction is conducted in the H2 / Ar atmosphere, and the rhodium cluster supported catalyst Rh / P-NC is prepared. In the hydroformylation reaction of olefin, an Rh / P-NC catalyst and an olefin substrate are added into a high-pressure reaction kettle, a CO / H2 mixed gas (V: V, 1: 1) is introduced, the reaction is performed for 4-12 hours at 100-140 DEG C, the olefin conversion rate is as high as 99.9%, the yield of aldehyde compounds is as high as 97.4%, and the catalyst can be recycled for 10 times and still keeps activity. According to the method, the preparation method of the Rh / P-NC catalyst is simple, Rh clusters are anchored on the surface of a P-NC carrier in a high-dispersion mode, rich catalytic hydroformylation active sites can be provided, and the utilization rate of Rh metal atoms is effectively increased.

Description

Technical Field

[0001] This invention relates to the field of new chemical materials technology, specifically a method for preparing a supported rhodium cluster catalyst and its application in the highly selective synthesis of aldehydes through the hydroformylation of olefins. Background Technology

[0002] The synthesis of aldehydes from olefins via hydroformylation of syngas is one of the most important reactions in the field of chemical catalysis, with a global annual production exceeding 24 million tons (J. Am. Chem. Soc., 2021, 143(49), 20907-20915). However, the carbonyl group can be inserted into either side of the C=C double bond in the hydroformylation reaction, and the products are generally a mixture of linear and branched aldehydes. The accompanying side reactions are usually olefin hydrogenation and isomerization, with corresponding products of alkanes and internal alkenes, respectively (Chem, 2022, 8(10), 2630-2658). Therefore, catalysis researchers have tried various methods to design new catalysts in order to improve the activity, chemoselectivity, and regioselectivity of the olefin hydroformylation reaction. Organophosphorus ligands in rhodium complexes exhibit excellent activity and linear aldehyde selectivity in the hydroformylation of olefins (Chem. Rev., 2012, 112(11), 5675-5732). In industrial catalysis, homogeneous rhodium-phosphorus complexes are mainly used as catalysts, enabling efficient conversion of olefins. However, this also brings new problems, such as rhodium metal leaching and loss, environmental pollution caused by phosphorus-containing waste discharge, poor catalyst recyclability, and difficulties in product separation (Science, 2003, 299, 1702–1706). Heterogeneous catalysts, on the other hand, show significant advantages in solving these problems. Therefore, designing heterogeneous Rh-based catalysts or developing new heterogeneous hydroformylation catalytic systems has become an increasingly important research focus for catalysis researchers, such as single-atom catalysts (SACs), bimetallic catalysts, and anchored homogeneous catalysts. Single-atom catalysts have the advantage of high atomic utilization of active sites, but due to their complex preparation process and low metal loading, they are difficult to achieve large-scale industrial application (Angew. Chem., Int. Ed., 2016, 55(52), 16054-16058). Bimetallic catalysts have poor catalytic activity and cannot meet the requirements for efficient conversion of olefin hydroformylation.

[0003] In recent years, heteroatom-doped polymers or carbon-based materials have attracted widespread research interest from catalysis researchers. Incorporating heteroatoms can improve catalyst activity. Doping with P atoms, which are less electronegative than N atoms, further modulates the electronic structure of the Rh metal center through charge transfer between P and Rh, thereby enhancing catalytic activity (ACS Catalysis., 2021, 11(3), 1787-1796). Furthermore, P atoms can also fix Rh, inhibiting Rh leaching and thus enhancing the thermal stability of the catalyst. In this research area, researchers have incorporated P from different sources into supports to prepare various phosphorus-rhodium complexes, which have been applied to catalytic reactions such as nitrogen fixation, hydrogen evolution, and hydrodesulfurization. Polyphosphazene materials derived from hexachlorotriphosphazene (HCCP) possess a stable network covalent organic framework and abundant P atoms, attracting widespread attention from researchers over the past decade. Cyclotriphosphazene (CTP) possesses characteristics similar to benzene rings in organocyclic compounds, such as hexasubstituted ability, the ability to construct organometallic hybrid materials, and polymerization potential, but it also differs from them (Prog. Mater. Sci., 2024, 142, 0079-6425). Furthermore, CTP exhibits the following characteristics: First, it is a six-membered ring composed of nitrogen and phosphorus atoms linked alternately by PN and P=N bonds, with the six constituent atoms almost in the same plane; second, the nitrogen and phosphorus atoms are tricoordinate and pentacoordinate, respectively, allowing for the substitution of groups attached to the phosphorus atom through nucleophilic reactions; third, the nitrogen atom in CTP possesses a lone pair of electrons, resulting in Lewis basicity, enabling the nitrogen atom to coordinate with metal ions or adsorb organic substituents, thereby increasing the number of substituents on the ring; finally, HCCP can undergo ring-opening polymerization, and the resulting product can be functionalized to form polyorganophosphates with unique properties. These characteristics give it enormous research potential in the field of organic-inorganic hybrid materials. Therefore, using hexachlorotriphosphazene as the original material, developing N and P dual-doped carbon-based support materials, preparing heterogeneous Rh-based catalysts with highly dispersed Rh active sites, and using them for efficient catalytic hydroformylation of olefins is of great research significance. Summary of the Invention

[0004] To address the problems encountered by homogeneous rhodium-based catalysts, rhodium single-atom catalysts, and rhodium bimetallic catalysts in hydroformylation reactions, this invention provides a method for preparing an N, P dual-doped carbon-based material anchored and supported Rh cluster catalyst; and utilizes the prepared catalyst to efficiently catalyze the hydroformylation of olefins to synthesize aldehydes (taking the hydroformylation of styrene as an example, see the following formula).

[0005]

[0006] The following technical solution is adopted to solve the technical problem of the present invention:

[0007] A method for preparing a rhodium cluster catalyst and its catalytic hydroformylation of olefins, wherein the specific method for preparing an N, P dual-doped carbon-based material anchored and supported Rh cluster catalyst is as follows: First, using 4-hydroxybenzaldehyde and hexachlorotriphosphazene as raw materials, a monomer material CTP-6-CHO is prepared through a condensation reaction; then, a certain amount of CTP-6-CHO is reacted with p-phenylenediamine through a self-assembly reaction to obtain an organic framework material QTD-COF; then, the obtained QTD-COF is calcined at 600℃ for 3h in an Ar atmosphere to obtain an N, P dual-doped carbon-based material (P-NC); finally, using P-NC as a support material, it is dispersed in anhydrous methanol, impregnated and adsorbed with RhCl3·3H2O, the solid is collected by filtration, dried under vacuum, and then reduced at high temperature in an H2 / Ar atmosphere for 1h to obtain the rhodium cluster supported catalyst Rh / P-NC.

[0008] The precursor material used in the prepared Rh / P-NC catalyst is QTD-COF, which is prepared by the self-assembly reaction of CTP-6-CHO with p-phenylenediamine. This precursor material possesses abundant micro-mesoporous structures and N, P, and other coordination sites, enabling efficient adsorption and coordination of Rh. 3+ The Rh cluster-supported catalyst Rh / P-NC can be prepared by high-temperature calcination in a reducing atmosphere.

[0009] In the Rh / P-NC catalyst preparation method, the precursor material QTD-COF can be calcined at high temperature in an inert atmosphere to derive a P-NC support with a large specific surface area, excellent stability, and hierarchical porous structure; the specific surface area of ​​the P-NC support is 94.1 m². 2 ·g -1 The average pore size is 14.0 nm; the large pore size distribution and high specific surface area are beneficial to the diffusion and transfer of reactant molecules during the catalytic hydroformylation reaction.

[0010] In the Rh / P-NC catalyst preparation method, the precursor material QTD-COF is calcined at 600℃ in an inert atmosphere at a heating rate of 5℃ / min; Rh is adsorbed and coordinated on the P-NC support. 3+ Subsequently, the calcination temperature in a reducing atmosphere is 200-500℃, and the reducing atmosphere is V. H2 V Ar =1:9, reducing gas flow rate is 20mL / min, and heating rate is 5℃ / min.

[0011] In the Rh / P-NC catalyst preparation method, the Rh clusters are highly dispersed and anchored on the surface of the P-NC support, which can provide abundant active sites for catalytic hydroformylation, effectively improve the utilization rate of Rh metal atoms, and prevent the loss of Rh active sites.

[0012] The mass ratio of metal to support in the prepared Rh / P-NC catalyst is Rh:P-NC = 0.0048:1.

[0013] The application of the Rh / P-NC catalyst in the hydroformylation of olefins is as follows: using the hydroformylation of styrene as a probe reaction, 5 mg of catalyst, 0.5 mmol of styrene, and 4 mL of solvent are added to a 50 mL high-pressure reactor. The reactor is then purged three times with a CO / H2 (1:1) mixture, followed by pressurization. The reactor is heated to a specified temperature and reacted for a period of time. After the reaction is completed, the reactor is removed and allowed to cool naturally to room temperature. The mixture is then slowly released to depressurize. The catalyst is recovered by filtration.

[0014] The olefin hydroformylation reaction is carried out at a pressure of 1.0-3.0 MPa, a reaction temperature of 100-140℃, and a reaction time of 4-12 h.

[0015] The olefin hydroformylation reaction was analyzed by gas chromatography, and the conversion rate of styrene reached 99.9%, and the yield of aldehydes reached 97.4%.

[0016] The Rh / P-NC catalyst can be recycled up to 10 times for the olefin hydroformylation reaction while maintaining stable catalytic activity.

[0017] Advantages of this invention: 1. The rhodium cluster catalyst Rh / P-NC designed and prepared in this invention mainly uses the organic framework precursor material QTD-COF calcined in an inert atmosphere to provide a P-NC support material with abundant N and P sites, and then Rh is adsorbed through impregnation. 3+ The Rh / P-NC catalyst was prepared by reduction under a hydrogen atmosphere. The catalyst preparation method is simple and the conditions are mild. 2. In the Rh / P-NC catalyst, Rh is anchored on the surface of the P-NC support material in a highly dispersed cluster form. The catalyst exhibits high activity and excellent stability, maintaining high activity even after 10 repeated uses, with no Rh loss. 3. The Rh / P-NC catalyst provided in this invention achieves high olefin conversion and aldehyde yield in the hydroformylation reaction of olefins. The hydroformylation reaction is simple to operate, which is beneficial for industrial application and scale-up production. Attached Figure Description

[0018] Figure 1 Transmission electron microscopy (TEM) images of QTD-COF (a), P-NC support material (b), and Rh / P-NC catalyst (c) prepared in Example 1 of this invention.

[0019] Figure 2The (a) N2 adsorption-desorption isotherm and (b) pore size distribution curve of the QTD-COF, P-NC support material and Rh / P-NC catalyst prepared in Example 1 of this invention are shown.

[0020] Figure 3 This is a diagram illustrating the effect of catalyst reuse in the hydroformylation reaction of styrene catalyzed by the Rh / P-NC catalyst in Example 1 of this invention. Detailed Implementation

[0021] Example 1

[0022] A method for preparing a rhodium cluster catalyst and its catalytic hydroformylation of olefins is disclosed. The specific operation method is as follows: First, 14.92 g of 4-hydroxybenzaldehyde is dissolved in 300 mL of THF. Then, 33.40 g of potassium carbonate is slowly added to the solution, and the mixture is stirred in an ice bath for 30 min. Next, 6.69 g of hexachlorotriphosphazene is dissolved in 50 mL of THF and slowly added to the above mixed solution. The mixture is stirred in an ice bath for 2 h, and then stirred at room temperature for 48 h. The filtrate is collected by filtration and distilled under reduced pressure. The resulting solid is CTP-6-CHO. Then, 1.72 g of CTP-6-CHO was dissolved in 30 mL of a mixture of 1,2-dichlorobenzene and n-butanol (v / v = 9:1), and 0.66 g of p-phenylenediamine was dissolved in the same mixture. Both solutions were transferred to a 100 mL hydrothermal reactor lined with polytetrafluoroethylene (PTFE). Acetic acid (6 M, 6 mL) was added with stirring, and the mixture was allowed to crystallize at 120 °C for 2 days in a sealed system. After the reaction, the solid was collected by filtration and washed with DMF, acetone, and THF, respectively. Vacuum drying yielded a pale yellow solid, which was QTD-COF. Next, the obtained QTD-COF was calcined at 600 °C for 3 h in an Ar atmosphere (heating rate: 5 °C·min). -1 The P-NC material was prepared by dispersing 160 mg of P-NC in 30 mL of anhydrous methanol, then adding 10 mL of 2.5 mg of RhCl3·3H2O methanol solution by impregnation, collecting the solid by filtration, and reducing it at 300 °C for 1 h in an H2 / Ar atmosphere to obtain 0.6% Rh / P-NC, a Rh cluster supported catalyst.

[0023] Example 2

[0024] A method for preparing a rhodium cluster catalyst and its catalytic hydroformylation of olefins is disclosed. The specific method is as follows: 5 mg of 0.6% Rh / P-NC catalyst from Example 1, 0.5 mmol of styrene, and 4 mL of 1,4-dioxane solvent were added to a high-pressure reactor. The reactor was then purged three times with a CO / H2 (1:1) mixed gas, followed by a pressure of 2 MPa. The reactor was heated to 120 °C and reacted for 12 h. After the reaction was completed, the reaction progress was analyzed by gas chromatography. The conversion rate of styrene was as high as 99.9%, and the yield of aldehydes was as high as 97.4%.

[0025] Example 3-17

[0026] A method for preparing a rhodium cluster catalyst and its catalytic hydroformylation of olefins is disclosed. The specific method is as follows: Following the method in Example 2, 5 mg of 0.6% Rh / P-NC catalyst, 0.5 mmol of olefin substrate, and 4 mL of 1,4-dioxane solvent from Example 1 were added to a 50 mL high-pressure reactor. A CO / H2 mixed gas (V:V, 1:1) at 2 MPa was introduced, and the reaction was carried out at 120 °C for 12 h. The olefin conversion rate and the selectivity of the aldehyde product were analyzed by gas chromatography and are shown in Table 1 below.

[0027] Table 1. Results of hydroformylation of different olefins catalyzed by 0.6% Rh / P-NC.

[0028]

[0029]

[0030] Example 18

[0031] A method for preparing a rhodium cluster catalyst and its catalytic hydroformylation of olefins is disclosed. The specific method is as follows: The 0.6% Rh / P-NC catalyst from Example 2 is filtered and washed, and then added to a 50 mL high-pressure reactor with 0.5 mmol styrene and 4 mL 1,4-dioxane. A CO / H2 mixture (V:V, 1:1) at 2 MPa is introduced, and the reaction is carried out at 120 °C for 12 h. During the reaction, the CO / H2 mixture is continuously introduced to keep the reaction pressure constant. Gas chromatography analysis shows that after 10 cycles of the 0.6% Rh / P-NC catalyst, the conversion rate of styrene is higher than 96%, and the selectivity of aldehydes is higher than 92%. ICP analysis shows that no Rh loss is observed.

Claims

1. A method for preparing a rhodium cluster catalyst and its catalytic hydroformylation of olefins, characterized in that: First, monomer material CTP-6-CHO was prepared by condensation reaction using 4-hydroxybenzaldehyde and hexachlorotriphosphazene as raw materials. Then, a certain amount of CTP-6-CHO was reacted with p-phenylenediamine to prepare organic framework material QTD-COF. Next, the obtained QTD-COF was calcined at 600℃ for 3h in Ar atmosphere to obtain N, P dual-doped carbon-based material (P-NC). Finally, using P-NC as a support material, it was dispersed in anhydrous methanol, impregnated and adsorbed with RhCl3·3H2O, the solid was collected by filtration, dried under vacuum, and then reduced at high temperature in H2 / Ar atmosphere for 1h to obtain rhodium cluster supported catalyst Rh / P-NC.

2. The method for preparing a rhodium cluster catalyst according to claim 1 and its catalytic hydroformylation of olefins, characterized in that: The precursor material used in the Rh / P-NC catalyst is QTD-COF, which is prepared by the self-assembly reaction of CTP-6-CHO with p-phenylenediamine. This precursor material possesses abundant micro-mesoporous structures and N and P coordination sites, enabling efficient adsorption and coordination of Rh. 3+ The Rh cluster-supported catalyst Rh / P-NC can be prepared by high-temperature calcination in a reducing atmosphere.

3. The method for preparing a rhodium cluster catalyst according to claim 1 and its catalytic hydroformylation of olefins, characterized in that: In the Rh / P-NC catalyst preparation method, the precursor material QTD-COF can be calcined at high temperature in an inert atmosphere to derive a P-NC support with a large specific surface area, excellent stability, and hierarchical porous structure; the specific surface area of ​​the P-NC support is 94.1 m². 2 ·g -1 The average pore size is 14.0 nm; the large pore size distribution and high specific surface area are beneficial to the diffusion and transfer of reactant molecules during the catalytic hydroformylation reaction.

4. The method for preparing a rhodium cluster catalyst according to claim 1 and its catalytic hydroformylation of olefins, characterized in that: In the Rh / P-NC catalyst preparation method, the precursor material QTD-COF is calcined at 600℃ in an inert atmosphere at a heating rate of 5℃ / min; Rh is adsorbed and coordinated on the P-NC support. 3+ Subsequently, the calcination temperature in a reducing atmosphere is 200-500℃, and the reducing atmosphere is V. H2 V Ar =1:9, reducing gas flow rate is 20mL / min, and heating rate is 5℃ / min.

5. The method for preparing a rhodium cluster catalyst according to claim 1 and its catalytic hydroformylation of olefins, characterized in that: In the Rh / P-NC catalyst preparation method, the Rh clusters are highly dispersed and anchored on the surface of the P-NC support, which can provide abundant active sites for catalytic hydroformylation, effectively improve the utilization rate of Rh metal atoms, and prevent the loss of Rh active sites; the mass ratio of metal to support in the Rh / P-NC catalyst is Rh:P-NC=0.0048:

1.

6. The method for preparing a rhodium cluster catalyst according to claim 1 and its catalytic hydroformylation of olefins, characterized in that: Add 5 mg of Rh / P-NC catalyst, 0.5 mmol of styrene, and 4 mL of solvent to a high-pressure reactor, and purge with a CO / H2 mixture of 1.0-3.0 MPa (V:V, 1:1). The reaction temperature is 100-140℃, and the reaction time is 4-12 h. The conversion rate of styrene is as high as 99.9%, and the yield of aldehydes is as high as 97.4%.

7. The preparation method of the olefin hydroformylation catalyst according to claims 1 and 6 and its application, characterized in that: The Rh / P-NC catalyst was applied to the hydroformylation reaction of styrene to evaluate the reusability and stability of the catalyst. The Rh / P-NC catalyst can be recycled 10 times while maintaining high catalytic activity and Rh is not lost. The conversion rate of styrene is higher than 96% and the selectivity of aldehydes is higher than 92%.

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