A P-coordinated Co-Rh bimetallic catalyst, synthesis method and application

Abstract

The invention discloses a P-coordinated Co-Rh bimetallic catalyst, a synthesis method and an application thereof. The catalyst comprises active metal atoms Co and Rh, a coordinated atom P, and a carrier of porous carbon; the metal atoms Co and Rh are uniformly distributed in the inner surface of the porous carbon pores; the P is uniformly distributed in the inner surface of the porous carbon pores near Rh; the P can significantly affect the electronic compound state of Rh, indicating the interaction between Rh and P. The synthesis method comprises the following steps: 1) preparing a carrier suspension; 2) preparing an active component impregnation solution; 3) high-temperature calcination of a catalyst sample. The prepared P-coordinated Co-Rh bimetallic metal is highly dispersed and uniform, and there are no metal particles on the surface; the P source content can significantly change the catalytic effect of the active center; and the localized electronic structure of Rh is adjusted at the same time. It exhibits better catalytic activity than bimetallic catalysis in isooctene carbonylation.

Description

Technical Field

[0001] The invention belongs to the technical field of catalyst synthesis and application, and specifically relates to a P-coordinated Co-Rh bimetallic catalyst, a synthesis method and application. Background Art

[0002] The olefin hydroformylation reaction system is one of the important reaction pathways for synthesizing aldehydes and is also one of the largest industrial applications in the world today. The annual output of carbonyl chemicals is abundant, and fine chemicals downstream of carbonyl chemicals such as soaps, medicines, and surfactants have been produced on a large scale. These products have a wide range of uses in our society and can meet the development of national living standards. However, olefin carbonylation reaction catalysts are currently monopolized by the foreign environment, and the domestic development level is still very low. Only a few companies have achieved the industrial production of low-chain olefins, and there are technical difficulties in the production of high-carbon alcohols and high-carbon carboxylic acids in the world.

[0003] However, as solid catalysts have been developed in the field of olefin carbonylation, scientists from various countries have put forward a large number of design guidelines for solid catalysts. Solid catalysts can solve the bottlenecks in industrial applications in terms of development. Solid single-atom catalytic technology has also been extended to the field of olefin hydroformylation. In addition, the synergistic catalytic effect of bimetallic catalysts has been confirmed in countless cases. The current technical bottlenecks faced by solid catalysts are low activity and poor stability. These drawbacks have undoubtedly hindered the development of solid catalysts. However, single-atom catalysts are already comparable to homogeneous catalysts. Designing precisely coordinated single-atom bimetallic catalysts is an important design guide currently proposed. Metals do not drive the reaction alone. Different types of coordination can improve the catalytic reaction of active centers. Therefore, finding the precise synthesis of coordination types and coordination numbers is a key starting point for us to solve the current drawbacks of solid catalysts. Summary of the invention

[0004] The first technical problem to be solved by the present invention is to provide a P-coordinated Co-Rh bimetallic catalyst.

[0005] The second technical problem to be solved by the present invention is to provide a method for synthesizing a P-coordinated Co-Rh bimetallic catalyst. The carbon substrate-modified P-coordinated bimetallic catalyst prepared by the synthesis method has a loose and porous morphology, wherein the coordination effect of P can effectively adjust the local electron density of Rh, the coordination number of P coordination can effectively adjust the catalytic activity of the active center, and the surface-loaded bimetallic catalyst is a uniformly dispersed nanostructure.

[0006] The third technical problem to be solved by the present invention is to provide an application of a P-coordinated Co-Rh bimetallic catalyst obtained by the above-mentioned synthesis method.

[0007] In order to solve the above-mentioned first technical problem, the present invention adopts the following technical solution:

[0008] A P-coordinated Co-Rh bimetallic catalyst comprising:

[0009] Active metal atoms Co and Rh, coordination atoms P, and the support is porous carbon;

[0010] The metal atoms Co and Rh are uniformly distributed in the inner surface of the porous carbon channel in the form of atoms, and the utilization rate of metal atoms is nearly 100%.

[0011] The P is evenly distributed in the inner surface of the porous carbon channel near Rh;

[0012] The P can significantly affect the electronic state of Rh, indicating the interaction between Rh and P.

[0013] To solve the above second technical problem, the present invention adopts the following technical solution:

[0014] A method for synthesizing a P-coordinated Co-Rh bimetallic catalyst comprises the following steps:

[0015] 1) Preparation of carrier suspension

[0016] Weigh 0.12-1.2 g of the carrier, add 60-300 mL of solvent for pre-impregnation, the pre-impregnation time is ≥ 1 hour, and then stir evenly to obtain a carrier suspension;

[0017] 2) Preparation of active component impregnation solution

[0018] Weigh 0.003-0.06g of Rh precursor, 0.0006-0.012g of Co precursor, and 0.002-0.04g of phosphorus source, add them to 4-6mL of solvent and dissolve them by ultrasonication to obtain a mixed solution; then add the mixed solution to the carrier suspension obtained in step 1) for impregnation to allow the active components to fully diffuse; age for 8-12min, separate the solid, wash it with a solvent for 2-4 times, centrifuge it, and dry it to obtain a P-Rh-Co bimetallic catalyst;

[0019] 3) High temperature calcination

[0020] The dried P-Rh-Co bimetallic catalyst prepared in step 2) is placed in a tubular furnace, heated to 300-800° C., and calcined at a constant temperature for 3 hours.

[0021] As a further improvement of the technical solution, in step 1), the carrier is porous activated carbon.

[0022] Preferably, in step 1), the solvent is anhydrous ethanol.

[0023] As a further improvement of the technical solution, in step 2), the Rh precursor is RhCl3·3H2O; the Co precursor is Co(NO3)2·6H2O; and the P source is triphenylphosphine (PPh3).

[0024] Preferably, in step 2), the solvent is anhydrous ethanol.

[0025] Preferably, in step 2), the immersion temperature is 30-45°C

[0026] Preferably, in step 2), the immersion time is 2-14 hours; more preferably, the immersion time is 4-10 hours.

[0027] Preferably, in step 2), the molar ratio of the Rh precursor, the Co precursor and the phosphorus source is 7-28:1-6:4-20.

[0028] As a further improvement of the technical solution, in step 3), the calcination temperature is 200-1000°C; more preferably, the calcination temperature is 300-800°C;

[0029] Preferably, in step 3), the calcination time is 2-6 hours, more preferably, the calcination temperature time is 3 hours.

[0030] Preferably, in step 3), the calcination heating rate is 2-10°C / min, and the temperature is raised to the target temperature.

[0031] In order to solve the third technical problem mentioned above, the present invention also provides an application of the P-coordinated bimetallic catalyst obtained by the above synthesis method in olefin carbonylation.

[0032] Any range described in the present invention includes the end value and any numerical value between the end values ​​and any sub-range formed by the end value or any numerical value between the end values.

[0033] Unless otherwise specified, all raw materials in the present invention can be purchased from the market, and the equipment used in the present invention can adopt conventional equipment in the relevant field or refer to the existing technology in the relevant field.

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

[0035] The P-coordinated Co-Rh bimetallic catalyst obtained by the present invention has a uniform substrate arrangement, wherein the carbon substrate has loose pores, a large specific surface area, and pore diameters concentrated in micropores and mesopores, which is very suitable for the diffusion of metals in the pores; P coordination can regulate the electron density around the metal, and at the same time can change the catalytic activity of the active center, with obvious differences. This catalyst with precise coordination and regulation of bimetallic catalytic activity can better drive the reaction. This series of catalysts shows excellent activity and stability in the catalysis of isooctene carbonylation reaction, which is superior to similar catalysts. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0037] Figure 1 This is a TEM image of the P-coordinated Co-Rh bimetallic catalyst obtained in Example 1 of the present invention.

[0038] Figure 2 This is the atomic distribution diagram of the P-coordinated Co-Rh bimetallic catalyst obtained in Example 1 of the present invention.

[0039] Figure 3 Schematic diagram of the catalytic activity of the P-coordinated Co-Rh bimetallic catalysts obtained in Example 1 of the present invention and Comparative Examples 1-4.

[0040] Figure 4 This is an XPS comparison chart of the P-coordinated Co-Rh bimetallic catalysts obtained in Example 1 of the present invention and Comparative Examples 1-3.

[0041] Figure 5 This is a comparison chart of XRD of the P-coordinated Co-Rh bimetallic catalysts obtained in Example 1 of the present invention and Comparative Examples 1-3. DETAILED DESCRIPTION

[0042] In order to explain the present invention more clearly, the present invention is further described below in conjunction with preferred embodiments. It should be understood by those skilled in the art that the following specific description is illustrative rather than restrictive, and should not be used to limit the scope of protection of the present invention.

[0043] As one aspect of the present invention, the present invention provides a P-coordinated Co-Rh bimetallic catalyst, comprising:

[0044] Active metal atoms Co and Rh, coordination atoms P, and the support is porous carbon;

[0045] The metal atoms Co and Rh are uniformly distributed in the inner surface of the porous carbon channel in the form of atoms, and the utilization rate of the metal atoms is nearly 100%; the specific utilization rate of the metal atoms is higher than 95%, 96%, 97%, 98%, or 99%;

[0046] The P is evenly distributed in the inner surface of the porous carbon channel near Rh;

[0047] The P can significantly affect the electronic state of Rh, indicating the interaction between Rh and P.

[0048] The P-coordinated Co-Rh bimetallic catalyst obtained by the present invention has a uniform substrate arrangement, wherein the carbon substrate has loose pores, a large specific surface area, and pore diameters concentrated in micropores and mesopores, which is very suitable for the diffusion of metals in the pores; P coordination can regulate the electron density around the metal and change the catalytic activity of the active center, with obvious differences. This catalyst with precise coordination and regulation of bimetallic catalytic activity can better drive the reaction.

[0049] As another aspect of the present invention, a method for synthesizing a P-coordinated Co-Rh bimetallic catalyst comprises the following steps:

[0050] 1) Preparation of carrier suspension

[0051] Weigh 0.12-1.2 g of the carrier, add 60-300 mL of solvent for pre-impregnation, the pre-impregnation time is ≥ 1 hour, and then stir evenly to obtain a carrier suspension;

[0052] 2) Preparation of active component impregnation solution

[0053] Weigh 0.003-0.06g of Rh precursor, 0.0006-0.012g of Co precursor, and 0.002-0.04g of phosphorus source, add them to 4-6mL of solvent and dissolve them by ultrasonication to obtain a mixed solution; then add the mixed solution to the carrier suspension obtained in step 1) for impregnation to allow the active components to fully diffuse; age for 8-12min, separate the solid, wash it with a solvent for 2-4 times, centrifuge it, and dry it to obtain a P-Rh-Co bimetallic catalyst;

[0054] 3) High temperature calcination

[0055] The dried P-Rh-Co bimetallic catalyst prepared in step 2) is placed in a tubular furnace, heated to 300-800° C., and calcined at a constant temperature for 3 hours.

[0056] As a further improvement of the technical solution, in step 1), the carrier is porous activated carbon.

[0057] In certain embodiments of the present invention, in step 1), the solvent is anhydrous ethanol.

[0058] In certain embodiments of the present invention, in step 2), the Rh precursor is RhCl3·3H2O; the Co precursor is Co(NO3)2·6H2O; and the P source is triphenylphosphine (PPh3).

[0059] In certain embodiments of the present invention, in step 2), the solvent is anhydrous ethanol.

[0060] In certain embodiments of the present invention, in step 2), the immersion temperature is 30-45°C

[0061] In certain embodiments of the present invention, in step 2), the immersion time is 2-14h, or 2-10h, or 2-8h, or 2-6h, or 2-4h, or 4-14h, or 4-10h, or 4-8h, or 4-6h, or 6-14h, or 6-10h, or 6-8h; more preferably, the immersion time is 4-10h.

[0062] In certain embodiments of the present invention, in step 2), the molar ratio of the Rh precursor, the Co precursor and the phosphorus source is 7-28:1-6:4-20.

[0063] In certain embodiments of the present invention, in step 3), the calcination temperature is 200-1000°C, or 200-900°C, or 200-800°C, or 200-700°C, or 200-600°C, or 200-500°C, or 200-400°C, or 200-300°C, or 300-1000°C, or 300-900°C, or 300-800°C, or 300-700°C, or 300-600°C, or 300-500°C, or 300-400°C, or 400-1000°C, or 400-900°C, or 400-800°C, or 400-700°C, or 400-600°C, or 400-500°C, or 500-1000°C, or 500-900°C, or 500-800°C, or 500-700°C, or 500-600°C, or 600-1000°C, or 600-900°C, or 600-800°C, or 600-700°C, or 700-1000°C, or 700-900°C, or 700-800°C, or 800-1000°C, or 800-900°C, or 900-1000°C; more preferably, the calcination temperature is 300-800°C;

[0064] In certain embodiments of the present invention, in step 3), the calcination time is 2-6h, or 2-5h, or 2-4h, or 2-3h or 3-6h, or 3-5h, or 3-4h, 4-6h, or 4-5h, or 5-6h, and more preferably, the calcination temperature time is 3h.

[0065] In certain embodiments of the present invention, in step 3), the calcination heating rate is 2-10°C / min, or 2-9°C / min, or 2-8°C / min, or 2-7°C / min, or 2-6°C / min, or 2-5°C / min, or 2-4°C / min, or 2-3°C / min, or 4-10°C / min, or 4-9°C / min, or 4-8°C / min, or 4-7°C / min, or 4-6°C / min, or 4-5°C / min, and the temperature is increased to the target temperature.

[0066] As another aspect of the present invention, the present invention also provides an application of a P-coordinated bimetallic catalyst obtained by the above-mentioned synthesis method in olefin carbonylation; preferably, the olefin is isooctene.

[0067] Example 1

[0068] A method for synthesizing a P-coordinated Co-Rh bimetallic catalyst comprises the following steps:

[0069] 1) Preparation of carrier suspension

[0070] Weigh 1.2 g of porous carbon support, add 300 mL of anhydrous ethanol for pre-impregnation for 1 h, and then stir evenly to obtain a support suspension;

[0071] 2) Preparation of active component impregnation solution

[0072] The weighed Rh precursor, Co precursor, and phosphorus source were added to 4-6 mL of anhydrous ethanol for ultrasonic dissolution, and the ratio was Rh:Co:P=7:1:4. The mixture was slowly added to the carrier suspension for impregnation to allow the active components to fully diffuse. The solid was separated after aging for 10 minutes, and washed with anhydrous ethanol for 3 times, centrifuged, and dried to obtain a P-Rh-Co bimetallic catalyst.

[0073] 3) High temperature calcination of catalyst samples

[0074] The dried sample was placed in a tube furnace, and the temperature was set to 400 °C for calcination for 3 h at a heating rate of 5 °C / min.

[0075] Figure 1 This is a TEM image of the P-coordinated Co-Rh bimetallic catalyst obtained in Example 1 of the present invention.

[0076] Figure 2 This is the atomic distribution diagram of the P-coordinated Co-Rh bimetallic catalyst obtained in Example 1 of the present invention.

[0077] Figure 3 Schematic diagram of the catalytic activity of the P-coordinated Co-Rh bimetallic catalysts obtained in Example 1 and Comparative Examples 1-4 of the present invention and their comparative samples.

[0078] Figure 4 This is an XPS comparison chart of the P-coordinated Co-Rh bimetallic catalysts obtained in Example 1 of the present invention and Comparative Examples 1-3.

[0079] Figure 5 This is a comparison chart of XRD of the P-coordinated Co-Rh bimetallic catalysts obtained in Example 1 of the present invention and Comparative Examples 1-3.

[0080] Example 2

[0081] Example 1 was repeated, except that the calcination temperature in step 3) was adjusted to 600°C.

[0082] Example 3

[0083] Example 1 was repeated, except that the heating rate in step 3) was adjusted to 4°C / min.

[0084] Example 4

[0085] Example 1 was repeated, except that the temperature rise rate in step 3) was 6°C / min.

[0086] After testing, Example 2, Example 3 and Example 4 can all obtain the same technical effect as Example 1. Compared with Example 1, Example 2, Example 3 and Example 4 can all obtain the same activity as Example 1, and the electron cloud density around Rh is not much different.

[0087] Example 5

[0088] An application of the P-coordinated bimetallic catalyst obtained by the synthesis method of Example 1 in olefin carbonylation comprises the following steps:

[0089] 1. Weigh the catalyst and put it into a test tube;

[0090] 2. Use a double-row tube to evacuate the air in the solvent storage tank and replace it with nitrogen at the same time. Repeat the replacement three times. Use a millimeter needle to take out the solvent and add it to the catalyst test tube;

[0091] 3. Use a pipette to draw up isobutylene and add it to the catalyst test tube. Then use a millimeter needle to add the catalyst suspension into the reactor for reaction;

[0092] 4. After the reaction is completed, wait for the reactor to cool down to room temperature, exhaust the air in the kettle, and extract the reaction liquid in the kettle; perform gas chromatography analysis; it can be seen that isobutylene has been carbonylated to obtain the carbonylated product isononanal.

[0093] Comparative Example 1

[0094] Example 1 was repeated, with the only difference being that in step 2), the ratio of Rh to Co to P was controlled to be Rh:Co:P=7:1:8, recorded as Rh7Co1P8.

[0095] After testing: the synthesized P-coordinated Co-Rh bimetallic catalyst has a lower activity in hydroformylation than the catalyst prepared in Example 1. XPS shows that the amount of P added has an effect on the charge effect of the Rh metal.

[0096] Comparative Example 2

[0097] Example 1 was repeated, except that in step 2), the molar ratio of Rh to Co to P was controlled to be Rh:Co:P=7:1:12, and was labeled as Rh7Co1P 12 .

[0098] After testing: the synthesized P-coordinated Co-Rh bimetallic catalyst has an activity in hydroformylation that is inferior to that of the catalyst prepared in Example 1, and its activity continues to decrease compared to that of Comparative Example 1. XPS shows that the amount of P added has an effect on the charge effect of the Rh metal.

[0099] Comparative Example 3

[0100] Example 1 was repeated, except that in step 2), the ratio of Rh to Co to P was controlled to be Rh:Co:P=7:1:16, which was labeled as Rh7Co1P 16 .

[0101] After testing: the synthesized P-coordinated Co-Rh bimetallic catalyst has an activity in hydroformylation that is inferior to that of the catalyst prepared in Example 1, and its activity continues to decrease compared to that of Comparative Example 1. XPS shows that the amount of P added has an effect on the charge effect of the Rh metal.

[0102] Comparative Example 4

[0103] Example 1 was repeated, with the only difference being that the catalyst reaction time was changed to 1 h and was labeled as Rh7Co1P4-1.

[0104] After testing, the synthesized P-coordinated Co-Rh bimetallic catalyst had a lower catalyst activity than that of comparative example 1. The catalyst conversion rate was 29.1%.

[0105] In summary, the synthesis method of a Co-Rh bimetallic catalyst of the present invention combines multiple investigation angles, impregnation temperature and time, regulation of the ratio of active components to coordinating atoms, programmed heating final temperature, programmed heating time, etc., which are coordinated and cooperated with each other to form a complete technical solution, so as to obtain the carbon substrate modified P coordinated Co-Rh bimetallic catalyst required by the present invention.

[0106] Obviously, the above embodiments of the present invention are merely examples for clearly explaining the present invention, and are not intended to limit the implementation methods of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is impossible to list all implementation methods here. Any obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A P-coordinated Co-Rh bimetallic catalyst, characterized in that: include: Active metal atoms Co and Rh, coordination atoms P, and the support is porous carbon; The metal atoms Co and Rh are evenly distributed on the inner surface of the porous carbon channels at the atomic level, and the utilization rate of metal atoms is nearly 100%; P is evenly distributed in the inner surface of the porous carbon channels near Rh; P can significantly affect the electronic state of Rh, indicating the interaction between Rh and P. The synthesis method of the P-coordinated Co-Rh bimetallic catalyst comprises the following steps: 1) Preparation of carrier suspension Weigh 0.12-1.2 g of the carrier, add 60-300 mL of solvent for pre-impregnation, the pre-impregnation time is ≥ 1 hour, and then stir evenly to obtain a carrier suspension; 2) Preparation of active component impregnation solution Weigh 0.003-0.06g of Rh precursor, 0.0006-0.012g of Co precursor, and 0.002-0.04g of phosphorus source, add them to 4-6mL of solvent and dissolve them by ultrasonication to obtain a mixed solution; then add the mixed solution to the carrier suspension obtained in step 1) for impregnation to allow the active components to fully diffuse; age for 8-12min, separate the solid, wash it with a solvent for 2-4 times, centrifuge it, and dry it to obtain a P-Rh-Co bimetallic catalyst; 3) High temperature calcination The dried P-Rh-Co bimetallic catalyst in step 2) is placed in a tubular furnace, heated to 300-800°C, and calcined at a constant temperature for 3 hours; In step 1), the carrier is porous activated carbon; In step 1), the solvent is anhydrous ethanol; In step 2), the Rh precursor is RhCl3·3H2O; the Co precursor is Co(NO3)2·6H2O; the P source is triphenylphosphine PPh3; In step 2), the solvent is anhydrous ethanol; In step 2), the immersion temperature is 30-45°C; In step 2), the immersion time is 2-14 hours; In step 2), the molar ratio of the Rh precursor, the Co precursor and the phosphorus source is 7-28:1-6:4-20; In step 3), the calcination heating rate is 2-10°C / min, and the temperature is raised to the target temperature.

2. A method for synthesizing a P-coordinated Co-Rh bimetallic catalyst as claimed in claim 1, characterized in that: The steps include: 1) Preparation of carrier suspension Weigh 0.12-1.2 g of the carrier, add 60-300 mL of solvent for pre-impregnation, the pre-impregnation time is ≥ 1 hour, and then stir evenly to obtain a carrier suspension; 2) Preparation of active component impregnation solution Weigh 0.003-0.06g of Rh precursor, 0.0006-0.012g of Co precursor, and 0.002-0.04g of phosphorus source, add them to 4-6mL of solvent and dissolve them by ultrasonication to obtain a mixed solution; then add the mixed solution to the carrier suspension obtained in step 1) for impregnation to allow the active components to fully diffuse; age for 8-12min, separate the solid, wash it with a solvent for 2-4 times, centrifuge it, and dry it to obtain a P-Rh-Co bimetallic catalyst; 3) High temperature calcination The dried P-Rh-Co bimetallic catalyst in step 2) is placed in a tubular furnace, heated to 300-800°C, and calcined at a constant temperature for 3 hours; In step 1), the carrier is porous activated carbon; In step 1), the solvent is anhydrous ethanol; In step 2), the Rh precursor is RhCl3·3H2O; the Co precursor is Co(NO3)2·6H2O; the P source is triphenylphosphine PPh3; In step 2), the solvent is anhydrous ethanol; In step 2), the immersion temperature is 30-45°C; In step 2), the immersion time is 2-14 hours; In step 2), the molar ratio of the Rh precursor, the Co precursor and the phosphorus source is 7-28:1-6:4-20; In step 3), the calcination heating rate is 2-10°C / min, and the temperature is raised to the target temperature.

3. The synthesis method according to claim 2, characterized in that: In step 3), the calcination temperature is 200-1000°C.

4. The synthesis method according to claim 2, characterized in that: In step 3), the calcination time is 2-6 hours.

5. Use of the P-coordinated Co-Rh bimetallic catalyst prepared by any synthesis method as claimed in any one of claims 2 to 4 in olefin carbonylation.

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