An olefin hydroformylation catalyst, its preparation and use

Abstract

The application discloses a nitrogen-doped carbon-coated Rh-Co composite catalyst CoRh@NC and a preparation method thereof, wherein the content of Rh is 0.1wt%-2.5wt% according to Rh atoms, and the content of Co is 0.5wt%-10wt% according to Co atoms based on the total weight of the catalyst. According to the composite catalyst, metal Co and Rh are added into the growth process of ZIF-8 to form a CoRh-ZIF-8 precursor, CoRh alloy nanoparticle catalysts confined in nitrogen-doped porous carbon are obtained through pyrolysis, and the catalysts are used in a diisobutylene hydroformylation reaction process. The catalyst has good stability, and still has good activity after being recycled for 7 times, and the olefin conversion rate and the selectivity of aldehydes are very high in the catalytic olefin hydroformylation reaction.

Description

Technical Field

[0001] This invention relates to the field of fine chemical technology, specifically to a catalyst for the hydroformylation of olefins and its preparation method, as well as the use of the catalyst in catalyzing the preparation of aldehyde compounds from olefins. Background Technology

[0002] Aldehydes are important chemical intermediates, and the hydroformylation reaction for synthesizing aldehydes from olefins is of great industrial significance. This reaction was discovered by Otto Roelen while studying the Fischer-Tropsch reaction. It primarily uses olefins and CO / H2 syngas as raw materials to synthesize high-value-added aldehydes under the action of a catalyst.

[0003] Currently, homogeneous Rh-based phosphine complex catalysts ([RhCl(PPh3)3]) are gradually replacing Co-based catalysts due to their superior performance. However, Rh-based homogeneous catalysts suffer from problems such as difficulty in separation and phosphine ligand contamination. To address these issues, various heterogeneous catalytic systems, including homogeneous catalyst immobilization and single-atom catalysts, have been developed and applied to the hydroformylation of olefins. Among these, bimetallic supported catalysts exhibit superior performance compared to monometallic supported catalysts due to the excellent synergistic effect between the metals.

[0004] In recent years, due to the unique organic-inorganic framework of metal-organic frameworks (MOFs), and their high porosity, large specific surface area, tunable pore size, and ease of functionalization, MOF-derived metal nanocatalysts encapsulated in nitrogen-doped carbon materials have attracted widespread attention. The zeolite-imidazolium system (ZIF-8), a subclass of MOFs, has been considered a suitable precursor for preparing transition metal and nitrogen-doped porous carbon composites via pyrolysis. Notably, the addition of bimetallic cations during ZIF-8 growth can introduce bimetallic active sites to improve catalytic performance. Furthermore, the uniform doping of zinc atoms in ZIF-8 helps regulate the coordination environment of the metal center and provides steric hindrance for potential aggregation during pyrolysis. In addition, the further integrated three-dimensional porous structure promotes the transport and diffusion of reactants.

[0005] Therefore, there is still a need to develop novel catalysts that can achieve high catalytic activity in the hydroformylation of aldehydes. Summary of the Invention

[0006] To address the aforementioned issues, this invention incorporates Co and Rh, metals with superior hydrogenation activity between non-noble metals, into the growth process of ZIF-8 to form a CoRh-ZIF-8 precursor. Through pyrolysis, a CoRh alloy nanoparticle catalyst confined within nitrogen-doped porous carbon is obtained and applied to the hydroformylation of diisobutylene. This catalyst exhibits good stability and demonstrates high olefin conversion and aldehyde selectivity in the catalytic hydroformylation of olefins.

[0007] According to one aspect of the present invention, an object of the present invention is to provide a nitrogen-doped carbon-coated Rh, Co composite catalyst CoRh@NC, wherein, based on the total weight of the catalyst, the Rh content is 0.1wt%-2.5wt%, preferably 0.1wt%-1.0wt%, more preferably 0.8wt%, and the Co content is 0.5wt%-10wt%, preferably 1.5wt%-6.0wt%, more preferably 3.45wt%, based on the Co atoms.

[0008] According to another aspect of the present invention, another object of the present invention is to provide a method for preparing the nitrogen-doped carbon-coated Rh, Co composite catalyst CoRh@NC, the preparation method being carried out as follows:

[0009] 1) Dissolve a mixture of cobalt salt precursor, rhodium salt precursor and zinc salt precursor in a certain amount of solvent 1 to form solution A, dissolve 2-methylimidazole in a certain amount of solvent 2 to form solution B, then quickly pour solution B into solution A and stir, then treat the mixture under hydrothermal conditions at 70-120℃ for 6-18 hours to obtain CoRh-ZIF-8 precursor;

[0010] 2) The precipitate obtained in step 1) is separated by centrifugation and washed three times with methanol. The product is dried under vacuum at 60°C. The resulting solid is ground and calcined at 600-1200°C for 1-4 hours under an inert atmosphere to obtain the catalyst CoRh@NC.

[0011] Preferably, the cobalt salt in step 1) is selected from cobalt nitrate hexahydrate, cobalt sulfate heptahydrate, and cobalt chloride hexahydrate;

[0012] Preferably, the rhodium salt in step 1) is selected from rhodium trichloride trihydrate, sodium hexachlororhodiumate, rhodium acetate, and rhodium nitrate;

[0013] Preferably, the zinc salt in step 1) is selected from zinc nitrate hexahydrate, zinc acetate, and zinc chloride;

[0014] Preferably, the hydrothermal conditions in step 1) are 90°C and the reaction time is 12 hours.

[0015] Preferably, the inert atmosphere in step 2) is a nitrogen atmosphere or an argon atmosphere.

[0016] Preferably, the roasting temperature in step 2) is 900°C and the time is 2 hours.

[0017] According to another aspect of the invention, another object of the invention is to provide the use of the nitrogen-doped carbon-coated Rh, Co composite catalyst CoRh@NC in the hydroformylation reaction of olefins.

[0018] According to another aspect of the present invention, another object of the present invention is to provide a method for the hydroformylation reaction of olefins using the nitrogen-doped carbon-coated Rh, Co composite catalyst CoRh@NC, the method being carried out as follows:

[0019] A certain amount of the CoRh@NC catalyst according to the present invention, olefins, and solvent are added to a high-pressure reactor. A high-pressure CO and H2 mixture with a volume ratio of 1:1 is then introduced into the reactor, and the reaction temperature is set to 120℃-140℃, with a reaction time of 6-18 hours.

[0020] Preferably, the gas pressure of the olefin hydroformylation reaction is 5.0-7.0 MPa, the reaction temperature is 120°C, and the reaction time is 12 hours.

[0021] Preferably, the solvent is selected from toluene, tetrahydrofuran, acetonitrile, n-hexane, and n-octane.

[0022] Preferably, the olefin is a C1-C6 olefin monomer containing at least one double bond, such as ethylene, propylene, n-butene, isobutene, diisobutene, etc.

[0023] Preferably, in the hydroformylation reaction method, the CoRh@NC catalyst can be reused up to 3 times, more preferably up to 5 times, and even more preferably up to 7 times, while still maintaining stable catalytic activity.

[0024] Beneficial effects

[0025] 1. The nitrogen-doped carbon-encapsulated CoRh@NC catalyst proposed in this invention is mainly prepared by a simple hydrothermal method and a calcination method. The preparation method of the catalyst is simple and easy to scale up for production.

[0026] 2. The nanoparticles in this CoRh@NC catalyst are uniformly dispersed and encapsulated in nitrogen-doped carbon material. The catalyst has good stability and maintains good activity after 7 cycles.

[0027] 3. The CoRh@NC catalyst provided in this invention has high olefin conversion and aldehyde selectivity in the catalytic hydroformylation reaction of olefins. The reaction is easy to control, simple to operate, and easy to apply and scale up in industrial production. Attached Figure Description

[0028] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0029] Figure 1 The XRD patterns of the materials and Co@NC and Rh@NC in Example 1 of this invention are shown.

[0030] Figure 2 This is a diagram illustrating the effect of catalyst reuse in the hydroformylation reaction of diisobutylene catalyzed by the CoRh@NC catalyst in Example 1 of this invention.

[0031] Figure 3 This is a TEM image of the CoRh@NC catalyst in Example 1 of the present invention. Detailed Implementation

[0032] The present invention will now be described in detail. Before proceeding with the description, it should be understood that the terminology used in this specification and the appended claims should not be construed as limited to its general or dictionary meaning, but rather should be interpreted according to the meaning and concept corresponding to the technical aspects of the invention, based on the principle that the inventors are allowed to appropriately define the terms for the best interpretation. Therefore, the description presented herein is merely a preferred example for illustrative purposes and is not intended to limit the scope of the invention. It should be understood that other equivalents or modifications can be obtained from it without departing from the spirit and scope of the invention.

[0033] In this document, the terms “comprising,” “including,” “having,” “containing,” or any other similar terms are open-ended conjunctions intended to cover non-exclusive inclusions. For example, a composition or article containing a plurality of elements is not limited to those listed herein, but may also include other elements not explicitly listed but typically inherent to the composition or article. Furthermore, unless explicitly stated to the contrary, the term “or” is inclusive, not exclusive. For example, the condition “A or B” is satisfied in any of the following cases: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); A and B are both true (or exist). Moreover, in this document, the terms “comprising,” “including,” “having,” and “containing” should be interpreted as specifically disclosed and simultaneously cover closed or semi-closed conjunctions such as “composed of” and “substantially composed of.”

[0034] In this document, all features or conditions defined in the form of numerical ranges or percentage ranges are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible secondary ranges and individual values ​​within those ranges, particularly integer values. For example, a range description of "1 to 8" should be considered as specifically disclosing all secondary ranges such as 1 to 7, 2 to 8, 2 to 6, 3 to 6, 4 to 8, 3 to 8, etc., particularly secondary ranges defined by all integer values, and should be considered as specifically disclosing individual values ​​within those ranges such as 1, 2, 3, 4, 5, 6, 7, 8, etc. Unless otherwise specified, the foregoing interpretation applies to all content throughout this invention, regardless of its scope.

[0035] If a quantity or other numerical value or parameter is expressed as a range, a preferred range, or a series of upper and lower limits, it should be understood that this document has specifically disclosed all ranges consisting of any upper or preferred value of that range and the lower or preferred value of that range, regardless of whether such ranges are separately disclosed. Furthermore, when a range of numerical values ​​is mentioned herein, unless otherwise stated, the range shall include its endpoints and all integers and fractions within the range.

[0036] In this document, numerical values ​​are to be understood as having a precision with significant digits, provided that the purpose of the invention can be achieved. For example, the number 40.0 should be understood to cover a range from 39.50 to 40.49.

[0037] In the nitrogen-doped carbon-coated Rh, Co composite catalyst CoRh@NC according to the present invention, the precursor material is CoRh-ZIF-8. ZIF-8 material provides carbon and nitrogen sources, and NC support with large specific surface area and excellent stability can be derived by high-temperature calcination in N2.

[0038] In the CoRh@NC catalyst, CoRh alloy nanoparticles are encapsulated in nitrogen-doped carbon material, effectively preventing the loss of active sites.

[0039] In step 1) of the preparation method of the CoRh@NC catalyst, zinc salt needs to be added to form a ZIF-8 structure with 2-methylimidazole. However, most of the zinc is removed during the calcination process in step 2). The final catalyst CoRh@NC contains a very small amount of Zn. The residual Zn will not affect the catalytic activity. The main active components are Co and Rh metal.

[0040] In the hydroformylation reaction method of olefins using the nitrogen-doped carbon-coated Rh, Co composite catalyst CoRh@NC according to the present invention, the CoRh@NC catalyst, olefin, and solvent are added to a high-pressure reactor. A high-pressure CO and H2 mixture with a volume ratio of 1:1 is then introduced into the reactor, and the reaction temperature is set to 120℃-140℃, with a reaction time of 6-18 hours.

[0041] Taking diisobutylene as an example, the specific method is as follows: A certain amount of CoRh@NC catalyst, diisobutylene, and solvent (toluene) are added to a high-pressure reactor. A high-pressure CO and H2 mixture with a volume ratio of V:V = 1:1 is then introduced into the reactor. The reaction temperature is set at 120℃, and the reaction time is 12 hours. After the reaction, the reaction products are analyzed using gas chromatography. The conversion rate of diisobutylene is as high as 86.76%, and the selectivity of aldehydes is as high as 99.95%. The reaction is shown in Reaction Equation 1 below, where the substrate can be... Both have the same hydroformylation product. As reaction substrates, they can be used alone or mixed in a molar ratio of 1:1 to 1:10, preferably 1:4.

[0042]

[0043] The following embodiments are merely examples illustrating implementations of the present invention and do not constitute any limitation on the present invention. Those skilled in the art will understand that modifications made without departing from the spirit and concept of the present invention fall within the protection scope of the present invention. Unless otherwise specified, the reagents and instruments used in the following embodiments are commercially available products.

[0044] Example 1: Preparation of Catalyst

[0045] 0.049 g of rhodium trichloride trihydrate, 0.055 g of cobalt nitrate hexahydrate, 1.16 g of zinc nitrate hexahydrate, and 40 mL of methanol were dissolved in a beaker to form solution A. 4.93 g of 2-methylimidazole was dissolved in 40 mL of methanol to form solution B. Solution B was then quickly poured into solution A. After thorough mixing, the mixture was poured into a 100 mL polytetrafluoroethylene-lined container and placed in a hydrothermal reactor. The reactor was placed in an oven and heated to 90 °C at a rate of 5 °C / min, and maintained at this temperature for 12 hours. The resulting precipitate was then centrifuged and washed three times with methanol. The product was dried overnight under vacuum at 60 °C. The resulting solid was ground and placed in a tube furnace, heated to 900 °C at a rate of 5 °C / min, and calcined under a nitrogen atmosphere for 2 hours to obtain the CoRh@NC catalyst. The catalyst contained 0.8 wt% Rh and 3.45 wt% Co.

[0046] Figure 1The XRD patterns of the materials and Co@NC and Rh@NC in this embodiment are shown. The purpose of Co@NC and Rh@NC is to find the specific positions of the peaks of Co and Rh, while the peak position of the CoRh alloy should be between the two.

[0047] Example 2: Hydroformylation of Olefins

[0048] 40 mg of CoRh@NC catalyst, 1 mL of diisobutylene, and 20 mL of toluene from Example 1 were added to a 100 mL high-pressure reactor, which was then filled with a CO / H2 mixture at 7 MPa (V:V = 1:1). The reaction was carried out at 120 °C for 12 h. Gas chromatography analysis showed that the conversion rate of diisobutylene was 86.76%, and the selectivity for aldehydes was 99.95%.

[0049] Example 3: Catalyst Cycling Test

[0050] After filtration, washing, and centrifugation, the CoRh@NC catalyst from Example 2 was added to a 100mL high-pressure reactor along with 1mL diisobutylene and 20mL toluene. A CO / H2 mixture (V:V, 1:1) at 7MPa was introduced, and the reaction was carried out at 120℃ for 12h. Gas chromatography analysis showed that the CoRh@NC catalyst was recycled 7 times, and the conversion rate of diisobutylene was higher than 80% in all cases. The selectivity of aldehydes was higher than 99% in all cases. ICP analysis showed no loss of Rh.

[0051] Example 4

[0052] 0.0663 g of rhodium trichloride trihydrate, 0.0367 g of cobalt nitrate hexahydrate, 1.16 g of zinc nitrate hexahydrate, and 40 mL of methanol were dissolved in a beaker to form solution A. 4.93 g of 2-methylimidazole was dissolved in 40 mL of methanol to form solution B. Solution B was then quickly poured into solution A. After thorough mixing, the mixture was poured into a 100 mL polytetrafluoroethylene-lined container and placed in a hydrothermal reactor. The reactor was placed in an oven and heated to 90 °C at a rate of 5 °C / min, and maintained at this temperature for 12 hours. The resulting precipitate was then centrifuged and washed three times with methanol. The product was dried overnight under vacuum at 60 °C. The resulting solid was ground and placed in a tube furnace, heated to 900 °C at a rate of 5 °C / min, and calcined under a nitrogen atmosphere for 2 hours to obtain the CoRh@NC catalyst. The catalyst contained 1.08 wt% Rh and 2.3 wt% Co.

[0053] Example 5: Hydroformylation of Olefins

[0054] 40 mg of CoRh@NC catalyst, 1 mL of diisobutylene, and 20 mL of toluene from Example 4 were added to a 100 mL high-pressure reactor, and a CO / H2 mixture (V:V = 1:1) at 7 MPa was introduced. The reaction was carried out at 120 °C for 12 h. Gas chromatography analysis showed that the conversion rate of diisobutylene was 67.76%, and the selectivity of aldehydes was 99.97%.

[0055] Example 6

[0056] 0.0331 g of rhodium trichloride trihydrate, 0.0733 g of cobalt nitrate hexahydrate, 1.16 g of zinc nitrate hexahydrate, and 40 mL of methanol were dissolved in a beaker to form solution A. 4.93 g of 2-methylimidazole was dissolved in 40 mL of methanol to form solution B. Solution B was then quickly poured into solution A. After thorough mixing, the mixture was poured into a 100 mL polytetrafluoroethylene-lined container and placed in a hydrothermal reactor. The reactor was placed in an oven and heated to 90 °C at a rate of 5 °C / min, maintaining this temperature for 12 hours. The resulting precipitate was then centrifuged and washed three times with methanol. The product was dried overnight under vacuum at 60 °C. The resulting solid was ground and placed in a tube furnace, heated to 900 °C at a rate of 5 °C / min, and calcined under a nitrogen atmosphere for 2 hours to obtain the CoRh@NC catalyst. The catalyst contained 0.53 wt% Rh and 4.65 wt% Co.

[0057] Example 7: Hydroformylation of Olefins

[0058] 40 mg of CoRh@NC catalyst, 1 mL of diisobutylene, and 20 mL of toluene from Example 6 were added to a 100 mL high-pressure reactor, and a CO / H2 mixture (V:V = 1:1) at 7 MPa was introduced. The reactor was reacted at 120 °C for 12 h. Gas chromatography analysis showed that the conversion rate of diisobutylene was 63.24%, and the selectivity for aldehydes was 99.94%.

[0059] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. The application of nitrogen-doped carbon-coated Rh, Co composite catalyst CoRh@NC in the hydroformylation of olefins, characterized in that, Based on the total weight of the catalyst, the Rh content is 0.1wt%-2.5wt% based on Rh atoms, and the Co content is 0.5wt%-10wt% based on Co atoms. The catalyst CoRh@NC was prepared according to the following method: 1) Dissolve a mixture of cobalt salt precursor, rhodium salt precursor and zinc salt precursor in a certain amount of methanol to form solution A, dissolve 2-methylimidazole in a certain amount of methanol to form solution B, then quickly pour solution B into solution A and stir, then treat the mixture under hydrothermal conditions at 70-120℃ for 6-18 hours to obtain CoRh-ZIF-8 precursor; 2) The precipitate obtained in step 1) is separated by centrifugation and washed three times with methanol. The product is dried under vacuum at 60°C. The resulting solid is ground and calcined at 600-1200°C for 1-4 hours under an inert atmosphere to obtain the catalyst CoRh@NC.

2. The use according to claim 1, characterized in that, Based on the total weight of the catalyst, the Rh content is 0.1wt%-1.0wt% based on Rh atoms, and the Co content is 1.5wt%-6.0wt% based on Co atoms.

3. The use according to claim 1, characterized in that, Based on the total weight of the catalyst, the Rh content is 0.8 wt% based on Rh atoms and the Co content is 3.45 wt% based on Co atoms.

4. The use according to claim 1, characterized in that, In step 1) of the catalyst preparation method, the cobalt salt is selected from cobalt nitrate hexahydrate, cobalt sulfate heptahydrate, and cobalt chloride hexahydrate; The rhodium salt mentioned in step 1) is selected from rhodium trichloride trihydrate, sodium hexachlororhodiumate, rhodium acetate, and rhodium nitrate; The zinc salt mentioned in step 1) is selected from zinc nitrate hexahydrate, zinc acetate, and zinc chloride; The hydrothermal conditions described in step 1) are 90°C and the reaction time is 12 hours.

5. The use according to claim 1, characterized in that, In step 2) of the catalyst preparation method, the inert atmosphere is a nitrogen atmosphere or an argon atmosphere; The roasting temperature in step 2) is 900℃ and the time is 2 hours.

6. The use according to claim 1, characterized in that, The hydroformylation reaction of the olefin is carried out as follows: A certain amount of the nitrogen-doped carbon-coated Rh, Co composite catalyst CoRh@NC, olefins, and solvent were added to a high-pressure reactor, and a high-pressure CO and H2 mixture with a volume ratio of 1:1 was introduced into it. The reaction temperature was set to 120℃-140℃, and the reaction time was 6-18h.

7. The use according to claim 6, characterized in that, The olefin hydroformylation reaction is carried out at a gas pressure of 5.0-7.0 MPa, a reaction temperature of 120°C, and a reaction time of 12 hours. The solvent is selected from toluene, tetrahydrofuran, acetonitrile, n-hexane, and n-octane; The olefin is a C2-C6 olefin monomer containing at least one double bond.

8. The use according to claim 6, characterized in that, The olefin is selected from ethylene, propylene, n-butene, isobutene, and diisobutene.

9. The use according to claim 6, characterized in that, In the hydroformylation reaction method, the CoRh@NC catalyst can be reused up to 7 times while maintaining stable catalytic activity.

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