A multi-activation site catalyst and its preparation method and application

Abstract

The invention discloses a multi-activation site catalyst and a preparation method and application thereof, belonging to the technical field of catalysts. The catalyst uses a COF / SiO2 composite material prepared by uniformly spreading COF on the surface of SiO2 as a carrier, and a metal salt is loaded on the carrier by a wet impregnation method, and further reduced to obtain a corresponding supported metal nanoparticle catalyst; based on the total weight of the catalyst, the COF content is 1-30%, and the metal content is 0.2-5%. The interaction between the functional group on the COF of the catalyst and the carbonyl group can preferentially activate the carbonyl group, and the overflow of the active hydrogen obtained by the rapid dissociation of H2 by the metal nanoparticles allows the COF-activated carbonyl group to be hydrogenated to generate alcohols, and the multi-site activation allows the catalyst to catalyze the selective hydrogenation of aldehyde / ketone compounds under relatively mild conditions with high activity and selectivity to generate corresponding alcohol compounds, and the catalyst has important application prospects in the selective hydrogenation of aldehyde / ketone compounds to generate alcohols.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysts, and in particular relates to a multi-activation site catalyst, a preparation method and application thereof in the selective hydrogenation reaction of aldehyde / ketone compounds. Background Art

[0002] Selective hydrogenation reactions are extremely important in the synthesis of spices, pesticides, and pharmaceuticals, as well as in the purification of industrial raw materials, such as hydrogenation of acetylene to ethylene, hydrogenation of nitrobenzene to hydroxylamine, and hydrogenation of aromatic ketones to aromatic alcohols. Among them, the selective reduction of unsaturated ketones / aldehydes to unsaturated alcohols is a fundamental transformation in organic synthetic chemistry, and has important applications in the fields of green chemistry and chemical engineering. The specific goal of the selective hydrogenation of unsaturated ketones / aldehydes is to hydrogenate C=O to generate the corresponding alcohol, while other unsaturated bonds in the molecule (such as C=C, C≡C, benzene ring, etc.) are not affected. Since substrates containing multiple unsaturated groups are involved, it is not easy to obtain the corresponding alcohol compounds with high selectivity. The selectivity of the products in the selective hydrogenation reaction mainly depends on the competitive adsorption and activation of different unsaturated groups, as well as the relative adsorption strength of reactants, intermediates, and products on the surface of metal nanoparticles. Therefore, the above factors need to be considered when designing catalysts.

[0003] In recent years, different strategies have been developed to improve the catalytic performance of supported metal nanoparticles, including reducing the size of metal nanoparticles to single atoms, forming bimetallic alloys, generating strong metal-support interactions (SMSI), modifying metal surfaces with organic ligands, etc. Although these strategies have some effects, it is still a challenging task to simultaneously improve the activity and selectivity of the selective hydrogenation of unsaturated ketones / aldehydes. Summary of the invention

[0004] In order to solve the above technical problems, the purpose of the present invention is to provide a multi-activated site catalyst, a preparation method and its application in the selective hydrogenation of aldehyde / ketone compounds. Compared with the comparative catalyst M / SiO2, the catalyst can carry out the selective hydrogenation reaction of aldehyde / ketone compounds with high activity and high selectivity to generate the corresponding alcohols.

[0005] The object of the present invention is achieved by the following methods:

[0006] The invention provides a multi-activation site catalyst. The catalyst uses a COF / SiO2 composite material prepared by evenly spreading COF on the surface of SiO2 as a carrier, a metal salt is loaded on the carrier by a wet impregnation method, and a corresponding loaded metal nanoparticle catalyst is obtained by reduction.

[0007] Based on the above technical solution, preferably, the COF content of the catalyst is 1-30% and the metal content is 0.2-5% based on the total weight of the catalyst.

[0008] Another aspect of the present invention provides a method for preparing the above-mentioned multi-activation site catalyst, which mainly comprises the following steps:

[0009] (1) preparing a COF / SiO2 carrier by a colloid method or a solvothermal method: adding a COF monomer to a reaction vessel, adding a solvent and a catalyst, stirring and mixing evenly, then adding SiO2, stirring for 12-48 hours or stirring for 1-12 hours and then heating to 90-120°C and maintaining for 12-48 hours, filtering and performing Soxhlet extraction, and drying to obtain a COF / SiO2 carrier;

[0010] (2) M / COF / SiO2 was prepared by wet impregnation method: the COF / SiO2 carrier was dispersed in H2O, and then the metal salt precursor solution was added. The mixture was stirred at room temperature for 4-24 hours and then centrifuged. The obtained solid was dried and reduced in H2 atmosphere at 150-300°C for 0.5-3 hours.

[0011] Based on the above technical scheme, preferably, the COF monomer in step (1) is composed of monomer one and monomer two, monomer one is one of 1,3,5-triformylphloroglucinol, 2,4-dihydroxy-1,3,5-pyromellitic trimesic acid, 2-hydroxy-1,3,5-pyromellitic trimesic acid, and pyromellitic trisaldehyde, monomer two is one of 2,4,6-tris(4'-aminophenyl)-1,3,5-triazine and 1,3,5-tris(4-aminophenyl)benzene, and the molar ratio of monomer one to monomer two is 1:1.

[0012] Based on the above technical scheme, preferably, in step (1), the solvent is one of dimethyl sulfoxide and dioxane; the catalyst is acetic acid solution, and the molar ratio of the catalyst to the monomer one is (100-1000):1.

[0013] Based on the above technical solution, preferably, in step (1), the concentration of monomer 1 in the reaction system is 0.0001-0.01 mol / L.

[0014] Based on the above technical solution, preferably, in step (1), SiO2 is SiO2 nanospheres or SiO2 microspheres, and the mass ratio of COF to SiO2 is 1:(2-100).

[0015] Based on the above technical scheme, preferably, in the process of preparing the COF / SiO2 carrier by the colloid method in step (1), after adding the solvent, a cationic surfactant solution (CTAB) and an anionic surfactant solution (SDS) are also added, and the molar ratio of the cationic surfactant to the monomer one is (10-50):1, and the molar ratio of the anionic surfactant to the monomer one is (0.5-10):1.

[0016] Based on the above technical scheme, preferably, the solvent for Soxhlet extraction in step (1) is tetrahydrofuran or ethanol, the temperature of Soxhlet extraction is 100-120° C., and the time is 12-48 h.

[0017] Based on the above technical solution, preferably, the metal salt precursor added in step (2) is chloroplatinic acid, chloroplatinate, chloropalladic acid or chloropalladate.

[0018] Based on the above technical solution, preferably, the mass ratio of the metal salt precursor and the COF / SiO2 carrier added in step (2) is (2-50):1000.

[0019] Based on the above technical solution, preferably, the specific process of drying in step (2) is drying in flowing air at 50-100° C. for 1-5 hours.

[0020] Based on the above technical scheme, preferably, the H2 reduction in step (2) is carried out in a tubular furnace, the H2 flow rate is 10-20 mL / min, the heating rate is 1-5°C / min, the reduction temperature is 165-200°C, and the reduction time is 1-3h.

[0021] Another object of the present invention is to provide the use of the above catalyst M / COF / SiO2 in the selective hydrogenation reaction of aldehyde / ketone compounds.

[0022] Based on the above technical scheme, preferably, the selective hydrogenation reaction conditions of aldehyde / ketone compounds are as follows: aldehyde / ketone compounds, alcohol and the catalyst are put into a closed high-pressure reactor, and hydrogenolysis reaction is carried out at a hydrogen pressure of 1-4 MPa and 50-80° C. for 0.5-4 h, and the temperature is reduced and the catalyst is separated to obtain the corresponding hydrogenation product.

[0023] Based on the above technical scheme, preferably, the aldehyde / ketone compounds include acetophenone, p-methylacetophenone, m-methylacetophenone, o-methylacetophenone, p-methoxyacetophenone, p-tert-butylacetophenone, p-isobutylacetophenone, p-trifluoromethylacetophenone, benzaldehyde, acetone, butyraldehyde, 4-phenyl-2-butanone, 4-methyl-2-pentanone, 2-hexanone, and dodecanal.

[0024] The catalyst prepared by the present invention has the following advantages:

[0025] 1. The COF / SiO2 carrier prepared by the present invention is coated evenly, and the prepared metal nanoparticles loaded with multi-active site catalysts have small particle sizes and are evenly distributed without obvious agglomeration.

[0026] 2. The interaction between the functional group on COF and the carbonyl group in the M / COF / SiO2 catalyst prepared by the present invention can preferentially activate the carbonyl group. The overflow of active hydrogen obtained by the rapid dissociation of H2 by metal nanoparticles allows the COF-activated carbonyl group to be hydrogenated to produce alcohols. Multi-site activation allows the catalyst to catalyze the selective hydrogenation of aldehyde / ketone compounds to produce corresponding alcohol compounds with high activity and selectivity under relatively mild conditions, which can significantly improve the selectivity and activity in the selective hydrogenation reaction of aldehyde / ketone compounds. The catalytic effect is significantly better than that of the comparative catalyst M / SiO2 catalyst. The catalyst has important application prospects in the selective hydrogenation of aldehyde / ketone compounds to produce alcohols. The synergistic catalysis of multi-site activation provides an effective way to simultaneously improve the activity and selectivity of hydrogenation of multi-functional substrates. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention, the drawings related to the embodiments are briefly introduced below.

[0028] Figure 1 This is a transmission electron microscope (TEM) photograph of the COF-1 / SiO2 carrier obtained in Example 1;

[0029] Figure 2 This is a transmission electron microscope (TEM) photograph of the COF-2 / SiO2 carrier obtained in Example 2;

[0030] Figure 3 This is a transmission electron microscope (TEM) photograph of the COF-3 / SiO2 carrier obtained in Example 3;

[0031] Figure 4 This is a transmission electron microscope (TEM) photograph of the COF-4 / SiO2 carrier obtained in Example 4;

[0032] Figure 5 This is a transmission electron microscope (TEM) photograph of the COF-5 / SiO2 carrier obtained in Example 5;

[0033] Figure 6 This is a transmission electron microscope (TEM) photograph of the COF-6 / SiO2 carrier obtained in Example 6;

[0034] Figure 7 This is a transmission electron microscope (TEM) photograph of the COF-7 / SiO2 carrier obtained in Example 7;

[0035] Figure 8 This is a high-resolution transmission electron microscope (HR-TEM) photograph of the catalyst obtained in Example 8;

[0036] Fig. 9is an argon adsorption-desorption curve diagram of the catalyst obtained in Example 8;

[0037] Fig.10 This is a high-resolution transmission electron microscope (HR-TEM) photograph of the catalyst obtained in Comparative Example 1;

[0038] Fig.11 This is the argon adsorption-desorption curve of the catalyst obtained in Comparative Example 1. DETAILED DESCRIPTION

[0039] The following embodiments are used to further illustrate the present invention, but they do not limit the scope of the invention defined by the appended claims.

[0040] Example 1: Synthesis of COF-1 / SiO2 carrier by colloid method

[0041] Add 2.3 mg of 1,3,5-triformylphloroglucinol and 3.9 mg of 2,4,6-tris(4'-aminophenyl)-1,3,5-triazine to a round-bottom flask, then add 0.1 mL of dimethyl sulfoxide and mix well. Dissolve 84 mg of CTAB and 2.4 mg of SDS in 9.5 mL of water, add to the COF monomer solution and mix well again, then add 0.5 mL of acetic acid and stir to mix well. After 48 hours, add 500 mg of SiO2 nanospheres (COF accounts for 1%-30% of the total catalyst by adjusting the amount of SiO2, in this case 1% COF / SiO2), stir for 24 hours, filter, extract in ethanol for 48 hours, and dry to obtain the COF-1 / SiO2 carrier.

[0042] Using transmission electron microscopy ( Figure 1 ) The carrier COF-1 / SiO2 was characterized. It can be seen that COF-1 / SiO2 is a small sphere with a particle size of about 26nm, and the COF coating on SiO2 is relatively uniform.

[0043] Example 2: Synthesis of COF-2 / SiO2 carrier by colloid method

[0044] The preparation process of this embodiment is basically the same as that of embodiment 1, except that the COF monomer used is replaced by 1,3,5-tri(4-aminophenyl)benzene from 2,4,6-tris(4'-aminophenyl)-1,3,5-triazine, and the obtained carrier is recorded as COF-2 / SiO2.

[0045] Example 3: Synthesis of COF-3 / SiO2 carrier by colloid method

[0046] The preparation process of this embodiment is basically the same as that of embodiment 1, except that the COF monomer used is replaced by triphenylaldehyde from 1,3,5-triformylphloroglucinol, and the obtained carrier is recorded as COF-3 / SiO2.

[0047] Example 4: Solvothermal synthesis of COF-4 / SiO2 carrier

[0048] Add 2.3 mg of 1,3,5-triformylphloroglucinol and 3.9 mg of 2,4,6-tris(4'-aminophenyl)-1,3,5-triazine to a round-bottom flask, then add 10 mL of dioxane and 0.1 mL of acetic acid, and stir to mix evenly. Add 500 mg of amino-modified SiO2 microspheres (COF accounts for 1%-30% of the total catalyst by adjusting the amount of SiO2, in this case 1% COF / SiO2), stir for 4 hours, and heat to 100°C for 24 hours. Then filter and Soxhlet extract in tetrahydrofuran for 24 hours, and dry to obtain the COF-4 / SiO2 carrier.

[0049] Example 5: Solvothermal synthesis of COF-5 / SiO2 carrier

[0050] The preparation process of this embodiment is basically the same as that of embodiment 4, except that the COF monomer used is replaced by 1,3,5-tri(4-aminophenyl)benzene from 2,4,6-tris(4'-aminophenyl)-1,3,5-triazine, and the obtained carrier is recorded as COF-5 / SiO2.

[0051] Example 6: Solvothermal synthesis of COF-6 / SiO2 carrier

[0052] The preparation process of this embodiment is basically the same as that of embodiment 4, except that the COF monomer used is replaced by 2,4-dihydroxy-1,3,5-benzenetricarbaldehyde from 1,3,5-triformylphloroglucinol, and the obtained carrier is recorded as COF-6 / SiO2.

[0053] Example 7: Solvothermal synthesis of COF-7 / SiO2 carrier

[0054] The preparation process of this embodiment is basically the same as that of embodiment 4, except that the COF monomer used is replaced by 2-hydroxy-1,3,5-trisformylphloroglucinol from 1,3,5-trisformylphloroglucinol, and the obtained carrier is recorded as COF-7 / SiO2.

[0055] Example 8: Synthesis of Pt / COF-1 / SiO2 by wet impregnation method

[0056] Add 200 mg COF-1 / SiO2 to 2 mL H2O, then add 0.1-2.9 mL H2PtCl6 aqueous solution with a mass concentration of 7.6 mg / mL, stir at room temperature for 12 hours, centrifuge, and discard the supernatant. The obtained solid is dried in flowing air at 100°C for 1 hour, and reduced with H2 at 200°C for 2 hours to obtain catalyst A.

[0057] When 0.1 mL of H2PtCl6 aqueous solution was added, the Pt metal content in the prepared catalyst was 0.2%; when 2.9 mL of H2PtCl6 aqueous solution was added, the Pt metal content in the prepared catalyst was 5%.

[0058] Using transmission electron microscopy ( Figure 8 ) The catalyst A was characterized, and it can be seen that the size of the Pt nanoparticles is about 1.6nm, well dispersed, and no obvious agglomeration. The argon adsorption results show that the specific surface area of ​​the material is 133m 2 g -1 ( Fig. 9 ).

[0059] Examples 9-14: Synthesis of Pt / COF-2-7 / SiO2 by wet impregnation

[0060] The preparation process of Examples 9 to 14 is basically the same as that of Example 8, except that the carriers used are COF-2 to 7 / SiO2, respectively, to obtain catalysts B to G.

[0061] Example 15: Synthesis of Pd / COF-1 / SiO2 by wet impregnation method

[0062] The preparation process of this embodiment is basically the same as that of embodiment 8, except that the metal salt used is sodium chloropalladate to obtain catalyst H.

[0063] Examples 16-21: Synthesis of Pd / COF-2-7 / SiO2 by wet impregnation

[0064] The preparation process of Examples 16 to 21 is basically the same as that of Example 15, the only difference being that the carriers used are COF-2 to 7 / SiO2, respectively, to obtain catalysts I to N.

[0065] Example 22: Catalyst A for selective hydrogenation of aldehyde / ketone compounds

[0066] Take the hydrogenation reaction of acetophenone as an example. Weigh 69 mg of solid catalyst 0.2% Pt / COF-1 / SiO2, 17 mg of substrate acetophenone and 2 mL of ethanol in a high-pressure reactor. Replace the air in the reactor with hydrogen for 5 times, and finally adjust the hydrogen pressure to 2 MPa, and stir the reaction at 60°C. After the reaction is completed, release the hydrogen, filter to remove the catalyst, and send the reaction liquid to the chromatographic analysis of the catalytic results.

[0067] When the other substrates (Table 1) were reacted, the amount of substrate was changed to S / C=200 (wherein acetone and benzaldehyde S / C=1000, furfural S / C=800), and the other conditions remained unchanged.

[0068] When catalysts with other metal contents were used in the reaction, the amount of substrate remained unchanged and the amount of catalyst was changed to S / C=200.

[0069] Examples 23-35: Catalyst BN for selective hydrogenation of aldehyde / ketone compounds

[0070] The reaction processes of Examples 23 to 35 are basically the same as those of Example 22, except that catalyst BN is added to the reaction system.

[0071] Comparative Example 1: Synthesis of Pt / SiO2 and its application in selective hydrogenation of aldehyde / ketone compounds

[0072] The Pt catalyst supported on silica was used to catalyze the hydrogenation reaction of acetophenone. The synthesis process of the catalyst is as follows: The catalyst was synthesized by the method reported in the literature (Journal of Catalysis, 2004, Vol. 225, pp. 203-212). 200 mg SiO2 was dispersed in 1.78 mL H2O with a pH of 9.5, and 4 mg Pt(NH3)4(NO3)2 was added. After stirring for 1 hour, the solid product was filtered, washed with water, and dried at 100°C in flowing air overnight. Then, it was calcined at 100°C for 3 hours in air at a heating rate of 1°C / min, and finally, it was reduced with H2 (5°C / min) at 250°C for 2 hours to obtain Pt / SiO2.

[0073] The catalytic reaction process is as follows: Comparative Example 1 is basically the same as Example 22, the only difference being that the added catalyst is the catalyst of Comparative Example 1, with a mass of 34 mg (the Pt metal content in the prepared catalyst is 0.4%).

[0074] Comparative Example 2: Synthesis of Pd / SiO2 and its application in selective hydrogenation of aldehyde / ketone compounds

[0075] The Pd catalyst supported on silica was used to catalyze the hydrogenation reaction of acetophenone. The synthesis process of the catalyst is as follows: The catalyst was synthesized by a method reported in the literature (ACS Catalysis, 2018, Volume 8, Pages 6476-6485). 250 mg of SiO2 was dispersed in 1.25 mL of H2O with a pH of 11, and 5 mg of Pt(NH3)4(NO3)2 was added. After ultrasonication for 30 minutes, the solid product was allowed to stand for 2 hours, and then filtered and dried in an oven at 60°C for 2 hours. Then, it was calcined at 125°C for 1 hour in air at a heating rate of 1°C / min. Finally, Pd / SiO2 was obtained by reduction with H2 (1°C / min) at 165°C for 2 hours.

[0076] The catalytic reaction process is as follows: Comparative Example 2 is basically the same as Example 22, the only difference being that the added catalyst is the catalyst of Comparative Example 2, with a mass of 19 mg (the Pd metal content in the prepared catalyst is 0.4%).

[0077] Table 1. Reaction evaluation results of the catalysts of Example 22 and Comparative Example 1

[0078]

[0079]

[0080] * The catalytic results of Example 22 are shown outside the brackets, and the catalytic results of Comparative Example 1 are shown inside the brackets.

[0081] From the above results, it can be seen that the Pt / COF / SiO2 catalyst of the present application has higher activity and selectivity in the hydrogenation reaction of aldehyde / ketone compounds than the Pt / SiO2 of the comparative example, indicating that the multi-activated site catalyst of the present application can effectively improve the activity and selectivity of the selective hydrogenation of aldehyde / ketone compounds to produce alcohols.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multi-activation site catalyst, characterized in that: The catalyst uses a COF / SiO2 composite material prepared by evenly spreading COF on the surface of SiO2 as a carrier, and uses a wet impregnation method to load a metal salt on the carrier, and then reduces it to obtain a supported metal nanoparticle catalyst; The preparation method of the multi-activation site catalyst comprises the following steps: (1) Prepare COF / SiO2 carrier by colloid method or solvothermal method: add COF monomer into a reaction vessel, add solvent and catalyst, stir and mix evenly, then add SiO2, stir for 12-48h or stir for 1-12h and then heat to 90-120℃ and keep for 12-48h, filter and perform Soxhlet extraction, and dry to obtain COF / SiO2 carrier; (2) Preparation of M / COF / SiO2 by wet impregnation method: Disperse the COF / SiO2 carrier in H2O, then add the metal salt precursor solution, stir at room temperature for 4-24 hours and centrifuge, dry the obtained solid, and reduce it in H2 atmosphere at 150-300°C for 0.5-3 hours; In step (1), the COF monomer consists of monomer one and monomer two, wherein monomer one is 1,3,5-triformylphloroglucinol, and monomer two is 2,4,6-tris(4'-aminophenyl)-1,3,5-triazine, and the molar ratio of monomer one to monomer two is 1:1; In step (1), the solvent is one of dimethyl sulfoxide and dioxane; the catalyst is an acetic acid solution, and the molar ratio of the catalyst to the monomer is (100-1000):1; SiO2 is SiO2 nanospheres or SiO2 microspheres, and the mass ratio of COF to SiO2 is 1:(2-100); In the process of preparing the COF / SiO2 carrier by the colloid method in step (1), after adding the solvent, a cationic surfactant solution and an anionic surfactant solution are also added, the molar ratio of the cationic surfactant to the monomer one is (10-50):1, and the molar ratio of the anionic surfactant to the monomer one is (0.5-10):1; In step (2), the metal salt precursor is chloroplatinic acid; the mass ratio of the metal salt precursor to the COF / SiO2 carrier is (2-50):1000.

2. The multi-active site catalyst according to claim 1, characterized in that The catalyst has a COF content of 1-30% and a metal content of 0.2-5% based on the total weight of the catalyst.

3. The multi-active site catalyst according to claim 1, characterized in that The solvent for Soxhlet extraction in step (1) is tetrahydrofuran or ethanol, the temperature for Soxhlet extraction is 100-120° C., and the time is 12-48 hours.

4. The multi-active site catalyst according to claim 1, characterized in that The specific process of drying in step (2) is drying in flowing air at 50-100°C for 1-5h; H2 reduction is carried out in a tubular furnace with a H2 flow rate of 10-20 mL / min, a heating rate of 1-5°C / min, a reduction temperature of 165~200°C, and a reduction time of 1-3h.

5. Use of the multi-activation site catalyst according to any one of claims 1 to 4 in the selective hydrogenation reaction of aldehyde / ketone compounds.

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