Iridium-rhenium bimetallic complex solid-supported catalyst and its preparation method and application

Abstract

The present invention provides an iridium-rhenium bimetallic complex solid-supported catalyst and its preparation method and application, belonging to the field of organic synthesis technology. The iridium-rhenium bimetallic complex solid-supported catalyst provided by the present invention has the transition metal iridium-rhenium as the active component and an organic salt aromatic compound centered on P as the ligand, and the two are complexed by reaction. The catalyst can effectively solve the problem of difficult catalyst separation after homogeneous catalytic reaction. Compared with traditional heterogeneous catalysts, the active component has high dispersion, high atomic utilization rate, high catalyst selectivity, economic feasibility, and has high raw material conversion rate and product selectivity when catalyzing enol isomerization to obtain the corresponding carbonyl compound.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis, and in particular relates to an iridium-rhenium bimetallic complex solid-supported catalyst and a preparation method and application thereof. Background Art

[0002] Enol isomerization is a reaction that converts an ol into a carbonyl compound. Traditionally, there are two approaches to converting an ol into a carbonyl compound. The first involves oxidizing the hydroxyl group on the ol to a carbonyl group, retaining the double bond, and then reducing the C=C to CC via hydrogenation. The second approach involves reversing the reaction sequence of the first approach, performing reduction followed by oxidation. Traditional redox reactions involve complex steps and require time to find a suitable redox agent. The product may also contain toxic byproducts. Enol isomerization reactions catalyzed by transition metal catalysts are green, environmentally friendly, and economical, with high reaction efficiency and good atom utilization.

[0003] The Strohmeier group (Strohmeier W, Weigelt L. Homogene katalytischeumlagerung von isobutenol zubutyraldehyd mit Rh HCO(PPh3)3andmetallhalogeniden[J]. Journal of Organometallic Chemistry, 1975, 86(1):C17–C19.) used iridium trichloride as a catalyst to catalyze the isomerization reaction of enols with two substituents on the double bond at 70°C, where the reaction solvent was trifluoroethanol. However, the reaction produced by-products and the atomic utilization rate did not reach 100%. Later, the Crabtree research group (Crabtree RH, Felkin H, Morris G E. Cationic iridium diolefin complexes as alkene hydrogenation catalysts and the isolation of some related hydrido complexes [J]. Journal of Organometallic Chemistry, 1977, 141 (2): 205-215.) used [(COD)Ir(PMe Ph2)2][PF6] to catalyze the isomerization reaction of enols. The test showed that the catalyst can well isomerize some simple enols. However, the catalytic effect is not very good for tri-substituted or poly-substituted enol raw materials such as geraniol. Most of them are raw materials, and the product yield is only 12%. Later, researchers (Sato SH, Matsuda I. Stereoselective annellation of trimethylsiloxyacetic acid acids and imines into 3-hydroxy-β-lactams [J]. Tetrahedron Lett. 1985, 26 (35): 4229-4242.) discovered that if the reaction process contains RhH (PPh 3) 3 catalyst, the enol isomerization reaction can achieve good results. Whether RhH (PPh 3) 3 is synthesized in situ or prepared from the beginning, it can effectively catalyze the isomerization reaction of polysubstituted enols. However, this catalyst has certain limitations. It is particularly sensitive to air and moisture, so strict requirements on the surrounding environment are required during the reaction process. Based on the limitations of this type of catalyst, researchers have developed a series of water-soluble catalysts for homogeneous isomerization.Early experiments using inorganic rhodium salts such as Rh2(SO4)3 and RhCl3, as well as organometallic rhodium precursors, as metal sources, achieved good results. The sodium sulfonate substituent made the catalytic system water-soluble. However, the water solubility of the catalyst made subsequent separation difficult, significantly impacting the isomerization process.

[0004] Some researchers in China have prepared heterogeneous isomerization catalysts. The researchers (Zhu Fengxia, Yang Xushi, Li Hexing. Preparation of mesoporous organometallic Ru(II) heterogeneous catalysts and study of their catalytic performance [J]. Molecular Chemistry, 2010, 24(01): 20-24.) used tetraethyl orthosilicate and organometallic Ru(II) silane to copolymerize under the action of template P123 to synthesize ordered mesoporous Ru(II) organometallic catalysts, which solved the problem of difficult catalyst separation. However, as the reaction time increased, the selectivity of the catalyst was only about 60%, which was a poor effect.

[0005] As can be seen from the above, current isomerization technology, using homogeneous catalysts, faces challenges such as high cost and difficulty in separation. Furthermore, these catalysts are still limited to laboratory trials and, for various reasons, remain difficult to commercialize. Existing heterogeneous catalysts, on the other hand, have complex preparation processes and poor selectivity. Therefore, it is necessary to develop a superior isomerization catalyst to address these challenges. Summary of the Invention

[0006] The present invention provides an iridium-rhenium bimetallic complex solid-supported catalyst, a preparation method, and an application thereof. The catalyst can effectively solve the problem of difficult catalyst separation after a homogeneous catalytic reaction. The active component has high dispersion, high atomic utilization, and high catalyst selectivity. When catalyzing the isomerization of enolate to obtain the corresponding carbonyl compound, the catalyst has high raw material conversion rate and product selectivity.

[0007] In order to achieve the above object, the present invention provides an iridium-rhenium bimetallic complex solid-supported catalyst, which uses transition metal iridium-rhenium as active components and an organic salt aromatic compound centered on P as a ligand, and the two are complexed by reaction.

[0008] Preferably, the organic salt aromatic compound centered on P is an organic phosphine, and its structure is as follows:

[0009]

[0010] Wherein, R1 to R3 are cobalt bromide or nickel bromide groups or hydrogen atoms, and R4 to R6 are methyl groups or hydrogen atoms.

[0011] Preferably, the organic phosphine can be selected from at least one of dibromobis(triphenylphosphine)nickel and bis(triphenylphosphine)cobalt dibromide.

[0012] Preferably, the organic phosphine can be prepared by the following method:

[0013] Add cobalt bromide hexahydrate or nickel bromide hexahydrate and anhydrous ethanol to a reaction container, stir at 40-60° C. for 1-3 hours, mix evenly, heat to 60-80° C., add methanol, and then add triphenylphosphine in 2-3 portions and continue stirring for 1-2 hours to allow sufficient reaction. After the stirring reaction is completed, filter, wash, and dry to obtain an organic phosphine ligand.

[0014] Preferably, the mass ratio of the added cobalt bromide hexahydrate or nickel bromide hexahydrate, methanol, and triphenylphosphine is (1-2): (3.5-5): (1-2).

[0015] The present invention also provides a method for preparing the iridium-rhenium bimetallic complex solid-supported catalyst according to the above technical solution, comprising the following steps:

[0016] A metal oxide with transition metal iridium-rhenium as an active component reacts with a ligand of an organic salt aromatic compound centered on P to form a complex;

[0017] The obtained complex powder is dissolved in a solvent, loaded onto a treated functionalized carrier by an impregnation method, and vacuum dried to obtain a solid-supported catalyst.

[0018] Preferably, the metal oxide is selected from at least two of rhenium heptoxide, rhenium dioxide, rhenium trioxide, rhenium trioxide, iridium dioxide, iridium trioxide, and iridium trioxide monohydrate;

[0019] The solvent is selected from at least one of ammonia water and deionized water.

[0020] Preferably, the mass ratio of the added metal oxide to the ligand is 0.8 to 1.2; the mass ratio of the added complex powder to the functionalized carrier is 1.8 to 2.2.

[0021] Preferably, during the temperature-raising reaction, the temperature is raised to 80-120° C. and the reaction is carried out for 22-26 hours;

[0022] The drying temperature of the obtained catalyst is 80-120° C., preferably 80-100° C., and the drying time is 2-6 hours, preferably 2-4 hours.

[0023] Preferably, the functionalized carrier is prepared by mixing the carrier, toluene, an organic silicon source and an organic titanium source, and refluxing at 120-150° C. for 10-14 hours;

[0024] The mass ratio of the carrier, toluene, organic silicon source and organic titanium source is (1-1.5): (30-40): (2-4): (2-4).

[0025] Preferably, the carrier is selected from at least one of SiO2 and TiO2; the organic silicon source is selected from one of organic silane and ethyl orthosilicate; and the organic titanium source is selected from at least one of butyl titanate, ethyl titanate and titanium trichloride.

[0026] The present invention also provides an application of the solid core-shell catalyst according to the above technical solution in an enolate isomerization reaction.

[0027] As a preferred method, the specific method is:

[0028] The molded catalyst is loaded into the micro fixed bed, N2 gas is introduced, the reaction temperature is set to 100-150°C, preferably 120-150°C, the N2 partial pressure is 2-6 MPa, preferably 2-4 MPa, and the liquid hourly space velocity is 1-3 h -1 , preferably 1 to 2.5 hours -1 After the system pressure stabilizes, the temperature is raised to the preset temperature, and the reaction raw materials are introduced. Sampling is taken at intervals of 1 h from the start of the reaction until the fixed bed is completely wetted, and the samples are analyzed by gas chromatography.

[0029] Preferably, when the enol is selected from 2,7-octadienol, 3-methyl-3-butene-1-ol or vinyl alcohol, the raw material conversion rate of the reaction is ≥96.8%, and the product selectivity is ≥86.2%.

[0030] Compared with the prior art, the advantages and positive effects of the present invention are:

[0031] 1. The iridium-rhenium bimetallic complex supported catalyst provided by the present invention has transition metal iridium-rhenium as active components and an organic salt aromatic compound centered on P as a ligand. The P in the organic phosphine ligand combines with rhenium-iridium to form a complex. The formed complex can be fully attached to the carrier, which can effectively solve the problem of difficult catalyst separation after homogeneous catalytic reaction. Compared with traditional heterogeneous catalysts, the active component has high dispersion, high atomic utilization, high catalyst selectivity, and is economically feasible.

[0032] 2. The present invention uses enol as a reaction substrate and catalyzes the isomerization of enol with an iridium-rhenium bimetallic complex solid-supported catalyst to obtain the corresponding carbonyl compound. The raw material conversion rate is ≥97.9%, and the product selectivity is ≥88.2%, which has high conversion rate and selectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Stability experiment of catalyst I provided for performance testing of the present invention. DETAILED DESCRIPTION

[0034] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0035] Example 1

[0036] Weigh 5.02 g of cobalt bromide hexahydrate into a three-necked flask, add 80 mL of anhydrous ethanol and stir at 50 ° C for 1 h to mix evenly. After mixing evenly, heat to 70 ° C and add 20 mL of methanol. Add a total of 8.25 g of triphenylphosphine in 2-3 times and continue stirring for 2 h. After the stirring reaction is completed, filter it, wash the filter cake three times with 20 mL of petroleum ether and vacuum dry it to obtain a solid, which is ligand A.

[0037] Weigh 4.38g of iridium trioxide monohydrate and 5.01g of rhenium heptoxide into a 100mL beaker, add 50mL of methanol to dissolve them, transfer the dissolved liquid to a three-necked flask, add 10g of the prepared ligand A, replace the air in the three-necked flask with nitrogen to maintain an oxygen-free environment, continue to heat to 100℃ and react for 24h. After the reaction is completed, cool to room temperature and precipitate is found. The precipitate is washed with methanol and then vacuum dried to obtain catalyst powder B.

[0038] 10 g of silica support, 400 mL of toluene, 30 mL of organosilane, and 30 mL of butyl titanate were weighed and mixed evenly, and then refluxed for 12 h. The refluxed support was dried at 120 ° C for 4 h to obtain a functionalized silica support;

[0039] 1.25 g of catalyst powder B was weighed and dissolved in 18 mL of ammonia water with stirring. The functionalized silica carrier was placed in the solution and allowed to stand overnight to allow the active components to be fully impregnated. The impregnated catalyst was dried at 100°C in vacuum for 3 hours and 2 hours to obtain a shaped catalyst C.

[0040] Example 2

[0041] Weigh 4.68 g of cobalt bromide hexahydrate into a three-necked flask, add 70 mL of anhydrous ethanol and stir at 50 ° C for 1 h to mix evenly. After mixing evenly, heat to 70 ° C and add 18 mL of methanol. Add a total of 7.93 g of triphenylphosphine in 2-3 times and continue stirring for 2 h. After the stirring reaction is completed, filter it, wash the filter cake three times with 20 mL of petroleum ether and dry it to obtain a solid, which is ligand D.

[0042] Weigh 4.25g of iridium dioxide and 5.32g of rhenium trioxide into a 100mL beaker, add 50mL of methanol to dissolve them, transfer the mixed liquid to a three-necked flask, add 10.13g of the prepared ligand D, replace the air in the three-necked flask with nitrogen to maintain an oxygen-free environment, continue to heat to 100℃ and react for 24h. After the reaction is completed, cool to room temperature, wash the obtained precipitate three times with methanol and vacuum dry to obtain catalyst powder E.

[0043] 10 g of a titanium dioxide-silica support, 400 mL of toluene, 30 mL of organosilane, and 30 mL of butyl titanate were weighed and mixed evenly, and then refluxed for 12 h. The refluxed support was dried at 120 ° C for 4 h to obtain a functionalized titanium dioxide-silica support;

[0044] 1.08 g of catalyst powder E was weighed and dissolved in 16 mL of ammonia water with stirring. The functionalized titanium dioxide-silica carrier was placed in the solution and allowed to stand overnight to allow the active components to be fully impregnated. The impregnated catalyst was dried at 90°C in vacuum for 3 h and 4 h to obtain a shaped catalyst F.

[0045] Example 3

[0046] Weigh 5.32 g of nickel bromide hexahydrate and add it into a three-necked flask, add 90 mL of anhydrous ethanol and stir at 50 ° C for 2 h to mix evenly, after mixing evenly, heat to 70 ° C and add 25 mL of methanol, add a total of 8.65 g of triphenylphosphine in batches and continue stirring for 2 h. After the stirring reaction is completed, filter it, wash the filter cake three times with 30 mL of petroleum ether and then dry it to obtain the solid ligand G.

[0047] Weigh 4.56 g of iridium dioxide and 5.35 g of rhenium trioxide into a 100 mL beaker, add 60 mL of methanol to dissolve them, transfer the dissolved liquid to a three-necked flask, add 10.21 g of the prepared ligand G, replace the air in the three-necked flask with nitrogen to maintain an oxygen-free environment, continue to heat to 100 ° C and react for 24 hours, cool to room temperature after the reaction is completed, wash the obtained precipitate three times with methanol and then vacuum dry to obtain catalyst powder H.

[0048] 10 g of silica support, 400 mL of toluene, 30 mL of organosilane, and 30 mL of ethyl titanate were weighed and mixed evenly, and then refluxed for 12 h. The refluxed support was washed three times with methanol and then dried in a vacuum at 80 ° C for 4 h to obtain a functionalized phosphated silica support.

[0049] 1.44 g of catalyst powder H was weighed and dissolved in 20 mL of ammonia water with stirring. The prepared support was placed in the solution and allowed to stand overnight to allow the active components to be fully impregnated. The impregnated catalyst was dried at 80°C in vacuum for 3 h and 6 h to obtain a molded catalyst I.

[0050] Performance Testing

[0051] Enol isomerization test

[0052] The formed catalysts prepared in Examples 1-3 above were respectively loaded into a fixed bed, with the upper and lower layers filled with quartz sand and the catalyst in the middle. The system pressure was maintained at 3 MPa by N2 and the airtightness of the device was checked. Then, the device was heated to 200°C, and 2,7-octadienol was used as the reaction substrate. Samples were taken at intervals of 1 h for chromatographic analysis. The specific reaction conditions and test results are shown in Table 1.

[0053] Table 1 Summary of reaction conditions for isomerization reaction test

[0054]

[0055] As can be seen from the data in Table 1, with 2,7-octadienol as the reaction substrate, the catalyst prepared by the present invention has a conversion rate of ≥97.9% and a selectivity of ≥88.2%, and has good reaction activity. After the reaction is completed, the catalyst can be taken out from the fixed bed reaction tube and obtained after separation from the quartz sand, thereby achieving catalyst separation.

[0056] Reaction effects of different reaction substrates

[0057] Catalyst I was loaded into the middle section of the fixed bed, and quartz sand was loaded into the upper and lower layers. After loading, N2 was introduced to raise the system pressure to 3 MPa to check the air tightness of the device. After the reaction temperature was adjusted to the preset temperature, the reaction raw materials were added. The reaction substrates were 2,7-octadienol, 3-methyl-3-butene-1-ol, and vinyl alcohol. Sampling was started after the reaction started and the reaction raw materials completely wetted the catalyst bed. Sampling was analyzed at intervals of 1 h. The products after the reaction were analyzed by gas chromatography. The specific reaction conditions and test results are shown in Table 2.

[0058] Table 2 Reaction effects of different reaction substrates

[0059]

[0060]

[0061] It can be seen from the data in Table 2 that the catalyst still maintains excellent activity under different substrates and different reaction conditions, and the catalyst can be separated at the end of the reaction.

[0062] Catalyst stability test

[0063] A 100-hour catalyst stability experiment was conducted as follows: Catalyst I was loaded into the middle section of the fixed bed, and quartz sand was loaded into the upper and lower layers. After loading, N2 was introduced to increase the system pressure to 3 MPa to check the air tightness of the device. After the reaction temperature was adjusted to 150°C, the reaction raw materials were added. The reaction substrate was 2,7-octadienol, and the reaction space velocity was 2 h -1 Sampling was started from the beginning of the reaction until the raw materials completely wetted the catalyst bed, and sampling was performed every 2 hours. The products after the reaction were analyzed by gas chromatography. The results were as follows: Figure 1 As shown, the catalyst maintained high conversion rate and high selectivity in the 100h stability experiment and did not show a downward trend, maintaining good stability.

Claims

1. A method for preparing an iridium-rhenium bimetallic complex supported catalyst, characterized in that: The following steps are involved: A metal oxide with transition metal iridium-rhenium as an active component and a ligand of an organic salt aromatic compound centered on P are reacted at elevated temperature in an oxygen-free environment to form a complex; The obtained complex powder is dissolved in a solvent, loaded onto a functionalized carrier by an impregnation method, and vacuum dried to obtain a solid-supported catalyst; Wherein, the organic salt aromatic compound centered on P is an organic phosphine, and the organic phosphine is selected from at least one of dibromobis(triphenylphosphine) nickel and bis(triphenylphosphine) cobalt dibromide; The functionalized carrier is prepared by mixing a carrier, toluene, an organic silicon source and an organic titanium source, and refluxing the mixture at 120-150° C. for 10-14 hours. The mass ratio of the carrier, toluene, the organic silicon source and the organic titanium source is (1-1.5): (30-40): (2-4): (2-4).

2. The preparation method according to claim 1, characterized in that The metal oxide is selected from at least one of rhenium heptoxide, rhenium dioxide, rhenium trioxide, and rhenium trioxide, and at least one of iridium dioxide, iridium trioxide, and iridium trioxide monohydrate; The solvent is selected from at least one of ammonia water and deionized water.

3. The preparation method according to claim 1 or 2, characterized in that The mass ratio of the added metal oxide to the ligand is 0.8-1.2; the mass ratio of the added complex powder to the functionalized carrier is 1.8-2.

2.

4. The preparation method according to claim 1, characterized in that During the temperature-raising reaction, the temperature is raised to 80-120°C and the reaction is carried out for 22-26 hours; The drying temperature of the obtained catalyst is 80-120° C., and the drying time is 2-6 hours.

5. The preparation method according to claim 1, characterized in that The carrier is selected from at least one of SiO2 and TiO2; the organic silicon source is selected from one of organic silane and ethyl orthosilicate; and the organic titanium source is selected from at least one of butyl titanate and ethyl titanate.

6. Use of the solid-supported catalyst obtained by the preparation method according to claim 1 in enol isomerization reaction.

7. The use according to claim 6, characterized in that When the enol is selected from 2,7-octadienol, 3-methyl-3-butene-1-ol or vinyl alcohol, the raw material conversion rate of the reaction is ≥96.8%, and the product selectivity is ≥86.2%.

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