Process for the preparation of a heterogeneous iridium-based catalyst and its use for the hydroformylation to produce aldehydes

Abstract

The application develops a kind of heterogeneous Ir-based catalyst for hydroformylation of propylene. Compared with Rh-based catalyst, the process cost is reduced; compared with homogeneous Ir-based catalyst, the recyclability is improved. In addition, the ratio of linear aldehyde / branched aldehyde of the heterogeneous Ir-based catalyst is less than 1, which has excellent branched chain selectivity and catalytic reaction efficiency, and the catalyst turnover number (TON) can be up to 21916, which has good industrial application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of organic chemical industry, and in particular to an iridium-based catalyst, a preparation method thereof and a method for catalyzing propylene aldehyde to produce aldehyde. BACKGROUND

[0002] Hydroformylation is an important reaction in the field of chemical industry, which usually uses olefins and synthesis gas (CO / H2) as reactants. The product of hydroformylation is an aldehyde with a carbon chain, which can be further used to prepare a series of chemical intermediates and fine chemicals such as alcohols, amines and carboxylic acids.

[0003] At present, the key technical problem of synthesizing high-value aldehyde compounds by olefin hydroformylation is how to realize the regioselectivity of CO insertion into different positions of C=C bond. The early developed Co-based catalyst has low catalytic activity and aldehyde group regioselectivity, and is later replaced by Rh-based phosphine complex catalyst (J. Catal., 2021, 401, 321-330.; New J. Chem., 2020, 44, 20-23.). From homogeneous catalysis to heterogeneous catalysis, Rh-based catalysts for olefin hydroformylation have been intensively studied. In terms of the selectivity ratio of linear aldehyde to branched aldehyde, the performance of Rh-based catalysts can reach 0.2-24.2 (J. Catal., 2006, 243, 318-328.; Green Chem., 2016, 18, 2995-3005.). However, due to the rapid increase of international Rh metal price, the corresponding process cost is increased, therefore, it is necessary to develop other catalytic systems with comparable performance for hydroformylation.

[0004] Since Ir and Rh are in the same group, theoretically, Ir-based catalysts have the ability to catalyze olefin hydroformylation reaction, but the existing Ir-based catalysts still have the following problems: (1) the catalytic hydroformylation reaction activity is very low (Chem. Eur. J. 2022, 28, e202104012.; Catal. Sci. Technol. 2016, 6, 208-214.; Org. Biomol. Chem. 2023, 21, 6410-6418.; J. Catal. 2019, 373, 215-221.), (2) from the results, the ratio of linear aldehyde to branched aldehyde is greater than 1, and there is also a certain demand for branched aldehyde such as isobutyraldehyde in the market, and the process with the ratio of linear aldehyde to branched aldehyde less than 1 is also the direction pursued by the industry. (3) At the same time, the existing Ir-based catalysts are mainly homogeneous catalytic systems, and the recyclability is still poor.

[0005] In view of the above problems, the application develops a kind of heterogeneous Ir-based catalyst for preparing aldehyde by propylene hydroformylation.The process cost is reduced compared with Rh-based catalyst;Compared with homogeneous Ir-based catalyst, the recyclability is improved.In addition, the straight-chain aldehyde / branched-chain aldehyde ratio of the heterogeneous Ir-based catalyst is less than 1, with excellent branched-chain selectivity and catalytic reaction efficiency, and the catalyst conversion number (TON) can reach 21916, with good industrial application prospect. SUMMARY

[0006] The first object of the application is to provide a heterogeneous Ir-based catalyst preparation method, which reduces the process cost compared with Rh-based catalyst;Compared with homogeneous Ir-based catalyst, the recyclability is improved.

[0007] The second object of the application is to provide a method for propylene aldehyde by Ir-based catalyst, which has excellent reaction activity for propylene hydroformylation, excellent branched-chain product selectivity, and straight-chain aldehyde / branched-chain aldehyde ratio less than 1.

[0008] The specific technical solutions of the application are as follows:

[0009] The application provides a heterogeneous Ir-based catalyst, and the chemical structural formula of the Ir-based catalyst is:

[0010]

[0011] The Ir catalyst (p-TBCP-Ir) is prepared by one-pot method, and the porous organic framework with Ir center active site is constructed by coordination polymerization of metal zirconium Zr and carboxyl functional derivative of phosphine ligand.The phosphine ligand used is carboxylic acid functionalized triphenyl phosphine compound, which can be TBCP or TDBCP.

[0012] The application also provides a preparation method of the Ir catalyst, comprising the following steps:

[0013] The first step is the preparation of carboxylic acid functionalized triphenyl phosphine compound, first, p-dibromobenzene, phosphorus trichloride and n-butyllithium are reacted in nitrogen atmosphere, then carbon dioxide is blown into the reaction system and n-butyllithium is used to pull bromine, and finally TBCP can be obtained after hydrochloric acid acidification;The second step is to place the synthesized phosphine ligand TBCP, cyclooctadiene iridium dimer (Ir2cod2Cl2), ZrCl4 and benzoic acid in DMF solution for one-pot hydrothermal polymerization, and finally the heterogeneous iridium-based catalyst p-TBCP-Ir can be obtained.The synthesis of TBCP based on dibromobenzene can be realized by 4,4-di-bromobiphenyl to realize the synthesis of TDBCP.

[0014] In the presence of the heterogeneous iridium-based catalyst, catalytic reaction is carried out at a certain temperature (T) with propylene, carbon monoxide and hydrogen as raw materials, and the prepared catalyst is more beneficial to the generation of branched products in the hydroformylation reaction, and the normal / iso ratio is less than 1, wherein the reaction formula is as follows:

[0015] BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 A structural schematic diagram of the heterogeneous iridium-based catalyst provided by the application is shown in the figure.

[0017] Figure 2 A phosphine ligand TBCP nuclear magnetic hydrogen spectrum provided by the application

[0018] Figure 3 An electron microscope image of the heterogeneous catalyst provided by the application DETAILED DESCRIPTION

[0019] The embodiments of the application will be described in detail below with reference to the examples, but those skilled in the art will understand that the following examples are only used to illustrate the application and should not be regarded as limiting the scope of the application. If the specific conditions are not indicated in the examples, the conventional conditions or the conditions recommended by the manufacturer are used. If the reagents or instruments used are not indicated by the manufacturer, they are all conventional products that can be purchased on the market.

[0020] Example 1:

[0021] The preparation method of the heterogeneous iridium-based catalyst is as follows:

[0022] Synthesis of TBCP: Under a nitrogen atmosphere, the hexane solution of n-butyllithium is added dropwise into p-dibromobenzene in dry tetrahydrofuran solution within 30 minutes. Then, phosphorus trichloride dissolved in anhydrous THF solution is added dropwise into the above suspension. The mixture is continuously stirred and reacted for 2 hours until the system slowly rises to ambient temperature. Subsequently, n-butyllithium is added within 30 minutes, and after stirring for 4 hours, dry carbon dioxide is introduced into the reaction mixture until the reaction solution turns white. Finally, the pH value is adjusted to about 1.0 with dilute hydrochloric acid, and then washed with water to pH=7, and dried under vacuum to obtain a white powder product (TBCP) with a yield of 65%.

[0023] Example 2:

[0024] Synthesis of p-TBCP-Ir: TBCP and Ir2cod2Cl2 were stirred in THF solution at ambient temperature for 2 hours, then the solvent was removed under vacuum to obtain the catalyst monomer; subsequently, ZrCl4, benzoic acid and N,N-dimethylformamide (DMF) were added to a pressure-resistant container, which was placed in a 100 °C environment for hydrothermal polymerization for 24 hours; finally, the heterogeneous iridium catalyst p-TBCP-Ir in the form of a light yellow powder can be obtained, with a yield of 70%.

[0025] Example 3:

[0026] Synthesis of TDBCP: Under a nitrogen atmosphere, a hexane solution of n-butyllithium was added dropwise to 4,4-dibromobiphenyl in dry tetrahydrofuran solution over 30 minutes. Then, phosphorus trichloride dissolved in anhydrous THF solution was added dropwise to the above suspension. The mixture was continuously stirred and reacted for 2 hours until the system slowly rose to ambient temperature. Subsequently, n-butyllithium was added over 30 minutes, and after stirring for 4 hours, dry carbon dioxide was introduced into the reaction mixture until the reaction solution turned white. Finally, after adjusting the pH to about 1.0 with dilute hydrochloric acid and washing with water to pH = 7, drying under vacuum to obtain the white powder product (TDBCP) with a yield of 70%.

[0027] Example 4:

[0028] Synthesis of p-TDBCP-Ir: The specific operation steps are the same as in Example 2. TDBCP and Ir2cod2Cl2 were stirred in THF solution at ambient temperature for 2 hours, then the solvent was removed under vacuum to obtain the catalyst monomer; subsequently, ZrCl4, benzoic acid and N,N-dimethylformamide (DMF) were added to a pressure-resistant container, which was placed in a 100 °C environment for hydrothermal polymerization for 24 hours; finally, the heterogeneous iridium catalyst p-TBCP-Ir in the form of a light yellow powder can be obtained, with a yield of 75%.

[0029] Example 5:

[0030] The operation steps of the aldolization reaction are as follows:

[0031] In a 50 mL high-pressure stainless steel reactor equipped with magnetic stirring and heating, 5 mg of heterogeneous Ir catalyst p-TBCP-Ir and 5 mL of solvent toluene were added. Then, propylene 8 bar, carbon monoxide 15 bar and hydrogen 15 bar were filled into the autoclave, respectively, and allowed to react for 16 h. After the reaction, the catalyst was separated by centrifugation, and the supernatant was detected by gas chromatography analysis, using n-butyl acetate as an internal standard to calculate the TON. According to the gas phase results, the catalyst conversion number TON can reach 21916, and the normal and isobutyl aldehyde selectivity is 99% (n-butyl aldehyde / isobutyl aldehyde = 0.6.

[0032] Example 6:

[0033] The operating steps of the hydroformylation reaction are as follows:

[0034] In a 50 mL high-pressure stainless steel reactor equipped with magnetic stirring and heating, 5 mg of heterogeneous Ir catalyst p-TDBCP-Ir and 5 mL of solvent toluene were added. Then, propylene 8 bar, carbon monoxide 15 bar and hydrogen 15 bar were filled into the autoclave, respectively, and allowed to react for 16 h. After the reaction, the catalyst was separated by centrifugation, and the supernatant was detected by gas chromatography analysis, using n-butyl acetate as an internal standard to calculate the TON. According to the gas chromatography results, the catalyst conversion number TON can reach 17421, and the normal and isobutyl aldehyde selectivity is 99% (normal butyl aldehyde / isobutyl aldehyde = 0.6.

[0035] Examples 7-10:

[0036] The effect of different temperatures on the propylene hydroformylation reaction was explored, and the results are shown in Table 1:

[0037] Table 1 Effect of temperature on propylene hydroformylation reaction

[0038] Examples Temperature (°C) Catalyst turnover number (TON) n-, iso-butyraldehyde selectivity (%) n-butyraldehyde / iso-butyraldehyde (n / i) 7 80 2669 99 0.88 8 100 21916 99 0.62 9 120 16103 99 0.63 10 140 12560 99 O.7

[0039] Examples 11-16:

[0040] The effect of different solvents on the propylene hydroformylation reaction was explored, and the results are shown in Table 2:

[0041] Table 1 Effect of different solvents on propylene hydroformylation reaction

[0042] Examples Solvent Catalyst turnover number (TON) n-, iso-butyraldehyde selectivity (%) n-butyraldehyde / iso-butyraldehyde (n / i) 11 acetonitrile 14130 99 0.78 12 N-methylpyrrolidone 4637 99 1.13 13 toluene 21916 99 0.62 14 N,N-dimethylformamide 2777 99 1 15 dioxane 20531 99 0.7 16 dimethylsulfoxide 4691 99 1.3

[0043] As can be seen from the above table, the hydroformylation reaction is best at a temperature of 100°C in the process of hydroformylation reaction using the heterogeneous iridium-based catalyst of the present application, and the present application obtains a normal butyl aldehyde / isobutyl aldehyde ratio of 0.6, which indicates that the catalyst of the present application has good production efficiency of branched aldehyde, and has high catalytic efficiency and certain industrial application prospect.

Claims

1. A heterogeneous iridium-based catalyst, characterized in that, The Ir catalyst p-TBCP-Ir was prepared via a one-pot method. A porous organic framework with Ir central active sites was constructed through coordination polymerization of zirconium (Zr) and a phosphine ligand. The phosphine ligand was a carboxylic acid-functionalized triphenylphosphine compound, which could be TBCP or TDBCP. When TBCP was used as the phosphine ligand, the chemical structure of the iridium-based catalyst was as follows: 。 2. The method for preparing the iridium-based catalyst according to claim 1, characterized in that, The preparation steps include the following: The first step is the preparation of carboxylic acid-functionalized triphenylphosphine compound. First, p-dibromobenzene, phosphorus trichloride and n-butyllithium are reacted in a nitrogen atmosphere. Then, carbon dioxide is bubbled into the reaction system and bromine is removed by n-butyllithium. Finally, after acidification with hydrochloric acid, TBCP can be obtained. The second step is to place the synthesized phosphine ligand TBCP, cyclooctadiene iridium chloride dimer Ir2cod2Cl2, ZrCl4 and benzoic acid in DMF solution for one-pot hydrothermal polymerization. Finally, the heterogeneous iridium-based catalyst p-TBCP-Ir can be obtained.

3. The preparation method according to claim 2, characterized in that, In the preparation of carboxylic acid-functionalized triphenylphosphine compounds, a method similar to that used in the synthesis of TBCP from dibromobenzene can be employed to synthesize TDBCP via 4,4-dibromobiphenyl.

4. The preparation method according to claim 2, characterized in that, The required reaction temperature is -70 to 40°C, followed by stirring for 1.5 to 6 hours; the required reaction temperature for the one-pot preparation of the heterogeneous iridium-based catalyst p-TBCP-Ir is 60 to 120°C, and the reaction time is 8 to 24 hours.

5. A method for acrylaldehyde oxidation using a heterogeneous catalyst prepared by the preparation method according to claim 1 or any one of claims 2-4, characterized in that, The process includes the following steps: A catalytic reaction is carried out using propylene, carbon monoxide, and hydrogen as raw materials in the presence of the heterogeneous iridium-based catalyst, wherein the reaction formula is shown below:

6. The method according to claim 5, characterized in that, The prepared catalyst is more conducive to the formation of branched products in the hydroformylation reaction, with a positive-to-negative ratio of less than 1.

7. The method according to claim 5, characterized in that, The reaction temperature of the catalytic reaction is 70–130°C; the reaction pressure is 0.5–3.0 MPa; the partial pressure ratio of propylene to carbon monoxide is 10:1–1:10; the partial pressure ratio of propylene to hydrogen is 10:1–1:10; and the mass of the catalyst is 0.005–5.0 wt% of the mass of the solvent used in the reaction.

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