An iridium-based catalyst, a preparation method thereof, and a method for catalytic hydroformylation of propylene

Abstract

The present invention provides an iridium-based catalyst, a preparation method thereof, and a method for catalytic hydroformylation of propylene. The structural formula of the iridium-based catalyst is where Ph is a phenyl group, x is any one of 0, 1, and 2, and X is any one of Cl, NO<subgt;3< / subgt;, BF<subgt;4< / subgt;, PF<subgt;6< / subgt;, and acac. The iridium-based catalyst disclosed in the present invention has good catalytic effect and high activity, and can still maintain high catalytic performance after being used multiple times.

Description

Technical Field

[0001] The present invention relates to the field of hydroformylation synthesis, and particularly to an iridium-based catalyst, a preparation method thereof, and a method for catalyzing the hydroformylation of propylene. Background Art

[0002] Aldehydes have always been an important chemical product with very wide applications, and can be further used for synthesizing pesticides, plasticizers, detergents and other high-value-added products. The global demand for aldehyde production capacity is as high as several million tons per year, and the hydroformylation of olefins and syngas to prepare aldehydes has attracted much attention due to its high atom economy and high selectivity for aldehydes.

[0003] So far, the catalysts commonly reported for catalyzing the hydroformylation reaction of olefins are mainly rhodium-based catalysts. For example, triphenylphosphine-rhodium is used as the catalyst in patents WO00200583, EP3712126A1, CN102826967 and CN114401940A; triphenylmethylphosphine trisodium m-sulfonate-rhodium is used as the catalyst in patent CN107737609A; trisilylphosphine-rhodium is used as the catalyst in patent CN111333680B; bidentate dialkylphosphine-rhodium is used as the catalyst in patent CN113754615A; bidentate phosphite-rhodium is used as the catalyst in patent CN106000470B; a rhodium catalyst with a complex structure of a tetradentate phosphine ligand is used in patent CN115124572A.

[0004] In addition to the above patents, there are also a large number of literatures on the optimization and improvement of ligands. For example, polyether phosphite is used as a ligand in Journal of Organometallic Chemistry. 2002, 654, 83 - 90; triphenylphosphine derivatives: sterically hindered phosphine ligands are used to improve the catalytic performance of rhodium-based catalysts in Molecular Catalysis. 2017, 434, 116–122; a chiral phosphoric acid ester phosphine ligand is used in Angew. Chem. Int\. Ed. 2019, 58, 2120–2124; diphosphorylimide is used as a ligand in Appl. Organometal. Chem. 2013, 27, 313–317.

[0005] However, in addition to triphenylphosphine-based ligands, the above-mentioned ligands not only have complex synthesis routes but also high synthesis costs, which will undoubtedly increase production costs. In addition, due to the high activity of traditional rhodium-based catalysts for catalyzing the hydroformylation reaction of olefins, people have focused on the optimization of rhodium-based catalysts in recent years. However, the price of rhodium is very expensive and it is not suitable for large-scale production.

[0006] In view of this, the present invention is specifically proposed. Summary of the Invention

[0007] The first object of the present invention is to provide an iridium-based catalyst, which has good activity, low cost, and remarkable catalytic effect. On the premise that tripyridylphosphine is used as a ligand, the effect of the iridium-based catalyst is superior to that of the rhodium-based catalyst, and the price of iridium metal is 1 / 4 of the price of rhodium metal. In actual industrial applications, the catalyst cost can be saved more.

[0008] The second object of the present invention is to provide a preparation method of the above-mentioned iridium-based catalyst, which has simple steps and can rapidly prepare a large amount of iridium-based catalyst with excellent catalytic effect.

[0009] The third object of the present invention is to provide a method for catalytic hydroformylation of propylene using the above-mentioned iridium-based catalyst, which has simple process, mild conditions, and the used iridium-based catalyst has a low price, can save production cost, and realize industrial production.

[0010] In order to achieve the above objects, the present invention specifically adopts the following technical solutions:

[0011] The present invention provides an iridium-based catalyst, and the structural formula of the iridium-based catalyst is ; wherein, Ph is phenyl, x is any one of 0, 1, and 2, X is any one of Cl, NO3, BF4, PF6, and acac, wherein Cl is chloride ion, NO3 is nitrate radical, BF4 is tetrafluoroborate radical, PF6 is hexafluorophosphate radical, and acac is acetylacetonate radical.

[0012] The present invention also provides a preparation method of the above-mentioned iridium-based catalyst, which includes the following steps: under the protection of inert gas, dropwise add the tetrahydrofuran solution of the phosphine ligand to the tetrahydrofuran solution of the iridium compound, stir after the dropping is completed, and vacuum-evaporate the tetrahydrofuran solution at 25-30 °C to obtain the target product.

[0013] For iridium-based catalysts, the temperature of vacuum evaporation needs to be particularly concerned about during the preparation process. It is necessary to ensure that the temperature of vacuum evaporation is limited between 25 - 30 °C. This is because when preparing iridium-based catalysts, evaporation at high temperatures will cause a decrease in the activity of the prepared catalysts. At the same time, it is also possible to generate metal clusters, resulting in the loss of activity of the prepared catalysts. Additionally, due to the fact that the structure of the iridium-based catalysts prepared in this invention is sensitive to temperature, the catalyst is easily deactivated when the temperature is high. Therefore, in order to ensure that the prepared iridium-based catalysts have good activity and excellent catalytic effects, it is necessary to limit the temperature of vacuum evaporation. Meanwhile, reducing the temperature can also prevent the phosphine ligand from being oxidized during the reaction process and ensure the stability of the iridium-based catalyst. Therefore, in order to ensure that the iridium-based catalyst with the above specific structure can be obtained, it is necessary to limit the temperature of vacuum evaporation.

[0014] Preferably, the temperature of the dropping is 0 - 30 °C, the temperature of the stirring is 20 - 40 °C, and the inert gas is one of argon or nitrogen;

[0015] Preferably, the temperature of the dropping is 5 °C, the temperature of the stirring is 30 °C, and the temperature of the vacuum evaporation is 30 °C.

[0016] Preferably, the molar ratio of the iridium compound to the phosphine ligand is 1:2; the iridium compound is cyclooctadiene iridium chloride.

[0017] Preferably, the phosphine ligand is any one or several of tripyridylphosphine, dipyridylphenylphosphine, and pyridyldiphenylphosphine.

[0018] Based on the current situation described in the background art, the objective of this invention is to develop a new catalyst that is cheaper than metal rhodium and has a catalytic effect comparable to that of rhodium-based catalysts. Since iridium and rhodium are elements in the same group, it is considered that iridium has a similar catalytic effect. However, the factors determining the catalytic effect are not only the metal element itself, but also the ligand plays an important role. After multiple experiments, the above-mentioned ligands are the three with the best effects. Therefore, this invention discloses the above iridium-based catalyst to solve the current situation in the background art.

[0019] This invention also provides a method for the hydroformylation reaction of propylene catalyzed by a catalyst, which includes the following steps:

[0020] Add the catalyst and the corresponding solvent, disperse them evenly, and then add propylene, carbon monoxide, and hydrogen for reaction;

[0021] The catalyst is selected as the above iridium-based catalyst;

[0022] The catalyst accounts for 0.01 - 1.0 wt% of the mass of the solvent;

[0023] Preferably, the catalyst accounts for 0.2 wt% of the mass of the solvent.

[0024] To further understand the reaction steps of the catalytic reaction, the following explanations are given:;

[0025] From the attached Figure 4 It can be seen that: when the iridium-based catalyst is reacting, the prepared iridium-based catalyst (1) consists of a central atom metal iridium and two phosphine ligands, which is a catalytic form with vacant coordination. Then propylene coordinates with the central atom metal iridium to form an intermediate (2). At this time, there are two possible reaction paths: 1) When following path A, the intermediate (2) inserts a β-carbon atom onto propylene and then directly bonds with the central atom metal iridium to form an intermediate (>C−Ir, 3); then CO is inserted and coordinates with the central atom metal iridium to form an intermediate (4); hydrogen is oxidatively added to the intermediate (4) to form an intermediate (5); finally, a reductive elimination reaction forms a complex of the ligand catalyst (6) and the branched hydroformylation product (isobutyraldehyde, 7). At the same time, the iridium-based catalyst is reduced to its original catalytic form (1), thus completing the catalytic cycle process. 2) The basic process of path B is similar to that of path A, except that when propylene inserts in the intermediate (2), the α-carbon atom at the end of propylene directly bonds with the central atom metal iridium to form an intermediate (−C−Ir, 8), and then a linear hydroformylation product (n-butyraldehyde, 12) is generated through a process similar to that of path A. In the above figure, what L represents is the phosphine ligand.

[0026] Preferably, the partial pressure ratio of carbon monoxide to hydrogen is 1:(0.2 - 5);

[0027] Preferably, the partial pressure ratio of carbon monoxide to hydrogen is 1:1.

[0028] Preferably, the solvent is one or a combination of several of n-butyraldehyde, isobutyraldehyde, toluene, acetonitrile, N-methylpyrrolidone, 1,4-dioxane, N,N-dimethylformamide;

[0029] Preferably, the solvent is acetonitrile.

[0030] Preferably, the temperature of the reaction is 80 - 120 °C, and the pressure of the reaction is 1.5 - 3.8 MPa;

[0031] Preferably, the temperature of the reaction is 100 °C, and the pressure of the reaction is 1.9 MPa.

[0032] Preferably, the addition amount of metal iridium in the iridium-based catalyst relative to the solvent is 0.003 - 0.3 wt%;

[0033] Preferably, the addition amount of iridium metal in the iridium-based catalyst relative to the solvent is 0.07 wt%.

[0034] Compared with the prior art, the present invention has at least the following excellent features:

[0035] (1) The iridium-based catalyst provided by the present invention uses tripyridylphosphine as a ligand, and its catalytic effect is far higher than that of the rhodium-based catalyst. At the same time, the price of iridium metal is 1 / 4 of the price of rhodium metal. In practical applications, a large amount of production costs can be saved.

[0036] (2) The iridium-based catalyst provided by the present invention has a simple synthesis method, mild conditions, and low energy consumption during preparation. Under the same reaction conditions, its reaction activity is significantly better than that of the rhodium-based catalyst.

[0037] (3) The present invention uses an iridium-based catalyst as the catalyst, and propylene, carbon monoxide, and hydrogen are used as reaction gases for hydroformylation. Due to the low price of iridium metal, the cost is greatly reduced. At the same time, since the catalyst used is an iridium-phosphine catalyst, the reaction conditions during the catalytic process are mild and the aldehyde normal / iso ratio can be adjusted. Description of the Drawings

[0038] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present invention. Moreover, throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0039] Figure 1 is the chromatogram of the hydroformylation of propylene catalyzed by the tripyridylphosphine-iridium-based catalyst provided in Example 1 of the present invention;

[0040] Figure 2 is the chromatogram of the hydroformylation of propylene catalyzed by the dipyridylphenylphosphine-iridium-based catalyst provided in Example 3 of the present invention;

[0041] Figure 3 is the chromatogram of the hydroformylation of propylene catalyzed by the pyridyldiphenylphosphine-iridium-based catalyst provided in Example 4 of the present invention;

[0042] Figure 4 is the reaction principle diagram of the present invention. Detailed Embodiments

[0043] The following will describe the implementation schemes of the present invention in detail in conjunction with the examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. Those not specified in the examples are carried out under conventional conditions or conditions recommended by the manufacturer. Those reagents or instruments not specified by the manufacturer can be obtained as conventional products through commercial purchase.

[0044] Example 1

[0045] This example provides a method for the hydroformylation of propylene catalyzed by a catalyst, which includes the following steps:

[0046] (1) Preparation of iridium-based catalyst

[0047] Under the protection of an argon atmosphere, in a 250 ml three-necked flask, add 100 ml of tetrahydrofuran, 5 g of iridium(III) chloride cyclooctadiene dimer, and 7.9 g of tripyridylphosphine. Stir at 5 °C for 2 h, and then remove tetrahydrofuran at 30 °C under vacuum conditions. 10.5 g of tripyridylphosphine-iridium catalyst can be obtained, which is the iridium-based catalyst.

[0048] (2) Hydroformylation reaction

[0049] Add 9 mg of the iridium-based catalyst prepared in step (1) and 5 ml of acetonitrile to a 50 ml high-pressure reactor. After replacing the gas three times with hydrogen, sequentially introduce 5 bar of propylene, 8 bar of carbon monoxide, and 8 bar of hydrogen. Stir and heat to 100 °C, and react for 8 h. After the reaction is completed, cool the reaction solution to 0 °C, slowly release the pressure, and take a sample for gas chromatography detection.

[0050] The detection method is as follows: Take a sample of the reaction solution and use the internal standard method of gas chromatography to calculate the yields of n-butanal and isobutanal. The ratio of n-butanal to isobutanal is the ratio of their respective yields. TON is the total yield (molar amount) of butanal divided by the amount of catalyst input (molar amount).

[0051] Its gas chromatogram is as shown in the appendix Figure 1 The detection results are as follows: The selectivity of n-butanal and isobutanal is 99.5%, the TON is 310, and the ratio of n-butanal to isobutanal is 1.7.

[0052] Example 2

[0053] The specific operation steps are the same as those in Example 1, except that the iridium-based catalyst used is different. The iridium-based catalyst used in this Example 2 is a tripyridylphosphine-iridium tetrafluoroborate catalyst, and its preparation includes the following steps:

[0054] Under the protection of a nitrogen atmosphere, add 100 ml of tetrahydrofuran and 3.2 g of silver tetrafluoroborate to a 250 ml three-necked flask, and react in the dark at room temperature for 6 h. Filter to remove insoluble substances, then add 7.9 g of tripyridylphosphine, stir at 5 °C for 2 h, and then remove tetrahydrofuran at 30 °C under vacuum conditions. 11.0 g of tripyridylphosphine-iridium tetrafluoroborate catalyst can be obtained, which is the iridium-based catalyst.

[0055] The prepared iridium-based catalyst was used for the catalytic reaction, and the gas chromatography detection results were as follows: the selectivity of n-butanal and isobutanal was 99.5%, the TON was 310, and the ratio of n-butanal to isobutanal was 1.6.

[0056] Example 3

[0057] The specific operation steps were the same as those in Example 1, except that the iridium-based catalyst used was different. The iridium-based catalyst used in this Example 3 was a dipyridylphenylphosphine-iridium-based catalyst, and its preparation included the following steps:

[0058] Under the protection of a nitrogen atmosphere, 100 ml of tetrahydrofuran, 5 g of cyclooctadiene iridium chloride, and 7.9 g of dipyridylphenylphosphine were added to a 250-ml three-necked flask, stirred at 5 °C for 2 h, and then tetrahydrofuran was removed at 30 °C under vacuum conditions. 10.6 g of dipyridylphenylphosphine-iridium catalyst was obtained, which was the iridium-based catalyst.

[0059] The prepared iridium-based catalyst was used for the catalytic reaction, and its gas chromatogram was as attached Figure 2 shown. The detection results were as follows: the selectivity of n-butanal and isobutanal was 99.7%, the TON was 306, and the ratio of n-butanal to isobutanal was 1.6.

[0060] Example 4

[0061] The specific operation steps were the same as those in Example 1, except that the iridium-based catalyst used was different. The iridium-based catalyst used in this Example 4 was a pyridyl diphenylphosphine-iridium-based catalyst, and its preparation included the following steps:

[0062] Under the protection of an argon atmosphere, 100 ml of tetrahydrofuran, 5 g of cyclooctadiene iridium chloride, and 7.8 g of pyridyl diphenylphosphine were added to a 250-ml three-necked flask, stirred at 5 °C for 2 h, and then tetrahydrofuran was removed at 30 °C under vacuum conditions. 10.4 g of pyridyl diphenylphosphine-iridium catalyst was obtained, which was the iridium-based catalyst.

[0063] The prepared iridium-based catalyst was used for the catalytic reaction, and its gas chromatogram was as attached Figure 3 shown. The detection results were as follows: the selectivity of n-butanal and isobutanal was 99.6%, the TON was 297, and the ratio of n-butanal to isobutanal was 1.8.

[0064] Example 5

[0065] The specific operation steps were the same as those in Example 1, except that the iridium-based catalyst used was different. The iridium-based catalyst used in this Example 5 was a tripyridylphosphine-iridium nitrate-based catalyst, and its preparation included the following steps:

[0066] Add 5 g of iridium(III) chloride cyclooctadiene, 2.8 g of silver nitrate, and 100 ml of tetrahydrofuran into a 250-ml three-necked flask. React under dark conditions at room temperature for 6 h. Filter to remove the insoluble substances, then add 7.9 g of tripyridylphosphine. The other operation steps are the same as those in Example 1. Finally, 9.8 g of the tripyridylphosphine-iridium nitrate-based catalyst is obtained, which is the iridium-based catalyst.

[0067] Use the iridium-based catalyst prepared above for the catalytic reaction. The gas chromatography detection results are as follows: the selectivity of n-butanal and isobutanal is 99.7%, the TON is 308, and the ratio of n-butanal to isobutanal is 1.7.

[0068] Examples 6 - 8

[0069] The specific operation steps are the same as those in Example 1, except that the reaction conditions in step (1) are changed. The specific situations are shown in Table 1 below:

[0070] Table 1 Influence of reaction conditions in step (1) on experimental results

[0071]

[0072] Examples 9 - 18

[0073] The specific operation steps are the same as those in Example 1, except that the reaction conditions in step (2) are changed. The specific situations are shown in Tables 2 - 3 below:

[0074] Table 2 Influence of reaction temperature on experimental results

[0075]

[0076] Table 3 Influence of partial pressure ratio of carbon monoxide to hydrogen on experimental results

[0077]

[0078] Examples 19 - 24

[0079] The specific operation steps are the same as those in Example 1, except that the selection of the solvent in step (2) is changed. The specific situations are shown in Table 4 below:

[0080] Table 4 Influence of different solvents on experimental results

[0081]

[0082] Examples 25 - 29

[0083] The specific operation steps are the same as those in Example 1. The only difference is that the mass ratio of the catalyst to the concentration of the solvent is changed. The specific situations are shown in Table 5 below:

[0084] Table 5 Influence of Catalyst Concentration on Experimental Results

[0085]

[0086] Comparative Example 1

[0087] The specific implementation manner is the same as that of Example 1, and the only difference is that the temperature of vacuum evaporation is selected as 50°C, and the prepared iridium-based catalyst is used for the catalytic reaction. The gas chromatography detection results are as follows: the selectivity of n-butanal and isobutanal is 99.6%, the TON is 228, and the ratio of n-butanal to isobutanal is 1.6.

[0088] It can be seen from the experimental data of Comparative Example 1 that when the temperature of vacuum evaporation exceeds the limited range of the present invention, the effect of the prepared catalyst is far lower than that of the catalyst in Example 1. This is because only within the temperature range of vacuum evaporation defined by the present invention can the phosphine ligand be prevented from being oxidized during the reaction process, ensuring that the phosphine ligand and iridium metal can exert good catalytic effects.

[0089] Experimental Example 1

[0090] Using tripyridylphosphine-iridium catalyst and tripyridylphosphine-rhodium catalyst as catalysts respectively, adding the same molar amount of catalyst, and reacting under the conditions described in Example 1, the results are shown in Table 6 below:

[0091] Table 6 Comparison of Reaction Results

[0092]

[0093] It can be seen from the results in Table 6 above that when using the same ligand (tripyridylphosphine), the catalytic activity of the tripyridylphosphine-iridium catalyst is better than that of the tripyridylphosphine-rhodium catalyst. This is because the pyridyl group in the tripyridylphosphine used in the present invention is an electron-deficient group relative to other ligands. During the catalytic reaction, the activation ability of the pyridyl group for rhodium metal is not high, but the pyridyl group in the tripyridylphosphine has good activation performance for iridium metal. When the pyridyl groups on the tripyridylphosphine are not substituted, the catalytic performance of the prepared tripyridylphosphine-iridium catalyst is the highest. At the same time, it can also be seen from the experimental data in Table 6 above that when using tripyridylphosphine as the ligand, the turnover number of the rhodium-based catalyst is far lower than that of the iridium-based catalyst, which further proves that the activation ability of the tripyridyl group for rhodium metal is far lower than that for iridium metal.

[0094] In the specific use process, the iridium-based catalyst prepared by the present invention can achieve the hydroformylation of propylene under relatively mild conditions, which can greatly reduce the production cost in production. And this iridium-based catalyst can still maintain good catalyst activity during the recycling process.

[0095] Experimental Example 2

[0096] The catalyst after the reaction in Example 1 was detected, and then the solvent was removed at 25°C by vacuum evaporation. The obtained catalyst was re-added to fresh solvent for catalyst recovery and reuse. The results are shown in Table 7 below:

[0097] Table 7 Experimental Results of Catalyst Recovery and Reuse

[0098]

[0099] From the above experimental data, it can be seen that the catalyst prepared by the present invention can still maintain good catalytic performance after being used multiple times. This indicates that the catalyst disclosed in the present invention can still participate in production after being used multiple times, which can greatly reduce the expenditure on catalysts and save resources.

[0100] Finally, it can be understood that the above embodiments are merely exemplary embodiments adopted to illustrate the principle of the present invention. However, the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the principle and essence of the present invention, and these modifications and improvements are also regarded as the protection scope of the present invention.

Claims

1. An iridium-based catalyst, characterized in that, The structural formula of the iridium-based catalyst is ； wherein, Ph is phenyl, x is any one of 0, 1, and 2, and X is any one of Cl, NO3, BF4, PF6, and acac.

2. The preparation method of the iridium-based catalyst according to claim 1, characterized in that, It includes the following steps: Under the protection of an inert gas, the tetrahydrofuran solution of the phosphine ligand is added dropwise to the tetrahydrofuran solution of the iridium compound. After the addition is completed, stirring is carried out, and the tetrahydrofuran solution is evaporated under vacuum at 25 - 30 °C to obtain the target product; The molar ratio of the iridium compound to the phosphine ligand is 1:2, and the iridium compound is cyclooctadiene iridium chloride; The phosphine ligand is any one or several of tripyridylphosphine, dipyridylphenylphosphine, and pyridyldiphenylphosphine.

3. The preparation method according to claim 2, wherein The temperature of the dropwise addition is 0 - 30 °C, the temperature of the stirring is 20 - 40 °C, and the inert gas is one of argon or nitrogen.

4. The preparation method according to claim 3, characterized in that, The temperature of the dropwise addition is 5 °C, the temperature of the stirring is 30 °C, and the temperature of the vacuum evaporation is 30 °C.

5. A method for the hydroformylation of propylene catalyzed by a catalyst, characterized in that, It includes the following steps: The catalyst and the corresponding solvent are added, and after being dispersed evenly, propylene, carbon monoxide, and hydrogen are added for reaction; The catalyst is the iridium-based catalyst described in Claim 1 or the iridium-based catalyst prepared according to any one of Claims 2 - 4; The catalyst accounts for 0.01 - 1.0 wt% of the mass of the solvent.

6. The method according to claim 5, characterized in that, The catalyst accounts for 0.2 wt% of the mass of the solvent.

7. The method according to claim 5, wherein The partial pressure ratio of carbon monoxide to hydrogen is 1:(0.2 - 5).

8. The method according to claim 5, wherein The partial pressure ratio of carbon monoxide to hydrogen is 1:

1.

9. The method according to claim 5, characterized in that, The solvent is one or a combination of several of n-butanal, isobutanal, toluene, acetonitrile, N-methylpyrrolidone, 1,4-dioxane, and N,N-dimethylformamide.

10. The method according to claim 9, wherein The solvent is acetonitrile.

11. The method according to claim 5, wherein The temperature of the reaction is 80 - 120 °C, and the pressure of the reaction is 1.5 - 3.8 MPa.

12. The method according to claim 5, characterized in that, The temperature of the reaction is 100 °C, and the pressure of the reaction is 1.9 MPa.

13. The method according to claim 5, characterized in that, The addition amount of metallic iridium in the iridium-based catalyst relative to the solvent is 0.003 - 0.3 wt%.

14. The method according to claim 13, wherein The addition amount of metallic iridium in the iridium-based catalyst relative to the solvent is 0.07 wt%.

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