Process for preparation of organic carboxylic acid esters from hydroesterification of olefins

Abstract

The invention discloses a method for preparing organic carboxylic ester through olefin hydroesterification, and belongs to the technical field of organic carboxylic ester preparation. According to the technical scheme, terminal olefin, CO and alcohol serve as reactants, organic carboxylic ester with one more carbon is generated under the action of an acid auxiliary with zwitterionic liquid serving as a solvent, a phosphine ligand and a catalyst of a Pd compound, the structure of the zwitterionic liquid simultaneously contains an imidazole group and a sulfonate group, and the structural formula of the zwitterionic liquid is shown in the description. The concentration of the zwitterionic liquid in the reaction system is the solvent amount; the molar ratio of the Pd compound to the ionic liquid is (0.1-1): (1000-10000), the molar ratio of the phosphine ligand to the ionic liquid is (0.1-1): (10-100), and the molar ratio of the acid to the ionic liquid is (0.1-1): (2-50). The method has the advantages of mild reaction conditions, wide raw material application range, high reaction activity, good stability and the like, and is a reaction system with a very good industrial application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of organic carboxylic acid esters, and in particular relates to a method for preparing organic carboxylic acid esters by hydroesterification of olefins. Background Art

[0002] Carboxylic acids and their esters have important uses in polymers, fine chemicals, coatings, microgels, surfactants, polymerization initiators and pesticides. The preparation of carboxylic acid esters by hydroesterification of olefins has 100% atom economy, meets the needs of green and sustainable development in today's society, and is a type of chemical reaction with great application prospects. The mechanism of olefin hydroesterification reaction is first the generation of transition metal hydride active species, followed by the coordination and addition process of olefin and transition metal hydrogen active species, then the coordination and insertion process of CO, and finally the attack of nucleophilic reagents, and the departure of metal hydrogen active species to form the target product. The type of P ligand and the type of acid auxiliary in the reaction have an important influence on the reaction activity and selectivity. In industry, homogeneous catalytic systems composed of palladium, phosphorus ligands and acids have attracted wide attention due to their good substrate adaptability and excellent catalytic performance. They are usually used as catalyst systems for olefin hydroesterification reactions, such as PdCl2 / PPh3 / CuCl2, [Pd(dtbpx)(dba)], [Pd(PPh3)2(olefin)], [PdCl2(dppp)] and other catalyst systems. Of course, these catalytic systems still have some problems in practical applications, such as the easy generation of Pd black during the reaction, which leads to a decrease in catalyst stability; the use of strong acid additives corrodes equipment, etc.

[0003] Room temperature ionic liquids are being recognized and accepted as a new type of solvent and catalyst system. Ionic liquids as reaction media or catalysts have well realized some important homogeneous catalytic reactions, such as alkylation, acylation, polymerization, isomerization, asymmetric ring opening, epoxidation, hydroformylation, olefin hydrogenation, esterification, cycloaddition, Beckman rearrangement, etc. Zhou Hancheng and others from Xiamen University used acidic ionic liquids to replace inorganic acid additives to catalyze olefin hydroesterification. Although acidic ionic liquids can also achieve the same catalytic effect as inorganic acid additives, the addition of acidic ionic liquids can only be catalytic (trace) and use acidic ionic liquids to provide protons and hydrogen for catalytic reactions. Adding too much will cause problems such as strong corrosion to equipment and catalyst instability. Summary of the invention

[0004] The present invention provides a method for preparing organic carboxylic acid esters by hydroesterification of olefins, wherein terminal olefins, CO and alcohol compounds are used as solvents in zwitterionic liquids composed of imidazole and sulfonate groups, and the organic carboxylic acid esters are generated under the catalytic action of Pd compounds, wherein the concentration of the zwitterionic liquid in the reaction system is the amount of solvent, accounting for 20%-90% of the mass concentration of the reaction liquid. The present invention has the advantages of mild reaction conditions, wide application range of raw materials, high reaction activity, good stability, etc., and is a reaction system with great industrial application prospects.

[0005] The technical solution of the present invention is:

[0006] The invention discloses a method for preparing organic carboxylic acid esters by hydroesterification of olefins, wherein terminal olefins, CO and alcohol are used as reactants, and an organic carboxylic acid ester with one more carbon is generated under the action of an acid auxiliary agent, a phosphine ligand and a Pd compound as a catalyst with a zwitterionic liquid as a solvent, wherein the structure of the zwitterionic liquid contains both an imidazole group and a sulfonate group, and the concentration of the zwitterionic liquid in the reaction system is the solvent amount.

[0007] Preferably, the cation in the zwitterionic liquid is an imidazolium cation, which is one of N-methylimidazole, 1-methylimidazole, imidazole, nitroimidazole, and benzimidazole, and the anion is a sulfonate-containing ion, which is one of chlorosulfonic acid, methanesulfonic acid, p-aminobenzenesulfonic acid, 1,4-butanesulfone, and 1,3-butanesulfone.

[0008] Preferably, the zwitterionic liquid is specifically:

[0009]

[0010] Preferably, the mass of the zwitterionic liquid accounts for 20%-90% of the total mass of the reaction solution.

[0011] Preferably, the acid auxiliary agent is one of hydrochloric acid, sulfuric acid, oxalic acid, acetic acid, methanesulfonic acid, and p-toluenesulfonic acid, and the molar ratio of the acid to the ionic liquid is 0.1-1:2-50.

[0012] Preferably, the phosphine ligand is one of triphenylphosphine, tri-n-butylphosphine, tricyclohexylphosphine, 1,2-bis[(di-tert-butylphosphino)methyl]benzene, and 1,4-bis(diphenylphosphino)butane. The molar ratio of the phosphine ligand to the ionic liquid is: 0.1-1:10-100.

[0013] Preferably, the Pd compound is one of palladium acetate, palladium chloride, palladium acetylacetonate, and allyl palladium chloride, and the molar ratio of Pd to the ionic liquid is: 0.1-1:1000-10000.

[0014] Preferably, the alcohol is one of methanol, ethanol, ethylene glycol, and propylene glycol, and the alcohol compound also serves as the solvent of the reaction system; the terminal olefin is one of ethylene, propylene, butylene, butadiene, and styrene.

[0015] Preferably, the reaction is carried out in a kettle reactor, alcohol, zwitterionic liquid, Pd compound, acid auxiliary agent, phosphine ligand are added to the reactor, sealed, filled with terminal olefins, the mass purity of the terminal olefins is 90%-100%, and then the reactor is pressurized with CO or a mixture of CO and N2, wherein the mass purity of CO or a mixture of CO and N2 is 90%-100%, the temperature is raised to react, and after the reaction is completed, it is cooled to room temperature, and the obtained product is an organic carboxylic acid ester.

[0016] Preferably, the reaction temperature is controlled at 50-180°C, preferably 80-120°C; the reaction pressure is controlled at 1-10 MPa, preferably 1-5 MPa; and the reaction time is controlled at 2-10 h.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The zwitterionic liquid containing imidazole groups of the present invention can be used as a solvent to stabilize metal Pd, prevent it from agglomerating to form Pd black, and significantly improve the stability of the catalyst.

[0019] 2. The zwitterionic liquid containing sulfonate groups in the present invention is used as a solvent, which can significantly improve the coordination effect between metal Pd and phosphine ligands, and further significantly improve the reaction activity of the catalyst.

[0020] 3. Compared with acidic ionic liquids as catalysts, the zwitterionic liquid synthesized in the present invention has a simple preparation method and weaker acidity, so it is less corrosive to equipment during use. The organic carboxylic acid ester raw material terminal olefin conversion rate prepared by the method of the present invention is 99%, the product organic carboxylic acid ester selectivity is 99%, and the generation of Pd black can be suppressed during the reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the NMR structure of the interaction between the Pd compound of the present invention and the imidazole group.

[0022] Figure 2 It is a schematic diagram of the nuclear magnetic structure of the ionic liquid IL-1 of the present invention and the comparative ionic liquid IL-Br interacting with the P ligand. DETAILED DESCRIPTION

[0023] Synthesis of zwitterionic liquids: 0.2 mol of imidazolium cation and 0.2 mol of anion with sulfonate group were mixed and placed in a 150 mL round-bottom flask, and 20 mL of methanol was used as solvent. Then, the mixture was refluxed and stirred at 60 ° C for 6 h, repeatedly washed with n-hexane to remove non-ionic residues, and vacuum dried to obtain zwitterionic liquids. The synthesized zwitterionic liquids include the following (IL-1 to IL-5).

[0024]

[0025] The imidazolium cations and anions with sulfonate groups in the raw materials of IL-1 to IL-5 are as follows:

[0026] Imidazolium cation Anions with sulfonate groups IL-1 N-Methylimidazole 1,4-Butanesultone IL-2 Nitroimidazole Methanesulfonic acid IL-3 Imidazole p-Toluenesulfonic acid IL-4 1-Methylimidazole 1,4-Butanesultone IL-5 Benzimidazole 1,3-Propane sultone

[0027] In order to verify the interaction between the Pd compound catalyst and the imidazole group, the pure IL-1 and the solution after the reaction in Example 1 were distilled to remove the methanol and the product samples were used for NMR characterization to explore the coordination between the Pd compound and IL-1 during the reaction. The specific operation is: the pure IL-1 and the reaction solution after the reaction in Example 1 were dissolved in deuterated methanol, and tested in a 600 MHz Bruker NMR spectrometer, and the NMR images were compared as shown in the figure below. Figure 1 As shown in the figure, it can be seen that after the reaction, the imidazole group in IL-1 has undergone an obvious displacement, indicating that Pd has a coordination effect with IL-1. This coordination effect is beneficial to stabilizing the Pd compound, inhibiting its aggregation, and improving the stability of the catalyst.

[0028] In order to verify that the zwitterionic liquid containing sulfonate groups as a solvent can significantly improve the coordination effect between metal Pd and phosphine ligands, and thus significantly improve the reaction activity of the catalyst, IL-1 and IL-Br (the preparation method of IL-Br is the same as that of IL-1 zwitterionic liquid, except that 1,4-butane sultone is replaced by bromobutyl) are coordinated with P in the phosphine ligand (1,2-bis[(di-tert-butylphosphino)methyl]benzene) and subjected to nuclear magnetic resonance measurement. The specific operation is: the sample is dissolved in deuterated methanol and tested in a 600 MHz Bruker nuclear magnetic spectrometer. The results are as follows: Figure 2 As can be seen from the figure, compared with the ionic liquid with Br, the coordination peak height of Pd and P in the ionic liquid with sulfonate anions is higher, indicating that the sulfonate anions in the ionic liquid are conducive to promoting the coordination of Pd and P. A large number of research reports have shown that the coordination of Pd and P has an important influence on the improvement of reaction activity and selectivity.

[0029] Example 1

[0030]

[0031] Among them, R1 is phenyl, R 2 It is methyl.

[0032] In a 250mL autoclave, add 25g IL-1 zwitterionic liquid, methanol (100mL), 2.2g methanesulfonic acid, 10mg palladium acetate, 0.1g 1,2-bis[(di-tert-butylphosphine)methyl]benzene ligand, add styrene (0.08mol), seal the autoclave, replace the autoclave with CO 3 times, and then fill CO until the pressure of the autoclave is 4MPa. The temperature is slowly raised to 110°C by the temperature controller, react for 4h, cool to room temperature, unload the autoclave, and the liquid obtained by the reaction is quantitatively analyzed by gas chromatograph Agilent 6890. The styrene conversion rate is 98%, the selectivity of the product methyl phenylpropionate is 99%, and no obvious Pd black is generated in the autoclave.

[0033] Example 2 Adjusting the ratio of methanol and ionic liquid in Example 2-5

[0034]

[0035] Among them, R 1 For -H, R 2 It is methyl.

[0036] In a 250mL autoclave, add 80g IL-3 zwitterionic liquid, methanol (50mL), 1.5g methanesulfonic acid, 20mg palladium acetate, 0.8g triphenylphosphine ligand, fill with ethylene (0.2mol), seal the autoclave, replace the autoclave with CO 3 times, and then fill with CO until the pressure of the autoclave is 2MPa. The temperature is slowly raised to 110°C by a temperature controller, react for 4h, cool to room temperature, unload the autoclave, and quantitatively analyze the liquid obtained by the reaction using Agilent 6890. The ethylene conversion rate is 99%, the selectivity of the product methyl propionate is 99%, and no obvious Pd black is generated in the autoclave.

[0037] Example 3

[0038]

[0039] Among them, R 1 For -H, R 2 It is methyl.

[0040] In a 250mL autoclave, add 90g IL-4 zwitterionic liquid, methanol (20mL), 2.2g acetic acid, 20mg palladium chloride, 0.1g tri-n-butylphosphine ligand, fill with ethylene (0.2mol), seal the autoclave, replace the autoclave with CO 3 times, and then fill with CO until the pressure of the autoclave is 2MPa. The temperature is slowly raised to 110°C by a temperature controller, react for 4h, cool to room temperature, unload the autoclave, and quantitatively analyze the liquid obtained by the reaction using Agilent 6890. The ethylene conversion rate is 97%, the selectivity of the product methyl propionate is 98%, and no obvious Pd black is generated in the autoclave.

[0041] Example 4

[0042]

[0043] Among them, R 1 For -H, R 2 It is methyl.

[0044] In a 250mL autoclave, add 80g IL-2 zwitterionic liquid, methanol (50mL), 3g acetic acid, 20mg palladium chloride, 0.1g 1,2-bis[(di-tert-butylphosphine)methyl]benzene ligand, fill with ethylene (0.1mol), seal the autoclave, replace the autoclave with CO 3 times, and then fill with CO until the pressure of the autoclave is 2MPa. The temperature is slowly raised to 110℃ by the temperature controller, react for 4h, cool to room temperature, unload the autoclave, and quantitatively analyze the liquid obtained by the reaction using Agilent 6890. The ethylene conversion rate is 99%, the selectivity of the product methyl propionate is 98%, and no obvious Pd black is generated in the autoclave.

[0045] Example 5

[0046]

[0047] Among them, R 1 For -H, R 2 It is methyl.

[0048] In a 250mL autoclave, add 60g IL-1 zwitterionic liquid, methanol (40mL), 3g p-toluenesulfonic acid, 15mg palladium chloride, 0.1g 1,2-bis[(di-tert-butylphosphine)methyl]benzene ligand, fill with ethylene (0.1mol), seal the autoclave, replace the autoclave with CO 3 times, and then fill with CO until the pressure of the autoclave is 2MPa. The temperature is slowly raised to 100℃ by the temperature controller, react for 3h, cool to room temperature, unload the autoclave, and quantitatively analyze the liquid obtained by the reaction using Agilent 6890. The ethylene conversion rate is 99%, the selectivity of the product methyl propionate is 97%, and no obvious Pd black is generated in the autoclave.

[0049] Comparative Example 1

[0050] Unlike Example 1, no IL-1 zwitterionic liquid was added in Comparative Example 1, and the other reactants and reaction conditions were the same as those in Example 1. The liquid obtained by the reaction was quantitatively analyzed by Agilent 6890. The styrene conversion rate was 90%, the selectivity of the product methyl phenylpropionate was 85%, and a large amount of Pd black was generated in the reactor.

[0051] Comparative Example 2

[0052] The difference from Example 2 is that IL-6 ionic liquid is used instead of IL-3 zwitterionic liquid in Comparative Example 2, and other reactant parameters and conditions are the same as those in Example 2, and the liquid obtained by the reaction is quantitatively analyzed by Agilent 6890. The ethylene conversion rate is 50%, the selectivity of the product methyl propionate is 80%, and a large amount of Pd black is generated in the reactor, and the reactor is severely corroded.

[0053] Among them, the preparation method of ionic liquid IL-6 is: take 0.2 mol of imidazole cation and 0.2 mol of anion with sulfonate group, mix them, put them into 150 mL round bottom flask, and use 20 mL of methanol as solvent. Then, the mixture is refluxed and stirred at 60 ° C for 6 hours, and the white solid zwitterion is repeatedly washed with n-hexane to remove non-ionic residues, and vacuum dried to obtain zwitterionic liquid. Then, in a 60 ° C methanol solution, equimolar methanesulfonic acid is added to the zwitterionic liquid to obtain an acidic ionic liquid (IL-6), and the structure of the acidic ionic liquid (IL-6) is as follows:

[0054]

[0055] Comparative Example 3

[0056] Different from Example 1, 5 g of IL-1 zwitterionic liquid was added in Comparative Example 3, and other reactant parameters and conditions were the same as those in Example 1. The liquid obtained by the reaction was quantitatively analyzed by Agilent 6890. The ethylene conversion rate was 88%, the selectivity of the product methyl propionate was 82%, and a large amount of Pd black was generated in the reactor.

[0057] Comparative Example 4

[0058] The difference from Example 3 is that 250 g of IL-1 zwitterionic liquid was added in Comparative Example 4, and other parameters and conditions of the reactants were the same as those in Example 3. The liquid obtained by the reaction was quantitatively analyzed by Agilent 6890. The ethylene conversion rate was 50%, and the selectivity of the product methyl propionate was 82%.

[0059] By comparing Example 1 with Comparative Example 1 and Example 1 with Comparative Example 3, it can be seen that when no or a small amount of zwitterionic liquid IL-1 is added, compared with Example 1, the styrene conversion rate and the selectivity of the product methyl phenylpropionate in Comparative Example 1 and Comparative Example 3 are reduced, and a large amount of Pd black is generated in the reactor; by comparing Example 2 with Comparative Example 2, the conversion rate of the raw material ethylene using the acidic ionic liquid IL-6 in Comparative Example 2 is significantly reduced, the selectivity of the product methyl propionate is 80%, a large amount of Pd black is generated in the reactor, and the reactor is severely corroded; by comparing Example 1 with Comparative Example 4, the ethylene conversion rate and the selectivity of the product methyl propionate are greatly reduced when a large amount of IL-1 zwitterionic liquid is added.

[0060] The zwitterionic liquid containing imidazole groups of the present invention is used as a solvent to stabilize metal Pd, prevent it from agglomerating to form Pd black, and significantly improve the stability of the catalyst; the zwitterionic liquid containing sulfonate groups of the present invention is used as a solvent to significantly improve the coordination effect between metal Pd and phosphine ligands, and further significantly improve the reaction activity of the catalyst; compared with acidic ionic liquids used as catalysts, the preparation method of the synthesized zwitterionic liquid of the present invention is simple, and the acidity is weaker, so the corrosion to the equipment during use is smaller; the conversion rate of terminal olefins of organic carboxylic acid ester raw materials prepared by the method of the present invention is 99%, the selectivity of product organic carboxylic acid ester is 99%, and the generation of Pd black can be suppressed during the reaction.

[0061] Although the present invention has been described in detail by referring to the accompanying drawings and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions shall be within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for preparing organic carboxylic acid esters by hydroesterification of olefins, characterized in that: With terminal olefins, CO and alcohol as reactants, an organic carboxylic acid ester with one more carbon is generated under the action of an acid auxiliary agent, a phosphine ligand and a Pd compound as a catalyst with a zwitterionic liquid as a solvent, wherein the structure of the zwitterionic liquid contains both an imidazole group and a sulfonate group, and the concentration of the zwitterionic liquid in the reaction system is the solvent amount.

2. The method for preparing organic carboxylic acid esters by hydroesterification of olefins according to claim 1, characterized in that: The cation in the zwitterionic liquid is an imidazolium cation, which is one of N-methylimidazole, 1-methylimidazole, imidazole, nitroimidazole, and benzimidazole; the anion is an ion with a sulfonate group, which is one of chlorosulfonic acid, methanesulfonic acid, p-aminobenzenesulfonic acid, 1,4-butanesulfone, and 1,3-butanesulfone.

3. The method for preparing organic carboxylic acid esters by hydroesterification of olefins according to claim 1, characterized in that: The zwitterionic liquid is specifically:

4. The method for preparing organic carboxylic acid esters by hydroesterification of olefins according to claim 1, characterized in that: The mass of the zwitterionic liquid accounts for 20%-90% of the total mass of the reaction solution.

5. The method for preparing organic carboxylic acid esters by hydroesterification of olefins according to claim 1, characterized in that: The acid auxiliary agent is one of hydrochloric acid, sulfuric acid, oxalic acid, acetic acid, methanesulfonic acid and p-toluenesulfonic acid, and the molar ratio of the acid to the ionic liquid is 0.1-1:2-50.

6. The method for preparing organic carboxylic acid esters by hydroesterification of olefins according to claim 1, characterized in that: The phosphine ligand is one of triphenylphosphine, tri-n-butylphosphine, tricyclohexylphosphine, 1,2-bis[(di-tert-butylphosphino)methyl]benzene and 1,4-bis(diphenylphosphino)butane, and the molar ratio of the phosphine ligand to the ionic liquid is 0.1-1:10-100.

7. The method for preparing organic carboxylic acid esters by hydroesterification of olefins according to claim 1, characterized in that: The Pd compound is one of palladium acetate, palladium chloride, palladium acetylacetonate, and allyl palladium chloride, and the molar ratio of Pd to the ionic liquid is: 0.1-1：1000-10000。 8. The method for preparing organic carboxylic acid esters by hydroesterification of olefins according to claim 1, characterized in that: The alcohol is one of methanol, ethanol, ethylene glycol and propylene glycol, and the alcohol is also used as a solvent of the reaction system; the terminal olefin is one of ethylene, propylene, butylene, butadiene and styrene.

9. The method for preparing organic carboxylic acid esters by hydroesterification of olefins according to claim 1, characterized in that: The reaction is carried out in a kettle reactor. Alcohol, zwitterionic liquid, Pd compound, acid auxiliary agent and phosphine ligand are added to the kettle. After sealing, terminal olefin is charged, and then the pressure of the kettle is supplemented with CO or a mixture of CO and N2. The temperature is increased to react. After the reaction is completed, it is cooled to room temperature. The obtained product is an organic carboxylic acid ester.

10. The method for preparing organic carboxylic acid esters by hydroesterification of olefins according to claim 8, characterized in that: The reaction temperature is controlled at 50-180°C, preferably 80-120°C; the reaction pressure is controlled at 1-10MPa, preferably 1-5MPa; and the reaction time is controlled at 2-10h.

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