Catalyst for alcohol transesterification reaction and application thereof, and method for synthesizing asymmetric dialkyl carbonate

Abstract

The present invention provides a catalyst for alcohol transesterification reaction and its application, as well as a method for synthesizing asymmetric dialkyl carbonate, and relates to the technical field of dialkyl carbonate synthesis. The catalyst for alcohol transesterification reaction of the present invention comprises a metal zinc compound and an auxiliary agent; the auxiliary agent is an organic amine strong base. The catalyst provided by the present invention can not only activate the ester carbonyl group, but also activate the alcohol hydroxyl group, thereby enhancing the nucleophilic attack ability of the alcohol raw material and making the ester carbonyl group more efficient in receiving electrophiles. The use of the catalyst of the present invention in alcohol transesterification reaction improves the reaction efficiency and solves the problem that the technical route for directly preparing asymmetric dialkyl carbonate by reacting two different monohydric alcohols with carbon dioxide is subject to thermodynamic limitations and extremely low efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of dialkyl carbonate synthesis, in particular to a catalyst for alcohol transesterification reaction and application thereof, and a method for synthesizing asymmetric dialkyl carbonate. Background Art

[0002] Dialkyl carbonates can be divided into symmetric and asymmetric carbonates. Asymmetric carbonates, with their moderate boiling point, low melting point, low viscosity, excellent low-temperature performance, corrosion resistance, self-cleaning properties, and strong dissolving power, are used as electrolytes for lithium-ion batteries, lubricant base oils, solvents for special coatings, and solvents for specialty fragrances. Compared to symmetric organic carbonates, lithium secondary batteries using asymmetric carbonates as electrolytes exhibit superior performance, including increased energy density, enhanced discharge capacity, longer lifespan, and improved safety, making them a more important lithium-ion battery electrolyte component than symmetric carbonates. Furthermore, as important organic synthesis intermediates, asymmetric carbonates can also serve as protecting groups for alcoholic and phenolic hydroxyl groups.

[0003] Asymmetric carbonates can be prepared by reacting different monohydric alcohols with CO2, but this reaction is thermodynamically limited and has extremely low efficiency. Taking the preparation of ethyl methyl carbonate by the "one-pot" reaction of methanol, ethanol and CO2 as an example, the reaction produces a mixed product system with components such as dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate. Moreover, this reaction is an equilibrium reaction, and the yield and content of all components are very low. Improving reaction efficiency and chemical selectivity must be carried out simultaneously, that is, overcoming thermodynamic limitations and developing chemically specific catalysts are the most critical. However, this topic is extremely challenging and there is no effective solution to date. Summary of the Invention

[0004] The present invention aims to provide a catalyst for alcohol transesterification reaction and its application, as well as a method for synthesizing asymmetric dialkyl carbonate, thereby solving the problem that the technical route for directly preparing asymmetric dialkyl carbonate by reacting two different monohydric alcohols with carbon dioxide is subject to thermodynamic limitations and extremely low efficiency.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The invention provides a catalyst for alcohol transesterification reaction, comprising a metal zinc compound and an auxiliary agent; the auxiliary agent is an organic amine strong base.

[0007] Preferably, the metallic zinc compound includes zinc acetate, zinc chloride, zinc phosphate or zinc oxide.

[0008] Preferably, the organic amine strong base includes 1,8-diazabicyclo[5.4.0]undec-7-ene, 1,5-diazabicyclo[4.3.0]-5-nonene, 1,1,3,3-tetramethylguanidine or triethylamine.

[0009] Preferably, the molar ratio of the metallic zinc compound to the auxiliary agent is 1:1 to 20.

[0010] The present invention provides use of the catalyst described in the above scheme in catalyzing the alcohol transesterification reaction between monohydric alcohol and β-oxypropyl carbonate to prepare dialkyl carbonate.

[0011] The present invention provides a method for synthesizing an asymmetric dialkyl carbonate, comprising the following steps: mixing a monohydric alcohol having a structure shown in Formula 1, a β-oxypropyl carbonate having a structure shown in Formula 2, the catalyst described in the above scheme, and a polar organic solvent, and performing an alcohol transesterification reaction to obtain an asymmetric dialkyl carbonate having a structure shown in Formula 3;

[0012] The β-oxypropyl carbonate is composed of a monohydric alcohol R 3 OH, propargyl alcohol having the structure shown in formula 4 and CO2 are prepared by a one-pot reaction;

[0013] R 4 OH formula 1;

[0014] In formulas 1 to 4, R 4 is an alkyl group, R 3 is an alkyl group or a benzyl group containing an aromatic ring, and R 3 With R 4 Different; R 1 and R 2 are independently H, alkyl or aromatic, and R 1 and R 2 At least one of them is an alkyl group.

[0015] Preferably, the amount of the metal zinc compound in the catalyst is 0.5 to 30 mol% of the β-oxypropyl carbonate.

[0016] Preferably, the molar ratio of the β-oxypropyl carbonate to the monohydric alcohol having the structure shown in Formula 1 is 1:1 to 50.

[0017] Preferably, the alcohol transesterification reaction is carried out at a temperature of 30 to 150° C. and for a time of 2 to 24 hours.

[0018] Preferably, the preparation method of β-oxypropyl carbonate comprises the following steps: 3OH, triphenylphosphine, a basic silver compound, propargyl alcohol having a structure shown in Formula 4 and an organic solvent are mixed, and CO2 is introduced into the obtained mixture under closed conditions to carry out a one-pot reaction to obtain the β-oxypropyl carbonate.

[0019] The present invention provides a catalyst for alcohol transesterification reaction, comprising a metal zinc compound and an auxiliary agent; the auxiliary agent is an organic amine strong base. Since β-oxypropyl carbonate itself is an asymmetric chain carbonate, but has a large number of alkyl substituents at both ends, it brings a certain steric hindrance effect to the active ester carbonyl group, making the alcohol transesterification reaction space effect significant, and thus the conversion efficiency is not high. In view of the molecular structure characteristics and catalytic reaction principles of this type of reaction, the catalyst provided by the present invention has multifunctional characteristics, which can not only activate the ester carbonyl group, but also activate the alcohol hydroxyl group, so that the nucleophilic attack ability of the alcohol raw material is enhanced, and the ester carbonyl group is more efficient in receiving electrophiles. The catalyst of the present invention is used in the alcohol transesterification reaction to improve the reaction efficiency.

[0020] The present invention proposes an intermittent step-by-step catalytic synthesis method for preparing asymmetric dialkyl carbonate by first preparing β-oxypropyl carbonate through a one-pot multi-component reaction of a monohydric alcohol, carbon dioxide and propargyl alcohol, and then using the β-oxypropyl carbonate and another monohydric alcohol to undergo an alcohol ester exchange reaction to prepare the asymmetric dialkyl carbonate. By developing a high-efficiency catalyst, the problem of extremely low efficiency of the technical route for preparing asymmetric dialkyl carbonate by direct reaction of a monohydric alcohol and carbon dioxide is solved, and the method has good technical application prospects. DETAILED DESCRIPTION

[0021] In the present invention, unless otherwise specified, all raw materials used are commercially available products well known in the art.

[0022] The invention provides a catalyst for alcohol transesterification reaction, comprising a metal zinc compound and an auxiliary agent; the auxiliary agent is an organic amine strong base.

[0023] In the present invention, the metal zinc compound preferably includes zinc acetate, zinc chloride, zinc phosphate or zinc oxide; the organic amine strong base preferably includes 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5-diazabicyclo[4.3.0]-5-nonene (DBN), 1,1,3,3-tetramethylguanidine (TMG) or triethylamine (Et3N); the molar ratio of the metal zinc compound to the auxiliary agent is preferably 1:1 to 20, more preferably 1:5 to 15, and further preferably 1:8 to 12.

[0024] The catalyst provided by the present invention has multifunctional properties and can activate not only ester carbonyl groups but also alcohol hydroxyl groups, thereby enhancing the nucleophilic attack ability of the alcohol raw material and making the ester carbonyl groups more efficient in accepting electrophiles. The catalyst of the present invention is used in alcohol transesterification reactions to improve reaction efficiency.

[0025] The present invention provides use of the catalyst described in the above scheme in catalyzing the alcohol transesterification reaction between monohydric alcohol and β-oxypropyl carbonate to prepare dialkyl carbonate.

[0026] In the present invention, the dialkyl carbonate is preferably a symmetrical dialkyl carbonate or an asymmetrical dialkyl carbonate.

[0027] The present invention provides a method for synthesizing an asymmetric dialkyl carbonate, comprising the following steps: mixing a monohydric alcohol having a structure shown in Formula 1, a β-oxypropyl carbonate having a structure shown in Formula 2, the catalyst described in the above scheme, and a polar organic solvent, and performing an alcohol transesterification reaction to obtain an asymmetric dialkyl carbonate having a structure shown in Formula 3;

[0028] The β-oxypropyl carbonate is composed of a monohydric alcohol R 3 OH, propargyl alcohol having the structure shown in formula 4 and CO2 are prepared by a one-pot reaction;

[0029] R 4 OH formula 1;

[0030] In formulas 1 to 4, R 4 is an alkyl group, R 3 is an alkyl group or a benzyl group containing an aromatic ring, and R 3 With R 4 Different; R 1 and R 2 are independently H, alkyl or aromatic, and R 1 and R 2 At least one of them is an alkyl group.

[0031] In the present invention, the preparation method of β-oxypropyl carbonate preferably comprises the following steps: 3 OH, triphenylphosphine, a basic silver compound, propargyl alcohol having a structure shown in Formula 4 and an organic solvent are mixed, and CO2 is introduced into the obtained mixture under closed conditions to carry out a one-pot reaction to obtain the β-oxypropyl carbonate.

[0032] In the present invention, the monohydric alcohol R 3 R in OH 3 is an alkyl group or a benzyl group containing an aromatic ring, when R 3 When R is an alkyl group, the alkyl group is preferably a straight-chain alkyl group, more preferably a straight-chain alkyl group with 1 to 25 carbon atoms, and further preferably a straight-chain alkyl group with 1 to 5 carbon atoms; when R 3 When it is an aromatic ring-containing benzyl group, the aromatic ring-containing benzyl group is preferably a benzyl group. In the present invention, the alkaline silver compound is preferably silver carbonate, silver phosphate or silver oxide; R in Formula 4 is 1 and R 2are independently H, alkyl or aromatic, and R 1 and R 2 At least one of them is an alkyl group, and the alkyl group is preferably a straight-chain alkyl group, more preferably a straight-chain alkyl group with 1 to 5 carbon atoms; in the embodiment of the present invention, the R 1 and R 2 is methyl, n-propyl or n-butyl. In the present invention, when the R 1 or R 2 When it is an aromatic group, the aromatic group preferably includes phenyl, p-methylphenyl or p-ethylphenyl. In the present invention, the organic solvent is preferably acetonitrile or N,N-dimethylformamide (DMF).

[0033] In the present invention, the amount of the alkaline silver compound is preferably monohydric alcohol R 3 5 to 20 mmol% of OH; the amount of triphenylphosphine is preferably monohydric alcohol R 3 5 to 40 mol% of OH; the monohydric alcohol R 3 The molar ratio of OH to propargyl alcohol having the structure shown in Formula 4 is 1:1 to 10, more preferably 1:3 to 8, and even more preferably 1:5 to 6. The present invention has no special requirements on the amount of the organic solvent, and can convert the monohydric alcohol R 3 OH and propargyl alcohol are completely dissolved.

[0034] In the present invention, the one-pot reaction is preferably carried out in a reactor. In the present invention, the amount of CO2 charged is preferably such that the pressure of the closed environment reaches 0.5 to 5.0 MPa, more preferably 1 to 4 MPa, and even more preferably 2 to 3 MPa. In the present invention, the temperature of the one-pot reaction is preferably 40 to 100°C, more preferably 60 to 80°C; the time of the one-pot reaction is preferably 5 to 24 hours, more preferably 10 to 20 hours, and even more preferably 14 to 16 hours. In the present invention, the one-pot reaction is preferably carried out under stirring conditions.

[0035] In the present invention, the equation of the one-pot reaction is as follows:

[0036]

[0037] After the one-pot reaction is completed, the present invention preferably waits for the reactor to cool to room temperature, slowly discharges the unreacted carbon dioxide, opens the reactor, takes out the mixed material, removes the organic solvent, and separates by column chromatography to obtain the product β-oxypropyl carbonate.

[0038] After obtaining β-oxypropyl carbonate, the present invention mixes a monohydric alcohol having a structure shown in Formula 1 with the β-oxypropyl carbonate, the catalyst described in the above scheme, and a polar organic solvent to carry out an alcohol transesterification reaction to obtain an asymmetric dialkyl carbonate having a structure shown in Formula 3.

[0039] In the present invention, in Formula 1, R 4 is an alkyl group, preferably a straight-chain alkyl group, more preferably a straight-chain alkyl group with 1 to 25 carbon atoms. 4 It is ethyl or n-propyl.

[0040] In the present invention, the amount of the metal zinc compound in the catalyst is preferably 0.5 to 30 mol %, more preferably 5 to 25 mol %, and further preferably 10 to 20 mol % of the β-oxypropyl carbonate.

[0041] In the present invention, the polar organic solvent is preferably acetonitrile or N,N-dimethylformamide (DMF). The present invention has no special requirements on the amount of the polar organic solvent, as long as it can completely dissolve the monohydric alcohol having the structure shown in Formula 1 and β-oxypropyl carbonate.

[0042] In the present invention, the molar ratio of the β-oxypropyl carbonate to the monohydric alcohol having the structure represented by Formula 1 is preferably 1:1-50, more preferably 1:5-45, further preferably 1:10-40, and even more preferably 1:20-30.

[0043] In the present invention, the alcohol transesterification reaction temperature is preferably 30 to 150°C, more preferably 50 to 130°C, and even more preferably 80 to 100°C; the reaction time is preferably 2 to 24 hours, more preferably 5 to 20 hours, and even more preferably 10 to 15 hours. The products of the alcohol transesterification reaction of the present invention are an asymmetric dialkyl carbonate and an α-hydroxyketone.

[0044] In the present invention, the equation for the alcohol transesterification reaction is as follows:

[0045]

[0046] After completing the alcohol transesterification reaction, the present invention preferably further comprises subjecting the resulting reaction product to column chromatography to obtain ethyl benzyl carbonate. In the present invention, the eluents used for the column chromatography separation are preferably ethyl acetate and n-hexane, and the volume ratio of ethyl acetate to n-hexane is preferably 1:5 to 50, more preferably 1:10 to 40, and even more preferably 1:20 to 30.

[0047] The catalyst for alcohol transesterification and its application, and the synthesis method of asymmetric dialkyl carbonate provided by the present invention are described in detail below with reference to the examples, but they should not be construed as limiting the scope of protection of the present invention.

[0048] The preparation process of β-oxypropyl carbonate used in the following examples and comparative examples is as follows:

[0049] In a 50 mL autoclave, 5 mol% silver carbonate (relative to monohydric alcohol), 10 mol% triphenylphosphine (relative to monohydric alcohol), monohydric alcohol (benzyl alcohol, R 3 =PhCH2) 0.01mol, propargyl alcohol (R 1 =R 2 =Me), a closed reactor was filled with CO2 at a pressure of 1.0 MPa, the reaction temperature was 80°C, the reaction time was 16 hours, and acetonitrile accounted for 30% of the reactor volume. After the reaction was completed, the reaction was cooled to room temperature, and the unreacted carbon dioxide was slowly discharged. The reactor was opened, the mixed material was taken out, and the product β-oxypropyl carbonate was measured by gas chromatography with a yield of 85%. The product β-oxypropyl carbonate was obtained by column chromatography separation, and different proportions of ethyl acetate and n-hexane (v 乙 :v 正 =1:3~1:20).

[0050] Example 1

[0051] 2 mol% anhydrous zinc acetate (relative to ethanol) and 4 mol% 1,8-diazabicyclo[5.4.0]undec-7-ene (relative to ethanol) were weighed and added into a 50 mL high-pressure reactor in a tetrafluoroethylene liner tube, a magnetic rod was placed, and then β-oxypropyl carbonate (R 1 =R 2 =Me), 0.01 mol of ethanol, 0.1 mol of ethanol, and 15 mL of N,N-dimethylformamide (DMF), with the liquid materials accounting for 30% of the reactor's effective volume, were stirred at 80°C for 8 hours. After the reaction, the mother liquor composition was analyzed and quantified. The conversion of β-oxopropyl carbonate was 80.5%, the yield of ethyl benzyl carbonate was 78.6%, and the yield of α-hydroxyketone was 79.2%.

[0052] Examples 2 to 7

[0053] The steps are the same as those in Example 1, and the specific reaction conditions are shown in Table 1.

[0054] Comparative Examples 1 to 3

[0055] The differences from Example 1 are shown in Table 1.

[0056] Table 1 Reaction conditions and reaction results of Examples and Comparative Examples

[0057]

[0058]

[0059]

[0060] As shown in Table 1, the catalyst provided by the present invention can activate not only the ester carbonyl group but also the alcohol hydroxyl group, thereby enhancing the nucleophilic attack ability of the alcohol raw material and making the ester carbonyl group more efficient in receiving the electrophile. The catalyst of the present invention is used in alcohol transesterification reactions to improve reaction efficiency, solve the problem of extremely low efficiency of the technical route for preparing asymmetric dialkyl carbonates by direct reaction of monohydric alcohols and carbon dioxide, and has a good technical application prospect.

[0061] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A catalyst for alcohol transesterification reaction in catalyzing the preparation of dialkyl carbonate by alcohol transesterification reaction of monohydric alcohol and β-oxypropyl carbonate, characterized in that: The β-oxypropyl carbonate has a structure shown in Formula 2: In formula 2, R 3 is an alkyl group or a benzyl group containing an aromatic ring; R 1 and R 2 are independently H, alkyl or aromatic, and R 1 and R 2 At least one of them is an alkyl group; The dialkyl carbonate is an asymmetric dialkyl carbonate; The catalyst for alcohol transesterification reaction comprises a metal zinc compound and an auxiliary agent; the auxiliary agent is an organic amine strong base.

2. The use according to claim 1, characterized in that The metal zinc compound includes zinc acetate, zinc chloride, zinc phosphate or zinc oxide.

3. The use according to claim 1, characterized in that The organic amine strong base includes 1,8-diazabicyclo[5.4.0]undec-7-ene, 1,5-diazabicyclo[4.3.0]-5-nonene, 1,1,3,3-tetramethylguanidine or triethylamine.

4. The use according to any one of claims 1 to 3, characterized in that The molar ratio of the metallic zinc compound to the auxiliary agent is 1:1-20.

5. A method for synthesizing an asymmetric dialkyl carbonate, characterized in that: The method comprises the following steps: mixing a monohydric alcohol having a structure shown in Formula 1, a β-oxypropyl carbonate having a structure shown in Formula 2, a catalyst and a polar organic solvent, and performing an alcohol ester exchange reaction to obtain an asymmetric dialkyl carbonate having a structure shown in Formula 3; the catalyst comprises a metallic zinc compound and an auxiliary agent; the auxiliary agent is an organic amine strong base; The β-oxypropyl carbonate is composed of a monohydric alcohol R 3 OH, propargyl alcohol having the structure shown in formula 4 and CO2 are prepared by a one-pot reaction; R 4 OH formula 1; In formulas 1 to 4, R 4 is an alkyl group, R 3 is an alkyl group or a benzyl group containing an aromatic ring, and R 3 With R 4 Different; R 1 and R 2 are independently H, alkyl or aromatic, and R 1 and R 2 At least one of them is an alkyl group.

6. The synthesis method according to claim 5, characterized in that The amount of the metal zinc compound in the catalyst is 0.5 to 30 mol% of the β-oxypropyl carbonate.

7. The synthesis method according to claim 5, characterized in that The molar ratio of the β-oxypropyl carbonate to the monohydric alcohol having the structure shown in Formula 1 is 1:1 to 50.

8. The synthesis method according to any one of claims 5 to 7, characterized in that The temperature of the alcohol transesterification reaction is 30 to 150° C., and the time is 2 to 24 hours.

9. The synthesis method according to claim 5, characterized in that The preparation method of the β-oxypropyl carbonate comprises the following steps: 3 OH, triphenylphosphine, a basic silver compound, propargyl alcohol having a structure shown in Formula 4 and an organic solvent are mixed, and CO2 is introduced into the obtained mixture under closed conditions to carry out a one-pot reaction to obtain the β-oxypropyl carbonate.

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