Application of acid accelerant in synthesis of methyl propionate through ethylene hydromethyl esterification

Abstract

The invention discloses an application of an acid accelerant in synthesis of methyl propionate through ethylene hydromethyl esterification, which comprises the following steps: taking vinyl acidic ionic liquid as a polymeric monomer, and obtaining an acidic polymeric ionic liquid acid accelerant through free radical polymerization and acidification of different organic acids, the structural formula of the sulfonic acid group acidic polymeric ionic liquid acid accelerant is shown in figure 1, X-represents organic acid radical anions, and n represents the polymerization degree of the acidic polymeric ionic liquid. The sulfonic acid group acidic polymeric ionic liquid acid accelerant is used for synthesizing methyl propionate through ethylene hydromethyl esterification, and high ethylene conversion rate and high methyl propionate selectivity can be obtained under mild reaction conditions. Due to the fact that the sulfonic acid-based polyion liquid can provide appropriate acid strength and acid density in the reaction, the reaction can be effectively promoted.

Description

Technical Field

[0001] The invention relates to the technical field of synthesizing organic chemical products through ethylene hydromethyl esterification, and in particular to application of an acidic polymeric ionic liquid in synthesizing methyl propionate through ethylene hydromethyl esterification. Background Art

[0002] Methyl propionate is a colorless, transparent organic liquid widely used as an additive in high-quality foods and cosmetics. It can also serve as an excellent preservative or flavoring agent in some foods and feeds. Methyl propionate can also react with formaldehyde to form methyl methacrylate (MMA), an important chemical synthesis raw material, through an aldol condensation reaction. It can also be used to produce acrylic acid, propionic acid, and propionic esters (such as benzyl propionate and isoamyl propionate) through saponification, hydrolysis, and transesterification reactions. Therefore, the development of a methyl propionate synthesis process is beneficial to the advancement and development of technologies for producing propionic acid, propionic acid salts, and propionic esters. Currently, the catalysts used for the hydromethylation of methyl propionate are transition metal complexes, primarily those of divalent palladium salts and phosphine ligands, and the reaction rate is accelerated by the addition of an acid promoter. For example, SHELL's patent CN87110635 involves a divalent palladium compound, an aromatic substituted monodentate phosphine, and an acid system to catalyze the hydromethylation of ethylene to methyl propionate; Chinese patent CN107497489 uses a Co complex as a main catalyst, triphenylphosphine or tri(3,4-dimethoxyphenyl)phosphine as a ligand, acidic substances such as phosphoric acid, phenylcarbonic acid, methylphenylcarbonic acid, sulfuric acid, salicylic acid as promoters, and polyfluorinated compounds such as BF3OEt2 as structural additives to catalyze the synthesis of methyl propionate from ethylene; Chinese patent CN103319337 selects palladium acetate as a main catalyst, triphenylphosphine or tri(3,4-dimethoxyphenyl)phosphine as a ligand, phosphoric acid, phenylcarbonic acid, 2,6-dichlorotoluic acid as an acid promoter, and cobalt acetate, ruthenium acetate, and nickel acetate as auxiliary agents to catalyze the hydromethylation of ethylene to methyl propionate. This type of catalyst features a metal complex as the primary active component, a phosphine ligand as an additive, and an acidic substance as an acid promoter, resulting in high conversion rates and selectivity. However, using an organic acid as an acid promoter can lead to equipment corrosion and make subsequent disposal difficult.

[0003] Therefore, there is an urgent need to research and develop an acid promoter with good catalyst activity, high selectivity, low corrosion to equipment, and easy separation from the product. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the deficiencies of the above-mentioned prior art and provide an application of an acid promoter in the synthesis of methyl propionate from ethylene hydromethylation. First, an ionic liquid monomer and a cross-linking agent are subjected to free radical polymerization to obtain an acidic polymerized ionic liquid precursor, which is then acidified with an organic acid to obtain a sulfonic acid-based acidic polymerized ionic liquid. The acidic polymerized ionic liquid can provide the characteristics of suitable acid density and acid strength, and promotes the palladium phosphine complex-catalyzed ethylene hydromethylation reaction to produce methyl propionate under mild conditions. The sulfonic acid-based acidic polymerized ionic liquid provided by the present invention has the advantages of good stability, easy separation from the product, low corrosion to equipment, and can be recycled multiple times.

[0005] Specific technical solutions for achieving the purpose of the present invention:

[0006] The invention discloses an acid accelerator for the synthesis of methyl propionate by the hydromethylation of ethylene. The invention is characterized in that an ionic liquid monomer and a crosslinking agent divinyl are subjected to free radical polymerization, and then acidified with an organic acid to obtain a sulfonic acid-based acidic polymeric ionic liquid, which is used as an acid accelerator for the hydromethylation of ethylene.

[0007] The synthesis steps of the sulfonic acid-based acidic polymeric ionic liquid acid promoter are as follows:

[0008] Step 1: Preparation of acidic polymerizable ionic liquid monomers

[0009] Dissolve 1,3-propane sultone and vinyl imidazole in acetone or tetrahydrofuran solution, heat to 60-100°C, and stir for 12-72 hours. After the reaction is completed, wash the white solid obtained by the reaction with acetone and ethanol for multiple times to obtain an acidic polymeric ionic liquid monomer.

[0010] Step 2: Preparation of acidic polymeric ionic liquid precursor

[0011] The acidic polymerized ionic liquid monomer obtained in step 1 and divinylbenzene are dissolved in a mixed solution of ethanol and water, the solution is deoxygenated, and then an initiator azobisisobutyronitrile (AIBN) is added to obtain a white solid by thermally initiating free radical polymerization. The white solid is washed with ethanol multiple times to obtain an acidic polymerized ionic liquid precursor; the molar ratio of the polymerized ionic liquid monomer to divinylbenzene is 1:0.1-100;

[0012] The mass of the initiator AIBN accounts for 1 to 10 wt% of the total mass of the polymerized ionic liquid monomer and the crosslinking agent;

[0013] The reaction temperature of the thermally initiated free radical polymerization is 70 to 110° C. and the reaction time is 24 to 48 hours.

[0014] Step 3: Preparation of acidic polymeric ionic liquid

[0015] The acidic polymeric ionic liquid precursor obtained in step 2 is placed in an organic acid solution, heated and stirred to obtain a white solid, and the white solid is vacuum dried to obtain an acidic polymeric ionic liquid, whose chemical structure is shown in the attached figure. Figure 1 As shown;

[0016] The organic acid is one or a mixture of methanesulfonic acid, ethanesulfonic acid, trifluoromethanesulfonic acid, trifluoroacetic acid, p-toluenesulfonic acid, benzenesulfonic acid, p-chlorobenzenesulfonic acid, p-fluorobenzenesulfonic acid, p-iodobenzenesulfonic acid, and p-bromobenzenesulfonic acid;

[0017] The molar concentration of the organic acid in the organic acid solution is 0.5 to 2.5 mol / L;

[0018] The heating temperature is 70-110°C;

[0019] The reaction time is 24 to 48 hours;

[0020] The application of acid promoters in promoting the hydromethylation of ethylene to produce methyl propionate catalyzed by palladium phosphine complexes is as follows:

[0021] In a high-pressure reactor, methanol, palladium acetate, 1,2-bis(di-tert-butylphosphinomethyl)benzene, and a sulfonic acidic polymeric ionic liquid acid promoter are sequentially added, and a mixed gas of ethylene and carbon monoxide is introduced to a pressure of 0.5 to 5.0 MPa. The reaction temperature is 50 to 150° C. After the reaction is completed, methyl propionate is obtained as a product, wherein the sulfonic acidic polyionic liquid can be repeatedly recycled after simple separation and recovery;

[0022] The amount of the sulfonic acidic polymeric ionic liquid of the present invention is 1 to 10 wt% of the amount of the methanol;

[0023] The present invention has the following advantages: It is the first to design and synthesize sulfonic acidic polymeric ionic liquids with different anions. These sulfonic acidic polymeric ionic liquids have different acid strengths depending on their anions, have controllable acid density, and have advantages such as good thermal stability. They can promote the ethylene hydromethylation reaction catalyzed by a palladium phosphine complex under mild conditions. Furthermore, compared with traditional liquid acid promoters, these sulfonic acidic polymeric ionic liquids cause less corrosion to equipment and can be separated from the product by simple technical means, thus enabling catalyst recovery and recycling. Cycling experiments have shown that the sulfonic acidic polymeric ionic liquid exhibits no significant decrease in its promoting effect after 10 cycles. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is the structural diagram of the sulfonic acidic polymeric ionic liquid of the present invention, X - Represents an organic acid anion. DETAILED DESCRIPTION

[0025] In order to make the present invention easier to understand, the present invention will be described in detail below with reference to examples. These examples are only for illustration and do not limit the scope of application of the present invention.

[0026] Example 1

[0027] To prepare the sulfonic acidic polymeric ionic liquid P-[VSpIm-TsOH], 1-vinyl-3-(3-sulfonic acid)propylimidazolium inner salt (2.16 g, 10 mmol), crosslinker divinylbenzene (1.30 g, 10 mmol), and initiator AIBN (0.17 g, 5 wt%) were dissolved in a mixture of ethanol and water. The mixture was ultrasonically deoxygenated for 30 minutes and reacted at 80°C for 24 hours. After completion of the reaction, the resulting white precipitate was washed several times with ethanol and water and dried to obtain a white solid. The resulting white solid was added to 10 mL of 1 mol / L aqueous p-toluenesulfonic acid solution and stirred at 80°C for 24 hours. The resulting white solid was centrifuged and dried under vacuum at 80°C for 24 hours to obtain the sulfonic acidic polymeric ionic liquid P-[VSpIm-TsOH].

[0028] Example 2

[0029] To prepare the sulfonic acidic polymeric ionic liquid P-[VSpIm-TfOH], 1-vinyl-3-(3-sulfonic acid)propylimidazolium inner salt (2.16 g, 10 mmol), crosslinker divinylbenzene (1.30 g, 10 mmol), and initiator AIBN (0.17 g, 5 wt%) were dissolved in a mixture of ethanol and water. The mixture was ultrasonically deoxygenated for 30 minutes and reacted at 80°C for 24 hours. After completion of the reaction, the resulting white precipitate was washed several times with ethanol and water and dried to obtain a white solid. The resulting white solid was added to 10 mL of 2 mol / L trifluoromethanesulfonic acid aqueous solution and stirred at 80°C for 24 hours. The resulting white solid was centrifuged and dried under vacuum at 80°C for 24 hours to obtain the sulfonic acidic polymeric ionic liquid P-[VSpIm-TfOH].

[0030] Example 3

[0031] To prepare the sulfonic acidic polymeric ionic liquid P-[VSpIm-MESA], 1-vinyl-3-(3-sulfonic acid)propylimidazolium inner salt (2.16 g, 10 mmol), crosslinker divinylbenzene (1.30 g, 10 mmol), and initiator AIBN (0.17 g, 5 wt%) were dissolved in a mixture of ethanol and water. The mixture was ultrasonically deoxygenated for 30 minutes and reacted at 80°C for 24 hours. After completion of the reaction, the resulting white precipitate was washed several times with ethanol and water and dried to obtain a white solid. The resulting white solid was added to 10 mL of 1 mol / L methanesulfonic acid aqueous solution and stirred at 80°C for 24 hours. The resulting white solid was centrifuged and dried under vacuum at 80°C for 24 hours to obtain the sulfonic acidic polymeric ionic liquid P-[VSpIm-MESA].

[0032] Example 4

[0033] To prepare the sulfonic acidic polymeric ionic liquid P-[VSpIm-BSA], 1-vinyl-3-(3-sulfonic acid)propylimidazolium inner salt (2.16 g, 10 mmol), crosslinker divinylbenzene (1.30 g, 10 mmol), and initiator AIBN (0.17 g, 5 wt%) were dissolved in a mixture of ethanol and water. The mixture was ultrasonically deoxygenated for 30 minutes and reacted at 80°C for 24 hours. After completion of the reaction, the resulting white precipitate was washed several times with ethanol and water and dried to obtain a white solid. The resulting white solid was added to 10 mL of 1 mol / L aqueous benzenesulfonic acid solution and stirred at 80°C for 24 hours. The resulting white solid was centrifuged and dried under vacuum at 80°C for 24 hours to obtain the sulfonic acidic polymeric ionic liquid P-[VSpIm-BSA].

[0034] Example 5

[0035] Sulfonic acidic polymeric ionic liquid P-[VSpIm-TsOH] was used as an acid promoter to promote the conversion of ethylene hydromethyl ester to methyl propionate. To a 20 mL autoclave equipped with a magnet, palladium acetate (0.0112 g, 0.05 mmol), 1,2-bis(di-tert-butylphosphinomethyl)benzene (0.0985 g, 0.25 mmol), sulfonic acidic polymeric ionic liquid P-[VSpIm-TsOH] (0.1036 g, 0.25 mol), and methanol (5 mL) were added sequentially. The mixture was then heated with stirring until it reached 80°C and a mixture of ethylene and carbon monoxide was introduced until the pressure reached 2 MPa. The reaction was stirred for 1 hour. After the reaction was completed, the mixture was cooled to room temperature, and the internal standard, isobutanol, was added to the reaction solution. Quantitative analysis using an Agilent gas chromatograph revealed an ethylene conversion of 94.2% and a methyl propionate selectivity of greater than 99.9%.

[0036] Example 6

[0037] Sulfonic acidic polymeric ionic liquid P-[VSpIm-TfOH] was used as an acid promoter to promote the conversion of ethylene hydromethyl ester to methyl propionate. To a 20 mL autoclave equipped with a magnet, palladium acetate (0.0112 g, 0.05 mmol), 1,2-bis(di-tert-butylphosphinomethyl)benzene (0.0985 g, 0.25 mmol), sulfonic acidic polymeric ionic liquid P-[VSpIm-TfOH] (0.0936 g, 0.25 mol), and methanol (5 mL) were added sequentially. The reactor was closed and heated with stirring. An ethylene-carbon monoxide mixture was introduced at 80°C until the pressure reached 2 MPa. The reaction was stirred for 1 hour. After the reaction was completed, the mixture was cooled to room temperature, and the internal standard, isobutanol, was added to the reaction solution. Quantitative analysis using an Agilent gas chromatograph revealed an ethylene conversion of 99.8% and a methyl propionate selectivity of greater than 99.9%.

[0038] Example 7

[0039] Sulfonic acidic polymeric ionic liquid P-[VSpIm-MESA] was used as an acid promoter to promote the conversion of ethylene hydromethyl ester to methyl propionate. To a 20 mL autoclave equipped with a magnet, palladium acetate (0.0112 g, 0.05 mmol), 1,2-bis(di-tert-butylphosphinomethyl)benzene (0.0985 g, 0.25 mmol), sulfonic acidic polymeric ionic liquid P-[VSpIm-MESA] (0.0801 g, 0.25 mol), and methanol (5 mL) were added sequentially. The mixture was then heated with stirring until it reached 80°C and a mixture of ethylene and carbon monoxide was introduced until the pressure reached 2 MPa. The reaction was stirred for 1 hour. After the reaction was completed, the mixture was cooled to room temperature, and the internal standard, isobutanol, was added to the reaction solution. Quantitative analysis using an Agilent gas chromatograph revealed an ethylene conversion of 99.8% and a methyl propionate selectivity greater than 99.9%.

[0040] Example 8

[0041] Sulfonic acidic polymeric ionic liquid P-[VSpIm-BSA] was used as an acid promoter to promote the conversion of ethylene hydromethyl ester to methyl propionate. To a 20 mL autoclave equipped with a magnet, palladium acetate (0.0112 g, 0.05 mmol), 1,2-bis(di-tert-butylphosphinomethyl)benzene (0.0985 g, 0.25 mmol), sulfonic acidic polymeric ionic liquid P-[VSpIm-BSA] (0.0956 g, 0.25 mol), and methanol (5 mL) were added sequentially. The reactor was closed and heated with stirring. An ethylene and carbon monoxide mixture was introduced until the pressure reached 2 MPa and the reaction was stirred for 1 hour. After the reaction was completed, the mixture was cooled to room temperature, and the internal standard, isobutanol, was added to the reaction solution. Quantitative analysis using an Agilent gas chromatograph revealed an ethylene conversion of 95.6% and a methyl propionate selectivity of greater than 99.9%.

[0042] Table 1 Recycling of acid accelerator P-[VSpIm-TsOH]

[0043] Number of cycles 1 2 3 4 5 Ethylene conversion rate / % 94.4 94.2 93.5 94.8 92.5 Methyl propionate selectivity / % ＞99 ＞99 ＞99 ＞99 ＞99 Number of cycles 6 7 8 9 10 Ethylene conversion rate / % 94.9 94.5 93.9 93.2 93.1 Methyl propionate selectivity / % ＞99 ＞99 ＞99 ＞99 ＞99

[0044] As can be seen from Table 1, the promoting effect of the acid promoter P-[VSpIm-TsOH] did not decrease significantly after being recycled 10 times, indicating that this type of sulfonic acid-based acidic polymeric ionic liquid has good stability and can be recycled multiple times.

[0045] The raw materials for preparing the acid accelerator used in the present invention can all be commercially available raw materials.

[0046] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation of the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. An application of an acid promoter in the synthesis of methyl propionate from ethylene hydromethyl ester, characterized in that: It can promote the hydromethylation reaction of ethylene, carbon monoxide and methanol to synthesize methyl propionate. The acid promoter is a sulfonic acid polymeric ionic liquid with the structural formula: Wherein X- represents an organic acid anion, and n is the degree of polymerization of the acidic polymeric ionic liquid.

2. The use according to claim 1, characterized in that The acid promoter is a sulfonic acid-based acidic polymerized ionic liquid obtained by free radical polymerization of an ionic liquid monomer and a crosslinking agent and then acidification with an organic acid.

3. The use according to claim 1, characterized in that The preparation method of sulfonic acidic polymeric ionic liquid is as follows: Step 1: Preparation of acidic polymerizable ionic liquid monomers Dissolve 1,3-propane sultone and vinyl imidazole in acetone or tetrahydrofuran solvent, stir at 60-100°C for 12-72 hours, and after the reaction, wash the obtained white solid with acetone and ethanol for multiple times to obtain an acidic polymeric ionic liquid monomer; Step 2: Preparation of acidic polymeric ionic liquid precursor The acidic polymerized ionic liquid monomer obtained in step 1 and divinylbenzene are dissolved in a mixed solvent of ethanol and water, and after deoxygenating the solution, an initiator azobisisobutyronitrile (AIBN) is added to obtain a white solid by thermally initiating free radical polymerization. The white solid is washed three times with ethanol to obtain an acidic polymerized ionic liquid precursor; The molar ratio of the polymerized ionic liquid monomer to divinylbenzene is 1:0.1 to 100; The mass of the initiator AIBN accounts for 2 to 10 wt% of the total mass of the polymerized ionic liquid monomer and the crosslinking agent; The reaction temperature of the thermally initiated free radical polymerization is 70 to 110° C., and the reaction time is 24 to 48 hours; Step 3: Preparation of acidic polymeric ionic liquid The acidic polymeric ionic liquid precursor obtained in step 2 is placed in an organic acid solution, heated and stirred to obtain a white solid, and the white solid is vacuum-dried to obtain an acidic polymeric ionic liquid; The organic acid is one or more of the following: methanesulfonic acid, ethanesulfonic acid, trifluoromethanesulfonic acid, trifluoroacetic acid, p-toluenesulfonic acid, benzenesulfonic acid, p-chlorobenzenesulfonic acid, p-fluorobenzenesulfonic acid, p-iodobenzenesulfonic acid, and p-bromobenzenesulfonic acid; The molar concentration of the organic acid in the organic acid solution is 0.5 to 2.5 mol / L; The heating temperature is 70-110° C., and the reaction time is 24-48 hours.

4. The use according to claim 1, wherein The applicable temperature range of the acidic polymeric ionic liquid is 50 to 150°C.

5. The use according to claim 1, characterized in that The amount of the acid promoter used accounts for 1 to 10 wt% of the methanol mass.

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