Solid-phase catalyst for synthesizing 3-mercaptopropionic acid and preparation method of solid-phase catalyst

Abstract

The invention belongs to the technical field of catalysis, and particularly relates to a solid-phase catalyst for synthesizing 3-mercaptopropionic acid and a preparation method of the solid-phase catalyst. The preparation method comprises the following steps: firstly, adding 3-chloropropylmethyldimethoxysilane into a mixed solution of ethanol and water, uniformly stirring, standing and hydrolyzing to form a pre-hydrolysate, then adding gamma-Al2O3 into the pre-hydrolysate, stirring, evaporating to dryness, carrying out heat treatment and curing in a nitrogen atmosphere, then adding the treated gamma-Al2O3 and p-phenylenediamine into an anhydrous toluene solvent, heating and refluxing, and carrying out vacuum drying, so as to obtain the catalyst. And washing and drying to obtain the target solid catalyst. The catalyst provided by the invention can effectively synthesize 3-mercaptopropionic acid, the whole synthesis process takes acrylic acid and hydrogen sulfide as raw materials and is carried out in a tank reactor, the process is simple, the catalyst can be recycled, and the problems that a homogeneous catalyst cannot be recycled and the reaction activity of an existing solid catalyst is low are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalysis technology, in particular to a solid-phase catalyst for synthesizing 3-mercaptopropionic acid and a preparation method thereof. BACKGROUND

[0002] 3-mercaptopropionic acid is an important organic synthesis intermediate, which is widely used in organic synthesis in the fields of medicine, pesticide and material. It has the characteristics of strong acidity and chelating ability, and is suitable for cleaning and descaling in the processes of metal processing and oil field exploitation. In addition, 3-mercaptopropionic acid can also be used to synthesize high refractive index polymers, which have high refractive index, light weight, easy processing and low cost, and can replace glass in the field of resin lenses. In the field of concrete water reducing agent, 3-mercaptopropionic acid is used in the largest amount, which is used as a chain transfer agent in the synthesis of polycarboxylic acid water reducing agent, so as to control the molecular weight of polycarboxylic acid and improve the water reducing rate and slump retention performance of concrete.

[0003] However, the existing method for synthesizing 3-mercaptopropionic acid has some problems. In the homogeneous reaction, water is often used as the solvent, NaHS and Na2S are used as mercapto reagents, and the reaction is carried out under strong alkaline conditions with acrylic acid or acrylonitrile. The product of the reaction with acrylic acid is the sodium salt form of 3-mercaptopropionic acid, which needs to be acidified and then extracted to obtain 3-mercaptopropionic acid; the product of the reaction with acrylonitrile needs to be further treated. In addition, in the reaction for synthesizing 3-mercaptopropionic acid from acrylic acid and hydrogen sulfide, the existing solid-phase catalyst is not easy to regenerate, the selectivity of 3-mercaptopropionic acid is low, and the homogeneous catalyst is not easy to recycle and utilize.

[0004] Some researches have been made to solve the problem of preparing mercaptopropionic acid from acrylic acid and hydrogen sulfide. CN119874577A discloses a method for synthesizing 3-mercaptopropionic acid from acrylic acid and hydrogen sulfide using an acidic molecular sieve as a catalyst. The method has the characteristics of high catalytic activity, high selectivity, high mechanical strength and regeneration. However, the method still has the problems of complex catalyst preparation process and high cost. CN119874576A proposes a method for synthesizing 3-mercaptopropionic acid using a MgO-loaded molecular sieve as a catalyst. The method first mixes a calcined molecular sieve, magnesium acetate powder and distilled water to obtain an impregnated solid mixture, and then calcines the solid mixture to obtain a MgO-loaded molecular sieve catalyst. However, the activity and selectivity of the catalyst still need to be further improved.

[0005] Therefore, it is of great practical significance and application value to develop a new type of solid-phase catalyst and preparation process to improve the selectivity and yield of 3-mercaptopropionic acid and reduce the production cost. SUMMARY

[0006] The application aims to provide a preparation method of a solid phase catalyst and its application in a reaction for preparing mercaptopropionic acid from acrylic acid and hydrogen sulfide as raw materials.

[0007] The application adopts the following technical scheme: A solid phase catalyst for synthesizing 3-mercaptopropionic acid and a preparation method thereof, comprising the following steps: (1) adding silane into a mixed solution of ethanol and water with a volume ratio of 1-2:1, stirring uniformly, and then hydrolyzing for 0.5-2 h to form a pre-hydrolysis solution; (2) adding γ-Al2O3 into the pre-hydrolysis solution obtained in step (1), stirring and evaporating to dryness at 60-80 ℃, and then solidifying for 1-3 h in a nitrogen atmosphere at 100-120 ℃; (3) adding treated alumina and organic amine obtained in step (2) into ethanol as a solvent, and heating and stirring to reflux for 8-10 h at 80-110 ℃; (4) filtering the mixed solution obtained in step (3), washing with ethanol and pure water alternately, and drying at 60 ℃ to obtain the target solid phase catalyst.

[0008] Further, in step (1), the silane is one of 3-chloropropylmethyldimethoxysilane, chloromethyltrimethoxysilane and chloromethyl(dimethyl)methoxysilane.

[0009] Further, in step (3), the organic amine is one of ethanolamine, p-phenylenediamine, dimethylacetamide and n-butylamine.

[0010] In the mixed solution of ethanol and water, the methoxy group (-OCH3) at the end of the silane is hydrolyzed to generate a highly reactive silicon hydroxyl group (-Si-OH), and a large number of hydroxyl groups exist on the surface of γ-Al2O3, which undergoes a dehydration condensation reaction with the silicon hydroxyl group generated by hydrolysis to form a stable Si-O-Al covalent bond, so as to realize the firm loading of the silane on the surface of alumina. The silane selected in the application is a chlorine-containing silane, and the chlorine on the silane is easy to be replaced. After adding the organic amine, the amine group on the organic amine performs nucleophilic substitution on the chlorine on the silane to generate a secondary amine structure and release HCl, so as to graft the organic amine to the carrier to obtain an alumina-loaded solid phase catalyst.

[0011] For the above preparation method, the application further provides a solid phase catalyst prepared by the method.

[0012] The application provides a preparation method of a solid phase catalyst and its application in a reaction for preparing mercaptopropionic acid from acrylic acid and hydrogen sulfide as raw materials.

[0013] In a high-pressure kettle, solid-phase catalyst, acrylic acid and methanol are added, hydrogen sulfide gas is introduced to 0.7-1.0 MPa, heated to 30-50℃, and reacted for 3-5 h to obtain mercaptopropionic acid.

[0014] The present application has the advantages that: The present application successfully grafts the organic amine to the alumina by loading the silane on the alumina carrier and then using the amine group of the organic amine to nucleophilically substitute the chlorine on the silane, and the solid-phase catalyst with good stability is prepared, the problems of the existing homogeneous catalysts that are not easy to recycle and use are solved, and the problems of the existing heterogeneous catalysts that are not high in activity and easy to deactivate are solved, the service life of the catalyst is prolonged, and the production cost is reduced. The solid-phase catalyst prepared by the present application has excellent selectivity and reactivity, can realize the high-selectivity synthesis of 3-mercaptopropionic acid under low temperature and pressure conditions, greatly improves the purity and yield of the product, and meets the requirements of industrial large-scale production. The preparation process of the catalyst of the present application is simple, easy to operate, and easy to scale up, the acrylic acid-hydrogen sulfide production route adopted is green and environmentally friendly, the process is simple, the production cost is reduced, and the market competitiveness of the product is improved. DETAILED DESCRIPTION

[0015] The examples and comparative examples of the present application are described in detail below, which are intended to explain the present application and cannot be understood as a limitation of the present application.

[0016] Example 1: 30 mL of ethanol and 20 mL of pure water are measured and stirred to mix uniformly, 1.0 g of 3-chloropropylmethyldimethoxysilane is added, stirred at room temperature for 1 h, then placed for 0.5 h, then 5.0 g of γ-Al2O3 is added, stirred and evaporated at 60℃, then solidified at 100℃ for 2 h in a nitrogen atmosphere.

[0017] The solidified alumina carrier is added to 50 mL of ethanol, 0.6 g of p-phenylenediamine is added, and stirred and refluxed at 100℃ for 8 h in a nitrogen atmosphere, then washed and filtered with ethanol and pure water alternately, and dried at 60℃ to obtain catalyst ①. The structural general formula is as follows:

[0018] Performance test: 1.0 g of the prepared catalyst ①, 10 g of acrylic acid and 16 g of methanol are added to a 50 mL high-pressure kettle, hydrogen sulfide gas is introduced to 0.7 MPa, heated to 50℃, and reacted for 5 h, then 1.5 g of the reaction solution is taken, 0.1 g of benzoic acid is added as an internal standard, diluted with ethanol, and analyzed by liquid chromatography.

[0019] Example 2: Take 30 mL of ethanol and 20 mL of pure water, mix well, add 1.0 g of chloromethyl trimethoxysilane, stir at room temperature for 1 h, then add 5.0 g of γ-Al2O3, stir at 60°C until dry, then solidify at 100°C for 2 h in a nitrogen atmosphere.

[0020] Add the solidified alumina carrier to 50 mL of ethanol, add 0.6 g of p-phenylenediamine, stir at 100°C under a nitrogen atmosphere for 8 h, wash with ethanol and pure water alternately, filter, and dry at 60°C to obtain catalyst ②.

[0021] Performance test: same as Example 1.

[0022] Example 3: Take 30 mL of ethanol and 20 mL of pure water, mix well, add 1.0 g of chloromethyl trimethoxysilane, stir at room temperature for 1 h, then add 5.0 g of γ-Al2O3, stir at 60°C until dry, then solidify at 100°C for 2 h in a nitrogen atmosphere.

[0023] Add the solidified alumina carrier to 50 mL of ethanol, add 0.6 g of p-phenylenediamine, stir at 100°C under a nitrogen atmosphere for 8 h, wash with ethanol and pure water alternately, filter, and dry at 60°C to obtain catalyst ③.

[0024] Performance test: same as Example 1.

[0025] Comparative Example 1: This comparative example provides a method for synthesizing 3-mercapto propionic acid using only γ-Al2O3 as a catalyst, comprising the following steps: Performance test: same as Example 1.

[0026] Comparative Example 2: This comparative example provides a method for synthesizing 3-mercapto propionic acid using a 3-chloropropyl methyl dimethoxysilane catalyst supported by γ-Al2O3, comprising the following steps: Take 30 mL of ethanol and 20 mL of pure water, mix well, add 2.0 g of 3-chloropropyl methyl dimethoxysilane, stir at room temperature for 1 h, then add 5.0 g of γ-Al2O3, stir at 60°C until dry, then solidify at 100°C for 2 h in a nitrogen atmosphere, wash with ethanol and pure water alternately, filter, and dry at 60°C to obtain catalyst ④.

[0027] Performance test: same as Example 1.

[0028] Comparative Example 3: The comparative example provides a method for synthesizing 3-mercaptopropionic acid only with p-phenylenediamine catalyst, comprising the following steps: In a 50 mL autoclave, 1.0 g of p-phenylenediamine, 10 g of acrylic acid and 16 g of methanol were added, hydrogen sulfide gas was introduced to 0.7 MPa, heated to 50°C, and reacted for 5 h. After the reaction was completed, 1.5 g of the reaction solution was taken, 0.1 g of benzoic acid was added as an internal standard, and then diluted with ethanol for liquid chromatography analysis.

[0029] Comparative Example 4: The comparative example provides a method for synthesizing 3-mercaptopropionic acid using a γ-Al2O3 supported 3-aminopropyl triethoxysilane catalyst, comprising the following steps: 30 mL of ethanol and 20 mL of pure water were measured and stirred to mix uniformly, 2.0 g of 3-aminopropyl triethoxysilane was added, stirred at room temperature for 1 h, then placed for 0.5 h, then 5.0 g of γ-Al2O3 was added, stirred and evaporated at 60°C, then solidified at 100°C in a nitrogen atmosphere for 2 h, washed and filtered with ethanol and pure water alternately, and dried at 60°C to obtain catalyst ⑤.

[0030] Performance test: same as Example 1.

[0031] Comparative Example 5: The comparative example provides a method for synthesizing 3-mercaptopropionic acid using a γ-Al2O3 supported 3-aminopropyl triethoxysilane catalyst, comprising the following steps: 30 mL of ethanol and 20 mL of pure water were measured and stirred to mix uniformly, 2.0 g of 3-aminopropyl triethoxysilane was added, stirred at room temperature for 1 h, then placed for 0.5 h, then 5.0 g of γ-Al2O3 was added, stirred and evaporated at 60°C, then solidified at 100°C in a nitrogen atmosphere for 2 h.

[0032] The solidified alumina carrier was added to 50 mL of ethanol, 0.6 g of p-phenylenediamine was added, and stirred and refluxed at 100°C in a nitrogen atmosphere for 8 h. Then, it was washed and filtered with ethanol and pure water alternately, and dried at 60°C to obtain catalyst ⑥.

[0033] Performance test: same as Example 1.

[0034] Table 1 Performance test results of examples and comparative examples

[0035] Stability test: The catalyst used for stability test in the present application is catalyst ① prepared in Example 1, and the stability test comprises the following steps: In a 50 mL autoclave, 3.0 g of catalyst ①, 10 g of acrylic acid and 16 g of methanol were added, hydrogen sulfide gas was introduced to 0.7 MPa, heated to 50℃, and reacted for 5 h. After the reaction, 1.5 g of the reaction solution was taken, 0.1 g of benzoic acid was added as an internal standard, diluted with ethanol, and then analyzed by liquid chromatography. After centrifugation of the reaction solution, the solid catalyst was collected and put into the autoclave. Acrylic acid, ethyl acetate and hydrogen sulfide were added, and the reaction was repeated for 5 cycles. The stability test results are shown in Table 2.

[0036] Table 2 Stability test results

[0037] From the above examples and comparative examples, it can be seen that the catalyst used in the present application has high conversion rate and selectivity for the reaction of preparing 3-mercaptopropionic acid from acrylic acid and hydrogen sulfide. The catalytically active species is the amine group on p-phenylenediamine, which is grafted onto γ-Al2O3 to prepare a solid catalyst. In a heterogeneous reaction system, it is easier to recover and recycle the catalyst, and the catalyst activity does not decrease after 5 cycles. The problem of catalyst recovery and recycling in a homogeneous reaction system is solved. In addition, the catalyst preparation method is simple, the synthesis of 3-mercaptopropionic acid is carried out at low temperature and low pressure, the cost is low, and it is easier to industrialize.

[0038] The above only describes typical embodiments of the present application, and any improvements and modifications made according to the present application should be considered within the scope of the present application.

Claims

1. A method for preparing a solid-phase catalyst for the synthesis of 3-mercaptopropionic acid, characterized in that, Includes the following steps: (1) Add silane to a mixture of ethanol and water, stir well, and let stand to hydrolyze to form a pre-hydrolyzed solution; (2) Add γ-Al2O3 to the pre-hydrolysate obtained in step (1), stir and evaporate to dryness, then heat-treat and solidify under an inert atmosphere, and dehydrate and condense to obtain a solid with silane loaded on γ-Al2O3. (3) The solid obtained in step (2) is heated and refluxed with an organic amine in an organic solvent to obtain a mixture; (4) The mixture obtained in step (3) is filtered, washed and dried to obtain a solid catalyst.

2. The method for preparing a solid-phase catalyst for the synthesis of 3-mercaptopropionic acid according to claim 1, characterized in that, In step (1), the silane is selected from one of 3-chloropropylmethyldimethoxysilane, chloromethyltrimethoxysilane, and chloromethyl(dimethyl)methoxysilane.

3. The method for preparing a solid-phase catalyst for the synthesis of 3-mercaptopropionic acid according to claim 1, characterized in that, In step (1), the mass fraction of silane in the pre-hydrolyzed solution is 1-5%, and the volume ratio of ethanol to water is 1-2:

1.

4. The method for preparing a solid-phase catalyst for the synthesis of 3-mercaptopropionic acid according to claim 1, characterized in that, In step (2), the stirring temperature is 60-80℃, the high-temperature curing temperature is 100-120℃, and the inert atmosphere is a nitrogen atmosphere.

5. The method for preparing a solid-phase catalyst for the synthesis of 3-mercaptopropionic acid according to claim 1, characterized in that, In step (3), the organic amine is selected from one of ethanolamine, p-phenylenediamine, dimethylacetamide, and n-butylamine.

6. The method for preparing a solid-phase catalyst for the synthesis of 3-mercaptopropionic acid according to claim 1, characterized in that, The organic solvent in step (3) is ethanol, the reflux temperature is 80~110℃, and the reaction time is 8~10 hours.

7. The method for preparing a solid-phase catalyst for the synthesis of 3-mercaptopropionic acid according to claim 1, characterized in that, In step (4), after filtration, the product is washed alternately with ethanol and water, and the drying temperature is 60-70℃.

8. A solid-phase catalyst, characterized in that, The catalyst prepared by the method according to any one of claims 1-7 is a solid material formed by grafting an organic amine onto a silane-modified γ-Al2O3 support.

9. The application of the solid-phase catalyst as described in claim 8 in the catalytic reaction of acrylic acid with hydrogen sulfide to synthesize 3-mercaptopropionic acid.

10. The application according to claim 9, characterized in that, A solid catalyst, acrylic acid, and methanol are added to a high-pressure reactor, hydrogen sulfide gas is introduced to 0.7-1.0 MPa, and the mixture is heated to 30-50℃ and reacted for 3-5 h to obtain mercaptopropionic acid.

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