A method for synthesizing 3-mercaptopropionic acid

Abstract

This invention belongs to the technical field of thiol compound preparation, and particularly relates to a method for synthesizing 3-mercaptopropionic acid. The method includes the following steps: reacting acrylic acid gas and hydrogen sulfide gas under the action of an acidic catalyst, followed by post-treatment to obtain 3-mercaptopropionic acid. The acidic catalyst is a supported solid acid catalyst containing nickel, molybdenum, and cobalt active components. The support includes one or more of silicon oxide, alumina, magnesium oxide, molecular sieves, titanium oxide, zirconium oxide, and hydrotalcite. This invention selects specific catalysts and improves the reaction form and post-treatment process to achieve a reaction conversion rate >98.5%, selectivity ≥97%, and yield ≥95.74%, effectively reducing production costs and facilitating industrial application.

Description

Technical Field

[0001] This invention belongs to the technical field of thiol compound preparation, and mainly relates to a gas-phase synthesis process, specifically a method for synthesizing 3-mercaptopropionic acid. Technical Background

[0002] 3-Mercaptopropionic acid (3-MPA) is a compound containing thiol and carboxyl groups. It appears as a colorless or pale yellow liquid with a strong, pungent odor in air, indicating toxicity. It is highly soluble, miscible with most solvents, including water, ethanol, benzene, toluene, ether, and chlorinated hydrocarbons. Due to the strong reducing power of the thiol group, 3-Mercaptopropionic acid is very unstable and is easily oxidized to disulfides by oxides. Currently, 3-Mercaptopropionic acid is an important industrial raw material widely used in industrial descaling, cleaning, rust prevention, biochemical reagents, water-reducing agents, and optical materials.

[0003] According to literature reports, there are three main methods for synthesizing 3-mercaptopropionic acid: First, the acrylonitrile route, which uses acrylonitrile and sodium hydrosulfide to prepare the product. This method produces a relatively high-quality product, but the process is lengthy, complex, and generates a large amount of waste. Second, the acrylic acid route, which uses acrylic acid and thiourea to prepare the product. For example, CN102229550 involves mixing thiourea and hydrochloric acid, then adding acrylic acid dropwise while maintaining the temperature at 80℃~90℃ for 1~7 hours. Sodium hydroxide is then added for hydrolysis to produce sodium mercaptopropionate and urea. Finally, hydrochloric acid is added for acidification to obtain an aqueous solution of 3-mercaptopropionic acid. This method has a long synthesis route, generates a large amount of waste, and has high production costs. Third, the hydrogen sulfide route, which uses hydrogen sulfide and acrylic acid to prepare the product. For example, CN1185432 involves reacting hydrogen sulfide and acrylic acid in an alkaline catalyst and N,N-dimethylformamide solvent at a pressure of 24 bar. This method has high atom economy, but the highest reaction selectivity is about 85%, and the reaction solvent is difficult to separate effectively, resulting in high production costs.

[0004] To further improve the reaction selectivity of the hydrogen sulfide-acrylic acid process and reduce separation costs, as described in CN107501147, acrylic acid and hydrogen sulfide are reacted in a plasma reactor in the gas phase to prepare 3-mercaptopropionic acid. While this avoids the use of organic solvents and reduces separation costs, the high reactivity of the plasma reactor makes the reaction difficult to control, leading to increased byproducts and decreased yield. Therefore, while gas-phase reaction for 3-mercaptopropionic acid can reduce separation costs, further improvement in reaction selectivity is still needed. Summary of the Invention

[0005] To address the shortcomings of existing gas-phase processes, this invention provides a method for synthesizing 3-mercaptopropionic acid. This method selects a specific catalyst and improves the reaction form and post-processing to achieve a reaction conversion rate >98.5%, selectivity ≥97%, and yield ≥95.74%, effectively reducing production costs and facilitating industrial applications.

[0006] Through in-depth research, the inventors discovered that by using a specific catalyst, plasma reactor activation is unnecessary. Ordinary reactors, such as fixed-bed reactors, can be directly selected, allowing hydrogen sulfide and acrylic acid to react efficiently. Furthermore, rapid cooling of the reaction solution effectively reduces side reactions and improves reaction selectivity, thus realizing this invention. This invention uses acrylic acid and hydrogen sulfide as raw materials to synthesize 3-mercaptopropionic acid via a Michael addition reaction under the action of a Lewis acidic catalyst. The specific technical solution is as follows:

[0007] A method for synthesizing 3-mercaptopropionic acid involves reacting acrylic acid gas and hydrogen sulfide gas under the action of an acidic catalyst, followed by post-treatment to obtain 3-mercaptopropionic acid. The acidic catalyst is a supported solid acid catalyst containing active components of nickel, molybdenum, and cobalt. The support includes one or more of silica, alumina, magnesium oxide, molecular sieves, titanium dioxide, zirconium oxide, and hydrotalcite. Acrylic acid exhibits higher reactivity in the gas phase, and the Michael addition reaction is more easily carried out in the gas-gas state when acrylic acid is in contact with hydrogen sulfide in gaseous form. On the other hand, the Lewis acidic catalyst can activate the C=C double bond in acrylic acid, making the reaction more favorable for the forward reaction direction, thereby improving the conversion rate of the raw materials and the selectivity of the target product.

[0008] Preferably, the acid catalyst is loaded using conventional methods already available in the prior art. Generally, an aqueous solution of a precursor such as nickel, molybdenum, or cobalt, such as an aqueous solution of nickel nitrate, nickel acetate, or ammonium molybdate, is absorbed by the support in equal volume and then calcined. The calcination temperature can be selected as 400℃-600℃.

[0009] More preferably, the mass ratio of nickel, molybdenum, and cobalt active components to the support in the acidic solid catalyst is 1-3:20. When the loading of active components is low, the reaction activity is low and the reaction conversion rate is reduced; when the loading of active components is too high, the active components are prone to aggregation during the reaction, the reaction activity decreases rapidly, and the catalyst lifetime is short.

[0010] Preferably, the volume hourly space velocity (VHSV) of the reaction is 200 h⁻¹. -1 -300h -1 That is, the raw material volumetric flow rate (20℃, L·h) -1 Catalyst volume (L) = 40 L·h -1 -60L·h -10.2L. A lower reaction space velocity reduces production efficiency and increases production costs; a higher reaction space velocity reduces the conversion rate and selectivity of the reaction, which is not conducive to subsequent separation.

[0011] Preferably, crude 3-mercaptopropionic acid is purified by vacuum distillation to obtain refined 3-mercaptopropionic acid.

[0012] Preferably, the post-treatment is as follows: the liquid obtained after the reaction needs to be rapidly cooled to below 70°C, followed by gas-liquid separation. Hydrogen sulfide gas is absorbed with an alkaline aqueous solution, and the reaction liquid is subjected to vacuum distillation to obtain 3-mercaptopropionic acid. Because 3-mercaptopropionic acid is unstable at high temperatures and can undergo condensation and dehydration side reactions, rapidly cooling the reaction liquid to below 70°C can effectively avoid side reactions. More preferably, the cooling time needs to be <30 min, and even more preferably <15 min.

[0013] Preferably, acrylic acid gas is obtained by heating and vaporizing acrylic acid or by oxidizing propylene. The acrylic acid vaporization temperature can be selected from 160℃ to 180℃. To avoid polymerization side reactions of acrylic acid during the vaporization process, acrylic acid gas is further preferably prepared by propylene oxidation.

[0014] Preferably, the molar ratio of acrylic acid to hydrogen sulfide is 1:2 to 1:10, the reaction temperature is 200℃-260℃, the reaction pressure is 0.8MPa-3.0MPa, and the reaction time is 5-15min. If the amount of hydrogen sulfide is too small, the selectivity of the reaction decreases; however, if the amount of hydrogen sulfide is too large, it does not improve the reaction efficiency, but increases the cost of hydrogen sulfide separation and recovery. Lowering the reaction temperature reduces the reaction conversion rate, while further increasing the reaction temperature easily promotes the occurrence of sulfide side reactions. Since the reaction is a volume-reducing reaction, increasing the pressure is beneficial to improving the selectivity, but when the pressure is increased to above 3MPa, the selectivity does not increase significantly, while energy consumption costs increase substantially, leading to higher production costs.

[0015] Preferably, the catalyst needs to undergo pre-sulfurization treatment at a temperature of 60℃-180℃, using hydrogen sulfide or a mixture of hydrogen sulfide and hydrogen gas for pre-sulfurization. Using a mixture of hydrogen sulfide and hydrogen gas for pre-sulfurization can suppress side reactions such as oxidative desulfurization. More preferably, the volume ratio of hydrogen to the mixed gas can be selected as 2%-5%.

[0016] This invention provides a method for synthesizing 3-mercaptopropionic acid. This method selects a specific catalyst and improves the reaction mode and post-processing to achieve an improved reaction conversion rate of >98.5%, selectivity ≥97%, and yield ≥95.74%, effectively reducing production costs and facilitating industrial application. Attached Figure Description

[0017] Figure 1 This is the liquid phase spectrum of 3-mercaptopropionic acid obtained in Example 1 of the present invention. Detailed Implementation

[0018] To further illustrate the present invention, the following detailed description of a method for synthesizing 3-mercaptopropionic acid using a gas-phase reaction, in conjunction with embodiments, is provided by the present invention, but should not be construed as limiting the scope of protection of the present invention.

[0019] The following reaction conversion rates and selectivity were calculated by quantitative gas chromatography determination of the contents of acrylic acid, 3-mercaptopropionic acid and thiodipropionic acid, respectively.

[0020] The catalyst prepared below is a catalyst supported on MoO3 active component prepared by an equal-volume impregnation method. The preparation steps of the MoO3 / alumina catalyst are as follows: (The content of the active component described below refers to the content of the active component in the total catalyst).

[0021] ① 5% wt% MoO3 / alumina catalyst:

[0022] (1) Select a specific surface area of ​​180m² 2 Using γ-Al2O3 with a pore volume of 0.48 mL / g as a carrier, the material was crushed and sieved to obtain particles of 20-30 mesh.

[0023] (2) Determination of water absorption of the carrier: 10.0 parts were weighed from the sieved γ-Al2O3 particles and the saturated water absorption was measured to be 0.674 mL / g;

[0024] (3) Take 0.53 parts of (NH4)6Mo7O 24 Dissolved in 6.48 parts of deionized water until completely dissolved;

[0025] (4) While stirring, add the above solution dropwise to 10 parts of γ-Al2O3 to fully wet the carrier. Then let it stand overnight at room temperature;

[0026] (5) Dry the impregnated γ-Al2O3 at 110℃ for 24h;

[0027] (6) The dried γ-Al2O3 was calcined at 450℃ for 5h. After the calcination was completed, the temperature was lowered to room temperature to obtain 5%wt% MoO3 / alumina catalyst.

[0028] ②8wt% MoO3 / alumina catalyst:

[0029] (1) and (2) are the same as above;

[0030] (3) Take 0.88 parts of (NH4)6Mo7O 24 Dissolved in 6.29 parts of deionized water until completely dissolved;

[0031] (4) While stirring, add the above solution dropwise to 10 parts of γ-Al2O3 to fully wet the carrier with the impregnation solution, and then let it stand overnight at room temperature;

[0032] (5) Dry the impregnated γ-Al2O3 at 110℃ for 24h;

[0033] (6) The dried γ-Al2O3 was calcined at 450℃ for 5h. After the calcination was completed, the temperature was lowered to room temperature to obtain 8wt% MoO3 / alumina catalyst.

[0034] ③ 10wt% MoO3 / alumina catalyst:

[0035] (1) and (2) are the same as above;

[0036] (3) Take 1.11 parts of (NH4)6Mo7O 24 Dissolve in 6.15 parts of deionized water until completely dissolved;

[0037] (4) While stirring, add the above solution dropwise to 10 parts of γ-Al2O3 to fully wet the carrier with the impregnation solution, and then let it stand overnight at room temperature;

[0038] (5) Dry the impregnated γ-Al2O3 at 110℃ for 24h;

[0039] (6) The dried γ-Al2O3 was calcined at 450℃ for 5h. After the calcination was completed, the temperature was lowered to room temperature to obtain 10wt% MoO3 / alumina catalyst.

[0040] Other MoO3 / alumina catalysts with different contents can be prepared using the above method, and other existing technologies can also be used to obtain MoO3 / alumina catalysts with different contents.

[0041] ④ Preparation of 10wt% MoO3 / molecular sieve MCM-41 catalyst:

[0042] 1) Select a specific surface area ≥ 800 m² 2 / g, MCM-41 molecular sieve with a pore size of 2-5nm was used as the support;

[0043] 2) Take 1.11 parts of (NH4)6Mo7O 24 Dissolve in 6.15 parts of deionized water until completely dissolved;

[0044] 3) While stirring, add the above solution dropwise to 10 parts of MCM-41 to fully wet the carrier, and then let it stand overnight at room temperature;

[0045] 4) Dry the impregnated MCM-41 at 110℃ for 24 hours;

[0046] 5) The dried MCM-41 was calcined at 400℃ for 8 hours. After the calcination was completed, the temperature was lowered to room temperature to obtain a 10wt% MoO3 / molecular sieve MCM-41 catalyst.

[0047] ⑤ Preparation of 15wt% MoO3 / molecular sieve MCM-41 catalyst:

[0048] 1) Select a specific surface area ≥ 800 m² 2 / g, MCM-41 molecular sieve with a pore size of 2-5nm was used as the support;

[0049] 2) 1.76 parts of (NH4)6Mo7O 24 Dissolved in 5.89 parts of deionized water until completely dissolved;

[0050] 3) While stirring, add the above solution dropwise to 10 parts of MCM-41 to fully wet the carrier, and then let it stand overnight at room temperature;

[0051] 4) Dry the impregnated MCM-41 at 110℃ for 24 hours;

[0052] 5) The dried MCM-41 was calcined at 400℃ for 8 hours. After the calcination was completed, the temperature was lowered to room temperature to obtain a 15wt% MoO3 / molecular sieve MCM-41 catalyst.

[0053] The catalysts described below can be prepared using the methods described above, other methods in the prior art, or can be purchased directly from the market.

[0054] Example 1

[0055] A method for synthesizing 3-mercaptopropionic acid:

[0056] (1) 0.2 L of MoO3 / alumina catalyst with a loading of 8 wt% was packed into a fixed-bed reactor, and then the mixed gas space velocity was adjusted to 200 h⁻¹. -1 The reactor sulfidation temperature is 150℃ and the sulfidation time is 5h. The catalyst is sulfidated. The mixed gas is hydrogen sulfide and hydrogen, with hydrogen accounting for 5% of the volume of the mixed gas.

[0057] (2) Acrylic acid gas and hydrogen sulfide gas are introduced into a reactor containing a catalyst after sulfidation in a molar ratio of 1:6 to carry out an addition reaction. The reaction parameters are as follows: gas hourly space velocity is 280 h⁻¹. -1 The reactor pressure was 2.0 MPa, the reaction temperature was 250℃, and the reaction time was 10 min.

[0058] (3) The reaction solution obtained above was rapidly cooled to 60°C in 15 min, and then the reaction solution was subjected to gas-liquid separation. Hydrogen sulfide gas was absorbed by sodium hydroxide solution with a mass percentage of 37%. After further vacuum distillation, the reaction solution was used to obtain high-quality 3-mercaptopropionic acid with an acrylic acid conversion rate of 99.0%, a 3-mercaptopropionic acid selectivity of 97.0%, and a product yield of 96.03%.

[0059] Example 2

[0060] A method for synthesizing 3-mercaptopropionic acid:

[0061] (1) 0.2 L of MoO3 / molecular sieve MCM-41 catalyst with a loading of 10 wt% was packed into a fixed-bed reactor, and then the mixed gas space velocity was adjusted to 240 h⁻¹. -1 The reactor sulfidation temperature is 150℃ and the sulfidation time is 5h. The catalyst is sulfidated. The mixed gas is hydrogen sulfide and hydrogen, with hydrogen accounting for 5% of the volume of the mixed gas.

[0062] (2) Acrylic acid gas and hydrogen sulfide gas are introduced into a reactor containing a catalyst after sulfidation at a molar ratio of 1:10 to carry out an addition reaction. The reaction parameters are: gas hourly space velocity of reaction is 300 h⁻¹. -1 The reactor pressure was 2.5 MPa, the reaction temperature was 250℃, and the reaction time was 8 min.

[0063] (3) The reaction solution obtained above was rapidly cooled to 60°C in 15 min, and then the reaction solution was subjected to gas-liquid separation. The hydrogen sulfide gas was absorbed by a 37% sodium hydroxide solution. After further vacuum distillation, the reaction solution was purified to obtain 3-mercaptopropionic acid. The acrylic acid conversion rate was 100%, the 3-mercaptopropionic acid selectivity was 98.2%, and the product yield was 98.2%.

[0064] Example 3

[0065] A method for synthesizing 3-mercaptopropionic acid:

[0066] (1) 0.2 L of MoO3 / alumina catalyst with a loading of 8 wt% was packed into a fixed-bed reactor, and then the space velocity of the mixed gas was adjusted to 200 h⁻¹. -1 The reactor sulfidation temperature is 180℃ and the sulfidation time is 5h. The catalyst is sulfidated. The mixed gas is hydrogen sulfide and hydrogen, with hydrogen accounting for 5% of the volume of the mixed gas.

[0067] (2) Acrylic acid gas and hydrogen sulfide gas are introduced into a reactor containing a catalyst after sulfidation at a molar ratio of 1:10 to carry out an addition reaction. The reaction parameters are as follows: gas hourly space velocity is 280 h⁻¹. -1The reactor pressure was 2.0 MPa, the reaction temperature was 250℃, and the reaction time was 8 min.

[0068] (3) The reaction solution obtained above was rapidly cooled to 60°C in 10 min, and then the reaction solution was subjected to gas-liquid separation. The hydrogen sulfide gas was absorbed by a 37% sodium hydroxide solution. After further vacuum distillation, the reaction solution was purified to obtain 3-mercaptopropionic acid. The acrylic acid conversion rate was 100%, the 3-mercaptopropionic acid selectivity was 98.8%, and the product yield was 98.8%.

[0069] Example 4

[0070] A method for synthesizing 3-mercaptopropionic acid:

[0071] (1) 0.2 L of a 5 wt% MoO3 / alumina catalyst was loaded into a fixed-bed reactor, and then the space velocity of the mixed gas was adjusted to 220 h⁻¹. -1 The reactor sulfidation temperature is 120℃ and the sulfidation time is 5h. The catalyst is pre-sulfided. The mixed gas is hydrogen sulfide and hydrogen, with hydrogen accounting for 5% of the volume of the mixed gas.

[0072] (2) Acrylic acid gas and hydrogen sulfide gas are introduced into a reactor containing a catalyst after sulfidation in a molar ratio of 1:6 to carry out an addition reaction. The reaction parameters are as follows: gas hourly space velocity is 280 h⁻¹. -1 The reactor pressure was 2.0 MPa, the reaction temperature was 220℃, and the reaction time was 8 min.

[0073] (3) The reaction solution obtained above was rapidly cooled to 60°C in 10 min, and then the reaction solution was subjected to gas-liquid separation. The hydrogen sulfide gas was absorbed by a 37% sodium hydroxide solution. After further vacuum distillation, the reaction solution was purified to obtain 3-mercaptopropionic acid. The acrylic acid conversion rate was 99.2%, the 3-mercaptopropionic acid selectivity was 97.0%, and the product yield was 96.22%.

[0074] Example 5

[0075] A method for synthesizing 3-mercaptopropionic acid:

[0076] (1) 0.2 L of a 10 wt% MoO3 / alumina catalyst was loaded into a fixed-bed reactor, and then the space velocity of the mixed gas was adjusted to 220 h⁻¹. -1 The reactor sulfidation temperature is 120℃ and the sulfidation time is 5h. The catalyst is sulfidated. The mixed gas is hydrogen sulfide and hydrogen, with hydrogen accounting for 5% of the volume of the mixed gas.

[0077] (2) Acrylic acid gas and hydrogen sulfide gas are introduced into a reactor containing a catalyst after sulfidation at a molar ratio of 1:10 to carry out an addition reaction. The reaction parameters are: gas hourly space velocity of reaction is 300 h⁻¹. -1 The reactor pressure was 2.0 MPa, the reaction temperature was 220℃, and the reaction time was 8 min.

[0078] (3) The reaction solution obtained above was rapidly cooled to 60°C in 10 min, and then the reaction solution was subjected to gas-liquid separation. The hydrogen sulfide gas was absorbed by a 37% sodium hydroxide solution. After further vacuum distillation, the reaction solution was purified to obtain 3-mercaptopropionic acid. The acrylic acid conversion rate was 98.5%, the 3-mercaptopropionic acid selectivity was 97.2%, and the product yield was 95.74%.

[0079] Example 6

[0080] A method for synthesizing 3-mercaptopropionic acid:

[0081] (1) 0.2 L of MoO3 / molecular sieve MCM-41 catalyst with a loading of 15 wt% was packed into a fixed-bed reactor, and then the space velocity of the mixed gas was adjusted to 240 h⁻¹. -1 The reactor sulfidation temperature is 150℃ and the sulfidation time is 5h. The catalyst is sulfidated. The mixed gas is hydrogen sulfide and hydrogen, with hydrogen accounting for 5% of the volume of the mixed gas.

[0082] (2) Acrylic acid gas and hydrogen sulfide gas are introduced into a reactor containing a catalyst after sulfidation at a molar ratio of 1:10 to carry out an addition reaction. The reaction parameters are as follows: gas hourly space velocity (GHSV) of 300 h⁻¹. -1 The reactor pressure was 2.5 MPa, the reaction temperature was 250℃, and the reaction time was 8 min.

[0083] (3) The reaction solution obtained above was rapidly cooled to 60°C in 15 min, and then the reaction solution was subjected to gas-liquid separation. After the separation was completed, crude 3-mercaptopropionic acid was obtained. Finally, the crude product was further purified by vacuum distillation to obtain refined 3-mercaptopropionic acid. The acrylic acid conversion rate was 99.8%, the 3-mercaptopropionic acid selectivity was 98.6%, and the product yield was 98.40%.

[0084] Comparative Example 1

[0085] A method for synthesizing 3-mercaptopropionic acid:

[0086] (1) 0.2 L of a 4 wt% magnesium oxide / silica catalyst (the 4 wt% magnesium oxide / silica catalyst disclosed in Example 2 of CN2017108487599) was loaded into a fixed-bed reactor, and then the space velocity of the mixed gas was adjusted to 200 h⁻¹. -1The reactor sulfidation temperature is 150℃ and the sulfidation time is 5h. The catalyst is sulfidated. The mixed gas is hydrogen sulfide and hydrogen, with hydrogen accounting for 5% of the volume of the mixed gas.

[0087] (2) Acrylic acid gas and hydrogen sulfide gas are introduced into a reactor containing a catalyst after sulfidation in a molar ratio of 1:6 to carry out an addition reaction. The reaction parameters are: gas hourly space velocity of reaction is 280 h⁻¹. -1 The reactor pressure was 2.0 MPa, the reaction temperature was 250℃, and the reaction time was 10 min.

[0088] (3) The reaction solution obtained above was rapidly cooled to 60°C in 15 min, and then the reaction solution was subjected to gas-liquid separation. The hydrogen sulfide gas was absorbed by a 37% sodium hydroxide solution. After further vacuum distillation, the reaction solution was purified to obtain 3-mercaptopropionic acid. The acrylic acid conversion rate was 84.7%, the 3-mercaptopropionic acid selectivity was 85.0%, and the product yield was 72.0%.

[0089] Comparative Example 2

[0090] A method for synthesizing 3-mercaptopropionic acid:

[0091] (1) 0.2 L of MoO3 / alumina catalyst with a loading of 8 wt% was packed into a fixed-bed reactor, and then the space velocity of the mixed gas was adjusted to 200 h⁻¹. -1 The reactor sulfidation temperature is 180℃ and the sulfidation time is 5h. The catalyst is sulfidated. The mixed gas is hydrogen sulfide and hydrogen, with hydrogen accounting for 5% of the volume of the mixed gas.

[0092] (2) Acrylic acid gas and hydrogen sulfide gas are introduced into a reactor containing a catalyst after sulfidation at a molar ratio of 1:10 to carry out an addition reaction. The reaction parameters are as follows: gas hourly space velocity is 280 h⁻¹. -1 The reactor pressure was 2.0 MPa, the reaction temperature was 250℃, and the reaction time was 8 min.

[0093] (3) The reaction solution obtained above was cooled to 60°C for 60 min, and then the reaction solution was subjected to gas-liquid separation. The hydrogen sulfide gas was absorbed by a 37% sodium hydroxide solution. After further vacuum distillation, the reaction solution was purified to obtain 3-mercaptopropionic acid. The acrylic acid conversion rate was 100%, the 3-mercaptopropionic acid selectivity was 78.5%, and the product yield was 78.5%.

[0094] Comparative Example 1, using a different catalyst compared to the Examples, showed significantly lower conversion rates, selectivity, and product yields of acrylic acid compared to the Examples. Comparative Example 2, compared to the Examples, had increased cooling time, leading to more side reactions, reduced selectivity, and lower product yield. Through the above examples and comparative examples, it was found that the acidic supported catalyst selected in this invention has high reactivity. Combined with specific post-treatment processes, in a fixed-bed reactor, it achieves a conversion rate >98.5%, selectivity ≥97%, and yield ≥95.74%, effectively reducing production costs and facilitating industrial application.

[0095] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for synthesizing 3-mercaptopropionic acid, characterized in that: Acrylic acid gas and hydrogen sulfide gas react under the action of an acidic catalyst, and 3-mercaptopropionic acid is obtained after post-treatment; the acidic catalyst is a supported solid acid catalyst containing molybdenum active components, and the support includes one or more of silicon oxide, alumina, magnesium oxide, molecular sieve, titanium oxide, zirconium oxide, and hydrotalcite.

2. The method for synthesizing 3-mercaptopropionic acid according to claim 1, characterized in that: The volume hourly space velocity (VHSV) of the reaction is 200 h⁻¹. -1 -300h -1 .

3. The method for synthesizing 3-mercaptopropionic acid according to claim 1, characterized in that: The mass ratio of molybdenum active component to support in the acidic solid catalyst is 1-3:

20.

4. The method for synthesizing 3-mercaptopropionic acid according to claim 1, characterized in that: The post-processing is as follows: the liquid obtained after the reaction needs to be rapidly cooled to below 70°C, and then gas-liquid separation is performed. The reaction liquid is then distilled under reduced pressure to obtain 3-mercaptopropionic acid.

5. The method for synthesizing 3-mercaptopropionic acid according to claim 4, characterized in that: The cooling time should be less than 30 minutes.

6. The method for synthesizing 3-mercaptopropionic acid according to claim 1, characterized in that, The molar ratio of acrylic acid to hydrogen sulfide is 1:2 to 1:

10.

7. The method for synthesizing 3-mercaptopropionic acid according to claim 1, characterized in that: The reaction temperature is 200℃-260℃, the reaction pressure is 0.8MPa-3.0MPa, and the reaction time is 5-15min.

8. The method for synthesizing 3-mercaptopropionic acid according to claim 1, characterized in that: Acrylic acid gas is obtained by heating and vaporizing acrylic acid or by oxidizing propylene.

9. The method for synthesizing 3-mercaptopropionic acid according to claim 1, characterized in that: The acidic catalyst is pre-sulfurized at a temperature of 60℃-180℃.

10. The method for synthesizing 3-mercaptopropionic acid according to claim 9, characterized in that: Pre-sulfurization is performed using hydrogen sulfide or a mixture of hydrogen sulfide and hydrogen.

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