A method for removing off-flavors from thiazole

Abstract

The application discloses a method for removing off-flavor of thiozole. The method comprises the following steps: (1) mixing crude thiozole to be treated with an oily solvent and standing; if the mixture is stratified, transferring the oily solvent layer to a new container; if the mixture is not stratified, directly performing subsequent operations; (2) performing vacuum distillation on the product of step (1) to remove the solvent and obtaining a paste; (3) adding a lower alcohol to the paste and heating to dissolve; (4) performing vacuum distillation on the solution of step (3) to remove the solvent; and (5) performing vacuum distillation on the product of step (4) again to distill thiozole products. The method removes off-flavor by-products in the crude thiozole through extraction with an oily solvent, removes part of impurities through dissolution and distillation with a lower alcohol, distills thiozole at last, separates high-boiling-point residue impurities, removes off-flavor, retains the characteristic odor of thiozole, makes the prepared thiozole smell like beef and have nutty aroma, and has no off-flavor, and thus meets the industry standard.

Description

Technical Field

[0001] This application relates to the field of thiothiazole preparation technology, and in particular to a method for removing off-flavors from thiothiazole. Background Technology

[0002] Thiazole, chemical name: 4-methyl-5-(β-hydroxyethyl)thiazole, is a widely used food flavoring with a unique aroma. It is also the basic structural ring of vitamin B1 and an important intermediate in the synthesis of vitamin B1, and has wide applications in drug synthesis.

[0003] The industry standard for thiothiazole as a food additive requires an aroma similar to beef or nuts. However, the chemical synthesis process of thiothiazole introduces various other impurities, resulting in off-flavors that fail to meet industry standards and lead to low-quality products.

[0004] Therefore, how to remove the off-flavors from the chemically synthesized thiothiazole remains a key research focus and challenge in this field. Summary of the Invention

[0005] The purpose of this application is to provide a novel method for removing off-flavors using thiothiazole.

[0006] The following technical solution is adopted in this application:

[0007] One aspect of this application discloses a method for removing off-flavors with thiothiazole, comprising the following steps:

[0008] (1) Mix the crude thiothiazole product to be treated with an oily solvent evenly and let it stand. If stratification occurs, transfer the oily solvent layer to a new container. If no stratification occurs, proceed directly to the next step.

[0009] (2) The product from step (1) is subjected to vacuum distillation to separate and remove the solvent, and an extract-like product is obtained.

[0010] (3) Add a lower alcohol to the extract and heat until the extract is completely dissolved;

[0011] (4) The solution from step (3) is subjected to vacuum distillation to separate and remove the solvent;

[0012] (5) The product from step (4) is subjected to vacuum distillation again to distill off thiothiazole, thus obtaining the thiothiazole product.

[0013] It should be noted that the method for removing the off-flavor of thiothiazole in this application first uses an oily solvent to extract and remove trace off-flavor byproducts from the crude thiothiazole product. Then, some impurities are removed by dissolving in a lower alcohol and distilling. Finally, some high-boiling-point waste is removed by distilling off the thiothiazole, further purifying the product and achieving the effect of removing off-flavors while retaining the characteristic odor of thiothiazole. The thiothiazole product obtained by this method meets industry standards. In one implementation of this application, the purity detected by gas chromatography is above 99.7%, with a maximum purity of 99.95%, and the product yield is above 89%, with a maximum yield of 90.23%.

[0014] Preferably, the oily solvent is one or more of aromatic hydrocarbons and organic esters.

[0015] Preferably, the oily solvent is one or more of toluene, ethylbenzene, o-xylene, p-xylene, m-xylene, ethyl acetate, propyl acetate, and isopropyl acetate.

[0016] Preferably, the oily solvent is toluene, ethyl acetate, ethylbenzene or propyl acetate.

[0017] It should be noted that the selection of the oily solvent in this application needs to consider at least two factors. First, the odor characteristics of the oily solvent itself should be harmonious with the odor of thiothiazole to avoid the odor of the oily solvent affecting the odor of thiothiazole. Second, it needs to be able to achieve evaporation and separation at a low temperature, that is, at this low temperature, the oily solvent can evaporate while the thiothiazole will not evaporate, for example, the temperature does not exceed 90°C. This is because the research in this application found that heating at higher temperatures will reduce the product quality of thiothiazole. Therefore, an oily solvent with an evaporation temperature not exceeding 90°C is preferred, that is, the oily solvent is one or more of aromatic hydrocarbons and organic esters with an evaporation temperature not exceeding 90°C.

[0018] Preferably, the weight ratio of the oily solvent to the crude thiothiazole is 3 to 8:1.

[0019] It should be noted that the amount of oily solvent used depends mainly on the impurity content in the crude thiothiazole. In principle, the more impurities there are, the more oily solvent is needed. Generally speaking, using 3 to 8 times the weight of crude thiothiazole in oily solvent can meet the usage requirements.

[0020] Preferably, in step (2), the temperature of vacuum distillation does not exceed 90°C, and the vacuum degree of vacuum distillation is -0.1 to -0.09 MPa.

[0021] Preferably, the temperature for vacuum distillation is 60–85°C.

[0022] It should be noted that the temperature for recovering the oily solvent depends first on the boiling point of the oily solvent at that pressure, and secondly, as this application found in experiments, prolonged or high-temperature heating of thiothiazole will degrade the product quality. Therefore, it is preferable that the temperature for evaporating and separating the oily solvent does not exceed 90°C, and preferably vacuum distillation is carried out at 60–85°C, which can effectively evaporate and separate the oily solvent while minimizing the impact on the quality of thiothiazole.

[0023] Preferably, the lower alcohol is a monohydric alcohol with less than 5 carbon atoms.

[0024] Preferably, the lower alcohol is one or more of ethanol, n-propanol, n-butanol and isobutanol.

[0025] Preferably, the amount of lower alcohol used is 2 to 6 times the weight of crude thiothiazole.

[0026] Preferably, in step (3), the temperature at which the paste-like product is heated to dissolve is 40–80°C.

[0027] Preferably, in step (4), the temperature of vacuum distillation is 30 to 100°C, and the vacuum degree of vacuum distillation is -0.1 to -0.09 MPa.

[0028] Preferably, the temperature for vacuum distillation is 50–90°C.

[0029] Preferably, in step (5), the temperature of vacuum distillation is 110-125°C and the pressure of vacuum distillation is 230-260 Pa.

[0030] It should be noted that the vacuum distillation in step (5) is mainly for distilling out thiothiazole, leaving some high-boiling-point by-products in the vacuum distillation apparatus. This study found that vacuum distillation at a temperature of 110–125°C and a pressure of 230–260 Pa can quickly and efficiently separate thiothiazole, thus further purifying it. Understandably, the temperature of the second vacuum distillation should not be too high, preferably not exceeding 125°C; otherwise, it will affect the product quality of thiothiazole and distill out other impurities, resulting in poor purification. Furthermore, the temperature of the second vacuum distillation should not be too low either; too low a temperature will prevent effective distillation of thiothiazole or prolong the distillation separation time, also affecting the product quality.

[0031] Another aspect of this application discloses the method for obtaining thiothiazole.

[0032] It should be noted that the thiothiazole of this application has a good characteristic odor. By visual inspection and smelling method, the finished thiothiazole of this application is a colorless to pale yellow oily liquid with an odor similar to beef and a nutty aroma, and has no off-flavors, which meets the industry standard. In one implementation of this application, the purity detected by gas phase is above 99.7%, and the highest purity can reach 99.95%.

[0033] The beneficial effects of this application are as follows:

[0034] The method for removing off-flavors from thiothiazole in this application involves extracting trace amounts of off-flavor byproducts from crude thiothiazole using an oily solvent. Further impurities are removed by dissolving in a lower alcohol, followed by distillation to remove some high-boiling-point waste impurities. Finally, the thiothiazole is distilled off, separating some high-boiling-point waste impurities for further purification. This method achieves the effect of removing off-flavors while retaining the characteristic odor of thiothiazole. The thiothiazole obtained by this method has a beef-like odor with a nutty aroma and no off-flavors, meeting industry standards. Detailed Implementation

[0035] The present application will now be described in detail with reference to specific embodiments. These embodiments are for illustrative purposes only and should not be construed as limiting the scope of the application. Unless otherwise specified, the materials used in the following experiments were all conventionally purchased.

[0036] Example 1

[0037] In this example, toluene, an oily solvent, was used to remove the off-odor from crude thiothiazole. The crude thiothiazole was brownish-red in color, had a medicinal odor with a slightly pungent smell, and a purity of 93.2%. The method for removing the off-odor from thiothiazole in this example included the following steps:

[0038] (1) Weigh 120.05g of crude thiothiazole, add 380.01g of toluene, turn on the stirrer to mix evenly, and let the mixture stand for 0.5-2h. In this example, the liquid surface separates after standing for 0.5h.

[0039] (2) Transfer the solvent layer to a pressure reducing distillation apparatus, adjust the vacuum degree to -0.1 to -0.09 MPa, for example -0.09 MPa, control the distillation temperature to not exceed 85°C, perform the first pressure reducing distillation, collect the toluene fraction, remove the solvent, and obtain the extract-like product.

[0040] (3) Cool the paste to room temperature, add 249.55g of ethanol solution, and heat to 50°C to completely dissolve the paste.

[0041] (4) Perform a second vacuum distillation on the solution from step (3) in a distillation apparatus, adjust the vacuum degree to -0.1 to -0.09 MPa, and collect the ethanol fraction at 55 to 70°C, i.e., separate and remove the ethanol solvent; wherein, the higher the vacuum degree of vacuum distillation, the lower the collection temperature can be, and conversely, if the collection temperature is too high, the vacuum degree requirement can be appropriately reduced; for example, collect the ethanol fraction at 55°C at -0.1 MPa, or collect the ethanol fraction at 70°C at -0.09 MPa.

[0042] (5) For the product of step (4), switch to a high vacuum device and perform a third vacuum distillation at 230-260 Pa and 110-125 °C, for example, 260 Pa and 110 °C. Collect the thiothiazole fraction and distill until no fraction flows out. Stop distillation and leave a small amount of residue in the reactor. The thiothiazole obtained by distillation is the thiothiazole product in this example.

[0043] The thiothiazole product in this case was tested by visual inspection and odor testing. The results showed that the thiothiazole product in this case was a colorless or pale yellow oily liquid with an odor similar to beef and a nutty aroma.

[0044] Gas chromatography analysis of the thiothiazole product in this example showed that the purity of the thiothiazole product was 99.75%, and the yield was 89.23%. Furthermore, a comparison of the gas chromatography results of the crude and finished thiothiazole products revealed that the finished product contained almost no other impurities, further validating the effectiveness of impurity removal.

[0045] Example 2

[0046] This example uses the oily solvent ethyl acetate to remove off-odors from crude thiothiazole. The crude thiothiazole is brown to dark brown in color, has a medicinal odor with a slightly pungent smell, and a purity of 92.9%. The method for removing off-odors from thiothiazole in this example includes the following steps:

[0047] (1) Weigh 120.12g of crude thiothiazole, add 365.01g of ethyl acetate, turn on the stirrer to mix evenly, and obtain a mixture. After standing, no obvious interface appeared in the system.

[0048] (2) Transfer all the mixture to a pressure reducing distillation apparatus, adjust the vacuum degree to -0.1 to -0.09 MPa, for example -0.1 MPa, control the distillation temperature to not exceed 68°C, carry out the first pressure reducing distillation, collect the ethyl acetate fraction, continue heating and distillation until a paste is formed at the bottom of the reactor.

[0049] (3) Cool the paste to room temperature, add 245.01g of ethanol solution, and heat to 52℃ to completely dissolve the paste.

[0050] (4) Perform a second vacuum distillation on the solution from step (3) in a distillation apparatus, adjust the vacuum degree to -0.1 to -0.09 MPa, and collect the ethanol fraction at 55 to 70°C, i.e., separate and remove the ethanol solvent; wherein, the higher the vacuum degree of vacuum distillation, the lower the collection temperature can be, and conversely, if the collection temperature is too high, the vacuum degree requirement can be appropriately reduced; for example, collect the ethanol fraction at 55°C at -0.1 MPa, or collect the ethanol fraction at 70°C at -0.09 MPa.

[0051] (5) For the product of step (4), switch to a high vacuum device and perform a third vacuum distillation at 230-260 Pa and 110-125 °C, for example, 230 Pa and 125 °C. Collect the thiothiazole fraction and distill until no fraction flows out. Stop distillation and leave a small amount of residue in the reactor. The thiothiazole obtained by distillation is the thiothiazole product in this example.

[0052] The thiothiazole product in this example was tested visually and by smell. The results showed that the thiothiazole product was a colorless to pale yellow oily liquid with a beef-like odor and a nutty aroma. Furthermore, due to the fruity aroma of ethyl acetate, the thiothiazole product had a richer and fuller aroma.

[0053] Gas chromatography analysis of the thiothiazole product in this example showed that the purity of the thiothiazole product was 99.89%, and the yield was 90.23%. A comparison of the gas chromatography results of the crude and finished thiothiazole products revealed that the finished product contained almost no other impurities.

[0054] Example 3

[0055] This example uses the oily solvent ethylbenzene to remove the off-odor from crude thiothiazole. The crude thiothiazole is brown to dark brown in color, has a medicinal odor with a slightly pungent smell, and a purity of 93.1%. The method for removing the off-odor from thiothiazole in this example includes the following steps:

[0056] (1) Weigh 120.08g of crude thiothiazole, add 410.10g of ethylbenzene, turn on the stirrer and mix evenly to obtain a mixture. Let it stand for 0.5-2h. In this example, the liquid surface will separate after standing for 0.5h.

[0057] (2) Transfer the solvent layer to the pressure reducing distillation apparatus, adjust the vacuum degree to -0.1 to -0.09 MPa, for example -0.09 MPa, control the distillation temperature to not exceed 90°C, carry out the first pressure reducing distillation, collect the ethylbenzene fraction, continue heating and distillation until a paste is formed at the bottom of the reactor.

[0058] (3) Cool the paste to room temperature, add 300.05g of n-propanol solution, and heat to 60℃ to completely dissolve the paste.

[0059] (4) Perform a second vacuum distillation on the solution from step (3) in a distillation apparatus, adjust the vacuum degree to -0.1 to -0.09 MPa, and collect the n-propanol fraction at 75 to 90°C, that is, separate and remove the n-propanol solvent; wherein, the higher the vacuum degree of vacuum distillation, the lower the collection temperature can be, and conversely, if the collection temperature is too high, the vacuum degree requirement can be appropriately reduced; for example, collect the n-propanol fraction at 75°C at -0.1 MPa, or collect the n-propanol fraction at 90°C at -0.09 MPa.

[0060] (5) For the product of step (4), switch to a high vacuum device and perform a third vacuum distillation at 230-260 Pa and 110-125 °C, for example 240 Pa and 120 °C. Collect the thiothiazole fraction and distill until no fraction flows out. Stop distillation and leave a small amount of residue in the reactor. The thiothiazole obtained by distillation is the thiothiazole product in this example.

[0061] The thiothiazole product in this case was tested by visual inspection and odor testing. The results showed that the thiothiazole product in this case was a colorless to pale yellow oily liquid with an odor similar to beef and a nutty aroma.

[0062] Gas chromatography analysis of the thiothiazole product in this example showed that the purity of the thiothiazole product was 99.95%, and the yield was 90.05%. Comparison of the gas chromatography analysis results of the crude and finished thiothiazole products revealed that the finished product contained almost no other impurities.

[0063] Example 4

[0064] In this example, propyl acetate, an oily solvent, was used to remove off-odors from crude thiothiazole. The crude thiothiazole was brown to dark brown in color, had a medicinal odor with a slightly pungent smell, and a purity of 93.5%. The method for removing off-odors from thiothiazole in this example included the following steps:

[0065] (1) Weigh 120.01g of crude thiothiazole, add 403.10g of propyl acetate, turn on the stirrer and mix evenly to obtain the mixture.

[0066] (2) Transfer all the mixture to the pressure reducing distillation apparatus, adjust the vacuum degree to -0.1 to -0.09 MPa, for example -0.09 MPa, control the distillation temperature to not exceed 80°C, carry out the first pressure reducing distillation, collect the propyl acetate fraction, continue heating and distilling until a paste is formed at the bottom of the reactor.

[0067] (3) Cool the paste to room temperature, add 400.05g of n-butanol solution, and heat to 60°C to completely dissolve the paste.

[0068] (4) Perform a second vacuum distillation on the solution from step (3) in a distillation apparatus, adjust the vacuum to -0.1 to -0.09 MPa, and collect the n-butanol fraction at 70 to 80°C, i.e., separate and remove the n-butanol solvent; specifically, for example, collect the n-butanol fraction at 70°C at -0.1 MPa, or collect the n-butanol fraction at 80°C at -0.09 MPa.

[0069] (5) For the product of step (4), switch to a high vacuum device and perform a second vacuum distillation at 230-260 Pa and 110-125 °C, for example 250 Pa and 115 °C, to collect the thiothiazole fraction. Distill until no fraction flows out, then stop distillation. A small amount of residue remains in the reactor. The thiothiazole obtained by distillation is the thiothiazole product in this example.

[0070] The thiothiazole product in this case was tested by visual inspection and odor testing. The results showed that the thiothiazole product in this case was a colorless to pale yellow oily liquid with an odor similar to beef and a nutty aroma.

[0071] Gas chromatography analysis of the thiothiazole product in this example showed that the purity of the thiothiazole product was 99.85%, and the yield was 89.23%. A comparison of the gas chromatography results of the crude and finished thiothiazole products revealed that the finished product contained almost no other impurities.

[0072] The above description, in conjunction with specific embodiments, provides a detailed explanation of this application and should not be construed as limiting the implementation of this application to these descriptions. For those skilled in the art, several simple deductions or substitutions can be made without departing from the basic inventive concept of this application.

Claims

1. A method for removing off-flavors with thiothiazole, characterized in that: Includes the following steps, (1) Mix the crude thiothiazole product to be treated with an oily solvent evenly and let it stand; if stratification occurs, transfer the oily solvent layer to a new container; if no stratification occurs, proceed directly to the next operation; the oily solvent is one or more of toluene, ethylbenzene, o-xylene, p-xylene, m-xylene, ethyl acetate, propyl acetate and isopropyl acetate. (2) The product of step (1) is subjected to vacuum distillation to separate and remove the solvent, and an extract-like product is obtained; the temperature of vacuum distillation shall not exceed 90℃, and the vacuum degree of vacuum distillation shall be -0.1 to -0.09 MPa; (3) Add a lower alcohol to the extract and heat until the extract is completely dissolved; (4) The solution from step (3) is subjected to vacuum distillation to separate and remove the solvent; the temperature of vacuum distillation is 30 to 100°C, and the vacuum degree of vacuum distillation is -0.1 to -0.09 MPa; (5) The product from step (4) is subjected to vacuum distillation again to distill out thiothiazole, thus obtaining the thiothiazole product; the vacuum distillation temperature is 110-125℃ and the vacuum distillation pressure is 230-260 Pa.

2. The method according to claim 1, characterized in that: The oily solvent is toluene, ethyl acetate, ethylbenzene, or propyl acetate.

3. The method according to claim 1, characterized in that: The weight ratio of the oily solvent to the crude thiothiazole is 3 to 8:

1.

4. The method according to claim 1, characterized in that: In step (2), the temperature of vacuum distillation is 60-85℃.

5. The method according to claim 1, characterized in that: The lower alcohol is a monohydric alcohol with less than 5 carbon atoms.

6. The method according to claim 5, characterized in that: The lower alcohol is one or more of ethanol, n-propanol, n-butanol, and isobutanol.

7. The method according to claim 1, characterized in that: The amount of the lower alcohol used is 2 to 6 times the weight of the crude thiothiazole.

8. The method according to claim 1, characterized in that: In step (3), the temperature at which the paste-like product is heated to dissolve is 40–80°C.

9. The method according to any one of claims 1-8, characterized in that: In step (4), the temperature of vacuum distillation is 50-90℃.