Preparation method of high-purity low-chromatography carnosic acid

Abstract

The application discloses a preparation method of high-purity low-color carnosic acid. The method adopts two-stage heat reflux to completely extract carnosic acid in rosemary powder, and the obtained extract is concentrated, precipitated by acid, and then subjected to secondary impurity removal through an alkali dissolution and acid precipitation process, and then subjected to two-stage solvent purification, so that the high-purity carnosic acid with a purity of more than 95% is obtained. The method is based on the synergistic effect between the processes, the purity of carnosic acid in the product in the intermediate step is controlled, and the two-stage purification process is used, so that the high-purity carnosic acid with a purity of more than 95% is obtained. The method does not need crystallization and color removal processes, does not need additional equipment, and is simple, which can ensure the product purity and effectively reduce the residual pigment, so that the high-purity white carnosic acid powder is obtained, and a linear relationship between the color and the purity of carnosic acid is established, so that the subsequent use and other ingredients can be matched.

Description

Technical Field

[0001] This invention relates to a method for preparing oxalic acid, specifically a method for preparing high-purity, low-color oxalic acid, belonging to the field of plant component purification technology. Background Technology

[0002] The "Regulations on the Supervision and Administration of Cosmetics" explicitly support the research and development of cosmetics using plant resources. Rosemary (Rosmarinus Officinal SL) is a natural medicinal plant rich in various active ingredients and possesses strong antioxidant properties, finding wide application in food, oils, healthcare, and daily chemical industries. Therefore, the extraction technology and application development of rosemary's active ingredients have attracted widespread attention both domestically and internationally, becoming a new focus in pharmaceutical research worldwide.

[0003] Sageric acid is the main fat-soluble active ingredient in fresh rosemary leaves. It is easily converted into other components during processing, exhibiting instability and posing challenges in its preparation and preservation. Furthermore, while sageric acid is an important quality indicator for fat-soluble rosemary antioxidants, the antioxidant performance of these antioxidants is not linearly correlated with sageric acid content, but rather shows a strong linear correlation with the total amount of fat-soluble diterpenoid phenols. Moreover, compared to fat-soluble rosemary antioxidants (which fall under the category of extracts), from a safety perspective, high-purity sageric acid, as a single compound (with clearly defined composition, structure, and toxicological safety data), is safer to add to daily chemical products.

[0004] In the industry, the purity of oxalic acid products is generally between 10% and 20%, with higher purity reaching 40% to 60%. Currently, there are many reports on oxalic acid extraction methods, but these methods all involve extraction with various solvents. Oxalic acid has poor stability in many solvents, is easily oxidized, and is difficult to separate. Column chromatography separation of oxalic acid is time-consuming, easily oxidized, has poor stability, and is inefficient. All extraction processes are cumbersome, costly, produce low-purity products, are not suitable for industrial production, and lack practical economic benefits.

[0005] The basic requirements for raw materials in the daily chemical industry include minimal odor, light color, and easy compatibility with other ingredients. Good daily chemical raw materials should have bright, clear, and gentle colors. If the color is dull, murky, or inconsistent in shade, it indicates a quality problem. Currently, high-purity oxalic acid products on the market vary in color, including brownish-yellow and grayish-green. These color differences make it difficult to distinguish the quality of the raw material and hinder its compatibility with other ingredients. Summary of the Invention

[0006] To address the problems existing in the prior art, the present invention aims to provide a method for preparing high-purity, low-color oxalic acid. This method, based on the synergistic effect between various processes, controls the purity of oxalic acid in the intermediate steps and utilizes a two-stage purification process to obtain high-purity oxalic acid with a purity of over 95%. This method eliminates the need for crystallization and decolorization processes, requires no additional equipment, is simple, and yields a white powder that is easy to combine with other raw materials.

[0007] To achieve the above-mentioned technical objectives, the present invention provides a method for preparing high-purity, low-chroma oxalic acid, comprising the following steps:

[0008] 1) After crushing the dried rosemary leaves, extract them by reflux with alcohol to obtain the extract;

[0009] 2) After concentrating the total extract, add acid solution and cool to room temperature. Then, allow it to stand for precipitation and filter and dry to obtain the rat oxalic acid precursor.

[0010] 3) Add alkaline solution to the oxalic acid precursor, filter, add acid solution until precipitation, filter and dry successively to obtain crude oxalic acid.

[0011] 4) The crude oxalic acid is purified sequentially by a single solvent and a mixed solvent to obtain the product; the ratio of the raw material to the solvent in the organic solvent purification and the mixed solvent purification is 1-10:60-98.

[0012] The preparation method provided by this invention is based on the synergistic effect between each step. It uses a two-stage hot reflux to completely extract carrageenan from rosemary, thereby improving the overall product yield. After the total extract is concentrated, it is subjected to acid precipitation to remove impurities. Then, it is subjected to a second impurity removal process through alkali dissolution and acid precipitation. The two impurity removal processes can effectively remove inorganic substances and terpenoid impurities from the product, but cannot remove residual pigments and sterol impurities. Furthermore, through two-stage solvent purification, the ratio of feedstock to reagents is precisely controlled, which can completely remove sterol impurities from the product and also effectively reduce residual pigments, thereby obtaining high-purity off-white carrageenan powder.

[0013] As a preferred embodiment, the dried rosemary leaves are crushed into powder with a particle size of 55-65 mesh; the alcohol concentration is 60-85%. More preferably, the alcohol concentration is 75-80%. The alcohol concentration must be strictly controlled according to the above requirements. If the alcohol concentration is too high, it will not only fail to improve the loss rate of subsequent recovery and increase costs, but will also extract more impurities and reduce the purity of the product; while if the alcohol concentration is too low, the oxalic acid cannot be completely extracted, reducing the utilization rate of raw materials.

[0014] As a preferred embodiment, the number of reflux extractions is ≥2. More preferably, the number of reflux extractions is 2.

[0015] As a preferred embodiment, the conditions for the heating and reflux extraction are: a temperature of 50–70°C, a time of 1–3 hours, and a mass ratio of dried rosemary leaves to alcohol of 1:10–20. More preferably, the conditions for the heating and reflux extraction are: a temperature of 60°C, a mass ratio of dried rosemary leaves to alcohol of 1:15, and a time of 2–3 hours.

[0016] As a preferred embodiment, the acid solution is phosphoric acid, hydrochloric acid, acetic acid, citric acid, and sodium acid salt, and the amount added is 0.1-5% of the mass of dried rosemary leaves. More preferably, the amount of acid solution added is 1-3% of the mass of dried rosemary leaves. Since caryopsisic acid is unstable in alcoholic solution and is easily oxidized to caryopsisol and other substances, adding acid can protect caryopsisic acid and prevent oxidation and deterioration; in addition, the addition of acid can facilitate the precipitation of caryopsisic acid from the solution.

[0017] As a preferred embodiment, the alkaline solution is sodium hydroxide, basic sodium salt, or basic potassium salt, and the pH of the alkaline solution is 8–11. More preferably, the pH of the alkaline solution is 9–10.

[0018] As a preferred embodiment, the pH value of the acid precipitation in step 3) is 2.9 to 3.1.

[0019] As a preferred embodiment, the content of oxalic acid in the oxalic acid precursor is 50-65%; the content of oxalic acid in the crude oxalic acid product is 70-80%. The purity of the products obtained in each step of this invention must strictly adhere to the above requirements. If the content of oxalic acid in the oxalic acid precursor is too low, the liquid phase during the alkali dissolution and acid precipitation process will be filled with impurity suspended colloids, making separation difficult. If the concentration of oxalic acid in the crude oxalic acid product is too low, the inorganic impurities in the oxalic acid cannot be separated during the second-stage solvent purification, which not only reduces the purity of the final product but also affects the product's color, resulting in a light yellow or grayish-green appearance.

[0020] As a preferred embodiment, the organic solvent is one of ethyl acetate, propyl acetate, butyl acetate, n-butanol, petroleum ether, and n-hexane;

[0021] As a preferred embodiment, the mixed solvent is at least two of ethyl acetate, propyl acetate, butyl acetate, n-butanol, petroleum ether, and n-hexane.

[0022] As a preferred embodiment, when the mixed solvent is any two of ethyl acetate, propyl acetate, butyl acetate, n-butanol, petroleum ether, and n-hexane, the mass ratio of the two solvents is 5-10:60-70. The mass ratio of the two solvents in the mixed solvent should strictly adhere to the above requirements. Considering the polarity of impurities and pigments, this ratio provides a suitable polarity for the mixed solvent. On the one hand, it can wash away pigments, achieving a decolorizing effect; on the other hand, it can remove impurities with similar polarity to oxalic acid, achieving a purification effect.

[0023] As a preferred embodiment, the organic solvent purification process is as follows: at 40–55°C, crude oxalic acid is thoroughly mixed with an organic solvent at a mass ratio of 1–10:50–98 for 0.5–2 hours, followed by filtration and drying to obtain purified oxalic acid. More preferably, the mass ratio of crude oxalic acid to the organic solvent is 5–10:60–98.

[0024] As a preferred embodiment, the purification process using the mixed solvent is as follows: at 45–60°C, the previously purified oxalic acid is thoroughly mixed with the mixed solvent at a mass ratio of 1–10:50–98 for 0.5–2 hours, followed by filtration and drying to obtain the final product. More preferably, the mass ratio of the previously purified oxalic acid to the organic solvent is 5–10:60–98.

[0025] The ratio of solvent to raw materials should be strictly followed according to the above requirements. If the ratio of raw materials is too high, the decolorization will be incomplete and the decolorization effect will not be achieved. If the ratio of raw materials is too low, the product yield will be reduced and the final product loss will be high.

[0026] This invention also provides a detailed method for preparing high-purity, low-color oxalic acid, comprising:

[0027] 1) Weigh dried rosemary leaves, pulverize them into rosemary leaf powder, add 60-90% alcohol at a material-to-liquid ratio of 1:10-20, heat and reflux at 50-60℃ for 2-3 hours, filter to obtain the first extract and the first residue. Continue to add alcohol to the first residue and repeat the above operation to obtain the second extract. Combine the two extracts.

[0028] 2) Concentrate the combined extracts until a brown oily substance is produced, then stop the concentration. Add 0.1-5% acid (by weight of the raw material), cool to room temperature, and allow to stand for a period of time to produce a brownish-yellow precipitate. Filter and dry to obtain crude sarsaparilla acid with a content of 60-65%.

[0029] 3) Take crude carrageenan, dissolve it in an alkaline solution with a pH of 8-11, filter to obtain a pink filtrate, then add acid to adjust the pH to between 2 and 4 until no more precipitate is formed in the filtrate, filter the precipitate and dry it to obtain carrageenan product with a purity of 80-85%.

[0030] 4) Add approximately 80% of the sage product to an organic solvent, stir at 40–55°C for 0.5–2 hours, filter, precipitate, and dry to obtain primary purified sage acid. Add the primary purified sage acid to a mixed solvent, stir at 45–60°C for 0.5–2 hours, filter, precipitate, and dry to obtain high-purity, low-color sage acid.

[0031] This invention defines a four-step process for preparation. By strictly controlling the types and amounts of reagents used in each step, the connection between the purification processes in each step is ensured. This not only effectively controls the introduction of impurities but also avoids the need for decolorization and crystallization processes, greatly simplifying the process flow. All reagents introduced in the above steps can be completely removed, ensuring the purity and color of the final product.

[0032] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0033] 1) In the technical solution provided by the present invention, a two-stage hot reflux process is used to completely extract carrageenan from rosemary, thereby improving the overall product yield. After the total extract is concentrated, the product is initially removed by acid precipitation, and then a second impurity removal process is carried out by alkali dissolution and acid precipitation. The two impurity removal processes can effectively remove inorganic substances and terpenoid impurities in the product, but cannot remove residual pigments and sterol impurities. Furthermore, by using two-stage solvent purification and precise control of the feed ratio, the sterol impurities in the product are completely removed while also effectively reducing the residual pigments, thereby obtaining high-purity off-white carrageenan powder.

[0034] 2) In the technical solution provided by this invention, based on the synergistic effect between each process, by controlling the purity of oxalic acid in the intermediate step, a two-stage purification process is used to obtain high-purity oxalic acid with a purity of over 95%. This method requires no crystallization or decolorization processes, no additional equipment, and is simple in process. The resulting product is an off-white powder, which is easy to combine with other raw materials.

[0035] 3) In the technical solution provided by the present invention, the four-step process strictly controls the types and amounts of reagents used in each step, ensuring the connection between the purification processes of each step. This not only effectively controls the introduction of impurities, but also avoids the decolorization and crystallization processes, greatly simplifying the process flow. All reagents introduced in the above steps can be completely removed, ensuring the purity and color of the final product. Attached Figure Description

[0036] The invention will be more fully understood through the following detailed description and in conjunction with the accompanying drawings:

[0037] Figure 1This is a sample image of oxalic acid provided in Example 3 of this application;

[0038] Figure 2 This is a high-performance liquid chromatogram of the oxalic acid product provided in Example 1 of this application;

[0039] Figure 3 This is a high-performance liquid chromatogram of the oxalic acid product provided in Example 2 of this application;

[0040] Figure 4 The high-performance liquid chromatogram of the arugula acid product provided in Comparative Example 1 of this application;

[0041] Figure 5 This is a high-performance liquid chromatogram of the oxalic acid product provided in Example 3 of this application;

[0042] Figure 6 shows the carbon and hydrogen spectra of the sarsaparilla acid product provided in Example 3 of this application;

[0043] in, Figure 6a This is the carbon spectrum of the sarsaparilla acid product provided in Example 3. Figure 6b The photoluminescence spectrum of the sarsaparilla acid product provided in Example 3 is shown below. Detailed Implementation

[0044] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0045] Example 1

[0046] 1000g of dried rosemary leaves were crushed into rosemary powder. Ten times the volume of 70% ethanol was added, and the mixture was stirred at 60℃ for 2 hours. The first extract and the first extract residue were obtained by filtration. Then, another ten times the volume of 70% ethanol was added, and the mixture was stirred at 60℃ for 2 hours. The second extract and the residue were obtained by filtration. The two extracts were combined to obtain the total extract. The total extract was concentrated until a brown oily substance was produced. Concentration was stopped, and 0.5% (by volume) of phosphoric acid was added. The mixture was cooled to room temperature and allowed to stand for a period of time to produce a brownish-yellow precipitate. This precipitate was filtered and dried to obtain the oxalic acid precursor (63.20%). The oxalic acid precursor was dissolved in a sodium hydroxide solution at pH 9. Impurities were filtered out to obtain the filtrate. Phosphoric acid was then added dropwise to adjust the pH until no precipitate was formed. The precipitate was filtered and dried to obtain the crude oxalic acid precipitate (purity 79.52%). The crude oxalic acid precipitate was added to n-hexane at a feed-to-liquid ratio of 10:98 (temperature 40℃, stirring time 1.5h), filtered and dried to obtain primary purified oxalic acid. The primary purified oxalic acid was then added to a mixed solvent of ethyl acetate and petroleum ether at a ratio of 10:60 (temperature 45℃, stirring time 1h), filtered and dried to obtain a milky-white oxalic acid product with a purity of 95.10%.

[0047] Example 2

[0048] 1000g of dried rosemary leaves were crushed into rosemary powder. Ten times the volume of 80% ethanol was added, and the mixture was stirred and extracted at 50℃ for 1 hour. The first extract and the first extract residue were then filtered. Ten times the volume of 80% ethanol was added again, and the mixture was stirred and extracted at 50℃ for 1 hour. The second extract and the residue were then filtered. The two extracts were combined to obtain the total extract. The total extract was concentrated until a brown oily substance was produced. Concentration was stopped, and 1% (by volume) of phosphoric acid was added. The mixture was cooled to room temperature and allowed to stand for a period of time to produce a brownish-yellow precipitate. This precipitate was filtered and dried to obtain the oxalic acid precursor (64.07%). The oxalic acid precursor was dissolved in a sodium bicarbonate solution at pH 8.2. Impurities were filtered out to obtain the filtrate. Hydrochloric acid was then added dropwise to adjust the pH until no precipitate was formed. The precipitate was filtered and dried to obtain crude oxalic acid (80.96% purity). Raphanic acid precipitate was added to n-hexane at a feed-to-liquid ratio of 10:85 (temperature 45℃, stirring time 1 h), filtered and dried to obtain primary purified raphanic acid. The primary purified raphanic acid was then added to a mixed solvent of isopropyl acetate and petroleum ether at a ratio of 10:70 (temperature 50℃, stirring time 1.5 h), filtered and dried to obtain a light white raphanic acid product with a purity of 96.73%.

[0049] Example 3

[0050] 1000g of dried rosemary leaves were crushed into rosemary powder. 18 times the volume of 85% ethanol was added, and the mixture was stirred at 65℃ for 3 hours. The mixture was filtered to obtain the first extract and the first extract residue. Then, 18 times the volume of 85% ethanol was added again, and the mixture was stirred at 65℃ for 3 hours. The mixture was filtered to obtain the second extract and the residue. The two extracts were combined to obtain the total extract. The total extract was concentrated until a brown oily substance was produced. Concentration was stopped, and 2% hydrochloric acid (by volume of the concentrated extract) was added. The mixture was cooled to room temperature and allowed to stand for a period of time to produce a brownish-yellow precipitate. This precipitate was filtered and dried to obtain the oxalic acid precursor (purity 64.05%). The oxalic acid precursor was dissolved in a potassium hydroxide solution at pH 9.5. Impurities were filtered out to obtain the filtrate. Hydrochloric acid was then added dropwise to adjust the pH until no precipitate formed. The precipitate was filtered and dried to obtain crude oxalic acid (purity 81.58%). Raphanic acid precipitate was added to n-hexane at a feed-to-liquid ratio of 8:75 (temperature 50℃, stirring time 30 min), filtered and dried to obtain primary purified raphanic acid. The primary purified raphanic acid was then added to a mixed solvent of ethyl acetate and petroleum ether at a ratio of 6:65 (temperature 45℃, stirring time 1 h), filtered and dried to obtain a pure white raphanic acid product with a purity of 97.90%.

[0051] Comparative Example 1

[0052] 1000g of dried rosemary leaves were crushed into rosemary powder, and 10 times their volume of 75% ethanol were added. The mixture was stirred and extracted at 55°C for 1.5 hours. The first extract and the first extract residue were obtained by filtration. Then, 10 times their volume of 75% ethanol were added again, and the mixture was stirred and extracted at 55°C for 1.5 hours. The second extract and the residue were obtained by filtration. The two extracts were combined to obtain the total extract. The total extract was concentrated until a brown oily substance was produced. Concentration was stopped, and 0.5% citric acid (by volume of the concentrated extract) was added. The mixture was cooled to room temperature and allowed to stand for a period of time to produce a brownish-yellow precipitate. The precipitate was filtered and dried to obtain the oxalic acid precursor (purity 58.08%). The oxalic acid precursor was dissolved in potassium hydroxide solution at pH 8.6. Impurities were filtered out to obtain the filtrate. Hydrochloric acid was then added dropwise to adjust the pH value until no precipitate was formed. The precipitate was filtered and dried to obtain crude oxalic acid (purity 76.61%) precipitate. Raphanic acid precipitate was added to n-hexane at a feed-to-liquid ratio of 6:70 (temperature 45℃, 1h), filtered and dried to obtain primary purified raphanic acid. The primary purified raphanic acid was then added to a mixed solvent of ethyl acetate and petroleum ether at a ratio of 5:75 (temperature 45℃, stirring time 1h), filtered and dried to obtain a light yellow raphanic acid product with a purity of 94.47%.

Claims

1. A method for preparing oxalic acid, characterized in that, Includes the following steps: 1) After crushing the dried rosemary leaves, extract them by reflux with alcohol to obtain the extract; 2) After concentrating the total extract, add acid solution and cool to room temperature. Then, allow it to stand for precipitation and filter and dry to obtain the rat oxalic acid precursor. 3) Add alkaline solution to the oxalic acid precursor, filter, add acid solution until precipitation, filter and dry successively to obtain crude oxalic acid. 4) The crude oxalic acid was purified successively by organic solvent and mixed solvent to obtain the final product; The ratio of materials to solvents in both organic solvent purification and mixed solvent purification is 1~10:60~98; The organic solvent is one of ethyl acetate, propyl acetate, butyl acetate, n-butanol, petroleum ether, and n-hexane; The mixed solvent is any two of ethyl acetate, propyl acetate, butyl acetate, n-butanol, petroleum ether, and n-hexane, with a mass ratio of 5~10:60~70 between the two solvents.

2. The method for preparing rat oxalic acid according to claim 1, characterized in that: The dried rosemary leaves are crushed into powder with a particle size of 55-65 mesh; the alcohol concentration is 60-85%.

3. The method for preparing rat oxalic acid according to claim 1, characterized in that: The number of reflux extractions is ≥2, and the conditions for alcohol reflux extraction are: temperature 50~70℃, time 1~3h, and mass ratio of dried rosemary leaves to alcohol 1:10~20.

4. The method for preparing rat oxalic acid according to claim 1, characterized in that: The acid solution is phosphoric acid, hydrochloric acid, acetic acid, citric acid and sodium acid salt, and the amount added is 0.1~5% of the weight of dried rosemary leaves.

5. The method for preparing rat oxalic acid according to claim 1, characterized in that: The alkaline solution is sodium hydroxide, basic sodium salt, and basic potassium salt, and the pH of the alkaline solution is 8-11.

6. The method for preparing rat oxalic acid according to claim 1, characterized in that: The oxalic acid precursor contains 50-65% oxalic acid; the crude oxalic acid product contains 70-80% oxalic acid.

7. The method for preparing rat oxalic acid according to claim 1, characterized in that: The organic solvent purification process is as follows: at 40~55℃, crude oxalic acid is thoroughly mixed with organic solvent at a mass ratio of 1~10:50~98 for 0.5~2 hours, and then filtered and dried to obtain purified oxalic acid.

8. The method for preparing oxalic acid according to claim 7, characterized in that: The purification process of the mixed solvent is as follows: at 45~60℃, the previously purified rat oxalic acid is thoroughly mixed with the mixed solvent at a mass ratio of 1~10:50~98 for 0.5~2 hours, and then filtered and dried to obtain the final product.

Images