A kind of preparation method of propoxyglycerol fatty acid ester
The use of a treated perfluorinated ion membrane catalyst in the esterification of propoxyglycerol fatty acid esters addresses high reaction temperatures and times, ensuring efficient, low-cost production with minimal residue and easy catalyst recycling.
Patent Information
- Application Number
- CN202310422331.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-04-19
- Publication Date
- 2024-12-13
- Estimated Expiration
- 2043-04-19
AI Technical Summary
Existing methods for preparing propoxyglycerol fatty acid esters face high reaction temperatures, long reaction times, high fatty acid content, and residual catalyst issues, leading to high energy consumption and purification difficulties.
A method involving the use of a treated perfluorinated ion membrane as a catalyst for esterification at reduced temperatures, with simultaneous dehydration, followed by refining steps to produce propoxyglycerol fatty acid ester efficiently and economically, allowing catalyst reuse and easy removal.
The method reduces reaction temperature and time, maintains equivalent fatty acid and glycerol polyoxypropylene ether ratios, minimizes fatty acid residue, and facilitates easy catalyst recycling, resulting in lower energy consumption and simplified refining processes.
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Abstract
Description
Technical Field
[0001] The invention relates to the technical field of preparation of propoxyglycerol fatty acid ester, in particular to a method for preparing propoxyglycerol fatty acid ester. Background Art
[0002] Propoxyglycerol fatty acid esters (EPG) were invented by ARCO Chemical Company in the 1980s. They can replace triglycerides as edible oils and are used in food. The structural difference between EPG and triglycerides is that a methylethoxy unit is inserted between glycerol and fatty acids. The methyl group prevents lipase from approaching the ester bond in a steric manner, thereby affecting the normal digestion and absorption of EPG. Therefore, EPG is basically not metabolized or stored in the body, which substantially reduces fat intake.
[0003] There are three synthetic routes for EPG. The first is the esterification of glycerol polyoxypropylene ether with fatty acids, the second is the ester exchange of glycerol polyoxypropylene ether with triglycerides, and the third is the ester exchange of glycerol polyoxypropylene ether with fatty acid esters. ARCO has reported on all three synthetic routes. The first route studied the esterification methods without catalyst, sulfonic acid catalyst, and metal catalyst. Whether it is sulfonic acid or metal catalyst, there is a problem of catalyst residue not meeting the standard. The second route has a low esterification rate, so glycerol is not easy to remove from the reaction system. The third route uses sodium / potassium methoxide as a catalyst, and metal ions are easily residual in the product.
[0004] EPG was officially put into large-scale production in 2016. It adopts the method of non-catalytic esterification of glycerol polyoxypropylene ether and fatty acid, which is also the only available method for synthesizing edible grade EPG so far. However, since this method does not add a catalyst, the reaction temperature is high, the reaction time is long, and the fatty acid content required to be added is high, which leads to high energy consumption and difficulty in purification. In addition, the free acid content after the reaction is very high, and the acid value is basically above 30mgKOH / g. The methods for removing free acid include solvent extraction, stripping and neutralization. Solvent extraction and neutralization are not advisable in industry. The organic solvent used for extraction needs to be recycled, which increases the cost; the large amount of soap produced by neutralization is difficult to remove and filtering is very difficult; stripping is a commonly used method for removing free acid in the oil and fat industry, but such a high content of free acid requires a long stripping time, resulting in very high energy consumption.
[0005] Therefore, it is necessary to develop a new preparation method or process for the preparation of propoxyglycerol fatty acid esters. The method should be able to add a catalyst to reduce the reaction temperature, increase the reaction rate, ensure that the input ratio of fatty acid and glycerol polyoxypropylene ether is equivalent, and the overall preparation method is simple, efficient, low-cost, and low in energy consumption; at the same time, the catalyst used is easy to remove, will not affect the product quality, and can be recycled and reused. Summary of the invention
[0006] The purpose of the present invention is to overcome the above technical deficiencies and solve the problems of high reaction temperature, long reaction time, large amount of fatty acid and large residual amount in the existing preparation technology of propoxyglycerol fatty acid ester; thus, a preparation method of propoxyglycerol fatty acid ester is provided, which reduces the reaction temperature and improves the reaction rate by adding a catalyst, and ensures that the feed ratio of the fatty acid and glycerol polyoxypropylene ether is equivalent, and there will be no large amount of fatty acid residue, and the overall preparation method is simple, efficient, low in cost and low in energy consumption; at the same time, the catalyst used is easy to remove, will not affect the product quality, and can be recycled and reused.
[0007] Specifically, the present invention discloses a method for preparing propoxylated glycerol fatty acid ester, comprising the following steps:
[0008] Glycerol polyoxypropylene ether and fatty acid are mixed, a catalyst is added, and an esterification reaction is carried out at a temperature of 120-180°C, and a dehydration operation is carried out at the same time. After filtering and refining, propoxyglycerol fatty acid ester is obtained.
[0009] Preferably, the average molecular weight of the glycerol polyoxypropylene ether is 300-1000; the fatty acid is selected from at least one of saturated fatty acids and unsaturated fatty acids, and the carbon chain length of the fatty acid is C8-C24.
[0010] Preferably, the molar ratio of the fatty acid to the glycerol polyoxypropylene ether is greater than or equal to 2.8.
[0011] Preferably, the catalyst is a cation exchange resin; the added amount of the catalyst is 0.05-0.6% of the sum of the mass of glycerol polyoxypropylene ether and fatty acid.
[0012] Preferably, the catalyst is a perfluorinated ion membrane.
[0013] Preferably, the perfluorinated ion membrane is obtained by treating discarded perfluorinated ion membrane; the treatment comprises washing and crushing the discarded perfluorinated ion membrane, adding an acidic aqueous solution to reflux for 2-5 hours, cooling and filtering, and then washing to a pH of 6-8.
[0014] Preferably, the esterification reaction time is 4-10 hours.
[0015] Preferably, the dehydration operation is selected from at least one of nitrogen purging, vacuum dehydration, and adding a water-absorbing molecular sieve.
[0016] Preferably, the refining includes deacidification, decolorization and deodorization; the deacidification is selected from one of thin film evaporation, molecular distillation, neutralization and stripping; the decolorization is adsorption decolorization; and the deodorization is stripping.
[0017] Preferably, the adsorption decolorization is performed by using a decolorizer, and the decolorizer is selected from at least one of activated clay, activated carbon, and diatomaceous earth.
[0018] Compared with the prior art, the beneficial effects of the present invention include:
[0019] (1) The method for preparing propoxylated glycerol fatty acid ester of the present invention reduces the reaction temperature and increases the reaction rate by adding a catalyst, while ensuring that the feed ratio of the fatty acid and the glycerol polyoxypropylene ether is equivalent (that is, the fatty acid fed can be only 2.8-3.2 times the molar amount of the glycerol polyoxypropylene ether), without a large amount of fatty acid residue, and the catalyst is easy to remove, does not affect the product quality, and can be recycled and reused.
[0020] (2) In the preparation method of propoxyglycerol fatty acid ester of the present invention, the discarded perfluoro ion membrane can be used as a catalyst after being treated, which can greatly reduce the reaction temperature, shorten the reaction time by at least half, and control the ratio of fatty acid to hydroxyl group to be equivalent. The catalyst can be removed by filtering without catalyst residue, and the catalyst can be recycled for more than 6 times. In addition, the discarded perfluoro ion membrane has a wide source. Previously, the domestic main treatment methods used were incineration or deep burial, which seriously polluted the environment and wasted resources. The present invention provides a treatment path for the discarded perfluoro ion membrane to be recycled, which reduces costs and is environmentally friendly.
[0021] (3) According to the method for preparing propoxyglycerol fatty acid ester of the present invention, the acid value of the crude product obtained by esterification reaction and dehydration operation can be controlled below 3 mgKOH / g in most cases, and the product can be directly deacidified by stripping or neutralization. Due to the low acid value, the subsequent operation is simple, the cost is low, and the filtration is simple. When the amount of fatty acid added is large, the acid value of some crude products is higher than 3 mgKOH / g, and the effect of removing free acid can be achieved by thin film evaporation or molecular distillation. At the same time, the temperature is low, the efficiency is high, and the energy consumption is reduced. If the neutralization method is adopted, the soap produced after neutralization can be effectively removed by using filter aids such as white clay, diatomaceous earth, and activated carbon after neutralization, and decolorization can be completed at the same time.
[0022] In the prior art, the acid value is basically above 30 mgKOH / g, and the methods for removing free acid include solvent extraction, steam stripping and neutralization. Solvent extraction and neutralization are not advisable in industry, and the organic solvent used for extraction needs to be recovered, which increases the cost; the large amount of soap produced by neutralization is difficult to remove and filtering is very difficult. Steam stripping is a commonly used method for removing free acid in the oil and fat industry, but such a high content of free acid requires a long steam stripping time, resulting in very high energy consumption.
[0023] That is, compared with the prior art, the preparation method of the present application can reduce the acid value of the crude product obtained through esterification reaction and dehydration operation, facilitate subsequent refining operations, and simplify subsequent operations, with higher efficiency, lower cost, and greater economy. DETAILED DESCRIPTION
[0024] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments, and are only used to explain the present invention, and are not used to limit the scope of protection of the present invention.
[0025] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making any creative work shall fall within the scope of protection of the present invention.
[0026] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.
[0027] It should also be understood that the terms used in this specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the specification of the present invention and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.
[0028] It should be further understood that the term "and / or" used in the present description and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.
[0029] A perfluorinated ion membrane,
[0030] It can be obtained by treating the discarded perfluorinated ion membrane; the treatment is to wash and crush the discarded perfluorinated ion membrane, add an acidic aqueous solution to reflux for 2-5 hours, cool and filter, and then wash to pH 6-8. The acidic aqueous solution is preferably a low-concentration acidic aqueous solution, which can be selected from dilute nitric acid, dilute hydrochloric acid, and dilute sulfuric acid, and the concentration is preferably 0.1-5%.
[0031] Specifically, 1 kg of discarded perfluorinated ion membrane was taken, and impurities were washed with clean water and then crushed into pieces of 0.5-5 mm. A 2% sulfuric acid solution was added and refluxed for 2-5 hours. After cooling and filtering, the mixture was washed with clean water until neutral, thereby obtaining a treated perfluorinated ion membrane sample 1.
[0032] The chlor-alkali industry discards up to 26.5 tons of perfluorinated ion membranes each year, and the cost of importing ion membranes is as high as $400 million each year. Previously, domestic discarded perfluorinated ion membranes were basically treated by incineration or deep burial, which seriously polluted the environment and wasted resources. Using discarded perfluorinated ion membranes as catalysts not only reduces the cost of EPG production, but also helps solve some waste disposal problems.
[0033] A method for preparing propoxyglycerol fatty acid ester (EPG),
[0034] The following steps are involved:
[0035] Glycerol polyoxypropylene ether and fatty acid are mixed, a catalyst is added, and an esterification reaction is carried out at a temperature of 120-180°C, and a dehydration operation is carried out at the same time. After filtering and refining, propoxyglycerol fatty acid ester is obtained.
[0036] Wherein, the average molecular weight of glycerol polyoxypropylene ether is 300-1000, preferably 350-600.
[0037] The fatty acid is selected from at least one of saturated fatty acids and unsaturated fatty acids, and the carbon chain length of the fatty acid is C8-C24. That is, the fatty acid can be selected from one or more mixtures of C8-C24 saturated fatty acids and C8-C24 unsaturated fatty acids. Specifically, the fatty acid can be preferably at least one of stearic acid, soybean oleic acid, rapeseed oleic acid, and palmitic acid.
[0038] Preferably, the molar ratio of fatty acid to glycerol polyoxypropylene ether is greater than or equal to 2.8; specifically, the molar ratio of fatty acid to glycerol polyoxypropylene ether may be 2.8-3.2.
[0039] The catalyst is a cation exchange resin. Preferably, the catalyst is a sulfonic acid ion exchange resin, and more preferably, the catalyst is a perfluorinated ion membrane; and the catalyst can also be a discarded perfluorinated ion membrane. That is, the perfluorinated ion membrane can be obtained by treating the discarded perfluorinated ion membrane. The treatment is to wash and crush the discarded perfluorinated ion membrane, add an acidic aqueous solution and reflux for 2-5 hours, cool and filter, and then wash to pH 6-8.
[0040] The amount of catalyst added is 0.05-0.6% of the sum of the mass of glycerol polyoxypropylene ether and fatty acid, that is, a small amount of catalyst can achieve an excellent catalytic effect and high catalytic efficiency.
[0041] The esterification reaction temperature is 120-180°C, preferably 140-160°C; the esterification reaction time is 4-10h, preferably 5-7h.
[0042] The dehydration operation is carried out simultaneously with the esterification reaction to remove the water generated during the reaction; the dehydration operation is selected from at least one of nitrogen purging, vacuum dehydration, and adding a water-absorbing molecular sieve. The water-absorbing molecular sieve is a molecular sieve, which can be preferably a commonly used 3A molecular sieve, 4A molecular sieve, 5A molecular sieve, 13X molecular sieve, NaY molecular sieve, etc.
[0043] Refining includes deacidification, decolorization and deodorization; deacidification is selected from one of thin film evaporation, molecular distillation, neutralization and stripping; decolorization is adsorption decolorization; deodorization is stripping. Among them, deacidification and deodorization can be combined and stripped together.
[0044] Adsorption decolorization is to use a decolorizing agent for adsorption decolorization, and the decolorizing agent is selected from at least one of activated clay, activated carbon, and diatomaceous earth.
[0045] Embodiment 1,
[0046] 232.5 g of glycerol polyoxypropylene ether (average molecular weight of 419) and 478 g of stearic acid were added to a four-necked bottle, and 3.5 g of crushed commercially available perfluoro ion membrane (DuPont Nafion) was added. Nitrogen was passed through the bottle and heated to 150°C. The reaction was continued for 4 hours to obtain a crude product. The catalyst was removed by filtration, and liquid alkali was added to neutralize the free fatty acids. 3.5 g of activated clay was added to decolorize and remove soap. The clay was removed by filtration, and the EPG product 1 was obtained by stripping at 150°C for 1 hour.
[0047] Among them, the molar ratio of glycerol polyoxypropylene ether to stearic acid is about 1:3.
[0048] Embodiment 2,
[0049] Add 232.5g of glycerol polyoxypropylene ether (average molecular weight of 419) and 478g of stearic acid into a four-necked bottle, add 3.5g of the treated perfluoroion membrane sample 1, pass nitrogen, heat to 150°C, and continue the reaction for 4h to obtain a crude product; filter out the catalyst, add liquid alkali to neutralize the free fatty acids, add 3.5g of activated white clay to decolorize and remove soap, filter out the white clay, and strip at 150°C for 1h to obtain EPG product 2.
[0050] Among them, the molar ratio of glycerol polyoxypropylene ether to stearic acid is about 1:3.
[0051] Embodiment 3,
[0052] In a four-necked bottle, 180 g of glycerol polyoxypropylene ether (average molecular weight of 300) and 518 g of rapeseed oil acid (average molecular weight of 308) were added, and 0.35 g of the treated perfluoroion membrane sample 1 was added, and the mixture was heated to 150°C. Vacuum dehydration was performed during the reaction, and the reaction was continued for 6 hours to obtain a crude product. The catalyst was removed by filtration, 3 g of activated carbon was added for decolorization, the activated carbon was removed by filtration, and the EPG product 3 was obtained by stripping at 200°C for 1 hour.
[0053] Among them, the molar ratio of glycerol polyoxypropylene ether to rapeseed oil acid is about 1:2.8.
[0054] Embodiment 4,
[0055] In a four-necked bottle, 350 g of glycerol polyoxypropylene ether (average molecular weight of 1000) and 311 g of soybean oleic acid (average molecular weight of 278) were added, and 1.7 g of the treated perfluoroion membrane sample 1 was added, nitrogen was passed through, and the mixture was heated to 180°C. The reaction was continued for 5 hours to obtain a crude product. The catalyst was removed by filtration, and the crude product was deacidified by molecular distillation at 155°C. 5 g of diatomaceous earth was added for decolorization, the diatomaceous earth was removed by filtration, and the EPG product 4 was obtained by stripping at 150°C for 1 hour.
[0056] Among them, the molar ratio of glycerol polyoxypropylene ether to soybean oleic acid is about 1:3.2.
[0057] Embodiment 5,
[0058] 280g of glycerol polyoxypropylene ether (average molecular weight of 600) and 382g of palmitic acid were added to a four-necked bottle, and 3.0g of the treated perfluoro ion membrane sample 1 was added, nitrogen was passed through, and the mixture was heated to 120°C and reacted for 5 hours to obtain a crude product; the catalyst was removed by filtration, and the mixture was deacidified by thin film evaporation at 170°C, 3g of activated clay was added for decolorization, and the clay was removed by filtration. EPG product 5 was obtained by stripping at 150°C for 1 hour.
[0059] Among them, the molar ratio of glycerol polyoxypropylene ether to palmitic acid is about 1:3.2.
[0060] The acid value of the crude product obtained in Example 1-5 and Product 1-5 was measured, and the hydroxyl value of Product 1-5 was measured at the same time, and the data obtained were shown in Table 1 below.
[0061] Table 1
[0062]
[0063] Among them, the crude product and the product correspond to their embodiments one by one.
[0064] It can be seen from Table 1 that the catalytic effects of the waste ion membrane and the new ion membrane are equivalent.
[0065] Embodiment 6,
[0066] The EPG product 6 was prepared by the same method as in Example 2; the difference being that the perfluorinated ion membrane used was recycled and reused, and the effects of repeated use are shown in Table 2 below.
[0067] Table 2
[0068]
[0069] Among them, the acid value after esterification reaction is the acid value of the crude product; the acid value after refining is the acid value of the product, and the hydroxyl value after refining is the hydroxyl value of the product.
[0070] It can be seen from Table 2 that the effect of recycling the waste ion membrane for multiple times is basically the same, that is, the catalyst can be recycled for more than 6 times.
[0071] Comparative Example 1,
[0072] 232.5 g of propoxyglycerol (average molecular weight 419) and 568 g of stearic acid were added to a four-necked bottle, nitrogen was passed through, heated to 250°C, and the reaction was continued for 11 hours. After distillation at about 100 Pa for 8 hours, a crude product was obtained. 7 g of white clay was added for decolorization, and after decolorization, the product was stripped at 260°C for 3 hours to obtain EPG comparative product 1.
[0073] Comparative Example 2,
[0074] Add 232.5g of glycerol polyoxypropylene ether (average molecular weight of 419) and 568g of stearic acid into a four-necked bottle, add 4.0g of p-toluenesulfonic acid, pass nitrogen, heat to 150°C, continue the reaction for 4h, and distill at about 100Pa for 8h to obtain a crude product. Wash twice with water to remove the catalyst, add liquid alkali to neutralize the catalyst and free fatty acids, add 3.5g of activated clay to decolorize and remove soap, filter to remove the clay, and steam strip at 150°C for 1h to obtain EPG comparative product 2.
[0075] Comparative Example 3
[0076] Add 232.5g of glycerol polyoxypropylene ether (average molecular weight of 419) and 568g of stearic acid into a four-necked bottle, add 4.0g of methylsulfonic acid, pass nitrogen, heat to 150°C, continue the reaction for 4h, and distill at about 100Pa for 8h to obtain a crude product. Wash twice with water to remove the catalyst, add liquid alkali to neutralize the catalyst and free fatty acids, add 3.5g of activated clay to decolorize and remove soap, filter to remove the clay, and strip at 150°C for 1h to obtain EPG comparative product 3.
[0077] Comparative Example 4
[0078] In a four-necked bottle, 232.5 g of glycerol polyoxypropylene ether (average molecular weight of 419) and 568 g of stearic acid were added, 4.8 g of stannous chloride was added, nitrogen was passed, the reaction was heated to 150°C, the reaction was continued for 7 hours, and after distillation at about 100 Pa for 8 hours, the catalyst was filtered out to obtain a crude product; washed twice with water, liquid alkali was added to neutralize the catalyst and free fatty acids, 3.5 g of activated white clay was added for decolorization and soap removal, the white clay was filtered out, and the EPG comparison product 4 was obtained by stripping at 150°C for 1 hour.
[0079] Comparative Example 5
[0080] Add 232.5g of glycerol polyoxypropylene ether (average molecular weight of 419) and 568g of stearic acid into a four-necked bottle, add 5.5g of isopropyl titanate, pass nitrogen, heat to 150°C, continue the reaction for 10h, distill at about 100Pa for 8h, filter out the catalyst to obtain a crude product; wash twice with water, add liquid alkali to neutralize the catalyst and free fatty acids, add 3.5g of activated white clay for decolorization and soap removal, filter out the white clay, and strip at 150°C for 1h to obtain EPG comparison product 5.
[0081] Table 3
[0082]
[0083] Among them, the crude product and the comparative product correspond to their comparative proportions one by one.
[0084] From the comparison of Tables 1 and 3, it can be seen that the comparison of Comparative Example 1 and the embodiment shows that both Comparative Example 1 and the embodiment can prepare products of similar quality, but since no catalyst is added in Comparative Example 1, its reaction temperature is high and the reaction rate is low, resulting in low efficiency and raising the preparation cost. In Comparative Examples 2-5, other catalysts are added, and the catalyst in the product is difficult to remove, which easily leads to the problem of catalyst residue not meeting the standard.
[0085] The above test results show that the preparation method of propoxyglycerol fatty acid ester of the present invention reduces the reaction temperature and increases the reaction rate by adding a catalyst, ensures that the input fatty acid and glycerol polyoxypropylene ether have a comparable feed ratio, does not have a large amount of fatty acid residue, and the catalyst is easy to remove, does not affect the product quality, and can be recycled and reused. At the same time, the acid value of the crude product obtained by esterification and dehydration operation can be reduced, the subsequent refining operation is convenient, and the subsequent operation is simplified, which is more efficient, low cost, and more economical.
[0086] The specific implementation of the present invention described above does not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.
Claims
1. A method for preparing propoxyglycerol fatty acid ester, characterized in that, The following steps are involved: Mixing glycerol polyoxypropylene ether and fatty acid, adding a catalyst, performing an esterification reaction at a temperature of 120-180° C., and performing a dehydration operation at the same time, and then filtering and refining to obtain propoxyglycerol fatty acid ester; the catalyst is a perfluorinated ion membrane; The perfluorinated ion membrane is obtained by treating the discarded perfluorinated ion membrane; The treatment comprises washing and crushing the discarded perfluorinated ion membrane, adding an acidic aqueous solution and refluxing for 2-5 hours, cooling and filtering, and then washing to a pH of 6-8; The amount of the catalyst added is 0.05-0.6% of the sum of the mass of glycerol polyoxypropylene ether and fatty acid. The molar ratio of the fatty acid to the glycerol polyoxypropylene ether is 2.8-3.
2.
2. The preparation method of propoxyglycerol fatty acid ester as claimed in claim 1, characterized in that, The average molecular weight of the glycerol polyoxypropylene ether is 300-1000; the fatty acid is selected from at least one of saturated fatty acids and unsaturated fatty acids, and the carbon chain length of the fatty acid is C8-C24.
3. The preparation method of propoxyglycerol fatty acid ester as claimed in claim 1, characterized in that, The esterification reaction time is 4-10h.
4. The preparation method of propoxyglycerol fatty acid ester as claimed in claim 1, characterized in that, The dehydration operation is selected from at least one of nitrogen purging, vacuum dehydration, and adding a water-absorbing molecular sieve.
5. The preparation method of propoxyglycerol fatty acid ester as claimed in claim 1, characterized in that, The refining includes deacidification, decolorization and deodorization; the deacidification is selected from one of thin film evaporation, molecular distillation, neutralization and steam stripping; the decolorization is adsorption decolorization; the deodorization is steam stripping.
6. The preparation method of propoxyglycerol fatty acid ester as claimed in claim 5, characterized in that, The adsorption decolorization is performed by using a decolorizer, and the decolorizer is selected from at least one of activated clay, activated carbon, and diatomaceous earth.