Oxidation decolorization method of long-chain dicarboxylic acid

Abstract

The invention provides an oxidative decolorization method of long-chain dicarboxylic acid, which comprises the following steps: S10, adjusting a material containing the long-chain dicarboxylic acid until the mass concentration of the long-chain dicarboxylic acid is 5-30%, and adjusting the pH value to be within the range of 3-10; s20, the materials are put into a reactor, an oxidizing agent is added, in the oxidation process, the temperature of the reactor is kept to be 101-133 DEG C, the pressure is kept to be 0.108-0.304 MPa, and the oxidation time is 0.2-2 h; the oxidizing agent is one or more of ozone, hydrogen peroxide or sodium hypochlorite, and the adding amount of the oxidizing agent is 0.2-6% of the mass of the long-chain dicarboxylic acid; and S30, naturally cooling the oxidized material to below 90 DEG C, and carrying out solid-liquid separation to obtain a target product containing the long-chain dicarboxylic acid. According to the method, the long-chain dicarboxylic acid-containing material is oxidized under the high-temperature and high-pressure conditions, so that the oxidation is more sufficient, the removal rate of impurities such as pigments and the like is greatly improved, and then a high-purity long-chain dicarboxylic acid water-phase crystallization product can be obtained.

Description

Technical Field

[0001] The invention relates to the technical field of long-chain dibasic acid preparation, and in particular to an oxidative decolorization method for long-chain dibasic acid. Background Art

[0002] Long-chain dibasic acids usually refer to aliphatic dicarboxylic acids with more than 10 carbon atoms in the carbon chain, including saturated and unsaturated dicarboxylic acids. They are a type of fine chemical products with important and extensive industrial uses. Long-chain dibasic acids can be used to prepare polymer materials, solvents, coatings, adhesives and plasticizers, etc., and can also replace some traditional petroleum-based materials, thereby reducing the impact on the natural environment. Due to the broad development potential of downstream products of long-chain dibasic acids, the demand for long-chain dibasic acids at home and abroad is increasing, and its market potential is huge. It is expected that in the next few years, the long-chain dibasic acid market will continue to grow, especially in the field of sustainable development, which has a broad prospect.

[0003] As a natural and green bio-based material, long-chain dibasic acids produced by biological methods have attracted more and more attention. Biological long-chain dibasic acids are produced by the oxidation of corresponding alkanes by engineered bacteria. The molecular weight is usually between 200 and 400, showing the structural characteristics of amide bonds, with high plasticity, durability and anti-aging properties. At present, the production cost of biological long-chain dibasic acids is gradually reduced, further improving their competitiveness in the market.

[0004] The biological production of long-chain dibasic acids is the application of microbial technology in the petrochemical industry that emerged in the 1970s. Its characteristics are that it uses n-alkanes as raw materials, utilizes the unique oxidation ability of microorganisms and the action of microbial intracellular enzymes, and oxidizes the two methyl groups at both ends of long-chain n-alkanes at normal temperature and pressure to generate various long-chain dibasic acids of corresponding chain lengths.

[0005] The biological method for producing long-chain dibasic acids overcomes the various shortcomings of simple chemical synthesis methods and vegetable oil cracking methods, and opens up a new way for the mass production of long-chain dibasic acids. Compared with chemical synthesis methods, the biological method for producing long-chain dibasic acids has undoubted advantages and is widely valued at home and abroad. The biological method can provide a series of long-chain dibasic acid monomers from C10 to C22, some of which cannot be produced by chemical methods.

[0006] The biological method for preparing long-chain dibasic acids has mild conditions and simple processes, but the fermentation broth formed in the process is a mixture of dibasic acids, residual alkanes, emulsions, bacteria, culture media and various secondary metabolites. If some pigments and nitrogen compounds remain during the extraction and purification process, it will affect the later polymerization. In industrial production, long-chain dibasic acid extraction is mainly carried out by solvent treatment and water treatment, and its decolorization process is mainly carried out in solvent and water. The technical route for purification in solvent relies on the tolerance of the solvent to impurities. The long-chain dibasic acid gradually grows in the process of slow cooling of the solvent, and the impurities are left in the mother liquor. As a result, a high-purity long-chain dibasic acid crystalline product can be obtained. However, the solvent method has a fatal disadvantage, that is, a large amount of organic solvents are used, which has a great pollution to the environment. Due to the organic solvent pollution problem of the solvent method, the process flow of aqueous phase refining of long-chain dibasic acids has become the focus of research for some companies.

[0007] Chinese patent CN109824507A (publication date May 31, 2019) proposes a method for purifying long-chain dibasic acids. After two activated carbon decolorizations, two acid precipitations, and multiple filtrations in the aqueous phase, a long-chain dibasic acid product can be obtained, but the process is lengthy, the yield is low, and the quality is unstable.

[0008] Chinese patent CN109134236B (authorization announcement date March 23, 2021) provides a method for decolorizing and deproteinizing long-chain dibasic acid fermentation broth, which uses an ultrafiltration membrane to remove protein and pigment, but this method is difficult to produce polymerization-grade long-chain dibasic acids.

[0009] The core technology of aqueous phase refining of long-chain dibasic acids is to remove as many impurities as possible from the material before the long-chain dibasic acid is acidified and crystallized. The solubility of long-chain dibasic acids in water is extremely low. During the acidification and crystallization process, the crystals do not grow slowly but are generated explosively, so it is extremely easy to carry impurities. If the material is not thoroughly decolorized and impurized before acidification and crystallization, it is difficult to obtain a high-purity long-chain dibasic acid product. Simply using activated carbon decolorization and ultrafiltration membrane decolorization in the aqueous phase refining process cannot achieve the desired effect.

[0010] Furthermore, the oxidation process is a commonly used long-chain dibasic acid decolorization process in the prior art. In the prior art, the long-chain dibasic acid oxidation is carried out at a relatively low temperature and normal pressure, and the oxidation effect is insufficient, so the decolorization effect is not good.

[0011] Chinese patent CN102976917B (authorization announcement date June 11, 2014) discloses a method for refining a long-chain dibasic acid in an aqueous phase, which proposes a two-stage purification method for a long-chain dibasic acid in an aqueous phase, wherein an oxidant is added after heating at a pH of 5 to 9 to shield the dibasic acid carboxyl group from reacting with reducing impurities, the heating temperature is controlled at 80 to 100° C., the oxidant is sodium hypochlorite or ozone, and the long-chain dibasic acid is obtained by acidification after oxidation. However, this method is still not ideal for removing impurities, and in the subsequent crystallization process, a crystallization aid such as an organic solvent still needs to be added, and the pH value in the crystallization process needs to be repeatedly adjusted, and the operation process is complicated.

[0012] Chinese patent CN109970548B (authorization announcement date: January 4, 2022) discloses a long-chain dibasic acid oxidation decolorization process, which proposes to use one or more of potassium permanganate, ozone or sodium hypochlorite to oxidize impurities such as pigments in the material under a pH of 11-12. This method is also difficult to obtain qualified aqueous phase pre-crystallization materials, and based on the applicant's understanding of the market, the owner of the patent has not used this method for its own actual industrial production.

[0013] Based on the above content, it can be seen that in the prior art, the purification of long-chain dibasic acids before crystallization mostly adopts methods such as activated carbon adsorption of impurities, ultrafiltration membrane filtration of impurities and oxidation to remove impurities. As mentioned above, the use of activated carbon decolorization and ultrafiltration membrane decolorization alone in the aqueous phase refining process cannot achieve the desired effect, and the oxidation method is carried out under normal pressure and low temperature range, and the temperature range is concentrated in 60-90°C. Within this temperature range, the effect of the oxidant is limited, and the effect of decolorization and impurity removal still does not meet the requirements. Even if it is used in combination with activated carbon decolorization and ultrafiltration membrane decolorization, it is difficult to produce polymerization-grade long-chain dibasic acid products. Summary of the invention

[0014] In view of the defects in the prior art, the purpose of the present invention is to provide a method for oxidative decolorization of long-chain dibasic acids under high temperature and high pressure conditions. The process method has a simple route, a high removal rate of impurities such as pigments, and higher production efficiency, and the quality of the obtained product is better.

[0015] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0016] A method for oxidative decolorization of a long-chain dibasic acid comprises the following steps:

[0017] S10, adjusting the material containing the long-chain dibasic acid to a mass concentration of the long-chain dibasic acid of 5% to 30%, and adjusting the pH value to a range of 3 to 10 according to the type of oxidant;

[0018] S20, putting the material obtained in step S10 into a reactor, and adding an oxidant for oxidation. During the oxidation process, the temperature of the reactor is maintained at 101-133° C., and the corresponding pressure is maintained at 0.108-0.304 MPa, and the oxidation time is 0.2-2 h;

[0019] The oxidant is one or more of ozone, hydrogen peroxide or sodium hypochlorite, and the amount of the oxidant added is 0.2% to 6% of the mass of the long-chain dibasic acid;

[0020] S30, allowing the material oxidized in step S20 to cool naturally to below 90°C, performing solid-liquid separation, and obtaining a target product containing a long-chain dibasic acid.

[0021] Preferably, in step S10, the material containing long-chain dibasic acids comes from the fermentation broth obtained after the production of long-chain dibasic acids by microbial fermentation; or comes from the crude long-chain dibasic acids obtained by treating the fermentation broth after the fermentation of long-chain dibasic acids to remove or reduce one or more of the bacteria, proteins, bacteria fragments, pigments, etc. in the fermentation broth; or comes from the crude mixed long-chain dibasic acids obtained by treating the waste liquid containing long-chain dibasic acids discharged during the production of long-chain dibasic acids.

[0022] Preferably, the long-chain dibasic acid is a mixture of one or more of sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedicarboxylic acid, hexadecanedioic acid, heptadecanedioic acid and octadecanedicarboxylic acid.

[0023] Preferably, in step S10, when the oxidant is ozone, the pH value is adjusted to a range of 8 to 10; when the oxidant is hydrogen peroxide, the pH value is adjusted to a range of 3 to 10; when the oxidant is sodium hypochlorite, the pH value is adjusted to a range of 6 to 8.

[0024] Preferably, in step S20, activated carbon is added as an oxidation catalyst, and the added amount of the activated carbon is 1% to 8% of the mass of the long-chain dibasic acid.

[0025] Preferably, in step S20, the pH is adjusted during the oxidation process so that the material is oxidized under different pH conditions.

[0026] Preferably, in step S20, the temperature of the reactor is maintained at 105-125° C., and the corresponding pressure is maintained at 0.124-0.239 MPa.

[0027] Preferably, in step S30, when the pH value of the material is lower than 6, the pH value is adjusted to 6 or above before solid-liquid separation to obtain a liquid containing a long-chain dibasic acid.

[0028] Preferably, in step S30, the solid-liquid separation method used is plate-and-frame decarburization.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The oxidative decolorization method of long-chain dibasic acid provided by the present invention places a material containing long-chain dibasic acid under high temperature and high pressure conditions for oxidation reaction, so that the oxidation is more complete and the removal rate of impurities such as pigments is increased, thereby obtaining a high-purity long-chain dibasic acid aqueous phase crystal product, and the obtained product quality is better. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments.

[0032] Therefore, the detailed description of the embodiments of the present application provided below is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

[0033] Unless otherwise specified, the materials, reagents, etc. used in the following examples can be obtained from commercial sources; the implementation methods used in the following examples are all conventional methods unless otherwise specified.

[0034] The present invention provides a method for oxidative decolorization of a long-chain dibasic acid, comprising the following steps:

[0035] S10, adjusting the material containing the long-chain dibasic acid to a mass concentration of the long-chain dibasic acid of 5% to 30%, and adjusting the pH value to a range of 3 to 10 according to the type of oxidant;

[0036] S20, putting the material obtained in step S10 into a reactor, and adding an oxidant for oxidation. During the oxidation process, the temperature of the reactor is maintained at 101-133° C., and the corresponding pressure is maintained at 0.108-0.304 MPa, and the oxidation time is 0.2-2 h;

[0037] S30, allowing the material oxidized in step S20 to cool naturally to below 90°C, performing solid-liquid separation, and obtaining a target product containing a long-chain dibasic acid.

[0038] Specifically, in step S10, the long-chain dibasic acid is a mixture of one or more of decanedioic acid, undecanedicarboxylic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedicarboxylic acid, hexadecanedioic acid, heptadecanedioic acid, and octadecanedicarboxylic acid. The material containing the long-chain dibasic acid comes from the fermentation liquid obtained after the long-chain dibasic acid is produced by microbial fermentation; or comes from the crude long-chain dibasic acid obtained by treating the fermentation liquid after the fermentation of the long-chain dibasic acid is finished, removing or reducing one or more of the bacteria, proteins, bacteria fragments, pigments, etc. in the fermentation liquid; or comes from the crude mixed long-chain dibasic acid obtained by treating the waste liquid containing the long-chain dibasic acid discharged during the production of the long-chain dibasic acid.

[0039] Furthermore, in step S10, the pH value is adjusted according to the type of oxidant. The oxidant selected in the present application is any one or more of ozone, hydrogen peroxide or sodium hypochlorite. When the oxidant is ozone, the pH value is adjusted to a range of 8 to 10; when the oxidant is hydrogen peroxide, the pH value is adjusted to a range of 3 to 10; when the oxidant is sodium hypochlorite, the pH value is adjusted to a range of 6 to 8. The amount of the oxidant added is 0.2% to 6% of the mass of the long-chain dibasic acid.

[0040] Furthermore, in step S20, during the oxidation process, activated carbon can be added as an oxidation catalyst according to actual needs, and the amount of activated carbon added is 1% to 8% of the mass of the long-chain dibasic acid. In addition, given that different substances have different oxidation degrees at different pH values, for example, substance A has the best oxidation effect at pH = 9.5, while substance B has the best oxidation effect at pH = 6. As the oxidation process proceeds, the specific substances contained in the material are also changing. The user can adjust the pH value according to actual needs during the oxidation process so that the material reacts under different pH conditions.

[0041] When the oxidation reaction is completed and step S30 is performed, the pH value of the material can be measured first. If the pH value is lower than 6, the pH value is first adjusted to 6 or above to obtain a liquid containing a long-chain dibasic acid, and then plate and frame decarbonization or other solid-liquid separation methods are used to obtain the target product containing a long-chain dibasic acid.

[0042] The following is a further explanation of the technical effects that can be achieved by this application through specific experimental data.

[0043] 1. Sample preparation

[0044] Example 1

[0045] Dodecanedioic acid, pH = 7.5, oxidized with sodium hypochlorite

[0046] The fermentation liquid of dodecanedioic acid obtained by fermentation was filtered through a ceramic membrane to obtain a ceramic membrane clear liquid, and the concentration of the ceramic membrane clear liquid was adjusted to 6.0%, and the pH value was adjusted to 7.5. 100g of the filtrate was placed in a high-pressure hydrothermal reactor, 0.5g of 13% sodium hypochlorite solution was added, the reactor was sealed, and heated and oxidized at 120°C in an oil bath at a pressure of about 0.198Mpa for 60 minutes, and the temperature was naturally cooled to room temperature after the oxidation was completed.

[0047] Comparative Example 1

[0048] Dodecanedioic acid, pH = 7.5, oxidized with sodium hypochlorite

[0049] The fermentation liquid of dodecanedioic acid obtained by fermentation was filtered through a ceramic membrane to obtain a ceramic membrane clear liquid, and the concentration of the ceramic membrane clear liquid was adjusted to 6.0%, and the pH value was adjusted to 7.5. 100g of the filtrate was placed in a high-pressure hydrothermal reactor, 0.5g of 13% sodium hypochlorite solution was added, the reactor was sealed, and heated and oxidized at 80°C in an oil bath at a pressure of about 0.1Mpa for 60 minutes, and the temperature was naturally cooled to room temperature after the oxidation was completed.

[0050] Example 2

[0051] Dodecanedioic acid, pH = 9.5, ozone oxidation

[0052] The fermentation liquid of dodecanedioic acid obtained by fermentation is filtered through a ceramic membrane to obtain a ceramic membrane clear liquid, and the concentration of the ceramic membrane clear liquid is adjusted to 6.0%, and the pH value is adjusted to 9.5. 1000g of the ceramic membrane clear liquid is taken and placed in a 10-liter fermentation tank, and the temperature in the fermentation tank is raised to 105°C and the pressure is about 0.124Mpa. The pressure and temperature are maintained, and ozone is introduced from the bottom of the fermentation tank for oxidation for 60 minutes (the ozone machine produces about 3g of ozone per hour). After the oxidation is completed, the temperature is naturally lowered to room temperature.

[0053] Comparative Example 2

[0054] Dodecanedioic acid, pH = 9.5, ozone oxidation

[0055] The dodecanedioic acid fermentation liquid obtained by fermentation is filtered through a ceramic membrane to obtain a ceramic membrane clear liquid, the concentration of the ceramic membrane clear liquid is adjusted to 6.0%, and the pH value is adjusted to 9.5. 1000g of the ceramic membrane clear liquid is taken and placed in a 10-liter fermentation tank, and the temperature in the fermentation tank is raised to 80°C and the pressure is about 0.1Mpa. The pressure and temperature are maintained, and ozone is introduced from the bottom of the fermentation tank for oxidation for 60 minutes (the ozone machine produces about 3g of ozone per hour). After the oxidation is completed, the temperature is naturally lowered to room temperature.

[0056] Example 3

[0057] Dodecanedioic acid, pH = 9.5, oxidized with hydrogen peroxide

[0058] The fermentation liquid of dodecanedioic acid obtained by fermentation was filtered through a ceramic membrane to obtain a ceramic membrane clear liquid, and the concentration of the ceramic membrane clear liquid was adjusted to 6.0%, and the pH value was adjusted to 9.5. 100g of the filtrate was placed in a high-pressure hydrothermal reactor, 0.2g of a 30% hydrogen peroxide solution was added, the reactor was sealed, and the oil bath was heated and oxidized at 101°C for 60 minutes under a pressure of about 0.108Mpa, and the temperature was naturally cooled to room temperature after the oxidation was completed.

[0059] Example 4

[0060] Dodecanedioic acid, pH = 9.5, oxidized with hydrogen peroxide

[0061] The fermentation liquid of dodecanedioic acid obtained by fermentation was filtered through a ceramic membrane to obtain a ceramic membrane clear liquid, and the concentration of the ceramic membrane clear liquid was adjusted to 6.0%, and the pH value was adjusted to 9.5. 100g of the filtrate was placed in a high-pressure hydrothermal reactor, 0.2g of a 30% hydrogen peroxide solution was added, the reactor was sealed, and the oil bath was heated and oxidized at 120°C for 60 minutes under a pressure of about 0.239Mpa, and the temperature was naturally cooled to room temperature after the oxidation was completed.

[0062] Example 5

[0063] Dodecanedioic acid, pH = 9.5, oxidized with hydrogen peroxide

[0064] The fermentation liquid of dodecanedioic acid obtained by fermentation was filtered through a ceramic membrane to obtain a ceramic membrane clear liquid, and the concentration of the ceramic membrane clear liquid was adjusted to 6.0%, and the pH value was adjusted to 9.5. 100g of the filtrate was placed in a high-pressure hydrothermal reactor, and 0.2g of a 30% hydrogen peroxide solution was added. The reactor was sealed, and heated and oxidized at 133°C in an oil bath at a pressure of about 0.304Mpa for 60 minutes. After the oxidation was completed, the solution was naturally cooled to room temperature and the transmittance of the solution was measured.

[0065] Comparative Example 3

[0066] Dodecanedioic acid, pH = 9.5, oxidized with hydrogen peroxide

[0067] The fermentation liquid of dodecanedioic acid obtained by fermentation was filtered through a ceramic membrane to obtain a ceramic membrane clear liquid, and the concentration of the ceramic membrane clear liquid was adjusted to 6.0%, and the pH value was adjusted to 9.5. 100g of the filtrate was placed in a high-pressure hydrothermal reactor, 0.2g of a 30% hydrogen peroxide solution was added, the reactor was sealed, and the oil bath was heated and oxidized at 80°C for 60 minutes under a pressure of about 0.1Mpa, and the temperature was naturally cooled to room temperature after the oxidation was completed.

[0068] 2. Transmittance measurement

[0069] The dibasic acid samples prepared in Examples 1 to 5 and Comparative Examples 1 to 3 were filtered, and the weight concentration of the dibasic acid samples was controlled at 6%. Then, the ceramic membrane clear solution with a concentration of 6%, and the dibasic acid samples prepared in Examples 1 to 5 and Comparative Examples 1 to 3 were tested for transmittance at 440 nm. The test results are shown in the following table:

[0070] sample temperature pressure 440nm transmittance 6% Ceramic membrane serum / / 42.3％ Example 1 120℃ About 0.198MPa 57.6％ Comparative Example 1 80℃ About 0.1MPa 48.6％ Example 2 105℃ About 0.124MPa 86.4％ Comparative Example 2 80℃ About 0.1MPa 60.3％ Example 3 101℃ About 0.108MPa 78.3％ Example 4 120℃ About 0.239MPa 88.5％ Example 5 133℃ About 0.304Mpa 90.7％ Comparative Example 3 80℃ About 0.1Mpa 65.5％

[0071] From the above measurement results, it can be seen that when the pH value and the oxidant used are consistent, when the temperature is between 101°C and 133°C (the corresponding pressure is between 0.108 and 0.304 MPa), the product transmittance of each embodiment is higher than that of the comparative example, indicating that the decolorization effect is better.

[0072] The above describes the specific embodiments of the present invention. Based on the above description, relevant personnel can make various changes and modifications without departing from the technical concept of the present invention.

Claims

1. A method for oxidative decolorization of a long-chain dibasic acid, characterized in that: The following steps are involved: S10, adjusting the material containing the long-chain dibasic acid to a mass concentration of the long-chain dibasic acid of 5% to 30%, and adjusting the pH value to a range of 3 to 10 according to the type of oxidant; S20, putting the material obtained in step S10 into a reactor, and adding an oxidant for oxidation. During the oxidation process, the temperature of the reactor is maintained at 101-133° C., and the corresponding pressure is maintained at 0.108-0.304 MPa, and the oxidation time is 0.2-2 h; The oxidant is one or more of ozone, hydrogen peroxide or sodium hypochlorite, and the amount of the oxidant added is 0.2% to 6% of the mass of the long-chain dibasic acid; S30, allowing the material oxidized in step S20 to cool naturally to below 90°C, performing solid-liquid separation, and obtaining a target product containing a long-chain dibasic acid.

2. The oxidative decolorization method of long-chain dibasic acid according to claim 1, characterized in that: In step S10, the material containing long-chain dibasic acids comes from the fermentation liquid obtained after the long-chain dibasic acid production is completed by microbial fermentation; or comes from the crude long-chain dibasic acid obtained by treating the fermentation liquid after the long-chain dibasic acid fermentation is completed to remove or reduce one or more of the bacteria, proteins, bacteria fragments, pigments, etc. in the fermentation liquid; or comes from the crude mixed long-chain dibasic acid obtained after the waste liquid containing long-chain dibasic acids discharged in the long-chain dibasic acid production process is treated.

3. The oxidative decolorization method of long-chain dibasic acid according to claim 1, characterized in that: The long-chain dibasic acid is a mixture of one or more of sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedicarboxylic acid, hexadecanedioic acid, heptadecanedioic acid and octadecanedicarboxylic acid.

4. The oxidative decolorization method of long-chain dibasic acid according to claim 1, characterized in that: In step S10, when the oxidant is ozone, the pH value is adjusted to a range of 8 to 10; when the oxidant is hydrogen peroxide, the pH value is adjusted to a range of 3 to 10; when the oxidant is sodium hypochlorite, the pH value is adjusted to a range of 6 to 8.

5. The oxidative decolorization method of long-chain dibasic acid according to claim 1, characterized in that: In step S20, activated carbon is added as an oxidation catalyst, and the added amount of the activated carbon is 1% to 8% of the mass of the long-chain dibasic acid.

6. The oxidative decolorization method of long-chain dibasic acid according to claim 1, characterized in that: In step S20, the pH is adjusted during the oxidation process so that the material is oxidized under different pH conditions.

7. The oxidative decolorization method of long-chain dibasic acid according to claim 1, characterized in that: In step S20, the temperature of the reactor is maintained at 105-125°C, and the corresponding pressure is maintained at 0.124-0.239 MPa.

8. The oxidative decolorization method of long-chain dibasic acid according to claim 1, characterized in that: In step S30, when the pH value of the material is lower than 6, the pH value is adjusted to 6 or above before solid-liquid separation to obtain a liquid containing a long-chain dibasic acid.

9. The oxidative decolorization method of long-chain dibasic acid according to claim 1, characterized in that: In step S30, the solid-liquid separation method adopted is plate and frame decarburization.