A method for preparing high-quality bio-based 1,9-nonanediol

Abstract

This invention discloses a method for preparing high-quality bio-based 1,9-nonanediol, comprising the following steps: transesterification, precipitation, fatty acid methyl ester refining, ozone oxidation pyrolysis, solvent recovery, esterification, dimethyl azelaate refining, and hydrogenation to obtain high-quality bio-based 1,9-nonanediol. This invention achieves gradient and full-component utilization of vegetable oil raw materials: the oil-based portion of triglycerides is used to produce high-quality bio-based 1,9-nonanediol, while simultaneously producing byproducts such as methyl palmitate, methyl stearate, propionic acid, hexanoic acid, and nonanoic acid; the glycerol-based portion of triglycerides is used as a byproduct of glycerol production. This invention utilizes esterification to reconstruct the products of ozone oxidation pyrolysis, converting the high-boiling-point monomethyl azelaate into the low-boiling-point dimethyl azelaate, achieving efficient separation from saturated fatty acid methyl esters. The dimethyl azelaate, as a raw material, is then hydrogenated to obtain high-quality nonanediol, significantly reducing production costs.

Description

Technical Field

[0001] This invention belongs to the field of oleochemical technology, specifically relating to a method for preparing high-quality bio-based 1,9-nonanediol from vegetable oil. Background Technology

[0002] 1,9-Nonanediol is a white powder or flaky crystal with a melting point of 45°C and a refractive index of 1.456. It is an important organic diol and a widely used organic raw material, extensively used in the production of polyesters, polyurethanes, plasticizers, fragrances, and synthetic lubricants.

[0003] The main preparation processes for 1,9-nonanediol include the nonanal reduction method and the fatty acid reduction method. Kuraray Corporation of Japan isomerizes n-octyldienol to n-octylenal, then hydroformylates it to 1,9-nonanedial, and finally reduces it with hydrogen to obtain 1,9-nonanediol (Chang Zhicheng, A New Method for Synthesizing N-Octanol and Various Diols Using Noble Metal Complex Catalysts, Surfactant Industry [J], 2000, No. 4). This mainstream preparation process heavily relies on non-renewable resources such as petroleum and coal. In contrast, bio-based nonanediol can effectively break free from dependence on petroleum resources. Therefore, there is an urgent need to develop a new method for preparing bio-based 1,9-nonanediol. Patent CN117623862 A discloses a method for preparing 1,9-nonanediol from polyazelic anhydride via hydrogenation; however, this method still suffers from problems such as limited raw material sources, immature process, low efficiency, unstable product quality, and high production costs. Summary of the Invention

[0004] In view of the above-mentioned problems existing in the prior art, the purpose of this invention is to provide a method for preparing high-quality bio-based 1,9-nonanediol from vegetable oil, providing a promising industrialized and sustainable production method for the preparation of high-quality bio-based nonanediol.

[0005] The technical solution adopted in this invention is as follows:

[0006] A method for preparing high-quality bio-based 1,9-nonanediol includes the following steps:

[0007] S1: The raw vegetable oil is successively subjected to transesterification, precipitation, and fatty acid methyl ester refining to obtain fatty acid methyl ester products;

[0008] S2: After fatty acid methyl esters are premixed with solvents, ozone is first introduced into the mixture for ozone oxidation and cracking reaction. Then, excess air is introduced for oxidation and cracking reaction. After the reaction, the solvent is recovered by distillation. At the same time, low carbonic acid containing propionic acid, malonic acid and nonanoic acid is produced as a byproduct. After the solvent is recovered, a liquid containing a high content of azelaic acid monomethyl ester is obtained. This liquid enters the next esterification reaction process.

[0009] S3: The liquid in step S2 undergoes an esterification reaction with methanol under the action of a solid acid catalyst. The liquid after the esterification reaction then enters the dimethyl azelaate refining process, which is to first remove alcohol and then separate it by high vacuum distillation to obtain dimethyl azelaate intermediate product with a purity of more than 99.5%. At the same time, saturated oil products containing methyl palmitate and methyl stearate are produced as by-products.

[0010] S4: Dimethyl azelaate undergoes a hydrogenation reaction under the action of a hydrogenation catalyst to obtain high-quality bio-based 1,9-nonanediol.

[0011] Further, step S1 specifically involves the following process: raw vegetable oil and methanol undergo transesterification under the action of an alkaline catalyst. After the reaction, the liquid is separated by sedimentation to obtain crude glycerol and crude fatty acid methyl ester. The crude glycerol is then purified to obtain glycerol product, while the crude fatty acid methyl ester proceeds to the next step of fatty acid methyl ester purification. The fatty acid methyl ester purification process involves the crude fatty acid methyl ester being de-alcoholized and distilled under high vacuum to obtain fatty acid methyl ester product.

[0012] Furthermore, the vegetable oil includes soybean oil, rapeseed oil, canola oil, or peanut oil, and the acid value of the raw vegetable oil is less than 1 mg KOH / g.

[0013] Furthermore, in the transesterification reaction process, the alkaline catalyst is sodium hydroxide, potassium hydroxide, sodium methoxide, or potassium methoxide; the amount of methanol is controlled at 20-40% of the weight of the vegetable oil; the amount of alkaline catalyst is controlled at 0.5-1.5% of the weight of the vegetable oil; the reaction temperature is controlled at 45-65℃; and the reaction time is controlled at 0.5-1.5h.

[0014] In the settling process, the settling temperature is controlled at 25~50℃ and the settling time is 0.5~1.5h.

[0015] Furthermore, in the de-alcoholization process of fatty acid methyl ester refining, the flash de-alcoholization pressure is atmospheric pressure, and the flash temperature is controlled at 90~105℃; the fatty acid methyl ester distillation conditions are that the kettle liquid temperature is controlled at 180~210℃, and the operating pressure is controlled at 100~600Pa.

[0016] Furthermore, in the ozone oxidation pyrolysis reaction process, the solvent is selected from hexanoic acid, octanoic acid, or nonanoic acid. The mass ratio of fatty acid methyl ester to solvent is controlled at 1:3~4. The molar ratio between the total amount of ozone introduced during the ozone oxidation pyrolysis reaction and the carbon-carbon double bond of the fatty acid methyl ester is controlled at 1.1-1.5:1. The ozone oxidation reaction temperature is controlled at 25~30℃, and the reaction time is controlled at 3~5h. The oxidation pyrolysis reaction under air is controlled at 80~100℃, and the reaction time is controlled at 5~7h. After the unsaturated fatty acid methyl ester undergoes ozone oxidation pyrolysis, a five-membered cyclic ozonide is generated. The five-membered cyclic ozonide is further oxidized and pyrolyzed by air to generate monomethyl azelaic acid, as well as byproducts such as nonanoic acid, hexanoic acid, and propionic acid.

[0017] Furthermore, in the distillation and solvent recovery process, the low carbonic acid byproduct of the ozone oxidation cracking reaction is separated and the solvent is recovered by high-vacuum distillation, with the pressure at the top of the column controlled at 100~600Pa and the temperature of the liquid in the bottom of the column controlled at 110~160℃.

[0018] Furthermore, in the esterification reaction process, a vaporized bed reactor is used for the reaction, and a solid acid catalyst is packed in the vaporized bed reactor; the solid acid catalyst is selected from macroporous strong acid ion exchange resins PX-801, DH-01, or LS-51; the catalyst bed temperature of the vaporized bed reactor is controlled at 120~150℃, and the feed molar ratio of methanol to monomethyl azelaic acid is controlled at 2~6:1.

[0019] Furthermore, in the dimethyl azelaate refining process of step S3, the flash evaporation pressure of the de-alcoholization process is atmospheric pressure, and the flash evaporation temperature is controlled at 110~130℃; the dimethyl azelaate distillation conditions are an operating pressure controlled at 100~600Pa and a kettle liquid temperature controlled at 130~160℃.

[0020] Furthermore, in the hydrogenation reaction process, a fixed-bed reactor is used for the reaction, and the fixed-bed reactor is filled with a hydrogenation catalyst; the hydrogenation catalyst is selected from RK-DC copper-based catalyst or CuCAT copper-based catalyst; the operating temperature of the fixed-bed reactor is controlled at 190~250℃, the operating pressure is 5-7MPa, and the ratio of the gas flow rate of hydrogen to the liquid flow rate of dimethyl azelate is controlled at 600~1000:1.

[0021] The beneficial effects achieved by this invention are:

[0022] 1. This invention provides an economical, green, and efficient method for preparing high-quality bio-based 1,9-nonanediol using vegetable oil as raw material. It features strong sustainability, high product quality, and ease of industrialization.

[0023] 2. The process of this invention features high atom economy and environmental friendliness, achieving gradient and full-component utilization of vegetable oil raw materials. The triglyceride portion of the vegetable oil is used to produce high-quality bio-based 1,9-nonanediol, while simultaneously producing byproducts such as methyl palmitate, methyl stearate, propionic acid, hexanoic acid, and nonanoic acid; the glycerol portion of the triglyceride portion of the vegetable oil is used to produce glycerol products, maximizing the utilization value of vegetable oil raw materials.

[0024] 3. This invention ingeniously utilizes esterification to reconstruct the products of ozone oxidation pyrolysis, converting high-boiling-point monomethyl azelaate (boiling point approximately 370-380℃) into low-boiling-point dimethyl azelaate (boiling point approximately 276℃), achieving efficient separation from saturated fatty acid methyl esters (boiling point approximately 330-350℃). The purity of the obtained dimethyl azelaate can be consistently maintained above 99.5%. Subsequent hydrogenation yields high-quality nonanediol, with the purified nonanediol maintaining a purity consistently above 99.9%, significantly reducing production costs and improving nonanediol quality. This method boasts advantages such as broad raw material applicability, high atom economy, green efficiency, and high product yield, making it particularly suitable for the stable industrial production of high-quality bio-based 1,9-nonanediol.

[0025] 4. Methanol serves as a carrier for the utilization and conversion of unsaturated oils. It is consumed as a reactant in the transesterification reaction of vegetable oils and the esterification reaction of monomethyl azelaic acid. At the same time, it is also regenerated as a product of the hydrogenation reaction of dimethyl azelaic acid, which can be recycled and significantly reduce production costs. Attached Figure Description

[0026] Figure 1 This is a process flow diagram for the production of high-quality bio-based 1,9-nonanediol in this application. Detailed Implementation

[0027] 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.

[0028] Example 1: The process for preparing 1,9-nonanediol from soybean oil includes the following steps (process flow diagram as shown). Figure 1 (as shown)

[0029] 1) Transesterification reaction section: The vegetable oil used in Example 1 was soybean oil, and its fatty acid composition distribution is shown in Table 1. 500g of soybean oil was preheated to 60°C and then transferred to the reaction vessel. A preheated NaOH methanol solution was added (the amount of NaOH was 1% of the weight of the soybean oil, and the amount of methanol was 30% of the weight of the soybean oil). The reaction time was 1 hour, and the triglycerides were completely converted (the concentration was below the detection limit).

[0030] Table 1. Fatty acid composition of soybean oil raw materials

[0031] .

[0032] 2) Sedimentation section: The material after the transesterification reaction is allowed to stand at 30°C for 1 hour, and then it settles and separates into two phases: the upper layer is crude soybean oil methyl ester and the lower layer is crude glycerol.

[0033] 3) Fatty acid methyl ester refining section: Crude soybean oil methyl ester is flash-distilled at atmospheric pressure and a flash temperature of 100℃ to remove methanol. The methanol removed can be reused in the transesterification reaction. After high-vacuum distillation of crude soybean oil methyl ester, soybean oil methyl ester product is obtained with a yield of 95.4%, a purity of 99.6%, and an iodine value of 116 gI2 / 100g oil, which is used in the next step of ozone oxidation cracking reaction. The plant bitumen remaining in the distillation column bottom is converted into high-value-added hydrocarbon liquid fuel after high-temperature gasification according to the technology disclosed in patent CN116120958.

[0034] 4) Glycerol refining section: Crude glycerol is flash-distilled at atmospheric pressure and a flash temperature of 115°C to remove methanol. The methanol removed can be reused for transesterification. Subsequently, the crude glycerol after methanol removal is distilled under high vacuum to obtain industrial-grade glycerol with a purity of >95% and a yield of 91.3%. The glycerol pitch remaining in the distillation column bottom is vaporized by microwave according to the technology disclosed in patent CN112678772 to obtain high-quality syngas and high-purity sulfate.

[0035] 5) Ozone oxidation and pyrolysis reaction section: 400g of refined soybean oil methyl ester and 1400g of hexanoic acid were premixed (the mass ratio of soybean oil methyl ester to solvent hexanoic acid was 1:3.5). An ozone-oxygen mixture with an inlet flow rate of 110g / h was introduced, and the ozonation reaction was carried out at 30℃ for 4h. The conversion rate of unsaturated fatty acid methyl ester was greater than 99%. The molar ratio of the total ozone introduced during the 4h reaction to the carbon-carbon double bonds of soybean oil methyl ester was 1.2:1. Then, the reaction temperature was increased to 90~95℃, and the oxidative pyrolysis reaction was carried out for 6h under the condition of air introduction. The final conversion rate of ozonides reached more than 98%. Analysis showed that the yield of monomethyl azelaic acid in the pyrolysis products reached about 83%.

[0036] 6) Solvent Recovery Section: The feed liquid after the ozone oxidation cracking reaction is subjected to high-vacuum distillation. The operating pressure at the top of the column is controlled at about 500 Pa, and the temperature of the bottom liquid is controlled at 110~160℃. The distillate at the top of the column after distillation yields hexanoic acid solvent and low-carbonic acid byproducts of the ozone oxidation cracking reaction, such as malonic acid and propionic acid. The resulting feed liquid can be further distilled to separate and recover the hexanoic acid solvent, and obtain byproducts such as propionic acid, malonic acid, and nonanoic acid. The bottom liquid of the column yields a feed liquid with a high content of monomethyl azelaic acid, of which the content of monomethyl azelaic acid is about 55.14%, and the content of other saturated methyl esters is about 44.86%.

[0037] 7) Esterification reaction section: The ozone oxidation cracking reaction liquid after solvent recovery is pumped into a vaporization bed reactor filled with LS-51 resin catalyst (purchased from Shaanxi Lanshen Special Resin Co., Ltd.), while methanol is pumped into the vaporization kettle. The temperature of the vaporization kettle is controlled at 140℃ to allow the methanol to vaporize rapidly. The residence time of the ozone oxidation cracking reaction liquid in the catalyst bed of the vaporization bed reactor is about 90 minutes, the bed temperature is 140℃, the molar ratio of methanol to azelaic acid monomethyl ester feed liquid is 4:1, and the conversion rate of azelaic acid monomethyl ester reaches more than 99.5%.

[0038] 8) Dimethyl azelaate refining section: The esterification reaction material is flash-distilled to remove methanol under normal pressure and temperature of 120℃. The removed methanol is recovered by distillation and can be reused in the esterification reaction. The esterification reaction liquid after methanol removal is further subjected to high-vacuum distillation. The operating pressure at the top of the column is controlled at about 500Pa, and the temperature of the liquid in the bottom of the column is controlled at 130~140℃. The distillation yields dimethyl azelaate intermediate with a purity greater than 99.5%, which is used in the subsequent hydrogenation reaction section. The distillation yield reaches 94.9%. The saturated methyl ester in the bottom of the column can be further distilled under high vacuum to obtain byproducts such as methyl palmitate and methyl stearate.

[0039] 9) Hydrogenation Reaction Section: Using RK-DC copper-based catalyst (20-40 mesh, from Dalian Ruike Technology Co., Ltd.), with a catalyst packing volume of 100 mL, a dimethyl azelaate flow rate of 0.2 mL / min, and a hydrogen flow rate of 180 mL / min, a hydrogenation reaction was carried out at an operating temperature of 210℃ and an operating pressure of 6.5 MPa to prepare 1,9-nonanediol. The conversion rate of dimethyl azelaate was approximately 100%, and the selectivity of 1,9-nonanediol was approximately 98.9%. Simultaneously, the byproduct methanol was recycled to the transesterification reaction section. The performance indicators of the bio-based 1,9-nonanediol product after separation and purification are shown in Table 2.

[0040] Table 2. Performance indicators of bio-based 1,9-nonanediol products prepared from soybean oil

[0041] .

[0042] Example 2: The process for preparing 1,9-nonanediol from peanut oil includes the following steps (process flow diagram as shown). Figure 1 (as shown)

[0043] 1) Transesterification reaction section: The vegetable oil used in Example 2 was peanut oil, and its fatty acid composition distribution is shown in Table 3. 500g of peanut oil was preheated to 60°C and then transported to the reaction vessel. A preheated methanol solution of KOH was added (KOH was used at 1% of the weight of peanut oil, and methanol was used at 30% of the weight of peanut oil). The reaction time was 1 hour, and the triglycerides were completely converted (concentration was below the detection limit).

[0044] Table 3. Fatty acid composition of peanut oil raw materials

[0045] .

[0046] 2) Sedimentation section: The material after the transesterification reaction is allowed to stand at 30℃ for 1 hour, and then it settles and separates into two phases. The upper layer is crude peanut oil methyl ester and the lower layer is crude glycerol.

[0047] 3) Fatty acid methyl ester refining section: Crude peanut oil methyl ester is flash-distilled at atmospheric pressure and a flash temperature of 105℃ to remove methanol. The methanol removed can be reused in the transesterification reaction. After high-vacuum distillation of crude peanut oil methyl ester, peanut oil methyl ester product is obtained with a yield of 95.5%, a purity of 99.7%, and an iodine value of 95 gI2 / 100g oil, which is used in the next step of ozone oxidation cracking reaction. The plant bitumen remaining in the distillation column is converted into high-value-added hydrocarbon liquid fuel by high-temperature gasification according to the technology disclosed in patent CN116120958.

[0048] 4) Glycerol Refining Section: Crude glycerol is flash-distilled at atmospheric pressure and a flash temperature of 110°C to remove methanol. The removed methanol can be reused in the transesterification reaction. The crude glycerol after methanol removal is then distilled under high vacuum to obtain industrial-grade glycerol with a purity >95%, with a yield of 90.5%. The glycerol pitch remaining in the distillation column bottom is vaporized using the technology disclosed in patent CN112678772 to obtain high-quality syngas and high-purity sulfate.

[0049] 5) Ozone oxidation and pyrolysis reaction section: 400g of refined peanut oil methyl ester and 1600g of octanoic acid were premixed (the mass ratio of peanut oil methyl ester to solvent octanoic acid was 1:4). An ozone-oxygen mixture with an inlet flow rate of 90g / h was introduced, and the ozonation reaction was carried out at 30℃ for 4h. The conversion rate of unsaturated fatty acid methyl ester was greater than 99%. The molar ratio of the total ozone introduced during the 4h reaction to the carbon-carbon double bonds of peanut oil methyl ester was 1.2:1. Then, the reaction temperature was increased to 90~95℃, and the oxidative pyrolysis reaction was carried out for 7h under the condition of air introduction. The final conversion rate of ozonides reached more than 98%. Analysis showed that the yield of monomethyl azelaic acid in the pyrolysis products reached about 85%.

[0050] 6) Solvent Recovery Section: The ozone oxidation cracking reaction liquid is subjected to high-vacuum distillation. The pressure at the top of the distillation column is controlled at 100 Pa, and the temperature of the bottom liquid is controlled at 110~160℃ to remove the solvent octanoic acid and the by-product of ozone oxidation cracking reaction, low carbonic acid. The bottom liquid after distillation yields high-purity monomethyl azelaate, with the following mass fractions: monomethyl azelaate 75.14%, methyl palmitate 15.82%, and methyl stearate 9.04%.

[0051] 7) Esterification reaction section: The ozone oxidation cracking reaction liquid after solvent recovery is pumped into a vaporization bed reactor filled with PX-801 resin catalyst (purchased from Hangzhou Disheng Technology Co., Ltd.), and methanol is pumped into the vaporization kettle at the same time. The temperature of the vaporization kettle is controlled at 130℃ to make methanol vaporize rapidly. The residence time of the vaporization bed is 90min, the bed temperature is 130℃, the molar ratio of methanol to monomethyl azelaic acid feed is 4:1, and the conversion rate of monomethyl azelaic acid reaches more than 99.5%.

[0052] 8) Dimethyl azelaate refining section: The esterification reaction product is flash-distilled at 130°C under normal pressure to remove methanol. The removed methanol can be reused in the esterification reaction. The reaction liquid after methanol removal is distilled at a bottom temperature of 130-140°C, with a distillation yield of 95.0% and a top pressure of 100Pa to obtain dimethyl azelaate with a purity of 99.8%. The remaining saturated methyl ester is distilled off at a bottom temperature of 180-210°C and a top pressure of 100Pa. The remaining plant bitumen in the bottom of the distillation column can be further processed for resource recovery.

[0053] 9) Hydrogenation Reaction Section: After separation of high-purity dimethyl azelaate, hydrogenation was carried out using a CuCAT copper-based catalyst (Xunkai Catalysis, 2400T, tablet particle size 3.2×3.4mm), with a catalyst packing volume of 100mL, a dimethyl azelaate flow rate of 0.2mL / min, a hydrogen flow rate of 180mL / min, a reaction temperature of 200℃, and a reaction pressure of 6MPa. The conversion rate of dimethyl azelaate was approximately 100%, and the selectivity of 1,9-nonanediol was approximately 99.1%. Simultaneously, the byproduct methanol was recycled to the transesterification reaction section. The performance indicators of the bio-based 1,9-nonanediol product obtained after separation and purification are shown in Table 4.

[0054] Table 4. Performance indicators of bio-based 1,9-nonanediol products prepared from peanut oil

[0055] .

[0056] In summary, this invention utilizes vegetable oil as a raw material to prepare high-quality bio-based 1,9-nonanediol, achieving a gradient full-component utilization of vegetable oil raw materials: the oil-based portion of the vegetable oil is used to produce high-quality bio-based 1,9-nonanediol, while simultaneously producing byproducts such as methyl palmitate, methyl stearate, propionic acid, hexanoic acid, and nonanoic acid; the glycerol-based portion of the vegetable oil is used as a byproduct of glycerol production. This process features high atom economy, is green, efficient, and easily industrialized. Furthermore, through esterification, the boiling range difference between the ozonolysis product, monomethyl azelaic acid, and saturated oil is increased, cleverly achieving its separation from saturated methyl ester. This yields dimethyl azelaic acid intermediate with a purity greater than 99.5%. The high-purity dimethyl azelaic acid is subsequently hydrogenated to ultimately obtain high-quality bio-based 1,9-nonanediol, with the purified 1,9-nonanediol product maintaining a purity consistently above 99.9%.

[0057] The contents described in this specification are merely an enumeration of the implementation forms of the inventive concept, and the scope of protection of this invention should not be regarded as limited to the specific forms described in the embodiments.

Claims

1. A method for preparing high-quality bio-based 1,9-nonanediol, characterized in that, Includes the following steps: S1: The raw vegetable oil is successively subjected to transesterification, precipitation, and fatty acid methyl ester refining to obtain fatty acid methyl ester products; S2: After fatty acid methyl esters are premixed with solvents, ozone is first introduced into the mixture for ozone oxidation and cracking reaction. Then, excess air is introduced for oxidation and cracking reaction. After the reaction, the solvent is recovered by distillation. At the same time, low carbonic acid containing propionic acid, malonic acid and nonanoic acid is produced as a byproduct. After the solvent is recovered, a liquid containing a high content of azelaic acid monomethyl ester is obtained. This liquid enters the next esterification reaction process. S3: The liquid in step S2 undergoes an esterification reaction with methanol under the action of a solid acid catalyst. The liquid after the esterification reaction then enters the dimethyl azelaate refining process, which is to first remove alcohol and then separate it by high vacuum distillation to obtain dimethyl azelaate intermediate product with a purity of more than 99.5%. At the same time, saturated oil products containing methyl palmitate and methyl stearate are produced as by-products. S4: Dimethyl azelate undergoes a hydrogenation reaction under the action of a hydrogenation catalyst to obtain high-quality bio-based 1,9-nonanediol; The vegetable oils mentioned include soybean oil, rapeseed oil, canola oil, or peanut oil, and the acid value of the raw vegetable oil is less than 1 mg KOH / g; Step S1 is as follows: Raw vegetable oil and methanol undergo transesterification under the action of an alkaline catalyst. After the reaction, the liquid is separated by sedimentation to obtain crude glycerol and crude fatty acid methyl ester. The crude glycerol is then refined to obtain glycerol product, while the crude fatty acid methyl ester enters the next step of fatty acid methyl ester refining. The fatty acid methyl ester refining process involves the crude fatty acid methyl ester being subjected to dealcoholization and high-vacuum distillation to obtain fatty acid methyl ester product. In the ozone oxidation pyrolysis reaction process, the solvent is selected as hexanoic acid, octanoic acid, or nonanoic acid, and the mass ratio of fatty acid methyl ester to solvent is controlled at 1:3~4; the molar ratio between the total amount of ozone introduced during the ozone oxidation pyrolysis reaction and the carbon-carbon double bond of fatty acid methyl ester is controlled at 1.1-1.5:1; the ozone oxidation reaction temperature is controlled at 25~30℃; and the reaction time is controlled at 3~5h. The oxidation pyrolysis reaction under air action is controlled at 80~100℃; and the reaction time is controlled at 5~7h. In the esterification reaction process, the feed molar ratio of methanol to monomethyl azelaic acid is controlled at 2~6:

1.

2. The method for preparing a high-quality bio-based 1,9-nonanediol as described in claim 1, characterized in that, In the transesterification reaction process, the alkaline catalyst is sodium hydroxide, potassium hydroxide, sodium methoxide, or potassium methoxide; the amount of methanol is controlled at 20-40% of the weight of the vegetable oil; the amount of alkaline catalyst is controlled at 0.5-1.5% of the weight of the vegetable oil; the reaction temperature is controlled at 45-65℃; and the reaction time is controlled at 0.5-1.5h. In the settling process, the settling temperature is controlled at 25~50℃ and the settling time is 0.5~1.5h.

3. The method for preparing a high-quality bio-based 1,9-nonanediol as described in claim 1, characterized in that, In the de-alcoholization process of fatty acid methyl ester refining, the flash de-alcoholization pressure is atmospheric pressure, and the flash temperature is controlled at 90~105℃; the fatty acid methyl ester distillation conditions are that the kettle liquid temperature is controlled at 180~210℃, and the operating pressure is controlled at 100~600Pa.

4. The method for preparing high-quality bio-based 1,9-nonanediol as described in claim 1, characterized in that, In the distillation and solvent recovery process, the low carbonic acid byproduct of the ozone oxidation cracking reaction is separated and the solvent is recovered by high-vacuum distillation. The pressure at the top of the column is controlled at 100~600Pa, and the temperature of the liquid in the bottom of the column is controlled at 110~160℃.

5. The method for preparing a high-quality bio-based 1,9-nonanediol as described in claim 1, characterized in that, In the esterification reaction process, a vaporized bed reactor is used for the reaction, and a solid acid catalyst is packed in the vaporized bed reactor; the solid acid catalyst is selected from macroporous strong acid ion exchange resins PX-801, DH-01, or LS-51; the catalyst bed temperature of the vaporized bed reactor is controlled at 120~150℃.

6. The method for preparing a high-quality bio-based 1,9-nonanediol as described in claim 1, characterized in that, In the dimethyl azelaate refining process of step S3, the flash evaporation pressure of the alcohol removal process is atmospheric pressure, and the flash temperature is controlled at 110~130℃; the dimethyl azelaate distillation conditions are an operating pressure controlled at 100~600Pa and a kettle liquid temperature controlled at 130~160℃.

7. The method for preparing a high-quality bio-based 1,9-nonanediol as described in claim 1, characterized in that, In the hydrogenation reaction process, a fixed-bed reactor is used for the reaction, and the fixed-bed reactor is filled with a hydrogenation catalyst. The hydrogenation catalyst is selected from RK-DC copper-based catalysts or CuCAT copper-based catalysts. The operating temperature of the fixed-bed reactor is controlled at 190~250℃, the operating pressure is 5-7MPa, and the volume ratio of hydrogen to dimethyl azelate is controlled at 600~1000:1.

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