Oxidative cleavage catalyst of oleic acid, and preparation method and application thereof

Abstract

This invention discloses an oleic acid oxidative cracking catalyst, its preparation method, and its application, belonging to the field of catalyst preparation technology. The catalyst for the oxidative cracking of oleic acid to azelaic acid is prepared by: uniformly mixing phosphotungstic acid with an organic onium salt, and then ball milling the mixture in a ball mill jar. The preparation method is simple, generates no waste, and produces a catalyst with high yield and high activity. In the process of oleic acid cracking to azelaic acid, the conversion rate of oleic acid reaches 100%, and the selectivity of azelaic acid reaches 96%.

Description

Technical Field

[0001] This invention relates to an oleic acid oxidative cracking catalyst, its preparation method and application, belonging to the field of catalyst preparation technology. Background Technology

[0002] Azelaic acid, also known as azelaic acid, is an important organic compound with a C9 long-chain dicarboxylic acid structure. Due to its unique physicochemical properties, it exhibits irreplaceable application value in high-end industrial manufacturing, biomedicine, and other fields, resulting in significant economic added value. In the field of industrial materials, azelaic acid is a core monomer for synthesizing high-performance engineering plastics such as Nylon-69 and Nylon-610. These plastics possess excellent mechanical strength, heat resistance, and corrosion resistance, and are widely used in high-end equipment manufacturing fields such as automobile manufacturing, electronics, and aerospace. Simultaneously, it can also serve as a plasticizer, lubricant, and raw material for specialty resins, further expanding its application boundaries in the fine chemical industry. In the biomedical field, azelaic acid can effectively inhibit the growth and reproduction of Propionibacterium acnes while regulating the skin's keratinization process, making it a key active pharmaceutical ingredient for treating acne and widely used in topical dermatological preparations.

[0003] Currently, the mainstream production process for azelaic acid both domestically and internationally is the ozone oxidation cracking process for oleic acid. While this process has a certain industrial application foundation, it suffers from significant technical bottlenecks and application limitations. On the one hand, the ozone oxidation reaction places extremely high demands on equipment materials, requiring specialized reaction devices with excellent corrosion resistance and sealing performance, leading to a substantial increase in initial equipment investment costs. On the other hand, the ozone oxidation process consumes a lot of energy, and the reaction produces a variety of complex byproducts. The subsequent separation, purification, and treatment of these byproducts are cumbersome and costly, and may also cause secondary pollution problems, which is inconsistent with the current trend of green chemical industry development.

[0004] Compared to traditional ozone oxidation, the hydrogen peroxide oxidation process has become an important development direction for azelaic acid production due to its core advantages of being green and environmentally friendly. Hydrogen peroxide, as an oxidant, features high reaction selectivity and excellent azelaic acid yield, and its only byproduct is water, with no pollutant emissions, aligning with the requirements of low-carbon and environmentally friendly industrial development. However, the industrial application of the hydrogen peroxide oxidation process still faces many technical challenges: Among existing technologies, the oxidation system using tungstic acid as a catalyst and 60% hydrogen peroxide as an oxidant is a relatively mature technical route, achieving an oleic acid conversion rate of approximately 90% at 100℃. However, this process has significant safety hazards and cost drawbacks—60% hydrogen peroxide has a high risk of thermal decomposition and explosion at 100℃, requiring strict temperature control and safety protection systems in industrial production, increasing safety costs; simultaneously, the catalyst dosage is as high as 10% of the reaction system mass, leading not only to high catalyst consumption but also increasing the difficulty of separating catalyst residues in subsequent products, thus hindering the industrial-scale promotion of the process.

[0005] To address the technical shortcomings of the hydrogen peroxide oxidation method, related research focuses on developing novel catalytic systems. Patent 202310009793.2 discloses a method for the oxidative cracking of oleic acid catalyzed by a sodium lignosulfonate quaternary ammonium salt supported phosphotungstic acid catalyst. Under optimized reaction conditions, this method achieves an oleic acid conversion rate of 89.2% and an azelaic acid selectivity of 96.7%, demonstrating excellent azelaic acid yield and selectivity. However, the catalyst preparation process has significant drawbacks: it requires multiple chemical reactions and involves the use of various organic reagents and acid / alkali solutions, increasing the operational complexity of catalyst preparation and generating large amounts of high-concentration organic and acid / alkali wastewater. This wastewater has complex components and high pollutant concentrations, requiring complex wastewater treatment processes before discharge, significantly increasing the catalyst preparation cost and the burden of waste treatment.

[0006] Therefore, developing a novel catalyst that is simple to prepare, low in cost, green and pollution-free, and can efficiently catalyze the oxidative cracking of oleic acid to produce azelaic acid is of great practical significance and industrial application value for breaking through the technical bottleneck of azelaic acid production, reducing production costs, and promoting the green and efficient development of the industry. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides an oleic acid oxidative cracking catalyst, its preparation method, and its application. The preparation method of this catalyst is simple, and the process generates no waste. Furthermore, the prepared catalyst has high yield and high activity. When used in the process of oleic acid cracking to prepare azelaic acid, the conversion rate of oleic acid reaches 100%, and the selectivity of azelaic acid reaches 96%.

[0008] To achieve the above objectives, the following technical solution is provided: The first objective of this invention is to provide a method for preparing a catalyst for the catalytic oxidative cracking of oleic acid to azelaic acid, the method comprising the following steps: Phosphotungstic acid and organic onium salt are mixed evenly and then ball-milled in a ball mill jar to obtain the final product.

[0009] In one embodiment, the organic onium salt is any one of quaternary ammonium salt, oxonium salt, thionium salt, and quaternary phosphonium salt.

[0010] In one embodiment, the quaternary ammonium salt includes one or more of hexadecyltrimethylammonium bromide (CTAB), trioctylmethylammonium chloride (TOMAC), and hexadecyltrimethylammonium chloride (CTAC).

[0011] In one embodiment, the molar ratio of the phosphotungstic acid to the organic onium salt is 1:0.5~3; preferably 1:1~2.

[0012] In one embodiment, the parameters of the ball mill are: 200~500 r / min, 10~30 min; preferably 500 r / min, 20 min.

[0013] A second objective of this invention is to provide a catalyst prepared by the method described above.

[0014] A third objective of this invention is to provide an application of the catalyst described above in the catalytic oxidative cracking of oleic acid.

[0015] The fourth objective of this invention is to provide a method for preparing azelaic acid by oxidative cracking of oleic acid, wherein the method uses oleic acid and hydrogen peroxide as raw materials and carries out a catalytic reaction using the catalyst described above.

[0016] In one embodiment, the amount of catalyst used is 0.5-3% of the mass of oleic acid; preferably 1-2%.

[0017] In one embodiment, the temperature of the catalytic reaction is 80~100℃, preferably 90~95℃.

[0018] In one embodiment, the catalytic reaction takes 2 to 6 hours, preferably 4 to 6 hours.

[0019] In one embodiment, the amount of hydrogen peroxide used is 3 to 7 times the molar amount of oleic acid; preferably 5 to 7 times; more preferably 5 times.

[0020] In one embodiment, the hydrogen peroxide has a mass fraction of 30%.

[0021] The fifth objective of this invention is to provide a method for improving the selectivity of azelaic acid in the process of oxidative cracking of oleic acid to prepare azelaic acid, wherein the method uses oleic acid and hydrogen peroxide as raw materials and carries out a catalytic reaction with the catalyst described above.

[0022] Beneficial effects: (1) The present invention uses ball milling to prepare a composite catalyst for oleic acid oxidative cracking. Compared with the traditional catalyst preparation method, the catalyst preparation method of the present invention is simple and no waste is generated in the production process. (2) The composite catalyst for oleic acid oxidative cracking of the present invention has a good catalytic effect in the reaction of cracking oleic acid to prepare azelaic acid. The conversion rate of oleic acid and the selectivity of azelaic acid are higher than those of ordinary catalysts, and the catalyst dosage is small and the activity is high. The conversion rate of oleic acid reaches 100% and the selectivity of azelaic acid reaches 96%. Attached Figure Description

[0023] Figure 1 The gas chromatogram of the composite catalyst prepared in Example 1 for oleic acid cracking; Figure 2 This is the mass spectrum of dimethyl azelaate, the product of methyl azelaate esterification. Detailed Implementation

[0024] To facilitate a further understanding of the present invention, the following embodiments are provided for more detailed description. However, these embodiments are only for the purpose of helping to better understand the invention and are not intended to limit the scope or implementation principles of the invention. The implementation of the present invention is not limited to the following.

[0025] Example 1 A method for preparing a phosphotungstic acid / hexadecyltrimethylammonium bromide (CTAB) composite catalyst based on ball milling includes the following steps: S1: Mix 288g of phosphotungstic acid and 36.4g of CTAB evenly to obtain solid I; S2: Put solid I into the ball mill jar, and place the ball mill jar containing the material symmetrically in the all-around planetary ball mill; S3: Ball mill at 500 r / min for 20 min, and the resulting solid is the target catalyst phosphotungstic acid / CTAB.

[0026] Example 2 A method for preparing a phosphotungstic acid / trioctylmethylammonium chloride (TOMAC) composite catalyst based on ball milling, the method comprising the following steps: S1: Mix 288g of phosphotungstic acid and 36.4g of TOMAC evenly to obtain solid I; S2: Put solid I into the ball mill jar, and place the ball mill jar containing the material symmetrically in the all-around planetary ball mill; S3: Ball mill at 500 r / min for 20 min, and the resulting solid is the target catalyst phosphotungstic acid / TOMAC.

[0027] Comparative Example 1 A method for preparing tungstic acid / CTAB composite catalyst based on ball milling includes the following steps: S1: Mix 25g of tungstic acid and 36.4g of CTAB evenly to obtain solid I; S2: Put solid I into the ball mill jar, and place the ball mill jar containing the material symmetrically in the all-around planetary ball mill; S3: Ball mill at 500 r / min for 20 min, and the resulting solid is the target catalyst, tungstic acid / CTAB composite catalyst.

[0028] Comparative Example 2 A method for preparing phosphomolybdic acid / CTAB composite catalyst based on ball milling includes the following steps: S1: Mix 184.3g of phosphomolybdic acid and 36.4g of CTAB evenly to obtain solid I; S2: Put solid I into the ball mill jar, and place the ball mill jar containing the material symmetrically in the all-around planetary ball mill; S3: Ball mill at 500 r / min for 20 min, and the resulting solid is the target catalyst phosphomolybdic acid / CTAB.

[0029] Comparative Example 3 A method for preparing phosphotungstic acid-CTAB composite catalyst based on aqueous phase precipitation includes the following steps: S1: Dissolve 288g of phosphotungstic acid in 1L of water and label it Solution I; dissolve 36.4g of CTAB in 500mL of water and label it Solution II; S2: Heat solution I to 60 degrees Celsius, mechanically stir at 120 rpm, then slowly add solution II dropwise over 1 hour, then keep warm and continue stirring for 3 hours, and filter to obtain the solid; S3: Dry the solid at 80°C. The resulting solid is the target catalyst phosphotungstic acid-CTAB.

[0030] Result characterization 1. Yield: Actual product amount / Theoretical product amount × 100%. The catalyst yields prepared in the above examples are shown in Table 1: Table 1 Yields of different catalysts

[0031] Application Example 1 A method for preparing azelaic acid by oleic acid cracking, comprising the following steps: (1) Preparation of azelaic acid by hydrolysis of oleic acid with hydrogen peroxide 180 g of oleic acid was mixed with 1.8 g of the ball-milled composite catalyst prepared in Examples 1 and 2 above and added to a 250 mL four-necked flask. The mixture was mechanically stirred at 200 r / min, and then a reflux condenser was added. The mixture was heated to 95 °C and kept at that temperature for 10 min. 362 g of H2O2 (30 wt%) was then pumped into the four-necked flask at a constant rate using a plunger pump. The pumping time was 1 h. After all the H2O2 was pumped in, the mixture was kept at that temperature for 4 h. (2) Product yield detection: After the reaction was completed, the oil phase was allowed to stand and separate into layers. 0.5 g of the oil phase was added to a 25 mL pressure-resistant tube, followed by 5 mL of methanol and 5 drops of concentrated sulfuric acid. The reaction was carried out at 80 °C for 1 h. After the reaction was completed, 5 mL of saturated sodium chloride and 10 mL of isooctane were added for extraction three times. The oil phase was retained and detected by gas chromatography to obtain the gas phase yield of azelaic acid and the conversion rate of oleic acid.

[0032] Application Comparative Example 1 A method for preparing azelaic acid by direct catalytic cracking of oleic acid using unreconstituted phosphotungstic acid and CTAB, comprising the following steps: (1) Preparation of azelaic acid by oxidizing oleic acid with hydrogen peroxide: 180 g of oleic acid, 4.8 g of phosphotungstic acid and 0.6 g of CTAB were mixed and added to a 250 mL four-necked flask. The mixture was mechanically stirred at 200 r / min, and a reflux condenser was added. The mixture was heated to 95℃ and kept warm for 10 min. 362 g of H2O2 was pumped into the four-necked flask at a constant rate using a plunger pump. The pumping time was 1 h. After all the H2O2 was pumped in, the mixture was kept warm for 4 h. (2) Product yield detection: After the reaction was completed, the oil phase was allowed to stand and separate into layers. 0.5 g of the oil phase was added to a 25 mL pressure-resistant tube, followed by 5 mL of methanol and 5 drops of concentrated sulfuric acid. The reaction was carried out at 80 °C for 1 h. After the reaction was completed, 5 mL of saturated sodium chloride and 10 mL of isooctane were added for extraction three times. The oil phase was retained and detected by gas chromatography to obtain the gas phase yield of azelaic acid and the conversion rate of oleic acid.

[0033] Application Comparative Example 2 A method for preparing azelaic acid by catalyzing the cracking of oleic acid using a phosphotungstic acid-CTAB composite catalyst synthesized in an aqueous phase, comprising the following steps: (1) Preparation of azelaic acid by oxidizing oleic acid by hydrolysis: 180 g of oleic acid and 10.8 g of phosphotungstic acid-CTAB (aqueous phase synthesis) catalyst prepared in Comparative Example 3 were added to a 250 mL four-necked flask and mechanically stirred at 200 r / min. A reflux condenser was added, and the mixture was heated to 95℃ and kept warm for 10 min. 362 g of H2O2 was pumped into the four-necked flask at a constant rate using a plunger pump. The pumping time was 1 h. After all the H2O2 was pumped in, the mixture was kept warm for 4 h. (2) Product yield detection: After the reaction was completed, the oil phase was allowed to stand and separate into layers. 0.5 g of the oil phase was added to a 25 mL pressure-resistant tube, followed by 5 mL of methanol and 5 drops of concentrated sulfuric acid. The reaction was carried out at 80 °C for 1 h. After the reaction was completed, 5 mL of saturated sodium chloride and 10 mL of isooctane were added for extraction three times. The oil phase was retained and detected by gas chromatography to obtain the gas phase yield of azelaic acid and the conversion rate of oleic acid.

[0034] Application Comparative Example 3 A method for preparing azelaic acid by catalyzing the cracking of oleic acid using a phosphotungstic acid-CTAB composite catalyst synthesized in an aqueous phase, comprising the following steps: (1) Preparation of azelaic acid by oxidizing oleic acid by hydrolysis: 180 g of oleic acid and 1.8 g of phosphotungstic acid-CTAB (aqueous phase synthesis) catalyst prepared in Comparative Example 3 were added to a 250 mL four-necked flask and mechanically stirred at 200 r / min. A reflux condenser was added, and the mixture was heated to 95℃ and kept warm for 10 min. 362 g of H2O2 was pumped into the four-necked flask at a constant rate using a plunger pump. The pumping time was 1 h. After all the H2O2 was pumped in, the mixture was kept warm for 4 h. (2) Product yield detection: After the reaction was completed, the oil phase was allowed to stand and separate into layers. 0.5 g of the oil phase was added to a 25 mL pressure-resistant tube, followed by 5 mL of methanol and 5 drops of concentrated sulfuric acid. The reaction was carried out at 80 °C for 1 h. After the reaction was completed, 5 mL of saturated sodium chloride and 10 mL of isooctane were added for extraction three times. The oil phase was retained and detected by gas chromatography to obtain the gas phase yield of azelaic acid and the conversion rate of oleic acid.

[0035] Application Comparative Example 4 A method for preparing azelaic acid by oleic acid cracking, comprising the following steps: (1) Preparation of azelaic acid by hydrolysis of oleic acid with hydrogen peroxide 180 g of oleic acid was mixed with 1.8 g of the ball-milled composite catalyst prepared in Comparative Examples 1 and 2, respectively, and added to a 250 mL four-necked flask. The mixture was mechanically stirred at 200 r / min, and then a reflux condenser was added. The mixture was heated to 95 °C and kept at that temperature for 10 min. 362 g of H2O2 (30 wt%) was then pumped into the four-necked flask at a constant rate using a plunger pump. The pumping time was 1 h. After all the H2O2 was pumped in, the mixture was kept at that temperature for 4 h. (2) Product yield detection: After the reaction was completed, the oil phase was allowed to stand and separate into layers. 0.5 g of the oil phase was added to a 25 mL pressure-resistant tube, followed by 5 mL of methanol and 5 drops of concentrated sulfuric acid. The reaction was carried out at 80 °C for 1 h. After the reaction was completed, 5 mL of saturated sodium chloride and 10 mL of isooctane were added for extraction three times. The oil phase was retained and detected by gas chromatography to obtain the gas phase yield of azelaic acid and the conversion rate of oleic acid.

[0036] Oleic acid conversion rate: (1 - oleic acid content in the reaction solution) * 100%; Azelaic acid selectivity: Azelaic acid content in the reaction solution / (Azelaic acid content + Nonanalic acid content + Epoxy fatty acid content + Dihydroxy fatty acid content in the reaction solution) * 100%; the results are shown in Table 2: Table 2. Effect of different catalysts on the catalytic cracking of oleic acid to azelaic acid

[0037] Application Example 2: Effect of different molar ratios of phosphotungstic acid / CTAB on the preparation of azelaic acid from oleic acid cracking The preparation of the phosphotungstic acid / CTAB composite catalyst differs from that in Example 1 only in that the molar ratio of phosphotungstic acid and CTAB is adjusted to 1:0.5~3; all other parameters and conditions are the same as in Example 1.

[0038] The composite catalyst prepared above was used to crack oleic acid to prepare azelaic acid, using the same method as in Application Example 1. The results are shown in Table 3.

[0039] Table 3. Effect of different molar ratios of CTAB-Na2WO4 on the preparation of azelaic acid from oleic acid cracking.

[0040] The results in the table show that the catalyst exhibits high activity when the molar ratio of phosphotungstic acid to CTAB is within the range of 1:(1-2). However, the catalytic activity significantly decreases when the surfactant content exceeds three times the molar amount of the tungsten-containing compound. Similarly, the catalytic activity also decreases when the surfactant content is lower than the amount of the tungsten-containing compound, likely because a small amount of surfactant is insufficient to ensure adequate mixing and contact between the oil and water phases. The best catalytic effect is achieved when the molar ratio of phosphotungstic acid to CTAB is 1:1, resulting in 100% oleic acid conversion and 96% azelaic acid yield.

[0041] Application Example 3: Effect of Different Phosphotungstic Acid / CTAB Composite Catalyst Doses on the Preparation of Azelaic Acid from Oleic Acid Cracking The only difference from Application Example 1 is that the amount of composite catalyst added (based on the mass of oleic acid) is adjusted; all other parameters and conditions are the same as in Application Example 1.

[0042] Table 4. Effect of different phosphotungstic acid / CTAB composite catalyst addition amounts on the production of azelaic acid from oleic acid cracking.

[0043] As shown in Table 4, the catalyst exhibits the best catalytic effect when the catalyst dosage is 1% of the oleic acid mass, achieving a 100% conversion rate for oleic acid and a 96% yield for azelaic acid. Reducing the catalyst dosage decreases both the reaction conversion rate and selectivity, while increasing the catalyst dosage does not increase either the reaction conversion rate or selectivity. This demonstrates that the appropriate dosage plays a crucial role in the catalyst's activity.

[0044] Application Example 4: Effect of different reaction temperatures on the preparation of azelaic acid from oleic acid cracking Taking the phosphotungstic acid / CTAB composite catalyst of Example 1 as an example, based on the application of Example 1, the effect of only changing the reaction temperature on the preparation of azelaic acid by cracking oleic acid was investigated.

[0045] The results are shown in Table 5. It can be seen that increasing the temperature is beneficial to the cracking of oleic acid to produce azelaic acid. The catalytic effect is best when the temperature is 95℃. When the temperature is further increased to 100℃, the yield of azelaic acid decreases significantly, which is considered to be the adverse effect of hydrogen peroxide boiling.

[0046] Table 5. Effect of reaction temperature on the preparation of azelaic acid from oleic acid cracking.

[0047] Application Example 5: Effect of Different Reaction Times on the Preparation of Azelaic Acid from Oleic Acid by Cracking Taking the phosphotungstic acid / CTAB catalyst of Example 1 as an example, based on the application of Example 1, only the effect of changing the heat preservation reaction time on the cracking of oleic acid to prepare azelaic acid was investigated.

[0048] The results are shown in Table 6. It can be seen that increasing the reaction time can improve the conversion rate of oleic acid and the yield of azelaic acid. When the holding time is 4 hours, oleic acid is completely converted and the yield of azelaic acid is relatively high. Further increasing the reaction time does not significantly change the yield of azelaic acid, but the color of the reaction solution deepens.

[0049] Table 6. Effect of changing reaction time on the preparation of azelaic acid from oleic acid cracking.

[0050] Application Example 6: Effect of Different Hydrogen Peroxide Doses on the Preparation of Azelaic Acid from Oleic Acid Crack Taking the phosphotungstic acid / CTAB composite catalyst of Example 1 as an example, based on the application of Example 1, only the amount of hydrogen peroxide was changed to affect the production of azelaic acid from oleic acid cracking.

[0051] The experimental results are shown in Table 5. It can be seen that increasing the amount of hydrogen peroxide can improve the conversion rate of oleic acid and the yield of azelaic acid. When the amount of hydrogen peroxide is 5 times the molar amount of oleic acid, oleic acid is completely converted, and the yield of azelaic acid is relatively high. Further increasing the reaction time does not significantly change the yield of azelaic acid, but the color of the reaction solution deepens.

[0052] Table 6. Effect of changing reaction time on the preparation of azelaic acid from oleic acid cracking.

[0053] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A method for preparing a catalyst for the catalytic oxidative cracking of oleic acid to azelaic acid, characterized in that, The method includes the following: Phosphotungstic acid and organic onium salt are mixed evenly and then ball-milled in a ball mill jar to obtain the final product.

2. The method according to claim 1, characterized in that, The organic onium salt is any one of quaternary ammonium salt, oxonium salt, thionium salt, and quaternary phosphonium salt.

3. The method according to claim 1, characterized in that, The quaternary ammonium salt includes one or more of hexadecyltrimethylammonium bromide (CTAB), trioctylmethylammonium chloride (TOMAC), and hexadecyltrimethylammonium chloride (CTAC).

4. The method according to claim 1, characterized in that, The molar ratio of the phosphotungstic acid and the organonium salt is 1:0.5~3.

5. The catalyst prepared by the method according to any one of claims 1 to 4.

6. The application of the catalyst according to claim 5 in the catalytic oxidative cracking of oleic acid.

7. A method for preparing azelaic acid by oxidative cracking of oleic acid, characterized in that, The method involves using oleic acid and hydrogen peroxide as raw materials and carrying out a catalytic reaction using the catalyst described in claim 5.

8. The method according to claim 7, characterized in that, The amount of catalyst used is 0.5-3% of the mass of oleic acid.

9. The method according to claim 7, characterized in that, The amount of hydrogen peroxide used is 3 to 7 times the molar amount of oleic acid.

10. A method for improving the selectivity of azelaic acid in the process of oxidative cracking of oleic acid to prepare azelaic acid, characterized in that, The method uses oleic acid and hydrogen peroxide as raw materials and carries out a catalytic reaction using the catalyst described in claim 5.

Images