Method for synthesizing 2-keto acid by oxidizing 2-hydroxy acid with alternating magnetic field assisted fe3n catalyst

Abstract

The application belongs to the field of industrial catalysis, and particularly relates to a method for synthesizing 2-keto acid by alternation magnetic field assisted Fe3N catalytic oxidation of 2-hydroxy acid, wherein 2-hydroxy acid of formula 1 ( ), an oxidizing agent and Fe3N are mixed and catalytic oxidation is carried out under the assistance of an alternation magnetic field to obtain 2-keto acid of formula 2 ( ). The application innovatively finds that the alternation magnetic field assisted Fe3N catalytic oxidation of 2-hydroxy acid can cyclically synthesize 2-keto acid with high selectivity and high stability under mild conditions; thus, the industrial amplification production of 2-keto acid can be facilitated.

Description

Technical Field

[0001] This invention belongs to the field of industrial compound catalytic preparation, specifically relating to the technical field of oxidative synthesis of 2-keto acids from 2-hydroxy acids. Background Technology

[0002] 2-Keto acids, such as typical pyruvate, are important platform compounds widely used in the pharmaceutical, food, cosmetic, and chemical industries. Industrial methods for producing pyruvate mainly include chemical synthesis, bio-fermentation, and enzymatic catalysis.

[0003] For example, patent document CN110603321A discloses a pyruvate carboxylase, DNA encoding the pyruvate carboxylase, a plasmid containing the DNA, a microorganism, and its applications. Patent document CN106544285A discloses a method for enhancing the synthesis of pyruvate from *Saccharomyces cerevisiae*. Patent document CN118667893A discloses a method for synthesizing pyruvate using CO2, obtaining a pyruvate synthesis pathway comprising a first reaction module for converting CO2 to formaldehyde, a second reaction module for converting formaldehyde to dihydroxyacetone, and a third reaction module for converting dihydroxyacetone to pyruvate. In addition, existing technologies also report methods for preparing pyruvate by lactic acid oxidation. For example, patent document CN109053414A discloses a method for preparing pyruvate by ultrasonic-enhanced oxidation of lactic acid, which includes the following steps: (1) weighing disodium hydrogen phosphate, sodium dihydrogen phosphate and sodium bromide and dissolving them in water, stirring to prepare solution A for later use; (2) weighing lactic acid and sodium hydroxide and dissolving them in water to prepare sodium lactate aqueous solution B for later use; wherein, the molar ratio of lactic acid and sodium hydroxide is 1:0.9~1.1; (3) mixing solution A and solution B, stirring and cooling to 10~15 ℃; (4) turning on stirring and ultrasonication, maintaining 10~15 ℃, and adding sodium hypochlorite dropwise within 30 minutes; (5) after the dropwise addition is completed, keeping the reaction at a warm temperature; (6) stirring, adding hydrochloric acid to the above reaction solution below 20 ℃, adjusting the pH, and adding dichloromethane to extract pyruvate; (7) desolvating the extract to obtain pyruvate.

[0004] In summary, although existing technologies have reported some methods for preparing keto acids, chemical methods often use strong oxidants, require harsh conditions, and cause significant environmental pollution; biological methods suffer from long cycles, high costs, and difficulties in product separation; and enzymatic methods are limited by the cost, stability, and recyclability of enzymes. Therefore, developing efficient, stable, and recyclable heterogeneous catalysts to achieve the efficient conversion of lactic acid to pyruvate under mild conditions has significant industrial value. Summary of the Invention

[0005] To address the problems of unsatisfactory reactivity, selectivity, and cyclic catalytic stability in existing methods for the oxidation of 2-hydroxy acids to 2-keto acids, the present invention aims to provide a method for the oxidation of 2-hydroxy acids to 2-keto acids catalyzed by Fe3N under alternating magnetic fields, which aims to improve the reactivity, selectivity, and cyclic stability of the oxidation of 2-hydroxy acids to 2-keto acids under mild conditions.

[0006] To address the problems existing in the industrial catalytic synthesis of 2-keto acids, this invention provides the following improvement:

[0007] A method for synthesizing 2-keto acid by Fe3N catalysis catalyzed by alternating magnetic field involves mixing 2-hydroxy acid of formula 1, an oxidant and Fe3N, and catalytically oxidizing them under the assistance of an alternating magnetic field to obtain 2-keto acid of formula 2.

[0008] Formula 1

[0009] Formula 2

[0010] In Formula 1, R is a C1 to C6 alkyl, phenyl, substituted alkyl, or substituted phenyl group; the substituents in the substituted alkyl or substituted phenyl group include at least one of amino, alkoxy, hydroxyl, nitro, or halogen.

[0011] This invention innovatively discovers that by using an alternating magnetic field to assist Fe3N in catalytic oxidation of 2-hydroxy acids, 2-keto acids can be synthesized cyclically with high selectivity and high stability under mild conditions; thus, it can facilitate the industrial-scale production of 2-keto acids.

[0012] In this invention, the combination of Fe3N and an alternating magnetic field can achieve synergy, which can promote the activation and transformation of the hydroxyalkyl CH bond in Formula 1, thereby enabling the effective transformation from Formula 1 to Formula 2 under mild conditions.

[0013] In this invention, Fe3N is a nanoparticle with a D50 of 50~500 nm, preferably 80~320 nm, and its saturation magnetization is not less than 100 emu / g, for example, it can be 100~200 emu / g.

[0014] In this invention, Fe3N is obtained by ammoniation roasting with an iron source in an ammonia-containing atmosphere at a temperature of 500-800 °C;

[0015] The iron source includes at least one of the following: an organic framework material of iron, an oxide, an inorganic salt, an organic salt, or an element.

[0016] In this invention, the ammoniation calcination process described above can yield Fe3N phase catalyst, which can be combined with an alternating magnetic field to synergistically enhance the oxidation of 2-hydroxy acids.

[0017] As an optional solution, the Fe3N nanomaterial is made by Fe 0 The material is obtained by high-temperature nitriding (ammoniation roasting).

[0018] In this invention, the Fe 0 The material is prepared by reacting an iron source with a reducing agent;

[0019] Preferably, the iron source is Fe. 2+ Water-soluble salts;

[0020] Preferably, the reducing agent is at least one of NaBH4, N2H4, or ascorbic acid;

[0021] In this invention, the drying process is carried out under a reducing atmosphere;

[0022] Preferably, the drying temperature is 100~500 ℃, more preferably 150~300 ℃;

[0023] Preferably, the drying time is 0.5 to 4 hours, and more preferably 1 to 2 hours.

[0024] In this invention, the volume content of ammonia in the ammonia-containing atmosphere is 50 vol% or more; for example, it can be pure ammonia.

[0025] The flow rate of the ammonia-containing atmosphere can be adjusted as needed, for example, it can be greater than or equal to 100 ml / min, and further, it can be 100~300 ml / min.

[0026] Preferably, the temperature for ammoniation roasting is 600~700 ℃.

[0027] The ammoniation calcination time is 0.5-5 h; preferably 3-5 h.

[0028] In this invention, R is a C1-C3 alkyl group.

[0029] In this invention, the amount of Fe3N used in the catalytic process can be reasonably adjusted as needed. Theoretically, increasing the amount of catalyst helps to improve the conversion rate until catalytic equilibrium is reached. As an optional scheme, the molar ratio of 2-hydroxy acid and Fe3N in Formula 1 is 1:0.02~0.12; more specifically, it can be 1:0.05~0.12; and even more specifically, it can be 1:0.07~0.11.

[0030] In this invention, the alternating magnetic field strength is 5~35 A / cm, preferably 12.5~30 A / cm, and more preferably 18~25 A / cm; the frequency is 50~500 kHz, and more preferably 250~350 kHz.

[0031] In this invention, the oxidant is any oxidant capable of oxidizing the hydroxyl group at the -2-position of the carboxyl group. Considering industrial composition, it can be an oxygen-containing atmosphere, and more specifically, it can be air or oxygen.

[0032] In this invention, the temperature of the catalytic oxidation reaction stage is 15~70 ℃; preferably 20~40 ℃.

[0033] In this invention, the catalytic oxidation time can be reasonably adjusted as needed. Theoretically, extending the time is expected to increase the catalytic conversion rate until equilibrium is reached. This invention benefits from the combination of the alternating magnetic field and Fe3N, which can enhance catalytic efficiency. The reaction time can be as low as 5 min, and considering efficiency, it can be further extended to 5-20 min, and even further extended to 8-12 min.

[0034] In this invention, the Fe3N is recycled.

[0035] Beneficial effects

[0036] (1) This invention reveals for the first time the significant enhancing effect of alternating magnetic field (AMF) on the Fe3N catalytic oxidation reaction, providing a new strategy for improving the energy efficiency and reaction rate of the catalytic process.

[0037] (2) The catalytic system of the present invention is mild (at room temperature and pressure), environmentally friendly and highly selective, providing a promising new approach for the green and efficient industrial production of pyruvate. Attached Figure Description

[0038] Figure 1 The image shows the X-ray diffraction (XRD) pattern of the Fe3N nanomaterial prepared in Example 1.

[0039] Figure 2 The images shown are transmission electron microscope (TEM) images of the Fe3N nanomaterials prepared in Example 1, where a is a TEM image and b is a high-resolution TEM image.

[0040] Figure 3 The images shown are XPS images of the Fe3N nanomaterials prepared in Example 1, where a is the full X-ray photoelectron spectroscopy (XPS) spectrum of the Fe3N nanoparticles; b is the N 1s XPS image of the Fe3N nanoparticles; and c is the Fe 2p XPS image of the Fe3N nanoparticles.

[0041] Figure 4 The hysteresis loop is the Fe3N nanomaterial prepared in Example 1.

[0042] Figure 5 The results show the detection of lactic acid consumption by Fe3N nanomaterials of different concentrations in Example 3.

[0043] Figure 6 This is a comparison chart of lactic acid conversion rates under different alternating magnetic field (AMF) intensities in Example 4.

[0044] Figure 7 The graph shows the recycling performance of the Fe3N catalyst in Example 5.

[0045] Figure 8 The graph shows the catalytic selectivity test results of Fe3N nanomaterials in Example 6. Detailed Implementation

[0046] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be understood that these preferred embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. After reading this description, any modifications or alterations made to the present invention based on its principles also fall within the scope defined by the claims.

[0047] Example 1

[0048] Step 1: Preparation of Fe3N nanomaterials

[0049] Step 1.1: Preparation of Fe3N nanoparticles: Dissolve 194.6 mg FeCl2·4H2O in 30 mL of deionized water and purge with nitrogen to remove oxygen. While stirring vigorously, add 100 mL of 0.1 mol L⁻¹ of [a specific solution / concentration] dropwise. -1 Aqueous solutions of NaBH4 immediately produce a black precipitate. The precipitate is collected by centrifugation, washed three times with deionized water and anhydrous ethanol, dried under vacuum at 150 °C for 1 h, and then dried further at 300 °C under a hydrogen atmosphere to obtain Fe. 0 Precursor; keep the dried product in a vacuum to avoid oxidation.

[0050] Step 1.2: Add Fe 0 The precursor was placed in a ceramic boat and loaded into a tube furnace. Nitrogen gas was used to purge the air in the tube furnace, and then the gas was switched to ammonia. Under a flowing NH3 atmosphere (100 sccm), the temperature was increased to 650 °C (labeled T) at 5 °C / min and held for 4 hours for nitriding. Subsequently, it was cooled to room temperature under nitrogen protection to obtain Fe3N nanoparticle powder.

[0051] Step 2: Lactic acid-AFM catalysis

[0052] 5 mM (approximately 450 μg mL) -1The reaction mixture was prepared by adding an aqueous solution of L-lactic acid; the Fe3N catalyst prepared in step 1 was added (the molar ratio of lactic acid to Fe3N catalyst was 1:0.051, calculated based on a Fe3N molar mass of 181.5 g / mol), and the reaction was stirred and catalytically oxidized for 10 min at room temperature (25 ± 5 ℃) under air atmosphere. The reaction solution was then filtered through a 0.22 μm filter membrane, and the lactic acid level was analyzed and determined using a lactic acid oxidation kit.

[0053] In addition, an alternating magnetic field generating coil (5 cm inner diameter) is placed outside the reaction tube during the entire catalytic process. The coil is connected to a high-frequency alternating power supply. The applied AMF magnetic field strength is 18.75 A / cm, and the frequency is 300 kHz.

[0054] Characterization of Fe3N nanomaterials

[0055] The material obtained in Example 1 was characterized as follows: Figure 1 As observed, the X-ray diffraction (XRD) pattern shows that all diffraction peaks are consistent with the standard card (JCPDS No. 01-071-5965) of hexagonal Fe3N, with no other impurity peaks. Transmission electron microscopy (TEM) shows that the material consists of uniform particles with a diameter of approximately 100–200 nm. Figure 2 a). High-resolution TEM showed clear lattice fringes, and the interplanar spacing was measured to be 0.21 nm, corresponding to the (111) crystal plane of Fe3N. Figure 2 b).

[0056] Figure 3 X-ray photoelectron spectroscopy (XPS) of Fe3N nanoparticles. Figure 3 The full spectrum of a confirmed that the material is mainly composed of Fe, N, C and O elements. Among them, the O element signal may originate from the unavoidable adsorption of oxygen or trace oxidation on the sample surface, and the C element signal may originate from the adsorption of organic pollutants from the air on the sample surface. Figure 3 After peak fitting, the N 1s spectrum of b showed a main peak at a binding energy of 397.7 eV, which can be clearly attributed to the N-Fe bond in Fe3N, providing direct evidence of successful nitridation of the material. The other two peaks at 398.5 and 400.2 eV may originate from nitrogen in ammonia and nitrogen oxides adsorbed on the particle surface. Fe 2p spectrum ( Figure 3 c) The deconvolution resulted in six distinct peaks, with the peaks at 711.37 and 713.72 eV attributed to Fe. 2+ and Fe 3+ Fe 2p 3 / 2 The peaks at 723.59 and 726.4 eV are attributed to Fe. 2+ and Fe 3+ Fe 2p 1 / 2The two peaks at 732.4 and 719.23 eV indicate Fe 2p 1 / 2 and Fe 2p 3 / 2 The accompanying peaks indicate that iron exists in various chemical environments.

[0057] The saturation magnetization of Fe3N nanoparticles is as high as 141.75 emu / g ( Figure 4 It possesses strong ferromagnetism and excellent magnetic field response capability.

[0058] Example 2

[0059] Compared with Example 1, the only difference is that in step 1.2, the temperature T is 600 °C and the reaction time is 5 h. All other operations and parameters are the same as in Example 1.

[0060] Comparative Example 1

[0061] Compared with Example 1, the only difference is that in step 2, no Fe3N catalyst was added; all other operations and parameters are the same as in Example 1.

[0062] Comparative Example 2

[0063] Compared with Example 1, the only difference is that in step 2, no alternating magnetic field was added during the oxidation process; all other operations and parameters are the same as in Example 1.

[0064] Comparative Example 3

[0065] Compared with Example 1, the only difference is that Co4N is used instead of Fe3N as the catalyst, while the molar amount of catalyst relative to lactic acid and other operations and parameters are the same as in Example 1.

[0066] Comparative Example 4

[0067] Compared with Example 1, the only difference is that Co4N is used instead of Fe3N as the catalyst, the molar amount of catalyst relative to lactic acid is the same as in Example 1, and ultrasonic enhancement is used in the oxidation process with an ultrasonic power of 200W. All other operations and parameters are the same as in Example 1.

[0068] Comparative Example 5

[0069] Compared to Example 1, the only difference is that in step 1.2, the temperature T is 400 °C. All other operations and parameters are the same as in Example 1. Insufficient nitriding temperature resulted in the failure to obtain Fe3N with high phase purity.

[0070] The lactic acid catalytic effects of Examples 1-2 and Comparative Examples 1-5 are shown in Table 1:

[0071]

[0072] As shown in Table 1, the alternating magnetic field (AMF)-assisted oxidation of Fe3N into form 1 improves the catalytic oxidation of lactic acid. Experiments also demonstrate that the enhancing effect of AMF on Fe3N is significantly better than that of ultrasound (US) on Co4N. Specifically, AMF increases the activity of Fe3N in catalyzing lactic acid oxidation by approximately 2.20 times, while US increases it by approximately 1.74 times for Co4N, demonstrating the technical advantages of this invention.

[0073] Example 3

[0074] Compared to Example 1, the difference in this example is that the amount of Fe3N catalyst added to the catalytic reaction system was changed. Specifically, the initial concentration of the lactic acid substrate was kept constant while the catalyst concentration was varied to investigate the effect of catalyst dosage on reaction efficiency. In the specific tests, the Fe3N catalyst concentrations were 0, 25, 50, 75, and 100 μg / mL. -1 The corresponding molar ratios of lactic acid to catalyst are approximately 1:0, 1:0.026, 1:0.051, 1:0.077, and 1:0.103, respectively. Figure 5 visible, Figure 5 In the markings, (1) to (5) correspond to a Fe3N catalyst concentration of 0 μg / mL, respectively. -1 25 μg mL -1 50 μg mL -1 75 μg mL -1 and 100 μgmL -1 The results showed that in the control experiment without a catalyst, the lactic acid concentration remained essentially constant. The lactic acid conversion rate increased with increasing catalyst concentration. Furthermore, observations at different time points revealed that, at any catalyst concentration, the lactic acid concentration decreased over time, and the initial reaction rate increased with increasing catalyst concentration.

[0075] The results of this embodiment show that in the AMF-assisted catalytic system, the lactic acid conversion efficiency is positively correlated with the amount of Fe3N catalyst. Within the test range, increasing the catalyst concentration can effectively improve the lactic acid consumption rate and the final conversion rate.

[0076] Example 4

[0077] Compared to Example 1, the only difference was the change in the intensity of the alternating magnetic field (AMF) applied during the catalytic reaction in step 2. The experimental groups were: (1): no AMF (as a control); (2): AMF intensity of 12.5 A / cm; (3): AMF intensity of 18.75 A / cm; (4): AMF intensity of 25 A / cm; other conditions remained unchanged. Figure 6It is evident that applying AMF significantly improves lactic acid conversion compared to conditions without AMF, and the lactic acid conversion rate increases with increasing AMF strength. This suggests that higher magnetic field strength may further promote the conversion of the reaction pathway to the target product through enhanced magnetocaloric effect.

[0078] Example 5

[0079] Compared to Example 1, the only difference is that after the first reaction, the catalyst was recovered by magnetic separation, washed with PBS buffer, and used for the next cycle test. This process was repeated 5 times, and the lactate conversion rate retention rate relative to the first cycle was recorded for each cycle.

[0080] Depend on Figure 7 As can be seen, the catalyst exhibits excellent cycling stability. After the 1st to 5th cycles, the lactic acid conversion rates remained at 100%, 97.4%, 94.6%, 92.8%, and 91.8%, respectively. This demonstrates that the Fe3N nanoparticles are structurally stable under AMF-assisted catalysis and can be reused.

[0081] Example 6

[0082] Compared to Example 1, the only difference is that the reaction substrates are replaced with other substrates at the same concentration, including: lysine, arginine, histidine, glutathione, ascorbic acid, and cysteine. Figure 8 It is evident that the Fe3N catalyst exhibits extremely high catalytic selectivity for lactic acid. Under the same conditions, the conversion rate of lactic acid is 37.32% ± 0.26%, while the conversion rates of lysine, arginine, histidine, glutathione, ascorbic acid, and cysteine ​​remain essentially unchanged. This strongly demonstrates that the Fe3N nanoparticle catalytic system of this invention possesses specific high catalytic oxidation activity for lactic acid molecules, rather than being a broad-spectrum oxidant.

[0083] Through the above embodiments, this invention specifically illustrates the preparation, characterization, and application potential of the Fe3N nanomaterial in multiple fields. The embodiments demonstrate the outstanding performance of this material in efficiently and selectively catalyzing the conversion of lactic acid to pyruvate under mild conditions, and reveal the significant enhancing effect of alternating magnetic field (AMF) on its catalytic activity and its convenient magnetic recovery characteristics. The above descriptions are merely specific implementation examples of this invention, and the scope of protection of this invention is not limited thereto. All equivalent changes and modifications made according to this invention should be covered within the patent protection scope of this invention.

Claims

1. A method for the synthesis of 2-keto acids by Fe3N catalysis assisted by an alternating magnetic field, characterized in that, The 2-hydroxy acid of Formula 1, an oxidant, and Fe3N were mixed and catalytically oxidized under the assistance of an alternating magnetic field to obtain the 2-keto acid of Formula 2. Formula 1 Formula 2 In Formula 1, R is a C1-C6 alkyl, phenyl, substituted alkyl, or substituted phenyl group; the substituents in the substituted alkyl or substituted phenyl group include at least one of amino, alkoxy, hydroxyl, nitro, or halogen. Fe3N is obtained by ammoniation roasting with an iron source in an ammonia-containing atmosphere at a temperature of 500-800 °C; The iron source mentioned includes elemental iron; The alternating magnetic field strength is 5~35 A / cm, and the frequency is 50~500 kHz; The oxidant is an oxygen-containing atmosphere.

2. The method for synthesizing 2-keto acids by Fe3N catalysis assisted by alternating magnetic field as described in claim 1, characterized in that, Fe3N consists of nanoparticles with a D50 of 50–500 nm and a saturation magnetization of not less than 100 emu / g.

3. The method for synthesizing 2-keto acids by Fe3N catalysis assisted by alternating magnetic field as described in claim 1, characterized in that, The volume content of ammonia in the ammonia-containing atmosphere is above 50 vol%.

4. The method for synthesizing 2-keto acids by Fe3N catalysis assisted by alternating magnetic field as described in claim 1, characterized in that, The temperature for ammoniation roasting is 600~700 ℃; The ammoniation roasting time is 0.5~5 h.

5. The method for synthesizing 2-keto acids by Fe3N catalysis assisted by alternating magnetic field as described in claim 1, characterized in that, The molar ratio of 2-hydroxy acid and Fe3N in Formula 1 is 1:0.02~0.

12.

6. The method for synthesizing 2-keto acids by Fe3N catalysis assisted by alternating magnetic field as described in claim 1, characterized in that, The temperature for the catalytic oxidation reaction stage is 15~70 ℃.

7. The method for synthesizing 2-keto acids by Fe3N catalysis assisted by alternating magnetic field as described in claim 1, characterized in that, The Fe3N is recycled.

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