Method for efficiently oxidizing benzaldehyde by using high oxygen dissolving capacity of fluorocarbon compound

Abstract

The application discloses a method for efficiently oxidizing benzaldehyde by using the high oxygen dissolving capacity of fluorocarbon compounds. The method uses the high oxygen dissolving capacity of fluorocarbon compounds, so that the oxygen dissolved in the fluorocarbon compounds and the benzaldehyde dissolved in the alkane can efficiently perform the oxidation reaction under normal temperature, normal pressure and low-speed stirring. Meanwhile, the fluorocarbon compounds can be separated by standing due to the chemical reaction inertness of the fluorocarbon compounds and the difference characteristics of the physical and chemical properties of the fluorocarbon compounds and the hydrocarbon compounds, so that the recycling of the fluorocarbon compounds is realized. The oxygen dissolved in the fluorocarbon compounds is used as a weak oxidizing agent, and the oxidation reaction occurs in the liquid phase, so that the effect of no residue of the oxidizing agent is realized. Compared with no addition of the fluorocarbon compounds, the conversion rate of the benzaldehyde is increased by 4 times, and the efficient oxidation of the benzaldehyde is realized.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology and relates to a method for efficiently oxidizing benzaldehyde using the oxygen-dissolving capacity of fluorocarbon compounds. Background Technology

[0002] Benzoic acid, as an important raw material, can be used to synthesize pharmaceuticals, dyes, plasticizers, mordants, and fragrances. For example, patent CN116327750A discloses that benzoic acid derivatives can be used to treat jellyfish stings. Meanwhile, as a representative of acidic food preservatives, the addition of appropriate amounts of benzoic acid can alter the pH value of the food system, thereby changing the cell membrane permeability of harmful microorganisms and effectively inhibiting their activity, which is of great significance for food preservation.

[0003] Among existing methods for synthesizing benzoic acid, oxidation is the most direct. However, current oxidative synthesis methods for benzoic acid are still limited by high-temperature and high-pressure reaction conditions, and often require the use of equivalent amounts of metal ion salts such as Co salts or Mn salts to activate the addition reaction. For example, using 6% MnO... x When using SBA-15 as a catalyst for the selective synthesis of benzoic acid from toluene, the toluene conversion rate reaches its maximum of 26.3% after 3 hours of reaction at 180℃ and an oxygen partial pressure of 1.0 MPa, with a benzoic acid selectivity of 83.9%. Furthermore, the benzoic acid selectivity decreases further as the reaction continues (Li Yongqiang, Research on Liquid-Phase Catalytic Oxidation of Toluene, Hunan Normal University, 2014). The above methods place high demands on temperature and pressure, resulting in high equipment costs, and the low reactant conversion rate is unfavorable for industrial mass production. Dodecylbenzenesulfonic acid (DBSA) can be used as a catalyst for the oxidation of benzaldehyde, but its preparation using an emulsion microreactor method results in low conversion efficiency due to the low oxygen content in the water, or the use of strong oxidants such as H2O2 (Jing Lu, Research on the Oxidative Esterification Reaction of Aldehydes in DBSA Microemulsions, Northeast Normal University, 2009).

[0004] Fluorocarbons, as nonpolar liquids, possess properties such as low viscosity, low surface tension, and high gas solubility, while oxygen, as a nonpolar gas, can dissolve in large quantities in fluorocarbon liquids. The oxygen-dissolving capacity of fluorocarbons is affected by temperature; at 37°C, up to 43 mL of oxygen can dissolve in every 100 mL of fluorocarbon liquid. The solubility of oxygen in fluorocarbons is approximately 25 times that in blood and water. This unique ability provides a pathway for hypoxia treatment, and fluorocarbons have great potential for application in reducing hypoxia-induced resistance to photodynamic therapy, radiotherapy, and chemotherapy. For example, patent CN115944610A discloses a method for preparing nucleic acid drugs using fluorocarbon nanotransfection reagents, and patent CN105142681B discloses a method for preparing contrast agents and contrast enhancers using semi-fluorocarbons. Currently, there are no reports of using fluorocarbons for the oxidative synthesis of benzoic acid. Summary of the Invention

[0005] The purpose of this invention is to provide a method for efficiently oxidizing benzaldehyde using the oxygen-dissolving capacity of fluorocarbons. This method uses a fluorocarbon compound saturated with oxygen and an alkane containing benzaldehyde as solvents, respectively, to synthesize benzoic acid through a mild oxidation reaction under the action of a catalyst. Because this system uses oxygen as the oxidant, and the benzaldehyde oxidation reaction takes place in the liquid phase, no oxidant residue is ultimately achieved. Simultaneously, since the carbon-hydrogen bonds in the fluorocarbon compound are replaced by higher-energy fluorocarbon bonds, the fluorocarbon compound exhibits strong chemical inertness and greater stability. After the reaction terminates, the fluorocarbon compound can be recovered through liquid-phase separation by allowing it to stand. Oxygen is then added to the fluorocarbon compound, along with reactants and a catalyst, to continue the reaction and synthesize benzoic acid, thus achieving the recycling of the fluorocarbon compound.

[0006] The technical solution for achieving the objective of this invention is as follows:

[0007] A method for efficiently oxidizing benzaldehyde using the oxygen-dissolving capacity of fluorocarbons includes the following steps:

[0008] (1) Dissolve the catalyst dodecylbenzenesulfonic acid (DBSA) in water to obtain an aqueous solution containing the catalyst;

[0009] (2) Dissolve benzaldehyde in an alkane to obtain an alkane solution, wherein the alkane is n-hexane, n-heptane or toluene;

[0010] (3) The aqueous solution containing the catalyst, the alkane solution and the fluorocarbon compound are directly mixed and allowed to stand until the liquid phase in the system is completely separated into three layers, from top to bottom: alkane solution, aqueous solution containing the catalyst and fluorocarbon compound, wherein the fluorocarbon compound is FC-770, HFE-7500, FC-43, perfluorooctane or perfluorohexane.

[0011] (4) Under normal pressure, oxygen is introduced into the bottom layer of fluorocarbon compound in the system to saturate the fluorocarbon compound with oxygen;

[0012] (5) Place the system in a water bath at 20℃~50℃ and stir to allow the reaction to continue, and obtain benzoic acid.

[0013] Furthermore, in step (1), the concentration of the catalyst in the aqueous solution containing the catalyst is 0.1 mmol / L to 5 mmol / L. In a specific embodiment of the present invention, 0.5 mmol / L is taken as an example.

[0014] Furthermore, in step (2), the concentration of benzaldehyde in the alkane solution is 1 mmol / L to 50 mmol / L. In a specific embodiment of the present invention, 5 mmol / L is taken as an example.

[0015] Further, in step (3), the volume ratio of the alkane solution to the fluorocarbon compound is 2:1 to 1:5, and the volume ratio of the total volume of the alkane solution and the fluorocarbon compound to the volume ratio of the aqueous solution containing the catalyst is 1:1 to 1:5. In a specific embodiment of the present invention, an example is taken where the volume ratio of the alkane solution to the fluorocarbon compound is 1:1, and the volume ratio of the total volume of the alkane solution and the fluorocarbon compound to the volume ratio of the aqueous solution containing the catalyst is 1:1.

[0016] Furthermore, in step (4), the atmospheric pressure is 100 kPa to 105 kPa.

[0017] Further, in step (4), the specific method for introducing oxygen is as follows: connect a needle to the oxygen bag tube opening, insert the needle into the fluorocarbon compound at the bottom of the system, press the oxygen bag, and introduce oxygen into the fluorocarbon compound at a rate of 3 to 7 bubbles per second.

[0018] Furthermore, in step (4), the oxygen is introduced for 3 to 10 minutes.

[0019] Furthermore, in step (5), the stirring speed is 300 rpm to 1500 rpm.

[0020] Furthermore, in step (5), the reaction time is 4 to 8 hours.

[0021] Furthermore, it also includes the following steps: (6) After the reaction is completed, benzoic acid is separated, the reaction system is placed in a low temperature environment of 0℃~15℃, and after all the alkanes dissolved in the fluorocarbons are precipitated, the fluorocarbons are separated and recovered.

[0022] (7) Using the recovered fluorocarbons, repeat steps (3) to (5).

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] (1) In this invention, oxygen is used as an oxidant and the benzaldehyde oxidation reaction is carried out in the liquid phase, which can achieve the purpose of no oxidant residue in the reaction system after the reaction is completed.

[0025] (2) In this invention, the reaction system is stirred under normal pressure and at 20℃~50℃. By stirring and water bath, the oxygen in the fluorocarbon compound and the benzaldehyde in the alkane are fully contacted, which accelerates the oxidation reaction rate and efficiently synthesizes benzoic acid. This avoids the high temperature of 180℃ and the high pressure environment of 1.0MPa oxygen partial pressure in the toluene liquid-phase selective oxidation method. The reaction conditions are milder, which effectively reduces the cost and the requirements of experimental equipment for the benzoic acid synthesis reaction.

[0026] (3) By controlling the stirring speed and reaction temperature, the present invention can regulate the conversion rate of the oxidation reaction, with a maximum conversion rate of 84.41%, which is significantly improved compared to the 26.3% reactant conversion rate in the traditional high temperature and high pressure oxidation method.

[0027] (4) In this invention, fluorocarbons are used as solvents to dissolve oxygen. The high bond energy of fluorocarbons makes them highly reactive. Therefore, they do not participate in the reaction. After the reaction, the fluorocarbons can still exist stably and can be recycled. In the first cycle, the recovery rate of fluorocarbons can reach 96%. After four cycles, the recovery rate of fluorocarbons remains at over 85%, which is green and environmentally friendly. Attached Figure Description

[0028] Figure 1 A schematic diagram of a method for efficiently oxidizing benzaldehyde using the oxygen-dissolving capacity of fluorocarbons.

[0029] Figure 2 The images show the physical reaction system before oxygen introduction (a), during oxygen introduction (b), and after the reaction is complete (c).

[0030] Figure 3 The figure shows the results of the oxygen solubility of fluorocarbon compound FC-770 and the effect of DBSA on the reaction kinetics of the oxidation reaction. In the figure, a is the FC-770 / n-heptane / water reaction system, b is the n-heptane / water reaction system, and c is the FC-770 / n-heptane / water reaction system without the addition of DBSA.

[0031] Figure 4 The figure shows the effect of stirring speed on the reaction kinetics of the oxidation reaction.

[0032] Figure 5 The figure shows the effect of temperature on the reaction kinetics of the oxidation reaction.

[0033] Figure 6 The figure shows the effect of alkane oil on the reaction kinetics of oxidation.

[0034] Figure 7 The figure shows the effect of fluorocarbon compounds on the reaction kinetics of oxidation.

[0035] Figure 8 The figure shows the effect of the number of FC-770 cycles on the reaction kinetics of the oxidation reaction.

[0036] Figure 9 The graph shows the effect of the number of FC-770 cycles on the FC-770 recovery rate. Detailed Implementation

[0037] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.

[0038] Example 1

[0039] The effect of oxygen solubility of fluorocarbon compound FC-770 on the reaction kinetics of oxidation reaction:

[0040] (1) FC-770 / n-heptane / water reaction system: DBSA was dissolved in water to obtain a 0.5 mmol / L DBSA aqueous solution, which served as the aqueous phase. Benzaldehyde was dissolved in n-heptane to obtain a 5 mmol / L benzaldehyde alkane solution. The aqueous solution, alkane solution, and FC-770 were mixed at a volume ratio of FC-770:n-heptane:water = 1:1:2, and allowed to stand until the reaction system completely separated into three layers, from top to bottom: alkane solution, aqueous solution, and FC-770. Under normal pressure, oxygen was introduced into the bottom layer of FC-770 for 3 minutes to saturate the fluorocarbons. The reaction system was placed in a 40℃ water bath and stirred at 800 rpm. Samples were taken every 30 minutes, and the peak area of ​​benzaldehyde at each reaction time was measured by liquid chromatography. A conversion curve was plotted, and the results are shown in [Figure number missing]. Figure 3 .

[0041] (2) Heptane / Water Reaction System: DBSA was dissolved in water to obtain a 0.5 mmol / L aqueous solution, which served as the aqueous phase. Benzaldehyde was dissolved in heptane to obtain a 5 mmol / L alkane solution. The aqueous and alkane solutions were mixed at a volume ratio of heptane:water = 1:1 and allowed to stand until the reaction system completely separated into two layers: the upper layer was heptane and the lower layer was water. Oxygen was introduced into the water at atmospheric pressure for 3 minutes until the oxygen reached saturation. The reaction system was placed in a 40℃ water bath and stirred at 800 rpm. Samples were taken every 30 minutes, and the peak area of ​​benzaldehyde at each reaction time was measured by liquid chromatography. A conversion curve was plotted, and the results are shown in [Figure number missing]. Figure 3 .

[0042] Table 1

[0043]

[0044] Table 1 shows the solubility of FC-770, n-heptane, water, and benzaldehyde in n-heptane, water, and FC-770, respectively. As can be seen from Table 1, n-heptane and FC-770 are insoluble in water, while FC-770 has a solubility of 59.3 mmol / L in n-heptane. Benzaldehyde is soluble only in n-heptane and insoluble in FC-770. Figure 3 In Figure a, the reaction system is FC-770 / n-heptane / water, and in Figure b, the reaction system is n-heptane / water. The comparison shows that with the addition of FC-770 fluorocarbon compound, both the oxidation reaction conversion rate and the reaction rate are significantly improved. The equilibrium conversion rate increases from 17.86% to 70.75%, indicating that the high oxygen solubility of fluorocarbon compound increases the equilibrium conversion rate by 4 times. The addition of fluorocarbon compound can effectively improve the conversion efficiency.

[0045] Example 2

[0046] Effect of catalyst DBSA on the reaction kinetics of oxidation reaction:

[0047] (1) FC-770 / n-heptane / water reaction system with DBSA added: DBSA was dissolved in water to obtain a 0.5 mmol / L DBSA aqueous solution, which served as the aqueous phase. Benzaldehyde was dissolved in n-heptane to obtain a 5 mmol / L benzaldehyde alkane solution. The aqueous solution, alkane solution, and FC-770 were mixed at a volume ratio of FC-770:n-heptane:water = 1:1:2, and allowed to stand until the reaction system completely separated into three layers, from top to bottom: alkane solution, aqueous solution, and FC-770. Under normal pressure, oxygen was introduced into the bottom layer of FC-770 for 3 minutes to saturate the fluorocarbons. The reaction system was placed in a 40℃ water bath and stirred at 800 rpm. Samples were taken every 30 minutes, and the peak area of ​​benzaldehyde at each reaction time was measured by liquid chromatography. A conversion curve was plotted, and the results are shown in [Figure number missing]. Figure 3 .

[0048] (2) FC-770 / n-heptane / water reaction system without DBSA: Benzaldehyde was dissolved in n-heptane to obtain an alkane solution with a benzaldehyde concentration of 5 mmol / L. The water, alkane solution, and FC-770 were mixed at a volume ratio of FC-770:n-heptane:water = 1:1:2, and allowed to stand until the reaction system completely separated into three layers, from top to bottom: alkane solution, water, and FC-770. Oxygen was introduced into the bottom layer of FC-770 under normal pressure for 3 minutes to saturate the fluorocarbons. The reaction system was placed in a 40℃ water bath and stirred at 800 rpm. Samples were taken every 30 minutes, and the peak area of ​​benzaldehyde at each reaction time was measured by liquid chromatography. A conversion curve was plotted, and the results are shown in [Figure number missing]. Figure 3 .

[0049] Figure 3 In Figure a, FC-770 / n-heptane / water reaction system with DBSA is represented, while in Figure c, FC-770 / n-heptane / water reaction system without DBSA is represented. The comparison shows that without the addition of the catalyst DBSA, the equilibrium conversion rate is only 12.36%. After adding 0.5 mmol / L DBSA, the equilibrium conversion rate increases to 70.75%. These results demonstrate that the addition of 0.5 mmol / L DBSA catalyst effectively improves the conversion rate and reaction rate of this oxidation reaction.

[0050] Example 3

[0051] Effect of stirring speed on the reaction kinetics of oxidation reaction:

[0052] DBSA was dissolved in water to obtain a 0.5 mmol / L aqueous solution, which served as the aqueous phase. Benzaldehyde was dissolved in n-heptane to obtain a 5 mmol / L alkane solution. The aqueous solution, alkane solution, and FC-770 were mixed at a volume ratio of FC-770:n-heptane:water = 1:1:2, and allowed to stand until the reaction system completely separated into three layers, from top to bottom: alkane solution, aqueous solution, and FC-770. Oxygen was introduced into the bottom layer, FC-770, at atmospheric pressure for 3 minutes to saturate the fluorocarbons. The reaction system was placed in a 40°C water bath and reacted at stirring speeds of 300 rpm, 500 rpm, 800 rpm, and 1500 rpm. Samples were taken every 30 minutes, and the peak area of ​​benzaldehyde at each reaction time was measured by liquid chromatography. The equilibrium conversion rate of the oxidation reaction at each stirring speed was calculated, and a bar chart was plotted. The results are shown in [Figure number missing]. Figure 4 .

[0053] Depend on Figure 4It can be seen that when the stirring speed is increased to 1500 rpm, the equilibrium conversion rate of the oxidation reaction is significantly higher than that at the other three stirring speeds, increasing from 17.25% to 84.41%. These results indicate that within the range of 300–1500 rpm, increasing the stirring speed can effectively improve the conversion rate of this oxidation reaction.

[0054] Example 4

[0055] The effect of temperature on the reaction kinetics of oxidation reactions:

[0056] DBSA was dissolved in water to obtain a 0.5 mmol / L aqueous solution, which served as the aqueous phase. Benzaldehyde was dissolved in n-heptane to obtain a 5 mmol / L alkane solution. The aqueous solution, alkane solution, and FC-770 were mixed at a volume ratio of FC-770:n-heptane:water = 1:1:2, and allowed to stand until the reaction system completely separated into three layers, from top to bottom: alkane solution, aqueous solution, and FC-770. Oxygen was bubbled into the bottom layer, FC-770, at atmospheric pressure for 3 minutes to saturate the fluorocarbons. The reaction system was placed in water baths at 20°C, 30°C, 40°C, and 50°C, respectively, with stirring at 800 rpm. Samples were taken every 30 minutes, and the peak area of ​​benzaldehyde at each reaction time was measured by liquid chromatography. The equilibrium conversion rate of the oxidation reaction at each temperature was calculated, and a bar chart was plotted. The results are shown in [Figure number missing]. Figure 5 .

[0057] Depend on Figure 5 It can be seen that when the temperature rises to 50℃, the equilibrium conversion rate of the oxidation reaction is significantly higher than that at other low temperatures, increasing from 40.47% to 80.12%. These results indicate that increasing the temperature within the range of 20–50℃ can effectively improve the conversion rate of this oxidation reaction. When the temperature rises to 45℃ and above, n-heptane and FC-770 reach their miscibility point, and the two phases dissolve into one. At this point, the contact area between oxygen and benzaldehyde further increases, and the collision probability is greatly enhanced, thus increasing the conversion rate by two times.

[0058] Example 5

[0059] Effect of alkane oils on the reaction kinetics of oxidation reactions:

[0060] DBSA was dissolved in water to obtain a 0.5 mmol / L aqueous solution, which served as the aqueous phase. Benzaldehyde was dissolved in cyclohexane, n-hexane, n-heptane, and toluene to obtain alkane solutions with a concentration of 5 mmol / L. The aqueous solution, alkane solution, and FC-770 were mixed at a volume ratio of FC-770:alkane:water = 1:1:2 and allowed to stand until the reaction system completely separated into three layers, from top to bottom: alkane solution, aqueous solution, and FC-770. Oxygen was bubbled into the bottom layer, FC-770, at atmospheric pressure for 3 minutes to saturate the fluorocarbons. The reaction system was placed in a 40°C water bath and stirred at 800 rpm. Samples were taken every 30 minutes, and the peak area of ​​benzaldehyde at each reaction time was measured by liquid chromatography. The equilibrium conversion rate of the oxidation reaction was calculated when different alkane oils were used as solvents, and a bar chart was plotted. The results are shown in [Figure number missing]. Figure 6 .

[0061] Depend on Figure 6 It can be seen that when benzaldehyde is dissolved using the above four alkane oils, the equilibrium conversion rate of the oxidation reaction is the highest when toluene is used as the solvent, the equilibrium conversion rate decreases slightly when n-heptane is used, and the equilibrium conversion rate is the lowest when cyclohexane is used.

[0062] Example 6

[0063] The effect of fluorocarbons on the reaction kinetics of oxidation reactions:

[0064] DBSA was dissolved in water to obtain a 0.5 mmol / L aqueous solution, which served as the aqueous phase. Benzaldehyde was dissolved in n-heptane to obtain a 5 mmol / L alkane solution. The aqueous solution and n-heptane solution were mixed with FC-770, HFE-7500, FC-43, and perfluorooctane respectively, at a volume ratio of fluorocarbon:n-heptane:water = 1:1:2. The mixtures were allowed to stand until the reaction system completely separated into three layers: n-heptane solution, aqueous solution, and fluorocarbon solution, from top to bottom. Oxygen was bubbled into the bottom fluorocarbon layer at atmospheric pressure for 3 minutes to saturate the fluorocarbon. The reaction system was placed in a 40°C water bath and stirred at 800 rpm. Samples were taken every 30 minutes, and the peak area of ​​benzaldehyde at each reaction time was measured by liquid chromatography. The equilibrium conversion rate of the oxidation reaction was calculated when using different fluorocarbons, and a bar chart was plotted. The results are shown in [Figure number missing]. Figure 7 .

[0065] Depend on Figure 7 It can be seen that FC-770 has the highest conversion rate because it is somewhat soluble in n-heptane, while the conversion rate is somewhat reduced when other fluorocarbon compounds are used.

[0066] Example 7

[0067] The effect of the number of cycles of fluorocarbon compound FC-770 on the reaction kinetics of oxidation reaction:

[0068] DBSA was dissolved in water to obtain a 0.5 mmol / L aqueous solution, which served as the aqueous phase. Benzaldehyde was dissolved in n-heptane to obtain a 5 mmol / L alkane solution. The aqueous solution, alkane solution, and FC-770 were mixed at a volume ratio of FC-770:alkane:water = 1:1:2, and allowed to stand until the reaction system completely separated into three layers: alkane solution, aqueous solution, and FC-770 from top to bottom. Oxygen was bubbled into the bottom layer, FC-770, at atmospheric pressure for 3 minutes to saturate the fluorocarbons. The reaction system was placed in a 40°C water bath and stirred at 800 rpm. Samples were taken every 30 minutes, and the peak area of ​​benzaldehyde at each reaction time was measured by liquid chromatography to calculate the equilibrium conversion rate of the oxidation reaction. After the reaction was complete, the synthesized benzoic acid was separated, and the reaction system was then placed in a 0°C environment. After the liquid stabilized at low temperature, the bottom transparent liquid was collected for separation, yielding pure FC-770. The obtained FC-770 was used as the solvent for dissolving oxygen in the next reaction, and the above oxidation reaction experiment was repeated. A bar chart was plotted using the equilibrium conversion rate calculated after each reaction. The results are shown in [Figure showing the results]. Figure 8 .

[0069] Depend on Figure 8 It can be seen that the reaction equilibrium conversion rate remains basically unchanged in the three cycles, indicating that FC-770 can be recycled.

[0070] Example 8

[0071] Effect of the number of FC-770 recycling cycles on the reaction kinetics of FC-770 recovery:

[0072] DBSA was dissolved in water to obtain a 0.5 mmol / L aqueous solution, which served as the aqueous phase. Benzaldehyde was dissolved in n-heptane to obtain a 5 mmol / L alkane solution. The aqueous solution, alkane solution, and FC-770 were mixed at a volume ratio of FC-770:alkane:water = 1:1:2 and allowed to stand until the reaction system completely separated into three layers, from top to bottom: alkane solution, aqueous solution, and FC-770. Oxygen was bubbled into the bottom layer of FC-770 at atmospheric pressure for 3 minutes to saturate the fluorocarbons. The reaction system was placed in a 40°C water bath and stirred at 800 rpm. After 8 hours of reaction, the reaction system was placed in a 0°C environment until all n-heptane precipitated from FC-770. The bottom layer of FC-770 was then removed with a needle, and its mass was measured. The ratio of this mass to the initial mass was calculated as the recovery rate of FC-770 in this cycle. The obtained FC-770 was used as the solvent for dissolving oxygen in the next reaction. Reactants and catalyst were replenished, and the above oxidation reaction experiment was repeated three times. A bar chart was plotted based on the recovery rate calculated after each reaction. The results are shown in [Figure Number]. Figure 9 .

[0073] Depend on Figure 9 It can be seen that after multiple cycles, the recovery rate of fluorocarbon compounds remains at around 90%, ranging from 82.89% to 96.23%. These results indicate that multiple cycles do not significantly affect the recovery rate of fluorocarbon compounds, demonstrating that fluorocarbon compounds can be reused multiple times, and that the synthesis method of this invention is green and environmentally friendly.

Claims

1. A method for efficiently oxidizing benzaldehyde using the high oxygen dissolving ability of fluorocarbon compounds, characterized by, The method comprises the following steps: (1) dissolving a catalyst dodecyl benzene sulfonic acid in water to obtain a water solution containing the catalyst; (2) dissolving benzaldehyde in an alkane to obtain an alkane solution, wherein the alkane is n-hexane, n-heptane or toluene; (3) directly mixing the water solution containing the catalyst, the alkane solution and a fluorocarbon compound, and standing until the liquid phase in the system is completely separated into three layers, wherein the alkane solution, the water solution containing the catalyst and the fluorocarbon compound are arranged from top to bottom, and the fluorocarbon compound is FC-770, HFE-7500, FC-43, perfluorooctane or perfluorohexane; (4) introducing oxygen into the fluorocarbon compound at the bottom of the system under normal pressure, so that the oxygen is saturated in the fluorocarbon compound; (5) placing the system in a water bath environment at 20-50 DEG C and stirring at a speed of 800-1500 rpm, so that the reaction continuously proceeds, and benzonic acid is obtained.

2. The method of claim 1, wherein, In step (1), the concentration of the catalyst in the water solution containing the catalyst is 0.1-5 mmol / L.

3. The method of claim 1, wherein, In step (2), the concentration of benzaldehyde in the alkane solution is 1-50 mmol / L.

4. The method of claim 1, wherein, In step (3), the volume ratio of the alkane solution to the fluorocarbon compound is 2:1-1:5, and the volume ratio of the total volume of the alkane solution and the fluorocarbon compound to the water solution containing the catalyst is 1:1-1:

5.

5. The method of claim 1, wherein, In step (1), the concentration of the catalyst in the water solution containing the catalyst is 0.5 mmol / L; in step (2), the concentration of benzaldehyde in the alkane solution is 5 mmol / L; in step (3), the volume ratio of the alkane solution to the fluorocarbon compound is 1:1, and the volume ratio of the total volume of the alkane solution and the fluorocarbon compound to the water solution containing the catalyst is 1:

1.

6. The method of claim 1, wherein, In step (4), the normal pressure is 100-105 kPa.

7. The method of claim 1, wherein, In step (4), the specific method for introducing oxygen is as follows: connecting a needle to the guide pipe of an oxygen bag, inserting the needle into the fluorocarbon compound at the bottom of the system, pressing the oxygen bag, and introducing oxygen into the fluorocarbon compound at a speed of 3-7 bubbles per second.

8. The method of claim 1, wherein, In step (4), the time for introducing oxygen is 3-10 min.

9. The method of claim 1, wherein, In step (5), the reaction time is 4-8 h.

10. The method of claim 1, wherein, The method further comprises the following steps: (6) after the reaction is completed, separating benzonic acid, and standing the reaction system in a low-temperature environment at 0-15 DEG C, and after all the alkane dissolved in the fluorocarbon compound is precipitated, recovering the fluorocarbon compound; (7) using the recovered fluorocarbon compound to repeat steps (3)-(5) to prepare benzonic acid.

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