Method for preparing sulfoxide through continuous photocatalysis of microreactor system

Abstract

The invention belongs to the technical field of fine chemical engineering, and particularly relates to a method for preparing sulfoxide through continuous photocatalysis of a microreactor system. A micro-reactor system adopted by the method comprises a photocatalytic micro-reactor, a xenon lamp and a micro-mixer, the photocatalytic micro-reactor comprises a gas phase channel and a liquid phase channel, the gas phase channel and the liquid phase channel are converged into a channel after passing through the micro-mixer, and the micro-mixer is embedded in the photocatalytic micro-reactor to form stable Taylor flow bubbles. The method has the advantages of mild reaction conditions, high conversion rate, high sulfoxide product selectivity, simple process and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical synthesis and process technology, and particularly relates to a method for continuously preparing methyl phenyl sulfoxide. Background Art

[0002] The selective oxidation of sulfides to synthesize sulfoxides is very important in the chemical industry. It involves many varieties and has a wide range of applications, and is one of the core processes in sulfur chemistry. For example, in the pharmaceutical field, a wakefulness promoter with a sulfoxide as the core functional group launched by Lafon Company in France in 1994 is used to enhance cognition, and its global sales in 2012 were 11.3 billion yuan. In the pesticide field, ethiprole and clothianidin are sulfoxide pesticides derived from the fipronil skeleton, and have higher activity and lower toxicity than fipronil in controlling rice pests. Sulfoxaflor has the characteristics of high efficiency, broad spectrum, rapidity and long residual period. In the fragrance field, the sulfoxide-containing fragrances alliin and allicin are widely used as food additives due to their strong antibacterial and anti-tumor activities and the ability to scavenge free radicals. Sulfoxide products, such as dimethyl sulfoxide, are widely used as organic solvents, extraction agents in the printing and dyeing industry, antifreeze agents in the automotive industry, etc., and the added value is more than 4 times higher than that of its raw material dimethyl sulfide. Benzyl sulfoxide is a commonly used pharmaceutical intermediate, and its added value is more than 10 times that of its raw material benzyl sulfide.

[0003] The methods for synthesizing sulfoxides from sulfides can be divided into two categories: (1) The stoichiometric oxidant oxidation method, such as using hydrogen peroxide, manganese dioxide, iodobenzene diacetate, etc., has problems such as poor product selectivity, safety, and poor atom economy. (2) The oxygen oxidation method, using transition metal salts and complexes as catalysts, often requires relatively harsh reaction conditions.

[0004] Photocatalytic selective oxidation of sulfides has the characteristics of high selectivity, mild conditions, high efficiency, environmental friendliness, catalyst diversity and wide application, and is a green and efficient oxidation method. Patent CN118874555A reports a technology for photocatalytic selective oxidation of sulfides by a TpBpy-COF catalyst, which has the advantages of mild conditions and easy recovery of the catalyst. However, the oxidation reaction process has disadvantages such as high preparation cost of the photocatalyst, limited gas-liquid mass transfer, and long reaction time.

[0005] Therefore, it is of great significance to develop a photocatalytic process for preparing sulfoxides with low catalyst cost, easy preparation, fast reaction rate, high product selectivity and mild reaction conditions. Summary of the Invention

[0006] The object of the present invention is to provide a method for continuously preparing sulfoxide under mild conditions, realizing the continuous production of sulfoxide through a photocatalytic microreactor, which has the characteristics of being green, efficient, and low in energy consumption, so as to overcome the defects of traditional reaction kettles and the problems existing in the prior art such as long production cycle, low reaction efficiency, high energy consumption, environmental pollution, and production insecurity.

[0007] To achieve the object of the present invention, the technical solution adopted is:

[0008] A method for continuously photocatalytically preparing sulfoxide by using a microreactor system, the microreactor system includes a photocatalytic microreactor, a xenon lamp, and a micromixer. The micromixer is a micromixer, and the micromixer is provided with a gas phase channel and a liquid phase channel. The gas phase channel and the liquid phase channel converge into one channel; in the middle of the microchannel inside the photocatalytic microreactor, there are a plurality of special-shaped channels in the shape of walnuts, and the special-shaped channels are arranged at the central position of the microchannel, dividing the microchannel into upper and lower microchannels.

[0009] The method for preparing sulfoxide includes the following steps:

[0010] (1) Prepare a reaction solution by using a solvent to configure a thioether solution and a photocatalyst.

[0011] (2) The reaction solution enters the liquid phase channel of the micromixer through the liquid phase inlet by an injection pump, and oxygen enters the gas phase channel of the micromixer through the gas phase inlet by an injection pump. After passing through the micromixer, a stable Taylor flow is formed; the reaction solution and oxygen are subjected to pressure and body force in the micromixer, are squeezed and compressed, and form stable Taylor flow bubbles and enter the photocatalytic microreactor.

[0012] (3) Turn on the xenon lamp, adjust the light power, and the mixed Taylor flow bubbles undergo a reaction in the photocatalytic microreactor to prepare sulfoxide.

[0013] The photocatalyst is tetraphenylporphyrin; the solvent is any one selected from methanol, ethanol, acetonitrile, and N,N-dimethylformamide.

[0014] Preferably, the molar ratio of the photocatalyst to the thioether is 0.025 - 0.15:1.

[0015] Preferably, the light is white light, the wavelength range is 400nm - 700nm, and the power is 10 - 30W.

[0016] Preferably, the micromixer is parallelly embedded in the photocatalytic microreactor, the micromixer has a symmetric structure, and the included angle between the liquid phase channel and the gas phase channel is 30° - 60°.

[0017] Preferably, the pressure in the gas phase channel is greater than that in the liquid phase channel, and the pressure difference between the initial gas phase channel and the liquid phase channel ranges from 100 to 1000 kPa; the liquid flow velocity is 0.01 to 0.1 mL / h, and the gas flow rate is 0.1 to 1.0 mL / h.

[0018] Preferably, the plurality of abnormal structure channels in the shape of walnuts are used to increase the gas-liquid contact area and enhance gas-liquid mass transfer, and the number of abnormal structure channels is 200 to 1000.

[0019] Preferably, the thioether is as shown in the general formula (I),

[0020]

[0021] wherein R1 and R2 are selected from one of hydrogen, methyl, methoxy, halogen, nitro, and hydroxyl.

[0022] Preferably, the temperature of the reaction is 20 to 50 °C, and the residence time of the thioether solution, oxygen, and photocatalyst in the photocatalytic microreactor is 1 to 30 min.

[0023] In the method for continuously preparing sulfoxide according to the present invention, the reaction process of sulfoxide and oxygen is carried out in the microchannels of the microreactor under light irradiation conditions. The intermolecular diffusion distance in the microchannels is short, the specific surface area of the microchannels is large, the light energy utilization rate is high, and the miniaturization of the size strengthens the heat transfer and mass transfer processes of the equipment. Therefore, in the method of the present invention, using a microreactor to replace the traditional reaction kettle to produce sulfoxide can overcome the disadvantages of the traditional production process and has great significance.

[0024] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0025] (1) In the present invention, a photocatalytic microreactor is used to synthesize sulfoxide, the reaction time is short (generally less than 15 min), the product conversion rate is high, the sulfoxide selectivity is high, and it is easy to operate.

[0026] (2) The external energy source of the present invention is light energy, which is a green and clean energy source, avoiding the use of highly polluting energy sources, and conforming to the production concept of green production;

[0027] (3) The oxygen source of the present invention is oxygen. Due to its advantages of being clean, green, rich in resources, and having no pollution in emissions, oxygen is theoretically the optimal oxygen source for all oxidation reactions.

[0028] (4) The reaction conditions of the present invention are mild, and the reaction temperature is 20 to 50 °C, avoiding high energy consumption and improving the production safety.

[0029] (5) In the present invention, through precise control of the reaction, continuous production can be achieved, with a short production cycle and avoidance of a large number of side reactions. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 FIG. is a schematic structural diagram of a photocatalytic microreactor used in the method for continuously preparing sulfoxide according to the present invention;

[0031] Figure 2 FIG. is a schematic diagram of the internal structural channels of the photocatalytic microreactor of the present invention;

[0032] Figure 3 FIG. is a schematic process diagram of the photocatalytic microreactor system of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] The following further describes in detail the specific embodiments of the present invention with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for the purpose of illustrating and explaining the present invention, and are not intended to limit the present invention.

[0034] The embodiments are only for the purpose of illustrating and explaining the present invention, and are not intended to limit the present invention.

[0035] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0036] Example 1

[0037] The method for continuously preparing sulfoxide according to the present invention includes: a method for continuously photocatalytically preparing sulfoxide using a microreactor system. The photocatalytic microreactor system includes a microreactor, a xenon lamp, and a micromixer.

[0038] As Figure 1 shown, in order to solve the problems of small gas-liquid contact area, poor gas-liquid mass transfer, and low light energy utilization rate during the photocatalytic oxidation of thioether, a photocatalytic microreactor is designed and constructed to achieve this. The channel width of the photocatalytic microreactor is 0.75 mm, the depth is 0.12 mm, and 532 walnut-shaped special-shaped structures are placed in the center of the microchannel, dividing the microchannel into upper and lower channels. This design can increase the gas-liquid contact area, enhance gas-liquid mass transfer, and improve light energy utilization rate.

[0039] As Figure 1The shown micro mixer includes a gas-phase channel and a liquid-phase channel. The two channels are distributed in a Y-shaped structure, with an included angle of 45° with the main channel, and converge into one channel to enter the photocatalytic micro reactor.

[0040] The preparation method comprises the following steps:

[0041] (1) Take thioether with the general formula (I) structure (R1 = CH3, R2 = H) (2 mmol), and 0.09 g of tetraphenylporphyrin is dissolved in methanol (10 mL) to prepare a thioether solution;

[0042] (2) The thioether solution and oxygen are respectively pumped into the microchannel reaction device through the gas-phase inlet and the liquid-phase inlet. After the thioether and oxygen are mixed by the micro mixer to form a stable Taylor flow, they enter the micro reactor for reaction;

[0043] (3) Turn on the xenon lamp, adjust the light power to 10 W, and the mixed Taylor flow bubbles undergo reaction through the photocatalytic micro reactor to prepare sulfoxide;

[0044] (4) Control the gas and liquid flow rates to be 0.07 mL / h and 0.7 mL / h respectively, the reaction temperature is 25 °C, the residence time is 9.5 min, the selectivity of the product sulfoxide is 99%, and the yield is 98%.

[0045] Example 2

[0046] (1) Take thioether with the general formula (I) structure (R1 = OCH3, R2 = CH3) (2 mmol), and tetraphenylporphyrin (0.09 g, 0.15 mmol) is dissolved in acetonitrile (10 mL) to prepare a thioether solution;

[0047] (2) The thioether solution and oxygen are respectively pumped into the microchannel reaction device through the gas-phase inlet and the liquid-phase inlet. After the thioether and oxygen are mixed by the micro mixer to form a stable Taylor flow, they enter the micro reactor for reaction;

[0048] (3) Turn on the xenon lamp, adjust the light power to 15 W, and the mixed Taylor flow bubbles undergo reaction through the photocatalytic micro reactor to prepare sulfoxide;

[0049] (4) Control the gas and liquid flow rates to be 0.07 mL / h and 0.7 mL / h respectively, the reaction temperature is 50 °C, the residence time is 9.54 min, the selectivity of the product methyl phenyl sulfoxide is 99%, and the yield is 97%.

[0050] Example 3

[0051] (1) Take thioether with the general formula (I) structure (R1 = Cl, R2 = NO2) (2 mmol), and tetraphenylporphyrin (0.09 g, 0.15 mmol) is dissolved in N,N-dimethylformamide (10 mL) to prepare a methyl phenyl thioether solution;

[0052] (2) The thioether solution and oxygen are respectively pumped into the microchannel reaction device through the gas-phase inlet and the liquid-phase inlet. After the thioether and oxygen are mixed by the micro-mixer to form a stable Taylor flow, they enter the micro-reactor for reaction;

[0053] (3) Turn on the xenon lamp and adjust the light power to 15 W. The mixed Taylor flow bubbles pass through the photocatalytic micro-reactor for reaction to prepare sulfoxide;

[0054] (4) Control the gas and liquid flow rates to be 0.07 mL / h and 0.7 mL / h respectively, the reaction temperature to be 20 °C, the residence time to be 8.16 min, the selectivity of the product methylphenyl sulfoxide to be 99%, and the yield to be 96%.

[0055] Example 4

[0056] (1) Take thioether (R1 = H, R2 = OH) (2 mmol) with the general formula (I) structure and tetraphenylporphyrin (0.09 g, 0.15 mmol), and dissolve them in ethanol (10 mL) to prepare a thioether solution;

[0057] (2) The thioether solution and oxygen are respectively pumped into the microchannel reaction device through the gas-phase inlet and the liquid-phase inlet. After the thioether and oxygen are mixed by the micro-mixer to form a stable Taylor flow, they enter the micro-reactor for reaction;

[0058] (3) Turn on the xenon lamp and adjust the light power to 15 W. The mixed Taylor flow bubbles pass through the photocatalytic micro-reactor for reaction to prepare sulfoxide;

[0059] (4) Control the gas and liquid flow rates to be 0.07 mL / h and 0.56 mL / h respectively, the reaction temperature to be 25 °C, the residence time to be 10.77 min, the selectivity of the product methylphenyl sulfoxide to be 99%, and the yield to be 97%.

[0060] Example 5

[0061] (1) Take thioether (R1 = OH, R2 = H) (2 mmol) with the general formula (I) structure and tetraphenylporphyrin (0.09 g, 0.15 mmol), and dissolve them in methanol (10 mL) to prepare a thioether solution;

[0062] (2) The thioether solution and oxygen are respectively pumped into the microchannel reaction device through the gas-phase inlet and the liquid-phase inlet. After the thioether and oxygen are mixed by the micro-mixer to form a stable Taylor flow, they enter the micro-reactor for reaction;

[0063] (3) Turn on the xenon lamp and adjust the light power to 15 W. The mixed Taylor flow bubbles pass through the photocatalytic micro-reactor for reaction to prepare sulfoxide;

[0064] (4) Control the gas and liquid flow rates to be 0.07 mL / h and 0.84 mL / h respectively, the reaction temperature to be 35 °C, the residence time to be 8.66 min, the selectivity of the product sulfoxide to be 99%, and the yield to be 89%.

[0065] Example 6

[0066] (1) Take thioether with the general formula (I) structure (R1 = NO2, R2 = CH3) (2 mmol), and tetraphenylporphyrin (0.045 g, 0.075 mmol) and dissolve them in acetonitrile (10 mL) to prepare a thioether solution;

[0067] (2) Pump the thioether solution and oxygen into the microchannel reaction device through the gas phase inlet and liquid phase inlet respectively. After the thioether and oxygen are mixed by the micro mixer to form a stable Taylor flow, they enter the micro reactor for reaction;

[0068] (3) Turn on the xenon lamp, adjust the light power to 15 W, and let the mixed Taylor flow bubbles pass through the photocatalytic micro reactor for reaction to prepare sulfoxide;

[0069] (4) Control the gas and liquid flow rates to be 0.07 mL / h and 0.70 mL / h respectively, the reaction temperature to be 40 °C, the residence time to be 8.66 min, the selectivity of the product sulfoxide to be 99%, and the yield to be 90%.

[0070] Example 7

[0071] (1) Take thioether with the general formula (I) structure (R1 = F, R2 = OCH3) (2 mmol), and tetraphenylporphyrin (0.18 g, 0.3 mmol) and dissolve them in N,N-dimethylformamide (10 mL) to prepare a thioether solution;

[0072] (2) Pump the thioether solution and oxygen into the microchannel reaction device through the gas phase inlet and liquid phase inlet respectively. After the thioether and oxygen are mixed by the micro mixer to form a stable Taylor flow, they enter the micro reactor for reaction;

[0073] (3) Turn on the xenon lamp, adjust the light power to 15 W, and let the mixed Taylor flow bubbles pass through the photocatalytic micro reactor for reaction to prepare sulfoxide;

[0074] (4) Control the gas and liquid flow rates to be 0.07 mL / h and 0.70 mL / h respectively, the reaction temperature to be 45 °C, the residence time to be

[0075] 8.66 min, the selectivity of the product sulfoxide to be 99%, and the yield to be 94%.

[0076] Example 8

[0077] (1) Take thioether (R1 = H, R2 = Br) (2 mmol) with the structure of general formula (I), and tetraphenylporphyrin (0.09 g, 0.15 mmol) and dissolve them in methanol (10 mL) to prepare a thioether solution;

[0078] (2) Pump the thioether solution and oxygen into the microchannel reaction device through the gas-phase inlet and liquid-phase inlet respectively. After the thioether and oxygen are mixed by the micro-mixer to form a stable Taylor flow, they enter the micro-reactor for reaction;

[0079] (3) Turn on the xenon lamp, adjust the light power to 15 W, and the mixed Taylor flow bubbles pass through the photocatalytic micro-reactor for reaction to prepare sulfoxide;

[0080] (4) Control the gas-liquid flow rates to be 0.07 mL / h and 0.70 mL / h respectively, the reaction temperature to be 25 °C, and the residence time to be

[0081] 8.66 min, the selectivity of the product sulfoxide is 99%, and the yield is 92%.

[0082] Example 9

[0083] (5) Take thioether (R1 = CH3, R2 = CH3) (2 mmol) with the structure of general formula (I), and tetraphenylporphyrin (0.09 g, 0.15 mmol) and dissolve them in N,N-dimethylformamide (10 mL) to prepare a thioether solution;

[0084] (6) Pump the thioether solution and oxygen into the microchannel reaction device through the gas-phase inlet and liquid-phase inlet respectively. After the thioether and oxygen are mixed by the micro-mixer to form a stable Taylor flow, they enter the micro-reactor for reaction;

[0085] (7) Turn on the xenon lamp, adjust the light power to 15 W, and the mixed Taylor flow bubbles pass through the photocatalytic micro-reactor for reaction to prepare sulfoxide;

[0086] (8) Control the gas-liquid flow rates to be 0.07 mL / h and 0.70 mL / h respectively, the reaction temperature to be 30 °C, and the residence time to be

[0087] 8.66 min, the selectivity of the product sulfoxide is 99%, and the yield is 92%.

[0088] It can be seen from the results of the above examples that when preparing sulfoxide according to the method of the present invention, the product yield is high, continuous production can be achieved, the production cycle is short (generally less than 10 min), it is easy to operate, and the safety is high.

[0089] Comparative Example 1

[0090] Take methyl phenyl sulfide (2 mmol) and tetraphenylporphyrin (0.09 g, 0.15 mmol), dissolve them in methanol (10 mL) to prepare a sulfide solution; introduce it into a photoreaction flask, turn on the xenon lamp, adjust the power to 10 W, stir and react for 9.5 min to obtain the product methyl phenyl sulfoxide with a selectivity of 99% and a yield of 11.6%.

Claims

1. A method for continuously preparing sulfoxide by photocatalysis using a microreactor system, wherein the microreactor system comprises a photocatalytic microreactor, a xenon lamp and a micromixer, characterized in that The micro mixer is a micro mixer, and the micro mixer is provided with a gas phase channel and a liquid phase channel, and the gas phase channel and the liquid phase channel are combined into one channel; a plurality of walnut-shaped special-shaped structure channels are provided in the middle of the microchannel inside the photocatalytic microreactor, and the special-shaped structure channels are arranged at the center of the microchannel, dividing the microchannel into two upper and lower microchannels; The method for preparing sulfoxide comprises the steps of: (1) using a solvent to prepare a sulfide solution and a photocatalyst as a reaction solution; (2) The reaction liquid enters the liquid phase channel of the micromixer through the liquid phase inlet by the syringe pump, and the oxygen enters the gas phase channel of the micromixer through the gas phase inlet by the syringe pump, and then converges through the micromixer to form a stable Taylor flow; (3) turning on the xenon lamp and adjusting the light power, and the mixed Taylor flow bubbles react through the photocatalytic microreactor to prepare sulfoxide; The photocatalyst is tetraphenylporphyrin; the solvent is any one selected from methanol, ethanol, acetonitrile and N,N-dimethylformamide.

2. The method for preparing sulfoxide by continuous photocatalysis using a microreactor system according to claim 1, characterized in that The molar ratio of the photocatalyst to the thioether is 0.025-0.15:

1.

3. A method for preparing sulfoxide by continuous photocatalysis using a microreactor system according to claim 1, characterized in that The light is white light with a wavelength ranging from 400nm to 700nm and a power of 10 to 30W.

4. A method for preparing sulfoxide by continuous photocatalysis using a microreactor system according to claim 1, characterized in that The micro mixer is embedded in the photocatalytic micro reactor in parallel, and the micro mixer has a symmetrical structure, and the angle between the liquid phase channel and the gas phase channel is 30° to 60°.

5. A method for preparing sulfoxide by continuous photocatalysis using a microreactor system according to claim 1, characterized in that The pressure in the gas phase channel is greater than the pressure in the liquid phase channel, and the initial pressure difference between the gas phase channel and the liquid phase channel ranges from 100 to 1000 kPa; the liquid phase flow rate is 0.01 to 0.1 mL / h, and the gas phase flow rate is 0.1 to 1.0 mL / h.

6. A method for preparing sulfoxide by continuous photocatalysis using a microreactor system according to claim 1, characterized in that The number of the special-shaped structural channels is 200 to 1000.

7. A method for preparing sulfoxide by continuous photocatalysis using a microreactor system according to claim 1, characterized in that The thioether is represented by the general formula (I), Wherein R1 and R2 are selected from one of hydrogen, methyl, methoxy, halogen, nitro and hydroxyl.

8. A method for preparing sulfoxide by continuous photocatalysis using a microreactor system according to claim 1, characterized in that The reaction temperature is 20-50° C., and the residence time of the sulfide solution, oxygen and photocatalyst in the photocatalytic microreactor is 1-30 minutes. The reaction liquid and oxygen are squeezed and compressed in the micro-mixer under pressure and volume force, forming stable Taylor flow bubbles that enter the photocatalytic micro-reactor. In the photocatalytic microreactor, there are a number of walnut-shaped special-shaped structures, which are used to increase the gas-liquid contact area and enhance the gas-liquid mass transfer.

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