A method for synthesizing p-methylchlorobenzene

Abstract

The application belongs to the technical field of organic chemical synthesis, and specifically provides a synthesis method of p-methyl chlorobenzyl, S1, raw material preparation: vaporize liquid chlorine into chlorine gas; premix dimethylbenzene with a photocatalyst, introduce supercritical CO2 into the premixed mixture for dispersion to obtain a mixture; S2, chlorination reaction: introduce the mixture obtained in S1 into a chlorination kettle, then introduce chlorine gas into the chlorination kettle, start a plasma generator and an ultraviolet light source in the chlorination kettle; S3, byproduct treatment: absorb HCl gas generated in the chlorination reaction in S2 in a falling film absorber with deionized water to generate a hydrochloric acid solution; S4, product separation and refinement: remove supercritical CO2 from the mixture generated in the chlorination reaction in S2 through a pressure reducing valve, filter out the photocatalyst through a filter, and perform microwave distillation on the filtered mixed liquid through a distillation kettle to obtain p-methyl chlorobenzyl. The above method can improve the selectivity and yield of p-methyl chlorobenzyl.

Description

Technical Field

[0001] This invention relates to the field of organic chemical synthesis technology, and in particular to a method for synthesizing p-methylbenzyl chloride. Background Technology

[0002] p-Methylbenzyl chloride, chemically known as 1-chloromethyl-4-methylbenzene, is an important fine chemical intermediate and organic synthesis raw material, widely used in pharmaceuticals, pesticides, dyes, and fragrances. The chloromethyl and methyl groups in its molecular structure endow it with high reactivity, making it a key precursor for the synthesis of corresponding aldehydes, acids, alcohols, and other derivatives.

[0003] Currently, the mainstream industrial method for synthesizing p-methylbenzyl chloride involves a thermally initiated free radical substitution chlorination reaction using xylene and chlorine as raw materials under heating conditions. This typical process involves reacting the raw materials in a chlorination reactor at a relatively high temperature of 100℃-150℃, with the aim of preferentially substituting the hydrogen atom on the xylene methyl group to generate the target product.

[0004] However, this traditional process has several technical challenges that urgently need to be addressed, among which the selectivity problem during synthesis is particularly prominent. Due to the inherent randomness of thermally initiated free radical reactions and the similarity of reactivity between ortho and para hydrogen atoms, the reaction selectivity is poor, resulting in the formation of some positional isomer byproducts such as ortho-methylbenzyl chloride. Furthermore, it is difficult to effectively suppress the formation of benzene ring chlorination and overchlorination products, which greatly increases the burden of subsequent separation and reduces the purity and yield of the final product. Summary of the Invention

[0005] To address the aforementioned shortcomings, this invention provides a method for synthesizing p-methylbenzyl chloride, which improves the selectivity and yield of p-methylbenzyl chloride.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for synthesizing p-methylbenzyl chloride, comprising:

[0007] S1. Raw material preparation: Liquid chlorine is vaporized into chlorine gas; xylene is premixed with a photocatalyst, wherein the photocatalyst is selected from either tetraphenylporphyrin zinc or tetracarboxyphenylporphyrin iron; supercritical CO2 is introduced into the premixed mixture for dispersion to obtain a mixture.

[0008] S2, Chlorination Reaction: The mixture obtained in S1 is passed into a chlorination reactor, and then chlorine gas is introduced into the reactor. Simultaneously, the plasma generator and ultraviolet light source inside the reactor are activated. The plasma generator has a power of 1 kW and a frequency of 10 kHz, and the ultraviolet light source has a wavelength of 254 nm and an intensity of 100 mW / cm². 2 The reaction yields a mixture and HCl gas;

[0009] S3. Byproduct treatment: The HCl gas generated by the S2 chlorination reaction is absorbed by deionized water in a falling film absorber to generate hydrochloric acid solution.

[0010] S4. Product separation and purification: The mixture generated by the S2 chlorination reaction is vaporized through a pressure reducing valve to remove supercritical CO2, and the photocatalyst is filtered out through a filter. The filtered mixed liquid is then microwave distilled through a distillation kettle to obtain p-methylbenzyl chloride.

[0011] As a further improvement of the present invention, the vaporization temperature of liquid chlorine in S1 is 70℃-85℃, and the output flow rate is 0.5L / min-2L / min.

[0012] As a further improvement of the present invention, the photocatalyst added in S1 is 1%-5% of the mass of xylene, the premixing temperature is 28℃-35℃, and the mixing time is 20min-30min.

[0013] As a further improvement of the present invention, the mass ratio of supercritical CO2 to xylene introduced in S1 is 0.8-1.2:1, the dispersion temperature is 35℃-50℃, the dispersion pressure is 8MPa-12MPa, the dispersion stirring speed is 300rpm-500rpm, and the dispersion time is 10-30 minutes.

[0014] As a further improvement of the present invention, the molar ratio of chlorine gas introduced in S2 to xylene used in S1 is 1-1.2:1, the chlorination reaction temperature is controlled at 40℃-60℃, the reaction pressure is 8MPa-12MPa, and the reaction time is 2h-3h.

[0015] As a further improvement of the present invention, the velocity of HCl gas entering the falling film absorber in S3 is 0.4 m / s, and the spray density of deionized water is 10 m³ / s. 3 / (m 2 ·h).

[0016] As a further improvement of the present invention, the pressure of the pressure reducing valve required for the supercritical CO2 vaporization of S4 is 0.1 MPa.

[0017] As a further improvement of the present invention, the photocatalyst solid filtered out in S4 is heated to 150℃-200℃ at a rate of 2℃ / min-5℃ / min under a nitrogen or argon atmosphere, and is kept at the same temperature for 1.4h-2h, and then cooled to 20℃-35℃ for reuse.

[0018] As a further improvement of the present invention, the microwave distillation in S4 specifically involves: firstly, distilling for 35-45 minutes at a microwave power of 600 W and a temperature of 80-90°C, and then increasing the microwave power to 900 W and controlling the temperature at 105-115°C for 50-60 minutes to obtain p-methylbenzyl chloride.

[0019] The beneficial effects of this invention are:

[0020] A highly efficient and selective synthesis system was constructed through the innovative synergy of photocatalysis, plasma activation, and supercritical CO2 dispersion technology. This synergistic system successfully overcomes the technical problems of poor selectivity, numerous byproducts, and harsh reaction conditions associated with traditional thermal chlorination methods. The photocatalyst, under ultraviolet light excitation, guides chlorine radicals to preferentially bind to the para-methyl group of xylene, improving selectivity; plasma activation significantly increases the reaction rate; and supercritical CO2, as the mass transfer medium, creates a uniform reaction environment, ensuring sufficient contact of all components at the molecular level, thus maximizing the efficiency of the former two methods. Attached Figure Description

[0021] Figure 1 This is the gas chromatogram of Example 1;

[0022] Figure 2 This is the gas chromatogram of Example 2;

[0023] Figure 3 This is the gas chromatogram of Example 3. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0025] This invention provides a method for synthesizing p-methylbenzyl chloride, comprising:

[0026] S1. Raw material preparation:

[0027] S101: Liquid chlorine is introduced from the cylinder into the vaporizer and vaporized into chlorine gas. The vaporization temperature is controlled at 70℃-85℃, and the output flow rate is controlled at 0.5L / min-2L / min.

[0028] S102: Premix xylene with the photocatalyst, with the mass of the photocatalyst being 1%-5% of the mass of xylene, the mixing temperature being 28℃-35℃, and the mixing time being 20min-30min.

[0029] As a further explanation of this embodiment, the photocatalyst is selected from either zinc tetraphenylporphyrin (ZnTPP) or iron tetracarboxyphenylporphyrin (Fe-TCPP).

[0030] S103: Transfer the premixed mixture to a pressure vessel, then introduce supercritical CO2 for dispersion. The mass ratio of supercritical CO2 to xylene is 0.8-1.2:1, the dispersion temperature is 35℃-50℃, the pressure inside the vessel is controlled at 8MPa-12MPa, the stirring speed is 300rpm-500rpm, and the dispersion time is 10-30 minutes to obtain the mixture.

[0031] S2, chlorination reaction:

[0032] The mixture obtained from S103 is introduced into a chlorination reactor, followed by the introduction of chlorine gas obtained from S101. The molar ratio of the introduced chlorine gas to xylene is 1-1.2:1. Simultaneously, the plasma generator and ultraviolet light source inside the chlorination reactor are activated. The plasma generator has a power of 1 kW and a frequency of 10 kHz, while the ultraviolet light source has a wavelength of 254 nm and an intensity of 100 mW / cm². 2 .

[0033] The reaction temperature is controlled at 40℃-60℃, the pressure is maintained at 8MPa-12MPa, and the reaction time is 2h-3h.

[0034] S3. By-product treatment:

[0035] The HCl gas generated in the chlorination reaction exits from the chlorination reactor and enters the falling film absorber at a velocity of 0.4 m / s, where it comes into contact with the countercurrent deionized water. The spray density of the deionized water is 10 m³ / s. 3 / (m 2 ·h), which absorbs and generates hydrochloric acid solution.

[0036] S4. Product separation and purification:

[0037] S401: Product separation. The mixture after the chlorination reaction is first transferred through a pressure reducing valve to reduce the pressure to atmospheric pressure (0.1 MPa), causing the supercritical CO2 to vaporize. The remaining mixture after vaporization contains p-methylbenzyl chloride, unreacted xylene, and photocatalyst. The remaining mixture is filtered to remove the solid photocatalyst, yielding a mixed liquid.

[0038] As a further explanation of this embodiment, the vaporized supercritical CO2 is condensed back into a liquid by a condenser and can be reused. The filtered photocatalyst solid is heated to 150°C-200°C at a rate of 2°C / min-5°C / min under a nitrogen or argon atmosphere and kept at that temperature for 1.4h-2h, and then cooled to 20°C-35°C under an inert atmosphere for reuse.

[0039] S402: Distillation and purification. The mixed liquid obtained from S401 is passed into a distillation kettle for microwave distillation. First, under the conditions of microwave power of 600 W and temperature of 80℃-90℃, the unreacted xylene is recovered by distillation for 35 min-45 min. Then, the microwave power is increased to 900 W and the temperature is controlled at 105℃-115℃, and the product is distilled for 50 min-60 min to obtain the p-methylbenzyl chloride product.

[0040] Example 1

[0041] S1. Raw material preparation:

[0042] S101: Liquid chlorine is introduced from the cylinder into the vaporizer, the vaporization temperature is controlled at 70℃, and the output flow rate of vaporized chlorine is controlled at 0.5L / min.

[0043] S102: Add 1% (by mass) of tetraphenylporphyrin zinc to xylene, mix at 28°C for 20 minutes.

[0044] S103: Transfer the premixed mixture to a pressure vessel, then introduce supercritical CO2 for dispersion. The mass ratio of supercritical CO2 to xylene is 0.8:1. The dispersion temperature is 35℃, the pressure inside the vessel is controlled at 8MPa, the stirring speed is 300rpm, and the dispersion time is 10 minutes to obtain the mixture.

[0045] S2, chlorination reaction:

[0046] The mixture obtained from S103 was introduced into a chlorination reactor, followed by the introduction of chlorine gas obtained from S101. The molar ratio of the introduced chlorine gas to xylene was 1:1. Simultaneously, the plasma generator and ultraviolet light source inside the chlorination reactor were activated. The plasma generator had a power of 1 kW and a frequency of 10 kHz, while the ultraviolet light source had a wavelength of 254 nm and an intensity of 100 mW / cm². 2 .

[0047] The reaction temperature was controlled at 40℃, the pressure was maintained at 8MPa, and the reaction time was 2h.

[0048] S3. By-product treatment:

[0049] The HCl gas generated in the chlorination reaction exits from the chlorination reactor and enters the falling film absorber at a velocity of 0.4 m / s, where it comes into contact with the countercurrent deionized water. The spray density of the deionized water is 10 m³ / s. 3 / (m 2 ·h), which absorbs and generates hydrochloric acid solution.

[0050] S4. Product separation and purification:

[0051] S401: Product separation. The mixture after the chlorination reaction is first transferred through a pressure reducing valve to reduce the pressure to atmospheric pressure (0.1 MPa), causing the supercritical CO2 to vaporize. The remaining mixture after vaporization is filtered to remove the solid photocatalyst, yielding a mixed liquid.

[0052] S402: Distillation and purification. The mixed liquid obtained from S401 is passed into a distillation kettle for microwave distillation. First, it is distilled for 35 minutes under the conditions of microwave power of 600 W and temperature of 80℃. Then, the microwave power is increased to 900 W and the temperature is raised to 105℃, and it is distilled for 50 minutes to obtain the p-methylbenzyl chloride product.

[0053] Example 2

[0054] S1. Raw material preparation:

[0055] S101: Liquid chlorine is introduced from the cylinder into the vaporizer, the vaporization temperature is controlled at 78℃, and the output flow rate of vaporized chlorine is controlled at 1.3L / min.

[0056] S102: Add 3% (by weight of xylene) of tetraphenylporphyrin zinc to xylene, mix at 32°C for 25 min.

[0057] S103: Transfer the premixed mixture to a pressure vessel, then introduce supercritical CO2 for dispersion. The mass ratio of the added supercritical CO2 to xylene is 1:1. The dispersion temperature is 42℃, the pressure inside the vessel is controlled at 10MPa, the stirring speed is 400rpm, and the dispersion time is 20 minutes to obtain the mixture.

[0058] S2, chlorination reaction:

[0059] The mixture obtained from S103 was introduced into a chlorination reactor, followed by the introduction of chlorine gas obtained from S101. The molar ratio of the introduced chlorine gas to xylene was 1.1:1. Simultaneously, the plasma generator and ultraviolet light source inside the chlorination reactor were activated. The plasma generator had a power of 1 kW and a frequency of 10 kHz, while the ultraviolet light source had a wavelength of 254 nm and an intensity of 100 mW / cm². 2 .

[0060] The reaction temperature was controlled at 50℃, the pressure was maintained at 10MPa, and the reaction time was 2.5h.

[0061] S3. By-product treatment:

[0062] The HCl gas generated in the chlorination reaction exits from the chlorination reactor and enters the falling film absorber at a velocity of 0.4 m / s, where it comes into contact with the countercurrent deionized water. The spray density of the deionized water is 10 m³ / s. 3 / (m 2·h), which absorbs and generates hydrochloric acid solution.

[0063] S4. Product separation and purification:

[0064] S401: Product separation. The mixture after the chlorination reaction is first transferred through a pressure reducing valve to reduce the pressure to atmospheric pressure (0.1 MPa), allowing the supercritical CO to be released. 2 Vaporization. The remaining mixture after vaporization is filtered to remove the solid photocatalyst, yielding a mixed liquid.

[0065] S402: Distillation and purification. The mixed liquid obtained from S401 is passed into a distillation vessel for microwave distillation. First, it is distilled for 40 minutes at a microwave power of 600 W and a temperature of 85°C. Then, the microwave power is increased to 900 W and the temperature is raised to 110°C, and it is distilled for 55 minutes to obtain the p-methylbenzyl chloride product.

[0066] Example 3

[0067] S1. Raw material preparation:

[0068] S101: Liquid chlorine is introduced from the cylinder into the vaporizer, the vaporization temperature is controlled at 85℃, and the output flow rate of vaporized chlorine is controlled at 2L / min.

[0069] S102: Add 5% (by weight of xylene) of tetraphenylporphyrin zinc to xylene, mix at 35°C for 30 minutes.

[0070] S103: Transfer the premixed mixture to a pressure vessel, then introduce supercritical CO2 for dispersion. The mass ratio of supercritical CO2 to xylene is 1.2:1. The dispersion temperature is 50℃, the pressure inside the vessel is controlled at 12MPa, the stirring speed is 500rpm, and the dispersion time is 30 minutes to obtain the mixture.

[0071] S2, chlorination reaction:

[0072] The mixture obtained from S103 was introduced into a chlorination reactor, followed by the introduction of chlorine gas obtained from S101. The molar ratio of the introduced chlorine gas to xylene was 1.2:1. Simultaneously, the plasma generator and ultraviolet light source inside the chlorination reactor were activated. The plasma generator had a power of 1 kW and a frequency of 10 kHz, while the ultraviolet light source had a wavelength of 254 nm and an intensity of 100 mW / cm². 2 .

[0073] The reaction temperature was controlled at 60℃, the pressure was maintained at 12MPa, and the reaction time was 3h.

[0074] S3. By-product treatment:

[0075] The HCl gas generated in the chlorination reaction exits from the chlorination reactor and enters the falling film absorber at a velocity of 0.4 m / s, where it comes into contact with the countercurrent deionized water. The spray density of the deionized water is 10 m³ / s. 3 / (m 2 ·h), which absorbs and generates hydrochloric acid solution.

[0076] S4. Product separation and purification:

[0077] S401: Product separation. The mixture after the chlorination reaction is first transferred through a pressure reducing valve to reduce the pressure to atmospheric pressure (0.1 MPa), causing the supercritical CO2 to vaporize. The remaining mixture after vaporization is filtered to remove the solid photocatalyst, yielding a mixed liquid.

[0078] S402: Distillation and purification. The mixed liquid obtained from S401 is passed into a distillation kettle for microwave distillation. First, it is distilled for 45 minutes under the conditions of microwave power of 600 W and temperature of 90℃. Then, the microwave power is increased to 900 W and the temperature is raised to 115℃, and it is distilled for 60 minutes to obtain the p-methylbenzyl chloride product.

[0079] Comparative Example

[0080] p-Methylbenzyl chloride was prepared by a conventional thermal chlorination method. Xylene and azobisisobutyronitrile (AIBN) were added to a reaction vessel and heated to 120°C. Chlorine gas was introduced at a molar ratio of chlorine to xylene of 1.1:1, and the reaction was carried out for 3 hours. The mixture after the reaction was directly separated by atmospheric-vacuum distillation to obtain p-methylbenzyl chloride.

[0081] The spectra of the foregoing embodiments are as follows Figures 1 to 3 As shown.

[0082] The yield, para-selectivity, and product purity of the p-methylbenzyl chloride products produced by the aforementioned examples and comparative processes are shown in the table below.

[0083]

[0084] As can be seen from the above data, the synthesis method provided by the present invention, through the synergistic application of photocatalysis, plasma activation and supercritical CO2 medium dispersion, is significantly superior to the traditional thermal chlorination process in terms of yield, selectivity and product purity of p-methylbenzyl chloride.

[0085] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above-described embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for synthesizing p-methylbenzyl chloride, characterized in that, include: S1. Raw material preparation: Liquid chlorine is vaporized into chlorine gas; xylene is premixed with a photocatalyst, wherein the photocatalyst is selected from either tetraphenylporphyrin zinc or tetracarboxyphenylporphyrin iron; supercritical CO2 is introduced into the premixed mixture for dispersion to obtain a mixture. S2, Chlorination Reaction: The mixture obtained in S1 is passed into a chlorination reactor, and then chlorine gas is introduced into the reactor. Simultaneously, the plasma generator and ultraviolet light source inside the reactor are activated. The plasma generator has a power of 1 kW and a frequency of 10 kHz, and the ultraviolet light source has a wavelength of 254 nm and an intensity of 100 mW / cm². 2 The reaction yields a mixture and HCl gas; S3. Byproduct treatment: The HCl gas generated by the S2 chlorination reaction is absorbed by deionized water in a falling film absorber to generate hydrochloric acid solution. S4. Product separation and purification: The mixture generated by the S2 chlorination reaction is vaporized through a pressure reducing valve to remove supercritical CO2, and the photocatalyst is filtered out through a filter. The filtered mixed liquid is then microwave distilled through a distillation kettle to obtain p-methylbenzyl chloride.

2. The method for synthesizing p-methylbenzyl chloride according to claim 1, characterized in that, The vaporization temperature of liquid chlorine in S1 is 70℃-85℃, and the output flow rate is 0.5L / min-2L / min.

3. The method for synthesizing p-methylbenzyl chloride according to claim 1, characterized in that, The photocatalyst added in S1 is 1%-5% of the mass of xylene, the premixing temperature is 28℃-35℃, and the mixing time is 20min-30min.

4. The method for synthesizing p-methylbenzyl chloride according to claim 1, characterized in that, The mass ratio of supercritical CO2 to xylene introduced in S1 is 0.8-1.2:1, the dispersion temperature is 35℃-50℃, the dispersion pressure is 8MPa-12MPa, the dispersion stirring speed is 300rpm-500rpm, and the dispersion time is 10-30 minutes.

5. The method for synthesizing p-methylbenzyl chloride according to claim 1, characterized in that, The molar ratio of chlorine gas introduced in S2 to xylene used in S1 is 1-1.2:

1. The chlorination reaction temperature is controlled at 40℃-60℃, the reaction pressure is 8MPa-12MPa, and the reaction time is 2h-3h.

6. The method for synthesizing p-methylbenzyl chloride according to claim 1, characterized in that, The velocity of HCl gas entering the falling film absorber in S3 is 0.4 m / s, and the spray density of deionized water is 10 m³ / s. 3 / (m 2 ·h).

7. The method for synthesizing p-methylbenzyl chloride according to claim 1, characterized in that, The pressure required by the pressure reducing valve during the supercritical CO2 vaporization of S4 is 0.1 MPa.

8. The method for synthesizing p-methylbenzyl chloride according to claim 1, characterized in that, The photocatalyst solid filtered out in S4 is heated to 150℃-200℃ at a rate of 2℃ / min-5℃ / min under a nitrogen or argon atmosphere, and kept at the same temperature for 1.4h-2h. Then it is cooled to 20℃-35℃ for reuse.

9. The method for synthesizing p-methylbenzyl chloride according to claim 1, characterized in that, The microwave distillation in S4 specifically involves: first, distilling at a microwave power of 600 W and a temperature of 80℃-90℃ for 35-45 minutes; then, increasing the microwave power to 900 W and controlling the temperature at 105℃-115℃ for 50-60 minutes to obtain p-methylbenzyl chloride.

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