Method for catalytic continuous synthesis of aryl methyl ether

Abstract

The invention provides a method for catalytic continuous synthesis of aryl methyl ether, and belongs to the field of aryl methyl ether. The method for catalytically and continuously synthesizing the aryl methyl ether is carried out in a manner of combining continuous reaction and continuous rectification. According to the method for catalytically and continuously synthesizing the aryl methyl ether, the continuous production of the aryl methyl ether can be realized while dimethyl sulfate is not adopted and a large amount of high-toxicity wastewater and solid wastes are prevented from being generated in the production process, and the continuous production of the aryl methyl ether is mild in reaction condition, low in requirement on production equipment, small in production risk and high in production efficiency; the yield of the aryl methyl ether prepared through large-scale production is high, and large-scale industrial production is facilitated.

Description

Technical Field

[0001] This invention relates to the field of aryl methyl ethers, and in particular to a method for the catalytic continuous synthesis of aryl methyl ethers. Background Technology

[0002] Existing methods for preparing aryl methyl ethers mainly involve using phenol or phenol containing R groups or functional groups as raw materials and dimethyl sulfate as a methylating agent to carry out the reaction.

[0003] The existing traditional production method for anisole uses phenol and dimethyl sulfate as raw materials to react and prepare anisole. For example, Chinese patent CN1105974A discloses a method for preparing anisole, which uses an excess of 10-30% dimethyl sulfate and sodium phenolate solution, reacts at 10-30°C for 1 hour, then at 40°C for 30 minutes; then at reflux temperature for another 30 minutes, followed by azeotropic distillation to obtain anisole, which is then dried to obtain the anisole product. However, the dimethyl sulfate used in this process is a highly toxic substance, and the production process generates a large amount of highly toxic wastewater and solid waste, causing serious environmental pollution. The post-treatment of highly toxic wastewater and solid waste is difficult, which is not conducive to the development of anisole as a core technology.

[0004] Meanwhile, existing technologies disclose methods for synthesizing anisole using dimethyl carbonate, which has lower toxicity, as a methylating agent. For example, Chinese patent CN110841663A discloses a method for synthesizing anisole using phenol and dimethyl carbonate as raw materials. This method uses phenol and dimethyl carbonate as raw materials, and prepares anisole under alkali metal halide or alkaline earth metal halide catalytic conditions, while simultaneously using metal halide auxiliaries. Although this method overcomes the aforementioned problem of high toxicity of dimethyl sulfate, it is a batch reaction and requires a high-pressure reaction environment of 3-7 MPa, placing high demands on production equipment and posing significant production risks. Furthermore, the reaction time is relatively long, and production trials have shown that the yield of this process can only reach 80%, which is not conducive to large-scale industrial production. Summary of the Invention

[0005] To address the technical problems existing in the prior art, this invention provides a method for the continuous catalytic synthesis of aryl methyl ethers. This method can achieve continuous production of aryl methyl ethers while avoiding the use of dimethyl sulfate and the generation of large amounts of highly toxic wastewater and solid waste during the production process. Furthermore, the continuous production of aryl methyl ethers has mild reaction conditions, low requirements for production equipment, low production risk, high production efficiency, and high yield of aryl methyl ethers prepared on a large scale, which is beneficial for large-scale industrial production.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A method for the catalytic continuous synthesis of aryl methyl ethers, which employs a combination of continuous reaction and continuous distillation; The continuous reaction method is as follows: m-methylphenol and dimethyl carbonate are mixed evenly and then fed into a tubular reactor simultaneously with 1-butyl-3-methylimidazolium chloride. The reaction temperature of the tubular reactor is controlled at 180-200℃ and the reaction pressure is 1.1-1.2MPa. Catalytic synthesis is carried out continuously to continuously obtain the reaction solution. The tubular reactor is fixedly filled with a synergistic catalyst. The preparation method of the synergistic catalyst is as follows: mesoporous activated carbon is treated with nitric acid to obtain modified mesoporous activated carbon; copper chloride, neodymium chloride and modified mesoporous activated carbon are added to an ethanol solution, stirred at room temperature, and then 1-butyl-3-methylimidazolium chloride is added. After stirring, the solid is separated and dried to obtain the synergistic catalyst. The continuous distillation method involves continuously distilling the reaction solution to obtain m-methyl anisole.

[0007] Preferably, in the continuous reaction, the total feed rate of m-methylphenol, dimethyl carbonate, and 1-butyl-3-methylimidazolium chloride simultaneously fed into the tubular reactor is 180-900 mL / h. The residence time of the material in the tubular reactor is 0.06-0.31 h.

[0008] Preferably, in the continuous reaction, the molar ratio of m-methylphenol to dimethyl carbonate is 1:3-4; The molar ratio of m-methylphenol to 1-butyl-3-methylimidazolium chloride is 1:1.

[0009] Preferably, in the continuous reaction, the loading weight of the synergistic catalyst is 5-6% of the total weight of the material fed into the tubular reactor within 1 hour.

[0010] Preferably, in the preparation of the synergistic catalyst, the volume concentration of the ethanol solution is 60-65%; The weight ratio of copper chloride, neodymium chloride, ethanol solution, modified mesoporous activated carbon, and 1-butyl-3-methylimidazolium chloride is 2.2-2.3:0.4-0.5:100-110:35-38:4-4.5.

[0011] Furthermore, in the preparation of the synergistic catalyst, the method of treating mesoporous activated carbon with nitric acid is as follows: the mesoporous activated carbon is added to a nitric acid solution, heated to reflux, kept at reflux, and then the solid is separated. The solid is washed and dried to obtain modified mesoporous activated carbon.

[0012] Preferably, in the process of treating mesoporous activated carbon with nitric acid, the concentration of the nitric acid solution is 6.5-7 mol / L; The weight ratio of mesoporous activated carbon to nitric acid solution is 1:6-8; The heat preservation and reflux time is 5-6 hours.

[0013] Furthermore, the continuous distillation method involves continuously feeding the reaction liquid into a continuous distillation column, controlling the bottom temperature of the continuous distillation column at 190°C, maintaining the top temperature within the range of 70-80°C, continuously performing atmospheric pressure distillation on the reaction liquid, and continuously distilling m-methyl anisole from the middle section of the continuous distillation column.

[0014] Preferably, in the continuous distillation, the distillation temperature of m-methyl anisole in the middle section of the continuous distillation column is 173°C.

[0015] Preferably, in the continuous distillation, methanol and dimethyl carbonate are continuously distilled out and condensed from the top of the continuous distillation column and recovered, while non-condensable gases are vented. The high-boiling point of the continuous distillation column is recovered, mixed with 1-butyl-3-methylimidazolium chloride, and then added to the continuous reaction.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The method for catalytic continuous synthesis of aryl methyl ether of the present invention uses m-methylphenol and dimethyl carbonate (DMC) as raw materials and 1-butyl-3-methylimidazolium chloride as an ionic liquid catalyst. The m-methyl anisole is prepared by a combination of tubular continuous reaction and continuous distillation. At the same time, a synergistic catalyst prepared by a specific method is used in the tubular continuous reaction process. First, the surface of mesoporous activated carbon is modified by nitric acid oxidation to activate the surface properties of the mesoporous activated carbon and obtain modified mesoporous activated carbon. Then, the modified mesoporous activated carbon is adsorbed and loaded with copper chloride and neodymium chloride, and then contacted and bonded with 1-butyl-3-methylimidazolium chloride to obtain the synergistic catalyst. The catalytic active component in the synergistic catalyst is combined with the ionic liquid catalyst to further improve the stability of the continuous reaction, improve the catalytic performance of the methylation reaction, reduce the reaction temperature and reaction pressure required for the continuous reaction, shorten the reaction time, improve the reaction efficiency, and improve the yield of continuously prepared m-methyl anisole. The aforementioned technical means work together synergistically to achieve continuous production of aryl methyl ethers while avoiding the use of dimethyl sulfate and the generation of large amounts of highly toxic wastewater and solid waste during the production process. Furthermore, the reaction conditions for continuous production of aryl methyl ethers are mild, the requirements for production equipment are low, the production risk is low, the production efficiency is high, and the yield of aryl methyl ethers prepared on a large scale is high, which is conducive to large-scale industrial production.

[0017] (2) The method for catalytic continuous synthesis of aryl methyl ether of the present invention uses m-methylphenol and dimethyl carbonate (DMC) as raw materials, and 1-butyl-3-methylimidazolium chloride as an ionic liquid catalyst, and in combination with a synergistic catalyst, effectively adapting to the continuous catalytic reaction environment. The preparation of m-methyl anisole is carried out by a combination of tubular continuous reaction and continuous distillation. The suitable reaction pressure is 1.2 MPa, the reaction temperature is 180-200℃, and the residence time of the material in the tubular reactor is 0.06-0.31 h. It can reduce the reaction pressure, shorten the reaction time, and improve the reaction efficiency. At the same time, it can achieve continuous catalytic reaction and be used in conjunction with a continuous distillation device to save energy and further improve the product yield.

[0018] (3) The method for catalytic continuous synthesis of aryl methyl ether of the present invention, under the premise of continuous reaction pressure of 1.2 MPa, continuous reaction temperature of 180-200℃ and material residence time of 0.06-0.31 h, can produce m-methyl anisole with a purity of 99.56 wt% and a yield of m-methyl anisole (based on m-methylphenol) of 98.54%. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of an apparatus for the catalytic continuous synthesis of aryl methyl ethers according to an embodiment of the present invention.

[0020] In the diagram, 1-mixing vessel; 2-catalyst circulation tank; 3-tubular reactor; 4-continuous distillation column. Detailed Implementation

[0021] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention are now described.

[0022] Example 1 This embodiment provides a method for the catalytic continuous synthesis of aryl methyl ethers, which employs a combination of continuous reaction and continuous distillation, specifically as follows: The continuous reaction method is as follows: m-Cresol and dimethyl carbonate (DMC) are continuously introduced into mixing tank 1 at a molar ratio of 1:3. After being mixed evenly in mixing tank 1, the mixture is metered and continuously fed into tubular reactor 3. Simultaneously, 1-butyl-3-methylimidazolium chloride, in an equimolar ratio with m-Cresol, is metered and continuously fed into tubular reactor 3 via catalyst circulation tank 2. The total feed rate of m-Cresol, DMC, and 1-butyl-3-methylimidazolium chloride to tubular reactor 3 is controlled at 180 mL / h. The reaction temperature in tubular reactor 3 is controlled at 180℃, the reaction pressure at 1.2 MPa, and the material residence time at 0.31 h, and the methylation reaction is continuously carried out to obtain the reaction solution.

[0023] The tubular reactor 3 is filled with a synergistic catalyst; the weight of the synergistic catalyst is 5% of the total weight of the material fed into the tubular reactor 3 within 1 hour.

[0024] The preparation method of the synergistic catalyst is as follows: mesoporous activated carbon is added to 6 times its weight of nitric acid solution, stirred for 10 min, heated to 65℃, kept at this temperature and stirred under reflux for 5 h, and then the solid is separated by centrifugation. The solid is washed with deionized water until neutral and then transferred to a constant temperature drying oven and dried at 110℃ to constant weight to obtain modified mesoporous activated carbon. Then, copper chloride and neodymium chloride are added to a 60% (v / v) ethanol solution, stirred for 20 min, and then the modified mesoporous activated carbon is added. After stirring at room temperature for 50 min, 1-butyl-3-methylimidazolium chloride is added. The addition of 1-butyl-3-methylimidazolium chloride is controlled to be completed within 30 min. After stirring for 2 h, the solid is separated by centrifugation and transferred to a vacuum drying oven. It is dried at 115℃ for 11 h under a vacuum of 0.08 MPa to obtain the synergistic catalyst.

[0025] The concentration of the nitric acid solution is 6.5 mol / L.

[0026] The weight ratio of copper chloride, neodymium chloride, ethanol solution, modified mesoporous activated carbon, and 1-butyl-3-methylimidazolium chloride is 2.2:0.4:100:35:4.

[0027] The continuous distillation method involves continuously feeding the reaction liquid into the lower part of the continuous distillation column 4, controlling the bottom temperature of the continuous distillation column 4 at 190℃, and maintaining the top temperature within the range of 75-80℃, and continuously distilling the reaction liquid under atmospheric pressure, and continuously distilling m-methyl anisole from the middle section of the continuous distillation column 4 (the distillation temperature of m-methyl anisole in the middle section of the continuous distillation column 4 is 173℃).

[0028] In the continuous atmospheric distillation process, methanol and dimethyl carbonate are continuously distilled and condensed from the top of the continuous distillation column 4 and recovered. At the same time, non-condensable gas (byproduct carbon dioxide) is condensed and vented. The material continuously collected from the bottom of the continuous distillation column 4 is refluxed back into the continuous distillation column 4 after heat exchange to maintain the bottom temperature of the continuous distillation column 4 at 190°C.

[0029] Furthermore, during the continuous atmospheric distillation process, the high-boiling-point substance (i.e., 1-butyl-3-methylimidazolium chloride) is discharged from the bottom of the continuous distillation column 4 at regular intervals. After heat exchange, the high-boiling-point substance is recovered into the catalyst circulation tank 2 to continue participating in subsequent reactions.

[0030] The catalytic continuous synthesis method for aryl methyl ethers in this embodiment, based on the feed amounts of 1464 g (13.54 mol) of m-methylphenol and 3662 g (40.65 mol) of dimethyl carbonate (DMC), uses 2365 g (13.54 mol) of 1-butyl-3-methylimidazolium chloride. The final mass of m-methyl anisole obtained is 1619.65 g, the purity is 99.55 wt%, and the molar yield (based on m-methylphenol) is 97.48%.

[0031] The catalytic continuous synthesis method for aryl methyl ethers in this embodiment uses an apparatus including: a mixing vessel 1, a catalyst circulation tank 2, a tubular reactor 3, and a continuous distillation column 4.

[0032] The mixing vessel 1 is connected to feed pipes for m-methylphenol and dimethyl carbonate (DMC) to continuously receive and mix the feed m-methylphenol and DMC. The bottom outlet of the mixing vessel 1 is connected to the feed pipe of the tubular reactor 3 via a feeding pump to continuously feed the mixed m-methylphenol and DMC into the tubular reactor 3.

[0033] The bottom outlet of the catalyst circulation tank 2 is connected to the feed pipe of the tubular reactor 3 via a feeding pump, which is used to continuously feed 1-butyl-3-methylimidazolium chloride into the tubular reactor 3.

[0034] The outlet of the tubular reactor 3 is connected to the lower inlet of the continuous distillation column 4 to continuously feed the reaction liquid after methylation into the continuous distillation column 4 for continuous distillation.

[0035] The top of the continuous distillation column 4 is equipped with a light component distillation outlet, which is used to continuously distill and condense methanol and dimethyl carbonate for recovery, while venting non-condensable gases (such as byproduct carbon dioxide).

[0036] The middle section of the continuous distillation column 4 is equipped with a product outlet for the continuous distillation of m-methyl anisole.

[0037] The bottom of the continuous distillation column 4 is provided with a heavy weight separation outlet, which is used to continuously extract material from the bottom of the continuous distillation column 4 for heat exchange and then return it to the continuous distillation column 4 to maintain the bottom temperature of the continuous distillation column 4 at 190℃.

[0038] Meanwhile, the recombinant extraction outlet at the bottom of the continuous distillation column 4 is also connected to the reflux port of the catalyst circulation tank 2 via a heat exchanger; this is used to extract the high-boiling-point substance (i.e., 1-butyl-3-methylimidazolium chloride) from the bottom of the continuous distillation column 4 at regular intervals during the continuous atmospheric distillation process, and after heat exchange, it is recovered into the catalyst circulation tank 2 to continue participating in subsequent reactions.

[0039] Example 2 This embodiment provides a method for the catalytic continuous synthesis of aryl methyl ethers, which employs a combination of continuous reaction and continuous distillation, specifically as follows: The continuous reaction method involves continuously introducing m-methylphenol and dimethyl carbonate (DMC) into mixing tank 1 at a molar ratio of 1:3. After being mixed evenly in mixing tank 1, the mixture is metered and continuously fed into tubular reactor 3. Simultaneously, 1-butyl-3-methylimidazolium chloride, in an equimolar ratio with m-methylphenol, is metered and continuously fed into tubular reactor 3 via catalyst circulation tank 2. The total feed rate of m-methylphenol, DMC, and 1-butyl-3-methylimidazolium chloride into tubular reactor 3 is controlled at 180 mL / h. The reaction temperature in tubular reactor 3 is controlled at 190℃, the reaction pressure at 1.2 MPa, and the material residence time at 0.31 h, continuously carrying out the methylation reaction to obtain the reaction solution.

[0040] The tubular reactor 3 is filled with a synergistic catalyst; the weight of the synergistic catalyst is 5.5% of the total weight of the material fed into the tubular reactor 3 within 1 hour.

[0041] The synergistic catalyst was prepared by adding mesoporous activated carbon to a nitric acid solution with a weight of 7, stirring for 15 min, heating to 68°C, and stirring under reflux for 5.5 h. The solid was then separated by centrifugation, washed with deionized water until neutral, and transferred to a constant-temperature drying oven for drying at 115°C to constant weight to obtain modified mesoporous activated carbon. Next, copper chloride and neodymium chloride were added to a 62% (v / v) ethanol solution, stirred for 25 min, and then the modified mesoporous activated carbon was added. After stirring at room temperature for 55 min, 1-butyl-3-methylimidazolium chloride was added, with the addition of 1-butyl-3-methylimidazolium chloride completed within 35 min. Stirring continued for 2.5 h, and the solid was separated by centrifugation and transferred to a vacuum drying oven for drying at 120°C for 12 h under a vacuum of 0.085 MPa to obtain the synergistic catalyst.

[0042] The concentration of the nitric acid solution was 6.9 mol / L.

[0043] The weight ratio of copper chloride, neodymium chloride, ethanol solution, modified mesoporous activated carbon, and 1-butyl-3-methylimidazolium chloride is 2.25:0.45:105:37:4.3.

[0044] The continuous distillation method involves continuously feeding the reaction liquid into the lower part of the continuous distillation column 4, controlling the bottom temperature of the continuous distillation column 4 at 190℃, and maintaining the top temperature in the range of 73-78℃, and continuously distilling the reaction liquid under atmospheric pressure, and continuously distilling m-methyl anisole from the middle section of the continuous distillation column 4 (the distillation temperature of m-methyl anisole in the middle section of the continuous distillation column 4 is 173℃).

[0045] In the continuous atmospheric distillation process, methanol and dimethyl carbonate are continuously distilled and condensed from the top of the continuous distillation column 4 and recovered. At the same time, non-condensable gas (byproduct carbon dioxide) is condensed and vented. The material continuously collected from the bottom of the continuous distillation column 4 is refluxed back into the continuous distillation column 4 after heat exchange to maintain the bottom temperature of the continuous distillation column 4 at 190°C.

[0046] Furthermore, during the continuous atmospheric distillation process, the high-boiling-point substance (i.e., 1-butyl-3-methylimidazolium chloride) is discharged from the bottom of the continuous distillation column 4 at regular intervals. After heat exchange, the high-boiling-point substance is recovered into the catalyst circulation tank 2 to continue participating in subsequent reactions.

[0047] The catalytic continuous synthesis method for aryl methyl ethers in this embodiment, based on the feed amounts of 1464 g (13.54 mol) of m-methylphenol and 3662 g (40.65 mol) of dimethyl carbonate (DMC), uses 2365 g (13.54 mol) of 1-butyl-3-methylimidazolium chloride. The final mass of m-methyl anisole obtained is 1637.59 g, the purity is 99.53 wt%, and the molar yield (based on m-methylphenol) is 98.54%.

[0048] The catalytic continuous synthesis method for aryl methyl ethers in this embodiment uses the same apparatus as in Example 1.

[0049] Example 3 This embodiment provides a method for the catalytic continuous synthesis of aryl methyl ethers, which employs a combination of continuous reaction and continuous distillation, specifically as follows: The continuous reaction method involves continuously introducing m-methylphenol and dimethyl carbonate (DMC) into mixing vessel 1 at a molar ratio of 1:3. After being mixed evenly in mixing vessel 1, the mixture is metered and continuously fed into tubular reactor 3. Simultaneously, 1-butyl-3-methylimidazolium chloride, in an equimolar ratio with m-methylphenol, is metered and continuously fed into tubular reactor 3 via catalyst circulation tank 2. The total feed rate of m-methylphenol, DMC, and 1-butyl-3-methylimidazolium chloride into tubular reactor 3 is controlled at 180 mL / h. The reaction temperature in tubular reactor 3 is controlled at 200℃, the reaction pressure at 1.2 MPa, and the material residence time at 0.31 h, continuously carrying out the methylation reaction to obtain the reaction solution.

[0050] The tubular reactor 3 is filled with a synergistic catalyst; the loading weight of the synergistic catalyst is 6% of the total weight of the material fed into the tubular reactor 3 within 1 hour.

[0051] The preparation method of the synergistic catalyst is as follows: mesoporous activated carbon is added to 8 times its weight of nitric acid solution, stirred for 20 min, heated to 70℃, kept at this temperature and stirred under reflux for 6 h, and then the solid is separated by centrifugation. The solid is washed with deionized water until neutral and then transferred to a constant temperature drying oven and dried at 120℃ to constant weight to obtain modified mesoporous activated carbon. Then, copper chloride and neodymium chloride are added to a 65% (v / v) ethanol solution, stirred for 30 min, and then the modified mesoporous activated carbon is added. After stirring at room temperature for 60 min, 1-butyl-3-methylimidazolium chloride is added. The addition of 1-butyl-3-methylimidazolium chloride is controlled to be completed within 40 min. After stirring for 3 h, the solid is separated by centrifugation and transferred to a vacuum drying oven. It is dried at 125℃ for 13 h under a vacuum of 0.09 MPa to obtain the synergistic catalyst.

[0052] The concentration of the nitric acid solution is 7 mol / L.

[0053] The weight ratio of copper chloride, neodymium chloride, ethanol solution, modified mesoporous activated carbon, and 1-butyl-3-methylimidazolium chloride is 2.3:0.5:110:38:4.5.

[0054] The continuous distillation method involves continuously feeding the reaction liquid into the lower part of the continuous distillation column 4, controlling the bottom temperature of the continuous distillation column 4 at 190℃, and maintaining the top temperature within the range of 75-80℃, and continuously distilling the reaction liquid under atmospheric pressure, and continuously distilling m-methyl anisole from the middle section of the continuous distillation column 4 (the distillation temperature of m-methyl anisole in the middle section of the continuous distillation column 4 is 173℃).

[0055] In the continuous atmospheric distillation process, methanol and dimethyl carbonate are continuously distilled and condensed from the top of the continuous distillation column 4 and recovered. At the same time, non-condensable gas (byproduct carbon dioxide) is condensed and vented. The material continuously collected from the bottom of the continuous distillation column 4 is refluxed back into the continuous distillation column 4 after heat exchange to maintain the bottom temperature of the continuous distillation column 4 at 190°C.

[0056] Furthermore, during the continuous atmospheric distillation process, the high-boiling-point substance (i.e., 1-butyl-3-methylimidazolium chloride) is discharged from the bottom of the continuous distillation column 4 at regular intervals. After heat exchange, the high-boiling-point substance is recovered into the catalyst circulation tank 2 to continue participating in subsequent reactions.

[0057] The catalytic continuous synthesis method for aryl methyl ethers in this embodiment, based on the feed amounts of 1464 g (13.54 mol) of m-methylphenol and 3662 g (40.65 mol) of dimethyl carbonate (DMC), uses 2365 g (13.54 mol) of 1-butyl-3-methylimidazolium chloride. The final mass of m-methyl anisole obtained is 1629.13 g, the purity is 99.56 wt%, and the molar yield (based on m-methylphenol) is 98.06%.

[0058] The catalytic continuous synthesis method for aryl methyl ethers in this embodiment uses the same apparatus as in Example 1.

[0059] Examples 4-9 Examples 4-9 adopt the technical solution of Example 2, except that: the total feed rate of m-methylphenol, dimethyl carbonate (DMC), and 1-butyl-3-methylimidazolium chloride is changed when they are fed into the tubular reactor 3; the molar ratio of m-methylphenol to DMC is changed; the residence time of materials in the tubular reactor 3 is changed; and the reaction temperature in the tubular reactor 3 is changed.

[0060] Meanwhile, the mass and molar yield (based on m-methylphenol) of the final m-methyl anisole obtained in Examples 4-9 were calculated based on a feed amount of 1464 g (13.54 mol) of m-methylphenol; the specific feed amount of dimethyl carbonate was converted from the molar ratio of dimethyl carbonate to m-methylphenol in the table below; the molar ratio of the total feed amount of 1-butyl-3-methylimidazolium chloride to the total feed amount of m-methylphenol was 1:1.

[0061] The specific process parameters for Examples 4-9 are shown in the table below:

[0062] As can be seen, the preferred process parameters in the catalytic continuous synthesis of aryl methyl ethers in the above embodiments are as follows: total feed rate 180-900 mL / h; molar ratio of m-methylphenol to dimethyl carbonate 1:3-4; material residence time 0.06-0.31 h; reaction temperature 180-200 °C; reaction pressure 1.2 MPa. The method for the continuous catalytic synthesis of aryl methyl ethers uses m-methylphenol and dimethyl carbonate (DMC) as raw materials and 1-butyl-3-methylimidazolium chloride as an ionic liquid catalyst. The preparation of m-methyl anisole is achieved through a combination of tubular continuous reaction and continuous distillation. Simultaneously, a synergistic catalyst prepared using a specific method is employed during the tubular continuous reaction. First, the surface of mesoporous activated carbon is modified using nitric acid oxidation to activate its surface properties. Then, copper chloride and neodymium chloride are adsorbed and loaded onto the modified mesoporous activated carbon, followed by contact bonding with 1-butyl-3-methylimidazolium chloride to obtain the synergistic catalyst. The catalytically active components in the synergistic catalyst, in combination with the ionic liquid catalyst, further improve the stability of the continuous reaction, enhance the catalytic performance for methylation reactions, reduce the reaction temperature and pressure required for the continuous reaction, shorten the reaction time, improve reaction efficiency, and increase the yield of continuously prepared m-methyl anisole. The aforementioned technical means work together synergistically to achieve continuous production of aryl methyl ethers while avoiding the use of dimethyl sulfate and the generation of large amounts of highly toxic wastewater and solid waste during the production process. Furthermore, the reaction conditions for continuous production of aryl methyl ethers are mild, the requirements for production equipment are low, the production risk is low, the production efficiency is high, and the yield of aryl methyl ethers prepared on a large scale is high, which is conducive to large-scale industrial production.

[0063] Comparative Example 1 This comparative example provides a method for the catalytic continuous synthesis of aryl methyl ethers, which employs a combination of continuous reaction and batch distillation, specifically as follows: The continuous reaction method involves continuously introducing m-methylphenol and dimethyl carbonate (DMC) into mixing tank 1 at a molar ratio of 1:3. After being mixed evenly in mixing tank 1, the mixture is metered and continuously fed into tubular reactor 3. Simultaneously, 1-butyl-3-methylimidazolium chloride, in an equimolar ratio with m-methylphenol, is metered and continuously fed into tubular reactor 3 via catalyst circulation tank 2. The total feed rate of m-methylphenol, DMC, and 1-butyl-3-methylimidazolium chloride into tubular reactor 3 is controlled at 180 mL / h. The reaction temperature in tubular reactor 3 is controlled at 180℃, the reaction pressure at 1.2 MPa, and the material residence time at 0.31 h. The methylation reaction is continuously carried out to obtain a reaction solution, which is then transferred to a temporary storage tank for further processing.

[0064] Meanwhile, no synergistic catalyst was used in the tubular reactor 3 of the comparative example.

[0065] The batch distillation method involves introducing the reaction liquid from the temporary storage tank into a batch distillation column and performing batch distillation under atmospheric pressure, controlling the reflux ratio at 3:1. First, the column bottom temperature is controlled within the range of 130-135℃, and the column top temperature within the range of 60-62℃. A mixture of methanol and dimethyl carbonate (DMC) is distilled from the top and condensed for recovery. Then, the column bottom temperature is controlled within the range of 181-182℃, and the column top temperature within the range of 165-170℃. A mixture of methanol, DMC, and a portion of m-methyl anisole is distilled from the top and condensed for recovery. Next, the column bottom temperature is controlled within the range of 200-205℃, and the column top temperature within the range of 175-180℃. m-methyl anisole is distilled from the top and condensed for collection. After the m-methyl anisole is distilled off, the remaining high-boiling product (i.e., 1-butyl-3-methylimidazolium chloride) in the batch distillation column bottom is recovered and transferred to catalyst circulation tank 2 to continue participating in subsequent reactions.

[0066] In this comparative example, the catalytic continuous synthesis of aryl methyl ethers, based on the feed amounts of 1464 g (13.54 mol) of m-methylphenol and 3662 g (40.65 mol) of dimethyl carbonate (DMC), and the feed amount of 1-butyl-3-methylimidazolium chloride being 2365 g (13.54 mol), yielded a final mass of 1370.24 g of m-methyl anisole with a purity of 99.31 wt% and a molar yield (based on m-methylphenol) of 82.27%.

[0067] Comparative Examples 2-9 Comparative Examples 2-9 adopted the technical scheme of Comparative Example 1, with the following differences: the total feed rate of m-methylphenol, dimethyl carbonate (DMC), and 1-butyl-3-methylimidazolium chloride was changed to be fed into the tubular reactor 3 simultaneously; the molar ratio of m-methylphenol to DMC was changed; the residence time of the materials in the tubular reactor 3 was changed; and the reaction temperature in the tubular reactor 3 was changed.

[0068] Meanwhile, the mass and molar yield (based on m-methylphenol) of the final m-methyl anisole obtained in Comparative Examples 2-9 were calculated based on a feed amount of 1464 g (13.54 mol) of m-methylphenol; the specific feed amount of dimethyl carbonate was converted from the molar ratio of dimethyl carbonate to m-methylphenol in the table below; the molar ratio of the total feed amount of 1-butyl-3-methylimidazolium chloride to the total feed amount of m-methylphenol was 1:1.

[0069] The specific process parameters for Comparative Examples 2-9 are shown in the table below:

[0070] Unless otherwise stated, all percentages used in this invention are mass percentages.

[0071] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for the catalytic continuous synthesis of aryl methyl ethers, characterized in that, The continuous reaction and continuous rectification are combined; The continuous reaction method is that the m-methylphenol and dimethyl carbonate are uniformly mixed, and then continuously fed into a tubular reactor (3) with 1-butyl-3-methylimidazolium chloride, the reaction temperature of the tubular reactor (3) is controlled to be 180-200 DEG C, the reaction pressure is controlled to be 1.1-1.2 MPa, and the continuous catalytic synthesis is continuously carried out to continuously obtain a reaction liquid; The tubular reactor (3) is fixedly filled with a synergistic catalyst; The preparation method of the synergistic catalyst is that the mesoporous activated carbon is treated with nitric acid to obtain modified mesoporous activated carbon, the copper chloride, neodymium chloride and the modified mesoporous activated carbon are put into an ethanol solution, stirred at room temperature, then the 1-butyl-3-methylimidazolium chloride is continuously put in, and the solid is separated after stirring, dried, and the synergistic catalyst is prepared. The continuous rectification method is that the reaction liquid is continuously rectified to obtain m-methyl anisole.

2. The process for the catalytic continuous synthesis of aryl methyl ethers according to claim 1, characterized in that, In the continuous reaction, the total feeding rate of the m-methylphenol, dimethyl carbonate and 1-butyl-3-methylimidazolium chloride into the tubular reactor (3) is 180-900 mL / h. The residence time of the material in the tubular reactor (3) is 0.06-0.31 h.

3. The process for the catalytic continuous synthesis of aryl methyl ethers according to claim 1, characterized in that, In the continuous reaction, the molar ratio of the m-methylphenol to the dimethyl carbonate fed into the tubular reactor (3) per unit time is 1:3-4. The molar ratio of the m-methylphenol to the 1-butyl-3-methylimidazolium chloride fed into the tubular reactor (3) per unit time is 1:

1.

4. The process for the catalytic continuous synthesis of aryl methyl ethers according to claim 1, characterized in that, In the continuous reaction, the loading weight of the synergistic catalyst is 5-6% of the total weight of the material fed into the tubular reactor (3) per hour.

5. The process for the catalytic continuous synthesis of aryl methyl ethers according to claim 1, characterized in that, In the preparation of the synergistic catalyst, the volume concentration of the ethanol solution is 60-65%; The weight ratio of the copper chloride, neodymium chloride, ethanol solution, modified mesoporous activated carbon, 1-butyl-3-methylimidazolium chloride is 2.2-2.3:0.4-0.5:100-110:35-38:4-4.

5.

6. The process for the catalytic continuous synthesis of aryl methyl ethers according to claim 1, characterized in that, In the preparation of the synergistic catalyst, the method for treating the mesoporous activated carbon with nitric acid is that the mesoporous activated carbon is put into a nitric acid solution, heated to reflux, and after the heat preservation and reflux treatment, the solid is separated, washed and dried to obtain the modified mesoporous activated carbon.

7. The process for the catalytic continuous synthesis of aryl methyl ethers according to claim 6, characterized in that, In the treatment of the mesoporous activated carbon with nitric acid, the concentration of the nitric acid solution is 6.5-7 mol / L; The weight ratio of the mesoporous activated carbon to the nitric acid solution is 1:6-8; The heat preservation and reflux treatment time is 5-6 h.

8. The process for the catalytic continuous synthesis of aryl methyl ethers according to claim 1, characterized in that, The continuous rectification method is that the reaction liquid is continuously fed into a continuous rectification column (4), the column bottom temperature of the continuous rectification column (4) is controlled to be 190 DEG C, the column top temperature is kept in the range of 70-80 DEG C, the reaction liquid is continuously rectified at normal pressure, and the m-methyl anisole is continuously distilled from the middle section of the continuous rectification column (4).

9. The process for the catalytic continuous synthesis of aryl methyl ethers according to claim 8, characterized in that, In the continuous rectification, the distillation temperature of the m-methyl anisole in the middle section of the continuous rectification column (4) is 173 DEG C.

10. The process for the catalytic continuous synthesis of aryl methyl ethers according to claim 8, characterized in that, In the continuous rectification, the methanol and dimethyl carbonate are continuously distilled from the column top of the continuous rectification column (4) and recovered by condensation, and the non-condensed gas is vented. The high-boiling-point material from the bottom of the continuous distillation column (4) is recovered, mixed with 1-butyl-3-methylimidazolium chloride, and then continued to participate in the continuous reaction.

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