Method for high-selectivity synthesis of o-methyl anisole

Abstract

The invention belongs to the technical field of organic synthesis, and particularly discloses a high-selectivity method for synthesizing o-methyl anisole, which comprises the following steps: loading a high-efficiency catalyst into a fixed bed reactor, heating to a reaction temperature after nitrogen replacement, mixing o-cresol and methanol according to a certain molar ratio, and reacting for 2-4 hours; continuously pumping the mixed material into a fixed bed reactor by using a pump, staying for reaction, and continuously discharging to obtain o-methyl anisole; the high-efficiency catalyst is obtained by soaking activated aluminum oxide in a hydrogenation reagent, washing, drying and roasting after soaking. The catalyst for catalyzing the reaction of o-cresol and methanol to prepare o-methyl anisole is a high-efficiency catalyst obtained by treating activated aluminum oxide by using an ion exchange method, soaking, washing, drying and roasting, and the catalyst is large in specific surface area and pore volume, dense in pore size distribution and multiple in acid sites; the catalyst has high activity and selectivity, is strong in stability, can be reused, and can be regenerated by roasting again after the activity is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis, relates to the synthesis of an intermediate o-methylanisole, and specifically relates to a method for synthesizing o-methylanisole with high selectivity. Background Art

[0002] o-Methylanisole, also known as o-methoxytoluene, is a colorless liquid with a molecular formula of C8H 10 O, CAS is 578-58-5. o-Methylanisole is an important chemical raw material intermediate, widely used in the fields of medicine, pesticides, plastics, spices, etc. Currently, the o-methylanisole available on the market is mainly prepared by the reaction of o-cresol and dimethyl sulfate or methyl chloride. Dimethyl sulfate is a highly active methylating agent, which is widely used in the pesticide, dye, medicine and spice industries. However, this substance is a highly toxic chemical, which has a strong corrosive and irritating effect on the respiratory system and skin, and will directly affect the nervous system and blood system. Methyl chloride vapor and air are easy to form an explosive mixture, and a large amount of hydrochloric acid will be produced during the reaction, causing serious corrosion to the equipment.

[0003] Due to the above-mentioned disadvantages of homogeneous reaction, the o-methyl anisole industry has developed a gas-solid phase reaction synthesis process with a fixed bed reactor as a reaction device. For example, in patent CN116651477, o-cresol and methanol are at 330°C, with homemade aluminum phosphate / silicon dioxide as catalyst, the conversion rate of o-cresol is 5-38%, and the selectivity of o-methyl anisole is 87-95%. The catalyst activity is poor and not easy to form. For example, in CN109277115, o-cresol and methanol are at 250°C to 500°C, and the product is obtained by a homemade etherification catalyst brought in by carrier gas. The conversion rate of o-cresol is 25-45%, and the selectivity of o-methyl anisole is 88-96%. The preparation method of the catalyst is relatively cumbersome, and the reaction temperature is high, which is not conducive to industrial production. Summary of the invention

[0004] In view of the deficiencies in the prior art, the object of the present invention is to provide a method for synthesizing o-methylanisole with high selectivity, wherein the catalyst used is simple and easy to obtain, has high catalyst activity and selectivity, and has strong catalyst stability and can be applied, and can be regenerated by calcining again after the activity decreases.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for synthesizing o-methyl anisole with high selectivity comprises the following steps:

[0007] The high-efficiency catalyst is loaded into a fixed bed reactor, and the temperature is raised to the reaction temperature after nitrogen substitution, and o-cresol and methanol are mixed in a certain molar ratio, and then the mixed material is continuously pumped into the fixed bed reactor by a pump, and after staying for reaction, the material is continuously discharged to obtain o-methylanisole;

[0008] The chemical reaction equation is as follows:

[0009]

[0010] The high-efficiency catalyst is obtained by soaking active alumina in a hydrogenation reagent, washing, drying and calcining after soaking.

[0011] A further improvement of the present invention is:

[0012] The reaction temperature is 190-230°C.

[0013] Furthermore, the molar ratio of o-cresol to methanol is 0.5-2:1.

[0014] Furthermore, when the activated alumina is immersed in the hydrogenation reagent, it is immersed 1-2 times, each immersion temperature is 30-90° C., and the immersion time is 30-60 minutes; the weight ratio of the activated alumina to the hydrogenation reagent is 1:0.5-1.5.

[0015] Furthermore, the hydrogenation reagent is one or a mixture of two or more of ammonium sulfate solution, ammonium carbonate solution or ammonium chloride solution; the concentration of the hydrogenation reagent is 0.5 mol / L to 2.5 mol / L.

[0016] Furthermore, the activated alumina is commercial γ-Al2O3, white spherical particles, and has a diameter of 1 to 5 mm.

[0017] Furthermore, the washing is washing with distilled water once.

[0018] Furthermore, the drying temperature is 100-120° C., and the drying time is 1-3 hours.

[0019] Furthermore, the calcination temperature is 400-500° C., and the calcination time is 3-5 hours.

[0020] The beneficial effects of the present invention are:

[0021] The catalyst modified by the present invention has much higher selectivity and activity than blank commercial γ-Al2O3 when preparing o-methylanisole, indicating that the specific surface area, pore volume and pore size of the modified commercial γ-Al2O3 have changed. During the modification process, the commercial γ-Al2O3 has undergone a rehydration process, which has changed the arrangement of the particles on the surface of the carrier, reduced the pore size on the surface, and made the pore size distribution denser, thereby increasing the specific surface area of ​​the catalyst. When the high-efficiency catalyst prepared by the present invention is used to prepare o-methylanisole, it has higher catalyst activity and selectivity, and the catalyst has strong stability and can be applied. It can be regenerated by roasting again after the activity decreases. DETAILED DESCRIPTION

[0022] The present invention is described in detail below in conjunction with specific embodiments.

[0023] The activated alumina used in the present invention is commercial γ-Al2O3 purchased from the market.

[0024] Example 1: Preparation of Catalyst

[0025] Soak 60g of activated alumina in 90g of 0.5mol / L ammonium chloride solution at 80°C for 1 hour, twice. Then wash the soaked activated alumina with 90g of distilled water at 80°C for 1 hour, once. Dry the washed activated alumina in an oven at 100 degrees for 2 hours. Finally, put it in a muffle furnace at 500 degrees and calcine it for 4 hours to obtain catalyst A: 59.5g.

[0026] Example 2: Preparation of Catalyst

[0027] Soak 60g of activated alumina in 90g of 0.5mol / L ammonium sulfate solution at 80°C for 1 hour, twice. Then wash the soaked activated alumina with 90g of distilled water at 80°C for 1 hour, once. Dry the washed activated alumina in an oven at 100 degrees for 2 hours. Finally, put it in a muffle furnace at 500 degrees and calcine it for 4 hours to obtain catalyst B: 59.7g.

[0028] Example 3: Preparation of Catalyst

[0029] Soak 60g of activated alumina in 90g of 0.5mol / L ammonium carbonate solution at 80°C for 1 hour, twice. Then wash the soaked activated alumina with 90g of distilled water at 80°C for 1 hour, once. Dry the washed activated alumina in an oven at 100 degrees for 2 hours. Finally, put it in a muffle furnace at 500 degrees and calcine it for 4 hours to obtain catalyst C: 59.2g.

[0030] Example 4: Preparation of o-methyl anisole

[0031] The catalysts prepared in Examples 1-3 and blank commercial γ-Al2O3 were respectively loaded into different fixed bed reactors, and the temperature was raised to 200°C after nitrogen replacement. The mixed material was then pumped into the reactor, and the molar ratio of o-cresol to methanol was 2:1, and the mass space velocity was 0.02 g / (g / min). After stable feeding for 1 hour, continuous sampling was performed for detection. The o-cresol conversion rate and o-methylanisole selectivity data are shown in the table below.

[0032]

[0033] Example 5: Preparation of o-methylanisole

[0034] The catalyst prepared in Example 1 was loaded into a fixed bed reactor, and the temperature was raised to 200°C after nitrogen replacement. The mixed material was then pumped into the reactor, the molar ratio of o-cresol to methanol was 2:1, the mass space velocity was 0.02 g / (g / min), and after stable feeding for 1 hour, continuous sampling and detection were performed, and the reaction was continued for 1000 hours. The o-cresol conversion rate and o-methylanisole selectivity data are shown in the table below.

[0035]

[0036] Example 6: Preparation of o-methyl anisole

[0037] The catalyst withdrawn from the reaction in Example 5 was placed in a muffle furnace, calcined at 500°C for 4 hours to obtain 58.1 g of catalyst D, which was loaded into a fixed bed reactor. After nitrogen replacement, the temperature was raised to 200°C, and the mixed material was pumped into the reactor. The molar ratio of o-cresol to methanol was 2:1, and the mass space velocity was 0.02 g / (g / min). After stable feeding for 1 hour, continuous sampling and detection were performed, and the reaction was continued for 500 hours. The o-cresol conversion rate and o-methylanisole selectivity data are shown in the table below.

[0038]

[0039] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent transformation or modification made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for synthesizing o-methyl anisole with high selectivity, characterized in that, The method comprises the following steps: loading a high-efficiency catalyst into a fixed bed reactor, heating to a reaction temperature after nitrogen replacement, mixing o-cresol and methanol in a certain molar ratio, and then continuously pumping the mixture into the fixed bed reactor with a pump, and continuously discharging the mixture after the mixture stays for reaction to obtain o-methylanisole; The high-efficiency catalyst is obtained by soaking active alumina in a hydrogenation reagent, washing, drying and calcining after soaking.

2. A method for synthesizing o-methylanisole with high selectivity according to claim 1, characterized in that: The reaction temperature is 190-230°C.

3. A method for synthesizing o-methylanisole with high selectivity according to claim 1, characterized in that: The molar ratio of o-cresol to methanol is 0.5-2:

1.

4. A method for synthesizing o-methylanisole with high selectivity according to claim 1, characterized in that: When the activated alumina is immersed in the hydrogenation reagent, it is immersed 1-2 times, each immersion temperature is 30-90°C, and the immersion time is 30-60 minutes; the weight ratio of the activated alumina to the hydrogenation reagent is 1:0.5-1.

5.

5. A method for synthesizing o-methylanisole with high selectivity according to claim 1 or 4, characterized in that: The hydrogenation reagent is one of ammonium sulfate solution, ammonium carbonate solution or ammonium chloride solution, or a mixture of two or more thereof; the concentration of the hydrogenation reagent is 0.5 mol / L to 2.5 mol / L.

6. A method for synthesizing o-methylanisole with high selectivity according to claim 1 or 4, characterized in that: The activated alumina is commercial γ-Al2O3, white spherical particles, and has a diameter of 1 to 5 mm.

7. A method for synthesizing o-methylanisole with high selectivity according to claim 1, characterized in that: The washing is washing with distilled water once.

8. A method for synthesizing o-methylanisole with high selectivity according to claim 1, characterized in that: The drying temperature is 100-120° C., and the drying time is 1-3 hours.

9. A method for synthesizing o-methylanisole with high selectivity according to claim 1, characterized in that: The calcination temperature is 400-500° C., and the calcination time is 3-5 hours.

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