Catalyst for synthesizing aromatic ethers by reacting phenolic compounds with dimethyl carbonate and preparation method thereof

Abstract

The present invention belongs to the technical field of catalysts, and particularly relates to a catalyst for the reaction of phenolic compounds with dimethyl carbonate to synthesize aromatic ethers and a preparation method thereof. Lignin is used to replace part of phenol, and a cesium-containing lignin-modified phenolic resin microsphere is obtained by adding a cesium salt during the curing stage of the phenolic resin microsphere. After high-temperature calcination of the microsphere in a nitrogen atmosphere, a cesium-containing lignin-modified phenolic resin carbon sphere is obtained, which is used to catalyze the oxy-methylation reaction of phenolic compounds with dimethyl carbonate. The conversion rate of catalyzing m-cresol and dimethyl carbonate to prepare m-methylanisole can be 98.5%, and the selectivity of m-methylanisole can be 99.1%.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and particularly relates to a catalyst for synthesizing aromatic ethers by the reaction of phenolic compounds with dimethyl carbonate and a preparation method thereof. Background Art

[0002] Industrially, methylating reagents such as dimethyl sulfate and methyl bromide are usually used to react with the phenolic hydroxyl groups of phenolic ether spices to obtain aromatic ethers. These reagents are highly active, but very toxic and have strong corrosiveness. Chen Bing (Synthesis of anisole from dimethyl carbonate and phenol catalyzed by nitrate [J]. Petrochemical Technology, 2009, 38(8): 897-902) used alkali metal salts to catalyze the reaction of dimethyl carbonate with phenol to produce anisole. The results showed that the catalytic activity was negatively correlated with the ionization of its cations. Cesium nitrate had the smallest ionization energy and the best catalytic effect. The conversion rate of phenol was 98.1%, and the selectivity of anisole was 99.2%. However, the by-product of the reaction was methanol, and cesium nitrate would dissolve in the reaction system. Gao Zhongfeng (Discussion on the phase transfer catalytic synthesis process of p-methylanisole [J]. Contemporary Chemical Industry, 2010, 39(3): 259-260) studied the oxy-methylation reaction of p-cresol with dimethyl sulfate catalyzed by tetrabutylammonium bromide. The yield of the product p-methylanisole was 92.36%, but the phase transfer catalyst dissolved in the reaction system and was difficult to recycle. Summary of the Invention

[0003] In order to overcome the disadvantages of existing catalysts such as easy loss of active components, difficulty in separating the catalyst from the product, and the carrier itself catalyzing the generation of by-products, lignin is used to replace part of phenol to reduce the preparation cost of phenolic aldehyde carbon spheres. Cesium salts are added in the microsphere curing stage, and phenolic resin carbon spheres containing cesium are obtained by high-temperature carbonization to catalyze the oxy-methylation reaction to obtain the corresponding aromatic ethers.

[0004] The present invention provides a synthesis method of cesium-containing lignin-modified phenolic resin carbon spheres, and the steps are as follows:

[0005] (1) Add lignin, phenol, formaldehyde, a catalyst, and a dispersant into a four-necked flask according to a certain mass ratio, stir and react, then add a certain amount of composite curing agent, raise the temperature and continue to stir and cure, filter and separate cesium-containing lignin-modified phenolic resin microspheres, then wash and filter by suction, and dry in an oven.

[0006] Among them, the dispersant is polyethylene glycol (molecular weight 1500), the catalyst is ammonia water, the dosage of lignin is 30% of the mass of phenol, the concentration of formaldehyde is 37%, the mass ratio of phenol to formaldehyde is 1:1, the dosage of the catalyst is 2% of the mass of phenol, and the dosage of the dispersant is 2% of the mass of phenol.

[0007] The reaction temperature is 70-90°C, and the reaction time is 2-6 h.

[0008] The composite curing agent is a composite of ethylenediamine and cesium carbonate with a mass ratio of 1:5 to 1:25. Among them, the dosage of ethylenediamine is 2% of the mass of phenol, the addition amount of cesium carbonate is 10-50% of the mass of phenol, the curing temperature is 90-110°C, and the curing time is 1-3 h.

[0009] (2) Put the prepared cesium-containing lignin-modified phenolic resin microspheres into a tubular furnace under a nitrogen atmosphere and carbonize them at a certain temperature and time.

[0010] The carbonization temperature is 800°C and the carbonization time is 1.5 h.

[0011] The cesium-containing lignin-modified phenolic resin carbon sphere catalyst prepared by the above method is used in a fixed-bed reactor to catalyze the reaction of phenolic compounds with dimethyl carbonate to synthesize the corresponding aromatic ethers. The specific method is as follows: Fill the cesium-containing phenolic resin carbon spheres in a fixed-bed reactor to continuously catalyze the oxyalkylation reaction of phenolic compounds with dimethyl carbonate to synthesize phenolic ether spices. After the reaction is completed and the product is cooled, then carry out vacuum distillation to purify the corresponding phenolic ether product to obtain the product.

[0012] Phenolic compounds include: phenol, p-cresol, o-cresol, m-cresol, eugenol, p-allylphenol.

[0013] The molar ratio of phenolic compounds to dimethyl carbonate is 1:1 to 1:4.

[0014] The space velocity during the reaction is less than 10 h -1 , the reaction temperature is 200-400°C, and the reaction pressure is 1 Pa-4.0 MPa.

[0015] The technological progress achieved by the present invention is:

[0016] The present invention uses lignin to replace part of phenol to prepare phenolic resin carbon spheres, which reduces the preparation cost of the catalyst. The carbon spheres are resistant to high temperature and high pressure and are suitable for the reaction conditions of dimethyl carbonate and phenolic compounds. Cesium ions have high conversion and selectivity in the oxyalkylation reaction of catalytic phenolic compounds. Adding cesium salts in the curing stage makes the stable active components uniformly dispersed and the active components are not easily lost. The carbon spheres have developed pores, a large specific surface area, and uniform particles. The catalyst can be simply separated from the product and recycled, and can be used for continuous production of aromatic ethers, improving the reaction yield and having high economic benefits. Description of the Drawings Detailed Embodiments

[0017] The following further illustrates the method of the present invention in combination with embodiments, which is not a limitation of the present invention.

[0018] Example 1

[0019] Add 25 ml of deionized water to a 100-ml four-necked flask, heat it to 85 °C, and then add 6.588 g of phenol, 9.411 g of formaldehyde, 2.823 g of lignin (substitution amount 30%), 2.0 wt% ammonia water, and 2.0 wt% polyethylene glycol. Carry out a condensation reaction at 85 °C for 4 h. In the curing stage, add 2.0 wt% of ethylenediamine, add 10 wt% of cesium carbonate, and raise the temperature to 100 °C and react for 2 h. Filter, wash, and dry the spheres, and then put them into a tubular furnace and carbonize at 800 °C for 1.5 h to obtain cesium-containing lignin-modified phenolic resin carbon spheres.

[0020] Fill the catalyst into a fixed-bed reactor to catalyze the reaction of phenol with dimethyl carbonate, and the space velocity is 10 h -1 , the reactor pressure is 1.0 MPa, the temperature is 200 °C, and the molar ratio of phenol to dimethyl carbonate is 1:1. The conversion rate of phenol is 75.9%, the selectivity of anisole is 98.3%, and no catalyst deactivation is observed after reacting for 12 h. The reaction formula is as follows:

[0021]

[0022] Example 2

[0023] In the curing stage of Example 1, increase the dosage of cesium carbonate to 20 wt%, keep the other conditions unchanged, wash and dry the microspheres, then put them into a tubular furnace and carbonize at 800 °C for 1.5 h to obtain cesium-containing lignin-modified phenolic resin carbon spheres.

[0024] Fill the catalyst into a fixed-bed reactor to catalyze the reaction of phenol with dimethyl carbonate, and the space velocity is 10 h -1 , the reactor pressure is 1.0 MPa, the temperature is 200 °C, and the molar ratio of phenol to dimethyl carbonate is 1:1. The conversion rate of phenol is 85.3%, the selectivity of anisole is 98.5%, and no catalyst deactivation is observed after reacting for 12 h. The reaction formula is as follows:

[0025]

[0026] Example 3

[0027] In the curing stage of Example 1, increase the dosage of cesium carbonate to 30 wt%, keep the other conditions unchanged, wash and dry the microspheres, then put them into a tubular furnace and carbonize at 800 °C for 1.5 h to obtain cesium-containing lignin-modified phenolic resin carbon spheres.

[0028] Fill the catalyst into a fixed-bed reactor to catalyze the reaction of phenol with dimethyl carbonate, and the space velocity is 10 h -1, the reactor pressure was 1.0 MPa, the temperature was 200 °C, and the molar ratio of phenol to dimethyl carbonate was 1:1. The conversion rate of phenol was 86.7%, the selectivity of anisole was 98.9%, and no catalyst deactivation was observed after 12 h of reaction. The reaction equation is as follows:

[0029]

[0030] Example 4

[0031] In the curing stage of Example 1, the amount of cesium carbonate was increased to 50 wt%, and the other conditions remained unchanged. The microspheres were washed and dried and then placed in a tubular furnace for carbonization at 800 °C for 1.5 h to obtain cesium-containing lignin-modified phenolic resin carbon spheres.

[0032] The catalyst was loaded into a fixed-bed reactor to catalyze the reaction of phenol with dimethyl carbonate, and the space velocity was 10 h -1 , the reactor pressure was 1.0 MPa, the temperature was 200 °C, and the molar ratio of phenol to dimethyl carbonate was 1:1. The conversion rate of phenol was 96.7%, the selectivity of anisole was 99.1%, and no catalyst deactivation was observed after 12 h of reaction. The reaction equation is as follows:

[0033]

[0034] Example 5

[0035] In the curing stage of Example 1, the amount of cesium carbonate was increased to 30 wt%, and the other conditions remained unchanged. The microspheres were washed and dried and then placed in a tubular furnace for carbonization at 800 °C for 1.5 h to obtain cesium-containing lignin-modified phenolic resin carbon spheres.

[0036] The catalyst was loaded into a fixed-bed reactor to catalyze the reaction of p-cresol with dimethyl carbonate, and the space velocity was 5 h -1 , the reactor pressure was 2.0 MPa, the temperature was 250 °C, and the molar ratio of p-cresol to dimethyl carbonate was 1:2. The conversion rate of p-cresol was 88.2%, the selectivity of p-methylanisole was 98.8%, and no catalyst deactivation was observed after 12 h of reaction. The reaction equation is as follows:

[0037]

[0038] Example 6

[0039] In the curing stage of Example 1, the amount of cesium carbonate was increased to 40 wt%, and the other conditions remained unchanged. The microspheres were washed and dried and then placed in a tubular furnace for carbonization at 800 °C for 1.5 h to obtain cesium-containing lignin-modified phenolic resin carbon spheres.

[0040] The catalyst was loaded into a fixed-bed reactor to catalyze the reaction of m-cresol with dimethyl carbonate, and the space velocity was 2 h -1, the reactor pressure was 3.0 MPa, the temperature was 350 °C, and the molar ratio of m-cresol to dimethyl carbonate was 1:3. The conversion rate of m-cresol was 98.5%, the selectivity of m-methylanisole was 99.1%, and no catalyst deactivation was observed after 24 h of reaction. The reaction equation is as follows:

[0041]

[0042] Example 7

[0043] During the curing stage of Example 1, the amount of cesium carbonate was increased to 50 wt%, and the other conditions remained unchanged. After washing and drying the microspheres, they were placed in a tubular furnace and carbonized at 800 °C for 1.5 h to obtain cesium-containing lignin-modified phenolic resin carbon spheres.

[0044] The catalyst was filled into a fixed-bed reactor to catalyze the reaction of m-cresol with dimethyl carbonate, and the space velocity was 2 h -1 , the reactor pressure was 4.0 MPa, the temperature was 350 °C, and the molar ratio of m-cresol to dimethyl carbonate was 1:4. The conversion rate of m-cresol was 98.1%, the selectivity of m-methylanisole was 99.2%, and no catalyst deactivation was observed after 24 h of reaction. The reaction equation is as follows:

[0045]

[0046] Comparative Example 1

[0047] The catalyst in Example 6 was used to catalyze the reaction of m-cresol with dimethyl carbonate in an autoclave reactor. The amount of catalyst added was 10% of the total mass of m-cresol + dimethyl carbonate. The reaction time was 0.5 h, the reaction pressure was 3.0 MPa, the temperature was 300 °C, and the molar ratio of m-cresol to dimethyl carbonate was 1:3. The conversion rate of p-cresol was 85.8%, and the selectivity of m-methylanisole was 97.2%.

[0048] Comparative Example 2

[0049] Activated carbon was used as the carrier, and cesium carbonate was loaded onto the activated carbon by the equal-volume impregnation method. The mass of the activated carbon was the same as the amount of the lignin-modified phenolic resin carbon spheres used in Example 6, and the mass of cesium carbonate was the same as the amount used in Example 6. After impregnation at 85 °C for 6 h, filtration and drying, it was placed in a tubular furnace and carbonized at 800 °C for 1.5 h under a nitrogen atmosphere to obtain a supported catalyst.

[0050] The catalyst was filled into a fixed-bed reactor to catalyze the reaction of m-cresol with dimethyl carbonate, and the space velocity was 2 h -1, the reactor pressure was 3.0 MPa, the temperature was 350 °C, and the molar ratio of m-cresol to dimethyl carbonate was 1:3. The conversion rate of m-cresol was 95.5%, the selectivity of m-methylanisole was 97.7%, and no catalyst deactivation was observed after 8 h of reaction.

[0051] Comparative Example 3

[0052] 25 ml of deionized water was added to a 100 ml four-necked flask, heated to 85 °C, and then 6.588 g of phenol, 9.411 g of formaldehyde, 2.823 g of lignin (substitution amount 30%), 2.0 wt% ammonia water and 2.0 wt% polyethylene glycol were added. A condensation reaction was carried out at 85 °C for 4 h. 2.0 wt% ethylenediamine was added, and the temperature was raised to 100 °C for a curing reaction for 2 h to obtain lignin-modified phenolic resin microspheres. After being filtered, washed and dried, they were placed in a tube furnace and carbonized at 800 °C for 1.5 h to obtain lignin-modified phenolic resin carbon spheres.

[0053] The space velocity was 10 h -1 , the reactor pressure was 1.0 MPa, the temperature was 200 °C, and the molar ratio of phenol to dimethyl carbonate was 1:1. The conversion rate of phenol was 0.92%, the selectivity of anisole was 0.17%, and the lignin-modified phenolic resin carbon spheres had basically no catalytic activity for the oxy-methylation reaction of phenol and dimethyl carbonate.

Claims

1. Preparation method of cesium-containing lignin modified phenolic resin carbon sphere catalyst, characterized in that, the steps of the preparation method are as follows: (1) Prepare cesium-containing lignin modified phenolic resin microspheres by suspension polymerization: Add lignin, phenol, formaldehyde, catalyst, and dispersant into a four-necked flask, stir well and heat up to 70-90 °C for reaction for 2-6 h, then add a composite curing agent, and continue to heat up to 90-110 °C for curing reaction for 1-3 h to obtain cesium-containing lignin modified phenolic resin microspheres; The dosage of lignin is 30% of the mass of phenol, the mass ratio of phenol to formaldehyde is 1:1, the dosage of the catalyst is 2% of the mass of phenol, and the dosage of the dispersant is 2% of the mass of phenol; The composite curing agent is a complex of ethylenediamine and cesium carbonate with a mass ratio of 1:5-1:25, the dosage of ethylenediamine is 2% of the mass of phenol, and the addition amount of cesium carbonate is 10-50% of the mass of phenol; (2) Dry the microspheres and then put them into a tube furnace with nitrogen flowing through for carbonization to obtain a cesium-containing lignin modified phenolic resin carbon sphere catalyst; the carbonization temperature is 800 °C and the carbonization time is 1.5 h.

2. Cesium-containing lignin modified phenolic resin carbon sphere catalyst prepared by the method according to claim 1.

3. Application of the cesium-containing lignin modified phenolic resin carbon sphere catalyst prepared by the method according to claim 1, characterized in that, the cesium-containing lignin modified phenolic resin carbon sphere catalyst is used in a fixed-bed reactor to catalyze the reaction of phenolic compounds with dimethyl carbonate to synthesize the corresponding aromatic ethers.

4. Application of the cesium-containing lignin modified phenolic resin carbon sphere catalyst according to claim 3, characterized in that, the phenolic compounds include: phenol, p-cresol, o-cresol, m-cresol, eugenol, p-allylphenol.

5. Application of the cesium-containing lignin modified phenolic resin carbon sphere catalyst according to claim 3, characterized in that, The molar ratio of the phenol compound to dimethyl carbonate is 1:1 to 1:4, and the space velocity is less than 10 h -1 , the reaction temperature is 200 to 400 °C, and the reaction pressure is 1 MPa to 4.0 MPa.

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