Dealkylation method for tert-butylphenol

Abstract

The invention belongs to the technical field of synthesis of chemical products, and discloses a dealkylation method of tert-butylphenol, which comprises the following steps: adding trace cresol sulfonic acid and bivalent iron salt into a reaction kettle filled with tert-butylphenol, so that iron ions can coordinate with phenol, thereby being beneficial to activation of phenol and enhancement of reaction activity of phenol; dealkylation reaction and rectification are carried out at a certain reaction temperature and pressure, isobutene and products are extracted from the top of the tower, and reaction rectification can be intermittent or continuous. The method has the advantages of small amount of required catalyst, mild reaction conditions, few side reactions and high product purity, and can realize continuous large-scale production.

Description

Technical Field

[0001] The present invention belongs to the technical field of the synthesis of chemical products, and particularly relates to a method for dealkylating tert-butylphenol. Background Art

[0002] p-Cresol and m-cresol are important chemical raw materials, which are widely used in the fields of medicine, pesticides, dyes, spices, coatings, rubber, plastics, etc. In addition, cresol can also be used as a solvent, preservative, disinfectant, etc. In addition to their wide range of uses, these compounds also have high added value. At present, an important way to obtain p-cresol and m-cresol is to synthesize them by the method of catalytic dealkylation of 2,6-di-tert-butyl-p-cresol or 4,6-di-tert-butyl-m-cresol.

[0003] In some application scenarios, it is necessary to carry out dealkylation treatment on tert-butylphenol to obtain other phenolic compounds with specific functions. The dealkylation reaction is the reverse process of the alkylation reaction, and its process conditions are relatively complex and harsh. For relatively large alkyl groups such as tert-butyl, although the dealkylation reaction can occur under certain conditions, the selectivity and yield of the reaction are often affected by various factors, such as the type of catalyst, reaction temperature, reaction pressure, and reaction time.

[0004] Traditional methods for dealkylating tert-butylphenol have many deficiencies. For example, some methods have complex and harsh process conditions, high production costs, and low yields. In addition, the production of one product is often accompanied by the generation of other by-products. For example, in the dealkylation process of p-tert-butylphenol, impurities such as p-bromophenol and 2,4-dibromophenol may be generated, and the separation and purification of these impurities further increase the production cost and process difficulty.

[0005] At present, the methods for dealkylating tert-butylphenol mainly focus on the research of catalysts. There are those using solid acids as catalysts and those using liquid acids as catalysts. Solid acid catalysts include strongly acidic cation exchange resins, acidic molecular sieves, and solid superacids, etc. Their advantages are that the catalyst is easy to separate from the reaction solution, and the disadvantages are that the catalyst activity is low and it is easy to deactivate. Liquid acid catalysts include sulfuric acid, phosphoric acid, p-toluenesulfonic acid, heteropolyacids, and acidic ionic liquids, etc. Their advantages are that the catalyst activity is high, and the disadvantages are that it is difficult to separate the catalyst from the reaction solution and it has a certain corrosion to the equipment. However, in actual production, liquid acid is still the preferred catalyst for dealkylating tert-butylphenol. The dosage of the dealkylation catalyst is generally 0.1%-0.5% of the mass of the raw material phenol, and the dealkylation temperature is generally 150-200°C. Due to the relatively high dealkylation temperature, side reactions are likely to increase, so it is still necessary to find a more efficient and mild catalyst to improve the current problems in production. Summary of the Invention

[0006] To overcome the deficiencies of the prior art, in the dealkylation reaction of tert-butylphenol, when a trace amount of cresol sulfonic acid and ferrous salt are used as catalysts, the reaction exhibits extremely high efficiency. Not only is the catalyst dosage less than that of the traditional process, but the reaction temperature is also lower. The technical solution is as follows:

[0007] A method for dealkylating tert-butylphenol, adding a trace amount of cresol sulfonic acid and ferrous salt to a reaction kettle containing tert-butylphenol. Ferrous ions can coordinate with phenol, which helps to activate the phenol and enhance its reaction activity. The dealkylation reaction is carried out under certain reaction temperature and pressure and then rectified. Isobutene and products are taken out from the top of the tower. The reactive distillation can be batch or continuous.

[0008] The tert-butylphenol includes one or more of 2,6-di-tert-butyl-p-cresol, 2-tert-butyl-p-cresol, 4,6-di-tert-butyl-m-cresol, 6-tert-butyl-m-cresol, and 6-tert-butyl-2,4-xylenol;

[0009] The cresol sulfonic acid includes one or more of o-cresol sulfonic acid, p-cresol sulfonic acid, and m-cresol sulfonic acid, and its dosage is 0.005% - 0.05% of the mass of tert-butylphenol;

[0010] The ferrous salt includes ferrous chloride, ferrous sulfate, ferrous hydroxide, ferrous cresol sulfonate, ferrous acetate, etc., and its dosage is 1% - 10% of the amount of substance of cresol sulfonic acid;

[0011] The reaction temperature is 130°C - 150°C;

[0012] The reaction pressure is -0.09 MPa - -0.06 MPa;

[0013] When continuous reactive distillation is adopted, the raw material tert-butylphenol can be continuously added from the feed inlet of the distillation tower or the reaction kettle.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0015] The present invention requires less catalyst dosage, has mild reaction conditions, fewer side reactions, high product purity, and can achieve continuous large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a reaction schematic diagram. DETAILED DESCRIPTION OF THE INVENTION

[0017] The present invention will be described in detail below through specific embodiments, but the protection scope of the present invention is not limited. Unless otherwise specified, the experimental methods adopted in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can be obtained from commercial channels.

[0018] Example 1

[0019] A specified amount of 2,6-di-tert-butyl-p-cresol, a catalyst, and an auxiliary agent are mixed in a molar ratio of 2,6-di-tert-butyl-p-cresol:p-cresol sulfonic acid:ferrous chloride = 100:0.03:0.001 and placed in a reaction kettle equipped with a rectifying column. The temperature is raised to 140 °C, and the pressure at the top of the column is controlled at -0.085 MPa. The isobutene produced by the reaction is sent to the previous process section for reuse after being cooled and compressed from the top of the column. The p-cresol produced after dealkylation is condensed from the top of the column. Part of it is used as the reflux liquid of the column, and part of it is taken out as the product. The purity of the p-cresol taken out is greater than 99.5%.

[0020] Example 2

[0021] A specified amount of 2-tert-butyl-p-cresol, a catalyst, and an auxiliary agent are mixed in a molar ratio of 2-tert-butyl-p-cresol:p-cresol sulfonic acid:ferrous sulfate = 100:0.05:0.002 and placed in a reaction kettle equipped with a rectifying column. The temperature is raised to 145 °C, and the pressure at the top of the column is controlled at -0.08 MPa. The isobutene produced by the reaction is sent to the previous process section for reuse after being cooled and compressed from the top of the column. The p-cresol produced after dealkylation is condensed from the top of the column. Part of it is used as the reflux liquid of the column, and part of it is taken out as the product. The purity of the p-cresol taken out is greater than 99.5%.

[0022] Example 3

[0023] A specified amount of 4,6-di-tert-butyl-m-cresol, a catalyst, and an auxiliary agent are mixed in a molar ratio of 4,6-di-tert-butyl-m-cresol:m-cresol sulfonic acid:ferrous m-cresol sulfonate = 100:0.01:0.0008 and placed in a reaction kettle equipped with a rectifying column. The temperature is raised to 138 °C, and the pressure at the top of the column is controlled at -0.088 MPa. After the reaction starts, a specified amount of 4,6-di-tert-butyl-m-cresol is continuously fed into the reaction kettle to control the stable liquid level of the reaction kettle. The isobutene produced by the reaction is sent to the previous process section for reuse after being cooled and compressed from the top of the column. The m-cresol produced after dealkylation is condensed from the top of the column. Part of it is used as the reflux liquid of the column, and part of it is taken out as the product. The purity of the m-cresol taken out is greater than 99.5%.

[0024] Example 4

[0025] A specified amount of 6-tert-butyl-m-cresol, a catalyst, and an auxiliary agent are mixed in a molar ratio of 6-tert-butyl-m-cresol:p-cresol sulfonic acid:ferrous m-cresol sulfonate = 100:0.006:0.0005 and placed in a reaction kettle equipped with a rectifying column. The temperature is raised to 150 °C, and the pressure at the top of the column is controlled at -0.07 MPa. After the reaction starts, a specified amount of 6-tert-butyl-m-cresol is continuously fed into the reaction kettle to control the stable liquid level of the reaction kettle. The isobutene produced by the reaction is sent to the previous process section for reuse after being cooled and compressed from the top of the column. The m-cresol produced after dealkylation is condensed from the top of the column. Part of it is used as the reflux liquid of the column, and part of it is taken out as the product. The purity of the m-cresol taken out is greater than 99.5%.

[0026] Example 5

[0027] A specified amount of 6-tert-butyl-2,4-xylenol, a catalyst and an auxiliary agent are mixed in a molar ratio of 6-tert-butyl-2,4-xylenol:p-toluenesulfonic acid:ferrous acetate = 100:0.04:0.001 and placed in a reaction kettle equipped with a rectifying column. The temperature is raised to 142°C, and the pressure at the top of the column is controlled at -0.09 MPa. After the reaction starts, 6-tert-butyl-2,4-xylenol is continuously fed into the reaction kettle quantitatively, and the liquid level of the reaction kettle is controlled to be stable. The isobutene generated by the reaction is sent to the previous section for reuse after being cooled and compressed at the top of the column. After dealkylation, the 2,4-xylenol generated is condensed at the top of the column. Part of it is used as the reflux liquid of the column, and part of it is taken out as the product. The purity of the taken-out 2,4-xylenol is greater than 99.5%.

[0028] Example 6

[0029] A specified amount of 2,6-di-tert-butyl-p-cresol, a catalyst and an auxiliary agent are mixed in a molar ratio of 2,6-di-tert-butyl-p-cresol:p-toluenesulfonic acid:ferrous chloride = 100:0.03:0.001 and placed in a reaction kettle equipped with a rectifying column. The temperature is raised to 142°C, and the pressure at the top of the column is controlled at -0.087 MPa. After the reaction starts, 2,6-di-tert-butyl-p-cresol is continuously fed into the reaction kettle quantitatively, and the liquid level of the reaction kettle is controlled to be stable. The isobutene generated by the reaction is sent to the previous section for reuse after being cooled and compressed at the top of the column. After dealkylation, the p-cresol and 2-tert-butyl-p-cresol generated are condensed at the top of the column. Part of it is used as the reflux liquid of the column, and part of it is taken out as the mixed intermediate product. By controlling the temperature at the top of the column, the ratio of the two products of p-cresol and 2-tert-butyl-p-cresol can be adjusted. The intermediate product can be further rectified to obtain p-cresol with a purity greater than 99.5% and 2-tert-butyl-p-cresol with a purity greater than 99.5%.

[0030] Example 7

[0031] A specified amount of 4,6 - di - tert - butyl - m - cresol, a catalyst, and an auxiliary agent are mixed in a molar ratio of 4,6 - di - tert - butyl - m - cresol: m - cresol sulfonic acid: ferrous m - cresol sulfonate = 100:0.01:0.0008 and placed in a reaction kettle equipped with a rectifying column. The temperature is raised to 144 °C, and the pressure at the top of the column is controlled at - 0.086 MPa. After the reaction starts, 4,6 - di - tert - butyl - m - cresol is continuously fed into the reaction kettle quantitatively, and the liquid level of the reaction kettle is controlled to be stable. The isobutene generated by the reaction is sent to the previous process section for reuse after being cooled and compressed at the top of the column. After dealkylation, the m - cresol and 6 - tert - butyl - m - cresol generated are condensed at the top of the column. Part of it is used as the reflux liquid of the column, and part of it is taken out as a mixed intermediate product. By controlling the temperature at the top of the column, the proportion of the two products, m - cresol and 6 - tert - butyl - m - cresol, can be adjusted. The intermediate product can be further rectified to obtain m - cresol with a purity greater than 99.5% and 6 - tert - butyl - m - cresol with a purity greater than 99.5%.

[0032] Comparative Example 1

[0033] The implementation scheme is the same as that of Example 1, but in the reaction system, the catalyst p - cresol sulfonic acid and the auxiliary agent ferrous chloride are not added. The reaction temperature is raised to 140 °C, and the pressure at the top of the column is controlled at - 0.085 MPa. No reaction occurs. The temperature is continued to be raised to 180 °C, and still no reaction occurs, and no product is collected at the top of the column. It shows that the reaction cannot occur without the catalyst and the auxiliary agent.

[0034] Comparative Example 2

[0035] The implementation scheme is the same as that of Example 1, but in the reaction system, the auxiliary agent ferrous chloride is not added. The reaction temperature is raised to 140 °C, and the pressure at the top of the column is controlled at - 0.085 MPa. A reaction occurs, but the reaction degree is weak. The temperature is continued to be raised to 180 °C, and p - cresol product is collected at the top of the column, but its purity is only about 99%, mainly because there are more by - product isobutene polymers.

[0036] Comparative Example 3

[0037] The implementation scheme is the same as that of Example 1, but in the reaction system, the catalyst p - cresol sulfonic acid is not added. The reaction temperature is raised to 140 °C, and the pressure at the top of the column is controlled at - 0.085 MPa. No reaction occurs. The temperature is continued to be raised to 180 °C, and still no reaction occurs, and no product is collected at the top of the column. It shows that the reaction cannot occur without the catalyst.

[0038] The above - described embodiments are only the preferred embodiments of the present invention, and not all the feasible embodiments of the present invention. For those of ordinary skill in the art, any obvious changes made without departing from the principles and spirit of the present invention should be considered to be included within the scope of the claims of the present invention.

Claims

1. A method for the dealkylation of tert-butylphenol, characterized in that, Add cresol sulfonic acid with a dosage of 0.005% - 0.05% of the mass of tert-butylphenol and ferrous salts with a dosage of 1% - 10% of the amount of substance of cresol sulfonic acid into the reactor. Carry out the dealkylation reaction under certain reaction temperature and pressure and then rectify. Iso-butene and products are taken out from the top of the column.

2. The method for dealkylating tert-butylphenol according to claim 1, wherein The tert-butylphenol includes one or more of 2,6-di-tert-butyl-p-cresol, 2-tert-butyl-p-cresol, 4,6-di-tert-butyl-m-cresol, 6-tert-butyl-m-cresol, and 6-tert-butyl-2,4-xylenol.

3. The method for dealkylating tert-butylphenol according to claim 1, characterized in that, The cresol sulfonic acid includes one or more of o-cresol sulfonic acid, p-cresol sulfonic acid, and m-cresol sulfonic acid.

4. The method for dealkylating tert-butylphenol according to claim 1, wherein The ferrous salts include ferrous chloride, ferrous sulfate, ferrous hydroxide, ferrous cresol sulfonate, and ferrous acetate.

5. The method for dealkylating tert-butylphenol according to claim 1, wherein The reaction temperature is 130°C - 150°C.

6. The method for dealkylating tert-butylphenol according to claim 1, characterized in that, The pressure is -0.09 MPa - -0.06 MPa.

7. The method for dealkylating tert-butylphenol according to claim 1, characterized in that, The rectification can be batch or continuous.

8. The method for dealkylating tert-butylphenol according to claim 7, characterized in that, When continuous reactive distillation is adopted, the raw material tert-butylphenol can be continuously added from the feed inlet of the distillation column or the reactor.

Images