Method for separating phenol monomer from industrial xylenol

Abstract

The invention belongs to the technical field of synthesis and separation of coalification products, and particularly relates to a method for separating phenol monomers from industrial xylenol. The method for separating the phenol monomer from the industrial xylenol comprises the following steps: mixing the industrial xylenol, 6-(1-methyl-pentadecyl)-2, 4-xylenol, hexadecene and sulfuric acid for a first reaction, after the reaction is finished, adjusting the pH value of a reaction solution to 7-8, washing with water, removing a water layer, and carrying out rectification treatment on a material layer. The method for separating the phenol monomer from the industrial xylenol has the beneficial effects that the hexadecene can react with the 2, 4-xylenol in the industrial xylenol under a certain condition to generate an antioxidant 6-(1-methyl-pentadecyl)-2, 4-xylenol, and the 2, 5-xylenol does not react with the hexadecene, so that the antioxidant 6-(1-methyl-pentadecyl)-2, 4-xylenol does not react with the hexadecene; the method comprises the following steps of: separating 2, 4, 5-xylenol and 1-methyl-pentadecyl-methyl-2, 4-xylenol, and rectifying and separating to obtain pure 6-(1-methyl-pentadecyl)-2, 4-xylenol and 99% 2, 5-xylenol, so that the separation of 2, 4 / 2, 5-xylenol is realized, and an efficient polymerization inhibitor 6-(1-methyl-pentadecyl)-2, 4-xylenol is produced as a byproduct.

Description

Technical Field

[0001] The present invention belongs to the technical field of synthesis and separation of coal chemical products, and particularly relates to a method for separating phenolic monomers from industrial xylenols. Background Art

[0002] Using crude phenol or industrial xylenol as raw materials, rectification is carried out to obtain 2,4 / 2,5-xylenol with a certain mixed content. Since the boiling points of 2,4-xylenol and 2,5-xylenol differ by less than 1°C, they cannot be well separated by traditional methods such as crystallization and rectification. The traditional method can react 2,4 / 2,5-xylenol with isobutene to generate 6-tert-butyl-2,4-xylenol and 4-tert-butyl-2,5-xylenol. The boiling points of the two differ by 16°C, so they can be separated by rectification. 6-tert-butyl-2,4-xylenol and 4-tert-butyl-2,5-xylenol are heated under acidic conditions to remove isobutene, and then secondary rectification is carried out to obtain 99% 2,4-xylenol and 99% 2,5-xylenol respectively, thus realizing the separation of 2,4 / 2,5-xylenol.

[0003] In the gasification phenol, especially in the refined 2,4 / 2,5-xylenol extracted from medium and low temperature phenol-containing coal tar, there are generally impurities with similar boiling points such as 2-ethyl-6-methylphenol, o-isopropylphenol, and 2,3-xylenol, which cannot be separated by rectification. It is very difficult to separate 2,5-xylenol and 2-ethyl-6-methylphenol by tert-butylation. Summary of the Invention

[0004] The present application provides a method for separating phenolic monomers from industrial xylenols, aiming to solve the problems of poor separation technology effect, low yield, and poor quality in the existing industrial xylenol separation technology.

[0005] The present application provides a method for separating phenolic monomers from industrial xylenols, including the following steps:

[0006] (1) Mix industrial xylenol, 6-(1-methyl-pentadecyl)-2,4-xylenol, hexadecene, and sulfuric acid for the first reaction. After the reaction ends, adjust the pH of the reaction solution to 7-8, wash with water and remove the water layer, and carry out rectification treatment on the material layer to obtain 2,5-xylenol, hexadecene, 6-(1-methyl-pentadecyl)-2,4-xylenol, a mixture of 6-(1-methyl-pentadecyl)-2,4-xylenol and 6-(1-methyl-pentadecyl)-2,3-xylenol, 6-(1-methyl-pentadecyl)-2,3-xylenol, a mixture of 6-(1-methyl-pentadecyl)-2,3-xylenol and 4-(1-methyl-pentadecyl)-2-ethyl-6-methylphenol, 4-(1-methyl-pentadecyl)-2-ethyl-6-methylphenol, and the kettle residue mainly composed of 4,6-bis(1-methyl-pentadecyl)-2-isopropylphenol;

[0007] (2) Mix 6-(1-methylpentadecyl)-2,3-xylenol, 4-(1-methylpentadecyl)-2-ethyl-6-methylphenol, and the still residue with sulfuric acid respectively for the second reaction. After the reaction is completed, adjust the pH of the reaction solution to 7-8, and then perform rectification to obtain 2,3-xylenol, 2-ethyl-6-methylphenol, and o-isopropylphenol.

[0008] In some embodiments of the method for separating phenolic monomers from industrial xylenol according to the present application, in step (1), the industrial xylenol includes 2,4 / 2,5-xylenol, 2,3-xylenol, 2-ethyl-6-methylphenol, and o-isopropylphenol.

[0009] In some embodiments of the method for separating phenolic monomers from industrial xylenol according to the present application, in step (1), the molar ratio of the industrial xylenol to the hexadecene is 1:(0.5-5), preferably 1:(1-3).

[0010] In some embodiments of the method for separating phenolic monomers from industrial xylenol according to the present application, in step (1), the mass ratio of the industrial xylenol to 6-(1-methylpentadecyl)-2,4-xylenol is 100:(0.01-0.5).

[0011] In some embodiments of the method for separating phenolic monomers from industrial xylenol according to the present application, the mass ratio of the industrial xylenol to sulfuric acid is 100:(1-10).

[0012] In some embodiments of the method for separating phenolic monomers from industrial xylenol according to the present application, in step (1), the temperature of the first reaction is 60-120 °C, and the time of the first reaction is 6-12 h.

[0013] In some embodiments of the method for separating phenolic monomers from industrial xylenol according to the present application, in step (1), an alkali solution is used to adjust the pH of the reaction solution to 7-8; preferably, the alkali solution includes one or more of an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, an aqueous potassium carbonate solution, an aqueous sodium carbonate solution, an aqueous potassium bicarbonate solution, and an aqueous sodium bicarbonate solution.

[0014] In some embodiments of the method for separating phenolic monomers from industrial xylenol according to the present application, the method further includes the step of distilling a mixture of 6-(1-methylpentadecyl)-2,4-xylenol and 6-(1-methylpentadecyl)-2,3-xylenol to obtain 6-(1-methylpentadecyl)-2,4-xylenol and 6-(1-methylpentadecyl)-2,3-xylenol.

[0015] According to some embodiments of the method for separating phenolic monomers from industrial xylenol described in the present application, a mixture of 6-(1-methyl-pentadecyl)-2,3-xylenol and 4-(1-methyl-pentadecyl)-2-ethyl-6-xylenol is subjected to distillation treatment to obtain 6-(1-methyl-pentadecyl)-2,3-xylenol and 4-(1-methyl-pentadecyl)-2-ethyl-6-xylenol.

[0016] According to some embodiments of the method for separating phenolic monomers from industrial xylenol described in the present application, in step (2), the mass ratio of the 6-(1-methyl-pentadecyl)-2,3-xylenol to sulfuric acid is 100:(0.5 - 3).

[0017] According to some embodiments of the method for separating phenolic monomers from industrial xylenol described in the present application, the temperature of the mixing reaction of the 6-(1-methyl-pentadecyl)-2,3-xylenol and sulfuric acid is 160 - 200 °C, and the reaction time is 1 - 4 h.

[0018] According to some embodiments of the method for separating phenolic monomers from industrial xylenol described in the present application, in step (2), the mass ratio of the 4-(1-methyl-pentadecyl)-2-ethyl-6-xylenol to sulfuric acid is 100:(0.5 - 3).

[0019] According to some embodiments of the method for separating phenolic monomers from industrial xylenol described in the present application, the temperature of the mixing reaction of the 4-(1-methyl-pentadecyl)-2-ethyl-6-xylenol and sulfuric acid is 160 - 200 °C, and the reaction time is 1 - 4 h.

[0020] According to some embodiments of the method for separating phenolic monomers from industrial xylenol described in the present application, in step (2), the mass ratio of the still residue to sulfuric acid is 100:(0.5 - 3).

[0021] According to some embodiments of the method for separating phenolic monomers from industrial xylenol described in the present application, the temperature of the mixing reaction of the still residue and sulfuric acid is 160 - 200 °C, and the reaction time is 1 - 4 h.

[0022] According to some embodiments of the method for separating phenolic monomers from industrial xylenol described in the present application, in step (2), the rectification is carried out under reduced pressure at -0.09 to -0.098 MPa.

[0023] According to some embodiments of the method for separating phenolic monomers from industrial xylenol described in the present application, the reflux ratio of the rectification is (5 - 10):1.

[0024] The beneficial effects of the present application include: The method for separating phenolic monomers from industrial xylenol according to the present application utilizes the fact that hexadecene can react with 2,4-xylenol in industrial xylenol under certain conditions to form antioxidant 6-(1-methyl-pentadecyl)-2,4-xylenol, while 2,5-xylenol does not react with hexadecene. Then, distillation separation is used to obtain pure 6-(1-methyl-pentadecyl)-2,4-xylenol and 99% 2,5-xylenol, thereby realizing the separation of 2,4 / 2,5-xylenol and by-producing highly efficient polymerization inhibitor 6-(1-methyl-pentadecyl)-2,4-xylenol. Detailed implementation mode

[0025] The embodiments of the present invention will be described in detail below. The examples of the embodiments are exemplary and are intended to explain the present invention, but should not be construed as limiting the present invention.

[0026] In the present invention, the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0027] The embodiment of the present application provides a method for separating phenolic monomers from industrial xylenol, including the following steps:

[0028] (1) Mix industrial xylenol, 6-(1-methyl-pentadecyl)-2,4-xylenol, hexadecene, and sulfuric acid for the first reaction. After the reaction is completed, adjust the pH of the reaction solution to 7-8, wash with water and remove the water layer, and perform distillation treatment on the material layer to obtain 2,5-xylenol, hexadecene, 6-(1-methyl-pentadecyl)-2,4-xylenol, a mixture of 6-(1-methyl-pentadecyl)-2,4-xylenol and 6-(1-methyl-pentadecyl)-2,3-xylenol, 6-(1-methyl-pentadecyl)-2,3-xylenol, a mixture of 6-(1-methyl-pentadecyl)-2,3-xylenol and 4-(1-methyl-pentadecyl)-2-ethyl-6-cresol, 4-(1-methyl-pentadecyl)-2-ethyl-6-cresol, and the still residue mainly composed of 4,6-bis(1-methyl-pentadecyl)-2-isopropylphenol;

[0029] (2) Mix 6-(1-methylpentadecyl)-2,3-xylenol, 4-(1-methylpentadecyl)-2-ethyl-6-cresol, and the residue in the kettle with sulfuric acid respectively for the second reaction. After the reaction is completed, adjust the pH of the reaction solution to 7-8, and then perform rectification to obtain 2,3-xylenol, 2-ethyl-6-cresol, and o-isopropylphenol.

[0030] The method for separating phenolic monomers from industrial xylenol described in this application utilizes the fact that hexadecene can react with 2,4-xylenol in industrial xylenol to form the antioxidant 6-(1-methylpentadecyl)-2,4-xylenol under certain conditions, while 2,5-xylenol does not react with hexadecene. Then, pure 6-(1-methylpentadecyl)-2,4-xylenol and 99% 2,5-xylenol are obtained by rectification separation, thereby realizing the separation of 2,4 / 2,5-xylenol and producing the high-efficiency polymerization inhibitor 6-(1-methylpentadecyl)-2,4-xylenol as a by-product.

[0031] In addition, industrial xylenol generally contains impurities such as 2-ethyl-6-cresol, o-isopropylphenol, and 2,3-xylenol with similar boiling points, which cannot be separated by rectification. It is difficult to separate 2,5-xylenol and 2-ethyl-6-cresol by tert-butylation. The method described in this application uses the hexadecene alkylation method. Since 2,5-xylenol does not react, 2-ethyl-6-cresol is separated by forming 4-(1-methylpentadecyl)-2-ethyl-6-cresol. At the same time, since the boiling point of 4-(1-methylpentadecyl)-2-ethyl-6-cresol is 15 °C higher than that of 6-(1-methylpentadecyl)-2,4-xylenol, about 10 °C higher than that of 6-(1-methylpentadecyl)-2,3-xylenol, and the boiling point of 4,6-bis(1-methylpentadecyl)-2-isopropylphenol is more than 10 °C higher than that of 4-(1-methylpentadecyl)-2-ethyl-6-cresol, 2,4-xylenol, 2,5-xylenol, 2,3-xylenol, o-isopropylphenol, and 2-ethyl-6-cresol can be separated through hexadecylation reaction, rectification, dehexadecene and isomerization, and secondary rectification.

[0032] Furthermore, the method described in this application obtains the antioxidant 6-(1-methylpentadecyl)-2,4-xylenol. Compared with synthesizing the antioxidant 6-(1-methylpentadecyl)-2,4-xylenol by alkylating pure 2,4-xylenol with hexadecene, the method described in this application has a lower material source cost, produces more product varieties, has good quality, and high yield.

[0033] In some embodiments of this application, in step (1), the industrial xylenol includes 2,4 / 2,5-xylenol, 2,3-xylenol, 2-ethyl-6-cresol, and o-isopropylphenol.

[0034] In some embodiments of the present application, in step (1), the molar ratio of the industrial xylenol to the hexadecene is 1:(0.5 - 5), such as 1:0.5, 1:1, 1:1.6, 1:2, 1:2.3, 1:3, 1:3.3, 1:4, 1:4.7, 1:5, etc.

[0035] In some embodiments of the present application, in step (1), the molar ratio of the industrial xylenol to the hexadecene is 1:(1 - 3).

[0036] In some embodiments of the present application, in step (1), the mass ratio of the industrial xylenol to the 6-(1-methyl-pentadecyl)-2,4-xylenol is 100:(0.01 - 0.5); such as 100:0.01, 100:0.05, 100:0.08, 100:0.1, etc.

[0037] In some embodiments of the present application, the mass ratio of the industrial xylenol to the sulfuric acid is 100:(1 - 10), such as 100:1, 100:3, 100:5, 100:7, 100:10, etc.

[0038] In some embodiments of the present application, in step (1), the temperature of the first reaction is 60 - 120°C, such as 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 100°C, 110°C, 120°C, etc., and the time of the first reaction is 6 - 12 h; such as 6 h, 8 h, 9 h, 11 h, 12 h, etc.

[0039] In some embodiments of the present application, in step (1), an alkali solution is used to adjust the pH of the reaction solution to 7 - 8; preferably, the alkali solution includes one or more of an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, an aqueous potassium carbonate solution, an aqueous sodium carbonate solution, an aqueous potassium bicarbonate solution, and an aqueous sodium bicarbonate solution.

[0040] In some embodiments of the present application, the method further includes the step of distilling a mixture of 6-(1-methyl-pentadecyl)-2,4-xylenol and 6-(1-methyl-pentadecyl)-2,3-xylenol to obtain 6-(1-methyl-pentadecyl)-2,4-xylenol and 6-(1-methyl-pentadecyl)-2,3-xylenol.

[0041] In some embodiments of the present application, a mixture of 6-(1-methyl-pentadecyl)-2,3-xylenol and 4-(1-methyl-pentadecyl)-2-ethyl-6-cresol is distilled to obtain 6-(1-methyl-pentadecyl)-2,3-xylenol and 4-(1-methyl-pentadecyl)-2-ethyl-6-cresol.

[0042] In some embodiments of the present application, in step (2), the mass ratio of 6-(1-methylpentadecyl)-2,3-xylenol to sulfuric acid is 100:(0.5 - 3); for example, 100:0.5, 100:0.8, 100:1, 100:1.6, 100:2.1, 100:3, etc.

[0043] In some embodiments of the present application, the temperature of the mixed reaction of 6-(1-methylpentadecyl)-2,3-xylenol and sulfuric acid is 160 - 200 °C, for example, 160 °C, 180 °C, 190 °C, 200 °C, etc., and the reaction time is 1 - 4 h, for example, 1 h, 2 h, 3 h, 4 h, etc.

[0044] In some embodiments of the present application, in step (2), the mass ratio of 4-(1-methylpentadecyl)-2-ethyl-6-methylphenol to sulfuric acid is 100:(0.5 - 3); for example, 100:0.5, 100:0.8, 100:1, 100:1.6, 100:2.1, 100:3, etc.

[0045] In some embodiments of the present application, the temperature of the mixed reaction of 4-(1-methylpentadecyl)-2-ethyl-6-methylphenol and sulfuric acid is 160 - 200 °C, for example, 160 °C, 180 °C, 190 °C, 200 °C, etc., and the reaction time is 1 - 4 h, for example, 1 h, 2 h, 3 h, 4 h, etc.

[0046] In some embodiments of the present application, in step (2), the mass ratio of the still residue to sulfuric acid is 100:(0.5 - 3); for example, 100:0.5, 100:0.8, 100:1, 100:1.6, 100:2.1, 100:3, etc.

[0047] In some embodiments of the present application, the temperature of the mixed reaction of the still residue and sulfuric acid is 160 - 200 °C, for example, 160 °C, 180 °C, 190 °C, 200 °C, etc., and the reaction time is 1 - 4 h, for example, 1 h, 2 h, 3 h, 4 h, etc.

[0048] In some embodiments of the present application, in step (2), the rectification is carried out under reduced pressure rectification at -0.09 to -0.098 MPa.

[0049] In some embodiments of the present application, the reflux ratio of the rectification is (5 - 10):1, for example, 5:1, 6:1, 8:1, 10:1, etc.

[0050] The technical solutions of the present application will be further described below with specific embodiments.

[0051] Example 1

[0052] Add 200 parts of industrial xylenol (containing 61.5% of 2,4-xylenol and 38.5% of 2,5-xylenol), 600 parts of hexadecene (the molar amount is 1.64 times that of industrial xylenol), 1 part of 6-(1-methyl-pentadecyl)-2,4-xylenol and 15 parts of concentrated sulfuric acid into the reactor. Start the stirring device of the reactor and heat it up to 90 °C in an oil bath and keep the reaction for 8 hours, then take a sample for analysis. The content of 2,4-xylenol being 0.11% is qualified (when the content of 2,4-xylenol ≤ 5% is qualified). Add 38.9 parts of an aqueous sodium hydroxide solution with a mass concentration of 31% and 100 parts of water to the above reaction solution to neutralize it to a pH of 8 for the reaction solution, then layer it. Wash the material layer with another 100 parts of water once, drain all the water, and add the material layer into a distillation column (the number of trays is 100). Under the conditions of -0.095 MPa and a reflux ratio of 3:1, perform vacuum distillation to obtain 69.5 parts of 2,5-xylenol with a mass percentage content of 99.6% and 345 parts of hexadecene. Then increase the vacuum degree to 67 Pa for distillation to obtain 321 parts of antioxidant 6-(1-methyl-pentadecyl)-2,4-xylenol with a mass percentage content of 99.1%, and the yield is 91.5%.

[0053] The antioxidant 6-(1-methyl-pentadecyl)-2,4-xylenol with a mass percentage content of 99.1% and 2,5-xylenol with a mass percentage content of 99.6% can both be sold as products.

[0054] Example 2

[0055] 1000 parts of industrial xylenol (containing 40.4% of 2,4-xylenol, 33.7% of 2,5-xylenol, 7.1% of 2,3-xylenol, 8.6% of 2-ethyl-6-methylphenol, and 10.2% of o-isopropylphenol), 2000 parts of hexadecene (the molar amount is 1.2 times that of industrial xylenol), 5 parts of 6-(1-methyl-pentadecyl)-2,4-xylenol, and 75 parts of concentrated sulfuric acid are added to the reactor. The stirring device of the reactor is started, and the temperature is raised to 120 °C by oil bath and kept for reaction for 6 hours, then sampled and analyzed. When the content of 2,4-xylenol is 0.18%, it is qualified. 194 parts of an aqueous sodium hydroxide solution with a mass concentration of 31% and 400 parts of water are added to the above reaction solution to neutralize the reaction solution to pH 8, and then layered. The material layer is washed with 200 parts of water again, and the water is completely separated. The material layer is added to a distillation column (the number of trays is 200). Under the conditions of -0.095 MPa and a reflux ratio of 3:1, vacuum distillation is carried out to obtain 329.2 parts of 2,5-xylenol with a mass percentage content of 99.1% and 740.2 parts of hexadecene. Then, the vacuum degree is increased to 67 Pa, and the reflux ratio is 15 - 20:1 for distillation to obtain 693.4 parts of antioxidant 6-(1-methyl-pentadecyl)-2,4-xylenol with a mass percentage content of 99.1%, a mixture of 6-(1-methyl-pentadecyl)-2,4-xylenol and 6-(1-methyl-pentadecyl)-2,3-xylenol of 516.5 parts (where the content of 6-(1-methyl-pentadecyl)-2,4-xylenol is 435.6 parts and the content of 6-(1-methyl-pentadecyl)-2,3-xylenol is 80.9 parts), 105.6 parts of 6-(1-methyl-pentadecyl)-2,3-xylenol with a mass percentage content of 99.2%, a mixture of 6-(1-methyl-pentadecyl)-2,3-xylenol and 4-(1-methyl-pentadecyl)-2-ethyl-6-methylphenol of 22.9 parts (where the content of 6-(1-methyl-pentadecyl)-2,3-xylenol is 10.8 parts and the content of 4-(1-methyl-pentadecyl)-2-ethyl-6-methylphenol is 12.1 parts), 203.5 parts of 4-(1-methyl-pentadecyl)-2-ethyl-6-methylphenol with a mass percentage content of 99.3%, and 426.9 parts of still residue (where the content of 4,6-bis(1-methyl-pentadecyl)-2-isopropylphenol is 424.8 parts).

[0056] The mixture of 6-(1-methyl-pentadecyl)-2,4-xylenol and 6-(1-methyl-pentadecyl)-2,3-xylenol is subjected to distillation treatment to obtain 6-(1-methyl-pentadecyl)-2,4-xylenol and 6-(1-methyl-pentadecyl)-2,3-xylenol;

[0057] The mixture of 6-(1-methylpentadecyl)-2,3-xylenol and 4-(1-methylpentadecyl)-2-ethyl-6-cresol is subjected to distillation treatment to obtain 6-(1-methylpentadecyl)-2,3-xylenol and 4-(1-methylpentadecyl)-2-ethyl-6-cresol.

[0058] 426.9 parts of the still residue (424.8 parts of 4,6-bis(1-methylpentadecyl)-2-isopropylphenol) are added to the decomposition kettle, and then 5 parts of 98% sulfuric acid (the dosage of sulfuric acid is 1.17% of the mass of the still residue) are added. The temperature is raised to 190 °C under stirring and maintained for 2.5 hours. When the content of 4,6-bis(1-methylpentadecyl)-2-isopropylphenol in the gas chromatography detection is 0.33%, the reaction is stopped (qualified when the content of 4,6-bis(1-methylpentadecyl)-2-isopropylphenol ≤ 0.5%). The temperature is lowered to 90 °C, and it is neutralized to pH 7.5 of the reaction solution with 13 parts of 31% sodium hydroxide aqueous solution. Then, vacuum rectification (the theoretical number of plates in the column is 200, -0.085 MPa, reflux ratio 8 - 10:1) is carried out to obtain 95.7 parts of o-isopropylphenol with a mass percentage content of 99.5%. 319.3 parts of hexadecene and isomers are recovered and reused.

[0059] 203.5 parts of 4-(1-methylpentadecyl)-2-ethyl-6-cresol with a mass percentage content of 99.3% are added to the decomposition kettle, and then 2.5 parts of 98% sulfuric acid (the dosage of sulfuric acid is 1.23% of the mass of 4-(1-methylpentadecyl)-2-ethyl-6-cresol) are added. The temperature is raised to 195 °C under stirring and maintained for 2 hours. When the content of 4-(1-methylpentadecyl)-2-ethyl-6-cresol in the gas chromatography detection is 0.14%, the reaction is stopped (qualified when the content of 4-(1-methylpentadecyl)-2-ethyl-6-cresol ≤ 0.5%). The temperature is lowered to 90 °C, and it is neutralized to pH 7.5 of the reaction solution with 31% sodium hydroxide aqueous solution. Then, vacuum rectification (the theoretical number of plates in the column is 200, -0.085 MPa, reflux ratio 8 - 10:1) is carried out to obtain 74.1 parts of 2-ethyl-6-cresol with a mass percentage content of 99.6%. 124 parts of hexadecene and isomers are recovered and reused.

[0060] 105.6 parts of 6-(1-methylpentadecyl)-2,3-xylenol with a mass percentage of 99.2% were added to the decomposition kettle, and then 1.5 parts of 98% sulfuric acid (the dosage of sulfuric acid was 1.42% of the mass of 6-(1-methylpentadecyl)-2,3-xylenol) were added. The temperature was raised to 195 °C under stirring and maintained for 2 hours. When the content of 6-(1-methylpentadecyl)-2,3-xylenol in the gas chromatography detection was 0.08%, the reaction was stopped (qualified when the content of 6-(1-methylpentadecyl)-2,3-xylenol ≤ 0.5%). The temperature was lowered to 90 °C, and it was neutralized to pH 7.5 of the reaction solution with a sodium hydroxide aqueous solution with a mass concentration of 31%. Then, vacuum distillation was carried out (the number of theoretical plates in the tower was 200, -0.085 MPa, reflux ratio 8 - 10:1) to obtain 36.1 parts of 2,3-xylenol with a mass percentage of 99.5%. 67 parts of hexadecene and isomers were recovered and reused.

[0061] 2,5-xylenol with a mass percentage of 99.1%, antioxidant 6-(1-methylpentadecyl)-2,4-xylenol with a mass percentage of 99.1%, o-cumenol with a mass percentage of 99.5%, 2-ethyl-6-cresol with a mass percentage of 99.6%, and 2,3-xylenol with a mass percentage of 99.5% can all be sold as products.

[0062] Example 3

[0063] 1000 parts of industrial xylenol (containing 61.5% of 2,4-xylenol and 38.5% of 2,5-xylenol), 1000 parts of hexadecene (the molar dosage was 0.54 times that of industrial xylenol), 1 part of 6-(1-methylpentadecyl)-2,4-xylenol, and 50 parts of concentrated sulfuric acid were added to the reactor. The stirring device of the reactor was started and the temperature was raised to 80 °C for heat preservation reaction for 10 hours, and then sampled and analyzed. When the content of 2,4-xylenol was 3.4%, it was qualified (qualified when the content of 2,4-xylenol ≤ 5%). 129.3 parts of a sodium hydroxide aqueous solution with a mass concentration of 31% and 300 parts of water were added to the above reaction solution to neutralize it to pH 8 of the reaction solution, and then it was stratified. The material layer was washed with 100 parts of water again, and the water was completely separated. The material layer was added to the distillation column (the number of trays was 100). Under the condition of -0.095 MPa and a reflux ratio of 3:1, vacuum distillation was carried out to obtain 447.4 parts of crude 2,5-xylenol with a mass percentage of 84.3% (70.1 parts of 2,4-xylenol and 377.3 parts of 2,5-xylenol). Then, the vacuum degree was increased to 67 Pa for distillation to obtain 1512.1 parts of antioxidant 6-(1-methylpentadecyl)-2,4-xylenol with a mass percentage of 99.5%, and the yield was 86.3%.

[0064] The antioxidant 6-(1-methyl-pentadecyl)-2,4-xylenol with a mass percentage content of 99.5% can be sold as a product; the crude 2,5-xylenol with a mass percentage content of 84.3% can be further refined to obtain 2,5-xylenol with a mass percentage content of 99%.

[0065] Although the above embodiments have been shown and described, it can be understood that the above embodiments are exemplary and should not be construed as limitations of the present invention. Any changes, modifications, substitutions, and variations made by those of ordinary skill in the art to the above embodiments are within the protection scope of the present invention.

Claims

1. A method for separating phenolic monomers from industrial xylenol, characterized in that, It includes the following steps: (1) Mix industrial xylenol, 6-(1-methylpentadecyl)-2,4-xylenol, hexadecene and sulfuric acid for the first reaction. After the reaction ends, adjust the pH of the reaction solution to 7-8, wash with water and remove the water layer, and perform rectification on the material layer to obtain 2,5-xylenol, hexadecene, 6-(1-methylpentadecyl)-2,4-xylenol, a mixture of 6-(1-methylpentadecyl)-2,4-xylenol and 6-(1-methylpentadecyl)-2,3-xylenol, 6-(1-methylpentadecyl)-2,3-xylenol, a mixture of 6-(1-methylpentadecyl)-2,3-xylenol and 4-(1-methylpentadecyl)-2-ethyl-6-cresol, 4-(1-methylpentadecyl)-2-ethyl-6-cresol, and the residue in the kettle with 4,6-bis(1-methylpentadecyl)-2-isopropylphenol as the main raw material; (2) Mix 6-(1-methylpentadecyl)-2,3-xylenol, 4-(1-methylpentadecyl)-2-ethyl-6-cresol and the residue in the kettle with sulfuric acid respectively for the second reaction. After the reaction is completed, adjust the pH of the reaction solution to 7-8, and then perform rectification to obtain 2,3-xylenol, 2-ethyl-6-cresol and o-isopropylphenol.

2. The method for separating phenolic monomers from industrial xylenol according to claim 1, characterized in that, In step (1), the industrial xylenol includes 2,4 / 2,5-xylenol, 2,3-xylenol, 2-ethyl-6-cresol and o-isopropylphenol.

3. The method for separating phenolic monomers from industrial xylenol according to claim 1, characterized in that, In step (1), the molar ratio of the industrial xylenol to the hexadecene is 1:(0.5-5), preferably 1:(1-3).

4. The method for separating phenolic monomers from industrial xylenol according to claim 1, characterized in that, In step (1), the mass ratio of the industrial xylenol to the 6-(1-methylpentadecyl)-2,4-xylenol is 100:(0.01-0.5); and / or, the mass ratio of the industrial xylenol to the sulfuric acid is 100:(1-10).

5. The method for separating phenolic monomers from industrial xylenol according to claim 1, characterized in that, In step (1), the temperature of the first reaction is 60-120°C, and the time of the first reaction is 6-12 h; and / or, in step (1), an alkali solution is used to adjust the pH of the reaction solution to 7-8; preferably, the alkali solution includes one or more of sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, potassium carbonate aqueous solution, sodium carbonate aqueous solution, potassium bicarbonate aqueous solution and sodium bicarbonate aqueous solution.

6. The method for separating phenolic monomers from industrial xylenol according to claim 1, characterized in that, The method further includes the step: distill the mixture of 6-(1-methylpentadecyl)-2,4-xylenol and 6-(1-methylpentadecyl)-2,3-xylenol to obtain 6-(1-methylpentadecyl)-2,4-xylenol and 6-(1-methylpentadecyl)-2,3-xylenol; and / or, distill the mixture of 6-(1-methylpentadecyl)-2,3-xylenol and 4-(1-methylpentadecyl)-2-ethyl-6-cresol to obtain 6-(1-methylpentadecyl)-2,3-xylenol and 4-(1-methylpentadecyl)-2-ethyl-6-cresol.

7. The method for separating phenolic monomers from industrial xylenol according to claim 1, characterized in that In step (2), the mass ratio of 6-(1-methylpentadecyl)-2,3-xylenol to sulfuric acid is 100:(0.5 - 3); and / or, the temperature of the mixing reaction of 6-(1-methylpentadecyl)-2,3-xylenol and sulfuric acid is 160 - 200 °C, and the reaction time is 1 - 4 h.

8. The method for separating phenolic monomers from industrial xylenol according to claim 1, characterized in that, In step (2), the mass ratio of 4-(1-methylpentadecyl)-2-ethyl-6-methylphenol to sulfuric acid is 100:(0.5 - 3); and / or, the temperature of the mixing reaction of 4-(1-methylpentadecyl)-2-ethyl-6-methylphenol and sulfuric acid is 160 - 200 °C, and the reaction time is 1 - 4 h.

9. The method for separating phenolic monomers from industrial xylenol according to claim 1, characterized in that, In step (2), the mass ratio of still residue to sulfuric acid is 100:(0.5 - 3); and / or, the temperature of the mixing reaction of still residue and sulfuric acid is 160 - 200 °C, and the reaction time is 1 - 4 h.

10. The method for separating phenolic monomers from industrial xylenol according to claim 1, characterized in that, In step (2), the rectification is carried out under reduced pressure at -0.09 to -0.098 MPa; and / or, the reflux ratio of the rectification is (5 - 10):1.