Method for separating phenol monomer from mixed phenol

Abstract

The invention belongs to the technical field of organic separation, and particularly relates to a method for separating phenol monomers from mixed phenol. The method for separating the phenol monomer from the mixed phenol comprises the following steps: mixing the mixed phenol, a catalyst and isobutene to carry out a first reaction, and carrying out distillation treatment on a reaction liquid; and purifying the product obtained by distillation. According to the method for separating the phenol monomer from the mixed phenol, 2, 4 / 2, 5-xylenol as a byproduct of a coal coking product and a coalification product can be used as raw materials, and products such as 6-tert-butyl-2, 4-xylenol, 2, 5-xylenol, m-cresol, p-cresol, high-purity 2, 4 / 2, 5-xylenol and high-purity m-cresol and p-cresol can be separated while o-isopropyl phenol and 2-ethyl-6-cresol are extracted, so that the method is suitable for industrial production. And the co-production cost is lower, and the market competitiveness is high.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic separation, and particularly relates to a method for separating phenolic monomers from mixed phenols. Background Art

[0002] The traditional synthesis method of o-isopropylphenol is mainly obtained by sulfonation and alkali fusion of isopropylbenzene, and can also be obtained by synthesizing phenol with isopropanol under the catalysis of phenol aluminum, or by propylating phenol and isopropanol in a fixed bed catalyst to synthesize o-isopropylphenol. However, the above methods for synthesizing o-isopropylphenol have many by-products and large pollution. Coupled with a relatively large amount of by-product diisopropylphenol (the market of diisopropylphenol is not as good as that of o-isopropylphenol), it is difficult to produce in large quantities.

[0003] 2-Ethyl-6-methylphenol can be obtained by reacting o-cresol with ethanol in a fixed bed equipped with an ethylation catalyst. However, this reaction method has a slow reaction rate (the reaction rate is significantly lower than the methylation reaction of methanol), and there are many by-products such as 4-ethyl-2-methylphenol and 2,4-diethyl-6-methylphenol, resulting in low reaction yield, high energy consumption, and high operating costs. In addition, the market demand for 2-ethyl-6-methylphenol is not very large, so it is almost economically infeasible to produce this product by fixed bed catalytic ethylation.

[0004] The contents of o-isopropylphenol and 2-ethyl-6-methylphenol in crude phenol from coal coking are about 0.1-0.6% and 0.05-0.5% respectively, and they mainly exist in the 2,4 / 2,5-xylenol mixed phenol fraction.

[0005] After rectification of crude phenol, phenol, o-cresol, three-mixed cresols, m / p-cresol containing 55% of the meta position, 99% m / p-cresol, and industrial xylenol are obtained, and they are directly sold as products without good fine separation. Industrial xylenol can be rectified to obtain 2,4 / 2,5-xylenol mixed phenol, which contains some impurities such as o-isopropylphenol and 2-ethyl-6-methylphenol. Since 2,4 / 2,5-xylenol accounts for a relatively high proportion and a large quantity in xylenol; o-isopropylphenol and 2-ethyl-6-methylphenol are relatively abundant in xylenol extracted from gasified crude phenol and medium / low-temperature phenol-containing coal tar, especially with a relatively high content in medium / low-temperature pyrolyzed phenol-containing coal tar and relatively less in high-temperature coal tar. Therefore, it is possible to consider extracting o-isopropylphenol and 2-ethyl-6-methylphenol from medium / low-temperature phenol-containing coal tar to avoid waste of raw materials.

[0006] Since the boiling point difference between 2,4 / 2,5-xylenol and o-isopropylphenol is only 1-2 °C, hundreds of theoretical plates and a reflux ratio of 50-100 are required for rectification, so they cannot be separated by conventional rectification.

[0007] The content of 2-ethyl-6-methylphenol and o-isopropylphenol in the crude phenol obtained by high-temperature coking of crude phenol and gasification of coal is low. Generally, 2,4-xylenol and 2,5-xylenol can be obtained by separation through tert-butylation. However, the content of o-isopropylphenol and 2-ethyl-6-methylphenol in the crude phenol extracted from medium- and low-temperature phenol-containing coal tar is high. Especially when the content of 2-ethyl-6-methylphenol is high, the difficulty of separation by tert-butylation increases significantly. This is mainly because the boiling points of 4-tert-butyl-2-ethyl-6-methylphenol and 4-tert-butyl-2,5-xylenol differ by only 3-4 °C, making it very difficult to separate them by distillation. It is basically impossible to separate the 2,4 / 2,5-xylenol mixture with a high content of 2-ethyl-6-methylphenol by conventional tert-butylation. Summary of the Invention

[0008] The present application provides a method for separating phenolic monomers from mixed phenols, aiming to solve the problems of many by-products, large amounts of three wastes, and high production costs in the synthesis of o-isopropylphenol.

[0009] The present application provides a method for separating phenolic monomers from mixed phenols, comprising the following steps:

[0010] (1) Mix the mixed phenols, a catalyst, and isobutene for a first reaction. After the first reaction ends (sampling and analysis shows that 6-tert-butyl-2-isopropylphenol ≤ 0.5% is qualified), perform distillation treatment on the reaction solution to obtain diisobutene, 6-tert-butyl-2,4-xylenol, crude 4-tert-butyl-2-ethyl-6-methylphenol, crude 4-tert-butyl-2,5-xylenol, and the kettle residue 4,6-di-tert-butyl-2-isopropylphenol;

[0011] (2) Mix the kettle residue 4,6-di-tert-butyl-2-isopropylphenol and sulfuric acid for a second reaction. After the second reaction ends (sampling and analysis shows that 6-tert-butyl-2-isopropylphenol ≤ 0.5% is qualified), adjust the pH of the reaction solution to 7-8 and perform rectification treatment to obtain o-isopropylphenol;

[0012] Mix the crude 4-tert-butyl-2-ethyl-6-methylphenol and sulfuric acid for a third reaction. After the third reaction ends, adjust the pH of the reaction solution to 7-8 and perform rectification treatment to obtain crude 2-ethyl-6-methylphenol;

[0013] Mix the crude 4-tert-butyl-2,5-xylenol and sulfuric acid for a fourth reaction. After the fourth reaction ends, adjust the pH of the reaction solution to 7-8 and perform rectification treatment to obtain crude 2,5-xylenol;

[0014] (3) Heat the crude 2-ethyl-6-methylphenol to 50-55 °C, then cool it to 43-45 °C for crystallization, separate the uncrystallized solution, and heat the crystals obtained by crystallization to 46-47 °C to obtain the molten material 2-ethyl-6-methylphenol;

[0015] Mix the crude 2,5-xylenol, acidic silica-alumina, olefin hydrogenation catalyst and sulfuric acid, introduce hydrogen in a closed environment for the fifth reaction. After the reaction ends, cool the reaction solution and filter to obtain the cracking product; perform rectification on the cracking product to obtain o-cresol and 2,5-xylenol.

[0016] According to some embodiments of the method for separating phenolic monomers from mixed phenols described in the present application, in step (1), the mixed phenols include o-isopropylphenol, 2-ethyl-6-methylphenol, m,p-cresol, o-ethylphenol and 2,3-xylenol.

[0017] According to some embodiments of the method for separating phenolic monomers from mixed phenols described in the present application, the mass percentage content of o-isopropylphenol in the mixed phenols is 1%-30%.

[0018] According to some embodiments of the method for separating phenolic monomers from mixed phenols described in the present application, the mass percentage content of 2-ethyl-6-methylphenol in the mixed phenols is 1%-20%.

[0019] According to some embodiments of the method for separating phenolic monomers from mixed phenols described in the present application, the mass percentage content of m,p-cresol in the mixed phenols is 0%-5%.

[0020] According to some embodiments of the method for separating phenolic monomers from mixed phenols described in the present application, the mass percentage content of o-ethylphenol in the mixed phenols is 0%-1%.

[0021] According to some embodiments of the method for separating phenolic monomers from mixed phenols described in the present application, the mass percentage content of 2,3-xylenol in the mixed phenols is 0%-5%.

[0022] According to some embodiments of the method for separating phenolic monomers from mixed phenols described in the present application, in step (1), the catalyst includes one or more of inorganic acids, organic acids or acidic resins; preferably, the catalyst is an acidic resin or sulfuric acid.

[0023] According to some embodiments of the method for separating phenolic monomers from mixed phenols described in the present application, in step (1), the mass ratio of the mixed phenols to the catalyst is 100:(0.5-30).

[0024] According to some embodiments of the method for separating phenolic monomers from mixed phenols described in the present application, in step (1), the mass ratio of the mixed phenols to the isobutene is 1:(0.5-5).

[0025] According to some embodiments of the method for separating phenolic monomers from mixed phenols described in the present application, in step (1), the temperature of the first reaction is 60-150°C, and the time of the first reaction is 4-12 h.

[0026] In some embodiments of the method for separating phenolic monomers from mixed phenols according to the present application, in step (1), the crude 4-tert-butyl-2-ethyl-6-methylphenol includes 4-tert-butyl-2-ethyl-6-methylphenol and 4-tert-butyl-2,5-dimethylphenol; wherein, the total mass percentage content of 4-tert-butyl-2-ethyl-6-methylphenol and 4-tert-butyl-2,5-dimethylphenol in the crude 4-tert-butyl-2-ethyl-6-methylphenol is ≥99%, and the mass percentage content of 4-tert-butyl-2-ethyl-6-methylphenol is ≥75%.

[0027] In some embodiments of the method for separating phenolic monomers from mixed phenols according to the present application, the crude 4-tert-butyl-2,5-dimethylphenol includes 4-tert-butyl-2,5-dimethylphenol and 4-tert-butyl-2-ethyl-6-methylphenol, wherein, the total mass percentage content of 4-tert-butyl-2,5-dimethylphenol and 4-tert-butyl-2-ethyl-6-methylphenol in the crude 4-tert-butyl-2,5-dimethylphenol is ≥99%, and the mass percentage content of 4-tert-butyl-2,5-dimethylphenol is ≥80%.

[0028] In some embodiments of the method for separating phenolic monomers from mixed phenols according to the present application, in step (2), the mass ratio of the kettle residue 4,6-di-tert-butyl-2-isopropylphenol to sulfuric acid is 100:(0.5 - 5).

[0029] In some embodiments of the method for separating phenolic monomers from mixed phenols according to the present application, in step (2), the temperature of the second reaction is 160 - 200°C, and the time of the second reaction is 1 - 4 h.

[0030] In some embodiments of the method for separating phenolic monomers from mixed phenols according to the present application, in step (2), the mass ratio of the crude 4-tert-butyl-2-ethyl-6-methylphenol to sulfuric acid is 100:(0.5 - 5).

[0031] In some embodiments of the method for separating phenolic monomers from mixed phenols according to the present application, in step (2), the temperature of the third reaction is 160 - 200°C, and the time of the third reaction is 1 - 4 h.

[0032] In some embodiments of the method for separating phenolic monomers from mixed phenols according to the present application, in step (2), the mass ratio of the crude 4-tert-butyl-2,5-dimethylphenol to sulfuric acid is 100:(0.5 - 5).

[0033] In some embodiments of the method for separating phenolic monomers from mixed phenols according to the present application, in step (2), the temperature of the fourth reaction is 160 - 200°C, and the time of the fourth reaction is 1 - 4 h.

[0034] In some embodiments of the method for separating phenolic monomers from mixed phenols according to the present application, in step (3), the cooling rate for cooling the crude 2-ethyl-6-methylphenol to 43-45 °C is 0.3-0.7 °C / h.

[0035] In some embodiments of the method for separating phenolic monomers from mixed phenols according to the present application, in step (3), the crystallization time is 3-5 h.

[0036] In some embodiments of the method for separating phenolic monomers from mixed phenols according to the present application, in step (3), the heating rate for heating the crystals obtained by crystallization is 0.1-0.5 °C / h.

[0037] In some embodiments of the method for separating phenolic monomers from mixed phenols according to the present application, in step (3), the mass ratio of silicon element to aluminum element in the acidic silicon-aluminum oxide is (0.1-50):1.

[0038] In some embodiments of the method for separating phenolic monomers from mixed phenols according to the present application, the acidic silicon-aluminum oxide includes silicon dioxide and aluminum oxide.

[0039] In some embodiments of the method for separating phenolic monomers from mixed phenols according to the present application, the olefin hydrogenation catalyst includes palladium-carbon catalyst and / or Raney nickel catalyst.

[0040] In some embodiments of the method for separating phenolic monomers from mixed phenols according to the present application, in step (3), the mass ratio of the crude 2,5-xylenol to sulfuric acid is 100:(0.5-3).

[0041] In some embodiments of the method for separating phenolic monomers from mixed phenols according to the present application, the mass ratio of the crude 2,5-xylenol to the acidic silicon-aluminum oxide is 100:(1-30).

[0042] In some embodiments of the method for separating phenolic monomers from mixed phenols according to the present application, the mass ratio of the acidic silicon-aluminum oxide to the olefin hydrogenation catalyst is 100:(0.01-0.5).

[0043] In some embodiments of the method for separating phenolic monomers from mixed phenols according to the present application, the temperature of the fifth reaction is 280-400 °C, and the time of the fifth reaction is 3-8 h.

[0044] In some embodiments of the method for separating phenolic monomers from mixed phenols according to the present application, the mass ratio of the crude 2,5-xylenol to hydrogen is 100:(10-50).

[0045] According to some embodiments of the method for separating phenolic monomers from mixed phenols described in the present application, in step (3), the temperature reduction treatment is to reduce the temperature of the reaction solution to ≤90°C at a temperature reduction rate of 60-80°C / h.

[0046] The beneficial effects of the present application include: The method for separating phenolic monomers from mixed phenols described in the present application has relatively low quality requirements for raw materials. Even if the 2,4 / 2,5-xylenol mixed phenols contain impurities such as m,p-cresol, 2,3-xylenol, and o-ethylphenol, the separation and extraction of o-isopropylphenol and 2-ethyl-6-methylphenol are less affected. Moreover, other phenolic products can also be separated incidentally, and the process has strong practicability.

[0047] The method for separating phenolic monomers from mixed phenols described in the present application can use the by-products of coal coking products, 2,4 / 2,5-xylenol, and coal chemical products as raw materials. While extracting o-isopropylphenol and 2-ethyl-6-methylphenol, products such as 6-tert-butyl-2,4-xylenol, 2,5-xylenol, m-cresol, p-cresol, high-purity 2,4 / 2,5-xylenol, and high-purity m,p-cresol can also be separated. The co-production cost is lower and the market competitiveness is strong.

[0048] The method for separating phenolic monomers from mixed phenols described in the present application can use the by-products of coal coking products, 2,4 / 2,5-xylenol, and coal chemical products as raw materials. The catalytic de-ethylation reaction of 2-ethyl-6-methylphenol in the crude 2,5-xylenol is carried out at a relatively low temperature (280-400°C, generally 350-800°C). The advantage of this is that it can reduce the demethylation reaction of 2,5-xylenol and also reduce the transfer and transposition reaction of methyl groups, and can ensure a high yield and low difficulty in obtaining 2,5-xylenol products.

[0049] The method for separating phenolic monomers from mixed phenols described in the present application has cheap and easily available raw materials, low treatment cost, less equipment investment, high separation efficiency, is suitable for the production of small batches of products, and has good economic benefits. Detailed Embodiments

[0050] The embodiments of the present invention are described in detail below. The examples of the embodiments are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

[0051] In the present invention, terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" 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 representations 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.

[0052] An embodiment of the present application provides a method for separating phenolic monomers from mixed phenols, including the following steps:

[0053] (1) Mix the mixed phenols, catalyst, and isobutene to carry out a first reaction. After the first reaction ends, filter the reaction solution and perform distillation treatment on the reaction solution to obtain diisobutene, 6-tert-butyl-2,4-xylenol, crude 4-tert-butyl-2-ethyl-6-methylphenol, crude 4-tert-butyl-2,5-xylenol, and still residue 4,6-di-tert-butyl-2-isopropylphenol;

[0054] (2) Mix the still residue 4,6-di-tert-butyl-2-isopropylphenol and sulfuric acid to carry out a second reaction. After the second reaction ends, adjust the pH of the reaction solution to 7-8 and perform rectification treatment to obtain o-isopropylphenol;

[0055] Mix the crude 4-tert-butyl-2-ethyl-6-methylphenol and sulfuric acid to carry out a third reaction. After the third reaction ends, adjust the pH of the reaction solution to 7-8 and perform rectification treatment to obtain crude 2-ethyl-6-methylphenol;

[0056] Mix the crude 4-tert-butyl-2,5-xylenol and sulfuric acid to carry out a fourth reaction. After the fourth reaction ends, adjust the pH of the reaction solution to 7-8 and perform rectification treatment to obtain crude 2,5-xylenol;

[0057] (3) Heat the crude 2-ethyl-6-methylphenol to 50-55 °C, then cool it to 43-45 °C for crystallization, separate the uncrystallized solution, and heat the crystals obtained by crystallization to 46-47 °C to obtain molten material 2-ethyl-6-methylphenol;

[0058] Mix the crude 2,5-xylenol, acidic aluminosilicate, olefin hydrogenation catalyst, and sulfuric acid, introduce hydrogen in a closed environment to carry out a fifth reaction. After the reaction ends, cool the reaction solution, filter to obtain the cracking product; perform rectification treatment on the cracking product to obtain o-cresol and 2,5-xylenol.

[0059] Since the 2,4 / 2,5-xylenol mixture (containing o-isopropylphenol and 2-ethyl-6-methylphenol) contains m,p-cresol, 2,3-xylenol, o-ethylphenol and other impurity phenols, the tert-butylation reaction of m-cresol, p-cresol, o-ethylphenol and 2,3-xylenol generates di-tert-butylated products such as 4,6-di-tert-butyl-3-methylphenol, 2,6-di-tert-butyl-4-methylphenol, 4,6-di-tert-butyl-2-ethylphenol, 4,6-di-tert-butyl-2,3-xylenol, etc. The boiling points of these di-tert-butylated products are significantly higher than that of 4-tert-butyl-2-ethyl-6-methylphenol, so they will not affect the purification of 4-tert-butyl-2-ethyl-6-methylphenol. After the de-tert-butylation of 4,6-di-tert-butyl-2-isopropylphenol, 4,6-di-tert-butyl-3-methylphenol, 2,6-di-tert-butyl-4-methylphenol, 4,6-di-tert-butyl-2-ethylphenol and 4,6-di-tert-butyl-2,3-xylenol, o-isopropylphenol (boiling point about 212°C), m,p-cresol (boiling point about 202°C), o-ethylphenol (boiling point about 203°C) and 2,3-xylenol (boiling point about 217.5°C) are obtained. Only 2,3-xylenol has a small impact on the rectification for extracting high-purity o-isopropylphenol, while m,p-cresol and o-ethylphenol have basically no impact. Coupled with the small amount of 2,3-xylenol contained in the 2,4 / 2,5-xylenol mixture (containing o-isopropylphenol and 2-ethyl-6-methylphenol), the small amounts of m,p-cresol, o-ethylphenol and 2,3-xylenol have little impact on the extraction of 2-ethyl-6-methylphenol and o-isopropylphenol from the 2,4 / 2,5-xylenol mixture (containing o-isopropylphenol and 2-ethyl-6-methylphenol), and they can also generate. Based on the fact that the boiling point differences between 2,6-di-tert-butyl-4-methylphenol, 4,6-di-tert-butyl-2-ethylphenol, 4,6-di-tert-butyl-3-methylphenol, 4,6-di-tert-butyl-2-isopropylphenol and 4,6-di-tert-butyl-2,3-xylenol are all about 10°C (except for the 5°C boiling point difference between 4,6-di-tert-butyl-2-isopropylphenol and 4,6-di-tert-butyl-2,3-xylenol), products such as p-cresol, m-cresol, o-ethylphenol, o-isopropylphenol and 2,3-xylenol can be obtained through rectification purification, de-tert-butylation reaction and secondary rectification.

[0060] o-Isopropylphenol: CAS88-69-7, oily liquid or crystalline solid, melting point 15-16°C, boiling point 212-213°C, used as an intermediate for plasticizers, surfactants and fragrances, and mainly used in the production of isoprocarb and MTMC in pesticides.

[0061] 2-Ethyl-6-methylphenol: CAS1687-64-5, boiling point 209.8°C, melting point 45-46°C, 2-ethyl-6-methylphenol has insecticidal and bactericidal properties; it is the raw material for preparing the important pesticide herbicide butachlor, the dye and the pharmaceutical intermediate 2-ethyl-6-methylaniline, and can also be used in other organic syntheses.

[0062] 2,5-Dimethylphenol (CAS# 95-87-4): Boiling point 211.2 °C, melting point 75 °C, it is an intermediate for organic medicine and dyes, and is used for synthesizing lipid-lowering drug gemfibrozil, intermediate 2,3,6-trimethylphenol for vitamin E, etc. 4-tert-Butyl-2,5-xylenol can extract 2,5-dimethylphenol, and can also produce high-quality 2,3,6-trimethylphenol for the production of vitamin E.

[0063] 2,4-Dimethylphenol (CAS# 105-67-9): Boiling point 211 °C, it is an intermediate for organic medicine, and is used for synthesizing high-efficiency polymerization inhibitor and intermediate 6-tert-butyl-2,4-dimethylphenol for medicine, intermediate 2,4-dimethyl-6-nitrophenol for pesticide bialaphos; meanwhile, it also has important applications in pesticides, plastics, rubbers, etc.

[0064] In some embodiments of the present application, in step (1), the mixed phenols include o-isopropylphenol, 2-ethyl-6-methylphenol, m / p-cresol, o-ethylphenol and 2,3-xylenol.

[0065] In some embodiments of the present application, the mass percentage content of o-isopropylphenol in the mixed phenols is 1% - 30%, such as 1%, 5%, 8%, 10%, 15%, 20%, 23%, 28%, 30%, etc.

[0066] In some embodiments of the present application, the mass percentage content of 2-ethyl-6-methylphenol in the mixed phenols is 1% - 20%, such as 1%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, etc.

[0067] In some embodiments of the present application, the mass percentage content of m / p-cresol in the mixed phenols is 0% - 5%, such as 0.1%, 0.5%, 1%, 2%, 2.3%, 2.8%, 3.2%, 3.7%, 4.3%, 5%, etc.

[0068] In some embodiments of the present application, the mass percentage content of o-ethylphenol in the mixed phenols is 0% - 1%, such as 0.1%, 0.6%, 0.8%, 1%, etc.

[0069] In some embodiments of the present application, the mass percentage content of 2,3-xylenol in the mixed phenols is 0% - 5%, such as 0.1%, 0.8%, 1.3%, 1.6%, 2.1%, 2.7%, 3.6%, 3.9%, 4.3%, 5%, etc.

[0070] In some embodiments of the present application, in step (1), the catalyst includes one or more of inorganic acids, organic acids or acidic resins; preferably, the catalyst is acidic resin or sulfuric acid.

[0071] In some embodiments of the present application, when the catalyst is an inorganic acid or an organic acid, it is also necessary to adjust the pH of the reaction solution. Specifically, the pH of the reaction solution is adjusted to 7-8, the reaction solution is stratified, the water layer is filtered off, the feed liquid is washed with water, and then the obtained feed layer is subjected to distillation treatment.

[0072] Since the rectification separation of the tert-butylation product must be neutral to weakly alkaline, there are two types of catalysts used in the present invention. After the reaction with the solid resin catalyst, only filtration is required. The filtrate is neutral after filtration and does not need to be neutralized, and then rectification can be carried out. For the liquid catalyst of organic acid or inorganic acid, filtration may not be required after the reaction, but the reaction solution must be neutralized to neutrality. Otherwise, under acidic conditions, tert-butylated phenol will decompose to remove the tert-butyl group, and tert-butylated phenol cannot be obtained.

[0073] In some embodiments of the present application, in step (1), the mass ratio of the mixed phenol to the catalyst is 100:(0.5-30); for example, 100:0.5, 100:1, 100:5, 100:12, 100:18, 100:21, 100:30, etc.

[0074] In some embodiments of the present application, in step (1), the mass ratio of the mixed phenol to the isobutene is 1:(0.5-5); for example, 1:0.5, 1:0.8, 1:1.2, 1:2.3, 1:3.3, 1:4.6, 1:5, etc.

[0075] In some embodiments of the present application, in step (1), the temperature of the first reaction is 60-150°C, such as 60°C, 80°C, 100°C, 120°C, 150°C, etc., and the time of the first reaction is 4-12h, such as 4h, 6h, 8h, 10h, 12h, etc.

[0076] In some embodiments of the present application, in step (1), the crude product of 4-tert-butyl-2-ethyl-6-methylphenol includes 4-tert-butyl-2-ethyl-6-methylphenol and 4-tert-butyl-2,5-dimethylphenol. Among them, the total mass percentage content of 4-tert-butyl-2-ethyl-6-methylphenol and 4-tert-butyl-2,5-dimethylphenol in the crude product of 4-tert-butyl-2-ethyl-6-methylphenol is ≥99%, and the mass percentage content of 4-tert-butyl-2-ethyl-6-methylphenol is ≥75%.

[0077] In some embodiments of the present application, the crude product of 4-tert-butyl-2,5-dimethylphenol includes 4-tert-butyl-2,5-dimethylphenol and 4-tert-butyl-2-ethyl-6-methylphenol. Among them, the total mass percentage content of 4-tert-butyl-2,5-dimethylphenol and 4-tert-butyl-2-ethyl-6-methylphenol in the crude product of 4-tert-butyl-2,5-dimethylphenol is ≥99%, and the mass percentage content of 4-tert-butyl-2,5-dimethylphenol is ≥80%.

[0078] In some embodiments of the present application, in step (2), the mass ratio of the still residue 4,6 - di - tert - butyl - 2 - isopropylphenol to sulfuric acid is 100:(0.5 - 5); for example, 100:0.5, 100:1, 100:2.1, 100:3, 100:3.3, 100:4.1, 100:5, etc.

[0079] In some embodiments of the present application, in step (2), the temperature of the second reaction is 160 - 200 °C, for example, 160 °C, 180 °C, 190 °C, 200 °C, etc., and the time of the second reaction is 1 - 4 h, for example, 1 h, 2 h, 3 h, 4 h, etc.

[0080] In some embodiments of the present application, in step (2), the mass ratio of the crude 4 - tert - butyl - 2 - ethyl - 6 - methylphenol to sulfuric acid is 100:(0.5 - 5); for example, 100:0.5, 100:1, 100:2.1, 100:3, 100:3.3, 100:4.1, 100:5, etc.

[0081] In some embodiments of the present application, in step (2), the temperature of the third reaction is 160 - 200 °C, for example, 160 °C, 180 °C, 190 °C, 200 °C, etc., and the time of the third reaction is 1 - 4 h; for example, 1 h, 2 h, 3 h, 4 h, etc.

[0082] In some embodiments of the present application, in step (2), the mass ratio of the crude 4 - tert - butyl - 2,5 - dimethylphenol to sulfuric acid is 100:(0.5 - 5); for example, 100:0.5, 100:1, 100:2.1, 100:3, 100:3.3, 100:4.1, 100:5, etc.

[0083] In some embodiments of the present application, in step (2), the temperature of the fourth reaction is 160 - 200 °C, for example, 160 °C, 180 °C, 190 °C, 200 °C, etc., and the time of the fourth reaction is 1 - 4 h, for example, 1 h, 2 h, 3 h, 4 h, etc.

[0084] In some embodiments of the present application, in step (3), the cooling rate for cooling the crude 2 - ethyl - 6 - methylphenol to 43 - 45 °C is 0.3 - 0.7 °C / h; for example, 0.3 °C / h, 0.4 °C / h, 0.5 °C / h, 0.7 °C / h, etc. Using this cooling rate can ensure the purity of the crystalline material.

[0085] In some embodiments of the present application, in step (3), the crystallization time is 3 - 5 h; for example, 3 h, 4 h, 5 h, etc.

[0086] In some embodiments of the present application, in step (3), the heating rate of the crystals obtained by heating crystallization is 0.1 - 0.5 °C / h, such as 0.1 °C / h, 0.2 °C / h, 0.3 °C / h, 0.5 °C / h, etc.

[0087] In some embodiments of the present application, in step (3), the mass ratio of silicon element to aluminum element in the acidic silicon-aluminum oxide is (0.1 - 50):1.

[0088] In some embodiments of the present application, the acidic silicon-aluminum oxide includes silicon dioxide and aluminum oxide.

[0089] In some embodiments of the present application, the olefin hydrogenation catalyst includes palladium-carbon catalyst and / or Raney nickel catalyst.

[0090] In some embodiments of the present application, in step (3), the mass ratio of the crude 2,5-xylenol to sulfuric acid is 100:(0.5 - 3), such as 100:0.5, 100:0.8, 100:1, 100:2, 100:2.3, 100:3, etc.

[0091] In some embodiments of the present application, the mass ratio of the crude 2,5-xylenol to the acidic silicon-aluminum oxide is 100:(1 - 30); such as 100:1, 100:5, 100:12, 100:18, 100:23, 100:28, 100:30, etc.

[0092] In some embodiments of the present application, the mass ratio of the acidic silicon-aluminum oxide to the olefin hydrogenation catalyst is 100:(0.01 - 0.5); such as 100:0.01, 100:0.05, 100:0.1, 100:0.2, 100:0.3, 100:0.5, etc.

[0093] In some embodiments of the present application, the temperature of the fifth reaction is 280 - 400 °C, such as 280 °C, 300 °C, 350 °C, 380 °C, 400 °C, etc., and the time of the fifth reaction is 3 - 8 h, such as 3 h, 5 h, 7 h, 8 h, etc.

[0094] In some embodiments of the present application, the mass ratio of the crude 2,5-xylenol to the hydrogen input amount is 100:(10 - 50); such as 100:10, 100:20, 100:30, 100:40, 100:50, etc.

[0095] In some embodiments of the present application, in step (3), the cooling treatment is to cool the reaction solution to ≤90 °C at a cooling rate of 60 - 80 °C / h.

[0096] The technical solution of the present application will be further described below in conjunction with specific embodiments.

[0097] Example 1

[0098] A method for separating phenolic monomers from mixed phenols, comprising the following steps:

[0099] (1) Add 2000 parts of mixed phenols (including 878.6 parts of 2,4-xylenol, 550 parts of 2,5-xylenol, 357.1 parts of o-isopropylphenol, and 214.3 parts of 2-ethyl-6-methylphenol), 200 parts of NKC-9 strongly acidic macroporous resin, and 200 parts of D001 strongly acidic macroporous resin into a reactor. Under stirring conditions, heat up to 110°C, control the pressure at about 0.6 MPa, and repeatedly introduce isobutene. Stop introducing gas when the pressure in the kettle no longer decreases when introducing isobutene. A total of 1500 parts of isobutene are introduced. Then, keep the temperature at 110°C for 2 hours for sampling and analysis. When the content of 6-tert-butyl-2-isopropylphenol is detected to be 0.35% (qualified when the mass content of 6-tert-butyl-2-isopropylphenol ≤ 0.5%), recover 281 parts of isobutene after the reaction, relieve the pressure to atmospheric pressure, slightly cool down to 80°C, and filter the filter cake for reuse. First, distill and recover diisobutene and 120.3 parts of the front fraction for reuse at -0.07 MPa and a reflux ratio of 2:1. Then, perform vacuum rectification at -0.095 MPa and a reflux ratio of 8:1 to obtain 1244.3 parts of 6-tert-butyl-2,4-xylenol with a mass percentage content of 99.1% (yield 96.2%). Perform vacuum rectification at -0.095 MPa and a reflux ratio of 25:1 to obtain 228.3 parts of crude 4-tert-butyl-2-ethyl-6-methylphenol with a mass percentage content of 86.5% (including 197.5 parts of 4-tert-butyl-2-ethyl-6-methylphenol and 30.1 parts of 4-tert-butyl-2,5-xylenol), and 834.7 parts of crude 4-tert-butyl-2,5-xylenol with a mass percentage content of 88.6% (including 92.9 parts of 4-tert-butyl-2-ethyl-6-methylphenol and 740.2 parts of 4-tert-butyl-2,5-xylenol); 640.1 parts of kettle residue (including 638.2 parts of 4,6-di-tert-butyl-2-isopropylphenol).

[0100] (2) Add 640.1 parts of 4,6-di-tert-butyl-2-isopropylphenol in the kettle residue into a decomposition kettle, and then add 8 parts of concentrated sulfuric acid. Heat up to 180°C under stirring and maintain for 4 hours. Stop the reaction when the mass percentage content of 6-tert-butyl-2-isopropylphenol detected by gas chromatography is 0.42% (the reaction is completed when the mass percentage content of 6-tert-butyl-2-isopropylphenol ≤ 0.5%). Slightly cool down and neutralize to pH 7.5 with 20.8 parts of 31% sodium hydroxide aqueous solution. Then, perform vacuum rectification at -0.09 MPa and a reflux ratio of 10:1 to obtain 332 parts of o-isopropylphenol with a mass percentage content of 99.3%, with a yield of 94.2%, and recover 282.4 parts of isobutene for reuse.

[0101] Add 228.3 parts of crude 4-tert-butyl-2-ethyl-6-methylphenol with a mass percentage content of 86.5% into a decomposition kettle, then add 2.5 parts of concentrated sulfuric acid. Stir and heat up to 195 °C and maintain for 2 hours. Stop the reaction when the mass percentage content of 4-tert-butyl-2-ethyl-6-methylphenol detected by gas chromatography is 0.18% (when the mass percentage content of 4-tert-butyl-2-ethyl-6-methylphenol ≤ 0.5%, it indicates that the reaction is completed). Slightly cool down and neutralize to pH 7.5 with 6.8 parts of sodium hydroxide aqueous solution with a mass concentration of 31%. Under -0.085 MPa and a reflux ratio of 20:1, carry out vacuum distillation to obtain 139.3 parts of crude 2-ethyl-6-methylphenol with a mass percentage content of 91.6% (127.6 parts of 2-ethyl-6-methylphenol), and recycle 76.6 parts of isobutene for reuse.

[0102] Add 834.7 parts of crude 4-tert-butyl-2,5-xylenol with a mass percentage content of 88.6% into a decomposition kettle, then add 10 parts of concentrated sulfuric acid. Stir and heat up to 195 °C and maintain for 2 hours. Stop the reaction when the mass percentage content of 4-tert-butyl-2,5-xylenol detected by gas chromatography is 0.18% (when the mass percentage content of 4-tert-butyl-2,5-xylenol ≤ 0.5%, it indicates that the reaction is completed). Slightly cool down and neutralize to pH 8 with 27.5 parts of sodium hydroxide aqueous solution with a mass concentration of 31%. Under -0.085 MPa and a reflux ratio of 5:1, carry out vacuum distillation to obtain 561 parts of crude 2,5-xylenol with a mass percentage content of 88.6% (63.8 parts of 2-ethyl-6-methylphenol, 497.2 parts of 2,5-xylenol), and recycle 254.7 parts of isobutene for reuse.

[0103] (3) Add 139.3 parts of crude 2-ethyl-6-methylphenol with a mass percentage content of 91.6% into a melt crystallizer, heat it up to 52 °C in an oil bath to dissolve it, then cool it down slowly at a cooling rate of 0.5 °C / h to 44 °C, and keep it warm for 5 hours to fully crystallize 2-ethyl-6-methylphenol, and then discharge 0.7 parts of the uncrystallized solution; then heat it up at a heating rate of 0.2 °C / h to 46 °C and keep it warm for 2 hours to melt part of the material, and collect 106.2 parts of 2-ethyl-6-methylphenol product with a mass content of 99.2%. After cooling, it is a white solid, and the yield of the first melt crystallization is 82.6%; then quickly heat up the remaining material to melt it, and after all melting, obtain 32.3 parts of the later fraction (21.8 parts of 2-ethyl-6-methylphenol, 10.5 parts of 2,5-xylenol);

[0104] (4) Charge 90 parts of acidic aluminosilicate solid catalyst (the acidic aluminosilicate solid catalyst described in this example includes silicon dioxide and aluminum oxide, and the mass ratio of silicon element to aluminum element is 1.8:1), 0.1 part of supported 1% palladium on carbon (the dosage is 0.11% of the acidic aluminosilicate) into a stainless-steel high-pressure reactor with an external stainless-steel condenser and an internal coil. Add 561 parts of 2,5-xylenol crude product with a mass percentage content of 88.6% (63.8 parts of 2-ethyl-6-methylphenol, 497.2 parts of 2,5-xylenol), 32.3 parts of the later fraction obtained in the third step (21.8 parts of 2-ethyl-6-methylphenol, 10.5 parts of 2,5-xylenol), and 5.5 parts of 96% sulfuric acid (the dosage is 0.98% of the mass of the 2,5-xylenol crude product). Seal the reactor, introduce 150 parts of hydrogen (the hydrogen dosage is 0.27 times the mass of the 2,5-xylenol crude product), heat up to 300 °C and react for 7 hours, gradually increase the pressure to 3.5 MPa. Take a sample for analysis. When the mass percentage content of 2-ethyl-6-methylphenol is 0.33%, end the reaction (qualified when the mass percentage content of 2-ethyl-6-methylphenol ≤ 0.5%). Slowly cool the heat transfer oil in the internal coil by programmed cooling (the temperature of the heat transfer oil gradually decreases from high temperature to 60 °C). The material is cooled to 90 °C at a cooling rate of about 60 °C / h, discharge the non-condensable gas and depressurize to atmospheric pressure; after discharging the gas, slightly cool the reaction material and displace it with nitrogen for 1 hour, and filter to obtain the cracked reaction product mixed phenol (containing 5.5 parts of sulfuric acid, 66.6 parts of o-cresol, 497.5 parts of 2,5-xylenol).

[0105] Add the cracked reaction product mixed phenol to the bottom of the distillation column (theoretical number of plates: 150), and carry out vacuum distillation (vacuum degree: -0.085 MPa, reflux ratio: 8:1) to obtain 64.8 parts of o-cresol with a mass percentage content of 99.8% and 481.5 parts of 2,5-xylenol with a mass percentage content of 99.9%.

[0106] Example 2

[0107] A method for separating phenolic monomers from mixed phenols, comprising the following steps:

[0108] (1) Add 4000 parts of mixed phenols (including 1500 parts of 2,4-xylenol, 1322 parts of 2,5-xylenol, 928 parts of o-isopropylphenol, and 250 parts of 2-ethyl-6-methylphenol) and 120 parts of 98% sulfuric acid into the reactor. While stirring, heat up to 80°C, control the pressure at about 1.5 MPa, and repeatedly introduce isobutene. The introduction time is 6 hours. Stop the gas introduction when the pressure in the kettle no longer decreases during the introduction of isobutene. A total of 4000 parts of isobutene are introduced. Then, keep the temperature at 80°C for 2 hours for sampling and analysis. When the content of 6-tert-butyl-2-isopropylphenol is 0.22%, it is qualified. After the reaction, recover 1487.6 parts of isobutene, relieve the pressure to atmospheric pressure, add 310 parts of 31% sodium hydroxide aqueous solution to neutralize to pH 7.5, let it stand for 1 hour, separate the lower water layer, and add the material layer into the distillation column (200 theoretical plates). First, distill and recover diisobutene and the front fraction of 332.9 parts at -0.6 MPa and a reflux ratio of 2:1 for reuse. Then, conduct vacuum distillation at -0.095 MPa and a reflux ratio of 20:1 to obtain 2107.1 parts of 6-tert-butyl-2,4-xylenol with a mass percentage content of 99.5% (yield 95.8%), 311.2 parts of crude 4-tert-butyl-2-ethyl-6-cresol with a mass percentage content of 76.1% (including 236.7 parts of 4-tert-butyl-2-ethyl-6-cresol and 74.2 parts of 4-tert-butyl-2,5-xylenol), and 1940.3 parts of crude 4-tert-butyl-2,5-xylenol with a mass percentage content of 94.1% (110.9 parts of 4-tert-butyl-2-ethyl-6-cresol and 1825.6 parts of 4-tert-butyl-2,5-xylenol); 1684.7 parts of still residue (containing 1675.3 parts of 4,6-di-tert-butyl-2-isopropylphenol).

[0109] (2) Add 1684.7 parts of the still residue 4,6-di-tert-butyl-2-isopropylphenol (1675.3 parts of 4,6-di-tert-butyl-2-isopropylphenol) into the decomposition kettle, then add 16 parts of concentrated sulfuric acid, heat up to 190°C while stirring and maintain for 3 hours. Stop the reaction when the content of 6-tert-butyl-2-isopropylphenol is 0.19% detected by gas chromatography. Cool down slightly and neutralize to pH 8 with 42 parts of 31% sodium hydroxide aqueous solution, let it stand for 1 hour, separate the water layer, and add the material layer into the distillation column (200 theoretical plates). Conduct vacuum distillation at -0.09 MPa and a reflux ratio of 10:1 to obtain 859.9 parts of o-isopropylphenol with a mass percentage content of 99.6%, with a yield of 92.9%, and recover 745.6 parts of isobutene for reuse.

[0110] 311.2 parts of crude 4-tert-butyl-2-ethyl-6-methylphenol with a mass percentage of 76.1% (236.7 parts of 4-tert-butyl-2-ethyl-6-methylphenol and 74.2 parts of 4-tert-butyl-2,5-dimethylphenol) were added to a decomposition kettle, and then 3 parts of concentrated sulfuric acid were added. The temperature was raised to 195 °C under stirring and maintained for 2 hours. The reaction was stopped when the content of 4-tert-butyl-2-ethyl-6-methylphenol was 0.14% detected by gas chromatography. After slightly cooling, it was neutralized to pH 7.5 with 8.2 parts of an aqueous sodium hydroxide solution with a mass concentration of 31%. Then, under a pressure of -0.085 MPa and a reflux ratio of 30:1, vacuum distillation was carried out to obtain 143.3 parts of crude 2-ethyl-6-methylphenol with a mass percentage of 92.4% (132.4 parts of 2-ethyl-6-methylphenol), and 90.5 parts of isobutene were recovered and reused.

[0111] 1940.3 parts of crude 4-tert-butyl-2,5-dimethylphenol with a mass percentage of 94.1% (110.9 parts of 4-tert-butyl-2-ethyl-6-methylphenol and 1825.6 parts of 4-tert-butyl-2,5-dimethylphenol) were added to a decomposition kettle, and then 20 parts of concentrated sulfuric acid were added. The temperature was raised to 195 °C under stirring and maintained for 2 hours. The reaction was stopped when the content of 4-tert-butyl-2,5-dimethylphenol was 0.21% detected by gas chromatography. After slightly cooling, it was neutralized to pH 8 with 55 parts of an aqueous sodium hydroxide solution with a mass concentration of 31%. Then, under a pressure of -0.085 MPa and a reflux ratio of 5:1, vacuum distillation was carried out to obtain 1303.2 parts of crude 2,5-dimethylphenol with a mass percentage of 94.1% (77 parts of 2-ethyl-6-methylphenol and 1226.2 parts of 2,5-dimethylphenol), and 611.9 parts of isobutene were recovered and reused.

[0112] (3) 143.3 parts of crude 2-ethyl-6-methylphenol with a mass percentage of 92.4% were added to a melting crystallizer. The temperature was raised to 52 °C in an oil bath to dissolve it, and then it was slowly cooled to 44.5 °C at a cooling rate of 0.4 °C / h and kept warm for 5 hours to fully crystallize 2-ethyl-6-methylphenol. Then, 0.9 part of the uncrystallized solution was discharged. Then, it was heated to 46 °C at a heating rate of 0.1 °C / h and kept warm for 2 hours to melt part of the material, and 101.8 parts of 2-ethyl-6-methylphenol product with a mass percentage of 99.6% were collected. After cooling, it was a white solid, and the yield of the first melting crystallization was 76.9%. The remaining material was quickly heated to melt, and after complete melting, 40.4 parts were obtained (30.8 parts of 2-ethyl-6-methylphenol and 9.6 parts of 2,5-dimethylphenol).

[0113] (4) Charge 150 parts of acidic aluminosilicate solid catalyst (the acidic aluminosilicate solid catalyst in this example contains silicon dioxide and aluminum oxide, and the mass ratio of silicon element to aluminum element is 3:1) and 0.1 part of 1% palladium on carbon (the dosage is 0.11% of the acidic aluminosilicate) into a stainless-steel high-pressure reactor with an external stainless-steel condenser and an internal coil. Add 1303.2 parts of 2,5-xylenol crude product with a mass percentage of 94.1% (which contains 77 parts of 2-ethyl-6-methylphenol and 1226.2 parts of 2,5-xylenol), the latter part obtained in the third step (30.8 parts of 2-ethyl-6-methylphenol and 9.6 parts of 2,5-xylenol), and 13 parts of 96% sulfuric acid (the dosage is 1% of the mass of the 2,5-xylenol crude product). Seal the reactor, introduce 300 parts of hydrogen (the hydrogen dosage is 0.23 times the mass of the 2,5-xylenol crude product), heat up to 350 °C and react for 6 hours, gradually increase the pressure to 3.9 - 4.0 MPa. Take samples for analysis, and end the reaction when the content of 2-ethyl-6-methylphenol is 0.25%. Slowly cool the heat transfer oil in the internal coil by programmed cooling (the temperature of the heat transfer oil gradually decreases from a high temperature to 60 °C), and cool the material to 90 °C at a cooling rate of about 60 °C / h, then discharge the non-condensable gas and depressurize to atmospheric pressure. After discharging the gas, slightly cool the reaction material and displace it with nitrogen for 0.5 hours, and filter to obtain the cracked reaction product mixed phenol (containing 13 parts of sulfuric acid, 59.9 parts of o-cresol, and 1201.7 parts of 2,5-xylenol).

[0114] Add the cracked reaction product mixed phenol to the bottom of a distillation column (the number of theoretical plates is 150), and conduct vacuum distillation (vacuum degree -0.085 MPa, reflux ratio 10:1) to obtain 57.9 parts of o-cresol with a mass percentage of 99.9% and 1158.4 parts of 2,5-xylenol with a mass percentage of 99.9%.

[0115] Example 3

[0116] A method for separating phenolic monomers from mixed phenols, comprising the following steps:

[0117] (1) Add 10,000 parts of mixed phenols (including 4,357 parts of 2,4-xylenol, 3,693 parts of 2,5-xylenol, 612 parts of o-isopropylphenol, 763 parts of 2-ethyl-6-methylphenol, 236 parts of 2,3-xylenol, 169 parts of m-cresol, 139 parts of p-cresol, 31 parts of o-ethylphenol), 300 parts of 98% sulfuric acid into the reactor. While stirring, heat up to 100°C, control the pressure at about 1.3 MPa, and repeatedly introduce isobutene. The introduction time is 5 hours. Stop the gas introduction when the pressure in the kettle no longer decreases during the introduction of isobutene. A total of 7,000 parts of isobutene are introduced. Then, keep the temperature at 100°C for a 3-hour holding reaction and take samples for analysis. The content of 6-tert-butyl-2-isopropylphenol being 0.13% is qualified. After the reaction, recover the isobutene parts, relieve the pressure to atmospheric pressure, add 774.5 parts of 31% sodium hydroxide aqueous solution by mass to neutralize to pH 7.5, let it stand for 1 hour, and separate the lower water layer. Add the material layer into the distillation column (200 theoretical plates). First, distill and recover diisobutene and the front fraction of 1,271.2 parts for recycling at -0.6 MPa and a reflux ratio of 2:1. Then, perform vacuum distillation at -0.095 MPa and a reflux ratio of 25:1 to obtain 6,171.8 parts of 6-tert-butyl-2,4-xylenol with a mass percentage content of 99.6% (yield 96.7%), 889.8 parts of crude 4-tert-butyl-2-ethyl-6-methylphenol with a mass percentage content of 78.3% (including 696.7 parts of 4-tert-butyl-2-ethyl-6-methylphenol and 193.1 parts of 4-tert-butyl-2,5-xylenol), 5,715 parts of crude 4-tert-butyl-2,5-xylenol with a mass percentage content of 89% (358.9 parts of 4-tert-butyl-2-ethyl-6-methylphenol, 5,087.2 parts of 4-tert-butyl-2,5-xylenol, 268.9 parts of 2,6-di-tert-butyl-4-methylphenol), 41.3 parts of 4,6-di-tert-butyl-2-ethylphenol with a mass percentage content of 99.1%; 1,846.8 parts of kettle residue (including 326.9 parts of 4,6-di-tert-butyl-3-methylphenol, 1,066.4 parts of 4,6-di-tert-butyl-2-isopropylphenol, 448.1 parts of 4,6-di-tert-butyl-2,3-xylenol).

[0118] (2) 1846.8 parts of the residue in the kettle (containing 326.9 parts of 4,6 - di - tert - butyl - 3 - methylphenol, 1066.4 parts of 4,6 - di - tert - butyl - 2 - isopropylphenol, and 448.1 parts of 4,6 - di - tert - butyl - 2,3 - dimethylphenol) are added to the decomposition kettle, and then 20 parts of concentrated sulfuric acid are added. The temperature is raised to 190 °C with stirring and maintained for 3 hours. The reaction is stopped when the content of 6 - tert - butyl - 2 - isopropylphenol is 0.16% detected by gas chromatography. After slightly cooling, it is neutralized to pH 8 with 51.6 parts of an aqueous sodium hydroxide solution with a mass concentration of 31%. It is left standing for 1 hour to separate the aqueous layer. The material layer is added to the distillation column (200 theoretical plates), and under a pressure of - 0.09 MPa and a reflux ratio of 25:1, vacuum distillation is carried out to obtain 146.7 parts of m - cresol with a mass percentage content of 99.6%, 424.3 parts of o - isopropylphenol with a mass percentage content of 99.3%, 172.7 parts of 2,3 - dimethylphenol with a mass percentage content of 99.1%, and 845.1 parts of isobutene are recovered and reused.

[0119] 889.8 parts of the crude product of 4 - tert - butyl - 2 - ethyl - 6 - methylphenol with a mass percentage content of 78.3% (containing 696.7 parts of 4 - tert - butyl - 2 - ethyl - 6 - methylphenol and 193.1 parts of 4 - tert - butyl - 2,5 - dimethylphenol) are added to the decomposition kettle, and then 9 parts of concentrated sulfuric acid are added. The temperature is raised to 195 °C with stirring and maintained for 2 hours. The reaction is stopped when the content of 4 - tert - butyl - 2 - ethyl - 6 - methylphenol is 0.18% detected by gas chromatography. After slightly cooling, it is neutralized to pH 7.5 with 24.5 parts of an aqueous sodium hydroxide solution with a mass concentration of 31%. Then, under a pressure of - 0.085 MPa and a reflux ratio of 25:1, vacuum distillation is carried out to obtain 438.3 parts of the crude product of 2 - ethyl - 6 - methylphenol with a mass percentage content of 92.1% (403.6 parts of 2 - ethyl - 6 - methylphenol), and 258.6 parts of isobutene are recovered and reused.

[0120] 5715 parts of the crude product of 4 - tert - butyl - 2,5 - dimethylphenol with a mass percentage content of 89% (358.9 parts of 4 - tert - butyl - 2 - ethyl - 6 - methylphenol, 5087.2 parts of 4 - tert - butyl - 2,5 - dimethylphenol, and 268.9 parts of 2,6 - di - tert - butyl - 4 - methylphenol) are added to the decomposition kettle, and then 60 parts of concentrated sulfuric acid are added. The temperature is raised to 195 °C with stirring and maintained for 2 hours. The reaction is stopped when the content of 4 - tert - butyl - 2,5 - dimethylphenol is 0.25% detected by gas chromatography. After slightly cooling, it is neutralized to pH 8 with 155 parts of an aqueous sodium hydroxide solution with a mass concentration of 31%. Then, under a pressure of - 0.085 MPa and a reflux ratio of 25:1, vacuum distillation is carried out to obtain 119.8 parts of p - cresol with a mass percentage content of 99.5%, 3659.9 parts of the crude product of 2,5 - dimethylphenol with a mass percentage content of 93.2% (249.9 parts of 2 - ethyl - 6 - methylphenol and 3410 parts of 2,5 - dimethylphenol), and 1805.2 parts of isobutene are recovered and reused.

[0121] 41.3 parts of 4,6 - di - tert - butyl - 2 - ethylphenol with a mass percentage content of 99.1% were added to the decomposition kettle, and then 0.5 part of concentrated sulfuric acid was added. The temperature was raised to 200 °C under stirring and maintained for 1.5 hours. The reaction was stopped when the content of 6 - tert - butyl - 2 - ethylphenol was 0.09% detected by gas chromatography. After slightly cooling, 1.3 parts of an aqueous sodium hydroxide solution with a mass concentration of 31% was used to neutralize to pH 7.5. Then, under a pressure of - 0.085 MPa and a reflux ratio of 5:1, vacuum distillation was carried out to obtain 21.1 parts of o - ethylphenol with a mass percentage content of 99.3%, and 19.3 parts of recycled isobutene was reused.

[0122] (3) 438.3 parts of the crude product of 2 - ethyl - 6 - methylphenol with a mass percentage content of 92.1% were added to the melt crystallizer. The temperature was raised to 52 °C in an oil bath to dissolve it. Then, it was slowly cooled at a cooling rate of 0.3 °C / h to 44.5 °C and kept warm for 5 hours to fully crystallize 2 - ethyl - 6 - methylphenol. Then, 2.9 parts of the uncrystallized solution were discharged. Then, it was heated at a heating rate of 0.2 °C / h to 46 °C and kept warm for 2 hours to melt part of the material. 314.8 parts of the 2 - ethyl - 6 - methylphenol product with a mass percentage content of 99.5% were collected. After cooling, it was a white solid, and the yield of the first - stage melt crystallization was 77.6%. The remaining material was quickly heated to melt, and after complete melting, 120.3 parts of the later fraction were obtained (87.4 parts of 2 - ethyl - 6 - methylphenol and 32.9 parts of 2,5 - xylenol).

[0123] (4) Charge 600 parts of acidic aluminosilicate solid catalyst (the acidic aluminosilicate solid catalyst in this example includes silica and aluminum oxide, and the mass ratio of silicon element to aluminum element is 5:2), 0.6 parts of recycled 1% palladium-carbon (the dosage is 0.1% of the acidic aluminosilicate) into a stainless-steel high-pressure reactor with an external stainless-steel condenser and an internal coil. Add 3659.9 parts of 93.2% crude 2,5-xylenol (249.9 parts of 2-ethyl-6-methylphenol, 3410 parts of 2,5-xylenol), 120.3 parts of the later fraction obtained by melting and crystallization of crude 2-ethyl-6-methylphenol (87.4 parts of 2-ethyl-6-methylphenol, 32.9 parts of 2,5-xylenol), and 60 parts of 98% sulfuric acid (the dosage is 1.59% of the mass of crude 2,5-xylenol). Seal the reactor, introduce 1000 parts of hydrogen (the hydrogen dosage is 0.26 times the mass of crude 2,5-xylenol), heat up to 300 °C and react for 7.5 hours. The pressure gradually rises to 3.4 MPa and remains stable. Take samples for analysis. When the content of 2-ethyl-6-methylphenol reaches 0.17%, end the reaction. Slowly cool the internal coil with heat-conducting oil with programmed temperature reduction (the temperature of the heat-conducting oil gradually decreases from high temperature to 60 °C slowly). The material cools down to 90 °C at a cooling rate of about 60 °C / h, discharge the non-condensable gas and depressurize to atmospheric pressure. After discharging the gas, let the reaction material cool slightly and displace it with nitrogen for 0.5 hours. Filter to obtain 3696.5 parts of the cracked reaction product mixed phenol (containing 60 parts of sulfuric acid, 262.5 parts of o-cresol, 3374 parts of 2,5-xylenol).

[0124] Add the cracked reaction product mixed phenol to the bottom of the distillation column (the number of theoretical plates is 150), and carry out vacuum distillation (vacuum degree -0.085 MPa, reflux ratio 10:1) to obtain 259.6 parts of o-cresol with a mass percentage content of 99.8% and 3323.2 parts of 2,5-xylenol with a mass percentage content of 99.7%.

[0125] 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 limiting 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 phenol monomers from mixed phenols, characterized in that: The following steps are involved: (1) mixing a mixed phenol, a catalyst and isobutylene for a first reaction, filtering the reaction solution after the first reaction is completed, and distilling the reaction solution to obtain diisobutylene, 6-tert-butyl-2,4-dimethylphenol, crude 4-tert-butyl-2-ethyl-6-methylphenol, crude 4-tert-butyl-2,5-dimethylphenol and still residue 4,6-di-tert-butyl-2-isopropylphenol; (2) mixing the still residual 4,6-di-tert-butyl-2-isopropylphenol with sulfuric acid for a second reaction, and after the second reaction is completed, adjusting the pH of the reaction solution to 7-8 and performing a rectification treatment to obtain o-isopropylphenol; The crude 4-tert-butyl-2-ethyl-6-methylphenol is mixed with sulfuric acid to carry out a third reaction, and after the third reaction is completed, the pH of the reaction solution is adjusted to 7-8 and distilled to obtain a crude 2-ethyl-6-methylphenol; The crude 4-tert-butyl-2,5-xylenol product and sulfuric acid are mixed to perform a fourth reaction, and after the fourth reaction is completed, the pH of the reaction solution is adjusted to 7-8 and distilled to obtain a crude 2,5-xylenol product; (3) heating the crude 2-ethyl-6-methylphenol to 50-55° C., then cooling to 43-45° C. for crystallization, separating the uncrystallized solution, and heating the crystals obtained by crystallization to 46-47° C. to obtain a molten material 2-ethyl-6-methylphenol; The crude 2,5-xymethylphenol, acidic silicon-aluminum oxide, olefin hydrogenation catalyst and sulfuric acid are mixed, and hydrogen is introduced in a closed environment to carry out a fifth reaction. After the reaction is completed, the reaction liquid is cooled and filtered to obtain a cracking product; the cracking product is distilled to obtain o-cresol and 2,5-xymethylphenol.

2. The method for separating phenol monomers from mixed phenols according to claim 1, characterized in that: In step (1), the mixed phenol includes o-isopropylphenol, 2-ethyl-6-methylphenol, m-p-cresol, o-ethylphenol and 2,3-xylenol; Preferably, the mass percentage of o-isopropylphenol in the mixed phenol is 1%-30%; Preferably, the mass percentage of 2-ethyl-6-methylphenol in the mixed phenol is 1%-20%; Preferably, the mass percentage of p-cresol in the mixed phenol is 0%-5%; Preferably, the mass percentage of o-ethylphenol in the mixed phenol is 0%-1%; Preferably, the mass percentage of 2,3-dimethylphenol in the mixed phenol is 0%-5%.

3. The method for separating phenol monomers from mixed phenols according to claim 1, characterized in that: In step (1), the catalyst includes one or more of an inorganic acid, an organic acid or an acidic resin; preferably, the catalyst is an acidic resin or sulfuric acid; And / or, in step (1), the mass ratio of the mixed phenol to the catalyst is 100:(0.5-30); And / or, in step (1), the mass ratio of the mixed phenol to the isobutylene is 1:(0.5-5); And / or, in step (1), the temperature of the first reaction is 60-150° C., and the time of the first reaction is 2-12 h.

4. The method for separating phenol monomers from mixed phenols according to claim 1, characterized in that: In step (1), the crude 4-tert-butyl-2-ethyl-6-methylphenol comprises 4-tert-butyl-2-ethyl-6-methylphenol and 4-tert-butyl-2,5-xylenol; wherein the total mass percentage content of 4-tert-butyl-2-ethyl-6-methylphenol and 4-tert-butyl-2,5-xylenol in the crude 4-tert-butyl-2-ethyl-6-methylphenol is ≥ 99%, and the mass percentage content of 4-tert-butyl-2-ethyl-6-methylphenol is ≥ 75%; And / or, the crude 4-tert-butyl-2,5-dimethylphenol includes 4-tert-butyl-2,5-dimethylphenol and 4-tert-butyl-2-ethyl-6-methylphenol, wherein the total mass percentage of 4-tert-butyl-2,5-dimethylphenol and 4-tert-butyl-2-ethyl-6-methylphenol in the crude 4-tert-butyl-2,5-dimethylphenol is ≥99%, and the mass percentage of 4-tert-butyl-2,5-dimethylphenol is ≥80%.

5. The method for separating phenol monomers from mixed phenols according to claim 1, characterized in that: In step (2), the mass ratio of the still residual 4,6-di-tert-butyl-2-isopropylphenol to sulfuric acid is 100:(0.5-5); And / or, in step (2), the temperature of the second reaction is 160-200° C., and the time of the second reaction is 1-4 h; And / or, in step (2), the mass ratio of crude 4-tert-butyl-2-ethyl-6-methylphenol to sulfuric acid is 100:(0.5-5); And / or, in step (2), the temperature of the third reaction is 160-200° C., and the time of the third reaction is 1-4 h; And / or, in step (2), the mass ratio of the crude 4-tert-butyl-2,5-dimethylphenol to sulfuric acid is 100:(0.5-5); And / or, in step (2), the temperature of the fourth reaction is 160-200° C., and the time of the fourth reaction is 1-4 h.

6. The method for separating phenol monomers from mixed phenols according to claim 1, characterized in that: In step (3), the temperature of the crude 2-ethyl-6-methylphenol is cooled to 43-45° C. at a cooling rate of 0.3-0.7° C. / h; And / or, in step (3), the crystallization time is 3-5h; And / or, in step (3), the heating rate of the crystals obtained by heating crystallization is 0.1-0.5°C / h.

7. The method for separating phenol monomers from mixed phenols according to claim 1, characterized in that: In step (3), the mass ratio of silicon element to aluminum element in the acidic silicon-aluminum oxide is (0.1-50):1; And / or, the acidic silicon-aluminum oxide comprises silicon dioxide and aluminum oxide; And / or, the olefin hydrogenation catalyst comprises a palladium-carbon catalyst and / or a fulminate-aluminum-nickel catalyst.

8. The method for separating phenol monomers from mixed phenols according to claim 1, characterized in that: In step (3), the mass ratio of the crude 2,5-dimethylphenol to sulfuric acid is 100:(0.5-3); and / or, the mass ratio of the crude 2,5-dimethylphenol to the acidic silica-aluminum oxide is 100:(1-30); And / or, the mass ratio of the acidic silica-alumina to the olefin hydrogenation catalyst is 100:(0.01-0.5).

9. The method for separating phenol monomers from mixed phenols according to claim 1, characterized in that: The temperature of the fifth reaction is 280-400° C., and the time of the fifth reaction is 3-8 hours; And / or, the mass ratio of the crude 2,5-dimethylphenol to the hydrogen is 100:(10-50).

10. The method for separating phenol monomers from mixed phenols according to claim 1, characterized in that: In step (3), the cooling treatment is to cool the reaction solution to ≤90°C at a cooling rate of 60-80°C / h.