A method for separating phenol monomers from mixed phenols

Abstract

The present invention provides a method for separating phenol monomers from mixed phenols, wherein diisobutylene is used as an octylation reaction reagent and also as a solvent, and is mixed evenly with various raw materials of mixed phenols and a catalyst to perform an octylation reaction, and the reaction product is subjected to subsequent treatments such as washing, atmospheric distillation, and vacuum distillation to finally obtain various phenol monomers. The method of the present invention has a simple process, mild and easy-to-control reaction conditions, and has a variety of product types, high purity, high yield, a wider range of applications, and is more practical, with significant economic benefits.

Description

Technical Field

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

[0002] Crude phenol is distilled to obtain mixed phenols such as m-cresol, 2,4 / 2,5-xylenol, m-ethylphenol, 3,5-xylenol / m-ethylphenol, or industrial xylenol. They are sold directly as products without fine separation. In fact, these mixed phenol raw materials can be further processed to obtain high-purity m-cresol, p-cresol, 2,4-xylenol, 2,5-xylenol, m-ethylphenol, p-ethylphenol, 3,5-xylenol, 3,4-xylenol, 2,3-xylenol, etc. and corresponding extended products, which can greatly improve the application value and economic value of the products, including:

[0003] Meta-cresol: It is an intermediate for organic medicines, pesticides and dyes. It is used to produce pesticides such as mefenamic acid and fenthion; to produce the dye disperse yellow SE-5R; pharmaceutical intermediates such as 2,3,6-trimethylphenol, 4-nitro-meta-cresol, tribromocresol, 3-phenoxytoluene, meta-toluene diether, calcium cresol sulfonate, meta-hydroxybenzaldehyde, 2-chloro-5-methylphenol, 4-chloro-3-methylphenol, and tinea versicolor powder; to produce spices such as sunflower seed musk, 1-tert-butyl-2-methoxy-4-methyl-3,5-dinitrobenzene, and 6-tert-butyl-meta-cresol; antioxidants such as CA and 300.

[0004] p-Cresol: used in organic synthesis to produce dyes such as Disperse Yellow SE-2GL and Disperse Yellow G; antioxidants such as 2-tert-butyl-p-cresol, 2,6-di-tert-butyl-p-cresol, and antioxidant 2246; dye intermediates such as 2-methoxy-5-methylaniline (Cresidenin) and o-nitro-p-cresol; paint printing adhesives; polyacrylate slurry GM-E; and spices such as p-cresyl acetate, p-methylanisic acid, 4-methyl-anisole, 3,4,5-methoxy-benzaldehyde, 2,4-dimethylphenol, and 2,4,6-trimethylphenol.

[0005] 2,4-Dimethylphenol is an organic pharmaceutical intermediate used to synthesize 6-tert-butyl-2,4-dimethylphenol and the pesticide dimethylamine glufosinate intermediate 2,4-dimethyl-6-nitrophenol; it can also produce the organic intermediate 6-amino-2,4-dimethylphenol; it also has important applications in pesticides, plastics, rubber, etc.

[0006] 2,5-Dimethylphenol is an organic pharmaceutical and dye intermediate, used in the synthesis of lipid-lowering drug gemfibrozil, vitamin E intermediate 2,3,6-trimethylphenol, etc.; it is also used in the production of intermediates such as 6-nitro-2,5-dimethylphenol, 4,6-dinitro-2,5-dimethylphenol, and 3,4,6-tribromo-2,5-dimethylphenol.

[0007] Meta-ethylphenol: an organic synthesis intermediate and a raw material for the synthesis of 2,4-dichloro-3-ethyl-6-nitrophenol, an important photosensitive chemical intermediate.

[0008] p-Ethylphenol: Organic synthesis intermediate, used in soy sauce flavoring, synthetic antioxidant DHEB, antioxidant 425, antioxidant 536, etc.

[0009] 3,5-Dimethylphenol is an organic synthetic raw material that can be used to prepare the highly effective and low-toxic insecticide chlorpyrifos, and to prepare 3,5-dimethylaniline, 4-chloro-3,5-dimethylphenol, 2,4-dichloro-3,5-dimethylphenol, trimethylbenzene, 2,3,5-trimethylphenol and other pharmaceutical intermediates; a certain amount of 3,5-dimethylphenol is used in the synthesis of special polyurethane materials to improve material properties; 3,5-dimethylphenol can also be used to manufacture resins, rubber vulcanization accelerators, disinfectants, preservatives and stabilizers for various organic compounds; 3,5-dimethylphenol is widely used as a cold rolling oil additive (anti-oxidation, anti-corrosion, anti-wear) in combination with phosphorus pentasulfide and chlorinated paraffin, which can extend the service life of cold rolling oil.

[0010] 3,4-Dimethylphenol is an organic chemical raw material used to produce fusible polyimide resins, which can be used as plastics, coatings, adhesives, fibers and laminates. It can withstand temperatures as low as -200°C and as high as 400°C, and has good mechanical properties, electrical insulation, corrosion resistance and radioactivity resistance, making it a special polymer material. 3,4-Dimethylphenol can be used as an antioxidant regulator for certain solvents and light-sensitive substances. 3,4-Dimethylphenol is a raw material for producing 2,6-dinitro-3,4-dimethylphenol (DMNT), an intermediate of the currently best-selling selective herbicide pendimethalin. In addition, 3,4-dimethylphenol can also be used to produce 2-isopropyl-4,5-dimethylphenol, 6-chloro-3,4-dimethylphenol, 2,6-dichloro-3,4-dimethylphenol, etc., which are used in disinfectants, pesticides, spices and fuels.

[0011] 2,3-Dimethylphenol: white crystal, slightly soluble in water, miscible with ethanol, ether, chloroform, etc., soluble in sodium hydroxide aqueous solution, mainly used in the manufacture of phenolic resins, plasticizers, antioxidants, lubricant additives, and can also be used in fixed-bed catalytic methylation to synthesize vitamin E main ring intermediate 2,3,6-trimethylphenol, etc.

[0012] However, since the boiling points of the various phenol monomers in the above-mentioned mixed phenols are too small, it is difficult to separate them well using conventional distillation methods. Therefore, it is of great significance to study the separation methods of these mixed phenols.

[0013] Tang Shifu et al., in the article "Experimental Study on Extraction of 3,5-Xylenol from Industrial Xylenol" published in "Sichuan Metallurgy" No. 2, 2002, pp. 49-50, introduced the method of preparing 3,5-xylenol from industrial xylenol by distillation and crystallization; Zhao Xuefei et al., in the article "Study on Separation of 3,5-Xylenol from Industrial Xylenol" published in "Fuel and Chemical Industry" No. 2, 2002, pp. 89-92, introduced that a narrow fraction of 3,5-xylenol with a purity of more than 90% can be obtained from industrial xylenol by distillation, and a 3,5-xylenol fraction with a purity of more than 90% can be obtained by recrystallization. Products with less than 99% 3,5-xylenol; Li Jian et al. published the article "Development of 3,5-xylenol" on pages 32-35 of "Coal Chemical Industry" in 2005, No. 33, which introduced the research and development of the new chemical product 3,5-xylenol: using the low value-added product industrial xylenol fraction in tar as raw material, a 3,5-xylenol product with a mass fraction of 95% can be obtained by distillation. Experiments show that while producing 95% 3,5-xylenol through one distillation, 95% 3,4-xylenol can also be obtained by crystallization and filtration. However, the extraction rate of 3,5-xylenol in these methods is too low, only 25-30%, the raw material resources are not fully utilized, and the relative production cost is high. Moreover, these methods are only applicable to industrial xylenol extracted from high-temperature coal tar, which is a by-product of high-temperature coking to produce coke, and are not applicable to industrial xylenol produced by medium-low temperature and gasified xylenol.

[0014] Anhui Haihua Technology CN201810102442.5 "A separation process for extracting 2,4-dimethylphenol and 2,5-dimethylphenol from crude phenol" uses isobutylene to react with high-content 2,4 / 2,5-dimethylphenol to generate 6-tert-butyl-2,4-dimethylphenol and 4-tert-butyl-2,5-dimethylphenol, and then distills to obtain pure 6-tert-butyl-2,4-dimethylphenol and 4-tert-butyl-2,5-dimethylphenol; then the isobutylene is removed at a high temperature of 180-200°C under the catalysis of sulfuric acid to generate 2,4-dimethylphenol and 2,5-dimethylphenol. This method of separating 2,4 / 2,5-dimethylphenol using isobutylene has high requirements for raw materials, and the steps of the method are relatively cumbersome, the product variety produced is relatively single, the process has a narrow scope of application, and the economic benefits are general. Summary of the invention

[0015] The present invention aims to solve one of the technical problems in the related art at least to a certain extent. To this end, an embodiment of the present invention provides a method for separating phenol monomers from mixed phenols.

[0016] In one aspect, an embodiment of the present invention provides a method for separating phenol monomers from mixed phenols. When the mixed phenol is m-p-cresol, the method comprises the following steps:

[0017] (1) weighing m-p-cresol, a catalyst, and diisobutylene in a mass ratio of 1:(0.01-0.3):(1-5), uniformly mixing, and performing an octylation reaction to obtain an octylation reaction product;

[0018] (2) After sampling and analysis, the octylation reaction product is neutralized by alkali washing to a pH of 7 to 8, separated into layers, and the layers are washed with water. After all the water is separated, the layers are firstly distilled out of diisobutylene under normal pressure, and then subjected to vacuum distillation to obtain 6-tert-octyl-meta-cresol with a content of ≥99% and 2,6-di-tert-octyl-p-cresol with a content of ≥99% in turn;

[0019] (3) Adding concentrated sulfuric acid at 1-2% of the weight of 6-tert-octyl-m-cresol, and reacting at 150-200° C. for 1-5 hours; then cooling the reaction solution to below 100° C., neutralizing with liquid alkali to neutrality, and then performing vacuum distillation to obtain m-cresol with a content of ≥99%.

[0020] Another aspect of the present invention is to provide a method for separating phenol monomers from mixed phenols. When the mixed phenol is 2,4 / 2,5-dimethylphenol, the method comprises the following steps:

[0021] (1) weighing 2,4 / 2,5-dimethylphenol, a catalyst, and diisobutylene in a mass ratio of 1:(0.01-0.3):(1-5), uniformly mixing, and performing an octylation reaction to obtain an octylation reaction product;

[0022] (2) After sampling and analysis, the octylation reaction product is neutralized by alkali washing to a pH of 7 to 8, separated into layers, and the layers are washed with water. After all the water is separated, the layers are firstly distilled out of diisobutylene under normal pressure, and then subjected to vacuum distillation to obtain 2,5-dimethylphenol with a content of ≥99% and 6-tert-octyl-2,4-dimethylphenol with a content of ≥99% in turn;

[0023] (3) adding concentrated sulfuric acid at 1-2% of the weight of 6-tert-octyl-2,4-dimethylphenol, and reacting at 150-200° C. for 1-5 hours; then cooling the reaction solution to below 100° C., neutralizing it with liquid alkali to neutrality, and then performing vacuum distillation to obtain 2,4-dimethylphenol with a content of ≥99%.

[0024] Another aspect of the present invention provides a method for separating phenol monomers from mixed phenols. When the mixed phenol is m-p-ethylphenol, the method comprises the following steps:

[0025] (1) weighing m-p-ethylphenol, a catalyst, and diisobutylene in a mass ratio of 1:(0.01-0.3):(1-5), uniformly mixing, and performing an octylation reaction to obtain an octylation reaction product;

[0026] (2) After sampling and analysis, the octylation reaction product is neutralized by alkali washing to a pH of 7 to 8, separated into layers, and the layers are washed with water. After all the water is separated, the layers are firstly distilled out of diisobutylene under normal pressure, and then subjected to vacuum distillation to obtain 6-tert-octyl-m-ethylphenol with a content of ≥99% and 2,6-ditert-octyl-p-ethylphenol with a content of ≥99% in turn;

[0027] (3) Adding concentrated sulfuric acid at 1-2% of the weight of 6-tert-octyl-m-ethyl phenol, and reacting at 150-200° C. for 1-5 hours; then cooling the reaction solution to below 100° C., neutralizing with liquid alkali to neutrality, and then performing vacuum distillation to obtain m-ethyl phenol with a content of ≥99%.

[0028] The embodiment of the present invention further provides a method for separating phenol monomers from mixed phenols. When the mixed phenol is 3,5-dimethylphenol / m-ethylphenol, the method comprises the following steps:

[0029] (1) weighing 3,5-dimethylphenol / m-ethylphenol, a catalyst, and diisobutylene in a mass ratio of 1:(0.01-0.3):(1-5), uniformly mixing, and performing an octylation reaction to obtain an octylation reaction product;

[0030] (2) After the sampling and analysis are qualified, the octylation reaction product is cooled and crystallized, and then filtered, and the filter cake is dried to obtain 3,5-dimethylphenol with a content of ≥99%; the filtrate is neutralized with alkali washing to a pH of 7-8, the layers are separated, and the material layer is washed with water. After the water is completely separated, the material layer is firstly distilled out of diisobutylene under normal pressure, and then vacuum distilled to obtain 6-tert-octyl-m-ethylphenol with a content of ≥99% and 2,6-di-tert-octyl-p-ethylphenol with a content of ≥99% in turn;

[0031] (3) adding concentrated sulfuric acid at 1-2% of the weight of 6-tert-octyl-m-ethylphenol, and reacting at 150-200° C. for 1-5 hours; then cooling the reaction solution to below 100° C., neutralizing with liquid alkali to neutrality, separating the layers, washing the layers with water, and after removing all the water, subjecting the layers to vacuum distillation to obtain m-ethylphenol with a content of ≥99%.

[0032] The embodiment of the present invention further provides a method for separating phenol monomers from mixed phenols. When the mixed phenol is industrial xylenol, the method comprises the following steps:

[0033] (1) weighing industrial xylenol, a catalyst, and diisobutylene in a mass ratio of 1:(0.01-0.3):(1-5), uniformly mixing, and performing an octylation reaction to obtain an octylation reaction product;

[0034] (2) After sampling and analysis, the octylation reaction product is neutralized by alkali washing to a pH of 7 to 8, separated, and the material layer is washed with water. After all the water is separated, the material layer is firstly distilled out of diisobutylene under normal pressure, and then vacuum distilled to obtain 2,5-dimethylphenol with a content of ≥99%, 3,5-dimethylphenol with a content of ≥99%, a first mixed fraction of 6-tert-octyl-2,3-dimethylphenol and 6-tert-octyl-2,4-dimethylphenol, and a second mixed fraction of 6-tert-octyl-2,3-dimethylphenol, 6-tert-octyl-m-ethylphenol and 6-tert-octyl-3,4-dimethylphenol; the still residue is 2,6-ditert-octyl-p-ethylphenol;

[0035] (3) adding concentrated sulfuric acid at 1-2% of the weight of the first mixed fraction and the second mixed fraction, respectively, and reacting at 150-200° C. for 1-5 hours; then cooling the reaction liquid to below 100° C., neutralizing with liquid alkali to neutrality, and then performing vacuum distillation, wherein the first mixed fraction is subjected to vacuum distillation to obtain 2,3-xylenol with a content of ≥99% and 2,4-xylenol with a content of ≥99%; the second mixed fraction is subjected to vacuum distillation to obtain 2,3-xylenol with a content of ≥99%, 3,4-xylenol with a content of ≥98%, and crude m-ethylphenol with a content of ≥92%;

[0036] Among them, taking the sum of the weights of 6-tert-octyl-2,3-dimethylphenol in the first mixed fraction and the second mixed fraction as 100%, the weight proportion of 6-tert-octyl-2,3-dimethylphenol in the first mixed fraction is ≥70%; the weight proportion of 6-tert-octyl-2,3-dimethylphenol in the second mixed fraction is ≤30%.

[0037] In some embodiments of the present invention, when the mixed phenol is industrial xylenol, the method further comprises: performing two-step crystallization on the crude meta-ethylphenol with a content of ≥92% obtained after vacuum distillation, the specific steps being: cooling the crude meta-ethylphenol with a content of ≥92% to -3 to -10°C, keeping the temperature for crystallization for 2 to 5 hours, filtering, recovering the filtrate, and obtaining a primary crystallization material of meta-ethylphenol from the filter cake; then heating the primary crystallization material of meta-ethylphenol to 3 to 10°C to dissolve the material; then cooling it to 1 to -10°C at a rate of 1.0 to 4.0°C / hr; then cooling it to -3 to -10°C at a rate of 0.1 to 1.0°C / hr, keeping the temperature for crystallization for 2 to 5 hours, discharging the uncrystallized solution and recovering it; then heating the crystals to -1 to -5°C at a rate of 0.1 to 1.0°C / hr, keeping the temperature for 2 to 5 hours, and obtaining a pure meta-ethylphenol with a content of ≥99%.

[0038] In some embodiments of the present invention, the composition of the industrial xylenol includes 20-30% of 2,4 / 2,5-xylenol, 15-35% of 3,5-xylenol, 25-35% of m-p-ethylphenol, 5-10% of 2,3-xylenol, and 8-12% of 3,4-xylenol.

[0039] In some embodiments of the present invention, the temperature of the octylation reaction is 50-150° C., and the reaction time is 6-12 hours.

[0040] In some embodiments of the present invention, the catalyst is one or a mixture of two or more of sulfuric acid, phosphoric acid, p-toluenesulfonic acid, aminosulfonic acid, a strong acid resin or a carrier solid acid.

[0041] In some embodiments of the present invention, the qualified analysis standard is: when the mixed phenol is m-cresol, the content of 2-tert-octyl-p-cresol is ≤0.5% for qualified; when the mixed phenol is 2,4 / 2,5-xylenol, the content of 2,4-xylenol is ≤0.3% for qualified; when the mixed phenol is m-ethylphenol, the content of 2-tert-octyl-p-ethylphenol is ≤0.5% for qualified; when the mixed phenol is 3,5-xylenol / m-p-ethylphenol, the content of 6-tert-octyl-p-ethylphenol is ≤0.5% for qualified; when the mixed phenol is industrial xylenol, the content of 2-tert-octyl-p-ethylphenol is ≤0.8% for qualified.

[0042] The advantages and beneficial effects of the present invention are as follows: in the method for separating phenol monomers from mixed phenols, diisobutylene is used as an octylation reaction reagent and also as a solvent, and various phenol monomers are separated from various mixed phenol raw materials. The method has low requirements on raw material quality and a wide range of raw material sources; the process is simple, the reaction conditions are mild and easy to control, there is little pollution, and it is easy to carry out industrial production and promotion; and the products obtained by the separation method are of various types, high purity, high yield, wider application range, more practicality, and significant economic benefits; in addition, compared with the prior art in which isobutylene is used as a solvent and a tert-butylation reaction reagent, which exists in a gaseous state at normal temperature and pressure, the diisobutylene in the method of the present invention is in a liquid state at normal temperature and pressure, and its transportation is more convenient, which can save a lot of transportation costs. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below. Obviously, the described embodiment is a part of the embodiment of the present invention, not all the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention.

[0044] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by those having ordinary skills in the field to which the present invention belongs.

[0045] In one aspect, an embodiment of the present invention provides a method for separating phenol monomers from mixed phenols. When the mixed phenol is m-p-cresol, the method comprises the following steps:

[0046] (1) weighing m-p-cresol, a catalyst, and diisobutylene in a mass ratio of 1:(0.01-0.3):(1-5), uniformly mixing, and performing an octylation reaction to obtain an octylation reaction product;

[0047] (2) After the sampling and analysis are qualified, the octylation reaction product is neutralized by alkali washing to a pH of 7 to 8, separated into layers, and the material layer is washed with water. After the water is completely separated, the material layer is firstly distilled out of diisobutylene under normal pressure, and then vacuum distilled to obtain 6-tert-octyl-meta-cresol with a content of ≥99% and 2,6-di-tert-octyl-p-cresol with a content of ≥99% in turn; wherein 2,6-di-tert-octyl-p-cresol is an antioxidant and can be directly sold as a product, or it can be further distilled to obtain p-cresol with a content of ≥99%, and the p-cresol can be sold as a product;

[0048] (3) adding concentrated sulfuric acid at 1-2% of the weight of 6-tert-octyl-meta-cresol, and reacting at 150-200° C. for 1-5 hours to remove diisobutylene; cooling the reaction solution after the removal of diisobutylene to below 100° C., neutralizing it with liquid alkali to neutrality, and then performing vacuum distillation to obtain meta-cresol with a content of ≥99%, which is sold as a product.

[0049] Another aspect of the present invention is to provide a method for separating phenol monomers from mixed phenols. When the mixed phenol is 2,4 / 2,5-dimethylphenol, the method comprises the following steps:

[0050] (1) weighing 2,4 / 2,5-dimethylphenol, a catalyst, and diisobutylene in a mass ratio of 1:(0.01-0.3):(1-5), uniformly mixing, and performing an octylation reaction to obtain an octylation reaction product;

[0051] (2) After sampling and analysis, the octylation reaction product is neutralized by alkali washing to a pH of 7-8, separated into layers, and the layers are washed with water. After all the water is separated, the layers are firstly distilled out of diisobutylene under normal pressure, and then distilled under reduced pressure to obtain 2,5-dimethylphenol with a content of ≥99% and 6-tert-octyl-2,4-dimethylphenol with a content of ≥99% in turn; wherein 2,5-dimethylphenol is directly sold as a product;

[0052] (3) Adding concentrated sulfuric acid at 1-2% of the weight of the 6-tert-octyl-2,4-dimethylphenol to the above-mentioned 6-tert-octyl-2,4-dimethylphenol, and reacting at 150-200° C. for 1-5 hours to remove diisobutylene; then cooling the reaction liquid after the removal of diisobutylene to below 100° C., neutralizing it with liquid alkali to neutrality, and then performing vacuum distillation to obtain 2,4-dimethylphenol with a content of ≥99%. 2,4-dimethylphenol is a raw material for high-temperature antioxidant, high-efficiency polymerization inhibitor and pharmaceutical intermediate 6-tert-butyl-2,4-dimethylphenol, and is directly sold as a product.

[0053] Another aspect of the present invention provides a method for separating phenol monomers from mixed phenols. When the mixed phenol is m-p-ethylphenol, the method comprises the following steps:

[0054] (1) weighing m-p-ethylphenol, a catalyst, and diisobutylene in a mass ratio of 1:(0.01-0.3):(1-5), uniformly mixing, and performing an octylation reaction to obtain an octylation reaction product;

[0055] (2) After sampling and analysis, the octylation reaction product is neutralized by alkali washing to a pH of 7 to 8, separated into layers, and the material layer is washed with water. After all the water is separated, the material layer is firstly distilled out of diisobutylene under normal pressure, and then vacuum distilled to obtain 6-tert-octyl-m-ethylphenol with a content of ≥99% and 2,6-ditert-octyl-p-ethylphenol with a content of ≥99% in turn; wherein the 2,6-ditert-octyl-p-ethylphenol can be directly exported as an antioxidant, or it can be further distilled to obtain p-ethylphenol with a content of ≥99%, and the p-ethylphenol can be sold as a product;

[0056] (3) Adding concentrated sulfuric acid at 1-2% of the weight of 6-tert-octyl-m-ethyl phenol to the above-mentioned 6-tert-octyl-m-ethyl phenol, and reacting at 150-200° C. for 1-5 hours to remove diisobutylene; then cooling the reaction liquid after the removal of diisobutylene to below 100° C., neutralizing it with liquid alkali to neutrality, and then performing vacuum distillation to obtain m-ethyl phenol with a content of ≥99%, which is sold as a product.

[0057] The embodiment of the present invention further provides a method for separating phenol monomers from mixed phenols. When the mixed phenol is 3,5-dimethylphenol / m-ethylphenol, the method comprises the following steps:

[0058] (1) weighing 3,5-dimethylphenol / m-ethylphenol, a catalyst, and diisobutylene in a mass ratio of 1:(0.01-0.3):(1-5), uniformly mixing, and performing an octylation reaction to obtain an octylation reaction product;

[0059] (2) After the sampling and analysis are qualified, the octylation reaction product is cooled and crystallized, and then filtered, and the filter cake is dried to obtain 3,5-dimethylphenol with a content of ≥99%; the filtrate is neutralized with alkali washing to a pH of 7-8, layered, and the material layer is washed with water. After the water is completely separated, the material layer is firstly distilled out of diisobutylene under normal pressure, and then vacuum distilled to obtain 6-tert-octyl-m-ethylphenol with a content of ≥99% and 2,6-di-tert-octyl-p-ethylphenol with a content of ≥99% in turn; among them, 3,5-dimethylphenol is sold as a product, and 2,6-di-tert-octyl-p-ethylphenol can be sold directly as a product, or it can be further distilled to obtain p-ethylphenol with a content of ≥99%, and the p-ethylphenol is sold as a product;

[0060] (3) Adding concentrated sulfuric acid at 1-2% of the weight of 6-tert-octyl-m-ethyl phenol to the above-mentioned 6-tert-octyl-m-ethyl phenol, and reacting at 150-200° C. for 1-5 hours to remove diisobutylene; then cooling the reaction solution after the removal of diisobutylene to below 100° C., neutralizing with liquid alkali to neutrality, separating the layers, washing the layers with water, and after removing all the water, subjecting the layers to vacuum distillation to obtain m-ethyl phenol with a content of ≥99%, which is sold as a product.

[0061] The embodiment of the present invention further provides a method for separating phenol monomers from mixed phenols. When the mixed phenol is industrial xylenol, the method comprises the following steps:

[0062] (1) weighing industrial xylenol, a catalyst, and diisobutylene in a mass ratio of 1:(0.01-0.3):(1-5), uniformly mixing, and performing an octylation reaction to obtain an octylation reaction product;

[0063] (2) After sampling and analysis, the octylation reaction product is neutralized by alkali washing to a pH of 7 to 8, separated into layers, and the material layer is washed with water. After all the water is separated, the material layer is firstly distilled out of diisobutylene under normal pressure, and then vacuum distilled to obtain 2,5-dimethylphenol with a content of ≥99%, 3,5-dimethylphenol with a content of ≥99%, a first mixed fraction of 6-tert-octyl-2,3-dimethylphenol and 6-tert-octyl-2,4-dimethylphenol, 6-tert-octyl-2,3-dimethylphenol, 6-tert-octyl-m-ethylphenol and 6-tert-octyl-m-ethylphenol. The second mixed fraction of 2,6-di-tert-octyl-3,4-dimethylphenol; the still residue is 2,6-di-tert-octyl-p-ethylphenol, and the still residue can be combined in batches and then distilled to obtain a 2,6-di-tert-octyl-p-ethylphenol antioxidant with a content of ≥99%; among them, 2,5-dimethylphenol and 3,5-dimethylphenol are directly sold as products; 2,6-di-tert-octyl-p-ethylphenol can be directly exported as an antioxidant, or it can be further distilled to obtain p-ethylphenol, and the p-ethylphenol is sold as a product;

[0064] (3) adding concentrated sulfuric acid at 1-2% of the weight of the first mixed fraction and the second mixed fraction, respectively, and reacting at 150-200° C. for 1-5 hours; then cooling the reaction liquid to below 100° C., neutralizing with liquid alkali to neutrality, and then performing vacuum distillation, wherein the first mixed fraction is subjected to vacuum distillation to obtain 2,3-xylenol with a content of ≥99% and 2,4-xylenol with a content of ≥99%; the second mixed fraction is subjected to vacuum distillation to obtain 2,3-xylenol with a content of ≥99%, 3,4-xylenol with a content of ≥98%, and crude m-ethylphenol with a content of ≥92%; 2,3-xylenol, 2,4-xylenol, and 3,4-xylenol are sold as products;

[0065] Among them, taking the sum of the weights of 6-tert-octyl-2,3-dimethylphenol in the first mixed fraction and the second mixed fraction as 100%, the weight proportion of 6-tert-octyl-2,3-dimethylphenol in the first mixed fraction is ≥70%; the weight proportion of 6-tert-octyl-2,3-dimethylphenol in the second mixed fraction is ≤30%.

[0066] In some embodiments of the present invention, when the mixed phenol is industrial xylenol, the method further comprises: performing two-step crystallization on the crude meta-ethylphenol with a content of ≥92% obtained after vacuum distillation, the specific steps being: cooling the crude meta-ethylphenol with a content of ≥92% to -3 to -10°C, keeping the temperature for crystallization for 2 to 5 hours, filtering, recovering the filtrate, and obtaining a primary crystallization material of meta-ethylphenol from the filter cake; then heating the primary crystallization material of meta-ethylphenol to 3 to 10°C to dissolve the material; then cooling it to 1 to -10°C at a rate of 1.0 to 4.0°C / hr; then cooling it to -3 to -10°C at a rate of 0.1 to 1.0°C / hr, keeping the temperature for crystallization for 2 to 5 hours, discharging the non-crystallized solution and recovering it; then heating the crystals to -1 to -5°C at a rate of 0.1 to 1.0°C / hr, keeping the temperature for 2 to 5 hours, obtaining a pure meta-ethylphenol with a content of ≥99%, and selling it as a product.

[0067] The method of the present invention utilizes diisobutylene to react with m-cresol, 2,4-xylenol, 2,3-xylenol, 3,4-xylenol, p-ethylphenol and m-ethylphenol instead of 3,5-xylenol and 2,5-xylenol in industrial xylenol. The diisobutylene reacts with m-cresol, p-cresol, 2,4-xylenol, 2,3-xylenol, 3,4-xylenol and m-ethylphenol to generate only corresponding 6-tert-octyl-m-cresol, 6-tert-octyl-2,4-xylenol, 6-tert-octyl-2,3-xylenol, 6-tert-octyl-3,4-xylenol and 6-tert-octyl-m-ethylphenol. P-cresol and p-ethylphenol can generate antioxidants 2,6-di-tert-octyl-p-cresol and 2,6-di-tert-octyl-p-ethylphenol. The boiling point difference of the products after tert-octylation is widened. , using the increased boiling point difference, considering that the boiling point difference between 6-tert-octyl-meta-cresol and 6-tert-octyl-2,4-xylenol is 5°C, the boiling point difference between 6-tert-octyl-2,4-xylenol and 6-tert-octyl-meta-ethylphenol is 8°C, the boiling point difference between 6-tert-octyl-2,3-xylenol and 6-tert-octyl-meta-ethylphenol is 5°C, the boiling point difference between m-cresol and 2,4-xylenol is 9°C, the boiling point difference between m-ethylphenol and 2,4-xylenol is 7°C, and the boiling point difference between m-ethylphenol and 3,4-xylenol is 7°C, so in order to effectively separate m-cresol, 2,4-xylenol, 2,3-xylenol, m-ethylphenol, 3,4-xylenol, etc., it is necessary to use a high-efficiency distillation tower for distillation, wherein the theoretical number of plates of the distillation tower is 100 to 250, preferably 180 to 220.

[0068] In some embodiments of the present invention, the composition of industrial xylenol includes 20-30% of 2,4 / 2,5-xylenol, 15-35% of 3,5-xylenol, 25-35% of m-p-ethylphenol, 5-10% of 2,3-xylenol, and 8-12% of 3,4-xylenol.

[0069] In some embodiments of the present invention, the temperature of the octylation reaction is 50-150° C., and the reaction time is 6-12 hours.

[0070] In some embodiments of the present invention, the catalyst is one or a mixture of two or more of sulfuric acid, phosphoric acid, p-toluenesulfonic acid, aminosulfonic acid, a strong acid resin or a carrier solid acid.

[0071] In some embodiments of the present invention, the qualified analysis standard is: when the mixed phenol is m-cresol, the content of 2-tert-octyl-p-cresol is ≤0.5% for qualified; when the mixed phenol is 2,4 / 2,5-xylenol, the content of 2,4-xylenol is ≤0.3% for qualified; when the mixed phenol is m-ethylphenol, the content of 2-tert-octyl-p-ethylphenol is ≤0.5% for qualified; when the mixed phenol is 3,5-xylenol / m-p-ethylphenol, the content of 6-tert-octyl-p-ethylphenol is ≤0.5% for qualified; when the mixed phenol is industrial xylenol, the content of 2-tert-octyl-p-ethylphenol is ≤0.8% for qualified.

[0072] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments.

[0073] Example 1

[0074] A method for separating phenol monomers from mixed phenols, when the mixed phenol is m-p-cresol, the method comprises the following steps:

[0075] (1) Add 600 g of m-cresol (containing 60% m-cresol and 40% p-cresol by mass), 30 g of p-toluenesulfonic acid, and 1500 g of diisobutylene into a 3000 ml four-necked bottle, start stirring, raise the temperature in an oil bath to 100° C., and keep the temperature to react for 8 hours. After the reaction is completed, an octylation reaction product is obtained;

[0076] (2) Sampling and analysis: wherein the content of 2-tert-octyl-p-cresol is 0.23%, which is qualified; then 29g of liquid alkali and 100ml of water are added to the above octylation reaction product to neutralize to pH 7-8, separate the layers, and wash the layers with 100ml of water once. After the water is completely separated, 616.5g of diisobutylene is firstly recovered by atmospheric distillation of the layers, and then vacuum distillation is performed to obtain 711.2g of 6-tert-octyl-m-cresol with a content of 99.2% and 705.8g of 2,6-di-tert-octyl-p-cresol with a content of 99.1% in turn;

[0077] (3) 14.2 g of concentrated sulfuric acid was added to the above 711.2 g of 6-tert-octyl-meta-cresol with a content of 99.2%, and the temperature was raised to 180° C. and maintained for 2 hours to remove diisobutylene. The reaction was stopped when the content of 6-tert-octyl-meta-cresol was 0.47% as detected by gas spectrum. The reaction solution after the removal of diisobutylene was cooled to below 100° C., neutralized to neutrality with 38 g of 30% liquid caustic soda, and then vacuum distilled to obtain 336.8 g of meta-cresol with a content of 99.5%, and 358.2 g of diisobutylene was recovered.

[0078] Example 2

[0079] A method for separating phenol monomers from mixed phenols, when the mixed phenol is 2,4 / 2,5-dimethylphenol, the method comprises the following steps:

[0080] (1) Add 300 g of 2,4 / 2,5-dimethylphenol (containing 61.5% of 2,4-dimethylphenol and 38.5% of 2,5-dimethylphenol by mass), 20 g of p-toluenesulfonic acid, and 500 g of diisobutylene into a 1000 ml four-necked bottle, start stirring, raise the temperature in an oil bath to 80° C., and keep the temperature to react for 10 hours. After the reaction is completed, an octylation reaction product is obtained;

[0081] (2) Sampling and analysis: wherein the content of 2,4-xylenol was 0.15%, which was qualified; then 19g of liquid alkali and 50ml of water were added to the above octylation reaction product to neutralize to pH 7-8, and the layers were separated, and the material layer was washed once with 50ml of water. After the water was separated, 315g of diisobutylene was first recovered by atmospheric distillation of the material layer, and then vacuum distillation was performed to obtain 109.1g of 2,5-xylenol with a content of 99.4% and 328.1g of 6-tert-octyl-2,4-xylenol with a content of 99.5% in turn;

[0082] (3) Add 6.6 g of concentrated sulfuric acid to the above 328.1 g of 6-tert-octyl-2,4-dimethylphenol, raise the temperature to 180° C. and maintain for 2 hours to remove diisobutylene, and stop the reaction when the content of 6-tert-octyl-2,4-dimethylphenol detected by gas spectrum is 0.38%; then cool the reaction solution after the removal of diisobutylene to below 100° C., neutralize with 17.8 g of 30% liquid alkali to neutrality, and then perform vacuum distillation to obtain 159.6 g of 2,4-dimethylphenol with a content of 99.1%, and recover 149.8 g of diisobutylene.

[0083] Example 3

[0084] A method for separating phenol monomers from mixed phenols, when the mixed phenol is m-p-ethylphenol, the method comprises the following steps:

[0085] (1) Add 500 g of m-ethylphenol (containing 65.7% m-ethylphenol and 34.3% p-ethylphenol by mass), 15 g of a catalyst, and 1000 g of diisobutylene into a 1000 ml four-necked bottle, start stirring, raise the temperature in an oil bath to 140° C., and keep the temperature to react for 10 hours. After the reaction is completed, an octylation reaction product is obtained;

[0086] (2) Sampling and analysis: wherein the content of 2-tert-octyl-p-ethylphenol is 0.33%, which is qualified; then 25g of liquid alkali and 89ml of water are added to the above octylation reaction product to neutralize to pH 7-8, separate the layers, and wash the layers with 90ml of water once. After the water is separated, 453g of diisobutylene is firstly recovered by atmospheric distillation of the layers, and then vacuum distillation is performed to obtain 608g of 6-tert-octyl-m-ethylphenol with a content of 99.4% and 439g of 2,6-ditert-octyl-p-ethylphenol with a content of 99.6% in turn;

[0087] (3) Add 10 g of concentrated sulfuric acid to the above 6-tert-octyl-m-ethyl phenol (the amount of concentrated sulfuric acid added is 1-2% of the weight of 6-tert-octyl-m-ethyl phenol), raise the temperature to 160° C. and maintain for 2 hours to remove diisobutylene, and stop the reaction when the content of 6-tert-octyl-m-ethyl phenol detected by gas spectrum is 0.25%; then cool the reaction solution after the removal of diisobutylene to below 100° C., neutralize it to neutrality with 30 g of 30% liquid caustic soda, and then perform vacuum distillation to obtain 299 g of m-ethyl phenol with a content of 99.3%.

[0088] Example 4

[0089] A method for separating phenol monomers from mixed phenols, when the mixed phenol is 3,5-dimethylphenol / m-p-ethylphenol, the method comprises the following steps:

[0090] (1) Add 400 g of mixed xylenol (containing 75% of 3,5-xylenol, 9.7% of p-ethylphenol, and 15.3% of m-ethylphenol by mass), 8 g of concentrated sulfuric acid, and 400 g of diisobutylene into a 1000 ml four-necked bottle, start stirring, raise the temperature in an oil bath to 100° C., and keep the temperature to react for 10 hours. After the reaction is completed, an octylation reaction product is obtained;

[0091] (2) Sampling and analysis: Among them, the content of 6-tert-octyl-p-ethylphenol is 0.18%, which is qualified; then the above octylation reaction product is cooled to 10°C, crystallized for 1 hour, filtered, and the filter cake is washed with a small amount of diisobutylene. The filter cake is dried to obtain 282.6g of 3,5-dimethylphenol with a content of 99.2%, and the extraction rate is 94.2%; the filtrate is neutralized with 21g of 30% liquid alkali and 50ml of water to pH 7-8, and the layer is separated, and the material layer is washed with 50ml of water again. After the water is separated, the material layer is first distilled out of 274.3g of diisobutylene under normal pressure for recovery, and then vacuum distilled to obtain 107.2g of 6-tert-octyl-m-ethylphenol with a content of 99.1% and 103.2g of 2,6-di-tert-octyl-p-ethylphenol with a content of 99.2% in turn;

[0092] (3) 2.2 g of concentrated sulfuric acid was added to the above 107.2 g of 6-tert-octyl-m-ethylphenol with a content of 99.1%, and the temperature was raised to 200° C. and maintained for 2 hours to remove diisobutylene. The reaction was stopped when the content of 6-tert-octyl-m-ethylphenol was 0.32% as detected by gas spectrum, and 54.3 g of diisobutylene was recovered. The reaction solution after the removal of diisobutylene was cooled to below 100° C. and neutralized to neutrality with 5.9 g of 30% liquid alkali. The material layer was washed once with 20 ml of water. After the water was completely separated, the material layer was subjected to vacuum distillation to obtain 54.1 g of m-ethylphenol with a content of 99.3%, and the total extraction rate of m-ethylphenol was 87.9%.

[0093] Example 5

[0094] A method for separating phenol monomers from mixed phenols, when the mixed phenol is industrial xylenol, the method comprises the following steps:

[0095] (1) Add 1000 g of industrial xylenol (containing 13.5% of 2,4-xylenol, 8.5% of 2,5-xylenol, 25% of 3,5-xylenol, 30% of m-p-ethylphenol, 6% of 2,3-xylenol, and 10% of 3,4-xylenol by mass), 75 g of concentrated sulfuric acid, and 1500 g of diisobutylene into a 5000 ml four-necked bottle, start stirring, heat the oil bath to 105° C., and react for 8 hours. After the reaction is completed, an octylation product is obtained;

[0096] (2) Sampling analysis: Among them, the content of 2-tert-octyl-p-ethylphenol is 0.79%, which is qualified; then 200g of 30% of liquid alkali and 100mL of water were used to neutralize to pH 7-8, and the layers were separated. The material layer was washed with 100mL of water again. After all the water was separated, 756.2g of diisobutylene was first distilled out of the material layer under normal pressure for recovery, and then vacuum distilled under 133Pa to obtain 79.0g of 2,5-dimethylphenol with a content of 99.1% and an extraction rate of 92.10%, 235.5g of 3,5-dimethylphenol with a content of 99.3% and an extraction rate of 94.20%, 353.28g of the first mixed fraction of 6-tert-octyl-2,4-dimethylphenol and 6-tert-octyl-2,3-dimethylphenol, 534.67g of the second mixed fraction of 6-tert-octyl-m-ethylphenol, 6-tert-octyl-2,3-dimethylphenol and 6-tert-octyl-3,4-dimethylphenol, and 373.75g of 2,6-di-tert-octyl-p-ethylphenol as the bottom of the kettle;

[0097] (3) Adding concentrated sulfuric acid at 2% by weight to the first mixed fraction, the second mixed fraction, and 2,6-dioctyl-p-ethylphenol, respectively, and heating to 180° C. and maintaining for 2 hours to remove diisobutylene; cooling the reaction liquid after the removal of diisobutylene to below 100° C., neutralizing with liquid alkali to neutrality, and then performing vacuum distillation respectively, wherein the first mixed fraction was vacuum distilled to obtain 27.0 g of 2,3-dimethylphenol with a content of 99.1%, an extraction rate of 65.7%, and 21.0 g of 2,4-dimethylphenol with a content of 99.3%. 6.5g, the extraction rate is 83.03%; after the second mixed fraction is vacuum distilled, 11.0g of 2,3-dimethylphenol with a content of 99.0% and an extraction rate of 62.7%, 95.0g of 3,4-dimethylphenol with a content of 98.5% and an extraction rate of 93.6%, and 173.6g of crude m-ethylphenol with a content of 92.3% and an extraction rate of 94.8% are obtained respectively; 120.5g of p-ethylphenol with a content of 99.2% is obtained after vacuum distillation of 2,6-di-tert-octyl p-ethylphenol; 620.1g of diisobutylene is recovered;

[0098] (4) The 173.6 g crude m-ethylphenol with a content of 92.3% obtained after the above vacuum distillation was subjected to a two-step crystallization, specifically comprising the following steps: adding the 173.6 g crude m-ethylphenol to a 250 ml four-necked flask, stirring, cooling the flask from room temperature to -8°C within 1 hour, keeping the temperature for 3 hours to allow slow crystallization, rapidly filtering in a -10°C cold bath, and obtaining 154.4 g of m-ethylphenol primary crystallization material from the filter cake, with a content of 97.2% and a crystallization yield of 91.5%, and recovering the filtrate; then adding the m-ethylphenol primary crystallization material to a 250 ml wing-type (eight-plate) stepwise crystallizer, using The hot water was heated to 5°C to dissolve all the materials; then the temperature was lowered to 0°C at 2°C / hr; then the temperature was lowered to -5°C at 0.5°C / hr, and the temperature was kept for crystallization for 3 hours, 2.6g of uncrystallized liquid was discharged and recovered; then the temperature was slowly raised to -3.0°C at 0.2°C / hr, and the temperature was kept for 5 hours to obtain 144.8g of pure m-ethyl phenol with a content of 99.1%, and the yield was 95.6%; the total yield of the two-step crystallization was 87.5%; the yield of m-ethyl phenol extracted from industrial xylenol was 83.0%; finally, the temperature was raised again to dissolve all the residual materials on the fins, and 6.8g of the dissolved materials were returned to the crude m-ethyl phenol for application.

[0099] Example 6

[0100] A method for separating phenol monomers from mixed phenols, when the mixed phenol is industrial xylenol, the method comprises the following steps:

[0101] (1) Add 1000 g of industrial xylenol (containing 12.4% of 2,4-xylenol, 9.6% of 2,5-xylenol, 16.9% of 3,5-xylenol, 34.4% of m-p-ethylphenol, 6.3% of 2,3-xylenol, and 10.4% of 3,4-xylenol by mass), 250 g of a strong acid resin, and 1500 g of diisobutylene into a 5000 ml four-necked bottle, start stirring, heat the oil bath to 105° C., and react for 10 hours. After the reaction is completed, an octylation product is obtained;

[0102] (2) Sampling and analysis: wherein the content of 2-tert-octyl-p-ethylphenol is 0.68%, which is qualified; then the octylation reaction product is filtered to recover the strong acid resin catalyst, 748.0 g of diisobutylene is first distilled out of the material layer under normal pressure, and then vacuum distilled under 133 Pa to obtain 90.1 g of 2,5-dimethylphenol with a content of 99.3% and an extraction rate of 94.2%, 158.2 g of 3,5-dimethylphenol with a content of 99.2% and an extraction rate of 92.8%, 329.72 g of the first mixed fraction of 6-tert-octyl-2,4-dimethylphenol and 6-tert-octyl-2,3-dimethylphenol, 611.2 g of the second mixed fraction of 6-tert-octyl-m-ethylphenol, 6-tert-octyl-2,3-dimethylphenol and 6-tert-octyl-3,4-dimethylphenol, and 483.1 g of 2,6-di-tert-octyl-p-ethylphenol as the still residue;

[0103] (3) Concentrated sulfuric acid was added to the first mixed fraction, the second mixed fraction and 2,6-dioctyl-p-ethylphenol at a weight percentage of 1%, and the temperature was raised to 200° C. and maintained for 2 hours to remove diisobutylene; the reaction liquids after the removal of diisobutylene were cooled to below 100° C., neutralized with liquid alkali to neutrality, and then subjected to vacuum distillation. After vacuum distillation of the first mixed fraction, 31.7 g of 2,3-dimethylphenol with a content of 99.3% was obtained, with an extraction rate of 65.8% and 1 g of 2,4-dimethylphenol with a content of 99.1%. 03.4g, the extraction rate is 82.66%; after the second mixed fraction is vacuum distilled, 10.0g of 2,3-dimethylphenol with a content of 99.0% and an extraction rate of 61.8%, 97.3g of 3,4-dimethylphenol with a content of 98.2% and an extraction rate of 91.9%, and 203.5g of crude m-ethylphenol with a content of 92.8% and an extraction rate of 95.2% are obtained respectively; 163.0g of p-ethylphenol with a content of 99.3% is obtained after vacuum distillation of 2,6-di-tert-octyl p-ethylphenol; 495g of diisobutylene is recovered;

[0104] (4) The 203.5 g crude m-ethyl phenol having a content of 92.8% obtained after the above vacuum distillation is subjected to two-step crystallization, specifically comprising the following steps: 203.5 g crude m-ethyl phenol is placed at room temperature to melt and then added to a 250 ml four-necked flask, the temperature is lowered from room temperature to -6°C within 1 hour under stirring and freezing liquid cooling, the temperature is kept for 4 hours to allow slow crystallization, and the filter cake is quickly filtered to obtain 174.9 g of m-ethyl phenol primary crystallization material with a content of 98.0% and a crystallization yield of 90.8%, and the filtrate is recovered; the m-ethyl phenol primary crystallization material is then added to a 250 ml wing-type (eight-piece) stepwise crystallizer In the process, the temperature is raised to 5°C with hot water to completely dissolve the materials; then the temperature is lowered to 0°C at 2°C / hr; then the temperature is lowered to -5°C at 0.5°C / hr, and the temperature is kept for crystallization for 3 hours, 2.8g of uncrystallized liquid is discharged and recovered; then the temperature is slowly raised to -3.0°C at 0.2°C / hr, and the temperature is kept for 5 hours to obtain 165.5g of pure m-ethyl phenol with a content of 99.3%, and the yield is 95.9%; the total yield of the two-step crystallization is 87.1%; the yield of m-ethyl phenol extracted from industrial xylenol is 80.7%; finally, the temperature is raised again to completely dissolve the residual materials on the fins, and the dissolved materials (6.4g) are returned to the crude m-ethyl phenol for application.

[0105] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction 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 described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0106] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for separating phenol monomers from mixed phenols, characterized in that: The mixed phenol is industrial xylenol, which comprises 20-30% of 2,4-xylenol and 2,5-xylenol, 15-35% of 3,5-xylenol, 25-35% of m-ethylphenol and p-ethylphenol, 5-10% of 2,3-xylenol, and 8-12% of 3,4-xylenol; The method comprises the following steps: (1) weighing industrial xylenol, a catalyst, and diisobutylene in a mass ratio of 1:(0.01-0.3):(1-5), uniformly mixing, and performing an octylation reaction to obtain an octylation reaction product; (2) After sampling and analysis, the octylation reaction product is neutralized by alkali washing to a pH of 7 to 8, separated, and the material layer is washed with water. After all the water is separated, the material layer is firstly distilled out of diisobutylene under normal pressure, and then vacuum distilled to obtain 2,5-dimethylphenol with a content of ≥99%, 3,5-dimethylphenol with a content of ≥99%, a first mixed fraction of 6-tert-octyl-2,3-dimethylphenol and 6-tert-octyl-2,4-dimethylphenol, and a second mixed fraction of 6-tert-octyl-2,3-dimethylphenol, 6-tert-octyl-m-ethylphenol and 6-tert-octyl-3,4-dimethylphenol; the still residue is 2,6-ditert-octyl-p-ethylphenol; (3) adding concentrated sulfuric acid at 1-2% of the weight of the first mixed fraction and the second mixed fraction, respectively, and reacting at 150-200° C. for 1-5 hours; then cooling the reaction liquid to below 100° C., neutralizing with liquid alkali to neutrality, and then performing vacuum distillation, wherein the first mixed fraction is subjected to vacuum distillation to obtain 2,3-xylenol with a content of ≥99% and 2,4-xylenol with a content of ≥99%; the second mixed fraction is subjected to vacuum distillation to obtain 2,3-xylenol with a content of ≥99%, 3,4-xylenol with a content of ≥98%, and crude m-ethylphenol with a content of ≥92%; Among them, taking the sum of the weights of 6-tert-octyl-2,3-dimethylphenol in the first mixed fraction and the second mixed fraction as 100%, the weight proportion of 6-tert-octyl-2,3-dimethylphenol in the first mixed fraction is ≥70%; the weight proportion of 6-tert-octyl-2,3-dimethylphenol in the second mixed fraction is ≤30%.

2. The method for separating phenol monomers from mixed phenols according to claim 1, characterized in that: The method further comprises: performing two-step crystallization on the crude meta-ethylphenol with a content of ≥92% obtained after vacuum distillation, and the specific steps are: cooling the crude meta-ethylphenol with a content of ≥92% to -3 to -10°C, keeping the temperature for crystallization for 2 to 5 hours, filtering, recovering the filtrate, and obtaining a primary crystallization material of meta-ethylphenol from a filter cake; then heating the primary crystallization material of meta-ethylphenol to 3 to 10°C to dissolve the material; then cooling it to 1 to -10°C at a rate of 1.0 to 4.0°C / hr; then cooling it to -3 to -10°C at a rate of 0.1 to 1.0°C / hr, keeping the temperature for crystallization for 2 to 5 hours, discharging the non-crystallized solution and recovering it; then heating the crystal to -1 to -5°C at a rate of 0.1 to 1.0°C / hr, keeping the temperature for 2 to 5 hours, and obtaining a pure meta-ethylphenol with a content of ≥99%.

3. The method for separating phenol monomers from mixed phenols according to claim 1, characterized in that: The temperature of the octylation reaction is 50-150° C., and the reaction time is 6-12 hours.

4. The method for separating phenol monomers from mixed phenols according to claim 1, characterized in that: The catalyst is one or a mixture of two or more of sulfuric acid, phosphoric acid, p-toluenesulfonic acid, aminosulfonic acid, strong acid resin or carrier solid acid.

5. The method for separating phenol monomers from mixed phenols according to claim 1, characterized in that: The qualified standard of the analysis is: the mixed phenol is industrial xylenol, and the content of 2-tert-octyl-p-ethylphenol is ≤ 0.8%.