Method for separating various phenols from cresol containing 2, 6-xylenol

Abstract

The embodiment of the invention provides a method for separating various phenols from cresol containing 2, 6-xylenol, which utilizes the characteristics that 2, 6-xylenol, 2, 4-xylenol, 2, 5-xylenol and isobutene can only generate mono-tert-butylated phenol, m-cresol, p-cresol and o-ethyl phenol, and o-cresol and isobutene can generate di-tert-butylphenol, and contains 2, 6-xylenol, 2, 4-xylenol, 2, 5-xylenol and 2, 4-xylenol. According to the method, cresol containing 2, 6-xylenol is subjected to the steps of monoalkylation, rectification, dialkylation, rectification, dealkylation, rectification and the like to realize separation of various phenols, so that the problem that the quality of m-cresol and p-cresol is influenced by 2, 6-xylenol when cresol extracted from medium-low temperature phenol-containing coal tar is separated is solved.

Description

Technical Field

[0001] The present application relates to the technical field of coal chemical industry, and in particular to a method for separating various phenols from cresol containing 2,6-dimethylphenol. Background Art

[0002] Industrial cresol is made from crude phenol, which is distilled to obtain phenol, o-cresol, cresol (including m-cresol), and industrial xylenol. Cresol (including m-cresol) accounts for only 0.6-2% in coal tar, and is mainly a mixture of o-cresol, m-cresol and p-cresol, including 0-25% o-cresol, 30-65% m-cresol, 15-50% p-cresol, 0-15% 2,6-xylenol, 0-15% o-ethylphenol, and 0-15% 2,4 / 2,5-xylenol. Among them, the contents of 2,6-dimethylphenol, o-ethylphenol and 2,4 / 2,5-dimethylphenol are very high in the process of gasifying and pyrolyzing phenol-containing coal tar to extract crude phenol. Since the boiling points of 2,6-dimethylphenol, m-cresol, p-cresol and o-ethylphenol differ by only 1 to 3°C, and the relative volatility of 2,6-dimethylphenol is higher than that of m-cresol at the same temperature, a large amount of 2,6-dimethylphenol appears between o-cresol and m-cresol during the distillation process, thus affecting the quality of the m-cresol product. Therefore, the m-cresol extracted from medium and low temperature phenol-containing coal tar cannot be separated by the traditional alkylation method. Summary of the invention

[0003] The present application aims to solve one of the technical problems in the related art at least to some extent.

[0004] On the one hand, the present application proposes a method for separating multiple phenols from cresol containing 2,6-dimethylphenol, separating 2,6-dimethylphenol with a content of 99.0% or 2,6-dimethylphenol with a content greater than 99.0% and 2,4-dimethylphenol with a content of 99.0%, thereby utilizing the important raw material 2,6-dimethylphenol.

[0005] According to an embodiment of the present application, a method for separating multiple phenols from cresol containing 2,6-dimethylphenol is proposed, comprising the following steps:

[0006] The cresol containing 2,6-dimethylphenol is mono-tert-butylated under the action of acid catalysis, and the water layer is separated from the first reaction liquid and then subjected to efficient distillation separation to obtain a tert-butylated phenol product and a first distillation still residue; or the distillation separation also includes a mixture of multiple mono-tert-butylated products;

[0007] The mixture of multiple mono-tert-butyl compounds is subjected to a tert-butylation reaction under acid catalysis and at a set temperature, and then the second reaction liquid is distilled and separated to obtain unreacted mono-tert-butyl compounds, di-tert-butyl compounds and second distillation still residue; the second distillation still residue is separated alone or combined with the first distillation still residue and then distilled to obtain still residue rectification product and third distillation still residue;

[0008] The unreacted mono-tert-butyl compound, the di-tert-butyl compound, the still residue and the third rectification still residue are subjected to de-tert-butylation reaction to remove isobutylene; the pH value of each reaction material after the isobutylene is removed is adjusted to neutral, and the material layer after stratification is distilled to obtain 2,6-dimethylphenol with a content of 99.0% or 2,6-dimethylphenol with a content greater than 99.0% and 2,4-dimethylphenol with a content of 99.0%;

[0009] In some embodiments, based on the cresol, the cresol includes 0-90% o-cresol, 1-80% 2,6-dimethylphenol, 0-90% m-para-cresol, 0-30% o-ethylphenol and 0-50% 2,4 / 2,5-dimethylphenol in terms of mass percentage.

[0010] In some embodiments, based on the cresol, in terms of mass percentage, the cresol includes 10-40% o-cresol, 5-30% 2,6-dimethylphenol, 30-70% m-p-cresol, and 2-15% o-ethylphenol.

[0011] In some embodiments, the plurality of mono-tert-butyl compound mixtures include at least two of 4-tert-butyl-2,6-dimethylphenol, 6-tert-butyl-3-methylphenol, 6-tert-butyl-2-ethylphenol, and 6-tert-butyl-2,4-dimethylphenol; and the first distillation still residue includes at least one of 4-tert-butyl-2,5-dimethylphenol, 2,6-di-tert-butyl-4-methylphenol, 4,6-di-tert-butyl-2-methylphenol, 4,6-di-tert-butyl-2-ethylphenol, and 4,6-di-tert-butyl-3-methylphenol.

[0012] In some embodiments, based on the mono-tert-butyl compound mixture, the multiple mono-tert-butyl compound mixtures include 1-95% of 4-tert-butyl-2,6-dimethylphenol, 1-95% of 6-tert-butyl-3-methylphenol, 0-95% of 6-tert-butyl-2,4-dimethylphenol and 0-95% of 6-tert-butyl-2-ethylphenol in terms of mass percentage.

[0013] In some embodiments, the mixture of multiple mono-tert-butyl compounds is further reacted with isobutylene at 30-150° C. under acid catalysis; the di-tert-butyl compound includes 4,6-di-tert-butyl-3-methylphenol and / or 4,6-di-tert-butyl-2-ethylphenol.

[0014] In some embodiments, in acid catalysis, the mass of the catalyst is 0.5-30% of the mass of the reactants.

[0015] In some embodiments, the catalyst includes at least one of sulfuric acid, phosphoric acid, benzenesulfonic acid, p-toluenesulfonic acid, aminosulfonic acid, a strong acid resin, or a solid acid.

[0016] In some embodiments, the number of plates for the high-efficiency distillation separation is 80-300.

[0017] In some embodiments, when the second distillation still residue is distilled separately, the still residue is 4,6-di-tert-butyl-2-ethylphenol; or

[0018] When the second distillation still residue is combined with the first distillation still residue and then distilled, the still residue distillation product is 4,6-di-tert-butyl-2-ethylphenol, and at least one of 2,6-di-tert-butyl-4-methylphenol, 4,6-di-tert-butyl-2-methylphenol, and 4-tert-butyl-2,5-xymethylphenol; and the third distillation still residue includes 4,6-di-tert-butyl-3-methylphenol.

[0019] The method of the embodiment of the present application is to first mono-tert-butylate cresol containing 2,6-xylenol and perform efficient distillation to obtain a mixture of multiple mono-tert-butylates, then perform a tert-butylation reaction and distillation on the multiple mono-tert-butylate mixture to obtain a di-tert-butylate, and finally perform a de-tert-butylation reaction and distillation on the di-tert-butylate to obtain high-purity petrochemical-grade 2,6-xylenol.

[0020] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0022] Figure 1 is a flow chart of a method for separating multiple phenols from cresol containing 2,6-dimethylphenol according to an embodiment of the present application;

[0023] Figure 2 The present invention is a flow chart of a method for separating various phenols from cresol containing 2,6-dimethylphenol according to an embodiment of the present invention. DETAILED DESCRIPTION

[0024] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be construed as limiting the present application. On the contrary, the present application includes all changes, modifications and equivalents that fall within the spirit and connotation of the appended claims.

[0025] Among them, crude phenol from the refining workshop of the coking enterprise is used as raw material and distilled to obtain phenol, o-cresol, cresol (including m-cresol), and industrial xylenol, among which cresol only accounts for 0.6-2% in coal tar. Cresol (including m-cresol) is a colorless to light red liquid, mainly a mixture of o-cresol, m-cresol and p-cresol. Specifically, based on cresol (including m-cresol), according to the mass percentage, cresol (including m-cresol) includes 0-25% o-cresol, 30-65% m-cresol, 15-50% p-cresol, 0-15% 2,6-xylenol, 0-15% o-ethylphenol, and 0-15% 2,4 / 2,5-xylenol. Cresol (including m-cresol) has a pungent phenol smell. Its color gradually darkens when left for a long time or exposed to light. It is miscible with alcohol, benzene, ether, etc., and slightly soluble in water. It is corrosive and toxic. Its specific gravity is 1.03-1.05, and its distillation range (95%) is 190-210°C.

[0026] At present, it is found that in the production of o-cresol by distillation of crude phenol, a mixed fraction consisting of o-cresol, 2,6-xylenol, m-p-cresol, naphthalene, decahydronaphthalene, etc. will be produced in the latter stage; the 2,6-xylenol, o-ethylphenol and 2,4 / 2,5-xylenol contents in crude phenol extracted by gasification and pyrolysis of phenol-containing coal tar are very high (the highest can reach 13%, 15% and 30-50% of the m-p-cresol content, respectively). Since the boiling points of 2,6-xylenol, m-cresol, p-cresol and o-ethylphenol differ by only 1-3°C, and the relative volatility of 2,6-xylenol at the same temperature is higher than that of m-p-cresol, a large amount of 2,6-xylenol is produced between o-cresol and m-p-cresol in distillation. It is very difficult to separate the mixture of o-cresol, 2,6-xylenol, m-cresol and o-ethylphenol in the cresol mixture by distillation. The presence of a large amount of 2,6-xylenol, o-ethylphenol and 2,4 / 2,5-xylenol will seriously affect the quality of the m-cresol product and the application of the m-cresol product in the downstream wire enamel and m-cresol separation industries. Therefore, the m-cresol extracted from medium and low temperature phenolic coal tar is not suitable for separating high-content m-cresol by traditional alkylation method; the traditional alkylation method includes the double alkylation method for producing m-cresol and antioxidant 264 or the single alkylation method for producing 2-tert-butyl-p-cresol and 6-tert-butyl-m-cresol.

[0027] At present, the annual output of medium and low temperature phenol-containing coal tar is about 8 million tons, of which the phenol content is about 6%, and 450,000 tons of crude phenol can be extracted. The amount of cresol is more than 100,000 tons, of which o-cresol, 2,6-dimethylphenol, o-ethylphenol, and 2,4 / 2,5-dimethylphenol are approximately 40-60%, 5-15%, 5-15%, and 30-50% of the amount of m-cresol, while the proportion of traditional gasified phenol on the market is about 30-40%, 1-3%, 0.5-2%, and 5-10%.

[0028] At present, the alkylation method is commonly used to separate m-cresol. The method is: using high-purity m-cresol (content 95-100%) and isobutylene alkylation reaction to produce di-tert-butyl cresol with different boiling points (2,6-di-tert-butyl-p-cresol 265°C, 4,6-di-tert-butyl-m-cresol 284°C), separation and purification, and then dealkylation reaction, pure m-cresol and p-cresol and their derivatives can be purified. This method will produce a certain amount of 2-tert-butyl-p-cresol, 6-tert-butyl-p-cresol and other products. Meta-cresol and 4-tert-butyl-2,6-dimethylphenol, among which 2-tert-butyl-p-cresol, 6-tert-butyl-m-cresol and 4-tert-butyl-2,6-dimethylphenol have boiling points of 237°C, 244°C and 249°C respectively. Therefore, although distillation can separate them, it requires very high tower efficiency and large reflux ratio, high operating cost and low yield. However, it is very difficult to separate meta-p-cresol with high content such as 2,6-dimethylphenol, o-cresol, o-ethylphenol and 2,4 / 2,5-dimethylphenol by traditional separation methods.

[0029] In the cresol mixture composed of o-cresol, 2,6-dimethylphenol, m-cresol and o-ethylphenol, naphthalene, decahydronaphthalene and the like contained therein are removed without reacting with isobutylene, and the aniline impurity contained therein has alkalinity and can be removed by reacting with an acidic catalyst, so non-phenolic impurities basically do not affect the separation of mixed phenols. The boiling points of 6-tert-butyl-2-methylphenol, 4,6-di-tert-butyl-2-methylphenol, 6-tert-butyl-2-ethylphenol and 4,6-di-tert-butyl-2-ethylphenol are 230°C, 267°C, 251°C and 274°C respectively. A mixture of 6-tert-butyl-2-methylphenol, 2-tert-butyl-4-methylphenol, 6-tert-butyl-3-methylphenol, 4-tert-butyl-2,6-xylenol and 6-tert-butyl-2-ethylphenol is obtained by using an efficient distillation tower. 6-tert-butyl-2-methylphenol and 2-tert-butyl-4-methylphenol are antioxidant intermediates, and the kettle residue is 2,6-di-tert-butyl-4-methylphenol (boiling point 265°C), 4,6 -di-tert-butyl-2-cresol (boiling point 267°C), 4,6-di-tert-butyl-2-ethylphenol, 4,6-di-tert-butyl-3-cresol mixture, so the presence of o-cresol and o-ethylphenol in the cresol raw material brings great trouble to the separation of m-cresol, and it is difficult to obtain high-quality antioxidant 2,6-di-tert-butyl-p-cresol by separation of m-cresol. Therefore, the m-cresol separation in the industry currently uses o-cresol ≤ 0.3%, o-ethylphenol ≤ 0.5%, 2,6-xylenol ≤ 0.1%, phenol ≤ 0.1%, 2,4 / 2,5-xylenol ≤ 1%. It is best to use 99% grade m-cresol.

[0030] In the related technology, 95% of m-cresol can be separated by di-tert-butylation to produce m-cresol and antioxidant 2,6-di-tert-butyl-p-cresol. The separated antioxidant 2,6-di-tert-butyl-p-cresol contains many impurities such as 4-tert-butyl-2,5-xylenol and 4,6-di-tert-butyl-2-cresol, and needs to be repeatedly crystallized and recrystallized with methanol or ethanol, and sometimes melt crystallization is required to produce the product antioxidant BHT that meets the requirements; the presence of o-ethylphenol, 2,4-xylenol and 2,6-xylenol will seriously affect the quality of the product m-cresol, so the content of o-cresol, 2,6-xylenol, o-ethylphenol and 2,4 / 2,5-xylenol in the raw material m-cresol must be strictly controlled.

[0031] There are also some related technologies that use the mono-tert-butylation method to produce 2-tert-butyl-p-cresol, 6-tert-butyl-m-cresol, and m-cresol. If the impurity content of 2,6-xylenol, o-ethylphenol, o-cresol, 2,4-xylenol and other impurities in the raw material 95% of m-cresol is high, the difficulty of separating m-cresol increases, and the product content and quality deteriorate. Therefore, it is required that the o-cresol and 2,6-xylenol in the 95% m-cresol raw material should be ≤0.1%, and the o-ethylphenol and 2,4-xylenol should be ≤0.5%.

[0032] The mixture of 6-tert-butyl-3-methylphenol, 4-tert-butyl-2,6-xylenol and 6-tert-butyl-2-ethylphenol continues to react with isobutylene, 4-tert-butyl-2,6-xylenol does not react with isobutylene, and the remaining mono-tert-butylphenol reacts with isobutylene to generate 4,6-di-tert-butyl-2-ethylphenol and 4,6-di-tert-butyl-3-methylphenol, thereby widening the boiling point difference. High-purity 4-tert-butyl-2,6-xylenol is obtained by distillation, and the distillation still residue is combined with the previous alkylation distillation still residue containing 2,6-di-tert-butyl-4-methylphenol, 4,6-di-tert-butyl-2-ethylphenol, and 4,6-di-tert-butyl-3-methylphenol, and distilled again to obtain antioxidant 2,6-di-tert-butyl-4-methylphenol, intermediate 4,6-di-tert-butyl-2-ethylphenol, and intermediate 4,6-di-tert-butyl-3-methylphenol.

[0033] However, if the cresol raw material contains 2,4 / 2,5-xylenol, the boiling points of the highly efficient inhibitors 6-tert-butyl-2,4-xylenol and 4-tert-butyl-2,5-xylenol are 249°C and 265°C, respectively. The presence of 2,4-xylenol will affect the distillation extraction of 4-tert-butyl-2,6-xylenol, so 4-tert-butyl-2,6-xylenol and 6-tert-butyl-2,4-xylenol cannot be produced directly, and only their mixture can be produced. However, the mixture of 2,6-xylenol and 2,4-xylenol after removing isobutylene from mono-tert-butylphenol can produce 99% 2,6-xylenol and 99% 2,4-xylenol (boiling points are 203°C and 211°C) by distillation. The presence of 4-tert-butyl-2,5-dimethylphenol will affect the production of antioxidant 2,6-di-tert-butyl-4-methylphenol, and only tert-butyl can be removed to produce p-cresol and 2,5-dimethylphenol. 4,6-di-tert-butyl-2-ethylphenol and 4,6-di-tert-butyl-3-methylphenol are deisobutylene and distilled under acid catalysis to obtain o-ethylphenol and m-cresol respectively.

[0034] Therefore, it is necessary to significantly improve the traditional m-cresol separation process to solve the problem that the traditional cresol separation method cannot separate 2,6-xylenol (boiling point 203°C, only 1°C different from m-cresol, and cannot be separated by distillation) and o-ethylphenol (boiling point 204.5°C) from m-cresol; and the boiling points of 6-tert-butyl-2-cresol, 2-tert-butyl-4-cresol, 6-tert-butyl-3-cresol, 4-tert-butyl-2,6-xylenol, and 6-tert-butyl-2-ethylphenol are 230°C, 237°C, 244°C, 249°C, and 251°C, respectively, and it is technically difficult to directly separate high-purity 2,6-xylenol, m-cresol, and o-ethylphenol, and to achieve component separation of cresol extracted from medium and low temperature phenol-containing coal tar.

[0035] Based on this, the technical solution of the embodiment of the present application provides a method. With respect to the method, the present application provides a method for separating various phenols from cresol containing 2,6-dimethylphenol, which realizes the separation of various phenols in the fractions after the production of cresol produced by coking crude phenol, gasifying crude phenol, medium and low temperature gasification and pyrolysis of phenolic tar, etc., and refined o-cresol, to obtain various phenol products of high purity petrochemical grade. The description of the specific technical solution is as follows.

[0036] In addition, in the present application, 6-tert-butyl-2-methylphenol is CAS 2219-82-1 white needle crystals, with a melting point of 25°C, a boiling point of 230°C, a relative density of 0.967 (20°C), and is an intermediate for the production of antioxidants, etc.

[0037] 2,6-Dimethylphenol is CAS576-26-1 white needle crystals. Melting point 45℃, boiling point 203℃, relative density 1.023 (17℃). This product is used to make polyphenylene ether plastics (PPO), phenolic resins, spices, explosives, disinfectants, etc. It is also a raw material for medicines such as slow heart rate and anti-AIDS. Fixed-bed catalytic amination of 2,6-dimethylphenol gives an important pesticide intermediate 2,6-dimethylaniline, which can be used to synthesize pesticides such as metalaxyl, furalaxyl, furamide, furamide, butachlor and dimethochlor; at the same time, 2,6-dimethylphenol can also be used to synthesize antioxidants such as Lowinox44 M26.

[0038] 4-tert-Butyl-2,6-dimethylphenol has a boiling point of 249°C and can be decomposed to produce 2,6-dimethylphenol. It can also be catalytically methylated to produce 4-tert-butyl-2,3,6-trimethylphenol, and then the tert-butyl group can be removed to produce 2,3,6-trimethylphenol, an important raw material for vitamin E.

[0039] At the same time, "scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be combined arbitrarily, that is, any lower limit can form a scope with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 listed, and if the maximum range values ​​3,4 and 5 are listed, the following scope can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0040] To achieve the above object, the present application provides a method for separating multiple phenols from cresol containing 2,6-dimethylphenol in the first aspect. Figure 1-Figure 2 As shown, the following steps are included:

[0041] S1: mono-tert-butylating cresol containing 2,6-dimethylphenol under acid catalysis, separating the first reaction liquid from the water layer and performing efficient distillation separation to obtain a tert-butylated phenol product and a first distillation still residue; or the distillation separation also includes a mixture of multiple mono-tert-butylated products;

[0042] S2: subjecting a mixture of multiple mono-tert-butyl compounds to a tert-butylation reaction under acid catalysis and at a set temperature, and then subjecting the second reaction liquid to distillation separation to obtain unreacted mono-tert-butyl compounds, di-tert-butyl compounds and second distillation still residue; subjecting the second distillation still residue to distillation separation alone or combining it with the first distillation still residue to obtain still residue distillation product and third distillation still residue;

[0043] S3: subjecting the unreacted mono-tert-butyl compound, di-tert-butyl compound, still residue and the third distillation still residue to de-tert-butylation reaction respectively to remove isobutylene; adjusting the pH value of each reaction material after the removal of isobutylene to neutral, and distilling the layered material to obtain 2,6-dimethylphenol with a content of 99.0% or 2,6-dimethylphenol with a content greater than 99.0% and 2,4-dimethylphenol with a content of 99.0%.

[0044] In step S1, the cresols generally containing 2,6-xylenol include 2,6-xylenol, o-ethylphenol, 2,4 / 2,5-xylenol, crude phenol extracted from medium- and low-temperature phenol-containing coal tar with relatively high content of o-cresol, such as coking crude phenol, gasification crude phenol, etc., or o-cresol, 2,6-xylenol, naphthalene, aniline, and m-cresol with relatively more polytoluene impurities, such as cresol produced by distillation of crude phenol extracted from medium- and low-temperature gasification and pyrolysis of phenol-containing tar, and the post-production fraction of refined o-cresol.

[0045] For example, take the cresol produced by extracting crude phenol distillation from phenolic tar through medium and low temperature gasification and pyrolysis as an example. Taking cresol as the benchmark, calculated by mass percentage, cresol includes 0-90% o-cresol, 1-80% 2,6-dimethylphenol, 0-90% m-cresol, 0-30% o-ethylphenol and 0-50% 2,4 / 2,5-dimethylphenol; further, cresol includes 10-40% o-cresol, 5-30% 2,6-dimethylphenol, 30-70% m-cresol and 2-15% o-ethylphenol.

[0046] Cresol containing 2,6-dimethylphenol can react with isobutylene under acid catalysis to perform mono-tert-butylation, wherein, in acid catalysis, the mass of the catalyst is 0.5-30% of the mass of the cresol, and the catalyst can be further preferably 1-20%. For example, the catalyst includes at least one of sulfuric acid, phosphoric acid, benzenesulfonic acid, p-toluenesulfonic acid, aminosulfonic acid, strong acid resin or solid acid, and the catalyst of the example is preferably sulfuric acid or strong acid resin. Add cresol and acid catalyst to the reactor, heat to the set temperature under stirring, then pass isobutylene and pass for a set time, and keep the reaction for a set time, then add liquid alkali to neutralize to pH 8 to obtain the first reaction liquid, and then add the dehydrated layer, and the material layer is added to the high-efficiency distillation tower and distilled at a reflux ratio of 15-20:1.

[0047] After the first reaction liquid is separated and dehydrated, high-efficiency distillation is performed, wherein high-efficiency distillation refers to distillation performed in a distillation tower with a theoretical plate number of 80 to 300 and filled with high-efficiency stainless steel fillers, and the exemplary theoretical plate number can be further 150 to 200, and distillation separation can obtain 4-tert-butyl-2,6-dimethylphenol and 6-tert-butyl-2-methylphenol, 2-tert-butyl-4-methylphenol, 6-tert-butyl-3-methylphenol, 6-tert-butyl-2, Two or more of 4-xymethylphenol, 4-tert-butyl-2,5-xymethylphenol, 6-tert-butyl-2-ethylphenol, 2,6-di-tert-butyl-4-methylphenol, 4,6-di-tert-butyl-2-methylphenol, 4,6-di-tert-butyl-2-ethylphenol and 4,6-di-tert-butyl-3-methylphenol; among them, 6-tert-butyl-2-methylphenol and 2-tert-butyl-4-methylphenol can be directly separated and sold as tert-butylated phenol products.

[0048] It should be understood that, for example, in some embodiments, when the content of only o-cresol in cresol is 0%, the first reaction liquid can be separated and dehydrated and then efficiently distilled to obtain 4-tert-butyl-2,6-dimethylphenol, 2-tert-butyl-4-methylphenol, 6-tert-butyl-3-methylphenol, 6-tert-butyl-2,4-dimethylphenol, 4-tert-butyl-2,5-dimethylphenol, 6-tert-butyl-2-ethylphenol, 2,6-di-tert-butyl-4-methylphenol, 4,6-di-tert-butyl-2-ethylphenol, and 4,6-di-tert-butyl-3-methylphenol.

[0049] For example, in some embodiments, when the content of 2,4 / 2,5-dimethylphenol in cresol is only 0%, the first reaction liquid is separated and the water layer is removed, and then the efficient distillation separation is carried out to obtain 4-tert-butyl-2,6-dimethylphenol and 6-tert-butyl-2-methylphenol, 2-tert-butyl-4-methylphenol, 6-tert-butyl-3-methylphenol, 6-tert-butyl-2-ethylphenol, 2,6-di-tert-butyl-4-methylphenol, 4,6-di-tert-butyl-2-methylphenol, 4,6-di-tert-butyl-2-ethylphenol, and 4,6-di-tert-butyl-3-methylphenol.

[0050] For example, in some embodiments, when the content of only o-cresol and 2,4 / 2,5-dimethylphenol in cresol is 0%, the first reaction liquid is separated and the water layer is removed, and then the high-efficiency distillation separation is carried out to obtain 4-tert-butyl-2,6-dimethylphenol, 2-tert-butyl-4-methylphenol, 6-tert-butyl-3-methylphenol, 6-tert-butyl-2-ethylphenol, 2,6-di-tert-butyl-4-methylphenol, 4,6-di-tert-butyl-2-ethylphenol, and 4,6-di-tert-butyl-3-methylphenol.

[0051] For example, in some embodiments, when the content of only o-cresol, 2,4 / 2,5-xymethylphenol and o-ethylphenol in cresol is 0%, the first reaction liquid is separated and the water layer is removed, and then high-efficiency distillation is performed to obtain 4-tert-butyl-2,6-xymethylphenol, 2-tert-butyl-4-methylphenol, 6-tert-butyl-3-methylphenol, 2,6-di-tert-butyl-4-methylphenol, and 4,6-di-tert-butyl-3-methylphenol.

[0052] For example, in some embodiments, when the content of only m-cresol, 2,4 / 2,5-dimethylphenol and o-ethylphenol in cresol is 0%, 6-tert-butyl-2-methylphenol and 4-tert-butyl-2,6-dimethylphenol can be obtained by efficient distillation after the water layer is separated from the first reaction liquid.

[0053] Therefore, it can be seen from the above contents that according to the component composition of cresol, the first reaction liquid is separated into a water layer and then subjected to efficient distillation separation to obtain a tert-butylated phenol product and a first distillation still residue, or the first reaction liquid is separated into a water layer and then subjected to efficient distillation separation to obtain a tert-butylated phenol product, a first distillation still residue and a mixture of multiple mono-tert-butylated products.

[0054] When the first reaction liquid is separated from the water layer and then subjected to efficient distillation to obtain the tert-butyl phenol product and the first distillation still residue, the tert-butyl phenol product can be sold directly, and the first distillation still residue can be further adaptively treated, which will be illustrated below and will not be described in detail here.

[0055] When the first reaction liquid is separated from the water layer and then subjected to efficient distillation to obtain a plurality of mono-tert-butyl compound mixtures, for example, the plurality of mono-tert-butyl compound mixtures include at least two of 4-tert-butyl-2,6-dimethylphenol, 6-tert-butyl-3-methylphenol, 6-tert-butyl-2-ethylphenol, and 6-tert-butyl-2,4-dimethylphenol; for example, based on the mono-tert-butyl compound mixture, in terms of mass percentage, the plurality of mono-tert-butyl compound mixtures include 1 to 95% of 4-tert-butyl-2,6-dimethylphenol, 0 to 95% of 6-tert-butyl-3-methylphenol, 0 to 50% of 6-tert-butyl-2,4-dimethylphenol, and 0 to 95% of 6-tert-butyl-2-ethylphenol. Further, the mixture of multiple mono-tert-butyl compounds includes 2-40% of 4-tert-butyl-2,6-dimethylphenol, 30-60% of 6-tert-butyl-3-methylphenol, 2-20% of 6-tert-butyl-2,4-dimethylphenol, and 5-20% of 6-tert-butyl-2-ethylphenol. Meanwhile, the residue of the first rectification still includes at least one of 4-tert-butyl-2,5-dimethylphenol, 2,6-di-tert-butyl-4-methylphenol, 4,6-di-tert-butyl-2-methylphenol, 4,6-di-tert-butyl-2-ethylphenol, and 4,6-di-tert-butyl-3-methylphenol.

[0056] Wherein, in step S2, the mixture of various mono-tert-butyl compounds in the above embodiment is subjected to tert-butylation reaction under acid catalysis and set temperature, wherein a mixture of at least two of 4-tert-butyl-2,6-dimethylphenol, 6-tert-butyl-3-methylphenol, 6-tert-butyl-2-ethylphenol, and 6-tert-butyl-2,4-dimethylphenol continues to react with isobutylene at a temperature of 30 to 150° C. under acid catalysis, wherein the temperature may preferably be 60 to 120° C.; in the acid catalysis process, the selection and use amount of the catalyst are not repeated with reference to the above content. After the reaction, the second reaction liquid is filtered, the filter cake is used, and the filtrate is subjected to vacuum distillation. Distillation separation can obtain di-tert-butyl compound and second distillation still residue; wherein the di-tert-butyl compound includes 4,6-di-tert-butyl-3-methylphenol and / or 4,6-di-tert-butyl-2-ethylphenol, in other words, the di-tert-butyl compound includes 4,6-di-tert-butyl-3-methylphenol, or 4,6-di-tert-butyl-2-ethylphenol, or a mixture of 4,6-di-tert-butyl-3-methylphenol and 4,6-di-tert-butyl-2-ethylphenol, namely, di-tert-butyl compound.

[0057] The second distillation still residue can be distilled separately to obtain a still residue distillate, that is, the intermediate 4,6-di-tert-butyl-2-ethylphenol; in some embodiments, the second distillation still residue can also be combined with the first distillation still residue and then distilled to obtain a still residue distillate and a third distillation still residue; wherein the still residue distillate is 4,6-di-tert-butyl-2-ethylphenol, and at least one of 2,6-di-tert-butyl-4-methylphenol, 4,6-di-tert-butyl-2-methylphenol, and 4-tert-butyl-2,5-xylenol. In other words, the still residue distillate is a mixture of one or two to three of 2,6-di-tert-butyl-4-methylphenol, 4,6-di-tert-butyl-2-methylphenol, and 4-tert-butyl-2,5-xylenol, and the intermediate 4,6-di-tert-butyl-2-ethylphenol. At the same time, the third distillation still residue is mainly 4,6-di-tert-butyl-3-methylphenol.

[0058] It should be noted that in some embodiments, when the second distillation still residue is combined with the first distillation still residue and then distilled, if the first distillation still residue contains 2,6-di-tert-butyl-4-methylphenol, 4,6-di-tert-butyl-2-methylphenol, and 4-tert-butyl-2,5-xymethylphenol, the still residue distillation product includes a mixture of 2,6-di-tert-butyl-4-methylphenol, 4,6-di-tert-butyl-2-methylphenol, and 4-tert-butyl-2,5-xymethylphenol, and the intermediate 4,6-di-tert-butyl-2-ethylphenol; at the same time, the third distillation still residue is mainly 4,6-di-tert-butyl-3-methylphenol.

[0059] Alternatively, in some embodiments, if there is no 4,6-di-tert-butyl-2-methylphenol and 4-tert-butyl-2,5-xymethylphenol in the first distillation still residue, the still residue comprises pure antioxidant 2,6-di-tert-butyl-4-methylphenol and intermediate 4,6-di-tert-butyl-2-ethylphenol; and the third distillation still residue is mainly 4,6-di-tert-butyl-3-methylphenol.

[0060] Alternatively, in some embodiments, if there is no 4,6-di-tert-butyl-2-methylphenol in the first distillation still residue, the still residue comprises a mixture of 2,6-di-tert-butyl-4-methylphenol and 4-tert-butyl-2,5-xymethylphenol and an intermediate 4,6-di-tert-butyl-2-ethylphenol; and the third distillation still residue is mainly 4,6-di-tert-butyl-3-methylphenol.

[0061] Alternatively, in some embodiments, if there is no 4-tert-butyl-2,5-dimethylphenol in the first distillation still residue, the still residue comprises a mixture of 2,6-di-tert-butyl-4-methylphenol and 4,6-di-tert-butyl-2-methylphenol and an intermediate 4,6-di-tert-butyl-2-ethylphenol; and the third distillation still residue is mainly 4,6-di-tert-butyl-3-methylphenol.

[0062] In step S3, 0.5-5% sulfuric acid corresponding to the mass of the materials is added to the 4-tert-butyl-2,6-dimethylphenol and / or 6-tert-butyl-2,4-dimethylphenol obtained in the above step S3, as well as at least one of 2,6-di-tert-butyl-4-methylphenol, 4,6-di-tert-butyl-2-methylphenol, and 4-tert-butyl-2,5-dimethylphenol, and 4,6-di-tert-butyl-2-ethylphenol and 4,6-di-tert-butyl-3-methylphenol, respectively, and the mixture is stirred and heated to about 150-200° C. to remove isobutylene, wherein the 4-tert-butyl-2,6-dimethylphenol and / or 6-tert-butyl-2,4-dimethylphenol are removed from the isobutylene. 2,6-xylenol or a mixture of 2,6-xylenol and 2,4-xylenol can be obtained; at least one of 2,6-di-tert-butyl-4-methylphenol, 4,6-di-tert-butyl-2-methylphenol and 4-tert-butyl-2,5-xylenol can be stripped of isobutylene to obtain p-cresol or o-cresol and 2-3 mixtures of p-cresol and 2,5-xylenol; 4,6-di-tert-butyl-2-ethylphenol can be stripped of isobutylene to obtain a mixture of 6-tert-butyl-2-ethylphenol and o-ethylphenol; 4,6-di-tert-butyl-3-methylphenol can be stripped of isobutylene to obtain a mixture of m-cresol and 6-tert-butyl-3-methylphenol; the isobutylene recovered at the same time can be used in an integrated manner.

[0063] Adjust the pH value of each reaction material after isobutylene removal to neutral, for example, add 10-30% of liquid alkali to each reaction material after isobutylene removal to neutralize to neutral, and continue to perform the following distillation on the material layer after stratification:

[0064] 2,6-xylenol or a mixture of 2,6-xylenol and 2,4-xylenol is distilled to obtain 99.0% 2,6-xylenol or 99.0% 2,6-xylenol fine product, 99.0% 2,4-xylenol, 2,6-xylenol fine product is melted and crystallized to obtain polymerization grade 2,6-xylenol, and 99.8% can be used to produce engineering plastic polyphenylene ether. Therefore, the present application melts and crystallizes 99% 2,6-xylenol to obtain a high-purity product, greatly improves the quality of coking 2,6-xylenol, and expands the application field of 2,6-xylenol.

[0065] p-cresol or a mixture of o-cresol, p-cresol and 2,5-xylenol is distilled to obtain a p-cresol product with a content of 99.0% or a product with a content of 99.5% of o-cresol, a content of 99.5% of p-cresol and a content of 99.0% of 2,5-xylenol. The o-cresol product with a content of 99.5%, a content of 99.5% of p-cresol and a content of 99.0% of 2,5-xylenol obtained here meets the standard of petrochemical-grade products. The o-cresol can be used to produce o-cresol epoxy phenolic resin, a plastic sealing material for electronics, and the 2,5-xylenol can be used to produce the lipid-lowering drug gemfibrozil and vitamin E.

[0066] The mixture of 6-tert-butyl-2-ethylphenol and o-ethylphenol is distilled to obtain o-ethylphenol with a content of 99.0% and 6-tert-butyl-2-ethylphenol, an intermediate of an antioxidant. The mixture of m-cresol and 6-tert-butyl-3-methylphenol is distilled to obtain m-cresol with a content of 99.5% and 6-tert-butyl-3-methylphenol, an intermediate of an antioxidant.

[0067] The 6-tert-butyl-2-methylphenol, 2-tert-butyl-4-methylphenol, 6-tert-butyl-2-ethylphenol, 6-tert-butyl-3-methylphenol, 4-tert-butyl-2,6-dimethylphenol, 2,6-dimethylphenol, o-cresol, p-cresol, m-cresol, o-ethylphenol, 2,4-dimethylphenol, 2,5-dimethylphenol, 2,6-di-tert-butyl-4-methylphenol obtained in the above examples are sold as products. The 4-tert-butyl-2,6-dimethylphenol, 2,6-dimethylphenol, o-cresol, p-cresol, o-ethylphenol, m-cresol, 2,5-dimethylphenol, 2,4-dimethylphenol obtained in this example have high purity and few impurities, and the product quality completely reaches the level of petrochemical grade 2,6-dimethylphenol and medical grade m-cresol, and can be used to prepare engineering plastic polyphenylene ether PPO (2,6-dimethylphenol as raw material), vitamin E and menthol (m-cresol as raw material). High-purity 4-tert-butyl-2,6-dimethylphenol can react with methanol to produce 4-tert-butyl-2,3,6-trimethylphenol. 4-tert-butyl-2,3,6-trimethylphenol can be removed from isobutylene to obtain 2,3,6-trimethylphenol. The purity of 2,3,6-trimethylphenol produced in this way is more than 99.5%, which fully meets the requirements of raw materials for the production of vitamin E. 2,5-dimethylphenol is used in the production of blood lipid-lowering drug gemfibrozil, 2,4-dimethylphenol is used in the production of high-efficiency antioxidant and polymerization inhibitor 6-tert-butyl-2,4-dimethylphenol for aviation, o-cresol and o-ethylphenol are used in the production of epoxy o-cresol-formaldehyde resin for electronic-grade packaging materials, and p-cresol and m-cresol can be used in the production of m-cresol-formaldehyde resin for photoresist and tricresyl phosphate for aviation.

[0068] The method of the embodiment of the present application utilizes the characteristics that 2,6-dimethylphenol, 2,4-dimethylphenol, 2,5-dimethylphenol and isobutylene can only generate mono-tert-butylated phenol, and m-cresol, p-cresol, o-ethylphenol, o-cresol and isobutylene can generate di-tert-butylphenol. The cresol containing 2,6-dimethylphenol is first mono-tert-butylated and efficiently distilled to obtain a variety of mono-tert-butylated mixtures, and then the di-tert-butylated mixtures are subjected to tert-butylation reaction and distillation to obtain di-tert-butylated products. Finally, the di-tert-butylated products are subjected to de-tert-butylation reaction and distillation to obtain high-purity petrochemical-grade 2,6-dimethylphenol. The present application realizes their separation through the steps of monoalkylation, distillation, dialkylation, distillation, dealkylation, distillation, etc., because each reaction is a process of refining and impurity removal, so the content of sulfide and nitrogen-containing compounds in these products obtained in the present application is very low, and the products fully meet the needs of medicine and material production.

[0069] To facilitate further understanding of the present application, the scheme of the present application is further described below in conjunction with the embodiments. Those skilled in the art will understand that the description in the present application is only part of the examples, and any other suitable specific examples are within the scope of the present application.

[0070] Example 1

[0071] (1) Tertiary butylation and distillation of cresol

[0072] 1000 parts of cresols, including 275 parts of o-cresol, 188 parts of 2,6-dimethylphenol, 276 parts of m-cresol, 184 parts of p-cresol, 73 parts of o-ethylphenol and 30 parts of sulfuric acid, were added into the reactor, the temperature was raised to 90°C under stirring, 850 parts of isobutylene were introduced for reaction, the isobutylene was introduced for 6 hours, the reaction was kept warm for 2 hours, 84 parts of 30% liquid alkali were added to neutralize to pH 8, the water layer was separated, the material layer was added into a high-efficiency distillation tower, and distilled at a reflux ratio of 15 to 20:1 to obtain 42.5 parts of the first part, 333 parts of 99.1% 6-tert-butyl-2- Cresol, 222.5 parts of 99.3% 2-tert-butyl-4-cresol, 703.5 parts of mixed tert-butylphenols (including 355.3 parts of 6-tert-butyl-3-cresol, 274.3 parts of 4-tert-butyl-2,6-xymethylphenol and 73 parts of 6-tert-butyl-2-ethylphenol), 301.2 parts of the first distillation still residue, including 112 parts of 4,6-di-tert-butyl-2-cresol, 75.4 parts of 2,6-di-tert-butyl-4-cresol, 85.5 parts of 4,6-di-tert-butyl-3-cresol and 24.9 parts of 4,6-di-tert-butyl-2-ethylphenol.

[0073] (2) Di-tert-butylation reaction and distillation of mono-tert-butyl compounds

[0074] 703.5 parts of mixed tert-butylphenol (including 355.3 parts of 6-tert-butyl-3-methylphenol, 274.3 parts of 4-tert-butyl-2,6-xylenol and 73 parts of 6-tert-butyl-2-ethylphenol) and 60 parts of strong acid resin are stirred, heated to 110°C, and 216 parts of isobutylene are introduced for 4 hours. The mixture is kept at 110°C for 1 hour for sampling and analysis. The 6-tert-butyl-3-methylphenol content of 0.12% is qualified. The mixture is filtered, the filter cake is used, and the filtrate is distilled under reduced pressure to obtain 25.3 parts of the first part, 268.8 parts of 99.6% high-purity 4-tert-butyl-2,6-xylenol, and 99.6% 4-tert-butyl-2,6-xylenol as products for sale.

[0075] At the same time, 574.3 parts of the second distillation still residue (including 95.9 parts of 4,6-di-tert-butyl-2-ethylphenol and 476.6 parts of 4,6-di-tert-butyl-3-methylphenol) and 301.2 parts of the first distillation still residue (including 112 parts of 4,6-di-tert-butyl-2-methylphenol, 75.4 parts of 2,6-di-tert-butyl-4-methylphenol, 85.5 parts of 4,6-di-tert-butyl-3-methylphenol and 24.9 parts of 4,6-di-tert-butyl-2-ethylphenol) were added to the high-efficiency distillation tower and distilled at -0.095 MPa to obtain 178.2 parts of 2,6-di-tert-butyl-4-methylphenol and 4,6-di-tert-butyl-2-methylphenol (including 4,6 -di-tert-butyl-2-methylphenol 107 parts, 2,6-di-tert-butyl-4-methylphenol 71.2 parts); 15.3 parts of intermediate distillate one (including 5.0 parts of 4,6-di-tert-butyl-2-methylphenol, 4.2 parts of 2,6-di-tert-butyl-4-methylphenol, 6.1 parts of 4,6-di-tert-butyl-2-ethylphenol), 99.2% of 4,6-di-tert-butyl-2-ethylphenol 106.5 parts, 48.8 parts of intermediate distillate two (including 40.6 parts of 4,6-di-tert-butyl-3-methylphenol, 8.2 parts of 4,6-di-tert-butyl-2-ethylphenol), and 516.5 parts of the third distillation kettle residue (including 4,6-di-tert-butyl-3-methylphenol).

[0076] The middle distillate 1 and the middle distillate 2 are sent to the distillation of the next batch of still residue.

[0077] (3) Deisobutylene and distillation of tert-butyl compounds

[0078] A. Add 106.5 parts of 99.2% 4,6-di-tert-butyl-2-ethylphenol into a reactor, add 2 parts of concentrated sulfuric acid, heat to 195°C with stirring, react for 3 hours, detect 0.26% of 6-tert-butyl-2-ethylphenol in gas phase, cool down, add 5.5 parts of 30% liquid alkali to neutralize to pH 7.5, separate the water layer, add the material into a distillation tower for distillation to obtain 55.0 parts of 99.5% o-ethylphenol, and recover 49.5 parts of isobutylene for application.

[0079] B. Add 516.5 parts of kettle residue (4,6-di-tert-butyl-3-cresol) and 8.5 parts of concentrated sulfuric acid into the reactor. Heat to 150°C and maintain for 2 hours. Stop the reaction when the content of 6-tert-butyl-m-cresol is 40.1% by gas spectrum detection. Slightly cool and neutralize with 22.5 parts of 30% liquid alkali to neutrality. Let stand to separate the water layer. Vacuum distill the material layer to obtain 149.5 parts of 99.8% high-purity m-cresol and 146.9 parts of 99.6% 6-tert-butyl-3-cresol. Recover 210 parts of isobutylene for application.

[0080] C, 2,6-di-tert-butyl-4-methylphenol and 4,6-di-tert-butyl-2-methylphenol 178.2 parts (including 4,6-di-tert-butyl-2-methylphenol 107 parts, 2,6-di-tert-butyl-4-methylphenol 71.2 parts), 3 parts of concentrated sulfuric acid, heated to 195 ° C for reaction for 3 hours under stirring, gas phase detection 6-tert-butyl-2-methylphenol 0.05%, cooling, adding 8.2 parts of 30% liquid alkali to neutralize to pH 7.5, separating the water layer, adding the material into the distillation tower for distillation to obtain 99.5% o-cresol 51.7 parts, 99.7% p-cresol 33.2 parts, and recovering 86.8 parts of isobutylene for application.

[0081] D, 100 parts of 99.6% high-purity 4-tert-butyl-2,6-dimethylphenol were added into the reactor, and 2 parts of concentrated sulfuric acid were added. The temperature was raised to 200°C with stirring and the reaction was carried out for 3 hours. The gas phase detected 0.08% of 4-tert-butyl-2,6-dimethylphenol. The temperature was lowered, and 5.5 parts of 30% liquid alkali were added to neutralize to pH 7.5. The water layer was separated and the material was added into a 2,6-dimethylphenol distillation tower for distillation to obtain 67.4 parts of 99.5% 2,6-dimethylphenol, and 30.5 parts of recovered isobutylene were used.

[0082] 67.4 parts of 99.5% 2,6-dimethylphenol are added to a melt crystallizer and first heated to 53°C to dissolve all the materials, then cooled to 47°C at 0.5°C / hour, then cooled to 40°C at 0.1°C / hour for crystallization, kept warm for 4 hours, and 0.8 parts of non-crystallized materials are released (returned to the raw material cresol); then heated to 43°C at 0.5°C / hour, 3.1 parts of melted materials are released (returned to the 2,6-dimethylphenol rectification kettle), then heated to 45°C at 0.1°C / hour, kept warm for 4 hours, 61.9 parts of 99.9% 2,6-dimethylphenol are released, and the yield is 92.2%; finally, the temperature is quickly raised to 55°C to dissolve all the remaining materials, and 1.4 parts of the dissolved materials are incorporated into the 2,6-dimethylphenol obtained in the next distillation for melt crystallization.

[0083] Example 2

[0084] (1) Tertiary butylation and distillation of cresol

[0085] 833 parts of cresols, including 243.2 parts of 2,6-dimethylphenol, 350.4 parts of m-cresol, 234.4 parts of p-cresol, 2.5 parts of o-ethylphenol and 30 parts of sulfuric acid, were added into the reactor, and the temperature was raised to 90°C under stirring, and 750 parts of isobutylene were introduced into the reactor for reaction. The isobutylene was introduced for 5 hours, and the reaction was kept warm for 2 hours after the introduction. 0.05% of 2,6-dimethylphenol was sampled and analyzed, and 241.8 parts of isobutylene were recovered for use; 84 parts of 30% liquid alkali were added to neutralize the reaction to pH 8, the water layer was separated, and the material layer was added into a high-efficiency distillation tower, and distilled at a reflux ratio of 15 to 20:1 to obtain 50.3 parts of the first part and 209.6 parts of 99.38% 2-tert-butyl-4-methylphenol (6-tert-butyl-3- cresol 1.1 parts, others 0.2 parts), 300.7 parts of 2-tert-butyl-4-cresol / 6-tert-butyl-3-cresol (92.3 parts of 2-tert-butyl-4-cresol, 208.1 parts of 6-tert-butyl-3-cresol, and 0.3 parts of others), 601.6 parts of mixed tert-butylphenol (including 249 parts of 6-tert-butyl-3-cresol, 351.1 parts of 4-tert-butyl-2,6-xymethylphenol, and 1.5 parts of 6-tert-butyl-2-ethylphenol), 156 parts of the first distillation still residue, including 61.4 parts of 2,6-di-tert-butyl-4-cresol, 92.3 parts of 4,6-di-tert-butyl-3-cresol, 1.4 parts of 4,6-di-tert-butyl-2-ethylphenol, and 0.9 parts of others.

[0086] The above-mentioned kettle residue was added to the kettle of the distillation tower, and distilled at -0.095MPa and reflux ratio of 15:1 to obtain 56.3 parts of 99.6% antioxidant 2,6-di-tert-butyl-4-cresol and 8.3 parts of transition fraction; then the distillation kettle residue was transferred to a 316L stainless steel kettle, 2 parts of 96% sulfuric acid was added, the temperature was raised to 200°C and maintained for 2 hours, and the reaction was stopped when the content of 6-tert-butyl-m-cresol was 0.19% by gas spectrum detection, and the temperature was slightly lowered and neutralized to neutrality with 2.7 parts of 30% liquid alkali, and the water layer was separated and allowed to stand, and the material layer was vacuum distilled (-0.085MPa, reflux ratio of 5:1, high-boiling point dimethyl benzene diether was pre-added in the distillation kettle as a bottom liquid) to obtain 40.6 parts of 99.85% high-purity m-cresol, and the recovered isobutylene was passed into the cresol tert-butyl synthesis kettle.

[0087] (2) Di-tert-butylation reaction and distillation of mono-tert-butyl compounds

[0088] The reaction product of cresol containing 2,6-dimethylphenol and isobutylene is added to the reactor, and then 601.6 parts of tert-butyl cresol mixture (containing 249 parts of 6-tert-butyl-3-cresol, 351.1 parts of 4-tert-butyl-2,6-dimethylphenol, and 1.5 parts of 6-tert-butyl-2-ethylphenol) and 60 parts of strong acid resin are obtained by rectification in a rectification tower. Stirring is started, the temperature is raised to 120° C., 130 parts of isobutylene are introduced for 4 hours, and the temperature is kept at 120° C. for reaction for 2 hours. Samples are analyzed, and those with a 6-tert-butyl-m-cresol content of 0.38% are qualified. Filtering, the filter cake is used, and the filtrate is vacuum-distilled to obtain 22.3 parts of the first portion, 332.8 parts of 99.75% high-purity 4-tert-butyl-2,6-dimethylphenol, and 99.5% 4-tert-butyl-2,6-dimethylphenol, which are sold as products.

[0089] 334 parts of 4,6-di-tert-butyl-meta-cresol residual in the kettle were added with 6.7 parts of concentrated sulfuric acid, and the temperature was raised to 190°C and maintained for 2 hours. The reaction was stopped when the content of 6-tert-butyl-meta-cresol was 0.33% by gas spectrum detection. The temperature was slightly lowered and neutralized to neutrality with 18 parts of 30% liquid alkali. The water layer was allowed to stand and the material layer was vacuum distilled to obtain 147.2 parts of 99.7% high-purity meta-cresol. The recovered isobutylene was passed into the tert-butyl cresol synthesis kettle.

[0090] Example 3

[0091] (1) Tertiary butylation and distillation of cresol

[0092] 1000 parts of cresol (229.1 parts of o-cresol, 156.7 parts of 2,6-xylenol, 230 parts of m-cresol, 153.3 parts of p-cresol, 60.8 parts of o-ethylphenol, 97.5 parts of 2,4-xylenol, 69.2 parts of 2,5-xylenol) and 30 parts of sulfuric acid were added to the reactor, and the temperature was raised to 90°C under stirring, and 817 parts of isobutylene were introduced for reaction. The isobutylene was introduced for 6 hours, and the reaction was kept warm for 2 hours after the introduction. 83.5 parts of 30% liquid alkali was added to neutralize to pH 8, the water layer was separated, and the material layer was added to a high-efficiency distillation tower and distilled at a reflux ratio of 18 to 23:1 to obtain 43 parts of diisobutylene, 276.9 parts of 99.3% 6-tert-butyl-2-methyl Phenol, 185.8 parts of 99.1% 2-tert-butyl-4-methylphenol, 728 parts of mixed tert-butylphenols (including 296.1 parts of 6-tert-butyl-3-methylphenol, 228.6 parts of 4-tert-butyl-2,6-dimethylphenol, 141.6 parts of 6-tert-butyl-2,4-dimethylphenol and 60.8 parts of 6-tert-butyl-2-ethylphenol), 351.5 parts of kettle residue (including 100.5 parts of 4-tert-butyl-2,5-dimethylphenol, 93.3 parts of 4,6-di-tert-butyl-2-methylphenol, 62.8 parts of 2,6-di-tert-butyl-4-methylphenol, 71.2 parts of 4,6-di-tert-butyl-3-methylphenol and 20.7 parts of 4,6-di-tert-butyl-2-ethylphenol).

[0093] (2) Di-tert-butylation reaction and distillation of mono-tert-butyl compounds

[0094] 728 parts of mixed tert-butylphenol (including 296.1 parts of 6-tert-butyl-3-methylphenol, 228.6 parts of 4-tert-butyl-2,6-xymethylphenol, 141.6 parts of 6-tert-butyl-2,4-xymethylphenol and 60.8 parts of 6-tert-butyl-2-ethylphenol) and 58 parts of strongly acidic resin were stirred, heated to 110°C, 185 parts of isobutylene were introduced for 4 hours, and then kept at 110°C for 1 hour for sampling and analysis. The 6-tert-butyl-3-methylphenol content of 0.16% was qualified. The mixture was filtered, the filter cake was used, and the filtrate was distilled under reduced pressure to obtain 21.2 parts of the first part and 360.7 parts (223.1 parts of 4-tert-butyl-2,6-xymethylphenol and 137.6 parts of 4-tert-butyl-2,4-xymethylphenol) in turn.

[0095] 478.6 parts of the still residue in (2) (including 79.9 parts of 4,6-di-tert-butyl-2-ethylphenol and 397.2 parts of 4,6-di-tert-butyl-3-methylphenol) and 351.5 parts of the still residue in (1) (including 100.5 parts of 4-tert-butyl-2,5-xymethylphenol, 93.3 parts of 4,6-di-tert-butyl-2-methylphenol, 62.8 parts of 2,6-di-tert-butyl-4-methylphenol, 71.2 parts of 4,6-di-tert-butyl-3-methylphenol and 20.7 parts of 4,6-di-tert-butyl-2-ethylphenol) were added to a high-efficiency distillation tower and distilled at -0.095 MPa to obtain 245 parts of a mixture of 2,6-di-tert-butyl-4-methylphenol, 4-tert-butyl-2,5-xymethylphenol and 4,6-di-tert-butyl-2-methylphenol (including 100.5 parts of 4-tert-butyl-2,5-xymethylphenol, 93.3 parts of 4,6-di-tert-butyl-2-methylphenol, 62.8 parts of 2,6-di-tert-butyl-4-methylphenol, 71.2 parts of 4,6-di-tert-butyl-3-methylphenol and 20.7 parts of 4,6-di-tert-butyl-2-ethylphenol). ,6-di-tert-butyl-2-methylphenol 89.2 parts, 4-tert-butyl-2,5-xymethylphenol 96.5 parts, 2,6-di-tert-butyl-4-methylphenol 59.3 parts), 16.3 parts of intermediate distillate one (including 4.2 parts of 4,6-di-tert-butyl-2-methylphenol, 3.5 parts of 2,6-di-tert-butyl-4-methylphenol, 3.5 parts of 4-tert-butyl-2,5-xymethylphenol, 5.1 parts of 4,6-di-tert-butyl-2-ethylphenol), 88.7 parts of 99.2% of 4,6-di-tert-butyl-2-ethylphenol, 40.6 parts of intermediate distillate two (including 33.8 parts of 4,6-di-tert-butyl-3-methylphenol and 6.8 parts of 4,6-di-tert-butyl-2-ethylphenol), and 430.4 parts of kettle residue (4,6-di-tert-butyl-3-methylphenol).

[0096] The middle distillate 1 and the middle distillate 2 are sent to the distillation of the next batch of still residue.

[0097] (4) Deisobutylene and distillation of tert-butyl compounds

[0098] A. Add 88.7 parts of 99.2% 4,6-di-tert-butyl-2-ethylphenol into a reactor, add 2 parts of concentrated sulfuric acid, heat to 195°C with stirring, react for 3 hours, detect 0.26% of 6-tert-butyl-2-ethylphenol in gas phase, cool down, add 5.5 parts of 30% liquid alkali to neutralize to pH 7.5, separate the water layer, add the material into a distillation tower for distillation to obtain 45.8 parts of 99.5% o-ethylphenol, and recover 41.2 parts of isobutylene for application.

[0099] B. Add 430.4 parts of kettle residue (4,6-di-tert-butyl-3-cresol) and 7.1 parts of concentrated sulfuric acid into the reactor. Heat to 150°C and maintain for 2 hours. Stop the reaction when the content of 6-tert-butyl-m-cresol is 40.1% by gas spectrum detection. Slightly cool and neutralize with 18.8 parts of 30% liquid alkali to neutrality. Let stand to separate the water layer. Vacuum distill the material layer to obtain 124.7 parts of 99.7% high-purity m-cresol and 122.6 parts of 99.3% 6-tert-butyl-3-cresol. Recover 175 parts of isobutylene for application.

[0100] C, 245 parts of a mixture of 2,6-di-tert-butyl-4-methylphenol, 4-tert-butyl-2,5-xylenol and 4,6-di-tert-butyl-2-methylphenol and 5 parts of concentrated sulfuric acid, heated to 200°C for reaction for 3 hours under stirring, 0.08% of 4-tert-butyl-2,5-xylenol was detected by gas phase detection, cooled, 13.7 parts of 30% liquid alkali was added to neutralize to pH 7.5, the water layer was separated, and the materials were added to a distillation tower for distillation to obtain 43.0 parts of 99.7% o-cresol, 27.6 parts of 99.8% p-cresol, 65.1 parts of 99.5% 2,5-xylenol, and 102 parts of recovered isobutylene were used.

[0101] D, 360.7 parts (223.1 parts of 4-tert-butyl-2,6-dimethylphenol and 137.6 parts of 4-tert-butyl-2,4-dimethylphenol) were added into the reactor, and 5 parts of concentrated sulfuric acid were added. The temperature was raised to 200°C with stirring and the reaction was carried out for 3 hours. The gas phase detected 0.08% of 4-tert-butyl-2,6-dimethylphenol. The temperature was lowered, and 14 parts of 30% liquid alkali were added to neutralize to pH 8.0. The water layer was separated and the material was added into a 2,6-dimethylphenol distillation tower for distillation to obtain 153.1 parts of 99.8% 2,6-dimethylphenol and 93.1 parts of 99.3% 2,4-dimethylphenol. 95.5 parts of recovered isobutylene were used.

[0102] Example 4

[0103] (1) Tertiary butylation and distillation of cresol

[0104] Add 1000 parts of cresol (2,6-dimethylphenol 259.3 parts, m-cresol 380.7 parts, p-cresol 253.8 parts, o-ethylphenol 100.7 parts, sulfide 0.28%, nitrogen-containing compound 0.23%) and 30 parts of sulfuric acid into the reactor, heat to 70°C under stirring, introduce 827 parts of isobutylene for reaction, introduce isobutylene for 7 hours, keep warm for 2 hours after introduction, add 80 parts of 30% liquid alkali to neutralize to pH 7.5, separate the water layer, add the material layer into the high-efficiency distillation tower, and distill at a reflux ratio of 15 to 20:1. 43.0 parts of diisobutylene, 306.9 parts of 99.3% 2-tert-butyl-4-methylphenol, 970.3 parts of mixed tert-butylphenols (including 490.1 parts of 6-tert-butyl-3-methylphenol, 378.3 parts of 4-tert-butyl-2,6-dimethylphenol and 100.7 parts of 6-tert-butyl-2-ethylphenol) and 259.4 parts of still residue (including 104.0 parts of 2,6-di-tert-butyl-4-methylphenol, 117.9 parts of 4,6-di-tert-butyl-3-methylphenol and 34.3 parts of 4,6-di-tert-butyl-2-ethylphenol) were obtained.

[0105] (2) Di-tert-butylation reaction and distillation of mono-tert-butyl compounds

[0106] 970.3 parts of mixed tert-butylphenol (including 490.1 parts of 6-tert-butyl-3-methylphenol, 378.3 parts of 4-tert-butyl-2,6-xylenol and 100.7 parts of 6-tert-butyl-2-ethylphenol) and 80 parts of strongly acidic resin are stirred, heated to 120°C, and 298 parts of isobutylene are introduced for 4 hours. The mixture is kept at 120°C for 1 hour for sampling and analysis. The 6-tert-butyl-3-methylphenol content of 0.18% is qualified. The mixture is filtered, the filter cake is used, and the filtrate is distilled under reduced pressure to obtain 34.9 parts of the first part, 370.7 parts of 99.6% high-purity 4-tert-butyl-2,6-xylenol, and 99.6% 4-tert-butyl-2,6-xylenol, which can be sold as a product.

[0107] 792.1 parts of the still residue in (2) (including 132.3 parts of 4,6-di-tert-butyl-2-ethylphenol and 657.4 parts of 4,6-di-tert-butyl-3-methylphenol) were added to a high-efficiency distillation tower and distilled at -0.095 MPa to obtain 123.8 parts of 99.5% 4,6-di-tert-butyl-2-ethylphenol, 37.7 parts of an intermediate fraction (including 32.2 parts of 4,6-di-tert-butyl-3-methylphenol and 5.3 parts of 4,6-di-tert-butyl-2-ethylphenol), and 621.8 parts of the still residue (621.9 parts of 4,6-di-tert-butyl-3-methylphenol).

[0108] The middle fraction is fed into the distillation of the next batch of still residue.

[0109] (3) Deisobutylene and distillation of tert-butyl compounds

[0110] A. Add 123.8 parts of 99.5% 4,6-di-tert-butyl-2-ethylphenol into a reactor, add 2.3 parts of concentrated sulfuric acid, heat to 195°C with stirring, react for 3 hours, detect 0.11% of 6-tert-butyl-2-ethylphenol in gas phase, cool down, add 6.3 parts of 30% liquid alkali to neutralize to pH 7.5, separate the water layer, add the material into a distillation tower for distillation to obtain 31.5 parts of 99.3% o-ethylphenol (25 ppm sulfide, 18 ppm nitrogen-containing compound), 44.5 parts of 99.5% 6-tert-butyl-2-ethylphenol, and recover 41.8 parts of isobutylene for application.

[0111] B. Add 621.8 parts of kettle residue (4,6-di-tert-butyl-3-cresol) and 7.4 parts of concentrated sulfuric acid into the reactor, raise the temperature to 150°C and maintain for 2 hours. Stop the reaction when the content of 6-tert-butyl-m-cresol is 40.5% as detected by gas spectrum. Slightly cool and neutralize with 19.6 parts of 30% liquid alkali to neutrality. Let stand to separate the water layer, and perform vacuum distillation on the material layer to obtain 180.1 parts of 99.8% high-purity m-cresol (46 ppm sulfide, 42 ppm nitrogen-containing compound), 176.8 parts of 99.5% 6-tert-butyl-3-cresol, and use 252 parts of recovered isobutylene for application.

[0112] C, 200 parts of 99.6% high-purity 4-tert-butyl-2,6-dimethylphenol were added to the reactor, and 5 parts of concentrated sulfuric acid were added. The temperature was raised to 200°C with stirring and the reaction was carried out for 3 hours. The gas phase detected 0.10% of 4-tert-butyl-2,6-dimethylphenol. The temperature was lowered, and 13.8 parts of 30% liquid alkali were added to neutralize to pH 7.5. The water layer was separated and the material was added to the 2,6-dimethylphenol distillation tower for distillation to obtain 135 parts of 99.3% 2,6-dimethylphenol, and 61 parts of recovered isobutylene were used.

[0113] 135 parts of 99.3% 2,6-xylenol are added to a melt crystallizer and first heated to 53°C to dissolve all the materials, then cooled to 47°C at 0.5°C / hour, then cooled to 40°C at 0.1°C / hour for crystallization, kept warm for 4 hours, and 1.5 parts of non-crystallized materials are discharged (returned to the raw material cresol); then heated to 43°C at 0.5°C / hour, 6.3 parts of melted materials are discharged (returned to the 2,6-xylenol rectification kettle), then heated to 45°C at 0.1°C / hour, kept warm for 4 hours, and 123.6 parts of 99.8% 2,6-xylenol are discharged, with a yield of 91.9%, 10 ppm of sulfide, and 16 ppm of nitride; finally, the temperature is quickly raised to 55°C to dissolve all the remaining materials, and 2.9 parts of the dissolved materials are incorporated into the 2,6-xylenol obtained in the next distillation for melt crystallization.

[0114] Example 5

[0115] (1) Tertiary butylation and distillation of cresol

[0116] 1000 parts of cresol (post-ortho-cresol fraction), including 670 parts of ortho-cresol, 225 parts of 2,6-xylenol, 57 parts of naphthalene, 48 parts of aniline and 50 parts of sulfuric acid, were added into the reactor, the temperature was raised to 110°C under stirring, 780 parts of isobutylene were introduced for reaction, the isobutylene was introduced for 5 hours, the reaction was kept warm for 1 hour, 0.03% of 2,6-xylenol was sampled and analyzed, 84 parts of 30% liquid alkali were added for neutralization, the lower water layer was removed by standing, 100 parts of water were added, the mixture was stirred and washed for 1 hour, and the mixture was stood for stratification; 25 parts of 20% sodium bicarbonate were added for washing for 0.5 hours, the mixture was stratified, and the three water layers were combined (acidic aqueous solution, and aniline was recovered separately); the washed material layer was added into a high-efficiency distillation tower (1 part of sodium bicarbonate was added), and 48.5 parts of the front part (39 parts of oligomeric isobutylene, 5.8 parts of water) were obtained by distillation at a reflux ratio of 15-20:1. , volatile phenol 2.3 parts, naphthalene 1.1 parts), 94.85% crude naphthalene 58.3 parts (55.3 parts naphthalene, 6-tert-butyl-2-methylphenol 2.8 parts), 808.3 parts 99.8% 6-tert-butyl-2-methylphenol, 27.3 parts 6-tert-butyl-2-methylphenol / 4-tert-butyl-2,6-dimethylphenol (including 6-tert-butyl-2-methylphenol 12.1 parts, 4-tert-butyl-2,6-dimethylphenol cresol 15.2 parts), 99.7% 4-tert-butyl-2,6-dimethylphenol 307.6 parts, 16.6 parts of the rear fraction (2,6-di-tert-butyl-4-methylphenol 4.6 parts, 4,6-di-tert-butyl-2-methylphenol 11.8 parts), the first distillation still residue 237.8 parts, including 4,6-di-tert-butyl-2-methylphenol 237.1 parts, 2,6-di-tert-butyl-4-methylphenol 0.2 parts.

[0117] 99.8% of 6-tert-butyl-2-methylphenol and 99.7% of 4-tert-butyl-2,6-dimethylphenol are sold out. 27.3 parts of 6-tert-butyl-2-methylphenol / 4-tert-butyl-2,6-dimethylphenol and the latter fraction are returned to the next batch of alkylation products to distill pure 6-tert-butyl-2-methylphenol and 4-tert-butyl-2,6-dimethylphenol products. Crude naphthalene can be further processed and sublimated to obtain refined naphthalene products.

[0118] (2) Aniline recovery

[0119] The combined water layer obtained in the previous step is added to an enameled reactor, stirring is started, and 46 parts of 30% liquid alkali are continuously added dropwise to neutralize to pH 8; 100 parts and 100 parts of toluene are added for extraction twice, the toluene layers obtained by layering are combined, and the water layer is sent to the three waste workshop; the toluene layer is washed once with 50 parts of water, and the toluene layer after water separation is sent to a distillation tower (50 parts of high-boiling dimethyl diphenyl ether have been added to the reactor), 197.3 parts of toluene are first recovered under normal pressure, and then distilled to obtain 44.6% of 99.1% aniline.

[0120] (3) Deisobutylene and distillation of tert-butyl compounds

[0121] 237.8 parts of the residue from the first distillation kettle in (1) were added to a 316L stainless steel kettle, 3 parts of concentrated sulfuric acid were added, the temperature was raised to 200°C with stirring, and the reaction was carried out for 2.5 hours. The gas phase detected 0.08% of 6-tert-butyl-2-methylphenol, the temperature was lowered, 8.3 parts of 30% liquid alkali was added to neutralize to pH 7.5, the water layer was separated, and the material was added to a distillation tower for vacuum distillation (-0.085 MPa, reflux ratio 5:1) to obtain 110.7 parts of 99.9% o-cresol, containing 0.5 ppm sulfide and 0.8 ppm pyridine base; 114.6 parts of recovered isobutylene were used.

[0122] It should be noted that if the cresol containing 2,6-dimethylphenol is directly di-tert-butylated, as long as m-cresol, o-cresol and o-ethylphenol are used to produce di-tert-butylated products, for example, in Example 1, theoretically, 99% of 2,6-dimethylphenol can be obtained by direct distillation after alkylation, but qualified antioxidant 2,6-di-tert-butyl-p-cresol cannot be obtained; for example, in Example 3, theoretically, qualified 2,6-dimethylphenol cannot be obtained by direct distillation after alkylation, but qualified 2,6-dimethylphenol and 2,4-dimethylphenol can be obtained by distillation after dealkylation, but qualified antioxidant 2,6-di-tert-butyl-p-cresol cannot be obtained, and qualified o-cresol, p-cresol and 2,5-dimethylphenol can be obtained by secondary distillation after dealkylation; for example, in Example 4, qualified 2,6-dimethylphenol, antioxidant 2,6-di-tert-butyl-p-cresol, m-cresol and o-ethylphenol can be obtained, but the separation difficulty is greater and the yield is low. Therefore, in the related art, according to the traditional method for separating m-cresol, the cresol containing 2,6-xylenol must simultaneously meet the minimum o-cresol content greater than or equal to 1%, o-ethylphenol content greater than or equal to 1%, 2,6-xylenol content greater than or equal to 1%, and 2,4 / 2,5-xylenol content greater than or equal to 1%.

[0123] The present application utilizes the characteristics that 2,6-xylenol, 2,4-xylenol and 2,5-xylenol can only generate mono-tert-butylated products 4-tert-butyl-2,6-xylenol, 6-tert-butyl-2,4-xylenol and 4-tert-butyl-2,5-xylenol, while the remaining cresols and ethylphenols can produce mono- and di-tert-butylated products for separation. The present application is particularly effective in separating cresols or m-p-cresols with high 2,6-xylenol and high o-ethylphenol content, and has high economic benefits. Therefore, the present invention is most effective in separating crude phenol from pyrolysis and gasification phenol-containing tar with high 2,6-xylenol and o-ethylphenol content, and refining the crude phenol to obtain a cresol mixture.

[0124] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means 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 application. 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 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.

[0125] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A method for separating multiple phenols from cresol containing 2,6-dimethylphenol, characterized in that: The following steps are involved: The cresol containing 2,6-dimethylphenol is mono-tert-butylated under the action of acid catalysis, and the water layer is separated from the first reaction liquid and then subjected to efficient distillation separation to obtain a tert-butylated phenol product and a first distillation still residue; or a mixture of multiple mono-tert-butylated products is obtained by distillation separation; The mixture of the plurality of mono-tert-butyl compounds is subjected to a tert-butylation reaction under acid catalysis and at a set temperature, and then the second reaction liquid is distilled and separated to obtain unreacted mono-tert-butyl compounds, di-tert-butyl compounds and a second distillation still residue; the second distillation still residue is separated alone or combined with the first distillation still residue and then distilled to obtain a still residue distillate and a third distillation still residue; The unreacted mono-tert-butyl compound, the di-tert-butyl compound, the still residue and the third distillation still residue are subjected to de-tert-butylation reaction to remove isobutylene; the pH value of each reaction material after the isobutylene is removed is adjusted to neutral, and the material layer after stratification is distilled to obtain 2,6-dimethylphenol with a content of 99.0% or 2,6-dimethylphenol with a content greater than 99.0% and 2,4-dimethylphenol with a content of 99.0%.

2. The method according to claim 1, characterized in that Taking the cresol as a reference, the cresol includes 0-90% of o-cresol, 1-80% of 2,6-dimethylphenol, 0-90% of m-para-cresol, 0-30% of o-ethylphenol and 0-50% of 2,4 / 2,5-dimethylphenol in terms of mass percentage.

3. The method according to claim 1 or 2, characterized in that: Taking the cresol as a reference, in terms of mass percentage, the cresol includes 10-40% of o-cresol, 5-30% of 2,6-dimethylphenol, 30-70% of m-p-cresol and 2-15% of o-ethylphenol.

4. The method according to claim 2, characterized in that: The plurality of mono-tert-butyl compound mixtures include at least two of 6-tert-butyl-2-methylphenol, 2-tert-butyl-4-methylphenol, 4-tert-butyl-2,6-xymethylphenol, 6-tert-butyl-3-methylphenol, 6-tert-butyl-2-ethylphenol, and 6-tert-butyl-2,4-xymethylphenol; and the first rectification still residue includes at least one of 4-tert-butyl-2,5-xymethylphenol, 2,6-di-tert-butyl-4-methylphenol, 4,6-di-tert-butyl-2-methylphenol, 4,6-di-tert-butyl-2-ethylphenol, and 4,6-di-tert-butyl-3-methylphenol.

5. The method according to claim 2, characterized in that: Taking the mono-tert-butyl compound mixture as a benchmark, according to the mass percentage content, the multiple mono-tert-butyl compound mixtures include 1-95% of 4-tert-butyl-2,6-dimethylphenol, 1-95% of 6-tert-butyl-3-methylphenol, 0-95% of 6-tert-butyl-2,4-dimethylphenol and 0-95% of 6-tert-butyl-2-ethylphenol.

6. The method according to claim 1, characterized in that The mixture of various mono-tert-butyl compounds is further reacted with isobutylene at 30-150° C. under the action of acid catalysis; the di-tert-butyl compounds include 4,6-di-tert-butyl-3-methylphenol and / or 4,6-di-tert-butyl-2-ethylphenol.

7. The method according to claim 1 or 6, characterized in that: In acid catalysis, the mass of the catalyst is 0.5 to 30% of the mass of the reactants.

8. The method according to claim 7, characterized in that The catalyst includes at least one of sulfuric acid, phosphoric acid, benzenesulfonic acid, p-toluenesulfonic acid, aminosulfonic acid, strong acid resin or solid acid.

9. The method according to claim 3, characterized in that: The number of plates for the efficient distillation separation is 80-300.

10. The method according to claim 3, characterized in that: When the second distillation still residue is distilled separately, the still residue is 4,6-di-tert-butyl-2-ethylphenol; or When the second distillation still residue is combined with the first distillation still residue and then distilled, the still residue distillation product is 4,6-di-tert-butyl-2-ethylphenol, and at least one of 2,6-di-tert-butyl-4-methylphenol, 4,6-di-tert-butyl-2-methylphenol, and 4-tert-butyl-2,5-xymethylphenol; and the third distillation still residue includes 4,6-di-tert-butyl-3-methylphenol.

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