Method for extracting methyl ethyl phenol from crude phenol refining residue and synthesizing tertiary butyl phenol

Abstract

The application discloses a method for extracting methyl ethyl phenol from crude phenol refining residues and synthesizing tertiary butyl phenol. The method directly produces linear methyl ethyl phenol aldehyde resin by utilizing the difference in reactivity of 3,4-methyl ethyl phenol mixture and formaldehyde; unreacted 3,4-methyl ethyl phenol / para-tertiary butyl phenol mixture and the like are evaporated out, and then the 3,4-methyl ethyl phenol / para-tertiary butyl phenol mixture is subjected to a tertiary butylation reaction, rectification, a de-tertiary butylation reaction and rectification to obtain high-quality products 3,4-methyl ethyl phenol, mono-tertiary butyl phenol and di-tertiary butyl phenol, so that the method is simple in process, convenient in operation, high in added value and capable of comprehensively utilizing waste.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis and separation technology, and in particular to a method for extracting methyl ethyl phenol from crude phenol refining residue and synthesizing tert-butyl phenol. Background Technology

[0002] The price of crude phenol distillation residue is only 1000-2000 yuan / ton, which is low, so it can only be used as fuel oil. Many phenolic substances contained in it, such as m-p-isopropylphenol, m-p-propylphenol, 3-methyl-5-ethylphenol, 2,3,5-trimethylphenol, 2,3-methylethylphenol, 3,4-methylethylphenol, and m-p-tert-butylphenol, are not utilized. Because 3,4-methylethylphenol has a similar boiling point to m-p-propylphenol, 3-methyl-5-ethylphenol, 2,3,5-trimethylphenol, and m-p-tert-butylphenol, it is impossible to obtain high-purity 3,4-methylethylphenol through distillation, but the 3,4-methylethylphenol fraction can be enriched.

[0003] The 3,4-methylethylphenol fraction contains small amounts of m-p-isopropyl / propylphenol, a certain amount of m-p-tert-butylphenol, 2,3,5-trimethylphenol, 3-methyl-5-ethylphenol, and other impurities. The reactivity of 2,3,5-trimethylphenol, m-isopropylphenol, m-propylphenol, m-tert-butylphenol, phenol, 3,4-methylethylphenol, p-isopropylphenol / p-propylphenol, and p-tert-butylphenol with formaldehyde are 1.5, 2.5, 2.1, 2.9, 1, 0.68, 0.3, and 0.25, respectively. The presence of 2,3,5-trimethylphenol and m-isopropylphenol can improve the heat resistance, dimensional stability, optical properties, and electrical properties of phenolic resins. The presence of numerous straight-chain 3,4-methylethylphenol groups on the phenolic resin chain increases its flexibility and improves its processing performance. Because p-tert-butylphenol reacts slowly with formaldehyde, p-tert-butylphenol can be obtained when 3,4-methylethylphenol reacts completely. Since the reaction rate of 3,4-methylethylphenol with formaldehyde is lower than that of phenol, unless producing phenolic resin for a specific purpose, it is generally not necessary to completely react the raw material 3,4-methylethylphenol. Therefore, the byproduct of obtaining phenolic resin is a mixture of 3,4-methylethylphenol and p-tert-butylphenol. Furthermore, since 3,4-methylethylphenol and p-tert-butylphenol have almost the same boiling point, they cannot be separated using conventional distillation methods.

[0004] Alternatively, tert-butylation can be used to react 3,4-methylethylphenol with p-tert-butylphenol to generate 6-tert-butyl-3,4-methylethylphenol and tri-tert-butylphenol, thereby increasing the boiling point difference between the two. High-purity 6-tert-butyl-3,4-methylethylphenol can be easily obtained by distillation. After removing the tert-butyl group and distilling again, high-purity 3,4-methylethylphenol can be obtained.

[0005] A mixture of tri-tert-butylphenol and phenol undergoes a disproportionation reaction under the action of an acidic catalyst and heating. The isobutylene decomposed from tri-tert-butylphenol reacts with phenol to give p-tert-butylphenol (boiling point 237℃) and o-tert-butylphenol (boiling point 221℃). Tri-tert-butylphenol decomposes to give 2,6-di-tert-butylphenol (boiling point 251℃), 2,4-di-tert-butylphenol (boiling point 263℃), p-tert-butylphenol, o-tert-butylphenol, etc. Various tert-butylphenols and di-tert-butylphenols can be easily obtained by distillation. Summary of the Invention

[0006] The present invention aims to at least partially solve one of the technical problems in the related art.

[0007] Therefore, this invention proposes a method for extracting methyl ethyl phenol from crude phenol refining residue and synthesizing tert-butyl phenol.

[0008] In a first aspect, the present invention provides a method for extracting methyl ethyl phenol from crude phenol refining residue and synthesizing tert-butyl phenol, comprising the following steps:

[0009] (1) The crude phenol refining residue was separated by distillation to obtain a mixture of 3,4-methylethylphenol; (2) The 3,4-methylethylphenol mixture is reacted with aldehydes, and the free phenol is removed by heating and distillation. The free phenol is then distilled to obtain a 3,4-methylethylphenol / p-tert-butylphenol mixture. The material from which the free phenol has been removed is heated and dehydrated under reduced pressure to obtain methylethylphenol aldehyde resin. (3) The 3,4-methylethylphenol / p-tert-butylphenol mixture and the catalyst were heated to carry out a tert-butylation reaction; 99% 6-tert-butyl-3,4-methylethylphenol and 99% tri-tert-butylphenol were obtained by vacuum distillation. (4) The 6-tert-butyl-3,4-methylethylphenol and sulfuric acid were heated and reacted; the mixture was cooled and neutralized to neutral by adding an aqueous sodium hydroxide solution; and 99% 3,4-methylethylphenol was obtained by vacuum distillation. (5) The tri-tert-butylphenol, phenol and sulfuric acid are reacted in a closed container; the mixture is cooled and neutralized to neutral by adding sodium hydroxide aqueous solution, and then distilled under reduced pressure to obtain tert-butylphenol, 2,4-di-tert-butylphenol and 2,6-di-tert-butylphenol.

[0010] Further, step (1) includes adding crude phenol refining residue to the reactor, heating to 90-130°C, adding concentrated sulfuric acid dropwise, distilling the material under reduced pressure after treatment, refluxing to remove water, and obtaining 3,4-methylethylphenol raw material at the top of the distillation column.

[0011] Furthermore, the crude phenol refining residue is the residue after crude phenol distillation of phenol, cresol, and xylenol, and the residue distillation range is ≥225℃.

[0012] Further, the 3,4-methylethylphenol mixture comprises 80-98 wt% 3,4-methylethylphenol / m-tert-butylphenol, 1-10 wt% 3-methyl-5-ethylphenol, 1-10 wt% 2,3,5-trimethylphenol, 0-1 wt% m-p-isopropylphenol, 0-1 wt% m-p-propylphenol, and 0-10 wt% other components; the 3,4-methylethylphenol comprises 4-ethyl-3-methylphenol and 3-ethyl-4-methylphenol, wherein the mass ratio of 3-ethyl-4-methylphenol to 4-ethyl-3-methylphenol is (0.2-1.5):1.

[0013] Furthermore, the amount of concentrated sulfuric acid added is 0.01~0.2 wt% of the crude phenol refining residue.

[0014] Furthermore, the conditions for the reduced pressure distillation are: 100-200 theoretical plates in the distillation column, a vacuum degree of -0.090 to -0.1 MPa, and a reflux ratio of 25-40:1.

[0015] Further, step (2) includes: The 3,4-methylethylphenol mixture and catalyst were added to a reaction vessel, and the temperature was raised to 80-100°C. Aldehydes were added dropwise over 2-6 hours. The mixture was kept at this temperature for 5-12 hours and then sampled for analysis. When the 3,4-methylethylphenol content was less than 15%, the free phenol in the material was removed by distillation. The material was distilled to a vessel temperature of 110-120°C. After the distillate volume decreased significantly, the material was cooled to 70-80°C. The free phenol distillate was allowed to stand to separate the oil layer. The aqueous layer was extracted and then combined with the oil layer to obtain the organic layer. The organic layer was then distilled to obtain solvent reuse. The distillation yielded a mixture of 3,4-methylethylphenol and p-tert-butylphenol. After the free phenols are distilled off, the material is evacuated to -0.08 to -0.095 MPa, heated and dehydrated under reduced pressure. The temperature is raised to 190 to 200°C for 2 to 4 hours, and then kept at that temperature for 1 to 2 hours. The vacuum is then broken with nitrogen, and the material is discharged into a stainless steel tray while still hot under nitrogen protection to obtain ethyl phenol formaldehyde resin.

[0016] Further, step (2) includes: The 3,4-methylethylphenol mixture and catalyst were added to a reaction vessel, and the temperature was raised to 80-100°C. The aldehydes were added dropwise over 2-6 hours, and the mixture was kept at this temperature for 5-12 hours before sampling and analysis. When the 3,4-methylethylphenol content was below 15%, glacial acetic acid or formic acid was added to neutralize the pH to 6-7. The vacuum was gradually increased to -0.07 to -0.1 MPa over 0.5-1 hours to begin dehydration. When the dehydration rate slowed down or the temperature dropped to around 70-75°C, the mixture was heated to continue dehydration. The final liquid temperature was controlled at 70-90°C until the water level reached the required value. The moisture content of the material was then sampled and analyzed to be ≤5%. Ethylene glycol is added to the reactor, stirred evenly, and samples are taken to analyze the moisture and viscosity. When the moisture content is 2-5%, the vacuum is stopped, and ethanol is added to adjust the viscosity to 10-30 Pa·s according to the requirements of different products. After the viscosity reaches the requirement, the temperature is lowered to 50°C and the material is discharged. The amount of ethylene glycol used is 1-10% of the total amount of phenolic raw materials.

[0017] Furthermore, the catalyst includes one or more of oxalic acid, formic acid, phosphoric acid, hydrochloric acid, benzoic acid, and benzenesulfonic acid.

[0018] Furthermore, the catalyst also includes at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, barium hydroxide, ammonia, or an organic base; Furthermore, the amount of the catalyst used is 0.1 to 5 wt% of the 3,4-methylethylphenol mixture.

[0019] Furthermore, the aldehydes include at least one of paraformaldehyde and an aqueous formaldehyde solution.

[0020] Furthermore, the amount of the aldehyde is 0.7 to 1.4 of the molar amount of the 3,4-methylethylphenol mixture.

[0021] Furthermore, the solvent is a non-aqueous solvent, including at least one of benzene, chlorinated hydrocarbons, chlorinated benzenes, ethers, ketones and esters, and the amount of the non-aqueous solvent is 0.05 to 0.5 of the water layer mass.

[0022] Furthermore, the distillation conditions are: 100-200 theoretical plates in the distillation column, pressure -0.08 to -0.090 MPa, and reflux ratio 1-10:1.

[0023] Further, step (3) includes heating the 3,4-methylethylphenol / p-tert-butylphenol mixture obtained in step (2) and the catalyst, then passing it through isobutylene for reaction. After sampling and analysis, if the 3,4-methylethylphenol content is ≤0.5wt% and it is qualified, the temperature is lowered to 40-80℃, and sodium hydroxide aqueous solution is added to neutralize to pH 7.5-9. The mixture is then subjected to vacuum distillation to obtain 99% 6-tert-butyl-3,4-methylethylphenol and 99% tri-tert-butylphenol.

[0024] Furthermore, the catalyst is at least one of sulfuric acid, benzenesulfonic acid, benzoic acid, and aminosulfonic acid.

[0025] Furthermore, the amount of catalyst used is 1 to 10% of the mass of the 3,4-methylethylphenol / p-tert-butylphenol mixture.

[0026] Furthermore, the heating is to raise the temperature to 60–120°C for the reaction.

[0027] Furthermore, the amount of isobutylene used is 1.5 to 5 times the molar amount of the 3,4-methylethylphenol / p-tert-butylphenol mixture.

[0028] Furthermore, the sodium hydroxide aqueous solution has a mass percentage of 10-35%.

[0029] Furthermore, the conditions for the reduced pressure distillation are: 100-200 theoretical plates in the distillation column, pressure -0.09 to -0.1 MPa, and reflux ratio 5-20:1.

[0030] Further, step (4) includes heating 6-tert-butyl-3,4-methylethylphenol and sulfuric acid to 180-200℃ and reacting for 0.5-3 hours. After sampling and analysis, if the 6-tert-butyl-3,4-methylethylphenol is ≤0.5% and qualified, the temperature is lowered to 40-80℃, and sodium hydroxide aqueous solution is added to neutralize to pH 7-8. 99% 3,4-methylethylphenol is obtained by vacuum distillation. The amount of sulfuric acid used is 0.5-3% of the mass of 6-tert-butyl-3,4-methylethylphenol. The conditions for vacuum distillation are 100-200 theoretical plates in the distillation column, pressure -0.08 to -0.095 MPa, and reflux ratio 5-20:1.

[0031] Further, step (5) includes heating the tri-tert-butylphenol, phenol, and sulfuric acid in a sealed container to 160-180°C for 2-4 hours, then cooling to 100-130°C for 2-6 hours. After sampling and analysis to ensure that the tri-tert-butylphenol content is ≤0.5%, the mixture is cooled and neutralized to neutral by adding an aqueous sodium hydroxide solution. The mixture is then distilled under reduced pressure to obtain at least two of the following: phenol, 2-tert-butylphenol, 4-tert-butylphenol, 2,4-di-tert-butylphenol, and 2,6-di-tert-butylphenol.

[0032] Furthermore, the phenol raw material is coal-derived phenol with a content of ≥99.5% and sulfur- and nitrogen-containing compounds of ≥100ppm.

[0033] Furthermore, the amount of phenol used is 0.18 to 1.0 times the mass of tri-tert-butylphenol.

[0034] Furthermore, the amount of sulfuric acid used is 0.5 to 3% of the mass of the tri-tert-butylphenol.

[0035] Furthermore, the conditions for the reduced pressure distillation are: 150-250 theoretical plate size in the distillation column, pressure -0.08 to -0.095 MPa, and reflux ratio 5-25:1.

[0036] Furthermore, the phenol product obtained by vacuum distillation has a phenol content of ≥99.5% and sulfur- and nitrogen-containing compounds of ≤5ppm.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention utilizes the difference in reactivity between a mixture of 3,4-methylethylphenol and formaldehyde to directly produce linear methylethylphenol-formaldehyde resin. Unreacted 3,4-methylethylphenol / p-tert-butylphenol mixtures are distilled off, and then the 3,4-methylethylphenol / p-tert-butylphenol mixture is further subjected to tert-butylation reaction, distillation, detert-butylation reaction, and distillation to obtain high-quality products 3,4-methylethylphenol, mono-tert-butylphenol, and di-tert-butylphenol. The process is simple, easy to operate, and has high added value, enabling comprehensive utilization of waste.

[0038] This invention transforms residue, valued at only about 2,000 yuan per ton, into high-purity phenolic monomers and resin products, significantly increasing added value. The high-purity 3,4-methylethylphenol obtained by this invention can replace tricresyl phosphate, which has some toxicity, in the production of the non-toxic, heat-resistant, flame-retardant plasticizer tricresyl phosphate. It can also replace 3,4-xylenol in the formation of fusible polyimide resins. Mono / di-tert-butylphenol is an important intermediate for antioxidants, phenolic resins, and other fine chemical products, with a clear and stable market demand. Attached Figure Description

[0039] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 This is a flowchart of the method for extracting methyl ethyl phenol from crude phenol refining residue and synthesizing tert-butyl phenol according to the present invention. Detailed Implementation

[0040] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0041] The following describes, in conjunction with the accompanying drawings, the method proposed in this invention for extracting methyl ethyl phenol from crude phenol refining residue and synthesizing tert-butyl phenol.

[0042] like Figure 1 As shown, the method of the present invention for extracting methyl ethyl phenol from crude phenol refining residue and synthesizing tert-butyl phenol includes the following steps: (1) The crude phenol refining residue was separated by distillation to obtain a mixture of 3,4-methylethylphenol; (2) The 3,4-methylethylphenol mixture is reacted with aldehydes, and the free phenol is removed by heating and distillation. The free phenol is then distilled to obtain a 3,4-methylethylphenol / p-tert-butylphenol mixture. The material from which the free phenol has been removed is heated and dehydrated under reduced pressure to obtain methylethylphenol aldehyde resin. (3) The 3,4-methylethylphenol / p-tert-butylphenol mixture and the catalyst were heated to carry out a tert-butylation reaction; 99% 6-tert-butyl-3,4-methylethylphenol and 99% tri-tert-butylphenol were obtained by vacuum distillation. (4) The 6-tert-butyl-3,4-methylethylphenol and sulfuric acid were heated and reacted; the mixture was cooled and neutralized to neutral by adding an aqueous sodium hydroxide solution; and 99% 3,4-methylethylphenol was obtained by vacuum distillation. (5) The tri-tert-butylphenol, phenol and sulfuric acid are reacted in a closed container; the mixture is cooled and neutralized to neutral by adding sodium hydroxide aqueous solution, and then distilled under reduced pressure to obtain tert-butylphenol, 2,4-di-tert-butylphenol and 2,6-di-tert-butylphenol.

[0043] In step (1), the crude phenol refining residue is distilled to obtain a mixture of 3,4-methylethylphenol. Specifically, crude phenol refining residue is added to a reaction vessel, the temperature is raised to 90-130°C, concentrated sulfuric acid is added dropwise, and after treatment, the material is distilled under reduced pressure, refluxed and dehydrated, and 3,4-methylethylphenol raw material is obtained at the top of the distillation column.

[0044] The crude phenol refining residue is the residue obtained after distilling phenol, cresol, and xylenol from crude phenol, with a distillation range ≥225℃. The amount of concentrated sulfuric acid added is 0.01~0.2wt% of the crude phenol refining residue, used to remove impurities. The purified crude phenol refining residue is then subjected to vacuum distillation under the following conditions: theoretical plate number of the distillation column 100~200, vacuum degree of -0.090~-0.1MPa, and reflux ratio of 25~40:1.

[0045] The 3,4-methylethylphenol mixture obtained by vacuum distillation includes 80-98 wt% 3,4-methylethylphenol / m-tert-butylphenol, 1-10 wt% 3-methyl-5-ethylphenol, 1-10 wt% 2,3,5-trimethylphenol, 0-1 wt% m-p-isopropylphenol, 0-1 wt% m-p-propylphenol, and 0-10 wt% other components; wherein the 3,4-methylethylphenol includes 4-ethyl-3-methylphenol and 3-ethyl-4-methylphenol, and the mass ratio of 3-ethyl-4-methylphenol to 4-ethyl-3-methylphenol is (0.2-1.5):1.

[0046] Step (2) is the aldehyde addition reaction process, in which the 3,4-methylethylphenol mixture is reacted with aldehydes, the free phenol is removed by distillation at a higher temperature, and the free phenol is distilled to obtain a 3,4-methylethylphenol / p-tert-butylphenol mixture; the material from which the free phenol has been removed is then dehydrated by heating under reduced pressure to obtain methylethylphenol aldehyde resin. Specifically, this includes: The 3,4-methylethylphenol mixture and catalyst were added to a reaction vessel, and the temperature was raised to 80-100°C. Aldehydes were added dropwise over 2-6 hours. The mixture was kept at this temperature for 5-12 hours and then sampled for analysis. When the 3,4-methylethylphenol content was less than 15%, the free phenol in the material was removed by distillation. The material was distilled to a vessel temperature of 110-120°C. After the distillate volume decreased significantly, the material was cooled to 70-80°C. The free phenol distillate was allowed to stand to separate the oil layer. The aqueous layer was extracted and then combined with the oil layer to obtain the organic layer. The organic layer was then distilled to obtain solvent reuse. The distillation yielded a mixture of 3,4-methylethylphenol and p-tert-butylphenol. After the free phenols are distilled off, the material is evacuated to -0.08 to -0.095 MPa, heated and dehydrated under reduced pressure. The temperature is raised to 190 to 200°C for 2 to 4 hours, and then kept at that temperature for 1 to 2 hours. The vacuum is then broken with nitrogen, and the material is discharged into a stainless steel tray while still hot under nitrogen protection to obtain ethyl phenol formaldehyde resin.

[0047] The catalyst comprises one or more of oxalic acid, formic acid, phosphoric acid, hydrochloric acid, benzoic acid, and benzenesulfonic acid, and the amount of the catalyst is 0.1-5 wt% of the 3,4-methylethylphenol mixture. The aldehyde comprises at least one of paraformaldehyde and formaldehyde aqueous solution, and the amount of the aldehyde is 0.7-1.4 molar of the 3,4-methylethylphenol mixture. The solvent is a non-aqueous solvent, including at least one of benzene, chlorinated hydrocarbons, chlorinated benzenes, ethers, ketones, and esters, and the amount of the non-aqueous solvent is 0.05-0.5% of the water layer mass. The distillation conditions are: theoretical plate count of 100-200, pressure of -0.08 to -0.090 MPa, and reflux ratio of 1-10:1.

[0048] In some embodiments, step (2) can also be performed in the following manner: The 3,4-methylethylphenol mixture and catalyst were added to a reaction vessel, and the temperature was raised to 80-100°C. The aldehydes were added dropwise over 2-6 hours, and the mixture was kept at this temperature for 5-12 hours before sampling and analysis. When the 3,4-methylethylphenol content was below 15%, glacial acetic acid or formic acid was added to neutralize the pH to 6-7. The vacuum was gradually increased to -0.07 to -0.1 MPa over 0.5-1 hours to begin dehydration. When the dehydration rate slowed down or the temperature dropped to around 70-75°C, the mixture was heated to continue dehydration. The final liquid temperature was controlled at 70-90°C until the water level reached the required value. The moisture content of the material was then sampled and analyzed to be ≤5%. Ethylene glycol is added to the polymerization reactor, stirred evenly, and samples are taken to analyze moisture and viscosity. Vacuuming is stopped when the moisture content is 2-5%. Ethanol is added to adjust the viscosity to 10-30 Pa·s according to the requirements of different products. After the viscosity reaches the requirement, the temperature is lowered to 50°C and the material is discharged. The amount of ethylene glycol used is 1-10% of the total amount of phenolic raw materials.

[0049] The catalyst further includes at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, barium hydroxide, ammonia, or an organic base; the amount of the catalyst is 0.1 to 5 wt% of the 3,4-methylethylphenol mixture. The aldehyde includes at least one of paraformaldehyde and an aqueous formaldehyde solution, and the amount of the aldehyde is 0.7 to 1.4 molar amounts of the 3,4-methylethylphenol mixture.

[0050] Step (3) is the tert-butylation process, in which the 3,4-methylethylphenol / p-tert-butylphenol mixture and the catalyst are heated to carry out the tert-butylation reaction; and 99% 6-tert-butyl-3,4-methylethylphenol and 99% tri-tert-butylphenol are obtained by vacuum distillation.

[0051] Step (3) includes heating the 3,4-methylethylphenol / p-tert-butylphenol mixture obtained in step (2) and the catalyst, then passing it through isobutylene for reaction. After sampling and analysis, if the 3,4-methylethylphenol content is ≤0.5wt% and it is qualified, the temperature is lowered to 40-80℃, and sodium hydroxide aqueous solution is added to neutralize to pH 7.5-9. The mixture is then subjected to vacuum distillation to obtain 99% 6-tert-butyl-3,4-methylethylphenol and 99% tri-tert-butylphenol.

[0052] The catalyst is at least one selected from sulfuric acid, benzenesulfonic acid, benzoic acid, and aminosulfonic acid. The amount of catalyst used is 1-10% of the mass of the 3,4-methylethylphenol / p-tert-butylphenol mixture. The temperature is increased to 60-120°C for the reaction. The amount of isobutylene used is 1.5-5 times the molar amount of the 3,4-methylethylphenol / p-tert-butylphenol mixture. The mass percentage of the sodium hydroxide aqueous solution is 10-35%. The conditions for vacuum distillation are: 100-200 theoretical plates in the distillation column, pressure -0.09 to -0.1 MPa, and reflux ratio 5-20:1.

[0053] Step (4) is the process of removing tert-butyl, in which the 6-tert-butyl-3,4-methylethylphenol and sulfuric acid are heated and reacted; the mixture is cooled and an aqueous sodium hydroxide solution is added to neutralize it to neutrality; and 99% 3,4-methylethylphenol is obtained by vacuum distillation.

[0054] Step (4) involves heating 6-tert-butyl-3,4-methylethylphenol and sulfuric acid to 180-200°C and reacting for 0.5-3 hours. After sampling and analysis, if the 6-tert-butyl-3,4-methylethylphenol content is ≤0.5%, the temperature is lowered to 40-80°C, and sodium hydroxide aqueous solution is added to neutralize to pH 7-8. 99% 3,4-methylethylphenol is obtained by vacuum distillation. The amount of sulfuric acid used is 0.5-3% of the mass of the 6-tert-butyl-3,4-methylethylphenol. The vacuum distillation conditions are: 100-200 theoretical plates in the distillation column, pressure -0.08 to -0.095 MPa, and reflux ratio 5-20:1.

[0055] In step (5), the tri-tert-butylphenol, phenol, and sulfuric acid are reacted in a closed system; the mixture is cooled and neutralized to neutral by adding an aqueous sodium hydroxide solution; and then distilled under reduced pressure to obtain tert-butylphenol, 2,4-di-tert-butylphenol, and 2,6-di-tert-butylphenol.

[0056] Step (5) specifically includes heating the tri-tert-butylphenol, phenol, and sulfuric acid in a sealed container to 160-180°C for 2-4 hours, then cooling to 100-130°C for 2-6 hours. After sampling and analysis, if the tri-tert-butylphenol content is ≤0.5%, the mixture is cooled and neutralized to neutral by adding sodium hydroxide aqueous solution. The mixture is then distilled under reduced pressure to obtain at least two of the following: phenol, 2-tert-butylphenol, 4-tert-butylphenol, 2,4-di-tert-butylphenol, and 2,6-di-tert-butylphenol.

[0057] In step (5), the phenol raw material used is coal-derived phenol with a content ≥99.5% and sulfur and nitrogen compounds ≥100ppm. The amount of phenol used is 0.18 to 1.0 times the mass of tri-tert-butylphenol. The phenol product obtained by vacuum distillation has a phenol content ≥99.5% and sulfur and nitrogen compounds ≤5ppm. The amount of sulfuric acid used is 0.5 to 3% of the mass of tri-tert-butylphenol. The phenol product obtained by vacuum distillation has a phenol content ≥99.5% and sulfur and nitrogen compounds ≤5ppm.

[0058] This invention addresses the shortcomings of existing technologies by using efficient distillation to extract 3,4-methylethylphenol from crude phenol refining residue, obtaining a mixture of 3,4-methylethylphenol. Taking advantage of the characteristic that the 3,4-methylethylphenol mixture reacts with aldehydes to form linear phenolic resin, the 3,4-methylethylphenol fraction is reacted with aldehydes to generate low-molecular-weight methylethylphenol resin. Then, the unreacted mixture of 3,4-methylethylphenol and p-tert-butylphenol is distilled off, followed by slow polymerization while simultaneously heating and dehydrating. Dehydration is maintained at 190–200°C to obtain linear methylethylphenol resin with good processing properties. Thus, the purpose of extracting the mixture of 3,4-methylethylphenol and p-tert-butylphenol is achieved simultaneously with the synthesis of phenolic resin.

[0059] Then, 6-tert-butyl-3,4-methylethylphenol and tri-tert-butylphenol are generated by tert-butylation reaction, thereby increasing the boiling point difference between the two. High-purity 6-tert-butyl-3,4-methylethylphenol can be easily obtained by distillation. After removing the tert-butyl group and distilling, high-purity 3,4-methylethylphenol is obtained. Tri-tert-butylphenol undergoes a disproportionation reaction with phenol, and distillation yields 2,6-di-tert-butylphenol, 2,4-di-tert-butylphenol, p-tert-butylphenol, and o-tert-butylphenol.

[0060] The high-purity 3,4-methylethylphenol obtained by this invention, since there is no alkyl group at the ortho position of the hydroxyl group, can be used to produce non-toxic, heat-resistant, flame-retardant plasticizer tri(methyl)ethyl phosphate, replacing the somewhat toxic tricresol phosphate; it can also replace 3,4-xylenol to generate fusible polyimide resins.

[0061] The p-tert-butylphenol obtained in this invention is used as an antioxidant and a raw material for phenolic resins; o-tert-butylphenol is mainly used as an antioxidant, plant protectant, intermediate for synthetic resins, pharmaceuticals, and pesticides, as well as a raw material for fragrances and flavors; 2,4-di-tert-butylphenol, as a core raw material for phosphite antioxidants, is widely used in the production of antioxidants 168, 626, etc., and is also a key component of light stabilizers and high-efficiency emulsifier intermediates; 2,6-di-tert-butylphenol is mainly used to manufacture antioxidants for natural and synthetic rubber, plastic antioxidants, fuel stabilizers, ultraviolet absorbers, and pesticide and dye intermediates, etc., with main varieties including antioxidants 1010, 1076, 702, 3114, 4426, methylene 4426-S, 2002, 330, 1098, 1088, etc.

[0062] The present invention will now be described in detail with reference to specific embodiments.

[0063] Example 1: (1) Refining and purification of phenolic residues by distillation The crude phenol refining residue (crude phenol extracted from medium- and low-temperature phenol-containing coal tar at re-extraction) was distilled, and a fraction before distillation at 238℃ was analyzed. This fraction accounted for 13.33% of the crude phenol refining residue. Chromatographic analysis showed the following components: 3,5-xylenol 0.12%, 2,4,6-trimethylphenol 0.57%, 2,4 / 2,5-methylethylphenol 0.81%, 3,4-xylenol 1.62%, and 2,3,6-trimethylphenol. 0.13%, o-tert-butylphenol 0.43%, p-isopropylphenol 8.84%, m-isopropylphenol 9.96%, 2,3-methylethylphenol 4.81%, p-propylphenol 3.82%, m-propylphenol 4.22%, 3-ethyl-5-methylphenol 28.84%, 2,3,5-trimethylphenol 16.12%, 3,4-methylethylphenol 15.29%, m-p-tert-butylphenol 1.46%, others 2.96%.

[0064] Add 450,000 parts of the crude phenol distillation residue to the bottom of a distillation column (200 trays), add 450 parts of 98% sulfuric acid, heat to 120℃, and then perform vacuum distillation (vacuum degree -0.09MPa, reflux ratio 30:1, top temperature 155-185℃). Samples are taken every hour to analyze the content of various phenols. The fraction containing ≤50% of the mixture of m- and p-isopropylphenol / m- and p-propylphenol is collected before distillation. Then, the m- and p-isopropylphenol mixture is collected. For the distillation sections of isopropylphenol / m-p-propylphenol / 2,3-methylethylphenol; when 3-ethyl-5-methylphenol ≥ 50%, crude 3-methyl-5-ethylphenol is collected instead; when 2,3,5-trimethylphenol ≥ 50%, crude 2,3,5-trimethylphenol is collected instead; when 3,4-methylethylphenol ≥ 50%, crude 3,4-methylethylphenol is collected instead; when 3,4-methylethylphenol ≤ 50%, collection of crude 3,4-methylethylphenol is stopped, the temperature is lowered, and distillation is stopped, leaving 388,542 parts of residue in the still.

[0065] The composition of each fraction is shown in Table 1 below: Table 1:

[0066] (2) Resin synthesis 2000 parts of 3,4-methylethylphenol fraction obtained from distillation in (1), 30 parts of oxalic acid (60 parts dissolved in water), and 15 parts of formic acid were added to the reactor. After feeding, the stirring was started, the reflux and venting devices were adjusted, the steam valve was opened to raise the temperature, and the steam pressure should not exceed 0.3 MPa. 1250 parts of 36.5% formaldehyde (the molar ratio of formaldehyde to 3,4-methylethylphenol fraction was 1.04:1) were gradually added dropwise at 100℃ for 3 hours. After the addition was completed, the reaction was kept at 98-100℃. The reaction was kept at 8 hours and the sample was taken for analysis. The liquid chromatography analysis showed that 4.6% of 3,4-methylethylphenol was qualified.

[0067] Steam distillation was performed to remove free phenols from the material. The condensate was observed to contain no obvious oily substances. When no obvious oily substances were found in the condensate, the temperature was increased to 115℃, indicating the removal of free phenols from the material was complete. The temperature was then slightly lowered. The distillate separated into layers. The lower layer was a mixture of p-tert-butylphenol and 3,4-methylethylphenol. The aqueous layer was extracted twice with toluene (100 parts each time, extraction temperature 40℃). The mixed phenol layer and the toluene layer were combined and distilled at atmospheric pressure to obtain 198.4 parts of toluene, which was then reused. Distillation at -0.085 MPa and a reflux ratio of 5:1 yielded 144.2 parts of a mixture of 3,4-methylethylphenol and p-tert-butylphenol (59.6 parts of p-tert-butylphenol, 83 parts of 3,4-methylethylphenol, and 1.6 parts of other substances).

[0068] After removing free phenol, adjust the vacuum device in the material, slowly vacuum and continue heating to dehydrate, controlling the final pressure at -0.090 to -0.095 MPa. First, heat to 120℃ and hold for 1 hour; then further increase the temperature to dehydrate. When the material temperature in the reactor reaches 200℃ and no liquid distills out, hold for 1 hour, stop dehydration, release the vacuum with nitrogen, and under nitrogen protection, release the hot material into a stainless steel pan to cool, then crush and bag it to obtain 2012.4 parts of ethyl phenol formaldehyde resin, which is light yellow and transparent, with a thermal decomposition temperature of 401.3℃.

[0069] (3) Separation of a mixture of 3,4-methylethylphenol and p-tert-butylphenol Add 72.1 parts of the mixture of 3,4-methylethylphenol and p-tert-butylphenol obtained in step (2) (29.8 parts of p-tert-butylphenol, 41.5 parts of 3,4-methylethylphenol, and 0.8 parts of other components) and 2 parts of sulfuric acid (2.77% of the mass of the mixture of 3,4-methylethylphenol and p-tert-butylphenol) to the reactor under stirring. Heat the reactor to 70°C and introduce 70 parts of isobutylene (2.77% of the molar mass of the mixture of 3,4-methylethylphenol and p-tert-butylphenol) for reaction. (45 times), isobutylene was introduced for 7.5 hours, followed by a 2-hour heat preservation reaction. Analysis showed 0.28% 3,4-methylethylphenol was within acceptable limits, and 24.3 parts of isobutylene were recovered and reused. 5.1 parts of 32% liquid sodium hydroxide aqueous solution were added to neutralize to pH 7.5, the aqueous layer was separated, and the remaining material was added to a high-efficiency distillation column (theoretical plate 160). Distillation was carried out at -0.095 MPa and a reflux ratio of 10:1 to obtain 3.2 parts of diisobutylene, 55.2 parts of 99.5% 6-tert-butyl-3,4-methylethylphenol, and 46.7 parts of 99.1% tri-tert-butylphenol.

[0070] (4) Synthesis of 3,4-methylethylphenol 55.2 parts of 99.5% 6-tert-butyl-3,4-methylethylphenol and 0.6 parts of 98% concentrated sulfuric acid (1.09% of the mass of 6-tert-butyl-3,4-methylethylphenol) were mixed and stirred, and the mixture was heated to 195℃ for 2 hours. Sampling and analysis showed that the 6-tert-butyl-3,4-methylethylphenol content was 0.33%, which is acceptable. The mixture was then cooled to 60℃ and neutralized to pH 8 with 1.55 parts of 32% alkaline sodium hydroxide aqueous solution. The mixture separated into layers. The material layer was then subjected to vacuum distillation at -0.09 MPa and a reflux ratio of 5:1 (theoretical plate 160) to obtain 36.7 parts of 99.6% 3,4-methylethylphenol, with a yield of 94.0%. 15.1 parts of isobutylene were recovered and reused.

[0071] (5) Synthesis of p-tert-butylphenol and o-tert-butylphenol 46.7 parts of 99.1% tri-tert-butylphenol, 46 parts of 99.6% phenol (obtained by refining crude phenol from coal tar extraction, containing 820 ppm nitrogen compounds and 127 ppm sulfides; the amount of phenol used is 0.98 times the mass of tri-tert-butylphenol), and 1 part of 98% sulfuric acid (2.14% of the mass of tri-tert-butylphenol) were added to a high-pressure reactor. The reactor was sealed, stirred, and heated to 180℃. The reaction was maintained at this temperature for 3 hours. Samples were taken for analysis. The levels of tri-tert-butylphenol (0.02%) and di-tert-butylphenol (0.43%) were found to be within acceptable limits. The temperature was then lowered to 110℃ and the reaction was continued for 5 hours. After 1 hour, the pressure inside the reactor stabilized at 0.03 MPa. The reaction was then stopped, the temperature was lowered to 60°C, and the pressure was released to atmospheric pressure. 2.55 parts of 32% liquid sodium hydroxide aqueous solution were added to neutralize to pH 7.5. The aqueous layer was separated, and the material layer was subjected to vacuum distillation (theoretical plate 200) at -0.09 MPa and a reflux ratio of 20:1 to obtain 12.5 parts of 99.8% phenol (containing 2.2 ppm of nitrogen compounds and 3.1 ppm of sulfides), 18.4 parts of 99.5% o-tert-butylphenol, and 45.4 parts of 99.7% p-tert-butylphenol.

[0072] Example 2 (1) The distillation preparation of the 3,4-methylethylphenol mixture is the same as in Example 1.

[0073] (2) Resin synthesis Add 500 parts of the 3,4-methylethylphenol mixture obtained by distillation in Example 1 (1) and 30 parts of 25% ammonia water to the reactor, stir evenly, turn on the steam to heat to 90-95°C, add 400 parts of 37% formaldehyde (the molar ratio of formaldehyde to 3,4-methylethylphenol fraction is 1.35:1) dropwise, add for 4 hours, and keep warm at 98-100°C for 6 hours.

[0074] After the reaction is complete, add glacial acetic acid to neutralize to neutral. Maintain neutrality for 10 minutes to determine if it is qualified. Then start the vacuum pump to draw a vacuum. After the vacuum stabilizes, start dehydration. Observe the dehydration speed as it slows down or until the temperature drops to about 70-75℃. Then turn on the jacket steam heating. During dehydration, the steam switch should be adjusted continuously according to the water output speed to make dehydration as low as possible. Specifically, control the temperature below 75℃ in the early stage of dehydration. After the water output slows down, continue to pass steam to control the final liquid temperature at about 90℃. When the water level drops to about 322 parts, take a sample to analyze the water content and viscosity. Stop vacuuming when the water content is 2.3% and add 13 parts of ethylene glycol to adjust the viscosity to the specified value of 18 Pa·s.

[0075] After the viscosity reaches the required level, the temperature is lowered to 50°C and 553 parts are discharged. The material is a yellow to light red transparent liquid, which is the thermosetting phenolic resin. It can be used as a binder for refractory materials, foaming materials, and thermal insulation materials.

[0076] The separated water was left to stand for 1 hour to separate into layers, yielding 48.1 parts of free phenol (15.8 parts of p-tert-butylphenol, 31.6 parts of 3,4-methylethylphenol, and 0.7 parts of other components). The separated water layer was sent to the waste treatment workshop for further processing.

[0077] (3) 48.1 parts of a mixture of 3,4-methylethylphenol and p-tert-butylphenol obtained in (2) (15.8 parts of p-tert-butylphenol, 31.6 parts of 3,4-methylethylphenol, and 0.7 parts of other components) and 1.5 parts of sulfuric acid (3.12% of the mass of the mixture of 3,4-methylethylphenol and p-tert-butylphenol) were heated to 110°C with stirring and 48 parts of isobutylene (2.5 times the molar mass of the mixture of 3,4-methylethylphenol and p-tert-butylphenol) were introduced for 4 hours. After a 1.5-hour heat preservation reaction, a sample analysis showed that 0.19% of 3,4-methylethylphenol was qualified, and 19.1 parts of isobutylene were recovered and reused. 1.22 parts of 32% liquid sodium hydroxide aqueous solution were added to neutralize to pH 7.5, the water layer was separated, and the material layer was added to a high-efficiency distillation column (theoretical plate 160). Distillation was carried out at -0.095 MPa and a reflux ratio of 10:1 to obtain 2.9 parts of diisobutylene, 41.9 parts of 99.3% 6-tert-butyl-3,4-methylethylphenol, and 24.7 parts of 99.2% tri-tert-butylphenol.

[0078] (4) Synthesis of 3,4-methylethylphenol 41.9 parts of 99.3% 6-tert-butyl-3,4-methylethylphenol and 0.5 parts of 98% concentrated sulfuric acid (1.19% of the mass of 6-tert-butyl-3,4-methylethylphenol) were mixed and stirred, and the temperature was raised to 190℃ for 3 hours. After sampling and analysis, the content of 6-tert-butyl-3,4-methylethylphenol was 0.26%, which is qualified. 1.27 parts of 32% alkaline sodium hydroxide aqueous solution were added to neutralize to pH 8, and the mixture was separated into layers. The material layer was subjected to vacuum distillation at -0.09 MPa and a reflux ratio of 10:1 (theoretical plate 160) to obtain 27.8 parts of 99.5% 3,4-methylethylphenol, with a yield of 93.8%. 11.8 parts of isobutylene were recovered and reused.

[0079] (5) Synthesis of 2,6-di-tert-butylphenol, 2,4-di-tert-butylphenol, etc. 24.7 parts of 99.2% tri-tert-butylphenol, 4.4 parts of 99.6% phenol (obtained by refining crude phenol from coal tar extraction, containing 820 ppm nitrogen compounds and 127 ppm sulfides; the amount of phenol used is 0.18 times the mass of tri-tert-butylphenol), and 0.7 parts of 98% sulfuric acid (2.83% of the mass of tri-tert-butylphenol) were added to a high-pressure reactor. The reactor was sealed, stirred, and heated to 170℃. The reaction was maintained at this temperature for 3 hours. Sampling and analysis showed that the tri-tert-butylphenol content was 0.31%, which was acceptable. The temperature was then lowered to 130℃ and the reaction was continued for 4 hours. At this point, the pressure inside the reactor stabilized at 0.05 MPa. The reaction was then stopped, and the temperature was lowered to 60℃. The pressure was released to atmospheric pressure, and 1.8 parts of 32% liquid sodium hydroxide aqueous solution were added to neutralize to pH 8. The aqueous layer was separated, and the material layer was subjected to vacuum distillation at -0.095 MPa and a reflux ratio of 20:1 (theoretical plate 200) in a single distillation to obtain 99.6% phenol. 10.1 parts of 2,6-di-tert-butylphenol and 15.2 parts of 99.5% 2,4-di-tert-butylphenol.

[0080] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms may refer to different embodiments or examples. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0081] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0082] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for extracting methyl ethyl phenol from crude phenol refining residue and synthesizing tert-butylphenol, characterized in that, Includes the following steps: (1) The crude phenol refining residue was separated by distillation to obtain a mixture of 3,4-methylethylphenol; (2) The 3,4-methylethylphenol mixture is reacted with aldehydes, and the free phenol is removed by heating and distillation. The free phenol is then distilled to obtain a 3,4-methylethylphenol / p-tert-butylphenol mixture. The material from which the free phenol has been removed is heated and dehydrated under reduced pressure to obtain methylethylphenol aldehyde resin. (3) The 3,4-methylethylphenol / p-tert-butylphenol mixture and the catalyst were heated to carry out a tert-butylation reaction; 99% 6-tert-butyl-3,4-methylethylphenol and 99% tri-tert-butylphenol were obtained by vacuum distillation. (4) The 6-tert-butyl-3,4-methylethylphenol and sulfuric acid were heated and reacted; the mixture was cooled and neutralized to neutral by adding an aqueous sodium hydroxide solution; and 99% 3,4-methylethylphenol was obtained by vacuum distillation. (5) The tri-tert-butylphenol, phenol and sulfuric acid are reacted in a closed container; the mixture is cooled and neutralized to neutral by adding sodium hydroxide aqueous solution, and then distilled under reduced pressure to obtain tert-butylphenol, 2,4-di-tert-butylphenol and 2,6-di-tert-butylphenol.

2. The method as described in claim 1, characterized in that, Step (1) includes adding crude phenol refining residue to a reactor, heating to 90-130°C, adding concentrated sulfuric acid dropwise, distilling the material under reduced pressure after treatment, refluxing to remove water, and obtaining 3,4-methylethylphenol raw material at the top of the distillation column. The crude phenol refining residue is the residue after distilling phenol, cresol, and xylenol from crude phenol, with a distillation range ≥225°C. The 3,4-methylethylphenol mixture includes 80-98 wt% 3,4-methylethylphenol / m-tert-butylphenol, 1-10 wt% 3-methyl-5-ethylphenol, and 1-10 wt% 2,3,5-trimethylphenol. The 3,4-methylethylphenol comprises 4-ethyl-3-methylphenol and 3-ethyl-4-methylphenol, wherein the mass ratio of 3-ethyl-4-methylphenol to 4-ethyl-3-methylphenol is (0.2-1.5):1; the amount of concentrated sulfuric acid added is 0.01-0.2 wt% of the crude phenol refining residue; and the conditions for vacuum distillation are: 100-200 theoretical plates in the distillation column, a vacuum degree of -0.090 to -0.1 MPa, and a reflux ratio of 25-40:

1.

3. The method as described in claim 2, characterized in that, Step (2) includes: The 3,4-methylethylphenol mixture and catalyst are added to a reaction vessel, and the temperature is raised to 80-100°C. Aldehydes are added dropwise over 2-6 hours, and the mixture is kept at this temperature for 5-12 hours before sampling and analysis. When the 3,4-methylethylphenol content is below 15%, the free phenol in the material is removed by distillation. The distillation is carried out until the vessel temperature reaches 110-120°C. After the distillate volume is significantly reduced, the material is cooled to 70-80°C. The catalyst includes one or more of oxalic acid, formic acid, phosphoric acid, hydrochloric acid, benzoic acid, and benzenesulfonic acid. The free phenol distillate is allowed to stand to separate the oil layer. After extraction of the aqueous layer, the oil layer is combined with the aqueous layer to obtain the organic layer. The organic layer is then distilled to obtain a solvent for reuse. The distillation yields a mixture of 3,4-methylethylphenol and p-tert-butylphenol. The solvent is a non-aqueous solvent, including at least one of benzene, chlorinated hydrocarbons, chlorinated benzenes, ethers, ketones, and esters. The amount of the non-aqueous solvent is 0.05 to 0.5 times the mass of the aqueous layer. The distillation conditions are: 100 to 200 theoretical plates in the distillation column, pressure -0.08 to -0.090 MPa, and reflux ratio 1 to 10:

1. After the free phenols are distilled off, the material is evacuated to -0.08 to -0.095 MPa, heated and dehydrated under reduced pressure. The temperature is raised to 190 to 200°C for 2 to 4 hours, and then kept at that temperature for 1 to 2 hours. The vacuum is then broken with nitrogen, and the material is discharged into a stainless steel tray while still hot under nitrogen protection to obtain ethyl phenol formaldehyde resin.

4. The method as described in claim 2, characterized in that, Step (2) includes: The 3,4-methylethylphenol mixture and catalyst are added to a reaction vessel, and the temperature is raised to 80-100°C. Aldehydes are added dropwise over 2-6 hours, and the mixture is kept at this temperature for 5-12 hours before sampling and analysis. When the 3,4-methylethylphenol content is less than 15%, glacial acetic acid or formic acid is added to neutralize the pH to 6-7. The vacuum is gradually increased to -0.07 to -0.1 MPa over 0.5-1 hours to begin dehydration. When the dehydration rate slows down or the temperature drops to around 70-75°C, heating is resumed to continue dehydration. The final liquid temperature is controlled at 70-90°C until the water level reaches the required value. The moisture content of the material is sampled and analyzed to be ≤5%. The catalyst also includes at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, barium hydroxide, ammonia, or an organic base. Ethylene glycol is added to the reactor, stirred evenly, and samples are taken to analyze the moisture and viscosity. When the moisture content is 2-5%, the vacuum is stopped, and ethanol is added to adjust the viscosity to 10-30 Pa·s according to the requirements of different products. After the viscosity reaches the requirement, the temperature is lowered to 50°C and the material is discharged. The amount of ethylene glycol used is 1-10% of the total amount of phenolic raw materials.

5. The method as described in claim 3 or 4, characterized in that, The amount of catalyst used is 0.1~5 wt% of the 3,4-methylethylphenol mixture; And / or, the aldehydes include at least one of paraformaldehyde and aqueous formaldehyde solution; And / or, the amount of the aldehyde is 0.7 to 1.4 molar amounts of the 3,4-methylethylphenol mixture.

6. The method as described in claim 1, characterized in that, Step (3) includes heating the 3,4-methylethylphenol / p-tert-butylphenol mixture obtained in step (2) and the catalyst, then passing it through isobutylene for reaction. After sampling and analysis, if the 3,4-methylethylphenol content is ≤0.5wt%, the mixture is cooled to 40-80℃, and sodium hydroxide aqueous solution is added to neutralize it to pH 7.5-9. The mixture is then subjected to vacuum distillation to obtain 99% 6-tert-butyl-3,4-methylethylphenol and 99% tri-tert-butylphenol.

7. The method as described in claim 6, characterized in that, The catalyst is at least one of sulfuric acid, benzenesulfonic acid, benzoic acid, and aminosulfonic acid; And / or, the amount of the catalyst used is 1 to 10% of the mass of the 3,4-methylethylphenol / p-tert-butylphenol mixture; And / or, the heating is to raise the temperature to 60–120°C for the reaction; And / or, the amount of isobutylene used is 1.5 to 5 times the molar amount of the 3,4-methylethylphenol / p-tert-butylphenol mixture; And / or, the sodium hydroxide aqueous solution has a mass percentage of 10-35%; And / or, the conditions for the reduced pressure distillation are: 100-200 theoretical plates in the distillation column, pressure -0.09--0.1 MPa, and reflux ratio 5-20:

1.

8. The method as described in claim 1, characterized in that, Step (4) involves heating 6-tert-butyl-3,4-methylethylphenol and sulfuric acid to 180-200°C and reacting for 0.5-3 hours. After sampling and analysis, if the 6-tert-butyl-3,4-methylethylphenol content is ≤0.5%, the temperature is lowered to 40-80°C, and sodium hydroxide aqueous solution is added to neutralize to pH 7-8. 99% 3,4-methylethylphenol is obtained by vacuum distillation. The amount of sulfuric acid used is 0.5-3% of the mass of the 6-tert-butyl-3,4-methylethylphenol. The vacuum distillation conditions are: 100-200 theoretical plates in the distillation column, pressure -0.08 to -0.095 MPa, and reflux ratio 5-20:

1.

9. The method as described in claim 1, characterized in that, Step (5) involves heating the tri-tert-butylphenol, phenol, and sulfuric acid in a sealed container to 160–180°C for 2–4 hours, then cooling to 100–130°C for 2–6 hours. After sampling and analysis to confirm that the tri-tert-butylphenol content is ≤0.5%, the mixture is cooled and neutralized to neutral by adding an aqueous sodium hydroxide solution. The mixture is then distilled under reduced pressure to obtain at least two of the following: phenol, 2-tert-butylphenol, 4-tert-butylphenol, 2,4-di-tert-butylphenol, and 2,6-di-tert-butylphenol.

10. The method as described in claim 9, characterized in that, The phenol raw material is coal-derived phenol with a content of ≥99.5% and sulfur- and nitrogen-containing compounds of ≥100ppm; And / or, the amount of phenol used is 0.18 to 1.0 times the mass of tri-tert-butylphenol; And / or, the amount of sulfuric acid used is 0.5% to 3% of the mass of the tri-tert-butylphenol; And / or, the conditions for the reduced pressure distillation are: 150-250 theoretical plates in the distillation column, pressure -0.08 to -0.095 MPa, and reflux ratio 5-25:1; And / or, the phenol product obtained by vacuum distillation has a phenol content of ≥99.5% and sulfur- and nitrogen-containing compounds of ≤5ppm.

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