Method for separating various phenols from mixed cresol

Abstract

The invention belongs to the field of synthesis and separation of coalification products, and particularly relates to a method for separating various phenols from mixed cresol. According to the method, the mixed cresol is used as a raw material, ethyl in o-ethyl phenol in the m-cresol / o-ethyl phenol mixture is removed through the dealkylation catalyst to generate phenol and ethylene, and due to the fact that the ethyl removal reaction is carried out in the presence of the specific catalyst at a low temperature, few methyl in phenolic substances can be subjected to removal and transposition reactions; the method comprises the following steps: firstly, decomposing ethylene, then quantitatively reacting the ethylene obtained by decomposition with o-cresol in a 2, 6-xylenol crude product under the catalysis of a cresol aluminum catalyst to generate 2-ethyl-6-cresol, and rarely reacting with 2, 6-xylenol to generate 4-ethyl-2, 6-xylenol, thereby achieving the purpose of purifying 2, 6-xylenol. The lysate and the alkylation reaction liquid are respectively rectified to obtain high-quality phenol, m-p-cresol, 2, 6-xylenol and 2-ethyl-6-cresol, and the method is simple and easy to operate, few in three wastes and low in production cost.

Description

Technical Field

[0001] This invention belongs to the field of coal chemical product synthesis and separation, and specifically relates to a method for separating multiple phenols from a mixture of cresols. Background Technology

[0002] Crude phenol is distilled to obtain phenol, o-cresol, tri-cresol, 45% m-p-cresol, 99% m-p-cresol, and industrial xylenol. These are sold directly as products without proper fine separation. Crude phenol extracted from high-temperature coal tar has a high o-ethylphenol content, reaching about 10% of the m-p-cresol content. Due to their similar boiling points, conventional distillation cannot separate them, which seriously limits the application of m-p-cresol. Because ethylphenol undergoes deethylation more readily than methylphenol at high temperatures or in the presence of a catalyst (especially an acidic catalyst), since the temperature required for demethylation is significantly higher than that required for deethylation, the ethyl group in o-ethylphenol can be removed by controlling the reaction temperature to produce phenol and ethylene. Then, using aluminum cresol as a catalyst for ortho-alkylation of phenolic hydroxyl groups, ethylene reacts with o-cresol in crude 2,6-xylenol to produce 2-ethyl-6-xylenol. 2,6-xylenol cannot undergo ortho-ethylation of phenolic hydroxyl groups with ethylene. After alkylation of o-cresol with ethylene catalyzed by aluminum cresol, the reaction solution contains 2,6-xylenol and 2-ethyl-6-xylenol. Further distillation yields petrochemical-grade high-purity 2,6-xylenol and high-purity pesticide intermediate 2-ethyl-6-xylenol, thus achieving the goal of purifying 2,6-xylenol.

[0003] The crude phenol extracted from high-temperature phenolic coal tar contains a relatively high content of 2,6-xylenol, which increases the difficulty of distilling to extract o-cresol. This process also produces a crude 2,6-xylenol product with a high 2,6-xylenol content. This crude 2,6-xylenol product contains a certain amount of o-cresol. Due to the relatively high volatility of 2,6-xylenol, purification by distillation alone is difficult. This invention uses aluminum phenolate as a catalyst to carry out the ortho-ethylation reaction of the phenolic hydroxyl group. By sampling and detecting, reaction data is obtained in a timely manner, thereby converting o-cresol in 2,6-xylenol into 2-ethyl-6-cresol. Since m- and p-cresol also undergo ortho-ethylation of the hydroxyl group, to reduce separation difficulty and avoid raw material waste, this invention has strict requirements on the m- and p-cresol content in the crude 2,6-xylenol product, preferably ≤1%. At the same time, to reduce the side reaction between 2,6-xylenol and ethylene, the o-cresol content is also controlled to ≤40%.

[0004] The reaction solution after removing the ethyl group from o-ethylphenol contains phenol and m-p-cresol (due to the lower temperature during ethyl removal, the cresol transposition reaction is less likely to occur). Because acidification is used, the phenol and m-p-cresol obtained by distillation of the reaction solution contain very few sulfur and nitrogen-containing compounds. Therefore, this invention obtains high-purity m-p-cresol while removing o-ethylphenol to produce 2-ethyl-6-cresol.

[0005] 2-Ethyl-6-cresol: CAS1687-64-5, mp48℃, bp214℃, is an alkylphenol isolated from the oncogenic neutral subfraction of cigarette smoke condensate. It has insecticidal and fungicidal activities and is a raw material for the synthesis of the pesticide intermediate 2-ethyl-N-(2-methoxy-1-methylethyl)-6-methylaniline.

[0006] 2,6-Dimethylphenol: CAS1576-26-1, mp43℃, bp203℃, is a white crystalline powder, readily soluble in alcohols, ethers, chloroform, benzene and alkaline solutions, slightly soluble in water. It is used in the production of polyphenylene ether resins, photographic chemicals, pesticides, polyesters and polyether resins, and is also a raw material for the antiarrhythmic drug Slow Rhythmia. Summary of the Invention

[0007] The technical problem to be solved by this invention is that the o-ethylphenol content in crude p-cresol extracted from phenolic coal tar is too high in the existing technology, which seriously affects the application of p-cresol products in separation, resin synthesis, and auxiliary agent synthesis. This invention provides a method that uses mixed cresols as raw materials, and selectively removes the ethyl group from the o-ethylphenol in the p-cresol / o-ethylphenol mixture to generate phenol and ethylene by using a suitable dealkylation catalyst at an appropriate temperature. Because the deethylation reaction is carried out under a specific catalyst and at a relatively low temperature, the methyl groups in the phenolic substances rarely undergo removal or transposition reactions. Then, the ethylene obtained from the decomposition reacts quantitatively with the o-cresol in crude 2,6-xylenol under the catalysis of aluminum cresol catalyst to generate 2-ethyl-6-cresol, while reacting very little with 2,6-xylenol to generate 4-ethyl-2,6-xylenol, thereby achieving the purpose of purifying 2,6-xylenol. The pyrolysis solution and alkylation reaction solution are separately distilled to obtain high-quality phenol, m-p-cresol, 2,6-xylenol, and 2-ethyl-6-cresol. This invention is simple to operate, produces little waste, and has low production costs.

[0008] To address the aforementioned technical problems, this invention discloses a method for separating multiple phenols from a mixture of cresols, comprising the following steps:

[0009] S1: Heat the mixed cresols, mix them with sulfuric acid, and transfer them to the bottom of the distillation column. Dehydrate them by distillation under reduced pressure. When the condensate at the top of the distillation column is clear, the dehydration is finished. Adjust the pressure to -0.07 to -0.09 MPa and reflux for 1 to 3 hours. Take samples every hour to analyze the gas chromatographic content of o-cresol and the moisture content. When the o-cresol content is ≥99% and the moisture content is ≤0.2%, adjust the reflux ratio to (15~20):1 and collect the o-cresol. Stop collecting when the o-cresol content is ≤99% for the second time.

[0010] S2. Add ethylene glycol to the bottom of the distillation column and reflux for 1-2 hours. Remove neutral oil at a pressure of -0.07 to -0.09 MPa and a reflux ratio of (0.5-2):1. Take samples for analysis every hour. When the neutral oil content decreases to ≤5% and the ethylene glycol content is ≤0.1%, adjust the reflux ratio to (10-20):1 and start collecting the o-cresol / 2,6-xylenol mixture. When the 2,6-xylenol content is ≥50%, collect the 2,6-xylenol / o-cresol mixture. When the 2,6-xylenol content is ≥99%, remove the mixture from the bottom of the distillation column. Sulfuric acid is added to the distillate at a reflux ratio of (10-15):1 to begin collecting 2,6-xylenol. When the 2,6-xylenol content is again ≤99%, collection of 2,6-xylenol is stopped, and the distillate is then collected at a reflux ratio of (20-25):1 for reuse to recover 2,6-xylenol. When the 2,6-xylenol content is ≤5%, the m-p-cresol / o-ethylphenol mixture is collected at a reflux ratio of (15-20):1. When the cresol fraction contains ≥5% 2,4-xylenol / 2,5-xylenol, distillation is stopped, and the bottom stock is transferred to the m-p-cresol distillate column.

[0011] S3. The mixture of m-p-cresol and o-ethylphenol is separated by a deethylation reaction to obtain phenol and m-p-cresol;

[0012] S4. The 2,6-xylenol / o-cresol mixture was separated by alkylation to obtain 2,6-xylenol and 2-ethyl-6-cresol.

[0013] The mixed cresol is derived from crude phenol refined by solvent extraction of phenol-containing coal tar.

[0014] In S1, the temperature of the heating is 100-130℃; the concentration of the sulfuric acid is 95-98%, and the amount used is 0.01-0.5% of the mass of the mixed cresol; the process parameters of the vacuum distillation dehydration are: 150-300 theoretical plates and a pressure of -0.01 to -0.07 MPa.

[0015] In S2, the neutral oil content is calculated based on the naphthalene content; the ethylene glycol is used in an amount 2 to 10 times the mass of the neutral oil in the mixed cresol; and the sulfuric acid has a concentration of 95 to 98% and is used in an amount of 0.01 to 0.5% of the mass of the mixed cresol.

[0016] Specifically, in some embodiments of the present invention, the following are separated using the above separation method:

[0017] Distillation yields ≥99.5% o-cresol (sulfides and pyridine bases are both less than 1 ppm), which can be used to produce o-cresol epoxy phenolic resin; a mixture of o-cresol and 2,6-xylenol is obtained (o-cresol ≥65%), which can be used to produce 4-tert-butyl-2,6-xylenol, 6-tert-butyl-o-cresol, and can also be used to produce o-methyl anisole and 2,6-dimethyl anisole, etc.

[0018] Distillation yields a 2,6-xylenol / o-cresol mixture (60-80% 2,6-xylenol, 20-40% o-ethylphenol, sulfides and pyridine bases ≤10 ppm), which is one of the raw materials for the production of 2-ethyl-6-cresol by ethylation of o-cresol in S3 of this invention. Distillation yields ≥99.5% 2,6-xylenol (sulfides and pyridine bases both less than 1 ppm), which can be used to produce polyphenylene ether (PPO), etc.; the resulting 2,6-xylenol fraction (≤30% 2,6-xylenol, ≥70% m-p-cresol) is used to blend with 35% cresol or 45% m-p-cresol for use in the production of enameled wire enamel.

[0019] Distillation yields ≥98% m-p-cresol / o-ethylphenol (requiring 2,6-xylenol ≤0.5%, 2,4 / 2,5-xylenol ≤0.5%, sulfides and pyridine bases ≤10ppm), which is one of the raw materials for the deethylation reaction in S2.

[0020] The specific steps of S3 are as follows:

[0021] S31. Add silicon aluminum oxide, zirconium phosphate and a mixture of m-cresol / o-ethylphenol to the reactor, heat up and react until the pressure stabilizes. When the o-ethylphenol content is ≤0.4%, stop the reaction, collect the ethylene discharged from the reaction into a spherical tank, filter to obtain the cracking reaction products and solid catalyst.

[0022] S32. The cracking reaction products are transferred to the bottom of a distillation column, sulfuric acid is added, and the product is distilled to obtain phenol and m-p-cresol.

[0023] Specifically, in S31, the m-p-cresol / o-ethylphenol mixture is the m-p-cresol / o-ethylphenol mixture obtained in S2 and / or a byproduct obtained by distillation during the xylene sulfonation alkaline fusion method to generate xylenol; the amount of the silicon aluminate oxide is 1-5% of the mass of the m-p-cresol / o-ethylphenol mixture; the amount of the zirconium phosphate is 1-10% of the mass of the silicon aluminate oxide; the silicon aluminate oxide is silicon dioxide and aluminum oxide, the mass ratio of silicon dioxide to aluminum oxide is 1:(0.01-50), and the particle size is 20-120 mesh; the temperature for heating is 250-300℃; and the reaction time is 6-10 hours.

[0024] Specifically, in S32, the sulfuric acid has a concentration of 95-98% and is used at a rate of 0.1-0.5% of the mass of the m-p-cresol / o-ethylphenol mixture; the distillation process parameters are: 100-200 theoretical plates, vacuum degree -0.085--0.095 MPa, and reflux ratio (10-25):1.

[0025] The specific steps of S4 are as follows:

[0026] S41. Add the 2,6-xylenol / o-cresol mixture and aluminum to the reactor, heat the reactor and react the mixture, then release the hydrogen gas produced in the reaction.

[0027] S42. The ethylene collected in S31 is fed into the reaction vessel of S41 to carry out the reaction. When o-cresol is ≤1.0%, the ethylene feeding is stopped, the reaction is ended, and a material layer is obtained.

[0028] S43. Transfer the material layer to the bottom of the distillation column, add sulfuric acid, and distill to obtain 2,6-xylenol and 2-ethyl-6-cresol.

[0029] Specifically, in S41, the aluminum is aluminum shavings and / or aluminum powder, and the amount of aluminum used is 0.1-1% of the mass of the 2,6-xylenol / o-cresol mixture; the heating is at a temperature of 150-170°C; and the reaction takes 0.5-1 hour.

[0030] Specifically, in S42, the ethylene is introduced under the following conditions: maintaining the reaction vessel temperature at 160–170°C, introducing ethylene until the reaction vessel pressure is maintained at 2.3–2.5 MPa; maintaining the reaction vessel temperature at 170–180°C, and then repeatedly introducing ethylene into the spherical tank until the reaction vessel pressure is 1.3–1.5 MPa; maintaining the reaction vessel temperature at 180–190°C, and repeatedly introducing ethylene until the reaction vessel pressure is 0.5–1 MPa.

[0031] Specifically, in S43, the sulfuric acid has a concentration of 95-98% and is used at a rate of 0.1-1% of the mass of the o-cresol / 2,6-xylenol mixture; the distillation process parameters are: 100-200 theoretical plates, vacuum degree -0.085--0.095 MPa, and reflux ratio (10-25):1.

[0032] Specifically, in some embodiments of the present invention, polyphenylene ether was successfully prepared by using 2,6-xylenol as a monomer, including the following steps:

[0033] 2,6-Xylenol is dissolved in a reactor containing 2–4 times its volume of benzene-based solvent (toluene, xylene, etc.), and then added to a pre-prepared polymerization catalyst (0.1–1% of 2,6-xylenol) and fatty acids (formic acid, acetic acid, etc., 0.01–0.05% of 2,6-xylenol). The mixture is heated to 30–60°C, and oxygen is introduced to react at a controlled rate (0.05–0.2% of the mass of 2,6-xylenol / min). The reactor is cooled with a refrigerant, and the reaction is controlled. The reaction should be carried out at a temperature of 30–60℃ for 2–6 hours. After that, oxygen supply should be stopped, and the mixture should be filtered at 40–50℃. The filter cakes should be washed twice with solvent (the amount of solvent should be 10–50 times the amount of catalyst). The reaction solution should be taken out and added to an alcohol solvent (methanol, ethanol, etc., the amount of which should be 2–10 times that of 2,6-xylenol). Polyphenylene ether will precipitate out. The mixture should be filtered, and the filter cakes should be washed twice with solvent (methanol, ethanol, etc., the amount of which should be 0.1–1 times that of 2,6-xylenol). The mixture should be dried to obtain a white powdered polyphenylene ether.

[0034] Specifically, the polymerization catalyst preparation steps are as follows: ZSM-5 and Y-type molecular sieve are mixed in a certain mass ratio (ZSM-5 to Y-type ratio 0.5 to 5:1), added to a container, and then cuprous chloride (cuprous chloride amount is 10 to 30% of the molecular sieve mass) and an aqueous solution of amine (the aqueous solution of amine is 3 to 10 times the mass of cuprous chloride) are added in a mass ratio. The mixture is stirred and mixed evenly, then dried at 105 to 120°C for 6 to 8 hours, and then dried at 180 to 200°C for 4 to 8 hours. The amine recovered by evaporation is reused, and the material is sieved to obtain the polymerization catalyst.

[0035] Beneficial effects:

[0036] 1. This invention obtains petrochemical-grade 99.5% o-cresol and 99.5% 2,6-xylenol from cresol raw materials extracted from medium- and low-temperature coal tar by adding an appropriate amount of concentrated sulfuric acid, removing impurities at a higher temperature, and then distilling. Simultaneously, it also yields m-p-cresol / o-ethylphenol and 2,6-xylenol / o-cresol with pyridine base and sulfide content ≤10ppm, thus providing the raw materials required for this invention.

[0037] 2. This invention removes ethyl groups from the mixture of m-p-cresol and o-ethylphenol in tar phenol extract at high temperature to obtain phenol and ethylene, and then distills them to obtain petrochemical-grade phenol and petrochemical-grade m-p-cresol, thereby increasing the added value.

[0038] 3. The present invention obtains the pesticide intermediate 2-ethyl-6-cresol by reacting the ethylene removed from o-ethylphenol with o-cresol in a mixture of 2,6-xylenol / o-cresol.

[0039] 4. This invention uses the reaction of ethylene and o-cresol, and controls the reaction depth of o-cresol impurities in 2,6-xylenol / o-cresol in a timely manner by detection, so as to accurately remove o-cresol impurities from 2,6-xylenol. Since the ethylation reaction of o-cresol produces 2-ethyl-6-cresol with a boiling point increased by 10°C, high-purity 2,6-xylenol can be produced. The engineering plastic polyphenylene ether synthesized from 2,6-xylenol obtained by this invention has properties close to those of commercially available polyphenylene ether synthesized from 2,6-xylenol, and can completely replace commercially available 2,6-xylenol.

[0040] 5. Polyphenylene ether was synthesized using 2,6-xylenol obtained in this invention in the presence of a suitable catalyst. The product performance was comparable to that of polyphenylene ether synthesized from petrochemical 2,6-xylenol (phenol-catalyzed methylation synthesis). Detailed Implementation

[0041] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0042] Example 1:

[0043] Step 1: Distillation of mixed cresols: 2,6-xylenol / o-cresol mixture, ≥98% m-p-cresol / o-ethylphenol

[0044] 400,000 parts of mixed cresol (39.18% o-cresol, 19.64% 2,6-xylenol, 17.55% p-cresol, 19.33% m-cresol, 3.52% o-ethylphenol, 0.24% 2,4-xylenol / 2,5-xylenol, and 0.43% naphthalene) were pumped into the stirred tank of the dosing unit using a booster pump. The mixture was heated to 120°C, and 400 parts of 98% sulfuric acid were added. The mixture was stirred for 1 hour. Then, the material was transferred by the booster pump to the bottom of a 2,6-xylenol distillation column for vacuum distillation (200 theoretical plates, -0.05 MPa). After heating to evaporate part of the medium in the 2,6-xylenol distillation column, the mixture was then cooled in the 2,6-xylenol distillation column. The condenser reaches the reflux tank of the 2,6-xylenol distillation column at a reflux ratio of 1:1. Part of the reflux liquid is returned to the 2,6-xylenol distillation column, and part enters the phenol water receiving tank. Dehydration ends when the condensate at the top of the distillation column becomes clear, yielding 882 portions of phenol water (pre-fraction). While the condensate is becoming clear, the pressure is adjusted to -0.085 MPa, and total reflux is carried out for 2 hours. Gas chromatography analysis of o-cresol content and moisture content is performed hourly. When the o-cresol content is ≥99%, 99.5% o-cresol is collected into the 99.5% o-cresol receiving tank at a reflux ratio of (10-15):1. Collection of 99.5% o-cresol is stopped when the o-cresol content is ≤99% twice.

[0045] Add 4000 parts of ethylene glycol to the distillation column, reflux for 2 hours, then distill off the neutral oil from the material at a reflux ratio of 1:1 and a pressure of -0.085 MPa. Samples are taken to test the neutral oil content (calculated as naphthalene) every hour. Collection of the middle distillate is stopped when the neutral oil content (mainly monitoring naphthalene) begins to decrease to ≤5% and ethylene glycol to ≤0.1%. 12280 parts of the middle distillate are obtained (ethylene glycol 31.84%, naphthalene 10.94%, o-cresol 25.65%, 2,6-xylenol 14.5%, m-p-cresol...). The mixture of o-cresol and 2,6-xylenol (14.58% phenol, 1.38% o-ethylphenol) was initially transferred to the o-cresol / 2,6-xylenol receiving tank at a reflux ratio of 15:1. When the 2,6-xylenol content was ≥50%, the mixture was collected and transferred to the 2,6-xylenol / o-cresol receiving tank (reflux ratio 20:1). When the 2,6-xylenol content was ≥99%, 200 parts of 98% sulfuric acid were added under constant pressure, and the 99.5% 2,6-xylenol was collected at a reflux ratio of (10-15):1. The collection of 99.5% 2,6-xylenol was then stopped when the 2,6-xylenol content was again ≤99%. 2,6-Xylenol; then, reflux ratio 20:1 is used to collect the 2,6-Xylenol fraction for recovery; after sampling and testing, 2,6-Xylenol ≤5%, reflux ratio 20:1 is used to collect ≥98% m-p-cresol / o-ethylphenol (2,6-Xylenol ≤0.5% and 2,4-Xylenol / 2,5-Xylenol ≤0.5% in m-p-cresol / o-ethylphenol), when the cresol fraction contains ≥5% 2,4-Xylenol / 2,5-Xylenol, distillation is stopped, and the bottom stock of about 21,302 portions (p-cresol 37.09%, m-cresol 49.04%, o-ethylphenol 7.1%, 2,4-Xylenol / 2,5-Xylenol 3.71%) is transferred to the m-p-cresol column (continuous column).

[0046] Distillation yielded 105,568 parts of 99.82% o-cresol (99.82% o-cresol, 0.12% 2,6-xylenol, and 0.06% naphthalene) with 0.6 ppm sulfur compounds, which can be used to produce o-cresol epoxy phenolic resin; and 59,588 parts of 99.43% o-cresol / 2,6-xylenol (69.18% o-cresol, 30.58% 2,6-xylenol, and 0.24% other compounds), which can be used to produce 4-tert-butyl-2,6-xylenol, 6-tert-butyl-o-cresol, and can also be used to produce o-methyl anisole and 2,6-dimethyl anisole, etc.

[0047] Distillation yielded 15,262 parts of a 2,6-xylenol / o-cresol mixture (30.4% o-cresol, 69.20% 2,6-xylenol, 0.40% other components, 9.5 ppm sulfides, and 7.9 ppm nitrides). This component can be used for the distillation of 99% 2,6-xylenol, or for the separation of 2,6-xylenol / o-cresol to produce 2-ethyl-6-cresol and 99% 2,6-xylenol, etc. The 2,6-xylenol / o-cresol mixture is the feedstock for the trialkylation step of this invention.

[0048] Distillation yielded 38,087 parts of 99.77% 2,6-xylenol (99.77% 2,6-xylenol, 0.18% o-cresol, and 0.05% other components), with sulfide content of 0.9 ppm and pyridine base content of 0.7 ppm, which can be used to produce polyphenylene oxide (PPO), etc.; 46,078 parts of the 2,6-xylenol fraction (19.57% 2,6-xylenol, 37.98% p-cresol, 38.11% m-cresol, 7.18% o-ethylphenol, and 0.45% other components) were used to blend with 35% cresol or 45% m-p-cresol for use in the production of enameled wire enamel.

[0049] Distillation yielded 101,278 parts of 99.48% m- / p-cresol / o-ethylphenol (p-cresol 44.14%, m-cresol 46.92%, o-ethylphenol 8.42%, 2,6-xylenol 0.31%, 2,4-xylenol / 2,5-xylenol 0.11%, other 0.1%, nitrides 8.9 ppm, sulfides 7.3 ppm), which can be used to produce m-cresol-formaldehyde resin for photoresists, or as a raw material for step two.

[0050] Step 2: Deethylation reaction

[0051] In a stainless steel high-pressure reactor equipped with an external stainless steel condenser and internal coil, 4000 parts of acidic silica-alumina oxide solid catalyst (silicon-alumina oxide mass ratio 1:2, particle size 60-80 mesh, where the silicon oxide is commercially available silicon dioxide and the aluminum oxide is commercially available acidic alumina), 120 parts of zirconium phosphate, and 25890 parts of a 99.48% m-p-cresol / o-ethylphenol mixture obtained in step one (containing 23575.4 parts of m-p-cresol, 2180 parts of o-ethylphenol, 134.6 parts of other components, 8.9 ppm of nitrides, and 7.3 ppm of sulfides) were added. The reactor was sealed and heated to 260°C for 7 hours, with the pressure gradually increased until it stabilized. At a pressure of 1.6–1.7 MPa, samples were taken for analysis. The o-ethylphenol content was 0.12%, which was within acceptable limits. The reaction was then terminated. The internal coil was cooled using a programmed cooling heat transfer oil (the heat transfer oil temperature was gradually and slowly reduced from a high temperature to 120°C), and the temperature was lowered to 160°C after 1 hour. The ethylene released during the reaction was gradually discharged. The discharged gas was pressurized to 5 MPa by a pressure pump and stored in a stainless steel spherical tank. After the gas was discharged, the condensate from the cracking reaction was cooled slightly to 80°C and purged with nitrogen for 0.5 hours. After filtration, 25221.7 parts of cracking reaction products were obtained (1656.7 parts of phenol, 23410 parts of m-p-cresol, 20.8 parts of o-ethylphenol, and 134.2 parts of other products). The solid catalyst was reused.

[0052] The 25221.7 parts of the cracking reaction products obtained from step two (1656.7 parts of phenol, 23410 parts of m-p-cresol, 20.8 parts of o-ethylphenol, and 134.2 parts of other products) were added to the bottom of a distillation column (theoretical plate 200). 30 parts of 98% sulfuric acid (0.12% of the mass of the m-p-cresol / o-ethylphenol mixture) were added, mixed well, and then distilled under reduced pressure (vacuum degree -0.085 MPa, reflux ratio (10-20):1) to obtain 1582.1 parts of 99.92% phenol (0.3 ppm of nitrides and 0.4 ppm of sulfides) and 22579.4 parts of 99.85% m-p-cresol (22545.5 parts of m-p-cresol, 19.2 parts of o-ethylphenol, and 14.7 parts of other products, with 0.4 ppm of nitrides and 0.4 ppm of sulfides).

[0053] Step 3: Synthesis of 2-ethyl-6-cresol and purification of 2,6-xylenol

[0054] Simultaneously with the deethylation reaction in step two, 4443 parts of the 2,6-xylenol / o-cresol mixture obtained in step one (containing 1350.7 parts of o-cresol, 3074.5 parts of 2,6-xylenol, 17.8 parts of other components, 9.5 ppm of sulfides, and 7.9 ppm of nitrides; the molar ratio of o-cresol in the o-cresol / 2,6-xylenol mixture to that in the 99.48% p-cresol / o-ethylphenol mixture in step two is 0.7:1) and 15 parts of aluminum powder (0.26% of the mass of the 2,6-xylenol / o-cresol mixture) were added to another stainless steel pressure vessel. Stirring was started, and the temperature was raised to 170°C and maintained for 50 minutes, releasing the hydrogen gas produced in the reaction. Then, the ethylene discharged from the cracking reaction in step two after cooling and stored in the spherical tank was simultaneously and slowly introduced under reduced pressure into the stainless steel pressure vessel for reaction, maintaining the vessel temperature at 160–170°C. Ethylene was introduced to the reactor until the pressure reached 2.3 MPa. When the pressure in the spherical tank dropped to 2.6 MPa, the reactor temperature was maintained at 170–180°C, and ethylene was repeatedly introduced until the pressure reached 1.5 MPa. When the pressure in the spherical tank dropped to 1.6 MPa, the reactor temperature was maintained at 180–190°C, and ethylene was continued until the pressure reached 1 MPa. When the pressure in the reactor no longer decreased, a sample was taken for analysis; the o-cresol content was 0.22%, which was acceptable. Ethylene introduction was stopped, and olefin introduction was performed for 10 hours. After 2 hours of holding the reaction at the bottom, the automatic analysis and detection system valve was opened for sample retesting; the o-cresol content was 0.18%, which was acceptable. The material layer was added to the bottom of the distillation column (theoretical plate number 250), and 40 parts of 98% sulfuric acid (0.9% of the mass of 2,6-xylenol / o-ethylphenol) were added. The temperature was raised to -0.085 MPa, and the reflux ratio was (15–20):1. Distillation yielded 99.8% olefins. 2,6-Dimethylphenol 2929.7 parts (containing 0.4 ppm sulfide and 0.3 ppm nitride), 99.5% 2-ethyl-6-methylphenol 1615.5 parts.

[0055] Step 4: Synthesis of polyphenylene ether

[0056] Add 5 parts each of ZSM-5 and Y-type molecular sieve to the reactor, add 3 parts of cuprous chloride and 10 parts of 25% ammonia water, stir and mix evenly, then dry at 105-120℃ for 6-8 hours, and then dry at 180-200℃ for 4-8 hours. The evaporated ammonia water is recovered and reused, and 12.1 parts of polymerization catalyst are obtained by sieving.

[0057] Dissolve 100 parts of 99.8% 2,6-xylenol obtained in step 3 in a reactor containing 200 parts of toluene, and add 0.5 parts of the pre-prepared polymerization catalyst and 0.05 parts of acetic acid. Heat to 40°C and introduce oxygen at a rate of 0.1 parts / min. Cool and control the reaction temperature at 40–45°C. After reacting for 4 hours, stop the oxygen supply. Filter at 40–45°C, and wash the filter cake twice with 10 parts of toluene each time. Take out the reaction solution and add 300 parts of methanol to precipitate polyphenylene ether. Filter, wash twice with 50 parts of methanol each time, and dry to obtain 88.5 parts of white powdered polyphenylene ether with an intrinsic viscosity of 0.49, a yield of 89.4%, and a copper content of 0.8 ppm.

[0058] Example 2

[0059] Step 1: Distillation of mixed cresols 2,6-xylenol / o-cresol mixture

[0060] See Example 1

[0061] Step 2: Deethylation reaction

[0062] In a stainless steel high-pressure reactor equipped with an external stainless steel condenser and internal coil, 4000 parts of acidic silica-alumina oxide solid catalyst (silicon-alumina oxide mass ratio 1:1, particle size 40-60 mesh), 100 parts of zirconium phosphate, and 20000 parts of a purchased raw material mixture of m-p-cresol and o-ethylphenol (derived from a byproduct of xylene (containing a small amount of ethylbenzene) sulfonation alkaline fusion to produce xylenol, containing 17711 parts of m-p-cresol, 2180 parts of o-ethylphenol, 109 parts of other components, 3.8 ppm of nitrides, and 1.9 ppm of sulfides) were added. The reactor was sealed and heated to 280℃ for 7 hours, with the pressure gradually increased to a stable level of 1.9-2 ppm. At 0.0 MPa, sampling and analysis showed that o-ethylphenol was 0.09%, which was within acceptable limits. The reaction was terminated, and the inner coil was cooled with programmed cooling heat transfer oil (the temperature of the heat transfer oil was gradually and slowly reduced from high temperature to 120℃), and cooled to 170℃ in 1 hour. The ethylene released in the reaction was gradually discharged. The discharged gas was pressurized to 5 MPa by a pressurizing pump and stored in a stainless steel spherical tank. After the gas was discharged, the pyrolysis reaction condensate was cooled slightly to 90℃ and purged with nitrogen for 0.5 hours. After filtration, 19306.3 parts of pyrolysis reaction products were obtained (1646.2 parts of phenol, 17533.9 parts of m-p-cresol, 18.9 parts of o-ethylphenol, and 107.3 parts of others). The solid catalyst was reused.

[0063] The 19306.3 parts of the cracking reaction products obtained from step two (1646.2 parts of phenol, 17533.9 parts of m-p-cresol, 18.9 parts of o-ethylphenol, and 107.3 parts of others) were added to the bottom of a distillation column (theoretical plate 200). 80 parts of 98% sulfuric acid (0.41% of the mass of the m-p-cresol / o-ethylphenol mixture) were added, mixed well, and then distilled under reduced pressure (vacuum degree -0.085MPa, reflux ratio 10-20:1) to obtain 1596.8 parts of 99.9% phenol (0.4ppm of nitrides and 0.5ppm of sulfides) and 16968.4 parts of 99.82% m-p-cresol (16937.7 parts of m-p-cresol, 18.1 parts of o-ethylphenol, and 12.6 parts of others, with 0.6ppm of nitrides and 0.4ppm of sulfides).

[0064] Based on the results of the content of refined phenol and refined m- and p-cresol products and the content of nitrogen- and sulfur-containing compounds obtained from Examples 1 and 2, the refined phenol and refined m- and p-cresol extracted from phenol-containing coal tar in this invention are of comparable quality.

[0065] Step 3: Synthesis of 2-ethyl-6-cresol and purification of 2,6-xylenol

[0066] Simultaneously with the deethylation reaction in step two, 5713 parts of the 2,6-xylenol / o-cresol mixture obtained from the distillation in step one (containing 1736.7 parts of o-cresol, 3953.4 parts of 2,6-xylenol, 22.9 parts of other components, 9.5 ppm of sulfides, and 7.9 ppm of nitrides; the molar ratio of o-cresol in the o-cresol / 2,6-xylenol mixture to that in the purchased raw material from step two, p-cresol / o-ethylphenol, is 0.9:1) and 15 parts of aluminum powder (aluminum being 0.26% of the mass of the o-cresol / 2,6-xylenol mixture) were added to another stainless steel pressure vessel. Stirring was started, and the temperature was raised to 160°C and maintained for 1 hour, during which the hydrogen gas released from the reaction was discharged. Then, the ethylene discharged from the cracking reaction in step two, stored in a spherical tank, was simultaneously and slowly introduced into the stainless steel pressure vessel under reduced pressure, maintaining the vessel temperature at 160–170°C. Ethylene was repeatedly introduced into the vessel until the pressure inside was reduced. The reaction was initiated at a pressure of 2.5 MPa. When the pressure in the spherical tank dropped to 2.6 MPa, the temperature was maintained at 170–180°C, and ethylene was repeatedly introduced until the pressure inside the tank reached 1.5 MPa. When the pressure in the spherical tank dropped to 1.6 MPa, the temperature was maintained at 180–190°C, and ethylene was continued until the pressure inside the tank reached 0.5 MPa. When the pressure in the spherical tank dropped to 0.6 MPa and the pressure in the pressure vessel no longer decreased, a sample was taken for analysis; the o-cresol content was 0.43%, which is acceptable. Ethylene introduction was stopped, and olefin introduction was performed for 9 hours. After the reaction was completed, the temperature was maintained for 2 hours, and the automatic analysis and detection system valve was opened for sample retesting; the o-cresol content was 0.41%, which is acceptable. The material layer was added to the bottom of the distillation column (theoretical plate number 250), and 30 parts of 98% sulfuric acid (0.52% of the mass of 2,6-xylenol / o-cresol) were added. The temperature was raised to -0.085 MPa, and the reflux ratio was (15–20):1. Distillation yielded 99.7% olefins. 3786.8 parts of 2,6-dimethylphenol (containing 0.6 ppm sulfide and 0.4 ppm nitride), 2087.9 parts of 99.3% 2-ethyl-6-methylphenol.

[0067] Step 4: Synthesis of polyphenylene ether

[0068] 100 parts of 99.77% 2,6-xylenol obtained in step 3 were dissolved in a reactor containing 200 parts of toluene. Then, 0.5 parts of a pre-prepared polymerization catalyst and 0.03 parts of formic acid were added. The mixture was heated to 40°C, and oxygen was introduced at a rate of 0.1 parts / min. The reaction was cooled and the temperature was controlled at 40–45°C. After 4 hours of reaction, oxygen introduction was stopped. The mixture was filtered at 40–45°C, and the filter cake was washed twice with 10 parts of toluene. The reaction solution was then removed, and 300 parts of methanol were added to precipitate the polyphenylene ether. The precipitate was filtered, washed twice with 50 parts of methanol, and dried to obtain 88.1 parts of white powdered polyphenylene ether with an intrinsic viscosity of 0.48, a yield of 88.9%, and a copper content of 0.7 ppm.

[0069] Comparative Example 1:

[0070] 100 parts of 99.85% 2,6-xylenol (obtained by fixed-bed catalytic methylation of petrochemical phenol) were dissolved in a reactor containing 200 parts of toluene. Then, 0.5 parts of a pre-prepared polymerization catalyst and 0.05 parts of acetic acid were added. The mixture was heated to 40°C, and oxygen was introduced at a rate of 0.1 parts / min. The reaction was cooled and the temperature was controlled at 40–45°C. After 4 hours of reaction, oxygen introduction was stopped. The mixture was filtered at 40–45°C, and the filter cake was washed twice with 10 parts of toluene. The reaction solution was then removed, and 300 parts of methanol were added to precipitate polyphenylene ether. The precipitate was filtered, washed twice with 50 parts of methanol, and dried to obtain 87.9 parts of white powdered polyphenylene ether with an intrinsic viscosity of 0.47, a yield of 88.6%, and a copper content of 0.8 ppm.

[0071] Based on the results of polyphenylene ether product yield, intrinsic viscosity, copper content, etc. of Examples 1, 2 and the comparative examples, the quality of polyphenylene ether synthesized from 2,6-xylenol obtained by the present invention is comparable to that of polyphenylene ether generated from commercially available 2,6-xylenol.

[0072] This invention provides a method for separating multiple phenols from a mixture of cresols. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A method for separating multiple phenols from a mixture of cresols, characterized in that, Includes the following steps: S1: Heat the mixed cresols, mix them with sulfuric acid, and transfer them to the bottom of the distillation column. Dehydrate them by distillation under reduced pressure. When the condensate at the top of the distillation column is clear, the dehydration is finished. Adjust the pressure to -0.07 to -0.09 MPa and reflux for 1 to 3 hours. Take samples every hour to analyze the gas chromatographic content and moisture of o-cresol. When the o-cresol content is ≥99% and the moisture content is ≤0.2%, adjust the reflux ratio to (15~20):1 and collect o-cresol. Stop collecting when the o-cresol content is ≤99% for the second time. S2. Add ethylene glycol to the bottom of the distillation column and reflux for 1-2 hours. Remove neutral oil at a pressure of -0.07 to -0.09 MPa and a reflux ratio of (0.5-2):

1. Take samples for analysis every hour. When the neutral oil content decreases to ≤5% and the ethylene glycol content is ≤0.1%, adjust the reflux ratio to (10-20):1 and start collecting the o-cresol / 2,6-xylenol mixture. When the 2,6-xylenol content is ≥50%, collect the 2,6-xylenol / o-cresol mixture. When the 2,6-xylenol content is ≥99%, remove the mixture from the bottom of the distillation column. Sulfuric acid is added to the distillate at a reflux ratio of (10-15):1 to begin collecting 2,6-xylenol. When the 2,6-xylenol content is again ≤99%, collection of 2,6-xylenol is stopped, and the distillate is then collected at a reflux ratio of (20-25):1 for reuse to recover 2,6-xylenol. When the 2,6-xylenol content is ≤5%, the m-p-cresol / o-ethylphenol mixture is collected at a reflux ratio of (15-20):

1. When the cresol fraction contains ≥5% 2,4-xylenol / 2,5-xylenol, distillation is stopped, and the bottom stock is transferred to the m-p-cresol distillate column. S3. The mixture of m-p-cresol and o-ethylphenol is separated by a deethylation reaction to obtain phenol and m-p-cresol; S4. The 2,6-xylenol / o-cresol mixture was separated by alkylation to obtain 2,6-xylenol and 2-ethyl-6-cresol.

2. The method according to claim 1, characterized in that, In S1, the temperature of the heating is 100-130℃; the concentration of the sulfuric acid is 95-98%, and the amount used is 0.01-0.5% of the mass of the mixed cresol; the process parameters of the vacuum distillation dehydration are: 150-300 theoretical plates and a pressure of -0.01 to -0.07 MPa.

3. The method according to claim 1, characterized in that, In S2, the content of the neutral oil is calculated based on the naphthalene content; the amount of ethylene glycol used is 2 to 10 times the mass of the neutral oil in the mixed cresol; the concentration of the sulfuric acid is 95 to 98%, and the amount used is 0.01 to 0.5% of the mass of the mixed cresol.

4. The method according to claim 1, characterized in that, The specific steps of S3 are as follows: S31. Add silicon aluminum oxide, zirconium phosphate and a mixture of m-cresol / o-ethylphenol to the reactor, heat up and react until the pressure stabilizes. When the o-ethylphenol content is ≤0.4%, stop the reaction, collect the ethylene discharged from the reaction into a spherical tank, filter to obtain the cracking reaction products and solid catalyst. S32. The cracking reaction products are transferred to the bottom of a distillation column, sulfuric acid is added, and the product is distilled to obtain phenol and m-p-cresol.

5. The method according to claim 4, characterized in that, In S31, the m-p-cresol / o-ethylphenol mixture is the m-p-cresol / o-ethylphenol mixture obtained in S2 and / or a byproduct of xylenol production via xylene sulfonation alkali fusion; the amount of the aluminosilicate is 1-5% of the mass of the m-p-cresol / o-ethylphenol mixture; the amount of the zirconium phosphate is 1-10% of the mass of the aluminosilicate; the aluminosilicate is silicon dioxide and aluminum oxide, with a mass ratio of silicon dioxide to aluminum oxide of 1:(0.01-50), and a particle size of 20-120 mesh; the temperature for heating is 250-300°C; and the reaction time is 6-10 hours.

6. The method according to claim 4, characterized in that, In S32, the sulfuric acid has a concentration of 95-98% and is used at a rate of 0.1-0.5% of the mass of the m-p-cresol / o-ethylphenol mixture; the distillation process parameters are: 100-200 theoretical plates, vacuum degree -0.085--0.095 MPa, and reflux ratio (10-25):

1.

7. The method according to claim 1, characterized in that, The specific steps of S4 are as follows: S41. Add the 2,6-xylenol / o-cresol mixture and aluminum to the reactor, heat the reactor and react the mixture, then release the hydrogen gas produced in the reaction. S42. The ethylene collected in S31 is fed into the reaction vessel of S41 to carry out the reaction. When o-cresol is ≤1.0%, the ethylene feeding is stopped, the reaction is ended, and a material layer is obtained. S43. Transfer the material layer to the bottom of the distillation column, add sulfuric acid, and distill to obtain 2,6-xylenol and 2-ethyl-6-cresol.

8. The method according to claim 7, characterized in that, In S41, the aluminum is aluminum shavings and / or aluminum powder, and the amount of aluminum used is 0.1-1% of the mass of the 2,6-xylenol / o-cresol mixture; the heating is at a temperature of 150-170°C; and the reaction takes 0.5-1 hour.

9. The method according to claim 7, characterized in that, In S42, the ethylene is introduced under the following conditions: maintaining the reaction vessel temperature at 160-170°C, introducing ethylene until the reaction vessel pressure is maintained at 2.3-2.5 MPa; maintaining the reaction vessel temperature at 170-180°C, and then repeatedly introducing ethylene into the spherical tank until the reaction vessel pressure is 1.3-1.5 MPa; maintaining the reaction vessel temperature at 180-190°C, and repeatedly introducing ethylene until the reaction vessel pressure is 0.5-1 MPa.

10. The method according to claim 7, characterized in that, In S43, the sulfuric acid has a concentration of 95-98% and is used in an amount of 0.1-1% of the mass of the o-cresol / 2,6-xylenol mixture; the distillation process parameters are: 100-200 theoretical plates, vacuum degree -0.085--0.095 MPa, and reflux ratio (10-25):1.