Method and system for preparing thymol from m-p-isopropyl phenol / m-p-propyl phenol

Abstract

The invention discloses a method and a system for preparing thymol from m-p-isopropyl phenol / m-p-propyl phenol, the method comprises the following steps: adding a m-p-isopropyl phenol / m-p-propyl phenol mixture into a reactor added with a catalyst, reacting at a certain temperature, carrying out a de-propyl reaction on isopropyl phenol and the like in the reaction to obtain a mixture of phenol, propylene and the like, and adding the mixture into a reaction kettle for reaction to obtain thymol. The reaction is completed under the control of a special online automatic analysis instrument; cooling the mixture to a certain temperature, pressurizing and storing propylene generated by the reaction in a spherical tank, adding an alkylation catalyst into another reaction kettle, and carrying out an alkylation reaction of phenol and propylene on the mixture of low-grade phenol and m-cresol, and rectifying the reaction liquid to obtain high-purity phenol, high-purity m-cresol, o-isopropyl phenol, crude p-isopropyl phenol, 2-isopropyl-5-cresol and 4-isopropylphenol-3-cresol. According to the method disclosed by the invention, the mixed m-p-isopropyl phenol / m-p-propyl phenol with low value and less market demand can be converted into o-isopropyl phenol, p-isopropyl phenol and other products with market scale.

Description

Technical Field

[0001] The present invention relates to a method for preparing thymol, specifically a method and system for preparing thymol from m / p-isopropylphenol / m / p-propylphenol, belonging to the technical field of organic synthesis and separation. Background Art

[0002] Crude phenol is rectified to obtain phenol, o-cresol, three-mixed cresols, m / p-cresol containing 55% of the meta-position, 99% m / p-cresol, and industrial xylenol. They are directly sold as products without good fine separation. In fact, there is still a fraction of m / p-isopropylphenol / m / p-propylphenol with a boiling point range of 227 - 231°C in the residue of industrial xylenol rectification. It is mainly composed of m-isopropylphenol, p-isopropylphenol, m-propylphenol, and p-propylphenol, and also contains some impurities such as 2-ethyl-3-methylphenol, 2-methyl-3-ethylphenol, 3-ethyl-5-methylphenol, and 2,4,5-trimethylphenol. Since it is difficult to separate m-isopropylphenol, p-isopropylphenol, m-propylphenol, and p-propylphenol by methods such as rectification and tert-butylation, and currently the market uses of m / p-isopropylphenol / m / p-propylphenol mixtures are few, it is necessary to carry out appropriate treatment to achieve the purpose of utilizing m / p-isopropylphenol / m / p-propylphenol mixtures.

[0003] The content of m / p-isopropylphenol / m / p-propylphenol in crude phenol extracted from high-temperature coal tar is relatively high, and it cannot be separated by conventional rectification; the tert-butylation reaction can only obtain mixtures of m-isopropylphenol / m-propylphenol and p-isopropylphenol / p-propylphenol, and their utilization value is still very low, so new separation methods need to be developed. Because isopropylphenol / propylphenol is more likely to undergo depropyl / isopropyl reaction at high temperature or in the presence of high temperature and a catalyst (especially in the presence of an acidic catalyst). Summary of the Invention

[0004] The purpose of the present invention is to solve the above problems by providing a method and system for preparing thymol from m / p-isopropylphenol / m / p-propylphenol. Using m / p-isopropylphenol / m / p-propylphenol mixture as raw material, by using a suitable dealkylating catalyst, at an appropriate temperature, selectively remove the isopropyl / propyl in m / p-isopropylphenol / m / p-propylphenol to generate phenol and propylene. Since the deisopropyl / propyl reaction is carried out under specific catalysts and at a lower temperature, the ethyl and methyl in phenolic substances rarely undergo dealkylation reactions; then react the decomposed propylene with acidic catalyst and excessive low-grade m-cresol, and rectify to obtain high-quality phenol, m-cresol, thymol, and the fungicide 3-methyl-4-isopropylphenol. The operation of the present invention is simple and easy, with less three wastes and low production cost.

[0005] The present invention relates to a method and system for preparing thymol from m / p-isopropylphenol / m / p-propylphenol, including the following steps:

[0006] Step 1: Deisopropyl / propyl reaction:

[0007] An acidic aluminosilicate oxide and zirconium phosphate (the amount of zirconium phosphate is 1-10% of the mass of the aluminosilicate oxide catalyst) are charged into a stainless steel high-pressure reactor (equipped with an external stainless steel condenser and an internal coil), and then a mixture of m,p-isopropylphenol / m,p-propylphenol is added. The reactor is sealed, heated to 210-280 °C and reacted for 5-8 hours, and the pressure is gradually increased to 1.3-3.0 MPa. When the pressure is stable, sampling is carried out through an automatic sampling system maintained at 50-60 °C. The collected sample enters an on-line automatic detection system for detection. The reaction is terminated when m-isopropylphenol ≤ 0.5% (if m-isopropylphenol ≥ 2%, additional catalyst needs to be added to continue the reaction; if m-isopropylphenol ≤ 2%, the temperature can be raised by 10-20 °C and continue the reaction until qualified). The heat transfer oil in the internal coil is cooled by programmed cooling (the temperature of the heat transfer oil gradually and slowly decreases from a high temperature to 100-120 °C), and rapidly cooled to ≤ 180 °C within 0.5-1 hour, and propylene released during the reaction is gradually discharged; the discharged gas is pressurized to 5 MPa by a pressure pump and stored in a stainless steel spherical tank; after the gas is discharged, the pyrolysis reaction condensate is slightly cooled and purged with nitrogen for 0.5 hours, and the pyrolysis reaction product (mainly containing phenol) is obtained by filtration, and the solid catalyst is recycled;

[0008] Step 2: Synthesis of thymol, etc.:

[0009] While carrying out the cracking and rearrangement reaction in the first step, add m-cresol or phenol or a mixture of m-cresol and phenol, an acidic catalyst, and an inhibitor to another stainless steel autoclave. Start stirring and heat up to 160°C. Slowly and synchronously reduce the pressure of the propylene stored in the spherical tank, which is discharged after the temperature of the first cracking reaction is reduced, and introduce it into the stainless steel autoclave for reaction. Keep the temperature in the autoclave at 170 - 200°C. Repeatedly introduce propylene into the autoclave until the pressure in the autoclave is maintained at 2.3 - 2.5 MPa; when the pressure in the spherical tank drops to 2.6 MPa and the pressure in the autoclave no longer decreases, discharge the unreacted gas in the autoclave; then continue to repeatedly introduce the propylene in the spherical tank for reaction until the pressure in the autoclave is 1.3 - 1.5 MPa. When the pressure in the spherical tank drops to 1.6 MPa and the pressure in the autoclave no longer decreases, discharge the unreacted gas; repeatedly introduce propylene for reaction until the pressure in the autoclave is 0.6 MPa. When the pressure in the spherical tank drops to 0.7 MPa and the pressure in the autoclave no longer decreases, discharge the unreacted gas; introduce propylene for reaction until the pressure in the autoclave is 0.1 MPa. When the pressure in the spherical tank drops to 0.1 MPa and the pressure in the autoclave no longer decreases, discharge the unreacted gas; then continue to introduce propylene for reaction until the pressure in the spherical tank is 0.03 MPa to end the gas introduction. The time for introducing propylene is 3 - 12 hours. After the gas introduction is completed, keep the temperature for reaction for 2 hours; the temperature of the autoclave is reduced to ≤90°C within 1 - 3 hours. Add 10 - 35% liquid caustic soda to the material in the autoclave to neutralize it to pH 7 - 8. Separate the brine layer. Add the material layer to the bottom of the distillation column. At -0.085 to -0.095 MPa and a reflux ratio of 10 - 20, distill to obtain 99.5% high-purity m-cresol, and then successively obtain ≥99% 2-isopropyl-5-cresol and ≥99% highly effective fungicide 4-isopropyl-3-cresol; or 99.5% phenol, 99% o-isopropylphenol, ≥96% crude p-isopropylphenol; or 99.5% phenol, 99.5% m-cresol, 99% o-isopropylphenol, ≥96% crude p-isopropylphenol, ≥99% 2-isopropyl-5-cresol, ≥99% highly effective fungicide 4-isopropyl-3-cresol;

[0010] Add the crude p-isopropylphenol and methanol to the reactor. Start stirring and heat up to 60 - 70°C to completely dissolve the material. Then first cool it to 30 - 40°C with circulating water for 2 - 3 hours, and then cool it to -10 - 10°C with chilled brine for 2 - 4 hours. Keep the temperature for 1 - 3 hours, filter, drain, and dry to obtain ≥99% p-isopropylphenol;

[0011] Step 3: Distillation separation:

[0012] Add the reaction product mixture obtained by filtration in the first step to the bottom of the distillation column and carry out vacuum distillation to obtain ≥99.5% high-grade phenol. Sometimes there will be a small amount of ≥85% crude 3-ethyl-5-cresol;

[0013] Add the crude product of 3-ethyl-5-methylphenol and methanol into the reactor, start stirring, heat up to 60-70 °C to completely dissolve the materials, then first cool down to 30-40 °C with circulating water for 2-3 hours, and then cool down to -10-10 °C with freezing brine for 2-4 hours, keep warm for 1-3 hours, filter, drain, and dry to obtain 3-ethyl-5-methylphenol with a purity of ≥99%.

[0014] Preferably, in step one, add a mixture of m,p-isopropylphenol / m,p-propylphenol, and the mixture of m,p-isopropylphenol / m,p-propylphenol is mainly composed of at least 2-4 of m-isopropylphenol, p-isopropylphenol, m-propylphenol, and p-propylphenol, with a content of 85-100%, 2,4,5-trimethylphenol 0-1%, 2-ethyl-3-methylphenol / 2-methyl-3-ethylphenol 0-1%, 3-ethyl-5-methylphenol 0-10%, and others 0-3%. Preferably, use a coal chemical m,p-isopropylphenol / m,p-propylphenol mixture.

[0015] Preferably, in step one, load acidic silica-aluminum oxide into a stainless-steel high-pressure reactor (equipped with an external stainless-steel condenser and an internal coil). The silica-aluminum oxide is silica and acidic alumina, and the mass ratio of silica to acidic alumina is 1:0.01-50, preferably 1:0.05-20; its dosage is 10-30% of the mass of the raw material m,p-isopropylphenol / m,p-propylphenol mixture.

[0016] Preferably, in step one, the temperature of the heat transfer oil gradually decreases slowly from a high temperature to 100-120 °C, and the high temperature is 50-70 °C lower than the deisopropyl / propyl reaction temperature.

[0017] Preferably, in step two, use an acidic catalyst. The acidic catalyst is at least one of sulfuric acid, phosphoric acid, p-toluenesulfonic acid, benzenesulfonic acid, solid acid catalysts, acidic resins, zirconia, acidic alumina, silica, etc. Preferably, use a mixed acid of sulfuric acid and phosphoric acid; the dosage of the mixed acid is 0.5-5% of the mass of m-cresol or phenol and their mixtures, and the mass ratio of sulfuric acid to phosphoric acid is 5-7:5-3.

[0018] Preferably, in step two, use an inhibitor. The inhibitor is hydroquinone, 2-methylhydroquinone, 2-tert-butylhydroquinone, 6-tert-butyl-2,4-dimethylphenol, p-methoxyphenol, etc. Preferably, use 2-methylhydroquinone.

[0019] Preferably, the sample collected in Step 1 enters an on-line automatic detection system for detection. The on-line automatic detection system consists of a solvent cleaning system, a sample metering pump (or flowmeter), a sample mixing system, a sample filtration system, a sample detection system, etc.; the solvent cleaning system consists of an explosion-proof metering pump (or flowmeter), an automatic control valve, pipelines, etc.; the sample mixing system refers to a system in which the sample and the solvent are metered by a metering pump (or flowmeter) and then mixed evenly through a static mixer; the sample detection system consists of a liquid injector, an explosion-proof gas chromatograph (hydrogen flame detector (FID)), etc.; the detection conditions: hydrogen flame detector (FID detector); the determination is carried out at a column temperature of 100 - 130 °C, an injector temperature of 240 - 260 °C, a detector temperature of 240 - 260 °C, a carrier gas linear velocity of 30 - 50 cm / min, a hydrogen flow rate of 20 - 40 ml / min, an air flow rate of 250 - 350 ml / min, a split ratio of 20 - 80, and a tail blow flow rate of 15 - 50 ml / min.

[0020] The solvent cleaning system provided by the present application is applied to a method for preparing thymol from m,p - isopropylphenol and m,p - propylphenol. The solvent cleaning system consists of an explosion-proof metering pump, an automatic control valve, pipelines, etc.

[0021] The sample mixing system provided by the present application is applied to a method for preparing thymol from m,p - isopropylphenol and m,p - propylphenol. The sample mixing system refers to a system in which the sample and the solvent are metered by a metering pump and then mixed evenly through a static mixer.

[0022] The sample detection system provided by the present application is applied to a method for preparing thymol from m,p - isopropylphenol and m,p - propylphenol. The sample detection system consists of a liquid injector, an explosion-proof gas chromatograph, etc.

[0023] Beneficial effects:

[0024] 1. In the present invention, isopropyl / propyl in the m,p - isopropylphenol / m,p - propylphenol mixture of the crude phenol rectification extract is removed by high temperature to obtain phenol and propylene, and then the removed propylene reacts with excessive low - grade m - cresol. Through rectification, petrochemical - grade phenol and petrochemical - grade m - cresol are obtained, and m,p - isopropylphenol / m,p - propylphenol is transformed into thymol and 3 - methyl - 4 - isopropylphenol products, thereby increasing the added value.

[0025] 2. In the present invention, isopropyl / propyl in the m,p - isopropylphenol / m,p - propylphenol mixture of the crude phenol rectification extract is removed by high temperature to obtain phenol and propylene, and then the removed propylene reacts with excessive low - grade phenol. Through rectification, petrochemical - grade phenol is obtained, and m,p - isopropylphenol / m,p - propylphenol is transformed into o - isopropylphenol and p - isopropylphenol products, thereby increasing the added value.

[0026] 3. For the mixed meta - para - isopropylphenol / meta - para - propylphenol raw material containing 3 - ethyl - 5 - methylphenol, the contents of 2 - ethyl - 3 - methylphenol / 2 - methyl - 3 - ethylphenol and 2,4,5 - trimethylphenol in the raw material are much lower than that of 3 - ethyl - 5 - methylphenol. Moreover, 2 - ethyl - 3 - methylphenol / 2 - methyl - 3 - ethylphenol can be partially catalytically transposed to obtain 3 - ethyl - 5 - methylphenol. The boiling point of 3 - ethyl - 5 - methylphenol is much higher than that of phenol. Therefore, in this invention, crude 3 - ethyl - 5 - methylphenol can sometimes be obtained by de - isopropyl / propyl. The crude product is crystallized by solvent to obtain 99% 3 - ethyl - 5 - methylphenol. It is very difficult to synthesize 3 - ethyl - 5 - methylphenol by chemical synthesis method, and its price is relatively high, which increases the variety of products.

[0027] 4. This invention uses an on - line automatic detection system to detect the de - propylene effect of meta - para - isopropylphenol, with timely and accurate control, reducing problems such as the trouble of manual sampling analysis, long analysis time, and untimely data guidance. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a flow chart of an automatic detection device for de - propylene of meta - para - isopropylphenol / meta - para - propylphenol mixture. DETAILED DESCRIPTION OF THE INVENTION

[0029] Example 1

[0030] A method for preparing thymol from meta - para - isopropylphenol / meta - para - propylphenol, comprising the following steps: Step 1: Cracking and transposition reaction:

[0031] In a stainless-steel high-pressure reactor with an external stainless-steel condenser and an internal coil, 2000 parts (silica-alumina ratio 1:1) of an acidic silica-alumina solid catalyst and 50 parts of zirconium phosphate are charged. 10000 parts of a m / p-isopropylphenol / m / p-propylphenol mixture (containing 3508 parts of m-isopropylphenol, 2898 parts of p-isopropylphenol, 1308 parts of m-propylphenol, 1158 parts of p-propylphenol, 66 parts of 2,4,5-trimethylphenol, 56 parts of 2-ethyl-3-methylphenol, 38 parts of 2-methyl-3-ethylphenol, 852 parts of 3-ethyl-5-methylphenol, and 116 parts of others) are added. The reactor is sealed and heated to 260 °C for reaction for 8 hours, and the pressure is gradually increased to be stabilized at 2.5 - 2.6 MPa. The online automatic detection system automatically detects that the m-isopropylphenol is 0.12% qualified, and the reaction ends. The heat transfer oil in the internal coil is cooled by programmed cooling (the temperature of the heat transfer oil gradually decreases slowly from a high temperature to 120 °C), and it is cooled to 170 °C in 1 hour; the propylene released during the reaction is gradually discharged; the discharged gas is pressurized by a pressure pump and stored in a stainless-steel spherical tank (about 5 MPa); after the gas is discharged, the pyrolysis reaction condensate is cooled to 90 °C and purged with nitrogen for 0.5 hour, and 7211.6 parts of pyrolysis reaction products are obtained by filtration (6063.5 parts of phenol, 40.5 parts of 2,4,5-trimethylphenol, 19.9 parts of 2-ethyl-3-methylphenol, 13.9 parts of 2-methyl-3-ethylphenol, 903 parts of 3-ethyl-5-methylphenol, and 170.8 parts of others), and the solid catalyst is recycled;

[0032] Step 2: Synthesis of 2-isopropyl-5-methylphenol and 4-isopropyl-3-methylphenol:

[0033] While performing the cracking and transposition reactions in Step 1, add 10642.6 parts of 99.3% m-cresol (containing 28 ppm of sulfide and 41 ppm of nitride) and 330 parts of a sulfuric acid / phosphoric acid mixed acid (the m-cresol is 1.5 times the molar mass of o-isopropyl / p-propyl phenol, 98% sulfuric acid:85% phosphoric acid mass ratio 6 - 7:4 - 3) into another stainless steel autoclave. Start stirring and heat up to 180°C. Slowly and synchronously introduce the propylene stored in the spherical tank, which is discharged after the first-step cracking reaction is cooled down, into the stainless steel autoclave under reduced pressure for reaction. Keep the temperature in the autoclave at 180 - 190°C for reaction. React with propylene until the pressure in the autoclave reaches 2.3 - 2.5 MPa. When the pressure in the spherical tank drops to 2.6 MPa and the pressure in the autoclave no longer decreases, discharge the unreacted gas. Then react with propylene until the pressure in the autoclave reaches 1.3 - 1.5 MPa. When the pressure in the spherical tank drops to 1.6 MPa and the pressure in the autoclave no longer decreases, discharge the unreacted gas. Continue to react with propylene until the pressure in the autoclave reaches 0.6 MPa. When the pressure in the spherical tank drops to 0.7 MPa and the pressure in the autoclave no longer decreases, discharge the unreacted gas. React with propylene until the pressure in the autoclave reaches 0.1 MPa. When the pressure in the spherical tank drops to 0.1 MPa and the pressure in the autoclave no longer decreases, discharge the unreacted gas. Then continue to react with propylene until the pressure in the spherical tank reaches 0.03 MPa to end the gas introduction. The time for introducing olefins is 9.5 hours. After the introduction, keep the temperature for reaction for 2 hours. Add 990 parts of 30% liquid alkali to the material in the autoclave to neutralize it to pH 7.5. Separate the brine layer. Add the material layer into the bottom of the distillation column (theoretical number of plates 200). At -0.095 MPa and a reflux ratio of 15 - 20, distill to obtain 3502.2 parts of 99.8% m-cresol ((containing 0.7 ppm of sulfide and 0.5 ppm of nitride)), and then successively obtain 5807.3 parts of 99.6% 2-isopropyl-5-methylphenol (thymol) and 3361.9 parts of 99.5% high-efficiency fungicide 4-isopropyl-3-methylphenol;

[0034] Step 3: Distillation separation of the reaction liquid:

[0035] Add 7211.6 parts of the cracking reaction product obtained by filtering in Step 1 (6063.5 parts of phenol, 40.5 parts of 2,4,5-trimethylphenol, 19.9 parts of 2-ethyl-3-methylphenol, 13.9 parts of 2-methyl-3-ethylphenol, 903 parts of 3-ethyl-5-methylphenol, and 170.8 parts of others) into the bottom of the distillation column (100 parts of high-boiling dimethyl diphenyl ether solvent has already been added to the bottom of the column, theoretical number of plates in the column is 300). Add 22 parts of 98% sulfuric acid and mix well. Perform vacuum distillation (vacuum degree -0.09 MPa, reflux ratio 20 - 25:1) to obtain 5845 parts of petrochemical-grade 99.9% phenol (0.5 ppm of nitride, 0.6 ppm of sulfide) and 1013.3 parts of 88.2% crude 3-ethyl-5-methylphenol;

[0036] Add 1013.3 parts of 88.2% crude 3-ethyl-5-methylphenol and 2000 parts of methanol to the reactor. Start stirring and heat up to 65 °C to completely dissolve the materials. Then, first cool down to 36 °C with a cold water bath for 2.5 hours, and then cool down to -5 °C with an ice water bath for 3 hours. Keep warm for 2 hours, filter, drain, and dry to obtain 714.3 parts of 99.6% 3-ethyl-5-methylphenol, with a refining yield of 79.6%.

[0037] Example 2

[0038] A method for preparing thymol from m / p-isopropylphenol / m / p-propylphenol, comprising the following steps: Step 1: Cracking and rearrangement reaction:

[0039] Load 1500 parts of acidic silica-alumina solid catalyst (silica-alumina ratio 1:1) and 35 parts of zirconium phosphate into a stainless steel high-pressure reactor with an external stainless steel condenser and an internal coil. Add 10000 parts of m / p-isopropylphenol mixture (containing 6428 parts of m-isopropylphenol and 3572 parts of p-isopropylphenol). Seal the reactor and heat it up to 250 °C for 8 hours of reaction. The pressure gradually rises and stabilizes at 2.7 - 2.8 MPa. Take samples for analysis with an automatic on-line detection system. When the content of m-isopropylphenol is 0.18% and meets the standard, end the reaction. Cool down the heat transfer oil in the internal coil with a programmed temperature decrease (the temperature of the heat transfer oil gradually decreases slowly from a high temperature to 110 °C), and cool down to 170 °C in 1 hour. Gradually discharge the propylene released during the reaction. The discharged propylene is pressurized by a pressure pump and stored in a stainless steel spherical tank (4.9 MPa). After exhausting the gas, cool the condensate of the cracking reaction to 90 °C and displace it with nitrogen for 0.5 hours. Filter to obtain 6868.1 parts of cracking reaction product (6830.3 parts of phenol and 37.8 parts of others), and reuse the solid catalyst.

[0040] Step 2: Synthesis of 2-isopropyl-5-methylphenol and 4-isopropyl-3-methylphenol:

[0041] While carrying out the cracking and rearrangement reaction in Step 1, add 12,700 parts of 99.3% m-cresol (containing 28 ppm of sulfide and 41 ppm of nitride) and 330 parts of a sulfuric acid / phosphoric acid mixed acid (the m-cresol is 1.6 times the molar mass of o-isopropyl / p-propyl phenol, and the mass ratio of 98% sulfuric acid to 85% phosphoric acid is 6 - 7:4 - 3) into another stainless-steel autoclave. Start stirring and heat up to 185°C. Slowly and synchronously introduce the propylene stored in the spherical tank, which is discharged after the first-step cracking reaction is cooled down, into the stainless-steel autoclave under reduced pressure for reaction. Keep the temperature in the autoclave at 180 - 190°C for reaction. React with propylene until the pressure in the autoclave reaches 2.3 - 2.5 MPa. When the pressure in the spherical tank drops to 2.6 MPa and the pressure in the autoclave no longer decreases, discharge the unreacted gas; then react with propylene until the pressure in the autoclave reaches 1.3 - 1.5 MPa. When the pressure in the spherical tank drops to 1.6 MPa and the pressure in the autoclave no longer decreases, discharge the unreacted gas; continue to react with propylene until the pressure in the autoclave reaches 0.6 MPa. When the pressure in the spherical tank drops to 0.7 MPa and the pressure in the autoclave no longer decreases, discharge the unreacted gas; react with propylene until the pressure in the autoclave reaches 0.1 MPa. When the pressure in the spherical tank drops to 0.1 MPa and the pressure in the autoclave no longer decreases, discharge the unreacted gas; then continue to react with propylene until the pressure in the spherical tank reaches 0.03 MPa to end the gas introduction. The time for introducing olefins is 10 hours, and keep the temperature for reaction for 2.5 hours after the gas introduction; add 990 parts of 30% liquid alkali to the material in the autoclave to neutralize to pH 7.5, separate the brine layer, and add the material layer into the bottom of the distillation column (the number of theoretical plates is 200). At -0.095 MPa and a reflux ratio of 15 - 20, distill to obtain 4,608.3 parts of petrochemical-grade 99.9% m-cresol ((containing 0.9 ppm of sulfide and 0.6 ppm of nitride)), and then successively obtain 6,363.2 parts of 99.8% 2-isopropyl-5-methylphenol (thymol) and 3,738.2 parts of 99.7% high-efficiency fungicide 4-isopropyl-3-methylphenol;

[0042] Step 3: Rectification and separation of the reaction liquid:

[0043] Add 6,868.1 parts of the cracking reaction product obtained by filtering in Step 1 (6,830.3 parts of phenol and 37.8 parts of others) into the bottom of the distillation column (100 parts of high-boiling-point solvent dimethyldiphenyl ether has been added to the bottom of the column, and the number of theoretical plates of the column is 200). Add 20 parts of 98% sulfuric acid and mix evenly. Carry out vacuum rectification (vacuum degree -0.09 MPa, reflux ratio 20 - 25:1) to obtain 6,718.8 parts of petrochemical-grade 99.93% phenol (nitride 0.6 ppm, sulfide 0.5 ppm).

[0044] Example 3

[0045] A method for preparing thymol from m,p-isopropylphenol / m,p-propylphenol, comprising the following steps: Step 1: Cracking and rearrangement reaction:

[0046] In a stainless-steel high-pressure reactor with an external stainless-steel condenser and an internal coil, 1500 parts (silica-alumina ratio 1:1) of an acidic silica-alumina solid catalyst and 35 parts of zirconium phosphate are charged. 10000 parts of a m,p-cumylphenol mixture (containing 6428 parts of m-cumylphenol and 3572 parts of p-cumylphenol) are added. The reactor is sealed and heated to 270 °C for reaction for 6.5 hours. The pressure is gradually increased and stabilized at 2.9 - 3.0 MPa. Samples are taken by an automatic on-line detection system for analysis. When the content of m-cumylphenol is 0.11% (qualified), the reaction is ended. The heat-conducting oil in the internal coil is cooled by programmed cooling (the temperature of the heat-conducting oil gradually and slowly decreases from a high temperature to 120 °C), and it is cooled to 170 °C in 1 hour. Propylene released during the reaction is gradually discharged; the discharged propylene is pressurized by a pressure pump and stored in a stainless-steel spherical tank (5.05 MPa); after the gas is completely discharged, the pyrolysis reaction condensate is cooled to 90 °C and purged with nitrogen for 0.5 hour, and 6867.5 parts of pyrolysis reaction products (6833.9 parts of phenol and 33.6 parts of others) are obtained by filtration. The solid catalyst is recycled;

[0047] Step 2: Synthesis of 2-isopropyl-5-methylphenol and 4-isopropyl-3-methylphenol:

[0048] While carrying out the cracking and rearrangement reaction in the first step, 6350 parts of 99.3% m-cresol (containing 28 ppm of sulfide and 41 ppm of nitride), 5527 parts of 99.1% phenol (containing 182 ppm of sulfide and 147 ppm of nitride), and 330 parts of a sulfuric acid / phosphoric acid mixed acid (the amounts of m-cresol and phenol are 1.6 times the molar mass of o-isopropyl / propyl phenol, and the mass ratio of 98% sulfuric acid to 85% phosphoric acid is 6 - 7:4 - 3) are added to another stainless-steel autoclave. Start stirring and heat up to 170°C. Synchronously and slowly reduce the pressure of the propylene stored in the spherical tank, which is discharged after the first-step cracking reaction is cooled down, and introduce it into the stainless-steel autoclave for reaction. Keep the temperature in the autoclave at 170 - 175°C for reaction. React with propylene until the pressure in the autoclave reaches 2.5 - 2.6 MPa. When the pressure in the spherical tank drops to 2.5 MPa and the pressure in the autoclave no longer decreases, discharge the unreacted gas; then react with propylene until the pressure in the autoclave reaches 1.3 - 1.5 MPa. When the pressure in the spherical tank drops to 1.6 MPa and the pressure in the autoclave no longer decreases, discharge the unreacted gas; continue to react with propylene until the pressure in the autoclave reaches 0.6 MPa. When the pressure in the spherical tank drops to 0.7 MPa and the pressure in the autoclave no longer decreases, discharge the unreacted gas; react with propylene until the pressure in the autoclave reaches 0.1 MPa. When the pressure in the spherical tank drops to 0.1 MPa and the pressure in the autoclave no longer decreases, discharge the unreacted gas; then continue to react with propylene until the pressure in the spherical tank reaches 0.03 MPa to end the gas injection. The time for injecting olefins is 10 hours, and keep the temperature for 4 hours after the injection; add 990 parts of 30% liquid caustic soda to the material in the autoclave to neutralize it to pH 7.5, separate the brine layer, and add the material layer to the bottom of the distillation column (the number of theoretical plates is 200). At -0.095 MPa and a reflux ratio of 20 - 30, distill to obtain 2045.8 parts of petrochemical-grade 99.8% phenol (containing 0.8 ppm of sulfide and 0.6 ppm of nitride), 2281.1 parts of petrochemical-grade 99.9% m-cresol (containing 0.6 ppm of sulfide and 0.5 ppm of nitride), and then successively obtain 2782.3 parts of 99.3% o-isopropyl phenol, 1696 parts of 97.4% p-isopropyl phenol crude product, 3073.4 parts of 99.6% 2-isopropyl-5-methyl phenol (thymol), and 1850.4 parts of 99.5% high-efficiency fungicide 4-isopropyl-3-methyl phenol;

[0049] Add 1696 parts of 97.4% p-isopropyl phenol crude product and 1500 parts of methanol to the reactor. Start stirring and heat up to 65°C to completely dissolve the materials. Then first cool down to 38°C with circulating water for 2 hours, and then cool down to 10°C with chilled brine for 2 hours. Keep the temperature for 2 hours, filter, drain, and dry to obtain 1502.9 parts of 99.8% p-isopropyl phenol, and the refining yield is 90.8%;

[0050] Step 3: Distillation separation of the reaction solution

[0051] Add 6867.5 parts of the cracking reaction product obtained by filtering in Step 1 (6833.9 parts of phenol and 33.6 parts of others) into the bottom of a distillation column (100 parts of a high-boiling dimethyl diphenyl ether solvent has been added to the bottom, and the column has 200 theoretical plates). Add 20 parts of 98% sulfuric acid, mix well, and perform vacuum distillation (vacuum degree: -0.09 MPa, reflux ratio: 10 - 20:1) to obtain 6697.2 parts of petrochemical-grade 99.9% phenol (0.8 ppm of nitride and 0.7 ppm of sulfide).

[0052] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be regarded as limiting the claims involved.

[0053] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing thymol from m / p - isopropylphenol / m / p - propylphenol, characterized in that, Including the following steps: Step 1: Depropylation / Isopropyl reaction: Load acidic aluminosilicate oxide and zirconium phosphate into a stainless-steel high-pressure reactor, then add a mixture of m,p-cumylphenol / m,p-propylphenol, seal the reactor, heat it up to 210-280°C and react for 5-8 hours, gradually increase the pressure to 1.3-3.0 MPa. When the pressure remains stable, sample through an automatic sampling system maintained at 50-60°C. The collected sample enters an on-line automatic detection system for detection. When the content of m-cumylphenol ≤ 0.5%, the reaction ends. Cool down with heat-conducting oil with programmed temperature reduction in the inner coil, quickly cool down to ≤ 180°C within 0.5-1 hour, and gradually discharge the propylene released during the reaction. The discharged gas is pressurized by a pressure pump and stored in a stainless-steel spherical tank. After discharging the gas, the pyrolysis reaction condensate is slightly cooled and replaced with nitrogen for 0.5 hour, filtered to obtain the pyrolysis reaction product, and the solid catalyst is recycled. Step 2: Synthesis of cumylphenol, thymol, etc.: During the pyrolysis and rearrangement reaction in Step 1, add m-cresol or phenol or a mixture of m-cresol and phenol, an acidic catalyst, and an inhibitor into another stainless-steel autoclave, start stirring, heat up to 160°C, and slowly and synchronously introduce the propylene stored in the spherical tank and discharged after cooling the pyrolysis reaction in the first step into the stainless-steel autoclave for reaction, maintaining the autoclave temperature at 170-200°C. Repeatedly introduce propylene multiple times until the pressure in the autoclave is maintained at 2.3-2.5 MPa; when the pressure in the spherical tank drops to 2.6 MPa and the pressure in the autoclave no longer decreases, discharge the unreacted gas in the autoclave; then continue to repeatedly introduce propylene in the spherical tank for reaction until the pressure in the autoclave is 1.3-1.5 MPa. When the pressure in the spherical tank drops to 1.6 MPa and the pressure in the autoclave no longer decreases, discharge the unreacted gas; repeatedly introduce propylene for reaction until the pressure in the autoclave is 0.6 MPa. When the pressure in the spherical tank drops to 0.7 MPa and the pressure in the autoclave no longer decreases, discharge the unreacted gas; introduce propylene for reaction until the pressure in the autoclave is 0.1 MPa. When the pressure in the spherical tank drops to 0.1 MPa and the pressure in the autoclave no longer decreases, discharge the unreacted gas; then continue to introduce propylene for reaction until the pressure in the spherical tank is 0.03 MPa to end the gas introduction. The time for introducing propylene is 3-12 hours, and after introducing the gas, keep it warm and react for 2 hours; cool down the autoclave to ≤ 90°C within 1-3 hours, add 10-35% liquid caustic soda to neutralize the material in the autoclave to pH 7-8, separate the brine layer, add the material layer into the bottom of the distillation column, and distill at -0.085--0.095 MPa with a reflux ratio of 10-20 to obtain 99.5% high-purity m-cresol, and then successively obtain ≥99% 2-isopropyl-5-methylphenol and ≥99% high-efficiency fungicide 4-isopropyl-3-methylphenol; or 99.5% phenol, 99% o-isopropylphenol, ≥96% crude p-isopropylphenol; or 99.5% phenol, 99.5% m-cresol, 99% o-isopropylphenol, ≥96% crude p-isopropylphenol, ≥99% 2-isopropyl-5-methylphenol, ≥99% high-efficiency fungicide 4-isopropyl-3-methylphenol; In a reactor, add crude p - isopropylphenol and methanol, start stirring, and heat up to 60 - 70°C to completely dissolve the materials. Then, first cool down to 30 - 40°C with circulating water for 2 - 3 hours, and then cool down to - 10 - 10°C with chilled brine for 2 - 4 hours. Keep warm for 1 - 3 hours, filter, drain thoroughly, and dry to obtain p - isopropylphenol with a purity of ≥99%. Step 3: Rectification separation: Add the reaction product mixture obtained by filtration in Step 1 to the bottom of a rectification column, and conduct vacuum rectification to obtain high - grade phenol with a purity of ≥99.5%. Sometimes, there will be a small amount of crude 3 - ethyl - 5 - methylphenol with a purity of ≥85%. In a reactor, add crude 3 - ethyl - 5 - methylphenol and methanol, start stirring, and heat up to 60 - 70°C to completely dissolve the materials. Then, first cool down to 30 - 40°C with circulating water for 2 - 3 hours, and then cool down to - 10 - 10°C with chilled brine for 2 - 4 hours. Keep warm for 1 - 3 hours, filter, drain thoroughly, and dry to obtain 3 - ethyl - 5 - methylphenol with a purity of ≥99%.

2. The method for preparing thymol from m / p-isopropylphenol / m / p-propylphenol according to claim 1, characterized in that In Step 1, add a m - p - isopropylphenol / m - p - propylphenol mixture, which is mainly composed of at least 2 - 4 of m - isopropylphenol, p - isopropylphenol, m - propylphenol, and p - propylphenol, with a content of 85 - 100%, 2,4,5 - trimethylphenol 0 - 1%, 2 - ethyl - 3 - methylphenol / 2 - methyl - 3 - ethylphenol 0 - 1%, 3 - ethyl - 5 - methylphenol 0 - 10%, and others 0 - 3%. Preferably, use a coal - chemical m - p - isopropylphenol / m - p - propylphenol mixture.

3. The method for preparing thymol from m / p-isopropylphenol / m / p-propylphenol according to claim 1, characterized in that, In Step 1, load acidic silica - alumina oxides into a stainless - steel high - pressure reactor. The silica - alumina oxides are silica and acidic alumina, and the mass ratio of silica to acidic alumina is 1:0.01 - 50, preferably 1:0.05 - 20.

4. The method for preparing thymol from m / p-isopropylphenol / m / p-propylphenol according to claim 3, wherein The dosage of the silica - alumina oxides is 10 - 30% of the mass of the raw material m - p - isopropylphenol / m - p - propylphenol mixture.

5. The method for preparing thymol from m / p-isopropylphenol / m / p-propylphenol according to claim 1, characterized in that, In Step 1, the temperature of the heat - transfer oil gradually decreases slowly from a high temperature to 100 - 120°C, and the high temperature is 50 - 70°C lower than the de - isopropyl / propyl reaction temperature.

6. The method for preparing thymol from m / p-isopropylphenol / m / p-propylphenol according to claim 1, wherein In Step 1, when the pressure is stable, sample through an automatic sampling system maintained at 50 - 60°C. The automatic sampling system consists of a 316L stainless - steel sampling tube inserted into the reactor, two sets of pneumatic control valves with insulation, steam tracing pipelines, etc.

7. The method for preparing thymol from m - / p -isopropylphenol / m - / p -propylphenol according to claim 1, characterized in that, The samples collected in Step 1 enter an on - line automatic detection system for detection. The on - line automatic detection system consists of a solvent cleaning system, a sample metering pump, a sample mixing system, a sample filtering system, a sample detection system, etc.

8. The solvent cleaning system according to claim 7, which is applicable to a method for preparing thymol from m - p - isopropylphenol / m - p - propylphenol, is characterized in that, The solvent cleaning system consists of an explosion - proof metering pump, automatic control valves, pipelines, etc.

9. The sample mixing system according to claim 7, which is applicable to a method for preparing thymol from m - p - isopropylphenol / m - p - propylphenol, is characterized in that, The sample mixing system refers to a system in which the sample and the solvent are metered by metering pumps and then mixed evenly through a static mixer.

10. The sample detection system according to claim 7, which is applicable to a method for preparing thymol from m - isopropylphenol / m - propylphenol, is characterized in that, The sample detection system consists of a liquid injector, an explosion - proof gas chromatograph, etc.

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