A method and system for preparing thymol from m-p- isopropylphenol / m-p-propylphenol

Abstract

The application discloses a method and system for preparing thymol from m-p-isopropyl phenol / m-p-propyl phenol, wherein the m-p-isopropyl phenol / m-p-propyl phenol mixture is added into a reactor with a catalyst, and a reaction is carried out at a certain temperature; in the reaction, the m-p-isopropyl phenol and the like are subjected to a depropylation reaction to obtain a mixture of phenol and propylene; the reaction is completed under the control of a special online automatic analyzer; the mixture is cooled to a certain temperature; the propylene generated in the reaction is pressurized and stored in a spherical tank; an alkylation catalyst, a mixture of low-grade phenol and m-cresol are added into another reactor to carry out an alkylation reaction of phenol and propylene; and the reaction liquid is subjected to rectification to obtain high-purity phenol, high-purity m-cresol, o-isopropyl phenol, p-isopropyl phenol, 2-isopropyl-5-methyl phenol and 4-isopropyl phenol-3-methyl phenol; and the application can convert the mixed m-p-isopropyl phenol / m-p-propyl phenol with low value and small market demand into the marketable o-isopropyl phenol and p-isopropyl phenol and the like.

Description

Technical Field

[0001] This invention relates to a method for preparing thymol, specifically a method and system for preparing thymol from m-isopropylphenol / m-propylphenol, belonging to the field of organic synthesis and separation technology. Background Technology

[0002] Crude phenol is distilled to obtain phenol, o-cresol, tricresol, m-p-cresol containing 55% meta-position, 99% m-p-cresol, and industrial xylenol. These are sold directly as products without proper fine separation. In fact, the distillation residue of industrial xylenol also contains a fraction of m-p-isopropylphenol / m-p-propylphenol with a boiling point of 227-231℃. This fraction mainly consists of m-isopropylphenol, p-isopropylphenol, m-propylphenol, and p-propylphenol, and also contains some impurities such as 2-ethyl-3-cresol, 2-methyl-3-ethylphenol, 3-ethyl-5-cresol, and 2,4,5-trimethylphenol. Since m-isopropylphenol, p-isopropylphenol, m-propylphenol, and p-propylphenol are difficult to separate using methods such as distillation and tert-butylation, and given that the m-p-isopropylphenol / m-p-propylphenol mixture currently has very little market use, it is necessary to properly process and utilize the m-p-isopropylphenol / m-p-propylphenol mixture.

[0003] The crude phenol extracted from high-temperature coal tar has a relatively high content of intermediate-p-isopropylphenol / m-p-propylphenol, which cannot be separated by conventional distillation. The tert-butylation reaction can only yield a mixture of m-isopropylphenol / m-propylphenol and a mixture of p-isopropylphenol / p-propylphenol, which still have very low utilization value and new separation methods need to be developed. This is because isopropylphenol / propylphenol is more likely to undergo depropylation / isopropylation reaction at high temperatures or in the presence of high temperatures and catalysts (especially acidic catalysts). Summary of the Invention

[0004] The purpose of this invention is to provide a method and system for preparing thymol from m-isopropylphenol / m-propylphenol in order to solve the above-mentioned problems. Using a mixture of m-isopropylphenol / m-propylphenol as raw material, and employing a suitable dealkylation catalyst at an appropriate temperature, the isopropyl / propyl groups in m-isopropylphenol / m-propylphenol are selectively removed to generate phenol and propylene. Because the deisopropyl / propylation reaction is carried out under a specific catalyst and at a relatively low temperature, the ethyl and methyl groups in the phenolic substances rarely undergo removal reactions. Then, the propylene obtained from the decomposition is reacted with an acidic catalyst and an excess of low-grade m-cresol, followed by distillation to obtain high-quality phenol, m-cresol, thymol, and the bactericide 3-methyl-4-isopropylphenol. This invention is simple to operate, produces less waste, and has low production costs.

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

[0006] Step 1: Deisopropyl / propyl reaction:

[0007] Acidic silica-alumina oxide and zirconium phosphate (1-10% of the silica-alumina oxide catalyst mass) are loaded into a stainless steel high-pressure reactor (with an external stainless steel condenser and internal coil). A mixture of m- and p-isopropylphenol / m- and p-propylphenol is then added. The reactor is sealed, and the temperature is raised to 210-280℃ for 5-8 hours. The pressure is gradually increased to 1.3-3.0 MPa. When the pressure stabilizes, samples are taken using an automatic sampling system maintained at 50-60℃. The collected samples are then analyzed by an online automatic detection system. The reaction is terminated when m- and p-isopropylphenol levels are ≤0.5% (if m- and p-isopropylphenol levels are not specified). If phenol ≥ 2%, catalyst needs to be added to continue the reaction; if m-isopropylphenol ≤ 2%, the temperature can be increased by 10-20℃ to continue the reaction until it is qualified. The inner coil is cooled with heat transfer oil with programmed cooling (the temperature of the heat transfer oil is gradually and slowly reduced from high temperature to 100-120℃), and then rapidly cooled to ≤ 180℃ within 0.5-1 hour to gradually remove the propylene released in the reaction; the removed gas is pressurized to 5MPa by a pressure pump and stored in a stainless steel spherical tank; after the gas is removed, the condensate of the cracking reaction is cooled slightly and replaced with nitrogen for 0.5 hours, filtered to obtain the cracking reaction products (mainly containing phenol), and the solid catalyst is reused.

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

[0009] Simultaneously with the cracking and transposition reaction in step one, m-cresol or phenol or a mixture of m-cresol and phenol, an acidic catalyst, and a polymerization inhibitor are added to another stainless steel pressure vessel. Stirring is started, and the temperature is raised to 160°C. Propylene, stored in a spherical tank after cooling from the first cracking reaction, is simultaneously and slowly introduced into the stainless steel pressure vessel under reduced pressure, maintaining the vessel temperature at 170–200°C. Propylene is repeatedly introduced until the pressure inside the vessel 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 pressure vessel no longer decreases, the unreacted gas is discharged. Then, the reaction is repeated several times with propylene in the spherical tank until the pressure inside the pressure vessel reaches 1.3–1.5 MPa. When the pressure in the spherical tank drops to 1.6 MPa and the pressure in the pressure vessel no longer decreases, the unreacted gas is discharged. The reaction is repeated again until the pressure inside the vessel reaches 0.6 MPa. When the pressure in the spherical tank drops to 0.7 MPa and the pressure in the pressure vessel no longer decreases, the unreacted gas is discharged. The reaction is repeated until the pressure inside the vessel reaches 0.1 MPa. When the pressure drops to 0.1 MPa and the pressure in the pressure vessel no longer decreases, the unreacted gas is discharged. Propylene is then introduced to continue the reaction until the pressure in the spherical tank reaches 0.03 MPa, at which point the gas introduction stops. The propylene introduction time is 3–12 hours, followed by a 2-hour heat preservation reaction. The pressure vessel is then cooled to ≤90℃ over 1–3 hours. 10–35% liquid alkali is added to the material in the vessel to neutralize it to pH 7–8. The brine layer is separated, and the material layer is added to the bottom of the distillation column. The pressure is maintained at -0.085–-0.095 MPa, with a reflux ratio of 10–2. 0. Distillation yields 99.5% high-purity m-cresol, followed by the sequential production of ≥99% 2-isopropyl-5-cresol and ≥99% highly effective bactericide 4-isopropyl-3-cresol; or 99.5% phenol, 99% o-isopropylphenol, and ≥96% crude p-isopropylphenol; or 99.5% phenol, 99.5% m-cresol, 99% o-isopropylphenol, and ≥96% crude p-isopropylphenol, ≥99% 2-isopropyl-5-cresol, and ≥99% highly effective bactericide 4-isopropyl-3-cresol.

[0010] Crude p-isopropylphenol and methanol were added to a reactor, and the mixture was stirred and heated to 60-70°C to completely dissolve the material. Then, the temperature was lowered to 30-40°C by circulating water for 2-3 hours, and then lowered to -10-10°C by freezing brine for 2-4 hours. The temperature was maintained for 1-3 hours, filtered, dried by vacuum, and then dried to obtain ≥99% p-isopropylphenol.

[0011] Step 3: Distillation and separation:

[0012] The reaction product mixture obtained by filtration in step one is added to the bottom of a distillation column and distilled under reduced pressure to obtain high-grade phenol with a purity of ≥99.5%, and sometimes a small amount of crude 3-ethyl-5-cresol with a purity of ≥85%.

[0013] Crude 3-ethyl-5-cresol and methanol were added to the reactor, and the mixture was stirred and heated to 60-70°C to completely dissolve the material. Then, the temperature was lowered to 30-40°C by circulating water for 2-3 hours, and then lowered to -10-10°C by freezing brine for 2-4 hours. The temperature was maintained for 1-3 hours, filtered, dried, and then dried to obtain ≥99% 3-ethyl-5-cresol.

[0014] Preferably, in step one, a mixture of m- and p-isopropylphenol / m- and p-propylphenol is added. The m- and p-isopropylphenol / m- and p-propylphenol mixture mainly consists of at least 2 to 4 of the following: m- and p-isopropylphenol, p- and p-propylphenol, with a content of 85 to 100%. It also contains 0 to 1% of 2,4,5-trimethylphenol, 0 to 1% of 2-ethyl-3-methylphenol / 2-methyl-3-ethylphenol, 0 to 10% of 3-ethyl-5-methylphenol, and 0 to 3% of other components. Preferably, it is a coal-processed m- and p-isopropylphenol / m- and p-propylphenol mixture.

[0015] Preferably, in step one, acidic silica-alumina oxide is loaded into a stainless steel high-pressure reactor (with an external stainless steel condenser and an internal coil). The silica-alumina oxide is silicon dioxide and acidic alumina, wherein the mass ratio of silicon dioxide to acidic alumina is 1:0.01 to 50, preferably 1:0.05 to 20; the amount used is 10 to 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 is gradually and slowly reduced from a high temperature to 100-120°C, where the high temperature is 50-70°C lower than the deisopropyl / propyl reaction temperature.

[0017] Preferably, the acidic catalyst in step two is at least one of sulfuric acid, phosphoric acid, p-toluenesulfonic acid, benzenesulfonic acid, solid acid catalyst, acidic resin, zirconium oxide, acidic alumina, and silicon oxide, preferably a mixture of sulfuric acid and phosphoric acid; the amount of the mixed acid is 0.5-5% of the mass of m-cresol or phenol and their mixtures, wherein the mass ratio of sulfuric acid to phosphoric acid is 5-7:5-3.

[0018] Preferably, the polymerization inhibitor in step two is hydroquinone, 2-methylhydroquinone, 2-tert-butylhydroquinone, 6-tert-butyl-2,4-dimethylphenol, p-methoxyphenol, etc., with 2-methylhydroquinone being the most preferred.

[0019] Preferably, the sample collected in step one is fed into an online automatic detection system for testing. This online automatic detection system comprises a solvent cleaning system, a sample metering pump (or flow meter), a sample mixing system, a sample filtration system, and a sample detection system. The solvent cleaning system consists of an explosion-proof metering pump (or flow meter), automatic control valves, and pipelines. The sample mixing system refers to a system where the sample and solvent are metered by the metering pump (or flow meter) and then mixed uniformly by a static mixer. The sample detection system consists of a liquid injector and an explosion-proof gas chromatograph (flame ionization detector (FID)). The detection conditions are as follows: flame ionization detector (FID detector); the measurement uses a column temperature of 100–130℃, an injector temperature of 240–260℃, a detector temperature of 240–260℃, 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 of 20–80, and a make-up flow rate of 15–50 ml / min.

[0020] The solvent cleaning system provided in this 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, automatic control valves, pipelines, etc.

[0021] The sample mixing system provided in this 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 solvent are mixed uniformly by a static mixer after being metered by a metering pump.

[0022] The sample detection system provided in this 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. This invention removes isopropyl / propyl groups from the crude phenol distillation extract m-p-isopropylphenol / m-p-propylphenol mixture at high temperature to obtain phenol and propylene. Then, the removed propylene is reacted with excess low-grade m-cresol to obtain petrochemical-grade phenol and petrochemical-grade m-cresol through distillation. This converts m-p-isopropylphenol / m-p-propylphenol into thymol and 3-methyl-4-isopropylphenol products, thereby increasing added value.

[0025] 2. This invention removes isopropyl / propyl groups from the crude phenol distillation extract m-p-isopropylphenol / m-p-propylphenol mixture at high temperature to obtain phenol and propylene. Then, the removed propylene is reacted with excess low-grade phenol and distilled to obtain petrochemical-grade phenol. This converts m-p-isopropylphenol / m-p-propylphenol into o-isopropylphenol and p-isopropylphenol products, thereby increasing added value.

[0026] 3. In this invention, for mixed m-p-isopropylphenol / m-p-propylphenol raw materials containing 3-ethyl-5-cresol, the content of 2-ethyl-3-cresol / 2-methyl-3-ethylphenol and 2,4,5-trimethylphenol in the raw materials is much lower than that of 3-ethyl-5-cresol. Moreover, 2-ethyl-3-cresol / 2-methyl-3-ethylphenol can also be partially catalytically transposed to 3-ethyl-5-cresol. The boiling point of 3-ethyl-5-cresol is much higher than that of phenol. Therefore, this invention can sometimes also obtain crude 3-ethyl-5-cresol by deisopropylating / propylating. The crude product is then crystallized in a solvent to obtain 99% 3-ethyl-5-cresol. 3-ethyl-5-cresol is difficult to synthesize chemically and is relatively expensive, thus increasing the variety of products.

[0027] 4. This invention uses an online automatic detection system to detect the depropylene effect of isopropylphenol, which is timely and accurate, reducing the problems of cumbersome sampling, long analysis time, and untimely data guidance caused by manual sampling and analysis. Attached Figure Description

[0028] Figure 1 This is a flowchart of an automatic detection device for the removal of propylene from a mixture of m- and p-isopropylphenol and m- and p-propylphenol. Detailed Implementation

[0029] Example 1

[0030] A method for preparing thymol from m-p-isopropylphenol / m-p-propylphenol includes the following steps: Step 1: Cleavage and transposition reaction:

[0031] In a stainless steel high-pressure reactor equipped with an external stainless steel condenser and internal coil, 2000 parts of acidic silica-alumina oxide solid catalyst (silicon-to-alumina ratio 1:1), 50 parts of zirconium phosphate, and 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 other components) were added. The reactor was sealed and heated to 260℃ for 8 hours. The pressure was gradually increased to a stable level of 2.5–2.6 MPa. An online automatic detection system was used to monitor the reaction. The reaction was terminated when the isopropylphenol content was 0.12%. The internal 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℃) for 1 hour to 170℃. The propylene released during the reaction was gradually discharged. The discharged gas was pressurized by a pressure pump and stored in a stainless steel spherical tank (about 5MPa). After the gas was discharged, the pyrolysis reaction condensate was cooled slightly to 90℃ and purged with nitrogen for 0.5 hours. After filtration, 7211.6 parts of pyrolysis reaction products were obtained (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). The solid catalyst was reused.

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

[0033] Simultaneously with the cracking and transposition reaction in step one, 10642.6 parts of 99.3% m-cresol (containing 28 ppm sulfides and 41 ppm nitrides) and 330 parts of a sulfuric acid / phosphoric acid mixture (m-cresol being 1.5 times the molar mass of o-isopropyl / propylphenol, with a mass ratio of 98% sulfuric acid to 85% phosphoric acid of 6-7:4-3) were added to another stainless steel pressure vessel. Stirring was started, and the temperature was raised to 180°C. Propylene, stored in a spherical tank after cooling from the first cracking reaction, was simultaneously and slowly introduced into the stainless steel pressure vessel under reduced pressure. The vessel temperature was maintained at 180-190°C. The reaction was continued until the pressure inside the vessel reached 2.3-2.5 MPa. When the pressure in the spherical tank dropped to 2.6 MPa and the pressure in the pressure vessel no longer decreased, the unreacted gas was discharged. Then, the reaction was continued until the pressure inside the vessel reached 1.3-1.5 MPa. When the pressure in the spherical tank dropped to 1.6 MPa and the pressure in the pressure vessel no longer decreased, the unreacted gas was discharged. The reaction was continued until the pressure inside the vessel reached 0... The pressure was increased to 0.6 MPa. When the pressure in the spherical tank dropped to 0.7 MPa and the pressure in the pressure vessel no longer decreased, the unreacted gas was discharged. Propylene was then introduced to react until the pressure inside the vessel reached 0.1 MPa. When the pressure in the spherical tank dropped to 0.1 MPa and the pressure in the pressure vessel no longer decreased, the unreacted gas was discharged. Propylene was then introduced to react until the pressure in the spherical tank reached 0.03 MPa, at which point the gas introduction was stopped. The olefin introduction time was 9.5 hours, followed by a 2-hour heat preservation reaction. 990 parts of 30% liquid alkali were added to the material in the vessel to neutralize it to pH 7. 5. Separate the brine layer and add the material layer to the bottom of the distillation column (theoretical plate number 200). Distill at -0.095 MPa and a reflux ratio of 15-20 to obtain 3502.2 parts of 99.8% m-cresol (containing 0.7 ppm sulfides and 0.5 ppm nitrides). Then, successively obtain 5807.3 parts of 99.6% 2-isopropyl-5-cresol (thymol) and 3361.9 parts of 99.5% high-efficiency bactericide 4-isopropyl-3-cresol.

[0034] Step 3: Distillation and separation of the reaction solution:

[0035] The cracking reaction products obtained from step one (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) were added to the bottom of a distillation column (100 parts of high-boiling-point dimethyl diphenyl ether solvent had been added to the bottom of the column, and the theoretical plate was 300). 22 parts of 98% sulfuric acid were added, mixed well, and the mixture was subjected to 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 nitrides and 0.6 ppm of sulfides) and 1013.3 parts of crude 88.2% 3-ethyl-5-methylphenol.

[0036] 1013.3 parts of crude 88.2% 3-ethyl-5-cresol and 2000 parts of methanol were added to the reactor. The mixture was stirred and heated to 65°C to completely dissolve the material. Then, the mixture was cooled to 36°C in a cold water bath for 2.5 hours, followed by a cooling to -5°C in an ice water bath for 3 hours. The mixture was kept at this temperature for 2 hours, filtered, dried under vacuum, and then dried to obtain 714.3 parts of 99.6% 3-ethyl-5-cresol, with a purification yield of 79.6%.

[0037] Example 2

[0038] A method for preparing thymol from m-p-isopropylphenol / m-p-propylphenol includes the following steps: Step 1: Cleavage and transposition reaction:

[0039] In a stainless steel high-pressure reactor equipped with an external stainless steel condenser and internal coil, 1500 parts of acidic silica-alumina oxide solid catalyst (silicon-alumina ratio 1:1), 35 parts of zirconium phosphate, and 10000 parts of a mixture of m- and p-isopropylphenol (containing 6428 parts of m-isopropylphenol and 3572 parts of p-isopropylphenol) were added. The reactor was sealed and heated to 250℃ for 8 hours. The pressure was gradually increased and stabilized at 2.7–2.8 MPa. An automatic online detection system was used for sampling and analysis. The m-isopropylphenol content was 0.18%, which is considered acceptable. The reaction was carried out in a coil, where the internal coil was cooled using a programmed cooling heat transfer oil (the temperature of the heat transfer oil was gradually and slowly reduced from a high temperature to 110℃), and then cooled to 170℃ after 1 hour. Propylene released during the reaction was gradually discharged. The discharged propylene was pressurized by a pressure pump and stored in a stainless steel spherical tank (4.9MPa). After the gas was discharged, the condensate from the cracking reaction was cooled slightly to 90℃ and purged with nitrogen for 0.5 hours. After filtration, 6868.1 parts of cracking reaction products were obtained (6830.3 parts of phenol and 37.8 parts of other products). The solid catalyst was reused.

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

[0041] Simultaneously with the cracking and transposition reactions in step one, 12,700 parts of 99.3% m-cresol (containing 28 ppm sulfides and 41 ppm nitrides) and 330 parts of a sulfuric acid / phosphoric acid mixture (m-cresol being 1.6 times the molar mass of o-isopropylphenol / propylphenol, with a mass ratio of 98% sulfuric acid to 85% phosphoric acid of 6-7:4-3) were added to another stainless steel pressure vessel. Stirring was started, and the temperature was raised to 185°C. Propylene, stored in a spherical tank after cooling from the first cracking reaction, was simultaneously and slowly introduced into the stainless steel pressure vessel under reduced pressure. The vessel temperature was maintained at 180-190°C. Propylene was introduced until the pressure inside the vessel reached 2.3-2.5 MPa. When the pressure in the spherical tank dropped to 2.6 MPa and the pressure in the pressure vessel no longer decreased, the unreacted gas was discharged. Then, propylene was introduced until the pressure inside the vessel reached 1.3-1.5 MPa. When the pressure in the spherical tank dropped to 1.6 MPa and the pressure in the pressure vessel no longer decreased, the unreacted gas was discharged. Propylene was then introduced again until the pressure inside the vessel reached 0.6 MPa. When the pressure in the spherical tank drops to 0.7 MPa and the pressure in the pressure vessel no longer decreases, the unreacted gas is discharged. Propylene is then introduced to react until the pressure inside the vessel reaches 0.1 MPa. When the pressure in the spherical tank drops to 0.1 MPa and the pressure in the pressure vessel no longer decreases, the unreacted gas is discharged. Propylene is then introduced to react until the pressure in the spherical tank reaches 0.03 MPa, at which point the gas introduction is stopped. The olefin introduction time is 10 hours, followed by a 2.5-hour heat preservation reaction. 990 parts of 30% liquid alkali are added to the material in the vessel to neutralize to pH 7.5. After separating the brine layer, the material layer was added to the bottom of the distillation column (theoretical plate number 200). Distillation was carried out at -0.095 MPa and a reflux ratio of 15-20 to obtain 4608.3 parts of petrochemical grade 99.9% m-cresol (containing 0.9 ppm sulfides and 0.6 ppm nitrides). Then, 6363.2 parts of 99.8% 2-isopropyl-5-cresol (thymol) and 3738.2 parts of 99.7% high-efficiency bactericide 4-isopropyl-3-cresol were obtained sequentially.

[0042] Step 3: Distillation and separation of the reaction solution:

[0043] The 6868.1 parts of the cracking reaction product obtained from the filtration in step one (6830.3 parts of phenol and 37.8 parts of other products) were added to the bottom of a distillation column (100 parts of high-boiling-point dimethyl diphenyl ether solvent had already been added to the bottom of the column, and the theoretical plate was 200). 20 parts of 98% sulfuric acid were added, mixed well, and the mixture was subjected to vacuum distillation (vacuum degree -0.09MPa, reflux ratio 20-25:1) to obtain 6718.8 parts of petrochemical grade 99.93% phenol (0.6 ppm of nitrides and 0.5 ppm of sulfides).

[0044] Example 3

[0045] A method for preparing thymol from m-p-isopropylphenol / m-p-propylphenol includes the following steps: Step 1: Cleavage and transposition reaction:

[0046] In a stainless steel high-pressure reactor equipped with an external stainless steel condenser and internal coil, 1500 parts of acidic silica-alumina oxide solid catalyst (silicon-to-alumina ratio 1:1), 35 parts of zirconium phosphate, and 10000 parts of a mixture of m- and p-isopropylphenol (containing 6428 parts of m-isopropylphenol and 3572 parts of p-isopropylphenol) were added. The reactor was sealed and heated to 270℃ for 6.5 hours. The pressure was gradually increased and stabilized at 2.9–3.0 MPa. An automatic online detection system was used for sampling and analysis. The m-isopropylphenol content was 0.11%, which is considered acceptable. After the reaction was completed, the internal 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 propylene released in the reaction was gradually discharged; the discharged propylene was pressurized by a pressure pump and stored in a stainless steel spherical tank (5.05MPa); after the gas was discharged, the pyrolysis reaction condensate was cooled slightly to 90℃ and purged with nitrogen for 0.5 hours, and filtered to obtain 6867.5 parts of pyrolysis reaction products (6833.9 parts of phenol and 33.6 parts of other products), and the solid catalyst was reused;

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

[0048] Simultaneously with the pyrolysis and transposition reaction in step one, 6350 parts of 99.3% m-cresol (containing 28 ppm sulfides and 41 ppm nitrides), 5527 parts of 99.1% phenol (containing 182 ppm sulfides and 147 ppm nitrides), and 330 parts of a sulfuric acid / phosphoric acid mixture (the amount of m-cresol and phenol is 1.6 times the molar mass of o-isopropyl / propylphenol, and the mass ratio of 98% sulfuric acid to 85% phosphoric acid is 6-7:4-3) are added to another stainless steel pressure vessel. Stirring is started, and the temperature is raised to 170°C. After cooling the first-step pyrolysis reaction, the mixture is discharged. Propylene stored in a spherical tank is simultaneously and slowly introduced into a stainless steel pressure vessel under reduced pressure to react, maintaining the vessel temperature at 170–175°C. The reaction continues until the pressure inside the vessel reaches 2.5–2.6 MPa. When the pressure in the spherical tank drops to 2.5 MPa and the pressure in the pressure vessel no longer decreases, unreacted gases are discharged. Then, propylene is introduced again until the pressure inside the vessel reaches 1.3–1.5 MPa. When the pressure in the spherical tank drops to 1.6 MPa and the pressure in the pressure vessel no longer decreases, unreacted gases are discharged. The reaction continues until the pressure inside the vessel reaches 0.6 MPa, and when the pressure in the spherical tank drops to 0.7 MPa… When the pressure in the pressure vessel no longer decreases, the unreacted gas is discharged. Propylene is introduced to react until the pressure inside the vessel reaches 0.1 MPa. When the pressure in the spherical tank drops to 0.1 MPa and the pressure in the pressure vessel no longer decreases, the unreacted gas is discharged. Propylene is then introduced to react until the pressure in the spherical tank reaches 0.03 MPa, at which point the gas introduction is stopped. The olefin introduction time is 10 hours, followed by a 4-hour heat treatment. 990 parts of 30% liquid alkali are added to the material in the vessel to neutralize to pH 7.5. The brine layer is separated, and the material layer is added to the bottom of a distillation column (theoretical tray number 200). The column is then treated at -0.095 MPa with a reflux ratio of 20 to 3. 0. Distillation yielded 2045.8 parts of petrochemical-grade 99.8% phenol (containing 0.8 ppm sulfides and 0.6 ppm nitrides), 2281.1 parts of petrochemical-grade 99.9% m-cresol (containing 0.6 ppm sulfides and 0.5 ppm nitrides), followed by 2782.3 parts of 99.3% o-isopropylphenol, 1696 parts of 97.4% crude p-isopropylphenol, 3073.4 parts of 99.6% 2-isopropyl-5-cresol (thymol), and 1850.4 parts of 99.5% highly effective bactericide 4-isopropyl-3-cresol.

[0049] 1696 parts of crude p-isopropylphenol (97.4%) and 1500 parts of methanol were added to the reactor. The mixture was stirred and heated to 65°C to completely dissolve the material. Then, the temperature was lowered to 38°C by circulating water for 2 hours, followed by cooling to 10°C by chilled brine for 2 hours. The mixture was kept at this temperature for 2 hours, filtered, dried under vacuum, and then dried to obtain 1502.9 parts of 99.8% p-isopropylphenol, with a purification yield of 90.8%.

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

[0051] The 6867.5 parts of the cracking reaction product obtained from the filtration in step one (6833.9 parts of phenol and 33.6 parts of other products) were added to the bottom of a distillation column (100 parts of high-boiling-point dimethyl diphenyl ether solvent had already been added to the bottom of the column, and the theoretical plate was 200). 20 parts of 98% sulfuric acid were added, mixed well, and the mixture was distilled under reduced pressure (vacuum degree -0.09MPa, reflux ratio 10-20:1) to obtain 6697.2 parts of petrochemical grade 99.9% phenol (0.8 ppm of nitrides and 0.7 ppm of sulfides).

[0052] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0053] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider 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, Includes the following steps: Step 1: Deisopropyl / propyl reaction: Acidic silica-alumina oxide and zirconium phosphate were loaded into a stainless steel high-pressure reactor, followed by the addition of a mixture of m- and p-isopropylphenol. The reactor was sealed, and the temperature was raised to 210–280°C for 5–8 hours, with the pressure gradually increased to 1.3–3.0 MPa. When the pressure stabilized, samples were taken using an automatic sampling system maintained at 50–60°C. The collected samples were then analyzed by an online automatic detection system. The reaction was terminated when the m-isopropylphenol concentration was ≤0.5%. The internal coil was cooled using programmed cooling heat transfer oil, rapidly reducing the temperature to ≤180°C within 0.5–1 hour, gradually discharging the propylene released during the reaction. The discharged gas was pressurized by a pressure pump and stored in a stainless steel spherical tank. After the gas was discharged, the pyrolysis reaction condensate was cooled slightly and purged with nitrogen for 0.5 hours. The pyrolysis reaction products were obtained by filtration, and the solid catalyst was reused. Step 2: Synthesis of isopropylphenol and thymol: Simultaneously with the cracking and transposition reaction in step one, m-cresol or phenol or a mixture of m-cresol and phenol, an acidic catalyst, and a polymerization inhibitor are added to another stainless steel pressure vessel. Stirring is started, and the temperature is raised to 160°C. Propylene, stored in a spherical tank after cooling from the first cracking reaction, is simultaneously and slowly introduced into the stainless steel pressure vessel under reduced pressure, maintaining the vessel temperature at 170–200°C. Propylene is repeatedly introduced until the pressure inside the vessel 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 pressure vessel no longer decreases, the unreacted gas is discharged. Then, the reaction is repeated several times with propylene in the spherical tank until the pressure inside the pressure vessel reaches 1.3–1.5 MPa. When the pressure in the spherical tank drops to 1.6 MPa and the pressure in the pressure vessel no longer decreases, the unreacted gas is discharged. The reaction is repeated again until the pressure inside the vessel reaches 0.6 MPa. When the pressure in the spherical tank drops to 0.7 MPa and the pressure in the pressure vessel no longer decreases, the unreacted gas is discharged. The reaction is repeated until the pressure inside the vessel reaches 0.1 MPa. When the pressure drops to 0.1 MPa and the pressure in the pressure vessel no longer decreases, the unreacted gas is discharged. Propylene is then introduced to continue the reaction until the pressure in the spherical tank reaches 0.03 MPa, at which point the gas introduction stops. The propylene introduction time is 3–12 hours, followed by a 2-hour heat preservation reaction. The pressure vessel is then cooled to ≤90℃ over 1–3 hours. 10–35% liquid alkali is added to the material in the vessel to neutralize it to pH 7–8. The brine layer is separated, and the material layer is added to the bottom of the distillation column. The pressure is maintained at -0.085–-0.095 MPa, with a reflux ratio of 10–2.

0. Distillation yields 99.5% high-purity m-cresol, followed by the sequential production of ≥99% 2-isopropyl-5-cresol and ≥99% highly effective bactericide 4-isopropyl-3-cresol; or 99.5% phenol, 99% o-isopropylphenol, and ≥96% crude p-isopropylphenol; or 99.5% phenol, 99.5% m-cresol, 99% o-isopropylphenol, and ≥96% crude p-isopropylphenol, ≥99% 2-isopropyl-5-cresol, and ≥99% highly effective bactericide 4-isopropyl-3-cresol. Crude p-isopropylphenol and methanol were added to a reactor, and the mixture was stirred and heated to 60-70°C to completely dissolve the material. Then, the temperature was lowered to 30-40°C by circulating water for 2-3 hours, and then lowered to -10-10°C by chilled brine for 2-4 hours. The temperature was maintained for 1-3 hours, filtered, dried by vacuum, and then dried to obtain ≥99% p-isopropylphenol. Step 3: Distillation and separation: The reaction product mixture obtained by filtration in step one is added to the bottom of a distillation column and distilled under reduced pressure to obtain high-grade phenol with a purity of ≥99.5%, and sometimes a small amount of crude 3-ethyl-5-cresol with a purity of ≥85%. Crude 3-ethyl-5-cresol and methanol were added to the reactor, and the mixture was stirred and heated to 60-70°C to completely dissolve the material. Then, the temperature was lowered to 30-40°C by circulating water for 2-3 hours, and then lowered to -10-10°C by freezing brine for 2-4 hours. The temperature was maintained for 1-3 hours, filtered, dried, and then dried to obtain ≥99% 3-ethyl-5-cresol.

2. The method for preparing thymol from m-p-isopropylphenol / m-p-propylphenol according to claim 1, characterized in that, In step one, a mixture of m- and p-isopropylphenol / m- and p-propylphenol is added. The m- and p-isopropylphenol / m- and p-propylphenol mixture mainly consists of at least 2 to 4 of the following: m- and p-isopropylphenol, p- and p-propylphenol, with a content of 85 to 100%. It also contains 0 to 1% 2,4,5-trimethylphenol, 0 to 1% 2-ethyl-3-methylphenol / 2-methyl-3-ethylphenol, 0 to 1% 3-ethyl-5-methylphenol, and 0 to 3% other compounds.

3. The method for preparing thymol from m-p-isopropylphenol / m-p-propylphenol according to claim 1, characterized in that, In step one, acidic silicon-aluminum oxide is loaded into a stainless steel high-pressure reactor. The acidic silicon-aluminum oxide is composed of silicon dioxide and acidic aluminum oxide, wherein the mass ratio of silicon dioxide to acidic aluminum oxide is 1:0.01 to 50.

4. The method for preparing thymol from m-p-isopropylphenol / m-p-propylphenol according to claim 3, characterized in that, The amount of acidic silica-alumina oxide used 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 one, the temperature of the heat transfer oil is gradually and slowly reduced from a high temperature to 100-120°C, where the high temperature is 50-70°C lower than the deisopropyl / propyl reaction temperature.

6. The method for preparing thymol from m-p-isopropylphenol / m-p-propylphenol according to claim 1, characterized in that, In step one, when the pressure is stable, the sample is taken by an automatic sampling system that is kept at 50-60°C. The automatic sampling system consists of a 316L stainless steel sampling tube inserted into the reactor, two sets of insulated pneumatic control valves, and a steam tracing pipeline.

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 one are then tested by an online automatic detection system, which consists of a solvent cleaning system, a sample metering pump, a sample mixing system, a sample filtration system, and a sample detection system.

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

9. The method for preparing thymol from m-p-isopropylphenol / m-p-propylphenol according to claim 7, characterized in that, The sample mixing system refers to a system in which the sample and solvent are mixed uniformly by a static mixer after being metered by a metering pump.

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

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