Process for preparing phenolic products from 2, 4-xylenol / 2, 5-xylenol

Abstract

The invention discloses a process for preparing phenol products from 2, 4-xylenol / 2, 5-xylenol, which comprises the following steps: adding a 2, 4-xylenol / 2, 5-xylenol mixture into a reactor added with silicon-aluminum-chromium oxide and an acidic catalyst, carrying out dealkylation reaction at 280-400 DEG C, removing propylene, ethylene and the like from o-isopropyl phenol, 2-methyl-6-ethyl phenol and the like in the reaction, and then carrying out dealkylation reaction to obtain the phenol products. The mixed phenol and olefin mixture contains phenol, cresol and 2, 4-xylenol / 2, 5-xylenol; the mixture is rapidly cooled and liquefied, olefin is discharged, rectification is carried out, and high-purity 2, 5-xylenol / 2, 4-xylenol without o-isopropyl phenol, 2-ethyl-6-cresol and the like is obtained; the preparation method comprises the following steps: reacting propylene with m-cresol by controlling the reaction temperature to obtain thymol, 4-isopropyl-3-cresol and the like, and reacting ethylene with phenol to obtain o-ethyl phenol and p-ethyl phenol; according to the method, ethyl in 2-ethyl-6-cresol and isopropyl / propyl in o-isopropyl phenol in alkylphenol are removed at high temperature, a purified 2, 5 / 2, 4-xylenol product is obtained, and a high-purity product is produced.

Description

Technical Field

[0001] The present invention relates to a process for preparing phenolic products, specifically a process for preparing phenolic products from 2,4-xylenol / 2,5-xylenol, and belongs to the technical field of organic synthesis and separation. Background Art

[0002] Crude phenol is rectified to obtain phenol, o-cresol, three-component cresol, m,p-cresol containing 55% of the meta-position, 99% m,p-cresol, and industrial xylenol, without very good fine separation. In fact, industrial xylenol can be rectified to obtain a mixed phenol of 2,4-xylenol / 2,5-xylenol with more than 80%, which contains some o-isopropyl / p-propylphenol, 2-ethyl-6-methylphenol, etc.; since the proportion of 2,4-xylenol / 2,5-xylenol in xylenol is relatively high and the quantity is also relatively large, the presence of impurities such as o-isopropyl / p-propylphenol and 2-methyl-6-ethylphenol will affect the performance and application of 2,4-xylenol / 2,5-xylenol, and it is necessary to consider separating o-isopropylphenol / o-propylphenol and 2-ethyl-6-methylphenol from the 2,4-xylenol / 2,5-xylenol mixture.

[0003] The content of 2,4-xylenol / 2,5-xylenol in the crude phenol extracted from high-temperature coal tar is relatively high, but the content of o-isopropylphenol / o-propylphenol and 2-methyl-6-ethylphenol is very low, so it will not affect the separation and application of 2,4-xylenol / 2,5-xylenol; the content of 2,4-xylenol / 2,5-xylenol in medium and low-temperature gasification crude phenol is not high, and the content of o-isopropylphenol / o-propylphenol and 2-ethyl-6-methylphenol is low, and the impact on the separation and application of 2,4-xylenol / 2,5-xylenol is not too large, and the economy of separating 2,4-xylenol / 2,5-xylenol is not very good; the content of 2,4-xylenol / 2,5-xylenol in the crude phenol extracted from medium and low-temperature phenol-containing coal tar and coal liquefaction phenol-containing tar is high, and the content of o-isopropylphenol / o-propylphenol and 2-methyl-6-ethylphenol is also high, and it is impossible to produce high-purity 2,4-xylenol / 2,5-xylenol products. Coupled with the fact that the boiling points of 4-tert-butyl-2-methyl-6-ethylphenol and 4-tert-butyl-2,5-xylenol after tert-butylation, and the boiling points of 6-tert-butyl o-isopropylphenol and 6-tert-butyl-2,4-xylenol are close, it is difficult to separate 2,4-xylenol / 2,5-xylenol by alkylation, and it is difficult to produce 99.5% 2,4-xylenol and 2,5-xylenol products, and new methods need to be developed. Summary of the Invention

[0004] The object of the present invention is to provide a process for preparing phenolic products from 2,4-xylenol / 2,5-xylenol in order to solve the above problems. The problems to be solved are that the extraction of phenolic products from traditional phenol-containing coal tar generally requires the following steps: first, the phenol-containing coal tar is rectified and cut to obtain a phenol oil fraction at 170-230°C, and then the phenol oil fraction is used to extract crude phenol and dephenolized phenol oil by the alkali dissolution and acid precipitation method or the solvent extraction method; the crude phenol is refined to obtain various phenolic products or mixtures; then, the mixed phenols (a mixture of phenol and o-cresol), o-cresol fraction (containing 2,6-xylenol), m / p-cresol, mixed xylenols, mixed trimethylphenols, etc. are separated by physical or chemical methods to obtain products such as phenol, o-cresol, m-cresol, p-cresol, 2,5-xylenol, 2,4-xylenol, 3,5-xylenol, 3,4-trimethylphenol, m-ethylphenol, p-ethylphenol, etc. However, there are problems such as a relatively complex process and poor economic benefits.

[0005] The present invention relates to a process for preparing phenolic products from 2,4-xylenol / 2,5-xylenol, which comprises the following steps:

[0006] Step 1: Pyrolysis and rearrangement reaction:

[0007] An acidic silica-aluminum-chromium oxide solid catalyst and zirconium phosphate are loaded into a stainless steel high-pressure reactor, and a 2,4-xylenol / 2,5-xylenol mixture is added. The reactor is sealed and heated to 280-400°C for 3-10 hours, and the pressure is gradually increased to 2.5-5.0 MPa. After the reaction is completed, the temperature is lowered by the heat-conducting oil with programmed cooling in the inner coil, and the temperature is rapidly lowered to 280-300°C within 1-2 hours, and then the temperature is lowered to ≤150°C within 0.5-1 hour. The propylene and ethylene released during the reaction are gradually discharged; the discharged gas is pressurized 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 hour, and the pyrolysis reaction product is obtained by filtration, and the solid catalyst is recycled.

[0008] Step 2: Synthesis of 2-isopropyl-5-methylphenol, 4-isopropyl-3-methylphenol, and / or o / p-isopropylphenol, and / or ethylphenol, including:

[0009] 2.1 Synthesis of thymol and o-isopropylphenol;

[0010] 2.1.1 Synthesis of thymol:

[0011] While carrying out the cracking and transposition reaction in Step 1, add m-cresol, an acidic catalyst, and a polymerization inhibitor into another stainless-steel autoclave. Start stirring and heat up to 160 - 170 °C. Slowly and synchronously introduce the olefins stored in the spherical tank, which are discharged after the cracking reaction in Step 1 is cooled down, into the stainless-steel autoclave under reduced pressure. Keep the temperature in the autoclave at 170 - 200 °C. Introduce the olefins from the spherical tank into the autoclave repeatedly 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 ethylene in the autoclave; then continue to introduce the olefins from the spherical tank into the autoclave repeatedly 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 ethylene; introduce the olefins into the autoclave repeatedly 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 ethylene; introduce the olefins into the autoclave 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 ethylene; continue to introduce the olefins into the autoclave until the pressure in the spherical tank is 0.03 MPa to end the gas introduction. The time for introducing the olefins is 3 - 12 hours. After the introduction, keep the temperature for reaction for 1 - 4 hours. A total of 160.7 parts of unreacted ethylene are collected. The ethylene is pressurized by a pressure pump and stored in the spherical tank (about 5 MPa); the temperature in 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, and add the material layer to the bottom of the distillation column. At -0.085 - -0.095 MPa and a reflux ratio of 10 - 20, distill to obtain the unreacted m-cresol for reuse, and then obtain ≥99% 2-isopropyl-5-cresol and ≥99% high-efficiency fungicide 4-isopropyl-3-cresol in sequence;

[0012] 2.1.2 Synthesis of o-isopropylphenol:

[0013] While performing the cracking and rearrangement reaction in Step 1, add phenol, an acidic catalyst, and an inhibitor to another stainless-steel autoclave. Start stirring and heat up to 160 - 170°C. Slowly and synchronously introduce the olefins stored in the spherical tank, which are discharged after the cracking reaction in Step 1 is cooled down, into the stainless-steel autoclave under reduced pressure. Maintain the autoclave temperature at 170 - 200°C. Repeatedly introduce olefins 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 ethylene in the autoclave; then continue to repeatedly introduce olefins 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 ethylene; repeatedly introduce olefins 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 ethylene; introduce olefins 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 ethylene; continue to introduce olefins for reaction until the pressure in the spherical tank is 0.03 MPa to end the gas introduction. The gas introduction time is 3 - 12 hours. After the gas introduction, keep the temperature for reaction for 2 hours, collect the unreacted ethylene, and store the ethylene pressurized by a pressure pump in the spherical tank (about 5 MPa); cool the autoclave 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, and distill at -0.085 - -0.095 MPa with a reflux ratio of 10 - 20 to obtain unreacted phenol for reuse, and then obtain crude o-isopropylphenol ≥99% and crude p-isopropylphenol ≥95% in sequence;

[0014] Add crude p-isopropylphenol and petroleum ether at 90 - 120°C to the reactor. Start stirring and heat up to 70 - 90°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 0 - 20°C with chilled brine for 2 - 4 hours. Keep the temperature for 1 - 3 hours, filter, drain, and dry to obtain p-isopropylphenol ≥99%;

[0015] 2.1.3 Synthesis of thymol and p-isopropylphenol:

[0016] While performing the cracking and rearrangement reactions in Step 1, m-cresol, phenol, an acidic catalyst, and an inhibitor are added to another stainless-steel autoclave. Stirring is started, and the temperature is raised to 160 - 170°C. The olefins stored in the spherical tank, which are discharged after the cracking reaction in Step 1 is cooled down, are slowly and simultaneously depressurized and introduced into the stainless-steel autoclave for reaction while maintaining the autoclave temperature at 170 - 200°C. The olefins are introduced repeatedly 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, the unreacted ethylene in the autoclave is discharged; then, the olefins in the spherical tank are introduced repeatedly for reaction 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, the unreacted ethylene is discharged; the olefins are introduced repeatedly for reaction 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, the unreacted ethylene is discharged; the olefins are introduced for reaction 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, the unreacted ethylene is discharged; then, the olefins are introduced for reaction until the pressure in the spherical tank reaches 0.03 MPa to end the gas introduction. The gas introduction time is 3 - 12 hours. After the gas introduction, the reaction is kept at a constant temperature for 2 hours, and the unreacted ethylene is collected. The ethylene is pressurized by a pressure pump and stored in the spherical tank; the autoclave is cooled to ≤90°C within 1 - 3 hours, 10 - 35% liquid caustic soda is added to the material in the autoclave 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. At -0.085 - 0.095 MPa and a reflux ratio of 10 - 20, the unreacted m-cresol and phenol are obtained by distillation for reuse, and then ≥99% o-isopropylphenol, ≥95% p-isopropylphenol, ≥99% 2-isopropyl-5-methylphenol, and ≥99% high-efficiency fungicide 4-isopropyl-3-methylphenol are obtained in sequence;

[0017] Crude p-isopropylphenol and petroleum ether at 90 - 120°C are added to the reactor. Stirring is started, and the temperature is raised to 70 - 90°C to completely dissolve the material. Then, it is first cooled to 30 - 40°C with circulating water for 2 - 3 hours, and then cooled to 0 - 20°C with chilled brine for 2 - 4 hours. It is kept at a constant temperature for 1 - 3 hours, filtered, drained, and dried to obtain ≥99% p-isopropylphenol;

[0018] 2.2 Synthesis of p-ethylphenol:

[0019] While synthesizing thymol and the like, add phenol and an acidic catalyst into a stainless steel autoclave, start stirring, and heat up to 210 - 250 °C. Slowly introduce the pressurized ethylene collected in the ethylene spherical tank in Step 2.1 into the stainless steel autoclave under reduced pressure for reaction, maintain the temperature in the autoclave at 220 - 250 °C for reaction, with a pressure of 0.9 - 1.0 MPa, and the olefin introduction time of 4 - 10 hours. Stop ventilation when the pressure on the spherical tank drops to 1.0 MPa, keep the autoclave for heat preservation reaction for 1 - 4 hours, and stop the reaction when the autoclave pressure is stable and does not decrease; cool the autoclave to ≤90 °C in 1 - 3 hours, add 10 - 35% liquid alkali to the material in the autoclave to neutralize to pH 7 - 8, separate the brine layer, add the material layer to the bottom of the distillation column, and under -0.085 - -0.095 MPa and a reflux ratio of 10 - 20, distill to obtain unreacted phenol for reuse, and then obtain ≥99% o-ethylphenol and ≥95% crude p-ethylphenol in sequence;

[0020] Add crude p-ethylphenol and methanol into the reactor, start stirring, 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 0 - 10 °C with chilled brine for 2 - 4 hours, keep it warm for 1 - 3 hours, filter, drain, and dry to obtain ≥99% p-ethylphenol;

[0021] Step Three: Rectification and separation of the cracking products:

[0022] Add the cracking reaction products in Step One into the bottom of the distillation column, and conduct vacuum distillation to obtain 99% phenol, 99% mixed cresols, ≥98% 2,5-xylenol / 2,4-xylenol (2,5-xylenol / 2,4-xylenol ≥98%, 2,5-xylenol ≥70%), mixed xylenols, ≥90% crude 3,5-xylenol, and ≥90% crude 3,4-xylenol;

[0023] 99% mixed cresols can be used for rectifying 99.5% o-cresol and ≥98% m,p-cresol products;

[0024] ≥98% 2,5-xylenol / 2,4-xylenol can be used for the separation of tert-butylation to produce 6-tert-butyl-2,4-xylenol and 4-tert-butyl-2,5-xylenol products, and can also be used to produce 2,5-xylenol by the solvent crystallization method; the crude 3,5-xylenol and crude 3,4-xylenol can be used to produce pure 3,5-xylenol and 3,4-xylenol by the solvent crystallization or melt crystallization method;

[0025] Mixed xylenols can be used for alkylation separation to produce 2,4-xylenol, 2,5-xylenol, 2,3-xylenol, m-ethylphenol, p-ethylphenol, etc.;

[0026] Step Four: Refinement of the crude products from cracking rectification:

[0027] 4.1 Add the crude 3,5-xylenol from Step 3 and the solvent into the reactor, start stirring, heat up to 60 - 90 °C to completely dissolve the materials, then first cool down to 30 - 40 °C with circulating water for 1 - 3 hours, and then cool down to 0 - 20 °C with chilled brine for 1 - 3 hours, keep warm for 1 - 2 hours, filter, drain thoroughly, and dry to obtain ≥99% 3,5-xylenol;

[0028] 4.2 Add the crude 3,4-xylenol from Step 3 and the solvent into the reactor, start stirring, heat up to 60 - 90 °C to completely dissolve the materials, then first cool down to 30 - 40 °C with circulating water for 1 - 3 hours, and then cool down to 0 - 20 °C with chilled brine for 1 - 3 hours, keep warm for 1 - 2 hours, filter, drain thoroughly, and dry to obtain ≥99% 3,4-xylenol;

[0029] 4.3 Add 500 parts of 2,5-xylenol / 2,4-xylenol from Step 3 and the solvent into the reactor, start stirring, heat up to 60 - 90 °C to completely dissolve the materials, then first cool down to 30 - 40 °C with circulating water for 1 - 3 hours, and then cool down to 0 - 20 °C with chilled brine for 1 - 3 hours, keep warm for 1 - 2 hours, filter, drain thoroughly, and dry to obtain ≥99% 2,5-xylenol;

[0030] Step 5: Alkylation separation of the mixed xylenols obtained by cracking and rectification:

[0031] 5.1 Octylation separation: Add the mixed xylenols and diisobutylene obtained in Step 3 into a pressure reactor, add an acidic catalyst, stir and heat up to 100 - 150 °C for reaction for 2 - 12 hours. Take samples for analysis. If the content of 2,3-xylenol is ≤0.5%, it is qualified. Filter, and rectify the filtrate to recover diisobutylene for reuse; then successively obtain ≥95% 2,5-xylenol, 99% 3,5-xylenol; 99% antioxidant 6-isooctyl-2,4-xylenol; obtain ≥95% 6-isooctyl-2,3-xylenol; The still residue mainly contains some 6-isooctyl-m-ethylphenol, 2,6-diisooctyl-p-ethylphenol, etc.;

[0032] Add ≥95% 6-isooctyl-2,3-xylenol into the decomposition kettle, start stirring, add ≥95% sulfuric acid, heat up to 180 - 200 °C for 0.5 - 2 hours. Take samples for analysis. If the content of 6-isooctyl-2,3-xylenol is ≤0.5%, it is qualified. After qualification, cool down to 70 - 90 °C, add 10 - 35% sodium hydroxide aqueous solution to neutralize to pH 7 - 7.5, rectify at atmospheric pressure to recover diisobutylene for reuse, and then rectify under reduced pressure to obtain 99% 2,3-xylenol;

[0033] Add ≥95% 2,5-xylenol and methanol into the crystallization 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 1 - 3 hours, and then cool down to 0 - 20°C with chilled brine for 1 - 3 hours, keep warm for 1 - 2 hours, filter, drain thoroughly, and dry to obtain ≥99% 2,5-xylenol;

[0034] 5.2 Isohexylation separation: Add the mixed xylenols and 6-isohexyl-2,4-xylenol obtained in step three into an autoclave, add strongly acidic resin, stir and heat up to 100 - 150°C for reaction, introduce vaporized isohexene until the pressure in the reaction kettle reaches 0.6 MPa. When the pressure in the kettle drops to 0.1 MPa, introduce vaporized isohexene again until it reaches 0.6 MPa, and react in this way for multiple times; when the pressure drop in the kettle is slow, take a sample for analysis. If the content of 2,3-xylenol is ≤0.5% which is qualified, the reaction time is 4 - 12 hours. After the reaction is completed, cool down to 70 - 90°C and filter. The filtrate is subjected to vacuum distillation to obtain ≥98% 2,5-xylenol, ≥99% 3,5-xylenol; obtain 99% 6-isohexyl-2,4-xylenol; obtain 95% 6-isohexyl-2,3-xylenol;

[0035] Add 6-isohexyl-2,3-xylenol into the decomposition kettle, start stirring, add sulfuric acid, heat up to 180 - 200°C and keep warm for reaction for 0.5 - 3 hours to remove isohexene, and perform distillation to obtain 99% 2,3-xylenol, and the isohexene is recycled;

[0036] Add ≤99% 2,5-xylenol and methanol into the reactor, start stirring, heat up to 65°C to completely dissolve the materials, then first cool down to 30 - 40°C with circulating water for 2 - 4 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 99.5% 2,5-xylenol;

[0037] Step six: 2,5-xylenol / 2,4-xylenol alkylation separation:

[0038] Add the ≥98% 2,5-xylenol / 2,4-xylenol and 6-isononyl-2,4-xylenol obtained in step three into an autoclave, add strongly acidic resin, stir and heat up to 100 - 180°C, dropwise add isononene for reaction, the dropping time is 4 - 12 hours, after dropping, keep warm for reaction for 1 - 4 hours, take a sample for analysis. If the content of 2,4-xylenol is ≤0.3% which is qualified, and for the dosage of isononene. After the reaction is completed, cool down to 70 - 100°C and filter. The filtrate is subjected to vacuum distillation (-0.09 - -0.1 MPa, reflux ratio 10 - 30:1) to obtain ≥99.5% 2,5-xylenol; ≥99% antioxidant 6-isononyl-2,4-xylenol.

[0039] Preferably, in step one, a 2,4-xylenol / 2,5-xylenol mixture is added. In the 2,4-xylenol / 2,5-xylenol mixture, the ratio of 2,4-xylenol to 2,5-xylenol is 0.5 - 2:1, and the content of 2,4 / 2,5-xylenol is 50 - 97%, preferably 70 - 90%; in the 2,4-xylenol / 2,5-xylenol mixture, the content of o-isopropylphenol / o-propylphenol is 1 - 30%, preferably 5 - 20%; the content of 2-ethyl-6-methylphenol is 0 - 30%, preferably 1 - 20%.

[0040] Preferably, in step one, an acidic silica-aluminum-chromium oxide solid catalyst is loaded into a stainless-steel high-pressure reactor (equipped with an external stainless-steel condenser and an internal coil). The silica-aluminum-chromium oxide system is silica, acidic alumina, and chromium oxide. The mass ratio of silica to acidic alumina is 0.1 - 10:10 - 0.1, preferably 0.2 - 5:5 - 0.2, and the dosage of chromium oxide is 0.01 - 0.2 of the mass of silica; the dosage of the silica-aluminum-chromium oxide system is 5 - 30% of the weight of the 2,4 / 2,5-xylenol mixture.

[0041] Preferably, in step one, the temperature of the heat transfer oil gradually decreases slowly from a high temperature to 80°C, and the high temperature is 50 - 100°C lower than the pyrolysis and rearrangement reaction temperature.

[0042] Preferably, in step one, the pyrolysis reaction product [a mixed phenol composed of 2,5-xylenol / 2,4-xylenol (mainly 2,5-xylenol), other xylenols (mainly 3,5-xylenol), and part of phenol, cresol (mainly m-cresol), etc.] is obtained by filtration. The cresol is a mixture composed of m-cresol, p-cresol, o-cresol, o-ethylphenol, etc., mainly m-cresol; in the 2,4-xylenol / 2,5-xylenol, the ratio of 2,4-xylenol to 2,5-xylenol is 1:2 - 5; the other xylenols are 3,5-xylenol, 2,3-xylenol, 3,4-xylenol, a small amount of m,p-ethylphenol, etc., mainly 3,5-xylenol.

[0043] Preferably, in step 2.1, 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 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 or a mixture of m-cresol and phenol, and the mass ratio of sulfuric acid to phosphoric acid is 5 - 7:5 - 3.

[0044] Preferably, in step 2.2, 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., and a mixed acid of sulfuric acid and phosphoric acid is preferred; the dosage of the mixed acid is 1-5% of the mass of phenol, and the mass ratio of sulfuric acid to phosphoric acid is 9-7:1-3.

[0045] Preferably, in step 2.1, the inhibitor is hydroquinone, 2-methylhydroquinone, 2-tert-butylhydroquinone, 6-tert-butyl-2,4-xylenol, p-methoxyphenol, etc., and 2-methylhydroquinone is preferred.

[0046] Preferably, in step 2.1.3, m-cresol and phenol are added to another stainless steel autoclave, and the mass ratio of m-cresol to phenol is 1:0.5-2.

[0047] Preferably, in step 3, the mixed xylenols are composed of two or more of 2,4-xylenol, 2,5-xylenol, 2,3-xylenol, 3,5-xylenol, a small amount of m,p-ethylphenol, etc., with 2,3-xylenol as the main component and the content generally not less than 50%.

[0048] Preferably, in steps 4.1, 4.2, and 4.3, the solvent is alcohols (such as methanol, ethanol, etc.), alkanes (including petroleum ether), ethers, esters, ketones, etc., and methanol and petroleum ether are preferred.

[0049] Preferably, in step 5, an acidic catalyst is added, and the acidic catalyst is inorganic acids such as sulfuric acid and phosphoric acid, organic acids such as sulfamic acid, benzenesulfonic acid, and toluenesulfonic acid, solid acids loaded with antimonate, strongly acidic resins, etc., and strongly acidic resins are preferred.

[0050] Beneficial effects:

[0051] 1. In the present invention, the ethyl group in 2-ethyl-6-methylphenol and the isopropyl group / propyl group in o-isopropylphenol / o-propylphenol in alkylphenols are removed at high temperature to obtain purified 2,5 / 2,4-xylenol products and produce high-purity products.

[0052] 2. In the present invention, the isopropyl group / propyl group in alkylphenols is removed at high temperature, and then the excess m-cresol is selectively reacted with the isopropyl group under the catalysis of an acidic substance, and 2-isopropyl-5-methylphenol and 4-isopropyl-3-methylphenol products are obtained by rectification, and petrochemical-grade m-cresol is produced as a by-product.

[0053] 3. In the present invention, the isopropyl group / propyl group in alkylphenols is removed at high temperature, and then the excess phenol is selectively reacted with the isopropyl group under the catalysis of an acidic substance, and petrochemical-grade o-isopropylphenol and p-isopropylphenol products are obtained by rectification, and petrochemical-grade phenol products are produced as a by-product.

[0054] 4. In the present invention, ethyl groups in alkylphenols are removed at high temperature, and then, in the presence of an acidic substance as a catalyst, the excess phenol reacts selectively with the ethyl groups. After rectification, petrochemical-grade o-ethylphenol and p-ethylphenol products are obtained, and petrochemical-grade phenol product is produced as a by-product.

[0055] 5. In the present invention, the transfer of other cresols to m-cresol, other xylenols to 3,5-xylenol and 2,5-xylenol, and other ethylphenols to m-ethylphenol is achieved through the high-temperature removal of alkyl groups in alkylphenols and the medium- and low-temperature alkyl group rearrangement reaction. Since the market values of m-cresol, m-ethylphenol, 3,5-xylenol, etc. are significantly higher than those of o-cresol, p-cresol, 2,4-xylenol, and o-ethylphenol before dealkylation and rearrangement, the value of phenolic products is greatly increased.

[0056] 6. In the present invention, the 2,5 / 2,4-xylenol mixture is alkylated with isononene to obtain high-purity 2,5-xylenol, an efficient polymerization inhibitor, and antioxidant 6-isononyl-2,4-xylenol, and at the same time, the separation of 2,5 / 2,4-xylenol can be effectively carried out.

[0057] 7. In the present invention, diisobutene, isohexene, etc. can also be used for the alkylation of xylenols to separate mixed xylenols, and by-products such as 3,5-xylenol, 3,4-xylenol, 2,3-xylenol, etc. are produced.

[0058] 8. The present invention is particularly suitable for the green extraction of crude phenol from medium- and low-temperature phenol-containing coal tar by the solvent method. The separation of the 2,4 / 2,5-xylenol mixture with high contents of o-isopropylphenol / o-propylphenol and 2-ethyl-6-methylphenol obtained by refining crude phenol has not been reported in relevant literature and patents. This part belongs to a brand-new research topic and has good economic and social benefits. Detailed implementation mode

[0059] Example 1

[0060] A process for preparing phenolic products from 2,4-xylenol / 2,5-xylenol, comprising the following steps. Step 1: Cracking and rearrangement reaction

[0061] Charge 750 parts of acidic silica-aluminum-chromium oxide solid catalyst (silica-aluminum-chromium ratio 1:2:0.2) and 50 parts of zirconium phosphate into a stainless-steel high-pressure reactor with an external stainless-steel condenser and an internal coil. Add 5000 parts of a 2,4-xylenol / 2,5-xylenol mixture (containing 15 parts of m / p-cresol, 1875 parts of 2,4-xylenol, 1375 parts of 2,5-xylenol, 750 parts of o-isopropylphenol / o-propylphenol, 920 parts of 2-ethyl-6-methylphenol, and 63 parts of 2,3-xylenol). Seal the reactor and heat it to 340 °C for 4 hours. Gradually increase the pressure to 3.8 - 3.9 MPa and end the reaction. Cool the internal coil with heat transfer oil whose temperature is decreased by a programmed method (the temperature of the heat transfer oil gradually decreases slowly from a high temperature to 80 °C), and cool it to 280 °C in 0.5 hours; then, in 40 minutes, cool the material temperature to 150 °C, and gradually discharge the propylene and ethylene released during the reaction; the discharged gas is pressurized by a pressure pump and stored in a stainless-steel spherical tank (about 5 MPa); after discharging the gas, slightly cool the condensate of the cracking reaction and displace it with nitrogen for 0.5 hours, and filter to obtain 4506.9 parts of the cracking reaction product (containing 694.8 parts of cresol, 9.8 parts of 6-ethyl-2-methylphenol, 497.8 parts of phenol, 431.3 parts of 2,4-xylenol, 1784.2 parts of 2,5-xylenol, 651.3 parts of 3,5-xylenol, 224.6 parts of 3,4-xylenol, 165.3 parts of 2,3-xylenol, 3.2 parts of o-ethylphenol, 6.5 parts of m / p-ethylphenol, and 38.1 parts of others); reuse the solid catalyst (it is necessary to supplement about 5% of the feed amount of silica-aluminum oxidant and zirconium phosphate in terms of silica-aluminum oxide and zirconium phosphate).

[0062] Step 2: Synthesis of 2-isopropyl-5-methylphenol, 4-isopropyl-3-methylphenol, and ethylphenol

[0063] 2.1 Synthesis of thymol, etc.

[0064] While carrying out the cracking and rearrangement reaction in Step 1, 953 parts of m-cresol and 30 parts of a sulfuric acid / phosphoric acid mixed acid (m-cresol is 1.6 times the molar mass of o-isopropyl / p-propylphenol, mass ratio of 98% sulfuric acid: 85% phosphoric acid is 7:3) were added to another stainless steel autoclave. Start stirring and heat up to 180°C. Slowly and simultaneously introduce the olefins stored in the spherical tank, which were discharged after the cracking reaction in Step 1 was cooled down, into the stainless steel autoclave under reduced pressure. Keep the temperature in the autoclave at 180 - 190°C for the reaction. When introducing the olefins, react 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 ethylene. Then continue to introduce the olefins 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 ethylene. Introduce the olefins 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 ethylene. Introduce the olefins 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 ethylene. Then continue to introduce the olefins until the pressure in the spherical tank reaches 0.03 MPa to end the gas introduction. The time for introducing the olefins is 10 hours. After the gas introduction, keep the temperature for reaction for 2 hours. A total of 160.7 parts of unreacted ethylene were collected. The ethylene was pressurized by a pressure pump and stored in the spherical tank (about 5 MPa). 90 parts of 30% liquid alkali were added to the material in the autoclave to neutralize it to pH 7.5. The brine layer was separated, and the material layer was added to the bottom of the distillation column (theoretical number of plates is 200). At -0.095 MPa and a reflux ratio of 15 - 20, distillation was carried out to obtain 344.5 parts of unreacted m-cresol for reuse. Then, 488.5 parts of 99.5% 2-isopropyl-5-methylphenol (thymol) and 279.9 parts of 99.6% high-efficiency fungicide 4-isopropyl-3-methylphenol were obtained in sequence;

[0065] 2.2 Synthesis of p-ethylphenol, etc.

[0066] While synthesizing thymol, 800 parts of phenol and 25 parts of sulfuric acid / phosphoric acid are added to a stainless-steel autoclave (the phenol is 1.26 times the molar mass of 2-ethyl-6-cresol, and the mass ratio of 98% sulfuric acid to 85% phosphoric acid is 8 - 9:2 - 1). Start stirring and heat up to 240°C. Slowly decompress and introduce the pressurized ethylene collected in the ethylene spherical tank in Step 2.1 into the stainless-steel autoclave for reaction. Keep the temperature in the autoclave at 230 - 240°C for reaction, with a pressure of 0.9 - 1.0 MPa. The time for introducing olefins is 6 hours. When the pressure on the spherical tank drops to 1.3 MPa, stop ventilation. Keep the autoclave at a constant temperature for reaction for 3 hours. When the pressure in the autoclave drops to 0.6 MPa or the pressure does not decrease, stop the reaction; add 70 parts of 30% liquid alkali to the materials in the autoclave to neutralize 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 -0.09 MPa and a reflux ratio of 10 - 15, distill to obtain 391.8 parts of unreacted phenol for reuse, and then obtain 176.6 parts of 99.6% o-ethylphenol and 319.8 parts of 96.37% crude p-ethylphenol (308.2 parts of p-ethylphenol, 11.3 parts of m-ethylphenol, and 0.3 parts of others) in sequence;

[0067] Add 319.8 parts of 96.37% crude p-ethylphenol and 300 parts of methanol to the reactor. Start stirring and heat up to 65°C to completely dissolve the materials. Then, first cool down to 35°C with a cold water bath for 2 hours, and then cool down to 0°C with an ice water bath for 3 hours. Keep warm for 2 hours, filter, drain, and dry to obtain 292.4 parts of 99.71% p-ethylphenol, with a refining yield of 94.6%;

[0068] Step 3: Rectification and separation of pyrolysis products

[0069] Add 4506.9 parts of the cracking reaction product from Step 1 to the bottom of a distillation column (100 parts of high-boiling dimethyl diphenyl ether solvent has already been added to the bottom), and conduct vacuum distillation (vacuum degree -0.088 MPa, reflux ratio 15 - 25:1) to obtain 457.5 parts of 99.23% phenol, 647.1 parts of 99.1% cresol (232.9 parts of o-cresol, 116.7 parts of p-cresol, 291.8 parts of m-cresol, 3.1 parts of o-ethylphenol), 2141.8 parts of 98.73% 2,4 / 2,5-xylenol (409.6 parts of 2,4-xylenol, 1705.1 parts of 2,5-xylenol, 9.8 parts of m / p-xylenol, 15.2 parts of 2,3-xylenol, 2.1 parts of others, 79.61% of 2,5-xylenol), 209.2 parts of mixed xylenol (12.4 parts of 2,4-xylenol, 41.3 parts of 2,5-xylenol, 139.2 parts of 2,3-xylenol, 12.3 parts of 3,5-xylenol, 4 parts of m / p-ethylphenol, 66.54% of 2,3-xylenol), 638.7 parts of 96.4% crude 3,5-xylenol (6.5 parts of 2,3-xylenol, 615.8 parts of 3,5-xylenol, 14.6 parts of 3,4-xylenol, 1.8 parts of m / p-ethylphenol), and 216.1 parts of 93.61% crude 3,4-xylenol (1.1 parts of 2,3-xylenol, 10.2 parts of 3,5-xylenol, 202.3 parts of 3,4-xylenol);

[0070] 647.1 parts of 99.1% cresol (232.8 parts of o-cresol, 116.7 parts of p-cresol, 291.8 parts of m-cresol, 3.2 parts of o-ethylphenol) can be used for distilling 99.5% o-cresol and 99% m / p-cresol products;

[0071] 98.73% 2,4 / 2,5-xylenol (with 79.61% of 2,5-xylenol content) can be used for separating and producing 6-tert-butyl-2,4-xylenol and 4-tert-butyl-2,5-xylenol products through tert-butylation, and can also be used for producing 2,5-xylenol by solvent crystallization method; 96.4% crude 3,5-xylenol and 93.61% crude 3,4-xylenol can be used for producing pure 3,5-xylenol and 3,4-xylenol by solvent crystallization or melt crystallization method;

[0072] 209.2 parts of mixed xylenol (12.4 parts of 2,4-xylenol, 41.3 parts of 2,5-xylenol, 139.2 parts of 2,3-xylenol, 12.3 parts of 3,5-xylenol, 4 parts of m / p-ethylphenol, 66.54% of 2,3-xylenol) can be used for separating and producing 2,4-xylenol, 2,5-xylenol, 2,3-xylenol, m-ethylphenol, p-ethylphenol, etc. through alkylation;

[0073] Step 4: Refine the crude products obtained from cracking and distillation

[0074] 4.1 Add 638.7 parts of the 96.4% crude 3,5-xylenol from Step 3 and 500 parts of methanol to the reactor. Start stirring and heat up to 60°C to completely dissolve the materials. Then, first cool down to 35°C with circulating water for 2 hours, and then cool down to 0°C with chilled brine for 2 hours. Keep warm for 2 hours, filter, drain, and dry to obtain 584.7 parts of 99.82% 3,5-xylenol, with a refining yield of 94.8%;

[0075] 4.2 Add 216.1 parts of the 93.61% crude 3,4-xylenol from Step 3 and 600 parts of petroleum ether at 90 - 120°C to the reactor. Start stirring and heat up to 70°C to completely dissolve the materials. Then, first cool down to 33°C with circulating water for 2.5 hours, and then cool down to 20°C with chilled brine for 2 hours. Keep warm for 2 hours, filter, drain, and dry to obtain 178.2 parts of 99.64% 3,4-xylenol, with a refining yield of 87.8%;

[0076] 4.3 Add 500 parts of the 98.73% 2,4 / 2,5-xylenol (79.61% 2,5-xylenol) from Step 3 and 300 parts of methanol to the reactor. Start stirring and heat up to 60°C to completely dissolve the materials. Then, first cool down to 35°C with circulating water for 2 hours, and then cool down to -10°C with chilled brine for 3 hours. Keep warm for 2 hours, filter, drain, and dry to obtain 261.5 parts of 99.85% 2,5-xylenol, with a refining yield of 65.6%;

[0077] Step 5: Separate the octylated mixed xylenols obtained by cracking and rectification

[0078] Add 209.2 parts of the mixed xylenols obtained in Step 3 (12.4 parts of 2,4-xylenol, 41.3 parts of 2,5-xylenol, 139.2 parts of 2,3-xylenol, 12.3 parts of 3,5-xylenol, 4 parts of m,p-ethylphenol) and 600 parts of diisobutene to the reaction kettle. Add 100 parts of strongly acidic resin, stir and heat up to 110°C for reaction. The reaction time is 10 hours. Take a sample for analysis. When the content of 4-isooctyl p-ethylphenol is 0.01% and it is qualified, filter. The filtrate is rectified to recover 435 parts of diisobutene for reuse; then, under reduced pressure rectification (-0.095 MPa, reflux ratio 25 - 30:1), successively obtain 38.2 parts of 98.32% 2,5-xylenol and 10.3 parts of 99.13% 3,5-xylenol, with yields of 90.9% and 83.2% respectively; 19.5 parts of 99.23% 6-isooctyl-2,4-xylenol as antioxidant, with a yield of 81.2%; obtain 207.9 parts of 97.35% 6-isooctyl-2,3-xylenol, with a yield of 75.8%; The residue in the kettle mainly contains some 2-isooctyl-5-ethylphenol, 2,6-diisooctyl-4-ethylphenol, etc.

[0079] Add 207.9 parts of 97.35% 6 - isooctyl - 2,3 - xylenol into the decomposition kettle, start stirring, add 5 parts of sulfuric acid, heat up to 200 °C for 1.5 hours, and obtain 103.3 parts of 99.38% 2,3 - xylenol by rectification, with a yield of 94.7%; (A high - boiling dimethyldiphenyl ether was pre - added to the bottom of the rectification column);

[0080] Add 38.2 parts of 98.32% 2,5 - xylenol and 24 parts of methanol into the reactor, start stirring, heat up to 60 °C to completely dissolve the materials, then first cool down to 35 °C with a cold - water bath, and then cool down to - 10 °C with an ice - water bath, keep warm for 2 hours, filter, drain, and dry to obtain 36.2 parts of 99.53% 2,5 - xylenol, with a refined yield of 95.9%;

[0081] Step Six: Alkylation separation of 2,5 / 2,4 - xylenol (crude 2,5 - xylenol)

[0082] Add 1000 parts of 98.73% 2,4 / 2,5 - xylenol (191.2 parts of 2,4 - xylenol, 796.1 parts of 2,5 - xylenol, 4.6 parts of m - p - cresol, 7.1 parts of 2,3 - xylenol, and 1 part of others) obtained in Step Three and 1 part of 6 - isononyl - 2,4 - xylenol into the autoclave, add 200 parts of strongly acidic resin, stir and heat up to 120 °C for reaction, add isononene dropwise for reaction, with a dropping time of 6 hours. After dropping, seal the equipment, heat up to 160 °C for reaction for 1 hour. Take a sample for analysis, and when the content of 2,4 - xylenol is 0.11% qualified, the amount of isononene used is 241 parts (the amount of isononene used is 1.22 times the molar amount of 2,4 - xylenol in 2,5 / 2,4 - xylenol). After the reaction is completed, cool down to 90 °C and filter. The filtrate is subjected to vacuum rectification (- 0.098 MPa, reflux ratio 20 - 25:1) to obtain 756.9 parts of 99.5% 2,5 - xylenol, with a yield of 94.6%; 349 parts of 99.0% 6 - isononyl - 2,4 - xylenol as antioxidant, with a yield of 88.9%.

[0083] Example 2

[0084] Step One: Pyrolysis reaction

[0085] In a stainless-steel high-pressure reactor with an external stainless-steel condenser and an internal coil, 1000 parts of an acidic silica-aluminum-chromium oxide solid catalyst (silica-aluminum-chromium ratio 1:2:0.1) and 30 parts of zirconium phosphate are charged. 4908 parts of a 2,4-xylenol / 2,5-xylenol mixture (containing 2361.6 parts of 2,4-xylenol, 1586.4 parts of 2,5-xylenol, and 960 parts of o-isopropylphenol / o-propylphenol) are added. The reactor is sealed and heated to 300 °C for reaction for 6 hours, and the pressure is gradually increased to 2.8 - 2.9 MPa. The reaction is ended. The heat-conducting oil in the internal coil is rapidly cooled by programmed cooling (the temperature of the heat-conducting oil gradually decreases from a high temperature to 80 °C slowly). When the material temperature drops to 150 °C, the propylene removed after the reaction is discharged. The cooling time is about 1 hour. The discharged gas is pressurized by a pressure pump and stored in a stainless-steel spherical tank (about 5 MPa); after the gas is completely discharged, it is slightly cooled and purged with nitrogen for 0.5 hour. 4606 parts of the cracking reaction product are obtained by filtration (15.2 parts of o-isopropylphenol, 23.2 parts of m / p-isopropylphenol, 624.4 parts of phenol, 628 parts of 2,4-xylenol, 2431.2 parts of 2,5-xylenol, 578.4 parts of 3,5-xylenol, 138.4 parts of 3,4-xylenol, 92.8 parts of 2,3-xylenol, and 74.4 parts of others);

[0086] Step 2: Synthesis of o-isopropylphenol and p-isopropylphenol

[0087] 1525 parts of phenol and 50 parts of 98% sulfuric acid (phenol is twice the molar mass of o-isopropyl / propylphenol) are added to a stainless-steel autoclave. Stirring is started and the temperature is raised to 160 °C. The propylene stored in the stainless-steel spherical tank and discharged after the temperature reduction of the cracking reaction in Step 1 is simultaneously introduced into the stainless-steel autoclave for reaction. The temperature in the autoclave is maintained at 160 - 170 °C for reaction, and the pressure is 0.8 - 0.9 MPa. The time for introducing propylene is 5 hours, and after introduction, the reaction is kept at a constant temperature for 3 hours; 133.5 parts of 30% liquid alkali are added to the material in the autoclave to neutralize to pH 7.0. The brine layer is separated, and the material layer is added to the bottom of a distillation column (theoretical number of plates 200). At -0.09 MPa and a reflux ratio of 15 - 20, 871.6 parts of unreacted phenol are obtained for recycling. Then, 537.6 parts of 99.1% o-isopropylphenol and 336.2 parts of 96.6% crude p-isopropylphenol (325.8 parts of p-isopropylphenol and 10.4 parts of m-isopropylphenol) are obtained in sequence;

[0088] 336.2 parts of 96.6% crude p-isopropylphenol and 1000 parts of petroleum ether at 90 - 120 °C are added to a reactor. Stirring is started and the temperature is raised to 70 °C to completely dissolve the material. Then, it is first cooled in a cold water bath for 3 hours to 35 °C, and then cooled in an ice water bath for 3 hours to 20 °C. It is kept at a constant temperature for 1 hour, filtered, drained, and dried to obtain 304.5 parts of 99.7% p-isopropylphenol, and the refining yield is 93.2%;

[0089] Step 3: Distillation of the cracking reaction product

[0090] Add 4606 parts of the cracking reaction product from Step 1 to the bottom of a distillation column (100 parts of high-boiling dimethyl diphenyl ether solvent has already been added to the bottom), and conduct vacuum distillation (vacuum degree -0.088 MPa, reflux ratio 10 - 30:1) to obtain 591.6 parts of 99.5% phenol, 2928.4 parts of 99.36% 2,5 / 2,4-xylenol (595.2 parts of 2,4-xylenol, 2314.4 parts of 2,5-xylenol, 10 parts of o-isopropylphenol, 2,5-xylenol 79.03%), 122.4 parts of mixed xylenol (5.2 parts of 2,4-xylenol, 21.2 parts of 2,5-xylenol, 80.8 parts of 2,3-xylenol, 14.4 parts of 3,5-xylenol, 0.8 part of others, 2,3-xylenol 66.01%), 584.4 parts of 93.91% crude 3,5-xylenol (9.2 parts of 2,3-xylenol, 548.8 parts of 3,5-xylenol, 24.8 parts of 3,4-xylenol), 118.4 parts of 92.57% crude 3,4-xylenol (1.2 parts of 2,3-xylenol, 7.6 parts of 3,5-xylenol, 109.6 parts of 3,4-xylenol), 26.2 parts of 87.02% m / p-isopropylphenol (22.8 parts of m / p-isopropylphenol, 0.3 part of 3,4-xylenol, 3.1 parts of others, m-isopropylphenol:p-isopropylphenol = 1.98:1);

[0091] 99.36% 2,5 / 2,4-xylenol can be used to produce 6-tert-butyl-2,4-xylenol and 4-tert-butyl-2,5-xylenol products through tert-butylation separation, and can also be used to produce 2,5-xylenol through solvent crystallization method; 93.91% crude 3,5-xylenol and 92.93% crude 3,4-xylenol can be used to produce pure 3,5-xylenol and 3,4-xylenol through solvent crystallization or melt crystallization method;

[0092] 87.02% m / p-isopropylphenol (22.8 parts of m / p-isopropylphenol, 0.3 part of 3,4-xylenol, 3.1 parts of others, m-isopropylphenol:p-isopropylphenol = 1.98:1) can be used as raw materials for enameled wire paint, flame-retardant plasticizer, photoresist, etc.; it can also be used for alkylation separation of m / p-isopropylphenol;

[0093] Step 4: Refinement of the crude product from cracking distillation

[0094] 4.1 Add 584.4 parts of 93.91% crude 3,5-xylenol obtained from Step 3 and 500 parts of petroleum ether at 90 - 120 °C to a reactor, start stirring, heat up to 75 °C to completely dissolve the materials, then first cool down to 40 °C with circulating water for 2.5 hours, and then cool down to 20 °C with chilled brine for 2 hours, keep warm for 2 hours, filter, drain, and dry to obtain 497.6 parts of 99.36% 3,5-xylenol, with a refinement yield of 90.1%;

[0095] 4.2 Add 118.4 parts of the 92.57% crude 3,4-xylenol obtained in Step 3 and 100 parts of petroleum ether at 90 - 120°C into the reactor. Start stirring and heat up to 70°C to completely dissolve the materials. Then, first cool down to 35°C with circulating water for 2.5 hours, and then cool down to 15°C with chilled brine for 2 hours. Keep warm for 2 hours, filter, drain, and dry to obtain 97.6 parts of 99.12% 3,4-xylenol, with a refining yield of 88.3%;

[0096] 4.3 Add 200 parts of the 99.36% 2,5 / 2,4-xylenol (79.03% 2,5-xylenol) obtained in Step 3 and 100 parts of methanol into the reactor. Start stirring and heat up to 60°C to completely dissolve the materials. Then, first cool down to 35°C with circulating water for 2 hours, and then cool down to -10°C with chilled brine for 3 hours. Keep warm for 2 hours, filter, drain, and dry to obtain 113 parts of 99.55% 2,5-xylenol, with a refining yield of 71.2%;

[0097] Step 5: Separate the octylated mixed xylenols obtained by cracking and rectification

[0098] Add 122.4 parts of the mixed xylenols obtained in Step 3 (5.2 parts of 2,4-xylenol, 21.2 parts of 2,5-xylenol, 80.8 parts of 2,3-xylenol, 14.4 parts of 3,5-xylenol, 0.8 part of others, 66.01% 2,3-xylenol) and 400 parts of diisobutene into the reaction kettle. Add 100 parts of strongly acidic resin, stir and heat up to 110°C for reaction. The reaction time is 10 hours. Take a sample for analysis. When the content of 4-isooctyl-4-ethylphenol is 0.05% and it is qualified, filter. The filtrate is rectified to recover 322.3 parts of diisobutene for reuse; then, under reduced pressure rectification (-0.095 MPa, reflux ratio 25 - 30:1), successively obtain 19.2 parts of 98.22% 2,5-xylenol and 11.7 parts of 99.33% 3,5-xylenol, with yields of 89.0% and 81.2% respectively; 8.1 parts of 99.05% 6-isooctyl-2,4-xylenol as antioxidant, with a yield of 80.3%; obtain 120.2 parts of 98.26% 6-isooctyl-2,3-xylenol, with a yield of 78.9%;

[0099] Add 120.2 parts of 98.26% 6-isooctyl-2,3-xylenol into the decomposition kettle. Start stirring, add 1.5 parts of sulfuric acid, heat up to 190°C for 2 hours, and rectify (-0.09 MPa, reflux ratio 25 - 30:1) to obtain 62.1 parts of 99.61% 2,3-xylenol, with a yield of 95.3% (a high-boiling dimethyldiphenyl ether was pre-added to the bottom of the rectification column);

[0100] Add 19.2 parts of 98.22% 2,5-xylenol and 15 parts of methanol into the reactor. Start stirring and heat up to 65 °C to completely dissolve the materials. Then, first cool down to 37 °C with a cold water bath for 2 hours, and then cool down to 0 °C with freezing brine for 2 hours. Keep warm for 2 hours, filter, drain, and dry to obtain 17.8 parts of 99.75% 2,5-xylenol, with a refining yield of 94.2%.

[0101] Step Six: Alkylation Separation of 2,5-Xylenol / 2,4-Xylenol (Crude 2,5-Xylenol)

[0102] Add 1000 parts of 99.36% 2,5-xylenol / 2,4-xylenol (203.3 parts of 2,4-xylenol, 790.3 parts of 2,5-xylenol, 3.4 parts of o-isopropylphenol), 1 part of 6-isononyl-2,4-xylenol into the autoclave. Add 200 parts of strongly acidic resin, stir and heat up to 140 °C for reaction, and add isononene dropwise. The dropping time is 6 hours. After dropping, keep warm and react for 2 hours. Take a sample for analysis. When the content of 2,4-xylenol is 0.07% and it is qualified, the dosage of isononene is 250 parts (the dosage of isononene is 1.19 times the molar amount of 2,4-xylenol in 2,5 / 2,4-xylenol). After the reaction, cool down to 90 °C and filter. The filtrate is subjected to vacuum distillation (-0.098 MPa, reflux ratio 10 - 20:1) to obtain 755.4 parts of 99.6% 2,5-xylenol, with a yield of 95.2%; 386.5 parts of 99.3% 6-isononyl-2,4-xylenol antioxidant, with a yield of 92.9%.

[0103] Example 3

[0104] Step One: Pyrolysis and Isomerization Reaction

[0105] In a stainless-steel high-pressure reactor with an external stainless-steel condenser and an internal coil, 2000 parts of an acidic silica-aluminum-chromium oxide solid catalyst (silica-aluminum-chromium ratio 1:2:0.2) and 200 parts of zirconium phosphate are charged. 10000 parts of a 2,4 / 2,5-xylenol mixture (extracted and refined from medium- and low-temperature phenol-containing coal tar, containing 4318 parts of 2,4-xylenol, 3635 parts of 2,5-xylenol, 1204 parts of o-isopropylphenol / o-propylphenol, 521 parts of 2-ethyl-6-methylphenol, 306 parts of 2,3-xylenol, and 16 parts of others) are added. The reactor is sealed and heated to 280 °C for reaction for 10 hours, and the pressure is gradually increased to 2.5 - 2.6 MPa. The reaction is ended, and the heat-conducting oil in the internal coil is cooled by programmed cooling (the temperature of the heat-conducting oil gradually decreases slowly from a high temperature to 80 °C), cooled to 250 °C within 10 minutes, and then the material temperature is reduced to about 150 °C within about 0.5 hours. Propylene and ethylene released during the reaction are 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 slightly cooled and purged with nitrogen for 0.5 hours, and 9790.2 parts of pyrolysis reaction products are obtained by filtration (containing 422.1 parts of cresol, 815.6 parts of phenol, 1164.8 parts of 2,4-xylenol, 4484.6 parts of 2,5-xylenol, 1799.8 parts of 3,5-xylenol, 612 parts of 3,4-xylenol, 450.1 parts of 2,3-xylenol, and 41.2 parts of others), and the solid catalyst is recycled (some silica-aluminum oxide needs to be supplemented);

[0106] Step 2: Synthesis of 2-isopropyl-5-methylphenol, 4-isopropyl-3-methylphenol, ethylphenol, etc.

[0107] 2.1 Synthesis of thymol, etc.

[0108] While performing the cracking and rearrangement reactions in Step 1, 907 parts of 99.3% coking m-cresol (containing 28 ppm of nitrogen compounds and 19 ppm of sulfur compounds), 790 parts of 99% coking phenol (containing 1080 ppm of nitrogen compounds and 462 ppm of sulfur compounds), and 50 parts of a sulfuric acid / phosphoric acid mixed acid (the amounts of m-cresol and phenol are 1.9 times the molar mass of o-isopropyl / propyl phenol, and the mass ratio of 98% sulfuric acid to 85% phosphoric acid is 7:3) are added to another stainless-steel autoclave. Stirring is started, and the temperature is raised to 190°C. The olefins stored in the spherical tank, which are discharged after the cracking reaction in Step 1 is cooled down, are slowly and simultaneously depressurized and introduced into the stainless-steel autoclave for reaction. The reaction is carried out while maintaining the autoclave temperature at 190 - 200°C. When the olefins are introduced until the pressure in the autoclave reaches 2.3 - 2.5 MPa and the pressure in the spherical tank drops to 2.6 MPa and the pressure in the autoclave no longer decreases, the unreacted ethylene is discharged; then, when the olefins are introduced until the pressure in the autoclave reaches 1.3 - 1.5 MPa and the pressure in the spherical tank drops to 1.6 MPa and the pressure in the autoclave no longer decreases, the unreacted ethylene is discharged; when the olefins are introduced until the pressure in the autoclave reaches 0.6 MPa and the pressure in the spherical tank drops to 0.7 MPa and the pressure in the autoclave no longer decreases, the unreacted ethylene is discharged; when the olefins are introduced until the pressure in the autoclave reaches 0.1 MPa and the pressure in the spherical tank drops to 0.1 MPa and the pressure in the autoclave no longer decreases, the unreacted ethylene is discharged; then, the olefins are continuously introduced until the pressure in the spherical tank reaches 0.03 MPa to end the gas introduction. The time for introducing the olefins is 10 hours. After the introduction, the reaction is kept at a constant temperature for 2 hours. A total of 106.2 parts of unreacted ethylene are collected. The ethylene is pressurized by a pressure pump and stored in the spherical tank (about 5 MPa); 150 parts of 30% liquid alkali are added to the material in the autoclave to neutralize it to pH 7.5. The brine layer is separated, and the material layer is added to the bottom of the distillation column (the number of theoretical plates is 250). At -0.095 MPa and a reflux ratio of 25 - 30, 271.6 parts of 99.9% petrochemical-grade phenol (containing 1.8 ppm of nitrogen compounds and 3.2 ppm of sulfur compounds), 528.4 parts of 99.8% petrochemical-grade m-cresol (containing 0.7 ppm of nitrogen compounds and 0.9 ppm of sulfur compounds) are obtained by distillation. Then, 418.1 parts of 99.6% o-isopropyl phenol, 263 parts of 96.5% crude p-isopropyl phenol (253.8 parts of p-isopropyl phenol and 9.2 parts of m-isopropyl phenol), 299.5 parts of 99.6% 2-isopropyl-5-methyl phenol (thymol), and 168.2 parts of 99.5% high-efficiency fungicide 4-isopropyl-3-methyl phenol are obtained in sequence;

[0109] 263 parts of 96.5% crude p-isopropyl phenol and 200 parts of methanol are added to the reactor. Stirring is started, and the temperature is raised to 65°C to completely dissolve the materials. Then, it is first cooled to 35°C with circulating water for 2.5 hours, and then cooled to 0°C with chilled brine for 3 hours. It is kept at a constant temperature for 2 hours, filtered, drained, and dried to obtain 241.3 parts of 99.6% p-isopropyl phenol, and the refining yield is 94.7%;

[0110] 2.2 Synthesis of p-ethyl phenol, etc.

[0111] While synthesizing thymol, etc., 685 parts of 99% coking phenol (containing 1080 ppm of nitrogen compounds and 462 ppm of sulfur compounds) and 25 parts of sulfuric acid / phosphoric acid (the phenol is 1.9 times the molar mass of 2-ethyl-6-methylphenol, mass ratio of 98% sulfuric acid: 85% phosphoric acid is 9:1) are added to a stainless steel autoclave. Start stirring and heat up to 220 °C. Slowly reduce the pressure of the pressurized ethylene collected in the ethylene spherical tank in Step 2.1 and introduce it into the stainless steel autoclave for reaction. Keep the temperature in the autoclave at 220 - 230 °C for reaction, with a pressure of 0.9 - 1.0 MPa. The time for introducing olefins is 8 hours. When the pressure on the spherical tank drops to 1.2 MPa, stop gas supply. Keep the autoclave at a constant temperature for reaction for 3 hours. When the pressure in the autoclave drops to 0.6 MPa or the pressure does not decrease, stop the reaction; add 70 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 to the bottom of the distillation column (theoretical number of plates is 200). At -0.09 MPa and a reflux ratio of 10 - 15, distill to obtain 407.6 parts of petrochemical-grade 99.9% phenol (containing 1.1 ppm of nitrogen compounds and 1.9 ppm of sulfur compounds), and then successively obtain 129.2 parts of 99.7% o-ethylphenol, 206 parts of 96.46% crude p-ethylphenol (198.7 parts of p-ethylphenol, 7.1 parts of m-ethylphenol, and 0.2 parts of others);

[0112] Add 206 parts of 96.46% crude p-ethylphenol and 120 parts of methanol to the reactor. Start stirring and heat up to 65 °C to completely dissolve the materials. Then, first cool down to 35 °C with a cold water bath for 2 hours, and then cool down to 0 °C with an ice water bath for 3 hours. Keep the temperature for 2 hours, filter, drain, and dry to obtain 190.6 parts of 99.53% p-ethylphenol, with a refining yield of 95.5%;

[0113] Step 3: Rectification separation of pyrolysis products

[0114] Add 9790.2 parts of the cracking reaction product (containing 422.1 parts of cresol, 815.6 parts of phenol, 1164.8 parts of 2,4-xylenol, 4484.6 parts of 2,5-xylenol, 1799.8 parts of 3,5-xylenol, 612 parts of 3,4-xylenol, 450.1 parts of 2,3-xylenol, and 41.2 parts of others) into the bottom of the distillation column (100 parts of high-boiling dimethyl diphenyl ether solvent have been added to the bottom), and conduct vacuum distillation (vacuum degree -0.088 MPa, reflux ratio 15 - 25:1) to obtain 171.1 parts of 99.1% phenol (applied to step two), 635.6 parts of petrochemical-grade 99.8% phenol (containing 0.9 ppm of nitride and 1.1 ppm of sulfide), 411.6 parts of 99.2% petrochemical-grade cresol (2.0 parts of phenol, 146.8 parts of o-cresol, 74.7 parts of p-cresol, 186.8 parts of m-cresol, 1.3 parts of o-ethylphenol, containing 0.6 ppm of nitride and 0.8 ppm of sulfide), 5502.4 parts of 99.12% 2,5 / 2,4-xylenol (1119.3 parts of 2,4-xylenol, 4334.7 parts of 2,5-xylenol, 6.6 parts of m / p-xylenol, 41.8 parts of 2,3-xylenol, 78.78% of 2,5-xylenol), 557.2 parts of mixed xylenol (33.8 parts of 2,4-xylenol, 105 parts of 2,5-xylenol, 382.9 parts of 2,3-xylenol, 34.3 parts of 3,5-xylenol, 1.2 parts of m / p-ethylphenol, 68.72% of 2,3-xylenol), 1776.4 parts of 96.76% 3,5-xylenol crude product (17.8 parts of 2,3-xylenol, 1718.9 parts of 3,5-xylenol, 39.2 parts of 3,4-xylenol, 0.5 part of m / p-ethylphenol), and 577.3 parts of 94.53% 3,4-xylenol crude product (3.1 parts of 2,3-xylenol, 28.5 parts of 3,5-xylenol, 545.7 parts of 3,4-xylenol);

[0115] 99.2% petrochemical-grade cresol can be used for rectifying 99.5% o-cresol and 99% m / p-cresol products, which are mainly used for preparing cresol novolac resin for photoresist, flame-retardant plasticizers, etc.;

[0116] 99.12% 2,5 / 2,4-xylenol (78.78% content of 2,5-xylenol) can be used for the separation of tert-butylation to produce 6-tert-butyl-2,4-xylenol and 4-tert-butyl-2,5-xylenol products, and can also be used to produce 2,5-xylenol by solvent crystallization method; 96.76% 3,5-xylenol crude product and 94.53% 3,4-xylenol crude product can be used to produce pure 3,5-xylenol and 3,4-xylenol by solvent crystallization or melt crystallization method;

[0117] Step Four: Refining of the cracked and rectified crude product

[0118] 4.1 Add 1776.4 parts of 96.76% crude 3,5-xylenol from Step 3 and 1500 parts of methanol into the reactor. Start stirring and heat up to 60°C to completely dissolve the materials. Then first cool down to 33°C with circulating water for 3 hours, and then cool down to -10°C with chilled brine for 3 hours. Keep warm for 2 hours, filter, drain thoroughly, and dry to obtain 1643.2 parts of 99.58% 3,5-xylenol, with a refining yield of 95.2%;

[0119] 4.2 Add 577.3 parts of 94.53% crude 3,4-xylenol from Step 3 and 1800 parts of petroleum ether at 90 - 120°C into the reactor. Start stirring and heat up to 80°C to completely dissolve the materials. Then first cool down to 38°C with circulating water for 3.5 hours, and then cool down to 15°C with chilled brine for 4 hours. Keep warm for 2 hours, filter, drain thoroughly, and dry to obtain 494.1 parts of 99.52% 3,4-xylenol, with a refining yield of 90.1%;

[0120] 4.3 Add 1000 parts of 99.12% 2,5 / 2,4-xylenol (78.78% 2,5-xylenol) from Step 3 and 500 parts of methanol into the reactor. Start stirring and heat up to 65°C to completely dissolve the materials. Then first cool down to 36°C with circulating water for 2 hours, and then cool down to -10°C with chilled brine for 3 hours. Keep warm for 2 hours, filter, drain thoroughly, and dry to obtain 544.3 parts of 99.68% 2,5-xylenol, with a refining yield of 68.9%;

[0121] Step 5: Separate the mixed xylenols obtained by cracking and rectification through isohexylation

[0122] Add 557.2 parts of the mixed xylenols obtained in Step 3 (33.8 parts of 2,4-xylenol, 105 parts of 2,5-xylenol, 382.9 parts of 2,3-xylenol, 34.3 parts of 3,5-xylenol, 1.2 parts of m,p-ethylphenol) and 1 part of 6-isobutyl-2,4-xylenol into an autoclave. Add 110 parts of strongly acidic resin, stir and heat up to 110 °C for reaction. Introduce vaporized isobutene until the pressure in the reaction kettle reaches 0.6 MPa. When the pressure in the kettle drops to 0.1 MPa, introduce isobutene again until 0.6 MPa, and react in this way for multiple times. When the pressure drop in the kettle is slow, take a sample for analysis. When the content of 2,3-xylenol is 0.32% qualified, the reaction time is 9 hours, and the dosage of isobutene is 342 parts (the dosage of isobutene is 1.19 times the molar amount of 2,4 / 2,3-xylenol in the mixed xylenols). After the reaction is completed, cool down to 80 °C and filter. The filtrate is subjected to vacuum distillation (-0.095 MPa, reflux ratio 25 - 30:1) to obtain 94.9 parts of 98.68% 2,5-xylenol and 28.5 parts of 99.33% 3,5-xylenol, with yields of 89.2% and 82.6% respectively; 47.7 parts of 99.09% 6-isobutyl-2,4-xylenol as an antioxidant, with a yield of 82.8%; 590.6 parts of 96.97% 6-isobutyl-2,3-xylenol, with a yield of 88.6%.

[0123] Add 590.6 parts of 96.97% 6-isobutyl-2,3-xylenol into a decomposition kettle, start stirring, add 5 parts of sulfuric acid, heat up to 190 °C for 2 hours to remove isobutene, and distill (-0.09 MPa, reflux ratio 25 - 30:1) to obtain 342.1 parts of 99.15% 2,3-xylenol, with a yield of 93.3%; High-boiling dimethyldiphenyl ether was pre-added to the bottom of the distillation column), and 237.8 parts of isobutene were recovered for reuse.

[0124] Add 94.9 parts of 98.68% 2,5-xylenol and 60 parts of methanol into a reactor, start stirring, heat up to 65 °C to completely dissolve the materials, then cool down to 34 °C with circulating water for 2 hours, and then cool down to -10 °C with chilled brine for 3 hours, keep warm for 2 hours, filter, drain, and dry to obtain 87.1 parts of 99.83% 2,5-xylenol, with a refined yield of 93.8%.

[0125] Step 6: Alkylation separation of 2,5-xylenol / 2,4-xylenol (crude 2,5-xylenol)

[0126] Add 2000 parts of 99.12% 2,5 / 2,4-xylenol (406.8 parts of 2,4-xylenol, 1575.6 parts of 2,5-xylenol, 2.4 parts of m,p-cresol, 15.2 parts of 2,3-xylenol), 2 parts of 6-isononyl-2,4-xylenol into an autoclave, add 300 parts of strongly acidic resin, stir and heat up to 130 °C, add isononene dropwise for 8 hours, keep the temperature for reaction for 2 hours after dropping, sample analysis shows that 0.15% of 2,4-xylenol is qualified, the dosage of isononene is 480 parts (the dosage of isononene is 1.14 times the molar amount of 2,4-xylenol in 2,5 / 2,4-xylenol). After the reaction is completed, cool down to 80 °C and filter. The filtrate is subjected to vacuum distillation (-0.095 MPa, reflux ratio 25-30:1) to obtain 1488.7 parts of 99.7% 2,5-xylenol, and the yield is 94.2%; 763.5 parts of 99.2% 6-isononyl-2,4-xylenol antioxidant, and the yield is 91.6%.

[0127] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. 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 included in the present invention.

[0128] 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 process for preparing phenolic products from 2,4-dimethylphenol / 2,5-dimethylphenol, characterized in that: The following steps are involved: Step 1: Cleavage and translocation reaction: A stainless steel high-pressure reactor is loaded with an acidic silicon-aluminum-chromium oxide solid catalyst and zirconium phosphate, and a 2,4-dimethylphenol / 2,5-dimethylphenol mixture is added, the reactor is sealed, and the temperature is raised to 280-400° C. for reaction for 3-10 hours, and the pressure is gradually raised to 2.5-5.0 MPa, and the reaction is terminated. The inner coil is cooled with a programmed cooling heat transfer oil, and the temperature is rapidly lowered to 280-300° C. within 1-2 hours, and then the temperature is lowered to ≤150° C. within 0.5-1 hour, and propylene and ethylene released in the reaction are gradually discharged; the discharged gas is pressurized by a pressure pump and stored in a stainless steel spherical tank; after the gas is discharged, the cracking reaction condensate is slightly cooled and replaced with nitrogen for 0.5 hours, and the cracking reaction product is obtained by filtration, and the solid catalyst is applied; Step 2: Synthesis of 2-isopropyl-5-methylphenol and 4-isopropyl-3-methylphenol and or o- / p-isopropylphenol and or ethylphenol, comprising: 2.1 Synthesis of thymol and o-isopropylphenol; 2.1.1 Synthesis of thymol: At the same time as the cracking and transposition reactions in step 1, m-cresol, an acidic catalyst and a polymerization inhibitor are added to another stainless steel autoclave, stirring is started, and the temperature is raised to 160-170° C. The olefins stored in the spherical tank discharged after the cracking reaction in step 1 is cooled are simultaneously slowly decompressed and introduced into the stainless steel autoclave for reaction, the autoclave temperature is maintained at 170-200° C. The olefins are repeatedly introduced 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 drops, the unreacted ethylene in the autoclave is discharged; then the olefins in the spherical tank are repeatedly introduced multiple times to react until the pressure in the autoclave is 1.3-1.5 MPa, and when the pressure in the spherical tank drops to 1.6 MPa and the pressure in the autoclave no longer drops, the unreacted ethylene is discharged; the olefins are repeatedly introduced into the autoclave for reaction until the pressure in the autoclave is 0.6 MPa, and when the pressure in the spherical tank drops to 0.7 MPa and the pressure in the autoclave no longer drops, the olefins are discharged. Unreacted ethylene; passing olefin to react until the pressure in the autoclave is 0.1MPa, and discharging unreacted ethylene when the pressure in the spherical tank drops to 0.1MPa and the pressure in the autoclave no longer decreases; continuing to pass olefin to react until the pressure in the spherical tank is 0.03MPa and then venting is terminated, the olefin passing time is 3 to 12 hours, and the reaction is carried out by heat preservation for 1 to 4 hours after the passing, and a total of 160.7 parts of unreacted ethylene are collected, and the ethylene is pressurized and stored in the spherical tank (about 5MPa) by a pressure pump; the autoclave is cooled to ≤90°C in 1 to 3 hours, 10 to 35% liquid alkali is added to the material in the autoclave to neutralize to pH7 to 8, the desalted water layer is separated, and the material layer is added to the autoclave of the distillation tower, and the unreacted m-cresol is obtained by distillation at -0.085 to -0.095MPa and a reflux ratio of 10 to 20, and then ≥99% 2-isopropyl-5-cresol and ≥99% high-efficiency fungicide 4-isopropyl-3-cresol are obtained in sequence; 2.1.2 Synthesis of o-isopropylphenol: In step 1, while the cracking and transposition reactions are being carried out, phenol, an acidic catalyst and a polymerization inhibitor are added to another stainless steel autoclave, stirring is started, and the temperature is raised to 160-170° C. The olefins stored in the spherical tank discharged after the cracking reaction in step 1 is cooled are simultaneously slowly decompressed and introduced into the stainless steel autoclave for reaction, the autoclave temperature is maintained at 170-200° C. The olefins are repeatedly introduced 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 drops, the unreacted ethylene in the autoclave is discharged; then the olefins in the spherical tank are repeatedly introduced multiple times to react until the pressure in the autoclave is 1.3-1.5 MPa, and when the pressure in the spherical tank drops to 1.6 MPa and the pressure in the autoclave no longer drops, the unreacted ethylene is discharged; the olefins are repeatedly introduced into the autoclave for reaction until the pressure in the autoclave is 0.6 MPa, and when the pressure in the spherical tank drops to 0.7 MPa, the pressure is discharged. When the pressure of the autoclave is no longer reduced, the unreacted ethylene is discharged; the olefin is passed through the reaction until the pressure in the autoclave is 0.1MPa, and the unreacted ethylene is discharged when the pressure of the spherical tank is reduced to 0.1MPa and the pressure of the autoclave is no longer reduced; the olefin is continued to react until the pressure of the spherical tank is 0.03MPa and the ventilation is terminated, the olefin passing time is 3 to 12 hours, and the heat preservation reaction is performed for 2 hours after the passing, and the unreacted ethylene is collected, and the ethylene is pressurized and stored in the spherical tank (about 5MPa) by a pressure pump; the pressure autoclave is cooled to ≤90°C in 1 to 3 hours, 10 to 35% liquid alkali is added to the material in the autoclave to neutralize to pH7 to 8, the salt water layer is separated, and the material layer is added to the reactor of the distillation tower, and the unreacted phenol is distilled at -0.085 to -0.095MPa and a reflux ratio of 10 to 20, and then ≥99% o-isopropyl phenol and ≥95% p-isopropyl phenol crude products are obtained in turn; Add crude p-isopropylphenol and 90-120°C petroleum ether into a reactor, start stirring, heat to 70-90°C to completely dissolve the materials, then cool to 30-40°C with circulating water for 2-3 hours, then cool to 0-20°C with frozen brine for 2-4 hours, keep warm for 1-3 hours, filter, drain, and dry to obtain p-isopropylphenol with a concentration of ≥99%; 2.1.3 Synthesis of thymol and p-isopropylphenol: At the same time as the cracking and transposition reactions in step 1, m-cresol, phenol, an acidic catalyst and a polymerization inhibitor are added to another stainless steel autoclave, stirring is started, the temperature is raised to 160-170° C., the olefins stored in the spherical tank discharged after the cracking reaction in step 1 is cooled down are simultaneously slowly decompressed and introduced into the stainless steel autoclave for reaction, the autoclave temperature is maintained at 170-200° C., the olefins are repeatedly introduced 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 drops, the unreacted ethylene in the autoclave is discharged; then the olefins in the spherical tank are repeatedly introduced multiple times to react until the pressure in the autoclave is 1.3-1.5 MPa, and when the pressure in the spherical tank drops to 1.6 MPa and the pressure in the autoclave no longer drops, the unreacted ethylene is discharged; the olefins are repeatedly introduced into the autoclave for reaction until the pressure in the autoclave is 0.6 MPa, and when the pressure in the spherical tank drops to 0.7 MPa and the pressure in the autoclave no longer drops, the unreacted ethylene is discharged. The corresponding ethylene; olefin is reacted until the pressure in the autoclave reaches 0.1MPa, and the unreacted ethylene is discharged when the pressure in the spherical tank drops to 0.1MPa and the pressure in the autoclave no longer decreases; the olefin is continued to react until the pressure in the spherical tank reaches 0.03MPa and the ventilation is terminated. The olefin is passed for 3 to 12 hours, and the reaction is carried out by heat preservation for 2 hours after the olefin is passed. The unreacted ethylene is collected and stored in the spherical tank under pressure by a pressure pump; the pressure autoclave is cooled to ≤90℃ in 1 to 3 hours, and then the pressure is reduced to ≤90℃. 10-35% liquid alkali is added to the materials in the kettle to neutralize to pH 7-8, the salt water layer is separated, and the material layer is added to the kettle of the distillation tower. At -0.085-0.095MPa and a reflux ratio of 10-20, unreacted m-cresol and phenol are distilled and used, and then ≥99% o-isopropylphenol, ≥95% p-isopropylphenol, ≥99% 2-isopropyl-5-methylphenol, and ≥99% high-efficiency fungicide 4-isopropyl-3-methylphenol are obtained in sequence; Add crude p-isopropylphenol and 90-120°C petroleum ether into a reactor, start stirring, heat to 70-90°C to completely dissolve the materials, then cool to 30-40°C with circulating water for 2-3 hours, then cool to 0-20°C with frozen brine for 2-4 hours, keep warm for 1-3 hours, filter, drain, and dry to obtain p-isopropylphenol with a concentration of ≥99%; 2.2 Synthesis of p-ethylphenol: While synthesizing thymol and the like, phenol and an acid catalyst are added to a stainless steel autoclave, stirring is started, and the temperature is raised to 210-250° C. The pressurized ethylene collected in the ethylene spherical tank in step 2.1 is slowly decompressed and introduced into the stainless steel autoclave for reaction, the autoclave temperature is maintained at 220-250° C., the pressure is 0.9-1.0 MPa, the olefin feeding time is 4-10 hours, and ventilation is stopped when the pressure on the spherical tank drops to 1.0 MPa, the autoclave is kept warm for reaction for 1-4 hours, and the reaction is stopped when the autoclave pressure is stable and does not decrease; the autoclave is cooled to ≤90° C. in 1-3 hours, 10-35% liquid caustic soda is added to the material in the autoclave to neutralize to pH 7-8, the desalted water layer is separated, the material layer is added to the autoclave of a distillation tower, and the unreacted phenol is obtained by distillation at -0.085--0.095 MPa and a reflux ratio of 10-20, and then ≥99% o-ethyl phenol and ≥95% crude p-ethyl phenol are obtained in sequence; Add crude p-ethylphenol and methanol into the reactor, start stirring, raise the temperature to 60-70°C to completely dissolve the materials, then cool it down to 30-40°C with circulating water for 2-3 hours, then cool it down to 0-10°C with frozen brine for 2-4 hours, keep it warm for 1-3 hours, filter, drain, and dry to obtain p-ethylphenol with a content of ≥99%; Step 3: Distillation and separation of pyrolysis products: Add the cleavage reaction product of step 1 to the reactor of a distillation tower, and perform vacuum distillation to obtain 99% phenol, 99% mixed cresols, ≥98% 2,5-xylenol / 2,4-xylenol (2,5-xylenol / 2,4-xylenol ≥98%, 2,5-xylenol ≥70%), mixed xylenols, ≥90% crude 3,5-xylenol, and ≥90% crude 3,4-xylenol; 99% mixed cresols can be used to distill 99.5% o-cresol and ≥98% m-cresol products; ≥98% 2,5-xylenol / 2,4-xylenol can be used for tert-butylation separation to produce 6-tert-butyl-2,4-xylenol and 4-tert-butyl-2,5-xylenol products, and can also be used to produce 2,5-xylenol by solvent crystallization; crude 3,5-xylenol and crude 3,4-xylenol can be used to produce pure 3,5-xylenol and 3,4-xylenol by solvent crystallization or melt crystallization; Mixed xylenols can be separated by alkylation to produce 2,4-xylenol, 2,5-xylenol, 2,3-xylenol, m-ethylphenol, p-ethylphenol, etc. Step 4: Refining of crude product by cracking and distillation: 4.1 Add the crude 3,5-xylenol from step 3 and the solvent into the reactor, start stirring, raise the temperature to 60-90°C to completely dissolve the materials, then cool it down to 30-40°C with circulating water for 1-3 hours, then cool it down to 0-20°C with frozen brine for 1-3 hours, keep it warm for 1-2 hours, filter, drain, and dry to obtain ≥99% 3,5-xylenol; 4.2 Add the crude 3,4-xylenol from step 3 and the solvent into the reactor, start stirring, raise the temperature to 60-90°C to completely dissolve the materials, then cool it down to 30-40°C with circulating water for 1-3 hours, then cool it down to 0-20°C with frozen brine for 1-3 hours, keep it warm for 1-2 hours, filter, drain, and dry to obtain ≥99% 3,4-xylenol; 4.3 Add 500 parts of 2,5-xylenol / 2,4-xylenol and solvent from step 3 into the reactor, start stirring, raise the temperature to 60-90°C to completely dissolve the materials, then cool it down to 30-40°C with circulating water for 1-3 hours, then cool it down to 0-20°C with frozen brine for 1-3 hours, keep it warm for 1-2 hours, filter, drain, and dry to obtain ≥99% 2,5-xylenol; Step 5: Alkylation and separation of the mixed xylenols obtained by cracking and distillation: 5.1 Octylation separation, add the mixed xylenol and diisobutylene obtained in step 3 into a pressure reactor, add an acidic catalyst, stir and heat to 100-150°C for reaction, the reaction time is 2-12 hours, sample and analyze 2,3-xylenol ≤0.5% qualified, filter, and distill the filtrate to recover diisobutylene for application; then obtain ≥95% 2,5-xylenol and 99% 3,5-xylenol; antioxidant 99% 6-isooctyl-2,4-xylenol; obtain ≥95% 6-isooctyl-2,3-xylenol; the reactor residue mainly contains part of 6-isooctyl-m-ethylphenol, 2,6-diisooctyl-p-ethylphenol, etc.; Add ≥95% 6-isooctyl-2,3-xylenol to a decomposition kettle, stir, add ≥95% sulfuric acid, heat to 180-200°C for 0.5-2 hours, take samples for analysis, and if 6-isooctyl-2,3-xylenol ≤0.5% is qualified, cool to 70-90°C, add 10-35% sodium hydroxide aqueous solution to neutralize to pH 7-7.5, perform atmospheric distillation to obtain diisobutylene, and then perform vacuum distillation to obtain 99% 2,3-xylenol; Add ≥95% 2,5-xylenol and methanol into a crystallization reactor, start stirring, heat to 60-70°C to completely dissolve the materials, then cool to 30-40°C with circulating water for 1-3 hours, then cool to 0-20°C with frozen brine for 1-3 hours, keep warm for 1-2 hours, filter, drain, and dry to obtain ≥99% 2,5-xylenol; 5.2 Isohexylation separation, add the mixed xylenol and 6-isohexyl-2,4-xylenol obtained in step 3 into a pressure autoclave, add strong acid resin, stir and heat to 100-150°C for reaction, introduce vaporized isohexene until the pressure of the reactor reaches 0.6MPa, and when the pressure in the reactor drops to 0.1MPa, introduce vaporized isohexene again to 0.6MPa, and react multiple times in this way; when the pressure in the reactor drops slowly, sample and analyze 2,3-xylenol ≤0.5% and pass, the reaction time is 4-12 hours, after the reaction is completed, cool to 70-90°C for filtration, and conduct vacuum distillation of the filtrate to obtain ≥98% 2,5-xylenol and ≥99% 3,5-xylenol; obtain 99% 6-isohexyl-2,4-xylenol; obtain 95% 6-isohexyl-2,3-xylenol; Add 6-isohexyl-2,3-xylenol into the decomposition kettle, start stirring, add sulfuric acid, heat to 180-200°C and keep the temperature for 0.5-3 hours to remove isohexene, and obtain 99% 2,3-xylenol by distillation. The isohexene can be used for recycling; Add ≤99% 2,5-dimethylphenol and methanol into the reactor, start stirring, heat to 65°C to completely dissolve the materials, then cool to 30-40°C with circulating water for 2-4 hours, then cool to -10-10°C with frozen brine for 2-4 hours, keep warm for 1-3 hours, filter, drain, and dry to obtain 99.5% 2,5-dimethylphenol; Step 6: Alkylation separation of 2,5-dimethylphenol / 2,4-dimethylphenol: The ≥98% 2,5-xylenol / 2,4-xylenol and 6-isononyl-2,4-xylenol obtained in step 3 are added into a pressure autoclave, a strong acid resin is added, the temperature is raised to 100-180°C with stirring, isononene is added dropwise for reaction, the addition time is 4-12 hours, and the reaction is kept warm for 1-4 hours after the addition is completed. The 2,4-xylenol is sampled and analyzed, and the qualified is ≤0.3%, the amount of isononene is analyzed, the reaction is completed, the temperature is lowered to 70-100°C, and the filtrate is subjected to vacuum distillation (-0.09--0.1MPa, reflux ratio 10-30:1) to obtain ≥99.5% 2,5-xylenol; ≥99% antioxidant 6-isononyl-2,4-xylenol.

2. A process for preparing phenolic products from 2,4-dimethylphenol / 2,5-dimethylphenol according to claim 1, characterized in that: In step 1, a 2,4-dimethylphenol / 2,5-dimethylphenol mixture is added, wherein the ratio of 2,4-dimethylphenol to 2,5-dimethylphenol is 0.5-2:1, the ratio of 2,4-dimethylphenol to 2,5-dimethylphenol is 50-97%, preferably 70-90%, the ratio of o-isopropylphenol to o-propylphenol in the 2,4-dimethylphenol / 2,5-dimethylphenol mixture is 1-30%, preferably 5-20%, and the ratio of 2-ethyl-6-methylphenol is 0-30%, preferably 1-20%.

3. A process for preparing phenolic products from 2,4-dimethylphenol / 2,5-dimethylphenol according to claim 1, characterized in that: In step 1, an acidic silicon-aluminum-chromium oxide solid catalyst is loaded into a stainless steel high-pressure reactor, wherein the silicon-aluminum-chromium oxide is silicon dioxide, acidic alumina, and chromium oxide, wherein the mass ratio of silicon dioxide to acidic alumina is 0.1-10:10-0.1, preferably 0.2-5:5-0.2, the amount of chromium oxide is 0.01-0.2 of the mass of silicon dioxide, and the amount of silicon-aluminum-chromium oxide is 5-50% of the weight of the 2,4-xylenol / 2,5-xylenol mixture.

4. A process for preparing phenolic products from 2,4-dimethylphenol / 2,5-dimethylphenol according to claim 1, characterized in that: In step 1, the temperature of the heat transfer oil is gradually and slowly reduced from a high temperature to 80° C., wherein the high temperature is 50 to 100° C. lower than the cracking and transposition reaction temperature.

5. A process for preparing phenolic products from 2,4-dimethylphenol / 2,5-dimethylphenol according to claim 1, characterized in that: In step one, the cleavage reaction product [mixed phenol composed of 2,5-xylenol / 2,4-xylenol (mainly 2,5-xylenol), other xylenols (mainly 3,5-xylenol) and some phenols, cresols (mainly m-cresol) and the like] is filtered, wherein the cresol is a mixture composed of m-cresol, p-cresol, o-cresol, o-ethylphenol and the like, with m-cresol as the main component, and the cleavage reaction product [mixed phenol composed of 2,5-xylenol / 2,4-xylenol (mainly 2,5-xylenol), other xylenols (mainly 3,5-xylenol) and some phenols, cresols (mainly m-cresol) and the like] is filtered, and the ratio of 2,4-xylenol to 2,5-xylenol in the 2,4-xylenol / 2,5-xylenol is 1:2-5.

6. A process for preparing phenolic products from 2,4-dimethylphenol / 2,5-dimethylphenol according to claim 1, characterized in that: In step 1, the cleavage reaction product [a mixed phenol composed of 2,5-xylenol / 2,4-xylenol (mainly 2,5-xylenol), other xylenols (mainly 3,5-xylenol) and some phenols, cresols (mainly m-cresol) etc.] is obtained by filtration, wherein the other xylenols are 3,5-xylenol, 2,3-xylenol, 3,4-xylenol, a small amount of m-p-ethylphenol etc., with 3,5-xylenol being the main component.

7. A process for preparing phenolic products from 2,4-dimethylphenol / 2,5-dimethylphenol according to claim 1, characterized in that: In step 2.1, the acidic catalyst is at least one of sulfuric acid, phosphoric acid, p-toluenesulfonic acid, benzenesulfonic acid, a solid acid catalyst, an acidic resin, zirconium oxide, acidic aluminum oxide, silicon oxide, etc., preferably a mixed acid of sulfuric acid and phosphoric acid, and the amount of the mixed acid is 0.5-5% of the mass of m-cresol or phenol or a mixture of m-cresol and phenol, wherein the mass ratio of sulfuric acid to phosphoric acid is 5-7:5-3.

8. A process for preparing phenolic products from 2,4-dimethylphenol / 2,5-dimethylphenol according to claim 1, characterized in that: In step 2.2, the acidic catalyst is at least one of sulfuric acid, phosphoric acid, p-toluenesulfonic acid, benzenesulfonic acid, a solid acid catalyst, an acidic resin, zirconium oxide, acidic aluminum oxide, silicon oxide, etc., preferably a mixed acid of sulfuric acid and phosphoric acid, the amount of the mixed acid is 1-5% of the mass of phenol, wherein the mass ratio of sulfuric acid to phosphoric acid is 9-7:1-3.

9. A process for preparing phenolic products from 2,4-dimethylphenol / 2,5-dimethylphenol according to claim 1, characterized in that: In step 2.1, the polymerization inhibitor is hydroquinone, 2-methylhydroquinone, 2-tert-butylhydroquinone, 6-tert-butyl-2,4-dimethylphenol, p-methoxyphenol, etc., preferably 2-methylhydroquinone. In step 2.1.3, m-cresol and phenol are added to another stainless steel pressure autoclave, and the mass ratio of m-cresol to phenol is 1:0.5-2.

10. A process for preparing phenolic products using 2,4-dimethylphenol / 2,5-dimethylphenol according to claim 1, characterized in that: In step 3, the mixed xylenol is composed of two or more of 2,4-xylenol, 2,5-xylenol, 2,3-xylenol, 3,5-xylenol, a small amount of m-p-ethylphenol, etc., 2,3-xylenol is the main component, and the content is generally not less than 50%. In step 4.1, 4.2, and 4.3, the solvent is alcohol, alkane, ether, ester, ketone, etc., preferably methanol and petroleum ether. In step 5, an acidic catalyst is added, and the acidic catalyst is an inorganic acid such as sulfuric acid and phosphoric acid, an organic acid such as aminosulfonic acid, benzenesulfonic acid, toluenesulfonic acid, a solid acid loaded with antimonic acid, etc., a strong acid resin, etc., preferably a strong acid resin.