Method for separating m-p-cresol / o-ethyl phenol mixture and by-producing 2, 4-xylenol

Abstract

The invention belongs to the technical field of coalification and synthesis and separation of organic products, and particularly relates to a method for separating a m-cresol / p-cresol / o-ethyl phenol mixture and producing a byproduct 2, 4-xylenol. The method comprises the following steps: carrying out fixed bed catalytic methylation reaction on a m-cresol and p-cresol mixture raw material with high o-ethyl phenol content and methanol, rectifying methylation reactants to obtain 2, 4, 6-tricresol and a mixture of 2, 3, 6-tricresol and 2-ethyl-4, 6-xylenol, and carrying out catalytic deethylation reaction on the 2, 4, 6-tricresol and the mixture of 2, 3, 6-tricresol and 2-ethyl-4, 6-xylenol to obtain the 2, 4, 6-tricresol. The method comprises the following steps of: adding a mixture of 3, 4-xylenol, 2, 4, 6-tricresol and 2, 3, 6-tricresol, and rectifying again to obtain 2, 4-xylenol, 2, 4, 6-tricresol and 2, 3, 6-tricresol, so that the application field of m-cresol and p-cresol is expanded, and the separation of m-cresol and p-cresol with high ethyl phenol content extracted from tar phenol is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of coalification and organic product synthesis and separation, and particularly relates to a method for separating a m-p-cresol / o-ethylphenol mixture and producing 2,4-xylenol as a by-product. Background Art

[0002] Phenol-containing coal tar is first distilled and cut to obtain a phenol oil fraction of 170-230°C or a phenol oil fraction of 170-300°C, and the phenol oil fraction is then used to extract crude phenol by alkali dissolution and acid precipitation or solvent extraction. The crude phenol is preliminarily refined to obtain various phenol products or mixtures such as a mixed phenol fraction, o-cresol fraction, tri-mixed cresols, m-p-cresol (including o-ethylphenol), and xylenol. The mixed phenol fraction, o-cresol fraction, m-p-cresol, and mixed xylenols are then separated by physical or chemical methods to obtain products such as o-cresol, m-cresol, p-cresol, 2,5-xylenol, 2,4-xylenol, 3,5-xylenol, 3,4-tri-cresol, m-ethylphenol, and p-ethylphenol.

[0003] CN201310317583.6 discloses a method for separating industrial mixed p-cresol to produce pure p-cresol and pure m-cresol. Using industrial mixed p-cresol as the raw material, pure p-cresol and pure m-cresol are prepared through a complexation separation process. Compared to previous separation methods, this method can produce both p-cresol and m-cresol products simultaneously. By coupling the p-cresol and m-cresol separation processes, the proportion of p-cresol in the m-cresol extraction raw material is increased, while the remaining m-cresol is recycled for separation, thereby maximizing the m-cresol extraction efficiency. The entire separation process does not produce three wastes, operates at normal pressure, and requires minimal equipment, making it an environmentally friendly and green separation process. Pure p-cresol is extracted by complexation with oxalic acid and a solvent, while pure m-cresol is extracted by complexation with urea and a solvent.

[0004] CN202311603930.1 discloses a method for separating mixed cresols: it includes selective oxidation, filtration, neutralization, secondary filtration and distillation steps in sequence, and the selective oxidation includes: adding mixed cresols, sodium hydroxide, sodium methoxide, a solvent and a catalyst to an oxidation kettle, heating, and introducing oxygen for selective oxidation. In this method, sodium methoxide is added in the selective oxidation step, and sodium methoxide can react with the water obtained in the salt-forming reaction step (i.e., sodium hydroxide reacts with mixed cresols to generate sodium phenolate and water) to generate methanol and sodium hydroxide, thereby promoting the selective oxidation reaction, thereby improving the yield; the method mainly involves selectively oxidizing p-cresol to p-hydroxybenzaldehyde with an oxidant in the presence of a solvent and an alkaline material, controlling the p-cresol reaction to be complete, and then refining and separating to obtain pure m-cresol and p-hydroxybenzaldehyde, thereby achieving the separation of m-cresol. Summary of the Invention

[0005] The present invention is based on the inventors' discovery and understanding of the following facts and problems: the existing crude phenol refining process is unable to solve the problem of separating high-ethylphenol content m-p-cresol extracted from phenol-containing coal tar, because the existing crude phenol refining process can only obtain a mixture of m-p-cresol and o-ethylphenol. The m-p-cresol extracted from phenol-containing coal tar has a high o-ethylphenol content (generally accounting for 8-15% of the m-p-cresol content), so it is impossible to obtain a product with ≥95% m-p-cresol. Only about 90% m-p-cresol is obtained. The m-p-cresol with a high o-ethylphenol content is difficult to use in the production of wire enamel. The difficulty and production cost of separating m-p-cresol by the alkylation method are greatly increased, and there are problems such as a relatively complicated process and poor economic benefits.

[0006] The present invention aims to at least partially address one of the technical problems in the related art. To this end, embodiments of the present invention provide a method for separating a mixture of m-p-cresol and o-ethylphenol and producing 2,4-dimethylphenol as a by-product. The method is simple, easy to operate, and has low production costs, resulting in better economic benefits.

[0007] The method for separating the m-p-cresol / o-ethylphenol mixture and producing 2,4-dimethylphenol as a by-product of the present invention comprises the following steps:

[0008] (1) A mixture of m-cresol / o-ethylphenol, methanol, and water is mixed, and a silica gel-supported iron alum strontium oxide catalyst and an olefin hydrogenation catalyst are added, and hydrogen is introduced to react. After the reaction is completed, the reaction is filtered, and the obtained filtrate is firstly removed from methanol and water, and then vacuum distilled to obtain a mixture containing 2,3,6-trimethylphenol, 2,4,6-trimethylphenol, and 2-ethyl-4,6-dimethylphenol;

[0009] (2) adding silicon aluminum oxide and zirconium phosphate to the mixture containing 2,3,6-trimethylphenol, 2,4,6-trimethylphenol and 2-ethyl-4,6-dimethylphenol obtained in step (1) to carry out a reaction, cooling and exhausting the mixture after the reaction is completed, replacing the obtained reaction solution with nitrogen and filtering the mixture to obtain a cracking reaction solution, wherein the cracking reaction solution contains 2,4-dimethylphenol, 2,3,6-trimethylphenol and 2,4,6-trimethylphenol;

[0010] (3) adding sulfuric acid solution to the cleavage reaction solution obtained in step (2) and performing vacuum distillation to obtain 2,4-dimethylphenol, 2,4,6-trimethylphenol and 2,3,6-trimethylphenol.

[0011] The method for separating a meta-para-cresol / o-ethylphenol mixture and producing 2,4-xylenol as a by-product in the embodiment of the present invention has the following advantages and technical effects: 1. The method of the embodiment of the present invention uses a catalytic methylation reaction to separate the meta-para-cresol / o-ethylphenol mixture, uses a fully available solid catalyst, and the catalyst can be reused, substantially generating no solid waste. Moreover, since most of the water can be reused, relatively little wastewater needs to be treated, making the entire process environmentally friendly and green. 2. The method of the embodiment of the present invention uses a hydrogenation catalyst and hydrogen to remove a small amount of sulfur-containing and nitrogen-containing compounds in the meta-para-cresol, thereby obtaining 2,4-xylenol, 2,4,6-trimethylol, and 2,3,6-trimethylol with very low contents of sulfides and nitrogen-containing compounds, which can fully meet the quality indicators of polymerization agents and pharmaceutical-grade intermediates, thereby improving economic benefits.

[0012] In some embodiments, in step (1), the m-cresol / o-ethylphenol mixture is obtained by extracting crude phenol from phenol-containing coal tar from medium- and low-temperature coal gasification or medium- and low-temperature coal pyrolysis;

[0013] And / or, the m-p-cresol / o-ethylphenol mixture comprises: 0-5wt% of phenol, 0-10wt% of o-cresol, 0-15wt% of 2,6-xylenol, 70-95wt% of m- / p-cresol, 5-15wt% of o-ethylphenol, 0-10wt% of 2,4-xylenol / 2,5-xylenol, and 0-10wt% of others.

[0014] In some embodiments, in step (1), the molar ratio of the m-p-cresol / o-ethylphenol mixture, methanol, and water is 1:8-15:0.5-1.0.

[0015] In some embodiments, in step (1), the particle size of the silica gel-supported strontium oxide iron alum catalyst is 50-200 mesh;

[0016] And / or, in the step (1), the mass ratio of iron oxide to vanadium oxide and strontium oxide in the iron alum strontium oxide is 0.5-5:1:0.01-0.05;

[0017] And / or, in the step (1), the olefin hydrogenation catalyst comprises at least one of 1-5% palladium on carbon or Raney nickel;

[0018] And / or, in step (1), the amount of the olefin hydrogenation catalyst is 0.1-1% of the mass of the silica gel-supported strontium oxide catalyst, and the amount of the silica gel-supported strontium oxide catalyst is 5-30% of the mass of the m-cresol / o-ethylphenol mixture.

[0019] In some embodiments, in step (1), the amount of hydrogen added is 0.01 to 0.2 times the mass of the m-p-cresol / o-ethylphenol mixture;

[0020] And / or, in step (1), the reaction pressure is normal pressure, the reaction temperature is 250-500° C., and the liquid hourly space velocity required for the reaction is 0.5-1.5 h −1 ; sampling and analysis show that the reaction is terminated when the conversion rate of m-cresol is ≥99.5% and the content of 2,4-dimethylphenol / 2,5-dimethylphenol is ≤0.5%;

[0021] And / or, in the step (1), the pressure for removing methanol and water is normal pressure to -0.07 MPa;

[0022] And / or, in the step (1), the pressure of the vacuum distillation is -0.08 to -0.98 MPa, and the reflux ratio is 10 to 30:1.

[0023] In some embodiments, in step (1), the reaction is carried out in a reactor, and the reactor is a tank reactor, a fixed bed reactor, a fluidized bed reactor, an ebullient bed reactor or a transport bed reactor.

[0024] In some embodiments, in step (2), the silicon-aluminum oxide comprises silicon dioxide and acidic aluminum oxide, and the mass ratio of silicon dioxide to acidic aluminum oxide is 1:0.01 to 50;

[0025] And / or, in step (2), the amount of zirconium phosphate used is 1-10% of the mass of the silica-aluminum oxide, and the amount of silica-aluminum oxide used is 1-5% of the mass of the raw material m-p-cresol / o-ethylphenol mixture.

[0026] In some embodiments, in step (2), the reaction temperature is 250-300° C., the reaction time is 4-6 hours, and the pressure gradually increases to 1.0-2.0 MPa during the reaction. When the pressure stabilizes, sampling and analysis are performed, and the reaction is terminated when the 2-ethyl-4,6-dimethylphenol concentration is ≤0.1%.

[0027] And / or, in step (2), the nitrogen replacement time is 0.5 to 1 hour.

[0028] In some embodiments, in step (2), the reaction is carried out in a stainless steel high-pressure reactor with an external stainless steel condenser and an inner coil; the cooling is performed by programmed cooling using heat transfer oil in the inner coil, and the cooling rate of the heat transfer oil is 100 to 200°C / h;

[0029] And / or, in step (2), the cooling is to reduce the temperature to below 200° C. within 0.5 to 1 hour.

[0030] In some embodiments, in step (3), the concentration of the sulfuric acid solution is 95-98%, and the amount of the sulfuric acid solution is 0.1-0.5% of the mass of the cleavage reaction solution;

[0031] And / or, in the step (3), the pressure of the vacuum distillation is -0.08 to -0.98 MPa, and the reflux ratio is 10 to 30:1. DETAILED DESCRIPTION

[0032] The following describes in detail embodiments of the present invention. The embodiments are exemplary and intended to explain the present invention, but are not to be construed as limiting the present invention.

[0033] The method for separating the m-p-cresol / o-ethylphenol mixture and producing 2,4-dimethylphenol as a by-product of the present invention comprises the following steps:

[0034] (1) A mixture of m-cresol / o-ethylphenol, methanol, and water is mixed, and a silica gel-supported iron alum strontium oxide catalyst and an olefin hydrogenation catalyst are added, and hydrogen is introduced to react. After the reaction is completed, the reaction is filtered, and the obtained filtrate is firstly removed from methanol and water, and then vacuum distilled to obtain a mixture containing 2,3,6-trimethylphenol, 2,4,6-trimethylphenol, and 2-ethyl-4,6-dimethylphenol;

[0035] (2) adding silicon aluminum oxide and zirconium phosphate to the mixture containing 2,3,6-trimethylphenol, 2,4,6-trimethylphenol and 2-ethyl-4,6-dimethylphenol obtained in step (1) to carry out a reaction, cooling and exhausting the mixture after the reaction is completed, replacing the obtained reaction solution with nitrogen and filtering the mixture to obtain a cracking reaction solution, wherein the cracking reaction solution contains 2,4-dimethylphenol, 2,3,6-trimethylphenol and 2,4,6-trimethylphenol;

[0036] (3) adding sulfuric acid solution to the cleavage reaction solution obtained in step (2) and performing vacuum distillation to obtain 2,4-dimethylphenol, 2,4,6-trimethylphenol and 2,3,6-trimethylphenol.

[0037] The method for separating a meta-para-cresol / o-ethylphenol mixture and producing 2,4-dimethylphenol as a by-product in the embodiment of the present invention adopts a catalytic methylation reaction to separate the meta-para-cresol, uses a fully available solid catalyst, and the catalyst can be reused, substantially generating no solid waste. Moreover, since most of the water can be reused, relatively little wastewater needs to be treated, and the entire process is environmentally friendly and green. The method of the embodiment of the present invention uses a hydrogenation catalyst and hydrogen to remove a small amount of sulfur-containing and nitrogen-containing compounds in the meta-para-cresol, thereby obtaining 2,4-dimethylphenol, 2,4,6-trimethylphenol, and 2,3,6-trimethylphenol with very low contents of sulfide and nitrogen-containing compounds, fully meeting the quality standards of polymerization agents and pharmaceutical-grade intermediates, and improving economic benefits.

[0038] In some embodiments, preferably, in step (1), the m-p-cresol / o-ethylphenol mixture is obtained by distilling crude phenol extracted from phenol-containing coal tar obtained from medium- and low-temperature coal gasification or medium- and low-temperature coal pyrolysis;

[0039] And / or, the m-p-cresol / o-ethylphenol mixture comprises: 0-5 wt% phenol, 0-10 wt% o-cresol, 0-15 wt% 2,6-xylenol, 70-95 wt% m- / p-cresol, 5-15 wt% o-ethylphenol, 0-10 wt% 2,4-xylenol / 2,5-xylenol, and 0-10 wt% of other ingredients. Further preferably, the m-p-cresol / o-ethylphenol mixture comprises: 80-90 wt% m-p-cresol, 7-12 wt% o-ethylphenol, and 0-8 wt% of other ingredients.

[0040] In some embodiments, preferably, in step (1), the molar ratio of the m-p-cresol / o-ethylphenol mixture, methanol and water is 1:8-15:0.5-1.0.

[0041] In some embodiments, preferably, in step (1), the particle size of the silica gel-supported strontium oxide iron sulfate catalyst is 50-200 mesh;

[0042] And / or, in the step (1), the mass ratio of iron oxide to vanadium oxide and strontium oxide in the iron strontium oxide is 0.5-5:1:0.01-0.05.

[0043] In some embodiments, preferably, in step (1), the olefin hydrogenation catalyst comprises at least one of 1-5% palladium on carbon or Raney nickel. Further preferably, the 1-5% palladium on carbon or Raney nickel has low activity, and the low activity is controlled by detecting the content of trimethylcyclohexanol in the catalytic methylation reaction solution, requiring the content of trimethylcyclohexanol to be as low as possible.

[0044] In some embodiments, preferably, in step (1), the amount of the olefin hydrogenation catalyst used is 0.1-1% of the mass of the silica gel-supported strontium iron oxide catalyst, and the amount of the silica gel-supported strontium iron oxide catalyst used is 5-30% of the mass of the m-cresol / o-ethylphenol mixture.

[0045] In some embodiments, preferably, in step (1), the amount of hydrogen added is 0.01 to 0.2 times the mass of the m-p-cresol / o-ethylphenol mixture.

[0046] In some embodiments, preferably, in step (1), the reaction pressure is normal pressure, the reaction temperature is 250-500° C., and the liquid hourly space velocity required for the reaction is 0.5-1.5 h-1; sampling and analysis show that the reaction is completed when the conversion rate of m-cresol is ≥99.5% and the content of 2,4-dimethylphenol / 2,5-dimethylphenol is ≤0.5%.

[0047] In some embodiments, preferably, in step (1), the pressure for removing methanol and water is from normal pressure to -0.07 MPa. Further preferably, the pressure for removing methanol and water is from normal pressure to -0.05 MPa.

[0048] In some embodiments, preferably, in the step (1), the pressure of the vacuum distillation is -0.08 to -0.98 MPa, and the reflux ratio is 10 to 30:1.

[0049] In some embodiments, preferably, in step (1), the reaction is carried out in a reactor, and the reactor is a tank reactor, a fixed bed reactor, a fluidized bed reactor, an ebullient bed reactor, or a transport bed reactor. Further preferably, the reactor is a fixed bed reactor.

[0050] In some embodiments, preferably, in step (2), the silicon-aluminum oxide comprises silicon dioxide and acidic aluminum oxide, and the mass ratio of silicon dioxide to acidic aluminum oxide is 1:0.01 to 50;

[0051] And / or, in step (2), the amount of zirconium phosphate used is 1-10% of the mass of the silica-alumina, and the amount of the silica-alumina used is 1-5% of the mass of the raw material m-p-cresol / o-ethylphenol mixture. Further preferably, the mass ratio of the silica to the acidic alumina is 1:0.05-20.

[0052] In some embodiments, preferably, in step (2), the reaction temperature is 250-300° C., the reaction time is 4-6 hours, and the pressure gradually increases to 1.0-2.0 MPa during the reaction. When the pressure stabilizes, sampling and analysis are performed, and the reaction is terminated when 2-ethyl-4,6-dimethylphenol is ≤0.1%.

[0053] And / or, in step (2), the nitrogen replacement time is 0.5 to 1 hour.

[0054] In some embodiments, preferably, in step (2), the reaction is carried out in a stainless steel high-pressure reactor with an external stainless steel condenser and an inner coil; the cooling is performed by programmed cooling using heat transfer oil in the inner coil, and the cooling rate of the heat transfer oil is 100 to 200°C / h;

[0055] And / or, in step (2), the cooling is to reduce the temperature to below 200° C. within 0.5 to 1 hour.

[0056] In some embodiments, preferably, in step (3), the concentration of the sulfuric acid solution is 95-98%, and the amount of the sulfuric acid solution is 0.1-0.5% of the mass of the cleavage reaction solution;

[0057] And / or, in the step (3), the pressure of the vacuum distillation is -0.08 to -0.98 MPa, and the reflux ratio is 10 to 30:1.

[0058] In some embodiments, preferably, in step (1) and / or step (3), the vacuum distillation is carried out in a distillation tower, and the number of theoretical plates of the distillation tower is 100 to 350. Further preferably, the number of theoretical plates of the distillation tower is 200 to 300.

[0059] The technical solution of the present invention is described in detail below in conjunction with specific embodiments.

[0060] Example 1

[0061] Step 1: Synthesis of 2,4,6-trimethylphenol, 2,3,6-trimethylphenol, and 2-ethyl-4,6-dimethylphenol

[0062] 600 parts of a catalyst prepared by loading strontium iron oxide on silica gel (all parts are calculated by weight in the examples) (60-80 mesh, strontium iron oxide mass ratio of 2:1:0.02) and 6 parts of 1.5% palladium carbon were loaded into a fixed bed reactor, and 10,000 parts of a mixture of m-cresol and o-ethylphenol (968 parts of o-cresol, 114 parts of 2,6-dimethylphenol, 3730 parts of m-cresol, 3392 parts of p-cresol, 668 parts of o-ethylphenol, 2,6-dimethylphenol) were added. A mixture of 489 parts of 4-xylenol, 407 parts of 2,5-xylenol, 82 parts of o-isopropylphenol, 102 parts of 2-ethyl-6-methylphenol, 48 parts of other phenols), 25,000 parts of methanol and 1,400 parts of water (8.64 times and 0.86 times the molar number of m-p-cresol, respectively) was injected into the reactor through the preheater by a plunger metering pump, and at the same time, 1,000 parts of quantitative hydrogen (the amount of hydrogen was 0.1 times that of m-p-cresol) was uniformly introduced into the fixed bed reactor. times), the reaction was carried out under normal pressure, 300 ° C and liquid hourly space velocity 0.5h-1, the conversion rate of m-cresol was 100%, and 0.25% of 2,4-dimethylphenol / 2,5-dimethylphenol was qualified. The obtained condensate was added to a distillation tower (theoretical plate number is about 100), and 19015.5 parts of methanol were obtained by atmospheric distillation, and 4350.5 parts of water were recovered at -0.02~-0.05MP, and part of the recovered water was used for the next batch of methylation reaction. ; Unused recycled water was sent for further treatment; -0.085~-0.09Mpa, reflux ratio 10~15:1 vacuum distillation obtained 79.6 parts of the first portion and 12167.6 parts of mixed trimethylols (including 6063.8 parts of 2,4,6-trimethylol, 5075.6 parts of 2,3,6-trimethylol, 915.1 parts of 2-ethyl-4,6-dimethylol, 96.9 parts of 2-isopropyl-4,6-dimethylol, and 16.2 parts of others).

[0063] Step 2: Mix trimethylol to deethylate and propylate to generate 2,4-dimethylphenol

[0064] A stainless steel high-pressure reactor (with an external stainless steel condenser and an inner coil) was charged with 600 parts of acidic silica-alumina (the mass ratio of silica to acidic alumina was 2:1) and 12 parts of zirconium phosphate. 12167.6 parts of the mixed trimethylol obtained in step 1 were then added. The reactor was sealed and heated to 280°C for 5 hours. The pressure was gradually increased to 1.8 MPa. When the pressure stabilized, samples were taken for analysis. 0.03% of 2-ethyl-4,6-dimethylphenol was added to terminate the reaction. The inner coil was heated using the procedure The heat transfer oil was cooled at a rate of 110 to 120°C / h, and the temperature was rapidly lowered to 170°C in 1 hour to gradually discharge the ethylene and propylene released in the reaction; after the gas was discharged, the cracking reaction condensate was slightly cooled and replaced with nitrogen for 0.5 hours, and 11927.1 parts of cracking reaction liquid (800.1 parts of 2,4-dimethylphenol, 5050.3 parts of 2,3,6-trimethylphenol, 6033.5 parts of 2,4,6-trimethylphenol, and 43.2 parts of others) were obtained by filtration, and the solid catalyst was applied.

[0065] The reaction product obtained by filtration was added to the bottom of a distillation tower (theoretical plate number is about 250), 24 parts of 98% sulfuric acid was added (the amount of sulfuric acid was 0.20% of the mass of the cracking reaction liquid), and the temperature was increased to -0.085 to -0.09 MPa and a reflux ratio of 20 to 25:1, and vacuum distillation was carried out to obtain 776.8 parts of 99.5% 2,4-dimethylphenol, 5711.1 parts of 99.2% 2,4,6-trimethylphenol, and 4695.3 parts of 99.6% 2,3,6-trimethylphenol.

[0066] Example 2

[0067] Step 1: Synthesis of 2,4,6-trimethylphenol, 2,3,6-trimethylphenol, and 2-ethyl-4,6-dimethylphenol

[0068] 600 parts of a catalyst prepared by supporting strontium iron oxide on silica gel (80-120 mesh, strontium iron oxide mass ratio of 3:1:0.01) and 3 parts of 1.5% palladium on carbon were loaded into a fixed-bed reactor, and 10,000 parts of a m-p-cresol / o-ethylphenol mixture (4,693 parts of m-cresol, 4,267 parts of p-cresol, 951 parts of o-ethylphenol, and 89 parts of other phenols), a mixture of 20,000 parts of methanol and 1,200 parts of water (6.83 times and 0.73 times the molar number of m-p-cresol, respectively) were injected into the reactor via a plunger metering pump through a preheater. Simultaneously, 1,000 parts of a fixed-bed reactor were evenly introduced with a fixed amount of hydrogen (0.1 times the amount of m-p-cresol). The reaction was carried out under normal pressure, 400° C. and a liquid hourly space velocity of 0.8 h −1 . The conversion rate of m-cresol was 100%, and the 2,4-xylenol / 2,5-xylenol ratio was 0.21%, which was qualified. The obtained condensate was added to a distillation tower (theoretical plate number was about 100), and 13753.8 parts of methanol were obtained by atmospheric distillation, and 4398.7 parts of water were recovered at -0.02 to -0.05 MPa. A part of the recovered water was applied to the next batch of methylation reaction; the unused recovered water was sent for further treatment; 61.5 parts of the first part and 12320.4 parts of mixed trimethylols were obtained by vacuum distillation at -0.085 to -0.09 MPa and a reflux ratio of 10 to 15:1 (including 5347.3 parts of 2,4,6-trimethylol, 5813.3 parts of 2,3,6-trimethylol, 1145.9 parts of 2-ethyl-4,6-xylenol, and 13.9 parts of others).

[0069] Step 2: Mix trimethylol to deethylate and propylate to generate 2,4-dimethylphenol

[0070] A stainless steel high-pressure reactor (with an external stainless steel condenser and an inner coil) was charged with 600 parts of acidic silica-alumina (mass ratio of silica to acidic alumina was 1:1) and 18 parts of zirconium phosphate. 12320.4 parts of the mixed trimethylol obtained in step 1 was then added. The reactor was sealed and heated to 300° C. for 4 hours. The pressure was gradually increased to 1.95 MPa. When the pressure remained stable, a sample was taken for analysis. 0.02% of 2-ethyl-4,6-dimethylphenol was used to terminate the reaction. The inner coil was filled with a process The heat transfer oil was cooled sequentially at a cooling rate of 140-150°C / h, and the temperature was rapidly lowered to 160°C in 1 hour to gradually discharge the ethylene released in the reaction; after the gas was discharged, the cracking reaction condensate was slightly cooled and replaced with nitrogen for 0.5 hours, and 12048.2 parts of cracking reaction liquid (922.7 parts of 2,4-dimethylphenol, 5784.2 parts of 2,3,6-trimethylphenol, 5320.5 parts of 2,4,6-trimethylphenol, and 20.8 parts of others) were obtained by filtration, and the solid catalyst was applied.

[0071] The reaction product obtained by filtration was added to the bottom of a distillation tower (theoretical plate number is about 250), 24 parts of 98% sulfuric acid was added (the amount of sulfuric acid was 0.20% of the mass of the cracking reaction liquid), and the temperature was increased to -0.085 to -0.09 MPa and a reflux ratio of 20 to 25:1, and vacuum distillation was carried out to obtain 900.4 parts of 99.6% 2,4-dimethylphenol, 4998.3 parts of 99.1% 2,4,6-trimethylphenol, and 5359.8 parts of 99.5% 2,3,6-trimethylphenol.

[0072] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

[0073] Although the above embodiments have been shown and described, it is understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. Changes, modifications, substitutions and variations of the above embodiments by those skilled in the art are all within the scope of protection of the present invention.

Claims

1. A method for separating a mixture of m-p-cresol and o-ethylphenol and producing 2,4-dimethylphenol as a by-product, characterized in that: The following steps are involved: (1) A mixture of m-cresol / o-ethylphenol, methanol, and water is mixed, and a silica gel-supported iron alum strontium oxide catalyst and an olefin hydrogenation catalyst are added, and hydrogen is introduced to react. After the reaction is completed, the reaction is filtered, and the obtained filtrate is firstly removed from methanol and water, and then vacuum distilled to obtain a mixture containing 2,3,6-trimethylphenol, 2,4,6-trimethylphenol, and 2-ethyl-4,6-dimethylphenol; (2) adding silicon aluminum oxide and zirconium phosphate to the mixture containing 2,3,6-trimethylphenol, 2,4,6-trimethylphenol and 2-ethyl-4,6-dimethylphenol obtained in step (1) to carry out a reaction, cooling and exhausting the mixture after the reaction is completed, replacing the obtained reaction solution with nitrogen and filtering the mixture to obtain a cracking reaction solution, wherein the cracking reaction solution contains 2,4-dimethylphenol, 2,3,6-trimethylphenol and 2,4,6-trimethylphenol; (3) adding sulfuric acid solution to the cleavage reaction solution obtained in step (2) and performing vacuum distillation to obtain 2,4-dimethylphenol, 2,4,6-trimethylphenol and 2,3,6-trimethylphenol.

2. The method for separating the m-p-cresol / o-ethylphenol mixture and producing 2,4-dimethylphenol as a by-product according to claim 1, wherein In the step (1), the m-p-cresol / o-ethylphenol mixture is obtained by extracting crude phenol from phenol-containing coal tar by medium-low temperature coal gasification or medium-low temperature coal pyrolysis; And / or, the m-p-cresol / o-ethylphenol mixture comprises: 0-5wt% of phenol, 0-10wt% of o-cresol, 0-15wt% of 2,6-xylenol, 70-95wt% of m- / p-cresol, 5-15wt% of o-ethylphenol, 0-10wt% of 2,4-xylenol / 2,5-xylenol, and 0-10wt% of others.

3. The method for separating the m-p-cresol / o-ethylphenol mixture and producing 2,4-dimethylphenol as a by-product according to claim 1, wherein: In the step (1), the molar ratio of the m-p-cresol / o-ethylphenol mixture, methanol and water is 1:8-15:0.5-1.

0.

4. The method for separating the m-p-cresol / o-ethylphenol mixture and producing 2,4-dimethylphenol as a by-product according to claim 1, wherein In the step (1), the particle size of the silica gel-supported strontium oxide iron alum catalyst is 50 to 200 meshes; And / or, in the step (1), the mass ratio of iron oxide to vanadium oxide and strontium oxide in the iron alum strontium oxide is 0.5-5:1:0.01-0.05; And / or, in the step (1), the olefin hydrogenation catalyst comprises at least one of 1-5% palladium on carbon or Raney nickel; And / or, in step (1), the amount of the olefin hydrogenation catalyst is 0.1-1% of the mass of the silica gel-supported strontium oxide catalyst, and the amount of the silica gel-supported strontium oxide catalyst is 5-30% of the mass of the m-cresol / o-ethylphenol mixture.

5. The method for separating the m-p-cresol / o-ethylphenol mixture and producing 2,4-dimethylphenol as a by-product according to claim 1, wherein: In the step (1), the amount of hydrogen added is 0.01 to 0.2 times the mass of the m-p-cresol / o-ethylphenol mixture; And / or, in step (1), the reaction pressure is normal pressure, the reaction temperature is 250-500° C., and the liquid hourly space velocity required for the reaction is 0.5-1.5 h −1 ; sampling and analysis show that the reaction is terminated when the conversion rate of m-cresol is ≥99.5% and the content of 2,4-dimethylphenol / 2,5-dimethylphenol is ≤0.5%; And / or, in the step (1), the pressure for removing methanol and water is normal pressure to -0.07 MPa; And / or, in the step (1), the pressure of the vacuum distillation is -0.08 to -0.98 MPa, and the reflux ratio is 10 to 30:

1.

6. The method for separating the m-p-cresol / o-ethylphenol mixture and producing 2,4-dimethylphenol as a by-product according to any one of claims 1 to 5, characterized in that: In the step (1), the reaction is carried out in a reactor, which is a tank reactor, a fixed bed reactor, a fluidized bed reactor, an ebullient bed reactor or a transport bed reactor.

7. The method for separating the m-p-cresol / o-ethylphenol mixture and producing 2,4-dimethylphenol as a by-product according to claim 1, characterized in that: In the step (2), the silicon-aluminum oxide comprises silicon dioxide and acidic aluminum oxide, and the mass ratio of silicon dioxide to acidic aluminum oxide is 1:0.01 to 50; And / or, in step (2), the amount of zirconium phosphate used is 1-10% of the mass of the silica-aluminum oxide, and the amount of silica-aluminum oxide used is 1-5% of the mass of the raw material m-p-cresol / o-ethylphenol mixture.

8. The method for separating the m-p-cresol / o-ethylphenol mixture and producing 2,4-dimethylphenol as a by-product according to claim 1, characterized in that: In the step (2), the reaction temperature is 250-300° C., the reaction time is 4-6 hours, and the pressure gradually increases to 1.0-2.0 MPa during the reaction. When the pressure stabilizes, sampling and analysis are performed, and the reaction is terminated when the 2-ethyl-4,6-dimethylphenol content is ≤0.1%. And / or, in step (2), the nitrogen replacement time is 0.5 to 1 hour.

9. The method for separating the m-p-cresol / o-ethylphenol mixture and producing 2,4-dimethylphenol as a by-product according to claim 1, 7 or 8, characterized in that: In the step (2), the reaction is carried out in a stainless steel high-pressure reactor with an external stainless steel condenser and an inner coil; the temperature is lowered by programmed cooling using the heat transfer oil in the inner coil, and the cooling rate of the heat transfer oil is 100 to 120°C / h; And / or, in step (2), the cooling is to reduce the temperature to below 200° C. within 0.5 to 1 hour.

10. The method for separating the m-p-cresol / o-ethylphenol mixture and producing 2,4-dimethylphenol as a by-product according to claim 1, characterized in that: In the step (3), the concentration of the sulfuric acid solution is 95-98%, and the amount of the sulfuric acid solution is 0.1-0.5% of the mass of the cleavage reaction solution; And / or, in the step (3), the pressure of the vacuum distillation is -0.08 to -0.98 MPa, and the reflux ratio is 10 to 30:1.