Method for separating 2, 4-xylenol / 2, 5-xylenol 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 2, 4-xylenol / 2, 5-xylenol mixture and producing 2, 4-xylenol as a byproduct. A 2, 4-xylenol / 2, 5-xylenol raw material with high 2-ethyl-6-cresol and o-isopropyl phenol content and methanol are subjected to a catalytic methylation reaction, then rectification is performed to obtain a mixture of 2, 4, 6-xylenol, 2, 3, 6-tricresol, 2-ethyl-4, 6-xylenol and 2-isopropyl-4, 6-xylenol, and then a catalytic ethyl and isopropyl removal reaction is performed to obtain 2, 4-xylenol, 2, 4, 6-tricresol, 2, 3, 6-tricresol and 2-isopropyl-4, 6-xylenol. According to the method, a mixture of 2, 4-xylenol, 2, 4, 6-tricresol and 2, 3, 6-tricresol is obtained through rectification, and 2, 4-xylenol, 2, 4, 6-tricresol and 2, 3, 6-tricresol are obtained through rectification again, so that separation of 2, 4-xylenol / 2, 5-xylenol with high 2-ethyl-6-cresol content and high o-isopropyl phenol content in tar phenol extraction 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 2,4-dimethylphenol / 2,5-dimethylphenol mixture and producing 2,4-dimethylphenol as a by-product. Background Art

[0002] Related technologies are unable to separate 2-ethyl-6-methylphenol and o-isopropylphenol from phenol-containing coal tar, resulting in a mixture of 2,4-xylenol / 2,5-xylenol. Conventional crude phenol refining processes only yield a mixture of 2,4-xylenol / 2,5-xylenol, 2-ethyl-6-methylphenol, and o-isopropylphenol. The 2,4-xylenol / 2,5-xylenol mixture extracted from phenol-containing coal tar contains high levels of 2-ethyl-6-methylphenol and o-isopropylphenol (typically accounting for 5-10% of the 2,4-xylenol / 2,5-xylenol content), making it difficult to obtain high-purity 2,4-xylenol / 2,5-xylenol. Furthermore, 2,4-xylenol / 2,5-xylenol containing high levels of 2-ethyl-6-methylphenol and o-isopropylphenol is difficult to use as a solvent for wire enamels. The difficulty and production cost of separating 2,4-dimethylphenol and 2,5-dimethylphenol by alkylation are both high, and there are problems such as a relatively complicated process and poor economic benefits. Summary of the Invention

[0003] 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 2,4-xylenol / 2,5-xylenol mixture and producing 2,4-xylenol as a byproduct. This method achieves the separation of 2,4-xylenol / 2,5-xylenol containing high levels of 2-ethyl-6-methylphenol and o-isopropylphenol, while simplifying the process, producing high-purity phenolic compounds, and achieving good economic benefits.

[0004] A method for separating a 2,4-xylenol / 2,5-xylenol mixture and producing 2,4-xylenol as a by-product in an embodiment of the present invention comprises the following steps:

[0005] (1) A 2,4-xylenol / 2,5-xylenol mixture, methanol and water are mixed, and a silica gel-supported iron alum strontium oxide catalyst and an olefin hydrogenation catalyst are added, and hydrogen is introduced at the same time to react. After the reaction is completed, the reaction is filtered, and the obtained filtrate is distilled to remove methanol and water, and then vacuum distilled to obtain a mixture containing 2,3,6-trimethylphenol, 2,4,6-trimethylphenol, 2-ethyl-4,6-xylenol and 2-isopropyl-4,6-xylenol; the 2,4-xylenol / 2,5-xylenol mixture comprises: 0-15 wt% of m-cresol, 0-10 wt% of p-cresol, 0-2 wt% of o-ethylphenol, 70-95 wt% of 2,4-xylenol / 2,5-xylenol, 1-15 wt% of 2-ethyl-6-methylphenol, 1-15 wt% of o-isopropylphenol and / or o-propylphenol, and 0-10 wt% of other components;

[0006] (2) adding silicon aluminum oxide and zirconium phosphate to the mixture containing 2,3,6-trimethylphenol, 2,4,6-trimethylphenol, 2-ethyl-4,6-xylenol and 2-isopropyl-4,6-xylenol to react, cooling and exhausting the mixture in sequence after the reaction, replacing the obtained reaction liquid with nitrogen after the exhaust, and filtering the mixture to obtain a cracking reaction liquid, wherein the cracking reaction liquid contains 2,4-xylenol, 2,3,6-trimethylphenol and 2,4,6-trimethylphenol;

[0007] (3) adding a sulfuric acid solution to the cleavage reaction solution obtained in step (2), and then performing vacuum distillation to obtain 2,4-dimethylphenol, 2,4,6-trimethylphenol and 2,3,6-trimethylphenol.

[0008] The advantages and technical effects brought by the method for separating the 2,4-dimethylphenol / 2,5-dimethylphenol mixture and producing 2,4-dimethylphenol as a by-product in the embodiment of the present invention are as follows: 1. The method of the embodiment of the present invention adopts a catalytic methylation reaction to separate 2,4-dimethylphenol / 2,5-dimethylphenol, uses a fully applicable solid catalyst, basically does not generate solid waste, and most of the water can be reused. In addition, the composition of the dissolved materials in the water is relatively simple, and the wastewater solution treatment is applicable, and the wastewater to be treated is relatively easy, so the treatment process is green and environmentally friendly; 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 2,4-dimethylphenol / 2,5-dimethylphenol, so that the content of sulfide and nitrogen-containing compounds in the obtained 2,4-dimethylphenol, 2,4,6-trimethylphenol, and 2,3,6-trimethylphenol is very low, which can fully meet the quality indicators of polymerization agents and pharmaceutical-grade intermediates, thereby improving the economic benefits of the products.

[0009] In some embodiments, in step (1), the 2,4-dimethylphenol / 2,5-dimethylphenol 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.

[0010] In some embodiments, in step (1), the molar ratio of the 2,4-dimethylphenol / 2,5-dimethylphenol mixture, methanol, and water is 1:4-10:0.5-1.0.

[0011] In some embodiments, in step (1), the particle size of the silica gel-supported strontium oxide iron alum catalyst is 50-200 mesh;

[0012] 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;

[0013] And / or, in the step (1), the olefin hydrogenation catalyst comprises 1-5% of at least one of palladium carbon or Raney nickel, the olefin hydrogenation catalyst is 0.1-1% by mass of the silica gel-supported strontium oxide ferroalloy catalyst, and the amount of the silica gel-supported strontium oxide ferroalloy catalyst is 5-30% by mass of the 2,4 / 2,5-xylenol mixture;

[0014] And / or, in step (1), the amount of hydrogen used is 0.1 to 1 times the mass of the 2,4-dimethylphenol / 2,5-dimethylphenol mixture.

[0015] In some embodiments, in step (1), the reaction is carried out in a tank reactor, a fixed bed reactor, a fluidized bed reactor, an ebullient bed reactor or a transport bed reactor;

[0016] And / or, in the step (1), the reaction pressure is normal pressure, the reaction temperature is 250-500° C., the reaction liquid hourly space velocity is 0.5-1.2 h −1 , and sampling and analysis show that the reaction is terminated when the 2,4-dimethylphenol / 2,5-dimethylphenol content is ≤0.5%;

[0017] And / or, in the step (1), the pressure for removing methanol and water is normal pressure to -0.07 MPa, the pressure for the vacuum distillation is -0.08 to -0.98 MPa, and the reflux ratio is 10 to 30:1.

[0018] In some embodiments, in step (2), the amount of zirconium phosphate is 1 to 10% of the mass of the silica-aluminum oxide, and the mass of the silica-aluminum oxide is 1 to 5% of the mass of the 2,4-dimethylphenol / 2,5-dimethylphenol mixture;

[0019] And / or, the silicon-aluminum oxide includes silicon dioxide and acidic aluminum oxide, and the mass ratio of silicon dioxide to acidic aluminum oxide is 1:0.01-50.

[0020] In some embodiments, in step (2), the reaction temperature is 250-300° C., the reaction time is 4-6 hours, and the pressure gradually rises to 1.0-2.0 MPa during the reaction. When the pressure stabilizes, sampling and analysis are performed. The reaction is terminated when the concentration of 2-ethyl-4,6-dimethylphenol and 2-isopropyl-4,6-dimethylphenol is ≤0.1%.

[0021] And / or, in step (2), the nitrogen replacement time is 0.5 to 1 hour.

[0022] 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 150°C / h;

[0023] And / or, in step (2), the cooling is to reduce the temperature to below 200° C. within 0.5 to 1 hour.

[0024] In some embodiments, in step (3), the concentration of the sulfuric acid solution is 95-98%, and the amount of the sulfuric acid solution used is 0.1-0.5% of the mass of the cleavage reaction solution.

[0025] In some embodiments, in 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

[0026] 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.

[0027] A method for separating a 2,4-xylenol / 2,5-xylenol mixture and producing 2,4-xylenol as a by-product in an embodiment of the present invention comprises the following steps:

[0028] (1) A 2,4-xylenol / 2,5-xylenol mixture, methanol and water are mixed, and a silica gel-supported iron alum strontium oxide catalyst and an olefin hydrogenation catalyst are added, and hydrogen is introduced at the same time to react. After the reaction is completed, the reaction is filtered, and the obtained filtrate is distilled to remove methanol and water, and then vacuum distilled to obtain a mixture containing 2,3,6-trimethylphenol, 2,4,6-trimethylphenol, 2-ethyl-4,6-xylenol and 2-isopropyl-4,6-xylenol; the 2,4-xylenol / 2,5-xylenol mixture comprises: 0-15 wt% of m-cresol, 0-10 wt% of p-cresol, 0-2 wt% of o-ethylphenol, 70-95 wt% of 2,4-xylenol / 2,5-xylenol, 1-15 wt% of 2-ethyl-6-methylphenol, 1-15 wt% of o-isopropylphenol and / or o-propylphenol, and 0-10 wt% of other components;

[0029] (2) adding silicon aluminum oxide and zirconium phosphate to the mixture containing 2,3,6-trimethylphenol, 2,4,6-trimethylphenol, 2-ethyl-4,6-xylenol and 2-isopropyl-4,6-xylenol to react, cooling and exhausting the mixture in sequence after the reaction, replacing the obtained reaction liquid with nitrogen after the exhaust, and filtering the mixture to obtain a cracking reaction liquid, wherein the cracking reaction liquid contains 2,4-xylenol, 2,3,6-trimethylphenol and 2,4,6-trimethylphenol;

[0030] (3) adding a sulfuric acid solution to the cleavage reaction solution obtained in step (2), and then performing vacuum distillation to obtain 2,4-dimethylphenol, 2,4,6-trimethylphenol and 2,3,6-trimethylphenol.

[0031] The method for separating a 2,4-dimethylphenol / 2,5-dimethylphenol mixture and producing 2,4-dimethylphenol as a by-product in the embodiment of the present invention utilizes a catalytic methylation reaction to separate 2,4-dimethylphenol / 2,5-dimethylphenol, uses a fully applicable solid catalyst, generates substantially no solid waste, and most of the water is applicable. Furthermore, the components of dissolved materials in the water are relatively simple, and the wastewater solution treatment is applicable, making the wastewater treatment relatively easy. Therefore, the treatment process is environmentally friendly. The method of the embodiment of the present invention utilizes a small amount of hydrogenation catalyst and hydrogen to remove a small amount of sulfur-containing and nitrogen-containing compounds in 2,4-dimethylphenol / 2,5-dimethylphenol, 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 the economic benefits of the products.

[0032] In some embodiments, preferably, in step (1), the 2,4-xylenol / 2,5-xylenol 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.

[0033] In some embodiments, preferably, in step (1), the 2,4-xylenol / 2,5-xylenol mixture comprises: 80-90 wt% of 2,4-xylenol / 2,5-xylenol, 5-10 wt% of 2-ethyl-6-methylphenol, 3-8 wt% of o-isopropylphenol / o-propylphenol, and 0-10 wt% of others.

[0034] In some embodiments, preferably, in step (1), the molar ratio of the 2,4-dimethylphenol / 2,5-dimethylphenol mixture, methanol and water is 1:4-10:0.5-1.0.

[0035] In some embodiments, preferably, in step (1), the particle size of the silica gel-supported strontium oxide iron sulfate catalyst is 50-200 mesh;

[0036] 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.

[0037] In some embodiments, preferably, in step (1), the olefin hydrogenation catalyst comprises at least one of 1-5% palladium-carbon or Raney nickel, the olefin hydrogenation catalyst is 0.1-1% by mass of the silica gel-supported strontium oxide catalyst, and the amount of the silica gel-supported strontium oxide catalyst is 5-30% by mass of the 2,4 / 2,5-dimethylphenol mixture. Further preferably, the 1-5% palladium-carbon and Raney nickel have 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.

[0038] In some embodiments, preferably, in step (1), the amount of hydrogen used is 0.1 to 1 times the mass of the 2,4-xylenol / 2,5-xylenol mixture. Further preferably, the amount of hydrogen used is 0.2 to 0.5 times the mass of the 2,4-xylenol / 2,5-xylenol mixture.

[0039] In some embodiments, preferably, in step (1), the reaction is carried out in a tank reactor, a fixed bed reactor, a fluidized bed reactor, an ebullient bed reactor or a transport bed reactor;

[0040] And / or, in the step (1), the reaction pressure is normal pressure, the reaction temperature is 250-500° C., the reaction liquid hourly space velocity is 0.5-1.2 h −1 , and sampling and analysis show that the reaction is terminated when the 2,4-dimethylphenol / 2,5-dimethylphenol content is ≤0.5%;

[0041] And / or, in step (1), the pressure for removing methanol and water is between normal pressure and -0.07 MPa, the pressure for vacuum distillation is between -0.08 and -0.98 MPa, and the reflux ratio is between 10 and 30:1. Further preferably, the reaction is carried out in a fixed bed reactor; the pressure for removing methanol and water is between normal pressure and -0.05 MPa.

[0042] In some embodiments, preferably, in the step (1), the filter cake obtained after the filtration treatment is reused.

[0043] In some embodiments, preferably, in step (2), the amount of zirconium phosphate used is 1 to 10% of the mass of the silica-aluminum oxide, and the mass of the silica-aluminum oxide is 1 to 5% of the mass of the 2,4-dimethylphenol / 2,5-dimethylphenol mixture;

[0044] And / or, 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. More preferably, the mass ratio of silicon dioxide to acidic aluminum oxide is 1:0.05 to 20.

[0045] 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 rises to 1.0-2.0 MPa during the reaction. When the pressure stabilizes, sampling and analysis are performed. The reaction is terminated when the concentrations of 2-ethyl-4,6-dimethylphenol and 2-isopropyl-4,6-dimethylphenol are ≤0.1%.

[0046] And / or, in step (2), the nitrogen replacement time is 0.5 to 1 hour.

[0047] 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 100-150°C / h;

[0048] And / or, in step (2), the cooling is to reduce the temperature to below 200° C. within 0.5 to 1 hour.

[0049] In some embodiments, preferably, in step (2), the solid catalyst obtained by the filtration treatment is applied.

[0050] 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 used is 0.1-0.5% of the mass of the cleavage reaction solution.

[0051] In some embodiments, preferably, in step (3), the pressure of the vacuum distillation is -0.08 to -0.98 MPa, and the reflux ratio is 10 to 30:1.

[0052] 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.

[0053] The technical solution of the present invention is described in detail below in conjunction with specific embodiments.

[0054] Example 1

[0055] Step 1: Synthesis of 2,4,6-trimethylphenol, 2,3,6-trimethylphenol, 2-ethyl-4,6-dimethylphenol and 2-isopropyl-4,6-dimethylphenol:

[0056] 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 2,4-dimethylphenol / 2,5-dimethylphenol mixture (containing 34 parts of m-paracresol, 3952 parts of 2,4-dimethylphenol, 3248 parts of 2,5-dimethylphenol, o-isopropyl / A mixture of 1205 parts of propylphenol, 1437 parts of 2-ethyl-6-methylphenol, 124 parts of 2,3-xylenol), 15000 parts of methanol and 1400 parts of water (5.88 times and 0.97 times the molar number of the 2,4-xylenol / 2,5-xylenol mixture, respectively) was injected into the reactor through the preheater by a plunger metering pump, and at the same time, 1500 parts of quantitative hydrogen (hydrogen dosage was 2,4-xylenol / 2,5-xylenol) was uniformly introduced into the fixed bed reactor. ,5-xylenol mixture 0.15 times), react under normal pressure, 300 ° C and liquid hourly space velocity 0.55h-1, 2,4-xylenol / 2,5-xylenol 0.28% qualified, the obtained condensate is added to the distillation tower (theoretical plate number is about 100), and 11853.8 parts of methanol are obtained by atmospheric distillation, -0.05MPa recovery of 2911.1 parts of water, part of the recovered water is applied to the next batch of methylation reaction; The recovered water was sent for further treatment; -0.085 to -0.09 MPa, reflux ratio 10 to 15:1 vacuum distillation was performed to obtain 62.3 parts of the first portion and 11112.6 parts of mixed trimethylols (including 4381.6 parts of 2,4,6-trimethylol, 3705.6 parts of 2,3,6-trimethylol, 1553.2 parts of 2-ethyl-4,6-dimethylol, 1423.9 parts of 2-isopropyl-4,6-dimethylol, and 48.3 parts of others).

[0057] Step 2: Mix trimethylol to deethylate and propylate to generate 2,4-dimethylphenol

[0058] 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. 11112.6 parts of the mixed trimethylol obtained in step 1 were added. The reactor was sealed and heated to 280° C. for 6 hours. The pressure was gradually increased to 2.0 MPa. When the pressure was 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 cooled by a program. The temperature of the reaction mixture was cooled by adding heat-conducting oil at a cooling rate of 100-110°C / h, and the temperature was rapidly cooled 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 hour, and 10414.8 parts of cracking reaction liquid (2322.5 parts of 2,4-dimethylphenol, 3679.6 parts of 2,3,6-trimethylphenol, 4350.9 parts of 2,4,6-trimethylphenol, and 61.8 parts of others) were obtained by filtration, and the solid catalyst was applied.

[0059] 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 0.23% 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 2282.7 parts of 99.3% 2,4-dimethylphenol, 4057.9 parts of 99.5% 2,4,6-trimethylphenol, and 3421.2 parts of 99.7% 2,3,6-trimethylphenol.

[0060] Example 2

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

[0062] 600 parts of a catalyst prepared by loading strontium oxide of iron alum on silica gel (80-120 mesh, strontium oxide of iron alum mass ratio of 3:1:0.01) and 6 parts of 3% palladium carbon were loaded into a fixed bed reactor, and 10000 parts of a 2,4-dimethylphenol / 2,5-dimethylphenol mixture (560 parts of m-cresol, 509 parts of p-cresol, 113 parts of o-ethylphenol, 4269 parts of 2,4-dimethylphenol, 3561 parts of 2,5-dimethylphenol, 68 parts of 2,3-dimethylphenol) were added. 3 parts of 2-ethyl-6-methylphenol, 141 parts of 2-ethyl-6-methylphenol, 117 parts of o-isopropylphenol, 47 parts of other phenols), a mixture of 15,000 parts of methanol and 1,200 parts of water (5.66 times and 0.80 times the molar number of the 2,4-xylenol / 2,5-xylenol mixture, respectively), is injected into the reactor through the preheater by a plunger metering pump, and at the same time, 2,000 parts of quantitative hydrogen (hydrogen dosage is 2,4-xylenol / 2,5-xylenol) is uniformly introduced into the fixed bed reactor. The mixture was 0.2 times the original weight), and the reaction was carried out under normal pressure, 400 ° C and liquid hourly space velocity 1.2h-1. The conversion rate of m-cresol was 100%, and the conversion rate of 2,4-dimethylphenol / 2,5-dimethylphenol was qualified at 0.12%. The condensate obtained was added to a distillation tower (theoretical plate number is about 100), and 11673.9 parts of methanol were obtained by atmospheric distillation, and 2843.8 parts of water were recovered at -0.02~-0.05MP. 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 to obtain 58.9 parts of the first portion and 11121.8 parts of mixed trimethylols (including 5319.2 parts of 2,4,6-trimethylol, 5351.6 parts of 2,3,6-trimethylol, 288.5 parts of 2-ethyl-4,6-dimethylol, 138.7 parts of 2-isopropyl-4,6-dimethylol, and 23.8 parts of others).

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

[0064] In a stainless steel high-pressure reactor (with an external stainless steel condenser and an inner coil), 600 parts of acidic silica-alumina (the mass ratio of silica to acidic alumina is 1:1) and 20 parts of zirconium phosphate are placed, and then 11121.8 parts of the mixed trimethylol obtained in step 1 are added. The reactor is sealed and heated to 300° C. for 3.5 hours. The pressure is gradually increased to 1.85 MPa. When the pressure stabilizes, sampling and analysis are performed. 0.04% of 2-ethyl-4,6-dimethylphenol is used to terminate the reaction. The heat transfer oil was cooled by programmed cooling at a cooling rate of 140-150°C / h. The temperature was rapidly cooled 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 hour. 10,877 parts of cracking reaction liquid (332.7 parts of 2,4-dimethylphenol, 5,271.3 parts of 2,3,6-trimethylphenol, 5,239.4 parts of 2,4,6-trimethylphenol, and 33.6 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), 30 parts of 98% sulfuric acid was added (the amount of sulfuric acid was 0.28% 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 317.3 parts of 99.8% 2,4-dimethylphenol, 4967 parts of 99.3% 2,4,6-trimethylphenol, and 4874.7 parts of 99.7% 2,3,6-trimethylphenol.

[0066] 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.

[0067] 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 2,4-xylenol / 2,5-xylenol mixture and producing 2,4-xylenol as a by-product, characterized in that: The following steps are involved: (1) A 2,4-xylenol / 2,5-xylenol mixture, methanol and water are mixed, and a silica gel-supported iron alum strontium oxide catalyst and an olefin hydrogenation catalyst are added, and hydrogen is introduced at the same time to react. After the reaction is completed, the reaction is filtered, and the obtained filtrate is distilled to remove methanol and water, and then vacuum distilled to obtain a mixture containing 2,3,6-trimethylphenol, 2,4,6-trimethylphenol, 2-ethyl-4,6-xylenol and 2-isopropyl-4,6-xylenol; the 2,4-xylenol / 2,5-xylenol mixture comprises: 0-15 wt% of m-cresol, 0-10 wt% of p-cresol, 0-2 wt% of o-ethylphenol, 70-95 wt% of 2,4-xylenol / 2,5-xylenol, 1-15 wt% of 2-ethyl-6-methylphenol, 1-15 wt% of o-isopropylphenol and / or o-propylphenol, and 0-10 wt% of other components; (2) adding silicon aluminum oxide and zirconium phosphate to the mixture containing 2,3,6-trimethylphenol, 2,4,6-trimethylphenol, 2-ethyl-4,6-xylenol and 2-isopropyl-4,6-xylenol to react, cooling and exhausting the mixture in sequence after the reaction, replacing the obtained reaction liquid with nitrogen after the exhaust, and filtering the mixture to obtain a cracking reaction liquid, wherein the cracking reaction liquid contains 2,4-xylenol, 2,3,6-trimethylphenol and 2,4,6-trimethylphenol; (3) adding a sulfuric acid solution to the cleavage reaction solution obtained in step (2), and then performing vacuum distillation to obtain 2,4-dimethylphenol, 2,4,6-trimethylphenol and 2,3,6-trimethylphenol.

2. The method for separating the 2,4-xylenol / 2,5-xylenol mixture and producing 2,4-xylenol as a by-product according to claim 1, characterized in that: In the step (1), the 2,4-xylenol / 2,5-xylenol 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.

3. The method for separating the 2,4-xylenol / 2,5-xylenol mixture and producing 2,4-xylenol as a by-product according to claim 1, characterized in that: In the step (1), the molar ratio of the 2,4-dimethylphenol / 2,5-dimethylphenol mixture, methanol and water is 1:4-10:0.5-1.

0.

4. The method for separating the 2,4-xylenol / 2,5-xylenol mixture and producing 2,4-xylenol as a by-product according to claim 1, characterized in that: 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 1-5% of at least one of palladium carbon or Raney nickel, the olefin hydrogenation catalyst is 0.1-1% by mass of the silica gel-supported strontium oxide ferroalloy catalyst, and the amount of the silica gel-supported strontium oxide ferroalloy catalyst is 5-30% by mass of the 2,4 / 2,5-xylenol mixture; And / or, in step (1), the amount of hydrogen used is 0.1 to 1 times the mass of the 2,4-dimethylphenol / 2,5-dimethylphenol mixture.

5. The method for separating the 2,4-xylenol / 2,5-xylenol mixture and producing 2,4-xylenol as a by-product according to claim 1, characterized in that: In the step (1), the reaction is carried out in a tank reactor, a fixed bed reactor, a fluidized bed reactor, an ebullient bed reactor or a transport bed reactor; And / or, in the step (1), the reaction pressure is normal pressure, the reaction temperature is 250-500° C., the reaction liquid hourly space velocity is 0.5-1.2 h −1 , and sampling and analysis show that the reaction is terminated when the 2,4-dimethylphenol / 2,5-dimethylphenol content is ≤0.5%; And / or, in the step (1), the pressure for removing methanol and water is normal pressure to -0.07 MPa, the pressure for 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 2,4-xylenol / 2,5-xylenol mixture and producing 2,4-xylenol as a by-product according to claim 1, characterized in that: In the step (2), the amount of the zirconium phosphate is 1 to 10% of the mass of the silica-aluminum oxide, and the mass of the silica-aluminum oxide is 1 to 5% of the mass of the 2,4-xylenol / 2,5-xylenol mixture; And / or, the silicon-aluminum oxide includes silicon dioxide and acidic aluminum oxide, and the mass ratio of silicon dioxide to acidic aluminum oxide is 1:0.01-50.

7. The method for separating the 2,4-xylenol / 2,5-xylenol mixture and producing 2,4-xylenol 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 rises to 1.0-2.0 MPa during the reaction. When the pressure stabilizes, sampling and analysis are performed. The reaction is terminated when the concentration of 2-ethyl-4,6-dimethylphenol and 2-isopropyl-4,6-dimethylphenol is ≤0.1%. And / or, in step (2), the nitrogen replacement time is 0.5 to 1 hour.

8. The method for separating the 2,4-xylenol / 2,5-xylenol mixture and producing 2,4-xylenol as a by-product according to claim 1, 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 150°C / h; And / or, in step (2), the cooling is to reduce the temperature to below 200° C. within 0.5 to 1 hour.

9. The method for separating the 2,4-xylenol / 2,5-xylenol mixture and producing 2,4-xylenol 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 used is 0.1-0.5% of the mass of the cleavage reaction solution.

10. The method for separating the 2,4-xylenol / 2,5-xylenol mixture and producing 2,4-xylenol as a by-product according to claim 1 or 9, characterized in that: 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.