Method for synthesizing 4-ethyl-2-cresol from m-ethylphenol and p-ethylphenol

Abstract

The invention relates to the technical field of synthesis and separation of organic products, and discloses a method for synthesizing 4-ethyl-2-cresol from m-ethyl phenol and p-ethyl phenol. The method comprises the following steps: carrying out fixed bed catalytic methylation reaction on a mixture of m-ethyl phenol and p-ethyl phenol and methanol, and rectifying to obtain a mixture of 4-ethyl-2-cresol / 5-ethyl-2-cresol, namely 3-ethyl-2-cresol; products such as 4-ethyl-2-cresol, 5-ethyl-2-cresol and the like are obtained through tert-butylation, rectification, tert-butyl removal and rectification of 4-ethyl-2-cresol / 5-ethyl-2-cresol, so that the application field of the coalification m-ethylphenol and p-ethylphenol mixture is expanded, and the application range of the coalification m-ethylphenol and p-ethylphenol mixture is widened. According to the method disclosed by the invention, the products such as the organic intermediate 4-ethyl-2-cresol and the like are produced by adopting the low-price m-p-ethyl phenol or p-ethyl phenol crude product, so that the production cost is low, and the method has relatively good market competitiveness.

Description

Technical Field

[0001] This invention relates to the field of organic product synthesis and separation technology, specifically to a method for synthesizing 4-ethyl-2-methylphenol from m-p-ethylphenol. Background Technology

[0002] Coal tar, an important byproduct of coal pyrolysis and coking, is rich in phenolic compounds and is a crucial source of chemicals such as phenol, cresol, and xylenol. Traditional crude phenol refining processes mostly involve distilling phenol-containing coal tar to obtain phenolic oil fractions. Crude phenols are then extracted using alkaline dissolution and acid precipitation or solvent extraction. Further distillation of the crude phenols can separate various phenolic products or mixtures, such as mixed phenol fractions, o-cresol fractions, tri-cresols, m- and p-cresol, and xylenol. High-efficiency distillation of mixed xylenols can further yield m- and p-ethylphenols as the main components, along with small amounts of 2,3-xylenol, 3,5-xylenol, and other m- and p-ethylphenol mixtures. However, existing crude phenol refining technologies face a bottleneck: the boiling points of m- and p-ethylphenols, as well as their interactions with components like 3,5-xylenol, are extremely close. Even with highly efficient distillation techniques, it is difficult to obtain single m- or p-ethylphenol products to meet the independent market demand; typically, only mixtures of these products are obtained.

[0003] Ethylcresol compounds such as 4-ethyl-2-cresol, 5-ethyl-2-cresol, and 3-ethyl-2-cresol are important organic synthesis intermediates, widely used in pesticides, fragrances, antioxidants, and polymer materials. The market demand is clear and the value is high. However, the current synthetic routes for these products have many limitations. Therefore, given the difficulties in separating mixtures of ethylphenols in crude phenol refining, the strong dependence of existing ethylcresol synthesis routes on high-purity single phenol raw materials, unsatisfactory selectivity, and high costs, there is an urgent need to develop an innovative technical route. Summary of the Invention

[0004] The purpose of this invention is to provide a method for synthesizing 4-ethyl-2-methylphenol from m- and p-ethylphenol. The problem to be solved is that because the boiling points of m- and p-ethylphenol and 3,5-dimethylphenol are close, traditional crude phenol refining processes cannot solve the problem of separating the m- and p-ethylphenol mixture, and cannot obtain pure m- and p-ethylphenol, p-ethylphenol, and 3,5-dimethylphenol. Therefore, a large amount of phenol resources cannot be utilized, resulting in poor economic benefits.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A method for synthesizing 4-ethyl-2-methylphenol from m-p-ethylphenol includes the following steps:

[0007] (1) Synthesis of a methylated mixture containing 4-ethyl-2-cresol and 5-ethyl-2-cresol: A supported iron oxide catalyst was packed into a reactor. The mixture of m- and p-ethylphenol was mixed with methanol and water and then introduced into the reactor for catalytic methylation. The reactants were separated to remove methanol and water. The unreacted m- and p-ethylphenol was recovered by distillation to obtain a methylated mixture containing 4-ethyl-2-cresol and 5-ethyl-2-cresol.

[0008] (2) Separation and conversion of the methylated mixture obtained in (1) by tert-butylation: The methylated mixture and isobutylene were subjected to tert-butylation reaction in the presence of an acidic catalyst. After the reaction, the material was neutralized, washed, separated and then distilled to obtain 6-tert-butyl-4-ethyl-2-cresol and 4-tert-butyl-5-ethyl-2-cresol, respectively. The tert-butylated material was heated under the action of concentrated sulfuric acid to carry out detert-butylation reaction. After the reaction, the material was neutralized and distilled to obtain 2-methyl-4-ethylphenol and 2-methyl-5-ethylphenol, respectively.

[0009] In this scheme, a mixture of raw materials is converted into a mixture of two target products through a directional methylation reaction using a supported iron oxide catalyst. Then, a tert-butylation reaction is carried out, utilizing the subtle differences in steric hindrance between the two molecules under acidic conditions to selectively graft large-volume tert-butyl groups onto isobutylene. This chemical modification alters the physical properties of the target products, widening the boiling point difference, thus enabling efficient and thorough separation via conventional vacuum distillation to obtain the corresponding single tert-butyl derivatives. Finally, an acid-catalyzed detert-butylation reaction is used to reconstitute the separated derivatives, yielding the high-purity target products.

[0010] Further, in step (1), the molar ratio of the m-p-ethylphenol mixture to methanol and water is 1:1-5:0.5-2.

[0011] Further, in step (1), the conditions for the catalytic methylation reaction are: reaction temperature 250-350℃, liquid hourly space velocity 0.5-1.5 / h.

[0012] Further, in step (1), the degree of catalytic methylation reaction is controlled such that the total content of 4-ethyl-2,6-dimethylphenol and 3-ethyl-2,6-dimethylphenol in the reaction product is ≤1%, and the total content of 4-ethyl-2-methylphenol and 5-ethyl-2-methylphenol is ≥10%.

[0013] Further, in step (1), the supported iron oxide and alum oxide are prepared by supporting iron oxide and alum oxide on a silica gel support; the particle size of the catalyst is 50-200 mesh; and the mass ratio of iron oxide to alum oxide is 0.5-5:1.

[0014] Further, in step (2), the acidic catalyst is concentrated sulfuric acid, and its amount is 1-5% of the methylation product mixture; the reaction temperature of the tert-butylation reaction is 60-120℃, and the amount of isobutylene is 1.1-3 times the molar mass of the methylation product mixture.

[0015] Further, in step (2), the degree of the tert-butylation reaction is controlled such that the total content of 4-ethyl-2-cresol and 5-ethyl-2-cresol in the reaction endpoint material is ≤5%, and the content of diisobutylene is ≤8%.

[0016] Furthermore, in step (2), the conditions for the detert-butylation reaction are: reaction temperature 180-200℃, time 1-4h.

[0017] Further, in step (2), the extent of the detert-butylation reaction is controlled such that the content of 6-tert-butyl-4-ethyl-2-cresol or 4-tert-butyl-5-ethyl-2-cresol in the reaction endpoint material is ≤1%.

[0018] Further, in step (1), the m- and p-ethylphenol mixture is derived from crude phenol obtained by refining phenolic coal tar, and its components are: the total content of m- and p-ethylphenol is 70-100%, and the content of 3,5-dimethylphenol is 0-30%.

[0019] The beneficial effects of this invention are:

[0020] 1. This invention uses a mixture of m- and p-ethylphenol with methanol for fixed-bed catalytic methylation. The reaction is controlled at a low methanol / m- and p-ethylphenol ratio, a low m- and p-ethylphenol conversion rate, and a low temperature. The methylation reaction mainly produces 4-ethyl-2-cresol, 5-ethyl-2-cresol, 3-ethyl-2-cresol, and 3-ethyl-4-cresol, with virtually no 4-ethyl-2,6-dimethylphenol or 3-ethyl-2,6-dimethylphenol. Further distillation yields a mixture of 4-ethyl-2-cresol / 5-ethyl-2-cresol and 3-ethyl-2-cresol. The 4-ethyl-2-cresol / 5-ethyl-2-cresol is then subjected to tert-butylation, distillation, detert-butylation, and distillation again to obtain 99% 4-ethyl-2-cresol and 99.5% 5-ethyl-2-cresol, thus expanding the application range of the m- and p-ethylphenol mixture in coal chemical processes.

[0021] 2. This invention uses inexpensive m- or p-ethylphenol or crude p-ethylphenol to produce organic intermediates such as 4-ethyl-2-methylphenol, resulting in low production costs and good market competitiveness.

[0022] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1

[0025] Sixty parts (60-80 mesh, iron oxide mass ratio 3:2) of a catalyst prepared by supporting iron oxide on silica gel were packed into a fixed-bed reactor. A mixture of 10,000 parts of a m- and p-ethylphenol mixture (containing 4,984 parts m-ethylphenol, 3,606 parts p-ethylphenol, and 1,410 parts 3,5-xylenol), 7,870 parts methanol, and 1,620 parts water (3.0 and 1.1 times the molar amounts of the m- and p-ethylphenol mixture, respectively) was injected into the reactor via a plunger metering pump through a preheater. The reaction was carried out under atmospheric pressure, 270°C, and a liquid hourly space velocity (LHSV) of 1.2 / h. The desired concentrations were 24.6% 4-ethyl-2-cresol, 25.3% 5-ethyl-2-cresol, and 2... The 0.38% xylenol and 0.41% 3-ethyl-2,6-xylenol were qualified. The resulting condensate was added to a distillation column (theoretical trays approximately 200). Distillation was carried out at atmospheric pressure and a reflux ratio of 2:1 to obtain 5907.9 parts of methanol, which was reused. Distillation was carried out at -0.05 MPa and a reflux ratio of 3-5:1 to recover 2549.6 parts of water. 50% of the recovered water was reused in the next batch of methylation reaction; the unreused recovered water was sent for further treatment. Distillation was carried out at -0.085 to -0.09 MPa and a reflux ratio of 20-25:1 to obtain 2630.9 parts of m- and p-ethylphenol (including 1008.5 parts of p-ethylphenol, 1437.8 parts of m-ethylphenol, and 184.6 parts of 3,5-xylenol) and 1 part of middle fraction. 1608.1 parts (including 284.4 parts of p-ethylphenol, 405.5 parts of m-ethylphenol, 52 parts of 3,5-xylenol, 451.5 parts of 4-ethyl-2-cresol, and 414.7 parts of 5-ethyl-2-cresol), 3162 parts of a mixture of 4-ethyl-2-cresol and 5-ethyl-2-cresol (including 1555.2 parts of 4-ethyl-2-cresol and 1606.8 parts of 5-ethyl-2-cresol), and 2 parts of middle distillate. 1236.5 parts (including 551.8 parts of 4-ethyl-2-cresol, 570.2 parts of 5-ethyl-2-cresol, and 114.5 parts of 3-ethyl-2-cresol), 436.8 parts of 99.1% 3-ethyl-2-cresol, 485.1 parts of a mixture of 2,3,5-trimethylphenol and 3-ethyl-2-cresol (131.8 parts of 3-ethyl-2-cresol and 313.3 parts of 2,3,5-trimethylphenol), 736.2 parts of 99.3% 2,3,5-trimethylphenol, and 113.1 parts of 99.1% 3-ethyl-4-cresol.

[0026] 3162 parts of a mixture of 4-ethyl-2-cresol and 5-ethyl-2-cresol (1555.2 parts of 4-ethyl-2-cresol and 1606.8 parts of 5-ethyl-2-cresol) and 90 parts of 98% sulfuric acid (2.85% of the mass of the 4-ethyl-2-cresol / 5-ethyl-2-cresol mixture) were added to the reactor. The mixture was purged with nitrogen three times, stirred, and heated to 80°C before isobutylene was introduced for 5 hours. After the reaction was complete, samples were taken for analysis after 2 hours of holding at this temperature. The 4-ethyl-2-cresol content was 0.83%, and the diisobutylene content was 5.2%, which met the requirements. A total of 2604 parts of isobutylene were introduced (isobutylene was used for...). The amount was twice the molar mass of the 4-ethyl-2-cresol / 5-ethyl-2-cresol mixture), and 1033 parts of isobutylene were recovered and reused. 232.5 parts of 31% liquid alkali were added to neutralize to pH 7.5, and the mixture was separated into layers. 100 parts of water were added to the material layer for washing to remove all water. The material layer was then distilled off under reduced pressure to remove diisobutylene and 313 parts of the preceding part (containing 233 parts of diisobutylene). The mixture was then subjected to reduced pressure distillation (150 theoretical plates, -0.090 MPa, reflux ratio 10:1) to obtain 2122.8 parts of 6-tert-butyl-4-ethyl-2-cresol with a purity of 99.5% and 2217.2 parts of 4-tert-butyl-5-ethyl-2-cresol with a purity of 99.1%.

[0027] 1000 parts of 99.5% 6-tert-butyl-4-ethyl-2-cresol were added to a decomposition vessel, along with 10 parts of 98% sulfuric acid. The mixture was heated to 200℃ and maintained for 1 hour with stirring. Gas chromatography analysis showed that 0.33% of 6-tert-butyl-4-ethyl-2-cresol was present, at which point the reaction was stopped. The mixture was then slightly cooled and neutralized to neutral with 25.9 parts of 31% liquid alkali. The solution was then subjected to vacuum distillation (100 theoretical plates, -0.085 MPa, reflux ratio 5:1) to obtain 687.1 parts of 99.7% 4-ethyl-2-cresol, with a yield of 97.2%. 285.8 parts of isobutylene were recovered and reused.

[0028] 2217.2 parts of 99.1% 4-tert-butyl-5-ethyl-2-cresol were added to a decomposition vessel, along with 20 parts of 98% sulfuric acid. The mixture was heated to 190°C and maintained for 1.5 hours with stirring. Gas chromatography analysis showed that 0.63% of 6-tert-butyl-5-ethyl-2-cresol was present, at which point the reaction was stopped. The mixture was then slightly cooled and neutralized to neutral with 51.8 parts of 31% liquid alkali. The mixture was then subjected to vacuum distillation (100 theoretical plates, -0.085 MPa, reflux ratio 5:1) to obtain 1523.2 parts of 99.6% 5-ethyl-2-cresol, with a yield of 96.6%. 633.7 parts of isobutylene were recovered and reused.

[0029] Example 2

[0030] Sixty parts (80-120 mesh, 1:1 mass ratio of iron oxide to silica gel) of a catalyst prepared by supporting iron oxide on silica gel were packed into a fixed-bed reactor. A mixture of 10,000 parts (containing 5,455 parts m-ethylphenol and 4,545 parts p-ethylphenol), 5,246 parts methanol, and 1,770 parts water (2 times and 1.2 times the molar amounts of the m- and p-ethylphenol mixture, respectively) was injected into the reactor via a plunger metering pump through a preheater. The reaction was carried out at atmospheric pressure, 290°C, and a liquid hourly space velocity of 1.0 h. 4-Ethyl-2-Cresol 35.1%, 5-Ethyl-2-Cresol 34.5%, 4-Ethyl-2,6-Dimethylphenol 0.43% / 3-Ethyl-2,6-Dimethylphenol 0.45% were all within acceptable limits. The resulting condensate was added to a distillation column (theoretical trays approximately 200). Distillation was carried out at atmospheric pressure and a reflux ratio of 2:1 to obtain 3267 parts of methanol, which was reused. At -0.05 MPa and a reflux ratio of 5:1, 2880.6 parts of water were recovered. 50% of the recovered water was reused in the next batch of methylation reaction; the unreused recovered water was sent for further treatment. The distillation was carried out at -0.085 to -0.09 MPa and a reflux ratio of 2:1. Reduced pressure distillation at a ratio of 0 to 25:1 yielded 2140.6 parts of m- and p-ethylphenol (1206.7 parts of m-ethylphenol and 933.9 parts of p-ethylphenol), 11520.6 parts of middle fraction (320.7 parts of m-ethylphenol, 248.2 parts of p-ethylphenol, 502.2 parts of 4-ethyl-2-cresol, and 449.5 parts of 5-ethyl-2-cresol), 5198.1 parts of a 4-ethyl-2-cresol / 5-ethyl-2-cresol mixture (2616.3 parts of 4-ethyl-2-cresol and 2581.8 parts of 5-ethyl-2-cresol), and 2 parts of middle fraction. 1114.5 parts (including 492.5 parts of 4-ethyl-2-cresol, 516.2 parts of 5-ethyl-2-cresol, and 105.8 parts of 3-ethyl-2-cresol), 424 parts of 99.3% 3-ethyl-2-cresol, and 166.6 parts of 99.4% 3-ethyl-4-cresol;

[0031] 5198.1 parts of a mixture of 4-ethyl-2-cresol and 5-ethyl-2-cresol (2616.3 parts of 4-ethyl-2-cresol and 2581.8 parts of 5-ethyl-2-cresol) and 150 parts of 98% sulfuric acid (2.89% of the mass of the 4-ethyl-2-cresol / 5-ethyl-2-cresol mixture) were added to the reactor. The mixture was purged with nitrogen three times, stirred, and heated to 70°C before isobutylene was introduced for 6 hours. After the reaction was complete, samples were taken for analysis after 3 hours of holding at this temperature. The 4-ethyl-2-cresol content was 0.77%, and the diisobutylene content was 4.6%, which met the requirements. A total of 4710 parts of isobutylene were introduced (the amount of isobutylene used...). The mixture was prepared at 2.3 times the molar mass of 4-ethyl-2-cresol / 5-ethyl-2-cresol mixture. 2193.3 parts of isobutylene were recovered for reuse. 387.5 parts of 31% liquid alkali were added to neutralize to pH 8, causing separation. The material layer was washed once with 300 parts of water to remove all water. The material layer was then distilled under reduced pressure to remove diisobutylene and 396.8 parts of the precursor (containing 240.1 parts of diisobutylene). This was then further distilled under reduced pressure (150 theoretical plates, -0.095 MPa, reflux ratio 10:1) to obtain 3623.2 parts of 99.7% pure 6-tert-butyl-4-ethyl-2-cresol and 3533.9 parts of 99.6% pure 4-tert-butyl-5-ethyl-2-cresol.

[0032] 1000 parts of 99.7% 6-tert-butyl-4-ethyl-2-cresol were added to a decomposition vessel, along with 10 parts of 98% sulfuric acid. The mixture was heated to 180°C and maintained for 2 hours with stirring. Gas chromatography analysis showed that 0.26% of 6-tert-butyl-4-ethyl-2-cresol was present, at which point the reaction was stopped. The mixture was then slightly cooled and neutralized to neutral with 25.9 parts of 31% liquid alkali. The solution was then subjected to vacuum distillation (100 theoretical plates, -0.09 MPa, reflux ratio 5:1) to obtain 687.8 parts of 99.8% 4-ethyl-2-cresol, with a yield of 96.9%. 287.1 parts of isobutylene were recovered and reused.

[0033] 3533.9 parts of 99.6% 4-tert-butyl-5-ethyl-2-cresol were added to a decomposition vessel, along with 40 parts of 98% sulfuric acid. The mixture was heated to 190℃ and maintained for 1.5 hours with stirring. Gas chromatography analysis showed that 0.47% of 6-tert-butyl-5-ethyl-2-cresol was present, at which point the reaction was stopped. The mixture was then slightly cooled and neutralized to neutral with 103.6 parts of 31% liquid alkali. The mixture was then subjected to vacuum distillation (100 theoretical plates, -0.085 MPa, reflux ratio 5:1) to obtain 2440.3 parts of 99.6% 5-ethyl-2-cresol, with a yield of 97.1%. 1006 parts of isobutylene were recovered and reused.

[0034] Example 3

[0035] Sixty parts (80-120 mesh, iron oxide mass ratio 1:2) of a catalyst prepared by supporting iron oxide on silica gel were packed into a fixed-bed reactor. A mixture of phenol and m- and p-ethylphenol was reacted with formaldehyde to produce phenolic resin byproducts. This mixture consisted of 10,000 parts (containing 220 parts m-ethylphenol and 9,780 parts p-ethylphenol), 5,246 parts methanol, and 1,623 parts water (representing 2 times and 1.1 times the molar amounts of the m- and p-ethylphenol mixture, respectively). The mixture was injected into the reactor via a plunger metering pump through a preheater and carried out at atmospheric pressure, 270°C, and a liquid hourly space velocity (LISH) of 1.0 h⁻¹. 4-Ethyl-2-cresol (61.36%) and 4-Ethyl-2,6-dimethylphenol (0.19%) were within acceptable limits. The resulting condensate was added to a distillation column (approximately 150 theoretical plates). Distillation at atmospheric pressure and a reflux ratio of 2:1 yielded 3303.4 parts of methanol, which was reused. Distillation at -0.05 MPa and a reflux ratio of 5:1 recovered 2634.1 parts of water, with 50% of the recovered water reused in the next batch of methylation reaction; the unused recovered water was sent for further treatment. Distillation under reduced pressure at -0.085 to -0.09 MPa and a reflux ratio of 15 to 20:1 yielded 96.83% p-ethylphenol. 2998 parts (including 65.6 parts of m-ethylphenol, 2903.1 parts of p-ethylphenol, 28.6 parts of 4-ethyl-2-cresol, and 0.7 parts of 5-ethyl-2-cresol), 7525 parts of 98.11% 4-ethyl-2-cresol (including 7382.9 parts of 4-ethyl-2-cresol and 142.1 parts of 5-ethyl-2-cresol), and 44.3 parts of residue from the autoclave (including 20.6 parts of 4-ethyl-2-cresol, 0.8 parts of 5-ethyl-2-cresol, 16.3 parts of 3-ethyl-2-cresol, and 6.6 parts of 3-ethyl-4-cresol);

[0036] 7525 parts of 98.11% 4-ethyl-2-cresol were added to a crystallization vessel, and 5000 parts of methanol were added with stirring. The temperature was raised to 60°C and held for 1 hour. The temperature was then lowered to 10°C and held for 1 hour over 3 hours. The mixture was filtered and dried to obtain 6841.1 parts of 99.5% 4-ethyl-2-cresol, with a crystallization yield of 92.2%.

[0037] After merging multiple batches of residue from the distillation vessel, it was used for distillation to extract 99% 3-ethyl-2-cresol and 3-ethyl-4-cresol.

[0038] Example 4

[0039] Six hundred parts (80-120 mesh, iron oxide mass ratio 1:3) of a catalyst prepared by supporting iron oxide on silica gel were packed into a fixed-bed reactor. A mixture of 10,000 parts (containing 9,980 parts m-ethylphenol and 20 parts p-ethylphenol), 5,246 parts methanol, and 1,623 parts water (representing 2 times and 1.1 times the molar amounts of the m- and p-ethylphenol mixture, respectively) obtained by tert-butylation separation of a m- and p-ethylphenol mixture was injected into the reactor via a plunger metering pump through a preheater. The reaction was carried out under atmospheric pressure, 285°C, and a liquid hourly space velocity of 1.0 h⁻¹. 5-Ethyl-2-cresol (50.42%) and 3-Ethyl-2,6-xylenol (0.33%) were within acceptable limits. The resulting condensate was added to a distillation column (approximately 200 theoretical plates). Distillation was performed at atmospheric pressure and a reflux ratio of 2:1 to obtain 3220.2 parts of methanol, which was reused. Water was recovered at -0.05 MPa and a reflux ratio of 5:1, totaling 2631.5 parts. 50% of the recovered water was reused in the next batch of methylation reaction; the unreused recovered water was sent for further treatment. (0.085~-0.09) Distillation under reduced pressure at MPa and a reflux ratio of 20–25:1 yielded 2594.2 parts of 99.0% m-ethylphenol (including 2569.4 parts of m-ethylphenol, 5.3 parts of p-ethylphenol, 0.7 parts of 4-ethyl-2-cresol, and 18.8 parts of 5-ethyl-2-cresol), 3909.2 parts of 99.2% 5-ethyl-2-cresol, 1328.7 parts of 99.1% 3-ethyl-2-cresol, and 491.3 parts of 99.5% 3-ethyl-4-cresol.

[0040] 99.0% m-ethylphenol is reused in the next batch of methylation reaction.

[0041] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0042] The above content is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the scope defined by the inventive concept, they should all fall within the protection scope of the present invention.

Claims

1. A method for synthesizing 4-ethyl-2-methylphenol from m-p-ethylphenol, characterized in that, Includes the following steps: (1) Synthesis of a methylated mixture containing 4-ethyl-2-cresol and 5-ethyl-2-cresol: A supported iron oxide catalyst was packed into a reactor. The mixture of m- and p-ethylphenol was mixed with methanol and water and then introduced into the reactor for catalytic methylation. The reactants were separated to remove methanol and water. The unreacted m- and p-ethylphenol was recovered by distillation to obtain a methylated mixture containing 4-ethyl-2-cresol and 5-ethyl-2-cresol. (2) Separation and conversion of the methylated mixture obtained in (1) by tert-butylation: The methylated mixture and isobutylene were subjected to tert-butylation reaction in the presence of an acidic catalyst. After the reaction, the material was neutralized, washed, separated and then distilled to obtain 6-tert-butyl-4-ethyl-2-cresol and 4-tert-butyl-5-ethyl-2-cresol, respectively. The tert-butylated material was heated under the action of concentrated sulfuric acid to carry out detert-butylation reaction. After the reaction, the material was neutralized and distilled to obtain 2-methyl-4-ethylphenol and 2-methyl-5-ethylphenol, respectively.

2. The method for synthesizing 4-ethyl-2-methylphenol from m-p-ethylphenol according to claim 1, characterized in that, In step (1), the molar ratio of the m-p-ethylphenol mixture to methanol and water is 1:1-5:0.5-2.

3. The method for synthesizing 4-ethyl-2-methylphenol from m-p-ethylphenol according to claim 1, characterized in that, In step (1), the conditions for the catalytic methylation reaction are: reaction temperature 250-350℃, liquid hourly space velocity 0.5-1.5 / h.

4. The method for synthesizing 4-ethyl-2-methylphenol from m-p-ethylphenol according to claim 1, characterized in that, In step (1), the degree of catalytic methylation is controlled such that the total content of 4-ethyl-2,6-dimethylphenol and 3-ethyl-2,6-dimethylphenol in the reaction product is ≤1%, and the total content of 4-ethyl-2-methylphenol and 5-ethyl-2-methylphenol is ≥10%.

5. The method for synthesizing 4-ethyl-2-methylphenol from m-p-ethylphenol according to claim 1, characterized in that, In step (1), the supported iron oxide and alum oxide catalyst is prepared by supporting iron oxide and alum oxide on a silica gel support; the particle size of the catalyst is 50-200 mesh; and the mass ratio of iron oxide to alum oxide is 0.5-5:

1.

6. The method for synthesizing 4-ethyl-2-methylphenol from m-p-ethylphenol according to claim 1, characterized in that, In step (2), the acidic catalyst is concentrated sulfuric acid, and its amount is 1-5% of the methylation product mixture; the reaction temperature of the tert-butylation reaction is 60-120℃, and the amount of isobutylene is 1.1-3 times the molar mass of the methylation product mixture.

7. The method for synthesizing 4-ethyl-2-methylphenol from m-p-ethylphenol according to claim 1, characterized in that, In step (2), the degree of the tert-butylation reaction is controlled such that the total content of 4-ethyl-2-cresol and 5-ethyl-2-cresol in the reaction endpoint material is ≤5%, and the content of diisobutylene is ≤8%.

8. The method for synthesizing 4-ethyl-2-methylphenol from m-p-ethylphenol according to claim 1, characterized in that, In step (2), the conditions for the detert-butylation reaction are: reaction temperature 180-200℃, time 1-4h.

9. The method for synthesizing 4-ethyl-2-methylphenol from m-p-ethylphenol according to claim 1, characterized in that, In step (2), the extent of the detert-butylation reaction is controlled such that the content of 6-tert-butyl-4-ethyl-2-cresol or 4-tert-butyl-5-ethyl-2-cresol in the reaction endpoint material is ≤1%.

10. The method for synthesizing 4-ethyl-2-methylphenol from m-p-ethylphenol according to claim 1, characterized in that, In step (1), the m- and p-ethylphenol mixture is derived from crude phenol obtained by refining phenolic coal tar, and its components are: the total content of m- and p-ethylphenol is 70-100%, and the content of 3,5-dimethylphenol is 0-30%.