A process for separating m-cresol and p-cresol

Abstract

The present disclosure relates to a method for separating m-isopropyl phenol and p-isopropyl phenol, comprising the following steps: (1) contacting an isopropyl phenol mixture containing m-isopropyl phenol and p-isopropyl phenol, an octylating agent and an acidic catalyst to carry out an octylating reaction, neutralizing, water washing and layering the mixture after the octylating reaction, and removing the water layer to obtain a first reaction material; (2) subjecting the first reaction material to rectification treatment. The method of the present disclosure is simple and easy to operate, has strong operability, low processing cost, less equipment investment, high separation efficiency, high product purity, is suitable for batch production, and has good economic benefits.

Description

Technical Field

[0001] This disclosure relates to the field of organic synthesis and separation, and more specifically, to a method for separating m-isopropylphenol and p-isopropylphenol. Background Technology

[0002] Crude phenol is distilled to obtain phenol, o-cresol, tri-cresol mixture, m-p-cresol containing 55% meta position, 99% m-p-cresol, and industrial xylenol. These are sold directly as products without proper fine separation. In fact, industrial xylenol can undergo further processing, distillation, and refining to obtain PU-grade 3,5-xylenol, mixed m-p-ethylphenol, 99% 2,4-xylenol, 99% or more 2,5-xylenol, 99% 3,5-xylenol, 98% 3,4-xylenol, 99% m-ethylphenol, 99% p-ethylphenol, and other related derivative products. The remaining materials after extracting the above products are the by-products tri-cresol mixture, m-p-cresol, and industrial xylenol, which are sold directly as products or used to synthesize phenolic resins and insulating varnishes. Meanwhile, the crude phenol residue after distillation of xylenol can also be used to collect the mixed fraction of m / p-isopropylphenol and 3,4-xylenol at 225~230℃ (i.e., the fraction after xylenol) for further extraction of other useful components.

[0003] In addition to m-isopropylphenol (boiling point 228℃) and p-isopropylphenol (boiling point 228.5℃), the mixture of m-isopropylphenol and p-isopropylphenol may also contain 3,4-xylenol (boiling point 225℃) and 2,3,6-trimethylphenol (boiling point 226℃), making it impossible to directly separate m-isopropylphenol, p-isopropylphenol, 2,3,6-trimethylphenol and 3,4-xylenol by distillation. Summary of the Invention

[0004] The purpose of this disclosure is to provide a method for separating m-isopropylphenol and p-isopropylphenol. This method is simple, easy to implement, highly operable, has low processing costs, requires little equipment investment, has high separation efficiency, produces high-purity products, is suitable for mass production, and has good economic benefits.

[0005] To achieve the above objectives, this disclosure provides a method for separating m-isopropylphenol and p-isopropylphenol, the method comprising the following steps: (1) An octylation reaction is carried out by contacting a mixture of isopropylphenol containing m-isopropylphenol and p-isopropylphenol, an octylation reagent and an acidic catalyst, and then neutralizing, washing and separating the mixture after the octylation reaction, and removing the water layer to obtain the first reaction material. (2) The first reactant is subjected to distillation.

[0006] Optionally, in step (1), the mass ratio of the isopropylphenol mixture to the octylating agent is 1:(2~6), preferably 1:(3~4). The mass of the acidic catalyst is 1-20% of the mass of the isopropylphenol mixture; The octylating agent includes 2,4,4-trimethyl-1-pentene and / or 2,4,4-trimethyl-2-pentene, preferably 2,4,4-trimethyl-1-pentene and 2,4,4-trimethyl-2-pentene; The acidic catalyst comprises a first inorganic acid and an organic acid, wherein the first inorganic acid comprises one or more of sulfuric acid, phosphoric acid, and aminosulfonic acid, and the concentration of the first inorganic acid is 85% to 100%; the organic acid comprises one or more of benzenesulfonic acid, benzoic acid, and p-toluenesulfonic acid, and the concentration of the organic acid is 98% to 100%.

[0007] Optionally, in step (1), the conditions for the octylation reaction include: a temperature of 80~150℃, preferably 90~120℃, and a time of 3~12h, preferably 4~10h.

[0008] Optionally, in step (1), the neutralization includes adjusting the pH of the mixture after the octylation reaction to 7-8 using a first alkaline solution; the first alkaline solution includes an aqueous solution of an inorganic alkaline solution, wherein the inorganic alkaline solution includes one or more of potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, potassium bicarbonate, and sodium bicarbonate; and the concentration of the aqueous solution of the inorganic alkaline solution is 10-35%.

[0009] Optionally, in step (1), the total weight content of m-isopropylphenol and p-isopropylphenol in the isopropylphenol mixture is 60-100%; Optionally, the isopropylphenol mixture further comprises 0-30% by weight of 3,4-xylenol and 0-20% by weight of 2,3,6-trimethylphenol; Optionally, the isopropylphenol mixture is the xylenol fraction extracted from crude phenol in coal tar.

[0010] Optionally, in step (2), the distillation process includes: (21) The first reactant is subjected to a first-stage distillation process to separate the unreacted octylating reagent; (22) The material obtained from the first stage of distillation is subjected to a third stage of distillation to obtain a 2-isooctyl-5-isopropylphenol stream and a 2,6-diisooctyl-4-isopropylphenol stream; or, The distillation process includes: (2a) The first reactant is subjected to a first-stage distillation process to separate the unreacted octylating reagent; (2b) The material obtained from the first stage of distillation is subjected to a second stage of distillation to obtain 2,3,6-tricresol stream; (2c) The material obtained from the second stage distillation is subjected to a third stage distillation to obtain 6-isooctyl-3,4-dimethylphenol stream, first mixed phenol stream, 2-isooctyl-5-isopropylphenol stream and 2,6-diisooctyl-4-isopropylphenol stream.

[0011] Optionally, the conditions for the first stage of distillation include: a theoretical plate number of 100-300 in the distillation column, a pressure of -0.05 to -0.07 MPa, and a reflux ratio of 1-3:1; and / or, The conditions for the second stage of distillation include: a theoretical plate number of 100-300 in the distillation column, a pressure of -0.085 to -0.090 MPa, and a reflux ratio of 5-10:1; and / or, The conditions for the third stage of distillation include: the theoretical plate number of the distillation column is 100 to 300, the pressure is -0.095 to -0.1 MPa, and the reflux ratio is 5 to 25:1.

[0012] Optionally, the 2-isooctyl-5-isopropylphenol stream is mixed with a second inorganic acid to undergo a deoctylation reaction. The mixture after the deoctylation reaction is neutralized, washed with water, and the aqueous layer is removed to obtain a second reactant. The second reactant layer is then subjected to a fourth distillation process to obtain the m-isopropylphenol product; and / or, The 6-isooctyl-3,4-xylenol stream is mixed with a second inorganic acid to undergo an octyl group removal reaction. The mixture after the octyl group removal reaction is neutralized, washed with water, and the aqueous layer is removed to obtain a second reactant. The second reactant layer is then subjected to a fourth distillation process to obtain the 3,4-xylenol product; and / or... The 2,6-diisooctyl-4-isopropylphenol stream was mixed with a second inorganic acid to undergo a deoctylation reaction. The mixture after the deoctylation reaction was neutralized, washed with water, and the aqueous layer was removed to obtain a second reactant. The second reactant layer was then subjected to a fourth distillation process to obtain the p-isopropylphenol product.

[0013] Optionally, the conditions for the deoctylation reaction include: a temperature of 160~200℃ and a time of 1~4h; The mass of the second inorganic acid is 0.5-3% of the mass of the 2-isooctyl-5-isopropylphenol stream; or, The mass of the second inorganic acid is 0.5-3% of the mass of the 6-isooctyl-3,4-dimethylphenol stream; or, The mass of the second inorganic acid is 0.5-3% of the mass of the 2,6-diisooctyl-4-isopropylphenol stream; The second inorganic acid includes one or more of sulfuric acid, phosphoric acid, and aminosulfonic acid; the concentration of the second inorganic acid is 85-100%. The neutralization of the mixture after the deoctylation reaction includes adjusting the pH of the mixture to 7-8 at 80-100°C using a second alkali solution; the concentration of the second alkali solution is 10-35%.

[0014] Optionally, the conditions for the fourth distillation include: the number of theoretical plates in the distillation column is 100 to 300, the pressure is -0.085 to -0.090 MPa, and the reflux ratio is 5 to 10:1.

[0015] Through the above technical solution, this disclosure utilizes the reaction of an octylating reagent with a mixture of isopropylphenol. Taking advantage of the characteristic that m-isopropylphenol reacts with the octylating reagent to produce only a mono-isooctylated product, while p-isopropylphenol reacts with the octylating reagent to produce di-isooctylphenol, the boiling points of m-isopropylphenol and p-isopropylphenol, which are close, are converted into octylated products with significantly different boiling points, and then separated by distillation. Furthermore, for an isopropylphenol mixture containing 3,4-xylenol and 2,3,6-trimethylphenol, an octylating reagent is used. 2,3,6-trimethylphenol does not react with the octylating reagent, while 3,4-xylenol reacts to produce a mono-isooctylated product. The boiling points of the 3,4-xylenol octylated product differ somewhat from those of the m-isopropylphenol and p-isopropylphenol octylated products, and this is further separated by a single distillation. The method disclosed herein is simple and easy to implement, highly operable, has low processing costs, requires little equipment investment, and has high separation efficiency. It is suitable for mass production and has good economic benefits.

[0016] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Detailed Implementation

[0017] The following provides a detailed description of specific embodiments of this disclosure. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit this disclosure.

[0018] This disclosure provides a method for separating m-isopropylphenol and p-isopropylphenol, the method comprising the following steps: (1) An octylation reaction is carried out by contacting a mixture of isopropylphenol containing m-isopropylphenol and p-isopropylphenol, an octylation reagent and an acidic catalyst, and then neutralizing, washing and separating the mixture after the octylation reaction, and removing the water layer to obtain the first reaction material. (2) The first reactant is subjected to distillation.

[0019] The present invention utilizes the above technical solution to react an octylating reagent with a mixture of isopropylphenol. Taking advantage of the characteristic that m-isopropylphenol reacts with the octylating reagent to produce only a mono-isooctylated product, while p-isopropylphenol reacts with the octylating reagent to produce di-isooctylphenol, the method converts m-isopropylphenol and p-isopropylphenol, which have similar boiling points, into octylated products with significantly different boiling points. These products are then separated by distillation. The method of this invention is simple, easy to implement, highly operable, has low processing costs, requires minimal equipment investment, and offers high separation efficiency. It is suitable for mass production and has good economic benefits.

[0020] p-Isopropylphenol: CAS 99-89-8, white crystalline powder, boiling point 228.5℃, organic synthesis and bactericide and fungicide. p-Isopropylphenol is an important fine chemical product, which is produced by alkylation reaction of phenol, acetone and sodium hydroxide. It is necessary to control the reaction conditions, wash thoroughly and purify.

[0021] m-Isopropylphenol (CAS 618-45-1) is a colorless to pale yellow transparent liquid with a pungent odor. Its melting point is 20-22℃, boiling point is 228℃, and density is between 0.976 and 0.985 g / cm³. It is insoluble in water but soluble in most organic solvents, such as ethanol, ether, and acetone. As a broad-spectrum and highly effective preservative, m-isopropylphenol is widely used in food and cosmetics. It also possesses good antioxidant properties, preventing the oxidative deterioration of oils and fats. Furthermore, it can be used to synthesize various pharmaceutical intermediates, such as anti-inflammatory drugs, antibacterial drugs, and antitumor drugs. Finally, it has certain insecticidal and bactericidal effects and can be used as a pesticide.

[0022] According to one embodiment of the present disclosure, in step (1), the total weight content of m-isopropylphenol and p-isopropylphenol in the isopropylphenol mixture can be 60-100%, wherein the mass ratio of m-isopropylphenol to p-isopropylphenol is not specifically limited, for example, it can be 0.5-2:1.

[0023] According to one embodiment of this disclosure, in step (1), the mass ratio of the isopropylphenol mixture to the octylating reagent is 1:(2~6), preferably 1:(3~4). This embodiment facilitates the octylation reaction of the isopropylphenol mixture, converting m-isopropylphenol and p-isopropylphenol into octylated products with significantly different boiling points, further facilitating the separation of m-isopropylphenol and p-isopropylphenol.

[0024] According to one embodiment of this disclosure, in step (1), the octylating agent includes 2,4,4-trimethyl-1-pentene and / or 2,4,4-trimethyl-2-pentene, preferably 2,4,4-trimethyl-1-pentene and 2,4,4-trimethyl-2-pentene. The above embodiment facilitates the octylation reaction of the isopropylphenol mixture, converting m-isopropylphenol and p-isopropylphenol into octylated products with significantly different boiling points, further facilitating the separation of m-isopropylphenol and p-isopropylphenol.

[0025] According to one embodiment of this disclosure, in step (1), the mass of the acidic catalyst is 1-20% of the mass of the isopropylphenol mixture, for example, it can be any value within the range of 1%, 2%, 3%, 4%, 5%, 7%, 9%, 10%, 13%, 15%, 17%, 19%, 20%, or any combination thereof, preferably 3-10%. The above embodiment facilitates the octylation reaction of the isopropylphenol mixture, converting m-isopropylphenol and p-isopropylphenol into octylated products with significantly different boiling points, further facilitating the separation of m-isopropylphenol and p-isopropylphenol.

[0026] According to one embodiment of this disclosure, in step (1), the acidic catalyst comprises a first inorganic acid and an organic acid, wherein the first inorganic acid comprises one or more of sulfuric acid, phosphoric acid, and aminosulfonic acid; the concentration of the first inorganic acid is 85% to 100%; the organic acid comprises one or more of benzenesulfonic acid, benzoic acid, and p-toluenesulfonic acid; and the concentration of the organic acid is 98% to 100%. The above embodiment facilitates the octylation reaction of the isopropylphenol mixture, converting m-isopropylphenol and p-isopropylphenol into octylated products with significantly different boiling points, further facilitating the separation of m-isopropylphenol and p-isopropylphenol.

[0027] According to one embodiment of this disclosure, in step (1), neutralizing the mixture after the octylation reaction includes adjusting the pH of the mixture after the octylation reaction to 7-8 using a first alkaline solution; the first alkaline solution includes an inorganic alkaline aqueous solution, wherein the inorganic alkaline solution includes one or more of potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, potassium bicarbonate, and sodium bicarbonate; and the concentration of the inorganic alkaline aqueous solution is 10-35%.

[0028] According to one embodiment of this disclosure, in step (1), the conditions for the octylation reaction include: a temperature of 80~150℃, for example, any value within the range of 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃ or any combination thereof, preferably 90~120℃; and a time of 3~12h, for example, any value within the range of 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h or any combination thereof, preferably 4~10h. In the above embodiments, the standard for a qualified octylation reaction can be determined by gas chromatography, which detects that the weight content of 2-isooctyl-4-isopropylphenol in the reaction system is less than 0.5%. This facilitates the octylation reaction of the isopropylphenol mixture, converting m-isopropylphenol and p-isopropylphenol into octylated products with significantly different boiling points, and further facilitating the separation of m-isopropylphenol and p-isopropylphenol.

[0029] According to one embodiment of this disclosure, the distillation process includes: (21) The first reactant is subjected to a first-stage distillation process to separate the unreacted octylating reagent; (22) The material obtained from the first stage of distillation is subjected to a third stage of distillation to obtain 2-isooctyl-5-isopropylphenol stream and 2,6-diisooctyl-4-isopropylphenol stream. The above embodiments facilitate the separation of the octylation products of m-isopropylphenol and p-isopropylphenol, and also facilitate the recovery of the octylation reagent.

[0030] According to one embodiment of this disclosure, the conditions for the first stage of distillation include: a theoretical plate number of 100-300, a pressure of -0.05 to -0.07 MPa, and a reflux ratio of 1-3:1; the conditions for the third stage of distillation include: a theoretical plate number of 100-300, a pressure of -0.095 to -0.1 MPa, and a reflux ratio of 15-25:1. The above embodiment is beneficial for improving the separation efficiency of octylation products, increasing product purity, and simultaneously improving the recovery rate of the octylation reagent.

[0031] According to one embodiment of this disclosure, the isopropylphenol mixture is a distillate of xylenol extracted from crude phenol in coal tar, and the isopropylphenol mixture further comprises 0-30% by weight of 3,4-xylenol and 0-20% by weight of 2,3,6-trimethylphenol; for example, the weight content of 3,4-xylenol can be any value within the range of 0, 5%, 10%, 15%, 20%, 25%, 30%, or any combination thereof; the weight content of 2,3,6-trimethylphenol can be any value within the range of 0, 5%, 10%, 15%, 20%, 25%, 30%, or any combination thereof.

[0032] 3,4-Dimethylphenol: CAS 95-65-8, a white crystalline powder with a melting point of 65-68℃ and a boiling point of 225℃. It is sparingly soluble in water but miscible with ethanol, chloroform, ether, benzene, etc. It is soluble in sodium hydroxide aqueous solution and is used in the production of dyes, disinfectants, solvents, pharmaceuticals, and as an antioxidant. It is mainly used to generate fusible polyimide, a special engineering plastic.

[0033] 2,3,6-Trimethylphenol: CAS2416-94-6, with a melting point of 63-64℃ and a boiling point of 226℃, is insoluble in water but soluble in organic solvents such as ethanol. It is a white or pale yellow solid and is used as a raw material for the synthesis of 2,3,5-trimethylhydroquinone, the main ring of vitamin E.

[0034] The inventors of this application discovered that by reacting an octylating reagent with a mixture of isopropylphenol, and utilizing the characteristics that 2,3,6-trimethylphenol in the mixture does not react with the octylating reagent, 3,4-dimethylphenol and m-isopropylphenol only generate mono-isooctylated products, while p-isopropylphenol generates di-isooctylphenol upon octylation, specifically, 3,4-dimethylphenol generates 6-isooctyl-3,4-dimethylphenol (boiling point approximately 289°C), m-isopropylphenol generates 2-isooctyl-5-isopropylphenol (boiling point approximately 295°C), and p-isopropylphenol generates 2,6-di-isooctyl-4-isopropylphenol (boiling point 330°C), substances with similar boiling points in the isopropylphenol mixture can be converted into octylated products with significantly different boiling points, which can then be further separated by distillation. The method disclosed herein is simple and easy to implement, highly operable, has low processing costs, requires little equipment investment, and has high separation efficiency. It is suitable for mass production and has good economic benefits.

[0035] According to one embodiment of this disclosure, the distillation process includes: (2a) The first reactant is subjected to a first-stage distillation process to separate the unreacted octylating reagent; (2b) The material obtained from the first stage of distillation is subjected to a second stage of distillation to obtain 2,3,6-tricresol stream; (2c) The material obtained from the second-stage distillation is subjected to a third-stage distillation to obtain a 6-isooctyl-3,4-xylenol stream, a first mixed phenol stream, a 2-isooctyl-5-isopropylphenol stream, and a 2,6-diisooctyl-4-isopropylphenol stream. The above embodiment facilitates the sequential separation of 2,3,6-trimethylphenol and the octylation product stream, while simultaneously recovering unreacted octylation reagents.

[0036] According to one embodiment of this disclosure, the conditions for the first stage of distillation include: a theoretical plate number of 100-300 in the distillation column, a pressure of -0.05 to -0.07 MPa, and a reflux ratio of 1-3:1. This embodiment is beneficial for improving the recovery rate of the octylating reagent.

[0037] According to one embodiment of this disclosure, the conditions for the second-stage distillation include: a theoretical plate number of 100-300 in the distillation column, a pressure of -0.085 to -0.090 MPa, and a reflux ratio of 5-10:1. This embodiment is beneficial for improving the yield and purity of 2,3,6-trimethylphenol.

[0038] According to one embodiment of this disclosure, the conditions for the third-stage distillation include: a theoretical plate number of 100-300 in the distillation column, a pressure of -0.095 to -0.1 MPa, and a reflux ratio of 5-25:1. For example, the reflux ratio can be any value within the range of 5:1, 7:1, 10:1, 13:1, 15:1, 17:1, 20:1, 23:1, 25:1, or any combination thereof. This embodiment is beneficial for improving the yield and purity of 6-isooctyl-3,4-dimethylphenol, 2-isooctyl-5-isopropylphenol, and 2,6-diisooctyl-4-isopropylphenol.

[0039] According to one embodiment of this disclosure, the 2-isooctyl-5-isopropylphenol stream is mixed with a second inorganic acid to undergo a deoctylation reaction. The mixture after the deoctylation reaction is neutralized, washed with water, and the aqueous layer is removed to obtain a second reactant. The second reactant layer is then subjected to a fourth distillation process to obtain the m-isopropylphenol product. In the above embodiment, the standard for the end of the deoctylation reaction can be determined by gas chromatography, which shows that the weight content of 2-isooctyl-5-isopropylphenol in the reaction system is below 0.5%, which is beneficial for the deoctylation of the 2-isooctyl-5-isopropylphenol stream to obtain the m-isopropylphenol product.

[0040] According to one embodiment of this disclosure, the mass of the second inorganic acid is 0.5-3% of the mass of the 2-isooctyl-5-isopropylphenol stream, preferably 1-2%. This embodiment facilitates the deoctylation of the 2-isooctyl-5-isopropylphenol stream to obtain the m-isopropylphenol product.

[0041] According to one embodiment of this disclosure, the 6-isooctyl-3,4-dimethylphenol stream is mixed with a second inorganic acid to undergo a deoctylation reaction. The mixture after the deoctylation reaction is neutralized, washed with water, and the aqueous layer is removed to obtain a second reactant. The second reactant layer is then subjected to a fourth distillation process to obtain the 3,4-dimethylphenol product. In the above embodiment, the standard for the end of the deoctylation reaction can be determined by gas chromatography, which shows that the weight content of 6-isooctyl-3,4-dimethylphenol in the reaction system is below 0.5%. This facilitates the deoctylation of 6-isooctyl-3,4-dimethylphenol to obtain the 3,4-dimethylphenol product and is beneficial for separating 3,4-dimethylphenol from the isopropylphenol mixture.

[0042] According to one embodiment of this disclosure, the mass of the second inorganic acid is 0.5-3% of the mass of the 6-isooctyl-3,4-dimethylphenol stream, preferably 1-2%. This embodiment facilitates the deoctylation of 6-isooctyl-3,4-dimethylphenol to obtain the 3,4-dimethylphenol product and facilitates the separation of 3,4-dimethylphenol from the isopropylphenol mixture.

[0043] According to one embodiment of this disclosure, the 2,6-diisooctyl-4-isopropylphenol stream is mixed with a second inorganic acid to undergo a deoctylation reaction. The mixture after the deoctylation reaction is neutralized, washed with water, and the aqueous layer is removed to obtain a second reactant. The second reactant layer is then subjected to a fourth distillation process to obtain the p-isopropylphenol product. In the above embodiment, the criterion for the end of the deoctylation reaction can be determined by gas chromatography, which shows that the weight content of 2-isooctyl-4-isopropylphenol in the reaction system is below 0.5%. This facilitates the deoctylation of 2,6-diisooctyl-4-isopropylphenol to obtain the p-isopropylphenol product and is beneficial for separating p-isopropylphenol from the isopropylphenol mixture.

[0044] According to one embodiment of this disclosure, the mass of the second inorganic acid is 0.5-3% of the mass of the 2,6-diisooctyl-4-isopropylphenol stream, preferably 1-2%. This embodiment facilitates the deoctylation of 2,6-diisooctyl-4-isopropylphenol to obtain p-isopropylphenol, and facilitates the separation of p-isopropylphenol from the isopropylphenol mixture.

[0045] According to one embodiment of this disclosure, 2,6-diisooctyl-4-isopropylphenol can also be sold as a product.

[0046] According to one embodiment of this disclosure, the conditions for the deoctylation reaction include: a temperature of 160-200°C, preferably 180-195°C, and a time of 1-4 hours, preferably 1.5-3 hours. This embodiment facilitates the deoctylation of the octylated product, thereby separating 3,4-dimethylphenol, m-isopropylphenol, and p-isopropylphenol.

[0047] According to one embodiment of this disclosure, the second inorganic acid includes one or more of sulfuric acid, phosphoric acid, and aminosulfonic acid; the concentration of the second inorganic acid is 85-100%.

[0048] According to one embodiment of this disclosure, the neutralization of the mixture after the deoctylation reaction includes adjusting the pH of the mixture after the deoctylation reaction to 7-8 using a second alkaline solution at 80-100°C; the concentration of the second alkaline solution is 10-35%.

[0049] According to one embodiment of this disclosure, the conditions for the fourth distillation include: a theoretical plate number of 100-300 in the distillation column, a pressure of -0.085 to -0.090 MPa, and a reflux ratio of 5-10:1. This embodiment is beneficial for improving the purity and yield of 3,4-xylenol, m-isopropylphenol, and p-isopropylphenol products.

[0050] According to one embodiment of this disclosure, the first mixed phenolic stream comprises 6-isooctyl-3,4-dimethylphenol and 2-isooctyl-5-isopropylphenol. The method further includes distilling the first mixed phenolic stream to obtain 6-isooctyl-3,4-dimethylphenol and 2-isooctyl-5-isopropylphenol. The above embodiment is beneficial for improving product yield.

[0051] According to one embodiment of this disclosure, 6-isooctyl-3,4-dimethylphenol and / or 2-isooctyl-5-isopropylphenol obtained by distillation can be mixed with the corresponding streams obtained by third-stage distillation to carry out a deoctylation reaction, thereby further improving the product yield.

[0052] The present disclosure will be further described in detail below with reference to the embodiments, but this does not limit the present disclosure.

[0053] In the following embodiments, the yield is calculated as follows: The yield of antioxidant 2,6-diisooctyl-4-isopropylphenol = (parts by weight of product × percentage by mass) / theoretical yield × 100%; The yield of m-isopropylphenol = (parts by weight of product × percentage by mass) / parts by weight of p-isopropylphenol in raw material × 100%; Yield of 2,3,6-trimethylphenol = (parts by weight of product × percentage by weight) / parts by weight of 2,3,6-trimethylphenol in raw material × 100%; Yield of 3,4-xylenol = (parts by weight of product × percentage by weight) / parts by weight of 3,4-xylenol in raw material × 100%; Example 1 (1) Add 1000 parts by weight of isopropylphenol mixture (containing 538 parts by weight of m-isopropylphenol and 462 parts by weight of p-isopropylphenol), 2000 parts by weight of 2,4,4-trimethyl-1-pentene, the mass ratio of isopropylphenol mixture to diisobutylene is 1:2), and 50 parts by weight of 98% concentrated sulfuric acid (the mass of sulfuric acid is 20% of the mass of isopropylphenol mixture) to the reactor, start stirring, heat to 90℃ and keep the reaction for 9 hours, take samples for analysis, the 2-isooctyl-4-isopropylphenol content is 0.23% by weight to be qualified, add 267 parts by weight of 15% sodium hydroxide aqueous solution to neutralize to pH 8, separate the layers, add 100 parts by weight of water to wash the material layer once to remove water, and obtain the first reaction material; (2) The first reactant was added to a distillation column (theoretical plate number is 100), and 756.1 parts by weight of diisobutylene were recovered under reduced pressure at a pressure of -0.05 MPa and a reflux ratio of 1:1. Under reduced pressure at a pressure of -0.095 MPa and a reflux ratio of 5:1, 968.1 parts by weight of 2-isooctyl-5-isopropylphenol with a content of 99.1% (octylation yield of 97.8%) and 1182.3 parts by weight of 2,6-diisooctyl-4-isopropylphenol with a content of 99.6% were obtained, with a yield of 96.3%. Among them, the 99.6% antioxidant 2,6-diisooctyl-4-isopropylphenol was sold as a product.

[0054] (3) 968.1 parts by weight of 99.1% 2-isooctyl-5-isopropylphenol were added to the decomposition vessel, and 10 parts by weight of 98% sulfuric acid (the mass of sulfuric acid was 1.03% of the mass of 2-isooctyl-5-isopropylphenol) were added. The mixture was heated to 190℃ and maintained for 2.5 hours under stirring. The gas chromatography-mass spectrometry showed that the weight content of 2-isooctyl-5-isopropylphenol was 0.28%, so the reaction was stopped. The mixture was cooled to 90℃ and neutralized to pH 7.5 with 53.5 parts by weight of 15% sodium hydroxide aqueous solution. The water layer was removed to obtain the second reaction material. The second reaction material was subjected to vacuum distillation. The distillation column had 100 theoretical plates, a pressure of -0.085 MPa, and a reflux ratio of 5:1 to obtain 515 parts by weight of 99.7% m-isopropylphenol. The yield of the dealkylation reaction was 97.6%, the total extraction rate was 95.4%, and 428 parts by weight of diisobutylene were recovered and reused.

[0055] Example 2 (1) Add 1000 parts by weight of a mixture of isopropylphenol (containing 398 parts by weight of m-isopropylphenol, 342 parts by weight of p-isopropylphenol, 123 parts by weight of 3,4-xylenol, and 137 parts by weight of 2,3,6-trimethylphenol) and 2600 parts by weight of diisobutylene (diisobutylene is a mixture of 2,4,4-trimethyl-1-pentene and 2,4,4-trimethyl-2-pentene, and the isopropylphenol mixture and diisobutylene...) to the reactor. The mixture was prepared with 100 parts by weight of concentrated sulfuric acid (the mass of sulfuric acid was 10% of the mass of the isopropylphenol mixture) in a weight ratio of 1:2.6. The mixture was stirred and heated to 110°C and kept at that temperature for 6 hours. Samples were taken for analysis. The 2-isooctyl-4-isopropylphenol content was found to be 0.15% by weight, which was considered acceptable. 533.6 parts by weight of 15% sodium hydroxide aqueous solution were added to neutralize the mixture to pH 7.5. The mixture was separated into layers. The first layer was washed once with 100 parts of water to remove all water and obtain the first reaction material. (2) The first reactant was added to a distillation column (theoretical plate number 100), and 1544.1 parts by weight of diisobutylene were recovered under reduced pressure at a pressure of -0.05 MPa and a reflux ratio of 3:1; 134.4 parts by weight of 2,3,6-trimethylphenol with a purity of 99.5% were obtained by distillation at a pressure of -0.085 MPa and a reflux ratio of 5:1, with a yield of 97.6%; 143.5 parts by weight of 6-isooctyl-3,4-dimethylphenol with a purity of 99.2% were obtained by distillation at a pressure of -0.095 MPa and a reflux ratio of 20:1 (octylation first distillation). The product yielded 60.3% extraction rate and ≥98.9% octylation reaction yield, 374.6 parts by weight of the first mixed phenolic stream (including 91.1 parts by weight of 6-isooctyl-3,4-dimethylphenol and 283.5 parts by weight of 2-isooctyl-5-isopropylphenol), 417.5 parts by weight of 2-isooctyl-5-isopropylphenol with a purity of 99.3% (octylation single distillation extraction rate of 57.1% and octylation reaction yield ≥96.2%), and 888.9 parts by weight of 2,6-diisooctyl-4-isopropylphenol with a purity of 99.5%, with a yield of 97.7%.

[0056] 99.5% 2,3,6-trimethylphenol and 99.5% antioxidant 2,6-diisooctyl-4-isopropylphenol are sold as products; the first mixed phenolic stream is used for re-distillation of 99% 6-isooctyl-3,4-dimethylphenol and 99% 2-isooctyl-5-isopropylphenol.

[0057] (3) 143.5 parts by weight of 6-isooctyl-3,4-dimethylphenol with 99.2% purity were added to the decomposition vessel, and 2 parts by weight of 98% sulfuric acid were added (the amount of sulfuric acid used was 1.39% of the residual mass of the vessel). The mixture was heated to 195°C and maintained for 2 hours under stirring. The gas chromatography-mass spectrometry showed that 0.23% of 6-isooctyl-3,4-dimethylphenol was present. The reaction was stopped. The mixture was cooled to 90°C and neutralized to pH 7.5 with 10.8 parts by weight of 15% sodium hydroxide aqueous solution. The mixture was then subjected to vacuum distillation (100 theoretical plates in the distillation column, pressure of -0.085 MPa, and reflux ratio of 5:1) to obtain 73.8 parts by weight of 3,4-dimethylphenol with 99.6% purity. The yield of the deoctylation reaction was 98.2%. 66.7 parts by weight of diisobutylene were recovered and reused.

[0058] 417.5 parts by weight of 99.3% 2-isooctyl-5-isopropylphenol were added to a decomposition vessel, along with 5 parts by weight of 98% sulfuric acid (the amount of sulfuric acid used was 1.2% of the residue mass of the vessel). The mixture was heated to 195°C and maintained for 2 hours with stirring. Gas chromatography analysis showed that the weight content of 2-isooctyl-5-isopropylphenol was 0.19%, and the reaction was stopped. The mixture was cooled to 70°C and neutralized to pH 7.5 with 26.8 parts by weight of 15% sodium hydroxide aqueous solution. The mixture was then subjected to vacuum distillation (the distillation column had 100 theoretical plates, a pressure of -0.085 MPa, and a reflux ratio of 5:1) to obtain 223.7 parts by weight of 99.8% m-isopropylphenol. The yield of the deoctylation reaction was 97.5%, and 183 parts by weight of diisobutylene were recovered and reused.

[0059] 99.6% 3,4-dimethylphenol and 99.8% m-isopropylphenol are sold as products.

[0060] Example 3 The method in this embodiment is the same as that in Example 1, except that the conditions for the octylation reaction are different. The specific method is as follows: (1) Add 1000 parts by weight of isopropylphenol mixture (containing 538 parts by weight of m-isopropylphenol and 462 parts by weight of p-isopropylphenol), 2000 parts by weight of 2,4,4-trimethyl-1-pentene (the mass ratio of isopropylphenol mixture to 2,4,4-trimethyl-1-pentene is 1:2), and 50 parts by weight of concentrated sulfuric acid (the amount of sulfuric acid used is 20% of the mass of isopropylphenol mixture) to the reactor, start stirring, heat to 60℃ and keep the reaction for 15 hours, take a sample for analysis, the content of 2-isooctyl-4-isopropylphenol is 15.8%, which is unqualified, add 267 parts by weight of 15% sodium hydroxide aqueous solution to neutralize to pH 8, separate the layers, add 100 parts by weight of water to wash the material layer once to remove the water, and obtain the first reaction material; (2) The first reactant was added to a distillation column (theoretical plate number is 100), and 831.9 parts by weight of diisobutylene were recovered under reduced pressure at a pressure of -0.05 MPa and a reflux ratio of 1:1. 670.4 parts by weight of a mixture of 2-isooctyl-4-isopropylphenol and 2-isooctyl-5-isopropylphenol (165.9 parts by weight of 2-isooctyl-4-isopropylphenol and 504.5 parts by weight of 2-isooctyl-5-isopropylphenol) were obtained under reduced pressure at a pressure of -0.095 MPa and a reflux ratio of 20:1. 427.2 parts by weight of 2-isooctyl-5-isopropylphenol with a content of 99.2% (the yield of the first distillation of octylation was 43.2%) and 950.8 parts by weight of 2,6-diisooctyl-4-isopropylphenol with a content of 99.3% were obtained, with a yield of 77.2%.

[0061] (3) 427.2 parts by weight of 99.2% 2-isooctyl-5-isopropylphenol were added to the decomposition vessel, and 5 parts by weight of 98% sulfuric acid were added (the amount of sulfuric acid was 1.17% of the mass of 2-isooctyl-5-isopropylphenol). The mixture was heated to 190°C and maintained for 2.5 hours under stirring. The gas chromatography-mass spectrometry showed that the weight content of 2-isooctyl-5-isopropylphenol was 0.21%, so the reaction was stopped. The mixture was cooled to 90°C and neutralized to pH 7.5 with 27 parts by weight of 15% sodium hydroxide aqueous solution. The water layer was removed to obtain the second reaction material. The second reaction material was subjected to vacuum distillation. The distillation column had 100 theoretical plates, a pressure of -0.085 MPa, and a reflux ratio of 5:1 to obtain 228.5 parts by weight of 99.5% m-isopropylphenol. The yield of the deoctyl reaction was 97.8%, and 187.6 parts by weight of diisobutylene were recovered and reused.

[0062] 400 parts by weight of 99.3% 2,6-diisooctyl-4-isopropylphenol were added to a decomposition vessel, along with 8 parts by weight of 98% sulfuric acid (the amount of sulfuric acid was 2% of the mass of 2-isooctyl-5-isopropylphenol). The mixture was heated to 195°C and maintained for 3 hours with stirring. Gas chromatography analysis showed that the weight content of 2-isooctyl-5-isopropylphenol was 0.13%, and the reaction was stopped. The temperature was lowered to 90°C, and the mixture was neutralized to pH 7.5 with 42.8 parts by weight of 15% sodium hydroxide aqueous solution. The aqueous layer was removed to obtain the second reactant. The second reactant was subjected to vacuum distillation in a distillation column with 100 theoretical plates, a pressure of -0.085 MPa, and a reflux ratio of 5:1 to obtain 145.4 parts by weight of 99.7% p-isopropylphenol. The yield of the deoctylation reaction was 96.6%, and 242.2 parts by weight of diisobutylene were recovered and reused.

[0063] The method disclosed herein is simple and easy to implement, highly operable, has low processing costs, requires minimal equipment investment, and boasts high separation efficiency. It is suitable for mass production, yields high-quality products with high purity, and offers significant economic benefits. A comparison of Examples 1 and 3 shows that within the preferred octylation reaction conditions of this disclosure, the octylation reaction is more complete, resulting in a higher yield of the octylation product 2-isooctyl-5-isopropylphenol, and further higher yields and purity of the antioxidant 2,6-dioctyl-4-isopropylphenol.

[0064] The preferred embodiments of this disclosure have been described in detail above. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0065] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0066] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A method for separating m-isopropylphenol and p-isopropylphenol, characterized in that, The method includes the following steps: (1) An octylation reaction is carried out by contacting a mixture of isopropylphenol containing m-isopropylphenol and p-isopropylphenol, an octylation reagent and an acidic catalyst, and then neutralizing, washing and separating the mixture after the octylation reaction, and removing the water layer to obtain the first reaction material. (2) The first reactant is subjected to distillation.

2. The method according to claim 1, wherein, In step (1), the mass ratio of the isopropylphenol mixture to the octylating agent is 1:(2~6), preferably 1:(3~4). The mass of the acidic catalyst is 1-20% of the mass of the isopropylphenol mixture; The octylating agent includes 2,4,4-trimethyl-1-pentene and / or 2,4,4-trimethyl-2-pentene, preferably 2,4,4-trimethyl-1-pentene and 2,4,4-trimethyl-2-pentene; The acidic catalyst comprises a first inorganic acid and an organic acid, wherein the first inorganic acid comprises one or more of sulfuric acid, phosphoric acid, and aminosulfonic acid, and the concentration of the first inorganic acid is 85% to 100%; the organic acid comprises one or more of benzenesulfonic acid, benzoic acid, and p-toluenesulfonic acid, and the concentration of the organic acid is 98% to 100%.

3. The method according to claim 1, wherein, In step (1), the conditions for the octylation reaction include: a temperature of 80~150℃, preferably 90~120℃, and a time of 3~12h, preferably 4~10h.

4. The method according to claim 1, wherein, In step (1), the neutralization includes adjusting the pH of the mixture after the octylation reaction to 7-8 using a first alkaline solution; the first alkaline solution includes an aqueous solution of an inorganic alkaline solution, wherein the inorganic alkaline solution includes one or more of potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, potassium bicarbonate, and sodium bicarbonate; and the concentration of the aqueous solution of the inorganic alkaline solution is 10-35%.

5. The method according to claim 1, wherein, In step (1), the total weight content of m-isopropylphenol and p-isopropylphenol in the isopropylphenol mixture is 60-100%; Optionally, the isopropylphenol mixture further comprises 0-30% by weight of 3,4-xylenol and 0-20% by weight of 2,3,6-trimethylphenol; Optionally, the isopropylphenol mixture is the xylenol fraction extracted from crude phenol in coal tar.

6. The method according to claim 5, wherein step (2) includes: (21) The first reactant is subjected to a first-stage distillation process to separate the unreacted octylating reagent; (22) The material obtained from the first stage of distillation is subjected to a third stage of distillation to obtain 2-isooctyl-5-isopropylphenol stream and 2,6-diisooctyl-4-isopropylphenol stream; or, The distillation process includes: (2a) The first reactant is subjected to a first-stage distillation process to separate the unreacted octylating reagent; (2b) The material obtained from the first stage of distillation is subjected to a second stage of distillation to obtain 2,3,6-tricresol stream; (2c) The material obtained from the second stage distillation is subjected to a third stage distillation to obtain 6-isooctyl-3,4-dimethylphenol stream, first mixed phenol stream, 2-isooctyl-5-isopropylphenol stream and 2,6-diisooctyl-4-isopropylphenol stream.

7. The method according to claim 6, wherein, The conditions for the first stage of distillation include: a theoretical plate number of 100-300 in the distillation column, a pressure of -0.05 to -0.07 MPa, and a reflux ratio of 1-3:1; and / or, The conditions for the second stage of distillation include: a theoretical plate number of 100-300 in the distillation column, a pressure of -0.085 to -0.090 MPa, and a reflux ratio of 5-10:1; and / or, The conditions for the third stage of distillation include: the theoretical plate number of the distillation column is 100 to 300, the pressure is -0.095 to -0.1 MPa, and the reflux ratio is 5 to 25:

1.

8. The method according to claim 6, wherein, The 2-isooctyl-5-isopropylphenol stream is mixed with a second inorganic acid to undergo an octyl group removal reaction. The mixture after the octyl group removal reaction is neutralized, washed with water, and the aqueous layer is removed to obtain a second reactant. The second reactant layer is then subjected to a fourth distillation process to obtain m-isopropylphenol product; and / or The 6-isooctyl-3,4-xylenol stream is mixed with a second inorganic acid to undergo an octyl group removal reaction. The mixture after the octyl group removal reaction is neutralized, washed with water, and the aqueous layer is removed to obtain a second reactant. The second reactant layer is then subjected to a fourth distillation process to obtain the 3,4-xylenol product; and / or... The 2,6-diisooctyl-4-isopropylphenol stream was mixed with a second inorganic acid to undergo a deoctylation reaction. The mixture after the deoctylation reaction was neutralized, washed with water, and the aqueous layer was removed to obtain a second reactant. The second reactant layer was then subjected to a fourth distillation process to obtain the p-isopropylphenol product.

9. The method according to claim 8, wherein, The conditions for the deoctylation reaction include: a temperature of 160~200℃ and a time of 1~4h; The mass of the second inorganic acid is 0.5-3% of the mass of the 2-isooctyl-5-isopropylphenol stream; or, The mass of the second inorganic acid is 0.5-3% of the mass of the 6-isooctyl-3,4-dimethylphenol stream; or, The mass of the second inorganic acid is 0.5-3% of the mass of the 2,6-diisooctyl-4-isopropylphenol stream; The second inorganic acid includes one or more of sulfuric acid, phosphoric acid, and aminosulfonic acid; the concentration of the second inorganic acid is 85-100%. The neutralization of the mixture after the deoctylation reaction includes adjusting the pH of the mixture to 7-8 at 80-100°C using a second alkali solution; the concentration of the second alkali solution is 10-35%.

10. The method according to claim 8, wherein, The conditions for the fourth distillation include: the theoretical plate number of the distillation column is 100 to 300, the pressure is -0.085 to -0.090 MPa, and the reflux ratio is 5 to 10:1.