Method for co-producing p-hydroxyanisole and o-hydroxyanisole through anisole hydroxylation reaction

Abstract

The invention discloses a method for co-producing p-hydroxyanisole and o-hydroxyanisole through hydroxylation reaction of anisole, which comprises the following steps: carrying out hydroxylation reaction on anisole and hydrogen peroxide under the action of a catalyst, and feeding the obtained anisole hydroxylation reaction liquid into a desolventizing tower for desolventizing; a mixture extracted from the top of the desolventizing tower is fed into a reactor for recycling, a material discharged from the bottom of the desolventizing tower is fed into an anisole tower for normal-pressure azeotropic rectification, a mixture extracted from the top of the desolventizing tower is fed into a liquid-liquid two-phase separator, a material discharged from the bottom of the anisole tower is fed into an o-hydroxyanisole tower for extracting an o-hydroxyanisole product, and a material at the bottom of the desolventizing tower is fed into a p-hydroxyanisole tower; and extracting a p-hydroxyanisole product from the p-hydroxyanisole tower. The method realizes co-production of p-hydroxyanisole and o-hydroxyanisole, has the advantages of simple and efficient technological process, convenient and stable operation in the technological process, high product purity, low operation temperature in the separation process, small deterioration loss and the like, and is especially suitable for industrial application.

Description

Technical Field

[0001] The invention belongs to the technical field of anisole hydroxylation reaction, and particularly relates to a method for co-producing p-hydroxyanisole and o-hydroxyanisole through anisole hydroxylation reaction. Background Art

[0002] p-Hydroxyanisole is a common fine chemical product. It can not only be used as a polymerization inhibitor, antioxidant and plasticizer for macromolecules, but also is an important intermediate in the production of industries such as medicine, spices and pesticides. Because p-Hydroxyanisole has good antioxidant properties, it is usually used as a stabilizer and is widely added in various types of macromolecular monomers to prevent oxidation and deterioration in transportation, storage and purification processes. In addition, due to the good polymerization inhibition effect, low consumption, and the characteristics of directly participating in mixing, p-Hydroxyanisole is also a very excellent inhibitor in the production of alkenyl monomers such as propionitrile, acrylic acid, and acrylates. P-Hydroxyanisole can give resin good storage stability, and can not delay and affect the gel time when resin is used. The solubility of p-Hydroxyanisole in organic solvents is the best, and the product color is the lightest. In addition, p-Hydroxyanisole is also used as the synthesis of antioxidants, plasticizers, food antioxidants, etc.

[0003] At present, the synthesis of p-hydroxyanisole at home and abroad mainly adopts the methylation of hydroquinone, with hydroquinone as raw material, methanol, dimethyl carbonate and dimethyl sulfate as common methylating agents. The disadvantage of this process is that the raw material price is high, and the single methylation of hydroquinone cannot be controlled during the methylation process, thereby generating dimethylated byproducts and tar-like byproducts.

[0004] o-Hydroxyanisole, also known as guaiacol, is an important fine chemical intermediate in the pharmaceutical, fragrance, pesticide, dye and other industries. Among many applications, the largest use of o-Hydroxyanisole is in the synthesis of vanillin.

[0005] The main production process of o-hydroxyanisole is the diazotization reaction method of o-methoxyaniline. With o-methoxyaniline as raw material, o-hydroxyanisole is prepared by diazotization and hydrolysis two-step reaction. The defect of this process is that the sewage discharge is large and the pollution is serious. In order to make the generated product leave the reaction system as quickly as possible and avoid the occurrence of side reactions such as coupling, the hydrolysis of diazonium salt needs to be carried out under higher temperature and high acidity conditions, the operating environment is relatively strict, and the yield is low.

[0006] Recently, it has been proposed to prepare hydroxyanisole using hydrogen peroxide and anisole as raw materials, which greatly reduces the reaction steps, is simple to operate, has mild reaction conditions, and does not produce harmful by-products. It is an excellent environmentally friendly preparation process with broad application prospects.

[0007] As disclosed in CN105985226A, a method for the hydroxylation of anisole is provided. By using a titanium silicalite molecular sieve with hollow-structured crystals as the catalyst, under the reaction conditions of a reaction temperature of 50 - 150 °C and a reaction pressure of atmospheric pressure to 1.0 MPa, the conversion rate of anisole is high, and the para-to-ortho ratio of the product hydroxyanisole remains at a relatively high level.

[0008] CN113731400A discloses the application of K7[MnV 13 O 38 ·18H2O as a catalyst in the hydroxylation reaction of aromatic hydrocarbons. This invention selects K7[MnV 13 O 38 ·18H2O as the catalyst for the hydroxylation reaction of aromatic hydrocarbons, which can significantly improve the conversion rate of anisole and the yield of the product (p-hydroxyanisole) in the hydroxylation reaction, thus effectively promoting the cleaner production of p-hydroxyanisole.

[0009] The literature (Aayesha Nasreen & Srinivas R. Adapa, ORGANIC PREPARATIONS AND PROCEDURES INT., 2000, 32(4): 373 - 375) reports the results of the hydroxylation reaction of anisole using copper sulfate as the catalyst and hydrogen peroxide as the hydroxylation reagent; the total yield of p-hydroxyanisole and o-methylanisole is 94%, and the para-to-ortho ratio of the product hydroxyanisole is 89:11. The hydroxyanisole prepared by the above technologies is a mixture of p-hydroxyanisole and o-methylanisole. How to separate the products of p-hydroxyanisole and o-hydroxyanisole to achieve the co-production of p-hydroxyanisole and o-hydroxyanisole is an urgent problem to be solved at present. On the other hand, both p-hydroxyanisole and o-methylanisole are heat-sensitive substances, which will cause deterioration and loss during the rectification process. The higher the rectification temperature, the more serious the deterioration and loss. This is also an urgent problem to be solved in the separation of the anisole hydroxylation reaction solution. Summary of the Invention

[0010] In order to overcome the deficiencies of the above-mentioned prior art, the present invention provides a method for the co-production of p-hydroxyanisole and o-hydroxyanisole by the hydroxylation reaction of anisole. This method realizes the co-production of p-hydroxyanisole and o-hydroxyanisole, and has the advantages of simple and efficient process flow, convenient and stable process operation, high product purity, low operation temperature and small deterioration loss during the separation process, and is particularly suitable for industrial application.

[0011] The object of the present invention is achieved by the following technical solutions: A method for the co-production of p-hydroxyanisole and o-hydroxyanisole by the hydroxylation reaction of anisole, which is characterized by including the following steps: (1) Anisole and hydrogen peroxide are subjected to a hydroxylation reaction under the action of a catalyst, and the obtained anisole hydroxylation reaction solution is sent to a solvent stripping column for solvent stripping; (2) The solvent stripping column is at atmospheric pressure or slightly positive pressure. All the solvent or a mixture of all the solvent and part of the water is taken out from the top of the column and sent back to the reactor for reuse, and the bottom discharge of the column is sent to the anisole column; (3) The anisole column adopts atmospheric azeotropic distillation, where the water content / anisole content in the anisole column ≥ 0.681. A mixture of anisole and water is taken out from the top of the column and sent to a liquid-liquid two-phase separator. The anisole separated from the upper layer of the liquid-liquid two-phase separator is returned to the reactor to continue as a raw material, and the bottom discharge of the anisole column is sent to the o-hydroxyanisole column; (4) The o-hydroxyanisole column operates under negative pressure, and the o-hydroxyanisole product is taken out from the top of the column, and the bottom material of the column is sent to the p-hydroxyanisole column; (5) The p-hydroxyanisole column operates under negative pressure, and the p-hydroxyanisole product is taken out from the top of the column, or the p-hydroxyanisole product is taken out and further purified by decolorization and melt crystallization separation to obtain a p-hydroxyanisole product with higher purity, and the bottom material of the column is discharged.

[0012] Further, the anisole hydroxylation reaction solution in step (1) is not treated or is treated by filtration and / or reduction before entering the solvent stripping column. The purpose of filtration is to filter out the solid catalyst, and the purpose of reduction is to remove hydrogen peroxide.

[0013] Further, the mass composition of the anisole hydroxylation reaction solution is: solvent 5 - 60%, water 5 - 20%, anisole 10 - 60%, o-hydroxyanisole 1 - 10%, p-hydroxyanisole 3 - 30%, tar 1 - 7% and catalyst 0 - 15%.

[0014] Further, the solvent is one or a mixture of several of alcohols, ketones, esters, nitriles and 1,4-dioxane solvents.

[0015] The catalyst described in the present invention includes a molecular sieve containing a transition metal element or a heterogeneous catalyst of a transition metal oxide, or a homogeneous catalyst such as a heteropolyacid and its salts, porphyrin compounds, transition metal salts or transition metal complexes, or sulfuric acid, phosphoric acid, pyrophosphoric acid, perchloric acid, or one or several of them; preferably titanium silicalite TS-1, titanium silicalite TS-2, Ti-MWW, vanadium silicalite VS-1, or iron oxide, molybdenum oxide, tungsten oxide, ferrate, molybdate, tungstate, phosphotungstic heteropolyacid, phosphomolybdic heteropolyacid, cobalt porphyrin, iron porphyrin, ferrous sulfate, ferric sulfate, cobalt acetate, cobalt sulfate, cobalt naphthenate, sulfuric acid, phosphoric acid, pyrophosphoric acid, perchloric acid, or one or several of them.

[0016] Further, a part of the water separated from the lower layer of the liquid-liquid two-phase separator in step (3) is returned to the anisole column, and the amount of water returned to the anisole column satisfies the following condition: (the amount of water in the logistics entering the anisole column + the amount of water returned to the anisole column) / the amount of anisole in the logistics entering the anisole column ≥ 0.681, and the other part of the water is discharged.

[0017] Further, the number of theoretical plates of the solvent stripping column is 10 - 50, and its operating conditions are: pressure 101.3 KPa - 150 KPa, top temperature 55 - 100 °C, bottom temperature 65 - 130 °C, number of theoretical plates 10 - 50, reflux ratio 0.5 - 10.

[0018] Further, the number of theoretical plates of the anisole column is 1 - 5, and its operating conditions are: pressure at atmospheric pressure, top temperature 90 - 105 °C, bottom temperature 95 - 150 °C, reflux ratio 0.1 - 3; the operating conditions of the liquid-liquid two-phase separator are: pressure at atmospheric pressure, temperature 20 - 50 °C.

[0019] Further, the number of theoretical plates of the o-hydroxyanisole column is 5 - 40, and its operating conditions are: pressure 2 KPa - 20 KPa, top temperature 70 - 120 °C, bottom temperature 130 - 200 °C, reflux ratio 1 - 5.

[0020] Further, the number of theoretical plates of the p-hydroxyanisole column is 5 - 40, and the operating conditions are: pressure 2 KPa - 20 KPa, top temperature 70 - 150 °C, bottom temperature 140 - 220 °C, reflux ratio 1 - 5.

[0021] Further, in step (5), the p-hydroxyanisole product is further purified by decolorization, melt crystallization separation, and drying to obtain a p-hydroxyanisole product with higher purity.

[0022] Since water and anisole can form a minimum azeotrope with an atmospheric boiling point of 95.5 °C, the present invention utilizes this property of the minimum azeotrope to separate anisole from the mixture at atmospheric pressure and relatively low rectification temperatures, reducing the thermal degradation losses of p-methoxyphenol and o-methoxyphenol. The weight ratio of the components of the minimum azeotrope formed by water and anisole is: water / anisole = 0.681. In order to completely separate anisole from the mixture at the azeotropic temperature, the water content / anisole content in the total feed stream to the anisole column should be at least equal to 0.681. If the water content / anisole content is less than 0.681, a portion of water should be added externally to meet the requirement that the water content / anisole content is at least equal to 0.681. In industrial practice, the externally added water can also be appropriately greater than the theoretically required amount of water. In this way, not only can anisole be completely separated from the mixture, but the rectification temperature will not increase too much. If the externally added water is much higher than the theoretically required amount of water, it is not advisable in industrial production. The anisole separated from the upper layer of the liquid-liquid two-phase separator is returned to the reactor for reuse, and a portion of the water separated from the lower layer of the liquid-liquid two-phase separator is returned to the anisole column as an azeotropic agent for anisole.

[0023] The present invention has the following beneficial effects: (1) The solvent removal column and the anisole column in the present invention operate at atmospheric pressure, with lower equipment manufacturing and maintenance costs, simple and stable operation. The anisole column uses azeotropic rectification to separate anisole, with a low rectification temperature and small rectification degradation losses of o-methoxyphenol and p-methoxyphenol.

[0024] (2) The o-methoxyphenol column and the p-methoxyphenol column in the present invention operate under a relatively high vacuum, with a low operating temperature, reducing the formation of phenolic tar, reducing the degradation losses of o / p-methoxyphenol products, and increasing the product yield. The yield of o-methoxyphenol > 94%, and the yield of p-methoxyphenol > 95%.

[0025] (3) The separation method of the anisole hydroxylation reaction solution of the present invention adopts a combined co-production process of a solvent removal column, an anisole column, an o-methoxyphenol column, and a p-methoxyphenol column, with a short process flow, low separation energy consumption, low raw material consumption, and high product purity. The purity of both o-methoxyphenol and p-methoxyphenol reaches 99.9%. Description of the Drawings

[0026] Figure 1 is a flow chart of the method for co-producing p-methoxyphenol and o-methoxyphenol by anisole hydroxylation in the present invention. Detailed Embodiments

[0027] The following provides a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only for the purpose of illustrating and explaining the present invention, and are not intended to limit the present invention.

[0028] In the following embodiments, the desolventizing column, anisole column, o-hydroxyanisole column and p-hydroxyanisole column used in the present invention are distillation columns.

[0029] The anisole hydroxylation reaction solution is a reaction solution for preparing hydroxyanisole from hydrogen peroxide and anisole as raw materials under different solvents and catalysts. Its mass composition is: solvent 5 - 60%, water 5 - 20%, anisole 10 - 60%, o-hydroxyanisole 1 - 10%, p-hydroxyanisole 3 - 30%, tar 1 - 7%, catalyst 0 - 15%.

[0030] Yield of o-hydroxyanisole = mass of o-hydroxyanisole product / mass of o-hydroxyanisole in anisole hydroxylation reaction solution * 100%.

[0031] Yield of p-hydroxyanisole = mass of p-hydroxyanisole product / mass of p-hydroxyanisole in anisole hydroxylation reaction solution * 100%. Example 1

[0032] According to Figure 1 the co-production process shown, anisole and hydrogen peroxide are subjected to a hydroxylation reaction using acetonitrile as a solvent and copper sulfate as a catalyst to obtain an anisole hydroxylation reaction solution with a mass composition of 46% acetonitrile, 13% water, 27% anisole, 7% o-hydroxyanisole, 4.5% p-hydroxyanisole, 2.5% tar and a small amount of catalyst copper sulfate. The untreated anisole hydroxylation reaction solution is fed into the desolventizing column at a flow rate of 500 kg / h. The desolventizing column has 30 theoretical plates, an operating pressure of atmospheric pressure, a reflux ratio of 3.5, a top temperature of 77 °C, and a bottom temperature of 110 °C. The azeotropic mixture of acetonitrile and water is taken out from the top of the column and sent back to the reactor for reuse. The material at the bottom of the column containing 9.38% water, 59.68% anisole, 15.47% o-hydroxyanisole, 9.94% p-hydroxyanisole, 5.53% tar and a small amount of catalyst is fed into the anisole column; the anisole column has 2 theoretical plates, an operating pressure of atmospheric pressure, a reflux ratio of 1, a top temperature of 97 °C, and a bottom temperature of 130 °C. The mixture of anisole and water is taken out from the top of the column and sent to a liquid-liquid two-phase separator. The anisole separated from the upper layer of the liquid-liquid two-phase separator is returned to the reactor to continue as a raw material. A part of the water separated from the lower layer of the liquid-liquid two-phase separator is used as an azeotropic agent with anisole and returned to the anisole column. The amount of water returned to the anisole column satisfies the following condition: (amount of water in the stream entering the anisole column + amount of water returned to the anisole column) / amount of anisole in the stream entering the anisole column is 0.681. Another part of the water is discharged. The operating conditions of the liquid-liquid two-phase separator are: pressure is atmospheric pressure, temperature is 40 °C. The material at the bottom of the column containing 49% o-hydroxyanisole, 32% p-hydroxyanisole, 19% tar and a small amount of catalyst is fed into the o-hydroxyanisole column.

[0033] The bottom material from the anisole column is further separated and purified in the o - hydroxyanisole column. The number of theoretical plates of the o - hydroxyanisole column is 20, and the operating conditions are: pressure 5 KPa, top temperature 150 °C, bottom temperature 200 °C, reflux ratio 3. The o - hydroxyanisole product with a purity of 99.9 (w)% is withdrawn from the top of the column. The bottom material containing tar, a small amount of catalyst and a mixture of p - hydroxyanisole is sent to the p - hydroxyanisole column. The number of theoretical plates of the p - hydroxyanisole column is 10, and its operating conditions are: pressure 2 KPa, top temperature 160 °C, bottom temperature 205 °C, reflux ratio 5. The p - hydroxyanisole product with a purity of 99.3 (w)% is withdrawn from the top of the column. Or the withdrawn p - hydroxyanisole product is subjected to decolorization and melt crystallization separation to obtain a p - hydroxyanisole product with a higher purity of 99.9 (w)%. The purity of the other stream separated by the melt crystallization separator is 99.2 (w)%. The bottom material containing tar, a small amount of catalyst and a small amount of p - hydroxyanisole is discharged.

[0034] In Example 1, the product yield of o - hydroxyanisole is 94.6%, and the product yield of p - hydroxyanisole is 95.3. Example 2

[0035] According to Figure 1 The co - production process shown, anisole and hydrogen peroxide are subjected to a hydroxylation reaction under the action of methyl ethyl ketone as a solvent and titanium - silicon molecular sieve as a catalyst. The reaction solution is filtered and reduced to obtain a hydroxylation reaction solution of anisole with a mass composition of 30% methyl ethyl ketone, 20% water, 32% anisole, 5.5% o - hydroxyanisole, 11% p - hydroxyanisole, and 1.5% tar. The hydroxylation reaction solution of anisole is fed into a solvent - stripping column at a flow rate of 500 kg / h. The number of theoretical plates of the solvent - stripping column is 25, the operating pressure is atmospheric pressure, the reflux ratio is 4, the top temperature is 76 °C, and the bottom temperature is 110 °C. Methyl ethyl ketone is withdrawn from the top of the column and sent back to the reactor for reuse. The bottom material containing 25% water, 48% anisole, 8.2% o - hydroxyanisole, 16.5% p - hydroxyanisole, and 2.3% tar is sent to the anisole column; the number of theoretical plates of the anisole column is 5, the operating pressure is atmospheric pressure, the reflux ratio is 0.5, the top temperature is 101 °C, and the bottom temperature is 135 °C. A mixture of anisole and water is withdrawn from the top of the column and sent to a liquid - liquid two - phase separator. The anisole separated from the upper layer of the liquid - liquid two - phase separator is returned to the reactor to continue as a raw material. A part of the water separated from the lower layer of the liquid - liquid two - phase separator is returned to the anisole column as an azeotropic agent with anisole. The amount of water returned to the anisole column satisfies the following condition: (the amount of water in the stream entering the anisole column + the amount of water returned to the anisole column) / the amount of anisole in the stream entering the anisole column is 0.7. Another part of the water is discharged. The operating conditions of the liquid - liquid two - phase separator are: pressure is atmospheric pressure, temperature is 35 °C. The mixture containing 29.8% o - hydroxyanisole, 61.4% p - hydroxyanisole, and 8.8% tar at the bottom is sent to the o - hydroxyanisole column.

[0036] The bottom material from the anisole column is further separated and purified in the o - hydroxyanisole column. The number of theoretical plates of the o - hydroxyanisole column is 10, and the operating conditions are: pressure 4 KPa, top temperature 150 °C, bottom temperature 200 °C, reflux ratio 5. The o - hydroxyanisole product with a purity of 99.9 (w)% is taken from the top of the column. The bottom material containing a mixture of tar and p - hydroxyanisole is sent to the p - hydroxyanisole column. The number of theoretical plates of the p - hydroxyanisole column is 20, and its operating conditions are: pressure 2 KPa, top temperature 160 °C, bottom temperature 210 °C, reflux ratio 1. The p - hydroxyanisole product with a purity of 99.5 (w)% is taken from the top of the column, and the bottom material containing tar and a small amount of p - hydroxyanisole is discharged.

[0037] In Example 2, the product yield of o - hydroxyanisole is 94.8%, and the product yield of p - hydroxyanisole is 96.7. Example 3

[0038] According to Figure 1 the co - production process shown, anisole and hydrogen peroxide react under the action of methanol and acetone as solvents and titanium - silicon molecular sieve as a catalyst to carry out a hydroxylation reaction. The reaction solution is filtered and reduced to obtain a hydroxylation reaction solution of anisole with a mass composition of 20% methanol, 23% acetone, 15% water, 25% anisole, 6% o - hydroxyanisole, 10% p - hydroxyanisole, and 1% tar. The hydroxylation reaction solution of anisole is fed into the solvent - stripping column at a flow rate of 500 kg / h. The number of theoretical plates of the solvent - stripping column is 15, the operating pressure is atmospheric pressure, the reflux ratio is 1, the top temperature is 60 °C, and the bottom temperature is 90 °C. Acetone and methanol are taken from the top of the column and sent back to the reactor for reuse. The bottom material containing 26.3% water, 43.9% anisole, 10.5% o - hydroxyanisole, 17.5% p - hydroxyanisole, and 1.8% tar is sent to the anisole column; the number of theoretical plates of the anisole column is 3, the operating pressure is atmospheric pressure, the reflux ratio is 5, the top temperature is 98 °C, and the bottom temperature is 135 °C. The mixture of anisole and water is taken from the top of the column and sent to a liquid - liquid two - phase separator. The anisole separated from the upper layer of the liquid - liquid two - phase separator is returned to the reactor as a raw material. A part of the water separated from the lower layer of the liquid - liquid two - phase separator is used as an azeotropic agent with anisole and returned to the anisole column. The amount of water returned to the anisole column meets the following condition: (the amount of water in the material flowing into the anisole column + the amount of water returned to the anisole column) / the amount of anisole in the material flowing into the anisole column is 0.7. The other part of the water is discharged. The operating conditions of the liquid - liquid two - phase separator are: pressure is atmospheric pressure, temperature is 28 °C. The mixture containing 32% o - hydroxyanisole, 61.5% p - hydroxyanisole, and 6.5% tar at the bottom is sent to the o - hydroxyanisole column.

[0039] The bottom material from the anisole column is further separated and purified in the o - hydroxyanisole column. The number of theoretical plates of the o - hydroxyanisole column is 30, and the operating conditions are as follows: pressure 3 KPa, top temperature 140 °C, bottom temperature 195 °C, reflux ratio 1. The o - hydroxyanisole product with a purity of 99.9 (w)% is withdrawn from the top of the column. The bottom material containing a mixture of tar and p - hydroxyanisole is sent to the p - hydroxyanisole column. The number of theoretical plates of the p - hydroxyanisole column is 10, and its operating conditions are: pressure 3 KPa, top temperature 175 °C, bottom temperature 205 °C, reflux ratio 3. The p - hydroxyanisole product with a purity of 99.5 (w)% is withdrawn from the top of the column, and the bottom material containing tar and a small amount of p - hydroxyanisole is discharged.

[0040] In Example 3, the product yield of o - hydroxyanisole is 94.6%, and the product yield of p - hydroxyanisole is 96.5. Comparative Example 1

[0041] According to Figure 1 In the co - production process shown, anisole and hydrogen peroxide undergo a hydroxylation reaction in the presence of acetonitrile as a solvent and copper sulfate as a catalyst. The mass composition of the anisole hydroxylation reaction solution obtained is 46% acetonitrile, 13% water, 27% anisole, 7% o - hydroxyanisole, 4.5% p - hydroxyanisole, 2.5% tar, and a small amount of catalyst copper sulfate. The untreated anisole hydroxylation reaction solution is fed into the solvent - stripping column at a flow rate of 500 kg / h. The number of theoretical plates of the solvent - stripping column is 30, the operating pressure is atmospheric pressure, the reflux ratio is 3.5, the top temperature is 77 °C, and the bottom temperature is 110 °C. The azeotropic mixture of acetonitrile and water is withdrawn from the top of the column and sent back to the reactor for reuse. The bottom material containing 9.38% water, 59.68% anisole, 15.47% o - hydroxyanisole, 9.94% p - hydroxyanisole, 5.53% tar, and a small amount of catalyst is sent to the anisole column; the number of theoretical plates of the anisole column is 15, the operating pressure is atmospheric pressure, the reflux ratio is 1, the top temperature is 140 °C, and the bottom temperature is 190 °C. The mixture of anisole and water is withdrawn from the top of the column and sent to a liquid - liquid two - phase separator. The anisole separated from the upper layer of the liquid - liquid two - phase separator is returned to the reactor as a raw material, and the water separated from the lower layer of the liquid - liquid two - phase separator is discharged. The operating conditions of the liquid - liquid two - phase separator are: pressure is atmospheric pressure, temperature is 20 - 35 °C. The bottom material containing 49% o - hydroxyanisole, 32% p - hydroxyanisole, 19% tar, and a small amount of catalyst is sent to the o - hydroxyanisole column.

[0042] The bottom material from the anisole column is further separated and purified in the o - hydroxyanisole column. The number of theoretical plates of the o - hydroxyanisole column is 20, and the operating conditions are: pressure 5 KPa, top temperature 150 °C, bottom temperature 200 °C, reflux ratio 3. The o - hydroxyanisole product with a purity of 99.9 (w)% is withdrawn from the top of the column. The column bottom material containing tar, a small amount of catalyst and a mixture of p - hydroxyanisole is sent to the p - hydroxyanisole column. The number of theoretical plates of the p - hydroxyanisole column is 10, and its operating conditions are: pressure 2 KPa, top temperature 160 °C, bottom temperature 205 °C, reflux ratio 5. The p - hydroxyanisole product with a purity of 99.3 (w)% is withdrawn from the top of the column, or the withdrawn p - hydroxyanisole product is subjected to decolorization and melt crystallization separation to obtain a p - hydroxyanisole product with a higher purity of 99.9 (w)%. The purity of the other stream separated by the melt recrystallization separator is 99.2 (w)%. The column bottom material containing tar, a small amount of catalyst and a small amount of p - hydroxyanisole is discharged.

[0043] In Comparative Example 1, the product yield of o - hydroxyanisole was 92.3%, and the product yield of p - hydroxyanisole was 93.0.

[0044] As can be seen from the above examples, the purity of the products after separation by the present invention is high, 99.9 (w)% for o - hydroxyanisole and 99.3 (w)% for p - hydroxyanisole. At the same time, the product yields are high, with the yield of o - hydroxyanisole > 94% and the yield of p - hydroxyanisole > 95%. It can be seen from Example 1 and Comparative Example 1 that in Example 1, anisole was separated by azeotropic distillation, the distillation temperature was low, and the product yields of o - hydroxyanisole and p - hydroxyanisole were high, 94.6% and 95.3% respectively. While in Comparative Example 1, anisole was separated by a conventional method, the distillation temperature was high, and the product yields of o - hydroxyanisole and p - hydroxyanisole were low, 92.3% and 93.0% respectively.

Claims

1. A method for co-producing p-hydroxyanisole and o-hydroxyanisole by the hydroxylation reaction of anisole, characterized in that The steps include: (1) anisole and hydrogen peroxide are subjected to a hydroxylation reaction under the action of a catalyst, and the obtained anisole hydroxylation reaction liquid is sent to a desolventizing tower for desolventizing; (2) The desolventizing tower is at normal pressure or slightly positive pressure, all the solvent or a mixture of all the solvent and part of the water is taken out from the top of the tower and sent to the reactor for reuse, and the bottom of the tower is sent to the anisole tower; (3) the anisole tower adopts normal pressure azeotropic distillation, wherein the water yield / anisole amount ≧0.681 in the anisole tower, the mixture of anisole and water is extracted from the tower top and sent into a liquid-liquid two-phase separator, the anisole separated in the upper strata of the liquid-liquid two-phase separator returns to the reactor and continues to be made as raw material, and the discharging at the bottom of the anisole tower is sent into the o-hydroxyanisole tower; (4) the o-hydroxyanisole tower is operated under negative pressure, the o-hydroxyanisole product is extracted from the tower top, and the tower bottoms are sent to the p-hydroxyanisole tower; (5) The p-hydroxyanisole tower is operated under negative pressure, and the p-hydroxyanisole product is extracted from the top of the tower, and the material at the bottom of the tower is discharged.

2. The method for co-producing p-hydroxyanisole and o-hydroxyanisole by the hydroxylation reaction of anisole according to claim 1, characterized in that, In step (1), the anisole hydroxylation reaction liquid is not treated or is filtered and / or reduced before entering the desolventizing tower.

3. The method for co-producing p-hydroxyanisole and o-hydroxyanisole by the hydroxylation reaction of anisole according to claim 2, characterized in that, The mass composition of the anisole hydroxylation reaction liquid is: 5-60% of solvent, 5-20% of water, 10-60% of anisole, 1-10% of o-hydroxyanisole, 3-30% of p-hydroxyanisole, 1-7% of tar and 0-15% of catalyst.

4. The method for co-producing p-hydroxyanisole and o-hydroxyanisole by the hydroxylation reaction of anisole according to claim 1, characterized in that, The solvent is one or a mixture of alcohols, ketones, lipids, nitriles and 1,4-dioxane solvents.

5. The method for co-producing p-hydroxyanisole and o-hydroxyanisole by the hydroxylation reaction of anisole according to claim 1, characterized in that, Part of the water separated from the lower layer of the liquid-liquid two-phase separator in step (3) is returned to the anisole tower, and the amount of water returned to the anisole tower satisfies the following condition: (the amount of water entering the anisole tower logistics + the amount of water returned to the anisole tower) / the amount of anisole entering the anisole tower logistics ≧0.681, and the other part of the water is discharged.

6. The method for co-producing p-hydroxyanisole and o-hydroxyanisole by the hydroxylation reaction of anisole according to claim 1, characterized in that, The theoretical plate number of the desolventizing tower is 10 to 50, and the operating conditions are: pressure 101.3 KPa to 150 KPa, tower top temperature 55 to 100° C., tower bottom temperature 65 to 130° C., theoretical plate number 10 to 50, and reflux ratio 0.5 to 10.

7. The method for co-producing p-hydroxyanisole and o-hydroxyanisole by the hydroxylation reaction of anisole according to claim 1, characterized in that, The anisole tower has a theoretical plate number of 1 to 5, and its operating conditions are: normal pressure, tower top temperature of 90 to 105°C, tower bottom temperature of 95 to 150°C, and reflux ratio of 0.1 to 3; the operating conditions of the liquid-liquid two-phase separator are: normal pressure, temperature of 20 to 50°C.

8. The method for co-producing p-hydroxyanisole and o-hydroxyanisole by the hydroxylation reaction of anisole according to claim 1, characterized in that, The o-hydroxyanisole tower has a theoretical plate number of 5-40, and its operating conditions are: pressure 2KPa-20KPa, tower top temperature 70-120°C, tower bottom temperature 130-200°C, and reflux ratio 1-5.

9. The method for co-producing p-hydroxyanisole and o-hydroxyanisole by the hydroxylation reaction of anisole according to claim 1, characterized in that, The theoretical plate number of the p-hydroxyanisole tower is 5-40, and the operating conditions are: pressure 2KPa-20KPa, tower top temperature 70-150°C, tower bottom temperature 140-220°C, and reflux ratio 1-5.

10. The method for co-producing p-hydroxyanisole and o-hydroxyanisole by the hydroxylation reaction of anisole according to claim 1, characterized in that, In step (5), the p-hydroxyanisole product is further purified by decolorization, melt crystallization separation, and drying to obtain a p-hydroxyanisole product with higher purity.

Images