System and method for separating and purifying mixed liquid of phenol and hydrogen peroxide hydroxylation reaction

Abstract

The present invention provides a separation and purification system and method for a mixed liquid of a hydroxylation reaction of phenol and hydrogen peroxide. The system includes a double-effect dehydration flash evaporator, a single-effect dehydration flash evaporator, a double-effect dehydration distillation tower, a single-effect dehydration phenol removal tower, a catechol removal tower, a catechol crude distillation tower, a catechol rectification tower, a tar crude distillation and dilution evaporation component, a resorcinol / hydroquinone separation tower, and a resorcinol rectification tower and a hydroquinone rectification tower respectively connected to the upper and lower parts of the resorcinol / hydroquinone separation tower, and also includes a phenol extraction component. When performing separation and purification, the reaction liquid is sequentially subjected to double-effect flash dehydration, double-effect rectification dehydration, single-effect dehydration phenol removal, catechol removal, catechol crude distillation and rectification, tar crude distillation, and mixed diphenol separation processes. Through this process, not only the energy consumption of the product is reduced, but also the product requirements of high-end customers in the market are met, and simple operation and stable production are also guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical separation, and in particular relates to a separation and purification system and method for a mixed liquid of a hydroxylation reaction of phenol and hydrogen peroxide. Background Art

[0002] Hydroquinone, with the molecular formula of C6H6O2, has three isomers: o-, m-, and p-. All three isomers are used as important chemical raw materials and intermediates and have a wide range of applications:

[0003] Catechol, also known as catechol, is a compound formed when the two ortho hydrogens of benzene are replaced by hydroxyl groups. It is an important basic organic chemical raw material and an important intermediate in the pharmaceutical industry. It is widely used in the production of dyes, light stabilizers, photosensitive materials, fragrances, preservatives, promoters, special inks, electroplating materials, and raw lacquer flame retardants. In addition, it is also a widely used astringent and antioxidant. In medicine, it is used to prepare drugs such as berberine and isoproterenol.

[0004] Hydroquinone, also known as hydroquinone, is a compound formed when the two ortho-hydrogens of benzene are replaced by hydroxyl groups. It is used in the manufacture of dyes, pharmaceutical intermediates, photographic developers, anti-oxidants, and plastic resin inhibitors. It can also interfere with the formation of melanin. Clinically, it has a fading effect on freckles, age spots, and liver spots induced by oral contraceptives.

[0005] Resorcinol, also known as resorcinol and resorcinol, is a compound formed when the two hydrogens at the meta-position of benzene are replaced by hydroxyl groups. Resorcinol is mainly used in rubber adhesives, synthetic resins, dyes, preservatives, medicines and analytical reagents.

[0006] The technology of preparing hydroquinone by hydroxylation of phenol and hydrogen peroxide has been studied and developed in my country since the late 1960s and is now industrialized. However, with the continuous development of catalysts, the composition and proportion of the reaction liquid have changed. At the same time, with the continuous development of high-end products in the downstream market of hydroquinone, the quality requirements for the intermediate hydroquinone have become more and more stringent. The existing hydroquinone products in the market cannot meet the requirements of high-end customers.

[0007] In order to solve the above technical problems, many explorations have been made in the prior art: for example, Tianjin University patents CN100344594C and CN101830780A both disclose a separation and purification system and purification method for phenol, o- / hydroquinone and tar aqueous solution, and the separation order is dehydration, dephenolization, decoking, o-catechol product distillation, and hydroquinone product distillation separation. Compared with CN100344594C, patent CN101830780A optimizes energy saving and consumption reduction, and improves the purity of hydroquinone products: in terms of energy saving, such as the first dephenolization tower adopts normal pressure operation, and the top of the tower adopts the internal return condenser by-product steam; the top gas phase pipe of the decoking distillation tower is directly connected to the o-catechol tower; in terms of product purification, such as adding a hydroquinone refining tower, and the finished hydroquinone is extracted from the side line at the top of the tower.

[0008] Patent CN101054340A of Shanghai Huayi Acrylic Acid Co., Ltd. also discloses a method for separating and purifying a reaction liquid of phenol and hydrogen peroxide, which is composed of water, phenol, o- / hydroquinone and tar, and the separation order is dehydration, phenol-water extraction, dephenolization, decoking, and o- / hydroquinone product distillation.

[0009] Rhodia Chemical Company's patent CN1450986A discloses a method and device for separating and purifying raw materials containing hydroquinone, resorcinol and possible tar or catechol. The method comprises the following steps: firstly, a distillation tower or a wiped film evaporator is used for continuous decoking. The decoking product is distilled in a catechol tower to obtain a finished catechol product. The material at the bottom of the catechol tower is fed into a crude distillation tower. The resorcinol is taken out from the top of the crude distillation tower to be melted and crystallized to obtain a finished resorcinol product. The material at the bottom of the crude distillation tower is fed into a hydroquinone refining tower. The hydroquinone is taken out from the top of the refining tower to be melted and crystallized to obtain a finished hydroquinone product.

[0010] However, these technologies still inevitably have certain defects: although the latter patent of Tianjin University optimizes energy saving and consumption reduction and the purity of hydroquinone products compared with the former, it still has the defects of excessive energy consumption of the dehydration tower and the quality of catechol products cannot meet the requirements of high-end customers in the market; at the same time, its process uses a deep steamer to extract products from tar, and there is tar expansion, resulting in more hydroquinone in the tar. Shanghai Huayi Acrylic Co., Ltd.'s patent CN101054340A puts the tar in the last step of separation. The tar stays for a long time and is prone to expansion, carbonization, and cracking, which makes normal production impossible and the product purity is contaminated.

[0011] Although the patents of Rhone-Poulenc and Rhodia Chemicals use scraped film evaporators for tar extraction, which reduces the content of hydroquinone in tar, the hydroquinone content in tar is still higher than 4% due to the characteristics of tar, and the tar has high viscosity, which makes it difficult to discharge and easily leads to production obstruction. The energy consumption for dehydration and dephenolization is high, and the quality of catechol products cannot meet the requirements of high-end customers in the market. In addition, the patent of Rhodia Chemicals uses a melt crystallizer to obtain resorcinol and hydroquinone, which is difficult to operate and has relatively high requirements for public works. Summary of the invention

[0012] The present invention is aimed at the defects of the prior art and the market demand, improves the prior art, and provides a separation and purification system and method for a mixed liquid of a hydroxylation reaction of phenol and hydrogen peroxide, in order to reduce the energy consumption of the product, meet the requirements of high-end customers in the market, and ensure simple operation and stable production.

[0013] The mixed solution of the hydroxylation reaction of phenol and hydrogen peroxide of the present invention comprises water, phenol, catechol, hydroquinone, resorcinol and tar, and the separation and purification method mainly comprises the following steps:

[0014] 1) Dehydration and dephenolization: The reaction mixture is first dehydrated by a double-effect dehydration flash evaporator and a double-effect distillation, and then dephenolized by a single-effect dehydration and dephenolization tower;

[0015] 2) Catechol process: the bottoms of the first-effect dehydration and dephenolization tower are passed through a decatecholization tower, a catechol crude distillation tower, and a catechol refining tower to obtain a finished catechol product;

[0016] 3) Tar and resorcinol process: the bottom material of the catechol removal tower is passed through a detarring crude distillation tower, a tar evaporator, a resorcinol / hydroquinone separation tower, and a resorcinol distillation tower to obtain the resorcinol finished product;

[0017] 4) Hydroquinone process: The bottom material of the isoquinone / hydroquinone separation tower is passed through a hydroquinone distillation tower to obtain the finished hydroquinone product.

[0018] In order to achieve the above object, the present invention specifically adopts the following technical solutions:

[0019] <Structure 1>

[0020] In a first aspect, the present invention provides a separation and purification system for a mixed liquid of a hydroxylation reaction of phenol and hydrogen peroxide, comprising a double-effect dehydration flash evaporator, a single-effect dehydration flash evaporator, a double-effect dehydration distillation tower, a single-effect dehydration phenol removal tower, a catechol removal tower, a catechol crude distillation tower, a catechol distillation tower, a tar crude distillation and dilution evaporation component, a resorcinol / hydroquinone separation tower, a resorcinol distillation tower and a hydroquinone distillation tower respectively connected to the upper and lower parts of the resorcinol / hydroquinone separation tower, and also comprising a phenol extraction component.

[0021] Preferably, in the separation and purification system provided by the present invention, the phenol extraction component consists of a centrifugal extractor and an extractive distillation tower connected in series.

[0022] Preferably, in the separation and purification system provided by the present invention, the tar crude distillation and dilution evaporation components include a tar crude distillation tower, a tar dilution kettle connected to the bottom of the tar crude distillation tower, and a tar evaporator connected to the tar dilution kettle, and the top of the tar evaporator is connected to the middle section of the tar crude distillation tower.

[0023] Preferably, in the separation and purification system provided by the present invention, the gas phase pipe of the first-effect dehydration flash evaporator is connected to the shell side of the double-effect dehydration flash evaporator heater, and the gas phase pipe of the double-effect dehydration distillation tower is connected to the shell side of the first-effect dehydration flash evaporator heater; the distillate pipe at the top of the tar crude distillation tower is connected to the isoquinone / hydroquinone separation tower, and the bottom is connected to a stirring dilution kettle with a double mechanical seal, the gas phase pipe at the top of the tar evaporator is connected to the middle of the tar crude distillation tower; the distillate pipeline at the top of the isoquinone / hydroquinone separation tower is connected to the catechol removal tower The upper side distillate pipeline is connected to the feed pipe of the resorcinol tower; the upper distillate pipeline of the resorcinol distillation tower is divided into two, one is connected to the feed pipe of the catechol removal tower, and the other is connected to the finished product receiving tank, and the bottom pipeline is connected to the feed pipeline of the resorcinol / hydroquinone separation tower; the upper distillate pipeline of the hydroquinone distillation tower is divided into two, one is connected to the feed pipe of the resorcinol / hydroquinone distillation tower, and the other is connected to the finished product receiving tank, and the bottom pipeline is connected to the feed pipeline of the tar crude distillation tower.

[0024] <Structure 2>

[0025] The second aspect of the present invention provides a method for separating and purifying a phenol and hydrogen peroxide hydroxylation reaction mixture, wherein the reaction mixture consists of water, phenol, catechol, hydroquinone, resorcinol, and tar. During the treatment, the reaction mixture is sequentially sent to a double-effect dehydration flash evaporator, a double-effect distillation tower, a catechol removal tower, a catechol crude distillation tower, a catechol refining tower, a tar crude distillation tower, a tar dilution kettle, a tar evaporator, a resorcinol / hydroquinone separation tower, a resorcinol distillation tower, and a hydroquinone distillation tower, and the phenol-containing water is sent to a centrifugal extractor and an extractive distillation tower. Specifically, the following steps are included:

[0026] (1) Double-effect flash dehydration

[0027] The reaction mixed liquid is sent to a double-effect dehydration flash evaporator, and the flashed gas phase in the flash evaporator is condensed and the vapor phase in the shell of the heater is heat exchanged to obtain phenolic water. The operating pressure is 25-35Kpa and the operating temperature is 70-80°C; the phenolic water is sent to the extraction process, and the remaining liquid in the flash evaporator is sent to a single-effect dehydration flash evaporator.

[0028] The flashed gas phase in the first-effect dehydration flash evaporator is used to heat the heat source of the double-effect dehydration flash heater. The flash heater shell side gas phase is heat exchanged to obtain phenolic water, which is sent to the extraction process or partially returned to the double-effect dehydration tower. The operating pressure is 45-55Kpa and the operating temperature is 80-90℃.

[0029] (2) Double-effect distillation dehydration

[0030] The double-effect distillation tower receives the bottoms of the first-effect dehydration flash evaporator, with an operating pressure of 70-90Kpa, a temperature in the tower of 90-140°C, a reflux ratio of 0.5-1.0, a pressure difference of 2-4Kpa between the top and the bottom of the tower, and the gas phase at the top of the tower is a heating source for the first-effect flash evaporator heater, and the bottoms of the tower enter the first-effect dehydration and phenol removal tower;

[0031] (3) Single-effect dehydration and phenol removal

[0032] The first-effect dehydration and phenol removal tower performs atmospheric distillation process, the temperature in the tower is 130-200°C, the pressure difference between the top and the bottom of the tower is 2-4Kpa, the reflux ratio is 1.5-2.0, the gas phase at the top of the tower is the heat source of the double-effect distillation tower heater, the phenol distilled from the side line at the top of the tower is returned to the reaction system for application, and the bottom of the tower enters the catechol removal tower;

[0033] (4) Removal of catechol

[0034] The operating pressure is 4-8Kpa, the temperature in the tower is 170-215℃, the pressure difference between the top and the bottom of the tower is 2-4Kpa, the reflux ratio is 2.5-2.7, the phenol product is distilled from the top of the de-catecholization tower, the crude catechol is distilled from the upper side line, and the bottoms are fed into the tar crude distillation tower;

[0035] (5) Crude distillation and rectification of catechol

[0036] The distillate from the upper part of the catechol crude distillation tower is returned to the first-effect dehydration and phenol removal tower, and the bottoms are sent to the catechol refining tower. The catechol finished product is distilled from the upper part of the catechol refining tower, and the bottoms are sent to the catechol removal tower; the operating pressure during crude distillation and rectification is 4-8Kpa, the pressure difference between the tower top and the tower bottom is 2-4Kpa, the temperature in the tower is 140-180℃, and the reflux ratio is 2.0-2.8;

[0037] (6) Tar crude distillation

[0038] The tar crude distillation tower receives the bottoms of the de-catecholization tower, the temperature in the tower is 170-220°C, the operating pressure is 2-5Kpa, the pressure difference between the top and the bottom of the tower is 2-4Kpa, and the reflux ratio is 1.0-1.5; the distillate rich in hydroquinone is distilled out from the upper part of the crude distillation tower to go to the isoquinone / hydroquinone separation tower, the bottoms are diluted with a solvent with a boiling point higher than 350°C and then evaporated, the gas phase of the evaporator returns to the tar crude distillation tower, and the bottom liquid phase is sent to the next process of tar treatment;

[0039] (7) Separation of mixed diphenols

[0040] The operating pressure of the isoquinone / hydroquinone separation tower is 2-5Kpa, the pressure difference between the top and the bottom of the tower is 2-4Kpa, the temperature in the tower is 170-220°C, the reflux ratio is 2.5-3.0, the upper distillate is returned to the catechol removal tower, the upper side distillate is sent to the isoquinone distillation tower, and the bottom liquid is sent to the hydroquinone distillation tower.

[0041] Preferably, the phenol and hydrogen peroxide hydroxylation reaction mixture comprises 30-70% phenol, 3-9% catechol, 2-9% hydroquinone, 0.2-0.5% resorcinol, 0.2-1.0% tar, and the balance is water.

[0042] Preferably, in step (1), the phenol content in the phenol-containing water obtained by the double-effect dehydration flash evaporator is 7-10%; when the obtained phenol-containing wastewater is subjected to the extraction process, it is first extracted by a centrifugal extraction device, the extract phase is sent to an extraction distillation tower for distillation, and the raffinate phase wastewater enters the next process for sewage treatment; the phenol-containing liquid extracted from the top of the extraction distillation tower is returned to the reaction system for application, and the solvent at the bottom of the tower is returned to the extraction equipment for recycling.

[0043] Preferably, the centrifugal extraction equipment is a single-stage or multi-stage series centrifugal extractor, the centrifugal speed is 3000-5000 rpm, the ratio of the extraction solvent to the phenolic water is 0.2-0.4, and the operating temperature is 40-50°C; the extraction solvent is selected from one or more mixtures of N,N-mixed alkyl acetamide, N,N-di(1-methylheptyl)hexanamide, trioctylamine, triethyl phosphate, trialkyl tertiary amine, nonanoic acid;

[0044] The operating conditions of the extractive distillation tower are a pressure of 2-4 KPa, a pressure difference of 2-4 KPa between the top and the bottom of the tower, a phenol content of more than 97% is distilled out from the top of the tower, and a solvent content of more than 98% flowing out from the bottom of the tower is returned to the centrifugal extraction for use.

[0045] Preferably, in step (2), the phenol content in the phenol-containing water distilled from the upper part of the double-effect distillation tower is 7-10%;

[0046] In step (3), the phenol content in the phenol-containing water distilled from the upper part of the first-effect dehydration and dephenolization tower is 10-20%, and the phenol content in the upper side distillate is 80-95%;

[0047] In step (4), a phenol finished liquid having a phenol content greater than 98% is distilled out from the upper part of the catechol removal tower, a catechol liquid having a catechol content greater than 90% is distilled out from the upper side line, and a heavy component at the bottom of the tower is rich in hydroquinone;

[0048] In step (5), the catechol product distilled from the top of the catechol refining tower has a purity greater than 99.5%; when the catechol content of the bottom component is less than 30%, it is transferred to the catechol removal tower;

[0049] In step (6), the distillate from the upper part of the crude tar distillation tower is rich in light components of hydroquinone, and the bottoms are tar with a hydroquinone content of less than 5-10%; the diluent of the bottoms is selected from one or a mixture of m-terphenyl, terpyridine, phenylmethyl silicone oil, and high carbon white oil; the tar evaporator is a falling film evaporator with an operating pressure of 1-3 Kpa, the gas phase from the upper part of the evaporator returns to the crude tar distillation tower, and the tar is discharged from the bottom to the next step, and the total content of hydroquinone products in the discharged tar is less than 2%;

[0050] In step (7), the resorcinol content in the side distillate from the top of the resorcinol / hydroquinone separation tower is greater than 90%, and is sent to the resorcinol distillation tower, and the bottom liquid is sent to the hydroquinone distillation tower.

[0051] Preferably, in step (7), the resorcinol distillation tower is a batch distillation tower, the operating pressure is 2-5Kpa, the pressure difference between the top and the bottom of the tower is 2-4Kpa, the temperature in the tower is 170-220°C, and the reflux ratio is 3.0-3.5; the unqualified light components distilled out from the gap at the top of the tower are returned to the resorcinol / hydroquinone separation tower, and when the resorcinol content is greater than 99%, they are sent to the resorcinol receiving tank as a qualified finished product, and the resorcinol content in the bottom liquid is less than 30%, which is transferred to the resorcinol / hydroquinone separation tower; the unqualified components distilled out from the upper part of the hydroquinone distillation tower are returned to the resorcinol / hydroquinone separation tower, and when the hydroquinone content is greater than 99%, they are sent to the hydroquinone receiving tank as a qualified finished product, and the hydroquinone content in the bottom liquid is less than 30%, which is transferred to the tar crude distillation tower.

[0052] Functions and Effects of the Invention

[0053] Compared with the prior art, the separation and purification system and method of the mixed liquid of phenol and hydrogen peroxide hydroxylation reaction provided by the present invention not only greatly reduces the energy consumption of the product, but also meets the requirements of high-end customers in the market, and also ensures simple operation and stable production, which is specifically described as follows:

[0054] (1) Since the water content of the reaction liquid is as high as 20-60%, dehydration consumes a lot of energy. The dehydration of the present invention adopts double-effect flash dehydration, double-effect distillation dehydration, and single-effect distillation dehydration and dephenolization to achieve energy saving.

[0055] (2) The first-effect dehydration and dephenolization tower uses normal pressure operation to dehydrate and dephenolize at the same time. The higher temperature gas phase obtained at the top of the tower is directly used as a double-effect dehydration heat source, so that the latent heat of water and phenol vaporization can be fully utilized; the phenol is removed and returned to the reaction system. Because the reaction system needs to add phenol-containing water process, it only needs to control the phenol content to be greater than 90% to meet the production demand, which greatly reduces the difficulty of dephenolization and equipment investment.

[0056] (3) After dephenolization, the catechol is distilled from the top of the catechol removal tower to a catechol crude distillation tower, thereby avoiding contamination by tar carbonization and cracking during decoking. The catechol is then purified by a refining tower, and the product content is higher than 99.7%, and there is no trace element impurity caused by tar cracking, thus meeting the requirements for the use of high-end pharmaceutical products and military products in the market.

[0057] (4) In the decoking process, the present invention adds a solvent with a boiling point of >350°C to the tar for dilution and dissolution after the material is roughly decoked, thereby reducing the viscosity of the tar, improving its fluidity, and making it suitable for falling film evaporator film spreading. Moreover, the content of hydroquinone in the tar after evaporation is less than 1%, and the tar has good fluidity after evaporation. At the same time, the falling film evaporator requires less investment than the scraped evaporator and has lower equipment requirements.

[0058] (5) The use of a distillation tower to purify the resorcinol-rich material is easier to operate and control than melt crystallization, requires fewer auxiliary equipment, and does not require a refrigerant with harsh conditions required for melt crystallization. In addition, the present invention uses intermittent distillation equipment and operation, which is suitable for small amounts of raw materials and overcomes the disadvantages of continuous distillation that the melting points are close and the products are difficult to separate.

[0059] (6) For the refining tower rich in hydroquinone, intermittent distillation equipment and operation are used to overcome the shortcomings of the direct flake formation and insufficient purity of the finished product extracted from the continuous distillation tower; compared with the continuous distillation tower, the further melt crystallization of hydroquinone extracted is easier to operate and control, with less auxiliary equipment and no need for refrigerant with harsh conditions required for melt crystallization.

[0060] (7) The phenol-containing water adopts a multi-stage continuous centrifugal extraction and extract phase distillation method to recover phenol and solvent, which greatly improves the extraction efficiency and can reduce the phenol content to below 400PPm. The extract phase is separated by a distillation tower, and phenol is distilled from the upper part of the tower. The phenol purity is relatively high and returning to the raw material tank does not affect the hydroxylation reaction of phenol and hydrogen peroxide.

[0061] Compared with the traditional technology, the separation and purification method of the present invention reduces the energy consumption from about 0.5 standard coal per ton of product of the traditional technology to about 0.46 standard coal per ton of product. In terms of product purity, the purity of phenol and three kinds of diphenols is increased from the traditional ≥98% to ≥99%, and the purity of catechol is increased to ≥99.7%, which meets the requirements of high-end customers for products; the tar yield is increased from the traditional ≤5% to ≤3%. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 The present invention is a schematic diagram of the separation and purification process of the mixed liquid of the hydroxylation reaction of phenol and hydrogen peroxide in an embodiment of the present invention. DETAILED DESCRIPTION

[0063] The present invention is described in detail below in conjunction with the embodiments and the accompanying drawings. However, the following embodiments should not be considered as limiting the scope of the present invention.

[0064] Example 1

[0065] The raw material liquid composed of 57% phenol, 33% water, 6.2% catechol, 3.2% hydroquinone, 0.2% resorcinol and 0.4% tar was treated. The treatment process is shown in Figure 1 .

[0066] (1) Double-effect dehydration

[0067] The raw material liquid is sent to the double-effect dehydration flash evaporator at a flow rate of 480Kg / h. The operating conditions of the double-effect dehydration flash evaporator are a pressure of 30Kpa and a temperature of 70-80°C. The raw material liquid is evaporated and condensed in the double-effect dehydration flash evaporator to obtain an aqueous solution containing 7.5% phenol. The residual liquid of the double-effect dehydration flash evaporator is sent to the first-effect dehydration flash evaporator. The evaporated gas phase of the material in the first-effect dehydration flash evaporator enters the shell side of the double-effect dehydration flash evaporator heater, and after condensation, an aqueous solution containing 7.8% phenol is obtained. The operating conditions of the first-effect dehydration flash evaporator are a pressure of 50Kpa and a temperature of 80-90°C. The residual liquid of the first-effect dehydration flash evaporator is sent to the second-effect dehydration tower. The upper gas phase of the second-effect dehydration tower enters the shell side of the heater of the first-effect flash evaporator, and after condensation, an aqueous solution containing 9.8% phenol is obtained. The bottom liquid of the tower is sent to the first-effect dehydration and dephenolization tower. The operating conditions of the second-effect dehydration distillation tower are a pressure of 70Kpa, a pressure difference of 2Kpa, a temperature in the tower of 90-140°C, and a reflux ratio of 1.0.

[0068] The phenol-containing aqueous solution obtained in the dehydration process is subjected to subsequent centrifugal extraction treatment to obtain a phenol finished product: the phenol-containing water with a phenol content of 8.0% and a flow rate of 172 kg / h is sent to a three-stage centrifugal extractor, N, N-di(1-methylheptyl)hexanamide is used as a solvent, the centrifugal speed is adjusted to 3000 rpm, the ratio of the solvent to the phenol-containing water is 0.3, the operating temperature is 40°C, phenol-containing waste water is discharged from the upper part of the centrifuge, and the phenol concentration is 420 ppm after detection. The extraction phase enters the extraction distillation, and the phenol content of the distilled water from the upper part of the extraction distillation tower is detected to be 98%, and the solvent content of the bottom of the tower is 98%, which is returned to the centrifugal extraction. The operating conditions of the extraction distillation tower are a pressure of 3 Kpa, a pressure difference between the top and the bottom of the tower of 2 Kpa, and a reflux ratio of 2.0.

[0069] (2) Single-effect dehydration and dephenolization

[0070] The upper gas phase of the first-effect dehydration and phenol removal tower enters the shell side of the heater of the second-effect dehydration tower, and after condensation, an aqueous solution containing 15% phenol is returned to the reaction system, and a 90% phenol content is withdrawn from the upper side line and returned to the reaction system. The operating conditions of the first-effect dehydration and phenol removal tower are atmospheric pressure, a pressure difference of 2Kpa, a tower temperature of 130-200°C, and a reflux ratio of 2.0.

[0071] (3) Catechol process

[0072] The bottom liquid of the first-effect dehydration dephenolization tower is sent to the catechol removal tower at a flow rate of 49Kg / h. The operating conditions of the catechol removal tower are pressure 4Kpa, pressure difference 2Kpa, tower temperature 170-215°C, and reflux ratio 2.5; catechol with a phenol content of 98.5% is taken out from the top of the catechol removal tower, and catechol with a phenol content of 92% is taken out from the upper side line and sent to the catechol crude distillation tower at a flow rate of 30.9Kg / h. The operating conditions of the catechol crude distillation tower are pressure 4Kpa, pressure difference 2K pa, the temperature in the tower is 140-180℃, the reflux ratio is 2.0, the bottom liquid of the catechol crude distillation tower is sent to the catechol refining tower at a flow rate of 28.9Kg / h, the operating conditions of the catechol refining tower are pressure 4Kpa, pressure difference 2Kpa, the temperature in the tower is 140-180℃, the reflux ratio is 2.5, the top distillate is 27Kg / h, the content is 99.8% catechol, the bottom liquid level is 60%, and when the catechol content is 29.6%, it is transferred to the de-catecholization tower.

[0073] (4) Defocusing

[0074] The bottom liquid of the decoking tower is fed to the decoking crude distillation tower at a flow rate of 18Kg / h. The operating conditions of the decoking crude distillation tower are pressure 4Kpa, pressure difference 2Kpa, temperature in the tower 170-210℃, reflux ratio 1.0, and the top distillate is rich in 93% hydroquinone and is fed to the mixed phenol tower at a flow rate of 16Kg / h. The tar in the bottom liquid is fed to the tar dilution kettle at a flow rate of 2.2Kg / h.

[0075] The tar dilution kettle adds solvent with a ratio of 1:3 to tar. After dilution, the tar is sent to the falling film evaporator. The gas phase at the top of the falling film evaporator returns to the decoking crude distillation tower, and the tar at the bottom is discharged to the tar treatment process. The operating conditions of the falling film evaporator are pressure 2Kpa and temperature 170-210℃.

[0076] (5) Resorcinol / hydroquinone separation

[0077] The upper part of the resorcinol / hydroquinone separation tower is extracted and sent to the catechol removal tower at a flow rate of 0.2Kg / h. The side distillate contains 90% resorcinol and is sent to the resorcinol distillation tower at a flow rate of 0.9Kg / h. The operating conditions of the mixed diphenol tower are pressure 3Kpa, pressure difference 2Kpa, tower temperature 170-210℃, and reflux ratio 2.6.

[0078] The resorcinol tower is operated intermittently and the unqualified resorcinol is distilled from the top of the tower and returned to the mixed phenol tower. The distillate content is detected to be 99.1%, and it is sent to the resorcinol receiving tank at 0.75Kg / h. The liquid level of the tower bottom is 60%. The resorcinol content is detected to be 29% and transferred to the mixed phenol tower; the operating conditions of the resorcinol tower are pressure 3Kpa, pressure difference 2Kpa, tower temperature 170-210℃, and reflux ratio 3.2.

[0079] The bottom of the isoquinone / hydroquinone separation tower is fed into the hydroquinone distillation tower at a flow rate of 15.5Kg / h, and the unqualified hydroquinone is distilled out in the gap above the tower and returned to the isoquinone / hydroquinone separation tower. The distillate is tested for hydroquinone content of 99.1%, and is fed into the hydroquinone receiving tank at a flow rate of 0.75Kg / h. The bottom liquid level is 60%, and 28.6% of the hydroquinone is detected and transferred to the polyphenol tower. The operating conditions of the hydroquinone tower are pressure 3Kpa, pressure difference 2Kpa, tower temperature 170-220°C, and reflux ratio 3.2.

[0080] Example 2

[0081] The raw material liquid composed of 39.4% phenol, 50% water, 3.0% catechol, 6.6% hydroquinone, 0.3% resorcinol and 0.7% tar was treated. The treatment process is shown in Figure 1 .

[0082] (1) Double-effect dehydration

[0083] The raw material liquid is sent to the double-effect dehydration flash evaporator at a flow rate of 480Kg / h. The operating conditions of the double-effect dehydration flash evaporator are a pressure of 30Kpa and a temperature of 70-80°C. The raw material liquid is evaporated and condensed in the double-effect dehydration flash evaporator to obtain an aqueous solution containing 7.2% phenol. The residual liquid of the double-effect dehydration flash evaporator is sent to the first-effect dehydration flash evaporator. The vapor phase of the material evaporated in the first-effect dehydration flash evaporator enters the shell side of the double-effect dehydration flash evaporator heater. After condensation, an aqueous solution containing 7.7% phenol is obtained. The operating conditions of the first-effect dehydration flash evaporator are a pressure of 50Kpa and a temperature of 80-90°C. The residual liquid of the first-effect dehydration flash evaporator is sent to the second-effect dehydration tower. The upper gas phase of the second-effect dehydration tower enters Enter the shell side of the heater of the first-effect flash evaporator, and after condensation, an aqueous solution containing 9.8% phenol is obtained. The bottom liquid of the tower is sent to the first-effect dehydration and phenol removal tower. The operating conditions of the second-effect dehydration and distillation tower are as follows: pressure 70Kpa, pressure difference 2Kpa, temperature in the tower 90-140°C, and reflux ratio 0.5; the upper gas phase of the first-effect dehydration and phenol removal tower enters the shell side of the heater of the second-effect dehydration tower, and after condensation, an aqueous solution containing 15% phenol is obtained and returned to the reaction system. The phenol content of 90.2% is recovered from the upper side line and returned to the reaction system. The operating conditions of the first-effect dehydration and phenol removal tower are as follows: pressure is normal pressure, pressure difference 2Kpa, temperature in the tower 130-200°C, and reflux ratio 1.5.

[0084] The phenol-containing aqueous solution obtained in the dehydration process is subjected to subsequent centrifugal extraction treatment to obtain a phenol finished product: the phenol-containing water with a phenol content of 7.5% and a flow rate of 100 kg / h is sent to a three-stage centrifugal extractor, N, N-di(1-methylheptyl)hexanamide is used as a solvent, the centrifugal speed is adjusted to 4000 rpm, the ratio of the solvent to the phenol-containing water is 0.4, the operating temperature is 40°C, phenol-containing waste water is discharged from the upper part of the centrifuge, and the phenol concentration is 350 ppm after detection. The extraction phase enters the extraction distillation, the phenol content of the distilled water from the upper part of the extraction distillation tower is detected to be 98%, the solvent content of the bottom of the tower is 98%, and the centrifugal extraction is applied. The operating conditions of the extraction distillation tower are a pressure of 3 Kpa, a pressure difference of 2 Kpa between the top and the bottom of the tower; and a reflux ratio of 2.5.

[0085] (2) Single-effect dehydration and dephenolization

[0086] The bottom liquid of the first-effect dehydration and dephenolization tower is fed into the decatecholization tower at a flow rate of 51.3 kg / h. The operating conditions of the decatecholization tower are pressure 4 Kpa, pressure difference 2 Kpa, tower temperature 170-215 ° C, and reflux ratio 2.7.

[0087] (3) Catechol process

[0088] The upper part of the catechol removal tower produces 98.6% phenol, and the upper side line produces 90.6% catechol, which is fed into the catechol crude distillation tower at a rate of 14.7 kg / h. The operating conditions of the catechol crude distillation tower are as follows: pressure 4 Kpa, pressure difference 2 Kpa, temperature in the tower 140-180° C., reflux ratio 2.8. The bottom liquid of the catechol crude distillation tower is fed into the catechol refining tower at a rate of 14.2 kg / h. The operating conditions of the catechol refining tower are as follows: pressure 4 Kpa, pressure difference 2 Kpa, temperature in the tower 140-180° C., reflux ratio 2.3, 13 kg / h of catechol is distilled from the top of the tower, with a content of 99.8% catechol, and a bottom liquid level of 60%. 28.7% of the catechol is detected and transferred to the catechol removal tower.

[0089] (4) Defocusing

[0090] The bottom liquid of the decoking tower is fed to the decoking crude distillation tower at a flow rate of 36.6 Kg / h. The operating conditions of the decoking crude distillation tower are pressure 4 Kpa, pressure difference 2 Kpa, temperature in the tower 170-220 ° C, reflux ratio 1.5, and the top distillate is rich in 95% hydroquinone and is fed to the mixed phenol tower at a flow rate of 33.2 Kg / h. The tar in the bottom liquid is fed to the tar dilution kettle at a flow rate of 3.7 Kg / h.

[0091] The tar dilution kettle adds solvent with a ratio of 1:3 to tar. After dilution, the tar is sent to the falling film evaporator. The gas phase at the top of the falling film evaporator returns to the decoking crude distillation tower, and the tar at the bottom is discharged to the tar treatment process. The operating conditions of the falling film evaporator are pressure 2Kpa and temperature 170-220℃.

[0092] (5) Resorcinol / hydroquinone separation

[0093] The upper part of the resorcinol / hydroquinone separation tower is extracted and sent to the catechol removal tower at a flow rate of 0.22 kg / h. The side distillate contains 90.2% resorcinol and is sent to the resorcinol distillation tower at a flow rate of 1.27 kg / h. The operating conditions of the mixed diphenol tower are pressure 3 Kpa, pressure difference 2 Kpa, tower temperature 170-220 ° C, and reflux ratio 3.0.

[0094] The resorcinol tower is operated intermittently and the unqualified resorcinol is distilled from the top of the tower and returned to the mixed phenol tower. The distillate content is detected to be 99.1%, and it is sent to the resorcinol receiving tank at 1.1Kg / h. The liquid level of the tower bottom is 60%. The resorcinol content is detected to be 29% and transferred to the mixed phenol tower; the operating conditions of the resorcinol tower are pressure 3Kpa, pressure difference 2Kpa, tower temperature 170-220℃, and reflux ratio 3.5.

[0095] The bottom of the isoquinone / hydroquinone separation tower is fed into the hydroquinone distillation tower at a flow rate of 30.2Kg / h, and the unqualified hydroquinone is distilled out in the gap above the tower and returned to the isoquinone / hydroquinone separation tower. The distillate is tested for hydroquinone content of 99.1%, and is fed into the hydroquinone receiving tank at 30.5Kg / h. The bottom liquid level is 60%, and 28.6% of the hydroquinone is detected and transferred to the polyphenol tower. The operating conditions of the hydroquinone tower are pressure 3Kpa, pressure difference 2Kpa, tower temperature 170-220°C, and reflux ratio 3.2.

[0096] Compared with the prior art, the above two embodiments have obvious advantages in technical effects, see Table 1 below:

[0097] Table 1 Summary of technical effects of Examples 1 and 2 compared with prior art

[0098]

[0099] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention. These changes and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A separation and purification system for a mixed liquid of a phenol and hydrogen peroxide hydroxylation reaction, characterized in that: It includes a double-effect dehydration flash evaporator, a single-effect dehydration flash evaporator, a double-effect dehydration distillation tower, a single-effect dehydration phenol removal tower, a catechol removal tower, a catechol crude distillation tower, a catechol distillation tower, a tar crude distillation and dilution evaporation component, a resorcinol / hydroquinone separation tower, a resorcinol distillation tower and a hydroquinone distillation tower respectively connected to the upper part and the lower part of the resorcinol / hydroquinone separation tower, and also includes a phenol extraction component. The tar crude distillation and dilution evaporation assembly comprises a tar crude distillation tower, a tar dilution kettle connected to the bottom of the tar crude distillation tower, and a tar evaporator connected to the tar dilution kettle, wherein the top of the tar evaporator is connected to the middle section of the tar crude distillation tower. The gas phase pipe of the first-effect dehydration flash evaporator is connected to the shell side of the double-effect dehydration flash evaporator heater, and the gas phase pipe of the double-effect dehydration distillation tower is connected to the shell side of the first-effect dehydration flash evaporator heater; The distillate pipe at the upper part of the crude tar distillation tower is connected to the resorcinol / hydroquinone separation tower, and the bottom is connected to a stirring dilution kettle with double mechanical seals, and the upper gas phase pipe of the tar evaporator is connected to the middle part of the crude tar distillation tower; The upper distillate pipeline of the resorcinol / hydroquinone separation tower is connected to the feed pipe of the decatecholization tower, and the upper sideline distillate pipeline is connected to the feed port of the resorcinol tower; The upper distillate pipeline of the resorcinol distillation tower is divided into two, one of which is connected to the feed pipe of the catechol removal tower, and the other is connected to the finished product receiving tank, and the bottom pipeline is connected to the feed pipeline of the resorcinol / hydroquinone separation tower; The upper distillate pipeline of the hydroquinone distillation tower is divided into two, one of which is connected to the feed pipe of the isoquinone / hydroquinone distillation tower, and the other is used to receive the finished product. The bottom pipeline is connected to the feed pipeline of the tar crude distillation tower.

2. The separation and purification system according to claim 1, characterized in that: in, The phenol extraction component is composed of a single-stage or multi-stage series-connected centrifugal extractor and an extraction distillation tower.

3. A method for separating and purifying a phenol-hydrogen peroxide hydroxylation reaction mixture using the separation and purification system of claim 1 or 2, wherein the reaction mixture consists of water, phenol, catechol, hydroquinone, resorcinol, and tar, characterized in that: The steps include: (1) Double-effect flash dehydration The reaction mixed liquid is sent to a double-effect dehydration flash evaporator, and the flashed gas phase in the flash evaporator is condensed and the vapor phase in the shell of the heater is heat exchanged to obtain phenolic water. The operating pressure is 25-35Kpa and the operating temperature is 70-80°C; the phenolic water is sent to the extraction process, and the remaining liquid in the flash evaporator is sent to a single-effect dehydration flash evaporator. The flashed gas phase in the first-effect dehydration flash evaporator is used to heat the heat source of the double-effect dehydration flash heater. The flash heater shell side gas phase is heat exchanged to obtain phenolic water, which is sent to the extraction process or partially returned to the double-effect dehydration tower. The operating pressure is 45-55Kpa and the operating temperature is 80-90℃. (2) Double-effect distillation dehydration The double-effect distillation tower receives the bottoms of the first-effect dehydration flash evaporator, with an operating pressure of 70-90Kpa, a temperature in the tower of 90-140°C, a reflux ratio of 0.5-1.0, a pressure difference of 2-4Kpa between the top and the bottom of the tower, and the gas phase at the top of the tower is a heating source for the first-effect flash evaporator heater, and the bottoms of the tower enter the first-effect dehydration and phenol removal tower; (3) Single-effect dehydration and phenol removal The first-effect dehydration and phenol removal tower performs atmospheric distillation process, the temperature in the tower is 130-200°C, the pressure difference between the top and the bottom of the tower is 2-4Kpa, the reflux ratio is 1.5-2.0, the gas phase at the top of the tower is the heat source of the double-effect distillation tower heater, the phenol distilled from the side line at the top of the tower is returned to the reaction system for application, and the bottom of the tower enters the catechol removal tower; (4) Removal of catechol The operating pressure is 4-8Kpa, the temperature in the tower is 170-215℃, the pressure difference between the top and the bottom of the tower is 2-4Kpa, the reflux ratio is 2.5-2.7, the phenol product is distilled from the top of the de-catecholization tower, the crude catechol is distilled from the upper side line, and the bottoms are fed into the tar crude distillation tower; (5) Crude distillation and rectification of catechol The distillate from the upper part of the catechol crude distillation tower is returned to the first-effect dehydration and phenol removal tower, and the bottoms are sent to the catechol refining tower. The catechol finished product is distilled from the upper part of the catechol refining tower, and the bottoms are sent to the catechol removal tower; the operating pressure during crude distillation and rectification is 4-8Kpa, the pressure difference between the tower top and the tower bottom is 2-4Kpa, the temperature in the tower is 140-180℃, and the reflux ratio is 2.0-2.8; (6) Tar crude distillation The tar crude distillation tower receives the bottoms of the de-catecholization tower, the temperature in the tower is 170-220°C, the operating pressure is 2-5Kpa, the pressure difference between the top and the bottom of the tower is 2-4Kpa, and the reflux ratio is 1.0-1.5; the distillate rich in hydroquinone is distilled out from the upper part of the crude distillation tower to go to the isoquinone / hydroquinone separation tower, the bottoms are diluted with a solvent with a boiling point higher than 350°C and then evaporated, the gas phase of the evaporator returns to the tar crude distillation tower, and the bottom liquid phase is sent to the next process of tar treatment; (7) Separation of mixed diphenols The operating pressure of the isoquinone / hydroquinone separation tower is 2-5Kpa, the pressure difference between the top and the bottom of the tower is 2-4Kpa, the temperature in the tower is 170-220°C, the reflux ratio is 2.5-3.0, the upper distillate is returned to the catechol removal tower, the upper side distillate is sent to the isoquinone distillation tower, and the bottom liquid is sent to the hydroquinone distillation tower.

4. The separation and purification method according to claim 3, characterized in that: in, The phenol and hydrogen peroxide hydroxylation reaction mixture comprises 30-70% phenol, 3-9% catechol, 2-9% hydroquinone, 0.2-0.5% resorcinol, 0.2-1.0% tar, and the balance is water.

5. The separation and purification method according to claim 3, characterized in that: in, In step (1), the phenol content in the phenol-containing water obtained by the first double-effect dehydration flash evaporator is 7-10%; When the obtained phenol-containing wastewater is subjected to the extraction process, it is first extracted by a centrifugal extraction device, the extract phase enters the extraction distillation tower for distillation, and the residual phase wastewater enters the next process for sewage treatment; the phenol-containing liquid extracted from the top of the extraction distillation tower is returned to the reaction system for application, and the solvent at the bottom of the tower is returned to the extraction equipment for recycling.

6. The separation and purification method according to claim 5, characterized in that: in, The centrifugal extraction equipment is a single-stage or multi-stage series centrifugal extractor, the centrifugal speed is 3000-5000 rpm, the ratio of extraction solvent to phenolic water is 0.2-0.4, and the operating temperature is 40-50° C.; the extraction solvent is selected from one or more of N,N-mixed alkyl acetamide, N,N-di(1-methylheptyl)hexanamide, trioctylamine, triethyl phosphate, trialkyl tertiary amine, nonanoic acid; The operating conditions of the extractive distillation tower are a pressure of 2-4 KPa, a pressure difference of 2-4 KPa between the top and the bottom of the tower, a phenol content of more than 97% is distilled out from the top of the tower, and a solvent content of more than 98% flowing out from the bottom of the tower is returned to the centrifugal extraction for use.

7. The separation and purification method according to claim 3, characterized in that: in, In step (2), the phenol content in the phenol-containing water distilled from the upper part of the double-effect distillation tower is 7-10%; In step (3), the phenol content in the phenol-containing water distilled from the upper part of the first-effect dehydration and dephenolization tower is 10-20%, and the phenol content in the upper side distillate is 80-95%; In step (4), the decatecholating tower distills out a phenol finished liquid having a phenol content greater than 98% at the top, distills out a catechol liquid having a catechol content greater than 90% at the top side line, and the heavy component at the bottom of the tower is rich in hydroquinone; In step (5), the catechol product distilled from the top of the catechol refining tower has a purity greater than 99.5%; when the catechol content of the bottom component is less than 30%, it is transferred to the catechol removal tower; In step (6), the distillate from the upper part of the crude tar distillation tower is rich in light components of hydroquinone, and the bottoms are tar with a hydroquinone content of 5-10%; the diluent of the bottoms is selected from one or a mixture of m-terphenyl, terpyridine, phenylmethyl silicone oil, and high carbon white oil; The tar evaporator is a falling film evaporator with an operating pressure of 1-3Kpa. The gas phase at the top of the evaporator returns to the tar crude distillation tower, and the tar is discharged from the bottom to the next process. The total content of dihydroxybenzene products in the discharged tar is less than 2%; In step (7), the resorcinol content in the side distillate from the top of the resorcinol / hydroquinone separation tower is greater than 90%, and is sent to the resorcinol distillation tower, and the bottom liquid is sent to the hydroquinone distillation tower.

8. The separation and purification method according to claim 3, characterized in that: in, In step (7), the resorcinol distillation tower is a batch distillation tower, the operating pressure is 2-5Kpa, the pressure difference between the tower top and the tower bottom is 2-4Kpa, the temperature in the tower is 170-220°C, and the reflux ratio is 3.0-3.5; the unqualified light components distilled out of the tower top gap are returned to the resorcinol / hydroquinone separation tower, and when the resorcinol content is greater than 99%, it is sent to the resorcinol receiving tank as a qualified finished product; when the resorcinol content in the tower bottom liquid is less than 30%, it is transferred to the resorcinol / hydroquinone separation tower; The operating conditions of the hydroquinone distillation tower are the same. The unqualified components distilled from the upper part are returned to the meta / hydroquinone separation tower. When the hydroquinone content is greater than 99%, it is sent to the hydroquinone receiving tank as a qualified finished product. The hydroquinone content in the bottom liquid is less than 30%, and it is transferred to the tar crude distillation tower.

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