METHOD For TREATING PRODUCTION WASTEWATER FROM THE PREPARATION OF PROPYLENE OXIDE BY CO-OXIDATION

Abstract

Provided is a method for treating production wastewater from the preparation of propylene oxide by co-oxidation, where the production wastewater includes a first portion of wastewater having a peroxide content of 2000 mg / L or more and a second portion of wastewater having a peroxide content of 50 mg / L or less. The method includes the following steps: (1) subjecting the first portion of wastewater to a catalytic oxidation treatment to obtain effluent wastewater; (2) rectifying mixed wastewater obtained by mixing the effluent wastewater with the second portion of wastewater by a first rectifying column to obtain a first overhead material and first concentrated wastewater as a first column kettle liquid, rectifying the first column kettle liquid by a second rectifying column to obtain a second overhead material and second concentrated wastewater as a second column kettle liquid, and rectifying the first overhead material and the second overhead material by a third rectifying column for oil-water separation; (3) subjecting the second column kettle liquid to an incineration treatment; and (4) subjecting the third column kettle liquid to a biochemical treatment. The treatment method is suitable for treating wastewater which is high in salinity, organic matter content and peroxide content, and can remove the peroxides therein, improve the biodegradability of wastewater, and reduce the difficulty and cost of wastewater treatment.

Description

Treatment method of propylene oxide production wastewater prepared by co-oxidation method TECHNICAL FIELD

[0001] The present application belongs to the field of wastewater treatment, in particular to a treatment method of propylene oxide production wastewater prepared by co-oxidation method. BACKGROUND

[0002] Propylene oxide (PO) is a colorless transparent, low boiling point flammable liquid, which is the third type of propylene derivative besides acrylonitrile and polypropylene, and plays an important role in organic chemical production. At present, the main methods for producing propylene oxide in China include chlorohydrination method, co-oxidation method (including co-production of methyl tert-butyl ether by co-oxidation of thiobarbituric acid, i.e. POMTBE; co-production of styrene by co-oxidation of ethylbenzene, i.e. POSM; cumene hydroperoxide method, i.e. POCHP), and direct oxidation method (including HPPO method using hydrogen peroxide as oxidant).

[0003] With the increasingly stringent requirements of energy saving, environmental protection and low-carbon production in China, the traditional chlorohydrination method production enterprises with serious pollution and the development space are increasingly restricted. Although the HPPO method has the advantages of mild reaction conditions and no pollution, the cost of catalyst and hydrogen peroxide is high. The co-oxidation method has co-production of isobutane or ethylbenzene in some processes, which is suitable for large-scale production. In summary, the POSM and POCHP processes of the co-oxidation method have more development value.

[0004] The wastewater produced by the PO production process represented by POSM and POCHP has the characteristics of large water quantity, high salt and organic matter content. At the same time, some streams of wastewater contain peroxides which are easy to decompose, and the safety risk is large. The methods commonly used in industry to treat the above wastewater are usually sodium thiosulfate reduction process, alkali decomposition process, fluidized bed catalytic decomposition and enzyme decomposition process to treat wastewater containing peroxides. After removing the peroxides, the wastewater is mixed with the rest of the wastewater from the device and then incinerated. However, the above methods have the disadvantages of low peroxide removal efficiency, long reaction time, high operation cost and large amount of oxygen generated, which are difficult to fundamentally improve the safety and stability of the process; at the same time, the direct incineration of wastewater has high cost, and valuable components in the wastewater cannot be recovered, resulting in an increase in production unit consumption.

[0005] At present, there is little research on the wastewater treatment process of POSM and POCHP processes, and there is no relatively mature system process. Therefore, it is urgent to develop a treatment process suitable for treating wastewater with high salt, high organic matter content and containing peroxides.

[0006] SUMMARY

[0007] Therefore, the present application aims to provide a treatment method for co-oxidation process propylene oxide production wastewater, which is suitable for treating wastewater with high salt content, high organic matter content and peroxide content, can remove peroxide in co-oxidation process propylene oxide production wastewater, improve the biodegradability of wastewater, and reduce the difficulty and cost of wastewater treatment.

[0008] To achieve the above object, the present application adopts the following technical solution:

[0009] A treatment method for co-oxidation process propylene oxide production wastewater, the production wastewater includes a first part of wastewater with peroxide content of 2000 mg / L or more and a second part of wastewater with peroxide content of less than 50 mg / L, the treatment method includes the following steps:

[0010] (1) The first part of wastewater is pre-treated by catalytic oxidation to remove peroxide therein, and the effluent wastewater is obtained;

[0011] (2) The mixed wastewater obtained by mixing at least part of the effluent wastewater and the second part of wastewater is input into a multi-effect evaporation unit for treatment, the multi-effect evaporation unit includes:

[0012] A first rectifying column for rectifying the input mixed wastewater to concentrate the mixed wastewater, obtaining a first column top material from the column top and a first column bottom liquid as a primary concentrated wastewater from the column bottom;

[0013] A second rectifying column for rectifying the first column bottom liquid from the first rectifying column to further concentrate the first column bottom liquid, obtaining a second column top material from the column top and a second column bottom liquid as a secondary concentrated wastewater (i.e., concentrated wastewater) from the column bottom;

[0014] A third rectifying column for rectifying the first column top material from the first rectifying column and the second column top material from the second rectifying column to separate oil and water, obtaining an oil phase (i.e., light oil removal phase) as a third column top material from the column top and an aqueous phase (i.e., light column bottom wastewater) as a third column bottom liquid from the column bottom;

[0015] (3) The second column bottom liquid is incinerated to obtain a salt residue;

[0016] (4) The third column bottom liquid is biologically treated to remove organic matter therein.

[0017] The process for preparing propylene oxide by co-oxidation method of the present application includes ethylbenzene co-oxidation method for co-producing styrene (i.e. POSM method) and cumene hydroperoxide method (i.e. POCHP method), which, as understood by those skilled in the art, mainly includes peroxidation unit, epoxidation unit and refining unit, etc. The production wastewater of propylene oxide by co-oxidation method of the present application refers to the production wastewater of propylene oxide by general co-oxidation method (including POSM method and POCHP method), for example, the peroxidation tail gas condensate aqueous phase from peroxidation tail gas absorption tower / condensate tank and the peroxide caustic washing wastewater from peroxide caustic washing settling tank as the first part of wastewater; the ethylbenzene caustic washing wastewater, styrene caustic washing wastewater, vacuum system condensate, propylene recovery system water separation and PO refining system water washing aqueous phase as the second part of wastewater. The process for preparing propylene oxide by POSM method can be found in "Technical Progress and Market Analysis of Propylene Oxide Production", Classification Number: F426.7, TQ223.26; Chen Lu, China Petroleum Chemical Industry Co., Ltd., Shanghai Petroleum Chemical Industry Research Institute.

[0018] The content of peroxide is calculated based on the content of hydrogen peroxide when the catalytic oxidation treatment of step (1) is performed; preferably, the content of peroxide in the first part of wastewater is 2000-28000 mg / L, preferably 3000-25000 mg / L; COD≤100000 mg / L, preferably COD≤80000 mg / L. Preferably, the catalytic oxidation treatment is performed in a catalytic oxidation reactor; the available catalytic oxidation reactor can be a fixed bed reactor.

[0019] When the pH of the material system in the catalytic oxidation reactor is low, it is acidic, which is not conducive to the catalytic oxidation reaction in the catalytic oxidation reactor. Therefore, in an embodiment, the effluent wastewater is partially recycled to the inlet of the catalytic oxidation reactor, and the recycling ratio is 1-5. The recycling ratio refers to the ratio of the amount of effluent wastewater recycled to the catalytic oxidation reactor to the total amount of effluent wastewater. Preferably, an alkaline solution (such as NaOH solution) is added to the recycled portion of the effluent wastewater to adjust its pH value, so that it is transported with the portion of the effluent wastewater to the catalytic oxidation reactor to increase the pH of the material system in the catalytic oxidation reactor, promote the catalytic oxidation reaction, and improve the reaction efficiency of the catalytic oxidation reaction. Further preferably, the amount of alkaline solution (such as NaOH solution) added to the recycled portion of the effluent wastewater is sufficient to increase the pH of the material system in the catalytic oxidation reactor to 6-13, preferably 9-10, to further improve the reaction efficiency of the catalytic oxidation reaction. Further preferably, the concentration of the NaOH solution is 20-40 wt%, such as 24 wt%, 28 wt%, 32 wt%, and 36 wt%. The partial recycling of the effluent wastewater can dilute the concentration of hydrogen peroxide in the feed wastewater, thereby improving the stability of the catalytic oxidation reactor. On the other hand, the addition of alkali in the recycling stream has less effect on the pH fluctuation in the catalytic decomposition reactor.

[0020] In an embodiment, the catalyst used in the catalytic oxidation treatment is a compounded catalyst of MnO2 and NiO, wherein the mass ratio of MnO2 to NiO is (0.5-2):1, such as 1:1, 1.2:1, and 1.5:1. The compounded catalyst of MnO2 and NiO can be obtained by mixing manganese nitrate and nickel nitrate in a certain ratio and calcining, and the calcination temperature is 500-600°C, and the calcination time is 1.5-2.5h. -1 -1 .

[0021] ​In the present application, the first part of wastewater is subjected to catalytic oxidation treatment alone, so as to make the peroxide in the first part of wastewater rapidly generate a large amount of active oxygen free radicals [O], thereby catalytically decomposing the refractory organic matter in the first part of wastewater into CO2, H2O, methanol and small molecule carboxylic acid and the like, and converting the peroxide therein into a reaction raw material (such as converting the peroxide EBHP (ethylbenzene hydroperoxide) / CHP (cumene hydroperoxide) into phenethyl alcohol / dimethyl benzyl alcohol), reducing the peroxide concentration while improving the biodegradability of the wastewater, reducing the difficulty and cost of wastewater treatment; at the same time, the disadvantage that the amount of wastewater to be treated by the catalytic oxidation reactor is large when the first part of wastewater and the second part of wastewater are mixed and treated together is avoided, and the material processing capacity of the catalytic oxidation reactor is reduced. The peroxide content in the effluent wastewater obtained after step (1) catalytic oxidation treatment is reduced to 50-1000 mg / L.

[0022] In the present application, the first part of wastewater is subjected to catalytic oxidation treatment alone, so as to make the peroxide in the first part of wastewater rapidly generate a large amount of active oxygen free radicals [O], thereby catalytically decomposing the refractory organic matter in the first part of wastewater into CO2, H2O, methanol and small molecule carboxylic acid and the like, and converting the peroxide therein into a reaction raw material (such as converting the peroxide EBHP (ethylbenzene hydroperoxide) / CHP (cumene hydroperoxide) into phenethyl alcohol / dimethyl benzyl alcohol), reducing the peroxide concentration while improving the biodegradability of the wastewater, reducing the difficulty and cost of wastewater treatment; at the same time, the disadvantage that the amount of wastewater to be treated by the catalytic oxidation reactor is large when the first part of wastewater and the second part of wastewater are mixed and treated together is avoided, and the material processing capacity of the catalytic oxidation reactor is reduced. The peroxide content in the effluent wastewater obtained after step (1) catalytic oxidation treatment is reduced to 50-1000 mg / L.

[0023] The peroxide CHP (cumene hydroperoxide) exists in the production wastewater of preparing propylene oxide by the process of POCHP. The cumene is the raw material of the peroxidation unit in the process of POCHP; the dimethyl benzyl alcohol converted from the peroxide CHP returns to the refining unit in the process of POCHP for refining and hydrogenolysis to obtain the cumene; the cumene returns to the peroxidation unit in the process of POCHP as the raw material, or is output as a byproduct for storage, use or sale. The method for treating the production wastewater of preparing propylene oxide by the co-oxidation method of the application can additionally recover 130 kg / h of cumene, and the economic benefit of one year is 8.32 million yuan according to the system operation of 8000 h per year and the market unit price of 8000 yuan / t of cumene. Therefore, the directional conversion of the peroxide CHP (cumene hydroperoxide) into dimethyl benzyl alcohol helps to reduce the capital consumption of preparing propylene oxide by the process of POCHP, which is equivalent to reducing the cumene consumption. The recovery rate of the peroxide CHP (cumene hydroperoxide) can reach more than 80% (molar percentage), or even more than 90%, and the loss is very small.

[0024] Therefore, the conversion of the peroxide in the first part of the wastewater into the reaction raw material (such as the directional conversion of the peroxide EBHP (ethylbenzene hydroperoxide) / CHP (cumene hydroperoxide) into phenethyl alcohol / dimethyl benzyl alcohol) helps to reduce the ethylbenzene / cumene consumption of preparing propylene oxide by the co-oxidation method.

[0025] When the step (2) is performed, the COD of the mixed wastewater obtained by mixing the outflow wastewater and the second part of the wastewater is less than or equal to 50000 mg / L, preferably 10000-30000 mg / L; the pH value is 5-12, preferably 8-10; and the salt content is 1-20 wt%, preferably 5-10 wt% (the salt herein includes sodium formate, sodium acetate and sodium benzoate, etc.).

[0026] The mixed wastewater is subjected to rectification treatment in the first rectification tower, most of the water and a small amount of organic substances in the wastewater are raised to the top of the tower to form a first overhead material, and the remaining water and salts are dropped to the bottom of the tower to form a first tower bottom liquid; the first tower bottom liquid is subjected to rectification treatment in the second rectification tower, most of the water and a small amount of organic substances in the wastewater are raised to the top of the tower to form a second overhead material, and the remaining water and salts are dropped to the bottom of the tower to form a second tower bottom liquid; the first overhead material from the first rectification tower and the second overhead material from the second rectification tower are subjected to rectification treatment in the third rectification tower, most of the organic substances are raised to the top of the tower to form a third overhead material (i.e., a light oil removal phase), and most of the water and a small amount of organic substances are dropped to the bottom of the tower to form a third tower bottom liquid (i.e., a light tower bottom wastewater, which contains more than 99.9 wt% of water). In the POSM process, the aforementioned organic substances mainly include phenylethanol, phenylethanone, ethylbenzene, styrene, small molecule aldehydes, and small molecule alcohols; in the POCHP process, the aforementioned organic substances mainly include dimethylbenzyl alcohol, cumene, methylstyrene, small molecule aldehydes, and small molecule alcohols.

[0027] Preferably, the tower bottom reboiler of the first rectification tower uses the third overhead material of the third rectification tower as a heat source to heat and reboil the material in the first rectification tower, and the third overhead material is cooled, preferably to 125-130°C. Preferably, the operating temperature of the first rectification tower is 100-150°C, such as 110-130°C; the operating pressure is 0.1-0.5 MPa, preferably 0.1-0.2 MPa; and the concentration ratio is 1.2-2, preferably 1.4-1.6. Preferably, the reflux ratio of the first rectification tower is 0.2-5, such as 1-2.

[0028] In the present application, the operating temperature of each rectification tower refers to the tower bottom temperature, and further limitation thereof facilitates the process control in the operation process of the present application. The change in the composition of wastewater caused by process fluctuation may result in a change in the tower top temperature, and therefore the tower top temperature has no guiding significance, which is not limited in the present application.

[0029] Preferably, the tower bottom reboiler of the second rectification tower uses the first overhead material of the first rectification tower as a heat source to heat and reboil the material in the second rectification tower, and the first overhead material is cooled, preferably to 100-105°C. Preferably, the operating temperature of the second rectification tower is 60-90°C, such as 70-80°C; the operating pressure is 20-80 kPa, preferably 30-50 kPa; and the concentration ratio is 1.5-5, preferably 2-4. Preferably, the reflux ratio of the second rectification tower is 0.2-5, such as 1-2. In the obtained second tower bottom liquid, COD is greater than 10 5 mg / L, and the salt content is 5-40 wt%.

[0030] In the present application, the concentration ratio refers to the flow ratio of the feed to the column bottom liquid of the corresponding rectifying column. For example, the concentration ratio of the first rectifying column refers to the flow ratio of the feed to the first column bottom liquid, i.e. the flow ratio of the mixed wastewater to the first column bottom liquid; the concentration ratio of the second rectifying column refers to the flow ratio of the feed to the second column bottom liquid, i.e. the flow ratio of the first column bottom liquid to the second column bottom liquid.

[0031] In the first rectifying column and the second rectifying column, since the acid possibly present in the wastewater is mainly formic acid and acetic acid, and the boiling points of formic acid and acetic acid are between water and the main organic substances (such as phenethyl alcohol, ethylbenzene, acetophenone, etc.) in the wastewater, the acid may be enriched in the middle and upper parts of the column, thereby causing corrosion to the equipment. In an embodiment, an alkaline solution (such as NaOH solution) is supplemented into the column from the upper part of the first rectifying column and the second rectifying column, respectively, to neutralize the acid possibly enriched in the middle and upper parts of the column, thereby avoiding corrosion to the equipment. Preferably, the concentration of the NaOH solution supplemented into the first rectifying column and the second rectifying column is 20-40 wt%, such as 24 wt%, 28 wt%, 32 wt% and 36 wt%, and the mass ratio of the added amount to the wastewater is 0.001-0.01, preferably 0.002-0.004, such as 0.003; the wastewater is the wastewater produced in the preparation of propylene oxide by the co-oxidation method. The supplementation of the alkaline solution can neutralize the acid possibly enriched in the middle and upper parts of the first rectifying column and the second rectifying column, thereby avoiding corrosion to the equipment.

[0032] Preferably, the column bottom reboiler of the third rectifying column uses steam as the heat source to heat and reboil the material in the third rectifying column. Preferably, the operating temperature of the third rectifying column is 120-170°C, such as 130°C, 140°C, 150°C and 160°C; the operating pressure is 0.1-1 MPa, preferably 0.3-0.5 MPa; and the reflux ratio is 10-50, preferably 20-30. In the obtained third column bottom liquid, COD < 2000 mg / L and B / C > 0.3. B / C refers to the biodegradability, wherein BOD refers to the biochemical oxygen demand, which is the amount of oxygen required for the biodegradation of organic matter in water, and is an index of the biodegradability of water; COD refers to the chemical oxygen demand, which is the amount of oxygen consumed in the determination of organic matter in water by potassium dichromate, and directly reflects the content of organic matter in water; the larger the value of B / C, the better the biodegradability of water. Preferably, the feed of the third rectifying column is preheated (preferably to 128-133°C) by a heat exchanger using the third column bottom liquid as the heat source, so as to achieve a suitable feed temperature, which is beneficial to the separation of the oil phase and the water phase in a short time. It can be understood by those skilled in the art that the heat exchanger is arranged on the feed line of the third rectifying column.

[0033] In the present application, through heat exchange between streams, the energy consumption for concentrating wastewater is reduced, the amount of second tower kettle liquid is reduced, thereby reducing the material processing amount during subsequent incineration treatment, and the construction and operation cost of the subsequent incineration unit is saved.

[0034] In an embodiment, the treatment method further comprises:

[0035] The third tower top material is input into an oil-water separation device for oil-water separation, an oil phase is obtained from the top thereof, and an aqueous phase is obtained from the bottom thereof;

[0036] The oil phase from the oil-water separation device is input into a recovery column for refining, light components (such as light components with a boiling point less than 120°C) are removed from the top of the column, and incineration treatment is performed, recovery column kettle liquid is obtained from the kettle, and is returned as feed to the refining unit in the propylene oxide system prepared by the co-oxidation method for refining treatment.

[0037] In this way, the reaction raw material converted from the peroxide in the first part of wastewater can be extracted and exist in the recovery column kettle liquid, and returned as feed to the refining unit in the propylene oxide system prepared by the co-oxidation method for refining treatment, the material converted from the peroxide in the first part of wastewater is refined by the refining unit in the propylene oxide system prepared by the co-oxidation method to produce by-products for sale or reuse as raw materials, reducing the capital consumption of the propylene oxide system prepared by the co-oxidation method, and reducing the production cost.

[0038] In an embodiment, the aqueous phase from the oil-water separation device can also be returned to flow, so that the aqueous phase from the oil-water separation device is again subjected to oil-water separation, so that the residual organic matter in the aqueous phase is separated out, the organic matter content in the aqueous phase is reduced, and the quality of the oil phase obtained by oil-water separation is improved.

[0039] The operating temperature of the recovery column can be 80-150°C, preferably 90-110°C; the operating pressure is 20-80 kPa, preferably 30-50 kPa; and the reflux ratio is 0.2-5, preferably 1-2.

[0040] Oil-water separation is mainly based on the density difference or chemical property difference between water and oil, and uses gravity sedimentation principle or other physicochemical reactions to remove impurities or complete oil-water separation. The recovery column is also a rectifying column, which uses the different boiling points of different substances in a mixture to separate different substances.

[0041] The present application can be carried out in a incinerator when carrying out the incineration process of step (3). After incineration, the salt residue mainly contains sodium carbonate, and also contains metal elements. The metal elements are generally caused by the falling of furnace bricks of the used equipment, and the types of the metal elements are different according to the used equipment. In the present application, the salt residue mainly contains sodium carbonate, and also contains metal elements Al, Fe, Ni, Ti and Ca. The total content of the metal elements Al, Fe, Ni, Ti and Ca is 10-500 mg / L.

[0042] In one embodiment, the treatment method further comprises transporting the salt residue to a salt residue treatment unit for treatment, and the salt residue treatment unit comprises:

[0043] a dissolving device for dissolving the salt residue to obtain an alkaline salt residue solution with a pH of about 11, in which the metal elements Al, Fe, Ni, Ti and Ca are mostly precipitated under alkaline conditions; preferably, the mass of the dissolving water is 2-10 times, preferably 2-5 times, of the mass of the salt residue during the dissolving process; preferably, the dissolving temperature is 40-60°C; the obtained salt residue solution has a suspended solid content of ≤50 mg / L; those skilled in the art can understand that the dissolving device can be a commonly used dissolving device in the art, such as a salt dissolving tank, a salt dissolving barrel and a salt dissolving pot, etc.;

[0044] a filtering device for filtering the salt residue solution to remove the precipitates therefrom to obtain a filtrate; the filtering device can be a commonly used filtering device in the art, such as a sintered filter, a ceramic membrane filter and a glass fiber filter, etc.; preferably, the filter hole aperture of the filtering device is 0.1-10 μm, preferably 0.5-2 μm. The total content of Al, Fe, Ni, Ti and Ca in the obtained filtrate after removing the precipitates by the filtering device is <0.1 mg / L, which can reach the discharge standard and can be discharged into the sea for treatment.

[0045] In the present application, the water phase obtained as the third column bottom liquid by the oil-water separation of the third rectifying column has a COD of <2000 mg / L, which can reach the biochemical water index requirement and can be sent for biochemical treatment, for example, by artificial aeration oxygen supply and microbial decomposition to remove soluble organic matter and part of the insoluble organic matter in the wastewater, which is a commonly used wastewater treatment method in the art and will not be described in detail herein. After the biochemical treatment of step (4), the third column bottom liquid can remove the organic matter therein to reach the discharge standard.

[0046] The present application has the following beneficial effects:

[0047] (1) The present application adopts catalytic oxidation process and catalytic oxidation reactor to make the peroxide in the first wastewater rapidly generate a large amount of active oxygen free radicals [O], so as to catalytically decompose the refractory organic matter in the first wastewater into CO2, H2O, methanol and small molecule carboxylic acid, etc., and completely convert the peroxide into substances that can be treated as product output or reused as raw material after the refining unit in the co-oxidation process for preparing propylene oxide system (such as the peroxide EBHP (ethylbenzene hydroperoxide) / CHP (cumene hydroperoxide) can be directionally converted into phenethyl alcohol / dimethyl benzyl alcohol), thereby reducing the peroxide concentration, improving the biochemical performance of the wastewater, and reducing the difficulty and cost of wastewater treatment; and the catalytic oxidation process can greatly reduce the oxygen generation amount in the wastewater treatment process, thereby improving the process safety;

[0048] (2) In the treatment method of the present application, when treated in the multi-effect evaporation unit, heat exchange between the streams can be achieved by matching the tower pressure between the first rectifying tower, the second rectifying tower and the third rectifying tower, thereby reducing the wastewater concentration energy consumption, reducing the amount of second tower kettle liquid, and thereby reducing the material processing amount of the incineration system unit, saving the construction and operation cost of the incineration unit; at the same time, the COD content of the wastewater after secondary concentration of the second tower kettle liquid is >10 5 mg / L, and the salt content is 5-40wt%, so that when it is input into the incineration unit for incineration, no additional fuel is needed, thereby saving the fuel cost;

[0049] (3) The third tower kettle liquid separated after the wastewater is concentrated has a COD of <2000mg / L and a B / C of >0.3, which can be directly delivered to the biochemical unit for biochemical treatment, thereby reducing the biochemical treatment cost;

[0050] (4) The oil phase obtained after the oil-water separation of the third tower top material separated after the wastewater is concentrated, and the substances converted from the peroxide (such as the benzyl alcohol / dimethyl benzyl alcohol converted from the peroxide EBHP / CHP) can be extracted and exist in the recovery tower kettle liquid, which can be returned to the refining unit in the co-oxidation process for preparing propylene oxide system for treatment, thereby outputting styrene byproduct / cumene byproduct, which can be stored, used or sold, and the recycling rate is high; the cumene byproduct can also be used as raw material for the peroxidation unit in the propylene oxide system prepared by the POCHP process; therefore, the directional conversion of the peroxide can reduce the unit consumption of ethylbenzene / cumene, thereby saving 8-13 million yuan of funds per year for the co-oxidation process for preparing propylene oxide system;

[0051] (5) The salt residue obtained by incinerating the secondary concentrated wastewater as the second kettle liquid in the incineration unit is sequentially subjected to dissolution and filtration treatment to remove metal elements Al, Fe, Ni, Ti and Ca therein, and the total content of Al, Fe, Ni, Ti and Ca in the obtained filtrate is <0.1 mg / L, reaching the sea discharge standard and being capable of being discharged into the sea for treatment, so that the incinerated salt residue can be avoided to be outsourced as hazardous waste, the solid waste treatment cost is reduced, and the solid waste treatment cost is reduced.

[0052] The term "optional" mentioned in the present application means "containing" or "not containing". BRIEF DESCRIPTION OF DRAWINGS

[0053] Fig. 1 is a process flow diagram of the treatment method of the propylene oxide production wastewater prepared by the co-oxidation method in the embodiment 1 of the present application. DETAILED DESCRIPTION

[0054] The technical scheme of the present application and its effects are further described by specific embodiments. The following embodiments are only used to illustrate the content of the present application, and are not used to limit the protection scope of the present application. Simple changes of the present application by applying the concept of the present application are within the scope of the present application.

[0055] In the following examples and comparative examples, the sources of the main raw materials are as follows:

[0056] In the MnO2 / NiO complex catalyst,

[0057] MnO2, analytical pure, purchased from Xiangtan Maien Trade Co., Ltd.;

[0058] NiO, analytical pure, purchased from Henan Sanwei Chemical Products Co., Ltd.;

[0059] NaOH, industrial grade, purchased from Cangzhou Zhiming Chemical Products Production and Sales Co., Ltd.

[0060] Gas phase analysis conditions:

[0061] Agilent chromatography online determination, using Agilent HP-5ms chromatographic column, vaporization chamber temperature 300℃, detector temperature 300℃; programmed temperature: 50℃ for 2min; 100℃ for 1min; 10℃ / min to 300℃ for 10min.

[0062] Metal element analysis conditions:

[0063] The sample is pretreated by microwave digestion, 800W for 10min, 1200W for 5min, and 5min cooling; the content of metal elements is analyzed by inductively coupled plasma atomic emission spectrometry, power is 1.2kW, atomizer flow is 15L / min, observation height is 8mm, sample injection flushing time is 30s, detection wavelength is 204nm, and pump speed is 7rad / min.

[0064] Example 1

[0065] As shown in Fig. 1, a treatment method of propylene oxide production wastewater prepared by a co-oxidation method is as follows:

[0066] (1) A first part of the wastewater is sent to a catalytic oxidation reactor 1 for catalytic oxidation reaction to remove peroxide therein, and the effluent wastewater from the outlet of the catalytic oxidation reactor 1; a part of the effluent wastewater from the catalytic oxidation reactor 1 is recycled to the catalytic oxidation reactor 1 from its inlet; and an alkaline solution is added to the recycled effluent wastewater to increase the pH of the material system in the catalytic oxidation reactor 1;

[0067] (2) The effluent wastewater is mixed with a second part of the wastewater to obtain mixed wastewater, which is input into a first rectifying column 21 in the multi-effect evaporation unit 2 for rectification treatment to concentrate, and the first column overhead material is obtained from the top of the column, and the first column liquid is obtained from the bottom of the column as once-concentrated wastewater; and the alkaline solution is input into the first rectifying column 21 from the upper part of the first rectifying column 21;

[0068] Then the first column liquid is input into a second rectifying column 22 for rectification treatment to further concentrate, and the second column overhead material is obtained from the top of the column, and the second column liquid is obtained from the bottom of the column as twice-concentrated wastewater; and the alkaline solution is input into the second rectifying column 22 from the upper part of the second rectifying column 22;

[0069] Then the first column overhead material and the second column overhead material are input into a third rectifying column 23 for rectification treatment to separate oil and water, and the oil phase is obtained from the top of the column as the third column overhead material, and the water phase is obtained from the bottom of the column as the third column liquid;

[0070] The first column reboiler uses the third column overhead material as a heat source to heat and reboil the material in the first rectifying column, and to cool the third column overhead material; the second column reboiler uses the first column overhead material as a heat source to heat and reboil the material in the second rectifying column, and to cool the first column overhead material; and the third column reboiler uses steam as a heat source to heat and reboil the material in the third rectifying column;

[0071] The heat exchanger 26 preheats the feed of the third rectifying column 23 by using the third column bottom liquid as heat source;

[0072] The third column top liquid is input into the oil-water separation device 24 for oil-water separation, and an oil phase is obtained from the top of the oil-water separation device 24, and a water phase is obtained from the bottom of the oil-water separation device 24; the water phase from the oil-water separation device 24 is refluxed;

[0073] The oil phase from the oil-water separation device 24 is input into the recovery column 25 for refining, so as to remove light components with a boiling point less than 150℃ from the top of the recovery column 25, and the recovery column bottom liquid is obtained from the column bottom of the recovery column 25;

[0074] The recovery column bottom liquid from the recovery column 25 is returned to the refining unit in the system 7 for preparing propylene oxide by the co-oxidation method;

[0075] (3) The second column bottom liquid is transported to the incineration unit 4 for incineration treatment, and salt slag is obtained; then the salt slag is sequentially subjected to dissolution and filtration treatment, so as to remove metal elements Al, Fe, Ni, Ti and Ca in the salt slag, and a filtrate is obtained; the dissolution treatment is that the salt slag from the incineration unit 4 is transported to the dissolution device 51 for dissolution, so as to obtain an alkaline salt slag dissolution liquid, and the metal elements Al, Fe, Ni, Ti and Ca in the salt slag are precipitated and separated out in an alkaline environment; the filtration treatment is that the salt slag dissolution liquid from the dissolution device 51 is transported to the filtration device 52 for filtration, so as to remove the precipitates in the salt slag dissolution liquid, and the filtrate is obtained;

[0076] (4) The third column bottom liquid is transported to the biochemical unit 3 for biochemical treatment, so as to remove organic matters in the third column bottom liquid;

[0077] The first part of the wastewater refers to the wastewater with a peroxide content greater than 2000 mg / L in the wastewater produced in the system for preparing propylene oxide by the co-oxidation method, and the second part of the wastewater refers to the wastewater with a peroxide content less than 50 mg / L in the wastewater produced in the system for preparing propylene oxide by the co-oxidation method.

[0078] The treatment conditions are as follows:

[0079] The system 7 for preparing propylene oxide by the co-oxidation method is a POSM system from Yantai Wanhua Industrial Park, in which the peroxide content in the first part of the wastewater is 25000 mg / L, and the COD is 80000 mg / L; the peroxide content in the second part of the wastewater is 40 mg / L;

[0080] The catalyst used in the catalytic oxidation reaction is a MnO2 / NiO complex catalyst, and the mass ratio of MnO2 to NiO is 0.5:1; the temperature of the catalytic oxidation reaction is 70℃, and the feed space velocity is 2h -1; the effluent wastewater obtained after the catalytic oxidation reaction is decomposed, the recycling ratio is 2; the alkaline solution input by the part of the recycled effluent wastewater is NaOH solution, the concentration is 32wt%, and the addition amount is to increase the pH of the material system in the catalytic oxidation reactor 1 to 9;

[0081] The mixed wastewater obtained after the effluent wastewater is mixed with the second part of the wastewater has a COD of 30000mg / L, a pH of 10, and a salt content of 5wt%;

[0082] The operating temperature of the first rectifying tower 21 is 110°C, the operating pressure is 0.1MPa, the concentration ratio is 1.4, the reflux ratio is 2, the alkaline solution added from the upper part of the first rectifying tower 21 is NaOH solution with a concentration of 32wt%, and the mass ratio of the addition amount to the wastewater is 0.002;

[0083] The operating temperature of the second rectifying tower 22 is 80°C, the operating pressure is 30kPa, the reflux ratio is 2, the concentration ratio is 2, the alkaline solution added from the upper part of the second rectifying tower 22 is NaOH solution with a concentration of 32wt%, the mass ratio of the addition amount to the wastewater is 0.002, the mass of the water for dissolving is 4 times the mass of the salt residue, the dissolving temperature is 50°C, and the filter used for filtering is a sintered filter with a filter hole diameter of 2μm;

[0084] The operating temperature of the third rectifying tower 23 is 150°C, the operating pressure is 0.5Mpa, the reflux ratio is 20, the operating temperature of the recovery tower 25 is 90°C, the operating pressure is 50kPa, and the reflux ratio is 2.

[0085] The treatment results are as follows:

[0086] The effluent wastewater obtained after the catalytic oxidation reaction is decomposed has a pH of 10 and a peroxide content of 100mg / L; the recovery rate of EBHP directed conversion of phenylethanol is 83%;

[0087] The second tower kettle liquid as the wastewater after secondary concentration has a COD of 1.2×10 5 mg / L and a salt content of 20wt%;

[0088] The total content of metal elements Al, Fe, Ni, Ti and Ca in the salt residue obtained by incinerating the second tower kettle liquid by the incineration system 4 is 50mg / L;

[0089] The suspended solid content in the salt residue solution obtained is 20mg / L;

[0090] The total content of metal elements Al, Fe, Ni, Ti and Ca in the filtrate obtained after filtering treatment is 0.09mg / L;

[0091] COD of the third tank liquid is 1900 mg / L, and B / C is 0.33, which meets the biochemical water index requirements; after biochemical treatment, COD is less than 50 mg / L.

[0092] Example 2

[0093] The treatment method is the same as that in Example 1;

[0094] The treatment conditions are as follows:

[0095] The co-oxidation method for preparing propylene oxide system 7 is a POSM system from Yantai Wanhua Industrial Park, the content of peroxide in the first part of the wastewater is 28000 mg / L, and the COD is 100000 mg / L; the content of peroxide in the second part of the wastewater is 45 mg / L;

[0096] The catalyst used in the catalytic oxidation reaction is a MnO2 / NiO complex catalyst, and the mass ratio of MnO2 to NiO is 2:1; the temperature of the catalytic oxidation reaction is 70°C, and the feed air speed is 2h -1 , the recycling ratio of the outfeed wastewater after catalytic oxidation reaction is 1.5; the alkaline solution input into the part of the recycled outfeed wastewater is NaOH solution, and the concentration is 25wt%, and the addition amount is to increase the pH of the material system in the catalytic oxidation reactor 1 to 10;

[0097] The COD of the mixed wastewater obtained by mixing the outfeed wastewater with the second part of the wastewater is 50000 mg / L, the pH value is 8, and the salt content is 8wt%;

[0098] The operating temperature of the first rectifying column 21 is 130°C, the operating pressure is 0.2MPa, the concentration ratio is 1.5, the reflux ratio is 5, the alkaline solution added from the upper part of the first rectifying column 21 is NaOH solution, the concentration is 25wt%, and the mass ratio of the addition amount to the wastewater is 0.004;

[0099] The operating temperature of the second rectifying column 22 is 90°C, the operating pressure is 20kPa, the concentration ratio is 5, the reflux ratio is 1, the alkaline solution added from the upper part of the second rectifying column 22 is NaOH solution, the concentration is 25wt%, and the mass ratio of the addition amount to the wastewater is 0.004; the mass of the water used for dissolution is 10 times the mass of the salt residue, and the dissolution temperature is 50°C; when filtering, the filter device used is a ceramic membrane filter with a filter hole diameter of 0.5μm;

[0100] The operating temperature of the third rectifying column 23 is 170°C, the operating pressure is 1MPa, and the reflux ratio is 20; the operating temperature of the recovery column 25 is 150°C, the operating pressure is 80kPa, and the reflux ratio is 1.

[0101] The treatment results are as follows:

[0102] The effluent wastewater obtained after catalytic oxidation reaction decomposition has a pH of 9 and a peroxide content of 1000 mg / L; the recovery rate of EBHP directed conversion of phenethyl alcohol is 81%;

[0103] In the second tower kettle liquid which is the wastewater after secondary concentration, the COD is 10 6 mg / L, and the salt content is 40 wt%;

[0104] In the salt residue obtained by incineration of the second tower kettle liquid in the incineration system 4, the total content of metal elements Al, Fe, Ni, Ti and Ca is 500 mg / L;

[0105] In the salt residue solution, the suspended solid content is 50 mg / L;

[0106] In the filtrate obtained after filtration treatment, the total content of metal elements Al, Fe, Ni, Ti and Ca is 0.09 mg / L;

[0107] In the third tower kettle liquid, the COD is 500 mg / L, and the B / C is 0.4, meeting the biochemical water entry index requirements; after biochemical treatment, the COD is <50 mg / L.

[0108] Example 3

[0109] The treatment method is the same as that in Example 1;

[0110] The treatment conditions are as follows:

[0111] The co-oxidation method for preparing propylene oxide system 7 is a POSM system from Yantai Wanhua Industrial Park, and in the wastewater produced by the system, the peroxide content in the first part of the wastewater is 20000 mg / L, and the COD is 10000 mg / L; the peroxide content in the second part of the wastewater is 30 mg / L;

[0112] The catalyst used in the catalytic oxidation reaction is a MnO2 / NiO complex catalyst, and the mass ratio of MnO2 to NiO is 1:1; the temperature of the catalytic oxidation reaction is 20°C, and the feed airspeed is 4h -1 After catalytic oxidation reaction decomposition, the obtained effluent wastewater has a recycling ratio of 1.5; the alkaline solution input into this part of the recycled effluent wastewater is NaOH solution with a concentration of 20 wt%, and the amount of addition is to increase the pH of the material system in the catalytic oxidation reactor 1 to 8;

[0113] In the mixed wastewater obtained by mixing the effluent wastewater with the second part of the wastewater, the COD is 10000 mg / L, the pH value is 12, and the salt content is 1 wt%;

[0114] The operating temperature of the first rectifying tower 21 is 150°C, the operating pressure is 0.5 MPa, the concentration ratio is 1.6, the reflux ratio is 1.5, the basic solution added from the upper part of the first rectifying tower 21 is NaOH solution with a concentration of 20 wt%, and the mass ratio of the added amount to the wastewater is 0.001;

[0115] The operating temperature of the second rectifying tower 22 is 75°C, the operating pressure is 40 kPa, the concentration ratio is 3, the reflux ratio is 5, the basic solution added from the upper part of the second rectifying tower 22 is NaOH solution with a concentration of 20 wt%, and the mass ratio of the added amount to the wastewater is 0.001; the mass of the water used for dissolution is 4.5 times the mass of the salt residue, the dissolution temperature is 50°C, and the filter used for filtration is a glass fiber filter with a filter hole diameter of 1 μm;

[0116] The operating temperature of the third rectifying tower 23 is 140°C, the operating pressure is 0.4 MPa, and the reflux ratio is 10; the operating temperature of the recovery tower 25 is 110°C, the operating pressure is 40 kPa, and the reflux ratio is 1.5.

[0117] The treatment results are as follows:

[0118] The pH of the effluent wastewater obtained after catalytic oxidation reaction and decomposition is 13, and the peroxide content is 200 mg / L; the recovery rate of EBHP directed conversion of phenethyl alcohol is 85%;

[0119] The COD of the second tower kettle liquid as the wastewater after secondary concentration is 300000 mg / L, and the salt content is 5 wt%;

[0120] The total content of metal elements Al, Fe, Ni, Ti and Ca in the salt residue obtained by incineration of the second tower kettle liquid in the incineration system 4 is 100 mg / L;

[0121] The suspended solid content in the obtained salt residue dissolution liquid is 10 mg / L;

[0122] The total content of metal elements in the filtrate obtained after filtration treatment is 0.05 mg / L;

[0123] The COD in the third tower kettle liquid is 1500 mg / L, and the B / C is 0.4, which meets the biochemical water inlet index requirements; after biochemical treatment, the COD is <50 mg / L.

[0124] Example 4

[0125] The treatment method is the same as that in Example 1;

[0126] The treatment conditions are as follows:

[0127] The propylene oxide system 7 prepared by the co-oxidation method is a POSM system from Yantai Wanhua Industrial Park, and the peroxide content in the first part of the wastewater produced by the system is 10000 mg / L, and the COD is 40000 mg / L; the peroxide content in the second part of the wastewater is 30 mg / L;

[0128] The catalyst used in the catalytic oxidation reaction is a MnO2 / NiO complex catalyst, and the mass ratio of MnO2 to NiO is 1.5:1; the temperature of the catalytic oxidation reaction is 50°C, and the feed air speed is 0.5h -1 The pH of the material system in the catalytic oxidation reactor 1 is increased to 8 by adding a NaOH solution with a concentration of 15wt% to the part of the circulating effluent wastewater;

[0129] The COD of the mixed wastewater obtained by mixing the effluent wastewater with the second part of the wastewater is 20000 mg / L, the pH value is 5, and the salt content is 20wt%;

[0130] The operating temperature of the first rectifying column 21 is 120°C, the operating pressure is 0.15MPa, the concentration ratio is 1.5, the reflux ratio is 0.2, and a NaOH solution with a concentration of 15wt% is added from the upper part of the first rectifying column 21, and the mass ratio of the addition amount to the wastewater is 0.01;

[0131] The operating temperature of the second rectifying column 22 is 60°C, the operating pressure is 80kPa, the concentration ratio is 2, the reflux ratio is 0.2, and a NaOH solution with a concentration of 15wt% is added from the upper part of the second rectifying column 22, and the mass ratio of the addition amount to the wastewater is 0.01; the mass of the dissolving water is 5 times the mass of the salt residue, and the dissolving temperature is 50°C; when filtering, a sintered filter with a filter hole diameter of 0.1μm is used;

[0132] The operating temperature of the third rectifying column 23 is 120°C, the operating pressure is 0.1MPa, and the reflux ratio is 50; the operating temperature of the recovery column 25 is 80°C, the operating pressure is 20kPa, and the reflux ratio is 0.2.

[0133] The treatment results are as follows:

[0134] The pH of the effluent wastewater obtained after catalytic oxidation reaction is 6, and the peroxide content is 300mg / L; the recovery rate of EBHP directed conversion of phenethyl alcohol is 92%;

[0135] The COD of the second column bottom liquid as the wastewater after secondary concentration is 200000mg / L, and the salt content is 30wt%.

[0136] The total content of metal elements Al, Fe, Ni, Ti and Ca in the salt residue obtained by incinerating the second kettle liquid through the incineration system 4 is 200 mg / L;

[0137] The content of suspended solids in the salt residue solution obtained is 10 mg / L;

[0138] The total content of metal elements Al, Fe, Ni, Ti and Ca in the filtrate obtained after filtration treatment is 0.06 mg / L;

[0139] The COD of the third kettle liquid is 1500 mg / L, and the B / C is 0.5, meeting the biochemical water entry index requirements; after biochemical treatment, the COD is less than 50 mg / L.

[0140] Example 5

[0141] The treatment method is the same as that of Example 1;

[0142] The treatment conditions are as follows:

[0143] The co-oxidation method for preparing propylene oxide system 7 is a POCHP system from Yantai Wanhua Industrial Park, wherein the peroxide content in the first part of the wastewater is 3000 mg / L, and the COD is 20000 mg / L; the peroxide content in the second part of the wastewater is 30 mg / L;

[0144] The catalyst used in the catalytic oxidation reaction is a MnO2 / NiO complex catalyst, and the mass ratio of MnO2 to NiO is 1.2:1; the temperature of the catalytic oxidation reaction is 60°C, and the feed airspeed is 1.5h -1 After the catalytic oxidation reaction, the recycling ratio of the discharged wastewater is 5; the alkaline solution input into the part of the recycled discharged wastewater is NaOH solution with a concentration of 10wt%, and the addition amount is to increase the pH of the material system in the catalytic oxidation reactor 1 to 9.5;

[0145] The COD of the mixed wastewater obtained by mixing the discharged wastewater with the second part of the wastewater is 50000 mg / L, the pH value is 9, and the salt content is 10wt%;

[0146] The operating temperature of the first rectifying column 21 is 100°C, the operating pressure is 0.12 MPa, the concentration ratio is 1.2, and the reflux ratio is 2; the alkaline solution added from the upper part of the first rectifying column 21 is NaOH solution with a concentration of 10wt%, and the mass ratio of the addition amount to the wastewater is 0.003;

[0147] The operating temperature of the second rectifying tower 22 is 70°C, the operating pressure is 50 kPa, the reflux ratio is 1.5, the concentration ratio is 4, the basic solution added from the upper part of the second rectifying tower 22 is NaOH solution with a concentration of 10wt%, the mass ratio of the added amount to the wastewater is 0.003, the mass of the water for dissolving is 4 times of the mass of the salt residue, the dissolving temperature is 50°C, and the ceramic membrane filter with a filter hole diameter of 10μm is used for filtering;

[0148] The operating temperature of the third rectifying tower 23 is 130°C, the operating pressure is 0.3MPa, the reflux ratio is 30, the operating temperature of the recovery tower 25 is 100°C, the operating pressure is 30kPa, and the reflux ratio is 5.

[0149] The treatment results are as follows:

[0150] The pH of the discharged wastewater after the catalytic oxidation reaction is 9.5, and the peroxide content is 50mg / L; the recovery rate of CHP directed conversion of dimethylbenzyl alcohol is 94%;

[0151] The COD of the second tower bottom liquid as the wastewater after secondary concentration is 300000mg / L, and the salt content is 25wt%;

[0152] The total content of metal elements Al, Fe, Ni, Ti and Ca in the salt residue obtained by incinerating the second tower bottom liquid in the incineration system 4 is 10mg / L;

[0153] The suspended solid content in the salt residue solution is 8mg / L;

[0154] The total content of metal elements Al, Fe, Ni, Ti and Ca in the filtrate obtained after filtering treatment is 0.08mg / L;

[0155] The COD in the third tower bottom liquid is 1800mg / L, and the B / C is 0.35, which meets the biochemical water inlet index requirements; after biochemical treatment, the COD is less than 50mg / L.

Claims

1. A method for treating wastewater from the co-oxidation process for preparing propylene oxide, wherein the wastewater comprises a first portion of wastewater with a peroxide content of 2000 mg / L or higher and a second portion of wastewater with a peroxide content of less than 50 mg / L, the treatment method comprising the following steps: (1) The first part of the wastewater is pre-treated by catalytic oxidation to remove the peroxides therein, and the resulting wastewater is discharged. (2) The mixed wastewater obtained by mixing the discharged wastewater with the second part of wastewater is fed into a multi-effect evaporation unit for treatment. The multi-effect evaporation unit includes: The first distillation column is used to distill the input mixed wastewater to concentrate the mixed wastewater, and obtains the first column top material from the top of the column and the first concentrated wastewater as the first column bottom liquid from the bottom of the column. The second distillation column is used to distill the first column bottom liquid from the first distillation column to further concentrate the first column bottom liquid, and to obtain the second column top material from the top of the column and the secondary concentrated wastewater as the second column bottom liquid from the bottom of the column. The third distillation column is used to distill the first overhead material from the first distillation column and the second overhead material from the second distillation column to separate oil and water, obtaining the oil phase as the third overhead material from the top of the column and the water phase as the bottom liquid of the third column from the bottom of the column. (3) The liquid in the second tower is incinerated to obtain salt residue; (4) The liquid in the third tower is subjected to biochemical treatment to remove organic matter.

2. The processing method according to claim 1, characterized in that, The processing method further includes the following steps: The material from the top of the third tower is fed into an oil-water separator for oil-water separation, resulting in an oil phase from the top and a water phase from the bottom. The oil phase from the oil-water separation unit is fed into the recovery tower for purification. Light components with a boiling point of less than 150°C are removed from the top of the tower. The bottom liquid of the recovery tower is obtained from the bottom of the tower and is fed back to the purification unit in the co-oxidation method for propylene oxide preparation for further purification.

3. The processing method according to claim 1 or 2, characterized in that, The processing method further includes conveying the salt residue to a salt residue processing unit for sequential dissolution and filtration, wherein the salt residue processing unit includes: A dissolving device is used to dissolve the salt residue to obtain an alkaline salt residue solution; A filtration device is used to filter the salt residue solution to remove the precipitate and obtain a filtrate.

4. The processing method according to any one of claims 1-3, characterized in that, The catalytic oxidation treatment is carried out in a catalytic oxidation reactor, and the treatment method further includes recycling a portion of the discharged wastewater to the inlet of the catalytic oxidation reactor, with a recycling ratio of 1-5. Preferably, the treatment method further includes adding an alkaline solution to the effluent wastewater of the circulating section to increase the pH of the material system in the catalytic oxidation reactor.

5. The processing method according to any one of claims 1-4, characterized in that, The treatment method further includes: adding alkaline solutions from the upper part of the first distillation column and the second distillation column to neutralize the acid accumulated in the upper and middle parts of the column.

6. The processing method according to claim 4 or 5, characterized in that, The alkaline solution is a NaOH solution with a concentration of 20-40 wt%.

7. The processing method according to any one of claims 1-6, characterized in that, The catalyst used in the catalytic oxidation treatment is a composite catalyst of MnO2 and NiO, wherein the mass ratio of MnO2 to NiO is (0.5-2):

1.

8. The processing method according to any one of claims 1-7, characterized in that, The catalytic oxidation conditions for the catalytic oxidation treatment are as follows: temperature 20-80℃, feed space velocity 0.5-4h. -1 .

9. The processing method according to any one of claims 1-8, characterized in that, The first distillation column operates at a temperature of 100-150℃, an operating pressure of 0.1-0.5MPa, and a concentration ratio of 1.2-2. The second distillation column operates at a temperature of 60-90℃, an operating pressure of 20-80 kPa, and a concentration ratio of 1.5-5. The operating temperature of the third distillation column is 120-170℃, the operating pressure is 0.1-1MPa, and the reflux ratio is 10-50.

10. The processing method according to any one of claims 1-9, characterized in that, In step (2), the reboiler of the first distillation column uses the third top material of the third distillation column as a heat source to heat and reboil the material in the first distillation column, and cools the material at the top of the third column. The reboiler in the bottom of the second distillation column uses the first top material of the first distillation column as a heat source to heat and reboil the material in the second distillation column, and to cool the first top material.

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