Method for reducing TOC content in salt-containing organic wastewater generated in dam preparation process

Abstract

A method for reducing TOC content in salt-containing organic wastewater generated in a DAM preparation process, comprising the following steps: using an extractant to extract an organic waste brine phase; carrying out steam stripping on the extracted waste brine, and adjusting the pH of the waste brine subjected to steam stripping; and then carrying out oxidation treatment. By adjusting the characteristic parameter Q<50 in the organic waste brine phase treatment process, the method achieves precise integration and control of organic waste brine treatment process parameters, thereby achieving the effect of reducing the TOC content in the organic waste brine.

Description

Method for reducing TOC content in saline organic wastewater generated during DAM preparation Technical Field

[0001] The invention relates to the technical field of preparation of diphenylmethane series diamines and polyamines (DAM), and in particular to a method for reducing the TOC content in saline organic wastewater generated during the preparation of DAM. Background Art

[0002] The preparation method of DAM (diphenylmethane series diamines and polyamines) is well known and is described in many open patents and publications, such as US-A 2009 / 0240077, EP-A-451442, and WO-A-99 / 40059. DAM is prepared by a continuous, semi-continuous, or discontinuous reaction process. Typically, aniline is reacted with hydrochloric acid to form aniline hydrochloride, and then formaldehyde is added to a reactor to form DAM hydrochloride. Neutralization, water washing, and separation of the organic and inorganic phases produce crude DAM and organic waste brine. The crude DAM is then refined to obtain DAM. To control the TOC content of the organic waste brine and meet chlor-alkali reuse requirements, treatment improvements are often achieved by controlling the impurity content of front-end reaction raw materials such as formaldehyde and aniline, combined with extraction, stripping, and advanced treatment processes. Such traditional treatment processes have high operating costs, are lengthy, and complex, and the various process parameters cannot be organically combined for precise control.

[0003] Chinese patent application CN 112094194A discloses a method for controlling TOC in waste brine during the production of DAM. This method controls the total impurity content of formaldehyde to below 1000 mg / L, and the alkali excess ratio of the neutralization reaction is 1.01-1.30, reducing the TOC content to below 15 mg / L. Chinese patent application CN 111960952B discloses a method for improving the quality of waste brine during the production of DAM. By controlling the aminophenol content in the raw material aniline to below 10 mg / L, the oxygen content in the system to no more than 0.01 mg / L, and maintaining a mass ratio of sodium chlorate in the caustic soda to aminophenol in the aniline to between 2:1 and 5:1, this method ensures that aminophenol is not detected in the waste brine, thus avoiding the production of explosive NCl3. This method is suitable for the downstream chlor-alkali industry. By controlling the content of individual impurity components at the formaldehyde and aniline raw material end, and coordinating with downstream deep treatment processes such as extraction, stripping, adsorption, and Fenton oxidation, the operating cost is high, and the process is lengthy and complex. The various process parameters cannot be organically combined for precise control. At the same time, it cannot cope with the situation where changes in multiple impurity components upstream lead to unqualified downstream treatment, and its universality is low.

[0004] Chinese patent application CN101665302A discloses a waste brine treatment process that uses a super-heavy rotating bed multi-stage extraction process to replace the traditional single-pole extraction process. The extracted brine is further subjected to a stripping process and then to oxidation and adsorption treatment to meet the requirements for chlor-alkali reuse. Chinese patent application CN101143753A discloses a method for deep treatment of MDI waste brine. This method uses a combination of oxidation and adsorption processes to deeply treat the brine. However, this route has the disadvantages of high energy consumption, high investment, complex equipment structure, and long process flow. At the same time, there is also the problem that the various process parameters cannot be organically combined for precise control, and it is unable to cope with the situation where the content of multiple impurity components in the upstream increases and the downstream treatment fails, and its universality is low.

[0005] Summary of the Invention

[0006] The present invention provides a method for reducing the TOC content in saline organic wastewater generated during the DAM production process. The method of the present invention treats saline organic wastewater generated during the DAM production process, facilitates precise control of process parameters for treating the organic wastewater, and effectively reduces the TOC content in the saline organic wastewater.

[0007] To achieve its purpose, the present invention provides the following technical solutions:

[0008] The present invention provides a method for reducing the TOC content in saline organic wastewater generated during the preparation of DAM. The method comprises the following steps: raw material formaldehyde and raw material aniline are subjected to a condensation reaction and a transposition reaction in the presence of an acidic catalyst to obtain a mixture, i.e., a mixture containing diphenylmethane series diamine hydrochlorides and polyamine hydrochlorides; alkali liquor is added to the mixture for neutralization reaction, and phase separation is performed to obtain an organic wastewater phase; and treatment of the organic wastewater phase comprises the following steps:

[0009] 1) extracting the organic waste brine phase with an extractant to obtain extracted waste brine;

[0010] 2) stripping the extracted waste brine to obtain stripped waste brine; the stripping comprises performing a first stripping and an optional second stripping on the extracted waste brine; preferably, the pH of the waste brine obtained by the first stripping is adjusted to 0.5≤pH<7 to obtain acidic waste brine, and the acidic waste brine is subjected to the second stripping;

[0011] 3) adjusting the pH of the stripped waste brine obtained in step 2) to obtain waste brine to be oxidized; oxidizing the waste brine to be oxidized with an oxidant to obtain treated saline organic wastewater;

[0012] Furthermore, the organic wastewater phase is treated in steps 1) to 3) under the condition that the characteristic parameter Q is less than 50, and the characteristic parameter Q is calculated as follows: Q = 5.0x10 -4 xC1+1.0x10 -3 xC2-10.0xB-10.0x D1-10.0xD2+2.0xP1-0.1xT+2.0xP2-O+2.5;

[0013] Among them, C1 is the impurity mass concentration in the raw material formaldehyde, mg / L; C2 is the impurity mass concentration in the raw material aniline, mg / L; B is the volume ratio of the extractant to the organic waste brine phase (i.e., the extraction ratio); D1 is the stripping ratio of the first stripping, and D2 is the stripping ratio of the second stripping; P1 is the pH of the acidic waste brine; P2 is the pH of the waste brine to be oxidized; T is the temperature for the oxidation treatment, °C; O is the molar ratio of the oxidant to TOC in the waste brine to be oxidized; when the second stripping is not performed, the value of D2 is 0, and the value of P2 is substituted into the formula as the value of P1 to calculate the characteristic parameter Q.

[0014] The present invention is directed to the treatment process of the above-mentioned organic waste water phase and proposes a method for reducing the TOC content by regulating the characteristic parameter Q. This method can achieve the purpose of reducing the TOC content in the organic waste water while relaxing the impurity content indicators of the upstream raw materials (such as aniline and / or formaldehyde) products.

[0015] Herein, "optional second stripping" means performing the second stripping or not performing the second stripping.

[0016] In a preferred embodiment, after the extraction in step 1), two stripping operations are performed, and the second stripping operation is performed under the condition that the waste brine after the first stripping treatment is adjusted to 0.5 ≤ pH < 7 (for example, 0.5, 1, 2, 3, 4, 5, 6, 6.5 or 6.8, etc.). The inventors have found that the two-stage stripping performed in this preferred manner is beneficial to further reduce the TOC content in the treated saline organic wastewater.

[0017] In some embodiments, after the extraction in step 1), only the first stripping is performed. In this case, there is no operation of adjusting the pH of the waste brine obtained by the first stripping to 0.5≤pH<7 to obtain acidic waste brine. In this case, when calculating the characteristic parameter Q, the value of D2 is 0, and P1 in the formula is substituted with the value of P2 for calculation.

[0018] In this article, "stripping ratio" refers to the mass ratio between the steam used in the stripping process and the stripped wastewater. Specifically, the stripping ratio of the first stripping process refers to the mass ratio of the steam used for stripping and the extracted waste brine, and the stripping ratio of the second stripping process refers to the mass ratio of the steam used for stripping and the acidic waste brine.

[0019] In this paper, “TOC” refers to the total organic carbon content in the aqueous phase, expressed as the mass concentration of carbon (C) (mg / L).

[0020] In the text, the pH of the solution is the pH measured at 25°C; when the pH of the solution at 25°C is less than 7, it is an acidic solution.

[0021] Specifically, the organic waste brine phase is treated under the condition that the characteristic parameter Q is controlled to be less than 50 (e.g., 0, 1, 10, 15, 20, 22, 24, 25, 30, 35, 40, 45, or 49, etc.). Specifically, for example, the characteristic parameter Q is controlled to be less than 50, Q less than 40, Q less than 30, Q less than 25, Q less than 20, or Q less than 15, etc. In a more preferred embodiment, for example, Q is controlled to be less than 25, more preferably, Q is controlled to be less than 20, and more preferably, Q is controlled to be less than 10, which can more significantly reduce the TOC content of the treated waste brine.

[0022] In some embodiments, in step 1), the extractant is aniline and / or toluene, and the volume ratio of the extractant to the organic waste water phase is 0.05-1.30, for example, 0.05, 0.10, 0.30, 0.50, 0.80, 1.00, 1.10, 1.30, etc., preferably 0.1-0.8; the extraction temperature is 50-120° C., for example, 50, 60, 80, 100, 110, 120° C., etc., preferably 60-110° C.;

[0023] Preferably, the extraction is carried out in a tower in which the extractant and the organic wastewater brine phase flow in countercurrent.

[0024] Furthermore, the first stripping and the second stripping are respectively carried out in a stripping tower; in some embodiments, the top temperature of the stripping tower of the first stripping is 80-160° C., for example, 80, 90, 100, 110, 130, 140, 160° C., etc., preferably 90-130° C.; the stripping ratio of the first stripping is 0.03-0.80, for example, 0.03, 0.05, 0.10, 0.30, 0.50, 0.80, etc., preferably 0.05-0.30;

[0025] The top temperature of the stripping tower for the second stripping is 80-160° C., for example, 80, 90, 100, 110, 130, 140, 160° C., etc., preferably 90-130° C.; the stripping ratio of the second stripping is 0.03-0.80, for example, 0.03, 0.05, 0.10, 0.30, 0.50, 0.80, etc., preferably 0.05-0.30; when performing the second stripping, the pH of the waste brine obtained by the first stripping is adjusted to 2-6 to obtain the acidic waste brine.

[0026] In some embodiments, in step 3), the oxidation treatment temperature is 30-90° C., for example, 30° C., 40° C., 50° C., 70° C., 80° C., 90° C., etc., preferably 40-70° C.; the pH of the waste brine to be oxidized is 2-14, for example, 2, 3, 4, 6, 8, 10, 11, 13, 14, etc., preferably 4-13;

[0027] Preferably, the oxidant is one or more of a chlorine-containing oxidant, ozone, and hydrogen peroxide; preferably, the chlorine-containing oxidant is one or more of sodium hypochlorite, chlorine gas, and sodium perchlorate.

[0028] Preferably, when the oxidant is a chlorine-containing oxidant, the molar ratio of the oxidant to TOC in the waste brine to be oxidized is 2-15, such as 2, 3, 4, 6, 8, 10, 11, 13, 14, 15, etc., preferably 2-10, calculated as available chlorine.

[0029] Preferably, the oxidation treatment includes deep oxidation treatment in an oxidation tower, and the deep oxidation treatment time is preferably 3-600 min, such as 3, 5, 10, 50, 100, 200, 300, 600 min, etc., preferably 5-300 min.

[0030] In the present invention, in step 3), the oxidation treatment of the waste brine to be oxidized with an oxidant can be carried out using an oxidation treatment process known in the art. Preferably, the waste brine to be oxidized is first mixed with the oxidant for pre-mixed oxidation, and then passed into an oxidation tower for deep oxidation treatment.

[0031] The production of DAM products by sequentially reacting formaldehyde and aniline in the presence of an acidic catalyst through a condensation reaction and a transposition reaction, followed by a subsequent alkali neutralization reaction, is well known in the art. Following the alkali neutralization reaction, an organic phase containing DAM and an organic wastewater phase are separated. The DAM-containing organic phase can be purified and refined to obtain refined DAM. Specifically, when reacting formaldehyde and aniline in the presence of an acidic catalyst to produce DAM, an aniline solution and an acidic catalyst can be first mixed to form aniline hydrochloride, and then a formaldehyde solution can be added to carry out a condensation reaction and a transposition reaction. The condensation reaction temperature is, for example, 35-95°C and the condensation reaction time is, for example, 0.1-5 hours, and the transposition reaction temperature is, for example, 95-150°C and the transposition reaction time is, for example, 0.5-5 hours. The above is merely an example, and those skilled in the art can also use other conventional production processes in the art to produce DAM by reacting formaldehyde, aniline, and an acid catalyst.

[0032] The method of the present invention is used to treat the organic wastewater phase generated during the production of DAM, and can produce treated saline organic wastewater with a low TOC content under relatively loose impurity content indicators of upstream raw materials. In some embodiments, the impurity mass concentration of the raw formaldehyde is 50-10,000 mg / L, such as 50, 100, 500, 1,000, 2,000, 4,000, 6,000, 8,000, 10,000 mg / L; in some embodiments, the impurity mass concentration of the raw aniline is 10-2,500 mg / L, such as 10, 50, 100, 500, 700, 1,000, 1,500, 2,000, 2,500 mg / L. Impurities contained in the raw formaldehyde include, but are not limited to, one or more of formic acid, acetic acid, methanol, methyl formate, and ethyl formate. The raw material aniline contains impurities such as, but not limited to, one or more of benzene, phenol, methylaniline, cyclohexylamine, cyclohexanone, and cyclohexanol. These impurities in aniline, during further reactions, can generate impurities such as aminophenol, acrolein, acrylic acid, propionic acid, formanilide, and / or acetanilide. During neutralization and phase separation, these impurities enter the wastewater phase, forming organic wastewater. Existing methods for controlling impurity levels in the raw materials are costly and difficult, resulting in high TOC levels in the wastewater, making it difficult to meet the requirements of the downstream chlor-alkali industry.

[0033] In some embodiments, the raw formaldehyde is a formaldehyde solution, such as a formaldehyde aqueous solution, and the mass fraction of formaldehyde in the formaldehyde solution is 15-55%, preferably 20-50%.

[0034] In some embodiments, the raw material aniline is an aniline solution, such as an aniline aqueous solution, and the mass fraction of aniline in the aniline solution is 90%-100%.

[0035] In some embodiments, the molar ratio of the formaldehyde to the aniline is 0.10 to 0.85, preferably 0.20 to 0.60.

[0036] In some embodiments, the acidic catalyst is selected from one or more of an organic acid, an inorganic acid, and a solid acid, preferably hydrochloric acid, more preferably 30-37 wt % hydrochloric acid. When the acidic catalyst is the organic acid and / or the inorganic acid, the H + The molar ratio of the acidic catalyst to the aniline is between 0.01 and 0.80, preferably between 0.05 and 0.40.

[0037] In some embodiments, the alkali solution is a sodium hydroxide solution, and the mass fraction of sodium hydroxide in the sodium hydroxide solution is preferably 20-55%, preferably 32-50%. Preferably, when the acidic catalyst is the organic acid and / or the inorganic acid, the acidic catalyst is H + The molar ratio of the sodium hydroxide in the sodium hydroxide solution to the acidic catalyst is 1.0 to 3.0, preferably 1.01 to 1.50.

[0038] In some embodiments, in step 1), the volume ratio of the extractant to the organic waste brine phase is controlled to be 0.05-1.30, preferably 0.1-0.8; the extraction temperature is 50-120°C, preferably 60-110°C; the top temperature of the stripping tower of the first stripping is controlled to be 80-160°C, preferably 90-130°C; the stripping ratio of the first stripping is 0.03-0.80, preferably 0.05-0.30; a second stripping is optionally performed, and the top temperature of the stripping tower of the second stripping is preferably controlled to be 80-160°C, preferably 90-130°C, and the stripping ratio of the second stripping is 0.03-0.80, preferably 0.05-0.30. The pH of the acidic waste brine is 2-6; in step 3), the temperature of the oxidation treatment is controlled to be 30-90°C, preferably 40-70°C; the pH of the waste brine to be oxidized is controlled to be 2-14, preferably 4-13; the molar ratio of the oxidant to the TOC in the waste brine to be oxidized is controlled to be 2-15, preferably 2-10, based on the available chlorine; on the basis of the above conditions, the treatment of the organic waste brine phase in steps (1)-(3) is simultaneously controlled under the condition that the characteristic parameter Q is less than 50. By the above method, the TOC removal effect of the saline organic wastewater can be significantly improved without placing strict requirements on the impurity content of the raw material formaldehyde and aniline. Specifically, for example, the impurity mass concentration of the raw material formaldehyde is 50-10000 mg / L, and the impurity mass concentration of the raw material aniline is 10-2500 mg / L.

[0039] In the present invention, during the DAM production process, while relaxing the impurity content requirements of upstream raw materials (such as aniline and / or formaldehyde), the characteristic parameter Q during the organic wastewater phase treatment process can be adjusted to less than 50, thereby achieving precise integrated control of the organic wastewater treatment process parameters. This can achieve the effect of reducing the TOC content in the organic wastewater, for example, to less than 10 mg / L. The solution of the present invention helps reduce the production costs of upstream raw materials.

[0040] The technical solution provided by the present invention has the following beneficial effects:

[0041] The present invention provides a method for reducing the TOC content in saline organic wastewater generated during DAM preparation. By controlling a characteristic parameter Q less than 50, the method can relax impurity content indicators of upstream raw material products, such as the impurity content in raw materials such as aniline and formaldehyde. By regulating the characteristic parameter Q, the TOC content of the treated wastewater is reduced, for example, to less than 10 mg / L, while simultaneously reducing the production cost of upstream raw materials, thereby achieving organic combination and precise regulation of parameters of the organic wastewater treatment system. DETAILED DESCRIPTION

[0042] In order to facilitate the understanding of the present invention, the present invention will be further described below in conjunction with examples. It should be understood that the following examples are only for a better understanding of the present invention and do not mean that the present invention is limited to the following examples.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one skilled in the art to which this invention belongs. The term "and / or" as may be used herein includes any and all combinations of one or more of the associated listed items. The terms "first," "second," etc., are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

[0044] Where specific experimental steps or conditions are not specified in the examples, the corresponding conventional experimental steps or conditions in the art can be used. Reagents or instruments used without specifying the manufacturer are all commercially available conventional products.

[0045] An Agilent 1260 InfinityⅡ high performance liquid chromatograph was used to analyze various impurities such as formic acid and acetic acid in formaldehyde. An Agilent 8890 GC System gas chromatograph was used to analyze various impurities such as phenol, methylaniline, and cyclohexanol in aniline. An Analytik Jena Multi N / C 3100 TOC / TN analyzer was used to analyze the TOC in the waste brine.

[0046] The "2S steam" used in the following examples and comparative examples refers to saturated water vapor with an absolute pressure of 3 MPaA.

[0047] In the following examples and comparative examples, the characteristic parameter Q is calculated as follows: Q = 5.0 x 10 -4 xC1+1.0x10 -3 xC2-10.0xB-10.0xD1-10.0xD2+2.0xP1-0.1xT+2.0x P2-O+2.5;

[0048] Wherein, C1 is the impurity mass concentration of formaldehyde (i.e., formaldehyde aqueous solution) used as the raw material for preparing DAM, mg / L; C2 is the impurity mass concentration of aniline (i.e., aniline aqueous solution) used as the raw material for preparing DAM, mg / L; B is the volume ratio of the extractant used for extraction in step 1) to the organic waste water phase; D1 is the stripping ratio for the first stripping in step 2), and D2 is the stripping ratio for the second stripping in step 2); P1 is the pH of the acidic waste water in step 2); P2 is the pH of the waste water to be oxidized in step 3); T is the temperature of the oxidation treatment in step 3), °C; O is the molar ratio of the oxidant (in terms of available chlorine) to the TOC in the waste water to be oxidized in step 3); when the treatment process of the organic waste water phase does not involve the second stripping, when calculating the characteristic parameter Q, the value of D2 is 0, and P1 is substituted into the formula using the value of P2 for calculation.

[0049] In the following examples and comparative examples, the alkali excess rate refers to the sodium hydroxide (in terms of OH) in the sodium hydroxide aqueous solution. - ) and hydrochloric acid (as H + The molar ratio of .

[0050] Example 1

[0051] The raw materials in this embodiment are described as follows:

[0052] Formaldehyde aqueous solution: concentration of 37 wt%, containing the following impurities by mass: 4000 mg / L formic acid, 1500 mg / L acetic acid, 3000 mg / L methanol, and 1500 mg / L lipid impurities (mainly methyl formate, ethyl formate, etc.);

[0053] Aniline aqueous solution: concentration is 94 wt%, containing the following impurities by mass: 50 mg / L phenol, 50 mg / L methylaniline, 100 mg / L cyclohexylamine, 700 mg / L cyclohexanone, and 100 mg / L cyclohexanol.

[0054] Hydrochloric acid aqueous solution: concentration 33wt%, containing 5mg / L chlorobenzene;

[0055] Sodium hydroxide aqueous solution: concentration is 50wt%.

[0056] Preparation of DAM: Aniline aqueous solution and hydrochloric acid aqueous solution were mixed in a static mixer to form aniline hydrochloride, and formaldehyde aqueous solution was added thereto under stirring. The condensation reaction was carried out at 35°C for 2 hours. The molar ratio of formaldehyde to aniline was 0.52, and the hydrochloric acid (as H + The molar ratio of aniline to aniline is 0.35;

[0057] The condensation reaction product was transferred to a transposition reactor, and the temperature was raised to 120° C. to carry out a transposition rearrangement reaction for 2 h to obtain a mixture of diamine hydrochloride and polyamine hydrochloride containing a diphenylmethane series;

[0058] The above mixture was transferred to a neutralization reactor, and sodium hydroxide aqueous solution was added with an alkali excess ratio of 1.30. The neutralization reaction was maintained at 95° C. for 30 minutes, and crude DAM (organic phase) and organic waste water phase were obtained after layering.

[0059] The organic wastewater phase obtained during the preparation of DAM was treated according to the following steps, and during the following treatment steps 1) to 3), the characteristic parameter Q was controlled to be 21.50:

[0060] 1) introducing the organic waste water phase from the top of the extraction tower and introducing the aniline extractant from the bottom of the tower for reverse extraction to obtain extracted waste water; wherein the volume ratio of aniline to the organic waste water phase is 0.30, and the extraction temperature is 80° C.;

[0061] 2) The extracted waste brine is introduced into a first stripping tower from the top, and 2S steam is introduced into the bottom of the tower for stripping treatment. The top temperature of the first stripping tower is maintained at 100° C., and the stripping ratio is 0.10. Light components such as aniline are removed from the top of the tower, and waste brine after the first stripping is obtained at the bottom of the tower; the obtained waste brine after the first stripping is introduced into an acid-base adjustment tank, and its pH is adjusted to 4 using 33wt% hydrochloric acid to obtain acidic waste brine, and the obtained acidic waste brine is introduced into a second stripping tower and 2S steam is introduced into the bottom of the tower for a second stripping. The top temperature of the second stripping tower is maintained at 105° C., and the stripping ratio is 0.10. Light components such as formic acid, acetic acid, and phenol are further removed from the top of the tower, and the bottom discharge is waste brine after stripping;

[0062] 3) The stripped waste brine obtained in step 2) was adjusted to a pH of 9.5 using a 50 wt% aqueous sodium hydroxide solution to obtain waste brine to be oxidized. The temperature was adjusted to 50°C, and the molar ratio of sodium hypochlorite (based on available chlorine) to TOC in the waste brine to be oxidized was controlled to be 4. The sodium hypochlorite and waste brine to be oxidized were introduced into the oxidation tower simultaneously from the bottom of the oxidation tower for deep oxidation treatment, with a residence time of 30 minutes. The material discharged from the top of the tower was the treated waste brine. The TOC content of the treated waste brine was tested, as shown in Table 1.

[0063] Example 2

[0064] The raw materials in this embodiment are described as follows:

[0065] Formaldehyde aqueous solution: concentration of 37 wt%, containing the following impurities by mass: 3000 mg / L formic acid, 500 mg / L acetic acid, 4000 mg / L methanol, 500 mg / L lipid impurities (mainly methyl formate, etc.);

[0066] Aniline aqueous solution: concentration of 99 wt%, containing the following impurities by mass: 50 mg / L phenol, 50 mg / L methylaniline, 700 mg / L cyclohexylamine, 650 mg / L cyclohexanone, and 50 mg / L cyclohexanol;

[0067] Hydrochloric acid aqueous solution: concentration 33wt%, containing 5mg / L chlorobenzene;

[0068] Sodium hydroxide aqueous solution: concentration is 50wt%.

[0069] Preparation of DAM: Aniline aqueous solution and hydrochloric acid aqueous solution were mixed in a static mixer to form aniline hydrochloride, and formaldehyde aqueous solution was added thereto under stirring. The condensation reaction was carried out at 80°C for 2 hours. The molar ratio of formaldehyde to aniline was 0.55, and the hydrochloric acid (as H + The molar ratio of aniline to aniline is 0.38;

[0070] The condensation reaction product was transferred to a transposition reactor, and the temperature was raised to 120° C. to carry out a transposition rearrangement reaction for 2 h to obtain a mixture of diamine hydrochloride and polyamine hydrochloride containing a diphenylmethane series;

[0071] The above mixture was transferred to a neutralization reactor, and sodium hydroxide aqueous solution was added with an alkali excess ratio of 1.50. The neutralization reaction was maintained at 98° C. for 30 minutes, and crude DAM (organic phase) and organic waste water phase were obtained after layering.

[0072] The organic wastewater phase obtained during the preparation of DAM was treated according to the following steps, and during the following treatment steps 1) to 3), the characteristic parameter Q was controlled to be 20.00:

[0073] 1) introducing the organic waste water phase from the top of the extraction tower and introducing the aniline extractant from the bottom of the tower for reverse extraction to obtain extracted waste water; wherein the volume ratio of aniline to the organic waste water phase is 0.20, and the extraction temperature is 90° C.;

[0074] 2) The extracted waste brine is introduced into a first stripping tower from the top, and 2S steam is introduced into the bottom of the tower for stripping treatment. The top temperature of the first stripping tower is maintained at 100° C., and the stripping ratio is 0.05. Light components such as aniline are removed from the top of the tower, and the first stripped waste brine is obtained at the bottom of the tower; the obtained first stripped waste brine is introduced into an acid-base adjustment tank, and its pH is adjusted to 3 using 33wt% hydrochloric acid to obtain acidic waste brine, and the obtained acidic waste brine is introduced into a second stripping tower and 2S steam is introduced into the bottom of the tower for a second stripping treatment. The top temperature of the second stripping tower is maintained at 105° C., and the stripping ratio is 0.05. Light components such as formic acid, acetic acid, and phenol are further removed from the top of the tower, and the bottom discharge is the stripped waste brine;

[0075] 3) The stripped waste brine obtained in step 2) is adjusted to a pH of 9.0 using a 50 wt% aqueous sodium hydroxide solution to obtain waste brine to be oxidized. The temperature is adjusted to 60°C, and the molar ratio of sodium hypochlorite (based on available chlorine) to TOC in the waste brine to be oxidized is controlled to be 3. The sodium hypochlorite and the waste brine to be oxidized are introduced into a static mixer in proportion for pre-mixing and oxidation. The mixture is then passed from the bottom of the oxidation tower into an oxidation tower for deep oxidation treatment with a residence time of 30 minutes. The material discharged from the top of the tower is the treated waste brine. The TOC content of the treated waste brine is tested, as shown in Table 1.

[0076] Example 3

[0077] The raw materials in this embodiment are described as follows:

[0078] Formaldehyde aqueous solution: concentration of 37 wt%, containing the following impurities by mass: 3000 mg / L formic acid, 500 mg / L acetic acid, 2000 mg / L methanol, 500 mg / L lipid impurities (mainly methyl formate, ethyl formate, etc.);

[0079] Aniline aqueous solution: concentration of 99 wt%, containing the following impurities by mass: 50 mg / L phenol, 50 mg / L methylaniline, 800 mg / L cyclohexylamine, 1000 mg / L cyclohexanone, and 100 mg / L cyclohexanol;

[0080] Hydrochloric acid aqueous solution: concentration 33wt%, containing 5mg / L chlorobenzene;

[0081] Sodium hydroxide aqueous solution: concentration is 50wt%.

[0082] Preparation of DAM: Aniline aqueous solution and hydrochloric acid aqueous solution were mixed in a static mixer to form aniline hydrochloride, and formaldehyde aqueous solution was added thereto under stirring. The condensation reaction was carried out at 60°C for 2 hours. The molar ratio of formaldehyde to aniline was 0.50, and the hydrochloric acid (as H + The molar ratio of aniline to aniline is 0.38;

[0083] The condensation reaction product was transferred to a transposition reactor, and the temperature was raised to 120° C. to carry out a transposition rearrangement reaction for 2 h to obtain a mixture of diamine hydrochloride and polyamine hydrochloride containing a diphenylmethane series;

[0084] The above mixture was transferred to a neutralization reactor, and sodium hydroxide aqueous solution was added with an alkali excess ratio of 1.50. The neutralization reaction was maintained at 98°C for 30 minutes, and after separation, crude DAM (organic phase) and organic waste water phase were obtained;

[0085] The organic wastewater phase obtained during the preparation of DAM was treated according to the following steps, and during the following treatment steps 1) to 3), the characteristic parameter Q was controlled to be 23.5:

[0086] 1) introducing the organic waste water phase from the top of the extraction tower and introducing the aniline extractant from the bottom of the tower for reverse extraction to obtain extracted waste water; wherein the volume ratio of aniline to the organic waste water phase is 0.25, and the extraction temperature is 90° C.;

[0087] 2) The extracted waste brine is introduced into a first stripping tower from the top, and 2S steam is introduced into the bottom of the tower for stripping treatment. The top temperature of the first stripping tower is maintained at 100° C., and the stripping ratio is 0.10. Light components such as aniline are removed from the top of the tower, and waste brine after the first stripping is obtained at the bottom of the tower; the obtained waste brine after the first stripping is introduced into an acid-base adjustment tank, and its pH is adjusted to 5 using 33wt% hydrochloric acid to obtain acidic waste brine, and the obtained acidic waste brine is introduced into a second stripping tower and 2S steam is introduced into the bottom of the tower for a second stripping. The top temperature of the second stripping tower is maintained at 105° C., and the stripping ratio is 0.10. Light components such as formic acid, acetic acid, and phenol are further removed from the top of the tower, and the bottom discharge is waste brine after stripping;

[0088] 3) The stripped waste brine obtained in step 2) is adjusted to a pH of 8.5 using a 50 wt% aqueous sodium hydroxide solution to obtain waste brine to be oxidized. The temperature is adjusted to 45°C, and the molar ratio of sodium hypochlorite (based on available chlorine) to TOC in the waste brine to be oxidized is controlled to be 2. The sodium hypochlorite and the waste brine to be oxidized are introduced into a static mixer in proportion for pre-mixing and oxidation. The mixture is then passed from the bottom of the oxidation tower into the oxidation tower for deep oxidation treatment with a residence time of 30 minutes. The material discharged from the top of the tower is the treated waste brine. The TOC content of the treated waste brine is tested, as shown in Table 1.

[0089] Example 4

[0090] The raw materials in this embodiment are described as follows:

[0091] Formaldehyde aqueous solution: concentration of 37 wt%, containing the following impurities by mass: 2500 mg / L formic acid, 1000 mg / L acetic acid, 1000 mg / L methanol, and 500 mg / L lipid impurities (mainly methyl formate, etc.);

[0092] Aniline aqueous solution: concentration of 99 wt%, containing the following impurities by weight: 50 mg / L phenol, 50 mg / L methylaniline, 800 mg / L cyclohexylamine, 1150 mg / L cyclohexanone, and 450 mg / L cyclohexanol;

[0093] Hydrochloric acid aqueous solution: concentration 33wt%, containing 5mg / L chlorobenzene;

[0094] Sodium hydroxide aqueous solution: concentration is 50wt%.

[0095] Preparation of DAM: Aniline aqueous solution and hydrochloric acid aqueous solution were mixed in a static mixer to form aniline hydrochloride, and formaldehyde aqueous solution was added thereto under stirring. The condensation reaction was carried out at 60°C for 2 hours. The molar ratio of formaldehyde to aniline was 0.55, and the hydrochloric acid (as H + The molar ratio of aniline to aniline is 0.20;

[0096] The condensation reaction product was transferred to a transposition reactor, and the temperature was raised to 120° C. to carry out a transposition rearrangement reaction for 2 h to obtain a mixture of diamine hydrochloride and polyamine hydrochloride containing a diphenylmethane series;

[0097] The above mixture was transferred to a neutralization reactor, and sodium hydroxide aqueous solution was added with an alkali excess ratio of 1.50. The neutralization reaction was maintained at 98°C for 30 minutes, and after separation, crude DAM (organic phase) and organic waste water phase were obtained;

[0098] The organic wastewater phase obtained during the preparation of DAM was treated according to the following steps, and during the following treatment steps 1) to 3), the characteristic parameter Q was controlled to be 24.00:

[0099] 1) introducing the organic waste water phase from the top of the extraction tower, and introducing the aniline extractant from the bottom of the tower for reverse extraction to obtain extracted waste water; wherein the volume ratio of aniline to the organic waste water phase is 0.15, and the extraction temperature is 95° C.;

[0100] 2) The extracted waste brine is introduced into a first stripping tower from the top, and 2S steam is introduced into the bottom of the tower for stripping treatment. The top temperature of the first stripping tower is maintained at 100° C., and the stripping ratio is 0.10. Light components such as aniline are removed from the top of the tower, and waste brine after the first stripping is obtained at the bottom of the tower; the obtained waste brine after the first stripping is introduced into an acid-base adjustment tank, and its pH is adjusted to 6 using 33wt% hydrochloric acid to obtain acidic waste brine, and the obtained acidic waste brine is introduced into a second stripping tower and 2S steam is introduced into the bottom of the tower for a second stripping. The top temperature of the second stripping tower is maintained at 105° C., and the stripping ratio is 0.10. Light components such as formic acid, acetic acid, and phenol are further removed from the top of the tower, and the bottom discharge is waste brine after stripping;

[0101] 3) The stripped waste brine obtained in step 2) is adjusted to a pH of 9.5 using a 50 wt% aqueous sodium hydroxide solution to obtain waste brine to be oxidized. The temperature is adjusted to 50° C., and the molar ratio of sodium hypochlorite (based on available chlorine) to TOC in the waste brine to be oxidized is controlled to be 6. The sodium hypochlorite and the waste brine to be oxidized are introduced into a static mixer in proportion for pre-mixing and oxidation. The mixture is then passed from the bottom of the oxidation tower into an oxidation tower for deep oxidation treatment with a residence time of 30 minutes. The material discharged from the top of the tower is the treated waste brine. The TOC content of the treated waste brine is tested, as shown in Table 1.

[0102] Example 5

[0103] The raw materials in this embodiment are described as follows:

[0104] Formaldehyde aqueous solution: concentration of 37 wt%, containing the following impurities by mass: 500 mg / L formic acid, 300 mg / L acetic acid, 100 mg / L methanol, and 100 mg / L lipid impurities (mainly methyl formate, etc.);

[0105] Aniline aqueous solution: concentration of 95 wt%, containing the following impurities by weight: 50 mg / L phenol, 50 mg / L methylaniline, 500 mg / L cyclohexylamine, 350 mg / L cyclohexanone, and 50 mg / L cyclohexanol;

[0106] Hydrochloric acid aqueous solution: concentration 33wt%, containing 5mg / L chlorobenzene;

[0107] Sodium hydroxide aqueous solution: concentration is 50wt%.

[0108] Preparation of DAM: Aniline aqueous solution and hydrochloric acid aqueous solution were mixed in a static mixer to form aniline hydrochloride, and formaldehyde aqueous solution was added thereto under stirring. The condensation reaction was carried out at 60°C for 2 hours. The molar ratio of formaldehyde to aniline was 0.50, and the hydrochloric acid (as H + The molar ratio of aniline to aniline is 0.20;

[0109] The condensation reaction product was transferred to a transposition reactor, and the temperature was raised to 120° C. to carry out a transposition rearrangement reaction for 2 h to obtain a mixture of diamine hydrochloride and polyamine hydrochloride containing diphenylmethane series;

[0110] The above mixture was transferred to a neutralization reactor, and sodium hydroxide aqueous solution was added with an alkali excess ratio of 1.50. The neutralization reaction was maintained at 98° C. for 30 minutes, and crude DAM (organic phase) and organic waste water phase were obtained after layering.

[0111] The organic wastewater phase obtained during the preparation of DAM was treated according to the following steps, and during the following treatment steps 1) to 3), the characteristic parameter Q was controlled to be 20.50:

[0112] 1) introducing the organic waste water phase from the top of the extraction tower, and introducing the aniline extractant from the bottom of the tower for reverse extraction to obtain extracted waste water; wherein the volume ratio of aniline to the organic waste water phase is 0.15, and the extraction temperature is 95° C.;

[0113] 2) The extracted waste brine is introduced into a first stripping tower from the top, and 2S steam is introduced into the bottom of the tower for stripping treatment. The top temperature of the first stripping tower is maintained at 100° C., and the stripping ratio is 0.10. Light components such as aniline are removed from the top of the tower, and waste brine after the first stripping is obtained at the bottom of the tower; the waste brine after the first stripping is introduced into an acid-base adjustment tank, and its pH is adjusted to 6 using 33wt% hydrochloric acid to obtain acidic waste brine, and the obtained acidic waste brine is introduced into a second stripping tower and 2S steam is introduced into the bottom of the tower for a second stripping. The top temperature of the second stripping tower is maintained at 105° C., and the stripping ratio is 0.10. Light components such as formic acid, acetic acid, and phenol are further removed from the top of the tower, and the bottom discharge is waste brine after stripping;

[0114] 3) The stripped waste brine obtained in step 2) is adjusted to a pH of 9.5 using a 50 wt% aqueous sodium hydroxide solution to obtain waste brine to be oxidized. The temperature is adjusted to 50° C., and the molar ratio of sodium hypochlorite (based on available chlorine) to TOC in the waste brine to be oxidized is controlled to be 6. The sodium hypochlorite and the waste brine to be oxidized are introduced into a static mixer in proportion for pre-mixing and oxidation. The mixture is then passed from the bottom of the oxidation tower into an oxidation tower for deep oxidation treatment with a residence time of 30 minutes. The material discharged from the top of the tower is the treated waste brine. The TOC content of the treated waste brine is tested, as shown in Table 1.

[0115] Example 6

[0116] The raw materials in this embodiment are described as follows:

[0117] Formaldehyde aqueous solution: concentration of 37 wt%, containing the following impurities by mass: 500 mg / L formic acid, 300 mg / L acetic acid, 100 mg / L methanol, and 100 mg / L lipid impurities (mainly methyl formate, etc.);

[0118] Aniline aqueous solution: concentration of 95 wt%, containing the following impurities by weight: 50 mg / L phenol, 50 mg / L methylaniline, 500 mg / L cyclohexylamine, 350 mg / L cyclohexanone, and 50 mg / L cyclohexanol;

[0119] Hydrochloric acid aqueous solution: concentration 33wt%, containing 5mg / L chlorobenzene;

[0120] Sodium hydroxide aqueous solution: concentration is 50wt%.

[0121] Preparation of DAM: Aniline aqueous solution and hydrochloric acid aqueous solution were mixed in a static mixer to form aniline hydrochloride, and formaldehyde aqueous solution was added thereto under stirring. The condensation reaction was carried out at 60°C for 2 hours. The molar ratio of formaldehyde to aniline was 0.50, and the hydrochloric acid (as H + The molar ratio of aniline to aniline is 0.20;

[0122] The condensation reaction product was transferred to a transposition reactor, and the temperature was raised to 120° C. to carry out a transposition rearrangement reaction for 2 hours to obtain a mixture of diamine hydrochloride and polyamine hydrochloride containing diphenylmethane series;

[0123] The above mixture was transferred to a neutralization reactor, and sodium hydroxide aqueous solution was added with an alkali excess ratio of 1.50. The neutralization reaction was maintained at 98° C. for 30 minutes, and crude DAM (organic phase) and organic waste water phase were obtained after layering.

[0124] The organic wastewater phase obtained during the preparation of DAM was treated according to the following steps, and during the following treatment steps 1) to 3), the characteristic parameter Q was controlled to be 28.50:

[0125] 1) introducing the organic waste water phase from the top of the extraction tower, and introducing the aniline extractant from the bottom of the tower for reverse extraction to obtain extracted waste water; wherein the volume ratio of aniline to the organic waste water phase is 0.15, and the extraction temperature is 95° C.;

[0126] 2) The waste brine after extraction is passed from the top into the first stripping tower, and 2S steam is passed into the bottom of the tower for stripping treatment. The top temperature of the first stripping tower is maintained at 100°C, and the stripping ratio is 0.10. Light components such as aniline are removed from the top of the tower, and the waste brine after the first stripping is obtained at the bottom of the tower;

[0127] 3) The stripped waste brine obtained in step 2) is adjusted to a pH of 9.5 using 50 wt% sodium hydroxide or / and 33% hydrochloric acid aqueous solution to obtain waste brine to be oxidized. The temperature is adjusted to 50°C, and the molar ratio of sodium hypochlorite (calculated as available chlorine) to TOC in the waste brine to be oxidized is controlled to be 6. The sodium hypochlorite and the waste brine to be oxidized are introduced into a static mixer in proportion for pre-mixing and oxidation, and then introduced into the bottom of the oxidation tower for deep oxidation treatment with a residence time of 30 minutes; the material discharged from the top of the tower is the treated waste brine. The TOC content of the treated waste brine is tested, as shown in Table 1.

[0128] Example 7

[0129] The raw materials in this embodiment are described as follows:

[0130] Formaldehyde aqueous solution: concentration of 37 wt%, containing the following impurities by mass: 4000 mg / L formic acid, 1500 mg / L acetic acid, 3000 mg / L methanol, and 1500 mg / L lipid impurities (mainly methyl formate, ethyl formate, etc.);

[0131] Aniline aqueous solution: concentration is 94 wt%, containing the following impurities by mass: 50 mg / L phenol, 50 mg / L methylaniline, 100 mg / L cyclohexylamine, 700 mg / L cyclohexanone, and 100 mg / L cyclohexanol.

[0132] Hydrochloric acid aqueous solution: concentration 33wt%, containing 5mg / L chlorobenzene;

[0133] Sodium hydroxide aqueous solution: concentration is 50wt%.

[0134] Preparation of DAM: Aniline aqueous solution and hydrochloric acid aqueous solution were mixed in a static mixer to form aniline hydrochloride, and formaldehyde aqueous solution was added thereto while stirring. The condensation reaction was carried out at 35°C for 2 hours. The molar ratio of formaldehyde to aniline was 0.52, and the hydrochloric acid (as H + The molar ratio of aniline to aniline is 0.35;

[0135] The condensation reaction product was transferred to a transposition reactor, and the temperature was raised to 120° C. to carry out a transposition rearrangement reaction for 2 h to obtain a mixture of diamine hydrochloride and polyamine hydrochloride containing a diphenylmethane series;

[0136] The above mixture was transferred to a neutralization reactor, and sodium hydroxide aqueous solution was added with an alkali excess ratio of 1.30. The neutralization reaction was maintained at 95° C. for 30 minutes. After layering, crude DAM (organic phase) and organic waste water phase were obtained.

[0137] The organic wastewater phase obtained during the preparation of DAM was treated according to the following steps, and during the following treatment steps 1) to 3), the characteristic parameter Q was controlled to be 13.50:

[0138] 1) introducing the organic waste water phase from the top of the extraction tower and introducing the aniline extractant from the bottom of the tower for reverse extraction to obtain extracted waste water; wherein the volume ratio of aniline to the organic waste water phase is 0.80, and the extraction temperature is 60° C.;

[0139] 2) The extracted waste brine is introduced into a first stripping tower from the top, and 2S steam is introduced into the bottom of the tower for stripping treatment. The top temperature of the first stripping tower is maintained at 90° C., and the stripping ratio is 0.10. Light components such as aniline are removed from the top of the tower, and waste brine after the first stripping is obtained at the bottom of the tower; the obtained waste brine after the first stripping is introduced into an acid-base adjustment tank, and its pH is adjusted to 6.5 using 33wt% hydrochloric acid to obtain acidic waste brine, and the obtained acidic waste brine is introduced into a second stripping tower and 2S steam is introduced into the bottom of the tower for a second stripping. The top temperature of the second stripping tower is maintained at 130° C., and the stripping ratio is 0.30. Light components such as formic acid, acetic acid, and phenol are further removed from the top of the tower, and the bottom discharge is waste brine after stripping;

[0140] 3) The stripped waste brine obtained in step 2) was adjusted to a pH of 9.5 using a 50 wt% aqueous sodium hydroxide solution to obtain waste brine to be oxidized. The temperature was adjusted to 50°C, and the molar ratio of sodium hypochlorite (based on available chlorine) to TOC in the waste brine to be oxidized was controlled to be 10. The sodium hypochlorite and waste brine to be oxidized were introduced into the oxidation tower simultaneously from the bottom of the oxidation tower for deep oxidation treatment, with a residence time of 30 minutes. The material discharged from the top of the tower was the treated waste brine. The TOC content of the treated waste brine was tested, as shown in Table 1.

[0141] Example 8

[0142] The raw materials in this embodiment are described as follows:

[0143] Formaldehyde aqueous solution: concentration of 37 wt%, containing the following impurities by mass: 4000 mg / L formic acid, 1500 mg / L acetic acid, 3000 mg / L methanol, and 1500 mg / L lipid impurities (mainly methyl formate, ethyl formate, etc.);

[0144] Aniline aqueous solution: concentration is 94 wt%, containing the following impurities by mass: 50 mg / L phenol, 50 mg / L methylaniline, 100 mg / L cyclohexylamine, 700 mg / L cyclohexanone, and 100 mg / L cyclohexanol.

[0145] Hydrochloric acid aqueous solution: concentration 33wt%, containing 5mg / L chlorobenzene;

[0146] Sodium hydroxide aqueous solution: concentration is 50wt%.

[0147] Preparation of DAM: Aniline aqueous solution and hydrochloric acid aqueous solution were mixed in a static mixer to form aniline hydrochloride, and formaldehyde aqueous solution was added thereto under stirring. The condensation reaction was carried out at 35°C for 2 hours. The molar ratio of formaldehyde to aniline was 0.52, and the hydrochloric acid (as H + The molar ratio of aniline to aniline is 0.35;

[0148] The condensation reaction product was transferred to a transposition reactor, and the temperature was raised to 120° C. to carry out a transposition rearrangement reaction for 2 h to obtain a mixture of diamine hydrochloride and polyamine hydrochloride containing a diphenylmethane series;

[0149] The above mixture was transferred to a neutralization reactor, and sodium hydroxide aqueous solution was added with an alkali excess ratio of 1.30. The neutralization reaction was maintained at 95° C. for 30 minutes, and crude DAM (organic phase) and organic waste water phase were obtained after layering.

[0150] The organic wastewater phase obtained during the preparation of DAM was treated according to the following steps, and during the following treatment steps 1) to 3), the characteristic parameter Q was controlled to be 23.50:

[0151] 1) introducing the organic waste water phase from the top of the extraction tower and introducing the aniline extractant from the bottom of the tower for reverse extraction to obtain extracted waste water; wherein the volume ratio of aniline to the organic waste water phase is 0.1, and the extraction temperature is 110° C.;

[0152] 2) The extracted waste brine is introduced into a first stripping tower from the top, and 2S steam is introduced into the bottom of the tower for stripping treatment. The top temperature of the first stripping tower is maintained at 130° C., and the stripping ratio is 0.30. Light components such as aniline are removed from the top of the tower, and waste brine after the first stripping is obtained at the bottom of the tower; the obtained waste brine after the first stripping is introduced into an acid-base adjustment tank, and its pH is adjusted to 6.5 using 33wt% hydrochloric acid to obtain acidic waste brine, and the obtained acidic waste brine is introduced into a second stripping tower, and 2S steam is introduced into the bottom of the tower for a second stripping. The top temperature of the second stripping tower is maintained at 130° C., and the stripping ratio is 0.30. Light components such as formic acid, acetic acid, and phenol are further removed from the top of the tower, and the bottom discharge is waste brine after stripping;

[0153] 3) The pH of the stripped waste brine obtained in step 2) was adjusted to 9.5 using a 50 wt% aqueous sodium hydroxide solution to obtain waste brine to be oxidized. The temperature was adjusted to 70°C, and the molar ratio of sodium hypochlorite (calculated as available chlorine) to TOC in the waste brine to be oxidized was controlled to be 3. The sodium hypochlorite and waste brine to be oxidized were introduced into the oxidation tower from the bottom of the tower in proportion for deep oxidation treatment, with a residence time of 30 minutes. The material discharged from the top of the tower was the treated waste brine. The TOC content of the treated waste brine was tested, as shown in Table 1.

[0154] Example 9

[0155] The raw materials in this embodiment are described as follows:

[0156] Formaldehyde aqueous solution: concentration of 37 wt%, containing the following impurities by mass: 4000 mg / L formic acid, 1500 mg / L acetic acid, 3000 mg / L methanol, and 1500 mg / L lipid impurities (mainly methyl formate, ethyl formate, etc.);

[0157] Aniline aqueous solution: concentration is 94 wt%, containing the following impurities by mass: 50 mg / L phenol, 50 mg / L methylaniline, 100 mg / L cyclohexylamine, 700 mg / L cyclohexanone, and 100 mg / L cyclohexanol.

[0158] Hydrochloric acid aqueous solution: concentration 33wt%, containing 5mg / L chlorobenzene;

[0159] Sodium hydroxide aqueous solution: concentration is 50wt%.

[0160] Preparation of DAM: Aniline aqueous solution and hydrochloric acid aqueous solution were mixed in a static mixer to form aniline hydrochloride, and formaldehyde aqueous solution was added thereto under stirring. The condensation reaction was carried out at 35°C for 2 hours. The molar ratio of formaldehyde to aniline was 0.52, and the hydrochloric acid (as H + The molar ratio of aniline to aniline is 0.35;

[0161] The condensation reaction product was transferred to a transposition reactor, and the temperature was raised to 120° C. to carry out a transposition rearrangement reaction for 2 h to obtain a mixture of diamine hydrochloride and polyamine hydrochloride containing a diphenylmethane series;

[0162] The above mixture was transferred to a neutralization reactor, and sodium hydroxide aqueous solution was added with an alkali excess ratio of 1.30. The neutralization reaction was maintained at 95° C. for 30 minutes. After layering, crude DAM (organic phase) and organic waste water phase were obtained.

[0163] The organic wastewater phase obtained during the preparation of DAM was treated according to the following steps, and during the following treatment steps 1) to 3), the characteristic parameter Q was controlled to be 47.50:

[0164] 1) introducing the organic waste water phase from the top of the extraction tower and introducing the aniline extractant from the bottom of the tower for reverse extraction to obtain extracted waste water; wherein the volume ratio of aniline to the organic waste water phase is 0.30, and the extraction temperature is 80° C.;

[0165] 2) The waste brine after extraction is passed from the top into the first stripping tower, and 2S steam is passed into the bottom of the tower for stripping treatment. The top temperature of the first stripping tower is maintained at 100°C, and the stripping ratio is 0.10. Light components such as aniline are removed from the top of the tower, and the waste brine after the first stripping is obtained at the bottom of the tower;

[0166] 3) The stripped waste brine obtained in step 2) is adjusted to a pH of 13 using 50 wt% sodium hydroxide or / and a 33% aqueous hydrochloric acid solution to obtain waste brine to be oxidized. The temperature is adjusted to 50°C, and the molar ratio of sodium hypochlorite (based on available chlorine) to TOC in the waste brine to be oxidized is controlled to be 4. The sodium hypochlorite and waste brine to be oxidized are introduced into the oxidation tower simultaneously from the bottom of the oxidation tower for deep oxidation treatment, with a residence time of 30 minutes. The material discharged from the top of the tower is the treated waste brine. The TOC content of the treated waste brine is tested, as shown in Table 1.

[0167] Comparative Example 1

[0168] The raw materials in this embodiment are described as follows:

[0169] Formaldehyde aqueous solution: concentration of 37 wt%, containing the following impurities by mass: 2500 mg / L formic acid, 1000 mg / L acetic acid, 1000 mg / L methanol, and 500 mg / L lipid impurities (mainly methyl formate, etc.);

[0170] Aniline aqueous solution: concentration of 99 wt%, containing the following impurities by weight: 50 mg / L phenol, 50 mg / L methylaniline, 800 mg / L cyclohexylamine, 1150 mg / L cyclohexanone, and 450 mg / L cyclohexanol;

[0171] Hydrochloric acid aqueous solution: concentration 33wt%, containing 5mg / L chlorobenzene;

[0172] Sodium hydroxide aqueous solution: concentration is 50wt%.

[0173] Preparation of DAM: Aniline aqueous solution and hydrochloric acid aqueous solution were mixed in a static mixer to form aniline hydrochloride, and formaldehyde aqueous solution was added thereto under stirring. The condensation reaction was carried out at 60°C for 2 hours. The molar ratio of formaldehyde to aniline was 0.55, and the hydrochloric acid (as H+ The molar ratio of aniline to aniline is 0.20;

[0174] The condensation reaction product was transferred to a transposition reactor, and the temperature was raised to 120° C. to carry out a transposition rearrangement reaction for 2 h to obtain a mixture of diamine hydrochloride and polyamine hydrochloride containing a diphenylmethane series;

[0175] The above mixture was transferred to a neutralization reactor, and sodium hydroxide aqueous solution was added with an alkali excess ratio of 1.50. The neutralization reaction was maintained at 98°C for 30 minutes, and after separation, crude DAM (organic phase) and organic waste water phase were obtained;

[0176] The organic wastewater phase obtained during the preparation of DAM was treated according to the following steps, and during the following treatment steps 1) to 3), the characteristic parameter Q = 52.00:

[0177] 1) introducing the organic waste water phase from the top of the extraction tower and introducing the aniline extractant from the bottom of the tower for reverse extraction to obtain extracted waste water; wherein the volume ratio of aniline to the organic waste water phase is 0.10, and the extraction temperature is 95° C.;

[0178] 2) The waste brine after extraction is passed from the top into the first stripping tower, and 2S steam is passed into the bottom of the tower for stripping treatment. The top temperature of the first stripping tower is maintained at 100°C, and the stripping ratio is 0.05. Light components such as aniline are removed from the top of the tower, and the waste brine after the first stripping is obtained at the bottom of the tower;

[0179] 3) The stripped waste brine obtained in step 2) is adjusted to a pH of 13 using 50 wt% sodium hydroxide or / and 33% hydrochloric acid aqueous solution to obtain waste brine to be oxidized. The temperature is adjusted to 40°C, and the molar ratio of sodium hypochlorite (calculated as available chlorine) to TOC in the waste brine to be oxidized is controlled to be 2. The sodium hypochlorite and the waste brine to be oxidized are introduced into a static mixer in proportion for pre-mixing and oxidation, and then passed into an oxidation tower from the bottom of the oxidation tower for deep oxidation treatment with a residence time of 30 minutes; the material discharged from the top of the tower is the treated waste brine. The TOC content of the treated waste brine is tested, as shown in Table 1.

[0180] Comparative Example 2

[0181] The raw materials in this embodiment are described as follows:

[0182] Formaldehyde aqueous solution: concentration of 37 wt%, containing the following impurities by mass: 4000 mg / L formic acid, 1500 mg / L acetic acid, 3000 mg / L methanol, and 1500 mg / L lipid impurities (mainly methyl formate, ethyl formate, etc.);

[0183] Aniline aqueous solution: concentration is 94 wt%, containing the following impurities by mass: 50 mg / L phenol, 50 mg / L methylaniline, 100 mg / L cyclohexylamine, 700 mg / L cyclohexanone, and 100 mg / L cyclohexanol.

[0184] Hydrochloric acid aqueous solution: concentration 33wt%, containing 5mg / L chlorobenzene;

[0185] Sodium hydroxide aqueous solution: concentration is 50wt%.

[0186] Preparation of DAM: Aniline aqueous solution and hydrochloric acid aqueous solution were mixed in a static mixer to form aniline hydrochloride, and formaldehyde aqueous solution was added thereto under stirring. The condensation reaction was carried out at 35°C for 2 hours. The molar ratio of formaldehyde to aniline was 0.52, and the hydrochloric acid (as H + The molar ratio of aniline to aniline is 0.35;

[0187] The condensation reaction product was transferred to a transposition reactor, and the temperature was raised to 120° C. to carry out a transposition rearrangement reaction for 2 h to obtain a mixture of diamine hydrochloride and polyamine hydrochloride containing a diphenylmethane series;

[0188] The above mixture was transferred to a neutralization reactor, and sodium hydroxide aqueous solution was added with an alkali excess ratio of 1.30. The neutralization reaction was maintained at 95° C. for 30 minutes. After layering, crude DAM (organic phase) and organic waste water phase were obtained.

[0189] The organic wastewater phase obtained during the preparation of DAM was treated according to the following steps, and during the following treatment steps 1) to 3), the characteristic parameter Q was not controlled to be less than 50:

[0190] 1) introducing the organic waste water phase from the top of the extraction tower and introducing the aniline extractant from the bottom of the tower for reverse extraction to obtain extracted waste water; wherein the volume ratio of aniline to the organic waste water phase is 0.10, and the extraction temperature is 80° C.;

[0191] 2) The waste brine after extraction is passed from the top into the first stripping tower, and 2S steam is passed into the bottom of the tower for stripping treatment. The top temperature of the first stripping tower is maintained at 100°C, and the stripping ratio is 0.05. Light components such as aniline are removed from the top of the tower, and the waste brine after the first stripping is obtained at the bottom of the tower;

[0192] 3) The stripped waste brine obtained in step 2) is adjusted to a pH of 13 using 50 wt% sodium hydroxide and / or 33% hydrochloric acid aqueous solution to obtain waste brine to be oxidized. The temperature is adjusted to 40°C, and the molar ratio of sodium hypochlorite (calculated as available chlorine) to TOC in the waste brine to be oxidized is controlled to be 2. The sodium hypochlorite and waste brine to be oxidized are simultaneously introduced into the oxidation tower from the bottom of the oxidation tower for deep oxidation treatment, with a residence time of 30 minutes; the material discharged from the top of the tower is the treated waste brine. The TOC content of the treated waste brine is tested, as shown in Table 1.

[0193] Table 1 Example and comparative example effect data Note: The values ​​of characteristic parameter Q listed in Table 1 are obtained by substituting the corresponding data of each embodiment or comparative example into formula (I) for calculation.

[0194] From the above experimental results, it can be seen that by adopting the method of the present invention, in the process of treating the saline organic wastewater generated in the DAM preparation process, combined with the impurity content of the raw materials formaldehyde and raw material aniline used to prepare DAM, controlling the characteristic parameter Q < 50 in the process of treating the saline organic wastewater, the TOC removal effect can be significantly improved, and treated wastewater with a low TOC content (for example, <10 mg / L) can be obtained.

[0195] It will be readily understood that the above embodiments are merely examples for clarity of description and are not intended to limit the present invention to these examples. Those skilled in the art will readily appreciate that other variations or modifications based on the above description are possible. It is not necessary and impossible to provide an exhaustive list of all possible implementations. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for reducing the TOC content in the salt-containing organic wastewater generated during the DAM preparation process, wherein, The raw material formaldehyde and the raw material aniline successively undergo a condensation reaction and a rearrangement reaction in the presence of an acidic catalyst to obtain a mixture; an alkali solution is added to the mixture for a neutralization reaction, and an organic waste brine phase is obtained through phase separation; it is characterized in that the treatment of the organic waste brine phase includes the following steps: 1) Extracting the organic waste brine phase with an extractant to obtain the waste brine after extraction; 2) Stripping the waste brine after extraction to obtain the waste brine after stripping; the stripping includes a first stripping of the waste brine after extraction and an optional second stripping; preferably, the pH of the waste brine obtained after the first stripping is adjusted to 0.5 ≤ pH < 7 to obtain an acidic waste brine, and the acidic waste brine is subjected to the second stripping; 3) Adjusting the pH of the waste brine after stripping obtained in step 2) to obtain the waste brine to be oxidized; oxidizing the waste brine to be oxidized with an oxidant to obtain the treated saline organic wastewater; And, under the condition that the control characteristic parameter Q < 50, the organic waste brine phase is subjected to the treatment of the steps 1)-3), and the calculation formula of the characteristic parameter Q is as follows: Q = 5.0x10 -4 xC1 + 1.0x10 -3 xC2 - 10.0xB - 10.0xD1 - 10.0xD2 + 2.0xP1 - 0.1xT + 2.0xP2 - O + 2.5; Wherein, C1 is the mass concentration of impurities in the raw material formaldehyde, mg / L; C2 is the mass concentration of impurities in the raw material aniline, mg / L; B is the volume ratio of the extractant to the organic waste brine phase; D1 is the stripping ratio of the first stripping, D2 is the stripping ratio of the second stripping; P1 is the pH of the acidic waste brine; P2 is the pH of the waste brine to be oxidized; T is the temperature for the oxidation treatment, °C; O is the molar ratio of the oxidant to the TOC in the waste brine to be oxidized; when the second stripping is not carried out, the value of D2 is 0, and the value of P2 is taken as the value of P1 and substituted into the formula.

2. The method according to claim 1, characterized in that, In step 1), the extractant is aniline and / or toluene, and the volume ratio of the extractant to the organic waste brine phase is 0.05 - 1.30, preferably 0.1 - 0.8; the extraction temperature is 50 - 120 °C, preferably 60 - 110 °C; Preferably, the extractant and the organic waste brine phase flow countercurrently in an extraction tower for the extraction.

3. The method according to any one of claims 1-2, characterized in that, The first stripping and the second stripping are respectively carried out in a stripping tower; The top temperature of the stripping tower for the first stripping is 80 - 160 °C, preferably 90 - 130 °C; the stripping ratio of the first stripping is 0.03 - 0.80, preferably 0.05 - 0.30; The top temperature of the stripping tower for the second stripping is 80 - 160 °C, preferably 90 - 130 °C; the stripping ratio of the second stripping is 0.03 - 0.80, preferably 0.05 - 0.30; when the second stripping is carried out, the pH of the waste brine obtained after the first stripping is adjusted to 2 - 6 to obtain the acidic waste brine.

4. The method according to any one of claims 1 to 3, characterized in that In step 3), the temperature of the oxidation treatment is 30 - 90 °C, preferably 40 - 70 °C; the pH of the waste brine to be oxidized is 2 - 14, preferably 4 - 13; Preferably, the oxidant is one or more of a chlorine-containing oxidant, ozone, and hydrogen peroxide; preferably, the chlorine-containing oxidant is selected from one or more of sodium hypochlorite, chlorine gas, and sodium perchlorate; Preferably, when the oxidant is a chlorine-containing oxidant, the oxidant is calculated as available chlorine, and the molar ratio of the oxidant to TOC in the waste salt water to be oxidized is 2-15, preferably 2-10; Preferably, the oxidation treatment includes performing deep oxidation treatment in an oxidation tower. Preferably, the deep oxidation treatment time is 3-600 min, preferably 5-300 min.

5. The method according to any one of claims 1-4, characterized in that, The mass concentration of impurities in the raw formaldehyde is 50-10,000 mg / L; And / or, the mass concentration of impurities in the raw aniline is 10-2,500 mg / L.

6. The method according to any one of claims 1-5, characterized in that, The impurities in the raw formaldehyde include one or more of formic acid, acetic acid, methanol, methyl formate, and ethyl formate; And / or, the impurities in the raw aniline include one or more of benzene, phenol, methylaniline, cyclohexylamine, cyclohexanone, and cyclohexanol.

7. The method according to any one of claims 1-6, characterized in that, The raw formaldehyde is a formaldehyde solution, and the mass fraction of formaldehyde in the formaldehyde solution is 15-55%, preferably 20-50%; And / or, the raw aniline is an aniline solution, and the mass fraction of aniline in the aniline solution is 90%-100%; And / or, the molar ratio of the amounts of formaldehyde and aniline used is 0.10-0.85, preferably 0.20-0.

60.

8. The method according to claim 7, wherein The acidic catalyst is selected from one or more of organic acids, inorganic acids, and solid acids, preferably hydrochloric acid, and more preferably 30-37 wt% hydrochloric acid; When the acidic catalyst is the organic acid and / or the inorganic acid, based on H + calculated, the molar ratio of the amount of the acidic catalyst to the amount of aniline is between 0.01 and 0.80, preferably between 0.05 and 0.

40.

9. The method according to claim 8, characterized in that The lye is a sodium hydroxide solution. Preferably, the mass fraction of sodium hydroxide in the sodium hydroxide solution is 20-55%, preferably 32-50%; Preferably, when the acidic catalyst is the organic acid and / or the inorganic acid, based on H + in terms of, the molar ratio of sodium hydroxide in the sodium hydroxide solution to the acidic catalyst is 1.0 to 3.0, preferably 1.01 to 1.50.

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