Method for reducing the toc content in a salt-containing organic waste water produced during the production of dam

Abstract

The present application relates to the technical field of preparation of diphenylmethane series diamines and polyamines, in particular to a method for reducing the TOC content in salt-containing organic wastewater generated in the preparation of DAM, and the method based on the present application is used to treat the salt-containing organic wastewater generated in the preparation of DAM, which is conducive to effectively reducing the TOC content in the salt-containing organic wastewater. In the method, the treatment of the organic waste salt water phase comprises the following steps: 1) extracting the organic waste salt water phase with an extractant; 2) stripping the waste salt water after extraction; 3) adjusting the pH of the waste salt water after stripping, and then performing oxidation treatment; the treatment of steps 1)-3) is performed under the condition that the characteristic parameter Q is controlled to be less than 50, 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.

Description

Technical Field

[0001] This invention relates to the field of preparation technology of diphenylmethane series diamines and polyamines (DAM), specifically to a method for reducing the TOC content in saline organic wastewater generated during the DAM preparation process. Background Technology

[0002] The preparation methods of DAM (diphenylmethane series diamines and polyamines) are well known and described in many published patents and publications, such as US-A 2009 / 0240077, EP-A-451442, and WO-A-99 / 40059. DAM is prepared through continuous, semi-continuous, or discontinuous reaction processes. Typically, aniline is reacted with hydrochloric acid to generate aniline hydrochloride, and then formaldehyde is added to the reactor to generate DAM hydrochloride. Through neutralization, water washing, and separation of the organic and inorganic phases, crude DAM and organic waste brine are obtained. The crude DAM is then purified to obtain DAM. In order to control the TOC content of the organic waste brine and meet the requirements for chlor-alkali reuse, measures such as controlling the impurity content in the upstream reaction raw materials, such as formaldehyde and aniline, are often combined with extraction, vaporization, and deep treatment processes for improvement. 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 112094194 A discloses a method for controlling TOC in waste brine during DAM production. This method controls the total impurity content in formaldehyde to below 1000 mg / L, and the excess alkali rate of the neutralization reaction is 1.01-1.30, thereby reducing the TOC content to below 15 mg / L. Chinese patent CN 111960952 B discloses a method for improving the quality of waste brine during DAM preparation. By controlling the aminophenol content in the raw material aniline to below 10 mg / L, the oxygen content in the system to no higher than 0.01 mg / L, and the mass ratio of sodium chlorate in caustic soda to aminophenol in aniline to be between 2:15:1, the method ensures that aminophenol is not detected in the waste brine by controlling the raw material quality and content ratio, thus avoiding the generation of explosive substances NCl3. This method is applicable to the downstream chlor-alkali industry. By controlling the content of individual impurity components in formaldehyde and aniline raw materials, and combining this with downstream deep treatment processes such as extraction, stripping, adsorption, and Fenton oxidation, the operating cost is high, the process is lengthy and complex, the process parameters cannot be organically combined for precise control, and it cannot cope with situations where changes in multiple impurity components upstream lead to substandard downstream treatment, resulting in low universality.

[0004] Chinese patent application CN101665302A discloses a waste brine treatment process that utilizes a multi-stage rotating bed extraction process to replace the traditional single-stage extraction process. The extracted brine is further processed through a stripping process, followed by oxidation and adsorption treatment to meet chlor-alkali reuse requirements. Chinese patent application CN101143753A discloses a deep treatment method for MDI waste brine, which combines oxidation and adsorption processes for deep treatment. However, this method suffers from high energy consumption, high investment, complex equipment structure, and a long process flow. Furthermore, it lacks the ability to precisely control various process parameters and cannot address situations where increased levels of multiple upstream impurities lead to substandard downstream treatment, resulting in low applicability. Summary of the Invention

[0005] This invention provides a method for reducing the TOC content in saline organic wastewater generated during DAM preparation. The method of this invention facilitates precise control of process parameters for organic wastewater treatment and effectively reduces the TOC content in the saline organic wastewater.

[0006] To achieve its objective, the present invention provides the following technical solution:

[0007] This invention provides a method for reducing the TOC content in saline organic wastewater generated during DAM preparation. The method involves sequentially reacting formaldehyde and aniline in the presence of an acidic catalyst via condensation and transposition reactions to obtain a mixture containing diphenylmethane series diamine hydrochloride and polyamine hydrochloride. An alkaline solution is added to the mixture for neutralization, followed by phase separation to obtain an organic wastewater brine phase. The treatment of the organic wastewater brine phase includes the following steps:

[0008] 1) Extract the organic wastewater phase with an extractant to obtain the extracted wastewater;

[0009] 2) The extracted waste brine is stripped to obtain stripped waste brine; the stripping includes a first stripping and an optional second stripping of the extracted waste brine; preferably, the pH of the waste brine obtained after 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.

[0010] 3) Adjust the pH of the stripped waste brine obtained in step 2) to obtain waste brine to be oxidized; oxidize the waste brine to be oxidized with an oxidant to obtain treated saline organic wastewater;

[0011] Furthermore, the organic wastewater phase is treated in steps 1)-3) under the condition that the characteristic parameter Q < 50. The formula for calculating the characteristic parameter Q is as follows: Q = 5.0 x 10 -4 xC1+1.0x10 -3 xC2-10.0xB-10.0xD1-10.0xD2+2.0xP1-0.1xT+2.0xP2-O+2.5;

[0012] Wherein, C1 is the mass concentration of impurities in the formaldehyde raw material, mg / L; C2 is the mass concentration of impurities in the aniline raw material, mg / L; B is the volume ratio (i.e., extraction 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 of 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 performed, the value of D2 is 0, and the value of P2 is used as the value of P1 and substituted into the formula to calculate the characteristic parameter Q.

[0013] This invention addresses the aforementioned treatment process for organic wastewater brine by proposing a method to reduce TOC content through adjusting the characteristic parameter Q. This method can reduce the TOC content in organic wastewater brine while relaxing the impurity content indicators of upstream raw materials (e.g., aniline and / or formaldehyde).

[0014] In the text, "optional second stripping" refers to performing a second stripping or not performing a second stripping.

[0015] In a preferred embodiment, after extraction in step 1), two stripping processes are performed, and the second stripping is carried out under conditions where the waste brine after the first stripping treatment is adjusted to 0.5 ≤ pH < 7 (e.g., 0.5, 1, 2, 3, 4, 5, 6, 6.5 or 6.8, etc.). The inventors have found that performing two-stage stripping in this preferred manner is beneficial for further reducing the TOC content in the treated saline organic wastewater.

[0016] In some implementations, after extraction in step 1), only the first stripping is performed. In this case, the operation of adjusting the pH of the waste brine obtained from the first stripping to 0.5 ≤ pH < 7 to obtain acidic waste brine is not involved. In this case, when calculating the characteristic parameter Q, the value of D2 is 0, and the value of P2 is substituted into P1 in the formula for calculation.

[0017] In this text, "stripping ratio" refers to the mass ratio between the steam used in the stripping process and the stripped wastewater. Specifically, the stripping ratio for the first stripping is the mass ratio between the steam used in the stripping and the extracted waste brine, and the stripping ratio for the second stripping is the mass ratio between the steam used in the stripping and the acidic waste brine.

[0018] In the text, "TOC" refers to the total organic carbon content in the aqueous phase, expressed as the mass concentration of carbon (C) (mg / L).

[0019] The pH of the solution mentioned in the text is the pH measured at 25°C; when the pH of the solution is less than 7 at 25°C, it is considered an acidic solution.

[0020] Specifically, the organic wastewater brine phase is treated under the condition that the characteristic parameter Q < 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 Q < 50, Q < 40, Q < 30, Q < 25, Q < 20, or Q < 15, etc.; in a more preferred embodiment, for example, Q < 25; more preferably, Q < 20; and even more preferably, Q < 10, which can more significantly reduce the TOC content of the treated wastewater brine.

[0021] In some embodiments, 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, 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℃, for example, 50, 60, 80, 100, 110, 120℃, etc., preferably 60-110℃;

[0022] Preferably, the extractant and the organic wastewater phase flow counter-currently in the extraction tower for the extraction process.

[0023] Further, the first stripping and the second stripping are carried out in stripping towers respectively; in some embodiments, the top temperature of the stripping tower for the first stripping is 80-160℃, such as 80, 90, 100, 110, 130, 140, 160℃, etc., preferably 90-130℃; the stripping ratio for the first stripping is 0.03-0.80, such as 0.03, 0.05, 0.10, 0.30, 0.50, 0.80, etc., preferably 0.05-0.30;

[0024] The top temperature of the stripping tower for the second stripping is 80-160℃, such as 80, 90, 100, 110, 130, 140, 160℃, etc., preferably 90-130℃; the stripping ratio for the second stripping is 0.03-0.80, such as 0.03, 0.05, 0.10, 0.30, 0.50, 0.80, etc., preferably 0.05-0.30; during the second stripping, the pH of the waste brine obtained from the first stripping is adjusted to 2-6 to obtain the acidic waste brine.

[0025] In some embodiments, in step 3), the oxidation treatment temperature is 30-90℃, such as 30℃, 40℃, 50℃, 70℃, 80℃, 90℃, etc., preferably 40-70℃; the pH of the waste brine to be oxidized is 2-14, such as 2, 3, 4, 6, 8, 10, 11, 13, 14, etc., preferably 4-13;

[0026] Preferably, the oxidant is one or more of a chlorine-containing oxidant, ozone, and hydrogen peroxide; more preferably, the chlorine-containing oxidant is selected from one or more of sodium hypochlorite, chlorine, and sodium perchlorate.

[0027] Preferably, when the oxidant is a chlorine-containing oxidant, the oxidant is calculated based on available chlorine, and the molar ratio of the oxidant to the TOC in the waste brine to be oxidized is 2-15, for example, 2, 3, 4, 6, 8, 10, 11, 13, 14, 15, etc., preferably 2-10.

[0028] 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.

[0029] In this invention, in step 3), the oxidation treatment of the waste brine to be oxidized with an oxidant can be carried out using an oxidation process known in the art. Preferably, the waste brine to be oxidized is first mixed with an oxidant for premixed oxidation, and then passed into an oxidation tower for deep oxidation treatment.

[0030] DAM products are well known in the art through a series of condensation and transposition reactions of formaldehyde and aniline in the presence of an acidic catalyst, followed by a subsequent alkaline neutralization reaction. After the alkaline neutralization reaction, a DAM-containing organic phase and an organic wastewater phase are separated. The DAM-containing organic phase can be purified to obtain refined DAM. Specifically, in the preparation of DAM by reacting formaldehyde and aniline in the presence of an acidic catalyst, an aniline solution and an acidic catalyst are first mixed to form aniline hydrochloride, and then a formaldehyde solution is added to carry out condensation and transposition reactions. The condensation reaction temperature is, for example, 35-95°C, and the condensation reaction time is, for example, 0.1-5 h; the transposition reaction temperature is, for example, 95-150°C, and the transposition reaction time is, for example, 0.5-5 h. The above is only one example; those skilled in the art can also use other conventional preparation processes in the art to prepare DAM based on the reaction of formaldehyde, aniline, and an acidic catalyst.

[0031] The method of this invention, used to treat the organic wastewater phase generated during DAM production, can yield treated saline organic wastewater with low TOC content under relatively lenient upstream raw material impurity content requirements. In some embodiments, the impurity mass concentration of the raw material formaldehyde is 50-10000 mg / L, for example, 50, 100, 500, 1000, 2000, 4000, 6000, 8000, 10000 mg / L; in other embodiments, the impurity mass concentration of the raw material aniline is 10-2500 mg / L, for example, 10, 50, 100, 500, 700, 1000, 1500, 2000, 2500 mg / L. The impurities contained in the raw material 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, methyl aniline, cyclohexylamine, cyclohexanone, and cyclohexanol. These impurities in aniline can further react to generate impurities including aminophenol, acrolein, acrylic acid, propionic acid, formamide, and / or acetaniline. During neutralization and phase separation, these impurities enter the waste brine phase, forming organic waste brine. Current technologies that control the impurity content of raw materials from the raw material end suffer from high costs and difficulties, easily resulting in high TOC (total organic matter) in the waste brine, making it difficult to meet the requirements of downstream chlor-alkali industries.

[0032] In some embodiments, the raw material formaldehyde is a formaldehyde solution, such as an aqueous formaldehyde solution, wherein the mass fraction of formaldehyde in the formaldehyde solution is 15-55%, preferably 20-50%.

[0033] In some embodiments, the raw material aniline is an aniline solution, such as an aqueous aniline solution, wherein the mass fraction of aniline in the aniline solution is 90%-100%.

[0034] In some embodiments, the molar ratio of formaldehyde to aniline is 0.10 to 0.85, preferably 0.20 to 0.60.

[0035] In some embodiments, the acidic catalyst is selected from one or more of organic acids, inorganic acids, and solid acids, preferably hydrochloric acid, more preferably 30-37 wt% hydrochloric acid. When the acidic catalyst is the organic acid and / or the inorganic acid, H+ is used. + The molar ratio of the acidic catalyst to the aniline is between 0.01 and 0.80, preferably between 0.05 and 0.40.

[0036] In some embodiments, the alkaline solution is a sodium hydroxide solution, preferably with a sodium hydroxide mass fraction of 20-55%, more preferably 32-50%. Preferably, when the acidic catalyst is the organic acid and / or the inorganic acid, the acidic catalyst is in the form of H+. + The molar ratio of sodium hydroxide to acidic catalyst in the sodium hydroxide solution is 1.0 to 3.0, preferably 1.01 to 1.50.

[0037] In some embodiments, in step 1), the volume ratio of the extractant to the organic wastewater phase is controlled to be 0.05-1.30, preferably 0.1-0.8; the extraction temperature is 50-120℃, preferably 60-110℃; the top temperature of the stripping tower for the first stripping is controlled to be 80-160℃, preferably 90-130℃; the stripping ratio for the first stripping is 0.03-0.80, preferably 0.05-0.30; optionally, a second stripping is performed, and preferably the top temperature of the stripping tower for the second stripping is controlled to be 80-160℃, preferably 90-130℃, and the stripping ratio for the second stripping is 0.03-0.80, preferably 0.05-0.30. The pH of the acidic wastewater is 2-6; in step 3), the temperature of the oxidation treatment is controlled at 30-90℃, preferably 40-70℃; the pH of the wastewater to be oxidized is controlled at 2-14, preferably 4-13; the molar ratio of the oxidant to the TOC in the wastewater to be oxidized, calculated as available chlorine, is controlled at 2-15, preferably 2-10; based on the above conditions, steps (1)-(3) are simultaneously controlled to treat the organic wastewater phase under the condition that the characteristic parameter Q < 50. Through the above method, the TOC removal effect of saline organic wastewater can be significantly improved, and there is no need to impose stringent requirements on the impurity content of the raw materials 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.

[0038] In this invention, during the DAM preparation process, while relaxing the impurity content indicators of upstream raw materials (e.g., aniline and / or formaldehyde), the characteristic parameter Q < 50 in the organic wastewater brine treatment process can be adjusted to achieve precise integrated control of the organic wastewater brine treatment process parameters. This can reduce the TOC content in the organic wastewater brine, for example, to less than 10 mg / L. Using the solution of this invention helps reduce the production cost of upstream raw materials.

[0039] The technical solution provided by this invention has the following beneficial effects:

[0040] This invention provides a method for reducing the TOC content in saline organic wastewater generated during DAM preparation. By controlling the characteristic parameter Q < 50, the impurity content index of upstream raw materials, such as aniline and formaldehyde, can be relaxed. Through the adjustment of the characteristic parameter Q, the TOC content of the treated wastewater can be reduced, for example, to less than 10 mg / L, while reducing the production cost of upstream raw materials. This achieves an organic combination and precise control of the parameters of the organic wastewater treatment system. Detailed Implementation

[0041] To facilitate understanding of the present invention, the following description, in conjunction with embodiments, will further illustrate the invention. It should be understood that the following embodiments are merely for a better understanding of the invention and do not imply that the invention is limited to these embodiments.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The term "and / or" as used herein may include 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 should not be construed as indicating or implying relative importance.

[0043] Where specific experimental steps or conditions are not specified in the examples, the corresponding conventional experimental steps or conditions in this technical field can be followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0044] Various impurities such as formic acid and acetic acid in formaldehyde were analyzed using an Agilent 1260Infinity II high-performance liquid chromatograph; various impurities such as phenol, methylaniline, and cyclohexanol in aniline were analyzed using an Agilent 8890GC System gas chromatograph; and the TOC in waste brine was analyzed using an Analytik Jena Multi N / C 3100TOC / TN analyzer.

[0045] In the following examples and comparative examples, "2S steam" refers to saturated water steam at an absolute pressure of 3 MPaA.

[0046] In the following examples and comparative examples, the formula for calculating the characteristic parameter Q is as follows:

[0047] Q = 5.0 x 10 -4 xC1+1.0x10 -3 xC2-10.0xB-10.0xD1-10.0xD2+2.0xP1-0.1xT+2.0x

[0048] P2-O+2.5;

[0049] Wherein, C1 is the mass concentration of impurities in the formaldehyde (i.e., formaldehyde aqueous solution) used in the preparation of DAM, mg / L; C2 is the mass concentration of impurities in the aniline (i.e., aniline aqueous solution) used in the preparation of DAM, mg / L; B is the volume ratio of the extractant used in step 1) to the organic waste brine phase; D1 is the stripping ratio of the first stripping in step 2), and D2 is the stripping ratio of the second stripping in step 2); P1 is the pH of the acidic waste brine in step 2); P2 is the pH of the waste brine 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 (calculated as available chlorine) to the TOC in the waste brine to be oxidized in step 3); when the treatment of the organic waste brine phase does not involve the second stripping, when calculating the characteristic parameter Q, the value of D2 is 0, and the value of P1 is substituted into the formula for calculation.

[0050] In the following examples and comparative examples, the alkali excess rate refers to the sodium hydroxide (in OH-) in the sodium hydroxide aqueous solution. - (calculated) and hydrochloric acid (in H) + The molar ratio (calculated).

[0051] Example 1

[0052] The raw materials described in this embodiment are as follows:

[0053] Formaldehyde aqueous solution: concentration is 37wt%, which contains the following impurities by mass: 4000mg / L formic acid, 1500mg / L acetic acid, 3000mg / L methanol and 1500mg / L lipid impurities (mainly methyl formate, ethyl formate, etc.);

[0054] Aqueous aniline solution: concentration of 94 wt%, containing the following impurities in the following mass amounts: 50 mg / L phenol, 50 mg / L methyl aniline, 100 mg / L cyclohexylamine, 700 mg / L cyclohexanone, and 100 mg / L cyclohexanol.

[0055] Hydrochloric acid aqueous solution: concentration 33wt%, containing 5mg / L chlorobenzene;

[0056] Sodium hydroxide aqueous solution: concentration 50 wt%.

[0057] Preparation of DAM: Aqueous aniline and aqueous hydrochloric acid were mixed in a static mixer to form aniline hydrochloride. Aqueous formaldehyde was then added while stirring, and 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 (in H2O) was added as follows: + The molar ratio of (calculated) to aniline is 0.35;

[0058] The condensation reaction product was transferred to a transposition reactor, and the temperature was increased to 120°C to carry out the transposition rearrangement reaction for 2 hours to obtain a mixture containing diphenylmethane series diamine hydrochloride and polyamine hydrochloride.

[0059] The mixture was transferred to a neutralization reactor, and sodium hydroxide aqueous solution was added. The excess alkali ratio was 1.30. The neutralization reaction was carried out at 95°C for 30 minutes. After separation, crude DAM (organic phase) and organic waste brine phase were obtained.

[0060] The organic wastewater phase obtained during the DAM preparation process was treated according to the following steps, and during the following treatment steps 1)-3), the characteristic parameter Q = 21.50 was controlled:

[0061] 1) The organic wastewater phase is introduced from the top of the extraction tower, and the aniline extractant is introduced from the bottom of the tower for counter-current extraction to obtain the extracted wastewater; wherein, the volume ratio of aniline to organic wastewater phase is 0.30, and the extraction temperature is 80℃.

[0062] 2) The extracted waste brine is fed into the first stripping tower from the top, and 2S steam is introduced into the bottom of the tower for stripping. The top temperature of the first stripping tower is maintained at 100℃, 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. 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. The obtained acidic waste brine is introduced into the second stripping tower, and 2S steam is introduced for the second stripping. The top temperature of the second stripping tower is maintained at 105℃, 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 of the tower is the stripped waste brine.

[0063] 3) Adjust the pH of the stripped waste brine obtained in step 2) to 9.5 using a 50wt% sodium hydroxide aqueous solution to obtain the waste brine to be oxidized. Adjust the temperature to 50℃, controlling the molar ratio of sodium hypochlorite (based on available chlorine) to TOC in the waste brine to be oxidized to 4. Simultaneously introduce sodium hypochlorite and the waste brine to be oxidized from the bottom of the oxidation tower for deep oxidation treatment, with a residence time of 30 minutes. The top discharge is the treated waste brine. The TOC content of the treated waste brine is measured, as shown in Table 1.

[0064] Example 2

[0065] The raw materials described in this embodiment are as follows:

[0066] Formaldehyde aqueous solution: concentration of 37wt%, containing the following impurities by mass: 3000mg / L formic acid, 500mg / L acetic acid, 4000mg / L methanol, and 500mg / L lipid impurities (mainly methyl formate, etc.);

[0067] Aqueous aniline solution: concentration of 99 wt%, containing the following impurities in the following mass amounts: 50 mg / L phenol, 50 mg / L methyl aniline, 700 mg / L cyclohexylamine, 650 mg / L cyclohexanone, and 50 mg / L cyclohexanol;

[0068] Hydrochloric acid aqueous solution: concentration 33wt%, containing 5mg / L chlorobenzene;

[0069] Sodium hydroxide aqueous solution: concentration 50 wt%.

[0070] Preparation of DAM: Aqueous aniline and aqueous hydrochloric acid were mixed in a static mixer to form aniline hydrochloride. Aqueous formaldehyde was then added while stirring, and 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 (in H2O) was... + The molar ratio of (calculated) to aniline is 0.38;

[0071] The condensation reaction product was transferred to a transposition reactor, and the temperature was increased to 120°C to carry out the transposition rearrangement reaction for 2 hours to obtain a mixture containing diphenylmethane series diamine hydrochloride and polyamine hydrochloride.

[0072] The mixture was transferred to a neutralization reactor, and sodium hydroxide aqueous solution was added. The alkali excess rate was 1.50. The neutralization reaction was carried out at 98°C for 30 minutes. After separation, crude DAM (organic phase) and organic wastewater phase were obtained.

[0073] The organic wastewater phase obtained during the DAM preparation process was treated according to the following steps, and during the following treatment steps 1)-3), the characteristic parameter Q = 20.00 was controlled:

[0074] 1) The organic wastewater brine phase is introduced from the top of the extraction tower, and the aniline extractant is introduced from the bottom of the tower for counter-current extraction to obtain the extracted wastewater brine; wherein, the volume ratio of aniline to organic wastewater brine phase is 0.20, and the extraction temperature is 90℃;

[0075] 2) The extracted waste brine is fed into the first stripping tower from the top, and 2S steam is introduced into the bottom of the tower for stripping. The top temperature of the first stripping tower is maintained at 100℃, 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. The obtained waste brine after the first stripping is introduced into an acid-base adjustment tank, and its pH is adjusted to 3 using 33wt% hydrochloric acid to obtain acidic waste brine. The obtained acidic waste brine is introduced into the second stripping tower, and 2S steam is introduced for the second stripping. The top temperature of the second stripping tower is maintained at 105℃, 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 of the tower is the stripped waste brine.

[0076] 3) Adjust the pH of the stripped waste brine obtained in step 2) to 9.0 using a 50wt% sodium hydroxide aqueous solution to obtain the waste brine to be oxidized. Adjust the temperature to 60℃, control the molar ratio of sodium hypochlorite (based on available chlorine) to TOC in the waste brine to be oxidized to 3, and simultaneously introduce sodium hypochlorite and the waste brine to be oxidized into a static mixer for pre-mixing oxidation. Then, pass the mixture from the bottom of the oxidation tower into the deep oxidation tower for a residence time of 30 minutes. The top discharge is the treated waste brine. The TOC content of the treated waste brine is measured, as shown in Table 1.

[0077] Example 3

[0078] The raw materials described in this embodiment are as follows:

[0079] Formaldehyde aqueous solution: concentration is 37wt%, which contains the following impurities by mass: 3000mg / L formic acid, 500mg / L acetic acid, 2000mg / L methanol, 500mg / L lipid impurities (mainly methyl formate, ethyl formate, etc.);

[0080] Aqueous aniline solution: concentration of 99 wt%, containing the following impurities in the following mass amounts: 50 mg / L phenol, 50 mg / L methyl aniline, 800 mg / L cyclohexylamine, 1000 mg / L cyclohexanone, 100 mg / L cyclohexanol;

[0081] Hydrochloric acid aqueous solution: concentration 33wt%, containing 5mg / L chlorobenzene;

[0082] Sodium hydroxide aqueous solution: concentration 50 wt%.

[0083] Preparation of DAM: Aqueous aniline and aqueous hydrochloric acid were mixed in a static mixer to form aniline hydrochloride. Aqueous formaldehyde was then added while stirring, and 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 (in H₂O) was... + The molar ratio of (calculated) to aniline is 0.38;

[0084] The condensation reaction product was transferred to a transposition reactor, and the temperature was increased to 120°C to carry out the transposition rearrangement reaction for 2 hours to obtain a mixture containing diphenylmethane series diamine hydrochloride and polyamine hydrochloride.

[0085] The mixture was transferred to a neutralization reactor, sodium hydroxide aqueous solution was added, the alkali excess rate was 1.50, and the neutralization reaction was carried out at 98°C for 30 min. After separation, crude DAM (organic phase) and organic waste brine phase were obtained.

[0086] The organic wastewater phase obtained during the DAM preparation process was treated according to the following steps, and during the following treatment steps 1)-3), the characteristic parameter Q was controlled to be 23.5:

[0087] 1) The organic waste brine phase is introduced from the top of the extraction tower, and the aniline extractant is introduced from the bottom of the tower for counter-current extraction to obtain the extracted waste brine; wherein, the volume ratio of aniline to organic waste brine phase is 0.25, and the extraction temperature is 90℃.

[0088] 2) The extracted waste brine is fed into the first stripping tower from the top, and 2S steam is introduced into the bottom of the tower for stripping. The top temperature of the first stripping tower is maintained at 100℃, 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. 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. The obtained acidic waste brine is introduced into the second stripping tower, and 2S steam is introduced for the second stripping. The top temperature of the second stripping tower is maintained at 105℃, 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 of the tower is the stripped waste brine.

[0089] 3) Adjust the pH of the stripped waste brine obtained in step 2) to 8.5 using a 50wt% sodium hydroxide aqueous solution to obtain the waste brine to be oxidized. Adjust the temperature to 45℃, controlling the molar ratio of sodium hypochlorite (based on available chlorine) to TOC in the waste brine to be oxidized to 2. Simultaneously introduce sodium hypochlorite and the waste brine to be oxidized into a static mixer for pre-mixing oxidation, then pass it through the bottom of the oxidation tower for deep oxidation treatment, with a residence time of 30 minutes. The top discharge is the treated waste brine. The TOC content of the treated waste brine is measured, as shown in Table 1.

[0090] Example 4

[0091] The raw materials described in this embodiment are as follows:

[0092] 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.);

[0093] Aqueous aniline solution: concentration of 99 wt%, containing the following impurities in the following mass amounts: 50 mg / L phenol, 50 mg / L methyl aniline, 800 mg / L cyclohexylamine, 1150 mg / L cyclohexanone, and 450 mg / L cyclohexanol;

[0094] Hydrochloric acid aqueous solution: concentration 33wt%, containing 5mg / L chlorobenzene;

[0095] Sodium hydroxide aqueous solution: concentration 50 wt%.

[0096] Preparation of DAM: Aqueous aniline and aqueous hydrochloric acid were mixed in a static mixer to form aniline hydrochloride. Aqueous formaldehyde was then added while stirring, and 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 (in H2O) was... + The molar ratio of (calculated) to aniline is 0.20;

[0097] The condensation reaction product was transferred to a transposition reactor, and the temperature was increased to 120°C to carry out the transposition rearrangement reaction for 2 hours to obtain a mixture containing diphenylmethane series diamine hydrochloride and polyamine hydrochloride.

[0098] The mixture was transferred to a neutralization reactor, sodium hydroxide aqueous solution was added, the alkali excess rate was 1.50, and the neutralization reaction was carried out at 98°C for 30 min. After separation, crude DAM (organic phase) and organic waste brine phase were obtained.

[0099] The organic wastewater phase obtained during the DAM preparation process was treated according to the following steps, and during the following treatment steps 1)-3), the characteristic parameter Q = 24.00 was controlled:

[0100] 1) The organic waste brine phase is introduced from the top of the extraction tower, and the aniline extractant is introduced from the bottom of the tower for counter-current extraction to obtain the extracted waste brine; wherein, the volume ratio of aniline to organic waste brine phase is 0.15, and the extraction temperature is 95℃.

[0101] 2) The extracted waste brine is fed into the first stripping tower from the top, and 2S steam is introduced into the bottom of the tower for stripping. The top temperature of the first stripping tower is maintained at 100℃, 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. 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. The obtained acidic waste brine is introduced into the second stripping tower, and 2S steam is introduced for the second stripping. The top temperature of the second stripping tower is maintained at 105℃, 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 of the tower is the stripped waste brine.

[0102] 3) Adjust the pH of the stripped waste brine obtained in step 2) to 9.5 using a 50wt% sodium hydroxide aqueous solution to obtain the waste brine to be oxidized. Adjust the temperature to 50℃, control the molar ratio of sodium hypochlorite (based on available chlorine) to TOC in the waste brine to be oxidized to 6, and simultaneously introduce sodium hypochlorite and the waste brine to be oxidized into a static mixer for pre-mixing oxidation. Then, pass the mixture from the bottom of the oxidation tower into the deep oxidation tower for a residence time of 30 minutes. The top discharge is the treated waste brine. The TOC content of the treated waste brine is measured, as shown in Table 1.

[0103] Example 5

[0104] The raw materials described in this embodiment are as follows:

[0105] Formaldehyde aqueous solution: concentration is 37 wt%, which contains the following impurities in mass content: 500 mg / L formic acid, 300 mg / L acetic acid, 100 mg / L methanol and 100 mg / L lipid impurities (mainly methyl formate, etc.);

[0106] Aniline aqueous solution: concentration of 95 wt%, containing the following impurities in mass content: 50 mg / L phenol, 50 mg / L methyl aniline, 500 mg / L cyclohexylamine, 350 mg / L cyclohexanone, 50 mg / L cyclohexanol;

[0107] Hydrochloric acid aqueous solution: concentration 33wt%, containing 5mg / L chlorobenzene;

[0108] Sodium hydroxide aqueous solution: concentration 50 wt%.

[0109] Preparation of DAM: Aqueous aniline and aqueous hydrochloric acid were mixed in a static mixer to form aniline hydrochloride. Aqueous formaldehyde was then added while stirring, and 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 (in H₂O) was... + The molar ratio of (calculated) to aniline is 0.20;

[0110] The condensation reaction product was transferred to a transposition reactor, and the temperature was increased to 120°C to carry out the transposition rearrangement reaction for 2 hours to obtain a mixture containing diphenylmethane-based diamine hydrochloride and polyamine hydrochloride.

[0111] The mixture was transferred to a neutralization reactor, and sodium hydroxide aqueous solution was added. The alkali excess rate was 1.50. The neutralization reaction was carried out at 98°C for 30 minutes. After separation, crude DAM (organic phase) and organic wastewater phase were obtained.

[0112] The organic wastewater phase obtained during the DAM preparation process was treated according to the following steps, and during the following treatment steps 1)-3), the characteristic parameter Q = 20.50 was controlled:

[0113] 1) The organic waste brine phase is introduced from the top of the extraction tower, and the aniline extractant is introduced from the bottom of the tower for counter-current extraction to obtain the extracted waste brine; wherein, the volume ratio of aniline to organic waste brine phase is 0.15, and the extraction temperature is 95℃.

[0114] 2) The extracted waste brine is fed into the first stripping tower from the top, and 2S steam is introduced into the bottom of the tower for stripping. The top temperature of the first stripping tower is maintained at 100℃, 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. 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. The obtained acidic waste brine is introduced into the second stripping tower, and 2S steam is introduced for the second stripping. The top temperature of the second stripping tower is maintained at 105℃, 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 of the tower is the stripped waste brine.

[0115] 3) Adjust the pH of the stripped waste brine obtained in step 2) to 9.5 using a 50wt% sodium hydroxide aqueous solution to obtain the waste brine to be oxidized. Adjust the temperature to 50℃, control the molar ratio of sodium hypochlorite (based on available chlorine) to TOC in the waste brine to be oxidized to 6, and simultaneously introduce sodium hypochlorite and the waste brine to be oxidized into a static mixer for pre-mixing oxidation. Then, pass the mixture from the bottom of the oxidation tower into the deep oxidation tower for a residence time of 30 minutes. The top discharge is the treated waste brine. The TOC content of the treated waste brine is measured, as shown in Table 1.

[0116] Example 6

[0117] The raw materials described in this embodiment are as follows:

[0118] Formaldehyde aqueous solution: concentration is 37 wt%, which contains the following impurities in mass content: 500 mg / L formic acid, 300 mg / L acetic acid, 100 mg / L methanol and 100 mg / L lipid impurities (mainly methyl formate, etc.);

[0119] Aniline aqueous solution: concentration of 95 wt%, containing the following impurities in mass content: 50 mg / L phenol, 50 mg / L methyl aniline, 500 mg / L cyclohexylamine, 350 mg / L cyclohexanone, 50 mg / L cyclohexanol;

[0120] Hydrochloric acid aqueous solution: concentration 33wt%, containing 5mg / L chlorobenzene;

[0121] Sodium hydroxide aqueous solution: concentration 50 wt%.

[0122] Preparation of DAM: Aqueous aniline and aqueous hydrochloric acid were mixed in a static mixer to form aniline hydrochloride. Aqueous formaldehyde was then added while stirring, and 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 (in H₂O) was... + The molar ratio of (calculated) to aniline is 0.20;

[0123] The condensation reaction product was transferred to a transposition reactor, and the temperature was increased to 120°C to carry out the transposition rearrangement reaction for 2 hours to obtain a mixture containing diphenylmethane-based diamine hydrochloride and polyamine hydrochloride.

[0124] The mixture was transferred to a neutralization reactor, and sodium hydroxide aqueous solution was added. The alkali excess rate was 1.50. The neutralization reaction was carried out at 98°C for 30 minutes. After separation, crude DAM (organic phase) and organic wastewater phase were obtained.

[0125] The organic wastewater phase obtained during the DAM preparation process was treated according to the following steps, and during the following treatment steps 1)-3), the characteristic parameter Q = 28.50 was controlled:

[0126] 1) The organic waste brine phase is introduced from the top of the extraction tower, and the aniline extractant is introduced from the bottom of the tower for counter-current extraction to obtain the extracted waste brine; wherein, the volume ratio of aniline to organic waste brine phase is 0.15, and the extraction temperature is 95℃.

[0127] 2) The extracted waste brine is fed into the 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℃ 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.

[0128] 3) Adjust the pH of the stripped waste brine obtained in step 2) to 9.5 using a 50wt% sodium hydroxide and / or 33% hydrochloric acid aqueous solution to obtain the waste brine to be oxidized. Adjust the temperature to 50℃, control the molar ratio of sodium hypochlorite (based on available chlorine) to TOC in the waste brine to be oxidized to 6, and simultaneously introduce sodium hypochlorite and the waste brine to be oxidized into a static mixer for pre-mixing oxidation. Then, introduce the mixture from the bottom of the oxidation tower for deep oxidation treatment, with a residence time of 30 minutes. The top discharge is the treated waste brine. The TOC content of the treated waste brine is measured, as shown in Table 1.

[0129] Example 7

[0130] The raw materials described in this embodiment are as follows:

[0131] Formaldehyde aqueous solution: concentration is 37wt%, which contains the following impurities by mass: 4000mg / L formic acid, 1500mg / L acetic acid, 3000mg / L methanol and 1500mg / L lipid impurities (mainly methyl formate, ethyl formate, etc.);

[0132] Aqueous aniline solution: concentration of 94 wt%, containing the following impurities in the following mass amounts: 50 mg / L phenol, 50 mg / L methyl aniline, 100 mg / L cyclohexylamine, 700 mg / L cyclohexanone, and 100 mg / L cyclohexanol.

[0133] Hydrochloric acid aqueous solution: concentration 33wt%, containing 5mg / L chlorobenzene;

[0134] Sodium hydroxide aqueous solution: concentration 50 wt%.

[0135] Preparation of DAM: Aqueous aniline and aqueous hydrochloric acid were mixed in a static mixer to form aniline hydrochloride. Aqueous formaldehyde was then added while stirring, and 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 (in H2O) was added as follows: + The molar ratio of (calculated) to aniline is 0.35;

[0136] The condensation reaction product was transferred to a transposition reactor, and the temperature was increased to 120°C to carry out the transposition rearrangement reaction for 2 hours to obtain a mixture containing diphenylmethane series diamine hydrochloride and polyamine hydrochloride.

[0137] The mixture was transferred to a neutralization reactor, and an aqueous sodium hydroxide solution was added. The excess alkali ratio was 1.30. The neutralization reaction was carried out at 95°C for 30 minutes. After separation, crude DAM (organic phase) and organic wastewater phase were obtained.

[0138] The organic wastewater phase obtained during the DAM preparation process was treated according to the following steps, and during the following treatment steps 1)-3), the characteristic parameter Q = 13.50 was controlled:

[0139] 1) The organic wastewater phase is introduced from the top of the extraction tower, and the aniline extractant is introduced from the bottom of the tower for counter-current extraction to obtain the extracted wastewater; wherein, the volume ratio of aniline to organic wastewater phase is 0.80, and the extraction temperature is 60℃.

[0140] 2) The extracted waste brine is fed into the first stripping tower from the top, and 2S steam is introduced into the bottom of the tower for stripping. The top temperature of the first stripping tower is maintained at 90℃, 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. 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. The obtained acidic waste brine is introduced into the second stripping tower, and 2S steam is introduced for the second stripping. The top temperature of the second stripping tower is maintained at 130℃, 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 of the tower is the stripped waste brine.

[0141] 3) Adjust the pH of the stripped waste brine obtained in step 2) to 9.5 using a 50wt% sodium hydroxide aqueous solution to obtain the waste brine to be oxidized. Adjust the temperature to 50℃, controlling the molar ratio of sodium hypochlorite (based on available chlorine) to TOC in the waste brine to be oxidized to 10. Simultaneously introduce sodium hypochlorite and the waste brine to be oxidized from the bottom of the oxidation tower for deep oxidation treatment, with a residence time of 30 minutes. The top discharge is the treated waste brine. The TOC content of the treated waste brine is measured, as shown in Table 1.

[0142] Example 8

[0143] The raw materials described in this embodiment are as follows:

[0144] Formaldehyde aqueous solution: concentration is 37wt%, which contains the following impurities by mass: 4000mg / L formic acid, 1500mg / L acetic acid, 3000mg / L methanol and 1500mg / L lipid impurities (mainly methyl formate, ethyl formate, etc.);

[0145] Aqueous aniline solution: concentration of 94 wt%, containing the following impurities in the following mass amounts: 50 mg / L phenol, 50 mg / L methyl aniline, 100 mg / L cyclohexylamine, 700 mg / L cyclohexanone, and 100 mg / L cyclohexanol.

[0146] Hydrochloric acid aqueous solution: concentration 33wt%, containing 5mg / L chlorobenzene;

[0147] Sodium hydroxide aqueous solution: concentration 50 wt%.

[0148] Preparation of DAM: Aqueous aniline and aqueous hydrochloric acid were mixed in a static mixer to form aniline hydrochloride. Aqueous formaldehyde was then added while stirring, and 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 (in H2O) was added as follows: + The molar ratio of (calculated) to aniline is 0.35;

[0149] The condensation reaction product was transferred to a transposition reactor, and the temperature was increased to 120°C to carry out the transposition rearrangement reaction for 2 hours to obtain a mixture containing diphenylmethane series diamine hydrochloride and polyamine hydrochloride.

[0150] The mixture was transferred to a neutralization reactor, and sodium hydroxide aqueous solution was added. The excess alkali ratio was 1.30. The neutralization reaction was carried out at 95°C for 30 minutes. After separation, crude DAM (organic phase) and organic waste brine phase were obtained.

[0151] The organic wastewater phase obtained during the DAM preparation process was treated according to the following steps, and during the following treatment steps 1)-3), the characteristic parameter Q = 23.50 was controlled:

[0152] 1) The organic waste brine phase is introduced from the top of the extraction tower, and the aniline extractant is introduced from the bottom of the tower for counter-current extraction to obtain the extracted waste brine; wherein, the volume ratio of aniline to organic waste brine phase is 0.1, and the extraction temperature is 110℃.

[0153] 2) The extracted waste brine is fed into the first stripping tower from the top, and 2S steam is introduced into the bottom of the tower for stripping. 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 the 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. The obtained acidic waste brine is introduced into the second stripping tower, and 2S steam is introduced for the 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 of the tower is the stripped waste brine.

[0154] 3) Adjust the pH of the stripped waste brine obtained in step 2) to 9.5 using a 50wt% sodium hydroxide aqueous solution to obtain the waste brine to be oxidized. Adjust the temperature to 70℃, controlling the molar ratio of sodium hypochlorite (based on available chlorine) to TOC in the waste brine to be oxidized to 3. Simultaneously introduce sodium hypochlorite and the waste brine to be oxidized from the bottom of the oxidation tower for deep oxidation treatment, with a residence time of 30 minutes. The top discharge is the treated waste brine. The TOC content of the treated waste brine is measured, as shown in Table 1.

[0155] Example 9

[0156] The raw materials described in this embodiment are as follows:

[0157] Formaldehyde aqueous solution: concentration is 37wt%, which contains the following impurities by mass: 4000mg / L formic acid, 1500mg / L acetic acid, 3000mg / L methanol and 1500mg / L lipid impurities (mainly methyl formate, ethyl formate, etc.);

[0158] Aqueous aniline solution: concentration of 94 wt%, containing the following impurities in the following mass amounts: 50 mg / L phenol, 50 mg / L methyl aniline, 100 mg / L cyclohexylamine, 700 mg / L cyclohexanone, and 100 mg / L cyclohexanol.

[0159] Hydrochloric acid aqueous solution: concentration 33wt%, containing 5mg / L chlorobenzene;

[0160] Sodium hydroxide aqueous solution: concentration 50 wt%.

[0161] Preparation of DAM: Aqueous aniline and aqueous hydrochloric acid were mixed in a static mixer to form aniline hydrochloride. Aqueous formaldehyde was then added while stirring, and 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 (in H2O) was added as follows: + The molar ratio of (calculated) to aniline is 0.35;

[0162] The condensation reaction product was transferred to a transposition reactor, and the temperature was increased to 120°C to carry out the transposition rearrangement reaction for 2 hours to obtain a mixture containing diphenylmethane series diamine hydrochloride and polyamine hydrochloride.

[0163] The mixture was transferred to a neutralization reactor, and an aqueous sodium hydroxide solution was added. The excess alkali ratio was 1.30. The neutralization reaction was carried out at 95°C for 30 minutes. After separation, crude DAM (organic phase) and organic wastewater phase were obtained.

[0164] The organic wastewater phase obtained during the DAM preparation process was treated according to the following steps, and during the following treatment steps 1)-3), the characteristic parameter Q = 47.50 was controlled:

[0165] 1) The organic wastewater phase is introduced from the top of the extraction tower, and the aniline extractant is introduced from the bottom of the tower for counter-current extraction to obtain the extracted wastewater; wherein, the volume ratio of aniline to organic wastewater phase is 0.30, and the extraction temperature is 80℃.

[0166] 2) The extracted waste brine is fed into the 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℃ 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.

[0167] 3) Adjust the pH of the stripped waste brine obtained in step 2) to 13 using a 50wt% sodium hydroxide and / or 33% hydrochloric acid aqueous solution to obtain the waste brine to be oxidized. Adjust the temperature to 50℃, control the molar ratio of sodium hypochlorite (based on available chlorine) to TOC in the waste brine to be oxidized to 4, and simultaneously introduce sodium hypochlorite and the waste brine to be oxidized from the bottom of the oxidation tower for deep oxidation treatment, with a residence time of 30 min; the top discharge is the treated waste brine. The TOC content of the treated waste brine is measured, as shown in Table 1.

[0168] Comparative Example 1

[0169] The raw materials described in this embodiment are as follows:

[0170] 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.);

[0171] Aqueous aniline solution: concentration of 99 wt%, containing the following impurities in the following mass amounts: 50 mg / L phenol, 50 mg / L methyl aniline, 800 mg / L cyclohexylamine, 1150 mg / L cyclohexanone, and 450 mg / L cyclohexanol;

[0172] Hydrochloric acid aqueous solution: concentration 33wt%, containing 5mg / L chlorobenzene;

[0173] Sodium hydroxide aqueous solution: concentration 50 wt%.

[0174] Preparation of DAM: Aqueous aniline and aqueous hydrochloric acid were mixed in a static mixer to form aniline hydrochloride. Aqueous formaldehyde was then added while stirring, and 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 (in H2O) was...+ The molar ratio of (calculated) to aniline is 0.20;

[0175] The condensation reaction product was transferred to a transposition reactor, and the temperature was increased to 120°C to carry out the transposition rearrangement reaction for 2 hours to obtain a mixture containing diphenylmethane series diamine hydrochloride and polyamine hydrochloride.

[0176] The mixture was transferred to a neutralization reactor, sodium hydroxide aqueous solution was added, the alkali excess rate was 1.50, and the neutralization reaction was carried out at 98°C for 30 min. After separation, crude DAM (organic phase) and organic waste brine phase were obtained.

[0177] The organic wastewater phase obtained during the DAM preparation process was treated according to the following steps, and during the following treatment steps 1)-3), the characteristic parameter Q = 52.00:

[0178] 1) The organic waste brine phase is introduced from the top of the extraction tower, and the aniline extractant is introduced from the bottom of the tower for counter-current extraction to obtain the extracted waste brine; wherein, the volume ratio of aniline to organic waste brine phase is 0.10, and the extraction temperature is 95℃.

[0179] 2) The extracted waste brine is fed into the 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℃ 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.

[0180] 3) Adjust the pH of the stripped waste brine obtained in step 2) to 13 using a 50wt% sodium hydroxide and / or 33% hydrochloric acid aqueous solution to obtain the waste brine to be oxidized. Adjust the temperature to 40℃, control the molar ratio of sodium hypochlorite (based on available chlorine) to TOC in the waste brine to be oxidized to 2, and simultaneously introduce sodium hypochlorite and the waste brine to be oxidized into a static mixer for pre-mixing oxidation. Then, pass the mixture from the bottom of the oxidation tower into the deep oxidation tower for a residence time of 30 minutes. The top discharge is the treated waste brine. The TOC content of the treated waste brine is measured, as shown in Table 1.

[0181] Comparative Example 2

[0182] The raw materials described in this embodiment are as follows:

[0183] Formaldehyde aqueous solution: concentration is 37wt%, which contains the following impurities by mass: 4000mg / L formic acid, 1500mg / L acetic acid, 3000mg / L methanol and 1500mg / L lipid impurities (mainly methyl formate, ethyl formate, etc.);

[0184] Aqueous aniline solution: concentration of 94 wt%, containing the following impurities in the following mass amounts: 50 mg / L phenol, 50 mg / L methyl aniline, 100 mg / L cyclohexylamine, 700 mg / L cyclohexanone, and 100 mg / L cyclohexanol.

[0185] Hydrochloric acid aqueous solution: concentration 33wt%, containing 5mg / L chlorobenzene;

[0186] Sodium hydroxide aqueous solution: concentration 50 wt%.

[0187] Preparation of DAM: Aqueous aniline and aqueous hydrochloric acid were mixed in a static mixer to form aniline hydrochloride. Aqueous formaldehyde was then added while stirring, and 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 (in H2O) was added as follows: + The molar ratio of (calculated) to aniline is 0.35;

[0188] The condensation reaction product was transferred to a transposition reactor, and the temperature was increased to 120°C to carry out the transposition rearrangement reaction for 2 hours to obtain a mixture containing diphenylmethane series diamine hydrochloride and polyamine hydrochloride.

[0189] The mixture was transferred to a neutralization reactor, and an aqueous sodium hydroxide solution was added. The excess alkali ratio was 1.30. The neutralization reaction was carried out at 95°C for 30 minutes. After separation, crude DAM (organic phase) and organic wastewater phase were obtained.

[0190] The organic wastewater phase obtained during the DAM preparation process was treated according to the following steps, and in the following treatment steps 1)-3), the characteristic parameter Q was not controlled to be <50:

[0191] 1) The organic waste brine phase is introduced from the top of the extraction tower, and the aniline extractant is introduced from the bottom of the tower for counter-current extraction to obtain the extracted waste brine; wherein, the volume ratio of aniline to organic waste brine phase is 0.10, and the extraction temperature is 80℃.

[0192] 2) The extracted waste brine is fed into the 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℃ 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.

[0193] 3) Adjust the pH of the stripped waste brine obtained in step 2) to 13 using a 50wt% sodium hydroxide and / or 33% hydrochloric acid aqueous solution to obtain the waste brine to be oxidized. Adjust the temperature to 40℃, controlling the molar ratio of sodium hypochlorite (based on available chlorine) to TOC in the waste brine to be oxidized to 2. Simultaneously introduce sodium hypochlorite and the waste brine to be oxidized from the bottom of the oxidation tower for deep oxidation treatment, with a residence time of 30 minutes. The top discharge is the treated waste brine. The TOC content of the treated waste brine is measured, as shown in Table 1.

[0194] Table 1. Results of Examples and Comparative Examples

[0195]

[0196]

[0197] Note: The values ​​of the characteristic parameter Q listed in Table 1 are all obtained by substituting the corresponding data of each embodiment or comparative example into formula (I) for calculation.

[0198] As can be seen from the above experimental results, by using the method of the present invention to treat the saline organic wastewater generated during the DAM preparation process, and by controlling the characteristic parameter Q < 50 in combination with the impurity content of the raw materials formaldehyde and aniline used in the preparation of DAM, the TOC removal effect can be significantly improved, and a treated wastewater with a low TOC content (e.g., < 10 mg / L) can be obtained.

[0199] It is readily understood that the above embodiments are merely illustrative examples for clear explanation and do not imply that the invention is limited thereto. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for reducing the TOC content of a salt-containing organic wastewater produced in a DAM production process, wherein, The raw material formaldehyde and the raw material aniline are subjected to condensation reaction and transposition reaction in the presence of an acid catalyst to obtain a mixture; a lye is added to the mixture to perform neutralization reaction, and phase separation is performed to obtain an organic waste brine phase; the treatment of the organic waste brine phase comprises the following steps: 1) extracting the organic waste brine phase with an extractant to obtain an extracted waste brine; 2) subjecting the extracted waste brine to stripping to obtain a stripped waste brine; the stripping comprises first stripping and optional second stripping of the extracted waste brine; the pH of the waste brine obtained through 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 stripped waste brine obtained in step 2) to obtain a waste brine to be oxidized; the waste brine to be oxidized is subjected to oxidation treatment with an oxidizing agent to obtain a treated salt-containing organic waste water; and, the treatment of said organic waste brine phase with said steps 1) - 3) under the condition of controlling a characteristic parameter Q < 50, said characteristic parameter Q being calculated according to the following formula: Q = 5.0 x 10 -4 ×C1+ 1.0 x 10 -3 ×C2- 10.0 x B - 10.0 x D1- 10.0 x D2+ 2.0 x P1- 0.1 x T + 2.0 x P2- 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, 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 of the oxidation treatment, ℃; O is the molar ratio of the oxidizing agent 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 taken as the value of P1 in the formula.

2. The method of claim 1, wherein, 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; the extraction temperature is 50-120 ℃.

3. The method of claim 2, wherein, In step 1), the volume ratio of the extractant to the organic waste brine phase is 0.1-0.8, and the extraction temperature is 60-110 ℃.

4. The method of claim 2, wherein, In step 1), the extractant and the organic waste brine phase flow countercurrently in an extraction tower to perform the extraction.

5. The method according to any one of claims 1 to 4, characterized in that, The first stripping and the second stripping are respectively performed in a stripping tower; The overhead temperature of the stripping tower of the first stripping is 80-160 ℃; the stripping ratio of the first stripping is 0.03-0.80; The overhead temperature of the stripping tower of the second stripping is 80-160 ℃; the stripping ratio of the second stripping is 0.03-0.80; when the second stripping is performed, the pH of the waste brine obtained through the first stripping is adjusted to 2-6 to obtain the acidic waste brine.

6. The method of claim 5, wherein, The overhead temperature of the stripping tower of the first stripping is 90-130 ℃, and the stripping ratio of the first stripping is 0.05-0.

30.

7. The method of claim 5, wherein, The overhead temperature of the stripping tower of the second stripping is 90-130 ℃; the stripping ratio of the second stripping is 0.05-0.

30.

8. The method according to any one of claims 1 to 4, characterized in that, In step 3), the temperature of the oxidation treatment is 30-90 ℃; the pH of the waste brine to be oxidized is 2-14.

9. The method of claim 8, wherein, In step 3), the temperature of the oxidation treatment is 40-70 ℃; The pH of the waste brine to be oxidized is 4-13.

10. The method of claim 8, wherein, The oxidizing agent is one or more of chlorine-containing oxidizing agent, ozone, hydrogen peroxide.

11. The method of claim 10, wherein, The chlorine-containing oxidizing agent is one or more of sodium hypochlorite, chlorine, sodium perchlorate.

12. The method of claim 10, wherein, When the oxidizing agent is a chlorine-containing oxidizing agent, the molar ratio of the oxidizing agent to TOC in the waste brine to be oxidized is 2-15, calculated based on available chlorine.

13. The method of claim 12, wherein, When the oxidizing agent is a chlorine-containing oxidizing agent, the molar ratio of the oxidizing agent to TOC in the waste brine to be oxidized is 2-10, calculated based on available chlorine.

14. The method of claim 8, wherein, The oxidation treatment includes deep oxidation treatment in an oxidation tower.

15. The method of claim 14, wherein, The deep oxidation treatment time is 3-600 min.

16. The method of claim 15, wherein, The deep oxidation treatment time is 5-300 min.

17. The method according to any one of claims 1-4, characterized in that, The impurity mass concentration in the raw material formaldehyde is 50-10000 mg / L. And / or, the impurity mass concentration in the raw material aniline is 10-2500 mg / L.

18. The method of any one of claims 1-4, wherein, The impurities in the raw material formaldehyde include one or more of formic acid, acetic acid, methanol, methyl formate, ethyl formate. And / or, the impurities in the raw material aniline include one or more of benzene, phenol, methyl aniline, cyclohexylamine, cyclohexanone, cyclohexanol.

19. The method according to any one of claims 1-4, characterized in that, The raw material formaldehyde is a formaldehyde solution, and the mass fraction of formaldehyde in the formaldehyde solution is 15-55%. And / or, the raw material 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 amount of the formaldehyde to the amount of the aniline is 0.10-0.

85.

20. The method of claim 19, wherein, The raw material formaldehyde is a formaldehyde solution, and the mass fraction of formaldehyde in the formaldehyde solution is 20-50%. And / or, the molar ratio of the amount of the formaldehyde to the amount of the aniline is 0.20-0.

60.

21. The method of claim 19, wherein, The acidic catalyst is one or more of organic acid, inorganic acid, solid acid. When the acidic catalyst is the organic acid and / or the inorganic acid, the amount of the acidic catalyst and the amount of the aniline are in a molar ratio of 0.01 to 0.

80. + When the acidic catalyst is the organic acid and / or the inorganic acid, the amount of the acidic catalyst and the amount of the aniline are in a molar ratio of 0.01 to 0.

80.

22. The method of claim 21, wherein, The acidic catalyst is hydrochloric acid.

23. The method of claim 22, wherein, The acidic catalyst is 30-37 wt% hydrochloric acid.

24. The method of claim 21, wherein, When the acidic catalyst is the organic acid and / or the inorganic acid, the amount of the acidic catalyst and the amount of the aniline are in a molar ratio of 0.05 to 0.40, calculated as H + When the acidic catalyst is the organic acid and / or the inorganic acid, the amount of the acidic catalyst and the amount of the aniline are in a molar ratio of 0.05 to 0.40, calculated as H 25. The method of claim 21, wherein, The lye is a sodium hydroxide solution.

26. The method of claim 25, wherein, The mass fraction of sodium hydroxide in the sodium hydroxide solution is 20-55%.

27. The method of claim 26, wherein, The mass fraction of sodium hydroxide in the sodium hydroxide solution is 32-50%.

28. The method of claim 25, wherein, When the acidic catalyst is the organic acid and / or the inorganic acid, the acidic catalyst is in the form of H + The molar ratio of sodium hydroxide in the sodium hydroxide solution to the acidic catalyst is 1.0 to 3.

0.

29. The method of claim 28, wherein, When the acidic catalyst is the organic acid and / or the inorganic acid, the acidic catalyst is in the form of H + The molar ratio of sodium hydroxide in the sodium hydroxide solution to the acidic catalyst is 1.01 to 1.50.

Images