WO2022067746A1 - 一种mda制备过程中产生的排盐水的处理方法 - Google Patents

一种mda制备过程中产生的排盐水的处理方法 Download PDF

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WO2022067746A1
WO2022067746A1 PCT/CN2020/119620 CN2020119620W WO2022067746A1 WO 2022067746 A1 WO2022067746 A1 WO 2022067746A1 CN 2020119620 W CN2020119620 W CN 2020119620W WO 2022067746 A1 WO2022067746 A1 WO 2022067746A1
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brine
content
treatment
aniline
mda
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PCT/CN2020/119620
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French (fr)
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邢津铭
李永锋
陈良进
章靓
吴雪峰
张宏科
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万华化学集团股份有限公司
万华化学（宁波）有限公司
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Priority to PCT/CN2020/119620 priority Critical patent/WO2022067746A1/zh
Publication of WO2022067746A1 publication Critical patent/WO2022067746A1/zh

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    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F9/00—Multistage treatment of water, waste water or sewage
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/34—Nature of the water, waste water, sewage or sludge to be treated from industrial activities not provided for in groups C02F2103/12 - C02F2103/32
    • C02F2103/36—Nature of the water, waste water, sewage or sludge to be treated from industrial activities not provided for in groups C02F2103/12 - C02F2103/32 from the manufacture of organic compounds

Definitions

  • the invention relates to the field of chemical wastewater treatment, in particular to a method for treating drained brine produced in the process of preparing MDA.
  • Diamines and polyamines of diphenylmethane are understood to be compounds of the following structures and mixtures thereof (hereinafter abbreviated as MDA).
  • n is a natural number
  • MDI is one of the main raw materials in the polyurethane industry. Using aniline and formaldehyde to prepare MDA, and then using MDA to react with phosgene to synthesize MDI is a well-known method in the industry. Methods for the preparation of MDA are also generally well known in the art and are described in many published patent documents and publications, such as US-A 2009/0240077, EP-A-451442 and WO-A-99/40059 . MDA is prepared by continuous, semi-continuous or discontinuous reaction process.
  • Aniline is first reacted with hydrochloric acid to generate aniline hydrochloride, and then formaldehyde is added to generate MDA salt through condensation reaction and translocation reaction, and then caustic soda is added for neutralization.
  • the brine layer (aqueous phase) and the polyamine layer (organic phase) are separated, and the polyamine layer is washed with water and then purified to obtain MDA products, which is one of the key links in the MDI preparation process.
  • the aqueous phase after neutralization of the reaction solution with caustic soda and the washing water after washing the organic phase are the drain brine produced in the preparation process of MDA.
  • phenol, aniline, MDA and other impurities will remain in it.
  • MDA is usually removed by extraction with an extraction agent such as aniline, and then the extraction agent is removed by means of rectification.
  • the drained brine usually still has a certain amount of organic matter remaining, mainly including carboxylates (such as formate, acetate, etc.), phenol, aniline, polyamine, etc., and the organic matter is generally removed by oxidation or catalytic oxidation. .
  • the purpose of the present invention is to provide a method for treating the brine discharged during the preparation process of MDA, which is simple in process, stable in operation, can effectively remove the organic matter in the brine, and has a good treatment effect. .
  • the invention provides a method for treating the salt water produced in the preparation process of MDA.
  • the MDA is prepared by using aniline, hydrochloric acid and formaldehyde as raw materials, and the salt water is processed through the following steps in turn:
  • the phenol content in the drained brine is controlled to be no more than 0.8 mg/L and/or the sodium bromide content is no more than 0.2 mg/L before being subjected to catalytic oxidation treatment.
  • the inventors have conducted long-term and targeted research on the brine formed during the preparation of MDA and found that, before the catalytic oxidation treatment, there are usually two impurities in the brine that affect the final water quality, namely phenol and sodium bromide.
  • the used extractant is usually arylamines, such as aniline.
  • the extraction agent is an important reason for introducing phenol, and there may also be a certain amount of phenol impurities in the raw material aniline, but the phenol at this time is easily consumed by phenolic polycondensation reaction with formaldehyde.
  • phenol was not detected in the brine before adding the extractant, so the source of phenol in the brine was mainly the extractant rather than the raw material aniline.
  • Sodium bromide is mainly derived from hydrogen bromide impurities in hydrochloric acid, another reaction raw material, and is formed after neutralization with caustic soda. Due to the existence of phenol and sodium bromide, bromide ions can easily replace hydrogen on phenol in the process of catalytic oxidation treatment to form bromophenols (mainly including monobromodichlorophenol, dibromomonochlorophenol, tribromophenol and their respective Isomers). Further research shows that, unlike chlorophenol, bromophenol cannot be degraded by conventional catalytic oxidation treatment, which is an important reason for incomplete removal of TOC and poor quality in brine, which affects the recycling of brine. and emissions.
  • the phenol content in the drained brine can be preferably controlled to be 0.02-0.8 mg/L (for example, it can be 0.02 mg/L, 0.05 mg/L, 0.1 mg/L) , 0.2mg/L, 0.3mg/L, 0.4mg/L, 0.5mg/L, 0.6mg/L, 0.7mg/L, 0.8mg/L and any interval thereof).
  • the sodium bromide content in the drained brine can preferably be controlled at 0.01-0.2 mg/L (for example, it can be 0.01 mg/L, 0.02 mg/L, 0.05 mg/L, 0.08 mg/L, 0.1 mg/L, 0.15 mg/L, 0.2 mg/L and any interval thereof).
  • any known method with industrial applicability can be used to control the phenol content and/or the sodium bromide content in the drained brine in any step before the catalytic oxidation treatment, for example, Impurities can be removed directly or indirectly through source of raw materials, process conditions, etc.
  • the phenol in the drain brine is primarily derived from extractants such as aniline. Therefore, in one embodiment of the treatment method according to the present invention, the extractant can be purified to a phenol content of not more than 0.5 mg/L, so as to control the phenol content in the drain brine (ie, method A). Wherein, any known method with industrial applicability can be adopted for the purification of the extractant, as long as the phenolic impurities can be removed without affecting the properties of the extractant.
  • the extractant can be purified to a phenol content of 0.1-0.5 mg/L (for example, 0.1 mg/L, 0.2 mg/L, 0.3 mg/L, 0.4 mg/L) L, 0.5mg/L and any interval thereof).
  • the inventor found that in the process of preparing MDA, in order to ensure complete neutralization and the stability of subsequent water and oil phases, the caustic soda used for neutralization is usually excessive (the pH value after neutralization is about 13-14). , the translocation reaction is mostly carried out at a high temperature of 80-100 ° C, plus the neutralization and exotherm, so the brine obtained at this time usually has the characteristics of high temperature and high pH value. If the extraction is carried out directly without treatment, the distribution coefficient of phenol impurities in the aqueous phase is much higher than that of the oil phase of the extractant under alkaline and high temperature conditions, which will cause the phenol in the extractant to directly enter the drained brine, which improves the efficiency of the extraction process.
  • the phenol content in the drained brine can also be controlled by controlling the extraction process conditions (ie method B), and the method B can be: after adding the extractant Before performing the extraction treatment, the pH value of the drained brine is adjusted to 4-8, and the temperature is controlled to be 10-50° C. during the extraction treatment.
  • the pH of brine is 5-7.
  • the temperature during the extraction process the lower the solubility of phenol in the drained brine, but when the temperature is further reduced from 30 °C down, there is a marginal effect on the decrease in solubility, and as the temperature decreases, the cooling cost also gradually increases, so During the extraction treatment, it is preferable to control the temperature to 30 to 40°C.
  • any known method with industrial applicability can be used to adjust the pH value, such as adding a dilute acid solution.
  • the pH value can be adjusted by adding 20-50 wt% hydrochloric acid solution, and the hydrogen bromide impurity in the commonly used technical-grade hydrochloric acid will not produce additional influence during the pH adjustment process.
  • any known method with industrial applicability can be used to reduce the temperature during the extraction treatment, such as a conventional condensation method, a heat exchange method, and the like.
  • the sodium bromide in the drained brine is mainly derived from the hydrogen bromide in the raw hydrochloric acid. Therefore, in one embodiment of the treatment method according to the present invention, the hydrochloric acid can be purified to the hydrogen bromide therein.
  • the hydrogen content is not more than 5.0 mg/L to control the sodium bromide content.
  • the raw material hydrochloric acid used in the industrial preparation of MDA usually contains no more than 100 mg/L of hydrogen bromide impurities. Bromide ion.
  • the purification of hydrochloric acid can adopt any known method with industrial applicability, as long as the hydrogen bromide impurity can be removed without affecting the properties of hydrochloric acid.
  • the hydrochloric acid can be purified to a hydrogen bromide content of 0.1-5.0 mg/L (for example, it can be 0.1 mg/L, 0.5 mg/L, 1.0 mg/L, 1.5 mg/L) /L, 2.0mg/L, 2.5mg/L, 3.0mg/L, 3.5mg/L, 4.0mg/L, 4.5mg/L, 5.0mg/L and any interval thereof).
  • the raw material hydrochloric acid may be the common concentration in the current industrial preparation of MDA, for example, the concentration of the hydrochloric acid may be 20-60 wt%. In a preferred embodiment, the concentration of hydrochloric acid used as one of the raw materials may be 30-40 wt%.
  • the extraction agent can be common arylamine substances used in the art, including but not limited to aniline, p-toluidine, o-toluidine, p-ethylaniline, o-ethylaniline , 2,4-dimethylaniline or any mixture thereof.
  • the extractant can be aniline, and the technical grade aniline generally used in industry contains no more than 150mg/L of phenolic impurities (according to GB2961-2014, the first-class product is no more than 100mg/L, The qualified product does not exceed 150mg/L), so when using aniline as the extractant, special consideration should be given to the influence of phenol impurities.
  • the aforementioned method for controlling the impurity content of phenol and/or sodium bromide can be selected based on factors such as the impurity content of the extractant, the impurity content of the raw material hydrochloric acid, and the treatment requirements for discharging brine. For example, when the purity of the extractant or raw hydrochloric acid is good and the impurity content is low, further purification methods can be considered, and when the impurity content in the extractant or raw hydrochloric acid is relatively high, the extraction process can be changed. .
  • the mass ratio of the extractant to the drained brine may be 0.05-0.5:1, and the MDA content in the drained brine after extraction does not exceed 0.5 mg/L, That is to say, the effect of extraction has been achieved.
  • the mass ratio of the extractant to the drained brine may be 0.1-0.3:1.
  • the MDA content in the drained brine after extraction does not exceed 0.3 mg/L, which means that the extraction effect is achieved.
  • the steam stripping treatment described in step S2 can use the process conditions currently used in industry.
  • the steam pressure of the steam stripping treatment may be 1-10 barg. In a preferred embodiment, the steam pressure of the steam stripping treatment can be 1-3 barg.
  • the catalytic oxidation treatment described in step S3 can use the process conditions currently used in industry.
  • the catalytic oxidation treatment may use sodium hypochlorite as an oxidant, and the mass ratio of the catalyst to the drained brine may be 1:1000-5000.
  • the catalyst used in the catalytic oxidation treatment can also be of a common type, such as using a catalytic oxidation reactor loaded with YRN-138 nickel-iron based catalyst.
  • the drained brine can be the drained brine produced in the current industrial process for preparing MDA.
  • the drained brine can be produced by the following process:
  • aniline is reacted with hydrochloric acid to prepare aniline hydrochloride, which is then subjected to condensation reaction and transposition reaction with formaldehyde;
  • step T2 adding 30-60 wt% NaOH solution to neutralize the reaction system in step T1, separating the obtained aqueous phase, washing the organic phase with 30-60% of its volume water, and combining the aqueous phase and the washing water to obtain the drainage brine.
  • the TOC content is less than or equal to 8 mg/L and/or the bromophenol content is less than or equal to 0.5 mg/L (the total of monobromodichlorophenol, dibromomonochlorophenol and tribromophenol The sum of the content), which can achieve the purpose of deep purification.
  • the method for treating the drained brine produced in the preparation process of MDA conducteds an in-depth analysis on the impurity components of the drained brine, and finds the root cause of the problem that the catalytic oxidation is incomplete and TOC cannot be effectively removed.
  • the content of phenol and sodium bromide in the brine can be effectively controlled, which can achieve the effect of deep purification.
  • the content of TOC and bromophenol in the treated brine is low, and the organic matter is completely removed. It can be used as a raw material for production.
  • the chlor-alkali process can also meet emission standards and reduce environmental pressure.
  • the treatment method provided by the invention has strong pertinence, simple process, convenient industrial implementation, stable operation, no need for a large amount of manpower and equipment investment, and has great application prospect.
  • Aniline Wanhua self-produced aniline with a purity of 99.9%, reaching the industrial grade specified in GB2961-2014;
  • Hydrochloric acid use Wanhua self-produced hydrochloric acid with a concentration of 34%;
  • Detection of bromophenol in brine (the sum of the total content of monobromodichlorophenol, dibromomonochlorophenol and tribromophenol): Agilent 1260S liquid chromatograph, DAD UV detector; direct sample injection analysis, respectively The external standard of the target substance to be detected is used for quantification, and the wavelength is 220 nm.
  • MDA detection in salt water American Agilent 1260S liquid chromatograph, DAD UV detector; the sample was directly injected for analysis, quantified with 4,4-MDA external standard, wavelength 280nm.
  • Bromine detection in brine or hydrochloric acid ion chromatography, the sample is directly analyzed after diluting with water, involving instruments: 881 ion chromatograph from Metrohm, Switzerland, with a conductivity detector, quantified by external standard bromide ion standard solution; according to the detected bromine element The content is correspondingly converted to the sodium bromide content in brine or the hydrogen bromide content in hydrochloric acid.
  • Detection of phenol in aniline gas chromatography, direct sample analysis, involving instruments: American Agilent 7890B gas chromatograph with FID hydrogen flame detector, quantified with phenol standard solution external standard.
  • the hydrochloric acid (in terms of HCl) with a molar ratio of 0.3:1 is reacted with aniline to generate aniline salt, and then formaldehyde is added to undergo condensation reaction and transposition reaction.
  • the molar ratio of formaldehyde to aniline is 0.35:1, and the reaction temperature is 50 ° C , and the reaction mixture containing the diamine salt of diaminodiphenyl and the polyamine salt is obtained after the reaction is completed.
  • Use excess 50% NaOH (the molar ratio of NaOH and hydrochloric acid is 1.10:1) to neutralize the reaction mixture, and send the neutralized mixture into a stratifier to separate the organic phase and the water phase, and the organic phase passes through water (water and hydrochloric acid).
  • the oil phase volume ratio is 0.4:1) After washing once, water and aniline are preliminarily separated by 10kPa flash distillation, and then MDA is obtained by 8barg steam rectification and refining.
  • MDA was prepared according to the preparation example, wherein the hydrogen bromide content in the raw material hydrochloric acid was 84.8 mg/L.
  • the effluent brine is subjected to 2 barg steam stripping treatment to remove aniline.
  • adding sodium hypochlorite oxidant (the mass ratio of the addition amount to the drained brine is 1:2000) and carrying out catalytic oxidation in the reactor loaded with YRN-138 nickel-iron-based catalyst to the drained brine after removing aniline, thereby obtaining
  • the TOC content in the brine is 5.7 mg/L
  • the bromophenol content is 0.25 mg/L.
  • MDA was prepared according to the preparation example, wherein the hydrogen bromide content in the raw material hydrochloric acid was 84.8 mg/L.
  • the discharged brine is subjected to the steam stripping treatment and catalytic oxidation treatment described in Example 1, thereby obtaining the advanced treated discharged brine, the TOC content in the brine is 6.4mg/L, and the bromophenol content is 0.47mg/L .
  • MDA was prepared according to the preparation example, wherein the hydrogen bromide content in the raw material hydrochloric acid was 84.8 mg/L.
  • the exhausted brine is subjected to the steam stripping treatment and catalytic oxidation treatment described in Example 1, thereby obtaining the exhausted brine after advanced treatment, the TOC content in the brine is 5.8mg/L, and the bromophenol content is 0.07mg/L .
  • MDA was prepared according to the preparation example, wherein the hydrogen bromide content in the raw material hydrochloric acid was 84.8 mg/L.
  • the discharged brine is subjected to the steam stripping treatment and catalytic oxidation treatment described in Example 1, thereby obtaining the advanced treated discharged brine, the TOC content in the brine is 6.5mg/L, and the bromophenol content is 0.18mg/L .
  • MDA was prepared according to the preparation example, wherein the hydrogen bromide content in the raw material hydrochloric acid was 84.8 mg/L.
  • the discharged brine is subjected to the steam stripping treatment and catalytic oxidation treatment described in Example 1, thereby obtaining the advanced treated discharged brine, the TOC content in the brine is 7.5mg/L, and the bromophenol content is 0.45mg/L .
  • MDA was prepared according to the preparation example, wherein the raw material hydrochloric acid was purified so that the hydrogen bromide content thereof was 4.7 mg/L before using the raw material hydrochloric acid.
  • the discharged brine is subjected to the steam stripping treatment and catalytic oxidation treatment described in Example 1, thereby obtaining the advanced treated discharged brine, the TOC content in the brine is 6.7mg/L, and the bromophenol content is 0.18mg/L .
  • MDA was prepared according to the preparation example, wherein the hydrogen bromide content in the raw material hydrochloric acid was 84.8 mg/L.
  • the discharged brine is subjected to the steam stripping treatment and catalytic oxidation treatment described in Example 1, thereby obtaining the advanced treated discharged brine, the TOC content in the brine is 5.2 mg/L, and the bromophenol content is 0.02 mg/L .
  • MDA was prepared according to the preparation example, wherein the hydrogen bromide content in the raw material hydrochloric acid was 84.8 mg/L.
  • the discharged brine is subjected to the steam stripping treatment and catalytic oxidation treatment described in Example 1, thereby obtaining the advanced treated discharged brine, the TOC content in the brine is 16.7mg/L, and the bromophenol content is 11.80mg/L .
  • MDA was prepared according to the preparation example, wherein the hydrogen bromide content in the raw material hydrochloric acid was 84.8 mg/L.
  • the discharged brine is subjected to the steam stripping treatment and catalytic oxidation treatment described in Example 1, thereby obtaining the advanced treated discharged brine, the TOC content in the brine is 12.5mg/L, and the bromophenol content is 6.18mg/L .
  • MDA was prepared according to the preparation example, wherein the hydrogen bromide content in the raw material hydrochloric acid was 84.8 mg/L.
  • the discharged brine is subjected to the steam stripping treatment and catalytic oxidation treatment described in Example 1, thereby obtaining the advanced treated discharged brine, the TOC content in the brine is 15.1 mg/L, and the bromophenol content is 9.64 mg/L .
  • the pH value of the extraction process is controlled at 4-8 and the extraction temperature is controlled at 10-50°C, or by controlling the concentration of the raw material hydrochloric acid
  • the hydrogen bromide content does not exceed 5mg/L, or the phenol content in the extraction agent aniline is controlled to not exceed 0.5mg/L, thereby effectively achieving the purpose of reducing the brominated phenol content and TOC content in the catalytic oxidation outlet. It can be reduced to below 0.5mg/L (even below 0.1mg/L), the TOC content can be reduced to below 8mg/L, and the organic matter in the treated brine is completely removed.

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Abstract

本发明提供了一种MDA制备过程中产生的排盐水的处理方法，在进行催化氧化处理之前，控制其中的苯酚含量不超过0.8mg/L和/或溴化钠含量不超过0.2mg/L。本发明提供的处理方法对排盐水的杂质成分进行了深入分析，通过对排盐水中的苯酚含量、溴化钠含量进行有效控制，能够达到深度净化的效果，处理后的排盐水中TOC含量、溴代苯酚含量都较低，有机物脱除彻底，减轻了环境压力，本发明提供的处理方法针对性强，工艺简便，便于工业化实施，运行稳定，无需大量的人力和设备投入，非常具有应用前景。

Description

一种MDA制备过程中产生的排盐水的处理方法 技术领域
本发明涉及化工废水处理领域，具体涉及一种MDA制备过程中产生的排盐水的处理方法。
背景技术
二苯基甲烷的二胺和多胺被理解为具有以下结构的化合物及其混合物(以下简称MDA)。
Figure PCTCN2020119620-appb-000001
其中n为自然数
MDI是聚氨酯行业的主要原料之一。利用苯胺和甲醛制备MDA，再利用MDA与光气反应合成MDI是行业内众所周知的方法。在本领域中，MDA的制备方法一般也是众所周知的，在许多公开的专利文件和出版物中都有描述，如US-A 2009/0240077、EP-A-451442和WO-A-99/40059中。MDA通过连续、半连续或不连续的反应过程制备，苯胺首先与盐酸反应生成苯胺盐酸盐，而后加入甲醛通过缩合反应及转位反应生成MDA酸盐，再加入烧碱进行中和，将所得到的盐水层(水相)和多胺层(有机相)分离，多胺层经过水洗后再进行精制，由此得到MDA产品，这是MDI制备工艺的关键环节之一。
在苯胺与甲醛制备MDA的制备过程中，反应液采用烧碱进行中和处理后的水相以及洗涤有机相后的洗涤水即为MDA的制备过程中产生的排盐水。通常其中会残留苯酚、苯胺、MDA及其它杂质，在已公开的技术中通常采用苯胺等萃取剂萃取的方式脱除MDA，再通过精馏等方式脱除萃取剂。此时的排盐水通常还残留一定量的有机物，主要包括羧酸盐(如甲酸盐、乙酸盐等)、苯酚、苯胺、多胺等，一般采用氧化或催化氧化方法对有机物进行脱除。但是，在实际的生产过程中发现，氧化或催化氧化并不能完全将排盐水中的 某些有机物脱除干净，甚至会出现氧化后盐水出现淡绿色的现象，严重影响了排放和再利用。因此，需要深入分析排盐水的杂质特点并开发一种工艺简便、运行稳定、处理效果好的排盐水处理方法。
发明内容
为克服现有技术中存在的不足，本发明的目的是提供一种MDA制备过程中产生的排盐水的处理方法，该方法工艺简便，运行稳定，能有效去除排盐水中的有机物，处理效果好。
本发明提供了一种MDA制备过程中产生的排盐水的处理方法，所述MDA以苯胺、盐酸和甲醛为原料制备，所述排盐水依次经过以下步骤进行处理：
S1：加入萃取剂进行萃取处理；
S2：将经萃取处理后的排盐水进行蒸汽汽提处理；以及
S3：将经蒸汽汽提处理后的排盐水进行催化氧化处理；
其中，所述排盐水在进行催化氧化处理之前，控制其中的苯酚含量不超过0.8mg/L和/或溴化钠含量不超过0.2mg/L。
发明人对MDA制备过程中形成的排盐水进行了长期的、针对性的研究后发现，在催化氧化处理之前，排盐水中通常会存在两种影响最终水质的杂质，即苯酚和溴化钠。具体来说，由于需要萃取出排盐水中的MDA并回收，因而所使用的萃取剂通常为芳基胺类，如苯胺。发明人发现萃取剂是引入苯酚的重要原因，原料苯胺中也可能存在一定量的苯酚杂质，但此时的苯酚很容易与甲醛发生酚醛缩聚反应而被消耗。在实际运行过程中，加入萃取剂之前的排盐水中也未检测到苯酚，因此说明排盐水中的苯酚来源主要是萃取剂而非原料苯胺。而溴化钠则主要来源于另一反应原料盐酸中的溴化氢杂质，经过烧碱中和后形成。由于苯酚和溴化钠的存在，溴离子在催化氧化处理的过程中容易取代苯酚上的氢而形成溴代苯酚(主要包括一溴二氯苯酚、二溴一氯苯酚、三溴苯酚及各自的同分异构体)。进一步的研究显示，与氯代苯酚不同的是，溴代苯酚无法通过常规的催化氧化处理被降解，因而是造成排盐水中TOC脱除不彻底、质量变差的重要原因，影响盐水的循环利用和排放。
综上可见，目前虽然已有一些研究是针对MDA制备过程中形成的排盐水的处理，但 都没有考虑到其中的苯酚和/或溴化钠的影响。基于此，发明人提出了上述针对排盐水中的苯酚含量和/或溴化钠含量的处理方法，通过降低催化氧化处理前的杂质含量，避免难降解的溴代苯酚的形成，因此经处理后的排盐水中有机物脱除更为彻底，水质更好，可用于下游氯碱生产，也能够满足排放标准。
在根据本发明的处理方法的一个实施方式中，所述排盐水中的苯酚含量可优选控制在0.02～0.8mg/L(例如，可以为0.02mg/L、0.05mg/L、0.1mg/L、0.2mg/L、0.3mg/L、0.4mg/L、0.5mg/L、0.6mg/L、0.7mg/L、0.8mg/L及其任意区间)。在根据本发明的处理方法的另一个实施方式中，所述排盐水中的溴化钠含量可优选控制在0.01～0.2mg/L(例如，可以为0.01mg/L、0.02mg/L、0.05mg/L、0.08mg/L、0.1mg/L、0.15mg/L、0.2mg/L及其任意区间)。
本发明提供的处理方法中，可以采用任意已知的、具有工业实用性的方法在催化氧化处理之前的任意步骤中来控制所述排盐水中的苯酚含量和/或溴化钠含量，例如，可以直接针对杂质进行去除，也可以通过原料来源、工艺条件等间接对杂质进行去除。
如前所述，排盐水中的苯酚主要来源于诸如苯胺的萃取剂。因此，在根据本发明的处理方法的一个实施方式中，可以将所述萃取剂纯化至其中的苯酚含量不超过0.5mg/L，以此来控制排盐水中的苯酚含量(即方法A)。其中，萃取剂的纯化可以采用任意已知的、具有工业实用性的方法，只要能够去除苯酚杂质且不影响萃取剂性质即可。在一个优选的实施方式中，可以将所述萃取剂纯化至其中的苯酚含量为0.1～0.5mg/L(例如，可以为0.1mg/L、0.2mg/L、0.3mg/L、0.4mg/L、0.5mg/L及其任意区间)。
此外，发明人还发现，在MDA制备过程中，为了保证中和完全以及后续水、油分相的稳定，通常中和用的烧碱是过量的(中和后pH值约为13-14)，此外，转位反应多在80-100℃的高温下进行，加上中和放热，因此此时所得的排盐水通常具有温度高、pH值高的特点。如果不加处理直接进行萃取，苯酚杂质在碱性及高温条件下在水相中的分配系数远高于萃取剂的油相，由此会造成萃取剂中的苯酚直接进入排盐水中，提高了排盐水中的苯酚含量。基于此，对萃取过程的pH值及温度进行有效控制可以控制进入排盐水中的苯酚含量。因此，在根据本发明的处理方法的另一个实施方式中，还可以通过控制萃取工艺条件来控制排盐水中的苯酚含量(即方法B)，所述方法B可以为：在加入所述萃取剂进行萃取处理之前调节所述排盐水的pH值为4～8，并且在萃取处理时控制温度为10～50℃。
进一步研究发现：排盐水的pH值控制得越低，其中的苯酚含量越低，但pH值过低时一方面酸用量大增加成本，另一方面更为重要的是低pH值会导致萃取剂成铵盐后过多地溶解于盐水中，造成后续汽提回收萃取剂过程能耗增加，因此pH值控制在中性及弱酸性为宜，即在加入所述萃取剂之前优选调节所述排盐水的pH值为5～7。此外，萃取处理时的温度越低，苯酚在排盐水中的溶解度越低，但温度从30℃向下进一步降低时，溶解度降低存在边际效应，而且随着温度降低，降温成本也逐步上升，因此在萃取处理时优选控制温度为30～40℃。
本发明提供的处理方法中，可以采用任意已知的、具有工业实用性的方法来调节pH值，例如加入稀酸溶液。在一个优选的实施方式中，可以通过加入20～50wt％的盐酸溶液来调节pH值，通常所使用的工业级盐酸中的溴化氢杂质在调节pH值过程中不会产生额外影响。
本发明提供的处理方法中，可以采用任意已知的、具有工业实用性的方法来降低萃取处理时的温度，例如常规的冷凝方法、热交换方法等。
如前所述，排盐水中的溴化钠主要来源于原料盐酸中的溴化氢，因此，在根据本发明的处理方法的一个实施方式中，可以通过将所述盐酸纯化至其中的溴化氢含量不超过5.0mg/L以控制所述溴化钠含量。目前工业上制备MDA工艺中所使用的原料盐酸，通常含有不超过100mg/L的溴化氢杂质，为保证排盐水中的溴化钠杂质含量，可以通过纯化原料盐酸的方式减少排盐水中的溴离子。其中，盐酸的纯化可以采用任意已知的、具有工业实用性的方法，只要能够去除溴化氢杂质且不影响盐酸性质即可。在一个优选的实施方式中，可以将所述盐酸纯化至其中的溴化氢含量为0.1～5.0mg/L(例如，可以为0.1mg/L、0.5mg/L、1.0mg/L、1.5mg/L、2.0mg/L、2.5mg/L、3.0mg/L、3.5mg/L、4.0mg/L、4.5mg/L、5.0mg/L及其任意区间)。
本发明提供的处理方法中，原料盐酸可以为目前工业上制备MDA工艺中的常见浓度，例如，盐酸的浓度可以为20～60wt％。在一个优选的实施方式中，用作原料之一的盐酸的浓度可以为30～40wt％。
本发明提供的处理方法中，所述萃取剂可以为本领域使用的常见芳基胺类物质，包括但不限于苯胺、对甲基苯胺、邻甲基苯胺、对乙基苯胺、邻乙基苯胺、2,4-二甲基苯胺或其任意混合物。在一个优选的实施方式中，所述萃取剂可以为苯胺，通常工业上所使用的 工业级苯胺中含有不超过150mg/L的苯酚杂质(按照GB2961-2014，一等品不超过100mg/L，合格品不超过150mg/L)，因此使用苯胺作为萃取剂时需特别考虑其中的苯酚杂质影响。
本发明提供的处理方法中，可基于萃取剂杂质含量状况、原料盐酸杂质含量状况、排盐水的处理要求等因素来选择前述控制苯酚和/或溴化钠杂质含量的方法。例如，当萃取剂或原料盐酸的纯度较好、杂质含量较低时，可考虑选择进一步纯化的方式，而当萃取剂或原料盐酸中杂质含量相对较高时，则可以通过改变萃取工艺的方式。
本发明提供的处理方法中，步骤S1所述的萃取处理除了前述的调节pH值以及萃取温度之外，其他工艺条件可以为目前工业上所使用的工艺条件。在根据本发明的处理方法的一个实施方式中，所述萃取剂与所述排盐水的质量比可以为0.05～0.5:1，萃取后所述排盐水中的MDA含量不超过0.5mg/L，即说明达到了萃取的效果。在一个优选的实施方式中，所述萃取剂与所述排盐水的质量比可以为0.1～0.3:1。在另一个优选的实施方式中，萃取后所述排盐水中的MDA含量不超过0.3mg/L，即说明达到了萃取的效果。
本发明提供的处理方法中，步骤S2所述的蒸汽汽提处理可以使用目前工业上所使用的工艺条件。在根据本发明的处理方法的一个实施方式中，所述蒸汽汽提处理的蒸汽压力可以为1～10barg。在一个优选的实施方式中，所述蒸汽汽提处理的蒸汽压力可以为1～3barg。
本发明提供的处理方法中，步骤S3所述的催化氧化处理可以使用目前工业上所使用的工艺条件。在根据本发明的处理方法的一个实施方式中，所述催化氧化处理可以以次氯酸钠作为氧化剂，其与所述排盐水的质量比可以为1:1000～5000。催化氧化处理所使用的催化剂也可以为常见类型，例如使用负载有YRN-138镍-铁基催化剂的催化氧化反应器。
本发明提供的处理方法中，所述排盐水可以为目前工业上制备MDA工艺中所产生的排盐水。在根据本发明的处理方法的一个实施方式中，所述排盐水可以经以下过程所产生：
T1：将苯胺与盐酸进行反应制备苯胺盐酸盐，再与甲醛发生缩合反应及转位反应；以及
T2：加入30～60wt％的NaOH溶液中和步骤T1的反应体系，分离出所得水相，有机相用其体积30～60％的水洗涤，合并所述水相以及洗涤水即得所述排盐水。
本发明提供的处理方法处理后的排盐水中，TOC含量≤8mg/L和/或溴代苯酚含量≤0.5 mg/L(以一溴二氯苯酚、二溴一氯苯酚和三溴苯酚的总含量之和计)，由此可实现深度净化的目的。
本发明提供的MDA制备过程中产生的排盐水的处理方法对排盐水的杂质成分进行了深入分析，发现了导致催化氧化不彻底、TOC无法有效脱除的问题根源，通过对催化氧化处理之前的排盐水中的苯酚含量、溴化钠含量进行有效控制，能够达到深度净化的效果，处理后的排盐水中TOC含量、溴代苯酚含量都较低，有机物脱除彻底，可作为生产原料送至氯碱工艺，也能够满足排放标准，减轻了环境压力。本发明提供的处理方法针对性强，工艺简便，便于工业化实施，运行稳定，无需大量的人力和设备投入，非常具有应用前景。
具体实施方式
以下结合具体实施例对本发明的技术方案做进一步详细说明。
本发明的制备例、实施例和对比例中使用的原料来源如下：
苯胺：采用万华自产苯胺，纯度99.9％，达到GB2961-2014规定的工业级；
盐酸：采用万华自产盐酸，浓度34％；
其他原料如无特别说明，均为市售产品。
本发明的制备例、实施例和对比例中使用的检测方法及仪器如下：
TOC测定：德国耶拿2100S TOC仪，TOC/TN双检测器；样品以盐酸调至pH＝2，进样分析，TOC以邻苯二甲酸钠外标定量。
盐水中的溴代苯酚检测(一溴二氯苯酚、二溴一氯苯酚以及三溴苯酚的总含量之和)：美国安捷伦1260S液相色谱仪，DAD紫外检测器；样品直接进样分析，分别采用所要检测的目标物质外标定量，波长220nm。
盐水中的苯酚检测：美国安捷伦1260S液相色谱仪，DAD紫外检测器；样品直接进样分析，苯酚外标定量，波长280nm。
盐水中的MDA检测：美国安捷伦1260S液相色谱仪，DAD紫外检测器；样品直接进样分析，以4,4-MDA外标定量，波长280nm。
盐水或盐酸中的溴检测：离子色谱法，样品以水稀释后直接分析，涉及仪器：瑞士Metrohm公司881离子色谱仪，带电导检测器，以溴离子标准溶液外标定量；根据检测的溴元素含量相应换算为盐水中的溴化钠含量或盐酸中的溴化氢含量。
苯胺中的苯酚检测：气相色谱法，样品直接分析，涉及仪器：美国Agilent公司7890B气相色谱仪，带FID氢火焰检测器，以苯酚标准溶液外标定量。
如无特别说明，本发明的制备例、实施例和对比例中所使用的百分数均为质量百分数。
制备例MDA的制备
将摩尔比为0.3:1的盐酸(以HCl计)与苯胺进行反应生成苯胺酸盐，再加入甲醛发生缩合反应及转位反应，甲醛与苯胺的摩尔比为0.35:1，反应温度为50℃，反应结束后得到包含二氨基二苯基的二胺盐和多胺盐的反应混合物。采用过量的50％NaOH(NaOH与盐酸的摩尔比为1.10:1)中和反应混合物，并将中和后的混合物送入分层器分离出有机相和水相，有机相经过水(水与油相体积比为0.4:1)洗涤一次后，通过10kPa闪蒸初步分离水和苯胺，再通过8barg蒸汽精馏精制得到MDA。
实施例1
按照制备例制备MDA，其中，原料盐酸中的溴化氢含量为84.8mg/L。
收集并合并中和及水洗过程中产生的水相和洗涤盐水得到排盐水，加入34％盐酸调节pH值至5.1，然后使用苯胺作为萃取剂进行萃取(苯胺中的苯酚含量为21.3mg/L)，萃取温度为30℃，苯胺与排盐水的质量比为0.2:1，萃取后的排盐水中MDA含量为0.03mg/L，达到了萃取MDA的目的，同时检测出排盐水中苯酚含量为0.27mg/L，溴化钠含量为3.74mg/L，苯胺含量为3.9％。接着，将排盐水经过2barg蒸汽汽提处理，脱除其中的苯胺。最后，向脱除苯胺后的排盐水中加入次氯酸钠氧化剂(加入量与排盐水的质量比为1:2000)并在负载YRN-138镍-铁基催化剂的反应器中经过催化氧化，由此得到深度处理后的排盐水，盐水中TOC含量为5.7mg/L，溴代苯酚含量为0.25mg/L。
实施例2
按照制备例制备MDA，其中，原料盐酸中的溴化氢含量为84.8mg/L。
收集并合并中和及水洗过程中产生的水相和洗涤盐水得到排盐水，加入34％盐酸调节pH值至7.9，然后使用苯胺进行萃取(苯胺中的苯酚含量为21.3mg/L)，萃取温度为30℃，苯胺与排盐水的质量比为0.2:1，萃取后的排盐水中MDA含量为0.02mg/L，达到了萃取 MDA的目的，同时检测出排盐水中苯酚含量为0.68mg/L，溴化钠含量为3.58mg/L，苯胺含量为3.6％。接着，将排盐水经过实施例1所述的蒸汽汽提处理和催化氧化处理，由此得到深度处理后的排盐水，盐水中TOC含量为6.4mg/L，溴代苯酚含量为0.47mg/L。
实施例3
按照制备例制备MDA，其中，原料盐酸中的溴化氢含量为84.8mg/L。
收集并合并中和及水洗过程中产生的水相和洗涤盐水得到排盐水，加入34％盐酸调节pH值至4.0，然后使用苯胺进行萃取(苯胺中的苯酚含量为21.3mg/L)，萃取温度为30℃，苯胺与排盐水的质量比为0.2:1，萃取后的排盐水中MDA含量为0.05mg/L，达到了萃取MDA的目的，同时检测出排盐水中苯酚含量为0.11mg/L，溴化钠含量为3.15mg/L，苯胺含量为5.1％。接着，将排盐水经过实施例1所述的蒸汽汽提处理和催化氧化处理，由此得到深度处理后的排盐水，盐水中TOC含量为5.8mg/L，溴代苯酚含量为0.07mg/L。
实施例4
按照制备例制备MDA，其中，原料盐酸中的溴化氢含量为84.8mg/L。
收集并合并中和及水洗过程中产生的水相和洗涤盐水得到排盐水，加入34％盐酸调节pH值至5.1，然后使用苯胺进行萃取(苯胺中的苯酚含量为21.3mg/L)，萃取温度为10℃，苯胺与排盐水的质量比为0.2:1，萃取后的排盐水中MDA含量为0.13mg/L，达到了萃取MDA的目的，同时检测出排盐水中苯酚含量为0.24mg/L，溴化钠含量为3.44mg/L，苯胺含量为3.9％。接着，将排盐水经过实施例1所述的蒸汽汽提处理和催化氧化处理，由此得到深度处理后的排盐水，盐水中TOC含量为6.5mg/L，溴代苯酚含量为0.18mg/L。
实施例5
按照制备例制备MDA，其中，原料盐酸中的溴化氢含量为84.8mg/L。
收集并合并中和及水洗过程中产生的水相和洗涤盐水得到排盐水，加入34％盐酸调节pH值至8.0，然后使用苯胺进行萃取(苯胺中的苯酚含量为21.3mg/L)，萃取温度为50℃，苯胺与排盐水的质量比为0.2:1，萃取后的排盐水中MDA含量为0.08mg/L，达到了萃取MDA的目的，同时检测出排盐水中苯酚含量为0.74mg/L，溴化钠含量为3.55mg/L，苯胺 含量为3.8％。接着，将排盐水经过实施例1所述的蒸汽汽提处理和催化氧化处理，由此得到深度处理后的排盐水，盐水中TOC含量为7.5mg/L，溴代苯酚含量为0.45mg/L。
实施例6
按照制备例制备MDA，其中，使用原料盐酸之前对其进行纯化使其中的溴化氢含量为4.7mg/L。
收集并合并中和及水洗过程中产生的水相和洗涤盐水得到排盐水，测定pH值为13.5，然后使用苯胺进行萃取(苯胺中的苯酚含量为21.3mg/L)，萃取温度为95℃，苯胺与排盐水的质量比为0.2:1，萃取后的排盐水中MDA含量为0.22mg/L，达到了萃取MDA的目的，同时检测出排盐水中苯酚含量为8.77mg/L，溴化钠含量为0.15mg/L，苯胺含量为3.6％。接着，将排盐水经过实施例1所述的蒸汽汽提处理和催化氧化处理，由此得到深度处理后的排盐水，盐水中TOC含量为6.7mg/L，溴代苯酚含量为0.18mg/L。
实施例7
按照制备例制备MDA，其中，原料盐酸中的溴化氢含量为84.8mg/L。
收集并合并中和及水洗过程中产生的水相和洗涤盐水得到排盐水，测定pH值为13.5，然后使用苯胺作为萃取剂进行萃取(使用苯胺之前对其进行纯化使其中的苯酚含量为0.48mg/L)，萃取温度为95℃，苯胺与排盐水的质量比为0.2:1，萃取后的排盐水中MDA含量为0.25mg/L，达到了萃取MDA的目的，同时检测出排盐水中苯酚含量为0.02mg/L，溴化钠含量为3.85mg/L，苯胺含量为3.6％。接着，将排盐水经过实施例1所述的蒸汽汽提处理和催化氧化处理，由此得到深度处理后的排盐水，盐水中TOC含量为5.2mg/L，溴代苯酚含量为0.02mg/L。
对比例1
按照制备例制备MDA，其中，原料盐酸中的溴化氢含量为84.8mg/L。
收集并合并中和及水洗过程中产生的水相和洗涤盐水得到排盐水，测定pH值为13.5，然后使用苯胺进行萃取(苯胺中的苯酚含量为21.3mg/L)，萃取温度为95℃，苯胺与排盐水的质量比为0.2:1，萃取后的排盐水中MDA含量为0.24mg/L，达到了萃取MDA的目的， 同时检测出排盐水中苯酚含量为8.61mg/L，溴化钠含量为3.87mg/L，苯胺含量为3.6％。接着，将排盐水经过实施例1所述的蒸汽汽提处理和催化氧化处理，由此得到深度处理后的排盐水，盐水中TOC含量为16.7mg/L，溴代苯酚含量为11.80mg/L。
对比例2
按照制备例制备MDA，其中，原料盐酸中的溴化氢含量为84.8mg/L。
收集并合并中和及水洗过程中产生的水相和洗涤盐水得到排盐水，加入34％盐酸调节pH值至8.0，然后使用苯胺进行萃取(苯胺中的苯酚含量为21.3mg/L)，萃取温度为95℃，苯胺与排盐水的质量比为0.2:1，萃取后的排盐水中MDA含量为0.26mg/L，达到了萃取MDA的目的，同时检测出排盐水中苯酚含量为4.58mg/L，溴化钠含量为3.87mg/L，苯胺含量为3.9％。接着，将排盐水经过实施例1所述的蒸汽汽提处理和催化氧化处理，由此得到深度处理后的排盐水，盐水中TOC含量为12.5mg/L，溴代苯酚含量为6.18mg/L。
对比例3
按照制备例制备MDA，其中，原料盐酸中的溴化氢含量为84.8mg/L。
收集并合并中和及水洗过程中产生的水相和洗涤盐水得到排盐水，测定pH值为13.5，然后使用苯胺进行萃取(苯胺中的苯酚含量为21.3mg/L)，萃取温度为30℃，苯胺与排盐水的质量比为0.2:1，萃取后的排盐水中MDA含量为0.27mg/L，达到了萃取MDA的目的，同时检测出排盐水中苯酚含量为6.02mg/L，溴化钠含量为3.75mg/L，苯胺含量为3.6％。接着，将排盐水经过实施例1所述的蒸汽汽提处理和催化氧化处理，由此得到深度处理后的排盐水，盐水中TOC含量为15.1mg/L，溴代苯酚含量为9.64mg/L。
通过上述实施例和对比例可以发现，实施了本发明提供的处理方法后，通过将萃取过程pH值控制在4-8且萃取温度控制在10-50℃的条件下，或者通过控制原料盐酸中溴化氢含量不超过5mg/L，或者通过控制萃取剂苯胺中苯酚含量不超过0.5mg/L，由此有效达到了降低催化氧化出口溴代苯酚含量及TOC含量的目的，溴代苯酚含量可降低至0.5mg/L以下(甚至可到0.1mg/L以下)，TOC含量可降低至8mg/L以下，处理后的排盐水有机物脱除彻底。
除非特别限定，本发明所用术语均为本领域技术人员通常理解的含义。
本发明所描述的实施方式仅出于示例性目的，并非用以限制本发明的保护范围，本领域技术人员可在本发明的范围内作出各种其他替换、改变和改进，因而，本发明不限于上述实施方式，而仅由权利要求限定。

Claims (10)

  1. 一种MDA制备过程中产生的排盐水的处理方法，所述MDA以苯胺、盐酸和甲醛为原料制备，所述排盐水依次经过以下步骤进行处理：
    S1：加入萃取剂进行萃取处理；
    S2：将经萃取处理后的排盐水进行蒸汽汽提处理；以及
    S3：将经蒸汽汽提处理后的排盐水进行催化氧化处理；
    其特征在于，所述排盐水在进行催化氧化处理之前，控制其中的苯酚含量不超过0.8mg/L和/或溴化钠含量不超过0.2mg/L。
  2. 根据权利要求1所述的处理方法，其特征在于，所述苯酚含量通过方法A和/或方法B进行控制，其中，所述方法A为：将所述萃取剂纯化至其中的苯酚含量不超过0.5mg/L；所述方法B为：在加入所述萃取剂进行萃取处理之前调节所述排盐水的pH值为4～8，优选为5～7，并且在萃取处理时控制温度为10～50℃，优选为30～40℃。
  3. 根据权利要求1或2所述的处理方法，其特征在于，所述溴化钠含量通过将所述盐酸纯化至其中的溴化氢含量不超过5.0mg/L进行控制。
  4. 根据权利要求3所述的处理方法，其特征在于，所述盐酸的浓度为20～60wt％；优选为30～40wt％。
  5. 根据权利要求1-4任一项所述的处理方法，其特征在于，所述萃取剂选自苯胺、对甲基苯胺、邻甲基苯胺、对乙基苯胺、邻乙基苯胺、2,4-二甲基苯胺或其任意混合物；优选为苯胺。
  6. 根据权利要求5所述的处理方法，其特征在于，所述萃取剂与所述排盐水的质量比为0.05～0.5:1，优选为0.1～0.3:1，萃取后所述排盐水中的MDA含量不超过0.5mg/L，优选不超过0.3mg/L。
  7. 根据权利要求1-6任一项所述的处理方法，其特征在于，所述蒸汽汽提处理的蒸汽压力为1～10barg，优选为1～3barg。
  8. 根据权利要求1-7任一项所述的处理方法，其特征在于，所述催化氧化处理以次氯酸钠作为氧化剂，其与所述排盐水的质量比为1:1000～5000。
  9. 根据权利要求1-8任一项所述的处理方法，其特征在于，所述排盐水经以下过程所产生：
    T1：将苯胺与盐酸进行反应制备苯胺盐酸盐，再与甲醛发生缩合反应及转位反应；以及
    T2：加入30～60wt％的NaOH溶液中和步骤T1的反应体系，分离出所得水相，有机相用其体积30～60％的水洗涤，合并所述水相以及洗涤水即得所述排盐水。
  10. 根据权利要求1-9任一项所述的处理方法，其特征在于，经所述处理方法处理后的排盐水中，TOC含量≤8mg/L和/或溴代苯酚含量≤0.5mg/L。
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