CN116496172B - Treatment method of high-acidity DMF (dimethyl formamide) rectification liquid and treatment method of DMF waste liquid - Google Patents
Treatment method of high-acidity DMF (dimethyl formamide) rectification liquid and treatment method of DMF waste liquid Download PDFInfo
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- 239000007788 liquid Substances 0.000 title claims abstract description 89
- 238000000034 method Methods 0.000 title claims abstract description 54
- 239000002699 waste material Substances 0.000 title claims description 24
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 title abstract description 364
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 claims abstract description 51
- BDAGIHXWWSANSR-UHFFFAOYSA-M Formate Chemical compound [O-]C=O BDAGIHXWWSANSR-UHFFFAOYSA-M 0.000 claims abstract description 47
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 29
- 235000019253 formic acid Nutrition 0.000 claims abstract description 26
- 239000000126 substance Substances 0.000 claims abstract description 26
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 claims abstract description 25
- 239000007787 solid Substances 0.000 claims abstract description 25
- 238000003756 stirring Methods 0.000 claims abstract description 24
- 238000002425 crystallisation Methods 0.000 claims abstract description 14
- 230000008025 crystallization Effects 0.000 claims abstract description 14
- 238000000926 separation method Methods 0.000 claims abstract description 10
- 238000002156 mixing Methods 0.000 claims abstract description 6
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical group [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 71
- 238000006243 chemical reaction Methods 0.000 claims description 31
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 25
- 239000000843 powder Substances 0.000 claims description 18
- 238000001035 drying Methods 0.000 claims description 8
- 238000004140 cleaning Methods 0.000 claims description 2
- 239000000463 material Substances 0.000 abstract description 16
- 238000001816 cooling Methods 0.000 abstract description 11
- 239000002994 raw material Substances 0.000 abstract description 8
- 239000000376 reactant Substances 0.000 abstract description 3
- 238000001556 precipitation Methods 0.000 abstract description 2
- 239000004280 Sodium formate Substances 0.000 description 50
- HLBBKKJFGFRGMU-UHFFFAOYSA-M sodium formate Chemical compound [Na+].[O-]C=O HLBBKKJFGFRGMU-UHFFFAOYSA-M 0.000 description 50
- 235000019254 sodium formate Nutrition 0.000 description 50
- 239000013078 crystal Substances 0.000 description 19
- 238000011084 recovery Methods 0.000 description 19
- 238000001914 filtration Methods 0.000 description 15
- 238000000354 decomposition reaction Methods 0.000 description 14
- 239000000243 solution Substances 0.000 description 13
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 12
- 238000002474 experimental method Methods 0.000 description 12
- 239000000203 mixture Substances 0.000 description 9
- 239000002904 solvent Substances 0.000 description 9
- 238000012360 testing method Methods 0.000 description 8
- ROSDSFDQCJNGOL-UHFFFAOYSA-N Dimethylamine Chemical compound CNC ROSDSFDQCJNGOL-UHFFFAOYSA-N 0.000 description 6
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 6
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical compound [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 description 6
- 238000010438 heat treatment Methods 0.000 description 6
- 239000012535 impurity Substances 0.000 description 6
- 239000011259 mixed solution Substances 0.000 description 6
- 238000005406 washing Methods 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 5
- 238000005904 alkaline hydrolysis reaction Methods 0.000 description 4
- 238000000746 purification Methods 0.000 description 4
- 230000018044 dehydration Effects 0.000 description 3
- 238000006297 dehydration reaction Methods 0.000 description 3
- 238000001514 detection method Methods 0.000 description 3
- 229910000030 sodium bicarbonate Inorganic materials 0.000 description 3
- 235000017557 sodium bicarbonate Nutrition 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 239000012670 alkaline solution Substances 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 238000000197 pyrolysis Methods 0.000 description 2
- 239000011734 sodium Substances 0.000 description 2
- 159000000000 sodium salts Chemical class 0.000 description 2
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
- UIIMBOGNXHQVGW-DEQYMQKBSA-M Sodium bicarbonate-14C Chemical compound [Na+].O[14C]([O-])=O UIIMBOGNXHQVGW-DEQYMQKBSA-M 0.000 description 1
- 238000010669 acid-base reaction Methods 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 239000005456 alcohol based solvent Substances 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000013064 chemical raw material Substances 0.000 description 1
- 239000012295 chemical reaction liquid Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 210000003298 dental enamel Anatomy 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 239000005457 ice water Substances 0.000 description 1
- VUZPPFZMUPKLLV-UHFFFAOYSA-N methane;hydrate Chemical compound C.O VUZPPFZMUPKLLV-UHFFFAOYSA-N 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- 239000011591 potassium Substances 0.000 description 1
- 238000010992 reflux Methods 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 238000009988 textile finishing Methods 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
- 239000002912 waste gas Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C231/00—Preparation of carboxylic acid amides
- C07C231/22—Separation; Purification; Stabilisation; Use of additives
- C07C231/24—Separation; Purification
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/41—Preparation of salts of carboxylic acids
- C07C51/412—Preparation of salts of carboxylic acids by conversion of the acids, their salts, esters or anhydrides with the same carboxylic acid part
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The application discloses a treatment method of high-acidity DMF (dimethyl formamide) rectifying liquid, which comprises the following steps: controlling the water content in DMF rectifying liquid to be 0.05-1% and the acidity to be 2-10%; adding alkaline substances into the DMF rectifying liquid at room temperature, uniformly mixing, controlling the pH value of a system to be 7-9, and reacting formic acid in the DMF rectifying liquid with the alkaline substances to generate formate; reducing the temperature of the system to 0-10 ℃, continuously stirring, and crystallizing and separating formate in the system; formate solids and DMF liquid are separated and recovered separately. According to the treatment method, the alkaline material is used as a reactant, formic acid and the alkaline material react to generate formate, and the formate is subjected to cooling crystallization precipitation separation to obtain DMF material with greatly reduced acidity and highly concentrated formate, wherein the DMF material can be further purified and recovered, and the formate is sold as a raw material after being washed, decontaminated and dried.
Description
Technical Field
The application belongs to the technical field of DMF waste liquid treatment, and particularly relates to a treatment method of high-acidity DMF rectification liquid and a treatment method of DMF waste liquid comprising the treatment step of the high-acidity DMF rectification liquid.
Background
DMF is used as an organic solvent commonly used in the textile finishing industry, and after being treated by using and combining with waste gas treatment facilities, DMF waste liquid with the concentration of 10% -50% is generated, if the waste liquid is directly abandoned, the waste liquid can generate great resource waste and environmental pollution, and the conventional recovery process is to purify and recover the waste liquid by rectification and purification, so that DMF contained in the waste liquid is effectively recovered, and the purposes of resource recovery and pollutant treatment up to the standard and emission are achieved.
The prior DMF recovery is carried out in a heating rectification mode, and the condition that DMF is decomposed to produce formic acid and dimethylamine occurs in the heating recovery process, so that DMF rectification liquid containing high-concentration formic acid is finally produced. In order to reduce the influence of formic acid in the DMF waste liquid recovery system, the most original treatment process is to directly and continuously add alkaline substances in the DMF heating and rectifying process, perform acid-base neutralization, reduce the acidity in the system, and reflux the neutralized mixture into a DMF solution storage tank for further purification. However, this treatment scheme has many drawbacks, such as: 1. the sodium salt generated in the treatment process remains in the system and is finally discharged in the form of rectification residues, and additional incineration treatment is needed, so that higher treatment cost is generated; 2. the generated sodium salt can enter a rectifying tower in the rectifying process, so that the risk of tower body blockage is increased; 3. there is a high potential safety hazard in production; 4. the direct addition of alkaline substances in the DMF heating and rectifying process can easily lead to the decomposition of DMF, and reduce the purity and yield of DMF.
In view of the above drawbacks, the method of adding alkaline substances directly in the heating and rectifying process of DMF is abandoned, and the improved process is adopted: the generated formic acid is required to be treated through pyrolysis, so that the formic acid is decomposed into carbon dioxide and water, and the treatment mode is harmless, but a large amount of electric energy is consumed in the treatment process, and the treatment cost is high; and formic acid is decomposed and cannot be recycled.
The foregoing background is only for the purpose of providing an understanding of the principles and concepts of the application and is not necessarily in the prior art to the application and is not intended to be used as an admission that the background of the application is prior art to the extent that it has been disclosed in advance of the filing date of the present application.
Disclosure of Invention
In view of the above, in order to overcome the defects of the prior art, the present application aims to provide an improved treatment method for high acidity DMF rectification liquid, which can realize separation and recovery of formic acid and DMF in the high acidity DMF rectification liquid under the condition of avoiding DMF decomposition.
In order to achieve the above purpose, the present application adopts the following technical scheme:
a method for treating high-acidity DMF rectification liquid comprises the following steps:
controlling the water content in DMF rectifying liquid to be 0.05-1% and the acidity to be 2-10%;
adding alkaline substances into the DMF rectifying liquid at room temperature, uniformly mixing, controlling the pH value of a system to be 7-9, and reacting formic acid in the DMF rectifying liquid with the alkaline substances to generate formate;
reducing the temperature of the system to 0-10 ℃, continuously stirring, and crystallizing and separating formate in the system;
formate solids and DMF liquid are separated and recovered separately.
The acidity in the application is the content of the formic acid in the DMF rectifying liquid and is obtained by referring to the method specified in national standard HG/T2028-2009 industrial dimethylformamide. Too low an acid level results in a low formate content, low removal rates and a relatively high acidity level, which is more advantageous, but when the acidity is excessively increased (greater than 10%) it can cause severe corrosion of the reactor equipment.
According to the treatment method of DMF rectification liquid, sodium hydroxide, potassium hydroxide or sodium bicarbonate is added, under the condition that substances affecting purity are not introduced, sodium or potassium is combined with formic acid to generate formate, the formate is crystallized and separated out by utilizing solubility difference, and the formate is separated out by a physical separation mode. The method avoids the harmless treatment mode of formic acid by using a pyrolysis method, and avoids the decomposition of DMF; the formate generated at the same time can be used as chemical raw material, thus greatly reducing the treatment cost.
According to some preferred embodiments of the application, the alkaline substance is a solid or an alkaline solution with a mass fraction greater than or equal to 50%, preferably a solid powder. The addition of the solid or high-concentration lye is intended to reduce the water content introduced and thus to reduce the dissolution of the formate produced and to increase the crystallization yield of the formate and thus to increase the formate removal rate.
According to some preferred embodiments of the application, the alkaline substance is one or more of sodium hydroxide, potassium hydroxide and sodium bicarbonate.
According to some preferred embodiments of the present application, the addition time of the alkaline substance is controlled within 10-20min. The addition of alkaline substances is relatively slow, avoiding DMF decomposition caused by local overbasing and local sudden increases in temperature.
According to some preferred embodiments of the application, the room temperature is 20-30 ℃. Namely, when alkaline substances are added, the temperature of the high-acidity DMF rectification liquid is maintained at 20-30 ℃, so that DMF decomposition caused by high temperature is avoided.
According to some preferred embodiments of the application, the temperature of the system is maintained between 20 and 30 ℃ during the reaction. And the reaction is operated at normal temperature, so that the acid-base reaction rate can be ensured, and the decomposition of DMF can be avoided.
According to some preferred embodiments of the present application, the reaction is continuously stirred for 30-60min after adding alkaline substances into the DMF rectification liquid, and the stirring speed is 60-120r/min.
According to some preferred embodiments of the application, the stirring time is 10-30min and the stirring rate is 15-30r/min during crystallization.
According to some preferred embodiments of the application, said step comprises a post-treatment of formate: and cleaning the formate obtained by filtering by adopting an alcohol substance and drying.
According to some preferred embodiments of the application, the acidity of the DMF liquid recovered after the separation is less than or equal to 0.01%.
The application also provides a method for treating DMF waste liquid comprising the treatment step of the high-acidity DMF rectification liquid.
Compared with the prior art, the application has the following advantages: according to the treatment method of the high-acidity DMF rectifying liquid, an alkaline material is used as a reactant, formic acid and the alkaline material react to generate formate by utilizing the characteristic of low water content in the DMF rectifying liquid, and the formate is subjected to cooling crystallization and precipitation separation to obtain DMF materials with greatly reduced acidity and high-purity formate, wherein the DMF materials can be returned to a recovery system for further purification and recovery, and the formate can be used or sold as a raw material after being washed, decontaminated and dried; and the decomposition of DMF is avoided by controlling the conditions.
Detailed Description
In order to better understand the technical solutions of the present application, the following description will clearly and completely describe the technical solutions of the embodiments of the present application, and it is obvious that the described embodiments are only some embodiments of the present application, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present application without making any inventive effort, shall fall within the scope of the present application.
According to the method, formic acid and alkaline materials are reacted to generate formate by utilizing the mode that the solubility of formate generated by formic acid and alkaline materials is poor and taking alkaline materials (sodium hydroxide, potassium hydroxide or sodium bicarbonate) as reactants and utilizing the characteristic of low water content in DMF (dimethyl formamide) rectifying liquid, the formate is cooled, crystallized and precipitated and separated to obtain DMF materials with greatly reduced acidity and highly concentrated formate, the DMF materials can be returned to a recovery system for further purification and recovery, and the formate can be used or sold as a raw material after being washed, decontaminated and dried. Meanwhile, the decomposition of DMF in the treatment process is avoided through the control of the conditions, and the effective content of DMF in a final system is improved. The reaction principle in the application is as follows:
HCOOH+Na + +OH - →NaCOOH+H 2 O
in the prior art, in some fields, it is also necessary to treat the DMF waste liquid, such as adding a strong base to the DMF waste liquid to perform alkaline hydrolysis of DMF, and the DMF alkaline hydrolysis (NaOH) reaction may generate dimethylamine and sodium formate. The principle is as follows:
HCON（CH 3 ） 2 +OH - →HCOO - +NH（CH 3 ） 2
however, in the process of DMF alkaline hydrolysis, the added alkaline substance is required to promote the decomposition of DMF, and at the same time, the pH value of the system is usually required to be controlled to be more than 10, and heating is required to promote the decomposition of DMF. The existing alkaline hydrolysis process is not suitable for the case and purpose in the present application.
In order to achieve the above objective, the treatment method of DMF rectification liquid in this embodiment includes the following steps:
controlling the water content in DMF rectifying liquid to be 0.05-1% and the acidity to be 2-10%.
The detection confirms that the water content in the DMF rectification liquid can influence the ionization decomposition and reaction rate after the medicament is added when the water content is too low. When the water content is higher, the dehydration time can be adjusted, and the water content is reduced. The acidity is accumulated along with the system, if the acidity of the system is far lower than 2%, the rectification can be continued, the acidity in the tower kettle is gradually accumulated, and the deacidification treatment can be carried out after the concentrated discharge when the concentration is higher (2% -10%). However, if the acidity is excessively increased (more than 10%), serious corrosion is caused to the reactor equipment.
And step two, adding alkaline substances into the DMF rectification liquid at the normal temperature at the temperature of 20-30 ℃, uniformly mixing, and controlling the addition amount of the alkaline substances by using a pH on-line monitor to ensure that the pH of the system is 7-9.
The alkaline substance is sodium hydroxide, potassium hydroxide and/or sodium bicarbonate, and is solid or alkaline solution with mass fraction of more than or equal to 50%; preferably a solid powder. The adding time of the alkaline substance is controlled within 10-20min, and DMF decomposition caused by local over-alkalinity and local sudden increase of temperature is avoided.
And thirdly, reacting for 30-60min under stirring, wherein the stirring speed is 60-120r/min.
The temperature of the system is maintained at 20-30 ℃ in the reaction process. If the temperature is too high and the alkalinity is too high, DMF decomposition can be avoided or reduced by controlling the reaction pH to be in an acidic to slightly alkaline environment and the reaction temperature to be at normal temperature.
Step four, the temperature of the system is reduced to 0-10 ℃, stirring is continued for 10-30min to crystallize, and the stirring speed is 15-30r/min; after filtration formate solids and DMF liquid were recovered separately. The acidity of the DMF liquid recovered after filtration is less than or equal to 0.01%.
During crystallization, the crystallization rate can be further improved by the growth of crystals of the materials, and the slow stirring is needed at the moment, so that the crushing of the crystals is reduced and the crystallization rate is improved while the materials are uniformly mixed.
And fifthly, carrying out aftertreatment on formate.
The formate obtained by filtration is washed with an alcohol such as methanol or ethanol and dried.
Preferably, the reaction is carried out in a jacketed enamel reaction kettle, and after the reaction is finished, low-temperature ice water is introduced into the jacket of the reaction kettle, and the temperature is reduced to 0-10 ℃. After cooling and crystallizing, a mixture of semi-mobile formate and DMF is formed in the reaction liquid, the mixture is pumped and discharged into a centrifugal filter device, the filtered solution is DMF solution with greatly reduced acidity, the solid part is formate crystal containing a small amount of DMF, and the formate crystal can be used or sold as a product after being washed by methanol, ethanol or other alcohol solvents and dried. And the application adopts normal temperature or low temperature treatment process, compared with the high temperature of the traditional process, the safety coefficient is increased, and the risk coefficient is lower.
Example 1
A solvent recovery company generates high acidity DMF rectification liquid in the treatment process of DMF waste liquid, the acidity is 8%, the water content is 0.1%, and 1L of sample is sampled for the following experiment.
70g of sodium hydroxide solid powder is added at 25 ℃, and the mixture is stirred for 30min at 100r/min, the pH of the system is 7.5, and the temperature of the system is kept at 25 ℃ in the reaction process. Stirring at a slow speed of 30r/min for reaction for 10min, cooling to 10 ℃ to obtain DMF mixed liquid containing sodium formate crystals, filtering and separating, testing to obtain DMF liquid with acidity reduced to 0.005%, washing sodium formate obtained by filtering by ethanol, drying at a low temperature of 80 ℃ to obtain 150g of crystalline sodium formate solid powder, and detecting that the purity of the crystalline sodium formate reaches 99.5%, wherein the crystalline sodium formate solid powder can be used as industrial raw materials.
The experiment inputs 70g of sodium hydroxide to produce 150g of sodium formate crystals, wherein the crystallization water and impurities are contained by about 32g, 118g of pure sodium formate, and the yield is 99.7% (calculated by 118.3g of sodium formate generated according to 80g of formic acid theory). After DMF was filtered, 0.98L remained, yield 98%. The residual DMF is in ethanol solution and can be recovered later by concentration.
Example 2
A coating company generates high-acidity DMF rectification liquid in the treatment process of DMF waste liquid, the acidity is 10%, the water content is 0.08%, and 5L of sample is sampled for the following experiment.
437g of sodium hydroxide solid powder was added at 25℃and mixed by rapid stirring at 80r/min for 50min, the pH of the system was 7.2, and the temperature of the system was maintained at 25℃during the reaction. Stirring at a slow speed of 30r/min for reaction for 15min, cooling to 10 ℃ to obtain DMF mixed liquid containing sodium formate crystals, filtering and separating, testing to obtain DMF liquid with acidity reduced to 0.009%, washing the filtered sodium formate with ethanol, drying at a low temperature of 80 ℃ to obtain 930g of crystalline sodium formate solid powder, and detecting that the purity of the crystalline sodium formate reaches 98.5%, wherein the crystalline sodium formate solid powder can be used as industrial raw materials.
The experiment was conducted with 437g of sodium hydroxide to yield 930g of sodium formate crystals containing about 206g of water of crystallization and impurities, 724g of pure sodium formate, and 98.0% yield (based on 739g of sodium formate produced by 500g of formic acid theory). After filtration, 4.92L remained, yield 98.4%. The residual DMF is in ethanol solution and can be recovered later by concentration.
Example 3
A solvent recovery company generates high-acidity DMF rectification liquid in the treatment process of DMF waste liquid, the acidity is 9%, the water content is 0.09%, and 10L of sample is sampled for the following experiment.
1580g of 50% sodium hydroxide solution is added at 20 ℃, and the mixture is stirred for 50min at 100r/min and mixed, the pH of the system is 7.1, and the temperature of the system is kept at 20 ℃ in the reaction process. Stirring at a slow speed of 30r/min for reaction for 20min, cooling to 5 ℃ to obtain DMF mixed solution containing sodium formate crystals, filtering and separating, testing to obtain DMF liquid with acidity reduced to 0.0095%, washing sodium formate obtained by filtering by ethanol, drying at a low temperature of 80 ℃ to obtain 1884g of crystalline sodium formate solid powder, and detecting that the purity of the crystalline sodium formate reaches 98.5%, wherein the crystalline sodium formate solid powder can be used as industrial raw materials.
The experiment was conducted with 790g of pure sodium hydroxide to yield 1884g of crystalline sodium formate solid powder containing about 671g of water of crystallization and impurities, 1213g of pure sodium formate and 91.2% yield (1330 g of sodium formate calculated from 900g of formic acid theory). After DMF was filtered, 9.96L remained, and DMF yield was not calculated due to the increase in water content. The residual DMF is in ethanol solution and can be recovered later by concentration.
Comparative example 1
A solvent recovery company generates high-acidity DMF rectification liquid in the treatment process of DMF waste liquid, the acidity is 9%, the water content is 0.12%, and 1L of sample is sampled for the following experiment.
At 20 deg.c, 790g of 10% sodium hydroxide solution was added, and the mixture was stirred rapidly at 100r/min for 50min to mix, with a pH of 7, and the temperature of the system was maintained at 20 deg.c during the reaction. Then stirring and reacting for 20min at a slow speed of 30r/min, cooling to 5 ℃, and not generating DMF mixed solution containing sodium formate crystals, wherein the acidity of the DMF liquid is reduced to 0.01% by test, but the obtained DMF solution is liquid with increased water content and formate content, and a large amount of crystals are generated in the subsequent rectification and dehydration process, so that a recovery pipeline is blocked.
Comparative example 2
A solvent recovery company generates high acidity DMF rectification liquid in the treatment process of DMF waste liquid, the acidity is 8%, the water content is 0.11%, and 1L of sample is sampled for the following experiment.
230g of 30% sodium hydroxide solution is added at 20 ℃, and the mixture is stirred for 50min at 100r/min, the pH of the system is 7.3, and the temperature of the system is kept at 20 ℃ in the reaction process. Then stirring and reacting for 20min at a slow speed of 30r/min, cooling to 10 ℃, and not generating DMF mixed liquid containing sodium formate crystals, wherein the acidity of the DMF liquid is reduced to 0.007% by test, but the obtained DMF solution is liquid with increased water content and formate content, and a large amount of crystals are generated in the subsequent rectification and dehydration process, so that a recovery pipeline is blocked.
Comparative example 3
A solvent recovery company generates high acidity DMF rectification liquid in the treatment process of DMF waste liquid, the acidity is 8%, the water content is 0.07%, and 1L of sample is sampled for the following experiment.
90g of sodium hydroxide solid powder is added at 25 ℃, and the mixture is stirred for 30min at 100r/min and mixed, wherein the pH is more than 10, and the temperature of the system is kept at 20 ℃ in the reaction process. Stirring at a slow speed of 30r/min for reaction for 10min, cooling to 10 ℃ to obtain DMF mixed solution containing sodium formate crystals, filtering and separating, testing to obtain DMF mixed solution with acidity reduced to 0, washing the filtered sodium formate with ethanol and drying at a low temperature of 80 ℃ to obtain 181g of mixed solid powder of crystalline sodium formate and sodium hydroxide, wherein the purity of the crystalline sodium formate reaches 95% through detection, and meanwhile, the crystalline sodium formate contains about 5% of sodium hydroxide and cannot be directly used as industrial raw materials.
The experiment was conducted with 90g of sodium hydroxide to yield 181g of mixed crystals of sodium formate containing about 45g of water of crystallization and impurities, 136g of pure sodium formate and 115% yield of sodium formate (based on 118.3g of sodium formate produced from 80g of formic acid). After DMF was filtered, 0.75L remained, yield 75%, and under the influence of alkaline environment, part of DMF was decomposed into formic acid and dimethylamine, resulting in increased sodium formate production, DMF decomposition, reduced residual material, and residual unreacted sodium hydroxide and sodium formate formed a mixture.
Comparative example 4
A solvent recovery company produced DMF rectification liquid during the treatment of DMF waste liquid, the acidity was 1%, the water content was 0.08%, and 10L was sampled for the following experiment.
87g of sodium hydroxide solid powder is added at 25 ℃,100r/min is rapidly stirred for 30min for mixing, the pH of the system is 7.1, and the temperature of the system is kept at 25 ℃ in the reaction process. Stirring and reacting for 10min at a slow speed of 30r/min to obtain DMF mixed solution containing sodium formate crystals, cooling to 10 ℃, testing to obtain DMF liquid with acidity reduced to 0.006% after filtration and separation, washing sodium formate obtained by filtration by ethanol, drying at a low temperature of 80 ℃ to obtain 163g of crystalline sodium formate solid powder, wherein the content of crystal water and impurities is about 38.5g, the purity of pure sodium formate reaches 96.5% through detection, and the reaction generated sodium formate is not thoroughly precipitated due to lower concentration of formic acid, and has lower yield and lower purity.
Comparative example 5
A solvent recovery company generates high-acidity DMF rectification liquid in the treatment process of DMF waste liquid, the acidity is 10%, the water content is 0.06%, and 1L of sample is sampled for the following experiment.
87g of sodium hydroxide solid powder is added at 25 ℃,100r/min is rapidly stirred for 30min for mixing, the pH of the system in the reaction is 7.2, the temperature of the system is not controlled in the reaction process, and the highest reaction temperature is raised to 55 ℃. Then stirring and reacting for 10min at a slow speed of 30r/min to obtain DMF mixed solution containing sodium formate crystals, cooling to 10 ℃, testing to obtain DMF liquid with acidity reduced to 1% after filtration and separation, wherein the pH value of the system is 4, washing sodium formate obtained by filtration by ethanol and drying at a low temperature of 80 ℃ to obtain 186.7g of crystalline sodium formate solid powder, wherein the content of crystal water and impurities is about 42.2g, 144.5g of pure sodium formate, the yield of sodium formate is 97.7% (calculated by 147.9g of sodium formate produced according to 87g of sodium hydroxide theory), and detecting that the purity of the crystalline sodium formate reaches 97.9%. And the DMF is severely decomposed due to the high-temperature reaction condition, so that liquid with higher acidity is finally generated.
According to the treatment method of the DMF rectifying liquid, an alkaline reagent is added into the DMF rectifying liquid with high acidity, formic acid in the rectifying liquid is neutralized to generate formate, the formate is crystallized at low temperature, the formic acid is removed from the DMF rectifying liquid in a solid-liquid separation mode, the acid content in a final solvent is greatly reduced, and the condition that a pipeline is blocked by crystallization is difficult to occur in the subsequent rectifying process. The formate separated in the crystallization mode is washed by a low-solubility solvent, so that an industrial grade formate finished product with higher purity can be obtained, and the formate can be sold as a byproduct raw material, thereby reducing the thermal decomposition treatment cost.
The above embodiments are only for illustrating the technical concept and features of the present application, and are intended to enable those skilled in the art to understand the present application and to implement the same, but are not intended to limit the scope of the present application, and all equivalent changes or modifications made according to the spirit of the present application should be included in the scope of the present application.
Claims (9)
1. A method for treating a high acidity DMF rectification liquid, comprising the steps of:
controlling the water content in DMF rectifying liquid to be 0.05-1% and the acidity to be 2-10%;
adding alkaline substances into the DMF rectifying liquid at room temperature, uniformly mixing, controlling the pH value of a system to be 7-9, and reacting formic acid in the DMF rectifying liquid with the alkaline substances to generate formate;
reducing the temperature of the system to 0-10 ℃, continuously stirring, and crystallizing and separating formate in the system;
separating and recovering formate solids and DMF liquid, respectively;
the alkaline substance is sodium hydroxide solid powder or sodium hydroxide solution with mass fraction of more than or equal to 50%.
2. The method according to claim 1, wherein the alkaline substance is added for a period of 10 to 20 minutes.
3. The process of claim 1, wherein the room temperature is 20-30 ℃.
4. The process of claim 1, wherein the temperature of the system is maintained between 20 ℃ and 30 ℃ during the reaction.
5. The process according to claim 1, wherein the reaction is continued for 30-60min with stirring after adding alkaline substances to the DMF rectification liquid, and the stirring rate is 60-120r/min.
6. The method according to claim 1, wherein the stirring time is 10 to 30 minutes and the stirring rate is 15 to 30r/min at the time of crystallization.
7. The process according to claim 1, characterized in that said step comprises a post-treatment of formate: and cleaning the formate obtained by separation by adopting an alcohol substance and drying.
8. A process according to claim 1, wherein the acidity of the DMF liquid recovered after separation is less than or equal to 0.01%.
9. A method for treating DMF waste liquid, wherein the treatment step of the DMF waste liquid treatment method comprises the treatment step of the treatment method for high-acidity DMF rectification liquid according to any one of claims 1 to 8.
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| CN111054203A (en) * | 2019-12-30 | 2020-04-24 | 陕西鼓风机（集团）有限公司 | Tail gas treatment method and system for DMF (dimethyl formamide) wastewater |
| CN111574394A (en) * | 2020-05-22 | 2020-08-25 | 安徽金禾实业股份有限公司 | Method for treating carboxylic acid-containing DMF (dimethyl formamide) in sucralose production |
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| CN101519362B (en) * | 2009-03-26 | 2012-03-14 | 华伦皮塑（苏州）有限公司 | Method for recovering dimethyl formamide |
| CN116496172B (en) * | 2023-06-27 | 2023-09-15 | 苏州巨联环保有限公司 | Treatment method of high-acidity DMF (dimethyl formamide) rectification liquid and treatment method of DMF waste liquid |
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| JPS539711A (en) * | 1976-07-12 | 1978-01-28 | Mitsubishi Rayon Co Ltd | Recovery of dimethylformamide |
| CN102408349A (en) * | 2011-11-19 | 2012-04-11 | 无锡双象超纤材料股份有限公司 | System for removing formic acid generated in dimethyl formamide recovery process |
| WO2017190299A1 (en) * | 2016-05-05 | 2017-11-09 | 章旭元 | Seven-tower five-effect rectification system for dmac or dmf waste liquid and method for recovering same |
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| CN112513007A (en) * | 2020-10-23 | 2021-03-16 | 安徽金禾实业股份有限公司 | DMF (dimethyl formamide) recovery method |
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