CN116332719A - Method for recycling dichloromethane waste solvent - Google Patents
Method for recycling dichloromethane waste solvent Download PDFInfo
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- CN116332719A CN116332719A CN202210914164.XA CN202210914164A CN116332719A CN 116332719 A CN116332719 A CN 116332719A CN 202210914164 A CN202210914164 A CN 202210914164A CN 116332719 A CN116332719 A CN 116332719A
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- YMWUJEATGCHHMB-UHFFFAOYSA-N Dichloromethane Chemical compound ClCCl YMWUJEATGCHHMB-UHFFFAOYSA-N 0.000 title claims abstract description 360
- 239000010887 waste solvent Substances 0.000 title claims abstract description 74
- 238000004064 recycling Methods 0.000 title claims abstract description 60
- 238000000034 method Methods 0.000 title claims abstract description 52
- 239000012043 crude product Substances 0.000 claims abstract description 40
- 229910017053 inorganic salt Inorganic materials 0.000 claims abstract description 38
- 239000012266 salt solution Substances 0.000 claims abstract description 27
- 238000001179 sorption measurement Methods 0.000 claims abstract description 14
- 230000018044 dehydration Effects 0.000 claims abstract description 12
- 238000006297 dehydration reaction Methods 0.000 claims abstract description 12
- 238000000622 liquid--liquid extraction Methods 0.000 claims abstract description 11
- 238000000638 solvent extraction Methods 0.000 claims abstract description 11
- 229920006395 saturated elastomer Polymers 0.000 claims abstract description 7
- 238000003860 storage Methods 0.000 claims abstract description 6
- BWHMMNNQKKPAPP-UHFFFAOYSA-L potassium carbonate Chemical compound [K+].[K+].[O-]C([O-])=O BWHMMNNQKKPAPP-UHFFFAOYSA-L 0.000 claims description 28
- NROKBHXJSPEDAR-UHFFFAOYSA-M potassium fluoride Chemical compound [F-].[K+] NROKBHXJSPEDAR-UHFFFAOYSA-M 0.000 claims description 25
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims description 23
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 20
- 238000010992 reflux Methods 0.000 claims description 20
- 238000001035 drying Methods 0.000 claims description 14
- 229910000027 potassium carbonate Inorganic materials 0.000 claims description 14
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 claims description 13
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 claims description 13
- 238000005086 pumping Methods 0.000 claims description 13
- 239000000203 mixture Substances 0.000 claims description 12
- 239000011698 potassium fluoride Substances 0.000 claims description 11
- 235000003270 potassium fluoride Nutrition 0.000 claims description 11
- 239000011780 sodium chloride Substances 0.000 claims description 10
- 229910052938 sodium sulfate Inorganic materials 0.000 claims description 10
- 235000011152 sodium sulphate Nutrition 0.000 claims description 10
- 230000001502 supplementing effect Effects 0.000 claims description 10
- 230000005855 radiation Effects 0.000 claims description 8
- CSDQQAQKBAQLLE-UHFFFAOYSA-N 4-(4-chlorophenyl)-4,5,6,7-tetrahydrothieno[3,2-c]pyridine Chemical compound C1=CC(Cl)=CC=C1C1C(C=CS2)=C2CCN1 CSDQQAQKBAQLLE-UHFFFAOYSA-N 0.000 claims description 7
- 239000002904 solvent Substances 0.000 claims description 7
- 239000001110 calcium chloride Substances 0.000 claims description 5
- 229910001628 calcium chloride Inorganic materials 0.000 claims description 5
- TWRXJAOTZQYOKJ-UHFFFAOYSA-L Magnesium chloride Chemical compound [Mg+2].[Cl-].[Cl-] TWRXJAOTZQYOKJ-UHFFFAOYSA-L 0.000 claims description 4
- 239000000391 magnesium silicate Substances 0.000 claims description 3
- 229910052919 magnesium silicate Inorganic materials 0.000 claims description 3
- 235000019792 magnesium silicate Nutrition 0.000 claims description 3
- ZADYMNAVLSWLEQ-UHFFFAOYSA-N magnesium;oxygen(2-);silicon(4+) Chemical compound [O-2].[O-2].[O-2].[Mg+2].[Si+4] ZADYMNAVLSWLEQ-UHFFFAOYSA-N 0.000 claims description 3
- 239000002808 molecular sieve Substances 0.000 claims description 3
- 239000000047 product Substances 0.000 claims description 3
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 claims description 3
- 239000003463 adsorbent Substances 0.000 claims description 2
- 239000002274 desiccant Substances 0.000 claims description 2
- 229910001629 magnesium chloride Inorganic materials 0.000 claims description 2
- 239000002699 waste material Substances 0.000 claims 3
- 238000005265 energy consumption Methods 0.000 abstract description 7
- 238000004519 manufacturing process Methods 0.000 abstract description 6
- 238000009776 industrial production Methods 0.000 abstract description 2
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 51
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 34
- TYJJADVDDVDEDZ-UHFFFAOYSA-M potassium hydrogencarbonate Chemical class [K+].OC([O-])=O TYJJADVDDVDEDZ-UHFFFAOYSA-M 0.000 description 33
- 239000000243 solution Substances 0.000 description 26
- 239000012535 impurity Substances 0.000 description 17
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 16
- 230000000052 comparative effect Effects 0.000 description 13
- 238000001514 detection method Methods 0.000 description 12
- 238000002156 mixing Methods 0.000 description 12
- 238000009835 boiling Methods 0.000 description 9
- 239000003795 chemical substances by application Substances 0.000 description 9
- 238000009924 canning Methods 0.000 description 8
- 238000007599 discharging Methods 0.000 description 8
- 238000011049 filling Methods 0.000 description 8
- 229910052757 nitrogen Inorganic materials 0.000 description 8
- 238000004321 preservation Methods 0.000 description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- 230000008569 process Effects 0.000 description 5
- 238000007781 pre-processing Methods 0.000 description 4
- 239000000284 extract Substances 0.000 description 3
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 2
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 2
- 229960000723 ampicillin Drugs 0.000 description 2
- AVKUERGKIZMTKX-NJBDSQKTSA-N ampicillin Chemical compound C1([C@@H](N)C(=O)N[C@H]2[C@H]3SC([C@@H](N3C2=O)C(O)=O)(C)C)=CC=CC=C1 AVKUERGKIZMTKX-NJBDSQKTSA-N 0.000 description 2
- NEHMKBQYUWJMIP-UHFFFAOYSA-N chloromethane Chemical compound ClC NEHMKBQYUWJMIP-UHFFFAOYSA-N 0.000 description 2
- 239000003814 drug Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000003912 environmental pollution Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 1
- 239000003242 anti bacterial agent Substances 0.000 description 1
- 229940088710 antibiotic agent Drugs 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 229960003408 cefazolin sodium Drugs 0.000 description 1
- FLKYBGKDCCEQQM-WYUVZMMLSA-M cefazolin sodium Chemical compound [Na+].S1C(C)=NN=C1SCC1=C(C([O-])=O)N2C(=O)[C@@H](NC(=O)CN3N=NN=C3)[C@H]2SC1 FLKYBGKDCCEQQM-WYUVZMMLSA-M 0.000 description 1
- 229920002301 cellulose acetate Polymers 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000013064 chemical raw material Substances 0.000 description 1
- 238000005660 chlorination reaction Methods 0.000 description 1
- 239000000287 crude extract Substances 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 239000000543 intermediate Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 239000003345 natural gas Substances 0.000 description 1
- 239000003973 paint Substances 0.000 description 1
- 230000000750 progressive effect Effects 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000003507 refrigerant Substances 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C17/00—Preparation of halogenated hydrocarbons
- C07C17/38—Separation; Purification; Stabilisation; Use of additives
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C17/00—Preparation of halogenated hydrocarbons
- C07C17/38—Separation; Purification; Stabilisation; Use of additives
- C07C17/383—Separation; Purification; Stabilisation; Use of additives by distillation
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C17/00—Preparation of halogenated hydrocarbons
- C07C17/38—Separation; Purification; Stabilisation; Use of additives
- C07C17/389—Separation; Purification; Stabilisation; Use of additives by adsorption on solids
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Extraction Or Liquid Replacement (AREA)
Abstract
The invention relates to the technical field of recycling of waste solvents, and discloses a recycling method of dichloromethane waste solvents, which comprises the following steps: s1, taking a waste solvent containing dichloromethane, adding a saturated inorganic salt solution as an extractant to perform liquid-liquid extraction, obtaining a raffinate-phase dichloromethane crude product on the lower layer, and obtaining an extract-phase inorganic salt solution crude product on the upper layer; s2, conveying the dichloromethane crude product to a first rectifying tower for normal pressure rectification and adsorption dehydration to obtain industrial-grade dichloromethane; s3, rectifying the crude inorganic salt solution under normal pressure to obtain an inorganic salt solution; and S4, storing the inorganic salt solution obtained in the step S3 into an inorganic salt storage tank, and continuously adding inorganic salt into the inorganic salt storage tank to obtain a saturated inorganic salt solution for recycling. The method saves the production cost by recycling the methylene dichloride, and has the advantages of high yield, low energy consumption, good quality, capability of recycling, simple and convenient production process, stable operation, suitability for industrial production and the like.
Description
Technical Field
The invention relates to the technical field of recycling of waste solvents, in particular to a recycling method of dichloromethane waste solvents
Background
Dichloromethane is colorless transparent liquid, has pungent smell similar to ether, is easy to volatilize, is the only incombustible low-boiling point solvent, can be dissolved in about 50 times of water, can form azeotropic mixture with water, ethanol, acetone, methanol and the like, is also commonly used as incombustible solvent of inflammables such as cellulose acetate, film strips and the like besides being used for organic synthesis, can also be used as paint remover, extractant, fire extinguishing agent, refrigerant and the like, and can be obtained by high-temperature chlorination of natural gas or chloromethane.
Dichloromethane is an important chemical raw material, is used in large quantity as a solvent in pharmaceutical enterprises, plays a vital role in synthesizing medicaments and medicament intermediates, and can be used for preparing antibiotics such as ampicillin, cefazolin sodium, and ampicillin. Because dichloromethane is extremely volatile at normal temperature and normal pressure, the dichloromethane is easy to be lost in the production process, thereby causing environmental pollution. The recovery of the dichloromethane waste solvent can effectively reduce environmental pollution, and can realize the recycling of resources to generate larger economic value, but the existing method is adopted to realize the most energy consumption and higher cost, the recovered dichloromethane is mostly lower in purity and higher in water content, and the residual water cannot be effectively removed, so that the application range of the recovered dichloromethane is limited.
Therefore, how to provide a method for recycling the waste solvent of the dichloromethane with low energy consumption, low water content and high purity is a technical problem to be solved by the person skilled in the art.
Disclosure of Invention
In view of the above, the invention provides a method for recycling the waste solvent of dichloromethane, which aims to solve the technical problems of higher water content, lower purity and high energy consumption in the recycling process of the dichloromethane obtained by the existing method.
In order to solve the technical problems, the invention adopts the following technical scheme:
the method for recycling the dichloromethane waste solvent comprises the following steps:
s1, taking a waste solvent containing dichloromethane, adding a saturated inorganic salt solution as an extractant to perform liquid-liquid extraction, obtaining a raffinate-phase dichloromethane crude product on the lower layer, and obtaining an extract-phase inorganic salt solution crude product on the upper layer;
s2, conveying the dichloromethane crude product to a first rectifying tower for normal pressure rectification and adsorption dehydration to obtain industrial-grade dichloromethane;
s3, pumping the crude inorganic salt solution to a second rectifying tower for normal pressure rectification to obtain an inorganic salt solution;
and S4, storing the inorganic salt solution obtained in the step S3 into an inorganic salt storage tank, and continuously supplementing inorganic salt into the inorganic salt storage tank to obtain a saturated inorganic salt solution for recycling.
Preferably, in the above method for recycling and reusing the dichloromethane waste solvent, the inorganic salt solution in step S1 includes sodium chloride, sodium sulfate, calcium chloride, magnesium chloride, potassium carbonate, and potassium fluoride.
Preferably, in the above method for recycling and reusing a dichloromethane waste solvent, the volume ratio of the waste solvent to the extractant in step S1 is 1: (0.2-2), further preferably 1:1.
preferably, in the above method for recycling and reusing the dichloromethane waste solvent, in the step S2, the bottom temperature of the first rectifying tower is 43-50 ℃, the top temperature of the first rectifying tower is 35-45 ℃, and the reflux ratio is 2-8.
Preferably, in the above method for recycling and reusing the dichloromethane waste solvent, before conveying the dichloromethane crude product to the first rectifying tower for normal pressure rectification in step S2, the method further includes: and drying and pre-treating the dichloromethane crude product.
Preferably, in the method for recycling the dichloromethane waste solvent, the drying agent used for the drying pretreatment comprises calcium hydride, magnesium silicate and molecular sieve.
Preferably, in the above method for recycling the dichloromethane waste solvent, the adsorbent used in the adsorption and dehydration in step S2 is activated carbon modified by microwave radiation, and the adsorption and dehydration effect of the activated carbon modified by microwave radiation on dichloromethane is particularly remarkable.
Preferably, in the above method for recycling and reusing the dichloromethane waste solvent, in the step S3, the bottom temperature of the second rectifying tower is 43-115 ℃, the top temperature is 40-98 ℃, and the reflux ratio is 5-10.
Preferably, in the above method for recycling the dichloromethane waste solvent, the crude inorganic salt solution in step S3 is used in an amount of 0.5-2m 3 Pumping the mixture to a second rectifying tower at a rate of/h, and obtaining an inorganic salt solution at a rate of 0.4-1.8m after the rectification is finished 3 Rate of discharge/h;
it is further preferred that the crude inorganic salt solution in step S3 is in the range of 1 to 1.5m 3 Pumping the mixture to a second rectifying tower at a rate of/h, and obtaining an inorganic salt solution at a rate of 0.8-1.2m after the rectification is finished 3 The rate of/h is discharged.
Preferably, in the above method for recycling the dichloromethane waste solvent, the mass fraction of the inorganic salt added in step S4 is 1 to 30%.
The invention provides a recycling method of dichloromethane waste solvent, which has the beneficial effects that compared with the prior art:
according to the method for recycling the dichloromethane waste solvent, disclosed by the invention, impurities in the waste solvent can be effectively removed through extraction separation, rectification and adsorption dehydration, the dichloromethane with the purity of 80-95% is purified to obtain the industrial grade dichloromethane with the purity of more than or equal to 99.9%, recycling of the dichloromethane waste solvent is realized, and the extractant can be effectively recycled, so that the energy consumption is reduced.
The method avoids the pollution of direct discharge of the waste solvent of the methylene dichloride to the environment, saves the production cost by recycling the methylene dichloride, and has the advantages of high yield, low energy consumption, good quality, recycling, simple and convenient production process, stable operation, suitability for industrial production and the like.
Detailed Description
The following description of the technical solutions in the embodiments of the present invention will be clear and complete, and it is obvious that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
The embodiment discloses a recycling method of dichloromethane waste solvent, which comprises the following steps:
s1, taking a waste solvent containing 90% of dichloromethane, adding saturated potassium carbonate solution with the same volume as the waste solvent into the waste solvent as an extracting agent, and performing liquid-liquid extraction, wherein the lower layer is a raffinate phase, and the raffinate phase is a dichloromethane crude product with the purity of 98%; 30% of potassium carbonate is separated out and collected and then recycled to the saturated potassium carbonate solution; the upper layer is crude product of extractive phase potassium carbonate solution, mainly potassium carbonate solution, methanol, ethanol and other impurities;
s2, drying and preprocessing a dichloromethane crude product through calcium hydride, conveying the dried dichloromethane crude product to a first rectifying tower for normal pressure rectification, wherein the bottom temperature of the first rectifying tower is 48 ℃, the top temperature of the first rectifying tower is 42 ℃, the reflux ratio is 5, performing adsorption dehydration through activated carbon modified by microwave radiation after rectification, canning after detection is qualified, and filling nitrogen for preservation, thus obtaining industrial-grade dichloromethane;
s3, mixing the crude potassium carbonate solution with 1m 3 Pumping the mixture to a second rectifying tower at the rate of/h for normal pressure rectification, wherein the temperature of the bottom of the second rectifying tower is 95 ℃, the temperature of the top of the tower is 88 ℃, the reflux ratio is 8, methanol, ethanol and other low-boiling impurities are removed from the top of the tower, and the temperature of the bottom of the tower is 1.2m 3 Discharging the potassium carbonate solution at a rate of/h;
and S4, mixing the potassium carbonate solution obtained in the step S3 with the potassium carbonate precipitated in the step S1, and continuously supplementing 5% of potassium carbonate to obtain a new saturated potassium carbonate solution for recycling.
Example 2
The embodiment discloses a recycling method of dichloromethane waste solvent, which comprises the following steps:
s1, taking a waste solvent containing 85% of dichloromethane, adding a saturated potassium fluoride solution with the volume which is 2 times that of the waste solvent into the waste solvent as an extracting agent, and performing liquid-liquid extraction, wherein the lower layer is a raffinate phase, and the raffinate phase is a dichloromethane crude product with the purity of 97%; after 25% of potassium fluoride is separated out and collected, the potassium fluoride is recycled to the saturated potassium fluoride solution; the upper layer is crude potassium fluoride solution of extract phase, mainly potassium fluoride solution, methanol, ethanol and other impurities;
s2, drying and pre-treating a dichloromethane crude product by magnesium silicate, conveying the dichloromethane crude product to a first rectifying tower for normal pressure rectification, wherein the temperature of the bottom of the first rectifying tower is 50 ℃, the temperature of the top of the tower is 45 ℃, the reflux ratio is 8, performing microwave radiation modified activated carbon adsorption dehydration after rectification, canning after detection is qualified, and filling nitrogen for preservation, thus obtaining industrial-grade dichloromethane;
s3, the crude potassium fluoride solution is processed by a process of 0.5m 3 Pumping the mixture to a second rectifying tower at the rate of/h for normal pressure rectification, wherein the temperature of the bottom of the second rectifying tower is 115 ℃, the temperature of the top of the tower is 98 ℃, the reflux ratio is 5, methanol, ethanol and other low-boiling impurities are removed from the top of the tower, and the bottom of the tower is 0.4m 3 Discharging the potassium fluoride solution at a rate of/h;
and S4, mixing the potassium fluoride solution obtained in the step S3 with the potassium fluoride separated out in the step S1, and continuously supplementing 8% of potassium fluoride to obtain a new saturated potassium fluoride solution for recycling.
Example 3
The embodiment discloses a recycling method of dichloromethane waste solvent, which comprises the following steps:
s1, taking a waste solvent containing 80% of dichloromethane, adding a saturated sodium chloride solution with the volume 1.5 times that of the waste solvent into the waste solvent as an extracting agent, and performing liquid-liquid extraction, wherein the lower layer is a raffinate phase, and the raffinate phase is a dichloromethane crude product with the purity of 97%; separating out and collecting 32% sodium chloride, and recycling to saturated sodium chloride solution; the upper layer is crude sodium chloride solution of extract phase, mainly sodium chloride solution, methanol, ethanol and other impurities;
s2, drying and preprocessing a dichloromethane crude product through a molecular sieve, conveying the dichloromethane crude product to a first rectifying tower for normal pressure rectification, wherein the temperature of the bottom of the first rectifying tower is 43 ℃, the temperature of the top of the tower is 38 ℃, the reflux ratio is 4, and after the rectification is finished, carrying out adsorption dehydration through activated carbon modified by microwave radiation, canning after the detection is qualified, and filling nitrogen for preservation, thus obtaining industrial-grade dichloromethane;
s3, the crude sodium chloride solution is treated by 2m 3 Pumping the mixture to a second rectifying tower at the rate of/h for normal pressure rectification, wherein the temperature of the bottom of the second rectifying tower is 85 ℃, the temperature of the top of the tower is 80 ℃, the reflux ratio is 10, methanol, ethanol and other low-boiling impurities are removed from the top of the tower, and the temperature of the bottom of the tower is 1.8m 3 Discharging sodium chloride solution at a rate of/h;
and S4, mixing the sodium chloride solution obtained in the step S3 with the sodium chloride precipitated in the step S1, and continuously supplementing 10% sodium chloride to obtain a new saturated sodium chloride solution for recycling.
Example 4
The embodiment discloses a recycling method of dichloromethane waste solvent, which comprises the following steps:
s1, taking a waste solvent containing 95% of dichloromethane, adding a saturated sodium sulfate solution with the volume of 0.2 times of that of the waste solvent into the waste solvent as an extracting agent, and performing liquid-liquid extraction, wherein the lower layer is a raffinate phase, and the raffinate phase is a dichloromethane crude product with the purity of 96%; separating out and collecting 28% sodium sulfate, and recycling to saturated sodium sulfate solution; the upper layer is crude extract phase sodium sulfate solution, mainly sodium sulfate solution, methanol, ethanol and other impurities;
s2, drying and pre-treating a dichloromethane crude product by calcium hydride, conveying the dichloromethane crude product to a first rectifying tower for normal pressure rectification, wherein the temperature of the bottom of the first rectifying tower is 43 ℃, the temperature of the top of the tower is 35 ℃, the reflux ratio is 2, adsorbing and dehydrating the dichloromethane crude product by active carbon modified by microwave radiation after the rectification is finished, canning after the detection is qualified, and filling nitrogen for preservation, thus obtaining industrial-grade dichloromethane;
s3, the crude sodium sulfate solution is processed by a process of 0.8m 3 Pumping the mixture to a second rectifying tower at the rate of/h for normal pressure rectification, wherein the temperature of the bottom of the second rectifying tower is 70 ℃, the temperature of the top of the tower is 63 ℃, the reflux ratio is 6, methanol, ethanol and other low-boiling impurities are removed from the top of the tower, and the temperature of the bottom of the tower is 1.0m 3 Discharging sodium sulfate solution at a rate of/h;
and S4, mixing the sodium sulfate solution obtained in the step S3 with the sodium sulfate precipitated in the step S1, and continuously supplementing 7% sodium sulfate to obtain a new saturated sodium sulfate solution for recycling.
Example 5
The embodiment discloses a recycling method of dichloromethane waste solvent, which comprises the following steps:
s1, taking a waste solvent containing 90% of dichloromethane, adding a saturated calcium chloride solution with the volume of 0.6 times of that of the waste solvent into the waste solvent as an extracting agent, and performing liquid-liquid extraction, wherein the lower layer is a raffinate phase, and the raffinate phase is a dichloromethane crude product with the purity of 96%; separating out and collecting 20% calcium chloride, and recycling to saturated calcium chloride solution; the upper layer is crude calcium chloride solution of extract phase, mainly calcium chloride solution, methanol, ethanol and other impurities;
s2, drying and preprocessing a dichloromethane crude product through calcium hydride, conveying the dried dichloromethane crude product to a first rectifying tower for normal pressure rectification, wherein the temperature of the bottom of the first rectifying tower is 46 ℃, the temperature of the top of the tower is 40 ℃, the reflux ratio is 3, and after rectification, carrying out adsorption dehydration through activated carbon modified by microwave radiation, canning after detection is qualified, and filling nitrogen for preservation, thus obtaining industrial-grade dichloromethane;
s3, crude calcium chloride solution is processed by a process of 1.5m 3 Pumping the mixture to a second rectifying tower at the rate of/h for normal pressure rectification, wherein the temperature of the bottom of the second rectifying tower is 110 ℃, the temperature of the top of the tower is 98 ℃, the reflux ratio is 8, methanol, ethanol and other low-boiling impurities are removed from the top of the tower, and the temperature of the bottom of the tower is 1.3m 3 Discharging the calcium chloride solution at a rate of/h;
and S4, mixing the calcium chloride solution obtained in the step S3 with the calcium chloride precipitated in the step S1, and continuously supplementing 12% of calcium chloride to obtain a new saturated calcium chloride solution for recycling.
The performance of the relevant index was measured on the methylene dichloride recovered by the method of examples 1 to 5, and the measurement items and measurement results are specifically shown in table 1.
TABLE 1 quality detection results of dichloromethane recovered in examples 1-5
Comparative example 1
The comparative example discloses a recycling method of dichloromethane waste solvent, which comprises the following steps:
s1, taking a waste solvent containing 90% of dichloromethane, adding saturated potassium carbonate solution with the same volume as the waste solvent into the waste solvent as an extracting agent, and performing liquid-liquid extraction, wherein the lower layer is a raffinate phase, and the raffinate phase is a dichloromethane crude product with the purity of 98%; 30% of potassium carbonate is separated out and collected and then recycled to the saturated potassium carbonate solution; the upper layer is crude product of extractive phase potassium carbonate solution, mainly potassium carbonate solution, methanol, ethanol and other impurities;
s2, conveying the dichloromethane crude product to a first rectifying tower for normal pressure rectification, wherein the bottom temperature of the first rectifying tower is 48 ℃, the top temperature of the first rectifying tower is 42 ℃, the reflux ratio is 5, and after rectification, canning and filling nitrogen for preservation, thus obtaining a dichloromethane product;
s3, mixing the crude potassium carbonate solution with 1m 3 Pumping the mixture to a second rectifying tower at the rate of/h for normal pressure rectification, wherein the temperature of the bottom of the second rectifying tower is 95 ℃, the temperature of the top of the tower is 88 ℃, the reflux ratio is 8, methanol, ethanol and other low-boiling impurities are removed from the top of the tower, and the temperature of the bottom of the tower is 1.2m 3 Discharging the potassium carbonate solution at a rate of/h;
and S4, mixing the potassium carbonate solution obtained in the step S3 with the potassium carbonate precipitated in the step S1, and continuously supplementing 5% of potassium carbonate to obtain a new saturated potassium carbonate solution for recycling.
Comparative example 2
The comparative example discloses a recycling method of dichloromethane waste solvent, which comprises the following steps:
s1, taking a waste solvent containing 90% of dichloromethane, adding saturated potassium carbonate solution with the same volume as the waste solvent into the waste solvent as an extracting agent, and performing liquid-liquid extraction, wherein the lower layer is a raffinate phase, and the raffinate phase is a dichloromethane crude product with the purity of 98%; 30% of potassium carbonate is separated out and collected and then recycled to the saturated potassium carbonate solution; the upper layer is crude product of extractive phase potassium carbonate solution, mainly potassium carbonate solution, methanol, ethanol and other impurities;
s2, drying and preprocessing the dichloromethane crude product through calcium hydride, conveying the dried dichloromethane crude product to a first rectifying tower for normal pressure rectification, wherein the temperature of the bottom of the first rectifying tower is 48 ℃, the temperature of the top of the tower is 42 ℃, the reflux ratio is 5, and after rectification, canning and filling nitrogen for preservation, thus obtaining a dichloromethane product;
s3, mixing the crude potassium carbonate solution with 1m 3 Pumping the mixture to a second rectifying tower at the rate of/h for normal pressure rectification, wherein the temperature of the bottom of the second rectifying tower is 95 ℃, the temperature of the top of the tower is 88 ℃, the reflux ratio is 8, methanol, ethanol and other low-boiling impurities are removed from the top of the tower, and the temperature of the bottom of the tower is 1.2m 3 Discharging the potassium carbonate solution at a rate of/h;
and S4, mixing the potassium carbonate solution obtained in the step S3 with the potassium carbonate precipitated in the step S1, and continuously supplementing 5% of potassium carbonate to obtain a new saturated potassium carbonate solution for recycling.
Comparative example 3
The comparative example discloses a recycling method of dichloromethane waste solvent, which comprises the following steps:
s1, taking a waste solvent containing 90% of dichloromethane, adding saturated potassium carbonate solution with the same volume as the waste solvent into the waste solvent as an extracting agent, and performing liquid-liquid extraction, wherein the lower layer is a raffinate phase, and the raffinate phase is a dichloromethane crude product with the purity of 98%; 30% of potassium carbonate is separated out and collected and then recycled to the saturated potassium carbonate solution; the upper layer is crude product of extractive phase potassium carbonate solution, mainly potassium carbonate solution, methanol, ethanol and other impurities;
s2, drying and pre-treating a dichloromethane crude product by calcium hydride, conveying the dichloromethane crude product to a first rectifying tower for normal pressure rectification, wherein the temperature of the bottom of the first rectifying tower is 48 ℃, the temperature of the top of the first rectifying tower is 42 ℃, the reflux ratio is 5, performing ultrasonic modified activated carbon adsorption dehydration after rectification, canning after detection is qualified, and filling nitrogen for preservation, thus obtaining industrial-grade dichloromethane;
s3, mixing the crude potassium carbonate solution with 1m 3 Pumping the mixture to a second rectifying tower at the rate of/h for normal pressure rectification, wherein the bottom temperature of the second rectifying tower is higher than that of the first rectifying towerThe temperature of the tower top is 95 ℃, the temperature of the tower top is 88 ℃, the reflux ratio is 8, methanol, ethanol and other low boiling impurities are removed from the tower top, and the tower bottom is 1.2m 3 Discharging the potassium carbonate solution at a rate of/h;
and S4, mixing the potassium carbonate solution obtained in the step S3 with the potassium carbonate precipitated in the step S1, and continuously supplementing 5% of potassium carbonate to obtain a new saturated potassium carbonate solution for recycling.
Performance detection of relevant indexes is carried out on the dichloromethane recovered by the method of comparative examples 1-3, and detection items and detection results are specifically shown in table 2.
TABLE 2 quality detection results of dichloromethane recovered in comparative examples 1 to 3
| Name of the name | Comparative example 1 | Comparative example 2 | Comparative example 3 |
| Purity (wt%) | 99.90 | 99.91 | 99.91 |
| Chromaticity (Hazen) | 6 | 6 | 5 |
| Moisture (wt%) | 0.028 | 0.015 | 0.014 |
| Mass fraction/%of acid (in HCL) | 0.0003 | 0.0003 | 0.0003 |
| Mass fraction/%of evaporation residue | 0.0005 | 0.0005 | 0.0005 |
As can be seen from Table 2, in the process of recovering and treating the dichloromethane, the pretreatment drying and the subsequent adsorption drying have important influence on various indexes of the dichloromethane, and in the adsorption drying process, not all the modified activated carbon can enable the dichloromethane to reach the industrial grade standard, and only when the activated carbon is the activated carbon modified by microwave treatment, various performances of the dichloromethane are optimal.
Comparative example 4
Comparative example 4 is substantially the same as example 1, except that: the ratio of the waste solvent to the extractant saturated inorganic salt solution in the step S1 is different.
The volume ratio of the waste solvent to the extractant is used as a variable for carrying out the test, the influence of the waste solvent to the quality detection result of the methylene dichloride is researched, and specifically, when the volume ratio of the waste solvent to the extractant potassium carbonate solution is respectively 1:0.1, 1:0.2, 1:1. 1: 2. 1: at 3, the quality test results of methylene chloride are shown in Table 3.
TABLE 3 influence of the volume ratio of spent solvent to extractant on the quality of methylene chloride
From the above table, when the addition amount of the extractant is too small, the purity and the water content of the dichloromethane are greatly affected, and when the volume ratio of the waste solvent to the extractant reaches 1:3, each item index of the dichloromethane does not change greatly any more, and even the quality of the dichloromethane can be influenced, so that when the volume ratio of the waste solvent to the extractant is 1: (0.2-2) is the optimal proportion.
In conclusion, the recycling method of the invention not only obtains industrial grade methylene dichloride, but also has the advantages of easy obtaining of the related extractant, low cost, cyclic utilization, effective reduction of energy consumption, remarkable technical effect and suitability for large-scale industrialized production.
In the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other. For the solution disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple, and the relevant points refer to the description of the method section.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. The method for recycling the dichloromethane waste solvent is characterized by comprising the following steps of:
s1, taking a waste solvent containing dichloromethane, adding a saturated inorganic salt solution as an extractant to perform liquid-liquid extraction, obtaining a raffinate-phase dichloromethane crude product on the lower layer, and obtaining an extract-phase inorganic salt solution crude product on the upper layer;
s2, conveying the dichloromethane crude product to a first rectifying tower for normal pressure rectification and adsorption dehydration to obtain industrial-grade dichloromethane;
s3, pumping the crude inorganic salt solution to a second rectifying tower for normal pressure rectification to obtain an inorganic salt solution;
and S4, storing the inorganic salt solution obtained in the step S3 into an inorganic salt storage tank, and continuously supplementing inorganic salt into the inorganic salt storage tank to obtain a saturated inorganic salt solution for recycling.
2. The method for recycling and reusing waste methylene chloride solvent according to claim 1, wherein the inorganic salt solution in step S1 comprises sodium chloride, sodium sulfate, calcium chloride, magnesium chloride, potassium carbonate, potassium fluoride.
3. The method for recycling and reusing the waste solvent of methylene chloride according to claim 1, wherein the volume ratio of the waste solvent to the extractant in the step S1 is 1: (0.2-2).
4. The method for recycling and reusing waste methylene chloride solvent according to claim 1, wherein the bottom temperature of the first rectifying tower in the step S2 is 43-50 ℃, the top temperature is 35-45 ℃ and the reflux ratio is 2-8.
5. The method for recycling and reusing the waste dichloromethane solvent according to claim 1, wherein before the crude dichloromethane product is sent to the first rectifying tower for normal pressure rectification in the step S2, the method further comprises: and drying and pre-treating the dichloromethane crude product.
6. The method for recycling dichloromethane waste solvent according to claim 5, wherein the drying agent used in the drying pretreatment comprises calcium hydride, magnesium silicate and molecular sieve.
7. The method for recycling dichloromethane waste solvent according to any one of claims 1 to 6, wherein the adsorbent used in the adsorption dehydration in the step S2 is activated carbon modified by microwave radiation.
8. The method for recycling and reusing waste solvent of methylene chloride according to claim 1, wherein the bottom temperature of the second rectifying tower in the step S3 is 43-115 ℃, the top temperature is 40-98 ℃ and the reflux ratio is 5-10.
9. The method for recycling and reusing waste solvent of methylene chloride according to claim 1, wherein the crude inorganic salt solution in step S3 is prepared in a concentration of 0.5-2m 3 Pumping the mixture to a second rectifying tower at a rate of/h, and obtaining an inorganic salt solution at a rate of 0.4-1.8m after the rectification is finished 3 The rate of/h is discharged.
10. The method for recycling and reusing a waste solvent of methylene chloride according to claim 1, wherein the mass fraction of the inorganic salt added in the step S4 is 1 to 30%.
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