CN114394881B - Refining method of high-yield high-purity trichloromethane - Google Patents
Refining method of high-yield high-purity trichloromethane Download PDFInfo
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Abstract
The invention provides a refining method of high-yield and high-purity trichloromethane. The method comprises the following steps: 1) Pre-treating a trichloromethane raw material: adding alkali and absolute ethyl alcohol into a trichloromethane raw material pretreatment tank, standing, detecting acidity and phosgene after standing is finished, filtering after the acidity and the phosgene are qualified, and transferring filtrate into a rectification procedure; 2) And (3) normal pressure rectification: putting the pretreated trichloromethane into a high-efficiency rectifying tower, adding silver nitrate, and performing normal-pressure rectification treatment to obtain refined trichloromethane; 3) Adding absolute ethyl alcohol into the refined trichloromethane obtained in the step 2) as a stabilizer. The method for refining high-yield and high-purity trichloromethane has the advantages of high trichloromethane yield, short production period and high working efficiency, and the product yield is increased from 50-60% to more than 85%.
Description
Technical Field
The invention relates to a refining method of high-yield high-purity trichloromethane, belonging to the field of chemical industry.
Background
Chloroform, also known as chloroform, is a heavy liquid which is a colorless transparent liquid at normal temperature, is very volatile, and has a pungent and sweet taste and a special aromatic smell. Chloroform is an important chemical raw material and is widely applied to industries such as viscose fiber, pesticide, mineral dressing agent and the like. Chloroform is miscible with ethanol, benzene, diethyl ether, petroleum ether, carbon tetrachloride, carbon disulfide, oils, and the like. The relative density of the trichloromethane is 1.4840, the freezing point is-63.5 ℃, and the boiling point is 61-62 ℃. Chloroform is an important organic synthetic raw material, is mainly used for producing freon (F-21, F-22 and F-23), dye and medicine, and is commonly used as an anesthetic in medicine. Can be used as solvent and extractant for antibiotics, perfume, oil, resin, and rubber. The trichloromethane and the carbon tetrachloride are mixed to prepare the non-freezing fireproof liquid. It is also used for propellant of aerosol, fumigant of grain and standard liquid for calibrating temperature. Trichloromethane is sensitive to light, and reacts with oxygen in the air when exposed to light, and is gradually decomposed to generate highly toxic phosgene (carbonyl chloride) and hydrogen chloride, which are easily decomposed at a higher temperature to generate chlorine-containing products. An important indicator in the production of pharmaceutical grade trichloromethane is chlorine containing decomposition products. One of the impurities in the British pharmacopoeia is that the relevant substances (including carbon tetrachloride, methylene chloride, total impurities, etc.) must be in the acceptable range. At present, the purification method of trichloromethane generally comprises a rectification method and an adsorption method. The rectification method is to separate impurities by utilizing different boiling points of substances; the adsorption method is to adsorb and separate impurities in the trichloromethane by using an adsorbent.
Patent 201410693063.X provides a preparation method of chromatographic grade trichloromethane, which adopts fruit shell activated carbon DV11 as a filler to carry out column chromatography adsorption treatment on industrial grade trichloromethane to prepare the chromatographic grade trichloromethane. Patent 202011215749.X provides a chloroform rectifying device and a rectifying method thereof, which are mainly suitable for large-scale production.
Disclosure of Invention
The invention aims to provide a refining method of trichloromethane with high yield and high purity, which comprises the steps of adding mixed alkali to remove chlorine-containing decomposition products such as phosgene and hydrogen chloride in trichloromethane and volatile impurities such as dichloromethane and carbon tetrachloride, and then removing heavy metals brought in the trichloromethane raw material by combining a high-efficiency rectification mode. The production process is simple, the period is short, the yield is improved to more than 85%, the production waste liquid is greatly reduced, and the productivity is improved. The industrial grade raw material is subjected to rectification pretreatment, rectification process control, addition of a stabilizer after rectification and light-shielding treatment in the whole process to prepare the high-purity trichloromethane which can simultaneously meet the requirements of Chinese pharmacopoeia, british pharmacopoeia and ACS grades.
The method for refining the trichloromethane provided by the invention comprises the following steps:
1) Pretreatment of a trichloromethane raw material: adding alkali and absolute ethyl alcohol into a trichloromethane raw material pretreatment tank, standing, detecting acidity and phosgene after standing is finished, filtering after the acidity and the phosgene are qualified, and transferring filtrate into a rectification procedure;
2) And (3) normal pressure rectification: and (3) putting the pretreated trichloromethane into a high-efficiency rectifying tower, adding silver nitrate, and carrying out normal-pressure rectifying treatment to obtain the refined trichloromethane.
In the step 1) of the method, the alkali is a mixed alkali, and specifically, the alkali may be a mixture of anhydrous sodium carbonate/anhydrous potassium carbonate and sodium bicarbonate in a mass ratio of 1.
The alkali is added in an amount of 0.1-0.5% by mass of the chloroform raw material.
The absolute ethyl alcohol is added in an amount of 0.5-1.5% of the volume of the chloroform raw material.
The standing time can be 12-48h, preferably 18-36h, and specifically can be 24h.
And blowing for 2-3 times by using a nitrogen pipeline during the standing period, wherein each time is 5-10 minutes.
The filtration is through the PTFE filtration membrane filtration of 0.5-2um, can specifically filter through the PTFE filtration membrane of 1 um.
In step 2), the ratio of the column diameter of the packed column to the packing diameter of the packed column in the high-efficiency rectification column is 50 to 300, preferably 100 to 250, and specifically may be 150; preferably, a glass spring filler is used.
The silver nitrate is added in the dark.
The addition amount of the silver nitrate is 0.008% -0.017% of the mass of the pre-treated trichloromethane.
After adding silver nitrate, starting heating reflux, wherein the heating reflux is 30-60min, the mass ratio of the distillate before the connection is 2-15%, transferring the product after the qualified middle control, controlling the tower top temperature of the rectifying tower to be 61-62 ℃, the tower middle temperature to be 57-58 ℃ and the reflux ratio to be 5-10.
Preferably, the mass ratio of the front cut fraction is 3-10%.
The above method may further comprise: 3) And (3) blending a stabilizer, namely adding absolute ethyl alcohol into the refined trichloromethane obtained in the step 2) to serve as the stabilizer.
In the step 3), the absolute ethyl alcohol is added to account for 0.5-1% of the volume of the obtained refined trichloromethane.
The refining method of high-yield and high-purity trichloromethane provided by the invention can effectively remove acidity, chlorine-containing decomposition products such as phosgene, hydrogen chloride and the like, and volatile impurities such as dichloromethane, carbon tetrachloride and the like in trichloromethane, the content of the product is improved to be more than 99.9%, the total amount of related organic volatile impurities is less than 0.05%, and the requirements of Chinese pharmacopoeia, british pharmacopoeia and ACS grades can be met at the same time. Storage tanks and packaging barrels for industrial production and storage of trichloromethane are stainless steel or galvanized barrels, trace metal elements such as chromium, lead, nickel, zinc and the like can be introduced in the production and storage processes, and related metal elements can be effectively reduced or removed after rectification and separation by an efficient separation and rectification tower.
The method for refining high-yield and high-purity trichloromethane has the advantages of high trichloromethane yield, short production period and high working efficiency, and the product yield is increased from 50-60% to more than 85%.
Detailed Description
The preferred embodiments of the present invention are described below, and it should be understood that the preferred embodiments described herein are only for illustrating and explaining the present invention and are not to be construed as limiting the present invention.
Example 1:
a refining method of high-yield high-purity trichloromethane comprises the following steps:
1. pretreatment: the method comprises the steps of adding mixed alkali (anhydrous sodium carbonate: sodium bicarbonate = 1) with the mass ratio of about 0.5% and absolute ethyl alcohol with the volume ratio of 1% into 300kg of chloroform raw material, standing for 24h, carrying out air blowing mixing for 2 times by using nitrogen, wherein the time is 10 minutes each time to ensure that the reaction is complete, detecting acidity and carbonyl chloride after the standing is finished, filtering the qualified mixture by using a 1um PTFE filter membrane, and transferring the qualified mixture to a rectification procedure.
2. And (3) normal pressure rectification: adding about 60kg of pretreated trichloromethane into a 50L efficient rectifying tower, wherein the ratio of the diameter of the tower to the diameter of a filler is 150;
3. and (3) blending a stabilizer: and after the rectification is finished, 51kg of finished product is obtained, the finished product trichloromethane is analyzed, the content of absolute ethyl alcohol is detected to be 0.5% (V/V), the absolute ethyl alcohol with the volume ratio of 0.5% is added for stabilizer adjustment, the standard of high-purity trichloromethane is met, and the stability of the product is ensured.
4. The product yield is as follows: 60kg of material is fed into the rectifying tower, 51kg of finished product is obtained, and the yield is 85%.
Example 2:
a refining method of high-yield and high-purity trichloromethane comprises the following steps:
1. pretreatment: adding mixed alkali (anhydrous sodium carbonate: sodium bicarbonate = 1) with the mass ratio of about 0.1% and absolute ethyl alcohol with the volume ratio of 1% into 300kg of chloroform raw material, standing for 24h, blowing and mixing for 3 times by using nitrogen, wherein the time is 10 minutes each time to ensure that the reaction is complete, detecting acidity and carbonyl chloride after the standing is finished, filtering by using a 1um PTFE filter membrane after the acidity and the carbonyl chloride are qualified, and transferring to a rectification procedure.
2. And (3) normal pressure rectification: adding about 59kg of pretreated trichloromethane into a 50L efficient rectifying tower, wherein the ratio of the diameter of the tower to the diameter of a filler is 150. The temperature of the top of the high-efficiency rectifying tower is 61 ℃, and the temperature of the middle part of the high-efficiency rectifying tower is 57 ℃;
3. and (3) blending a stabilizer: and after the rectification is finished, 53kg of finished product is obtained, the finished product trichloromethane is analyzed, the content of absolute ethyl alcohol is detected to be 0.5 percent (V/V), the absolute ethyl alcohol with the volume ratio of 0.5 percent is added for stabilizer adjustment, the standard of high-purity trichloromethane is met, and the stability of the product is ensured.
4. The product yield is as follows: 59kg of material is fed into the rectifying tower, 53kg of finished product is obtained, and the yield is 89.8%.
Example 3:
a refining method of high-yield high-purity trichloromethane comprises the following steps:
1. pretreatment: the method comprises the steps of adding mixed alkali (anhydrous sodium carbonate: sodium bicarbonate = 1) with the mass ratio of about 0.1% and absolute ethyl alcohol with the volume ratio of 1% into 300kg of chloroform raw material, standing for 24h, blowing and mixing for 2 times by using nitrogen, wherein the time is 10 minutes each time to enable the mixed alkali to react completely, detecting acidity and carbonyl chloride after standing is finished, filtering by using a PTFE filter membrane with the diameter of 1um after the mixed alkali and the carbonyl chloride are qualified, and transferring to a rectification procedure.
2. And (3) normal pressure rectification: taking about 60kg of pretreated trichloromethane, adding the trichloromethane into a 50L efficient rectifying tower, wherein the ratio of the tower diameter to the packing is 150. The temperature of the top of the high-efficiency rectifying tower is 61 ℃, and the temperature of the middle part of the high-efficiency rectifying tower is 58 ℃;
3. and (3) blending a stabilizer: and after the rectification is finished, 55kg of finished product is obtained, the finished product trichloromethane is analyzed, the content of absolute ethyl alcohol is detected to be 0.5 percent (V/V), and absolute ethyl alcohol with the volume ratio of 0.5 percent is added for stabilizer adjustment, so that the standard of high-purity trichloromethane is met, and the stability of the product is ensured.
4. The product yield is as follows: 60kg of feed is fed into the rectifying tower, 55kg of finished product is fed into the rectifying tower, and the yield is 91.7 percent
Example 4:
a refining method of high-yield and high-purity trichloromethane comprises the following steps:
1. pretreatment: the method comprises the steps of adding mixed alkali (anhydrous sodium carbonate: sodium bicarbonate = 1) with the mass ratio of about 0.5% and absolute ethyl alcohol with the volume ratio of 1% into 300kg of chloroform raw material, standing for 24h, carrying out air blowing mixing for 2 times by using nitrogen, wherein the time is 10 minutes each time to ensure that the reaction is complete, detecting acidity and carbonyl chloride after the standing is finished, filtering the qualified mixture by using a 1um PTFE filter membrane, and transferring the qualified mixture to a rectification procedure.
2. And (3) normal pressure rectification: and (2) adding about 64kg of pretreated trichloromethane into a 50L efficient rectifying tower, wherein the ratio of the diameter of the tower to the diameter of a filler is 150. The temperature of the top of the high-efficiency rectifying tower is 61 ℃, and the temperature of the middle part of the high-efficiency rectifying tower is 57 ℃;
3. and (3) blending a stabilizer: and after the rectification is finished, 55kg of finished product is obtained, the finished product trichloromethane is analyzed, the content of absolute ethyl alcohol is detected to be 0.5 percent (V/V), and absolute ethyl alcohol with the volume ratio of 0.5 percent is added for stabilizer adjustment, so that the high-purity trichloromethane standard is met, and the stability of the product is ensured.
4. The product yield is as follows: 64kg of feed is fed into the rectifying tower, 55kg of finished product is obtained, and the yield is 85.9%
Comparative example 1:
1. pretreatment: adding 1% absolute ethyl alcohol by volume ratio into 300kg of chloroform raw material, and uniformly mixing;
2. and (3) normal pressure rectification: and (2) adding about 60kg of pretreated trichloromethane into a 50L efficient rectifying tower, wherein the ratio of the diameter of the tower to the diameter of a packing is 150. The temperature of the top of the high-efficiency rectifying tower is 61 ℃, the temperature of the middle part of the high-efficiency rectifying tower is 57 ℃, and the actual plate number of the high-efficiency rectifying tower is 66;
3. and (3) blending a stabilizer: and after the rectification is finished, 33kg of finished product trichloromethane is obtained, the finished product trichloromethane is analyzed, the content of absolute ethyl alcohol is detected to be 0.5 percent (V/V), and absolute ethyl alcohol with the volume ratio of 0.5 percent is added to adjust the stabilizer, so that the standard of high-purity trichloromethane is met, and the stability of the product is ensured.
4. The product yield is as follows: 60kg of feed is fed into the rectifying tower, 33kg of finished product is obtained, and the yield is 55%.
Comparative example 2:
1. pretreatment: adding 0.5 percent of mixed alkali and 1 percent of absolute ethyl alcohol by volume ratio into 300kg of chloroform raw material, standing for 24h, and blowing and mixing for 2 times by nitrogen, wherein each time lasts for 10 minutes, so that the chloroform raw material is reacted completely;
2. and (3) normal pressure rectification: and (2) adding about 60kg of pretreated trichloromethane into a 50L efficient rectifying tower, wherein the ratio of the diameter of the tower to the diameter of a packing is 150. The temperature of the top of the high-efficiency rectifying tower is 61 ℃, the temperature of the middle part of the high-efficiency rectifying tower is 57 ℃, and the actual number of plates of the high-efficiency rectifying tower is 66;
3. and (3) stabilizer blending: and after the rectification is finished, 35kg of finished product is obtained, the finished product trichloromethane is analyzed, the content of absolute ethyl alcohol is detected to be 0.5 percent (V/V), and absolute ethyl alcohol with the volume ratio of 0.5 percent is added for stabilizer adjustment, so that the high-purity trichloromethane standard is met, and the stability of the product is ensured.
4. The product yield is as follows: 60kg of feed is fed into the rectifying tower, 35kg of finished product is fed into the rectifying tower, and the yield is 58.3 percent.
Comparative example 3:
1. pretreatment: adding anhydrous sodium carbonate with the mass ratio of about 0.5% and anhydrous ethanol with the volume ratio of 1% into 300kg of chloroform raw material, standing for 24h, blowing and mixing for 2 times by using nitrogen, wherein the time is 10 minutes each time to ensure that the reaction is complete, detecting acidity and phosgene after standing is finished, filtering the qualified chloroform raw material by using a 1um PTFE filter membrane, and transferring the obtained product to a rectification procedure.
2. And (3) normal pressure rectification: adding about 60kg of pretreated trichloromethane into a 50L efficient rectifying tower, adding 10g of silver nitrate under the condition of keeping out of the sun, heating and refluxing for 30 min, then adding 13L of front fraction, controlling acidity, carbonyl chloride and chlorine-containing decomposition products in the middle, and starting to add a finished product after the products are qualified, wherein the reflux ratio is controlled to be 5;
3. and (3) stabilizer blending: and after the rectification is finished, 32kg of finished product is obtained, the finished product trichloromethane is analyzed, the content of absolute ethyl alcohol is detected to be 0.5 percent (V/V), and absolute ethyl alcohol with the volume ratio of 0.5 percent is added for stabilizing agent adjustment, so that the standard of high-purity trichloromethane is met, and the stability of the product is ensured.
4. The product yield is as follows: 60kg of feed is fed into the rectifying tower, 32kg of finished product is obtained, and the yield is 53.3%.
Comparative example 4:
1. pretreatment: adding 0.5 percent of sodium bicarbonate and 1 percent of absolute ethyl alcohol by volume ratio into 300kg of chloroform raw material, standing for 24h, blowing and mixing for 2 times by using nitrogen, wherein each time is 10 minutes, so that the reaction is complete, detecting acidity and phosgene after standing is finished, filtering by using a 1um PTFE filter membrane after the acidity and phosgene are qualified, and transferring to a rectification procedure.
2. And (3) normal pressure rectification: adding about 60kg of pretreated trichloromethane into a 50L efficient rectifying tower, adding 10g of silver nitrate under the condition of keeping out of the sun, heating and refluxing for 30 min, then adding 12L of front fraction, controlling acidity, carbonyl chloride and chlorine-containing decomposition products in the middle, and starting to add a finished product after the products are qualified, wherein the reflux ratio is controlled to be 5;
3. and (3) stabilizer blending: 33kg of finished product is obtained after the rectification is finished, the finished product trichloromethane is analyzed, the content of absolute ethyl alcohol is detected to be 0.5 percent (V/V), the absolute ethyl alcohol with the volume ratio of 0.5 percent is added for stabilizer adjustment, the standard of high-purity trichloromethane is met, and the stability of the product is ensured.
4. The product yield is as follows: 60kg of feed is fed into the rectifying tower, 33kg of finished product is obtained, and the yield is 55%.
And (4) checking the result:
note that (1) Taking 20ml of water, adding 4 drops of phenolphthalein indicator solution, dropwise adding sodium hydroxide titration solution (0.01 mol/L), and shaking while dropping until the solution is light red; dividing into 2 equal parts, placing into 50ml color comparison tubes with stoppers, adding 20ml of the product into tube A, shaking, mixing, adding sodium hydroxide titration solution (0.01 mol/L), shaking while dripping until the reproduced pink color is consistent with that of tube B, and maintaining for 15 min without fading, and consuming sodium hydroxide titration solution (0.01 mol/L) not more than 0.20ml
Note that (2) Taking 4ml of sulfuric acid solution under the easily carbonized substance, carefully adding 10ml of water, shaking up, and clarifying; only a minimal odor of ethanol, ether or esters must occur upon heating. Diluting with 10ml water, and clarifying; when 3 drops of silver nitrate test solution are added, no turbidity can occur within 1 minute.
From the above results of the tests of examples 1, 2, 3 and 4 and comparative examples 1 to 4, it can be seen that high-purity trichloromethane can be obtained in high yield by this purification method.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (4)
1. A method for refining trichloromethane is characterized by comprising the following steps:
1) Pre-treating a trichloromethane raw material: adding alkali and absolute ethyl alcohol into a trichloromethane raw material pretreatment tank, standing, detecting acidity and phosgene after standing is finished, filtering after the acidity and the phosgene are qualified, and transferring filtrate into a rectification procedure;
2) And (3) normal pressure rectification: putting the pretreated trichloromethane into a high-efficiency rectifying tower, adding silver nitrate, starting heating reflux, heating reflux for 30-60min, controlling the mass ratio of the fractions before connection to be 2-15%, transferring the qualified products to a finished product after central control, controlling the tower top temperature of the rectifying tower to be 61-62 ℃, the tower middle temperature to be 57-58 ℃ and the reflux ratio to be 5-10, and obtaining the refined trichloromethane;
in the step 1), the alkali is a mixture of anhydrous sodium carbonate and sodium bicarbonate according to a mass ratio of 1; absolute ethyl alcohol is added in an amount which is 0.5 to 1.5 percent of the volume of the chloroform raw material;
in the step 2), the silver nitrate is added under the condition of keeping out of the sun, and the addition amount of the silver nitrate is 0.008% -0.017% of the mass of the pre-treated trichloromethane.
2. The method of claim 1, wherein: the standing time is 12-48h; and blowing for 2-3 times by using a nitrogen pipeline during the standing period, wherein each time is 5-10 minutes.
3. The method of claim 1, wherein: the method further comprises the following steps: 3) And (3) blending a stabilizer, namely adding absolute ethyl alcohol into the refined trichloromethane obtained in the step 2) to serve as the stabilizer.
4. The method of claim 3, wherein: in the step 3), the added absolute ethyl alcohol accounts for 0.5-1% of the volume of the obtained refined trichloromethane.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4922044A (en) * | 1988-11-04 | 1990-05-01 | Allied-Signal Inc. | Purification of chloroform |
| CN104402666A (en) * | 2014-10-20 | 2015-03-11 | 太仓沪试试剂有限公司 | Purification method for MOS-grade chloroform |
| CN111333484A (en) * | 2020-04-29 | 2020-06-26 | 高永宝 | Ultrahigh-purity methane chloride production system and process |
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- 2022-01-26 CN CN202210096226.0A patent/CN114394881B/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4922044A (en) * | 1988-11-04 | 1990-05-01 | Allied-Signal Inc. | Purification of chloroform |
| CN104402666A (en) * | 2014-10-20 | 2015-03-11 | 太仓沪试试剂有限公司 | Purification method for MOS-grade chloroform |
| CN111333484A (en) * | 2020-04-29 | 2020-06-26 | 高永宝 | Ultrahigh-purity methane chloride production system and process |
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