CN115304456A - Separation process for separating metacresol from urea - Google Patents
Separation process for separating metacresol from urea Download PDFInfo
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- C07C37/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom of a six-membered aromatic ring
- C07C37/68—Purification; separation; Use of additives, e.g. for stabilisation
- C07C37/685—Processes comprising at least two steps in series
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- C—CHEMISTRY; METALLURGY
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- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C37/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom of a six-membered aromatic ring
- C07C37/68—Purification; separation; Use of additives, e.g. for stabilisation
- C07C37/70—Purification; separation; Use of additives, e.g. for stabilisation by physical treatment
- C07C37/74—Purification; separation; Use of additives, e.g. for stabilisation by physical treatment by distillation
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C37/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom of a six-membered aromatic ring
- C07C37/68—Purification; separation; Use of additives, e.g. for stabilisation
- C07C37/86—Purification; separation; Use of additives, e.g. for stabilisation by treatment giving rise to a chemical modification
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Abstract
The invention relates to the technical field of chemical industry, in particular to a separation process for separating metacresol from urea; the separation process comprises the following steps: 1) Separating out o-cresol from the mixed cresol by adopting a distillation method; 2) Adding an oxalic acid complexing agent and a solvent into the mixed cresol obtained in the step 1), heating to boil, reacting for a period of time, cooling to crystallize, and then carrying out solid-liquid separation to obtain a filtrate serving as a mixed cresol raw material for later use; 3) Heating the mixed cresol raw material obtained in the step 2) and urea at the temperature of 70-95 ℃ for 40-80 min; after the reaction is finished, cooling to a certain temperature, dropping a mixed solvent of toluene, n-hexane and cyclohexane at a constant speed, cooling to-15 to-10 ℃ at a constant speed, and carrying out crystallization reaction for 120-150min; adding water into the obtained solid, heating and dissolving to obtain an oil layer to obtain m-cresol. The method adopts a mixed solvent system of toluene, normal hexane and cyclohexane to obtain m-cresol with higher yield and better purity when the urea complexation method is used for separating the m-cresol.
Description
Technical Field
The invention relates to the technical field of chemical industry, in particular to a separation process for separating m-cresol from urea.
Background
Cresol is an organic chemical of formula C 7 H 8 O, a clear liquid which is almost colorless, purplish red or brownish yellow, has odor similar to phenol and slight burnt odor, and a saturated aqueous solution shows neutral or weak acidic reaction, and is used for preparing a surfactant, lubricating oil and synthesizingMaterial auxiliary agent and dye intermediate. Cresol is a general name of a mixture of three isomers of p-cresol, m-cresol and o-cresol, and the use of the mixture of three isomers of cresol is much less than that of each monomer, for example, p-cresol is industrially used for the production of pesticides, dyes, plastics and the like, and is medically used as intestinal anthelmintic, disinfectant, local anticorrosive agent and the like; m-cresol is an important raw material for synthesizing antioxidants, pesticides, vitamin E, cosmetics and medicines, and also has important applications in the aspects of synthetic resins, color film developers, adhesives and the like. It is therefore generally necessary in industrial production to obtain monomeric cresols in high purity, and it is important in particular to separate off industrially valuable m-cresol.
The separation of o-cresol from the mixture of p-cresol, m-cresol and o-cresol is relatively simple and can be realized by the traditional distillation method, and the separation and purification of p-cresol and m-cresol are very difficult because the boiling points of p-cresol and m-cresol are very close. In the prior art, the separation method of p-cresol and m-cresol is mainly divided into a physical method and a chemical method, wherein the physical method comprises an extraction method, a crystallization method, an adsorption separation method, an azeotropic method and the like; the chemical method comprises the following steps: alkylation, chelation, and urea complexation.
The inventor finds that in the prior art, in the technology for separating and purifying m-cresol by using urea, the organic benzene solvent is added, so that the environmental pollution is large, or the process is complex, the energy consumption is high, and the industrial application is not facilitated.
The information disclosed in this background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.
Disclosure of Invention
The invention aims to provide a separation process for separating m-cresol from urea, which separates o-cresol and p-cresol in mixed cresol to improve the percentage content of m-cresol in the mixed cresol, and then purifies the m-cresol by adopting a urea complexation method.
In order to achieve the purpose, the invention provides the following technical scheme:
in a first aspect of the present invention, there is provided a process for separating m-cresol from urea, the process comprising the steps of:
1) Separating out o-cresol from the mixed cresol by adopting a distillation method;
2) Adding an oxalic acid complexing agent and a solvent into the mixed cresol obtained in the step 1), heating to boil, reacting for a period of time, cooling to crystallize, and then carrying out solid-liquid separation to obtain a filtrate serving as a mixed cresol raw material for later use;
3) Heating the mixed cresol raw material obtained in the step 2) and urea at the temperature of 70-95 ℃ for 40-80 min; after the reaction is finished, cooling to a certain temperature, dropping a mixed solvent of toluene, n-hexane and cyclohexane at a constant speed, cooling to-15 to-10 ℃ at a constant speed, and carrying out crystallization reaction for 120-150min; and (4) carrying out suction filtration, adding water into the obtained solid, heating and dissolving to obtain an oil layer, and carrying out rotary distillation to obtain the m-cresol pure product.
In the invention, o-cresol and p-cresol in the mixed cresol are separated, so that the percentage content of the m-cresol in the raw material for extracting the m-cresol is greatly increased, the complexing effect of urea on the m-cresol is better when the m-cresol is separated by adopting a urea complexing method subsequently, and the yield and the purity of the m-cresol are improved.
In the prior art, when the m-cresol is separated by using a urea complexation methodToluene is generally used as solventExperiments show that the mixed solvent adopted when the urea complexation method is used for separating the m-cresol influences the separation effect of the m-cresol. The invention discovers that when the mixed solvent system of toluene, normal hexane and cyclohexane is used for separating the m-cresol, the m-cresol in the mixed cresol can be better separated, and the obtained m-cresol has higher yield and better purity. And the m-cresol crystals can be better separated under the conditions of reaction time, crystallization temperature and the like in the invention.
In one or more embodiments of the present invention, the solvent in step 2) is cyclohexane or petroleum ether.
In one or more embodiments of the invention, the temperature for cooling and crystallizing in the step 2) is 4 to 15 ℃, and the crystallization time is 2~4 hours.
In one or more embodiments of the invention, after the reaction in step 3), cooling to 50-60 ℃, and then dropping a mixed solvent of toluene, n-hexane and cyclohexane at a constant speed; preferably, the temperature is reduced to 50 ℃, and a mixed solvent of toluene, normal hexane and cyclohexane is dripped at a constant speed when the temperature is 55 ℃ or 60 ℃.
In one or more embodiments of the present invention, the volume ratio of the toluene, n-hexane, and cyclohexane in the mixed solvent of step 3) is 1:1~2:1~2;
the volume ratio of the toluene to the n-hexane to the cyclohexane in the mixed solvent is 1:1~2:1~2, the ratio gives m-cresol with higher purity, which is more favorable to the separation of m-cresol and p-cresol than other ratios, and when the volume ratio of the three solvents is changed, the recovery rate and purity of the m-cresol are affected and reduced.
In one or more embodiments of the present invention, the volume ratio of the mixed cresol raw material and the mixed solvent in the step 3) is 1:1~3, preferably the volume ratio of mixed cresol raw material and mixed solvent is 1:1.5,1:2 or 1:3.
the volume ratio of the mixed cresol raw material to the mixed solvent is 1:1~3, the impurities can be dissolved more thoroughly with the increase of the solvent dosage, the purity of the m-cresol crystals can be improved, but the solvent dosage is too large, the purity of the m-cresol crystals cannot be infinitely increased, and the solvent waste and the environmental pollution can be caused, so that the volume ratio of the mixed cresol raw material to the mixed solvent is 1:1~3 is most suitable.
In one or more embodiments of the present invention, the heating temperature for adding water to the solid obtained in step 3) and heating for hot melting is 50 to 55 ℃.
In a second aspect of the present invention, there is provided m-cresol separated by the process for separating m-cresol from urea according to the first aspect.
Compared with the prior art, the invention has the beneficial effects that:
the invention discovers through experiments that the separation effect of the m-cresol is influenced by adopting the mixed solvent when the m-cresol is separated by using a urea complexation method. The invention discovers that when the mixed solvent system of toluene, normal hexane and cyclohexane is used for separating the m-cresol, the m-cresol in the mixed cresol can be better separated, and the obtained m-cresol has higher yield and better purity.
The m-cresol obtained by separating the mixed solvent of toluene, normal hexane and cyclohexane has higher purity and yield than the m-cresol obtained by separating the mixed solvent of toluene, normal hexane and cyclohexane by using a single toluene solvent, and the method can also reduce the using amount of toluene and is more environment-friendly.
In the invention, o-cresol and p-cresol in the mixed cresol are separated, so that the percentage content of the m-cresol in the raw material for extracting the m-cresol is greatly increased, the complexing effect of urea on the m-cresol is better when the m-cresol is separated by adopting a urea complexing method subsequently, and the yield and the purity of the m-cresol are improved.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The mass ratio of the simulated dosages of o-cresol, p-cresol and m-cresol in the mixed cresol used in the following examples was 1:1:1.
example 1
A process for separating metacresol from urea comprises the following steps:
1) Separating out o-cresol from the mixed cresol by adopting a distillation method;
2) Adding oxalic acid complexing agent and cyclohexane ether solvent into the mixed cresol obtained in the step 1), and heating and boiling to react for 1 h; crystallizing 2 h at 4 ℃, and performing solid-liquid separation to obtain filtrate as mixed cresol raw material for later use;
3) Adding the mixed cresol raw material obtained in the step 2) and urea into a reactor together, and heating for 40 min through a water bath at 70 ℃; after the reaction is finished, cooling to 50 ℃, and dropwise adding the mixture at a constant speed, wherein the volume ratio is 1:1:1, cooling the mixed solvent of toluene, normal hexane and cyclohexane to-15 ℃ at a constant speed, and carrying out crystallization reaction for 120 min; and (3) carrying out suction filtration, adding 3 times of water by mass into the filter cake, heating to 50 ℃ for dissolution, and carrying out rotary distillation on the obtained oil layer to obtain a pure m-cresol product.
Example 2
A separation process for separating m-cresol from urea comprises the following steps:
1) Separating out o-cresol from the mixed cresol by adopting a distillation method;
2) Adding oxalic acid complexing agent and petroleum ether solvent into the mixed cresol obtained in the step 1), heating and boiling to react with 1 h; crystallizing 3 h at 6 deg.C, separating solid and liquid, and collecting filtrate as mixed cresol raw material;
3) Adding the mixed cresol raw material obtained in the step 2) and urea into a reactor together, and heating for 50min through a water bath at 80 ℃; after the reaction is finished, cooling to 55 ℃, and dropwise adding the mixture at a constant speed, wherein the volume ratio is 1:1.5:1.5, cooling the mixed solvent of toluene, normal hexane and cyclohexane to-12 ℃ at a constant speed, and carrying out crystallization reaction for 13 minutes; and (3) carrying out suction filtration, adding 3 times of water by mass into the obtained solid, heating to 55 ℃ for hot melting, and carrying out rotary distillation on the obtained oil layer to obtain a pure m-cresol product.
Example 3
A separation process for separating m-cresol from urea comprises the following steps:
1) Separating out o-cresol from the mixed cresol by adopting a distillation method;
2) Adding oxalic acid complexing agent and cyclohexane solvent into the mixed cresol obtained in the step 1), heating and boiling to react with 2 h; crystallizing 3 h at 8 ℃, performing solid-liquid separation, and taking the obtained filtrate as a mixed cresol raw material for later use;
3) Adding the mixed cresol raw material obtained in the step 2) and urea into a reactor together, and heating for 60 min through a water bath at 85 ℃; after the reaction is finished, cooling to 60 ℃, and dropwise adding at a constant speed according to a volume ratio of 1:2:1, cooling the mixed solvent of toluene, n-hexane and cyclohexane to-11 ℃ at a constant speed, and carrying out crystallization reaction for 140 min; and (3) carrying out suction filtration, adding 3 times of water by mass into the obtained solid, heating to 60 ℃ for hot melting, and carrying out rotary distillation on the obtained oil layer to obtain a pure m-cresol product.
Example 4
A separation process for separating m-cresol from urea comprises the following steps:
1) Separating out o-cresol from the mixed cresol by adopting a distillation method;
2) Adding oxalic acid complexing agent and petroleum ether solvent into the mixed cresol obtained in the step 1), heating and boiling to react with 5 h; crystallizing 4 h at 15 ℃, performing solid-liquid separation, and taking the obtained filtrate as a mixed cresol raw material for later use;
3) Adding the mixed cresol raw material obtained in the step 2) and urea into a reactor together, and heating for 80 min by an oil bath at 95 ℃; after the reaction is finished, cooling to 60 ℃, and dropwise adding at a constant speed according to a volume ratio of 1:2:2, cooling the mixed solvent of toluene, n-hexane and cyclohexane to-10 ℃ at a constant speed, and carrying out crystallization reaction for 150min; adding 3 times of water into the obtained solid, heating to 60 ℃ for hot melting, and carrying out rotary distillation on the obtained oil layer to obtain a pure m-cresol product.
Comparative example 1: compared with the example 1, the method has no step 1) of separating the o-cresol, and the rest steps are the same as the example 1.
Comparative example 2: compared with example 1, there is no step of 2) separating p-cresol, and the rest of the steps are the same as example 1.
Comparative example 3: compared with example 1, there are no step 1) of separating o-cresol and step 2) of separating p-cresol, and the rest steps are the same as example 1.
Comparative example 4: compared with the example 1, a single solvent toluene is adopted in the step 3), and the rest steps are the same as the example 1.
Comparative example 5: compared with the example 1, the single solvent of n-hexane is adopted in the step 3), and the rest steps are the same as the example 1.
Comparative example 6: compared with the example 1, the single solvent cyclohexane is adopted in the step 3), and the rest steps are the same as the example 1.
Comparative example 7: compared with the embodiment 1, the volume ratio adopted in the step 3) is 2:1:1, toluene, n-hexane and cyclohexane, and the remaining steps were the same as in example 1.
Comparative example 8: compared with the embodiment 1, the volume ratio of 1:3:3 of toluene, n-hexane and cyclohexane, and the rest of the procedure was the same as in example 1.
The purity and recovery of the m-cresol products obtained in examples 1-4 and comparative examples 1-4 are shown in Table 1:
TABLE 1
| Purity of m-cresol% | The recovery rate of m-cresol is% | |
| Example 1 | 99.63 | 78.51 |
| Example 2 | 99.56 | 77.97 |
| Example 3 | 99.71 | 78.12 |
| Example 4 | 99.68 | 78.24 |
| Comparative example 1 | 98.16 | 75.63 |
| Comparative example 2 | 98.21 | 74.51 |
| Comparative example 3 | 98.05 | 70.02 |
| Comparative example 4 | 98.34 | 74.15 |
| Comparative example 5 | 95.31 | 74.21 |
| Comparative example 6 | 93.54 | 74.13 |
| Comparative example 7 | 98.17 | 75.52 |
| Comparative example 8 | 98.16 | 75.35 |
As can be seen from Table 1, the process for separating m-cresol from urea of examples 1-4 of the present invention provides a higher purity and recovery of m-cresol product than the process for separating m-cresol from urea of comparative examples 1-8. Compared to comparative examples 1-3, the process of step 1) of the examples of the present invention separates out o-cresol first and step 2) separates p-cresol, thereby reducing the effect of o-cresol and p-cresol on the complexation of m-cresol and urea. Comparative example 1 o-cresol was not separated out, which affects the separation of m-cresol, so that the recovery rate of m-cresol is reduced and the purity is also affected; comparative example 2 does not separate out p-cresol, which affects the separation of m-cresol, so that the recovery rate of m-cresol is reduced and the purity is also affected; likewise, comparative example 3 did not separate out o-cresol and p-cresol, which affected the separation of m-cresol, so that the recovery rate of m-cresol was lowered and the purity was also affected.
The mixed solvent selected in the embodiments 1-4 realizes better separation of m-cresol in mixed cresol, and the obtained m-cresol has higher yield and better purity. In comparative example 4, the traditional single solvent toluene is adopted, in comparative example 5, the single solvent n-hexane is adopted, in comparative example 6, the single solvent cyclohexane is adopted, and as can be seen from the table, when the single solvent n-hexane or cyclohexane is adopted, the recovery rate and the purity reduction of the obtained m-cresol are both low, but the yield rate and the purity of the obtained m-cresol are higher and better when the mixed solvent selected in the embodiment is adopted, so that the good synergistic effect among the mixed solvent toluene, n-hexane and cyclohexane is shown. However, in comparative examples 7 and 8, the volume ratio of the toluene, n-hexane and cyclohexane mixed solvent is changed, so that the separated m-cresol recovery rate and purity are reduced, which indicates that the mixed solvent of toluene, n-hexane and cyclohexane in the invention can obtain good effect only under a certain proportion.
The result shows that under the condition of the invention, o-cresol and p-cresol in mixed cresol are separated, and then the mixed cresol raw material and urea are heated for 40 to 80 min at the temperature of 70 to 95 ℃; after the reaction is finished, adding a mixture of 1:1~2:1~2, and crystallizing at-15 to-10 ℃ to obtain m-cresol pure product with highest purity and highest recovery rate.
In the description herein, references to the description of "one embodiment," "an example," "a specific example" or the like are intended to mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The preferred embodiments of the invention disclosed above are intended to be illustrative only. The preferred embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention. The invention is limited only by the claims and their full scope and equivalents.
Claims (10)
1. A separation process for separating m-cresol from urea is characterized by comprising the following steps: the separation process comprises the following steps:
1) Separating out o-cresol from the mixed cresol by adopting a distillation method;
2) Adding an oxalic acid complexing agent and a solvent into the mixed cresol obtained in the step 1), heating to boil, reacting for a period of time, cooling to crystallize, and then carrying out solid-liquid separation to obtain a filtrate serving as a mixed cresol raw material for later use;
3) Heating the mixed cresol raw material obtained in the step 2) and urea at the temperature of 70-95 ℃ for 40-80 min; after the reaction is finished, cooling to a certain temperature, dropping a mixed solvent of toluene, n-hexane and cyclohexane at a constant speed, cooling to-15 to-10 ℃ at a constant speed, and carrying out crystallization reaction for 120-150min; and (4) carrying out suction filtration, adding water into the obtained solid, heating and dissolving to obtain an oil layer, and carrying out rotary distillation to obtain the m-cresol pure product.
2. The process according to claim 1, characterized in that: the solvent in the step 2) is cyclohexane or petroleum ether.
3. The process according to claim 1, characterized in that: the temperature for cooling and crystallizing in the step 2) is 4 to 15 ℃, and the crystallization time is 2~4 hours.
4. The process for separating m-cresol from urea according to claim 1, wherein the mixed solvent of toluene, n-hexane and cyclohexane is added dropwise at a constant speed when the temperature is reduced to 50 to 60 ℃ after the reaction in step 3).
5. The process of claim 1, wherein the temperature is reduced to 50 ℃ after the reaction in step 3), and a mixed solvent of toluene, n-hexane and cyclohexane is uniformly added dropwise at 55 ℃ or 60 ℃.
6. The process of claim 1, wherein the volume ratio of the toluene to the mixed solvent of n-hexane and cyclohexane in step 3) is 1:1~2:1~2.
7. The process of claim 1, wherein the volume ratio of the mixed cresol raw material to the mixed solvent in the step 3) is 1:1~3, the volume ratio of mixed cresol raw material and mixed solvent is preferably 1:1.5,1:2 or 1:3.
8. the process of claim 1, wherein the volume ratio of the mixed cresol raw material to the mixed solvent is 1:1.5,1:2 or 1:3.
9. the process for separating m-cresol from urea according to claim 1, wherein the solid obtained in step 3) is dissolved by adding water and heating at a temperature of 50 to 55 ℃.
10. M-cresol obtained by a process for separating m-cresol from urea according to any one of claims 1 to 9.
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| CN104058936A (en) * | 2014-06-20 | 2014-09-24 | 苏州飞翔新材料研究院有限公司 | Method for separation and purification of p-cresol |
| CN104230669A (en) * | 2014-09-11 | 2014-12-24 | 苏州飞翔新材料研究院有限公司 | Separation and purification method of m-cresol |
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| CN104058936A (en) * | 2014-06-20 | 2014-09-24 | 苏州飞翔新材料研究院有限公司 | Method for separation and purification of p-cresol |
| CN104230669A (en) * | 2014-09-11 | 2014-12-24 | 苏州飞翔新材料研究院有限公司 | Separation and purification method of m-cresol |
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| 尚四华 等: "尿素与间甲酚共晶法分离间/对甲酚" * |
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