CN115304456B - Separation process for separating m-cresol from urea - Google Patents
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- C07C37/685—Processes comprising at least two steps in series
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- 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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- 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 m-cresol from urea; the separation process comprises the following steps: 1) Separating out the o-cresol in the mixed cresol by adopting a distillation method; 2) Adding oxalic acid complexing agent and solvent into the mixed cresol obtained in the step 1), heating and boiling, cooling for crystallization after reacting for a period of time, and then carrying out solid-liquid separation to obtain filtrate which is used as a mixed cresol raw material for standby; 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, uniformly dripping a mixed solvent of toluene, normal hexane and cyclohexane, uniformly cooling to-15 to-10 ℃, and carrying out crystallization reaction for 120-150min; and adding water into the obtained solid, heating and dissolving to obtain an oil layer to obtain m-cresol. The invention adopts a mixed solvent system of toluene, normal hexane and cyclohexane to obtain the 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 with the molecular formula C 7 H 8 O, a clear liquid which is almost colorless, light purple or light brown yellow, has an odor similar to phenol, is slightly burnt odor, and the saturated aqueous solution shows neutral or weak acidic reaction, and is a raw material for manufacturing surfactants, lubricating oils, synthetic material auxiliaries and dye intermediates. Cresol is generally a general term for three-isomer mixtures of p-cresol, m-cresol and o-cresol, and the use of the three-isomer mixtures of cresol is far less than that of each monomer, for example, the p-cresol can be used for the industrial production of pesticides, dyes, plastics and the like, and can be used as an intestinal insect repellent, disinfectant, local anticorrosive and the like in medicine; m-cresol is an important raw material for synthesizing antioxidants, pesticides, vitamin E, cosmetics and medicines, and has important application in the aspects of synthetic resins, color film developers, adhesives and the like. Therefore, it is generally necessary to obtain monomeric cresols of relatively high purity in industrial production, and it is particularly important to separate off the commercially valuable m-cresol.
In the mixture of the p-cresol, the m-cresol and the o-cresol, the separation of the o-cresol is relatively simple, the separation can be realized by a traditional distillation method, and the separation and purification of the p-cresol and the m-cresol are very difficult due to the very close boiling points. The separation method of the p-cresol and the m-cresol in the prior art 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 discovers that in the technology of separating and purifying m-cresol by using urea in the prior art, the organic benzene solvent is often added to cause great environmental pollution, or the technology 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 of ordinary skill in the art.
Disclosure of Invention
The invention aims to provide a separation process for separating urea from m-cresol, which is characterized in that the o-cresol and p-cresol in mixed cresol are separated, the percentage of the m-cresol in the mixed cresol is increased, and then the m-cresol is purified by adopting a urea complexation method.
In order to achieve the above purpose, the present invention provides the following technical solutions:
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 the o-cresol in the mixed cresol by adopting a distillation method;
2) Adding oxalic acid complexing agent and solvent into the mixed cresol obtained in the step 1), heating and boiling, cooling for crystallization after reacting for a period of time, and then carrying out solid-liquid separation to obtain filtrate which is used as a mixed cresol raw material for standby;
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, uniformly dripping a mixed solvent of toluene, normal hexane and cyclohexane, uniformly cooling to-15 to-10 ℃, and carrying out crystallization reaction for 120-150min; filtering, adding water into the obtained solid, heating for dissolving, obtaining an oil layer, and performing rotary distillation to obtain the m-cresol pure product.
According to the invention, the o-cresol and the p-cresol in the mixed cresol are separated, so that the percentage of the m-cresol in the raw materials used for extracting the m-cresol is greatly increased, and the complexation effect of urea on the m-cresol is better when the urea complexation method is adopted for separating the m-cresol in the follow-up process, thereby improving the yield and purity of the m-cresol.
In the prior art, when the urea complexation method is used for separating the m-cresolToluene is generally used as solventExperiments show that the mixed solvent can influence the separation effect of the m-cresol when the urea complexation method is used for separating the m-cresol. The invention discovers that when the mixed solvent system of toluene, normal hexane and cyclohexane is adopted to separate the m-cresol, better separation of the m-cresol in the mixed cresol can be realized, and the obtained m-cresol has higher yield and better purity. In addition, the reaction time, crystallization temperature and other conditions in the invention can better separate the m-cresol crystals.
In one or more embodiments of the invention, the solvent in step 2) is cyclohexane or petroleum ether.
In one or more embodiments of the present invention, the temperature at which the crystallization is performed by cooling in step 2) is 4 to 15 ℃ and the crystallization time is 2 to 4 hours.
In one or more embodiments of the invention, after the reaction in the step 3), the mixed solvent of toluene, normal hexane and cyclohexane is dropwise added at a constant speed when the temperature is reduced to 50-60 ℃; preferably, the temperature is reduced to 50 ℃,55 ℃ or 60 ℃ and the mixed solvent of toluene, n-hexane and cyclohexane is added dropwise at a constant speed.
In one or more embodiments of the present invention, the volume ratio of the three solvents in the mixed solvent of toluene, n-hexane and cyclohexane in step 3) is 1: 1-2: 1-2;
in the invention, the volume ratio of the toluene, the normal hexane and the cyclohexane in the mixed solvent is 1: 1-2: 1-2, the purity of the obtained m-cresol is higher than other ratios, and the separation of the m-cresol and the p-cresol is more facilitated, and when the volume ratio of the three solvents is changed, the recovery rate and the purity of the obtained m-cresol are influenced and reduced.
In one or more embodiments of the present invention, the volume ratio of the cresol feedstock and the mixed solvent in step 3) is 1: 1-3, preferably, the volume ratio of the mixed cresol raw material to the mixed solvent is 1:1.5,1:2 or 1:3.
in the invention, the volume ratio of the mixed cresol raw material to the mixed solvent is 1: 1-3, can more thoroughly get the dissolved impurity along with the increase of solvent quantity, can improve and obtain the purity of metacresol crystal, but solvent quantity too big also can not infinitely increase the purity of metacresol crystal, still can cause solvent waste and environmental pollution, consequently select and use the volume ratio of mixing cresol raw materials and mixed solvent to be 1:1 to 3 are most suitable.
In one or more embodiments of the present invention, the heating temperature of adding water to the obtained solid in step 3) to heat and melt is 50-55 ℃.
In a second aspect of the present invention, there is provided m-cresol separated by the urea-separating process for separating m-cresol according to the first aspect.
Compared with the prior art, the invention has the beneficial effects that:
experiments show that the mixed solvent can influence the separation effect of the m-cresol when the urea complexation method is used for separating the m-cresol. The invention discovers that when the mixed solvent system of toluene, normal hexane and cyclohexane is adopted to separate the m-cresol, better separation of the m-cresol in the mixed cresol can be realized, and the obtained m-cresol has higher yield and better purity.
The purity and the yield of the m-cresol obtained by separating the mixed solvent of toluene, normal hexane and cyclohexane are higher than those of the m-cresol obtained by using a single toluene solvent, and the dosage of toluene can be reduced, so that the method is more environment-friendly.
According to the invention, the o-cresol and the p-cresol in the mixed cresol are separated, so that the percentage of the m-cresol in the raw materials used for extracting the m-cresol is greatly increased, and the complexation effect of urea on the m-cresol is better when the urea complexation method is adopted for separating the m-cresol in the follow-up process, thereby improving the yield and purity of the m-cresol.
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.
The mixed cresols used in the following examples were o-cresol, p-cresol and m-cresol in a simulated amount by mass ratio of 1:1:1.
example 1
A separation process for separating m-cresol from urea comprises the following steps:
1) Separating out the o-cresol in 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 1 h; crystallizing 2 h at 4deg.C, and performing solid-liquid separation to obtain 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 the mixture for 40 min through a water bath at 70 ℃; after the reaction is finished, the volume ratio of the uniform dropping to the mixture is 1 when the temperature is reduced to 50℃:1:1, toluene, n-hexane and cyclohexane mixed solvent, cooling to-15 ℃ at constant speed, and carrying out crystallization reaction for 120 min; filtering, adding 3 times of water into the filter cake, heating to 50 ℃ for dissolution, and carrying out rotary distillation on the obtained oil layer to obtain the m-cresol pure product.
Example 2
A separation process for separating m-cresol from urea comprises the following steps:
1) Separating out the o-cresol in 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, and reacting 1 h; crystallizing 3 h at 6deg.C, and performing solid-liquid separation to obtain 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 the mixture for 50min through a water bath at 80 ℃; after the reaction is finished, the volume ratio of the uniform dropping to the mixture is 1 when the temperature is reduced to 55℃:1.5:1.5 toluene, n-hexane and cyclohexane mixed solvent, cooling to-12 ℃ at constant speed, and carrying out crystallization reaction for 13 0min; filtering, adding 3 times of water into the obtained solid, heating to 55 ℃ for thermosol, and carrying out rotary distillation on the obtained oil layer to obtain the m-cresol pure product.
Example 3
A separation process for separating m-cresol from urea comprises the following steps:
1) Separating out the o-cresol in 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, and reacting 2 h; crystallizing 3 h at 8deg.C, and performing solid-liquid separation to obtain 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 the mixture for 60 minutes through a water bath at the temperature of 85 ℃; after the reaction is finished, the volume ratio of the uniform dropping to the mixture is 1 when the temperature is reduced to 60℃:2:1, toluene, n-hexane and cyclohexane mixed solvent, cooling to-11 ℃ at constant speed, and carrying out crystallization reaction for 140 min; filtering, adding 3 times of water into the obtained solid, heating to 60 ℃ for thermosol, and carrying out rotary distillation on the obtained oil layer to obtain the m-cresol pure product.
Example 4
A separation process for separating m-cresol from urea comprises the following steps:
1) Separating out the o-cresol in 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, and reacting 5 h; crystallizing 4 h at 15 ℃, and carrying out solid-liquid separation to obtain filtrate which is used as a raw material of mixed cresol for standby;
3) Adding the mixed cresol raw material obtained in the step 2) and urea into a reactor together, and heating for 80 min through an oil bath at 95 ℃; after the reaction is finished, the volume ratio of the uniform dropping to the mixture is 1 when the temperature is reduced to 60℃:2:2, toluene, n-hexane and cyclohexane mixed solvent are cooled to-10 ℃ at constant speed, and crystallization reaction is carried out 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 the m-cresol pure product.
Comparative example 1: in comparison with example 1, there was no step of separating o-cresol in step 1), and the rest was the same as in example 1.
Comparative example 2: in comparison with example 1, there is no step of separating p-cresol in step 2), and the rest is the same as in example 1.
Comparative example 3: in comparison with example 1, there were no steps of separating o-cresol in step 1) and separating p-cresol in step 2), and the remaining steps were the same as in example 1.
Comparative example 4: in comparison with example 1, toluene as a single solvent was used in step 3), and the rest of the procedure was the same as in example 1.
Comparative example 5: in comparison with example 1, in step 3) a single solvent n-hexane was used, the rest of the procedure being the same as in example 1.
Comparative example 6: in comparison with example 1, in step 3) a single solvent cyclohexane was used, the rest of the procedure being the same as in example 1.
Comparative example 7: in comparison with example 1, a volume ratio of 2 is used in step 3): 1:1 toluene, n-hexane and cyclohexane, and the rest of the procedure was the same as in example 1.
Comparative example 8: in comparison with example 1, a volume ratio of 1 is used in step 3): 3:3 toluene, n-hexane and cyclohexane, and the rest of the procedure is the same as in example 1.
The purity and recovery of the m-cresol products obtained in examples 1 to 4 and comparative examples 1 to 4 are shown in Table 1:
TABLE 1
| Purity of m-cresol% | Recovery of m-cresol% | |
| 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 purity and recovery rate of the m-cresol product obtained by the separation process for urea separation of m-cresol of examples 1 to 4 of the present invention are higher than those of the separation process for urea separation of m-cresol of comparative examples 1 to 8, and the step 1) of the present invention separates the o-cresol first and the step 2) separates the p-cresol, thereby reducing the influence of the o-cresol and p-cresol in the mixed cresol on urea complexation of m-cresol, relative to the separation process for urea separation of m-cresol of comparative examples 1 to 3. In comparative example 1, the o-cresol was not separated out, and the o-cresol affects the separation of the m-cresol, so that the recovery rate of the m-cresol is reduced, and the purity is also affected; comparative example 2 did not separate out the para-cresol, which affects the separation of the meta-cresol, so that the recovery rate of the meta-cresol was reduced and the purity was 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 solvents selected in examples 1-4 achieved better separation of the m-cresol from the mixed cresols, and the obtained m-cresol was higher in yield and purity. In comparative example 4, toluene was used as a conventional single solvent, n-hexane was used as a single solvent, cyclohexane was used as a single solvent in comparative example 5, and cyclohexane was used as a single solvent in comparative example 6, and it can be seen from the table that the recovery rate and purity of the obtained m-cresol were lower when n-hexane or cyclohexane was used as a single solvent, but the mixed solvent selected in examples gave a higher yield of m-cresol and a better purity, indicating a good synergy among toluene, n-hexane and cyclohexane as mixed solvents. However, the volume ratio of toluene, n-hexane and cyclohexane in the mixed solvents in comparative examples 7 and 8 is changed, so that the recovery rate and purity of the m-cresol obtained by separation are reduced, and it is shown that the mixed solvents toluene, n-hexane and cyclohexane in the invention can obtain good effects only at a certain ratio.
The result shows that under the condition of the invention, the o-cresol and the p-cresol in the mixed cresol are separated, and then the mixed cresol raw material and urea are heated for 40-80 min at the temperature of 70-95 ℃; after the reaction is finished, the volume ratio of the mixture is 1: 1-2: 1-2 toluene, n-hexane and cyclohexane mixed solvent, and crystallizing at-15 to-10 ℃ to obtain the m-cresol product with highest purity and highest recovery rate.
In the description of the present specification, the descriptions of the terms "one embodiment," "example," "specific example," and the like, 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 present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. 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 only to assist in the explanation of the invention. The preferred embodiments are not exhaustive or to limit the invention to the precise form 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 understand and utilize the invention. The invention is limited only by the claims and the full scope and equivalents thereof.
Claims (5)
1. A separation process for separating m-cresol from urea is characterized in that: the separation process comprises the following steps:
1) Separating out the o-cresol in the mixed cresol by adopting a distillation method; the mass ratio of the o-cresol to the p-cresol to the m-cresol in the mixed cresol is 1:1:1, a step of;
2) Adding oxalic acid complexing agent and solvent into the mixed cresol obtained in the step 1), heating and boiling, cooling for crystallization after reacting for a period of time, and then carrying out solid-liquid separation to obtain filtrate which is used as a mixed cresol raw material for standby; the solvent in the step 2) is cyclohexane or petroleum ether; the temperature of the step 2) is reduced to 4-15 ℃ for crystallization, and the crystallization time is 2-4 hours;
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, uniformly dripping a mixed solvent of toluene, normal hexane and cyclohexane, uniformly cooling to-15 to-10 ℃, and carrying out crystallization reaction for 120-150min; filtering, adding water into the obtained solid, heating for dissolving to obtain an oil layer, and performing rotary distillation to obtain a pure m-cresol product;
the volume ratio of the toluene, the normal hexane and the cyclohexane in the mixed solvent in the step 3) is 1: 1-2: 1-2;
the volume ratio of the cresol raw material and the mixed solvent in the step 3) is 1: 1-3.
2. The process for separating m-cresol from urea according to claim 1, wherein the mixed solvent of toluene, n-hexane and cyclohexane is dropwise added at a constant speed when the temperature is reduced to 50-60 ℃ after the reaction in the step 3).
3. The process for separating m-cresol from urea according to claim 1, characterized in that the mixed solvent of toluene, n-hexane and cyclohexane is added dropwise at a constant speed at a temperature of 55 ℃ or 60 ℃ after the completion of the reaction in step 3).
4. The process for separating m-cresol from urea according to claim 1, characterized in that the volume ratio of the mixed cresol raw material to the mixed solvent is 1:1.5,1:2 or 1:3.
5. the process for separating m-cresol from urea according to claim 1, wherein the heating temperature for dissolving the solid obtained in step 3) by adding water and heating is 50-55 ℃.
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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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