阅读说明：本技术 分离间甲酚和对甲酚的方法 (Method for separating m-cresol and p-cresol ) 是由 易争明 肖文龙 罗和安 艾秋红 于 2021-07-05 设计创作，主要内容包括：本发明提供一种分离间甲酚和对甲酚的方法。所述分离间甲酚和对甲酚的方法包括络合结晶工艺和熔融结晶工艺,所述络合结晶工艺用于提取间甲酚,所述熔融结晶工艺用于提取对甲酚。本发明提供的分离间甲酚和对甲酚的方法利用络合结晶工艺和熔融结晶工艺的结合分别对间甲酚和对甲酚进行提取分离,不仅同时获得纯度高的间甲酚和对甲酚,而且熔融结晶的工艺条件温度在对甲酚晶体熔点(34.69℃)以下,能耗低,所述络合剂、解络剂及溶剂均可再生循环使用,绿色无污染。(The invention provides a method for separating m-cresol and p-cresol. The method for separating m-cresol and p-cresol comprises a complex crystallization process and a melt crystallization process, wherein the complex crystallization process is used for extracting m-cresol, and the melt crystallization process is used for extracting p-cresol. The method for separating m-cresol and p-cresol provided by the invention utilizes the combination of the complexation crystallization process and the melt crystallization process to respectively extract and separate m-cresol and p-cresol, not only can obtain high-purity m-cresol and p-cresol simultaneously, but also has low energy consumption because the temperature of the process condition of melt crystallization is below the melting point (34.69 ℃) of p-cresol crystals, and the complexing agent, the decomplexing agent and the solvent can be regenerated and recycled, thereby being green and pollution-free.)

1. The method for separating m-cresol and p-cresol is characterized by comprising a complex crystallization process and a melt crystallization process, wherein the complex crystallization process is used for extracting m-cresol, and the melt crystallization process is used for extracting p-cresol.

2. The method of separating m-cresol and p-cresol according to claim 1, wherein the complex crystallization process comprises: and (2) carrying out complexation reaction on the mixed cresol containing m-cresol and p-cresol and a complexing agent, adding a solvent for cooling crystallization, adding a crystal obtained by separation into a decomplexing agent for decomplexing to obtain m-cresol with the purity of more than 99.9%, and rectifying the filtrate obtained by separation to separate out the solvent to obtain the mixed cresol 1.

3. The method of separating m-cresol and p-cresol according to claim 2, wherein the melt crystallization process comprises: and adding the mixed cresol 1 into a melt crystallization device for melt crystallization to obtain the p-cresol with the purity of more than 99.9 percent.

4. The method of separating m-cresol and p-cresol according to claim 2, wherein the mixed cresol is a mixture of m-cresol and p-cresol.

5. The method for separating m-cresol and p-cresol according to claim 2, wherein the complexing agent is a nitrogen-containing water-soluble basic compound.

6. The method for separating m-cresol and p-cresol according to claim 2, wherein the solvent is an organic solvent which is easily recycled.

7. The method for separating m-cresol and p-cresol according to claim 2, wherein after the crystals are decomplexed by the decomplexing agent and m-cresol is separated out, the formed mixed solution of the complexing agent and the decomplexing agent is rectified and separated to obtain the decomplexing agent and the complexing agent respectively, and both the decomplexing agent and the complexing agent can be recycled.

8. The method for separating m-cresol and p-cresol according to claim 2, wherein the solvent separated from the filtrate by distillation is recycled.

9. The method for separating m-cresol and p-cresol according to claim 2, wherein the mass fraction of p-cresol in the mixed phenol 1 is not less than 64%.

10. The method for separating m-cresol and p-cresol according to claim 3, wherein the melt crystallization also obtains mixed cresol 2, and the mixed cresol 2 is subjected to m-cresol extraction by repeating the complex crystallization process and enters the whole separation process again.

11. The method for separating m-cresol and p-cresol according to claim 3, wherein the melt crystallization device further comprises a pump and a stirring member, the pump is installed outside the melt crystallization device, the stirring member is installed inside the melt crystallization device, and the pump and the melt crystallization device cooperate to promote circulation of a molten liquid and enhance mass transfer between solid and liquid.

12. The method of claim 3, wherein the melt crystallization device comprises a crystallization section, a sweating section and a melting section, the crystallization section is located at an upper part of the melt crystallization device, the melting section is located at a lower part of the melt crystallization device, and the sweating section is located between the crystallization section and the melting section.

13. The process for separating m-cresol and p-cresol according to claim 12, wherein the temperature of the crystallization zone is not less than 2 ℃.

Technical Field

The invention relates to the field of chemical separation, in particular to a method for separating m-cresol and p-cresol.

Background

There are two main routes of acquisition of cresol at present: the obtained cresol is a mixed component of three isomers of o-cresol, m-cresol and p-cresol, the economic added value is low, and the product with high purity can be greatly improved only by deep fine separation.

According to physicochemical properties, the boiling point of o-cresol is greatly different from the boiling points of m-cresol and p-cresol (about 20 ℃), and the o-cresol is directly separated and purified by a rectification method; m-cresol and p-cresol are a group of isomers with the boiling point difference of only 0.3 ℃, the separation is relatively difficult by adopting a traditional rectification method, although the melting points of the m-cresol and the p-cresol are greatly different, the defects of eutectic point and high-viscosity fluid exist at the same time, the concentration of raw material components is also required, and the application of the conventional crystallization method is limited. Therefore, how to separate m-cresol and p-cresol green and efficiently becomes a big problem.

The prior art method for separating m-cresol and p-cresol mainly comprises a complex crystallization method, an adsorption separation method, an alkylation method and the like.

CN107445806A discloses a process for separating and purifying m-cresol by a complex crystallization method, which comprises the steps of taking triethylene diamine as a complexing agent, taking n-butyl ether as a solvent, and selectively reacting the triethylene diamine with p-cresol to generate a complex, thereby obtaining the p-cresol. Then the filtrate in the operation is used as a reactant, sodium acetate is used as a complexing agent, toluene is used as a solvent, and the sodium acetate selectively reacts with m-cresol to generate a complex, so that the m-cresol is purified. Although the process can simultaneously obtain m-cresol and p-cresol products, the purity of the p-cresol product is difficult to reach more than 99.9 percent, and the solvent is difficult to recover due to excessive use of the solvent, thereby increasing unnecessary energy consumption.

CN111689838A discloses a separation method for adsorbing and separating m-cresol and p-cresol mixture, which comprises the steps of taking m-cresol and p-cresol mixture as raw materials, taking a molecular sieve as an adsorbent, introducing the mixed cresol raw materials into an adsorption zone of a liquid-phase simulated moving bed to contact with the adsorbent, adsorbing p-cresol by the adsorbent, not adsorbing m-cresol, taking out the adsorbed p-cresol and m-cresol as raffinate, and introducing a desorption agent into the adsorbent to obtain high-purity p-cresol and m-cresol products respectively. The adsorption separation method has high requirements on the adsorbent, and has a certain path for reaching the industrial requirements.

CN101863742A discloses a separation method of m-cresol and p-cresol, which comprises the steps of taking mixed cresol as a raw material, carrying out alkylation reaction under the condition that alkylating agent isobutene and catalyst exist to obtain mixed liquid of 2-tert-butyl-p-cresol and 6-tert-butyl-m-cresol, rectifying the mixed liquid to obtain high-purity 2-tert-butyl-p-cresol and 6-tert-butyl-m-cresol, and then carrying out dealkylation reaction respectively to obtain high-purity m-cresol and p-cresol products. The alkylation method is an industrially applied method at present, can simultaneously obtain high-purity m-cresol and p-cresol products, but has high energy consumption and complex equipment and flow.

Therefore, the existing method for separating m-cresol and p-cresol still has the defects and needs to be improved.

Disclosure of Invention

The invention provides a method for separating m-cresol and p-cresol by utilizing complex crystallization and melt crystallization, aiming at solving the technical problems that the separation energy consumption of m-cresol and p-cresol is high and m-cresol and p-cresol products with high purity cannot be obtained simultaneously.

A method for separating m-cresol and p-cresol comprises a complex crystallization process and a melt crystallization process, wherein the complex crystallization process is used for extracting m-cresol, and the melt crystallization process is used for extracting p-cresol.

Preferably, the complex crystallization process comprises: and (2) carrying out complexation reaction on the mixed cresol containing m-cresol and p-cresol and a complexing agent, adding a solvent for cooling crystallization, adding a crystal obtained by separation into a decomplexing agent for decomplexing to obtain m-cresol with the purity of more than 99.9%, and rectifying the filtrate obtained by separation to separate out the solvent to obtain the mixed cresol 1.

Preferably, the melt crystallization process comprises: and adding the mixed cresol 1 into a melt crystallization device for melt crystallization to obtain the p-cresol with the purity of more than 99.9 percent.

Preferably, the mixed cresol A is a mixture of m-cresol and p-cresol.

Preferably, the complexing agent is a nitrogen-containing water-soluble alkaline compound, such as monoethanolamine, diethanolamine, triethanolamine, ethylenediamine, triethylenediamine, urea, piperazine, and the like.

Preferably, the solvent is an organic solvent that is easily recycled.

Preferably, after the crystal is decomplexed by the decomplexing agent and m-cresol is separated out, the formed mixed solution of the complexing agent and the decomplexing agent is rectified and separated to obtain the decomplexing agent and the complexing agent respectively, and both the decomplexing agent and the complexing agent can be recycled.

Preferably, the solvent separated from the filtrate by rectification can be recycled.

Preferably, the mass fraction of p-cresol in the mixed phenol 1 is not less than 64%.

Preferably, the mixed cresol 2 is obtained through melt crystallization, and the mixed cresol 2 is subjected to m-cresol extraction through repeated complex crystallization process and enters the whole separation process again.

Preferably, the melt crystallization device further comprises a pump and a stirring component, the pump is installed outside the melt crystallization device, the stirring component is installed inside the melt crystallization device, and the pump and the melt crystallization device cooperate to promote circulation of molten liquid and strengthen mass transfer between solid and liquid.

Preferably, the melt crystallization device comprises a crystallization section, a sweating section and a melting section, wherein the crystallization section is positioned at the upper part of the melt crystallization device, the melting section is positioned at the lower part of the melt crystallization device, and the sweating section is positioned between the crystallization section and the melting section.

Preferably, the temperature of the crystallization zone is not less than 2 ℃.

Compared with the prior art, the method for separating m-cresol and p-cresol provided by the invention respectively extracts and separates m-cresol and p-cresol by combining the complex crystallization process and the melt crystallization process, and has the following beneficial effects:

in the complexing crystallization process, because the p-cresol and the complexing agent do not generate complexing reaction, the m-cresol and the complexing agent react to generate a stable m-cresol complex, the m-cresol complex is cooled in a solvent to form m-cresol complex crystals, the p-cresol is dissolved in the solvent, the m-cresol complex and the p-cresol are easily separated, the m-cresol complex crystals are decomplexed by pyrolysis, and the purity of the m-cresol extracted through the complexing crystallization is up to more than 99.9%;

meanwhile, the complexing agent, the decomplexing agent and the solvent can be regenerated and recycled, so that the material consumption and the generation of three wastes are reduced;

the melt crystallization is carried out by controlling the temperature to be slightly lower than the melting point (34.69 ℃) of the p-cresol crystals and keeping for a relatively long period of time, the appearance properties of the p-cresol crystals become soft, impurity liquid in the p-cresol crystals is discharged, the p-cresol crystals with higher purity are obtained, and the purity of the p-cresol extracted by the melt crystallization is up to more than 99.9%;

the temperature of the process condition of melt crystallization is below the melting point (34.69 ℃) of the p-cresol crystals, and the energy consumption is low.

Drawings

FIG. 1 is a flow chart of a process for separating m-cresol and p-cresol provided by the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all 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.

Referring to fig. 1, fig. 1 is a flow chart of a process for separating m-cresol and p-cresol according to the present invention. The method for separating the m-cresol and the p-cresol comprises a complex crystallization process and a melt crystallization process, wherein the complex crystallization process is used for extracting the m-cresol, and the melt crystallization process is used for extracting the p-cresol.

The complex crystallization process specifically comprises the following steps:

and (3) complexing reaction: carrying out complex reaction on mixed cresol containing m-cresol and p-cresol and a complexing agent;

and (3) crystallization separation: adding a solvent into the reaction liquid after the complex reaction for cooling crystallization, and then separating crystals and filtrate by filtration;

dissolving and decomplexing: adding a decomplexing agent into the separated crystal for decomplexing to obtain m-cresol with the purity of more than 99.9%;

and (3) rectification: rectifying the filtrate obtained in the crystallization separation step to separate out a solvent to obtain mixed cresol 1, wherein the mixed cresol 1 enters a p-cresol extraction step, and the solvent can be reused; and after the complex crystal dissolved and decomplexed is dissolved by water and m-cresol is separated out, the formed complexing agent aqueous solution is rectified and separated to respectively obtain a decomplexer and a complexing agent, and the decomplexer and the complexing agent can be recycled. Preferably, the decomplexing agent is water.

The melt crystallization process specifically comprises the following steps:

melting and crystallizing: and adding the mixed cresol 1 into a melt crystallization device for melt crystallization to obtain p-cresol and mixed cresol 2 with the purity of more than 99.9%, repeating the steps for the mixed cresol 2 to extract m-cresol, and entering the whole separation process again.

The melt crystallization device comprises a crystallization section, a sweating section and a melting section, wherein the crystallization section is positioned at the upper part of the melt crystallization device, the melting section is positioned at the lower part of the melt crystallization device, and the sweating section is positioned between the crystallization section and the melting section. Preferably, the temperature of the crystallization zone is not less than 2 ℃.

The melt crystallization device also comprises a pump and a stirring component, wherein the pump is arranged outside the melt crystallization device, the stirring component is arranged inside the melt crystallization device, and the pump and the melt crystallization device are matched to promote the circulation of molten liquid and strengthen the mass transfer between solid and liquid.

The whole process only has a raw material mixed cresol inlet and m-cresol and p-cresol product outlets, other solvents, decomplexers and complexing agents can circulate in the system, and lost solvents, decomplexers and complexing agents can be replenished in the process at any time.

Example 1

50g of m-cresol and p-cresol in a mass ratio of 3: 2, adding industrial cresol into a three-neck flask, and adding complexing agent urea into the three-neck flask. After the addition, the three-neck flask is put into an oil bath, the temperature of the complex reaction is 95 ℃, the reaction time is 1h, and the nitrogen protection is carried out in the reaction process. And (4) taking out the three-neck flask and adding a solvent toluene when the complexation reaction time is over. And after the toluene is dropwise added, transferring the three-neck flask to a low-temperature constant-temperature tank, and crystallizing for 2 hours at the temperature of-20 ℃. And after the crystallization is finished, quickly carrying out vacuum filtration on the reaction liquid, separating to obtain m-cresol complex crystals and filtrate, and storing the filtrate for later use. Adding de-complexing agent deionized water with the mass being three times that of the m-cresol complex crystal into the m-cresol complex crystal obtained after suction filtration for decomplexing; and (3) forming a mixed solution of an organic phase and a water phase after the crystals of the m-cresol complex are completely pyrolyzed, wherein the m-cresol generated after pyrolysis exists in the organic phase, and the urea is dissolved in the water phase. The solution after pyrolysis was poured into a separatory funnel and allowed to stand to separate into a lower aqueous phase and an upper organic phase. Separating the lower aqueous phase to obtain the upper organic phase, namely obtaining m-cresol, wherein the purity of the m-cresol is more than 99.9%.

And taking the filtrate rich in the p-cresol, and performing rotary evaporation to remove toluene to obtain a mother solution for melt crystallization. Adding a certain amount of the mother liquor of the melt crystallization into a three-neck flask, stirring and cooling to 5 ℃, adding p-cresol seed crystals, keeping the temperature of 5 ℃ constant for 12 hours, crystallizing the p-cresol in the mother liquor of the melt crystallization, and changing the reaction liquid into a pasty crystal liquid mixture. Adding a small amount of quartz cotton into the bottom of a crystallization tube, adding 25g of the crystal liquid mixture into the crystallization tube after the temperature in the crystallization tube is stabilized at 5 ℃, inserting a dryer into the upper end of the crystallization tube, starting to exhaust air from an exhaust opening after crystals in the crystallization tube are stabilized for 10 minutes, starting to flow uncrystallized mother liquor into a flask from the lower end of the crystallization tube, starting to perform heating and sweating operation, heating the p-cresol crystals to 10 ℃ for 12 hours, separating impurity liquid in the p-cresol crystals after 12 hours, weighing the impurity liquid, analyzing the component content of the impurity liquid through gas chromatography, and heating and sweating to obtain the p-cresol crystals. After the sweating is finished, the p-cresol crystals are heated to 35 ℃ to melt out and discharge all liquid, and the liquid is a p-cresol product with the purity of more than 99.9%.

Compared with the prior art, the method for separating m-cresol and p-cresol provided by the invention respectively extracts and separates m-cresol and p-cresol by combining the complex crystallization process and the melt crystallization process, and has the following beneficial effects:

in the complexing crystallization process, because the p-cresol and the complexing agent do not generate complexing reaction, the m-cresol and the complexing agent react to generate a stable m-cresol complex, the m-cresol complex is cooled in a solvent to form m-cresol complex crystals, the p-cresol is dissolved in the solvent, the m-cresol complex and the p-cresol are easily separated, the m-cresol complex crystals are decomplexed by pyrolysis, and the purity of the m-cresol extracted through the complexing crystallization is up to more than 99.9%;

meanwhile, the complexing agent, the decomplexing agent and the solvent can be regenerated and recycled, so that the material consumption and the generation of three wastes are reduced;

the melt crystallization is carried out by controlling the temperature to be slightly lower than the melting point (34.69 ℃) of the p-cresol crystals and keeping for a relatively long period of time, the appearance properties of the p-cresol crystals become soft, impurity liquid in the p-cresol crystals is discharged, the p-cresol crystals with higher purity are obtained, and the purity of the p-cresol extracted by the melt crystallization is up to more than 99.9%;

the temperature of the process condition of melt crystallization is below the melting point (34.69 ℃) of the p-cresol crystals, and the energy consumption is low.

The above description is only an embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes, which are made by using the contents of the present specification and the accompanying drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.