KR101819217B1 - Method for separating position isomer of cresol - Google Patents

Abstract

The present invention relates to a method for separating a cresol position isomer, and more specifically, to a method for separating cresol in high purity from a cresol isomer by using an alkylation reaction for cresol isomers having similar physical and chemical properties, and for recycling byproducts. The method of the present invention includes an alkylation process of producing a first reaction product mixture, a first separation process, a second separation process, and a recycling process.

Description

METHOD FOR SEPARATING POSITION ISOMER OF CRESOL < RTI ID = 0.0 >

The present invention relates to a process for separating cresol regioisomers and more particularly to a process for separating cresol with high purity by using an alkylation reaction for a cresol isomer having similar physical and chemical properties, And a method for separating isomers.

Cresol is a methyl phenol aromatic organic compound, which may or may not be naturally occurring and may also be produced by organic synthesis.

Such cresol is also used as a local anesthetic, a disinfectant, a fumigant, an industrial solvent, a herbicide, a surfactant, and the like. In particular, in the field of various medicines and chemicals such as manufacturing of synthetic resin such as semiconductor encapsulating material, basic petrochemical product, , And is also widely used as a raw material for organic synthesis.

Cresol is sometimes found in the form of tartaric acid in many kinds of plants (wood tar), crude oil, coal tar (coal tar), etc., and is formed by decomposition of natural organic matter by soil and underwater microorganisms.

The cresol compound may be obtained by distillation purification, which is contained in a mixture present in nature as described above, or may be obtained by organic synthesis.

However, since natural materials such as coal tar contain many physical chemical properties similar to cresol, such as pyridine, methylpyridine, aniline, and xylenol, it is difficult to distill, and these substances remain in the purified product, It is not easy to obtain a cresol having a high purity and is not suitable for use in the above applications.

The alkylation reaction of phenol is widely used industrially, and a magnesium oxide catalyst or an iron-vanadium catalyst is widely used as an alkylation catalyst. However, there are problems in view of severe reaction conditions, catalytic activity, and life span, There are also environmental problems that arise from doing.

In addition, in the alkylation reaction as described above, zeolenol, trimethylphenol, poly (alkyl) phenol, and high molecular weight polymer materials are generated as byproducts, which can inhibit the reaction. Such byproducts have a boiling point similar to that of cresol, There is a problem that is difficult to bet.

In particular, cresol may be present in the form of ortho, o-, meta, m-, para-, and para- isomers, and natural or synthetic cresols are mixed therewith. Can be separated by a distillation method using a difference in boiling point. However, isomers of benzene ring compounds have similar physical and chemical properties, so it is difficult to separate them in high purity by using a general distillation column. Also, in the case of cresol, it is very difficult to separate by the distillation method because the meta and para isomers have very similar boiling points.

Therefore, it is still necessary to study a method for separating cresol positional isomers, which can separate positional isomers of cresol with high purity.

The present invention relates to a process for separating cresol position isomers which can be separated at high purity using alkylation and de-alkylation for cresol position isomers having similar physical and chemical properties.

The present invention relates to a process for the preparation of a cure compound which comprises reacting a cresol-regioisomeric mixture with an ethylenically unsaturated compound having 2 to 10 carbon atoms to form an unreacted cresol, a mono-alkylated cresol, a di-alkylated cresol, An alkylation step to produce a first reaction product mixture comprising a tri-alkylated cresol;

Separating the first reaction product mixture into a low-boiling by-product having a boiling point of 180 캜 or less, a di-alkylated cresol, and a high boiling point product having a boiling point of 300 캜 or higher;

Separating the positional isomers of di-alkylated cresol by fractional distillation according to the difference in boiling point, and de-alkylating to obtain a positional isomer of the separated cresol, respectively; And

Wherein the low boiling point byproduct and the high boiling point by-product are recycled to the alkylation step after de-alkylation.

To provide a method for separating cresol positional isomers.

According to the separation method of the cresol position isomer of the present invention, it is possible to separate the positional isomer of cresol from the reaction system with high purity, and the by-product can be reintroduced into the reactor again, Cresol positional isomers.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a conceptual diagram of a continuous reaction apparatus capable of performing a separation method of a cresol position isomer according to an example of the present invention. FIG.

The cresol position isomer separation method of the present invention comprises reacting a cresol position isomer mixture with an ethylenically unsaturated compound having 2 to 10 carbon atoms to produce an unreacted cresol, a mono-alkylated cresol, a di- alkylated cresol, and tri-alkylated cresol, wherein the first reaction product mixture comprises a first reaction product mixture;

Separating the first reaction product mixture into a low-boiling by-product having a boiling point of 180 캜 or less, a di-alkylated cresol, and a high boiling point product having a boiling point of 300 캜 or higher;

Separating the positional isomers of di-alkylated cresol by fractional distillation according to the difference in boiling point, and de-alkylating to obtain a positional isomer of the separated cresol, respectively; And

Wherein the low boiling point byproduct and the high boiling point by-product are recycled to the alkylation step after de-alkylation.

According to an embodiment of the present invention, in the first separation step, the unreacted cresol and the mono-alkylated cresol in the first reaction product mixture may be separately recycled to the alkylation step have.

The low boiling point byproduct may include a product resulting from self-alkylation of the ethylenically unsaturated compound, and the high boiling point byproduct may include an O-alkylation tri- alkylated cresol.

Also, the positional isomer of cresol obtained by separation in the second separation step may include m-cresol and p-cresol.

According to another embodiment of the invention, the alkylation step may be carried out at a temperature of from 50 to 80 DEG C and a pressure of from 1 to 3 bar, in which the cresol and the ethylenically unsaturated compound are reacted in an amount of from about 1: May be included in a weight ratio of about 1: 3.

The alkylation step may be carried out in the presence of an acid catalyst.

According to another embodiment of the invention, the second separation step may be carried out at a temperature of about 200 to about 250 DEG C and a pressure of about 1 to about 3 bar.

The above-described process proceeds in a continuous circulation process in view of the separation yield of the cresol position isomer and the recycling efficiency of the by-product.

In the present invention, the terms first, second, etc. are used to describe various components, and the terms are used only for the purpose of distinguishing one component from another.

The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, the terms "comprises" or "having", etc., are intended to specify that there are performed features, numbers, steps, components, or combinations thereof, and that one or more other features, Elements, or combinations thereof, as a matter of principle.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Throughout this specification, the cresol position isomer encompasses all ortho-, meta-, and para-cresol unless otherwise specified.

And, the cresol-regioisomer mixture means a mixture comprising at least one of the cresols of the above-mentioned type, and further comprising another separable compound.

Unless otherwise specified, alkyl-substituted cresol refers to ortho-, meta-, and para-cresol as described above, and mono-alkyl substituted cresol refers to an alkyl substituted cresol having 2 to 3 carbon atoms in which a benzene ring is substituted with a hydroxy group and a methyl group Means a form in which an alkyl group is further substituted in one of unsubstituted arbitrary benzene ring carbons in a substituted form of cresol, and the term "di-alkyl substituted cresol" means a form in which a benzene ring is substituted with a hydroxyl group and a methyl group Means a form in which two of the unsubstituted benzene ring carbons in the cresol are further substituted with an alkyl group. The term "tri-alkyl substituted cresol" refers to a form in which in a cresol of a disubstituted form in which a benzene ring is substituted with a hydroxy group and a methyl group, Means a form in which two of the unsubstituted arbitrary benzene ring carbon atoms are further substituted with an alkyl group.

Hereinafter, the present invention will be described in more detail.

A method for separating cresol regioisomers according to one aspect of the present invention comprises reacting a cresol regioisomeric mixture with an ethylenically unsaturated compound having from 2 to 10 carbon atoms to produce unreacted cresol, mono-alkylated cresol, An alkylation step to produce a first reaction product mixture comprising di-alkylated cresol, and tri-alkylated cresol;

Separating the first reaction product mixture into a low-boiling by-product having a boiling point of 180 캜 or less, a di-alkylated cresol, and a high boiling point product having a boiling point of 300 캜 or higher;

Separating the positional isomers of di-alkylated cresol by fractional distillation according to the difference in boiling point, and de-alkylating to obtain a positional isomer of the separated cresol, respectively; And

Wherein the low boiling point byproduct and the high boiling point by-product are recycled to the alkylation step after de-alkylation.

Cresol is a compound in which a benzene ring is substituted with a hydroxy group and a methyl group. Depending on the substitution position, there are three isomers of an ortho-isomer, a meta-isomer and a para-isomer. Of these, o-cresol has a boiling point different from m- and p-cresol, and can be easily separated into high purity by a precision distillation method.

However, since m- and p-cresol have a boiling point difference of only about 0.8 degree, they can not be separated according to a conventional distillation method, and it is very difficult to separate them into high purity even if a precision distillation method is used.

Accordingly, the present invention employs a method of reacting a cresol positional isomer mixture and an ethylenically unsaturated compound having 2 to 10 carbon atoms to introduce an alkyl group into a benzene ring of cresol.

The ethylenically unsaturated compound can introduce an alkyl group into the benzene ring through an alkylation reaction under an acid catalyst. Such an ethylenically unsaturated compound is a linear or branched alkene compound having 2 to 10 carbon atoms containing a carbon-carbon double bond and specifically includes, for example, ethene, propene, butene, butene, isobutene, pentene, isopentene, and hexene. However, the present invention is not limited thereto.

Particular preference is given to propyne (CH ₂ ═CH-CH ₃ ), butyne (CH ₂ ═CH-CH ₂ -CH ₃ ) or isobutene (CH ₂ ═C (CH ₃ ) ₂ , It may be most preferable to use isobutene in order to secure an easy boiling point difference.

According to an embodiment of the present invention, the alkylation reaction as described above may be performed under acid catalyst conditions, and more preferably, it may be carried out under a pH of about 1 or less.

In such acidic conditions, the ethylenically unsaturated compound described above may be introduced in the form of an alkyl group in the aromatic ring after undergoing a carbon cationic reaction intermediate form.

And wherein the alkylation step may be conducted at a temperature of about 50 to about 80 < 0 > C and a pressure of about 1 to about 3 bar.

Under the conditions of the temperature and the pressure lower than the reaction conditions of the above range, the progress of the reaction may be remarkably slowed, and in particular, the ratio of the mono-alkyl substituted cresol product which does not greatly contribute to the separation of the cresol position isomer If the reaction is carried out under the conditions of temperature and pressure higher than the above range, the degree of substitution becomes too high and separation may become difficult.

Also, as an example, in the alkylation step, the cresol and the ethylenically unsaturated compound may preferably be included in a weight ratio of about 1: 1.5 to about 1: 3. When the content of the ethylenically unsaturated compound is lower than the above range, the reaction rate may become slower and the proportion of the mono-alkyl-substituted cresol product may be increased. When the content of the ethylenically unsaturated compound is higher than the above range, The degree of substitution of the alkyl group in the benzene ring becomes too high, so that separation may become difficult.

When the alkylation reaction is complete, the pH is neutralized by treatment with a base to terminate the reaction, and the unreacted cresol, mono-alkylated cresol, di-alkylated cresol, and tri Lt; RTI ID = 0.0 > tri-alkylated < / RTI > cresol.

And separating the first reaction product mixture into low-boiling by-products having a boiling point of 180 ° C or lower, di-alkylated cresol, and high-boiling by-products having a boiling point of 300 ° C or higher from the boiling point difference do. For separation using boiling point difference, that is, fractional distillation, one or more distillation columns may be connected in parallel.

When using a distillation column, for example, the low boiling point byproduct may be discharged to the top of the distillation column, and the unreacted cresol, mono-alkylated cresol as described above may be discharged to the side of the distillation column, Di-alkylated cresol and high boiling point byproducts having a boiling point of 300 DEG C or higher can be discharged to the bottom of the distillation column.

At this time, in the first separation step, the unreacted cresol and the mono-alkylated cresol in the first reaction product mixture are separated and discharged to the side of the distillation column, . Alkyl-substituted cresol and mono-alkyl-substituted cresol have a boiling point that is significantly different from the di-alkyl substituted cresol, which is the desired reaction intermediate in the present invention, so it is not difficult to separate them by distillation, The separation efficiency can be increased.

The recycled unreacted cresol and mono-alkylated cresol are further subjected to an alkylation reaction in the alkylation stage to produce a di-alkylated cresol and / or a high boiling point having a boiling point of at least 300 & By-products.

The positional isomers of the di-alkylated cresol may be separated by fractional distillation according to the difference in boiling point, and may be subjected to de-alkylation to obtain separated positional isomers of cresol. That is, when a di-alkyl substituted cresol position isomer mixture is formed from the first reaction product, the di-alkyl substituted m-cresol and the di-alkyl substituted p-cresol can be separated by distillation using boiling point difference.

When m-cresol and p-cresol have different substituent positions in the benzene ring, the position of the reaction where the alkylation takes place is changed when a disubstituted alkylation reaction is carried out. As a non-limiting example, In the case of m-cresol, the product in which the alkyl group is substituted at positions 4 and 6 is main, and in the case of p-cresol, the product in which the alkyl group is substituted at positions 1 and 6 is main.

As the substitution positions of the alkyl groups in the respective products are different from each other, the boiling points of the final products are also different from each other. Specifically, for example, when two t-butyl groups are substituted on the benzene ring of the cresol , The boiling point of di-t-butyl-m-cresol and di-t-butyl-p-cresol differs by about 20 ° C. Therefore, when distillation is carried out using this, it becomes possible to separate the compound derived from m-cresol and the compound derived from p-cresol, respectively, with high purity.

Thereafter, it is possible to obtain m-cresol and p-cresol by di-alkylation from di-alkyl substituted m-cresol and di-alkyl substituted p-cresol, respectively, separated by distillation.

According to one example, the dealkylation of the second separation step may be conducted at a temperature of from about 200 to about 250 < 0 > C and a pressure of from about 1 to about 3 bar.

When the temperature or the pressure is lower than the above range, the activation energy required for the alkyl removing reaction is not sufficiently provided, and the reaction may not proceed smoothly. If the temperature or the pressure is higher than the above range, The energy efficiency becomes low and the economical efficiency becomes low.

The low boiling point byproduct and the high boiling point by-product are each re-introduced into the alkylation step after de-alkylation.

The low boiling point byproduct is a mixture containing a group of compounds having a boiling point of about 180 DEG C or lower, such as a product resulting from the self-alkylation reaction of the ethylenically unsaturated compound, and can be discharged to the upper portion of the distillation column. And after the separation, it can be regenerated as the original ethylenically unsaturated compound by proceeding with the dialkylation. Specifically, for example, the low boiling point byproduct may include an oligomer such as a dimer, a trimer, or the like of the ethylenically unsaturated compound. Can be reintroduced into the alkylation reaction in the form of the ethylenically unsaturated compound thus isolated and regenerated.

The higher boiling point byproduct may be a tri-alkyl substituted cresol, and more specifically, an O-alkylation tri-alkylated cresol such as alkylated at an oxygen atom position, ≪ / RTI > and mixtures thereof. These high boiling point byproducts can also be easily separated since they have a very high boiling point and can be discharged to the bottom of the distillation column. When the dialkylation is carried out after separation, the original cresol, mono-substituted cresol, or di- Can be converted and, in this form, can be reintroduced into the alkylation reaction.

At this time, it is preferable that the dealkylation in the second separation step proceeds in the reverse reaction of the above-mentioned alkylation reaction under pH conditions at which the acid catalyst can be regenerated. That is, the separation yield of cresol can be greatly increased under the condition that the reverse reaction of the alkylation is dominant, in which the alkyl group derived from the alkylation of the ethylenically unsaturated compound is removed from the benzene ring and then regenerated with the original ethylenically unsaturated compound .

Thereafter, the pH is adjusted through the base treatment, so that each cresol isomer, which is the final product, can be obtained.

The separation method according to an example of the present invention is advantageous in terms of separation efficiency and by-product recycling that proceeds by a continuous circulation process.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a conceptual diagram of a continuous reaction apparatus capable of performing a separation method of a cresol position isomer according to an example of the present invention. FIG.

1, the continuous reaction apparatus includes an alkylation reactor 100 for carrying out an alkylation reaction between a cresol-regioisomer mixture and an ethylenically unsaturated compound having 2 to 10 carbon atoms;

Separating the first reaction product mixture into low boiling point byproducts having a boiling point of 180 占 폚 or less, di-alkylated cresol, and high boiling point products having a boiling point of 300 占 폚 or higher; Distillation section 200;

A second distillation section 300 for carrying out a second separation step in which the positional isomer of di-alkylated cresol is separated by fractional distillation according to the boiling point difference;

Dialkylation reactors 410 and 420 to remove alkyl groups from each of the di-alkyl substituted m-cresol and di-alkyl substituted p-cresol to obtain m-cresol and p-cresol (510 and 520) can do.

The low boiling point byproduct and the high boiling point byproduct may be re-introduced into the alkylation reactor 100 after the alkyl group is removed through a separate dialysis reactor 430 in which the reaction for removing the alkyl group proceeds, .

Specific reactions and conditions undergoing each step are as described above.

Best Mode for Carrying Out the Invention Hereinafter, the operation and effect of the invention will be described in detail with reference to specific embodiments of the invention. It is to be understood, however, that these embodiments are merely illustrative of the invention and are not intended to limit the scope of the invention.

< Example >

Halotoluene  And basic aqueous solution

The mixture in which the cresol and the ethylenically unsaturated compound were mixed in the same weight ratio as shown in Table 1 was introduced into an alkylation reactor of a continuous separator and subjected to an alkylation reaction at a reaction temperature of 60 ° C and a reaction pressure of 2 Bar for 4 hours . The pH of the reaction was below 1, and sulfuric acid was used as the acid catalyst, which does not directly affect the reactants or products of the alkylation reaction.

In the following Tables 1 to 3, the ratio (%) of each compound means% by weight.

m-cresol 22% p-cresol 11% Iso-butylene 67%

The reaction was stopped by adding an equivalent amount of NaOH required for neutralization to the inside of the reactor using a decanter, and the composition of the first reaction product mixture was confirmed.

Cresol One% Mono-butyl-cresol (1 alkyl substituted) 10% di-butyl-m-cresol (2 alkyl substituted) 27% di-butyl-p-cresol (di alkyl substituted) 49% Low-boiling by-product 10% High boiling point byproduct 3%

In the first reaction product mixture, Mono-butyl-cresol, low-boiling by-products, and high boiling point by-products were separated through a distillation unit of a continuous-type reaction apparatus and, if necessary, subjected to a dialkylation reaction and then re- Di-butyl-m-cresol and di-butyl-p-cresol, which are two alkyl-substituted cresols, were each separated through a distillation unit of a continuous reaction apparatus and transferred to a reactor for removing alkyl groups.

The transferred di-butyl-m-cresol and di-butyl-p-cresol were subjected to a dealkylation reaction at a reaction temperature of 230 ° C. and a reaction pressure of 2 Bar for 2 hours. During the reaction, the pH was less than 1 and the pH was controlled by using sulfuric acid.

As a result of separating cresol through the continuous reaction, m-cresol and p-cresol could be separated at the purity as shown in Table 3 below.

The isolated p-cresol moiety The isolated m-cresol moiety m-cresol 0.5% m-cresol 99% p-cresol 99% p-cresol 0.5% Mono-butyl-p-cresol 0.5% Mono-butyl-p-cresol 0.5%

Referring to Table 3, it can be seen that m-cresol and p-cresol having almost no difference in boiling point were separated at a high purity of about 99% according to the embodiment of the present invention.

100: alkylation reactor
200: first distillation section
201: low boiling point byproduct
300: Second Distillation Unit
301: high boiling point byproduct
410, 420: a dealkylation reactor in the second separation stage
430: Dealkylation reactor in the recycle stage
510, 520: cresol

Claims (10)

The cresol positional isomeric mixture is reacted with isobutene to yield unreacted cresol, mono-alkylated cresol, di-alkylated cresol, and tri-alkylated cresol. An alkylation step to produce a first reaction product mixture;
Separating the first reaction product mixture into a low-boiling by-product having a boiling point of 180 캜 or less, a di-alkylated cresol, and a high boiling point product having a boiling point of 300 캜 or higher;
The positional isomer of di-alkylated cresol is fractionally distilled according to the difference in boiling point to separate di-t-butyl-m-cresol and di-t-butyl-p-cresol, alkylation to obtain m-cresol and p-cresol, respectively; And
Wherein the low boiling point byproduct and the high boiling point by-product are recycled to the alkylation step after de-alkylation.
A method for separating cresol positional isomers.
The method according to claim 1,
In the first separation step, the unreacted cresol and the mono-alkylated cresol in the first reaction product mixture are separated and re-introduced directly into the alkylation step.
The method according to claim 1,
Wherein the low boiling point byproduct comprises a product by isobutene self alkylation reaction.
The method according to claim 1,
Wherein the high boiling point byproduct comprises an O-alkylation tri-alkylated cresol at an oxygen atom position.
delete The method according to claim 1,
Wherein the alkylation step is carried out at a temperature of from 50 to 80 &lt; 0 &gt; C and a pressure of from 1 to 3 bar.
The method according to claim 1,
In the alkylation step, the cresol enriched isomer mixture and isobutene are contained in a weight ratio of 1: 1.5 to 1: 3.
The method according to claim 1,
Wherein the alkylation step is carried out in the presence of an acid catalyst.
The method according to claim 1,
Wherein the second separation step is carried out at a temperature of from 200 to 250 DEG C and a pressure of from 1 to 3 bar.
The method according to claim 1,
Wherein the process proceeds to a continuous recycle process.

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