KR101753291B1 - Method for extracting cresol - Google Patents

Abstract

A method for extracting cresol, comprising the steps of: producing cresol (cresol ion) through hydrolysis of halotoluene in a basic aqueous solution; Adding an acid to the product of the step of producing the cresol and adjusting the pH to convert the cresolate to cresol; Separating the pH-controlled product into an oil-soluble layer and a water-soluble layer, and then recovering the oil-soluble layer; And adding an organic solvent to the separated water-soluble layer to extract residual cresol from the water-soluble layer into the organic solvent layer.

Description

{METHOD FOR EXTRACTING CRESOL}

And a method for extracting cresol.

Cresol is widely used as a raw material for organic synthesis in medical and chemical fields such as being used for the production of synthetic resin such as local anesthetic agent, disinfectant, surfactant and semiconductor sealing agent.

Cresol can be obtained in natural state such as crude oil, coal, tar, etc., or by organic synthesis. However, since the natural cresol contains many organic materials having similar physical properties to cresol, such as pyridine, aniline, and xylenol, it is difficult to purify the cresol. Therefore, in applications where high purity cresol is required, cresol production by organic synthesis is preferred .

Thus, cresol is produced by organic synthesis in various industrial fields, and there is a problem that cresol is a very harmful substance to the environment and human body.

Therefore, the residual cresol should not be detected in the waste liquid generated during the cresol manufacturing process. Therefore, it is necessary to maximize the yield by collecting the entire amount of cresol produced.

The prior art of the cresol production process through the hydrolysis reaction requires that the cresol remaining in the receptive layer is extracted at least twice after the hydrolysis reaction and after the pH adjustment to completely remove the remaining cresol in the receptive layer. Accordingly, a multi-stage extraction column is required in an actual commercial process, which complicates the extraction process and increases the operating cost and investment cost due to the complexity of the process.

Therefore, it is required to develop a process for separating cresol from a product formed by a hydrolysis reaction more easily and reliably by simplifying the extraction process of cresol.

One embodiment of the present invention is a method for extracting cresol which can increase the extraction efficiency and reduce the operation cost and the investment cost by simplifying the extraction process at the time of cresol extraction in the product after the production of cresol by hydrolysis and pH control .

One embodiment of the present invention is a method for producing cresol (cresol ion) by hydrolysis of halotoluene in a basic aqueous solution; Adding an acid to the product of the step of producing the cresolate and adjusting the pH to convert the cresolate to cresol; Separating the pH-controlled product into an oil-soluble layer and a water-soluble layer, and then recovering the oil-soluble layer; And adding an organic solvent to the separated water-soluble layer to extract residual cresol from the water-soluble layer into the organic solvent layer.

Separating the pH-controlled product into an oil-soluble layer and a water-soluble layer, and recovering the oil-soluble layer, wherein the cresol recovered through the oil-soluble layer comprises 99% or more, and the concentration of cresol in the separated water-soluble layer may be 10,000 ppm or less.

The extracting may be performed one or more times.

The step of adding the acid and adjusting the pH to convert the cresolate to cresol may be carried out using an acid having a pKa value of -6 or less.

In the step of adding the acid and adjusting the pH to convert the cresolate to cresol, the pH may be adjusted to 2.5 or less.

The step of producing the cresolate may be carried out under a condition of pH 11 or higher.

In the step of extracting the cresol, the organic solvent may have a DI value of 20 or less.

In the step of extracting the cresol, the amount of the added organic solvent may be 10 parts by weight or more and 200 parts by weight or less based on 100 parts by weight of the total amount of the products produced in the step of producing the cresol.

Separating the pH-controlled product into an oil-soluble layer and a water-soluble layer, and recovering the oil-soluble layer may be carried out by decanting.

Separating the pH-controlled product into an oil-soluble layer and a water-soluble layer, and recovering the oil-soluble layer may be performed at a temperature of 0 ° C or higher and 100 ° C or lower have.

The step of extracting the cresol may be performed at a temperature of 0 ° C or higher and 55 ° C or lower.

According to the cresol extraction method of the embodiment of the present invention, the extraction efficiency of the cresol produced through the simplified process can be greatly increased, and the extraction solvent consumed in the extraction process can be minimized, The effect of reducing the investment cost can be realized.

In addition, since the extraction efficiency is increased, the amount of residual organic compounds in the reaction waste is reduced at a low cost, which is advantageous in terms of economy and environment.

Unless defined otherwise, all terms (including technical and scientific terms) used herein may be used in a sense commonly understood by one of ordinary skill in the art to which this invention belongs. Whenever a component is referred to as "including" an element throughout the specification, it is to be understood that the element may include other elements, not the exclusion of any other element, unless the context clearly dictates otherwise. Also, singular forms include plural forms unless the context clearly dictates otherwise.

Throughout this specification, the term "cresol" encompasses both ortho, meta, and para cresols.

The term "halotoluene" as used throughout the present specification refers to a compound in which one of the hydrogen atoms of the benzene ring in toluene is replaced with a halogen atom including chlorine (Cl), bromine (Br), or fluorine (F) Also, it covers both ortho, meta, and para forms.

One embodiment of the present invention is directed to a process for producing cresol, comprising: producing cresolate through hydrolysis of halotoluene in a basic aqueous solution; Adding an acid to the product of the step of producing the cresolate and adjusting the pH to convert the cresolate to cresol; Separating the pH-controlled product into an oil-soluble layer and a water-soluble layer, and then recovering the oil-soluble layer; And adding an organic solvent to the separated water-soluble layer to extract residual cresol from the water-soluble layer into the organic solvent layer.

The prior art of the cresol production process through the hydrolysis reaction requires at least two extractions after the hydrolysis and pH adjustment to completely remove the remaining cresol in the water-soluble layer. Therefore, a multi-stage extraction column is required in an actual commercial process, and the extraction process becomes complicated, and there is a problem that the operation cost and the investment cost are increased due to the complexity of the process. The method of extracting cresol according to an embodiment of the present invention was invented by the present inventors after the study of Django to solve such a problem.

Hereinafter, specific contents and advantageous effects of each step of the cresol extraction method according to an embodiment of the present invention will be described.

Separating the pH-controlled product into an oil-soluble layer and a water-soluble layer, and then recovering the oil-soluble layer

 In the method of extracting cresol according to an embodiment of the present invention, prior to solvent extraction of cresol in a water-soluble layer, the oil-soluble layer and the water-soluble layer are preferentially separated. Thus, a considerable amount of cresol produced by the hydrolysis reaction and the pH control process can be separated first through separation of the oil-soluble layer, and a small amount of cresol dissolved in the water-soluble layer can be completely separated by one extraction process. Specifically, the concentration of the residual cresol in the water-soluble layer may be less than 10 ppm by only one extraction step. As a result, the extraction efficiency of cresol can be greatly increased, and the extraction solvent consumed in the extraction process can be minimized according to the simplification of the extraction process, thereby reducing the operation cost and the investment cost for the entire extraction process. In addition, as the extraction process is simplified, the cresol can be separated with high efficiency using only one mixer-settler, so that the operation cost and the investment cost of the extraction process can be reduced as the process is simplified. In addition, the amount of residual organic compounds in the reaction waste can be reduced at low cost, which is advantageous in economic and environmental aspects.

The product in the step of producing cresolate (cresol ion) through the hydrolysis reaction of halotoluene in a basic aqueous solution includes water as a solvent, cresolate, by-products and reaction residues and the like. The cresolate is converted into cresol by controlling the pH. At this time, the water-soluble substance such as cresol and water are not mixed with each other, so that the layer can be separated. As a result, an oil-soluble layer containing a significant amount of the generated cresol and a water-soluble layer containing a small amount of cresol dissolved in water are layered. At this time, the cresol recovered through the oil-soluble layer may be more than 99% of the total generated cresol.

Recovering the pH-regulated product into an oil-soluble layer and a water-soluble layer, and then recovering the oil-soluble layer, wherein the recovery of the oil-soluble layer comprises: Recovery of only the water-soluble layer in the separated state, or the like.

At this time, the concentration of cresol in the separated water-soluble layer may be 10,000 ppm or less. This is because prior to solvent extraction of the cresol in the water soluble layer, a significant amount of cresol was first removed through separation of the oil soluble layer. Since the concentration of cresol in the separated water-soluble layer is 10,000 ppm or less, separation can be performed so that the concentration of the remaining cresol in the water-soluble layer is less than 10 ppm by one extraction step. The concentration of cresol in the separated water-soluble layer is more specifically 5,000 ppm or less; Or 2,000 ppm or more and 5,000 ppm or less.

The extracting step may be performed one or more times, and the effect according to one embodiment of the present invention is that the residual cresol in the water-soluble layer can be separated with high efficiency even if the extraction step is performed only once .

In this step, various known methods can be adopted as a method of separating the oil-soluble layer and the water-soluble layer. As an example, it can be separated by decanting.

In addition, this step may be performed at a temperature of 0 ° C or more and 100 ° C or less. As supported in the examples described below, when decanting is carried out in this temperature range, the concentration of cresol in the separated water-soluble layer exhibits a level of 3,000 ppm to 4,000 ppm. The higher the temperature, the more the cresol content tends to increase. The higher the temperature, the more the cresol solubility increases slightly. However, since the difference in solubility according to temperature is not large, the efficiency of decanting by temperature can be considered to be determined by the layer separation time. Accordingly, the operation temperature can be adjusted between 0 ° C and 100 ° C depending on the situation, but when the actual operation cost is taken into consideration, the temperature of 40 ° C to 60 ° C may be appropriate.

In a basic aqueous solution Halotoluene  Through the hydrolysis reaction Cresolate  Steps to create

Halotoluene can be converted to hydroxide ion in a basic aqueous solution by a halogen atom to produce various types of cresol isomer mixtures. This can be done under high temperature and high pressure conditions.

At this time, the step of reacting the halotoluene and the basic aqueous solution may be carried out at a pH of 11 or higher. The hydroxide ion used may preferably be derived from a metal hydroxide aqueous solution such as sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide or the like, but the present invention is not necessarily limited thereto.

That is, in the hydrolysis reaction for the reaction, the hydroxide ion may be added in an excess amount relative to the halotoluene, and after the reaction, the acceptor layer may show a very strong basicity due to excessive hydroxide ions. Therefore, the product cresolate is present in the water-soluble layer as an anion, and as a result, the equilibrium migration of the whole reaction can be led toward the reactant, thereby increasing the yield of cresol.

The hydrolysis reaction of halotoluene can be carried out under temperature conditions of 200 ° C or more and 450 ° C or less and pressure conditions of 100atm or more and 500atm or less.

When the reaction temperature is too low in the hydrolysis reaction, the conversion of halotoluene and the selectivity and yield of cresolate may be decreased. When the temperature is too high, the operation ratio for high temperature operation becomes high, There is a possibility that the economical efficiency is low.

Also, when the reaction pressure is too low, the conversion of halotoluene and the selectivity and yield of cresolato decrease, and when the pressure is too high, there is a problem that the apparatus ratio increases due to the provision of high-pressure equipment.

remind Cresolate  The acid is added to the product of the producing step and the pH is adjusted to convert the cresolate to cresol step

After reaction, most of the product cresol isomers are present in the water-soluble layer in the form of cresolates (cresol anions). Since cresolates can not be commercialized when they are dissolved in a water-soluble layer, they need to be cresolized and extracted from a water-soluble layer.

To this end, an acid may be added after the hydrolysis reaction to acidify.

The added acid may be a strong acid having a pKa value of about -6 or less. For example, hydrochloric acid, chloric acid, chloric acid, bromic acid, nitric acid, dilute sulfuric acid and the like can be mentioned, but the present invention is not necessarily limited thereto, and it is also possible to provide sufficient hydrogen atoms to the cresol anion or cresol, Can be used without any particular limitation.

The pH of the product formed by the hydrolysis reaction through the addition of the acid is 2.5 or less, specifically -5 or more and 2.5 or less, more specifically -5 or more and 1.5 or less; Or -5 or higher and 1.0 or lower. The range of pH is related to the separation efficiency in the subsequent separation of the oil-soluble layer and the water-soluble layer. As can be seen from the following examples, the lower the pH, the faster the separation of the oil-soluble layer and the water-soluble layer. At pH 1, the separation of the two layers can be almost completed within 2 minutes upon decanting.

In addition, when the pH was 1, the cresol concentration of the water soluble layer was lower than 3,000 ppm after decanting, and the lower the pH, the lower the cresol concentration of the water soluble layer.

Extracting cresol from the water-soluble layer to the organic solvent layer

The cresol converted from the water-soluble cresolate to the oil-soluble form by the acid treatment can be extracted from the water-soluble layer by adding an organic solvent. The organic solvent usable here may be any organic solvent capable of classifying the cresol in the receptive layer, and may have an DI value of about 20 or less. The DI value refers to the dielectric constant or relative permittivity and the value refers to the ratio of the absolute permittivity of the material to the vacuum permittivity. That is, the higher the dielectric constant, the more polarity like water, and the smaller the dielectric constant, the more nonpolar it is for extraction from the receiving layer.

For example, benzene, toluene, methyl tert-butyl ether (MTBE), methyl isobutyl ketone (MIBK), isobutyl acetate (iBA) or a mixture thereof may be used. In addition, hexane, heptane, , Or xylene, etc., can be used without any particular limitation.

The organic solvent may be at least 10 parts by weight and at most 200 parts by weight based on 100 parts by weight of the total amount of the products produced in the step of producing the cresol. More specifically, it may be 20 parts by weight or more and 100 parts by weight or less.

When the organic solvent is used in an excessively small amount relative to the reaction product mixture containing cresol, separation of the cresol in the water-soluble layer is not easy, which may cause environmental problems due to excessive cresol in the water-receiving layer. There is a problem that the purity drops. When the organic solvent is too much in comparison with the reaction product mixture containing cresol, the content of the organic solvent in the cresol after the extraction process is high, which requires a separate process for separating the organic solvent.

The extracting may be performed at a temperature of 0 ° C or higher and 55 ° C or lower. More specifically at a temperature of 20 ° C or more and 40 ° C or less. If the temperature is too low during the extraction, there may be a problem of lowering the extraction rate. In addition, since the optimum operation temperature of the upper layer separation step before the extraction step is 40 ° C to 60 ° C, there is no need to carry out a cooling process more than necessary. On the other hand, when the MTBE used in the examples is used as an extraction solvent, considering that the boiling point of MTBE is 55 ° C, if the temperature is too high during extraction, the solvent may easily volatilize or the pressure may increase have.

Hereinafter, preferred embodiments and comparative examples of the present invention will be described. However, the following examples are only a preferred embodiment of the present invention, and the present invention is not limited to the following examples.

Examples 1 to 5

Production of Cresolate by Hydrolysis Reaction : In a continuous reactor, an aqueous solution of NaOH (10 wt%) and chlorotoluene were fed in a molar ratio of 2.5: 1 (NaOH: chlorotoluene) and maintained at 400 ° C. and 300 atm for 30 minutes , The hydrolysis reaction of chlorotoluene proceeded under basic conditions having a pH of about 13 to produce a cresolate (cresol ion) mixture.

pH adjustment and separation of the oil-soluble layer and the water-soluble layer : After 5 samples of 300 g of the resultant hydrolysis reaction, HCl was added to each of them to adjust the pH of the product to 1, 4, 7, 9 and 13 , Corresponding to Examples 1 to 5). It was then transferred to a decanter and decanting was carried out at 60 ° C for 5 minutes to separate the oil-soluble and water-soluble layers. The lower the pH was, the faster the separation of the oil-soluble layer and the water-soluble layer proceeded. In the case of Example 1, which was pH 1, the separation was almost completed within 2 minutes.

At this time, about 50 g of the oil-soluble layer and about 290 g of the water-soluble layer were separated at the top of the decanter in each example. Here, about 280 g of the lower water-soluble layer excluding the interface was separately sampled, and the oil-soluble layer was separately recovered. Thereafter, the concentration of cresol in the sampled water-soluble layer was measured. The concentration of cresol was analyzed using high performance liquid chromatography (HPLC), and a C18 column was used, where the lower limit of the detectable concentration was 10 ppm. As a result of the measurement, the concentration of cresol in the water-soluble layer sampled was not more than 1 wt% (10,000 ppm) in all of Examples 1 to 5, and the lower the pH, the lower the concentration of cresol was. Particularly, in Example 1 in which the pH was adjusted to 1, the concentration was as low as about 3,000 ppm.

Extraction of Cresol : Each of the above-mentioned receptive layer samples was cooled to 40 占 폚, and 140 g of MTBE (Methyl Tertiary Butyl Ether) at 40 占 폚 was added to each. Thereafter, the mixture was stirred for about 20 seconds, and once extracted for 5 minutes. Then, a portion of the water-soluble layer in the upper MTBE layer and the lower water-soluble layer was sampled to analyze the residual cresol concentration. The concentration of residual cresol was analyzed using high performance liquid chromatography (HPLC) and a C18 column was used, with a lower limit of detectable concentration of 10 ppm. As a result of the measurement, all of them were judged as "not detectable", which means that the concentration of residual cresol is less than 10 ppm.

Examples 6 to 9

The effect of temperature on the decanting of the oil-soluble and water-soluble layers was analyzed. A cresolate mixture was produced in the same manner as in the hydrolysis reaction of Examples 1 to 5 above. Thereafter, the product obtained by the hydrolysis reaction was sampled four times in an amount of 300 g each, and HCl was added thereto to adjust the pH of the product to 1.

Then, each sample was subjected to decanting at a temperature of 20 캜, 40 캜, 60 캜 and 80 캜 (corresponding to Examples 6 to 9 in order). As a result, after about 1 minute 20 seconds to 1 minute 40 seconds at 20 ° C, about 40 seconds to 55 seconds at 40 ° C, about 30 seconds to 35 seconds at 60 ° C, and about 25 seconds to 30 seconds at 80 ° C, And the water-soluble layer was stabilized at the interface.

After 5 minutes from the start of decanting each sample, about 280 g of the lower water-soluble layer was sampled to measure the concentration of cresol in the water-soluble layer. The concentration of cresol was analyzed using high performance liquid chromatography (HPLC), and a C18 column was used, where the lower limit of the detectable concentration was 10 ppm.

As a result of the analysis, the concentration of cresol in the water-soluble layer was in the range of 3,000 to 4,000 ppm in Examples 6 to 9, and the cresol content tended to increase slightly as the temperature of decanting was higher. It is interpreted that the higher the temperature, the smaller the solubility of cresol. However, since the difference in solubility according to temperature is not large, the efficiency of decanting by temperature can be considered to be determined by the layer separation time. Depending on the circumstances, the operating temperature can be adjusted between 0 ° C and 100 ° C, but a temperature between 40 ° C and 60 ° C is appropriate considering the actual operating cost.

Thereafter, the water-soluble layers sampled in Examples 6 to 9 were each heated or cooled to 40 占 폚, and 140 g of MTBE (Methyl Tertiary Butyl Ether) at 40 占 폚 was added to each. After the mixture was stirred for about 20 seconds, the mixture was subjected to extraction for 5 minutes, and then a portion of the water-soluble layer in the upper MTBE layer and the lower water-soluble layer was sampled to analyze the residual cresol concentration. The concentration of residual cresol was analyzed using high performance liquid chromatography (HPLC) and a C18 column was used, with a lower limit of detectable concentration of 10 ppm. As a result of the measurement, all of them were judged as "not detectable", which means that the concentration of residual cresol is less than 10 ppm.

Comparative Example

Production of Cresolate by Hydrolysis Reaction : In a continuous reactor, an aqueous solution of NaOH (10 wt%) and chlorotoluene were fed in a molar ratio of 2.5: 1 (NaOH: chlorotoluene) and maintained at 400 ° C. and 300 atm for 30 minutes The hydrolysis reaction of chlorotoluene proceeded under basic conditions with a pH of about 13 to produce a cresolate mixture.

pH adjustment : 40 g of HCl was added to 300 g of the product as a result of the hydrolysis reaction to adjust the pH of the product to 1.

Extraction of cresol : After the hydrolysis reaction product was heated to 40 占 폚, 170 g of MTBE (Methyl Tertiary Butyl Ether) was added. After the mixture was stirred for about 20 seconds, the mixture was subjected to extraction for 5 minutes, and then a portion of the water-soluble layer in the upper MTBE layer and the lower water-soluble layer was sampled to analyze the residual cresol concentration. The concentration of residual cresol was analyzed using high performance liquid chromatography (HPLC) and a C18 column was used, with a lower limit of detectable concentration of 10 ppm. As a result of measurement, the concentration of residual cresol was 100 to 500 ppm. Therefore, in the case of the comparative example in which decanting is not performed, it can be confirmed that an additional extraction step is required to lower the concentration of residual cresol in the water-soluble layer to less than 10 ppm.

As can be seen from the above examples and comparative examples, when the extraction process is directly introduced after the pH control for the cresolato mixture produced after the hydrolysis reaction, the extraction process is required twice or more to lower the concentration of the residual cresol in the water-soluble layer As a result, introduction of Multi-Stage Extractor is required. However, as in the present invention, when the cresol is first separated by separating the oil-soluble layer and the water-soluble layer through decanting before the extraction process, it is possible to completely separate the cresol in the receiving layer with only one mixer-settler Do. Thus, the process can be dramatically simplified, and the operating cost and investment cost of the process can be greatly reduced.

Claims (11)

Producing a cresolate through a hydrolysis reaction of halotoluene in a basic aqueous solution at a temperature of 200 ° C or more and 450 ° C or less and a pressure of 100atm or more and 500atm or less;
Converting the cresolate to cresol by adding an acid to the product of the step of producing the cresolate and adjusting the pH to a value of greater than or equal to -5 and less than or equal to 1;
Separating the pH-controlled product into an oil-soluble layer and a water-soluble layer, and then recovering the oil-soluble layer; And
Adding an organic solvent to the separated water-soluble layer to extract remaining cresol from the water-soluble layer into an organic solvent layer,
Separating the pH-controlled product into an oil-soluble layer and a water-soluble layer, and then recovering the oil-soluble layer, wherein the concentration of cresol in the separated water-soluble layer is not more than 3000 ppm ,
Wherein the step of extracting the remaining cresol is performed once.
Extraction method of cresol. delete delete The method of claim 1,
Wherein the step of adding the acid and adjusting the pH to convert the cresolate to cresol is carried out using an acid having a pKa value of -6 or less,
Extraction method of cresol. delete The method of claim 1,
Wherein the step of producing the cresolate is carried out at a pH of 11 or higher.
Extraction method of cresol. The method of claim 1,
In the step of extracting the cresol, the organic solvent has a DI value of 20 or less.
Extraction method of cresol. 8. The method of claim 7,
Wherein the amount of the organic solvent to be added is 10 parts by weight or more and 200 parts by weight or less based on 100 parts by weight of the total amount of the product produced in the step of producing the cresol,
Extraction method of cresol. The method of claim 1,
Separating the pH-controlled product into an oil-soluble layer and a water-soluble layer, and recovering the oil-soluble layer,
Wherein the reaction is carried out by decanting.
Extraction method of cresol. The method of claim 9,
Separating the pH-controlled product into an oil-soluble layer and a water-soluble layer, and then recovering the oil-soluble layer;
RTI ID = 0.0 > 0 C < / RTI > and 100 C,
Extraction method of cresol. The method of claim 1,
Extracting the cresol,
RTI ID = 0.0 > 0 C < / RTI > and 55 C,
Extraction method of cresol.