GB2291056A

GB2291056A - Method of separating meta-and para-ethylphenol

Info

Publication number: GB2291056A
Application number: GB9513488A
Authority: GB
Inventors: Masao Matsumoto; Tomonori Hakozaki; Tsutomu Idai; Mitsunori Shimura; Yoshikazu Yokota; Yoshimi Shiroto
Original assignee: Maruzen Petrochemical Co Ltd
Current assignee: Maruzen Petrochemical Co Ltd
Priority date: 1994-07-04
Filing date: 1995-07-03
Publication date: 1996-01-17
Anticipated expiration: 2015-07-03
Also published as: JPH0820551A; GB2291056B; FI953291A0; FI953291A; CN1129208A; ZA955189B; GB9513488D0

Abstract

A method of separating m-ethylphenol and p-ethylphenol from a mixture containing ethylphenol isomers with high separation efficiency in an industrial scale is provided. Specifically, the method is directed to separation of m- and p-ethylphenol from a mixture containing ethylphenol isomers by an adsorption and desorption treatment which comprises subjecting the feed mixture to the adsorption and desorption treatment using K-Y type zeolite as an absorbent and one of C2 - C4 aliphatic alcohols or a mixture of two or more of the alcohols, at a temperature of not less that the boiling point of the desorbent under a pressure capable of keeping the feed materials, desorbent and separated and purified products present in a liquid state, and recovering m-ethylphenol as a raffinate and p-ethylphenol as an extract.

Description

METHOD OF SEPARATING META- AND PARA-ETHYLPHENOL BAG1GROUND OF THE INVENTION 1. FIELD OF TilE INVENTION The present invention relates to a method of separating meta- (hereinafter simply referred to as m-) and para (hereinafter simply referred to as p-) ethylphenol, and more specifically, to a method of industrially separating and recovering m-ethylphenol and p-ethylphenol which comprises the steps of subjecting a feed isomeric mixture containing m- and p-ethylphenol to an adsorption and desorption treatment using a zeolite absorbent.

2. DESCRIPTION OF RELATED ART Alkylphenols have been widely used as a feed material for the production of synthetic resins, agricultural chemicals, medicines, plasticizers and the like. Particularly, p-ethylphenol is a raw material of poly p-vinylphenol resins, antioxidants, medicines, agricultural chemicals, pigments and the like. Various methods of separating it from a mixture of ethylphenol isomers have been proposed and put into practical use.

For example, JP-B-Sho-61-52129 (1986) proposes a method of separating p-ethylphenol from its isomeric mixture by an adsorption and desorption treatment using a zeolite absorbent as an absorbent and a mixture of ketone and straight-chain alcohol as a desorbent ("the term "JP-B" used herein means an examined published Japanese patent application).

In the above proposed method, an absorbent and a desorbent to be used have been selected primarily based on adsorptivity of the desorbent (selective adsorptivity). Namely, a desorbent comprising a mixture of ketone and straight-chain alcohol has been selected because it is hardly adsorbed by an absorbent under the conditions that it is present in a high concentration. More specifically, a desorbent comprising a mixture of ketone and straight-chain alcohol has been selected based on the results of measuring selective adsorptivity of the desorbent on an absorbent in a desorbent concentration of nearly 100%.Accordingly, selective adsorptivity of a target substance to be separated by an adsorption and desorption treatment is evaluated based on a result of determination of a separation factor of a feed material to be subjected to an adsorption and desorption treatment, or an isomeric mixture, by a dynamic pulse response test under the conditions that the feed material is present in the desorbent in a very low concentration.

However, it is difficult to realize separation of an isomeric mixture of, for example, alkylphenol, in an industrial scale by means of an adsorption and desorption treatment such as a simulated counter current moving bed system, by applying a separation factor determined under such specific conditions that a feed material is present in a low concentration as described above, which is different from the actual practical conditions.

On the other hand, many of the other conventional methods of separating an isomeric mixture by means of an adsorption and desorption treatment utilize the batch system adsorption equilibrium method, which comprises determining a separation factor of each isomer contained in an isomeric mixture to be separated at equilibrium and selecting an absorbent and a desorbent.

In the above conventional batch system adsorption equilibrium method, only a separation factor of each isomer at equilibrium is determined and no investigation is made for determining time required for attaining adsorption and desorption equilibrium in the continuous adsorption and desorption operations. The time required for attaining adsorption and desorption equilibrium is an important factor to determine a necessary amount of an absorbent and is essential for effecting separation of isomers in an industrial scale by means of a adsorption and desorption treatment such as a simulated counter current moving bed system.

SUMMARY OF THE INVENTION Under the circumstance that industrially enable and realistic selection of an absorbent and a desorbent has not been established in the method of separating each isomer contained in an isomeric mixture of, for example alkylphenol, by means of an adsorption and desorption treatment, an object of the present invention is to investigate and establish a system of selecting an absorbent and desorbent to be used for efficient and continuous separation of each isomer contained in a feed isomeric mixture of m- and p-ethylphenol in an industrial scale by an adsorption and desorption treatment.Another object of the present invention is to provide a method of efficiently separating and recovering m- and p-ethylphenol contained in a feed isomeric mixture of m- and p-ethylphenol in an industrial scale by an adsorption and desorption treatment with high practicability, which comprises using an absorbent and a desorbent selected by the selection system established according to the above-described manner. In order to achieve the above objects, the present inventors have selected various combination of an absorbent with a desorbent and measured elution patterns of each isomer to be separated in a realistic concentration of the feed material by the so-called break-through response test.From the elution patterns obtained by the above method, a mass transfer rate has calculated to determine a practically applicable separation factor of each is omer and time required for attaining adsorption and desorption equilibrium. As a result, it has been found that an absorbent and a desorbent, which are expected to be industrially applicable, can be selected and thus the present invention has been completed.

The present invention provides a method of separating m- and p-ethylphenol contained in a feed mixture of ethyl phenol isomers by an adsorption and desorption treatment, which comprises subjecting the feed mixture to the adsorption and desorption treatment using K-Y type zeolite as an absorbent and one of C2CA aliphatic alcohols or a mixture of two or more of the alcohols as a desorbent at a temperature of not less than the boiling point of the desorbent under the pressure capable of keeping the feed mixture to be treated, the desorbent and the separated and purified products present in a liquid state, and recovering m-ethylphenol as a raffinate and p-ethylphenol as an extract.

In the method of separating m- and p-ethylphenol of the present invention, a simulated counter current moving bed system can be preferably used as an adsorption and desorption treatment.

This simulated counter current moving bed system is well known in the art as described below.

The present invention also provides a method of purifying p-ethylphenol which comprises recrystallizing an extract obtained by the above-described method of separating m- and p-ethylphenol.

According to the method of separating m- and p-ethylphenol of the present invention, m- and p-ethylphenol can be efficiently separated by subjecting a feed mixture containing ethylphenol isomers to an adsorption and desorption treatment by means of, for example chromatography, preferably a simulated counter current moving bed system, using K-Y type zeolite as an absorbent and one of C2-C4 aliphatic alcohols or a mixture of two or more of the alcohols as a desorbent under the predetermined conditions.

Since the absorbent. - the desorbent and the adsorption and desorption treatment conditions are selected in accordance with a break-through response test which is asst:ed to correspond to an actual adsorption and desorption treatrent, p-ethylphenol to be adsorbed can be efficiently separated from m-ethylphenol without causing tailing making use of a predetermined amount of a desorbent. Therefore, this method is highly practicable and useful for industrial application.

In order that tne invention ray be illustrated, more easily appreciated and readily carried ito effect by one skilled in this art, embodiments c' the invention will now be described t 3 cf non-limiting examples only, and with reference to the accompanying drawings, wherein:: Fig. 1 shows a conceptual drawing of the elution pattern of each component obtained in the break-through response test according to the present invention; Fig. 2 schematically shows the absorption and desorption treatment by means of the stimulated counter current moving bed system; Fig. 3 shoves an elution pattern obtained in the break-through response test as an example; and Fig. 4 shows an elution pattern obtained in the break-through response test as a comparative example.

According to the present invent ion, each isomer, m- and p-ethylphenol, can be separated by subjecting a feed ethylphenol isomeric mixture containing m- and p-ethylphenol to an adsorption ard desorption treatment. K-Y type zeolite absorbent can be used as an absorbent and one of C2-C4 aliphatic alcohols or a mixture of two or more of the alcohols can be used as a desorbent. These absorbent and desorbent can be selected based on a break-through response test.More specifically, from elution patterns of each isomer obtained in the break-through response test, a separation factor of an isomer to be separated to an absorbent and a separation factor of a desorbent to the absorbent are determined under the conditions that a range of a concentration of a feed isomeric mixture falls within the range applicable to actual industrial use. Simultaneously, total mass transfer capacity coefficient (SLAV) is calculated from the elution pattern by a conventional manner to determine time required for attaining adsorption and desorption equilibrium. In consequence, the method of separating m- and p-ethylphenol of the present invention is highly practicable and useful for industrial application.

The term adsorption and desorption treatment used herein means a treatment which comprises allowing p-ethylphenol contained in a feed mixture of ethylphenol isomers to selectively adsorb on the above-described K-Y type zeolite absorbent bed, desorbing sorbed p-ethylphenol from the absorbent using the above desorbent to elute as an extract and simultaneously eluting the other components including m-ethylphenol as a raffinate. Examples of the treatment include an adsorption and desorption treatment by means of the so-called simulated counter current moving bed system and other chromatographic separation treatment comprising removing an isomer sorbed on the absorbent to be separated using the desorbent.

In the adsorption and desorption treatment of the present invention, an absorbent is selected from the conventionally used zeolite absorbents. K-Y type zeolite, which is Y type zeolite containing potassium (1Ç) as a cation, is preferably used. The K-Y type zeolite absorbent used in the present invention may be a commercially available product or may be synthesized.

The desorbent and Ihe adsorption and desorption conditions are determined by a break-through response test using the above-described K-Y type zeolite.

As described in Example 1 below, the test is carried out by passing, through a column in which the K-Y type zeolite is packed, an isomeric mixture containing m- and p-ethylphenol and supplemented with 1,3,5-triisopropylbenzene (TIPB) as a standard substance which is not substantially adsorbed by the absorbent or a mixture containing an isomeric mixture -of m- and p-ethylphenol supplemented with TIPB and the desorbent in a predetermined mixing ratio.After replacing the fluid passing through the column with the desorbent alone, an elution pattern is prepared by plotting a standardized concentration (C/CQ), which is a ratio of a concentration of each component in the eluate (C) to a concentration of each component in the feed material (cho) against a standardized elution time (t/t1), which is a ratio of time for elution of each isomer, m- and p-ethylphenol, or break-through time (t), to time for elution of TIPB of a predetermined concentration (usually 50%) (to).

Fig. 1 shows a conceptual drawing of the elution pattern thus prepared. A relative separation factor (ss ) can be calculated simply from the following formula (I) based on the respective standardized elution time (tt, tm and tp) when the respective standardized concentration of each component, TIPB, m-ethylphenol and p-ethylphenol, (C1/C0, 1, Cm/C0. and Cp/CO p) become 0.5 in the elution pattern shown in Fig. 1: : ss = equilibrium constant of p-ethylphenol/ equilibrium constant of m-ethylphenol = tp - ti/tm - t1 (I) When the value of the thus-obtained relative separation factor P is high, separation of p-ethylphenol from m-ethylphenol is efficiently carried out. The separation factor ss is preferably not less than 2.

In the elution pattern, it can be observed whether tailing occurs or not at about the concentration of p-ethylphenol to be separated in the eluate which becomes nearly zero. When the desorbent and the treatment conditions are selected so that p-ethylphenol, which is an adsorbent, may cause tailing in the break-through response test, a considerably large amount of the desorbent is required for complete desorption of p-ethylphenol within the desorbing zone. Such conditions do not suit for industrial application. When the desorbent is used in a small amount, p-ethylphenol is kept adsorbed by the absorbent and is eluted with a raffinate because the operating zone of the adsorption and desorption treatment changes in the simulated counter current moving bed system.Accordingly, purity of m-ethylphenol is lowered and recovery of p-ethylphenol is reduced, which renders separation efficiency of m- and p-ethylphenol remarkably low and thus unpractical.

As described above, the combination of the desorbent and the adsorption and desorption treatment conditions including temperature and pressure is determined so that the separation factor p should be not less than 2 in accordance with the break-through response test and no tailing should be found in the elution pattern of p-ethylphenol. As a result, it has been found that m- and p-ethylphenol can be separated with high separation efficiency by subjecting a feed mixture of m- and p-ethylphenol to separation method using the adsorption and desorption treatment such as a simulated counter current moving bed system.

Based on the above finding, the combination of the absorbent, desorbent and the adsorption and desorption conditions according to the present invention are selected. Namely, -Y type zeolite can be used as an absorbent and one of C2-C4 aliphatic alcohols or a mixture of two or more of the alcohols can be used as a absorbent. Examples of the alcohols include ethanol, 1-propanol, 2-propanol, 1-butanol and the like.The adsorption and desorption treatment using the above absorbent and desorbent can be carried out at a temperature of not less than the boiling point of the desorbent, preferably 0 to 100E higher than the boiling point, and under a pressure capable of keeping the fluids involved in the adsorption and the desorption treatment system, including the feed mixture to be treated, the separated and purified products and the desorbent, present in a liquid state. For example, when the desorbent is ethanol, 1-propanol, 2-propanol or a mixture thereof, the temperature and the pressure range from 100 to 2009=, , 1 to 20 kg/cm2G, respectively. Preferably, the temperature and the pressure range from 120 to 180E, 5 to 20 kg/cm2G, respectively.

Separation of ethylphenol isomers by the adsorption and desorption treatment according to the present invention can be effected by chromatography, preferably a simulated counter current moving bed system, as described above. The adsorption and desorption treatment by means of a simulated counter current moving bed system is an already established technique and put into practice for separation of a mixture of xylene isomers. It has been reported in, for example, JP-B-Sho-42-15681 (1967), JP-B-Sho-50-10547 (1975) (U.S. Patent 3,761,533) and the like.

The adsorption and desorption treatment of a mixture of ethylphenol isomers using a simulated counter current moving bed system according to te present invention is ilIustested below.

Basic operation of the adsorption and desorption treatment comprises the following steps: (i) adsorption operation; (ii) concentration operation; (iii) desorption operation; and (iv) desorbent-recovering operation. These steps are carried out continuously by circulating system.

In the adsorption step (i), a feed mixture containing ethylphenol isomers is applied to and contacted with K-Y type zeolite absorbent as well as the desorbent and p-ethylphenol is selectively adsorbed since it is a highly adsorbable component, whereas m-ethylphenol which is slightly adsorbable is recovered as a raffinate eluate together with the desorbent.

In the concentration step (ii), the absorbent which has selectively adsorbed p-ethylphenol is brought into contact with a part of an extract eluate as described below, the feed mixture and the like remaining on the absorbent are removed and p-ethylphenol adsorbed is concentrated.

In the desorption step (iii), the absorbent containing concentrated p-ethylphenol is brought into contact with the desorbent and p-ethylphenol is eluted from the absorbent to recover p-ethylphenol as an extract together with the desorbent.

In the desorbent-recovering step (iv), the absorbent which has substantially adsorbed only the desorbent is contacted with a part of the above-described raffinate eluate and a part of the desorbent adsorbed by the absorbent is recovered as a desorbent-recovering eluate.

The adsorption and desorption treatment using a simulated counter current moving bed system is further described in detail with reference to Fig. 2 which schematically shows the treatment.

In Fig. 2, each of adsorbing zones 1 to 16 is packed with K-Y type zeolite absorbent and connected with each other. The adsorbing zones 1 and 16 are connected through a recycling line 17, which is equipped with a pump for causing the fluid flow 18 to provide cyclic fluid flow. In the circulating system comprising multiple adsorbing zones shown in Fig. 2, a desorbent supplying line 19, an extract draining line 20, a feed mixture supplying line 21 and a raffinate draining line 22 are arranged at the respective positions of the connecting means of the adsorbing zones. In the illustrated stage, the adsorbing zones 1 to 3 are performing the desorption, the adsorbing zones 4 to 8 are performing the concentration, the adsorbing zones 9 to 13 are performing the adsorption and the adsorbing zones 14 to 16 are performing the recovery of the desorbent.

In the simulated counter current moving bed system, the respective supplying and draining lines are periodically advanced by one adsorbing zone in the direction of the fluid flow by switching the valves.

In the next stage subsequent to the illustrated stage shown in Fig. 2 advanced by valve switching, the desorption, the concentration, the adsorption and the recovery of the desorbent are carried out in the adsorbing zones 2 to 4, the adsorbing zones 5 to 9, the adsorbing zones 10 to 14 and the adsorbing zones 15 to 1, respectively. In Fig. 2, 16 adsorbing zones are shown, but the number of the zones are not particularly limited and can be optionally selected depending on various applied conditions.

According to the present invention, m-ethylphenol and p-ethylphenol can be separated from each other with high efficiency by subjecting a feed mixture containing ethylphenol isomers to the respective steps of the above-described adsorption and desorption treatment subsequently using the above-described absorbent, desorbent and the treatment conditions which are selected by the above-described break-through response test.

Further, according to the present invention, after removing the desorbent from the extract containing p-ethylphenol which is separated and recovered by the adsorption and desorption treatment such as the simulated counter current moving bed system, p-ethylphenol can be obtained with high purity by crystallizing the extract in the absence or presence of a solvent such as n-heptane or the like.

The following Examples are given to illustrate the present invention in more detail, but are not to be construed to limit the scope of the present invention.

EXAMPLE 1 About 23 ml of l(-Y type zeolite absorbent was packed into an adsorption column having an internal diameter of 10.7 mm and a length of 250 mm and the break-through response test was carried out.

In the break-through response test, a 1-propanol solution containing 30 wt% of a feed oil mixture of ethylphenol isomers, which contained 34.5 wt% of p-ethylphenol, 64.6 wt% of m-ethylphenol, 0.2 wt% of o-ethylphenol, 0.5 wt% of other alkylphenols and 0.3 wt% of hydrocarbons, and 3 wt% of TIPB was previously passed through the above-described column packed with li-Y type zeolite absorbent at 150t under 7 kg/cm2G at a flow rate of 20 ml/min for about 30 minutes. Thereafter, only 1-propanol was passed through the column and eluate from the adsorption column was fractionated at regular time intervals.

p-ethylphenol, m-ethylphenol and TIPB contained in the eluate were analyzed and the respective elution patterns were prepared.

Fig. 3 shows the thus prepared elution patterns.

The separation factors shown in the elution pattern of Fig.

3 and calculated by the above-described formula (I) were both 4.6. It is evident from the elution pattern of Fig. 3 that tailing was observed a little in the elution pattern of p-ethylphenol and the total mass transfer capacity coefficient (LAV) was 0.08 (1/sex).

From these results, it can be found that high separation efficiency is obtained under the adsorption and desorption conditions of a temperature of 150E and a pressure of 7 kg/cm2G when K-Y type zeolite is used as the absorbent and 1-propanol having the boiling point of 98"C as the desorbent.

COMPARATIVE EXAMPLE 1 The break-through response test was carried out in the same manner as in Example 1 except for using l-hexanol in place of 1-propanol and under the conditions of a temperature of 150C and a pressure of 1 kg/cm2G. The resulting elution patterns are shown in Fig. 4.

Though the separation factors shown in Fig. 4 and calculated by the above-described formula (I) were not less than 2, p-ethylphenol caused tailing as evident from Fig. 4. Thus, it can be found that p-ethylphenol cannot be efficiently separated under a pressure of 1 kg/cm2G and using l-hexanol as the desorbent.

EXAMPLE 2 The break-through response test was carried out in the same manner as in Example 1 except for using ethanol as the desorbent at 150C under 20 kg/cm2G. As a result, .the separation factor calculated by the above-described formula (I) was 4.2, no tailing of p-ethylphenol was observed and the total mass transfer capacity coefficient (LAV) was 0.09 (1/sex).

EXAMPLE 3 The break-through response test was carried out in the same manner as in Example 1 except for using a mixture containing 80 wt% of 1-propanol and 20 wt% of 2-propanol as the desorbent at 150E under 20 kg/cm2G. As a result, the separation factor calculated by the above-described formula (I) was 3.8, no tailing of p-ethylphenol was observed and the total mass transfer capacity coefficient (I5LAS) was 0.08 (1/sex).

EXAMPLE 4 A feed mixture containing ethylphenol isomers obtained by ethylating phenol as shown in Table 1 was subjected to the adsorption and desorption treatment using a simulated counter current moving bed apparatus comprising 16 adsorption zones similar to that shown in Fig. 2.

A content of about 70 ml of the same K-Y type zeolite absorbent as used in Example 1 was packed in the respective column adsorption zones 1 to 16, the mixture of ethyl phenol isomers was fed at a feed rate of 140.0 g/hr through the line 21 and the desorbent, l-propanol, was fed at a feed rate of 820 g/hr through the line 19. Simultaneously, an extract was drained through the line 20 at a rate of 780 g/hr and a raffinate was drained through the line 22 at a rate of.180 g/hr.

As the treatment conditions, the temperature of each adsorption zone was adjusted to 180E and the suction pressure of the pump for causing the fluid flow 18 was adjusted to 15 kg/cm2G. The respective feeding lines for the feed mixture and the desorbent and the respective draining lines for the extract and the raffinate were set so as to simultaneously shift by one adsorption zone in te direction of the fluid flow at intervals of 60 seconds by switching the valves.

TABLE 1

COMPONENTS COMPOSITION RATE (wiz) p-ethylphenol 64.39 m-ethylphenol 34. 81 o-ethylphenol 0. 04 diethylphenol 0.05 o-n-propylphenol 0. 04 2-methynaphthalene 0.49 others 0.18 As a result, p-ethylphenol was recovered from the extract and the desorbent, 1-propanol, had a concentration of 98 wt% at the free base. On the other hand, m-ethylphenol was recovered from the raffinate and the desorbent, 1-propanol, had a concentration of 97 wt% in the case of the free base.

EXAMPLE 5 The adsorption and desorption treatment was carried out in the same manner as in Example 4 except that the feed mixture was fed at a feed rate of 200 g/hr and the extract was drained at a rate of 840 g/hr.

As a result, p-ethylphenol recovered from the extract had a concentration of 86 wt% in the case of the desorbent, 1-propanol, free base. On the other hand, m-ethylphenol recovered from the raffinate had a concentration of 97 wt% in the case of the desorbent, 1-propanol, free base.

Then, the desorbent, l-propanol, was removed by distillation from the mixture of p-ethylphenol and 1-propanol. About 100 g of the thus-obtained p-ethylphenol concentrate was cooled to 10C to precipitate crystals followed by centrifugation. Thus, about 59 g of the crystals of p-ethylphenol having a purity of 99% was obtained.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the forgoing description, and all the changes which come within the meaning and range of equfvalency of the claims are therefore intended to be embraced therein.

Claims

1. A method of separating rLeta- and para-ethylphenol from a feed mixture containing ethyiphenol isomers by an adsorption and desorption treatment, comprising the steps of: (1) using K-Y type zeolite and one of alcohols selected from a C2-CA aliphatic alcohols or a mixture of two or more of the alcohols as an absorbent and a desorbent, respectively, in the adsorption and desorption treatment; (2) passing the feed mixture containing ethylphenol isomers and the desorbent through the absorbent at a temperature of not lower than the boiling point of the desorbent under a pressure capable of keeping the feed materials, desorbent and separated and purified products present in a liquid state to contact the feed mixture with the absorbent;; (3) selectively separating p-ethylphenol from the feed mixture by adsorption and simultaneously recovering m-ethylphenol as a raffinate together with the desorbent; and (4) desorbing the p-ethylphenol from the absorbent by the desorbent to recover it as an extract.

2. The method according to Claim 1, wherein the desorbent is at least one member selected from the group consisting of ethanol, 1-propanol, 2-propanol and 1-butanol.

3. The method according to Claim 1, wherein the desorbent is 1-propanol, the temperature is from 120 to 180E and the pressure is from 5 to 20 kg/cm2G during the adsorption and desorption treatment.

4. The method according to Claim 1, wherein the desorbent is ethanol, the temperature is from 120 to 180E and the pressure is from 5 to 20 kg/cm2G during the adsorption and desorption treatment.

5. The method according to Claim 1, wherein the desorbent is a mixture of 1-propanol and 2-propanol, the temperature is from 120 to 180C and the pressure is from 5 to 20 kg/cm2G during the adsorption and desorption treatment.

6. The method according to any one of Claims 1 to 5, wherein the adsorption and desorption treatment is carried out using a simulated counter current moving bed system which comprises a fixed bed containing at least four serially interconnected zones having packed therein the absorbent, each zone having an inlet and an outlet which are connected to each other to thereby provide cyclic fluid flow in the system, the treatment comprising the steps of:: (a) contacting the feed mixture with the first fixed bed which is maintained under the adsorbing conditions to selectively adsorb p-ethylphenol; (b) maintaining the second fixed bed which is positioned upstream of the first fixed bed under the desorbing conditions; (c) maintaining the third fixed bed which is connected between the first fixed bed and the second fixed bed under the concentrating conditions; (d) maintaining the fourth fixed bed which is connected to the first fixed bed under the desorbent-recovering conditions; (e) introducing the feed mixture to the first fixed bed, introducing the desorbent to the second fixed bed, recovering m-ethylphenol as a raffinate from the first fixed bed and simultaneously recovering p-ethylphenol as an extract from the second fixed bed; and (f) moving the introducing and recovering points of each fixed bed by one fixed bed at regular time intervals.

7. The method according to any one of Claims 1 to 6, wherein the recovered extract is further crystallized to purify and recover p-ethylphenol.

8. The method according to Claim 7, wherein the crystallization is a cooling treatment.

9. A method as claimed in any preceding claim substantially as herein described.

10. A method as claimed in any preceding claim substantially as described with reference to any of the examples other than comparative examples.

11. A method as claimed in any preceding claim substantially as herein illustrated in any one of the accompanying drawings.