JPH0466460B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field] The present invention relates to a method for selectively adsorbing and separating 2,6-methylisopropylnaphthalene from a mixture of methylmonoisopropylnaphthalene isomers. [Prior Art] Conventionally, it is widely known that terephthalic acid or 2,6-naphthalene dicarboxylic acid is subjected to a polymerization reaction with glycol in order to obtain polyester.
Polyester obtained from 2,6-naphthalene dicarboxylic acid has superior physical properties such as heat resistance compared to those obtained from terephthalic acid, so 2,6-dinaphthalene is industrially advantageous as a raw material for polyester. It is desired to establish a manufacturing method. Conventionally, as a method for industrially producing 2,6-naphthalene dicarboxylic acid, a method of using 2,6-dimethylnaphthalene as a raw material and oxidizing it has been considered as a general method. In the case of this method, an important technical issue is how to obtain 2,6-dimethylnaphthalene, which is a raw material for 2,6-naphthalene dicarboxylic acid, at low cost and with high purity. 2,6-dimethylnaphthalene is contained in the dimethylnaphthalene fraction obtained by distilling petroleum or coal tar. This dimethylnaphthalene fraction contains many substances whose boiling points are very close to each other, such as ethylnaphthalene, bifnyl, and acenaphthene. It includes isomers such as 2,3-dimethylnaphthalene. Therefore, it is extremely difficult to selectively separate 2,6-dimethylnaphthalene from such other compounds and isomer mixtures. In particular, since the boiling points of the 2,6-isomer and 2,7-isomer are extremely similar, it is extremely difficult to separate the two, and it is virtually impossible to separate the two by distillation. It is possible. Conventionally, 2,6-dimethylnaphthalene and 2,7-
An adsorption separation method using a zeolite adsorbent has been proposed as an industrially advantageous method for separating isomers containing dimethylnaphthalene from a mixture of isomers (Japanese Patent Publication No. 49-27578, Japanese Patent Publication No. 52-945). ). However, in this adsorption separation method, 2,6-
Since the 2,7-isomer is adsorbed by the adsorbent with higher selectivity than the isomer, this method is superior as a high-purity separation method for the 2,7-isomer. - It is unsatisfactory as a high-purity separation method for isomers. In order to adsorb and separate the 2,6-isomer with high purity, the 2,6-isomer is preferable to the 2,7-isomer.
Although it is necessary to develop an adsorbent that adsorbs isomers with high selectivity, no satisfactory adsorbent has yet been proposed. [Objective] An object of the present invention is to solve the above-mentioned problems encountered in the process for producing 2,6-naphthalene dicarboxylic acid using 2,6-dimethylnaphthalene as a raw material. [Structure] According to the present invention, when separating a 2,6-isomer from a methyl monoisopropyl naphthalene isomer mixture, the mixture is mainly treated with one or two selected from alkali metals and alkaline earth metals. The first having a Y-type structure substituted with more than one cation
After contacting with a zeolite adsorbent and adsorbing the 2,6-isomer and 2,7-isomer contained in the mixture to the first adsorbent with higher selectivity than other isomers,
a first step of desorbing the adsorbed material from the first adsorbent; and a first step of desorbing the adsorbed material from the first step, and the desorbed material obtained in the first step is mainly composed of one or two selected from alkali metals other than sodium and alkaline earth metals. The second zeolite adsorbent having a Y-type structure substituted with the above cations is brought into contact with the 2,7-isomer contained in the desorbed product with a higher selectivity than the 2,6-isomer. 2,6- characterized in that it consists of a second step of desorbing the adsorbate from the second adsorbent after adsorption to the adsorbent.
A method for adsorptive separation of methylisopropylnaphthalene is provided. The methyl monoisopropyl naphthalene isomer mixture in the present invention can be obtained by reacting methyl naphthalene with propylene in the presence of a catalyst and separating the methyl monoisopropyl naphthalene fraction from the resulting isopropylation product. . The methylnaphthalene used as the raw material for isopropylation may be of any type produced from petroleum oil, coal oil, or the like. However, if it contains components that may poison the isopropylation catalyst, such as sulfur compounds or nitrogen compounds,
It is preferable to remove these compounds by methods such as conventionally well-known purification techniques, hydrorefining, and activated clay treatment. The isopropylation reaction is a conventionally well-known reaction, and is carried out as a liquid phase or gas phase reaction according to a conventionally known method. Catalysts include solid acid catalysts such as silica/alumina, crystalline aluminosilicate, nickel oxide/silica, silver oxide/silica alumina, silica/magnesia, alumina/boria, solid phosphoric acid, aluminum chloride, hydrogen fluoride, and phosphorous. A Friedel-Crafts catalyst such as an acid is used. In this isopropylation reaction, the isopropyl group attached to the naphthalene ring is easily rearranged to another naphthalene ring by a transalkylation reaction in the presence of the alkylation reaction catalyst as described above. Therefore, this isopropylation reaction is considered to be a reversible reaction, and an equilibrium composition exists between methylnaphthalene and methylmonoisopropylnaphthalenes. The amount of methylmonoisopropylnaphthalene produced depends on the ratio of methylnaphthalene to propylene in the reaction, temperature, type and amount of catalyst, etc. When performing the isopropylation reaction using a Friedel-Crafts catalyst, the reaction is carried out at a temperature of room temperature to 150°C, preferably 50 to 100°C, a pressure of normal pressure to 10 atmospheres,
Catalyst to feed ratio 0.05-1.0, preferably 0.08
It is performed under the condition of ~0.5. In order to increase the yield of methylmonoisopropylnaphthalene, 0.5 to 3.0 mol of propylene per 1 mol of methylnaphthalene,
Preferably, the reaction is carried out so that 1.0 to 2.5 moles are reacted. When using a solid acid catalyst, the reaction temperature is 150~
500℃, pressure 0~50Kg/ ^cm2G , contact time 0.02~
6.0hr range, preferably temperature 200~350℃,
The pressure ranges from 0 to 35 Kg/cm ² G, and the contact time ranges from 0.4 to 2.5 hr. If the temperature is high or the contact time is long,
A decomposition reaction occurs and by-products are produced. Furthermore, when the temperature is low or the contact time is short, the yield of methylmonoisopropylnaphthalene decreases. In this isopropylation reaction step, an isopropylation product containing unreacted methylnaphthalene, methylmonoisopropylnaphthalene, methylisopropylnaphthalene and more methylpolyisopropylnaphthalene is obtained, and the proportion of methylmonoisopropylnaphthalene therein is: Usually 10-60% by weight. In addition, when carrying out this isopropylation reaction step, a low boiling point fraction consisting of methylnaphthalene obtained in the subsequent distillation separation step of the isopropylation reaction product and a high boiling point fraction consisting of methylpolyisopropylnaphthalene of methyldiisopropylnaphthalene or higher are also used. Preferably, a portion of the isopropylation reaction is recycled to the isopropylation reaction step. When performing an isopropylation reaction by circulating such a fraction, an isopropylation reaction occurs due to the reaction between unreacted methylnaphthalene and propylene that constitute the recycled low-boiling fraction, resulting in methylmonoisopropylnaphthalene. In addition, a transalkylation reaction between methylpolyisopropylnaphthalene and methylnaphthalene, which is higher than methyldiisopropylnaphthalene constituting the high boiling point fraction, occurs to produce methylmonoisopropylnaphthalene, and The yield of methylmonoisopropylnaphthalene is increased. In the present invention, the isopropylated product is subjected to distillation treatment to be separated into a low-boiling fraction consisting of methylnaphthalene and a high-boiling fraction consisting of methylmonoisopropylnaphthalene and methylpolyisopropylnaphthalene higher than methyldiisopropylnaphthalene. Then, the methylmonoisopropylnaphthalene fraction obtained from this distillation process is subjected to a two-stage adsorption separation process to separate and recover 2,6-methylisopropylnaphthalene with high purity. In this case, since the polar substances contained in the methyl monoisopropylnaphthalene fraction are more strongly adsorbed by the adsorbent than methylisopropylnaphthalene, it is preferable to remove them in advance. This polar substance is produced by the partial oxidation of aromatic hydrocarbons such as methylnaphthalene and methylisopropylnaphthalene, and is produced by the partial oxidation of aldehydes, ketones, alcohols, etc.
It is composed of phenol and the like, and can be removed by conventionally known appropriate means, such as faujasite-type zeolite or L-type zeolite.
In the first adsorption separation step, the methyl monoisopropylnaphthalene fraction is brought into contact with a first zeolite adsorbent that selectively adsorbs both 2,6-methylisopropylnaphthalene and 2,7-methylisopropylnaphthalene. Through this adsorption treatment,
2,6- as a strongly adsorbed component contained in the fraction
Methylisopropylnaphthalene and 2,7-methylisopropylnaphthalene are adsorbed with higher selectivity than other isomers as weakly adsorbed components. Next, this adsorbate is desorbed using a desorbent to obtain a mixture of 2,6-methylisopropylnaphthalene and 2,7-methylisopropylnaphthalene as a desorbent.
The first zeolite adsorbent used in this first stage adsorption separation process has selective adsorption properties for both 2,6-isomer and 2,7-isomer as strongly adsorbed components among methyl monoisopropyl naphthalene isomers. It suffices if it also indicates. Such adsorbents include
Metal ions selected from alkali metals or alkaline earth metals, such as potassium, lithium,
rubidium, cesium, barium, calcium,
An X-type or Y-type zeolite substituted with one or more metal ions selected from magnesium, strontium, lanthanum, and lanthanide metals is used. Moreover, such a zeolite adsorbent can also contain other metal ions such as lead, iridium, yttrium, and zirconium in addition to the metal ions mentioned above. In addition, in the second stage adsorption separation process, the 2,6-
A mixture of methylisopropylnaphthalene and 2,7-methylisopropylnaphthalene was converted into 2,6-
A second compound that shows stronger adsorption to 2,7-methylisopropylnaphthalene than to methylisopropylnaphthalene.
Contact with zeolite adsorbent. Through this adsorption treatment, 2,7-methylisopropylnaphthalene as a strongly adsorbed component is replaced with 2,6-methylisopropylnaphthalene as a weakly adsorbed component.
Adsorbs to the adsorbent with higher selectivity than methylisopropylnaphthalene. Next, this adsorbed material is desorbed using a desorbent. In this way, 2,6-methylisopropylnaphthalene and 2,7-methylisopropylnaphthalene can be separated from each other with high purity. The second zeolite adsorbent is
Any material that exhibits selective adsorption to 2,7-methylisopropylnaphthalene over 2,6-methylisopropylnaphthalene may be used. Such adsorbents include Y-type zeolites substituted with metal ions selected from alkali metals or alkaline earth metals other than sodium, preferably potassium ions and/or barium ions. In addition to the metal ions mentioned above, this zeolite adsorbent can also contain other metal ions such as lead, iridium, yttrium, and zirconium. The particle size of the zeolite adsorbent is approximately 3 to 300 mesh, and may be appropriately selected depending on the type of adsorption bed. Furthermore, it is also possible to improve the adsorption selectivity of the zeolite adsorbent by adjusting its water content. The water present in the zeolite is partially contained at the cation or base exchange sites or is contained within the cavities of the adsorbent. Desirably, the moisture content, as measured by weight loss under scorching heat at 1000 DEG C., is in the range of 5 to 20 wt%, based on the weight of the adsorbent. The moisture content can be adjusted by adding an appropriate amount of water to the raw material mixture. When adsorbing and separating using zeolite adsorbent,
The conditions for the adsorption/desorption step are a temperature of 50 to 300°C, preferably 80 to 200°C, and a pressure of 1 to 20 atm, preferably 5 to 200°C.
The pressure is 15 atm. The desorbent used in the desorption step may be a substance that is quickly adsorbed to the adsorbent and has the ability to desorb the already adsorbed substance. If the adsorption force is weak, a large amount of desorbent is required to desorb the product, the concentration of the desorbent in the product increases, and the cost required to separate the desorbent increases. On the other hand, if the adsorption power of the desorbent is too strong, the adsorption capacity of the product decreases as the desorbent is not sufficiently desorbed from the adsorbent during adsorption of the product, and the cost required for separation in the product when recovering the product. increases. Therefore, a substance with appropriate adsorption power is selected as the desorbent. Furthermore, when considering the separation of the product and the raffinate by distillation, it is desirable that the boiling point difference between the desorbent and the product and the raffinate is 10°C or more, preferably 20°C or more. As such a desorbent, aromatic hydrocarbons, alkyl aromatic hydrocarbons, hydrides thereof, paraffins, etc. are usually used. The adsorption separation according to the invention may be carried out in fixed bed, fluidized bed, chromatographic methods, preferably in a condensed moving bed method. Adsorption separation using a condensed moving bed method is an already established technology and has been applied to the adsorption separation of xylene isomer mixtures. It is described in. As mentioned above, in the two-stage adsorption separation method of the present invention, the target 2,6-methylisopropylnaphthalene can be separated and recovered with high purity from other components that have similar boiling points and are most difficult to separate from each other. I can do it. According to the adsorption separation technology using the above-mentioned condensed moving bed method, 2,6-methylisopropylnaphthalene can be separated and recovered with a high purity of 99% by weight or more. To explain in more detail the adsorption separation using the above-mentioned condensed moving bed method, this adsorption separation technology is carried out by continuously cycling the following basic operations: adsorption operation, concentration operation, desorption operation, and desorbent recovery operation. be done. (1) Adsorption operation: The raw material to be treated is brought into contact with the zeolite adsorbent, and the target component to be adsorbed as a strongly adsorbed component is selectively adsorbed, and other components that are weakly adsorbed components are recovered together with the desorbent as a roughinate stream. Ru. (2) Concentration operation: The adsorbent that has selectively adsorbed the target component is brought into contact with a portion of the extract, which will be described later, and the weakly adsorbed components remaining on the adsorbent are driven out and the strongly adsorbed components are removed. Concentrated. (3) Desorption operation: The adsorbent containing concentrated strongly adsorbed components is brought into contact with a desorbent, the strongly adsorbed components are expelled from the adsorbent, and are recovered as an extract stream along with the desorbent. (4) Desorbent recovery operation: The adsorbent that has substantially adsorbed only the desorbent comes into contact with a portion of the roughinate stream, and a portion of the desorbent contained in the adsorbent is recovered as a desorbent recovery stream. The figure shows a schematic diagram of the adsorption separation operation using a coagulated moving bed. In this figure, numerals 1 to 12 are adsorption chambers containing zeolite adsorbents, which are interconnected. 13 is a desorbent supply line, 14 is an extract extraction line, 16 is a roughinate extraction line, and 17 is a recycle line. In the arrangement state of adsorption chambers 1 to 12 and each line 13 to 16 shown in the drawing, desorption operation is performed in adsorption chambers 1 to 3, and desorption operation is performed in adsorption chambers 4 to 6.
A concentration operation is performed in the adsorption chambers 7 to 10, an adsorption operation is performed in the adsorption chambers 11 to 12, and a desorbent recovery operation is performed in the adsorption chambers 11 to 12. In such a condensed moving bed, each supply and withdrawal line is moved by one adsorption chamber in the liquid flow direction at regular time intervals by valve operation. Therefore, in the next arrangement of adsorption chambers, adsorption chambers 2 to 4 will carry out the desorption operation, adsorption chambers 5 to 7 will carry out the concentration operation, adsorption chambers 8 to 11 will carry out the adsorption operation, and adsorption chambers 12 to 1 will carry out the desorbent recovery operation. Each will be carried out. By sequentially performing such operations, adsorption separation treatment using a coagulated moving bed is achieved. Note that although the number of adsorption chambers is specified as 12 in the drawings, it should be noted that the number of adsorption chambers is not limited. In the present invention, the flow rate of each operation zone is an important operation variable in order to efficiently perform adsorption separation treatment using a condensed moving bed, and when the raw material supply amount is F,
It is preferable to set as follows on a volume basis per unit time. (1) Adsorption operation zone flow rate L ₁ : 0.2F+E・S＜L ₁ ＜
3.5F＋E・S (2) Concentration operation zone flow rate L ₂ : 0.2F＋E・S＜L ₂ ＜
3.5F+E・S (3) Desorption operation zone flow rate L ₃ :0.5F+E・S<L ₃ (4) Desorbent recovery operation zone flow rate L ₄ :L ₄ <0.5F+
E·S However, in the above formula, E represents the porosity of the adsorbent layer, and S represents the condensed movement speed of the adsorbent. In the adsorption operation zone, it is desirable to adsorb strongly adsorbed components and to avoid adsorbing weakly adsorbed components as much as possible. In addition, in the concentration operation zone, it is necessary to desorb weakly adsorbed components as much as possible and concentrate strongly adsorbed components into the adsorbent. Therefore, the flow rates of these two operation zones need to be set within an appropriate flow rate range depending on the adsorption characteristics of the components to be separated from each other. Next, in the desorption operation zone, it is necessary to completely desorb strongly adsorbed components, and it is desirable to set the flow rate as large as possible after considering the flow rate balance with other operation zones. In addition, in the desorbent recovery operation zone, in order to reduce the concentration of adsorbent components (methyl mole isopropyl naphthalene isomer) in the desorbent recycled from the outlet of this zone to zero, the flow rate is kept as low as possible to completely remove the adsorbent components. It is necessary to adsorb it to an adsorbent. Taking these into consideration, it is preferable to set the flow rate of each operation zone as described above. In addition, in the two-stage adsorption separation process of the present invention, the 2,6-
When a mixture containing isomers and 2,7-isomers is injected into the second stage separation process, the desorbent contained in the mixture may or may not be removed by distillation or other operations. . In the manner described above, 2,6-methylisopropylnaphthalene can be obtained continuously with high purity using methylnaphthalene and propylene as raw materials. The 2,6-methylisopropylnaphthalene thus obtained can be converted into 2,6-naphthalene dicarboxylic acid by oxidizing it. [Effect] According to the present invention, a 2,6-isomer can be separated with high purity from a 2,6-methylisopropylnaphthalene isomer mixture. The 2,6-methylisopropylnaphthalene obtained in the present invention is a 2,6-methylisopropylnaphthalene used as a raw material for polyester.
It is suitable as a raw material for producing naphthalene dicarboxylic acid. [Example] Next, the present invention will be explained in more detail with reference to Examples. In addition, the relative separation coefficient β value shown below is the value of the mixed component based on 2,6-methylisopropylnaphthalene when a raw material mixture containing 2,6-methylisopropylnaphthalene is adsorbed using a zeolite adsorbent. It gives an index of the relative strength of adsorption force and is expressed by the following formula. β[i]=K[i]/K[2,6] (1) β[i]: Relative separation coefficient K[i] of mixture component i: Solid-liquid equilibrium constant K[2,6] of mixture component i : Solid-liquid equilibrium constant K[i] of 2,6-methylisopropylnaphthalene = weight % of component i in the adsorption phase/component i in the liquid phase
% by weight of (2) K[2,6] = % by weight of 2,6-isomer in the adsorbed phase/2 in the liquid phase
, 6-isomer weight% (3) Example 1 Table 1 obtained by isopropylating methylnaphthalene with propylene and fractionating methylmonoisopropylnaphthalene from the product by distillation.
An adsorption separation experiment was conducted using a methyl monoisopropyl naphthalene isomer mixture having the composition shown in the following as a raw material. The adsorbents used in the adsorption separation experiment are shown in Table-
The seven types of zeolites shown in 2 are ion-exchanged with Ba, Ba and K, and Ba and Pb. Ion exchange was performed by the method shown below. (Ba ion exchange) About 100 g of BaCl ₂ aqueous solution (0.5 mol/) was added to about 10 g of Na-type Y-type zeolite, and the mixture was left at a temperature of 90 to 100° C. for 2 hours. After repeating the above operation three times, it was dried and then baked at a temperature of 400°C for 3 hours. (Ba, K ion exchange) BaCl ₂ (0.5 mol/
), about 100 g of an aqueous solution of KNO ₃ (1.0 mol/) was added, and the mixture was left at a temperature of 90 to 100° C. for 2 hours. After repeating the above operation 3 times, after drying, 3 times at a temperature of 400℃
Baked for an hour. (Ba, Pb ion exchange) Approximately 20g of Y-type zeolite ion-exchanged with Ba.
Approximately 100g of 10wt% Pb(NO ₃ ) ₂ aqueous solution was added, and the temperature
It was left at 90-100°C for 5 hours. After drying the zeolite, it was calcined at a temperature of 400°C for 3 hours. The adsorption separation experiment was carried out using the method shown below. Approximately 4 adsorbents are placed in an autoclave with an internal volume of 30 c.c.
About 8 g of raw material oil were charged, the temperature was kept constant while stirring, and the temperature was kept constant for 120 minutes. The adsorbent and the raw material residue were separated by filtration, and the adsorbent in the adsorbent was desorbed by Soxhlet extraction using a toluene solvent after washing the adsorbent with isooctane. The compositions of the raw material residual liquid (liquid phase) and the adsorbate (adsorption phase) were analyzed by gas chromatography and are shown in Tables 3 and 4. As is clear from the results in Table 3, the four types of zeolite adsorbents shown in Table 3 all have 2,6-
There is almost no difference in β value between methylisopropylnaphthalene and 2,7-methylisopropylnaphthalene (for adsorbent D, the 2,4-isomer is also included), but there is a The β value differs by about 2 times, 2
It is suitable as an adsorbent for use in the first stage of staged adsorption separation. Also, from the results shown in Table-4, Table-
The three types of adsorbents shown in 4 are different in β value of 2,6-methylisopropylnaphthalene and 2,7-methylisopropylnaphthalene by more than twice, and are suitable as adsorbents for use in the second stage of two-stage adsorption separation. Appropriate.

【table】

【table】

【table】

[Table] Example 2 Adsorption separation of 2,6-methylisopropylnaphthalene from raw material 1 shown in Table 1 was carried out using a condensed moving bed continuous chromatographic separation apparatus shown in FIG. Separation of 2,6-methylisopropylnaphthalene was carried out in two stages as shown below. First, in the first stage, 2,6-methylisopropylnaphthalene and 2,7-methylisopropylnaphthalene are taken out as extracts from the raw material mixture, and in the second stage, 2,6-methylisopropylnaphthalene is extracted from the raw material mixture. -Methylisopropylnaphthalene was separated as roughinate. In the apparatus shown in FIG. 1, in the first stage,
Adsorbent B shown in Example 3 was packed into adsorbent columns 1 to 12 having an internal volume of 40 ml. From line 15 to table -
Raw material-1 shown in 1 was supplied at 100 ml/HR, and the desorbent was supplied from line 13 at 165 ml/HR.
Extract was extracted from line 14 at 136ml/HR, and roughinate was extracted from line 16 at 129ml/HR.
It was extracted at ml/HR. At this time, at 150 second intervals, column 1 becomes 12, 11 becomes 10, 7 becomes 6, 4 becomes 3
was moved at the same time. The concentration of 2,6-methylisopropylnaphthalene in the extract obtained in the first stage is approximately
The concentration of 70wt% 2,7-methylisopropylnaphthalene was about 30wt%, and the recovery rate of 2,6-methylisopropylnaphthalene was 98%. Next, in the second stage, the desorbent was removed by distillation from the extract obtained in the first stage and used as a raw material. Adsorbent columns 1 to 12 were filled with adsorbent G shown in Example 1. The raw material mixture was supplied from line 15 at a rate of 100 ml/HR, and the desorbent was supplied from line 13 at a rate of 110 ml/HR. Extract was extracted from line 14 at a rate of 110 ml/HR, and roughinate was extracted from line 16 at a rate of 100 ml/HR. At this time, change column 1 to 12 and 1 at 120 second intervals.
I moved 1 to 10, 7 to 6, and 4 to 3 at the same time. The purity of 2,6-methylisopropylnaphthalene in the raffinate obtained in the second stage was 99 wt% on a desorbent-free basis, and the recovery rate based on the first stage raw material was 90%.

[Brief explanation of the drawing]

The drawing is a schematic diagram of an adsorption separation operation using a coagulated moving bed. 1-12...Adsorption chamber, 13...Desorbent supply line, 14...Extract extraction line, 15...
... Raw material mixture line, 16 ... Roughinate extraction line, 17 ... Recycle line, 18 ... Pump.

Claims (1)

[Claims] 1. When separating the 2,6-isomer from a methyl monoisopropyl naphthalene isomer mixture, the mixture is substituted with one or more cations mainly selected from alkali metals and alkaline earth metals. contact with a first zeolite adsorbent having a Y-type structure, and transfer the 2,6-isomer and 2,7-isomer contained in the mixture to the first adsorbent with higher selectivity than other isomers. After the adsorption, there is a first step of desorbing the adsorbed material from the first adsorbent, and the desorbed material obtained in the first step is mainly selected from alkali metals other than sodium and alkaline earth metals. Contact with a second zeolite adsorbent having a Y-type structure substituted with one or more cations to select the 2,7-isomer contained in the desorbed product more highly than the 2,6-isomer. 2. A method for adsorption and separation of 2,6-methylisopropylnaphthalene, comprising a second step of adsorbing the adsorbent onto the second adsorbent at a certain rate, and then desorbing the adsorbate from the second adsorbent.