JPS6041622A - Separation of p-xylene from p-xylene-containing mixture - Google Patents

Abstract

PURPOSE:To separate p-xylene from a p-xylene-containing mixture in high selectivity in high recovery ratio advantageously, by preparing an inclusion compound of p-xylene and metacyclophane. CONSTITUTION:Preferably 0.01-100mol compound shown by the formula based on 1mol p-xylene in a p-xylene-containing mixture is brought into contact with the p-xylene-containing mixture preferably at 0-200 deg.C so that p-xylene is included in the compound shown by the formula, and the formed inclusion compound is separated by solid-liquid separation. The compound is heated preferably at 120-280 deg.C so that p-xylene is separated and recovered from the inclusion compound. The compound shown by the formula has merits of improved performance, its inexpensive synthesis, free selection of economic process, etc., and advantageously the inclusion compound can easily desorb p-xylene by various processes in high purity.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for separating p-xylene from a p-xylene-containing mixture using metacyclophane represented by the following formula.

Conventionally, regarding clathrate compounds of P-xylene, for example, (1) clathrates with tri-thymotide; see Am+ Chem, Soc. 3747 (1952) and 2339 (1958) ( 11) Inclusion complex with α-cyc p-dextrin; see US Pat. No. 3,456,028 Specification 1F OiD Inclusion complex with natural or synthetic zeolite; see Japanese Patent Publication No. 37-5155. The present invention was achieved as a result of various studies on inclusion bodies different from known inclusion bodies of P-xylene and their uses.

That is, the present invention involves contacting metacyclophane represented by the following formula (I) with a P-xylene-containing mixture to form an inclusion compound containing the metacyclophane KP-xylene, and forming an inclusion compound containing the metacyclophane KP-xylene. This is a method for separating P-xylene from a mixture containing P-xylene, which is characterized by separating the compound and separating and recovering P-xylene from the clathrate compound.

In the present invention, it has never been known that P-xylene is included in the metacyclophane to form an inclusion composition, and based on this phenomenon, P-xylene is included from a P-xylene-containing mixture. can be separated with high selectivity and high recovery rate.

The present invention will be explained in detail below.

The methanecrophane of the present invention may be any cyclic compound represented by the above formula CI), and can be obtained by various production methods. For example, the manufacturing methods include (a) Helvet's force, Kimika, γ-futa (Helvet's force),
i ca.

Chimica Acta) 50 volumes F25cicu
lus 7 (1967) No. 204 (b) Synthesis 424
(1974) and others.

In the present invention, various methods can be applied to obtain the clathrate compound of metasic Iff fan and P-xylene of the general formula CI).

For example, the metacyclophane may be added to a mixture containing P-xylene, or the mixture obtained by adding metacyclophane as described above may be heated to completely achieve inclusion. It can also be obtained by preparing a solution dissolved in water, cooling the solution, and separating the resulting crystals.

Metacyclophane can be easily converted to P- by either method.
A clathrate compound containing xylene can be obtained.

The amount of metacyclophane of formula CI) used is P --
Proportions of from 0.01 to 100 mol, preferably from 0.1 to 10 mol, in particular from 0.2 to 2 mol, are advantageous per mole of [1]-xylene in the mixture containing 1'-silene.

As mentioned above, when P-xylene is included in metacyclophane, the temperature is generally -50 to 350°C, preferably 0 to 350°C.
It is carried out at a temperature of 200°C, especially in the range from 20 to 150°C. In order to separate the clathrate compound thus formed from a mixture containing it, it is usually preferable to use solid-liquid separation (for example, filtration, centrifugation, sedimentation, etc.) or to remove the solvent component by evaporation by distillation. I can do it.

No matter which method is used, the temperature for repeated cultivation is between 150 and 120.
℃, preferably in the range of 0 to 90℃.

In the present invention, the "P-xylene-containing mixture" from which P-xylene is separated may be one that contains P-xylene, or contains components other than p-xylene that inhibit inclusion. Any material may be used as long as it does not easily desorb P-xylene from the generated clathrate compound, and in particular, one that does not easily dissolve the clathrate compound is preferred.

The content of P-xylene in the P-xylene-containing mixture is
Even if the content of P-xylene is extremely low, the clathrate compound can be removed, so a wide range may be used. For example, when C8 aromatic hydrocarbons are used as a P-xylene-containing mixture, the P-xylene clathrate compound can be easily separated from the C8 aromatic hydrocarbons by adding metacyclophane to clathrate it. can do.

"C8 aromatic hydrocarbons" means three types of xylenes, O-xylene, m-xylene, and P-xylene, and ethylbenzene, and these four types of 08 aromatic hydrocarbons have very close boiling points. Therefore, it is extremely difficult to carry out distillation separation industrially. In particular, the difference in boiling point between m-xylene and p-xylene is small and it is extremely difficult to isolate them even by ordinary laboratory precision distillation.

However, the difference in boiling points between ethylbenzene and P-xylene is also small, making it difficult to separate them by distillation.

Currently, industrially known methods include a crystallization separation method that utilizes the abnormally high melting point of P-xylene, and a separation method that utilizes the formation of a complex compound of HP-BF and m-xylene. There were problems such as deep cooling of raw oil, handling of crystals, and corrosion of equipment.

In recent years, adsorption separation methods using zeolites have been industrialized. Since this method does not have the problems of eutectic point and solubility in the crystallization separation method, it improves the recovery rate of KP-xylene and improves its utility.

It is expected that the equipment will be converted into a shed. However, on the other hand, the use of expensive adsorbents, the decline in adsorption capacity (equipment capacity) over time,
It is not necessarily an advantageous process because of problems such as a complicated desorption mechanism and separation of the desorbent and xylene.

However, the metacyclophane used in the present invention has not only excellent performance, but also the fact that it can be synthesized at low cost.
It has advantages such as being able to freely choose economic processes.

Further, in the inclusion composition of metacyclophane and P-xylene, P-xylene can be easily desorbed by various methods, and pure P-xylene can be obtained.

In the present invention, when separating P-xylene from the clathrate compound of metasic+:+77 and P-xylene, various methods are employed, for example, (a) separating the clathrate compound from 9
A method for separating P-xylene by heating to a temperature in the range of 0 to 350°C, preferably 120 to 280°C, (b) inclusion compounds such as n-hexane, benzene, and cyclohexane.

A method of separating P-xylene by bringing it into contact with a solvent such as acetone is advantageously applied.

The clathrate compound of the present invention will be explained below. The isolated crystal (clathrate compound) was vacuum dried to remove deposits, and the results of analysis were as follows.

+11 Infrared analysis; Metacyclophane 3050-2850.1610.1590°1490
+1455 1 Los'o +890 +790.

700, 460α-1 P-xylene 3050-2850 +1515.790.485cm
-'Inclusion composition 3050-2850, 1610.1590°1515.
1490, 1453, 1080, 890°790 +7
00.485 +460cm ”Therefore, no absorption other than that due to metacyclophane and P-xylene (15151485) was observed.

(2) Gas chromatography analysis: When the crystal (clathrate compound) was subjected to force μ analysis, the concentration of P-xylene clathrated in the crystal relative to other components was approximately 95% or more, and the majority was P-xylene. It was suspected that it was xylene.

+31 Differential thermal analysis; Differential thermal analysis of the crystal (clathrate compound) revealed that it was 90-1
A weight loss was observed at 15° C., and the amount of weight loss was found to be due to the inclusion ratio (P-xylene/metacyclophane = 0.99 C molar ratio). This result shows that P-xylene: 11 (molar ratio) is included in metacyclophane.

The above results show that even if the P-xylene mixture contains one or more components other than P-xylene in arbitrary proportions, the clathrate compound of the present invention can be obtained. This shows that P-xylene can be selectively included and separated from a P-xylene-containing mixture by using metacyclophane.

The present invention will be described in detail below with reference to Examples.

In the examples, "me" means metacyclophane, "px" means P-xylene, "mx" means m-xylene,
EB indicates ethylbenzene.

In addition, the selectivity (8) in Examples is a value determined based on the following formula.

Example 1 0.05 part of me is added to 0.5 parts of each PX+mx+EB at room temperature. At this time, only PX becomes cloudy, but mx
+ FB is completely dissolved. When each of these solutions is heated to 80° C. and maintained for about 2 minutes to completely dissolve each solution, and then cooled to room temperature, a large amount of needle-shaped crystals are generated from only the PX solution. The other mX+EB solutions were in a dissolved state and no crystals were formed even after being left for a long time.

Example 2 0.2 part of me is added to 3 parts of a mixed solution of 1 part each of PX, rnX + EB, heated to 100°C, completely dissolved, and then lowered to room temperature to form needle-shaped crystals. . This mixture was filtered, resulting in 100 ml of crystalline room temperature
Dry with gobs for 1 hour to remove attached xylene,
0.22 parts of white, needle-shaped crystals were obtained. When a part of this crystal was analyzed using Gask p, the selectivity was βPX/mX-
24. Since βPX/EB=68 and the PX concentration in the crystal is PX/(PX+mX+F B )=0.95, it was found that mX T EB was hardly contained in the crystal. Furthermore, the infrared analysis data of this crystal is: 3050~2850.1610+1590.1515°1490.1453,1080,890.790 +7
00+485.460 low 1, absorption by mc and absorption by PX (1515,
No absorption of (mX + eB) other than 485) was observed.

From these results, this crystal is considered to be an almost pure PX clathrate with no xylenes deposits.

Next, when 0.0083 part of this white needle-like crystal was analyzed using an indicative thermostat, it was found that 0.001 part at 90-115°C.
A weight loss of 2 parts was observed, and the inclusion rate (p
x+mx+FB)/me (molar ratio)=0.
A value of 99 was obtained.

Example 3 2 parts of nicO was added to 2 parts of a mixed solution consisting of 1 part each of pX + mX, and the same operation as in Example 2 was performed to obtain 0.2 parts of nicO.
One part of white needle-like crystals was obtained. When this crystal was analyzed using gask p, a value of βpx/mx=1.9 was obtained.

Examples 4 to 9 0.1 part of me was added to a mixed solution of 1.0 part of the following solvent and 1.0 part of px, and after heating and dissolving at 70 to 130°C, it was slowly cooled to room temperature to form crystals. After separating the crystals from the solution by suction filtration at room temperature,
Dry under reduced pressure for 1 hour. The white crystals thus obtained were dissolved in another solvent and subjected to gas chromatography analysis to determine the separation factor β.
The results shown in the table below were obtained as px/5olv.

Example 0 0.1 part of the white needle-like crystals obtained in Example 2 was added to 2 parts of methanol, and the mixture was stirred for 10 minutes at 10° C. to obtain 0.09 part of white needle-like crystals. When a part of this crystal was subjected to gas chromatography analysis, px/(px+mx +EB) =
0.94, which was the same as before contact with methanol.

Example 11 White needle-like crystals obtained in the same manner as in Example 2 (set #::
(px +mx +EB)/mc= 0.99 (
rno//mo/'), pxlCpx+mxtenFB
) = 0.95 (moIV/moA!))0.
Add 1.0 part of benzene to 2 parts and place in a sealed tube, 130
After heating to ℃ to completely dissolve the crystals, the mixture was cooled to room temperature to form needle-shaped crystals again.

The total amount of the residual liquid obtained by separating the cake from the mixture by filtration and the washing liquid obtained by washing the cake with 0.5 part of benzene (hereinafter referred to as liquid F) was 1.1 parts.

When this P liquid was analyzed by gas chromatography, Cpx-1-mχ1E
B)/benzene = 2.1 (wt%), px/(
px+mx+EB)-0,95(moJ/moJ)
Met. In this way, by evaporating and removing benzene from the f liquid, 0px (containing a trace amount of mx + EB) was reduced to 80
% recovery rate.

Patent creator Teijin Ltd. 〆・１・、・・

Claims (1)

[Scope of Claims] Metacyclophane represented by the following formula and a P-xylene-containing mixture are brought into contact to form an inclusion compound in which P-xylene is included in the metacyclophane, and the inclusion compound is 1. A method for separating P-xylene from a P-xylene-containing mixture, the method comprising separating the clathrate and recovering P-xylene from the clathrate.