JPS5818627B2 - Ekita chromatography - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method for separating mixtures by liquid chromatography.

More particularly, the present invention relates to improved elution chromatographic separation methods performed on two columns or on a single column.

The procedure of the invention is particularly suitable for the separation of C8 aromatic isomer mixtures.

In the liquid chromatographic separation of mixtures for recovery of desired components on a commercial scale, it is economically desirable to operate under conditions that keep the elution volume/feed ratio low.

The reasons for this depend primarily on the costs involved in distilling the carrier and eluent after the feed components have been eluted from the chromatographic column, which costs increase as the elution volume/feed ratio increases.

One of the main causes of high elution volumes in these methods is that the peaks eluted last from the column have a larger half width than the peaks eluted earlier.
It is related to the phenomenon of having

As used above and below, elution volume/feed ratio means ``the combined volume of eluent and carrier/volume of feed to be separated''.

Chromatography is a method by which components contained in a fluid mixture can be separated from that mixture.

This is accomplished by selectively retarding one or more components in the fluid mixture as the fluid moves uniformly through a "column containing a stationary substrate."

This delay results from the partitioning of components in the mixture between the substrate and the fluid as the fluid passes through the stationary phase.

One particular type of chromatography used is called elution chromatography.

In this technique, the feed mixture and "carrier liquid + eluent" are passed through the column one after the other.

A carrier fluid is defined herein as a liquid material that is not significantly adsorbed to the substrate in the presence of the feed mixture components.

An eluent is an eluent that is adsorbed onto a substrate and separates feed components and adsorption sites (
This is a term used to describe a liquid substance that competes for adsor-ption 5ites).

This continuous passage of feed and carrier eluent results in differential movement of each component depending on its distribution between the phases.

If the sample components have different partition coefficients, separation of each component is achieved as each component is eluted successively from the end of the stationary phase.

In normal elution development, the retention capacity, or retardation factor, is required for optimal separation.
factors) are only within a narrow rangeG).

The partition coefficient must be large enough to prevent each of the initially eluted components from being pushed out of the column in a series of unseparated bands, but it must also be large enough to avoid excessive elution times. It must be appropriately small to avoid spreading of the seed peak.

Moreover, the distribution coefficients of each component must be different so that separation of each component can be achieved.

The gradient elution development method described herein
lution development) makes it possible to automatically and gradually acquire the necessary elution capacity for each component.

In gradient elution, the development of the chromatogram is characterized by intentionally varying the elution conditions (including the composition of multiple phases, column pressure, and column temperature) during the separation process.

In liquid column chromatography, adjusting the composition of the eluent-carrier fluid is the most readily available research tool.

It is well known in the separation art that certain adsorbents, generally consisting of crystalline aluminosilicates, are used to separate certain hydrocarbons from feed mixtures.

In the separation of aromatic hydrocarbons, particularly in the separation of C8 aromatic hydrocarbons, it is generally accepted that certain crystalline aluminosilicates are effective for certain C8 aromatic hydrocarbons.

An example of the prior art is Neuzil, US Pat. No. 3,558,732, which teaches an improved adsorption separation process, the improvement of which consists in using toluene as the desorption agent.

Other researchers have taught the use of different types of X and Y zeolites to separate baraxylene from mixtures of C8 aromatic isomers (see e.g. Neutwill U.S. Pat. No. 3,626,020). thing).

U.S. Patent 36 of Tine et al.
No. 36,121 describes a dual adsorption and isomerization process for the recovery and isomerization of various 08 aromatic isomers, and diethylbenzene is the preferred eluent for operating the process.

The present invention relates to liquid chromatography for the separation of one or more components contained in a mixture in a feed stream, the method comprising: (a) transferring a feed stream mixture containing the components to be separated to a crystalline aluminosilicate adsorbent; (b) contacting the bed with an eluent selected from the group consisting of aromatic compounds (including substituted aromatic compounds); (C) recovering from the bed a stream(s) containing at least a portion of the less selectively adsorbed component; and (d) the concentration of the selectively adsorbed component being higher than that of the other components in the feed stream. Each step consists of recovering a significantly increased stream(s) compared to the components, the improvement of which is to increase the eluent concentration in the fluid carrier during the operation of steps (a) and (b) above. The objective is to perform the desired separation under conditions that can increase the elution volume/feed ratio, thereby resulting in a lower elution volume/feed ratio.

This improved liquid chromatography method finds particular applicability in the separation of paraxylene and ethylbenzene from C8 aromatic isomer mixtures containing ethylbenzene.

The present invention relates primarily to an improved single column liquid chromatographic separation method for C8 aromatic mixtures.

This process is aimed at the ultimate recovery of pure para-xylene or "para-xylene and ethylbenzene" with a purity greater than 99 parts, and in this process 90 parts of the para-xylene introduced as feed is recovered.

Preferably, the process according to the invention is carried out using type Y zeolites, such as potassium-exchanged type Y (KY), potassium-ammonium exchanged type Y (KY),
Type Y zeolites such as ammonium KY) and barium-potassium exchanged type Y are used.

These sieves are described in U.S. Pat. No. 3,696.
107 and 3626020, by the typical cation exchange method described in each specification.

When p-xylene alone or p-xylene and ethylbenzene is desired as a product, KY Receive is preferred and the process involves the use of typical manufacturing steps used in liquid elution chromatography methods.

i.e., contacting a feed mixture, e.g., a KY receive, under conditions that effect preferential adsorption of paraxylene and ethylbenzene: contacting a KY receive bed containing selectively adsorbed paraxylene and ethylbenzene with a carrier eluent mixture (thereby recovery of a stream containing meta-xylene, ortho-xylene, para-xylene, ethylbenzene, and mixtures thereof from the bed containing its KY-receives, and ultimately the production of para-xylene and ethylbenzene. It is to collect it as a flow.

The technical idea of gradient elution of the present invention is to - tailing effect of strongly adsorbed components;
The enrichment of the overall chromatogram obtained by selective separation of C8 aromatic isomers by decreasing t) provides a means of reducing the total elution volume/feed ratio.

One of three methods is used to perform this gradient elution technique.

That is, in the first method, the eluent concentration in the carrier eluent is increased stepwise over time.

Alternatively, a second method involves continuously increasing the eluent concentration in the carrier eluent over time as the feed mass passes through the bed.

The third method is a less preferred method, in which a weak eluent is replaced by a strong eluent during the elution of the feed components.

Perform gradient elution with displacement.

This substitution may be carried out in a stepwise or sequential manner as described above.

The improved process according to the invention resulting in a reduction in total elution volume by the gradient technique described above is aimed at the recovery of ethylbenzene and baraxylene product streams.

It has been discovered that increasing recirculation while increasing the ratio of scavenger to fresh feed also increases the amount of ethylbenzene recovered.

Accordingly, in another embodiment, the process of the present invention is operated with recirculation ranging from 0 to about 100 parts on the fresh feed, resulting in recovery of about 20 to about 80 parts of ethylbenzene.

Additionally, it has been discovered that an improved process for recycling unseparated components can be performed that eliminates the need to distill the recycle agglomerate to separate the xylenes.

It has been shown that leaving the carrier eluent together with the recycled xylenes in the recycle mass has no significant effect on the subsequent feed mass to be separated.

This embodiment achieves significant savings in operating costs for the overall process due to the reduction in the amount of distillation required.

Metadiisopropylbenzene, m-
When DIPB is used in a carrier eluent stream consisting of 10-100% metadiisopropylbenzene, the ethylbenzene peak from the varaxylene peak is reduced compared to similar systems using orthodichlorobenzene or 0DCB or toluene as the eluent. It has also been discovered that the resolution is significantly increased, and this is therefore another aspect of the invention.

The eluent can be any inert diluent as a carrier, such as a C6 to C2ON, preferably a C11 to C15 paraffin, such as n-dodecane, n-decane, n-tridecane, n-tetradecane, n-hexadecane, eicosane, etc. It can also be used in combination with

Typically an amount of about 25% m-DIPB and 75% n-dodecane is used.

However, in operating a gradient elution method, this initial 25% concentration of eluent in the carrier eluent is approximately 95% in the carrier eluent stream by any of the methods described above.
The final concentration is increased to:

The invention can be operated under a wide range of conditions.

For example, the pressure is not critical, and the method of the present invention
50 atmospheres, preferably 0.1 to 10 atmospheres, most preferably 1
It may be operated under pressures ranging from ~5 atmospheres.

When applying the present invention to commercial liquid chromatographic separations of C8 aromatic isomers, the specific parameters used, such as optimum feed volume, eluent, column length, temperature, sieves, etc. It can be changed accordingly.

However, generally the temperature will be in the range 25-200<0>C, preferably 160-200<0>C.

Normally, the process of the invention is operated isothermally.

Furthermore, the process of the invention can be operated without or with recirculation.

The amount of this recirculation is expressed as the amount divided by the amount of fresh feed multiplied by 100;
, preferably about 10. ~75%.

The method of the invention is preferably carried out using a single 9 column scheme (Col
Although described as an improvement to the two-column scheme, the operations of various aspects described herein are also useful as improvements to the two-column scheme.

This scheme uses a critical feed rate that is at least twice, and preferably at least four times, the highest feed rate used to obtain the three pure components in a single column scheme.

Although m-DIPB is described herein as a suitable eluent, the method of the present invention is suitable for use with 0DCB and other eluents such as varadiisopropylbenzene or its m-DIPB.
It can also be operated using a mixture with DIPB as eluent.

A typical operating scheme employs a gradient elution method in which the eluent concentration in the liquid carrier is increased, e.g.
If the eluent is used, increase the amount stepwise from 25 to 50%, or from 25 to 95% if the eluent is used. (if used).

The method of the present invention is carried out using a column with KY receive.

The column was washed with 20% m-D I P B.
- carrier eluent consisting of 80% n-dodecane is 91
crrL (0,3 ft) 7 min linear velocity and 130
Pass under column temperature of °C.

The column was thoroughly cleaned with 20% p-xylene, 20% by weight.

The flow of carrier eluent is stopped when a feed consisting of 0-xylene, 20% ethylbenzene, and 40% m-xylene is injected into the column.

Attached is the first chromatogram showing the separation of each component.
As shown in the figure.

Immediately after the feed injection, the carrier eluent, (Dl) is allowed to flow down again.

The composition of the carrier eluent stream was determined to be a separate 100% m-D
I Three-boat/three-way valve (th) from the PB-containing storage tank
ree port.

Stepwise change to D2 by two-way valve).

The composition of this carrier eluent stream is eluted more than Dl.

The operation of changing to D2, which has a higher concentration of agent, is accomplished a certain period of time after the column composition cross section shown in FIG. 1A is achieved.

The effect of D2 on the elution evolution of the feed in the column is shown in Figure 1B, where p-xylene elutes more rapidly, while m-xylene and o-xylene elute as product streams. Indicates that it will be removed.

A fixed amount of D2 is passed through the column, followed by the next feed injection involving the utilization of carrier eluent stream D1.

The column composition cross-section shown in FIG. 10 illustrates the removal of ethylbenzene as a product stream.

Figure 1D shows p- removed as a product stream together with detachment agent D2.
Indicates xylene.

The specific time for changing from Dl to D2 mentioned above depends on the temperature, flow rate,
It is a function of column size, detachment agent and sieve.

The time must be chosen so that the p-xylene peak primarily elutes from the column in the presence of detachment agent D2.

When the gradient elution method is used by continuously increasing the eluent concentration in the carrier eluent stream, a typical operating scheme is to perform a stepwise transition from Dl to D2 instead of The scheme is similar to the above scheme except that the initial composition of agent D1 is changed continuously until composition 2 is reached.

This process can be carried out by conventional means, such as using a mixing tee to vary the flow rates of the two streams D1 and D2 to produce any desired change from D1 to D2.

The third gradient elution method, or displacement method, has a Dl of 25 to 100.
It is a weak eluent for m-DIPB, but D2 is 25
The scheme is similar to the above except that a strong eluent such as 0DCB of ~100 is used.

The invention will be more easily understood with reference to FIG.

In Figure 2, which depicts a typical commercial scale application of the invention, feed stream 1 is introduced into a chromatographic column.

The feed is followed by a stream 14 of weak release agent.

The weak release agent is then followed by a stream 15 of strong release agent.

The strong release agent is the most strongly retained component in the feed (
i.e., valaxylene) is eluted into a stream containing primarily only the strong release agent.

Product recovery is accomplished by sending the eluted stream to another fractionator.

Stream 2 (first fraction) is separated to produce a mixed xylene product (stream 7)
, a bottom stream of weak release agent (stream 5) and a side stream of strong release agent (stream 5).
Flow 6).

This release agent stream is sent to a storage drum for reuse.

Stream 3 (second fraction) is fractionated into an ethylbenzene product (stream 9) and a weak scavenger bottoms stream (stream 8).

Stream 4 was combined with the disparate xylene product (Stream 13) and the strong release agent bottom stream (Stream 13).
Separate into Stream 12).

In the illustrated fractionation scheme, both the strong and weak detachment agents must have a higher boiling point than the product, and the strong detachment agent must have a lower boiling point than the weak detachment agent.

This becomes true when 100% metadiisopropylbenzene is used as the strong release agent and a mixture of metadiisopropylbenzene and tridecane is used as the weak release agent.

If it is desired to increase the recovery of ethylbenzene, take another product containing ethylbenzene in admixture with other C8 aromatics (stream 16) and recycle it into the column with the fresh feed. Circulate.

The following examples are provided to further illustrate the improved method of the present invention.

However, it should be understood that the details should not be considered a limitation of the invention.

This is because, as those skilled in the art will understand, they are subject to modification.

Example 1 (see Figure 3) (Comparative example) Potassium Y sieve was ground to 20 to 40 mesh, and about 3
(Bi' is 2.74 m (9 ft) long, outer diameter 0.6
35c1rl (0.25 inch), inner diameter 0.457Cr
It was placed in a rL (o, is inch) stainless steel column.

25% m-D I P B and 75% n C12
A carrier eluent mixture consisting of paraffin was heated at 130°C.
was fed to the column at a constant flow rate of 1.51111/min.

Stop the carrier eluent flow and add 2.0 ml of 20
Samples consisting of xylene, 20 fb ethylbenzene, ortho-xylene 20, and 40 fb xylene were collected using a 6-port sample loop valve (1 loop valve).
) to the system headstream of the packed column (sy
stem upstream).

The carrier eluent stream was restarted immediately and samples of the stream eluting from the end of the column were taken periodically.

Each sample was analyzed by gas chromatography to determine the weight of the C8 aromatic compound.

The results are shown graphically in FIG. 3, which shows the elution of the various 08 aromatic isomers as a function of elution volume.

This result is shown in Figure 3, and as the name suggests, the ethylbenzene peak does not overlap with the para-xylene peak; therefore, when the elution volume reaches 58-6877 Il, the ethylbenzene in the carrier eluent stream is pure ethylbenzene (other than pure ethylbenzene). 08 isomer) and that the total elution volume of C8 aromatic isomer was 140771
1.

Therefore, the elution volume/feed ratio is 140 ml/2. Oru
l=70.

Example 2 (see Figure 3) (Comparative example) Eluent-carrier mixture: 80% n
The procedure of Example 1 was repeated using C12 paraffin.

The results showed that the amount of ethylbenzene recovered was reduced compared to Example 1, the total elution volume was 110 ml, and the ethylbenzene and baraxylene peaks overlapped to a greater extent than in Example 1. This indicates that this was the cause of a decline in recovery.

Example 3 (see Figure 3) (comparative example) 25%0DCB75%n as carrier eluent mixture
The procedure of Example 1 was repeated using C1□ paraffin.

The results showed that no pure ethylbenzene was recovered, the total elution volume was 100 ml, and the ethylbenzene and baraxylene peaks were either Example 1 or Example 2.
This shows that the overlap was worse than in either case.

Example 4 (See Figure 3) (Comparative Example) The operation of Example 1 was repeated using an ammonium-potassium Y sieve prepared by replacing the sodium Y sieve with a mixed aqueous solution of ammonium and potassium salts.

The results show that less pure ethylbenzene was recovered than in Example 1 and that the total elution volume increased from 140 ml in Example 1 to 1857'Ill.

Example 5 (See Figure 3) (Comparative Example) The procedure of Example 3 was repeated using the same ammonium potassium Y sieve as in Example 4.

The results showed that only a very small amount of pure ethylbenzene was obtained and that the total elution volume increased from 100 ml in Example 3 to 11 ml.
01rLl and that the overlap of the varaxylene-ethylbenzene peaks occurred as before.

Example 6 (see Figure 3) 20 minutes after injecting the feed.
Example 1 was repeated substituting 100% m-DIPB for 5% m-DI'PB-75% nC]2 paraffin.

The results show that the amount of ethylbenzene recovered is the same as in Example 1, and the total elution volume is reduced to 90 ml.

Example 7 (See Figure 3) Example 3 using 60% 0DCB-40% n C12 paraffin instead of 25%-OD CB 75% n C12 paraffin as the carrier eluent 25 minutes after injection of the feed. The operation was repeated.

The result is that no pure ethylbenzene is recovered;
and the total elution volume was reduced to 65 TrLl, and the recovery of p-xylene was good.

If you start gradient elution earlier, the peak of p-xylene will elute earlier together with the peak of ethylbenzene.
-Increasing the overlap of xylene-ethylbenzene, p-
This would reduce xylene recovery.

Example 8A (see Figure 3) (Comparative Example) The procedure of Example 3 was repeated with the feed used in Example 3 (5.0 ml) injected into the column.

The results are discussed below.

Example 8B (See Figure 3) (Comparative Example) In this part of the example, 5.0 ml of the feed used in Example 8A and 5.0 TrL of 25% 0DCB-75% n-
The procedure of Example 8A was repeated by injecting 100 rnl of feed consisting of 01□ paraffin carrier.

The results of Examples 8A and 8B resulted in the separation of C8 aromatic isomers observed even in the presence of carrier in the feed.

indicates that there was no change.

Example 9 Examples 2, 4 and 5 were repeated in a series of experiments using the gradient elution method described herein.

The result is balaxylene and as a product stream. Ethylbenzene is recovered and the total elution volume is as shown in Example 2 above.
, 4 and 5.

Example 10 Barium/potassium Y sieve (rice) as sieve.

The procedure of Example 1 was repeated using a sample prepared according to US Pat. No. 3,663,638).

2. Using 25% by weight toluene-75% n-dodecane as the initial eluent. Twenty minutes after injection of the Orrtl C8 aromatics mixture, the initial eluent was added to 50% by weight of toluene.

I changed it to n.

The results show that pure ethylbenzene is not recovered, but recovery of paraxylene occurs with a total elution volume of about 100 ml or less.

Example 11 Modified potassium Y zeolite as sieve (U.S. Pat. No. 3
686,343) and using 17% by weight ortho-dichlorobenzene-83% n-dodecane as the initial eluent;
．． Twenty minutes after the injection of 25 ml of the 50150(7) ethylbenzene/valaxylene mixture, the mixture was changed to 60% by weight ortho-dichlorohensen.

The results show that pure paraxylene was recovered and that the total elution volume was less than 100 Tll.

Under these conditions, pure ethylbenzene cannot be recovered from a feed mixture containing all four C8 aromatic isomers because meta-xylene elutes in the ethylbenzene recovery.

Example 12 After 20 minutes of injection of the C8 aromatic isomer (2.0 ml), the procedure of Example 2 was repeated, increasing the toluene concentration from the initial 25% to 60%.

As a result, pure ethylbenzene is not recovered, but pure paraxylene is recovered, and the total elution volume is 100 m
This indicates that the value was 1 or less.

Operating the process at relatively high temperatures, such as about 160°C or higher, preferably between 160 and 200°C, results in smaller elution volumes and relatively larger feeds to obtain lower total elution volume/feed ratios. It has now been found in the present invention to provide an economical method for producing scales and thus varaxylene using a material size.

According to this aspect of the invention, when the process is conducted at a temperature of at least 160° C. and a relatively large feed size is used, an average reduction in elution volume/feed ratio of a factor of 40 is achieved; This is due to the increase in size and the decrease in elution volume.

Increasing the temperature of the bed during operation of this gradient elution method will concentrate the chromatogram and bring the peaks closer together.

When the process is carried out at elevated temperatures while decreasing the elution volume, the ethino and lebenzene peaks overlap with the meta-xylene/ortho-xylene peaks, resulting in a slight decrease in the amount of ethylbenzene recovered.

Surprisingly, however, the reduction in elution volume/feed ratio completely outweighs any negatives that must be taken into account by the reduction in ethylbenzene recovery.

In operation of the present invention, a length of 2.74 m (9 feet)
, 20~ with inner diameter 0.457CrfL (0.18 inch)
A column packed with a -Y receive of 49 mesh was used, and m-diisopropylbenzene/dodecane was used as the carrier eluent at a rate of 9. A feed volume of about 2.5 ml was found to be optimal when used at a flow rate of ICrfL (0,37 id) and carried out at a temperature of 160 to about 200<0>C.

It was also found that the recovery efficiency of baraxylene was significantly improved.

The elution volume/feed ratio in this example is lower than the elution volume/feed ratio in Comparative Example 2.

Similarly, Example 6. Nucleation in Example 7 is Comparative Example 1, Comparative Example 3
lower than the nuclearization in .

These facts are summarized in Table 1.

Example 13゜20/20/20/40 baraxylene-ethylbenzene-orthoxylene-meta-xylene (2,5rrLl)
The procedure of Example 6 was repeated by injecting a sample of .

The elution volume/feed ratio decreased to 36, and the ethylbenzene recovery decreased from 30 parts to 1 part per total ethylbenzene injected.
It decreases to 5%.

Example 14゜ The procedure of Example 13 was repeated using a column temperature of 160°C.

As a result, the elution volume was 64ml! elution volume/
It shows that the feed ratio decreases to 25.6.

The amount of ethylbenzene recovered is 10% of the total ethylbenzene injected, which is only a slight decrease.

EXAMPLE 1 The procedure of fIJ14 was repeated using 75% meta-diisopropylbenzene-25% para-diisopropylbenzene in place of the m-DIPB used in the 5° carrier eluent stream.

First 20 minutes: 25%m-DIPB-75%n
C1□20 minutes after paraffin: 75% m-D I P B-25
%pDIPB Substantially identical results to those obtained in Example 14 were reproduced.

In all of Examples 13-15, recovery of para-xylene exceeded 90 parts of the para-xylene introduced as feed.

The relationship of the present invention will be described as follows.

(1) for separating at least one component of the mixture in the feed stream by liquid chromatography; (a) at least one component in the feed stream mixture is selectively retained by a crystalline aluminosilicate adsorbent; (b) flowing an eluent selected from the group consisting of aromatic compounds through the bed; (c) contacting the feed stream mixture with a bed-forming crystalline aluminosilicate adsorbent under conditions such as; (d) collecting stream(s) containing at least a portion of the components not preferentially adsorbed from the stream; In a liquid chromatographic separation method consisting of steps (a) and (b) above, the concentration of the eluent in the liquid carrier is increased during the operations of steps (a) and (b), under conditions which result in a lower elution volume/feed ratio. The liquid chromatography separation method described above achieves the desired separation.

(2) The method of paragraph (1), wherein the feed stream mixture is an ethylbenzene-containing C8 aromatic feed stream and the crystalline aluminosilicate adsorbent is potassium Y aluminosilicate.

(3) The method according to item (2), wherein the selectively adsorbed components are paraxylene and ethylbenzene.

(4) the initial concentration of the eluent is about 25%, and step (a)
and (b), wherein the concentration is increased to a final concentration within the range of about 50 to about 100 parts.

(5) To separate baraxylene and ethylbenzene from a C8 aromatic mixture: (a) contacting the feed stream mixture with a bed containing potassium Y or ammonium-potassium Y sieves; (b) from ortho-dichlorobenzene and meta-diisopropylbenzene; (c) recovering from the bed a stream containing at least a portion of components that are not preferentially adsorbed; (d) m-xylene, o-xylene, ethylbenzene and p-xylene; - recycling at least a portion of the stream(s) consisting of a mixture comprising a component selected from the group consisting of xylene, (e) significantly increasing the concentration of para-xylene and ethylbenzene relative to other feed stream components; In a separation process consisting of steps in which a depleted stream or streams are recovered, the eluent concentration in the eluent-liquid carrier is increased from an initial concentration of about 25% to a final concentration of about 50 to about 100% during the adsorption operation. The method according to item (1), wherein the improvement is to increase the concentration to a concentration of .

(6) To separate baraxylene contained in a C8 aromatic isomer mixture containing ethylbenzene (a) C8 aromatic isomer mixture consisting of potassium-¥1 ammonium-potassium-Y and barium-potassium-Y (b) an eluent selected from the group consisting of m-DIPB, 0DCB, and toluene; flowing through the sieve; (C) recovering from the bed a stream(s) comprising at least a portion of the feedstream components not preferentially adsorbed by the sieve; and (d) a portion of the adsorbed components of the feedstream. and (e) recovering a stream(s) with a significantly increased concentration of paraxylene, comprising: step (a) and □ in the liquid carrier during operation (b).
The method according to paragraph (1), wherein the concentration of the eluent is increased.

(7) The components that are not preferentially adsorbed are m-xylene, 0-
The method according to item (6), wherein the material is selected from the group consisting of xylene and ethylbenzene.

(8) The method according to items (1) to (7), wherein the temperature of the bed is within the range of 160 to 200°C.

[Brief explanation of the drawing]

Attached FIG. 1 is a chromatogram development showing the separation of the components, and FIG. 2 shows a typical commercial scale application of the invention. Numbers and letters) have the following meanings: D...Withdrawal agent, D2...Withdrawal agent, P
X...p-xylene, OX...0-xylene, MX...m=xylene, EB...
...Ethylbenzene, 1...Feed, 2...
...1st fraction, 3...2nd fraction, 4...
...Third fraction, 5...Weak eluent bottom flow, 6...
...Strong eluent side stream, 7...Mixed xylene product, 8...Weak eluent bottom flow, 9...
Ethylbenzene product, 12...Strong eluent bottom stream, 13...Baraxylene product, 14...
・Weak eluent flow, 15... Strong eluent flow, 16...
... Products containing ethylbenzene and other 08 aromatic compounds, 100 ... Chromatographic columns, 101 ... Detachment agent D1 storage tank, 102 ...
...Detachment agent D2 storage tank, 103...Mixed xylene recovery column, 104...Ethylbenzene recovery column, 105...P-xylene recovery column. FIG. 3 shows the elution state of each component on each side. Samples are taken periodically from the effluent from the end of the column,
Measure the weight ratio of each isomer in each sample and
I created a diagram. The vertical axis represents the weight ratio, and the horizontal axis represents the elution volume in ml. As the elution progresses, peaks in the concentration of each isomer appear. The corresponding curve diagram on each side therefore shows the weight distribution of the components in the feed formulation for each portion of the carrier eluent stream.

Claims (1)

[Claims] 1 Purification of para-xylene or para-xylene and ethylbenzene from a mixture of C8 aromatic isomers using Y-type zeolite by gradient elution chromatography using metadiisopropylbenzene (m-DIPB) or m-DIPB as the eluent in a liquid carrier. Orthodichlorobenzene (o
- DCB).