阅读说明：本技术 具有减少数量的床和旁路流体流动的模拟移动床分离方法与装置 (Simulated moving bed separation process and apparatus with reduced number of beds and bypass fluid flows ) 是由 D.莱内库格尔勒科克 G.奥捷 P-Y.勒戈夫 F.朗贝尔 于 2019-06-20 设计创作，主要内容包括：原料(F)的模拟移动床(SMB)分离方法,其中：至少一个区域(1、2、3、4)含有少于三个床,如果界定所述区域并位于所述区域上游的料流(D、E、F、R)经由旁路管线L<Sub>i/i+1</Sub>在板P<Sub>i</Sub>处注入或取出,那么界定该区域并位于所述区域下游的料流经由旁路管线L<Sub>j/j+1</Sub>在板P<Sub>j</Sub>处注入/取出,并且如果界定所述区域并位于所述区域下游的料流经由旁路管线L<Sub>i-1/i</Sub>在板P<Sub>i</Sub>处注入或取出,那么界定所述区域并位于所述区域上游的料流经由旁路管线L<Sub>j-1/j</Sub>在板P<Sub>j</Sub>处注入/取出。(Process for the Simulated Moving Bed (SMB) separation of a starting material (F), in which: at least one zone (1, 2, 3, 4) contains less than three beds if the stream (D, E, F, R) bounding said zone and located upstream of said zone is passed via a bypass line L i/i+1 At the plate P i Is injected or withdrawn, the stream which delimits the region and is located downstream of said region is passed via a bypass line L j/j+1 At the plate P j Is injected/withdrawn and, if the zone is delimited and located downstream of the zone, the stream is passed via a bypass line L i‑1/i At the plate P i Is injected or withdrawn, the stream which defines the region and is located upstream of the region is passed via a bypass line L j‑1/j At the plate P j And is injected/withdrawn.)

1. A process for separating a raw material (F) in a simulated moving bed separation apparatus,

the device includes:

at least one comprises a plurality of adsorbent beds (A)_i) Through plates (P) each comprising a distribution/extraction system_i) Separating; and

directly connecting two successive plates (P)_i、P_i+1) External bypass line (L)_i/i+1) Each external bypass line comprising a fluid (F, D) feed point and an effluent (E, R) withdrawal point,

in the method:

feeding the feedstock (F) and the desorbent (D) to at least one column and withdrawing from said at least one column at least one extract (E) and at least one raffinate (R), the feeding point and the withdrawal point being shifted in the course of time by an amount corresponding to one adsorbent bed, having a transition period (ST) and defining a plurality of operating zones of the plant, in particular the following main zones:

zone 1 for desorbing a compound from the extract, which zone is comprised between the feed of desorbent (D) and the withdrawal of extract (E),

a zone 2 for desorbing the compounds from the raffinate, which zone is comprised between the extraction (E) and the feed of starting material (F),

a zone 3 for adsorbing compounds from the extract, which zone is comprised between the feed of starting material (F) and the withdrawal of raffinate (R), and

a zone 4 located between the withdrawal of raffinate (R) and the feed of desorbent (D);

in the method:

at least one zone contains less than three beds,

if the stream (D, E, F, R) which contains less than three beds (1, 2, 3, 4) and is located upstream of the said zones (1, 2, 3, 4) is defined via a bypass line L_i/i+1At the plate P_iIs injected or withdrawn, then definesThe stream (E, F, R, D) of this zone and located downstream of the zones (1, 2, 3, 4) is passed via a bypass line L_j/j+1At the plate P_jIs injected/withdrawn, and

if the stream (E, F, R, D) which contains less than three beds (1, 2, 3, 4) and is located downstream of said zones (1, 2, 3, 4) is defined via a bypass line L_i-1/iAt the plate P_iIs injected or withdrawn, the stream (D, E, F, R) bounding the zone (1, 2, 3, 4) and located upstream of said zone (1, 2, 3, 4) is passed via a bypass line L_j-1/jAt the plate P_jTo be injected/taken out from the injection/taking-out part,

the board P_iIn correspondence of one of the plates of the tower,

the board P_jCorresponds to P_iThe plates other than the plates are provided with,

the bypass line L_i-1/iIs to connect two successive plates P_i-1And P_iThe line (b) of (a),

the bypass line L_i/i+1Is to connect two successive plates P_iAnd P_i+1The line (b) of (a),

the bypass line L_j-1/jIs to connect two successive plates P_j-1And P_jThe line (b) of (a),

the bypass line L_j/j+1Is to connect two successive plates P_jAnd P_j+1The line of (2).

2. The method of claim 1, wherein:

if zone 1 contains on average less than three beds, when desorbent (D) is passed through bypass line L_i/i+1At the plate P_iIn the case of the upper injection, the extract (E) is passed through a bypass line L_j/j+1At the plate P_jTaking out the upper part;

when the feed (F) passes through the bypass line L if zone 2 contains on average less than three beds_i-1/iAt the plate P_iIn the case of the upper injection, the extract (E) is passed through a bypass line L_j-1/jAt the plate P_jTaking out the upper part;

if zone 3 contains on average less than three beds, thenThe feed (F) being passed via a bypass line L_i/i+1At the plate P_iIn the case of the upper injection, the raffinate (R) is passed via a bypass line L_j/j+1At the plate P_jTaking out the upper part; and

if zone 4 contains on average less than three beds, when desorbent (D) is passed through bypass line L_i-1/iAt the plate P_iIn the case of the upper injection, the raffinate (R) is passed via a bypass line L_j-1/jAt the plate P_jAnd taking out.

3. The method of claim 1 or claim 2, wherein:

if zone 1 contains on average less than three beds, then when extract (E) is passed via bypass line L_i-1/iAt the plate P_iWhen taken out upward, the desorbent (D) passes through the bypass line L_j-1/jAt the plate P_jUpper injection;

if zone 2 contains on average less than three beds, then when extract (E) is passed via bypass line L_i/i+1At the plate P_iWhen the raw material (F) is taken out upward, the raw material (F) passes through a bypass line L_j/j+1At the plate P_jUpper injection;

when the raffinate (R) passes through the bypass line L if zone 3 contains on average less than three beds_i-1/iAt the plate P_iWhen the raw material (F) is taken out upward, the raw material (F) passes through a bypass line L_j-1/jAt the plate P_jUpper injection; and

when the raffinate (R) passes through the bypass line L, if zone 4 contains on average less than three beds_i/i+1At the plate P_iWhen taken out upward, the desorbent (D) passes through the bypass line L_j/j+1At the plate P_jAnd (4) upper injection.

4. The method of any one of the preceding claims, wherein the panel P is_iAnd a bypass line L_i-1/iConnected to and with the bypass line L_i/i+1Are connected.

5. The method according to any one of the preceding claims, wherein each plate (P) is_i) Comprising a plurality of flatDistributor-mixer-extractor panels of the row-sector type, with asymmetrical feeding.

6. The process according to any one of the preceding claims, wherein the feedstock (F) contains para-xylene or meta-xylene in a C8 aromatic mixture.

Technical Field

The present invention relates to the field of separating natural or chemical products that are difficult to separate by distillation. A class of processes and related apparatus, hereinafter abbreviated as "SMB", referred to as simulated moving bed separation processes or apparatus, using simulated counter-current flow or simulated co-current flow, is thus employed.

The fields concerned are, in particular and not exclusively:

on the one hand, normal paraffins are separated off, and on the other hand, normal paraffins are separated from branched paraffins, naphthenes and aromatics;

olefin/paraffin separation;

separation of para-xylene from other C8 aromatic isomers;

separation of meta-xylene from other C8 aromatic isomers; and

separation of ethylbenzene from the other C8 aromatic isomers.

In addition to oil refineries and petrochemical complexes, there are many other applications including glucose/fructose separation, separation of cresol positional isomers, optical isomers, and the like.

Prior Art

SMB separation is well known in the art. As a general rule, a column using the simulated moving bed technique comprises at least three zones, and possibly four or five, each of which is constituted by a certain number of successive beds and each of which is defined by its position between the feed point and the withdrawal point. Typically, at least one feedstock to be fractionated and a desorbent (sometimes referred to as an eluent) are fed to an SMB column, and at least one raffinate and extract are withdrawn from the column.

The feed point and take-off point vary with the course of time, generally moving in the same direction by an amount corresponding to one bed.

By definition, each operating region is represented by a number:

zone 1 = the zone where compounds are desorbed from the extract, which is comprised between the injection of desorbent and the tapping off of the extract;

zone 2 = the zone where the compounds are desorbed from the raffinate, which zone is comprised between tapping off the extract and injecting the feed to be fractionated;

zone 3 = the zone where the compounds are adsorbed from the extract, comprised between the injection of the feedstock and the withdrawal of the raffinate; and

optional zone 4, located between the withdrawal of raffinate and the injection of desorbent.

Summary of The Invention

In the context of the above description, a first object of the present specification is to provide an SMB separation process that uses a smaller number of beds and is capable of extracting solute from a feedstock in higher purity for the same yield. In particular, when using SMB units comprising at least one zone containing on average less than three beds, the applicant company has been able to surprisingly determine the operating mode of a limited number of bypass lines and injection and withdrawal lines, which enables commercial purity levels to be achieved with high yields. A second object is to provide a process which enables the extraction of solutes from a feedstock in higher yields for the same purity.

The foregoing objects, as well as other advantages, are achieved according to a first aspect by a simulated moving bed separation process of a feedstock in a simulated moving bed separation unit,

the device includes:

at least one column comprising a plurality of adsorbent beds separated by plates each comprising a distribution/extraction system; and

an external bypass line directly connecting two successive plates, each external bypass line comprising a fluid feed point and an effluent withdrawal point,

in the method:

feeding the feedstock and the desorbent to at least one column and withdrawing from said at least one column at least one extract and at least one raffinate, the feeding point and the withdrawal point being shifted in time course by an amount corresponding to one adsorbent bed, having a switching period and defining a plurality of operating zones of the plant, in particular the following main zones:

zone 1 for desorbing a compound from the extract, which zone is comprised between the desorbent feed and the extract withdrawal,

a zone 2 for desorbing compounds from the raffinate, which zone is comprised between the extract withdrawal and the feed,

a zone 3 for adsorption of compounds from the extract, which zone is comprised between the feed of raw material and the withdrawal of raffinate, and

a zone 4 between raffinate withdrawal and desorbent feed;

in the method:

if a zone contains less than 3 beds,

then, if a relevant zone is defined and the stream located upstream of said zone is passed via the bypass line L_i/i+1At the plate P_iIs injected or withdrawn, the stream which delimits the region and is located downstream of said region is passed via a bypass line L_j/j+1At the plate P_jIs injected/withdrawn, and

if the stream which defines the relevant zone and is located downstream of said zone is passed via a bypass line L_i-1/iAt the plate P_iIs injected or withdrawn, the stream which delimits the region and is located upstream of said region then passes via the bypass line L_j-1/jAt the plate P_jTo be injected/taken out from the injection/taking-out part,

the board P_iIn correspondence of one of the plates of the tower,

the board P_jCorresponds to P_iThe plates other than the plates are provided with,

the bypass line L_i-1/iIs to connect two successive plates P_i-1And P_iThe line (b) of (a),

the bypass line L_i/i+1Is to connect two successive plates P_iAnd P_i+1The line (b) of (a),

the bypass line L_j-1/jIs to connect two successive plates P_j-1And P_jThe line (b) of (a),

the bypass line L_j/j+1Is to connect two successive plates P_jAnd P_j+1The line of (2).

According to one or more embodiments, if zone 1 contains on average less than three beds, then when desorbent is passed through bypass line L_i/i+1At the plate P_iFor the upper injection, the extract is passed via the bypass line L_j/j+1At the plate P_jTaking out the upper part;

when the feed passes through the by-pass line L if zone 2 contains on average less than three beds_i-1/iAt the plate P_iWhen injected, the extractTaking the articles via a bypass line L_j-1/jAt the plate P_jTaking out the upper part;

when the feed passes through the by-pass line L if zone 3 contains on average less than three beds_i/i+1At the plate P_iIn the case of upper injection, the raffinate is passed via the bypass line L_j/j+1At the plate P_jTaking out the upper part; and

if zone 4 contains on average less than three beds, then when desorbent is passed through bypass line L_i-1/iAt the plate P_iIn the case of upper injection, the raffinate is passed via the bypass line L_j-1/jAt the plate P_jAnd taking out.

According to one or more embodiments, if zone 1 contains on average less than three beds, then when the extract is passed through the by-pass line L_i-1/iAt the plate P_iWhen taken up, the desorbent is passed via the bypass line L_j-1/jAt the plate P_jUpper injection;

if zone 2 contains on average less than three beds, then the extract is passed via bypass line L_i/i+1At the plate P_iWhen taken out upward, the feed is passed through a bypass line L_j/j+1At the plate P_jUpper injection;

if zone 3 contains on average less than three beds, when the raffinate is passed through the by-pass line L_i-1/iAt the plate P_iWhen taken out upward, the feed is passed through a bypass line L_j-1/jAt the plate P_jUpper injection; and

if zone 4 contains on average less than three beds, when the raffinate is passed through by-pass line L_i/i+1At the plate P_iWhen taken up, the desorbent is passed via the bypass line L_j/j+1At the plate P_jAnd (4) upper injection.

According to one or more embodiments, the plate P_iAnd a bypass line L_i-1/iConnected to and with the bypass line L_i/i+1Are connected.

According to one or more embodiments, each plate comprises a plurality of distribution-mixing-extraction panels of the parallel sector type, with asymmetric feeding.

According to one or more embodiments, the feedstock contains para-xylene or meta-xylene in a C8 aromatic hydrocarbon mixture.

Other features and advantages of the embodiments of the first aspect and of the method of the first aspect will become apparent upon reading the following description, which is given by way of illustration and not of limitation, and with reference to the following drawings.

Brief description of the drawings

FIG. 1 depicts an SMB apparatus comprising a series of plates (P) for use in the process of embodiments of the present description_i-1、P_i、P_i+1、P_i+2) Bed (A)_i-1、A_i、A_i+1、A_i+2) And an external bypass line (L)_i-1/i、L_i/i+1、L_i+1/i+2) The column of (1).

FIG. 2 depicts an SMB apparatus for use in the process of embodiments of the present description in a mode of operation wherein zone 1 for desorbing compounds from the extract is included in plate P_iWith the desorbent feed and the plate P_jBetween the extractions taken out.

FIG. 3 depicts an SMB unit for use in the process of embodiments of the present description in an operating mode wherein zone 2 for desorbing compounds from the raffinate is included in plate P_jExtract is taken out of and mixed with the plate P_iBetween the feeds of feedstock F.

FIG. 4 depicts an SMB apparatus used in the process of embodiments of the present description in a mode of operation wherein zone 3 for adsorption of compounds from the extract is included in plate P_iRaw material feed and plate P_jBetween the raffinate withdrawal.

FIG. 5 depicts an SMB apparatus for use in the process of embodiments of the present description, the apparatus being in a mode of operation wherein zone 4 is included in plate P_jExtract of (B) and plate P_iBetween desorbent feeds.

Detailed Description

It is an object of the present invention to improve the performance of a simulated bed separation process when using an SMB unit comprising at least one zone containing on average less than three beds, compared with the teachings of patents US 5,972,224, US 6,110,364 and FR 2,935,100.

Referring to fig. 1, in order to achieve high separation performance using SMB technology with a limited number of beds, the present invention proposes a process for SMB separation of feedstock F in an SMB unit having at least one column consisting of a plurality of adsorbent beds a_iConstituted by a plurality of adsorbent beds passing through plates P each containing a distribution/extraction system_iAnd (4) separating. The SMB device further comprises a direct connection of two successive plates P_i、P_i+1External bypass line L of_i/i+1In particular to allow rinsing of the plate. These bypass lines L_i/i+1Each may contain an automatic device for adjusting the flush flow rate.

According to one or more embodiments, the column comprises n adsorbent beds a_i. According to one or more embodiments, n is a natural integer from 6 to 15, preferably from 8 to 12, and i is a natural integer from 1 to n.

The SMB separation method comprises the following steps: the feedstock F and the desorbent D are fed and at least one extract E and at least one raffinate R are withdrawn, the feeding point and the withdrawal point being shifted in the course of time by an amount corresponding to one adsorbent bed, having a transition period (a time period called ST between two successive feeding/withdrawal transitions) and defining a plurality of operating zones of the SMB unit, in particular the following main zones:

zone 1 for desorbing a compound from the extract, which zone is comprised between the feed of desorbent D and the withdrawal of extract E,

a zone 2 for desorbing the compounds from the raffinate, which zone is comprised between the extract E withdrawal and the feed of starting material F,

a zone 3 for adsorption of compounds from the extract, which zone is comprised between the feed of raw material and the withdrawal of raffinate R, and

a zone 4 located between the withdrawal of raffinate R and the feed of desorbent D.

It should be noted that when positioned on the plate P_iAnd P_i+1A bed A between_iIn the case of belonging to a zone, directly connecting two successive plates P_i、P_i+1External bypass line L of_i/i+1Are said to belong to said area. In addition, n adsorbent beds A are distributed between zones 1 to 4_iThe configuration is called a/b/c/d type, which means that the bed is distributed as follows:

a is the average number of beds in zone 1;

b is the average bed number in zone 2;

c is the average number of beds in zone 3; and is

d is the average bed number in zone 4.

In this specification, a region where "average" contains less than three beds corresponds to the following region: it contains more than two beds at the isolation point for part of the switching period ST (e.g. when the injection point and the withdrawal point are switched differently), but where the average number of beds per switching period ST is strictly below 3.

In accordance with one or more embodiments of the present invention,

a = (n * 0.208) * (1 ± 0.2)；

b = (n * 0.375) * (1 ± 0.2)；

c = (n * 0.292) * (1 ± 0.2)；

d = (n * 0.125) * (1 ± 0.2)。

when in the plate P_iIn the injection of a fluid (feed F or desorbent D) or in the withdrawal of a fluid (extract E or raffinate R), the corresponding injection line L is used_FOr L_DOr take-off line L_EOr L_RConnected to two bars and the plate P_iOne of the connected bypass lines (L)_i-1/iOr L_i/i+1) The above.

The method of the invention is characterized by following rules:

a/if a zone contains less than 3 beds,

then, if a relevant zone is defined and the stream located upstream of said zone is passed via the bypass line L_i/i+1At the plate P_iIs injected or withdrawn, the stream which delimits the region and is located downstream of said region is passed via a bypass line L_j/j+1At the plate P_jIs injected/withdrawn, and

b/if bound correlationThe stream of the zone and downstream of said zone is passed via a bypass line L_i-1/iAt the plate P_iIs injected or withdrawn, the stream which delimits the region and is located upstream of said region then passes via the bypass line L_j-1/jAt the plate P_jTo be injected/taken out from the injection/taking-out part,

the board P_iIn correspondence of one of the plates of the tower,

the board P_jCorresponds to P_iThe plates other than the plates are provided with,

the bypass line L_i-1/iIs to connect two successive plates P_i-1And P_iThe line (b) of (a),

the bypass line L_i/i+1Is to connect two successive plates P_iAnd P_i+1The line (b) of (a),

the bypass line L_j-1/jIs to connect two successive plates P_j-1And P_jThe line (b) of (a),

the bypass line L_j/j+1Is to connect two successive plates P_jAnd P_j+1The line of (2).

j is a natural integer from 1 to n and is different from i.

If the zone contains more than 3 beds, then bypass line L can be passed_i/i+1Or a bypass line L_i-1/iInjection or withdrawal, provided that rules A/and B/, are adhered to.

j is a natural integer from 1 to n and is different from i.

According to one or more embodiments, if zone 1 contains on average less than three beds, then when desorbent is passed through bypass line L_i/i+1At the plate P_iFor the upper injection, the extract is passed via the bypass line L_j/j+1At P_jAnd taking out the plate. For example, referring to FIG. 2, if zone 1 contains less than three beds on average, then if desorbent is passed through bypass line L_i/i+1At the plate P_iIf injected upwards, the extract must then pass through the bypass line L_j/j+1At the plate P_jAnd taking out.

According to one or more embodiments, when the feedstock passes through the by-pass line L if zone 2 contains on average less than three beds_i-1/iAt the plate P_iFor the upper injection, the extract is passed via the bypass line L_j-1/jAt the plate P_jAnd taking out. For example, referring to FIG. 3, if zone 2 contains on average less than three beds, then if the feed is via bypass line L_i-1/iAt the plate P_iIf injected upwards, the extract must then pass through the bypass line L_j-1/jAt the plate P_jAnd taking out.

According to one or more embodiments, if zone 3 contains on average less than three beds, then when the feed passes through bypass line L_i/i+1At the plate P_iIn the case of upper injection, the raffinate is passed via the bypass line L_j/j+1At the plate P_jAnd taking out. For example, referring to FIG. 4, if zone 3 contains on average less than three beds, then if the feed is via bypass line L_i/i+1At the plate P_iIf injected upwards, the raffinate must then pass through the bypass line L_j/j+1At the plate P_jAnd taking out.

According to one or more embodiments, if zone 4 contains on average less than three beds, then when desorbent is passed through bypass line L_i-1/iAt the plate P_iIn the case of upper injection, the raffinate is passed via the bypass line L_j-1/jAt the plate P_jAnd taking out. For example, referring to FIG. 5, if zone 4 contains on average less than three beds, then if the desorbent passes through bypass line L_i-1/iAt the plate P_iIf injected upwards, the raffinate must then pass through the bypass line L_j-1/jAt the plate P_jAnd taking out.

According to one or more embodiments, if zone 1 contains on average less than three beds, then when the extract is passed through by-pass line L_i-1/iAt the plate P_iWhen taken up, the desorbent is passed via the bypass line L_j-1/jAt the plate P_jAnd (4) upper injection.

According to one or more embodiments, if zone 2 contains on average less than three beds, then when the extract is passed through by-pass line L_i/i+1At the plate P_iWhen taken out upward, the feed is passed through a bypass line L_j/j+1At the plate P_jAnd (4) upper injection.

According to one orEmbodiments when the raffinate passes through the by-pass line L if zone 3 contains on average less than three beds_i-1/iAt the plate P_iWhen taken out upward, the feed is passed through a bypass line L_j-1/jAt the plate P_jAnd (4) upper injection.

According to one or more embodiments, if zone 4 contains on average less than three beds, then when the raffinate is passed through by-pass line L_i/i+1At the plate P_iWhen taken up, the desorbent is passed via the bypass line L_j/j+1At the plate P_jAnd (4) upper injection.

Each plate P_iComprising two chambers for carrying out sequential operations of feeding raw material F or injecting desorbent D and extracting raffinate R or extract E. The invention relates to each plate P_iA column having two chambers. There are many possible solutions using two chambers, each of which can be used to inject or withdraw one or more streams. According to one or more embodiments, the first chamber may be operated to inject feed F or desorbent D, and the other chamber is operated to withdraw raffinate R or extract E. According to one or more embodiments, one chamber is used for the injection of feed F and the withdrawal of raffinate R, and the other chamber handles the injection of desorbent D and the withdrawal of extract E. The above examples are non-limiting and other uses of the two chambers are possible. Each bed i is equipped with a bypass line connecting one chamber of the upstream plate with one chamber of the downstream plate.

According to one or more embodiments, the feedstock is selected from a mixture of substantially C8 aromatic compounds (e.g., xylene and ethylbenzene). According to one or more embodiments, the mixture comprises at least 95%, preferably at least 97% (e.g., at least 99%) of the substantially C8 aromatic compound.

The process of the present invention is more particularly suitable for the separation of a feed containing para-xylene and/or meta-xylene in a mixture of C8 aromatic hydrocarbons. According to one or more embodiments, the feedstock comprises at least 15 wt% of para-xylene and/or 30 wt% of meta-xylene, based on the total weight of the feedstock.

One example of an SMB separation process of paramount industrial importance is the separation of a C8 aromatic fraction to produce para-xylene in commercial purity (typically at least 99.7% by weight purity), and a raffinate rich in ethylbenzene, ortho-xylene, and meta-xylene.

According to one or more embodiments, the adsorbent is selected from zeolites of the faujasite type, NaY, BaX, BaKX, BaLSX type. Preferably, the adsorbent is selected from BaX, BaKX, NaY.

According to one or more embodiments, the desorbent is selected from one or more isomers of diethylbenzene and toluene. Preferably, the desorbent is selected from the group consisting of p-diethylbenzene and toluene.

According to one or more embodiments, the temperature of the column is from 120 ℃ to 190 ℃. Preferably, the temperature of the column is from 150 ℃ to 180 ℃.

According to one or more embodiments, the pressure in the column is from 0.3 MPa to 3 MPa. According to one or more embodiments, the pressure in the column is from 0.5 MPa to 3 MPa. According to one or more embodiments, the pressure in the column is from 0.8MPa to 3 MPa. Preferably, the pressure in the column is from 1 MPa to 2 MPa.

According to one or more embodiments, the transition period ST used is from 20 seconds to 120 seconds. Preferably, the transition period ST used is 40 seconds to 100 seconds.

Of course, these application examples are purely non-limiting and other applications are possible, in particular in the field of the separation of normal paraffins and iso-paraffins or normal olefins and iso-olefins.

Examples

The invention will be better understood by reading the following examples.