阅读说明：本技术 具有旁路流体流动的模拟移动床分离方法和装置 (Simulated moving bed separation process and apparatus with by-pass fluid flow ) 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)的模拟移动床分离方法,其中当使用连接到所述所选板(P<Sub>i</Sub>)的外部旁路管线(L<Sub>i-1/i</Sub>、L<Sub>i/i+1</Sub>)向所选板(P<Sub>i</Sub>)中注入或从所选板(P<Sub>i</Sub>)中取出流体/流出物(原料F、解吸剂D、萃取物E、萃余物R)时,控制所述外部旁路管线(L<Sub>i-1/i</Sub>、L<Sub>i/i+1</Sub>)中的流速,使得：将主要比例的流体/流出物(F、D、E、R)注入所选板(P<Sub>i</Sub>)中或从所选板(P<Sub>i</Sub>)中取出；并且次要比例的流体/流出物(F、D、E、R)注入与所述外部旁路管线(L<Sub>i-1/i</Sub>、L<Sub>i/i+1</Sub>)相连的相邻板(P<Sub>i-1</Sub>、P<Sub>i+1</Sub>)或从与所述外部旁路管线(L<Sub>i-1/i</Sub>、L<Sub>i/i+1</Sub>)相连的相邻板(P<Sub>i-1</Sub>、P<Sub>i+1</Sub>)中取出。(Process for the simulated moving bed separation of a feedstock (F), wherein use is made of a separation membrane connected to said selected plate (P) i ) External bypass line (L) i‑1/i 、L i/i+1 ) To the selected plate (P) i ) Into or from the selected plate (P) i ) While withdrawing the fluids/effluents (feed F, desorbent D, extract E, raffinate R), the external bypass line (L) is controlled i‑1/i 、L i/i+1 ) Such that: injecting a major proportion of fluid/effluent (F, D, E, R) into a selected plate (P) i ) In or from selected plates (P) i ) Taking out; and a minor proportion of the fluid/effluent (F, D, E, R) is injected into the external bypass line (L) i‑1/i 、L i/i+1 ) Adjacent plates (P) connected i‑1 、P i+1 ) Or from the external bypass line (L) i‑1/i 、L i/i+1 ) Adjacent plates (P) connected i‑1 、P i+1 ) Taking out.)

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);

when passing through the selected board (P)_i) Connected external bypass line (L)_i-1/i、L_i/i+1) To the selected plate (P)_i) Controlling the external bypass line (L) upon injection of a fluid (F, D)_i-1/i、L_i/i+1) So as to be directed to the selected plate (P)_i) Injecting a major proportion of said fluid (F, D) and into said external bypass line (L)_i-1/i、L_i/i+1) Adjacent plates (P) connected_i-1、P_i+1) Injecting a minor proportion of the fluid (F, D); and/or

When passing through the selected board (P)_i) Connected external bypass line (L)_i-1/i、L_i/i+1) From the selected plate (P)_i) Controlling the external bypass line (L) when the effluent (E, R) is withdrawn_i-1/i、L_i/i+1) So that the flow rate from the selected plate (P) is higher than the flow rate of the other plate (P)_i) Of said effluent (E, R) and from said external by-pass line (L)_i-1/i、L_i/i+1) Adjacent plates (P) connected_i-1、P_i+1) A minor proportion of the effluent (E, R) is withdrawn.

2. The method of claim 1, wherein:

regulating the flow to and from the external bypass line (L)_i-1/i、L_i/i+1) Adjacent plates (P) connected_i-1、P_i+1) A minor proportion of a fluid (F, D) is injected to cause the adjacent plates (P)_i-1、P_i+1) The flush level of (a) is equal to 100% +/-30%; and/or

Regulating the secondary and said external bypass line (L)_i-1/i、L_i/i+1) Adjacent plates (P) connected_i-1、P_i+1) A minor proportion of the effluent (E, R) being withdrawn to cause the adjacent panel (P)_i-1、P_i+1) The flush level of (a) is equal to 100% +/-30%,

the adjacent plate (P)_i-1、P_i+1) Is located at the selected plate (P)_i) Upstream adjacent plate (P) of upstream_i-1) Or on a selected plate (P)_i) Downstream adjacent plate (P)_i+1），

Upstream adjacent plate (P)_i-1) Is washed by Q_i-1×ST/(V_i-1 + VL_i-1/iThe/2) of the first group of the group,

downstream adjacent plate (P)_i+1) Is washed by Q_i+1×ST/(V_i+1 + VL_i/i+1The/2) of the first group of the group,

n is the number of adsorbent beds in the column,

i is a natural integer from 1 to n,

Q_i-1denotes the adjacent plate (P) from upstream_i-1) The volume flow rate of the effluent is,

Q_i+1indicating flow to the adjacent downstream plate (P)_i+1) The volumetric flow rate of (a) is,

V_i-1denotes an upstream adjacent plate (P)_i-1) The volume of the distribution/extraction system of (1),

V_i+1indicating the downstream adjacent plate (P)_i+1) The volume of the distribution/extraction system of (1),

VL_i-1/idenotes an upstream adjacent plate (P)_i-1) With selected plate (P)_i) Upstream external bypass line (L) therebetween_i-1/i) The volume of (a) to (b),

VL_i/i+1indicates the selected plate (P)_i) Adjacent to the downstream plate (P)_i+1) Downstream external bypass line (L) therebetween_i/i+1) The volume of (a) to (b),

ST denotes a transition period.

3. The method of claim 2, wherein:

regulating the flow to and from the external bypass line (L)_i-1/i、L_i/i+1) Adjacent plates (P) connected_i-1、P_i+1) A minor proportion of a fluid (F, D) is injected to cause the adjacent plates (P)_i-1、P_i+1) The flush level of (a) is equal to 100% +/-20%; and/or

Regulating the secondary and said external bypass line (L)_i-1/i、L_i/i+1) Adjacent plates (P) connected_i-1、P_i+1) A minor proportion of the effluent (E, R) being withdrawn to cause the adjacent panel (P)_i-1、P_i+1) The level of flushing is equal to 100% +/-20%.

4. The method of any of the preceding claims, wherein:

at each other external bypass line (L)_j/L_j+1) In which a synchronization of +/-10% is established,

synchronous flow rate is composed of_j + V_j+1 + V_j/j+1) the/ST is defined by the definition of,

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

n is the number of adsorbent beds in the column,

i is a natural integer from 1 to n;

V_jand V_j+1Represents the other external bypass line (L)_j/L_j+1) Connected panel (P)_jAnd P_j+1) The corresponding volume of the distribution/extraction system of (a),

VL_j/j+1represents the further external bypass line (L)_j/L_j+1) The volume of (a) to (b),

ST denotes a transition period.

5. The method as claimed in claim 4, wherein at each other external bypass line (L)_j/L_j+1) Establishing +/-5% synchronicity.

6. The method of any one of claims 2 to 5, wherein n is a natural integer from 6 to 24.

7. The method according to any one of the preceding claims, wherein each plate (P) is_i) Connected to an upstream adjacent plate (P)_i-1) And the plate (P)_i) Upstream external bypass line (L) therebetween_i-1/i) And/or the plate (P)_i) Adjacent to the downstream plate (P)_i+1) Downstream external bypass line (L) therebetween_i/i+1）。

8. The method of any one of the preceding claimsMethod, wherein each plate (P)_i) Comprising a plurality of distribution-mixing-extraction panels of the parallel sector type, with asymmetrical feeding.

9. The process according to any one of the preceding claims, wherein feed (F) comprises 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 utilizing simulated counter-current flow or simulated co-current flow is subsequently 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:

region 1 = the region where the compound is desorbed from the extract, which is comprised between injecting desorbent and tapping off (tapping-off) 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 compound is 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 description is to provide a simulated moving bed separation process which is capable of extracting solutes from a feedstock in higher yields for the same purity, in particular by providing a leakage flow on a bypass line through which the stream is injected or withdrawn. A second object is to provide a process which enables the extraction of solutes from a feedstock in higher purity for the same yield.

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;

controlling a flow rate in the external bypass line such that a major proportion of the fluid is injected into the selected plate and a minor proportion of the fluid is injected into an adjacent plate connected to the external bypass line when the fluid is injected into the selected plate via the external bypass line connected to the selected plate; and/or

When effluent is withdrawn from a selected plate via an external bypass line connected to the selected plate, the flow rate in the external bypass line is controlled such that a major proportion of the effluent is withdrawn from the selected plate and a minor proportion of the effluent is withdrawn from an adjacent plate connected to the external bypass line.

According to one or more embodiments, the minor proportion of fluid injected into the adjacent plates connected to the external bypass line is adjusted so that the flush level of the adjacent plates is equal to 100% +/-30%; and/or adjusting the minor proportion of effluent withdrawn from the adjacent plate connected to the external bypass line so that the flush level of the adjacent plate is equal to 100% +/-30%,

the adjacent plate is an upstream adjacent plate located upstream of the selected plate, or a downstream adjacent plate located downstream of the selected plate,

the flushing level of the upstream adjacent plate is represented by Q_i-1×ST / (V_i-1 + VL_i-1/iThe/2) of the first group of the group,

flushing level of downstream adjacent plates by Q_i+1×ST / (V_i+1 + VL_i/i+1The/2) of the first group of the group,

n is the number of adsorbent beds in the column,

i is a natural integer from 1 to n,

Q_i-1representing the volumetric flow rate from the upstream adjacent plate,

Q_i+1representing the volumetric flow rate to the adjacent plate downstream,

V_i-1representing the volume of the distribution/extraction system of the adjacent plate upstream,

V_i+1representing the volume of the distribution/extraction system of the adjacent plate downstream,

VL_i-1/irepresenting the volume of the upstream external bypass line between the upstream adjacent plate and the selected plate,

VL_i/i+1representing the volume of the downstream external bypass line between the downstream adjacent plate and the selected plate,

ST denotes a transition period.

According to one or more embodiments, the minor proportion of fluid injected into the adjacent plates connected to the external bypass line is adjusted so that the flush level of the adjacent plates is equal to 100% +/-20%; and/or adjusting a minor proportion of the effluent withdrawn from an adjacent plate connected to the external bypass line so that the flush level of the adjacent plate is equal to 100% +/-20%.

In accordance with one or more embodiments, a synchronization of +/-10% is established in each of the other external bypass lines,

synchronous flow rate is composed of_j + V_j+1 + V_j/j+1) the/ST is defined by the definition of,

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

n is the number of adsorbent beds in the column,

i is a natural integer from 1 to n;

V_jand V_j+1Representing the respective volume of the distribution/extraction system of the plate connected to said other external bypass line,

VL_j/j+1representing the volume of the other external bypass line,

ST denotes a transition period.

According to one or more embodiments, a +/-5% synchronicity is established in each of the other external bypass lines.

According to one or more embodiments, n is a natural integer from 6 to 24, preferably from 8 to 15.

According to one or more embodiments, each plate is connected to an upstream external bypass line between an upstream adjacent plate and the plate and to a downstream external bypass line between the plate and a downstream adjacent plate.

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).

Detailed Description

The object of the present invention is to improve the performance of the simulated bed separation unit compared to the teaching of patents US 5,972,224, US 6,110,364 and FR 2,935,100.

Referring to fig. 1, in order to improve the separation performance achievable with SMB technology, the present invention proposes a process for SMB separation of feed F in an SMB unit having at least one column consisting of a plurality of adsorbent beds a_iComposition of said adsorbent bed A_iPlates P each comprising 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 automatic equipment for regulating flushingFlow 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 24, preferably from 8 to 15, and i is a natural integer from 1 to n.

The SMB separation method comprises the following steps: feeding the feedstock F and the desorbent D and withdrawing at least one extract E and at least one raffinate R, the feeding point and the withdrawal point being shifted in time course by an amount corresponding to one adsorbent bed, having a transition period (called ST) 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 number of beds in zone 1;

b is the number of beds in zone 2;

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

d is the number of beds in zone 4.

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)。

patent FR 2,935,100 teaches that it is necessary to close a by-pass line for each injected stream (feed and desorbent) and for each withdrawn stream (extract and raffinate).

In contrast, in the method of the present invention, the bypass line remains open and controls the resulting leakage flow rate.

More specifically, the fluid (feedstock S or desorbent D) is injected into the selected plate P_iWhile using the injection line L_FOr L_D. This line is connected to a bypass line connected to the plate, i.e. to the bypass line L_i-1/iOn or connected to a by-pass line L_i/i+1The above. If the associated bypass line is line L_i-1/iIf so, the "adjacent plate connected to the bypass line" is referred to as plate P_i-1Or if the associated bypass line is line L_i/i+1Is called plate P_i+1. Whether or not the bypass line is connected to the injection line used, the flow rate in said line is controlled so that the majority of the injected stream flows to the selected plate P_iAnd a (non-zero) proportion of the injected stream flows to the adjacent plate to which the bypass line is connected (e.g. 1% to 20% of the stream).

According to one or more embodiments, the flow of the minor proportion to the adjacent plate connected to the bypass line is regulated so as to ensure a flushing level of the adjacent plate connected to the bypass line equal to 100% +/-30%, preferably equal to 100% +/-20% and preferably equal to 100% +/-10%.

Also, in the case of the selected panel P_iWhen the effluent (extract E or raffinate R) is taken out, a take-out line L is used_EOr L_R. The withdrawal line is connected to a bypass line connected to the plate, i.e. to the bypass line L_i-1/iOn or connected to a by-pass line L_i/i+1The above. If the associated bypass line is line L_i-1/iIf so, the "adjacent plate connected to the bypass line" is referred to as plate P_i-1Or if the associated bypass line is line L_i/i+1Is called plate P_i+1. Whether or not the bypass line is connected to the withdrawal line used, the flow rate in said line is controlled so that the majority of the withdrawn stream is drawn off from the selected plate P_iAnd a (non-zero) proportion of the withdrawn stream is withdrawn from the adjacent plate connected to the by-pass line.

According to one or more embodiments, the minor proportion of the stream flowing from the adjacent plate connected to the bypass line is adjusted so as to ensure a flush level of the adjacent plate connected to the bypass line equal to 100% +/-20%.

At the plate adjacent to the selected plate Pi is located at the selected plate (P)_i) Upstream adjacent plate (P) of upstream_i-1) Or on a selected plate (P)_i) Downstream adjacent plate (P)_i+1) In the case of the plate P_i-1Is defined as Q_i-1×ST/(V_i-1 + VL_i-1/i/2) and plate P_i+1The level of flushing of is defined as Q_i+1×ST/(V_i+1 + VL_i/i+1/2). In these expressions:

Q_i-1showing the slave plate P_i-1The volume flow rate of the effluent;

Q_i+1indicating the flow direction plate P_i+1The volumetric flow rate of (a);

V_i-1indicating an upstream adjacent plate P_i-1The volume of the distribution/extraction system of (a);

V_i+1indicating downstream adjacent panel P_i+1The volume of the distribution/extraction system of (a);

VL_i/i+1is shown at P_iAnd P_i+1A volume of the bypass line extending therebetween;

VL_i-1/iis shown at P_i-1And P_iA volume of the bypass line extending therebetween; and is

ST denotes a transition period.

Flow rates corresponding to synchronicity are established in all other by-pass lines of the process of the invention, i.e. by-pass lines into which no fluid (e.g. feed or desorbent) is injected or from which no effluent (e.g. extract or raffinate) is withdrawnWithin +/-10%, preferably within +/-5%, of the synchronous flow rate of (V)_j + V_j+1 + VL_j/j+1) and/ST, in the expression:

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

V_jand V_j+1Represents the other external bypass line (L)_j/L_j+1) Connected plates (P)_jAnd P_j+1) The respective volume of the distribution/extraction system of (a);

VL_j/j+1is shown at P_jAnd P_j+1A volume of the bypass line extending therebetween; and is

ST denotes a transition period.

Each plate P of the tower_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. For example, a first chamber may be operated to inject feed F or desorbent D, and another chamber may be operated to withdraw raffinate R or extract E. Another possibility is to use one chamber for the injection of feed F and the withdrawal of raffinate R, the other chamber handling the injection of desorbent D and the withdrawal of extract E. These two 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 or meta-xylene in a mixture of C8 aromatic hydrocarbons. According to one or more embodiments, the feedstock comprises at least 15% by weight of para-xylene and/or 30% by weight [ to be completed ] 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.