WO2002089946A1

WO2002089946A1 - Separation process by simulated moving bed chromatography

Info

Publication number: WO2002089946A1
Application number: PCT/FI2002/000399
Authority: WO
Inventors: Heikki Heikkilä; Jari Lewandowski; Jarmo Kuisma
Original assignee: Danisco Sweeteners Oy
Priority date: 2001-05-09
Filing date: 2002-05-08
Publication date: 2002-11-14
Also published as: US7229558B2; US20030006191A1; JP4924964B2; AU2002255027A1; FI20010977A0; DK1392411T3; EP1392411B1; DE60239605D1; ES2361733T3; CA2445072A1; US6896811B2; FI20010977A; US20050115904A1; EP1392411A1; JP2004533919A; CA2445072C; ATE503538T1

Abstract

A method for fractionating a solution into two or more fractions. More particularly the invention relates to a method for fractionating a solution by a chromatographic simulated moving bed (SMB) process in which the dissolved substances present in the feedstock are separated in the partial packed beds, and the formed separation profile is circulated more than once or less than once through the chromatographic separation loop during one cycle.

Description

Separation process by simulated moving bed chromatography

Field of the invention

The present invention relates to a method for fractionating a solution into two or more fractions advantageously enriched with different compo- nents, and more particularly to a method for fractionating a solution by a chromatographic simulated moving bed (SMB) process in which the dissolved substances present in the feedstock are separated in the chromatographic separation loop of partial packed beds, and the formed separation profile (i.e. dry solids profile) is circulated more than once or less than once through one chromatographic separation loop during one cycle. In a preferred embodiment of the invention the separation profile is circulated twice through the separation loop during one cycle. In another preferred embodiment of the invention the feeding point is circled to a different point compared to the feeding point in the previous cycle. This is called feeding point advancement of separation profile and the feeding point advancement can be done more than once or less than once through the chromatographic separation loop during one cycle.

The novel chromatographic SMB method improves the separation capacity by better utilisation of the resin bed.

Background of the invention The continuous simulated moving bed process has been disclosed already in US Patent 2 985 589 (Broughton et al.). In accordance with this process the mixture to be fractionated is introduced into one partial packed bed and eluant is introduced into another partial packed bed, and two product fractions are withdrawn substantially simultaneously. There are at least four partial packed beds, forming a single loop with continuous circulation of a dry substance profile, and the feed and product withdrawal points are shifted continuously stepwise in the downstream direction in the loop of packing material beds essentially at the speed of the circulation of the dry substance profile in the loop. For simulated moving bed chromatographic separation processes two or more loop and two or more profile modes have been developed in order to better utilise the chromatographic separation resin bed to achieve increased separation capacity, increased yields and fraction purities and fraction dry substance concentrations. A sequential simulated moving bed process applied to the recovery of betaine and sucrose from beet molasses is described in the Applicant's Finnish Patent 86 416. In this method, one complete or essentially complete dry solids profile is circulated in a partial packing material loop. Also the Appli- cant's publications US Patent 6 093 326 and US Patent 5 637 225 relate to the simulated moving bed method, the first applied to the fractionation of molasses and the latter to the fractionation of sulphite cooking liquor. As is described in these publications, the simulated moving bed method may include multiple loops; and dry solids profile(s) is circulated in each loop. Finnish Patent 86 416 referred to above discloses a method for recovering betaine and sucrose from beet molasses employing the simulated moving bed process. The chromatographic system comprises at least 3 chromatographic partial packed beds in series. In the method, betaine and sucrose are separated during the same sequence comprising a molasses feeding pha- se wherein the molasses feedstock is supplied to one of said partial packed beds and eluant water is supplied substantially simultaneously to another of said partial packed beds, an eluant feeding phase, and a circulating phase.

These phases are repeated either once or several times during the sequence.

In the method disclosed in the above US Patent 6 093 326, the liq- uid flow is effected in a system comprising at least two partial packed beds, and the product or products are recovered during a multistep sequence. A sequence comprises feeding, eluting and circulating phases. During the circulating phase, the liquid present in the partial packed beds with its dry solids profile is circulated in two or more loops comprising one, two or more partial packed beds. A loop may be closed or "open", in other words, when liquid is circulated in one loop, eluant can be introduced into the other loop and a product fraction can be withdrawn therefrom. During the feed and elution, the flow through the packing material beds may take place between successive loops, wherein the flows carry material from one loop to another. During the circulat- ing phase, the column or columns form a closed loop and are separated from the other loops. An essentially complete dry solids profile is circulated in each loop.

Publication WO 97/45185 discloses a method for fractionating a solution into two or more fractions by a chromatographic simulated moving bed process, wherein the separation system comprises at least two separation profiles in the same loop. The method can be used for fractionating a sulphite cooking liquor to give a fraction rich in monosaccharides and/or a fraction rich in lignosulphonates. Furthermore, molasses or vinasse can be fractionated in that way to obtain fractions rich in sugar, such as sucrose, and/or betaine. In the method of the above mentioned publication, there are at least two separa- tion profiles in the same loop. The minimum bed length required for the method is at least the length of two separation profiles without excess overlapping.

One of the problems associated with the above arrangements is that in order to get a good separation result, high yields, purities and product fraction dry substance concentration, long chromatographic separation beds have to be used.

Another problem with the earlier arrangements is also that the dry substance profile(s) in the chromatographic separation beds do not necessarily fill the whole bed length or they may overfill the bed. As a rule, the dry sub- stance profile should be formed so that high product fraction yields, purities, concentrations and high separation capacities are achieved. This means that chromatographic column load has to be high, e.g. the feed volume has to be large, in order to achieve high product fraction dry substance concentration and high separation capacities. High dry substance concentration means that the concentration is at least close to the partial concentration of the components) in the feed.

On the other hand, the height of the chromatographic separation bed(s) has to be long to contain high enough number of theoretical plates in order to achieve high product purities and product yields.

L = N HETP (1 )

wherein L = length of the resin bed

N = number of the theoretical plates

HETP = height equivalent of the theoretical plate

V_e = elution volume

W = peak width. In one situation the separation profile is narrow and the chromatographic separation bed is long which may lead to a situation where part of the chromatographic separation column is not loaded with the separation profile, which causes poor utilisation of the bed. Alternatively, if in another situation the dry substance profile is long and the chromatographic separation bed needed for good separation is short, leading to the overlapping of the dry substance profile from both ends of the profile occurs causing low purities and low yields.

In the above mentioned situations more advanced methods are re- quired and the present invention provides a solution to the problems associated with both situations.

Brief description of the invention

An object of the present invention is thus to provide a method to solve the above problems. The objects of the invention are achieved by a method characterized by what is stated in the independent claims. The preferred embodiments of the invention are disclosed in the dependent claims.

The present invention is based on a method for fractionating a solution by a chromatographic simulated moving bed (SMB) process in which the dissolved substances present in the feedstock are separated in the partial packed beds, and the formed separation profile is circulated more than once or less than once through the chromatographic separation loop during one cycle. In other words, the separation profile is circulated through the chromatographic separation loop in the separation system a number of times, which is substantially different than one. A separation profile is formed by the feed so- lution and the dry substance recirculated. The separation profile can be formed either directly from the feed or if the feed is fed from one loop to another, the separation profile is formed from the fraction or fractions of the previous loop. The feeding point of the separation profile is advanced during one cycle either less than once or more than once through the chromatographic separation loop.

Normally, and especially in a sequential simulated moving bed (SMB) chromatographic separation the new sequence is started from the same location as the previous sequence. This means that the first step of the complete sequence is done again at the same location after the last step of the previous complete sequence. In the present invention a cycle is formed of determined steps, which are carried out from 1 to several times during the same cycle. Typically the cycles are repeated until an equilibrium is reached and then the process is continued advantageously in equilibrium. The equilibrium is defined by the equilibrium of the dry substance profile, and the equilibrium of the dry substance profile is normally reached after approximately 7 cycles.

A complete sequence comprises all the steps. A complete sequence is complete when the steps are repeated at the same location. A complete sequence may consist of several cycles. A cycle is a predetermined se- quence of steps, and one cycle determines all steps, which are circulating the separation profile during the cycle. Advantageously the cycle is repeated so that its steps are at some phase repeated at the same locations in the columns. The order of the steps is predetermined, but not the location. In one embodiment, the first step of the cycle is the feed step. In the sequential simulated moving bed process, all of the fluid streams do not flow continuously. The streams are: the supply of feed solution and eluant, the circulating of the separation profile, and the withdrawal of products (eluting phase; two to four or more products). The flow rate and the volumes of the different feeds and product fractions may be adjusted in accor- dance with the separation goals (yield, purity, capacity). The process commonly comprises three basic phases: feeding, eluting and circulating. During the feeding phase, a feed solution, and possibly also an eluant during a simultaneous eluting phase, is introduced into predetermined partial packed bed or predetermined partial packed beds, and during these phases two, three, four or even more product fractions are withdrawn. During the eluting phase eluant is fed into the predetermined partial packed beds. During the circulating phase, no feed solution or eluant is supplied to the partial packed beds and no products are withdrawn. During one or several steps in a sequence, simultaneous circulating phase and/or feeding and/or eluting phase can be in one loop or in different loops.

A novel simulated moving bed method has now been developed to solve the above mentioned problems. In one of the embodiments of the present invention the first step of the next cycle is not started at the same location after the previous cycle. In another embodiment of the present invention the first step is started at the same location after the previous cycles. In the new chromatographic separation method one or more separation profiles is/are cir- culated more than once or less than once through the chromatographic separation loop before all of the predetermined fractions are taken out or before the next feed or feeds and eluant or eluant feeds of the next cycle are fed in.

Detailed description of the invention The present invention relates to a method for fractionating a solution by a chromatographic simulated moving bed process in which the liquid flow is effected in a system comprising one or more columns containing one or more partial packed beds. The dissolved substances present in the feedstock are separated in the partial packed beds, and a separation (i.e. dry solids) pro- file is formed. The columns/partial packed beds form one or several loops. The novel method is characterized in that the separation profile is circulated through the loop more than once or less than once during one cycle, in a preferred embodiment of the invention the separation profile is circulated twice during one cycle. This means that the separation profile is circulated through the loop in the separation system a number of times, which is substantially different than one.

Typical retention volumes of the desired products can be found in publications. The retention volume of each compound depends on various parameters, for example packing material quality (e.g. ion form), and elution conditions such as separation temperature and flow. Typically retention volumes for monosaccharides and disaccharides are 40 - 80% of the bed volumes, when cation exchange resins are used as a column filling material and water as an eluant. Retention volumes can be calculated in SMB-system e.g. from the volumes of the steps which are advancing the feeding point(s) of the separation profile.

In the method of the invention the product or products are recovered using a multi-step sequence comprising the following phases: feeding phase, eluting phase and circulating phase.

In the feeding phase the solution to be fractionated is introduced in- to the sectional packing material bed and simultaneously a corresponding amount of product fraction is withdrawn from a later point downstream in the same sectional packing material bed or from a downstream sectional packing material bed connected with said bed. The feeding phase may include all sectional packing material beds in the chromatographic separation loop. Several feeds can be introduced during one cycle.

In the circulating phase the liquid present in the sectional packing material bed with its dry solids profile is circulated in a loop comprising one, two or several sectional packing material beds. This may also include all the sectional packing material beds in the chromatographic separation loop of the system. The eluting phase comprises feeding of an eluant into a sectional packing material bed and respectively withdrawal of a product fraction or fractions from a downstream point of the packing material bed or a downstream sectional packing material bed.

A process step comprises one or more of the above simultaneous identical or different phases, and said steps are repeated from 1 to 50 times during the cycle.

Said phases are employed to form cycles comprising several successive process steps. In accordance with the invention a cycle preferably comprises 1 to 50 steps. A sequence comprising said steps is repeated five to seven times to equilibrate the system, whereafter the process is continued essentially in a state of equilibrium.

Typically from 1 to 28, preferably from 2 to 12, most preferably from 2 to 6 chromatographic sectional packing material beds combined into one or more loops are employed in the method of the invention. A loop may comprise one, two or several sectional packing material beds packed into one or more columns. The method comprises the use of loops in series or in parallel. The method can also be used either in one or several loops. It is also possible that there are several separation profiles in one loop. A separation profile is formed by the feed solution and the dry substance recirculated. The separation profile is a complete or essentially complete dry solids profile. If the loops are in series the separation profile can be formed of a part of the separation profile from the previous loop. The separation profile can also be formed of the subprofile fraction or fractions of the pro- file present in the previous or same loop. The separation profile comprises constituents present in the feedstock of the profile, i.e. part of the constituents having a low migration rate, part of the constituents having an intermediate migration rate, and/or part of the constituents having a high migration rate. Accordingly the separation profile is a complete or an essentially complete dry solids profile. Part of the constituent having the highest migration rate may be withdrawn prior to the circulating phase. Product fraction is a fraction taken out of the chromatographic separation process. There can be more than one product fractions.

Residue fraction is a fraction which contains less valuable product or products or by-product or by-products. There can be more than one residue fractions.

Recycle is a fraction which is recycled back to the column(s) as such or combined with a starting material. There may also be an operation before returning the recycle to the column, for example it may be concentrated by evaporation. There can be more than one recycle fractions. The method of the invention is particularly well suited for separating substances that are difficult to separate from mixtures containing them. Such mixtures may include sulphite cooking liquors, molasses, especially B- molasses and C-molasses, vinasse, fructose/glucose syrups, beet-derived juices, invert sugar mixtures, starch hydrolysates, wood hydrolysates, milk whey solutions and other lactose-containing solutions, lactulose-containing solutions, maltose-containing solutions, maltitol-containing solutions, solutions containing amino acids, fermentation broths containing various organic acids, such as citric acid, gluconic acid, bagasse hydrolysates, and solutions containing rhamnose, arabinose, mannose, raffinose, inositol, mannitol, sorbitol, xyli- tol, erythhtol, glutamic acid, glycerol and/or tagatose, and isomaltulose and trehalulose solutions and the like. Preferably the solution to be fractionated is sulphite cooking liquor or beet molasses.

In this context sulphite cooking liquor means a liquor employed in the cooking of sulphite cellulose or a part thereof, a liquor ensuing from the cooking or a part thereof, a liquor used in the sulphite cooking or a part thereof or liquor removed from the sulphite cooking during the cooking or a part thereof.

The products of the method of the present invention may be selected from the group consisting of glucose, fructose, sucrose, betaine, rham- nose, arabinose, mannose, raffinose, lactose, lactulose, maltose, maltitol, inositol, mannitol, glycerol, xylitol, xylose, sorbitol, erythritol, organic acids, especially amino acids, such as glutamic acid.

The chromatographic apparatus employed typically comprises one column or several columns connected in series, fluid conduits connecting the columns, solution and eluant containers, feed and eluant conduits, circulation, eluant, recycle and feed pumps, heat exchangers, product fraction withdrawal conduits, and valves, flow and pressure regulators and on-line measurements as concentration, density, optical activity and conductivity meters. The process is advantageously proceeded essentially within a state of equilibrium. The state of equilibrium is typically reached when the cycle is repeated approxi- mately 6 or 7 times.

The number of columns is 1 to 28, preferably 2 to 12, most preferably from 2 to 6. Preferably, a column comprises one or several partial packed beds.

As packing material a column comprises advantageously an ion ex- change resin, especially a cation or anion exchange resin. The cation exchange resin is a weakly acid cation exchange resin or a strongly acid cation exchange resin. A strongly acid cation exchange resin, such as Finex CS 13 GC (manufacturer Finex Oy) is preferably used as a column packing material.

The temperature is preferably between 10 and 90°C. The pressure is preferably from 1 to 15 bar.

The eluant employed is a solvent, such as alcohol, especially etha- nol or water or a mixture thereof, especially a mixture of ethanol and water. Preferably the eluant used is water.

The linear flow rate may range from 0.4 to 20 m/h, preferably the li- near flow rate is from 1 to 12 m/h.

In one embodiment of the present invention the method is characterized in that the separation system comprises at least one column and a cycle in the separation system comprises the following phases: a) a feeding phase, wherein the feed solution is fed into one of the columns and optionally substantially simultaneously eluant is fed into the next column, and during the feeding phase at least one product and/or at least one fraction other than the product is collected from the same or from a subsequent column, b) a circulating phase, wherein nothing is fed into or collected from the loop, c) an eluting phase, wherein the eluant is fed into the column and residue and optionally a second product are collected from the same or from the subsequent columns, phases from a) to c) are used during a cycle, 1 to several times. One or more of the phases a) to c) can be in use simultaneously. Phases a) to c) can also be carried out simultaneously in one step, one loop, in a column or in a part of a column.

In another embodiment of the present invention the method is characterized in that the cycle in the separation system comprises the following phases a) a feeding phase, wherein the feed solution is fed into one of the columns and optionally substantially simultaneously eluant is fed into the next column, and the first product and/or recycle and the residue are collected from the same or from the subsequent column, b) a circulating phase, wherein nothing is fed into or collected from the chromatographic separation loop, c) an eluting phase, wherein the eluant is fed into the first column and residue and optionally a second product are collected from the same or from the subsequent column, phases a) and c) are used as many times as necessary until the separation profile has circulated through the chromatographic separation loop more than once or less than once during one cycle.

In one embodiment of the present invention the separation profile is narrow and the chromatographic separation resin bed required for good sepa- ration result is long. In this embodiment the separation profile is circulated through the chromatographic separation loop more than once, then the resin bed is well utilised. Well utilised means in this context that the separation profile essentially fills all packing material. The separation profile can be circulated for example 1.5 times, 1.7 times, twice, or 3 times etc. depending on the number of the columns. If the dry substance profile is circulated 1.5 times, it means that in a 6-column system the first step of the cycle is repeated during the next cycle three columns later. Advantageously the separation profile is circulated twice.

In another embodiment of the present invention the separation pro- file is long, i.e. broad and the bed length needed for the good separation is short then the separation profile is circulated less than once through the chromatographic separation loop before the first step of the next cycle. The separation profile can also be circulated, for example 0.7 times, through the chromatographic separation loop. This means that for example in a 10-column sys- tern the first step of the next cycle is repeated already after 7 columns. An advantageous feature of the method of the invention is that an optimized performance for the series of columns can be achieved. Another advantage of the present invention is that the same or improved capacity can be reached with a short total column length and with a less number of col- umns. Less number of columns means a lower investment cost.

It will be obvious to a person skilled in the art that, as technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described below but may vary within the scope of the claims.

EXAMPLES

Example 1 Chromatographic separation of xylose from sulphite cooking liquor

The test equipment included two columns connected in series, a feed pump, circulation pump, an eluant water pump as well as inlet and prod- uct valves for the various process streams. The height of each column was 4.6 m and each column had a diameter of 0.1 11 m. The columns were packed with a strong acid gel type cation exchange resin (Finex CS13GC) in Mg²⁺ - form. The mean bead size was 0.36 mm and the divinylbenzene content was 6.5%. Sulphite cooking liquor from an Mg ⁺ -based cooking process was used as a feed and the aim was to separate the xylose contained therein.

The liquor was filtered using diatomaceous earth and diluted to a concentration of 48% by weight. The pH was 3.0. The sulphite cooking liquor was composed as set forth below, whereby the percentages are given on a dry substance weight basis.

TABLE 1

Composition of Feed % on PS

Xylose 14.3

Glucose 1.6

Galactose + rhamnose 1.5

Mannose 1.9

Xylonic acid 5.7

Others 75.0 The fractionation was performed by way of a 9-step SMB sequence as set forth below. The feed and the eluant were used at a temperature of 65°C and water was used as an eluant.

Step 1 : Feed solution was pumped into the first column at a flow rate of 45 l/h, first 2 I of recycle fraction and then 2.5 I of xylose fraction were collected from the second column.

Step 2: 1 1 ,2 I of feed solution was pumped into the first column at a flow rate of 45 l/h and a residue fraction was collected from the same column. Simultaneously water was pumped into the second column at a flow rate of 31 l/h and first 5.7 I of xylose fraction and then 2 I of recycle fraction were collected from the same column.

Step 3: 14.9 I was circulated in the column set loop (separation profile circulation was continued), formed with all columns, at a flow rate of 45 l/h.

Step 4: 1 1.5 I of water was pumped into the first column at a flow rate of 45 l/h and a residue fraction was collected from the second column.

Step 5: 14.9 I was circulated in the column set loop, formed with all columns, at a flow rate of 50 l/h.

Step 6: 1 1.5 I of water was pumped into the second column at a flow rate of 50 l/h and a residue fraction was collected from the first column. Step 7: 14.4 I was circulated in the column set loop, formed with all columns, at a flow rate of 50 l/h.

Step 8: 11.5 I of water was pumped into the first column at a flow rate of 55 l/h and a residue fraction was collected from the second column.

Step 9: 10.4 I was circulated in the column set loop, formed with all columns, at a flow rate of 50 l/h.

With described steps, separation profile was circulated twice over the loop, during one cycle. After equilibration of the system, the following fractions were drawn from the system: Two residue fractions from both columns, xylose-containing fraction from the second column and two recycle fractions from second column. The results including HPLC analyses for combined fractions are set forth in the table below. TABLE 2

Xylose Residue Recycle

Volume, I 8.2 45.7 4.0

Dry solids, g/100ml 22.3 14.6 19.4

Xylose, % on DS 54.5 1.0 48.8

Glucose, % on DS 3.7 0.9 3.8

Galactose + Rham- 5.3 0.2 4.7 nose, % on DS

Mannose, % on DS 6.1 0.3 5.8

Xylonic acid, % on DS 10.5 3.5 12.0

Others, % on DS 20.0 94.1 24.9

PH 3.0 3.6 3.1

The overall xylose yield calculated from these fractions was 93.7%. Example 2 Chromatographic separation of molasses.

The test equipment includes three columns connected in series, feed pump, circulation pumps, an eluant water pump as well as inlet and product valves for the various process streams. The height of each column is 4 m and each column has a diameter of 0.1 11 m. The columns are packed with a strong acid gel type cation exchange resin in Na⁺ -form. The mean bead size is 0.36 mm and the divinylbenzene content is 6.5%.

The feed material is beet molasses, especially B-molasses. The molasses is diluted to 60% by weight and carbonated with sodium carbonate (1.5% on DS basis, temperature 60°C, 3 h reaction time). The carbonated so- lution is then filtered with a Seitz pressure filter using Kenite 300 as a filtering aid (precoat 1 kg/m², bodyfeed 0.5% on DS basis). The feed concentration is adjusted to 68.5 g/100 ml. The composition is set forth in the table below, whereby the percentages are given on a dry substance weight basis.

TABLE 3

Composition of feed % on DS

Sucrose 72.2

Betaine 3.9

Others 23.9 The fractionation is performed by way of a 14-step SMB sequence as set forth below. The feed and the eluant are used at a temperature of 85°C and water is used as an eluant.

Step 1 : 3.0 I of feed solution is pumped into the first column at a flow rate of 40 l/h and a recycle fraction is collected from column 3.

Step 2: 7.1 I of feed solution is pumped into the first column at a flow rate of 30 l/h and a residue fraction is collected from the same column.

Simultaneously water is pumped into column 2 at a flow rate of 70 l/h and first

3 I of recycle fraction and then 13.6 I of sucrose-containing fraction are col- lected from column 3.

Step 3: 5.0 I of feed solution is pumped into the first column at a flow rate of 40 l/h and sucrose-containing fraction is collected from column 3.

Step 4: 6.9 I is circulated in the column set loop (separation profile circulation is continued), formed with all columns, at a flow rate of 45 l/h. Step 5: 7.1 I of water is pumped into the first column at a flow rate of 45 l/h and a residue fraction is collected from column 2. Simultaneously 4 I of water is pumped into column 3 at a flow rate of 25 l/h and betaine- containing fraction is collected from the same column.

Step 6: 12.2 I of water is pumped into the first column at a flow rate of 40 l/h and betaine-containing fraction is collected from column 3.

Step 7: 7.1 I of water is pumped into the first column at a flow rate of 40 l/h and residue fraction is collected from column 3.

Step 8: 12.2 I is circulated in the column set loop, formed with all columns, at a flow rate of 45 l/h. Step 9: 7.1 I of water is pumped into column 2 at a flow rate of 45 l/h and residue fraction is collected from column 1 .

Step 10: 12.2 I is circulated in the column set loop, formed with all columns, at a flow rate of 45 l/h.

Step 11 : 7.1 I of water is pumped into column 3 at a flow rate of 45 l/h and residue fraction is collected from column 2.

Step 12: 12.2 I is circulated in the column set loop, formed with all columns, at a flow rate of 45 l/h.

Step 13: 7.1 I of water is pumped into the first column at a flow rate of 45 l/h and residue fraction is collected from column 3. Step 14: 9.2 I is circulated in the column set loop, formed with all columns, at a flow rate of 45 l/h. With described steps, the separation profile is circulated twice over the loop, during one cycle. After equilibration of the system, the following fractions are drawn from the system: two residue fractions from all columns, sucrose-containing fractions from column 3, recycle fraction from column 3 and betaine-containing fractions from column 3. The results including HPLC analyses for combined fractions are set forth in the table below.

TABLE 4

Fractions Sucrose Betaine Recycle Residue

Volume, I 18.6 16.2 6.0 42.6

Concentration, 36.3 4.1 17.2 4.8 g/100ml

Sucrose, % on DS 94.8 4.8 61 .9 16.0

Betaine, % on DS 0.0 60.4 0.0 0.4

Others, % on DS 5.2 34.8 38.1 83.6

The overall yield calculated from the product fractions is 94.7% for sucrose and 98.0% for betaine.

Example 3 Chromatographic separation of xylose from sulphite cooking liquor. The test equipment includes four columns connected in series, a feed pump, circulation pump, an eluant water pump as well as inlet and product valves for the various process streams. The height of each column is 5.0 m and each column has a diameter of 0.2 m. The columns are packed with a strong acid gel type cation exchange resin (Finex CS13GC) in Mg²⁺ -form. The mean bead size is 0.36 mm and the divinylbenzene content is 6.5%.

Sulphite cooking liquor from an Mg²⁺ -based cooking process is used as a feed and the aim is to separate the xylose contained therein.

The liquor is filtered using diatomaceous earth and diluted to a concentration of 48% by weight. The sulphite cooking liquor is composed as set forth below, whereby the percentages are given on a dry substance weight basis. TABLE 5

Composition of Feed % on DS

Xylose 14.9

Glucose 1.9

Galactose + rhamnose 1.6

Mannose 1.9

Others 79.7

The fractionation is performed by way of a 24-step SMB sequence as set forth below. The feed and the eluant are used at a temperature of 65°C and water is used as an eluant.

Step 1 : 39 I of feed solution is pumped into the first column at a flow rate of 140 l/h and a residue fraction is collected from the same column. Simultaneously water is pumped into the second column at a flow rate of 1 10 l/h and first 5 I of recycle fraction and then 21 I of xylose fraction and finally 5 I of recycle fraction are collected from the column 4.

Step 2: 50.5 I is circulated in the loop (separation profile circulation is continued), formed with all columns, at a flow rate of 140 l/h.

Step 3: 40.5 I of water is pumped into the column 3 at a flow rate of 140 l/h and a residue fraction is collected from the second column. Step 4: 50.5 I is circulated in the column set loop, formed with all columns, at a flow rate of 140 l/h.

Step 5: 40.5 I of water is pumped into the column 4 at a flow rate of 140 l/h and a residue fraction is collected from the column 3.

Step 6: 50.5 I is circulated in the column set loop, formed with all columns, at a flow rate of 140 l/h.

Step 7: 39 I of feed solution is pumped into the column 4 at a flow rate of 140 l/h and a residue fraction is collected from the same column. Simultaneously water is pumped into the first column at a flow rate of 1 10 l/h and first 5 I of recycle fraction and then 21 I of xylose fraction and finally 5 I of recy- cle fraction are collected from the column 3.

Step 8: 50.5 I is circulated in the column set loop, formed with all columns, at a flow rate of 140 l/h.

Step 9: 40.5 I of water is pumped into the second column at a flow rate of 140 l/h and a residue fraction is collected from the first column. Step 10: 50.5 I is circulated in the column set loop, formed with all columns, at a flow rate of 140 l/h.

Step 1 1 : 40.5 I of water is pumped into the column 3 at a flow rate of 140 l/h and a residue fraction is collected from the second column. Step 12: 50.5 I is circulated in the column set loop, formed with all columns, at a flow rate of 140 l/h.

Step 13: 39 I of feed solution is pumped into the column 3 at a flow rate of 140 l/h and a residue fraction is collected from the same column. Simultaneously water is pumped into the column 4 at a flow rate of 1 10 l/h and first 5 I of recycle fraction and then 21 I of xylose fraction and finally 5 I of recycle fraction are collected from the second column.

Step 14: 50.5 I is circulated in the column set loop, formed with all columns, at a flow rate of 140 l/h.

Step 15: 40.5 I of water is pumped into the first column at a flow rate of 140 l/h and a residue fraction is collected from the column 4.

Step 16: 50.5 I is circulated in the column set loop, formed with all columns, at a flow rate of 140 l/h.

Step 17: 40.5 I of water is pumped into the second column at a flow rate of 140 l/h and a residue fraction is collected from the first column. Step 18: 50.5 I is circulated in the column set loop, formed with all columns, at a flow rate of 140 l/h.

Step 19: 39 I of feed solution is pumped into the second column at a flow rate of 140 l/h and a residue fraction is collected from the same column. Simultaneously water is pumped into the column 3 at a flow rate of 1 10 l/h and first 5 I of recycle fraction and then 21 I of xylose fraction and finally 5 I of recycle fraction are collected from the first column.

Step 20: 50.5 I is circulated in the column set loop, formed with all columns, at a flow rate of 140 l/h.

Step 21 : 40.5 I of water is pumped into the column 4 at a flow rate of 140 l/h and a residue fraction is collected from the column 3.

Step 22: 50.5 I is circulated in the column set loop, formed with all columns, at a flow rate of 140 l/h.

Step 23: 40.5 I of water is pumped into the first column at a flow rate of 140 l/h and a residue fraction is collected from the column 4. Step 24: 50.5 I is circulated in the column set loop, formed with all columns, at a flow rate of 140 l/h. With described steps, the separation profile is circulated 3/4 times over the loop, during one cycle. After equilibration of the system, the following fractions are drawn from the system: three residue fractions from all columns, one xylose-containing fraction from all columns and two recycle fractions from all columns. The results including HPLC analyses for the combined fractions are set forth in the table below.

TABLE 6

Xylose Residue Recycle

Volume, I 21.0 120.0 10.0

Dry solids, g/100ml 23.2 13.8 19.8

Xylose, % on DS 50.3 1.1 43.9

Glucose, % on DS 3.9 1.2 4.1

Galactose + Rhamnose, % on DS 5.5 0.2 4.9

Mannose, % on DS 5.8 0.3 5.9

Others, % on DS 34.5 97.2 41.2

The overall xylose yield calculated from these fractions is 93.1 %.

Example 4 Chromatographic separation of fructose syrup

The test equipment included two columns connected in series, a feed pump, recycling pump, an eluent water pump as well as inlet and product valves for the various process streams. The height of each column was 4.0 m and each column had a diameter of 0.2 m. The columns were packed with a strong acid gel type cation exchange resin (Finex CS 1 1 GC) in Ca²⁺ -form. The mean bead size was 0.36 mm and the divinylbenzene content was 5.5%. With these resin properties typical retention for the fructose peak is approxi- mately 75% of the bed volume.

Syrup from fructose process was used as a feed and the aim was to separate the fructose contained therein.

The liquor was filtered using 10 micron filter bag and diluted to a concentration of 66 g/100ml. The pH was 4.4. The fructose syrup was com- posed as set forth below, whereby the percentages are given on a dry substance weight basis. TABLE 7

Composition of Feed

Fructose, % on DS 93.4

Glucose, % on DS 2.0

Disaccharides, % on DS 3.7

Others, % on DS 0.9

The fractionation was performed by way of a 14-step SMB sequence as set forth below. The feed and the eluent were used at a tempera- ture of 65°C and water was used as an eluent.

Step 1 : 9 I of feed solution was pumped into the first column at a flow rate of 90 l/h and a recycle fraction was collected from the second column.

Step 2: 31 I of feed solution was pumped into the first column at a flow rate of 90 l/h and a residue fraction was collected from the same column. Simultaneously 49 I of water was pumped into the second column at a flow rate of 143 l/h and fructose fraction was collected from the same column.

Step 3: 60 I was circulated in the column set loop (separation profile circulation was continued), formed with all columns, at a flow rate of 90 l/h. Step 4: 29 I of water was pumped into the first column at a flow rate of 90 l/h and a residue fraction was collected from the second column.

Step 5: 60 I was circulated in the column set loop, formed with all columns, at a flow rate of 90 l/h.

Step 6: 31 I of water was pumped into the second column at a flow rate of 90 l/h and a residue fraction was collected from the first column.

Step 7: 51 I was circulated in the column set loop, formed with all columns, at a flow rate of 90 l/h.

Step 8: 9 I of feed solution was pumped into the second column at a flow rate of 90 l/h and a recycle fraction was collected from the first column. Step 9: 31 I of feed solution was pumped into the second column at a flow rate of 90 l/h and a residue fraction was collected from the same column. Simultaneously 49 I of water were pumped into the first column at a flow rate of 143 l/h and fructose fraction was collected from the same column.

Step 10: 60 I was circulated in the column set loop, formed with all columns, at a flow rate of 90 l/h. Step 11 : 29 I of water was pumped into the second column at a flow rate of 90 l/h and a residue fraction was collected from the first column.

Step 12: 60 I was circulated in the column set loop, formed with all columns, at a flow rate of 90 l/h. Step 13: 31 I of water was pumped into the first column at a flow rate of 90 l/h and a residue fraction was collected from the second column.

Step 14: 51 I was circulated in the column set loop, formed with all columns, at a flow rate of 90 l/h.

With described steps, the separation profile was circulated 3/2 times over the loop, during one cycle. This can be calculated from the step volumes: 9 I + 31 I + 60 I + 29 I + 60 I + 31 I + 51 I = 271 I, which is 107.8% of the test equipment bed volume. Retention volume for fructose fraction is 271 I + 9 I = 280 I, which calculated for 3/2 circulations over the loop is 74.3% of bed volume. This is in the range of the typical retention for the resin used in this example.

After equilibration of the system, the following fractions were drawn from the system: Three residue fractions from both columns, one fructose containing fraction and one recycle fraction from both columns. The result including HPLC analyses for combined fractions are set forth in the table below.

TABLE 8

Fructose Residue Recycle

Volume, I 98 182 18

Dry solids, g/100ml 41.3 2.3 44.7

Fructose, % on DS 97.0 49.8 95.7

Glucose, % on DS 0.2 22.5 0.9

Disaccharides, % on DS 2.1 18.1 2.6

Others, % on DS 0.7 9.6 0.8

PH 4.2 4.3 4.3

The overall fructose yield calculated from these fractions was 95.0%.

Example 5 Chromatographic separation of maltose syrup

The test equipment included three columns connected in series, a feed pump, recycling pumps, an eluent water pump as well as inlet and product valves for the various process streams. The height of each column was 3.4 m and each column had a diameter of 0.2 m. The columns were packed with a strong acid gel type cation exchange resin in Na⁺ -form. The mean bead size was 0.35 mm and the divinylbenzene content was 5.5%. With these resin properties typical retention for the maltose peak is approximately in the range of 54% of the bed volume.

The maltose syrup was evaporated to 55% by weight and then filtered with a Seitz pressure filter using Kenite 300 as a filtering aid (precoat 1 kg/m², bodyfeed 0.5% on DS basis). The feed concentration was adjusted to 55.5 g/100 ml. The pH was 4.1. The composition is set forth in the table below, whereby the percentages are given on a dry substance weight basis.

TABLE 9

Composition of feed

Maltose, % on DS 84.6

Malto-oligomers, % on DS 4.7

Maltotriose, % on DS 1.6

Glucose, % on DS 7.3

Others, % on DS 1.8

The fractionation was performed by way of a 14-step SMB se- quence as set forth below. The feed and the eluent were used at a temperature of 80°C and water was used as an eluent.

Step 1 : 3 I of feed solution was pumped into the first column at a flow rate of 80 l/h and a recycle fraction was collected from column 3.

Step 2: 15 I of feed solution was pumped into the first column at a flow rate of 80 l/h and a residue fraction was collected from the same column. Simultaneously water was pumped into column 2 at a flow rate of 200 l/h and first 8 I of recycle fraction and then 32 I of maltose-containing fraction were collected from column 3.

Step 3: 32 I of feed solution was pumped into the first column at a flow rate of 80 l/h and maltose-containing fraction was collected from column 3.

Step 4: 8 I was circulated in the column set loop (separation profile circulation is continued), formed with all columns, at a flow rate of 120 l/h.

Step 5: 14 I of water was pumped into the column 3 at a flow rate of 120 l/h and a residue fraction was collected from column 2. Step 6: 30 I was circulated in the column set loop, formed with all columns, at a flow rate of 120 l/h.

Step 7: 20 I of water was pumped into the first column at a flow rate of 120 l/h and residue fraction was collected from column 3. Step 8: 30 I was circulated in the column set loop, formed with all columns, at a flow rate of 120 l/h.

Step 9: 20 I of water was pumped into column 2 at a flow rate of 120 l/h and residue fraction was collected from column 1.

Step 10: 29 I was circulated in the column set loop, formed with all columns, at a flow rate of 120 l/h.

Step 1 1 : 18 I of water was pumped into column 3 at a flow rate of 120 l/h and residue fraction was collected from column 2.

Step 12: 38 I was circulated in the column set loop, formed with all columns, at a flow rate of 120 l/h. Step 13: 15 I of water was pumped into the first column at a flow rate of 120 l/h and residue fraction was collected from column 3.

Step 14: 35 I was circulated in the column set loop, formed with all columns, at a flow rate of 120 l/h.

With described steps, separation profile was circulated two times over the loop, during one cycle. This can be calculated from the step volumes: 3 I + 15 I + 32 I + 8 l+ 14 I + 30 I + 20 I + 30 I + 20 I + 29 I + 18 I + 38 I + 15 I + 35 I + = 307 I, which is 95.9% of the test equipment bed volume. Retention volume for maltose fraction is 307 I + 3 I - 8 I = 318 I, which when calculated for two circulations over the loop is 49.6% of bed volume. This is in the range of the typical values for maltose retention for the resin used in the example.

After equilibration of the system, the following fractions were drawn from the system: Two residue fractions from all columns, maltose-containing fraction from column 3 and recycle fraction from column 3. The result including HPLC analyses for combined fractions are set forth in the table below.

TABLE 10

Fractions Maltose Recycle Residue

Volume, I 64 1 1 102

Concentration, g/100ml 32.3 20.1 4.6

Maltose, % on DS 96.6 93.1 27.0

Malto-oligomers, % on DS 0.6 2.7 24.0

Maltot ose, % on DS 0.6 2.5 5.5

Glucose, % on DS 2.2 1.6 35.9

Others, % on DS - 0.1 7.6

PH 4.5 4.8 4.2

The overall maltose yield calculated from the product fractions was 94%.

Claims

1. A method for fractionating a solution into two or more fractions by a chromatographic simulated moving bed (SMB) process, character- i z e d in that the separation profile is circulated through the chromatographic separation loop in the separation system more than once or less than once during one cycle.

2. A method according to claim ^ characterized in that the separation profile is circulated through the chromatographic separation loop in the separation system a number of times, which is substantially different than one.

3. A method according to claim 1 or 2, characterized in that the separation profile is circulated twice through the chromatographic separation loop in the separation system during one cycle.

4. A method according to claim 1 or 2, characterized in that the separation system comprises at least one column and the cycle in the separation system comprises the following phases: a) a feeding phase, wherein the feed solution is fed into one of the columns and optionally substantially simultaneously eluant is fed into a subse- quent column, and during the feeding phase at least one product fraction and/or at least one fraction other than the product is collected from the same or from a subsequent column, b) a circulating phase, wherein nothing is fed into or collected from the chromatographic separation loop, c) an eluting phase, wherein the eluant is fed into one of the columns and residue fraction and optionally a second product fraction or fractions is/are collected from the same or from the subsequent columns, phases from a) to c) are used during one cycle 1 to several times.

5. A method according to any one of the preceding claims, c h a r- acterized in that two or more of the phases a) to c) are carried out simultaneously.

6. A method according to claim 4, characterized in that phases a) to c) are carried out simultaneously in one step, one loop, in a column or in a part of a column.

7. A method according to any one of the preceding claims, characterized in that the simulated moving bed method is sequential.

8. A method according to any one of the preceding claims, characterized in that the chromatographic separation system comprises one or more loops.

9. A method according to claim 8, characterized in that the loops comprise one or more separation profiles.

10. A method according to any one of the preceding claims, characterized in that the column comprises / columns comprise one or several partial packing material bed or beds.

11. A method according to any one of the preceding claims, characterized in that the partial packing material bed is an ion exchange resin bed.

12. A method according to any one of the preceding claims, characterized in that the partial packing material bed is a cation exchange resin bed.

13. A method according to claim 12, characterized in that the packing material is a weakly acid cation exchange resin.

14. A method according to claim 12, characterized in that the packing material is a strongly acid cation exchange resin.

15. A method according to any one of the preceding claims, characterized in that the number of columns is from 1 to 28, preferably from 2 to 12, most preferably from 2 to 6.

16. A method according to any one of the preceding claims, characterized in that the number of steps is 1 to 50 during one cycle.

17. A method according to any one of the preceding claims, characterized in that the eluant is water.

18. A method according to any one of the preceding claims, characterized in that the linear flow rate is from 0.4 to 20 m/h, preferably from 1 to 12 m/h.

19. A method according to any one of the preceding claims, characterized in that the solution to be fractionated is selected from the group consisting of molasses, especially B-molasses and C-molasses, vi- nasse, fructose/glucose syrups, beet-derived juices, invert sugar mixtures, starch hydrolysates, wood hydrolysates, milk whey solutions and other lactose- containing solutions, lactulose-containing solutions, maltose-containing solu- tions, maltitol-containing solutions, solutions containing amino acids, fermentation broths containing various organic acids, such as citric acid, bagasse hy- drolysates, and solutions containing rhamnose, arabinose, mannose, raffinose, inositol, mannitol, sorbitol, xylitol, erythhtol, glutamic acid, glycerol, and/or tagatose, or isomaltulose and trehalulose solutions.

20. A method according to any one of the preceding claims, characterized in that the solution to be fractionated is a sulphite cooking spent liquor.

21. A method according to any one of the preceding claims, characterized in that the solution to be fractionated is beet molasses.

22. A method according to any one of the preceding claims, characterized in that the product(s) is/are selected from a group consisting of glucose, fructose, sucrose, betaine, rhamnose, lactose, lactulose, maltose, maltitol, arabinose, mannose, raffinose, inositol, mannitol, glycerol, xylitol, xylose, sorbitol, erythritol, organic acids, especially amino acids, such as glutamic acid.

23. A method according to any one of the preceding claims, characterized in that the cycle in the separation system comprises the following phases: a) a feeding phase wherein the feed solution is fed into one of the columns and optionally substantially simultaneously eluant is fed into the sub- sequent column, and the first product fraction and/or recycle fraction and the residue fraction are collected from the same or from the subsequent column, b) a circulating phase, wherein nothing is fed into or collected from the chromatographic separation loop, c) an eluting phase, wherein the eluant is fed into the first column and residue fraction and optionally a second product fraction are collected from the same or from the subsequent column, phases a) and c) are repeated as many times as necessary until the separation profile has circulated through the chromatographic separation loop more than once or less than once during one cycle.

24. A method according to any one of the preceding claims, characterized in that when the separation profile in the chromatographic separation loop in the separation system is narrow the separation profile is circulated through the chromatographic separation loop more than once.

25. A method according to any one of the preceding claims, characterized in that when the separation profile in the chromatographic separation loop in the separation system is broad the separation profile is circulated through the chromatographic separation loop less than once.