CA1119102A - Process and equipment for chromatographic separation of fructose/dextrose solutions - Google Patents

Abstract

ABSTRACT
An improved process for separating a fluid feed stream containing a mixture of substances (fructose and dextrose solutions) into a plurality of streams richer in one or more of the substances by alternately passing the mixed fluid feed stream and an elution fluid stream through a chromatographic separation column to obtain an effluent stream. She column has a chamber containing an adsorbent which has a selective affinity for one of the substances in the fluid feed stream so that portions of the effluent stream have higher concentrations of one of the substances.
Thereafter, separate successive portions are collected of the effluent stream having higher concentrations of at least one of the substances. The process involves first densely packing the adsorbent in the chamber of the separ-ation column, and the chamber is devoid of any internal flow distributing structure. The adsorbent is such that it contracts to a reduced volume in the presence of a selected reagent, and swells when the excess of concen-trated reagent is removed. The adsorbent is disposed in the separation column chamber in its reduced volume condition and is effectively confined in the chamber of the separation column. She excess of the concentrated reagent is removed from the adsorbent so that the adsor-bent swells to completely and uniformly pack the separa-tion column chamber and thus eliminates channeling and turbulent flow, and improves the uniformity of the cross-sectional flow rate across the column chamber. The pro-cess provides one output stream rich in fructose and another output stream rich in dextrose.

Description

9~L02 BACKGROUMD OF THE INVENIION

The use of strong cationic exchange resins has been disclosed for the separation of fructose and dextrose sugars. In the past, such mixtures were characteristic by-products in the preparation of sucrose from sugar beets or sugar cane. Invert sugar, containing about 50% fructose and 50%
dextrose, has been separated by means of liquid chromatography into a fructose-rich portion and a dextrose-rich portion. mis process is sometimes called molecular exclusion. Recently, isomerization processes have made possible the commercialization of high fructose corn syrup sweeteners which contain 40-45% fructose, 40-50% dextrose and about 3-8%
higher polysaccharides, but such products are not quite as sweet as sucrose.
Froducts containing 55-65% fructose have about the same level of sweetness as sucrose, and can be directly substituted for sucrose in food recipes.
me cost of increasing the fructose level higher than about 45% by enzyme treatment accelerates drastically using present commercial processes, so efforts have been made to further increase the fructose content of such sugar mixtures by liquid chromatography.

Chromatographic separation of sugar solutions containing fructose and dextrose has been proposed and used as a means of further increasing the fructose content of fructose/dextrose containing syrups by passing the mlxture through an adsorbent resin bed ao~taining a cationic salt of a nuclearly sulfonated, crosslinked polystyrene resin or other adsorbent.
When the above named resin is used, fructose has greater affinity than dextrose has for the resin, and the fructose is "held back" in the resin bed, while dextrose passes on through as an effluent stream. me sugar solution and an elution water stream are alternately fed into the resin bed, and the effluent stream contains a dextrose-rich portion followed by a fructose-rich portion which are collected separately. Much effort has been dlrected towards improving the efficiency of the separation so that it can 3 be scaled up to large volume commercial systems. Flow dynamics through ,,' ,

- 2 -, c ~ 1~19~0~ , through large separaticn colu~ns m~st be carefully controlled in order to obtain an optimum separation.

DES~RIPTION OF THE PRIOR ART

- Various processes and systems haYe been proposed ~ most efficient~y separating fructose from dextrose by means of molecular exclusion.
United States Patent 2,911,362 which issued November 3, 1959 broadly discloses the concept ol utilizing a strong cationic exchange resin ~or the separation of two or more water-soluble organic substances,.includir4s glucose, acetone, sucrose, glycerin, and trlethyleneglycol. This reference generally discloses that aldehydes and ketones can be separated. Among ~ e resins disclosed in this patent is included the granular cationic exchan~e resins of the general type used here, but in hydrogen form~ The resin 1~ a sulfonated copolymer of styrene, ethylvinylbenzene and divinylbenzene.

Chromatographic absorption on aluminum to produce h~ghl~ ~ctive streptomycin was described by Williams et al., "Chromatography", Chemica~
Engineering, November, 1948, Vol. 55:133-8. In addition to aluminum, oth~r absorbents are disclosed, including activated carbon, silica geI, ~loridin and Zeolites. Absorption columns up to 3 feet in diameter and 12 feet in height are described in this reference.

lhe separation of D-glucose and D-fructose ~rom~invert sugar or sucrose is disclosed in United States Patent 2,813,810 issued November 19, 1957. DLglucose is separated from invert sugar or mixtures of equal parts o~ D-glucose or DLsucrose by shaking the mixture with a ketone containing a small amount of water in the presence of a cationic exchange resin. The ~ eferred cationic exchange resins are the sulfonated type such as sulfonated phenalformaldehyde exch~nge resins, nuclearly sulfonated polystyrene ion exchange resins (hydrogen ion form), sulfonated coal and the like.

United States Patents 3,044,904, '905 and 1906 disclose chromatographic separation of dextrose and levulose using various resin sa~ts * Trade Mark - ~19~02 of a nuclearly sulfonated styrene cationic exchange resin. The levulose (fructose) in a mixed fructose/dextrose feed stream is preferentially adsorbed by the resin, leaving a ma~or portion of the dextrose dissolved in s- the liquid surrounding the cationic exchange resin. Iihe dextrose is then forced out of the column by elution water which washes out the fructose separately from the dextrose. me typical separation column disclosed in '904 is approximately 3.75 inches in internal diameter and was filled to a depth of 38 inches. me calcium salt form of the resin was employed in this patent. Flow rates of .1 to .5 gallons per minute per square foot of -~
cross sectional area were found satisfactory, and a temperature range of 50-70C. was preferred.

A recycle system for chromatographic separation processes such as described in Patent '904 is disclosed in U. S. Patent 3,416,961 issued December 17, 1968. u. S. Patent 3,817,787 issued June 18, 1974 utilizes the same cationic exchange resins and describes a preferred column length for more efficient separation.

A dynamic packing method for packing ion exchange resins in ~-chromatographic columns is described in Journal of Chromatography, Vol. 42, ~ (1969) pp. 263-65. However, it shiould be noted that the resin particles i 20 being packed range in size from 5-1o microns, and that the column diamieters ,~ were only 0.62 centimieters. The packing methods disclosed involved first packlng the resin in a cartridge or chamber, and then displacing the resin in the cartridge or chamber forcing it into the column. No mention of swelling ;~ the resin i8 made here.

It has been observed that the calcium salt form of the nuclearly sulfonated polystyrene cationic exchange resin occupies less volume in the ' presence of a strong salt solution, but no useful application of this phenomenon has been found in the prlor art- See, for example~ United States Patent 3,928,193, issued December 23, 1975.

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~L~19~02 e swelling and shrinking of the resin bed ls described as a "nuisance" in Patent '193. This patent describes the problems created by non-uniform flow of feed stream and elution water, and proposes an open top resin bed over which the feed stream and the elution streams are alternately sprayed to insure uniform flow of liquid through the column.

me above U. S. Patent '193 refers to two other U. S. Patents, Nos. 3,250,058 issued May 10, 1966 and 3,539,505 issued November 10, 1970.
In addition, U. S. Patent 3,374,606 issued on the same parent application on which U. S. Patent 3,250,058 was based. All three of these patents are directed to distribution structures for improving the separation ability of the resin bed columns. Mechanical flow distributor devices are inserted in the columns at intervals to improve the resolving power of the large diameter columns by redistributing the flow patterns to cancel the effects of channeling and turbulence in the resin beds.

Patent '058 includes disk-shaped and doughnut-shaped baffles alternately dlsposed at intervals in the length of the bed no greater than ~; the diameter of the column. me relatively "large diameter" glass tube ~ columns described in this patent had an internal diameter of about 49 ;~ millimeters (about .2 inch). The columns were about four feet in length.
(See sentence bridging Columns 4 and 5 of Patent '058.) ; Related Patent 3,374,606 discloses the use of s~ieve plates disposed at regular intervals in a chromatographic column. The "large diameter" column disclosed here was a 4 inch diameter column (6.16 centimeters).
Ihe detailed description appears to be directed to gas chromatography columns employing carrier liquids such as helium, nitrogen, argon, hydrogen methane, steam or the like. See Column 3, lines 61-63 of Patent '606.

U. S. Patent 3,539,505 is specifically directed to "large scale"
columns for chromatographic separation of liquid streams. Fluid mixing means ; are disposed at intervals throughout the column to prevent "distorted .: , ~ .- .
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running" of the fronts of liquids of different concentrations developing in the column length as the feed stream a~d elution stream are alternately fed through the column. This reference points out that "distorted running"
cannot be avoided even when proceeding very carefully. The largest of-the so called "large diameter" columns disclosed in Patent '505 is 1.2 meters in diameter (about 3.96 feet) and 15 meters (48.2 feet) long. See Example 5, of Patent '505.

Timmins et al., "Large-Scale Chromatography: -New Separation rrool", Chemical Engineering, Vol. 76, pp. 170-178, May 1969 discloses a fourteen foot diameter gas chromatographic column (p. 177), but this column included "radial mixing means to control nonuniformities" (p. 178), probably of the type described in United States Patent 3,250,058. The sub~ect reference also describes liquid chromatography columns which also include radial mixing means, but the largest diameter liquid separation columns described is only about four foot in diameter, which indicates that channeling and ; turbulent flow were considered more difficult to control in liquid systems even with radial mixing means such as described in United States Patent

3,250,058.

There are a number of more recent patents directed to modifications of the process described in United States Patent 3,044,904. For example, United States Patent 3,483,031 issued December 9, 1969 claims a process for inverting sucrose, and then recovering fructose and glucose by contacting the aqueous ~olution of sucrose or sucrose containing invert sugar with an lon exchanger charged with calcium ions containing 1 to 30% f~ee acid groups. United States Patent 3,416,961 describes the type of process disclosed in U. S. 1904 in which the effluent stream is divided into at least six fractions, and at least two of the six fractions are recycled through the separation column.

The columns employed by the '031 patentees had diameters of 15 centimeters (@5.9 inches). It should be noted that the shrinking and ( c`
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and swelling phenom~non of the resin is described at column 5, lines 11-14 as a disadvantage which might cause bursting of the glass columns. T~
avoid this undesirable effect caused by this resin property, these patentees employ six glass tubes, each 2 meters in length and they maintain a resin bed depth of only 1.5 meters in each glass tube for a total resin bed depth of about 9 meters (about 32.7 feet),and a diameter of only 15 centimeters (@ 5.9 inches). The '961 patentees describe a resin bed with a space above it, also. See '961, column 7, lines 48-50.

SUMMARY OF THE INVENIION

The method and apparatus of the'sub~ect invention provides means for substanti~lly improving the efficiency of chromatographic separation o~
~ixed sugar solutions by means of large diameter separation columns contai~L~ng a densely and unifornly packed particulate adsorbent. The method for packing adsorbent in the separation columns utili~es'-to advantage the fact certain adsorbents shrink in volume when exposed to concentrated salt solutions and subsequently expand in volume when the adsorbent is washed 11 to remove excess unbound salt. A separation column is filled to capacity ;l with contracted adsorbent, the column is then closed aPd the adsorbent washed, causing it to swell and become densely packed in the column chamber.

The packing system described is particularly applicable to calcium-salts of crosslinked, nuclearly sulfonated polystyrene resins. Ihese resI~s are particularly suited for the separation of mixed fructose and dextrose sugar solution, and are sold under various trade~ames, including Amberlite ;

XE-200 (Rohm & Haas, Inc.), Dowex 50WX4 (Dow Chemical~ Inc.) and ZeoKarb 225 (Permutit, Inc.).

Such resins are usually sold in the hydrogen or sodium ion form, and have a normal void volume of about 30%. When treated with a strong calcium chloride solution, the resin shrinks''in total volume to less than * Trade Mark 7 ,~, , ... .
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90% of the original volume. A separation column is then filled with the contracted resin, and the resin is confined therein.

The confined resin is then washed with water to remove unbound salt. The resin expands, creating a positive expansion pressure within the separation column. miS expansion pressure uniformly and densely packs the resin in the column, and when liquid is passed through the column, channeling effects and turbulence are prevented by the densely packed resin bed. me resin packing method of the invention makes poss~ble the utilization of large diameter adsorbent beds wlthout a requirement for internal baffl;ng or flow distributing structures. Separation column resin beds up to 14 feet in diameter and 7 feét in height are described herein, and it is contemplated that substantially larger diameter resin beds may be utilized without the need for internal flow distributing structures, thereby , substantially increasing the total output volume from the system.

; 15 In the system described~, a plurality of 14 feet diameter, 7 feet tall cyclindrical columns are disposed in series. Each column contains the densely and uniformly packed particulate adsorbent~ and each . column is provided with flow means communicating through the successive columns for conveying therethrough a feed stream, an elution stream and a possible recycle stream in a predetermined sequence. me volume and total time of flow of a particular feed stream into the column can be controlled by the desired output and the input streams. me output streams can be controlled by refractive index sensing means or optical rotation sensing means and timing devices, or combinations of these.

The volume of the input feed stream may vary from 0.3 to 1.0 of the bed volume per cycle of feed stream. For the system described, the elution water volume required is about 0.6 of the bed volume when the input feed stream is about 0.5 of the bed volume.

Using an input feed stream containing 42% fructose, 50% dextrose 3 and 8% higher saccharides at about 50% dry solids, it is possible to control ~ ~g aoz the effluent streams to obtain a ~ructose concentration ~rQm 30-2~%. The flow rate presently contemplated through the system i6 about Q,4-0,7 gallons per minute/ft.2, and the system is operated at a te~lperature in the range of 120-160F. to obtain the best results~

The large diameter separa~ion columns of the sub~ect invention provide an economical system for the chromatographic separation of mixed su OE solutions containing fructose and dextrose and other higher sugars.
Such higher fructose su OE s are derived from corn starch which is in plentiful supply. These higher fructose corn sweeteners provide equivalent sweetening to sucrose at less cost and with less calories.

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BRIEF DESCRIPIION OF THE DRAWINGS

Figure 1 is a plan view of a large volume commercial fructose/
dextrose separation system;

Figure 2 is a dia~rammatic side view partially in section showing details of the construction of a separation column employed in the system of Figure l;

Figure 3 is a diagrammatic view with parts omitted, taken generally on line 3-3 of Figure 2 showi~g the annular configuration of the top and bottom reinforcements ror the separation column; .

Figure 4 is an enlarged detailed sectional view taken generally at area A Or Figure 2 showing the resin retaining means and a detail of the ~low distribution system; and Fig~re 5 is a typical concentration profile for the output stre of a three column series.

DETAILED DESCRIFTlON OF IHE INVENTION

In the present embodiment of the separation system shown in Figure 1, the separa~ion column 1-1 to 1-9 are initially loaded with Amberlite 1.
~. XE~200 resin from a resin loading tank 2. The resin is first slurried in a 20-25% by weight calcium chiloride solution, so that it èhrlnks to a desired I .
vo~d.volume. The calcium chloride solution is supplied to the resin ~ loading tank from elution water tank 3 through wa~h water line 4a, E~ch i separation column 1-1 to 1-9 is completely filled with the shrunken resin, : and the column is sealed, except for the wash water llne 4a~ Deionized ..
water is then fed into each column containing shrunken resin to wash away .
2~ excess calcium ion, thereby causing the resin to swell. Since the columns .
are sealed the resin can only expand against itselr, thereby decreasing the : void volume of the resin, and packing the resin particles densely together.

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The swelling of the res~n also causes a positive pressure against the separation column which ranges from 3-17 psig, depending on the degree of contraction and subsequent expansion which are directly proportional to the concentration of calcium chloride solution employed. The resin expansion pressure is independent of the column height, although measurements taken near the base of the column must be corrected for the added pressure of the column. Typical expansion pressure exerted on the column walls when a 20%
calcium chloride solution is used is about 3~10 ps~g.~

Each separation column 1-1 to 1-9 is generally constructed as shown in Figure 2-4 of the drawings. The present columns are cylindrical, having a cylindrical side wall 5, a top wall 6 and a bottom wall 7. Top wall 6 is reinforced by a hemispherical header 8, and bottom wall 7 is reinforced ; by a similar hemispherical header 9. The present columns 1-1 through 1-9 are all about seven feet in resin bed height, and about fourteen feet in diameter. Because of the resin packing method employed, there is no requirement for internal baffles in the columns.

Headers 8 and 9 include flow distribution conduits 10 which communicate with inlet lines 11 and outlet lines 12 shown in Figure 1~ The ; headers 8 and 9 are also provided with a plurality of annular supporting rings 13 which maintain the top wall 6 and the bottom wall 7 in substantially rigid,horizontal parallel planes. It is important for proper separation ; efficiency that the liquid flow through the separation columns be as uniform as possible throughout the width of the bed. Concentration of effluent across the lowermost horizontal plane in the resin bed of the third separation column should be as uniform as possible to obtain the most efficient fructose/dextrose separation.

Normally sealed access opening 14 can be used as a means for loading resin into the column. A similar, normally sealed access opening 15 is dlsposed near the base of the side wall 5, and can be used as a means 3 for unloading resin frcm the column, and as an access for making repairs inside the column.

s Top wall 6 2nd bottom wall 7 each comprise an inner stalnless steel retaining screen 16 which confines the resin in the column. At present, NEVA-CLOG Screen, available fron Multi-Metal Wire Cloth, Inc., Tappan, New York, is used as the resin retaining screen. It is described in United States Patent 3,052,360. A stainless steel spacer means 17 is disposed ~ust outwardly from the ret~ining screen 16 to space the retaining screen 16 and resin 18 from the respective end walls 6 and 7 of the column. The spacer means 17 provides a distribution flow means for the liquid feed stream and elution water entering and leaving the column through the conduits 10 which communicate through a plurality of openings 19 in the respecti~e end walls 6 and 7 of the column. At present, the spacer means 17 comprises #16 gall~e expanded stainless steel having .095~ openings~ T~e part~cul~r space~
means 17 presently employed is sold under the trademark POR-O-SEPTA, and is also available from Mhlti-Metal Wire Cloth, Inc., Tappan, New York.

Figure 4 shcws a detail illustrating the connection of conduit 10 thrcugh the end wall 7. Conduits 10 are disposed at regular spaced inter~als across the end walls 6 and 7 to provide uni~orm liquid flow distribution through the end walls 6 and 7 to and fron the spacer means 17 which ls contiguous to the resin retaining screen 16. The direction o~ liquid fl can be reversed for purposes of backwashing the system, if this is found ' to be necessary.

The resin 18 presently employed in the columns ~s Amberlite XE-200 obtained fron Rohm & Haas Corporation, Philadelphia, Pennsylvania. The resin ,, i8 recelved in the sodium salt form, an~ is converted to the calcium salt 2~ forn by the column loading procedure described above. The XE-200 resin is described as a strongly cationic, crosslinked nuclearly sulfonated polystryene resin. The resin is crosslinked with about 4-6% by weight divinylbenzene to make it more stable. The resin particle size is in the range of 200-50a ~crons ~Q 50 mesh~

* Trade Mark - 12 -:

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The resin is capable of separating fructose frcm a feed streamcontaining fructose and dextrose, and higher sugars when the feed stream is forced through the column at a controlled flow rate in successive pulses of a predetermined volume each pulse followed by a pulse of elution water.
Due to the difference in affinity between the resin and the respective sugars, the sugars leave the column in sequence. Higher sugars come out first, followed by dextrose and then fructose. The successive pulses of elution water release the fructose into the elution water to give a fructose-rich pulse of elution water following the preceding dextrose and higher sugars-rich pulse of the treated feed stream. The separation becomes more pronouncedin direct relationship to the length of the resin bed and the amount of elution water used to remove the fructose from the bed. me fructose-rich elution water is collected by cyclic diversion of the output (effluent) stream from the last separation column in the series to the product tank when the fructose content is above 27-32%.

e various streams are pumped through the system in time controlled sequence by means of pumps 20. Flow of feed stream and elution water through each column is controlled by valves 21 and 22 which are operated by dual control means 23 to close valve 21 when 22 is open, and vice versaj thereby alternating the feed stream and elution water stream according to signals received fron control means 23. In the present systen~separation columns 1-1 to 1-3 are operated in series. Separation columns 1-4 to 1-6 are operated in a second series, and separation columns 1~7 and 1~ are operated as a third series of colum~s, The three adjacent series of columns are typically operated together in parallel, and operated as a unit. Additional series of columns may be added to increase the total output of the system in direct proportion to the number of columns added. me columns may be operated on identical time cycles, or staggered so that one series of colu~ns is receiving feed stream while another is receiving elution water.

The last separation column in the series includes an outlet line 24 which has two outlets 25 and 26. Direction of flow to outlets 25 and 26 is controlled by valves 27 and 28, respectively, which are controlled z by a dual control means 29 which is similar to control means 23, so that as valve 27 closes, valve 28 opens. The output line 25 is controlled to be open when fructose~rich elution water is leaving column 1~3 through line 24.

The fructose content of the output stream is monitored by a refraction index meter 30 and an optical rotation meter 31 to further insure accurate control o~ the valves 27 and 28 and to insure that the desired product is directed through line 25 to product tank 32. When product is not being conducted into outlet 25, valve 28 is open, and the output from -line 24 of the colum~s is directed to return stream tank 33. The material in return stream tank 33 can be recycled through the system to remove any remaining fructose, or it can be directed to other processing, such as isomerization process or an enzymatic conversion system employing gluco-amylase to further convert its higher sugar content to dextrose. The return stream can also be sold as a lower grade product depending upon the economic returns possible. Product in product tank 32 is usually at a lower concentration than commercially desired, and requires evaporation to reduce its water content. A typical high fructose product after evaporation has ;
about 74-78% dry solids and comprises about 55% by weight fructose, 42% by weight dextrose and 3% by weight higher saccharides.

Heaters 34 and 35 are provided on elution water tank 3 and the syrup feed tank 37, respectively, to maintain the elution water and the feed stream at a temperature in the range of 140-160F. Gperation at a lower temperature may allow microbial contamination of the resin beds, whereas temperatures higher than 160F. creates a risk of product discoloration. The desired product at present is colorless.

When the system is in operation, the fluid pressure rises and falls in a cyclic fashion as the fluid flows through the packed bed of the separation column 1-1 to 1-9. In the normal separation operation, the degree of compaction of the resin bed, the column height, and the flow rate are substantially constant. The main variable is the cyclic fluid .

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pressure change caused by the viscosity change as the concentration of the feed syrup varies from minimum water to the hig~est syrup concentration.

The XE-200 resin is capable of separating dextrose from fructose by m~lecular exclusion. The fructose is loosely retained by the resin bed in what is believed to be a calcium-fructose complex. The fructose remains intimately associated with the resin until the elution water stream apparently weakens the attraction of the fructose for the resin, and elutes the fructose from the resin in a cyclic manner as indicated by Figure 5.

It is possible to increase the concentration of fructose in the elution stream by increasing the amount of elution water, or recycling the enriched fructose streams to further separate dextrose and higher sugars from the fructose. ~y employing various recycle systems and by using additional elution water, it is possible to obtain substantially pure fructose, but economic factors must be taken into account. The time and energy involved with recycling streams,and energy costs to evaporate more dilute product~ and commercial demand all are factors which must be-considered in determining the concentration level of fructose to be manufactured by the system.

At the present time, all of the above factors dictate product having a fructose concentration in the range of 55-65% by weight fructose.
The dextrose content of such a product is in the range of about 40-50% by weight. Higher sugar content can be kept below about 8% by weight.

Figure 5 shows the concentration profile for the above system when the input feed stream is deionized 42% fructose, 50% dextrose, 8% higher saccharide corn syrup at about 50% dry solids. The feed syrup is obtained from enzymatic isomerization. Deionized elution water is sent through the separation column system through the line 4, alternating with feed syrup fed through the line 38.

Employing the above 42% fructose feed stream in the separation system described, the completed cycle through columns 1-1 to 1-3 takes about 3 330 minutes at a flow rate of .5 gal/min/sq. ft. During the typical 330 l~g~OZ

minute cycle, the concentration of the effluent lncreases from 1-48% by weight dry solids in about 150 minutes, and then decreases to 1% dry solids in 180 minutes.

During the same period of time, the fructose content of the effluent stream increases from 0-90% fructose in about 250 minutes and then rapidly decreases to about 0% concentratlon in the next 80 minutes.
: When a 55% fructose product is desired, the e~fluent is d~rected to the product tank 32 when the fructose content is in the range of 28-32~ and higher. The effluent is directed to the return stream tank 33 when the fructose content is lower than 28-32%.

~ The input feed and elution water should both be maintained within a ; rate of about .4-2.0 gpm/sq. ft. As flow rate is increased, a hi~her pressure drop across the column, and somewhat less efficient separation results, but the output volume increases. The optimum flow rate must be determined for a particular system based on the overall process economics.

~hen it is desired to make a 90% fructose product using the above separation system, the following steps may be employed. A feed stream, as described before, containing 42% fructose, 50% dextrose, 8% higher sugars at 50% dry solids is fed to the column for a period of time to feed a volume equal 0.2-0.3 of the resin volume per cycle. The flow rate is 0.4-0.7 gpm~ft2.

When the effluent stream from the system is at 60-75% fructose, and at 20-30% dry 801ids, or higher, the effluent stream is diverted back through ; the columns as a recycle stream. Immediately after the above recycle stream is fed to the columns, elution water is added at a pH of 4-5. The total volume of elution water should be in the range of 0.2-0.7 of the resin volume per cycle at a flow rate of 0.4-0.7 gpm/ft2. When the recycle stream effluent from the system reaches 80-87% fructose, and over 5% dry solids, the effluent is directed to a product tank and collected as product.

The overall fructose concentration of this fraction is about ~ 90% fructose, or higher. me average dry solids of the products stream is .
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about 16%, and the product may be further refined such as by filtering~
evaporatin and deionizing to produce a product having a dry solids of 79.5-80.5% and 90-92.5% fructose, about 5-7% dextrose and about 1-3% higher sugars.

The above detailed description illustrates the system and method of the invention has considerable flexibility. ~ructose containing syrups ranging from a minimum of fructose to substantially pure fructose can be economically separated from mixed sugars containing fructose, dextrose and other polysaccarides. The same mixtures of sugars can produce product ;
streams containing a minor amount of dextrose to substantially pure dextrose.
Although the separation cost increases substan~ially as the concentration of fructose increases from 55-95%, it is estimated that a 95% fructose syrup can be produced at a cost of only about three times more than the cost of a 55% fructose syrup using the above system, and such intensely sweet products are in special demand in pharmaceuticals and as special dietary ingredients.
Recycling of the elution water and other effluent fractions can further reduce the costs.

m e resin packing system of the invention is a substantial advantage because it enables use of large capacity columns in excess of 12-14 feet in diameter without the added cost of an internal baffling systems. The liquid distribution system prcvided between the columns further insures uniform flow through the total column system, and more effective product separation.

m e input to each column section of the total system may be varied in almost l~mitless combinations, depending on the desired product output.

m e flow pattern can be modified to efficiently accommodate any recycle stream to obtain a particular desired product. Portions of the effluent stream may be diverted at different times to different alternative process systems.

Effluent streams high in dextrose are typically used to obtain additional fructose by lsomerization. At the present time, the portion of the effluent stream containing about 12% fructose, 72% dextrose, or higher, and 6% high sugars at 18-19% dry solids is returned to the isomerization plant. Portions of the effluent stream rich in higher saccarides can be directed to a gluco amylase enzyme conversion system. me effluent streams can also be further divided, and part can be sent to either the isomerization plant or the gluco amylase enzyme conversion. It is also possible to further refine and sell the effluent by-products as low level sweeteners and for other uses.

The process and equipment of the sub~ect invention for separation of mixed sugar solutions provides an improved, commercially feasible system to produce high fructose sweeteners from corn starch. For typical applications, a product containing 55-65% fructose is believed to be fully equivilent -~
to sucrose sweeteners, and competitive in cost. Corn is grown over much wider areas and in substantially larger volume than sugar cane so that ~table supplies at stable prices of raw material can be contemplated. In contrast, sugar cane and sugar beets are sub~ect to the vagaries of weather ~-and political conditions, so supplies of sucrose can fluctuate widely.

The above described process and system optimizes the chromatographic column separation of mixed sugars containing both fructose and dextrose to make possible a series of sweetener products derived fr~m corn starch which are competitive with sucrose sweeteners, and in many cases, such products are more economical. The large diameter~ densely packed series of separatlon columns are capable of continuous operation at large production rates, which can be adjusted as necessary, to produce 55-99% fructose from a ~eed stream containing 40-45% fructose and dextrose. me densely packed separation columns require no internal baffles or flow redistribution structures to produce good sugar separation because the tightly packed adgorbent bed ls not sub~ect to ch~nneling, "front ruNning", or other irregularltles in llquid flow through the successive separation columns.

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Claims (28)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-

1. In an improved process for separating a fluid feed stream containing a mixture of substances into a plurality of streams richer in one or more of said substances by alternately passing said fluid feed stream and an elution fluid stream through a chromatographic separation column to obtain an effluent stream, said column having a chamber containing an adsorbent which has a selective affinity for one of said substances in said fluid feed stream so that portions of said effluent stream have higher concentrations of one of the sub-stances, and thereafter separately collecting successive portions of the effluent stream having higher concentrations of at least one of the substances, the process including first densely packing the ad-sorbent in the chamber of said separation column, the steps compris-ing:
a) disposing an adsorbent, said adsorbent being one which contracts to a reduced volume condition in the presence of a reagent in concentrated form and swells when the excess of concentrated re-agent is removed, in said separation column chamber;
b) treating said adsorbent with said concentrated reagent either before or after said disposition of said adsorbent in said chamber to provide said adsorbent in its reduced volume condition;
c) confining said adsorbent in its reduced volume condition within said separation column chamber having a total fixed volume of less than the total volume occupied by the adsorbent upon removal of excess concentrated reagent from the adsorbent;
d) removing the excess of said concentrated reagent from said confined adsorbent, whereby said adsorbent is caused to swell to completely and uniformly pack the adsor-bent throughout the separation column chamber to eliminate channelling and turbulent flow and to improve the uniform-ity of the cross-sectional flow rate across the column cham-ber when a fluid stream is passed therethrough; and e) thereafter separating a fluid feed stream contain-ing a mixture of substances into a plurality of streams richer in one or more of said substances by alternately passing said fluid feed stream and an elution fluid stream through said chromatographic separation column to obtain an effluent stream.

2. A process for separating a mixed fluid feed stream comprising a plurality of substances into a plura-lity of fluids, each containing a higher concentration of one of said substances than the mixed feed stream, which comprises alternately passing the mixed feed stream and an elution feed stream through a separation column having a chamber containing an adsorbent which has a selective affinity for one of said substances to obtain an effluent stream, portions of which have higher concentrations of one of the substances, and thereafter separately collecting successive portions of the effluent stream having a higher concentration of at least one of the substances, the adsor-bent having been densely packed in the separation column by a process which comprises treating the adsorbent with an excess of concentrated reagent which causes the adsorbent to contract in its presence, the adsorbent being capable of swelling when the excess concentrated reagent is removed, and removing the excess of the concentrated reagent from the adsorbent in its reduced volume condition confined in the chamber of the separation column whereby the adsorbent is caused to swell to completely and uniformly pack the ad-sorbent throughout the separation column chamber to eli-minate channeling and turbulent flow, and to improve the uniformity of the cross-sectional flow rate across the column chamber when the fluid stream is passed therethrough.

3. The process of claim 2 in which the chamber is at least 6 feet wide.

4. In an improved process for separating a mixed fluid feed stream into a plurality of fluids, each contain-ing a higher concentration of one of said substances, by alternately passing said mixed fluid feed stream and an elution fluid stream through a separation column having a chamber containing an adsorbent which has a selective af-finity for one of said substances to obtain an effluent stream, portions of which have higher concentrations of one of the substances, and thereafter separately collecting successive portions of the effluent stream having higher concentrations of at least one of the substances, the pro-cess comprising:
a) treating an adsorbent with a reagent in concen-trated form which causes the adsorbent to contract in its presence, said adsorbent being capable of swelling when the excess concentrated reagent is removed therefrom;
b) confining said adsorbent in its reduced volume condition in the separation column;
c) removing the excess of said concentrated reagent from said confined adsorbent whereby said adsorbent is caused to swell to completely and uniformly pack the ad-sorbent throughout the separation column chamber to eli-minate channeling and turbulent flow and to improve the uniformity of the cross-sectional flow rate across the column chamber when a fluid stream is passed therethrough;
and d) thereafter separating a mixed fluid feed stream into a plurality of fluids, each containing a higher concentration of one of said substances, by alternately passing said mixed fluid feed stream and an elution fluid stream through said separation column to obtain an effluent stream.

5. The process of claim 4 in which the chamber is at least 6 feet wide.

6. In an improved process for separating a mixed fluid feed stream into a plurality of fluids, each containing a higher concentra-tion of one of said substances, by alternately passing said mixed fluid feed stream and an elution fluid stream through a separation column having a chamber containing an adsorbent which has a selective affinity for one of said substances to obtain an effluent stream, por-tions of which have higher concentrations of one of the substances, and thereafter separately collecting successive portions of the effluent stream having higher concentrations of at least one of the substances, the process comprising:
a) treating an adsorbent with a reagent in concentrated form which causes the adsorbent to contract in its presence, said adsor-bent being capable of swelling when the excess concentrated reagent is removed;
b) disposing said adsorbent in its reduced volume condition in the separation column;
c) confining said adsorbent in its reduced volume condition within said separation column chamber having a total fixed volume of less than the total volume occupied by the adsorbent upon removal of excess concentrated reagent from the adsorbent;
d) removing the excess of said concentrated reagent from said confined adsorbent whereby said adsorbent is caused to swell to com-pletely and uniformly pack the adsorbent throughout the separation column chamber to eliminate channeling and turbulent flow and to improve the uniformity of the cross-sectional flow rate across the co-lumn chamber when a fluid stream is passed therethrough;
and e) thereafter separating a mixed fluid feed stream into a plurality of fluids, each containing a higher con-centration of one of said substances, by alternately passing said mixed fluid feed stream and an elution fluid stream through said separation column to obtain an efflu-ent stream.

7. The process of claim 6 in which the chamber is at least 6 feet wide.

8. The process of claim 1, in which the chamber of the separation column is devoid of any internal flow re-distributing structure.

9. The process of claim 1 in which the column cham-ber is at least 6 feet in diameter.

10. The process of claim 1 in which the column cham-ber is more than six feet in diameter and at least seven feet in height.

11. The process of claim 1, in which the column cham-ber has a diameter within the range of from about 6 feet to about 30 feet.

12. The process of claim 1, in which the mixed sub-stances to be separated include monosaccharides, and at least one of the fluid streams is a liquid.

13. The process of claim 12, in which the substances to be separated include fructose and dextrose, and the mixed fluid feed stream is an aqueous solution.

14. The process of claim 13, in which the adsorbent is a crosslinked, nuclearly sulfonated polystyrene cationic resin.

15. The process of claim 14, in which the resin is crosslinked with 3-8% divinylbenzene.

16. The process of claim 15, in which the initial particle size of the resin is from 200-500 microns (30-50 mesh).

17. The process of claim 16, in which the cation bound to the resin is selected from the group consisting of alkali metals, alkaline earth metals, and silver.

18. The process of claim 17, in which the cation of the resin is selected from the group consisting of cal-cium, barium, strontium and silver.

19. The process of claim 17, in which the cation in concentrated salt solution employed to shrink the resin comprises the same cation as the cation bound to the resin.

20. The process of claim 19, in which the cation bound to the resin and the cation of the concentrated salt solution are calcium.

21. In an improved process for separating a plur-ality of saccharides from a solution by liquid chromato-graphy, the steps comprising:
a) alternately passing a feed stream and an elution water stream through a large capacity separation column having a chamber therein containing a densely packed bed of a cross-linked nuclearly sulfonated polystyrene resin in a cationic form and substantially devoid of internal flow redistribution means; and b) separately collecting portions of the effluent streams having higher concentrations of the respective saccharides; said resin having been packed in the chamber by c) disposing said resin, said resin being such that it contracts to a reduced volume condition in the presence of a reagent in concen-trated form and which swells when the excess of concentrated reagent is removed, in said chamber;
d) treating said resin with said concentrated reagent either be-fore or after said disposition of said resin in said chamber to provide said resin in its reduced volume condition;
e) confining said resin in its reduced volume condition within said separation column chamber having a total fixed volume of less than the total volume occupied by the resin upon removal of excess concen-trated reagent from the resin; and f) thereafter removing the excess of said concentrated reagent from said confined resin, whereby said resin is caused to swell to completely and uniformly pack the resin throughout said chamber to eliminate channeling and turbulent flow and to improve the uniformity of the cross-sectional flow rate across the chamber when said feed stream and said elution water stream are passed therethrough.

22. me process of claim 21, in which the cation of the resin is selected from the group consisting of alkali metals, alkaline earth metals, and silver.

23. The process of claim 22, in which the cation of the resin is selected from the group consisting of calcium, barium, strontium and silver.

24. The process of claim 21, in which the cation of the resin is calcium, and the concentrated selected reagent used to initially reduce the volume of said resin contains 10-35% by weight calcium chloride.

25. The process of claim 24, in which the initial particle size of the resin is from 200 to 500 microns and the final void volume of the densely packed resin is less than the initial void volume of the resin when in the sodium salt form prior to contacting the resin with con-centrated calcium chloride solution.

26. Apparatus for large-scale separation of a fluid mixture of substances passed therethrough into a plurality of streams richer in one or more of said substances by al-ternately passing said fluid mixture and an elution fluid stream through a chromatographic separation column to ob-tain a fluid effluent stream comprising in combination:
a) a separation column which includes a side wall and generally horizontal top and bottom walls defining a chamber, said chamber having a horizontal dimension of at least 6 feet and a vertical dimension of at least 4 feet, and said chamber being free of any internal flow distributing structures;
b) an adsorbent material which has a normal void volume, said adsorbent material being packed densely in said chamber and having a void volume substantially re-duced from its normal void volume so that it exerts a positive pressure on the walls of said chamber;
c) fluid flow distributing means including adsorbent confining means disposed in said top and bottom walls of said chamber to uniformly distribute a fluid stream across the cross-sectional, horizontal plane of said adsorbent and to uniformly collect a fluid effluent stream from across the cross-sectional, horizontal plane of said ad-sorbent; and d) fluid collecting means for separately collecting portions of said fluid effluent stream flowing from said fluid flow distributing means when a fluid mixture of sub-stance is passed through said apparatus.

27. The apparatus of claim 26 in which the chamber has a horizontal dimension within the range of from about 6 feet to about 30 feet.

28. The apparatus of claim 26 or 27 including a plurality of said separation columns connected in series to increase the degree of separation per given volume of input feed stream, in which the adsorbent is a cationic, nuclearly sulfonated polystyrene resin in which the cation of the cationic resin is selected from the group consist-ing of alkali metals, alkaline earth metals, and silver, and the resin is crosslinked with 3-8% divinylbenzene.