US2890972A - Purification of sugars - Google Patents

Description

United States Patent O PURIFICATION F SUGARS Robert M. Wheaton, Midland, Mich., assignor to The Dow Chemical Company, Midland, Mich., a corporation of Delaware Application June 2, 1955, Serial No. 512,651

14 Claims. (Cl. 127-46) This invention concerns a method for the treatment of aqueous solutions that contain at least one sugar and at least one highly ionized solute whereby there are obtained at least one fraction of aqueous sugarcon taining solution that is substantially free of ionized solutes and at least one fraction of aqueous solution of ionized solutes that is substantially free of sugars. The invention pertains more particularly to a method wherein an aqueous solution containing a sugar and a highly ionized solute is contacted with certain solid ion exchange resins under such conditions that the sugar is selectively absorbed into the aqueous medium within the solid resin, leaving the ionized solute in the surrounding aqueous liquid, and wherein the surrounding aqueous liquid solution of the ionized solute is removed from contact with the solid ion exchange resin, after which the absorbed sugar solution is washed out of the ion exchange material. The method is advantageously employed in the treatment of sugar solutions such as the crude sugar solutions that are obtained in the manufacture of cane sugar, beet sugar, corn sugar, invert sugar, sugar syrups, and the like, whereby such sugar solutions are demineralized and decolorized, and whereby valuable by-products such as potassium aconitate can be readily recovered.

ln the manufacture of sugar products from natural sources, there are frequently encountered aqueous solutions that contain one or more sugars such as D-glucose, D-xylose, or sucrose together with non-sugar ingredients such as potassium aconitate, other ionized solutes, and color bodies. From these sugary solutions it is often desired to obtain colorless sugar solutions that are substantially free of non-sugar solutes or to obtain pure crystalline sugars. Also, it is sometimes desired to obtain the valuable by-products from such solutions, such as potassium aconitate.

An object of this invention is to provide a method for the treatment of` aqueous sugar solutions whereby there can be obtained at least one fraction of aqueous sugar solution that is substantially free of color and of ionized solutes and/ or at least one fraction of aqueous solution of ionized solutesthat is substantially free of sugars.

A more particular object is to provide such a method wherein an aqueous solution containing a sugar and a highly ionized solute is contacted with a solid ion exchange resin that selectively absorbs the sugar, leaving the ionized solute in the surrounding aqueous liquid, and wherein the surrounding aqueous liquid solution of the ionized solute is separated from the ion exchange resin, after which the absorbed sugar solution is washed out of the ion exchange resin material.

A specific object is to provide such a method for the treatment of sugary solutions that are obtained from natural sources whereby an aqueous sugar solutionl that is substantially free of color and of ionized solutes is readily obtained.

Another object is to provide such a method for the treatment of sugary solutions that are obtained from rice natural sources and `which contain valuable ionic solutes `whereby such ionic solutes can be obtained in a form that is substantially free of sugars.

Another object is to provide such a method for the recovery of sugar-free potassium aconitate from sugary solutions that contain the same.

Other objects and advantages of the invention will be yapparent in the following description.

The objects of this invention have now been attained in a method that is based on the discovery that certain solid, insoluble, ion exchange materials are capable of readily, rapidly, effectively, and selectively absorbing sugars from aqueous solutions thereof. The method of the invention comprises contacting an aqueous solution containing a sugar and a highly ionized solute with a solid, insoluble, ion exchange resin lthat is capable of readily, rapidly, effectively Iand selectively absorbing the sugar into the aqueous medium Within the resin, leaving the ionized solute in the surrounding aqueous liquid, removing the surrounding liquid solution of the ionized solute from out of contact with the solid ion exchange resin, and Washing the absorbed sugar solution out of the ion exchange material, The sugar and the ionized solute are thereby separated from one another.

lon exchange resins that are suitable in the practice of this invention can be either cation exchange resins or anion exchange resins of kinds that are more particularly speciiied hereinafter. The ion exchange material preferably, but not necessarily, contains an associated ion of the same kind as one of the ions of the ionized solute. lt is not necessary that an ion exchange reaction occur during any step of the present process, and, where such ion exchange does occur, the ion exchange reaction is merely a concomitant reaction that is not an essential part of the mechanism of the present method.

The method of the invention should not be confused with usual ion exchange processes such as have hitherto been employed in the treatment of sugar solutions. In the usual ion exchange process, it is an ion, rather than a compound, that is removed by the ion exchange material. The removal involves a chemical reaction whereby an ion from the ion exchange starting material is released into the aqueous contacting solution in exchange for a different one of the ions from such solution that is then retained by the resin. Both the solution and the resin are thereby chemically converted into different materials, ie., having ionic compositions different from their respective starting compositions. An ion thus taken up by an ion exchange material 'in an ion exchange process can be displaced therefrom only by another chemical reaction, e.g. with a chemical regeneratnig agent. In contrast, in the present method, the sugar from an aque ous solution is removed into the ion `exchange resins by a process of physical `absorption that does not involve chemical reaction. Moreover, the absorbed sugar can be physically displaced from the resin merely by washing with a liquid, eg. water. Furthermore, the ionic solutes contained in the original solution are usually not changed save in regard to the removal of sugar.

The present method is based on a discovery of certain ion exchange materials, and conditions for their eiective employment, that are capable of absorbing sugars from aqueous solutions of sugars and highly ionized solutes.

The water-insoluble ion exchange materials that are suitable for use in the present method are organolites (preferably but not necessarily synthetic organolites) that contain ion-active groups (either cation-active groups, anion-active groups, or both groups) in a highly ionized form, that do not cause undesired chemical reactions of the sugar, and that have a relatively open gel struc Yture. -A- suitable measure of the nature of the gel structure of ion exchange resin materials is the gel water content, i.e., the proportion of water that is contained Withinthefgelfstructurewhen ythe resin is saturated with l"-water. I Onlythe amount of'waterthat is actually within the gel structure of the resin -is significant, and is the Iamount'lof'lwater that remains within the resin particles fwhenf the same= areiirst thoroughly soaked in water, then separated and superiicially dried without loss of water x fromtheinternal gel structure. Water that is contained in physical voidsy inthe resin body, such as in. pockets, F'crevassesyl pits, holes,` foramens and the like, is confsidered tol beHpart of the external Water system and is 1 notfapartofthe gel' water content, i.e., water within the 'i gelf-fstructure; `forthe purpose of .the present denition. A-rrnethodsuitable for determination of the gel water content ofrion,exchangematerials on a weight basis is described by'` Pepper, Paisley and Young in Journal of the-#ChemicalfSociety (1953), page 4097. From these @data andthe known values for the absolute density of the dryfionvexchange:materials, kthe gel water content of ion exchangematerials on a volume basis can readily be com- '.puted. Ion exchange resins that. are suitable for use in `thelfpresent methodare'those Vthat have a gel water con- 1 tent between about 50. and about 90, preferably between about 60 and about 80, volume percent, i.e., that have betweenabout 50 and about 90, preferably between about w60 and 'about 80, percent by volume of water within their gel structure when the same is saturated With absorbed yWVallel'.

AThe ion exchange materials that are particularly suitr able :forfpractice of the present method are the synthetic -xorganolites that contain a crosslinked polymer structure l.that is substituted with ion-active groups, the extent of *the cross-linking of the polymer structure being one that :provides a gel structure. that is capable 1 of absorbing -fwaterito'the. extentthat is indicated above. .Ion exchange `materials ofthis kind are already known, such as those Whose polymer structure contains crosslinked alkenylaromatic' compounds, e.g. the crosslinked polystyrene or 'vinyltoluene resins. .The polymer structure of such mayterials .is rendered insoluble by crosslinkages that are rproduced by small amounts of crosslinking agents such as' thek polyalkenylaromatic compounds, e.g. divinylben- .':zene. -Thel extent of crosslinking of the resin and hence the capacity of the resulting ion exchange material to ab- L*sorb'water can bey at least partially determined by the :proportionof such crosslinking agents that are chemically combined in the polymer structure. In general, the

:more extensively the ion exchange material'is crosslinked,

.thefless Water its gel structure is capable of holding.

-Theeationeactive groups* can be suIfOnate, phosphate "aortcarboxylategroups in highly ionized form. Preferably,. but not necessarily-,the cation exchange resins should-be onesi that areionizable to an extent such that f uponi adding a -gram portion ofthe acidic form of such resin gto 100'"mls.' of a 0.1 normal aqueous sodium chlo- W ride solution, a mixture having a pH value of less than 3 is-produced. :Examples of typical cation exchange resins `f'that'are preferred for use in the present method are the v-s'ulforiated copolymers of styrene and divinylbenzene, suchas are disclosed in U.S. Patent No. 2,366,007. The water contents of such cation exchange resins when saturated with water depends, at least in part, upon the pro- 1' portion-of 'divinylbenzene chemically combined therein approximately as follows:

Gel Water Content, Percent by Volume, Approximate Divinylbenzene, Percent by Weight In suitable anionexchange resins, the anion-active groups are usually amine or quaternary ammonium salt groups. Preferably, but not necessarily, the anion exchange resins should be ones that are ionizable to an extent such that upon adding a IO-gram portion of the basic form of such resin to mls. of a 0.1-normal aqueous sodium chloride solution, a mixture having a pH value of more than 1l is-produced. Examples of typical anion exchange resins that are preferred for-use in the present method are those that contain quaternary ammonium groups substituted on resinous polymers of styrene and divinylbenzene, such as those disclosed in U.S. Patents Nos. 2,591,573' and 2,614,099. The water contents of such aniony exchange resins when saturated with water depend in part on the mode of preparation and in part on the proportion of divinylbenzene chemically combined therein and are approximately as follows:

Gel Water Gontent, Percent by Volume, Approximate Weakly basic anion exchange resins, such as those disclosed in U.S. Patent No. 2,591,574, are also useful, particularly in the treatment of acidic sugar solutions, provided such resins have a sufficiently open gel structure as hereinbefore specified.

lon exchange materials that contain both cation-active groups and anion-active groups and mixtures of ion exchange materials can also be used provided that the ionactivegroups, are in a highly ionized form and provided that the resin is capable'of absorbing sugars without reacting chemically therewith.

The term sugar vis used hereinin'its generic sense as relating broadly to Ywater-soluble saccharoses,including the monosaccharoses,v disaccharoses and water-soluble polysaccharoses. A few specific examples of typical sugars are D-xylose, D-glucose, D-fructose, sucrose, maltose, andV lactose. Many other natural and synthetic sugars are'known.

The present method is advantageous for the treatment of aqueous solutions that containk at least one sugar and at leastl one highly ionized solute. YThe highly ionized solutes can be rinorganic orforganic compounds and can exist in the Iform of acids, bases,or salts in the sugar solution. The solutes thatcan readily be separated from sugars by the present method are those Whose ionization constants, K, arel atleast ashigh as 5x10-3 and preferably greater than 2 10-1. ASolutes whose ionization constants are below 5 X10-2; and whichrare not readily separated from sugars byl this method, can sometimes be separatedv by first converting the solute `to a more highly ionized state. For example, Valthough acetic acid in 'its free acid form is not separablefrom sugars by this method, a mixture of a sugar and acetic -acid'in aqueous solution can be separated by first makingthe solution neutral or slightly alkaline with a strongl base such as sodium hydroxide, thereby converting therweakly ionized acid to a highly ionized salt, e.g.A sodium acetate, and then proceeding according tothis invention.

The solutions to be treatedl in f accordance with the invention usually contain aV highly yionized solute,'or a Vmixture of highly ionized solutes, -in a not greater than 7-normal, and preferablyless ythan '2-normal, concentration. The degree of separationfthat `isaccomplished in practice of the invention frequently becomes greater with decrease in concentration of `the `more* highly ion-ized solute inthe solution-'used as. a starting material. A

. change in the concentration of the sugar or `sugars in the vstarting solution usually hasl little, if any, effect on the degree' ofI separation' thatH-is obtained, i.e., therstarting `associ-'2 solution -may contain a sugar or sugars in any desired Concentration.

The process of the invention may be carried out at temperatures between that at which the solution under treatment congeals, i.e. becomes at least partially crystalline or of such a high viscosity that flow is impaired, and the boiling point of the solution. In most instances, the extent of separation obtained by the process becomes greater as the temperature of the solution is raised. However, a rise in temperature increases the tendency for occurrence of undesired eddy currents and may necessitate more careful control, eg. of liquid ilow rates, in carrying out the process. For convenience, the process is usually carried out at temperatures from about room temperature, e.g. about 25 C., to about 80 C.

In practice of the invention, a bed of granular ion exchange resin is flooded with water. In general, the degree of separation that is obtained in practice of the invention yfrequently becomes greater with decrease in the size of the granules of ion exchange material. However, the rate of flow of liquid through a given depth of resin bed decreases with a decrease in particle size of the resin granules, and the pressure drop over a certain depth of the bed increases. Those skilled in the use of ion exchange materials can readily employ their skill in selecting a size of resin granule and arranging a bed of such resin granules for the purpose of carrying out the present Iprocess.

An aqueous solution of at least one sugar and at least one highly ionized solute is then fed slowly to the bed so as to displace an equal Volume of water therefrom. 'Ihe resultant flow of liquid through the bed may be in any direction, but is preferably either upward or downward. This flow should be quite slow so as to avoid, as far as possible, comingling of the solution with the water that is being displaced from the bed. The volume of solution fed -to the bed is preferably, but not necessarily, less than lthe volume of water that was initially absorbed in the resin of the bed. Upon contact with the solution, the resin rapidly absorbs the sugar into the water contained within the gel structure of the resin while leaving most, if not all, of the highly ionized solute in the surrounding liquid. The latter is then flushed from the bed by an inflow of fresh water. The How of fresh water is continued in order to extract and wash the absorbed sugar or sugars from the resin bed. The total amount of wash water thus fed to the bed preferably, but not necessarily, exceeds somewhat Ithe volume of the starting solution previously fed to the bed. It is merely necessary that the volume of wash water be as large as, or larger than, the volume of water that was initially absorbed in the resin, ie., the volume of wash water may be less than the volume of the solution previously fed to the bed, particularly in instances in which said Volume of the solution exceeds ythe volume of water initially absorbed in the resin bed.

During passage of the aqueous liquids, ie., the starting solution and the fresh water wash, through lthe bed of ion exchange resin, there are collected, as successive fractions of the effluent liquid: (a) water flushed from the bed; (b) an aqueous fraction rich in the highly ionized solute, but impoverished with respect to sugar; (c) usually, but not always, an intermediate fraction that contains little if any of either solute; (d) an aqueous fraction rich in sugar that contains little if any of the highly ionized solute; and (e) water, Irelatively free of either solute. The bed of resin is then in condition for reemployment in treating a further amount of the starting solution,

It will be understood that each of the fractions referred i to above may be one part or may consist of a plurality and-thereafter feeding water to the bed to ilush the solutes therefrom, the feed of the starting solution may be resumed before collection of the above-mentioned effluent fractions is completed. In other words, the amount of feed Water need not be sufficient, of itself, to flush all of the fractions (b)-(d) from .the :resin bed. It is merely necessary that the volume of water be as large as, or preferably larger than, the volume of water initially absorbed in the resin. When such an amount of water is used, and feed of the starting solution is resumed before completing the collection of the above-mentioned fractions (b)-(d), the water serves as a cushion between the inllowing solution and the effluent liquid and forces the remainder of the fractions (b)-(d) from the -bed ahead of the same. While functioning in this manner, at least a portion of the water is consumed in desorbing the sugar from the resin particles` When, in a given cycle of the above-mentioned operations, the volume of starting solution that is fed to the bed of ion exchange material is equal to or less than the volume of water initially absorbed in the resin, a major amount, by weight, of the solutes in the starting solution is collected in the above fractions (b) and (d) which contain the highly ionized solutes and the sugar, respectively. When the starting solution is fed to the bed 4in amount exceeding the volume of water initially absorbed in the resin, there are obtained fractions (b) and (d) which are at least as large in volume and are quite similar in chemical composition to the respective volumes (b) and (d) that are obtained when using a lesser amount of the starting solution. However, the aforementioned fraction (c) usually then is of a composition corresponding approximately to that of the starting solution, ie., fraction (c) 4then usually consists. substantially of the portion of the starting solution feed material that exceeded the volume of water initially absorbed in the resin. In such instance, the fraction (c) may be recycled to recover the solutes therefrom. Accordingly, in a given cycle of operations of this process, the starting solution is preferably fed -to the resin bed in amount not exceeding the volume of water initially absorbed in the resin, but it may conveniently and satisfactorily be fed in larger amounts to the bed.

The accompanying drawing illustrates graphically the changes in composition of successive fractions of the effluent liquor collected during a single cycle of operations in each of several experiments that were carried out. The drawing will be referred to in greater det-ail in examples hereinafter presented.

The above-described cycle of operations may be repeated many times, using the same bed of ion exchange resin and successive portions of a starting solution, to separate further amounts of the highly ionized solute and the sugar contained in the solution.

Two or more beds of an ion exchange resin may be advantageously employed in the process, with feed of a starting solution to one bed while ushing treated liquid and absorbed material from another bed. By thus employing the beds in parallel with one another and by employing them alternately for the treatment of a starting solution, the process may be carried out in continuous manner. Continuous operation can also be obtained by moving the resin granules continuously or rhythmically through zones of continuous flow of starting solution and of fresh water in a manner analogous to that already known for continuous operation of ion exchange processes.

The method as just described may be applied to a wide variety of aqueous solutions, each containing a highly ionized solute and a sugar, to separate these solutes from one another. Either or both can be obtained in the form of aqueous solutions, each substantially free of the other, and each chemically unchanged relative to the starting solution save in regard to the removal of the other solute. The method is particularly, but not exclusively, useful in sugar -rening processes, eig. for Vthe demineralization and decolorizatiou of sugar solutions such as defecated sugar juice. When crude sugar solutions, eg. from cane or vbeet sugar operations, are treated according to this invention, the color bodies largely accompany the ionized Asolute fraction and the suigar fraction is substantially freeQof color as well as free of ionized solutes. This is in contrast lto the ordinary use of ion exchange materials for decolorization of sugar solutions in which the ion exchange material absorbs a part (but usualiy not all) of the color out of sugar `solutions passed therethrough. Such color-burdened resins are usually very diilicult to regenerate and rapidly become ineiective for further use. ln the .present method, the color bodies in the starting sulgar solutions are not `retained by the resin and so do not accumulate therein. Furthermore, the present method is advantageously employed for recovering valuable ionic by-products from crude sugar solutions, such as potassium aconitate from sucrose extraction liquors. For this purpose, the preferred ion exchange material is the potassium salt of a sulfonated crosslinked vinylaromatic polymer of a kind hereinbefore speciiied.

lThe following examples illustrate some of the ways in which the invention has been practiced, but are not to be construed as limiting its scope'.

EXAMPLE l For the purpose of demonstrating the separation of a sugar from a `highly ionized solute, a synthetic solution was prepared containing 5 percent by Weight of sodium chloride and 'l0 percent'by weight of Daglucose dissolved in Water. v

A glass tube of approximately l-inch internal diameter was charged to a depth of 36V inches with wet granules of the sodium salt of a nuclear sulfonated copolymer of Iapproximately 93.5 percent by weight styrene, 2.5 percent ethylvinylbenzene, and 4 percent divinylbenzene. The granules were of from 50 to 10u() mesh size according to the U.S. Standard screen scale, i.e., from about 0.l5 to about 0.30 mm. yin diameter. The gel Water content of the ion exchange material was about 73 volume percent. The tube was held in a vertical position and the resin bed was flooded with water so as to immerse the granules of resin. The subsequent operations were carried out at room temperature, i.e., at about 25-30 C.

A total of l mls. of the solution containing 5 percent by weight of sodium chloride and l0 percent by weight of D-,glucose was fed to the tube at a rate of mls. per minute, thereby displacing an equal volume of water from the tube. Water was then fed to the tube at the same rate. The liquid which was displaced from the tube by the feed of the two liquids, i.e., the starting solution and the wash water, was collected in 25-ml. portions and each portion was analyzed for sodium chloride and 'for D-glucosesubstantially pure water. Thereafter, the diierent fractions contained sodium chloride'and Daglucose in the yconcentrations expressed in percent by weight given in The rst 150 mls. of eiiiuent was Fig. l of the drawing is a graphical representation showing the changes in the concentration of sodium Achloride and of D-glucose in the above-mentioned .fractions ofthe efiiuent liquid.

When the operations just described were carried out with less extensively crosslinked ion exchange resins 'of the same kind but having a larger .gel wafer content, eg., a sodium salt of a nuclear sulfonated copolymer of approximately 96.7 percent by weight styrene, 1.3 Vpercent ethylvinylbenzene, and 2 percent divinylbenzene having a gel water content of 83 volume percent, a similarly effective separation of sugar from the ionized solute was obtained, but the aqueous fractions of efuent .liquid were somewhat more dilute in respect to the solutey therein. When these operations were carried out Jwith more extensively crosslinked ion exchange resins of the same kind, eg., a sodium salt of a nuclear sulfonated copolyrner of approximately 87 percent by weight styrene, -5 percent ethylvinylbenzene, and 8 percent divinylbenzene hav ing a gel water content of 56 volume percent, theudegree of separation of the solutes wasA decreased, i.e., smaller proportions of the suigar and of the sodium chloride were obtained in the Aform `oteiiiuent fractions lthat were substantially free of` the other ,solute-r/ EXAMPLE 2 For the purpose of showing the effect of temperature on the separation of a sugar from a highly ionized solute by the present method, the procedural steps of Example 1 were repeated, using ythe same bed of ion exchange'resin and another portion of the same starting solution, but carrying out the subsequent operations ata temperature of VC. The temperature was maintained by r'passing hot water through a jacket surrounding ,the Vtube icontaining the resin lbed. l i

A total of ,l0 mls. of the solution of 5 percent by weight of sodium chlorideand l0 percent by weightjofv D`glucose was fed tothe tube at a rate of 5 mls. ,perminute v'Water was then fed to the tube at the same rate. The liquid that was thereby displaced from the tube by the liquid feeds was collected in portions and each portion was analyzed. The first 150 mls. of efuen-t wassubstantially pure water. Thereafter the fractions of eiucnt contained sodiumchloride and D-glucose in the concentrations expressedin percent by weight glven 1n Table II.

VT able Il Solute in Effluent Liquid Fraction, Percent by Weight Effluent Liquid'Fi-action, Milliliters Sodium D-Glucose Chloride nil nil 0. 131 nil 0. 579 nil 1. 166 nil 0. 298 nil 0 004 nil nil- 1.125 nil l. nil 0.30 nil nil Fig. 2 of the drawing is a graphical representation of `these data showing the changes in the concentration of sodium chloride and of D-glucose in the above-mentioned fractions of the eiiiuent liquid. n

Comparison of the data shown in Table Il (Fig. 2) with those shown in Table I (Fig. l) shows that the separation of sodium chloride from D-glucose is slightly better at 80 C. than at room temperature. The principal fractions of effluent liquid were slightly more concentrated in `respect to the solute thereinwhen the operations were carried out at the higher of these temperatures. The effect of temperature on the .separation of sugar from ionic solutes is generally more marked With themore highly crosslinked ion exchange resins and less marked With the low crosslinked resins.

EXAMPLE 3 This example illustrates the use of an anion exchange resin in the process of the invention.

A glass tube of approximately l-inch internal diameter was charged to a depth of 36 inches with wet granules of a resinous copolymer of approximately 93.5 percent byweight styrene, 2.5 percent ethylvinylbenzene, and 4 percent divinylbenzene, which copolymer contained -CH2N(CH3)3C1 radicals as substituents on aromatic nuclei therein. The granules were of from 50 to 100 mesh size according to the U.S. Standard screen scale, i.e., from about 0.15 to about 0.30 mm. in diameter. The gel water content of the ion exchange resin was about 62 lvolume percent. The tube was held in a vertical position and the resin 'bed was iiooded with water so as to immerse the resin granules. The subsequent operations were carried out at a temperature of about 80 C., maintaining that temperature `by passing hot water through a jacket surrounding the tube containing the resin bed. The procedural steps were similar to those described in previous examples. i

A total of 10 mls. of the solution (described in Example 1) containing 5 percent by weight of sodium chloride and l percent by weight of D-glucose was fed to the tube at a rate of 5 mls. per minute. Water was then fed to the tube at the same rate. The liquid that was thereby `displaced from the tube by the liquid feeds was collected in S25-ml. portions and each portion was analyzed. The first 150 mls. of effluent liquid was nearly pure water. Thereafter the fractions contained sodium chloride and D- glucose in the concentrations expressed in percent by weight given in Table III.

Fig. 3 of the drawing is a graphical representation of these data showing the changes in the concentration of sodium chloride and of D-glucose in the above-mentioned fractions of the etiiuent liquid.

Comparison of the data shown in Table III (Fig. 3) with those shown in Table II (Fig. 2) shows that the sepa ration of sodium chloride from D-glucose is substantially the same for the operation that employed a highly ionized anion exchange resin as for the one that employed a highly ionized cation exchange resin.

In order to facilitate the making of comparisons, the foregoing examples were carried out with the same kind of starting solution, viz., a water solution containing 5 percent by weight of sodium chloride and percent by weight of D-glucose. However, other experiments were carried out with other sugars, e.g. D-xylose and sucrose, with other ionic solutes, and with other concentrations of solutes, using the specified ion exchange resins and procedures, and effective separations of sugars from ionic solutes were obtained.

EXAMPLE 4 This example illustrates the treatment of `a raw sugar `cedural steps were similar to those described in by the process of this invention. The raw sugar, obtained from sugar cane by a commercial refinery operation, was dark brown, somewhat sticky, and contained some ionic material. The sugar was principally sucrose and the impurities were of unknown constitution. l f

Aiglass tube of approximately 0.6-inch internal diam eter was filled to a depth of 22.3 inches `with wet granules of the cation exchange resin that was described `inlxample l. The tube was held in a vertical position and the resin bed was flooded with Water so as to immerse the resin granules. The subsequent operations were carried out at a temperature of C., maintaining that temperature by passing hot water through aijacket surrounding the tube containing the resin bed. The proprevious examples.

A total of 2 mls. of a water solution containing 15 percent by weight of the above-described raw sugar was fed to the resin bed, thereby displacing an equal volume of water. Water was then fed to the tube at a rate of 1 ml. per minute. The liquid which was thereby displaced from the tube was collected in portions of about 2 mls. each, and each portion was analyzed. The concentration of sucrose was computed from the `index of refraction of the fraction of eluent liquid. The color of each fraction of eilluent was observed visually. Some of the fractions were diluted to 2 percent by volume with deionized Water and the specicresistance (in ohms) Was measured. Some of these data are shown IThe color symbols have these meanings: Colorless-l-slight color; -I--lmuch color.

Fig. 4 of the drawing is a graphical representation of these data showing the changes in the concentration of sucrose, color, andspeciiic resistance of the above-nien- `tioned fractions of the eluent liquid. The specific resistance is a measure ofthe presence of ionic solutes,

`thespecitic resistance being lower with an increase in concentration of ionized solutes in the eilluent fraction. These data show that both the color bodies andthe ionic impurities in the raw sugar passed from the resin bed in fractions of effluent that preceded the principal sucrose fractions, and that the latter were substantially free of color and of ionic ingredients.

EXAMPLE 5 p 'This example illustrates the separation of potassium aconitate from sucrose. lFor convenience, a `synthetic `composition was `prepared containing 10 percent by Yyghli-9f-sllcrose and, 1 percent by weight` of potassium aconitjate dissolved in Water.

A glass tube of, approximately l-inch interval diameter was charged toa depth'of 36 inches with wetfgranules of the potassium form, of a cation exchange resinvof ,the kind described in Example 1. The subsequent op- @rations were carried out in a manner similar ,to that described in Example 1.

A total of 46 mls. of the solution described above, containing sucrose .and potassium aconitate, 'was fed to `the tube 4at a rate of 5 mls. per minute. Water was then fed tothe tube at the same rate. The liquid which was thereby displaced from the tube was collected in small ,portions and the portions were analyzed. The concentrations of sucrose and of potassium aconitate in the eiuent liquid fractions are shown in Table V.

Table V ,Solute iniEluent Liquid Fractions; Percent by Weight'.

@een France. Munsters Potassium Sucrose s Aconitate OCA? ...sessie 05003 `nil nil nil nil nil nil nil nil EXAMPLEJ 6 This exemple illustrateslhe treatment f e molasses by the'present method.

Into a standard 10G-ml. buret was placed a cation exchange resin like that described in Example l. The bedf 0f resin was flooded With Water so as to immerse the granules of resin. l Y

To the resin bed so prepared was fed 5 mls. of a dilute molasses solution at a flow rate of about 1.5 mls. perlminute, thereby displacing water from the column. The dilute molasses solution was prepared by adding 70V parts by Weight of Water to 30 parts by Weight of commercial cane sugar molasses. Aftery the molasses solution, water was fed to the resin bed at the same rate of, about 1.5 mls. per minute. All of the operations were lcarried out at room temperature. The efuent liquid from the resin bed was taken in fractions and analyzed. The refractive index of the fractionswas determined.y It may be mentioned that the` refractive index constitutesV an indirect, but readily determined, measure of the concentration of solute present inthe respective fractions. The electrical resistance ofthe fractions WasV also measured. Such resistance is an Vindir,ect,fbuty readily determined, ,inverse measure of the concentration of electrolytes (ionized solutes) in the respective fractions. The color vof the respective fractions Was compared with the color of standard solutions of cobaltous chloroplatinate (American Public Health Association. Standard. usually. referred. to .as APHA Co1cr"*) These ,data aresh0wni1i--ableVL- wherein are ,shcwnthe retraits/.einden ,the electrical tesis, use. in

12 ohms, andthe APHA color in parts per million of platinum for the respective fractions `of. efliue-nt liquid. The fractions from about 54 to about 78 mls. of effluent liquid contained the sugar ingredients of the molasses starting material.

Table VI Refractive Electrical Color, Elluent Fractions, Milliliters Index, Resistance, APHA,

' 35 OJD. Ohms. p pm. Pt

2, ooo, ooo

These data are shown graphically in Fig. 5 of the drawing. It is`evident that the colored impurities in the molasses, together with the ionic ingredients, 'were separated from the sugar fractions by the described treatment. i i

I claim:

1. A method for the treatment of an aqueous sugar solutioncontaining as solutes therein at least one sugar having from 5 to 12 carbon atoms in its molecular structure and at least one highly ionized solute having an ionization constant at least as great as 5x10-2, which method comprises feeding such aqueous sugar solution to, and thereby displacing Water from, a Water-immersed bed of particles of an ion exchange resin, which ion exchange resin is in a highly ionized form and has a gel Water content of from about 50 to about 90 percent by volume, thereafter feeding Water to the bed and collecting successive fractions of the displaced effluent liquid, whereby there is -obtained at least one fraction of aqueous solution that comprises at least one of the solutes and is substantially free of at least one other of the solutes present Vin the starting aqueous sugary solution.

2. A method for the treatment of an aqueous sugar solution containing at least one sugar having from 5 to 12 carbon atoms in its molecular structure and at least one highly ionized solute having an ionization constant at least as greatas 5x10-2, which method comprises feeding .such aqueous sugar solution to, and thereby displaclng water from, a wateryimmersed bed of particles o f an ion exchange resin, which ion exchange yresin is in a highly ionized form and has a gel water content offrom about SO to about percent by volume, thereafter feeding water to the bed to displace a further amount of liquid from the bed and collecting fractions of the displaced effluent liquid to obtain a fraction of the effluent liquid that contains a major portion of the highly ionized solute and a fraction of the effluent liquidV that contains a major portion of the sugar.y y

3. A method according to claim 2 wherein the ion exchange resin is a cation exchange resin in a highly ionized form, which cation exchange resin is capa-ble of existing in an acidic form that is ionized to an extent such that the addition of va IO-gram portion thereof to milliliters of a 0.1 normal aqueous solution of sodium chloride brings the solution to a pHkvalue of lesskthan`v 3.

4. A method according to claim 2 wherein the ion exchange resin is a nuclear sulfonated copolymer of a 13 major amount of at least one polymerizable monoalkenylaromatic hydrocarbon and a minor amount of a polyvinylbenzene.

5. A method according to claim 2 wherein the ion exchange resin is a nuclear sulfonated copolymer of a major amount of styrene and minor amounts of ar-ethylstyrene and divinylbenzene and has a gel water content of from about 60 to about S0 percent by volume.

6. A method according to claim 2 wherein the ion exchange resin is an anion exchange resin in a highly ionized form, which anion exchange resin is capable of existing in a basic formthat is ionized to an extent such that the addition of a -gram portion thereof to 100 milliliters of a 0.1 normal aqueous solution of sodium chloride brings the solution to a pH value greater than l1.

7. A method according to claim 2 wherein the ion exchange resin is an anion exchange resin that contains quaternary ammonium radicals as the functional groups thereof.

8. A method according to claim 2 wherein the ion exchange resin is an anion exchange resin that contains quaternized amino-methyl radicals as the functional groups thereof attached to a copolymer of a major amount of styrene and minor amounts of ar-ethylstyrene and divinylbenzene and that has a gel water content of from about 60 to about 80 percent by volume.

9. A method wherein the steps described in claim 2 are repeated using a further amount of the starting aqueous sugar solution and the same bed of ion exchange resin.

10. A method according to claim 2 wherein the aqueous sugar solution is a crude sugar solution obtained froma source in nature and containing ionic solutes as impurities, whereby there are obtained an effluent liquid fraction that contains the ionic solutes substantially free of sugars and an effluent liquid fraction that contains the sugar substantially free of ionic impurities.

11. A method according to claim 2 wherein the aqueous sugar solution is a crude sucrose solution.

12. A method according to claim 2 wherein the aqueous sugar solution is a crude sugar solution containing potassium aconitate and the ion exchange resin is the potassium salt of a nuclear sulfonated copolymer of a major amount of styrene and minor amounts of ar-ethylstyrene and divinylbenzene and has a gel water content of from about '60 to about 80 percent by volume, Whereby there is obtained an eiiuent liquid fraction that con- 14 tains potassium aconitate and is substantially free of sugars.

13. A method according to claim 2 wherein the operations are carried out with the temperature of the liquid in contact with the ion exchange resin particles being maintained from about 25 to about 89 C.

14. A method for the treatment of an aqueous sugar solution containing as solutes therein at least one sugar having from 5 to l2 carbon atoms in its molecular structure and at least one highly ionized solute having an ionization constant at least as great as 5 10*2, which method comprises contacting water-immersed particles of an ion exchange resin, which ion exchange resin is in a highly ionized form and has a gel water content of from about to about 80 percent by volume, :successively with portions of the aqueous sugar solution and with portions of water, the portions of aqueous sugar solution being in amount having a volume not greater than the volume of water initially absorbed in the resin and the portions of water being in amount having a volume at least as great as the volume of water initially absorbed in the resin, and separating successive portions of liquid from contact with such ion exchange resin, whereby there are obtained a portion of aqueous solution that contains a major part of the ionized solute and a separate portion of aqueous solution that contains a major part of the sugar.

References Cited in the file of this patent UNITED STATES PATENTS Bauman July 20, 1954 Simpson et al. Nov. 20, 1956 OTHER REFERENCES

Claims (1)

1. A METHOD FOR THE TREATMENT OF AN AQUEOUS SUGAR SOLUTION CONTAINING AS SOLUTES THEREIN AT LEAST ONE SUGAR HAVING FROM 5 TO 12 CARBON ATOMS IN ITS MOLECULAR STRUCTURE AND AT LEAST ONE HIGHLY IONIZED SOLUTE HAVING AN IONIZATION CONSTANT AT LEAST AS GREAT AS 5X10-2, WHICH METHOD COMPRISES FEEDING SUCH AQUEOUS SUGAR SOLUTION TO, AND THEREBY DISPLACING WATER FROM, A WATER-IMMERSED BED OF PARTICLES OF AN ION EXCHANGE RESIN, WHICH ION EXCHANGE RESIN IS IN A HIGHLY IONIZED FORM AND HAS A GEL WATER CONTENT OF FROM ABOUT 50 TO ABOUT 90 PERCENT BY VOLUME, THEREAFTER FEEDING WATER TO THE BED AND COLLECTING SUCCESSIVE FRACTIONS OF THE DISPLACED EFFLUENT LIQUID, WHEREBY THERE IS OBTAINED AT LEAST ONE FRACTION OF AQUEOUS SOLUTION THAT COMPRISES AT LEAST ONE OF THE SOLUTES AND IS SUBSTANTIALLY FREE OF AT LEAST ONE OTHER OF THE SOLUTES PRESENT IN THE STARTING AQUEOUS SUGAR SOLUTION.

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