WO2016032923A1

WO2016032923A1 - Method for the chromatographic separation of sorbitol from dextrose

Info

Publication number: WO2016032923A1
Application number: PCT/US2015/046462
Authority: WO
Inventors: Thomas P. Binder; John G. Soper
Original assignee: Archer Daniels Midland Company
Priority date: 2014-08-25
Filing date: 2015-08-24
Publication date: 2016-03-03

Abstract

A method for the continuous production and separation of sorbitol from dextrose to produce a high purity sorbitol product is described. The method comprises hydrogenating a dextrose composition in a continuous reaction to produce a mixture of sorbitol and dextrose, and contacting the mixture with a matrix containing a strong acid cation exchange resin in a simulated moving bed chromatography apparatus. An extract stream comprising 99.5% or greater sorbitol and a raffinate stream depleted of sorbitol and enriched in dextrose relative to the mixture are recovered from the apparatus. The method can also be used to produce hydrogenated maltodextrins and hydrogenated isomaltodextrins.

Description

METHOD FOR THE CHROMATOGRAPHIC SEPARATION

OF SORBITOL FROM DEXTROSE CROSS-REFERENCE TO RELATED APPLICATION(S)

[0001] This application claims the benefit of U.S. Provisional Patent Application No.

62/041,407 filed August 25, 2014, the contents of the entirety of which are incorporated by this reference.

FIELD OF THE INVENTION

[0002] This invention is related to the field of chromatographic separation of sorbitol and dextrose, more particularly to separating sorbitol and dextrose in a mixture obtained from hydrogenation of dextrose to produce sorbitol, and still more particularly to such a separation accomplished by using continuous simulated moving bed technology in combination with continuous operation of a dextrose hydrogenation reactor. DESCRIPTION OF RELATED ART

[0003] Sorbitol is used in a number of commercial applications, including in food, medicine, and cosmetics, such as mouthwash and toothpaste. Sorbitol required for food and most cosmetic uses, referred to herein as food applications, must have high purity, generally over 99.5%. Sorbitol is generally formed from the catalytic hydrogenation of dextrose using a nickel or ruthenium catalyst. Batch reactions can successfully convert a high percentage of the dextrose to sorbitol, resulting in purities suitable for food applications.

[0004] Continuous heterogeneous catalytic hydrogenation reactions for converting dextrose to sorbitol have been developed. Continuous reactions require smaller reactors and leach much less nickel into the sorbitol product than in conventional batch processes. However the hydrogenation reaction cannot be run to completion in the continuous reaction system, resulting in lower purity sorbitol and residual unreacted dextrose. Although the residual dextrose is present in low concentrations, it is present in amounts higher than allowed for food applications of sorbitol. One known way of improving the sorbitol purity is to react the residual dextrose with sodium borohydride to reduce more of it to dextrose, followed by removal of the residual boron using ion exchange. This increases the complexity and cost of the continuous hydrogenation reaction.

[0005] There is, therefore, a need in the art to improve the production of sorbitol from dextrose, preferably using a continuous hydrogenation procedure coupled with the ability to obtain sorbitol at high purity with low production costs. BRIEF SUMMARY OF THE INVENTION

[0006] Certain aspects of the present invention are directed to a method for continuous production of sorbitol and separation thereof from dextrose. In certain embodiments, the method comprises hydrogenating a dextrose composition to produce a mixture of sorbitol and dextrose in a continuous reaction. The mixture is contacted with a matrix containing a strong acid cation exchange resin in a simulated moving bed chromatography apparatus. An extract stream comprising 99.5% or greater sorbitol, preferably comprising greater than 99.7% or 99.9% sorbitol, is recovered from the apparatus. A raffinate stream depleted of sorbitol and enriched in dextrose relative to the mixture is also recovered. In certain aspects of the invention, the raffinate stream is recycled into the hydrogenation step.

[0007] The mixture contacting the simulated moving bed apparatus may comprise 1 % dextrose or less. Alternatively, a dextrose composition comprising dextrose and maltodextrins or isomaltodextrins is fed into the hydrogenation reaction. Such dextrose composition result from the conversion of starch to dextrose and maltodextrin or isomaltodextrin. The mixture of sorbitol and dextrose produced by the hydrogenation reaction additionally comprises hydrogenated maltodextrin or hydrogenated isomaltodextrin. When the mixture contacts the simulated moving bed apparatus, the raffinate stream is enriched in dextrose and hydrogenated maltodextrin or hydrogenated isomaltodextrin relative to the mixture. The hydrogenated maltodextrin or hydrogenated isomaltodextrin may be removed from the raffinate before the raffinate is recycled back into the hydrogenation reaction.

[0008] In certain embodiments of the present invention, the method of the present invention comprises continuous production and separation of a desired compound from a mixture of compounds contained in the product of a continuous hydrogenation reaction. The mixture, comprising the desired compound and one or more secondary compounds, contacts a matrix containing a strong acid cation exchange resin in a simulated moving bed chromatography apparatus. The extract stream enriched in the desired compound relative to the mixture and substantially free of the secondary compounds is recovered from the apparatus. A raffinate stream depleted of the desired compound and enriched in the secondary compounds relative to the mixture is also recovered. In certain preferred embodiments, the desired compound is sorbitol and the secondary compounds are selected form the group consisting of dextrose, maltodextrin, and isomaltodextrin.

[0009] Additional aspects of the invention, together with the advantages and novel features appurtenant thereto, will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned from the practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 shows the results of an HPLC separation of sorbitol, dextrose and other sugars using a strong cation exchange resin in calcium form.

[0011] FIG. 2 is a schematic top view of a simulated moving bed chromatography apparatus used in exemplary embodiments of the present invention.

[0012] FIG. 3 is a graph charting the results of a pulse test.

[0013] FIG. 4 is a schematic side view of a simulated moving bed chromatography configuration developed after initial pulse testing using a solution of 95% sorbitol and 5% dextrose.

[0014] FIG. 5 is a schematic side view of a simulated moving bed chromatography configuration developed with a hydrogenation mixture containing at least 98% sorbitol and about 0.5% dextrose.

[0015] FIG. 6 is a graph charting the results of a pulse test using a calcium cation column.

[0016] FIG.7 is a graph charting the results of a pulse test using a nickel cation column.

[0017] FIG. 8 is a graph charting the results of a breakthrough test using a cation exchange column in the H⁺ form as a guard column to remove nickel prior to entry into a SMB apparatus containing an ion exchange resin in the calcium form.

[0018] FIG. 9 are graphs illustrating comparative pulse tests between different cation exchange resins in the calcium cation form for separating sorbitol and dextrose with panel A illustrating Dowex 99 320 and panel B Purolite PCR 642.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

[0019] The present invention is directed to a method for the continuous production and separation of sorbitol from dextrose. The method comprises hydrogenating a dextrose composition in a continuous reaction to produce a mixture of sorbitol and dextrose, and contacting the mixture with a matrix containing a strong acid cation exchange resin in a simulated moving bed chromatography apparatus. An extract stream comprising 99.5% or greater sorbitol and a raffinate stream depleted of sorbitol and enriched in dextrose relative to the mixture are recovered from the apparatus. The method results in the recovery of a high purity sorbitol suitable for use in food applications.

[0020] As used herein, unless expressly defined otherwise, a reference to a“X% sorbitol” refers to an aqueous solution containing sorbitol possibly mixed with dextrose and other carbohydrates, where sorbitol represents X % of the total solids in the mixture the remaining solids accounting for (100-X)%. Thus, 95% sorbitol means the proportion of solids that is sorbitol is 95% and the proportion that is dextrose, maltose, mannose or other carbon containing compound is 5%. The same convention applies to the relative percentages of other sugars. For example, 90% dextrose and 10% isomaltodextrins, means the proportion of sugar that is dextrose is 90% and the proportion that is isomaltodextrins is 10%. “X % concentration”, on the other hand, refers to the wt/wt percent of the referenced dissolved species per total aqueous solution weight unless with express reference to“dissolved solids content” which is the total wt/wt percent of sorbitol and dextrose combined per weight of solution. Thus for example, a 95% sorbitol solution at a dissolved solids content of 20% means there are 20 g of total dissolved sugars per 100 g of solution weight, and out of the 20 grams of sugar 19 g is sorbitol and 1 g is dextrose, maltose, mannose or other carbohydrate, with the concentration of sorbitol in the solution being 19 % g/g and the concentration of dextrose, maltose, mannose and other being 1 % g/g.

[0021] The mixture fed into the simulated moving bed apparatus is the reaction product of a continuous hydrogenation reaction for converting dextrose to sorbitol. As used herein, a continuous reaction is one in which reactants can be continuously added and products continuously removed without interruption of the reaction. The mixture contains a high percentage of sorbitol, but not high enough for food applications. Typically, ion exchange technology is better suited to extracting the desired compound from higher concentrations of secondary products. However, it has been found that the method of the present invention is able to extract sorbitol from even very low concentrations of dextrose. In some embodiments of the invention, the mixture fed into the simulated moving bed apparatus comprises 1% or less dextrose. The method of the present invention is also able to extract sorbitol from mixtures containing non- crystalized dextrose. The method of the present invention is further able to produce high purity sorbitol with the recovery of only two streams, an extraction stream and a raffinate stream, from the apparatus.

[0022] The method of the present invention allows recovery of highly pure sorbitol from the mixture. In certain embodiments, the extraction stream comprises 99.5% sorbitol, more preferably 99.7% sorbitol and even more preferably 99.9% sorbitol. Thus, purities reaching 100% can be achieved. Such high purities of sorbitol are critical for producing sorbitol for food applications.

[0023] Furthermore, the method of the present invention results in high yields of sorbitol recovery. In certain embodiments, greater than 98%, of the sorbitol in the dextrose/sorbitol mixture is recovered, and preferably greater than 99% recovery is achieved.

[0024] Because the sorbitol will be purified from the dextrose using the process of the present invention, there is less need to produce a hydrogenation product having very high sorbitol content. This allows the continuous hydrogenation reaction to be run based on optimal hydrogenation reactor productivity, rather than based on a need to produce low dextrose concentrations in the reaction product. In certain embodiments, the hydrogenation product contacting the simulated moving bed apparatus is a sorbitol and dextrose mixture comprising between 1% and 10% dextrose. In some embodiments, the hydrogenation product comprises 5% dextrose. Similarly, a lower purity dextrose composition can be fed into hydrogenation reaction.

[0025] In certain embodiments, the dextrose composition fed into the hydrogenation reaction comprises additional compounds of commercial interest to be reduced in the hydrogenation reaction. These additional compounds are typically byproducts of the enzymatic saccharification of starch to dextrose. Generally, starch is reacted with α– amylase to produce gluco-oligosaccharides, which are then hydrolyzed into dextrose by glucoamylase. In some embodiments, the glucoamylase reaction is not run to completion, which produces a dextrose composition comprising dextrose and maltodextrins, which are gluco-oligosaccharides comprising chains of 2-20 dextrose residues (e.g., a 2-20 degree of polymerization (DP)). With this definition, the lowest molecular weight maltodextrin would have a DP2 which is the gluco-disaccharide maltose. The most typical maltodextrins produced in the process of starch saccharification are generally DP4 to DP6 chains with a dextrose equivalent (DE) value of 15-20. Typically the ratio of dextrose to maltodextrin in a dextrose composition obtained by saccharification of starch is 85% to 98% dextrose and 2% to 15% maltodextrin. Reaction times and conditions to produce a dextrose composition comprising desired amounts of dextrose and maltodextrins are known or can be readily determined by those of ordinary skill in the art.

[0026] In some cases, the glucoamylase reaction can be run past completion, resulting in a portion of the dextrose being reverted, i.e. re-coupled to itself to form isomaltodextrins. This results in a dextrose composition comprising dextrose and isomaltodextrins. Isomaltodextrins contain α 1:6 linkages, rather than the α 1 :4 linkages in maltodextrins. Isomaltodextrins produced in this type of reaction are generally DP2 or DP3 sugars, although isomaltodextrins having up to DP6 can be produced. In some cases the dextrose composition useful for the present invention comprises 90% dextrose and 10% isomaltodextrin. Reaction times and conditions to produce a dextrose composition comprising desired amounts of sorbitol, dextrose and isomaltodextrins are known or can be readily determined by those of ordinary skill in the art.

[0027] The method of the present invention can more generally be used in a continuous method for producing and separating a mixture of products obtained from the hydrogenation of carbohydrates. The mixture, comprising a desired compound and one or more secondary compounds, is contacted with a matrix containing a strong acid cation exchange resin in a simulated moving bed chromatography apparatus. An extract stream containing the desired compound and substantially free of the secondary compounds is recovered. A raffinate stream depleted of the desired compound and enriched in the secondary compounds relative to the mixture is also recovered. In the exemplified embodiments, the hydrogenation process and the separation process are linked in a continuously operating process, the starting carbohydrate for the hydrogenation is a dextrose solution, the desired compound is sorbitol and the secondary compounds obtained in the raffinate stream are selected from the group consisting of dextrose, maltodextrins, and isomaltodextrins.

[0028] In certain embodiments, the simulated moving bed chromatography apparatus is a standard simulated moving bed chromatography apparatus. A standard apparatus is one that employs contact of the column segments containing the resin (solid phase) with the liquid to be processed (mobile phase) running counter-current to the direction the column segments containing the solid phase are moving. This is accomplished through the movement of the column segments beneath fixed position valves (Adsep) or the switching of valve positions atop fixed position column segments (Calgon type C-SEP), where in each case the valve switching (or column stepping) for all columns is done at the same time. This is distinguished from sequential simulated moving bed (SSMB) and improved or incremental simulated moving bed (I-SMB), both of which are more complex in terms of operation and understanding (due to the activation of different valves at different times for different columns in the case of the SSMB, and the intermittent operation with recycle in the case of the I-SMB) than the standard SMB systems. The SSMB and I-SMB configurations and methods of use also cost more for the same resin volume.

[0029] HPLC analysis shows that sorbitol can be separated from dextrose and other sugars on a strong anion exchange resin in the calcium form, as shown in Figure 1. The ability to achieve the high purity sorbitol using a standard simulated moving bed apparatus as described herein would not have been expected and is a significant improvement over chromatographic processes using SSMB or I-SMB. In some embodiments, the standard simulated moving bed apparatus is a carousel or Adsep (UOP) - type system.

[0030] Simulated moving bed chromatography operates by dividing a column bed into multiple discrete inter-connected column segments, introducing an input feed and eluent feed in a common flow direction over the linked column segments while essentially moving the column segments in a direction opposite the flow direction of the input and eluent streams. In some designs this is accomplished directly by actually rotating the column segments in a circular carousel in a direction opposite to the flow of the input and eluent streams. In other designs, the column segments are stationary but the ports for input and output of the column segments are rotated in the same direction as the flow of input and eluent streams. In either case the effect is the same, the material that preferentially retards with the stationary phase in the column segments (e.g., sorbitol) is preferentially carried with the column segments opposite in direction to the flow of material that preferentially flows with the moving phase eluent (e.g., dextrose with water) across the whole length of the interconnected column segments. The material that preferentially retards with the stationary phase is collected as an extract product and the material that preferentially flows with the moving phase eluent is collected in a raffinate stream.

[0031] When input and eluent stream flow rates are properly coordinated with column segment movements, the result is a continuous standing wave of zones of feedstock input, zones of enrichment, zones of elution, and zones of recover (optional).

[0032] A schematic of one embodiment of the present invention is illustrated in Figure 2, which shows a top view of an eighteen segment standard simulating moving bed (SMB) chromatographic apparatus 10 in fluid communication with an input flow 16 of sorbitol and residual dextrose from a continuous hydrogenation reactor 12. SMB apparatus 10 includes a contiguous stationary phase cation exchange column bed 14 separated into a plurality of column segments 14(_1-18) on a carousel. The output from the bottom of each column segment 14(n) enters the top of the next column 14(_n+1) and the segments 14 are linked in this manner into a loop on the carousel. The carousel provides for simultaneous step wise movement of column segments. 14(_1-18) in stationary phase movement direction 22 that is opposite in direction to the flow of the liquid phase through the column in mobile phase direction 20. By way of example, on a column movement step, column segment 14(₁₄) would shift to the position of column segment 14(₁₃) and column segment 14(₁₃) would shift to the position of column segment 14(₁₂), while the liquid flow continues in the opposite direction from column segment 14(₁₄) through column segment 14(₁₅).

[0033] As earlier mentioned an alternative configuration of a standard simulated moving bed chromatography apparatus is one where the physical position of the column segments 14(_n+1) remains constant and instead a set of valves mounted on a moving carousel atop the column segments moves in a stepwise fashion in the same direction as mobile phase flow 20, which has the same effect as moving the column segments 14(_n+1). In such an alternative configuration, for example, the input feed 16 position would be moved sequentially from position 14(₁₁) to 14(₁₂) and output flow 30 would be moved from position 14(₆) to 14(₇), etc.

[0034] An aqueous solution of dextrose 18 (which in some cases includes maltodextrins or isomaltose) is fed into continuous hydrogenation reactor 12 where at least 90% of the dextrose is converted to sorbitol and exits the reactor 12 as a mixture of sorbitol and dextrose that flows into the SMB apparatus 10 as input feed 16. As depicted, input feed 16 is at column segment 14(₁₁) and constitutes the mobile phase that flows from the bottom of column segment 14(₁₁) to the top of the next adjacent column segment 14(₁₂) in fluid flow direction 20. At the same time, the plurality of column segments 14(_n+1) are rotated in the carousel in column movement direction 22 that is counter to the fluid flow direction 20. Sorbitol in input feed 16 preferentially partitions with the stationary phase of column segments 14(_n+1) relative to dextrose, maltodextrins, isomaltose or other carbohydrates having reducing sugars. Therefore, as the column segments 14(_n+1) are rotated in stationary phase movement direction 22, the sorbitol preferentially moves with the stationary phase through a product enrichment zone of the SMB apparatus 10, which as depicted would correspond to column segments14(₇) to 14(₁₀). In contrast, the dextrose and other reducing sugars in the input feed 16 preferentially partition with the liquid phase relative to sorbitol and therefore preferentially flow in fluid flow direction 20 into an adsorption zone, which as depicted would correspond to column positions 14(₁₂) -14((₁₆).

[0035] An eluent feed input 26 comprising water is pumped into SMB apparatus 10 at column segment 14(₁) in the same mobile phase flow direction 20 forming an elution zone, which as depicted, would correspond to column positions 14(₁)-14(₅). The eluent feed 26 displaces sorbitol from the stationary phase of the column segments and is collected from the SMB apparatus 10 at column segment 14(₆) as sorbitol enriched containing extract mixture 30. In optional embodiments, a portion of the extract mixture 30 may be recycled back onto the SMB apparatus in flow direction 20 by loading at a column segment within the enrichment zone between positions 14(₇) and 14(₁₀), which would serve as an enrichment stream to further concentrate the ultimate sorbitol extract stream 30. Simultaneously, the dextrose (and maltodexrin or isomaltose if present) which preferentially flow with the mobile phase through the adsorption zone between columns 14(₁₂) and 14(₁₅) are removed from the SMB apparatus 10 at column position 14(₁₆) providing a dextrose enriched raffinate output stream 32, which may be mixed with additional dextrose 18 and recycled back to hydrogenation reactor 12. In an optional embodiment, a portion of the raffinate output stream 32 is reloaded back to a column segment within the absorption zone of the SMB apparatus 10 between columns 14(₁₂) and 14(₁₅) to help concentrate the raffinate output stream 32 collected.

[0036] When the overall fluid flow between input feed 16, eluent feed 26 and if desired, enrichment feed and reload feed, is properly balanced with the overall outflow of extract mixture 30, raffinate stream 32, the effect is to establish continuous chromatographic separation that can be conducted indefinitely, subject only to the life of the column bed, producing enriched extract product 30 comprising highly purified sorbitol. The SMB apparatus 10 is preferably operated to maximize the sorbitol concentration while minimizing dextrose content in the extract product 30 and to concentrate and recycle the separated dextrose back to the reactor 12, thereby maximizing product purity while minimizing waste.

[0037] The simulated moving bed apparatus of the present invention is loaded with a stationary phase in the column segments that is preferably a matrix containing a strong acid cation exchange resin. Typically a strong acid cation resin contains a polymeric backbone matrix, such as polystyrene, which is cross-linked to divinyl-benzene cross- linkages and contain a sulfonic acid functionality. The sulfonic acid functionality forms strong salt bonds with cations, especially divalent cations such as calcium and nickel.

[0038] In other embodiments, a weak cation exchange resin may also be used, however, a strong cation exchange resin is preferable to weak cation exchange resins because the strong acid functionality allows for the more permanent incorporation of cations onto the resin by strong salt bonds. In the process of this invention, the separation over the SMB apparatus is not an ion exchange separation because no cation is present (or the input solutions has very little cations) to exchange with the cation bound to the strong acid resin. Rather, the separation is by a conventional chromatographic process where the cation in combination with the hydrophobic polystyrene matrix together serve as an adsorbent for the species in the mixture being separated. The salt bond between the sulfonic acid group and the cation (i.e. calcium, in the case of a calcium form resin) only negligibly leaches in water and any cation leached thereby rapidly reforms a salt bond, allowing the strong acid resin to have much more“permanent” utility without having to be frequently regenerated. In contrast, a weak acid resin creates salt bonds that easily are displaced from the matrix reducing the adsorbent quality of the resin for the present invention and requiring frequent regeneration.

[0039] In certain embodiments, the method of the present invention utilizes a resin selected from the group consisting of a calcium form cation resin and a nickel form cation resin. Commercial examples of such resins include Dowex 99 320 Ca++ and Dowex 99 320 Ni++ (Dow Chemical Company, Midland, MI). Another preferred commercial example is Purolite PCR642 (Purolite Inc., Bala Cynwyd, PA) which showed tighter zone compaction for sorbitol and dextrose than the Dowex resin and therefore the possibility of higher concentration loads for the SMB apparatus. Although the specification sheets for the Dowex and Purolite resins look nearly identical in terms of particle size, materials, and composition, there were certain empirical differences in results. Accordingly, reference to a cation exchange resin by its trade name are used herein, means the product as made by the named manufacturer on the filing date of this application.

[0040] When a calcium cation resin is used it is preferable to pretreat the sorbitol dextrose mixture coming from the hydrogenation reactor to an ordinary cation exchange process to remove nickel and other cations or alternatively to pre-treat the dextrose composition to remove cations prior to hydrogenation. In this case the same or different cation exchange resin in acid form can be used in true cation exchange capacity as a guard column to immobilize the nickel prior to loading of the SMB apparatus. Figure 8 illustrates the nickel breakthrough capacity of one exemplary guard column prepared using a Dowex 88 resin in H⁺ form. When a nickel containing cation resin is used in the SMB apparatus, such compositions can be made without pretreatment. However, the extract stream and raffinate streams are then preferably treated by cation exchange for removal of trace nickel that leaches from the SMB resin.

[0041] The method of the present invention can utilize larger bead resins, preferably beads of 320 microns or larger. This allows use of all types of industrial simulated moving bed equipment and systems, unlike smaller bead resins that can be used only with limited types of systems.

[0042] In an exemplary embodiment, a 12 segment SMB apparatus with a total column volume of 250 ml was operated with the parameters shown in Table 1 below. In such a system, the flow velocity of the system can be between 1.8 m/h (5.3 ml/min) and 12.7 m/h (37.5 ml/min) and even higher. The solids content of the feed is preferably between 30-35%. In the Table below the inputs flows into the SMB device are as follows:

Feed - the flow of initially input sorbitol glucose mixture

Enrichment– the flow of a portion of the sorbitol extract outflow that is recycled back into SMB apparatus to a column segment within the enrichment zone Water– the flow of eluent into the input elution segment of the SMB apparatus Reload– the flow of a portion of the output from the raffinate that is reloaded to a column segment within an adsorption zone of the SMB apparatus

Product– the outflow of the sorbitol enriched product

Raffinate– the outflow of the dextrose enriched material separated from the sorbitol

[0043] Other exemplary embodiments are illustrated by the following non-limiting examples.

EXAMPLE 1

Pulse test to demonstrate separation with calcium resin

[0044] A pulse test is used to determine if a selected column matrix can be usefully implemented in a simulated moving bed configuration by demonstrating whether the species desired to be separated can be separated in a single discrete pass over the resin. Pulse tests were run using the following procedures:

[0045] Bed Conditioning: 100 ml of desired resin (slurried in deionized (DI) water) was loaded into a jacketed glass (15mm x 600mm) column and any air bubbles in resin bed were removed. The resin was rinsed with approximately 5 Bed Volumes (BV) of DI water, conditioned with approximately 10 BV of 5% hydrochloric acid, and followed with 5 BV of DI water. 10 BV of 5% calcium chloride was run through the resin, and chased with 10 BV of DI water.

[0046] Pulse Test: The column jacket was connected to a water bath and the temperature set to 50°C. After the resin was conditioned, the valve on top of column was opened, then liquid level was lowered until even with top of resin bed. A pulse of feed material (10 ml of sorbitol spiked with 5% dextrose) was added and again the liquid level was lowered to the top of resin bed. 1-2 ml of DI water was added onto top of resin bed and the valve on top closed. DI water elution flow was started at 4 mls per min and 8 ml fraction collection was begun. Suitable separation of sorbitol and dextrose over a Dowex 99 320 Ca+ resin was demonstrated as shown in Figure 3.

EXAMPLE 2

Comparative pulse testing for calcium and nickel form resins [0047] Pulse testing was performed essentially as described in Example 1. The results are shown in Figures 6 and 7. Although the resolution of the separation was lower with nickel the results show the resin can separate the dextrose from the sorbitol in the nickel form or calcium form. The successful use of a nickel cation exchange resin is surprising because nickel is not known to be used in the separation of carbohydrates, and may be particularly useful in the present invention for separating sorbitol from dextrose if the hydrogenation reaction uses nickel as the hydrogenation catalyst because there is no need to remove nickel from the SMB input apparatus as any input nickel will bind to vacant anion residues on the cation exchange resin.

EXAMPLE 3

SMB separation of sorbitol and dextrose with a pilot test mixture

[0048] The results of the pulse test were used to configure parameters for operating a simulated moving bed configuration for a pilot C-SEP™ system comprised of a 3000 ml column divided into 12 segments as schematically depicted in Figure 4. The system was run using an initial feed of about 30% wt/wt sorbitol spiked with 5% wt/wt dextrose. The feed was loaded into column segment 8, the product collected from column segment 3, the raffinate collected from column segment 12 and the water eluent was input into column segment 2. Operating conditions and separations results were as shown in Table 2. Results showed quantitative recovery of sorbitol with 100% rejection of dextrose from the sorbitol extract.

EXAMPLE 4

SMB separation of sorbitol and dextrose mixture from a hydrogenation reactor

[0049] After several test of the system with larger amounts of the pilot text mixture, an actual dextrose/sorbitol mixture produced from a hydrogenation reactor was tested, which contained about 34% wt/wt total dissolved solids including 0.5% or less dissolved dextrose. The system configuration was modified as shown in Figure 5. The feed was loaded into column segment 9, the product collected from column segment 5, the raffinate collected from column segment 12 and the water eluent was input into column segment 2. Operating conditions and separations results were as shown in Table 3.

[0050] The results showed quantitative recovery of sorbitol and dextrose with 100% rejection of the dextrose from the final sorbitol extract.

EXAMPLE 5

Guard column for pretreatment to remove nickel

[0051] Resin Conditioning: 100 ml of Dowex 88 resin (slurried in DI water) was loaded into a jacketed glass (15mm x 600mm) column and any air bubbles in resin bed were removed. The resin was rinsed with approximately 5 Bed Volumes (BV) of DI water, conditioned with approximately 10 BV of 5% hydrochloric acid, to convert the resin into the hydrogen form; and followed with 5 BV of DI water. The resin was maintained in the conditioned sulfonate form.

[0052] Breakthrough Test: After the resin was conditioned, the feed pump was set to 10 ml/min and the fraction collector set to 0.8 minutes step time. The feed was a sorbitol/dextrose mixture obtained from a hydrogenation reactor having a nickel catalyst and contained about 0.5% dextrose with the remainder being sorbitol. The flow was started at 10 mls per min and 8 ml fraction collection was begun. The breakthrough test results indicated the guard column had the capacity to remove nickel from the input with a resin capacity of 1.76 Eq/L. A graph showing the breakthrough profile is shown in Figure 8.

EXAMPLE 6

Purolite cation exchange

[0053] After the initial experimentation using the Dowex 99320 resin, a Purolite cation exchange resin was tested in the SMB apparatus because comparative pulse tests shown in Figure 9 indicated less peak spreading for both sorbitol and dextrose using the Purolite resin, which means that higher concentrations of the mixture may be separated. Purolite PCR642 was installed and operated in the same C-SEP apparatus configuration as set forth in Figure 5. The system was then run with same dextrose/sorbitol mixture produced by the hydrogenation reaction (~0.5% dextrose. The run conditions and results are set forth in Table 4.

Table 4

Results with SMB separation using Purolite Resin

[0054] Again results showed near quantitative recovery of sorbitol with 100% rejection of dextrose from the final sorbitol extract.

[0055] From the foregoing it will be seen that this invention is one well adapted to attain all ends and objectives herein-above set forth, together with the other advantages which are inherent to the invention.

[0056] Since many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matters herein set forth or shown in the accompanying drawings are to be interpreted as illustrative, and not in a limiting sense.

[0057] While specific embodiments have been shown and discussed, various modifications may of course be made, and the invention is not limited to the specific forms or arrangement of parts and steps described herein, except insofar as such limitations are included in the following claims. Further, it will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

Claims

1. A method for continuous production and separation of sorbitol from dextrose comprising:

hydrogenating a dextrose composition to produce an outflow mixture of sorbitol and dextrose in a continuous reaction;

contacting the outflow mixture with a matrix containing a strong acid cation exchange resin in a simulated moving bed chromatography apparatus;

recovering an extract stream comprising 99.5% or greater sorbitol; and

recovering a raffinate stream depleted of sorbitol and enriched in dextrose relative to the outflow mixture.

2. The method of claim 1, wherein said extract stream comprises at least 99.7% sorbitol.

3. The method of claim 2, wherein said extract stream comprises at least 99.9% sorbitol.

4. The method of claim 1, further comprising a step of recycling said raffinate stream to said hydrogenation step.

5. The method of claim 1, wherein said mixture comprises 5% or less dextrose.

6. The method of claim 1, wherein the dextrose composition comprises dextrose and maltodextrin and the mixture of sorbitol and dextrose additionally comprises hydrogenated maltodextrin, and wherein the raffinate stream is enriched in dextrose and hydrogenated maltodextrin relative to the mixture.

7. The method of claim 6, further comprising steps of removing the hydrogenated maltodextrin from the raffinate and recycling the remaining raffinate stream into said hydrogenation step.

8. The method of claim 1, further comprising, recycling a portion of the extract stream into an enrichment zone of the simulated moving bed chromatography apparatus.

9. The method of claim 1 further comprising continuously operating the simulated moving bed apparatus while continuously performing the hydrogenation.

10. The method of claim 1, wherein the dextrose composition comprises dextrose and isomaltodextrin and the mixture of sorbitol and dextrose additionally comprises hydrogenated isomaltodextrin and wherein the raffinate stream is enriched in dextrose and hydrogenated isomaltodextrin relative to the mixture.

11. The method of claim 10, further comprising, prior to said hydrogenating step, a step of forming the dextrose composition by contacting a starch with sufficient glucoamylase for a period of time to convert a portion of the starch to isomaltodextrin.

12. The method of claim 10, wherein said dextrose composition comprises up to 10% isomaltodextrin.

13. The method of claim 10, further comprising steps of removing the hydrogenated isomaltodextrin from the raffinate and of recycling said raffinate stream into said hydrogenation step.

14. The method of any of claim 1 to 13, wherein said simulated moving bed apparatus is a standard simulated moving bed apparatus.

15. The method of any of claims 1 to 13, wherein said dextrose composition is obtained by saccharifying a starch by contacting the starch with a sufficient amount of alpha amylase and glucoamylase to form the dextrose composition containing at least 90% dextrose.

16. The method of any of claims 1 to 13, comprising recovery of no more than two streams from said apparatus.

17. The method of any of claims 1 to 13, wherein the matrix comprises beads 320 microns or larger.

18. The method of any of claims 1 to 13, wherein said resin is selected from the group consisting of a calcium cation resin and a nickel cation resin.

19. The method of any of claims 1 to 13, wherein prior to contacting the outflow mixture with the matrix of cation exchange resin, the outflow mixture is contacted with a cation exchange resin in an acid form thereby removing cations from outflow mixture.

20. A method for continuous production and separation of a desired hydrogenated compound from a mixture of compounds contained in the product of a continuous carbohydrate hydrogenation reaction, comprising:

continuously obtaining the mixture of compounds from a reaction that hydrogenates a carbohydrate;

contacting the mixture with a matrix containing a strong acid cation exchange resin in a standard simulated moving bed chromatography apparatus, wherein the mixture comprises the desired hydrogenated compound and one or more secondary compounds;

recovering an extract stream enriched in the desired hydrogenated compound and depleted of the secondary compounds relative to the mixture of compounds; and

recovering a raffinate stream depleted of the desired compound and enriched in the secondary compounds relative to the mixture of compounds.

21. The method of claim 20, wherein the desired compound is sorbitol and the secondary compounds are selected form the group consisting of dextrose, hydrogenated maltodextrin, and hydrogenated isomaltodextrin.