KR900001221B1 - Process for purifying arabinose - Google Patents

Abstract

An arabinose is recovered by selective solid bed adsorption from the aq. raw mixt. contg. monosaccharide (selected from a gp. of aldopentose and aldohexose) and arabinose. The process comprises (a) contacting the mixt. with barium-glass adsorbent i.e. y-type zeolite for selective adsorbing arabinose, (b) removing non-adsorbed at the contacting state (with desorbent i.e. water) by the simulated moving bed flow, and (c) desorbing/recovering highly pure arabinose.

Description

How to separate arabinose

1 is a schematic representation of the retention of adsorbents on sugars and pigments.

2 is a graphical representation of the relative retention of sugars by adsorbents.

3 is a schematic representation of the retention of sugars by the X-type adsorbent.

The technical field of the present invention relates to solid-bed adsorptive separation of monosaccharides. In particular, the present invention relates to a method for separating arabinose from a mixture consisting of arabinose and one or more additional pentose and / or hexose. This method uses an adsorbent consisting of crystalline aluminosilicate that selectively adsorbs arabinose from the feed mixture.

Methods of using crystalline aluminum silicates to separate hydrocarbons are well known in the separation art. Examples of such separation methods are described in US Pat. Nos. 2,985,589 and 3,201,491, in which A-type zeolites are used to separate normal paraffins from side chain paraffins. Methods of using phossite to separate olefin hydrocarbons from paraffin hydrocarbons are described in US Pat. Nos. 3,265,750 and 3,510,423.

For the separation of non-hydrocarbons, certain monosaccharas from carbohydrate stock mixtures

In particular, the present invention relates to a method for separating arabinose from another monosaccharide. The production of pure arabinose is of commercial importance in terms of efficiency as starting material for the production of L-glucose, a non-nutritive sweetener. Common sources of arabinose include, but are not limited to, products of hemicellulose in the manufacture of pulp from wood, or products produced in the process of converting plant tissues to sugars by biomass operations. . Regardless of these sources, arabinose is typically found in a mixture of many monosaccharides. Therefore, a simple method for separating arabinose from other monosaccharides present in the source mixture is of paramount importance. However, when arabinose is finally used as food, the separation process should not contain impurities that form adjunct products unsuitable for human consumption or contaminate arabinose.

Particular methods of isolating arabinose are known in the art. US Patent No. 3,160,624 describes a method for separating D (L) -arabinose from D (L) -ribose by chromatography using cellulose powder ion exchange resin.

US Pat. No. 4,516,566 describes a method for separating L-arabinose from sugar mixtures present in the hydrolyzate of wood and beet pulp. In the present invention, X-type zeolites exchanged with barium cations are described as adsorbents. Because of the toxicity of barium, this separation process involves application difficulties to produce edible arabose. Therefore, a barium-glass adsorbent is needed to carry out this separation.

Additional data on adsorbents that can be used to separate mannose from other monosaccharides are described in US Pat. No. 4,471,114. The patent records data relating to the use of a Y-type poser site containing calcium cations as adsorbent to separate mannose from other monosaccharides. Contrary to the above, it has been found that barium-glass poser sites containing calcium ions at the cation exchange site are suitable adsorbents for separating arabinose from other monosaccharide aldoses. Moreover, these zeolites having calcium cations instead of barium cations are used to purify arabinose in a process suitable for the food industry.

A broad object of the present invention is to separate arabinose from a raw mixture containing arabinose and aldopentose or aldohexose using an X or Y type zeolite having a calcium cation at the calcium site of the cation exchange site. To provide a way.

In brief, the present invention is a method for separating arabinose from a raw mixture consisting of arabinose and at least one other monosaccharide selected from the group consisting of aldopentose and aldohexose. The method comprises contacting a monosaccharide mixture with a barium-glass adsorbent composed of X-type zeolite or Y-type zeolite containing calcium cations at the cation exchange site under adsorption conditions, and substantially removing other monosaccharides to remove arabinose. After adsorbing selectively, the raw material mixture of the non-adsorbed portion is removed in contact with the adsorbent, and then the purified arabinose is desorbed and recovered under desorption conditions.

As will be described later with another object (and specific examples) of the present invention, it relates to certain raw material mixtures, adsorbent desorbents, operating conditions and flow arrangements.

In these processes, it is useful and advantageous to define the terms used herein in order to clearly understand the operating state and the object.

The term "raw mixture" means at least one extract component and at least one raffinate component separated by this process. "Raw material stream" refers to a stream of raw material mixture through an adsorbent used in this process.

"Extraction component" means a component that is more selectively adsorbed by an adsorbent. The term “desorbent material” generally refers to a substance that can desorb an extract component. "Desorbent stream" or "desorbent" "inlet stream" refers to a stream passing through the adsorbent in the desorbent material, and "rapinate stream" or "rapinate effluent stream" is a stream in which the raffinate component is removed from the desorbent. Means. The composition of the raffinate stream can vary from essentially 100% desorbent to 100% raffinate component. ＂Extraction Stream＂ or ＂＂ ＂＂ ＂＂

The barium-glass adsorbent material of the present invention consists of Form X and Form Y crystalline aluminosilicates with calcium cations at cation exchange sites. Form X and Form Y crystalline aluminosilicates or zeolites can also be classified as poser sites. As in the general case of all zeolites, these crystalline compounds are described as a three-dimensional network structure of basic structural units consisting of silicon-simulated Sio ₄ and aluminum-simulated AlO ₄ tetrahedra linked together to share oxygen atoms at their vertices.

The spaces between the tetrahedrons are filled with water molecules, resulting in a continuous or partial dehydration at the molecular level, resulting in crystal structures intertwined with molecular channels. Zeolites are described and defined in more detail in US Pat. Nos. 2,883,244 and 3,120,007, which are incorporated herein by reference. X or Y zeolites in dehydrated or partially dehydrated form may be represented by molar oxides, respectively, as shown in Structural Formulas 1 and 2 below.

[Formula 1]

(0.9 ± 0.2) M ₂ ' _n O: AL ₂ O ₃ : (2.50 ± 0.5) SiO ₂ : yH ₂ O

[Formula 2]

(0.9 ± 0.2) M ₂ ' _n O AL ₂ O ₃ : wSiO ₂ : yH ₂ O

The electrical valence of this tetrahedron occupies a cation exchange site in the zeolite, and the structural formula is balanced by the cation ＂M＂. These cations, which are sodium at the time of manufacture, can be replaced by other cations by conventional ion exchange methods well known to those skilled in the art of crystalline aluminosilicates. This method is generally carried out by contacting the zeolite or adsorbent material, including the zeolite, with an aqueous solution of the preferred cation or soluble salt of the cation when present on the zeolite. After the desired exchange has occurred, these sieves are removed from the aqueous solution, washed and dried to the desired water content.

By this method, sodium cations and non-sodium cations that are likely to occupy exchange sites in the impurity state in sodium -X or sodium -Y zeolites can be partially or nearly completely different cations. It is essential that the zeolites used in the process of the invention contain calcium cations at the cation exchange site.

Typically the adsorbents used in the separation process contain zeolite crystals and amorphous materials. Zeolites are generally present in the adsorbent in the range of about 75% to about 98% by weight based on the nonvolatile material. Residues of adsorbents generally consist of amorphous materials such as silica or silica-alumina mixtures or mixtures such as clay.

Typically, the adsorbents are in the form of particles such as extracts, aggregates, tablets, macrospheres or granules having a range of desirable particle sizes. The adsorbents used in this process preferably have a particle size range of about 16-40 mesh (US standard mesh) equal to a nominal aperture of 0.42-1.19 mm. The inventors have found that X or Y zeolites with calcium cations and amorphous binders have selectivity and other necessary conditions as described above, and therefore are suitable for use in this process. However, calcium exchanged Y-type zeolites are particularly preferred.

Carbohydrates or simple sugars are classified as monosaccharides. These monosaccharides are hydroxy aldehydes or hydroxy ketones with one ketone or aldehyde unit per molecule and two or more alcohol functional groups. Such monosaccharides are classified as alloses or ketoses based on their carbonyl units. Keroose and aldose are also classified by their carbon skeleton length. Thus, monosaccharides of carbon 5 and carbon 6 are named pentoses and hexose, respectively. Known aldohexose or glucose, mannose and galactose.

Arabinos and xylose are well known as aldofenose. Examples of common ketohexose include fructose and sorbose. The present invention is another egg

Thus, the raw mixture used in the process of the present invention consists of a mixture of arabinose and at least one other aldose. In fact, potential raw mixtures containing actual amounts of aldose removed from other monosaccharides are generally found in hydrolysates of plant tissues. Such mixtures usually contain significant amounts of monosaccharides such as xylose, arabinose, mannose, glucose, and galactose. In addition to these common sugars, the raw mixtures derived from natural sources contain a small amount of monosaccharides which are not well known.

Exemplary raw material mixtures of the present invention are based on the weight percent of solids, xylose, arabino in each ratio in the range of 0.5% -50%, 4.0% -25%, 1.0% -5.0% and 50% -20%. It contains os, mannose, glucose and galactose. In addition, it contains less-known sugars up to 10% by weight solids. However, the present invention can be used not only for the separation of natural raw material mixtures, but also for the separation of arabinose from other aldoses in sugar mixtures synthesized or produced by the carbohydrate processing.

It is not clear how the nature of the adsorbent is involved in the separation of arabinose as described herein, but it cannot be said that only the process size selectivity of the adsorbent contributes to the separation. Since arabinose is separated from sugar molecules of similar size, steric factors as well as electrostatic attraction play an important role in the separation. After all, it is impossible to assert assertively that molecular attraction is responsible for adsorption, but it is possible to explain that the open processing on the adsorbent combines cationic attraction that changes the orientation of a particular sugar molecule.

This altered orientation can provide a suitable arrangement of sugar molecules and corresponding special structures, such as the shape of the open pores of the adsorbent, altered by the presence of certain cations. Therefore, the mechanism for this separation can be provided not only by physical and stoichiometric considerations but also by electrostatic interactions.

Although it is possible to produce high purity arabinose by the process of the present invention, the extraction component is not completely adsorbed by the adsorbent and the raffinate component is not completely adsorbed by the adsorbent, therefore, a small amount of raffinate component It can appear in this extraction stream, and likewise, small amounts of extraction components can appear in the raffinate stream.

The extract and raffinate stream are then further classified to each other and further classified from the raw mixture by the concentration ratio of the extract component and the specific raffinate component present in the particular fraction. For example, the concentration ratio of optionally more adsorbed arabinose to the concentration of selectively less adsorbed sugars is highest in the extraction stream, then higher in the feed mixture, and lowest in the raffinate stream. Likewise, the ratio of selectively less adsorbed sugars to optionally more adsorbed arabinose is highest in the raffinate stream, then higher in the feed mixture, and lowest in the extract stream.

Desorbent materials used in the various adsorptive separation processes of the prior art vary depending on factors such as the type of work used. The selection of desorbents is not critical in bed systems where selectively adsorbed raw material components are removed from the adsorbent by the purge stream.

In general, however, in adsorptive separation processes operated continuously to maintain a liquid phase at a constant pressure and temperature, the desorbent material is carefully selected to meet many criteria.

Secondly, the desorbent material must be compatible with certain adsorbents and certain raw material mixtures. More specifically, the desorbent material should not reduce or destroy the critical selectivity by the adsorbent of the extract component to the raffinate component.

In addition, the desorbent material must not react chemically or cause a chemical reaction of the extract or raffinate component. The extract stream and the raffinate stream are typically removed from the adsorbent in admixture with the desorbent material, and any chemical reaction involving the desorbent and the extracting or raffinate component may be used to extract the extract or raffinate product, or both. Decreases the purity. Since the raffinate stream and the extract stream typically contain a desorbent material, additionally the desorbent material must be a material that can be easily separated from the raw mixture passing through the process. If at least some of the desorbent material present in the extract stream and the raffinate stream is not separated, the concentration of the extract component in the extract product and the concentration of the raffinate component in the raffinate product are not very high, and the desorbent material is not useful. Cannot be reused in this process.

At least a portion of the desorbent material will be separated from the extract and raffinate streams by distillation or evaporation, but also other separation methods such as reverse osmosis alone or distillation.

In the prior art, although not absolutely necessary, it has been recognized that adsorbents and desorbents having specific properties are highly desirable for successful implementation of selective adsorption processes. This property is equally important in this process. Such characteristics include adsorption capacity expressed as the volume of extraction component per volume of adsorbent; Selective adsorption of the extract component to the raffinate component and the desorbent material; And sufficiently fast adsorption and desorption rates of the extraction components to and from the adsorbent. Of course, the capacity of the adsorbent to adsorb a specific volume of extraction components is essential; Without this capacity, the adsorbent is useless in the adsorptive separation process. Moreover, the higher the capacity of the adsorbent for the extract component, the better the adsorbent.

Increasing the capacity of a particular adsorbent may reduce the amount of adsorbent required to separate the extract component of known concentration at a particular charge rate of the feed mixture. The cost of the separation process can be reduced by reducing the amount of adsorbent required for a particular adsorptive separation. It is important that the good initial capacity of the adsorbent be maintained economically desirable during the separation process under practical use. The second necessary adsorbent property is the ability of the adsorbent to separate the components of the raw material. In other words, the adsorbent has adsorption selectivity (B) for one component as compared to the other components. Relative selectivity is not only for one raw material component compared to the other ingredients, but also for the raw material mixture component and the desorbent

[Equation 1]

In the above formula, C and D are two components of the raw material expressed in weight percent, and subscripts A and U represent adsorption and nonadsorption phases, respectively.

Equilibrium is defined when the composition of the raw material passing over the adsorbent bed does not change even after contact with the adsorbent bed. In other words, there is no total mass transfer between the nonadsorbed and adsorption phases. If the selectivity of the two components is close to 1.0, no preferential adsorption of the components to the other components by the adsorbent occurs; That is, the two components are adsorbed (or non-adsorbed) to the same extent to each other. If (B) is less than or greater than 1.0, one component is preferentially adsorbed to another component by the adsorbent. Comparing the selectivity by component C adsorbent with respect to component D, when (B) is at least 1.0, component C is preferentially adsorbed in the adsorbent.

When (B) is 1.0 or less, component D preferentially adsorbs, leaving more component C in the non-adsorption phase and leaving more component D in the adsorption phase. Ideally, the desorbent materials should all have a selectivity equal to or slightly less than about 1 for the extract component, which means that all extract components desorb at the proper flow rate of the desorbent and the extract components are subjected to a continuous adsorption step. In order to be able to substitute the desorbent material. In contrast, raffinate

Due to the fast exchange rate, a small amount of desorbent material is pumped through the process and again a small amount of desorbent material is separated from the extract stream for reuse.

The desorption-sorption operation is carried out in a dense fixed bed which is in alternating contact with the raw material mixture and the desorbent material, in which case the process proceeds only semi-continuously. In another specific example, commonly referred to as a wing bed system, two or more sets of stationary beds of adsorbent are used with appropriate valves so that the raw material mixture passes through one or more sets of adsorbent beds, and the desorbent material It is intended to pass through one or more of the other beds in a set. The flow of raw mixture and desorbent material is present above or below through the adsorbents in these beds. Any device used for fluid-solid contact in a stationary bed may be used.

However, this bed or similar moving bed flow system has a higher separation efficiency than a fixed bed system and is therefore preferred. In this bed or similar moving bed process

D.B. Broughtion's US Patent No. 2,985,589 describes the principle and sequence of operation of such a flow system, as well as the “Continuous Adsorptive Processing--A New Separation Technology” (34th Annual Meeting, Tokyo, Japan, April 1, 1969). A pseudo mobile bed countercurrent process flow schematic is described in more detail in a paper entitled DBBroughtion's presentation of the Society of Chemical Enginner. Another specific example of a pseudo mobile bed flow system suitable for use in the process of the present invention describes a highly efficient cocurrent pseudo mobile bed process described in US Pat. No. 4,402,832 to Gerhold, which is incorporated herein by reference.

While the present invention is practiced in any form of flow system, the method of operation will affect the adsorbent selection. Since the swing bed system is less sensitive to desorbent selection, the process will work well with any material selected from the broad class of desorbents mentioned above. However, in general, in adsorptive separation processes operated at constant pressure and temperature to maintain a liquid phase, the desorbent material must be selected more carefully.

The process in which the abovementioned preferred class of desorbents provides the greatest advantage is in the continuous separation process.

At least a portion of the extract effluent stream passes through the separation device and at least there

Both liquid and vapor phase operations can be used in many adsorptive separation processes, but liquid phase operations are required for this process because they yield higher yields than the yields of extractable products obtainable by vapor phase operations and require low temperatures. Adsorption conditions include a temperature in the range of about 20 ° C. to about 200 ° C. (preferably about 20 ° C. to about 100 ° C.) and a pressure range of about 500 psing (3448 kPa gage) (preferably to maintain the liquid phase at atmospheric pressure). Pressure). Desorption conditions include the same temperature and pressure ranges as used for adsorption conditions.

The size of the unit that can utilize the process of the present invention can vary anywhere from the pilot plant scale (unit of reference to U.S. Patent No. 3,706,812, the assignee of this application, to commercial scale, from a small flow rate of several CCs per hour) They range from a flow rate of thousands of gallons per hour.

The following examples are disclosed to illustrate the process of the invention and are not intended to limit the scope of the appended claims.

Mechanical test equipment was used to test various adsorbents with raw material mixtures and desorbent materials to measure adsorbent properties such as adsorption capacity, selectivity and exchange rate. The apparatus consists of an approximately 70 cc volume adsorption reactor with inlets and outlets at opposite ends of the reactor. The reactor is in a thermostat, in addition a pressure regulator is used to operate the reactor at a predetermined constant pressure. A chromatographic analyzer can be attached to the outlet line of the reactor and used to quantitatively inspect or quantitatively examine one or more components in the discharge stream exiting the adsorption reactor. Pulse tests performed using this apparatus and the following general process are used to determine selectivity and other data for various adsorbent systems. The adsorbent is filled to equilibrate with the particular desorbent material by passing the desorbent material through the adsorbent reactor. At any time, a pulse of stock is injected for several minutes containing a known concentration of non-adsorbed polysaccharide chase maltrin-DP ₄₊ aldodo and other trace sugars diluted with desorbent.

The tracer and aldose are eluted as a liquid-solid chromatographic operation after resumption of the desorbent flow. Emissions are collected fractionally and analyzed using the chromatographic apparatus and the trajectory of the envelope corresponding to the developed component peaks.

From the information obtained in the test, the adsorbent performance can be estimated by the retention volume for the extract or raffinate component, the selectivity of one component for the other, and the desorption rate of the extract component by the desorbent.

The retention volume of the extract and raffinate component is peak ³ of the extract or raffinate component.

The following examples are disclosed to further illustrate the process of the present invention, not to limit the scope of the process.

The examples show the test results for various desorbent materials and adsorbent materials when using the mechanical test apparatus.

Example 1

In this example, the test was carried out using Y-type zeolites with Ca ions at the cation exchange site to determine the separation of arabinose from the carbohydrate mixture. The calcium exchanged Y-type zeolite of this example is bound to the organic binder and has an average bulk density of 0.71 gm / ml. The adsorbent is packed in a 8.4 mm diameter column with a total volume of 70 cc. The raw material mixture, consisting of 30 ml of the carbohydrate mixture shown in Table 1, was diluted with 70 ml distilled water to obtain a solution containing 22% solids.

Table 1

In addition, the raw material mixture contains a small amount of the dye. The experiment was started by passing a water desorbent through the column at a flow rate of 1.22 cc / min and a temperature of 65 ° C. At any time, 10 ml of raw material were injected into the column after the flow of the desorbent started immediately. 1 is a schematic representation of the retention of adsorbents on sugars and pigments.

The profile of the chromosome was determined by measuring ultraviolet adsorption at 320 mm.

The mean midpoint of each concentration curve represents the optimal separation of arabinose from the chromosomes as well as other raw material mixture sugars. It is clear that arabinose is the most selectively retained ingredient. On the other hand, although some arabinose curves are actually in the xylose-galactose curves, this is due to the large number of unseparated xyloses present in the raw material and does not mean that they are ineffective in carrying out the separation. From the data obtained from the experiments, the selectivity in Table 2 was calculated.

[Table 2]

These selectivity clearly indicates that the arabinose has been separated to a significant extent.

Example 2

To demonstrate the separation of arabinose from other raw material mixtures, another test was conducted using the Y zeolite of Example I and the same test apparatus. The raw material mixture consists of the carbohydrate mixture of Table 3 diluted with distilled water to be a solution containing 20% by weight solids.

Table 3

The experiment was started by passing the water desorbent through the column in an upflow manner at a flow rate of 0.81 cc / min and a temperature of 65 ° C. At one point, 10 ml of the raw mixture per pulse was injected into the column immediately after the flow of the desorbent began. Figure 2 graphically shows the relative retention of sugars by adsorbents.

Considering the mean midpoint of the component envelope, it is clear that arabinose was well separated from mannose and glucose. From this information, the selectivity of arabinose to glucose is 2.63 and the selectivity of arabinose to mannose is 1.23, and calcium-Y type adsorbent can quantitatively separate mannose as well as glucose from arabinose. It can be shown. In addition, these data indicate that the separation of arabinose from fructose does not occur, so adsorbents make this significant prediction.

Example 3

The use of calcium-X zeolites as adsorbents is demonstrated in this test. Type X zeolites in this experiment contain calcium ions at the cation exchange site, are bound in organic binders, and have an average bulk density of 0.83 gm / ml. This adsorbent was packed into a 8.4 mm diameter column with a total volume of 70 cc. One hop raw material was prepared, diluted with water desorbent and containing the carbohydrates of Table 4.

Table 4

Initially, the desorbent was passed through the column at a flow rate of 1.08 cc / min and a temperature of 65 ° C. Thereafter, 10 ml of the raw material solution was injected into the column. After injection, the desorbent flow resumed. The retention of sugars by the type X adsorbent is shown schematically in FIG. By comparing the mean midpoints for each component curve, it can be seen that arabinose was well separated from other raw mixture sugars. In this data, the overall midpoint for the arabinose curve is clearly located to the right of the other curve. Therefore, the separation of the present invention can be carried out using an X-type zeolite.

Claims (7)

A method for separating arabinose from a water-soluble raw material mixture comprising monosaccharides and arabinose selected from the group consisting of aldopentose and aldo hexose, wherein the adsorption condition has a calcium cation A barium-glass adsorbent composed of Y or X zeolite is contacted with the mixture and selectively adsorbs the arabinose to exclude the monosaccharide, and the non-adsorbed portion of the raw material mixture is in contact with the desorbent After the removal in a desorbed conditions, the desorption conditions of the arabinose, characterized in that to recover a high purity arabinose. The method of claim 1, wherein the raw material mixture comprises monosaccharides and arabinose selected from the group consisting of xylose, glocoose, galactose, mannose and rhamnose. The method of claim 1 wherein the desorbent is comprised of water. 4. A method according to claim 3, wherein the adsorbent consists of a Y-type zeolite having a calcium cation in the exchangeable cation site. The method of claim 1, wherein said separation is performed in a simulated moving bed flow scheme. 6. The method of claim 5 wherein said pseudo moving bed flow uses a countercurrent flow. 6. The method of claim 5 wherein said pseudo moving bed flow uses cocurrent flow.

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