FI59388C - FOERFARANDE FOER FRAMSTAELLNING AV EN PAO XYLITOL ANRIKAD VATTENLOESNING AV POLYOLER - Google Patents

Description

RSrTI ΓβΊ ANNOUNCEMENT PUBLICATION, SU CO 7Qfl IBJ (11) utlAgg NI NGSSKm FT 5 90ÖÖ • 25 C (4¾ Fat'-riUi α ^ η-t; y 10 00 1001 ^ (51) Kv.ik.3 / mt.a. 3 CO? C 31/18, 29/76 ENGLISH I - FI N LAN D (21) P »t« mlh »k« mu * - Pw «it« n.eknln | 1281/74 (22) HikwnliptMl - Arattknlngtdig 25 OU 74

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National Board of Patents and Patent Administration .... ...... ..., ___.

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Patent- och ragitterstyraiMn 'AmBfcan utlagd och uti.skrifttn public · ™ * 30. OU. 81 (32) (33) (31) «ruolk ·» · »—Begird prlorlm 25.0U. 73 USA (US) 354391 (71) Suomen Sokeri Osakeyhtiö, Mannerheimintie 15, 00250 Helsinki 25, Finland (Finland) (72) Asko J. Melaja, Kantvik, Lauri Hämäläinen, Kantvik, Heikki Olavi Heikkilä ^ Kantvik, Finland-Finland The present invention relates to a process for the preparation of an aqueous solution of xylitol-enriched polyols from a mixture obtained by hydrolysis of xylitol-enriched polyols by hydrolysis. the raw material under acidic conditions, removing suspended solids by mechanical filtration, removing inorganic salts and most of the dyes and other organic impurities by ion exclusion, removing the rest of the dyes and other organic impurities by treating the solution with optionally hydrolyzing resin and / or activated carbon, after chromatographic fractionation.

In the prior art, there are many methods for making xylitol from natural products such as birch wood, corn cobs, cottonseed husks, and the like. The Russian-language article by Pro R. Vieil and G. D. Soboleva, Proizvotro Ksilita (Manufacture of Xylitol), Moscow, 1962, provides a review of well-known methods.

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Recent publications on this subject include, for example, U.S. Patent Nos. 3,212,932 and 3,558,725 »and also British Patent No. 1,209,900 and Soviet Patent No. 167 8 ^ 5, 1965.

Previous methods have not been used on any large scale on a commercial scale because they are not economically viable. Thus, for example, the xylose-containing solutions obtained from wood chips have been so impure that a number of expensive purification steps have been required before a solution is obtained so pure that it can be hydrogenated to form xylitol.

It is known that sugar alcohols and sugars can be separated on analytical columns using alcohol or alcohol-water mixtures containing more than 80% ethanol as eluents (see e.g. Acta Chemica Scandinavia 22 (1968) 1252-1258). However, it is not known to separate, for example, xylitol on a technical scale using water as eluent. The eluent used strongly influences the separation (see e.g. J. Chromatography, 68 (1972) 267-269, especially the table on page 268). The analytical method cannot be scaled up to a technical scale because the high flow resistance of the column, the uneven flow in the column and the high dilution of the solutions obtained make the method uneconomical. Thus, the prior art method of preparing xylitol cannot be predicted from the prior art.

According to the present invention, an improved process for the preparation of xylitol from raw materials containing pentosan, in particular xylan, has now been developed. The process according to the invention is characterized in that an aqueous polyol solution containing 25-55% by weight of polyols is passed through a 2.5-5 m long column packed with 3-6% of divinylbenzene crosslinked with Fe +++ or

With a polystyrene sulfonate cation exchange resin in the form of an Al +++ salt, 3. . . ....

at a flow rate of about 0.2-1.5 m per hour and a cross-section of the resin column per square meter, and eluting with water, the xylitol-enriched fractions are recovered in a manner known per se.

f

The raw materials used as raw materials for obtaining pentosan-containing solutions are preferably lignocellulosic materials, for example wood from various wood species, such as birch and beech. Also useful are oat husks, corn ears and stalks, coconut shells, almond shells, straw, bagasse and cottonseed shells. In the case of the use of wood, it is reduced to chips, planer chips or sawdust, for example.

The invention will be described in more detail with reference to Figures 1-7 · 59388 3

Figure 1 is a flow chart generally showing the steps in the preparation of xylose and xylitol.

Figure 2 is a flow chart showing the recovery of xylitol from a hydrogenated pentose solution.

Figure 3 is a flow chart showing a process for preparing xylitol from wood chips.

Figure 1 * shows the distribution of sorbitol and xylitol in successive fractions; co. the chromatographic separation method using the resin in Subform is explained in more detail in Example 1.

Figure 5 shows the distribution of five polyols in successive fractions; co. the chromatographic separation method is explained in more detail in Example 2.

Figure 6 shows the distribution of different polyols into successive fractions; co. the chromatographic separation method is explained in more detail in Example 3-

Figure 7 shows the distribution of different polyols into successive fractions; co. the chromatographic separation method is explained in more detail in Example U.

As can be seen from the figure, the raw material is hydrolyzed following a method well known in the art. Suitable methods disclosed in the literature include, for example, those described in U.S. Patent Nos. 2,730,836, 2,759,856, 2,801,939, 2,976,067, and 3,212,932. and that the resulting pentose-containing solution is neutralized using substances that do not adversely affect; a suitable base is sodium hydroxide. In the case where the pentose material is obtained by methods other than acid hydrolysis, the desalting step (ion exclusion step) described below is not always required.

The next step is to purify the hydrolysis product. The purification step comprises two main steps: (1) removal of the salt (usually sodium sulfate) and most of the organic impurities and dyes by ion exclusion methods, and (2) final removal of the dyes.

The ion exclusion method removes the salt from the solution; similar methods have been used in the sugar industry for the purification of molasses (see U.S. Patents Nos. 2,890,972 and 2,937,959); and then passing the solution through a column containing further adsorbent or activated carbon. These methods are also known in the sugar industry (see U.S. Patent No. 3,558,725, and J. Stamberg and V. Valter's * 59388 "Entfärbungsharze", Akademie Verlag, Berlin, 1970 and P. Smit , "Ionenaustauscher und Adsorber bei der Hestellung und Reinigung von Zuckern, Pektinen und verwandten Stoffen", Akademie Verlag, Berlin, 1969 and J · Hassler, "Activated carbon", Leonard Hill, London, 1967.

The purification step can be further improved by adding a step using a synthetic macroreticular adsorbent such as Amberlite XZD 2 to remove organic impurities. The macroreticular adsorbent can be used in a purification treatment immediately following the ion separation step, but before the cation exchanger. Alternatively, it may be the final step in the cleaning treatment.

The resulting purified pentose solution is hydrogenated and treated according to the method shown in Figure 2. The hydrogenation treatment is carried out in the same way as for the hydrogenation of glucose to sorbitol (see W. Schnyder's dissertation "The Hydrogenation of Glucose to Sorbitol with Raney Nickel Catalyst",

Polytechnical Institute of Brooklyn, 1962.

Thus, it has now been discovered that xylitol can be fractionated from a hydrogenated hydrolyzate solution using ion exchange chromatographic methods. At the same time, the non-hydrogenated sugars in solution, which are eluted from the column before the polyols, can be removed. Thus, the process of the present invention can produce pure polyols even if the hydrogenation is incomplete; if desired, the hydrogenation can be carried out as a continuous process.

The cation exchange resin used is sulfonated polystyrene crosslinked with divinylbenzene. Resins in the form of Al +++ or Fe +++ have several advantages over resin in the alkaline earth metal form. For example, the polyols elute from the resin in the Al +++ or Fe +++ form in a different order from the resin in the alkaline earth metal form.

The method according to the invention thus gives e.g. improved mainly by the separation of the impurity, sorbitol; thus, thanks to the process according to the invention, it is possible to avoid the accumulation of sorbitol in the polyol solution to be fractionated.

Example 1 This example illustrates the separation of sorbitol from xylitol in aqueous solution of sorbitol and xylitol using 3.5 / 5 divinylbenzene crosslinked sulfonated polystyrene cation exchange resins which were cationic +. +. ++. +++ + +++. ++ forms: H, Li, Ni, Mg, Fe, NH 4, Al and Cu, and eluting with water.

..... +++ +++

The female of the cations Fe and Al gave the best results. The results of the experiments are shown in the following table: 5 59388

Fractionation result of xylitol and sorbitol

Test number Cation Kp Kp HETP (cm) Rg sorbitol xylitol xylitol 1 H + 0,5 ^ 0,79 0,10 0,30 2 Li + 0,52 0,53 0,23 0,07 3 Mg ++ 0,1 + 9 0 .5 * + 0.1 + 0 0.27 1+ Ni ++ 0.1 + 2 0.1 + 5 0.13 0.2h 5 Fe +++ 0, U2 0.1 + 8 0.11 0.1 + 1 + 6 NH 4 + 0.5 * + 0.59 0.11 0.33 7 Al +++ 0.1 + 1 0.1 + 8 0.10 0.1 + 8 8 Cu ** 0.1 + 5 0.50 0.12 0.1 + 1

Calculated values: Kp = Partition coefficient HETP = height equivalent of the theoretical base R = resolution s

Partition coefficients, HETP values, and resolution values for difference treatments were calculated. These values are parameters normally used to evaluate column separations and are calculated according to the following formulas:

V -V

«B - 2-2- - s —hs

R

8 m2 + m1

Kp = Partition coefficient HETP = height equivalent of the theoretical base R * resolution s

Ve = peak elution volume VQ = resin column cavity volume = total resin column volume h = resin column height N - number of theoretical bases M = width of the eluted peak, measured on the volume (or time) axis in volume (or time) units.

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From an examination of the table above, it is apparent that sorbitol elutes before xylitol and that Fe +++ and Al +++ give the best difference.

The conditions used in the experiments were as follows: column: height 81+ cm; diameter U, l + cm

temperature: 50 ° C

feed rate 32 ml / minute resin: polystyrene sulfonate, crosslinked with 3-1 + / f divinylbenzene; grain size 0.18 mm; A mixture of sorbitol and xylitol (1: 1) to be treated in the form of Al +++; total amount 25 g substance: dry matter; concentration 35 weight #.

The results obtained are shown in Figure 1+, where curve 1 represents the starting material mixture, curve 2 xylitol and curve 3 sorbitol.

Example 2 This example shows the separation of each of the five polyols from the hydrated wood hydrolysates using the cation exchange resin described in Example 1 in the Fe +++ form. The results are shown graphically in Figure 5, where curve 1 represents the starting material, curve 2 xylitol, curve 3 mannitol, curve U sorbitol, curve 5 galactitol and curve 6 arabinitol. The conditions in this example were as follows: column: height 8U cm; diameter U, U cm

temperature: 52 ° C

feed rate: 32 ml / minute resin: polystyrene sulfonate, crosslinked with 3-1 * i di vinylbenzene; grain size 0.18 mm; Aqueous polyol solution to be treated in Fe form; total amount 23.5 g dry matter; total substance: concentration 35% The composition of the solution was as follows: mannitol θ, 9 ί arabinitol 9.1% galactitol 5.1% xylitol 6h, 0% sorbitol 12.9% eluent: water Example 3 This example illustrates the presence of separation of five polyols using the cation exchange resin described in Example 1 in the AI form. The separation conditions were as follows: column: height 82 cm; diameter 1 +, 1 + cm

temperature: 51 ° C

feed rate: 32 ml / minute resin: same as in Example 1, aqueous polyol solution treated in Al +++ form; total dry matter 23.5 g, content substance:. 34.9 composition the same as in Example 2.

eluent: water

The results obtained are shown in the following table.

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Table • +++

Separation of polyols using AI resin

Fraction No. Mannitol Arabinitol Galactitol Xylitol Sorbitol (20 ml) ggggg 1 a) b) 0.09 0.09 - - - 0.02 0.02 2 0.18 0.27 - - 0.05 0.05 - - 0.18 0.20 3 0.27 0.5 ** 0.07 0.07 0.13 0.18 0.02 0.02 0.3 ** 0.5 * + ** 0.39 0 .93 0.18 0.25 0.23 0, ** 1 0.23 0.25 0.56 1.10 5 0.1 * 3 1.36 0.27 0.52 0.27 0.68 0 .52 0.77 0.66 1.76 6 0.3 * 4 1.70 0.39 0.91 0.23 0.91 1.92 2.69 0.56 2.32 2_ 0.23 1, 93 0.1 * 3 1.3 ** 0.16 1.07 3.05 5.7 * + 0.3 ** 2.66 8 0.11 2, oi * 0.39 1.73 0.09 1.16 3.29 9.03 0.21 2.87 9 0.05 2.09 0.29 2.02 0.05 1.21 3.05 12.08 0.11 2.98 10 - 0, 13 2.15 - - 2.03 1 **, 11 0.05 3.03 11 - - - 0.79 1 * 4.90 12 - - - 0.13 15.03 Total 2.09 2.15 1 .21 15.03 3.03 8.9% 9.1% 5.1% 61 «.0% 12.9%

Distribution of polyols when fractions are combined a) 1-6 / 7-12 or b) 1-7 / 8-12.

Combination a) Combination b)

Polyol and content (% of total amount) 1 ^ 6 7 ~ 12_1-7 8-12 mannitol 82% 18% 92% S% arabinitol 1 * 2 58 62 38 galactitol 76 2 * + 89 11 xylitol 18 82 38 62 the results are also shown in Figure 6, where curves 1-6 represent the same as in Figure 5 (see Example 2).

Example U

This example illustrates a method similar to Example 3 above and differs from it only in the feed rate used. The dimensions of the column and the resins used were the same as in Example 3. The temperature used was 50 ° C and the feed rate was 22 ml per minute. The feed solution was an aqueous polyol solution of 25 g in total and containing 35% dry matter.

The results obtained in this example are shown in Figure 7. where the curves Ι-c · represent the same as in Figures 5 and 6.