FI61518C - FOERFARANDE FOER FRAMSTAELLNING AV XYLOSLOESNING - Google Patents

Description

1% λβ »» · 1 [Β] ni> ADVERTISING PUBLICATION

Ma IBJ ν ') UTLÄGG NINGSSKRI FT O \ 0 \ ö ^ ^ (51) Kv.lk?/lnt.CI.3 C 13 K 13/00 FINLAND —FINLAND (21) P »t» nttlh «k * n ^ -P «t.nt« «» BknJn, 792520 (22) H * k * ml * ptJvt — An * 5knln (* d * f lU.08.79 ^ ^ (23) AlkuplM— GHtlghetadag 25 · 0L. 71 * (41 ) Tullut JulklMkal - Bllvtt lU. 08.79

Patent and Registry Administrators .......... .___ θΛ _ *. (44) Nlhttvllulpmon | » the date of the month. - 30.0U.82

Patent · och raglttarstyralaan Anaftktn utl * | d oeh utl ^ krlftan puMlnred (32) (33) (31) Pyydrtty ttuollwui — fttglrd priortut 25 .OU.73 USA (US) 35U391 (71) Suomen Sokeri Osakeyhtiö, Mannerheimintie 15, 00250 Helsinki 25,

Finland-Finland (FI) (72) Asko J. Melaja, Kantvik, Lauri Hämäläinen, Kantvik, Heikki Olavi Heikkilä, Kantvik, Finland-Finland (FI) (7U) Oy Kolster Ab (5U) Method for preparing xylose solution - Förfarande för framställ- The present invention relates to a process for preparing a solution of xylose containing 85 to 90% by weight of xylose, based on dry matter, from a solution which is separated from the application of 1281 / 7U (patent 59388) -Avdelad frän trap 1281 / 7U (patent 59388). has been obtained by acid hydrolysis of a pentosan-containing feedstock.

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

Recent publications on this subject include, for example, U.S. Patent Nos. 3,212,932 and 3,558,725, as well as British Patent No. 1,209,960 and Soviet Patent No. 167,845, 1965.

2 61518 These 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 numerous expensive purification steps have been required before such a pure xylose solution is obtained.

It is known from Acta Chem. Scand. 22 (1968) No. 4, 1252-1258 distinguishes e.g. sugars in aqueous-ethanol mixtures by chromatographic method. However, this known method is an analytical method and cannot be applied industrially because, firstly, very dilute solutions are used and, secondly, the columns are very small and filled with a very fine resin 11a.

Instead, the method according to the invention is well suited for industrial use.

It is also known to purify sugar solutions by the ion-exclusion method (FI 1 355/72 and DOS 2 224 794).

The ion exclusion method separates sugars from inorganic substances and high molecular weight substances. However, this difference is not sufficient to obtain pure xylose. In addition to xylose, glucose, galactose, mannose, arabinose and other sugars derived from the raw material are present in the starting solution, and the xylose purity of the solution is low (70-75% of the dry matter). Pure xylose cannot be separated from the solution thus purified, for example by crystallization.

According to the invention, the separation of xylose is carried out chromatographically, using a resin in the form of an alkaline earth metal. The resulting xylose solution can be directly hydrogenated to xylitol to give pure xylitol.

The process according to the invention is characterized by the following combination of steps known per se: a) removing inorganic salts and most of the organic impurities and dye by ion exclusion, b) removing the rest of the dye and other organic impurities by treating the solution with ion exchange resin 11a or activated carbon, and c) with a dry matter content of 25 to 55% by weight, by chromatographic ion exchange methods 1 "· · 3 61518, using an alkaline earth metal salt of a polystyrene sulfonate cation exchanger crosslinked with divinylbenzene, and the solution is uniformly passed to the top of the resin column at a rate of 0.2. , 5 m hours] per square meter of resin column cross-section, and successively recovering from the downstream side of the resin layer 1) a dilute fraction containing mostly water but also other pentoses and a little xylose, 2) an intermediate fraction with a high xylose content. a containing small amounts of other pentoses, and 3) a final fraction containing mainly non-xylose pentoses.

It is surprising that the process according to the invention makes it possible to prepare a solution of xylose with a purity of 85-90% with respect to xylose from a rather complex starting material mixture. The resulting xylose solution is so pure that it can be directly hydrogenated to xylitol on an industrial scale if desired.

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 1-3.

Fig. 1 is a flow chart generally showing a method according to the present invention.

Figure 2 is a flow chart showing four options for purifying pentose sugar solutions prior to the chromatographic step.

Fig. 3 is a flow chart showing a material equilibrium diagram for making xylose from wood chips.

As shown in Figure 1, the feedstock is hydrolyzed in the first step of the present invention following a method well known in the art. Suitable methods disclosed in the literature include, for example, those described in U.S. Patent Nos. 2,734,836, 2,759,856, 2,801,939, 2,974,067 and 3,212,932.

4,61518 The most important considerations in selecting a suitable hydrolysis method are the maximum yield of pentoses that can be achieved and the fact that the resulting pentose-containing solution is neutralized using substances that do not adversely affect; a suitable base is sodium hydroxide.

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 to refine molasses (see U.S. Patent Nos. 2,890,972 and 2,937,959).

The small amounts of organic and inorganic impurities remaining in the solution are removed by ion exchange systems comprising a strong cation exchanger followed by a weak anion exchanger, followed by 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 in J. Stamberg and V. Valter, "Entfärbungsharze", Akademie Verlag, Berlin, 1970, and P. Smit, "Ionenaustauscher und Adsorber of the Manufacture and Processing of Zuckern, Pectic and Verwandten Stoffen ", Akademie Verlag, Berlin, 1969 and J. Hassler," Activated carbon ", Leonard Hill, London, 1967.

The purification step can be further improved (see Figure 2) 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 the purification treatment immediately following the ion exclusion step, but before the cation exchanger (see Figure 2). Alternatively, it may be the final step in the cleaning treatment.

Xylose is separated from the purified pentose solution obtained in the purification step, as shown in Figure 1, by chromatographic fractionation to obtain a solution of high purity for xylose. The fractionation uses a strongly acidic cation exchanger, namely a 3.5% divinylbenzene crosslinked sulfonated s 61518 polystyrene resin in the form of an alkaline earth metal salt. Elute with water, and sequentially collect three groups of fractions, of which the intermediate fraction contains xylose. The pentose molasses formed by the non-selected fractions may be subjected to further chromatographic fractionation treatments to recover one or more other sugars therein. Alternatively, it can be used as a source of carbohydrate in fermentation processes.

The following examples illustrate the invention.

Example I

Birch in the form of chips is used to produce xylose according to the method of the present invention. The mass balance diagram for this example is shown in Figure 3.

Hydrolyze an amount of birch wood chips equivalent to 1 000 g of dry matter with sulfuric acid to give a mixture of hydrolyzate and pulp containing a total of 225 g of xylose. The pulp containing 51 g of xylan is removed from the hydrolyzate and either discarded or used for some other purpose. The rest of the mixture is neutralized with sodium hydroxide to give a hydrolyzate containing 204 g of xylose, 110 g of other organic matter and 67 g of inorganic matter. The hydrolyzate is then heated to remove volatile acids and water, and the salts are then removed by ion exclusion. Finally, the solution is purified by passing it sequentially through layers of a strong cation scavenger and a weak anion exchanger. As shown in the figure, m g of xylose is then removed together with the main part of the inorganic substance and some organic matter (so-called salt fraction). The sugar fraction, which contains most of the xylose and some of the organic impurities and a small amount of inorganic impurities, is re-evaporated. The resulting concentrated sugar solution is passed through a decolorization step and an activated carbon layer. The solution thus purified contains 181 g of xylose together with 40 g of organic matter.

The resulting xylose-rich solution is further purified by chromatographic fractionation on an ion exchange resin column using the method described below. The composition of the solids content of the xylose-rich solution, determined by gas chromatographic analysis, is as follows: r> -; '6 61518

Sugar Content (%) arabinose 6 xylose 78 mannose 7.5 galactose 5 glucose H, 5 The resin used is a sulphonated polystyrene resin cross-linked with 3.5% divinylbenzene in the form of calcium. The average grain size of the resin is 0.32 mm. The separation is performed at 49 ° C. The height of the column is 350 cm and the diameter is 22.5 cm.

The column is immersed in water. The xylose-rich solution is fed uniformly to the cross section of the column at a rate of 17 l / h. The total amount of sugar fed to the column is 4 kg and the solids content of the solution is 26%.

The liquid initially leaving the column, in an amount of 88 liters, mostly comprising water, is discarded. Successive fractions are then pooled and analyzed to give the following results:

Fraction Glucose- Xylo- Mannoo- Galacto- Arabinose (g) si (g) si (g) si (g) si (g) 18 41-- 2 91 165 3 75 497 4 8 704 25 5 - 720 91 25 6 - 580 124 83 7 - 289 58 41 8 8 - 83 7 66 9 - 8 99 10 - 66

Fractions 3-6 are combined to give 35 liters of a xylose-silica solution having the following composition: *; ; 7 61518

Sugar Amount (g) arabinose xylose 2,483 (= 85%) mannose 240 galactose 108 glucose 83

Example II

The xylose-rich solution obtained as described in Figure 1 is purified by chromatography on a 1.0 m high, 9.4 cm diameter column with a strontium form of 3.5% divinylbenzene crosslinked sulfonated polystyrene resin. Water is applied to the column, followed by a solution of pentose with a dry matter content of 25% and the following composition:

Sugar Content (% of dry matter) xylose 73 arabinose 6.1 mannose 9.0 galactose 5.1 glucose 6.8

The solution is fed to the top of the column uniformly with respect to the cross-section at a rate of 27 ml per minute until a total of 60 g of solids have been fed to the column. The first 108 ml of material that has passed through the column, consisting mainly of water initially in the column, is discarded. The analysis of the fractions obtained is shown in Table II below.

. n - 61518 8

Table II

Sugar content of fractions (g)

Fraction Glucose- Xylo- Mannoo- Galactic- Arabinose si toli si 1 0.2 2 0.35 3 0.75 0.2 - 4 1.1 0.9 5 1.0 4.4 0.05 6 0.45 9.05 0.3 0.1 7 0.2 11.65 0.6 0.3 8 0.05 9.8 1.0 0.6 9 - 5.0 1.3 0.9 10 - 1.85 1, 05 0.6 0.5 11 - 0.75 0.7 0.35 0.8 12 - 0, 2 0.35 0.15 1, 1 13 0.05 0.05 0, 8 14 - 0.4 15 - 0.1

Combining fractions 6, 7 and 8 gives a solution with a xylose purity of 89% (calculated on dry weight).

Example III

The xylose-rich solution obtained by hydrolyzing birch wood and then performing desalting and decolorization treatments as described above is further purified by chromatographic fractionation. The composition of the solids content of the xylose-rich solution, determined by gas chromatographic analysis, is as follows:

Sugar Content (%) arabinose 6.5 xylose 77 mannose 8 galactose 4 glucose 4.5 The resin used is a sulphonated polystyrene resin crosslinked with 3.5% divinylbenzene in the form of strontium. The average particle size of the resin is 0.32 mm. The separation is performed at a temperature of 51,61818 ° C. The height of the column is 350 cm and the diameter is 22.5 cm.

The column is immersed in water. The xylose-rich solution is fed uniformly to the column cross-section at a rate of 15 liters per hour and the total amount of sugar fed to the column is 4 kg and the solution has a new solids content of 2 8%.

The liquid leaving the column first, 88 liters and consisting mainly of water, is discarded. Successive fractions are then pooled and analyzed to give the following results:

Fraction Glucose- Xylo- Mannoo- Galacto-Arabinose (g) si (g) si (g) si (g) si (g) 1 8 41 2 83 157 3 75 447 4 7 662 - 5 - 696 33 8 6 - 580 91 40 7 - 331 108 75 25 8 - 124 66 33 91 9 - 41 17 7 99 10 - 10 41

Fractions 3-6 are combined to give 35 liters of a xylose solution with a concentration of:

Sugar Content (g) arabinose xylose 2,385 (= 90%) mannose 124 galactose 48 glucose 82

Claims (1)

A process for preparing a xylose solution containing 85 to 90% by weight of xylose, calculated on the dry matter, from a solution obtained by acid hydrolysis of a pentosan-containing raw material, characterized by the following combination of steps known per se: a) removing inorganic salts and most of the organic inorganic b) removing the remainder of the dye and other organic impurities by treating the solution with an ion exchange resin or activated carbon, and c) fractionating the resulting solution with a dry matter content of 25-55% by weight by chromatographic ion exchange methods using cross-linked polysilenized polybenzylbenzene an alkaline earth metal salt of a sulfonate cation exchanger, and the solution is uniformly applied to the top surface of the resin column at a flow rate of 0.2-1.5 m per hour and per square meter of resin column cross-section, and successively recovered downstream of the resin layer. from 1. a dilute fraction containing mostly water but also other pentoses and little xylose, 2. an intermediate fraction with a high xylose content containing small amounts of other pentoses, and 3. a final fraction containing mainly pentoses other than xylose. ·.