JPH0617327B2 - Method for producing xylitol - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of the Invention The present invention comprises the steps of steaming or blasting a xylan-containing natural product,
The present invention relates to a method for producing xylitol, which is useful as an infusion solution, by hydrolyzing an aqueous solution obtained by extraction with water under a pressure of hydrogen using a catalyst and simultaneously adding hydrogen.

2. Description of the Related Art As a conventionally known method for producing xylitol, a hemicellulose aqueous solution containing xylan as a main component, which is obtained by steaming or blasting a xylan-containing natural product and then extracting it, is hydrolyzed with 2 to 5% sulfuric acid. To obtain an aqueous xylose solution, which is then subjected to purification operations such as neutralization, decolorization and deionization, concentration and crystallization to obtain xylose crystals, which are further dissolved in water and under hydrogen pressure using a catalyst such as nickel. Hydrogenation and a series of purification steps followed by concentration and crystallization to obtain xylitol, and as described in Japanese Patent Publication No. 49-48288, xylan-containing natural products are pretreated with a small amount of acid. Washing with water, removing ash from xylan-containing natural products and adding strong acid salt etc. as a hydrolyzing agent together with a hydrogenation catalyst in an acid or acidic aqueous solution, and extracting and hydrolyzing under high temperature and hydrogen pressure. A method is known in which xylitol is obtained by simultaneously performing hydrogenation.

Problems to be Solved by the Invention However, the conventional methods have various drawbacks. For example, in the method proposed above, xylose is obtained by hydrolyzing a xylan-containing natural product with sulfuric acid. In this case, since xylose is a sugar that is relatively weak to acid, xylose is decomposed or colored. There are drawbacks such as peeling off and a decrease in yield, and further, a neutralization step is required,
There were also drawbacks such as the difficulty in separating the calcium sulfate formed at that time, and the fact that xylose was held in the calcium sulfate and the xylose yield was further reduced.

The above-mentioned method proposed as an improved method also has many drawbacks. For example, when xylan is extracted from a xylan-containing natural product or when the xylan is hydrolyzed, an acid is added as a hydrolyzing agent, which causes poisoning of the hydrogenation catalyst and reduction in its activity. Furthermore, those acids must be removed during the refining process, which means that an ion exchange load is added during the process. Moreover, since the process directly carries out extraction, hydrolysis and hydrogenation simultaneously from the xylan-containing natural product, it is almost impossible to recover the catalyst from the reaction residue, and it is extremely difficult to reuse the catalyst or use the extraction residue. There is also the drawback that

In addition, the use of acid also has a significant impact on equipment materials. In other words, all equipment from the process of adding acid to the process of neutralization or deionization must be acid resistant equipment, which requires extremely expensive glass lining equipment and titanium-clad equipment, which is very economical. It was a disadvantage.

Means for Solving the Problems As a result of intensive studies to overcome the various drawbacks as described above, the present inventors have steamed or blasted a xylan-containing natural product under specific conditions, and extracted xylan with water. The obtained aqueous solution is hydrolyzed under a specific condition under a hydrogen pressure by using a catalyst and hydrogenated at the same time, so that the yield of xylitol is not lowered so much, and the acid-resistant equipment is not required in a short process. Moreover, we have completed an extremely advantageous method for producing xylitol, which allows the reuse of catalysts and reaction residues.

That is, a xylan-containing natural product is steamed or exploded by a known technique, but the reaction condition is set to a temperature of 130.
-230 ° C, time 1-60 minutes to release the acetyl group in the xylan-containing natural product that has been blasted or steamed to make the pH of the solution 3-4 and facilitate the subsequent extraction with water or warm water. I found that I can do it. To the liquid obtained by extracting the xylan-containing natural product treated in this way with water or warm water, activated carbon of about 5 to 10% of the solid content of the solution is added to adsorb catalyst poisons such as proteins in the solution, and filtered. After the activated carbon is removed by the above, the hydrolysis is carried out, and at the same time, a hydrogenation reaction is carried out.

At this time, the reaction conditions must be delicately selected so that the hydrolysis of xylan and the xylose produced can be immediately hydrogenated in the same reaction vessel. It is preferable that the reaction conditions are low pH and high temperature for a relatively long time in order to carry out hydrolysis sufficiently, but since xylose produced as a result of hydrolysis of xylan is a chemically weak sugar, conditions for hydrogenation reaction are required. Is because it is advantageous to be as mild as possible.

That is, by using a Raney nickel catalyst for hydrogenation or a ruthenium catalyst for hydrogenation with about 5 to 20% of solid content in the solution, the hydrogen pressure is 50 to 150 kg / cm ² , the temperature is 160 to 200 ° C., and the reaction time is 60 to 180 minutes. We succeeded in hydrolyzing xylan sufficiently and hydrogenating while suppressing the decomposition of xylose produced. Further, the catalyst was removed from the reaction solution and purified by a conventional method such as deionization, concentrated and crystallized to obtain xylitol crystals.

As described above, in the present invention, a known cooking / explosion technique is used for extracting hemicellulose (xylan) from a xylan-containing natural product, but in order to facilitate the subsequent operations and reactions. The steaming and blasting conditions are limited to a certain range before use.

Further, since water or warm water can be used when extracting hemicellulose, it is possible to react without hydrolyzing a hemicellulose without newly adding a hydrolyzing agent such as an acid, since there is no need for neutralization. The purification load is low, the activity of the catalyst can be suppressed, and the catalyst can be recovered, resulting in a high xylitol yield and a xylitol production method that has significantly improved the drawbacks of the conventional method.

Next, the present invention will be specifically described with reference to examples.

Example 1 10 kg of air-dried birch chips were steamed at 200 ° C. for 10 minutes, and then 20 kg of water was used to wash out hemicellulose from the birch steamed product to obtain an extract having a concentration of 8%.

To 500 g of this extract, 2.0 g of activated carbon was added, and
After stirring for hours, the activated carbon is filtered. Commercially available Raney nickel catalyst (Nikko Rikagaku Sangyo Co., Ltd.) 3.0 g in the filtrate
And add it to an electromagnetic stirring stainless steel autoclave with an internal volume of 1. Hydrogen gas of 100 kg / cm ^{2 was} filled in this, and the reaction was carried out by stirring at a temperature of 180 ° C. for 2 hours.

After filtering the catalyst, the filtrate was subjected to a conventional method by using Amberlite IR-120H type 120 ml and IRA-410OH type 2
Deionized and purified with 40 ml (Organo Shokai), the deionized solution was concentrated under reduced pressure to a total amount of 35 g, 35 ml of methanol was added, and the mixture was allowed to stand for a day and night to precipitate colorless xylite crystals. This was filtered and dried to obtain 16.0 g of xylit (melting point: 90.2 ° C).

Example 2 10 kg of air-dried cotton seed shells were subjected to blasting treatment at 230 ° C. for 1 minute and then extracted with 30 kg of water to obtain a liquid having a concentration of 10%.

To 500 g of this extract, 4.0 g of nickel catalyst was added and charged with hydrogen gas of 50 kg / cm ² , and the reaction was carried out at a reaction temperature of 200 ° C. for 60 minutes in the apparatus of Example 1.

Then, the same treatment as in Example 1 was performed to obtain 45 g of deionized liquid.
After concentrating, the mixture was added with 45 ml of methanol to obtain 24.5 g of xylite crystals (melting point 91.5 ° C).

Example 3 10 kg of air-dried bagasse was steam-treated at 150 ° C. for 30 minutes and then extracted with 30 kg of water to obtain a liquid having a concentration of 4%.

To 500 g of this extract, 4 g of 0.5% ruthenium carbon catalyst (manufactured by Nippon Engelhard) was added to obtain 130 kg of hydrogen gas.
/ Cm ² and the reaction is carried out in the apparatus of Example 1 at a reaction temperature of 160 ° C. for 180 minutes.

Thereafter, the same treatment as in Example 1 was performed to obtain 15 g of deionized liquid.
The mixture was concentrated to 15 ml and methanol (15 ml) was added to obtain 7.8 g of xylite crystals (melting point: 90.5 ° C).

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Yoshimasa Onuki Yoshimasa Onuki 1112-19 Araijuku, Kawaguchi City, Saitama, Ryosei Dormitory (56) References JP 46-1815 (JP, A) JP 54-85287 (JP, A) JP-A-53-35005 (JP, A) JP-B-51-33177 (JP, B1) JP-B-49-48288 (JP, B1)

Claims (1)

[Claims] 1. A xylan-containing natural product at a temperature of 130 to 230.
After steaming or blasting at 1 ℃ for 60 minutes, extract with water to obtain an aqueous solution under hydrogen pressure at a temperature of 150 to 2
A method for producing xylitol, which comprises hydrolyzing at the same time with Raney nickel catalyst or ruthenium catalyst under conditions of 00 ° C. for 60 to 180 minutes and hydrogenating.