KR0144348B1 - Method of manufacturing lactulose - Google Patents

Abstract

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Description

Method of manufacturing lactulose

The present invention relates to a method for producing lactulose, wherein an alkaline aqueous solution of lactulose and borax is prepared, heated at a temperature of 80 ° C. or lower, and the actulose is separated from the resulting conversion product. This method is known, for example, from Chemical Abstracts 86: 173382h. Since conversion requires an alkaline medium, an additional sodium hydroxide solution is added. This method has a relatively high yield; Boric acid forms a complex with lactulose, which shifts the equilibrium away from lactose. Moreover, galactose, tagatose, other sugars, organic acids, dyes and the like are formed as conversion products from lactorose. It is an object of the present invention to provide a method for preparing lactulose which is similar in terms of economics but is safer in state. According to the present invention, this object is achieved by the fact that, apart from borax in the above-mentioned process, it can also be carried out even when substantially no alkaline substances are added to the solution. Therefore, the sewage load by the alkaline salt (which is formed upon regeneration of the divorce exchanger after alkali ions are removed by the ion exchanger) is significantly reduced. As an additional step in this regard, the process can recycle sodium ions according to two modified embodiments of the present invention: one embodiment comprises boric acid in an aqueous boric acid solution, preferably containing lactose simultaneously. And sodium ions are transferred from the conversion product solution to the boric acid solution by electrodialysis. In this way, complete recycling of sodium ions is possible. For this purpose, only two compartments separated by a cation exchange membrane are needed. One compartment is a cathode compartment, through which a boric acid solution, preferably a boric acid-lactose solution flows. The conversion product solution flows through another compartment, the anode compartment. Under the applied voltage, sodium ions migrate to the first compartment and a borax solution is formed in this compartment. In another embodiment, the sodium ions are removed from the conversion product solution as substantially as safely as possible by the weak acid ion exchanger and then the strong acid ion exchanger, preferably the weak acid ion exchanger is at least partially regenerated by boric acid, and then the borax formed Includes at least partially reused.

In other words: As long as the sodium ion concentration in the conversion product solution is high so that the weak acid ion exchanger can also bind to sodium ions, such ion exchanger can be used. The strong acid ion exchanger is then only used to completely separate the sodium ions from the solution. As a result of the preferred regeneration of the weak acid ion exchanger with boric acid, the bound sodium ions thereby remain in the production cycle. Only the rest is removed from the sewage. However, even when the weak acid ion exchanger is not regenerated by boric acid, its use is beneficial. In any case it can be regenerated by weak acids and is better from an ecological point of view. For example, carbonic acid is ecologically safe.

In a further embodiment of the process according to the invention, in order to separate lactulose, the sodium ions are separated and then evaporated, preferably 15 to 20% dry matter, before or after the separation of the borate ions, The product solution is passed through a long vessel, preferably at 30 to 60 ° C., as a chromatography column in which water is used as eluent and packed with a weak base ion exchanger. This new use of ion exchangers allows for excellent separation of not only lactulose but also galactose from the mixture of reaction products. Lactulose can be obtained with a purity of 99% or more, which could have been possible on an industrial scale only until very expensive until recently. To prepare lactulose powder as a final step of the process and modified embodiments of the present invention, a concentrated lactulose solution, preferably with stirring, of a concentrated lactulose solution having a purity of at least 90% based on the dry matter It is added very slowly to the powder, preferably sprayed, and very rapidly and very finely distributed so that the lactulose solution always forms only a thin thin film on the surface of the powder particles, thereby allowing the solid material to grow in the powder particles. Finally suggest.

It is known that lactulose cannot be crystallized only by concentrating the aqueous solution. To date, methanol or other organic solvents have been added to prepare lactulose powders, in which lactulose has low solubility and precipitates. Thereafter, the mechanically separated and dried powder is always contaminated by solvent residues. On the other hand, the proposed novel method can produce freely-flowing, high purity hygroscopically weak lactulose powder. An important point in this method is the slow addition of lactulose syrup onto the granules, rapid dispensing and spreading to form a thin film. Only local accumulation of syrup should be avoided. First of all, the already crystallized material should not be re-dissolved in the syrup. Suitable for this purpose are, for example, hot air dryers with spray dryers, paddle dryers and stirring devices. Formation of borax solution by electrodialysis, removal of sodium ions from inverted product by weak acid ion exchanger, separation of lactulose by weak base ion exchanger as chromatography column and preparation of lactulose powder Although advantageously combined within, each of these methods may also be used individually to obtain certain advantages.

EXAMPLE

175 kg of lactose-monohydrate, 46.3 kg of borax and 800 kg of deionized water are heated at 95 ° C. and maintained at this temperature for 3 hours. A mixture of reaction products is formed, comprising substantially 74.2 kg of lactulose, 75.3 kg of lactose, 8.0 kg of galactose and 0.8 kg of tagatose. The resulting sugar mixture solution is passed through a weak acid ion exchanger and then through a strong acid ion exchanger to remove sodium ions derived from borax. The solution is then evaporated to 15% dry matter. The solution at this concentration is passed through a chromatography column containing weak base ion exchanger. In fact, the column is about 90 cm in diameter and 2 m in height and is a hollow cylinder filled with 1000 L of weak base ion exchange resin. 1000 L of the solution is added to a column already filled with water and continuously replenished with water at a flow rate of 1 to 2 bed volumes / hour at a temperature of 40 to 60 ° C.

The diagram below shows the separation of the solution components. There is only a small loss and an almost pure lactulose fraction can be obtained in the absence of other sugars. The clear separation of lactose and lactulose is particularly surprising.

The fished lactulose solution is liberated from boric acid in the boron-specific exchanger and then evaporated to 65% lactulose content, for example under a vacuum of 40 mbar. In this way, a commercially available syrup is obtained. Such syrup can also be converted into a powder. For example, for this purpose, a steam gun with a total capacity of 200 L and a usable content of 130 L and a stirrer speed of 10 rpm

Use early (Dedietrich SP 200). 20 kg of lactulose powder are placed in a container and a total of 100 kg of syrup heated at 60 ° C. is flowed out at a flow rate of 2 L / hour. The whole is then dried for 30 minutes. 20 kg of the resulting powder is left as a sample for the next batch. Instead of adding borax as mentioned above, the following method may be used. 175 kg of lactose-monohydrate, 30 kg of boric acid and 600 kg of deionized water are dissolved under stirring at about 45 ° C. and passed through a weak acid ion exchanger loaded with sodium ions. Elution is carried out using deionized water. Regenerate the ion exchanger at least partially with boric acid and adjust the resulting solution to pH8.3 (ie, pH-value of lactose-borax solution) using sodium hydroxide solution.

Subsequently, the conversion takes place with the solution.

Claims (10)

In the process for preparing an alkaline aqueous solution of lactose and borax, heating at a temperature of 80 ℃ or more, and separating the lactulose from the resulting conversion product to produce lactulose, apart from borax, an alkaline substance is added to the solution. Characterized by substantially no addition. The process of claim 1 wherein borax is prepared in an aqueous boric acid solution containing lactose simultaneously, wherein sodium ions are transferred from the conversion product solution to the boric acid solution by electrodialysis. The process according to claim 1, wherein the lactulose separation step is carried out by passing the inverted product solution through the weak acid ion exchanger and subsequently through the strong acid ion exchanger. The method according to claim 3, wherein the weak acid ion exchanger is regenerated in whole or in part by boric acid, and all or part of the borax formed during regeneration is used for the initial preparation of the lactose-borax solution. 5. The reaction product solution according to claim 1, wherein water is used as eluent and a weak base ion exchanger is used to separate lactulose, before separating sodium ions and then separating borate ions. Characterized by passing through a long chromatographic column at 30-60 ° C. The method according to any one of claims 1 to 4, wherein in order to produce lactulose powder, a concentrated lactulose solution having a purity of 90% or more based on the dry matter is added very slowly to the moving lactulose powder. And very rapidly and finely decomposing so that the lactulose solution always forms a thin film on the surface of the powder particles, thereby allowing the solid material to grow in the powder particles. The reaction product solution according to claim 5, wherein water is used as eluent and the weak base ion exchange isolating sodium ions to separate lactulose and then evaporating with 15 to 20% dry matter and then separating borate ions. Passing through a long sieve filled column chromatography at 30-60 ° C. The method according to claim 5, in order to prepare lactulose powder, a concentrated lactulose solution having a purity of 90% or more based on dry matter is added very slowly to the moving lactulose powder, and very rapidly and finely. Dispensing so that the lactulose solution always forms a thin film on the surface of the particles so that the solid material grows in the powder particles. The method of claim 6, wherein the concentrated lactulose solution is added by spraying the stirred lactulose powder. The method of claim 8 wherein the concentrated lactulose solution is added by spraying the stirred lactulose powder.