JPH03232894A - Preparation of alkylglycoside - Google Patents

Abstract

PURPOSE:To prepare the subject compound having no color and no odor and having a high quality by bringing an alkylglycoside or a crude alkyl glycoside containing an unreacted alcohol and impurities into contact with a polar adsorbent and subsequently successively bringing the treated adsorbent into contact with an unreacted alcohol-releasing solvent and then with an alkylglucoside- isolating solvent. CONSTITUTION:A crude alkylglycoside prepared by acetalizing a saccharide with a higher alcohol, or a solution of the crude alkylglycoside in an unreacted alcohol-releasing solvent is brought into contact with a polar adsorbent (preferably activated alumina or silica gel having particle sizes of 100-500mum and pore diameters of 50-200Angstrom ) preferably at 30-50 deg.C to adsorb the crude alkylglycoside. The treated polar adsorbent is mixed with the unreacted alcohol- releasing solvent (e.g. toluene or acetone) with stirring to elute the unreacted alcohol and the impurities, and the polar adsorbent is further mixed with an alkylglycoside-releasing solvent (e.g. water or methanol) with stirring to elute the alkylglycoside, thereby providing the objective purified compound.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention is directed to the separation of unreacted alcohol from crude alkyl glycoside containing alkyl glycoside, unreacted alcohol, and impurities. In addition to not producing or mixing impurities, it is also possible to remove impurities that have already been produced or mixed in each step, including previous reactions, along with unreacted alcohol, which could not be produced using conventional methods. The present invention relates to a method for producing alkyl glycosides of extremely high quality in terms of color and odor.

[Prior Art] Alkyl glycoside, which is a sugar derivative surfactant, is a mild surfactant, and although it is a nonionic surfactant, it generates stable foam by itself, and
It is known to act as a foam stabilizer for other anionic surfactants, and has been attracting attention in recent years.

Such alkyl glycosides are usually produced by reacting sugars with higher alcohols, or using higher alcohols in excess of sugars, and the alkyl glycosides produced by the reaction, unreacted higher alcohols, and It is necessary to separate unreacted alcohol and impurities from the mixture with impurities such as colored substances (hereinafter referred to as impurities) produced by the reaction. Generally known methods such as distillation are used to separate this unreacted alcohol, but in this case heating to a high temperature is essential, and it is necessary to avoid causing undesirable color and odor deterioration of the alkyl glycoside. do not have. This is because the boiling point of higher alcohols is generally high, the viscosity of crude alkyl glycosides containing impurities such as higher alcohols and coloring substances is high, and the diffusion rate of unreacted alcohol inside is slow, so the fluidity of crude alkyl glycosides is low. Heating to a high temperature is necessary to improve the temperature and reduce the amount of residual unreacted alcohol by distillation or the like. However, the thermal stability of alkyl glycosides is limited, and some of the alkyl glycosides decompose when heated to high temperatures.
Moreover, at the same time, unfavorable conditions for the quality of the alkyl glycoside may occur, such as denaturation of reducing sugars that are present in a small amount in the crude alkyl glycoside or that are produced by decomposition of the alkyl glycoside.

At the same time, for the economical production of alkyl glycosides, it is important to recover and reuse excess residual unreacted higher alcohols after separating them from the crude alkyl glycosides. This also causes a decrease in the quality of this recovered unreacted alcohol, and therefore, in the subsequent production of alkyl glycoside using this, a significant decrease in the quality of the alkyl glycoside will be caused.

One way to solve the above problem is to use a thin film evaporator to turn the reaction product containing excess unreacted higher alcohol into a thin film, and evaporate the excess unreacted alcohol in an extremely short residence time at a relatively high temperature. , Japanese Patent Publication No. 58-1.949
This is proposed in Publication No. 02. Although this method suppresses the thermal decomposition of alkyl glycosides by extremely shortening the residence time, a certain degree of thermal decomposition cannot be avoided, resulting in deterioration of color and odor.

Alternatively, a method for separating unreacted alcohol that does not require heating to high temperatures is proposed in US Pat. No. 4,571,306. This method uses silicalite, which has a molecular sieving effect, as an adsorbent to preferentially adsorb alcohol, which has a smaller molecular size than alkyl glycosides, to purify alkyl glycosides. However, this method has the problem that there is a limit to the degree of purification of alkyl glycosides because the amount of alcohol adsorbed onto the adsorbent is small and the selectivity of adsorption between alkyl glycosides and alcohol is low.

[Problems to be Solved by the Invention] The present inventors have worked hard to develop a method for producing alkyl glycosides that does not require heating to high temperatures, especially in the step of separating unreacted higher alcohols that remain after the reaction. As a result of our investigation, we discovered that by utilizing the difference in adsorption of impurities such as alkyl glycocontate and unreacted alcohol to the adsorbent, it is possible to effectively separate the two, and we have also conducted numerous studies on how to do this. , we have completed the present invention.

Means for Solving Problem 1] That is, the present invention purifies alkyl glycosides by bringing crude alkyl glycosides containing alkyl glycosides, unreacted alcohol, and impurities into contact with an adsorbent that selectively adsorbs alkyl glycosides or impurities. The present invention relates to a method for producing an alkyl glycoside, characterized in that the following steps a''=c are performed in this order.

(a) A step of adsorbing the crude alkyl glycoside by contacting the crude alkyl glycoside containing the alkyl glycoside, unreacted alcohol, and impurities or a solution obtained by dissolving it in an unreacted alcohol desorption solvent with a polar adsorbent (b) ) Desorbing unreacted alcohol and impurities by bringing the polar adsorbent into contact with an unreacted alcohol-removing solvent (c) Desorbing the alkyl glycoside by bringing the polar adsorbent into contact with an alkyl glycoside-removing solvent. The above-mentioned alkyl glycoside can be obtained by a well-known method, for example, by directly acetalizing sugars and higher alcohols in the presence of an acid catalyst, or by pre-desorbing sugars with methanol, ethanol, propatool, etc. ,
Any method may be used, such as acetalization with a lower alcohol such as butanol to form a lower alkyl glycoside, followed by acetal exchange reaction with a higher alcohol.

Monosaccharides, oligosaccharides, or polysaccharides are used as the saccharides that serve as raw materials for the alkyl glycosides according to the present invention. Specific examples of monosaccharides include aldoses, such as ehaallose, aldose, glucose, mannose, gulose, idose, galactose, gulose, ribose, arabinose, xylose, and lyxose.

Specific examples of oligosaccharides include maltose, lactose,
Examples include sucrose and maltotriose.

Specific examples of polysaccharides include hemicellulose, inulin, dextrin, dextran, xylan, starch, and hydrolyzed starch.

Examples of the higher alcohol serving as a raw material for the alkyl glycoside according to the present invention include alcohols represented by the following formula (1).

RO(AO)nH(1) (wherein, R represents a linear or branched alkyl group having 6 to 22 carbon atoms, an alkenyl group, or an alkylphenyl group, and A represents an alkylene group having 2 to 4 carbon atoms. (n is an integer whose average value is 0 to 5.) Note that the alcohol may be unreacted alcohol recovered from the crude alkyl glycoside.

In the alkyl glycoside synthesis method of the present invention, catalysts, reaction conditions, etc. can be determined using known methods, such as Japanese Patent Publication No. 47-24.532 and U.S. Pat. No. 383931.
No. 8, European Patent No. 092355, JP-A No. 1983-
13937, JP-A-58-189195, etc. may be followed.

Next, the reaction mixture of alkyl glycosides obtained as described above, i.e., the crude alkyl glycosides containing impurities such as unreacted higher alcohols and colored substances, is subjected to the above (a).
Purify according to steps (c).

In addition, before starting the purification operation, it is also possible to partially remove unreacted higher alcohols etc. from the crude alkyl glycoside by preliminary distillation under relatively mild conditions that do not cause decomposition of the alkyl glycoside. good.

The adsorbent used in this method is preferably a polar adsorbent, such as activated alumina, silica gel, etc. As for the particle size of the adsorbent, it is better to have a large particle size in order not to increase the pressure drop in the packed column, but on the other hand, it is better to have a small particle size in order to increase the amount of adsorption. Furthermore, in order to prevent drifting, it is desirable that the particle size be as uniform as possible. As such, a thickness of preferably 50 to 1000 μm, more preferably 100 to 500 μm is desirable.

Further, the pore size of the adsorbent is preferably 20 to 1000, preferably 50 to 200. For adsorbents with a pore size of less than 20 pores, diffusion within the pores becomes rate-limiting, and the amount of alkyl glycoside adsorbed is significantly reduced.

The unreacted alcohol removal solvent used in this method is n
- Saturated aliphatic hydrocarbons such as hexane, n-heptane, n-octane, 1so-octane, and n-decane, cycloaliphatic hydrocarbons such as cyclohexane, cyclopenkune, and decalin, and aromatic compounds such as benzene, toluene, and p-xylene. Examples include hydrocarbons, acetone, ketones such as methyl ethyl ketone and diethyl ketone, esters such as ethyl acetate, carbon disulfide, carbon tetrachloride, petroleum ether, etc., and either pure products or mixtures thereof can be used.

Preferably, when silica gel is used as an adsorbent, diethyl ether, toluene, etc.
) I/I is preferably 7 to 9, and when activated alumina is used, ethyl acetate, acetone, etc. have an sp value of 9.
~12 is desirable.

Examples of solvents for removing alkyl glycosides include water, methanol, ethanol, lower aliphatic alcohols such as n-propatool, 1so-propatool, n-butanol, and 1so-butanol, and ketones such as acetone, methyl ethyl ketone, and diethyl ketone. esters such as ethyl acetate, methylene chloride, chloroform, acetonitrile,
Examples include DMF, DMS○, etc., and either pure products or mixtures thereof can be used.

Preferably, when using silica gel as the adsorbent,
water, methanol, ethanol, 1so-propertool,
It is preferable to use acetone or the like having an sp value of 9 or more. In addition, when activated alumina is used, it is preferable to use activated alumina having an sp value of 11 or more, such as water, methanol, ethanol, 1so-propyl, etc.

The temperature at which the unreacted alcohol solution containing the alkyl glycoside and impurities is brought into contact with the polar adsorbent is within the temperature range (10-90'
C) If the temperature is too low, the viscosity of the alkyl glycoside solution will increase and the diffusion rate will decrease, which is undesirable.On the other hand, if the temperature is too high, the alkyl glycoside will easily deteriorate, and the boiling point of the solvent used will increase. If the temperature is higher, it becomes uneconomical because operation under pressurized conditions is required. A particularly preferable operating temperature range is about 30 to 50'C.

The detailed flow of this method is shown below.

a) A crude alkyl glycoside containing alkyl glycoside, unreacted alcohol, and impurities, or a solution of it dissolved in an unreacted alcohol removal solvent, is placed in a stirring tank, and a polar adsorbent is added at a weight ratio of 0 to the crude alkyl glycoside. .0
A method of adsorbing crude alkyl glycosides by adding 5 to 1.0 times the amount and stirring for 05 to 30 hours (contact filtration method), or a packed tower filled with a polar adsorbent containing alkyl glycosides, unreacted alcohol, and impurities. There is a method (fixed bed flow method) in which crude alkyl glycosides are adsorbed by flowing and contacting crude alkyl glycosides or a solution of the crude alkyl glycosides in an unreacted alcohol removal solvent, but the liquid flow rate in the fixed bed flow method is Any method can be applied as long as the flow rate is sufficient for the crude alkyl glycont to be adsorbed on the polar adsorbent, but in particular, the space velocity or 00
It is desirable to operate within the range of 5 to 10 hr-1.

b) Unreacted alcohol and impurity desorption step Next, the unreacted alcohol desorption solvent is brought into contact with the polar adsorbent to desorb unreacted alcohol and impurities.

When the above-mentioned contact filtration method is applied, after the unreacted alcohol-eliminating solvent in the tank is filtered and fractionated, the unreacted alcohol-eliminating solvent is newly added to the polar adsorbent and stirred. By repeating this process several times, unreacted alcohol and impurities are desorbed.

There is no particular restriction on the coulometric ratio of the unreacted alcohol-eliminating solvent to the polar adsorbent, and it is preferably used within a range of 0.5 to 1000 times. Furthermore, when a fixed bed flow method is applied, unreacted alcohol and impurities are desorbed by flowing the unreacted alcohol desorption solvent through a packed column. Any flow rate can be used as long as the flow rate is sufficient to desorb unreacted alcohol and impurities, but as in the adsorption process, the space velocity is 0.05 to 10 hr. It is desirable to operate within the range of -'. Further, at this time, some of the alkyl glycosides existing without being adsorbed are eluted, but this can be recovered by distilling off the unreacted alcohol desorption solvent, and then adsorption and desorption can be performed.

C) Alkyl glycoside desorption step Next, the alkyl glycoside is desorbed by bringing the alkyl glycoside desorption solvent into contact with a polar adsorbent.

When the above-mentioned contact filtration method is applied, after the alkyl glycoside-eliminating solvent in the tank is filtered and fractionated, the alkyl glycoside-eliminating solvent is added and stirred, and this process is repeated 1 to 5 times to obtain alkyl glycoside. can be refined.

When the fixed bed flow method described above is applied, the alkyl glycoside can be desorbed by flowing the alkyl glycoside desorption solvent through the polar adsorbent. Any flow rate can be used as long as the flow rate is sufficient to desorb the adsorbed alkyl glycosides, but it is particularly recommended to flow at a space velocity of 0.05 to 10 hr. It is effective.Also, it is possible to use only one type of alkyl glycoside desorption solvent used during desorption, or to use a variety of solvents, and by gradually increasing the polarity and passing the liquid, the alkyl glycoside can be further removed. May be separated efficiently.

After the desorption is completed, the polar adsorbent used can be used repeatedly by washing it with an alcohol desorption solvent or drying it at a high temperature of 100° C. or higher.

[Effects of the Invention] According to the present invention, in the step of separating unreacted alcohol from crude alkyl glycoside containing alkyl glycoside, unreacted alcohol, and impurities, impurities such as new coloring substances and odor substances are not generated or mixed. In addition, it is possible to remove impurities that have already been generated or mixed in each process, including the previous reactions, along with unreacted alcohol, resulting in colors and colors that could not be produced using conventional methods. It is possible to produce alkyl glycosides of extremely high quality in terms of odor.

[Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples.

Example 1 Decyl alcohol 11400! + (72, Omol),
Anhydrous glucose 3240g (L8.Omol) and p
Toluenesulfonic acid monohydrate 96I? (0.5 mol)
30g of the mixture was heated and stirred in a reaction tank. After raising the temperature to 95°C, the system internal pressure was set to 40 mmHg to start the dehydration reaction. At this time, N was blown into the reaction mixture at a rate of 5N 1/min to efficiently remove the generated water. 5
After a period of time, after confirming that glucose was completely consumed, the vacuum was released, cooled, and neutralized with NaOH2017. By-product polysaccharides are filtered out, and alkyl glycosides and unreacted decyl alcohol are 33% by weight and 66% by weight, respectively.
12,730 g of crude alkyl glycoside containing the following ratio was obtained.

Next, the crude alkyl glycoside was purified by a fixed bed flow method using a packed column with an inner diameter of 3 cvr and a length of 25 gm maintained at 35°C. As an adsorbent,
Using activated alumina (D-3 manufactured by Suiko Kagaku), which is a polar adsorbent, 70 g was filled, and crude alkyl glycoside], 8
It was introduced at a flow rate of ml/ml (SV = 0.82 hr-'), and after the crude alkyl glycoside was saturated and adsorbed, 1.8 ml/ml was introduced using acetone as a solvent for removing unreacted alcohol.
Unreacted alcohol and impurities were desorbed at a flow rate of min. After flowing 500 cc of acetone, methanol, which is an alkyl glycoside removal solvent, was introduced at 1.8 ml/m.
The alkyl glycosides were desorbed. By distilling off methanol from the obtained alkyl glycosi I'/methanol solution at 70°C, 102 g
A colorless 7-al-half glycoside was obtained. The amount of alkyl glycoside adsorbed per adsorbent was 0.15 g/g-adsorbent, and the purity was 99.7%. In addition, there was almost no odor (the hue of the 50% aqueous solution was Gardner 1 or less).

Comparative Example 1 Using the crude alkyl glycoside obtained in Example 1 as a raw material, a thin film evaporator (heat transfer area: 0.032 m2) described in JP-A-58-1.94902 was used at a raw material supply rate of 0. , ], L 5 k'j/hr, processing temperature 1
Unreacted decyl alcohol was removed under conditions of 80° C. and 0.5 mmHg pressure. The obtained alkyl glycoside had a purity of 99.4%, but was colored deep yellow and had a purity of 50%.
In the aqueous solution state, a burnt odor was observed, which was thought to be due to thermal decomposition of cardboo-6), alkyl glycosides, or sugars.

Claims (2)

[Claims] (1) In purifying the alkyl glycoside by bringing the crude alkyl glycoside containing the alkyl glycoside, unreacted alcohol, and impurities into contact with an adsorbent that selectively adsorbs the alkyl glycoside and impurities, the following steps a to c are carried out. A method for producing an alkyl glycoside characterized by carrying out the steps in this order. (a) A step of adsorbing the crude alkyl glycoside by contacting the crude alkyl glycoside or a solution of it in a solvent for removing unreacted alcohol with a polar adsorbent (b) Eliminating unreacted alcohol on the polar adsorbent A step of adsorbing unreacted alcohol and impurities by contacting a solvent; (c) a step of desorbing alkyl glycosides by bringing an alkyl glycoside desorption solvent into contact with the polar adsorbent; (2) The method for producing an alkyl glycoside according to claim 1, characterized in that silica gel or activated alumina is used as the polar adsorbent.