WO1994009019A1

WO1994009019A1 - Process for the preparation of alkylglycosides

Info

Publication number: WO1994009019A1
Application number: PCT/EP1993/002810
Authority: WO
Inventors: Herman Van Bekkum; Maria Petra J. Van Deurzen; Antonius Theodorus J. W. De Geode; Frederik Van Rantwijk
Original assignee: Unichema Chemie B.V.
Priority date: 1992-10-14
Filing date: 1993-10-12
Publication date: 1994-04-28
Also published as: AU5151093A

Abstract

A process for the preparation of alkylglycosides, preferably alkylfructosides, comprises reacting a monosaccharide or a short chain alkylglycoside with an alcohol, preferably a monohydric alcohol in the presence of an acid clay or an activated silia-alumina based craking catalyst. The alkylfructosides can be used as surfactants, emulsifiers, and the like.

Description

PROCESS FOR THE PREPARATION OF ALKYLGLYCOSIDES

The present invention relates to a process for the preparation of alkylglycosides by reacting an alcohol with a saccharide or a short chain alkylglycoside in the presence of an acid catalyst. More particularly, the invention relates to a process for the preparation of alkylfructosides by reacting an alcohol with fructose or a short chain alkylfructoside in the presence of an acid catalyst.

Alkylglycosides, in particular the higher alkylglycosides (having at least 8 carbons in the alkyl chain) are well known as mild biodegradable surfactants of the nonionic type and it has been proposed to use these higher alkylglycosides either alone or in combination with other surfactants in detergent fomulations, where they act as detergent surfactants and as foam builders. Also because of their surfact active properties they are used as wetting agents and emulsifiers, both in food and non-food uses.

The preparation of alkylglycosides from glucose and other reducing sugars has extensively been described in the patent literature, but although it is often stated that the method of preparation in question is effective with any type of reducing sugar, almost all examples are for the preparation of alkylglucosides, i.e. glucose is the only sugar exemplified.

It has been found that when the known processes are applied for the preparation of (higher) alkylfructosides, very little useful material is produced, because the reaction conditions, particularly the use of strongly acidic catalysts, effect a degradation of the fructose to polymerized and dehydrated products. There is thus no commercially useful process to prepare alkylfructosides from fructose. Fructose is available in commercial quantities from the isomerization of glucose and the introduction of new agricultural crops, which can be used as sources of fructose, will increase the supply of fructose further, making technology to exploit this raw material even more attractive.

During extensive investigations it has now been found that alkylfructosides (and particularly the higher alkylfructosides) can be prepared efficiently and with little degradation of the fructose occurring by using as a catalyst acid clays or silica-alumina based cracking catalysts, and mixtures thereof.

Therefore the present invention relates to a process for the preparation of alkylglycosides by reacting an alcohol with a saccharide or a short chain alkylglycoside in the presence of an acid catalyst, which is characterized in that the catalyst is selected from the group consisting of acid clays, activated silica-alumina-based cracking catalysts, and mixtures thereof.

Preferably the saccharide is fructose and the short chain alkylglycoside preferably is an alkylfructoside of which the alkyl chain has up to 6 carbon atoms.

The cracking catalyst preferably is an amorphous silica- aluminate. They are synthetised starting with an Si0₂ matrix which is reacted with aluminium hydroxide, which causes activation of the surface particles. Acid groups are formed on the contact area and both Lewis and Brδnsted acid sites can be formed. By the absorption of water the catalyst is inactivated. Before the catalyst is used it has appeared necessary to activate or re-activate the catalyst. The optimum temperature for such an activation or re¬ activation treatment was found to be from 300°C to 800°C. At a temperature higher than 800°C, it was found that the activity of the cracking catalyst rapidly diminished because of degradation of the catalyst surface. At temperatures below about 400°C Brδnsted acid sites are formed and at temperature over 400°C Lewis acid sites appeared to be formed. The temperature at which the one type is formed or the other is somewhat dependent on the specific type of the cracking catalyst. The acid clays used according to the present invention are acid-treated clays, such as those of the Filtrol (Trade Mark) type, such as Filtrol 24, or of the Tonsil (Trade Mark) type, such as Tonsil A/C, Tonsil COG, Tonsil Supreme FF and Tonsil Optimum FF (both of the fast filtraticr tyP^e) _/ ^or of the Activol (Trade Mark) type, such as . ^tivol B/C. Also mixtures of the acid-treated clay and the silica- alumina-based cracking catalysts, or mixtures -of clays, or mixtures of various cracking catalysts may be used.

In J. Chem. Soc. , Chem. Commun. .15, 1171-1172 (1987) a stereoselective synthesis of 3-amino-2,3,6-trideoxy- hexopyranoses has been described in the presence of K-10 montmorillonite (an acidic montmorillonite type phyllosilicate) . But in this synthesis the starting material is a sugar of which the anomeric hydroxyl group is esterified with acetic acid and this compound is then converted into an acetal. No fructoside is used, however, and there is no indication or suggestion that the montmorillonite is capable of catalysing the reaction of unprotected fructose with alcohols to give fructosides.

In Starch/Starke, Vol. 39, No. 10, 362-368 (1987) there has been described a process for the preparation of long- chain alkyl D-glucosides by alcoholysis of 1,2:5,6-di-O- isopropylidene-alpha-D-glucofuranose. The alcoholysis was effected using 1-butanol, 1-hexanol, 1-decanol, 1-dodecanol and 1-hexadecanol, using different acidic catalysts. Also a silica-alumina cracking catalyst (ex Ketjen, High Alumina- High Pore Volume catalyst, The Netherlands; surface area 524 m² /g activated at 700°C before use) was used in the reaction with 1-butanol. It was found that the use of this catalyst lead to an appreciable amount of isomerization and, compared to the use of sulphuric acid and macroporous ion exchange resin of the sulphonic acid type, the yield of butyl D-glucopyranoside was relatively low. Also no data have been given for the reaction, using higher alcohols than 1-butanol. There is no suggestion or indication that this reaction can also be applied to unprotected fructose, in which the hydroxyl groups have not been blocked. On the contrary, it can be expected that with the reactive hydroxyl groups available, there will be considerable isomerization.

The alcohol used in the process according to the present invention preferably is a monohydric alcohol having from 6 to 24 carbon atoms, and it may be primary or secondary alcohols, straight or branched chained, saturated or unsaturated, alkyl or aralkyl alcohols, ether alcohols, cyclic alcohols or heterocyclic alcohols. A preferred group of alcohols is the fatty alcohols having from 12 to 22 carbon atoms. Also polyhydric saturated aliphatic alcohols may be used so as to provide hydroxyalkyl glycosides.

The present invention is particularly advantageous in the preparation of alkylfructosides, but also other hexoses and pentoses may be used. Also the monohydrates may be used. If the starting material is a lower alkylglycoside, then this compound may be derived from the same type of saccharides. The alkyl chain in the lower alkylglycosides has up to 6 carbon atoms, preferably up to 5 carbon atoms.

The amount of catalyst used may be from 10 % to 300 % based upon the weight of the saccharide or the short chain alkylglycoside used. In general it has been found that if the amount of catalyst is increased, the maximum conversion of the saccharide is reached faster. A suitable amount appeared to be about 100 % based upon the weight of the saccharide, in other words, equal amounts by weight of catalyst and sugar (fructose) are preferably used. The molar ratio of the preferably monohydric alcohol to the saccharide or the short chain alkylglycoside is suitably between about 5 to about 50 and preferably between about 10 to about 40. For the preparation of alkylfructosides the temperature at which the reaction is carried out is about 65°C to 140°C, preferably 65°C to 85°C, most preferably about 70°C to 75°C at 15 mm Hg. The vacuum is used to facilitate the removal of the more volatile reaction products. The water which is formed in the reaction may be absorbed by the use of zeolites.

After the reaction has been terminated, the catalyst can be filtered off and may , after re-activation, be used again.

In the reaction a crude reaction mixture of the various forms of the fructosides is formed. Thus, if methylfructoside was formed from 3.0 grams of fructose and 50 ml of dry methanol in the presence of 3.0 grams of a silica-alumina cracking catalyst (Ketjencat HA-HPV ex AKZO, Netherlands; Trade Mark, activated for 24 hrs at 430°C) , then after 24 hrs a yield of 94 % of methylfructosides was obtained having the following composition:

49 wt % of methyl-alpha-D-fructofuranoside 40 wt % of methyl-beta-D-fructofuranoside 3 wt % of methyl-alpha-D-fructopyranoside 7 wt % of methyl-beta-D-fructopyranoside.

One of the advantages of the present invention is the possibility to use such a crude reaction mixture directly as surface active agent, wetting agent, emulsifier, and the like. 5

The present invention therefore also relates to the use of a crude reaction product, prepared by the method according to the present invention, from which only the excess unreacted alcohol has been removed, in detergent compositions, cosmetic compositions or foodstuffs.

The reaction mixture of alkylglycosides obtained in the method according to the present can, however, also be split into its various components in manners known per se. Such separate components can be used as wetting agent, surface active agent, emulsifier, drug, and the like.

The invention is now further illustrated on hand of the following examples.

EXAMPLE I

3.0 grams of fructose and 49.6 grams of 1-dodecanol were brought into a round bottom flask. The mixture was brought in 15 minutes to a temperature of 70°C at a pressure of 15mm Hg. Subsequently 3.0 grams of a silica-alumina cracking catalyst (Ketjencat HA-HPV ex AKZO, Netherlands; Trade Mark, a high alumina cracking catalyst having the following composition (in wt%)= alumina 25.0%; sodium oxide 0.01%; iron 0.03%; sulphate 1.0%; balance silicium dioxide; apparent bulk density (lh,600°C) 0.37g/ml; particle size distribution in wt%: 0-20 microns 3.0%; 0-40 microns 18.0%, 0-80 microns 64.5%; 0-105 microns 86.0%;0-149 microns 28.5%) which had been activated by heating it to 430°C for 24 hrs were introduced and the mixture was again brought to 70°C at 15 mm HG. After 24 hrs 49.2 grams of the reaction mixture were diluted with 500 ml dichloromethane. This solution was brought onto a silica gel column and subsequently dichloromethane was continuously passed through the column, the dichloromethane was refluxed and fed back to the top of the column. It appeared that after 30 hrs no more alcohol came out of the column. Then the column was washed out with methanol and a solution of the dodecyl fructosides in methanol was obtained. The methanol was evaporated off and 2.62 grams of a mixture of 2-0-dodecyl fructosides were obtained (yield 45%) . The mixture composition was 46% 2-0- dodecyl α-D-fructofuranoside, 20% 2-O-dodecyl β-D- fructofuranoside, 34% 2-0-dodecyl beta-D-fructopyranoside.

Example II

3.0 grams of fructose in 50 ml of 1-butanol were brought into a round-bottomed flask which was connected to a

Soxhlet apparatus, in such a way that the reaction could be carried out under vacuum. The mixture was brought to 70°C at such a pressure that constant reflux of 1-butanol was obtained. After 5 minutes 3.0 grams of a silica-alumina cracking catalyst (Ketjencat HA-HPV ex AKZO, Netherlands, Trade Mark) , which had been previously activated for 24 hrs at 430°C, were added. The water formed during the reaction was absorbed by a cationic zeolite type A (average pore size 3 Angstrom) which was contained in the Soxhlet apparatus. After 1.8 hrs the reaction was stopped, the reaction mixture was filtered and washed with diethyl ether. The filtrate was subjected to film evaporation and was dried at 50°C under vacuum. To the recovered catalyst 150 ml of methanol at 60°C were added. The solution obtained was filtered and the filtrate was subjected to film-evaporation and vacuum drying at 50°C. It was found that 0.2 grams of unconverted fructose, butyl fructosides and polymerization products had been deposited onto the catalyst during the reaction. The yield of n-butyl fructosides was 3.7 grams (yield 95%).

EXAMPLE III

3.7 grams of n-butylfructosides, prepared as ir. described in example II, and 49.6 grams of 1-dodecanol were treated as described in example I. After 4.5 hrs a conversion of 64% to dodecyl fructosides was reached. The reaction was stopped and the reaction mixture was filtered over a glass filter and the residue washed with diethyl ether and cooled to -8°C upon which the 2-O-dodecyl β-D-fructopyranoside precipitated. After filtration of the pyranoside, the crude pyranoside was recrystallised from ethyl acetate (yield 0.72 grams, 12%) . (This corresponds with 72% of the pyranoside present in the reaction mixture) .

Claims

1. A process for the preparation of alkylglycosides by reacting an alcohol with a saccharide or a short chain alkylglycoside in the presence of an acid catalyst, characterized in that the catalyst is selected from the group consisting of acid clays, activated silica-alumina-based cracking catalysts, and mixtures thereof.

2. A process according to Claim 1, characterized in that the saccharide is fructose.

3. A process according to Claim 1, characterized in that the short chain alkylglycoside is an alkylfructose in which the alkyl chain has up to 6 carbon atoms.

4. A process according to Claim 1, in which the alcohol is a monohydric alcohol having from 6 to 24 carbon atoms.

5. A process according to Claim 1, in which the alcohol is a saturated aliphatic polyhydric alcohol.

6. A process according to Claim 1, in which the acid clay is an acid treated clay of the Filtrol type.

7. A process according to Claim 1, in which the silica- alumina based cracking catalyst is activated by heating it to a temperature between 300°C and 800°C.

8. A process according to Claim 1, in which the amount of catalyst used is from 10% to 300 % by weight based upon the weight of the saccharide or the short chain alkylglycoside used.

9. A process according to Claim 1, in which the molar ratio of the alcohol to the saccharide or the short chain alkylglycoside is from 5 to 50.

10. A process according to Claim 1, in which the temperature at which the reaction is carried out is from 65°C to 140°C.

11. A process according to Claim 1, in which the water of reaction formed is absorbed by zeolites.

12. Use of a crude reaction mixture comprising alkylfructosides whenever prepared by a process according to any one of Claims l-ll in detergent compositions, cosmetic compositions or foodstuffs.