Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Patent
1996-02-14
1998-02-10
Kight, John
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
510470, 536 186, 536120, 536124, C07H 1504, C07H 106
Patent
active
057170819
DESCRIPTION:
BRIEF SUMMARY
This application claims benefit of international application PCT/EP94/03028, filed Sep. 8, 1994.
The present invention relates to a process for producing an alkylglycoside by reaction of an alcohol with a saccharide or reaction of a higher alcohol with a lower alkylglycoside in the presence of an acidic catalyst and to the alkylglycosides thus produced, as well as to their use in surface-active compositions. The invention also relates to an apparatus for carrying out the process of the present invention.
It is known to prepare alkylglycosides from a saccharide and alcohols by glycosidation or by reglycosidation of lower alkylglycosides and higher alcohols in the presence of acidic catalysts. A review of the synthesis of a number of alkylglycosides was published by Dr Th. Bocker and Prof Dr T. Thiem in Tenside Surf. Det., Vol. 26, No. 5, 318-324 (1989).
One of the problems in the production of alkylglycosides is the quick removal of the water formed in the reaction, so that the reaction rate will be economically acceptable.
It has now been found alkylglycosides can be obtained at a higher reaction rate and a higher final conversion, by using pervaporation to continuously remove the reaction water. In pervaporation, a liquid feed (containing a more permeable and a less permeable component) is maintained in contact with a permeable membrane and a pressure drop is maintained across the membrane. Out of the feed liquid the component to be removed passes through the membrane. The permeate which passes through the membrane and is in vapor form, may be recovered by condensation at low temperature or may be carried away by using a moving stream of gas.
Preferably, the permeate side of the membrane is maintained at a low pressure in the magnitude of 5 mm Hg (0.67 KPa). The residual feed kept in the separation unit is called the retentate or concentrate. In the process of vapor permeation, the feed mixture is first evaporated and then the vapor is passed along the membrane.
The pervaporation process has been described in more detail in W. S. Winston Ho and K. k. Sirkar "Membrane Handbook", Van Nostrund Reinhold Publishing Corp., New York, 1992 on pages 105-159.
Therefore, the present invention relates to a process for producing an alkylglycoside by reaction of an alcohol with a saccharide or reaction of a higher alcohol with a lower alkylglycoside in the presence of an acidic catalyst, which is characterized in that at least one pervaporation membrane is provided in the process apparatus, such that the water of reaction is continuously removed from the reaction mixture through the membrane.
The saccharide which can be used in the process of the present invention comprises preferably water-soluble monosaccharides, such as glucose, fructose, galactose, mannose, xylose, arabinose and the like, as well as preferably water-soluble polysaccharides such as sucrose, maltose, maltotriose, lactose, and the like and also mixtures of monosaccharides and polysaccharides. The saccharide material is preferably used in the form of a slurry or dispersion in alcohol from which the alkylglycoside is formed. The use of glucose and fructose is preferred.
As the alcohol a monohydric, saturated, straight or branched chain alcohol having from 1 to 6 carbon atoms is used, such as methanol, ethanol, propanol, iso-propanol, butanol, and mixtures thereof. Also polyhydric saturated aliphatic alcohols like ethylene glycols, propylene glycols, glycerol, and the like may be used, in which case hydroxyalkylglycosides are formed.
As the lower alkylglycoside there may be used a C.sub.1 -C.sub.6 alkylglycoside, like methylglycoside, ethylglycoside, hexylglycoside, and the like.
The higher alcohol which is used in the reglycosidation reaction according to the present invention is selected from the straight or branched chain monohydric alcohols, having from 8 to 24 carbon atoms, like octanol, dodecyl alcohol, and the like. Usually, mixtures of fatty alcohols having from 12 to 18 carbon atoms are used.
In general, a reaction temperature between 60.degree.
REFERENCES:
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Nakagawa, et al: "Method for preparation of ether compounds and purification by pervaporation", Chemical Abstracts, vol. 118, No. 17, Apr. 26, 1993, abstract No. 168695j, p. 839, col. 2, see abstract & JP,A,04 253 931.
Kight John
Lee Howard C.
Unichema Chemie B.V.
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