Preparation of alkyl glycosides

Details Preparation of alkyl glycosides Preparation of alkyl glycosides

1994-09-15

1996-09-10

Kunz, Gary L.

Organic compounds -- part of the class 532-570 series

Organic compounds

Carbohydrates or derivatives

536 185, C07H 100, C07H 1504

Patent

active

055547427

DESCRIPTION:

BRIEF SUMMARY
PREPARATION OF ALKYL GLYCOSIDES

The present invention relates to an improved process for preparing alkyl glycosides by reaction of aqueous glycoses having a water content of 10-80% by weight with aliphatic primary alcohols having from 8 to 30 C atoms.
Surface-active alkyl glycosides, which are mainly used in the detergent and cleaner sector, have been known for a long time and are prepared on the industrial scale by two different types of process. Either the long-chain alcohol component is directly linked to the sugar component with elimination of water by direct synthesis or a short-chain alkyl glycoside is first prepared as intermediate by the transacetalization method and is then reacted in a second step by transacetalization with long-chain alcohols to give the surface-active alkyl glycoside. However, the transacetalization method has a number of disadvantages in principle compared with direct synthesis, such as the additional use of a short-chain alcohol, a poorer space-time yield or the formation of relatively complex product mixtures.
EP-A 0,252,241 may be mentioned as an example of the transacetalization method. According to this, butyl oligoglycosides are prepared by acid-catalyzed reaction, for example using sulfuric acid or p-toluenesulfonic acid, of aqueous saccharide syrups with the addition of butyl oligosaccharides. The short-chain butyl glycosides can then be subjected to a transacetalization to give longer-chain alkyl glycosides.
In EP-A 0,362,671, and also in the references cited below, a direct synthesis of longer-chain alkyl glycosides is described. This specification recommends the use of acidic catalysts such as sulfuric acid, phosphoric acid or aliphatic or aromatic sulfonic acids for the acetalization reaction. The glycoses used for the reaction, such as glucose, should be as anhydrous as possible. The reaction is carried out, for example, by adding a suspension of the glycose in a fatty alcohol continuously to a mixture of acidic catalyst and fatty alcohol and at the same time removing the resulting water of reaction by distillation under reduced pressure.
A process is described in EP-A 0,096,917 in which a monosaccharide, such as glucose, suspended in a fatty alcohol is added continuously or in portions to a mixture of fatty alcohol and an acidic catalyst such as sulfuric acid or toluenesulfonic acid at from 80.degree. to 150.degree. C. in such a manner that no more than 10% of unreacted monosaccharide is present in the reaction mixture. Anhydrous glucose of a specific particle size is employed.
As the acidic catalyst for the direct synthesis of alkyl glycosides, EP-B 0,132,043 recommends the acid form of an anionic surfactant, by whose use instead of customary catalysts, such as sulfuric acid or p-toluenesulfonic acid, it is intended to improve the color quality of the product and to reduce the content of undesired polysaccharides in the final product. In the process of this reference only a small excess of fatty alcohol is employed, preferably 2 mol of fatty alcohol per mole of glucose, which is used in its anhydrous form, and during the neutralization of the acidic catalyst with a base a pH of from 6.6 to 7 is maintained.
WO-A-90/07516 and DE-A 3,927,919 also describe the use of surface-active acidic catalysts of this type, dinonylnaphthalenesulfonic acid or sulfosuccinic acid, to obtain an alkyl glycoside having a paler color and a low content of polysaccharides.
US-A-4,721,780 describes a process for preparing alkyl polyglucosides in which aqueous monosaccharide solutions are reacted with monohydric C.sub.2 - to C.sub.6 -aliphatic alcohols in a homogeneous aqueous phase in the presence of acidic catalysts at from 60.degree. to 200.degree. C. and water is removed from the reaction mixture in such a manner that a separate phase of an aqueous monosaccharide solution is not formed.
A corresponding process is disclosed in U.S. Pat. No. 4,996,306 for the preparation of C.sub.7 - to C.sub.30 -alkyl polyglucosides, in which aqueous mono- or oligosaccharide solutions are reacted with

REFERENCES:
patent: 4721780 (1988-01-01), McDaniel, Jr. et al.
patent: 4996306 (1991-02-01), McDaniel, Jr. et al.

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