CA2164277A1

CA2164277A1 - Process for the removal of fatty alcohols from alkylpolyglycoside solutions by distillation

Info

Publication number: CA2164277A1
Application number: CA002164277A
Authority: CA
Inventors: Jurgen Grutzke; Stefan Schmidt
Original assignee: Huels AG
Current assignee: Huels AG
Priority date: 1994-12-03
Filing date: 1995-12-01
Publication date: 1996-06-04
Also published as: EP0714906A1; KR960022554A; CN1131156A; DE4443087A1; JPH08231576A

Abstract

Disclosed is a process for the removal of fatty alcohols having 8 to 30 carbon atoms from fatty alcohol alkylpolyglycoside solutions by distillation. Distillation is carried out in several steps, one or more falling film evaporators and an afterconnected short path evaporator being used.

Description

Process for the Removal of Fatty Alcohols from Alkylpolyglycoside Solutions by Distillation The invention relates to a process for the removal of fatty alcohols having 8 to 30 carbon atoms, in particular from 8 to 18 carbon atoms, from fatty alcohol alkylpolyglycoside solutions by distillation.
Distillation is carried out here in several steps, one or more falling film evaporators being combined with an afterconnected short path evaporator.
alkylpolyglycosides are non-toxic and easily degradable surface-active substances which are prepared entirely or partly from renewable raw materials and which are used as detergents, cleaning agents, emulsifiers and dispersants. The alkylpolyglycosides can be prepared in one step or two steps by glycosylation and transglycosylation.
They contain alkyl groups having 8 to 30, in particular having 8 to 18 carbon atoms, alkyl groups having 12 to 16 carbon atoms being particularly preferred. The average degree of polymer-ization is usually 1.05 to 1.5, preferably 1.2 to 1.5 and very particularly preferably 1.2 to 1.4. Carbohydrates which can be employed are moncsaccharides, such as pentoses and hexoses, disaccharides, such as sucrose and maltose, and polysaccharides, such as starch. A one-step preparation process is generally known. One particular process is described in German Patent Publication 41 01 252.
A two-step process is also generally well known.
One particular process is described in EP-A-0 306 652, in which an n-butylglycoside is first prepared by glycosylation with n-butanol and, from this, the desired long-chain alkyl-glycoside is prepared by transglycoslation with a long-chain alcohol. The reaction between the above-mentioned carbohydrates and the fatty alcohols is carried out, as a rule, using a large excess of the alcohol. As this excess alcohol interferes with the application properties of the alkylpolyglycosides, it is removed after termination of the reaction. As the alkylpolyglycosides or the unreacted carbohydrates decompose at temperatures of over 150C with a result of dark colouration, the removal of the alcohols by distillation must be carried out in a medium high vacuum.
DE 41 29 587 discloses a process for the removal of the fatty alcohols with the aid of a thin-film evaporator with setting of a Reynolds number of 30 to 18,000. In EP O 092 876, the fatty alcohols are distilled from fatty alcohol alkylpoly-glycoside solutions, also with the aid of a thin-film evaporator. In this case the Reynolds number should be > 20,000. DE 39 32 172 discloses a process in which the unreacted alcohols are removed in two steps, a falling film evaporator being employed in the first step and a thin-film evaporator in the second step. All the above-mentioned processes, however, have the disadvantage that the maximum vacuum which can be achieved in the thin-film evaporator is restricted (about 1 mbar), and therefore a high bottom temperature for the temperature-sensitive alkylpolyglycosides has to be set in the thin-layer evaporator. This leads to undesirakle product discolourations which have to be removed in a further working-up step.

It is therefore a major object according to the present invention tc provide a process for working up the fatty alcohol alkylpolyglycoside solutions by distillation which minimizes the thermal stress and the dark colouration associated therewith.
According to the present invention, one or mcre falling film evaporators are combined with an afterconnected short path evaporator.
The invention therefore provides a process for the removal of fatty alcohols from fatty alcohol alkylpolyglycoside solutions by distillation, characterized in that one or more falling film evaporators and an afterconnected short path evaporator are used. The falling film evaporator or evaporators are operated generally at a heating medium temperature of 120 to 160C, preferably 130 to 150C, at an operating pressure of 2 to 20 mbar, preferably 3 to 10 mbar, and a bottom temperature of between 100 and 140C, preferably 110 to 130C. The number of falling film evaporators is preferably one or two.
In the case of the afterconnected short path evaporator, generally the heating medium temperature is 160 -200C, the operating pressure is 0.1 - 1 mbar and the bottom temperature is 140 - 180C. As a result of the good vacuum which can be achieved in the short path evaporator, the bottom temperature - and thus the thermal product stress - can be distinctly reduced without a rise in the residual fatty alcohol content having to be expected. Distinctly lighter products can be obtained in this way.

Claims

1. A process for the removal of a long-chain fatty alcohol from a solution of an alkylpolyglycoside in the fatty alcohol, which comprises:
distilling the fatty alcohol from the solution by using one or more falling film evaporators and a short path evaporator connected after the falling film evaporators.

2. A process according to claim 1, wherein two falling film evaporators and one short path evaporator are used.

3. A process according to claim 1, wherein one falling film evaporator and one short path evaporator are used.

4. A process according to claim 1, wherein the falling film evaporators are operated at a heating medium temperature of 120 to 160°C.

5. A process according to claim 1, wherein the falling film evaporators are operated at an operating pressure of 2 to 20 mbar.

6. A process according to claim 1, wherein the falling film evaporators are operated at a bottom temperature of 100 to 140°C.

7. A process according to claim 1, wherein the falling film evaporators are operated at a bottom temperature of 110 to 130°C.

8. A process according to any one of claims 1 to 7, wherein the fatty alcohol has 8 to 30 carbon atoms.

9. A process according to claims 1 to 7, wherein the fatty alcohol has 8 to 18 carbon atoms.

10. A process for the removal of a fatty alcohol having 8 to 18 carbon atoms from a solution of an alkylpolyglycoside having an alkyl group of 8 to 18 carbon atoms and an average polymerization degree of monosaccharide of 1.05 to 1.5 dissolved in the fatty alcohol, which comprises:
distilling the fatty alcohol from the alkylpoly-glycoside solution by using one or more falling film evaporators each operated at a heating medium temperature of 120 to 160°C, at an operating pressure of 2 to 20 mbar and at a bottom temperature of 100 to 140°C, and further distilling the fatty alcohol by using a short path evaporator at a heating medium temperature of 160 to 200°C, at an operating pressure of 0.1 to 1 mbar and at a bottom temperature of 140 to 180°C, the short path evaporator being connected after the falling film evaporators.

11. The process according to claim 10, wherein one or two falling film evaporators are used.