PROCESS FOR THE REMOVAL OF FATTY ALCOHOLS FROM ALKYLPOLYGLYCOSIDE SOLUTIONS BY DISTILLATION

METHODE POUR ELIMINER PAR DISTILLATION LES ALCOOLS GRAS DANS LES SOLUTIONS D'ALKYLPOLYGLYCOSIDES

English 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.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
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.
- 4 -

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.
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Description

21 64277
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
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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.
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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.
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