Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Reexamination Certificate
2000-04-24
2001-11-27
Killos, Paul J. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
Reexamination Certificate
active
06323362
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a process for continuous manufacture of esters, or in particular of acetates, by a catalytic transesterification reaction in a homogeneous liquid phase.
British patent application GB-2 017 083 describes a process for the manufacture of ethylmonoglycol ether acetate by a catalytic transesterification reaction using ethyl acetate and ethylmonoglycol ether. The reaction is carried out in a heterogeneous phase in the presence of a catalyst consisting of a solid ion exchange resin at a relatively low temperature, lower than 100° C.
U.S. Pat. No. 3,700,726 discloses a process for the manufacture of (poly)ethylene glycol ether acetate by a catalytic transesterification reaction using an alkyl acetate with a (poly)ethylene glycol ether in the presence of a catalyst chosen from metal alcoholates. During the reaction only one alcohol is used, which is a (poly)ethylene glycol ether.
U.S. Pat. No. 4,370,491 and French patent FR-2 611 704 disclose processes for the manufacture of acetate by a catalytic transesterification reaction using an acetate and an alcohol in the presence of a catalyst chosen from metal alcoholates.
It has been noticed that an industrial unit continuously manufacturing esters, or in particular acetates, according to the processes as described above must be stopped for several days each time that the type of ester to be manufactured is changed. It has been observed that, in general, such an industrial unit can thus be stopped for one or two months a year, which corresponds to considerable losses of output.
Furthermore, search is continuing for processes which enable esters, or in particular acetates, to be manufactured with a high degree of purity, that is to say containing very few by-products.
SUMMARY OF THE INVENTION
A very economical process has just been found, making it possible to manufacture continuously and simultaneously at least two, preferably two, esters, or in particular two acetates, with high degrees of purity.
The subject-matter of the present invention is therefore a process for the manufacture of esters, or in particular of acetates, by transesterification reaction in a homogeneous liquid phase, characterized in that at least two, preferably two, esters, or in particular acetates, are manufactured continuously and simultaneously by at least two, preferably two, simultaneous transesterification reactions in a homogeneous liquid phase, which are carried out in a reaction zone (RZ),
(a) by continuously introducing into the said zone (1) a catalyst, (2) an organic ester, in particular an ester of a carboxylic, in particular aromatic or preferably aliphatic acid, for example from C
1
to C
12
, preferably from C
1
to C
6
, for example an acetate, and (3) simultaneously at least two, preferably two, different alcohols in particular from C
1
to C
16
, preferably from C
1
to C
12
, it being possible for at least one of the two alcohols to be chosen from primary or secondary alcohols and the other alcohol from secondary or tertiary alcohols, it being possible for the difference in boiling temperature of at least the two alcohols at atmospheric pressure to be furthermore advantageously from 10 to 60° C., preferably from 20 to 50° C., and
(b) by continuously drawing off from the said zone at least the two, preferably the two, esters manufactured, or in particular the acetates manufactured, and by separating them continuously by means of at least two, preferably two, successive distillations of the reaction mixture present in the said zone.
The process is very particularly suitable for continuously and simultaneously manufacturing at least two, preferably two, acetates (IV) and (V), by at least two, preferably two, simultaneous transesterification reactions in a homogeneous liquid phase, which are carried out in a reaction zone (RZ), by bringing into contact in the presence of a catalyst:
(i) an acetate of formula
CH
3
COOR (1)
in which R denotes an alkyl radical, in particular from C
1
to C
4
with
(ii) at least two, preferably two, alcohols of formulae
R
1
OH (II)
and
R
2
OH (III)
in which R
1
and R
2
, being different, denote alkyl radicals with a linear or branched chain, in particular from C
4
to C
12
, or radicals of formula
R
3
(OCH
2
CR
4
R
4
&Parenclosest;
m
in which R
3
denotes an alkyl radical, in particular from C
1
to C
6
, R
4
and R
5
, being identical or different, denote a hydrogen atom or an alkyl radical in particular from C
1
to C
4
, preferably C
1
or C
2,
for example methyl, and m is an integer ranging from 1 to 4, preferably equal to 1 or 2,
the products resulting from these reactions including at least the two, preferably the two, desired acetates, of formulae
CH
3
COOR
1
(IV)
and
CH
3
COOR
2
(V)
in which formulae R
1
and R
2
have the same definitions as above.
The process of the present invention may advantageously include the following operations:
(a) at least the two, preferably the two, simultaneous transesterification reactions are simultaneously carried out continuously in the reaction zone (RZ), the products resulting from these reactions being at least the two, preferably the two, desired esters, or in particular acetates, in particular of formulae (IV) and (V), and an alcohol, in particular of formula
ROH (VI)
in which R has the same definition as above, the products brought into contact in the reaction zone (RZ) forming a reaction mixture with the products resulting from these reactions,
(b) a distillation (D
1
) of the reaction mixture is carried out continuously at a pressure which is substantially identical with that existing in the reaction zone (RZ), by continuously separating a light fraction containing at least one azeotropic mixture (M
1
) formed of the initial ester (used), or in particular the acetate (I), with the alcohol formed, in particular of type (VI), from a heavy fraction containing at least the two, preferably the two, esters manufactured, or in particular acetates (IV) and (V),
(c) a distillation (D
2
) of the light fraction from (D
1
) is carried out continuously at a pressure which differs from that existing in (D
1
), so as to separate off continuously a portion of the alcohol formed in particular of type (VI), and
(d) at least two, preferably two, successive distillations (D
3
) and (D
4
) of the heavy fraction from (D
1
) are carried out continuously, so as to separate off continuously at least the two, preferably the two, esters manufactured or in particular acetates (IV) and (V).
REFERENCES:
patent: 1425624 (1922-08-01), Backhaus
patent: 3700726 (1972-10-01), Johnson, Jr. et al.
patent: 4370491 (1983-01-01), Bott et al.
patent: 4458088 (1984-07-01), Hardman et al.
patent: 4559180 (1985-12-01), Green
patent: 4960927 (1990-10-01), Canonge et al.
patent: 5350879 (1994-09-01), Engel et al.
patent: 5405992 (1995-04-01), Funk et al.
patent: 2 017 083 A (1979-10-01), None
Brun-Buisson Daniel
Grenouiller Bruno
Lalanne-Magne Philippe
BP Chemicals Limited
Finnegan, Henderson Farabow, Garrett and Dunner L.L.P.
Killos Paul J.
Oh Taylor V
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