[Technical field]
The present patent application relates to a process for the continuous production of ω-bromoalkanoic
acids and esters by hydrobromination. It also relates to a process for the production 5 of aminocarboxylic
acids and esters and of polyamide or of copolyamide from said ω-bromoalkanoic acids or esters.
[Prior art]
ω-Bromoalkanoic acids or esters, in particular the compounds of formula (II) below:
10 Br-(CH2)n+2-COOR (II)
are advantageous precursors in the polymer industry. In particular, they constitute intermediates for
the amino acids and amino esters necessary for the manufacture of polyamides. Thus, 11-
bromoundecanoic acid is the precursor of 11-aminoundecanoic acid, used on the industrial scale for
the manufacture of polyamide 11.
15 These compounds can be obtained by hydrobromination of a terminally unsaturated carboxylic acid
or ester, of formula (I):
CH2=CH-(CH2)n-COOR (I)
in which n is an integer of between 7 and 9, R is chosen from H or a linear or branched alkyl radical
comprising from 1 to 10 carbon atoms. The hydrobromination is carried out by addition of anti-
20 Markovnikov type of HBr to the compound of formula (I) in the presence of a radical initiator and of
one or more solvents.
Although it is possible to carry out the hydrobromination in batch mode, this requires recurrent
interventions, poses difficulties in recovering the residual gaseous HBr and is problematic to control
because of the high exothermicity of the reaction. The hydrobromination is thus generally carried out
25 continuously.
The already old patent FR 928 265 describes the hydrobromination of 10-undecenoic acid continuously
in a column maintained at a temperature of 30°C through which a solution of 10-undecenoic acid in
toluene passes and, countercurrentwise, HBr in excess and air. This process works well but produces
approximately 20% of 10-bromoundecanoic acid, which severely limits the yield.
30 Semyonov et al. provide (Maslozhirova Promyshlennost, 1971, Vol. 37, pp. 31-33) such a process
having a markedly higher yield (> 90%) in which the reaction is carried out in toluene in a plug-flow
reactor at a temperature of 0-5°C. Cooling the reactor to a very low temperature makes this process
not very energy efficient and requires major capital expenditures.
The patent CN 103804209 B describes the hydrobromination of 10-undecenoic acid continuously in a
35 system of two stirred reactors in series. The injection is carried out of a mixture of 10-undecenoic acid
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in toluene and benzene, 1% to 5% by weight of azobisisobutyronitrile or benzoyl peroxide as radical
initiator and of HBr into the first stirred reactor, maintained at a temperature of 10-30°C, with a
residence time of 30 to 90 minutes. The reaction medium from the first reactor is withdrawn
continuously and injected into an item of separation equipment heated to 65-80°C. The residual HBr
released in the gas form is returned to the first reactor. The maximum 5 yield indicated is 92.1%. This
process requires a prolonged residence time for a moderate yield. Furthermore, the large amount of
radical initiator can be the source of troublesome residues in the product.
All of these continuous processes operate with benzene, a carcinogenic and mutagenic solvent, and/or
toluene, a solvent capable of producing benzyl bromide, a lachrymatory compound.
10 In point of fact, today the aim is increasingly to replace benzene and toluene with other solvents having
a more favorable toxicity profile or generating less in the way of byproducts.
The patent EP 3 030 543 B1 provides a process for the continuous hydrobromination of 10-undecenoic
acid which makes it possible to at least partially replace benzene with cyclohexane and/or
methylcyclohexane. In this process, 10-undecenoic acid is reacted with HBr in liquid form. The
15 document teaches that the implementation of the process in a countercurrent column with
modification of solvent leads to a loss in yield, which can be compensated for when two successive
reactors are used, the first with a turbulent flow and the second a laminar flow. This method exhibits
the disadvantage of requiring an HBr in liquid form, which has the consequence of constraints in terms
of HBr purity and considerable energy expenditures and capital costs in order to cool the HBr or an HBr
20 solution to temperatures markedly below 0°C in order for the solubility of the HBr to be sufficient.
[Summary of the invention]
An aim of the invention is thus to provide a process for the continuous synthesis of ω-bromoalkanoic
acids and esters by hydrobromination not employing benzene and/or toluene, which exhibits a
25 satisfactory yield of product of formula (II), preferably of at least 92% and in particular of at least 94%.
According to one embodiment, an aim of the invention is to provide a continuous synthesis process
which saves energy, in particular requiring neither high pressure nor a temperature below 5°C.
According to another embodiment, an aim of the invention is to provide a continuous synthesis process
making possible the use of HBr contaminated with hydrogen, HCl or water.
30 According to another embodiment, an aim of the invention is to provide a continuous synthesis
process making it possible to reduce the amount of HBr introduced into the process, this compound
being expensive to produce and to remove.
According to yet another embodiment, an aim of the invention is to provide a continuous synthesis
process with a reduced residence time, in particular of less than 30 minutes and very particularly of
35 less than 15 minutes.
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According to another embodiment, an aim of the invention is to provide a continuous synthesis process
making it possible to produce a compound of formula (II) comprising nothing or little in the way of
impurities.
According to another embodiment, an aim of the invention is to provide a continuous synthesis process
not requiring solid radical initiators, which are reagents 5 at risk of violent decomposition.
According to another embodiment, an aim of the invention is a process for the production of
aminocarboxylic acid or ester from a compound of formula (II).
Finally, according to another embodiment, an aim of the invention is a process for the production of a
polyamide or copolyamide from a compound of formula (II).
10 In point of fact, the present invention is based on the observation that it is possible to replace benzene
and toluene, in the continuous production of ω-bromoalkanoic acids and esters by hydrobromination,
with aliphatic solvents while maintaining a high yield under the condition of ensuring a sufficient molar
excess of HBr during the reaction.
In order to obtain a high yield of compound of formula (II), it is important to properly control the
15 thermal conditions because a high temperature promotes the appearance of entities not carrying
bromine at the chain end.
Consequently, according to a first aspect, a subject matter of the invention is a process for the
continuous synthesis of a compound of formula (II) Br-(CH2)n+2-COOR, comprising a stage consisting of:
(a) the hydrobromination of a compound of formula (I) CH2=CH-(CH2)n-COOR:
20 where, in the formulae (I) and (II), n is an integer of between 7 and 9, and R is chosen from H
or a linear or branched alkyl radical comprising from 1 to 10 carbon atoms, in particular methyl,
ethyl, isopropyl or propyl,
with HBr in the presence of a radical initiator and of at least one solvent;
said process being characterized in that the reaction is carried out in the absence of benzene and of
25 toluene and in that, in stage (a), the HBr is injected into the reaction mixture in the gaseous form and
in stoichiometric excess.
Advantageously, the ratio of the molar flow rate of HBr injected in stage (a) to the molar flow rate of
the compound of formula (I) injected in stage (a) is from 1.2 to 3, preferably from 1.3 to 2.2, more
preferentially from 1.4 to 2 and in particular from 1.5 to 1.9.
30 According to one embodiment, the outlet stream from the reactor of the liquid reaction mixture on
conclusion of stage (a) comprises at least 2%, preferably at least 3%, and more preferentially at least
3.5% and in particular at least 4% by weight of HBr.
Preferably, the process of the invention additionally comprises the subsequent stages consisting of:
(b) the separation of the excess HBr from the liquid reaction mixture resulting from stage (a);
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(b1) optionally, separation of the excess HBr from the gaseous reaction mixture resulting from
stage (a); and
(c) the recycling of the HBr separated in stage (b) and (b1) if appropriate to stage (a).
Advantageously, the process of the invention comprises the stages consisting of:
(a1) introduction of the compound of formula (I), of the 5 HBr, of the initiator and of the
solvent(s) into a first reactor at an appropriate temperature for an appropriate
residence time;
(a2) withdrawal of the reaction mixture from the first reactor and introduction into an
item of separation equipment; if appropriate, followed by a subsequent stage of:
10 (b) separation of the residual HBr from the reaction mixture; and
(c) recycling of the separated HBr to stage (a1).
Stage (a) can be carried out in a reaction medium saturated with HBr. It can be carried out at a
temperature of between 5 and 50°C, preferably between 10 and 40°C and very particularly from 20 to
30°C.
15 The radical initiator can be molecular oxygen used as is or as a mixture with inert gases, for example
air or oxygen-enriched air.
The first reactor can in particular be a stirred vessel with a self-priming turbine or a jet loop reactor
comprising a venturi. The item of separation equipment can in particular be a stirred vessel or a
column.
20 Advantageously, the process according to the invention is carried out in the absence of aromatic
solvent.
The product of formula (I) can be chosen from 11-bromoundecanoic acid, 10-bromodecanoic acid and
9-bromononanoic acid.
The solvent can be chosen from cyclohexane, methylcyclohexane, methylcyclopentane, n-hexane, 2-
25 methylhexane, 3-methylhexane, n-heptane, isooctane, petroleum ether, tetralin, 1,1,1-
trichloroethane, dibromoethane, chloroform, carbon tetrachloride, tetrachlorethylene, 1-
bromopropane, dimethyl carbonate, tetrahydrofuran, 1,4 dioxane, 2-methyltetrahydrofuran,
tetrahydropyran, 1-propoxypropane, 1-ethoxybutane, 2-isopropoxypropane, acetonitrile and their
mixtures.
30 According to another aspect, the invention relates to a process for the synthesis of a compound of
formula (III) NH2-(CH2)n+2-COOR, comprising a stage consisting of:
(i) ammonolysis on the compound of formula (II) obtained by the above
process; and
(ii) separation of the compound of formula (III) NH2-(CH2)n+2-COOR formed.
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Finally, according to another aspect, the invention relates to a process for the synthesis of a polyamide
or copolyamide comprising the stage of polycondensation of the compound of formula (III) obtained
by the above process, alone or as a mixture with other monomers.
[Brief 5 description of the figures]
A better understanding of the invention will be obtained in the light of the description which follows
and of the figures, which show:
Fig. 1: a diagram of an installation for the implementation of a process according to one
embodiment of the invention;
10 Fig. 2: a diagram of an installation for the implementation of a process according to one
embodiment of the invention comprising a venturi and an external heat exchanger;
Fig. 3: a diagram of an installation for the implementation of a process according to one
embodiment of the invention comprising a venturi.
15 [Description of the embodiments]
Definition of the terms
In the context of the present disclosure, the term "stoichiometric excess, in the context of a
continuous process,” is understood to mean a greater molar flow rate of reactant than that required
for the reaction envisaged. For example, one mole/hour of HBr is required to carry out the
20 hydrobromination of one mole/hour of compound of formula (I). Consequently, a ratio of the molar
flow rate of HBr/molar flow rate of the compound of formula (I) > 1 constitutes a stoichiometric excess
of HBr.
In the context of the present disclosure, the term "residence time” is understood to mean the ratio of
the volume occupied by the liquid reaction mixture to the sum of the flow rates by volume of
25 compound of formula (I) and of solvents introduced into the process.
In the context of the present disclosure, the term "ω-bromoalkanoic acids or esters” is understood to
denote alkanoic acids or esters carrying at least one bromine atom on the terminal carbon atom. ω-
Alkanoic acids or esters having a linear chain are preferred.
The process of the invention is targeted at producing in particular ω-bromoalkanoic acids or esters of
30 formula (II) below:
Br-(CH2)n+2-COOR (II)
in which n is an integer of between 7 and 9, and R is chosen from H or a linear or branched alkyl radical
comprising from 1 to 10 carbon atoms, in particular methyl, ethyl, isopropyl or propyl.
The process is particularly advantageous for the manufacture of 12-bromododecanoic acid, 11-
35 bromoundecanoic acid and 10-bromodecanoic acid.
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Compound of formula (I)
ω-Bromoalkanoic acids or esters of formula (II) can be obtained by hydrobromination of a terminally
unsaturated carboxylic acid or ester, of formula (I):
5 CH2=CH-(CH2)n-COOR (I)
in which n is an integer of between 7 and 9, and R is chosen from H or a linear or branched alkyl radical
comprising from 1 to 10 carbon atoms, in particular methyl, ethyl, isopropyl or propyl.
The compound of formula (I) is advantageously 10-decenoic acid, 11-undecenoic acid or 12-
dodecenoic acid or one of their esters, in particular their methyl, ethyl, isopropyl or propyl ester.
10 These compounds are commercially available or can be synthesized by employing conventional organic
chemistry reactions. Some of these compounds can be obtained from starting materials which are
sustainable because of plant origin. Thus, 11-undecenoic acid is advantageously from castor oil, as
described in particular in FR 952 985.
The compounds of formula (I) are preferably employed in liquid form, either in molten form or in
15 solution in a suitable solvent.
Advantageously, the compound of formula (I) is employed at a temperature of 10 to 70°C and in
particular of 20 to 50°C.

CLAIMS
1. A process for the continuous synthesis of a compound of formula (II) Br-(CH2)n+2-COOR,
comprising a stage consisting of:
(a) the hydrobromination of a compound 5 of formula (I) CH2=CH-(CH2)n-COOR:
where, in the formulae (I) and (II), n is an integer of between 7 and 9, and R is chosen
from H or a linear or branched alkyl radical comprising from 1 to 10 carbon atoms,
in particular methyl, ethyl, isopropyl or propyl,
with HBr in the presence of a radical initiator and of at least one solvent;
10 said process being characterized in that the reaction is carried out in the absence of
benzene and of toluene and in that, in stage (a), the HBr is injected into the reaction
mixture in the gaseous form and in stoichiometric excess.
2. The process as claimed in claim 1, characterized in that the ratio of the molar flow rate
of HBr injected in stage (a) to the molar flow rate of the compound of formula (I)
15 injected in stage (a) is from 1.2 to 3, preferably from 1.3 to 2.2, more preferentially
from 1.4 to 2 and in particular from 1.5 to 1.9.
3. The process as claimed in claim 1 or 2, characterized in that the outlet stream from the
reactor of the liquid reaction mixture on conclusion of stage (a) comprises at least 2%,
preferably at least 3%, and more preferentially at least 3.5% and in particular at least
20 4% by weight of HBr.
4. The process as claimed in one of claims 1 to 3, characterized in that the process
additionally comprises the subsequent stages consisting of:
(b) the separation of the excess HBr from the liquid reaction mixture resulting from
stage (a);
25 (b1) optionally, separation of the excess HBr from the gaseous reaction mixture
resulting from stage (a); and
(c) the recycling of the HBr separated in stage (b) and (b1) if appropriate to stage
(a).
and
30 (c) the recycling of the HBr separated in stage (b) to stage (a).
5. The process as claimed in one of claims 1 to 4, comprising the stages consisting of:
(a1) introduction of the compound of formula (I), of the HBr, of the initiator and of
the solvent(s) into a first reactor at an appropriate temperature for an
appropriate residence time;
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(a2) withdrawal of the reaction mixture from the first reactor and introduction into
an item of separation equipment; if appropriate, followed by a subsequent
stage of:
(b) separation of the residual HBr from the reaction mixture; and
(c) recycling 5 of the separated HBr to stage (a1).
6. The process as claimed in one of claims 1 to 5, characterized in that stage (a) is carried
out at a temperature of between 5 and 50°C, preferably between 10 and 40°C and very
particularly from 20 to 30°C.
7. The process as claimed in one of claims 1 to 6, characterized in that the radical initiator
10 is molecular oxygen used as is or as a mixture with inert gases, for example air or
oxygen-enriched air.
8. The process as claimed in claim 4 to 7, characterized in that the first reactor is a stirred
vessel with a self-priming turbine or a jet loop reactor comprising a venturi.
9. The process as claimed in one of claims 4 to 8, characterized in that the item of
15 separation equipment is a stirred vessel or a column.
10. The process as claimed in one of claims 1 to 9, characterized in that it is carried out in
the absence of aromatic solvent.
11. The process as claimed in one of claims 1 to 10, characterized in that the product of
formula (I) is chosen from 11-bromoundecanoic acid, 10-bromodecanoic acid and 9-
20 bromononanoic acid.
12. The process as claimed in one of claims 1 to 11, characterized in that the solvent is
chosen from cyclohexane, methylcyclohexane, heptane, methylcyclopentane, nhexane,
2-methylhexane, 3-methylhexane, n-heptane, isooctane, petroleum ether,
tetralin, 1,1,1-trichloroethane, dibromoethane, chloroform, carbon tetrachloride,
25 tetrachlorethylene, 1-bromopropane, dimethyl carbonate, tetrahydrofuran, 1,4
dioxane, 2-methyltetrahydrofuran, tetrahydropyran, 1-propoxypropane, 1-
ethoxybutane, 2-isopropoxypropane, acetonitrile and their mixtures.
13. The process as claimed in one of claims 4 to 12, additionally comprising, during stage
(b) of separation of the excess HBr from the gaseous reaction mixture resulting from
30 stage (a).
14. A process for the synthesis of a compound of formula (III) NH2-(CH2)n+2-COOR,
comprising a stage consisting of:
(i) ammonolysis on the compound of formula (II) obtained by the process as
claimed in one of claims 1 to 13; and
35 (ii) separation of the compound of formula (III) NH2-(CH2)n+2-COOR formed.
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15. A process for the synthesis of a polyamide or copolyamide comprising the stage of
polycondensation of the compound of formula (III) obtained by the process as claimed
in claim 14, alone or as a mixture with other monomers.