Process for the synthesis of C11 and C12 omega-aminoalkanoic acid esters
comprising a nitrilation step
The work leading to this invention received financing from the European Union as part of
Framework Programme 7 (FP712007-2013) under project number 241718 EUROBIOREF.
The invention is directed to a process for synthesizing esters of C11 and C12
waminoalkanoic acids, comprises a step of metathesis, using esters of C10 and C11
walkenenoic acids as starting material.
The polyamides industry uses a whole range of monomers consisting of long-chain w-amino
acids, commonly termed Nylon, which are characterized by the length of methylene chain
(-CH,), separating two amide functions -CO-NH-. Known, accordingly, are nylon 6, nylon 6-
6, nylon 6-10, nylon 7, nylon 8, nylon 9, nylon 11, and nylon 13, etc. The "higher" nylons 11
and 13, for example, which use w-amino acids as monomer, occupy a separate place in this
class, insofar as they are synthesized not from petroleum-derived products (C2 to C4 olefins,
cycloalkanes or benzene), but from fatty acidslesters which are present in natural oils.
One example of a process using a fatty acid as starting material is that of the preparation of
fatty nitriles and/or amines from fatty acids extracted from plant or animal oils. This process
is described in the Kirk-Othmer encyclopedia, vol. 2, 4th edition, page 41 1. The fatty amine is
obtained in a number of steps. The first step involves methanolysis or hydrolysis of a plant oil
or of an animal fat, producing, respectively, the methyl ester of a fatty acid, or a fatty acid.
The methyl ester of the fatty acid may subsequently be hydrolyzed to form the fatty acid. The
fatty acid is subsequently converted into nitrile by reaction with ammonia, and finally into
amine by hydrogenation of the resultant nitrile.
Within the field of chemistry, moreover, present environmental developments are resulting in
preference being given to the exploitation of natural raw materials originating from a
renewable source. It is for this reason that certain research and development studies have
been taken up for the purpose of industrial development of processes using fatty acidslesters
as starting material for preparation of these w-at'nino acid monomers.
The main studies have looked at the synthesis of 9-amino nonanoic acid, the precursor to
Nylon 9, from oleic acid of natural origin. With regard to this monomer, it is possible to cite
the work "n-Nylons, Their Synthesis, Structure and Properties" - 1997, published by J. Wiley
and Sons, in which section 2.9 (pages 381 to 389) is devoted to 9-Nylon.
Industrially, for the preparation of polyamide polymerization monomers, there are only few
examples of processes using natural oils as starting material. One of the rare examples of an
industrial process using a fatty acid as starting material is the preparation process, from the
methyl ester of ricinoleic acid, extracted from castor oil, of I l-amino undecanoic acid, which
forms the basis for the synthesis of Rilsan 1 I@. This process is described in the work "Les
Procedes de Petrochimie" by A. Chauvel et al., published by Editions TECHNIP (1986). The
1 l-amino undecanoic acid is obtained in a number of steps. The first involves a methanolysis
of the castor oil in a basic medium, producing methyl ricinoleate, which is subsequently
subjected to pyrolysis to give heptanaldehyde on the one hand and methyl undecylenate on
the other. The latter is converted into acid form by hydrolysis. The acid formed is
subsequently subjected to hydrobromination, to give the w-brominated acid, which is
converted by ammonolysis into I I -amino undecanoic acid.
The applicant has since continued work on the processes for synthesis of these higher
monomers, based on the use of natural oils which are sources of oleic, ricinoleic, lesquerolic,
erucic or other acids. The applicant, accordingly, has explored a pathway wherein the acid
function was converted during the process into nitrile function by nitrilation (ammonization)
and then, after introduction of an acid or ester function into the molecule, by oxidative
cleavage or metathesis with an acrylate, was reduced to primary amine function at the end of
the conversions. This is the context in which the applicant filed a patent application,
W02010/055273, covering different versions of implementation of the process, all of them
involving the formation of an w-unsaturated fatty nitrile.
In the process of the invention, one important step is the nitrilation of the acidtester function
of the unsaturated fatty acid.
The reaction scheme for the synthesis of nitriles from a fatty acid may be summarized as
follows.
N H3
R-COOH -[ R-COO@NH ?] ---+ [R-CONH~] - R-CN + H20
+
H20
There are two types of processes based on this reaction scheme: a (generally batch)
process in liquid phase, and a (generally continuous) process in vapor phase.
In the batch process (liquid phase), the fatty acid or a mixture of fatty acids is charged with a
catalyst, which is generally a metal oxide and usually zinc oxide. The reaction mixture is
brought to approximately 150°C with stirring, and then the introduction of gaseous ammonia
is commenced. In a first phase, an ammonium salt or ammonium soap is formed. The
temperature of the reaction mixture is then brought to around 250"-300°C, still with
introduction of ammonia. The ammonium salt undergoes conversion to amide, with release
of a first molecule of water. Then, in a second phase and with the aid of the catalyst, the
amide undergoes conversion into nitrile, with formation of a second molecule of water. This
water formed is removed continuously from the reactor, carrying with it the unreacted
ammonia and a small amount of the lighter fatty chains.
In the (continuous) gas-phase process, the charge is evaporated and brought into contact
with ammonia which is at a temperature of between 250 and 600°C, in the presence of a
catalyst. This catalyst is generally selected from the class of metal oxides consisting of the
oxides of metals, taken alone or as a mixture, such as Zr, Ta, Ga, In, Sc, Nb, Hf, Fe, Zn, Sn
or alumina, silica, a thorium oxide, and particularly doped alumina.
These reactions, in their various forms, are mentioned in the Ullmann encyclopedia, vol. A2,
page 20, and the Kirk Othmer encyclopedia, vol. 2, pages 41 1-412, and have been a subject
of numerous patents, filed in particular by the company KAO. These include US patents
6,005,134, 6,080,891, and 7,259,274, which describe the synthesis of aliphatic nitriles in
liquid phase from fatty acids in the presence of a titanium catalyst. For the same applicant
and for the same type of process, there are Japanese applications 1 1-1 17990 (2610411 999)
with a niobium catalyst, and 9-4965 (1410111997) with a zirconium catalyst. There is also a
US patent, No. 4,801,730, which describes the nitrilation of glycerides in liquid phase, and a
Japanese application in the name of Lion Corp, of 13/03/1991 (publication No. JP 4283549),
which is directed to the synthesis of nitrile in gaseous phase.
In the studies it has conducted, the applicant has observed that the nitrilation step played an
important part, particularly in view of the fact that it was carried out on an w-unsaturated acid.
The reason is that the location of the double bond at the chain end, and therefore with little
protection, is able to give rise to formation of isomers, owing to the shifting of the double
bond. Having observed these phenomena, the applicant noted that this drawback could be
largely limited by working with the ester rather than with the corresponding acid, which would
allow operation under "milder conditions. The reason is that, since the boiling point of the
ester was lower than that of the corresponding acid, it was possible to obtain stronger vapor
tensions with the ester. Moreover, by working in a reactor operating continuously either in
gas phase or in mixed liquid-gas phase, the residence time of the reactants in contact with
the catalysts was significantly less than in conventional (batch) liquid phase, allowing
isomerization during the process to be limited.
The prior art essentially describes the liquid-phase nitrilation of the acid, and those which talk
of gas phase ignore the problem of the isomerization of the terminal double bonds, their
objectives being greatly different from those of the process of the invention.
The process of the invention aims to overcome the drawbacks of the prior art.
The invention provides a process for synthesizing acids or esters of w-aminoalkanoic acids
comprising 11 or 12 carbon atoms from w-unsaturated acid or ester comprising respectively
10 or 11 carbon atoms, characterized in that it comprises three main steps:
1) nitrilation of the w-unsaturated acidlester of the charge, of formula CH2=CH-(CH2),-
COOR, in which n is 7 or 8 and R is either H or an alkyl radical comprising 1 to 4 carbon
atoms, by action of ammonia, in a reactor operating continuously in gas phase or in mixed
gas-liquid phase, in the presence of a solid catalyst, then
2) conversion of the resulting nitrile of formula CH2=CH-(CH2),-CN by metathesis with
an acrylate of formula CH2=CH-COOR1, where R1 is either H or an alkyl radical comprising 1
to 4 carbon atoms, and lastly
3) hydrogenative reduction of the nitrile function of the compound of formula R100CCH=
CH-(CH2),-CN to give an amino acid or an amino ester of formula R100C-(CH2)n+2 -
CH2NH2.
The nitrilation step is carried out in a reactor operating continuously, in other words in which
the reactants, whether gaseous or liquid in origin, are introduced (and the products are
extracted) into (and from) the reactor continuously in accordance with predetermined flow
rates.
In a first embodiment, the two reactants may be introduced into the reactor in the gaseous
state (pure gaseous phase).
In the other embodiment (mixed phase), the ammonia is introduced in the form of gas while
the ester (acid) is introduced, after optional preheating, into the reactor close to the catalyst
bed, at least partly in liquid form at a rate determined so as to flow in the form of a film (trickle
bed) over the heated catalyst bed, in contact with which a fraction of the liquid is evaporated.
The reaction, or reaction series, takes place on contact with the surface of the catalyst, or in
its immediate proximity .This "trickle bed" technique is well-known and widely employed in
the petroleum industry. The flow of ammonia may be cocurrent or counter-current to the flow
of ester.
The process of the invention uses as its charge w-unsaturated acids or esters comprising
either 10 atoms or 11 atoms of carbon per molecule. The first - particularly methyl
9-decenoate - are sold in ester form by ELEVANCE Renewable Sciences; the second -
particularly methyl 10-undecenoate - are produced by the company ARKEMA in its
aforementioned castor oil-based process, with the methyl undecylenate being obtained after
pyrolysis.
The acrylate used in the second step will be selected from acrylic acid, methyl acrylate, ethyl
acrylate, n-propyl or isopropyl acrylate, or n-butyl, isobutyl, sec-butyl or tert-butyl acrylate.
The reaction scheme for the process is as follows:
CH2zCH-(CH2)n-COOR + NH3 3 CH2=CH-(CH2),-CN + ROH + H20
Nitrilation step
The process of catalytic nitrilation of-fatty acids is carried out at a reaction temperature of
generally between 200 and 400°C and preferably between 250 and 350°C. The wunsaturated
fatty acidslesters charge is evaporated and brought to a temperature of between
180 and 350°C in contact with ammonia introduced at a temperature of between 150 and
600°C.
The pressure is between 0.1 and 10 atmospheres (absolute) and preferably between 0.5 and
5, and more preferably between 1 and 3 atm.
When the nitrilation step is carried out in gas phase, the wunsaturated ester of fatty acids is
evaporated and brought at a temperature of between 180 and 350°C in contact with
ammonia introduced at a temperature of between 150 and 600°C and under a pressure of
between 0.1 and 10 atmospheres (absolute), preferably between 0.5 and 5, and more
preferably between 1 and 3 atmospheres, in the presence of solid catalyst; the reaction
temperature is preferably between 200°C and 400°C.
In the variant embodiment of the process that is entirely in gas phase, the rates at which the
reactants are introduced are such that the contact time with the solid catalyst is between 1
second and 300 seconds. In this case, the contact time is determined by the ratio calculated
as follows: {volume of catalyst (in liters) x 3600) 1 {[flow rate of unsaturated ester (in moleslh)
+ flow rate of ammonia (in moleslh)] x 22.4}=contact time in seconds.
In a variant of the process, the step of nitrilation of the w-unsaturated fatty acid ester is
carried out in mixed phase according to the trickle bed technique, the w-unsaturated ester of
fatty acids, optionally preheated, being passed progressively in trickling liquid form over the
solid catalyst, which is heated at a temperature such that there is partial, progressive
evaporation of the ester, allowing the reactions with ammonia on contact with the surface of
the catalyst or in its immediate proximity. The reaction temperature is generally between 200
and 400°C and preferably between 250 and 350°C. The rate at which the ester is introduced
is such that the mean residence time of the liquid phase in the reactor is less than 1 hour,
and preferably less than 30 minutes. This contact time is determined by the following
calculation: volume of catalyst (in liters) 1 flow rate of unsaturated ester (in liquid liters at 25°C
per hour), or the inverse of the liquid hourly liquid volume rate.
In this embodiment, it is possible to work in cocurrent, meaning that the gas current and the
liquid flow are descending, or in countercurrent, with the gas flow being ascending and the
liquid flow descending. This latter variant is preferred in the process of the invention. The
countercurrent version, with gas ascending and ester descending, may be of particular
advantage for limiting the hydrolysis of the nitrile formed. The reason is that in this
configuration, the ammonia is injected at the bottom, and the water and alcohol emerge at
the top; the ester enters at the top, and the nitrile emerges at the bottom. At the bottom,
therefore, the concentration of nitrile and of ammonia is high, and at the top the
concentration of ester, water, and alcohol is high, and the concentration of ammonia is less.
It is therefore possible to shift the equilibria, particularly that of the hydrolysis of the nitrile,
which restores the acid.
The molar NH3/fatty ester ratio of the reactants is between 1 and 50, preferably between 3
and 30, and more preferably between 5 and 20.
The reaction is carried out in the presence of a solid catalyst.
This catalyst is selected from the class of metal oxides or mixed metal oxides, consisting of
the oxides of metals, alone or as a mixture, such as Zr, Ce, Ti, Mo, W, V, S, P, Ta, Ga, In,
Sc, Nb, Hf, Fe, Zn, Sn, Al, Si. The oxides or mixed oxides constituting the catalyst may be
doped with other metals for the purpose of enhancing the catalytic performance levels. The
dopants which are suitable for the application include the following: rare earths, La, Pr, Nd,
Sm, Eu, Dy, Gd, Ho, Yb, and also Cu, Ni, Fe, Pb, Sn, In, Mn, Co, Mo, W, Nb, Zn, Cr, Si, Mg,
Ca, Sr, Sc, Y.
Preferred catalysts in the process of the invention are oxides based on zirconium, on cerium,
on titanium, on niobium, or on aluminum.
With zirconium oxide, the dopant used will comprise rare earths, in an amount of 5 to
50 mol%, and preferably from 8% to 15%, but also P, S, Cu, Ni, Fe, Pb, Sn, In, Mn, Mo, W,
Nb, Zn, Cr, Si with amount of 1% to 30% and preferably greater than 5%.
With cerium oxide, the dopant used will preferably be as follows: Mg, Ca, Sr, Sc, Y, and rare
earths, with amounts of 1% to 50%, and preferably more than 10%.
With titanium oxide, the dopant preferred will be W, Mo, P, S, Fe, Nb, Sn, Si, with amounts of
1 % to 50% and preferably of 5% to 20%.
As a method for preparing the catalysts, there are a number of possible candidate methods,
including coprecipitation, atomization, mixing, and impregnation. PreCursors of the oxides in
various forms may be used, particularly in oxide, nitrate, carbonate, chloride, sulfate
(including oxysulfate), phosphate, organometallic compound, acetate, and acetylacetonate
form. It is also possible to use the salts in sulfate or phosphate form in the preparation of
catalysts insofar as S or P are used as dopants of the catalyst. In that case, the preparation
of a catalyst from zirconium or titanium oxysulfate leads to a catalyst suitable for the process
of the invention.
The catalysts have a specific surface area of between 10 and 500 mZ/g, and preferably of
between 40 and 300 m21g.
The catalysts are formed by techniques which are suitable according to the type of reactor
used.
A number of reactor technologies may be suitable for the process of the invention: fixed bed
reactors, fluidized bed reactors in gas phase.
For the fixed bed reactors, the catalysts are present in the form of particles with a particle
size of 1 to 10 mm, or in the form of porous monoliths. The catalyst may in that case have a
variety of forms: beads, cylinders - hollow or not - sticks, etc. The reactor is used either
solely in gas phase or else as a trickle bed, where a gas phase coexists with a liquid phase.
The reactor may be employed as a fluidized bed. In this case, the catalyst is preset in the
form of a powder with a diameter of 40 to 500 microns and preferably with an average
particle size of 80 to 250 microns. The gas flow rate of NH3 reactant (majority gas in the
reactor) is sufficient to ensure fluidization of the solid. The fatty acids and esters have high
boiling points and so it may be advantageous to inject these reactants still in liquid form
directly into the fluidized bed of solid, with contact with the hot catalyst ensuring rapid
evaporation of the reactants, and also an increase in the gas volume ensuring fluidization.
The temperature of the reactor is regulated partly by the entry of liquid and gaseous
reactants at a high temperature, and partly by spines for circulation of a heat transfer fluid
that are installed actually within the reactor.
Metathesis step
Metathesis reactions have been known for a long time, although their industrial applications
are relatively limited. With regard to their use in the conversion of fatty acids (esters),
reference may be made to the article by J.C. Mol "Catalytic metathesis of unsaturated fatty
acid esters and oil" in Topics in Catalysis, vol. 27, Nos. 1-4, February 2004, p. 97 (Plenum
Publishing).
Catalysis of the metathesis reaction has been the subject of a great many studies and the
development of sophisticated catalyst systems. Mention may be made, for example, of the
tungsten complexes developed by Schrock et al. (J. Am. Chem. Soc. 108 (1986) 2771 or
Basset et al. Angew. Chem., Ed. Engl. 31 (1992) 628. Having appeared more recently are
catalysts known as Grubbs catalysts (Grubbs et al., Angew. Chem., Ed. Engl. 34 (1995)
2039 and Organic Lett. 1 (1999) 953), which are ruthenium-benzylidene complexes. This is a
homogeneous catalysis. Heterogeneous catalysts have also been developed, based on
metals such as rhenium, molybdenum, and tungsten that are deposited on alumina or silica.
Finally, studies have been carried out for the production of immobilized catalysts, these being
catalysts whose active principle is that of the homogeneous catalyst, especially the
ruthenium-carbene complexes, but is immobilized on an inert support. The objective of thee
studies is to enhance the selectivity of the cross metathesis reaction with regard to sidereactions,
such as the "homo-metatheses" between the reactants when combined. The
studies relate not only to the structure of the catalysts but also to the effect of the reaction
medium and to the additives that may be introduced. They also relate to the methods of
recovering the catalyst after reaction.
In the process of the invention, any active and selective metathesis catalyst will be able to be
used. Preferably, however, ruthenium-based catalysts will be used.
The cross metathesis reaction with the acrylate compound is carried out under very wellknown
conditions. The reaction temperature is between 20 and 100°C, generally at
atmospheric pressure, in a stream of inert gas or under partial vacuum, to allow easy release
of ethylene in the presence of a ruthenium-based catalyst.
The ruthenium catalysts are selected preferably from charged or noncharged catalysts of
general formula:
in which:
a, b, c, and d are integers, with a and b being 0, 1 or 2; c and d being 0, 1, 2, 3, or 4,
XI and X2, which are identical or different, each represent a charged or noncharged
unidentate or multidentate ligand; examples include halides, sulfate, carbonate, carboxylates,
alkoxides, phenoxides, amides, tosylate, hexafluorophosphate, tetrafluoroborate, bistriflylamide,
tetraphenylborate, and derivatives.
XI or X2 may be bonded to L1 or L2 or to the (carbene C) so as to form a bidentate (or
chelate) ligand on the ruthenium, and
L1 and L2, which are identical or different, are electron-donating ligands such as
phosphine, phosphite, phosphonite, phosphinite, arsine, stilbine, an olefin or an aromatic, a
carbonyl compound, an ether, an alcohol, an amine, a pyridine or derivative, an imine, a
thioether, or a heterocyclic carbene,
L1 or L2 may be bonded to the (carbene C) so as to form a bidentate or chelate ligand,
The (carbene C) may be represented by the general formula: C-(R1)-(R2), for which R1 and
R2 are identical or different, such as hydrogen or any other saturated or unsaturated cyclic,
branched, or linear hydrocarbon group, or aromatic hydrocarbon group. Examples include
complexes of ruthenium with alkylidenes, or with cumulenes such as vinylidenes
Ru=C=CHR, or with allenylidenes Ru=C=C=CRl R2, or with indenylidenes.
A functional group which enhances the retention of the ruthenium complex in the ionic liquid
may be grafted on at least one of the ligands XI, X2, L1, L2, or on the carbene C. This
functional group may be charged or noncharged, such as, preferably, an ester, an ether, a
thiol, an acid, an alcohol, an amine, a nitrogen-containing heterocycle, a sulfonate, a
carboxylate, a quaternary ammonium, a guanidinium, a quaternary phosphonium, a
pyridinium, an imidazolium, a morpholinium, or a sulfonium.
Hydrogenation step
The step of synthesizing w-amino esters or w-amino fatty acids from unsaturated fatty (acid)
nitrile-esters involves a conventional hydrogenation referred to in the Encyclopedias
mentioned above, in the same sections and chapters. Hydrogenation of the nitrile function
automatically entails saturation of the double bond present in the molecule.
The reduction of the nitrile function to primary amine is well known to the skilled person. The
hydrogenation may be carried out in the presence of precious metals (Pt, Pd, Rh, Ru, etc.) at
a temperature of between 20 and 100°C under a pressure of 1 to 5 bar. It may also be
carried out in the presence of catalysts based on iron, nickel, or cobalt, which may entail
more severe conditions, with temperatures of the order of 150°C and with high pressures of
several tens of bar. The catalysts are numerous, but preference is given to using Raney
nickels and Raney cobalts. In order to promote the formation of primary amine, a partial
pressure of ammonia is employed.
With preference, the step of reducing fatty (acid) nitrile-esters to w-amino esters or w-amino
fatty acids involves a hydrogenation using any conventional catalyst and preferably Raney
nickels and Raney cobalts.
The charge treated is preferably in the form of w-unsaturated fatty acid ester.
The process of the invention is illustrated by the examples which follow, which are qiven
without limitation.
Example I : Nitrilation
The active element of the catalyst that is used is an Anatase ST 31 119 titanium oxide
produced by the company Saint-Gobain, having a specific surface area of 48 mZ/g. The
titanium oxide is impregnated with an ammonium paratungstate solution to give a
homogeneous coating of tungsten oxide of 5% by weight. The solid is subsequently calcined
in a stream of air at 400°C for 2 hours.
1 g of catalyst is placed in a tubular reactor with a diameter of 10 mm. Silicon carbide is
placed over the catalyst bed, and ensures preheating of the reactants. The reactor is
supplied with a gas mixture of ammonia and methyl undecylenate, in a molar ratio of 511 and
with a HSV of 600 h", or a contact time of approximately 5 seconds. The reactants are
preheated very rapidly to 250°C before entering the reactor. Following reaction, the gases
are cooled to approximately 120°C, to allow condensation of the nitrile, and of unconverted
reactants, and to keep the ammonia and also the water and methanol produced in the gas
phase. The products of the reaction are subsequently analyzed by chromatography.
The conversion of the methyl undecylenate is 99.5%, and the yield of nitrile is 96%, at a
reaction temperature of 300°C. The selectivity for 10-cyanodecene (omega unsaturated
nitrile) is 95%, relative to the entirety of the nitriles produced.
Example 2 (comparative)
This example illustrates the conventional liquid-phase nitrilation step converting
10-undecenoic acid into nitrile of formula CN-(CH2)8-CH=CH2.
The nitrilation reaction of 10-undecenoic acid (3.5 g) to form the w-unsaturated nitrile of
formula CN-(CH2)8-CH=CHi2s carried out batchwise. The reaction mixture is heated to 160°C
at a rate of 1°C per minute. Introduction of ammonia (0.417 literlkg acid.min) commences
when the 160°C have been reached stably, and this temperature is maintained until the acid
index of the mixture falls below 0.1 mg KOHlg. The temperature is subsequently increased to
265°C (the temperature is limited by the very substantial evaporation of the mixture at the
operating pressure). The reaction is halted after 18 hours. Through the synthesis, a
dephlegmator located downstream of the reactor is maintained at 130°C. The reaction is
carried out at atmospheric pressure in the presence of a zinc oxide catalyst (0.0625% by
weight relative to the acid). Continuous removal of the water formed entrains the excess
ammonia and allows rapid completion of the reaction. 2.6 g of the nitrile are recovered, and
are separated by vacuum distillation. The omega unsaturated nitrile represents 90% of the
nitriles obtained.
Example 3: Cross metathesis
This example illustrates the cross metathesis reaction of undecenenitrile of formula CN-
(CH&-CH=CH2 with methyl acrylate, with the Hoveyda-Grubbs II catalyst:
A 50 ml Schlenk tube purged with nitrogen is charged with 83 mg of 10-undecenenitrile
(0.5 mmol), 86 mg of methyl acrylate (1 mmol) and 10 ml of toluene distilled over sodium
benzophenone. 9.5 mg of 2nd-generation Hoveyda-Grubbs catalyst (1.5x10-~ mmol) are
added, and the mixture is heated at 100°C for 1 hour.
Analysis by gas chromatography shows that the conversion of 10-undecenitrile is 100% and
that the yield of usaturated nitrile-ester is 98%.
Example 4: Hydrogenation
The reaction mixture obtained from example 3 is then transferred to a 50 ml Parr bomb (filled
to 22 ml). 10 mg of I % PdlC catalyst and 17 mg of potassium tert-butoxide (0.15 mmol) are
added and the bomb is pressurized under 20 bar of hydrogen. Heating is carried out at 80°C
for 48 hours with magnetic stirring.
Analysis by gas chromatography shows that the conversion of the unsaturated nitrile-ester is
9O0/0 and that the yield of methyl 12-amino-dodecanoate is 64%.
Example 5 (com~arative)
This example illustrates the step of conventional liquid-phase nitrilation converting the methyl
ester of 10-undecenoic acid into nitrile of formula CN-(CH2)*-CH=CH2.
The nitrilation reaction of the ester of 10-undecenoic acid (3.77 g) to form the w-unsaturated
nitrile of formula CN-(CH2)8-CH=CH2is carried out batchwise, and in liquid phase. The
procedure is as for example 2. The reaction mixture is heated to 160°C at a rate of 1°C per
minute. Introduction of ammonia (0.417 literlkg acid.min) commences when the 160°C have
been reached stably. The acid index remains low since an ester is present. The temperature
is subsequently raised to 240°C (the temperature is limited by the boiling point of the methyl
ester). The reaction is carried out with total reflux of the methyl ester and is therefore very
difficult to carry out, and energy-consuming. The reaction temperature increases gradually
with the conversion of the methyl ester, reaching a plateau due to the boiling of the desired
product: 10-undecenenitrile. The reaction is halted after 18 hours. Throughout the synthesis,
a dephlegmator located downstream of the reactor is maintained at 130°C. The reaction is
carrie'd out at atmospheric pressure in the presence of a zinc oxide catalyst (0.0625% by
weight relative to the acid). Continuous removal of the water formed entrains the excess
ammonia and allows rapid completion of the reaction. 1.2 g of the nitrile are recovered, and
are separated by vacuum distillation. The omega unsaturated nitrile represents 85% of the
nitriles obtained.
Example 6: Nitrilation
Nb205, freshly prepared by hydrolysis of niobium chloride (until chloride is absent from the
washing liquors in the silver nitrate test), then calcining at 300°C in air for 1 hour, is used as
catalyst.
5 g of catalyst are placed in a tubular reactor with a diameter of 10 mm. Silicon carbide is
placed over the catalyst bed, and ensures preheating of the reactants. The reactor is
supplied with a gas mixture of ammonia and methyl undecylenate, in a molar ratio of 511 and
with a HSV of 120 h-', or a contact time of approximately 30 seconds. The reactants are
preheated very rapidly to 200°C before entering the reactor. Following reaction, the gases
are cooled to approximately 120°C, to allow condensation of the nitrile, and of unconverted
reactants, and to keep the ammonia and also the water and methanol produced in the gas
phase. The products of the reaction are subsequently analyzed by chromatography.
The conversion of the methyl undecylenate is 97%, and the yield of nitrile is 95%, at a
reaction temperature of 250°C. The selectivity for 10-cyanodecene or 10-undecenenitrile
(omega unsaturated nitrile) is 96%, relative to the entirety of the nitrites produced.

CLAIMS
1. A process for synthesizing acids or esters of w-aminoalkanoic acids comprising 11 or 12
carbon atoms from w-unsaturated acid or ester comprising respectively 10 or 11 carbon
atoms, characterized in that it comprises three main steps:
- nitrilation of the w-unsaturated acidtester of the charge, of formula CH2=CH-(CH2),-
COOR, in which n is 7 or 8 and R is either H or an alkyl radical comprising 1 to 4 carbon
atoms, by action of ammonia, in a reactor operating continuously in gas phase or in mixed
gas-liquid phase, in the presence of a solid catalyst, then
- conversion of the resulting nitrile of formula CH2=CH-(CH2),-CN by metathesis with
an acrylate of formula CH2=CH-COOR1, where R1 is either H or an alkyl radical comprising 1
to 4 carbon atoms, and lastly
- hydrogenative reduction of the nitrile function of the compound of formula R1OOCCH=
CH-(CH2),-CN to give an amino acid or an amino ester of formula R100C--(CH2),,2-
CH2NH2.
2. The process as claimed in claim 1, characterized in that in the nitrilation step performed in
gas phase, the w-unsaturated fatty acid ester is evaporated and brought at a temperature of
between 180 and 350°C into contact with ammonia introduced at a temperature of between
150 and 600°C and under a pressure of between 0.1 and 10 atmospheres (absolute),
preferably between 0.5 and 5, and more preferably between I and 3 atmospheres, in the
presence of the solid catalyst.
3. The process as claimed in claim 2, characterized in that the reaction temperature is
generally between 200 and 400°C and preferably between 250 and 35OoC, and in that the
rates at which the reactants are introduced are such that the contact time with the solid
catalyst is between 1 second and 300 seconds.
4. The process as claimed in claim 1, characterized in that the step of nitrilation of the wunsaturated
fatty acid ester is carried out in mixed phase according to the trickle bed
technique, with the optionally preheated w-unsaturated fatty acid ester being conveyed
progressively in trickling liquid form over the solid catalyst heated at a temperature such that
there is partial, progressive evaporation of the ester, permitting the reactions with ammonia
on contact with the surface of the catalyst or in its immediate proximity.
O R l ~ l ~2 ~R JLAN 2*0a1 4 - -- --
Ry";. i' . i. 7 : l , ; f , ; ;C4 ' k _ p E 4 , b'
\ '9
5. The process as claimed in claim 4, characterized in that the reaction temperature is
generally between 200 and 400°C and preferably between 250 and 350°C, and in that the
rate at which the ester is introduced is such that the mean residence time of the liquid phase
in the reactor is less than 1 hour, and preferably less than 30 minutes.
6. The process as claimed in any of claims 1 to 5, characterized in that the molar NHs/fatty
ester ratio of the reactants is between 1 and 50, preferably between 3 and 30, and more
preferably between 5 and 20..
7. The process as claimed in any of claims 1 to 6, characterized in that the solid catalyst is
selected from the class of metal oxides consisting of the oxides of metals, alone or in a
mixture, such as Zr, Ce, Ti, Mo, W, V, S, P, Ta, Ga, In, Sc, Nb, Hf, Fe, Zn, Sn, Al, Si.
8. The process as claimed in claim 7, characterized in that the oxides or mixed oxides that
constitute the catalyst may be doped with other metals, the dopants suitable for application
including the following: rare earths, La, Pr, Nd, Sm, Eu, Dy, Gd, Ho, Yb, and also Cu, Ni, Fe,
Pb, Sn, In, Mn, Co, Mo, W, Nb, Zn, Cr, Si, Mg, Ca, Sr, Sc, and Y.
9. The process as claimed in either of claims 7 and 8, characterized in that the catalysts have
a specific surface area between 10 and 500 m2/g, and preferably of between 40 and
300 m2/g.
10. The process as claimed in any of claims 1 to 9, characterized in that the cross metathesis
reaction with the acrylate compound is carried out at a temperature of between 20 and
1 OO°C, generally at atmospheric pressure, to allow easy release of ethylene, in the presence
of a ruthenium-based catalyst.
11. The process as claimed in any of claims 1 to 10, characterized in that the ruthenium
catalysts are selected preferably from charged or noncharged catalysts of general formula:
(X1)a (X2)bRu(carbene C) ( ~ l ) c ( ~ 2 j d
in which:
a, b, c, and d are integers, with a and b being 0, I or 2; c and d being 0, 1, 2, 3, or 4,
XI and X2, which are identical or different, each represent a charged or noncharged
unidentate or multidentate ligand,
0x1 or X2 may be bonded to L1 or L2 or to the (carbene C) so as to form a bidentate (or
chelate) ligand on the ruthenium, and
L1 and L2, which are identical or different, are electron-donating ligands such as
phosphine, phosphite, phosphonite, phosphinite, arsine, stilbine, an olefin or an aromatic, a
carbonyl compound, an ether, an alcohol, an amine, a pyridine or derivative, an imine, a
thioether, or a heterocyclic carbene,
L1 or L2 may be bonded to the (carbene C) so as to form a bidentate or chelate ligand,
the (carbene C) may be represented by the general formula: C-(R1)-(RZ), for which R1
and R2 are identical or different, such as hydrogen or any other saturated or unsaturated
cyclic, branched, or linear hydrocarbon group, or aromatic hydrocarbon group.
12. The process as claimed in any of claims 1 to 11, characterized in that the step of
reduction of the fatty (acid) nitrile esters to w-amino esters or w-amino-fatty acids involves a
hydrogenation using any conventional catalyst and preferably Raney nickels and Raney
cobalts.
13. The process as claimed in any of claims 1 to 12, characterized in that the treated charge
is in the form of an w-unsaturated fatty acid ester.
Dated this 281h day of January, 2014
[S WATI PAHUJA]
OF REMFRY & SAGAR
ATTORNEY FOR THE APPLICANT[SJ