Technical field
The present invention relates to the production of (meth)acrylic ester according
to a continuous transesterification process, and in particular the production of N,Ndimethylaminoethyl
acrylate (hereinafter denoted ADAME).
10 The invention provides a process for producing a (meth)acrylic ester with
improved productivity, by transesterification of a light alkyl (meth)acrylate with a
heavy alcohol. The process of the invention includes the recycling of the valuable
products recovered after heat treatment of heavy fractions generated during synthesis,
said heat treatment being carried out in the presence of a dialkyl phthalate, the alkyl
15 chain of which corresponds to that of the light alkyl (meth)acrylate.
Prior art and technical problem
The economic viability of industrial processes for producing (meth)acrylic
derivatives is strongly linked to the recycling of fractions generated during the process
20 for purification of the crude products, these fractions being liable to contain unreacted
reagents, reclaimable by-products and/or the desired compound, in not inconsiderable
amounts, and also the reaction catalyst.
Transesterification processes involve a "short" chain, C1-C4, alkyl
(meth)acrylate, referred to as light alkyl (meth)acrylate or light (meth)acrylate, which
25 reacts with an alcohol with a "longer" carbon-based chain, referred to as heavy alcohol,
generally in the presence of a catalyst and of polymerization inhibitors, according to the
30
following gene~~l formula (1 ): i.''
H2C=C(R)COOR1 + R20H "' Iii H2C=C(R)COOR2 + R10H (1)
with R = H or CH3 ; R1 = C1-C4 alkyl chain; R20H =heavy alcohol
In order to shift the equilibrium towards the formation of "long" chain alkyl
(meth)acrylate, the light alcohol R1 OH released during the reaction is continuously
eliminated in the form of an azeotrope with the light (meth)acrylate. Due to the presence
5
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of light alcohol, this azeotrope is advantageously recycled to the unit for producing light
(meth)acrylate, the synthesis of which is based on the direct esterification of
(meth)acrylic acid with the light alcohol.
The transesterification reaction of (meth)acrylic derivatives leads to the
formation of impurities, such as Michael adducts resulting from Michael addition
reactions of an alcohol molecule (containing a labile hydrogen atom) onto the double
bond ofthe (meth)acrylic ester.
For example, in the case of the production of ADAME by transesterification
10 between a light acrylate, such as methyl acrylate (MA) or ethyl acrylate (EA), and N,N-
15
20
25
dimethylarninoethanol (DMAE), the as yet unreacted alcohol or the light alcohols
generated during the reaction (methanol or ethanol) are added at the double bond of the
already formed ADAME or of the unreacted light acrylate (MA or EA), to form heavy
Michael addition by-products [DMAE +ADAME] of formula:
or [DMAE + MAIEA] of formula:
c~
N~ ~COOR cH( o
A characteristic of these heavy by-products is that thei:.:-'boiling point is above
the boiling points of the products used in the reaction and of the desired ADAME.
These heavy by-products are generally concentrated in a "heavy fraction",
separated during the process for purifying the crude ADAME, this heavy fraction
possibly comprising, within the context of the present invention, not only Michael
adducts but also, generally, the transesterification catalyst, the polymerization inhibitors
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which were added to the reaction, and also a minor fraction of residual reagents and/or
of ADAME.
The elimination ofthis heavy fraction generally poses a problem since it must be
incinerated, and leads to significant losses of raw materials (especially DMAE) and of
5 finished product (ADAME) which are present in this fraction in free form or in the form
of Michael adducts.
The residual reagents and/or the ADAME present in the heavy fraction are
valuable products since recycling thereof makes it possible to directly increase the
productivity of the process. Recycling all of the heavy fraction cannot be envisaged in a
10 continuous industrial process because it would lead to an accumulation of Michael
adducts in the purification loop unless the Michael adducts were thermally cracked
beforehand to give their constituent components.
To this end, patent application WO 2013/045786, in the applicant's name,
proposed carrying out thermal cracking of the heavy (meth)acrylic fractions generated
15 during the production of (meth)acrylic esters by transesterification, to recover the
valuable products in the form of a stream of recyclable distillate. This process is
especially characterized by the introduction of at least one antifouling agent and
optionally a viscosity-reducing agent (or fluxing agent) into the heavy fractions, in order
to carry out thermal cracking so as to avoid fouling the apparatus used and obtain a final
20 residue that is sufficiently fluid to be transported by means of a pump and eliminated by
incineration.
However, the applicant has observed that the presence of an antifouling
compound such as a phosphoric ester, or of a compound fulfilling the role both of
antifouling agent and fluxing agent, such as the product sold by Nalco under the name
25 Nalco ® EC3368A, leads to the formation of impurities in the distillate generated during
the thermal cracking.
particular; the presence of a not inconsiderable amount of methanol has been
observed in the abovementioned process for synthesising ADAME from EA using the
Nalco® EC 3368A product as fluxing agent. The presence of methanol is particularly
30 bothersome because the methanol is found in the various recycling loops, thereby
polluting, upstream the reaction, the azeotrope which is used to at least partially
synthesize the ethyl acrylate, and consequently polluting the ethyl acrylate.
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Surprisingly, the inventors have now discovered that the use of a dialkyl
phthalate, the alkyl chain of which corresponds to that of the light alkyl (meth)acrylate,
for carrying out the thermal cracking of heavy fractions generated during the production
of (meth)acrylic esters by transesterification of a light alkyl (meth)acrylate with a heavy
5 alcohol, not only makes it possible to avoid fouling of the apparatus used and to obtain a
final residue which is transportable by means of a pump in order to be incinerated, but
also avoids the potential pollution risks. This use thus expands the possibilities for
recycling valuable, reclaimable products. In addition, unexpectedly, it has been possible
to demonstrate that such a compound has a beneficial effect on the effectiveness of the
1 0 thermal cracking.
One of the aims of the present invention is thus to overcome the drawbacks of
the abovementioned process described in document WO 2013/045786. The present
invention makes it possible to recycle, at different stages of the purification section,
valuable products (starting compounds or finished product) which can be potentially
15 recovered from the heavy fraction generated in a process for synthesizing (meth)acrylic
esters by transesterification of a light alkyl (meth)acrylate, in particular in a process for
synthesizing dialkylaminoalkyl (meth)acrylate. This enhancement leads to improving
the material balance of the process and reducing the final amounts of residue to be
incinerated, and it consequently represents an economic advantage.
20 It has moreover become apparent to the inventors that the present invention
could also be applied to, the.production of alkyl (meth)acrylate with a linear or branched
alkyl chain comprising from 5 to 12 carbon atoms.
Summary of the invention
25 Therefore, a subject of the present invention is a process for recovering valuable
products from a heavy (meth)acrylic fraction generated during production of a
(meth)acrylic ester by transesterification reaction of a light C1-C4 alkyl (meth)acrylate
with a heavy alcohol in the presence of a catalyst, the heavy fraction comprising at least
valuable products and Michael adducts resulting from addition reactions on the
30 (meth)acrylic double bonds and also the catalyst, said process comprising the heat
treatment of said heavy fraction at a temperature sufficient to crack the Michael adducts
into their constituent valuable components, the recovery of the valuable products in the
5
wo 2016/124837 PCT/FR2016/050177
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form of a distillate and the elimination of the fluid final residue by means of a pump,
characterized in that the heat treatment is carried out in the presence of at least one
dialkyl phthalate, the alkyl chain of which corresponds to that of the light alkyl
(meth)acrylate.
According to one embodiment of the invention, at least a portion of the heavy
fraction is recycled to the transesterification reaction, the other portion being subjected
to said heat treatment.
According to one embodiment of the invention, the heavy fraction is subjected
10 beforehand to purification by passage over a film evaporator, at least a portion of the
bottom stream from the film evaporator being recycled to the transesterification
reaction, the other portion being subjected to said heat treatment. The light compounds
present in the top stream from the film evaporator may thus advantageously be recycled.
The heavy fraction contains a significant amount of catalyst, possibly
15 representing up to 50% by weight. Recycling of the still active catalyst to the
transesterification reaction, via the recycling of at least a portion of the heavy fraction,
makes it possible to significantly reduce the feed of fresh catalyst into the reactor.
20
The term "(meth)acrylic" means acrylic or methacrylic; the term
"(meth)acrylate" means acrylate or methacrylate.
Valuable products is intended to mean unreacted reagents (heavy alcohol and
light (meth)acrylate used in the transesterification . reaction) . and . the. desired
(meth)acrylic ester.
Heavy alcohol is intended to mean a primary or secondary alcohol comprising a
linear or branched alkyl chain ranging from 4 to 18 carbon atoms, possibly being
25 interrupted by one or more heteroatoms such as N or 0.
The heavy fraction comprises Michael adducts and valuable products, but also
' generally the transesterification catalyst and the polymerization inhibitors which have
been added to the reaction.
According to the invention, the addition of at least one dialkyl phthalate into the
30 heavy fraction makes it possible to obtain an improved degree of thermal cracking, and
minimizes the residual amount of Michael adduct in the final residue.
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According to the invention, associating the nature of the dialkyl phthalate,
introduced as antifouling/fluxing agent in the step of cracking of the Michael adducts, to
the nature of the light alkyl (meth)acrylate used as starting material in the process,
avoids the generation of impurities which are damaging for the recycling of the valuable
5 products.
10
According to one embodiment of the invention, the heavy alcohol 1s an
aminoalcohol of formula (II):
HO-A-N (R'2)(R'3) (II)
in which
-A is a linear or branched C1-C5 alkylene radical,
- R' 2 and R' 3, which are identical to ,or different from one another, each
represent a C1-C4 alkyl radical.
The heavy alcohol may for example be N,N-dimethylaminoethanol (DMAE),
15 N,N-diethylaminoethanol, or N,N-dimethylaminopropanol.
According to a preferred embodiment of the invention, the aminoalcohol is N,Ndimethylaminoethanol
(DMAE), and the (meth)acrylic ester is N,N-dimethylaminoethyl
acrylate (ADAME).
According to one embodiment of the invention, the heavy alcohol is an alcohol
20 of formula R20H, in which R2 represents a linear or branched C5-C12 alkyl chain. The
heavy alcohol may be primary or secondary. The heavy alcohol is, for example, 2-
ethylhexanol or 2-octanol.
According to a preferred embodiment of the invention, the light alkyl
(meth)acrylate is methyl acrylate and the dialkyl phthalate is dimethyl phthalate.
25 According to a preferred embodiment of the invention, the light alkyl
(meth)acrylate is ethyl acrylate and the dialkyl phthalate is diethyl phthalate.
According to a preferred embodiment of the invention, the light alkyl
(meth)acrylate is butyl acrylate and the Jialkyl phthalate is dibutyl phthalate.
30 A second subject of the invention is a process for producing a (meth)acrylic
ester by transesterification reaction between a light C1-C4 alkyl (meth)acrylate and a
heavy alcohol,
5
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said process comprising at least the following steps:
a) subjecting a reaction mixture, comprising a light alkyl (meth)acrylate, a heavy
alcohol, a transesterification catalyst and at least one polymerization inhibitor, to
transesterification conditions in order to form i) a mixture of products
comprising the (meth)acrylic ester and the unreacted light alkyl (meth)acrylate
and heavy alcohol, the catalyst, the polymerization inhibitors, Michael adducts
resulting from addition reactions onto the (meth)acrylic double bonds, and other
heavy compounds such as oligomers or polymers; and ii) an azeotropic mixture
oflight alkyl (meth)acrylate/free light alcohol;
10 b) distilling the mixture i) of products in order to recover, at the top, a stream
15
20
composed essentially of the desired (meth)acrylic ester and light products,
comprising a minority fraction of Michael adducts, heavy products and
polymerization inhibitors, but free or substantially free of catalyst, and in order
to leave, at the bottom, a heavy fraction comprising catalyst, polymerization
inhibitors, Michael adducts and heavy compounds, with a minority fraction of
the desired (meth)acrylic ester and heavy alcohol and traces of light products;
c) purifying the top stream, making it possible to obtain the purified (meth)acrylic
ester;
d) subjecting at least a portion of the heavy fraction to a process for recovering the
valuable products in the form of a distillate as defined above;
e) recycling at least a portion of said distillate into at least one step chosen from
step a) of reaction, step b) of distillation and step c) of purification;
f) optionally recycling the azeotropic mixture ii) formed in step a), to the light
alkyl (meth)acrylate production unit;
25 g) optionally recycling at least a portion of the fluid final residue resulting from
step d), to step a) of reaction;
h) incinerating the fluid final residue resulting from step d);
i) optionally recycling a portion of the heavy fraction to step a) of reaction.
30 According to one embodiment of the invention, the step of purification c) is
carried out by means of two distillation columns series and at least a portion of the
distillate resulting from step d) is recycled to the top of the first purification column.
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According to one embodiment of the invention, the heavy fraction is at least
partially subjected beforehand to purification by passage over a film evaporator before
step d).
According to one embodiment, a portion of the bottom stream from the film
5 evaporator is recycled to step a) of reaction.
The invention is advantageously carried out for the production of N,Ndimethylaminoethyl
(ADAME) by the transesterification reaction between ethyl
acrylate (EA) and N,N-dimethylaminoethanol (DMAE), step d) being carried out in the
10 presence of diethyl phthalate.
The invention is now described in more detail and nonlimitingly in the following
description, with reference to the appended figure 1 which schematically represents
different embodiments according to the invention in a facility for a continuous process
15 for producing ADAME by transesterification starting from EA and DMAE.
Detailed description of the invention
In the process according to the invention, the heat treatment of the heavy
fraction is carried out in the presence of at least one C1-C4 dialkyl phthalate, and the
20 alkyl chain is similar to the alkyl chain of the light alkyl (meth)acrylate used as starting
material for producing the (meth)acrylic ester.
According to one embodiment of the invention, the light alkyl (meth)acrylate is
ethyl acrylate (EA), the heavy alcohol is N,N-dimethylaminoethanol (DMAE), the
(meth)acrylic ester is N,N-dimethylaminoethyl acrylate (ADAME), and the dialkyl
25 phthalate is diethyl phthalate.
According to one embodiment of the invention, the light alkyl (meth)acrylate is
methyl acrylate (MA), the heavy alcohol is N,N-dimethylaminoethanol (DMAE), the
(meth)acrylic ester is N,N-dimethylaminoethyl acrylate (ADAME), and the dialkyl
phthalate is dimethyl phthalate.
30 According to one embodiment of the invention, the light alkyl (meth)acrylate is
butyl acrylate (BuA), the heavy alcohol is N,N-dimethylaminoethanol (DMAE), the
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(meth)acrylic ester is N,N-dimethylaminoethyl acrylate (ADAME), and the dialkyl
phthalate is dibutyl phthalate.
According to one embodiment of the invention, the light alkyl (meth)acrylate is
methyl acrylate (MA), the heavy alcohol is 2-ethylhexanol, the (meth)acrylic ester is 2-
5 ethylhexyl acrylate (2EHA), and the dialkyl phthalate is dimethyl phthalate.
According to one embodiment of the invention, the light alkyl (meth)acrylate is
ethyl acrylate (EA), the heavy alcohol is 2-ethylhexanol, the (meth)acrylic ester is 2-
ethylhexyl acrylate (2EHA), and the dialkyl phthalate is diethyl phthalate.
According to one embodiment of the invention, the light alkyl (meth)acrylate is
10 butyl acrylate (BuA), the heavy alcohol is 2-ethylhexanol, the (meth)acrylic ester is 2-
ethylhexyl acrylate (2EHA), and the dialkyl phthalate is dibutyl phthalate.
According to one embodiment of the invention, the light alkyl (meth)acrylate is
methyl acrylate (MA), the heavy alcohol is 2-octanol, the (meth)acrylic ester is 2-octyl
acrylate (20CTA), and the dialkyl phthalate is dimethyl phthalate.
15 According to one embodiment of the invention, the light alkyl (meth)acrylate is
ethyl acrylate (EA), the heavy alcohol is 2-octanol, the (meth)acrylic ester is 2-octyl
acrylate (20CTA), and the dialkyl phthalate is diethyl phthalate.
According to one embodiment of the invention, the light alkyl (meth)acrylate is
butyl acrylate (BuA), the heavy alcohol is 2-octanol, the (meth)acrylic ester is 2-octyl
20 acrylate (20CTA), and the dialkyl phthalate is dibutyl phthalate.
dialkyl phthalate may be introduced as is into the heavy fraction at the
cracking reactor, or introduced in solution in a solvent, or else in solution in one of the
reagents of the process.
25 The dialkyl phthalate may be introduced at a concentration ranging from 0.001%
to 1% by weight, especially from 0.01% to 5% by weight, preferably from 0.1% to
0.5% by weight into the heavy fraction to be treated.
The dialkyl phthalate has the advantage of acting both as antifouling agent and
viscosity-reducing agent (fluxing agent) in the heat treatment step. The result thereof is
30 a residue having a suitable viscosity for being readily transportable by means of a
pump, this viscosity generally being less than 200 cP, preferably less than 50 cP.
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The heavy fraction contains virtually all of the catalyst used to carry out the
transesterification reaction.
The heavy fraction to be treated may contain various polymerization inhibitors
among which mention may be made of phenothiazine (PTZ), hydroquinone (HQ) and
5 derivatives thereof such as hydroquinone methyl ether, 2,6-di-tert-butyl-4-methylphenol
(BHT), N-oxyl compounds of 4-hydroxy-2,2,6,6-tetramethylpiperidinoxyl (4-0HTEMPO)
type and mixtures thereof in any proportions. It is possible to add an amount
of polymerization inhibitor ranging from 500 to 5000 ppm before subjecting the heavy
fraction to the heat treatment.
10 The heat treatment is carried out at a temperature ranging from 1 oooc to 250°C,
preferably from 150 to 200°C, making it possible to eliminate, by distillation, the
valuable products initially present and the valuable products resulting from the thermal
cracking ofthe,Michael adducts.
The heat treatment is carried out without adding additional catalyst into the
15 heavy fraction to be treated.
20
The heat treatment may be carried out in batch or continuous mode in a jacketed
reactor or in a reboiler surmounted by a column which above all has the role of demister
in order to limit the rise of the inhibitors.
The residence time is generally between 30 min and two hours.
It may be advantageous to only subject a portion of the heavy fraction to the heat
treatment, and to recycle the other portion to the transesterification reaction.
According to this embodiment, the amount of fresh catalyst to be introduced into
the transesterification reactor may be reduced down to 50% by weight, without
observing an increase in the concentration of heavy compounds in the reactor.
25 From 5% to 50%, more particularly from 10% to 30% by weight of the heavy
fraction are preferably recycled to the reaction, the remainder being. subjected to the
heat treatment.
In a preferred variant of the invention, prior to the heat treatment, the heavy
fraction is conveyed over a film evaporator order to recover and recycle the light
30 compounds present in trace amounts.
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According to this variant, it is also advantageous to only subject a portion of the
bottom stream from the film evaporator to the heat treatment, and to recycle the other
portion to the transesterification reaction.
From 5% to 50%, more particularly from 10% to 30% by weight of the bottom
5 stream from the film evaporator are preferably recycled to the reaction, the remainder
being subjected to the heat treatment.
At the end of the heat treatment, the valuable products, essentially the desired
(meth)acrylic ester and the umeacted alcohol, are recovered in the form of a distillate,
after distillation under nitrogen atmosphere or air depleted to 8 vol% of oxygen and
10 under reduced pressure, for example from 10 to 50 mbar. The use of depleted air is
preferred.
The valuable products recovered in this way are reclaimed by recycling them in
the facility, at different steps of the process; either at the reaction or at the steps for
purification of the crude reaction product.
15 Since the temperature of the medium remains greater than 60°C, the final residue
is sufficiently fluid to be directly transportable by means of a pump.
The final residue is rich in transesterification catalyst and may advantageously
be at least partially recycled to the step of reaction by transesterification.
From 5% to 50%, more particularly from 10% to 20% by weight of final residue
20 are preferably recycled to the reaction, the remainder being finally eliminated by
incineration.
Appended figure 1 illustrates a continuous process for producing ADAME by
transesterification starting from EA and DMAE, in which steps (a) to (i) are more
25 generally applicable to the production of (meth)acrylic esters by transesterification
starting from light C1-C4 alkyl (meth)acrylates, and from heavy alcohols defined in the
process according to the invention.
According to a first step (a), the transesterification reaction between EA and
DMAE is carried out in the reactor 1 in the presence of a catalyst, preferentially
30 tetraethyl titanate, and polymerization inhibitors. The reactor 1 is surmounted by a
distillation column 2 which serves to eliminate the light alcohol formed (ethanol) as it is
formed, and to thereby shift the reaction equilibrium towards the formation of ADAME.
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The azeotropic fraction generated during the transesterification reaction is
advantageously recycled to the unit for producing light alkyl (meth)acrylate (step (f)),
since it does not contain any bothersome impurities liable to form (meth)acrylic byproducts.
5 According to step (b) of the process, the reaction mixture is subjected to
10
distillation on a distillation column (tailing column 3). At the top of the column 3, a
stream 7 is recovered which has had virtually all the catalyst and polymerization
inhibitors removed from it and which comprises the ADAME produced and light
compounds with a minority fraction of Michael ad ducts and heavy products.
At the bottom of the column 3, a heavy fraction 4 is recovered, comprising the
catalyst, the polymerization inhibitors, the Michael adducts and the heavy compounds
such as oligomers and polymers with a minority fraction of ADAME and DMAE and
traces of light compounds.
According to step (c) of the process, the stream 7 is subjected to purification
15 which is carried out by means of the distillation column 8, the top stream 9 of which is
recycled to the reaction, the bottom stream 10 being directed to a distillation column 11,
making it possible to obtain purified ADAME 12 at the top and a stream 13 at the
bottom which is rich in inhibitors and which is recycled to the stream of crude reaction
mixture supplying the column 3.
20
25
According to step (d) of the process, the heavy fraction 4 originating from the
bottom of the column 3, which especially contains the catalyst, is partially (stream 22)
subjected to the process according to invention for recovering valuable products
(ADAME and DMAE) in the reactor 15, the other portion (stream 24) being able to be
recycled to the reactor 1 (step (i) of the process).
At least one portion (stream 25) of the heavy fraction may be concentrated
beforehand on a film evaporator 5 which makes it possible to separate the traces of light
compounds which are then recycled to the feed of column 3. The heavy fraction 6
originating from the evaporator generally contains, by weight, approximately 1% to
20% of DMAE, 10% to 30% of ADAME, 10% to 40% of Michael adducts [DMAE -
30 ADAME], the remainder essentially consisting of from 10% to 50% by weight of
catalyst and polymerization inhibitors and other heavy by-products.
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A portion of this stream 6 may be recycled to the reaction (stream 19) in order to
reduce the feed of fresh catalyst.
A portion of.the heavy fraction 6, with the light compounds removed from it, is
conveyed into the reactor 15 (stream 23) after addition of a dialkyl phthalate 14 under
5 the conditions indicated above.
As a variant, a portion of the heavy fraction 4 (stream 21) may be mixed with
the bottom stream from the film evaporator, in order to at least partially be subjected to
the heat treatment. In the absence or presence of film evaporator, a portion of the heavy
fraction may be eliminated by incineration.
10 The reactor 15 may be of the jacketed type or reboiler type surmounted by a
distillation column 17 oflow efficacy (1 to 3 theoretical plates) which more accurately
serves as demister.
In the reactor 15, the heavy fraction comprising the Michael adducts is subjected
to thermal cracking making it possible to recover a stream 18 rich in DMAE and
15 ADAME at the top ofthe column 17.
The thermal cracking carried out under the conditions according to the invention
makes it possible to recover, by simple distillation, more than 80% by weight of the
valuable products (ADAME and DMAE) contained in the fraction 6 originating from
the evaporator 5, and to obtain a degree of cracking of the Michael adducts of more than
20 60 wt%, or even more than 70 wt% .
25
30
. The stream 18 may be recycled, according to step (e) of the pmcess, at the
synthesis reactor 1, at the inlet of the topping column 3, or at the inlet of the column 8
for purification of the ADAME; a combination of these different modes of recycling is
possible.
The final residues 16 at the outlet of the reactor 15, rich in catalyst and
polymerization inhibitors, may be at least partially recycled into the synthesis reactor 1
(stream 20), the remainder being incinerated, in the final step (h).
It is understood that the process of the invention may comprise any combination
of the different variants described.
The examples below illustrate the present invention without however limiting
the scope thereof.
5
10
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EXAMPLES
Unless indicated otherwise, the percentages are expressed as percentages by weight.
The following abbreviations are used;
EA: Ethyl acrylate
DMAE: N,N-dimethylaminoethanol
ADAME: N,N-dimethylaminoethyl acrylate
AP A: Michael adduct resulting from the addition of DMAE onto ADAME:
[DMAE-ADAME]
EPA: Michael adduct resulting from the addition of DMAE onto EA:
[DMAE+EA]
Example 1 (comparative)
300 g of a heavy residue originating from an ADAME synthesis starting from EA and
15 DMAE are introduced into a mechanically stirred glass reactor, heated by means of an
electrical heating mantle and surmounted by a Vigreux column with condenser, vacuum
distillation receiver and collecting vessels.
The composition by weight of this residue is as follows:
DMAE: 15.8%- ADAME: 17.5%- APA: 22.3%- EPA: 2.5%- q.s. 100%: heavy
20 products + catalyst + inhibitors. This residue does not contain methanol.
25
30
5000 ppm.ofthe compound Nalco® EC3368A were added to the mixture, before heating
the residue with stirring and nitrogen bubbling for 90 min at 180°C under a working
pressure of 50 mbar. The following were recovered:
Distillate: 15 0 g
Final residue: 132 g
The composition by weight of the distillate is:
DMAE: 22.3%
ADAME: 50.5%
APA: 11.66%
EA: 0.44%
Methanol: 95 ppm
Other heavy products: q.s. 100%
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There is minimal fouling of the reactor, the final residue is viscous but does not solidify
at room temperature.
Example 2 (according to the invention)
5 Example 1 was reproduced, replacing the compound Nalco® EC3368A with diethyl
phthalate from Sigma Aldrich.
10
15
The subsequent treatment is similar to example 1.
The following were recovered:
Distillate: 155 g
Final residue: 133 g
The composition by weight of the distillate is:
DMAE:23.7%
ADAME: 57.2%
APA: 6.52%
EA: 0.84%
Methanol: 0 ppm
Other heavy products: q.s. 100%
There is minimal fouling of the reactor, the final residue is viscous but does not solidify
at room temperature. Moreover, the use of diethyl phthalate as fluxing/dispersing agent
20 made it possible to avoid the formation of methanol in the distillate, which can thus be
recyded without generating impurities in the process for synthesizing ADAME.
Example 3 (continuous, comparative)
A heavy fraction from an ADAME synthesis was introduced by means of a membrane
25 pump into a glass reactor consisting of a thermosiphon reboiler. The feed flow rate is
regulated by measuring the weight of residue in the tank. The reboiler is heated by
means of a jacketed oil bath with a power of 160 W order to minimize the skin
temperature. The assembly is lagged and the heating temperature is adjusted to have the
required temperature in the reboiler. At the top of the reboiler, a column element
30 equipped with a multiknit element serving as demister has been added.
The bottom fraction was recovered by overflowing into the reboiler then taken up by a
pump to be directed towards a receiver.
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The operations were carried out under reduced pressure (50 mbar) and with nitrogen
bubbling.
The composition by weight of the heavy fraction introduced is as follows:
DMAE: 5%
5 ADAME: 21.6%
APA: 35.7%
EA: 0.4%
10
15
q.s. 100%: heavy products +catalyst+ inhibitors.
The heavy fraction does not contain methanol.
5000 ppm of the compound Nalco® EC3368A were added to the mixture.
The operating parameters of the micropilot plant are as follows:
Feed flow rate: 110 g/h
Residence time: 90 min
Pressure: 50 mbar
Reboi1er temperature: l80°C
After one hour of reaction, 51 g of distillate and 59 g of final residue were recovered.
The composition by weight of the distillate is:
DMAE: 23.3%
20 ADAME: 66.1%
APA:O%
EA: 2.9%
Methanol: 104 ppm
The composition by weight of the residue is:
25 DMAE: 13.2%
ADAME: 2.7%
APA: 29.9%
EA: 0.04%
Absence of methanol.
30 Heavy products+ catalyst+ inhibitors: q.s. 100%
The weight balances from this test are as follows:
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17
- ADAME: from 23.8 g present in the free state in the heavy fraction, 33.7 g are
recovered, a portion of which originates from the thermal cracking of the AP A.
- DMAE: from 5.5 g present in the free state in the heavy fraction, 11.8 g are recovered,
a portion of which originates from the thermal cracking of the AP A.
5 - APA: from 39.3 g present in the heavy fraction, there is only 17.6 g remaining after
thermal cracking of the AP A.
The degree of cracking of the AP A, expressed as the weight of AP A which has
disappeared by cracking relative to the weight present, is of the order of 55%.
The reactor is perfectly clean (no attachment of solids) and the final residue is perfectly
10 fluid under hot conditions.
However, a not inconsiderable amount of ethanol is present in the distillate, which leads
to the presence of a bothersome impurity during the recycling of the distillate in the
synthesis process.
15 Example 4 (continuous, according to the invention)
Example 3 was reproduced with a heavy fraction of the following composition:
DMAE: 10.3%
ADAME: 15.3%
APA: 22.1%
20 EA: 0.08%
Absence of methanoL
q.s. 100%: heavy products +catalyst+ inhibitors.
The compound Nalco® EC3368A was replaced by diethyl phthalate (5000 ppm).
25 The operating parameters of the micropilot plant are as follows:
Feed flow rate: 200 g/h
Residence time: 90 min
Reboiler temperature: 180°C
After one hour of reaction, 125 g of distillate and 7 5 g of final residue were recovered.
30 The composition by weight of the distillate is:
DMAE: 19.9%
ADAME: 68.2%
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APA: 0%
EA: 1.46%
Absence of methanol.
18
The composition by weight of the residue is:
PCT/FR2016/050177
5 DMAE: 8.9%
ADAME: 0.9%
APA: 8.6%
EA: 0.005%
10
Absence of methanol.
q.s. 100%: heavy products+ catalyst+ inhibitors.
Weight balance:
- ADAME: from 30.6 g present in the free state in the heavy fraction, 85.25 g are
recovered, a portion of which originates from the thermal cracking of the AP A.
15 - DMAE: from 20.6 g present in the free state in the heavy fraction, 24.8 g are
recovered, a portion of which originates from the thermal cracking of the AP A.
- APA: from 44.2 g present in the heavy fraction, there is only 8.7 g remaining after
thermal cracking of the AP A.
20 Under these conditions, the degree of cracking of the AP A is of the order of 80%, the
reactor is perfectly clean (no .attachment of solids) and the final residue is perfectly fluid
under hot conditions. Moreover, the distillate does not contain any methanol, which
makes it possible to advantageously return this fraction to a step of the synthesis and/or
purification process.
25 The use of the diethyl phthalate made it possible both to avoid returning methanol to the
distillate fraction but also to improve the degree of cracking of the heavy by-products.
Example 5 (continuous, according to the invention)
Example 4 was reproduced with the following conditions:
30 The composition by weight of the heavy fraction introduced is as follows:
DMAE: 16%- ADAME: 14%- APA: 24%- q.s. 100%: heavy products+ catalyst+
inhibitors.
5
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5000 ppm of diethyl phthalate were added.
The operating parameters of the micropilot plant are as follows:
Feed flow rate: 200 glh
Residence time: 90 min
Pressure: 50 mbar
Reboiler temperature: 180°C
Degree of depletion: 50%
PCT/FR2016/050177
After one hour of reaction, 100 g of distillate and 100 g of final residue were recovered.
The composition by weight of the distillate is:
10 DMAE: 23.1%
ADAME: 60.5%
APA: 0.06%
EA: 2.5%
EPA: 0%
15 The composition by weight of the residue is:
DMAE: 14.5%
ADAME: 1.7%
APA: 9.6%
Heavy products + catalyst+ inhibitors: q.s. 100%
20 The weight balances demonstrate the reclamation of the ADAME and the DMAE
recovered during the proc~ss according to the invention: '· · , , .
- ADAME: from 28.9 g present in the free state in the heavy fraction, 61.1 g are
recovered, a portion of which originates from the thermal cracking of the AP A.
- DMAE: from 33.3 g present in the free state the heavy fraction, 23.3 g are
25 recovered, a portion of which originates from the thermal cracking of the AP A.
- APA: from 48.4 g present in the heavy fraction, there is only 9.8 g remaining after
thermal cracking of the AP A. The degree of cracking is 79 .8%.
The reactor is clean and the final residue is fluid under hot conditions.
30 Example 6: effect of recycling the catalyst present the bottom stream from the film
evaporator
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DMAE (2.73 mol), EA (4.7 mol, 1.6 molar eq.), and 21.84 mmol of Ti(OEt)4 as
transesterification catalyst are introduced into a 1 liter glass reactor mechanically heated
by means of a jacket.
According to the tests, the catalyst used is an 85/15 solution by weight of pure Ti(OEt)4
5 in DMAE, or a mixture of this solution with Ti(OEt)4 resulting from a stream of heavy
products originating from the bottom of a film evaporator from an industrial ADAME
unit.
The reaction medium is then heated at 11 ooc for 3 h, the EA!EtOH azeotropic mixture
is withdrawn to shift the equilibrium.
10 The crude reaction product is then analyzed to calculate the yield. Analysis of the crude
product is carried out by gas chromatography.
15
20
The yield of ADAME formed under these conditions is determined from the number of
moles of ADAME produced relative to the number of moles ofDMAE introduced.
Table 1
Test Ti(OEt)4 catalyst in Ti( 0 Et )4 from Yield of ADAME, %
DMAE, recycling,
mmoles ofTi(OEt)4 mmoles of Ti(OEt)4
1 21.84 0 77
2 17.47 0 71
3 10.92 0 57
4 17.47 4.37 '' ·' 76· .,
' ..
5 10.92 10.92 76
The results of the tests carried out, collated in table 1 above, show that recycling the
heavy fraction separated on a film evaporator makes it possible to save almost 50% by
weight of esterification catalyst, with equivalent production.

CLAIMS
PCT/FR2016/050177
1. A process for recovering valuable products from a heavy (meth)acrylic
fraction generated during production of a (meth)acrylic ester by transesterification
5 reaction of a light C1-C4 alkyl (meth)acrylate with a heavy alcohol in the presence of a
catalyst, the heavy fraction comprising at least valuable products and Michael adducts
resulting from addition reactions on the (meth)acrylic double bonds and also the
catalyst, said process comprising the heat treatment of said heavy fraction at a
temperature sufficient to crack the Michael adducts into their constituent valuable
10 components, the recovery of the valuable products in the form of a distillate and the
elimination of the fluid fmal residue by means of a pump, characterized in that the heat
treatment is carried out in the presence of at least one dialkyl phthalate, the alkyl chain
of which corresponds to that of the light alkyl (meth)acrylate.
15 2. The process as claimed in claim 1, characterized in that the light alkyl
(meth)acrylate is methyl acrylate and the dialkyl phthalate is dimethyl phthalate.
3. The process as claimed in claim 1, characterized in that the light alkyl
(meth)acrylate is ethyl acrylate and the dialkyl phthalate is diethyl phthalate.
20
.4, The process as claimed in claim 1, characterized in that the light alkyl
(meth)acrylate is butyl acrylate and the dialkyl phthalate is dibutyl phthalate.
5. The process as claimed in any one of the preceding claims, characterized
25 that the dialkyl phthalate is added at a concentration ranging from 0.001% to 1% by
weight, especially from 0.01% to 5% by weight, preferably from 0.1% to 0.5% by
weight into the heavy fraction to be treated.
30 ill
The process as claimed any one of the preceding claims, characterized
the heavy alcohol is an aminoalcohol of formula (II):
HO-A-N (R'2)(R'3) (II)
in which
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22
-A is a linear or branched C1-C5 alkylene radical,
- R'2 and R'3, which are identical to or different from one another, each
represent a C1-C4 alkyl radical.
5 7. The process as claimed m claim 6, characterized in that the heavy
alcohol is N,N-dimethylaminoethanol.
8. The process as claimed in any one of claims 1 to 5, characterized in that
the heavy alcohol is an alcohol of formula R20H, in which R2 represents a linear or
10 branched C5-C12 alkyl chain, for example 2-ethylhexanol or 2-octanol.
15
9. The process as claimed in any one of the preceding claims, characterized
in that at least a portion of the heavy fraction' is recycled to the transesterification
reaction, the other portion being subjected to said heat treatment.
10. The process as claimed in any one of the preceding claims, characterized
in that the heavy fraction is subjected beforehand to purification by passage over a film
evaporator, at least a portion of the bottom stream from the film evaporator being
recycled to the transesterification reaction, the other portion being subjected to said heat
20 treatment.
A process for producing a (meth)acrylic ester by transesterification
reaction between a light C1-C4 alkyl (meth)acrylate and a heavy alcohol, said process
comprising at least the following steps:
25 a) subjecting a reaction mixture, comprising a light alkyl (meth)acrylate, a heavy
30
alcohol, a transesterification catalyst and at least one polymerization inhibitor, to
transesterification conditions in order to form i) a mixture of products
comprising the (meth)acrylic ester and the umeacted light alkyl (meth)acrylate
and heavy alcohol, the catalyst, the polymerization inhibitors, Michael adducts
resulting from addition reactions onto the (meth)acrylic double bonds, and other
heavy compounds such as oligomers or polymers; and ii) an azeotropic mixture
of light alkyl (meth)acrylate/free light alcohol;
5
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b) distilling the mixture i) of products in order to recover, at the top, a stream
composed essentially of the desired (meth)acrylic ester and light products,
comprising a minority fraction of Michael adducts, heavy products and
polymerization inhibitors, but free or substantially free of catalyst, and in order
to leave, at the bottom, a heavy fraction comprising catalyst, polymerization
inhibitors, Michael adducts and heavy compounds, with a minority fraction of
the desired (meth)acrylic ester and heavy alcohol and traces of light products;
c) purifying the top stream, making it possible to obtain the purified (meth)acrylic
ester;
10 d) subjecting at least a portion of the heavy fraction to a process for recovering the
valuable products in the form of a distillate as defined in any one of claims 1 to
10;
e) recycling at least a portion of said distillate into at least one step chosen from
step a) of reaction, step b) of distillation and step c) of purification;
15 f) optionally recycling the azeotropic mixture ii) formed in step a), to the light
alkyl ( meth )acrylate production unit;
g) optionally recycling at least a portion of the fluid final residue resulting from
step d), to step a) of reaction;
h) incinerating the fluid fmal residue resulting from step d);
20 i) optionally recycling a portion of the heavy fraction to step a) of reaction.
25
The process as claimed claim 11, characterized in that said heavy
fraction is subjected beforehand to purification by passage over a film evaporator before
step d).
13. The process as claimed in claim 12, characterized in that a portion of the
bottom stream from the film evaporator is recycled to step a) of reaction.
The process as claimed any one of claims 11 to 13, characterized in
30 that the step of purification c) is carried out by means of two distillation columns in
series and at least a portion of the distillate resulting from step d) is recycled to the top
of the first purification column.
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15. The process as claimed in any one of claims 11 to 14, characterized in
that the (meth)acrylic ester is N,N-dimethylaminoethyl acrylate resulting from the
transesterification reaction between N,N-dimethylaminoethanol and ethyl acrylate, and
5 step d) is carried out in the presence of diethyl phthalate.