PROCESS FOR RECOVERING NOBLE PRODUCTS IN A PROCESS FOR
PRODUCING DIALKYLAMINOALKYL (METH) ACRYLATES
Field of technology
The present invention relates to the manufacture
of dialkylaminoalkyl (meth)acrylate, in particular N,N~
dimethylaminoethyl acrylate, by transesterification
reaction of an alkyl (meth)acrylate with an amino
alcohol, and relates more particularly to a process for
recovering the heavy byproducts generated during said
manufacture, permitting the recycling of noble products
to the dialkylaminoalkyl (meth)acrylate purification
unit.
Prior art and technical problem
The dialkylaminoalkyl (meth)acrylates
corresponding to formula (I):
H2C = C (R'i)- C(0)- 0 - A - N (R'2) (R»3) (I)
in which:
- R'i is a hydrogen atom or a methyl radical
-A is a linear or branched C1-C5 alkylene radical
- R'2 and R13, which may be identical or different, each
represent a C1-C4 alkyl radical,
are generally obtained by a transesterification
reaction between an amino alcohol of formula (II):
HO-A- N(R'2) (R'3) (II)
in which A, R'2 and R'3 are as defined above,
and a light alkyl (meth)acrylate of formula (III):
CH2=C (R'i) -COOR '4 (III)
in which R' i is as defined above and R! 4 represents the
methyl or ethyl radical.
The reaction is generally carried out in a stirred
reactor in the presence of a transesterification
catalyst and at least one polymerization inhibitor and
the light alkyl (meth)acrylate (III) / light alcohol
R'4OH azeotropic mixture generated during
transesterif!cation is withdrawn continuously during
the reaction.
The problems that arise during manufacture of the
dialkylaminoalkyl (meth)acrylates, notably the
formation of heavy byproducts resulting from Michael
addition reactions between the compounds present in the
reaction mixture, will now be described, for
convenience, on the basis of the example of N,Ndimethylaminoethyl
acrylate (designated ADAME
hereinafter) corresponding to the following formula
(la) :
H2C=CH-COOCH2CH2N(CH3)2 (la)
obtained by transesterification reaction between a
light alkyl acrylate and N,N-dimethylaminoethanol
(DMAE) .
The problems and the solution proposed by the
invention are the same in the case when on the one hand
a light alkyl methacrylate, or on the other hand amino
alcohols other than DMAE, are used in the
transesterification reaction.
The industrial process for manufacturing ADAME,
such as that described for example in the applicant's
patents EP 0960 0877 or FR 2 811 986, consists of a
transesterification reaction between ethyl acrylate
(EA) or methyl acrylate (MA) and N,N-~
dimethylaminoethanol (DMAE).
This reaction is generally catalyzed by a
tetraalkyl- titanate such as tetraethyl titanate.. .in
solution in the DMAE in the case of the ADAME prepared
starting from EA, and by a tin derivative (dibutyltin
oxide (DBTO) or distannoxane) in the case of ADAME
prepared starting from MA.
The reaction is generally carried out in the
presence of a polymerization inhibitor and in the
presence of air depleted to 8% oxygen (% by volume).
The light alcohol, methanol or ethanol, that forms
during the reaction is distilled as it is formed, in
the form of an MA/methanol or EA/ethanol azeotrope.
This process can be carried out as a batch process or
continuously, for example in a stirred reactor.
The crude reaction product generally contains the
ADAME produced, unreacted light ester (EA or MA), light
alcohol generated (ethanol or methanol), residual DMAE
alcohol, heavy byproducts, the catalyst, and. the
polymerization inhibitors.
Regarding the side reactions leading to the
formation of heavy byproducts during the manufacture of
(meth)acrylic monomers, there is notably a reaction of
Michael addition of a molecule containing a labile
hydrogen atom (such as an alcohol) on the double bond
of a (meth)acrylic compound.
For example, in the case of the manufacture of
ADAME, the DMAE alcohol that has not yet reacted or the
light alcohols formed {methanol or ethanol) add onto
the double bond of the ADAME already formed or of the
unreacted light acrylate (MA or EA) , to form heavy
byproducts of Michael addition [DMAE+ADAME] of formula:
or [DMAE+MA/EA] of formula:
R = CH3 or C2H5
A Michael addition of the DMAE alcohol on
oligomers of ADAME or of EA or of MA is also possible.
A characteristic of these heavy byproducts is that
their boiling point is above the boiling points of the
products used in the reaction and of the desired ADAME.
In the conventional process/ generally the
transesterification reaction is followed by various
purification steps, generally by distillation, for
final recovery of the purified ADAME.
One method consists for example of submitting the
crude reaction product to a distillation {tailing to
remove the catalyst and the heavy products) in order to
separate the ADAME with the residual light products at
the top of the distillation column, and the catalyst,
the heavy byproducts, the polymerization inhibitors
with a minor fraction of ADAME and of DMAE and traces
of light compounds at the bottom of the distillation
column.
The compounds distilling at the top of the tailing
column are then separated in two other distillation
columns in series (topping and final rectification) to
recover pure ADAME at the top of the last column.
The bottom fraction from the tailing column can be
sent to a film evaporator in order to recover and
recycle the traces of light compounds. The bottom
fraction from the evaporator is then generally
discarded.
The presence of the heavy byproducts in this
fraction that is discarded poses a treatment problem,
as the heavy byproducts must be incinerated for
disposal. There is also a problem of large losses of
raw materials {notably DMAE) and of finished product
{ADAME), which are present in this fraction in free
form or in the form of Michael adducts.
To recover the upgradable products present in a
residue from separation of the catalyst in a process
for producing (meth)acrylic esters by
transesterification, it was proposed in document US
7,268,251 to treat the residue thermally according to a
method comprising the following steps:
- step 1: cracking the residue in the presence or
absence of a catalyst at a temperature of 100-220°C.
The light products from cracking are then recycled to
one of the distillation columns of the purification
train.
- step 2: the residue from step 1 comprising the
polymerization inhibitors, polymers and the catalyst,
is submitted to a transesterification reaction at 80-
150°C in the presence of a heavy alcohol such as
glycerol or 2-ethylhexanol in order to adjust the
viscosity of this fraction and make the residue
pumpable. The light products generated are recycled to
the reaction.
The process described in this document for
recovering the upgradable materials contained in the
residue of heavy byproducts is difficult to implement
and has the following drawbacks:
- the residue from the first step is very viscous
and therefore difficult to transport by pump; that is
why it must be modified by post-transesterification;
- there is severe fouling of the cracking reactor,
necessitating frequent cleaning with large decreases in
heat exchange capacities;
- cleaning is very difficult - because the fouling
materials adhere very strongly to the wall of the
cracking reactor;
- the light alcohols generated in step 2 of posttransesterification
are recycled with considerable risk
of contamination by the impurities present in the heavy
alcohol used in this step;
~ the introduction of a heavy alcohol that is
completely alien to the products naturally present in
the ADAME facility imposes management constraints and
presents risks of contamination.
To tackle the problem of deposition of heavy
compounds during the synthesis, purification or
regeneration of (meth)acrylic monomers, document FR
2 876 374 proposes the use of phosphorus-containing
antifouling agents; however, there is no question in
this document of recovering the noble products from a
heavy fraction generated during the production of
(meth)acrylic esters by transesterification, leading to
a fluid final residue.
In the process for synthesis of Ci-C4 alkyl
(meth)acrylates described in document FR 2 901 272, the
heavy byproducts are upgraded on the basis of a
treatment of distillation/thermal cracking of a bottom
product. This document relates to a synthesis by direct
esterification in the presence of sulfuric acid, and
the operation of thermal cracking also requires the
presence of sulfuric acid.
Therefore there is still a need for a simplified
process for recovery of the upgradable compounds
contained in a residue of heavy (meth)acrylic
byproducts.
One of the aims of the present invention is
therefore to upgrade the noble products (starting
compounds or finished product) potentially recoverable
from the heavy fraction generated in a process for
synthesis of (meth)acrylic esters by
transesterification. This upgrading leads to
improvement of the materials balance of the process and
to reduction of the final amounts of residue to be
incinerated, and consequently it represents an economic
advantage.
The present invention relates to a treatment
process for . upgrading a . heavy fraction .containing
distillable or potentially distillable products after
cracking, said process only requiring a moderate number
of steps without fouling the equipment used and
producing a final residue of low enough viscosity to be
transported by pump and incinerated.
The process of the invention is particularly
advantageous compared to the process described in
patent US 7,268,251 since it does not employ heavy
alcohol that is alien to the process, thus avoiding the
risk of contamination by recycling the compounds
recovered.
Summary of the invention
The present invention therefore relates to a
process for recovery of noble products from heavy
(meth)acrylic fractions generated during the production
of (meth)acrylic esters by transesterification, the
heavy fractions comprising at least the noble products
and Michael adducts resulting from reactions of
addition on the (meth)acrylic double bonds, said
process comprising the steps of:
(i) adding at least one antifouling agent and
optionally a viscosity-reducing compound to the heavy
fractions; • *
(ii) submitting the mixture to a sufficient
temperature and to distillation conditions for cracking
the Michael adducts into their constituent components;
(iii) recovering the noble products in the form of
a stream of distillate, and of a final residue that is
sufficiently fluid to be transported by means of a
pump.
"Noble products" are products whose recycling is
useful for optimizing the economic balance of an
industrial process.
The expression "heavy fraction" used in the
definition of the invention is a stream, generally a
residue obtained at the bottom- .of. a . distillation
column, comprising heavy byproducts whose boiling point
is above the boiling points of the products employed in
the reaction and of the desired product. They are
notably Michael adducts, formed as explained above, as
well as oligomers or polymers that have formed. The
heavy fraction also generally comprises the
transesterification catalyst as well as the
polymerization inhibitors added to the reaction, as
well as a minor fraction of noble products and traces
of light compounds.
In this particular case, the heavy fraction
submitted to the process according to the invention
comprises, as noble products, the unreacted reactants,
i.e. the light alkyl (meth) acrylate (EA or MA) and the
alcohol, as well as the (meth)acrylic ester produced,
recycling of which makes it possible to increase the
productivity of the (meth)acrylic ester manufacturing
process.
The process of the invention is particularly
suitable for optimizing the productivity and the
economic balance of a process for manufacturing
dialkylaminoalkyl (meth)acrylates by
transesterification of a light alkyl' (meth)acrylate
with an amino alcohol, preferably of a process for
manufacturing N,N-dimethylaminoethyl acrylate (ADAME)
by transesterification reaction between a light alkyl
acrylate and N,N-dimethylaminoethanol (DMAE).
The process according to the - invention can be
carried out in batch (discontinuous) mode or
continuously.
The heavy fraction submitted to the process
according to the invention then comprises, as noble
products, at least one dialkylaminoalkyl (meth)acrylate
and an amino alcohol, preferably at least N,Ndimethylaminoethyl
acrylate and N,Ndimethylaminoethanol.(
DMAE). .....
A second object of the invention therefore
consists of a process for manufacturing a
dialkylaminoalkyl (meth)acrylate of formula (I):
H2C = C (R'i)- C(0)- 0 - A - N (R'2) (R'3) (I)
in which:
- R'i is a hydrogen atom or a methyl radical
-A is a linear or branched C1-C5 alkylene radical
- R'2 and Rf
3, which may be identical or different,
each represent a C1-C4 alkyl radical,
by transesterification reaction between an amino
alcohol of formula (II):
HO-A- N(R'2) (R'3) (II)
in which A, R'2 and R'3 are as defined above, and a
light alkyl (meth)acrylate of formula (III):
CH2=C(R/i)-COOR,
4 (III)
in which R'i is as defined above and R*4 represents
the methyl or ethyl radical;
said process comprising at least the following steps:
a) submitting a reaction mixture comprising a
compound of formula (III) , an amino alcohol of
formula (11)/ a transesterification catalyst,
and at least one polymerization inhibitor, to
transesterifIcation conditions to " form a
mixture of products comprising the
(meth)acrylic ester (I) , the unreacted
compounds (II) and (III) , the catalyst, the
polymerization inhibitor, Michael adducts
resulting from reactions of addition on the
(meth)acrylic double bonds, and other heavy
compounds such as oligomers or polymers;
b) distilling the mixture of products, recovering,
at the top, a stream composed essentially of
the required (meth)acrylic ester (I) and light
products, comprising a minor fraction of
Michael adducts and of heavy products, but free
or almost free from catalyst, and leaving, at
. the .bottom, a heavy. fraction comprising the
catalyst, the polymerization inhibitor, the
Michael adducts and the heavy compounds, with a
minor fraction of the required (meth)acrylic
ester (I) and of the amino alcohol and traces
of light products;
c) purifying the overhead stream so as to obtain
the purified dialkylaminoalkyl (meth)acrylate
(i);
d) submitting at least a proportion of the heavy
fraction to a process for recovery of the noble
products comprising the steps of: (i)
introducing at least one antifouling agent and
optionally a viscosity-reducing compound; (ii)
submitting the mixture to a sufficient
temperature and to distillation conditions for
cracking the Michael adducts into their
constituent components; (iii) recovering the
noble products in the form of a stream of
distillate, and of a final residue that is
sufficiently fluid to be transported by means
of a pump;
e) recycling, to the purification step c), at
least a proportion of said stream of distillate
• " " comprising at least one compound selected from
the (meth)acrylic ester (I), the amino alcohol
(II) or the alkyl (meth)acrylate (III);
f) disposal of the final residue for example by
incineration.
According to one embodiment of the invention, the
purification step c) is carried out using two
distillation columns in series, and at least a
proportion of the stream of distillate from step d) is
recycled to the top of the first purification column.
The invention is advantageously implemented for
producing N/N-dimethylaminoethyl acrylate (ADAME) by
transesterification . reaction between methyl acrylate
(MA) or ethyl acrylate (EA) and N,Ndimethylaminoethanol
(DMAE).
A more detailed, nonlimiting description of the
invention is now presented below, referring to the
accompanying Fig. 1, which shows schematically a
preferred embodiment of an installation according to
the invention for a continuous process for producing
ADAME by transesterification starting from EA and DMAE.
Detailed account of the invention
For carrying out the invention, in a first step
(i), an antifouling agent is used, whose role is to
prevent agglomeration of the solid particles present in
the heavy fraction and deposition of them on the walls
of the equipment used.
A viscosity-reducing compound (so-called "fluxing
agent") can also be added, whose role is to ensure
fluidity of the final residue so that it can be
transported by pump.
One or more polymerization inhibitors are
generally already present in the heavy fraction, but it
is possible to add them to the heavy fraction to be
treated to prevent any polymerization reaction in the
equipment.
As antifouling agent, a compound is selected such
that its effectiveness and its effect on the viscosity
of the mixture are suitable for the matrix in which it
is introduced.
The compounds of formula (A) can advantageously be
used as antifouling agent:
in which:
R1 represents a C3-C30 alkyl radical, an aryl
radical or an alkaryl radical, and these radicals can
be interrupted or attached to the oxygen of the
molecule by a chain -(0R4)0- where the R4 each represent
independently an ethylene, propylene or butylene chain
and o is an integer from 1 to 50;
R2 represents R1, a hydrogen atom or a
counter-ion;
R3 represents a hydrogen atom or a counterion.
The compounds of formula (A) are notably selected
from those in which R1 and R2 each represent
independently the radical
where p is an integer from 4 to 12, preferably 8 or 9,
and q is an integer from 4 to 50, preferably from 6 to
20; and R3 represents a hydrogen atom or a counter-ion;
and/or those in which R1 represents the radical
where r is an integer from 4 to 12, preferably 8 or 9,
and s is an integer from 4 to 50, preferably from 6 to
20; and R2 and R3 each represent independently a
hydrogen atom or a counter-ion.
As counter-ion included in the definition of R2 and
R3, we may mention those resulting from neutralization
of the OH function in the case when R2 and/or R3 = H by
the alkanolamines and the hydroxides of alkali metals
or alkaline-earth metals. As particular examples, we
may mention N+(CH2CH2OH) 3, Na+. and K+..
The compound or compounds (A) can be introduced as
they are in the heavy fraction. They can also be
introduced in solution in a solvent, or in solution in
one of the (meth)acrylic monomers of the process.
The compound or compounds (A) can be introduced at
a concentration in the range from 0.01 to 1 wt%,
notably from 0.1 to 1 wt%, preferably from 0.1 to
0.5 wt% in the heavy fraction to be treated.
Among the antifouling agents that can be used, we
may mention nonlimitatively the products marketed by
the company CECA under the brand name BEYCOSTATS®, and
more particularly BEYCOSTATc' FB 095.
Surprisingly, the compounds of formula (A) proved
to be effective as antifouling agents, despite the
nature of the heavy fractions, notably the heavy
fractions of a process for synthesis of ADAME starting
from dimethylaminoethanol. In fact, these fractions
contain the transesterification catalyst. In this
environment, there is a risk of the amino alcohol
reacting with the antifouling agent, in particular of a
phosphoric ester nature, which can lead to the
1 formation of a dimethylaminoethyl phosphate, whose
chemical structure no longer has dispersant properties
owing to disappearance of the hydrophilic and
hydrophobic groups of the starting phosphoric ester.
As viscosity-reducing compounds, it is possible to
use any liquefying compound that is able to lower the
viscosity to around 200 centipoise at 80°C for the
final residue.
A viscosity-reducing compound that can be used is
for example the product marketed by the company NALCO
under the designation NALCOG EC 3368A.
The viscosity-reducing compound is added to the
heavy fraction in sufficient amount so that the final
residue from step (ii) of the process according to the
invention is pumpable. This amount is generally between
0.01 and 0.5 wt%.
As a variant, it is possible to add, to the heavy
fractions, according to step (i) of the process of the
invention, a single compound acting simultaneously as
antifouling agent and as viscosity-reducing agertt. In
this case it is possible to use, for example, the
product marketed by the company NALCO under the
designation NALCO® EC 3368A.
The heavy fraction can contain various
polymerization inhibitors, among which v/e may mention
phenothiazine (PTZ), hydroquinone (HQ) and its
derivatives such as hydroquinone methyl ether/ 2,6-ditert-
butyl-4-methylphenol (BHT), the N-oxyl compounds
of the 4~hydroxy-2,2, 6,6-tetramethyl piperidinoxyl (4-
OH TEMPO) type and mixtures thereof in all proportions.
Advantageously, an amount of polymerization inhibitor
in the range from 500 to 5000 ppm will be added in step
(i).
Implementation of the invention according; to step
(ii) is done by heating the heavy fraction with
additive to a temperature in the range from 100°C to
250°C, preferably from 150 to 200°C for removing, by
distillation, the noble products present initially and
the noble products that result from thermal cracking of
the Michael adducts.
The operation of thermal cracking according to
step (ii) of the process of the invention can be
carried out without further addition of catalyst to the
heavy fraction to be treated, in particular without
adding acid catalyst, which limits the side reactions
with the antifouling agent added.
In a preferred variant of the invention, before
step (i) of adding the antifouling agent, the heavy
fraction is sent beforehand to a film evaporator in
order to recover and recycle the light compounds that
are present in trace amounts.
The noble products, essentially- the -required
(meth)acrylic ester and the unreacted alcohol, are
recovered according to step (iii) by distillation under
atmosphere of nitrogen or of air depleted to 8 vol% of
oxygen and under reduced pressure, for example from 10
to 50 mbar. The use of nitrogen is preferred.
The treatment can be carried out in batch or
continuous mode in a double-jacketed reactor or in a
still surmounted by a column which in particular
performs the role of splash head in order to limit the
rise of the inhibitors.
The residence time is generally between 30 min and
one hour.
The noble products thus recovered are utilized by
recycling them to the installation, at various steps of
the process, preferably in step (c) of purification of
the crude reaction product.
The final residue is then cooled to 60°C; it is in
principle sufficiently fluid to be transported by pump
directly. Nevertheless, from 5 to 30% of solvent,
preferably methanol, can be added to this residue to
facilitate transport by pump at this temperature.
The final residues are then incinerated.
A preferred embodiment of the invention will now
be described in more detail, referring to the
accompanying Fig. 1 for a continuous process for
producing ADAME by transesterification starting from EA
and DMAE, in which steps (a) to (f) are applicable more
generally to the production of the {meth)acrylates of
formula (I) by transesterification starting from the
alkyl (meth)acrylates of formula (III) and amino
alcohol (II), 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 reactor 1 in the presence . of. a catalyst,,
preferably tetraethyl titanate, and polymerization
inhibitors. Reactor 1 is surmounted by a distillation
column 2 to remove the light alcohol formed (ethanol)
as it is formed and thus shift the equilibrium of the
reaction toward the formation of ADAME.
According to step (b) of the process, the reaction
mixture is submitted to distillation in a distillation
column (tailing column 3) . At the top of column 3, a
stream 7 is recovered that is free from the catalyst
and the polymerization inhibitors and comprises the
ADAME produced and light compounds with a minor
fraction of Michael adducts and heavy products.
A heavy fraction 4 comprising the catalyst, the
polymerization inhibitors, the Michael adducts and the
heavy compounds such as oligomers and polymers with a
minor fraction of ADAME and of DMAE and traces of lightscompounds
is recovered at the bottom of column 3.
According to step (c) of the process, stream 7 is
submitted to purification, which is carried out by
means of distillation column 8, whose overhead stream 9
is recycled to the reaction, the bottom stream 10 being
sent to a distillation column 11 for obtaining the
purified ADAME 12 at the top and, at the bottom, a
stream 13 rich in inhibitors, which is recycled to the
stream of crude reaction mixture feeding column 3.
According to step (d) of the process, the heavy
fraction 4 from the bottom of column 3, which notably
contains the catalyst, is partly recycled to the
reactor 1 and partly submitted to the process according
to the invention for recovery of the noble products
20 (ADAME and DMAE) in reactor 15.
The heavy fraction can first be concentrated on a
film evaporator 5, for separating the traces of light
compounds, which are then recycled to the feed of
column 3. The heavy fraction 6 from the evaporator is
then sent to reactor 15 after adding an antifouling
agent and optionally a viscosity-reducing compound.
The reactor 15 can be of the double-jacketed
reactor type or a still surmounted by a distillation
column 17 of low efficiency (1 to 3 theoretical
plates), which rather performs the role of splash head.
In reactor 15, the heavy fraction, notably
comprising the Michael adduct [DMAE - ADAME] which
results from addition of DMAE on ADAME, undergoes
thermal cracking to recover a stream 18 rich in DMAE
and ADAME at the top of column 17, which is recycled,
according to step (e) of the process, to the inlet of
the ADAME purification column 8.
In the last step (f) , the final residues 16 are
incinerated.
Examples of compositions of streams in this
process for manufacturing ADAME are:
- heavy fraction 6 generally contains about 1 to
20% of DMAE, 10 to 30% of ADAME, 10 to 35% of Michael
adducts [DMAE - ADAME], the remainder essentially
consisting of other heavy byproducts, polymers,
catalyst and polymerization inhibitors.
The process according to the invention makes it
possible to recover, by simple distillation, more than
•90 wt% of the noble products {ADAME and DMAE) contained
in fraction 6 from the evaporator 5, and to crack
respectively to ADAME/DMAE, and DMAE/EA, 30 mol% of the
Michael adducts [DMAE+ADAME] and [DMAE+EA].
The following examples illustrate the present
invention but without limiting its scope.
EXAMPLES
The percentages are expressed in percentages by weight.
The following abbreviations are used:
EA*. ethyl acrylate
DMAE: N,N-dimethylaminoethanol
- ADAME: N,N~dimethylaminoethyl acrylate
- APA: Michael adduct resulting from addition, of
DMAE on ADAME: [DMAE-ADAME]
- APE: Michael adduct resulting from addition of
DMAE on EA: [DMAE+EA]
- PTZ: Phenothiazine
- 40H-TEMPO: 4-hydroxy-2,2,6,6-tetramethyl
piperidinoxyl
Example 1 (comparative):
A glass reactor with mechanical stirrer, heated by an
electric flask heater and surmounted by a Vigreux
column with condenser, vacuum separator, receiver and
trap is charged with 500 g of heavy residue (6)
obtained from the outlet of the evaporator (5).
The composition by weight of this residue is as
follows:
DMAE: 17.3% - ADAME: 11.9% - APA: 28% - q.s. 100%:
heavy fractions + catalyst + inhibitors.
1000 pprn of PTZ and 500 ppm of 40H-TEMPO are added.
The residue is heated, with stirring and bubbling with
nitrogen, for 60 min at 160 °C at an operating pressure
from 100 mbar to 30 mbar at the end. The following are
recovered:
Distillate: 218 g
Final residue: 262 g
The composition by weight of the distillate is:
DMAE: 48.7%
ADAME: 40.6%
APA: 57%
EA: 1%
Other heavy fractions: q.s. 100%
20 There is considerable fouling of the reactor and it is
impossible to clean. The residue is very viscous when
hot and solidifies at room temperature.
Example 2 (according to the invention):
Example 1 is repeated with addition of 2000 ppm of
compound BEYCOSTAT®. FB 0-95, marketed . by the company
CECA, to the initial charge.
The rest of the treatment is similar to example 1.
There is very little fouling of the reactor, the final
residue is viscous but does not solidify at room
temperature.
Example 3 (according to the invention):
A glass reactor with mechanical stirrer, heated by an
electric flask heater and surmounted by a Vigreux
column with condenser, vacuum separator, receiver and
trap is charged with 510 g of heavy residue (6)
obtained from the outlet of the evaporator (5).
The composition by weight of this residue is as
follows:
DMAE: 2.9% - ADAME: 19.2% - APA: 30.2% - q.s. 100%:
heavy fractions + catalyst +.inhibitors.
500 ppm of PTZ, 500 ppm of BEYCOSTAT® FB 095 and 1000
ppm of NALCO® EC 3368A marketed by the company NALCO are
added.
The residue is heated, with stirring and bubbling with
nitrogen, for 65 min at 160-180°C under an operating
pressure of 20 mbar. The following are recovered:
Distillate: 182 g
Final residue: 325 g
The composition by weight of the distillate is:
DMAE: 16.1%
ADAME; 70.2%
APA: 7.5%
EA: 0.6%
APE: 3.8%
The composition by weight of the residue is:
DMAE: 11.9%
ADAME: 0.1%
APA: 9.8%
Heavy fractions + catalyst + inhibitors: q.s. 100%
The balances by weight demonstrate the upgrading of
ADAME and DMAE recovered during the process according
to the invention:.
- ADAME: for 98 g present in the free state in the
residue, 128 g is recovered, a proportion of which is
from thermal cracking of APA.
- DMAE; for 14.6 g present in the free state in the
residue, 68.3 g is recovered, a proportion of which is
from thermal cracking of APA.
- APA: for 154.2 g present in the residue, only 45.3 g
remains after thermal cracking of APA.
The reactor is perfectly clean (no adhering solid) and
the final residue is perfectly fluid when hot.
The residue is then cooled to 60°C and 30% of methanol
is added to it.
After this addition/ it can be transported by pump
without difficulty (viscosity at 60°C: 50.5 mPa).
Example 4 {according to the invention):
Example 3 is reproduced using 2000 ppm of NALCO
EC3368A. At the end of reaction, the reactor is
perfectly clean and the residue remains transportable
when hot.
CLAIMS
1. A process for recovering noble products starting
from heavy {meth)acrylic fractions generated during the
production of {meth)acrylic esters by
transesterification, the heavy fractions comprising at
least the noble products and Michael adducts resulting
from reactions of addition on the (meth)acrylic double
bonds, said process comprising the steps of:
(i) adding at least one antifouling agent and
optionally a viscosity-reducing compound to the heavy
fractions;
(ii) submitting the mixture to a sufficient temperature
and to distillation conditions for cracking the Michael
adducts into their constituent components;
(iii) recovering the noble products in the form of a
stream of distillate, and of a final residue that is
sufficiently fluid to be transported by means of a
pump.
2. The process as claimed in claim 1, characterized
in that the antifouling agent is a compound of formula
(A) :
in which:
R1 represents a C3-C30 alkyl radical, an aryl
radical or an alkaryl radical, and these radicals can
be interrupted or attached to the oxygen of the
molecule by a chain ~(0R4)o-, where the R4 each
represent independently an ethylene, propylene or
butylene chain and o is an integer from 0 to 50;
R2 represents R1, a hydrogen atom or a counter-ion;
R3 represents a hydrogen atom or a counter-ion.
3. The process as claimed in claim 2, characterized
in that the compounds of formula (A) are selected from
those in which R1 and R2 each represent independently
the radical
where p is an integer from 4 to 12, preferably 8 or 9,
and q is an integer from 4 to 50, preferably from 6 to
20; and R3 represents a hydrogen atom or a counter-ion;
and/or
those in which R1 represents the radical
15
where r is an integer from 4 to 12, preferably 8 or 9,
and s is an integer from 4 to 50, preferably from 6 to
20; and R2 and R3 each represent independently a
hydrogen atom or a counter-ion.
4. The process as claimed in any one of the preceding
claims, characterized in that the antifouling agent is
added at a content in the range from 0.01 to 1 wt%,
preferably from 0.1 to 1 wt%, to the heavy fraction to
be treated.
5. The process as claimed in any one of the preceding
claims, characterized in that the conditions of
cracking and of distillation comprise a temperature in
the range from 100°C to 250°C, preferably from 150°C to
200°C.
6. The process as claimed in any one of the preceding
claims, characterized in that the viscosity-reducing
compound is introduced in sufficient amount so that the
final residue from step (ii) is pumpable.
7. The process as claimed in any one of the preceding
claims, characterized in that a single compound acting
simultaneously as antifouling agent and as viscosityreducing
agent is added in step (i).
8. The process as claimed in any one of the preceding
claims, characterized in that the noble products
comprise at least one dialkylaminoalkyl (meth)acrylate
and an amino alcohol, and in particular comprise N,Ndimethylaminoethyl
acrylate and N,Ndimethylaminoethanol.
9. A process for manufacturing a dialkylaminoalkyl
(meth)acrylate of formula (I):
H2C = C (R'i)- C(0)- 0 - A ~ N (R'2) (R'3) (I)
in which:
- R'i is a hydrogen atom or a methyl radical
-A is a linear or branched C1-C5 alkylene radical
- R'2 and R'3, which may be identical or different,
each represent a C1-C4 alkyl radical,
by transesterification reaction between an amino
alcohol of formula (II):
HO-A- N