Note: Descriptions are shown in the official language in which they were submitted.
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PF 70339
Process for preparing aminocarboxylates low in by-products
The present invention relates to a process for preparing aminocarboxylates
proceeding
from the amines 1 and 4 by employing a reaction sequence composed of
ethoxylation
to the amino alcohols 2 and 5 and subsequent oxidative dehydrogenation to the
corresponding aminocarboxylates 3 and 6 (for example the alkali metal or
alkaline
earth metal salts of the complexing agents MGDA (methylglycinediacetic acid),
EDTA
(ethylenediaminetetraacetic acid) or GLDA (glutamic acid diacetic acid) or the
free
acids thereof).
0
N, 1-12 XOH
X00C N C 00X
R' RR.
- H2 R COOX
1 2 3
HO
0 Nee \ N rj.-1-"Nõ.0H
XOH X00
1-12144.-R.\
1---r-coox
- Hz X0 OC)
OH X00C
OH
4 5 6
1 0
R = alkyl, alkenyl, alkynyl, aryl, aralkyl, alkylenecarboxyl, hydroxyalkyl,
hydroxyaralkyl, alkylenesulfonate
rcoox
NCOOX
where A = Cl to C12 alkylene bridge or a chemical bond
coox
R' = COOX, CH2OH
= alkylene
X = alkali metals or alkaline earth metals, preferably sodium and potassium
N=1-10
The ethoxylation of amines is performed on the industrial scale, typically at
temperatures greater than 120 C. For instance, ethanolamines are prepared
proceeding from ammonia (solution of 20 to 30% by mass in water) and ethylene
oxide
at temperatures around 150 C and at pressures of 30 to 150 bar (H.-J. Arpe,
lndustrielle Organische Chemie [Industrial Organic Chemistry]). N-
Alkylethanolamines
are even prepared at temperatures up to 170 C (Ullmann's Encyclopedia). WO
98/38153 describes the ethoxylation of ethylenediamine in isopropanol as a
solvent
with 4 equivalents of ethylene oxide at standard pressure and a reaction
temperature of
140 to 180 C. The corresponding ethoxylation in pure substance is described in
US
3 907 745, at somewhat lower temperatures of 120 to 130 C.
The oxidative dehydrogenation of amino alcohols with alkali metal hydroxides
is
typically performed under pressure and at temperatures of 140 to 220 C using
copper
I I
CA 2790161 2017-05-05
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catalysts. The catalysts consist, for example, of doped or undoped Raney Cu
(described, for
example, in EP 1 125 633, EP 1 125 634, WO 04/24091, WO 00/066539, EP 1 067
114, WO
00/032310). The dopants used are generally one or more metals, for example Pt,
Fe, Cr (EP 1
125 633, EP 1 125 634) Cr, Mo, V, Bi, Sn, Sb, Pb, Ge (WO 04/24091) or Ag (EP 1
067 114).
In other examples, Cu is applied to alkali-stable supports directly or via
anchor metals (e.g. Os,
Ir, Rh, Pt, Pd) (e.g. WO 01/77054, WO 03/022140, WO 98/50150). Precipitated Cu
catalysts
with further metal oxides have also been described (e.g. WO 03/051513 (Cu,
Fe), EP 0 506
973, WO 98/13140 (Cu, Zr, Ca)). There have also been isolated reports about
conversion over
noble metal systems (e.g. EP 0 201 957).
A problem in the preparation especially of complexing agents such as MGDA
(methylglycinediacetic acid), EDTA (ethylenediaminetetraacetic acid) or GLDA
(glutamic acid
diacetic acid) and salts thereof is that relatively high contents of by-
products are obtained in a
simple performance of the two process steps. In order to keep the content of
such by-products
in the end product low, expensive operations, which are complex in terms of
apparatus, to
purify the end product and/or the intermediate are required.
It is therefore an object of the present invention to provide a process which
does not have the
disadvantage mentioned, i.e. which affords an end product with a low by-
product content and
in which operations to purify the end product and/or intermediate are
dispensable.
According to the invention, the object is achieved by a process for preparing
aminocarboxylates, in which, in a first stage, an amine is ethoxylated at a
reaction temperature
in the range from 30 to 100 C to give an alkanolamine, and the alkanolamine
thus formed is
dehydrogenated in a second stage oxidatively to give an aminocarboxylate,
where the salts
which form can also be converted to the corresponding aminocarboxylic acids.
Preference is given to a process in which the amine is selected from the group
of the amines of
the formula 1 or 4
j,R"
NH H,N-
R/L,
W
1 4
where
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R is an alkyl, alkenyl, alkynyl, aryl, aralkyl, alkylenecarboxyl,
hydroxyalkyl, hydroxy-
aralkyl, alkylenesulfonate or a substituent
,coox
A N COOX
y
coox
where A = Cl to C12 alkylene bridge, or a chemical bond
R' is COOX or CH2OH,
R* is an alkylene radical,
X is an alkali metal or alkaline earth metal and
n is from 1 to 10.
R is more preferably relatively long alkyl or alkenyl radicals of Cl to C30
alkyl and C2
to C30 alkenyl, alkylenecarboxylates or else alkylenesulfonates, hydroxyalkyl
or
hydroxyaryl groups and double alkylglycinediacetic acids such as
diaminosuccinic acid
(A = "chemical bond") or diaminopimelic acid (A = -(CH2)3-) with
(Coax
Ay N COOX
R= coox
where A = a Cl to C12 alkylene bridge or a chemical bond.
Particular preference is given to a process in which the amine is selected
from the
group consisting of alanine, glutamic acid and salts thereof, and
ethylenediamine.
With regard to the process parameters, there are preferred embodiments.
Preference
is thus given to a process in which the reaction temperature in the first
stage is in the
range from 40 to 90 C, preferably in the range from 60 to 80 C.
With regard to the temperature profile too, there are preferred variants.
Preference is
thus given to a process in which the reaction temperature in the first stage
varies by
less than 60 C, preferably by less than 40 C, over the reaction time.
The performance of the process as a batchwise, semibatchwise or continuous
process
is preferred. A process in which (at least) one reactor selected from the
group
consisting of stirred tank reactor, loop reactor and tubular reactor is used
is particularly
preferred.
This is possible using various reactor models such as stirred tank reactors of
various
designs, loop reactors (gas circulation reactor, plunging jet reactor, jet
nozzle reactor or
high-loading packed column) or tubular reactors (gas phase-free or with gas
phase).
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A process in which the reactor consists essentially of a material with a
thermal
conductivity coefficient greater than 5 W/K*m is particularly suitable.
"Essentially"
means that more than 50%, preferably more than 80% and more preferably more
than
90% of the reactor material consists of a material with a corresponding
thermal
conductivity coefficient.
Particularly suitable materials for this purpose are found to include 1.4541
(V2A steel),
1.4571 (V4A steel), 2.4610 (HC4) with a thermal conductivity coefficient
greater than
5 W/K*m, in order to enable efficient removal of heat in the industrial
process.
Equally preferred is a process in which the solvent of the first stage is
selected from
protic solvents such as water, alcohols, preferably short-chain alcohols, and
especially
methanol, ethanol, 2-propanol and/or polar aprotic solvents such as dimethyl
sulfoxide,
dimethylformamide or N-methylpyrrolidone.
A process in which the alkanolamine formed in the first stage is
dehydrogenated
directly constitutes a further preferred embodiment. Direct dehydrogenation
means that
preference is given to those processes in which there is no apparatus for
removing
substances with boiling points greater than 200 C (at standard pressure), on
the basis
of different boiling points, between the first and second stages. This is
simpler in
apparatus terms and hence saves one process step with comparably good end
product
quality.
Particular preference is given to a process in which the end product too is
not purified
further, but is used directly in the corresponding applications, for example
as an
additive for industrial cleaning formulations for hard surfaces of metal,
plastic, coating
material or glass, in alkaline cleaning formulations for the drinks and foods
industry,
especially for bottle cleaning in the drinks industry and in apparatus
cleaning in dairies,
in breweries, in the preserves industry, in the bakery industry, in the sugar
industry, in
the fat-processing industry and in the meat-processing industry, in dishware
cleaning
formulations, especially in phosphate-free compositions for machine
dishwashing in
machine dishwashers in the household or in commercial premises, for example
large
kitchens or restaurants, in bleaching baths in the paper industry, in
photographic
bleaching and bleach fixing baths, in pretreatment and bleaching in the
textile industry,
in electrolytic baths for masking of contaminating heavy metal cations, and
also in the
field of plant foods for remedying heavy metal deficits as copper, iron,
manganese and
zinc complexes. In principle, use is advantageous anywhere where
precipitations of
calcium, magnesium or heavy metal salts disrupt industrial processes and
should be
prevented (prevention of deposits and encrustations in tanks, pipelines, spray
nozzles
or generally on smooth surfaces), and also for stabilization of phosphates in
alkaline
degreasing baths and prevention of the precipitation of lime soaps, in order
thus to
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PF 70339
prevent the tarnishing of non-iron surfaces and to prolong the service life of
alkaline
cleaning baths. In addition, they find use in pulverulent or liquid detergent
formulations
for textile washing as builders and preservatives. In soaps, they prevent
metal-
catalyzed oxidative decompositions, and also in pharmaceuticals, cosmetics and
foods.
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The dehydrogenation is effected with the aid of a base from the group of the
alkali
metal and alkaline earth metal hydroxides, preferably NaOH or KOH, particular
preference being given to NaOH. The temperature of the second stage is
typically in
the range from 140 to 240 C, preferably in the range from 150 to 210 C and
more
preferably in the range from 160 to 200 C. The pressure is typically in the
range from
standard pressure to 100 bar, preferably from 5 to 50 bar and more preferably
in the
range from 8 to 20 bar and even more preferably from 10 to 20 bar.
A process in which the dehydrogenation is performed with a catalyst, the main
and
secondary constituents of which is/are selected from groups 4 to 12 of the
Periodic
Table, is particularly preferred; very particular preference is given to a
process in which
the dehydrogenation is performed with a catalyst which comprises (at least)
one metal
which is selected from the group consisting of: Cu, Fe, Co, Ni, Zr, Hf, Ag, Pd
and Pt.
The catalyst can be used, for example, in the form of powder or shaped bodies
(e.g.
extrudates, tablets etc.), or in the form of an unsupported catalyst or
supported
catalyst, and may consist of metals and metal oxides.
A process in which the NTA content in the direct product of the second stage
is less
than 1% by mass, based on the main product, forms a further part of the
subject matter
of the present invention.
In addition to the salts (aminocarboxylates) themselves, the corresponding
amino-
carboxylic acids are also obtainable after acidification. The direct product
of the second
stage is understood to mean the reaction discharge as obtained in the
oxidative
dehydrogenation. Thereafter, in the case of a suspension method, the catalyst
can be
sedimented and filtered off. In addition, a desired water content can
subsequently be
established or a bleaching can be carried out, for example with hydrogen
peroxide or
UV light.
The present invention is illustrated in detail hereinafter by nonlimiting
examples:
Example 1:
3.743 kg (20.00 mol) of glutamic acid monosodium salt monohydrate are
suspended in
5.599 kg of water and admixed with 1.578 kg (20.00 mol) of 50.7% by mass
sodium
hydroxide solution. The resulting mixture was charged into a 20 I autoclave
(2.4610
material) and, after appropriate inertization, nitrogen was injected to 20
bar.
Subsequently, 2.026 kg (46.00 mol) of ethylene oxide were metered in at 40-45
C
PF 70339 CA 02790161 2012-08-16
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within 8 h, and the mixture was stirred at this temperature for a further 2 h.
After the
removal of the unconverted residues of ethylene oxide, the autoclave was
emptied. In
this way, 12.862 kg of aqueous reaction discharge were obtained as a clear,
colorless,
viscous solution.
418 g (0.650 mol based on glutamic acid monosodium salt monohydrate) of this
crude
product were initially charged with 53.0 g (1.33 mol) of sodium hydroxide
powder,
12.7 g of water and 7.5 g of a copper-iron catalyst prepared according to WO
03/051513 in a 1.21 autoclave (2.4610 material). The reactor was closed,
nitrogen was
injected to 5 bar, and the reactor was then heated to 190 C. The temperature
was held
for 6 h. The stirrer speed over the entire experimental duration was 700 rpm.
The
hydrogen which formed was removed continuously through a 15 bar pressure-
regulating valve. After the end of the experiment, the reactor was purged with
nitrogen
at room temperature and then emptied. The product was obtained as a clear,
colorless,
viscous solution. By iron binding capacity, a glutamic acid-/V,N-diacetic acid
tetrasodium salt (GLDA-Na4) content of 42.2% by mass was determined, which
corresponds to a yield of 88.6% of theory based on glutamic acid monosodium
salt
monohydrate used.
Example 2:
4.365 kg (49.00 mol) of alanine were suspended in 2.600 kg of water and
admixed with
3.920 kg (49.00 mol) of 50% by mass sodium hydroxide solution. The resulting
mixture
was charged into a 20 I autoclave (2.4610 material) and, after appropriate
inertization,
nitrogen was injected to 20 bar. Subsequently, 4.749 kg (107.8 mol) of
ethylene oxide
were metered in at 40-45 C within 8 h, and the mixture was stirred at this
temperature
for a further 2 h. After the removal of the unconverted residues of ethylene
oxide, the
autoclave was emptied. In this way, 15.597 kg of aqueous reaction discharge
were
obtained as a clear, colorless, viscous solution.
328 g (1.03 mol based on alanine) of this crude produce were initially charged
with
197 g (2.46 mol) of 50% by mass sodium hydroxide solution, 18 g of water and
45 g of
Raney copper (from Evonik Degussa GmbH) in a 1.71 autoclave (2.4610 material).
The
reactor was closed, nitrogen was injected to 5 bar, and the reactor was then
heated to
190 C within 2.25 h. This temperature was held for 16 h. The stirrer speed
over the
entire experimental duration was 500 rpm. The hydrogen which formed was
removed
continuously through a 10 bar pressure-regulating valve. After the end of the
experiment, the reactor was purged with nitrogen at room temperature, the
reaction
discharge was diluted with 484 g of water and the reactor was then emptied.
The
product was obtained as a clear, colorless, viscous solution. By means of
HPLC, a
yield of methylglycine-N,N-diacetic acid trisodium salt (MGDA-Na3) of 92.0% of
theory
based on alanine used was determined.
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Example 3:
178 g (2.00 mol) of alanine were suspended in 1069 of water and admixed with
1609
(2.00 mol) of 50% by mass sodium hydroxide solution. The resulting mixture was
charged into a 2.5 I autoclave (1.4571 material) and, after appropriate
inertization,
nitrogen was injected to 1 bar. Subsequently, 189 g (4.30 mol) of ethylene
oxide were
metered in at 80-89 C within 2 h, and the mixture was stirred at this
temperature for a
= further 3 h. After the removal of the unconverted residues of ethylene
oxide, the
autoclave was emptied. In this way, 624 g of aqueous reaction discharge were
obtained as a clear, colorless, viscous solution.
328 g (1.05 mol based on alanine) of this crude produce were initially charged
with
208 g (2.60 mol) of 50% by mass sodium hydroxide solution, 39 g of water and
45 g of
Raney copper (from Evonik Degussa GmbH) in a 1.7 I autoclave (2.4610
material). The
reactor was closed, nitrogen was injected to 5 bar, and the reactor was then
heated to
190 C within 2.25 h. This temperature was held for 16 h. The stirrer speed
over the
entire experimental duration was 500 rpm. The hydrogen which formed was
removed
continuously through a 10 bar pressure-regulating valve. After the end of the
experiment, the reactor was purged with nitrogen at room temperature, the
reaction
discharge was diluted with 403 g of water and the reactor was then emptied.
The
product was obtained as a clear, colorless, viscous solution. By means of
HPLC, a
yield of methylglycine-N,N-diacetic acid trisodium salt (MGDA-Na3) of 91.3% of
theory
based on alanine used was determined.
Comparative example:
267 g (3.00 mol) of alanine were suspended in 159 g of water and admixed with
240 g
(3.00 mol) of 50% by mass sodium hydroxide solution. The resulting mixture was
charged into a 2.5 I autoclave (1.4571 material) and, after appropriate
inertization,
nitrogen was injected to 20 bar. Subsequently, 291 g (6.60 mol) of ethylene
oxide were
metered in at 140-145 C within 5 h, and the mixture was stirred at this
temperature for
a further 2 h. After the removal of the unconverted residues of ethylene
oxide, the
autoclave was emptied. In this way, 930 g of aqueous reaction discharge were
obtained as a clear, yellowish, viscous solution.
322 g (1.04 mol based on alanine) of this crude produce were initially charged
with
208 g (2.60 mol) of 50% by mass sodium hydroxide solution, 40 g of water and
45 g of
Raney copper (from Evonik Degussa GmbH) in a 1.71 autoclave (2.4610 material).
The
reactor was closed, nitrogen was injected to 5 bar, and the reactor was then
heated to
190 C within 2.25 h. This temperature was held for 16 h. The stirrer speed
over the
entire experimental duration was 500 rpm. The hydrogen which formed was
removed
continuously through a 10 bar pressure-regulating valve. After the end of the
experiment, the reactor was purged with nitrogen at room temperature, the
reaction
discharge was diluted with 424 g of water and the reactor was then emptied.
The
,
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PF 70339 CA 02790161 2012-08-16
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product was obtained as a clear, colorless, viscous solution. By HPLC, in
spite of full
conversion, a yield of methylglycine-N,N-diacetic acid trisodium salt (MGDA-
Na3) of
only 74.4% of theory based on alanine used was determined.
