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Патент USA US2126600

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Aug- 99 193.,
a‘ E. ANDREWS ET AL
E9W6?U
S EPARATI ON OF METHYLAMINES
Filed April 18, 1956
.27
;
FRACTIONATING
COLUMNS
.1
-—~>
FRACTIONA
COLUMN
HEA R
‘
{METHYL
EMINE
DIMETHYL
Amms
men/ions‘:
C/zesZerE?ncZr-ezos
dncljeryylué‘perwe,
2,126,600
. Patented Ali'- 9, 1938
I UNlTED STATES
PATENT. OFFICE
2,126,800
SEPARATION OF METHYLAMINES
Chester E. Andrews. Oven-brook, and Le Roy U.
Spence, Cheltenham, Po... assignors to Rollin
& Hm Company, Philadelphia, Pa,
Application April 18, 1938, Serial No. ‘75,122
14 Claims.
This invention relates to a process for the sep
aration of monomethylamlne, dimethylamine and
trimethylamine from their mixtures, particularly
from the mixtures obtained in the catalytic prep
‘ aration of methylamines.
The product obtained when methanol and am
monia are passed at suitable temperatures over
, an amination catalyst, after removal of high boil
ing materials, such as water, methanol and forum
[0 aldehyde, consists of a mixture of ammonia,
monomcthylamine, dimethylamine and trimcthyl
amine._ A number of methods for separating
this mixture have been suggested.
it the mix
methylamine mixture varies if the distillation is
conducted at dl?crent pressures. We have found
‘that the mixture obtained by distillation at at
mospheric pressure contains about 30% by weight
of trimethylamine and that as the distilling pres
sure is increased the trimethylamine concentra
tion decreases until at 60 lbs. gauge it is about
15% and at 210 lbs. gauge about 7%.
In the present invention we utilize our discovery
that monomethylamine and trimethylamine form M
a constant boiling mixture to separate them from
dimethylamine, and then by rte-distilling the
mono-tr! mixture at different pressures, separate
ture is distilled, the ammonia may be removed as
W a constant boiling mixture with trimethylamine
it into its components. Essentially, our process
consists in ?rst removing ammonia from the M5
and if su?lcicnt ammonia is added, the trimethyl
amine may be completely removed with the am
monia. With the trimethylamine removed, the
monomethylamine and dimethylamine may be
U separated by distillation. A disadvantage of this
method is that it requires large quantities of am
monia and makes necessary a-separate process
for recovering it from the constant boiling mix
ture formed.
35 Another method for the removal of ammonia
consists in adding dimethyl ether to the mixed
mixed amines, then iractionatlng them to separ
ate trimethylamine and monomethylamine from
dimethylamine, and ?nally by cycling the mixed
amines and distilling to separate vthe ammonia
as a constant boiling mixture with dimethyl’
ether. The three methylamines are thus obtained
It) tree from ammonia but their separation one from
the other is complicated by the formation of con
stant boiling mixtures of monomethylamine and
trimethylamine and by the fact that dimethyl
amine and trimethylamine boil at very nearly the
35 same temperature. These di?iculties have pre
vented the ei?cient separation of the methyl
amines by distillation.
‘
An object of this invention is to provide a prac
tical method for the separation of monomethyl
g) amine, dimethylamine and trimethylamine from
their mixtures.
Another object is to provide a
method of separating dimethylamine from tri
methylamine. A further object is to separate
monomethylamine and trimethylamine from
is each other in mixtures containing no dimethyl
amine.
I
mono- and trl- fraction through two fraction
ating columns, one of which is operated at a
relatively high pressure as compared with ‘the
other, separate the mono-amine from the tri-.
The mixture of amines used as the starting ma
terial may be obtained irom either a catalytic or
non-catalytic process of manufacturing methyl
amines. The ammonia is removed by any suit~
able method, such as by distilling with dimethyl
other. Preferably it is distilled out with part‘ of
the trimethylamine and returned to the reaction
chamber ‘for further reaction with methanol.
If in the mixture of amines to be separated, the
ratio o'l' trimethylamine to monomethylamine ex
ceeds that of the constant boiling mixture, the
proportion of the monomethylamine must be in
creased so ,that all the trimethylaminc can be re- “
moved. This may be done by the addition of pure
monomethylamine or by the addition of an amine
mixture rich in monomethylamine obtained as
hereinafter described. If the monomethylamine
present exceeds the amount necessary for the
constant boiling mixture, the excess may be re
moved along with the mixture by suitably adjust
ing the operation of the column.
To further explain our invention, reference will
be made to the accompanying drawing which
schematically illustrates suitable apparatus for
In our prior application, Serial No. 538,262
?led May 18, 1931, now Patent No. 2,061,889
carrying out our process.
granted November 24, 1936, of which this applica
fractionating columns that are connected as indi
cated by pipes I to 1. Letter P represents a pump
that forces the distillate from columns A and C
50 tions is in part a continuation, we have shown
that monomethylamine and trimethylamine form
In the drawing, letters A, B and C represent
a constant boiling mixture which can be utilized into the high pressure column B.
to separate trimethylamine from dimethylamine.
In the operation of this apparatus the mixture
We have now further found that the composition of amines prepared by the catalytic amination of
is or the constant boiling monomethylamine-tri , alcohol or any other process, after the removal of 55
2
2,126,600
amines containing 59.6% monomethylamine,
28.0% dlmethylamine and 12.4% trlmethylamine,
of substantially pure dlmethylamine and a dis
tillate portion containing practically all the mono
methylamine and trlmethylamine. Pressure in
can be separated into 97% pure dlmethylamine,
better than 96% pure trlmethylamine and 98%
this column should be maintained as low as ex
by mixing with the initial amine mixture an equal
amount of distillate from column B and maln—
taining gauge pressures oi’ 60 lbs. per sq. in. in
columns A and C and 210 lbs. per sq. in. in col
umn B. The temperatures in the three columns
were 36“ C. at the top of column A and 54° C. at
the bottom; 76° C. at the top of column B and
103° C. at the bottom; 36° C. at the top of col
umn C and 37° C. at the bottom.
pedient, for as explained above, the lower the
distilling pressure the greater the concentration
10 of trlmethylamine in the constant boiling mixture
evolved. We have found a distilling pressure of
60 pounds gauge to be convenient, for at lower
pressures arti?cial refrigeration must be resorted
to to condense the vapors.
The distillate from column A passes through
15
pipes 2 and 3, pump P, and pipe 4 to tractionating
column B in which it is again subjected to a frac
tional distillation, this time under a relatively
high pressure. While the speci?c pressure main
20 tained in column B is not critical, we have found
an operating pressure of 210 pounds’ gauge con
venient when the pressure in column A is main
tained at 60. pounds. By maintaining a high
pressure in column B the composition of the con
15
By means of our process a mixture of methyl
high boiling materials and ammonia, is conducted
through pipe I to i'ractionating column A where
it is separated into a residual portion consisting
stant boiling monomethylamine-trlmethylamine
fraction that is vaporized is altered so that it
contains a substantially lower proportion of tri
pure monomethylamine.
This is accomplished
We have described our invention as a complete
continuous process for the separation of all three
methylamines, but it is apparent that it can be
carried out as a batch process and also that the
various steps can be utilized as such where it is
desired to separate a single or only two of the
components. Thus, the steps of adding mono
methylamine to the initial mixture and distilling,
can be utilized to obtain pure dlmethylamine
without subsequently separating the mono from
the tri. Also, if dlmethylamine and trlmethyl
pipe line 5 to column C, and is again fractionated
at a low pressure, conveniently 60 pounds’ gauge.
amine are the only desired components, the low
pressure distillation in column C can be omitted.
The monoamine rich distillate from column B
can then, if desired, be reacted with more meth
anol to convert it to the higher amines. Further
more, it pure monomethylamine is the desired
The low pressure in this column again alters the
component, the fractionation in column A can be
composition of the constant boiling monomethyl
omitted and both dimethylamine and trlmethyl
amine separated in column B. It is to be under
stood that our invention comprises the various
methylamine. The remaining trlmethylamine is
drawn oil’ at the bottom of the column.
The distillate from column B passes through
amine-trlmethylamine mixture, so that the dis
tillate coming of! has substantially the same com
position as that coming from column A. The
excess monoamine is withdrawn from the bottom
of the column. The distillate from column C is
40 drawn off through pipe 6, mixed with the distil
late from column A and returned through pipe 3,
pump P and pipe 4 to the high pressure distilling
column B.
The pipe line 1 connecting the top of frac
tionating column B and the entrance to column A
is provided to permit the recirculation of the
mixture high in monomethylamine evolved from
column B back to column A. In this way the
relative concentration of monomethylamine and
trlmethylamine in the initial mixture may be
suitably adjusted to insure the presence of suffi
cient monomethylamine to vaporize in column A
all the trlmethylamine as a constant boiling mix
ture. Where the composition of the initial mix
ture is such that the addition of more mono is
unnecessary, the recirculation of distillate
through pipe ‘I is unnecessary. It will be ap
parent that where the ratio of mono to tri in the
initial mixture is very high, the distillate from
60 column A will likewise be high in monomethyl
amine. Under such operating conditions, it may
be desirable to reverse the order in which the
mono and tri are removed, by passing the distil
late from column A ?rst through column C and
V65 then through column B.
The distillation temperatures maintained in
the three columns will depend entirely upon the
pressure at which they are operated, and while
we have indicated a preference for an operating
70 pressure of about 60 pounds’ gauge in columns A
and C and of about 210 pounds’ gauge in column
B, other pressures can be chosen to obtain the
same result, so long as the pressure in column B
is maintained above that used in columns A
75 and C.
steps of our process as well as the complete com
bination.
It will also be apparent that our process lends
itself to various modi?cations to adapt it to spe
ci?c operating requirements. Thus, where the
mixture of amines to be separated contains non
condensable gases, it is desirable to provide a
means for removing these from the system, pref
erably in the re?ux condenser of column A. Or,
if the mixture of amines fed to column A con
tains some high boiling materials, such as meth
anol and water, these may be removed with the
dlmethylamine from the bottom of the column,
and later removed by a subsequent distillation.
Other similar modi?cations can be resorted to
without departing from the scope of the present
invention as de?ned in the following claims.
We claim:
1. In the process of separating dimethylamine cu
from a mixture of methylamines from which am
monia has been removed the steps of adding to
the mixture monomethylamine and distilling to
remove the trlmethylamine in a constant boiling
monomethylamine-trimethylamine mixture.
2. The process of separating dlmethylamine
from its mixtures with trimethylamine from
which ammonia has been removed which com
prises adding to the mixture su?lcient mono
methylamine to remove the trlmethylamine in a
constant boiling monomethylamine-trimethyla
mine mixture and distilling.
3. The process of separating a puri?ed dlmeth
ylamine and a puri?ed trlmethylamine from a
mixture of methylamines from which ammonia
has been removed which comprises adjusting the
monomethylamine concentration of the mixture
to permit the removal of trlmethylamine in a
constant boiling monomethylamine-trimethyla
mine mixture, distilling to remove the mono
areaeco
methylamine and trimethylamine, and redistill
ent distilling to remove the monomethylamine
and trimethylamine, redistilling the mixture of
monomethylamine and trimethylamine under a
ing the mixture of monomethylamine and tri
methylamine under a higher pressure to separate
part of the trimethylamine.
4. The process ofseparating a puri?ed dimeth
higher pressure to remove part of the trimethyl
ylamine and a puri?ed trimethylamine from a
mixture ‘of methylamines from which ammonia
tained under a pressure not as high to remove
amine and redistilling the distillate thus ob
a part of the monomethylamine.
has been removed which comprises adjusting the
monomethylamine concentration of the mixture
9. The process of separating methylamines
containing su?icient monomethylamine to re
to permit‘the removal of trimethylamine in a
move all the trimethylamine in a constant boii~ 10
constant boiling monomethylamine-trimethyla
ing monomethylamine-trimethylamine mixture
mine mixture, distilling under about 60 pounds’
gauge pressure to remove the monomethylamine
and trimethylamine, andredistilling the mixture
which comprises separating any ammonia pres
ent distilling under about 60 pounds’ gauge pres
sure to remove the monomethylamine and tri
methylamine, distilling the mixture of mono
of monomethylamine and trimethylamine under
about 210 pounds’ gauge pressure to separate part
of the trimethylamine.
5. The process of separating methylamines
containing su?icient monomethylamine to re ‘
obtained under about 60 pounds’ gauge pressure
monomethylamine-trimethylamine mixture which
to remove a part of the monomethylamine.
20
10. The process of separating a mixture con_
move all the trimethylamine in a constant boiling
comprises separating any ammonia present dis
tilling to remove. the monomethylamine and tri
methylamine, and redistilling the mixture of
monomethylamine and trimethylamine under a
higher pressure to separate part of the trimeth
ylamine.
.
l
'
6. The process of- separating a mixture of
methylamines from which ammonia has been
removed which comprises adjusting the mono
methylamine concentration of the mixture to
permit the removal of trimethylarnine in a con
stant boiling monomethylamine-trimethirlamine
mixture, distilling to remove the monomethyla
mine and trimethylamine, redistilling the mix-.
ture of monomethylamine and trimethylamine
under a higher pressure to remove part of the
trimethylamine and redistilling the distillate
thus obtained under a pressure not as high to
remove a part of ‘the monomethylamine.
- 7. The process of separating a mixture of
methylamines from which‘ ammonia has been
methylamine and trimethylamine under about
210 pounds’ gauge pressure to remove part of the
trimethylamine and redistilling the distillate thus
sisting essentially of monomethylamine and tri~
methylamine which comprises fractionating the
mixtureat one pressure and then iractionating
the distillate obtained at a di?’erent presure, the 25
difference in the fractionating pressures being
sufficient to change the composition of the con
stant boiling monomethylamine-trimethylamine
mixture.
11. The process of separating puri?ed mono 30
methylamine from a mixture of methylamines
from ‘which ammonia has been removed which
comprises fractionating at one pressure to- sep
arate monomethylamine and part of the tri-_
methylamine from dimethylamine, and then
fractionating the distillatejat lower pressure to
separate part of the monomethylamine.
permit theremoval of trimethylamine in a con
stant boiling monomethylamine-triméthylamine
mixture, distilling under about 60 pounds? gauge
pressure to remove the monomethylamine and
,
35
_
12. The process of separating amixture con
sisting,essentialli;r of monomethylne and tri
methylamine which comprises fractionating the
mixture under one pressure to separate a part
40
of trimethylamine and then 'fractionating the
removed which comprises adjusting the mono- > distillate under lower pressure.
methylamine concentration of the mixture to
15
-
.13. The process of separating a mixture con
sisting essentially o1’ monomethylamine and tri
methylamine which comprises fractionating the 45
mixture under about 210 pounds’ gauge pressure
to separate a ‘part of trimethylamineancl then
trimethylamine, redistilling the mixture of mon- ‘ fractionating the distillate under about 60 pounds’
omethylamine and trimethylamine under about
210 pounds’ gauge pressure to remove part of the
trimethylamine and redistilling thedistil'iate thus
obtained under about 60 pounds’ gauge pressure
to remove a part of the monomethylamine.
,
8. The process of separating methylamines
containing suf?cient monomethylamine to re
move all the trimethylamine in a-constant boi1—
ing monomethylamine-trimethylamine mixture
which comprises separating any ammonia pres
gauge pressure.
‘
14. The process- of separating a mixture con
50
sisting essentially of monomethylamine and tri~=
methylamine which‘ comprises fractionating the
mixture underione pressure to separate part of‘
the monoinethylamine, and then fractionating
the distillate under higher pressure to separate‘ 55
part‘ot theitrimethyiamine.
V
'
-
,
V
CHESTER E. ANDS.
‘7 'LE ROY U. SPENCE.
’
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