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Patented
cc. 1?, 1946
STATS
2,412,650
PROCESS OF SEPARATING 3-PICOLINE,
4-PICOLINE, AND 2,6-LUTIDINE
George Riethof, Mount Lebanon. Pa.
No Drawing. Application June 15, 1945,
Serial No. 599,766
7 Claims. (Cl. 202-42)
1
2
This invention relates to a separation process;
and more particularly it relates to the separation
of 3-picoline, é-picoline, and 2,6-luticline from one
another.
in that the beta picoline can be obtained sub
stantlally pure and in a much simpler operation.
There is no separation to be carried out before
the beta picoline comes over, as the fractional
pounds, 3-picoline, 4-picoline, and 2,6-lutidine is
distillation of the maximum azeotrope has only
to separate the beta picoline from the gamma by
the basic coal tar oils in which they commonly
occur associated with one another. These basic
coal tar oils may be practically fractionated to
an operation which in effect is similar to a ?rst
cut in a distillation procedure.
It is a principal object of this invention to pro
One of the principal sources of these three com
produce certain cuts composed predominately of 10 vide a process for the separation of B-picoline,
a mixture of 3-picoline, é-picoline and 2,6
lutidine. Hence, these materials are generally
commercially obtained as a basic oil mixture
4-picoline and 2.6-1utidine from one another and
from basic coal tar oils comprised predominately
of these compounds.
It is a further object to provide a process for
boiling about 140-145" C. Since these compounds
boil so closely together, it is not commercially 15 resolving 3-picoline, 4-picoline and 2,6-lutidine
containing oils into their separate components
feasible to fractionate such basic oil mixtures into
which can be easily operated with close control
their separate components.
so as to yield commercially pure products.
In my co-pending application, Serial No.
It is a still further object to provide a new
535,397, ?led May 12, 1944, now Patent 2,383,016,
granted August 21, 1945, I have disclosed that 20 separation process which employs the use or"
maximum boiling azeoptropic mixtures.
such bases may be separated from each other and
Additional objects and the entire applicability
recovered by azeotropic distillation utilizing a
of the present process will become more apparent
maximum boiling azeotrope and the process is
from the description of the invention given here
carried out by admixing a suitable quantity of
is’) in inafter.
phenol with the basic oils.
The objects are accomplished according to the
I have now discovered that formic acid may be
process of my invention by admixing the indi
employed to recover such bases by a process of
cated basic oils with a suitable quantity of formic
azeotropic distillation utilizing a maximum boil
acid and distilling from this mass the maximum
ing point azeotrope. The use of such acid has
boiling azeotropes of the basic components of
certain advantages over phenol.
the oil with the acid and separately collecting the
The azeotrope formed with formic acid boils
various fractions,
between 155° and 165° C. but by using these high
The process of this invention is more fully illus
temperatures, the formic acid decomposes rapid
trated in the following example, in which all
ly and therefore is not useable. I have found
parts are by weight unless otherwise speci?ed.
that formic acid becomes useable if the distilla
tion is carried out under a sufficiently reduced
Example
pressure, e. g., 100 mm. to 200 mm. of mercury to
thereby lower the temperature of the maximum
azeotrope so far, that none or very little decom
A commercial mixture of 300 parts of a basic
coal tar oil containing approximately 30% 2,6.
lutidine, 35% 3-picoline and 35% 4-picoline is
position of formic acid occurs. Moreover, and 41
quite unexpectedly there is obtained a new result.
charged into the still pot of a rather high e?~
That is, I ?nd in all other maximum azeotropes
ciency fractionating column. To this basic oil is
such as those produced with phenol, acetic, pro
added 450 parts of formic acid (90% concentra
pionic and isobutyric acids, the order of dis
tion) , a ratio of acid to basic oil of about 4 to 3.
tilling over of the different picolines is ?rst, 2-6 a 1.1 The acid/basic oil mixture is then subjected to
lutidine, 2nd, beta picoline and 3rd, gamma pico
fractional distillation through the column under
line. On the other hand, the formic acid azeo
trope distills over in a different order namely,
first beta-picoline, 2nd, gamma picoline, and 3rd,
2-6 lutidine. Thus, the lowest boiling maximum
azeotrope in the case of the phenol and the all
phatic acids becomes the highest boiling azeo
a pressure of about 200 mm. of mercury and a
temperature of about 110 to 125° C. or a pressure
of about 100 mm. of mercury and a temperature
of about 98 to 110° C. A forerun of approxi~
mately 100 cc. of the total mixture, mostly of
aqueous formic acid, is collected after which the
trope by using formic acid. Since the most valu
maximum boiling azeotropes of B-plcoline, Isl-pic
able component of the basic oils is the beta pico- ‘
oline and 2.6-lutidine distill over and are collect
line, this formic acid process has great advantage 55
ed in that order.
-
2,412,850
4
3
In order to obtain 3-picoline of even higher
purity the ?rst cut or 3-picoline/acid azeotrope
is again fractionated through a similar column
and a fraction of 80% to 90% is collected. This
middle fraction is then treated with an excess of
sodium hydroxide solution and the 3-picoline is
distilled off.
The 2,6-lutidine and the 4-picoline fractions
are treated in a similar fashion in order to obtain
the substantially pure compounds.
The temperature range as given above as Well
as the pressure ranges may of course be varied
but pressures and temperatures are utilized of an
2. The process-of claim 1 wherein the distillates
are acid azeotropes of said bases.
3. The process of claim 1 wherein the distillate
fractions boiling in the range between substan
tially 98-125° C. under a pressure of about 200 to
100 mm. of mercury are separately collected.
4. The process of claim 1 wherein the distillate
fractions boiling in the range between substan
tially 98-125” C. under a pressure of about 200 to
10 100 mmv of mercury
separately collected and
redistilled.
5. The process of claim 1 wherein the distillate
fractions boiling in the range between substan
order which is effective to prevent decomposition
tially 98-125" C. under a pressure of about 200 to
of the formic acid and assure that the fractions 15 100 mm. of mercury are separately collected and
redistilled and wherein the redistilled fractions
will distill over in the manner above described
with the beta picoline constituting the ?rst cut.
are treated to recover the substantially pure base
The ratio of formic acid to basic oils as illus
contained therein.
6. The process of separating a mixture con
trated in the above example may be varied but
preferably more acid by weight is employed than
taining at least two of the bases S-picoline, é-plc
the weight of the oil and it has been found best
oline and 2,6-lutidine which comprises including
to employ an amount of the acid effective to form
in the mixture formic acid, fractionally distilling
an azcotrope with all of the basic oil present, plus
the mass, and thereafter recovering from the
allowance for some decomposition of formic acid.
fractions the substantially pure case contained
The composition of the basic oil being treated 25 therein, the fractional distillation being under re
may be varied. However, this process is princi
duced pressure and at a temperature effective to
pally applicable to those basic oils which are com
susbtantially prevent decomposition of the formic
posed predominately of 3-picoline, 4-picoline and
2,6-lutidine. The ratio by weight of these latter
acid,
'7. The process of separating a mixture pre
materials may be varied relative to one another. 30 dominately containing at least two of the bases
Iclaim:
l. The process of separating a mixture pre
3-picoline, el-picoline, and 2,6-lutidine which
comprises including in the mixture formic acid
dominately containing at least two of the bases
and fractionally distilling the mass under re—
B-picoline, é-picoline, and 2,6-lutidine which
duced pressure, the fractions distilling over as
comprises including in the mixture formic acid 35 3-picoline, 4-picoline and 2,6-lutidine in the order
and fractionaiiy distilling the mass under reduced
named.
pressure.
.
GEORGE RIETHOF'.
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