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Патент USA US2404167

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Patented July 16, 1946
Karl Henry E'rigel, Teaneck, N. J ., assignor to ‘Al
lied Chemical & Dye Corporation, New York,
N. Y., a_ corporation of New York
No‘Drawing. Application March 10, 1943,
Serial No. 478,637
10 Claims.- (Cl. 260-290)
This invention relates to the resolution of
mixtures of heterocyclic nitrogen compounds
containing pyridine homologs such as 3-picoline,
4-picoline and 2,6-lutidine.
chemicals. Nicotinic acid, for example, a member
of the vitamin B complex, may be readily ob
tained by oxidation of '3-picoline.
- The piccl-ines, other homologs of pyridine, and
Since the three components making up the
usual nitrogen base fractions boiling in the range
pyrrole are customarily extracted, along with
140°-l48° C. (2,6-lutidine, 3-picoline', and 4-pic
oline) have substantially the same boiling points,
and since pyrrole, present in some of these frac
these heterocyclic nitrogen compounds by means
tions, forms azeotropes with these bases, frac
of an aqueous solution of mineral acids, usually
sulfuric acid, and are ‘liberated from the acid 10 tional distillation is obviously unsatisfactory as
a means for resolving the mixtures. Other
solutions by the addition of alkali hydroxide or
vmethods of resolving such mixtures heretofore
carbonates. Mixtures of nitrogen compounds
described in the published prior art have been
thus liberated are then fractionally distilled.
generally unsatisfactory in regard to products,
Bases such as pyridine, boiling point 116° 0., and
2-picoline, boiling point l29.4° C‘., can generally 15 yields, and production costs. Such other meth
ods have usually depended upon fractional crys;
be obtained in reasonably pure form by frac
tallization of the more common salts of the bases‘
tional distillation, but for the most part the re
present, e. g., the chlorides, sulfates, oxalates,
maining compounds cannot be separated by dis
chlorates, picrates, ferrocyanides, and the like.
tillation methods alone. Instead, the fractions
obtained, even when they are of relatively nar 20 Isolation or puri?cation of individual bases by
such methods has been found to be extremely
row boiling range, contain increasing numbers of
cumbersome and generally insu?ciently sharp to
pyridine. homologs or their isomers. Mixtures of
obtain compounds of a purity demanded in in-,
this kind have found limited practical application
dustry. These methods‘ also have often pre
mainly as special solvents and are of relatively
low economic value. The individual/compounds, 25 sented other drawbacks such as prohibitive cost,
explosive hazards,v and toxicity.
however, if they could be readily isolated would
It is an object of this invention to provide a
be of far greater value, for example, in the prep
pyridine, from coal tar oils and other sources of
aration of derivatives, especially pharmaceutical
products and dyes. The requirements for purity
in these ?elds are extremely severe.
~ commercially attractive process of obtaining pure
or enriched 4-picoline and 3-picoline from mix
30 tures of these compounds and other heterocyolic'
Of especially high potential value are the ni
nitrogen compounds not readily separable there
trogen compounds in the fractions having a boil
ing range of about l40°-148° C. A typical mix
from by distillation.
It is a further object of this'invention to pro
ture recovered fromrmost types of coal tar, for
example, is the fractionvboilingin the vicinity of
ing the usual fractions of heterocyclic nitrogen
143°-145° C. containing as predominant compo
compounds, particularly tar-base‘fractions boil
vide- a' commercially feasible process for resolv
ing in the range l40°-l48° C;, which fractions
nents three pyridine homologs of substantially
generally contain 2,6-lutidine,’3-picoline and 4
the same boiling point in roughly equal propor
picoline in substantial proportions, and may con
tions; i. e., 2,6-lutidine, boiling point 143.8° 0.,
E-picoline (beta-picoline) , boiling point 143.8u C., 40 tain pyrrole.~
I have discovered, that mixtures containing 3
and 4-pico1ine (gamma-picoline), boiling point,
picoline, 4-picoline, and 2,6-lutidine may be re
144.8° C. This fraction may also contain small
solved into separate fractions, each enriched in
proportions of lower or higher boiling Pyridine
one of these bases, by subjecting to dry distilla
homolog such as 2-picoline and" 2,4-lutidine.
Mixtures of heterocyclic nitrogen compounds re 45 tion, preferably under reduced pressure, a cal
covered from some of the less common coal tars
cium chloride addition product of such base mix
tures. I have found there are sharp: differences
may contain substantial proportions of pyrrole
in decomposition vapor pressures between'the instead of, or in addition to, the 2,6-lutidi1ie. Al
calcium chloride addition compounds of the three
though pyrrole alone boils at'129.8° C‘., with 3
and 4-p-icolines it forms high-boiling azeotropes 50 pyridine homologs, 2,6-lutidine compounds hav
ing by far the highest vapor tension, S-picoline
boiling about 145°-l48° C., the components of
compounds a lower one, and 4-picoline com
which are inseparable by ordinary distillation
poundsv the lowest. Thus, it is possible, to obtain
methods. Derivatives of many of‘ these com
pounds are becoming of increasingly greater im
as a ?rst distillate from a calcium- chloride addi- _
portance . as» pharmaceuticals and- agricultural 55 tion product of a 2,6-lutidine-3-picoline-4-pico
two of the pyridine homologs >3-picoline, 4
picoline and 2,6-lutidine in substantial propor
line mixture a 2,6-lutidine concentrate containing
generally about 87% 2,6-lutidine with 3-picoline
and. very little ‘ii-picoline present. -A further dis:
\ tions, and. generally contains all three of these
bases. As above pointed out, such a mixture‘
taining about 72% 3-picoline and 28% 4-pic0-‘ 5 may also contain pyrrole, and may contain small
line. 'The ?nal distillate consists of a 4-picoline
amounts of bases boiling outside the range
140°-148° C., e. g., bases such, as Z-picoline and
concentrate containing generally about 92% 4-7
tillate consists of a 3-picoline concentrate con
picoline, with 8% 3-picoline present. This is
particularly surprising since 3-‘ and ll-picolines“
:My invention further comprises a process in
and 2,6-lutidine,'all being pyridinehomologs of 10 which the above-described dry distillation of calcium chloride addition compound is com
like boiling point, might be expected to form ade
dition compounds of substantially identical prop
erties. When pyrrole is present‘ in theioriginal
base mixture, it will distil over in the ?rst frac
tion, the 2,6-lutidine concentrate, and the luti-l 15
dine content of this fraction will be accordingly
bined with additional treatments, as described
below, forv isolating substantially pure bases
from the various base concentrates obtained by
the dry distillation of the calcium chloride addition compounds.
In a preferred method of practicing my in
The process of my invention may also be ap-‘ ' 'vention, a pyridine homolog fraction, as above
plied, of course, to producing concentrates of
described, boiling in the range 140°-148° C'. is
individual bases, as above described, from base 20 converted into a mixture of calcium chloride
addition compounds, preferably by adding the ,,
mixtures containing any two of the bases 3:
base mixture gradually to a charge of anhydrous
‘picoline, lit-picoline and; 2,6-lutidine. Thus, a
3- and Iii-picoline mixture may be resolved into
calcium chloride. The proportion of - calcium
a 3-pico1ine concentrate and , a e-picoline cone
chloride to crude basesin' this charge is prefer
centrate; similarly, a mixture of 2,6-lutidine 25 ably. approximately in a molar ratio of 1 to 2.
Somewhat smaller ratios in which the bulk of
withreither 3- or ll-picoline may be resolved into
the 2,6-lutidine is left uncombined are also
a 2,6-lutidine concentrate and a 3-picoline or
‘Jr-picoline concentrate. '
feasible. At the minimum, however, su?icient
The bases 3-picoline, ‘ll-picoline and 2,6
calcium, chloride should be providedto combine
lutidine .arepresent generally in the heterocyclic 30 with the 3- and 4-picolines present in a ratio
‘nitrogen, compound ,mixtures separated from
of one mol of calcium chloride to two of base.
materials such as coke-oven distillates, cracked
petroleum, shale tar, bone oils and other natural,
as well as synthetic, nitrogenous materials. As
Excess calcium chloride over that required to
combine with all bases present is not harmful.
The dry-distillation operation resembles in
above pointed out, when two or more of‘ the 35 principle the drying of a solid at successive tem
perature levels and accordingly I have found it
bases S-picoline, é-picoline and_2n,6-lutidine are
‘present in such mixtures, ordinary fractional
advantageous to carry out the distillation in an
apparatus of a type often employed as a drier
distillation is. not effective to isolate these bases
for solids, consisting of a rotary iron vessel pro
from'eachother. ,Instead, upon fractional dis
tillation, these three pyridine homologs, differing 49 vided with a slowly revolving, agitator, a trap to
by not more thana degree centigrade in their
retain dust, a vapor outlet connecting with a
boiling ,points, become concentrated in fractions
condenser cooled with a circulating water, and
boiling in the range PLO-148° C.‘ For example,
receivers.‘ The‘ drier-condenser system is pref
the beta-gamma picoline fraction recovered
erablyconnected to a vacuum pump to main
from pyrrole-free coal tar generally boils in the 45 ,taina desired constantpressure. Vapor losses
range 140°-145° C. and has the following ap-v
through the exhaust of the pump may be avoided
‘2,6-lutidine ____ __'_ ____ __' __________ ______ 20-45
_________ .;_ ______________ __
_' _______________________ _;_ 30-40
by passing such vapors through suitable scrubbers
which retain bases, preferably through scrub
bers containing solutions of mineral acids. The
»50 drier may be ?red directly, e. g., with gas, or
may be jacketed for heating with a fluid heating
In addition, this fraction may contain a small
43A ?nely'ground, :moisture-free' calcium chlo
percentage of 2-picolin'e and 2,4-lutidine, When
ride is ‘preferably used for the charge. In regu
pyrrole is present, a close-cut fraction contain 55 vlar-operation, the greater part of the calcium
.ing these bases and pyrrole generally boils in the
chloriderequired'for a charge will be the residual
‘range >145°—148° C.
A vfraction to which the process ofmy inven
tion is applicable may thus be obtained from-a
_heterocyclic nitrogen compound mixture that
calcium chloride left in the vdrier at the con
clusion of the dry distillation of a previous
' ,batch,'sinc_e this calcium chloride is in the de
60 sired powdered anhydrous form. Small me
contains two or more ofthe pyridine homologs‘
chanical‘losses of calcium chloride, such as loss
.3-picolinegp4-picoline, and 2,6-lutidine; .my in
,throughdust traps, maybe made up, between
vention may thus comprise fractionating such, a
successive charges, by addition of a technical
.heterocyclic nitrogen compound mixture to ob
~ grade ,ofcalcium chloride (78% to 80%). Mois
tain a close-cut fraction boiling predominantly 565 .tureiwhich such material contains is distilled,
in‘ the range 140°-148° C., converting bases in
as -ajpreliminary fraction, before taking off the
this close-cut fraction to theirgcalcium chloridev
desired base distillate fractions.
addition‘ compounds, and subjecting-to dry dis;
.' As abovestated, the base mixture is slowly
added .to a charge of calcium chloride. A small
as; above described. In some of the claims _I =70 amount of calcium chloride-lutidine-picolines
haverindicated the dry distillation is to be ap
‘addition compound, saved‘from a preceding oper
.plied toa calcium chloride addition-product of
ation ‘and su?icient for crystal inoculation, is
. tillatipnto obtain individual base concentrates,
a‘ mixture of “pyridine ,homologs boiling in the
range ,140°-l48° C._”_; this, expression is intended.v
itoydeeoteis :rpixtilrergwhich, contains at, least
preferably- dispersed throughout the powdered
calcium chloride to ,initiate :prompt crystalliza
175 tion. , This, isrdcsirable inorder to make certain
~ 2,404,167
185° C., and‘ the 4-picoline concentrate in the
neighborhood of 275° C. In this case also, the
that-combination of base with‘calcium chloride
occurs about as rapidly as the base is added, since
distillate fractions would be taken through a
range extending considerably, below and. above
accumulations of unreacted free base may lead to
?nal rapid reaction and formation of large solid
aggregates which makes further. agitation
these temperatures. Pressures lower than 5 mm.
and higher than 100 mm. may-be employed. ‘In
general, I have found that low pressures (and
The charge is agitated, and, uniformly and
gradually heated, preferably under a reduced
pressure varying from about 5 to about 100 mm.
mercury. Vapors consisting of free bases are
carefully condensed in a series of receivers. The
?rst nitrogen base distillate fractiontaken con
sists of a 2,6-lutidine concentrate which under
correspondingly low temperatures) permit the
sharpest separation. However, the use of prose
sures lower than about 5 mm. requires the use
of lower condenser temperatures, even brine cool
ing in some instances, to condense thefree base i
that distils off, whereas the use of pressures'higher
than about 100
may require temperatures of
equilibrium conditions contains about 87% of 2,6
lutidine‘when the starting material is a’ base mix V15 300° C. or higherto decompose the most stable of
the addition products, namely the addition prod
ture that contains no substantial amount of .ma
uct of the 4-picoline concentrate.
terial other than 2,6-lutidine, 3-picoline and 4
‘I have found that 40-60 mm. represents the
picoline. The 2,6-lutidine‘concentrate thus ob
most'advantageous pressure for general opera‘
tained contains also about 9% 3-picoline and
about 4% 4-picoline. - When pyrrole is present in 20 tion. 'At' these pressures, the free bases that
the original base mixture, it will come over with
the 2,6-lutidine concentrate and the proportion
of 2,6-lutidine will be accordingly decreased. This
lutidine concentrate continues to come over until
more than 95% of the 2,6-lutidine has been re
distil over can be condensed Withordinary cool
ing water and the entire distillation can be car
ried out at temperatures substantially below 300°
C. Employing a pressure within the range 40-60
mnr, e. g., a pressure of 50 1nm., the ?rst fraction,
the 2,6-lutidine concentrate, is taken at a distilla
moved from the mixture in the still.
tion temperature of about 65°~95° C. The second
When about 4% of the 2,6-lutidine still remains
small intermediate fraction is then taken at a
in the material in the still, the distillation tem
temperature upto 130° C.; the third fraction, the
perature rises and at a higher temperature level
a small quantity of an intermediate fraction (gen 30 3-pic0line concentrate, is taken from that point
up to a temperature of about 215° C.; and the last .
erally about one-tenth of the volume of the prin
fraction, the 4'-picoline concentrate, is taken from
cipal fractions) distils over until the 2,6-lutidine
that point up to a temperature. of about 280° C.
has been completely removed; this fraction under
The products obtained by the process‘ of my in
equilibrium conditions contains about 35% 2,6
vention are dry, water-white products which ?nd
lutidine, about 45% 3'-picoline, and about 20% 4
a ready market without further treatment. ‘The
picoline. This small quantity of mixed base is re
3-picoline concentrate, e. g., containing 72% of
turned ‘to the process, i; e., 'is- added to the next
3-picoline, may be used directly for production of
nicotinic acid by oxidation. When substantially
at a higher temperature level a 3-picoline concen 40 pure bases are desired, these may be prepared
from the various base concentrates by=methods
trate is taken on as distillate. This concentrate
isclosed in copending’ applications. Pure 2,6
under equilibrium conditions contains about 72%
The temperature of distillation rises again and
3-picoline and about 28% 4-picoline.
The base component of the material remain
ing in the still at this point contains about 92% 45
4-picoline and about 8% 3-picoline. This 4
picoline concentrate may be distilled off at a still
higher temperature or may be recovered by ad
dition of water to the still residue, thus decom
posing the calcium chloride addition compounds. 50
lutidine may be prepared from 2,6-lutidine, con
centrate, for example, by precipitation as phos
phate, in accordance with my copending applica
tion Serial No. 346,347, ?led July. 19, 1940. .When
pyrrole is present in the ?rst distillate fraction,
this may be removed by the process of one of my
copending applications, Serial No. 463,736, ?led
October 29, 1942, or ‘Serial No. 487,975, ?led May
21, 1943. Pure 3-picoline vmay be prepared from
the 3~pico1ine concentrate by precipitation as
4-picoline is then obtained by steam distillation
or partial evaporation of the mixture. It is pref
phosphate, in accordance with the process of my
erable to remove the 4-picoline concentrate by dry
copending application Serial No. 346,347, referred
distillation, since this leaves powdered anhydrous
calcium chloride ready to be reused for forming -55 to above, or by distillation in the form of its hy
drochloride, in accordance with the process of co
the calcium chloride addition product of the next
batch of base mixture. When water has been
added to the still residue and the 4-picoline con
pending application Serial No. 452,369, ?led .July
25, 1942. Pure 4-picoline may be obtained, if de
sired, from the 4-picoline concentrate by crystal
to reuse the calcium chloride it is necessary to 60 lizing the calcium chloride addition compound of
evaporate the residual solution to dryness and to
this base, in accordance with the process of co
grind the solid calcium chloride thus obtained. '
pending application Serial No. 441,557,‘?led May
centrate removed by steam distillation, in order
As above stated, a reduced pressure of about 5
2, 1942,
to 100 mm. mercury is preferably employed dur
The following. example is illustrative of the
ing the dry distillation. At a pressure of 5 mm.
process of my invention:
mercury, the 2,6-lutidine concentrate distils o?
The mixture of heterocyclic bases used in this
in the neighborhood of 15° C., the 3-picoline con
example had a boiling range (bulb distillation) of
centrate in the neighborhood of 70° C‘., and the
-140.6° to l44.4° C., corrected temperatures.
4-picoline concentrate in the neighborhood of 175°
speci?c gravity at 20° C. was 0.943. The material
C. In actual operation, the fractions would gen 70 had approximately the following composition:
erally'be taken through a range extending from
Per cent
10° to 20° below and above these temperatures.
At a pressure of 100 mm. the 2,6-lutidine concen
trate comes off in the neighborhood of'80" C., the
__-_ ______________________ _‘____;_ 35
3epi'coline concentrate in‘ the“ neighborhood of 75
______ -l _____ -1‘ ____ __'___'_ _____ __
-__‘_ ___________________ __- ____ __~
2540451 67
the remainder consisting ‘of 2-picoline and 2,4
ample, losses amounted ; toi 3% {of total bases
7' changes
, may be made in carrying
The apparatus consisted of a gas-heated sta- ,
tionary drier of iron constrution, provided with a
‘out the above process withoutdeparting from the
slowly revolving agitator, a trap to retain~~dusted 5 scope of the invention, it is intended that all mat:
in'o‘aterials,v a condenser cooled with circulating
ter contained in the above description shall be
water at about 5-10“ C., and receivers.
interpreted as illustrative and not in a limiting
The drier -
was connected to a vacuum pump to maintain a
desired constant pressure‘. The drier was charged
with 600 parts by weight, of powdered anhydrous 10
1. In a process'for separating components of a
calcium chloride. A supply of calcium chloride
mixture of pyridine homologs boiling in the range
lutidineepicolines additioncompound saved from ‘
140°-148° C., the steps which comprise subject
' a preceding operation, and sufficient for proper
inoculation, was dispersed throughout the pow
dered calcium chloride to initiate prompt crys
A mixture of bases was gradually
ing to dry distillation a calcium chloride addi
tion product of such'miXture, and recovering at
least one‘distillate fraction enriched in one of
said pyridine homologs.
, added to the the calcium chloride at atmospheric
‘ 2. In a process for separating components of a
pressure, making certain that combination oc
mixture of pyridine homologs boiling in the range,
curred about as rapidly as the addition proceeded,
l40°-14"8° C.,‘ the steps which comprise subject
and that the complete addition compounds were 20 ing to dry distillation a calcium chloride addition
dispersed throughout the mixture.
The combination of the materials resulted in
product of such mixture, and recovering distillate
fractions each enriched in one of- said pyridine
the’ liberation of heat, the temperature of the
charge rising from roomtemperature to about
70“ C.
At the completion of the mixing opera
pyridine homologs boiling in the range l40°-148°
C., the steps which comprise subjecting to dry
distillation, under a pressure in the range of '
about 5 mm. to about 100 mm. mercury, a calcium
chloride addition product of’ such mixture, and
recovering at least one distillate fraction enriched’
rial had'the following composition:
in one of said pyridine homologs.
_____________________________ __ 8'7
a The remaining 4% consisted mainly of Z-picoline
with possible/traces of 4-picoline.
Receivers were changed at this point. Distilla
tion was continued, removing a small intermediate
' fraction, 3.5% of original bases, while the drier
temperature rose to 130° C.
' The'intermediate fraction'had the following
_ ,
4. In a process for recovering a 2,6-lutidine
concentrate from a mixture containing this base
Per cent
___________ _i _________________ __
and otherlyrnitrogen bases not readily separable
therefrom by distillation, thesteps which com
prise forming a calcium chloride addition prod
not of said mixture, carrying out a dry fractional
distillation of said product and collecting a dis
tillate fraction enriched in 2,6-lutidine.
5. In a process for recovering a 3-picoline con
centrate from a mixture containing this base and
other nitrogen bases not readily separable there
Per cent
from by ‘distillation, the steps which , comprise
__________________ -'. _________ __ 35
45 forming a calcium chloride addition product of
25 a mixture containing substantial proportions of
tion, the atmosphere of the drier was partly evace
uated to maintain constant pressure at about 50
mm. Distillate was taken off until 33.5% of the
original mixture of heterocyclic bases had been
collected, the temperature inside of the drier ris
ing from 65° C. to 95° C; The distilled mate
3. In a process for separating components‘ of
said mixture, carrying out a dry fractional, dis- ,
tillation of said product and collecting a dis- ,' ‘
tillate fraction enriched in 3-picoline. I
Distillation was continued until the drier tem-.
6. In a process for recovering a 4-picoline
perature rose to 215° C., 39.0% of the original mix 50 concentrate from a mixture containing this base
4-pico1ine _____ _.'_ ________________________ __
ture of bases being collected in the receiver. The
material had the following composition:
Per cent
______________________________ __ 72
______________________________ __ 28
and other nitrogen bases not readily separable
therefrom by distillation, the steps which com
prise forming a calcium chloride addition prod
,uct of said mixture, carrying out a dry fractional
distillation of said product and collecting a frac
tion enriched in 4-picoline.
After changing receivers, ‘distillation was com-j
'7. A process for resolving a mixture of 2,6
pleted by raising the temperature‘ inside of the
lutidine, 3-picoline vand 4-picoline into a 2,6
drier gradually to 280° C. The material collected
lutidine concentrate. a_ 3-picoline concentrate,
in this fraction represented 19% of the original
mixture of bases and had the following composi 60 and a 4-pic01ine concentrate, which comprises
treating the mixture with an amount of calcium
chloride at least sufficient to react with the picc
Per cent
_______________ _; ____________ __-_
lines, subjecting this calcium chloride addition
product to dry fractional distillation, under a
4-picoline ______________________________ ..r' 92 65
pressure of about ,5 mm. to about 100 mm. mer
The small intermediate fraction representing
‘3.5% of the total bases, was returned to a sub
sequent batch to be re-worked. The calcium chlo
ride remaining as a, residue consisted of a ?nev
cury, and collecting successively a 2,6-lutidine
concentrate, a 3-picoline-concentrate, and a 4
picoline concentrate.
8. A process for recovering a 2,6-lutidine con-V,
powder which, after cooling, was ready to be 70 centrate, a S-picoline concentrate, and a 4-pico
In addition to the distillates, collected in the
above fractions, material recovered in scrubber
from exhaust gases amounted to 2% of total bases
line concentrate from a mixture of coal tar bases '
» containing (2,6-lutidine, 3-picoline and ll-pico
line, which comprises fractionating the base mix
ture to obtain a cut boiling in the range 140°-148°
charged, ‘Under conditionsemployesi'in' this ,ex- *15 IC., treating this cut withlan amount or calcium
chloride at least su?icient tov react with the
' picolines, subjecting this calcium'chloride addi
tion product to dry fractional distillation under
reduced pressure and collecting successively a
2,6-lutidine concentrate, a 3-‘pic01ine concentrate,
and a é-picoline concentrate.
9. In a process for separating components of
a mixture of pyridine homologs boiling within
the range 140°—148° C., the steps which come
prise treating the mixture with calcium chloride,
then dry distilling the resultant reaction prod
uct and collecting as distillate at least one frac
tion enriched in one of said pyridine homologs.
10. In aprocess for resolving a mixture of 2,6
lutidine, 3-picoline and 4-picoline, the steps which‘
‘ comprise treating the mixture with an amount of
’ calcium chloride at least su?icient to react with
the picolines, thereafter dry distilling» the result
ant reaction product and separately collecting
three fractions having respectively a relatively’
high concentration of 2,6-1utid1'ne, 3-picoline and
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