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Патент USA US2096734

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Oct.. 26, 1937.PROCESS
`C.
C_OUTOR
_
`Film1 May 18, 1934
QQ
\
2,096,734 '
_
FOR CONCENTRATING AND PURIFYI NG
ACID FROM PYROLIGNEOUS PRODUCTS
ACETIC
. ’
" f 2,096,734]
' Patented Oct. 26, 1937
ÍL/J‘l'trrrab _'s-TATES.. PATENT oFElCEÍ
Í
2,096,134
PROCESS FOB CONCENTRAKTING AND PU
VBIFYING: ACETIC. ACID"»FBOM PYBOLIG
'Charles Coutor, Premery, France, assigner to
Sociétéy Etablissements Lambioue Frei-es,
Premery, France
Application May 1s, 1934, semi No. 128,395
InFrance September 2, 1933
- s claims.
Y It is well known to concentrate aqueous solu-v
' tions of acetic acid by distillation in the presence
of auxiliary substances: Marckwald in the .year
1904 used xylol (D. R. P. No. 172,931); Evence
I Coppee uses toluol, ethers, ketones (F. P. Nos.
558,875 and 565,265) and ever since a great many
methods were proposed which employ certain
ethers, ketones, wood oils and generally oxygen
containing substances. --All these methods, which
l0 apply satisfactorily to simple aqueous acetic acid
solutions, entail serious disadvantages when acid
from pyroligneous acid is treated, as the latter,
even , after distillation, contains considerable
amounts of more or less volatile impurities which
u become concentrated with lthe acetic acid, a raw
acid thus being obtained which is highly impure
and the’puri?lcationl of which is very diilicult
and costly.
v
'
The object of this invention is a method which
20 is more advantageous than those already known
and laccording to which the acetic acid from
pyroligneous acid is puriñed and concentrated
at the same time by the action of entraining or
withdrawing substances, which generally consist
25 of a mixture of an oxygen-containingsubstance
and a hydrocarbon, for reasons of efficiency.A
‘ For instance, the mixture of butyl acetate and
xylol, containing 20 to,50% xylol, may be used;
such a mixtureis a good solvent for acetic acid
the tar, wood oils and higher acids so that the
product'issuing- from the dephlegmator 2 through '
the pipe I9 and entering the bottom ofthe col-umn 3 is essentially only a mixture of -water va
por, acetic acid and vaporlzed entraining liquid. k5 y ~ '
The entraining liquid entering the dephlegmator
2 will be vaporized'by the latent heat developedl ` '
by the condensation ofthe tar, woodÍoils and
higher acids.
,
"‘
‘
'_
l
y
condensed in the dephlegmatory 2 by the stream '
or redux of the entraining liquid will usually con
tain a small amount of water'and acetic acid.
'I‘he amount of the entraining liquid reñux is so
regulated as to- condensev atleast all-of the tar, 15
wood oils, ‘ and the higher acids with a yminimumy ,
quantity of water and acetic acid; This mixture - "
containing the impurities ñows through the pipe
20 and is introduced ‘into the top- of a column 4
which is heated at 'theA bottom by a coil.r This 20
column removes from the tar,‘wood oilsaand high- >
er acids, any water or acetic acid that mayhave 1
been returned through the pipe 20 'and 'returns
thesame ‘in vaporous form to the column 2
through the pipe 2l. Thev tar and Wood -oils'are 25
collected at the bottom of ,column 4 and dis
charged through a pipe 22 and the higher'acids ' '
are drawn on through a pipe >23 and'c'ondensed
" in the cooler I3.
\
The puriiied vapors of pyroligneous acid enter 30
80 and the oils in the pyroligneous ‘acid and 'also> the column 3 through the pipe i9 -where lthey
forms with water lanjazeotropic mixture having ymeet on the plates of thiscolumn a reflux or ‘the
a minimum lßoiline'point7
,
'
`
`
,.
î
Anembodiment of the method comprising my
invention, as well as `an apparatus` for carrying
~
The tar, wood oils` and higher acids which are 10
'
ff
entraining or withdrawing'ïliquid which ‘enters
the column 3 ¿through a'pipe ~26 and whichdis
solves' the acetic acid and allows the water vapor 35l
35 it into practice, is diagrammatically illustrated by to 'pass upward through the column in azeotropic
way of example in the drawing forming apart of vcombination with the entrainlng liquid. As the
the speciiication. '
v
vapor passes upward »through this column the
The'de-‘alcoholized pyroligneous~ acid is intro
amount of acid contained thereinis proportion
duced vthrough a pipe I5 into a still l which is ately decreased and at the ïtop of thecolumn 40
40 heated by a'steam coil. Thev acid may be de ` through a pipe 24 the azeotropic lmixture of en
' alc'ohollzed by any lmown method. `A portion training liquid and water having 4a minimum'boil- '
of the tar contained in the pyroligneous acid, not
ing point is removed. Thisis' condensed at 3a
being volatile at the temperaturev normally em
3b and then' led through a pipe 25 to a de
ployed iny vaporlzing acetic acid, flows through and
5. 'I‘he latter permits the mixture to sep'- 45
45 the pipe >I6 -whilethe vapors of the pyroligneous canter
arate into two distinct layers.` The entraining
acid ñow Vthrough the pipe I‘l‘ and enter 4the liquid ñows back through’the pipe 26 to thev top
dephlegmator 2. 'I'he pyroligneous acid vapor, as of the column 3 and the water flows through the
is well known, contains water "and fatty acids pipe 26a. to the top of column 9 inwhich there I ,
along with‘wood oils and tar. The dephlegmator . is removed the small amount of entraining‘liquid 50
5° or column 2receives at the top through the pipe (usually less than 2‘or’3%) which is dissolved in l _
I8 a controlledstream or reflux >of entraining‘ a water. 'I‘his entraining liquidU is recovered by
liquid which has been decanted _at the bottom of causing steam to bubble` through it at the bottom
the column-3, as will be described in more detail of the column 9 andthe recovered 'vapors ofen- , .
later. The> dephlegmator- 2 functions to purify
55 the vapors of the pyroligneous acid by condensing training agent ilow through kthe pipe‘21’and into 55
2
9,096,784
the vapors exiting from the column 8 in the pipe
2l. 'I'he water is drawn oi! at> the bottom of
column 9 through a pipe 2l. This water will con
tain usually less than .03% -acetic acid and chief
ly formic acid.
`
The liquid at the bottom of the column 3 con
stitutes two distinct layers: a layer of the en
training or withdrawing liquid which is returned
through pipe i8 to form the stream or reflux for
the dephlegmator 2 as described above. and a
layer of aqueous solution of acetic acid. the
strength of which is not over 45%. ’I'he concen
tration of the acetic acid is not permitted to
exceed this ñgure and as a consequence the acid
15
and the entraining liquid will separate in dis
tinct layersI and also only a small amount of
purified entrainingliquid is returned from the
bottom of the column I 0 through pipes 43 'and
“a to the dephleamator 2.
¿
v
The tars issuing from the still i and from the
bottom of the column may advantageously be
submitted to a steam carry-0n' treatment to re
cover an aqueous -acid therefrom which is re
cycled into the apparatus.
'
The de-alcoholized pyroligneous acid may be
decantedpreparatorily and the tar treated sep 10
arately yields an aqueous acid which is added to
the aqueous pyroligneous acid layer submitted
to distillation inthe still I; however, the pyro
yligneous acid may also be distilled together .with
its tar without inconvenience.
It is advantageous to preparatorily free the
pyroligneous acid from its wood alcohol content.
acid.
The dephlegmator 2 utilizes part» of the en
'I‘he acid solution is-drawnoii' througha pipe » training liquid which is recycled automatically as
20 29 and introduced into the top of the columnv t
a result of the dehydration. An adjustment of` 20
heated at the bottom by a steam coil. In this the amounts thus recycled into the dephlegmator
column the acid is dehydrated by recti?cation 2 will sufiice to >keep the concentration >of the`
and the vapors in the column which are poorer aqueous phase streaming towards 6 from ex
entraining liquid will be dissolved in the acetic
in acid than the liquid in pipe 29 are sent back
25 to the column 3 through pipe 3l. Any entrain
ing liquid dissolved in the acid and returning to
the column 6 -is vaporized in the upper portion
of this column.` A thermostatio regulator ta ac
> tuated atone of the plates of column l controls
30
the heat applied at the bottom »of the column.
'I'his is usually controlled so that the tempera
ture is around 108° C. near the middle of the
column. 'I'he concentrated acetic acid in the
form of vapors at the bottom of column e or a
35 few plates above is removed through a pipe Il
and condensed in the cooler 1. This acid is sub
stantially anhydrous and colorless and is the s0
called technical acetic acid which is suitable for
most industrial purposes. It will contain a small
40 amount of formic acid but only tracesioi' higher
acids.
-
a
f
In order to avoid accumulation in the bottom
of the column 6 oi' certain impurities which are
but slightly volatile and which wouldform res
ins on the heating coil, a small quantity of the
liquid is withdrawn Íthrough a pipe I2 and a
greater part of this liquid is vaporized yin the
heater 8 which sends its vapors back to the col
Vumn 8 through pipe I3. The impurities are dis
50 charged through the pipe 24 to the tar column I.
If a so-called “tasteful" (edible) acetic- acid
is desired, the vapors are sent from the bottom`
of the column 6 through a pipe ß to the bottom
of the rectifying `column il, the reiiux of which
55 returns to the columnrß 'through the pipe 36.
At the bottom of column `Ii an acetic acid which
is rich in formic acid is withdrawn through the
pipe 3l.Y The pure acidV is withdrawn through
the pipe `38 from a plate located near the top of
60 the column. This acid issent to the top of col
umn i2 _which removes an additional quantity
of formic acid from the product and sends the
formic acid vapors through a pipe Il to the col
umn ll. The y“tasteful” acetic acid is taken
65 from the base of the column I2 through a pipe
40 and thisacid is condensed in a cooler il.
The entraining liquid may become slightly
modiñed during use and it is advantageous to
ceeding ya definite limit.
.
,
`
It will be appreciated that the purification is
costless as far as heat is concerned,~because they
heat 4required to vaporize the entraining liquid
in the dephlegmator 2 is provided by the con
densation of the tar, wood oils and higher acids.`
. 'I'he entraining liquid lends itself to high-tein
peraturedecantation (89° CJ: >the connections
fromr the decanter to the condenser malle.~ it
possible, whereby the expenditureat the bottom
of columns land 6 is limited to the mere vapori
zation of the entraining liquid decanted- at l. 35
Where “tasteful” acetic acid is produced it is
suitable to heat the recovery column 9 with the
aid of column il from the top of which the
vapours issue at about 107° C.; the columns `I2
and l may also be> arranged above each other, 40
so that some steam may be spared.
‘In no instance the expenditure to _obtain “taste
ful” acid will be higher than -twice the steam
necessary. to vaporize the pyroligneous acid, even
if «the concentration of the same should' be as 45
highasl5percent.
.a
.
f
A
_
It is unimportantthat the pyroligneous acid is
taken in at the bottom of column 2 in the liquid
instead of the vapour phase; it is only necessary
then to suitably design the heater for column 4, in
order that the pyroligneous acid may be inthe
vapor phase when it is _contacted with` the en
training liquid in thedephlegmator 2.
, 'I'he use of the butyl lacetate-xylol mixture as Y I
mentioned above is not limitative and the princi 55
ple of the invention is not modified by vthe use
of any otherasuitable mixture. An oxygen-con
taining substance and a hydrocarbon willprefer
ably be chosen; for instance, a mixture of mesityl
oxide with a petrol boiling from about 125 to
135° C. is quite suitable.
.
The expression"‘entraining liquid” used herein
refers to a stable, non-reactive liquid or mixture
of liquids having the property of forming an
azeotropic mixture with water in the presence of 65
acetic acid. 'I’he'materials suitable for this pur
eliminate the products in_the entraining liquid
pose are well known in the'prior art and the re
quirements for such an entraining liquid are set
forth in detail in French Patent No. 622.680.
v
consumption. `To accomplish this,_a small quan
Generally speaking, the oxygen-containing sub 70
stance imparts ‘solving properties to the auxiliary
70 which would progressively increase the steam
tity of the entraining liquid is drawn oil' through
a pipe ll and introduced into a rectifying column
I0 heated by a steam coil. 'I'he impurities pass
75 to the condenser I 0o through a pipe 42 and the
mixture, while the hydrocarbon will decrease said
properties somewhat at the same time as they will
allow itv to remain not very soluble in the concen- , Y'
trated acid present at the bottom of I.
75
¿096,734
training liquid introduced asa reiiux and con
I claim:
, 1. In a process for the separation of a substan
trolled in amount to condense the wood oils, high- `
tially pure anhydrous acetic acid from de-alco
holized pyroligneous acid from which the bulk of
the tar has beenremoved, the steps which com
prise contacting said pyroligneous acid in a vapor
phase with a water entraining liquid introduced
simultaneously to vaporize said entraining liquid
bythe latent heat of vaporization‘ ,given up by
the condensed products, and contacting the puri
as a reflux and controlled in amount to condense
er acids, and remaining tar contained therein and »
iied vapors with an additional quantity of the
same entraining liquid to dehydrate the acid by
the wood oils. higher acids, and remaining tar r 4itzeotropic distillation, the entraining> liquid used
in the condensation of the impurities being ob-‘
10 contained therein and simultaneously to vaporize ' tained from a point in the dehydrating operation
said entraining liquid by- the latent heat o!
vaporization given up bythe condensed products, and being one adapted to form with water any
azeotrope of minimum boiling point.
and contacting the pui-ined vapors with an addi
4. In a process for the separation of a substan
tional quantity of the same entraining liquid to
dehydrate the acid by azeotropic distillation, the
15 said
entraining liquid being one adapted to form
withy water an azeotrope of minimum boiling
point. g
~
Y 2. In a process i'or the separation of a substan
tially pure anhydrous acetic acid from de-alco
holized pyroligneous acid the steps which .com
prise `vaporizing the pyroligneous acid to elimi
nate the bulk of the tar, contacting said pyro
ligneous acid in a vapor phase with a water en
training liquid introduced as a reflux and con
trolled in amount to condense the wood oils, high-.
er acids, and remaining tar contained therein and
tially pure anhydrous acetic acid from de-alco
holized'pyroligneous acid the steps which com
prise vaporizing the pyroligneous acid to elimi
nate the bulk of the tar, contacting said pyro
ligneous acid in a vapor phase with a. water en
training liquid introduced as a reñux and con 20
trolled in amount to condense the wood oils,
higher acids, and remaining tar contained there
in andslmultaneously to vaporize said entrain- .
ing liquid by the latent heat of vaporization i
given up by the condensed products, and con 25
tacting the puriñed vapors with an additional"
quantity o1' the same entraining liquid to dehyfV
simultaneously to vaporize said entraining liquid
lby the latent heat of vaporization given> up by
the condensed products, and contacting the -puri
fled vapors with an additional quantity oi the
training liquid used in the condensation of the
impurities being obtained from a point in the de
azeotropic distillation, the said entraining liquid
point."
drate the acid by azeotropic distillation, the en- i À
hydrating column and being one adapted to form .
y same entraining liquid 'to dehydrate the acidbyA with water an _azeotrope of minimum boiling
being one adaptedV to form with water an azeo
trope of minimum boiling point.
‘ 3. In a process for the separation of a substan
‘
'
.ï
c
l
5. The process described in claim 2 m which the ’
entraining liquid comprises a mixture of butyl' 35
acetate and xyiol.
v
v
_ holized pyroligneous acid the steps which com
6. The process described in claim V2 in which _the
entraining liquid comprises a mixture of mesityl
prise vaporizing the pyroligneous acid to elimi
oxide and a petrol boiling from 125° to 135° C. l ~
nate the bulk-of the tar, contacting said pyro
40 ylignecus acid in a. vapor phase with a water en
cmlnms coU'roR.- "
tialLv pure anhydrous acetic acid from de-alco
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