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Патент USA US3079336

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Feb. 26, 1963
M. B. NEUWORTH
3,079,326
DOUBLE SOLVENT REFINING OF TAR
Filed March so, 1960
2 Sheets-Sheet 1
PRIMARY
74R
’/
2
r3
AQUEOUS
r
‘
METf/A/VOL
z IQU/D -L IQU/D
£X7Q4C‘770A/ VESSEL
r4
NAPl/THA
*‘
50L VENT
AQUEOUS METl/A/VOL EXTRACT
PITCH PHASE
IN VEN TOR.
M4477” 5 . Nil/WORTH
Feb. 26, 1963
M. B. NEUWORTH
3,079,326
DOUBLE SOLVENT REFINING OF TAR
Filed March $0, 1960
2 Sheets-Sheet 2
P115, 2
BY
3,079,326
tPa‘tented Feb. 26, 1%53
2
economically from other sources. In still other methods,
relatively expensive solvents are required in large volumes
3,079,326
BOUBLE SOLVENT REFENENG 0F TAR
Martin 3. Neuworth, Pittsburgh, Pa, assignor to Con
solidation Coal Company, Pittsburgh, Pa., 2 corpora
tion of Pennsylvania
Filed Mar. 39, B66, Ser. No. 18,695
in treating the tar in order to avoid gumming and plug
ging of equipment and associated operability problems‘.
In yet others of these plans, attempts have been made to
?rst remove ?nely divided particles present by use of con
ventional mechanical separation techniques such as ?ltra
6 Claims. (Cl. 2ti8—45)
tion, centrifugation and settling. Such techniques with
out further modi?cation have been generally found lack
This invention relates to a process wherein a double
ing with respect to operability and commercial feasibility,
solvent treatment is used for fractionating the liquid prod
ucts obtained by the low-temperature pyrolysis of natu
particularly where a high percentage of solids is present
in the tar. In general, the foregoing plans either intro
duce additional processing steps that are frequently costly
and hence of laboratory interest only, or signi?cantly
rally occurring carbonaceous solids. It is particularly
concerned with the fractionation of primary low-tempera
ture tar using aqueous methanol and a para?inic naphtha
fraction as solvents under selected conditions.
alter the basic c“aracteristics of the tar, whereby a lesser
amount of valuable liquid products is recovered.
Fractional distillation has been principally used here~
When naturally occurring carbonaceous solid fuels, such
as bituminous coal and lignite, are subjected to low-tem
tofore to eifect an initial fractionation of the primary
perature carbonization, i.e., at a temperature below
tar. By “topping” of the tar, the more volatile tar acid
1400° F., the product tar is evolved as a vapor. Sub
sequent condensation of the vapor produces a highly 20 oils may be recovered therefrom as an overhead distils
late. However, depending on the nature of the tarv and
viscous liquid tar product that is variously designated as
the thermal treatment, many of the tar constituents may
primary, whole, unprocessed, unre?ned, raw or crude tar.
polymerize, decompose or be carbonized. As a conse
The term “primary tar” is ordinarily applied to tar ob
quence, valuable liquid ‘constituents present are lost by
tained at low temperatures where a maximum yield of
tar is obtained with a minimum of tar decomposition or 25 conversion to simpler hydrocarbons of 'less value or to
alteration. These conditions represent an ideal state, and
Because of the highly complex chemical composition
consequently no tar can be said to be entirely primary.
of primary low-temperature tar, the initial treatment of
As used herein, the terms “primary,” “whole,” and “raw”
the whole tar by selective solvent techniques to effect
are considered essentially synonymous to indicate that
substantially all of the low-temperature tar obtained as 30 separation of the valuable constituents of the tar has
been considered too difficult to be of commercial im
a liquid product by condensation of the tar vapors is ini
portance. Direct solvent treatment of the whole tar
tially subjected to a solvent treatment process as de
must overcome problems of high t-ar viscosity, poor mis
scribed herein, and is not fractionally distilled prior to
core.
'
this solvent treatment. This tar product contains virtually
cibility of the tar with most solvents, and prolonged
all of the condensable ingredients of the carbonization
period of contact required between the
for complete extraction and separation
together with high solvent to tar ratios.
?nely divided solids present must first
vapors along with entrained ?nely divided particles of
coal and partially carbonized coal. The recovery of valu
able constituents contained in the tar is of considerable
tar and solvent
of components,
Ordinarily, any
be removed to
prevent plugging of the equipment. Emulsi?cation and
agglomeration occurring in the tar-solvent system fur
ther interfere with operability. Also, the lack of selec+
tivity of various solvent systems used introduces the fur
ther problem of after-recovery of sought-for constituents
from both the extract and the reject phases of the sol
Wherethe tar is obtained by a low-temperature car 45 vent system. In addition, solvent techniques suitable for
high-temperature tar are not ordinarily applicable to low
bonization process under ?uidized conditions, additional
temperature tar because of the considerably different
problems of recovery are presented. First, the ?nely
physical and chemical properties of the two types of
divided particles of coal and partially devolatilized coal
commercial importance. The process of this invention
enables the recovery of these valuable constituents from
low-temperature tar, Whether derived from low rank non
coking coals, e.g., lignite, brown coal and sub-bituminous
coals, or from high-volatile highly caking coals, e.g.,
Pittsburgh seam bituminous coal.
tar. At present, then, no satisfactory technique of com
contained in the ?uidized low~temperature tar are un
usually small in size and are present in greater quantity 50 mercial utility is known for the initial solvent treatment
of primary low-temperature tar. Where .the low-tem
because of the attrition and entrainment caused by the
perature tar is produced under ?uidized conditions, the
turbulent conditions prevailing within a ?uidized low
problem of separation becomes even more di?icult.
temperature carbonization processing vessel. Such tars
Accordingly, it is an object of the present invention to
may contain 25 percent or more by weight of ?nely di
vided particles of coal and partially carbonized coal. 55 provide a process for the fractionation of primary tar
free from the disadvantagesv heretofore known.
‘ .
Second, the tars obtained from ?uidized low-tempera
It is a further object to fractionate tar by an initial
ture carbonization processes tend to be of a more primary
solvent treatment into useful acidic and neutral tarfrac
character, i.e., the tar constituents tend to be closely
related in structure to the constituents of the coal that
is carbonized because there is little opportunity for crack
ing'the constituents prior to recovery. Hence these tars
tend to be more viscous than other types of low-tempera
ture tars.
-
Various techniques and plans have been proposed for
processing primary tar for recovery of the valuable liquid
constituents therein. All of these plans suffer from cer
tain drawbacks. In some, operability is achieved at the
expense of signi?cant tar yield. In others, fractional dis
tillation of the tar, reducing its primary character, results
in the cracking of the more valuable constituents to yield
tions.
60
-
v
-
It is yet another object to provide a method for the
continuous countercurrent extraction of primary tar ob
tained by the low-temperature carbonization of bitumi
nous coal under ?uidizedconditions.
’
In accordance with the broad aspects of this invention,
one volume of a primary low-temperature tar is treated
under liquid-liquid contacting conditions at a tempera
ture between 50 and 150° C. in a liquid-liquid extrac
tion system operated at autogenous pressure and includ
ing one or more extraction zones, with a double solvent
extraction system consisting of (1) 0.5 to 5 volumes of
aqueous methanol containing 40 to 80 weight percent
less valuable constituents that may be obtained more ' ' methanol and the balance ‘water andv (2) 0.5 to 5. vol
8,079,326
3
4
umes of a para?inic naphtha fraction having a boi'ing
range between 60 and 130° C. and a density less than
0.80, whereby the tar is fractionated into three phases.
The volume ratio of the two solvents is further ma n
tained between 0.5 and 2.
In the more speci?c and commercially preferred as
pects of this invention, a primary low-temperature tar
naphtha extract in the extraction
separation of these two phases.
a?inic naphtha combines all of
and accordingly is preferred as
column to effect a ready
The hexane cut of par
these critical properties
the naphtha solvent in
this invention. WhiIe the process of this invention may
be practiced with either the naphtha fraction or the
obtained by the carbonization of naturally occurring
aqueous methanol as the continuous phase in the tar
contacting portion of the extraction column, it is pre
carbonaceous solids at a temperature below 1400° F.,
ferred to use the naphtha fraction as the continuous
and preferably between 8C0 and 1400° F., is fed into 10 phase, particularly because the pitch phase also contains
the central portion of a continuous countercurrent dou
ble solvent center-feed vertical extraction column. The
tar is simultaneously contacted by an aqueous methanol
naphtha solvent associated therewith. Also, by using the
naphtha fraction as the continuous phase, separation be
tween the aqueous methanol extract and the pitch phase
is facilitated.
by a low boiling essentially para?‘inic naphtha fraction,
In operating this system, temperatures below 40° C.
which is fed into the bottom of the column. The aque
are unsuitable. Where the temperature in the column
ous methanol passes downwardly through the column
falls below 40° C., the tar becomes gummy, cannot be
dissolving substantially all of the low-boiling tar acids,
readily extracted and plugs the column. An extraction
a substantial portion of the high-boiling tar acids, and
temperature of about 50° C. is therefore conside ed
a small portion of neutral oils. The naphtha fraction, 20 minimal. To prevent boiling of the solvents and conse
being lighter than the aqueous methanol, passes up
quent interference with extraction, a pressurized system
wardly through the column and contains almost all of
is required, the pressure maintained being the pressure
the neutral oils. In this process, three phases are formed:
that is internally generated. Temperatures above 150°
21 methanol extract, which is essentially acidic; a naphtha
C. are not contemplated because of the undesirably high
extract, which is essentially neutral; and a pitch phase, 25 associated pressures. For the operative temperature
which is a conglomerate mixture. This latter phase is
range of 50 to 150° C., which is considered critical, the
not miscible with either the aqueous methanol extract
corresponding internally generated pressures will range
or the naphtha extract. Since the pitch phase is heavier
from about 1 to 20 atmospheres. It is generally pre
solution, which is fed into the top of the column, and
than both of the solvent streams, it drops through the
ferred to preheat the tar, methanol, and naphtha frac
extraction tower and may be decanted from the aqueous 30 tion to the extraction temperature used. A preferred
methanol extract.
temperature range is between 75 and 125° C.; at these
The process of this invention is generally suitable for
temperatures the tar shows a suitable ?uidity, the pres
the treatment of tars obtained by the pyrolytic decom
sure is convenient to maintain, and satisfactory sepa-'
position of carbonaceous solids at temperatures below
ration between the three phases is obtained.
1400° F. Such carbonaceous solids include all ranks 35
The achieving of adequate contact between the solvents
of coal, such as bituminous, sub-bituminous, brown coal,
and the tar is of considerable importance for obtaining
lignite and the like. This process may also be used for
satisfactory phase separation and extraction e?iciency
the treatment of those tars obtained by the low-tem
in a continuous countercurrent extraction process. Vari
perature carbonization of bituminous coals, e.g., high
ous systems are known for achieving continuous counter‘
volatile caking bituminous coals, under ?uidized condi 40 current liquid-liquid extraction. For example, a hori
tions. The resulting tars contain varying amounts of
zontal multistage contactor may be used with highly
?nely divided solids and are ordinarily particularly dit?
viscous liquids such as tars. Of the many types of veri
cult to treat without substantial loss of valuable crn
tical columns that have been used in liquid extraction
stituents. Where an excessive amount of ?nely d'vided
processes, such as packed columns, spray columns, ba?ie‘
45
solids is present, these are preferably removed by ag
columns, and perforated plate columns, not all are suit‘
glomerating them by a prior solvent treatment of the
able for use with highly viscous tars. In ‘general, col~
tar, followed by ?ltration, e.g., as shown in US. 2,774,
umns containing packing are to be avoided because of
716.
impedance to proper ?ow of the tar and interference
‘Certain critical conditions must be observed in order
with the maintenance of suitable phase separation. Be
to obtain operability in this process. Thus to achieve 50 cause of the ordinarily highly viscous nature of primary
effective continuous countercurrent extraction of the pri
low-temperature tar, in addition to operating the extrac
mary low-temperature tar, it is considered critical that
tion column at a temperature between 50 and 150° C.,
the aqueous methanol solution contain from about 40
the use of a rotating disk contactor column is considered
to 80 weight percent methanol and the balance water.
particularly suitable for obtaining the required continuous
In concentrations below 40 percent, emulsi?cation more 55 countercurrent extraction e?iciency while maintaining the
readily occurs and phase separation consequently be
desired phase separation. Various rotating shaft extrac
comes almost unobtainable.
When the methanol con
tion columns are known and may be used.
However,
centration of the solvent exceeds 80 percent by weight, . because of the physical characteristics of low-temperature
selectivity begins to fall off markedly, with excessive
tar, it is preferred that the settling or calming sections
amounts of neutral oils being dissolved along with the 60 of such columns be free from packing and thus be in
tar acids which are in solution. In general, for opti
unobstructed communication with the mixing sections‘.
mum phase separation and selectivity, a methanol con
centration of the aqueous methanol solvent between 55
and 70 percent by weight is preferred. The process of
In operating a rotating disk contactor column, a rotor
speed providing a peripheral disk velocity of between
0.5 and 5 feet per second is generally preferred. Where
this invention is further critically conditioned by the 65 the rotor speed falls below the preferred range, there is
characteristics of the naphtha solvent. It must be es
poor contact between the tar and the solvents with rela
sentially para?inic in character. Such solvents may be
tively low extraction efficiency. At higher speeds, emulsi
obtained from the distillationv of para?inic petroleum
?cation occurs with consequent poor phase separation.
stocks. Its boiling range should be 60° to 130° C.,
and preferably 60° to 100° C. in order to simplify the 70 An extraction ef?ciency obtained with from 10 to 20 sec
tions is suitable. Elimination of packing in the calming
subsequent separation of the naphtha fraction from the
sections will not deleteriously affect plate e?iciency. At
naphtha extract by distillation. And ?nally, the densi'y
of the naphtha fraction should be lessthan 0.80v and ' ' the same time this eliminates interference with the ready
transportof solids by the countercurrently ?owing liquids.
preferably less than 0.75 to insuresu?icient gravity dif
ference. between the aqueous methanol extract and the 75 Ease of transport is particularly important where there-is
8,079,326
6
U
a substantial amount of-?nely divided-carbonaceous solids
present in the tar.
Inasmuch as both the methanol extract and the im
miscible pitch phase descend to the bottom of the tower,
this bottom portion is so constructed as to permit ready
density,-may be removed through a conduit 8. This ex~
tract is essentially an acidic tar fraction. The pitch
phase, which is not miscible with either of the other two
phases, is the most dense phase and may be removed
through a conduit 9. The pitch phase, which is a con
settling of the pitch phase and decantation of the super
glomerate mixture, may be suitably processed to form
natant extract therefrom. In general, from 0.5 to 5 vol—
electrode carbon.
umes of aqueous methanol and from 0.5 to 5 volumes
In FIG. 2 is shown a preferred commercial embodi
of naphtha solvent per volume of tar will be required
ment for processing low-temperature tar in accordance
for e?‘icient countercurrent extraction While still main 10 with this invention. Referring to FIG. 2, a suitably pre
taining the desired phase separation. Further, the vol
heated tar obtained by a low-temperature carbonization
ume ratio of the aqueous methanol to naphtha solvent
(LTC) process is pumped from a storage tank 10 con
should be maintained between 0.5 and 2. By further
tinuously through a conduit 11 into a countercurrent
suitable regulation of the relative feed rates of the aque
double solvent center teed vertical extraction column 12.
ous methanol and of the naphtha fraction, either solvent 15 Subject to the limitations previously mentioned, the ex
may be maintained as the continuous phase. It is pre
traction column may be of any convenient design capable
ferred that the naphtha solvent be the continuous phase.
of providing a sut?cient number of theoretical extraction
For a more complete understanding of this invention,
stages to produce effective extraction of the tar. The
its objects, features and advantages, reference should
tar will be introduced at any suitable point intermediate
be had to the accompanying drawings in which:
20 the bottom and top of the column, generally at a point
' KG. 1 is a generalized schematic illustration of the
above the geometric center of the extraction column.
process of fractionating primary tar by an initial double
Aqueous methanol solution is fed continuously from
solvent treatment using aqueous methanol and a naphtha
_a methanol storage tank 13 through a conduit 14 into
fraction as solvents.
the top of extraction column 12. A naphtha fraction is
FIG. 2 is a preferred commercial embodiment, shown 25 fed continuously from a naphtha storage tank 15 through
schematically, for fractionating primary tar by an initial
a conduit 16 into the bottom of extraction column 12.
double solvent treatment in a continuous countercurrent
center-feed vertical extraction column using aqueous
methanol and a naphtha fraction as solvents.
Referring to FIG. 1, a low-temperature primary tar
The feed point of the naphtha fraction to the extraction
column will be above the point at which the aqueous
methanol extract and pitch phase are removed from the
bottom of column 12.
Since the density of the aqueous methanol solution
contained in a storage vessel 1 is fed through a suitable
conduit to a stirred liquid-liquid extraction vessel 2.
‘exceeds the density of the naphtha fraction, the aqueous
Aqueous methanol contained in a storage vessel 3 is fed
methanol solution descends through the column and dis
through a suitable conduit to vessel 2. Naphtha solvent
solves tar acids, both low-boiling and high-boiling, while
contained in a storage vessel 4 is fed through a suitable 35 the lighter naphtha fraction passes countercurrently up
conduit to vessel 2. The primary tar is obtained by the
ward through the column and dissolves neutral oils con
pyrolytic decomposition of carbonaceous solids at tem
peratures below l400° F., and is not fractionally distilled
prior to solvent treatment.
The aqueous methanol solu~
tion contains from about 40 to 80 weight percent metha
nol and the balance water.
The naphtha solvent is es
sentially para?inic in character, having a boiling range
between 60 and 130° C. and a density less than 0.80.
The liquid-liquid extraction vessel 2 may consist of a
single unit or of several units combined for multistage 45
operation.‘ The system shown in HS. 1 may be op-‘
.erated on a batch basis, for example, when the extrac
tion and settling steps are performed in a single zone,
or it may be operated as a continuous countercurrent
system. A preferred commercial embodiment of a con 50
tinuous countercurrent system will be subsequently dis
cussed.
Preferably the primary tar, aqueous methanol and
naphtha solvent are preheated to the reaction tempera
ture before being fed to vessel 2. The extraction tem
perature is maintained between 50 and 150° C. as critical ‘
tained in the tar. At the same time the pitch phase, which
includes high molecular weight components of the tar
such as some acidic asphaltenes, and almost all of the
neutral asphaltenes, and may include ?nely divided par
ticles of partially carbonized and carbonized carbona
ceous solids, drops through extraction column 12 to the
bottom thereof.
~
Asphaltenes are de?ned as that fraction of solids-free
tar insoluble at room temperature (20-25° C.) in petro
leum ether (boiling range 35-60" C.) at a dilution of
1 gram tar per 120 ml. of petroleum ether. Acidic
asphaltenes, most of which will appear in the aqueous
methanol extract, are soluble in dilute alkali and have
a distillation temperature range at about 375° C., "com
pleting their distillation at above 550° C. The neutral
asphaltenes, which are insoluble in dilute alkali, do not
distill below 550° C., and are therefore considered es
sentially
non-distillable.
’
'
_
'
Aqueous methanol extract contained as a supernatant
layer 17 is withdrawn continuously from extraction col
:operative limits. Vessel 2 is operated at the appropriate
umn 12 through a conduit 18 and fed into a distillation
autogenous pressure, i.e., at the combined pressure gen
'erated within the vessel. This will in all instances result
‘column 19 for the separation of the methanol solvent
from the water and tar acids, both of which, leave dis
in the maintenance of liquid-liquid extraction conditions. 60 tillation column 19 as a bottoms product through a con
From 0.5 to 5 volumes of aqueous methanol and from‘
duit 20 and pass into a phase separation tank 21. Since
0.5 to 5 volumes of naphtha solvent are used per volume
the solubility of tar acids in water decreases with reduc
of tar.
The ratio of the aqueous methanol to the
naphtha solvent is maintained between 0.5 and v2. Where
the system shown in FIG. 1 is operated in a continuous
countercurrent manner, the feed rates to vessel 2 are
suitably controlled so as to maintain the desired solvent
to solvent and solvent to tar ratios.
'
_
Following completion of the extraction in vessel 2,
tion in temperature, a cooler 22 may be placed in con
duit 20 to cool the water and tar acids passing through
conduit 20 and thereby decrease the proportion of residual
tar acids in the aqueous layer in phase separation tank
21. Puri?ed tar acids, being virtually immiscible in wa
ter, separate from the aqueous layer in phase separation
tank 21 and are withdrawn either continuously or inter
the products are conducted through a conduit 5 to a .70 mittently as a bottoms product through a conduit 23.
settling tank 6 where, upon settling, three phases are
formed. The naphtha solvent extract is the least dense
phase and may be removed through a conduit 7. This
The tar acids obtained may be separated by fractional dis
tillation at a temperature between 200 and 300° C. to
extract is essentially a neutral tar fraction.
ly, those tar acids boiling below 230° C. are the most
The aqueous
methanol extract, which is the next phase with respect to
low-boiling and high-boiling tar acid fractions. General
valuable components commercially.
The supernatant
3,079,326
7
aqueous phase from tank 21 is withdrawn through a con
duit 24 and sent to the aqueous methanol storage tank
13 for recirculation.
Anhydrous methanol passes overhead from distillation
column 19 through a conduit 25 to a re?ux condenser
26. Condensed anhydrous methanol leaves re?ux con
denser 26 and passes through a conduit 27 to aqueous
methanol storage tank 13 for recirculation. A portion
of the condensed methanol may be returned through a
conduit 28 to the top of distillation column 19 as re?ux.
It should be noted that in the preparation of the
aqueous methanol solution contained in storage tank
13, caution should be exercised where the solution is
but is not intended as a limitation thereof. A ?ltered
whole tar prepared by a low-temperature carbonization
(Disco process) of a bituminous coal was solvent re?ned
in a single-stage extraction and recovery zone using aque
ous methanol and hexane as a solvent pair to give a three
phase system.
In the single-stage fractional extraction
system used, 245 grams (223 ml.) of low-temperature tar
was added to a 2-liter pressure vessel.
To this was then
added 446 ml. of aqueous methanol (50 percent meth
anol by weight) and then 446 ml. of n-hexane. Thus the
aqueous methanol and hexane to tar volume ratios used
were 2.0:1, with an aqueous methanol to hexane ratio of
1:1. The pressure vessel was sealed, the stirrer was
prepared and its composition regulated by speci?c gravity
started, and the temperature was brought to 100° C. from
measurement. The recirculated methanol is saturated 15 room temperature in about 11/2 hours. When the tem
perature had leveled off, the stirrer was stopped and the
with naphtha solvent and this fact must of course be
phases formed were allowed to separate for about one
considered in determining the speci?c gravity required to
hour. The three phases obtained consisted of an aqueous
produce a solution containing 40 to 80 weight percent
methanol extract phase, a hexane-soluble fraction, and
methanol. Fresh make-up methanol may be added to
aqueous methanol storage tank 13 through a conduit 29 20 pitch. These three phases were then removed and ana
lyzed. The product distribution was as shown in Table I.
to make the necessary 40 to 80 weight percent methanol
solution.
TABLE I
The naphtha extract phase containing dissolved neu
tral oils, particularly the high boiling neutral oils, leaves
Double Solvent Extraction of Low-Temperature Tar
the top of extraction column 12 through a conduit 30
and passes to a distillation column 31 where the naphtha
solvent is separated from the neutral oils. This naphtha
fraction passes overhead from distillation column 31
through a conduit 32 and a re?ux condenser 33.
Aqueous Methanol
Concentration
(by weight)
Phase
A
_
50% methanol
portion of the condensed naphtha may be returned 30
through a conduit 34 as re?ux for distillation column 31.
The remainder of the naphtha fraction is returned
through conduit 32 to naphtha storage tank 15 for recir
culat-ion. The neutral oil 35 which leaves distillation
Weight percent of tar
Hexanc.
70.0.
Aqueous Methanol ____________________________ __
18.0.
column 31 as a bottoms product through a conduit 36
is of utility as a carbon black feedstock. Particularly
Pitch.
12.0.
preferred as a carbon black feedstock is that portion of
neutral oil 35 which includes substantially all of the
constituents thereof boiling above an initial boiling tem
perature between 300 and 425° C. To obtain this desired
carbon black feedstock fraction, neutral oil 35 is fed
Tar In
acids
methanol-soluble
to 270°
traction _______________ _- 5.9 (98% purity).
through a conduit 37 to a distillation column 38 and frac
The following ultimate analyses of the hexane and
pitch phases were obtained:
tionally distilled therein.
The low-boiling constituents
In original tar ______________________________ --
Pitch, ring and ball softening point, ° C ________ __ 92-96.
are removed as an overhead product through a conduit
39, leaving the desired carbon black feedstock as a bot 45
toms residue. This may be removed through a conduit
40. A cooler 41 may be inserted in exit conduit 40 to
0001 this carbon black feedstock product. Depending
upon the composition of the speci?c fraction of tar
present in the naphtha extract, which may be varied by
varying the methanol concentration of the aqueous metha
nol solvent, the neutral oil bottoms products 35 may also
be of utility as a hydrogenation feedstock for gasoline.
A cooler 42 may be inserted in exit conduit 36 to cool
11.5.
Hexane
Phase
Hydrogen
7. 80
as“
Oxygen-
83-22
5. 86
‘ rmmn
Sulfur
A sh
_
1. O2
0. 02
Pitch
Phase
6. 12
_
8. 61
1. 59
O. 09
In a double-solvent run made using aqueous methanol
containing 30 weight percent methanol, very low tar acid
the neutral oil product.
55 yields were obtained.
The lower or subjacent pitch'phase layer 43 is removed
According to the provision of the patent statutes, I have
from the bottom of extraction column 12 at the lowest
explained the principle, preferred construction, and mode
point in the column through a conduit 44. Where the
of operation of my invention and have illustrated and de
pitch phase layer contains a relatively high amount of
scribed what I now consider to represent its best embodi
?nely divided solids, these are preferably removed there
ment. However, I desire to have it understood that with
from by a ?ltration process, or by a combined agglomera
in the scope of the appended claims, the invention may
tion and ?ltration process, as shown for example in US.
be practiced otherwise than as speci?cally illustrated and
2,774,716. The pitch phase is then fed through conduit
described.
44 to a distillation column 45 where it is freed of traces
I claim:
of solvent. Ordinarily only small amounts of naphtha 65
1. A process for the fractionation of primary low-tem
solvent will be included with the pitch, and these may be
perature tar by double solvent extraction of said tar ob
readily removed as an overhead from distillation column
tained from the low-temperature carbonization of bitumi
45 through a conduit 46 and a re?ux condenser 47. If de
nous coal, which comprises the steps of feeding to a liq
sired, a portion of the condensed naphtha fraction may
uid-liquid extraction zone one volume of said primary
'be returned through a conduit 48 as re?ux for distillation 70 low-temperature tar, from 0.5 to 5 volumes of a ?rst sol
column 45. The remainder of the naphtha fraction is
vent consisting of an aqueous methanol solution contain~
‘returned to naphtha storage tank 15 through conduit 46
ing about 40 to 80 weight percent methanol and the
for recirculation. The pitch may be recovered from
balance water, and from 0.5 to 5 volumes of a second
solvent consisting of a para?inic naphtha fraction boiling
column 45 through a conduit 49.
The following example is illustrative of this invention 75 within the range of 60 to 130° C. and having a density of
3,079,326
less than 0.8, the volume ratio of the ?rst and second
solvents being maintained between 0.5 and 2, maintaining
said tar, aqueous methanol and naphtha fraction under
liquid-liquid contacting conditions at a temperature be
tween 50 and 150° C. whereby three phases are formed,
recovering an aqueous methanol extract containing tar
liquid-liquid contacting conditions at a temperature be»
tween 75 and 125° C. whereby three phases are formed,
recovering an aqueous methanol extract containing tar
acids as a ?rst phase, recovering a naphtha extract as
a second phase, and recovering an insoluble pitch residue
as a third phase.
acids as a ?rst phase, recovering a naphtha extract as a
4. The process according to claim 3 wherein said sec
ond solvent is a hexane cut of the parat?nic naphtha frac
as a third phase.
tion.
2. A process for preparing a carbon black feedstock 10
5. A process for preparing a carbon black feedstock
from primary low-temperature tar by double solvent
from primary low-temperature tar by double solvent ex
extraction of said tar obtained from the low-temperature
traction of said tar obtained from the low-temperature
second phase, and recovering an insoluble pitch residue
carbonization of bituminous coal, which comprises the
carbonization of bituminous coal, which comprises the
steps of feeding to a liquid-liquid extraction zone one
steps of feeding to a liquid-liquid extraction zone one
volume of said primary low-temperature tar, from 0.5 15 volume of said primary low-temperature tar, from 0.5
to 5 volumes of a ?rst solvent consisting of an aqueous
to 5 volumes of a ?rst solvent consisting of an aqueous
methanol solution containing about 40 to 80 weight per
methanol solution containing about 40 to 80 Weight per
cent methanol and the balance water, and from 0.5 to 5
cent methanol and the balance water, and from 0.5 to 5
volumes of a second solvent consisting of a paraffinic
volumes of a second solvent consisting of a para?‘inic
naphtha fraction boiling Within the range of 60 to 130° 20 naphtha fraction boiling Within the range of 60 to 130°
C. and having a density of less than 0.8, the volume
ratio of the ?rst and second solvents being maintained
between 0.5 and 2, maintaining said tar, aqueous meth—
anol and naphtha fraction under contacting conditions at
a temperature between 50 and 150° C. whereby three 25
C. and having a density of less than 0.8, the volume ratio
of the ?rst and second solvents being maintained be
tween O.5 and 2, maintaining said tar, aqueous methanol
and naphtha fraction under contacting conditions at a
temperature between 75 and 125° C. whereby three phases
phases are formed, recovering an aqueous methanol
are formed, recovering an aqueous methanol extract con—
extract containing tar acids as a ?rst phase, recovering a
taining tar acids as a ?rst phase, recovering a naphtha
naphtha extract as a second phase, recovering an insolu
extract as a second phase, recovering an isoluble pitch
ble pitch residue as a third phase, and further recovering
residue as a third phase, and further recovering from
from said naphtha extract as a carbon black feedstock 30 said naphtha extract as a carbon black feedstock sub
substantially all of the constituents thereof boiling above
stantially all of the constituents thereof boiling above
an initial boiling temperature between 300 and 425° C.
an initial boiling temperature between 300 and 425° C.
3. A process for the fractionation of primary low
6. The process according to claim 5 wherein said sec
temperature tar by double solvent extraction of said tar
ond solvent is a hexane cut of the paraffinic naphtha
obtained from the low-temperature carbonization of bitu
minous coal, which comprises the steps of feeding to a
liquid-liquid extraction Zone one volume of said primary
low-temperature tar, from 0.5 to 5 volumes of a ?rst sol
vent consisting of an aqueous methanol solution contain
ing about 40 to 80 weight percent methanol and the bal 40
fraction.
References Cited in the ?le of this patent
UNITED STATES PATENTS
2,955,079
Foley ________________ __ Oct. 4, 1960
ance water, and from 0.5 to 5 volumes of a second sol
OTHER REFERENCES
vent consisting of a paraf?nic naphtha fraction boiling
Low-Temperature Carbonization of Bituminous Coal,
McCulloch & Simpkins, H. F. and G. Witherby, London,
1923, pp. 25, 26.
Coal, Coke and Coal Chemicals, Wilson and Wells,
McGraW-Hill, N.Y., 1950, page 421.
Within the range of 60 to 130° C. and having a density
of less than 0.8, the volume ratio of the ?rst and second
solvents being maintained between 0.5 and 2, maintaining
said tar, aqueous methanol and naphtha fraction under
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