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Патент USA US3082280

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March 19, 1963
A, c, McK'INNlS
3,082,270
SOLVENT EXTRACTION METHOD
Filed July 31, 1961
woA/Aeo/wl 7765
‘£245;
440/144 77:5
401/5005
A4455
£XTEACT
1
SOLVE/VT
,4QUEOU5
A4455
ART
INVENTOR.
:3 44¢ K/A/M/S
BY )JLN'W
United States Patent
3,082,270
nee
Patented Mar. 19, 1963
1
3,082,270
Art C. McKinnis, North Long Beach, Calif, assignor'to
SOLVENT EXTRACTION METHOD
Union Oil Company of California, Los Angeles, Cairn,
a corporation of California
Filed July 31, 1961, Ser. No. 128,244
20 Claims. (Cl. 260-674)
This invention relates to. a solvent extraction method
2
pl-oying a particular type of amine-acid solvent by means
of which componential segregation ‘of aromatics is read
ily and economically feasible.
In addition to the problem of separating like boiling
aromatics of differing degrees of aromaticity, there is a
parallel problem of separating aromatics from nonaro
matics of like boiling ranges.
There are many such mix
tures, exemplary of which are those petroleum fractions
known to contain monoaromatics such as polyalkyl ben
for separating hydrocarbons of greater aromaticity from 10 zenes boiling within the range from about 400° to about
hydrocarbons of lesser aromaticity in admixture there
450° F. as well as nonaromatics such as parat?ns and
with. More speci?cally, the invention relates to such a
method in which mixtures of ammonia and/ or amines and
thiocyanic and/ or cyanic acid are employed as selective
naphthenes of the same boiling range.
solvents for the hydrocarbons of greater aromaticity.
The invention has particular utility for the recovery of
diaromatic hydrocarbons, such as naphthalene or the like,
from mixtures thereof with monoaromatic hydrocarbons
of substantially equivalent boiling points, such as alkyl
sired separation and the solvent extraction method of
this invention furnishes a simple and practical solution
benzenes or the like.
There are a number of known solvent extraction pro
cedures for isolating various components of hydrocarbon
mixtures and numerous materials have been proposed for
use as selective solvents in such procedures, typically
representative of which are sulfur dioxide, furfural, di
ethylene glycol, nitriles, organic bases, etc. Such solvent
Here again, as in
the case of the like ‘boiling aromatics, fractional distilla
tion fails as a practical means of accomplishing the de
to the problem.
I
' It is thus a principal object ofrthis invention to provide
an improved solvent extraction method by means of which
20 componential fractions of various aromaticity levels can
be segregated from mixtures of such aromatic compounds.
It is another object of the invention to provide a solvent
extraction method for readily and economically separating
aromatic compounds from like boiling nonar'omatic com
pounds in admixture therewith.
A more speci?c object of the invention is to provide
extraction procedures have been attempted with varying
an economical solvent extraction method by means of
degrees of success on mixtures of aromatic and nonaro
which diaromatic compounds are readily separable from
like boiling mon-oaromatic compounds in admixture there
with. ‘Other objects and advantages of the invention will
matic hydrocarbons for purposes of extracting all of the
aromatics therefrom, but heretofore it has not been pos
sible to bring about any kind of effective fractional sep~
matic components of differing degrees of aromaticity can
be economically and effectively fractionated.
There are many hydrocarbon mixtures, as, for example,
be apparent from the complete description thereof which
follows.
The degrees of aromaticity of organic compounds of
roughly equivalent boiling points depend upon the num
ber of aromatic rings (benzene nuclei) in their respective
molecules, the higher the number of such rings the greater
thearomaticity of a given compound. Thus diaromatic
compounds, those having two aromatic rings per mole
various petroleum processing fractions, which contain
substantial proportions of diaromatic hydrocarbons such
ticity'than the monoaromatic compounds which have
as naphthalene and its alkyl and polyalkyl derivatives,
molecular structures containing only one such ring. It
makes little difference, insofar as degree of aromaticity
aration of the aromatic components from each other by
solvent extraction means.
1 have now discovered an improved method of solvent
extraction for use on hydrocarbon mixtures whereby aro—
and also monoaromatic hydrocarbons which can be mono
cule, are considered to have a greater degree of aroma
is concerned, whether polyarom-atic compounds have
alkyl t'etralins, alkyl indanes, alkyl indenes and the like 45 individual or condensed ring systems. Thus, diaromatics
of individual ring systems such as hiphenyl, diphenyl
which boil within the same boiling range as the diaro
cyclic, such as alkyl benzenes, and/or bicyclic, such as
methane, etc., are considered to have roughly the same
matics. The boiling range of the diaromatics in hydro
degree of aromaticity as the dinuclear aromatics (di
carbon mixtures of this ‘type is typically from about 400°
aromatics having condensed ring systems), such as naph~
to about 450° F. A speci?c example of such a hydro
carbon mixture is the heavy reformate fraction obtained 50 thalene, etc., at least insofar as this invention is con
cerned.
in the catalytic reforming of naphthenes. This fraction
The method of this invention is not limited to the
normally boils above about 400° F. and contains from
treatment of organic mixtures in which the aromatics
about 40 to about 80 percent by weight naphthalene and
methyl naphthalenes, the remainder being largely made
up of monoaromatic compounds such as alkyl benzenes,
tetralins, indanes, indenes, and the like, or of such mono
aromatics plus a signi?cant proportion of nonaromatics
such as naphthenes, para?ins, etc. Many other fractions
of highest possible degree of aromaticity are diaromatics,
and mixtures containing higher polyaromatic compounds
are also amenable to separation by said method. For
example, it is within the scope of the invention to sub~
ject hydrocarbon mixtures containing triaromatic com
pounds, such as anthracene and phenanthrene, and di~
conversion operations, such as catalytic cracking, thermal 60 aromatic compounds of roughly the same boiling range
to solvent extraction as taught herein, to separate the
cracking, catalytic reforming, catalytic cycle oil, etc. oper
triaromatics from the diaromatics.
ations, also ?t the above described category.
The method of this invention is not limited in appli
Hydrocarbon mixtures such as those described are di?i
cation to the treatment of organic mixtures having clear
cult of separation into their componential fractions, i.e.,
ly obvious differences in the degree of aromaticity among
fractions containing separate or like components Within
its various components. There are many organic mix
the ‘diaromatic, monoaromatic, etc., categories by conven
tures containing aromatic components not sharply dis
tional fractionation means. For one thing, the like boil
tinguishable from others present in degree of aromaticity
ing point ranges of the diaromatics and monoaromatics
and the treatment of such “grey area” mixtures, either for
normally found ‘in such mixtures precludes the possibility
of getting effective separation between these two classes of 70 the separation of the aromatics in toto or for further
obtained in the practice of petroleum fractionating and
materials by fractional distillation techniques. The pres
separation of said aromatics into fractions of varying
ent invention comprises a method of solvent extraction em
degrees of aromaticity, lies within the purview of my in
3,082,270
4
3
vention. It is more difficult to separate such “grey area”
aromatics into distinct fractions than it is to separate more
sharply “black” and “white" aromatics, such as diaro~
matics and monoaromatics of roughly the same boiling
range, but such separations are possible and hence within
the scope of my invention.
Among the above noted
peratures should preferably not exceed the boiling points
of any of the various components present in the system
since this would obviously have a deleterious effect on
the operation.
Reasons have been given why extremes of tempera
ture in either direction are undesirable in solvent ex
“grey area” aromatic compounds of intermediate de
traction operations.
grees of aromaticity may be mentioned those substituted
aromatics containing functional groups of such nature
the operating temperature below a certain level are not
However, the effects of lowering
necessarily all bad since such lowering frequently re
sults in an increase of solvent selectivity. Furthermore,
not all of the effects of an excessive elevation of tem
the aromaticity of their unsubstituted counterparts. It
perature are necessarily deleterious, since such elevation
will be clear that a wide variety of feed mixtures can
normally brings about a shortening of the time required
be resolved by the method taught herein.
for phase separation as well as an improvement in the
Attention is now directed to the accompanying draw
ing which schematically illustrates a preferred process for 15 solvent power of selective solvents. It will be apparent
from the above-noted considerations that the selection of
the practice of my invention.
‘an optimum temperature range for solvent extraction pur
Referring speci?cally to the drawing, there is shown a
poses depends on many factors and entails a balancing
continuous countercurrent solvent extraction process em
of the advantages and disadvantages inherent in various
ploying a solvent of the type described more fully here
after, such as for example, triethylammonium thiocyanate, 20 temperature adjustments, taking into consideration the
as to have a signi?cant effect of one sort or another on
the reaction product of stoichiometric quantities of tri
ethylamine and thiocyanic acid. While it is possible to
characteristics of the components present in the system,
prepare triethylammonium thiocyanate
timum operating pressures for solvent extraction opera
tions is subject to the consideration of other factors of
the operating pressures, etc. So too, the selection of op
25 an in?uencing nature. Thus operating pressures can vary
by simply mixing equivalent molar amounts of triethyl
amine and thiocyanic acid, my preferred way of pre
paring that material is to mix equimolar proportions of
triethylamine and NH4SCN and then fractionate off the
NH;;:
My reasons for preferring ammonium thiocyanate to
from subatmospheric, through atmospheric, to superat
mospheric ranges depending upon the peculiarities of the
given system.
Returning now to the discussion of the drawing, I have
30 discovered that solvent extraction column 1 is effectively
operative on typical systems of the type contemplated
when maintained at atmospheric pressure and within an
operating temperature range from about 20° to about
thiocyanic acid as a starting material for the prepara
150° C.,, the preferred temperature range being from
tion of my amine-thiocyanic acid solvent mixtures are the 35 about 30° to about 60° C.
cheapness, greater availability and relative stability of the
former by comparison with the latter.
The yield and purity of the ra?inate and extract prod
ucts, identi?ed infra, from column 1 are, as previously
A feed stream containing both aromatic and non
indicated, partially dependent upon the number of ex
aromatic hydrocarbons of like boiling ranges such as
traction stages in said column. It is, as a general rule,
a heavy reformate petroleum fraction containing diaro 40 true that the greater the number of stages in a solvent
matics (naphthalene, alkylated naphthalenes, etc.,);
extraction column, the greater will be the yield and
monoarornatics (alkyl benzenes, alkyl tetralins, alkyl
purity of a product of the column. However, as those
indanes, etc.,); and nonaromatics (naphthenes and paraf
skilled in the solvent extraction art will appreciate, the
?ns) is continuously fed into the bottom of a counter
selection of an optimum number of stages is a matter of
current solvent extraction column 1 through line 3 as
economics
since as the number is increased a point of
shown. There simultaneously, solvent is recycled into 45 diminishing returns is reached beyond which the relatively
the top of column 1 through line 5, from a source here
small improvement per additional stage makes it imprac
inafter disclosed. Solvent extraction column 1 is so
tical to proceed. I have found that solvent extraction
designed and the conditions of operation so ?xed and
column 1 is operatively effective for use in processes of
controlled as to result in the extraction of substantially
the contemplated type when it has from about 2 to about
all of the aromatic components from the feedstock as it
15, and preferably from 7 to 11, stages.
circulates upward in countercurrent contact with the sol
Referring again to the drawing, an extract phase is
vent in said column.
withdrawn from the bottom of solvent extraction column
As those skilled in the art realized, there are gen
1 through line 7 and a raf?nate phase is withdrawn from
erally four important things to be considered in the 55 the top of the column through line 9 as shown. When
practice of countercurrent solvent extraction, namely:
column 1 is designed and operated according to the pre
(1) the operating temperature; (2) the operating pres
ferred precepts and conditions set forth above, aromatic
sures; (3) the number of extraction stages; and (4) the
hydrocarbon yields of from about 85 to about 99 percent
solvent/feed ratio. Careful selection and control of op
by weight and purities of from about 90 to about 99 per
erating conditions in the above four areas is important in
60 cent by weight are attainable in the extract phase. The
order to achieve optimum phase separation, selectivity,
extract phase contains most of the solvent passing through
and solvent power, all of which have a bearing on prod
column 1, in addition to that portion of the feedstock
uct yield and purity.
which the solvent has extracted in its travel within the
The operating temperature level is important in solvent
column. The ra?’inate phase from column 1, under pre
extraction operations since in the usual case too low a
ferred conditions of operation, typically contains between
65
temperature results in an inordinately high feed vis
about 90 and about 99.5 percent, by weight, nonaromatic
cosity which in turn results in unnecessarily long phase
separation periods. Additionally, too low a temperature
hydrocarbons, the remainder being solvent.
other hand, excessively high temperatures are undesirable
since they usually have the effect of reducing solvent
through valve 11, with valve 13 closed, without further
selectivity and tend to make the extract and ra?inate
ent extraction column 17 through line 15, as shown on the
drawing, for removal of traces of the amine-acid solvent
The ra?inate phase from column 1, as the drawing
is undesirable in that it normally has a detrimental ef
shows, is subject to an alternate choice of disposition.
fect on the solvent power of selective solvents. On the 70 Thus, the raf?nate can be withdrawn from the process
phases mutually miscible. Where solvent extraction is
treatment, or it can be circulated to countercurrent solv
carried out at atmospheric pressure, the operating tem 76 picked up in column 1, using water as ‘the solvent. Ob
3,082,270
6
5
wherein the amine-acid solvent ‘(being water soluble, as
pointed out supra) is selectively extracted therefrom With
water. The extraction. of the solvent from the extract
to remove amine-acid solvent therefrom is possible be
phase is not limited to the use of water as the extracting
cause the solvent, as will be emphasized later, is quite
agent and any other material which is a relatively stable
soluble in water.
liquid under the conditions-of service, and in which the
For ease of illustration, and simplicity of explanation,
amine-acid solvent is substantially miscible, may be em
the process shown on the drawing and described here is
ployed for the purpose if desired. It is, of course, ob
depicted as one yielding a recovery of all feedstock aro
vious that the chosen material must also be substantially
matics in one pass through column 1. However, it is
to be understood that, as explained above, my method of 10 immiscible with the hydrocarbon, or hydrocarbons, in the
extract phase.
solvent extraction is equally applicable to the separation
The products from column 25 are an aqueous solution
of aromatics into fractions dilfering as to degree of aro
of the amine-acid solvent (aqueous phase) which is with
maticity, such as for example the recovery of diaromatics
drawn from the bottom of the column through line 27,
from a feedstock comprising both diaromatic and mono
aromatic components. To accomplish this type of sepa 15 and the hydrocarbon product consisting of the aromatic
fraction of the feedstock in substantially pure form, which
ration it is only necessary to assure the proper number
is withdrawn through line 29 to storage or other dis
of stages in column 1 and the proper operating conditions
position.
'
to accomplish the purpose. The determination of opti
The aqueous solution of solvent from column 25 is
mum plate plurality and operating conditions to achieve
passed through line127 ‘to a distillation column 33 in
this, or any other result Within the‘ scope of my inven
which the water is separated from the solvent, the water
tion, is a relatively simple matter to those skilled in the
passing off through line 31 as an overhead and the solvent
solvent extraction art, in the light of the teachings here
Ibeing withdrawn through line 5 as a ‘bottoms product.
in, requiring at most a minimum amount of routine ex
viously, valve 13 is kept open and valve 11 closed in the
latter event. Water extraction of the column 1 ra?inate
perimentation.
Primarily, the achievement of maximum separating
et?cacy among compounds of varying degrees of aro
maticity is a matter of having a su?iciently high number
of extraction stages in column 1. In this respect it is
pointed out that more stages are required for such selec
The water overhead from column 33 is condensed in
condenser 35 and then recirculated to solvent extraction
column 25 through line 37 as shown on the‘ drawing.
The solvent bottoms product from column 33 is recycled
through line 5 to solvent extraction column '1.‘
Column 25 is shown schematically as a countercurrent
tive extraction, all other things being equal, than for 30 solvent extraction column and the preferred technique for
practicing the subject process is by continuous operation
mere separation of a mixture into aromatic and nonaro
matic fractions.
of that unit as well as all other units in the process. How
ever, it is possible to replace column 25 by batch ap
paratus ‘for solvent extraction if desired. It is also pos
from a mixture containing both aromatics of differing
aromaticities and nonaromatics, the subject process can 35 sible to modify the process in other ways obvious to
those skilled in the art without substantial alteration
by relatively simple modi?cation be made to accommo
of its purpose or accomplishments. One such modi?ca
date this requirement. One Way of accomplishing this is
If it is desired to obtain two or more aromatic fractions
to add one or more additional solvent extraction columns
tion is, for example, the incorporation of puri?cation
techniques for the treatment of one or more of the prod
similar to column 1 to the process, with appropriate lines,
?ttings, and other equipment, where needed, to handle 40 ucts of separation from solvent extraction column 25
as well as distillation column 33'. Makeup amine-acid
the various streams in the system. For example, if it is
solvent is introduced into the system through line 39‘ and
desired to separate a diaromatic fraction and a monoaro
valve 441 as needed.
'
‘
'
matic fraction from a feedstock containing diaromatics,
There are a number of things to consider in the selec
monoaromatics and nonaromatics, this can be done by in
corporating an additional solvent extraction column in 45 tion of solvents for solvent extraction purposes, among
which are: (1) the stability of the candidate material
series with column 1; using column 1 to extract the
.diaromatics from the feedstock; and utilizing the addi
tional column to separate the monoaromatics from the
nonaromatics in the raffinate phase from column 1.
While the instant method is preferably practiced as a
continuous or ?ow process, and that aspect of operation
is stressed in this description, it functions equally well as
a batch process provided column 1 is considered to repre
sent suitable apparatus for batch extraction, countercur
rent batch extraction, or the like, purposes.
To continue with the detailed description of the
process shown on the drawing, in the event the raflinate
phase from column 1 is routed to solvent extraction
under'the conditions (heat, pressure, etc.) of service; (2)
the selectivity of said material under service conditions,
with respect to the mixture to be extracted; (3) the
tendency or lack of such tendency of a material to react
chemically with any of the components of systems in
which it will be used; (4) its boiling point relative to
the boiling points of the components of the mixtures to
be separated; (5) its melting point; (6) its corrosiveness
towards the materials of construction of the equipment to
be employed; (7) its toxicity (which is important from
an operational standpoint); (8) its water solubility; and
(9) its density relative to the densities of the‘ components
of the mixtures to be separated. I have now discovered
column 17, it is there countercurrently contacted with
water which is introduced into said column through line 60 that mixtures of ammonia and/or amines and cyanic
and/ or thiocyanic acids varying widely as to component
19. The water extracts substantially all of the solvent
proportions satisfy all of the requirements inherent in
contaminant from the ra?inate phase which is then With
the above points of consideration to qualify as excellent
drawn through line 21 to storage, or other disposition.
solvents for the selective extraction of aromatic hydro~
The aqueous phase from the extraction operation is with
carbons from organic mixtures of the type previously dis
drawn from column 17 through line 23 as shown and
closed. I have further found that, in addition to having
either discarded, recycled for reuse in column 17, or other
an extraordinary selectivity for aromatic hydrocarbons in
wise disposed of. The amount of amine-acid solvent
general, such amine-acid mixtures have relatively greater
picked up by the water passing through column 17 is so
selectivities for aromatics of relatively greater degrees of
slight as to rule out the practicality, in most cases, of
aromaticity, thus making the separation of aromatics by
any attempt to recover amine-acid solvent from said
degree, as discussed in detail supra, possible by solvent
aqueous phase. Any other liquid having properties suit
able for the purpose may be substituted for the Water em
extraction means.
ployed in column 17, if desired.
The extract phase from solvent extraction column 1 is
passed into solvent extraction column 25, through line '7,
for use in my invention must, of necessity, be liquid under
the service conditions of my solvent extraction method.
The amine-acid mixtures suitable as selective solvents
3,082,270
8
N-methylpiperidine
N-methylmorpholine
N,N'-dimethylpiperazine
The term “amine-acid,” without further modi?cation,
is used throughout this speci?cation to refer to the unique
solvent mixtures of this invention. It is, of course, to be
understood that the amine-acid ingredient combinations
thereby contemplated are those combinations within the
scope of this invention as de?ned and exempli?ed here
Pyridine
N-ethylpiperidine
Methylethylisobutylamine
Triethylenediamine
in.
Triphenylarnine
The amines of most e?ectiveness as solvent ingredients
Dimethylaniline
Methyldiphenylamine
l-methylpyrrole
1,3-dimethylpyrrole
l-dimethylamino-B-butene
for purposes of this invention are those amines having
from about 1 to about 15, and preferably from about 1
to about 9, molecular carbon atoms. The amines may
be wholly or predominantly of aromatic, aliphatic or
heteroeyclic character, or they may partake, in varying
degrees, of the characteristics of compounds in any two,
or all three, of those categories. Amines which are 15
otherwise suitable, having substituent groups of a sub
stantially neutral character with respect to other com~
ponents in the system can be employed for my purpose
if desired.
The amine-acid solvents of this invention are not 20
amides but merely, in effect, mixtures of ammonia and/ or
amines and acids. Such mixtures are sometimes referred
to as salts. However, the term “salts” has been, to a
large extent, avoided herein to diminish the possibility
of misunderstanding as to its meaning. Although as in 25
dicated above, my class of amine-acid solvents is ex—
elusive of amides, this poses no particular problem in
the selection of suitable amines as solvent ingredients
a-Pieoline
3 ,5 -lutidine
2,4,6-collidine
,e-Picoline
Quinoline
Quinaldine
Isoquinoline
Conyrine
Conine
Tropane
Tripropylamine
N-benzylideneaniline
N- l-ethylbutylidine-p-toluidine
Examples of secondary amines which can be employed
as solvent ingredients for purposes of this invention are
given below. Here again, as in the ease of the tertiary
since, insofar as I am aware, no amines form amides with
the acids of this invention. Any mixture of eyanie acid, 30 amines, the list is exemplary only and not exhaustive.
thiocyanic acid or a combination of those acids, and
ammonia, any amine, combination of amines, or am
monia-amine combination which is liquid under the serv
ice conditions of my solvent extraction method, is a use
ful solvent for purposes of, and within the scope of, this 35
Diethylamine
Ethyl-sec-butylamine
Di-isopropylamine
Dimethylamine
invention. Primary, secondary and tertiary amines, and
Diethanolamine
mixtures thereof, are all suitable amine ingredients for
my solvent mixtures.
Although, for the reason given above, I have de
emphasized use of the term “salts” in connection with my 40
amine-acid solvents. I have found that a stoichiometric
proportion of ammonia or amine to acid, which results
in a high salt content solvent, is optimum for purposes
of this invention. I attribute the superiority of stoiehi
ometrically balanced solvent mixtures to the fact that
Acetylisobutylamine
Piperizine
Diphenylamine
Monomethylaniline
Dibenzylamine
Benzylaniline
Butylaniline
Methylaniline
cyanic and thioeyanic acids are‘substantially less stable
The following list is, as in the case of the tertiary and
the secondary amines, exemplary only.
Z-aminopropane
2-amino-Z-methylpropane
Ethylarnine
Methylarnine
Aniline
tively stable by comparison with eyanic or thiocyanic
acid).
A list of tertiary amines useful as solvent ingredients 60
for purposes of this invention appears below. It should
be emphasized that this list is merely representative, and
not lirnitative of the class of tertiary amines suitable for
my purpose.
- Diethyloctylamine
Diethylpropylamine
N,N,N’,N’-tetramethylethylenediamine
N-ethylpyrrolidine
N-methylpyrrolidine
Examples of primary amines suitable as solvent in~
gredients for purposes of this invention are listed below.
than their ammonium and substituted ammonium salts.
While it is preferable not to have large excesses of
cyanic or thiocyanic acid present in my solvent mixtures,
because of the tendency of those acids toward instability,
it is nevertheless within the scope of this invention to
employ amine2acid molar ratios other than the stoiehi
ometric ratio (1:1). In this connection, I have deter~
mined that the preferred range of molar ratios is from
about 0.5 :1 to about 2:1, although ratios outside of this
range are also operative, particularly in those cases in
which the amine is present in excess (amines being rela
Triethylamine
Trimethylamine
Methyldibutylamine
Dimethylbutylamine
Ethylmethylpropylamine
Ethyldipropylamine
Morpholine
n-Propylamine
n-Butylamine
Sec-butylamine
Tert-butylamine
Isobutylamine
n-Amylamine
n-Hexylamine
Ethylenediamine
Tetramethylenediamine
Pentamethylenediamine
Ethanolamine
Diethylenetriamine
Putreseine
Cadaverine
Aniline
70
Benzylamine
?-Phenylethylamine
p-Bromoanaline
p-Aminophenyl
p-Phenylencdiamine
As already indicated, my novel amine-acid solvents are
3,082,270
10
limited acid-wise to the inclusion of cyanic or thiocyanic
acid vor mixtures of those two acids. One method of
preparing the solvents is to simply mix the appropriate
amine and acid starting materials by stirring or other
means. However, for previously indicated reasons, a
preferred method, in many cases, of preparing my sol
vents is to react a suitable acid derivative with the chosen
that the incorporation of a dialkylamine, such as diethyl
amine, thereinto, results in an increase in product purity,
with no sacri?ce of recovery, when such mixtures are
employed for the d-i?icult extraction of naphthalene from
hydrocarbon mixtures containing, in major proportion,
monoaromatics rand nonaromatics. The use of a dialkyl
amine in conjunction with a trialkylarnine in the manner
A suitable acid derivative for such purpose, is
suggested has an additional advantage in that it normally
one which reacts with the amine in such fashion as to
results in a solvent ‘which is liquid at room temperature,
amine.
yield an amine-acid product of substantially the same type 10 whereas without the dialkylamine the solvent would ordi
narily have a melting point higher than room temperature
(e.'g., where the ingredients are thiocyanic acid and tri
et-hylamine, the melting point of the solvent, in its pre
ferred formulation, is about 30° C.).
‘An important ‘factor in arriving at optimum conditions
excellent acid derivatives for the purpose since the am 15
of operation in solvent extraction processes is the rapid
monia by-product is readily eliminated as a gas and does
ity with which the r-af?nate phase separates from the ex
not contaminate the solvent.
tract phase under various circumstances. Relatively
Another reason for the excellence of the ammonium
rapid separation of these two bases takes place when using
salts of cyanic and thiocyanic acid as starting materials
for the preparation of my amine-acid solvent mixtures 20 the novel amine-acid solvents of my invention at room
as that resulting from a straight mixture of the same
amine with the acid corresponding to the derivative.
Thus, ammonium salts of cyanic and thiocyanic acids
(ammonium cyanate and ammonium thiocyanate) are
temperature. At higher temperatures, phase separation
is the fact that those salts are themselves solvents within
is faster and the solvent power of the amine-acid solvent
the scope of this invention. Thus, excesses of ammonium
is greater, but temperature increases have-an adverse ef
cyanate or ammonium thiocyanate present in my amine
fect on selectivity of the solvent towards aromatics. The
.acid solvents are not present as contaminants but as sol
,vent of an ammonia-acid rather than an amine-acid type. 25 previously recommended temperature ranges for the prac
tice of my invention (about 20° to about 150° C., prefer
Solvent mixtures such as the instant one, as Well as mix
ably from about 30° to‘about 60° C.) were determined by
tures of any of the nitrogen base compounds (ammonia
taking the aforesaid factors into consideration.
and amines) and acids disclosed herein, are all within
The solvents of this invention are relatively non-toxic
the scope of my invention.
As already made clear, my amine-acid solvent must 30 at standard, as well as operating, conditions. Also, these
solvents are miscible with water, as previously indicated,
be liquid under the service conditions of my solvent ex~
traction method. This does not mean that the amine-acid
thus making it an easy matter to recover them from ex
tract phases, \as well as raf?nate phases, by water extrac
solvent must be liquid at standard temperature and pres
tion, for recycling or other purposes. In addition, the
sure conditions although such is frequently the case. It
is within the scope of my invention to employ amine and/ 35 solvents of this invention are unreactive with the feed
stock components throughout the temperature range to
,or acid (or acid salt) starting materials which are solid,
or form solid or semisolid mixtures, at standard con
which they are subjected in service.
.
The solvent extraction process of my invention can be
ditions, so long as the resulting amine~acid mixtures are
carried out in various ways, the most common mode of
liquid under the operating conditions contemplated. .
In the preparation of solvent mixtures according to 40 operation comprising the use of a spray, packed, or bub
ble plate tower wherein the hydrocarbon feed mixture is
this invention, if theingredients are all liquid at room
temperature simple stirring is usually suf?cient to effect
rapid homogenity of the mix. Where not all of the in~
gredients are liquid at the temperature of preparation it
might be necessary to use more rigorous means of achiev
ing uniformity of mix, such as, for example, kneading or
the like. In either event, the application of heat to
change the viscosity characteristics of the system can be
employed if desired.
As ‘emphasized previously, .the amine-acid mixtures of
contacted by the stream of amine-acid solvent ?owing,
usually countercurrently, therethrough. It is within the
scope of my invention to add a minor amount of water,
or other inert agent, to my amine-acid solvents where such
can be done without colorable modi?cation of those sol
vent properties necessary to the proper functioning of the
process. For example, where'it is proposed to subject
.a mixture of hydrocarbons of varying degrees of aromat
icity to solvent extraction according to my method, and
this invention exhibit extraordinary powers of selectivity 50 the hydrocarbons are all extremely soluble in the chosen
solvent, the incorporation of a minor amount of water into
toward aromatics when used as solvents in this invention.
the solvent, prior to or during the extraction operation,
In addition to being highly selective toward aromatic hy
to assure the rapid and distinct formation of two liquid
drocarbons, the amine-acid solvents of this invention also
phases is within the spirit and scope of my invention.
exhibit high solvent power, i.e., relatively small quan
tities of solvent dissolve relatively large quantities of aro 55 When water is added for such purpose, the proportion
used should normally not exceed about 20% of the weight
matics. In striking illustration of this, I have found that
of the solvent ‘and preferably fall within the range from
a stoichiometrically proportioned mixture of triethyl
about 2 to about 5% of the solvent weight.
amine and thiocyanic acid exhibits a solvent power with
If desired, my process cm be carried out by distilling
respect to u-methylnaphtalene, an aromatic hydrocarbon,
in the presence of decalin, of 23.8 by comparison with a 60 the hydrocarbon \feed mixture in the presence of an
amine-acid solvent, of the type disclosed herein, as an ex
solvent power of 8.0, under the same circumstances, for
tractive distillation process. In the practice of extractive
'phenol, a known solvent for aromatic hydrocarbons.
distillation,.the feed mixture to be separated is distilled
These solvent power values were arrived at by multiply
in the presence of a selective solvent which has a substan
ing the difference in a-methylnaphthalene concentration
tial-1y lower volatility than any of the components of said
between the solvent~free extract and the feedstock times
vmixture, as a result of which an overhead enriched in
'the percent a-methylnaphthalene recovery in the extract
that portion of the feed mixture not selectively extracted
times 10—2. The trialkylamines are particularly suitable
is removed, leaving behind a bottoms product which com
for use as amine ingredients in my novel solvents.
prises a solution of solvent and selectively extracted ma
, While the amine~acid mixtures of this invention, and 70 terial.
particularly the stoichiometrically balanced trialkylamine
thiocyanic or cyanic acid mixtures, are highly selective
for aromatics (as will be illustrated in an example to
.follow, showing a recovery of 97%, of 93% naphthalene,
from a 40% naphthalene feedstock), I have discovered
It is pointed out, however, that a number of my
amine-acid solvents tend toward instability at elevated
temperatures and therefore when considering the desir
ability of a particular solvent for an extractive distilla
tion operation attention must be paid to the nature of the
75 material to be separated in order to avoid those tempera
3,082,270
12
11
Example IV
tur'es potentially destructive of the solvent. One possible
way of avoiding this di?iculty, where the separation of
high boiling mixtures is contemplated, is the use of re
duced pressures during the operation.
This is an example of the use of an antisolvent in the
practice of my invention.
A single stage solvent extraction operation is carried
out at 25° C. by treating a mixture of 14 ml. of dodecane
and 6 m1. of methylnaphthalene vwith 16 m1. of triethyl
amine-thiocyanic acid solvent (approximately 68% thio
cyanic acid) at a weight ratio of solvent to hydrocarbon
feed mixture of approximately 1.821. The solvent-hy
drocarbon mixture is moderately agitated and a solvent
rich extract phase is separated therefrom.
The solvent rich extract phase is washed with pentane,
Still another way in which my process can be carried
out is to employ an antisolvent in conjunction with the
amine-acid solvent, in any manner known to those skilled
in the art. The use of such antisolvents in hydrocarbon
solvent extraction processes is Well known and need not
be considered in detail here. Typical ant-isolvents for
purposes of this invention are para?ins such as pentane,
heptane, octane, isooctane, and the like; water; etc.
In order to more fully illustrate the invention the fol~
as an antisolvent, to selectively extract dodecane which
lowing examples are set forth. These examples are to be
is dissolved therein as a contaminant. As a result of
considered as illustrative only and not limitative of the 15 the washing operation, two phases (a pentane rich phase
scope of the invention.
containing dodecane and a solvent rich phase containing
methylnaphthalene) are formed. The two phases are
Example I
separated ‘and the solvent rich phase is subjected to water
extraction treatment to remove the triethylamine-thio~
cyanic acid mixture as a solvent in the method of my 20 cyanic acid solvent therefrom and recover the methyl
invention.
naphthalene as an extract product.
This example illustrates the use of a triethylaminethio
A 100 gram hydrocarbon feed sample comprising
Example V
paramns, naphthenes, alkyl indanes, alkyl indenes, alkyl
tetralins, and the like, in the amount of 67%, and methyl~
This example illustrates the use of a tributylamine
naphthalene in the amount of 33% was treated with 67 25 cyanic acid mixture as a solvent in the method of my in
g. of a triethylamine-thiocyanic ‘acid mixture, in which
vention.
the acid and amine components were present in stoichi
A 100 g. hydrocarbon feed sample comprising paraf?ns,
ometric proportions, having a density of 0.998, in a one
naphthenes, alkyl indanes, alkyl indenes, and alkyl tetra
stage solvent extraction process. After separation of the
lins, in the amount of 67% by weight, and methylnaph
phases it was found that the hydrocarbon portion of the 30 thalene in the amount of 33% by Weight is treated with
extract phase contained approximately 45% of the methyl
100 ‘grams of a stoichiometrically proportioned tributyl
naphthalene in the feed sample and had a purity of ap
amine-cyanic acid mixture in a one stage solvent extrac
The solvent was most effective as
tion operation. The solvent-hydrocarbon feed mixture is
evidenced by the yield and purity of the methylnaphtha
moderately agitated and a solvent rich extract phase is
35 sepanated therefrom.
lene extract product.
The solvent rich extract phase is subjected ‘to a water
Example II
‘extraction treatment whereby its tributylamine-cyanic acid
This example serves to illustrate the e?Fect of increasing
solvent portion is selectively extracted by the water. The
the number of operating stages and the ratio of solvent to
remaining hydrocarbon portion is enriched in methyl
proximately 90%.
feed in my solvent extraction method.
40
A hydrocarbon dealkylation product containing 40%
naphthalene.
Example VI
naphthalene and 60% alkylated monoaromatics and non~
aromatics such as naphthenes, alkyl indanes, alkyl in
This example illustrates the use of an aniline-thiocyanic
denes, alkyl tetralins, and the like, was subjected to
acid mixture as a solvent in the method of my invention.
solvent extraction treatment according to the method of 45
A 100 g. hydrocarbon feed sample comprising paral?ns,
this invention utilizing the same solvent as that employed
naphthenes, alkyl indenes, alkyl indanes and alkyl tetralins
in Example I. Five theoretical operating stages were
in the amount of 67 % by weight, and methylnaphthalene
in the amount of 33 % by weight, is treated with 100 grams
employed and the solventfeed ratio was 1.25.
An ‘analysis of the extract phase showed a recovery of
of a stoichiometrically proportioned mixture of aniline
naphthalene of approximately 97% and a purity of ap
and thiocyanic acid in a one stage solvent extraction
proximately 93%. A comparison of these results with
operation. The solvent-hydrocarbon feed mixture is
those of Example I, in which the weight ratio of solvent
moderately agitated and a solvent rich extract phase is
separated therefrom.
to feed was little more than half that here, and in which
only one stage, rather than ?ve, was employed, sharply
The extract phase from the solvent extraction opera
points up the bene?cial effects on recovery and purity, 55 tion is subjected to a water extraction treatment whereby
its aniline-thiocyanic acid solvent portion is selectively
and particularly the ‘former, of an increase in solvent:feed
ratio and number of solvent extraction stages.
extracted by the water. The remaining hydrocarbon
Example III
60
This example illustrates the use of a triethylamine
cyanic acid mixture as a solvent in the method of my in.
vention.
A 100 g. hydrocarbon feed sample comprising para?’ins,
naphthenes, alkyl indanes, alkyl indenes, and alkyl
tetralins, in the amount of 67% ‘by weight, and methyl
naphthalene in the amount of 33% by weight, is treated
with 100 grams of a stoichiometrically proportioned tri
portion is enriched in methylnaphthalene.
Example VII
This example illustrates the use of a Z-aminopropane
cyanic acid mixture as a solvent in the method of my in
vention.
A 100 g. hydrocarbon feed sample comprising para?ins,
naphthenes, alkyl indanes, alkyl indenes, and alkyl tetra
lins, in the amount of 67% by weight, and methyl naph
thalene in the amount of 33% by weight is treated with
100 grams of a Z-amino-propane-cyanic acid mixture (in
which the acid and amine ingredients are present in
ethylamine-cyanic acid mixture in a l-stage solvent ex
traction process.
70 stoichiometric proportions) in a one stage solvent extrac
The extract phase from the solvent extraction process
tion operation. The solvent-hydrocarbon feed mixture
is subjected to a water extraction treatment whereby its
is moderately agitated and a solvent rich extract phase is
triethylamiue-cyanic acid solvent portion is selectively
extracted by the water. The remaining hydrocarbon por
tion of the extract phase is enriched in methylnaphthalene.
separated therefrom.
The extract phase from the solvent extraction opera
tion is subjected to a Water extraction treatment whereby
3,082,276
13
7
its Z-amino-propane-cyanic acid solvent portion is selec
tively extracted by the water. The remaining hydrocar
bon portion is enriched in methylnaphthalene.
It will be apparent that many modi?cations of my proc
ess can be practiced simply by varying the permissible
solvent components, feed materials, and operating tech
niques within the limits taught herein. All percentage
data in the above examples and elsewhere in this disclo
_
.
.
14
.
t
,
tract phase by extracting the amine-‘acid solvent from that
phase with water.
6. A method of extracting hydrocarbon material of
greater aromaticity from a mixture thereof with hydro
carbon material of lesser aromaticity which comprises:
(1) contacting said mixture-with a substantially amide
free mixture of a material selected from the group con
sisting of ammonia and amines and an acid material se
sure are on a weight basis unless otherwise speci?ed. The
present invention is not limited to the use of water ex
lected from the group consisting of thiocyanic acid, cyanic
acid and mixtures of thiocyanic and cyanic acids, to form
traction for recovery of the hydrocarbon portion of the
extract phase, and any other means known to those skilled
in the art to accomplish this purpose may be employed if
desired. For example, it is possible, in some cases at
least, to recover the hydrocarbon portion of the extract
phase by distillation techniques. The success of such tech
niques depends in many instances on the use of reduced
pressures to avoid destruction of the solvent, if it is of a
type substantially unstable at elevated temperatures.
an extract phase containing hydrocarbon material rich in
said hydrocarbon material of greater aromaticity and a
minor amount of said hydrocarbon material of lesser
aromaticity, and a raf?nate phase; (2) treating the ex
tract phase with an antisolvent to extract said hydrocarbon
material of lesser aromaticity therefrom; and (3) recov
ering, substantially all of the hydrocarbon material of
greater aromaticity from the extract phase.
7. The method of extracting diaromatic hydrocarbons
The preferred solvent: hydrocarbon feedstock weight 20 from a feedstock containing diaromatic, monoaromatic
and non-aromatic hydrocarbons comprising: (1) continu
ously contacting said feedstock, in countercurrent relation
ratios for purposes of this invention are from about 0.25 :1
to about 3.0:1. However, my process is not limited to
this range of ratios and the ratio may vary within wide
limits. within the scope of the invention.
ship, with a solvent consisting essentially of a mixture of
thiocyanic acid and a trialkylamine at a molar ratio of
The present process is particularly well adapted to pre 25 the former to the latter of from about 120.5 to about 1:2,
paring feedstocks for dealkylation processes. Thus, a
heavy reformate fraction containing alkyl naphthalenes
and non-naphthalenic ,materialspcan be treated in accord
ance with the invention to obtain an alkylnaphthalene
concentrate which is thereafter dealkylated to form naph
thalene by any of the conventional catalytic or thermal
dealkylation processes.
I claim:
whereby an extract phase rich in said solvent and con
taining a portion of the feedstock enriched in diaromatic
hydrocarbons and a ra?inate phase containing substantial
ly all of the remaining portion of the feedstock- and a minor
amount of said solvent, are obtained; (2) subjecting the
extract phase from step 1 to water extraction to form an
aqueous phase containing water and substantially all of
the solvent in said extract phase, and a hydrocarbon phase
1. A method of separating hydrocarbon material of
greater aromaticity from a mixture thereof with hydro
containing substantially all of the diaromatic hydrocarbons
from said extract phase; (3) subjecting the aqueous phase
carbon material of lesser aromaticity which comprises
from step (2) to fractional distillation to form an over
head product of substantially pure Water and a bottoms
contacting said mixture with a substantially amide-free
mixture of a material selected from the group consisting
of ammonia and amines and an acid material selected
product of substantially pure solvent; ( 4) recycling the sol
vent bottoms product from step (3) to solvent extraction
from the group consisting of thiocyanic acid, cyanic acid 40 step (1); (5) condensing the overhead water product from
step (3); and (6) recycling the condensed water from step
and mixtures of thiocyanic and cyanic acids.
(5) to water extraction step (3).
2. A method of separating hydrocarbon material of
8. The method of claim 7 in which the trialkylamine
greater aromaticity from a mixture thereof with hydro
is triethylamine.
carbon material of lesser aromaticity but roughly the same
boiling point which comprises subjecting said mixture to 45 9. The method of claim 7 in which the acid and amine
extractive distillation in the presence of a substantially
amide-free mixture of a material selected from the group
ingredients of the solvent are present in stoichiometric pro
portions.
10. The method of claim 7 in which the ra?inate phase
from step 1 is subjected to water extraction treatment to
selected from the group consisting of thiocyanic acid,
remove substantially all of the solvent therefrom and to
cyanic acid and mixtures of thiocyanic and cyanic acids.
3. A method of extracting hydrocarbon material of 50 obtain a substantially solvent free ra?inate hydrocarbon
consisting of ammonia and amines and an acid material
greater aromaticity from a mixture thereof with hydro
carbon material of lesser aromaticity which comprises con
product.
'
11. The method of claim 7 in which step 1 is conducted
‘at atmospheric pressure and at a temperature Within the
tacting said mixture With a solvent comprising a substan
range from about 20° to about 150° C.
tially amide-free mixture of a material selected from the
12. The method of claim 7 in which the ratio of solvent
group consisting of ammonia and amines and an acid 55
to hydrocarbon feedstock in step 1 is from about 0.25 to
about 3.0 parts by weight of the former to about 1 part by
weight of the latter.
acids, to form an extract phase containing hydrocarbon
13. The method of extracting diaromatic hydrocarbon
material rich in said hydrocarbon material of greater
60 material from a mixture comprising said diaromatic hy
aromaticity, and a rai?nate phase.
drocarbon material and monoaromatic hydrocarbon ma
4. A method of extracting hydrocarbon material of
greater aromaticity from a mixture thereof with hydro
terial which comprises: (1) contacting said mixture with
a mixture of va tertiary amine and thiocyanic acid, whereby
carbon material of lesser aromaticity which comprises: (1)
an extract phase containing hydrocarbon material rich in
contacting said mixture with a substantially amide-free
mixture of a material selected from the group consisting 65 said diaromatic hydrocarbon material and a ra?inate
phase, are formed and (2) subjecting said extract phase
of ammonia and amines and an acid material selected
from the group consisting of thiocyanic acid, cyanic acid
to water extraction treatment whereby substantially all
and mixtures of thiocyanic and cyanic acids, to form an
of the amine-acid mixture is removed therefrom leaving
extract phase containing hydrocarbon material rich in
substantially all of the diaromatic hydrocarbon material as
said hydrocarbon material of greater aromaticity, and a 70 the extract product of the process.
material selected from the group consisting of thiocyanic
acid, cyanic acid and mixtures of thiocyanic and cyanic
raf?nate phase and (2) recovering substantially all of the
14. A method of extracting hydrocarbon material of
greater aromaticity from a mixture thereof with hydro
tract phase.
carbon material of lesser aromaticity which comprises:
5. The method of claim 4 in which the hydrocarbon
( 1) contacting said mixture with a solvent comprising a
material of greater aromaticity is recovered from the ex 75 substantially amide-free mixture of a material selected
hydrocarbon material of greater aromaticity from said ex
3,082,270
16
15
for the aromatic hydrocarbon material is a stoichiomet
from the group consisting of ammonia and amines and
an acid material selected from the group consisting of thio
rically proportioned mixture of triethylamine and thio
cyanic acid, cyanic acid and mixtures of thiocyanic and
cyanic acid.
20. A method of extracting naphthalene and alkyl
cyanic acids, and containing a minor amount of water,
to form an extract phase containing hydrocarbon material
rich in said hydrocarbon material of greater aromaticity
naphthalenes from a feedstock containing these compounds
and close-boiling mono-aromatic hydrocarbons compris
ing: (1) continuously contacting said feedstock, in coun
and a raf?nate phase.
15. The method of claim 14 in Which the water is pres
tercurrent relationship, with a solvent consisting of a
stoichiometrically proportioned mixture of thiocyanic acid
by weight thereof.
10 and triethylamine, whereby an extract phase rich in said
solvent and containing a portion of the feedstock enriched
16. In the method of extracting aromatic hydrocarbon
in naphthalene and alkylnaphthalenes, and a ra?inate
material from a mixture thereof with nonaromatic hydro
phase containing susbtantially all of the remaining por
carbon material which comprises contacting said mixture
ent in the solvent in an amount from about 2 to about 5%
with a solvent for the aromatic hydrocarbon material to
tion of the feedstock and a minor amount of said solvent,
form an extract phase containing hydrocarbon material
rich in said aromatic hydrocarbon material, and a ra?inate
phase; the improvement which comprises employing a sub
to water extraction to form an aqueous phase containing
are obtained; (2) subjecting the extract phase from step 1
water and substantially all of the solvent in said extract
phase, and a hydrocarbon phase containing substantially
all of the naphthalene and alkylnaphthalenes from said
material selected from the group consisting of thiocyanic 20 extract phase; (3) subjecting the aqueous phase from
step 2 to fractional distillation to form an overhead prod
acid, cyanic acid and mixtures of thiocyanic and cyanic
stantially amide-free mixture of -a material selected from
the group consisting of ammonia and amines and an acid
uct of substantially pure water and a bottoms product of
acids, as the solvent for the aromatic hydrocarbon material.
17. The improvement of claim 16 in which the solvent
for the aromatic hydrocarbon material is a mixture of a.
tertiary amine and thiocyanic acid.
18. The improvement of claim 16 in which the solvent
for the aromatic hydrocarbon material is a mixture of a
25
substantially pure solvent; (4) recycling the solvent bot
toms product from step 3 to solvent extraction step 1; (5)
condensing the overhead water product from step 3; and
(6) recycling the condensed water from step 5 to water ex
traction step 3.
trialkylamine and thiocyanic acid.
19. The improvement of claim 16 in which the solvent
No references cited.
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