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Патент USA US2131422

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Sept. 27, 1938.
Filed Feb. 20, 1937
/nvcr7/0r:A/v/n R linderson
By his A/f0rneg;___,___._ _____ __ -
Patented Sept. 27, 1938
Alvin P. Anderson, Alton, IlL, assignor to Shell’ ‘
Development Company, San'Francisco, Calii'.,
a corporation of Delaware
Application February 20, 1937, Serial No. 126,889
10 Claims.
(Cl. 196-13)
This invention relates to a' process for the
treatment of hydrocarbon oils, such as petroleum
fractions, with selective solvents comprising cre
which is at least partially immiscible with the se
lective solvent in the presence of the oil, and the
oil is subjected to the extracting action of these
countercurrent streams by introducing it into the
system either with the auxiliary solvent, or at a 5
point intermediate to the points of introduction
of the selective and auxiliary solvents respec
tively. Such a process is described in the Tuttle
' sylic acid, and is particularly useful in the ex
5 traction of higher-boiling residual or distillate
oils, such as cylinder oil, lubricating distillates,
spindle oil, transformer oil, but may be applied
also to the treatment of lower boiling fractions.
The types of hydrocarbons occurring in petro
-_Patent No. 1,912,349. In certain processes‘ the
auxiliary solvent is introduced into the system at
a plurality of points, as, for example, near the
point of removal of the extract, at the point of
introduction of the oil,‘ and at a point lying 'be
tween the points of introduction of the oil and
10 leum fractions and their relative concentration
vary with the source and the boiling range of the
fraction, and these variations ‘in initial composi
tion, as well as the quality of the desired extrac
tion product, determine the exact nature of the
15 separation e?ected in the extraction processes.
the selective solvent, respectively.
Particularly useful as auxiliary solvents in such
In general, however, the purpose of the process
is to dissolve those components of the initial oil
a process are liquid or lique?ed hydrocarbon dis
which are more aromatic, naphthenic, and/or _ tillates boiling below about 45° 0., although high
er. boiling preferably 1 aromatic-free distillates
olefinic in nature, i. e., those which have a rela
20 tively lower hydrogen-carbon ratio, while leav-v I may be employed. Propane, either alone, or in
ing undissolved the relatively more para?inic admixture with small amounts of methane,
components. In the case of lubricating oils, the ethane, and butane is especially useful, but higher
more paraf?nio hydrocarbons present in crude aliphatic solvents, such as butanes and pentanes,
particularly iso-butane and 2-methyl butane, are
also suitable.
lubricating oil fractions are more desirable be
cause, as compared with themore soluble hydro
carbons, their viscosity is not so greatly affected
by changes in temperature, are chemically more
inert and stable, and exhibit less tendency to
wards the formation of undesirable resinous or
30 sludge forming constituents on contact with air
at elevated temperatures. This group of hydro
carbons, in the case of lubricating oils, does not .
The quantity of-ra?inate which can be pro
duced in an extraction unit in a given time de
pends upon the rapidity with which the raf?nate'
and extract phases can be parted in each-of the
extraction stages. According to the present in 30
vention it was found that when operating a
process of the type‘ described above, involving
the ?ow of an oil and an auxiliary solvent coun
tercurrently to a selective solventcomprising cre
include those compounds usually designated as
“wax" or “petrolatum.”
sylic acid through several stages (which stages
As a matter of convenience hereafter the com
ponent or group of components of the initial oil
which it is desired to remove in the extraction
process by preferential dissolution in the selec
tive solvent as the extract will be designated as
packed towers), the maximum rate of throughput
40 “non-para?inic” constituents, and the component
of the oil is often undesirably limited by the slow
may be either real, as when a series of intercon
nected mixers and settlers or centrifuges is pro
vided, or virtual, as when using one or more
or group of components which it is desired to re- ' or incomplete separation of the phases in one or
more stages. Thus, when feeding too much of
cover as the raftinate will be designated as “paraf
the initial oil into the system, whether or not the
rate of ?ow of selective solvent is varied, the
?nic,” it being understood that these’ terms are
relative, and are to be interpreted with regard
45 to the composition of the initial material and the
mixture in one or more stages becomes cloudy or 45
emulsi?ed, causing some of the extract phase to
move in the wrong direction by being intermixed
with the ra?lnate; as a result the sharpness of
extraction products produced, the “non-paraffin
ic” portion being in each case more readily sol
uble in the extract phase than the “para?inic”
' the separation is lowered as indicated, for ex
According to one mode of carrying out such an
extraction process, a selective solvent consisting
of cresylic acid, or of a mixture of cresylic acid
with a similar second solvent, such as phenol, is ,
passed through a packed tower or a multi-stage
treater countercurrently to an auxiliary solvent .
ample, by a decrease in theviscosity index or 50
para?inicity of the raillnate oil,and anincrease in
that of the extract oil, due to entrainment of
railinate in the extract. This condition may pro
gress so far as eventually to result in the coales- cence of the two phases, with the result that the
however, undesirable because it was found that in
extraction zone is ?ooded with a solution of oil
and solvents and the extraction ceases.
According to the present invention it was found
quantities of water employed in the present proc
that‘the speed of separation of the phases, wheth
ess are detrimental to the selectivity of cresylic
er effected in a settling tank, in a centrifuge,
or in a tower, can be materially increased by
The expression “cresylic acid,” as employed in
the absence of an auxiliary solvent even the small
employing, instead of anhydrous selective sol
the present speci?cation and claims, is intended '
vent, a mixture of a cresylic acid-containing se
to include o-, m-, and p-hydroxy toluene, mix
lective solvent and a small amount of water. It
was found that, when extracting viscous residual
oils, at least 0.3% of water are necessary to effect
an improvement in the settling rates, and that
for safe uniform operation the water content
should be maintained at above 0.4% by weight,
tures of two or more of these as well as mixtures
containing their higher homologues, such as ethyl 10
hydroxy benzenes. The expression "cresylic acid
containing,” as applied to selective solvents, is
intended to designate a selective solvent which
may, save for the small amount of water specified
15 based on the selective solvent, while the best op- , according to the present invention, consist en 15
eration occurs when the water content is kept tirely of cresylic acid, as de?ned above, as well
within the range from 0.5 to 0.7%. Other water as selective solvents containing quantities (not
over 65% by weight) of other aromatic and par
miscible low-molecular oxygenated organic com
pounds, such as methyl alcohol, glycerol, glycol,
20 acetone, etc., may be employed in place of or
together with water to improve the settling rates.
When such compounds are employed in addition
to water, the quantity of water -may be as low
as 0.2%.
It has, moreover, been found that it is essential
that the water concentration be maintained be
low 1.0% and, preferably, below 0.8%.
more than this amount of water is employed,
there is a decided shift in the solubility equilibria
30 toward increases in the _ sizes of the ra?inate
layers, and towards decreased oil concentrations
in the extract phases, causing larger quantities
of hydrocarbons of intermediate solubility to be
dissolved in the rail‘lnate phase, thereby lowering
35 the quality of the ultimate ra?inate.
Such a
ticularly phenolic solvents, such as phenol. By
way of example, excellent results have been ob 20
tained by employing 0.6% of water in an extrac
tion process employing as the selective solvent a
mixture of 70% cresylic acid and 30% of phenol.
It was, moreover, found that the settling rate
can be increased by using a selective solvent 25
which contains a concentration of phenol higher.
than 40%. Thus, using the same quantity of
water, a solvent in which the ratio of cresylic acid
to phenol is 35:65 causes more rapid settling than
a solvent in which this ratio is higher, as, for 30
example, 65:35, or the solvent mixture described
The water used may be added to the selective
solvent prior to its introduction into the process,
or it may be separately introduced at one or 35
more points in the process. One method of add
shift in equilibria upsets the extraction process
and prevents the production of a ra?inate of the ' ing water, described below, was found to be par
ticularly useful in that it also improved the
desired quality in an apparatus of a ?xed num
separation of dissolved solvent from the ra?inate
ber of real or virtual stages. While it is some
_ 40
times possible partially to restore the equilibria phase.
The process may, for example, be operated in
by increasing the temperature, this is undesirable
because an increase in temperature was found to an apparatus of the type illustrated schematically
cause slower rates of partition between the
It should be noted that the water or other ma
in the drawing, which is a flow diagram of one
embodiment of the present invention. In the
drawing, A and B represent cylindrical shells, 45
terial is, in the present process, added merely to
improve the rate of settling, the amount present
?lled with a plurality of partitions so as to pro
vide settling chambers or stages I to 8. Each
in the system being insuflicient to cause a sub
stage is equipped with a mixing device Ia. to 8a,
which may be provided with means for distribut
ing a liquid mixture or emulsion into the cham 50
stantial lowering of the solvent power of the
selective solvent for oil. This distinguishes the
present invention from prior processes in which
such substances have been employed in larger
concentrations with the purpose of regulating the
solvent power of the selective solvent. Thus, ac
cording to the present invention the quantity of
water or other polar agent is su?lciently small
not to cause the oil concentration in the extract
phase in the stage at which the fresh solvent is
introduced to be lowered by more than about
60 20%, as compared to and based on the concen
tration of oil in the corresponding extract phase
when anhydrous selective solvent is employed.
The present invention, therefore, is based upon
the discovery that there is a critical range of con
65 centrations of water which materially improves
the rate of separation of the ra?inate phase from
the extract phase without causing so great a
shift in the solubility equilibria as to upset the
extraction process.
While the addition of small amounts of water
is especially useful in extraction processes em
ploying propane as the auxiliary solvent, other
equivalent auxiliary solvents, as outlined above,
may also be employed. The addition of water in
75 _ rocesses operating without auxiliary solvents is,
bers with a minimum of turbulence. The cham
bers are interconnected by conduits, as shown.
Cresylic acid enters mixer 8a from tank 9 via
line H) by the action of pump 8e through valve l2.
An auxiliary solvent, like propane, is fed into 55
mixer la from storage tank l3 via line H, con
trolled by valve l5. Raw oil, such as a topped
crude, is introduced into one of the intermediate
stages, such as, for example, stage 3 from tank i6
via line I‘! and pump l8, at a rate controlled by 60
valve l9.
As a- result of feeding the cresylic acid solvent,
propane, and initial oil into mixers 8a, Ia, and 3a,
respectively, the cresylic acid solvent and propane
flow countercurrently to one another through the 65
several sections in the following manner: The
phase discharged from each of the mixers strati
?es in the chambers l to 8 to form relatively
lighter ra?inate phases and relatively heavier ex
tract phases. The extract phases settle and are 70
withdrawn via lines lc to 80, while the ra?inate
phases are withdrawn via lines Id to 8d. Extract
phases from‘ stages 2 to 8 are fed into mixers la
to ‘la, respectively, by pumps le to ‘la, and rai?nate
phases from stages I to ‘I are fed into mixers 2a
to 8a, respectively, via valves U to 8!. The ulti
mate ra?lnate phase is withdrawn through valve
reused in the extraction of additional quantities
20, and may be treated for the recovery of the
propane and cresylic acid solvent in any desired
manner. The ultimate extract phase is with
drawn through a valve 2| in line lc for a similar
The degree of improvement obtainable by the
of oil.
addition of water may be seen from the fol
lowing data. Employing a solvent mixture con
taining 30% phenol and 70% cresylic acid in a
double countercurrent extraction system, a com
The improvement according to the present in
bination with. propane as the-auxiliary solvent,
vention resides in employing in the settling cham
bers a cresylic acid solvent containing small
quantities of water, as described above. The
solvent in“ the tank 9 may contain this water.
When this solvent is anhydrous or substantially
for the extraction of a residual oil having an
initial viscosity index between 60 and '72, the
phases withdrawn from the extraction stage
nearest the point of introduction of the solvent
were ?owed through an eductor tube at the rate
so, water may be introduced at one or more points
of 17 feet per second, .and the rate of settling
in the process, as, for example, into the line l0 . determined by ?owing the mixture through a 24 15
through a valve 22.
inch long gauge glass bomb. Without water the
Instead of adding all of the water through the ' average rate of settling was about 0.3 foot per
valve 22, I prefer to add the major portion of the second, which was increased to 0.83 foot per sec
water used in accordance with this invention to ond when 0.8% of water were added, employing
the ultimate ra?lnate phase withdrawn from the the same temperature.
chamber 8, either before or after this phase is
I claim as my invention:
freed of the auxiliary solvent. Thus, the ra?inate
1. A process for the separation of para?'lni'c
phase may be flowed through a ?ashing stage 23' and non-paramnio portions of a petroleum lu
wherein propane is separated and withdrawn at bricating oil ‘fraction containing the same, com
24. The residual portion of the ramnate phase prising the steps of ?owing concurrent streams of 25
is mixed with water fed via the valve 25, and the said oil and a liquid auxiliary solvent for the
resulting mixture is strati?ed in settling tank 26. para?inic portion of the oil, consisting predom
The addition of water causes separation of the
mixture into two secondary liquid phases: one
consists of a substantially oil-free concentrated
aqueous solution of cresylic acid, which is with
drawn at the bottom and combined with substan-'
tially anhydrous cresylic acid from the tank 9
via the line 2‘! and the valve 28; the other consists
substantially of the re?ned rafilnate oil contain
ing a very small amount of cresylic acid, and may
be withdrawn at 29.
The latter phase may be
further treated, for instance, by vacuum distilla
tion, to recover a solvent~free oil ra?inate.
anhydrous cresylic acid in the tank 9 may be
either the fresh make-up solvent or that re
covered by distillation or by some other methodv
from the extract phase produced in the same
process. The proportions in which the anhy
drous solvent and its aqueous solution are com
bined, either prior to or after being introduced
into the extraction zone, are regulated to produce
a solvent containing the desired concentration
of water within the above speci?ed range. Fol
lowing is an illustrative example of this preferred
form of the process:
The rai?nate phase produced by a continuous
method of countercurrent extraction in which
initial oil was introduced at an intermediate point
into counter?owing .streams of propane and
cresylic acid was found to',contain about 16% of
the total cresylic acid used in the process. It was
subjected to the following treatment to separate
the bulk of cresylic acid from the oil: propane
was ?ashed off by reducing the pressure on the
ra?inate phase. A small quantity of water (about
3% based on cresylic acid in this phase) was
then added to the residual portion of the ra?inate
phase, whereupon the oil-cresylic acid solution
separated into an oil layer and an aqueous
cresylic acid layer. The addition of such a large
amount of water greatly improved the speed of
separation between the oil and acid layers, as
compared to prior processes in which small
amounts of water (about 1%) were added. The
layers were separated and the aqueous cresylic
acid was combined with an anhydrous cresylic acid
forming an aqueous cresylic acid solution with
water content of about .6%; this solution was
inantly of one or more liquid or lique?ed hydro
carbons containing lessthan six carbon atoms
in the molecule through an extraction zone coun
ter-currently to a stream of a cresylic acid-con
taining selective solvent containing between
about 0.3% and 1.0% water under conditions to
cause‘ the formation of counter?owing raf?nate
and extract phases, separating said phases, and 35
removing the separated phases at spaced points
in the extraction zone.
2. The process according to claim 1 in which
the water concentration in the selective solvent
is between about 0.5 and 0.7%.
3. The process according to claim 1 in which
the auxiliary solvent consists predominantly of
4. The process according to claim 1 in which
the liquid phases are separated by settling.
5. A process for 'the separation of para?inic
and non-para?lnic portions of hydrocarbon oil
containing the same which comprises ?owing
said oil through an extraction zone countercur
rently to -a cresylic acid-containing selective
solvent containing between about 0.3% and 1.0%
water in the presence of a liquid auxiliary solvent
for the parai?nic portion of the oil which, when
mixed with said selective solvent in the presence
of the oil, is capable of forming two liquid phases, 55
thereby producing liquid extract and ra?lnate
phases, separating said phases and withdrawing
the separated phases at di?erent points in the
extraction zone.
6. A continuous process for the separation of 60
para?inic and non-para?inic portions of hydro
carbon oil containing the same, which comprises
continuously ?owing said oil through a counter
current extraction apparatus countercurrently
to a cresylic-acid containing selective solvent in 65V the presence of a liquid auxiliary solvent for
para?inic portions of the oil which, when mixed
with said selective solvent in the presence of the
oil is capable of causing the formationof liquid
raftinate and extract phases, continuously sep 70
arating and withdrawing raf?nate and extract
phases from said apparatus at spaced points
thereof, adding a quantity of water to the with
drawn ra?‘inate phase to cause the formation of a
liquid aqueous solvent phase and a liquid oil 75
phase, separating said aqueous solvent phase from
the oil phase, mixing said separated aqueous sol
vent with substantially anhydrous cresylic acid
containing selective solvent, and continuously in
troducing the resulting mixture of anhydrous and
9. A process for the separation of para?lnic
and non-para?lnic portions of hydrocarbon oil
containing the same which comprises contacting
said oil with a cresylic acid-containing selective
solvent containing between 0.2% and 1.0% of
aqueous solvents into the apparatus for the ex
water and in addition a small quantity of a low
traction of oil, said quantity 01' water being such
molecular oxygenated water-miscible organic
compound in the presence of a liquid auxiliary
solvent for the para?lnic portion of the oil which,
as to cause said resulting mixture of anhydrous
and aqueous solvents to have a water concentra
when mixed with said selective solvent in the 10
presence of the oil, is capable of forming two
the said quantity of water is such that the water ' liquid phases, and separating said phases.
10. A process for the separation of paraf?nic
concentration in said resulting mixture of an
hydrous and aqueous solvents is between about and non-paramnic portions of hydrocarbon 011
containing the same which comprises contacting 15
15 0.5% and 0.7%.
8. A process for the separation of para?lnic said oil with a cresylic acid-containing selective
and non-para?lnic portions of hydrocarbon 011 solvent containing between about 0.3% and 1.0%
of a separating aid of the class consisting of
containing the same which comprises contact
water, methyl alcohol, glycerol, and glycol in the
ing said oil with a cresylic acid-containing se
presence of a liquid auxiliary solvent consisting 20
20 lective solvent containing between about 0.3%
10 tion of between 0.3% and 1.0%.
'7. The process according to claim 6 in which
and 1.0% of a separating aid of the class con
predominantly of hydrocarbons normally boiling
sisting of water, methyl alcohol, glycerol, and
below 45° C. which, when mixed with said selec
tive solvent in the presence of the oil, is capable
glycol in the presence of a liquid auxiliary solvent
for the parafflnic portion of the oil which, when
25 mixed with said selective solvent in the presence
of the oil, is capable of forming two liquid phases,
and separating said phases.
of forming two liquid phases, and separating
said phases.
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