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Патент USA US2096950

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Oct. 26, 1937.
R. E. WILSON
2,096,950
REF INING MINERAL OILS
Filed Oct. 6, 1932
INVENTOR
bcrtECUzZ
ATTORNEY
‘
n
2,096,950
Patented Oct. 26, 1937
UNITED s'rATss PATENT OFFICE
2,096,950
REFINING MINERAL OILS
Robert .E. Wilson, Chicago, Ill., assignor to
Standard Oil Company, Chicago, 111, ‘a corpo
ration of Indiana
'
Application October 8, 1932, Serial No.- 636,492
8 Claims.
This invention relates to a process and appa
ratus for re?ning mineral oils and it pertains
more particularly‘to the recovery of solvents used
in the extraction of lubricating oils for improv
5 ing their viscosity indices.'
It has recently been found‘ that the quality of
a lubricating oil can be remarkably improved by
extracting it with a solvent, such as dichlorethyl
ether. Further recent developments have shown
10 that even better results are obtained when the oil
is extracted with a mixture oi such solvents with
- other solvents, particularly ketones such
as
acetone, esters, and ethers such as isopropyl
' ether.
Thus, an excellent solvent for extraction
5 purposes may consist of equal volumes of acetone
and dichlorethyl ether, or from one-half to four
volumes of dichlorethyl ether to one volume of
acetone. Dichlorethyl ether is an example of
what has been called a primary extracting solvent,
90 other examples of which are nitrobenzene, an
iline, dichlorbenzene, furfural, etc. Likewise,
acetone is herein referred to as an example of a
,
tionable because the steam will cause the hydroly
sis of solvents such as dichlorethyl ether, yield
ing corrosive acid. Furthermore, when steam is
used to distil a mixture containing a water soluble v5
component such as acetone, the latter is removed
in the condensed water, making it necessary to
recover and dry the acetone before reuse. It has
been proposed to use natural gas as a stripping
means, but here again it has been found that 10
solvents, such as dichlorethyl ether, are slightly
polymerized, and it is very di?lcult to scrub and/or
recover the acetone from the gases. I avoid all
of these di?lculties by heating the ra?lnate or
the extract to such a temperature that both of 15
the solvents are substantially vaporized ‘when in
troduced into a ?ash chamber or fractionating
tower. By suitable rectifying means, such as
bubble plates, I knock back all of the oil and I
withdraw the primary solvent at a point in the 20
system above the introduction of the heated mix--
the top of the fractionating system as a vapor, is
methylethyl ketone, diethyl ketone, methyl ace
condensed, and a part of it is revaporized and
the individual solvents. The process of extracting
80 oils with .these mixed solvents forms no part of
the present invention, it being described in a co
-
ture. The secondary solvent is removed from
secondary solvent, other examples of which are
2‘ tone, etc. By using this‘ combination of solvents,
the resulting mixture possesses greater selectivity
for naphthenic, naphthenic-like and aromatic
portions of mixed base oils than is possessed by
35
(Cl. 196-13)
ra?lnate and the oil extract with steam is objec
introduced at a point below the introduction of 25
the mixture so that it serves as a stripping means
to remove the last traces of the primary solvent
from the oil.
'
‘
The invention will be more clearly understood
from the detailed description of a preferred em- 30
bodiment illustrated in the accompanying draw
pending application ?led by Fred F. Diwoky and
Arthur B. Brown, Serial 605,814, ?led April 18,
ing, which forms a part of this speci?cation and
1932.
system.
The primary solvents have considerably higher
boiling points than the secondary solvents, and
In the following example I have described my 35
invention as used in the extraction of a mixed
they are therefore diilicult to recover from the
mineral oil extract and ra?inate. They are also
base Mid-Continent lubricating distillate having
frequently subject to decomposition at the tem
40 perature of distillation, particularly at those tem
peratures required to separate them from the oil.
- Furthermore, they often cannot be distilled with
the aid of steam, as they are frequently decom
posed by water, particularly the chlorinated com
pounds. The word primary in this case means
higher boiling and not necessarily more chemical
ly active or in . larger proportions. Secondary
solvents are usually more volatile and water-solu
ble. The object of my invention is to provide a
50 method and apparatus for recovering both the
primary and secondary solvents from the ra?lnate
and from the oil extract without decomposing or
vhydrolyzing the solvents and without‘ incurring
appreciable solvent losses. '
.
'
The conventional process of stripping the
which diagrammatically illustratessmy improved
>
a viscosity of 114 seconds Saybolt at 210° F., a
viscosity index of about 56 and a gravity of about
21.6 A. P. r. Iwill describe the use of an ex- 40
tracting liquid consisting of one volume of di
chlorethyl ether and one volume of acetone, and
I will use two volumes of this liquid to one volume
of oil to be extracted. It should be understood,
however, that the invention is equally applicable 45
to the extraction of any oil by the use of mixed
solvents, that any primary and secondary solvents
may be employed as long as they have different
boiling points, and that the volumes of the pri
mary and secondary solvents may be varied 50
throughout a wide range.
-
The untreated wax-bearing distillate from heat
ed storage tank I0 is withdrawn through pipe H
and forced by pump I2 to mixer l3.
This 011 is -
preferably at a temperature of about 125-135° F. 55
2.
2,096,950
so that it will flow freely and so that all of the
wax will be in solution. Dichlorethyl ether from
storage tanks l4 or I5 is withdrawn through pipe
l5, mixed with acetone from storage tanks 11
and I8, and withdrawn through pipe l9,—the
mixture of acetone and ether being ?nally passed
through pipe 20, pump 2| and heat exchanger 22
to mixer I3. The heat exchanger may be of
any desired form, but I prefer to use a steam ex
10 changer and I prefer to heat the mixture to about
135 or 140° F. The solvents are thoroughly and
intimately mixed with the oil in mixer l3, which
may be in the form of a horizontal tank provided
with perforated, transverse ba?les. In some cases
15 it may be desirable to have an extended period of
contact which may be obtained by using a large
mixer or by placing a soaking drum after the
mixer.
~
After the oil has been thoroughly contacted
20 with the mixed solvent, the mixture is passed
through cooler 23 and pipe 24 to centrifuge 25,
the lighter raf?nate fraction of extracted 011 being
withdrawn through pipe 26 to storage tank 21,
and the ether extract and the heavier fraction,
25 which is called black-oil or ether extract, is with
drawn through pipe 28 to storage tank 29. Chil
lers 23 should be provided with mechanical stir
rers or scrapers because the mixture is preferably
cooled to a temperature of about 40° F., and at
If a
wax-"free oil is used there will be no necessity for
using scrapers. Similarly, if a waxy oil is being
extracted it will be necessary to provide heating
coils in the ra?in'ate storage tank so that the oil
35 withdrawn therefrom will not clog up the pipes
due to solidi?ed wax.
30 this temperature the wax is in solid form.
The separation of the extracting liquids from
exchanger 44 to storage tank 45, from which it is
forced by pump 46 through pipes 41 and 48 to
storage tanks l4 and I5.
A small amount of the acetone is withdrawn
from collector 40 through pipe 49 and forced by
pump 50 through heat exchanger 44, coils in pipe
still 32 and introduced by pipe 52 into the frac
tionating tower at a point below stripping plates
35. The acetone is vaporized in exchanger 44
and superheated in the pipe still coils so that 10
when it is introduced at the base of the frac
tionating tower it effectively strips the last por
tions of the primary solvent from the ?nished oil,
which is withdrawn from the base of the frac
tionating tower through pipe 53. Because of the 15
high vapor pressure of the acetone, however, sub
stantially none will remain dissolved in the oil.
The amount of acetone which is used as a strip
ping medium will depend upon the desired degree
of stripping and can be readily calculated for any 20
particular system. The temperature to which
the acetone is heated is preferably about 5 or 10°
hotter than that to which the oil mixture is
heated.
.
As above stated, I prefer to provide re?ux in 25
the top of the fractionating tower by means of
condenser coils 31. Alternatively I may pump
back acetone through pipe 54 to a point above the
primary solvent drawo?.
,
From the above description it will be seen that 30v
I have provided an effective method of removing
all of the solvent or extracting liquids from the.
oil without the use of steam and without the in
troduction of extraneous gases. Practically all '
of the primary solvents have boiling points so
high that they could not be completely removed
the oil fractions is the same for the ra?lnate as
from the oil by simple distillation. The expense
of vacuum distillation would be prohibitive. I
for the ether extract, and for the sake of simplic
have found, however, that the secondary or light
40 ity I will describe only the separation‘ of the mixed
solvents or extracting liquids from the ra?inate
fraction. It should be understood, of course,
that the ra?inate only contains about 5 to 15%
of mixed solvents, and the ether extract contains
a very large proportion thereof--the exact per
centage depending on the quality of the oil under
going treatment.
‘
The mixture of oil with mixed solvents is with
drawn from storage tank 2'! by pipe 30 and forced
by pump 3| through tube heater or pipe still 32
wherein the mixture is heated to a su?icient tem
perature to cause substantial volatilization of all
diluents. Under ordinary conditions the outlet
temperature may be 400° F., but this temperature
55 will vary with the nature of the mixture and with
the pressure in the system. The hot mixture is
then introduced by pipe 33 into an intermediate
point of fractionating tower 34. Below the point
of introduction I provide stripping plates 35 and
60 above the point of introduction I provide frac
tionating plates 36. I also provide a suitable re
?ux coil 31 in the top of the tower and I prefer to
passall or a part of the feed stock through this
coil in order effectively to utilize the heat in the
65 system and to provide re?ux for the purpose of
solvent is practically insoluble in the oil at the
elevated temperatures in the recovery system, and
I have found that the primary solvent can read
ily be stripped out of the oil by means of the
superheated secondary solvent.
While I have disclosed a process in which the
secondary solvent is superheated in extra pipe
stills of the furnace, it should be understood that.
45,
I do not limit myself to these details. I may heat
the oil mixture to such high temperature that
liquid acetone may be injected in the base of the 50
fractionating tower, the extra heat in the oil
being su?icient to vaporize and drive out the ace
tone. Likewise I may pump acetone vapors from
the top of the tower, into the base thereof for use
as a stripping medium, or I may pump these 55
vapors through a suitable heater and then intro
duce them into the base of the fractionating
tower.
.
Also, heat economy may be secured by various
expedients, such as exchanging the-heat of the 60.
?nished oil such as by passing the finished oil
through exchanger 54 for preheating the OH on
its way to the pipe still. The drawing of my sys
tem is diagrammatic only and it should be
understood that suitable regulating valves, pres 65
fractionation. Relatively pure vapors of the sec
ondary solvent (acetone) are removed from the
sure and vacuum valves, collecting tanks, con
top of the tower through pipe 38, condensed in
stirring means, etc. may be employed wherever
such expedients are necessary. I do not limit
myself to any of the details hereinabove described 70
except as defined by the following claims, which
should be construed as broadly as the prior art
coils 39, collected in storage tank 40, and returned
through pipes 4i and 42 to acetone storage tanks
l1 and I8.
_
'
Relatively pure primary solvent liquid (dichlor
ethyl ether) is withdrawn from one of the plates
above the introduction of oil and solvent from the
75 pipe still and is conveyed in pipe 43 through heat
duits, insulating means, heat exchanger means,
will permit.
*
‘
-
I claim;
1. The method of removing dichlorethyl ether 75
3 .
9,096,950
and acetone from mineral oil which comprises
heating a mixture of these solvents, with Oil to a
temperature of about 400° F., introducing the
heated mixture at an intermediate point into a
rectifying zone, adding liquid acetone at the upper
part of said rectifying zone, withdrawing dichlor
ethyl ether between the point of introduction oi’
the acetone and the point of introduction of the
heated mixture, introducing hot acetone at a
10 point below the point of introduction of the mix
ture whereby it serves as a stripping medium, and
withdrawing ?nished oil from the base of said
fractionation zone.
I,
2. The method of removing dichlorethyl ether
.15 and isopropyl ether from mineral oil which com
prises heating a mixture of these solvents with
oil to a temperature of about 400° F'., introducing
the heated mixture at an‘intermediate point into
a rectifying zone, adding liquid isopropyl ether
at the upper part of said rectifying zone, with
drawing dichlorethyl ether between the point of
introduction of the isopropyl ether and the point‘
of introduction of the heated mixture, introduc
ing hot isopropyl ether at a point below the point
25 of introduction of the mixture whereby it serves
as a stripping medium; and withdrawing ?nished
oil from the base of said fractionation zone.
3. The method of removing dichlorethyl ether
and ethyl acetate from mineral oil which com
the high boiling solvent from the oil, and means
for introducing vaporized low boiling solvent at a
low point to contact directly with the high boiling
solvent and oil for removing the last traces of
high boiling solvent fromthe oil.
5. A method of re?ning petroleum oil which
comprises separating naphthenic from para?inic
constituents of the oil with a solvent mixture in
which the solvents have a boiling point lower
than that of the oil and at least one solvent has a 10
boiling point lower than any other solvent, sepa
rately heating the naphthenic and paramnio frac
tions to temperatures suilicient to vaporize most
of the solvent mixture contained therein, vaporiz
ing the mixed solvents from the heated oil, recti 15
fyingthe vapors to remove oil from the solvents,
and introducing a portion of the lower boiling
solvent into the non-vaporized oil at a tempera
ture sufficient to produce the complete vapori
zation of said lower boiling solvent whereby it 20
serves as a stripping gas to remove the last traces
of solvent from the oil.
,
6. An oil re?ning process which comprises sep
arating para?lnic from naphthenic constituents
of a petroleum oil by extracting said oil with a 25
mixture of a high boiling and a low boiling sol
vent, both of said solvents and the solvent mix
ture having a boiling point below that of the oil,
separately heating the parai?nic and naphthenic '
fractions to-a temperature su?icient to cause va 30
to a temperature of about 400° 'F., introducing , porization of both solvents, separating the va
30 prises heating a mixture of these solvents with oil
the heated mixture at an intermediate point into
a rectifying zone, adding liquid ethyl acetate at
porized solvents from unvaporized oil contami
nated with solvents, rectifying the vaporized sol
the upper part of said rectifying zone, withdraw
vents to remove oil therefrom, introducing con
35 ing dichlorethyl ether between the point of in
‘ densed low boiling solvent for use as a re?ux liq
troduction of the ethyl acetate and the point of
introduction of the heated mixture, introducing
' hot ethyl acetate at a point below the point of
introduction of the mixture whereby it serves as
40 a stripping medium, and withdrawing ?nished
oil from the base of said fractionation zone.
4. In a system of the type described, means for
extracting mineral oil with a mixture of a high
boiling and a low boiling solvent, means for heat
45 ing the extracted oil contaminated with said sol
vents to a temperature at which substantially all
of said solvents are vaporized, means for rectify
ing the vapors to effectively fractionate the low
boiling and high boiling solvent and to separate
uid in said rectifying step, and introducing a por
tion‘ of said low boiling solvent into said unva
porized oil at a temperature high enough to cause
complete vaporization of said low boiling solvent
whereby it serves as a stripping means for re
moving the remaining high boiling solvent from
the unvaporized. oil.
-
'7. Themethod of claim 5 wherein the low boil
ing solvent is superheated prior‘ to its use as a
stripping agent.
'
8. The method of claim 6 wherein the low boil
ing solvent is superheated prior to its use as a
stripping agent.
'
ROBERT E. WILSON.
40
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