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Патент USA US2137209

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Patented Nev. 15, 193s
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2,137,209`
_UNITED STATES PATENT oFF1cE~
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»2,137,209
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i
DEWAXING MINERAL UIL
Edwin C. Knowles, Beacon, N. Y., assigner to The
Texas Company, NewYork, N. Y., a corpora
tion of Delaware
`
_ Application September 20, 1935, Serial No.`41,`393
5 Claims. ((1196-18)
This invention relates to the separation of wax jected to the preliminary heating stepoi' my in
from oil.
„
.
«
vention.
'I'he invention contemplates a process of de_ waxing wax-bearing mineral oil containing either
5 a naturally-occurring or an added wax crystal
modifying substance, wherein the oil is mixed
with a solvent liquid, the resulting mixture of oil
and solventheated to an elevated temperature,
and the heated mixture thereafter chilled to pre10 cipitate the wax constituents which are subse. quently removed.
_
,
,
The filter cake obtained by the practice of my
invention is less voluminous, retains less oil, and
comprlsesahigher content of parafiin wax. Fur- 5
thermore, there is an increase in the yield of- wax
free oil obtained as a result of followingthe pro- '
cedure of my invention.
This improvement in filtration rate is appar
ently due to the beneficial change inthe nature
mmof the crystal formation of the'wax precipitated ,
The invention has particular reference to de-
from mixtures which have been subjected to the
waxing relatively viscous oils having a Saybolt
preliminary heating'step, although the reason for .
Universal viscosity above about 80 seconds at 210°
this change in'_ the crystal structure is not_ en
15> F. as, for example, an oil of around 90 or 100 sec-ß _ tirely understood.
_
15
onds at 210° F. and containing naturally-occur- ` ’ It is my thought that, in the case of- viscous
ring asphaltic and resinous constituents which
zoils, certain of the naturally-occurring asphaltic _
apparently modify the crystal form of the wax,
and resinous hydrocarbon constituents constitute
as will be more fully explained below.
wax -crystal modifying substances.
The in-
20 vention involvesI dewaxing oil of >this 'character
under conditions such that these naturally-occurring constituents apparently facilitate crys-
These con-
_
stltuents are believed to >be less soluble than wax 2o
in the dewaxing solvent liquid, and at the min
imum temperature at which the wax-bearing oil -
¿tallization of the wax in a more readily separable - appears to be in complete solution, these constit- .
and ñiterable form.
25
uents are not in true solution _but rather »are pres
'The invention is also applicable to‘dewaxing
oils containing Wax crystal modifying substances
or materials which have been added thereto. I
have found it advantageous toV add wax crystal
modifying materialto relatively low viscosity oils
3o which are dencient in the naturallyeocé'urring
modifying material above referred to, and then
ent as a colloidal solution.
'
25
In this form,theSE SubSiîanCeS DOSSìblXfOI‘mÍ'ìÍmS
011 the-Small Plate-WPG paraffin Crystals formed
during preliminary precipitation of the wax from
the solution, and these films inhibit the normal '
transformation of the plate-type wax crystals 30
111130 the mOI'e easily ñlterable type of crystals.
dewax them by the process of my invention.By 'heating t0 temperatures 0fA 15° to 50‘.’ F.
The invention specifically contemplates heating above this minimum temperature of apparent
the mixture of dewaxing solvent and waxmeàrmg complete solution, these colloidal or lowI solubility
36 oil containing such Wax crystal modifying sub- "substances are apparently completely diâsolved in 35
stance to a. temperature of around 15° to 50° F_
the solvent. It is believed that upon chilling the
above the minimum temperature at which the heated solution, they precipitate f_rom the solu
oil and wax appears to be completely dissolved ,tion substantially ‘5o-extensively with the wax m
in the solvent, and thereafter chilling the heated
40 mixture to a temperature of the order of o., E
.in order to precipitate the wax ‘constituents in
‘ readily separable form
I have discovered thatwhen such wax-bearing
oil and solvent mixture is subjected to heating'y
,
at thef‘e elevated temperatures prior to chilling'
there 1s a marked improvement in the character
of the wax precipitated from the chilled
t
, ure'
Th
i
the form of nuclear particles which actually fa" l
cilitate crystallization. of wax _in a more readily 4
separable and mtemble form' .It is thought that l
the optimum effect is realized when the modify
ing substance continues to preciplta'te from .the
“mon over the entire range of Wax crystalhza
on.
_
,
Ihave found that the modifying action of added
45
wax crystal modiñers may be greatly enhanced
t l t
t
.
m x' ' by the procedure of my invention, and particu
e “YS -2' s fue ure of the Wax is Such l. larly in the case of relatively less viscous oils as,.
50 that the wax 1s more readily separated from the ' for example' oils having a, viscosity up to about -50
mïxtm‘e and can be more fapldly ñlßeœd there-_ "15 Saybolt Universal seconds at 210° F. Some
.fIOm- _AS a CODSSQUÉDCG, the filter rates can _be
improvement results, however, even in thecase
increased ten 'or twelve times over the rate ob-
of the more viscous oils by adding some of this
taining in the ordinary de-waxing procedure
material thereto and lproceeding by the method
55 where the mlxtul‘e 0f Oil and Solvent 1§ not Sub-
of this invention. Such added modiñers may 55
2
2,137,209
comprise small amounts of Montan wax, or syn
thetic modifying substances such as derived by
condensation of chlorinated wax and naphtha
lene, and aluminum stearate, etc. The amount
of such modifying material added may be of the
order of 0.20 to about 1% by weightof the wax
bearing oil.
,
. . It is thought that, as in the case ofthe nat
urally-occurring Wax crystal modifying sub
10 stances, these added substances probably are
precipitated from the previously heated solution
in a form in which they act as nuclear particles
serving to modify wax crystallization, with the
result that the Wax can be more readily filtered
15 from the chilled solution.
'I'he minimum temperature at which the wax~
bearing oil appears, on visual inspection, to be
completely soluble in the dewaxing` solvent, orin
homogeneous admixture therewith, depends upon
20 >the nature of the oil as weil as upon the solvent.
In the case of a selective dewaxing solvent of the
.character of a mixture of about 30% acetone and
_ 70% benzol, for example, the minimum tempera
' ture of apparent complete solution of wax-bear
25 ing oil in the-solvent may range from around 90°
to 125° F., the minimum temperature for rela
tively viscous oils being in the upper portion of
this temperature range.
.
~
My invention, therefore, comprises heating the
four parts of solvent mixture to one part of oil.
After heating the mixture to the desired solution
temperature, it was then introduced to a chilling
vessel wherein it was chilled by indirect contact
with cold brine to a temperature of --10° F. 'I‘he
chilled mixtures were all filtered at this tem
perature to remove the wax and produce nitrates
containing oil of about 0° F. pour. Filter rate
calculations are all based on the passage of an
equal volume of wax-free oil through the filter 10
surface, that is, 0.2 gallon of wax-free oil per
square foot of ñltering surface.
As shown by curve A1 where the solvent and
wax-bearing oil mixtures were heated to a tem
perature of only 120° F. prior to chilling, a filtra
tion rate of about 1.7 gallons of wax-free oil persquare foot of filtering surface per hour was
realized.- On the other hand, when the solution
was heated to a temperature of 150° F. prior to
chilling, the filter rate was increased to 24 gallons
of -Wax-free oil per square foot of ñltering surface
per hour.
1
'
-
It will be observed that heating the mixtures
to temperatures in the range below 120° F. andV
also in the range above i60-170° F. does not ap
pear to affect the filtration rate, but between
these points the increase in filtration rate with
increasing mixing temperatures is quite rapid;
In the experiments represented by curve _A1,
30 mixture of wax-bearing oil and selective solvent,
the mixture of wax-bearing oil and solvent was 30
l`such as a mixture of acetone and benzol, to tem- , subjected during the chilling step to mild agita- -
peratures in the range of about 125° to 175° F.,
and then chilling the heated mixture to tempera'
tures of 0° F. and below in order to precipitate
35 the wax constituents.
These wax constituents
are then separated from the cold mixture,- advan
tageously by filtration.
'
'I'he invention is particularly advantageous as
applied to the dewaxing of distillate and residual
40 wax-bearing oils which contain small amounts of
asphaltic and resinous matter. For this reason,
it is particularly adapted to dewax relatively vis
cous oils, including those which have been sub
jected to previous solvent reñning action to re
move relatively low viscosity index constituents,
and which are ordinarily rather difficult to dewax.
The improvement in filtration rate is indicated
by reference to Figure 1 of the accompanying
l drawings.
Curves A1, A2 and B in this 'figure
represent graphically the relationship between
filtration rate and the temperature of heating
prior tœchilling in the case of dewaxing both a
distillate and a residual type of stock, each of
tion by bubbling pre-cooled nitrogen gas through
the mixture at the rate of about 4.8 cubic feet
of gas »per hour per square foot of horizontal
cross-sectional areal of the vertical chilling vessel.
The chilling vessel comprised a vertical cylin
drical vessel, and the gas was introducedl into the
battom thereof and caused to bubble upwardly
through the mixture of oil and solvent contained
therein.
_
'
.
"
40
.
Curve Az represents the filtering rates ob
tained with the same stock, using the same sol
vent but employing mechanical stirring instead
of gaseous agitation. The mechanical stirring in
this instance .-was effected by inserting a mechan 45
ical stirring arm into the same chilling vessel
used in the preceding experiments. The stirring
arm was rotated 'at a uniform rate of about five
revolutions per minute.
Under these conditions, the optimum ñltration- 5.0i
rate,_îwhen heating to temperatures of 150° F., is
only about eight gallons of wax-free oil per
square foot of filtering surface per hour.
How
which had been previously subjected _tg solvent ever, without such preliminary heating as, -for
65 extraction for the removal of relativelyv low vis
temperature of around 120° _F., the filtration
late to dewaxing the same _,distillatestock, while
ratev is only about one gallon per square foot of
filtering surface per^hour at the same rate of
` curve _B relates to dewaxing the residual stock,
60
using methyl- ethyl ketone and benzol -as a de
mechanical agitation.
«
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It appears, therefore, that in order to rea
waxing solvent. Laboratory inspection tests
made on these two stocks gave the following the optimum effect of preliminary heating, it is
results:
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'
desirable to employ relatigely mild agitation
_.
Distillate
stock
Gravity, "A, P. I _________________________ __
S. U. viscosity at 160° F
S. U. viscosity at 210° F
70
example, when heating the oil and solvent to a 55
cosity index constituents. Cur'v/es A1 and Az re
Percent carbon residue.
Percent paraffin _________ _,
Pour test °F ..... __,__-. __________________ __
during the subsequent chilling "step, and prefer
ably the type of agitation such yas is realized by
Residual ’ bubbling a stream of gas at a relatively low rate
65
stock
through the chilling mixture.-- _ cessiveqme
26.9
28.4
282
112
260
107
. 32
11. 5
. 29
10.9
120
11o-115
In both cases, the solvent comprised a‘ mixture
composed of 40% methyl ethyl ketone and 60%
75 benzol, mixed with the oil in the proportion- of
chanical agitation or violent l.agit _ tion of any
type tends to deform the wax crystals and ender
the wax much more difficult to filter.
Curve B represents the results obtained in the 70
case of a residual lubricating oil stock, and since
mechanical agitation, rather than gaseous agi
tation, was lemployed in chilling the solutions of
residual oil and solvent, the curve is very similar
to curve Aa for the distillate oil dewaxed under
3
2,137,209
the same conditions.
In any case, as shown by
curve B, heating the mixture _of residual stock
and solvent to a temperature of about 160° F.
results in a very great increase in the rate of
CIL filtration. The general characteristic of curve B
is similar to that of curve A1, indicating that the
application of the'process of this invention to
residual stocks produces the same improved re
sults as in the case of -viscous distillate lubricat
10
ing oil stocks, providing that the mixture, during
the chilling step, is subjected to relatively mild
agitation.
/
per square foot of iilter surface area per hour was
realized.
It will be observed, however, that in general
much higher rates of filtration were realized
where gaseous agitation was employed. There
was less variation in theñlter rate over the range
investigated, and the results indicated that when
the mixture undergoing chilling is agitated, by
bubbling gas through it at the rate of about 4.8
cubic feet of gast per hour per square foot of 10
cross-sectional area, a high filter rate is obtained.
It appears, therefore, that when the mixture l
The following tabulation affords a comparison
of the eiïect upon filter rates ~by varying thel
degree and type of agitation employed during the
is >agitated by bubbling gas therethrough. at a
relatively low rate, the wax crystals are sub
jected to less deformation than when subjected to
chilling step in dewaxing a distillate stock, such , mechanical stirring. Mild agitation, of course,
as that described above, with the same proportion
of solvent mixture of the same solvent composi
tion 2`
_
maximum degree of benefit by preliminary heat
ing of the wax-bearing oil and solvent _is depend
ent upon employing the proper ratio of solvent
Mechanical agitation ’
Tempera
ture of
solution
prior to
chilling
165
»
Filter rate
140
1.3
l. 2
sired as, for example, as high as four lor six parts
140
`l00 Y
l. 4
165
55
2.3
5
1l. 4
of solvent to yone part of oil.
îure of
solution
prior to
» Wax-bearing oil from a source not shown .is
Filter rate
delivered by a pump I to a mixer and heater 2.
The dewaxing solvent, from a source not shown,
feet of gas gallons of wax
persquare
free oil per
foot per
square foot
hour
per hour
°F.
170
170
170
150
`150
15. 1
4. 8
l. 6
22. 0
18.0
16.8
16. 8
12. 0
12. 5
15.3
150V
15.1
i7. 7
chilling .
110
Cubic
is delivered by a pump _3_to the mixer and heater
."2 wherein it undergoes mixing with the Wax
In making these comparisons, the mixture of
wax-bearing oil and solvent was subjected to
chilling in the same chillingvessel, regardless of
the type of agitation employed. Mechanical agi
tation comprised the insertion of a rotating
stirrerin the chilling vessel which was caused
to revolve _at rates varying from 5 to 140 revolu
tions per minute.
v
~
30
v
In order to more fully describe the -operation
of my invention, reference will now be made vto
Figure 2 of the drawings, illustrating a method
of flowadapted to the practice of my invention.
Gaseous agitation
Tempera-
In the case of oils up to about
'15 seconds viscosity at 210°
a suitable mix
ture comprises one part of oil to one part of sol
'vent. For more viscous oils, the \mixture may
comprise two parts 'of solvent to onèîpart of oil.
Larger proportions of solvent may be used if -de
165
165 f
mixture to oil.
Revolu- gallons of wax
tions per
free oil per
; minute
square foot
per hour
165
~
is necessary in ord-er to realize uniform chilling
of the mixture.
I have also found `that the obtaining of the
’
The gaseous agitation was effected by bubbling
nitrogen gas through the mixture in the chilling
vessel, with the stirrer removed, at rates of from
1.6 to 22 cubic feet of gas per hour per square foot
of horizontal cross-sectional area of the vertical
60
chilling vessel.
,
In the runs in which the mechanical stirrer
was employed, the mixture of wax-bearing oil
vand solvent was heated to the same solution tem
perature of 165° F. prior to chilling. 'I'he results -
obtained indicated that where rapid mechanical
agitation is employed as, for example,' at rates
of around 50 to 140 revolutions per minute of the
stirrer, the filtration rate is relatively low, in the
neighborhood of one or two gallons per square
foot of filtering surface per hour.v However, by
reducing the stirring rate to around ñve revo
lutions per minute, there is a very marked in
crease in the filtration rate; that
with this
75 low-rate-of stirring, a filter rate of 11:4 gallons
bearing oil, and theresulting mixture is heated 40
to a super-solution temperature, for example, in
the range -of about 130° to 170° F.
From this mixer, the heated mixture is then
conducted through a pre-cooler 5 wherein it is
cooled by indirect heat exchange with a cooling
medium which may comprise water.
The cooled> mixture is thereafter conducted
through heat exchanger 6 wherein it is further
cooled as, for example, by indirect heat exchange`>
with a flowing ‘stream of dewaxed oil, leaving the
filter-referred Ato later.
,
The resulting cooled mixture is then introduced
to the top of a vertical pipe chiller or series of
» such vertical pipe chillers 1.
The chiller 'l ad
vantageously comprises a vertical vessel provided
with an annular jacket through which cold brine
is circulated.
'
'
'
f 'I‘his chiller 1 is provided with an internal scroll
type of scraper >il adapted to scrape adhering Wax
from theinterior surfaces of the chiller. A dis 60
tributor 9 is positioned in the bottor'n of the chill
er for introducing gas to the lower portion
_ thereof.
'
`
The mixture of wax-bearing oil and solvent in
troduced to the upper portion of the chiller 1
moves downwardly therethrough countercurrent
1y to the rising gas, which latter is introduced
at a rate suiiìcient to eñect relatively mild agi
tation of the body of liquid within the chiller 1.
From vthe bottom of the chiller 1, the chilled
mixture, at a temperature of the order of 0° F.
and ïbelow, and containing precipitated wax, is
removed, either directly to a filter I0, or to a
surge tank“ ll.
‘
Thesurge tank Il also advaiïtageously'bom- 75
4
ci
2,137,209
prises a vertical vessel provided-with means for
introducing gas through a distributor I2 for the
purpose of maintaining the contents in a gently
cake. The-ñlter cake was removed without wa‘sh
ing with a solvent. This cake, after removal of
agitated condition.
around 44% to 46% of paramn wax of 146° to 148°
`
The iilter I0 advantageously comprises a con
tinuous type of vacuum filter` by means of which
the precipitated wax is removed from the cold
solution as a filter cake.
‘
The resulting ñltrate, which is still at a low
10 temperature, may be passed, all or in part, in
heat exchange relationship with the fresh charge
flowing through the heat -exchanger 6.
Thereafter, the warm dewaxed solution is con
ducted to a solvent recovery system not shown,
15 wherein the solvent is stripped from the dewaxed
oil and returned for further use.
The gas used for agitation purposes in the
chiller l and the surge tank Ii may comprise any
suitable inert gas, such as carbon dloxidefnitro
20 gen, ilue gas, or a volatile petroleum hydrocarbon.
the solvent, comprised -slack wax containing
F. melting point.
The filtrate, after removal of the solvent, had a
pour test of around 0° F. and comprised 71% of
the‘ undewaxed distillate. This filtrate was pro
duced at the rate- of 22 to 25 gallons per hour
per square foot of filtering surface, when calcu 10
lated on the basis previously given.
The results thus Obtained indicated that the
i‘llter rate was increased approximately twelve
times over _that obtained when the mixture of
wax-bearing oil and solvent wasv not subjected 15
to heating above 115° or 120° F. prior to chilling.
The yield of wax-free oil, without subjecting the
filter cake to a solvent wash.' was increased
around 10%. At -the same time, the volume of
the wax cake was about 35% less, While the 20
The make-up gas is taken from a gasometer ~ paraiiln vwax content of this wax cake was in- i
I3 by means 'of a pump or compressor I4 and creased by about '7% or 8%.~ o
-
delivered along with the recycling gas to the lower
portion of a gas chiller I5 wherein it is chilled
to the appropriate temperature, preferably
around 0° F. and below. »
In the gas chiller I5, the circulating gas is
brought into indirect heat exchange relationship
with a refrigerant, such as vaporizing- ammonia.
30
If desired, the circulating gas may be caused
The ?lter cake comprised- crystalline wax
which was compact and relatively free from oll,
characterized by the fact that it ñltered or 25
'drained quite easily as contrasted with the mushy,
bulky and slow-filtering filter cakes obtained in
prior methods of dewaxing.
‘
While a speciñc example using a solvent mix
ture composed of methyl ethyl ketone and 30
to bubble through a body of liquid, such as a por-> »benzol has been referred to, nevertheless the
tion of the dewaxing solvent, which ls main
tained in indirect contact with a refrigerant fluid.
It may be of advantage to employ the latter
means of cooling the circulating gas so that the
latter will always be saturated with dewaxing
solvent vapor, and thus not disturb the ratio of
solvent to oil being maintained within the
chiller 1.
40
.
'
The chilled .circulating gas is conducted from
the upper portion of the gas chiller I5 to the
distributor 9 in the bottom of thel chiller 1.
In a similar manner, a portion of the chilled
gas is circulated through the contents of the
surge tank I I, and from there returned to the gas
chiller
I5.
_
’
_ As a specific example in the carrying out of
method of this invention is also applicable to de
waxing with other solvents or solvent mixtures.
I have found that substantially the same results
are obtained when employing a solvent mixture
consisting of 30% acetone and 70% benzol with
the same wax-bearing stock.
As examples of other solvents which may be
used in connection with this invention, methyl
isobutyl ketone may be mentioned, and mixtures
of methyl ethyl ketone and aliphatic ethers, such
as isopropyl ether and dibutyl ether. I have
found that the method of this invention is par
ticularly advantageous in the'case of mixtures
consisting of about equal parts of methyl ethyl
ketone and isopropyl ether, for example.
Solvent mixtures composed of mixed aliphatic
ketones, such‘as a mixture of dipropyl ketone
distillate was ilrstextracted with furfural to re
with methyl ethyl ketone or with methyl isobutyl
move the relatively low voscoslty index co‘iistit
ketone, may also be advantageously .employed in 50
uents, then dewaxed according to the following the practice of my invention.
I have found that the application of the step
This wax distillate was derived from Mid-Con
of heating the wax-bearing oil and solvent mix
tinent crude, and after solvent extraction with ture prior to chilling produces improved results
55 furfural had tests similar to those of the distillate "v in the case of dewaxing with the foregoing
stock already referred t6 in connection with the solvents or solvent mixtures.
`
discussion of «Figure 1.
`
Thus, for example, when dewaxing the above
This=furfural-reiined-iwax distillate was mixed -~ lubricating oil distillate stock and methyl isobutyl
with a mixture consisting of 40% methyl ethyl
ketone, I have found that a illtering rate as high
60 ketone and 60%- benzol in the proportion of four as 63 gallons per square foot of filtering surface 60
parts of solvent mixture to one part of distillate. per hour may be ~obtained by ilrst heating the
This mixture _of oil and solvent was then heated mixture of oil and solvent to a temperature of
toa temperature of 140° F.
175° F. prior to chilling. This is to be compared
Following this, the hot mixture was cooled to with a ñltering rate of only about one gallon per
- a temperature of -10° F. during which cooling it square foot of filtering surface per ho'ur where
was subjected to mild agitation by bubbling the mixture is not heated to temperatures above 65
nitrogen gas therethrough. The cooling was ef
130° F. prior to chilling. ’_This comparison was
fected in a vertical cylindrical vessel provided made using four parts of solvent to one part of
with means for introducing gas to the lower por
oil and dewaxing at 0° F. to produce` an oil of
tion thereof. The gas was thus introduced to the around zero pour test.`
v
70
chilling vessel at the rate of aboutiive cubic
The examples referred to above specifically
the process of my invention, a sample of wax
procedure.
'
’
'
feet per hour per square foot of horizontal cross
describe dewaxing relatively viscous oils. Itis
sectional area of the chiller.
The ~cold mixturewas then ñltered in a vacu
contemplated, however, that the invention is ap
plicable to the treatment of relatively less viscous
um ñlter to remove the solidified wax as a ñlter
oils containing wax crystal modifying substances.
A
~
5
2,137,209
ture not inexcess of about 125° F., and such that
Obviously, many modiñcations and variations
upon chilling amixture of the oil and solvent to
precipitate wax, and removing the waxso pre
of the invention, as hereinbefore set forth, may
be made Without departing from the spirit and
scope thereof, and therefore only such limitations
cipitated, the resulting dewaxed oil, after removal
should be imposed as are indicated in the ap--
pended claims.
I claim:
of the solvent, will have a pour test correspond
ing Isubstantially to the temperature at which the
wax was removed, heating the solution to a tem
perature around 160 to 170° F. such that upon
chilling to about 0° F. and filtering, the rate of
iìltration is substantially greater than that 0b 10
tained, and a waxv cake is secured having a bulk
.
1. The method of separating wax from mineral
oil which comprises mixing the oil and Wax con
taining Wax crystal modifying material with a
selective solvent such that the wax and oil appear
to be completely dissolved therein at a tempera
ture not in excess of about 125° F., and such that
upon chillinga mixture of the oil and solvent to
not more than two-thirds the bulk secured, by -
Vheating only to about 125° F., chilling the heated
mixture to precipitate wax and removing the Wax
precipitate wax, and removing the wax so pre
_ cipitated, the resulting dewaxed oil, after removal
. of the solvent, will have a pour test correspond
ing lsubstantially to the temperature at which the
wax was removed, heating the solution to a tem
20 perature above 150° F. such that uponlchilling to
about 0° F. and filtering, the rate of filtration is
thus precipitated.
`
5. The method of separating wax from mineral
oil which comprises mixing the oil and wax con
taining wax crystal modifying material with a
selective solvent comprising a mixture of a low
molecular I weight aliphatic ketone and an 20
aromatic hydrocarbon such that the wax and oil
substantially greater than that obtained, and a ‘ appear to be completely dissolved therein at a
wax cake is secured having a bulk not more than temperature not in excess of about 125° F., and
~. two-thirds the bulk secured, by heating only to
A25 about 125° F., chilling the’heated mixture to pre
cipitate wax and removing lthe wax thus pre
cipitated.
such that upon chilling a. mixture of the oil and
solvent to precipitate wax, and removing the 'wax
so precipitated, the resulting dewaxed oil, after
25'
' removal of the solvent, will have a pour test cor
2. The method, according to claim 1, in which I responding substantially to the temperature at
which the wax was removed, heating the solution
the selective solvent comprises a mixture consist
30 ing of a. low molecular weight aliphatic ketone to a temperature around 160 to 170° F. such that 30
upon chilling to about 0° F. and ñltering, the“
>and an aromatic hydrocarbon.
3. The method, according to claim 1, in which
the selective solvent comprises an aliphatic
ketone containing up to seven carbon atoms.
35
.
rate of ñltration is substantially greater than
that obtained, and a wax cake is secured having
a bulk not more than two-thirds the bulk secured,
v4. The method of separating wax from mineral by heating only to about 125° F., chilling the as
heated mixture to precipitatewax and removing
oil which comprises mixing the oil and wax con
taining wax crystal modifying material with a >the wax thus precipitated.
selective solvent such that the wax and oil appear
. to be completely dissolved therein at a tempera
Enwm c. rcuovvrnsus.A ' i
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