U.S. patent number 3,617,476 [Application Number 04/815,233] was granted by the patent office on 1971-11-02 for lubricating oil processing.
This patent grant is currently assigned to Texaco Inc.. Invention is credited to Robert A. Woodle.
United States Patent |
3,617,476 |
Woodle |
November 2, 1971 |
LUBRICATING OIL PROCESSING
Abstract
Lubricating oils of high-viscosity index are produced in good
yield by a sequence involving mild hydrogenation, solvent refining
and dewaxing. The process is particularly effective for the
treatment of lube oil fractions containing at least 1 percent
Conradson Carbon Residue using N-methyl pyrrolidone as the
solvent.
Inventors: |
Woodle; Robert A. (Nederland,
TX) |
Assignee: |
Texaco Inc. (New York,
NY)
|
Family
ID: |
25217250 |
Appl.
No.: |
04/815,233 |
Filed: |
April 10, 1969 |
Current U.S.
Class: |
208/36; 208/18;
208/96; 208/80; 208/143 |
Current CPC
Class: |
C10G
21/12 (20130101); C10G 2400/10 (20130101) |
Current International
Class: |
C10G
21/00 (20060101); C10G 21/12 (20060101); C10G
67/04 (20060101); C10G 67/00 (20060101); C10g
043/08 () |
Field of
Search: |
;208/18,80,108,36,309,96,143 |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
3414506 |
December 1968 |
Van Lookern Compagne |
3472757 |
October 1969 |
Morris et al. |
3201344 |
August 1965 |
Broughton |
3425932 |
February 1969 |
Surrena et al. |
3436334 |
April 1969 |
Orkin et al. |
|
Primary Examiner: Levine; Herbert
Claims
I claim:
1. A method for refining a lubricating oil stock which consists of
passing said lubricating oil stock into contact with a
hydrogenation catalyst under mild hydrogenation conditions
including a temperature between 575.degree. and 800.degree. F., and
a pressure between about 250 and 600 p.s.i.g., to obtain a product
liquid yield of substantially 100 percent, subjecting the resulting
hyrogenation product to solvent extraction at a temperature between
about 120.degree. and 250.degree. F. with a solvent having an
affinity for aromatic hydrocarbons at a solvent to oil volume ratio
of between 1:1 and 6:1 to produce an aromatic-rich extract and an
aromatic-poor raffinate, and dewaxing the raffinate using as
solvent a mixture comprising an alkyl ketone containing from three
to eight carbon atoms and an aromatic hydrocarbon selected from the
group consisting of benzene, toluene and xylene.
2. The process of claim 1 in which the hydrogenation catalyst
comprises nickel and molybdenum.
3. The process of claim 1 in which the solvent having an affinity
for aromatics comprises N-methyl pryrrolidone.
4. The process of claim 3 in which the temperature is between
120.degree. and 180.degree. F.
5. The process of claim 1 in which the dewaxing solvent comprises
methyl ethyl ketone and toluene.
6. The process of claim 1 in which the hydrogenation temperature is
not greater than 650.degree. F. and the hydrogenation pressure does
not exceed 500 p.s.i.g.
7. The process of claim 3 in which the lubricating oil stock
contains at least 1 percent Conradson Carbon.
8. The process of claim 3 in which the solvent to oil volume ratio
is between 1:1 and 3:1.
9. A process for the production of a lubricating oil which
comprises fractionating a crude petroleum oil to recover a naphtha
fraction therefrom, recovering a lubricating oil stock from the
heavier than naphtha fraction, catalytically reforming the naphtha
fraction, separating from the reformer effluent a hydrogen-rich
stream, treating said lubricating oil stock in a process which
consists of contacting same with a hydrogenation catalyst in the
presence of at least a portion of said hydrogen-rich stream at a
temperature between about 575.degree. and 800.degree. F. and a
pressure between about 250 and 600 p.s.i.g, the pressure in the
hydrogenation zone being substantially equal to the pressure in the
catalytic reforming zone, subjecting the resulting hydrogenation
product to solvent extraction at a temperature between about
120.degree. and 250.degree. F. with a solvent having an affinity
for aromatic hydrocarbons at a solvent to oil volume ratio of
between 1:1 and 6:1 to produce an aromatic-rich extract and an
aromatic-poor raffinate, and dewaxing the raffinate using as
solvent a mixture comprising an alkyl ketone containing from three
to eight carbon atoms and an aromatic hydrocarbon selected from the
group consisting of benzene, toluene and xylene.
10. The process of claim 9 in which the hydrogen-rich stream is
passed through the hydrogenation zone on a once-through basis.
Description
This invention is concerned with the treatment of lubricating oil
stocks. More particularly, it is concerned with a novel processing
scheme whereby lubricating oil stocks are converted in good yields
into high quality lubricating oils.
Various procedures are available for the refining of lubricating
oils. For example solvent refining is used to remove low VI
aromatic compounds and reactive impurities by contacting the oil
with a solvent which preferentially dissolves aromatic compounds.
As a substitute for solvent refining, it has been proposed to
subject the lubricating oil stock to relatively severe catalytic
hydrotreating conditions for the saturation of aromatic compounds.
This generally carried out at a pressure between about 1,000 and
2,000 p.s.i.g. Another step in the refining of the lube oil stocks
is solvent dewaxing for the removal of high-melting point wax and
correspondingly a reduction in the pour point of the oil. This is
accomplished by adding a preferential solvent for the oil, chilling
and filtering. Clay contacting has been employed to remove color
clay bodies from the oil to produce an oil of improved color. Color
improvement can also be effected by mild hydrogenation, for
example, at a relatively low temperature and pressure as
distinguished from the hydrogen treatment for aromatic saturation
to improve the viscosity index.
In conventional lube oil refining the solvent extraction step is
carried out first to recover about 45-75 percent of the charge as
refined oil and to reject about 25-55 percent of the charge as dark
colored viscous extract. Since the extract amounts to a relatively
large percentage of the charge and is not suitable for upgrading by
dewaxing and either clay contacting or mild hydrogenation to a
satisfactory quality level for use as a lube oil, solvent
extraction has, up to the present, been the most logical and
economical process to apply first.
The refiner then has the option of removing color bodies from the
oil by mild hydrogenation or clay treating and then reducing the
pour point of the oil by solvent dewaxing or by following the
solvent refining with solvent dewaxing and then with clay
contacting or mild hydrogenation. The choice between these two
sequences is usually made on the basis of which one is the most
practical for a given refinery. For example, if a finished refined
wax is to be produced dewaxing may be chosen ahead of mild
hydrogenation to permit separate treatment of the wax. Different
conditions would then be used on the dewaxed oil than would be used
if the hydrogenation were to precede the solvent dewaxing in which
case wax would be present in the charge to the hydrogenation
reactor.
It is an object of the present invention to provide a novel
sequence for the treatment of the lube oil stocks to increase the
yield of high quality lubricating oils. Another object is to
produce lubricating oils of improved properties such as viscosity
index and color. Another object is to reduce the amount of solvent
necessary for the solvent refining of a particular lubricating oil.
These and other objects will be obvious to those skilled in the art
from the following disclosure.
According to my process, a lubricating oil stock is first subjected
to mild hydrogenation, the hydrogenation product is then solvent
refined and the solvent refined material is then dewaxed. I have
found that by the process of my invention yields of refined oil
obtained in the solvent refining step are in the range of about
10-20 percent higher by volume basis charge to the extraction zone
when refining to the same quality level than when no mild
hydrogenation precedes the solvent refining. In addition, as
compared to raw stocks the mildly hydrogenated stocks have higher
API gravities, lower refractive indexes and higher viscosity
indexes. My novel process also permits reduction in the severity of
the solvent extraction conditions whereby refining solvent dosages
can be reduced when charging the mildly hydrogenated stocks. This
means that in existing units the capacity can be increased or, in
units to be built, smaller units can handle the desired
throughput.
The process of my invention may be applied to any lubricating oil
stock such as a distillate obtained by the vacuum distillation of
crude petroleum or by the deasphalting of a vacuum residuum.
Sources of lubricating oil stocks which may be processed according
to the invention are West Texas crude, Louisiana crude, Coastal
crude and the like. It is an unexpected feature of my invention
that the mild hydrogenation conditions result in increased solvent
refining response not only in light "clean" stocks but also in
relatively dirty stocks containing at least 1percent Conradson
Carbon such as deasphalted residuum. In addition, the combination
of mild hydrogenation with N-methyl pyrrolidone as the solvent
results in products of good color, even when the stock contains
more than 1 percent Conradson Carbon.
The first step in my process is a mild hydrogenation. It is to be
distinguished from the severe hydrorefining used as a substitute
for solvent extraction for the saturation of aromatics to improve
the VI of the lubricating oil. The mild hydrogenation conditions
include a pressure not greater than 600 p.s.i.g, preferably 300-500
p.s.i.g. Temperatures may range from about 575.degree. to about
800.degree. F., preferred range being 575.degree.-650.degree. F.
Hydrogen is introduced into the reaction zone at a rate of
300-5,000 or more s.c.f.b. (standard cubic feet per barrel of
charge), a preferred rate being from 500-2,000 s.c.f.b. Space
velocities (volumes of oil per volume of catalyst per hour) may
range from about 0.2-3, preferably from 0.5-1.5.
The catalyst used in the mild hydrogenation step comprises a
hydrogenating component advantageously carried on an inert support.
Suitable hydrogenating components comprise Group VIII metals or
their compounds such as the oxides or sulfides or mixtures thereof.
Examples of Group VIII metals are iron, nickel, cobalt, platinum
and palladium. Advantageously the Group VIII metal or compound is
used in conjunction with the Group VI metal such as molybdenum,
tungsten or chromium or compounds thereof. The catalyst support
suitably comprises a refractory inorganic oxide material such as
silica, alumina, magnesia, titania or mixtures thereof. The support
should be relatively inert and have little if any activity at
reaction conditions.
Particularly suitable catalysts are those containing from 2-8
percent cobalt or nickel and 5-20 percent molybdenum or 2-10
percent nickel and 10-30 percent tungsten by weight of the total
catalyst composite supported on alumina. Due to the mildness of the
hydrogenating conditions, the liquid yield of product is
essentially 100 percent that of the charge.
The mildly hydrogenated oil is then subjected to solvent refining
with a solvent having an affinity for aromatic hydrocarbons which
is at most only partially soluble in the oil so that two phases can
be formed, an extract phase containing solvent and dissolved
aromatics and a raffinate phase. Suitable solvents are furfural,
nitrobenzene, dimethyl formamide, liquid SO.sub.2 and the like.
Solvents are generally used at dosages of 100-600 percent, at
temperatures between 120.degree.-250.degree. F., preferred
conditions being dosages of 100-300 percent and temperatures
between 120.degree. and 180.degree. F. A particularly suitable
solvent is N-methyl pyrrolidone which can be used at a lower
temperature and lower dosage than the other solvents mentioned
above. In addition N-methyl 2-pyrrolidone is preferred because of
its chemical stability and its ability to produce even lighter
colored refined oils. The other solvents mentioned above also have
a tendency to produce refined oils that are degraded and darkened
in color.
To improve the pour point of the oil the raffinate recovered from
the solvent refining is dewaxed. Dewaxing is generally effected by
contacting the raffinate from the solvent extraction with a
preferential solvent to separate waxy from nonwaxy material.
Suitable solvents comprise a mixture of an aromatic hydrocarbon
such as benzene, toluene or xylene with an alkyl ketone containing
from three to eight carbon atoms such as acetone, methyl ethyl
ketone, methyl propyl ketone and the like. Depending on the desired
pour point and miscibility characteristics, the solvent may contain
from about 40-60 percent ketone and 60-40 percent aromatic
hydrocarbon. Dilution is generally in the range of 1.5-5 parts of
solvent per part of oil. The mixture is chilled, filtered and
washed, the filtering temperature being selected in accordance with
the desired pour point. Generally, the filtering is carried out at
a temperature of from +20.degree. F. to -30.degree. F.
In the following example which is submitted for illustrative
purposes only, oil 1 is a light distillate derived from a mixed
base crude, oil 2 is also a light distillate derived from Louisiana
crude, oil 3 is deasphalted residuum from West Texas Crude and oil
4 is derived from mixed base crude.
In each case, the hydrogenation catalyst contains 2.3 percent Ni
and 10.0 percent Mo (as the oxide) supported on alumina, the
solvent used in the solvent extraction step is N-methyl
2-pyrrolidone and that used in the dewaxing step is a mixture
containing 50 percent methyl ethyl ketone and 50 percent toluene.
Data for the treatment of the various oils appear in table I below.
##SPC1##
It can be seen from the foregoing that the mildly hydrogenated oils
have higher API gravities, lower refractive indexes and higher VI's
than the charge stocks. The mildly hydrogenated oils are also
improved charge stocks for the solvent extraction resulting in
yield increases of up to 10 percent when refining to the same
quality level. This is true even when charge stocks containing more
than 1 percent Conradson Carbon are used. In addition, the
combination of mild hydrogenation followed by extraction using
N-methyl pyrrolidone as the solvent results in finished products of
good color.
Since the hydrogenation step is carried out at such a low-pressure,
my process has advantages over prior art processes. In a specific
embodiment of my invention, a crude oil is fractionated to produce
a naptha, a lubricating oil stock is recovered from the heavier
than naphtha fraction either by vacuum distillation or by
deasphalting the residuum or both, the naphtha is catalytically
reformed and effluent hydrogen without repressuring or purification
is used for the mild hydrogenation of the lube oil stock.
Advantageously, the reformer hydrogen can be used in the mild
hydrogenation step on a once-through basis and returned to the
reformer recycle stream.
Other modifications of the invention as hereinbefore set forth may
be made without departing from the spirit and scope, thereof, and
therefore, only such limitations should be imposed as are indicated
in the appended claims.
* * * * *