Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
OIL COMPOSITIONS
The invention is concerned with improving the
oxidation stability of certain base oils.
Base oil, e.g. lubricating oils,transmission
fluids or industrial oils~ are prepared from various
petroleum feedstocks, e.g. vacuum distillates or de~
asphalted vacuum residues or mixtures thereo~. One
important class of base oil is those base oils having
a viscosity index (V.I.) of at least 94. Since most
feedstocks have a V.I. of below 94j e.g. of from
20 to 85, lt lS important to subject such feedstocks
to a processing step which increases the V.I. thereof
to at least ~4.
It is possible to increase t'ne V.I.cf a feedstock
by solvent extraction alone or by hydrotreating alone
or by both solvent extraction and hydrotreating. The
present invention is particularly concerned with those
base oils prepared by both solvent extraction of the
feedstock, e.g. to an extent such that the solvent-
,
-
'
extracted raffinate has a V.I. of at most 92, and
hydrotreating the solvent-extracted raffinate, e.g.
to an extent such that the resultant base oil has
a V.I. of at least 94. One characteristic of such
base oils is that they sometimes darken and/or form
sludge when exposed to oxygen. This phenomenon is
usually described as oxidation instability.
It has now been found that the oxidation stability
of such base oils is improved by the addition thereto
of a sol~ent-extracted raffinate having a viscosity
index of at most 92 and/or by the addition of a de-
asphalted vacuum residue and/or a hydrotreated de-
; asphalted vacuum residue.
Accordingly, the present invention is concerned
with a base oil composition comprising:(a) a base oil having a viscosity index of at
least 94 obtained by hydrotreating a solvent-
extracted raffinate having a viscosity index of
at most 92, and
(b) a solvent-extrac~ed raffinate having a viscosity
index of at most 92, and/or a deasphalted vacuum
residue and/or a hydrotreated deasphalted vacuum
residue.
The base oil of the base oil composition may be
prepared from an~ suitable petroleum feedstock. As
~z~
stated above the V.I. of such feedstocks is usually
from 20 to 85. Examples of suitable feedstocks in-
clude vacuum distillates, deasphalted residues of
vacuum distillations (deasphalted vacuum residues)
and mixtures thereof derived from crude oils, e.g.
paraffinic crude oils. Distillate feedstocks usually
;~ have a V.I. of from 20 to 60 and residual feedstocks
- usually have a V.I. of from 60 to 85.
Such feedstocks are then solvent-extracted to in-
crease the V.I. Preferably, the ~.I. of the solvent-
extracted raffinate is from 75 to 92. In the case of
a feedstock already having a V.I. of above 75 it is
desirable that it is solvent-extracted to an extent
such that the V.I. of the raffinate is at least 5 V.I.
units above the V.I. of the feedstock. Solvent ex-
traction is a well known technique and suitable solvents
include phenol, furfural or sulphur dioxide. After
extraction an aromatic extract and a solvent~extracted
raffinate are obtained.
~he solvent-extracted raffinate is then hydro-
treated to an extent such that the resultant base oil
has a V.I. of at least 94, suitably of from 95 to 110,
althou~h the V.I. of the resultant base oil ~ay be as
; high as 120 or higher, e.g. above 140 (extra-high
V.I. base oil). Hydrotreating is a well known technique
and usually comprises treating the raffinate with
hydrogen at a temperature of from 350C to 500C, a
pressure of from 60 to 200 bars in the presence of
a catalyst using space velocities of from 0.1 to
2.0 kg feed per litre catalyst per hour. Suitable
catalysts usually comprise one or more of the metals
molybdenum, chromium, tungsten, vanadium, platinum,
nickel, copper, iron and cobalt or their oxides and/or
sulphides, either supported on a suitable carrier~
such as alumina or silica or unsupported. Particularly
advantageous catalysts are the iron transition metals
(iron, cobalt and nickel) and the Group VIB metals
(chromium, molybdenum and tungsten) especially com-
binations of metals from each of these groups, for
instance cobalt and molybdenum, nickel and tungsten,
and nickel and molybdenum supported on alumina. The
catalyst may also contain promoters, such as co~.pounds
containing phosphorus, fluorine or borium. Usually
the V.I. of the solvent-extracted raffinate is in-
creased by at least 5 V.I. units by the hydrotreatment.
It is preferred to add a solvent-extracted raf-
finate having a viscosity index of at most 92 to the
base oil. Suitable amounts of such raffinates are
; from 0.1 to 20%~r, preferably from 0.1 to 10%w based
on the ~reight of the base oil. Suitable solvent
~ :~22~3i~
extracted raffinates having a viscosity index of at
most 92 are those prepared as described above for the
preparation of the base oil. The petroleum feedstocks,
from which such raffinates may be prepared may be
vacuum distillates, deasphalted vacuum distillates or
mixtures thereof. Various combinations are possible,
e.g. a solvent-extracted raffinate derived from a
deasphalted vacuum residue may be added to a base oil
derived from a vacuum distillate or from a deasphalted
vacuum residue, and a solvent-extracted raffinate
derived from a vacuum distillate may be added to a
base oil derived from a deasphalted vacuum residue
or from a vacuum distillate.
The base oil from which the compositions of the
present invention are obtained may be~ or may have
been, subjected to one or more additional processing
; steps, such as a finishing step and/or a distillation
step andlor a dewaxing step. The base oil may be
subjected to a distillation step in order to remove
the more volatile components therefrom. For example
the volatile material boiling below a temperature in
the range of from 200 to 550C may be removed. De-
waxing serves to decrease the pour point of the feed-
stocks by removing wax therefrom and is usually carried
out after the hydrotreatment step. Finishing steps
:
` -
include clay and/or acid treatments and/or hydro-
finishing treatment.
In addition, the solvent-extracted raffinate,
which is preferably added to the base oil, may be,
or may have been, subjected to one or more processing
steps, such as a dewaxing step. Tne raffinate may be
dewaxed in admixture with the base oil.
The base oil compositions of the present in-
vention are suitably used as lubricating oil com-
positions for internal combustion engines and maycontain one or more conventional additives~ such as
viscosity index improvers, anti-wear/extreme-pressure
additives, detergents, anti--rust additives, pour
point depressants and other anti-oxidants~ e.g.
secondary amines, and/or other daylight stabilizers,
such as quinones (e.g. tetrabutyldipheno~uinone).
The invention will now be illustrated by reference
to the follo~ing Examples. In the Examples the ~.I.'s
and viscosities were determined on dewaxed samples.
EX~MPLES 1, 2 and 3
~ base oil was prepared by extracting a vacuum
distillate (derived from a light paraffinic crude oil)
having a V.I. of 54.5 and a viscosity of 5.03 centi-
stokes at 98.9C. The extractant used was furfural and
the solvent extracted raffinate had a V.I. of 87
,. ~
The raffinate thus obtained was treated with hydrogen
using a Ni/~.~ alumina supported catalyst, at a temper
ature of 361C, a pressure of 90 bar and a space
velocity of 1.5 kg feed per litre catalyst per hour.
The hydrotreated base oil was then distilled to re-
move components having a boiling point of below about
365C and dewaxed with a mixture (50/50) of methyl-
ethylketone (MEK) and toluene. The V.I. and viscosity
of the dewaxed and distilled hydrotreated base oil
was 95 and 4.27 centistokes at 98.9C respecti.vely.
The final base oil was subjected to an oxidation
stability test. This test comprised blow~ng air through
the base oil at a temperature of 160C for 168 hours
at the end of the test the amount of sl.udge formed,
the acidity and the viscosity increase of the base oil
were determined. The results (~xample (a)) are given
in Table I.
Base oil compositions according to the present
invention were then prepared by adding various amounts
of a solvent-extracted raffinate having a V.I. of 88
and a viscosity of 40.8 centistokes at 98.9~. The
raffinate ~as prepared by ex.tracting a deasphalted
vacuum residue ~derived from a light paraffinic crude
oil) having a V.I. of 66 and a viscosity of 56.9 centi-
stokes at 98.9C with furfural followed by dewaxing
~ . ,
with a mixture (50/50) of MEK and toluene. The baseoil compositions obtained were subjected to the
oxidation stability test as described above. The
results (Examples (1) and (2)) are also given in
Table I.
Another base oil composition according to the
present invention was prepared by replacing the
solvent-extracted raffinate with the deasphalted
vacuum residue, after dewaxing as described above,
from which it was prepared. The base oil composition
was also subjected to the oxidation stability test
as described above. The results (Example (3)) are
. also given in Table I.
,~.` .
.2~ 9~
TABLE I
. _ -- ,_, __. r ., ~ . _~
Ex- Additive (%w) on Oxidation stability
_ base oil I
ample solvent de- sludge, acid- vis-
extract- asphalt- %w on it~J, cosity
ed raf- ed vacuum com- mg in-
finate residue position 100 g crease
: (a) _ _10 3o 510
1 52 ~ 77 ~.2 24
; 3 _ 2l.9 ~.~ ~ ,
EXAl~PLE 4
Example 2 was repeated with the differences that
the vacuum distillate, from which the base oil was
prepared, had a V.I. of 29 and a viscosi.ty o~ 18.0
centistokes at 98.9C, that the solvent-extracted
raffinate had a V.I. of 88 and a viscosity of 12.2
centistokes at 98.9C and that the base oil~ after
hydrotreatment, had a V.I. of 97 and a viscosity of
10.5 centistokes at 98.9C. The solvent-extracted
raffinate added thereto was as described for Example
2. The base oil (Example (b)) and the base oil com-
position were subjected to the oxidation stability
2~
test; as described abo.ve. The result;s are given in
Table II.
TABLE II
. _ _ .. ._
Ex- Additive (%w) on Oxidation stability
ample base oil _
sludge, acid- vis-
%w on ity, cosity
: com- mg in-
~ position eq / crease
. . .. _ ___ _ . _ _ . _
(b) _ 0.05 26 360
4 5 0.05 1.4 17
EXAMPLES 5 and 6
A base oil was prepared by extracting a vacuum
~:5 distillate (derived from a paraffinic crude oil)
having a V.I. of 48 and a viscosity of 17.~ centi-
stokes at 98.9C. The extractant used was furfural
and the solvent-extracted raffinate had a V.I of
82 and a viscosity of 13.5 centistokes at 98.9C.
.lO The solvent-extracted raffinate was hydrotreated,
distilled and dewaxed as described in Examples l and
2 and the V.I. and viscosity of the dewaxed and
distilled hydrotreated base oil was 96 and 10.15
centistokes at 98.9C, respectively. This base oil
(Example (c)) ~las then subjected to the oxidation
stability test as described above.
Base oil compositions according to the present
invention were then prepared by adding to the base
oil various amounts of the solvent-extracted raf-
finate having a V.I. of 82 and a viscosity of 13.5
centistokes at 98.9C after dewaxing with a mixture
(50/50) of MEK and toluene, and also subjected to
the oxidation stability test. The results are given
in Table III.
TABLE III
Ex- Additive (~w) on Oxidation stability
. amplebase oil ~
: . . sludge~ acid- V15-
%w on ity, cosity
com- mg in-
_ t}on es / cr~ase
(c) _ nil 14.9 94
0.5 nil 3.6 15 ~:
; 6 3.0 nil 1.7 7-7
. _ _ . ~ . .
