Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~8447
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The invention relates to a process for the preparation
of a lubricating oil with a low pour point.
It is known to prepare lubricating oils by a two-step
hydrotreatlng of deasphalted waxy mineral oil fractions~
followed by a dewaxing step. The yield of :Lubricating oil
with a preset viscosity index often leaves to be desired.
It has now surprisingly been found that the yield of -~
lubricating oil which can be achieved, depends on a proper -~
choice of temperature and catalyst in the two steps, and
on the use of the liquid effluent from the first hydro-
treating step in the composition in which it becomes
available as feed for the second hydrotreating step.
Acoordingly, the invention provides a process for the
I preparation of a lubricating oil with a low pour point,
¦ 15 which comprises contacting in a firist zone a substantially
¦ asphaltene-free waxy mineral oil fraction with a supported
catalyst containing one or more metals ~nd/or compounds
- thereof) of Group VI and/or of Group VIII of the Periodic
Table of Elements, in the presence of hydrogen at a temper-
ature of ~rom 390-450C, contacting in a seoond zone at
least part of the liquid effluent of the first zone in the
composition in which it becomes available, with an acidic
supported catalyst containing one or more metals (and/or
oompounds thereof) of Group VI and one or more non-noble
metals ~and/or compounds thereof) of Group VIII of the
Periodic Table of E1ementsg in the presence of hydrogen at
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~1088447
a temperature between 350 and 390C, and optionally
dewaxing all or part of the effluent of the said second
zone. ~-
Suitable starting materials for the process according
to the invention are high-boiling hydrocarbon mixtures,
e.g., heavy petroleum fractions, and also heavy fractions
obtained by pyrolysi~ of coal, bituminous shale or tar
sand, which in the context of this invention are con-
sidered to come within the term substantially asphaltene-
free waxy mineral oil fraction. Petroleum fractions boilingat least in part above the boiling range of lubricating
oil may be used to advantage. As feed ~or the present
process use i8, preferab~, made of a distillate ~raction
reoovered by vacuum distillation from a residual oil
fraction obtained by atmospheric distillation. The boiling
range of such a vacuum distillate is usually between 350C
and 550C. However, dea~phalted residual petroleum fractions
may also be used.
The process according to the invention is carried out
at ~levated temperature and pres~ure and in the presence of
hydrogen or a hydrogen-containing gas in the first and second
zones. Pure hydrogen may be used, but this is not necessary.
~ A gas with a hydrogen content of 70% or more by volume is
i ~ perfectly suitable. In practice it will be preferable to use -
.. . .
-' 25 a hydrogen-containing gas originating from a catalytic re-
I forming plant. Such a gas not only has a high hydrogen content
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but also contains low-boiling hydrocarbonsl for example,
methane, and a small quantity of propane. 1~
Pressures lower than 50 kg/cm2 in the first and the ~ -
second zone are less desirable since they reduce the life
.... .: . .:
of the catalysts while involving the risk of too high an
aromatics content in the product, as a result of which ;-
the viscosity index is adversely affected. A pressure
above 250 kg/cm2 would require a very costly installation.
It is preferable to use a pressure between 100 and 200
kg/cm2.
!
The liquid hourly space velocity and the hydrogen/oil
ratio may be selected between wide limits. It is pre~erred,
however, to select a liquid hourly space velocity between :
0,1 and 10 kg o~ oil per hour per litre of catalyst. A
liquid hourly space velocity of less than 0.1 kg/hour per
litre Or catalyst would require uneconomically large re-
!: actors for a given degree of conversion, whereas a liquid ~;
hourly space velocity~of more than 10 kg per hour per
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litre of catalyst would give only a low degree of conversion
into the desired product. The hydrogen/oil ratio is, prefer- ;
ably, between 100 and 5,000 standard litres (litre~ at
1 bar and at 0C) per kg o~ oil. A very low H2/oil ratio
would adversely affect the life o~ the catalyst, whereas
~ a very~high H2/oil ratio would cause a considerable 1099
! :~ 25~ o;~pres6ure over~the~oatalyst beds, so that much energy~for
~ oompression would bé required for circulating the hydrogen-~
1 ~ ~ rich~gas~
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The support of the catalyst of the first zone may be
..
any refractory material. Suitable materials are, for ~
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- example, alumina (aluminium oxide), silica (silicium
oxide), magnesia (magnesium oxide), titanium oxide,
zirconia (zirconium oxide), thoria (thorium oxide), boria
(borium oxide) and mixtures and compounds of these metal
oxides. It is preferred that the supports of the catalysts
in the first an~ the second zone consist for the greater -
part of alumina. Mixtures of alumina and silica, and in
.. .
particular alumina and boria are very suitable. ~
.
In the first zone supported catalysts which contain
one or more of the metals nickel, cobalt, molybdenum and
tun~sten are very suitable, in particular catalysts which
1~ contain one of the metals nickel and cobalt and one of the
1 15 metals molybdenum and tungsten. A catalyst which consists
of nickel and tungsten (or compounds, in particular oxides -
., ~.
thereof) on an alumina/boria support i8 mostly preferred in ~-
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the first zone.
The presence of phosphorus and/or fluor in the catalyst
in the ~rst zone is often of advantage.
~he amounts of the metals present in the catalyst in
I the first zone may vary between wide limits. Very suitably
j ~ the oatalyst contains from 10 to 30 parts by weight of a
- Group VI~metal and~from 2 to 15 parts by weight Or a Group ~ ~ -
25 ~ VIII metal per 100 parts of cataly~t.
~he metals in the fresh catalysts are very suitable in
the oxidic form.
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The effluent of the first zone may be treated in order
to remove therefrom undesired gaseous compounds, such as
hydrogen sulphide (e.g., by adsorption of H2S in an aqueous
amine solution, such as a solut~n of di-i~opropanolamine).
However, it is preferred to forward the total product
emerging from the first zone into the second zone. -
The preferred pressure, liquid hourly space velocity
and hydrogen/oil ratio in the second zone are equal to those
described for the firæt zone. The temperature of the second
zone ~ould be between 350 and 390C; it should always be
lower than the temperature of the first zone.
The cataly8t of the second zone should be an acidic
~upported catalysk. By the8e catalysts are meant those
!I which, when adsorbing the indicator butter yellow (= di-
; y C6H5 N=N-C6H4-N-(CH3)2~ and other still
weaker basic indicators, show a colour change of these
indioators, indicative of an acid medium.
:! - .
Suitable supports for the acidic supported cataly~ts
are, for in~3tance, compounds of silica and alumina, such as
8ilica-alumina cracking catalysts, compounds o~ silica and
zirconium dio~ide, compound8 of boron trioxide and alumina,
compounds of boron trioxide and silica, compounds of
alumina and halogen, such as alumina and fluorine or
alumina, silica and fluorine, and the like.
The metal8 (or t;heir compounds) and comblnations thereof
and the amounts thereof whioh are very suitable or preferred in the
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catalyst of the second zone are the same as those of the
first zone. Very attractive catalysts for the second zone
are nickel and tungsten (or compounds (e.g., oxides) there-
of) on an alumina/boria support, and fluorinated nickel and
tungsten (or compounds (e.g., oxides) thereof) on a
silica-alumina carrier. -
In many cases it will be attractive to use the same
catalyst in the first and the second zone.
In case the pour point of the liquid effluent from the
second zone is too high, this effluent may be dewaxed as
such. However, it i9 preferred to remove therefrom lower
boiling materials (e.g., by distillation) before dewaxing.
Very suitably all compounds which have a boiling point up
to 400-450C are removed before dewaxing.
The dewaxing may be carried out in any desired manner,
e.g., by mixing the liquid to be dewaxed with a suitable
liquid (e.g , a mixture of methylethyl ketone and toluene),
cooling the mixture to a temperature of about -20C and
removing the solid wax.
It is preferred to carry out the dewaxing operation
catalytically by oontacting the liquid to be dewaxed with
a catalyst in the presence o~ hydrogen. Very suitable
catalysts comprise one or more metals or compounds~ thereof
.
of Group VI and VI~ of the Periodic Table supported on a
j 25 cryatalline mordenite. As examples of very suitable metals
may be mentioned platinum, palladium and tungsten. ~ ;
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Pressures of from 40-120 kg~cm2, temperatures of from ;-
300-400C (in particular of from 300-350C~ and liquid
hourly space velocities of from 0 1-2 kg oll per litre
catalyst per hour are very suitable.
If desired,the effluent of the catalytic dewaxing may ~ ;
be topped in order to remove low-boiling constituents and/or
extracted with a suitable extracting agent (e.g., sulphur
dioxide, sulfolane) in order to remove aromatic constituents.
EXAMPLE
A waxy distillate having a boiling range of between
430C and 550C, obtained from a Middle East crude, was
' passed together with hydrogen over two con~ecutive cat,alyst
I beds at a pressure of 140 kg/cm2, a liquid hourly ~pace
velocity of 0.~ kg/l of oatalyst/hour, the hydrogen/oil
ratio being 1750 Nl/kg.
The fir;3t reactor contained a catalyst having the fol- f
lowing composition: :
Al23 57.5%; B203 - 6%; WO~ - 30%; NiO - 6 5`%
; ~ ~ The composition of the oatalyst in the second reactor
-~, 20 was~
23 57-5%; B203 - 6%; W03 - 30%; NiO - 6 5%
In this particular ca~e the composition of the cataly~t ~ ;
in the second reactor;is therefore identical to that in the
first reaotor. The temperatures of the two reactors vary, f ~;f~
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25-~ a~d Table I shows the yield of oil with a viscosity index
' ~ of 95 t% by weight in relation to the total liquid effluent -
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from the second reactor), obtained after topping at 430C~:
and after catalytic dewaxing of the said liquid effluent. :-
The catalytic dewaxing was carried out by passing the . :
said liquid effluent (after topping at 430C) at a
pressure of 60 kg/cm2, a liquid hourly space velocity of
0.5 kg/l of catalyst/hour, at a temperature of 315C, over
a catalyst consisting of 10% by weight of tungsten (in r~
oxidic form) supported on a synthetic mordenite.
Similar experiments were carried out, the only dif-
ference being the temperatures. ~ .
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TABLE I
Temperature of 1st zone402 401 397 395
Temperature o~ 2nd zone320 340 360 370
Yield o~ oil, %w 5 51 52 58.5
Table I shows that the highest yields of oil with a
viscosity index of 95 are obtained at a temperature of about
395C in the first reactor, while the temperature in the . :
seoond reactor lies between 360C and 390C; the yield
diminishes as the temperature in the second reactor decreases. .
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