Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
- 1 Z009830
T 5934
IMPROVEMENTS RELATING TO LUBRICATING BASE OILS
This invention relates to lubricat$ng base oils and is
particularly concerned with a process for the manufacture of such
base oils with a high viscosity index and to lubricating base oils
which can be obtained by that process.
Lubricating base oils are derived from various mineral crude
oils by a variety of refining processes, generally directed to
obtaining a lubricating base oil with a suitable viscosity index
for the intended end use.
The preparation of high viscosity index lubricating base oils
can be carried out as follows. A crude oil is separated by
distillation at atmospheric pressure into a number of distillate
fractions and a residue, known as long residue. The long residue is
than separated by distillation at reduced pressure into a number of
vacuum distillates and a vacuum residue known as short residue.
From the vacuum distillate fractions lubricating base oils are
prepared by refining processes which include wax removal from the
vacuum distillate fractions. From the short residue asphalt can be
removed by known deasphalting processes to give a deasphalted oil
from which wax can subsequently be removed to yield a residual
lubricating base oil, known as bright stock. The wax obtained
during refining of the various lubricating base oil fractions is
designated as slack wax.
Such slack waxes can be catalytically hydrotreated to yield
high viscosity index lubricating base oils uslng processes such as
those described in GB 1j429,494 and European patent applicaeion
No. 324 528.
The high viscosity index base oils obtained by such processes
have excellent characteristics in many respects, especially as they
~ obviate the need for the addition of polymeric viscosity index
!~ 30 improvers. However, as a result of the processing involved in their
, manufacture, they have a low aromaticity when compared with
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lubricating base olls of lower viscosity index. Thus they have a
reduced ability to solubilize other materials, for example
materials resulting from oxidation reactions which occur in the
commercial lubricants prepared therefrom.
The present invention is directed to the preparation of novel
lubricating base oils having a high viscosity index together with
comparatively high aromaticity. Surprisingly it has been found that
such aromatics-containing base oils can be obtained by
dehydrogenating and selectively rehydrogenating a high viscosity
index lubricating base oil while still maintaining the desired high
viscosity index.
Accordingly, one aspect of the present invention provides a
novel process for introducing aromaticity to a lubricating base oil
comprising contacting a lubricating base oil feedstock having a
high viscosity index with a dehydrogenating catalyst and recovering
a product having enhanced aromaticity therefrom. By high viscosity
index is understood a viscosity index of at least 125 as determined
by ASTM D-567. The feedstock preferably has an extra high viscosity
index of at least 135.
At least a portion of the product having enhanced aromaticity
may be subjected, in accordance with a further aspect of the
present invention, immediately downstream of the dehydrogenation or
after further processing and/or transportation, to hydrotreating in
the presence of hydrogen and a suitable catalyst and recavering a
hydrotreated product therefrom.
It has also surprisingly been found that the hydrotreating
does not substantially decrease the aromaticity, so that there is
obtained a product of increased aromaticity from which olefinic
unsaturation has substantially been removed by the hydrotreatment.
Furthermore, the product has been found to maintaln a high
viscosity index, together with an increased aromatic content.
Suitably, the aromatic content i9 increased by contact with the
dehydrogenating catalyst by an amount of at least 3 mmol/100 g.
Therefore, in accordance with a still further aspect of the
invention, there are provided, as novel products, lubricating base
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oils having an extra high viscosity index of at least 135 and an
aromatic content of at least 3 mmol/100 g. These base oils may be
the direct products of the dehydrogenation, containing some
olefinic unsaturation, or the products of the subsequent
hydrotreatment to give base oils from which the olefinic
unsaturation has substantially been re~oved.
The lubricating base oil feedstock having a high viscosity
index may be obtained for example by the processes described in
GB 1,429,494 and EP 324 528. The viscosity index as determined by
ASTM D-567 is at least 125 and is preferably at least 135, more
preferably above 140. The base oils suitably also have a low pour
point below -10 C (as determined by ASTM D-27).
The dehydrogenating catalyst employed to introduce aromaticity
to the lubricating base oil is preferably a cGmposite catalyst
comprising a Group VIII noble metal component, a Group IVA metal
component and a refractory oxide support. The Group VIII noble
metal component is preferably platinum and is preferably present in
an amount of 0.1 to 1 ~wt, preferably 0.3 to 0.5 ~wt. The Group IVA
metal component is preferably tin and is preferably present in an
amount of 0.1 to 1 ~wt, preferably 0.3 to 0.5 ~wt. The refractory
oxide support is preferably alumina but may also be materials such
as silica, silica-alumina, magnesia, zirconia, titania or mixtures
thereof.
It is possible, though not essential, to neutralize the
catalyst support, for example with an alkali metal or alkaline
earth metal component, preferably lithium, or, alternatively
potassium. Suitable catalysts are described, for example, in US
Patent No. 4,672,146.
The dehydrogenation reaction is normally carried out at a
relatively high temperature and moderate pressure. Suitable
temperatures are in the range of 300 C to 600 C, preferably from
400 to 500 C, with a hydrogen partial pressure of l to 30 bar,
preferably from 5 to 15 bar. Suitable sp~ce velocities range from
0.2 to 20, preferably from 2 to 10 kg/l catalyst.h. A suitable
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gas/feedstock ratio ranges from 200 to 2500 Nl/kg, preferably from
500 to 1200 Nl/kg.
The product having increased aromaticity may be subjected to
subsequent hydrotreating immediately downstream of the
dehydrogenation and with or without removal of, for example,
gaseous products. Alternatively the product may be sub~ected to
further processing, such as deep dewaxing, solvent extraction
and/or transportation to a separate station for subsequent
hydrotreatment.
The catalyst used in the hydrotreatment contains at least one
hydrogenating metal component. The metal component is suitably
selected from the Groups VIB and/or VIII of the Periodic Tab}e of
the Elements. These Groups include the noble metals platinum and
palladium. It is however preferred to use nickel and/or cobalt, and
molybdenum and/or tungsten compounds.
The amount of nickel and/or cobalt present in the catalyst can
sultably vary between 1 and 20a by weight, calculated as metal on
total catalyst, preference being given to amounts in the range of
1.5 to 12% by weight. The amounts of molybdenum and/or tungsten may
advantageously vary between 5 and 40~ by weight, calculated as
metal on total catalyst, preference being given to amounts in the
range of 8 to 30~ by weight.
The metal components may be incorporated on a support by any
conventional technique, such as impregnation, dry-impregnation,
precipitation or a combination thereof. Any suitable support
material may be used, such as the refractory oxides silica,
alumina, silica-alumina, magnesia, zirconia, titania or mixtures
thereof. Silica, silica-alumina and alumina are preferred support
materials, in particular alumina. Natural and synthetic crystalline
aluminosilicates can also be used, such as fau~asite-type zeolites,
in particular zeolite Y, mordenite-type zeolites and ZSN-5 type
zeolites, or mixtures containing such a zeolite.
The catalysts are normally sulphided and may be fluorided by
techniques known in the art. The catalyst preferably further
comprises phosphorus, advantageously in an amount of from 0.5 to
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12% by weight calculated as elemental phosphorus, based on total
catalyst.
The hydrotreating reaction is suitably carried out under
comparatively mild conditions. Suitable temperatures are in the
range of 100-400 C, preferably from 200-300 C with a hydrogen
partial pressure in the range of 20 to~l50 bar, preferably from 40
to 60 bar. Suitable space velocities range from 0.1 to 5 kg/l
catalyst.h, preferably from 0.5 to 2 kg/l catalyst.h, while a
suitable gas/feedstock ratio ranges from 200 to 2000 Nl/kg,
preferably from 400 to 1000 Nl/kg.
The invention will now be illustrated by means of the
following examples.
EXANPLE 1
A high viscosity index lubricating base oil was used as
feedstock. This oil had the following characteristics:
kinematic viscosity at 100 C (Vk 100) 5.39 mm2/s
pour point -18 C
viscosity index 144.4
aromatics content (mmol/100 g) mono 0.388
di 0.010
poly 0.017
bromine index (mg/100 g) lO
The feedstock was used for a series of dehydrogenation
experiments in an automated one-reactor trickle-flow unit under gas
once-through mode of operation and using temperatures as given in
Table 1, a hydrogen pressure of 10 bar, a gas/feedstock ratio of
700 Nl/kg, and a space velocity of 4 kg/l.h. The catalyst employed
was a platinum/tin catalyst on a lithlum-neutralized alumina
support and contained 0.40 ~wt platinum and 0.41 ~wt tin, with an
initial pore volume of 0.93 cm3/g and an initial surface area of
131 m /g. Aromatics content was determined by W absorption.
The results of the experiments are given in Table l.
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TABLE 1
Experiment No. 1 2 3 4 5 6
Average Temp. 440 460 400 430 450 470
Yield, ~wt on feedstock
< 370 C 9.110.1 1.4 7.1 8.2 11.8
> 370 C 90.989.9 98.692.9 91.8 88.2
Oil Properties
Vk 100 mm2/s 4.724.71 5.334.93 4.82 4.68
VI 143.5 142.7145.5144.4 142.8 141.3
pour point C -15 -15 -18
Aromatics, mmol/100 g
mono 27.10 31.653.0310.75 18.69 25.70
di 1.031.29 0.0670.3980.737 1.11
poly 0.605 0.8740.0730.230 0.413 0.752
It will be seen from the above results that aromaticity has
been introduced to the lubricating base oil while maintaining a
high viscosity index over a range of operating temperatures. The
products were found to have a content of olefinic unsaturation (by
determination of the bromine number in accordance with ASTM
D-1159-82) of from 1 to 6.
EXAMPLE 2
A high viscosity index, high aromatics lubricating base oil
obtained as described in Example 1 and having the propertles given
in Table 2 below was hydrotreated in a one-reactor micro-flow unit
under gas once-through mode of operation. The conditions of
operation were a temperature of 260 C, a hydrogen pressure of
50 bar, a gas/feedstock ratio of 500 Nl/kg and a space velocity of
1 kg/l.h. The catalyst employed was a hydrotreating catalyst
comprising 2.5~ by weight of nickel, 13.5~ by weigh~ of molybdenum
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and 2.9~ by weight of phosphorus on alumina, the percentages being
based on total catalyst. Aromatics content was determined by W
absorption.
The results are given in Table 2.
TABLE 2
Feed Product
Oil Properties
Vk 100 mm /s 4.718 4.746
VI 143.5 143
pour point C -15 -12
Aromatics, mmol/100 g
mono 28.4 23.3
di 1.2
poly 0.62 0.14
Bromine number (mg/100 g) 4
The yield of > 370 C, ~wt on feedstock, was 99~.
It will be seen from the above results that hydrotreatment of
the aromat~zed lubricating base oil has given a product in which
the aromaticity and the viscosity index have not been adversely
affected. The product was found to have a low content of olefinic
unsaturation by determination of the bromine index (ASTN D-1491-78
which was found to be 20 mg/100 g.
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