U.S. patent application number 12/513926 was filed with the patent office on 2009-12-17 for lubricant composition for use the reduction of piston ring fouling in an internal combustion engine.
This patent application is currently assigned to Shell Internationale Research Maatschappij B.V.. Invention is credited to David Colbourne, David John Wedlock.
Application Number | 20090312205 12/513926 |
Document ID | / |
Family ID | 39364878 |
Filed Date | 2009-12-17 |
United States Patent
Application |
20090312205 |
Kind Code |
A1 |
Colbourne; David ; et
al. |
December 17, 2009 |
LUBRICANT COMPOSITION FOR USE THE REDUCTION OF PISTON RING FOULING
IN AN INTERNAL COMBUSTION ENGINE
Abstract
The present invention relates to a lubricant composition
comprising a base oil or base oil blend and one or more additives,
wherein the lubricant composition has a kinematic viscosity at
100.degree. C. of more than 5.0 mm.sup.2/s (cSt), a cold cranking
simulated dynamic viscosity at -15.degree. C. according to ASTM D
5293 of less than 9500 mPas (cP) and a mini rotary viscosity test
value of less than 60000 mPas at -20.degree. C. according to ASTM D
4684, and wherein the base oil or base oil blend has been obtained
from a waxy paraffinic Fischer-Tropsch synthesized hydrocarbon
fraction and comprises a continuous series of isoparaffins having
n, n+1, n+2, n+3 and n+4 carbon atoms, wherein n is between 15 and
35, suitable for the reduction of piston ring fouling in an
internal combustion engine.
Inventors: |
Colbourne; David; (
Cheshire, GB) ; Wedlock; David John; (Cheshire,
GB) |
Correspondence
Address: |
SHELL OIL COMPANY
P O BOX 2463
HOUSTON
TX
772522463
US
|
Assignee: |
Shell Internationale Research
Maatschappij B.V.
HR The Hague
NL
|
Family ID: |
39364878 |
Appl. No.: |
12/513926 |
Filed: |
November 9, 2007 |
PCT Filed: |
November 9, 2007 |
PCT NO: |
PCT/EP2007/062141 |
371 Date: |
July 24, 2009 |
Current U.S.
Class: |
508/110 |
Current CPC
Class: |
C10N 2020/02 20130101;
C10N 2030/45 20200501; C10N 2020/065 20200501; C10M 105/04
20130101; C10N 2040/25 20130101; C10N 2030/42 20200501; C10N
2030/04 20130101; C10N 2030/43 20200501; C10M 2205/173
20130101 |
Class at
Publication: |
508/110 |
International
Class: |
C10M 169/04 20060101
C10M169/04 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 10, 2006 |
EP |
06123806.9 |
Claims
1. A lubricant composition comprising a base oil or base oil blend,
saturated cyclic hydrocarbons in an amount of 5 to 10 wt %, based
on total lubricant composition, and one or more additives, and
having a kinematic viscosity at 100.degree. C. of more than 5.0
mm.sup.2/s (cSt), a cold cranking simulated dynamic viscosity at
-15.degree. C. according to ASTM D 5293 of less than 9500 mPas (cP)
and a mini rotary viscosity test value of less than 60000 mPas at
-20.degree. C. according to ASTM D 4684, and wherein the base oil
or base oil blend has been obtained from a waxy paraffinic
Fischer-Tropsch synthesized hydrocarbon fraction and comprises a
continuous series of iso-paraffins having n, n+1, n+2, n+3 and n+4
carbon atoms, wherein n is between 15 and 35, having a Top Groove
fill of below 50% vol. according to the Nissan TD25 Detergency Test
(Japanese Automobile Standards Organization (JASO) M336: 1998).
2. A lubricant composition according to claim 1, having a residual
carbon content of less than 4.8% wt. according to the Nissan TD25
Detergency Test (Japanese Automobile Standards Organization (JASO)
M336: 1998).
3. A lubricant composition according to claim 1 or 2, wherein the
base oil or base oil blend has a kinematic viscosity at 100.degree.
C. of from 3 to 25 mm.sup.2/s.
4. A lubricant composition according to claim 1, wherein the base
oil has a pour point of less than -39.degree. C. and a kinematic
viscosity at 100.degree. C. of between 3.8 and 8.5 mm.sup.2/s
(cSt), and wherein the lubricant composition has a kinematic
viscosity at 100.degree. C. of between 9.3 and 12.5 mm.sup.2/s
(cSt).
5. A lubricant composition according to claim 1, wherein the
lubricant composition comprises less than 10 wt % of an additional
base oil not derived from a Fischer-Tropsch process.
6. A lubricant composition according to claim 1, wherein the
lubricant composition comprises no additional base oil.
7. A lubricant composition according to claim 1, wherein the base
oil or base oil blend comprises at least 98 wt % saturates.
8. A lubricant composition according to claim 7, wherein the
saturates fraction comprises between 10 and 40 wt % of
cyclo-paraffins.
9. A method of reducing piston ring fouling in an internal
combustion engine comprising using in said engine a lubricant
composition comprising a base oil or base oil blend, saturated
cyclic hydrocarbons in an amount 5 to 10 wt %, based on the total
lubricant, and one or more additives, and having a kinematic
viscosity at 100.degree. C. of more than 5.0 mm.sup.2/s (cSt), a
cold cranking simulated dynamic viscosity at -15 .degree. C.
according to ASTM D 5293 of less than 9500 mPas (cP) and a mini
rotary viscosity test value of less than 60000 mPas at -20.degree.
C. according to ASTM D 4684, and wherein the base oil or base oil
blend has been obtained from a waxy paraffinic Fischer-Tropsch
synthesized hydrocarbon fraction and comprises a continuous series
of iso-paraffins having n, n+1, n+2, n+3 and n+4 carbon atoms,
wherein n is between 15 and 35.
10. A method according to claim 9, wherein the base oil or base oil
blend is obtainable from a process comprising the following steps:
(a) hydrocracking/hydroisomerisating a Fischer-Tropsch product
having a weight ratio of compounds having at least 60 or more
carbon atoms and compounds having at least 30 carbon atoms of at
least 0.2 and wherein at least 30 wt % of compounds in the
Fischer-Tropsch product have at least 30 carbon atoms, (b)
separating the product of step (a) into at least one or more fuel
fractions and a base oil precursor fraction, and (c) performing a
catalytic dewaxing step to the base oil precursor fraction obtained
in step (b), and optionally (d) separating the products obtained in
step (c) into at least one or more base oil fractions, and a lower
boiling fraction.
11. A method according to claim 9, wherein the Fischer-Tropsch
product used in step (a) has at least 50 wt %, and more preferably
at least 55 wt % of compounds having at least 30 carbon atoms and
wherein the weight ratio of compounds having at least 60 or more
carbon atoms and compounds having at least 30 carbon atoms of the
Fischer-Tropsch product is at least 0.4 and wherein the
Fischer-Tropsch product comprises a C.sub.20+ fraction having an
ASF-alpha value (Anderson-Schulz-Flory chain growth factor) of at
least 0.925.
12. A method of lubricating a compression-ignited internal
combustion engine comprising operating the engine and lubricating
the engine with a lubricating oil composition comprising a base oil
or base oil blend, saturated cyclic hydrocarbons in an amount 5 to
10 wt %, based on the total lubricant, and one or more additives,
wherein the lubricant composition has a kinematic viscosity at
100.degree. C. of more than 5.0 mm.sup.2/s (cSt), a cold cranking
simulated dynamic viscosity at -15.degree. C. according to ASTM D
5293 of less than 9500 mPas (cP) and a mini rotary viscosity test
value of less than 60000 mPas at -20.degree. C. according to ASTM D
4684, and wherein the base oil or base oil blend has been obtained
from a waxy paraffinic Fischer-Tropsch synthesized hydrocarbon
fraction and comprises a continuous series of iso-paraffins having
n, n+1, n+2, n+3 and n+4 carbon atoms, wherein n is between 15 and
35.
13. (canceled)
Description
FIELD OF INVENTION
[0001] The present invention relates to a lubricant composition,
and to the use of the lubricant composition for the reduction of
piston ring deposits in a combustion engine.
BACKGROUND OF THE INVENTION
[0002] In the recent decades, use of internal combustion engines
for transportation and other means of energy generation has become
widespread. In particular compression ignited internal combustion
engines which are also known as "Diesel engines" after Rudolf
Diesel, who invented the first compression ignition engine in 1892,
feature among the main type of engines employed for passenger cars
in Europe, and globally for heavy duty applications, as well as for
stationary power generation as a result of their high energy
efficiency. In a compression-ignited internal combustion engine a
fuel/air mixture is ignited by being compressed until it ignites
due to the temperature increase due to compression, rather than by
a separate source of ignition, such as a spark plug as in gasoline
engines.
[0003] In recent years, compression-ignited internal combustion
engines have been developed with a specific power output of as high
as 60 kW/litre. Such engines have such high energy output that the
heat can no longer be dissipated through heat exchange through the
engine block or cylinder head and the coolant or lubricant, while
at the top ring groove, temperatures can exceed 250.degree. C. As a
result, deposits on the piston and cylinder surfaces, such as soot
and oil sludge are formed in increased amounts in such engines.
This in turn can lead to ring-sticking or eventual failure of e.g.
piston rings, and other related problems in their operation. A
further issue at the high pressures and temperatures involved
resides in the fact that the piston ring sealing performance may be
compromised, resulting in gases from the combustion process to
enter the lubricated parts of the engine. The result is enhanced
oxidation and fouling of the lubricating oils employed. This one on
hand will shorten the required exchange intervals, or can even lead
to failure of the lubricating oil, and deposition of sludge in the
engine.
[0004] Furthermore, sulphated ash, sulphur and phosphorus
concentrations of lubricating oil compositions conventionally used
in internal combustion engines may have adverse effects on engine
cleanliness.
[0005] Hence, there is a need for a reduction of deposits formed on
pistons and cylinders in diesel engine exhaust gases.
[0006] It has now surprisingly been found by applicants that when a
lubricant composition based on highly paraffinic base oils
comprising a continuous series of iso-paraffins having n, n+1, n+2,
n+3 and n+4 carbon atoms, wherein n is between 15 and 35, and
derived from a Fischer-Tropsch process, is employed to lubricate a
compression-ignited internal combustion engine, deposits on the
pistons and the piston ring grooves in the Nissan TD25 piston
cleanliness tests are strongly diminished as compared to mineral
oil based lubricants.
SUMMARY OF THE INVENTION
[0007] Accordingly, the present invention relates to a lubricant
composition comprising a base oil or base oil blend and one or more
additives, wherein the lubricant composition has a kinematic
viscosity at 100.degree. C. of more than 5.0 mm.sup.2/s (cSt), a
cold cranking simulated dynamic viscosity at -15.degree. C.
according to ASTM D 5293 of less than 9500 mPas (cP) and a mini
rotary viscosity test value of less than 60000 mPas at -20.degree.
C. according to ASTM D 4684, and wherein the base oil or base oil
blend has been obtained from a waxy paraffinic Fischer-Tropsch
synthesized hydrocarbon fraction and comprising a continuous series
of iso-paraffins having n, n+1, n+2, n+3 and n+4 carbon atoms,
wherein n is between 15 and 35, for the reduction of piston ring
fouling in an internal combustion engine, having a Top Groove fill
in of below 50% vol. according to the Nissan TD25 Detergency Test
(Japanese Automobile Standards Organization (JASO) M336: 1998).
Preferably, the lubricant composition has a residual carbon content
of less than 4.8% wt. according to the Nissan TD25 Detergency Test
(Japanese Automobile Standards Organization (JASO) M336: 1998).
[0008] The present invention accordingly relates to the use of a
lubricant used to lubricate a compression-ignited internal
combustion engine, i.e. a Diesel Engine, a reciprocating engine,
Wankel engine and similar designed engine in which combustion is
intermittent. As set out above, applicants have found that the use
of a lubricant comprising a Fischer-Tropsch derived base oil leads
to a significant and unexpected synergistic increase in piston
cleanliness. Without wishing to be bound to ay particular theory,
it is believed that this may be related to the fact that the base
oil properties result in a reduction of the amounts of additives
required to achieve a suitable viscosity behaviour of the lubricant
composition, as well as due to physical properties such as thermal
diffusion coefficient as compared to mineral oil derived base
oils.
[0009] The engine for which the package according to the invention
is to be employed is lubricated, i.e. the lubricant forms a film
between surfaces of parts moving against each other so as to
minimize direct contact between them. This lubricating film
decreases friction, wearing, and production of excessive heat
between the moving parts. Also as a moving fluid, the lubricant
transposes heat from surfaces of lubricated parts due to friction
from parts moving against each other or the oil film. Typically, an
internal combustion engine has a crankcase, cylinder head, and
cylinders. The lubricant is typically present in the crankcase,
where crankshaft, bearings, and bottoms of rods connecting pistons
to the crankshaft are submerged in the lubricant. The rapid motion
of these parts causes the lubricant to splash and lubricate the
contacting surfaces between the piston rings and interior surfaces
of the cylinders. This lubricant film also serves as a seal between
the piston rings and cylinder walls to separate the combustion
volume in the cylinders from the space in the crankcase.
[0010] Without wishing to be bound to any particular theory, it is
believed that the presence of the residual lubricant film reduces
the temperature of the piston and interior surfaces of the
cylinder, thereby reducing the formation of soot and sludge.
[0011] By "Fischer-Tropsch derived" is meant that a base oil is, or
derives from, a synthesis product of a Fischer-Tropsch condensation
process. The term "non-Fischer-Tropsch derived" may be interpreted
accordingly. A Fischer-Tropsch derived fuel may also be referred to
as a GTL (Gas-To-Liquids) fuel.
[0012] The Fischer-Tropsch reaction converts carbon monoxide and
hydrogen into longer chain, usually paraffinic, hydrocarbons :
n(CO+2H.sub.2)=(--CH.sub.2--).sub.n+nH.sub.2O +heat,
in the presence of an appropriate catalyst and typically at
elevated temperatures (eg, 125 to 300.degree. C., preferably 175 to
250.degree. C.) and/or pressures (eg, 5 to 100 bar, preferably 12
to 50 bar). Hydrogen:carbon monoxide ratios other than 2:1 may be
employed if desired. The carbon monoxide and hydrogen may
themselves be derived from organic or inorganic, natural or
synthetic sources, typically either from natural gas or from
organically derived methane.
[0013] An example of a Fischer-Tropsch based process is the SMDS
(Shell Middle Distillate Synthesis) described in "The Shell Middle
Distillate Synthesis Process", van der Burgt et al (supra). This
process (also sometimes referred to as the Shell "Gas-To-Liquids"
or "GTL" technology) produces middle distillate range products by
conversion of a natural gas (primarily methane) derived synthesis
gas into a heavy long chain hydrocarbon (paraffin) wax which can
then be hydroconverted and fractionated to produce liquid transport
fuels such as the gas oils useable in diesel fuel compositions. A
version of the SMDS process, utilising a fixed bed reactor for the
catalytic conversion step, is currently in use in Bintulu, Malaysia
and its gas oil products have been blended with petroleum derived
gas oils in commercially available automotive fuels.
[0014] By virtue of the Fischer-Tropsch process, a Fischer-Tropsch
derived base oil has essentially no, or undetectable levels of,
sulphur and nitrogen. Compounds containing these heteroatoms tend
to act as poisons for Fischer-Tropsch catalysts and are therefore
removed from the synthesis gas feed. This can yield additional
benefits, in terms of effect on catalyst performance, in fuel
compositions in accordance with the present invention.
[0015] The lubricant compositions may be used to lubricate
mechanical engine components, particularly an internal combustion,
such as a compression-ignited, engine, by adding the lubricating
oil thereto. The lubricant composition preferably comprises less
than 10 wt % of an additional base oil not derived from
Fischer-Tropsch process. Again more preferably, the lubricant
composition comprises no additional base oil.
[0016] Preferably, the lubricant composition is a multigrade
crankcase lubricating oil composition comprising, or made by
admixing: (a) a major amount of a base oil having lubricating
viscosity, comprised of at least 50% wt., more preferably at least
60% wt., yet more preferably at least 70% wt., again more
preferably 80% wt., yet more preferably 90% wt., and most
preferably 100% wt. of a Fischer-Tropsch derived base oil; and
minor amounts of:
(b) a dispersant, such as an ashless dispersant; (c) a metal
detergent, such as a calcium and/or magnesium detergent; (e) one or
more other lubricant additive components selected from
anti-oxidants, anti-wear agents and friction modifiers; and (f) a
viscosity modifier.
[0017] Typical Fischer-Tropsch products comprise a continuous
series of paraffins having n, n+1, n+2, n+3 and n+4 carbon atoms.
The paraffins will be isomerized as set out below in order to
achieve suitable viscometric properties for use as a lubricating
oil. The base oils suitably employed in the present process
comprise a continuous series of iso-paraffins having n, n+1, n+2,
n+3 and n+4 carbon atoms, wherein n is between 15 and 35.
[0018] The base oil or base oil blend preferably has a paraffin
content of greater than 80 wt % paraffins and a saturates content
of greater than 98 wt %. Preferably, the base oil or base oil blend
comprises at least 98 wt % saturates and wherein the saturates
fraction consists of between 10 and 40 wt % of cyclo-paraffins.
[0019] The base oil may be a single base oil fraction, or a blend
of base oil fractions of differing viscosity.
[0020] More preferably, the saturates fraction consists of more
than 12 wt % of cyclo-paraffins.
[0021] The base oil preferably is a Fischer-Tropsch derived base
oil, having a paraffin content of greater than 80 wt % paraffins, a
saturates content of greater than 98 wt % and comprises a
continuous series of iso-paraffins having n, n+1, n+2, n+3 and n+4
carbon atoms, wherein n is between 15 and 35, and wherein n is
between 15 and 35.
[0022] The base oil further preferably comprises preferably at
least 98 wt % saturates, more preferably at least 99.5 wt %
saturates and most preferably at least 99.9 wt %. The saturates
fraction in the base oil preferably comprises between 10 and 40 wt
% of cyclo-paraffins. Again preferably, the content of
cyclo-paraffins is less than 30 wt % and more preferably less than
20 wt %. Preferably the content of cyclo-paraffins is at least 12
wt % and more preferably at least 15 wt %. Such base oils are
further characterized in that the weight ratio of 1-ring
cyclo-paraffins relative to cyclo-paraffins having two or more
rings is greater than 3 preferably greater than 5. It was found
that this ratio is suitably smaller than 15.
[0023] Any suitable method may be used to determine the content and
the presence of the cyclo-paraffins and of a continuous series of
the series of iso-paraffins having n, n+1, n+2, n+3 and n+4 carbon
atoms in the base oil or base oil blend. A particularly suitable
method comprises the following steps:
[0024] The base oil sample is first separated into a polar
(aromatic) phase and a non-polar (saturates) phase by making use of
a high performance liquid chromatography (HPLC) method IP368/01,
wherein as mobile phase pentane is used instead of hexane as the
method states. The saturates and aromatic fractions are then
analyzed using a Finnigan MAT90 mass spectrometer equipped with a
Field desorption/Field Ionisation (FD/FI) interface, wherein FI (a
"soft" ionisation technique) is used for the semi-quantitative
determination of hydrocarbon types in terms of carbon number and
hydrogen deficiency. The type classification of compounds in mass
spectrometry is determined by the characteristic ions formed and is
normally classified by "z number". This is given by the general
formula for all hydrocarbon species: CnH.sub.2n+z.
[0025] Because the saturates phase is analysed separately from the
aromatic phase it is possible to determine the content of the
different (cyclo)-paraffins having the same stoichiometry. The
results of the mass spectrometer are processed using commercial
software (poly 32; available from Sierra Analytics LLC, 3453 Dragoo
Park Drive, Modesto, Calif. GA95350 USA) to determine the relative
proportions of each hydrocarbon type and the average molecular
weight and polydispersity of the saturates and aromatics
fractions.
[0026] The base oil composition preferably has a content of
aromatic hydrocarbon compounds of less than 1 wt %, more preferably
less than 0.5 wt % and most preferably less 0.1 wt %, a sulphur
content of less than 20 ppm and a nitrogen content of less than 20
ppm. The pour point of the base oil is preferably less than
-30.degree. C. and more preferably lower than -40.degree. C. The
viscosity index is preferably higher than 120. It has been found
that the novel base oils typically have a viscosity index of below
140. The kinematic viscosity at 100.degree. C. of the base oil is
preferably between 2 and 25 mm.sup.2/s (cSt), preferably between 3
and 15 mm.sup.2/s, and more preferably between 4 and 8 mm.sup.2/s
and the Noack volatility is preferably lower than 14 wt %.
[0027] The base oils as described above are suitably obtained by
hydroisomerisation of a Fischer-Tropsch derived paraffinic wax,
preferably followed by some type of dewaxing, such as solvent or
catalytic dewaxing.
[0028] The base oils as derived from a Fischer-Tropsch wax as here
described will be referred to in this description as
Fischer-Tropsch derived base oils. Blends of different base oil
grades or fractions having different viscosity may also be
employed. This has the advantage that a large range of lubricant
viscosity is available.
[0029] The base oil or base oil blend is suitably obtainable from a
process comprising the following steps:
[0030] (a) hydrocracking/hydroisomerisating a Fischer-Tropsch
product having a weight ratio of compounds having at least 60 or
more carbon atoms and compounds having at least 30 carbon atoms of
at least 0.2 and wherein at least 30 wt % of compounds in the
Fischer-Tropsch product have at least 30 carbon atoms,
[0031] (b) separating the product of step (a) into at least one or
more fuel fractions and a base oil precursor fraction, and
[0032] (c) performing a catalytic dewaxing step to the base oil
precursor fraction obtained in step (b), and optionally
[0033] (d) separating the products obtained in step (c) into at
least one or more base oil fractions, and a lower boiling
fraction.
[0034] Preferably, the Fischer-Tropsch product used in step (a) has
at least 50 wt %, and more preferably at least 55 wt % of compounds
having at least 30 carbon atoms and wherein the weight ratio of
compounds having at least 60 or more carbon atoms and compounds
having at least 30 carbon atoms of the Fischer-Tropsch product is
at least 0.4 and wherein the Fischer-Tropsch product comprises a
C.sub.20+ fraction having an ASF-alpha value (Anderson-Schulz-Flory
chain growth factor) of at least 0.925.
[0035] Examples of Fischer-Tropsch processes which for example can
be used to prepare the above-described Fischer-Tropsch derived base
oil are the so-called commercial Slurry Phase Distillate technology
of Sasol, the Shell Middle Distillate Synthesis Process and the
"AGC-21" Exxon Mobil process. These and other processes are for
example described in more detail in U.S. Pat. No. 4,943,672, U.S.
Pat. No. 5,059,299, WO-A-9934917 and WO-A-9920720. Typically these
Fischer-Tropsch synthesis products will comprise hydrocarbons
having 1 to 100 and even more than 100 carbon atoms. This
hydrocarbon product will comprise normal paraffins, iso-paraffins,
oxygenated products and unsaturated products. If base oils are one
of the desired iso-paraffinic products it may be advantageous to
use a relatively heavy Fischer-Tropsch derived feed. The relatively
heavy Fischer-Tropsch derived feed has at least 30 wt %, preferably
at least 50 wt %, and more preferably at least 55 wt % of compounds
having at least 30 carbon atoms. Furthermore the weight ratio of
compounds having at least 60 or more carbon atoms and compounds
having at least 30 carbon atoms of the Fischer-Tropsch derived feed
is preferably at least 0.2, more preferably at least 0.4 and most
preferably at least 0.55. Preferably the Fischer-Tropsch derived
feed comprises a C.sub.20+ fraction having an ASF-alpha value
(Anderson-Schulz-Flory chain growth factor) of at least 0.925,
preferably at least 0.935, more preferably at least 0.945, even
more preferably at least 0.955. Such a Fischer-Tropsch derived feed
can be obtained by any process, which yields a relatively heavy
Fischer-Tropsch product as described above. Not all Fischer-Tropsch
processes yield such a heavy product. An example of a suitable
Fischer-Tropsch process is described in WO-A-9934917. The
Fischer-Tropsch derived base oil will contain no or very little
sulphur and nitrogen containing compounds. This is typical for a
product derived from a Fischer-Tropsch reaction, which uses
synthesis gas containing almost no impurities. Sulphur and nitrogen
levels will generally be below the detection limits, which are
currently 5 mg/kg for sulphur and 1 mg/kg for nitrogen
respectively.
[0036] The process will generally comprise a Fischer-Tropsch
synthesis, a hydroisomerisation step and an optional pour point
reducing step, wherein said hydroisomerisation step and optional
pour point reducing step are performed as:
[0037] (a) hydrocracking/hydroisomerisating a Fischer-Tropsch
product, (b) separating the product of step (a) into at least one
or more distillate fuel fractions and a base oil or base oil
intermediate fraction.
[0038] If the viscosity and pour point of the base oil as obtained
in step (b) is as desired no further processing is necessary and
the oil can be used as the base oil according the invention. If
required, the pour point of the base oil intermediate fraction is
suitably further reduced in a step (c) by means of solvent or
preferably catalytic dewaxing of the oil obtained in step (b) to
obtain oil having the preferred low pour point. The desired
viscosity of the base oil may be obtained by isolating by means of
distillation from the intermediate base oil fraction or from the
dewaxed oil the a suitable boiling range product corresponding with
the desired viscosity. Distillation may be suitably a vacuum
distillation step.
[0039] The hydroconversion/hydroisomerisation reaction of step (a)
is preferably performed in the presence of hydrogen and a catalyst,
which catalyst can be chosen from those known to one skilled in the
art as being suitable for this reaction of which some will be
described in more detail below. The catalyst may in principle be
any catalyst known in the art to be suitable for isomerising
paraffinic molecules. In general, suitable
hydroconversion/hydroisomerisation catalysts are those comprising a
hydrogenation component supported on a refractory oxide carrier,
such as amorphous silica-alumina (ASA), alumina, fluorided alumina,
molecular sieves (zeolites) or mixtures of two or more of these.
One type of preferred catalysts to be applied in the
hydroconversion/hydroisomerisation step in accordance with the
present invention are hydroconversion/hydroisomerisation catalysts
comprising platinum and/or palladium as the hydrogenation
component. A very much preferred hydroconversion/hydroisomerisation
catalyst comprises platinum and palladium supported on an amorphous
silica-alumina (ASA) carrier. The platinum and/or palladium is
suitably present in an amount of from 0.1 to 5.0% by weight, more
suitably from 0.2 to 2.0% by weight, calculated as element and
based on total weight of carrier. If both present, the weight ratio
of platinum to palladium may vary within wide limits, but suitably
is in the range of from 0.05 to 10, more suitably 0.1 to 5.
Examples of suitable noble metal on ASA catalysts are, for
instance, disclosed in WO-A-9410264 and EP-A-0582347. Other
suitable noble metal-based catalysts, such as platinum on a
fluorided alumina carrier, are disclosed in e.g. U.S. Pat. No.
5,059,299 and WO-A-9220759. A second type of suitable
hydroconversion/hydroisomerisation catalysts are those comprising
at least one Group VIB metal, preferably tungsten and/or
molybdenum, and at least one non-noble Group VIII metal, preferably
nickel and/or cobalt, as the hydrogenation component. Both metals
may be present as oxides, sulphides or a combination thereof. The
Group VIB metal is suitably present in an amount of from 1 to 35%
by weight, more suitably from 5 to 30% by weight, calculated as
element and based on total weight of the carrier. The non-noble
Group VIII metal is suitably present in an amount of from 1 to 25
wt %, preferably 2 to 15 wt %, calculated as element and based on
total weight of carrier. A hydroconversion catalyst of this type,
which has been found particularly suitable, is a catalyst
comprising nickel and tungsten supported on fluorided alumina.
[0040] The above non-noble metal-based catalysts are preferably
used in their sulphided form. In order to maintain the sulphided
form of the catalyst during use some sulphur needs to be present in
the feed. Preferably at least 10 mg/kg and more preferably between
50 and 150 mg/kg of sulphur is present in the feed.
[0041] A preferred catalyst, which can be used in a non-sulphided
form, comprises a non-noble Group VIII metal, e.g., iron, nickel,
in conjunction with a Group IB metal, e.g., copper, supported on an
acidic support. Copper is preferably present to suppress
hydrogenolysis of paraffins to methane. The catalyst has a pore
volume preferably in the range of 0.35 to 1.10 ml/g as determined
by water absorption, a surface area of preferably between 200-500
m.sup.2/g as determined by BET nitrogen adsorption, and a bulk
density of between 0.4-1.0 g/ml. The catalyst support is preferably
made of an amorphous silica-alumina wherein the alumina may be
present within wide range of between 5 and 96 wt %, preferably
between 20 and 85 wt %. The silica content as SiO.sub.2 is
preferably between 15 and 80 wt %. Also, the support may contain
small amounts, e.g., 20-30 wt %, of a binder, e.g., alumina,
silica, Group IVA metal oxides, and various types of clays,
magnesia, etc., preferably alumina or silica. The preparation of
amorphous silica-alumina microspheres has been described in Ryland,
Lloyd B., Tamele, M. W., and Wilson, J. N., Cracking Catalysts,
Catalysis: volume VII, Ed. Paul H. Emmett, Reinhold Publishing
Corporation, New York, 1960, pp. 5-9.
[0042] The catalyst is prepared by co-impregnating the metals from
solutions onto the support, drying at 100-150.degree. C., and
calcining in air at 200-550.degree. C. The Group VIII metal is
present in amounts of about 15 wt % or less, preferably 1-12 wt %,
while the Group IB metal is usually present in lesser amounts,
e.g., 1:2 to about 1:20 weight ratio respecting the Group VIII
metal.
[0043] A typical catalyst is shown below:
Ni, wt % 2.5-3.5
Cu, wt % 0.25-0.35
Al.sub.2O.sub.3--SiO.sub.2 wt % 65-75
[0044] Al.sub.2O.sub.3 (binder) wt % 25-30 Surface Area 290-325
m.sup.2/g Pore Volume (Hg) 0.35-0.45 ml/g Bulk Density 0.58-0.68
g/ml
[0045] Another class of suitable hydroconversion/hydroisomerisation
catalysts are those based on molecular sieve type materials,
suitably comprising at least one Group VIII metal component,
preferably Pt and/or Pd, as the hydrogenation component. Suitable
zeolitic and other aluminosilicate materials, then, include Zeolite
beta, Zeolite Y, Ultra Stable Y, ZSM-5, ZSM-12, ZSM-22, ZSM-23,
ZSM-48, MCM-68, ZSM-35, SSZ-32, ferrierite, mordenite and
silica-alumino-phosphates, such as SAPO-11 and SAPO-31.
[0046] Examples of suitable hydroisomerisation/hydroisomerisation
catalysts are for instance described in WO-A-9201657. Combinations
of these catalysts are also possible. Very suitable
ydroconversion/hydroisomerisation processes are those involving a
first step wherein a zeolite beta or ZSM-48 based catalyst is used
and a second step wherein a ZSM-5, ZSM-12, ZSM-22, ZSM-23, ZSM-48,
MCM-68, ZSM-35, SSZ-32, ferrierite, mordenite based catalyst is
used. Of the latter group ZSM-23, ZSM-22 and ZSM-48 are preferred.
Examples of such processes are described in US-A-20040065581, which
disclose a process comprising a first step catalyst comprising
platinum and zeolite beta and a second step catalyst comprising
platinum and ZSM-48. These processes are capable of yielding a base
oil product which does not require a further dewaxing step.
[0047] Combinations wherein the Fischer-Tropsch product is first
subjected to a first hydroisomerisation step using the amorphous
catalyst comprising a silica-alumina carrier as described above
followed by a second hydroisomerisation step using the catalyst
comprising the molecular sieve has also been identified as a
preferred process to prepare the base oil to be used in the present
invention. More preferred the first and second hydroisomerisation
steps are performed in series flow. Most preferred the two steps
are performed in a single reactor comprising beds of the above
amorphous and/or crystalline catalyst.
[0048] In step (a) the feed is contacted with hydrogen in the
presence of the catalyst at elevated temperature and pressure. The
temperatures typically will be in the range of from 175 to
380.degree. C., preferably higher than 250.degree. C. and more
preferably from 300 to 370.degree. C. The pressure will typically
be in the range of from 10 to 250 bar and preferably between 20 and
80 bar. Hydrogen may be supplied at a gas hourly space velocity of
from 100 to 10000 Nl/l/hr, preferably from 500 to 5000 Nl/l/hr. The
hydrocarbon feed may be provided at a weight hourly space velocity
of from 0.1 to 5 kg/l/hr, preferably higher than 0.5 kg/l/hr and
more preferably lower than 2 kg/l/hr. The ratio of hydrogen to
hydrocarbon feed may range from 100 to 5000 Nl/kg and is preferably
from 250 to 2500 Nl/kg.
[0049] The conversion in step (a) as defined as the weight
percentage of the feed boiling above 370.degree. C. which reacts
per pass to a fraction boiling below 370.degree. C., is at least 20
wt %, preferably at least 25 wt %, but preferably not more than 80
wt %, more preferably not more than 65 wt %. The feed as used above
in the definition is the total hydrocarbon feed fed to step (a),
thus also any optional recycle of a high boiling fraction which may
be obtained in step (b).
[0050] In step (b) the product of step (a) is preferably separated
into one or more distillate fuels fractions and a base oil or base
oil precursor fraction having the desired viscosity properties. If
the pour point is not in the desired range the pour point of the
base oil is further reduced by means of a dewaxing step (c),
preferably by catalytic dewaxing. In such an embodiment it may be a
further advantage to dewax a wider boiling fraction of the product
of step (a). From the resulting dewaxed product the base oil and
oils having a desired viscosity can then be advantageously isolated
by means of distillation. Dewaxing is preferably performed by
catalytic dewaxing as for example described in WO-A-02070629, which
publication is hereby incorporated by reference. The final boiling
point of the feed to the dewaxing step (c) may be the final boiling
point of the product of step (a) or lower if desired.
[0051] Suitably, the base oil or base oil blend has a kinematic
viscosity at 100.degree. C. of from 3 to 25 mm.sup.2/s. Preferably,
it has a kinematic viscosity at 100.degree. C. of from 3 to 15
mm.sup.2/sec, more preferably of from 3.5 to 9.5 mm.sup.2/sec, yet
more preferably from 3.75 to 8.5 mm2/sec.
[0052] Preferably, the base oil has a pour point of less than
-39.degree. C. and a kinematic viscosity at 100.degree. C. of
between 3.8 and 8.5 mm.sup.2/s (cSt), and wherein the lubricant
composition has a kinematic viscosity at 100.degree. C. of between
9.3 and 12.5 mm.sup.2/s (cSt). Yet more preferably, it has a
kinematic viscosity at 100.degree. C. below 15.5 mm.sup.2/s, more
preferably below 14 mm.sup.2/s, most preferably below 13
mm.sup.2/s.
[0053] The pour point of the base oil is preferably below
-30.degree. C. The flash point of the base oil as measured by ASTM
D92 preferably is greater than 120.degree. C., more preferably even
greater than 140.degree. C.
[0054] The base oil used in the lubricant composition in the
package according to the invention preferably has a viscosity index
in the range of from 100 to 600, more preferably a viscosity index
in the range of from 110 to 200, and even more preferably a
viscosity index in the range of from 120 to 150.
[0055] The lubricant used in the package according to the invention
may comprise as the base oil component exclusively the paraffinic
base oil, or a combination of the paraffinic base oils and ester as
described above, or alternatively in combination with another
additional base oil. The additional base oil will suitably comprise
less than 20 wt %, more preferably less than 10 wt %, again more
preferably less than 5 wt % of the total fluid formulation.
Examples of such base oils are mineral based paraffinic and
naphthenic type base oils and synthetic base oils, for example poly
alpha olefins, poly alkylene glycols and the like. The amounts are
limited by the nitrous oxide reduction that is to be attained.
Preferably, the lubricant further comprises saturated cyclic
hydrocarbons in an amount of from 5 to 10% by weight, based on the
total lubricant since this improves the low temperature
compatibility of the different components in the lubricant.
[0056] The lubricant according to the invention further preferably
comprises a viscosity improver in an amount of from 0.01 to 30% by
weight. Viscosity index improvers (also known as VI improvers,
viscosity modifiers, or viscosity improvers) provide lubricants
with high- and low-temperature operability. These additives impart
shear stability at elevated temperatures and acceptable viscosity
at low temperatures. The lubricant used in the package according to
the invention further preferably comprises at least one other
additional lubricant component in effective amounts, such as for
instance polar and/or non-polar lubricant base oils, and
performance additives such as for example, but not limited to,
metallic and ashless oxidation inhibitors, metallic and ashless
dispersants, metallic and ashless detergents, corrosion and rust
inhibitors, metal deactivators, metallic and non-metallic, low-ash,
phosphorus- containing and non-phosphorus, sulphur-containing and
non-sulphur-containing anti-wear agents, metallic and non-metallic,
phosphorus-containing and non-phosphorus, sulphur-containing and
non-sulphurous extreme pressure additives, anti-seizure agents,
pour point depressants, wax modifiers, viscosity modifiers, seal
compatibility agents, friction modifiers, lubricity agents,
anti-staining agents, chromophoric agents, anti foaming agents,
demulsifiers, and other usually employed additive packages. For a
review of many commonly used additives, reference is made to D.
Klamann in Lubricants and Related Products, Verlag Chemie,
Deerfield Beach, Fla.; ISBN 0-89573-177-0, and to "Lubricant
Additives" by M. W. Ranney, published by Noyes Data Corporation of
Parkridge, N.J. (1973).
[0057] Preferably, the lubricant composition has low sulphated ash,
sulphur and phosphorus concentrations, which will result in
additional engine cleanliness such as piston cleanliness. More
preferably, the lubricant composition has a sulphur content of in
the range of from 0.01 to 0.3 wt. %, a phosphorus content in the
range of from 0.01 to 0.1 wt. % and a sulphated ash content in the
range of from 0.1 to 1.2 wt. %, based on the total weight of the
lubricant composition, which comprises the synthetic base oil as
described herein-above.
[0058] In a preferred embodiment of the present invention, R is an
optionally substituted branched or straight chain alkyl group
containing from 4 to 49 carbon atoms, more preferably from 6 to 40
carbon atoms; R1 is hydrogen or an optionally substituted branched
or straight chain alkyl group containing from 3 to 50 carbon atoms,
more preferably from 4 to 49 carbon atom, even more preferably from
6 to 40 carbon atoms; and X is an integer from 10 to 9,000, more
preferably from 20 to 8,000.
[0059] In the present invention, the phrase "optionally substituted
branched or straight chain alkyl group" is used to describe alkyl
groups optionally containing one or more "inert"
heteroatom-containing functional groups. By "inert" is meant that
the functional groups do not interact to any substantial degree
with the other components of the lubricating oil composition.
Non-limiting examples of such inert groups are amines and halides,
such as fluoride and chloride. Examples of compounds of formula I
include those described in US-B1-6331510, US-B1-6204224 and
US-B1-6372696. Compounds of formula I include those available ex.
Rohmax under the trade designations "Acryloid 985", "Viscoplex
6-054", "Viscoplex 6-954" and "Viscoplex 6-565" and that available
ex. The Lubrizol Corporation under the trade designation "LZ
7720C". Compounds of formula I may be conveniently prepared by
conventional methods. In particular, said compounds may be prepared
according to the methods described in U.S. Pat. No. 3,506,574 and
EP-A2-0750031.
[0060] The lubricating oil composition may comprise a single zinc
dithiophosphate or a combination of two or more zinc
dithiophosphates, the or each zinc dithiophosphate being selected
from zinc dialkyl-, diaryl- or alkylaryl-dithiophosphates, provided
that the total phosphorus content of the lubricating oil
composition is in the range of from 0.01 to 0.1 wt. %.
[0061] Zinc dithiophosphate is a well known additive in the art and
may be conveniently represented by general formula II;
##STR00001##
wherein R2 to R5 may be the same or different and are each a
primary alkyl group containing from 1 to 20 carbon atoms preferably
from 3 to 12 carbon atoms, a secondary alkyl group containing from
3 to 20 carbon atoms, preferably from 3 to 12 carbon atoms, an aryl
group or an aryl group substituted with an alkyl group, said alkyl
substituent containing from 1 to 20 carbon atoms preferably 3 to 18
carbon atoms.
[0062] Zinc dithiophosphate compounds in which R2 to R5 are all
different from each other can be used alone or in admixture with
zinc dithiophosphate compounds in which R2 to R5 are all the
same.
[0063] Preferably, the or each zinc dithiophosphate used in the
present invention is a zinc dialkyl dithiophosphate. Suitable zinc
dithiophosphates which are commercially available include primary
zinc dithiophosphates such as those available ex. Lubrizol
Corporation under the trade designations "Lz 1097" and "Lz 1395",
those available ex. Chevron Oronite under the trade designations
"OLOA 267" and "OLOA 269R", and that available ex. Ethyl under the
trade designation "HITEC 7197"; secondary zinc dithiophosphates
such as those available ex. Lubrizol Corporation under the trade
designations "Lz 677A", "Lz 1095" and "Lz 1371", that available ex.
Chevron Oronite under the trade designation "OLOA 262" and that
available ex. Ethyl under the trade designation "HITEC 7169"; and
aryl type zinc dithiophosphates such as those available ex.
Lubrizol Corporation under the trade designations "Lz 1370" and "Lz
1373" and that available ex. Chevron Oronite under the trade
designation "OLOA 260".
[0064] The lubricating oil composition according to the present
invention may generally comprise in the range of from 0.1 to 1.0
wt. % of zinc dithiophosphate, (if primary or secondary alkyl
type), preferably in the range of from 0.2 to 0.8 wt. % and most
preferably in the range of from 0.4 to 0.7 wt. %, based on total
weight of the lubricating oil composition.
[0065] The amount of phosphorus in the lubricating oil composition
of the present invention is therefore generally in the range of
from 0.01 to 0.10 wt. %, preferably in the range of from 0.02 to
0.08 wt. %, most preferably in the range of from 0.04 to 0.07 wt.
%.
[0066] At phosphorus levels of 0.01 wt. % and below, there is
insufficient anti-wear performance. At phosphorus levels of 0.1 wt.
% and above, the phosphorus may have a detrimental effect on
vehicle after-treatment devices.
[0067] The lubricating oil composition of the present invention
generally has a sulphated ash content in the range of from 0.1 to
1.2 wt. %, preferably in the range of from 0.3 to 1.2 wt. %, more
preferably in the range of from 0.5 to 1.1 wt. % and most
preferably in the range of from 0.6 to 1.0 wt. %, based on the
total weight of the lubricating oil composition.
[0068] The lubricating oil composition of the present invention
generally has a sulphur content in the range of from 0.01 to 0.3
wt. %, preferably in the range of from 0.06 to 0.3 wt. %, more
preferably in the range of from 0.1 to 0.25 wt. % and most
preferably in the range of from 0.12 to 0.20 wt. %, based on the
total weight of the lubricating oil composition.
[0069] Preferred compositions according to the present invention
have one or more of the following features:
(i) greater than 0.01 wt. % of phosphorus; (ii) greater than 0.035
wt. % of phosphorus; (iii) at least 0.035 wt. % of phosphorus; (iv)
less than 0.07 wt. % of phosphorus; (v) less than 0.10 wt. % of
phosphorus; (vi) at most 0.08 wt. % of phosphorus; (vii) not
greater than 1.0 wt. % of sulphated ash; (viii) not greater than
0.9 wt. % of sulphated ash; (ix) not greater than 0.7 wt. % of
sulphated ash; (x) not greater than 0.3 wt. % of sulphur; (xi) not
greater than 0.1 wt. % of sulphur; and (xii) not greater than 0.05
wt. % of sulphur, based on the total weight of the lubricating oil
composition.
[0070] In a further aspect, the present invention provides for a
method of lubricating a compression-ignited internal combustion
engine comprising operating the engine and lubricating the engine
with a lubricating oil composition of the first aspect. In yet a
further aspect, the present invention provides a method of
improving piston cleanliness and reducing the ring-sticking
tendencies of a compression-ignited internal combustion engine
comprising adding to the engine a lubricating oil composition
according to the present invention. In yet a further aspect, the
present invention provides a combination comprising the crankcase
of a compression-ignited internal combustion engine, preferably
having a specific power output of 25 kW/litre or greater, and a
lubricating oil composition according to the invention.
[0071] The invention will be further illustrated by the following,
non-limiting examples:
EXAMPLE 1
[0072] Two low sulfur, low sulphated ash, and low phosphorus
content 5W-40 lubricant compositions were prepared.
[0073] The lubricant formulation according to the present invention
was formulated using two Fischer-Tropsch derived base oils having
the properties as disclosed in Table 1.
[0074] For comparison, a lubricant formulation was prepared based
on two mineral oil-derived Group III base oils commercially
available as Yubase 4 and Yubase 6 from SK Corporation (Yubase is a
registered trademark of SK Corporation). A "Group III" base oil is
a base oil according to the definitions of American Petroleum
Institute (API) category I and II. Such API categories are defined
in API Publication 1509, 15th Edition, Appendix E, April 2002.
Group III base oils contain greater than or equal to 90% saturates
and less than or equal to 0.03% sulphur and have a viscosity index
of greater than 120, according to the afore-mentioned ASTM methods.
The following additives were employed: VISCOPLEX 6-054, a
commercially available dispersant and viscosity index improver
(VISCOPLEX is a registered trademark of Rohm GmbH & Co. KG); a
commercially available heavy duty diesel engine oil soot
dispersant; Infineum SV200 and Infineum SV150, both commercially
available viscosity index improvers ("Infineum" is a trademark of
Infineum International Ltd.; SV, is an abbreviation for ShellVis,
the latter is a trademark of Shell Chemical Company), and a
commercially available overbased detergent (Infineum C9371).
Lubricant compositions were blended to comparable VdCCS (cold crank
viscosity) at -30.degree. C. and comparable Vk100C by appropriately
balancing the pair of base oils in each case and also the viscosity
modifier treat in each case.
TABLE-US-00001 TABLE 1 Blends for Nissan TD25 piston cleanliness
tests Comparative Example 1 Example Components [% m/m] GTL base oil
1 63.60 -- (5 mm.sup.2/s (cSt)) GTL base oil 2 7.50 -- [8
mm.sup.2/s (cSt)] Yubase 4 -- 62.00 Yubase 6 -- 6.36 Ashless
dispersant 14.00 14.00 Overbased detergent 2.40 2.40 Viscosity
modifier 1.50 1.50 Viscoplex 6-054 Viscosity modifiers 11.00 (5.5 +
5.5) 13.76 (5.76 + 8.00) (Infineum SV151 & 201) Antifoam agent
[ppm] 264 264 Inspection Properties VK @ 100.degree. C. [mm.sup.2/s
(cSt)] 15.47 15.69 VK @ 40.degree. C. [mm.sup.2/s (cSt)] 93.25
94.59 VdCCS @ -30.degree. C. [mPas (cP)] 6357 6583 Noack
evaporative loss 7.9, 8.0 12.3, 12.5 ASTM D-5800 [% m/m]
[0075] A Nissan TD25 Detergency Test (Japanese Automobile Standards
Organization (JASO) M336: 1998)) was performed which evaluates the
detergency of automobile diesel oils under high temperature and
high load, in a simulation of a high-speed highway service of a
diesel-powered passenger car or light truck. JASO Specifications:
The Nissan TD25 detergency procedure is part of JASO Specifications
JASO DH-1 and JASO DL-1.
[0076] The test engine was a 2.5 L four-cylinder, in-line TD25
diesel engines manufactured by Nissan Diesel (Nissan Diesel is a
registered trademark of Nissan Diesel Motor CO., LTD.). The engine
was mounted into an engine dynamometer test stand. As a test fuel,
a class 2 light gas oil, as specified by JIS K 2202 was
employed.
[0077] The engine test included running the engine continuously at
a speed of 4,300 rpm under full load and maximal torque for a
duration of 200 hours, with the exception of a complete oil change
at 100 hours. The engine oil temperature was 120.degree. C., the
coolant temperature 90.degree. C. After the test, piston state and
sludge formed were rated. Equally, the wear amount of the piston
rings and metals bearings, of the oil rings, the camshaft and
cylinder liners were determined. Furthermore, an analysis of the
used oils was performed. Pistons and rings were evaluated for
lacquer deposits, wear, and ring sticking. Oil rings were rated for
clogging. Cylinder liners were evaluated for deposits and wear.
Cylinder heads were rated for combustion chamber deposits.
Oil-contact surfaces in the engine were rated for sludge formation.
The used lubricant was evaluated for kinematic viscosity, soot
content, sulphated ash, total acid number, total base number,
insoluble matter, water, fuel dilution and wear metals. The results
for piston ring deposits and top groove fill are depicted in Table
2:
TABLE-US-00002 TABLE 2 Nissan TD25 test results Components Example
1 Comparative Example Piston detergency Residual carbon [% wt.]
4.75 4.94 Top Groove fill [% vol.] 37.0 57.1
[0078] Accordingly, the tests clearly illustrate the increased
piston cleanliness and reduced top groove fill of a GT1-based
formulation with respect to a mineral oil Group II base oil based
formulation.
* * * * *