U.S. patent application number 12/014223 was filed with the patent office on 2008-05-22 for process to prepare a lubricating base oil and a gas oil.
Invention is credited to Gilbert Robert Bernard GERMAINE.
Application Number | 20080116110 12/014223 |
Document ID | / |
Family ID | 8182643 |
Filed Date | 2008-05-22 |
United States Patent
Application |
20080116110 |
Kind Code |
A1 |
GERMAINE; Gilbert Robert
Bernard |
May 22, 2008 |
PROCESS TO PREPARE A LUBRICATING BASE OIL AND A GAS OIL
Abstract
Process to prepare two or more lubricating base oil grades and a
gas oil by (a) hydrocracking/hydroisomerisating a Fischer-Tropsch
product, wherein weight ratio of compounds having at least 60 or
more carbon atoms and compounds having at least 30 carbon atoms in
the Fischer-Tropsch product is 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 one or
more gas oil fractions and a base oil precursor fraction, (c)
performing a pour point reducing step to the base oil precursor
fraction obtained in step (b), and (d) separating the effluent of
step (c) in two or more base oil grades.
Inventors: |
GERMAINE; Gilbert Robert
Bernard; (Petit Couronne, FR) |
Correspondence
Address: |
Shell Oil Company
910 Louisiana
Houston
TX
77002
US
|
Family ID: |
8182643 |
Appl. No.: |
12/014223 |
Filed: |
January 15, 2008 |
Current U.S.
Class: |
208/107 |
Current CPC
Class: |
C10N 2030/00 20130101;
C10G 65/043 20130101; C10N 2040/30 20130101; C10G 2400/10 20130101;
C10G 65/12 20130101; C10M 171/008 20130101; C10N 2040/08 20130101;
C10N 2040/042 20200501; C10G 45/58 20130101; C10G 2/00 20130101;
C10M 2205/173 20130101; C10G 67/04 20130101; C10N 2020/02 20130101;
C10N 2040/50 20200501; C10M 2205/17 20130101; C10M 109/02 20130101;
C10M 171/02 20130101; C10N 2040/255 20200501; C10N 2040/36
20130101; C10N 2040/14 20130101; C10G 67/02 20130101; C10N 2030/02
20130101 |
Class at
Publication: |
208/107 |
International
Class: |
C10G 47/00 20060101
C10G047/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 5, 2001 |
EP |
01400563.1 |
Claims
1. Process to prepare two or more lubricating base oil grades and a
gas oil by (a) hydrocracking/hydroisomerisating a Fischer-Tropsch
product, wherein weight ratio of compounds having at least 60 or
more carbon atoms and compounds having at least 30 carbon atoms in
the Fischer-Tropsch product is 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 one or
more gas oil fractions and a base oil precursor fraction, (c)
performing a pour point reducing step to the base oil precursor
fraction obtained in step (b), and (d) separating the effluent of
step (c) in two or more base oil grades.
2. Process according to claim 1, wherein at least 50 wt % of
compounds in the Fischer-Tropsch product have at least 30 carbon
atoms.
3. Process according to any one of claims 1-2, wherein the weight
ratio of compounds having at least 60 or more carbon atoms and
compounds having at least 30 carbon atoms in the Fischer-Tropsch
product is at least 0.4.
4. Process according to any one of claims 1-3, wherein the
conversion in step (a) is between 25 and 70 wt %.
5. Process according to any one of claims 1-4, wherein the base oil
precursor fraction has an initial boiling point of between 330 and
400.degree. C.
6. Process according to any one of claims 1-5, wherein step (c) is
performed by means of solvent dewaxing.
7. Process according to any one of claims 1-5, wherein step (c) is
performed by means of catalytic dewaxing.
8. Process according to claim 7, wherein the catalytic dewaxing
catalyst comprises a zeolite having a pore diameter of between 0.35
and 0.8 nm, a Group VIII metal and a binder.
9. Process according to claim 8, wherein the binder is a low
acidity refractory oxide binder which is essentially free of
alumina and wherein the catalyst is obtained by contacting an
extrudate of zeolite and binder with an aqueous solution of
fluorosilicate salt.
10. Process according to claim 9, wherein step (c) is performed at
a temperature between 275 and 375.degree. C. and a pressure of
between 40 and 70 bars to obtain base oils having a pour point of
below -60 and up to -10.degree. C.
11. Base oil having a kinematic viscosity at 100.degree. C. of
between 12 and 30 cSt, a viscosity index of greater than 125 and an
evaporation loss after 1 hour at 250.degree. C. of at most 0.5 wt
%.
12. Use of base oil according to claim 11 as a plasticizer.
13. Use of the base oil according to claim 11 as a mould release
process oil.
Description
[0001] The invention is directed to a process to prepare a
lubricating base oil and a gas oil from a Fischer-Tropsch
product.
[0002] Such a process is known from EP-A-776959. This publication
describes a process wherein the high boiling fraction of a
Fischer-Tropsch synthesis product is first hydroisomerised in the
presence of a silica/alumina supported Pd/Pt catalyst. The
isomerised product having a content of non-cyclic iso-paraffins of
more than 80 wt % is subsequently subjected to a pour point
reducing step. The disclosed pour point reducing step in one of the
examples is a catalytic dewaxing step performed in the presence of
a silica supported dealuminated ZSM-23 catalyst at 310.degree.
C.
[0003] A disadvantage of such a process is that only one grade of
base oils is prepared. A next disadvantage is that the
hydroisomerisation step is performed on a narrow boiling range
fraction of a Fischer-Tropsch synthesis product, which
hydroisomerisation step is especially directed to prepare a base
oil precursor fraction having the desired properties. The
hydroisomerisation process step can also yield valuable middle
distillates next to base oil precursor fractions if the feed would
also include more lower boiling compounds. There is thus a desire
to prepare base oils from a waxy paraffinic fraction as obtainable
from a hydroisomerisation process step which yields both middle
distillates, such as naphtha, kerosine and gas oil, and the waxy
paraffinic fraction having a content of non-cyclic iso-paraffins of
more than 90 wt %. There is also a desire to have a flexible
process wherein two or more base oils having different viscosity
properties are obtained of excellent quality.
[0004] The object of the present invention is to provide a process
wherein a high yield to gas oils is achieved and wherein two or
more high quality base oils are prepared having different
viscosities from a waxy Fischer-Tropsch product.
[0005] This object is achieved by the following process. Process to
prepare two or more lubricating base oil grades and a gas oil
by
[0006] (a) hydrocracking/hydroisomerisating a Fischer-Tropsch
product, wherein weight ratio of compounds having at least 60 or
more carbon atoms and compounds having at least 30 carbon atoms in
the Fischer-Tropsch product is 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 one or more gas oil
fractions and a base oil precursor fraction,
(c) performing a pour point reducing step to the base oil precursor
fraction obtained in step (b), and
(d) separating the effluent of step (c) in two or more base oil
grades.
[0007] Applicants found that by performing the
hydro-cracking/hydroisomerisation step with the relatively heavy
feedstock a higher yield of gas oils as calculated on the feed to
step (a) can be obtained. A further advantage is that both fuels,
for example gas oil, and material suited for preparing base oils
are prepared in one hydrocracking/hydroisomerisation process step.
This line up is more simple than a line up wherein a dedicated base
oil hydrocracking/hydroisomerisation step is performed on a
Fischer-Tropsch wax boiling mainly above 370.degree. C. as
described in for example WO-A-0014179. Another advantage is that
two or more base oil grades having different kinematic viscosities
at 100.degree. C. ranging from about 2 cSt to above 12 cSt can be
prepared simultaneously.
[0008] A further advantage is that base oils are prepared having a
relatively high content of cyclo-paraffins, which is favourable to
achieve desired solvency properties. The content of cyclo-paraffins
in the saturates fraction of the obtained base oil may be between 5
and 40 wt %. Base oils having a cyclo-paraffin content in the
saturates fraction of between 12 and 20 wt % have been found to be
excellent base stocks to formulate motor engine lubricants.
[0009] The process of the present invention also results in middle
distillates having exceptionally good cold flow properties. These
excellent cold flow properties could perhaps be explained by the
relatively high ratio iso/normal and especially the relatively high
amount of di- and/or trimethyl compounds. Nevertheless, the cetane
number of the diesel fraction is more than excellent at values far
exceeding 60, often values of 70 or more are obtained. In addition,
the sulphur content is extremely low, always less than 50 ppmw,
usually less than 5 ppmw and in most case the sulphur content is
zero. Further, the density of especially the diesel fraction is
less than 800 kg/m.sup.3, in most cases a density is observed
between 765 and 790 kg/m.sup.3, usually around 780 kg/m.sup.3 (the
viscosity for such a sample being about 3.0 cSt). Aromatic
compounds are virtually absent, i.e. less than 50 ppmw, resulting
in very low particulate emissions. The polyaromatic content is even
much lower than the aromatic content, usually less than 1 ppmw.
T95, in combination with the above properties, is below 380.degree.
C., often below 350.degree. C.
[0010] The process as described above results in middle distillates
having extremely good cold flow properties. For instance, the cloud
point of any diesel fraction is usually below -18.degree. C., often
even lower than -24.degree. C. The CFPP. is usually below
-20.degree. C., often -28.degree. C. or lower. The pour point is
usually below -18.degree. C., often below -24.degree. C.
[0011] The relatively heavy Fischer-Tropsch product used in step
(a) 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 product is at least 0.2, preferably at least
0.4 and more preferably at least 0.55. Preferably 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, preferably at least 0.935, more preferably at least
0.945, even more preferably at least 0.955. The initial boiling
point of the Fischer-Tropsch product is preferably below
200.degree. C. Preferably any compounds having 4 or less carbon
atoms and any compounds having a boiling point in that range are
separated from a Fischer-Tropsch synthesis product before being
used in step (a). The Fischer-Tropsch product as described in
detail above is a Fischer-Tropsch product which has not been
subjected to a hydroconversion step as defined according to the
present invention. The content of non-branched compounds in the
Fischer-Tropsch product will therefore be above 80 wt %. In
addition to the Fischer-Tropsch product also other fractions may be
additionally processed in step (a). Possible other fractions to be
fed to step (a) may suitably be part of the base oil precursor
fraction which cannot be processed in step (c) and/or off-spec base
oil fractions as obtained in step (d).
[0012] Such a Fischer-Tropsch product can be obtained by any
process which yields a relatively heavy Fischer-Tropsch product.
Not all Fischer-Tropsch processes yield such a heavy product. An
example of a suitable Fischer-Tropsch process is described in
WO-A-9934917 and in AU-A-698392. These processes may yield a
Fischer-Tropsch product as described above.
[0013] The Fischer-Tropsch product 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 thus generally be below 1 ppmw respectively.
[0014] The Fischer-Tropsch product may be obtained by subjecting
the reaction product of the Fischer-Tropsch reaction to a mild
hydrotreatment step in order to remove any oxygenates and saturate
any olefinic compounds. Such a hydrotreatment is described in
EP-B-668342. The mildness of the hydrotreating step is preferably
expressed in that the degree of conversion in this step is less
than 20 wt % and more preferably less than 10 wt %. The conversion
is here defined as the weight percentage of the feed boiling above
370.degree. C., which reacts to a fraction boiling below
370.degree. C. After such a mild hydrotreatment lower boiling
compounds, having four or less carbon atoms and other compounds
boiling in that range, will preferably be removed from the effluent
before it is used in step (a) as the above described
Fischer-Tropsch product.
[0015] The hydrocracking/hydroisomerisation reaction of step (a) is
preferably performed in the presence of hydrogen and a catalyst,
known to one skilled in the art as being suitable for this
reaction. Catalysts for use in step (a) typically comprise an
acidic functionality and a hydrogenation/dehydrogenation
functionality. Preferred acidic functionalities are refractory
metal oxide carriers. Suitable carrier materials include silica,
alumina, silica-alumina, zirconia, titania and mixtures thereof.
Preferred carrier materials for inclusion in the catalyst for use
in the process of this invention are silica, alumina and
silica-alumina. A particularly preferred catalyst comprises
platinum supported on a silica-alumina carrier. If desired,
applying a halogen moiety, in particular fluorine, or a phosphorous
moiety to the carrier, may enhance the acidity of the catalyst
carrier.
[0016] Preferred hydrogenation/dehydrogenation functionalities are
Group VIII noble metals, for example palladium and more preferably
platinum. The catalyst may comprise the
hydrogenation/dehydrogenation active component in an amount of from
0.005 to 5 parts by weight, preferably from 0.02 to 2 parts by
weight, per 100 parts by weight of carrier material. A particularly
preferred catalyst for use in the hydroconversion stage comprises
platinum in an amount in the range of from 0.05 to 2 parts by
weight, more preferably from 0.1 to I parts by weight, per 100
parts by weight of carrier material. The catalyst may also comprise
a binder to enhance the strength of the catalyst. The binder can be
non-acidic. Examples are clays and other binders known to one
skilled in the art. Examples of suitable
hydrocracking/hydro-isomerisation processes and suitable catalysts
are described in WO-A-0014179, EP-A-532118, EP-A-666894 and the
earlier referred to EP-A-776959.
[0017] 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 bara and preferably between 20
and 80 bara. 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.
[0018] 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 70 wt %. The feed as used above
in the definition is the total hydrocarbon feed fed to step (a),
including for example any recycle streams.
[0019] In step (b) the product of step (a) is separated into one or
more gas oil fractions and a base oil precursor fraction. The base
oil fraction will suitably have an initial boiling point of between
330 and 400.degree. C. The separation is preferably performed by
means of a distillation at about atmospheric conditions, preferably
at a pressure of between 1.2-2 bara, wherein the gas oil product
and lower boiling fractions, such as naphtha and kerosine
fractions, are separated from the higher boiling fraction of the
product of step (a).
[0020] In step (c) the base oil precursor fraction obtained in step
(b) is subjected to a pour point reducing treatment. With a pour
point reducing treatment is understood every process wherein the
pour point of the base oil is reduced by more than 10.degree. C.,
preferably more than 20.degree. C., more preferably more than
25.degree. C.
[0021] The pour point reducing treatment can be performed by means
of a so-called solvent dewaxing process or by means of a catalytic
dewaxing process. Solvent dewaxing is well known to those skilled
in the art and involves admixture of one or more solvents and/or
wax precipitating agents with the base oil precursor fraction and
cooling the mixture to a temperature in the range of from
-10.degree. C. to -40.degree. C., preferably in the range of from
-20.degree. C. to -35.degree. C., to separate the wax from the oil.
The oil containing the wax is usually filtered through a filter
cloth which can be made of textile fibres, such as cotton; porous
metal cloth; or cloth made of synthetic materials. Examples of
solvents which may be employed in the solvent dewaxing process are
C.sub.3-C.sub.6 ketones (e.g. methyl ethyl ketone, methyl isobutyl
ketone and mixtures thereof), C.sub.6-C.sub.10 aromatic
hydrocarbons (e.g. toluene), mixtures of ketones and aromatics
(e.g. methyl ethyl ketone and toluene), autorefrigerative solvents
such as liquefied, normally gaseous C.sub.2-C.sub.4 hydrocarbons
such as propane, propylene, butane, butylene and mixtures thereof.
Mixtures of methyl ethyl ketone and toluene or methyl ethyl ketone
and methyl isobutyl ketone are generally preferred. Examples of
these and other suitable solvent dewaxing processes are described
in Lubricant Base Oil and Wax Processing, Avilino Sequeira, Jr,
Marcel Dekker Inc., New York, 1994, Chapter 7.
[0022] Preferably step (c) is performed by means of a catalytic
dewaxing process. With such a process it has been found that base
oils having a pour point of below -40.degree. C. can be prepared
when starting from a base oil precursor fraction as obtained in
step (b) of the present process.
[0023] The catalytic dewaxing process can be performed by any
process wherein in the presence of a catalyst and hydrogen the pour
point of the base oil precursor fraction is reduced as specified
above. Suitable dewaxing catalysts are heterogeneous catalysts
comprising a molecular sieve and optionally in combination with a
metal having a hydrogenation function, such as the Group VIII
metals. Molecular sieves, and more suitably intermediate pore size
zeolites, have shown a good catalytic ability to reduce the pour
point of a base oil precursor fraction under catalytic dewaxing
conditions. Preferably the intermediate pore size zeolites have a
pore diameter of between 0.35 and 0.8 nm. Suitable intermediate
pore size zeolites are ZSM-5, ZSM-12, ZSM-22, ZSM-23, SSZ-32,
ZSM-35 and ZSM-48. Another preferred group of molecular sieves are
the silica-aluminaphosphate (SAPO) materials of which SAPO-11 is
most preferred as for example described in U.S. Pat. No. 4,859,311.
ZSM-5 may optionally be used in its HZSM-5 form in the absence of
any Group VIII metal. The other molecular sieves are preferably
used in combination with an added Group VIII metal. Suitable Group
VIII metals are nickel, cobalt, platinum and palladium. Examples of
possible combinations are Ni/ZSM-5, Pt/ZSM-23, Pd/ZSM-23, Pt/ZSM-48
and Pt/SAPO-11. Further details and examples of suitable molecular
sieves and dewaxing conditions are for example described in
WO-A-9718278, U.S. Pat. No. 5,053,373, U.S. Pat. No. 5,252,527 and
U.S. Pat. No. 4,574,043.
[0024] The dewaxing catalyst suitably also comprises a binder. The
binder can be a synthetic or naturally occurring (inorganic)
substance, for example clay, silica and/or metal oxides. Natural
occurring clays are for example of the montmorillonite and kaolin
families. The binder is preferably a porous binder material, for
example a refractory oxide of which examples are: alumina,
silica-alumina, silica-magnesia, silica-zirconia, silica-thoria,
silica-beryllia, silica-titania as well as ternary compositions for
example silica-alumina-thoria, silica-alumina-zirconia,
silica-alumina-magnesia and silica-magnesia-zirconia. More
preferably a low acidity refractory oxide binder material, which is
essentially free of alumina is used. Examples of these binder
materials are as silica, zirconia, titanium dioxide, germanium
dioxide, boria and mixtures of two or more of these of which
examples are listed above. The most preferred binder is silica.
[0025] A preferred class of dewaxing catalysts comprise
intermediate zeolite crystallites as described above and a low
acidity refractory oxide binder material which is essentially free
of alumina as described above, wherein the surface of the
aluminosilicate zeolite crystallites has been modified by
subjecting the aluminosilicate zeolite crystallites to a surface
dealumination treatment. A preferred dealumination treatment is by
contacting an extrudate of the binder and the zeolite with an
aqueous solution of a fluorosilicate salt as described in for
example U.S. Pat. No. 5,157,191 or WO-A-0029511. Examples of
suitable dewaxing catalysts as described above are silica bound and
dealuminated Pt/ZSM-5, silica bound and dealuminated Pt/ZSM-23,
silica bound and dealuminated Pt/ZSM-12, silica bound and
dealuminated Pt/ZSM-22, as for example described in WO-A-0029511
and EP-B-832171.
[0026] Catalytic dewaxing conditions are known in the art and
typically involve operating temperatures in the range of from 200
to 500.degree. C., suitably from 250 to 400.degree. C., hydrogen
pressures in the range of from 10 to 200 bar, preferably from 40 to
70 bar, weight hourly space velocities (WHSV) in the range of from
0.1 to 10 kg of oil per litre of catalyst per hour (kg/l/hr),
suitably from 0.2 to 5 kg/l/hr, more suitably from 0.5 to 3 kg/l/hr
and hydrogen to oil ratios in the range of from 100 to 2,000 litres
of hydrogen per litre of oil. By varying the temperature between
275 and more preferably between 315 and 375.degree. C. at between
40-70 bars, in the catalytic dewaxing step it is possible to
prepare base oils having different pour point specifications
varying suitably from below -60 up to -10.degree. C.
[0027] The effluent of step (c) is optionally subjected to an
additional hydrogenation step prior to step (d) or after performing
step (d), also referred to as a hydrofinishing step for example if
the effluent contains olefins or when the product is sensitive to
oxygenation or when colour needs to be improved. This step is
suitably carried out at a temperature between 180 and 380.degree.
C., a total pressure of between 10 to 250 bar and preferably above
100 bar and more preferably between 120 and 250 bar. The WHSV
(Weight hourly space velocity) ranges from 0.3 to 2 kg of oil per
litre of catalyst per hour (kg/l.h).
[0028] The hydrogenation catalyst is suitably a supported catalyst
comprising a dispersed Group VIII metal. Possible Group VIII metals
are cobalt, nickel, palladium and platinum. Cobalt and nickel
containing catalysts may also comprise a Group VIII metal, suitably
molybdenum and tungsten. Suitable carrier or support materials are
amorphous refractory oxides Examples of suitable amorphous
refractory oxides include inorganic oxides, such as alumina,
silica, titania, zirconia, boria, silica-alumina, fluorided
alumina, fluorided silica-alumina and mixtures of two or more of
these.
[0029] Examples of suitable hydrogenation catalysts are
nickel-molybdenum containing catalyst such as KF-847 and KF-8010
(AKZO Nobel) M-8-24 and M-8-25 (BASF), and C-424, DN-190, HDS-3 and
HDS-4 (Criterion); nickel-tungsten containing catalysts such as
NI-4342 and NI-4352 (Engelhard) and C-454 (Criterion);
cobalt-molybdenum containing catalysts such as KF-330 (AKZO-Nobel),
HDS-22 (Criterion) and HPC-601 (Engelhard). Preferably platinum
containing and more preferably platinum and palladium containing
catalysts are used. Preferred supports for these palladium and/or
platinum containing catalysts are amorphous silica-alumina.
Examples of suitable silica-alumina carriers are disclosed in
WO-A-9410263. A preferred catalyst comprises an alloy of palladium
and platinum preferably supported on an amorphous silica-alumina
carrier of which the commercially available catalyst C-624 of
Criterion Catalyst Company (Houston, Tex.) is an example.
[0030] In step (d) lower boiling non-base oil fractions are
suitably first removed, preferably by means of distillation,
optionally in combination with an initial flashing step. After
removal of these lower boiling compounds the dewaxed product is
separated, suitably by means of distillation, into two or more base
oil grades. In order to meet the desired viscosity grades and
volatility requirements of the various base oil grades preferably
off-spec fractions boiling between, above and/or below the desired
base oil grades are also obtained as separate fractions. These
fractions may advantageously be recycled to step (a) if they have
an initial boiling point of above 340.degree. C. Any fractions
obtained boiling in the gas oil range or below may suitably be
recycled to step (b) or alternatively directly blended with the end
gas oil product. The separation into the various fractions may
suitably be performed in a vacuum distillation column provided with
side stripers to separate the fraction from said column.
[0031] FIG. 1 shows a preferred embodiment of the process according
to the present invention. To a hydrocracker reactor (2) a
Fischer-Tropsch product (1) is fed. After separation of gaseous
products the effluent (3) is separated into a naphtha fraction (5),
a kerosene fraction (6), a gas oil fraction (7) and a base oil
precursor fraction (8). Part of this fraction (8) is recycled via
(10) and (21) to reactor (2) and part is fed to dewaxing reactor
(11), usually a packed bed reactor, via (9).
[0032] An intermediate product (13) is obtained by separating the
gaseous fraction and part of the gas oil fraction and those
compounds boiling within that range (12), which are formed during
the catalytic dewaxing process, from the effluent of reactor (11)
Intermediate product (13) is fed to a vacuum distillation column
(14), which column (14) is provided with means, e.g. side
strippers, to discharge along the length of the tower different
fractions boiling between the top and bottom distillation products.
In FIG. 1 tops (15), a gas oil fraction (19), a light base oil
grade (16), an intermediate base oil grade (17) and a heavy base
oil grade (18) are obtained as distillate products of column (17).
In order to meet volatility requirements of grades (17) and (18)
intermediate fractions (20) are withdrawn from the column and
recycled via (21) to hydrocracker (2). Gas oil fractions obtained
as (12) and (19) may be recycled to distillation column (4) (not
shown). Alternatively it may also be possible that the bottom
distillate product of column (14) cannot be used as a base oil
grade. In such a situation the bottom distillate product is
suitably recycled to reactor (2) (not shown).
[0033] The process according to the invention can be suitably
applied to simultaneously prepare the following base oil grades,
(i) base oils having a kinematic viscosity at 100.degree. C. (vK @
100) of between about 2 and 4 cSt suitable for electrical oils,
(ii) base oils of vK @ 100 between about 2 and 15 cSt suitable for
refrigerator oils and/or (iii) base oils having a vK @ 100 of
between about 2 and up to 30 cSt suitable for process oil
applications or as medicinal white oil applications. Especially
base oils having a vK @ 100 of between 12 and 30 cSt may be
prepared having a VI of above 125 and an evaporation loss after 1
hour at 250.degree. C. of at most 0.5 wt %. Such novel base oils
may find use as plasticizers or as a mould release process oil.
Such a mould release agent may find advantageous use in food
packaging applications.
[0034] The base oil as obtainable by the process according to the
invention can be advantageously find use in electrical and
refrigerator oils, because of its low pour point. Especially the
grades having a pour point of below -40.degree. C. are very suited.
The base oils as obtained by the present invention are furthermore
advantageous for this use because of their higher resistance to
oxidation compared to low pour point naphthenic type base oils
which are presently used.
[0035] Medicinal white oils having a vK @ 100 in the range 4 to 25
cSt, preferably 6 to 9 cSt, can be blended using a base oils as
obtained by the above process. UV spectroscopy has shown that these
base oils have excellent potential to meet US Food and Drug
Administration FDA.sctn.178.3620 b and FDA.sctn.178.3620 c
requirements.
[0036] Process oils and especially cutting oils are preferably
based on these base oils because less additives are required to
formulate the process oil. Additives are to be avoided as much as
possible in these applications due to the fact that process oils
frequently come into contact with the skin of persons operating
machines, for example a cutting machine, in which the process oil
is used. Additives can give rise to skin irritation when the
process oil comes into contact with the skin of the operator.
[0037] The base oils can also be advantageously used in a turbine
or hydraulic fluid. The very highly inhibited oxidative stability
needed for such applications can be achieved by using the base oils
obtainable by the process of this invention in combination with
supplementary antioxidants. Preferred antioxidants are of the
aminic or hindered phenolic type.
[0038] Other base oils obtainable by the above process include base
oils suitable for automatic transition fluids (ATF). Preferably a
base oil is used having a low pour point of below -40.degree. C. as
obtainable when step (c) is performed by means of catalytic
dewaxing. Base oils is having a vK @ 100 of about 4 cSt can be
optionally blended with a grade having a vK @ 100 of about 2 cSt to
obtain a base oil suitable for an ATF. The lower viscosity base
oil, having a kinematic viscosity of about 2 to 3 cSt, can suitably
be obtained by catalytic dewaxing of a suitable gas oil fraction as
obtained in the atmospheric and/or vacuum distillation in step (b).
The Automatic Transmission Fluid will comprise the base oil as
described above, preferably having a vK @ 100 of between 3 and 6
cSt, and one or more performance additives. Examples of such
performance additives are an antiwear agent, an antioxidant, an
ashless dispersant, a pour point depressant, and antifoam agent, a
friction modifier, a corrosion inhibitor and a viscosity
modifier.
[0039] The base oils obtained by the present process having vK @
100 values of between 2 and 9 cSt, are also suitable for use in
automotive engine oils. Especially the base oils having the very
low pour points, suitably lower than -40.degree. C., have been
found to be very suitable for use in lubricant formulations such as
high performance gasoline engine oils of the 0W-xx specification
according to the SAE J-300 viscosity classification, wherein xx can
be 20, 30, 40, 50, 60. It has been found that these high tier
lubricant formulations can be prepared with the base oils
obtainable by the process of the current invention. Other
automotive engine oil applications are the 5W-xx and the 10W-xx
formulations, wherein the xx is as above. The automotive engine oil
formulation will suitably comprise one or more of the above
described base oil(s) and one or more additives. Examples of
additive types which may form part of the composition are ashless
dispersants, detergents, preferably of the over-based type,
viscosity modifying polymers, extreme pressure/antiwear additives,
preferably of the zinc dialkyl dithiophosphate type (ZDTP),
antioxidants, preferably of the hindered phenolic or aminic type,
pour point depressants, emulsifiers, demulsifiers, corrosion
inhibitors, rust inhibitors, antistaining additives and/or friction
modifiers. Specific examples of such additives are described in for
example Kirk-Othmer Encyclopedia of Chemical Technology, third
edition, volume 14, pages 477-526.
[0040] Food approved white oils can also be suitably based on the
base oil grades as obtained by the present process. The base oils
are very suitable for such an application because of the absence or
very low content of unsaturated cyclic molecules in the base
oil.
[0041] Greases may also be based on these base oils because it
seems that more soap thickeners can be included, as compared to
when conventional high viscosity index base oils are used, in order
to arrive at the same desired grease viscosity specifications.
Increased thickener inclusion is advantageous because it results in
greases of higher high temperature mechanical stability. Thus with
the base oils as obtainable by the present process it has been
found possible to formulate greases with a low pour point and an
improved high temperature mechanical stability. These greases
furthermore have an enhanced inhibited oxidational stability.
[0042] The invention will be illustrated with the following
non-limiting example.
EXAMPLE 1
[0043] The C.sub.5-C750.degree. C..sup.+fraction of the
Fischer-Tropsch product, as obtained in Example VII using the
catalyst of Example III of WO-A-9934917, was continuously fed to a
hydrocracking step (step (a)). The feed contained about 60 wt %
C.sub.30+ product. The ratio C.sub.60+/C.sub.30+ was about 0.55. In
the hydrocracking step the fraction was contacted with a
hydrocracking catalyst of Example 1 of EP-A-532118. The effluent of
step (a) was continuously distilled under vacuum to give lights,
fuels and a residue "R" boiling from 370.degree. C. and above. The
yield of gas oil fraction on fresh feed to hydrocracking step was
43 wt %. The properties of the gas oil thus obtained are presented
in Table 3.
[0044] The main part of the residue "R" was recycled to step (a)
and a remaining part was sent to a catalytic dewaxing step (c). The
conditions in the hydrocracking step (a) were: a fresh feed Weight
Hourly Space Velocity (WHSV) of 0.8 kg/l.h, recycle feed WHSV of
0.25 kg/l.h, hydrogen gas rate =1000 Nl/kg, total pressure =40 bar,
and a reactor temperature of 335.degree. C.
[0045] In the dewaxing step, the fraction described above boiling
from 370.degree. C. to above 750.degree. C. was contacted with a
dealuminated silica bound ZSM-5 catalyst comprising 0.7% by weight
Pt and 30 wt % ZSM-5 as described in Example 9 of WO-A-0029511. The
dewaxing conditions were 40 bar hydrogen, WHSV=1 kg/l.h and a
temperature of 355.degree. C.
[0046] The dewaxed oil was distilled into three base oil fractions
boiling between 305 and 410.degree. C. (yield based on feed to
dewaxing step was 13.4 wt %), between 410-460.degree. C. (yield
based on feed to dewaxing step was 13.6 wt %) and a fraction
boiling above 510.degree. C. (yield based on feed to dewaxing step
was 41.2 wt %).
[0047] The base oil fraction boiling between 410 and 460.degree. C.
and the fraction boiling between 305 and 410.degree. C. were
analysed in more detail (see Table 1). From Table 1 it can be seen
that a base oil according to the API Group III specifications was
obtained. TABLE-US-00001 TABLE 1 Grade 3 Grade 4 density at
20.degree. C. 805.5 814.5 pour point (.degree. C.) -54 -48
kinematic viscosity at 40.degree. C. (cSt) 9.05.4 17.99 kinematic
viscosity at 100.degree. C. (cSt) 3.0 4.011 VI 103 122 sulphur
content (% w) <0.001 <0.001 saturates (% w) >95
EXAMPLE 2
[0048] Example 1 was repeated except that the dewaxing temperature
was 365.degree. C. The dewaxed oil was distilled into three base
oil fractions boiling between 305 and 420.degree. C. (yield based
on feed to dewaxing step was 16.1 wt %), between 420-510.degree. C.
(yield based on feed to dewaxing step was 16.1 wt %) and a fraction
boiling above 510.degree. C. (yield based on feed to dewaxing step
was 27.9 wt %). The base oil fraction boiling between 420 and
510.degree. C. and the heavier fraction was analysed in more detail
(see Table 2). TABLE-US-00002 TABLE 2 Heavy Grade 5 Grade density
at 20.degree. C. 818.5 837.0 pour point (.degree. C.) -59 +9
kinematic viscosity at 40.degree. C. (cSt) 24.5 kinematic viscosity
at 100.degree. C. (cSt) 4.9 22.92 VI 128 178 sulphur content (% w)
<0.001 <0.001 saturates (% w) >95
EXAMPLE 3-4
[0049] Example 1 was repeated except that the temperature in step
(a) was varied (see Table 3). The gas oil fraction was further
analysed (see Table 3). Cloud point, Pour point and CFPP were
determined by ASTM D2500, ASTM D97 and IP 309-96 respectively.
Establishment of the C.sub.5+, C.sub.30+ and C.sub.60+ fractions
were done by gas chromatography.
COMPARATIVE EXPERIMENT A and B
[0050] Example 1 was repeated (Experiment A) starting from a
Fischer Tropsch material made with a cobalt/zirconia/silica
catalyst as described in EP-A-426223. The C.sub.5+ fraction
contained about 30 wt % C.sub.30+ product, the ratio
C.sub.60+/C.sub.30+ was 0.19. Experiment B was performed as
Experiment A except that the reaction temperature in step (a) was
different (See Table 3). The properties of the gas oil fractions
are summarised in Table 3. TABLE-US-00003 TABLE 3 Example 3 1 4 A B
Temperature 330 335 340 330 335 Cloud Point -13 -20 <-24 +1 -2
CFPP -14 -21 -28 0 -5 Pour Point -18 <-24 <-24 0 -6 Normals
(wt %) 27.6 21.3 19.9 50.4 41.2 Iso's (wt %) 72.4 78.7 80.1 49.6
58.8 Mono-methyl 37.3 39.5 39.5 29.2 32.2 Di-methyl 21.7 25.5 26.7
13.9 18.1 Others 13.4 13.8 14.1 6.4 8.5 Density (kg/l) 0.78 0.78
0.78 0.78 0.78 Cetane (D976m) 78 77 76 80 78 Cetane (D4737m) 87 85
86 90 85 T95 363 360 358 -- --
* * * * *