[0001] The present invention relates to a process for producing lubricating base oils from
Fischer-Tropsch waxes, and in particular lubricating base oils having a viscosity
index (VI) of at least 150.
[0002] Processes for producing base oils having VI's above 150 from Fischer-Tropsch waxes
are known in the art. For instance, in EP-A-0,515,256 a process for producing such
base oils is disclosed, said process comprising the steps of:
(a) contacting the synthetic or Fischer-Tropsch wax with hydrogen in the presence
of an alumina-based hydroconversion catalyst;
(b) contacting the effluent of step (a) with a hydro-isomerisation catalyst comprising
a matrix, a specific zeolite Y and a hydrogenation component;
(c) separating the effluent of step (b) into at least one lighter fraction and a heavy
fraction; and
(d) dewaxing the heavy fraction thereby yielding the base oil and a wax fraction.
This wax fraction may be partly or totally recycled to hydro-isomerisation step (b).
The Fischer-Tropsch wax used as the feed in the working examples of EP-A-0,515,256
has a broad boiling range (difference between 90 %wt boiling point and 10 %wt boiling
point is as high as 249 °C) which implies that a large variety of paraffinic molecules
is present in said wax. Due to the presence of such large variety of different paraffinic
molecules, it will be very difficult to meet the specifications as regards volatility
when the base oils produced should be used as lubricating base oils.
[0003] In US-A-4,943,672 a process is disclosed for producing lubricating base oils having
a VI of at least 130 from Fischer-Tropsch waxes, in which process the wax is first
hydrotreated under severe conditions, then the hydrotreated wax is hydro-isomerised
by contacting it with a fluorided Group VIII (noble) metal-on-alumina catalyst, subsequently
the effluent from the hydro-isomerisation step is fractionated to produce a lubricating
oil fraction and finally this lubricating oil fraction is dewaxed to produce the desired
lubricating base oil. Unconverted wax recovered in the final dewaxing step may be
recycled to the hydro-isomerisation step. The Fischer-Tropsch wax used should be a
high boiling wax, since it is the intention to convert in the severe hydrotreating
step that material present in the wax that has a boiling point above about 565 °C.
In the Example of US-4,943,672 a Fischer-Tropsch wax is used which was obtained as
the 370 °C+ fraction from the distillation of a Fischer-Tropsch synthesis product.
Accordingly, the waxes used as the feedstocks are relatively high boiling waxes having
a broad boiling range and a large heavy tail. Due to the broad boiling range and particularly
due to the large heavy tail present in the wax, the fractionation after the hydroisomerisation
step, or -if applied- after the hydrofinishing step, should remove both the lightest
fraction (boiling below 338 °C) and the heaviest fraction (boiling above 538 °C) from
the hydroprocessed wax in order to obtain a final base oil product having acceptable
volatility properties.
[0004] In US-A-5,059,299 a process for producing lubricating base oils having a VI of at
least 130 and a pour point of -21 °C or lower from waxy feeds is disclosed, in which
process the waxy feed -after an optional hydrotreating step- is first isomerised in
an isomerisation zone at a predefined level of conversion, the total product of the
isomerisation zone is then fractionated yielding a lube fraction boiling in the luboil
range (i.e. above 330 °C and preferably above 370 °C) and this lube fraction is finally
solvent dewaxed to yield the desired lubricating base oil and unconverted wax. This
unconverted wax may be recycled to the isomerisation zone. The wax used as the feed
may be a synthetic wax from a Fischer-Tropsch process or could be a slack wax obtained
from a dewaxing process. No specific demands are made upon the Fischer-Tropsch waxes
to be useful as a feed in the process disclosed. The Fischer-Tropsch wax used in Example
1 of US-A-5,059,299 is a high boiling wax having a relatively broad boiling range,
which, as has already been stated above, results in the base oil product having unacceptable
volatility properties. The isomerisation catalyst used suitably comprises a hydrogenating
component on a halogenated refractory oxide support. The preferred catalyst is disclosed
to be platinum on fluorided alumina.
[0005] Although the prior art processes perform satisfactory in many respects, there is
still room for optimisation and improvement. The present invention aims to provide
such improved process. More specifically, the present invention aims to provide a
process for preparing base oils having a VI of at least 150 from a Fischer-Tropsch
wax, which process involves a single hydroprocessing stage and a fractionation stage,
wherein only the lighter components need to be removed from the hydroprocessed effluent.
Furthermore, it is an object of the present invention to provide base oils having
excellent properties, particularly in terms of VI and volatility, at commercially
attractive yields.
[0006] It has been found that these objects can be effectively achieved by using as the
feed a specific Fischer-Tropsch wax having a relatively narrow boiling range and meeting
certain requirements as to its congealing point.
[0007] Accordingly, the present invention relates to a process for the preparation of lubricating
base oils , having a VI of at least 150 from a Fischer-Tropsch wax feed, which process
comprises the steps of:
(a) contacting the Fischer-Tropsch wax feed with a hydro-isomerisation catalyst under
hydroconversion conditions involving operating temperatures in the range of from 275
to 450 °C, a hydrogen partial pressure in the range of from 25 to 200 bar, a weight
hourly space velocity (WHSV) in the range of from 0.1 to 10 kg/l/h, and a gas rate
in the range of from 100 to 5,000 Nl/kg,
(b) separating the hydroconverted effluent obtained in step (a) into at least one
lighter fraction and a heavy fraction, the effective cut point of the heavy fraction
being in the range of from 325 to 450°C, and
(c) dewaxing the heavy fraction yield the base oil,
wherein the Fischer-Tropsch wax feed has a congealing point of at least 50 °C and
has such boiling range that the difference between the 90 %wt boiling point and the
10 %wt boiling point (T
90-T
10) is in the range of from 40 to 150 °C.
[0008] The Fischer-Tropsch wax used as the feed for the present process, is obtained via
the well-known Fischer-Tropsch hydrocarbon synthesis process. In general, such Fischer-Tropsch
hydrocarbon synthesis involves the preparation of hydrocarbons from a mixture of carbon
monoxide and hydrogen at elevated temperature and pressure in the presence of a suitable
catalyst. The Fischer-Tropsch catalyst normally is selective for preparing paraffinic
molecules, mostly straight-chain paraffins, and the product from a Fischer-Tropsch
synthesis reaction therefore usually is a mixture of a large variety of paraffinic
molecules. Those hydrocarbons that are gaseous or liquid at room temperature are recovered
separately, for instance as fuel gas (C
5-), solvent feedstocks and detergent feedstocks (up to C
17). The more heavy paraffins (C
18+) are recovered as one or more wax fractions, commonly referred to as Fischer-Tropsch
wax(es) or synthetic wax(es). For the purpose of the present invention only those
Fischer-Tropsch waxes are useful as the feed, which meet the aforementioned requirements
with respect to their boiling range and congealing point.
[0009] Within the limits defined hereinbefore, preferred Fischer-Tropsch wax feeds are those
having a congealing point in the range of from 55 to 150 °C, preferably from 60 to
120 °C and/or such boiling range that the T
90-T
10 is in the range of from 50 to 130 °C. Those Fischer-Tropsch waxes melting below 100
°C, suitably have a kinematic viscosity at 100 °C (Vk100) of at least 3 mm
2/s, preferably between 3 and 12 mm
2/s, more preferably between 4 and 10 mm
2/s. Those Fischer-Tropsch waxes melting above 100 °C suitably have a kinematic viscosity
at a temperature T, which is 10 to 20 °C higher than their melting point, in the range
of from 8 to 15 mm
2/s, preferably from 9 to 14 mm
2/s.
[0010] The hydroconversion catalyst used in step (a) may in principle be any catalyst known
in the art to be suitable for isomerising paraffinic molecules. In general, suitable
hydroconversion catalysts are those comprising a hydrogenation component supported
on a refractory oxide carrier, such as amorphous silica-alumina, 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 step in accordance with
the present invention are hydroconversion catalysts comprising platinum and/or palladium
as the hydrogenation component. A very much preferred hydroconversion 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
(calculated as element) 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-94/10264 and EP-A-0,582,347. Other
suitable noble metal-based catalysts, such as platinum on a fluorided alumina carrier,
are disclosed in e.g. US-A-5,059,299 and WO-A-92/20759.
[0011] A second type of suitable hydroconversion 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.
Usually both metals are 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 catalyst. 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.
[0012] A third class of suitable hydroconversion catalysts are those based on an intermediate
pore size zeolitic material, suitably comprising at least one Group VIII metal component,
preferably Pt and/or Pd, as the hydrogenation component. Suitable zeolitic materials,
then, include ZSM-5, ZSM-22, ZSM-23, ZSM-35, SSZ-32, ferrierite, zeolite beta, mordenite
and silica-aluminophosphates, such as SAPO-11 and SAPO-31. Examples of suitable hydroisomerisation
catalysts are, for instance, described in WO-A-92/01657.
[0013] The hydroconversion conditions applied in step (a) are those known to be suitable
in hydro-isomerisation operations. The conditions, then, involve operating temperatures
in the range of from 275 to 450 °C, preferably 300 to 425 °C, a hydrogen partial pressure
in the range of from 25 to 200 bar, a weight hourly space velocity (WHSV) in the range
of from 0.1 to 10 kg/l/h, preferably 0.2 to 5 kg/l/h, and a gas rate in the range
of from 100 to 5,000 Nl/kg, preferably 500 to 3,000 Nl/kg.
[0014] In step (b) of the present process the hydroconverted effluent from step (a) is separated
into at least one lighter fraction and a heavy fraction. The effective cutpoint of
the heavy fraction is suitably in the range of from 325 to 450 °C and even more suitably
is in the range of from 350 to 420 °C, particularly when the lubricating base oils
to be obtained are to be used in engine oils. The effective cutpoint of the heavy
fraction is the temperature above which at least at least 85% by weight and preferably
at least 90% by weight, of the hydrocarbons present in this heavy fraction has its
boiling point. This separation or fractionation can be achieved by techniques known
in the art, such as atmospheric and vacuum distillation or vacuum flashing.
[0015] The heavy fraction obtained in step (b) is subsequently subjected to a dewaxing treatment
in step (c) to arrive at the desired pour point. The dewaxing carried out in step
(c) may in principle be carried out via any known dewaxing process. Examples of suitable
dewaxing operations are the conventional solvent dewaxing processes, particularly
those wherein methylethylketone, toluene or a mixture thereof is used as the dewaxing
solvent, and the catalytic dewaxing processes. Both types of dewaxing operations are
well known in the art. The most commonly applied solvent dewaxing process is the methyl
ethyl ketone (MEK) solvent dewaxing route, wherein MEK is used as the dewaxing solvent,
possibly in admixture with toluene. Catalytic dewaxing generally involves cracking
and/or isomerising linear and slightly branched paraffinic hydrocarbon molecules -which
negatively influence the cold flow properties of the base oil- in the presence of
hydrogen and a dewaxing catalyst under appropriate dewaxing conditions. Suitable dewaxing
catalysts which mainly favour cracking of paraffinic hydrocarbons are those comprising
ZSM-5, ferrierite and/or silicalite and optionally a hydrogenation component. Examples
of catalysts which mainly favour isomerisation of linear or slightly branched hydrocarbons,
include catalysts comprising a silicoaluminophosphate (SAPO), such as e.g. SAPO-11,
SAPO-31 and SAPO-41, ZSM-23 and SSZ-32. Another class of suitable dewaxing catalysts
for use in dewaxing step (c) are those catalysts based on a molecular sieve having
pores with a diameter in the range of from 0.35 to 0.80 nm and containing covalently
bound alumina moieties in its framework, which molecular sieve has been modified to
reduce the mole percentage of alumina, suitably by a surface dealumination treatment.
This type of catalysts and dewaxing operations wherein such catalysts are used, are
disclosed in European patent application No. 95401379.3/ref. TS 5518). Accordingly,
a particularly suitable class of dewaxing catalysts comprise a hydrogenation component
supported on surface deactivated molecular sieve and optionally a low acidity refractory
oxide binder material. The hydrogenation component may comprise at least one Group
VIB metal component (e.g. one or more of tungsten, molybdenum and chromium) and/or
at least one Group VIII metal component (e.g. one or more of palladium, platinum,
nickel and cobalt). It has been found particularly preferred for the purpose of the
present invention to employ a hydrogenation component comprising platinum and/or palladium,
suitably present in an amount of from 0.2 to 3.0% by weight (calculated as element
and based on total weight of support, i.e. modified molecular sieve plus optional
binder). Suitable molecular sieves include MFI-type zeolites, such as ZSM-5 and silicalite,
offretite, ferrierite, ZSM-35 and zeolites of the MTT-type, such as ZSM-23 and SSZ-32.
Of these, the MTT-type zeolites, ferrierite, ZSM-5 and mixtures thereof are preferred
for the purpose of the present invention. If present at all, suitable binder materials
include low acidity refractory oxides such as silica, zirconia, titanium dioxide,
germanium dioxide, boria and mixtures of two or more of these with silica being most
preferred. The weight ratio of surface deactivated molecular sieve to binder may range
from 10/90 to 100/0.
[0016] The slack wax obtained in the dewaxing treatment of step (c) is suitably recycled,
i.e. all or part of this slack wax is routed back to the hydroconversion step (a),
most conveniently by blending it with the fresh Fisher-Tropsch wax feed. In this way
the final yield of lubricating base oil can be maximised.
[0017] The lubricating base oils obtained by the process according to the present invention
can be used in a variety of oils. For instance, those lubricating base oils obtained
from Fischer-Tropsch waxes having a T
90 between about 400 and 500 °C are very useful in electrical oils, transformer oils
and refrigerator oils. Those base oils obtained from Fischer-Tropsch waxes having
a T
90 above 450 °C, suitably between 450 and 575 °C, are very useful as lubricating base
oils used for the more sophisticated lubricants required in, for instance, automotive
engines.
[0018] The invention is now further illustrated by the following examples without restricting
the scope of the invention to these specific embodiments.
Example 1
[0019] A Fischer-Tropsch wax having the properties as listed in Table I was contacted with
a fluorided NiW/alumina catalyst (5.0 %wt Ni, 23.1 %wt W, 4.6 %wt F, all based on
total weight of carrier) at a temperature of 383 °C, a hydrogen partial pressure of
140 bar, a WHSV of 1 kg/l/h and a gas rate of 1,500 Nl/kg. The effluent was fractionated
and the 390 °C+ fraction (obtained at a yield of 87.8% by weight based on total effluent)
was subsequently solvent dewaxed using MEK/toluene at -20 °C. The resulting base oil
had a VI of 165, a pour point of -15 °C, a kinematic viscosity at 100 °C (Vk100) of
4.95 mm
2/s and a Noack volatility (as determined by CEC-L-40-T87) of 8.3% by weight. Total
yield of lubricating base oil amounted up to 41% by weight based on Fischer-Tropsch
wax feed.
TABLE I
Properties of Fischer-Tropsch wax |
T10 (°C) |
432 |
T50 (°C) |
482 |
T90 (°C) |
527 |
T90-T10 (°C) |
95 |
CPt (°C) |
69 |
Vk100 (mm2/s) |
5.67 |
Example 2
[0020] The same Fischer-Tropsch wax as used in Example 1 was contacted with a PtPd/ASA (0.3
%wt Pt, 1 %wt Pd, ASA: silica/alumina molar ratio is 55/45) catalyst at a temperature
of 332 °C, whilst the other conditions were the same as applied in Example 1. The
effluent was fractionated and the 390 °C+ fraction (obtained at a yield of 88.3% by
weight based on total effluent) was subsequently solvent dewaxed using MEK/toluene
at -20 °C. The resulting base oil had a VI of 167, a pour point of -15 °C, a kinematic
viscosity at 100 °C (Vk100) of 4.86 mm
2/s and a Noack volatility of 7.4% by weight. Total yield of lubricating base oil amounted
up to 39% by weight based on Fischer-Tropsch wax feed.
Example 3
[0021] The procedure of Example 2 was repeated except that the 390 °C+ fraction obtained
was catalytically dewaxed instead of solvent dewaxed. Catalytic dewaxing was carried
out by passing said 390 °C+ fraction over a dewaxing catalyst comprising 0.7% by weight
of Pt on silica-bound surface dealuminated ZSM-23 (70 %wt surface dealuminated ZSM-23,
30 %wt silica; surface dealumination carried out according to the method disclosed
in U.S. Patent No. 5,157,191 using ammonium hexafluorosilicate) at a temperature of
310 °C, a hydrogen partial pressure of 40 bar, a WHSV of 1 kg/l/h and a gas rate of
693 Nl/kg.
[0022] The resulting base oil had a VI of 151, a pour point of -27 °C, a kinematic viscosity
at 100 °C (Vk100) of 4.96 mm
2/s and a Noack volatility (as determined by CEC-L-40-T87) of 8.8% by weight. Total
yield of lubricating base oil amounted up to 62.4% by weight based on Fischer-Tropsch
wax feed.
1. Process for the preparation of lubricating base oils having a VI of at least 150 from
a Fischer-Tropsch wax feed, which process comprises the steps of:
(a) contacting the Fischer-Tropsch wax feed with a hydro-isomerisation catalyst under
hydroconversion conditions involving operating temperatures in the range of from 275
to 450 °C, a hydrogen partial pressure in the range of from 25 to 200 bar, a weight
hourly space velocity (WHSV) in the range of from 0.1 to 10 kg/l/h, and a gas rate
in the range of from 100 to 5,000 Nl/kg,
(b) separating the hydroconverted effluent obtained in step (a) into at least one
lighter fraction and a heavy fraction, the effective cut point of the heavy fraction
being in the range of from 325 to 450°C, and
(c) dewaxing the heavy fraction to yield the base oil,
wherein the Fischer-Tropsch wax feed has a congealing point of at least 50 °C and
has such boiling range that the difference between the 90 %wt boiling point and the
10 %wt boiling point. (T
90-T
10) is in the range of from 40 to 150 °C.
2. Process according to claim 1, wherein T90-T10 is in the range of from 50 to 130 °C.
3. Process according to claim 1 or 2, wherein the Fischer-Tropsch wax feed has a congealing
point in the range of from 55 to 150 °C, preferably from 60 to 120 °C.
4. Process according to any one of the preceding claims, wherein the hydroconversion
catalyst comprises a hydrogenation component supported on a refractory oxide carrier.
5. Process according to claim 4, wherein the hydroconversion catalyst comprises platinum
and/or palladium as the hydrogenation component.
6. Process according to claim 5, wherein the hydroconversion catalyst comprises platinum
and palladium supported on an amorphous silica-alumina carrier.
7. Process according to claim 4, wherein the hydroconversion catalyst comprises at least
one Group VIB metal, preferably tungsten, and at least one non-noble Group VIII metal,
preferably nickel, as the hydrogenation component.
8. Process according to any one of the preceding claims, wherein the heavy fraction is
obtained in step (b) at an effective cutpoint in the range of from 350 to 420 °C.
9. Process according to any one of the preceding claims, wherein the dewaxing in step
(c) is carried out by solvent dewaxing.
10. Process according to any one of claims 1 to 8, wherein the dewaxing in step (c) is
carried out by catalytic dewaxing.
1. Verfahren zur Herstellung von Schmiermittelgrundölen mit einem Viskositätsindex von
wenigstens 150 aus einem Fischer-Tropsch-Wachs-Einsatzmaterial, welches Verfahren
die folgenden Schritte umfaßt:
(a) Inkontaktbringen des Fischer-Tropsch-Wachs-Einsatzmaterials mit einem Hydroisomerisationskatalysator
unter Hydrokonversionsbedingungen, umfassend Arbeitstemperaturen im Bereich von 275
bis 450°C, einen Wasserstoffpartialdruck im Bereich von 25 bis 200 bar, eine gewichtsbezogene
Raumgeschwindigkeit (WHSV) im Bereich von 0,1 bis 10 kg/l/h und einen Gasdurchsatz
im Bereich von 100 bis 5.000 Nl/kg,
(b) Auftrennen des im Schritt (a) erhaltenen hydrokonvertierten Abstroms in eine erste
leichtere Fraktion und in eine schwere Fraktion, wobei der effektive Schnittpunkt
der schweren Fraktion im Bereich von 325 bis 450°C liegt, und
(c) Entwachsen der schweren Fraktion zur Ausbildung des Grundöls,
worin das Fischer-Tropsch-Wachs-Einsatzmaterial einen Erstarrungspunkt von wenigstens
50°C hat und einen solchen Siedebereich aufweist, daß der Unterschied zwischen dem
90 Gew.-% Siedepunkt und dem 10 Gew.-% Siedepunkt (T
90-T
10) im Bereich von 40 bis 150°C liegt.
2. Verfahren nach Anspruch 1, worin T90-T10 im Bereich von 50 bis 130°C liegt.
3. Verfahren nach Anspruch 1 oder 2, worin das Fischer-Tropsch-Wachs-Einsatzmaterial
einen Erstarrungspunkt im Bereich von 55 bis 150°C, vorzugsweise von 60 bis 120°C
aufweist.
4. Verfahren nach einem der vorstehenden Ansprüche, worin der Hydrokonversionskatalysator
eine auf einen Feuerfestoxidträger aufgebrachte Hydrierkomponente umfaßt.
5. Verfahren nach Anspruch 4, worin der Hydrokonversionskatalysator Platin und/oder Palladium
als die Hydrierkomponente umfaßt.
6. Verfahren nach Anspruch 5, worin der Hydrokonversionskatalysator Platin und Palladium,
aufgebracht auf einen amorphen Siliciumoxid-Aluminiumoxid-Träger, umfaßt.
7. Verfahren nach Anspruch 4, worin der Hydrokonversionskatalysator wenigstens ein Gruppe
VIB-Metall, vorzugsweise Wolfram, und wenigstens ein Gruppe VIII-Unedelmetall, vorzugsweise
Nickel, als Hydrierkomponente umfaßt.
8. Verfahren nach einem der vorstehenden Ansprüche, worin die schwere Fraktion im Schritt
(b) bei einem effektiven Schnittpunkt im Bereich von 350 bis 420°C erhalten wird.
9. Verfahren nach einem der vorstehenden Ansprüche, worin das Entwachsen im Schritt (c)
durch Lösungsmittelentwachsen vorgenommen wird.
10. Verfahren nach einem der Ansprüche 1 bis 8, worin das Entwachsen im Schritt (c) durch
katalytisches Entwachsen vorgenommen wird.
1. Procédé pour la préparation d'huiles de base lubrifiantes ayant un VI d'au moins 150
à partir d'une charge de cires de Fischer-Tropsch, lequel procédé comprend les étapes
suivantes :
(a) la mise en contact de la charge de cires de Fischer-Tropsch avec un catalyseur
d'hydroisomérisation dans des conditions d'hydroconversion, impliquant des températures
de fonctionnement dans la plage de 275 à 450°C, une pression d'hydrogène partielle
dans la plage de 25 à 200 bars, une vitesse spatiale horaire en poids (WHSV) dans
la plage de 0,1 à 10 kg/l/h et un débit de gaz dans la plage de 100 à 5000 Nl/kg;
(b) la séparation de l'effluent hydroconverti obtenu à l'étape (a) en au moins une
fraction plus légère et une fraction lourde, le point de fractionnement efficace de
la fraction lourde se situant dans la plage de 325 à 450°C;
(c) le déparaffinage de la fraction lourde pour donner l'huile de base, où la charge
de cires de Fischer-Tropsch a un point de congélation d'au moins 50°C et a une plage
d'ébullition telle que la différence entre le point d'ébullition à 90% en poids et
le point d'ébullition à 10% en poids (T90-T10) se situe dans la plage de 40 à 150°C.
2. Procédé selon la revendication 1, dans lequel la différence T90-T10 se situe dans la plage de 50 à 130°C.
3. Procédé selon la revendication 1 ou 2, dans lequel la charge de cires de Fischer-Tropsch
a un point de congélation dans la plage de 55 à 150°C, de préférence de 60 à 120°C.
4. Procédé selon l'une quelconque des revendications précédentes, dans lequel le catalyseur
d'hydroconversion comprend un composant d'hydrogénation supporté sur un support d'oxyde
réfractaire.
5. Procédé selon la revendication 4, dans lequel le catalyseur d'hydroconversion comprend
du platine et/ou du palladium comme composant d'hydrogénation.
6. Procédé selon la revendication 5, dans lequel le catalyseur d'hydroconversion comprend
du platine et du palladium supportés sur un support amorphe de silice-alumine.
7. Procédé selon la revendication 4, dans lequel le catalyseur d'hydroconversion comprend
au moins un métal du groupe VIB, de préférence du tungstène, et au moins un métal
non noble du groupe VIII, de préférence du nickel, comme composant d'hydrogénation.
8. Procédé selon l'une quelconque des revendications précédentes, dans lequel la fraction
lourde est obtenue à l'étape (b) avec un point de fractionnement efficace dans la
plage de 350 à 420°C.
9. Procédé selon l'une quelconque des revendications précédentes, dans lequel le déparaffinage
à l'étape (c) est effectué par déparaffinage au solvant.
10. Procédé selon l'une quelconque des revendications 1 à 8, dans lequel de déparaffinage
à l'étape (c) est effectué par déparaffinage catalytique.