CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is related to co-pending application Serial No. 08/017,949 (continuation
of S.N. 07/548,702) entitled Production of High Viscosity Index Lubricants, which
describes a two-step process for producing high Viscosity Index lubricants by hydrocracking
and hydroisomerization of petroleum wax feeds using a low acidity zeolite beta hydroisomerization
catalyst. Serial No. 08/017,955, also entitled Production of High Viscosity Index
Lubricants, describes a wax hydroisomerization process using zeolite catalysts of
controlled low acidity at high pressures. The instant application is a continuation-in-part
of Serial No. 08/017,955. The instant application is also a continuation-in-part of
Serial No. 08/017,949. Serial No. 08/017,955 is incorporated by reference in the instant
application. Corresponding European Patent No. 464,547A1, (which specifies the use
of low acidity zeolite beta for wax isomerization) is also incorporated by reference.
The instant application is also related to co-pending application S.N. 08/303,091,
in which two dewaxing catalysts operate synergistically to produce a lubricant of
high Viscosity Index.
FIELD OF THE INVENTION
[0002] This invention relates to the production of high Viscosity Index lubricants by isomerizing
petroleum waxes using large pore zeolites of small crystal size. The waxes may be
hydrocracked prior to isomerization. The isomerization product may be further dewaxed
by either solvent or catalytic means in order to achieve a target pour point.
BACKGROUND OF THE INVENTION
[0003] Mineral oil based lubricants are conventionally produced by a separative sequence
carried out in the petroleum refinery which comprises fractionation of a paraffinic
crude oil under atmospheric pressure followed by fractionation under vacuum to produce
distillate fractions (neutral oils) and a residual fraction which, after deasphalting
and severe solvent treatment may also be used as a lubricant basestock. This refined
residual fraction is usually referred to as bright stock. Neutral oils, after solvent
extraction to remove low viscosity index (V.I.) components, are conventionally subjected
to dewaxing, either by solvent or catalytic dewaxing processes, to achieve the desired
pour point. The dewaxed lube stock may be hydrofinished to improve stability and remove
color bodies. Viscosity Index (V.I.) is a reflection of the amount of viscosity decrease
a lubricant undergoes with an increase in temperature. The products of solvent dewaxing
are dewaxed lube oil and slack wax. Slack wax typically contains 60% to 90% wax with
the balance being entrained oil. In some instances it is desirable to purify the slack
wax of entrained oil by subjecting the slack wax to a deoiling step in which the slack
wax is diluted with dewaxing solvents and filtered at a temperature higher than that
used in the filtering step used to produce the slack wax. The purified wax is termed
deoiled wax, and contains greater than 95% wax. The byproduct of the second filtration
typically contains 50% wax and is termed foots oil.
[0004] Catalytic dewaxing of lube stocks is accomplished by converting waxy molecules to
light products by cracking, or by isomerizing waxy molecules to form species which
remain in the dewaxed lube. Dewaxing catalysts preserve high yield primarily by having
pore structures which inhibit cracking of cyclic and highly branched species, those
generally associated with dewaxed lube, while permitting easier access to catalytically
active sites to near-linear molecules, of which wax is generally composed. Catalysts
which significantly reduce the accessibility of species on the basis of molecular
size are termed shape selective. Increasing the shape selectivity of a dewaxing catalyst
will frequently increase the yield of dewaxed oil.
[0005] The shape selectivity of a dewaxing catalyst is limited practically by its ability
to convert waxy molecules which have a slightly branched structure. These types of
species are more commonly associated with heavier lube stocks, such as bright stocks.
Highly shape selective dewaxing catalysts may be unable to convert heavy, branched
wax species leading to a hazy lube appearance at ambient temperature and high cloud
point relative to pour point.
[0006] Conventional lube refining techniques rely upon the proper selection and use of crude
stocks, usually of a paraffinic character, which produce lube fractions with desired
qualities in adequate amounts. The range of permissible crude sources may, however,
be extended by the lube hydrocracking process which is capable of utilizing crude
stocks of marginal or poor quality, usually with a higher aromatic content than the
best paraffinic crudes. The lube hydrocracking process, which is well established
in the petroleum refining industry, generally comprises an initial hydrocracking step
carried out under high pressure, at high temperature, and in the presence of a bifunctional
catalyst which effects partial saturation and ring opening of the aromatic components
which are present in the feed. The hydrocracked product is then subjected to dewaxing
in order to reach the target pour point since the hydrocracked product usually contains
species with relatively high pour points. Frequently the liquid product from the dewaxing
step is subjected to a low temperature, high pressure hydrotreating step to reduce
the aromatic content of the lube to the desired level.
[0007] Current trends in the design of automotive engines are associated with higher operating
temperatures as the efficiency of the engines increases. These higher operating temperatures
require successively higher quality lubricants. One of the requirements is for higher
viscosity indices (V.I.) in order to reduce the effects of the higher operating temperatures
on the viscosity of the engine lubricants. High V.I. values have conventionally been
attained by the use of V.I. improvers e.g. polyacrylates and polystyrenes. V.I. improvers
tend to undergo degradation due to high temperatures and high shear rates encountered
in the engine. The more stressing conditions encountered in high efficiency engines
result in even faster degradation of oils which employ significant amounts of V.I.
improvers. Thus, there is a continuing need for automotive lubricants which are based
on fluids of high Viscosity Index and which are resistant to the high temperature,
high shear rate conditions encountered in modern engines.
[0008] Synthetic lubricants produced by the polymerization of olefins in the presence of
certain catalysts have been shown to possess excellent V.I. values, but they are relatively
expensive to produce. There is therefore a need for the production of high V.I. lubricants
from mineral oil stocks which may be produced by techniques comparable to those presently
employed in petroleum refineries.
[0009] U.S. Patent No. 4,975,177 discloses a two-stage dewaxing process for producing lube
stocks of high V.I. from waxy feedstocks. In the first stage of this process, the
waxy feed is catalytically dewaxed by isomerization over zeolite beta containing a
noble metal. The examples employ pressures below 6996 kPa
a (1000 psig) and a catalyst of moderate acidity, with an alpha value of about 55.
The product of the isomerization step still contains waxy species and requires further
dewaxing to meet target pour point. The second-stage dewaxing employs either solvent
dewaxing, in which case the rejected wax may be recycled to the isomerization stage
to maximize yield, or catalytic dewaxing. Catalysts which may be used in the second
stage are ZSM-5, ZSM-22, ZSM-23, and ZSM-35. To preserve yield and V.I., the second
stage dewaxing catalyst should have selectivity similar to solvent dewaxing. U.S.
Patent 4,919,788 also teaches a two-stage dewaxing process in which a waxy feed is
partially dewaxed by isomerization over a siliceous Y or beta catalyst containing
a noble metal. Examples indicate pressures below 10030 kPa
a and a zeolite beta catalyst of moderate acidity with an alpha value of 55. This product
is subsequently dewaxed to desired pour point using either solvent dewaxing or catalytic
dewaxing. Dewaxing catalysts with high shape selectivity, such as ZSM-22 and ZSM-23,
are preferred catalysts.
[0010] Serial No. 08/017,949 discloses a two stage hydrocracking and hydroisomerization
process. The first stage employs a bifunctional catalyst comprising a metal hydrogenation
component on an amorphous acidic support. The second stage, the hydroisomerization
step, is carried out over zeolite beta. Subsequent dewaxing is optional but recommended.
Either solvent dewaxing or catalytic dewaxing maybe used subsequently in order to
obtain target V.I. and pour point.
[0011] In S.N. 08/017,955, petroleum wax feed is subjected to hydroisomerization over a
noble metal-containing zeolite catalyst of low acidity. The paraffins present in the
feed are selectively converted to iso-paraffins of high V.I. but lower pour point
so that a final lube product of good viscometric properties is produced with a minimal
degree of subsequent dewaxing. The process, which operates under high pressure, is
well suited for upgrading waxy feeds such as slack wax with aromatic contents greater
than about 15 wt% to high Viscosity Index lubricating oils with high single pass yields
and limited requirement for product dewaxing.
[0012] U.S. Pat. No. 5,302,279 (and the analogous European patent application EP 464 547
Al) teaches the use of a low acidity form of zeolite beta for isomerizing and dewaxing
furfural raffinates. The improved selectivity of a catalyst of low acidity over one
of high acidity was demonstrated in the examples.
[0013] U.S. Pat. No. 5,282,958 has demonstrated improved isomerization selectivity for n-hexadecane
using unipore zeolites of small crystal size, although the crystal sizes quoted are
all.extremely small and are inconsistent with measurements made by others in the field
of catalyst preparation. Additionally, constrained intermediate pore zeolites such
as ZSM-22 and ZSM-23, which are used in this patent, do not permit access to the framework
of the catalyst as readily as other intermediate and large pore molecular sieves.
Reactions of lubricant-type molecules are likely to occur near the pore mouth of intermediate
pore catalysts. The crystal size of ZSM-22 or ZSM-23 is not likely to impact isomerization
selectivity as strongly as for catalysts with a less restrictive pore structure.
SUMMARY OF THE INVENTION
[0014] The concept of the instant invention involves a process for isomerizing and dewaxing
waxy feedstocks using large pore molecular sieves with small crystal size for producing
high quality, at least 130 VI lubricant base stocks. Large pore molecular sieves applicable
to this invention are defined as having a Constraint Index less than one and include
zeolites beta, mordenite and Y. Large pore molecular sieves have accessible pore structures
for forming highly branched paraffins from waxy feed stocks, particularly those stocks
containing high molecular weight species. Such branched paraffins have a high VI and
low pour point. Because isomerization occurs within the pores of the catalyst, small
crystal size enables branched paraffins to readily diffuse from the zeolite pores
without cracking, thus resulting in high lube yields.
[0015] The instant invention involves processing a waxy hydrocarbon feedstock over an isomerization
catalyst which converts waxy species to branched paraffins. The formation of these
branched paraffins which have high Viscosity Indices and low pour points, results
in a lubricant base stock having superior quality.
[0016] The feedstocks used in this invention contain at least 20% wax and preferably they
contain more than 50% wax. The feedstock may be pretreated prior to isomerization
to remove nitrogen and sulfur-containing species and to reduce its aromatics content.
The raw or pretreated feedstock is contacted with a noble metal-containing low-acidity
large pore molecular sieve over which a substantial fraction of the wax in the feed
is isomerized to form species typically associated with lube base stocks. Isomerization
occurs typically at a pressure between 4238 kPa
a(600 psig) and 20,786 kPa
a (3000 psig) . The effluent from isomerization may be hydrotreated to remove residual
aromatics. The zeolite beta catalyst discussed in the examples of this invention has
a crystal diameter of less than 0.1 microns in order to maximize the relative rates
of isomerization to cracking. Small diameter crystals allow isomerized species to
diffuse readily from the catalyst framework, thereby reducing the potential for their
cracking. The prior art, discussed in the Background, supra, demonstrates improved
selectivity of a catalyst of low acidity over one of higher acidity. Low zeolitic
acidity coupled with high metals activity is necessary for high isomerization selectivity
but does not guarantee such selectivity. The crystal size of the certain molecular
sieves has been found to be an important factor impacting isomerization selectivity.
Large crystals increase the diffusion path for isomerized species to exit the framework,
thus increasing the possibility that the isomerized molecule will crack within the
framework. The invention detailed here illustrates the selectivity benefit for isomerizing
waxy feeds, such as slack waxes, with a small crystal, low-acidity zeolite beta catalyst.
[0017] The instant invention employs zeolite beta loaded with a noble metal such as Pt to
selectively isomerize waxy species to high VI lubricants. This catalyst has high isomerization
selectivity, tolerance for moderate levels of sulfur and nitrogen, and an accessible
pore structure to permit conversion of bulky wax molecules. The selectivity of zeolite
beta loaded with Pt is optimized if it has low zeolitic acidity, high metals dispersion
and small crystal size.
DESCRIPTION OF THE DRAWING
[0018] The Figure compares the selectivity for wax isomerization for two low-acidity silica-bound
zeolite beta catalysts loaded with Pt. One possesses a small crystal size and the
other possesses a large crystal size.
DETAILED DESCRIPTION OF THE INVENTION
[0019] In the present process feeds with a relatively high wax content are converted to
high V.I. lubricants in a hydroisomerization process using a low acidity zeolite hydroisomerization
catalyst having a small crystal size. Subsequent dewaxing may be required to remove
residual wax from the isomerization step. The products are characterized by good viscometric
properties including high-viscosity index, typically at least 140 at -17.78°C (0°F)
pour point and usually in the range 143 to 147.
Feed
[0020] The processes of the instant invention are capable of operating with a wide range
of feeds of mineral oil origin to produce a range of lubricant products with good
performance characteristics. Such characteristics include low pour point, low cloud
point, and high Viscosity Index. The quality of the product and the yield in which
it is obtained is dependent upon the quality of the feed and its amenability to processing
by the catalysts of the instant invention. Products of the highest V.I. are obtained
by using preferred wax feeds such as slack wax, foots oil, deoiled wax, vacuum distillates
derived from waxy crudes, wax from Fischer-Tropsch process, petrolatum, vacuum gas
oil or raffinate from solvent extraction of vacuum distillate. Products with lower
V.I. values may also be obtained from other feeds which contain a lower initial quantity
of waxy components.
[0021] The feeds which may be used should have an initial boiling point which is no lower
than the initial boiling point of the desired lubricant. A typical initial boiling
point of the feed exceeds 343°C (650°F). Feeds of this type which may be used include
vacuum gas oils as well as other high boiling fractions such as distillates from the
vacuum distillation of atmospheric resids, raffinates from the solvent extraction
of such distillate fractions, hydrocracked vacuum distillates and waxes from the solvent
dewaxing of raffinates and hydrocrackates.
[0022] The feed may require preparation in order to be treated satisfactorily in the hydroisomerization
step. The preparation steps which are generally necessary are those which remove low
V.I. components such as aromatics and polycyclic naphthenes, as well as nitrogen and
sulfur containing species.
[0023] Suitable pre-treatment steps for preparing feeds for the hydroisomerization are those
which remove the aromatics and others low V.I. components from the initial feed. Hydrotreatment
is an effective pretreatment step, particularly at high hydrogen pressures which are
effective for aromatics saturation e.g. 5,600 kPa
a (800 psig) or higher. Mild hydrocracking may also be employed as pretreatment and
is preferred in the instant invention, if pretreatment is required. Example 3, infra,
discusses the hydrocracking conditions employed in the instant invention in order
to prepare a feed for the dewaxing process. Pressures over 6996 kPa
a (1000 psig) are preferred for hydrocracking treatment. Hydrocracking removes nitrogen
containing and sulfur-containing species and reduces aromatics content as Table 6
below illustrates. Hydrocracking, in this example, has also slightly altered the boiling
range of the feed, causing it to boil in a lower range. Commercially available catalysts
such as fluoride nickel-tungsten on alumina (NiWF-/Al
2O
3) may be employed for the hydrocracking pretreatment.
[0024] The preferred gas oil and vacuum distillate feeds are those which have a high wax
content, as determined by ASTM D-3235, preferably over about 30 wt% and more preferably
over 50 wt%. Feeds of this type include certain South-East Asian and mainland China
oils. Minas Gas oil, from Indonesia, is such a feed. These feeds usually have a high
paraffin content, as determined by a conventional analysis for paraffins, naphthenes,
and aromatics. The properties of typical feeds of this type are described in S.N.
07/017,955. A preferred feed has a wax content of at least 40 wt.% and an aromatics
content of less than 25 wt.%.
[0025] As stated previously, the wax content of the preferred feeds is high, generally at
least 30 wt% (as determined by ASTM Test D-3235) prior to pretreatment. The wax content
before pretreatment is more usually at least 60 to 80 wt% with the balance being occluded
oil comprising iso-paraffins, aromatics and naphthenics. These waxy, highly paraffinic
wax stocks usually have low viscosities because of their relatively low content of
aromatics and naphthenes although the high content of waxy paraffins gives them melting
points and pour points which render them unacceptable as lubricants without further
processing. Wax feeds are discussed further in S.N. 07/017,955.
[0026] The most preferred type of wax feeds are the slack waxes, (see Table 2, infra). These
are the waxy products obtained directly from a solvent dewaxing process, e.g. an MEK
(methyl ethyl ketone)/toluene or MEK/MIBK (methyl isobutyl ketone) or propane dewaxing
process. The slack wax, which is a solid to semi-solid product, comprising primarily
highly waxy paraffins (mostly n- and mono-methyl paraffins) together with occluded
oil, may be used as such or it may be subjected to an initial deoiling step of a conventional
character in order to remove the occluded oil. Removal of the oil results in a harder,
more highly paraffinic wax which may then be used as the feed. The byproduct of the
deoiling step is termed Foots Oil and it may also be used as feed to the process.
Foots Oil contains most of the aromatics present in the original slack wax and with
these aromatics, most of the heteroatoms. Slack wax and foots oil typically require
pretreatment prior to catalytic dewaxing. The oil content of deoiled waxes may be
quite low and for this purpose, measurement of the oil content by the technique of
ASTM D721 may be required for reproducibility, since the D-3235 test referred to above
tends to be less reliable at oil contents below about 15 wt%.
[0027] The compositions of some typical waxes are given in Table 1 below.
Table 1
Wax Composition - Arab Light Crude |
|
A |
B |
C |
D |
Paraffins, wt. pct. |
94.2 |
81.8 |
70.5 |
51.4 |
Mono-naphthenes, wt. pct. |
2.6 |
11.0 |
6.3 |
16.5 |
Poly-naphthenes, wt. pct. |
2.2 |
3.2 |
7.9 |
9.9 |
Aromatics, wt. pct. |
1.0 |
4.0 |
15.3 |
22.2 |
[0028] A typical slack wax feed has the composition shown in Table 2 below. This slack wax
is obtained from the solvent (MEK) dewaxing of a 65 mm
2/s (cSt) at 40°C (300 SUS) neutral oil obtained from an Arab Light crude.
Table 2
Slack Wax Properties |
API |
39 |
Hydrogen, wt. pct. |
15.14 |
Sulfur, wt. pct. |
0.18 |
Nitrogen, ppmw |
11 |
Melting point, °C (°F) |
57 (135) |
KV at 100°C, cSt |
5.168 |
PNA, wt pct: |
|
Paraffins |
70.3 |
Naphthenes |
13.6 |
Aromatics |
16.3 |
Simulated Distillation: |
% |
°C |
(°F) |
5 |
375 |
(710) |
10 |
413 |
(775) |
30 |
440 |
(825) |
50 |
460 |
(860) |
70 |
482 |
(900) |
90 |
500 |
(932) |
95 |
507 |
(945) |
[0029] Another slack wax suitable for use in the present process has the properties set
out in Table 6 infra as part of Example 3. This wax is prepared by the solvent dewaxing
of a heavy neutral furfural raffinate. As discussed previously, hydrocracking may
be employed to prepare the slack wax for hydroisomerization.
Hydrocracking Process (Optional)
[0030] If hydrocracking is employed as a pretreatment step an amorphous bifunctional catalyst
is preferably used to promote the saturation and ring opening of the low quality aromatic
components in the feed to produce hydrocracked products which are relatively more
paraffinic. Hydrocracking is carried out under high pressure to favor aromatics saturation
but the boiling range conversion is maintained at a relatively low level in order
to minimize cracking of the saturated components of the feed and of the products obtained
from the saturation and ring opening of the aromatic materials. Consistent with these
process objectives, the hydrogen pressure in the hydrocracking stage is at least about
5500 kPa
a. (800 psig) and usually is in the range of 6900 kPa
a (1,000 psig) to 20700 kPa
a (3,000 psig). Normally, hydrogen partial pressures of at least 10500 kPa
a (1500 psig) are best in order to obtain a high level of aromatic saturation. Hydrogen
circulation rates of at least about 178 n.l.l.
-1 (1000 SCF/Bbl), preferably in the range of 900 n.l.l.
-1 (2,000 SCF/Bbl) to 1800 n.l.l.
-1 (8000 SCF/Bbl) are suitable.
[0031] In the hydrocracking process, the conversion of the feed to products boiling below
the lube boiling range, typically to 345°C- (650°F-) products is limited to no more
than 50 wt% of the feed and will usually be not more than 30 wt% of the feed in order
to maintain the desired high single pass yields which are characteristic of the process.
The actual conversion is dependent on the quality of the feed with slack wax feeds
requiring a lower conversion than petrolatum where it is necessary to remove more
low quality polycyclic components. For slack wax feeds derived from the dewaxing of
neutral stocks, the conversion to 345°C-(650°F-) products will, for all practical
purposes not be greater than 10 to 20 wt%, with 5-15 wt% being typical for most slack
waxes. Higher conversions may be encountered with petrolatum feeds because they typically
contain more low quality components. With petrolatum feeds, the hydrocracking conversion
will typically be in the range of 15 to 25 wt% to produce high VI products. The conversion
may be maintained at the desired value by control of the temperature in the hydrocracking
stage which will normally be in the range 315° to 430°C (600° to 800°F) and more usually
in the range of about 345° to 400°C (650° to 750°F). Space velocity variations may
also be used to control severity although this will be less common in practice in
view of mechanical constraints on the system. Generally, the space velocity will be
in the range of 0.25 to 2 LHSV, hr.
-1 and usually in the range of 0.5 to 1.5 LHSV.
[0032] A characteristic feature of the hydrocracking operation is the use of a bifunctional
catalyst comprising an acidic support. In general terms, these catalysts include a
metal component for promoting the desired aromatics saturation reactions and usually
a combination of base metals is used, with one metal from the iron group (Group VIII)
in combination with a metal of Group VIB. Thus, the base metal such as nickel or cobalt
is used in combination with molybdenum or tungsten. The preferred combination is nickel/tungsten
since it has been found to be highly effective for promoting the desired aromatics
hydrocracking reaction. Noble metals such as platinum or palladium may be used since
they have good hydrogenation activity in the absence of sulfur but they will normally
not be preferred. The amounts of the metals present on the catalyst are conventional
for lube hydrocracking catalysts of this type and generally will range from 1 to 10
wt% of the Group VIII metal and 10 to 30 wt% of the Group VI metal, based on the total
weight of the catalyst. If a noble metal component such as platinum or palladium is
used instead of a base metal such as nickel or cobalt, relatively lower amounts are
in order in view of the higher hydrogenation activities of these noble metals, typically
from about 0.5 to 5 wt% being sufficient. The metals may be incorporated by any suitable
method including impregnation onto the porous support after it is formed into particles
of the desired size or by addition to a gel of the support materials prior to calcination.
Addition to the gel is a preferred technique when relatively high amounts of the metal
components are to be added e.g. above 10 wt% of the Group VIII metal and above 20
wt% of the Group VI metal. These techniques are conventional in character and are
employed for the production of lube hydrocracking catalysts.
[0033] The metal component of the catalyst is generally supported on a porous, amorphous
metal oxide support and alumina is preferred for this purpose although silica-alumina
may also be employed. Other metal oxide components may also be present in the support
although their presence is less desirable. Consistent with the requirements of a lube
hydrocracking catalyst, the support should have a pore size and distribution which
is adequate to permit the relatively bulky components of the high boiling feeds to
enter the interior pore structure of the catalyst where the desired hydrocracking
reactions occur. To this extent, the catalyst will normally have a minimum pore size
of about 50 Å i.e with no less than about 5 percent of the pores having a pore size
less than 5 nm (50 Å) pore size, with the majority of the pores having a pore size
in the range of 5-40 nm (50-400 Å) (no more than 5 percent having a pore size above
40 nm (400 Å)), preferably with no more than about 30 percent having pore sizes in
the range of 20-40 nm (200-400 Å). Preferred catalysts for hydrocracking have at least
60 percent of the pores in the 5-20 nm (50-200 Å) range. The pore size distribution
and other properties of some typical lube hydrocracking (LHDC) catalysts suitable
for use in the hydrocracking are shown in Table 3 below:
Table 3
LHDC Catalyst Properties |
Form |
1.5mm cyl. |
1.5 mm. tri. |
1.5 mm.cyl. |
Pore Volume, cc/gm |
0.331 |
0.453 |
0.426 |
Surface Area, m2/gm |
131 |
170 |
116 |
Nickel, wt. pct. |
4.8 |
4.6 |
5.6 |
Tungsten, wt. pct. |
22.3 |
23.8 |
17.25 |
Fluorine, wt. pct. |
- |
- |
3.35 |
SiO2/Al2O3 binder |
- |
- |
62.3 |
|
Real Density, gm/cc |
4.229 |
4.238 |
4.023 |
Particle Density, gm/cc |
1.744 |
1.451 |
1.483 |
Packing Density, gm/cc |
1.2 |
0.85 |
0.94 |
[0034] If necessary in order to obtain the desired conversion, the catalyst may be promoted
with fluorine, either by incorporating fluorine into the catalyst during its preparation
or by operating the hydrocracking in the presence of a fluorine compound which is
added to the feed. Fluorine containing compounds may be incorporated into the catalyst
by impregnation during its preparation with a suitable fluorine compound such as ammonium
fluoride (NH
4F) or ammonium bifluoride (NH
4F•HF) of which the latter is preferred. The amount of fluorine used in catalysts which
contain this element is preferably from about 1 to 10 wt%, based on the total weight
of the catalyst, usually from about 2 to 6 wt%. The fluorine may be incorporated by
adding the fluorine compound to a gel of the metal oxide support during the preparation
of the catalyst or by impregnation after the particles of the catalyst have been formed
by drying or calcining the gel. If the catalyst contains a relatively high amount
of fluorine as well as high amounts of the metals, as noted above, it is preferred
to incorporate the metals and the fluorine compound into the metal oxide gel prior
to drying and calcining the gel to form the finished catalyst particles.
[0035] The catalyst activity may also be maintained at the desired level by
in situ fluoriding in which a fluorine compound is added to the stream which passes over
the catalyst in this stage of the operation. The fluorine compound may be added continuously
or intermittently to the feed or, alternatively, an initial activation step may be
carried out in which the fluorine compound is passed over the catalyst in the absence
of the feed e.g. in a stream of hydrogen in order to increase the fluorine content
of the catalyst prior to initiation of the actual hydrocracking.
In situ fluoriding of the catalyst in this way is preferably carried out to induce a fluorine
content of about 1 to 10 percent fluorine prior to operation, after which the fluorine
can be reduced to maintenance levels sufficient to maintain the desired activity.
Suitable compounds for
in situ fluoriding are orthofluorotoluene and difluoroethane.
[0036] The metals present on the catalyst are preferably used in their sulfide form and
to this purpose pre-sulfiding of the catalyst should be carried out prior to initiation
of the hydrocracking. Sulfiding is an established technique and it is typically carried
out by contacting the catalyst with a sulfur-containing gas, usually in the presence
of hydrogen. The mixture of hydrogen and hydrogen sulfide, carbon disulfide or a mercaptan
such as butol mercaptan is conventional for this purpose. Presulfiding may also be
carried out by contacting the catalyst with hydrogen and a sulfur-containing hydrocarbon
oil such as a sour kerosene or gas oil.
Hydroisomerization
[0037] The paraffinic components present in the original wax feed possess high viscosity
indices but have relatively high pour points. The objective of the process of the
invention is, therefore, to effect a selective conversion of waxy species while minimizing
conversion of more branched species characteristic of lube components. The conversion
of wax occurs preferentially by isomerization to form more branched species which
have lower pour points and. cloud points. Some degree of cracking accompanies isomerization,
the extent of cracking varying with the degree of wax conversion.
Hydroisomerization Catalyst
[0038] The catalyst used in hydroisomerization in this invention is one which has a high
selectivity for the isomerization of waxy, linear or near linear paraffins to less
waxy, isoparaffinic products. Catalysts of this type are bifunctional in character,
comprising a metal component on a large pore size, porous support of relatively low
acidity. The acidity is maintained at a low level in order to reduce conversion to
products boiling outside the lube boiling range during this stage of the operation.
In general terms, the catalyst should have an alpha value not more than 30 prior to
metals addition, with preferred values not more than 20. (See Example 1)
The alpha value is an approximate indication of the catalytic cracking activity of
the catalyst compared to a standard catalyst. The alpha test gives the relative rate
constant (rate of normal hexane conversion per volume of catalyst per unit time) of
the test catalyst relative to the standard catalyst which is taken as an alpha of
1 (Rate Constant = 0.016 sec
-1). The alpha test is described in U.S. Patent 3,354,078 and in
J. Catalysis, 1, 527 (1965); 6, 278 (1966); and
61, 395 (1980), to which reference is made for a description of the test. The experimental
conditions of the test used to determine the alpha values referred to in this specification
include a constant temperature of 538 °C and a variable flow rate as described in
detail in
J. Catalysis, 61, 395 (1980).
[0039] The hydroisomerization catalyst comprises a large pore molecular sieve, generally
a zeolite or silica: aluminophosphate. The large pore sieve is supported by a porous
binder. Large pore zeolites usually have at least one pore channel consisting of twelve-membered
oxygen rings . Zeolites beta, Y and mordenites are large pore zeolites. The catalysts
of this invention possess a crystal diameter of less than 0.1 micrometers in order
to maximize the relative rates of isomerization to cracking. Small diameter crystals
allow isomerized species to diffuse readily from the crystal framework reducing the
potential for their cracking.
[0040] The preferred hydroisomerization catalyst employs zeolite beta since this zeolite
has been shown to possess outstanding activity for paraffin isomerization in the presence
of aromatics, as disclosed in U.S. 4, 419 , 220. The low acidity forms of zeolite
beta may be obtained by synthesis of a highly siliceous form of the zeolite e.g with
a silica-alumina ratio above about 500:1 or, more readily, by steaming zeolites of
lower silica-alumina ratio to the requisite acidity level. They may also be obtained
by extraction with acids such as dicarboxylic acid, as disclosed in U.S. Patent No.
5,200,168. U.S. Patent No. 5,238,677 discloses the synthesis of dealuminated mordenite
by oxalic acid extraction. U.S. Patent No. 5,164,169 discloses the preparation of
highly siliceous zeolite beta employing a chelating agent such as tertiary alkenolamines
in the synthesis mixture. U.S. Patent No. 3,308,069 describes the synthesis of zeolite
beta with a crystal size ranging from 0.01 to 0.05 microns. Catalysts with crystal
sizes of this range are used in the instant invention. The crystal size in the instant
invention is not to exceed 0.1 micron, although crystal size between 0.01 and 0.05
microns are preferred.
[0041] The most preferred zeolites are severely steamed and possess a framework silica-alumina
ratio if at least 200:1 and more preferably above 400:1.
[0042] The steaming conditions should be adjusted in order to attain the desired alpha value
in the final catalyst and typically utilize atmospheres of 100 percent steam, at temperatures
of from about 427° to 595°C (800° to about 1100°F). Normally, the steaming will be
carried out at temperatures above 538°C (1000°F), for about 12 to 120 hours, typically
about 96 hours, in order to obtain the desired reduction in acidity.
[0043] Another method of producing a low acidity zeolite beta catalyst is by replacement
of a portion of the framework aluminum of the zeolite with another trivalent element
such as boron which results in a lower intrinsic level of acid activity in the zeolite.
The preferred zeolites of this type are those which contain framework boron. Boron
is usually added to the zeolite framework prior to the addition of other metals. In
zeolites of this type, the framework consists principally of silicon tetrahedral coordinated
and interconnected with oxygen bridges. The minor amount of an element (alumina in
the case of alumina-silicate zeolite beta) is also coordinated and forms part of the
framework. The zeolite also contains material in the pores of the structure although
these do not form part of the framework constituting the characteristic structure
of the zeolite. The term "framework" boron is used here to distinguish between material
in the framework of the zeolite which is evidenced by contributing ion exchange capacity
to the zeolite, from material which is present in the pores and which has no effect
on the total ion exchange capacity of the zeolite. Zeolite beta possesses a constraint
index between 0.60 and 2.0 at temperatures between 316°C and 399°C although Constraint
Indexes less than 1 are preferred.
[0044] Methods for preparing high silica content zeolites containing framework boron are
known and are described, for example, in U.S. Patents Nos. 4,269,813. A method for
preparing zeolite beta containing framework boron is disclosed in U.S. Patent No.
4,672,049. As noted there, the amount of boron contained in the zeolite may be varied
by incorporating different amounts of borate ion in the zeolite forming solution e.g.
by the use of varying amounts of boric acid relative to the forces of silica and alumina.
Reference is made to these disclosures for a description of the methods by which these
zeolites may be made.
[0045] The low acidity zeolite beta catalyst should contain at least 0.1 wt% framework boron,
preferably at least 0.5 wt% boron. Boron may be added to the framework prior to the
addition of other metals. Normally, the maximum amount of boron will be about 5 wt%
of the zeolite and in most cases not more than 2 wt% of the zeolite. The framework
will normally include some alumina. The silica:alumina ratio will usually be at least
30:1, in the conditions of the zeolite as synthesized. A preferred boron-substituted
zeolite beta catalyst is made by steaming an initial boron-containing zeolite containing
at least 1 wt% boron (as B
2O
3) to result in an ultimate alpha value no greater than about 20 and preferably no
greater than 10.
Properties
[0046] Acidity may be reduced by the introduction of nitrogen compounds, e.g. NH
3 or organic nitrogen compounds, with the feed to the hydroisomerization catalyst.
However, the total nitrogen content of the feed should not exceed 100 ppm and should
be preferably less than 20 ppm. The catalyst may also contain metals which reduce
the number of strong acid sites of the catalyst and improve the selectivity of isomerization
reactions to cracking reactions. Metals which are preferred for this purpose are those
belong to the class of Group IIA metals such as calcium and magnesium.
[0047] The zeolite will be composites with a matrix material to form the finished catalyst
and for this purpose conventional very low-acidity matrix materials such as alumina,
silica-alumina and silica are suitable although aluminas such as alpha boehmite (alpha
alumina monohydrate) may also be used, provided that they do not confer any substantial
degree of acidic activity on the matrixed catalyst. The zeolite is usually composited
with the matrix in amounts from 80:20 to 20:80 by weight, typically from 80:20 to
50:50 zeolite:matrix. Compositing may be done by conventional means including mulling
the materials together followed by extrusion into the desired finished catalyst particles.
A preferred method for extruding the zeolite with silica as a binder is disclosed
in U.S. 4,582,815. If the catalyst is to be steamed in order to achieve the desired
low acidity, it is performed after the catalyst has been formulated with the binder,
as is conventional. The preferred binder for the steamed catalyst is alumina.
[0048] The hydroisomerization catalyst also includes a metal component in order to promote
the desired hydroisomerization reactions which, proceeding through unsaturated transitional
species, require mediation by a hydrogenation-dehydrogenation component. In order
to maximize the isomerization activity of the catalyst, metals having a strong hydrogenation
function are preferred and for this reason, platinum and the other noble metals such
as rhenium, gold, and palladium are given a preference. The amount of the noble metal
hydrogenation component is typically in the range 0.1 to 5 wt% of the total catalyst,
usually from 0.1 to 2 wt%: a preferred catalyst comprises 0.3 to 2 %wt. Pt on a support
comprising zeolite beta. The platinum may be incorporated into the catalyst by conventional
techniques including ion exchange with complex platinum cations such as platinum tetraamine
or by impregnation with solutions of soluble platinum compounds, for example, with
platinum tetraammine salts such as platinum tetraamminechloride. The catalyst may
be subjected to a final calcination under conventional conditions in order to convert
the noble metal to its reduced form and to confer the required mechanical strength
on the catalyst. Prior to use the catalyst may be subjected to presulfiding as described
above for the . hydrocracking pretreatment catalyst.
Hydroisomerization Conditions
[0049] The conditions for hydroisomerization (also called isomerization) are adjusted to
achieve the objective of isomerizing the waxy, linear and near-linear paraffinic components
in the waxy feed to less waxy but high V.I. isoparaffinic materials of relatively
lower pour point. The process is preferably carried out in the presence of hydrogen
to convert from 40 to 90 wt.% of the wax contained in the feed. This end is achieved
while minimizing conversion to non-lube boiling range products 345°C- (650°F-) materials.
Since the catalyst used for hydroisomerization has a low acidity, conversion to lower
boiling products is usually at a relatively low level and by appropriate selection
of severity, the operation of the process may be optimized for isomerization over
cracking. At conventional space velocities of about 1, using a Pt/zeolite beta catalyst
with an alpha value below 20, temperatures for the hydroisomerization will typically
be in the range of about 288 to 427°C (550-800°F), preferably 300° to 415°C (about
570° to about 780°F) with conversion to 345°C- (650°F-) typically being from about
5 to 30 wt%, more usually 10 to 25 wt%, of the waxy feed.
[0050] Hydroisomerization is accomplished at hydrogen partial pressures (reactor inlet)
of at least 5516 kPa
a (800 psig), usually 5516 to 20785 kPa
a (800 to 3000 psig) and in most cases 5516 to 17340 kPa
a (800-2500 psig). Hydrogen circulation rates are usually in the range of about 90
to 900 n.l.l.
-1 (500 to 5000 SCF/Bbl). Since some saturation of aromatic components present in the
original feed takes place in the presence of the noble metal hydrogenation component
on the catalyst, hydrogen is consumed in the hydroisomerization even though the desired
isomerization reactions are in hydrogen balance; for this reason, hydrogen circulation
rates may need to be adjusted in accordance with the aromatic content of the feed
and also with the temperature used in the hydroisomerization since higher temperatures
will be associated with a higher level of cracking and, consequently, with a higher
level of olefin production, some of which will be in the lube boiling range so that
product stability will need to be assured by saturation. Hydrogen circulation rates
of at least 180 n.l.l.
-1 (1000 SCF/Bbl) will normally provide sufficient hydrogen to compensate for the expected
hydrogen consumption as well as to ensure a low rate of catalyst aging.
[0051] An interbed quench is desirable to maintain temperature in the process. Cold hydrogen
is generally used as the quench, but a liquid quench, usually recycled product, may
also be used.
Dewaxing
[0052] Although a final dewaxing step may be necessary in order to achieve the desired product
pour point, depending on the wax content of the feed. It is a notable feature of the
present process that the extent of dewaxing required is relatively small. Typically,
the loss during the final dewaxing step will be no more than 15-20 wt% of the dewaxer
feed and may be lower. Either catalytic dewaxing or solvent dewaxing may be used at
this point and if a solvent dewaxer is used, the removed wax may be recycled to the
hydroisomerization for a second pass through the isomerization step. The demands on
the dewaxer unit for the product are relatively low and in this respect the present
process provides a significant improvement over the process employing solely amorphous
catalysts where a significant degree of dewaxing is required. The high isomerization
selectivity of the large-pore zeolite catalysts enables high single pass wax conversions
to be achieved, typically about 80% as compared to 50% for the amorphous catalyst
process so that unit throughput is significantly enhanced.
[0053] A shape-selective dewaxing catalyst maybe alternately employed rather than a solvent
dewaxing approach. This catalyst removes the n-paraffins together with the waxy, slightly
branched chain paraffins, while leaving the more branched chain iso-paraffins in the
process stream. Shape-selective catalytic dewaxing processes employ catalysts which
are more highly selective for removal of n-paraffins and slightly branched chain paraffins
than is the large-pore isomerization catalyst, such as zeolite beta. Selective catalytic
dewaxing is carried out as described in U.S. Patent No. 4,919,788, to which reference
is made for a description of: this phase. The catalytic dewaxing step in the present
process is preferably carried out with a constrained, shape-selective dewaxing catalyst
based on a constrained intermediate pore crystalline material, such as an aluminosilicate.
A constrained intermediate crystalline material has at least one channel of 10-membered
oxygen rings with any intersecting channel having 8-membered rings. ZSM-23 is the
preferred zeolite for this purpose although other highly shape-selective zeolites
such as ZSM-22 or the synthetic ferrierite ZSM-35 may also be used, especially with
lighter stocks. Silicoaluminophosphates such as SAPO-11 and SAPO-41 maybe used as
selective dewaxing catalysts.
[0054] The preferred catalysts for use as the dewaxing catalysts are the relatively constrained
intermediate pore size zeolites. Such preferred zeolites have a Constraint Index in
the range of 1-12, as determined by the method described in U.S. Patent No. 4,016,218.
These preferred zeolites are also characterized by specific sorption properties related
to their relatively constrained diffusion characteristics. These sorption characteristics
are those which are set out in U.S. Patent No. 4,810,357 for the zeolites such as
zeolite ZSM-22, ZSM-23, ZSM-35 and ferrierite. These zeolites have pore openings which
result in a specific combination of sorption properties, namely, (1) a ratio of sorption
of n-hexane to o-xylene, on a volume percent basis, of greater than about 3, wherein
sorption is determined at a P/P
o of 0.1 and at a temperature of 50°C for n-hexane and 80°C for o-xylene and (2) by
the ability of selectively cracking 3-methylpentane (3MP) in preference to the doubly
branched 2,3-dimethylbutane (DMB) at 1000°F and 1 atmosphere pressure from a 1/1/1
weight ratio mixture of n-hexane/3-methyl-pentane/2,3-dimethylbutane, with the ratio
of rate constants k
3MD/k
DMB determined at a temperature of 538°C (1000°F) being in excess of about 2.
[0055] The expression, "P/P
o", is accorded its usual significance as described in the literature, for example,
in "The Dynamical Character of Adsorption" by J.H. deBoer, 2nd Edition, Oxford University
Press (1968) and is the relative pressure defined as the ratio of the partial pressure
of sorbate to the vapor pressure of sorbate at the temperature of sorption. The ratio
of the rate constants, k
3MP/k
DMB, is determined from 1st order kinetics, in the usual manner, by the following equation:
where k is the rate constant for each component, T
c is the contact time and ε is the fractional conversion of each component.
[0056] Zeolites conforming to these sorption requirements include the naturally occurring
zeolite ferrierite as well as the synthetic zeolites ZSM-22, ZSM-23 and ZSM-35. These
zeolites are at least partly in the acid or hydrogen form when they are used in the
present process.
[0057] The preparation and properties of zeolite ZSM-22 are described in U.S. Patent No.
4,810,357 (Chester) to which reference is made for such a description.
[0058] The synthetic zeolite ZSM-23 is described in U.S. Patent Nos. 4,076,842 and 4,104,151
to which reference is made for a description of this zeolite, its preparation and
properties.
[0059] The intermediate pore-size synthetic crystalline material designated ZSM-35 ("zeolite
ZSM-35" or simply "ZSM-35"), is described in U.S. patent No. 4,016,245, to which reference
is made for a description of this zeolite and its preparation. The synthesis of SAPO-11
is described in U.S. Patent Nos. 4,943,424 and 4,440,871. The synthesis of SAPO-41
is described in U.S. Patent No. 4,440,871.
[0060] Ferrierite is a naturally-occurring mineral, described in the literature, see, e.g.,
D.W. Breck, ZEOLITE MOLECULAR SIEVES, John Wiley and Sons (1974), pages 125-127, 146,
219 and 625, to which reference is made for a description of this zeolite.
[0061] The dewaxing catalysts used in the shape-selective catalytic dewaxing preferably
include a metal hydrogenation-dehydrogenation component. Although it may not be strictly
necessary to promote the selective cracking reactions, the presence of this component
has been found to be desirable to promote certain isomerization reactions which contribute
to the synergy of the two catalyst dewaxing system. The presence of the metal component
leads to product improvement, especially VI, and stability as well as helping to retard
catalyst aging. The shape-selective, catalytic dewaxing is normally carried out in
the presence of hydrogen under pressure. The metal will be preferably platinum or
palladium. The amount of the metal component will typically be 0.1 to 10 percent by
weight. Matrix materials and binders may be employed as necessary.
[0062] Shape selective dewaxing using the highly constrained, highly shape-selective catalysts
may be carried out in the same general manner as other catalytic dewaxing processes,
such as those described above for. the initial isomerization phase. Reference is made
to U.S. Patent 4,919,788 for a more extended discussion of the shape-selective catalytic
dewaxing step.
[0063] The degree of conversion to lower boiling species in the dewaxing stage will vary
according to the extent of dewaxing desired at this point, i.e. on the difference
between the target pour point and the pour point of the effluent from the isomerization
stage. It will also depend upon the selectivity of the shape-selective catalyst which
is used. At lower product pour points, and with relatively less selective dewaxing
catalysts, higher conversions and correspondingly higher hydrogen consumptions will
be encountered.
[0064] After the pour point of the oil has been reduced to the desired value by selective
dewaxing, the dewaxed oil may be subjected to treatments such as hydrotreating, in
order to remove color bodies and produce a lube product of the desired characteristics.
Fractionation may be employed to remove light ends and to meet volatility specifications.
Suitable hydrotreating procedures are set forth in claims 15, 16, 27 and 28.
Products
[0065] The products from the process are high VI, low pour point materials which are obtained
in excellent yield. Besides having excellent viscometric properties they are also
highly stable, both oxidatively and thermally and to ultraviolet light. VI values
in the range of 130 to 150 are typically obtained with the preferred wax feeds to
the process and values of at least 140, are readily achievable with product yields
of at least 50 wt%, usually at least 60 wt%, based on the original wax feed.
EXAMPLES
Example 1
[0066] A low-acidity zeolite beta-containing catalyst was prepared by first extruding a
mixture of 65 parts by weight of zeolite beta with 35 parts by weight silica (SiO
2). The zeolite beta used in this preparation has a SiO
2:Al
2O
3 ratio of 600, an average crystal size of 1-3 micrometres as measured using scanning
electron microscopy (SEM). Details of the synthesis are given in U.S. patents 5,232,579,
5,164,169, and 5,164,170. The mixture of zeolite beta and silica was mixed with an
aqueous caustic solution to form a paste and extruded following standard procedures
known to those skilled in the art of catalyst preparation. The extrudate was dried
for 8 hours at 121°C (250°F), contacted with 5 v/v of a 1N NH
4NO
3 solution to reduce its sodium level. The sodium-reduced extrudate was then heated
in N
2 to 482°C (900°F) and held there for 3 hours before exposure to air at 538°C (1000°F)
for 6 hours to decompose the organic compounds used in the preparation of the zeolite
beta. This catalyst was then exposed to 100% steam at 101 kPa
a (0 psig) for a sufficient time (24 hours) to reduce its alpha activity to below 15.
[0067] This steam-deactivated zeolite beta containing material was then exchanged with an
aqueous solution of platinum tetrammine chloride dihydrate maintained at a pH of between
7-8. The platinum exchanged catalyst was rinsed with water. to remove chlorides and
then heated to 349°C (660°F) in air and held there for 3 hours. The final catalyst
contained 0.6 wt% platinum and has properties given in Table 4.
Table 4
Silica-Bound Pt/β Catalyst Properties |
Catalyst |
Example 1 |
Example 2 |
Platinum, wt% |
0.5 |
0.5 |
Sodium, ppm |
130 |
245 |
|
Surface Area, m2/g |
318 |
316 |
Pore Volume, cc/g |
- |
0.97 |
|
Alpha (prior to Pt Addition) |
13 |
8 |
Crystal Size, µ |
1-3 |
0.05 |
Example 2
[0068] A zeolite beta-containing catalyst was prepared by first extruding a mixture of 65
parts by weight of zeolite beta with 35 parts by weight silica (SiO
2). The zeolite beta used in this preparation had a SiO
2:Al
2O
3 ratio of 50, an average crystal size of less than 0.05 microns as measured using
SEM, and was synthesized following standard. procedures for MIDW-grade zeolite beta.
The mixture of zeolite beta and silica was mixed with an aqueous caustic solution
to form a paste and extruded following standard procedures known to those in the catalyst
art. The extrudate was dried for 8 hours at 121°C (250°F). The sodium-containing extrudates
were then heated in N
2 to 482°C (900°F) and held there for 3 hours before exposure to air at 538°C (1000°F)
for 6 hours to decompose the organic compounds used in the preparation of the zeolite
beta. This catalyst was then exposed to an 2M aqueous solution of: oxalic acid for
a total of 6 hours at 71°C (160°F). The oxalic-acid treated zeolite beta catalyst
was then heated to 538°C (1000°F) for 2 hours. This material had an alpha value less
then 10 and a sodium content of 525 ppmw.
[0069] This oxalic acid-treated zeolite beta catalyst was then exchanged with an aqueous
solution of platinum tetrammine chloride dihydrate maintained at a pH of between 5-6.
The platinum exchanged catalyst was rinsed with water to remove chlorides and then
heated to 349°C (660°F) in air and held there for 3 hours. The final catalyst contained
0.5 wt% platinum and has properties given in Table 4, supra.
Example 3
[0070] A slack wax derived from solvent dewaxing a 97 mm
2/s (cSt) (450 SUS) heavy neutral furfural raffinate was hydrocracked at mild severity
to reduce its sulfur and nitrogen contents. Conditions for the mild hydrocracking
step were: 2 LHSV, 404°C (760°F), 13891 kPa
a (2000 psig H
2) partial pressure. Properties of the slack wax and the stripped hydrocracked product
are given by Table 5.
[0071] The mild hydrocracking step converted 16% of the slack wax feed to products boiling
below 343°C (650°F) and also converted 17% of the wax in the feed. Wax conversion
and lube yield are calculated by the following equations. Dewaxed oil yield was corrected
to a 0°F pour point for consistency.
Table 5
Feed Stock Properties |
|
450 Heavy Neutral Slack Wax |
Mildly Hydrocracker 450 Heavy Neutral Slack Wax |
Description |
|
|
Oil Content on 343°C+ (650°F+) Basis, % |
38 |
48 |
|
Nitrogen, ppm |
68 |
<7 |
Sulfur, ppm |
1920 |
<20 |
Simulated Distillation. °C |
IBP |
366 |
128 |
5% Off |
420 |
245 |
10% |
441 |
312 |
20% |
459 |
397 |
50% |
495 |
463 |
90% |
550 |
527 |
FBP |
586 |
572 |
343°F+ Solvent Dewaxed Oil |
Kinematic Viscosity at 100°C, cst |
11.3 |
6.1 |
VI at -17.78°C (0°F) Pour |
92 |
138 |
Yield, wt% Heavy Neutral Slack Wax |
37 |
33 |
|
343°C (650°F+) Conversion, % |
- |
16 |
Wax Conversion, % |
- |
17 |
Example 4
[0072] The mildly hydrocracked slack wax of Example 3 was reacted over the Pt/β catalysts
of Example 1 and 2 in separate experiments. Reaction conditions were 13891 kPa
a (2000 psig) and 1 LHSV for the catalyst of Example 1 and 1.25 LHSV for the catalyst
of Example 2. Catalyst temperature was varied to effect changes in reaction severity.
Prior to the introduction of liquid feed, both catalysts were presulfided with a mixture
of 2 vol% H
2S/98 vol% H
2 to a maximum temperature of 371°C (700°F).
[0073] The reactor effluent from these experiments was analyzed by simulated distillation
to determine the conversion to 343°C (650°F-) products and then distilled to a nominal
343°C (650°F) cutpoint. Wax and lube yields and wax conversions were calculated based
on the equations of Example 3 and are given by Table 6. The Figure illustrates the
relative dependence of lube yield on wax conversion for the two catalysts.
[0074] The wax isomerization selectivity of the small crystal catalyst (Example 2) was significantly
higher than that of the large crystal catalyst (Example 1). Lube yield peaked at 64%
for the small crystal Pt/β catalyst while reaching only 52% for the large crystal
catalyst. Consistent with the sequential reaction network of isomerization followed
by shape-selective cracking, both catalysts gave similar yields at low wax conversions
(less than 40%). However, as the reaction severity was increased, the rate of cracking
in the large crystal catalyst relative to the isomerization rate increased substantially
so that at 50% wax conversion, the rate of creation of lube by isomerization matched
the rate of lube loss by cracking. Increasing the wax conversion beyond that point
resulted in a decrease in lube yield. In contrast, the ratio of isomerization to cracking
remained high for the small crystal catalyst up to high wax. conversions. The rates
of the two reactions did not become equivalent until 80% wax conversion was reached.
[0075] The practical application of the invention, beyond the obvious higher yields for
the small crystal catalyst, is the catalyst's ability to selectively function at high
wax: conversion. This reduces the amount of wax recycle and reduces the size of the
reactors required to produce a given quantity of high VI base stock.
[0076] Zeolitic acidity can also play an important role in determining isomerization selectivity.
While the large crystal Pt/β catalyst had a higher alpha value compared to the small
crystal version (13 vs. 8), it is likely that the selectivity difference observed
between the catalysts was not primarily a function of acidity. The difference in alpha
values is not significantly large.
Table 6
Wax Isomerization Selectivity of Silica-Bound Pt/β Catalysts |
Example 1 Catalyst (1-3µ, 13∝) |
Pt/β
Temp., °C |
343°C+ Conv.
Over Pt/β % |
Wax Conv.
Over Pt/β % |
343°C+ Lube
Yield % HNSW |
343°C+Lube
VI at-17.78°C Pour |
313 |
1 |
26 |
46 |
141 |
316 |
3 |
34 |
49 |
142 |
322 |
5 |
45 |
52 |
144 |
325 |
10 |
51 |
51 |
142 |
333 |
21 |
63 |
48 |
143 |
Example 2 Catalyst (0.05 µ, 8∝) |
Pt/β
Temp.,°C |
343°C+ Conv.
Over Pt/β % |
Wax Conv.
Over Pt/β % |
343°C+ Lube
Yield % HNSW |
343°C+ Lube
VI at -17.78°C
(0°F) Pour |
307 |
3 |
30 |
46 |
144 |
312 |
4 |
49 |
54 |
145 |
321 |
11 |
75 |
61 |
142 |
324 |
12 |
84 |
64 |
144 |
324 |
15 |
82 |
61 |
142 |
327 |
18 |
86 |
61 |
142 |
329 |
24 |
93 |
59 |
141 |
1. A process for producing an at least 130 Viscosity Index (VI) lubricant from a waxy
hydrocarbon feed having a wax content of at least 20 %wt, which comprises catalytically
dewaxing waxy paraffins present in the feed primarily by isomerization, in the presence
of hydrogen and in the presence of a low acidity large pore molecular sieve selected
from the group consisting of zeolite beta, Y and mordenite having at least one pore
channel with a major dimension greater than 0.7 nm and having a crystal size of less
than 0.1 micron, an alpha value of not more than 30 and containing a noble metal hydrogenation
component.
2. The process of claim 1 wherein the large pore molecular sieve possesses at least one
pore channel of 12-membered oxygen rings.
3. The process of claim 1, wherein the zeolite beta has an alpha value of not greater
than 20.
4. The process claim 1, wherein the large pore molecular sieve has a crystal size less
than 0.05 micron.
5. The process of claim 1, wherein the large pore molecular sieve is a low acidity zeolite
beta which has been steamed, having a framework silica: alumina ratio of at least
200:1.
6. The process of claim 1, in which the large pore molecular sieve comprises a boron-containing
zeolite beta isomerization catalyst in which the boron is present as a framework component
of the zeolite beta.
7. The process of claim 1, in which the large pore molecular sieve comprises from 0.3
to 2 wt% Pt on a support comprising zeolite beta.
8. The process of claim 1 in which the feed comprises a waxy hydrocarbon feed having
a wax content of at least 40 wt% and an aromatic content of less than 25 wt%.
9. The process of claim 1 wherein the feedstock is selected from the group consisting
of a slack wax, deoiled wax, wax from Fischer-Tropsch process, foots oils, petrolatum,
vacuum gas oil, or a raffinate from solvent extraction of a vacuum distillate.
10. The process of claim 1, in which the process is carried out in the presence of hydrogen
to convert from 40 to 90 wt% of the wax contained in the feed.
11. The process of claim 1, wherein conditions include a hydrogen partial pressure ranging
from 4238 to 20786 kPaa (600 to 3000 psig) and a temperature from 288°C to 427°C (550 to 800 °F).
12. The process of claim 1 in which the catalytically dewaxed feed is subjected to further
selective dewaxing to achieve target pour point.
13. The process of claim 12 , in which said further dewaxing is accomplished by either
solvent or catalytic means.
14. The process of claim 1, in which the catalytically dewaxed feed is hydrotreated by
contacting it with a catalyst comprising a metal hydrogenation component on a porous
support material at a pressure in the range from about 3549 to about 20786 kPaa (500 to about 3000 psig), a reaction temperature in the range from about 260°C to
about 427°C (500°F to about 800°F), a space velocity which is in a range from about
0.1 to about 10 LHSV, and a once-through hydrogen circulation rate which extends from
about 178 to about 1780 n.l.l."1 (1000 SCF/B to about 10 , OOOSCF/B) , in order to improve the thermal and oxidative
stability of the lubricant.
15. The process of claim 12, in which the feed is hydrotreated following selective dewaxing
by contacting it with a catalyst comprising a metal hydrogenation component on a porous
support material at a pressure in the range from about 3549 to about 20786 kPaa (500 to about 3000 psig) , a reaction temperature in the range from about 260 °C
to about 427°C (500°F to about 800°F), a space velocity which is in a range from about
0 . 1 to about 10 LHSV, and a once-through hydrogen circulation rate which extends
from about 178 to about 1780 n.l.l.-1 (1000 SCF/B) to about 10, 000SCF/B, in order to improve the thermal and oxidative
stability of the lubricant.
16. A process for producing an at least 130 Viscosity Index (VI) lubricant from a waxy
hydrocarbon feed having a wax content 20 of at least 20 wt%, the process comprising
the following steps:
(a) hydrocracking of the feed in order to reduce its nitrogen content as well as to
remove naphthenic and aromatic components, thereby improving VI, the hydrocracking
process comprising contacting the feed with a catalyst composed of a metal hydrogenation
component on air acidic support;
(b) catalytically dewaxing waxy paraffins present in the feed primarily by isomerization,
in the presence of hydrogen and in the presence of a low acidity large pore molecular
sieve selected from the group consisting of zeolite beta, Y and mordenite having at
least one pore channel with a major dimension greater than 0.7nm and a crystal size
of less than 0.1 micron, an alpha value of not more than 30 and containing a noble
metal hydrogen component.
17. The process of claim 16, wherein the large pore molecular sieve possesses at least
one pore channel of 12-membered oxygen rings.
18. The process of claim 16, wherein the zeolite beta has an alpha value of not greater
than 20.
19. The process of claim 16, wherein the large pore molecular sieve is a low acidity zeolite
beta which has been steamed, having a framework silica: alumina ratio of at least
200:1.
20. The process of claim 16, in which the large pore molecular sieve comprises from 0.3
to 2 wt% Pt on a support comprising zeolite beta.
21. The process of claim J7, wherein the feedstock is selected from the group consisting
of a slack wax, deoiled wax, foots oil, wax from Fischer-Tropsch process, petrolatum,
vacuum gas oil, or a raffinate from solvent extraction of a vacuum distillate.
22. The process of claim 16, wherein conditions of step (b) include a hydrogen partial
pressure ranging from 4238 to 20786 kPaa (600 to 3000 psig) and a temperature from 288°C to 427°C (550 to 800°F).
23. The process of claim 16, in which the effluent of step (b) is subjected to further
selective dewaxing to achieve target pour point.
24. The process of claim 23, in which said further dewaxing is accomplished by either
solvent or catalytic means.
25. The process of claim 16, in which at least a portion of the effluent of step (b) is
hydrotreated by contacting it with a catalyst comprising a metal hydrogenation component
on a porous support material at a pressure in the range from about 3549 to about 20786
kPaa (500 to about 3000 psig), a reaction temperature in the range from about 260°C to
427°C (500°F to about 800°F), a space velocity which is in a rage from about 0.1 to
about 10 LHSV, and a once-through hydrogen circulation rate which extends from about
178 to 1780 n.l.l.-1 (1000 SCF/B to about 10,000 SCF/B), in order to improve the thermal and oxidative
stability of the lubricant.
26. The process of claim 23 in which the effluent of step (b) of claim 16 is subjected,
following further selective dewaxing to hydrotreating by contacting it with a catalyst
comprising a metal hydrogenation component on a porous support material at a pressure
in the range from about 3549 to about 20 786 kPaa (500 to 3000 psig), a reaction temperature in the range from about 260°C to 427°C
(500°F to about 800°F), a space velocity which is in a range from about 0.1 to about
10 LSHV, and a once-through hydrogen circulation rate which extends from about 178
to 1780 n.l.l.-1 (1000 SCT/B to about 10,000SCF/B), in order to improve the thermal and oxidative
stability of the lubricant.
1. Verfahrens zur Herstellung eines Schmiermittels mit einem Viskositätsindex (VI) von
mindestens 130 aus einer wachsartigen Kohlenwasserstoffbeschickung mit einem Wachsgehalt
von mindestens 20 Gew.-%, das das katalytische Entparaffinieren von in der Beschickung
vorhandenen wachsartigen Paraffinen, primär durch Isomerisieren, in Gegenwart von
Wasserstoff und in Gegenwart eines Molekularsiebs mit großen Poren und geringer Acidität
umfaßt, das aus der Gruppe ausgewählt ist, die aus Zeolith Beta, Y und Mordenit mit
mindestens einem Porenkanal mit einer Hauptabmessung von mehr als 0,7 nm und mit einer
Kristallgröße von weniger als 0,1 µm und mit einem α-Wert von nicht mehr als 30 besteht
und eine Hydrierungskomponente aus einem Edelmetall enthält.
2. Verfahren nach Anspruch 1, wobei das Molekularsieb mit großen Poren mindestens einen
Porenkanal aus 12-gliedrigen Sauerstoffringen besitzt.
3. Verfahren nach Anspruch 1, wobei der Zeolith Beta einen α-Wert von nicht mehr als
20 aufweist.
4. Verfahren nach Anspruch 1, wobei das Molekularsieb mit großen Poren eine Kristallgröße
von weniger als 0,05 µm aufweist.
5. Verfahren nach Anspruch 1, wobei das Molekularsieb mit großen Poren ein Zeolith Beta
mit geringer Acidität ist, der der Dampfbehandlung unterzogen wurde, der ein Verhältnis
von Siliciumdioxid:Aluminiumoxid des Gitters von mindestens 200:1 aufweist.
6. Verfahren nach Anspruch 1, wobei das Molekularsieb mit großen Poren einen Isomerisierungskatalysator
aus einem borhaltigen Zeolith Beta umfaßt, bei dem das Bor als Gitterkomponente des
Zeoliths Beta vorliegt.
7. Verfahren nach Anspruch 1, wobei das Molekularsieb mit großen Poren 0,3 bis 2 Gew.-%
Pt auf einem Träger umfaßt, der Zeolith Beta umfaßt.
8. Verfahren nach Anspruch 1, wobei die Beschickung eine wachsartige Kohlenwasserstoffbeschickung
mit einem Wachsgehalt von mindestens 40 Gew.-% und einem Aromatengehalt von weniger
als 25 Gew.-% umfaßt.
9. Verfahren nach Anspruch 1, wobei das Beschickungsmaterial aus der Gruppe ausgewählt
ist, die aus Rohparaffin, entöltem Wachs, Wachs von einem Fischer-Tropsch-Verfahren,
Bodenölen, Petrolatum, Vakuumgasöl oder einem Raffinat von der Lösungsmittelextraktion
eines Vakuumdestillats besteht.
10. Verfahren nach Anspruch 1, wobei das Verfahren in Gegenwart von Wasserstoff durchgeführt
wird, wodurch 40 bis 90 Gew.-% des in der Beschickung enthaltenen Wachses umgewandelt
werden.
11. Verfahren nach Anspruch 1, wobei die Bedingungen einen Partialdruck von Wasserstoff
im Bereich von 4238 bis 20786 kPaa (600 bis 3000 psig) und eine Temperatur von 288 bis 427°C (550 bis 800°F) einschließen.
12. Verfahren nach Anspruch 1, wobei die katalytisch entparaffinierte Beschickung einem
weiteren selektiven Entparaffinieren unterzogen wird, um den zu erzielenden Pourpoint
zu erreichen.
13. Verfahren nach Anspruch 12, wobei das weitere Entparaffinieren entweder durch Lösungsmittel
oder katalytische Maßnahmen erreicht wird.
14. Verfahren nach Anspruch 1, wobei die katalytisch entparaffinierte Beschickung der
Wasserstoffbehandlung unterzogen wird, indem sie bei einem Druck im Bereich von etwa
3549 bis etwa 20786 kPaa (500 bis etwa 3000 psig), einer Reaktionstemperatur im Bereich von etwa 260 bis etwa
427°C (500 bis etwa 800°F), einer Raumgeschwindigkeit, die im Bereich von etwa 0,1
bis etwa 10 LHSV liegt, und bei einer Zirkulationsrate von Wasserstoff bei einem Durchgang,
die von etwa 178 bis etwa 1780 nl/l (1000 bis etwa 10000 scf/b) reicht, mit einem
Katalysator in Kontakt gebracht wird, der eine Hydrierungskomponente aus einem Metall
auf einem porösem Trägermaterial umfaßt, um die Wärme- und Oxidationsbeständigkeit
des Schmiermittels zu verbessern.
15. Verfahren nach Anspruch 12, wobei die Beschickung nach dem selektiven Entparaffinieren
der Wasserstoffbehandlung unterzogen wird, indem sie bei einem Druck im Bereich von
etwa 3549 bis etwa 20786 kPaa (500 bis etwa 3000 psig), einer Reaktionstemperatur im Bereich von etwa 260 bis etwa
427°C (500 bis etwa 800°F), einer Raumgeschwindigkeit, die im Bereich von etwa 0,1
bis etwa 10 LHSV liegt, und bei einer Zirkulationsrate von Wasserstoff bei einem Durchgang,
die von etwa 178 bis etwa 1780 nl/l (10000 scf/b) reicht, mit einem Katalysator in
Kontakt gebracht wird, der eine Hydrierungskomponente aus einem Metall auf einem porösem
Trägermaterial umfaßt, um die Wärme- und Oxidationsbeständigkeit des Schmiermittels
zu verbessern.
16. Verfahren zur Herstellung eines Schmiermittels mit einem Viskositätsindex (VI) von
mindestens 130 aus einer wachsartigen Kohlenwasserstoffbeschickung mit einem Wachsgehalt
von 20 von mindestens 20 Gew.-%, wobei das Verfahren die folgenden Schritte umfaßt:
a) Hydrocracken der Beschickung, um sowohl deren Stickstoffgehalt zu verringern als
auch naphthenische und aromatische Komponenten zu entfernen, wodurch der VI verbessert
wird, wobei das Hydrocrackverfahren den Kontakt der Beschickung mit einem Katalysator
umfaßt, der aus einer Hydrierungskomponente aus einem Metall auf Luft saurem Träger
besteht.
b) Katalytisches Entparaffinieren der in der Beschickung vorhandenen wachsartigen
Paraffine, primär durch Isomerisierung, in Gegenwart von Wasserstoff und in Gegenwart
eines Molekularsiebs mit großen Poren und geringer Acidität, das aus der Gruppe ausgewählt
ist, die aus Zeolith Beta, Y und Mordenit mit mindestens einem Porenkanal mit einer
Hauptabmessung von mehr als 0,7 nm und einer Kristallgröße von weniger als 0,1 µm,
einem α-Wert von nicht mehr als 30 besteht und eine Wasserstoffkomponente aus einem
Edelmetall enthält.
17. Verfahren nach Anspruch 16, wobei das Molekularsieb mit großen Poren mindestens einen
Porenkanal aus 12-gliedrigen Sauerstoffringen besitzt.
18. Verfahren nach Anspruch 16, wobei der Zeolith Beta einen α-Wert von nicht mehr als
20 aufweist.
19. Verfahren nach Anspruch 16, wobei das Molekularsieb mit großen Poren ein Zeolith Beta
mit geringer Acidität ist, der der Dampfbehandlung unterzogen wurde, der ein Verhältnis
von Siliciumdioxid:Aluminiumoxid des Gitters von mindestens 200:1 aufweist.
20. Verfahren nach Anspruch 16, wobei das Molekularsieb mit großen Poren 0,3 bis 2 Gew.-%
Pt auf einem Träger umfaßt, der Zeolith Beta umfaßt.
21. Verfahren nach Anspruch J7, wobei das Beschickungsmaterial aus der Gruppe ausgewählt
ist, die aus Rohparaffin, entöltem Wachs, Bodenöl, Wachs vom Fischer-Tropsch-Verfahren,
Petrolatum, Vakuumgasöl oder einem Raffinat von der Lösungsmittelextraktion eines
Vakuumdestillats besteht.
22. Verfahren nach Anspruch 16, wobei die Bedingungen des Schrittes (b) einen Partialdruck
von Wasserstoff im Bereich von 4238 bis 20786 kPaa (600 bis 300 psig) und eine Temperatur von 288 bis 427°C (550 bis 800°F) einschließen.
23. Verfahren nach Anspruch 16, wobei der Abfluß vom Schritt (b) einem weiteren selektiven
Entparaffinieren unterzogen wird, um den zu erzielenden Pourpoint zu erreichen.
24. Verfahren nach Anspruch 23, wobei das weitere Entparaffinieren entweder durch ein
Lösungsmittel oder durch katalytische Maßnahmen erreicht wird.
25. Verfahren nach Anspruch 16, wobei zumindest ein Teil des Abflusses vom Schritt (b)
der Wasserstoffbehandlung unterzogen wird, indem er bei einem Druck im Bereich von
etwa 3549 bis etwa 20786 kPaa (500 bis etwa 3000 psig), einer Reaktionstemperatur im Bereich von etwa 260 bis etwa
427°C (500 bis etwa 800°F), einer Raumgeschwindigkeit, die im Bereich von etwa 0,1
bis etwa 10 LHSV liegt, und bei einer Zirkulationsrate von Wasserstoff bei einem Durchgang,
die von etwa 178 bis etwa 1780 nl/l (1000 bis etwa 10000 scf/b) reicht, mit einem
Katalysator in Kontakt gebracht wird, der eine Hydrierungskomponente aus einem Metall
auf einem porösem Trägermaterial umfaßt, um die Wärme- und Oxidationsbeständigkeit
des Schmiermittels zu verbessern.
26. Verfahren nach Anspruch 23, wobei der Abfluß vom Schritt (b) von Anspruch 16 nach
dem weiteren selektiven Entparaffinieren der Wasserstoffbehandlung unterzogen wird,
indem er bei einem Druck im Bereich von etwa 3549 bis etwa 20786 kPaa (500 bis etwa 3000 psig), einer Reaktionstemperatur im Bereich von etwa 260 bis etwa
427°C (500 bis etwa 800°F), einer Raumgeschwindigkeit, die im Bereich von etwa 0,1
bis etwa 10 LHSV liegt, und bei einer Zirkulationsrate von Wasserstoff bei einem Durchgang,
die von etwa 178 bis etwa 1780 nl/l (1000 sct/b bis etwa 10000 scf/b) reicht, mit
einem Katalysator in Kontakt gebracht wird, der eine Hydrierungskomponente aus einem
Metall auf einem porösem Trägermaterial umfaßt, um die Wärme- und Oxidationsbeständigkeit
des Schmiermittels zu verbessern.
1. Procédé de production d'un lubrifiant ayant un indice de viscosité (VI) d'au moins
130 à partir d'une charge d'hydrocarbures cireux ayant une teneur en cire d'au moins
20 % en poids, qui consiste à déparaffiner de manière catalytique les paraffines cireuses
présentes dans la charge essentiellement par isomérisation, en présence d'hydrogène
et en présence d'un tamis moléculaire à larges pores de faible acidité choisi dans
le groupe constitué de la zéolite béta, Y et mordénite ayant au moins un canal de
pore avec une dimension majeure supérieure à 0,7 nm et ayant une taille de cristal
inférieure à 0,1 micron, une valeur alpha ne dépassant pas 30 et contenant un composant
d'hydrogénation de type métal noble.
2. Procédé selon la revendication 1 dans lequel le tamis moléculaire à larges pores possède
au moins un canal de pore composé de noyaux à oxygène à 12 chaînons.
3. Procédé selon la revendication 1 dans lequel la zéolite béta a une valeur alpha ne
dépassant pas 20.
4. Procédé selon la revendication 1 dans lequel le tamis moléculaire à larges pores possède
une taille de cristal inférieure à 0,05 micron.
5. Procédé selon la revendication 1 dans lequel le tamis moléculaire à larges pores est
une zéolite béta de faible acidité qui a été balayée par de la vapeur, ayant un rapport
silice:alumine dans le squelette d'au moins 200:1.
6. Procédé selon la revendication 1 dans lequel le tamis moléculaire à larges pores comprend
un catalyseur d'isomérisation à base de zéolite béta contenant du bore, dans lequel
le bore est présent en tant que composant de squelette de la zéolite béta.
7. Procédé selon la revendication 1 dans lequel le tamis moléculaire à larges pores comprend
0,3 à 2 % en poids de Pt sur un support comprenant de la zéolite béta.
8. Procédé selon la revendication 1 dans lequel la charge comprend une charge d'hydrocarbures
cireux ayant une teneur en cire d'au moins 40 % en poids et une teneur en composés
aromatiques de moins de 25 % en poids.
9. Procédé selon la revendication 1 dans lequel la charge d'alimentation est choisie
dans le groupe comprenant une paraffine huileuse, une cire déshuilée, une cire issue
d'un procédé de Fischer-Tropsch, des huiles de queues, du pétrolatum, du gas-oil sous
vide, ou un raffinat issu d'une extraction au solvant d'un distillat sous vide.
10. Procédé selon la revendication 1 dans lequel le procédé est effectué en présence d'hydrogène
pour convertir 40 à 90 % en poids de la cire contenue dans la charge.
11. Procédé selon la revendication 1 dans lequel les conditions incluent une pression
partielle d'hydrogène allant de 4238 à 20 786 kPaa (600 à 3000 psi au manomètre) et une température de 288°C à 427°C (550 à 800°F).
12. Procédé selon la revendication 1 dans lequel la charge déparaffinée de manière catalytique
est soumise à un déparaffinage sélectif supplémentaire pour parvenir à un point d'écoulement
cible.
13. Procédé selon la revendication 12 dans lequel ledit déparaffinage supplémentaire est
accompli par des moyens de type solvant ou catalytiques.
14. Procédé selon la revendication 1 dans lequel la charge déparaffinée de manière catalytique
est hydrotraitée par mise en contact de celle-ci avec un catalyseur comprenant un
composant d'hydrogénation métallique sur un matériau support poreux à une pression
dans la gamme d'environ 3549 à environ 20 786 kPaa (500 à environ 3000 psi au manomètre), une température réactionnelle dans la gamme
d'environ 260°C à environ 427°C (500°F à environ 800°F), une vitesse spatiale qui
se situe dans une gamme d'environ 0,1 à environ 10 LHSV, et une vitesse de circulation
d'hydrogène en circuit ouvert qui s'étend d'environ 178 à environ 1780 n.l.l.-1 (1000 SCF/B à environ 10 000 SCF/B), afin d'améliorer la stabilité thermique et oxydative
du lubrifiant.
15. Procédé selon la revendication 12 dans lequel la charge est hydrotraitée à la suite
du déparaffinage sélectif par mise en contact de celle-ci avec un catalyseur comprenant
un composant d'hydrogénation métallique sur un matériau support poreux à une pression
dans la gamme d'environ 3549 à environ 20 786 kPaa (500 à environ 3000 psi au manomètre), une température réactionnelle dans la gamme
d'environ 260°C à environ 427°C (500°F à environ 800°F), une vitesse spatiale qui
se situe dans une gamme d'environ 0,1 à environ 10 LHSV, et une vitesse de circulation
d'hydrogène en circuit ouvert qui s'étend d'environ 178 à environ 1780 n.l.l.-1 (1000 SCF/B à environ 10 000 SCF/B), afin d'améliorer la stabilité thermique et oxydative
du lubrifiant.
16. Procédé de production d'un lubrifiant ayant un indice de viscosité (VI) d'au moins
130 à partir d'une charge d'hydrocarbures cireux ayant une teneur en cire d'au moins
20 % en poids, le procédé comprenant les étapes suivantes :
(a) l'hydrocraquage de la charge afin de réduire sa teneur en azote et d'enlever des
composants naphténiques et aromatiques, améliorant ainsi le VI, le procédé d'hydrocraquage
consistant à mettre en contact la charge avec un catalyseur composé d'un composant
d'hydrogénation métallique sur un support acide aérien ;
(b) le déparaffinage catalytique des paraffines cireuses présentes dans la charge
essentiellement par isomérisation, en présence d'hydrogène et en présence d'un tamis
moléculaire à larges pores de faible acidité choisi dans le groupe constitué de la
zéolite béta, Y et mordénite ayant au moins un canal de pore avec une dimension majeure
supérieure à 0,7 nm et une taille de cristal inférieure à 0,1 micron, une valeur alpha
ne dépassant pas 30 et contenant un composant d'hydrogénation de type métal noble.
17. Procédé selon la revendication 16, dans lequel le tamis moléculaire à larges pores
possède au moins un canal de pore composé de noyaux à oxygène à 12 chaînons.
18. Procédé selon la revendication 16 dans lequel la zéolite béta a une valeur alpha ne
dépassant pas 20.
19. Procédé selon la revendication 16 dans lequel le tamis moléculaire à larges pores
est une zéolite béta de faible acidité qui a été balayée par de la vapeur, ayant un
rapport silice:alumine dans le squelette d'au moins 200:1.
20. Procédé selon la revendication 16 dans lequel le tamis moléculaire à larges pores
comprend 0,3 à 2 % en poids de Pt sur un support comprenant de la zéolite béta.
21. Procédé selon la revendication 17 dans lequel la charge d'alimentation est choisie
dans le groupe comprenant une paraffine huileuse, une cire déshuilée, une huile de
queues, une cire issue d'un procédé de Fischer-Tropsch, du pétrolatum, du gas-oil
sous vide, ou un raffinat issu d'une extraction au solvant d'un distillat sous vide.
22. Procédé selon la revendication 16 dans lequel les conditions de l'étape (b) incluent
une pression partielle d'hydrogène allant de 4238 à 20 786 kPaa (600 à 3000 psi au manomètre) et une température de 288°C à 427°C (550 à 800°F).
23. Procédé selon la revendication 16 dans lequel l'effluent de l'étape (b) est soumis
à un déparaffinage sélectif supplémentaire pour parvenir à un point d'écoulement cible.
24. Procédé selon la revendication 23 dans lequel ledit déparaffinage supplémentaire est
accompli par des moyens de type solvant ou catalytiques.
25. Procédé selon la revendication 16 dans lequel au moins une portion de l'effluent de
l'étape (b) est hydrotraité par mise en contact de celui-ci avec un catalyseur comprenant
un composant d'hydrogénation métallique sur un matériau support poreux à une pression
dans la gamme d'environ 3549 à environ 20 786 kPaa (500 à environ 3000 psi au manomètre), une température réactionnelle dans la gamme
d'environ 260°C à environ 427°C (500°F à environ 800°F), une vitesse spatiale qui
se situe dans une gamme d'environ 0,1 à environ 10 LHSV, et une vitesse de circulation
d'hydrogène en circuit ouvert qui s'étend d'environ 178 à environ 1780 n.l.l.-1 (1000 SCF/B à environ 10 000 SCF/B), afin d'améliorer la stabilité thermique et oxydative
du lubrifiant.
26. Procédé selon la revendication 23 dans lequel l'effluent de l'étape (b) selon la revendication
16 est soumis, à la suite du déparaffinage sélectif supplémentaire, à un hydrotraitement
par mise en contact de celui-ci avec un catalyseur comprenant un composant d'hydrogénation
métallique sur un matériau support poreux à une pression dans la gamme d'environ 3549
à environ 20 786 kPaa (500 à 3000 psi au manomètre), une température réactionnelle dans la gamme d'environ
260°C à environ 427°C (500°F à environ 800°F), une vitesse spatiale qui se situe dans
une gamme d'environ 0,1 à environ 10 LHSV, et une vitesse de circulation d'hydrogène
en circuit ouvert qui s'étend d'environ 178 à environ 1780 n.l.l.-1 (1000 SCF/B à environ 10 000 SCF/B), afin d'améliorer la stabilité thermique et oxydative
du lubrifiant.