Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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INTEGRATED PROCESS FOR CATALYTIC DEWAXING
FIELD OF THE INVENTION
[0001] This invention related to an integrated catalytic hydrodewaxing process
for hydrocarbon feeds. More particularly, a feedstock containing sulfur and
nitrogen contaminants is subject to a process including hydrotreating,
hydrodewaxing and/or hydrofinishing without disengagement between the process
steps.
BACKGROUND OF THE INVENTION
[0002] Dewaxing of hydrocarbon feedstocks is conventionally used to improve
theflow properties of the feed, typically by lowering the pour point. Dewaxing
catalysts remove waxy components of feeds by either selective hydrocracking or
isomerization. The selectivity of dewaxing catalysts may be improved by
employing constrained intermediate pore molecular sieves. The activity of such
selective catalysts may be improved by employing a metal
hydrogenation/dehydrogenation component.
[0003] One problem encountered with dewaxing catalysts is that they are
sensitive to environments containing sulfur and/or nitrogen contaminants. Such
contaminants negatively impact catalyst activity, catalyst aging and catalyst
selectivity. Thus it is common to employ a hydrotreating and/or hydrocracking
step prior to the dewaxing step to convert nitrogen and sulfur containing
contaminants to ammonia and hydrogen sulfide and to remove these gaseous
contaminants from the process prior to the dewaxing step.
[0004] The disadvantage of processes involving separate dewaxing and
hydrofinishing steps is that considerable capital investment is involved in
the
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equipment for these steps. Processes which are directed to lubricants with
high VI
and low pour points and which combine hydrotreating with conventional dewaxing
catalysts such as ZSM-5 run a substantial yield debit since the hydrotreating
step is
run at more severe conditions in order to compensate for VI loss during
hydrodewaxing. More recent dewaxing catalysts which function by isomerization
typically require clean feeds, i.e., feeds with very low concentrations of
sulfur and
nitrogen contaminants. When combined with a pre-hydrotreating step, separation
and stripping of gaseous contaminants are normally required to protect
catalyst
activity.
[0005] It would be desirable to have an integrated process using dewaxing
catalysts which are capable of operating in environments containing
substantial
concentrations of sulfur- and or nitrogen-containing contaminants while
maintaining catalyst properties such as selectivity, activity and aging which
process
functions without the need for a disengagement step to remove gaseous sulfur-
and
nitrogen containing contaminants.
SUMMARY OF THE INVENTION
[0006] The present invention relates to an integrated dewaxing process capable
of operating with highly contaminated feedstocks. The integrated process for
dewaxing a raffinate feedstock containing up to 20,000 ppmw sulfur and up to
1000
ppmw nitrogen comprises: (a) contacting the feedstock with a hydrotreating
catalyst under hydrotreating conditions to produce a hydrotreated feedstock
and
gaseous nitrogen- and sulfur-containing contaminants, and (b) passing at least
a
portion of the hydrotreated feedstock and gaseous components from step (a)
without disengagement to a hydrodewaxing zone containing a dewaxing catalyst
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including at least one of ZSM-48, ZSM-22, ZSM-23, ZSM-5, ZSM-35, Beta, SSZ-
31,SAP0-11, SAPO-31, SAPO-41, MAPO-11, ECR-42, synthetic ferrierites,
mordenite, offretite, erionite, and chabazite and hydrodewaxing the
hydrotreated
feedstock under hydrodewaxing conditions, said dewaxing catalyst including a
metal hydrogenation component which is at least one Group 6 metal, at least
one
Group 8-10 metal, or mixtures of Group 6 and Group 8-10 metals, to form a
hydrodewaxed product. As used herein, ZSM-48 includes EU-2, EU-11 and ZBM-
20 which are structurally equivalent to ZSM-48.
[0007] Another embodiment relates to an integrated process for dewaxing a
raffmate feedstock containing up to 20,000 ppmw sulfur and up to 1000 ppmw
nitrogen which comprises: (a) contacting the feedstock with a hydrotreating
catalyst under hydrotreating conditions to produce a hydrotreated feedstock
and
gaseous nitrogen- and sulfur-containing contaminants, (b) passing at least a
portion
of the hydrotreated feedstock and gaseous sulfur- and nitrogen-containing
contaminants from step (a) without disengagement to a hydrodewaxing zone
containing a dewaxing catalyst including at least one of ZSM-48, ZSM-22, ZSM-
23, ZSM-5, ZSM-35, Beta, SSZ- 31,SAP0-11, SAPO-31, SAPO-41, MAPO-11, ECR-
42, synthetic ferrierites, mordenite, offretite, erionite, and chabazite and
hydrodewaxing the hydrotreated feedstock under hydrodewaxing conditions, said
dewaxing catalyst including a metal hydrogenation component which is at least
one
Group 6 metal, at least one Group 8-10 metal, or mixtures of Group 6 and Group
8-10 metals, said hydrodewaxing zone also containing a second dewaxing
catalyst
wherein the second dewaxing catalyst is tolerant of the sulfur- and nitrogen
containing contaminants.
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[0008] Yet another embodiment relates to an integrated process for dewaxing a
raffinate feedstock containing up to 20,000 ppmw sulfur and up to 1000 ppmw
nitrogen which comprises: (a) contacting the feedstock with a dewaxing
catalyst
including at least one of ZSM-48, ZSM-22, ZSM-23, ZSM-5, ZSM-35, Beta, SSZ-
31,SAPO-11, SAPO-31, SAPO-41, MAPO-1 l, ECR-42, synthetic ferrierites,
mordenite, offretite, erionite, and chabazite under hydrodewaxing conditions,
said
dewaxing catalyst including a metal hydrogenation component which is at least
one
Group 6 metal, at least one Group 8-10 metal, or mixtures of Group 6 and Group
8-
metals, to form a hydrodewaxed product, and (b) passing at least a portion of
the
hydrodewaxed product and gaseous components from step (b) to a hydrofinishing
zone and hydrofmishing the hydrodewaxed product under hydrofmishing
conditions.
[0009] A still further embodiment relates to an integrated process for
dewaxing
a raffinate feed which comprises: (a) solvent dewaxing the raffinate to form a
raffinate and a slack wax, (b) deoiling the slack wax to produce a foots oil,
(c)
contacting the foots oil with a hydrotreating catalyst under hydrotreating
conditions
to produce a hydrotreated foots oil and gaseous nitrogen- and sulfur-
containing
contaminants and (d) passing at least a portion of the hydrotreated foots oil
and
gaseous sulfur- and nitrogen-containing contaminants from step (c) without
disengagement to a hydrodewaxing zone containing a dewaxing catalyst including
at least one of ZSM-48, ZSM-22, ZSM-23, ZSM-5, ZSM-35, Beta, SSZ-31,SAPO-
11, SAPO-31, SAPO-41, MAPO-11, ECR-42, synthetic ferrierites, mordenite,
offretite, erionite, and chabazite and hydrodewaxing the hydrotreated foots
oil
under hydrodewaxing conditions, said dewaxing catalyst including a metal
hydrogenation component which is at least one Group 6 metal, at least one
Group
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8-10 metal, or mixtures of Group 6 and Group 8-10 metals to from a
hydrodewaxed
product.
[0010] Another embodiment relates to an integrated process for dewaxing a
feedstock containing up to 20,000 ppmw sulfur and up to 1000 ppmw nitrogen
comprises: (a) blending a raffinate feedstock and at least one of a slack wax
or
foots oil to form a blended feedstock, (b) contacting the blended feedstock
with a
hydrotreating catalyst under hydrotreating conditions to produce a
hydrotreated
feedstock and gaseous nitrogen- and sulfur-containing contaminants, and (c)
passing at least a portion of the hydrotreated feedstock and gaseous
components
from step (b) without disengagement to a hydrodewaxing zone containing a
dewaxing catalyst including at least one of ZSM-48, ZSM-22, ZSM-23, ZSM-5,
ZSM-35, Beta, SSZ- 31,SAP0-11, SAPO-31, SAPO-41, MAPO-11, ECR-42, synthetic
ferrierites, mordenite, offretite, erionite, and chabazite and hydrodewaxing
the
hydrotreated feedstock under hydrodewaxing conditions, said dewaxing catalyst
including a metal hydrogenation component which is at least one Group 6 metal,
at
least one Group 8-10 metal, or mixtures of Group 6 and Group 8-10 metals, to
form
a hydrodewaxed product.
DESCRIPTION OF THE DRAWINGS
[0011] Figure 1 is a graph showing average reactor temperature at given pour
point .
[0012] Figure 2 is a graph showing polar tolerance of the catalyst.
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[0013] Figure 3 is a graph showing lube yields for dewaxing a medium neutral
foots oil over a Crosfield hydrotreating catalyst followed by a Pt/ZSM-48
dewaxing
catalyst.
[0014] Figure 4 is a graph showing viscosity of the dewaxed medium neutral
foots oil.
[0015] Figure 5 is a graph showing VI of the dewaxed medium neutral foots oil.
[0016] Figure 6 is a graph showing cloud points of the dewaxed medium neutral
foots oil.
DETAILED DESCRIPTION OF THE INVENTION
[0017] In the present process, the steps are integrated, i.e., a process that
incorporates a sequence of steps which are interrelated and dependent on
either
earlier or later steps, said steps occurring without disengagement between the
sequence of steps.
[0018] Dewaxing catalysts which are isomerization catalysts are normally shape
selective intermediate pore molecular sieves loaded with a hydrogenation
metal,
particularly noble metals. However, such isomerization dewaxing catalysts are
considered susceptible to poisoning by sulfur- and nitrogen-containing
contaminants such as NH3 and H2S. They are thus normally protected by a
preceding treatment to remove such poisons. An example of such pre-treatment
is
conversion of sulfur- and nitrogen-containing contaminants to H2S and NH3,
respectively, by hydrotreatment. However, hydrotreatement is followed by
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disengagement to remove (strip) the sulfur- and nitrogen-containing
contaminants
prior to dewaxing so as not to poison the catalyst.
[0019] Feeds for the present integrated dewaxing process include raffinates.
Raffinates are obtained from solvent extraction processes that selectively
dissolve
the aromatic components in an extract phase while leaving the more paraffinic
components in a raffmate phase. Naphthenes are distributed between the extract
and raffinate phases. Typical solvents for solvent extraction include phenol,
furfural and N-methyl pyrrolidone. By controlling the solvent to oil ratio,
extraction temperature and method of contacting feed to be extracted with
solvent,
one can control the degree of separation between the extract and raffinate
phases.
The raffmates may be wide cut or narrow cut.
[0020] The raffmates from solvent extraction may be further subject to solvent
dewaxing to separate a Tube oil fraction and a slack wax. Solvent dewaxing may
be
accomplished by treating the raffmates with a solvent such as propane, ketones
and
mixtures of ketones with aromatics such as benzene, toluene and/or xylene and
chilling to crystallize and separate wax molecules. The resulting slack wax is
then
deoiled to separate a foots oil (soft wax) from microciystalline wax (hard
wax).
The slack wax or foots oil may be blended with a raffinate to form a blended
feedstock. The ratio of raffinate to slack wax or foots oil in the blended
feedstock
may range from 99:1 to 1:99.
[0021] The raffmate, slack wax or foots oil feeds are characterized in that
they
may contain high levels up to 20,000 ppmw of sulfur containing contaminants
and
up to 1,000 ppmw of nitrogen containing contaminants.
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[0022] An important purpose of hydrotreating is to reduce the sulfur and
nitrogen content of a feed. Hydrotreating for the present process is not
primarily
concerned with boiling point conversion of the feed. Hydrotreating catalysts
usually contain at least one of Group 6 and Group 8-10 metal (Groups based on
the
IUPAC Periodic Table format having groups from 1 to 18), on a less acidic
support
such as alumina or silica. Catalysts may also be bulk metal catalysts wherein
the
amount of metal may be 30 wt.% or more. Examples include Ni/Mo, Co/Mo and
Ni/W catalysts. Preferred hydrotreating catalysts are low acidity, high metals
content catalysts such as I~F-848 (Akzo Nobel), DN 190 (Criterion catalysts)
and
RT 721 (Akzo Nobel). The amount of metal is from 0.1 to 95 wt.%, based on
catalyst. Hydrotreating conditions include temperatures of 315 - 425°C,
pressures
of 2170 - 20786 kPa (300 - 3000 psig), liquid hourly space velocities (LHSV)
of
0.1 - 10 and hydrogen treat rates of 89 - 1780 m3/m3 (500 - 10,000 scf/bbl).
[0023] If a hydrotreating step is used prior to the dewaxing step of the
present
process, there is no need for disengagement between the hydrotreating and
dewaxing step. Disengagement involves depressurization, stripping and
repressurization and therefor requires expensive pumps, separators and
heaters.
This disadvantage is avoided because the present dewaxing catalysts can
operate in
a sour environment. In the case of raffinates, it may be possible to simply
pass the
raffinate directly to the dewaxing step without any prior hydrotreatment.
[0024] It has been discovered that certain dewaxing catalysts can function in
a
sour environment. The present dewaxing catalysts include ZSM-48, ZSM-22,
ZSM-23, ZSM-5, ZSM-35, Beta, SSZ- 31,SAP0-11, SAPO-31, SAPO-41, MAPO-11,
ECR-42, synthetic ferrierites, mordenite, offretite, erionite, and chabazite,
with
ZSM-48, ZSM-22, ZSM-5, ZSM-23 and ZSM-35 being preferred while ZSM-48 is
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a more preferred embodiment. ZSM-48 is a unidimensional intermediate pore 10
ring zeolite having a pore size of 5.3 A x 5.6 A. ZSM-48 is commercially
available
and its preparation is described in U.S. patents 4,397,827, 4,448,675 and
5,075,269.
ZSM-22 is described in U.S. Patent 4,556,477, ZSM-23 in U.S. patent 4,076,342
and ZSM-35 in U.S. patent 4,016,245.
[0025] The dewaxing catalysts are bifunctional, i.e., they are loaded with a
metal
hydrogenation component, which is at least one Group 6 metal, at least one
Group
8 - 10 metal, or mixtures thereof. Preferred metals are Groups 9 -10 metals.
Especially preferred are Groups 9 - 10 noble metals such as Pt, Pd or mixtures
thereof (based on the IUPAC Periodic Table format having Groups from 1 to 18).
These metals are loaded at the rate of 0.1 to 30 wt.%, based on catalyst.
Catalyst
preparation and metal loading methods are described for example in U.S. Patent
No. 6,294,077, and include for example ion exchange and impregnation using
decomposable metal salts. Metal dispersion techniques and catalyst particle
size
control are described in U.S. Patent No. 5,282,958. Catalysts with small
particle
size and well-dispersed metal are preferred.
[0026] The dewaxing catalysts are typically composited with binder materials
which are resistant to high temperatures which may be employed under dewaxing
conditions to form a finished dewaxing catalyst or may be binderless (self
bound).
The binder materials are usually inorganic oxides such as silica, alumina,
silica-
aluminas, binary combinations of silicas with other metal oxides such as
titania,
magnesia, thoria, zirconia and the like and tertiary combinations of these
oxides
such as silica-alumina -thoria and silica-alumina magnesia. The amount of
molecular sieve in the finished dewaxing catalyst is from 10 to 100,
preferably 35
to 100 wt.%, based on catalyst. Such catalysts are formed by methods such
spray
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drying, extrusion and the like. The dewaxing catalyst may be used in the
sulfided
or unsulfided form, and is preferably in the sulfided form.
[0027] The temperature for the present dewaxing process is in the range from
360 to 425°C . Due to the catalyst structure, these temperatures may be
higher than
the temperatures normally used for catalytic dewaxing without the cracking
that
might otherwise be expected from such higher temperatures. Other process
conditions include hydrogen pressures of from 2859 - 20786 kPa (400 to 3000
psig), liquid hourly space velocities of 0.1 to 10 LHSV and hydrogen treat gas
rates
of from 53.4 - 1780 m3/m3 (300 to 10,000 scf/bbl).
[0028] The hydrodewaxing catalyst may contain a second catalytic component
which may be admixed with the ZSM-48 dewaxing catalyst or may be in a stacked
(layered) configuration with the second component in the upper layer. The
second
catalyst is tolerant of sulfur- and nitrogen-containing contaminants. Typical
catalysts that are tolerant of such contaminants include ZSM-5 and larger pore
catalysts such as zeolite beta. A convenient measure of the extent to which a
dewaxing catalyst provides control molecules of varying sizes to its internal
structure is the Constraint Index of the zeolite. Zeolites which provide a
highly
restricted access to and egress from its internal structure have a high value
for the
Constraint Index, and zeolites of this kind usually have pores of small size.
On the
other hand, zeolites which provide relatively free access to the internal
zeolite
structure have a low value for the Constraint Index. The method by which
Constraint Index is determined is described fully in U.S. Pat. No.4,016,218,
to
which reference is made for details of the method. Large pore zeolites having
Constraint Indices less than 1 include TEA mordenite (0.4), dealuminized Y
(0.5),
ZSM-4 (0.5), ZSM-20 (0.5), mordenite (0.5), REY (0.4) and ultrastable Y.
Zeolite
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beta is also within the scope of large pore zeolites. The second catalytic
component
may also be acidic porous amorphous materials, such as amorphous
aluminosilicate, halogenated alumina, acidic clay, alumina or silica-alumina.
[0029] At least a portion of the products from the hydrodewaxing zone or step
may then be passed to a hydrofinishing step again without the need of
disengagement between the hydrodewaxing and hydrofinishing steps.
Catalysts for hydrofinishing can the same as those used for the preliminary
hydrotreating step, if any, i.e., those containing at least one of Group 6 and
Group
8-10 metal on a support such as alumina or silica. Examples include Ni/Mo,
Co/Mo and Ni/W catalysts. Preferred hydrotreating catalysts include catalyst
such
as KF-840, I~F-848 (Akzo Nobel), DN 190 (Criterion catalysts) and RT 721 (Akzo
Nobel).
[0030] The hydrofinishing catalyst may also be a crystalline mesoporous
material belonging to the M41 S class or family of catalysts. The M41 S family
of
catalysts are crystalline mesoporous materials having high silica contents
whose
preparation is further described in J. Amer. Chem. Soc., 1992, 114, 10834.
Examples included MCM-41, MCM-48 and MCM-50. A preferred member of this
class is MCM-41 whose preparation is described in US Patent No. 5,098,684.
MCM-41 is characterized by having a hexagonal crystal structure with a
unidimensional arrangement of pores having a cell diameter greater than 13
Angstroms. The physical structure of MCM-41 is like a bundle of straws wherein
the opening of the straws (the cell diameter of the pores) ranges from 13 to
100+
Angstroms. MCM-48 has a cubic symmetry and is described for example is U.S.
Patent No. 5,198,203 whereas MCM-50 has a lamellar structure and is described
in
US Patent No. 5,246,689.
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[0031] The amount of metal is from 0.1 to 5 wt.%, preferably 0.2 to 2 wt.%,
based on catalyst. Hydrofinishing conditions include temperatures of 150 -
350°C,
preferably 180 - 300°C, pressures of 100 - 3000 psig (790 - 20786 kPa),
preferably
50 - 2500 psig (1135 - 17339 kPa), LHSV of 0.1 - 20, preferably 0.2 - 15 and
treat
gas rates of 300 - 10000 scf/bbl (53 - 1780 m3/m3), preferably 450 -5000 scf/B
(80
- 890 m3/m3).
[0032] If the raffmate feed is passed directly to hydrodewaxing without a
preliminary hydrotreating step, then dewaxed product from hydrodewaxing is
passed to hydrofinishing without disengagement. The preferred hydrofinishing
conditions will include a temperature range of from 150 - 300°C.
[0033] The product from the hydrofmishing step is typically passed to a
separator which may include stripping and /or fractionation. In the separation
zone, sulfur- and nitrogen containing contaminants, especially hydrogen
sulfide and
ammonia, are separated together with other gaseous components from liquid
product. The liquid product may be fractionated to obtain various cuts of
lubricating oil products based on boiling range.
[0034] The process sequence may include the following steps in various
combinations. A waxy feed is first solvent extracted to separate a raffinate
and an
extract. The raffinate may then be sent directly to hydrotreating, may be
hydrodewaxed directly or may be solvent dewaxed to produce a lubricating oil
and
a slack wax. Upon deoiling, the slack wax yields a hard wax and foots oil
which
may then be sent to hydrotreating.
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[0035] In the sequence raffinate to hydrotreating to hydrodewaxing and
optionally hydrofinishing, there is no disengagement between any of the
process
sequence steps. The hydrotreating and hydrodewaxing steps may take place
sequentially in separate reactors or may occur as stacked beds in a single
reactor.
Any hydrofinishing step will occur in a separate reactor. If the hydrodewaxing
step
involves more than one dewaxing catalyst, then the hydrodewaxing step may
involve a mixture of dewaxing catalysts in a single reactor, stacked beds in a
single
reactor, or separate reactors in sequence each containing a dewaxing catalyst.
[0036] The process sequence involving foots oils may include hydrotreating,
hydrodewaxing and optionally hydrotreating. As in the case of raffinates, the
sequence may take place sequentially in separate reactors or may occur as
stacked
beds in a single reactor.
[0037] The invention is further illustrated by the following examples which
are
not intended as limiting.
EXAMPLES
Example 1
[0038] Table 1 compares three processing configurations for dewaxing a 260
Neutral raffinate containing 6680 wppm sulphur and 50.6 wppm nitrogen and a
dry
wax content of 16.75 wt.% on feed at -18 pour point. Column A illustrates the
properties of a dewaxed oil obtained by solvent dewaxing with methylisobutyl
ketone at a feed to solvent ratio of 3:1, the 260 Neutral raffinate. Prior to
solvent
dewaxing, the raffinate had been hydrotreated over an Alczo KF-848
hydrotreated
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catalyst at an average reactor temperature of 350°C, 0.53 LHSV, at a
treat gas rate
of 2600 SCF H2Ibb1 of feed and 1800psig. The sulphur and nitrogen contents of
the
hydrotreated raffinate were less than 2 wppm.
Table 1
A ~ B C
Process Hydrotreating Hydrotreating Untreated
+ + feed +
Solvent Dewaxingdepressurization hydrodewaxing
+
h drodewaxin
HDW Average Reactorn/a 310 370
Temperature, C
Yield of 370C+ DWO 61.2 70.2 65.1
on Raw Feed, wt%
Dewaxed Oil Properties
Viscosity, cSt at 6.1 5.6 5.4
100C
Viscosity, cSt at 36.8 31.4 29.7
40C
Viscosity Index 113 120 117
Pour Point,C -17 -17 -16
Cloud Point, C -14 -6 -13
Cloud -Pour Spread,3 11 3
C
[0039] Column B illustrates the properties of the product made by
hydrotreating
the 260N raffinate over Alczo KF 848 at an average reactor temperature of
350°C,
0.53LHSV, 1800psig and at a treat gas rate of 2600SCF H2/bll of feed but
followed
by catalytic dewaxing over a hydrodewaxing catalyst containing ZSM-48. The
process conditions during hydrodewaxing were 0.76 LHSV, 1650SCF/B H2, and
1800psig. In this example the gas phase polar species (e.g., ammonia and
hydrogen
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sulphide) were removed before the hydrodewaxing step. Comparing the products
in columns A and B it can be seen that the yield and VI of product after
hydrodewaxing in increased over that obtained by solvent dewaxing at constant
pour point. One other item to note is that the cloud - pour spread of the
hydrodewaxed product is considerably larger than that of the solvent dewaxed
product.
[0040] Colurnll C illustrates the properties of the product made by
hydrotreating
the 260N raffinate over Akzo KF 848 at an average reactor temperature of
350°C,
0.53LHSV and at a treat gas rate of 2600SCF H2/bbl of feed but hydrodewaxing
over a hydrodewaxing catalyst containing ZSM-48. The process conditions in the
hydrodewaxing stage were 0.76 LHSV, 1650SCFlB H~, and 1800psig. In this
illustration, the gas phase polar species generated during the hydrotreating
stage,
were cascaded with the hydrogen over the hydrodewaxing stage which required
that the temperature of the dewaxing stage was higher than that in column B.
Comparing the products in columns A and B with the product in column C, it can
be seen that the yield and VI of product after hydrodewaxing in increased over
that
obtained by solvent dewaxing. It is noted that the cloud - pour spread of the
hydrodewaxed product made at elevated reactor temperature in a sour gas
environment is similar to that of the solvent dewaxed product.
Example 2
[0041] Table 2 compares three processing configurations for dewaxing a 130
Neutral raffinate containing 2500wppm sulphur and 25 wppm nitrogen and a dry
wax content of 16.44 wt.% on feed at -16°C pourpoint. Column A
illustrates the
properties of a dewaxed oil obtained by solvent dewaxing with methylisobutyl
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ketone at a feed to solvent ratio of 3:1, the 130 Neutral raffinate. Prior to
solvent
dewaxing, the raffinate had been hydrotreated over an Akzo KF848 hydrotreated
catalyst at an average reactor temperature of 350°C, 0.53LHSV, at a
treat gas rate
of 2600SCF HZ/bll of feed and 1800psig. The sulphur and nitrogen contents of
the
hydrotreated raffinate were less than 2wppm.
Table 2
A B C
Process Hydrotreating Hydrotreating Untreated feed
+ + +
Solvent Dewaxingdepressurizationhydrodewaxing
+
h drodewaxin
HDW Average Reactorn/a 310 370
Temperature, C
Yield of 370C+ DWO 57.12 57.6 44.23
on Raw Feed, wt%
Dewaxed Oil Properties
Viscosity, cSt at 4.28 4.04 3.654
100C
Viscosity, cSt at 20.752 18.352 15.823
40C
Viscosity Index 112 120 116
Pour Point,C -27 -27 -26
Cloud Point, C -28 -17 -24
Cloud -Pour spread,C- 10 2
[0042] Column B illustrates the properties of the product made by
hydrotreating
the 130N raffinate over Akzo KF 848 at an average reactor temperature of
350°C,
0.53LHSV, 1800psig and at a treat gas rate of 2600SCF H2/bll of feed but
followed
by catalytic dewaxing over a hydrodewaxing catalyst containing ZSM-48. The
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process conditions during hydrodewaxing were 0.76 LHSV, 1650SCF/B H2, and
1800psig. In this example the gas phase polar species (e.g., ammonia and
hydrogen
sulphide) were removed before the hydrodewaxing step. Comparing the products
in columns A and B it can be seen that the yield and VI of product after
hydrodewaxing in increased over that obtained by solvent dewaxing at constant
pour point. One other item to note is that the cloud - pour spread of the
hydrodewaxed product is considerably larger than that of the solvent dewaxed
product.
[0043] Column C illustrates the properties of the product made by
hydrotreating
the 130N raffinate over Akzo KF 848 at an average reactor temperature of
350°C,
0.53LHSV and at a treat gas rate of 2600SCF Ha/bll of feed but hydrodewaxing
over a hydrodewaxing catalyst containing ZSM-48. The process conditions in the
hydrodewaxing stage were 0.76 LHSV, 1650SCF/B H2, and 1800psig. In this
illustration, the gas phase polar species generated during the hydrotreating
stage,
were cascaded with the hydrogen over the hydrodewaxing stage which required
that the temperature of the dewaxing stage was higher than that in column B.
Comparing the products in columns A and B with the product in column C, it can
be seen that the yield and VI of product after hydrodewaxing increased over
that
obtained by solvent dewaxing at the same pour point. It is noted that the
cloud -
pour spread of the hydrodewaxed product made at elevated reactor temperature
in a
sour gas environment, column C, is similar to that of the solvent dewaxed
product.
Example 3
[0044] This example illustrates the effect of treat gas rate on the
hydrodewaxing
stage operating in a sour gas environment. The 130N raffinate was hydrotreated
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over Akzo KF 848 at an average reactor temperature of 350°C, 0.53LHSV
and at a
treat gas rate of 2600SCF H2/bll of feed and hydrodewaxing over a
hydrodewaxing
catalyst containing ZSM-48. The process conditions in the hydrodewaxing stage
were 0.76 LHSV, 1650 to 2500SCF/B HZ, and 1800psig. In this illustration, the
gas phase polar species generated during the hydrotreating stage were cascaded
with the hydrogen over the hydrodewaxing stage. The hydrodewaxing catalyst is
a
ZSM-48 bound with alumina (35/65 wt ratio respectively) operating under a
series
of conditions shown in Figure 1. The figure illustrates that by increasing the
treat
gas rate from 1650SCFH2/B feed to 2100 and then to 2500SCFH2/B feed, the
Average Reactor Temperature required to maintain a feed pour point of
10°F
decreases from 690 to 680°F for a 130N raffinate.
Examine 4
[0045] This example illustrates the application of a hydrodewaxing catalyst
catalyst, containing ZSM-48 and alumina 65/35wt%, for hydrodewaxing a 130N
waxy raffinate containing , 7270 wppm sulfur and 32.6 wppm of total nitrogen,
and
a dry wax content of l7wt% on feed at a pour point of -18°Cat 400 psig
H2 and
2500SCF/B H2 without pre-hydrotreating_but having a hydrofinishing step.
[0046] The processing conditions were as listed in Table 3 and the product
quality data in Table 4.
Table 3
LHSV Pressure Gas Rate Average Reactor
,
Psi SCFIB feed Tem erature, C
H drodewaxin 0.5-1.0 __400 2500 350 - 38_0
Hydrofinishing0.5-1.0 400 ~ 2500 ~ -- 290
~
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Table 4
A B
Process Solvent Dewaxing Untreated feed
+
h drodewaxin
HDW Average Reactorn/a 370
Tem erature, C
Yield of 370C+ DWO 82.9 72.4
on Raw Feed, wt%
Dewaxed Oil Properties
Viscosity, cSt at 4.93 4.44
100C
Viscosity, cSt at 28.45 23.06
40C
Viscosity Index 94 102
Pour Point,C -19 -19
[0047] Table 4 illustrates that hydrodewaxing the unhydrotreated waxy
raffinate
gives a 370°C+ product having an eight point higher VI than that
produced by
solvent dewaxing.
[0048] Figure 2 illustrates the polar tolerance of the catalyst given 50 days
on
stream with the unhydrotreated 130N Raffinate feedstock.
Examine 5
[0049] This Example illustrates the cascade dewaxing of a foots oil feed. Two
soft wax feeds, a medium neutral Foots oil (MNFO) and light neutral Foots oil
(LNFO), were used for the dewaxing study. The properties of the feeds are
summarized as follows.
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Table 5
Properties of Foots Oils
Feed Medium Neutral Light Neutral
Foots Oil Foots
Oil
KV@100C, cSt 5.513 3.207
ITV@40C, cSt - 23.84
Pour Point, C 45 36
Density, g/cc 0.8453 0.8241
N content, ppm 19 < 8
S content, ppm 1851 1807
Aromatics, % 12.1 8.9
Boiling Range, F 715-950 650-918
Oil Content, % 38.12 33.7
[0050] Two catalysts were employed for dewaxing the Foots oil feeds.
Crosfield 599 was used as a pre-hydrotreating catalyst followed by Pt/ZSM-48
dewaxing catalyst. Crosfield 599 is a commercial catalyst containing a mixture
of
Ni0 and Mo03 supported on alumina. The properties and metal contents of the
catalyst are shown below.
[0051] Crosfield 599: 224 m2/g (surface area), 1.37 g/cc (particle density),
35%
Al, 3.8% Ni, 17% Mo.
[0052] The dewaxing catalyst was alumina (35 wt.%) bound, ZSM-48 crystals
containing 0.6 wt.% platinum.
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[0053] The dewaxing experiments were performed using a microunit equipped
with two cascaded down-flow trickle bed tubular reactors and two three-zone
furnaces. The unit was heat-traced to avoid freezing of the waxy feedstocks.
To
reduce feed bypassing and lower zeolite pore diffusion resistance, the
catalyst
extrudates were crushed and sized to 60-80 mesh. The first reactor was then
loaded
with a mixture of 7.5 cc of the sized Crosfield 599 and 3 cc of 80-120 mesh
sand.
The second reactor was loaded with a mixture of 15 cc of the sized Pt/ZSM-48
and
cc of 80-120 mesh sand.
[0054] After pressure testing of the unit, the catalysts were dried and
reduced at
204°C (400°F) for one hour under 1 atmosphere, 255 cc/min
hydrogen flow. The
catalysts were then sulfided at 371°C (700°F) for 12 h using 100
cc/min, 2% H2S in
H2. The MNFO was first processed over the cascaded Crosfield 599/Pt-ZSM-48,
followed by switching feed to the LNFO. Isomerization and dewaxing of the
Foots
oil feeds was conducted under 2860-6996 kPa (400-1000 psig) H2 at 2.0 h-1 LHSV
based on Crosfield 599 and 1.0 h-1 LHSV based on Pt/ZSM-48. Hydrogen/feed
ratio was set at 1015 m3/m3 (5700 scf/bbl). The dewaxing experiments were
started
first by saturating the catalyst beds with feed at 204°C
(400°F), then heating the
two reactors to initial operating temperature (the two reactors were
maintained at
same temperature). Material balances were carried out overnight for 16 h after
8 h
lineout. Reactors temperature was then gradually changed to vary pour point.
[0055] Off gas samples were analyzed by GC. Total liquid products (TLPs)
were weighed and analyzed by simulated distillation. TLPs were distilled into
initial boiling point (IBP) -166°C (-330°F) naphtha, 166-
343°C (330-650°F)
distillate, and 343°C+ (650°F+) Tube fractions. The
343°C+ (650°F+) Tube
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fractions were again analyzed by simulated distillation (Simdis) to ensure
accuracy
of the actual distillation operations. The pour point and cloud point of
343°C+
650°F+ lubes were measured according to corresponding ASTM D97 and
D2500
methods, and their viscosities were determined at both 40°C and
100°C according
to ASTM D445-3 and D445-5 methods, respectively.
[0056] The dewaxing of the MNFO was carried out under 6996 kPa (1000 psig)
H2 at 2.0 h-1 LHSV based on Crosfield 599 and 1.0 h-1 LHSV based on Pt/ZSM-48.
Hydrogen/feed ratio of 1015 m3/m3 (5700 scf/bbl) was used. The temperature of
both Reactor 1 (containing Crosfield 599) and Reactor 2 (containing Pt/ZSM-48)
was kept same. The dewaxed oil yields and properties are summarized in Table
6.
For further clarification, the dewaxing results are also illustrated in
Figures 3-6.
Table 6
Lube Yield and Properties for Dewaxin~ the MNFO under 1000 psi~ HZ
650F+ Pour Cloud
Temp Yield, KV@100C VI Point Point S N Tot.
C wt% Feed cSt C C (ppm) (ppm) Arom
(mmol/Kg)
354 82 5.364 141.818 30 29 < 5 223
360 73 5.224 135.89 22 28 < 5 227
363 67 5.342 132.86 17 < 25 < 5 230
368 60 5.436 125.8-3 5 < 25 < 5 249
374 49 5.851 114.6-27 -18 < 25 < 5 270
379 34 5.727 106.6< -54 < -54 < 25 < 5 305
[0057] The results show that the cascaded dual catalysts system consisting of
first bed Crosfield 599 pre-hydrotreating catalyst followed by second bed
Pt/ZSM-
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48 dewaxing catalyst is capable of converting the medium neutral Foots oil to
high
VI (> 120) Group III lube base stocks with low sulfur (< 25 ppm) and nitrogen
(< 5
ppm) contents. Lube yield of about 60% was obtained at conventional pour
point.
Example 6
[0058] To test the pressure effects on the catalysts performance and Tube
product
properties, the dewaxing of the MNFO was also performed under 2859 kPa (400
psig) Ha. Other conditions, such as LHSV, hydrogen/feed ratio, were similar to
those used in the previous process under 6996 kPa (1000 psig) HZ. The
temperature of Reactor 1 (containing Crosfield 599) and Reactor 2 (containing
Pt/ZSM-48) was kept same. The dewaxed oil yields and properties are summarized
in Table 7.
Table 7
Lube Yield and Prouerties for Dewaxin~ the MNFO under 400 psi~ H~
343C+ Pour Cloud
Temp Yield, KV@100C VI Point Point S N Tot. Arom
C wt% Feed cSt C C (ppm) (ppm) (mmol/Kg)
354 77.6 5.429 142.0 24 36 - - -
360 73.6 5.557 136.4 18 24 - - -
363 71.3 5.442 132.2 12 21 - - -
366 67.7 5.513 129.2 9 18 - - -
368 62.0 5.372 125.0 -3 8 49 < 5 402
371 57.4 5.916 119.3 -6 2 48 < 5 425
374 54.5 5.409 116.3 -24 -5 37 < 5 478
377 50.8 5.933 111.1 -33 -17 - - -
379 45.7 5.316 108.4 < -54 -51 - - -
[0059] The above results demonstrate that the cascaded dual catalysts system
remains effiective for dewaxing Foots oil at hydrogen pressure as low as 2859
kPa
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(400 psig). Low pressure process has significant advantages versus high
pressure
operation because of the simplicity and low cost in design and construction of
low
pressure reactors. By comparing to the dewaxing data obtained at 6996 kPa
(1000
psig) H2, the hydrogen pressure effects on catalysts activity was found to be
minimal for this particular feed with high contents of sulfur and nitrogen.
Upon
decreasing H2 pressure, the Tube yield is slightly higher at conventional pour
point
with essentially no change in lube VI. At a low hydrogen pressure, the
effectiveness of the pre-hydrotreating catalyst (Crosfield 599) decreases; as
the
result, both sulfur and aromatic contents in the lube products increase (see
Tables 6
and 7).
Example 7
[0060] This example shows the dewaxing of LNFO at 6996 kPa H2. The process
conditions used for dewaxing the LNFO were similar to those for the MNFO. The
experiments were carried out under 6996 kPa (1000 psig) HZ at 2.0 h-1 LHSV
based
on Crosfield 599 and 1.0 h-1 LHSV based on Pt/ZSM-48. Hydrogen/feed ratio of
5700 scf/bbl (1015 m3/m3) was employed. The temperature of Reactor 1
(containing Crosfield 599) and Reactor 2 (containing Pt/ZSM-48) was kept same.
The dewaxed oil yields and properties are summarized in Table 8; and for
further
clarification, the results are depicted in Figures 5-8.
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Table 8
Lube Yield and Properties for Dewaxin~ the LNFO under 1000 psi~ HZ
343 C+ Pour Cloud
DOS Temp Yield, KV@100C VI Point Point S
(days) F wt% Feed cSt C C (ppm)
27 650 82.0 3.280 141.0 24 27 < 25
28 660 78.0 3.435 140.0 21 23 -
30 675 67.6 3.458 132.5 9 19 < 25
31 680 61.2 3.530 128.6 3 7 < 25
32 685 57.2 3.464 123.1 -9 -1 < 25
34 695 46.6 4.122 120.9 -33 -10 < 25
42 670 66.6 3.193 130.6 0 5 < 25
[0061] These results demonstrate that the cascaded dual catalysts system is
also
effective and selective in converting the light neutral Foots oil to high VI
(> 120),
low sulfur (< 25 ppm) Group III lube base stocks. Lube yield of about 57% was
obtained at conventional pour point.
[0062] In addition, the data in Table 8 show that after 10 days on stream upon
switching feed from the MNFO to the LNFO, the catalyst activity increases by
approximately 10°F, along with small lube yield (+5%) and VI (+2)
increase.
Example 8
[0063] Byproduct Yields for Dewaxing the MNFO and LNFO were determined
as follows. The processes were carried out under 6996 kPa (1000 psig) H2 at
2.0 h-1
LHSV based on Crosfield 599 and 1.0 h-1 LHSV based on Pt/ZSM-48.
Hydrogen/feed ratio of 1015 m3/m3 (5700 scf/bbl was employed. The temperature
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of Reactor 1 (containing Crosfield 599) and Reactor 2 (containing Pt/ZSM-48)
was
kept same. The yields of dewaxed oil and lighter byproducts are summarized in
Table 9. For both MNFO and LNFO dewaxing, the major byproducts were
distillate and naphtha with relatively small amount (< 8%) of C1-C4 gases.
Table 9
Byproduct Yields (wt% Feed) for Dewaxin~ the MNFO and LNFO
Process 343CF+ 166-343CCS-166C
Feed Temp Lube PP 343C+ DistillateNaphtha CI-Cq
C C Lube Yield Yield Offgas
Yield Yield
MNFO 368 -3 60.0 19.1 17.9 5.1
LNFO 363 -9 57.2 21.8 13.9 6.2
LNFO 368 -33 46.6 26.1 23.2 7.7
