U.S. patent application number 13/171916 was filed with the patent office on 2012-01-05 for process for the preparation of group ii and group iii lube base oils.
This patent application is currently assigned to EXXONMOBIL RESEARCH AND ENGINEERING COMPANY. Invention is credited to Michel Daage, Richard Charles Dougherty.
Application Number | 20120000818 13/171916 |
Document ID | / |
Family ID | 45398874 |
Filed Date | 2012-01-05 |
United States Patent
Application |
20120000818 |
Kind Code |
A1 |
Dougherty; Richard Charles ;
et al. |
January 5, 2012 |
PROCESS FOR THE PREPARATION OF GROUP II AND GROUP III LUBE BASE
OILS
Abstract
A process for the preparation of Group II and Group III lube oil
base stocks wherein liquid-continuous aromatics saturation is used
to treat lube hydrocrackate. The treated hydrocrackate is then be
sent to dewaxing unit and then optionally to a hydrotreating
step.
Inventors: |
Dougherty; Richard Charles;
(Moorestown, NJ) ; Daage; Michel; (Hellertown,
PA) |
Assignee: |
EXXONMOBIL RESEARCH AND ENGINEERING
COMPANY
Annandale
NJ
|
Family ID: |
45398874 |
Appl. No.: |
13/171916 |
Filed: |
June 29, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61360113 |
Jun 30, 2010 |
|
|
|
Current U.S.
Class: |
208/97 |
Current CPC
Class: |
C10G 2300/302 20130101;
C10G 2400/10 20130101; C10G 45/54 20130101; C10G 2300/301 20130101;
C10G 65/12 20130101; C10G 2300/202 20130101; C10G 45/48 20130101;
C10G 2300/1074 20130101; C10M 101/02 20130101; C10M 2203/1045
20130101; C10G 65/08 20130101; C10G 45/50 20130101; C10G 2300/4081
20130101; C10G 45/44 20130101; C10M 2203/1025 20130101; C10G
2300/1062 20130101; C10G 45/58 20130101; C10G 45/64 20130101; C10G
2300/1077 20130101; C10G 65/043 20130101; C10G 45/62 20130101 |
Class at
Publication: |
208/97 |
International
Class: |
C10G 69/02 20060101
C10G069/02 |
Claims
1. A process for the production of high quality lube base oils,
which process comprising: i) hydrocracking a lube oil feedstock
having a boiling point above 600.degree. F. and containing
polycyclic aromatics in the presence of hydrogen and a
hydrocracking catalyst to produce a hydrocrackate having a boiling
point above 600.degree. F. which hydrocrackate contains a lesser
amount of polycyclic aromatics than said lube oil feedstock; ii)
hydrotreating at least a portion of said hydrocrackate in the
presence of an aromatics saturation catalyst under effective
aromatics saturation conditions in a liquid-continuous reactor to
form a hydrotreated hydrocrackate having a waxy paraffinic
component; and iii) catalytically dewaxing said hydrotreated
hydrocrackate in the presence of hydrogen and a dewaxing catalyst
under effective dewaxing conditions including a temperature from
500.degree. F. to 750.degree. F. and a pressure up to 2200 psig and
at an effective contact time of feed to catalyst that will remove
at least a portion of the waxy paraffinic components by
isomerization to less waxy iso-paraffinic components, thereby
producing a lube base oil containing of at least 90 wt. %
saturates, less than 0.03 wt. % sulfur and a viscosity index of at
least 80.
2. The process of claim 1 wherein the lube oil feedstock is
selected from the group consisting of vacuum gas oils, hydrocracked
gas oils, hydrocracked vacuum gas oils, deasphalted oils, slack
waxes, foots oils, coker tower bottoms, reduced crude, vacuum tower
bottoms, deasphalted vacuum resids, fluid catalytic cracking tower
bottoms, and cycle oils.
3. The process of claim 2 wherein the lube oil feedstock is a
vacuum gas oil.
4. The process of claim 1 wherein a portion of the hydrotreated
hydrocrackate is recycled to the liquid-continuous reactor and
again hydrotreated with fresh hydrocrackate.
5. The process of claim 4 wherein the volume ratio of recycled
hydrotreated hydrocrackate to fresh hydrocrackate to the
liquid-continuous reactor is from 0.5 to 1 to 5 to 1.
6. The process of claim 4 wherein the volume ratio of recycled
hydrotreated hydrocrackate to fresh hydrocrackate to the
liquid-continuous reactor is from 1 to 1 to 3 to 1.
7. The process of claim 1 wherein a portion of the hydrotreated
hydrocrackate from the liquid-continuous reactor is withdrawn and
saturated with hydrogen then recycled back to the liquid-continuous
reactor.
8. The process of claim 1 wherein the aromatics saturation catalyst
is comprised of one or more catalytic metals selected from Groups
VIB and Group VIII of the Periodic Table of the Elements on an
amorphous or crystalline refractory support.
9. The process of claim 8 wherein the support is a mesoporous
material.
10. The process of claim 9 wherein the mesoporous material is
MCM-41.
11. The process of claim 9 wherein the catalytic metal is selected
from the group consisting of Pt and Pd.
12. The process of claim 1 wherein the hydrocracking of step i)
results in at least a 50% reduction of aromatics compared to the
amount of aromatics in the lube oil feedstock.
13. The process of claim 1 wherein the process conditions for
aromatics saturation during hydrotreating includes temperatures
from 400.degree. F. to 750.degree. F. and pressures from 500 psig
to 2500 psig.
14. The process of claim 1 wherein the catalytic dewaxing
temperature is from 500.degree. F. to 750.degree. F.
15. The process of claim 1 wherein the catalytic dewaxing catalyst
is selected from the group consisting of crystalline
aluminosilicates and silicoaluminophosphates.
16. The process of claim 15 wherein the catalytic dewaxing catalyst
is a crystalline aluminosilicate selected from the group consisting
of ZSM-22, ZSM-23, ZSM-35 and ZSM-48, and combinations thereof.
17. The process of claim 16 wherein the catalytic dewaxing catalyst
contains a binder material selected from the group consisting of
alumina, titania, silica, silica-alumina, zirconia, and
combinations thereof.
18. The process of claim 16 wherein the catalytic dewaxing catalyst
contains at least one metal selected from the group consisting of
Pt, Pd, and Ni.
19. The process of claim 18 wherein the catalytic dewaxing catalyst
also contains a metal selected from W and Mo.
20. The process of claim 1 wherein the dewaxed lube oil is
subjected to hydrofinishing in the presence of hydrogen and a
hydrofinishing catalyst at a temperature from 300.degree. F. to
675.degree. F. and total pressures from 400 to 3000 psig.
21. The process of claim 20 wherein the hydrofinishing catalyst is
comprised of one or more metals selected from Group VIII and Group
VIB of the Periodic Table of the Elements.
22. The process of claim 21 wherein the hydrofinishing catalyst
contains at least one metal from Group VIII and at least one metal
from Group VIB.
23. The process of claim 21 wherein the hydrofinishing catalyst is
comprised of a noble metal selected from Pt and Pd on a mesoporous
crystalline support.
24. The process of claim 23 wherein the mesoporous crystalline
support is MCM-41.
25. A process for the production of high quality lube base oils,
which process comprising: i) hydrocracking a lube oil feedstock
having a boiling point above 600.degree. F. and containing
polycyclic aromatics in the presence of hydrogen and a
hydrocracking catalyst to produce a hydrocrackate having a boiling
point above 600.degree. F. which contains a lesser amount of
polycyclic aromatics than said lube oil feedstock; ii)
hydrotreating at least a portion of said hydrocrackate in the
presence of an aromatics saturation catalyst under effective
aromatics saturation conditions in a liquid-continuous reactor to
form a hydrotreated hydrocrackate having a waxy paraffinic
component; iii) catalytically dewaxing said hydrotreated
hydrocrackate in the presence of hydrogen and a dewaxing catalyst
under effective dewaxing conditions including a temperature from
500.degree. F. to 750.degree. F. and a pressure up to 2200 psig and
at an effective contact time of feed to catalyst that will remove
at least a portion of the waxy paraffinic components by
isomerization to less waxy iso-paraffinic components; and iv)
subjecting the dewaxed hydrotreated hydrocrackate to hydrofinishing
in the presence of hydrogen and a hydrofinishing catalyst and at
hydrofinishing conditions thereby resulting in a lube base oil
comprised of at least 90 wt. % saturates, less than 0.03 wt. %
sulfur and a viscosity index of at least 80.
26. The process of claim 25 wherein the lube oil feedstock is
selected from the group consisting of vacuum gas oils, hydrocracked
gas oils, hydrocracked vacuum gas oils, deasphalted oils, slack
waxes, foots oils, coker tower bottoms, reduced crude, vacuum tower
bottoms, deasphalted vacuum resids, fluid catalytic cracking tower
bottoms, and cycle oils.
27. The process of claim 26 wherein the lube oil feedstock is a
vacuum gas oil.
28. The process of claim 26 wherein a portion of the hydrotreated
hydrocrackate is recycled to the liquid-continuous reactor and
again hydrotreated with fresh hydrocrackate.
29. The process of claim 28 wherein the volume ratio of recycled
hydrotreated hydrocrackate to fresh hydrocrackate to the
liquid-continuous reactor is from 0.5 to 1 to 5 to 1.
30. The process of claim 28 wherein the volume ratio of recycled
hydrotreated hydrocrackate to fresh hydrocrackate to the
liquid-continuous reactor is from 1 to 1 to 3 to 1.
31. The process of claim 25 wherein a portion of the hydrotreated
hydrocrackate from the liquid-continuous reactor is withdrawn and
saturated with hydrogen then recycled back to the liquid-continuous
reactor.
32. The process of claim 25 wherein the aromatics saturation
catalyst is comprised of one or more catalytic metals selected from
Groups VIB and Group VIII of the Periodic Table of the Elements on
an amorphous or crystalline refractory support.
33. The process of claim 32 wherein the support is a mesoporous
material.
34. The process of claim 33 wherein the mesoporous material is
MCM-41.
35. The process of claim 33 wherein the catalytic metal is selected
from the group consisting of Pt and Pd.
36. The process of claim 25 wherein the hydrocracking of step i)
results in at least a 50% reduction of aromatics compared to the
amount of aromatics in the lube oil feedstock.
37. The process of claim 25 wherein the process conditions for
aromatics saturation during hydrotreating includes temperatures
from 400.degree. F. to 750.degree. F. and pressures from 500 psig
to 2500 psig.
38. The process of claim 25 wherein the catalytic dewaxing
temperature is from 500.degree. F. to 750.degree. F.
39. The process of claim 25 wherein the catalytic dewaxing catalyst
are selected from the group consisting of crystalline
aluminosilicates and silicoaluminophosphates.
40. The process of claim 39 wherein the catalytic dewaxing catalyst
is a crystalline aluminosilicate selected from the group consisting
of ZSM-22, ZSM-23, ZSM-35 and ZSM-48, and combinations thereof.
41. The process of claim 40 wherein the catalytic dewaxing catalyst
contains a binder material selected from the group consisting of
alumina, titania, silica, silica-alumina, zirconia, and
combinations thereof.
42. The process of claim 40 wherein the catalytic dewaxing catalyst
contains at least one metal selected from the group consisting of
Pt, Pd, and Ni.
43. The process of claim 42 wherein the catalytic dewaxing catalyst
also contains a metal selected from W and Mo.
44. The process of claim 25 wherein the hydrofinishing catalyst is
comprised of one or more metals selected from Group VIII and Group
VI of the Periodic Table of the Elements.
45. The process of claim 44 wherein the hydrofinishing catalyst
contains at least one metal from Group VIII and at least one metal
from Group VIB.
46. The process of claim 44 wherein the hydrofinishing catalyst is
comprised of a noble metal selected from Pt and Pd on a mesoporous
crystalline support.
47. The process of claim 46 wherein the mesoporous crystalline
support is MCM-41.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a Non-provisional application that claims priority
to U.S. Provisional Application No. 61/360,113 filed Jun. 30, 2010,
which is herein incorporated by reference in its entirety.
FIELD
[0002] This disclosure relates to the preparation of Group II and
Group III lube base oils wherein liquid-continuous aromatics
saturation is used to treat a lube hydrocrackate. The treated
hydrocrackate is then dewaxed and then optionally
hydrofinished.
BACKGROUND
[0003] Crude petroleum is distilled and fractionated into many
products such as gasoline, kerosene, jet fuel, asphaltenes, and the
like. One portion of the crude petroleum forms the base of
lubricating base oils used in, inter alia, the lubricating of
internal combustion engines. Lube oil users are demanding ever
increasing base oil quality, and refiners are finding that their
available equipment is becoming less and less able to produce base
oils that meet these higher quality specifications. New processes
are required to provide refiners with the tools for preparing high
quality modern base oils, particularly using existing equipment at
lower cost and with safer operation.
[0004] Finished lubricants used for such things as automobiles,
diesel engines, and industrial applications generally are comprised
of a lube base oil and additives. In general, a few lube base oils
are used to produce a wide variety of finished lubricants by
varying the mixtures of individual lube base oils and individual
additives. Typically, lube base oils are simply hydrocarbons
prepared from petroleum or other sources. Lube base oils are
normally manufactured by making narrow cuts of vacuum gas oils from
a crude vacuum tower. The cut points are set to control the final
viscosity and flash point of the lube base oil.
[0005] Group I base oils, those with greater than 300 ppm sulfur
and 10 wt. % aromatics are generally produced by first extracting a
vacuum gas oil (or waxy distillate) with a polar solvent, such as
N-methyl-pyrrolidone, furfural, or phenol. The resulting waxy
raffinates produced from solvent extraction process are then
dewaxed, either catalytically with the use of a dewaxing catalyst
such as ZSM-5, or by solvent dewaxing. The resultant base oil may
be hydrofinished to improve color and other lubricant
properties.
[0006] Group II base oils, those with less than 300 ppm sulfur and
10 wt. % aromatics, and with a viscosity index range of 80-120, are
typically produced by hydrocracking followed by selective catalytic
dewaxing and hydrofinishing. Hydrocracking upgrades the viscosity
index of the entrained oil in the feedstock by ring cracking and
aromatics saturation. The degree of aromatics saturation is limited
by the high temperature of the hydrocracking stage. In the second
stage of the process, the hydrocracked oil is dewaxed, either by
solvent dewaxing or by catalytic dewaxing, with catalytic dewaxing
typically being the preferred dewaxing technology. The dewaxed oil
is then preferably hydrofinished at mild temperatures to remove
polynuclear aromatics which were not converted in the first stage
and the dewaxing stage and which have a strongly detrimental impact
on lube base oil quality.
[0007] Group III base oils have the same sulfur and aromatics
specifications as Group II base stocks but have viscosity indices
above 120. These materials are manufactured with the same type of
catalytic technology employed to produce Group II base oils but
with either the hydrocracker being operated at much higher
severity, or with the use very waxy feedstocks.
[0008] A typical lube hydroprocessing plant consists of two primary
processing stages. In the lead stage, a feedstock, typically a
vacuum gas oil, deasphalted oil, processed gas oils, or any
combination of these materials, is hydrocracked or solvent
extracted. The hydrocracking stage upgrades the viscosity index of
the entrained oil in the feedstock by ring cracking and aromatics
saturation. The degree of aromatics saturation is limited by the
high temperature of the hydrocracking stage. In a second stage, the
hydrocracked oil is dewaxed, preferably with the use of a highly
shape-selective catalyst capable of wax conversion by
isomerization. The dewaxed oil can be subsequently hydrofinished at
mild temperatures to remove polynuclear aromatics that were not
converted in the upstream hydrocracking and dewaxing stages and
which have a strongly detrimental impact on lube base oil quality.
Operation of the final hydrofinishing step is optimized to convert
polynuclear aromatics; conversion of these species and significant
conversion of one ring and two ring aromatics cannot be
accomplished in the final hydrofinishing step because of its low
operating temperature.
[0009] Group II or III base stocks specifications limit total
aromatics content to less than 10 wt. %. However, specific
marketing requirements for these materials can be more demanding
limiting aromatics contents to 5% or even less. The processing of
heavier, more aromatics feedstocks requires a higher degree of
aromatics conversion in the hydrocracking and dewaxing zones, which
is difficult for conventional lube processing technology. There is
a need in the art for improved process technology to allow for the
use of heavier feeds for the production of Group II and Group III
base stocks.
SUMMARY
[0010] In accordance with the present disclosure there is provided
a process for the production of lube base oils, which process
comprising:
[0011] i) hydrocracking a lube oil feedstock having a boiling point
above 600.degree. F. and containing polycyclic aromatics in the
presence of hydrogen and a hydrocracking catalyst to produce a
hydrocrackate having a boiling point above 600.degree. F. which
hydrocrackate contains a lesser amount of polycyclic aromatics than
said lube oil feedstock;
[0012] ii) hydrotreating at least a portion of said hydrocrackate
in the presence of an aromatics saturation catalyst under effective
aromatics saturation conditions in a liquid-continuous reactor to
form a hydrotreated hydrocrackate having a waxy paraffinic
component; and
[0013] iii) catalytically dewaxing said hydrotreated hydrocrackate
in the presence of hydrogen and a dewaxing catalyst under effective
dewaxing conditions including a temperature from 550.degree. F. to
800.degree. F. and a pressure up to 2200 psig and at an effective
contact time of feed to catalyst that will remove at least a
portion of the waxy paraffinic components by isomerization to less
waxy iso-paraffinic components, thereby producing a lube base oil
containing at least 90 wt. % saturates, less than 0.03 wt. % sulfur
and a viscosity index of at least 80.
[0014] In a preferred embodiment, the dewaxed liquid effluent is
hydrofinished, by treating it with a hydrofinishing catalyst, in
the presence of hydrogen and at effective hydrofinishing conditions
that result in the removal of at least a portion of any remaining
aromatics, heteroatoms, or both.
BRIEF DESCRIPTION OF THE FIGURE
[0015] The FIGURE hereof is a simplified flow diagram of a
preferred embodiment of the present disclosure showing the primary
process units.
DETAILED DESCRIPTION
[0016] All numerical values within the detailed description and the
claims herein are modified by "about" or "approximately" the
indicated value, and take into account experimental error and
variations that would be expected by a person having ordinary skill
in the art.
[0017] The present disclosure is directed to the preparation of
Group II and Group III lube base oils. API Publication 1509: Engine
Oil Licensing and Certification System, "Appendix E-API Base Oil
Interchangeability Guidelines for Passenger Car Motor Oil and
Diesel Engine Oils" describes base stock categories. A Group II
base oil will contain greater than or equal to 90 wt. % saturates
and less than or equal to 0.03 wt. % sulfur and will have a
viscosity index (VI) greater than or equal to 80 and less than 120.
A Group III base oil will contain greater than or equal to 90 wt. %
saturates and less than or equal to 0.03 wt. % sulfur and will have
a VI greater than or equal to 120. The VI of an oil is an arbitrary
relative measure of the oil's change in viscosity with temperature.
The smaller the change in viscosity of an oil at a given
temperature the higher the VI value of the oil. A high VI is
desirable in high quality motor oils. The term "viscosity index"
(VI) refers to the measurement defined by ASTM D2270.
[0018] Lube hydroprocessing refineries are continually challenged
to increase throughput and to process more refractory feedstocks.
The limitation on refineries to accomplish these objectives is
increasingly becoming the refinery's ability to convert aromatics
in the feed to meet Group II specification (10 wt. % max) or
specific market requirements.
[0019] Both increasing through-put and increasing feed difficulty,
work against high aromatics conversion. Increasing throughput and
feed aromatics increases the temperature at which hydrocracking
must be operated. This limits the amount of aromatics conversion
that can occur because of equilibrium constraints. Additionally,
increasing throughput and declining feed quality, while increasing
the aromatics content of the material entering the
dewaxing/hydrotreating zone, also increases the degree of nitrogen
slip to this stage. Increases in both aromatics and nitrogen result
in lower dewaxing catalyst life, high dewaxing catalyst operating
temperature, and less ability of the dewaxing stage to convert
aromatics remaining from the hydrocracking zone.
[0020] U.S. Pat. No. 5,951,848 teaches the use of a hydrotreating
catalyst in the dewaxing reactor upstream of the dewaxing catalyst.
The purposes of this hydrotreating catalyst, which typically
contains a noble metal on an amorphous support (alumina or
silica-alumina), are to: a) reduce the aromatics content of the oil
reaching the dewaxing catalyst as aromatics have been shown to
detrimentally impact dewaxing catalyst life; and b) decouple
aromatics saturation from dewaxing so that the exotherm associated
with aromatics conversion becomes isolated from the dewaxing
catalyst (which has aromatics saturation capability). This allows
the dewaxing catalyst to operate more isothermally which increases
its life and its selectivity for base oil production.
[0021] Increasing rate and feed refractoriness requires greater
dewaxing catalyst volume to maintain cycle length. In a
conventional configuration, this would result in displacement of
some of the hydrotreating catalyst in the dewaxing reactor which
results in less ability to convert aromatics. A solution is
represented by the present disclosure with the addition of a
hydrocracking reactor, particularly a liquid-continuous reactor,
upstream of the dewaxing.
[0022] A typical process scheme for manufacturing Group II base
oils from vacuum gas oils includes combining a lube oil feedstock
with hydrogen, typically at a rate of 2,000 to 10,000 standard
cubic feet per barrel (scf/bbl), and hydrocracking it in the
presence of hydrogen and a hydrocracking catalyst, typically in a
multi-bed reactor, or in multiple reactors. Hydrocracking is
typically operated at a temperature from 600 to 850.degree. F. with
a liquid flow rate to hydrocracking catalyst volume from 0.2 to 5
liquid hourly space velocity.
[0023] The nature of hydrocracking catalysts are known to those
having ordinary skill in the art and typically contain at least one
Group VIII metal, including non-noble metals such as Co and Ni, and
noble metals such as Pt and Pd, in combination with at least one
Group VIB metal, preferably selected from Mo and W. These metals
are supported on a refractory support such as alumina, amorphous
silica-alumina, structured aluminosilicates such as zeolites, or a
combination of supports. Such catalysts are described in U.S. Pat.
No. 3,852,207, which is incorporated herein by reference. The
non-noble metals (such as nickel-molybdenum) are usually present in
the final catalyst composition as oxides.
[0024] Preferred non-noble metal catalyst compositions contain in
excess of 5 wt. %, preferably 5 wt. % to 40 wt. % molybdenum and/or
tungsten, and at least 0.5 wt. %, and generally 1 wt. % to 15 wt. %
of nickel and/or cobalt determined as the corresponding oxides, and
are converted to sulfide form prior to use. The noble metal (such
as platinum) catalysts contain in excess of 0.01 wt. % metal,
preferably between 0.1 wt. % to 1 wt. % metal. Combinations of
noble metals may also be used, such as mixtures of platinum and
palladium. All Groups referred to in this document are groups of
the a Periodic Table of the Elements, such as the Sargent-Welch
Periodic Table of the Elements copyrighted in 1968 by the
Sargent-Welch Scientific Company.
[0025] The product from the hydrocracking reactions is separated
into gaseous products, liquid products, and a heavy hydrocrackate.
Off-gas from the hydrocracking process is usually purified of
contaminant gases such as ammonia and H.sub.2S before being
recycled. The hydrocrackate liquid is either stored in tankage
before further processing, or is fed directly to a second stage of
the process. Aromatics reduction during the hydrocracking stage
will vary with operating temperature, as set by feed quality and
catalyst life within its operating cycle. Aromatics reduction will
preferably be at least 50% of the total aromatics in the feed. The
pour point of the hydrocrackate will typically be above 80.degree.
F., and can often be above 120.degree. F.
[0026] The hydrocracking reactor operation is controlled primarily
to meet a finished base oil VI target. Aromatics and nitrogen
conversion are also parameters, but have secondary importance in
the control of the hydrocracking stage. Because the hydrocracking
and dewaxing stages often operate at elevated temperatures that do
not favor the conversion of condensed aromatic species, a final low
temperature hydrofinishing step is typically employed to reduce the
polynuclear aromatics content to improve oxidation stability and
color. Because the hydrofinishing stage operates at low
temperature, it is not particularly effective at reducing total
aromatics. As described above, overall aromatics conversion occurs
over each step of the catalytic lubes refining process. Increasing
the refractory nature of the feedstock, or increasing throughput,
increases the temperature required for both the hydrocracking and
dewaxing stages. This makes it more difficult to convert aromatics
by conventional processing techniques.
[0027] Feedstocks suitable for use herein may be one or a
combination of refinery streams having a normal boiling point of at
least 600.degree. F. (316.degree. C.), although the process is also
useful with oils that have initial boiling points as low as
435.degree. F. (224.degree. C.). By having a normal boiling point
of at least 600.degree. F. (316.degree. C.) is meant that 85% by
volume of the feedstock has a boiling point at atmospheric pressure
of at least 600.degree. F. (316.degree. C.). While higher boiling
lube oil feedstocks can be processed in accordance with the present
disclosure, the preferred feedstock will have a boiling range such
that at least 85% by volume of the feedstock has a normal boiling
point of at most 1250.degree. F. (677.degree. C.), and more
preferably at most 1100.degree. F. (593.degree. C.). Such
feedstocks, particularly vacuum gas oils, will contain from 35 wt.
% to 70 wt. % aromatics, at least 40% of them being 2-ring and
higher aromatics. Representative feedstocks that can be treated
using the present process include gas oils and vacuum gas oils
(VGO), hydrocracked gas oils and vacuum gas oils, deasphalted oils,
slack waxes, foots oils, coker tower bottoms, reduced crude, vacuum
tower bottoms, deasphalted vacuum resids, FCC tower bottoms and
cycle oils and raffinates from a solvent extraction process. The
nitrogen, sulfur and saturate contents of these feeds will vary
depending on a number of factors. The preferred feedstocks for the
present disclosure will have an entrained oil viscosity index of
greater than 30. In a more preferred embodiment, the entrained oil
in the feedstock will have a viscosity index in the range of 40 to
60.
[0028] The process of the present disclosure is better understood
with reference to the FIGURE hereof. This FIGURE illustrates the
primary pieces of equipment for practicing the present disclosure
and does not show ancillary equipment, such as valves, pumps,
compressors, heat exchanger, heaters and the like. The function of
such equipment is well known to those skilled in the art. A lube
oil feedstock is conducted to hydrocracking reactor 100 via line
10. Makeup hydrogen can be added as need via line 11. Feed
molecules are reshaped and some are cracked into smaller molecules
in hydrocracking reactor 100. Almost all of the sulfur and nitrogen
are removed, and aromatic compounds are saturated with hydrogen.
Molecular reshaping occurs as isoparaffins and saturated ring
compounds are formed. These compounds have high VIs and low pour
points. However, waxy compounds, chiefly normal-paraffins are
largely unaffected by hydrocracking and must be removed in a
subsequent process in order to reduce the pour point.
[0029] The resulting hydrocracker effluent is conducted via line 12
to first separation zone 200, which is preferably a hot
high-pressure separator wherein a gaseous effluent fraction is
separated from a liquid effluent fraction. The gaseous effluent
fraction, via line 14, can be treated to remove acidic components
and recycled to the hydrocracking reactor 100. The liquid
hydrocrackate effluent from first separation zone 200 is passed via
line 16 to liquid-continuous aromatics saturation reactor 300.
Makeup hydrogen, as needed, can be introduced via line 17. It will
be understood that the makeup hydrogen can be added at any suitable
point to the feed line or even directly into the reactor 300. It is
also within the scope of this disclosure that the liquid effluent
from separation zone 200 can be contacted with a fraction of
recycle liquid effluent from liquid-continuous aromatics saturation
reactor 300, either directly from the reactor, or from a low
pressure separator (not shown).
[0030] The liquid effluent from separation zone 200 is also
contacted with a hydrogen-rich treat gas in sufficient quantity and
in the presence of a suitable aromatics saturation catalyst to
saturate at least a fraction of the aromatics of the liquid
effluent entering reactor 300. Catalysts suitable for use in
liquid-continuous aromatics saturation reactor 300 can comprise a
support component and one or catalytic metal components of metal
from Groups VIB (Mo, W, Cr) and/or non-noble (Co, Mo) and noble
metals, such as Pt and Pd from Group VIII. The metal or metals may
be present from as little as 0.1 wt % for noble metals, to as high
as 40 wt % of the catalyst composition for supported non-noble
metals. Preferred support materials are low in acid and include,
for example, amorphous or crystalline metal oxides such as alumina,
silica, silica alumina, titania, zirconia, silica-alumina and ultra
large pore crystalline materials known as mesoporous crystalline
materials, of which MCM-41 is a preferred support component. The
preparation and use of MCM-41 is disclosed, for example, in U.S.
Pat. Nos. 5,098,684, 5,227,353 and 5,573,657, both of which are
incorporated herein by reference.
[0031] Bulk multimetallic catalysts can also be used for aromatics
saturation in the practice of the present disclosure. Such
catalysts are described in U.S. Pat. Nos. 6,156,695; 6,162,350; and
6,299,760, all of which are incorporated herein by reference. The
catalysts described in these patents are bulk multimetallic
catalysts comprised of at least one Group VIII non-noble metal and
at least two Group VIB metals, wherein the ratio of Group VIB metal
to Group VIII non-noble metal is from 10:1 to 1:10. These catalysts
are prepared from a precursor having the formula:
(X).sub.a(Mo).sub.b(w).sub.dO.sub.z
where X is a Group VIII non noble metal, wherein the molar ratio of
and a, b, and c, are such that 0.1<(b+c)/b<10, and
z=[2a+6(b+c)]/2. The precursor has x-ray diffraction peaks at
d=2.53 and 1.70 Angstroms. The precursor is sulfided to produce the
corresponding activated catalyst.
[0032] It is also within the scope of this disclosure that the
gas-liquid flow to liquid-continuous aromatics saturation reactor
300 be blended under static mixing conditions. By static mixing
conditions we mean one or more, preferably more, of geometric
mixing elements fixed within a pipe that use the energy of the
moving stream to create mixing between two or more fluids. The
advantage of the static mixers of the present disclosure over
dynamic mixers, other than the fact that static mixers have no
moving parts, is that static mixers split the stream hundreds, or
even thousands of times, thus resulting in a continuous phase
containing very fine droplets of discontinuous phase. This results
in a much larger surface area when compared with dynamic mixers.
The gas-liquid mixture can also be flashed in a suitable vessel
before entering reactor 300 to remove at least a portion of any
excess gas. Alternatively, excess gas can be vented (not shown)
directly from reactor 300.
[0033] To ensure that sufficient hydrogen is present in the liquid
phase for reaction, and to mitigate coking, it may be necessary to
recycle liquid product from the liquid-continuous aromatics
saturation reactor 300. The recycled liquid serves as a carrier for
additional solubilized hydrogen. Alternatively, or in combination
with this liquid recycle, hydrogen may be added to the reactor by
withdrawing liquid at one or more points, preferably at one or more
axial points, along the reactor, resaturating the liquid with
hydrogen, and reinjecting it back into the reactor. This approach
may be used to reduce the amount of liquid recycle required.
[0034] Because the liquid effluent from the reactor 300 contains
only dissolved gas, it is not necessary to have a high-pressure
separation step downstream of the reactor. Only a low-pressure
flash step is required to vent dissolved and excess gas before
product fractionation. Elimination of high-pressure product
recovery vessels significantly reduces the cost of the
debottlenecking.
[0035] As previously mentioned, reactor 300 is operated such that
the liquid phase represents the continuous phase in the reactor.
Traditionally, hydroprocessing, including aromatics saturation, is
conducted in trickle-bed reactors where an excess of gas results in
a continuous gas phase in the reactor. In a liquid-continuous
reactor, the feedstock is exposed to one or more beds of catalyst.
The liquid hydrocrackate preferably enters from the top or upper
portions of the reactor and flows downward through the reactor.
This downward liquid flow can assist in allowing the catalyst to
remain in place in the catalyst bed.
[0036] A hydroprocessing process can typically involve exposing a
feed to a suitable catalyst in the presence of hydrogen at
effective hydroprocessing conditions. Without being bound by any
particular theory, in a conventional trickle-bed reactor, the
reactor can be operated so that three "phases" are present in the
reactor. The hydroprocessing catalyst corresponds to the solid
phase. Another substantial portion of the reactor volume is
occupied by a gas phase. This gas phase (second-phase) includes the
hydrogen for hydroprocessing, optionally some diluent gases, and
other gases such as contaminant gases that are formed during
hydroprocessing. The amount of hydrogen gas in the gas phase is
typically present in substantial excess relative to the amount
required for the hydroprocessing reaction. In a conventional
trickle-bed reactor, the solid hydroprocessing catalyst and the gas
phase can occupy at least 80% of the reactor volume, or at least
85%, or at least 90%. The third "phase" can correspond to the
liquid feedstock. In a conventional trickle-bed reactor, the
feedstock may only occupy a small portion of the volume, such as
less than 20%, or less than 10%, or less than 5%. As a result, the
liquid feedstock may not form a continuous phase. Instead, the
liquid "phase" may include, for example, thin films of feedstock
that coat the hydroprocessing catalyst particles.
[0037] Without being bound by any particular theory, a
liquid-continuous reactor provides a different type of processing
environment as compared to a trickle-bed reactor. In a
liquid-continuous reactor, the reaction zone is primarily composed
of two phases. One phase is a solid phase corresponding to the
hydroprocessing catalyst, in this case an aromatics saturation
(ASAT) catalyst. The second phase is a liquid phase corresponding
to the hydrocrackate feedstock. The liquid feedstock phase will be
present as a continuous phase in the liquid-continuous reactor of
the present disclosure. In an embodiment, the hydrogen that will be
consumed during the aromatic saturation reaction is dissolved in
the liquid phase. Depending on the quantity of hydrogen used, a
portion of the hydrogen can also be in the form of bubbles of
hydrogen in the liquid phase. This hydrogen corresponds to hydrogen
that is in addition to the hydrogen dissolved in the liquid phase.
In another embodiment, hydrogen dissolved in the liquid phase can
be depleted as the reactions progress in the liquid-continuous
reactor. In such an embodiment, hydrogen initially present in the
form of gaseous bubbles can dissolve into the liquid phase to
resaturate the liquid phase and provide additional hydrogen for the
reactions taking place in the reactor. In various embodiments, the
volume occupied by a gas phase in the liquid-continuous reactor can
be less than 10% of the reactor volume, or even less than 5%.
[0038] The liquid feed to reactor 300 is preferably mixed with a
hydrogen-containing treat gas. The hydrogen-containing treat gas
will preferably contain at least 50 vol % of hydrogen, more
preferably at least 80 vol %, even more preferably at least 90 vol
%, and most preferably at least 95 vol %. Excess gas can be vented
from the mixture before it enters the reactor, or excess gas can be
vented directly from the reactor. The liquid level in the reactor
is preferably controlled so that the catalyst in the reactor is
completely wetted.
[0039] In some embodiments, the hydroprocessing reactions in a bed,
stage, and/or reactor can require more hydrogen than can be
dissolved in a liquid. In such embodiments, one or more techniques
can be used to provide additional hydrogen for the hydroprocessing
reaction. One option is to recycle a portion of the product from
the reactor. A recycled portion of product has already passed
through a hydroprocessing stage, and therefore will likely have a
reduced hydrogen consumption as it passes again through the
hydroprocessing stage. Additionally, the solubility of the recycled
feed can be higher than a comparable unprocessed feed. As a result,
including a portion of recycled product with fresh feed can
increase the amount of hydrogen available for reaction with the
fresh feed.
[0040] Another option can be to introduce additional streams of
hydrogen into the reactor directly. One or more additional hydrogen
streams can be introduced at any convenient location in the
reactor. The additional hydrogen streams can include a stream of
make-up hydrogen, a stream of recycled hydrogen, or any other
convenient hydrogen-containing stream. In some embodiments, both
product recycle and injection of additional hydrogen streams along
the axial dimension of the reactor can be used to provide
sufficient hydrogen for a reaction.
[0041] In embodiments involving recycle of the product from
liquid-continuous aromatics saturation zone 300 can be used as part
of the input to the liquid-continuous aromatics saturation zone,
or, reactor 300. The ratio of the amount by volume of product
recycle to the amount of fresh feed into the zone 300 can be at
least 0.5 to 1, or at least 1 to 1, or at least 1.5 to 1. The ratio
of the amount by volume of product recycle to the amount of fresh
feed can be 5 to 1 or less, or 3 to 1 or less, or 2 to 1 or
less.
[0042] Aromatics saturation is performed by exposing a feedstock to
an aromatics saturation catalyst under effective aromatics
saturation conditions. Effective aromatics saturation conditions
can include a temperature of at least 400.degree. F. (204.degree.
C.), or at least 450.degree. F. (232.degree. C.), or at least
500.degree. F. (260.degree. C.). Alternatively, the temperature can
be 750.degree. F. (399.degree. C.) or less, or 700.degree. F.
(371.degree. C.) or less, or 650.degree. F. (343.degree. C.) or
less. The pressure can be at least 500 psig (3.3 MPa), or at least
800 psig (5.3 MPa), or at least 1000 psig (6.6 MPa). Alternatively,
the pressure can be 2500 psig (16.6 MPa) or less, or 2000 psig
(13.3 MPa) or less, or 1500 psig (10 MPa) or less. The liquid
hourly space velocity (LHSV) over the dewaxing catalyst can be at
least 0.25 hr.sup.-1, or at least 0.5 hr.sup.-1, or at least 0.75
hr.sup.-1. Alternatively, the LHSV can be 15 hr.sup.-1 or less, or
hr.sup.-1 or less, or 5 hr.sup.-1 or less. In still another
embodiment, the temperature, pressure, and LHSV for a
liquid-continuous reactor can be conditions suitable for use in a
trickle-bed reactor.
[0043] In embodiments where excess gas is vented from the liquid
effluent, the available hydrogen in the reactor will correspond to
the amount of hydrogen dissolved in the liquid. Thus, a higher
treat gas rate may not lead to an increase in the amount of
available hydrogen. In such a situation, the effective treat gas
rate within a reactor may be dependent on the solubility limit of
the feedstock. The hydrogen solubility limit for a typical
hydrocarbon feedstock is 30 scf/bbl to 200 scf/bbl.
[0044] One advantage of a liquid-continuous reactor is that a large
excess of hydrogen is not fed to the reactor. The use of a large
excess of hydrogen typically requires complex and expensive
separation equipment to allow for recovery, and often recycling, of
the excess hydrogen. Typically, the recycle compressor used for
hydrogen recycle in a trickle-bed reactor corresponds to 10 to 15
wt. % of the total cost of the processing unit. Instead, it is
desirable for a liquid-continuous reactor will desirably supply
only an amount of hydrogen comparable to the amount needed for a
hydroprocessing reaction and to mitigate catalyst coking.
[0045] Returning now to the FIGURE hereof, the effluent stream from
300 is conducted via line 18 to fractionator 400 wherein a lube oil
liquid effluent fraction is separated and passed via line 20 to
catalytic dewaxing stage 500. Make-up hydrogen-containing treat gas
can be introduced via line 24 when needed. Any predetermined
additional fractions can be separated and are collected from
fractionator 400 via lines 22. It will be understood that catalytic
dewaxing stage 500 can also be operated in liquid-continuous mode.
It is within the scope of this disclosure that the liquid effluent
from the liquid-continuous aromatics saturation zone can be
conducted directly to catalytic dewaxing and the effluent from
catalytic dewaxing fractionated.
[0046] Catalytic dewaxing can be performed by exposing the
feedstock to a dewaxing catalyst under effective (catalytic)
dewaxing conditions. Effective dewaxing conditions can include a
temperature of at least 500.degree. F. (260.degree. C.), or at
least 550.degree. F. (288.degree. C.), or at least 600.degree. F.
(316.degree. C.), or at least 650.degree. F. (343.degree. C.).
Alternatively, the temperature can be 750.degree. F. (399.degree.
C.) or less, or 700.degree. F. (371.degree. C.) or less, or
650.degree. F. (343.degree. C.) or less. The pressure can be at
least 200 psig (1.4 MPa), or at least 400 psig (2.8 MPa), or at
least 750 psig (5.2 MPa), or at least 1000 psig (6.9 MPa).
Alternatively, the pressure can be 1500 psig (10.3 MPa) or less, or
1200 psig (8.2 MPa) or less, or 1000 psig (6.9 MPa) or less, or 800
psig (5.5 MPa) or less. The liquid hourly space velocity (LHSV)
over the dewaxing catalyst can be at least 0.1 hr.sup.-1, or at
least 0.2 hr.sup.-1, or at least 0.5 hr.sup.-1, or at least 1.0
hr.sup.-1, or at least 1.5 hr.sup.-1. Alternatively, the LHSV can
be 10.0 hr.sup.-1 or less, or 5.0 hr.sup.-1 or less, or 3.0
hr.sup.-1 or less, or 2.0 hr.sup.-1 or less. In still another
embodiment, the temperature, pressure, and LHSV for a
liquid-continuous reactor can be the same conditions typically used
for a trickle-bed reactor.
[0047] Catalytic dewaxing involves the removal and/or isomerization
of long chain, paraffinic molecules from feeds. Catalytic dewaxing
can be accomplished by selective cracking or by hydroisomerizing
these linear molecules. Hydrodewaxing catalysts can be selected
from molecular sieves such as crystalline aluminosilicates
(zeolites) or silico-aluminophosphates (SAPOs). In an embodiment,
the molecular sieve can be a 1-D or 3-D molecular sieve. In another
embodiment, the molecular sieve can be a 10-member ring 1-D
molecular sieve. Examples of molecular sieves which have shown
dewaxing activity in the literature can include ZSM-48, ZSM-22,
ZSM-23, ZSM-35, Beta, USY, ZSM-5, and combinations thereof. In an
embodiment, the molecular sieve can be ZSM-22, ZSM-23, ZSM-35,
ZSM-48, or a combination thereof. In still another embodiment, the
molecular sieve can be ZSM-48, ZSM-23, ZSM-5, or a combination
thereof. In yet another embodiment, the molecular sieve can be
ZSM-48, ZSM-23, or a combination thereof. Optionally, the dewaxing
catalyst can include a binder for the molecular sieve, such as
alumina, titania, silica, silica-alumina, zirconia, or a
combination thereof.
[0048] One feature of molecular sieves that can impact the activity
of the molecular sieve is the ratio of silica to alumina in the
molecular sieve. In an embodiment, the molecular sieve can have a
silica to alumina ratio of 200 to 1 or less, or 120 to 1 or less,
or 100 to 1 or less, or 90 to 1 or less, or 75 to 1 or less. In an
embodiment, the molecular sieve can have a silica to alumina ratio
of at least 30 to 1, or at least 50 to 1, or at least 65 to 1.
[0049] The dewaxing catalyst can also include a metal hydrogenation
component, such as a Group VIII metal. Suitable Group VIII metals
can include Pt, Pd, Ni, or a combination thereof.
[0050] The dewaxing catalyst can include at least 0.1 wt % of a
Group VIII metal, or at least 0.3 wt %, or at least 0.5 wt %, or at
least 1.0 wt %, or at least 2.5 wt %, or at least 5.0 wt %.
Alternatively, the dewaxing catalyst can include 10.0 wt % or less
of a Group VIII metal, or 5.0 wt % or less, or 2.5 wt % or less, or
1.5 wt % or less, or 1.0 wt % or less.
[0051] In some embodiments, the dewaxing catalyst can also include
at least one Group VIB metal, such as W or Mo. Such Group VIB
metals are typically used in conjunction with at least one Group
VIII metal, such as Ni or Co. An example of such an embodiment is a
dewaxing catalyst that includes Ni and W, Mo, or a combination of W
and Mo. In such an embodiment, the dewaxing catalyst can include at
least 0.5 wt % of a Group VIB metal, or at least 1.0 wt %, or at
least 2.5 wt %, or at least 5.0 wt %. Alternatively, the dewaxing
catalyst can include 20.0 wt % or less of a Group VIB metal, or
15.0 wt % or less, or 10.0 wt % or less, or 5.0 wt % or less, or
1.0 wt % or less. In an embodiment, the dewaxing catalyst can
include Pt, Pd, or a combination thereof. In another embodiment,
the dewaxing catalyst can include Co and Mo, Ni and W, Ni and Mo,
or Ni, W, and Mo.
[0052] The catalytic dewaxer can be operated at pressures
significantly lower than the hydrocracker. That is, at least 300
psi, or at least 500 psi, and even at least 1000 psi lower than the
hydrocracking stage. Both stages being high pressure is far more
common and consistent with high quality lube production.
[0053] Returning again to the FIGURE hereof, the effluent from
catalytic dewaxing stage 500 is sent to hydrofinishing stage 600.
The hydrofinishing step following dewaxing offers further
opportunity to improve product quality without significantly
affecting its pour point. Hydrofinishing is a mild, relatively cold
hydrotreating process, that employs a catalyst, hydrogen and mild
reaction conditions to remove trace amounts of heteroatom
compounds, aromatics and olefins, to improve primarily oxidation
stability and color. Hydrofinishing reaction conditions include
temperatures from 300.degree. F. to 675.degree. F. (149.degree. C.
to 357.degree. C.), preferably from 300.degree. F. to 480.degree.
F. (149.degree. C. to 249.degree. C.), a total pressure of from 400
to 3000 psig (2859 to 20786 kPa), a liquid hourly space velocity
ranging from 0.1 to 5 LHSV (hr.sup.-1), preferably 0.5 to 3
hr.sup.-1. The hydrotreating catalyst will comprise a support
component and one or more catalytic metal components. The one or
more metals are selected from Group VIB (Mo, W, Cr) and Group VIII
(Ni, Co and the noble metals Pt and Pd). The metal or metals may be
present from as little as 0.1 wt % for noble metals, to as high as
30 wt % of the catalyst composition for non-noble metals. Preferred
support materials are low in acid and include, for example,
amorphous or crystalline metal oxides such as alumina, silica,
silica alumina and ultra large pore crystalline materials known as
mesoporous crystalline materials, of which MCM-41 is a preferred
support component. Unsupported base metal (non-noble metal)
catalysts are also applicable as hydrofinishing catalysts.
[0054] The effluent stream from hydrofinishing zone 600 is passed
via line 26 to second separation zone 700 wherein a gaseous
effluent stream is separated from the resulting liquid phase lube
oil base stock. The gaseous effluent stream, a portion of which
will be unreacted hydrogen-containing treat gas can be recycled via
line 28 to hydrocracking stage 100. The resulting lube oil base
stock, which will meet Group II or Group III base oil requirements,
is collected via line 30.
[0055] All patents and patent applications, test procedures (such
as ASTM methods, UL methods, and the like), and other documents
cited herein are fully incorporated by reference to the extent such
disclosure is not inconsistent with this disclosure and for all
jurisdictions in which such incorporation is permitted.
[0056] When numerical lower limits and numerical upper limits are
listed herein, ranges from any lower limit to any upper limit are
contemplated. While the illustrative embodiments of the disclosure
have been described with particularity, it will be understood that
various other modifications will be apparent to and can be readily
made by those skilled in the art without departing from the spirit
and scope of the disclosure. Accordingly, it is not intended that
the scope of the claims appended hereto be limited to the examples
and descriptions set forth herein but rather that the claims be
construed as encompassing all the features of patentable novelty
which reside in the present disclosure, including all features
which would be treated as equivalents thereof by those skilled in
the art to which the disclosure pertains.
[0057] The present disclosure has been described above with
reference to numerous embodiments and specific examples. Many
variations will suggest themselves to those skilled in this art in
light of the above detailed description. All such obvious
variations are within the full intended scope of the appended
claims.
* * * * *